Phosphate Framework Electrode Materials for Sodium Ion Batteries

PubMed Central

Fang, Yongjin; Zhang, Jiexin; Xiao, Lifen; Ai, Xinping; Yang, Hanxi

2017-01-01

Sodium ion batteries (SIBs) have been considered as a promising alternative for the next generation of electric storage systems due to their similar electrochemistry to Li‐ion batteries and the low cost of sodium resources. Exploring appropriate electrode materials with decent electrochemical performance is the key issue for development of sodium ion batteries. Due to the high structural stability, facile reaction mechanism and rich structural diversity, phosphate framework materials have attracted increasing attention as promising electrode materials for sodium ion batteries. Herein, we review the latest advances and progresses in the exploration of phosphate framework materials especially related to single‐phosphates, pyrophosphates and mixed‐phosphates. We provide the detailed and comprehensive understanding of structure–composition–performance relationship of materials and try to show the advantages and disadvantages of the materials for use in SIBs. In addition, some new perspectives about phosphate framework materials for SIBs are also discussed. Phosphate framework materials will be a competitive and attractive choice for use as electrodes in the next‐generation of energy storage devices. PMID:28546907

Fiber reinforcement of concrete structures

DOT National Transportation Integrated Search

2002-09-01

Deterioration of concrete structures due to steel corrosion is a matter of considerable concern since the repairing of these structures proved to be a costly process. Repair and rehabilitation of the civil structures needs an enduring repair material...

Timber - Material of the Future - Examples of Small Wooden Architectural Structures

NASA Astrophysics Data System (ADS)

Żmijewki, Tomasz; Wojtowicz-Jankowska, Dorota

2017-10-01

The aim of this article is to present various types of wood-based products, classified as engineered timber, while specifying the implications of their structural properties for their forms. Timber is used as a construction material due to its fire resistance, good structural characteristics and insulating properties. The advent of new technologies of wood processing and wood-based materials production has converted timber into a high-tech material, thus encouraging the architects to consider it ever more often in their projects. As wooden technologies overcome constraints, timber begins to compete with steel and concrete. The design characteristics of new wood-based products allow wooden structures to be higher, have larger spans, and more diverse forms than ever. Wood-based materials include materials made of solid wood, veneers, strand, and wood which, due to its inferior quality, would otherwise be unfit for constructions. Elements and layers of these products are glued using different kinds of strong and water-resistant adhesives. The article presents the history of development of new wood technologies, discussing increasingly popular wood-based materials such as glued laminated timber, cross-laminated timber, or structural composite lumber. The paper analyses their technical and fire-resistance properties, and points to ecological aspect, as factors contributing to the growing popularity of these materials. Finally, the timber’s characteristics are contrasted with those of steel and concrete. The article lists examples of wooden objects representing the so-called small architecture structures from across Europe. They illustrate the potential, the uniqueness and the versatility that wood-based materials offer for constructors and architects. All these features form sufficient grounds for stating that timber truly is a construction material of the 21st century.

MoTe2, A novel anode material for sodium ion battery

NASA Astrophysics Data System (ADS)

Panda, Manas Ranjan; Anish Raj, K.; Bao, Qiaoliang; Mitra, Sagar

2018-04-01

2D layered transition metal dichalcogenides are considered as a potential anode for sodium-ion batteries due to their high specific capacity, structural stability and its well-developed two-dimensional layers. 2D layered structure Molybdenum ditelluride (MoTe2) provides a superior Na-ion storage properties in sodium ion battery due to its comparative more interlayer spacing (0.699 nm). In the current study MoTe2 polycrystalline powder sample has been prepared by solid state reaction process, the structural and morphological studies have been carried out by XRD, FE-SEM and EDS etc. XRD study revealsthe well crystalline structure of the material having hexagonal structure. FE-SEM and EDS studies depict the uniformflakes like structure of the material. When it is tested as sodium-ion battery anode by applying a potential window 0.1-2.5 V, the material demonstrates a high capacity and high power performances. The as prepared MoTe2 shows an initial discharge capacity of 376 mA h g-1 and a corresponding discharge capacity of 303 mA h g-1 after the 50th cycle at a current density of 500 mA g-1.

The thermal and mechanical stability of composite materials for space structures

NASA Technical Reports Server (NTRS)

Tompkins, S. S.; Sykes, G. F.; Bowles, D. E.

1985-01-01

A continuing research objective of the National Aeronautical and Space Administration (NASA) is to develop advanced composite materials for space structures. The thrust of this research is to gain fundamental understanding of the performance of advanced composites in the space environment. The emphasis has been to identify and model changes in the thermal-physical properties due to induced damage and develop improved materials.

Additive Technology: Update on Current Materials and Applications in Dentistry.

PubMed

Barazanchi, Abdullah; Li, Kai Chun; Al-Amleh, Basil; Lyons, Karl; Waddell, J Neil

2017-02-01

Additive manufacturing or 3D printing is becoming an alternative to subtractive manufacturing or milling in the area of computer-aided manufacturing. Research on material for use in additive manufacturing is ongoing, and a wide variety of materials are being used or developed for use in dentistry. Some materials, however, such as cobalt chromium, still lack sufficient research to allow definite conclusions about the suitability of their use in clinical dental practice. Despite this, due to the wide variety of machines that use additive manufacturing, there is much more flexibility in the build material and geometry when building structures compared with subtractive manufacturing. Overall additive manufacturing produces little material waste and is energy efficient when compared to subtractive manufacturing, due to passivity and the additive layering nature of the build process. Such features make the technique suitable to be used with fabricating structures out of hard to handle materials such as cobalt chromium. The main limitations of this technology include the appearance of steps due to layering of material and difficulty in fabricating certain material generally used in dentistry for use in 3D printing such as ceramics. The current pace of technological development, however, promises exciting possibilities. © 2016 by the American College of Prosthodontists.

Nonlinear ultrasonics for material state awareness

NASA Astrophysics Data System (ADS)

Jacobs, L. J.

2014-02-01

Predictive health monitoring of structural components will require the development of advanced sensing techniques capable of providing quantitative information on the damage state of structural materials. By focusing on nonlinear acoustic techniques, it is possible to measure absolute, strength based material parameters that can then be coupled with uncertainty models to enable accurate and quantitative life prediction. Starting at the material level, this review will present current research that involves a combination of sensing techniques and physics-based models to characterize damage in metallic materials. In metals, these nonlinear ultrasonic measurements can sense material state, before the formation of micro- and macro-cracks. Typically, cracks of a measurable size appear quite late in a component's total life, while the material's integrity in terms of toughness and strength gradually decreases due to the microplasticity (dislocations) and associated change in the material's microstructure. This review focuses on second harmonic generation techniques. Since these nonlinear acoustic techniques are acoustic wave based, component interrogation can be performed with bulk, surface and guided waves using the same underlying material physics; these nonlinear ultrasonic techniques provide results which are independent of the wave type used. Recent physics-based models consider the evolution of damage due to dislocations, slip bands, interstitials, and precipitates in the lattice structure, which can lead to localized damage.

Structural, electronic and magnetic properties of Pr-based filled skutterudites: A first principle study

NASA Astrophysics Data System (ADS)

Yadav, Priya; Nautiyal, Shashank; Verma, U. P.

2018-04-01

Ternary skutterudites materials exhibit good electronic properties due to the unpaired d- and f- electrons of the transition and rare-earth metals, respectively. In this communication, we have performed the structural optimization of Pr-based filled skutterudite (PrCo4P12) for the first time and obtained the electronic band structure, density of states and magnetic moments by using the full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). Our obtained magnetic moment of PrCo4P12 is ˜ 1.8 µB in which main contribution is due to Pr atom. Behavior of this material is metallic and it is most stable in body centered cubic (BCC) structure.

Study on the Aging Behaviors of Rubber Materials in Tension and Compression Loads

NASA Astrophysics Data System (ADS)

Jiang, Can; Wang, Hongyu; Ma, Xiaobing

Rubber materials are widely used in aviation, aerospace, shipbuilding, automobile and other military field. However, rubber materials are easy to aging, which largely restricts its using life. In working environment, due to the combined effect of heat and oxygen, vulcanized rubber will undergo degradation and crosslinking reaction which will cause elasticity decease and permanent deformation, so mostly rubber products are used under stress state. Due to the asymmetric structure and asymmetric stress distribution, mechanical stress may cause serious damage to molecular structure; therefore, this paper is aimed to analyze the aging behavior of rubber materials under tensile and compressive loadings, through analyzing experiment data, and adopting Gauss function to describe stress relaxation coefficient, to build an aging equation containing compression ratio parameter and aging time.

Nondestructive ultrasonic testing of materials

DOEpatents

Hildebrand, Bernard P.

1994-01-01

Reflection wave forms obtained from aged and unaged material samples can be compared in order to indicate trends toward age-related flaws. Statistical comparison of a large number of data points from such wave forms can indicate changes in the microstructure of the material due to aging. The process is useful for predicting when flaws may occur in structural elements of high risk structures such as nuclear power plants, airplanes, and bridges.

Nondestructive ultrasonic testing of materials

DOEpatents

Hildebrand, B.P.

1994-08-02

Reflection wave forms obtained from aged and unaged material samples can be compared in order to indicate trends toward age-related flaws. Statistical comparison of a large number of data points from such wave forms can indicate changes in the microstructure of the material due to aging. The process is useful for predicting when flaws may occur in structural elements of high risk structures such as nuclear power plants, airplanes, and bridges. 4 figs.

Advanced structural analysis of nanoporous materials by thermal response measurements.

PubMed

Oschatz, Martin; Leistner, Matthias; Nickel, Winfried; Kaskel, Stefan

2015-04-07

Thermal response measurements based on optical adsorption calorimetry are presented as a versatile tool for the time-saving and profound characterization of the pore structure of porous carbon-based materials. This technique measures the time-resolved temperature change of an adsorbent during adsorption of a test gas. Six carbide and carbon materials with well-defined nanopore architecture including micro- and/or mesopores are characterized by thermal response measurements based on n-butane and carbon dioxide as the test gases. With this tool, the pore systems of the model materials can be clearly distinguished and accurately analyzed. The obtained calorimetric data are correlated with the adsorption/desorption isotherms of the materials. The pore structures can be estimated from a single experiment due to different adsorption enthalpies/temperature increases in micro- and mesopores. Adsorption/desorption cycling of n-butane at 298 K/1 bar with increasing desorption time allows to determine the pore structure of the materials in more detail due to different equilibration times. Adsorption of the organic test gas at selected relative pressures reveals specific contributions of particular pore systems to the increase of the temperature of the samples and different adsorption mechanisms. The use of carbon dioxide as the test gas at 298 K/1 bar provides detailed insights into the ultramicropore structure of the materials because under these conditions the adsorption of this test gas is very sensitive to the presence of pores smaller than 0.7 nm.

COMPOSITE CONTROL ROD

DOEpatents

Rock, H.R.

1963-12-24

A composite control rod for use in controlling a nuclear reactor is described. The control rod is of sandwich construction in which finned dowel pins are utilized to hold together sheets of the neutron absorbing material and nonabsorbing structural material thereby eliminating the need for being dependent on the absorbing material for structural support. The dowel pins perform the function of absorbing the forces due to differential thermal expansion, seating further with the fins into the sheets of material and crushing before damage is done either to the absorbing or non-absorbing material. (AEC)

Microstructure and calorimetric behavior of laser welded open cell foams in CuZnAl shape memory alloy

NASA Astrophysics Data System (ADS)

Biffi, Carlo Alberto; Previtali, Barbara; Tuissi, Ausonio

Cellular shape memory alloys (SMAs) are very promising smart materials able to combine functional properties of the material with lightness, stiffness, and damping capacity of the cellular structure. Their processing with low modification of the material properties remains an open question. In this work, the laser weldability of CuZnAl SMA in the form of open cell foams was studied. The cellular structure was proved to be successfully welded in lap joint configuration by using a thin plate of the same alloy. Softening was seen in the welded bead in all the investigated ranges of process speed as well as a double stage heat affected zone was identified due to different microstructures; the martensitic transformation was shifted to higher temperatures and the corresponding peaks were sharper with respect to the base material due to the rapid solidification of the material. Anyways, no compositional variations were detected in the joints.

Computational characterization of ordered nanostructured surfaces

NASA Astrophysics Data System (ADS)

Mohieddin Abukhdeir, Nasser

2016-08-01

A vital and challenging task for materials researchers is to determine relationships between material characteristics and desired properties. While the measurement and assessment of material properties can be complex, quantitatively characterizing their structure is frequently a more challenging task. This issue is magnified for materials researchers in the areas of nanoscience and nanotechnology, where material structure is further complicated by phenomena such as self-assembly, collective behavior, and measurement uncertainty. Recent progress has been made in this area for both self-assembled and nanostructured surfaces due to increasing accessibility of imaging techniques at the nanoscale. In this context, recent advances in nanomaterial surface structure characterization are reviewed including the development of new theory and image processing methods.

Structural Evolution of Li xNi yMn zCo 1-y-zO 2 Cathode Materials during High-Rate Charge and Discharge

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

Hwang, Sooyeon; Jo, Eunmi; Chung, Kyung Yoon

Ni-rich lithium transition metal oxides have received significant attention due to their high capacities and rate capabilities determined via theoretical calculations. Although the structural properties of these materials are strongly correlated with the electrochemical performance, their structural stability during the high-rate electrochemical reactions has not been fully evaluated yet. In this work, transmission electron microscopy is used to investigate the crystallographic and electronic structural modifications of Ni-based cathode materials at a high charge/discharge rate of 10 C. It is found that the high-rate electrochemical reactions induce structural inhomogeneity near the surface of Ni-rich cathode materials, which limits Li transport andmore » reduces their capacities. Furthermore, this study establishes a correlation between the high-rate electrochemical performance of the Ni-based materials and their structural evolution, which can provide profound insights for designing novel cathode materials having both high energy and power densities.« less

Structural Evolution of Li xNi yMn zCo 1-y-zO 2 Cathode Materials during High-Rate Charge and Discharge

DOE PAGES

Hwang, Sooyeon; Jo, Eunmi; Chung, Kyung Yoon; ...

2017-11-08

Ni-rich lithium transition metal oxides have received significant attention due to their high capacities and rate capabilities determined via theoretical calculations. Although the structural properties of these materials are strongly correlated with the electrochemical performance, their structural stability during the high-rate electrochemical reactions has not been fully evaluated yet. In this work, transmission electron microscopy is used to investigate the crystallographic and electronic structural modifications of Ni-based cathode materials at a high charge/discharge rate of 10 C. It is found that the high-rate electrochemical reactions induce structural inhomogeneity near the surface of Ni-rich cathode materials, which limits Li transport andmore » reduces their capacities. Furthermore, this study establishes a correlation between the high-rate electrochemical performance of the Ni-based materials and their structural evolution, which can provide profound insights for designing novel cathode materials having both high energy and power densities.« less

Double differential light charged particle emission cross sections for some structural fusion materials

NASA Astrophysics Data System (ADS)

Sarpün, Ismail Hakki; n, Abdullah Aydı; Tel, Eyyup

2017-09-01

In fusion reactors, neutron induced radioactivity strongly depends on the irradiated material. So, a proper selection of structural materials will have been limited the radioactive inventory in a fusion reactor. First-wall and blanket components have high radioactivity concentration due to being the most flux-exposed structures. The main objective of fusion structural material research is the development and selection of materials for reactor components with good thermo-mechanical and physical properties, coupled with low-activation characteristics. Double differential light charged particle emission cross section, which is a fundamental data to determine nuclear heating and material damages in structural fusion material research, for some elements target nuclei have been calculated by the TALYS 1.8 nuclear reaction code at 14-15 MeV neutron incident energy and compared with available experimental data in EXFOR library. Direct, compound and pre-equilibrium reaction contribution have been theoretically calculated and dominant contribution have been determined for each emission of proton, deuteron and alpha particle.

Smart materials and structures: what are they?

NASA Astrophysics Data System (ADS)

Spillman, W. B., Jr.; Sirkis, J. S.; Gardiner, P. T.

1996-06-01

There has been considerable discussion in the technical community on a number of questions concerned with smart materials and structures, such as what they are, whether smart materials can be considered a subset of smart structures, whether a smart structure and an intelligent structure are the same thing, etc. This discussion is both fueled and confused by the technical community due to the truly multidisciplinary nature of this new field. Smart materials and structures research involves so many technically diverse fields that it is quite common for one field to completely misunderstand the terminology and start of the art in other fields. In order to ascertain whether a consensus is emerging on a number of questions, the technical community was surveyed in a variety of ways including via the internet and by direct contact. The purpose of this survey was to better define the smart materials and structures field, its current status and its potential benefits. Results of the survey are presented and discussed. Finally, a formal definition of the field of smart materials and structures is proposed.

(abstract) Oblique Insonification Ultrasonic NDE of Composite Materials for Space Applications

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.; Lih, S. S.; Mal, A. K.

1997-01-01

In recent years, a great deal of research has been exerted to developing NDE methods for the characterization of the material properties of composites as well as other space structural materials. The need for information about such parameters as the elastic properties, density, and thickness are critical to the safe design and operation of such structural materials. Ultrasonics using immersion methods has played an important role in these efforts due to its capability, cost effectiveness, and ease of use. The authors designed a series of ultrasonic oblique insonification experiments in order to develop a practical field applicable NDE method for space structures.

Potential of Glassy Carbon and Silicon Carbide Photonic Structures as Electromagnetic Radiation Shields for Atmospheric Re-entry

NASA Technical Reports Server (NTRS)

Komarevskiy,Nikolay; Shklover, Valery; Braginsky, Leonid; Hafner, Christian; Lawson, John W.

2012-01-01

During high-velocity atmospheric entries, space vehicles can be exposed to strong electromagnetic radiation from ionized gas in the shock layer. Glassy carbon (GC) and silicon carbide (SiC) are candidate thermal protection materials due to their high melting point and also their good thermal and mechanical properties. Based on data from shock tube experiments, a significant fraction of radiation at hypersonic entry conditions is in the frequency range from 215 to 415 THz. We propose and analyze SiC and GC photonic structures to increase the reflection of radiation in that range. For this purpose, we performed numerical optimizations of various structures using an evolutionary strategy. Among the considered structures are layered, porous, woodpile, inverse opal and guided-mode resonance structures. In order to estimate the impact of fabrication inaccuracies, the sensitivity of the reflectivity to structural imperfections is analyzed. We estimate that the reflectivity of GC photonic structures is limited to 38% in the aforementioned range, due to material absorption. However, GC material can be effective for photonic reflection of individual, strong spectral line. SiC on the other hand can be used to design a good reflector for the entire frequency range.

Potential of glassy carbon and silicon carbide photonic structures as electromagnetic radiation shields for atmospheric re-entry.

PubMed

Komarevskiy, Nikolay; Shklover, Valery; Braginsky, Leonid; Hafner, Christian; Lawson, John

2012-06-18

During high-velocity atmospheric entries, space vehicles can be exposed to strong electromagnetic radiation from ionized gas in the shock layer. Glassy carbon (GC) and silicon carbide (SiC) are candidate thermal protection materials due to their high melting point and also their good thermal and mechanical properties. Based on data from shock tube experiments, a significant fraction of radiation at hypersonic entry conditions is in the frequency range from 215 to 415 THz. We propose and analyze SiC and GC photonic structures to increase the reflection of radiation in that range. For this purpose, we performed numerical optimizations of various structures using an evolutionary strategy. Among the considered structures are layered, porous, woodpile, inverse opal and guided-mode resonance structures. In order to estimate the impact of fabrication inaccuracies, the sensitivity of the reflectivity to structural imperfections is analyzed. We estimate that the reflectivity of GC photonic structures is limited to 38% in the aforementioned range, due to material absorption. However, GC material can be effective for photonic reflection of individual, strong spectral line. SiC on the other hand can be used to design a good reflector for the entire frequency range.

Hierarchical photonic structured stimuli-responsive materials as high-performance colorimetric sensors

NASA Astrophysics Data System (ADS)

Lu, Tao; Zhu, Shenmin; Chen, Zhixin; Wang, Wanlin; Zhang, Wang; Zhang, Di

2016-05-01

Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity responsive properties and a tremendous colour change. The colour change is induced by the refractive index change which is in turn due to the swollen nature of the polymer when the relative humidity changes. The butterfly wing scales also showed an excellent durability which is due to the chemical bonds formed between the polymer and wing scales. The synthesis strategy provides an avenue for the promising applications of stimuli-responsive PCs with hierarchical structures.Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity responsive properties and a tremendous colour change. The colour change is induced by the refractive index change which is in turn due to the swollen nature of the polymer when the relative humidity changes. The butterfly wing scales also showed an excellent durability which is due to the chemical bonds formed between the polymer and wing scales. The synthesis strategy provides an avenue for the promising applications of stimuli-responsive PCs with hierarchical structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01875k

Optomechanics of two- and three-dimensional soft photonic crystals

NASA Astrophysics Data System (ADS)

Krishnan, Dwarak

Soft photonic crystals are a class of periodic dielectric structures that undergo highly nonlinear deformation due to strain or other external stimulus such as temperature, pH etc. This can in turn dramatically affect optical properties such as light transmittance. Moreover certain classes of lithographically fabricated structures undergo some structural distortion due to the effects of processing, eventually affecting the optical properties of the final photonic crystal. In this work, we study the deformation mechanics of soft photonic crystal structures using realistic physics-based models and leverage that understanding to explain the optomechanics of actual 2-D and 3-D soft photonic crystals undergoing similar symmetry breaking nonlinear deformations. We first study the optomechanics of two classes of 3-D soft photonic crystals: (1) hydrogel and (2) elastomer based material systems. The hydrogel based inverse face-centered-cubic structure undergoes swelling with change in pH of the surrounding fluid. The inverse structure is a network of bulky domains with thin ligament-like connections, and it undergoes a pattern transformation from FCC to L11 as a result of swelling. A continuum scale poroelasticity based coupled fluid-diffusion FEM model is developed to accurately predict this mechanical behavior. Light transmittance simulation results qualitatively explain the experimentally observed trends in the optical behavior with pH change. The elastomer based, lithographically fabricated material experiences shrinkage induced distortion upon processing. This behavior is modeled using FEM with the material represented by a neo-Hookean constitutive law. The light transmittance calculations for normal incidence are carried out using the transfer matrix method and a good comparison is obtained for the positions of first and second order reflectance peaks. A unit cell based approach is taken to compute the photonic bandstructure to estimate light propagation through the structure for other angles of light incidence. To obtain a detailed picture of the change in optical properties due to a pattern transformation, we study simple 2-D elastomer photonic crystals which undergo an interesting structural pattern transformation from simple circular holes to alternately oriented ellipses in a square lattice due to uniaxial compression. The incident light does not have any effect on the properties of the elastomer material. A decomposition of the deformation gradient quickly shows that the pattern transformation is induced by alternating rotations of the interstitial regions and the bending of interconnecting ligaments. Numerical simulations of light transmittance using vector element based FEM analysis of Maxwells equations shows changes in the light energy localization within the material especially in the high energy/low wavelength regions of the spectra. Additionally, with bandstructure calculations on a unit cell of the structure, the optomechanical behavior is completely explained. Finally, computational evidence is provided for a hypothetical 2-D photonic crystal made of a light-sensitive material, which undergoes a structural pattern transformation primarily due to the effect of incident light. The model takes into account the order kinetics of optically induced isomerization (of trans to cis configuration) in the azobenzene-liquid crystal elastomer to compute the transformational strain. This strain, in turn, deforms the structure and hence changes its periodicity and dielectric properties and thus affects the manner in which light gets localized within the material system. This consequently changes the profile of the imposed transformational strain on the deformed structure. The macroscopic strain history shows that prior to the mechanical instability that causes the pattern transformation, there is a period of structural relaxation which initiates the pattern transformation. After the symmetry breaking pattern transformation, the photonic bandstructure is altered significantly. Light does not get localized in the spot regions anymore and stress relaxation dominates. Due to this, the compressive macroscopic strain of the pattern transformed structure starts to decrease indicating a possible cyclical behavior.

Electronic and structural properties of M3(HITP)2 (M = Ni, Cu and Co) metal-organic frameworks

NASA Astrophysics Data System (ADS)

Silveira, Orlando; Chacham, Helio; Alexandre, Simone

Theoretical and experimental works have demonstrated that electrical and structural properties of metal-organic frameworks (MOF) can be significantly changed by the identity of the metal center, leading to a potential strategy for tuning the selectivity of the material toward different types of technological applications. In this work, we use first principle calculations to investigate the electronic properties of 2D MOF M3(HITP)2 (M is Ni, Cu and Co and HITP = 2,3,6,7,10,11 - hexaiminotriphenylene). Our results show that for M=Ni and Co, the structures are perfect planar and there is a full charge delocalization in the 2D plane of stacking due to the predominance of π - π bonding. The band structure for M = Ni shows that this material is a semiconductor with an indirect band gap of 132 meV, whilst for M = Co the band structure shows that this material is a ferromagnetic semiconductor with a direct band gap of 386 meV for spin down and a indirect band gap of 246 meV for spin up. For M=Cu, the material is a metal and adopts a distorted structure due to a different hybridization of the metal atom in comparison with its counterparts. We also propose a tight binding model that can represent the electronic structure near the Fermi level of this family of MOF.

Materials and structures for stretchable energy storage and conversion devices.

PubMed

Xie, Keyu; Wei, Bingqing

2014-06-11

Stretchable energy storage and conversion devices (ESCDs) are attracting intensive attention due to their promising and potential applications in realistic consumer products, ranging from portable electronics, bio-integrated devices, space satellites, and electric vehicles to buildings with arbitrarily shaped surfaces. Material synthesis and structural design are core in the development of highly stretchable supercapacitors, batteries, and solar cells for practical applications. This review provides a brief summary of research development on the stretchable ESCDs in the past decade, from structural design strategies to novel materials synthesis. The focuses are on the fundamental insights of mechanical characteristics of materials and structures on the performance of the stretchable ESCDs, as well as challenges for their practical applications. Finally, some of the important directions in the areas of material synthesis and structural design facing the stretchable ESCDs are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Review of Structure Construction of Silk Fibroin Biomaterials from Single Structures to Multi-Level Structures.

PubMed

Qi, Yu; Wang, Hui; Wei, Kai; Yang, Ya; Zheng, Ru-Yue; Kim, Ick Soo; Zhang, Ke-Qin

2017-03-03

The biological performance of artificial biomaterials is closely related to their structure characteristics. Cell adhesion, migration, proliferation, and differentiation are all strongly affected by the different scale structures of biomaterials. Silk fibroin (SF), extracted mainly from silkworms, has become a popular biomaterial due to its excellent biocompatibility, exceptional mechanical properties, tunable degradation, ease of processing, and sufficient supply. As a material with excellent processability, SF can be processed into various forms with different structures, including particulate, fiber, film, and three-dimensional (3D) porous scaffolds. This review discusses and summarizes the various constructions of SF-based materials, from single structures to multi-level structures, and their applications. In combination with single structures, new techniques for creating special multi-level structures of SF-based materials, such as micropatterning and 3D-printing, are also briefly addressed.

Using of Aerogel to Improve Thermal Insulating Properties of Windows

NASA Astrophysics Data System (ADS)

Valachova, Denisa; Zdrazilova, Nada; Panovec, Vladan; Skotnicova, Iveta

2018-06-01

For the best possible thermal-technical properties of building structures it is necessary to use materials with very low thermal conductivity. Due to the increasing thermal-technical requirements for building structures, the insulating materials are developed. One of the modern thermal insulating materials is so-called aerogel. Unfortunately, this material is not used in the field of external thermal insulation composite systems because of its price and its properties. The aim of this paper is to present possibilities of using this insulating material in the civil engineering - specifically a usage of aerogel in the production of windows.

Developing polymer composite materials: carbon nanotubes or graphene?

PubMed

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

2013-10-04

The formation of composite materials represents an efficient route to improve the performances of polymers and expand their application scopes. Due to the unique structure and remarkable mechanical, electrical, thermal, optical and catalytic properties, carbon nanotube and graphene have been mostly studied as a second phase to produce high performance polymer composites. Although carbon nanotube and graphene share some advantages in both structure and property, they are also different in many aspects including synthesis of composite material, control in composite structure and interaction with polymer molecule. The resulting composite materials are distinguished in property to meet different applications. This review article mainly describes the preparation, structure, property and application of the two families of composite materials with an emphasis on the difference between them. Some general and effective strategies are summarized for the development of polymer composite materials based on carbon nanotube and graphene. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Shockwave Consolidation of Nanostructured Thermoelectric Materials

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Taylor, Patrick; Nemir, David

2014-01-01

Nanotechnology based thermoelectric materials are considered attractive for developing highly efficient thermoelectric devices. Nano-structured thermoelectric materials are predicted to offer higher ZT over bulk materials by reducing thermal conductivity and increasing electrical conductivity. Consolidation of nano-structured powders into dense materials without losing nanostructure is essential towards practical device development. Using the gas atomization process, amorphous nano-structured powders were produced. Shockwave consolidation is accomplished by surrounding the nanopowder-containing tube with explosives and then detonating. The resulting shock wave causes rapid fusing of the powders without the melt and subsequent grain growth. We have been successful in generating consolidated nano-structured bismuth telluride alloy powders by using the shockwave technique. Using these consolidated materials, several types of thermoelectric power generating devices have been developed. Shockwave consolidation is anticipated to generate large quantities of nanostructred materials expeditiously and cost effectively. In this paper, the technique of shockwave consolidation will be presented followed by Seebeck Coefficient and thermal conductivity measurements of consolidated materials. Preliminary results indicate a substantial increase in electrical conductivity due to shockwave consolidation technique.

Review on the EFDA programme on tungsten materials technology and science

NASA Astrophysics Data System (ADS)

Rieth, M.; Boutard, J. L.; Dudarev, S. L.; Ahlgren, T.; Antusch, S.; Baluc, N.; Barthe, M.-F.; Becquart, C. S.; Ciupinski, L.; Correia, J. B.; Domain, C.; Fikar, J.; Fortuna, E.; Fu, C.-C.; Gaganidze, E.; Galán, T. L.; García-Rosales, C.; Gludovatz, B.; Greuner, H.; Heinola, K.; Holstein, N.; Juslin, N.; Koch, F.; Krauss, W.; Kurzydlowski, K. J.; Linke, J.; Linsmeier, Ch.; Luzginova, N.; Maier, H.; Martínez, M. S.; Missiaen, J. M.; Muhammed, M.; Muñoz, A.; Muzyk, M.; Nordlund, K.; Nguyen-Manh, D.; Norajitra, P.; Opschoor, J.; Pintsuk, G.; Pippan, R.; Ritz, G.; Romaner, L.; Rupp, D.; Schäublin, R.; Schlosser, J.; Uytdenhouwen, I.; van der Laan, J. G.; Veleva, L.; Ventelon, L.; Wahlberg, S.; Willaime, F.; Wurster, S.; Yar, M. A.

2011-10-01

All the recent DEMO design studies for helium cooled divertors utilize tungsten materials and alloys, mainly due to their high temperature strength, good thermal conductivity, low erosion, and comparably low activation under neutron irradiation. The long-term objective of the EFDA fusion materials programme is to develop structural as well as armor materials in combination with the necessary production and fabrication technologies for future divertor concepts. The programmatic roadmap is structured into four engineering research lines which comprise fabrication process development, structural material development, armor material optimization, and irradiation performance testing, which are complemented by a fundamental research programme on "Materials Science and Modeling". This paper presents the current research status of the EFDA experimental and testing investigations, and gives a detailed overview of the latest results on fabrication, joining, high heat flux testing, plasticity, modeling, and validation experiments.

Electric measurements of PV heterojunction structures a-SiC/c-Si

NASA Astrophysics Data System (ADS)

Perný, Milan; Šály, Vladimír; Janíček, František; Mikolášek, Miroslav; Váry, Michal; Huran, Jozef

2018-01-01

Due to the particular advantages of amorphous silicon or its alloys with carbon in comparison to conventional crystalline materials makes such a material still interesting for study. The amorphous silicon carbide may be used in a number of micro-mechanical and micro-electronics applications and also for photovoltaic energy conversion devices. Boron doped thin layers of amorphous silicon carbide, presented in this paper, were prepared due to the optimization process for preparation of heterojunction solar cell structure. DC and AC measurement and subsequent evaluation were carried out in order to comprehensively assess the electrical transport processes in the prepared a-SiC/c-Si structures. We have investigated the influence of methane content in deposition gas mixture and different electrode configuration.

Method of making quasi-grain boundary-free polycrystalline solar cell structure and solar cell structure obtained thereby

DOEpatents

Gonzalez, Franklin N.; Neugroschel, Arnost

1984-02-14

A new solar cell structure is provided which will increase the efficiency of polycrystalline solar cells by suppressing or completely eliminating the recombination losses due to the presence of grain boundaries. This is achieved by avoiding the formation of the p-n junction (or other types of junctions) in the grain boundaries and by eliminating the grain boundaries from the active area of the cell. This basic concept can be applied to any polycrystalline material; however, it will be most beneficial for cost-effective materials having small grains, including thin film materials.

Thermal Conductivity in Nanoporous Gold Films during Electron-Phonon Nonequilibrium

DOE PAGES

Hopkins, Patrick E.; Norris, Pamela M.; Phinney, Leslie M.; ...

2008-01-01

The reduction of nanodevices has given recent attention to nanoporous materials due to their structure and geometry. However, the thermophysical properties of these materials are relatively unknown. In this article, an expression for thermal conductivity of nanoporous structures is derived based on the assumption that the finite size of the ligaments leads to electron-ligament wall scattering. This expression is then used to analyze the thermal conductivity of nanoporous structures in the event of electron-phonon nonequilibrium.

Changes in Structural Health Monitoring System Capability Due to Aircraft Environmental Factors

DTIC Science & Technology

2009-09-01

and R. Ikegami . “Hot-Spot Fatigue Crack Monitoring of Inaccessible Structural Regions in Air- craft Subsystems Using Structural Health Monitoring...national Society for Optical Engineering, volume 4702 of Smart Structures and Materials 2002, 29–40. Newport Beach, CA: SPIE, 2002. 54. Ikegami , R

Modeling and Analysis of Composite Wing Sections for Improved Aeroelastic and Vibration Characteristics Using Smart Materials

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi

1996-01-01

The objective of this research is to develop analysis procedures to investigate the coupling of composite and smart materials to improve aeroelastic and vibratory response of aerospace structures. The structural modeling must account for arbitrarily thick geometries, embedded and surface bonded sensors and actuators and imperfections, such as delamination. Changes in the dynamic response due to the presence of smart materials and delaminations is investigated. Experiments are to be performed to validate the proposed mathematical model.

A Review of Structure Construction of Silk Fibroin Biomaterials from Single Structures to Multi-Level Structures

PubMed Central

Qi, Yu; Wang, Hui; Wei, Kai; Yang, Ya; Zheng, Ru-Yue; Kim, Ick Soo; Zhang, Ke-Qin

2017-01-01

The biological performance of artificial biomaterials is closely related to their structure characteristics. Cell adhesion, migration, proliferation, and differentiation are all strongly affected by the different scale structures of biomaterials. Silk fibroin (SF), extracted mainly from silkworms, has become a popular biomaterial due to its excellent biocompatibility, exceptional mechanical properties, tunable degradation, ease of processing, and sufficient supply. As a material with excellent processability, SF can be processed into various forms with different structures, including particulate, fiber, film, and three-dimensional (3D) porous scaffolds. This review discusses and summarizes the various constructions of SF-based materials, from single structures to multi-level structures, and their applications. In combination with single structures, new techniques for creating special multi-level structures of SF-based materials, such as micropatterning and 3D-printing, are also briefly addressed. PMID:28273799

Method and Apparatus for Non-Destructive Evaluation of Materials

NASA Technical Reports Server (NTRS)

Washabaugh, Andrew P. (Inventor); Lyons, Robert (Inventor); Thomas, Zachary (Inventor); Martin, Christopher (Inventor); Goldfine, Neil J. (Inventor)

2017-01-01

Methods and apparatus for characterizing composite materials for manufacturing quality assurance (QA), periodic inspection during the useful life, or for forensic analysis/material testing. System are provided that relate eddy-current sensor responses to the fiber layup of a composite structure, the presence of impact damage on a composite structure with or without a metal liner, volumetric stress within the composite, fiber tow density, and other NDE inspection requirements. Also provided are systems that determine electromagnetic material properties and material dimensions of composite materials from capacitive sensor inspection measurements. These properties are related to the presence of buried defects in non-conductive composite materials, moisture ingress, aging of the material due to service or environmental/thermal exposure, or changes in manufacturing quality.

Method and Apparatus for Non-Destructive Evaluation of Materials

NASA Technical Reports Server (NTRS)

Lyons, Robert (Inventor); Martin, Christopher (Inventor); Washabaugh, Andrew P. (Inventor); Goldfine, Neil J. (Inventor); Thomas, Zachary (Inventor); Jablonski, David A. (Inventor)

2015-01-01

Methods and apparatus for characterizing composite materials for manufacturing quality assurance (QA), periodic inspection during the useful life, or for forensic analysis/material testing. System are provided that relate eddy-current sensor responses to the fiber layup of a composite structure, the presence of impact damage on a composite structure with or without a metal liner, volumetric stress within the composite, fiber tow density, and other NDE inspection requirements. Also provided are systems that determine electromagnetic material properties and material dimensions of composite materials from capacitive sensor inspection measurements. These properties are related to the presence of buried defects in non-conductive composite materials, moisture ingress, aging of the material due to service or environmental/thermal exposure, or changes in manufacturing quality.

Environmental Suitability of Weathering Steel Structures in Florida – Materials Selection, Phase : summary.

DOT National Transportation Integrated Search

2017-09-01

The results of this project may increase the opportunities to use weathering steel in transportation structures, which offers significant cost savings due to lower maintenance and longer service life.

Designing Microstructures/Structures for Desired Functional Material and Local Fields

DTIC Science & Technology

2015-12-02

utilized to engineer multifunctional soft materials for multi-sensing, multi- actuating , human-machine interfaces. [3] Establish a theoretical framework...model for surface elasticity, (ii) derived a new type of Maxwell stress in soft materials due to quantum mechanical-elasticity coupling and...elucidated its ramification in engineering multifunctional soft materials, and (iii) demonstrated the possibility of concurrent magnetoelectricity and

Holmium Doped Solid State Laser Resonantly Pumped and Q-Switched by Novel GaSb-Based Photonic Devices

DTIC Science & Technology

2011-08-31

increased overlap with p-cladding, presumably due to dominant role of inter valence band absorption [7]. Details of the conduction band structure of the...absorption to total loss. In the specific structures used here the n-cladding composition resulted into material with three valleys in conduction band to...materials. The beam properties of the high power 2 μm emitting GaSb -based diode lasers was improved by utilization of the waveguide structure with

Spacecraft Shielding: An Experimental Comparison Between Open Cell Aluminium Foam Core Sandwich Panel Structures and Whipple Shielding.

NASA Astrophysics Data System (ADS)

Pasini, D. L. S.; Price, M. C.; Burchell, M. J.; Cole, M. J.

2013-09-01

Spacecraft shielding is generally provided by metallic plates in a Whipple shield type configuration [1] where possible. However, mission restrictions such as spacecraft payload mass, can prevent the inclusion of a dedicated protective structure for prevention against impact damage from micrometeoroids. Due to this, often the spacecraft's primary structure will act as the de facto shield. This is commonly an aluminium honeycomb backed with either glass fibre reinforced plastic (GFRP) or aluminium faceplates [2]. Such materials are strong, lightweight and relatively cheap due to their abundance used within the aerospace industry. However, these materials do not offer the best protection (per unit weight) against hypervelocity impact damage. A new material for shielding (porous aluminium foam [3]) is suggested for low risk space missions. Previous studies by NASA [4] have been performed to test this new material against hypervelocity impacts using spherical aluminium projectiles. This showed its potential for protection for satellites in Earth orbit, against metallic space debris. Here we demonstrate the material's protective capabilities against micrometeoroids, using soda-lime glass spheres as projectiles to accurately gauge its potential with relation to silicatious materials, such as micrometeoroids and natural solar system debris. This is useful for spacecraft missions beyond Earth orbit where solar system materials are the dominant threat (via hypervelocity impacts) to the spacecraft, rather than manmade debris.

Thermal characteristics of carbon fiber reinforced epoxy containing multi-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Lee, Jin-woo; Park, Soo-Jeong; Kim, Yun-hae; Riichi-Murakami

2018-06-01

The material with irregular atomic structures such as polymer material exhibits low thermal conductivity because of the complex structural properties. Even materials with same atomic configurations, thermal conductivity may be different based on their structural properties. It is expected that nanoparticles with conductivity will change non-conductive polymer base materials to electrical conductors, and improve the thermal conductivity even with extremely small filling amount. Nano-composite materials contain nanoparticles with a higher surface ratio which makes the higher interface percentage to the total surface of nanoparticles. Therefore, thermal resistance of the interface becomes a dominating factor determines the effective thermal conductivity in nano-composite materials. Carbon fiber has characteristic of resistance or magnetic induction and Also, Carbon nanotube (CNT) has electronic and thermal property. It can be applied for heating system. These characteristic are used as heating composite. In this research, the exothermic characteristics of Carbon fiber reinforced composite added CNT were evaluated depend on CNT length and particle size. It was found that the CNT dispersed in the resin reduces the resistance between the interfaces due to the decrease in the total resistance of the heating element due to the addition of CNTs. It is expected to improve the life and performance of the carbon fiber composite material as a result of the heating element resulting from this paper.

Fiber Reinforced Concrete (FRC) for High Rise Construction: Case Studies

NASA Astrophysics Data System (ADS)

Gharehbaghi, Koorosh; Chenery, Rhea

2017-12-01

Due to its material element, Fiber Reinforced Concrete (FRC) could be stronger than traditional Concrete. This is due to FRC internal material compounds and elements. Furthermore, FRC can also significantly improve flexural strength when compared to traditional Concrete. This improvement in flexural strength can be varied depending on the actual fibers used. Although not new, FRC is gradually gaining popularity in the construction industry, in particular for high rise structures. This is due to its flexural strength, especially for high seismic zones, as it will provide a better solution then reinforced Concrete. The main aim of this paper is to investigate the structural importance of FRC for the high rise construction. Although there has been numerous studies and literature in justifying the FRC for general construction; this paper will consider its use specifically for high rise construction. Moreover, this paper will closely investigate eight case studies from Australian and United States as a part of the FRC validation for high rise construction. In doing so, this paper will examine their Structural Health Monitoring (SHM) to determine their overall structural performance.

Field of smart structures as seen by those working in it: survey results

NASA Astrophysics Data System (ADS)

Spillman, William B., Jr.; Sirkis, James S.; Gardiner, Peter T.

1995-04-01

There has been considerable discussion in the technical community on a number of questions concerned with smart materials and structures, such as what they are, whether smart materials can be considered a subset of smart structures, whether a smart structure and an intelligent structure are the same thing, etc. This discussion is both fueled and confused by the technical community due to the truly multidisciplinary nature of this new field. Smart materials and structures research involves so many technically diverse fields that it is quite common for one field to completely misunderstand the terminology and state-of-the-art in other fields. In order to ascertain whether a consensus is emerging on a number of these questions, the technical community was surveyed in a number of ways including via the Internet and by direct contact. The purpose of this survey in the final analysis was to better define the smart materials and structures field, its current status and its potential benefits. Results of the survey are presented and discussed.

Structural kinematics based damage zone prediction in gradient structures using vibration database

NASA Astrophysics Data System (ADS)

Talha, Mohammad; Ashokkumar, Chimpalthradi R.

2014-05-01

To explore the applications of functionally graded materials (FGMs) in dynamic structures, structural kinematics based health monitoring technique becomes an important problem. Depending upon the displacements in three dimensions, the health of the material to withstand dynamic loads is inferred in this paper, which is based on the net compressive and tensile displacements that each structural degree of freedom takes. These net displacements at each finite element node predicts damage zones of the FGM where the material is likely to fail due to a vibration response which is categorized according to loading condition. The damage zone prediction of a dynamically active FGMs plate have been accomplished using Reddy's higher-order theory. The constituent material properties are assumed to vary in the thickness direction according to the power-law behavior. The proposed C0 finite element model (FEM) is applied to get net tensile and compressive displacement distributions across the structures. A plate made of Aluminum/Ziconia is considered to illustrate the concept of structural kinematics-based health monitoring aspects of FGMs.

Self-assembled hierarchically structured organic-inorganic composite systems.

PubMed

Tritschler, Ulrich; Cölfen, Helmut

2016-05-13

Designing bio-inspired, multifunctional organic-inorganic composite materials is one of the most popular current research objectives. Due to the high complexity of biocomposite structures found in nacre and bone, for example, a one-pot scalable and versatile synthesis approach addressing structural key features of biominerals and affording bio-inspired, multifunctional organic-inorganic composites with advanced physical properties is highly challenging. This article reviews recent progress in synthesizing organic-inorganic composite materials via various self-assembly techniques and in this context highlights a recently developed bio-inspired synthesis concept for the fabrication of hierarchically structured, organic-inorganic composite materials. This one-step self-organization concept based on simultaneous liquid crystal formation of anisotropic inorganic nanoparticles and a functional liquid crystalline polymer turned out to be simple, fast, scalable and versatile, leading to various (multi-)functional composite materials, which exhibit hierarchical structuring over several length scales. Consequently, this synthesis approach is relevant for further progress and scientific breakthrough in the research field of bio-inspired and biomimetic materials.

Triangular Black Phosphorus Atomic Layers by Liquid Exfoliation.

PubMed

Seo, Soonjoo; Lee, Hyun Uk; Lee, Soon Chang; Kim, Yooseok; Kim, Hyeran; Bang, Junhyeok; Won, Jonghan; Kim, Youngjun; Park, Byoungnam; Lee, Jouhahn

2016-03-30

Few-layer black phosphorus (BP) is the most promising material among the two-dimensional materials due to its layered structure and the excellent semiconductor properties. Currently, thin BP atomic layers are obtained mostly by mechanical exfoliation of bulk BP, which limits applications in thin-film based electronics due to a scaling process. Here we report highly crystalline few-layer black phosphorus thin films produced by liquid exfoliation. We demonstrate that the liquid-exfoliated BP forms a triangular crystalline structure on SiO2/Si (001) and amorphous carbon. The highly crystalline BP layers are faceted with a preferred orientation of the (010) plane on the sharp edge, which is an energetically most favorable facet according to the density functional theory calculations. Our results can be useful in understanding the triangular BP structure for large-area applications in electronic devices using two-dimensional materials. The sensitivity and selectivity of liquid-exfoliated BP to gas vapor demonstrate great potential for practical applications as sensors.

Triangular Black Phosphorus Atomic Layers by Liquid Exfoliation

PubMed Central

Seo, Soonjoo; Lee, Hyun Uk; Lee, Soon Chang; Kim, Yooseok; Kim, Hyeran; Bang, Junhyeok; Won, Jonghan; Kim, Youngjun; Park, Byoungnam; Lee, Jouhahn

2016-01-01

Few-layer black phosphorus (BP) is the most promising material among the two-dimensional materials due to its layered structure and the excellent semiconductor properties. Currently, thin BP atomic layers are obtained mostly by mechanical exfoliation of bulk BP, which limits applications in thin-film based electronics due to a scaling process. Here we report highly crystalline few-layer black phosphorus thin films produced by liquid exfoliation. We demonstrate that the liquid-exfoliated BP forms a triangular crystalline structure on SiO2/Si (001) and amorphous carbon. The highly crystalline BP layers are faceted with a preferred orientation of the (010) plane on the sharp edge, which is an energetically most favorable facet according to the density functional theory calculations. Our results can be useful in understanding the triangular BP structure for large-area applications in electronic devices using two-dimensional materials. The sensitivity and selectivity of liquid-exfoliated BP to gas vapor demonstrate great potential for practical applications as sensors. PMID:27026070

Prediction of a New Phase of Cu x S near Stoichiometric Composition

DOE PAGES

Khatri, Prashant; Huda, Muhammad N.

2015-01-01

Cumore » 2 S is known to be a promising solar absorber material due to its suitable band gap and the abundance of its constituent elements. 2 S is known to have complex phase structures depending on the concentration of vacancies. Its instability of phases is due to favorable formation of vacancies and the mobility of atoms within the crystal. Understanding its phase structures is of crucial important for its application as solar absorber material. In this paper, we have predicted a new crystal phase of copper sulfide ( x S) around chemical composition of x = 1.98 by utilizing crystal database search and density functional theory. We have shown that this new crystal phase of x S is more favorable than low chalcocite structure even at stoichiometric composition of x = 2 . However, vacancy formation probability was found to be higher in this new phase than the low chalcocite structure.« less

Rice Husk Silica-Derived Nanomaterials for Battery Applications: A Literature Review.

PubMed

Shen, Yafei

2017-02-08

Silica-rich rice husk (RH) is an abundant and sustainable agricultural waste. The recovery of value-added products from RH or its ash to explore an economic way for the valorization of agricultural wastes has attracted wide attention. For instance, RH can be converted to biofuels and biochars simultaneously via thermochemical processes. In general, the applications of RH biochars include soil remediation, pollutant removal, silicon battery materials, and so forth. This review concludes recent progress in the synthesis of RH-derived silicon materials for lithium-ion battery (LIB) applications. Silica nanomaterials produced from RH are initially discussed. RH amorphous silica can also be fabricated to crystal silicon used for battery materials via widely used magnesiothermic reduction. However, the RH-derived Si nanoparticles suffer from a low Coulombic efficiency in the initial charge/discharge and limited cycle life as anode materials due to high surface reactions and low thermodynamic stability. The synthesis of Si materials with nano/microhierarchical structure would be an ideal way to improve their electrochemical performances. Embedding nano-Si into 3D conductive matrix is an effective way to improve the structural stability. Among the Si/carbon composite materials, carbon nanotubdes (CNTs) are a promising matrix due to the wired morphology, high electronic conductivity, and robust structure. Additionally, CNTs can easily form 3D cross-linked conducting networks, ensuring effective electron transportation among active particles. Si nanomaterials with microhierarchical structures in which CNTs are tightly intertwined between the RH-derived Si nanoparticles have been proven to be ideal LIB anode materials.

Functional Nanoclay Suspension for Printing-Then-Solidification of Liquid Materials.

PubMed

Jin, Yifei; Compaan, Ashley; Chai, Wenxuan; Huang, Yong

2017-06-14

Additive manufacturing (AM) enables the freeform fabrication of complex structures from various build materials. The objective of this study is to develop a novel Laponite nanoclay-enabled "printing-then-solidification" additive manufacturing approach to extrude complex three-dimensional (3D) structures made of various liquid build materials. Laponite, a member of the smectite mineral family, is investigated to serve as a yield-stress support bath material for the extrusion printing of liquid build materials. Using the printing-then-solidification approach, the printed structure remains liquid and retains its shape with the help of the Laponite support bath. Then the completed liquid structures are solidified in situ by applying suitable cross-linking mechanisms. Finally, the solidified structures are harvested from the Laponite nanoclay support bath for any further processing as needed. Due to its chemical and physical stability, liquid build materials with different solidification/curing/gelation mechanisms can be fabricated in the Laponite bath using the printing-then-solidification approach. The feasibility of the proposed Laponite-enabled printing-then-solidification approach is demonstrated by fabricating several complicated structures made of various liquid build materials, including alginate with ionic cross-linking, gelatin with thermal cross-linking, and SU-8 with photo-cross-linking. During gelatin structure printing, living cells are included and the postfabrication cell viability is above 90%.

Scale effects in crystal plasticity

NASA Astrophysics Data System (ADS)

Padubidri Janardhanachar, Guruprasad

The goal of this research work is to further the understanding of crystal plasticity, particularly at reduced structural and material length scales. Fundamental understanding of plasticity is central to various challenges facing design and manufacturing of materials for structural and electronic device applications. The development of microstructurally tailored advanced metallic materials with enhanced mechanical properties that can withstand extremes in stress, strain, and temperature, will aid in increasing the efficiency of power generating systems by allowing them to work at higher temperatures and pressures. High specific strength materials can lead to low fuel consumption in transport vehicles. Experiments have shown that enhanced mechanical properties can be obtained in materials by constraining their size, microstructure (e.g. grain size), or both for various applications. For the successful design of these materials, it is necessary to have a thorough understanding of the influence of different length scales and evolving microstructure on the overall behavior. In this study, distinction is made between the effect of structural and material length scale on the mechanical behavior of materials. A length scale associated with an underlying physical mechanism influencing the mechanical behavior can overlap with either structural length scales or material length scales. If it overlaps with structural length scales, then the material is said to be dimensionally constrained. On the other hand, if it overlaps with material length scales, for example grain size, then the material is said to be microstructurally constrained. The objectives of this research work are: (1) to investigate scale and size effects due to dimensional constraints; (2) to investigate size effects due to microstructural constraints; and (3) to develop a size dependent hardening model through coarse graining of dislocation dynamics. A discrete dislocation dynamics (DDD) framework where the scale of analysis is intermediate between a fully discretized (e.g. atomistic) and fully continuum is used for this study. This mesoscale tool allows to address all the stated objectives of this study within a single framework. Within this framework, the effect of structural and the material length scales are naturally accounted for in the simulations and need not be specified in an ad hoc manner, as in some continuum models. It holds the promise of connecting the evolution of the defect microstructure to the effective response of the crystal. Further, it provides useful information to develop physically motivated continuum models to model size effects in materials. The contributions of this study are: (a) provides a new interpretation of mechanical size effect due to only dimensional constraint using DDD; (b) a development of an experimentally validated DDD simulation methodology to model Cu micropillars; (c) a coarse graining technique using DDD to develop a phenomenological model to capture size effect on strain hardening; and (d) a development of a DDD framework for polycrystals to investigate grain size effect on yield strength and strain hardening.

Multi-stage responsive 4D printed smart structure through varying geometric thickness of shape memory polymer

NASA Astrophysics Data System (ADS)

Teoh, Joanne Ee Mei; Zhao, Yue; An, Jia; Chua, Chee Kai; Liu, Yong

2017-12-01

Shape memory polymers (SMPs) have gained a presence in additive manufacturing due to their role in 4D printing. They can be printed either in multi-materials for multi-stage shape recovery or in a single material for single-stage shape recovery. When printed in multi-materials, material or material-based design is used as a controlling factor for multi-stage shape recovery. However, when printed in a single material, it is difficult to design multi-stage shape recovery due to the lack of a controlling factor. In this research, we explore the use of geometric thickness as a controlling factor to design smart structures possessing multi-stage shape recovery using a single SMP. L-shaped hinges with a thickness ranging from 0.3-2 mm were designed and printed in four different SMPs. The effect of thickness on SMP’s response time was examined via both experiment and finite element analysis using Ansys transient thermal simulation. A method was developed to accurately measure the response time in millisecond resolution. Temperature distribution and heat transfer in specimens during thermal activation were also simulated and discussed. Finally, a spiral square and an artificial flower consisting of a single SMP were designed and printed with appropriate thickness variation for the demonstration of a controlled multi-stage shape recovery. Experimental results indicated that smart structures printed using single material with controlled thickness parameters are able to achieve controlled shape recovery characteristics similar to those printed with multiple materials and uniform geometric thickness. Hence, the geometric parameter can be used to increase the degree of freedom in designing future smart structures possessing complex shape recovery characteristics.

Evaluation of Materials and Concepts for Aircraft Fire Protection

NASA Technical Reports Server (NTRS)

Anderson, R. A.; Price, J. O.; Mcclure, A. H.; Tustin, E. A.

1976-01-01

Woven fiberglass fluted-core simulated aircraft interior panels were flame tested and structurally evaluated against the Boeing 747 present baseline interior panels. The NASA-defined panels, though inferior on a strength-to-weight basis, showed better structural integrity after flame testing, due to the woven fiberglass structure.

Negative-pressure polymorphs made by heterostructural alloying.

PubMed

Siol, Sebastian; Holder, Aaron; Steffes, James; Schelhas, Laura T; Stone, Kevin H; Garten, Lauren; Perkins, John D; Parilla, Philip A; Toney, Michael F; Huey, Bryan D; Tumas, William; Lany, Stephan; Zakutayev, Andriy

2018-04-01

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures-a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixing two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2× to 4× lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. This example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties-materials that are otherwise nearly impossible to make.

Experimental validation of 3D printed material behaviors and their influence on the structural topology design

NASA Astrophysics Data System (ADS)

Yang, Kai Ke; Zhu, Ji Hong; Wang, Chuang; Jia, Dong Sheng; Song, Long Long; Zhang, Wei Hong

2018-05-01

The purpose of this paper is to investigate the structures achieved by topology optimization and their fabrications by 3D printing considering the particular features of material microstructures and macro mechanical performances. Combining Digital Image Correlation and Optical Microscope, this paper experimentally explored the anisotropies of stiffness and strength existing in the 3D printed polymer material using Stereolithography (SLA) and titanium material using Selective Laser Melting (SLM). The standard specimens and typical structures obtained by topology optimization were fabricated along different building directions. On the one hand, the experimental results of these SLA produced structures showed stable properties and obviously anisotropic rules in stiffness, ultimate strengths and places of fractures. Further structural designs were performed using topology optimization when the particular mechanical behaviors of SLA printed materials were considered, which resulted in better structural performances compared to the optimized designs using `ideal' isotropic material model. On the other hand, this paper tested the mechanical behaviors of SLM printed multiscale lattice structures which were fabricated using the same metal powder and the same machine. The structural stiffness values are generally similar while the strength behaviors show a difference, which are mainly due to the irregular surface quality of the tiny structural branches of the lattice. The above evidences clearly show that the consideration of the particular behaviors of 3D printed materials is therefore indispensable for structural design and optimization in order to improve the structural performance and strengthen their practical significance.

Experimental validation of 3D printed material behaviors and their influence on the structural topology design

NASA Astrophysics Data System (ADS)

Yang, Kai Ke; Zhu, Ji Hong; Wang, Chuang; Jia, Dong Sheng; Song, Long Long; Zhang, Wei Hong

2018-02-01

The purpose of this paper is to investigate the structures achieved by topology optimization and their fabrications by 3D printing considering the particular features of material microstructures and macro mechanical performances. Combining Digital Image Correlation and Optical Microscope, this paper experimentally explored the anisotropies of stiffness and strength existing in the 3D printed polymer material using Stereolithography (SLA) and titanium material using Selective Laser Melting (SLM). The standard specimens and typical structures obtained by topology optimization were fabricated along different building directions. On the one hand, the experimental results of these SLA produced structures showed stable properties and obviously anisotropic rules in stiffness, ultimate strengths and places of fractures. Further structural designs were performed using topology optimization when the particular mechanical behaviors of SLA printed materials were considered, which resulted in better structural performances compared to the optimized designs using `ideal' isotropic material model. On the other hand, this paper tested the mechanical behaviors of SLM printed multiscale lattice structures which were fabricated using the same metal powder and the same machine. The structural stiffness values are generally similar while the strength behaviors show a difference, which are mainly due to the irregular surface quality of the tiny structural branches of the lattice. The above evidences clearly show that the consideration of the particular behaviors of 3D printed materials is therefore indispensable for structural design and optimization in order to improve the structural performance and strengthen their practical significance.

Low cost, SPF aluminum cryogenic tank structure for ALS

NASA Technical Reports Server (NTRS)

Anton, Claire E.; Rasmussen, Perry; Thompson, Curt; Latham, Richard; Hamilton, C. Howard; Ren, Ben; Gandhi, Chimata; Hardwick, Dallis

1992-01-01

Past production work has shown that cryogenic tank structure for the Shuttle Booster Rockets and the Titan system have very high life cycle costs for the fuel tank structure. The tanks are machined stiffener-skin combination that are subsequently formed into the required contour after machining. The material scrap rate for these configurations are usually high, and the loss of a tank panel due to forming or heat treatment problems is very costly. The idea of reducing the amount of scrap material and scrapped structural members has prompted the introduction of built-up structure for cryogenic tanks to be explored on the ALS program. A build-up structure approach that has shown improvements in life cycle cost over the conventional built-up approach is the use of superplastically formed (SPF) stiffened panels (reducing the overall part count and weight for the tank) resistance spot welded (RSW) to outer tank skin material. The stiffeners provide for general stability of the tank, while the skin material provides hoop direction continuity for the loads.

Discrete Model for the Structure and Strength of Cementitious Materials

NASA Astrophysics Data System (ADS)

Balopoulos, Victor D.; Archontas, Nikolaos; Pantazopoulou, Stavroula J.

2017-12-01

Cementitious materials are characterized by brittle behavior in direct tension and by transverse dilatation (due to microcracking) under compression. Microcracking causes increasingly larger transverse strains and a phenomenological Poisson's ratio that gradually increases to about ν =0.5 and beyond, at the limit point in compression. This behavior is due to the underlying structure of cementitious pastes which is simulated here with a discrete physical model. The computational model is generic, assembled from a statistically generated, continuous network of flaky dendrites consisting of cement hydrates that emanate from partially hydrated cement grains. In the actual amorphous material, the dendrites constitute the solid phase of the cement gel and interconnect to provide the strength and stiffness against load. The idealized dendrite solid is loaded in compression and tension to compute values for strength and Poisson's effects. Parametric studies are conducted, to calibrate the statistical parameters of the discrete model with the physical and mechanical characteristics of the material, so that the familiar experimental trends may be reproduced. The model provides a framework for the study of the mechanical behavior of the material under various states of stress and strain and can be used to model the effects of additives (e.g., fibers) that may be explicitly simulated in the discrete structure.

Bio-inspired active materials

NASA Astrophysics Data System (ADS)

Fratzl, Peter

Biological tissues are naturally interactive and adaptive. In general, these features are due to the action of cells that provide sensing, actuation as well as tissue remodelling. There are also examples of materials synthesized by living organisms, such as plant seeds, which fulfil an active function without living cells working as mechanosensors and actuators. Thus the activity of these materials is based on physical principles alone, which provides inspiration for new concepts for artificial active materials. We will describe structural principles leading to movement in seed capsules triggered by ambient humidity and discuss the influence of internal architecture on the overall mechanical behaviour of materials, including actuation and motility. Several conceptual systems for actuating planar structures will be discussed.

Statistical Physics of Rupture in Heterogeneous Media

NASA Astrophysics Data System (ADS)

Sornette, Didier

The damage and fracture of materials are technologically of enormous interest due to their economic and human cost. They cover a wide range of phenomena like cracking of glass, aging of concrete, the failure of fiber networks in the formation of paper and the breaking of a metal bar subject to an external load. Failure of composite systems is of utmost importance in naval, aeronautics and space industry [1]. By the term composite, we refer to materials with heterogeneous microscopic structures and also to assemblages of macroscopic elements forming a super-structure. Chemical and nuclear plants suffer from cracking due to corrosion either of chemical or radioactive origin, aided by thermal and/or mechanical stress.

The Optical Janus Effect: Asymmetric Structural Color Reflection Materials.

PubMed

England, Grant T; Russell, Calvin; Shirman, Elijah; Kay, Theresa; Vogel, Nicolas; Aizenberg, Joanna

2017-08-01

Structurally colored materials are often used for their resistance to photobleaching and their complex viewing-direction-dependent optical properties. Frequently, absorption has been added to these types of materials in order to improve the color saturation by mitigating the effects of nonspecific scattering that is present in most samples due to imperfect manufacturing procedures. The combination of absorbing elements and structural coloration often yields emergent optical properties. Here, a new hybrid architecture is introduced that leads to an interesting, highly directional optical effect. By localizing absorption in a thin layer within a transparent, structurally colored multilayer material, an optical Janus effect is created, wherein the observed reflected color is different on one side of the sample than on the other. A systematic characterization of the optical properties of these structures as a function of their geometry and composition is performed. The experimental studies are coupled with a theoretical analysis that enables a precise, rational design of various optical Janus structures with highly controlled color, pattern, and fabrication approaches. These asymmetrically colored materials will open applications in art, architecture, semitransparent solar cells, and security features in anticounterfeiting materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlling the electronic and geometric structures of 2D insertions to realize high performance metal/insertion-MoS2 sandwich interfaces.

PubMed

Su, Jie; Feng, Liping; Zeng, Wei; Liu, Zhengtang

2017-06-08

Metal/insertion-MoS 2 sandwich interfaces are designed to reduce the Schottky barriers at metal-MoS 2 interfaces. The effects of geometric and electronic structures of two-dimensional (2D) insertion materials on the contact properties of metal/insertion-MoS 2 interfaces are comparatively studied by first-principles calculations. Regardless of the geometric and electronic structures of 2D insertion materials, Fermi level pinning effects and charge scattering at the metal/insertion-MoS 2 interface are weakened due to weak interactions between the insertion and MoS 2 layers, no gap states and negligible structural deformations for MoS 2 layers. The Schottky barriers at metal/insertion-MoS 2 interfaces are induced by three interface dipoles and four potential steps that are determined by the charge transfers and structural deformations of 2D insertion materials. The lower the electron affinities of 2D insertion materials, the more are the electrons lost from the Sc surface, resulting in lower n-type Schottky barriers at Sc/insertion-MoS 2 interfaces. The larger the ionization potentials and the thinner the thicknesses of 2D insertion materials, the fewer are the electrons that accumulate at the Pt surface, leading to lower p-type Schottky barriers at Pt/insertion-MoS 2 interfaces. All Sc/insertion-MoS 2 interfaces exhibited ohmic characters. The Pt/BN-MoS 2 interface exhibits the lowest p-type Schottky barrier of 0.52 eV due to the largest ionization potential (∼6.88 eV) and the thinnest thickness (single atomic layer thickness) of BN. These results in this work are beneficial to understand and design high performance metal/insertion-MoS 2 interfaces through 2D insertion materials.

Transverse isotropic modeling of the ballistic response of glass reinforced plastic composites

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

Taylor, P.A.

1997-12-31

The use of glass reinforced plastic (GRP) composites is gaining significant attention in the DoD community for use in armor applications. These materials typically possess a laminate structure consisting of up to 100 plies, each of which is constructed of a glass woven roving fabric that reinforces a plastic matrix material. Current DoD attention is focused on a high strength, S-2 glass cross-weave (0/90) fabric reinforcing a polyester matrix material that forms each ply of laminate structure consisting anywhere from 20 to 70 plies. The resulting structure displays a material anisotropy that is, to a reasonable approximation, transversely isotropic. Whenmore » subjected to impact and penetration from a metal fragment projectile, the GRP displays damage and failure in an anisotropic manner due to various mechanisms such as matrix cracking, fiber fracture and pull-out, and fiber-matrix debonding. In this presentation, the author will describe the modeling effort to simulate the ballistic response of the GRP material described above using the transversely isotropic (TI) constitutive model which has been implemented in the shock physics code, CTH. The results of this effort suggest that the model is able to describe the delamination behavior of the material but has some difficulty capturing the in-plane (i.e., transverse) response of the laminate due to its cross-weave fabric reinforcement pattern which causes a departure from transverse isotropy.« less

Decoration of wide bandgap semiconducting materials for enhancing photoelectrochemical efficiency of PEC systems.

NASA Astrophysics Data System (ADS)

Bakranov, N.; Zhabaikhanov, A.; Kudaibergenov, S.; Ibraev, N.

2018-03-01

The production of photoanodes based on wide-band gap materials such as TiO2 is economically viable because of the low cost of synthesis methods. Contrary to economic aspects, wide-band gap semiconductor materials have a significant disadvantage due to low sensitivity to photons of visible light. To increase the photoactive parameters of the material of the electrodes in the visible range, the methods for decorating nanomasses of titanium dioxide by narrow-gap semiconductors are used. One of the most suitable narrow-gap semiconductor materials are CdS and Fe2O3. Controlled deposition of such materials on wide-gap semiconductors allows to regulate both the diffusion time of charge carriers and the band structure of TiO2/Fe2O3 and TiO2/CdS composites. The dimensions of the structure of the photoelectrode material of the cell have a large influence on the characteristics of the photocatalyst created. Thus, in the hematite structures of nanometre dimension, the rate of recombination of charge carriers fades away in comparison with bulk structures. Reducing the size of CdS structures also positively affects the nature of the photocatalytic reaction.

Experimental determination of material damping using vibration analyzer

NASA Technical Reports Server (NTRS)

Chowdhury, Mostafiz R.; Chowdhury, Farida

1990-01-01

Structural damping is an important dynamic characteristic of engineering materials that helps to damp vibrations by reducing their amplitudes. In this investigation, an experimental method is illustrated to determine the damping characteristics of engineering materials using a dual channel Fast Fourier Transform (FFT) analyzer. A portable Compaq III computer which houses the analyzer, is used to collect the dynamic responses of three metal rods. Time-domain information is analyzed to obtain the logarithmic decrement of their damping. The damping coefficients are then compared to determine the variation of damping from material to material. The variations of damping from one point to another of the same material, due to a fixed point excitation, and the variable damping at a fixed point due to excitation at different points, are also demonstrated.

Synthesis of One-Dimensional and Hyperbranched Nanomaterials for Lithium-Ion Battery Solid Electrolytes

NASA Astrophysics Data System (ADS)

Yang, Ting

Lithium-ion batteries can fail and catch fire when overcharged, exposed to high temperatures or short-circuited due to the highly flammable organic liquid used in the electrolyte. Using inorganic solid electrolyte materials can potentially improve the safety factor. Additionally, nanostructured electrolyte materials may further enhanced performance by taking advantage of their large aspect ratio. In this work, the synthesis of two promising nanostructured solid electrolyte materials was explored. Amorphous lithium niobate nanowires were synthesized through the decomposition of a niobium-containing complex in a structure-directing solvent using a reflux method. Lithium lanthanum titanate was obtained via solid state reaction with titanium oxide nanowires as the titanium precursor, but the nanowire morphology could not be preserved due to high temperature sintering. Hyperbranched potassium lanthanum titanate was synthesized through hydrothermal route. This was the first time that hyperbranched nanowires with perovskite structure were made without any catalyst or substrate. This result has the potential to be applied to other perovskite materials.

Porous graphene materials for water remediation.

PubMed

Niu, Zhiqiang; Liu, Lili; Zhang, Li; Chen, Xiaodong

2014-09-10

Water remediation has been a critical issue over the past decades due to the expansion of wastewater discharge to the environment. Currently, a variety of functional materials have been successfully prepared for water remediation applications. Among them, graphene is an attractive candidate due to its high specific surface area, tunable surface behavior, and high strength. This Concept paper summarizes the design strategy of porous graphene materials and their applications in water remediation, such as the cleanup of oil, removal of heavy metal ions, and elimination of water soluble organic contaminants. The progress made so far will guide further development in structure design strategy of porous materials based on graphene and exploration of such materials in environmental remediation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improving material identification by combining x-ray and neutron tomography

NASA Astrophysics Data System (ADS)

LaManna, Jacob M.; Hussey, Daniel S.; Baltic, Eli; Jacobson, David L.

2017-09-01

X-rays and neutrons provide complementary non-destructive probes for the analysis of structure and chemical composition of materials. Contrast differences between the modes arise due to the differences in interaction with matter. Due to the high sensitivity to hydrogen, neutrons excel at separating liquid water or hydrogenous phases from the underlying structure while X-rays resolve the solid structure. Many samples of interest, such as fluid flow in porous materials or curing concrete, are stochastic or slowly changing with time which makes analysis of sequential imaging with X-rays and neutrons difficult as the sample may change between scans. To alleviate this issue, NIST has developed a system for simultaneous X-ray and neutron tomography by orienting a 90 keVpeak micro-focus X-ray tube orthogonally to a thermal neutron beam. This system allows for non-destructive, multimodal tomography of dynamic or stochastic samples while penetrating through sample environment equipment such as pressure and flow vessels. Current efforts are underway to develop methods for 2D histogram based segmentation of reconstructed volumes. By leveraging the contrast differences between X-rays and neutrons, greater histogram peak separation can occur in 2D vs 1D enabling improved material identification.

Promising Thermoelectric Bulk Materials with 2D Structures.

PubMed

Zhou, Yiming; Zhao, Li-Dong

2017-12-01

Given that more than two thirds of all energy is lost, mostly as waste heat, in utilization processes worldwide, thermoelectric materials, which can directly convert waste heat to electricity, provide an alternative option for optimizing energy utilization processes. After the prediction that superlattices may show high thermoelectric performance, various methods based on quantum effects and superlattice theory have been adopted to analyze bulk materials, leading to the rapid development of thermoelectric materials. Bulk materials with two-dimensional (2D) structures show outstanding properties, and their high performance originates from both their low thermal conductivity and high Seebeck coefficient due to their strong anisotropic features. Here, the advantages of superlattices for enhancing the thermoelectric performance, the transport mechanism in bulk materials with 2D structures, and optimization methods are discussed. The phenomenological transport mechanism in these materials indicates that thermal conductivities are reduced in 2D materials with intrinsically short mean free paths. Recent progress in the transport mechanisms of Bi 2 Te 3 -, SnSe-, and BiCuSeO-based systems is summarized. Finally, possible research directions to enhance the thermoelectric performance of bulk materials with 2D structures are briefly considered. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Ga substitution on the structural and magnetic properties of half metallic Fe2MnSi Heusler compound

NASA Astrophysics Data System (ADS)

Pedro, S. S.; Caraballo Vivas, R. J.; Andrade, V. M.; Cruz, C.; Paixão, L. S.; Contreras, C.; Costa-Soares, T.; Caldeira, L.; Coelho, A. A.; Carvalho, A. Magnus G.; Rocco, D. L.; Reis, M. S.

2015-01-01

The so-called half-metallic magnets have been proposed as good candidates for spintronic applications due to the feature of exhibiting a hundred percent spin polarization at the Fermi level. Such materials follow the Slater-Pauling rule, which relates the magnetic moment with the valence electrons in the system. In this paper, we study the bulk polycrystalline half-metallic Fe2MnSi Heusler compound replacing Si by Ga to determine how the Ga addition changes the magnetic, the structural, and the half-metal properties of this compound. The material does not follow the Slater-Pauling rule, probably due to a minor structural disorder degree in the system, but a linear dependence on the magnetic transition temperature with the valence electron number points to the half-metallic behavior of this compound.

Theoretical backgrounds of non-tempered materials production based on new raw materials

NASA Astrophysics Data System (ADS)

Lesovik, V. S.; Volodchenko, A. A.; Glagolev, E. S.; Chernysheva, N. V.; Lashina, I. V.; Feduk, R. S.

2018-03-01

One of the trends in construction material science is development and implementation of highly effective finish materials which improve architectural exterior of cities. Silicate materials widely-used in the construction today have rather low decorative properties. Different coloring agents are used in order to produce competitive materials, but due to the peculiarities of the production, process very strict specifications are applied to them. The use of industrial wastes or variety of rock materials as coloring agents is of great interest nowadays. The article shows that clay rock can be used as raw material in production of finish materials of non-autoclaved solidification. This raw material due to its material composition actively interacts with cementing component in steam treatment at 90–95 °C with formation of cementing joints that form a firm coagulative-cristalized and crystallization structure of material providing high physic-mechanical properties of silicate goods. It is determined that energy-saving, colored finish materials with compression strength up to 16 MPa can be produced from clay rocks.

High renewable content sandwich structures based on flax-basalt hybrids and biobased epoxy polymers

NASA Astrophysics Data System (ADS)

Colomina, S.; Boronat, T.; Fenollar, O.; Sánchez-Nacher, L.; Balart, R.

2014-05-01

In the last years, a growing interest in the development of high environmental efficiency materials has been detected and this situation is more accentuated in the field of polymers and polymer composites. In this work, green composite sandwich structures with high renewable content have been developed with core cork materials. The base resin for composites was a biobased epoxy resin derived from epoxidized vegetable oils. Hybrid basalt-flax fabrics have been used as reinforcements for composites and the influence of the stacking sequence has been evaluated in order to optimize the appropriate laminate structure for the sandwich bases. Core cork materials with different thickness have been used to evaluate performance of sandwich structures thus leading to high renewable content composite sandwich structures. Results show that position of basalt fabrics plays a key role in flexural fracture of sandwich structures due to differences in stiffness between flax and basalt fibers.

Electrochemical and kinetic studies of ultrafast laser structured LiFePO4 electrodes

NASA Astrophysics Data System (ADS)

Mangang, M.; Gotcu-Freis, P.; Seifert, H. J.; Pfleging, W.

2015-03-01

Due to a growing demand of cost-efficient lithium-ion batteries with an increased energy and power density as well as an increased life-time, the focus is set on intercalation cathode materials like LiFePO4. It has a high practical capacity, is environmentally friendly and has low material costs. However, its low electrical conductivity and low ionic diffusivity are major drawbacks for its use in electrochemical storage devices or electric vehicles. By adding conductive agents, the electrical conductivity can be enhanced. By increasing the surface of the cathode material which is in direct contact with the liquid electrolyte the lithium-ion diffusion kinetics can be improved. A new approach to increase the surface of the active material without changing the active particle packing density or the weight proportion of carbon black is the laser-assisted generation of 3D surface structures in electrode materials. In this work, ultrafast laser radiation was used to create a defined surface structure in LiFePO4 electrodes. It was shown that by using ultrashort laser pulses instead of nanosecond laser pulses, the ablation efficiency could be significantly increased. Furthermore, melting and debris formation were reduced. To investigate the diffusion kinetics, electrochemical methods such as cyclic voltammetry and galvanostatic intermittent titration technique were applied. It could be shown that due to a laser generated 3D structure, the lithium-ion diffusion kinetic, the capacity retention and cell life-time can be significantly improved.

A Fundamental Study of Inorganic Clathrate and Other Open-Framework Materials

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

Nolas, George

Due to formidable synthetic challenges, many materials of scientific and technological interest are first obtained as microcrystalline powders. High purity, high yield processing techniques are often lacking and thus care must be taken in interpretation of the observed structural, chemical, and physical properties of powder or polycrystalline materials, which can be strongly influenced by extrinsic properties. Furthermore, the preparation of high-quality single crystals for many materials by traditional techniques can be especially challenging in cases where the elemental constituents have greatly differing melting points and/or vapor pressures, when the desired compound is thermodynamically metastable, or where growth with participation ofmore » the melt is generally not possible. New processing techniques are therefore imperative in order to investigate the intrinsic properties of these materials and elucidate their fundamental physical properties. Intermetallic clathrates constitute one such class of materials. The complex crystal structures of intermetallic clathrates are characterized by mainly group 14 host frameworks encapsulating guest-ions in polyhedral cages. The unique features of clathrate structures are intimately related to their physical properties, offering ideal systems for the study of structure-property relationships in crystalline solids. Moreover, intermetallic clathrates are being actively investigated due to their potential for application in thermoelectrics, photovoltaics and opto-electronics, superconductivity, and magnetocaloric technologies. We have developed different processing techniques in order to synthesize phase-pure high yield clathrates reproducibly, as well as grow single crystals for the first time. We also employed these techniques to synthesize new “open-framework” compounds. These advances in materials processing and crystal growth allowed for the investigation of the physical properties of a variety of different clathrate compositions for the first time.« less

TRANSFORMATION OF DEVELOPMENTAL NEUROTOXICITY DATA INTO STRUCTURE-SEARCHABLE TOXML DATABASE IN SUPPORT OF STRUCTURE-ACTIVITY RELATIONSHIP (SAR) WORKFLOW.

EPA Science Inventory

Early hazard identification of new chemicals is often difficult due to lack of data on the novel material for toxicity endpoints, including neurotoxicity. At present, there are no structure searchable neurotoxicity databases. A working group was formed to construct a database to...

Structural hierarchies define toughness and defect-tolerance despite simple and mechanically inferior brittle building blocks

NASA Astrophysics Data System (ADS)

Sen, Dipanjan; Buehler, Markus J.

2011-07-01

Mineralized biological materials such as bone, sea sponges or diatoms provide load-bearing and armor functions and universally feature structural hierarchies from nano to macro. Here we report a systematic investigation of the effect of hierarchical structures on toughness and defect-tolerance based on a single and mechanically inferior brittle base material, silica, using a bottom-up approach rooted in atomistic modeling. Our analysis reveals drastic changes in the material crack-propagation resistance (R-curve) solely due to the introduction of hierarchical structures that also result in a vastly increased toughness and defect-tolerance, enabling stable crack propagation over an extensive range of crack sizes. Over a range of up to four hierarchy levels, we find an exponential increase in the defect-tolerance approaching hundred micrometers without introducing additional mechanisms or materials. This presents a significant departure from the defect-tolerance of the base material, silica, which is brittle and highly sensitive even to extremely small nanometer-scale defects.

Human Brain Modeling with Its Anatomical Structure and Realistic Material Properties for Brain Injury Prediction.

PubMed

Atsumi, Noritoshi; Nakahira, Yuko; Tanaka, Eiichi; Iwamoto, Masami

2018-05-01

Impairments of executive brain function after traumatic brain injury (TBI) due to head impacts in traffic accidents need to be obviated. Finite element (FE) analyses with a human brain model facilitate understanding of the TBI mechanisms. However, conventional brain FE models do not suitably describe the anatomical structure in the deep brain, which is a critical region for executive brain function, and the material properties of brain parenchyma. In this study, for better TBI prediction, a novel brain FE model with anatomical structure in the deep brain was developed. The developed model comprises a constitutive model of brain parenchyma considering anisotropy and strain rate dependency. Validation was performed against postmortem human subject test data associated with brain deformation during head impact. Brain injury analyses were performed using head acceleration curves obtained from reconstruction analysis of rear-end collision with a human whole-body FE model. The difference in structure was found to affect the regions of strain concentration, while the difference in material model contributed to the peak strain value. The injury prediction result by the proposed model was consistent with the characteristics in the neuroimaging data of TBI patients due to traffic accidents.

Temperature and saturation dependence in the vapor sensing of butterfly wing scales.

PubMed

Kertész, K; Piszter, G; Jakab, E; Bálint, Zs; Vértesy, Z; Biró, L P

2014-06-01

The sensing of gasses/vapors in the ambient air is the focus of attention due to the need to monitor our everyday environment. Photonic crystals are sensing materials of the future because of their strong light-manipulating properties. Natural photonic structures are well-suited materials for testing detection principles because they are significantly cheaper than artificial photonic structures and are available in larger sizes. Additionally, natural photonic structures may provide new ideas for developing novel artificial photonic nanoarchitectures with improved properties. In the present paper, we discuss the effects arising from the sensor temperature and the vapor concentration in air during measurements with a photonic crystal-type optical gas sensor. Our results shed light on the sources of discrepancy between simulated and experimental sensing behaviors of photonic crystal-type structures. Through capillary condensation, the vapors will condensate to a liquid state inside the nanocavities. Due to the temperature and radius of curvature dependence of capillary condensation, the measured signals are affected by the sensor temperature as well as by the presence of a nanocavity size distribution. The sensing materials used are natural photonic nanoarchitectures present in the wing scales of blue butterflies. Copyright © 2014 Elsevier B.V. All rights reserved.

Metal-Organic Framework-Derived Materials for Sodium Energy Storage.

PubMed

Zou, Guoqiang; Hou, Hongshuai; Ge, Peng; Huang, Zhaodong; Zhao, Ganggang; Yin, Dulin; Ji, Xiaobo

2018-01-01

Recently, sodium-ion batteries (SIBs) are extensively explored and are regarded as one of the most promising alternatives to lithium-ion batteries for electrochemical energy conversion and storage, owing to the abundant raw material resources, low cost, and similar electrochemical behavior of elemental sodium compared to lithium. Metal-organic frameworks (MOFs) have attracted enormous attention due to their high surface areas, tunable structures, and diverse applications in drug delivery, gas storage, and catalysis. Recently, there has been an escalating interest in exploiting MOF-derived materials as anodes for sodium energy storage due to their fast mass transport resulting from their highly porous structures and relatively simple preparation methods originating from in situ thermal treatment processes. In this Review, the recent progress of the sodium-ion storage performances of MOF-derived materials, including MOF-derived porous carbons, metal oxides, metal oxide/carbon nanocomposites, and other materials (e.g., metal phosphides, metal sulfides, and metal selenides), as SIB anodes is systematically and completely presented and discussed. Moreover, the current challenges and perspectives of MOF-derived materials in electrochemical energy storage are discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

First-principles design of nanostructured hybrid photovoltaics based on layered transition metal phosphates

DOE PAGES

Lentz, Levi C.; Kolpak, Alexie M.

2017-04-28

The performance of bulk organic and hybrid organic-inorganic heterojunction photovoltaics is often limited by high carrier recombination arising from strongly bound excitons and low carrier mobility. Structuring materials to minimize the length scales required for exciton separation and carrier collection is therefore a promising approach for improving efficiency. In this work, first-principles computations are employed to design and characterize a new class of photovoltaic materials composed of layered transition metal phosphates (TMPs) covalently bound to organic absorber molecules to form nanostructured superlattices. Using a combination of transition metal substitution and organic functionalization, the electronic structure of these materials is systematicallymore » tuned to design a new hybrid photovoltaic material predicted to exhibit very low recombination due to the presence of a local electric field and spatially isolated, high mobility, two-dimensional electron and hole conducting channels. Furthermore, this material is predicted to have a large open-circuit voltage of 1.7 V. Here, this work suggests that hybrid TMPs constitute an interesting class of materials for further investigation in the search for achieving high efficiency, high power, and low cost photo Zirconium phosphate was chosen, in part, due to previous experiment voltaics.« less

First-principles design of nanostructured hybrid photovoltaics based on layered transition metal phosphates

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

Lentz, Levi C.; Kolpak, Alexie M.

The performance of bulk organic and hybrid organic-inorganic heterojunction photovoltaics is often limited by high carrier recombination arising from strongly bound excitons and low carrier mobility. Structuring materials to minimize the length scales required for exciton separation and carrier collection is therefore a promising approach for improving efficiency. In this work, first-principles computations are employed to design and characterize a new class of photovoltaic materials composed of layered transition metal phosphates (TMPs) covalently bound to organic absorber molecules to form nanostructured superlattices. Using a combination of transition metal substitution and organic functionalization, the electronic structure of these materials is systematicallymore » tuned to design a new hybrid photovoltaic material predicted to exhibit very low recombination due to the presence of a local electric field and spatially isolated, high mobility, two-dimensional electron and hole conducting channels. Furthermore, this material is predicted to have a large open-circuit voltage of 1.7 V. Here, this work suggests that hybrid TMPs constitute an interesting class of materials for further investigation in the search for achieving high efficiency, high power, and low cost photo Zirconium phosphate was chosen, in part, due to previous experiment voltaics.« less

Graphite/Ultra-High Modulus Polyethylene Hybrid Fiber Composites with Epoxy and Polyethylene Matrices for Cosmic Radiation Shielding

NASA Technical Reports Server (NTRS)

2003-01-01

One of the most significant technical challenges in long-duration space missions is that of protecting the crew from harmful radiation. Protection against such radiation on a manned Mars mission will be of vital importance both during transit and while on the surface of the planet. The development of multifunctional materials that serve as integral structural members of the space vehicle and provide the necessary radiation shielding for the crew would be both mission enabling and cost effective. Additionally, combining shielding and structure could reduce total vehicle mass. Hybrid laminated composite materials having both ultramodulus polyethylene (PE) and graphite fibers in epoxy and PE matrices could meet such mission requirements. PE fibers have excellent physical properties, including the highest specific strength of any known fiber. Moreover, the high hydrogen (H) content of polyethylene makes the material an excellent shielding material for cosmic radiation. When such materials are incorporated into an epoxy or PE matrix a very effective shielding material is expected. Boron (B) may be added to the matrix resin or used as a coating to further increase the shielding effectiveness due to B s ability to slow thermal neutrons. These materials may also serve as micrometeorites shields due to PE s high impact energy absorption properties. It should be noted that such materials can be fabricated by existing equipment and methods. It is the objective of this work therefore to: (a) perform preliminary analysis of the radiation transport within these materials; (b) fabricate panels for mechanical property testing before and after radiation exposure. Preliminary determination on the effectiveness of the combinations of material components on both shielding and structural efficiency will be made.

Explicit parametric solutions of lattice structures with proper generalized decomposition (PGD) - Applications to the design of 3D-printed architectured materials

NASA Astrophysics Data System (ADS)

Sibileau, Alberto; Auricchio, Ferdinando; Morganti, Simone; Díez, Pedro

2018-01-01

Architectured materials (or metamaterials) are constituted by a unit-cell with a complex structural design repeated periodically forming a bulk material with emergent mechanical properties. One may obtain specific macro-scale (or bulk) properties in the resulting architectured material by properly designing the unit-cell. Typically, this is stated as an optimal design problem in which the parameters describing the shape and mechanical properties of the unit-cell are selected in order to produce the desired bulk characteristics. This is especially pertinent due to the ease manufacturing of these complex structures with 3D printers. The proper generalized decomposition provides explicit parametic solutions of parametric PDEs. Here, the same ideas are used to obtain parametric solutions of the algebraic equations arising from lattice structural models. Once the explicit parametric solution is available, the optimal design problem is a simple post-process. The same strategy is applied in the numerical illustrations, first to a unit-cell (and then homogenized with periodicity conditions), and in a second phase to the complete structure of a lattice material specimen.

Shape optimization of solid-air porous phononic crystal slabs with widest full 3D bandgap for in-plane acoustic waves

NASA Astrophysics Data System (ADS)

D'Alessandro, Luca; Bahr, Bichoy; Daniel, Luca; Weinstein, Dana; Ardito, Raffaele

2017-09-01

The use of Phononic Crystals (PnCs) as smart materials in structures and microstructures is growing due to their tunable dynamical properties and to the wide range of possible applications. PnCs are periodic structures that exhibit elastic wave scattering for a certain band of frequencies (called bandgap), depending on the geometric and material properties of the fundamental unit cell of the crystal. PnCs slabs can be represented by plane-extruded structures composed of a single material with periodic perforations. Such a configuration is very interesting, especially in Micro Electro-Mechanical Systems industry, due to the easy fabrication procedure. A lot of topologies can be found in the literature for PnCs with square-symmetric unit cell that exhibit complete 2D bandgaps; however, due to the application demand, it is desirable to find the best topologies in order to guarantee full bandgaps referred to in-plane wave propagation in the complete 3D structure. In this work, by means of a novel and fast implementation of the Bidirectional Evolutionary Structural Optimization technique, shape optimization is conducted on the hole shape obtaining several topologies, also with non-square-symmetric unit cell, endowed with complete 3D full bandgaps for in-plane waves. Model order reduction technique is adopted to reduce the computational time in the wave dispersion analysis. The 3D features of the PnC unit cell endowed with the widest full bandgap are then completely analyzed, paying attention to engineering design issues.

Noncontact power/interrogation system for smart structures

NASA Astrophysics Data System (ADS)

Spillman, William B., Jr.; Durkee, S.

1994-05-01

The field of smart structures has been largely driven by the development of new high performance designed materials. Use of these materials has been generally limited due to the fact that they have not been in use long enough for statistical data bases to be developed on their failure modes. Real time health monitoring is therefore required for the benefits of structures using these materials to be realized. In this paper a non-contact method of powering and interrogating embedded electronic and opto-electronic systems is described. The technique utilizes inductive coupling between external and embedded coils etched on thin electronic circuit cards. The technique can be utilized to interrogate embedded sensors and to provide > 250 mW for embedded electronics. The system has been successfully demonstrated with a number of composite and plastic materials through material thicknesses up to 1 cm. An analytical description of the system is provided along with experimental results.

Density functional theory study of phase stability and defect thermodynamics in iron-oxyhydroxide mineral materials

NASA Astrophysics Data System (ADS)

Pinney, Nathan Douglas

Due to their high surface area and reactivity toward a variety of heavy metal and oxyanion species of environmental concern, Fe-(oxyhydr)oxide materials play an important role in the geochemical fate of natural and anthropogenic contaminants in soils, aquifers and surface water environments worldwide. In this research, ab initio simulations describe the bulk structure, magnetic properties, and relative phase stability of major Fe-(oxyhydr)oxide materials, including hematite, goethite, lepidocrocite, and ferrihydrite.These bulk models are employed in further studies of point defect and alloy/dopant thermodynamics in these materials, allowing construction of a phase stability model that better replicates the structure and composition of real materials. Li + adsorption at the predominant goethite (101) surface is simulated using ab initio methods, offering energetic and structural insight into the binding mechanisms of metal cations over a range of surface protonation conditions.

Organic-Inorganic Hybrid Materials: Multi-Functional Solids for Multi-Step Reaction Processes.

PubMed

Díaz, Urbano; Corma, Avelino

2018-03-15

The design of new hybrid materials with tailored properties at the nano-, meso-, and macro-scale, with the use of structural functional nanobuilding units, is carried out to obtain specific multi-functional materials. Organization into controlled 1D, 2D, and 3D architectures with selected functionalities is key for developing advanced catalysts, but this is hardly accomplished using conventional synthesis procedures. The use of pre-formed nanostructures, derived either from known materials or made with specific innovative synthetic methodologies, has enormous potential in the generation of multi-site catalytic materials for one-pot processes. The present concept article introduces a new archetype wherein self-assembled nanostructured builder units are the base for the design of multifunctional catalysts, which combine catalytic efficiency with fast reactant and product diffusion. The article addresses a new generation of versatile hybrid organic-inorganic multi-site catalytic materials for their use in the production of (chiral) high-added-value products within the scope of chemicals and fine chemicals production. The use of those multi-reactive solids for more nanotechnological applications, such as sensors, due to the inclusion of electron donor-acceptor structural arrays is also considered, together with the adsorption-desorption capacities due to the combination of hydrophobic and hydrophilic sub-domains. The innovative structured hybrid materials for multipurpose processes here considered, can allow the development of multi-stage one-pot reactions with industrial applications, using the materials as one nanoreactor systems, favoring more sustainable production pathways with economic, environmental and energetic advantages. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neural network approach for characterizing structural transformations by X-ray absorption fine structure

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

Timoshenko, Janis; Frenkel, Anatoly I.; Cintins, Arturs

The knowledge of coordination environment around various atomic species in many functional materials provides a key for explaining their properties and working mechanisms. Many structural motifs and their transformations are difficult to detect and quantify in the process of work (operando conditions), due to their local nature, small changes, low dimensionality of the material, and/or extreme conditions. Here we use artificial neural network approach to extract the information on the local structure and its in-situ changes directly from the X-ray absorption fine structure spectra. We illustrate this capability by extracting the radial distribution function (RDF) of atoms in ferritic andmore » austenitic phases of bulk iron across the temperature-induced transition. Integration of RDFs allows us to quantify the changes in the iron coordination and material density, and to observe the transition from body-centered to face-centered cubic arrangement of iron atoms. Furthermore, this method is attractive for a broad range of materials and experimental conditions« less

Neural network approach for characterizing structural transformations by X-ray absorption fine structure

DOE PAGES

Timoshenko, Janis; Frenkel, Anatoly I.; Cintins, Arturs; ...

2018-05-25

The knowledge of coordination environment around various atomic species in many functional materials provides a key for explaining their properties and working mechanisms. Many structural motifs and their transformations are difficult to detect and quantify in the process of work (operando conditions), due to their local nature, small changes, low dimensionality of the material, and/or extreme conditions. Here we use artificial neural network approach to extract the information on the local structure and its in-situ changes directly from the X-ray absorption fine structure spectra. We illustrate this capability by extracting the radial distribution function (RDF) of atoms in ferritic andmore » austenitic phases of bulk iron across the temperature-induced transition. Integration of RDFs allows us to quantify the changes in the iron coordination and material density, and to observe the transition from body-centered to face-centered cubic arrangement of iron atoms. Furthermore, this method is attractive for a broad range of materials and experimental conditions« less

Neural Network Approach for Characterizing Structural Transformations by X-Ray Absorption Fine Structure Spectroscopy

NASA Astrophysics Data System (ADS)

Timoshenko, Janis; Anspoks, Andris; Cintins, Arturs; Kuzmin, Alexei; Purans, Juris; Frenkel, Anatoly I.

2018-06-01

The knowledge of the coordination environment around various atomic species in many functional materials provides a key for explaining their properties and working mechanisms. Many structural motifs and their transformations are difficult to detect and quantify in the process of work (operando conditions), due to their local nature, small changes, low dimensionality of the material, and/or extreme conditions. Here we use an artificial neural network approach to extract the information on the local structure and its in situ changes directly from the x-ray absorption fine structure spectra. We illustrate this capability by extracting the radial distribution function (RDF) of atoms in ferritic and austenitic phases of bulk iron across the temperature-induced transition. Integration of RDFs allows us to quantify the changes in the iron coordination and material density, and to observe the transition from a body-centered to a face-centered cubic arrangement of iron atoms. This method is attractive for a broad range of materials and experimental conditions.

Continuous and embedded solutions for SHM of concrete structures using changing electrical potential in self-sensing cement-based composites

NASA Astrophysics Data System (ADS)

Downey, Austin; Garcia-Macias, Enrique; D'Alessandro, Antonella; Laflamme, Simon; Castro-Triguero, Rafael; Ubertini, Filippo

2017-04-01

Interest in the concept of self-sensing structural materials has grown in recent years due to its potential to enable continuous low-cost monitoring of next-generation smart-structures. The development of cement-based smart sensors appears particularly well suited for monitoring applications due to their numerous possible field applications, their ease of use and long-term stability. Additionally, cement-based sensors offer a unique opportunity for structural health monitoring of civil structures because of their compatibility with new or existing infrastructure. Particularly, the addition of conductive carbon nanofillers into a cementitious matrix provides a self-sensing structural material with piezoresistive characteristics sensitive to deformations. The strain-sensing ability is achieved by correlating the external loads with the variation of specific electrical parameters, such as the electrical resistance or impedance. Selection of the correct electrical parameter for measurement to correlate with features of interest is required for the condition assessment task. In this paper, we investigate the potential of using altering electrical potential in cement-based materials doped with carbon nanotubes to measure strain and detect damage in concrete structures. Experimental validation is conducted on small-scale specimens including a steel-reinforced beam of conductive cement paste. Comparisons are made with constant electrical potential and current methods commonly found in the literature. Experimental results demonstrate the ability of the changing electrical potential at detecting features important for assessing the condition of a structure.

Impact of graphene-based nanomaterials (GBNMs) on the structural and functional conformations of hepcidin peptide

NASA Astrophysics Data System (ADS)

Singh, Krishna P.; Baweja, Lokesh; Wolkenhauer, Olaf; Rahman, Qamar; Gupta, Shailendra K.

2018-03-01

Graphene-based nanomaterials (GBNMs) are widely used in various industrial and biomedical applications. GBNMs of different compositions, size and shapes are being introduced without thorough toxicity evaluation due to the unavailability of regulatory guidelines. Computational toxicity prediction methods are used by regulatory bodies to quickly assess health hazards caused by newer materials. Due to increasing demand of GBNMs in various size and functional groups in industrial and consumer based applications, rapid and reliable computational toxicity assessment methods are urgently needed. In the present work, we investigate the impact of graphene and graphene oxide nanomaterials on the structural conformations of small hepcidin peptide and compare the materials for their structural and conformational changes. Our molecular dynamics simulation studies revealed conformational changes in hepcidin due to its interaction with GBMNs, which results in a loss of its functional properties. Our results indicate that hepcidin peptide undergo severe structural deformations when superimposed on the graphene sheet in comparison to graphene oxide sheet. These observations suggest that graphene is more toxic than a graphene oxide nanosheet of similar area. Overall, this study indicates that computational methods based on structural deformation, using molecular dynamics (MD) simulations, can be used for the early evaluation of toxicity potential of novel nanomaterials.

Insert Design and Manufacturing for Foam-Core Composite Sandwich Structures

NASA Astrophysics Data System (ADS)

Lares, Alan

Sandwich structures have been used in the aerospace industry for many years. The high strength to weight ratios that are possible with sandwich constructions makes them desirable for airframe applications. While sandwich structures are effective at handling distributed loads such as aerodynamic forces, they are prone to damage from concentrated loads at joints or due to impact. This is due to the relatively thin face-sheets and soft core materials typically found in sandwich structures. Carleton University's Uninhabited Aerial Vehicle (UAV) Project Team has designed and manufactured a UAV (GeoSury II Prototype) which features an all composite sandwich structure fuselage structure. The purpose of the aircraft is to conduct geomagnetic surveys. The GeoSury II Prototype serves as the test bed for many areas of research in advancing UAV technologies. Those areas of research include: low cost composite materials manufacturing, geomagnetic data acquisition, obstacle detection, autonomous operations and magnetic signature control. In this thesis work a methodology for designing and manufacturing inserts for foam-core sandwich structures was developed. The results of this research work enables a designer wishing to design a foam-core sandwich airframe structure, a means of quickly manufacturing optimized inserts for the safe introduction of discrete loads into the airframe. The previous GeoSury II Prototype insert designs (v.1 & v.2) were performance tested to establish a benchmark with which to compare future insert designs. Several designs and materials were considered for the new v.3 inserts. A plug and sleeve design was selected, due to its ability to effectively transfer the required loads to the sandwich structure. The insert material was chosen to be epoxy, reinforced with chopped carbon fibre. This material was chosen for its combination of strength, low mass and also compatibility with the face-sheet material. The v.3 insert assembly is 60% lighter than the previous insert designs. A casting process for manufacturing the v.3 inserts was developed. The developed casting process, when producing more than 13 inserts, becomes more economical than machining. An exploratory study was conducted looking at the effects of dynamic loading on the v.3 insert performance. The results of this study highlighted areas for improving dynamic testing of foam-core sandwich structure inserts. Correlations were developed relating design variables such as face-sheet thickness and insert diameter to a failure load for different load cases. This was done through simulations using Computer Aided Engineering (CAE) software, and experimental testing. The resulting correlations were integrated into a computer program which outputs the required insert dimensions given a set of design parameters, and load values.

Probabilistic structural analysis methods and applications

NASA Technical Reports Server (NTRS)

Cruse, T. A.; Wu, Y.-T.; Dias, B.; Rajagopal, K. R.

1988-01-01

An advanced algorithm for simulating the probabilistic distribution of structural responses due to statistical uncertainties in loads, geometry, material properties, and boundary conditions is reported. The method effectively combines an advanced algorithm for calculating probability levels for multivariate problems (fast probability integration) together with a general-purpose finite-element code for stress, vibration, and buckling analysis. Application is made to a space propulsion system turbine blade for which the geometry and material properties are treated as random variables.

An overview of the applications of graphene-based materials in supercapacitors.

PubMed

Huang, Yi; Liang, Jiajie; Chen, Yongsheng

2012-06-25

Due to their unique 2D structure and outstanding intrinsic physical properties, such as extraordinarily high electrical conductivity and large surface area, graphene-based materials exhibit great potential for application in supercapacitors. In this review, the progress made so far for their applications in supercapacitors is reviewed, including electrochemical double-layer capacitors, pseudo-capacitors, and asymmetric supercapacitors. Compared with traditional electrode materials, graphene-based materials show some novel characteristics and mechanisms in the process of energy storage and release. Several key issues for improving the structure of graphene-based materials and for achieving better capacitor performance, along with the current outlook for the field, are also discussed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polyimide Prepregs With Improved Tack

NASA Technical Reports Server (NTRS)

Vanucci, R.

1987-01-01

Drape and tack improved without loss of strength. Composites made with PMR-15 (or equivalent) polyimides have gained acceptance as viable engineering materials for high-use-temperature applications. Acceptance due to both thermo-oxidative stability of PMR-15 (or equivalent) and ease which PMR-15 (or equivalent) prepreg materials processed into composite structures.

Optical and structural properties of Mo-doped NiTiO3 materials synthesized via modified Pechini methods

NASA Astrophysics Data System (ADS)

Pham, Thanh-Truc; Kang, Sung Gu; Shin, Eun Woo

2017-07-01

In this study, molybdenum (Mo)-doped nickel titanate (NiTiO3) materials were successfully synthesized as a function of Mo content through a modified Pechini method followed by a solvothermal treatment process. Various characterization methods were employed to investigate the optical and structural properties of the materials. XRD patterns clearly showed that the NiTiO3 structure maintained a single phase with no observed crystalline structure transformations, even after the addition of 10 wt.% Mo. In the Raman spectra and XRD patterns, peak positions shifted with a change in Mo content, confirming that the NiTiO3 lattice was doped with Mo. On the other hand, Mo doping of NiTiO3 materials changed their optical properties. DRS-UV demonstrated that the addition of Mo increased photon absorption within the UV region. Relaxation processes were inhibited by Mo doping, which was evident in the PL spectra. Structural properties of the prepared materials were studied via FE-SEM and HR-TEM. The measured surface area increased proportionally with Mo content due to a reduction in grain size of the materials.

Ab initio modeling of complex amorphous transition-metal-based ceramics.

PubMed

Houska, J; Kos, S

2011-01-19

Binary and ternary amorphous transition metal (TM) nitrides and oxides are of great interest because of their suitability for diverse applications ranging from high-temperature machining to the production of optical filters or electrochromic devices. However, understanding of bonding in, and electronic structure of, these materials represents a challenge mainly due to the d electrons in their valence band. In the present work, we report ab initio calculations of the structure and electronic structure of ZrSiN materials. We focus on the methodology needed for the interpretation and automatic analysis of the bonding structure, on the effect of the length of the calculation on the convergence of individual quantities of interest and on the electronic structure of materials. We show that the traditional form of the Wannier function center-based algorithm fails due to the presence of d electrons in the valence band. We propose a modified algorithm, which allows one to analyze bonding structure in TM-based systems. We observe an appearance of valence p states of TM atoms in the electronic spectra of such systems (not only ZrSiN but also NbO(x) and WAuO), and examine the importance of the p states for the character of the bonding as well as for facilitating the bonding analysis. The results show both the physical phenomena and the computational methodology valid for a wide range of TM-based ceramics.

FRP : Strengthened RC Structures

NASA Astrophysics Data System (ADS)

Teng, J. G.; Chen, J. F.; Smith, S. T.; Lam, L.

2002-01-01

The strengthening of reinforced concrete (RC) structures using advanced fibre-reinforced polymer (FRP) composites, and in particular the behaviour of FRP-strengthened RC structures is a topic which has become very popular in recent years. This popularity has arisen due to the need to maintain and upgrade essential infrastructure in all parts of the world, combined with the well-known advantages of FRP composites, such as good corrosion resistance and ease for site handling due to their light weight. The continuous reduction in the material cost of FRP composites has also contributed to their popularity. While a great amount of research now exists in the published literature on this topic, it is scattered in various journals and conference proceedings. This book therefore provides the first ever comprehensive, state-of-the-art summary of the existing research on FRP strengthening of RC structures, with the emphasis being on structural behaviour and strength models. The main topics covered include: Bond behaviour Flexural and shear strengthening of beams Column strengthening Flexural strengthening of slabs. For each area, the methods of strengthening are discussed, followed by a description of behaviour and failure modes and then the presentation of rational design recommendations, for direct use in practical design of FRP strengthening measures. Researchers, practicing engineers, code writers and postgraduate students in structural engineering and construction materials, as well as consulting firms, government departments, professional bodies, contracting firms and FRP material suppliers will find this an invaluable resource.

The effect of high-pressure torsion on the microstructure and properties of magnesium

NASA Astrophysics Data System (ADS)

Figueiredo, Roberto B.; Sabbaghianrad, Shima; Langdon, Terence G.

2017-05-01

High-pressure torsion provides the opportunity to introduce significant plastic strain at room temperature in magnesium and its alloys. It is now established that this processing operation produces ultrafine-grained structures and changes the properties of these materials. The present paper shows that the mechanism of grain refinement differs from f.c.c. and b.c.c. materials. It is shown that fine grains are formed at the grain boundaries of coarse grains and gradually consume the whole structure. Also, the processed material exhibits unusual mechanical properties due to the activation of grain boundary sliding at room temperature.

Monolithic Gyroidal Mesoporous Mixed Titanium–Niobium Nitrides

PubMed Central

2015-01-01

Mesoporous transition metal nitrides are interesting materials for energy conversion and storage applications due to their conductivity and durability. We present ordered mixed titanium–niobium (8:2, 1:1) nitrides with gyroidal network structures synthesized from triblock terpolymer structure-directed mixed oxides. The materials retain both macroscopic integrity and mesoscale ordering despite heat treatment up to 600 °C, without a rigid carbon framework as a support. Furthermore, the gyroidal lattice parameters were varied by changing polymer molar mass. This synthesis strategy may prove useful in generating a variety of monolithic ordered mesoporous mixed oxides and nitrides for electrode and catalyst materials. PMID:25122534

Simulation of Impact Phenomena on the Composite Structures Containing Ceramic Plates and High Entropy Alloys

NASA Astrophysics Data System (ADS)

Geantă, V.; Cherecheș, T.; Lixandru, P.; Voiculescu, I.; Ștefănoiu, R.; Dragnea, D.; Zecheru, T.; Matache, L.

2017-06-01

Due to excellent mechanical properties, high entropy alloys from the system AlxCrFeCoNi can be used successfully to create composite structures containing both metallic and ceramic plates, which resists at dynamic load during high speeds impact (like projectiles, explosion). The paper presents four different composite structures made from a combination of metallic materials and ceramics plates: duralumin-ceramics, duralumin-ceramics-HEA, HEA-ceramics-HEA, HEA-ceramics-duralumin. Numerical simulation of impact behavior of the composite structures was performed by virtual methods, taking into account the mechanical properties of both materials. The best results were obtained using composite structures HEA-ceramics-HEA, HEA-ceramics-duralumin.

Material Properties Analysis of Structural Members in Pumpkin Balloons

NASA Technical Reports Server (NTRS)

Sterling, W. J.

2003-01-01

The efficient design, service-life qualification, and reliability predictions for lightweight aerospace structures require careful mechanical properties analysis of candidate structural materials. The demand for high-quality laboratory data is particularly acute when the candidate material or the structural design has little history. The pumpkin-shaped super-pressure balloon presents both challenges. Its design utilizes load members (tendons) extending from apex to base around the gas envelope to achieve a lightweight structure. The candidate tendon material is highly weight-efficient braided HM cord. Previous mechanical properties studies of Zylon have focused on fiber and yarn, and industrial use of the material in tensile applications is limited. For high-performance polymers, a carefully plamed and executed properties analysis scheme is required to ensure the data are relevant to the desired application. Because no directly-applicable testing standard was available, a protocol was developed based on guidelines fiom professional and industry organizations. Due to the liquid-crystalline nature of the polymer, the cord is very stiff, creeps very little, and does not yield. Therefore, the key material property for this application is the breaking strength. The pretension load and gauge length were found to have negligible effect on the measured breaking strength over the ranges investigated. Strain rate was found to have no effect on breaking strength, within the range of rates suggested by the standards organizations. However, at the lower rate more similar to ULDB operations, the strength was reduced. The breaking strength increased when the experiment temperature was decreased from ambient to 183K which is the lowest temperature ULDB is expected to experience. The measured strength under all test conditions was well below that resulting from direct scale-up of fiber strength based on the manufacturers data. This expected result is due to the effects of the braiding process and material ageing.

New group-V elemental bilayers: A tunable structure model with four-, six-, and eight-atom rings

NASA Astrophysics Data System (ADS)

Kong, Xiangru; Li, Linyang; Leenaerts, Ortwin; Liu, Xiong-Jun; Peeters, François M.

2017-07-01

Two-dimensional group-V elemental materials have attracted widespread attention due to their nonzero band gap while displaying high electron mobility. Using first-principles calculations, we propose a series of new elemental bilayers with group-V elements (Bi, Sb, As). Our study reveals the dynamical stability of four-, six-, and eight-atom ring structures, demonstrating their possible coexistence in such bilayer systems. The proposed structures for Sb and As are large-gap semiconductors that are potentially interesting for applications in future nanodevices. The Bi structures have nontrivial topological properties with a direct nontrivial band gap. The nontrivial gap is shown to arise from a band inversion at the Brillouin zone center due to the strong intrinsic spin-orbit coupling in Bi atoms. Moreover, we demonstrate the possibility of tuning the properties of these materials by enhancing the ratio of six-atom rings to four- and eight-atom rings, which results in wider nontrivial band gaps and lower formation energies.

Effects of Ga substitution on the structural and magnetic properties of half metallic Fe{sub 2}MnSi Heusler compound

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

Pedro, S. S., E-mail: sandrapedro@uerj.br; Caraballo Vivas, R. J.; Andrade, V. M.

2015-01-07

The so-called half-metallic magnets have been proposed as good candidates for spintronic applications due to the feature of exhibiting a hundred percent spin polarization at the Fermi level. Such materials follow the Slater-Pauling rule, which relates the magnetic moment with the valence electrons in the system. In this paper, we study the bulk polycrystalline half-metallic Fe{sub 2}MnSi Heusler compound replacing Si by Ga to determine how the Ga addition changes the magnetic, the structural, and the half-metal properties of this compound. The material does not follow the Slater-Pauling rule, probably due to a minor structural disorder degree in the system,more » but a linear dependence on the magnetic transition temperature with the valence electron number points to the half-metallic behavior of this compound.« less

A Hollow-Structured Manganese Oxide Cathode for Stable Zn-MnO₂ Batteries.

PubMed

Guo, Xiaotong; Li, Jianming; Jin, Xu; Han, Yehu; Lin, Yue; Lei, Zhanwu; Wang, Shiyang; Qin, Lianjie; Jiao, Shuhong; Cao, Ruiguo

2018-05-05

Aqueous rechargeable zinc-manganese dioxide (Zn-MnO₂) batteries are considered as one of the most promising energy storage devices for large scale-energy storage systems due to their low cost, high safety, and environmental friendliness. However, only a few cathode materials have been demonstrated to achieve stable cycling for aqueous rechargeable Zn-MnO₂ batteries. Here, we report a new material consisting of hollow MnO₂ nanospheres, which can be used for aqueous Zn-MnO₂ batteries. The hollow MnO₂ nanospheres can achieve high specific capacity up to ~405 mAh g −1 at 0.5 C. More importantly, the hollow structure of birnessite-type MnO₂ enables long-term cycling stability for the aqueous Zn-MnO₂ batteries. The excellent performance of the hollow MnO₂ nanospheres should be due to their unique structural properties that enable the easy intercalation of zinc ions.

Negative-pressure polymorphs made by heterostructural alloying

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

Siol, Sebastian; Holder, Aaron; Steffes, James

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures - a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixingmore » two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2x to 4x lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. Lastly, this example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties - materials that are otherwise nearly impossible to make.« less

Negative-pressure polymorphs made by heterostructural alloying

DOE PAGES

Siol, Sebastian; Holder, Aaron; Steffes, James; ...

2018-04-20

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures - a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixingmore » two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2x to 4x lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. Lastly, this example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties - materials that are otherwise nearly impossible to make.« less

Thermal modeling using enthalpy methods to aid in the study of microstructural changes of multilayered phase change optical memories

NASA Astrophysics Data System (ADS)

Nagpal, Swati; Aurora, Aradhna

1999-11-01

In DOW type of phase change optical memories the focus has been mainly on gestate based systems due to their good overwriting capability and very high order cyclability. To avoid the material deterioration problems such as material flow, high melting point, high viscosity or high-density components such as CrTe, (which have the same refractive index) can be added to the active layer. This has led to an improved performance of overwrite cycles from 105 to 106. Material flow occurs due to void formation. Voids and sinks are formed due to porosity of the active layer because the active layer has a density lower than that of the bulk material. One of the reasons for the formation and coalescence of voids is the way in which the film is deposited viz. Sputtering which makes Ar atoms accumulate in the films during deposition. Also the mechanical strength of the protective layer effects the repeatability of the active layer. All the above mentioned processes occur during melting and re- solidification of the nano-sized spots which are laser irradiated. Since the structure of the protective layers is very important in controlling the void formation, it is very important to study the thermal modeling of the full layer structure.

Sensitivity and Limitations of Structures from X-ray and Neutron-Based Diffraction Analyses of Transition Metal Oxide Lithium-Battery Electrodes

DOE PAGES

Liu, Hao; Liu, Haodong; Lapidus, Saul H.; ...

2017-06-21

Lithium transition metal oxides are an important class of electrode materials for lithium-ion batteries. Binary or ternary (transition) metal doping brings about new opportunities to improve the electrode’s performance and often leads to more complex stoichiometries and atomic structures than the archetypal LiCoO 2. Rietveld structural analyses of X-ray and neutron diffraction data is a widely-used approach for structural characterization of crystalline materials. But, different structural models and refinement approaches can lead to differing results, and some parameters can be difficult to quantify due to the inherent limitations of the data. Here, through the example of LiNi 0.8Co 0.15Al 0.05Omore » 2 (NCA), we demonstrated the sensitivity of various structural parameters in Rietveld structural analysis to different refinement approaches and structural models, and proposed an approach to reduce refinement uncertainties due to the inexact X-ray scattering factors of the constituent atoms within the lattice. Furthermore, this refinement approach was implemented for electrochemically-cycled NCA samples and yielded accurate structural parameters using only X-ray diffraction data. The present work provides the best practices for performing structural refinement of lithium transition metal oxides.« less

Sensitivity and Limitations of Structures from X-ray and Neutron-Based Diffraction Analyses of Transition Metal Oxide Lithium-Battery Electrodes

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

Liu, Hao; Liu, Haodong; Lapidus, Saul H.

Lithium transition metal oxides are an important class of electrode materials for lithium-ion batteries. Binary or ternary (transition) metal doping brings about new opportunities to improve the electrode’s performance and often leads to more complex stoichiometries and atomic structures than the archetypal LiCoO 2. Rietveld structural analyses of X-ray and neutron diffraction data is a widely-used approach for structural characterization of crystalline materials. But, different structural models and refinement approaches can lead to differing results, and some parameters can be difficult to quantify due to the inherent limitations of the data. Here, through the example of LiNi 0.8Co 0.15Al 0.05Omore » 2 (NCA), we demonstrated the sensitivity of various structural parameters in Rietveld structural analysis to different refinement approaches and structural models, and proposed an approach to reduce refinement uncertainties due to the inexact X-ray scattering factors of the constituent atoms within the lattice. Furthermore, this refinement approach was implemented for electrochemically-cycled NCA samples and yielded accurate structural parameters using only X-ray diffraction data. The present work provides the best practices for performing structural refinement of lithium transition metal oxides.« less

Waste management for different fusion reactor designs

NASA Astrophysics Data System (ADS)

Rocco, Paolo; Zucchetti, Massimo

2000-12-01

Safety and Environmental Assessment of Fusion Power (SEAFP) waste management studies performed up to 1998 concerned three power tokamak designs. In-vessel structural materials consist of V-alloys or low activation martensitic (LAM) steel; tritium-producing materials are Li 2O, Pb-17Li, Li 4SiO 4 with a Be-multiplier; coolants are helium or water. The strategy chosen reduces permanent radwaste by recycling the in-vessel materials and by clearance of the other structures. Limits of the contact dose rate and specific activity of the waste allowing such options are defined accordingly. SEAFP activities for 1999 enlarge the analysis to three additional reactors with in-vessel structures made with SiC/SiC composites. These materials cannot be recycled due to their form and, according to national regulations of E.C. countries, long-lived activation products hinder near-surface burial (NSB).

Nanostructured Coatings of Inner Surfaces in Microporous Matrixes

DTIC Science & Technology

2000-01-01

SURFACE ENERGY _.I", DISPERSED MATERIAL............................ ,BULK MATERIp,’ t. i02 10’ iol LM Figure 1. a) Surface arising due to process of...material dispersion . b) Surface energy per cm3 of dispersed material versus characteristic size of dispersed particles - nanostructures with different...growth and lateral microstructuring techniques have made it possible to realise low-dimensional electronic systems with quantum confined energy structure

Possible 6-qubit NMR quantum computer device material; simulator of the NMR line width

NASA Astrophysics Data System (ADS)

Hashi, K.; Kitazawa, H.; Shimizu, T.; Goto, A.; Eguchi, S.; Ohki, S.

2002-12-01

For an NMR quantum computer, splitting of an NMR spectrum must be larger than a line width. In order to find a best device material for a solid-state NMR quantum computer, we have made a simulation program to calculate the NMR line width due to the nuclear dipole field by the 2nd moment method. The program utilizes the lattice information prepared by commercial software to draw a crystal structure. By applying this program, we can estimate the NMR line width due to the nuclear dipole field without measurements and find a candidate material for a 6-qubit solid-state NMR quantum computer device.

The efficiency of the use of composite materials in electrotechnical equipment

NASA Astrophysics Data System (ADS)

Kim, K.; Ivanov, S.

2018-02-01

The indicators of the efficiency of electrical installations are directly connected with the creating and using of new composite materials with the desired performance properties. The practical application of composite materials is one of the perspective scientific and technical directions, providing the increase of the efficiency of electrical installations due to the sealing of current parts by protecting them from the external medium. The technical characteristics of the composite material match to its structure and depend on the properties of the individual components. The verification of the compliance of material parameters is implemented by the methods of the computer analysis of a model of composite material in the form of the structure in which the individual elements have thermodynamic properties of the corresponding phase state. In the study the topology of individual elements in the material structure is defined by the conditional boundaries of the section within the studied composite. The efficiency of using the composite materials includes the raising of electrical safety, increasing the durability, reducing the costs of maintenance and repair and the extension of the scope of installations.

On the conservation of easel paintings: evaluation of microbial contamination and artists materials

NASA Astrophysics Data System (ADS)

Salvador, Cátia; Bordalo, Rui; Silva, Mara; Rosado, Tânia; Candeias, António; Caldeira, Ana Teresa

2017-01-01

Easel paintings have been considered one of the most important art expressions, constituting today outstanding works of art with important historic and cultural value. Unfortunately, due to the presence of several organic materials, these artworks have been affected by microbial contamination that among other factors can be responsible for different aesthetic and structural alterations. For this study, four easel paintings from the late nineteenth century by Giorgio Marini with evident chromatic and structural alterations due to biocontamination were analysed in order to better understand the materials used and the source of high microbial contamination within a focused conservation intervention process. For this end, both the biofilms and the painting materials were characterised by several analytical techniques. Fungal communities were found to prevail in areas with evident structural and aesthetic damages, which were confirmed by scanning electron microscopy analyses that allowed the observation of the fungal hyphae proliferation capacity. Energy-dispersive X-ray spectroscopy, μ-X-ray diffraction, μ-Raman, μ-FTIR and optical microscopy were used to further identify the painting materials. Immunological assays revealed the presence of a mixture of proteins of ovalbumin, collagen and casein, suggesting that the presence of these proteinaceous materials in these paintings is one of the main reasons of microbial biofilms appearance on the painting's surface. These approaches contribute for a better knowledge of these artworks providing at the same time relevant information for the ongoing conservation-restoration intervention.

Methoxydiphenylamine-substituted fluorene derivatives as hole transporting materials: role of molecular interaction on device photovoltaic performance.

PubMed

Tiazkis, Robertas; Paek, Sanghyun; Daskeviciene, Maryte; Malinauskas, Tadas; Saliba, Michael; Nekrasovas, Jonas; Jankauskas, Vygintas; Ahmad, Shahzada; Getautis, Vytautas; Khaja Nazeeruddin, Mohammad

2017-03-10

The molecular structure of the hole transporting material (HTM) play an important role in hole extraction in a perovskite solar cells. It has a significant influence on the molecular planarity, energy level, and charge transport properties. Understanding the relationship between the chemical structure of the HTM's and perovskite solar cells (PSCs) performance is crucial for the continued development of the efficient organic charge transporting materials. Using molecular engineering approach we have constructed a series of the hole transporting materials with strategically placed aliphatic substituents to investigate the relationship between the chemical structure of the HTMs and the photovoltaic performance. PSCs employing the investigated HTMs demonstrate power conversion efficiency values in the range of 9% to 16.8% highlighting the importance of the optimal molecular structure. An inappropriately placed side group could compromise the device performance. Due to the ease of synthesis and moieties employed in its construction, it offers a wide range of possible structural modifications. This class of molecules has a great potential for structural optimization in order to realize simple and efficient small molecule based HTMs for perovskite solar cells application.

Manganese oxide octahedral molecular sieves: Synthesis, self-assembly, control over morphologies and tunnel structure

NASA Astrophysics Data System (ADS)

Yuan, Jikang

Direct architecture of complex nanostructures is desirable and still remains a challenge in areas of materials science. Due to their size-, shape-dependent electronic and optical properties, much effort has been made to control morphologies of transition metal oxide nanoparticles and to organize them into complicated 3D structures using templates. In particular, manganese oxides have attracted much attention because they have extensive applications in many chemical processes due to their porous structures, acidity, ionexchange, separation, catalysis, and energy storage in secondary batteries. Using organic templates such as trimethylamine (TMA), manganese oxides have been successfully organized into macroscopic rings and helices via sol-gel processes. However, the methods mentioned above all need further purification, so impurities will be avoided. Subsequent procedures are needed to obtain pure products. Thus facile and template-free methods are highly desired for synthesis of manganese oxide nanaoparticles with complex 3D structures. Manganese oxide octahedral molecular sieves (OMS) are a class of microporous transition metallic oxides with various kinds of tunnel structures that can be synthesized via controlling synthetic conditions such as temperature, concentration, pH, and cations. Manganese oxide molecular sieves are semiconducting mixed-valence catalysts that utilize electron transport to catalyze reactions such as selective oxidation of alcohols. OMS has distinct advantages over aluminosilicate molecular sieve materials for applications in catalysis due to the mixed valence character. The synthesis of manganese oxide OMS materials will be much more complicated than those of main group metallic oxides because of different coordination numbers and oxidation states. OMS-type materials with desirable morphologies formed under mild synthetic conditions are highly desirable. Herein, we report a template-free, low temperature preparation of porous cryptomelane-type manganese oxide (OMS-2) 3D nanostructures. The objectives of this research include exploration of new methods to oxidize Mn2+ in aqueous solution either under low-temperature reflux or hydrothermal conditions. Various oxidants were used with precisely controlled synthetic parameters such as temperature, concentrations of starting materials, pH, and kinds of templates. A variety of techniques including powder X-ray diffraction and transmission electron microscopy (TEM) scanning electron microscopy are used to investigate the structures of synthesized materials. Atomic force microscopy (AFM) and scanning electron microscopy are utilized to studying the morphology and topography. The surface areas of the materials is measured by the BET method. Inductively coupled argon plasma atomic emission spectrometer (ICP-AES) are utilized to investigate the chemical composition of the materials. Thermal-stability of the materials is investigated by thermal gravimetric analysis (TGA). The objectives of this research includes exploring new synthetic approach such as oxidation of Mn2+ in aqueous solution by selecting suitable oxidants so as to control redox potential, varying pH of reaction systems, and controlling tunnel structures using hard templates (cations) under hydrothermal conditions.

Comparison of the performance of concrete-filled steel tubular and hollow steel diagrid buildings

NASA Astrophysics Data System (ADS)

Peter, Minu Ann; S, Sajith A.; Nagarajan, Praveen

2018-03-01

In the recent construction scenario, diagrid structures are becoming a popular high-rise building structural system. Diagrid structures consist of diagonals in the perimeter and an interior core. The corner and interior vertical columns are not required due to the structural efficiency of diagrid structural systems. Steel and concrete are commonly used material for diagrid. An alternate material for diagrid is concrete-filled steel tube (CFST). CFST incorporates the advantages of both steel and concrete. In CFST, the inward buckling of the steel tube is effectively prevented by the filled concrete. The compressive strength of concrete increases due to the tri-axial state of stress in concrete induced by the steel tube. The longitudinal as well as lateral reinforcement to the concrete core is also provided by the steel tube. This paper compares the performance of CFST and steel diagrid buildings using linear static analysis. For this purpose, a 12 storey and 36 storey building are analysed using finite element method and CFST diagrid building is found to perform better.

An Investigation of Porous Structure of TiNi-Based SHS-Materials Produced at Different Initial Synthesis Temperatures

NASA Astrophysics Data System (ADS)

Khodorenko, V. N.; Anikeev, S. G.; Kokorev, O. V.; Yasenchuk, Yu. F.; Gunther, V. É.

2018-02-01

An investigation of structural characteristics and behavior of TiNi-based pore-permeable materials manufactured by the methods of selfpropagating high-temperature synthesis (SHS) at the initial synthesis temperatures T = 400 and 600°C is performed. It is shown that depending on the temperature regime, the resulting structure and properties of the material can differ. It is found out that the SHS-material produced at the initial synthesis temperature T = 400°C possesses the largest number of micropores in the pore wall surface structure due to a high phase inhomogeneity of the alloy. The regime of structure optimization of the resulting materials is described and the main stages of formation of the pore wall microporous surfaces are revealed. It is demonstrated that after optimization of the surface structure of a TiNi-based fine-pore alloy by its chemical etching, the fraction of micropores measuring in size less than 50 nm increased from 59 to 68%, while the number of pores larger than 1 μm increased twofold from 11 to 22%. In addition, peculiar features of interaction between certain cell cultures with the surface of the SHS-material manufactured at different initial synthesis temperatures are revealed. It is found out that the dynamics of the cell material integration depends on the pore wall surface morphology and dimensions of macropores.

Sunlight Diffusing Tent for Lunar Worksite

NASA Technical Reports Server (NTRS)

Burleson, Blair; Clark, Todd; Deese, Todd; Gentry, Ernest; Samad, Abdul

1990-01-01

The purpose is to provide a solution to problems astronauts encounter with sunlight on the lunar surface. Due to the absence of an atmosphere the Moon is subjected to intense sunlight creating problems with color and contrast. This problem can be overcome by providing a way to reduce intensity and diffuse the light in a working environment. The solution to the problem utilizes an umbrella, tent-like structure covered with a diffusing material. The design takes into account structural materials, stresses, fabrics, and deployment.

Material degradation due to moisture and temperature. Part 1: mathematical model, analysis, and analytical solutions

NASA Astrophysics Data System (ADS)

Xu, C.; Mudunuru, M. K.; Nakshatrala, K. B.

2016-11-01

The mechanical response, serviceability, and load-bearing capacity of materials and structural components can be adversely affected due to external stimuli, which include exposure to a corrosive chemical species, high temperatures, temperature fluctuations (i.e., freezing-thawing), cyclic mechanical loading, just to name a few. It is, therefore, of paramount importance in several branches of engineering—ranging from aerospace engineering, civil engineering to biomedical engineering—to have a fundamental understanding of degradation of materials, as the materials in these applications are often subjected to adverse environments. As a result of recent advancements in material science, new materials such as fiber-reinforced polymers and multi-functional materials that exhibit high ductility have been developed and widely used, for example, as infrastructural materials or in medical devices (e.g., stents). The traditional small-strain approaches of modeling these materials will not be adequate. In this paper, we study degradation of materials due to an exposure to chemical species and temperature under large strain and large deformations. In the first part of our research work, we present a consistent mathematical model with firm thermodynamic underpinning. We then obtain semi-analytical solutions of several canonical problems to illustrate the nature of the quasi-static and unsteady behaviors of degrading hyperelastic solids.

An efficient method to predict and include Bragg curve degradation due to lung-equivalent materials in Monte Carlo codes by applying a density modulation

NASA Astrophysics Data System (ADS)

Baumann, Kilian-Simon; Witt, Matthias; Weber, Uli; Engenhart-Cabillic, Rita; Zink, Klemens

2017-05-01

Sub-millimetre-sized heterogeneities such as lung parenchyma cause Bragg peak degradation which can lead to an underdose of the tumor and an overdose of healthy tissue when not accounted for in treatment planning. Since commonly used treatment-planning CTs do not resolve the fine structure of lungs, this degradation can hardly be considered. We present a mathematical model capable of predicting and describing Bragg peak degradation due to a lung-equivalent geometry consisting of sub-millimetre voxels filled with either lung tissue or air. The material characteristic ‘modulation power’ is introduced to quantify the Bragg peak degradation. A strategy was developed to transfer the modulating effects of such fine structures to rougher structures such as 2 mm thick CT voxels, which is the resolution of typically used CTs. This is done by using the modulation power to derive a density distribution applicable to these voxels. By replacing the previously used sub-millimetre voxels by 2 mm thick voxels filled with lung tissue and modulating the lung tissue’s density in each voxel individually, we were able to reproduce the Bragg peak degradation. Hence a solution is found to include Bragg curve degradation due to lung-equivalent materials in Monte Carlo-based treatment-planning systems.

Molecular level assessment of thermal transport and thermoelectricity in materials: From bulk alloys to nanostructures

NASA Astrophysics Data System (ADS)

Kinaci, Alper

The ability to manipulate material response to dynamical processes depends on the extent of understanding of transport properties and their variation with chemical and structural features in materials. In this perspective, current work focuses on the thermal and electronic transport behavior of technologically important bulk and nanomaterials. Strontium titanate is a potential thermoelectric material due to its large Seebeck coefficient. Here, first principles electronic band structure and Boltzmann transport calculations are employed in studying the thermoelectric properties of this material in doped and deformed states. The calculations verified that excessive carrier concentrations are needed for this material to be used in thermoelectric applications. Carbon- and boron nitride-based nanomaterials also offer new opportunities in many applications from thermoelectrics to fast heat removers. For these materials, molecular dynamics calculations are used to evaluate lattice thermal transport. To do this, first, an energy moment term is reformulated for periodic boundary conditions and tested to calculate thermal conductivity from Einstein relation in various systems. The influences of the structural details (size, dimensionality) and defects (vacancies, Stone-Wales defects, edge roughness, isotopic disorder) on the thermal conductivity of C and BN nanostructures are explored. It is observed that single vacancies scatter phonons stronger than other type of defects due to unsatisfied bonds in their structure. In pristine states, BN nanostructures have 4-6 times lower thermal conductivity compared to C counterparts. The reason of this observation is investigated on the basis of phonon group velocities, life times and heat capacities. The calculations show that both phonon group velocities and life times are smaller in BN systems. Quantum corrections are also discussed for these classical simulations. The chemical and structural diversity that could be attained by mixing hexagonal boron nitride and graphene provide further avenues for tuning thermal and electronic properties. In this work, the thermal conductivity of hybrid graphene/hexagonal-BN structures: stripe superlattices and BN (graphene) dots embedded in graphene (BN) are studied. The largest reduction in thermal conductivity is observed at 50% chemical mixture in dot superlattices. The dot radius appears to have little effect on the magnitude of reduction around large concentrations while smaller dots are more influential at dilute systems.

A geomorphic process law for detachment-limited hillslopes

NASA Astrophysics Data System (ADS)

Turowski, Jens

2015-04-01

Geomorphic process laws are used to assess the shape evolution of structures at the Earth's surface over geological time scales, and are routinely used in landscape evolution models. There are two currently available concepts on which process laws for hillslope evolution rely. In the transport-limited concept, the evolution of a hillslope is described by a linear or a non-linear diffusion equation. In contrast, in the threshold slope concept, the hillslope is assumed to collapse to a slope equal to the internal friction angle of the material when the load due to the relief exists the material strength. Many mountains feature bedrock slopes, especially in the high mountains, and material transport along the slope is limited by the erosion of the material from the bedrock. Here, I suggest a process law for detachment-limited or threshold-dominated hillslopes, in which the erosion rate is a function of the applied stress minus the surface stress due to structural loading. The process law leads to the prediction of an equilibrium form that compares well to the shape of many mountain domes.

Organic Analysis in Miller Range 090657 and Buckley Island 10933 CR2 Chondrites: Part 1 In-Situ Observation of Carbonaceous Material

NASA Technical Reports Server (NTRS)

Cao, T.; Nakamura-Messenger, K.; Berger, E. L.; Burton, A. S.; Messenger, S.; Clemett, S. J.

2016-01-01

Primitive carbonaceous chondrites contain a wide variety of organic material, ranging from soluble discrete molecules to insoluble unstructured kerogen-like component as well as structured nano-globules of macromolecular carbon. The relationship between the soluble organic molecules, macromolecular organic material, and host minerals are poorly understood. Due to the differences in extractability of soluble and insoluble organic materials, the analysis methods for each differ and are often performed independently. The combination of soluble and insoluble analyses, when performed concurrently, can provide a wider understanding on spatial distribution, and elemental, structural and isotopic composition of organic material in primitive meteorites. Furthermore, they can provide broader perspective on how extraterrestrial organic ma-terials potentially contributed to the synthesis of life's essential compounds such as amino acids, sugar acids, activated phosphates and nucleobases.

Impact of microstructure on the thermoelectric properties of the ternary compound Ce{sub 3}Cu{sub 3}Sb{sub 4}

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

Witas, Piotr, E-mail: pwitas@us.edu.pl

We present detailed structural and thermoelectric studies of the ternary compound Ce{sub 3}Cu{sub 3}Sb{sub 4}. This material is of interest due to previously reported considerable thermopower above room temperature (∼ 100 μV/K) and low thermal conductivity (2 W/(m K)). Here, we present detailed studies concerning microstructural and thermoelectric data, their variation across the samples and possible explanations for the observed behaviour. We have used X-ray diffraction, scanning electron microscopy (SEM), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) for microstructural analysis. The thermoelectric properties were examined using a physical property measurement system (PPMS). We analyse the impact of the sample qualitymore » on the thermoelectric properties. The most unstable parameter is the material resistivity which varies between 1.5 and 15 mΩ cm at room temperature. The properties variability is mainly due to structural defects caused by stresses during material preparation and also due to formation of foreign phases CeCuSb{sub 2} and CeSb. The figure of merit ZT is also strongly dependent on the quality of the sample. The largest value ZT ≈ 0.15 at 400 K is determined for the almost stoichiometric sample with small amounts of a impurity phases. - Highlights: •The Ce{sub 3}Cu{sub 3}Sb{sub 4} has considerable thermoelectric properties and potential for further chemical and/or structural modification. •The control over foreign phases formation is challenging. •The defects arising during arc melting process highly deteriorate ZT of material.« less

Production and characterization of a composite insulation material from waste polyethylene teraphtalates

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

Kurtulmus, Erhan; Karaboyacı, Mustafa; Yigitarslan, Sibel

2013-12-16

The pollution of polyethylene teraphtalate (PET) is in huge amounts due to the most widely usage as a packaging material in several industries. Regional pumice has several desirable characteristics such as porous structure, low-cost and light-weight. Considering the requirements approved by the Ministry of Public Works on isolation, composite insulation material consisting of PET and pumice was studied. Sheets of composites differing both in particle size of pumice and composition of polymer were produced by hot-molding technique. Characterization of new composite material was achieved by measuring its weight, density, flammability, endurance against both to common acids and bases, and tomore » a force applied, heat insulation and water adsorption capacity. The results of the study showed that produced composite material is an alternative building material due to its desirable characteristics; low weight, capability of low heat conduction.« less

Interface structure and mechanics between graphene and metal substrates: a first-principles study

NASA Astrophysics Data System (ADS)

Xu, Zhiping; Buehler, Markus J.

2010-12-01

Graphene is a fascinating material not only for technological applications, but also as a test bed for fundamental insights into condensed matter physics due to its unique two-dimensional structure. One of the most intriguing issues is the understanding of the properties of graphene and various substrate materials. In particular, the interfaces between graphene and metal substrates are of critical importance in applications of graphene in integrated electronics, as thermal materials, and in electromechanical devices. Here we investigate the structure and mechanical interactions at a graphene-metal interface through density functional theory (DFT)-based calculations. We focus on copper (111) and nickel (111) surfaces adhered to a monolayer of graphene, and find that their cohesive energy, strength and electronic structure correlate directly with their atomic geometry. Due to the strong coupling between open d-orbitals, the nickel-graphene interface has a much stronger cohesive energy with graphene than copper. We also find that the interface cohesive energy profile features a well-and-shoulder shape that cannot be captured by simple pair-wise models such as the Lennard-Jones potential. Our results provide a detailed understanding of the interfacial properties of graphene-metal systems, and help to predict the performance of graphene-based nanoelectronics and nanocomposites. The availability of structural and energetic data of graphene-metal interfaces could also be useful for the development of empirical force fields for molecular dynamics simulations.

From kinetic-structure analysis to engineering crystalline fiber networks in soft materials.

PubMed

Wang, Rong-Yao; Wang, Peng; Li, Jing-Liang; Yuan, Bing; Liu, Yu; Li, Li; Liu, Xiang-Yang

2013-03-07

Understanding the role of kinetics in fiber network microstructure formation is of considerable importance in engineering gel materials to achieve their optimized performances/functionalities. In this work, we present a new approach for kinetic-structure analysis for fibrous gel materials. In this method, kinetic data is acquired using a rheology technique and is analyzed in terms of an extended Dickinson model in which the scaling behaviors of dynamic rheological properties in the gelation process are taken into account. It enables us to extract the structural parameter, i.e. the fractal dimension, of a fibrous gel from the dynamic rheological measurement of the gelation process, and to establish the kinetic-structure relationship suitable for both dilute and concentrated gelling systems. In comparison to the fractal analysis method reported in a previous study, our method is advantageous due to its general validity for a wide range of fractal structures of fibrous gels, from a highly compact network of the spherulitic domains to an open fibrous network structure. With such a kinetic-structure analysis, we can gain a quantitative understanding of the role of kinetic control in engineering the microstructure of the fiber network in gel materials.

Morphological and performance measures of polyurethane foams using X-ray CT and mechanical testing.

PubMed

Patterson, Brian M; Henderson, Kevin; Gilbertson, Robert D; Tornga, Stephanie; Cordes, Nikolaus L; Chavez, Manuel E; Smith, Zachary

2014-08-01

Meso-scale structure in polymeric foams determines the mechanical properties of the material. Density variations, even more than variations in the anisotropic void structure, can greatly vary the compressive and tensile response of the material. With their diverse use as both a structural material and space filler, polyurethane (PU) foams are widely studied. In this manuscript, quantitative measures of the density and anisotropic structure are provided by using micro X-ray computed tomography (microCT) to better understand the results of mechanical testing. MicroCT illustrates the variation in the density, cell morphology, size, shape, and orientation in different regions in blown foam due to the velocity profile near the casting surface. "Interrupted" in situ imaging of the material during compression of these sub-regions indicates the pathways of the structural response to the mechanical load and the changes in cell morphology as a result. It is found that molded PU foam has a 6 mm thick "skin" of higher density and highly eccentric morphological structure that leads to wide variations in mechanical performance depending upon sampling location. This comparison is necessary to understand the mechanical performance of the anisotropic structure.

Strategies for Multi-Modal Analysis

NASA Astrophysics Data System (ADS)

Hexemer, Alexander; Wang, Cheng; Pandolfi, Ronald; Kumar, Dinesh; Venkatakrishnan, Singanallur; Sethian, James; Camera Team

This section on soft materials will be dedicated to discuss the extraction of the chemical distribution and spatial arrangement of constituent elements and functional groups at multiple length scales and, thus, the examination of collective dynamics, transport, and electronic ordering phenomena. Traditional measures of structure in soft materials have relied heavily on scattering and imaging based techniques due to their capacity to measure nanoscale dimensions and their capacity to monitor structure under conditions of dynamic stress loading. Special attentions are planned to focus on the application of resonant x-ray scattering, contrast-varied neutron scattering, analytical transmission electron microscopy, and their combinations. This session aims to bring experts in both scattering and electron microscope fields to discuss recent advances in selectively characterizing structural architectures of complex soft materials, which have often multi-components with a wide range of length scales and multiple functionalities, and thus hopes to foster novel ideas to decipher a higher level of structural complexity in soft materials in future. CAMERA, Early Career Award.

Analysis of Thermal Power Generation Capacity for a Skutterudite-Based Thermoelectric Functional Structure

NASA Astrophysics Data System (ADS)

Sun, Yajing; Chen, Gang; Bai, Guanghui; Yang, Xuqiu; Li, Peng; Zhai, Pengcheng

2017-05-01

Due to military or other requirements for hypersonic aircraft, the energy supply devices with the advantages of small size and light weight are urgently needed. Compared with the traditional energy supply method, the skutterudite-based thermoelectric (TE) functional structure is expected to generate electrical energy with a smaller structural space in the hypersonic aircraft. This paper mainly focuses on the responded thermal and electrical characteristics of the skutterudite-based TE functional structure (TEFS) under strong heat flux loads. We conduct TE simulations on the transient model of the TEFS with consideration of the heat flux loads and thermal radiation in the hot end and the cooling effect of the phase change material (PCM) in the cold end. We investigate several influential factors on the power generation capacity, such as the phase transition temperature of the PCM, the heat flux loads, the thickness of the TE materials and the thermal conductivity of the frame materials. The results show that better power generation capacity can be achieved with thicker TE materials, lower phase transition temperature and suitable thermal conductivity of the frame materials.

Structural and electronic properties of high pressure phases of lead chalcogenides

NASA Astrophysics Data System (ADS)

Petersen, John; Scolfaro, Luisa; Myers, Thomas

2012-10-01

Lead chalcogenides, most notably PbTe and PbSe, have become an active area of research due to their thermoelectric properties. The high figure of merit (ZT) of these materials has brought much attention to them, due to their ability to convert waste heat into electricity. Variation in synthesis conditions gives rise to a need for analysis of structural and thermoelectric properties of these materials at different pressures. In addition to the NaCl structure at ambient conditions, lead chalcogenides have a dynamic orthorhombic (Pnma) intermediate phase and a higher pressure yet stable CsCl phase. By altering the lattice constant, we simulate the application of external pressure; this has notable effects on ground state total energy, band gap, and structural phase. Using the General Gradient Approximation (GGA) in Density Functional Theory (DFT), we calculate the phase transition pressures by finding the differences in enthalpy from total energy calculations. For each phase, elastic constants, bulk modulus, shear modulus, Young's modulus, and hardness are calculated, using two different approaches. In addition to structural properties, we analyze the band structure and density of states at varying pressures, paying special note to thermoelectric implications.

In situ plasma fabrication of ceramic-like structure on polymeric implant with enhanced surface hardness, cytocompatibility and antibacterial capability.

PubMed

Liu, Jun; Zhang, Wei; Shi, Haigang; Yang, Kun; Wang, Gexia; Wang, Pingli; Ji, Junhui; Chu, Paul K

2016-05-01

Polymeric materials are commonly found in orthopedic implants due to their unique mechanical properties and biocompatibility but the poor surface hardness and bacterial infection hamper many biomedical applications. In this study, a ceramic-like surface structure doped with silver is produced by successive plasma implantation of silicon (Si) and silver (Ag) into the polyamine 66 (PA66) substrate. Not only the surface hardness and elastic modulus are greatly enhanced due to the partial surface carbonization and the ceramic-like structure produced by the reaction between energetic Si and the carbon chain of PA66, but also the antibacterial activity is improved because of the combined effects rendered by Ag and SiC structure. Furthermore, the modified materials which exhibit good cytocompatibility upregulate bone-related genes and proteins expressions of the contacted bone mesenchymal stem cells (BMSCs). For the first time, it explores out that BMSCs osteogenesis on the antibacterial ceramic-like structure is mediated via the iNOS and nNOS signal pathways. The results reveal that in situ plasma fabrication of an antibacterial ceramic-like structure can endow PA66 with excellent surface hardness, cytocompatibility, as well as antibacterial capability. © 2016 Wiley Periodicals, Inc.

Process parameter and surface morphology of pineapple leaf electrospun nanofibers (PALF)

NASA Astrophysics Data System (ADS)

Surip, S. N.; Aziz, F. M. A.; Bonnia, N. N.; Sekak, K. A.; Zakaria, M. N.

2017-09-01

In recent times, nanofibers have attracted the attention of researchers due to their pronounced micro and nano structural characteristics that enable the development of advanced materials that have sophisticated applications. The production of nanofibers by the electrospinning process is influenced both by the electrostatic forces and the viscoelastic behavior of the polymer. Process parameters, like solution feed rate, applied voltage, nozzle-collector distance, and spinning environment, and material properties, like solution concentration, viscosity, surface tension, conductivity, and solvent vapor pressure, influence the structure and properties of electrospun nanofibers. Significant work has been done to characterize the properties of PALF nanofibers as a function of process and material parameters.

High-Temperature Storage Testing of ACF Attached Sensor Structures

PubMed Central

Lahokallio, Sanna; Hoikkanen, Maija; Vuorinen, Jyrki; Frisk, Laura

2015-01-01

Several electronic applications must withstand elevated temperatures during their lifetime. Materials and packages for use in high temperatures have been designed, but they are often very expensive, have limited compatibility with materials, structures, and processing techniques, and are less readily available than traditional materials. Thus, there is an increasing interest in using low-cost polymer materials in high temperature applications. This paper studies the performance and reliability of sensor structures attached with anisotropically conductive adhesive film (ACF) on two different organic printed circuit board (PCB) materials: FR-4 and Rogers. The test samples were aged at 200 °C and 240 °C and monitored electrically during the test. Material characterization techniques were also used to analyze the behavior of the materials. Rogers PCB was observed to be more stable at high temperatures in spite of degradation observed, especially during the first 120 h of aging. The electrical reliability was very good with Rogers. At 200 °C, the failures occurred after 2000 h of testing, and even at 240 °C the interconnections were functional for 400 h. The study indicates that, even though these ACFs were not designed for use in high temperatures, with stable PCB material they are promising interconnection materials at elevated temperatures, especially at 200 °C. However, the fragility of the structure due to material degradation may cause reliability problems in long-term high temperature exposure. PMID:28793735

Macroscopically Oriented Porous Materials with Periodic Ordered Structures: From Zeolites and Metal-Organic Frameworks to Liquid-Crystal-Templated Mesoporous Materials.

PubMed

Cho, Joonil; Ishida, Yasuhiro

2017-07-01

Porous materials with molecular-sized periodic structures, as exemplified by zeolites, metal-organic frameworks, or mesoporous silica, have attracted increasing attention due to their range of applications in storage, sensing, separation, and transformation of small molecules. Although the components of such porous materials have a tendency to pack in unidirectionally oriented periodic structures, such ideal types of packing cannot continue indefinitely, generally ceasing when they reach a micrometer scale. Consequently, most porous materials are composed of multiple randomly oriented domains, and overall behave as isotropic materials from a macroscopic viewpoint. However, if their channels could be unidirectionally oriented over a macroscopic scale, the resultant porous materials might serve as powerful tools for manipulating molecules. Guest molecules captured in macroscopically oriented channels would have their positions and directions well-defined, so that molecular events in the channels would proceed in a highly controlled manner. To realize such an ideal situation, numerous efforts have been made to develop various porous materials with macroscopically oriented channels. An overview of recent studies on the synthesis, properties, and applications of macroscopically oriented porous materials is presented. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Different Structural Materials on Neutronic Performance of a Hybrid Reactor

NASA Astrophysics Data System (ADS)

Übeyli, Mustafa; Tel, Eyyüp

2003-06-01

Selection of structural material for a fusion-fission (hybrid) reactor is very important by taking into account of neutronic performance of the blanket. Refractory metals and alloys have much higher operating temperatures and neutron wall load (NWL) capabilities than low activation materials (ferritic/martensitic steels, vanadium alloys and SiC/SiC composites) and austenitic stainless steels. In this study, effect of primary candidate refractory alloys, namely, W-5Re, T111, TZM and Nb-1Zr on neutronic performance of the hybrid reactor was investigated. Neutron transport calculations were conducted with the help of SCALE 4.3 System by solving the Boltzmann transport equation with code XSDRNPM. Among the investigated structural materials, tantalum had the worst performance due to the fact that it has higher neutron absorption cross section than others. And W-5Re and TZM having similar results showed the best performance.

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

Multi-functional metal-dielectric photonic structures

NASA Astrophysics Data System (ADS)

Smith, Kyle J.

In RF circuits and integrated photonics, it is important to effectively control an electromagnetic signal. This includes protecting of the network from high power and/or undesired signal flow, which is achieved with device functionalities such as isolation, circulation, switching, and limiting. In an attempt to develop light-weight, small-footprint, better protection devices, new designs have been sought utilizing materials that have been otherwise avoided due to some primary downside. For example, ferromagnetic metals like Iron and Cobalt, despite being powerful magnets, have been completely shunned for uses in nonreciprocal devices due to their overwhelming electric losses and high reflectivity. How could we utilize lossy materials in electromagnetic applications? In this thesis research, we design and fabricate metal-dielectric photonic structures in which metal can be highly transmissive, while the desired response (e.g., magneto-photonic response) is strongly enhanced. Moreover, the metal-dielectric structures can be designed to exhibit a sharp transition from the induced transmission to broadband opacity for oblique incidence and/or due to a tiny alteration of the photonic structure (e.g., because of nonlinearity). Thus, the photonic structures can be tailored to produce collimation and power-limiting effects. In the case of ferromagnetic metals, the metal-dielectric structure can be realized as an omnidirectional isolator passing radiation in a single direction and for a single frequency. The effectiveness of such structures will be verified in microwave measurements. Additionally, metal-dielectric structures including a nonlinear component will be shown to function as a reflective power limiter, thus providing a far superior alternative to absorptive, and often sacrificial, limiters.

Acoustic emission and acousto-ultrasonic signature analysis of failure mechanisms in carbon fiber reinforced polymer materials

NASA Astrophysics Data System (ADS)

Carey, Shawn Allen

Fiber reinforced polymer composite materials, particularly carbon (CFRPs), are being used for primary structural applications, particularly in the aerospace and naval industries. Advantages of CFRP materials, compared to traditional materials such as steel and aluminum, include: light weight, high strength to weight ratio, corrosion resistance, and long life expectancy. A concern with CFRPs is that despite quality control during fabrication, the material can contain many hidden internal flaws. These flaws in combination with unseen damage due to fatigue and low velocity impact have led to catastrophic failure of structures and components. Therefore a large amount of research has been conducted regarding nondestructive testing (NDT) and structural health monitoring (SHM) of CFRP materials. The principal objective of this research program was to develop methods to characterize failure mechanisms in CFRP materials used by the U.S. Army using acoustic emission (AE) and/or acousto-ultrasonic (AU) data. Failure mechanisms addressed include fiber breakage, matrix cracking, and delamination due to shear between layers. CFRP specimens were fabricated and tested in uniaxial tension to obtain AE and AU data. The specimens were designed with carbon fibers in different orientations to produce the different failure mechanisms. Some specimens were impacted with a blunt indenter prior to testing to simulate low-velocity impact. A signature analysis program was developed to characterize the AE data based on data examination using visual pattern recognition techniques. It was determined that it was important to characterize the AE event , using the location of the event as a parameter, rather than just the AE hit (signal recorded by an AE sensor). A back propagation neural network was also trained based on the results of the signature analysis program. Damage observed on the specimens visually with the aid of a scanning electron microscope agreed with the damage type assigned by the signature analysis program. The load level at which significant damage occurred in the specimens was evaluated using ASME Boiler and Pressure Vessel criteria. AU testing proved inconclusive for characterization of the damage due to common problems associated with AU testing such as: reproducibility difficulties due to degradation of the attachment of the sensors, damage not detected unless in the line of sight between sensors, and large intrinsic variation of the data.

Piezo impedance sensors to monitor degradation of biological structure

NASA Astrophysics Data System (ADS)

Annamdas, Kiran Kishore Kumar; Annamdas, Venu Gopal Madhav

2010-04-01

In some countries it is common to have wooden structures in their homes, especially Japan. However, metals and its alloys are the most widely used engineering materials in construction of any military or civil structure. Re-visiting natural disasters like the recent Haiti earthquake (12 Jan 2010) or Katrina (cyclones) reminds the necessity to have better housing infrastructure with robust monitoring systems. Traditionally wood (green material) was accepted as excellent rehabilitation material, after any disaster. In recent times, the recycling materials extracted from inorganic, biodegradable wastes are converted into blocks or sheets, and are also used to assist public in rehabilitation camps. The key issue which decreases the life of these rehabilitated structure including green materials (like wood) is unnecessary degradation or deterioration over time due to insect or acid attack or rain/ice fall. The recycling material also needs monitoring to protect them against acid or rain/ice attacks. Thus, a few health monitoring techniques have emerged in the recent past. Electromechanical Impedance technique is one such technique, which is simple but robust to detect variations in the integrity of structures. In this paper, impedance based piezoceramic sensor was bonded on wooden sample, which was subjected to degradation in presence of acids. Variations in mass of plank are studied.

Structural Evaluation of the RSRM Nozzle Replacement Adhesive

NASA Technical Reports Server (NTRS)

Batista-Rodriguez, A.; McLennan, M. L.; Palumbos, A. V.; Richardson, D. E.

1999-01-01

This paper describes the structural performance evaluation of a replacement adhesive for the Reusable Solid Rocket Motor (RSRM) nozzle utilizing finite element analysis. Due to material obsolescence and industrial safety issues, the two current structural adhesives, EA 913 and EA 946 are to be replaced with a new adhesive. TIGA 321. The structural evaluation in support of the adhesive replacement effort includes residual stress, transportation, and flight analyses. Factors of safety are calculated using the stress response from each analysis. The factors of safety are used as the limiting criteria to compare the replacement adhesive against the current adhesives. Included in this paper are the analytical approach, assumptions and modeling techniques as well as the results of the evaluation. An important factor to the evaluation is the similarity in constitutive material properties (elastic modulus and Poisson's ratio) between TIGA 321 and EA 913. This similarity leads to equivalent material response from the two adhesives. However, TIGA 321 surpasses EA 913's performance due to higher material capabilities. Conversely, the change in stress response from EA 946 to TIGA 321 is more apparent: this is primarily attributed to the difference in the modulii of the two adhesives, which differ by two orders of magnitude. The results of the bondline evaluation indicate that the replacement adhesive provides superior performance than the current adhesives with only minor exceptions. Furthermore, TIGA 321 causes only a minor chance in the response of the phenolic and metal components.

Carbon Nanofibrous Materials from Electrospinning: Preparation and Energy Applications

NASA Astrophysics Data System (ADS)

Aboagye, Alex

Carbon nanofibers with diameters that fall into submicron and nanometer range have attracted growing attention in recent years due to their superior chemical, electrical, and mechanical properties in combination with their unique one-dimensional nanostructures. Unlike catalytic synthesis, electrospinning polyacrylonitrile (PAN) followed by stabilization and carbonization has become a straightforward and convenient route to make continuous carbon nanofibers. The overall objective of this research was the design and production fiber based carbon nanomaterials, investigation of their structures and use in functional applications. Specifically, these carbon nanofibrous materials were employed as electrode material for energy storage and conversion devices such as dye sensitized solar cells and supercapacitors Morphology and structure of the carbon nanofibrous materials were investigated and their performance in corresponding applications were evaluated.

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.

Influence of the local structure in phase-change materials on their dielectric permittivity.

PubMed

Shportko, Kostiantyn V; Venger, Eugen F

2015-01-01

Ge-Sb-Te alloys, which belong to the phase-change materials, are promising materials for data storage and display and data visualization applications due to their unique properties. This includes a remarkable difference of their electrical and optical properties in the amorphous and crystalline state. Pronounced change of optical properties for Ge-Sb-Te alloys is linked to the different bonding types and different atomic arrangements in amorphous and crystalline states. The dielectric function of phase-change materials has been investigated in the far infrared (FIR) range. Phonons have been detected by FTIR spectroscopy. Difference of the dispersion of the dielectric permittivity of amorphous and crystalline samples is caused by different structures in different states which contribute to the dielectric permittivity.

Negative-pressure polymorphs made by heterostructural alloying

PubMed Central

Perkins, John D.

2018-01-01

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material’s structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures—a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixing two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2× to 4× lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. This example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties—materials that are otherwise nearly impossible to make. PMID:29725620

SVAS3: Strain Vector Aided Sensorization of Soft Structures.

PubMed

Culha, Utku; Nurzaman, Surya G; Clemens, Frank; Iida, Fumiya

2014-07-17

Soft material structures exhibit high deformability and conformability which can be useful for many engineering applications such as robots adapting to unstructured and dynamic environments. However, the fact that they have almost infinite degrees of freedom challenges conventional sensory systems and sensorization approaches due to the difficulties in adapting to soft structure deformations. In this paper, we address this challenge by proposing a novel method which designs flexible sensor morphologies to sense soft material deformations by using a functional material called conductive thermoplastic elastomer (CTPE). This model-based design method, called Strain Vector Aided Sensorization of Soft Structures (SVAS3), provides a simulation platform which analyzes soft body deformations and automatically finds suitable locations for CTPE-based strain gauge sensors to gather strain information which best characterizes the deformation. Our chosen sensor material CTPE exhibits a set of unique behaviors in terms of strain length electrical conductivity, elasticity, and shape adaptability, allowing us to flexibly design sensor morphology that can best capture strain distributions in a given soft structure. We evaluate the performance of our approach by both simulated and real-world experiments and discuss the potential and limitations.

Delithiated states of layered cathode materials: doping and dispersion interaction effects on the structure

NASA Astrophysics Data System (ADS)

Eremin, Roman; Zolotarev, Pavel; Bobrikov, Ivan

2018-04-01

Here we present results of density functional theory (DFT) study of delithiated structures of layered LiNiO2 (LNO, Li12Ni12O24 model) cathode material and its doped analogue LiNi0.833Co0.083Al0.083O2 (N10C1A1, Li12Ni10CoAlO24 model). The paper is aimed at independent elucidation of doping and dispersion interaction effects on the structural stability of cathode materials studied. For this purpose, the LNO and N10C1A1 configurational spaces consisting of 87 and 4512 crystallographically independent configurations (obtained starting from 2×2×1 supercell of R-3m structure of LNO) are optimized within a number of DFT models. Based on a comparison of the calculated dependencies for the lattice parameters with the results of in situ neutron diffraction experiments, the most pronounced effect of cathode material stabilization is due to the dispersion interaction. In turn, the doping effect is found to affect cathode structure behavior at the latest stages of delithiation only.

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

Jiang, Xiujuan; Whalen, Scott A.; Darsell, Jens T.

Soft magnetic materials are often limited in scalability due to conventional processes that do not retain beneficial microstructures, and their associated physical properties, during densification. In this work, friction consolidation (FC) has been studied to fabricate Fe-Si soft magnetic materials from gas-atomized powder precursors. Fe-Si powder is consolidated using variable pressure and tool rotation speed in an effort to evaluate this unique densification approach for potential improvements in magnetic properties. FC, due to the high shear deformation involved, is shown to result in uniform gradual grain structure refinement across the consolidated workpiece from the center nearest the tool to themore » edge. Magnetic properties along different orientations indicate little, if any, textural orientation in the refined grain structure. The effect of annealing on the magnetic properties is evaluated and shown to decrease coercivity. FC processing was able to retain the magnetization of the original gas-atomized powders but further process optimization is needed to reach the optimal coercivity for the soft magnetic materials applications.« less

Pressure induced structural transitions in Lead Chalcogenides and its influence on thermoelectric properties

NASA Astrophysics Data System (ADS)

Petersen, John; Spinks, Michael; Borges, Pablo; Scolfaro, Luisa

2012-03-01

Lead chalcogenides, most notably PbTe and PbSe, have become an active area of research due to their thermoelectric (TE) properties. The high figure of merit (ZT) of these materials has brought much attention to them, due to their ability to convert waste heat into electricity, with a possible application being in engine exhaust. Here, we examine the effects of altering the lattice parameter on total ground state energy and the band gap using first principles calculations performed within Density Functional Theory and the Projector Augmented Wave approach and the Vienna Ab-initio Simulation Package (VASP-PAW) code. Both PbTe and PbSe, in NaCl, orthorhombic, and CsCl structures are considered. It is found that altering the lattice parameter, which is analogous to applying external pressure on the material experimentally, has notable effects on both ground state energy and the band gap. The implications of this behavior in the TE properties of these materials are analyzed.

Exploring the significance of structural hierarchy in material systems-A review

NASA Astrophysics Data System (ADS)

Pan, Ning

2014-06-01

Structural hierarchy and heterogeneity are inherent features in biological materials, but their significance in affecting the system behaviors is yet to be fully understood. In Sec. I, this article first identifies the major characteristics that manifest, or are resulted from, such hierarchy and heterogeneity in materials. Then in Sec. II, it presents several typical natural material systems including wood, bone, and others from animals to illustrate the proposed views. The paper also discusses a man-made smart material, textiles, to demonstrate that textiles are hierarchal, multifunctional, highly complex, and arguably the engineered material closest on a par with biological materials in complexity, and, more importantly, we can still learn quite a few new things from them in development of novel materials. In Sec. III, the paper summarizes several general approaches in developing a hierarchal material system at various scales, including structure thinning and splitting, laminating and layering, spatial and angular orientation, heterogenization and hybridization, and analyzes the advantages associated with them. It also stresses the adverse consequences once the existing structural hierarchy breaks down due to various mutations in biological systems. It discusses, in particular, the influences of moisture and air on material properties, given the near ubiquitousness of both air and water in materials. It next deals with in Sec. IV, some theoretical issues in material research including packing and ordering, the bi-modular mechanics, the behavior non-affinities due to disparity in hierarchal levels, the importance of system dimensionality in a hierarchal material system, and more philosophically, the issues of Nature's wisdom versus Intelligent Design. Section V then offers some concluding remarks, including a recap of the major issues covered in this article, and some general conclusions derived from the analyses and discussions. The main purpose of this paper is to make an effort to explore, identify, derive, or theorize some generic principles based on the existing results, not to offer another comprehensive review of current research activities in the fields for that there already exist some excellent ones. This paper examines the related topics with several approaches to not only reveal the underlying geometrical and physical mechanisms but also to emphasize the ways in which such mechanisms may be applied to developing engineered material systems with novel properties.

Crash energy management on the base of Movable cellular automata method

NASA Astrophysics Data System (ADS)

Psakhie, Serguei; Dmitriev, Andrei; Shilko, Evgueni; Tatarintsev, Evgueni; Korostelev, Serguei

2001-06-01

One of the main problems of materials science is increasing of structure's viability under dynamic loading. In general, a solution is the management of transformation of the energy of loading to the energy of destroying of the least important parts and details of the structure. It has to be noted that similar problem also exists in materials science, since a majority of modern materials are heterogeneous and have a complex internal structure. To optimize this structure for working under dynamic loading it is necessary to take into account the redistribution of elastic energy including phase transformation, generation and accumulation of micro-damages, etc. As far as real experiments on destroying the complex objects are sufficiently expensive and getting of detailed information is often associates with essential difficulties, the methods of computer modeling are used in solving the similar problems. As a rule, these are the methods of continuum mechanics. Although essential achievements have been obtained on the basis of these methods the continuum approach has several limitations, connected first of all with the possibility of description of generation of damages, formation and development of cracks and mass mixing effects. These problems may be solved on the basis of the Movable Cellular Automata (MCA) method, which has been successfully used for modeling fracture of the different material and structures In the paper behavior and peculiarities of failure of complex structures and materials under dynamic loading are studied on the basis of computer modeling. The results shown that sometimes even small changes of the internal structure leads to the significant increasing of the viability of the complex structures and materials. It is due to the elastic energy flux change over during the dynamical loading. This effect may be explained by the fact that elastic energy fluxes define the current stress concentration. Namely, because the area of inclusions are subjected by the largest displacement and due to less Young modulus of inclusions the loading pulses are transferred towards the other parts of the sample. This leads to "blurring" of the stress concentrators and conservation of wholeness of the structure. In its turn, this leads to essential raising up of threshold value of "injected" energy, i.e. the energy absorbed by the structure before loss of its carrying capacity. Practically, elastic energy "circulates" in the structure until a stress concentrator appears, which power will be sufficient for forming a macro-cracks. The results demonstrate a possibility of managing the fracture process under dynamic loading and raising viability of structures and heterogeneous materials by changing their internal structure, geometry, so by entering the specific inclusions.

Crash simulation of hybrid structures considering the stress and strain rate dependent material behavior of thermoplastic materials

NASA Astrophysics Data System (ADS)

Hopmann, Ch.; Schöngart, M.; Weber, M.; Klein, J.

2015-05-01

Thermoplastic materials are more and more used as a light weight replacement for metal, especially in the automotive industry. Since these materials do not provide the mechanical properties, which are required to manufacture supporting elements like an auto body or a cross bearer, plastics are combined with metals in so called hybrid structures. Normally, the plastics components are joined to the metal structures using different technologies like welding or screwing. Very often, the hybrid structures are made of flat metal parts, which are stiffened by a reinforcement structure made of thermoplastic materials. The loads on these structures are very often impulsive, for example in the crash situation of an automobile. Due to the large stiffness variation of metal and thermoplastic materials, complex states of stress and very high local strain rates occur in the contact zone under impact conditions. Since the mechanical behavior of thermoplastic materials is highly dependent on these types of load, the crash failure of metal plastic hybrid parts is very complex. The problem is that the normally used strain rate dependent elastic/plastic material models are not capable to simulate the mechanical behavior of thermoplastic materials depended on the state of stress. As part of a research project, a method to simulate the mechanical behavior of hybrid structures under impact conditions is developed at the IKV. For this purpose, a specimen for the measurement of mechanical properties dependet on the state of stress and a method for the strain rate depended characterization of thermoplastic materials were developed. In the second step impact testing is performed. A hybrid structure made from a metal sheet and a reinforcement structure of a Polybutylenterephthalat Polycarbonate blend is tested under impact conditions. The measured stress and strain rate depended material data are used to simulate the mechanical behavior of the hybrid structure under highly dynamic load with impact velocities up to 5 m/s. The mechanical behavior of the plastics structure is simulated using a quadratic yield surface, which takes the state of stress and the strain rate into account. The FE model is made from mid surface elements to reduce the computing time.

Metal segregation in hierarchically structured cathode materials for high-energy lithium batteries

DOE PAGES

Lin, Feng; Xin, Huolin L.; Nordlund, Dennis; ...

2016-01-11

Controlling surface and interfacial properties of battery materials is key to improving performance in rechargeable Li-ion devices. Surface reconstruction from a layered to a rock salt structure in metal oxide cathode materials is commonly observed and results in poor high-voltage cycling performance, impeding attempts to improve energy density. Hierarchically structured LiNi 0.4Mn 0.4Co 0.2O 2 (NMC-442) spherical powders, made by spray pyrolysis, exhibit local elemental distribution gradients that deviate from the global NMC-442 composition; specifically, they are Ni-rich and Mn-poor at particle surfaces. These materials demonstrate improved Coulombic efficiencies, discharge capacities, and high-voltage capacity retention in lithium half-cell configurations. Themore » subject powders show superior resistance against surface reconstruction due to the tailored surface chemistry, compared to conventional NMC-442 materials. This paves the way towards the development of a new generation of robust and stable high-energy NMC cathodes for Li-ion batteries.« less

Preparation and Sound Absorption Properties of a Barium Titanate/Nitrile Butadiene Rubber–Polyurethane Foam Composite with Multilayered Structure

PubMed Central

Jiang, Xueliang; Yang, Zhen; Wang, Zhijie; Zhang, Fuqing; You, Feng

2018-01-01

Barium titanate/nitrile butadiene rubber (BT/NBR) and polyurethane (PU) foam were combined to prepare a sound-absorbing material with an alternating multilayered structure. The effects of the cell size of PU foam and the alternating unit number on the sound absorption property of the material were investigated. The results show that the sound absorption efficiency at a low frequency increased when decreasing the cell size of PU foam layer. With the increasing of the alternating unit number, the material shows the sound absorption effect in a wider bandwidth of frequency. The BT/NBR-PU foam composites with alternating multilayered structure have an excellent sound absorption property at low frequency due to the organic combination of airflow resistivity, resonance absorption, and interface dissipation. PMID:29565321

Preparation and Sound Absorption Properties of a Barium Titanate/Nitrile Butadiene Rubber-Polyurethane Foam Composite with Multilayered Structure.

PubMed

Jiang, Xueliang; Yang, Zhen; Wang, Zhijie; Zhang, Fuqing; You, Feng; Yao, Chu

2018-03-22

Barium titanate/nitrile butadiene rubber (BT/NBR) and polyurethane (PU) foam were combined to prepare a sound-absorbing material with an alternating multilayered structure. The effects of the cell size of PU foam and the alternating unit number on the sound absorption property of the material were investigated. The results show that the sound absorption efficiency at a low frequency increased when decreasing the cell size of PU foam layer. With the increasing of the alternating unit number, the material shows the sound absorption effect in a wider bandwidth of frequency. The BT/NBR-PU foam composites with alternating multilayered structure have an excellent sound absorption property at low frequency due to the organic combination of airflow resistivity, resonance absorption, and interface dissipation.

Challenges for Insertion of Structural Nanomaterials in Aerospace Applications

NASA Technical Reports Server (NTRS)

Sochi, Emilie J.

2012-01-01

In the two decades since Iijima's report on carbon nanotubes (CNT), there has been great interest in realizing the benefits of mechanical properties observed at the nanoscale in large-scale structures. The weight savings possible due to dramatic improvements in mechanical properties relative to state-of-the-art material systems can be game changing for applications like aerospace vehicles. While there has been significant progress in commercial production of CNTs, major aerospace applications that take advantage of properties offered by this material have yet to be realized. This paper provides a perspective on the technical challenges and barriers for insertion of CNTs as an emerging material technology in aerospace applications and proposes approaches that may reduce the typical timeframe for technology maturation and insertion into aerospace structures.

Development of a composite geodetic structure for space construction, phase 1A

NASA Technical Reports Server (NTRS)

1980-01-01

The development of a geodetic beam and beam builder for on orbit construction of large truss type space structures is discussed. The geodetic beam is a lightweight, open lattice structure composed of an equilateral gridwork of crisscrossing rods. The beam provides a high degree of stiffness and minimizes structural distortion, due to temperature gradients, through the incorporation of a new graphite and glass reinforced thermoplastic composite material with a low coefficient of thermal expansion. A low power consuming, high production rate, beam builder automatically fabricates the geodetic beams in space using rods preprocessed on Earth. Three areas of the development are focused upon; (1) geodetic beam designs for local attachment of equipment or beam to beam joining in a parallel or crossing configurations, (2) evaluation of long life pultruded rods capable of service temperatures higher than possible with the HMS/P1700 rod material, and (3) evalaution of high temperature joint encapsulant materials.

Amorphous Mn oxide-ordered mesoporous carbon hybrids as a high performance electrode material for supercapacitors.

PubMed

Nam, Inho; Kim, Nam Dong; Kim, Gil-Pyo; Park, Junsu; Yi, Jongheop

2012-07-01

A supercapacitor has the advantages of both the conventional capacitors and the rechargeable batteries. Mn oxide is generally recognized one of the potential materials that can be used for a supercapacitor, but its low conductivity is a limiting factor for electrode materials. In this study, a hybrid of amorphous Mn oxide (AMO) and ordered mesoporous carbon (OMC) was prepared and characterized using X-ray diffraction, transmission electron microscopy, N2/77 K sorption techniques, and electrochemical analyses. The findings indicate that the electrochemical activities of Mn oxide were facilitated when it was in the hybrid state because OMC acted as a pathway for both the electrolyte ions and the electrons due to the characteristics of the ordered mesoporous structure. The ordered mesoporous structure of OMC was well maintained even after hybridization with amorphous Mn oxide. The electrochemical-activity tests revealed that the AMO/OMC hybrid had a higher specific capacitance and conductivity than pure Mn oxide. In the case where the Mn/C weight ratio was 0.75, the composite showed a high capacitance of 153 F/g, which was much higher than that for pure Mn oxide, due to the structural effects of OMC.

FEM modeling of postseismic deformation of poroelastic material

NASA Astrophysics Data System (ADS)

Kawamoto, S.; Ito, T.; Hirahara, K.

2004-12-01

Following a large earthquake, postseismic deformation in the focal region has been observed by GPS, leveling measurements and the other geodetic measurements. To explain the postseismic deformation, researchers have proposed and well investigated two physical mechanisms of afterslip and viscoelastic relaxation. In some cases, however, there have been observed postseismic deformation which can not be explained by these mechanisms. Therefore, another mechanism has been proposed, where the crust is treated as "poroelastic material". This concept is called "poroelasticity". In this concept, postseismic deformation is caused by pore fluid flow due to the coseismic stress redistribution. We explored, therefore, the postseismic deformation due to pore fluid flow in a poroelastic material using finite element method (FEM), which can easily handle lateral variations of hydraulic diffusivity and elastic or plastic property. We used the FEM program 'CAMBIOT3D' originally developed by Geotech. Lab. Gunma University, Japan (2003). Because this program was developed for soil mechanics, we must have modified so as to calculate deformation due to earthquake faulting. We implemented the 'split node technique' (Melosh and Refsky, 1981) to calculate the coseismic deformation. In addition to this, we modified the program to calculate the deformation taking into account the Skempton's B. This coefficient B determines what fraction of the coseismic stress due to an earthquake is allotted to pore pressure. Without Skempton's B, coseismic pore pressure becomes too large and hence postseismic deformation is calculated too large. We evaluated the postseismic deformation in a poroelastic material to show that the poroelastic deformation is quite different from that of afterslip and viscoelastic relaxation models. In this presentation, we show the postseismic deformation due to pore fluids flow in a poroelastic material and the effect of Skempton's B. Especially, we discuss what different pattern of postseismic deformation is produced depending on the lateral variation of hydraulic diffusivity structures in and around the fault zone, which structures have been differently inferred from fault zone core sampling researches and so on.

Environment and human friendly colored materials prepared using black and white components.

PubMed

Takeoka, Yukikazu

2018-05-10

Our lives in the present age are full of colorful items. However, when many coloring materials cannot be used due to environmental concerns, this colorful life that has been constructed will be diminished. Maintaining our rich lifestyle necessitates the development of technologies that can make safe and secure color materials from materials with less burden on people and the environment. Herein, the author reveals that structural colored materials with little angle dependence can be prepared using various materials with short-range order in the refractive index, which is comparable to the wavelength of visible light, and with the aid of a black substance. This approach enables the preparation of colorful materials from materials that have a low environmental burden and are non-toxic to living things; examples of such materials include silica, carbon black, and iron oxide. If we can achieve mechanical stabilization and hue stabilization of these coloring materials, we can develop new green pigments with low toxicity, good color development, and high durability. The use of conventional angular-dependent structural colored materials has been limited. However, structural colored materials with no angle dependence, such as those prepared by the author, can be used in fields where pigments have traditionally been used. For example, they could be used in coating materials for automobiles and buildings, and in pigments used by artists. Environmentally friendly green color materials are expected to promote sustainable development. In this review, I will describe how to prepare structural colored materials with less angle dependency using white and black substances previously reported by the author.

Optimization of SMA layers in composite structures to enhance damping

NASA Astrophysics Data System (ADS)

Haghdoust, P.; Cinquemani, S.; Lecis, N.; Bassani, P.

2016-04-01

The performance of lightweight structures can be severely affected by vibration. New design concepts leading to lightweight, slender structural components can increase the vulnerability of the components to failure due to excessive vibration. The intelligent approach to address the problem would be the use of materials which are more capable in dissipating the energy due to their high value of loss factor. Among the different materials available to achieve damping, much attention has been attached to the use of shape memory alloys (SMAs) because of their unique microstructure, leading to good damping capacity. This work describes the design and optimization of a hybrid layered composite structure for the passive suppression of flexural vibrations in slender and light structures. Embedding the SMA layers in composite structure allows to combine different properties: the lightness of the base composite (e.g. fiber glass), the mechanical strength of the insert of metallic material and the relevant damping properties of SMA, in the martensitic phase. In particular, we put our attention on embedding the CuZnAl in the form of thin sheet in a layered composite made by glass fiber reinforced epoxy. By appropriately positioning of the SMA sheets so that they are subjected to the maximum curvature, the damping of the hybrid system can be considerably enhanced. Accordingly analytical method for evaluating the energy dissipation of the thin sheets with different shapes and patterns is developed and is followed by a shape optimization based on genetic algorithm. Eventually different configurations of the hybrid beam structure with different patterns of SMA layer are proposed and compared in the term of damping capacity.

Probabilistic material degradation model for aerospace materials subjected to high temperature, mechanical and thermal fatigue, and creep

NASA Technical Reports Server (NTRS)

Boyce, L.

1992-01-01

A probabilistic general material strength degradation model has been developed for structural components of aerospace propulsion systems subjected to diverse random effects. The model has been implemented in two FORTRAN programs, PROMISS (Probabilistic Material Strength Simulator) and PROMISC (Probabilistic Material Strength Calibrator). PROMISS calculates the random lifetime strength of an aerospace propulsion component due to as many as eighteen diverse random effects. Results are presented in the form of probability density functions and cumulative distribution functions of lifetime strength. PROMISC calibrates the model by calculating the values of empirical material constants.

Stabilization of Wide Band-Gap p-Type Wurtzite MnTe Thin Films on Amorphous Substrates

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

Zakutayev, Andriy A; Siol, Sebastian; Han, Yanbing

An important challenge in the development of optoelectronic devices for energy conversion applications is the search for suitable p-type contact materials. For example, p-type MnTe would be a promising alternative back contact to due to their chemical compatibility, but at normal conditions it has too narrow band gap due to octahedrally coordinated nickeline (NC) structure. The tetrahedrally coordinated wurtzite (WZ) polymorph of MnTe has not been reported, but it is especially interesting due to its predicted wider band gap, and because of better structural compatibility with CdTe and related II-VI semiconductor materials. Here, we report on the stabilization of WZ-MnTemore » thin films on amorphous indium zinc oxide (a-IZO) substrates relevant to photovoltaic applications. Optical spectroscopy of the WZ-MnTe films shows a wide direct band gap of Eg = 2.7 eV, while PES measurements reveal weak p-type doping with the Fermi level 0.6 eV above the valence band maximum. The results of electron microscopy and photoelectron spectroscopy (PES) measurements indicate that the WZ-MnTe is stabilized due to interdiffusion at the interface with IZO. The results of this work introduce a substrate stabilized WZ-MnTe polymorph as a potential p-type contact material candidate for future applications in CdTe devices for solar energy conversion and other optoelectronic technologies.« 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 Review: Fundamental Aspects of Silicate Mesoporous Materials

PubMed Central

ALOthman, Zeid A.

2012-01-01

Silicate mesoporous materials have received widespread interest because of their potential applications as supports for catalysis, separation, selective adsorption, novel functional materials, and use as hosts to confine guest molecules, due to their extremely high surface areas combined with large and uniform pore sizes. Over time a constant demand has developed for larger pores with well-defined pore structures. Silicate materials, with well-defined pore sizes of about 2.0–10.0 nm, surpass the pore-size constraint (<2.0 nm) of microporous zeolites. They also possess extremely high surface areas (>700 m2 g−1) and narrow pore size distributions. Instead of using small organic molecules as templating compounds, as in the case of zeolites, long chain surfactant molecules were employed as the structure-directing agent during the synthesis of these highly ordered materials. The structure, composition, and pore size of these materials can be tailored during synthesis by variation of the reactant stoichiometry, the nature of the surfactant molecule, the auxiliary chemicals, the reaction conditions, or by post-synthesis functionalization techniques. This review focuses mainly on a concise overview of silicate mesoporous materials together with their applications. Perusal of the review will enable researchers to obtain succinct information about microporous and mesoporous materials.

Non-linear Mechanics of Three-dimensional Architected Materials; Design of Soft and Functional Systems and Structures

NASA Astrophysics Data System (ADS)

Babaee, Sahab

In the search for materials with new properties, there have been significant advances in recent years aimed at the construction of architected materials whose behavior is governed by structure, rather than composition. Through careful design of the material's architecture, new mechanical properties have been demonstrated, including negative Poisson's ratio, high stiffness to weight ratio and mechanical cloaking. However, most of the proposed architected materials (also known as mechanical metamaterials) have a unique structure that cannot be recon figured after fabrication, making them suitable only for a specific task. This thesis focuses on the design of architected materials that take advantage of the applied large deformation to enhance their functionality. Mechanical instabilities, which have been traditionally viewed as a failure mode with research focusing on how to avoid them, are exploited to achieve novel and tunable functionalities. In particular I demonstrate the design of mechanical metamaterials with tunable negative Poisson ratio, adaptive phononic band gaps, acoustic switches, and reconfigurable origami-inspired waveguides. Remarkably, due to large deformation capability and full reversibility of soft materials, the responses of the proposed designs are reversible, repeatable, and scale independent. The results presented here pave the way for the design of a new class of soft, active, adaptive, programmable and tunable structures and systems with unprecedented performance and improved functionalities.

Two-Dimensional Porous Carbon: Synthesis and Ion-Transport Properties.

PubMed

Zheng, Xiaoyu; Luo, Jiayan; Lv, Wei; Wang, Da-Wei; Yang, Quan-Hong

2015-09-23

Their chemical stability, high specific surface area, and electric conductivity enable porous carbon materials to be the most commonly used electrode materials for electrochemical capacitors (also known as supercapacitors). To further increase the energy and power density, engineering of the pore structures with a higher electrochemical accessible surface area, faster ion-transport path and a more-robust interface with the electrolyte is widely investigated. Compared with traditional porous carbons, two-dimensional (2D) porous carbon sheets with an interlinked hierarchical porous structure are a good candidate for supercapacitors due to their advantages in high aspect ratio for electrode packing and electron transport, hierarchical pore structures for ion transport, and short ion-transport length. Recent progress on the synthesis of 2D porous carbons is reported here, along with the improved electrochemical behavior due to enhanced ion transport. Challenges for the controlled preparation of 2D porous carbons with desired properties are also discussed; these require precise tuning of the hierarchical structure and a clarification of the formation mechanisms. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Probabilistic fatigue life prediction of metallic and composite materials

NASA Astrophysics Data System (ADS)

Xiang, Yibing

Fatigue is one of the most common failure modes for engineering structures, such as aircrafts, rotorcrafts and aviation transports. Both metallic materials and composite materials are widely used and affected by fatigue damage. Huge uncertainties arise from material properties, measurement noise, imperfect models, future anticipated loads and environmental conditions. These uncertainties are critical issues for accurate remaining useful life (RUL) prediction for engineering structures in service. Probabilistic fatigue prognosis considering various uncertainties is of great importance for structural safety. The objective of this study is to develop probabilistic fatigue life prediction models for metallic materials and composite materials. A fatigue model based on crack growth analysis and equivalent initial flaw size concept is proposed for metallic materials. Following this, the developed model is extended to include structural geometry effects (notch effect), environmental effects (corroded specimens) and manufacturing effects (shot peening effects). Due to the inhomogeneity and anisotropy, the fatigue model suitable for metallic materials cannot be directly applied to composite materials. A composite fatigue model life prediction is proposed based on a mixed-mode delamination growth model and a stiffness degradation law. After the development of deterministic fatigue models of metallic and composite materials, a general probabilistic life prediction methodology is developed. The proposed methodology combines an efficient Inverse First-Order Reliability Method (IFORM) for the uncertainty propogation in fatigue life prediction. An equivalent stresstransformation has been developed to enhance the computational efficiency under realistic random amplitude loading. A systematical reliability-based maintenance optimization framework is proposed for fatigue risk management and mitigation of engineering structures.

Multi-Scale Analyses of Three Dimensional Woven Composite 3D Shell With a Cut Out Circle

NASA Astrophysics Data System (ADS)

Nguyen, Duc Hai; Wang, Hu

2018-06-01

A composite material are made by combining two or more constituent materials to obtain the desired material properties of each product type. The matrix material which can be polymer and fiber is used as reinforcing material. Currently, the polymer matrix is widely used in many different fields with differently designed structures such as automotive structures and aviation, aerospace, marine, etc. because of their excellent mechanical properties; in addition, they possess the high level of hardness and durability together with a significant reduction in weight compared to traditional materials. However, during design process of structure, there will be many interruptions created for the purpose of assembling the structures together or for many other design purposes. Therefore, when this structure is subject to load-bearing, its failure occurs at these interruptions due to stress concentration. This paper proposes multi-scale modeling and optimization strategies in evaluation of the effectiveness of fiber orientation in an E-glass/Epoxy woven composite 3D shell with circular holes at the center investigated by FEA results. A multi-scale model approach was developed to predict the mechanical behavior of woven composite 3D shell with circular holes at the center with different designs of material and structural parameters. Based on the analysis result of laminae, we have found that the 3D shell with fiber direction of 450 shows the best stress and strain bearing capacity. Thus combining several layers of 450 fiber direction in a multi-layer composite 3D shell reduces the stresses concentrated on the cuts of the structures.

Rigidified pneumatic composites

NASA Astrophysics Data System (ADS)

van Dessel, Steven

2000-10-01

The overall objective of the research presented in this dissertation was to address global issues of adequate housing for all and the need for more sustainable human settlement. In order to address these, the emerging technology of rigidified pneumatic composites was investigated. Rigidified pneumatic composites (RPC) are defined as thin flexible membrane structures that are pneumatically deployed. After deployment, these structures harden due to chemical or physical change of the membrane. Because of this change, these structures do no longer require pneumatic pressure to maintain their shape. For the first time, a systematic listing of the various means available to develop polymeric materials useful in RPC technology is presented. With the aim to reduce the cost of RPC structures, a new material was proposed, developed, and evaluated. This material involved the formation of a semi-interpenetrating polymer network based on poly vinyl chloride and an acrylate based reactive plasticizer. The economical and environmental performances of RPC structures using this new material were assessed by means of a case study. In this study, the performance of RPC technology was compared with that of a typical wood light frame structure in the application of a small single-family house. The study indicated that the cost of ownership in present day value for the RPC structure was approximately 33% less than the cost of a comparable wood light frame structure. The study also indicated that significant environmental benefits exist with the use of RPC structures. It was found that the RPC structure used significantly less resources compared to the wood light frame structure. About 3.5 times less materials coming from non-renewable fossil resources, about 2.5 times less materials coming from trees, and about 19 times less materials coming from inorganic resources was used in the RPC structure relative to the wood light frame structure. The study concluded with pointing out various means available to further increase the economical and environmental performance of RPC technology. Directions were provided to guide future developments of RPC technology.

Active printed materials for complex self-evolving deformations.

PubMed

Raviv, Dan; Zhao, Wei; McKnelly, Carrie; Papadopoulou, Athina; Kadambi, Achuta; Shi, Boxin; Hirsch, Shai; Dikovsky, Daniel; Zyracki, Michael; Olguin, Carlos; Raskar, Ramesh; Tibbits, Skylar

2014-12-18

We propose a new design of complex self-evolving structures that vary over time due to environmental interaction. In conventional 3D printing systems, materials are meant to be stable rather than active and fabricated models are designed and printed as static objects. Here, we introduce a novel approach for simulating and fabricating self-evolving structures that transform into a predetermined shape, changing property and function after fabrication. The new locally coordinated bending primitives combine into a single system, allowing for a global deformation which can stretch, fold and bend given environmental stimulus.

Active Printed Materials for Complex Self-Evolving Deformations

PubMed Central

Raviv, Dan; Zhao, Wei; McKnelly, Carrie; Papadopoulou, Athina; Kadambi, Achuta; Shi, Boxin; Hirsch, Shai; Dikovsky, Daniel; Zyracki, Michael; Olguin, Carlos; Raskar, Ramesh; Tibbits, Skylar

2014-01-01

We propose a new design of complex self-evolving structures that vary over time due to environmental interaction. In conventional 3D printing systems, materials are meant to be stable rather than active and fabricated models are designed and printed as static objects. Here, we introduce a novel approach for simulating and fabricating self-evolving structures that transform into a predetermined shape, changing property and function after fabrication. The new locally coordinated bending primitives combine into a single system, allowing for a global deformation which can stretch, fold and bend given environmental stimulus. PMID:25522053

The Characterization of Material Properties and Structural Dynamics of the Manduca Sexta Forewing for Application to Flapping Wing Micro Air Vehicle Design

DTIC Science & Technology

2012-09-13

2.1.1 Wing Morphology. Insect wings are formed from a complex makeup of polymer based chains, Chitin , that form the Cuticle, which provides the strong... Chitin , a long-chain polymer and a deriva- tive of glucose, is the main component of the exoskeletons and wings of insects . Due to the ability of the...biological specimen to vary the bonding chains, assemblage of nanofibers, and crystalline structure, the material properties of chitin can vary over a

Photonic band structures in one-dimensional photonic crystals containing Dirac materials

NASA Astrophysics Data System (ADS)

Wang, Lin; Wang, Li-Gang

2015-09-01

We have investigated the band structures of one-dimensional photonic crystals (1DPCs) composed of Dirac materials and ordinary dielectric media. It is found that there exist an omnidirectional passing band and a kind of special band, which result from the interaction of the evanescent and propagating waves. Due to the interface effect and strong dispersion, the electromagnetic fields inside the special bands are strongly enhanced. It is also shown that the properties of these bands are invariant upon the lattice constant but sensitive to the resonant conditions.

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

NASA Astrophysics Data System (ADS)

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

2017-07-01

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

Deterioration of organic packing materials commonly used in air biofiltration: effect of VOC-packing interactions.

PubMed

Lebrero, Raquel; Estrada, José M; Muñoz, Raúl; Quijano, Guillermo

2014-05-01

The abiotic deterioration of three conventional organic packing materials used in biofiltration (compost, wood bark and Macadamia nutshells) caused by their interaction with toluene (used as a model volatile organic compound) was here studied. The deterioration of the materials was evaluated in terms of structural damage, release of co-substrates and increase of the packing biodegradability. After 21 days of exposure to toluene, all packing materials released co-substrates able to support microbial growth, which were not released by the control materials not exposed to toluene. Likewise, the exposure to toluene increased the packing material biodegradability by 26% in wood bark, 20% in compost and 17% in Macadamia nutshells. Finally, scanning electron microscopy analysis confirmed the deterioration in the structure of the packing materials evaluated due to the exposure to toluene, Macadamia nutshells being the material with the highest resistance to volatile organic compound attack. Copyright © 2014 Elsevier Ltd. All rights reserved.

Robust ferromagnetism in monolayer chromium nitride

PubMed Central

Zhang, Shunhong; Li, Yawei; Zhao, Tianshan; Wang, Qian

2014-01-01

Design and synthesis of two-dimensional (2D) materials with robust ferromagnetism and biocompatibility is highly desirable due to their potential applications in spintronics and biodevices. However, the hotly pursued 2D sheets including pristine graphene, monolayer BN, and layered transition metal dichalcogenides are nonmagnetic or weakly magnetic. Using biomimetic particle swarm optimization (PSO) technique combined with ab initio calculations we predict the existence of a 2D structure, a monolayer of rocksalt-structured CrN (100) surface, which is both ferromagnetic and biocompatible. Its dynamic, thermal and magnetic stabilities are confirmed by carrying out a variety of state-of-the-art theoretical calculations. Analyses of its band structure and density of states reveal that this material is half-metallic, and the origin of the ferromagnetism is due to p-d exchange interaction between the Cr and N atoms. We demonstrate that the displayed ferromagnetism is robust against thermal and mechanical perturbations. The corresponding Curie temperature is about 675 K which is higher than that of most previously studied 2D monolayers. PMID:24912562

Evading the strength–ductility trade-off dilemma in steel through gradient hierarchical nanotwins

PubMed Central

Wei, Yujie; Li, Yongqiang; Zhu, Lianchun; Liu, Yao; Lei, Xianqi; Wang, Gang; Wu, Yanxin; Mi, Zhenli; Liu, Jiabin; Wang, Hongtao; Gao, Huajian

2014-01-01

The strength–ductility trade-off has been a long-standing dilemma in materials science. This has limited the potential of many structural materials, steels in particular. Here we report a way of enhancing the strength of twinning-induced plasticity steel at no ductility trade-off. After applying torsion to cylindrical twinning-induced plasticity steel samples to generate a gradient nanotwinned structure along the radial direction, we find that the yielding strength of the material can be doubled at no reduction in ductility. It is shown that this evasion of strength–ductility trade-off is due to the formation of a gradient hierarchical nanotwinned structure during pre-torsion and subsequent tensile deformation. A series of finite element simulations based on crystal plasticity are performed to understand why the gradient twin structure can cause strengthening and ductility retention, and how sequential torsion and tension lead to the observed hierarchical nanotwinned structure through activation of different twinning systems. PMID:24686581

Micromechanics Fatigue Damage Analysis Modeling for Fabric Reinforced Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Min, J. B.; Xue, D.; Shi, Y.

2013-01-01

A micromechanics analysis modeling method was developed to analyze the damage progression and fatigue failure of fabric reinforced composite structures, especially for the brittle ceramic matrix material composites. A repeating unit cell concept of fabric reinforced composites was used to represent the global composite structure. The thermal and mechanical properties of the repeating unit cell were considered as the same as those of the global composite structure. The three-phase micromechanics, the shear-lag, and the continuum fracture mechanics models were integrated with a statistical model in the repeating unit cell to predict the progressive damages and fatigue life of the composite structures. The global structure failure was defined as the loss of loading capability of the repeating unit cell, which depends on the stiffness reduction due to material slice failures and nonlinear material properties in the repeating unit cell. The present methodology is demonstrated with the analysis results evaluated through the experimental test performed with carbon fiber reinforced silicon carbide matrix plain weave composite specimens.

Detection of electromagnetic radiation using nonlinear materials

DOEpatents

Hwang, Harold Y.; Liu, Mengkun; Averitt, Richard D.; Nelson, Keith A.; Sternbach, Aaron; Fan, Kebin

2016-06-14

An apparatus for detecting electromagnetic radiation within a target frequency range is provided. The apparatus includes a substrate and one or more resonator structures disposed on the substrate. The substrate can be a dielectric or semiconductor material. Each of the one or more resonator structures has at least one dimension that is less than the wavelength of target electromagnetic radiation within the target frequency range, and each of the resonator structures includes at least two conductive structures separated by a spacing. Charge carriers are induced in the substrate near the spacing when the resonator structures are exposed to the target electromagnetic radiation. A measure of the change in conductivity of the substrate due to the induced charge carriers provides an indication of the presence of the target electromagnetic radiation.

Embrittlement and Flow Localization in Reactor Structural Materials

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

Xianglin Wu; Xiao Pan; James Stubbins

2006-10-06

Many reactor components and structural members are made from metal alloys due, in large part, to their strength and ability to resist brittle fracture by plastic deformation. However, brittle fracture can occur when structural material cannot undergo extensive, or even limited, plastic deformation due to irradiation exposure. Certain irradiation conditions lead to the development of a damage microstructure where plastic flow is limited to very small volumes or regions of material, as opposed to the general plastic flow in unexposed materials. This process is referred to as flow localization or plastic instability. The true stress at the onset of neckingmore » is a constant regardless of the irradiation level. It is called 'critical stress' and this critical stress has strong temperature dependence. Interrupted tensile testes of 316L SS have been performed to investigate the microstructure evolution and competing mechanism between mechanic twinning and planar slip which are believed to be the controlling mechanism for flow localization. Deformation twinning is the major contribution of strain hardening and good ductility for low temperatures, and the activation of twinning system is determined by the critical twinning stress. Phases transform and texture analyses are also discussed in this study. Finite element analysis is carried out to complement the microstructural analysis and for the prediction of materaials performance with and without stress concentration and irradiation.« less

Thermal Analysis by Numerical Methods of Debonding Effects near the Crack Tip under Composite Repairs

NASA Astrophysics Data System (ADS)

Tsamasphyros, G. J.; Kanderakis, G. N.; Marioli-Riga, Z. P.

2003-05-01

Composite patch repair of metallic structures has become a rapidly grown technology in the aerospace field due to the demand for significant increases in the useful life of both military and civilian aircraft. This has led to significant advances overall in the repair technology of cracked metallic structures. Adhesively bonded composite reinforcements offer remarkable advantages such as mechanical efficiency, repair time, cost reduction, high structural integrity, repair inspectability, damage tolerance to further causes of future strains, anticorrosion and antifretting properties. However, because of the different nature and properties of the materials that form a repair (metals, composites, adhesives), side-effects may occur: debonding due to high stress concentration in the vicinity of the crack, thermal residual stresses because of different thermal expansion coefficients of the adherents, etc. In this paper a three-dimensional finite elements analysis of the area around a patch repaired crack of a typical aircraft fuselage is performed, taking into account both the properties and the geometry of the involved materials. Examined in this case are 2024-T3 aluminum alloy as base material, FM-73 as the adhesive system and F4/5521 boron/epoxy prepreg as the patch material. Through the thickness stresses near the crack tip and along the patch edges with and without temperature effects are calculated and debonding near the crack tip is examined. Finally, the calculated results are compared with existing theories.

Research Developments in Nondestructive Evaluation and Structural Health Monitoring for the Sustainment of Composite Aerospace Structures at NASA

NASA Technical Reports Server (NTRS)

Cramer, K. Elliott

2016-01-01

The use of composite materials continues to increase in the aerospace community due to the potential benefits of reduced weight, increased strength, and manufacturability. Ongoing work at NASA involves the use of the large-scale composite structures for spacecraft (payload shrouds, cryotanks, crew modules, etc). NASA is also working to enable both the use and sustainment of composites in commercial aircraft structures. One key to the sustainment of these large composite structures is the rapid, in-situ characterization of a wide range of potential defects that may occur during the vehicle's life. Additionally, in many applications it is necessary to monitor changes in these materials over their lifetime. Quantitative characterization through Nondestructive Evaluation (NDE) of defects such as reduced bond strength, microcracking, and delamination damage due to impact, are of particular interest. This paper will present an overview of NASA's applications of NDE technologies being developed for the characterization and sustainment of advanced aerospace composites. The approaches presented include investigation of conventional, guided wave, and phase sensitive ultrasonic methods and infrared thermography techniques for NDE. Finally, the use of simulation tools for optimizing and validating these techniques will also be discussed.

Split off-specular reflection and surface scattering from woven materials

NASA Astrophysics Data System (ADS)

Pont, Sylvia C.; Koenderink, Jan J.

2003-03-01

We measured radiance distributions for black lining cloth and copper gauze using the convenient technique of wrapping the materials around a circular cylinder, irradiating it with a parallel light source and collecting the scattered radiance by a digital camera. One family of parallel threads (weave or weft) was parallel to the cylinder generator. The most salient features for such glossy plane weaves are a splitting up of the reflection peak due to the wavy variations in local slopes of the threads around the cylinders and a surface scattering lobe due to the threads that run along the cylinder. These scattering characteristics are quite different from the (off-)specular peaks and lobes that were found before for random rough specular surfaces. The split off-specular reflection is due to the regular structures in our samples of man-made materials. We derived simple approximations for these reflectance characteristics using geometrical optics.

Low-dimensional quantum magnetism in Cu (NCS) 2: A molecular framework material

NASA Astrophysics Data System (ADS)

Cliffe, Matthew J.; Lee, Jeongjae; Paddison, Joseph A. M.; Schott, Sam; Mukherjee, Paromita; Gaultois, Michael W.; Manuel, Pascal; Sirringhaus, Henning; Dutton, Siân E.; Grey, Clare P.

2018-04-01

Low-dimensional magnetic materials with spin-1/2 moments can host a range of exotic magnetic phenomena due to the intrinsic importance of quantum fluctuations to their behavior. Here, we report the structure, magnetic structure, and magnetic properties of copper ii thiocyanate, Cu(NCS ) 2, a one-dimensional coordination polymer which displays low-dimensional quantum magnetism. Magnetic susceptibility, electron paramagnetic resonance spectroscopy, 13C magic-angle spinning nuclear magnetic resonance spectroscopy, and density functional theory investigations indicate that Cu(NCS ) 2 behaves as a two-dimensional array of weakly coupled antiferromagnetic spin chains [J2=133 (1 ) K , α =J1/J2=0.08 ] . Powder neutron-diffraction measurements confirm that Cu(NCS ) 2 orders as a commensurate antiferromagnet below TN=12 K , with a strongly reduced ordered moment (0.3 μB ) due to quantum fluctuations.

Investigation on the diffusion bonding of tungsten and EUROFER97

NASA Astrophysics Data System (ADS)

Basuki, Widodo Widjaja; Aktaa, Jarir

2011-10-01

Due to its advantages, tungsten is selected as armor and structural material for use in future fusion power plants. To apply tungsten as structural material, a joint to EUROFER97 is foreseen in current divertor design for which the diffusion bonding is considered in this work. The joining must have acceptable strength and ductility without significant change in microstructures. So far, numerous diffusion bonding experiments without and with post bonding heat treatment (PBHT) are performed at 1050 °C for various bonding duration. For the bonding processes without PBHT, the bonding seams obtained are defect free and have a very high tensile strength. However they are brittle due to a thin layer of FeW intermetallic phase and metal carbides. For the bonding processes with PBHT, the bonding specimens fail at the bonding seam.

Electronic structure of polycrystalline CVD-graphene revealed by Nano-ARPES

NASA Astrophysics Data System (ADS)

Chen, Chaoyu; Avila, José; Asensio, Maria C.

2017-06-01

The ability to explore electronic structure and their role in determining material’s macroscopic behaviour is essential to explain and engineer functions of material and device. Since its debut in 2004, graphene has attracted global research interest due to its unique properties. Chemical vapor deposition (CVD) has emerged as an important method for the massive preparation and production of graphene for various applications. Here by employing angle-resolved photoemission spectroscopy with nanoscale spatial resolution ˜ 100 nm (Nano-ARPES), we describe the approach to measure the electronic structure of polycrystalline graphene on copper foils, demonstrating the power of Nano-ARPES to detect the electronic structure of microscopic single crystalline domains, being fully compatible with conventional ARPES. Similar analysis could be employed to other microscopic materials

Soft Chemistry, Coloring and Polytypism in Filled Tetrahedral Semiconductors: Toward Enhanced Thermoelectric and Battery Materials.

PubMed

White, Miles A; Medina-Gonzalez, Alan M; Vela, Javier

2018-03-12

Filled tetrahedral semiconductors are a rich family of compounds with tunable electronic structure, making them ideal for applications in thermoelectrics, photovoltaics, and battery anodes. Furthermore, these materials crystallize in a plethora of related structures that are very close in energy, giving rise to polytypism through the manipulation of synthetic parameters. This Minireview highlights recent advances in the solution-phase synthesis and nanostructuring of these materials. These methods enable the synthesis of metastable phases and polytypes that were previously unobtainable. Additionally, samples synthesized in solution phase have enhanced thermoelectric performance due to their decreased grain size. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of Anticorrosive Polymer Nanocomposite Coating for Corrosion Protection in Marine Environment

NASA Astrophysics Data System (ADS)

Mardare, L.; Benea, L.

2017-06-01

The marine environment is considered to be a highly aggressive environment for metal materials. Steels are the most common materials being used for shipbuilding. Corrosion is a major cause of structural deterioration in marine and offshore structures. Corrosion of carbon steel in marine environment becomes serious due to the highly corrosive nature of seawater with high salinity and microorganism. To protect metallic materials particularly steel against corrosion occurrence various organic and inorganic coatings are used. The most used are the polymeric protective coatings. The nanostructured TiO2 polymer coating is able to offer higher protection to steel against corrosion, and performed relatively better than other polymer coatings.

Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

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

Nicholson, Don M; Odbadrakh, Khorgolkhuu; Shassere, Benjamin

2014-01-01

Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations.

FUEL ELEMENT FOR A NUCLEAR REACTOR

DOEpatents

Davidson, J.K.

1963-11-19

A fuel element structure particularly useful in high temperature nuclear reactors is presented. Basically, the structure comprises two coaxial graphite sleeves integrally joined together by radial fins. Due to the high structural strength of graphite at high temperatures and the rigidity of this structure, nuclear fuel encased within the inner sleeve in contiguous relation therewith is supported and prevented from expanding radially at high temperatures. Thus, the necessity of relying on the usual cladding materials with relatively low temperature limitations for structural strength is removed. (AEC)

External electric field driving the ultra-low thermal conductivity of silicene.

PubMed

Qin, Guangzhao; Qin, Zhenzhen; Yue, Sheng-Ying; Yan, Qing-Bo; Hu, Ming

2017-06-01

The manipulation of thermal transport is in increasing demand as heat transfer plays a critical role in a wide range of practical applications, such as efficient heat dissipation in nanoelectronics and heat conduction hindering in solid-state thermoelectrics. It is well established that the thermal transport in semiconductors and insulators (phonons) can be effectively modulated by structure engineering or materials processing. However, almost all the existing approaches involve altering the original atomic structure of materials, which would be hindered due to either irreversible structure change or limited tunability of thermal conductivity. Motivated by the inherent relationship between phonon behavior and interatomic electrostatic interaction, we comprehensively investigate the effect of external electric field, a widely used gating technique in modern electronics, on the lattice thermal conductivity (κ). Taking two-dimensional silicon (silicene) as a model, we demonstrate that by applying an electric field (E z = 0.5 V Å -1 ) the κ of silicene can be reduced to a record low value of 0.091 W m -1 K -1 , which is more than two orders of magnitude lower than that without an electric field (19.21 W m -1 K -1 ) and is even comparable to that of the best thermal insulation materials. Fundamental insights are gained from observing the electronic structures. With an electric field applied, due to the screened potential resulting from the redistributed charge density, the interactions between silicon atoms are renormalized, leading to phonon renormalization and the modulation of phonon anharmonicity through electron-phonon coupling. Our study paves the way for robustly tuning phonon transport in materials without altering the atomic structure, and would have significant impact on emerging applications, such as thermal management, nanoelectronics and thermoelectrics.

Structural materials for Gen-IV nuclear reactors: Challenges and opportunities

NASA Astrophysics Data System (ADS)

Murty, K. L.; Charit, I.

2008-12-01

Generation-IV reactor design concepts envisioned thus far cater toward a common goal of providing safer, longer lasting, proliferation-resistant and economically viable nuclear power plants. The foremost consideration in the successful development and deployment of Gen-IV reactor systems is the performance and reliability issues involving structural materials for both in-core and out-of-core applications. The structural materials need to endure much higher temperatures, higher neutron doses and extremely corrosive environment, which are beyond the experience of the current nuclear power plants. Materials under active consideration for use in different reactor components include various ferritic/martensitic steels, austenitic stainless steels, nickel-base superalloys, ceramics, composites, etc. This paper presents a summary of various Gen-IV reactor concepts, with emphasis on the structural materials issues depending on the specific application areas. This paper also discusses the challenges involved in using the existing materials under both service and off-normal conditions. Tasks become increasingly complex due to the operation of various fundamental phenomena like radiation-induced segregation, radiation-enhanced diffusion, precipitation, interactions between impurity elements and radiation-produced defects, swelling, helium generation and so forth. Further, high temperature capability (e.g. creep properties) of these materials is a critical, performance-limiting factor. It is demonstrated that novel alloy and microstructural design approaches coupled with new materials processing and fabrication techniques may mitigate the challenges, and the optimum system performance may be achieved under much demanding conditions.

Thin Films and Inflatable Applications in Exploration Habitat Structures

NASA Technical Reports Server (NTRS)

Frazier, Donald O.; Paley, Mark S.; Strong, Janet D.

2005-01-01

NASA's vision to return to the Moon and then extend human exploration to Mars will benefit from human habitat technology development using new and creative applications of polymer materials and concepts. Thin Film and Inflatable (TFVI) materials are particularly interesting for exploration applications due to their light weight and low volume. Whereas TF/I materials can be launched and carried from Earth to multiple and distant exploration sites without the constraints of upmass limitations, eventually, with recycling and reclamation efforts, these materials may be developed using in-situ resources. These materials can be useful for fabricating, patching and repairing vehicles, replacement parts and even habitat structures, as well as for developing stand-alone habitat structure technologies and for nested and integrated applications. TF/Is can also be ideal environmental containment vessels within lunar or Martian regolith walls or as liners inside caves or raw regolith exterior structures for the provisions of atmosphere containment, debris protection and cleanliness. Further, TFOs can be specialized and matured for various and diverse applications. The desired range of applications will require materials specification for such properties as transparency, elasticity, thermal conductivity, mechanical strength, heat capacity, chemical resistance, and permeability. This paper will discuss Marshall Space Flight Center's plans to analyze and prioritize TF/I materials properties and classifications and to develop applications for these highly desirable materials in human habitat construction projects on the Moon and Mars.

Radiation Transport Properties of Polyethylene-Fiber Composites

NASA Technical Reports Server (NTRS)

Kaul, Raj K.; Barghouty, A. F.; Dahche, H. M.

2003-01-01

Composite materials that can both serve as effective shielding materials against cosmic-ray and energetic solar particles in deep space as well as structural materials for habitat and spacecraft remain a critical and mission enabling piece in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density coupled with high hydrogen content. Polyethylene fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of Polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at NASA's Marshall Space Flight Center and tested against 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Space radiation transport properties of polyethylene-based composites.

PubMed

Kaul, R K; Barghouty, A F; Dahche, H M

2004-11-01

Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Shear wave propagation in anisotropic soft tissues and gels

PubMed Central

Namani, Ravi; Bayly, Philip V.

2013-01-01

The propagation of shear waves in soft tissue can be visualized by magnetic resonance elastography (MRE) [1] to characterize tissue mechanical properties. Dynamic deformation of brain tissue arising from shear wave propagation may underlie the pathology of blast-induced traumatic brain injury. White matter in the brain, like other biological materials, exhibits a transversely isotropic structure, due to the arrangement of parallel fibers. Appropriate mathematical models and well-characterized experimental systems are needed to understand wave propagation in these structures. In this paper we review the theory behind waves in anisotropic, soft materials, including small-amplitude waves superimposed on finite deformation of a nonlinear hyperelastic material. Some predictions of this theory are confirmed in experimental studies of a soft material with controlled anisotropy: magnetically-aligned fibrin gel. PMID:19963987

Space radiation transport properties of polyethylene-based composites

NASA Technical Reports Server (NTRS)

Kaul, R. K.; Barghouty, A. F.; Dahche, H. M.

2004-01-01

Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Attrition Rate of Oxygen Carriers in Chemical Looping Combustion Systems

NASA Astrophysics Data System (ADS)

Feilen, Harry Martin

This project developed an evaluation methodology for determining, accurately and rapidly, the attrition resistance of oxygen carrier materials used in chemical looping technologies. Existing test protocols, to evaluate attrition resistance of granular materials, are conducted under non-reactive and ambient temperature conditions. They do not accurately reflect the actual behavior under the unique process conditions of chemical looping, including high temperatures and cyclic operation between oxidizing and reducing atmospheres. This project developed a test method and equipment that represented a significant improvement over existing protocols. Experimental results obtained from this project have shown that hematite exhibits different modes of attrition, including both due to mechanical stresses and due to structural changes in the particles due to chemical reaction at high temperature. The test methodology has also proven effective in providing reactivity changes of the material with continued use, a property, which in addition to attrition, determines material life. Consumption/replacement cost due to attrition or loss of reactivity is a critical factor in the economic application of the chemical looping technology. This test method will allow rapid evaluation of a wide range of materials that are best suited for this technology. The most important anticipated public benefit of this project is the acceleration of the development of chemical looping technology for lowering greenhouse gas emissions from fossil fuel combustion.

Influence of lithium vacancies on the polaronic transport in olivine phosphate structure

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

Murugavel, Sevi, E-mail: murug@physics.du.ac.in; Sharma, Monika; Shahid, Raza

2016-01-28

Intercalation and deintercalation of lithium ions in cathode materials are of principal to the operation of current rechargeable lithium ion batteries. The performance of lithium ion batteries highly relies on the active cathode material which includes cell potential, power/energy density, capacity, etc. An important issue in this class of material is to resolve the factors governing the electron and ion transport in olivine phosphate structure. In this class of material, there is still an open debate on the mechanism of charge transport including both polarons and lithium ions. On the one hand, this is due to the large disparity betweenmore » the experimental results and the theoretical model predictions. On the other hand, this is also due to the lack of precise experimental measurement without any parasitic phases in a given cathode material. Here, we present the polaronic conduction in lithiated triphylite LiFePO{sub 4} (LFP) and delithiated heterosite FePO{sub 4} (FP) by means of broadband ac impedance spectroscopy over wide range temperatures and frequency. It is found that the LFP phase possess two orders of higher polaronic conductivity than FP phase despite having similar mobility of polarons in both phases. We show that the differences in the polaronic conductivity of two phases are due to the significant differences in concentration of polarons. It is found that the formation energy of polarons in individual phases is mainly determined by the corresponding defect state associated with it. The temperature dependent dc conductivity has been analyzed within the framework of Mott model of polaronic conduction and explored the origin of polaronic conduction mechanism in this class of material.« less

Concept for a 3D-printed soft rotary actuator driven by a shape-memory alloy

NASA Astrophysics Data System (ADS)

Yuan, Han; Chapelle, Frédéric; Fauroux, Jean-Christophe; Balandraud, Xavier

2018-05-01

In line with the recent development of soft actuators involving shape-memory alloys (SMAs) embedded in compliant structures, this paper proposes a concept for a rotary actuator driven by a SMA wire placed inside a 3D-printed helical structure. The concept consists of using the one-way memory effect of the SMA (activated by Joule heating) to create the rotation of a material point of the structure, while the inverse rotation is obtained during the return to ambient temperature thanks to the structure’s elasticity. The study was performed in three steps. First, a prototype was designed from a chain of design rules, and tested to validate the feasibility of the concept. Thermal and geometrical measurements were performed using infrared and visible-range stereo cameras. A clockwise rotation (250°) followed by an anti-clockwise rotation (‑200°) were obtained, enabling us to validate the concept despite the partial reversibility of the movement. Second, finite element simulations were performed to improve rotation reversibility. The high compliance of the mechanical system required a framework of large displacements for the calculations (in the strength of materials sense), due to the high structural flexibility. Finally, a second prototype was constructed and tested. Attention was paid to the rotation (fully reversible rotation of 150° reached) as well as to parasitic movements due to overall structural deformation. This study opens new prospects for the design and analysis of 3D-printed soft actuators activated by smart materials.

Preparing "Chameleon Balls" from Natural Plants: Simple Handmade pH Indicator and Teaching Material for Chemical Education

NASA Astrophysics Data System (ADS)

1996-05-01

Some of the structures in Figure 1 from "Preparing "Chameleon Balls" from Natural Plants: Simple Handmade pH Indicator and Teaching Material for Chemical Education"[Kanda, N.; Asano, T.; Itoh, T.; Onoda, M. J. Chem. Educ. 1995, 72, 1131] were incorrect due to a staff error. The correct figure appears below.

Biomass and carbon attributes of downed woody materials in forests of the United States

Treesearch

C.W. Woodall; B.F. Walters; S.N. Oswalt; G.M. Domke; C. Toney; A.N. Gray

2013-01-01

Due to burgeoning interest in the biomass/carbon attributes of forest downed and dead woody materials (DWMs) attributable to its fundamental role in the carbon cycle, stand structure/diversity, bioenergy resources, and fuel loadings, the U.S. Department of Agriculture has conducted a nationwide field-based inventory of DWM. Using the national DWM inventory, attributes...

Functional liquid structures by emulsification of graphene and other two-dimensional nanomaterials.

PubMed

Large, Matthew J; Ogilvie, Sean P; Meloni, Manuela; Amorim Graf, Aline; Fratta, Giuseppe; Salvage, Jonathan; King, Alice A K; Dalton, Alan B

2018-01-25

Pickering emulsions stabilised with nanomaterials provide routes to a range of functional macroscopic assemblies. We demonstrate the formation and properties of water-in-oil emulsions prepared through liquid-phase exfoliation of graphene. Due to the functional nature of the stabiliser, the emulsions exhibit conductivity due to inter-particle tunnelling. We demonstrate a strain sensing application with a large gauge factor of ∼40; the highest reported in a liquid. Our methodology can be applied to other two-dimensional layered materials opening up applications such as energy storage materials, and flexible and printable electronics.

An Ag-grid/graphene hybrid structure for large-scale, transparent, flexible heaters.

PubMed

Kang, Junmo; Jang, Yonghee; Kim, Youngsoo; Cho, Seung-Hyun; Suhr, Jonghwan; Hong, Byung Hee; Choi, Jae-Boong; Byun, Doyoung

2015-04-21

Recently, carbon materials such as carbon nanotubes and graphene have been proposed as alternatives to indium tin oxide (ITO) for fabricating transparent conducting materials. However, obtaining low sheet resistance and high transmittance of these carbon materials has been challenging due to the intrinsic properties of the materials. In this paper, we introduce highly transparent and flexible conductive films based on a hybrid structure of graphene and an Ag-grid. Electrohydrodynamic (EHD) jet printing was used to produce a micro-scale grid consisting of Ag lines less than 10 μm wide. We were able to directly write the Ag-grid on a large-area graphene/flexible substrate due to the high conductivity of graphene. The hybrid electrode could be fabricated using hot pressing transfer and EHD jet printing in a non-vacuum, maskless, and low-temperature environment. The hybrid electrode offers an effective and simple route for achieving a sheet resistance as low as ∼4 Ω per square with ∼78% optical transmittance. Finally, we demonstrate that transparent flexible heaters based on the hybrid conductive films could be used in a vehicle or a smart window system.

Ultimate strength capacity of a square hollow section filled with fibrous foamed concrete

NASA Astrophysics Data System (ADS)

Amirah Azra Khairuddin, Siti; Rahman, Norashidah Abd; Jamaluddin, Norwati; Jaini, Zainorizuan Mohd; Ali, Noorwirdawati

2017-11-01

Concrete-filled sections used as building columns have become popular due to their architectural and structural elements. In recent years, there has been a renewed call for the improvement of materials used as concrete to fill the composite columns. Among these materials, foamed concrete has received great attention due to its structural characteristics and its potential as a construction material used in hollow sections. However, its behaviors as infill material in a hollow section, such as its strength and failure mode, should be investigated. In this study, experimental research was conducted to compare the experimental and theoretical values of its ultimate strength capacity. Eight specimens of hollow steel sections with two different thicknesses were filled with fibrous foamed concrete and then subjected to compression load. The obtained results were compared with those obtained from a hollow section with the same thicknesses, but were filled with normal foamed concrete. Results show that the ultimate strength capacity of the experimental value is the same as that of the theoretical value based on Eurocode 4. The largest percentage values between theoretical and experimental results for thicknesses of 2 and 4 mm are 58% and 55%, respectively.

Damage evolution during actuation fatigue in shape memory alloys (SPIE Best Student Paper Award)

NASA Astrophysics Data System (ADS)

Phillips, Francis R.; Wheeler, Robert; Lagoudas, Dimitris C.

2018-03-01

Shape Memory Alloys (SMAs) are unique materials able to undergo a thermomechanically induced, reversible phase transformation. Additionally, SMA are subject to two types of fatigue, that is structural fatigue due to cyclic loading as experienced by most materials, as well as actuation fatigue due to repeated thermally induced phase transformation. The evolution of multiple material characteristics is presented over the actuation fatigue lifetime of NiTiHf actuators, including the accumulation of irrecoverable strain, the evolution of internal voids, and the evolution of the effective modulus of the actuator. The results indicate that all three of these material characteristics are clearly interconnected and careful analysis of each of these characteristics can help to understand the evolution of the others, as well as help to understand how actuation fatigue leads to ultimate failure of the actuator.

Porous titanium materials with entangled wire structure for load-bearing biomedical applications.

PubMed

He, Guo; Liu, Ping; Tan, Qingbiao

2012-01-01

A kind of porous metal-entangled titanium wire material has been investigated in terms of the pore structure (size and distribution), the strength, the elastic modulus, and the mechanical behavior under uniaxial tensile loading. Its functions and potentials for surgical application have been explained. In particular, its advantages over competitors (e.g., conventional porous titanium) have been reviewed. In the study, a group of entangled titanium wire materials with non-woven structure were fabricated by using 12-180 MPa forming pressure, which have porosity in a range of 48%-82%. The pores in the materials are irregular in shape, which have a nearly half-normal distribution in size range. The yield strength, ultimate tensile strength, and elastic modulus are 75 MPa, 108 MPa, and 1.05 GPa, respectively, when its porosity is 44.7%. The mechanical properties decrease significantly as the porosity increases. When the porosity is 57.9%, these values become 24 MPa, 47.5 MPa, and 0.33 GPa, respectively. The low elastic modulus is due to the structural flexibility of the entangled titanium wire materials. For practical reference, a group of detailed data of the porous structure and the mechanical properties are reported. This kind of material is very promising for implant applications because of their very good toughness, perfect flexibility, high strength, adequate elastic modulus, and low cost. Copyright © 2011 Elsevier Ltd. All rights reserved.

Laser processing of thick Li(NiMnCo)O2 electrodes for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Rakebrandt, J.-H.; Smyrek, P.; Zheng, Y.; Seifert, H. J.; Pfleging, W.

2017-02-01

Lithium-ion batteries became the most promising types of mobile energy storage devices due to their high gravimetric and volumetric capacity, high cycle life-time, and low self-discharge. Nowadays, the cathode material lithium nickel manganese cobalt oxide (NMC) is one of the most widely used cathode material in commercial lithium-ion batteries due to many advantages such as high energy density (>150 Wh kg-1) on cell level, high power density (650 W kg-1 @ 25 °C and 50 % Depth of Discharge) [1], high specific capacity (163 mAh g-1) [2], high rate capability and good thermal stability in the fully charged state. However, in order to meet the requirements for the increasing demand for rechargeable high energy batteries, nickel-rich NMC electrodes with specific capacities up to 210 mAh g-1 seem to be the next generation cathodes which can reach on cell level desired energy densities higher than 250 Wh kg-1 [3]. Laser-structuring now enables to combine both concepts, high power and high energy lithium-ion batteries. For this purpose, lithium nickel manganese cobalt oxide cathodes were produced via tape casting containing 85-90 wt% of active material with a film thickness of 50-260 μm. The specific capacities were measured using galvanostatic measurements for different types of NMC with varying nickel, manganese and cobalt content at different charging/discharging currents ("C-rates"). An improved lithium-ion diffusion kinetics due to an increased active surface area could be achieved by laser-assisted generating of three dimensional architectures. Cells with unstructured and structured cathodes were compared. Ultrafast laser ablation was used in order to avoid a thermal impact to the material. It was shown that laser structuring of electrode materials leads to a significant improvement in electrochemical performance, especially at high charging and discharging C-rates.

Comparison of dissimilarity measures for cluster analysis of X-ray diffraction data from combinatorial libraries

NASA Astrophysics Data System (ADS)

Iwasaki, Yuma; Kusne, A. Gilad; Takeuchi, Ichiro

2017-12-01

Machine learning techniques have proven invaluable to manage the ever growing volume of materials research data produced as developments continue in high-throughput materials simulation, fabrication, and characterization. In particular, machine learning techniques have been demonstrated for their utility in rapidly and automatically identifying potential composition-phase maps from structural data characterization of composition spread libraries, enabling rapid materials fabrication-structure-property analysis and functional materials discovery. A key issue in development of an automated phase-diagram determination method is the choice of dissimilarity measure, or kernel function. The desired measure reduces the impact of confounding structural data issues on analysis performance. The issues include peak height changes and peak shifting due to lattice constant change as a function of composition. In this work, we investigate the choice of dissimilarity measure in X-ray diffraction-based structure analysis and the choice of measure's performance impact on automatic composition-phase map determination. Nine dissimilarity measures are investigated for their impact in analyzing X-ray diffraction patterns for a Fe-Co-Ni ternary alloy composition spread. The cosine, Pearson correlation coefficient, and Jensen-Shannon divergence measures are shown to provide the best performance in the presence of peak height change and peak shifting (due to lattice constant change) when the magnitude of peak shifting is unknown. With prior knowledge of the maximum peak shifting, dynamic time warping in a normalized constrained mode provides the best performance. This work also serves to demonstrate a strategy for rapid analysis of a large number of X-ray diffraction patterns in general beyond data from combinatorial libraries.

Recent Progress in Some Amorphous Materials for Supercapacitors.

PubMed

Li, Qing; Xu, Yuxia; Zheng, Shasha; Guo, Xiaotian; Xue, Huaiguo; Pang, Huan

2018-05-14

A breakthrough in technologies having "green" and sustainable energy storage conversion is urgent, and supercapacitors play a crucial role in this area of research. Owing to their unique porous structure, amorphous materials are considered one of the best active materials for high-performance supercapacitors due to their high specific capacity, excellent cycling stability, and fast charging rate. This Review summarizes the synthesis of amorphous materials (transition metal oxides, carbon-based materials, transition metal sulfides, phosphates, hydroxides, and their complexes) to highlight their electrochemical performance in supercapacitors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comments on the interaction of materials with atomic oxygen

NASA Technical Reports Server (NTRS)

Torre, Larry P.; Pippin, H. Gary

1987-01-01

An explanation of the relative resistance of various materials to attack by atomic oxygen is presented. Data from both ground based and on-orbit experiments is interpreted. The results indicate the importance of bond strengths, size and structure of pendant groups, and fluorination to the resistance of certain polymers to atomic oxygen. A theory which provides a partial explanation of the degradation of materials in low Earth orbit due to surface recombination of oxygen atoms is also included. Finally, a section commenting on mechanisms of material degradation is provided.

Superlattice structure modeling and simulation of High Electron Mobility Transistor for improved performance

NASA Astrophysics Data System (ADS)

Munusami, Ravindiran; Yakkala, Bhaskar Rao; Prabhakar, Shankar

2013-12-01

Magnetic tunnel junction were made by inserting the magnetic materials between the source, channel and the drain of the High Electron Mobility Transistor (HEMT) to enhance the performance. Material studio software package was used to design the superlattice layers. Different cases were analyzed to optimize the performance of the device by placing the magnetic material at different positions of the device. Simulation results based on conductivity reveals that the device has a very good electron transport due to the magnetic materials and will amplify very low frequency signals.

Low-dimensional carbon and MXene-based electrochemical capacitor electrodes.

PubMed

Yoon, Yeoheung; Lee, Keunsik; Lee, Hyoyoung

2016-04-29

Due to their unique structure and outstanding intrinsic physical properties such as extraordinarily high electrical conductivity, large surface area, and various chemical functionalities, low-dimension-based materials exhibit great potential for application in electrochemical capacitors (ECs). The electrical properties of electrochemical capacitors are determined by the electrode materials. Because energy charge storage is a surface process, the surface properties of the electrode materials greatly influence the electrochemical performance of the cell. Recently, graphene, a single layer of sp(2)-bonded carbon atoms arrayed into two-dimensional carbon nanomaterial, has attracted wide interest as an electrode material for electrochemical capacitor applications due to its unique properties, including a high electrical conductivity and large surface area. Several low-dimensional materials with large surface areas and high conductivity such as onion-like carbons (OLCs), carbide-derived carbons (CDCs), carbon nanotubes (CNTs), graphene, metal hydroxide, transition metal dichalcogenides (TMDs), and most recently MXene, have been developed for electrochemical capacitors. Therefore, it is useful to understand the current issues of low-dimensional materials and their device applications.

Crowd-Sourcing (Semantically) Structured Multilingual Educational Content (CoSMEC)

ERIC Educational Resources Information Center

Tarasowa, Darya; Auer, Sören; Khalili, Ali; Unbehauen, Jörg

2014-01-01

The support of multilingual content becomes crucial for educational platforms due to the benefits it offers. In this paper we propose a concept that allows content authors to use the power of the crowd to create (semantically) structured multilingual educational content out of their material. To enable the collaboration of the crowd, we expand our…

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

Thermal-stress-free fasteners for joining orthotropic materials

NASA Technical Reports Server (NTRS)

Blosser, M. L.

1987-01-01

Hot structures fabricated from orthotropic materials are an attractive design option for future high speed vehicles. Joining subassemblies of these materials with standard cylindrical fasteners can lead to loose joints or highly stressed joints due to thermal stress. A method has been developed to eliminate thermal stresses and maintain a tight joint by shaping the fastener and mating hole. This method allows both materials (fastener and structure), with different coefficients of thermal expansion (CTEs) in each of the three material directions, to expand freely with temperature yet remain in contact. For the assumptions made in the analysis, the joint will remain snug, yet free of thermal stress at any temperature. Finite element analysis was used to verify several thermal-stress-free fasteners and to show that conical fasteners, which are thermal-stress-free for isotropic materials, can reduce thermal stresses for transversely isotropic materials compared to a cylindrical fastener. Equations for thermal-stress-free shapes are presented and typical fastener shapes are shown.

Fabrication of smooth patterned structures of refractory metals, semiconductors, and oxides via template stripping.

PubMed

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

2013-10-09

The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics.

Nanoporous Metals with Structural Hierarchy: A Review

DOE PAGES

Juarez, Theresa; Biener, Juergen; Weissmüller, Jörg; ...

2017-08-09

Nanoporous (np) metals have generated much interest since they combine several desirable material characteristics, such as high surface area, mechanical size effects, and high conductivity. Most of the research has been focused on np Au due to its relatively straightforward synthesis, chemical stability, and many promising applications in the fields of catalysis and actuation. Other materials, such as np-Cu, Ag, and Pd have also been studied. Here, this review discusses recent advances in the field of np metals, focusing on new research areas that implement and leverage structural hierarchy while using np metals as their base structural constituents. First, wemore » focus on single-element porous metals that are made of np metals at the fundamental level, but synthesized with additional levels of porosity. Second, we discuss the fabrication of composite structures, which use auxiliary materials to enhance the properties of np metals. Important applications of these hierarchical materials, especially in the fields of catalysis and electrochemistry, are also reviewed. Lastly, we conclude with a discussion about future opportunities for the advancement and application of np metals.« less

Nanoporous Metals with Structural Hierarchy: A Review

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

Juarez, Theresa; Biener, Juergen; Weissmüller, Jörg

Nanoporous (np) metals have generated much interest since they combine several desirable material characteristics, such as high surface area, mechanical size effects, and high conductivity. Most of the research has been focused on np Au due to its relatively straightforward synthesis, chemical stability, and many promising applications in the fields of catalysis and actuation. Other materials, such as np-Cu, Ag, and Pd have also been studied. Here, this review discusses recent advances in the field of np metals, focusing on new research areas that implement and leverage structural hierarchy while using np metals as their base structural constituents. First, wemore » focus on single-element porous metals that are made of np metals at the fundamental level, but synthesized with additional levels of porosity. Second, we discuss the fabrication of composite structures, which use auxiliary materials to enhance the properties of np metals. Important applications of these hierarchical materials, especially in the fields of catalysis and electrochemistry, are also reviewed. Lastly, we conclude with a discussion about future opportunities for the advancement and application of np metals.« less

Inorganic glass ceramic slip rings

NASA Technical Reports Server (NTRS)

Glossbrenner, E. W.; Cole, S. R.

1972-01-01

Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

A laboratory evaluation of modified asphalt : final report.

DOT National Transportation Integrated Search

1981-01-01

Quality aggregate availability in southern Louisiana has reached an alarmingly low level, while naturally occurring materials (sands) have been ignored due to their poor structural properties. Recent research reported by Chem-Crete Corporation indica...

Radio frequency and capacitive sensors for dielectric characterization of low-conductivity media

NASA Astrophysics Data System (ADS)

Sheldon, Robert T.

Low-conductivity media are found in a vast number of applications, for example as electrical insulation or as the matrix polymer in high strength-to-weight ratio structural composites. In some applications, these materials are subjected to extreme environmental, thermal, and mechanical conditions that can affect the material's desired performance. In a more general sense, a medium may be comprised of one or more layers with unknown material properties that may affect the desired performance of the entire structure. It is often, therefore, of great import to be able to characterize the material properties of these media for the purpose of estimating their future performance in a certain application. Low-conductivity media, or dielectrics, are poor electrical conductors and permit electromagnetic waves and static electric fields to pass through with minimal attenuation. The amount of electrical energy that may be stored (and lost) in these fields depends directly upon the material property, permittivity, which is generally complex, frequency-dependent and has a measurable effect on sensors designed to characterize dielectric media. In this work, two different types of dielectric sensors: radio frequency resonant antennas and lower-frequency (<1 MHz) capacitive sensors, are designed for permittivity characterization in their respective frequency regimes. In the first part of this work, the capability of characterizing multilayer dielectric structures is studied using a patch antenna, a type of antenna that is primarily designed for data communications in the microwave bands but has application in the field of nondestructive evaluation as well. Each configuration of a patch antenna has a single lowest resonant (dominant mode) frequency that is dependent upon the antenna's substrate material and geometry as well as the permittivity and geometry of exterior materials. Here, an extant forward model is validated using well-characterized microwave samples and a new method of resonant frequency and quality factor determination from measured data is presented. Excellent agreement between calculated and measured values of sensor resonant frequency was obtained for the samples studied. Agreement between calculated and measured quality factor was good in some cases but incurred the particular challenge of accurately quantifying multiple contributions to loss from the sensor structure itself, which at times dominates the contribution due to the sample material. Two later chapters describe the development of capacitive sensors to quantify the low-frequency changes in material permittivity due to environmental aging mechanisms. One embodiment involves the application of coplanar concentric interdigital electrode sensors for the purpose of investigating polymer-matrix degradation in glass-fiber composites due to isothermal aging. Samples of bismaleimide-matrix glass-fiber composites were aged at several high temperatures to induce thermal degradation and capacitive sensors were used to measure the sensor capacitance and dissipation factor, parameters that are directly proportional to the real and imaginary components of complex permittivity, respectively. It was shown that real permittivity and dissipation factor decreased with increasing aging temperature, a trend that was common to both interdigital sensor measurements and standard parallel plate electrode measurements. The second piece of work involves the development of cylindrical interdigital electrode sensors to characterize complex permittivity changes in wire insulation due to aging-related degradation. The sensor was proven effective in detecting changes in irradiated nuclear power plant wiring insulation and in aircraft wiring insulation due to liquid chemical immersion. In all three cases, the results indicate a clear correlation of measured capacitance and dissipation factor with increased degradation.

Experimental Tensile Strength Analysis of Woven-Glass/Epoxy Composite Plates with Central Circular Hole

NASA Astrophysics Data System (ADS)

Hadi, Bambang K.; Rofa, Bima K.

2018-04-01

The use of composite materials in aerospace engineering, as well as in maritime structure has increased significantly during the recent years. The extensive use of composite materials in industrial applications should make composite structural engineers and scientists more aware of the advantage and disadvantage of this material and provide them with necessary data and certification process. One of the problems in composite structures is the existence of hole. Hole can not be avoided in actual structures, since it may be the necessity of providing access for maintenance or due to impact damage. The presence of hole will weaken the structures. Therefore, in this paper, the effect of hole on the strength of glass-woven/epoxy composite will be discussed. Extensive tests have been carried out to study the effect of hole-diameter on the tensile strengths of these specimens. The results showed that the bigger the hole-diameter compared to the width of the specimens has weakened the structures further, as expected. Further study should be carried in the future to model it with the finite element and theoretical analysis precisely.

The prediction of crystal structure by merging knowledge methods with first principles quantum mechanics

NASA Astrophysics Data System (ADS)

Ceder, Gerbrand

2007-03-01

The prediction of structure is a key problem in computational materials science that forms the platform on which rational materials design can be performed. Finding structure by traditional optimization methods on quantum mechanical energy models is not possible due to the complexity and high dimensionality of the coordinate space. An unusual, but efficient solution to this problem can be obtained by merging ideas from heuristic and ab initio methods: In the same way that scientist build empirical rules by observation of experimental trends, we have developed machine learning approaches that extract knowledge from a large set of experimental information and a database of over 15,000 first principles computations, and used these to rapidly direct accurate quantum mechanical techniques to the lowest energy crystal structure of a material. Knowledge is captured in a Bayesian probability network that relates the probability to find a particular crystal structure at a given composition to structure and energy information at other compositions. We show that this approach is highly efficient in finding the ground states of binary metallic alloys and can be easily generalized to more complex systems.

Nanomechanics of Ferroelectric Thin Films and Heterostructures

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

Li, Yulan; Hu, Shenyang Y.; Chen , L.Q.

2016-08-31

The focus of this chapter is to provide basic concepts of how external strains/stresses altering ferroelectric property of a material and how to evaluate quantitatively the effect of strains/stresses on phase stability, domain structure, and material ferroelectric properties using the phase-field method. The chapter starts from a brief introduction of ferroelectrics and the Landau-Devinshire description of ferroelectric transitions and ferroelectric phases in a homogeneous ferroelectric single crystal. Due to the fact that ferroelectric transitions involve crystal structure change and domain formation, strains and stresses can be produced inside of the material if a ferroelectric transition occurs and it is confined.more » These strains and stresses affect in turn the domain structure and material ferroelectric properties. Therefore, ferroelectrics and strains/stresses are coupled to each other. The ferroelectric-mechanical coupling can be used to engineer the material ferroelectric properties by designing the phase and structure. The followed section elucidates calculations of the strains/stresses and elastic energy in a thin film containing a single domain, twinned domains to complicated multidomains constrained by its underlying substrate. Furthermore, a phase field model for predicting ferroelectric stable phases and domain structure in a thin film is presented. Examples of using substrate constraint and temperature to obtain interested ferroelectric domain structures in BaTiO3 films are demonstrated b phase field simulations.« less

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.

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.

Long-Term Lunar Radiation Degradation Effects on Materials

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; ORourke, Mary Jane; Koontz, Steve; Alred, John; Hill, Charles; Devivar, Rodrigo; Morera-Felix, Shakira; Atwell, William; Nutt, Steve; Sabbann, Leslie

2010-01-01

The National Aeronautics and Space Administration (NASA) is focused on developing technologies for extending human presence beyond low Earth orbit. These technologies are to advance the state-of-the-art and provide for longer duration missions outside the protection of Earth's magnetosphere. One technology of great interest for large structures is advanced composite materials, due to their weight and cost savings, enhanced radiation protection for the crew, and potential for performance improvements when compared with existing metals. However, these materials have not been characterized for the interplanetary space environment, and particularly the effects of high energy radiation, which is known to cause damage to polymeric materials. Therefore, a study focusing on a lunar habitation element was undertaken to investigate the integrity of potential structural composite materials after exposure to a long-term lunar radiation environment. An overview of the study results are presented, along with a discussion of recommended future work.

SVAS3: Strain Vector Aided Sensorization of Soft Structures

PubMed Central

Culha, Utku; Nurzaman, Surya G.; Clemens, Frank; Iida, Fumiya

2014-01-01

Soft material structures exhibit high deformability and conformability which can be useful for many engineering applications such as robots adapting to unstructured and dynamic environments. However, the fact that they have almost infinite degrees of freedom challenges conventional sensory systems and sensorization approaches due to the difficulties in adapting to soft structure deformations. In this paper, we address this challenge by proposing a novel method which designs flexible sensor morphologies to sense soft material deformations by using a functional material called conductive thermoplastic elastomer (CTPE). This model-based design method, called Strain Vector Aided Sensorization of Soft Structures (SVAS3), provides a simulation platform which analyzes soft body deformations and automatically finds suitable locations for CTPE-based strain gauge sensors to gather strain information which best characterizes the deformation. Our chosen sensor material CTPE exhibits a set of unique behaviors in terms of strain length electrical conductivity, elasticity, and shape adaptability, allowing us to flexibly design sensor morphology that can best capture strain distributions in a given soft structure. We evaluate the performance of our approach by both simulated and real-world experiments and discuss the potential and limitations. PMID:25036332

Bioinspired Single-Walled Carbon Nanotubes as a Spider Silk Structure for Ultrahigh Mechanical Property.

PubMed

Luo, Chengzhi; Li, Fangying; Li, Delong; Fu, Qiang; Pan, Chunxu

2016-11-16

Due to its unique hierarchical structure, natural spider silk features exceptional mechanical properties such as high tensile strength and great extensibility, making it one of the toughest materials. Herein, we design bioinspired spider silk single-walled carbon nanotubes (BISS-SWCNTs) that combine the hierarchical structure of spider silk and the high strength and conductivity of SWCNTs. To imitate the hierarchical structure, Fe nanoparticles are embedded on the surface of directly synthesized SWCNTs skeleton followed by coating an amorphous carbon layer. The carbon layer forms the spider silk-featured skin-core structure with SWCNTs, thus making the tube junction tougher. The embedded Fe nanoparticles act as glue spots for preventing interfacial slippages between the BISS-SWCNTs and the reinforced matrix. With only 2.1 wt % BISS-SWCNTs added, the tensile strength and Young's modulus of the BISS-SWCNTs/PMMA composites can be improved by 300%. More importantly, the BISS-SWCNTs also retain the high conductivity and transmittance of the pristine SWCNTs film. This unique bioinspired material will be of great importance in applications of multifunctional composite materials and has important implications for the future of biomimetic materials.

Quasiparticle band gap of organic-inorganic hybrid perovskites: Crystal structure, spin-orbit coupling, and self-energy effects

NASA Astrophysics Data System (ADS)

Gao, Weiwei; Gao, Xiang; Abtew, Tesfaye A.; Sun, Yi-Yang; Zhang, Shengbai; Zhang, Peihong

2016-02-01

The quasiparticle band gap is one of the most important materials properties for photovoltaic applications. Often the band gap of a photovoltaic material is determined (and can be controlled) by various factors, complicating predictive materials optimization. An in-depth understanding of how these factors affect the size of the gap will provide valuable guidance for new materials discovery. Here we report a comprehensive investigation on the band gap formation mechanism in organic-inorganic hybrid perovskites by decoupling various contributing factors which ultimately determine their electronic structure and quasiparticle band gap. Major factors, namely, quasiparticle self-energy, spin-orbit coupling, and structural distortions due to the presence of organic molecules, and their influences on the quasiparticle band structure of organic-inorganic hybrid perovskites are illustrated. We find that although methylammonium cations do not contribute directly to the electronic states near band edges, they play an important role in defining the band gap by introducing structural distortions and controlling the overall lattice constants. The spin-orbit coupling effects drastically reduce the electron and hole effective masses in these systems, which is beneficial for high carrier mobilities and small exciton binding energies.

Tinene: a two-dimensional Dirac material with a 72 meV band gap.

PubMed

Cai, Bo; Zhang, Shengli; Hu, Ziyu; Hu, Yonghong; Zou, Yousheng; Zeng, Haibo

2015-05-21

Dirac materials have attracted great interest for both fundamental research and electronic devices due to their unique band structures, but the usual near zero bandgap of graphene results in a poor on-off ratio in the corresponding transistors. Here, we report on tinene, monolayer gray tin, as a new two-dimensional material with both Dirac characteristics and a remarkable 72 meV bandgap based on density functional theory calculations. Compared with silicene and germanene, tinene has a similar hexagonal honeycomb monolayer structure, but it has an obviously larger buckling height (∼0.70 Å). Interestingly, such a moderate buckling structure results in phonon dispersion without appreciable imaginary modes, indicating the strong dynamic stability of tinene. Significantly, a distinct transformation is discovered from the band structure that six Dirac cones would appear at high symmetry K points in the first Brillouin zone when gray tin is thinned from the bulk to monolayer, but a bandgap as large as 72 meV is still preserved. Considering the recent successful realization of silicene and germanene with a similar structure, the predicted stable tinene with Dirac characteristics and a suitable bandgap is a possibility for the "more than Moore" materials and devices.

Nanoscale Charge Balancing Mechanism in Calcium-Silicate-Hydrate Gels: Novel Complex Disordered Materials from First-principles

NASA Astrophysics Data System (ADS)

Ozcelik, Ongun; White, Claire

Alkali-activated materials which have augmented chemical compositions as compared to ordinary Portland cement are sustainable technologies that have the potential to lower CO2 emissions associated with the construction industry. In particular, calcium-silicate-hydrate (C-S-H) gel is altered at the atomic scale due to changes in its chemical composition. Here, based on first-principles calculations, we predict a charge balancing mechanism at the molecular level in C-S-H gels when alkali atoms are introduced into their structure. This charge balancing process is responsible for the formation of novel structures which possess superior mechanical properties compared to their charge unbalanced counterparts. Different structural representations are obtained depending on the level of substitution and the degree of charge balancing incorporated in the structures. The impact of these charge balancing effects on the structures is assessed by analyzing their formation energies, local bonding environments, diffusion barriers and mechanical properties. These results provide information on the phase stability of alkali/aluminum containing C-S-H gels, shedding light on the fundamental mechanisms that play a crucial role in these complex disordered materials. We acknowledge funding from the Princeton Center for Complex Materials, a MRSEC supported by NSF.

New Amniotic Membrane Based Biocomposite for Future Application in Reconstructive Urology

PubMed Central

Tworkiewicz, Jakub; Kowalczyk, Tomasz; van Breda, Shane V.; Tyloch, Dominik; Kloskowski, Tomasz; Bodnar, Magda; Skopinska-Wisniewska, Joanna; Marszałek, Andrzej; Frontczak-Baniewicz, Malgorzata; Kowalewski, Tomasz A.; Drewa, Tomasz

2016-01-01

Objective Due to the capacity of the amniotic membrane (Am) to support re-epithelisation and inhibit scar formation, Am has a potential to become a considerable asset for reconstructive urology i.e., reconstruction of ureters and urethrae. The application of Am in reconstructive urology is limited due to a poor mechanical characteristic. Am reinforcement with electrospun nanofibers offers a new strategy to improve Am mechanical resistance, without affecting its unique bioactivity profile. This study evaluated biocomposite material composed of Am and nanofibers as a graft for urinary bladder augmentation in a rat model. Material and Methods Sandwich-structured biocomposite material was constructed from frozen Am and covered on both sides with two-layered membranes prepared from electrospun poly-(L-lactide-co-E-caprolactone) (PLCL). Wistar rats underwent hemicystectomy and bladder augmentation with the biocomposite material. Results Immunohistohemical analysis (hematoxylin and eosin [H&E], anti-smoothelin and Masson’s trichrome staining [TRI]) revealed effective regeneration of the urothelial and smooth muscle layers. Anti-smoothelin staining confirmed the presence of contractile smooth muscle within a new bladder wall. Sandwich-structured biocomposite graft material was designed to regenerate the urinary bladder wall, fulfilling the requirements for normal bladder tension, contraction, elasticity and compliance. Mechanical evaluation of regenerated bladder wall conducted based on Young’s elastic modulus reflected changes in the histological remodeling of the augmented part of the bladder. The structure of the biocomposite material made it possible to deliver an intact Am to the area for regeneration. An unmodified Am surface supported regeneration of the urinary bladder wall and the PLCL membranes did not disturb the regeneration process. Conclusions Am reinforcement with electrospun nanofibers offers a new strategy to improve Am mechanical resistance without affecting its unique bioactivity profile. PMID:26766636

Permeability and flammability study of composite sandwich structures for cryogenic applications

NASA Astrophysics Data System (ADS)

Bubacz, Monika

Fiber reinforced plastics offer advantageous specific strength and stiffness compared to metals and has been identified as candidates for the reusable space transportation systems primary structures including cryogenic tanks. A number of carbon and aramid fiber reinforced plastics have been considered for the liquid hydrogen tanks. Materials selection is based upon mechanical properties and containment performance (long and short term) and upon manufacturing considerations. The liquid hydrogen tank carries shear, torque, end load, and bending moment due to gusts, maneuver, take-off, landing, lift, drag, and fuel sloshing. The tank is pressurized to about 1.5 atmosphere (14.6psi or 0.1 MPa) differential pressure and on ascent maintains the liquid hydrogen at a temperature of 20K. The objective of the research effort into lay the foundation for developing the technology required for reliable prediction of the effects of various design, manufacturing, and service parameters on the susceptibility of composite tanks to develop excessive permeability to cryogenic fuels. Efforts will be expended on developing the materials and structural concepts for the cryogenic tanks that can meet the functional requirements. This will include consideration for double wall composite sandwich structures, with inner wall to meet the cryogenic requirements. The structure will incorporate nanoparticles for properties modifications and developing barriers. The main effort will be extended to tank wall's internal skin design. The main requirements for internal composite stack are: (1) introduction of barrier film (e.g. honeycomb material paper sheet) to reduce the wall permeability to hydrogen, (2) introduction of nanoparticles into laminate resin to prevent micro-cracking or crack propagation. There is a need to characterize and analyze composite sandwich structural damage due to burning and explosion. Better understanding of the flammability and blast resistance of the composite structures needs to be evaluated.

A new solution chemical method to make low dimensional thermoelectric materials

NASA Astrophysics Data System (ADS)

Ding, Zhongfen

2001-11-01

Bismuth telluride and its alloys are currently the best thermoelectric materials known at room temperature and are therefore used for portable solid-state refrigeration. If the thermal electric figure of merit ZT could be improved by a factor of about 3, quiet and rugged solid-state devices could eventually replace conventional compressor based cooling systems. In order to test a theory that improved one-dimensional or two-dimensional materials could enhance ZT due to lower thermal conductivity, we are developing solution processing methods to make low dimensional materials. Bismuth telluride and its p-type and n-type alloys have layered structures consisting of 5 atom thick Te-Bi-Te-Bi-Te sheets, each sheet about 10 A thick. Lithium ions are intercalated into the layered materials using liquid ammonia. The lithium-intercalated materials are then exfoliated in water to form colloidal suspensions with narrow particle size distributions and are stable for more than 24 hours. The layers are then deposited on substrates, which after annealing at low temperatures, form highly c-axis oriented thin films. The exfoliated layers can potentially be restacked with other ions or layered materials in between the sheets to form novel structures. The restacked layers when treated with nitric acid and sonication form high yield nanorod structured materials. This new intercalation and exfoliation followed by sonication method could potentially be used for many other layered materials to make nanorod structured materials. The low dimensional materials are characterized by powder X-ray diffraction, atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively coupled plasma (ICP) and dynamic light scattering.

Porous media modeling and micro-structurally motivated material moduli determination via the micro-dilatation theory

NASA Astrophysics Data System (ADS)

Jeong, J.; Ramézani, H.; Sardini, P.; Kondo, D.; Ponson, L.; Siitari-Kauppi, M.

2015-07-01

In the present contribution, the porous material modeling and micro-structural material parameters determination are scrutinized via the micro-dilatation theory. The main goal is to take advantage of the micro-dilatation theory which belongs to the generalized continuum media. In the first stage, the thermodynamic laws are entirely revised to reach the energy balance relation using three variables, deformation, porosity change and its gradient underlying the porous media as described in the micro-dilatation theory or so-called void elasticity. Two experiments over cement mortar specimens are performed in order to highlight the material parameters related to the pore structure. The shrinkage due to CO2 carbonation, porosity and its gradient are calculated. The extracted values are verified via 14C-PMMA radiographic image method. The modeling of swelling phenomenon of Delayed Ettringite Formation (DEF) is studied later on. This issue is performed via the crystallization pressure application using the micro-dilatation theory.

Strong tissue glue with tunable elasticity.

PubMed

Kelmansky, Regina; McAlvin, Brian J; Nyska, Abraham; Dohlman, Jenny C; Chiang, Homer H; Hashimoto, Michinao; Kohane, Daniel S; Mizrahi, Boaz

2017-04-15

Many bio-adhesive materials adhere weakly to tissue due to their high water content and weak structural integrity. Others provide desirable adhesive strength but suffer from rigid structure and lack of elasticity after administration. We have developed two water-free, liquid four-armed PEG pre-polymers modified with NHS or with NH 2 end groups which upon mixing changed from liquids to an elastic solid. The sealant and adhesive properties increased with the amount of the %v/v PEG 4 -NHS pre-polymer, and achieved adhesive properties comparable to those of cyanoacrylate glues. All mixtures showed minimal cytotoxicity in vitro. Mixtures of 90%v/v PEG 4 -NHS were retained in the subcutaneous space in vivo for up to 14days with minimal inflammation. This material's combination of desirable mechanical properties and biocompatibility has potential in numerous biomedical applications. Many bio-adhesive materials adhere weakly to tissue (e.g. hydrogels) due to their high water content and weak structural integrity. Others provide desirable mechanical properties but suffer from poor biocompatibility (e.g. cyanoacrylates). This study proposes a new concept for the formation of super strong and tunable tissue glues. Our bio-materials' enhanced performance is the product of new neat (without water or other solvents) liquid polymers that solidify after administration while allowing interactions with the tissue. Moreover, the elastic modulus of these materials could easily be tuned without compromising biocompatibility. This system could be an attractive alternative to sutures and staples since it can be applied more quickly, causes less pain and may require less equipment while maintaining the desired adhesion strength. Copyright © 2017 Acta Materialia Inc. All rights reserved.

Thermoelectric Behavior of Low Thermal Conductivity Cu-based and IV-V Chalcogenides

NASA Astrophysics Data System (ADS)

Olvera, Alan Anthony

In an ever-changing global environment, energy-related issues have become a central feature in the day-to-day conversations of the general public. A niche field that has recently made major advancements in conversion performance is thermoelectric (TE) energy conversion, where progress in material optimization has resulted in the highest efficiency thermoelectric materials to date. This includes superionic copper chalcogenides and IV-VI selenide compounds, such as Cu2Se and PbSe. Hence, this work focuses on the reliable synthesis and characterization of thermoelectric Cu-based and IV-V compounds. The electronic and optical properties of Cu-based energy conversion materials are greatly affected by synthesis-induced defects. To alleviate this issue, a novel method is developed using the topochemical redox reaction of CuSe 2 into the desired material. It is predicted that CuSe2 -serves as a sacrificial structural template for the facile synthesis of structurally related materials. This was specifically verified in the case of CuInSe 2, where CuSe2 is gradually transformed into CuInSe 2 when reacted with elemental indium. Evidently, this synthetic method is a potential avenue for new material prediction and fabrication of novel composite materials. Using the method described, a composite of CuInSe2 and the known TE material, Cu2Se, is formed. Considering the structural similarity of both compounds, the efficiency of Cu2Se is drastically increased due to enhanced carrier mobility provided by tetrahedral indium subunits. These subunits simultaneously disrupt phonon propagation which result in reduced thermal conductivity and increased TE efficiency (ZT ≈ 2.6 at 850K). More significant is the increased chemical stability of Cu2Se while under applied current and temperature. It is observed that 1 mol % indium stabilizes Cu-ion migration, encouraging the commercialization of Cu 2Se. Currently, CuAgSe is the only promising n-type Cu-based superionic TE material. Accordingly, to find a compatible material for p-type Cu2Se at high temperatures, a series of materials with the formula Cu4-xAgxSe2 were synthesized. It was found that the composition of Cu3AgSe2 ( x = 1) is a two-phase mixture at low temperatures but becomes a single-phase p-type superionic material above 440 K. On the other hand, CuAg 3Se2 (x = 3) remains a two-phase n-type mixture throughout the measured temperature range, contrary to reports of CuAg3Se2 as a single-phase high temperature material. The most important finding is the high temperature n-type behavior of CuAgSe (x = 2), which is the first instance of CuAgSe as an n-type superionic material above 470 K. It is proposed that off-stoichiometry leads to p-type behavior of CuAgSe. Moving to IV-V compounds, a detailed experimental and computational study of the material Pb7Bi4Se13 shows excellent thermoelectric properties for a non-optimized system. It behaves as an n-type material with a small band gap of about 0.23 eV, which is confirmed by band structure calculations and experimental results. It demonstrates ultralow thermal conductivity largely due to the complex atomic-scale structure and heavy constituent atoms. This results in a ZT of approximately 0.9 at 775 K, which is a promising value for further optimization. Additional results from CuSe2 structural template reactions show that several composite materials and new materials can be predicted and synthesized. This includes Cu2Se-Cu(Ga,Al)Se2 composites and new materials such as Cu(Zn,Ni)1.5Se2 and CuPb 0.75Se2. Further work in Sn-Bi-Se compounds is discussed due their complex crystal structure that may result in promising thermoelectric properties. Finally, the preliminary results of high entropy chalcogenides are presented with discussion on future development.

Cryogenic Fracture Toughness Evaluation of an Investment Cast Al-Be Alloy for Structural Applications

NASA Technical Reports Server (NTRS)

Gamwell, W. R.; McGill, P. B.

2006-01-01

Aluminum-Beryllium metal matrix composite materials are useful due to their desirable performance characteristics for aerospace applications. Desirable characteristics of this material includes light-weight, dimensional stability, stiffness, good vibration damping characteristics, low coefficient of thermal expansion, and workability, This material is 3.5 times stiffer and 22% lighter than conventional aluminum alloys. electro-optical systems, advanced sensor and guidance components for flight and satellite systems, components for light-weight high-performance aircraft engines, and structural components for helicopters. Aluminum-beryllium materials are now available in the form of near net shape investment castings. In this materials properties characterization study, the cryogenic tensile and fracture properties of an investment casting alloy, Beralcast 363, were determined. Tensile testing was performed at 21 C (70 F), -73.3 C (-100 F), -195.5 C (-320 F) and -252.8 C (-423 F), and fracture (K(sub lc) and da/dN) testing was performed at -73.3 C (-100 F), -195.5 C (-320 F) and -252.8 C (-423 F). Their use is attractive for weight critical structural applications such as advanced

High-temperature testing of high performance fiber reinforced concrete

NASA Astrophysics Data System (ADS)

Fořt, Jan; Vejmelková, Eva; Pavlíková, Milena; Trník, Anton; Čítek, David; Kolísko, Jiří; Černý, Robert; Pavlík, Zbyšek

2016-06-01

The effect of high-temperature exposure on properties of High Performance Fiber Reinforced Concrete (HPFRC) is researched in the paper. At first, reference measurements are done on HPFRC samples without high-temperature loading. Then, the HPFRC samples are exposed to the temperatures of 200, 400, 600, 800, and 1000 °C. For the temperature loaded samples, measurement of residual mechanical and basic physical properties is done. Linear thermal expansion coefficient as function of temperature is accessed on the basis of measured thermal strain data. Additionally, simultaneous difference scanning calorimetry (DSC) and thermogravimetry (TG) analysis is performed in order to observe and explain material changes at elevated temperature. It is found that the applied high temperature loading significantly increases material porosity due to the physical, chemical and combined damage of material inner structure, and negatively affects also the mechanical strength. Linear thermal expansion coefficient exhibits significant dependence on temperature and changes of material structure. The obtained data will find use as input material parameters for modelling the damage of HPFRC structures exposed to the fire and high temperature action.

Three dimensional (3D) microstructure-based finite element modeling of Al-SiC nanolaminates using focused ion beam (FIB) tomography

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

Mayer, Carl R.

Al-SiC nanolaminate composites show promise as high performance coating materials due to their combination of strength and toughness. Although a significant amount of modeling effort has been focused on materials with an idealized flat nanostructure, experimentally these materials exhibit complex undulating layer geometries. This work utilizes FIB tomography to characterize this nanostructure in 3D and finite element modeling to determine the effect that this complex structure has on the mechanical behavior of these materials. A sufficiently large volume was characterized such that a 1 × 2 μm micropillar could be generated from the dataset and compared directly to experimental results.more » The mechanical response from this nanostructure was then compared to pillar models using simplified structures with perfectly flat layers, layers with sinusoidal waviness, and layers with arc segment waviness. The arc segment based layer geometry showed the best agreement with the experimentally determined structure, indicating it would be the most appropriate geometry for future modeling efforts. - Highlights: •FIB tomography was used to determine the structure of an Al-SiC nanolaminate in 3D. •FEM was used to compare the deformation of the nanostructure to experimental results. •Idealized structures from literature were compared to the FIB determined structure. •Arc segment based structures approximated the FIB determined structure most closely.« less

Comparative Study on Cushion Performance Between 3D Printed Kelvin Structure and 3D Printed Lattice Structure

NASA Astrophysics Data System (ADS)

Priyadarshini, Lakshmi

Frequently transported packaging goods are more prone to damage due to impact, jolting or vibration in transit. Fragile goods, for example, glass, ceramics, porcelain are susceptible to mechanical stresses. Hence ancillary materials like cushions play an important role when utilized within package. In this work, an analytical model of a 3D cellular structure is established based on Kelvin model and lattice structure. The research will provide a comparative study between the 3D printed Kelvin unit structure and 3D printed lattice structure. The comparative investigation is based on parameters defining cushion performance such as cushion creep, indentation, and cushion curve analysis. The applications of 3D printing is in rapid prototyping where the study will provide information of which model delivers better form of energy absorption. 3D printed foam will be shown as a cost-effective approach as prototype. The research also investigates about the selection of material for 3D printing process. As cushion development demands flexible material, three-dimensional printing with material having elastomeric properties is required. Further, the concept of cushion design is based on Kelvin model structure and lattice structure. The analytical solution provides the cushion curve analysis with respect to the results observed when load is applied over the cushion. The results are reported on basis of attenuation and amplification curves.

Triboluminescent Materials for Smart Optical Damage Sensors for Space Applications

NASA Technical Reports Server (NTRS)

Aggarwal, Mohan D.; Penn, Benjamin G.; Miller, Jim

2007-01-01

Triboluminescence is light that is produced by pressure, friction or mechanical shock. New composite materials are constantly being reengi neered in an effort to make lightweight spacecrafts for various NASA missions. For these materials there is interest in monitoring the con dition of the composite in real time to detect any delamination or cr acking due to damage, fatigue or external forces. Methods of periodic inspection of composite structures for mechanical damage such as ult rasonic testing are rather mature. However, there is a need to develop a new technique of damage detection for composites, which could dete ct cracking or delamination from any desired location within a materi al structure in real time. This could provide a valuable tool in the confident use of composite materials for various space applications. Recently, triboluminnescent materials have been proposed as smart sen sors of structural damage. To sense the damage, these materials can b e epoxy bonded or coated in a polymer matrix or embedded in a composi te host structure. When the damage or fracture takes place in the hos t structure, it will lead to the fracture of triboluminescent crystal s resulting in a light emission. This will warn, in real time, that a structural damage has occurred. The triboluminescent emission of the candidate phosphor has to be sufficiently bright, so that the light signal reaching from the point of fracture to the detector through a fiber optic cable is sufficiently strong to be detected. There are a large number of triboluminescent materials, but few satisfy the above criterion. Authors have synthesized a Eu based organic material know n as Europium tetrakis (dibenzoylmethide) triethylammonium .(EuD(sub 4)TEA), one of the bright triboluminescent materials, which is a pote ntial candidate for application as a damage sensor and could be made into a wireless sensor with the addition of microchip, antenna and el ectronics. Preliminary results on the synthesis and characterization of this material shall be presented.

Filament Winding Multifunctional Carbon Nanotube Composites of Various Dimensionality

NASA Astrophysics Data System (ADS)

Wells, Brian David

Carbon nanotubes (CNT) have been long considered an optimal material for composites due to their high strength, high modulus, and electrical/thermal conductivity. These composite materials have the potential to be used in the aerospace, computer, automotive, medical industry as well as many others. The nano dimensions of these structures make controlled alignment and distribution difficult using many production techniques. An area that shows promise for controlled alignment is the formation of CNT yarns. Different approaches have been used to create yarns with various winding angles and diameters. CNTs resemble traditional textile fiber structures due to their one-dimensional dimensions, axial strength and radial flexibility. One difference is, depending on the length, CNTs can have aspect ratios that far exceed those of traditional textile fibers. This can complicate processing techniques and cause agglomeration which prevents optimal structures from being created. However, with specific aspect ratios and spatial distributions a specific type of CNT, vertically aligned spinnable carbon nanotubes (VASCNTs), have interesting properties that allow carbon nanotubes to be drawn from an array in a continuous aligned web. This dissertation examines the feasibility of combining VASCNTs with another textile manufacturing process, filament winding, to create structures with various levels of dimensionality. While yarn formation with CNTs has been largely studied, there has not been significant work studying the use of VASCNTs to create composite materials. The studies that have been produces revolve around mixing CNTs into epoxy or creating uni-directional wound structures. In this dissertation VASCNTs are used to create filament wound materials with various degrees of alignment. These structures include 1 dimensional coatings applied to non-conductive polymer monofilaments, two dimensional multifunctional adhesive films, and three dimensional hybrid-nano composites. The angle of alignment between the individual CNTs relative to the overall structure was used to affect the electrical properties in all of these structures and the mechanical properties of the adhesive films and hybrid-nano composites. Varying the concentration of CNT was also found to have a significant effect on the electrical and mechanical properties. The variable properties that can be created with these production techniques allow users to engineer the structure to match the desired property.

The Structure Of The Gaia Deployable Sunshield Assembly

NASA Astrophysics Data System (ADS)

Pereira, Carlos; Urgoiti, Eduardo; Pinto, Inaki

2012-07-01

GAIA is an ESA mission with launch date in 2013. Its main objective is to map the stars. After launch it will unfold a 10.2 m diameter sunshield .The structure of this shield consists of twelve 3.5 meter long composite trusses which act as scaffold to two multilayer insulation blankets. Due to thermal stability constraints the planarity of the shield must be better than 1.0 mm. The trusses are therefore lightweight structures capable of withstanding the launch loads and once deployed, the thermal environment of the spacecraft with a minimum of distortion. This paper details: • The material selection for the composite structure • Validation of the chosen materials and truss layout • The modification of manufacturing process in order to lightweight the structure • The extensive structural and thermal stability testing The sunshield has been delivered to the satellite prime after successful mechanical, thermal and deployment tests.

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).

Spotting the differences in two-dimensional materials - the Raman scattering perspective.

PubMed

Zhang, Shishu; Zhang, Na; Zhao, Yan; Cheng, Ting; Li, Xiaobo; Feng, Rui; Xu, Hua; Liu, Zhirong; Zhang, Jin; Tong, Lianming

2018-05-08

Two-dimensional (2D) layered materials have attracted tremendous attention and led to a prosperous development in both fundamental investigation and device applications in various fields, such as nanoelectronics, flexible devices, sustainable energy and catalysts. The precise characterization of the structure and properties of 2D materials is in urgent need. Raman scattering spectroscopy is one of the most popular characterization tools that is convenient, rapid and non-invasive. It provides information on both the lattice structure from the frequency of phonon modes and the electronic band structure through the intensity due to electronic resonance Raman scattering. Although a few morphological characterization tools can image 2D materials with atomic resolution, Raman scattering measurements are more tolerant to the conditions of sample preparation such as the substrate and less technically demanding, and have been one of the routine tools for the characterization of 2D materials. In this review, we focus on the characterization of 2D materials using Raman scattering spectroscopy, in particular, the revealing of differences from primitive 2D materials, such as defects, doping effects, van der Waals heterostructures and the interaction with molecules. The characteristic Raman features of such differences and the corresponding interpretation will be discussed. We hope that this review will be useful for wide research communities of materials, physics, chemistry and engineering.

Numerical Simulation of the Motion of Aerosol Particles in Open Cell Foam Materials

NASA Astrophysics Data System (ADS)

Solovev, S. A.; Soloveva, O. V.; Popkova, O. S.

2018-03-01

The motion of aerosol particles in open cell foam material is studied. The porous medium is investigated for a three-dimensional case with detailed simulation of cellular structures within an ordered geometry. Numerical calculations of the motion of particles and their deposition due to inertial and gravitational mechanisms are performed. Deposition efficiency curves for a broad range of particle sizes are constructed. The effect deposition mechanisms have on the efficiency of the porous material as a filter is analyzed.

Structure-property relationships of Thai silk-microcrystalline cellulose biocomposite materials fabricated from ionic liquid.

PubMed

DeFrates, Kelsey; Markiewicz, Theodore; Callaway, Kayla; Xue, Ye; Stanton, John; Salas-de la Cruz, David; Hu, Xiao

2017-11-01

Biomaterials made from natural proteins and polysaccharides have become increasingly popular in the biomedical field due to their good biocompatibility and tunable biodegradability. However, the low miscibility of polysaccharides with proteins presents challenges in the creation of protein-polysaccharide composite materials. In this study, neat 1-allyl-3-methylimidazolium chloride (AMIMCl) ionic liquid was used to regenerate Thailand gold Bombyx mori silk and microcrystalline cellulose blended films. This solvent was found to not only effectively dissolve both natural polymers, but also preserve the structure and integrity of the polymers. A single glass transition temperature for each blend was found in DSC curves, indicating good miscibility between the Thai silk and cellulose molecules. The structural composition as well as the morphology and thermal stability of blend films were then determined using FTIR, SEM and TGA. It was found that by varying the ratio of Thai silk to cellulose, the thermal and physical properties of the material could be tuned. Blended films tended to be more thermally stable which could be due to the presence of hydrophobic-hydrophobic or electrostatic interactions between the silk and cellulose. These studies offered a new pathway to understand the tunable properties of protein-polysaccharide composite biomaterials with controllable physical and biological properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Probabilistic analysis of the torsional effects on the tall building resistance due to earthquake even

NASA Astrophysics Data System (ADS)

Králik, Juraj; Králik, Juraj

2017-07-01

The paper presents the results from the deterministic and probabilistic analysis of the accidental torsional effect of reinforced concrete tall buildings due to earthquake even. The core-column structural system was considered with various configurations in plane. The methodology of the seismic analysis of the building structures in Eurocode 8 and JCSS 2000 is discussed. The possibilities of the utilization the LHS method to analyze the extensive and robust tasks in FEM is presented. The influence of the various input parameters (material, geometry, soil, masses and others) is considered. The deterministic and probability analysis of the seismic resistance of the structure was calculated in the ANSYS program.

Numerical study for identification of influence of energy absorption and frontal crush for vehicle crashworthiness

NASA Astrophysics Data System (ADS)

Suman, Shwetabh; Shah, Haard; Susarla, Vaibhav; Ravi, K.

2017-11-01

According to the statistics it has been seen that everyday nearly 400 people are killed due to road accidents. Due to this it has become an important concern to concentrate on the safety of the passengers which can be done by improving the crashworthiness of the vehicle. During the impact, a large amount of energy is released which if not absorbed, will be transmitted to the passenger compartment. For the safety of the passenger this energy has to be absorbed. Front rail is one of the main energy absorbing components in the vehicle front structure. When it comes to the structure and material of the part or component of the vehicle that is to be designed for crash, it is done based on three parameters: Specific Energy of Absorption, Mass of the front rail and maximum crush force. In this work, we are considering different internal geometries with different materials to increase the energy absorbing capacity of the front rail. Based on the extensive analysis carried aluminium seizes to be the opt material for frontal crash.

Isotropic band gaps and freeform waveguides observed in hyperuniform disordered photonic solids

PubMed Central

Man, Weining; Florescu, Marian; Williamson, Eric Paul; He, Yingquan; Hashemizad, Seyed Reza; Leung, Brian Y. C.; Liner, Devin Robert; Torquato, Salvatore; Chaikin, Paul M.; Steinhardt, Paul J.

2013-01-01

Recently, disordered photonic media and random textured surfaces have attracted increasing attention as strong light diffusers with broadband and wide-angle properties. We report the experimental realization of an isotropic complete photonic band gap (PBG) in a 2D disordered dielectric structure. This structure is designed by a constrained optimization method, which combines advantages of both isotropy due to disorder and controlled scattering properties due to low-density fluctuations (hyperuniformity) and uniform local topology. Our experiments use a modular design composed of Al2O3 walls and cylinders arranged in a hyperuniform disordered network. We observe a complete PBG in the microwave region, in good agreement with theoretical simulations, and show that the intrinsic isotropy of this unique class of PBG materials enables remarkable design freedom, including the realization of waveguides with arbitrary bending angles impossible in photonic crystals. This experimental verification of a complete PBG and realization of functional defects in this unique class of materials demonstrate their potential as building blocks for precise manipulation of photons in planar optical microcircuits and has implications for disordered acoustic and electronic band gap materials. PMID:24043795

Studies on Tribological Behavior of Aluminum Nitride-Coated Steel

NASA Astrophysics Data System (ADS)

Ionescu, G. C.; Nae, I.; Ripeanu, R. G.; Dinita, A.; Stan, G.

2017-02-01

The new opportunities introduced by the large development of the IoT (internet of things) are increasing the demand for sensors to be located as close as possible to the supervised process. The Aluminum Nitride (AIN) is one of the most promising materials for sensors due to its piezoelectric, excellent mechanical properties, chemical inertness and high melting point. Due to these material properties, the AlN sensors are suitable to operate in high temperature and harsh environment conditions and therefore are very promising to be employed in industrial applications. In this article are presented the studies conducted on several Aluminum Nitride-Coated Steel structures with the goal of producing sensors embedded in the ball bearings, bearings and other mobile parts of machine tools. The experiments were conducted on simple coatings structures without lubricating materials and the obtained results are promising, demonstrating that, with some limitations the AIN could be used in such applications. This paper was accepted for publication in Proceedings after double peer reviewing process but was not presented at the Conference ROTRIB’16

Meteorite as raw material for Direct Metal Printing: A proof of concept study

NASA Astrophysics Data System (ADS)

Lietaert, Karel; Thijs, Lore; Neirinck, Bram; Lapauw, Thomas; Morrison, Brian; Lewicki, Chris; Van Vaerenbergh, Jonas

2018-02-01

Asteroid mining as such is not a new concept, as it has been described in science fiction for more than a century and some of its aspects have been studied by academia for more than 30 years. Recently, there is a renewed interest in this subject due the more and more concrete plans for long-duration space missions and the need for resources to support industrial activity in space. The use of locally available resources would greatly improve the economics and sustainability of such missions. Due to its economy in material, use of additive manufacturing (AM) provides an interesting route to valorize these resources for the production of spare parts, tools and large-scale structures optimized for their local microgravity environment. Proof of concept has already been provided for AM of moon regolith. In this paper the concept of In-Situ Resource Utilization is extended towards the production of metallic objects using powdered iron meteorite as raw material. The meteorite-based powder was used to produce a structural part but further research is needed to obtain a high density part without microcracks.

Porous structures from bio-based polymers via supercritical drying

USDA-ARS?s Scientific Manuscript database

Natural biobased polymers (biopolymers or biomacromolecules) such as polysaccharides, proteins, and polylactic acid derived from plant and animal sources are interesting materials due to their abundance, renewability, low cost, biodegradability, biocompatibility, and interesting chemistry. Many biop...

Damage Simulation in Composite Materials: Why It Matters and What Is Happening Currently at NASA in This Area

NASA Technical Reports Server (NTRS)

McElroy, Mack; de Carvalho, Nelson; Estes, Ashley; Lin, Shih-yung

2017-01-01

Use of lightweight composite materials in space and aircraft structure designs is often challenging due to high costs associated with structural certification. Of primary concern in the use of composite structures is durability and damage tolerance. This concern is due to the inherent susceptibility of composite materials to both fabrication and service induced flaws. Due to a lack of general industry accepted analysis tools applicable to composites damage simulation, a certification procedure relies almost entirely on testing. It is this reliance on testing, especially compared to structures comprised of legacy metallic materials where damage simulation tools are available, that can drive costs for using composite materials in aerospace structures. The observation that use of composites can be expensive due to testing requirements is not new and as such, research on analysis tools for simulating damage in composite structures has been occurring for several decades. A convenient approach many researchers/model-developers in this area have taken is to select a specific problem relevant to aerospace structural certification and develop a model that is accurate within that scope. Some examples are open hole tension tests, compression after impact tests, low-velocity impact, damage tolerance of an embedded flaw, and fatigue crack growth to name a few. Based on the premise that running analyses is cheaper than running tests, one motivation that many researchers in this area have is that if generally applicable and reliable damage simulation tools were available the dependence on certification testing could be lessened thereby reducing overall design cost. It is generally accepted that simulation tools if applied in this manner would still need to be thoroughly validated and that composite testing will never be completely replaced by analysis. Research and development is currently occurring at NASA to create numerical damage simulation tools applicable to damage in composites. The Advanced Composites Project (ACP) at NASA Langley has supported the development of composites damage simulation tools in a consortium of aerospace companies with a goal of reducing the certification time of a commercial aircraft by 30%. And while the scope of ACP does not include spacecraft, much of the methodology and simulation capabilities can apply to spacecraft certification in the Space Launch System and Orion programs as well. Some specific applications of composite damage simulation models in a certification program are (1) evaluation of damage during service when maintenance may be difficult or impossible, (2) a tool for early design iterations, (3) gaining insight into a particular damage process and applying this insight towards a test coupon or structural design, and (4) analysis of damage scenarios that are difficult or impossible to recreate in a test. As analysis capabilities improve, these applications and more will become realized resulting in a reduction in cost for use of composites in aerospace vehicles. NASA is engaged in this process from both research and application perspectives. In addition to the background information discussed previously, this presentation covers a look at recent research at NASA in this area and some current/potential applications in the Orion program.

Nanoscale Engineering of Heterostructured Anode Materials for Boosting Lithium-Ion Storage.

PubMed

Chen, Gen; Yan, Litao; Luo, Hongmei; Guo, Shaojun

2016-09-01

Rechargeable lithium-ion batteries (LIBs), as one of the most important electrochemical energy-storage devices, currently provide the dominant power source for a range of devices, including portable electronic devices and electric vehicles, due to their high energy and power densities. The interest in exploring new electrode materials for LIBs has been drastically increasing due to the surging demands for clean energy. However, the challenging issues essential to the development of electrode materials are their low lithium capacity, poor rate ability, and low cycling stability, which strongly limit their practical applications. Recent remarkable advances in material science and nanotechnology enable rational design of heterostructured nanomaterials with optimized composition and fine nanostructure, providing new opportunities for enhancing electrochemical performance. Here, the progress as to how to design new types of heterostructured anode materials for enhancing LIBs is reviewed, in the terms of capacity, rate ability, and cycling stability: i) carbon-nanomaterials-supported heterostructured anode materials; ii) conducting-polymer-coated electrode materials; iii) inorganic transition-metal compounds with core@shell structures; and iv) combined strategies to novel heterostructures. By applying different strategies, nanoscale heterostructured anode materials with reduced size, large surfaces area, enhanced electronic conductivity, structural stability, and fast electron and ion transport, are explored for boosting LIBs in terms of high capacity, long cycling lifespan, and high rate durability. Finally, the challenges and perspectives of future materials design for high-performance LIB anodes are considered. The strategies discussed here not only provide promising electrode materials for energy storage, but also offer opportunities in being extended for making a variety of novel heterostructured nanomaterials for practical renewable energy applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon-centered radicals in γ-irradiated bone substituting biomaterials based on hydroxyapatite.

PubMed

Sadlo, Jaroslaw; Strzelczak, Grazyna; Lewandowska-Szumiel, Malgorzata; Sterniczuk, Marcin; Pajchel, Lukasz; Michalik, Jacek

2012-09-01

Gamma irradiated synthetic hydroxyapatite, bone substituting materials NanoBone(®) and HA Biocer were examined using EPR spectroscopy and compared with powdered human compact bone. In every case, radiation-induced carbon centered radicals were recorded, but their molecular structures and concentrations differed. In compact bone and synthetic hydroxyapatite the main signal assigned to the CO(2) (-) anion radical was stable, whereas the signal due to the CO(3) (3-) radical dominated in NanoBone(®) and HA Biocer just after irradiation. However, after a few days of storage of these samples, also a CO(2) (-) signal was recorded. The EPR study of irradiated compact bone and the synthetic graft materials suggest that their microscopic structures are different. In FT-IR spectra of NanoBone(®), HA Biocer and synthetic hydroxyapatite the HPO(4) (2-) and CO(3) (2-) in B-site groups are detected, whereas in compact bone signals due to collagen dominate.

Synthesis and structure determination of uranyl peroxide nanospheres in the presence of organic structure directing agents

NASA Astrophysics Data System (ADS)

Forbes, T. Z.; Burns, P. C.

2007-12-01

Recently, actinyl peroxide nanoclusters containing 20, 24, 28, or 32 actinyl polyhedra have been synthesized and their structures identified with single crystal X-ray diffraction [1]. Most nanomaterials are composed of main group elements or transition metals, therefore, these actinyl nanospheres may display vastly different chemical and physical properties due to the presence of filled f-orbitals. A major goal of our research group is to create novel actinyl materials, focusing on nano- and mesoporous materials. The original nanosphere syntheses were limited to inorganic crystallization agents, such as monovalent cations. Over the last decade, the use of organic compounds and surfactants have received increased attention as structure-directing agents for the generation of novel inorganic materials. Using structure-directing organic amines we have successfully synthesized and determined the structures of uranyl nanospheres containing 40 and 50 uranyl polyhedra. The topology of the skeletal U-50 nanosphere is identical to the C50Cl10 fullerene [2]. The topographical relationship between the actinyl nanospheres and fullerene or fullerene-like material may provide additional insight into stable configurations for lower fullerenes. [1] Burns et al., Actinyl peroxide nanospheres. Angewandte Chemie, International Edition, 2005. 44(14): p. 2135. [2] Xie et al., Capturing the Labile Fullerene[50] as C50Cl10. Science, (2004) 305(5671): p. 699.

Optimum design of structures of composite materials in response to aerodynamic noise and noise transmission

NASA Technical Reports Server (NTRS)

Yang, J. C. S.; Tsui, C. Y.

1977-01-01

Elastic wave propagation and attenuation in a model fiber matrix was investigated. Damping characteristics in graphite epoxy composite materials were measured. A sound transmission test facility suitable to incorporate into NASA Ames wind tunnel for measurement of transmission loss due to sound generation in boundary layers was constructed. Measurement of transmission loss of graphite epoxy composite panels was also included.

Polyhedral Oligomeric Silsesquioxane (POSS)-Containing Polymer Nanocomposites

PubMed Central

Ayandele, Ebunoluwa; Sarkar, Biswajit; Alexandridis, Paschalis

2012-01-01

Hybrid materials with superior structural and functional properties can be obtained by incorporating nanofillers into polymer matrices. Polyhedral oligomeric silsesquioxane (POSS) nanoparticles have attracted much attention recently due to their nanometer size, the ease of which these particles can be incorporated into polymeric materials and the unique capability to reinforce polymers. We review here the state of POSS-containing polymer nanocomposites. We discuss the influence of the incorporation of POSS into polymer matrices via chemical cross-linking or physical blending on the structure of nanocomposites, as affected by surface functional groups, and the POSS concentration. PMID:28348318

Diagnostic tool for structural health monitoring: effect of material nonlinearity and vibro-impact process

NASA Astrophysics Data System (ADS)

Hiwarkar, V. R.; Babitsky, V. I.; Silberschmidt, V. V.

2013-07-01

Numerous techniques are available for monitoring structural health. Most of these techniques are expensive and time-consuming. In this paper, vibration-based techniques are explored together with their use as diagnostic tools for structural health monitoring. Finite-element simulations are used to study the effect of material nonlinearity on dynamics of a cracked bar. Additionally, several experiments are performed to study the effect of vibro-impact behavior of crack on its dynamics. It was observed that a change in the natural frequency of the cracked bar due to crack-tip plasticity and vibro-impact behavior linked to interaction of crack faces, obtained from experiments, led to generation of higher harmonics; this can be used as a diagnostic tool for structural health monitoring.

Space environmental effects on spacecraft: LEO materials selection guide, part 1

NASA Astrophysics Data System (ADS)

Silverman, Edward M.

1995-08-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 1 covers spacecraft design considerations for the space environment; advanced composites; polymers; adhesives; metals; ceramics; protective coatings; and lubricants, greases, and seals.

Space environmental effects on spacecraft: LEO materials selection guide, part 2

NASA Astrophysics Data System (ADS)

Silverman, Edward M.

1995-08-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 2 covers thermal control systems, power systems, optical components, electronic systems, and applications.

Space environmental effects on spacecraft: LEO materials selection guide, part 2

NASA Technical Reports Server (NTRS)

Silverman, Edward M.

1995-01-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 2 covers thermal control systems, power systems, optical components, electronic systems, and applications.

Space environmental effects on spacecraft: LEO materials selection guide, part 1

NASA Technical Reports Server (NTRS)

Silverman, Edward M.

1995-01-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 1 covers spacecraft design considerations for the space environment; advanced composites; polymers; adhesives; metals; ceramics; protective coatings; and lubricants, greases, and seals.

Material damage modeling and detection in a thin metallic sheet and sandwich panel using passive acoustic transmission

NASA Astrophysics Data System (ADS)

Jiang, Hao

A method is developed for modeling, detecting, and locating material damage in homogeneous thin metallic sheets and sandwich panels. Analytical and numerical models are used along with non-contact, passive acoustic transmission measurements. It is shown that global and local damage mechanisms characterized by both material and geometrical changes in structural components can be detected using passive acoustic transmission measurements. Theoretical models of a flat sheet and sandwich panel are developed to describe the effects of global material damage due to density, modulus, or thickness changes on backplane radiated sound pressure level distributions. To describe the effects of local material damage, a three-segment stepped beam model and finite element beam, plate, and sandwich panel models are developed and analyzed using the acoustic transmission approach. It is shown that increases or decreases in transmitted sound energy occur behind a damaged material component that exhibits changes in thickness or other geometric or material properties. The damage due to thickness and density changes can be detected from the acoustic transmission, but modulus changes cannot. If the damage is located at an anti-node of a certain forced vibration pattern, the damage can be more readily observed in the data. Higher excitation frequencies within the operating spectrum are preferred to lower frequencies for damage detection. With the finite element beam, plate, and sandwich panel models, local damage detection has been performed in simulations. Experiments on a baffled homogeneous sheet and sandwich panel subjected to broadband acoustic energy show that transmitted intensity measurements with non-contact probes can be used to identify and locate material defects in the sheet and sandwich panel. Material damage is most readily identified where the changes in transmitted sound intensity are largest in the resonant frequency range of the panel. The three main contributions of this research are: (1) the use of non-contact sensing to detect global and localized damage in structural components; (2) the analytical and numerical modeling of material and geometrical damage mechanisms in structural components; and, (3) the experimental verification of acoustic transmission measurements for detecting both material and geometric damage mechanisms.

A design pathfinder with material correlation points for inflatable systems

NASA Astrophysics Data System (ADS)

Fulcher, Jared Terrell

The incorporation of inflatable structures into aerospace systems can produce significant advantages in stowed volume to mechanical effectiveness and overall weight. Many applications of these ultra-lightweight systems are designed to precisely control internal or external surfaces, or both, to achieve desired performance. The modeling of these structures becomes complex due to the material nonlinearities inherent to the majority of construction materials used in inflatable structures. Furthermore, accurately modeling the response and behavior of the interfacing boundaries that are common to many inflatable systems will lead to better understanding of the entire class of structures. The research presented involved using nonlinear finite element simulations correlated with photogrammetry testing to develop a procedure for defining material properties for commercially available polyurethane-coated woven nylon fabric, which is representative of coated materials that have been proven materials for use in many inflatable systems. Further, the new material model was used to design and develop an inflatable pathfinder system which employs only internal pressure to control an assembly of internal membranes. This canonical inflatable system will be used for exploration and development of general understanding of efficient design methodology and analysis of future systems. Canonical structures are incorporated into the design of the phased pathfinder system to allow for more universal insight. Nonlinear finite element simulations were performed to evaluate the effect of various boundary conditions, loading configurations, and material orientations on the geometric precision of geometries representing typical internal/external surfaces commonly incorporated into inflatable pathfinder system. The response of the inflatable system to possible damage was also studied using nonlinear finite element simulations. Development of a correlated material model for analysis of the inflatable pathfinder system has improved the efficiency of design and analysis techniques of future inflatable structures. KEYWORDS: Nonlinear Finite Element, Inflatable Structures, Gossamer Space Systems, Photogrammetry Measurements, Coated Woven Fabric.

Shock Wave Propagation in Cementitious Materials at Micro/Meso Scales

NASA Astrophysics Data System (ADS)

Rajendran, Arunachalam

2015-06-01

The mechanical and constitutive response of materials like cement, and bio materials like fish scale and abalone shell is very complex due to heterogeneities that are inherently present in the nano and microstructures. The intrinsic constitutive behaviors are driven by the chemical composition and the molecular, micro, and meso structures. Therefore, it becomes important to identify the material genome as the building block for the material. For instance, in cementitious materials, the genome of C-S-H phase (the glue or the paste) that holds the various clinkers, such as the dicalcium silicate, tricalcium silicate, calcium ferroaluminates, and others is extremely complex. Often mechanical behaviors of C-S-H type materials are influenced by the chemistry and the structures at all nano to micro length scales. By explicitly modeling the molecular structures using appropriate potentials, it is then possible to compute the elastic tensor from molecular dynamics simulations using all atom method. The elastic tensors for the C-S-H gel and other clinkers are determined using the software suite ``Accelrys Materials Studio.'' A strain rate dependent, fracture mechanics based tensile damage model has been incorporated into ABAQUS finite element code to model spall evolution in the heterogeneous cementitious material with all constituents explicitly modeled through one micron element resolution. This paper presents results from nano/micro/meso scale analyses of shock wave propagation in a heterogeneous cementitious material using both molecular dynamic and finite element codes.

Mechanical features of various silkworm crystalline considering hydration effect via molecular dynamics simulations.

PubMed

Kim, Yoonjung; Lee, Myeongsang; Choi, Hyunsung; Baek, Inchul; Kim, Jae In; Na, Sungsoo

2018-04-01

Silk materials are receiving significant attention as base materials for various functional nanomaterials and nanodevices, due to its exceptionally high mechanical properties, biocompatibility, and degradable characteristics. Although crystalline silk regions are composed of various repetitive motifs with differing amino acid sequences, how the effect of humidity works differently on each of the motifs and their structural characteristics remains unclear. We report molecular dynamics (MD) simulations on various silkworm fibroins composed of major motifs (i.e. (GAGAGS) n , (GAGAGA) n , and (GAGAGY) n ) at varying degrees of hydration, and reveal how each major motifs of silk fibroins change at each degrees of hydration using MD simulations and their structural properties in mechanical perspective via steered molecular dynamics simulations. Our results explain what effects humidity can have on nanoscale materials and devices consisting of crystalline silk materials.

Review of Recent Progress of Plasmonic Materials and Nano-Structures for Surface-Enhanced Raman Scattering

PubMed Central

Wang, Alan X.; Kong, Xianming

2015-01-01

Surface-enhanced Raman scattering (SERS) has demonstrated single-molecule sensitivity and is becoming intensively investigated due to its significant potential in chemical and biomedical applications. SERS sensing is highly dependent on the substrate, where excitation of the localized surface plasmons (LSPs) enhances the Raman scattering signals of proximate analyte molecules. This paper reviews research progress of SERS substrates based on both plasmonic materials and nano-photonic structures. We first discuss basic plasmonic materials, such as metallic nanoparticles and nano-rods prepared by conventional bottom-up chemical synthesis processes. Then, we review rationally-designed plasmonic nano-structures created by top-down approaches or fine-controlled synthesis with high-density hot-spots to provide large SERS enhancement factors (EFs). Finally, we discuss the research progress of hybrid SERS substrates through the integration of plasmonic nano-structures with other nano-photonic devices, such as photonic crystals, bio-enabled nanomaterials, guided-wave systems, micro-fluidics and graphene. PMID:26900428

Crystal structure and crystal growth of the polar ferrimagnet CaBaFe4O7

NASA Astrophysics Data System (ADS)

Perry, R. S.; Kurebayashi, H.; Gibbs, A.; Gutmann, M. J.

2018-05-01

Magnetic materials are a cornerstone for developing spintronic devices for the transport of information via magnetic excitations. To date, relatively few materials have been investigated for the purpose of spin transport, mostly due to the paucity of suitable candidates as these materials are often chemically complex and difficult to synthesize. We present the crystal growth and a structure solution on the high-temperature crystal structure of the layered, polar ferrimagnet CaBaFe4O7 , which is a possible new contender for spintronics research. The space group is identified as P 3 by refinement of single crystal and powder neutron diffraction data. At 400 K, the trigonal lattice parameters are a =11.0114 (11 )Å and c =10.330 (3 )Å . The structure is similar to the low-temperature phase with alternating layers of triangular and Kagome-arranged Fe-O tetrahedra. We also present details of the crystal growth by traveling solvent method.

Copper oxide nanowires as better performance electrode material for supercapacitor application

NASA Astrophysics Data System (ADS)

Yar, A.; Dennis, J. O.; Mohamed, N. M.; Mian, M. U.; Irshad, M. I.; Mumtaz, A.

2016-11-01

Supercapacitors are highly attractive energy storage devices which are capable of delivering high power, with fast charging and long cycle life. Carbon based material rely on physical charging with less capacitance while metal oxide store charge by fast redox reaction with increased capacitance. Among metal oxide, copper oxide compounds are widely use in the form of nano and micro structures with no definite control over structure. In this work we utilized the well-controlled structure copper wires, originated from AAO template. Such well controlled structure offer better capacitance values due to easily excess of ions to the surface of wires. Performance of material was check in 3 M of potassium hydroxide (KOH). Specific capacitance (Cs) was calculated by using cyclic voltammetry (CV) and Charge discharge (CDC) test. The capacitance calculate on base on CV at 25 mV/s was 101.37 F/g while CDC showed the capacitance of 90 F/g at 2 A/g.

Raman vibrational spectra of bulk to monolayer Re S 2 with lower symmetry

DOE PAGES

Feng, Yanqing; Zhou, Wei; Wang, Yaojia; ...

2015-08-26

Lattice structure and symmetry of two-dimensional (2D) layered materials are of key importance to their fundamental mechanical, thermal, electronic and optical properties. Raman spectroscopy, as a convenient and nondestructive tool, however has its limitations on identifying all symmetry allowing Raman modes and determining the corresponding crystal structure of 2D layered materials with high symmetry like graphene and MoS 2. Due to lower structural symmetry and extraordinary weak interlayer coupling of ReS 2, we successfully identified all 18 first-order Raman active modes for bulk and monolayer ReS 2. Without van der Waals (vdW) correction, our local density approximation (LDA) calculations successfullymore » reproduce all the Raman modes. Our calculations also suggest no surface reconstruction effect and the absence of low frequency rigid-layer Raman modes below 100 cm -1. As a result, combining with Raman and LDA thus provides a general approach for studying the vibrational and structural properties of 2D layered materials with lower symmetry.« less

Review of Recent Progress of Plasmonic Materials and Nano-Structures for Surface-Enhanced Raman Scattering.

PubMed

Wang, Alan X; Kong, Xianming

2015-06-01

Surface-enhanced Raman scattering (SERS) has demonstrated single-molecule sensitivity and is becoming intensively investigated due to its significant potential in chemical and biomedical applications. SERS sensing is highly dependent on the substrate, where excitation of the localized surface plasmons (LSPs) enhances the Raman scattering signals of proximate analyte molecules. This paper reviews research progress of SERS substrates based on both plasmonic materials and nano-photonic structures. We first discuss basic plasmonic materials, such as metallic nanoparticles and nano-rods prepared by conventional bottom-up chemical synthesis processes. Then, we review rationally-designed plasmonic nano-structures created by top-down approaches or fine-controlled synthesis with high-density hot-spots to provide large SERS enhancement factors (EFs). Finally, we discuss the research progress of hybrid SERS substrates through the integration of plasmonic nano-structures with other nano-photonic devices, such as photonic crystals, bio-enabled nanomaterials, guided-wave systems, micro-fluidics and graphene.

Detecting Damage in Composite Material Using Nonlinear Elastic Wave Spectroscopy Methods

NASA Astrophysics Data System (ADS)

Meo, Michele; Polimeno, Umberto; Zumpano, Giuseppe

2008-05-01

Modern aerospace structures make increasing use of fibre reinforced plastic composites, due to their high specific mechanical properties. However, due to their brittleness, low velocity impact can cause delaminations beneath the surface, while the surface may appear to be undamaged upon visual inspection. Such damage is called barely visible impact damage (BVID). Such internal damages lead to significant reduction in local strengths and ultimately could lead to catastrophic failures. It is therefore important to detect and monitor damages in high loaded composite components to receive an early warning for a well timed maintenance of the aircraft. Non-linear ultrasonic spectroscopy methods are promising damage detection and material characterization tools. In this paper, two different non-linear elastic wave spectroscopy (NEWS) methods are presented: single mode nonlinear resonance ultrasound (NRUS) and nonlinear wave modulation technique (NWMS). The NEWS methods were applied to detect delamination damage due to low velocity impact (<12 J) on various composite plates. The results showed that the proposed methodology appear to be highly sensitive to the presence of damage with very promising future NDT and structural health monitoring applications.

Topological Magnon Bands in a Kagome Lattice Ferromagnet.

PubMed

Chisnell, R; Helton, J S; Freedman, D E; Singh, D K; Bewley, R I; Nocera, D G; Lee, Y S

2015-10-02

There is great interest in finding materials possessing quasiparticles with topological properties. Such materials may have novel excitations that exist on their boundaries which are protected against disorder. We report experimental evidence that magnons in an insulating kagome ferromagnet can have a topological band structure. Our neutron scattering measurements further reveal that one of the bands is flat due to the unique geometry of the kagome lattice. Spin wave calculations show that the measured band structure follows from a simple Heisenberg Hamiltonian with a Dzyaloshinkii-Moriya interaction. This serves as the first realization of an effectively two-dimensional topological magnon insulator--a new class of magnetic material that should display both a magnon Hall effect and protected chiral edge modes.

Patched bimetallic surfaces are active catalysts for ammonia decomposition.

PubMed

Guo, Wei; Vlachos, Dionisios G

2015-10-07

Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

NASA Technical Reports Server (NTRS)

Cox, Sarah B.; Lui, Donovan; Gou, Jihua

2014-01-01

The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, which allows a shape to be formed prior to the cure, and is then pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Basalt fibers are used for the reinforcement in the composite system. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material.

Friction Stir Welding of ODS and RAFM Steels

DOE PAGES

Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; ...

2015-09-14

Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this paper, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW onmore » grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Finally, post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.« less

Preparation and Electrochemical Characterization of Mesoporous Polyaniline-Silica Nanocomposites as an Electrode Material for Pseudocapacitors

PubMed Central

Zu, Lei; Cui, Xiuguo; Jiang, Yanhua; Hu, Zhongkai; Lian, Huiqin; Liu, Yang; Jin, Yushun; Li, Yan; Wang, Xiaodong

2015-01-01

Mesoporous polyaniline-silica nanocomposites with a full interpenetrating structure for pseudocapacitors were synthesized via the vapor phase approach. The morphology and structure of the nanocomposites were deeply investigated by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis and nitrogen adsorption-desorption tests. The results present that the mesoporous nanocomposites possess a uniform particle morphology and full interpenetrating structure, leading to a continuous conductive polyaniline network with a large specific surface area. The electrochemical performances of the nanocomposites were tested in a mixed solution of sulfuric acid and potassium iodide. With the merits of a large specific surface area and suitable pore size distribution, the nanocomposite showed a large specific capacitance (1702.68 farad (F)/g) due to its higher utilization of the active material. This amazing value is almost three-times larger than that of bulk polyaniline when the same mass of active material was used. PMID:28788006

How mobile are protons in the structure of dental glass ionomer cements?

PubMed Central

Benetti, Ana R.; Jacobsen, Johan; Lehnhoff, Benedict; Momsen, Niels C. R.; Okhrimenko, Denis V.; Telling, Mark T. F.; Kardjilov, Nikolay; Strobl, Markus; Seydel, Tilo; Manke, Ingo; Bordallo, Heloisa N.

2015-01-01

The development of dental materials with improved properties and increased longevity can save costs and minimize discomfort for patients. Due to their good biocompatibility, glass ionomer cements are an interesting restorative option. However, these cements have limited mechanical strength to survive in the challenging oral environment. Therefore, a better understanding of the structure and hydration process of these cements can bring the necessary understanding to further developments. Neutrons and X-rays have been used to investigate the highly complex pore structure, as well as to assess the hydrogen mobility within these cements. Our findings suggest that the lower mechanical strength in glass ionomer cements results not only from the presence of pores, but also from the increased hydrogen mobility within the material. The relationship between microstructure, hydrogen mobility and strength brings insights into the material's durability, also demonstrating the need and opening the possibility for further research in these dental cements. PMID:25754555

Bioinspired Thermoresponsive Photonic Polymers with Hierarchical Structures and Their Unique Properties.

PubMed

Lu, Tao; Zhu, Shenmin; Ma, Jun; Lin, Jinyou; Wang, Wanlin; Pan, Hui; Tian, Feng; Zhang, Wang; Zhang, Di

2015-10-01

Thermoresponsive photonic materials having hierarchical structures are created by combining a template of Morpho butterfly wings with poly(N-isopropylacrylamide) (PNIPAM) through a chemical bonding and polymerization route. These materials show temperature-induced color tunability. Through reacting with both NIPAM monomers and the amino groups of chitosan in wing scales, glutaraldehyde workes as a bridge by creating chemical bonding between the biotemplate and the PNIPAM. The corresponding reflection peaks red-shift with increase in temperature-an opposite phenomenon to previous studies, demonstrating a thermoresponsive photonic property. This unique phenomenon is caused by the refractive index change due to the volume change of PNIPAM during the temperature rising. This work sets up an efficient strategy for the fabrication of stimuli-responsive photonic materials with hierarchical structures toward extensive applications in science and technology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

How mobile are protons in the structure of dental glass ionomer cements?

NASA Astrophysics Data System (ADS)

Benetti, Ana R.; Jacobsen, Johan; Lehnhoff, Benedict; Momsen, Niels C. R.; Okhrimenko, Denis V.; Telling, Mark T. F.; Kardjilov, Nikolay; Strobl, Markus; Seydel, Tilo; Manke, Ingo; Bordallo, Heloisa N.

2015-03-01

The development of dental materials with improved properties and increased longevity can save costs and minimize discomfort for patients. Due to their good biocompatibility, glass ionomer cements are an interesting restorative option. However, these cements have limited mechanical strength to survive in the challenging oral environment. Therefore, a better understanding of the structure and hydration process of these cements can bring the necessary understanding to further developments. Neutrons and X-rays have been used to investigate the highly complex pore structure, as well as to assess the hydrogen mobility within these cements. Our findings suggest that the lower mechanical strength in glass ionomer cements results not only from the presence of pores, but also from the increased hydrogen mobility within the material. The relationship between microstructure, hydrogen mobility and strength brings insights into the material's durability, also demonstrating the need and opening the possibility for further research in these dental cements.

Patched bimetallic surfaces are active catalysts for ammonia decomposition

NASA Astrophysics Data System (ADS)

Guo, Wei; Vlachos, Dionisios G.

2015-10-01

Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

A Review of Tribological Coatings for Control Drive Mechanisms in Space Reactors

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

CJ Larkin; JD Edington; BJ Close

2006-02-21

Tribological coatings must provide lubrication for moving components of the control drive mechanism for a space reactor and prevent seizing due to friction or diffusion welding to provide highly reliable and precise control of reflector position over the mission lifetime. Several coatings were evaluated based on tribological performance at elevated temperatures and in ultrahigh vacuum environments. Candidates with proven performance in the anticipated environment are limited primarily to disulfide materials. Irradiation data for these coatings is nonexistent. Compatibility issues between coating materials and structural components may require the use of barrier layers between the solid lubricant and structural components tomore » prevent deleterious interactions. It would be advisable to consider possible lubricant interactions prior to down-selection of structural materials. A battery of tests was proposed to provide the necessary data for eventual solid lubricant/coating selection.« less

Investigations of the structure and "interfacial" surface chemistry of Bioglass (RTM) materials by solid-state multinuclear NMR spectroscopy

NASA Astrophysics Data System (ADS)

Sarkar, Gautam

Bioactive materials such as BioglassRTM 45S5 (45% SiO 2, 24.5% CaO, 24.5% Na2O, and 6% P2O5 by weight) are sodium-phosphosilicate glasses containing independent three-dimensional silicate and phosphate networks and Na+ and Ca2+ ions as modifying cations. Due to their bioactivity, these materials are currently used as implants and for other surgical and clinical applications. The bioactivity of BioglassesRTM is due to their unique capability to form chemical bonds to tissues through an octacalciumphosphate (OCP)- and/or hydroxyapatite-like (HA) "interfacial" matrix. The formation of OCP and/or HA is preceded by the formation of a silica-rich surface layer and the subsequent growth of an amorphous calcium phosphate (a-CP) layer. Structural characterization of a series of commercial and synthesized Bioglass materials 45S5 52S, 55S, 60S, and synthesized 17O-labelled "Bioglass materials 45S, 52S, 55S and 60S" have been obtained using solid-state single-pulse magic-angle spinning (SP/MAS) 17O, 23Na, 29Si and 31P NMR. The 17O NMR isotropic chemical shifts and estimates of the quadrupole coupling constants (Cq) [at fixed asymmetry parameter ( hQ ) values of zero] have been obtained from solid-state spin-echo 17O SP/MAS NMR spectra of 17O-labelled "Bioglasses". The simulation results of these spectra reveal the presence of both bridging-oxygens (BO, i.e. ≡ Si-17OSi ≡ ) and non-bridging oxygens (NBO, i.e. ≡ Si-17O-Na+/Ca2+ ) in the silicate networks in these materials. 17O NMR spectra of these Bioglass materials do not show any direct evidence for the presence of BO and NBO atoms in the phosphate units; however, they are expected to be present in small amounts. In vitro reactions of BioglassRTM 45S5, 60S and 77S powders have been used to study the "interfacial" surface chemistry of these materials in simulated body-fluid (SBF, Kyoto or K9 solution) and/or 17O-enriched tris-buffer solution. 29Si and 31P SP/MAS NMR have been used to identify and quantify the extent of formation of surface silica species and follow the formation of phosphate species, respectively, while cross-polarization magic-angle spinning (CP/MAS) 29Si and 31P NMR have provided information about low intensity NMR peaks due to various silicon- and phosphorus-species present in the vicinity of associated protons on the surface of in vitro reacted BioglassRTM materials. The solid-state NMR investigations of the "interfacial" surface reactions of BioglassRTM materials are discussed in the context of the structure of these materials and the influence of this structure on the kinetics and the mechanism of their "interfacial" surface chemistry. (Abstract shortened by UMI.) BioglassRTM, trademark, University of Florida, Gainesville, FL, 32611.

Behaviour of a ZnO thin film as MSG for biosensing material in sub-wavelength regime

NASA Astrophysics Data System (ADS)

Iftimie, N.; Steigmann, R.; Danila, N. A.; Iacomi, F.; Faktorova, D.; Savin, A.

2016-11-01

Zinc oxide nanostructured materials, such as films and nanoparticles, could provide a suitable platform for development of high performance biosensing material due to their unique fundamental material properties. In this study, the enzyme biosensing consisting of a zinc oxide (ZnO) nanoparticles were grown on SiO2/Si substrates by vacuum thermal evaporation method and their sensing characteristics are examined in air and investigated. The film morphology is characterized by X-ray diffraction (XRD) the film crystalline quality and by scanning electron microscopy (SEM). Also, the interest in surface waves appeared due to evanescent waves in the metallic strip grating structure (MSG-Ag/ZnO/SiO2/Si) in sub-wavelength regime. Before testing the sensor with metamaterials (MMs) lens in the sub-wavelength regime, a simulation of the evanescent wave's formation has been performed at the edge of Ag strips, with thicknesses in the range of micrometers.

Development of a six-year research needs assessment for timber transportation structures

Treesearch

Terry J. Wipf; Michael A. Ritter; Sheila Rimal Duwadi; Russell C. Moody

1993-01-01

A timber bridge, once a thing of the past, is now becoming a thing of the present. Interest in timber bridges and other transportation structures has been rapidly increasing. Much of this is due to new technologies in design and construction as well as advances in material manufacturing and presevative treatments. Although timber bridges and other transportation...

Lamellae spatial distribution modulates fracture behavior and toughness of african pangolin scales

DOE PAGES

Chon, Michael J.; Daly, Matthew; Wang, Bin; ...

2017-06-10

Pangolin scales form a durable armor whose hierarchical structure offers an avenue towards high performance bio-inspired materials design. In this paper, the fracture resistance of African pangolin scales is examined using single edge crack three-point bend fracture testing in order to understand toughening mechanisms arising from the structures of natural mammalian armors. In these mechanical tests, the influence of material orientation and hydration level are examined. The fracture experiments reveal an exceptional fracture resistance due to crack deflection induced by the internal spatial orientation of lamellae. An order of magnitude increase in the measured fracture resistance due to scale hydration,more » reaching up to ~ 25 kJ/m 2 was measured. Post-mortem analysis of the fracture samples was performed using a combination of optical and electron microscopy, and X-ray computerized tomography. Interestingly, the crack profile morphologies are observed to follow paths outlined by the keratinous lamellae structure of the pangolin scale. Most notably, the inherent structure of pangolin scales offers a pathway for crack deflection and fracture toughening. Finally, the results of this study are expected to be useful as design principles for high performance biomimetic applications.« less

Lamellae spatial distribution modulates fracture behavior and toughness of african pangolin scales.

PubMed

Chon, Michael J; Daly, Matthew; Wang, Bin; Xiao, Xianghui; Zaheri, Alireza; Meyers, Marc A; Espinosa, Horacio D

2017-12-01

Pangolin scales form a durable armor whose hierarchical structure offers an avenue towards high performance bio-inspired materials design. In this study, the fracture resistance of African pangolin scales is examined using single edge crack three-point bend fracture testing in order to understand toughening mechanisms arising from the structures of natural mammalian armors. In these mechanical tests, the influence of material orientation and hydration level are examined. The fracture experiments reveal an exceptional fracture resistance due to crack deflection induced by the internal spatial orientation of lamellae. An order of magnitude increase in the measured fracture resistance due to scale hydration, reaching up to ~ 25kJ/m 2 was measured. Post-mortem analysis of the fracture samples was performed using a combination of optical and electron microscopy, and X-ray computerized tomography. Interestingly, the crack profile morphologies are observed to follow paths outlined by the keratinous lamellae structure of the pangolin scale. Most notably, the inherent structure of pangolin scales offers a pathway for crack deflection and fracture toughening. The results of this study are expected to be useful as design principles for high performance biomimetic applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Calculations vs. Measurements for Remnant Dose Rates from SNS Spent Structures

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

Popova, Irina I.; Gallmeier, Franz X.; Trotter, Steven M.

The Spallation Neutron Source (SNS) in Oak Ridge, Tennessee, is an accelerator driven neutron scattering facility for materials research. Presently SNS is capable to operate at 1.4 MW proton beam power incident on a mercury target with a proton beam energy of 1 GeV and 60 Hz repetition rate. SNS target system components are periodically replaced because they reach their end-of-life due to radiation induced material damage. Target vessel, which houses mercury target, is exchanged about two-three times per year and the proton beam window (PBW) is exchanged every two – three years.Each spent structure that leaves the SNS sitemore » requires supporting documentation with radionuclide inventory and dose rate prediction for the time of the transportation. Neutronics analyses are performed, assuming realistic irradiation history and decay case to ensure that the container/package, housing the structure, is compliant with the waste management regulations. Analyses are complex due to geometry, multi-code usage and following data treatment.To validate analyses, measurements of dose rates from the spent target vessel # 13 and PBW module #5 were performed. Neutronics analyses were performed to calculate residual dose rates from both structures for the time of measurements.« less

Lamellae spatial distribution modulates fracture behavior and toughness of african pangolin scales

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

Chon, Michael J.; Daly, Matthew; Wang, Bin

Pangolin scales form a durable armor whose hierarchical structure offers an avenue towards high performance bio-inspired materials design. In this paper, the fracture resistance of African pangolin scales is examined using single edge crack three-point bend fracture testing in order to understand toughening mechanisms arising from the structures of natural mammalian armors. In these mechanical tests, the influence of material orientation and hydration level are examined. The fracture experiments reveal an exceptional fracture resistance due to crack deflection induced by the internal spatial orientation of lamellae. An order of magnitude increase in the measured fracture resistance due to scale hydration,more » reaching up to ~ 25 kJ/m 2 was measured. Post-mortem analysis of the fracture samples was performed using a combination of optical and electron microscopy, and X-ray computerized tomography. Interestingly, the crack profile morphologies are observed to follow paths outlined by the keratinous lamellae structure of the pangolin scale. Most notably, the inherent structure of pangolin scales offers a pathway for crack deflection and fracture toughening. Finally, the results of this study are expected to be useful as design principles for high performance biomimetic applications.« less

Analysis of singular interface stresses in dissimilar material joints for plasma facing components

NASA Astrophysics Data System (ADS)

You, J. H.; Bolt, H.

2001-10-01

Duplex joint structures are typical material combinations for the actively cooled plasma facing components of fusion devices. The structural integrity under the incident heat loads from the plasma is one of the most crucial issues in the technology of these components. The most critical domain in a duplex joint component is the free surface edge of the bond interface between heterogeneous materials. This is due to the fact that the thermal stress usually shows a singular intensification in this region. If the plasma facing armour tile consists of a brittle material, the existence of the stress singularity can be a direct cause of failure. The present work introduces a comprehensive analytical tool to estimate the impact of the stress singularity for duplex PFC design and quantifies the relative stress intensification in various materials joints by use of a model formulated by Munz and Yang. Several candidate material combinations of plasma facing armour and metallic heat sink are analysed and the results are compared with each other.

Exceptionally high cavitation erosion and corrosion resistance of a high entropy alloy.

PubMed

Nair, R B; Arora, H S; Mukherjee, Sundeep; Singh, S; Singh, H; Grewal, H S

2018-03-01

Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation. High entropy alloys (HEAs) are a relatively new class of advanced structural materials with exceptional properties. In the present work, we report on the cavitation erosion behavior of Al 0.1 CoCrFeNi HEA in two different media: distilled water with and without 3.5wt% NaCl. For comparison, conventionally used stainless steel SS316L was also evaluated in identical test conditions. Despite lower hardness and yield strength, the HEA showed significantly longer incubation period and lower erosion-corrosion rate (nearly 1/4th) compared to SS316L steel. Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface. The Al 0.1 CoCrFeNi HEA showed lower corrosion current density, high pitting resistance and protection potential compared to SS316L steel. Further, HEA showed no evidence of intergranular corrosion likely due to the absence of secondary precipitates. Although, the degradation mechanisms (formation of pits and fatigue cracks) were similar for both the materials, the damage severity was found to be much higher for SS316L steel compared to HEA. Copyright © 2017 Elsevier B.V. All rights reserved.

Bond-slip detection of concrete-encased composite structure using electro-mechanical impedance technique

NASA Astrophysics Data System (ADS)

Liang, Yabin; Li, Dongsheng; Parvasi, Seyed Mohammad; Kong, Qingzhao; Lim, Ing; Song, Gangbing

2016-09-01

Concrete-encased composite structure is a type of structure that takes the advantages of both steel and concrete materials, showing improved strength, ductility, and fire resistance compared to traditional reinforced concrete structures. The interface between concrete and steel profiles governs the interaction between these two materials under loading, however, debonding damage between these two materials may lead to severe degradation of the load transferring capacity which will affect the structural performance significantly. In this paper, the electro-mechanical impedance (EMI) technique using piezoceramic transducers was experimentally investigated to detect the bond-slip occurrence of the concrete-encased composite structure. The root-mean-square deviation is used to quantify the variations of the impedance signatures due to the presence of the bond-slip damage. In order to verify the validity of the proposed method, finite element model analysis was performed to simulate the behavior of concrete-steel debonding based on a 3D finite element concrete-steel bond model. The computed impedance signatures from the numerical results are compared with the results obtained from the experimental study, and both the numerical and experimental studies verify the proposed EMI method to detect bond slip of a concrete-encased composite structure.

Elastomeric Cellular Structure Enhanced by Compressible Liquid Filler

NASA Astrophysics Data System (ADS)

Sun, Yueting; Xu, Xiaoqing; Xu, Chengliang; Qiao, Yu; Li, Yibing

2016-05-01

Elastomeric cellular structures provide a promising solution for energy absorption. Their flexible and resilient nature is particularly relevant to protection of human bodies. Herein we develop an elastomeric cellular structure filled with nanoporous material functionalized (NMF) liquid. Due to the nanoscale infiltration in NMF liquid and its interaction with cell walls, the cellular structure has a much enhanced mechanical performance, in terms of loading capacity and energy absorption density. Moreover, it is validated that the structure is highly compressible and self-restoring. Its hyper-viscoelastic characteristics are elucidated.

Timoshenko beam model for chiral materials

NASA Astrophysics Data System (ADS)

Ma, T. Y.; Wang, Y. N.; Yuan, L.; Wang, J. S.; Qin, Q. H.

2017-12-01

Natural and artificial chiral materials such as deoxyribonucleic acid (DNA), chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a Timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. The governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton's principle. The static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. This study is helpful not only for understanding the mechanical behavior of chiral materials such as DNA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.

Timoshenko beam model for chiral materials

NASA Astrophysics Data System (ADS)

Ma, T. Y.; Wang, Y. N.; Yuan, L.; Wang, J. S.; Qin, Q. H.

2018-06-01

Natural and artificial chiral materials such as deoxyribonucleic acid (DNA), chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a Timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. The governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton's principle. The static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. This study is helpful not only for understanding the mechanical behavior of chiral materials such as DNA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.

Room-temperature ferromagnetism in Fe-based perovskite solid solution in lead-free ferroelectric Bi0.5Na0.5TiO3 materials

NASA Astrophysics Data System (ADS)

Hung, Nguyen The; Bac, Luong Huu; Trung, Nguyen Ngoc; Hoang, Nguyen The; Van Vinh, Pham; Dung, Dang Duc

2018-04-01

The integration of ferromagnetism in lead-free ferroelectric materials is important to fabricate smart materials for electronic devices. In this work, (1 - x)Bi0.5Na0.5TiO3 + xMgFeO3-δ materials (x = 0-9 mol%) were prepared through sol-gel method. X-ray diffraction characterization indicated that MgFeO3-δ materials existed as a well solid solution in lead-free ferroelectric Bi0.5Na0.5TiO3 materials. The rhombohedral structure of Bi0.5Na0.5TiO3 materials was distorted due to the random distribution of Mg and Fe cations into the host lattice. The reduced optical band gap and the induced room-temperature ferromagnetism were due to the spin splitting of transition metal substitution at the B-site of perovskite Bi0.5Na0.5TiO3 and the modification by A-site co-substitution. This work elucidates the role of secondary phase as solid solution in Bi0.5Na0.5TiO3 material for development of lead-free multiferroelectric materials.

Strengthening of σ phase in a Fe20Cr9Ni cast austenite stainless steel

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

Wang, Y.Q., E-mail: yqwang@ahut.edu.cn; School of Materials Science and Engineering, Anhui University of Technology, Maanshan, Anhui, 243002; Han, J.

2013-10-15

The strengthening mechanism of σ phase in a Fe20Cr9Ni cast austenite stainless steel used for primary coolant pipes of nuclear power plants has been investigated. The yield and ultimate tensile strengths of aged specimens increased comparing with those of the unaged ones. It was found that the increase of strengths is due to the hard and brittle (σ + γ{sub 2}) structure which decomposed from α phase in the steel. Fracture surfaces of specimens after in situ tensile test showed that the inhibition of (σ + γ{sub 2}) structure on the dislocation movements was more significant than ferrite although cracksmore » started predominately at σ/γ{sub 2} interfaces. The (σ + γ{sub 2}) structure behaves like a fiber reinforced composite material. - Highlights: • The strengthening mechanism of σ phase in a Fe20Cr9Ni CASS is investigated. • The yield and ultimate tensile strengths increase with increasing of σ phase. • The increase of strengths is due to hard and brittle (σ + γ{sub 2}) structure. • The (σ + γ{sub 2}) structure in CASS behaves like a fibre reinforced composite material. • The σ/γ{sub 2} and α/σ/γ{sub 2} boundaries hinder the movement of dislocation.« less

Biomineralization of superhydrophilic vertically aligned carbon nanotubes.

PubMed

Marsi, Teresa Cristina O; Santos, Tiago G; Pacheco-Soares, Cristina; Corat, Evaldo J; Marciano, Fernanda R; Lobo, Anderson O

2012-03-06

Vertically aligned carbon nanotubes (VACNT) promise a great role for the study of tissue regeneration. In this paper, we introduce a new biomimetic mineralization routine employing superhydrophilic VACNT films as highly stable template materials. The biomineralization was obtained after VACNT soaking in simulated body fluid solution. Detailed structural analysis reveals that the polycrystalline biological apatites formed due to the -COOH terminations attached to VACNT tips after oxygen plasma etching. Our approach not only provides a novel route for nanostructured materials, but also suggests that COOH termination sites can play a significant role in biomimetic mineralization. These new nanocomposites are very promising as nanobiomaterials due to the excellent human osteoblast adhesion.

Use of lightweight concrete for reducing cracks in bridge decks.

DOT National Transportation Integrated Search

2016-04-01

Cracks in bridge decks can be due to many factors related to environmental effects, chemical reactions, and structural : loads. Careful selection of materials and mixture proportions can minimize cracking to some degree. To reduce cracking, : shrinka...

Monitoring bridge scour using fiber optic sensors.

DOT National Transportation Integrated Search

2015-04-01

The scouring process excavates and carries away materials from the bed and banks of streams, and from : around the piers and abutments of bridges. Scour undermines bridges and may cause bridge failures due to : structural instability. In the last 30 ...

Progress Update: Stack Project Complete

ScienceCinema

Cody, Tom

2017-12-12

Progress update from the Savannah River Site. The 75 foot 293 F Stack, built for plutonium production, was cut down to size in order to prevent injury or release of toxic material if the structure were to collapse due to harsh weather.

Tungsten Oxides for Photocatalysis, Electrochemistry, and Phototherapy.

PubMed

Huang, Zhen-Feng; Song, Jiajia; Pan, Lun; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

2015-09-23

The conversion, storage, and utilization of renewable energy have all become more important than ever before as a response to ever-growing energy and environment concerns. The performance of energy-related technologies strongly relies on the structure and property of the material used. The earth-abundant family of tungsten oxides (WOx ≤3 ) receives considerable attention in photocatalysis, electrochemistry, and phototherapy due to their highly tunable structures and unique physicochemical properties. Great breakthroughs have been made in enhancing the optical absorption, charge separation, redox capability, and electrical conductivity of WOx ≤3 through control of the composition, crystal structure, morphology, and construction of composite structures with other materials, which significantly promotes the efficiency of processes and devices based on this material. Herein, the properties and synthesis of WOx ≤3 family are reviewed, and then their energy-related applications are highlighted, including solar-light-driven water splitting, CO2 reduction, and pollutant removal, electrochromism, supercapacitors, lithium batteries, solar and fuel cells, non-volatile memory devices, gas sensors, and cancer therapy, from the aspect of function-oriented structure design and control. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Jiang, X., E-mail: Xiujuan.jiang@pnnl.gov

Soft magnetic materials are often limited in scalability due to conventional processes that do not retain beneficial microstructures, and their associated physical properties, during densification. In this work, friction consolidation (FC) has been studied to fabricate Fe−Si soft magnetic materials from gas-atomized powder precursors. Fe−Si powder is consolidated using variable pressure and tool rotation speed in an effort to evaluate this unique densification approach for potential improvements in magnetic properties. FC, due to the high shear deformation involved, is shown to result in uniform gradual grain structure refinement across the consolidated workpiece from the center nearest the tool to themore » edge. Magnetic properties along different orientations indicate little, if any, textural orientation in the refined grain structure. The effect of annealing on the magnetic properties is evaluated and shown to decrease coercivity. FC processing was able to retain the magnetization of the original gas-atomized powders but further process optimization is needed to reach the optimal coercivity for the soft magnetic materials applications. - Highlights: •Friction stir processing was utilized to consolidate Fe−Si soft magnetic powders. •The resultant microstructure and magnetic properties were correlated to the processing conditions. •Friction consolidation refined the grain size of the materials by ~ 40%. •Annealing successfully reduced the coercivity induced by the stress during processing. •The results shine light on the possible scaling up of nanostructured materials.« less

3D Printing of Hierarchical Silk Fibroin Structures.

PubMed

Sommer, Marianne R; Schaffner, Manuel; Carnelli, Davide; Studart, André R

2016-12-21

Like many other natural materials, silk is hierarchically structured from the amino acid level up to the cocoon or spider web macroscopic structures. Despite being used industrially in a number of applications, hierarchically structured silk fibroin objects with a similar degree of architectural control as in natural structures have not been produced yet due to limitations in fabrication processes. In a combined top-down and bottom-up approach, we exploit the freedom in macroscopic design offered by 3D printing and the template-guided assembly of ink building blocks at the meso- and nanolevel to fabricate hierarchical silk porous materials with unprecedented structural control. Pores with tunable sizes in the range 40-350 μm are generated by adding sacrificial organic microparticles as templates to a silk fibroin-based ink. Commercially available wax particles or monodisperse polycaprolactone made by microfluidics can be used as microparticle templates. Since closed pores are generated after template removal, an ultrasonication treatment can optionally be used to achieve open porosity. Such pore templating particles can be further modified with nanoparticles to create a hierarchical template that results in porous structures with a defined nanotopography on the pore walls. The hierarchically porous silk structures obtained with this processing technique can potentially be utilized in various application fields from structural materials to thermal insulation to tissue engineering scaffolds.

Visualization of the structural changes in plywood and gypsum board during the growth of Chaetomium globosum and Stachybotrys chartarum.

PubMed

Lewinska, Anna M; Hoof, Jakob B; Peuhkuri, Ruut H; Rode, Carsten; Lilje, Osu; Foley, Matthew; Trimby, Patrick; Andersen, Birgitte

2016-10-01

Fungal growth in indoor environments is associated with many negative health effects. Many studies focus on brown- and white-rot fungi and their effect on wood, but there is none that reveals the influence of soft-rot fungi, such as Stachybotrys spp. and Chaetomium spp., on the structure of building materials such as plywood and gypsum wallboard. This study focuses on using micro-computed tomography (microCT) to investigate changes of the structure of plywood and gypsum wallboard during fungal degradation by S. chartarum and C. globosum. Changes in the materials as a result of dampness and fungal growth were determined by measuring porosity and pore shape via microCT. The results show that the composition of the building material influenced the level of penetration by fungi as shown by scanning electron microscopy (SEM). Plywood appeared to be the most affected, with the penetration of moisture and fungi throughout the whole thickness of the sample. Conversely, fungi grew only on the top cardboard in the gypsum wallboard and they did not have significant influence on the gypsum wallboard structure. The majority of the observed changes in gypsum wallboard occurred due to moisture. This paper suggests that the mycelium distribution within building materials and the structural changes, caused by dampness and fungal growth, depend on the type of the material. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of the composite material thermal expansion on embedded highly birefringent polymer microstructured optical fibers

NASA Astrophysics Data System (ADS)

SzelÄ g, M.; Lesiak, P.; Kuczkowski, M.; Domański, A. W.; Woliński, T. R.

2013-05-01

Results of our research on embedded highly birefringent polymer microstructured fibers are presented. A composite material sample with fibers embedded between two layers of a multi-layer composite structure is fabricated and characterized. Temperature sensitivities of the polymer fibers are measured in a free space and compared with the fibers embedded in the composite material. It appeared that highly birefringent polymer microstructured fibers exhibit a strong increase in temperature sensitivity when embedded in the composite material, which is due to the stress-induced changes in birefringence created by thermally-induced strain.

Biodegradable Magnesium Alloys: A Review of Material Development and Applications

PubMed Central

Persaud-Sharma, Dharam; McGoron, Anthony

2012-01-01

Magnesium based alloys possess a natural ability to biodegrade due to corrosion when placed within aqueous substances, which is promising for cardiovascular and orthopedic medical device applications. These materials can serve as a temporary scaffold when placed in vivo, which is desirable for treatments when temporary supportive structures are required to assist in the wound healing process. The nature of these materials to degrade is attributed to the high oxidative corrosion rates of magnesium. In this review, a summary is presented for magnesium material development, biocorrosion characteristics, as well as a biological translation for these results. PMID:22408600

Enhanced photon absorption in spiral nanostructured solar cells using layered 2D materials.

PubMed

Tahersima, Mohammad H; Sorger, Volker J

2015-08-28

Recent investigations of semiconducting two-dimensional (2D) transition metal dichalcogenides have provided evidence for strong light absorption relative to its thickness attributed to high density of states. Stacking a combination of metallic, insulating, and semiconducting 2D materials enables functional devices with atomic thicknesses. While photovoltaic cells based on 2D materials have been demonstrated, the reported absorption is still just a few percent of the incident light due to their sub-wavelength thickness leading to low cell efficiencies. Here we show that taking advantage of the mechanical flexibility of 2D materials by rolling a molybdenum disulfide (MoS(2))/graphene (Gr)/hexagonal boron nitride stack to a spiral solar cell allows for optical absorption up to 90%. The optical absorption of a 1 μm long hetero-material spiral cell consisting of the aforementioned hetero stack is about 50% stronger compared to a planar MoS(2) cell of the same thickness; although the volumetric absorbing material ratio is only 6%. A core-shell structure exhibits enhanced absorption and pronounced absorption peaks with respect to a spiral structure without metallic contacts. We anticipate these results to provide guidance for photonic structures that take advantage of the unique properties of 2D materials in solar energy conversion applications.

Summary of Research Report

NASA Technical Reports Server (NTRS)

Elishakoff, Isaac

1998-01-01

Ten papers, published in various publications, on buckling, and the effects of imperfections on various structures are presented. These papers are: (1) Buckling mode localization in elastic plates due to misplacement in the stiffner location; (2) On vibrational imperfection sensitivity on Augusti's model structure in the vicinity of a non-linear static state; (3) Imperfection sensitivity due to elastic moduli in the Roorda Koiter frame; (4) Buckling mode localization in a multi-span periodic structure with a disorder in a single span; (5) Prediction of natural frequency and buckling load variability due to uncertainty in material properties by convex modeling; (6) Derivation of multi-dimensional ellipsoidal convex model for experimental data; (7) Passive control of buckling deformation via Anderson localization phenomenon; (8)Effect of the thickness and initial im perfection on buckling on composite cylindrical shells: asymptotic analysis and numerical results by BOSOR4 and PANDA2; (9) Worst case estimation of homology design by convex analysis; (10) Buckling of structures with uncertain imperfections - Personal perspective.

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.

Close coupling of pre- and post-processing vision stations using inexact algorithms

NASA Astrophysics Data System (ADS)

Shih, Chi-Hsien V.; Sherkat, Nasser; Thomas, Peter D.

1996-02-01

Work has been reported using lasers to cut deformable materials. Although the use of laser reduces material deformation, distortion due to mechanical feed misalignment persists. Changes in the lace patten are also caused by the release of tension in the lace structure as it is cut. To tackle the problem of distortion due to material flexibility, the 2VMethod together with the Piecewise Error Compensation Algorithm incorporating the inexact algorithms, i.e., fuzzy logic, neural networks and neural fuzzy technique, are developed. A spring mounted pen is used to emulate the distortion of the lace pattern caused by tactile cutting and feed misalignment. Using pre- and post-processing vision systems, it is possible to monitor the scalloping process and generate on-line information for the artificial intelligence engines. This overcomes the problems of lace distortion due to the trimming process. Applying the algorithms developed, the system can produce excellent results, much better than a human operator.

Investigation of Basalt Woven Fabrics for Military Applications

DTIC Science & Technology

2011-11-01

investigates the use of basalt fibers in a composite along with SC-15 epoxy resin for ballistic protection. Basalt fibers are not known as a ballistic...material but rather as a structural one. Even though basalt fibers are not expected to outperform some of the higher ballistic performing materials...such as the aramid and polyethylene fibers ; however, due to the lower manufacturing costs, basalt fibers are an interesting alternative. The objective

Understanding the Size-Dependent Sodium Storage Properties of Na2C6O6-Based Organic Electrodes for Sodium-Ion Batteries.

PubMed

Wang, Yaqun; Ding, Yu; Pan, Lijia; Shi, Ye; Yue, Zhuanghao; Shi, Yi; Yu, Guihua

2016-05-11

Organic electroactive materials represent a new generation of sustainable energy storage technology due to their unique features including environmental benignity, material sustainability, and highly tailorable properties. Here a carbonyl-based organic salt Na2C6O6, sodium rhodizonate (SR) dibasic, is systematically investigated for high-performance sodium-ion batteries. A combination of structural control, electrochemical analysis, and computational simulation show that rational morphological control can lead to significantly improved sodium storage performance. A facile antisolvent method was developed to synthesize microbulk, microrod, and nanorod structured SRs, which exhibit strong size-dependent sodium ion storage properties. The SR nanorod exhibited the best performance to deliver a reversible capacity of ∼190 mA h g(-1) at 0.1 C with over 90% retention after 100 cycles. At a high rate of 10 C, 50% of the capacity can be obtained due to enhanced reaction kinetics, and such high electrochemical activity maintains even at 80 °C. These results demonstrate a generic design route toward high-performance organic-based electrode materials for beyond Li-ion batteries. Using such a biomass-derived organic electrode material enables access to sustainable energy storage devices with low cost, high electrochemical performance and thermal stability.

SEM viewing of gypsiferous material and study of their influence on electrical resistivity

NASA Astrophysics Data System (ADS)

Dafalla, M.; Fouzan, F. Al

2012-04-01

The gypsum rich material is often linked to the cavity formation due to the high solubility of cal-cium carbonate in the presence of acidic media. This work is dedicated to a close-up look to the structure of materials rich of gypsum and material of less or traces of sulfate ions. Electrical resistivity measurements were conducted along extended lines on sections involving cavities and the resulting profiles were examined for any changes. Forms and features of gypsum and minerals containing sulfates were studied and compared to sam-ples tested using SEM (scanning electron microscope). The chemical analyses (EDAX) using electron beam was carried out and the elements present within these samples were established. Quantitative chemical testing for some parameters including sulfate ions was carried out. Structural forms variation and changes are studied in view of the chemical composition. The electrical resistivity was measured using Syscal R1 electerical resis-tivity equipment for several spots near surface. Statistical correlations between sulfate ions content and elec-trical resistivity, for near surface soils, is presented. This study is aiming at utilizing the geophysical testing methods of sulfate rich soils and predicting future cavity formation in areas of high risk to cavities due to chemical weathering.

Theoretical investigation of the structural, elastic, electronic and optical properties of the ternary indium sulfide layered structures AInS2 (A = K, Rb and Cs)

NASA Astrophysics Data System (ADS)

Bouchenafa, M.; Sidoumou, M.; Halit, M.; Benmakhlouf, A.; Bouhemadou, A.; Maabed, S.; Bentabet, A.; Bin-Omran, S.

2018-02-01

Ab initio calculations were performed to investigate the structural, elastic, electronic and optical properties of the ternary layered systems AInS2 (A = K, Rb and Cs). The calculated structural parameters are in good agreement with the existing experimental data. Analysis of the electronic band structure shows that the three studied materials are direct band-gap semiconductors. Density of states, charge transfers and charge density distribution maps were computed and analyzed. Numerical estimations of the elastic moduli and their related properties for single-crystal and polycrystalline aggregates were predicted. The optical properties were calculated for incident radiation polarized along the [100], [010] and [001] crystallographic directions. The studied materials exhibit a noticeable anisotropic behaviour in the elastic and optical properties, which is expected due to the symmetry and the layered nature of these compounds.

Nanowire modified carbon fibers for enhanced electrical energy storage

NASA Astrophysics Data System (ADS)

Shuvo, Mohammad Arif Ishtiaque; (Bill) Tseng, Tzu-Liang; Ashiqur Rahaman Khan, Md.; Karim, Hasanul; Morton, Philip; Delfin, Diego; Lin, Yirong

2013-09-01

The study of electrochemical super-capacitors has become one of the most attractive topics in both academia and industry as energy storage devices because of their high power density, long life cycles, and high charge/discharge efficiency. Recently, there has been increasing interest in the development of multifunctional structural energy storage devices such as structural super-capacitors for applications in aerospace, automobiles, and portable electronics. These multifunctional structural super-capacitors provide structures combining energy storage and load bearing functionalities, leading to material systems with reduced volume and/or weight. Due to their superior materials properties, carbon fiber composites have been widely used in structural applications for aerospace and automotive industries. Besides, carbon fiber has good electrical conductivity which will provide lower equivalent series resistance; therefore, it can be an excellent candidate for structural energy storage applications. Hence, this paper is focused on performing a pilot study for using nanowire/carbon fiber hybrids as building materials for structural energy storage materials; aiming at enhancing the charge/discharge rate and energy density. This hybrid material combines the high specific surface area of carbon fiber and pseudo-capacitive effect of metal oxide nanowires, which were grown hydrothermally in an aligned fashion on carbon fibers. The aligned nanowire array could provide a higher specific surface area that leads to high electrode-electrolyte contact area thus fast ion diffusion rates. Scanning Electron Microscopy and X-Ray Diffraction measurements are used for the initial characterization of this nanowire/carbon fiber hybrid material system. Electrochemical testing is performed using a potentio-galvanostat. The results show that gold sputtered nanowire carbon fiber hybrid provides 65.9% higher energy density than bare carbon fiber cloth as super-capacitor.

Decay assessment through thermographic analysis in architectural and archaeological heritage

NASA Astrophysics Data System (ADS)

Gomez-Heras, Miguel; Martinez-Perez, Laura; Fort, Rafael; Alvarez de Buergo, Monica

2010-05-01

Any exposed stone-built structure is subject to thermal variations due to daily, seasonal and secular environmental temperature changes. Surface temperature is a function of air temperature (due to convective heat transfer) and of infrared radiation received through insolation. While convective heat transfer homogenizes surface temperature, stone response to insolation is much more complex and the temporal and spatial temperature differences across structures are enhanced. Surface temperature in stone-built structures will be affected by orientation, sunlight inclination and the complex patterns of light and shadows generated by the often intricate morphology of historical artefacts and structures. Surface temperature will also be affected by different material properties, such as albedo, thermal conductivity, transparency and absorbance to infrared radiation of minerals and rocks. Moisture and the occurrence of salts will also be a factor affecting surface temperatures. Surface temperatures may as well be affected by physical disruptions of rocks due to differences in thermal inertia generated by cracks and other discontinuities. Thermography is a non-invasive, non-destructive technique that measures temperature variations on the surface of a material. With this technique, surface temperature rates of change and their spatial variations can be analysed. This analysis may be used not only to evaluate the incidence of thermal decay as a factor that generates or enhances stone decay, but also to detect and evaluate other factors that affect the state of conservation of architectural and archaeological heritage, as for example moisture, salts or mechanical disruptions.

Fabrication of Smooth Patterned Structures of Refractory Metals, Semiconductors, and Oxides via Template Stripping

PubMed Central

2013-01-01

The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics. PMID:24001174

Studying impact damage on carbon-fiber reinforced aircraft composite panels with sonicir

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

Han Xiaoyan; Zhang Ding; He Qi

2011-06-23

Composites are becoming more important materials in commercial aircraft structures such as the fuselage and wings with the new B787 Dreamliner from Boeing which has the target to utilize 50% by weight of composite materials. Carbon-fiber reinforced composites are the material of choice in aircraft structures. This is due to their light weight and high strength (high strength-to-weight ratio), high specific stiffness, tailorability of properties, design flexibility etc. Especially, by reducing the aircraft's body weight by using such lighter structures, the cost of fuel can be greatly reduced with the high jet fuel price for commercial airlines. However, these compositesmore » are prone to impact damage and the damage may occur without any observable sign on the surface, yet resulting in delaminations and disbonds that may occur well within the layers. We are studying the impact problem with carbon-fiber reinforced composite panels and developing SonicIR for this application as a fast and wide-area NDE technology. In this paper, we present our results in studying composite structures including carbon-fiber reinforced composite materials, and preliminary quantitative studies on delamination type defect depth identification in the panels.« less

Critical Role of Monoclinic Polarization Rotation in High-Performance Perovskite Piezoelectric Materials.

PubMed

Liu, Hui; Chen, Jun; Fan, Longlong; Ren, Yang; Pan, Zhao; Lalitha, K V; Rödel, Jürgen; Xing, Xianran

2017-07-07

High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic M_{A} structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic M_{B}, rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.

Computational screening of organic polymer dielectrics for novel accelerator technologies

DOE PAGES

Pilania, Ghanshyam; Weis, Eric; Walker, Ethan M.; ...

2018-06-18

The use of infrared lasers to power accelerating dielectric structures is a developing area of research. Within this technology, the choice of the dielectric material forming the accelerating structures, such as the photonic band gap (PBG) structures, is dictated by a range of interrelated factors including their dielectric and optical properties, amenability to photo-polymerization, thermochemical stability and other target performance metrics of the particle accelerator. In this direction, electronic structure theory aided computational screening and design of dielectric materials can play a key role in identifying potential candidate materials with the targeted functionalities to guide experimental synthetic efforts. In anmore » attempt to systematically understand the role of chemistry in controlling the electronic structure and dielectric properties of organic polymeric materials, here we employ empirical screening and density functional theory (DFT) computations, as a part of our multi-step hierarchal screening strategy. Our DFT based analysis focused on the bandgap, dielectric permittivity, and frequency-dependent dielectric losses due to lattice absorption as key properties to down-select promising polymer motifs. In addition to the specific application of dielectric laser acceleration, the general methodology presented here is deemed to be valuable in the design of new insulators with an attractive combination of dielectric properties.« less

Synthesis and structure of pyridine-functionalized mesoporous SBA-15 organosilicas and their application for sorption of diclofenac

NASA Astrophysics Data System (ADS)

Barczak, Mariusz

2018-02-01

A series of pyridine-functionalized mesoporous silicas have been prepared for the first time via direct co-condensation of tetraethoxysilane (TEOS) and 2-(2-pyridyl)ethyltrimethoxysilane (PETS) using the block copolymer Pluronic P123 as a structure-directing agent. The obtained materials were fully characterized by a wide range of instrumental techniques and employed as adsorbents for the removal of a diclofenac which is considered a priority hazardous drug. The synthesized materials exhibit a high adsorption capacities and rapid adsorption rates. The structural and adsorption properties depend largely on the relative amount of PETS/TEOS ratio: the gradual degradation of ordered structure and porosity was observed with the increasing amount of PETS. However due to the highest loading of pyridine units the most structurally degraded material had the highest adsorption uptake (631 mg g-1) indicating that the surface chemistry plays - along with porosity - an important role in governing the adsorption process. The experimental adsorption data were modelled using the Langmuir, Freundlich and Langmuir-Freundlich isotherms - among them the Langmuir-Freundlich model turned out to be the most suitable for describing adsorption behaviour of diclofenac onto the materials. The collected data show that the pyridine-functionalized mesoporous silicas can be a promising absorbent of pharmaceuticals.

Results of Simulated Galactic Cosmic Radiation (GCR) and Solar Particle Events (SPE) on Spectra Restraint Fabric

NASA Technical Reports Server (NTRS)

Peters, Benjamin; Hussain, Sarosh; Waller, Jess

2017-01-01

Spectra or similar Ultra-high-molecular-weight polyethylene (UHMWPE) fabric is the likely choice for future structural space suit restraint materials due to its high strength-to-weight ratio, abrasion resistance, and dimensional stability. During long duration space missions, space suits will be subjected to significant amounts of high-energy radiation from several different sources. To insure that pressure garment designs properly account for effects of radiation, it is important to characterize the mechanical changes to structural materials after they have been irradiated. White Sands Test Facility (WSFTF) collaborated with the Crew and Thermal Systems Division at the Johnson Space Center (JSC) to irradiate and test various space suit materials by examining their tensile properties through blunt probe puncture testing and single fiber tensile testing after the materials had been dosed at various levels of simulated GCR and SPE Iron and Proton beams at Brookhaven National Laboratories. The dosages were chosen based on a simulation developed by the Structural Engineering Division at JSC for the expected radiation dosages seen by space suit softgoods seen on a Mars reference mission. Spectra fabric tested in the effort saw equivalent dosages at 2x, 10x, and 20x the predicted dose as well as a simulated 50 year exposure to examine the range of effects on the material and examine whether any degradation due to GCR would be present if the suit softgoods were stored in deep space for a long period of time. This paper presents the results of this work and outlines the impact on space suit pressure garment design for long duration deep space missions.

Monitoring the integrity of massive aluminum structures using PZT transducers and the technique of impedance

NASA Astrophysics Data System (ADS)

da Costa, Rosalba; Maia, Joaquim M.; Assef, Amauri A.; Pichorim, Sergio F.; Costa, Eduardo T.; L. S. N. Button, Vera

2015-04-01

Safety, performance, economy and durability are essential items to qualify materials for the manufacturing of structures used in different areas. Generally, the materials used for this purpose are formed by composites and sometimes they can present failure during the manufacturing process. Such failures can also occur during use due to fatigue and wear, causing damage often difficult to be visually detected. In these cases, the use of non destructive testing (NDT) has proven to be a good choice for assessing the materials quality. The objective of this work was the electromechanical impedance evaluation of massive aluminum structures using ultrasonic transducers to detect discontinuities in the material. The tests have been done using an impedance analyzer (Agilent 4294A), an ultrasound transducer (1.6 MHz of central frequency), two types of PZT ceramics (0.267 mm and 1 mm thickness) and four aluminum samples (250 x 50 x 50 mm) with the transducer placed at three different regions. One sample was kept intact (reference) and the others were drilled in three positions with different sizes of holes (5 mm. 8 mm and 11 mm). The electromechanical impedance was recorded for each sample. The root mean square deviation index (RMSD) between the impedance magnitude of the reference and damaged samples was calculated and it was observed an increase in the RMSD due to the increase of the diameter of the holes (failures) in the samples completely drilled. The results show that the proposed methodology is suitable for monitoring the integrity of aluminum samples. The technique may be evaluated in characterizing other materials to be used in the construction of prostheses and orthoses.

Layered double hydroxide materials coated carbon electrode: New challenge to future electrochemical power devices

NASA Astrophysics Data System (ADS)

Djebbi, Mohamed Amine; Braiek, Mohamed; Namour, Philippe; Ben Haj Amara, Abdesslem; Jaffrezic-Renault, Nicole

2016-11-01

Layered double hydroxides (LDHs) have been widely used in the past years due to their unique physicochemical properties and promising applications in electroanalytical chemistry. The present paper is going to focus exclusively on magnesium-aluminum and zinc-aluminum layered double hydroxides (MgAl & ZnAl LDHs) in order to investigate the property and structure of active cation sites located within the layer structure. The MgAl and ZnAl LDH nanosheets were prepared by the constant pH co-precipitation method and uniformly supported on carbon-based electrode materials to fabricate an LDH electrode. Characterization by powder x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy revealed the LDH form and well-crystallized materials. Wetting surface properties (hydrophilicity and hydrophobicity) of both prepared LDHs were recorded by contact angle measurement show hydrophilic character and basic property. The electrochemical performance of these hybrid materials was investigated by mainly cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry techniques to identify the oxidation/reduction processes at the electrode/electrolyte interface and the effect of the divalent metal cations in total reactivity. The hierarchy of the modified electrode proves that the electronic conductivity of the bulk material is considerably dependent on the divalent cation and affects the limiting parameter of the overall redox process. However, MgAl LDH shows better performance than ZnAl LDH, due to the presence of magnesium cations in the layers. Following the structural, morphological and electrochemical behavior studies of both synthesized LDHs, the prepared LDH modified electrodes were tested through microbial fuel cell configuration, revealing a remarkable, potential new pathway for high-performance and cost-effective electrode use in electrochemical power devices.

Ab initio study of novel carbon nanofoam structure as an anode material for Li secondary battery

NASA Astrophysics Data System (ADS)

Park, Hanjin; Park, Sora; Kang, Seoung-Hun; Kwon, Young-Kyun

2014-03-01

Using ab inito density functional theory, we investigate the adsorption and diffusion properties of Li atoms on a new carbon nanostructure, which may be used as an anode of Li secondary battery. We focus on a special carbon nanofoam structure consisting of Schwarzite structures with negative Gaussian curvature as core parts, which are interconnected through (4,4) CNT segments. Considering the symmetry of the nanofoam structure, we find various Li adsorption sites exhibiting relatively large binding energies (>= 2 . 00 eV). Based on these adsorption sites, we identify several diffusion paths on the outside or inside surface of the nanofoam structure and examine the diffusion barriers along the paths. Our results show that Li atom can diffuse almost freely due to its low energy barriers on both outside and inside surfaces. Finally, we also evaluate the energy gain tendency and the volume expansion as well as the average binding energy while adding Li atoms to estimate the Li-capacity and recyclability of the system, which are important characterisitics for anode materials. We conclude that the carbon nanofoam structure would be better as an anode material than graphite in Li capacity and volume expansion.

On the Development and Use of Large Chemical Similarity Networks, Informatics Best Practices and Novel Chemical Descriptors towards Materials Quantitative Structure Property Relationships

ERIC Educational Resources Information Center

Krein, Michael

2011-01-01

After decades of development and use in a variety of application areas, Quantitative Structure Property Relationships (QSPRs) and related descriptor-based statistical learning methods have achieved a level of infamy due to their misuse. The field is rife with past examples of overtrained models, overoptimistic performance assessment, and outright…

Thermoelectric Transport in Nanocomposites

PubMed Central

Liu, Bin; Hu, Jizhu; Zhou, Jun; Yang, Ronggui

2017-01-01

Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit (ZT). In the past two decades, the introduction of nanostructures into bulk materials was believed to possibly enhance ZT. Nanocomposites is one kind of nanostructured material system which includes nanoconstituents in a matrix material or is a mixture of different nanoconstituents. Recently, nanocomposites have been theoretically proposed and experimentally synthesized to be high efficiency thermoelectric materials by reducing the lattice thermal conductivity due to phonon-interface scattering and enhancing the electronic performance due to manipulation of electron scattering and band structures. In this review, we summarize the latest progress in both theoretical and experimental works in the field of nanocomposite thermoelectric materials. In particular, we present various models of both phonon transport and electron transport in various nanocomposites established in the last few years. The phonon-interface scattering, low-energy electrical carrier filtering effect, and miniband formation, etc., in nanocomposites are discussed. PMID:28772777

Thermoelectric Transport in Nanocomposites.

PubMed

Liu, Bin; Hu, Jizhu; Zhou, Jun; Yang, Ronggui

2017-04-15

Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit ( ZT ). In the past two decades, the introduction of nanostructures into bulk materials was believed to possibly enhance ZT . Nanocomposites is one kind of nanostructured material system which includes nanoconstituents in a matrix material or is a mixture of different nanoconstituents. Recently, nanocomposites have been theoretically proposed and experimentally synthesized to be high efficiency thermoelectric materials by reducing the lattice thermal conductivity due to phonon-interface scattering and enhancing the electronic performance due to manipulation of electron scattering and band structures. In this review, we summarize the latest progress in both theoretical and experimental works in the field of nanocomposite thermoelectric materials. In particular, we present various models of both phonon transport and electron transport in various nanocomposites established in the last few years. The phonon-interface scattering, low-energy electrical carrier filtering effect, and miniband formation, etc., in nanocomposites are discussed.

25th Anniversary Article: Ordered Polymer Structures for the Engineering of Photons and Phonons

PubMed Central

Lee, Jae-Hwang; Koh, Cheong Yang; Singer, Jonathan P; Jeon, Seog-Jin; Maldovan, Martin; Stein, Ori; Thomas, Edwin L

2014-01-01

The engineering of optical and acoustic material functionalities via construction of ordered local and global architectures on various length scales commensurate with and well below the characteristic length scales of photons and phonons in the material is an indispensable and powerful means to develop novel materials. In the current mature status of photonics, polymers hold a pivotal role in various application areas such as light-emission, sensing, energy, and displays, with exclusive advantages despite their relatively low dielectric constants. Moreover, in the nascent field of phononics, polymers are expected to be a superior material platform due to the ability for readily fabricated complex polymer structures possessing a wide range of mechanical behaviors, complete phononic bandgaps, and resonant architectures. In this review, polymer-centric photonic and phononic crystals and metamaterials are highlighted, and basic concepts, fabrication techniques, selected functional polymers, applications, and emerging ideas are introduced. PMID:24338738

Band structure of comb-like photonic crystals containing meta-materials

NASA Astrophysics Data System (ADS)

Weng, Yi; Wang, Zhi-Guo; Chen, Hong

2007-09-01

We study the transmission properties and band structure of comb-like photonic crystals (PC) with backbones constructed of meta-materials (negative-index materials) within the frame of the interface response theory. The result shows the existence of a special band gap at low frequency. This gap differs from the Bragg gaps in that it is insensitive to the geometrical scaling and disorder. In comparison with the zero-average-index gap in one-dimensional PC made of alternating positive- and negative-index materials, the gap is obviously deeper and broader, given the same system parameters. In addition, the behavior of its gap-edges is also different. One gap-edge is decided by the average permittivity whereas the other is only subject to the changing of the permeability of the backbone. Due to this asymmetry of the two gap-edges, the broadening of the gap could be realized with much freedom and facility.

Recent Development of Thermoelectric Polymers and Composites.

PubMed

Yao, Hongyan; Fan, Zeng; Cheng, Hanlin; Guan, Xin; Wang, Chen; Sun, Kuan; Ouyang, Jianyong

2018-03-01

Thermoelectric materials can be used as the active materials in thermoelectric generators and as Peltier coolers for direct energy conversion between heat and electricity. Apart from inorganic thermoelectric materials, thermoelectric polymers have been receiving great attention due to their unique advantages including low cost, high mechanical flexibility, light weight, low or no toxicity, and intrinsically low thermal conductivity. The power factor of thermoelectric polymers has been continuously rising, and the highest ZT value is more than 0.25 at room temperature. The power factor can be further improved by forming composites with nanomaterials. This article provides a review of recent developments on thermoelectric polymers and polymer composites. It focuses on the relationship between thermoelectric properties and the materials structure, including chemical structure, microstructure, dopants, and doping levels. Their thermoelectric properties can be further improved to be comparable to inorganic counterparts in the near future. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multi-scale Modeling of Radiation Damage: Large Scale Data Analysis

NASA Astrophysics Data System (ADS)

Warrier, M.; Bhardwaj, U.; Bukkuru, S.

2016-10-01

Modification of materials in nuclear reactors due to neutron irradiation is a multiscale problem. These neutrons pass through materials creating several energetic primary knock-on atoms (PKA) which cause localized collision cascades creating damage tracks, defects (interstitials and vacancies) and defect clusters depending on the energy of the PKA. These defects diffuse and recombine throughout the whole duration of operation of the reactor, thereby changing the micro-structure of the material and its properties. It is therefore desirable to develop predictive computational tools to simulate the micro-structural changes of irradiated materials. In this paper we describe how statistical averages of the collision cascades from thousands of MD simulations are used to provide inputs to Kinetic Monte Carlo (KMC) simulations which can handle larger sizes, more defects and longer time durations. Use of unsupervised learning and graph optimization in handling and analyzing large scale MD data will be highlighted.

Synthesis of nanostructured bio-related materials by hybridization of synthetic polymers with polysaccharides or saccharide residues.

PubMed

Kaneko, Yoshiro; Kadokawa, Jun-Ichi

2006-01-01

In the first part of this review, we describe the synthesis of nanostructured hybrid materials composed of polysaccharides and synthetic polymers. Amylose-synthetic polymer inclusion complexes were synthesized by amylose-forming polymerization using phosphorylase enzyme in the presence of synthetic polymers such as polyethers and polyesters. Alginate-polymethacrylate hybrid materials were prepared by free-radical polymerization of cationic methacrylate in the presence of sodium alginate. These methods allow the simultaneous control of the nanostructure with polymerization, giving well-defined hybrid materials. In the second part of this review, we describe the synthesis of novel glycopolymers with rigid structures. Polyaniline-based glycopolymers were synthesized by means of oxidative polymerization of N-glycosylaniline. Polysiloxane-based glycopolymers were prepared by means of introduction of sugar-lactone to the rodlike polysiloxane. These glycopolymers had regular higher-ordered structures due to their rigid polymer backbones, resulting in control of the three-dimensional array of sugar-residues.

Effects of Contamination and Cleaning on Parachute Structural Textile Elements

NASA Technical Reports Server (NTRS)

Mollmann, Catherine

2017-01-01

Throughout their lifecycle, parachute textiles come into contact with various other substances. This contact may occur during manufacturing and repair, storage and transportation, packing, or actual use. While this interaction does not always result in negative repercussions, it may cause a loss in material strength. This paper examines the strength degradation due to several contaminants as well as the effects of cleaning agents on common parachute materials. Materials tested were: Kevlar cord and webbing, Nylon broadcloth and webbing, and Vectran cord; all of these constitute the major structural elements for CPAS (Capsule Parachute Assembly System), the parachute system for the NASA Orion Crew Module. Contaminants tested were: sewing machine oil, dried stamping ink, dirt, basting glue, Sergene, and rust. Recommendations for cleaning (or not cleaning) these materials with respect to each of the contaminants are given in this paper, as well as recommendations for future tests.

Processing and Material Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics.

NASA Technical Reports Server (NTRS)

Cox, Sarah B.

2014-01-01

The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.

Crystallographic changes in lead zirconate titanate due to neutron irradiation

DOE PAGES

Henriques, Alexandra; Graham, Joseph T.; Landsberger, Sheldon; ...

2014-11-17

Piezoelectric and ferroelectric materials are useful as the active element in non-destructive monitoring devices for high-radiation areas. Here, crystallographic structural refinement (i.e., the Rietveld method) is used to quantify the type and extent of structural changes in PbZr 0 .5Ti 0 .5O 3 after exposure to a 1 MeV equivalent neutron fluence of 1.7 × 10 15 neutrons/cm 2. The results show a measurable decrease in the occupancy of Pb and O due to irradiation, with O vacancies in the tetragonal phase being created preferentially on one of the two O sites. The results demonstrate a method by which themore » effects of radiation on crystallographic structure may be investigated.« less

Determination of orthotropic mechanical properties of 3D printed parts for structural health monitoring

NASA Astrophysics Data System (ADS)

Poissenot-Arrigoni, Bastien; Scheyer, Austin; Anton, Steven R.

2017-04-01

The evolution of additive manufacturing has allowed engineers to use 3D printing for many purposes. As a natural consequence of the 3D printing process, the printed object is anisotropic. As part of an ongoing project to embed piezoelectric devices in 3D printed structures for structural health monitoring (SHM), this study aims to find the mechanical properties of the 3D printed material and the influence of different external factors on those properties. The orthotropic mechanical properties of a 3D printed structure are dependent on the printing parameters used to create the structure. In order to develop an orthotropic material model, mechanical properties will be found experimentally from additively manufactured samples created from polylactic acid (PLA) using a consumer-level fused deposition modeling (FDM) printer; the Lulzbot TAZ 6. Nine mechanical constants including three Young's moduli, three Poisson's ratios, and three shear moduli are needed to fully describe the 3D elastic behavior of the material. Printed specimens with different raster orientations and print orientations allow calculation of the different material constants. In this work, seven of the nine mechanical constants were found. Two shear moduli were unable to be measured due to difficulties in printing two of the sample orientations. These mechanical properties are needed in order to develop orthotropic material models of systems employing 3D printed PLA. The results from this paper will be used to create a model of a piezoelectric transducer embedded in a 3D printed structure for structural health monitoring.

Multifunctional composites for energy storage

NASA Astrophysics Data System (ADS)

Shuvo, Mohammad Arif I.; Karim, Hasanul; Rajib, Md; Delfin, Diego; Lin, Yirong

2014-03-01

Electrochemical super-capacitors have become one of the most important topics in both academia and industry as novel energy storage devices because of their high power density, long life cycles, and high charge/discharge efficiency. Recently, there has been an increasing interest in the development of multifunctional structural energy storage devices such as structural super-capacitors for applications in aerospace, automobiles and portable electronics. These multifunctional structural super-capacitors provide lighter structures combining energy storage and load bearing functionalities. Due to their superior materials properties, carbon fiber composites have been widely used in structural applications for aerospace and automotive industries. Besides, carbon fiber has good electrical conductivity which will provide lower equivalent series resistance; therefore, it can be an excellent candidate for structural energy storage applications. Hence, this paper is focused on performing a pilot study for using nanowire/carbon fiber hybrids as building materials for structural energy storage materials; aiming at enhancing the charge/discharge rate and energy density. This hybrid material combines the high specific surface area of carbon fiber and pseudo-capacitive effect of metal oxide nanowires which were grown hydrothermally in an aligned fashion on carbon fibers. The aligned nanowire array could provide a higher specific surface area that leads to high electrode-electrolyte contact area and fast ion diffusion rates. Scanning Electron Microscopy (SEM) and XRay Diffraction (XRD) measurements were used for the initial characterization of this nanowire/carbon fiber hybrid material system. Electrochemical testing has been performed using a potentio-galvanostat. The results show that gold sputtered nanowire hybrid carbon fiber provides 65.9% better performance than bare carbon fiber cloth as super-capacitor.

Influence of physical activity on tibial bone material properties in laying hens

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

Rodriguez-Navarro, A. B.; McCormack, H. M.; Fleming, R. H.

Laying hens develop a type of osteoporosis that arises from a loss of structural bone, resulting in high incidence of fractures. In this study, a comparison of bone material properties was made for lines of hens created by divergent selection to have high and low bone strength and housed in either individual cages, with restricted mobility, or in an aviary system, with opportunity for increased mobility. Improvement of bone biomechanics in the high line hens and in aviary housing was mainly due to increased bone mass, thicker cortical bone and more medullary bone. However, bone material properties such as corticalmore » and medullary bone mineral composition and crystallinity as well as collagen maturity did not differ between lines. However, bone material properties of birds from the different type of housing were markedly different. The cortical bone in aviary birds had a lower degree of mineralization and bone mineral was less mature and less organized than in caged birds. Here, these differences can be explained by increased bone turnover rates due to the higher physical activity of aviary birds that stimulates bone formation and bone remodeling. Multivariate statistical analyses shows that both cortical and medullary bone contribute to breaking strengthThe cortical thickness was the single most important contributor while its degree of mineralization and porosity had a smaller contribution. Lastly, bone properties had poorer correlations with mechanical properties in cage birds than in aviary birds presumably due to the greater number of structural defects of cortical bone in cage birds.« less

Influence of physical activity on tibial bone material properties in laying hens

DOE PAGES

Rodriguez-Navarro, A. B.; McCormack, H. M.; Fleming, R. H.; ...

2017-11-03

Laying hens develop a type of osteoporosis that arises from a loss of structural bone, resulting in high incidence of fractures. In this study, a comparison of bone material properties was made for lines of hens created by divergent selection to have high and low bone strength and housed in either individual cages, with restricted mobility, or in an aviary system, with opportunity for increased mobility. Improvement of bone biomechanics in the high line hens and in aviary housing was mainly due to increased bone mass, thicker cortical bone and more medullary bone. However, bone material properties such as corticalmore » and medullary bone mineral composition and crystallinity as well as collagen maturity did not differ between lines. However, bone material properties of birds from the different type of housing were markedly different. The cortical bone in aviary birds had a lower degree of mineralization and bone mineral was less mature and less organized than in caged birds. Here, these differences can be explained by increased bone turnover rates due to the higher physical activity of aviary birds that stimulates bone formation and bone remodeling. Multivariate statistical analyses shows that both cortical and medullary bone contribute to breaking strengthThe cortical thickness was the single most important contributor while its degree of mineralization and porosity had a smaller contribution. Lastly, bone properties had poorer correlations with mechanical properties in cage birds than in aviary birds presumably due to the greater number of structural defects of cortical bone in cage birds.« less

Investigating Resulting Residual Stresses during Mechanical Forming Process

NASA Astrophysics Data System (ADS)

Akinlabi, Stephen A.; Fatoba, Olawale S.; Mashinini, Peter M.; Akinlabi, Esther T.

2018-03-01

Most manufacturing processes such as machining, welding, heat treatment, laser forming, laser cladding and, laser metal deposition, etc. are subjected to a form of heat or energy to change the geometrical shape thus changing the inherent engineering and structural properties of the material. These changes often cause the development of locked up stresses referred to as residual stresses as a result of these activities. This study reports on the residual stresses developed due to the mechanical forming process to maintain a suitable structural integrity for the formed components. The result of the analysis through the X-ray diffraction confirmed that residual stresses were induced in the manufactured parts and further revealed that residual stresses were compressive in nature as found in the parent material but with values less than the parent material.

Changes In Mechanical Properties Of Heat Resisting Alloy For A Satellite Propulsion System After A Nitriding Process

NASA Astrophysics Data System (ADS)

Kagawa, Hideshi; Fujii, Go; Kajiwara, Kenichi; Kuroda, Daisuke; Suzuki, Takuya; Yamabe-Mitarai, Yoko; Murakami, Hideyuki; Ono, Yoshinori

2012-07-01

Haynes25 (L-605) is a common heat resistant alloy used in mono-propellant structures and screen materials for catalyst beds. The lifetime requirements for thrusters have expanded dramatically after studies conducted in the 1970s on mono-propellant materials used to extend the service life. The material design had long remained unchanged, and the L-605 was still used as thruster material due to its good heritage. However, some important incidents involving degradation were found during the test-unit break-up inspection following the thruster life tests. The Japanese research team focused on the L-605 degradations found on the catalyst bed screen mesh used for mono-propellant thruster and analysed the surface of the wire material and the cross- section of the wire screen mesh used in the life tests. The investigation showed that the degradation was caused by nitriding L-605 component elements. The team suggested that the brittle fracture was attributable to tungsten (W) carbides, which formed primarily in the grain boundaries, and chromium (Cr) nitride, which formed mainly in the parts in contact with the hot firing gas. The team also suggested the installation of a platinum coating on the material surface as a countermeasure L-605 nitric degradation. Inconel 625 is now selected as a mono-propellant structure material due to its marginal raw material characters and cost. The team believes that Inconel 625 does not form W carbides since it contains no tungsten component, but does contain Cr and Fe, which form nitrides easily. Therefore, the team agreed that for the Inconel 625, there was a need to evaluate changes in the microstructure and mechanical properties following exposure to hot nitrogen gases. This paper will describe these changes of Inconel 625.

Influence of thermal and radiation effects on microstructural and mechanical properties of Nb-1Zr

NASA Astrophysics Data System (ADS)

Leonard, Keith J.; Busby, Jeremy T.; Zinkle, Steven J.

2011-07-01

The microstructural changes and corresponding effects on mechanical properties, electrical resistivity and density of Nb-1Zr were examined following neutron irradiation up to 1.8 dpa at temperatures of 1073, 1223 and 1373 K and compared with material thermally aged for similar exposure times of ˜1100 h. Thermally driven changes in the development of intragranular and grain boundary precipitate phases showed a greater influence on mechanical and physical properties compared to irradiation-induced defects for the examined conditions. Initial formation of the zirconium oxide precipitates was identified as cubic structured plates following a Baker-Nutting orientation relationship to the β-Nb matrix, with particles developing a monoclinic structure on further growth. Tensile properties of the Nb-1Zr samples showed increased strength and reduced elongation following aging and irradiation below 1373 K, with the largest tensile and hardness increases following aging at 1098 K. Tensile properties at 1373 K for the aged and irradiated samples were similar to that of the as-annealed material. Total elongation was lower in the aged material due to a strain hardening response, rather than a weak strain softening observed in the irradiated materials due in part to an irregular distribution of the precipitates in the irradiated materials. Though intergranular fracture surfaces were observed on the 1248 K aged tensile specimens, the aged and irradiated material showed uniform elongations >3% and total elongation >12% for all conditions tested. Cavity formation was observed in material irradiated to 0.9 dpa at 1073 and 1223 K. However, since void densities were estimated to be below 3 × 10 17 m -3 these voids contributed little to either mechanical strengthening of the material or measured density changes.

The effect of rare earth ions on structural, morphological and thermoelectric properties of nanostructured tin oxide based perovskite materials

NASA Astrophysics Data System (ADS)

Rajasekaran, P.; Alagar Nedunchezhian, A. S.; Yalini Devi, N.; Sidharth, D.; Arivanandhan, M.; Jayavel, R.

2017-11-01

Metal oxide based materials are promising for thermoelectric applications especially at elevated temperature due to their high thermal stability. Recently, perovskite based oxide materials have been focused as a novel thermoelectric material due to their tunable electrical conductivity. Thermoelectric properties of BaSnO3 has been extensively investigated. However, the effect of various rare earth doping on the thermoelectric properties of BaSnO3 is not studied in detail. In the present work, Ba1-x RE x SnO3 (RE  =  La and Sr) materials with x  =  0.05 were prepared by polymerization complex (PC) method in order to study the effect of RE incorporation on the structural, morphological and thermoelectric characteristics of BaSnO3. The structural and morphological properties of the synthesized materials were studied by XRD and TEM analysis. XRD analysis confirmed the mixed phases of the synthesized samples. The TEM images of Ba1-x Sr x SnO3 shows hexagonal and cubic morphology while, Ba1-x La x SnO3 exhibit rod like morphology. Various functional groups of the perovskite material were identified using FTIR analysis. Formation of the perovskite material was further confirmed by XPS analysis. The Seebeck coefficient of Ba0.95La0.05SnO3 was relatively higher than that of Ba0.95Sr0.05SnO3, especially at high temperature. The rod like morphology of Ba0.95La0.05SnO3 may facilitate fast electron transport which results high thermal power compared to Ba0.95Sr0.05SnO3 despite of its poor crystalline nature. The substitution of La3+ on the Ba2+ site could vary the carrier density which results high Seebeck coefficient of Ba0.95La0.05SnO3 compared to Ba0.95Sr0.05SnO3. From the experimental results, it is obvious that Ba0.95La0.05SnO3 could be a promising thermoelectric material for high temperature application.

Performance and properties of atomic oxygen protective coatings for polymeric materials

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Lamoreaux, Cynthia

1992-01-01

Such large LEO spacecraft as the Space Station Freedom will encounter high atomic oxygen fluences which entail the use of protective coatings for their polymeric structural materials. Such coatings have demonstrated polymer mass losses due to oxidation that are much smaller than those of unprotected materials. Attention is here given to protective and/or electrically conductive coatings of SiO(x), Ge, and indium-tin oxide which have been exposed to atomic oxygen in order to ascertain mass loss, electrical conductivity, and optical property dependence on atomic oxygen exposure.

Next Generation Tissue Engineering of Orthopedic Soft Tissue-to-Bone Interfaces.

PubMed

Boys, Alexander J; McCorry, Mary Clare; Rodeo, Scott; Bonassar, Lawrence J; Estroff, Lara A

2017-09-01

Soft tissue-to-bone interfaces are complex structures that consist of gradients of extracellular matrix materials, cell phenotypes, and biochemical signals. These interfaces, called entheses for ligaments, tendons, and the meniscus, are crucial to joint function, transferring mechanical loads and stabilizing orthopedic joints. When injuries occur to connected soft tissue, the enthesis must be re-established to restore function, but due to structural complexity, repair has proven challenging. Tissue engineering offers a promising solution for regenerating these tissues. This prospective review discusses methodologies for tissue engineering the enthesis, outlined in three key design inputs: materials processing methods, cellular contributions, and biochemical factors.

Evaluation of reinforced concrete structures using the electromagnetic method

NASA Astrophysics Data System (ADS)

Chady, Tomasz; Frankowski, Paweł; Waszczuk, Paweł; Zieliński, Adam

2018-04-01

Reinforced concrete has been a universally dominant construction material for over a century, although structures made of this material are often exposed to many types of damage and deterioration due to different causes and external conditions. The most important problem is corrosion of the reinforcement. Currently, most of the inspection methods of rebar in concrete are of an indirect nature or they are partially destructive. Moreover, none of the well-known systems allow for direct and non-destructive evaluation of the rebar corrosion. The purpose of this paper is to present the new, direct and non-destructive method, which allows detection of cracks and corrosion of the reinforcement bars.

Plasmon modes supported by left-handed material slab waveguide with conducting interfaces

NASA Astrophysics Data System (ADS)

Taya, Sofyan A.

2018-07-01

Theoretical analysis of left-handed material core layer waveguide in the presence of interface free charge layers is presented. The thickness of the interface charge layer can be neglected compared with the incident wavelength. The tangential component of the magnetic field is no longer continuous due to the conducting interfaces. The non-homogeneous boundary conditions are solved and the corresponding dispersion relation is found. The dispersion properties are studied. The proposed structure is found to support even as well as odd plasmon modes. Moreover, the structure shows abnormal dispersion property of decreasing the effective index with the increase of the frequency which means negative group velocity.

Next Generation Tissue Engineering of Orthopedic Soft Tissue-to-Bone Interfaces

PubMed Central

Boys, Alexander J.; McCorry, Mary Clare; Rodeo, Scott; Bonassar, Lawrence J.; Estroff, Lara A.

2017-01-01

Soft tissue-to-bone interfaces are complex structures that consist of gradients of extracellular matrix materials, cell phenotypes, and biochemical signals. These interfaces, called entheses for ligaments, tendons, and the meniscus, are crucial to joint function, transferring mechanical loads and stabilizing orthopedic joints. When injuries occur to connected soft tissue, the enthesis must be re-established to restore function, but due to structural complexity, repair has proven challenging. Tissue engineering offers a promising solution for regenerating these tissues. This prospective review discusses methodologies for tissue engineering the enthesis, outlined in three key design inputs: materials processing methods, cellular contributions, and biochemical factors. PMID:29333332

Mechanical behavior of precipitation hardenable steels exposed to highly corrosive environment

NASA Technical Reports Server (NTRS)

Rosa, Ferdinand

1994-01-01

Unexpected occurrences of failures, due to stress corrosion cracking (SCC) of structural components, indicate a need for improved characterization of materials and more advanced analytical procedures for reliably predicting structures performance. Accordingly, the purpose of this study was to determine the stress corrosion susceptibility of 15 - 5 PH steel over a wide range of applied strain rates in a highly corrosive environment. The selected environment for this investigation was a 3.5 percent NaCl aqueous solution. The material selected for the study was 15 - 5 PH steel in the H 900 condition. The Slow Strain Rate technique was used to test the metallic specimens.

Photoelastic colloidal gel for a high-sensitivity strain sensor.

PubMed

Pan, Hui; Chen, Zhixin; Zhu, Shenmin; Jiang, Chun; Zhang, Di

2018-04-27

Nanoparticles, having the ability to self-assemble into an ordered structure in their suspensions, analogous to liquid crystals, have attracted extensive attention. Herein, we report a new type of colloidal gel with an ordered crystal structure assembled from 1D and 2D nanoparticles. The material has high elasticity and, more interestingly, it shows significant photoelasticity. Its refractive index can be tuned under external stress and exhibits an ultra-wide dynamic range (Δn) of the order of 10 -2 . Due to the large Δn, the material shows an extremely high strain sensibility of 720 nm/ε, an order of magnitude higher than the reported ones.

Photoelastic colloidal gel for a high-sensitivity strain sensor

NASA Astrophysics Data System (ADS)

Pan, Hui; Chen, Zhixin; Zhu, Shenmin; Jiang, Chun; Zhang, Di

2018-04-01

Nanoparticles, having the ability to self-assemble into an ordered structure in their suspensions, analogous to liquid crystals, have attracted extensive attention. Herein, we report a new type of colloidal gel with an ordered crystal structure assembled from 1D and 2D nanoparticles. The material has high elasticity and, more interestingly, it shows significant photoelasticity. Its refractive index can be tuned under external stress and exhibits an ultra-wide dynamic range (Δn) of the order of 10-2. Due to the large Δn, the material shows an extremely high strain sensibility of 720 nm/ɛ, an order of magnitude higher than the reported ones.

Investigation of a novel approach for the cross-linking characterization of SU-8 photoresist materials by means of optical dispersion measurements

NASA Astrophysics Data System (ADS)

Taudt, Ch.; Baselt, T.; Koch, E.; Hartmann, P.

2014-03-01

The increase in efficiency and precision in the production of semiconductor structures under the use of polymeric materials like SU-8 is crucial in securing the technological innovation within this industry. The manufacturing of structures on wafers demands a high quality of materials, tools and production processes. In particular, deviations in the materials' parameters (e.g. cross-linking state, density or mechanical properties) could lead to subsequent problems such as a reduced lifetime of structures and systems. In particular problems during the soft and post-exposure bake process can lead to an inhomogeneous distribution of material properties. This paper describes a novel approach for the characterization of SU-8 material properties in relation to a second epoxy-based material of different cross-linking by the measurement of optical dispersion within the material. A white-light interferometer was used. In particular the setup consisted of a white-light source, a Michelson-type interferometer and a spectrometer. The investigation of the dispersion characteristics was carried out by the detection of the equalization wavelength for different positions of the reference arm in a range from 400 to 900 nm. The measured time delay due to dispersion ranges from 850 to 1050 ps/m. For evaluation purposes a 200μm SU-8 sample was characterized in the described setup regarding its dispersion characteristics in relation to bulk epoxy material. The novel measurement approach allowed a fast and high-resolution material characterization for SU-8 micro structures which was suitable for integration in production lines. The outlook takes modifications of the experimental setup regarding on-wafer measurements into account.

Fatigue strength degradation of metals in corrosive environments

NASA Astrophysics Data System (ADS)

Adasooriya, N. D.; Hemmingsen, T.; Pavlou, D.

2017-12-01

Structures exposed to aggressive environmental conditions are often subjected to time-dependent loss of coating and loss of material due to corrosion; this causes reduction in the cross-sectional properties of the members, increased surface roughness, surface irregularities and corrosion pits, and degradation of material strengths. These effects have been identified and simulated in different research studies. However, time and corrosive media dependent fatigue strength curves for materials have not been discussed in the design or assessment guidelines for structures. This paper attempts to review the corrosion degradation process and available approaches/models used to determine the fatigue strength of corroded materials and to interpolate corrosion deterioration data. High cycle fatigue and full range fatigue life formulae for fatigue strength of corroded materials are proposed. The above formulae depend on the endurance limit of corroded material, in addition to the stress-life fatigue curve parameters of the uncorroded material. The endurance limit of corroded material can either be determined by a limited number of tests in the very high-cycle fatigue region or predicted by an analytical approach. Comparison with experimentally measured corrosion fatigue behavior of several materials is provided and discussed.

New Trends in Forging Technologies

NASA Astrophysics Data System (ADS)

Behrens, B.-A.; Hagen, T.; Knigge, J.; Elgaly, I.; Hadifi, T.; Bouguecha, A.

2011-05-01

Limited natural resources increase the demand on highly efficient machinery and transportation means. New energy-saving mobility concepts call for design optimisation through downsizing of components and choice of corrosion resistant materials possessing high strength to density ratios. Component downsizing can be performed either by constructive structural optimisation or by substituting heavy materials with lighter high-strength ones. In this context, forging plays an important role in manufacturing load-optimised structural components. At the Institute of Metal Forming and Metal-Forming Machines (IFUM) various innovative forging technologies have been developed. With regard to structural optimisation, different strategies for localised reinforcement of components were investigated. Locally induced strain hardening by means of cold forging under a superimposed hydrostatic pressure could be realised. In addition, controlled martensitic zones could be created through forming induced phase conversion in metastable austenitic steels. Other research focused on the replacement of heavy steel parts with high-strength nonferrous alloys or hybrid material compounds. Several forging processes of magnesium, aluminium and titanium alloys for different aeronautical and automotive applications were developed. The whole process chain from material characterisation via simulation-based process design to the production of the parts has been considered. The feasibility of forging complex shaped geometries using these alloys was confirmed. In spite of the difficulties encountered due to machine noise and high temperature, acoustic emission (AE) technique has been successfully applied for online monitoring of forging defects. New AE analysis algorithm has been developed, so that different signal patterns due to various events such as product/die cracking or die wear could be detected and classified. Further, the feasibility of the mentioned forging technologies was proven by means of the finite element analysis (FEA). For example, the integrity of forging dies with respect to crack initiation due to thermo-mechanical fatigue as well as the ductile damage of forgings was investigated with the help of cumulative damage models. In this paper some of the mentioned approaches are described.

Laboratory investigations into fracture propagation characteristics of rock material

NASA Astrophysics Data System (ADS)

Prasad, B. N. V. Siva; Murthy, V. M. S. R.

2018-04-01

After Industrial Revolution, demand of materials for building up structures have increased enormously. Unfortunately, failures of such structures resulted in loss of life and property. Rock is anisotropic and discontinuous in nature with inherent flaws or so-called discontinuities in it. Rock is apparently used for construction in mining, civil, tunnelling, hydropower, geothermal and nuclear sectors [1]. Therefore, the strength of the structure built up considering rockmass as the construction material needs proper technical evaluation during designing stage itself to prevent and predict the scenarios of catastrophic failures due to these inherent fractures [2]. In this study, samples collected from nine different drilling sites have been investigated in laboratory for understanding the fracture propagation characteristics in rock. Rock material properties, ultrasonic velocities through pulse transmission technique and Mode I Fracture Toughness Testing of different variants of Dolomites and Graywackes are determined in laboratory and the resistance of the rock material to catastrophic crack extension or propagation has been determined. Based on the Fracture Toughness values and the rock properties, critical Energy Release Rates have been estimated. However further studies in this direction is to be carried out to understand the fracture propagation characteristics in three-dimensional space.

The effect of strontium and barium doping on perovskite-structured energy materials for photovoltaic applications

NASA Astrophysics Data System (ADS)

Wu, Ming-Chung; Chen, Wei-Cheng; Chan, Shun-Hsiang; Su, Wei-Fang

2018-01-01

Perovskite solar cell is a novel photovoltaic technology with the superior progress in efficiency and the simple solution processes. Develop lead-free or lead-reduced perovskite materials is a significant concern for high-performance perovskite solar cell. Among the alkaline earth metals, the Sr2+ and Ba2+ are suitable for Pb2+ replacement in perovskite film due to fitting Goldschmidt's tolerance factor. In this study, we adopted Ba-doped and Sr-doped perovskite structured materials with different doping levels, including 1.0, 5.0, and 10.0 mol%, to prepare perovskite solar cells. Both Ba-doped and Sr-doped perovskite structured materials have a related tendency in absorption behavior and surface morphology. At 10.0 mol% doping level, the power conversion efficiency (PCE) of Sr-doped perovskite solar cells is only ∼0.5%, but the PCE of Ba-doped perovskite solar cells can be achieved to ∼9.7%. Ba-doped perovskite solar cells showed the acceptable photovoltaic characteristics than Sr-doped perovskite solar cells. Ba dopant can partially replace the amount of lead in the perovskite solar cells, and it could be a potential candidate in the field of lead-free or lead-reduced perovskite energy materials.

Graphene-based hybrid structures combined with functional materials of ferroelectrics and semiconductors.

PubMed

Jie, Wenjing; Hao, Jianhua

2014-06-21

Fundamental studies and applications of 2-dimensional (2D) graphene may be deepened and broadened via combining graphene sheets with various functional materials, which have been extended from the traditional insulator of SiO2 to a versatile range of dielectrics, semiconductors and metals, as well as organic compounds. Among them, ferroelectric materials have received much attention due to their unique ferroelectric polarization. As a result, many attractive characteristics can be shown in graphene/ferroelectric hybrid systems. On the other hand, graphene can be integrated with conventional semiconductors and some newly-discovered 2D layered materials to form distinct Schottky junctions, yielding fascinating behaviours and exhibiting the potential for various applications in future functional devices. This review article is an attempt to illustrate the most recent progress in the fabrication, operation principle, characterization, and promising applications of graphene-based hybrid structures combined with various functional materials, ranging from ferroelectrics to semiconductors. We focus on mechanically exfoliated and chemical-vapor-deposited graphene sheets integrated in numerous advanced devices. Some typical hybrid structures have been highlighted, aiming at potential applications in non-volatile memories, transparent flexible electrodes, solar cells, photodetectors, and so on.

Graphene-based hybrid structures combined with functional materials of ferroelectrics and semiconductors

NASA Astrophysics Data System (ADS)

Jie, Wenjing; Hao, Jianhua

2014-05-01

Fundamental studies and applications of 2-dimensional (2D) graphene may be deepened and broadened via combining graphene sheets with various functional materials, which have been extended from the traditional insulator of SiO2 to a versatile range of dielectrics, semiconductors and metals, as well as organic compounds. Among them, ferroelectric materials have received much attention due to their unique ferroelectric polarization. As a result, many attractive characteristics can be shown in graphene/ferroelectric hybrid systems. On the other hand, graphene can be integrated with conventional semiconductors and some newly-discovered 2D layered materials to form distinct Schottky junctions, yielding fascinating behaviours and exhibiting the potential for various applications in future functional devices. This review article is an attempt to illustrate the most recent progress in the fabrication, operation principle, characterization, and promising applications of graphene-based hybrid structures combined with various functional materials, ranging from ferroelectrics to semiconductors. We focus on mechanically exfoliated and chemical-vapor-deposited graphene sheets integrated in numerous advanced devices. Some typical hybrid structures have been highlighted, aiming at potential applications in non-volatile memories, transparent flexible electrodes, solar cells, photodetectors, and so on.

Thermomechanical In Situ Monitoring of Bi2Te3 Thin Film and Its Relationship with Microstructure and Thermoelectric Performances

NASA Astrophysics Data System (ADS)

Jeong, Min-Woo; Na, Sekwon; Shin, Haishan; Park, Hong-Bum; Lee, Hoo-Jeong; Joo, Young-Chang

2018-07-01

Performance enhancement has been studied for thin-film thermoelectric materials for small-scale energy applications. The microstructural evolution of bismuth telluride (Bi2Te3) was investigated with respect to performance enhancement via in situ thermomechanical analysis due to the post-annealing process. The thermomechanical behavior of Bi2Te3 changes gradually at approximately 200 °C with the formation of a quintuple-layer structure, which was confirmed by X-ray diffraction, transmission electron microscopy and Raman spectroscopy. It was found that highly oriented (006), (0015) was formed with a quintuple-layer structure parallel to the substrate, and the E g 2 Raman vibration mode of Bi2Te3 significantly increased after forming the layer structure with decreased defects. Therefore, the slope of the stress curve was affected by the longer atomic distance of the van der Waals bonds with the formation of (00 l) oriented layered-structure grain. The decreased number of defects in the layer structure affects the electrical and thermal properties of the Bi2Te3 thin film. Due to the microstructural evolution, the power factor of Bi2Te3 was enhanced by approximately 14.8 times by the quintuple-layer structure of Bi2Te3 formed during the annealing process, which contributed to a better understanding of the performance enhancement via post-annealing and to research on other highly oriented layer structure materials.

Thermomechanical In Situ Monitoring of Bi2Te3 Thin Film and Its Relationship with Microstructure and Thermoelectric Performances

NASA Astrophysics Data System (ADS)

Jeong, Min-Woo; Na, Sekwon; Shin, Haishan; Park, Hong-Bum; Lee, Hoo-Jeong; Joo, Young-Chang

2018-04-01

Performance enhancement has been studied for thin-film thermoelectric materials for small-scale energy applications. The microstructural evolution of bismuth telluride (Bi2Te3) was investigated with respect to performance enhancement via in situ thermomechanical analysis due to the post-annealing process. The thermomechanical behavior of Bi2Te3 changes gradually at approximately 200 °C with the formation of a quintuple-layer structure, which was confirmed by X-ray diffraction, transmission electron microscopy and Raman spectroscopy. It was found that highly oriented (006), (0015) was formed with a quintuple-layer structure parallel to the substrate, and the Eg 2Raman vibration mode of Bi2Te3 significantly increased after forming the layer structure with decreased defects. Therefore, the slope of the stress curve was affected by the longer atomic distance of the van der Waals bonds with the formation of (00l) oriented layered-structure grain. The decreased number of defects in the layer structure affects the electrical and thermal properties of the Bi2Te3 thin film. Due to the microstructural evolution, the power factor of Bi2Te3 was enhanced by approximately 14.8 times by the quintuple-layer structure of Bi2Te3 formed during the annealing process, which contributed to a better understanding of the performance enhancement via post-annealing and to research on other highly oriented layer structure materials.

The effect of thermal damage on the mechanical properties of polymer regrinds

NASA Technical Reports Server (NTRS)

Kundu, Nikhil K.

1990-01-01

Reprocessed polymers are subjected to high processing temperatures that result in the breakdown of molecular chains and changes in the molecular structures. These phenomena are reflected in the mechanical properties of materials. Practically every regrind is seen as a new material. These experiments deal with the molding, regrinding, and reprocessing of test specimens for the study of their mechanical properties. The comparative test data from each recycled material would give students an insight of the molecular structures and property degradation. Three important rheological and mechanical properties such as melt flow, impact strength, and flexural strength are to be determined. These properties play key roles in the selection of engineering materials. The material selected for demonstration was Makrolon 3000L, a polycarbonate thermoplastic from Bayer AG. The thermal degradation due to repeated processing is reflected in the decrease in molecular weight and breakdown of molecular chains causing increase in melt flow. The Izod-impact resistance and the flexural strength deteriorate gradually.

Bioactive Nanocomposites for Tissue Repair and Regeneration: A Review

PubMed Central

Bramhill, Jane; Ross, Sukunya; Ross, Gareth

2017-01-01

This review presents scientific findings concerning the use of bioactive nanocomposites in the field of tissue repair and regeneration. Bioactivity is the ability of a material to incite a specific biological reaction, usually at the boundary of the material. Nanocomposites have been shown to be ideal bioactive materials due the many biological interfaces and structures operating at the nanoscale. This has resulted in many researchers investigating nanocomposites for use in bioapplications. Nanocomposites encompass a number of different structures, incorporating organic-inorganic, inorganic-inorganic and bioinorganic nanomaterials and based upon ceramic, metallic or polymeric materials. This enables a wide range of properties to be incorporated into nanocomposite materials, such as magnetic properties, MR imaging contrast or drug delivery, and even a combination of these properties. Much of the classical research was focused on bone regeneration, however, recent advances have enabled further use in soft tissue body sites too. Despite recent technological advances, more research is needed to further understand the long-term biocompatibility impact of the use of nanoparticles within the human body. PMID:28085054

Ultrafast carrier dynamics in the large-magnetoresistance material WTe 2

DOE PAGES

Dai, Y. M.; Bowlan, J.; Li, H.; ...

2015-10-07

In this study, ultrafast optical pump-probe spectroscopy is used to track carrier dynamics in the large-magnetoresistance material WTe 2. Our experiments reveal a fast relaxation process occurring on a subpicosecond time scale that is caused by electron-phonon thermalization, allowing us to extract the electron-phonon coupling constant. An additional slower relaxation process, occurring on a time scale of ~5–15 ps, is attributed to phonon-assisted electron-hole recombination. As the temperature decreases from 300 K, the time scale governing this process increases due to the reduction of the phonon population. However, below ~50 K, an unusual decrease of the recombination time sets in,more » most likely due to a change in the electronic structure that has been linked to the large magnetoresistance observed in this material.« less

Composite fiber structures for catalysts and electrodes

NASA Technical Reports Server (NTRS)

Marrion, Christopher J.; Cahela, Donald R.; Ahn, Soonho; Tatarchuk, Bruce J.

1993-01-01

We have recently envisioned a process wherein fibers of various metals in the 0.5 to 15 micron diameter range are slurried in concert with cellulose fibers and various other materials in the form of particulates and/or fibers. The resulting slurry is cast via a wet-lay process into a sheet and dried to produce a free-standing sheet of 'composite paper.' When the 'preform' sheet is sintered in hydrogen, the bulk of the cellulose is removed with the secondary fibers and/or particulates being entrapped by the sinter-locked network provided by the metal fibers. The resulting material is unique, in that it allows the intimate contacting and combination of heretofore mutually exclusive materials and properties. Moreover, due to the ease of paper manufacture and processing, the resulting materials are relatively inexpensive and can be fabricated into a wide range of three-dimensional structures. Also, because cellulose is both a binder and a pore-former, structures combining high levels of active surface area and high void volume (i.e., low pressure drop) can be prepared as freestanding flow through monoliths.

Decoupling Polymer Properties to Elucidate Mechanisms Governing Cell Behavior

PubMed Central

Wang, Xintong; Boire, Timothy C.; Bronikowski, Christine; Zachman, Angela L.; Crowder, Spencer W.

2012-01-01

Determining how a biomaterial interacts with cells (“structure-function relationship”) reflects its eventual clinical applicability. Therefore, a fundamental understanding of how individual material properties modulate cell-biomaterial interactions is pivotal to improving the efficacy and safety of clinically translatable biomaterial systems. However, due to the coupled nature of material properties, their individual effects on cellular responses are difficult to understand. Structure-function relationships can be more clearly understood by the effective decoupling of each individual parameter. In this article, we discuss three basic decoupling strategies: (1) surface modification, (2) cross-linking, and (3) combinatorial approaches (i.e., copolymerization and polymer blending). Relevant examples of coupled material properties are briefly reviewed in each section to highlight the need for improved decoupling methods. This follows with examples of more effective decoupling techniques, mainly from the perspective of three primary classes of synthetic materials: polyesters, polyethylene glycol, and polyacrylamide. Recent strides in decoupling methodologies, especially surface-patterning and combinatorial techniques, offer much promise in further understanding the structure-function relationships that largely govern the success of future advancements in biomaterials, tissue engineering, and drug delivery. PMID:22536977

Strain characterization of embedded aerospace smart materials using shearography

NASA Astrophysics Data System (ADS)

Anisimov, Andrei G.; Müller, Bernhard; Sinke, Jos; Groves, Roger M.

2015-04-01

The development of smart materials for embedding in aerospace composites provides enhanced functionality for future aircraft structures. Critical flight conditions like icing of the leading edges can affect the aircraft functionality and controllability. Hence, anti-icing and de-icing capabilities are used. In case of leading edges made of fibre metal laminates heater elements can be embedded between composite layers. However this local heating causes strains and stresses in the structure due to the different thermal expansion coefficients of the different laminated materials. In order to characterize the structural behaviour during thermal loading full-field strain and shape measurement can be used. In this research, a shearography instrument with three spatially-distributed shearing cameras is used to measure surface displacement gradients which give a quantitative estimation of the in- and out-of-plane surface strain components. For the experimental part, two GLARE (Glass Laminate Aluminum Reinforced Epoxy) specimens with six different embedded copper heater elements were manufactured: two copper mesh shapes (straight and S-shape), three connection techniques (soldered, spot welded and overlapped) and one straight heater element with delaminations. The surface strain behaviour of the specimens due to thermal loading was measured and analysed. The comparison of the connection techniques of heater element parts showed that the overlapped connection has the smallest effect on the surface strain distribution. Furthermore, the possibility of defect detection and defect depth characterisation close to the heater elements was also investigated.

A Study of Flexible Composites for Expandable Space Structures

NASA Technical Reports Server (NTRS)

Scotti, Stephen J.

2016-01-01

Payload volume for launch vehicles is a critical constraint that impacts spacecraft design. Deployment mechanisms, such as those used for solar arrays and antennas, are approaches that have successfully accommodated this constraint, however, providing pressurized volumes that can be packaged compactly at launch and expanded in space is still a challenge. One approach that has been under development for many years is to utilize softgoods - woven fabric for straps, cloth, and with appropriate coatings, bladders - to provide this expandable pressure vessel capability. The mechanics of woven structure is complicated by a response that is nonlinear and often nonrepeatable due to the discrete nature of the woven fiber architecture. This complexity reduces engineering confidence to reliably design and certify these structures, which increases costs due to increased requirements for system testing. The present study explores flexible composite materials systems as an alternative to the heritage softgoods approach. Materials were obtained from vendors who utilize flexible composites for non-aerospace products to determine some initial physical and mechanical properties of the materials. Uniaxial mechanical testing was performed to obtain the stress-strain response of the flexible composites and the failure behavior. A failure criterion was developed from the data, and a space habitat application was used to provide an estimate of the relative performance of flexible composites compared to the heritage softgoods approach. Initial results are promising with a 25% mass savings estimated for the flexible composite solution.

Chromatographic performance of monolithic and particulate stationary phases. Hydrodynamics and adsorption capacity.

PubMed

Leinweber, Felix C; Tallarek, Ulrich

2003-07-18

Monolithic chromatographic support structures offer, as compared to the conventional particulate materials, a unique combination of high bed permeability, optimized solute transport to and from the active surface sites and a high loading capacity by the introduction of hierarchical order in the interconnected pore network and the possibility to independently manipulate the contributing sets of pores. While basic principles governing flow resistance, axial dispersion and adsorption capacity are remaining identical, and a similarity to particulate systems can be well recognized on that basis, a direct comparison of sphere geometry with monolithic structures is less obvious due, not least, to the complex shape of theskeleton domain. We present here a simple, widely applicable, phenomenological approach for treating single-phase incompressible flow through structures having a continuous, rigid solid phase. It relies on the determination of equivalent particle (sphere) dimensions which characterize the corresponding behaviour in a particulate, i.e. discontinuous bed. Equivalence is then obtained by dimensionless scaling of macroscopic fluid dynamical behaviour, hydraulic permeability and hydrodynamic dispersion in both types of materials, without needing a direct geometrical translation of their constituent units. Differences in adsorption capacity between particulate and monolithic stationary phases show that the silica-based monoliths with a bimodal pore size distribution provide, due to the high total porosity of the material of more than 90%, comparable maximum loading capacities with respect to random-close packings of completely porous spheres.

Porosity and permeability studies of Virginia aggregates : final report.

DOT National Transportation Integrated Search

1972-01-01

It is generally recognized that the volume and geometry of included pores within a mineral aggregate have a significant effect on the physical and chemical behavior of the aggregate when used as a structural material. However due to the technical dif...

High index glass thin film processing for photonics and photovoltaic (PV) applications

NASA Astrophysics Data System (ADS)

Ogbuu, Okechukwu Anthony

To favorably compete with fossil-fuel technology, the greatest challenge for thin film solar-cells is to improve efficiency and reduce material cost. Thickness scaling to thin film reduces material cost but affects the light absorption in the cells; therefore a concept that traps incident photons and increases its optical path length is needed to boost absorption in thin film solar cells. One approach is the integration of low symmetric gratings (LSG), using high index material, on either the front-side or backside of 30 um thin c-Si cells. In this study, Multicomponent TeO2--Bi2O 3--ZnO (TBZ) glass thin films were prepared using RF magnetron sputtering under different oxygen flow rates. The influences of oxygen flow rate on the structural and optical properties of the resulting thin films were investigated. The structural origin of the optical property variation was studied using X-ray diffraction, X-ray photoelectron spectroscopy, Raman Spectroscopy, and transmission electron microscopy. The results indicate that TBZ glass thin film is a suitable material for front side LSG material photovoltaic and photonics applications due to their amorphous nature, high refractive index (n > 2), broad band optical transparency window, low processing temperature. We developed a simple maskless method to pattern sputtered tellurite based glass thin films using unconventional agarose hydrogel mediated wet etching. Conventional wet etching process, while claiming low cost and high throughput, suffers from reproducibility and pattern fidelity issues due to the isotropic nature of wet chemical etching when applied to glasses and polymers. This method overcomes these challenges by using an agarose hydrogel stamp to mediate a conformal etching process. In our maskless method, agarose hydrogel stamps are patterned following a standard soft lithography and replica molding process from micropatterned masters and soaked in a chemical etchant. The micro-scale features on the stamp are subsequently transferred into glass and polymer thin films via conformal wet etching. High refractive index chalcogenide glass (n = 2.6) thin films with composition As20Se80 was selected for backside LSG material due to their attractive properties. We developed an optimized integration protocol for LSG integration and successfully integrated these LSG structures at the back side of both 30 microm c-Si solar cells and standalone 30 microm c-Si wafers. Optical and electrical characterization of LSG on thin c-Si cells shows that LSG structures create higher absorption enhancement and external quantum efficiency at long wavelengths.

New Surface-Treatment Technique of Concrete Structures Using Crack Repair Stick with Healing Ingredients

PubMed Central

Ahn, Tae-Ho; Kim, Hong-gi; Ryou, Jae-Suk

2016-01-01

This study focused on the development of a crack repair stick as a new repair method along with self-healing materials that can be used to easily repair the cracks in a concrete structure at the construction site. In developing this new repair technique, the self-healing efficiency of various cementitious materials was considered. Likewise, a crack repair stick was developed to apply to concrete structures with 0.3 mm or lower crack widths. The crack repair stick was made with different materials, such as cement, an expansive material (C12A7), a swelling material, and calcium carbonate, to endow it with a self-healing property. To verify the performance of the crack repair stick for concrete structures, two types of procedures (field experiment and field absorption test) were carried out. As a result of such procedures, it was concluded that the developed crack repair stick could be used on concrete structures to reduce repair expenses and for the improved workability, usability, and serviceability of such structures. On the other hand, to evaluate the self-healing performance of the crack repair stick, various tests were conducted, such as the relative dynamic modulus of elasticity test, the water tightness test, the water permeability test, observation via a microscope, and scanning electron microscope (SEM) analysis. From the results, it is found that water leakage can be prevented and that the durability of a concrete structure can be improved through self-healing. Also, it was verified that the cracks were perfectly closed after 28 days due to application of the crack repair stick. These results indicate the usability of the crack repair stick for concrete structures, and its self-healing efficiency. PMID:28773776

Process for fabricating a microelectromechanical structure

DOEpatents

Sniegowski, Jeffry J.; Krygowski, Thomas W.; Mani, Seethambal S.; Habermehl, Scott D.; Hetherington, Dale L.; Stevens, James E.; Resnick, Paul J.; Volk, Steven R.

2004-10-26

A process is disclosed for forming a microelectromechanical (MEM) structure on a substrate having from 5 to 6 or more layers of deposited and patterned polysilicon. The process is based on determining a radius of curvature of the substrate which is bowed due to accumulated stress in the layers of polysilicon and a sacrificial material used to buildup the MEM structure, and then providing one or more stress-compensation layers on a backside of the substrate to flatten the substrate and allow further processing.

Problems on the Theory of Heat Resistance of Alloys

DTIC Science & Technology

1960-07-26

same material under real service conditions is conceded; in this case, the shapes and dimensions of the product, the vibrations, the sharp and...as the load duration factor). The introduction of a newly created material some- times proves unsuccessful due to the fact that, though meeting all...structural nonuniformity of real solids on the mechanism of the development of deformation in them and on their mechanical properties*; (d) the influence of

Development of Rolling Schedules for AZ31 Magnesium Alloy Sheets

DTIC Science & Technology

2015-06-01

Materials 2 2.2 Hot Rolling 3 2.2 Sample Characterization: Microstructure and Tensile Properties 3 3. Rolling Experiments 5 3.1 High-Temperature...material systems for protective and structural applications, especially in ground vehicles. Magnesium (Mg), due to its low density (~25% that of steel ...applications, wrought Mg is difficult to produce in thin sheets because of its inherently low ductility . As a result, Mg sheet is often produced at

Perovskite Oxide Thin Film Growth, Characterization, and Stability

NASA Astrophysics Data System (ADS)

Izumi, Andrew

Studies into a class of materials known as complex oxides have evoked a great deal of interest due to their unique magnetic, ferroelectric, and superconducting properties. In particular, materials with the ABO3 perovskite structure have highly tunable properties because of the high stability of the structure, which allows for large scale doping and strain. This also allows for a large selection of A and B cations and valences, which can further modify the material's electronic structure. Additionally, deposition of these materials as thin films and superlattices through techniques such as pulsed laser deposition (PLD) results in novel properties due to the reduced dimensionality of the material. The novel properties of perovskite oxide heterostructures can be traced to a several sources, including chemical intermixing, strain and defect formation, and electronic reconstruction. The correlations between microstructure and physical properties must be investigated by examining the physical and electronic structure of perovskites in order to understand this class of materials. Some perovskites can undergo phase changes due to temperature, electrical fields, and magnetic fields. In this work we investigated Nd0.5Sr 0.5MnO3 (NSMO), which undergoes a first order magnetic and electronic transition at T=158K in bulk form. Above this temperature NSMO is a ferromagnetic metal, but transitions into an antiferromagnetic insulator as the temperature is decreased. This rapid transition has interesting potential in memory devices. However, when NSMO is deposited on (001)-oriented SrTiO 3 (STO) or (001)-oriented (LaAlO3)0.3-(Sr 2AlTaO6)0.7 (LSAT) substrates, this transition is lost. It has been reported in the literature that depositing NSMO on (110)-oriented STO allows for the transition to reemerge due to the partial epitaxial growth, where the NSMO film is strained along the [001] surface axis and partially relaxed along the [11¯0] surface axis. This allows the NSMO film enough freedom of movement to undergo a shear strain along the [11¯0] axes, allowing the NSMO film to switch phases. It was found that the desired magnetic and electrical properties were closely tied to the structural properties, which were highly sensitive to the precise growth conditions. These perovskite oxides can be further geometrically constrained by patterning, resulting in additional novel magnetic and electrical properties. One such method of patterning involves implanting Ar into a film to locally destabilize the ordered perovskite structure, therefore suppress the magnetic and electrical properties. However, to fully integrate this technique into devices which require multi-planar processes, the ability for a patterned perovskite film to withstand high temperature anneals is crucial in creating more advanced structures. The stability of Ar-implanted La0.7Sr0.3MnO 3 (LSMO) thin films was studied upon annealing at 400°C, 500°C, and 600°C. The LSMO retained its amorphous structure with little ferromagnetism after a 400°C anneal, but anneals at 500°C and 600°C resulted in partial recrystallization and a return of the ferromagnetic properties. This recrystallized film displayed semiconducting properties with a lower Curie temperature than the as deposited film. The deposition of an La 0.7Sr0.3FeO3 (LSFO) film onto an Ar implanted LSMO film at 400°C caused the LSMO film to almost fully recrystallize, suggesting that the deposition process also recrystallizes the Ar-implanted film. In conclusion, two perovskites films were explored in this thesis. NSMO films proved to be very sensitive to growth conditions, and Ar-implanted LSMO films quickly recrystallized past 400°C or a subsequent film deposition. These studies provide useful information on the structural and electronic transformations these films go through during heat treatment and strain engineering.

Fracture mechanics. [review of fatigue crack propagation and technology of constructing safe structures

NASA Technical Reports Server (NTRS)

Hardrath, H. F.

1974-01-01

Fracture mechanics is a rapidly emerging discipline for assessing the residual strength of structures containing flaws due to fatigue, corrosion or accidental damage and for anticipating the rate of which such flaws will propagate if not repaired. The discipline is also applicable in the design of structures with improved resistance to such flaws. The present state of the design art is reviewed using this technology to choose materials, to configure safe and efficient structures, to specify inspection procedures, to predict lives of flawed structures and to develop reliability of current and future airframes.

Development of accurate potentials to explore the structure of water on 2D materials

NASA Astrophysics Data System (ADS)

Bejagam, Karteek; Singh, Samrendra; Deshmukh, Sanket; Deshmkuh Group Team; Samrendra Group Collaboration

Water play an important role in many biological and non-biological process. Thus structure of water at various interfaces and under confinement has always been the topic of immense interest. 2-D materials have shown great potential in surface coating applications and nanofluidic devices. However, the exact atomic level understanding of the wettability of single layer of these 2-D materials is still lacking mainly due to lack of experimental techniques and computational methodologies including accurate force-field potentials and algorithms to measure the contact angle of water. In the present study, we have developed a new algorithm to measure the accurate contact angle between water and 2-D materials. The algorithm is based on fitting the best sphere to the shape of the droplet. This novel spherical fitting method accounts for every individual molecule of the droplet, rather than those at the surface only. We employ this method of contact angle measurements to develop the accurate non-bonded potentials between water and 2-D materials including graphene and boron nitride (BN) to reproduce the experimentally observed contact angle of water on these 2-D materials. Different water models such as SPC, SPC/Fw, and TIP3P were used to study the structure of water at the interfaces.

Poling of PVDF matrix composites for integrated structural load sensing

NASA Astrophysics Data System (ADS)

Haghiashtiani, Ghazaleh; Greminger, Michael A.; Zhao, Ping

2014-03-01

The purpose of this study is to create and evaluate a smart composite structure that can be used for integrated load sensing and structural health monitoring. In this structure, PVDF films are used as the matrix material instead of epoxy resin or other thermoplastics. The reinforcements are two layers of carbon fiber with one layer of Kevlar separating them. Due to the electrical conductivity properties of carbon fiber and the dielectric effect of Kevlar, the structure acts as a capacitor. Furthermore, the piezoelectric properties of the PVDF matrix can be used to monitor the response of the structure under applied loads. In order to exploit the piezoelectric properties of PVDF, the PVDF material must be polarized to align the dipole moments of its crystalline structure. The optimal condition for poling the structure was found by performing a 23 factorial design of experiment (DoE). The factors that were studied in DoE were temperature, voltage, and duration of poling. Finally, the response of the poled structure was monitored by exposing the samples to an applied load.

Effective recycling of manganese oxide cathodes for lithium based batteries

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

Poyraz, Altug S.; Huang, Jianping; Cheng, Shaobo

Rechargeable lithium ion batteries (LIBs) occupy a prominent consumer presence due to their high cell potential and gravimetric energy density, there are also limited opportunities for electrode recycling. Currently used or proposed cathode recycling processes are multistep procedures which involve sequences of mechanical, thermal, and chemical leaching, where only the base material is recovered and significant processing is required to generate a recycled electrode structure. Another significant issue facing lithium based batteries is capacity fade due to structural degradation of the electroactive material upon extending cycling. Herein, inspired by heterogeneous catalyst thermal regeneration strategies, we present a new facile cathodemore » recycling process, where previously used cathodes are removed from a cell, heat treated, and then inserted into a new cell restoring the delivered capacity and cycle life. An environmentally sustainable manganese based material is employed, where binder-free self-supporting (BFSS) electrodes are prepared using a fibrous, high aspect ratio manganese oxide active material. After 200 discharge–charge cycles, the recycled BFSS electrodes display restored crystallinity and oxidation state of the manganese centers with the resulting electrochemistry (capacity and coulombic efficiency) reminiscent of freshly prepared BFSS cathodes. Of note, the BFSS electrode structure is robust with no degradation during the cell disassembly, electrode recovery, washing, and heat treatment steps; thus no post-processing is required for the recycled electrode. Furthermore, this work shows for the first time that a thermal regeneration method previously employed in catalyst systems can fully restore battery electrochemical performance, demonstrating a novel electrode recycling process which could open up new possibilities for energy storage devices with extended electrode lifecycles.« less

Effective recycling of manganese oxide cathodes for lithium based batteries

DOE PAGES

Poyraz, Altug S.; Huang, Jianping; Cheng, Shaobo; ...

2016-02-29

Rechargeable lithium ion batteries (LIBs) occupy a prominent consumer presence due to their high cell potential and gravimetric energy density, there are also limited opportunities for electrode recycling. Currently used or proposed cathode recycling processes are multistep procedures which involve sequences of mechanical, thermal, and chemical leaching, where only the base material is recovered and significant processing is required to generate a recycled electrode structure. Another significant issue facing lithium based batteries is capacity fade due to structural degradation of the electroactive material upon extending cycling. Herein, inspired by heterogeneous catalyst thermal regeneration strategies, we present a new facile cathodemore » recycling process, where previously used cathodes are removed from a cell, heat treated, and then inserted into a new cell restoring the delivered capacity and cycle life. An environmentally sustainable manganese based material is employed, where binder-free self-supporting (BFSS) electrodes are prepared using a fibrous, high aspect ratio manganese oxide active material. After 200 discharge–charge cycles, the recycled BFSS electrodes display restored crystallinity and oxidation state of the manganese centers with the resulting electrochemistry (capacity and coulombic efficiency) reminiscent of freshly prepared BFSS cathodes. Of note, the BFSS electrode structure is robust with no degradation during the cell disassembly, electrode recovery, washing, and heat treatment steps; thus no post-processing is required for the recycled electrode. Furthermore, this work shows for the first time that a thermal regeneration method previously employed in catalyst systems can fully restore battery electrochemical performance, demonstrating a novel electrode recycling process which could open up new possibilities for energy storage devices with extended electrode lifecycles.« less

High-volume use of self-cementing spray dry absorber material for structural applications

NASA Astrophysics Data System (ADS)

Riley, Charles E.

Spray dry absorber (SDA) material, or spray dryer ash, is a byproduct of energy generation by coal combustion and sulfur emissions controls. Like any resource, it ought to be used to its fullest potential offsetting as many of the negative environmental impacts of coal combustion as possible throughout its lifecycle. Its cementitious and pozzolanic properties suggest it be used to augment or replace another energy and emissions intensive product: Portland cement. There is excellent potential for spray dryer ash to be used beneficially in structural applications, which will offset CO2 emissions due to Portland cement production, divert landfill waste by further utilizing a plentiful coal combustion by-product, and create more durable and sustainable structures. The research into beneficial use applications for SDA material is relatively undeveloped and the material is highly underutilized. This dissertation explored a specific self-cementing spray dryer ash for use as a binder in structural materials. Strength and stiffness properties of hydrated spray dryer ash mortars were improved by chemical activation with Portland cement and reinforcement with polymer fibers from automobile tire recycling. Portland cement at additions of five percent of the cementitious material was found to function effectively as an activating agent for spray dryer ash and had a significant impact on the hardened properties. The recycled polymer fibers improved the ductility and toughness of the material in all cases and increased the compressive strength of weak matrix materials like the pure hydrated ash. The resulting hardened materials exhibited useful properties that were sufficient to suggest that they be used in structural applications such as concrete, masonry block, or as a hydraulic cement binder. While the long-term performance characteristics remain to be investigated, from an embodied-energy and carbon emissions standpoint the material investigated here is far superior to Portland cement.

Enhanced Raman Scattering on In-plane Anisotropic Layered Materials

DOE PAGES

Liang, Liangbo; Meunier, Vincent; Sumpter, Bobby G.; ...

2015-11-19

Surface-enhanced Raman scattering (SERS) on two-dimensional (2D) layered materials has provided a unique platform to study the chemical mechanism (CM) of the enhancement due to its natural separation from electromagnetic enhancement. The CM stems from the basic charge interactions between the substrate and molecules. Despite the extensive studies of the energy alignment between 2D materials and molecules, an understanding of how the electronic properties of the substrate are explicitly involved in the charge interaction is still unclear. Lately, a new group of 2D layered materials with anisotropic structure, including orthorhombic black phosphorus (BP) and triclinic rhenium disulphide (ReS2), has attractedmore » great interest due to their unique anisotropic electrical and optical properties. Herein, we report a unique anisotropic Raman enhancement on few-layered BP and ReS2 using copper phthalocyanine (CuPc) molecules as a Raman probe, which is absent on isotropic graphene and h-BN. According to detailed Raman tensor analysis and density functional theory calculations, anisotropic charge interactions due to the anisotropic carrier mobilities of the 2D materials are responsible for the angular dependence of the Raman enhancement. Our findings not only provide new insights into the CM process in SERS, but also open up new avenues for the exploration and application of the electronic properties of anisotropic 2D layered materials.« less

Activation characteristics of candidate structural materials for a near-term Indian fusion reactor and the impact of their impurities on design considerations

NASA Astrophysics Data System (ADS)

H, L. SWAMI; C, DANANI; A, K. SHAW

2018-06-01

Activation analyses play a vital role in nuclear reactor design. Activation analyses, along with nuclear analyses, provide important information for nuclear safety and maintenance strategies. Activation analyses also help in the selection of materials for a nuclear reactor, by providing the radioactivity and dose rate levels after irradiation. This information is important to help define maintenance activity for different parts of the reactor, and to plan decommissioning and radioactive waste disposal strategies. The study of activation analyses of candidate structural materials for near-term fusion reactors or ITER is equally essential, due to the presence of a high-energy neutron environment which makes decisive demands on material selection. This study comprises two parts; in the first part the activation characteristics, in a fusion radiation environment, of several elements which are widely present in structural materials, are studied. It reveals that the presence of a few specific elements in a material can diminish its feasibility for use in the nuclear environment. The second part of the study concentrates on activation analyses of candidate structural materials for near-term fusion reactors and their comparison in fusion radiation conditions. The structural materials selected for this study, i.e. India-specific Reduced Activation Ferritic‑Martensitic steel (IN-RAFMS), P91-grade steel, stainless steel 316LN ITER-grade (SS-316LN-IG), stainless steel 316L and stainless steel 304, are candidates for use in ITER either in vessel components or test blanket systems. Tungsten is also included in this study because of its use for ITER plasma-facing components. The study is carried out using the reference parameters of the ITER fusion reactor. The activation characteristics of the materials are assessed considering the irradiation at an ITER equatorial port. The presence of elements like Nb, Mo, Co and Ta in a structural material enhance the activity level as well as the dose level, which has an impact on design considerations. IN-RAFMS was shown to be a more effective low-activation material than SS-316LN-IG.

Template-free hydrothermal synthesis of beaded nanochain bundles of ZnO and their application as photoanode in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Ballal, Reshma; Shinde, Manish; Waghadkar, Yogesh; Arbuj, Sudhir; Rane, Sunit; Chauhan, Ratna

2018-02-01

ZnO shows promising candidature as photoanode material for dye-sensitized solar cells (DSSCs) due to its high bulk electron mobility and easily tailorable geometrical structures. The objective of this study is to facilitate the development of highly porous hierarchical ZnO for enhanced power conversion efficiency in dye-sensitized solar cells (DSSC) due to its greater dye adsorption. This study investigated the influence of reaction temperatures of 120 °C (sample Z-1) and 180 °C (sample Z-2) in hydrothermal synthesis on structural, morphological and optical properties of resultant ZnO nanostructures and their performance as photoanode material in DSSCs. The synthesized beaded nanochain bundles of ZnO, with multilayered and highly ordered texture, have diameters of several micrometers. Structural and morphological analysis shows that the ZnO beaded nanochain-like architectures possess wurtzite crystalline nature. These morphological improvements (beaded nanochains) of ZnO were found to exhibit higher dye loading and conversion efficiency due to increase in the surface area while reducing charge recombination. The maximum conversion efficiency was obtained with Z-1 and Z-2 is 2.95 and 3.56% with photocurrent of 7.73 and 9.24 mA/cm2, respectively. The obtained results pertaining to the DSSC performance studies were corroborated by the impedance spectroscopy data.

Multifunctional transparent ZnO nanorod films.

PubMed

Kwak, Geunjae; Jung, Sungmook; Yong, Kijung

2011-03-18

Transparent ZnO nanorod (NR) films that exhibit extreme wetting states (either superhydrophilicity or superhydrophobicity through surface chemical modification), high transmittance, UV protection and antireflection have been prepared via the facile ammonia hydrothermal method. The periodic 1D ZnO NR arrays showed extreme wetting states as well as antireflection properties due to their unique surface structure and prevented the UVA region from penetrating the substrate due to the unique material property of ZnO. Because of the simple, time-efficient and low temperature preparation process, ZnO NR films with useful functionalities are promising for fabrication of highly light transmissive, antireflective, UV protective, antifogging and self-cleaning optical materials to be used for optical devices and photovoltaic energy devices.

Application of low temperature plasmas for restoration/conservation of archaeological objects

NASA Astrophysics Data System (ADS)

Krčma, F.; Blahová, L.; Fojtíková, P.; Graham, W. G.; Grossmannová, H.; Hlochová, L.; Horák, J.; Janová, D.; Kelsey, C. P.; Kozáková, Z.; Mazánková, V.; Procházka, M.; Přikryl, R.; Řádková, L.; Sázavská, V.; Vašíček, M.; Veverková, R.; Zmrzlý, M.

2014-12-01

The low-temperature low-pressure hydrogen based plasmas were used to study the influence of processes and discharge conditions on corrosion removal. The capacitive coupled RF discharge in the continuous or pulsed regime was used at operating pressure of 100-200 Pa. Plasma treatment was monitored by optical emission spectroscopy. To be able to study influence of various process parameters, the model corroded samples with and without sandy incrustation were prepared. The SEM-EDX analyzes were carried out to verify corrosion removal efficiency. Experimental conditions were optimized for the selected most frequent materials of original metallic archaeological objects (iron, bronze, copper, and brass). Chlorides removal is based on hydrogen ion reactions while oxides are removed mainly by neutral species interactions. A special focus was kept for the samples temperature because it was necessary to avoid any metallographic changes in the material structure. The application of higher power pulsed regime with low duty cycle seems be the best treatment regime. The low pressure hydrogen plasma is not applicable for objects with a very broken structure or for nonmetallic objects due to the non-uniform heat stress. Due to this fact, the new developed plasmas generated in liquids were applied on selected original archaeological glass materials.

Optical and structural properties of Al-doped ZnO thin films by sol gel process.

PubMed

Jun, Min-Chul; Koh, Jung-Hyuk

2013-05-01

Transparent conducting oxide (TCO) materials with high transmittance and good electrical conductivity have been attracted much attention due to the development of electronic display and devices such as organic light emitting diodes (OLEDs), and dye-sensitized solar cells (DSSCs). Aluminum doped zinc oxide thin films (AZO) have been well known for their use as TCO materials due to its stability, cost-effectiveness, good optical transmittance and electrical properties. Especially, AZO thin film, which have low resistivity of 2-4 x 10(-4) omega x cm which is similar to that of ITO films with wide band gap semiconductors. The AZO thin films were deposited on glass substrates by sol-gel spin-coating process. As a starting material, zinc acetate dihydrate (Zn(CH3COO)2 x 2H2O) and aluminum chloride hexahydrate (AlCl3 6H2O) were used. 2-methoxyethanol and monoethanolamine (MEA) were used as solvent and stabilizer, respectively. After deposited, the films were preheated at 300 degrees C on a hotplate and post-heated at 650 degrees C for 1.5 hrs in the furnace. We have studied the structural and optical properties as a function of Al concentration (0-2.5 mol.%).

Characterization of DC Magnetron Sputtering Plasma Used for Deposition of Amorphous Carbon Nitride

NASA Astrophysics Data System (ADS)

Camps, Enrique; Escobar-Alarcón, Luis; López, J.; Zambrano, G.; Prieto, P.

2006-12-01

Amorphous carbon nitride (a-CNx) thin films are attractive due to their potential applications, in different areas. This material can be hard and used as a protective coating, or can be soft and porous and used as the active element in gas sensors, it can also be used as a radiation detector due to its thermoluminescent response. The use of this material for one or another application, will depend on the material's structure, which can be changed by changing the deposition parameters. When using the d.c. magnetron sputtering technique it means mainly the change of discharge power, type of Ar/N2 gas mixture, and the working gas pressure. The variation of these deposition parameters has an important influence on the characteristics of the plasma formed in the discharge. In this work we studied the plasma characteristics, such as the type of excited species, plasma density, and electron temperature under different deposition conditions, using Optical Emission Spectroscopy (OES), and a single Langmuir probe. These parameters were correlated with the properties of a-CNx films deposited under those characterized regimes, in order to establish the role that the plasma parameters play on the formation of the different structures of CNx films.

Machined Titanium Heat-Pipe Wick Structure

NASA Technical Reports Server (NTRS)

Rosenfeld, John H.; Minnerly, Kenneth G.; Gernert, Nelson J.

2009-01-01

Wick structures fabricated by machining of titanium porous material are essential components of lightweight titanium/ water heat pipes of a type now being developed for operation at temperatures up to 530 K in high-radiation environments. In the fabrication of some prior heat pipes, wicks have been made by extruding axial grooves into aluminum unfortunately, titanium cannot be extruded. In the fabrication of some other prior heat pipes, wicks have been made by in-situ sintering of metal powders shaped by the use of forming mandrels that are subsequently removed, but in the specific application that gave rise to the present fabrication method, the required dimensions and shapes of the heat-pipe structures would make it very difficult if not impossible to remove the mandrels due to the length and the small diameter. In the present method, a wick is made from one or more sections that are fabricated separately and assembled outside the tube that constitutes the outer heat pipe wall. The starting wick material is a slab of porous titanium material. This material is machined in its original flat configuration to form axial grooves. In addition, interlocking features are machined at the mating ends of short wick sections that are to be assembled to make a full-length continuous wick structure. Once the sections have been thus assembled, the resulting full-length flat wick structure is rolled into a cylindrical shape and inserted in the heatpipe tube (see figure). This wick-structure fabrication method is not limited to titanium/water heat pipes: It could be extended to other heat pipe materials and working fluids in which the wicks could be made from materials that could be pre-formed into porous slabs.

Recent advances in the fabrication and structure-specific applications of graphene-based inorganic hybrid membranes.

PubMed

Zhao, Xinne; Zhang, Panpan; Chen, Yuting; Su, Zhiqiang; Wei, Gang

2015-03-12

The preparation and applications of graphene (G)-based materials are attracting increasing interests due to their unique electronic, optical, magnetic, thermal, and mechanical properties. Compared to G-based hybrid and composite materials, G-based inorganic hybrid membrane (GIHM) offers enormous advantages ascribed to their facile synthesis, planar two-dimensional multilayer structure, high specific surface area, and mechanical stability, as well as their unique optical and mechanical properties. In this review, we report the recent advances in the technical fabrication and structure-specific applications of GIHMs with desirable thickness and compositions. In addition, the advantages and disadvantages of the methods utilized for creating GIHMs are discussed in detail. Finally, the potential applications and key challenges of GIHMs for future technical applications are mentioned.

Nonlinear Optics with 2D Layered Materials.

PubMed

Autere, Anton; Jussila, Henri; Dai, Yunyun; Wang, Yadong; Lipsanen, Harri; Sun, Zhipei

2018-06-01

2D layered materials (2DLMs) are a subject of intense research for a wide variety of applications (e.g., electronics, photonics, and optoelectronics) due to their unique physical properties. Most recently, increasing research efforts on 2DLMs are projected toward the nonlinear optical properties of 2DLMs, which are not only fascinating from the fundamental science point of view but also intriguing for various potential applications. Here, the current state of the art in the field of nonlinear optics based on 2DLMs and their hybrid structures (e.g., mixed-dimensional heterostructures, plasmonic structures, and silicon/fiber integrated structures) is reviewed. Several potential perspectives and possible future research directions of these promising nanomaterials for nonlinear optics are also presented. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

M-Polynomials and topological indices of V-Phenylenic Nanotubes and Nanotori.

PubMed

Kwun, Young Chel; Munir, Mobeen; Nazeer, Waqas; Rafique, Shazia; Min Kang, Shin

2017-08-18

V-Phenylenic nanotubes and nanotori are most comprehensively studied nanostructures due to widespread applications in the production of catalytic, gas-sensing and corrosion-resistant materials. Representing chemical compounds with M-polynomial is a recent idea and it produces nice formulas of degree-based topological indices which correlate chemical properties of the material under investigation. These indices are used in the development of quantitative structure-activity relationships (QSARs) in which the biological activity and other properties of molecules like boiling point, stability, strain energy etc. are correlated with their structures. In this paper, we determine general closed formulae for M-polynomials of V-Phylenic nanotubes and nanotori. We recover important topological degree-based indices. We also give different graphs of topological indices and their relations with the parameters of structures.

Detection of Non-Symmetrical Damage in Smart Plate-Like Structures

NASA Technical Reports Server (NTRS)

Blanks, H. T.; Emeric, P. R.

1998-01-01

A two-dimensional model for in-plane vibrations of a cantilever plate with a non-symmetrical damage is used in the context of defect identification in materials with piezoelectric ceramic patches bonded to their surface. These patches can act both as actuators and sensors in a self-analyzing fashion, which is a characteristic of smart materials. A Galerkin method is used to approximate the dynamic response of these structures. The natural frequency shifts due to the damage are estimated numerically and compared to experimental data obtained from tests on cantilever aluminum plate-like structures damaged at different locations with defects of different depths. The damage location and extent are determined by an enhanced least square identification method. Efficacy of the frequency shift based algorithms is demonstrated using experimental data.

Quantitative NDE of Composite Structures at NASA

NASA Technical Reports Server (NTRS)

Cramer, K. Elliott; Leckey, Cara A. C.; Howell, Patricia A.; Johnston, Patrick H.; Burke, Eric R.; Zalameda, Joseph N.; Winfree, William P.; Seebo, Jeffery P.

2015-01-01

The use of composite materials continues to increase in the aerospace community due to the potential benefits of reduced weight, increased strength, and manufacturability. Ongoing work at NASA involves the use of the large-scale composite structures for spacecraft (payload shrouds, cryotanks, crew modules, etc). NASA is also working to enable the use and certification of composites in aircraft structures through the Advanced Composites Project (ACP). The rapid, in situ characterization of a wide range of the composite materials and structures has become a critical concern for the industry. In many applications it is necessary to monitor changes in these materials over a long time. The quantitative characterization of composite defects such as fiber waviness, reduced bond strength, delamination damage, and microcracking are of particular interest. The research approaches of NASA's Nondestructive Evaluation Sciences Branch include investigation of conventional, guided wave, and phase sensitive ultrasonic methods, infrared thermography and x-ray computed tomography techniques. The use of simulation tools for optimizing and developing these methods is also an active area of research. This paper will focus on current research activities related to large area NDE for rapidly characterizing aerospace composites.

Large-scale synthesis of coiled-like shaped carbon nanotubes using bi-metal catalyst

NASA Astrophysics Data System (ADS)

Krishna, Vemula Mohana; Somanathan, T.; Manikandan, E.; Umar, Ahmad; Maaza, M.

2018-02-01

Carbon nanomaterials (CNMs), especially carbon nanotubes (CNTs) with coiled structure exhibit scientifically fascinating. They may be projected as an innovative preference to future technological materials. Coiled carbon nanotubes (c-CNTs) on a large-scale were successfully synthesized with the help of bi-metal substituted α-alumina nanoparticles catalyst via chemical vapor deposition (CVD) technique. Highly spring-like carbon nanostructures were observed by field emission scanning electron microscope (FESEM) examination. Furthermore, the obtained material has high purity, which correlates the X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) analysis. Raman spectroscopy reveals that the carbon multi layers are well graphitized and crystalline, even if they have defects in its structure due to coiled morphology. High-resolution transmission electron microscope (HRTEM) describes internal structure and dia of the product. Ultimately, results support the activity of bi-metal impregnated α-alumina nanoparticles catalyst to determine the high yield, graphitization and internal structure of the material. We have also studied the purified c-CNTs magnetic properties at room temperature and will be an added advantage in several applications.

Flexible supercapacitors with high areal capacitance based on hierarchical carbon tubular nanostructures

NASA Astrophysics Data System (ADS)

Zhang, Haitao; Su, Hai; Zhang, Lei; Zhang, Binbin; Chun, Fengjun; Chu, Xiang; He, Weidong; Yang, Weiqing

2016-11-01

Hierarchical structure design can greatly enhance the unique properties of primary material(s) but suffers from complicated preparation process and difficult self-assembly of materials with different dimensionalities. Here we report on the growth of single carbon tubular nanostructures with hierarchical structure (hCTNs) through a simple method based on direct conversion of carbon dioxide. Resorting to in-situ transformation and self-assembly of carbon micro/nano-structures, the obtained hCTNs are blood-like multichannel hierarchy composed of one large channel across the hCTNs and plenty of small branches connected to each other. Due to the unique pore structure and high surface area, these hCTN-based flexible supercapacitors possess the highest areal capacitance of ∼320 mF cm-2, as well as good rate-capability and excellent cycling stability (95% retention after 2500 cycles). It was established that this method can control the morphology, size, and density of hCTNs and effectively construct hCTNs well anchored to the various substrates. Our work unambiguously demonstrated the potential of hCTNs for large flexible supercapacitors and integrated energy management electronics.

Preparation of γ-LiV2O5 from polyoxovanadate cluster Li7[V15O36(CO3)] as a high-performance cathode material and its reaction mechanism revealed by operando XAFS

NASA Astrophysics Data System (ADS)

Wang, Heng; Isobe, Jin; Shimizu, Takeshi; Matsumura, Daiju; Ina, Toshiaki; Yoshikawa, Hirofumi

2017-08-01

γ-phase LiV2O5, which shows superior electrochemical performance as cathode material in Li-ion batteries, was prepared by annealing the polyoxovanadate cluster Li7 [V15O36(CO3)]. The reaction mechanism was studied using operando X-ray absorption fine structure (XAFS), powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS) analyses. The X-ray absorption near edge structure (XANES) and XPS results reveal that γ-LiV2O5 undergoes two-electron redox reaction per V2O5 pyramid unit, resulting in a large reversible capacity of 260 Ah/kg. The extended X-ray absorption fine structure (EXAFS) and PXRD analyses also suggest that the V-V distance slightly increases, due to the reduction of V5+ to V4+ during Li ion intercalation as the material structure is maintained. As a result, γ-LixV2O5 shows highly reversible electrochemical reaction with x = 0.1-1.9.

Multicharged and/or water-soluble fluorescent dendrimers: properties and uses.

PubMed

Caminade, Anne-Marie; Hameau, Aurélien; Majoral, Jean-Pierre

2009-09-21

The fluorescence of water-soluble dendritic compounds can be due to the whole structure or to fluorophores used as core, as peripheral groups, or as branches. Highly sophisticated precisely defined structures with other functional groups usable for material or biological purposes have been synthesised, but many recent examples have shown that dendrimers can be used as versatile platforms for statistically linking various types of functional groups.

Structural Technology Evaluation and Analysis Program (STEAP). Delivery Order 0045: Progressive Failure Analysis of Translaminar Reinforced Composite Structures

DTIC Science & Technology

2011-11-01

Approved for public release; distribution unlimited. See additional restrictions described on inside pages STINFO COPY AIR...pin density, diameter and length are some of the parameters related to the effectiveness of z-pins for increasing the delamination resistance...has received considerable attention in recent years due to increased use of composite materials in aerospace and related industries. Mainly in the

Synthesis and Characterization of Composite Membranes made of Graphene and Polymers of Intrinsic Microporosity

DTIC Science & Technology

2016-02-16

group of polymers with molecular sieve behaviour due to their rigid, contorted macromolecular backbones. They show great potential in organophilic...ageing is expected by adding graphene as a nanofiller. Little is experimentally known about how the material disperses in the polymer. Here we used Raman...effective understanding of the structure-property relationships of the composite. Obtaining such structural infor- mation, however, is experimentally

Wireless and embedded carbon nanotube networks for damage detection in concrete structures

NASA Astrophysics Data System (ADS)

Saafi, Mohamed

2009-09-01

Concrete structures undergo an uncontrollable damage process manifesting in the form of cracks due to the coupling of fatigue loading and environmental effects. In order to achieve long-term durability and performance, continuous health monitoring systems are needed to make critical decisions regarding operation, maintenance and repairs. Recent advances in nanostructured materials such as carbon nanotubes have opened the door for new smart and advanced sensing materials that could effectively be used in health monitoring of structures where wireless and real time sensing could provide information on damage development. In this paper, carbon nanotube networks were embedded into a cement matrix to develop an in situ wireless and embedded sensor for damage detection in concrete structures. By wirelessly measuring the change in the electrical resistance of the carbon nanotube networks, the progress of damage can be detected and monitored. As a proof of concept, wireless cement-carbon nanotube sensors were embedded into concrete beams and subjected to monotonic and cyclic loading to evaluate the effect of damage on their response. Experimental results showed that the wireless response of the embedded nanotube sensors changes due to the formation of cracks during loading. In addition, the nanotube sensors were able to detect the initiation of damage at an early stage of loading.

Causes and Prevention of Structural Materials Failures in Naval Environments.

DTIC Science & Technology

1984-01-01

atomic hydrogen as the first step; (iii) creation of elastic-plastic zones near the crack tip region due to movement of dislocations under applied...sodium tellurate is added to the charging solution. There is a dramatic drop in hydrogen permeation current due to the reduction of the tellurate ...effect of tellurium which has been deposited. Thus it has been shown that the tellurate ion, an electron acceptor, can delay the production of hydrogen

Integral Ring Carbon-Carbon Piston

NASA Technical Reports Server (NTRS)

Northam, G. Burton (Inventor)

1999-01-01

An improved structure for a reciprocating internal combustion engine or compressor piston fabricate from carbon-carbon composite materials is disclosed. An integral ring carbon-carbon composite piston, disclosed herein, reduces the need for piston rings and for small clearances by providing a small flexible, integral component around the piston that allows for variation in clearance due to manufacturing tolerances, distortion due to pressure and thermal loads, and variations in thermal expansion differences between the piston and cylinder liner.

The crystal chemistry of inorganic metal borohydrides and their relation to metal oxides.

PubMed

Černý, Radovan; Schouwink, Pascal

2015-12-01

The crystal structures of inorganic homoleptic metal borohydrides are analysed with respect to their structural prototypes found amongst metal oxides in the inorganic databases such as Pearson's Crystal Data [Villars & Cenzual (2015). Pearson's Crystal Data. Crystal Structure Database for Inorganic Compounds, Release 2014/2015, ASM International, Materials Park, Ohio, USA]. The coordination polyhedra around the cations and the borohydride anion are determined, and constitute the basis of the structural systematics underlying metal borohydride chemistry in various frameworks and variants of ionic packing, including complex anions and the packing of neutral molecules in the crystal. Underlying nets are determined by topology analysis using the program TOPOS [Blatov (2006). IUCr CompComm. Newsl. 7, 4-38]. It is found that the Pauling rules for ionic crystals apply to all non-molecular borohydride crystal structures, and that the latter can often be derived by simple deformation of the close-packed anionic lattices c.c.p. and h.c.p., by partially removing anions and filling tetrahedral or octahedral sites. The deviation from an ideal close packing is facilitated in metal borohydrides with respect to the oxide due to geometrical and electronic considerations of the BH4(-) anion (tetrahedral shape, polarizability). This review on crystal chemistry of borohydrides and their similarity to oxides is a contribution which should serve materials engineers as a roadmap to design new materials, synthetic chemists in their search for promising compounds to be prepared, and materials scientists in understanding the properties of novel materials.

Enhanced Photocatalytic Activity of Bismuth Precursor by Rapid Phase and Surface Transformation Using Structure-Guided Combustion Waves.

PubMed

Lee, Kang Yeol; Hwang, Hayoung; Kim, Tae Ho; Choi, Wonjoon

2016-02-10

The development of an efficient method for manipulating phase and surface transformations would facilitate the improvement of catalytic materials for use in a diverse range of applications. Herein, we present the first instance of a submicrosecond time frame direct phase and surface transformation of Bi(NO3)3 rods to nanoporous β-Bi2O3 rods via structure-guided combustion waves. Hybrid composites of the prepared Bi(NO3)3·H2O rods and organic fuel were fabricated by a facile preparation method. The anisotropic propagation of combustion waves along the interfacial boundaries of Bi(NO3)3·H2O rods induced direct phase transformation to β-Bi2O3 rods in the original structure due to the rapid pyrolysis, while the release of gas molecules enabled the formation of nanoporous structures on the surfaces of rods. The developed β-Bi2O3 rods showed improved photocatalytic activity for the photodegradation of rhodamine B in comparison with Bi(NO3)3·H2O rods and α-Bi2O3 rods due to the more suitable interdistance and the large contact areas of the porous surfaces. This new method of using structure-guided combustion waves for phase and surface transformation may contribute to the development of new catalysts as well as the precise manipulation of diverse micronanostructured materials.

Additive Manufacturing: Unlocking the Evolution of Energy Materials

PubMed Central

Zhakeyev, Adilet; Wang, Panfeng; Shu, Wenmiao; Wang, Huizhi

2017-01-01

Abstract The global energy infrastructure is undergoing a drastic transformation towards renewable energy, posing huge challenges on the energy materials research, development and manufacturing. Additive manufacturing has shown its promise to change the way how future energy system can be designed and delivered. It offers capability in manufacturing complex 3D structures, with near‐complete design freedom and high sustainability due to minimal use of materials and toxic chemicals. Recent literatures have reported that additive manufacturing could unlock the evolution of energy materials and chemistries with unprecedented performance in the way that could never be achieved by conventional manufacturing techniques. This comprehensive review will fill the gap in communicating on recent breakthroughs in additive manufacturing for energy material and device applications. It will underpin the discoveries on what 3D functional energy structures can be created without design constraints, which bespoke energy materials could be additively manufactured with customised solutions, and how the additively manufactured devices could be integrated into energy systems. This review will also highlight emerging and important applications in energy additive manufacturing, including fuel cells, batteries, hydrogen, solar cell as well as carbon capture and storage. PMID:29051861

Additive Manufacturing: Unlocking the Evolution of Energy Materials.

PubMed

Zhakeyev, Adilet; Wang, Panfeng; Zhang, Li; Shu, Wenmiao; Wang, Huizhi; Xuan, Jin

2017-10-01

The global energy infrastructure is undergoing a drastic transformation towards renewable energy, posing huge challenges on the energy materials research, development and manufacturing. Additive manufacturing has shown its promise to change the way how future energy system can be designed and delivered. It offers capability in manufacturing complex 3D structures, with near-complete design freedom and high sustainability due to minimal use of materials and toxic chemicals. Recent literatures have reported that additive manufacturing could unlock the evolution of energy materials and chemistries with unprecedented performance in the way that could never be achieved by conventional manufacturing techniques. This comprehensive review will fill the gap in communicating on recent breakthroughs in additive manufacturing for energy material and device applications. It will underpin the discoveries on what 3D functional energy structures can be created without design constraints, which bespoke energy materials could be additively manufactured with customised solutions, and how the additively manufactured devices could be integrated into energy systems. This review will also highlight emerging and important applications in energy additive manufacturing, including fuel cells, batteries, hydrogen, solar cell as well as carbon capture and storage.

Membrane materials for storing biological samples intended for comparative nanotoxicological testing

NASA Astrophysics Data System (ADS)

Metelkin, A.; Kuznetsov, D.; Kolesnikov, E.; Chuprunov, K.; Kondakov, S.; Osipov, A.; Samsonova, J.

2015-11-01

The study is aimed at identifying the samples of most promising membrane materials for storing dry specimens of biological fluids (Dried Blood Spots, DBS technology). Existing sampling systems using cellulose fiber filter paper have a number of drawbacks such as uneven distribution of the sample spot, dependence of the spot spreading area on the individual biosample properties, incomplete washing-off of the sample due to partially inconvertible sorption of blood components on cellulose fibers, etc. Samples of membrane materials based on cellulose, polymers and glass fiber with applied biosamples were studied using methods of scanning electron microscopy, FT-IR spectroscopy and surface-wetting measurement. It was discovered that cellulose-based membrane materials sorb components of biological fluids inside their structure, while membranes based on glass fiber display almost no interaction with the samples and biological fluid components dry to films in the membrane pores between the structural fibers. This characteristic, together with the fact that membrane materials based on glass fiber possess sufficient strength, high wetting properties and good storage capacity, attests them as promising material for dry samples of biological fluids storage systems.

High pressure X-ray diffraction studies on Bi2-xSbxTe3 (x=0,1,2) materials

NASA Astrophysics Data System (ADS)

Jacobsen, Matthew; Kumar, Ravhi; Cornelius, Andrew

2007-06-01

Recently Bi2Te3 based thermoelectric materials have gained importance due to their high thermoelectric figure of merit in thin films [3]. Pressure tuning of the thermoelectric figure of merit has been reported for several materials [1],[2]. In order to investigate the bulk properties of Bi2Te3, Sb2Te3, and their solid solution in detail, we have performed structural studies up to 20 GPa. Our diffraction results show that all three compounds transform from the ambient pressure structure to a high pressure phase between 5 and 7 GPa. Details of the results will be discussed in this presentation. [1]Chen, G., Dresselhaus, M.S., Dresselhaus, G., Fleurial, J.-P., and Caillat, T. Recent developments in themoelectric materials. International Materials Reviews, 48, 45-66 (2003). [2]Rowe, D.M. CRC Handbook of Thermoelectric Materials. CRC Press, 1995. [3]Venkatasubramanian, R., Silvola, E., Colpitts, T., and O'Quinn, B. Thin-film thermoelectric devices with high room-temperature figures of merit. Nature, 413, 597-602, 2001.

Bone tissue engineering using silica-based mesoporous nanobiomaterials:Recent progress.

PubMed

Shadjou, Nasrin; Hasanzadeh, Mohammad

2015-10-01

Bone disorders are of significant concern due to increase in the median age of our population. It is in this context that tissue engineering has been emerging as a valid approach to the current therapies for bone regeneration/substitution. Tissue-engineered bone constructs have the potential to alleviate the demand arising from the shortage of suitable autograft and allograft materials for augmenting bone healing. Silica based mesostructured nanomaterials possessing pore sizes in the range 2-50 nm and surface reactive functionalities have elicited immense interest due to their exciting prospects in bone tissue engineering. In this review we describe application of silica-based mesoporous nanomaterials for bone tissue engineering. We summarize the preparation methods, the effect of mesopore templates and composition on the mesopore-structure characteristics, and different forms of these materials, including particles, fibers, spheres, scaffolds and composites. Also, the effect of structural and textural properties of mesoporous materials on development of new biomaterials for production of bone implants and bone cements was discussed. Also, application of different mesoporous materials on construction of manufacture 3-dimensional scaffolds for bone tissue engineering was discussed. It begins by giving the reader a brief background on tissue engineering, followed by a comprehensive description of all the relevant components of silica-based mesoporous biomaterials on bone tissue engineering, going from materials to scaffolds and from cells to tissue engineering strategies that will lead to "engineered" bone. Copyright © 2015 Elsevier B.V. All rights reserved.

Parameterizing water quality analysis and simulation program (WASP) for carbon-based nanomaterials

EPA Science Inventory

Carbon nanotubes (CNT) and graphenes are among the most popular carbon-based nanomaterials due to their unique electronic, mechanic and structural properties. Exposure modeling of these nanomaterials in the aquatic environment is necessary to predict the fate of these materials. ...

Substantial bulk photovoltaic effect enhancement via nanolayering

DOE PAGES

Wang, Fenggong; Young, Steve M.; Zheng, Fan; ...

2016-01-21

Spontaneous polarization and inversion symmetry breaking in ferroelectric materials lead to their use as photovoltaic devices. However, further advancement of their applications are hindered by the paucity of ways of reducing bandgaps and enhancing photocurrent. By unravelling the correlation between ferroelectric materials’ responses to solar irradiation and their local structure and electric polarization landscapes, here we show from first principles that substantial bulk photovoltaic effect enhancement can be achieved by nanolayering PbTiO 3 with nickel ions and oxygen vacancies ((PbNiO 2) x(PbTiO 3) 1–x). The enhancement of the total photocurrent for different spacings between the Ni-containing layers can be asmore » high as 43 times due to a smaller bandgap and photocurrent direction alignment for all absorption energies. This is due to the electrostatic effect that arises from nanolayering. Lastly, this opens up the possibility for control of the bulk photovoltaic effect in ferroelectric materials by nanoscale engineering of their structure and composition.« less

Large Area Nano-transfer Printing of Sub-50-nm Metal Nanostructures Using Low-cost Semi-flexible Hybrid Templates

NASA Astrophysics Data System (ADS)

Nagel, Robin D.; Haeberle, Tobias; Schmidt, Morten; Lugli, Paolo; Scarpa, Giuseppe

2016-03-01

In this work, we present a method for printing metal micro- and nanopatterns down to sub-50-nm feature sizes using replicated, defect-tolerant stamps made out of OrmoStamp®; material. The relevant parameters for a successful transfer over large areas were investigated and yields above 99 % have been achieved. Comparing our results to conventional nano-transfer printing using PDMS stamps, we find that the more rigid hybrid polymer used here prevents unintended transfer from interspaces between structures of large distance due to roof collapse and deformation of nano-sized structures due to lateral collapse. Yet, our stamps are flexible enough to ensure intimate contact with the underlying substrate over large areas even in the presence of defect particles. Additionally, the presented patterning technique is resist-, solvent-, and chemical-free and is therefore ideally suited for applications in organic nanoelectronics where standard nanostructuring methods can harm or destroy the organic material.

Effect of ultraviolet radiation in the photo-oxidation of High Density Polyethylene and Biodegradable Polyethylene films

NASA Astrophysics Data System (ADS)

Martínez-Romo, A.; González Mota, R.; Bernal, J. J. Soto; Frausto Reyes, C.; Rosales Candelas, I.

2015-01-01

One of the most widely used plastics in the world is the High density polyethylene (HDPE), it is a stable material due to its carbon-carbon bonds, causing their slow degradation; which is why we are looking for alternative ways to accelerate the degradation process of this polymer. An alternative is the addition of oxidized groups in its molecular structure, which results in the development of polymers susceptible to biodegradation (PE-BIO). In this paper, HDPE and PE-BIO films were exposed to UV-B radiation (320-280 nm) at different exposure times, 0-60 days. The effects of UV radiation in samples of HDPE and PE-BIO were characterized using infrared spectroscopy with attenuated total reflectance (ATR). The results show that the exposed materials undergo changes in their molecular structure, due to the infrared bands formed which corresponds to the photo-oxidation of HDPE and PE films when submitted to UV-B radiation.

Corrosion behavior of a superduplex stainless steel in chloride aqueous solution

NASA Astrophysics Data System (ADS)

Dabalà, Manuele; Calliari, Irene; Variola, Alessandra

2004-04-01

Super duplex stainless steels (SDSS) have been widely used as structural materials for chemical plants (especially in those engaged in phosphoric acid production), in the hydrometallurgy industries, and as materials for offshore applications due to their excellent corrosion resistance in chloride environments, compared with other commercial types of ferritic stainless steels. These alloys also possess superior weldability and better mechanical properties than austenitic stainless steels. However, due to their two-phase structure, the nature of which is very dependent on their composition and thermal history, the behavior of SDSS regarding localized corrosion appears difficult to predict, especially in chloride environments. To improve their final properties, the effect of the partition of the alloying elements between the two phases, and the composition and microstructure of each phase are the key to understanding the localized corrosion phenomena of SDSS. This paper concerns the effects of the SDSS microstructure and heat treatment on the SDSS corrosion resistance in aqueous solutions, containing different amounts of NaCl at room temperature.

Measuring Moisture Levels in Graphite Epoxy Composite Sandwich Structures

NASA Technical Reports Server (NTRS)

Nurge, Mark; Youngquist, Robert; Starr, Stanley

2011-01-01

Graphite epoxy composite (GEC) materials are used in the construction of rocket fairings, nose cones, interstage adapters, and heat shields due to their high strength and light weight. However, they absorb moisture depending on the environmental conditions they are exposed to prior to launch. Too much moisture absorption can become a problem when temperature and pressure changes experienced during launch cause the water to vaporize. The rapid state change of the water can result in structural failure of the material. In addition, heat and moisture combine to weaken GEC structures. Diffusion models that predict the total accumulated moisture content based on the environmental conditions are one accepted method of determining if the material strength has been reduced to an unacceptable level. However, there currently doesn t exist any field measurement technique to estimate the actual moisture content of a composite structure. A multi-layer diffusion model was constructed with Mathematica to predict moisture absorption and desorption from the GEC sandwich structure. This model is used in conjunction with relative humidity/temperature sensors both on the inside and outside of the material to determine the moisture levels in the structure. Because the core materials have much higher diffusivity than the face sheets, a single relative humidity measurement will accurately reflect the moisture levels in the core. When combined with an external relative humidity measurement, the model can be used to determine the moisture levels in the face sheets. Since diffusion is temperaturedependent, the temperature measurements are used to determine the diffusivity of the face sheets for the model computations.

Self-healing nanocomposite using shape memory polymer and carbon nanotubes

NASA Astrophysics Data System (ADS)

Liu, Yingtao; Rajadas, Abhishek; Chattopadhyay, Aditi

2013-04-01

Carbon fiber reinforced composites are used in a wide range of applications in aerospace, mechanical, and civil structures. Due to the nature of material, most damage in composites, such as delaminations, are always barely visible to the naked eye, which makes it difficult to detect and repair. The investigation of biological systems has inspired the development and characterization of self-healing composites. This paper presents the development of a new type of self-healing material in order to impede damage progression and conduct in-situ damage repair in composite structures. Carbon nanotubes, which are highly conductive materials, are mixed with shape memory polymer to develop self-healing capability. The developed polymeric material is applied to carbon fiber reinforced composites to automatically heal the delamination between different layers. The carbon fiber reinforced composite laminates are manufactured using high pressure molding techniques. Tensile loading is applied to double cantilever beam specimens using an MTS hydraulic test frame. A direct current power source is used to generate heat within the damaged area. The application of thermal energy leads to re-crosslinking in shape memory polymers. Experimental results showed that the developed composite materials are capable of healing the matrix cracks and delaminations in the bonded areas of the test specimens. The developed self-healing material has the potential to be used as a novel structural material in mechanical, civil, aerospace applications.

Observation of van Hove Singularities in Twisted Silicene Multilayers.

PubMed

Li, Zhi; Zhuang, Jincheng; Chen, Lan; Ni, Zhenyi; Liu, Chen; Wang, Li; Xu, Xun; Wang, Jiaou; Pi, Xiaodong; Wang, Xiaolin; Du, Yi; Wu, Kehui; Dou, Shi Xue

2016-08-24

Interlayer interactions perturb the electronic structure of two-dimensional materials and lead to new physical phenomena, such as van Hove singularities and Hofstadter's butterfly pattern. Silicene, the recently discovered two-dimensional form of silicon, is quite unique, in that silicon atoms adopt competing sp(2) and sp(3) hybridization states leading to a low-buckled structure promising relatively strong interlayer interaction. In multilayer silicene, the stacking order provides an important yet rarely explored degree of freedom for tuning its electronic structures through manipulating interlayer coupling. Here, we report the emergence of van Hove singularities in the multilayer silicene created by an interlayer rotation. We demonstrate that even a large-angle rotation (>20°) between stacked silicene layers can generate a Moiré pattern and van Hove singularities due to the strong interlayer coupling in multilayer silicene. Our study suggests an intriguing method for expanding the tunability of the electronic structure for electronic applications in this two-dimensional material.

Applications of Carbon Nanotubes for Lithium Ion Battery Anodes

PubMed Central

Xiong, Zhili; Yun, Young Soo; Jin, Hyoung-Joon

2013-01-01

Carbon nanotubes (CNTs) have displayed great potential as anode materials for lithium ion batteries (LIBs) due to their unique structural, mechanical, and electrical properties. The measured reversible lithium ion capacities of CNT-based anodes are considerably improved compared to the conventional graphite-based anodes. Additionally, the opened structure and enriched chirality of CNTs can help to improve the capacity and electrical transport in CNT-based LIBs. Therefore, the modification of CNTs and design of CNT structure provide strategies for improving the performance of CNT-based anodes. CNTs could also be assembled into free-standing electrodes without any binder or current collector, which will lead to increased specific energy density for the overall battery design. In this review, we discuss the mechanism of lithium ion intercalation and diffusion in CNTs, and the influence of different structures and morphologies on their performance as anode materials for LIBs. PMID:28809361

Formation of metallic cation-oxygen network for anomalous thermal expansion coefficients in binary phosphate glass

NASA Astrophysics Data System (ADS)

Onodera, Yohei; Kohara, Shinji; Masai, Hirokazu; Koreeda, Akitoshi; Okamura, Shun; Ohkubo, Takahiro

2017-05-01

Understanding glass structure is still challenging due to the result of disorder, although novel materials design on the basis of atomistic structure has been strongly demanded. Here we report on the atomic structures of the zinc phosphate glass determined by reverse Monte Carlo modelling based on diffraction and spectroscopic data. The zinc-rich glass exhibits the network formed by ZnOx (averaged x<4) polyhedra. Although the elastic modulus, refractive index and glass transition temperature of the zinc phosphate glass monotonically increase with the amount of ZnO, we find for the first time that the thermal expansion coefficient is very sensitive to the substitution of the phosphate chain network by a network consisting of Zn-O units in zinc-rich glass. Our results imply that the control of the structure of intermediate groups may enable new functionalities in the design of oxide glass materials.

Formation of metallic cation-oxygen network for anomalous thermal expansion coefficients in binary phosphate glass.

PubMed

Onodera, Yohei; Kohara, Shinji; Masai, Hirokazu; Koreeda, Akitoshi; Okamura, Shun; Ohkubo, Takahiro

2017-05-31

Understanding glass structure is still challenging due to the result of disorder, although novel materials design on the basis of atomistic structure has been strongly demanded. Here we report on the atomic structures of the zinc phosphate glass determined by reverse Monte Carlo modelling based on diffraction and spectroscopic data. The zinc-rich glass exhibits the network formed by ZnO x (averaged x<4) polyhedra. Although the elastic modulus, refractive index and glass transition temperature of the zinc phosphate glass monotonically increase with the amount of ZnO, we find for the first time that the thermal expansion coefficient is very sensitive to the substitution of the phosphate chain network by a network consisting of Zn-O units in zinc-rich glass. Our results imply that the control of the structure of intermediate groups may enable new functionalities in the design of oxide glass materials.

Mesoporous LiFeBO3/C hollow spheres for improved stability lithium-ion battery cathodes

NASA Astrophysics Data System (ADS)

Chen, Zhongxue; Cao, Liufei; Chen, Liang; Zhou, Haihui; Zheng, Chunman; Xie, Kai; Kuang, Yafei

2015-12-01

Polyanionic compounds are regarded as one of the most promising cathode materials for the next generation lithium-ion batteries due to their abundant resource and thermal stability. LiFeBO3 has a relatively higher capacity than olivine LiFePO4, however, moisture sensitivity and low conductivity hinder its further development. Here, we design and synthesize mesoporous LiFeBO3/C (LFB/C) hollow spheres to enhance its structural stability and electric conductivity, two LiFeBO3/C electrodes with different carbon content are prepared and tested. The experimental results show that mesoporous LiFeBO3/C hollow spheres with higher carbon content exhibit superior lithium storage capacity, cycling stability and rate capability. Particularly, the LFB/C electrode with higher carbon content demonstrates good structural stability, which can maintain its original crystal structure and Li storage properties even after three months of air exposure at room temperature. The exceptional structural stability and electrochemical performance may justify their potential use as high-performance cathode materials for advanced lithium-ion batteries. In addition, the synthesis strategy demonstrated herein is simple and versatile for the fabrication of other polyanionic cathode materials with mesoporous hollow spherical structure.

Controlled mechanical buckling for origami-inspired construction of 3D microstructures in advanced materials.

PubMed

Yan, Zheng; Zhang, Fan; Wang, Jiechen; Liu, Fei; Guo, Xuelin; Nan, Kewang; Lin, Qing; Gao, Mingye; Xiao, Dongqing; Shi, Yan; Qiu, Yitao; Luan, Haiwen; Kim, Jung Hwan; Wang, Yiqi; Luo, Hongying; Han, Mengdi; Huang, Yonggang; Zhang, Yihui; Rogers, John A

2016-04-25

Origami is a topic of rapidly growing interest in both the scientific and engineering research communities due to its promising potential in a broad range of applications. Previous assembly approaches of origami structures at the micro/nanoscale are constrained by the applicable classes of materials, topologies and/or capability of control over the transformation. Here, we introduce an approach that exploits controlled mechanical buckling for autonomic origami assembly of 3D structures across material classes from soft polymers to brittle inorganic semiconductors, and length scales from nanometers to centimeters. This approach relies on a spatial variation of thickness in the initial 2D structures as an effective strategy to produce engineered folding creases during the compressive buckling process. The elastic nature of the assembly scheme enables active, deterministic control over intermediate states in the 2D to 3D transformation in a continuous and reversible manner. Demonstrations include a broad set of 3D structures formed through unidirectional, bidirectional, and even hierarchical folding, with examples ranging from half cylindrical columns and fish scales, to cubic boxes, pyramids, starfish, paper fans, skew tooth structures, and to amusing system-level examples of soccer balls, model houses, cars, and multi-floor textured buildings.

Development of ultralight, super-elastic, hierarchical metallic meta-structures with i3DP technology

NASA Astrophysics Data System (ADS)

Zhang, Dongxing; Xiao, Junfeng; Moorlag, Carolyn; Guo, Qiuquan; Yang, Jun

2017-11-01

Lightweight and mechanically robust materials show promising applications in thermal insulation, energy absorption, and battery catalyst supports. This study demonstrates an effective method for creation of ultralight metallic structures based on initiator-integrated 3D printing technology (i3DP), which provides a possible platform to design the materials with the best geometric parameters and desired mechanical performance. In this study, ultralight Ni foams with 3D interconnected hollow tubes were fabricated, consisting of hierarchical features spanning three scale orders ranging from submicron to centimeter. The resultant materials can achieve an ultralight density of as low as 5.1 mg cm-3 and nearly recover after significant compression up to 50%. Due to a high compression ratio, the hierarchical structure exhibits superior properties in terms of energy absorption and mechanical efficiency. The relationship of structural parameters and mechanical response was established. The ability of achieving ultralight density <10 mg cm-3 and the stable \\bar{E}˜ {\\bar{ρ }}2 scaling through all range of relative density, indicates an advantage over the previous stochastic metal foams. Overall, this initiator-integrated 3D printing approach provides metallic structures with substantial benefits from the hierarchical design and fabrication flexibility to ultralight applications.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

PubMed Central

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-01-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10–40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage. PMID:24145684

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors.

PubMed

Oakes, Landon; Westover, Andrew; Mares, Jeremy W; Chatterjee, Shahana; Erwin, William R; Bardhan, Rizia; Weiss, Sharon M; Pint, Cary L

2013-10-22

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-10-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Numerical simulation of high-temperature thermal contact resistance and its reduction mechanism.

PubMed

Liu, Donghuan; Zhang, Jing

2018-01-01

High-temperature thermal contact resistance (TCR) plays an important role in heat-pipe-cooled thermal protection structures due to the existence of contact interface between the embedded heat pipe and the heat resistive structure, and the reduction mechanism of thermal contact resistance is of special interests in the design of such structures. The present paper proposed a finite element model of the high-temperature thermal contact resistance based on the multi-point contact model with the consideration of temperature-dependent material properties, heat radiation through the cavities at the interface and the effect of thermal interface material (TIM), and the geometry parameters of the finite element model are determined by simple surface roughness test and experimental data fitting. The experimental results of high-temperature thermal contact resistance between superalloy GH600 and C/C composite material are employed to validate the present finite element model. The effect of the crucial parameters on the thermal contact resistance with and without TIM are also investigated with the proposed finite element model.

Three-dimensional analysis of anisotropic spatially reinforced structures

NASA Technical Reports Server (NTRS)

Bogdanovich, Alexander E.

1993-01-01

The material-adaptive three-dimensional analysis of inhomogeneous structures based on the meso-volume concept and application of deficient spline functions for displacement approximations is proposed. The general methodology is demonstrated on the example of a brick-type mosaic parallelepiped arbitrarily composed of anisotropic meso-volumes. A partition of each meso-volume into sub-elements, application of deficient spline functions for a local approximation of displacements and, finally, the use of the variational principle allows one to obtain displacements, strains, and stresses at anypoint within the structural part. All of the necessary external and internal boundary conditions (including the conditions of continuity of transverse stresses at interfaces between adjacent meso-volumes) can be satisfied with requisite accuracy by increasing the density of the sub-element mesh. The application of the methodology to textile composite materials is described. Several numerical examples for woven and braided rectangular composite plates and stiffened panels under transverse bending are considered. Some typical effects of stress concentrations due to the material inhomogeneities are demonstrated.

Numerical simulation of high-temperature thermal contact resistance and its reduction mechanism

PubMed Central

Zhang, Jing

2018-01-01

High-temperature thermal contact resistance (TCR) plays an important role in heat-pipe-cooled thermal protection structures due to the existence of contact interface between the embedded heat pipe and the heat resistive structure, and the reduction mechanism of thermal contact resistance is of special interests in the design of such structures. The present paper proposed a finite element model of the high-temperature thermal contact resistance based on the multi-point contact model with the consideration of temperature-dependent material properties, heat radiation through the cavities at the interface and the effect of thermal interface material (TIM), and the geometry parameters of the finite element model are determined by simple surface roughness test and experimental data fitting. The experimental results of high-temperature thermal contact resistance between superalloy GH600 and C/C composite material are employed to validate the present finite element model. The effect of the crucial parameters on the thermal contact resistance with and without TIM are also investigated with the proposed finite element model. PMID:29547651

High-resolution soft X-ray spectra of Scorpius X-1 - The structure of circumsource accreting material

NASA Technical Reports Server (NTRS)

Kahn, S. M.; Seward, F. D.; Chlebowski, T.

1984-01-01

Four observations of Scorpius X-1 with the Objective Grating Spectrometer of the Einstein Observatory have provided high-resolution spectra (lambda/Delta lambda = approximately 20-50) in the wavelength range 7-46 A. The spectra reveal the presence of absorption structure due to oxygen, nitrogen, and iron, and variable emission structure associated with ionized iron and nitrogen. The strengths of these features suggest that the N/O abundance ratio in the absorbing and line emitting gas is anomalously high, which might indicate that these spectral components are associated with processed material, probably accreting matter transferred from the surface of an evolved companion. Constraints on the inclination of the system, however, imply that this cool, dense, accreting material must be well out of the plane of the binary system. Possible models for the origin and nature of this circumsource medium are discussed. An extensive discussion of the calibration of the Objective Grating Spectrometer and of the analysis of spectra acquired by that instrument is also provided.

Analysis of occupational accidents with biological material among professionals in pre-hospital services.

PubMed

de Oliveira, Adriana Cristina; Paiva, Maria Henriqueta Rocha Siqueira

2013-02-01

To estimate the prevalence of accidents due to biological material exposure, the characteristics and post-accident conduct among professionals of pre-hospital services of the four municipalities of Minas Gerais, Brazil. A cross-sectional study, using a structured questionnaire that was developed to enable the calculation of prevalence, descriptive analysis and analytical analysis using logistic regression. The study included 228 professionals; the prevalence of accidents due to biological material exposure was 29.4%, with 49.2% percutaneous, 10.4% mucousal, 6.0% non-intact skin, and 34.4% intact skin. Among the professionals injured, those that stood out were nursing technicians (41.9%) and drivers (28.3%). Notification of the occurrence of the accident occurred in 29.8% of the cases. Percutaneous exposure was associated with time of work in the organization (OR=2.51, 95% CI: 1.18 to 5.35, p<0.017). Notification about accidents with biological material should be encouraged, along with professional evaluation/monitoring.

Physico-Chemical Alternatives in Lignocellulosic Materials in Relation to the Kind of Component for Fermenting Purposes

PubMed Central

Coz, Alberto; Llano, Tamara; Cifrián, Eva; Viguri, Javier; Maican, Edmond; Sixta, Herbert

2016-01-01

The complete bioconversion of the carbohydrate fraction is of great importance for a lignocellulosic-based biorefinery. However, due to the structure of the lignocellulosic materials, and depending basically on the main parameters within the pretreatment steps, numerous byproducts are generated and they act as inhibitors in the fermentation operations. In this sense, the impact of inhibitory compounds derived from lignocellulosic materials is one of the major challenges for a sustainable biomass-to-biofuel and -bioproduct industry. In order to minimise the negative effects of these compounds, numerous methodologies have been tested including physical, chemical, and biological processes. The main physical and chemical treatments have been studied in this work in relation to the lignocellulosic material and the inhibitor in order to point out the best mechanisms for fermenting purposes. In addition, special attention has been made in the case of lignocellulosic hydrolysates obtained by chemical processes with SO2, due to the complex matrix of these materials and the increase in these methodologies in future biorefinery markets. Recommendations of different detoxification methods have been given. PMID:28773700

Topology optimization of hyperelastic structures using a level set method

NASA Astrophysics Data System (ADS)

Chen, Feifei; Wang, Yiqiang; Wang, Michael Yu; Zhang, Y. F.

2017-12-01

Soft rubberlike materials, due to their inherent compliance, are finding widespread implementation in a variety of applications ranging from assistive wearable technologies to soft material robots. Structural design of such soft and rubbery materials necessitates the consideration of large nonlinear deformations and hyperelastic material models to accurately predict their mechanical behaviour. In this paper, we present an effective level set-based topology optimization method for the design of hyperelastic structures that undergo large deformations. The method incorporates both geometric and material nonlinearities where the strain and stress measures are defined within the total Lagrange framework and the hyperelasticity is characterized by the widely-adopted Mooney-Rivlin material model. A shape sensitivity analysis is carried out, in the strict sense of the material derivative, where the high-order terms involving the displacement gradient are retained to ensure the descent direction. As the design velocity enters into the shape derivative in terms of its gradient and divergence terms, we develop a discrete velocity selection strategy. The whole optimization implementation undergoes a two-step process, where the linear optimization is first performed and its optimized solution serves as the initial design for the subsequent nonlinear optimization. It turns out that this operation could efficiently alleviate the numerical instability and facilitate the optimization process. To demonstrate the validity and effectiveness of the proposed method, three compliance minimization problems are studied and their optimized solutions present significant mechanical benefits of incorporating the nonlinearities, in terms of remarkable enhancement in not only the structural stiffness but also the critical buckling load.

Analysis and Modeling of Small Crack Detection in Pressurized Fuselages for Structural Health Monitoring Applications (Preprint)

DTIC Science & Technology

2012-07-01

airframe failures resulting in the total loss of the aircraft [ Parton and Morozov (1978); Piascik (1999)]. More recently, in April 1988, the Aloha...a material [ Parton and Morozov (1978)]. The size of the region covered by the plastic flow depends on the material properties and the loading...crack length due to uniaxial loads applied normal to the crack orientation. The Griffith-Orowan-Irwin concept [ Parton (1992)] establishes that the

Optimization, Alternative Materials and Improvements in Body Armor Shields

DTIC Science & Technology

2007-05-10

performance structures such as protective clothing , bullet-proof vests and helmets due to their high-specific strength and stiffness. The ballistic...regard each layer of the woven composite as made of weft and warp yarns, and divide each yam into 3D solid elements. It is found that the frame...0.25 mm thick layers is modeled as an orthotropic material. Even though the woven composite armor is made of yams and each yarn is made of fibers

Silicon carbide multilayer protective coating on carbon obtained by thermionic vacuum arc method

NASA Astrophysics Data System (ADS)

Ciupină, Victor; Lungu, Cristian Petrica; Vladoiu, Rodica; Prodan, Gabriel; Porosnicu, Corneliu; Belc, Marius; Stanescu, Iuliana M.; Vasile, Eugeniu; Rughinis, Razvan

2014-01-01

Thermionic vacuum arc (TVA) method is currently developing, in particular, to work easily with heavy fusible material for the advantage presented by control of directing energy for the elements forming a plasma. The category of heavy fusible material can recall C and W (high-melting point materials), and are difficult to obtain or to control by other means. Carbon is now used in many areas of special mechanical, thermal, and electrical properties. We refer in particular to high-temperature applications where unwanted effects may occur due to oxidation. Changed properties may lead to improper functioning of the item or device. For example, increasing the coefficient of friction may induce additional heat on moving items. One solution is to protect the item in question by coating with proper materials. Silicon carbide (SiC) was chosen mainly due to compatibility with coated carbon substrate. Recently, SiC has been used as conductive transparent window for optical devices, particularly in thin film solar cells. Using the TVA method, SiC coatings were obtained as thin films (multilayer structures), finishing with a thermal treatment up to 1000°C. Structural properties and oxidation behavior of the multilayer films were investigated, and the measurements showed that the third layer acts as a stopping layer for oxygen. Also, the friction coefficient of the protected films is lower relative to unprotected carbon films.

Immediate effects of EVA midsole resilience and upper shoe structure on running biomechanics: a machine learning approach

PubMed Central

Gavião Neto, Wilson P.; Roveri, Maria Isabel; Oliveira, Wagner R.

2017-01-01

Background Resilience of midsole material and the upper structure of the shoe are conceptual characteristics that can interfere in running biomechanics patterns. Artificial intelligence techniques can capture features from the entire waveform, adding new perspective for biomechanical analysis. This study tested the influence of shoe midsole resilience and upper structure on running kinematics and kinetics of non-professional runners by using feature selection, information gain, and artificial neural network analysis. Methods Twenty-seven experienced male runners (63 ± 44 km/week run) ran in four-shoe design that combined two resilience-cushioning materials (low and high) and two uppers (minimalist and structured). Kinematic data was acquired by six infrared cameras at 300 Hz, and ground reaction forces were acquired by two force plates at 1,200 Hz. We conducted a Machine Learning analysis to identify features from the complete kinematic and kinetic time series and from 42 discrete variables that had better discriminate the four shoes studied. For that analysis, we built an input data matrix of dimensions 1,080 (10 trials × 4 shoes × 27 subjects) × 1,254 (3 joints × 3 planes of movement × 101 data points + 3 vectors forces × 101 data points + 42 discrete calculated kinetic and kinematic features). Results The applied feature selection by information gain and artificial neural networks successfully differentiated the two resilience materials using 200(16%) biomechanical variables with an accuracy of 84.8% by detecting alterations of running biomechanics, and the two upper structures with an accuracy of 93.9%. Discussion The discrimination of midsole resilience resulted in lower accuracy levels than did the discrimination of the shoe uppers. In both cases, the ground reaction forces were among the 25 most relevant features. The resilience of the cushioning material caused significant effects on initial heel impact, while the effects of different uppers were distributed along the stance phase of running. Biomechanical changes due to shoe midsole resilience seemed to be subject-dependent, while those due to upper structure seemed to be subject-independent. PMID:28265506

Immediate effects of EVA midsole resilience and upper shoe structure on running biomechanics: a machine learning approach.

PubMed

Onodera, Andrea N; Gavião Neto, Wilson P; Roveri, Maria Isabel; Oliveira, Wagner R; Sacco, Isabel Cn

2017-01-01

Resilience of midsole material and the upper structure of the shoe are conceptual characteristics that can interfere in running biomechanics patterns. Artificial intelligence techniques can capture features from the entire waveform, adding new perspective for biomechanical analysis. This study tested the influence of shoe midsole resilience and upper structure on running kinematics and kinetics of non-professional runners by using feature selection, information gain, and artificial neural network analysis. Twenty-seven experienced male runners (63 ± 44 km/week run) ran in four-shoe design that combined two resilience-cushioning materials (low and high) and two uppers (minimalist and structured). Kinematic data was acquired by six infrared cameras at 300 Hz, and ground reaction forces were acquired by two force plates at 1,200 Hz. We conducted a Machine Learning analysis to identify features from the complete kinematic and kinetic time series and from 42 discrete variables that had better discriminate the four shoes studied. For that analysis, we built an input data matrix of dimensions 1,080 (10 trials × 4 shoes × 27 subjects) × 1,254 (3 joints × 3 planes of movement × 101 data points + 3 vectors forces × 101 data points + 42 discrete calculated kinetic and kinematic features). The applied feature selection by information gain and artificial neural networks successfully differentiated the two resilience materials using 200(16%) biomechanical variables with an accuracy of 84.8% by detecting alterations of running biomechanics, and the two upper structures with an accuracy of 93.9%. The discrimination of midsole resilience resulted in lower accuracy levels than did the discrimination of the shoe uppers. In both cases, the ground reaction forces were among the 25 most relevant features. The resilience of the cushioning material caused significant effects on initial heel impact, while the effects of different uppers were distributed along the stance phase of running. Biomechanical changes due to shoe midsole resilience seemed to be subject-dependent, while those due to upper structure seemed to be subject-independent.

Robotically Assembled Aerospace Structures: Digital Material Assembly using a Gantry-Type Assembler

NASA Technical Reports Server (NTRS)

Trinh, Greenfield; Copplestone, Grace; O'Connor, Molly; Hu, Steven; Nowak, Sebastian; Cheung, Kenneth; Jenett, Benjamin; Cellucci, Daniel

2017-01-01

This paper evaluates the development of automated assembly techniques for discrete lattice structures using a multi-axis gantry type CNC machine. These lattices are made of discrete components called digital materials. We present the development of a specialized end effector that works in conjunction with the CNC machine to assemble these lattices. With this configuration we are able to place voxels at a rate of 1.5 per minute. The scalability of digital material structures due to the incremental modular assembly is one of its key traits and an important metric of interest. We investigate the build times of a 5x5 beam structure on the scale of 1 meter (325 parts), 10 meters (3,250 parts), and 30 meters (9,750 parts). Utilizing the current configuration with a single end effector, performing serial assembly with a globally fixed feed station at the edge of the build volume, the build time increases according to a scaling law of n4, where n is the build scale. Build times can be reduced significantly by integrating feed systems into the gantry itself, resulting in a scaling law of n3. A completely serial assembly process will encounter time limitations as build scale increases. Automated assembly for digital materials can assemble high performance structures from discrete parts, and techniques such as built in feed systems, parallelization, and optimization of the fastening process will yield much higher throughput.

Robotically Assembled Aerospace Structures: Digital Material Assembly using a Gantry-Type Assembler

NASA Technical Reports Server (NTRS)

Trinh, Greenfield; Copplestone, Grace; O'Connor, Molly; Hu, Steven; Nowak, Sebastian; Cheung, Kenneth; Jenett, Benjamin; Cellucci, Daniel

2017-01-01

This paper evaluates the development of automated assembly techniques for discrete lattice structures using a multi-axis gantry type CNC machine. These lattices are made of discrete components called "digital materials." We present the development of a specialized end effector that works in conjunction with the CNC machine to assemble these lattices. With this configuration we are able to place voxels at a rate of 1.5 per minute. The scalability of digital material structures due to the incremental modular assembly is one of its key traits and an important metric of interest. We investigate the build times of a 5x5 beam structure on the scale of 1 meter (325 parts), 10 meters (3,250 parts), and 30 meters (9,750 parts). Utilizing the current configuration with a single end effector, performing serial assembly with a globally fixed feed station at the edge of the build volume, the build time increases according to a scaling law of n4, where n is the build scale. Build times can be reduced significantly by integrating feed systems into the gantry itself, resulting in a scaling law of n3. A completely serial assembly process will encounter time limitations as build scale increases. Automated assembly for digital materials can assemble high performance structures from discrete parts, and techniques such as built in feed systems, parallelization, and optimization of the fastening process will yield much higher throughput.

40 CFR 280.11 - Interim prohibition for deferred UST systems.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) Will prevent releases due to corrosion or structural failure for the operational life of the UST system; (2) Is cathodically protected against corrosion, constructed of noncorrodible material, steel clad... substance. (b) Notwithstanding paragraph (a) of this section, an UST system without corrosion protection may...

40 CFR 280.11 - Interim prohibition for deferred UST systems.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) Will prevent releases due to corrosion or structural failure for the operational life of the UST system; (2) Is cathodically protected against corrosion, constructed of noncorrodible material, steel clad... substance. (b) Notwithstanding paragraph (a) of this section, an UST system without corrosion protection may...

40 CFR 280.11 - Interim prohibition for deferred UST systems.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) Will prevent releases due to corrosion or structural failure for the operational life of the UST system; (2) Is cathodically protected against corrosion, constructed of noncorrodible material, steel clad... substance. (b) Notwithstanding paragraph (a) of this section, an UST system without corrosion protection may...

40 CFR 280.11 - Interim prohibition for deferred UST systems.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) Will prevent releases due to corrosion or structural failure for the operational life of the UST system; (2) Is cathodically protected against corrosion, constructed of noncorrodible material, steel clad... substance. (b) Notwithstanding paragraph (a) of this section, an UST system without corrosion protection may...

40 CFR 280.11 - Interim prohibition for deferred UST systems.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) Will prevent releases due to corrosion or structural failure for the operational life of the UST system; (2) Is cathodically protected against corrosion, constructed of noncorrodible material, steel clad... substance. (b) Notwithstanding paragraph (a) of this section, an UST system without corrosion protection may...

Carbon materials for enhancing charge transport in the advancements of perovskite solar cells

NASA Astrophysics Data System (ADS)

Hu, Ruiyuan; Chu, Liang; Zhang, Jian; Li, Xing'ao; Huang, Wei

2017-09-01

Organic-inorganic halide perovskite solar cells (PSCs) have become a new favorite in the photovoltaic field, due to the boosted efficiency up to 22.1%. Despite a flow of achievements, there are certain challenges to simultaneously meet high efficiency, large scale, low cost and high stability. Due to the low cost, extensive sources, high electrical conductivity and chemical stability, carbon materials have made undeniable contributions to play positive roles in developing PSCs. Carbon materials not only have the favorable conductivity but also bipolar advantage, which can transfer both electrons and holes. In this review, we will discuss how the carbon materials transfer charge or accelerate charge transport by incorporation in PSCs. Carbon materials can replace transparent conductive oxide layers, and enhance electron transport in electron transport layers. Moreover, carbon materials with continuous structure, especially carbon nanotubes and graphene, can provide direct charge transport channel that make them suitable additives or even substitutes in hole transport layers. Especially, the successful application of carbon materials as counter electrodes makes the devices full-printable, low temperature and high stability. Finally, a brief outlook is provided on the future development of carbon materials for PSCs, which are expected to devote more contributions in the future photovoltaic market.

Determining the Environmental Benefits of Ultra High Performance Concrete as a Bridge Construction Material

NASA Astrophysics Data System (ADS)

Lande Larsen, Ingrid; Granseth Aasbakken, Ida; O'Born, Reyn; Vertes, Katalin; Terje Thorstensen, Rein

2017-10-01

Ultra High Performance Concrete (UHPC) is a material that is attracting attention in the construction industry due to the high mechanical strength and durability, leading to structures having low maintenance requirements. The production of UHPC, however, has generally higher environmental impact than normal strength concrete due to the increased demand of cement required in the concrete mix. What is still not sufficiently investigated, is if the longer lifetime, slimmer construction and lower maintenance requirements lead to a net environmental benefit compared to standard concrete bridge design. This study utilizes life cycle assessment (LCA) to determine the lifetime impacts of two comparable highway crossing footbridges spanning 40 meters, designed respectively with UHPC and normal strength concrete. The results of the study show that UHPC is an effective material for reducing lifetime emissions from construction and maintenance of long lasting infrastructure, as the UHPC design outperforms the normal strength concrete bridge in most impact categories.

Comparison of structural response and fatigue endurance of aircraft flap-like box structures subjected to acoustic loading

NASA Astrophysics Data System (ADS)

Xiao, Y.; White, R. G.; Aglietti, G. S.

2005-05-01

The results of an extensive test program to characterize the behavior of typical aircraft structures under acoustic loading and to establish their fatigue endurance are presented. The structures tested were the three flap-like box-type of structures. Each structure consisted of one flat (bottom) and one curved (top) stiffener stiffened skin panel, front, and rear spars, and ribs that divided the structures into three bays. The three structures, constructed from three different materials (aircraft standard aluminum alloy, Carbon Fibre Reinforced Plastic, and a Glass Fibre Metal Laminate, i.e., GLARE) had the same size and configuration, with only minor differences due to the use of different materials. A first set of acoustic tests with excitations of intensity ranging from 140 to 160 dB were carried out to obtain detailed data on the dynamic response of the three structures. The FE analysis of the structures is also briefly described and the results compared with the experimental data. The fatigue endurance of the structures was then determined using random acoustic excitation with an overall sound pressure level of 161 dB, and details of crack propagation are reported. .

Evolution of plastic anisotropy for high-strain-rate computations

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

Schiferl, S.K.; Maudlin, P.J.

1994-12-01

A model for anisotropic material strength, and for changes in the anisotropy due to plastic strain, is described. This model has been developed for use in high-rate, explicit, Lagrangian multidimensional continuum-mechanics codes. The model handles anisotropies in single-phase materials, in particular the anisotropies due to crystallographic texture--preferred orientations of the single-crystal grains. Textural anisotropies, and the changes in these anisotropies, depend overwhelmingly no the crystal structure of the material and on the deformation history. The changes, particularly for a complex deformations, are not amenable to simple analytical forms. To handle this problem, the material model described here includes a texturemore » code, or micromechanical calculation, coupled to a continuum code. The texture code updates grain orientations as a function of tensor plastic strain, and calculates the yield strength in different directions. A yield function is fitted to these yield points. For each computational cell in the continuum simulation, the texture code tracks a particular set of grain orientations. The orientations will change due to the tensor strain history, and the yield function will change accordingly. Hence, the continuum code supplies a tensor strain to the texture code, and the texture code supplies an updated yield function to the continuum code. Since significant texture changes require relatively large strains--typically, a few percent or more--the texture code is not called very often, and the increase in computer time is not excessive. The model was implemented, using a finite-element continuum code and a texture code specialized for hexagonal-close-packed crystal structures. The results for several uniaxial stress problems and an explosive-forming problem are shown.« less

Composite Development and Applications for RLV Tankage

NASA Technical Reports Server (NTRS)

Wright, Richard J.; Achary, David C.; McBain, Michael C.

2003-01-01

The development of polymer composite cryogenic tanks is a critical step in creating the next generation of launch vehicles. Future launch vehicles need to minimize the gross liftoff weight (GLOW), which is possible due to the 28%-41% reduction in weight that composite materials can provide over current aluminum technology. The development of composite cryogenic tanks, feedlines, and unpressurized structures are key enabling technologies for performance and cost enhancements for Reusable Launch Vehicles (RLVs). The technology development of composite tanks has provided direct and applicable data for feedlines, unpressurized structures, material compatibility, and cryogenic fluid containment for highly loaded complex structures and interfaces. All three types of structure have similar material systems, processing parameters, scaling issues, analysis methodologies, NDE development, damage tolerance, and repair scenarios. Composite cryogenic tankage is the most complex of the 3 areas and provides the largest breakthrough in technology. A building block approach has been employed to bring this family of difficult technologies to maturity. This approach has built up composite materials, processes, design, analysis and test methods technology through a series of composite test programs beginning with the NASP program to meet aggressive performance goals for reusable launch vehicles. In this paper, the development and application of advanced composites for RLV use is described.

Laser-etch patterning of metal oxide coated carbon nanotube 3D architectures.

PubMed

Aksu, Cemile; Ingram, Wade; Bradford, Philip D; Jur, Jesse S

2018-08-17

This paper describes a way to fabricate novel hybrid low density nanostructures containing both carbon nanotubes (CNTs) and ceramic nanotubes. Using atomic layer deposition, a thin film of aluminum oxide was conformally deposited on aligned multiwall CNT foams in which the CNTs make porous, three-dimensional interconnected networks. A CO 2 laser was used to etch pure alumina nanotube structures by burning out the underlying CNT substrate in discrete locations via the printed laser pattern. Structural and morphological transitions during the calcination process of aluminum oxide coated CNTs were investigated through in situ transmission electron microscopy and high-resolution scanning electron microscopy. Laser parameters were optimized to etch the CNT away (i.e. etching speed, power and focal length) while minimizing damage to the alumina nanotubes due to overheating. This study opens a new route for fabricating very low density three dimensionally patterned materials with areas of dissimilar materials and properties. To demonstrate the attributes of these structures, the etched areas were used toward anisotropic microfluidic liquid flow. The demonstration used the full thickness of the material to make complex pathways for the liquid flow in the structure. Through tuning of processing conditions, the alumina nanotube (etched) regions became hydrophilic while the bulk material remained hydrophobic and electrically conductive.

Functional and stability orientation synthesis of materials and structures in aprotic Li-O2 batteries.

PubMed

Zhang, Peng; Zhao, Yong; Zhang, Xinbo

2018-04-23

The lithium-O2 battery is one of most promising energy storage and conversion devices due to its ultrahigh theoretical energy density and hence has broad application potential in electrical vehicles and stationary power systems. However, the present Li-O2 battery suffers from a series of challenges for its practical application, such as its low capacity and rate capability, poor round-trip efficiency and short cycle life. These challenges mainly arise from the sluggish and unsustainable discharge and charge reactions at lithium and oxygen electrodes, which determine the performance and durability of a battery. In this review, we first provide insights on the present understanding of the discharge/charge mechanism of such a battery and follow up with establishing a correlation between the specific materials/structures of the battery modules and their functionality/stability within the recent progress in electrodes, electrolytes and redox mediators. Considerable emphasis is paid to the importance of functional orientation design and the synthesis of materials/structures towards accelerating and sustaining the electrode reactions of Li-O2 batteries. Moreover, the future directions and perspectives of rationally constructed material and surface/interface structures, as well as their optimal combinations are proposed for enhancement of the electrode reaction rate and sustainability, and consequently for a better performance and durability of such batteries.

Probabilistic analysis of the behavior of polymer matrix composite materials reinforced by different types of fibers

NASA Astrophysics Data System (ADS)

Harb, N.; Bezzazi, B.; Mehraz, S.; Hamitouche, K.; Dilmi, H.

2017-11-01

The requests of lightening of the structures and gains in performance lead to search for new materials and the associated processes for aeronautical and space applications. Long-fiber composites have been used for many years for these applications; they make it possible to reduce the mass of the structures because of their excellent compromise of mass/rigidity / resistance. The materials in general contain defects which are essentially due to their nature and their mode of elaboration. To this purpuse, we carried out a probabilistic analysis of the mechanical behavior in three-point bending of composite materials with a thermosetting matrix in order to highlight the influence of the number of folds of the fibers and the nature of the fibers on the dispersion of the defects in the stratified structures fiberglass, carbon fiber laminates and hybrid (carbon / glass) laminates. From the results obtained, the dispersion of the defects is lower in the laminates of greater number of plies of the fibers and the hybrid laminates; the more the number of folds increases the more the mechanical characteristics increase; the hybrid laminates exhibit better mechanical properties compared to laminates of the same type of fiber. Finally, a morphological analysis of fracture structures and facies was investigated by scanning electron microscope (SEM) observations.

Influence of processing factors over concrete strength.

NASA Astrophysics Data System (ADS)

Kara, K. A.; Dolzhenko, A. V.; Zharikov, I. S.

2018-03-01

Construction of facilities of cast in-situ reinforced concrete poses additional requirements to quality of material, peculiarities of the construction process may sometimes lead to appearance of lamination planes and inhomogeneity of concrete, which reduce strength of the material and structure as a whole. Technology compliance while working with cast in-situ concrete has a significant impact onto the concrete strength. Such process factors as concrete curing, vibration and compaction of the concrete mixture, temperature treatment, etc., when they are countered or inadequately followed lead to a significant reduction in concrete strength. Here, the authors experimentally quantitatively determine the loss of strength in in-situ cast concrete structures due to inadequate following of process requirements, in comparison with full compliance.

The research of structure and mechanical properties of superhard electro-spark coatings for hardwearing mining tools

NASA Astrophysics Data System (ADS)

Bajin, P. A.; Chijikov, A. P.; Leybo, D. V.; Chuprunov, K. O.; Yudin, A. G.; Alymov, M. A.; Kuznetsov, D. V.

2016-01-01

The development of low cost and hardwearing mining tools is one of the most important areas in mining industry. It is especially important for technologies of rare and rare earth metals mining due to high hardness of related ores. Coatings for electrodes, produced by extrusion of self-propagating high temperature synthesis (SHS) products from hard-alloyed materials with nanosized structure, for further application in processes of electrospark alloying and deposition were studied in this work. The results of microstructure and properties of deposited layers, interaction of support with SHS produced electrodes, comparison of frictional properties of obtained materials as well as some industrial testing results are presented in this work.

Double-Zero-Index Structural Phononic Waveguides

NASA Astrophysics Data System (ADS)

Zhu, Hongfei; Semperlotti, Fabio

2017-12-01

We report on the theoretical and experimental realization of a double-zero-index elastic waveguide and the corresponding acoustic cloaking and supercoupling effects. The proposed waveguide uses geometric tapers in order to induce Dirac-like cones at k → =0 due to accidental degeneracy. The nature of the degeneracy is explored by a k .p perturbation method adapted to thin structural waveguides. The results confirm the linear nature of the dispersion around the degeneracy and the possibility to map the material to effective-medium properties. Effective parameters numerically extracted using boundary medium theory confirm that the phononic waveguide maps into a double-zero-index material. Numerical and experimental results confirm the expected cloaking and supercoupling effects.

Lightning strike protection of composites

NASA Astrophysics Data System (ADS)

Gagné, Martin; Therriault, Daniel

2014-01-01

Aircraft structures are being redesigned to use fiber-reinforced composites mainly due to their high specific stiffness and strength. One of the main drawbacks from changing from electrically conductive metals to insulating or semi-conducting composites is the higher vulnerability of the aircraft to lightning strike damage. The current protection approach consists of bonding a metal mesh to the surface of the composite structure, but this weight increase negatively impact the fuel efficiency. This review paper presents an overview of the lightning strike problematic, the regulations, the lightning damage to composite, the current protection solutions and other material or technology alternatives. Advanced materials such as polymer-based nanocomposites and carbon nanotube buckypapers are promising candidates for lightweight lightning strike protection technology.

Many faces of carbon

NASA Astrophysics Data System (ADS)

Wang, Qian; Zhang, Shunhong; Jena, Puru

2016-12-01

Due to the special electronic configuration, small atomic size, light mass, and flexible bonding features, carbon exhibits many different structural configurations with very different physical and chemical properties. Here we focus our discussion on three recent forms of carbon, namely, metallic carbon, magnetic carbon, and all-pentagon-based carbon. The metallic carbon can be used for metallic interconnects in future electronic circuits, nano devices and microprocessors while the magnetic carbon can have applications in spintronics. All-pentagon-based carbon nano-structure, penta-graphene, not only expands the family of carbon materials with a number of new features, but also provides the materials basis for the 2D packing of pentagons pursued by mathematicians for almost a century.

Integrally rigidized acoustic interior spacecraft panel

NASA Technical Reports Server (NTRS)

1976-01-01

A sandwich panel concept is described which utilizes a monolithic I-beam design as the core. The core and skins are integrally bonded with thermosetting resin into a homogeneous structure. In addition to possessing a high strength to weight ratio, the panel resists combustion, delamination, aging due to fatigue, localized stresses, and exhibits good acoustic properties. Since the panel concept has definite potential as a high flame retardant and low smoke emission panel with excellent structural integrity, aerospace materials were used to optimize the construction for highly demanding space shuttle applications. The specific materials of construction were chosen for low flammability and off-gassing properties as well as for strength, light weight, and sound dampening.

Processing of Building Binder Materials to Increase their Activation

NASA Astrophysics Data System (ADS)

Fediuk, R. S.; Garmashov, I. S.; Kuzmin, D. E.; Stoyushko, N. Yu; Gladkova, N. A.

2018-01-01

The paper deals modern physical methods of activation of building powder materials. During mechanical activation a composite binder active molecules cement minerals occur in the destruction of the molecular defects in the areas of packaging and breaking metastable phase decompensation intermolecular forces. The process is accompanied by a change in the kinetics of hardening of Portland cement. Activated concrete has a number of features that are used as design characteristics of structures and are due to the structure of the activated binder and its contacts with concrete aggregates. These features also have a significant impact on the nature of the destruction of concrete under load, changing the boundaries of its microcracks and durability.

Microgravity

NASA Image and Video Library

2004-04-15

Comparison of ground-based (left) and Skylab (right) electron beam welds in pure tantalum (Ta) (10X magnification). Residual votices left behind in the ground-based sample after the electron beam passed were frozen into the grain structure. These occurred because of the rapid cooling rate at the high temperature. Although the thermal characteristics and electron beam travel speeds were comparable for the skylab sample, the residual vortices were erased in the grain structure. This may have been due to the fact that final grain size of the solidified material was smaller in the Skylab sample compared to the ground-based sample. The Skylab sample was processed in the M512 Materials Processing Facility (MPF) during Skylab SL-2 Mission. Principal Investigator was Richard Poorman.

Modulating the band structure and sub-bandgap absorption of Co-hyperdoped silicon by co-doping with shallow-level elements

NASA Astrophysics Data System (ADS)

Dong, Xiao; Fang, Xiuxiu; Wang, Yongyong; Song, Xiaohui; Lu, Zhansheng

2018-06-01

Hyperdoped group-III elements can lower the Fermi energy in the band structures of Co-hyperdoped silicon. When the Co-to-X (X = B, Al, Ga) ratio is 2:1, the intermediate band (IB) in the bandgap includes the Fermi energy and is partially filled by electrons, which is in accordance with the requirement of an IB material. The hyperdoped X atoms can cause the blueshift of the sub-bandgap absorption of the compound compared with the material with no shallow-level elements, which is due to the enlargement of the electronic excitation energy of the Co,X-co-doped silicon.

Self-Assembly of an α-Helical Peptide into a Crystalline Two-Dimensional Nanoporous Framework

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

Magnotti, Elizabeth L.; Hughes, Spencer A.; Dillard, Rebecca S.

Sequence-specific peptides have been demonstrated to self-assemble into structurally defined nanoscale objects including nanofibers, nanotubes, and nanosheets. The latter structures display significant promise for the construction of hybrid materials for functional devices due to their extended planar geometry. Realization of this objective necessitates the ability to control the structural features of the resultant assemblies through the peptide sequence. The design of a amphiphilic peptide, 3FD-IL, is described that comprises two repeats of a canonical 18 amino acid sequence associated with straight α-helical structures. Peptide 3FD-IL displays 3-fold screw symmetry in a helical conformation and self-assembles into nanosheets based on hexagonalmore » packing of helices. Biophysical evidence from TEM, cryo-TEM, SAXS, AFM, and STEM measurements on the 3FD-IL nanosheets support a structural model based on a honeycomb lattice, in which the length of the peptide determines the thickness of the nanosheet and the packing of helices defines the presence of nanoscale channels that permeate the sheet. The honeycomb structure can be rationalized on the basis of geometrical packing frustration in which the channels occupy defect sites that define a periodic superlattice. In conclusion, the resultant 2D materials may have potential as materials for nanoscale transport and controlled release applications.« less

Making on-orbit structural repairs to Space Station

NASA Technical Reports Server (NTRS)

Haber, Harry S.; Quinn, Alberta

1989-01-01

One of the key factors dictating the safety and durability of the proposed U.S. Space Station is the ability to repair structural damage while remaining in orbit. Consequently, studies are conducted to identify the engineering problems associated with accomplishing structural repairs on orbit, due to zero gravity environment and exposure to extreme temperature variations. There are predominant forms of structural failure, depending on the metallic or composite material involved. Aluminum is the primary metallic material used in space vehicle applications. Welding processes on aluminum alloy structures were tested, resulting in final selection of electron beam welding as the primary technique for metallic material repair in Space. Several composite structure repair processes were bench-tested to define their applicability to on-orbit EVA requirements: induction heating prevailed. One of the unique problems identified as inherent in the on-orbit repair process is that of debris containment. The Maintenance Work Station concept provides means to prevent module contamination from repair debris and ensure the creation of a facility for crew members to work easily in a microgravity environment. Different technologies were also examined for application to EVA repair activities, and the concept selected was a spring-loaded, collapsible, box-like Debris Containement and Collection Device with incorporated fold-down tool boards and handholes in the front panel.