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Sample records for bilayer material properties

  1. Determining the Gaussian Modulus and Edge Properties of 2D Materials: From Graphene to Lipid Bilayers

    Science.gov (United States)

    Zelisko, Matthew; Ahmadpoor, Fatemeh; Gao, Huajian; Sharma, Pradeep

    2017-08-01

    The dominant deformation behavior of two-dimensional materials (bending) is primarily governed by just two parameters: bending rigidity and the Gaussian modulus. These properties also set the energy scale for various important physical and biological processes such as pore formation, cell fission and generally, any event accompanied by a topological change. Unlike the bending rigidity, the Gaussian modulus is, however, notoriously difficult to evaluate via either experiments or atomistic simulations. In this Letter, recognizing that the Gaussian modulus and edge tension play a nontrivial role in the fluctuations of a 2D material edge, we derive closed-form expressions for edge fluctuations. Combined with atomistic simulations, we use the developed approach to extract the Gaussian modulus and edge tension at finite temperatures for both graphene and various types of lipid bilayers. Our results possibly provide the first reliable estimate of this elusive property at finite temperatures and appear to suggest that earlier estimates must be revised. In particular, we show that, if previously estimated properties are employed, the graphene-free edge will exhibit unstable behavior at room temperature. Remarkably, in the case of graphene, we show that the Gaussian modulus and edge tension even change sign at finite temperatures.

  2. Bilayered graphene/h-BN with folded holes as new nanoelectronic materials: modeling of structures and electronic properties

    Science.gov (United States)

    Chernozatonskii, Leonid A.; Demin сtor A., Vi; Bellucci, Stefano

    2016-11-01

    The latest achievements in 2-dimensional (2D) material research have shown the perspective use of sandwich structures in nanodevices. We demonstrate the following generation of bilayer materials for electronics and optoelectronics. The atomic structures, the stability and electronic properties of Moiré graphene (G)/h-BN bilayers with folded nanoholes have been investigated theoretically by ab-initio DFT method. These perforated bilayers with folded hole edges may present electronic properties different from the properties of both graphene and monolayer nanomesh structures. The closing of the edges is realized by C-B(N) bonds that form after folding the borders of the holes. Stable ≪round≫ and ≪triangle≫ holes organization are studied and compared with similar hole forms in single layer graphene. The electronic band structures of the considered G/BN nanomeshes reveal semiconducting or metallic characteristics depending on the sizes and edge terminations of the created holes. This investigation of the new types of G/BN nanostructures with folded edges might provide a directional guide for the future of this emerging area.

  3. Electronic properties of graphene-based bilayer systems

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    Rozhkov, A.V., E-mail: arozhkov@gmail.com [CEMS, RIKEN, Saitama 351-0198 (Japan); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412 Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, 141700 (Russian Federation); Sboychakov, A.O. [CEMS, RIKEN, Saitama 351-0198 (Japan); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412 Moscow (Russian Federation); Rakhmanov, A.L. [CEMS, RIKEN, Saitama 351-0198 (Japan); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412 Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, 141700 (Russian Federation); All-Russia Research Institute of Automatics, Moscow, 127055 (Russian Federation); Nori, Franco, E-mail: fnori@riken.jp [CEMS, RIKEN, Saitama 351-0198 (Japan); Physics Department, The University of Michigan, Ann Arbor, MI 48109-1040 (United States)

    2016-08-23

    This article reviews the theoretical and experimental work related to the electronic properties of bilayer graphene systems. Three types of bilayer stackings are discussed: the AA, AB, and twisted bilayer graphene. This review covers single-electron properties, effects of static electric and magnetic fields, bilayer-based mesoscopic systems, spin–orbit coupling, dc transport and optical response, as well as spontaneous symmetry violation and other interaction effects. The selection of the material aims to introduce the reader to the most commonly studied topics of theoretical and experimental research in bilayer graphene.

  4. Electronic properties of graphene-based bilayer systems

    Science.gov (United States)

    Rozhkov, A. V.; Sboychakov, A. O.; Rakhmanov, A. L.; Nori, Franco

    2016-08-01

    This article reviews the theoretical and experimental work related to the electronic properties of bilayer graphene systems. Three types of bilayer stackings are discussed: the AA, AB, and twisted bilayer graphene. This review covers single-electron properties, effects of static electric and magnetic fields, bilayer-based mesoscopic systems, spin-orbit coupling, dc transport and optical response, as well as spontaneous symmetry violation and other interaction effects. The selection of the material aims to introduce the reader to the most commonly studied topics of theoretical and experimental research in bilayer graphene.

  5. Alcohol's Effects on Lipid Bilayer Properties

    Science.gov (United States)

    Ingólfsson, Helgi I.; Andersen, Olaf S.

    2011-01-01

    Alcohols are known modulators of lipid bilayer properties. Their biological effects have long been attributed to their bilayer-modifying effects, but alcohols can also alter protein function through direct protein interactions. This raises the question: Do alcohol's biological actions result predominantly from direct protein-alcohol interactions or from general changes in the membrane properties? The efficacy of alcohols of various chain lengths tends to exhibit a so-called cutoff effect (i.e., increasing potency with increased chain length, which that eventually levels off). The cutoff varies depending on the assay, and numerous mechanisms have been proposed such as: limited size of the alcohol-protein interaction site, limited alcohol solubility, and a chain-length-dependent lipid bilayer-alcohol interaction. To address these issues, we determined the bilayer-modifying potency of 27 aliphatic alcohols using a gramicidin-based fluorescence assay. All of the alcohols tested (with chain lengths of 1–16 carbons) alter the bilayer properties, as sensed by a bilayer-spanning channel. The bilayer-modifying potency of the short-chain alcohols scales linearly with their bilayer partitioning; the potency tapers off at higher chain lengths, and eventually changes sign for the longest-chain alcohols, demonstrating an alcohol cutoff effect in a system that has no alcohol-binding pocket. PMID:21843475

  6. Electronic properties of a biased graphene bilayer

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    Castro, Eduardo V; Lopes dos Santos, J M B [CFP and Departamento de Fisica, Faculdade de Ciencias Universidade do Porto, P-4169-007 Porto (Portugal); Novoselov, K S; Morozov, S V; Geim, A K [Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Peres, N M R [Centre of Physics and Departamento de Fisica, Universidade do Minho, P-4710-057 Braga (Portugal); Nilsson, Johan; Castro Neto, A H [Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215 (United States); Guinea, F [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain)

    2010-05-05

    We study, within the tight-binding approximation, the electronic properties of a graphene bilayer in the presence of an external electric field applied perpendicular to the system-a biased bilayer. The effect of the perpendicular electric field is included through a parallel plate capacitor model, with screening correction at the Hartree level. The full tight-binding description is compared with its four-band and two-band continuum approximations, and the four-band model is shown to always be a suitable approximation for the conditions realized in experiments. The model is applied to real biased bilayer devices, made out of either SiC or exfoliated graphene, and good agreement with experimental results is found, indicating that the model is capturing the key ingredients, and that a finite gap is effectively being controlled externally. Analysis of experimental results regarding the electrical noise and cyclotron resonance further suggests that the model can be seen as a good starting point for understanding the electronic properties of graphene bilayer. Also, we study the effect of electron-hole asymmetry terms, such as the second-nearest-neighbour hopping energies t' (in-plane) and {gamma}{sub 4} (inter-layer), and the on-site energy {Delta}.

  7. Electronic properties of a biased graphene bilayer.

    Science.gov (United States)

    Castro, Eduardo V; Novoselov, K S; Morozov, S V; Peres, N M R; Lopes dos Santos, J M B; Nilsson, Johan; Guinea, F; Geim, A K; Castro Neto, A H

    2010-05-01

    We study, within the tight-binding approximation, the electronic properties of a graphene bilayer in the presence of an external electric field applied perpendicular to the system-a biased bilayer. The effect of the perpendicular electric field is included through a parallel plate capacitor model, with screening correction at the Hartree level. The full tight-binding description is compared with its four-band and two-band continuum approximations, and the four-band model is shown to always be a suitable approximation for the conditions realized in experiments. The model is applied to real biased bilayer devices, made out of either SiC or exfoliated graphene, and good agreement with experimental results is found, indicating that the model is capturing the key ingredients, and that a finite gap is effectively being controlled externally. Analysis of experimental results regarding the electrical noise and cyclotron resonance further suggests that the model can be seen as a good starting point for understanding the electronic properties of graphene bilayer. Also, we study the effect of electron-hole asymmetry terms, such as the second-nearest-neighbour hopping energies t' (in-plane) and γ(4) (inter-layer), and the on-site energy Δ.

  8. Optimizing non-Pb radiation shielding materials using bilayers

    Energy Technology Data Exchange (ETDEWEB)

    McCaffrey, J. P.; Mainegra-Hing, E.; Shen, H. [Institute for National Measurement Standards, National Research Council of Canada, Building M-35, 1200 Montreal Road, Ottawa K1A 0R6 (Canada)

    2009-12-15

    Purpose: The objective of this study was to demonstrate that the weight of non-Pb radiation shielding materials can be minimized by structuring the material as a bilayer composed of different metal-powder-embedded elastomer layers. Methods: Measurements and Monte Carlo (MC) calculations were performed to study the attenuation properties of several non-Pb metal bilayers over the x-ray energy range 30-150 keV. Metals for the layers were chosen on the basis of low cost, nontoxicity, and complementary photoelectric absorption characteristics. The EGSnrc user code cavity.cpp was used to calculate the resultant x-ray fluence spectra after attenuation by these metal layers. Air kerma attenuation was measured using commercially manufactured metal/elastomer test layers. These layers were irradiated using the primary standard calibration beams at the Institute for National Measurement Standards in Ottawa, Canada utilizing the six x-ray beam qualities recommended in the German Standard DIN 6857. Both the measurements and the calculations were designed to approximate surface irradiation as well as penetrating radiation at 10 mm depth in soft tissue. The MC modeling point and the position of the measurement detector for surface irradiation were both directly against the downstream face of the attenuating material, as recommended in DIN 6857. Results: The low-Z upstream/high-Z downstream ordering of the metal bilayers provided substantially more attenuation than the reverse order. Optimal percentages of each metal in each bilayer were determined for each x-ray radiation beam quality. Conclusions: Depending on the x-ray quality, appropriate choices of two complementary metal-embedded elastomer layers can decrease the weight of radiation shielding garments by up to 25% compared to Pb-based elastomer garments while providing equivalent attenuation.

  9. Hydrophobic silver nanoparticles trapped in lipid bilayers: Size distribution, bilayer phase behavior, and optical properties

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    Bothun Geoffrey D

    2008-11-01

    Full Text Available Abstract Background Lipid-based dispersion of nanoparticles provides a biologically inspired route to designing therapeutic agents and a means of reducing nanoparticle toxicity. Little is currently known on how the presence of nanoparticles influences lipid vesicle stability and bilayer phase behavior. In this work, the formation of aqueous lipid/nanoparticle assemblies (LNAs consisting of hydrophobic silver-decanethiol particles (5.7 ± 1.8 nm embedded within 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC bilayers is demonstrated as a function of the DPPC/Ag nanoparticle (AgNP ratio. The effect of nanoparticle loading on the size distribution, bilayer phase behavior, and bilayer fluidity is determined. Concomitantly, the effect of bilayer incorporation on the optical properties of the AgNPs is also examined. Results The dispersions were stable at 50°C where the bilayers existed in a liquid crystalline state, but phase separated at 25°C where the bilayers were in a gel state, consistent with vesicle aggregation below the lipid melting temperature. Formation of bilayer-embedded nanoparticles was confirmed by differential scanning calorimetry and fluorescence anisotropy, where increasing nanoparticle concentration suppressed the lipid pretransition temperature, reduced the melting temperature, and disrupted gel phase bilayers. The characteristic surface plasmon resonance (SPR wavelength of the embedded nanoparticles was independent of the bilayer phase; however, the SPR absorbance was dependent on vesicle aggregation. Conclusion These results suggest that lipid bilayers can distort to accommodate large hydrophobic nanoparticles, relative to the thickness of the bilayer, and may provide insight into nanoparticle/biomembrane interactions and the design of multifunctional liposomal carriers.

  10. Exceptional Optoelectronic Properties of Hydrogenated Bilayer Silicene

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    Bing Huang

    2014-05-01

    Full Text Available Silicon is arguably the best electronic material, but it is not a good optoelectronic material. By employing first-principles calculations and the cluster-expansion approach, we discover that hydrogenated bilayer silicene (BS shows promising potential as a new kind of optoelectronic material. Most significantly, hydrogenation converts the intrinsic BS, a strongly indirect semiconductor, into a direct-gap semiconductor with a widely tunable band gap. At low hydrogen concentrations, four ground states of single- and double-sided hydrogenated BS are characterized by dipole-allowed direct (or quasidirect band gaps in the desirable range from 1 to 1.5 eV, suitable for solar applications. At high hydrogen concentrations, three well-ordered double-sided hydrogenated BS structures exhibit direct (or quasidirect band gaps in the color range of red, green, and blue, affording white light-emitting diodes. Our findings open opportunities to search for new silicon-based light-absorption and light-emitting materials for earth-abundant, high-efficiency, optoelectronic applications.

  11. Bilayer properties of hydroxytyrosol- and tyrosol-phosphatidylcholine lipids

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    Tyrosol and hydroxytyrosol are the phytochemicals abundantly found in olive oil. Transphosphatidylation of tyrosol and hydroxytyrosol with dioleoylphosphocholine resulted in phospholipids with antioxidant properties. The ability of these phyto-phospholipids to form liposomes and supported bilayers w...

  12. Electronic properties of asymmetrically doped twisted graphene bilayers

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    Trambly de Laissardière, Guy; Namarvar, Omid Faizy; Mayou, Didier; Magaud, Laurence

    2016-06-01

    Rotated graphene bilayers form an exotic class of nanomaterials with fascinating electronic properties governed by the rotation angle θ . For large rotation angles, the electron eigenstates are restricted to one layer and the bilayer behaves like two decoupled graphene layers. At intermediate angles, Dirac cones are preserved but with a lower velocity and van Hove singularities are induced at energies where the two Dirac cones intersect. At very small angles, eigenstates become localized in peculiar moiré zones. We analyze here the effect of an asymmetric doping for a series of commensurate rotated bilayers on the basis of tight-binding calculations of their band dispersions, density of states, participation ratio, and diffusive properties. While a small doping level preserves the θ dependence of the rotated bilayer electronic structure, larger doping induces a further reduction of the band velocity in the same way as a further reduction of the rotation angle.

  13. Combined effect of the transition layer and interfacial coupling on the properties of ferroelectric bilayer film

    Institute of Scientific and Technical Information of China (English)

    Sun Pu-Nan; Cui Lian; Lü Tian-Quan

    2009-01-01

    Within the framework of modified Ginzburg-Landau-Devonshire phenomenological theory,a ferroelectric bilayer film with a transition layer within each constituent film and an interfacial coupling between two materials has been studied.Properties including the Curie temperature and the spontaneous polarization of a bilayer film composed of two equally thick ferroelectric constituent films are discussed.The results show that the combined effect of the transition layer and the interfacial coupling plays an important role in explaining the interesting behaviour of ferroelectric multilayer structures consisting of two ferroelectric materials.

  14. Investigations of the mechanical properties of bi-layer and trilayer fiber reinforced composites

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    Jayakrishna, K.; Balasubramani, K.; Sultan, M. T. H.; Karthikeyan, S.

    2016-10-01

    Natural fibers are renewable raw materials with an environmental-friendly properties and they are recyclable. The mechanical properties of bi-layer and tri-layer thermoset polymer composites have been analyzed. The bi-layer composite consists of basalt and jute mats, while the tri-layer composite consists of basalt fiber, jute fiber and glass fiber mats. In both cases, the epoxy resin was used as the matrix and PTFE as a filler in the composites. The developed trilayer natural fiber composite can be used in various industrial applications such as automobile parts, construction and manufacturing. Furthermore, it also can be adopted in aircraft interior decoration and designed body parts. Flexural, impact, tensile, compression, shear and hardness tests, together with density measurement, were conducted to study the mechanical properties of both bi-layer and tri-layer composites. From the comparison, the tri-layer composite was found to perform in a better way in all tests.

  15. Magnetic properties of a doped graphene-like bilayer

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    Guo, An-Bang [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Jiang, Wei, E-mail: weijiang.sut.edu@gmail.com [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Zhang, Na [Shenyang Normal University, Shenyang 110034 (China)

    2017-05-15

    A doped graphene-like bilayer is described using a four-sublattice Heisenberg model both ferromagnetic and antiferrimagnetic couplings. The magnetic properties of the bilayer system are studied using the Heisenberg model, retarded Green's function and the linear spin-wave approximation. The spin-wave spectra, energy gap, and the magnetization and quantum fluctuation of the system at the ground state are calculated with various intra- and interlayer couplings. The results indicate that the effect of antiferromagnetic exchange coupling on the magnetic properties of the system is significant. Magnetizations at low temperature show intersection points due to the quantum effects.

  16. BI-LAYER HYBRID BIOCOMPOSITES: CHEMICAL RESISTANT AND PHYSICAL PROPERTIES

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    Mohammad Jawaid,

    2012-02-01

    Full Text Available Bi-layer hybrid biocomposites were fabricated by hand lay-up technique by reinforcing oil palm empty fruit bunch (EFB and jute fibre mats with epoxy matrix. Hybrid composites were prepared by varying the relative weight fraction of the two fibres. The physical (void content, density, dimensional stability, and chemical resistant properties of hybrid composites were evaluated. When the jute fibre loading increased in hybrid composites, physical and chemical resistant properties of hybrid composites were enhanced. Void content of hybrid composites decreased with an increase in jute fibre loading because jute fibres showed better fibre/matrix interface bonding, which leads to a reduction in voids. The density of hybrid composite increased as the quantity of jute fibre loading increased. The hybridization of the jute fibres with EFB composite improved the dimensional stability of the hybrid composites. The performance of hybrid composites towards chemical reagents improved with an increase in jute fibre loading as compared to the EFB composite. The combination of oil palm EFB/jute fibres with epoxy matrix produced hybrid biocomposites material that is competitive to synthetic composites.

  17. Properties of bilayer contacts to porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Gallach, D.; Torres-Costa, V.; Garcia-Pelayo, L.; Climent-Font, A.; Martin-Palma, R.J.; Manso, M. [Universidad Autonoma de Madrid, Departamento de Fisica Aplicada, Madrid (Spain); Barreiros-das-Santos, M.; Sporer, C.; Samitier, J. [Institute for Bioengineering of Catalonia (IBEC), Nanobioengineering Group, Barcelona (Spain)

    2012-05-15

    The aim of the present work is the growth by PVD techniques and ulterior characterization of electrical contacts to columnar porous silicon (PSi) as an approach to reliable PSi sensor devices. Contacts consist of a NiCr (40:60) and Au bilayer on the PSi surface deposited by magnetron sputtering. These structures show a good adhesion to the rough surface of columnar PSi. The morphology of these electrical contacts is characterized by electron microscopy and their crystalline structure by X-ray diffraction. Compositional profiles are determined by Rutherford backscattering spectroscopy and energy dispersive X-ray spectroscopy, which demonstrate that the infiltration of NiCr into the PSi is at the origin of the metallic thin film adhesion improvement. I-V characteristics and impedance spectroscopy measurements show that this configuration provides rectifying electrical contacts to PSi, for which a simple equivalent circuit based on one resistor and two capacitors can be modeled. These results further support the use of PSi electrical structures for sensing purposes. (orig.)

  18. Influence of silybin on biophysical properties of phospholipid bilayers

    Institute of Scientific and Technical Information of China (English)

    Olga WESO(L)OWSKA; Krystyna MICHALAK; Barbara (L)ANIA-PIETRZAK; Micha(l) KU(Z)D(Z)A(L); Kamila STA(N)CZAK; Daniela MOSI(A)DZ; Piotr DOBRYSZYCKI; Andrzej O(Z)YHAR; Ma(l)gorzata KOMOROWSKA; Andrzej B HENDRICH

    2007-01-01

    Aim: Silybin (silibinin)is major biologically active flavonolignan extracted from milk thistle (Sylibum marianum). Its biological activities include hepato-protection, anticancer properties, and antioxidant- and membrane-stabilizing functions. Al-though membranes are postulated to be one of the cellular targets for silybin, little is known about its interaction with phospholipid bilayers. Methods: In the present work, the interactions of silybin with phosphatidylcholine bilayers were studied in detail using fluorescence spectroscopy, microcalorimetry and electron spin resonance techniques. Results: The results showed that silybin interacted with the surface of lipid bilayers. It affected the generalized polarization of the fluores-cent probe Prodan, while not influencing the more deeplylocated Laurdan. Silybin lowered the main phospholipid phase transition temperature as judged by microcalorimetry, and caused the immobilization of spin probe Tempo-palmitate located on the surface of membranes. The mobility of spin probes 5-and 16-doxylstearic acid was not affected by silybin. Silybin-induced quenching of 1,6-diphe-nyl-1,3,5-hexatriene fluorescence indicated that some flavonoid molecules parti-tioned into the hydrophobic region of membranes, which did not change signifi-cantly the biophysical properties of the deeper membrane regions. Conclusion: Such a behavior of silybin in membranes is in accordance with its postulated biological functions and neglectable side effects of therapies using silybin.

  19. Strain Modulation of Electronic and Heat Transport Properties of Bilayer Boronitrene

    Science.gov (United States)

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

    2017-10-01

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

  20. Stacking order dependent mechanical properties of graphene/MoS{sub 2} bilayer and trilayer heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Elder, Robert M., E-mail: robert.elder26.ctr@mail.mil, E-mail: mahesh.neupane.ctr@mail.mil; Neupane, Mahesh R., E-mail: robert.elder26.ctr@mail.mil, E-mail: mahesh.neupane.ctr@mail.mil; Chantawansri, Tanya L. [U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

    2015-08-17

    Transition metal dichalcogenides (TMDC) such as molybdenum disulfide (MoS{sub 2}) are two-dimensional materials that show promise for flexible electronics and piezoelectric applications, but their weak mechanical strength is a barrier to practical use. In this work, we perform nanoindentation simulations using atomistic molecular dynamics to study the mechanical properties of heterostructures formed by combining MoS{sub 2} with graphene. We consider both bi- and tri-layer heterostructures formed with MoS{sub 2} either supported or encapsulated by graphene. Mechanical properties, such as Young's modulus, bending modulus, ultimate tensile strength, and fracture strain, are extracted from nanoindentation simulations and compared to the monolayer and homogeneous bilayer systems. We observed that the heterostructures, regardless of the stacking order, are mechanically more robust than the mono- and bi-layer MoS{sub 2}, mainly due to the mechanical reinforcement provided by the graphene layer. The magnitudes of ultimate strength and fracture strain are similar for both the bi- and tri-layer heterostructures, but substantially larger than either the mono- and bi-layer MoS{sub 2}. Our results demonstrate the potential of graphene-based heterostructures to improve the mechanical properties of TMDC materials.

  1. Gas adsorption, energetics and electronic properties of boron- and nitrogen-doped bilayer graphenes

    Science.gov (United States)

    Fujimoto, Yoshitaka; Saito, Susumu

    2016-10-01

    We study stabilities and electronic properties of several environmental polluting or toxic gas molecules (CO, CO2, NO, and NO2) adsorbed on B and N atoms in bilayer graphene using first-principles electronic-structure calculations. We find that NO and NO2 molecules can be bound chemically on B-doped bilayer graphene with large adsorption energies, while CO and CO2 molecules are not adsorbed chemically on B-doped one. In the case of the N-doped graphene, all four gases do not bind with chemical bonds but adsorb rather physically with small adsorption energies at long distances between gases and graphene. The adsorptions of NO and NO2 molecules on B-doped bilayer graphene induce the acceptor states above the Fermi energy, and we also find that the charge transfer takes place when the NO and the NO2 molecules are adsorbed. Thereby, the B-doped bilayer graphene is expected to be useful for NO and NO2 gas sensor materials.

  2. Modeling the Elastic Properties of Lipid Bilayer Membranes

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    Barry, Edward; Gibaud, Thomas; Zakhary, Mark; Dogic, Zvonimir

    2011-03-01

    Model membranes such as lipid bilayers have been indispensable tools for our understanding of the elastic properties of biological membranes. In this talk, I will introduce a colloidal model for membranes and demonstrate that the physical properties of these colloidal membranes are identical to lipid bilayers. The model system is unique in that the constituent molecules are homogenous and non-amphiphilic, yet their self-assembly into membranes and other hierarchical assemblages, such as a lamellar type phases and chiral ribbons, proceeds spontaneously in solution. Owing to the large size of the constituent molecules, individual molecules can be directly visualized and simultaneous observations at the continuum and molecular lengthscales are used to characterize the behavior of model membranes with unprecedented detail. Moreover, once assembled in solution, molecular interactions can be controlled in situ. In particular, the strength of chiral interactions can be varied, leading to fascinating transitions in behavior that resembles the formation of starfish vesicles. These observations point towards the important role of line tension, and have potential implications for phase separated lipid mixtures or lipid rafts.

  3. A Molecular Dynamics Study of the Structural and Dynamical Properties of Putative Arsenic Substituted Lipid Bilayers

    Directory of Open Access Journals (Sweden)

    Ratna Juwita

    2013-04-01

    Full Text Available Cell membranes are composed mainly of phospholipids which are in turn, composed of five major chemical elements: carbon, hydrogen, nitrogen, oxygen, and phosphorus. Recent studies have suggested the possibility of sustaining life if the phosphorus is substituted by arsenic. Although this issue is still controversial, it is of interest to investigate the properties of arsenated-lipid bilayers to evaluate this possibility. In this study, we simulated arsenated-lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-arsenocholine (POAC, lipid bilayers using all-atom molecular dynamics to understand basic structural and dynamical properties, in particular, the differences from analogous 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, (POPC lipid bilayers. Our simulations showed that POAC lipid bilayers have distinct structural and dynamical properties from those of native POPC lipid bilayers. Relative to POPC lipid bilayers, POAC lipid bilayers have a more compact structure with smaller lateral areas and greater order. The compact structure of POAC lipid bilayers is due to the fact that more inter-lipid salt bridges are formed with arsenate-choline compared to the phosphate-choline of POPC lipid bilayers. These inter-lipid salt bridges bind POAC lipids together and also slow down the head group rotation and lateral diffusion of POAC lipids. Thus, it would be anticipated that POAC and POPC lipid bilayers would have different biological implications.

  4. Superconducting properties of lithium-decorated bilayer graphene

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    Szczȩśniak, Dominik

    2015-07-01

    The present study provides a comprehensive theoretical analysis of the superconducting phase in selected lithium-decorated bilayer graphene nanostructures. The numerical calculations, conducted within the Eliashberg formalism, give quantitative estimations of the most important thermodynamic properties such as the critical temperature, specific heat, critical field and others. It is shown that discussed lithium-graphene systems present enhancement of their thermodynamic properties comparing to the monolayer case, e.g., the critical temperature can be raised to ∼15 \\text{K} . Furthermore, estimated characteristic thermodynamic ratios exceed predictions of the Bardeen-Cooper-Schrieffer theory suggesting that the considered lithium-graphene systems can be properly analyzed only within the strong-coupling regime.

  5. Effect of charge on the mechanical properties of surfactant bilayers.

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    Bradbury, Robert; Nagao, Michihiro

    2016-11-23

    Charge effects on the mechanical properties of surfactant bilayers have been measured, for a system with a low ionic strength, using small-angle neutron scattering and neutron spin echo spectroscopy. We report that, not only does increasing the surface charge density lead to greater structural ordering and a stiffening of the membrane, which is consistent with classical theory of charge effects on membranes, but also that the relaxation rate of the membrane thickness fluctuations decreases without affecting the fluctuation amplitude. From the relaxation rate we demonstrate, using recent theory, that the viscosity of the surfactant membrane is increased with surface charge density, which suggests that the amount of charge controls the diffusion behavior of inclusions inside the membrane. The present results confirm that the thickness fluctuation relaxation rate and amplitude are tuned independently since the membrane viscosity is only influencing the relaxation rate. This work demonstrates that charge stabilization of lamellar bilayers is not merely affected by intermembrane interactions and structural ordering but that intramembrane dynamics also have a significant contribution.

  6. Phosphatidyl-hydroxytyrosol and phosphatidyl-tyrosol bilayer properties.

    Science.gov (United States)

    Evans, Kervin O; Compton, David L

    2017-01-01

    Hydroxytyrosol and tyrosol phospholipids were enzymatically synthesized and investigated for their bilayer properties. Dynamic light scattering demonstrated that hand extrusion at 100nm consistently resulted in liposomes of nearly 85nm diameter for both phosphatidyl-hydroxytyrosol (DOPHT) and phosphatidyl-tyrosol (DOPT). Transmission electron microscopy showed DOPT and DOPHT liposomes extruded at 100-nm to be spherical and non-distinctive from one another. Zeta potential measurements resulted in surface charges<-25mV, demonstrating both DOPT and DOPHT form highly stable liposomes. Quartz crystal microbalance with dissipation monitoring measurements demonstrated that liposomal adsorption was dependent on a combination of DOPT (or DOPHT) mole-percent and calcium ions concentration. Fluorescence anisotropy measurements indicated that melting temperatures of DOPT and DOPHT were below 4°C, suggesting that adsorption behavior and liposome formation was limited by electrostatic interactions and not gel-state formation.

  7. Optical and electrical properties of bi-layers organic devices

    Science.gov (United States)

    Trad, Hager; Rouis, Ahlem; Davenas, Jöel; Majdoub, Mustapha

    2014-10-01

    The influence of interfacial charges on the device characteristics of bi-layers structure LEDs with poly[5-methoxy-2-octyloxy-1,4-phenylenevinylene] (MO-PPV) as active polymer layer is investigated. The concept to improve device performance is presented using: a diacetate cellulose (DAC) and a new synthetized 5-{2-(2-chloroethoxy)ethoxy}-2-{(E)-(2-pyridyl)azo}phenol (PDEG) components. The DAC and mixed (DAC+PDEG) layers were inserted between indium tin oxide (ITO) and MO-PPV polymer. The optical properties (UV-Vis) of MO-PPV, PDEG and mixed (DAC+PDEG) in solutions were studied and compared to those on thin films. Detailed current-voltage measurements of the bi-layers devices showed improvements of the threshold voltage (Vth) of the ITO/(DAC+PDEG)/MO-PPV/Al device attributed to the enhancement of carriers injection and transport resulted from the modified electrode structures. Conduction mechanisms of structure LEDs were matched with space-charge-limited current (SCLC) one. The impedance spectra for all devices can be discussed in terms of an equivalent circuit model designed as a parallel resistor Rp and capacitor Cp network in series with resistor Rs. The ITO/(DAC+PDEG)/MO-PPV/Al device showed the lowest impedance attributed to the removal of contaminants and to changes in the work function of ITO. The frequency-dependent electrical properties of the ITO/(DAC+PDEG)/MO-PPV/Al structure is analyzed by impedance spectroscopy as function of bias. We have extracted numerical values of the equivalent circuit model parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution.

  8. Thickness dependencies of structural and magnetic properties of cubic and tetragonal Heusler alloy bilayer films

    Science.gov (United States)

    Ranjbar, R.; Suzuki, K. Z.; Sugihara, A.; Ando, Y.; Miyazaki, T.; Mizukami, S.

    2017-07-01

    The thickness dependencies of the structural and magnetic properties for bilayers of cubic Co-based Heusler alloys (CCHAs: Co2FeAl (CFA), Co2FeSi (CFS), Co2MnAl (CMA), and Co2MnSi (CMS)) and D022-MnGa were investigated. Epitaxy of the B2 structure of CCHAs on a MnGa film was achieved; the smallest thickness with the B2 structure was found for 3-nm-thick CMS and CFS. The interfacial exchange coupling (Jex) was antiferromagnetic (AFM) for all of the CCHAs/MnGa bilayers except for unannealed CFA/MnGa samples. A critical thickness (tcrit) at which perpendicular magnetization appears of approximately 4-10 nm for the CMA/MnGa and CMS/MnGa bilayers was observed, whereas this thickness was 1-3 nm for the CFA/MnGa and CFS/MnGa films. The critical thickness for different CCHAs materials is discussed in terms of saturation magnetization (Ms) and the Jex .

  9. Direct Nanoimprint of Metal Bilayer for Tunnable Metal Photonic Properties

    Science.gov (United States)

    Sung, Sangkeun; Kim, Chul-Hyun; Choi, Dae-Geun; Lee, Jihye; Choi, Jun-Hyuk; Lee, Eung-Sug

    2013-10-01

    Tunable metal optical properties were realized by directly nanoimprinting metal onto silver-coated poly(methyl methacrylate) (PMMA) bilayer glass substrates. Imprinting at elevated temperatures enabled the molding of a stamp pattern consisting of a hexagonal pillar array with a 265 nm diameter and 530 nm pitch size, which produced a corrugated-metal nanohole array. The transmittance of the sample imprinted at 200 °C and 50 bar was uniquely improved from below 20% to more than 30% in the visible-infrared region, and its reflectance was reduced by more than 65% compared to a reference sample. The optical properties of the investigated metal depended significantly on the imprint temperature and relatively less on the imprint pressure and deposited silver film thickness. The improved transmittance was obtained only for the direct-imprinted silver-PMMA and not when the silver was simply deposited onto the predefined PMMA pattern. The presented fabrication strategy enables the provision of accessible optical tunability as well as improved cost-labor effectiveness for metal nanostructuring.

  10. A comparison of the transport properties of bilayer graphene,monolayer graphene, and two-dimensional electron gas

    Institute of Scientific and Technical Information of China (English)

    Sun Li-Feng; Dong Li-Min; Wu Zhi-Fang; Fang Chao

    2013-01-01

    we studied and compared the transport properties of charge carriers in bilayer graphene,monolayer graphene,and the conventional semiconductors (the two-dimensional electron gas (2DEG)).It is elucidated that the normal incidence transmission in the bilayer graphene is identical to that in the 2DEG but totally different from that in the monolayer graphene.However,resonant peaks appear in the non-normal incidence transmission profile for a high barrier in the bilayer graphene,which do not occur in the 2DEG.Furthermore,there are tunneling and forbidden regions in the transmission spectrum for each material,and the division of the two regions has been given in the work.The tunneling region covers a wide range of the incident energy for the two graphene systems,but only exists under specific conditions for the 2DEG.The counterparts of the transmission in the conductance profile are also given for the three materials,which may be used as high-performance devices based on the bilayer graphene.

  11. High field transport properties of a bilayer graphene

    Science.gov (United States)

    Bhargavi, K. S.; Kubakaddi, S. S.

    2014-02-01

    The high electric field transport properties namely, hot electron energy loss rate P, momentum loss rate Q, electron temperature Te and drift velocity Vd are studied theoretically in a bilayer graphene (BLG) by employing the momentum and energy balance technique. P and Q are investigated as a function of Te by considering the electron interaction with the acoustic phonons (APs) and the surface polar phonons (SPPs). In the Bloch-Grüneisen regime P (Q) due to APs is ~Te4 (Te2.5), with a new feature of a kink appearing due to the chiral nature of the electrons. The predicted Te4 is consistent with the recent experimental observation of heat resistance (Yan et al. Nature Nanotechnology 3 (2012) 472 [35]). Hot phonon effect is taken into account for SPPs. A dip has been observed in the hot phonon distribution of SPPs, a new feature, which is not found in conventional two-dimensional electron gas, and this can be attributed to the chiral nature of the electrons. P (Q) due to SPPs is found to be dominant at about Te>150 (180) K for a lattice temperature T=4.2 K. It is observed that the hot phonon effect is found to reduce P and Q due to SPPs significantly. Te and Vd are calculated as a function of the electric field E by taking into account the additional channels for momentum relaxation due to Coulomb impurity (CI) and short-range disorder (SD). Te is found to increase with the increasing electric field and is significantly enhanced by the hot phonon effect. Low field Vd is found to be limited by CI, SD and APs and in the high field region it reaches a near saturation value. The hot phonon effect tends to reduce the value of Vd. The presence of disorders CI and SD reduces Vd significantly and in clean samples larger saturation velocity can be achieved at a relatively smaller E.

  12. Mechanical properties of electrospun bilayer fibrous membranes as potential scaffolds for tissue engineering.

    Science.gov (United States)

    Pu, Juan; Komvopoulos, Kyriakos

    2014-06-01

    Bilayer fibrous membranes of poly(l-lactic acid) (PLLA) were fabricated by electrospinning, using a parallel-disk mandrel configuration that resulted in the sequential deposition of a layer with fibers aligned across the two parallel disks and a layer with randomly oriented fibers, both layers deposited in a single process step. Membrane structure and fiber alignment were characterized by scanning electron microscopy and two-dimensional fast Fourier transform. Because of the intricacies of the generated electric field, bilayer membranes exhibited higher porosity than single-layer membranes consisting of randomly oriented fibers fabricated with a solid-drum collector. However, despite their higher porosity, bilayer membranes demonstrated generally higher elastic modulus, yield strength and toughness than single-layer membranes with random fibers. Bilayer membrane deformation at relatively high strain rates comprised multiple abrupt microfracture events characterized by discontinuous fiber breakage. Bilayer membrane elongation yielded excessive necking of the layer with random fibers and remarkable fiber stretching (on the order of 400%) in the layer with fibers aligned in the stress direction. In addition, fibers in both layers exhibited multiple localized necking, attributed to the nonuniform distribution of crystalline phases in the fibrillar structure. The high membrane porosity, good mechanical properties, and good biocompatibility and biodegradability of PLLA (demonstrated in previous studies) make the present bilayer membranes good scaffold candidates for a wide range of tissue engineering applications.

  13. Regulation of membrane protein function by lipid bilayer elasticity—a single molecule technology to measure the bilayer properties experienced by an embedded protein

    DEFF Research Database (Denmark)

    Lundbæk, Jens August

    2008-01-01

    , in the general regulation of membrane protein function, is unclear. This is to a large extent due to lack of a generally accepted framework in which to understand the many observations. The present review summarizes studies which have demonstrated that the hydrophobic interactions between a membrane protein...... and the host lipid bilayer provide an energetic coupling, whereby protein function can be regulated by the bilayer elasticity. The feasibility of this ‘hydrophobic coupling mechanism’ has been demonstrated using the gramicidin channel, a model membrane protein, in planar lipid bilayers. Using voltage...... properties experienced by an embedded protein has been developed. A theoretical and technological framework, to study the regulation of membrane protein function by lipid bilayer elasticity, has been established....

  14. Electronic and transmission properties of magnetotunnel junctions of cobalt/iron intercalated bilayer two dimensional sheets

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, N.; Xie, M.D. [Department of Physics, Xiangtan University, Xiangtan 411105, Hunan (China); Zhou, P. [Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105 (China); Sun, L.Z., E-mail: lzsun@xtu.edu.cn [Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105 (China)

    2015-10-23

    Highlights: • The TMR ratio reaches 169% for Co intercalated Ni|bi-GBN|Ni MTJs. • The TMR ratio reaches 173% for Fe intercalated Ni|bi-GBN|Ni MTJs. • Intercalated Co/Fe effectively modulates the spin filtering of bilayer systems. - Abstract: Density functional theory and the nonequilibrium Green's function method are used to study the electronic properties and tunneling magnetoresistance (TMR) of magnetotunnel junctions (MTJs) based on Co/Fe intercalated bilayer graphene (bi-Gr), bilayer hexagonal boron nitride (bi-h-BN), and bilayer Gr-h-BN (bi-GBN). The spin-polarized bands around the Fermi energy of the two dimensional bilayer sheets are modulated by the intercalated cobalt. The TMR ratio reaches 169.94% and 173.00% for cobalt and iron intercalated Ni|bi-GBN|Ni MTJs, respectively. We observe that the Co/Fe intercalated bi-GBN is a promising candidate as a spacer in MTJs for spintronics.

  15. Elastic Properties and Line Tension of Self-Assembled Bilayer Membranes

    CERN Document Server

    Li, Jianfeng; Shi, An-Chang; Schmid, Friederike; Zhou, Jiajia

    2013-01-01

    The elastic properties of a self-assembled bilayer membrane are studied using the self-consistent field theory, applied to a model system composed of flexible amphiphilic chains dissolved in hydrophilic polymeric solvents. Examining the free energy of bilayer membranes with different geometries allows us to calculate their bending modulus, Gaussian modulus, two fourth-order membrane moduli, and the line tension. The dependence of these parameters on the microscopic characteristics of the amphiphilic chain, characterized by the volume fraction of the hydrophilic component, is systematically studied. The theoretical predictions are compared with the results from a simple monolayer model, which approximates a bilayer membrane by two monolayers. Finally the region of validity of the linear elasticity theory is analyzed by examining the higher-order contributions.

  16. Theoretical study on strain induced variations in electronic properties of 2H-MoS{sub 2} bilayer sheets

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Liang; Dongare, Avinash M., E-mail: dongare@uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Namburu, Raju R. [Computational and Information Sciences Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); O' Regan, Terrance P.; Dubey, Madan [Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland 20783 (United States)

    2014-02-03

    The strain dependence of the electronic properties of bilayer sheets of 2H-MoS{sub 2} is studied using ab initio simulations based on density functional theory. An indirect band gap for bilayer MoS{sub 2} is observed for all variations of strain along the basal plane. Several transitions for the indirect band gap are observed for various strains for the bilayer structure. The variation of the band gap and the carrier effective masses for the holes and the electrons for the bilayer MoS{sub 2} structure under conditions of uniaxial strain, biaxial strain, as well as uniaxial stress is investigated.

  17. Magnetic properties of epitaxial bismuth ferrite-garnet mono- and bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Semuk, E.Yu.; Berzhansky, V.N.; Prokopov, A.R.; Shaposhnikov, A.N.; Karavainikov, A.V. [Taurida National V.I. Vernadsky University, Vernadsky Avenue, 4, 95007 Simferopol (Ukraine); Salyuk, O.Yu. [Institute of Magnetism NASU and MESU, 36-B Vernadsky Blvd., 03142 Kiev (Ukraine); Golub, V.O., E-mail: golub@imag.kiev.ua [Institute of Magnetism NASU and MESU, 36-B Vernadsky Blvd., 03142 Kiev (Ukraine)

    2015-11-15

    Magnetic properties of Bi{sub 1.5}Gd{sub 1.5}Fe{sub 4.5}Al{sub 0.5}O{sub 12} (84 nm) and Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} (180 nm) films epitaxially grown on gallium-gadolinium garnet (GGG) single crystal (111) substrate as well as Bi{sub 1.5}Gd{sub 1.5}Fe{sub 4.5}Al{sub 0.5}O{sub 12}/Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} bilayer were investigated using ferromagnetic resonance technique. The mismatch of the lattice parameters of substrate and magnetic layers leads to formation of adaptive layers which affect on the high order anisotropy constant of the films but practically do not affect on uniaxial perpendicular magnetic anisotropy The magnetic properties of the bilayer film were explained in supposition of strong exchange coupling between magnetic layers taking into account film-film and film-substrate elastic interaction. - Highlights: • Magnetic parameters of epitaxial Bi-YIG films and bilayers on GGG substrate. • Adaptive layers affect on high order magnetic anisotropy. • Magnetic properties of bilayers are result of strong exchange interaction.

  18. Thiazolidinedione insulin sensitizers alter lipid bilayer properties and voltage-dependent sodium channel function: implications for drug discovery.

    Science.gov (United States)

    Rusinova, Radda; Herold, Karl F; Sanford, R Lea; Greathouse, Denise V; Hemmings, Hugh C; Andersen, Olaf S

    2011-08-01

    The thiazolidinediones (TZDs) are used in the treatment of diabetes mellitus type 2. Their canonical effects are mediated by activation of the peroxisome proliferator-activated receptor γ (PPARγ) transcription factor. In addition to effects mediated by gene activation, the TZDs cause acute, transcription-independent changes in various membrane transport processes, including glucose transport, and they alter the function of a diverse group of membrane proteins, including ion channels. The basis for these off-target effects is unknown, but the TZDs are hydrophobic/amphiphilic and adsorb to the bilayer-water interface, which will alter bilayer properties, meaning that the TZDs may alter membrane protein function by bilayer-mediated mechanisms. We therefore explored whether the TZDs alter lipid bilayer properties sufficiently to be sensed by bilayer-spanning proteins, using gramicidin A (gA) channels as probes. The TZDs altered bilayer elastic properties with potencies that did not correlate with their affinity for PPARγ. At concentrations where they altered gA channel function, they also altered the function of voltage-dependent sodium channels, producing a prepulse-dependent current inhibition and hyperpolarizing shift in the steady-state inactivation curve. The shifts in the inactivation curve produced by the TZDs and other amphiphiles can be superimposed by plotting them as a function of the changes in gA channel lifetimes. The TZDs' partition coefficients into lipid bilayers were measured using isothermal titration calorimetry. The most potent bilayer modifier, troglitazone, alters bilayer properties at clinically relevant free concentrations; the least potent bilayer modifiers, pioglitazone and rosiglitazone, do not. Unlike other TZDs tested, ciglitazone behaves like a hydrophobic anion and alters the gA monomer-dimer equilibrium by more than one mechanism. Our results provide a possible mechanism for some off-target effects of an important group of drugs, and

  19. Electronic properties of bilayer graphenes strongly coupled to interlayer stacking and an external electric field

    Science.gov (United States)

    Park, Changwon; Ryu, Junga; Hong, Suklyun; Sumpter, Bobby; Kim, Gunn; Yoon, Mina

    2015-03-01

    In the design of bilayer graphene (BLG)-based switching devices, it is critical to understand the complex stacking structures observed experimentally and their impact on the overall electronic properties. Using a maximally localized Wannier function, a highly accurate tight-binding Hamiltonian based on density functional theory was constructed and the stacking-dependent evolution of BLGs electronic band structures and their response to an external electric field were systematically investigated. Although the crossing band structures remain at any stacking configurations (i.e., no energy gap opens), the wavefunction characteristics around the Fermi level can differ qualitatively for different stackings. This difference is conveyed to energy gap opening properties in the presence of an external electric field. We, for the first time, established a phase diagram summarizing the stacking-dependent electronic structures of BLG, separating metallic and semiconducting characteristics for a given external field. The research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

  20. Graphene supported graphone/graphane bilayer nanostructure material for spintronics.

    Science.gov (United States)

    Ray, Sekhar C; Soin, Navneet; Makgato, Thuto; Chuang, C H; Pong, W F; Roy, Susanta S; Ghosh, Sarit K; Strydom, André M; McLaughlin, J A

    2014-01-24

    We report an investigation into the magnetic and electronic properties of partially hydrogenated vertically aligned few layers graphene (FLG) synthesized by microwave plasma enhanced chemical vapor deposition. The FLG samples are hydrogenated at different substrate temperatures to alter the degree of hydrogenation and their depth profile. The unique morphology of the structure gives rise to a unique geometry in which graphane/graphone is supported by graphene layers in the bulk, which is very different from other widely studied structures such as one-dimensional nanoribbons. Synchrotron based x-ray absorption fine structure spectroscopy measurements have been used to investigate the electronic structure and the underlying hydrogenation mechanism responsible for the magnetic properties. While ferromagnetic interactions seem to be predominant, the presence of antiferromagnetic interaction was also observed. Free spins available via the conversion of sp(2) to sp(3) hybridized structures, and the possibility of unpaired electrons from defects induced upon hydrogenation are thought to be likely mechanisms for the observed ferromagnetic orders.

  1. Chemically deposited TiO2/CdS bilayer system for photoelectrochemical properties

    Indian Academy of Sciences (India)

    P R Deshmukh; U M Patil; K V Gurav; S B Kulkarni; C D Lokhande

    2012-12-01

    In the present investigation, TiO2, CdS and TiO2/CdS bilayer system have been deposited on the fluorine doped tin oxide (FTO) coated glass substrate by chemical methods. Nanograined TiO2 was deposited on FTO coated glass substrates by successive ionic layers adsorption and reaction (SILAR) method. Chemical bath deposition (CBD)method was employed to deposit CdS thin film on pre-deposited TiO2 film. A further study has beenmade for structural, surface morphological, optical and photoelectrochemical (PEC) properties of FTO/TiO2, FTO/CdS and FTO/TiO2/CdS bilayers system. PEC behaviour of FTO/TiO2/CdS bilayers was studied and compared with FTO/CdS single system. FTO/TiO2/CdS bilayers system showed improved performance of PEC properties over individual FTO/CdS thin films.

  2. Electronic Properties of Bilayer Zigzag Graphene Nanoribbons: First Principles Study

    Institute of Scientific and Technical Information of China (English)

    OUYANG Fang-Ping; CHEN Li-Jian; XIAO Jin; ZHANG Hua

    2011-01-01

    @@ Based on the density functional theory, we calculate the dependence of the band structures of bilaver ziezaff-edzed grapnene nanonooons(BZGNRs) upon ribbon width, interlayer distance and stacking styles.Unlike monolayer zigzag GNR, whose energy gap is always zero under different ribbon widths, the gap of BZGNR varies greathy with the ribbon width or the interlayer distance.The greatest gaps for AA-stacking and AB-stacking BZGNRs are about 0.22eV and 0.12eV, respectively, which implies that gap-tuning of AA-BZGNRs is more effective than that of AB-BZGNRs.These results present a way to tune the band structures of BZGNRs and also provide theoretical guidance for the fabrication of GNR-based piezoelectric devices.%Based on the density functional theory, we calculate the dependence of the band structures of bilayer zigzag-edged graphene nanoribbons (BZGNRs) upon ribbon width, interlayer distance and stacking styles. Unlike monolayer zigzag GNR, whose energy gap is always zero under different ribbon widths, the gap of BZGNR varies greatly with the ribbon width or the interlayer distance. The greatest gaps for AA-stacking and AR-stacking BZGNRs are about 0.22 eV and O.12eV, respectively, which implies that gap-tuning of AA-BZGNRs is more effective than that of AB-BZGNRs. These results present a way to tune the band structures of BZGNRs and also provide theoretical guidance for the fabrication of GNR-based piezoelectric devices.

  3. Improved prediction of bilayer and monolayer properties using a refined BMW-MARTINI force field.

    Science.gov (United States)

    Miguel, Virginia; Perillo, Maria A; Villarreal, Marcos A

    2016-11-01

    Coarse-grained (CG) models allow enlarging the size and time scales that are reachable by atomistic molecular dynamics simulations. A CG force field (FF) for lipids and amino acids that possesses a polarizable water model has been developed following the MARTINI parametrization strategy, the BMW-MARTINI [1]. We tested the BMW-MARTINI FF capability to describe some structural and thermodynamical properties of lipid monolayers and bilayers. We found that, since the surface tension values of oil/water interfaces calculated with the model are not correct, compression isotherms of lipid monolayers present artifacts. Also, this FF predicts DPPC and DAPC bilayers to remain in the Lα phase at temperatures as low as 283K, contrary to the expected from their experimental Tm values. Finally, simulations at constant temperature of bilayers of saturated lipids belonging to PC homologous, showed an increase in the mean molecular area (Mma) upon increasing the chain length, inversely to the experimental observation. We refined BMW-MARTINI FF by modifying as few parameters as possible in order to bring simulated and experimental measurements closer. We have also modified structural parameters of the lipid geometry that do not have direct influence in global properties of the bilayer membranes or monolayers, but serve to approach the obtained CG geometry to atomistic reference values. The refined FF is able to better reproduce phase transition temperatures and Mma for saturated PC bilayers than BMW-MARTINI and MARTINI FF. Finally, the simulated surface pressure-Mma isotherms of PC monolayers resemble the experimental ones and eliminate serious artifacts of previous models.

  4. Modification of thermal and electronic properties of bilayer graphene by using slow Na+ ions

    Science.gov (United States)

    Ryu, Mintae; Lee, Paengro; Kim, Jingul; Park, Heemin; Chung, Jinwook

    2016-12-01

    Bilayer graphene (BLG) has an extensive list of industrial applications in graphene-based nanodevices such as energy storage devices, flexible displays, and thermoelectric devices. By doping slow Na+ ions on Li-intercalated BLG, we find significantly improved thermal and electronic properties of BLG by using angle-resolved photoemission and high-resolution core level spectroscopy (HRCLS) with synchrotron photons. Our HRCLS data reveal that the adsorbed Na+ ions on a BLG produced by Li-intercalation through single layer graphene (SLG) spontaneously intercalate below the BLG, and substitute Li atoms to form Na-Si bonds at the SiC interface while preserving the same phase of BLG. This is in sharp contrast with no intercalation of Na+ ions on SLG though neutral Na atoms intercalate. The Na+-induced BLG is found to be stable upon heating up to T = 400 °C, but returns to SLG when heated at T d = 500 °C. The evolution of the π-bands upon doping the Na+ ions followed by thermal annealing shows that the carrier concentration of the π-band may be artificially controlled without damaging the Dirac nature of the π-electrons. The doubled desorption temperature from that (T d = 250 °C) of the Na-intercalated SLG together with the electronic stability of the Na+-intercalated BLG may find more practical and effective applications in advancing graphene-based thermoelectric devices and anode materials for rechargeable batteries.

  5. Theoretical study of electronic transport properties of a graphene-silicene bilayer

    Science.gov (United States)

    Berdiyorov, G. R.; Bahlouli, H.; Peeters, F. M.

    2015-06-01

    Electronic transport properties of a graphene-silicene bilayer system are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Depending on the energy of the electrons, the transmission can be larger in this system as compared to the sum of the transmissions of separated graphene and silicene monolayers. This effect is related to the increased electron density of states in the bilayer sample. At some energies, the electronic states become localized in one of the layers, resulting in the suppression of the electron transmission. The effect of an applied voltage on the transmission becomes more pronounced in the layered sample as compared to graphene due to the larger variation of the electrostatic potential profile. Our findings will be useful when creating hybrid nanoscale devices where enhanced transport properties will be desirable.

  6. Theoretical study of electronic transport properties of a graphene-silicene bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Berdiyorov, G. R. [Qatar Environment and Energy Research Institute, Qatar Foundation, P.O. Box 5825, Doha (Qatar); Bahlouli, H. [Department of Physics, King Fahd University of Petroleum and Minerals, 31261 Dhahran (Saudi Arabia); Saudi Center for Theoretical Physics, 31261 Dhahran (Saudi Arabia); Peeters, F. M. [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)

    2015-06-14

    Electronic transport properties of a graphene-silicene bilayer system are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Depending on the energy of the electrons, the transmission can be larger in this system as compared to the sum of the transmissions of separated graphene and silicene monolayers. This effect is related to the increased electron density of states in the bilayer sample. At some energies, the electronic states become localized in one of the layers, resulting in the suppression of the electron transmission. The effect of an applied voltage on the transmission becomes more pronounced in the layered sample as compared to graphene due to the larger variation of the electrostatic potential profile. Our findings will be useful when creating hybrid nanoscale devices where enhanced transport properties will be desirable.

  7. Stability of topological properties of bismuth (1 1 1) bilayer

    Science.gov (United States)

    Bieniek, Maciej; Woźniak, Tomasz; Potasz, Paweł

    2017-04-01

    We investigate the electronic and transport properties of the bismuth (1 1 1) bilayer in the context of the stability of its topological properties against different perturbations. The effects of spin-orbit coupling variations, geometry relaxation and interaction with a substrate are considered. The transport properties are studied in the presence of Anderson disorder. Band structure calculations are performed within the multi-orbital tight-binding model and density functional theory methods. A band inversion process in the bismuth (1 1 1) infinite bilayer and an evolution of the edge state dispersion in ribbons as a function of spin-orbit coupling strength are analyzed. A significant change in the orbital composition of the conduction and valence bands is observed during a topological phase transition. The topological edge states are shown to be weakly affected by the effect of ribbon geometry relaxation. The interaction with a substrate is considered for narrow ribbons on top of another bismuth (1 1 1) bilayer. This corresponds to a weakly interacting case and the effect is similar to an external perpendicular electric field. Robust quantized conductance is observed when the Fermi energy lies within the energy gap, where only two counter-propagating edge states are present. For energies where the Fermi level crosses more in-gap states, scattering is possible between the channels lying close in the k-space. When the energy of the edge states overlaps the valence states, no topological protection is observed.

  8. Investigating Hydrophilic Pores in Model Lipid Bilayers Using Molecular Simulations: Correlating Bilayer Properties with Pore-Formation Thermodynamics.

    Science.gov (United States)

    Hu, Yuan; Sinha, Sudipta Kumar; Patel, Sandeep

    2015-06-23

    Cell-penetrating and antimicrobial peptides show a remarkable ability to translocate across physiological membranes. Along with factors such as electric-potential-induced perturbations of membrane structure and surface tension effects, experiments invoke porelike membrane configurations during the solute transfer process into vesicles and cells. The initiation and formation of pores are associated with a nontrivial free-energy cost, thus necessitating a consideration of the factors associated with pore formation and the attendant free energies. Because of experimental and modeling challenges related to the long time scales of the translocation process, we use umbrella sampling molecular dynamics simulations with a lipid-density-based order parameter to investigate membrane-pore-formation free energy employing Martini coarse-grained models. We investigate structure and thermodynamic features of the pore in 18 lipids spanning a range of headgroups, charge states, acyl chain lengths, and saturation. We probe the dependence of pore-formation barriers on the area per lipid, lipid bilayer thickness, and membrane bending rigidities in three different lipid classes. The pore-formation free energy in pure bilayers and peptide translocating scenarios are significantly coupled with bilayer thickness. Thicker bilayers require more reversible work to create pores. The pore-formation free energy is higher in peptide-lipid systems than in peptide-free lipid systems due to penalties to maintain the solvation of charged hydrophilic solutes within the membrane environment.

  9. Optical properties of Bernal-stacked bilayer graphene: A theoretical study

    Science.gov (United States)

    Kadi, Faris; Malic, Ermin

    2014-01-01

    We present a microscopic study of optical properties of Bernal-stacked bilayer graphene. Our focus lies on the absorption spectrum explicitly including the impact of fully momentum-dependent optical and Coulomb matrix elements. Our approach is based on the density matrix formalism combined with tight-binding wave functions. The energy dispersion of bilayer graphene exhibits four parabolic bands resulting in interesting optical features: We find a pronounced low-energy peak, which can be clearly ascribed to cross transitions at the Dirac point. Furthermore, the bilayer spectrum shows two energetically close absorption peaks in the ultraviolet region resulting from interband transitions at the saddle point of the Brillouin zone. We discuss the impact of the carrier-light coupling element containing the optical selection rules and determining the oscillator strength of all possible optical transitions. Furthermore, we show the influence of the Coulomb interaction accounting for a considerable overall energy renormalization and the formation of electron-hole pairs at the saddle point.

  10. Static and dynamic properties of critical fluctuations in lipid bilayers

    Science.gov (United States)

    Honerkamp-Smith, Aurelia Rose

    A current popular view in cell biology is that sub-micron, dynamic heterogeneity in lipid and protein composition arises within the plasma membranes of resting cells. Local changes in membrane composition may affect protein activity, which is sensitive to the lipid environment. We have observed dynamic heterogeneity in lipid membranes in the form of composition fluctuations near a miscibility critical point. In this thesis we quantitatively describe the dynamic and static properties of these fluctuations. We evaluate the temperature dependence of line tension between liquid domains and of fluctuation correlation lengths in lipid membranes in order to extract a critical exponent, nu. We obtain nu = 1.2 +/- 0.2, consistent with the Ising model prediction nu = 1. From probability distributions of pixel intensities in fluorescence images of membranes, we also extract an independent critical exponent of beta = 0.124 +/- 0.03, which is consistent with the Ising prediction of beta = 1/8. We have systematically measured the effective dynamic critical exponent z eff in a lipid membrane while cooling the system toward a critical point. We observe that zeff slightly increases from a value of roughly 2.6 as xi → 0, to zeff = 3.0 +/- 0.15 at xi = 13 sm. Our measurements are consistent with the prediction that zeff → 3.00 as T → Tc for a 2-D system with conserved order parameter in contact with a bulk 3-D liquid. To our knowledge, no other systematic measurement of zeff with increasing xi exists for a 2-D system with conserved order parameter. We also report the solubility limit of several biologically relevant sterols in electroformed giant unilamellar vesicle membranes containing phosphatidylcholine (PC) lipids in ratios of 1:1:X DPPC:DOPC:sterol. We find solubility limits of cholesterol, lanosterol, ergosterol, stigmasterol, and beta-sitosterol using nuclear magnetic resonance.

  11. Nanomechanical properties of lipid bilayer: Asymmetric modulation of lateral pressure and surface tension due to protein insertion in one leaflet of a bilayer

    Science.gov (United States)

    Maftouni, Negin; Amininasab, Mehriar; Ejtehadi, Mohammad Reza; Kowsari, Farshad; Dastvan, Reza

    2013-02-01

    The lipid membranes of living cells form an integral part of biological systems, and the mechanical properties of these membranes play an important role in biophysical investigations. One interesting problem to be evaluated is the effect of protein insertion in one leaflet of a bilayer on the physical properties of lipid membrane. In the present study, an all atom (fine-grained) molecular dynamics simulation is used to investigate the binding of cytotoxin A3 (CTX A3), a cytotoxin from snake venom, to a phosphatidylcholine lipid bilayer. Then, a 5-microsecond coarse-grained molecular dynamics simulation is carried out to compute the pressure tensor, lateral pressure, surface tension, and first moment of lateral pressure in each monolayer. Our simulations reveal that the insertion of CTX A3 into one monolayer results in an asymmetrical change in the lateral pressure and corresponding spatial distribution of surface tension of the individual bilayer leaflets. The relative variation in the surface tension of the two monolayers as a result of a change in the contribution of the various intermolecular forces may potentially be expressed morphologically.

  12. Formation, Energetics, and Electronic Properties of Graphene Monolayer and Bilayer Doped with Heteroatoms

    Directory of Open Access Journals (Sweden)

    Yoshitaka Fujimoto

    2015-01-01

    Full Text Available Doping with heteroatoms is one of the most effective methods to tailor the electronic properties of carbon nanomaterials such as graphene and carbon nanotubes, and such nanomaterials doped with heteroatom dopants might therefore provide not only new physical and chemical properties but also novel nanoelectronics/optoelectronics device applications. The boron and nitrogen are neighboring elements to carbon in the periodic table, and they are considered to be good dopants for carbon nanomaterials. We here review the recent work of boron and nitrogen doping effects into graphene monolayer as well as bilayer on the basis of the first-principles electronic structure calculations in the framework of the density-functional theory. We show the energetics and the electronic properties of boron and nitrogen defects in graphene monolayer and bilayer. As for the nitrogen doping, we further discuss the stabilities, the growth processes, and the electronic properties associated with the plausible nitrogen defect formation in graphene which is suggested by experimental observations.

  13. Correlation of Magnetic Properties of Co/Cr Bilayer Thin Films with Grain Boundary Diffusion

    Institute of Scientific and Technical Information of China (English)

    Gaowu Qin; Bo Yang; Wenli Pei; Yuping Ren

    2009-01-01

    The microstructure and magnetic properties of Co/Cr bilayer films were examined before and after post-deposition annealing by using transmission electron microscopy (TEM), X-ray diffraction (XRD) technique and vibrating sample magnetometer (VSM). A model of grain boundary (GB) Cr-rich phase growth involving GB diffusion derived from the Cr underlayer was proposed to elucidate the kinetics of the paramagnetic Cr-rich phase growth along Co GBs within the Co layer. The correlation of the GB Cr-rich phase formation with the magnetic Co grain isolation and accordingly, improvement of magnetic properties was experimentally investigated and discussed in detail. Our analysis results are well consistent with previous micromagnetic simulations on the improvement of magnetic properties by the magnetic grain isolation. The results provide some insights into the processing-structure-property relationships of the Co/Cr bilayer films, and thus suggest that the magnetic grain isolation be feasible not only in longitudinal recording media, but also be effective in tuning the exchange coupling of magnetic grains in perpendicular recording media via the GB diffusion from underlayer and/or overlayer.

  14. Electrical properties of materials

    CERN Document Server

    Solymar, L; Syms, R R A

    2014-01-01

    An informal and highly accessible writing style, a simple treatment of mathematics, and clear guide to applications have made this book a classic text in electrical and electronic engineering. Students will find it both readable and comprehensive. The fundamental ideas relevant to the understanding of the electrical properties of materials are emphasized; in addition, topics are selected in order to explain the operation of devices having applications (or possible future applications) in engineering. The mathematics, kept deliberately to a minimum, is well within the grasp of a second-year student. This is achieved by choosing the simplest model that can display the essential properties of a phenomenom, and then examining the difference between the ideal and the actual behaviour. The whole text is designed as an undergraduate course. However most individual sections are self contained and can be used as background reading in graduate courses, and for interested persons who want to explore advances in microele...

  15. Composition, structure and properties of POPC–triolein mixtures. Evidence of triglyceride domains in phospholipid bilayers

    DEFF Research Database (Denmark)

    Duelund, Lars; Jensen, Grethe Vestergaard; Hannibal-Bach, Hans Kristian

    2013-01-01

    We have in this study investigated the composition, structure and spectroscopical properties of multilamellar vesicles composed of a phospholipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and up to 10mol% of triolein (TO), a triglyceride. We found in agreement with previous result......% TO contained pure TO domains. These observations are consistent with an earlier MD simulation study by us and our co-workers suggesting triglycerides to be located in lens shaped, blister-like domains between the two lipid bilayer leaflets (Khandelia et al. (2010) [26])....

  16. An inverse problem of thickness design for bilayer textile materials under low temperature

    Science.gov (United States)

    Xu, Dinghua; Cheng, Jianxin; Chen, Yuanbo; Ge, Meibao

    2011-04-01

    The human heat-moisture-comfort level is mainly determined by heat and moisture transfer characteristics in clothing. With respect to the model of steady-state heat and moisture transfer through parallel pore textiles, we propose an inverse problem of thickness design for bilayer textile material under low temperature in this paper. Adopting the idea of regularization method, we formulate the inverse problem solving into a function minimization problem. Combining the finite difference method for ordinary differential equations with direct search method of one-dimensional minimization problems, we derive three kinds of iteration algorithms of regularized solution for the inverse problem of thickness design. Numerical simulation is achieved to verify the efficiency of proposed methods.

  17. Phase-transition properties of glycerol-dipalmitate lipid bilayers investigated using molecular dynamics simulation.

    Science.gov (United States)

    Laner, Monika; Hünenberger, Philippe H

    2015-06-01

    The phase- and phase-transition properties of glycerol-dipalmitate (GDP) bilayer patches are investigated using molecular dynamics simulations. This permits to characterize the influence of introducing a second aliphatic lipid tail by comparison to previously reported simulations of glycerol-1-monopalmitate (GMP). To this purpose, a set of 67 simulations (up to 300ns duration) of 2×8×8GDP bilayer patches are performed, considering the two GDP isomers glycerol-1,3-dipalmitate (13GDP) and glycerol-1,2-dipalmitate (12GDP; racemic), two hydration levels (12GDP only), and temperatures in the range 250-370K. In agreement with experiment, the GDP simulations reveal an increase in the main transition temperature by about 25K relative to GMP, and the occurrence of non-bilayer phases at high temperatures (inverted-cylinder or stacked phases). Structurally, the GDP system tends to evidence a tighter packing of the chains, a reduced extent of tilting, increased order parameters and a reduced fluidity. These differences are easily interpreted in terms of two key changes in molecular properties when going from GMP to GDP: (i) the reduction of the headgroup polarity and hydration (from two free hydroxyl groups to a single one); (ii) the increase in the effective tail cross-section relative to the (hydrated) headgroup cross-section, conferring to GDP a particular wedge shape. These two effects contribute to the relative instability of the liquid-crystalline phase, the stability being recovered in nature when the diglyceride headgroup is functionalized by a bulky or/and polar substituent.

  18. Ionizable Nitroxides for Studying Local Electrostatic Properties of Lipid Bilayers and Protein Systems by EPR

    Science.gov (United States)

    Voinov, Maxim A.; Smirnov, Alex I.

    2016-01-01

    Electrostatic interactions are known to play one of the major roles in the myriad of biochemical and biophysical processes. In this Chapter we describe biophysical methods to probe local electrostatic potentials of proteins and lipid bilayer systems that is based on an observation of reversible protonation of nitroxides by EPR. Two types of the electrostatic probes are discussed. The first one includes methanethiosulfonate derivatives of protonatable nitroxides that could be used for highly specific covalent modification of the cysteine’s sulfhydryl groups. Such spin labels are very similar in magnetic parameters and chemical properties to conventional MTSL making them suitable for studying local electrostatic properties of protein-lipid interfaces. The second type of EPR probes is designed as spin-labeled phospholipids having a protonatable nitroxide tethered to the polar head group. The probes of both types report on their ionization state through changes in magnetic parameters and a degree of rotational averaging, thus, allowing one to determine the electrostatic contribution to the interfacial pKa of the nitroxide, and, therefore, determining the local electrostatic potential. Due to their small molecular volume these probes cause a minimal perturbation to the protein or lipid system while covalent attachment secure the position of the reporter nitroxides. Experimental procedures to characterize and calibrate these probes by EPR and also the methods to analyze the EPR spectra by least-squares simulations are also outlined. The ionizable nitroxide labels and the nitroxide-labeled phospholipids described so far cover an exceptionally wide pH range from ca. 2.5 to 7.0 pH units making them suitable to study a broad range of biophysical phenomena especially at the negatively charged lipid bilayer surfaces. The rationale for selecting proper electrostatically neutral interface for calibrating such probes and example of studying surface potential of lipid bilayer is

  19. Structural properties and transfer characteristics of sputter deposition AlN and atomic layer deposition Al2O3 bilayer gate materials for H-terminated diamond field effect transistors

    Science.gov (United States)

    Banal, Ryan G.; Imura, Masataka; Liu, Jiangwei; Koide, Yasuo

    2016-09-01

    Significant improvements in electrical properties are achieved from AlN/Al2O3 stack gate H-terminated diamond metal-insulator-semiconductor field-effect transistors (MISFETs) upon improving the structural quality of an AlN insulating layer. The 5-nm-thick Al2O3 layer and 175-nm-thick AlN film are successively deposited by atomic layer deposition and sputter deposition techniques, respectively, on a (100) H-diamond epitaxial layer substrate. The AlN layer exhibits a poly-crystalline structure with the hexagonal wurtzite phase. The crystallite growth proceeds along the c-axis direction and perpendicular to the substrate surface, resulting in a columnar grain structure with an average grain size of around ˜40 nm. The MIS diode fabricated provides a leak current density as low as ˜10-5 A/cm2 at gate voltage bias in the range of -8 V and +4 V. The MISFET fabricated shows normally off enhancement mode transfer characteristic. The drain-source current maximum, threshold voltage, and maximum extrinsic conductance of the FET with 4 μm gate length are -8.89 mA/mm, -0.22 V, and 6.83 mS/mm, respectively.

  20. Structure and electronic properties of bilayer graphene functionalized with half-sandwiched transition metal-cyclopentadienyl complexes.

    Science.gov (United States)

    Yao, Xiaojing; Zhang, Xiuyun; Ye, Xiaoshan; Wang, Jinlan

    2016-08-10

    Tuning the electronic and magnetic properties of graphene is a crucial problem in the design of practical on-off electronic devices. Using density functional theory calculations, we explore the electronic and magnetic properties of bilayer graphene functionalized by cyclopentadienyl (Cp = cyclopentadienyl, C5H5) based half-sandwich ligands, CpTM (TM = Sc-Ni). It is found that the adsorption of CpTM ligands can introduce high magnetic moments and open the band gap of bilayer graphene, due to the electron doping as well as the asymmetric charge distribution between two graphene layers. Furthermore, the p-n doping of bilayer graphene by co-binding F/NO2 and CpTM on two external sides of BLG can further widen the band gap up to 366.1 meV. This study proposes an effective way to the modulation of the electronic and magnetic properties of graphene.

  1. Growth, structure and magnetic properties of single crystalline Fe/CoO/Ag(001) bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Abrudan, R.M.

    2007-07-16

    The structural and magnetic properties of epitaxially deposited single-crystalline CoO layers and Fe/CoO bilayers on Ag(001) were investigated. CoO films on Ag(001) exhibit (1 x 1) Low Energy Electron Diffraction (LEED) patterns similar to the clean Ag(001) substrate. The vertical interlayer spacing of the CoO films, deduced from a kinematic analysis of LEED I(E) curves, is a {sub perpendicular} {sub to} /2=2.17 Aa, slightly expanded along the film normal. Scanning Tunneling Microscopy (STM) show a big improvement in the surface roughness after annealing the CoO films at 750 K in oxygen atmosphere. Magnetic measurements using the magneto-optical Kerr effect (MOKE) show a characteristic increase of the coercive field when the Fe/CoO bilayer system is cooled down from room temperature to 150 K. The ordering temperature for the antiferromagnetic layer is in the same range as the Neel temperature for bulk CoO (T{sub N}=290 K). X-ray absorption spectroscopy was employed to probe magnetic and electronic properties with elemental selectivity. Absorption spectra taken from bilayers with different amounts of deposited Fe show only a weak indication for the formation of Fe oxide at the Fe/CoO interface (0.3 ML Fe). From the spectral shape it is concluded that an FeO type of oxide is formed. X-ray Magnetic Circular Dichroism (XMCD) measurements exhibit a sizeable induced ferromagnetic signal at the Co L{sub 2,3} absorption edge, corresponding to an interface layer of 1.1 ML in which the magnetic spins couple with the Fe layer. The angular dependence of the X-ray Magnetic Linear Dichroism (XMLD) and X-ray Magnetic Circular Dichroism XMCD at both the Co and Fe L{sub 2,3} edges shows the orientation of the Co and Fe moments in the bilayers with respect to the crystallographic direction. PhotoElectron Emission Microscope (PEEM) is used to image each ferromagnetic and antiferromagnetic layer separately. Magnetic contrast due to the induced magnetic spins at the interface is also

  2. Modeling Yeast Organelle Membranes and How Lipid Diversity Influences Bilayer Properties.

    Science.gov (United States)

    Monje-Galvan, Viviana; Klauda, Jeffery B

    2015-11-17

    Membrane lipids are important for the health and proper function of cell membranes. We have improved computational membrane models for specific organelles in yeast Saccharomyces cerevisiae to study the effect of lipid diversity on membrane structure and dynamics. Previous molecular dynamics simulations were performed by Jo et al. [(2009) Biophys J. 97, 50-58] on yeast membrane models having six lipid types with compositions averaged between the endoplasmic reticulum (ER) and the plasma membrane (PM). We incorporated ergosterol, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol lipids in our models to better describe the unique composition of the PM, ER, and trans-Golgi network (TGN) bilayers of yeast. Our results describe membrane structure based on order parameters (SCD), electron density profiles (EDPs), and lipid packing. The average surface area per lipid decreased from 63.8 ± 0.4 Å(2) in the ER to 47.1 ± 0.3 Å(2) in the PM, while the compressibility modulus (KA) varied in the opposite direction. The high SCD values for the PM lipids indicated a more ordered bilayer core, while the corresponding lipids in the ER and TGN models had lower parameters by a factor of at least 0.7. The hydrophobic core thickness (2DC) as estimated from EDPs is the thickest for PM, which is in agreement with estimates of hydrophobic regions of transmembrane proteins from the Orientation of Proteins in Membranes database. Our results show the importance of lipid diversity and composition on a bilayer's structural and mechanical properties, which in turn influences interactions with the proteins and membrane-bound molecules.

  3. Electronic transport properties and first-principles study of graphene/h-BN and h-BN bilayers

    Science.gov (United States)

    Ashhadi, M.; Hadavi, M. S.; Sarri, Z.

    2017-03-01

    We use a tight binding approach to study of electron transport properties of bilayers of zig-zag graphene/h-BN nanoribbon (GBNNR) and h-BN nanoribbon (BNNR) embedded between two bilayer of zig-zag graphene nanoribbons (GNR), which are considered as electrodes. In this study, the parameters of tight biding hopping and on-site energies are obtained by comparing the tight binding band structure graphene/h-BN and h-BN bilayers with density functional theory (DFT) calculations. We numerically compute the transport properties in terms of transmission and current-voltage characteristic. Our calculations show that the electron transport can open a conduction gap in the GNR/BNNR/GNR structure.

  4. Curcumin is a modulator of bilayer material properties

    NARCIS (Netherlands)

    Ingolfsson, Helgi I; Koeppe, Roger E; Andersen, Olaf S

    2007-01-01

    Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) is the major bioactive compound in turmeric (Curcuma longa) with antioxidant, antiinflammatory, anticarcinogenic, and antimutagenic effects. At low muM concentrations, curcumin modulates many structurally and functionally unrelat

  5. Comparative study on the nonlinear properties of bilayer graphene and silicene under tension

    Science.gov (United States)

    Xu, Peng; Yu, Zhongyuan; Yang, Chuanghua; Lu, Pengfei; Liu, Yumin; Ye, Han; Gao, Tao

    2014-11-01

    Atomic structures and nonlinear properties of single layer graphene (SLG), bilayer graphene (BLG), single layer silicene (SLS), and bilayer silicene (BLS) under equiaxial tension and uniaxial tensions along armchair and zigzag directions have been investigated comparatively using first-principles calculations. First, we have calculated the dependences of atomic structures (bond length, interlayer distance, and buckling height) of BLG and BLS on strain under three types of tensions. There exists the weak Van der Waals interaction between two layers of BLG and the interlayer distance is not variable with strain for three types of tensions. However, the interlayer of BLS is the covalent bond interaction, and the distance decreases with the increasing strain for three types of tensions. The continuum description of elastic response is formulated by expanding the elastic strain energy density in a Taylor series in strain truncated after the third-order term. The in-plane second- and third-order elastic constants of BLG and BLS have been obtained by fitting to the strain energy density versus Lagrangian strain relationships. The results show the in-plane stiffnesses of BLG and BLS become slightly larger than those of their single layer counterparts. In spite of the interlayer Si-Si covalent bond between two layers of BLS, its stiffness is still much less than BLG and SLG. Poisson's ratios of BLG and BLS basically maintain unchanged compared to their single layer counterparts.

  6. Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene

    Science.gov (United States)

    Sun, Yi-Yang; Zhang, Shengbai

    2016-07-01

    Bulk black phosphorus has two optical phonon modes labeled as Ag2 and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag2 modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B2u-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.

  7. Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene.

    Science.gov (United States)

    Sun, Yi-Yang; Zhang, Shengbai

    2016-07-14

    Bulk black phosphorus has two optical phonon modes labeled as Ag (2) and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag (2) modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B2u-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.

  8. SnO2/TiO2 bilayer thin films exhibiting superhydrophilic properties

    Science.gov (United States)

    Talinungsang, Nibedita Paul; Purkayastha, Debarun Dhar

    2017-05-01

    Nanostructured thin films of TiO2, SnO2, and SnO2/TiO2 have been deposited by sol-gel method. The films are characterized by X-ray diffraction, wettability and optical properties. In the present work, we have achieved a way of converting hydrophilic to super-hydrophilic state by incorporating TiO2 buffer layer in between substrate and SnO2 film, which has its utility in anti-fogging surfaces. The decrease in contact angle of water over SnO2/TiO2 bilayer is attributed to the increase in roughness of the film as well as surface energy of the substrate.

  9. First-leaflet phase effect on properties of phospholipid bilayer formed through vesicle adsorption on LB monolayer.

    Science.gov (United States)

    Park, Jin-Won

    2010-10-01

    Phospholipid bilayers were formed on mica using the Langmuir-Blodgett technique and liposome fusion, as a model system for biomembranes. Nanometer-scale surface physical properties of the bilayers were quantitatively characterized upon the different phases of the first leaflets. Lower hydration/steric forces on the bilayers were observed at the liquid phase of the first leaflet than at the solid phase. The forces appear to be related to the low mechanical stability of the lipid bilayer, which was affected by the first leaflet phase. The first leaflet phase also influenced the long-range repulsive forces over the second leaflet. Surface forces, measured using a modified probe with an atomic force microscope, showed that lower long-range repulsive forces were also found at the liquid phase of the first leaflet. Force measurements were performed at 300 mM sodium chloride solution so that the effect of the phase on the long-range repulsive forces could be investigated by reducing the effect of the repulsion between the second-leaflet lipid headgroups on the long-range repulsive forces. Forces were analyzed using the Derjaguin-Landau-Verwey-Overbeek theory so that the surface potential and surface charge density of the lipid bilayers were quantitatively acquired for each phase of the first leaflet.

  10. Study on the optical and electrical properties of tetracyanoethylene doped bilayer graphene stack for transparent conducting electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Limbu, Tej B., E-mail: tejnembang@yahoo.com; Barrionuevo, Danilo; Katiyar, Ram S.; Morell, Gerardo [Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931 (United States); Department of Physics, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico 00931 (United States); Mendoza, Frank [Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931 (United States); Carpena, Jennifer [National Research Council, Washington D.C. 20001 (United States); Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States); Maruyama, Benji [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States); Weiner, Brad R. [Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931 (United States); Department of Chemistry, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico 00931 (United States)

    2016-03-15

    We report the optical and electrical properties of chemically-doped bilayer graphene stack by tetracyanoethylene, a strong electron acceptor. The Tetracyanoethylene doping on the bilayer graphene via charge transfer was confirmed by Raman spectroscopy and Infrared Fourier transform spectroscopy. Doped graphene shows a significant increase in the sheet carrier concentration of up to 1.520 × 10{sup 13} cm{sup −2} with a concomitant reduction of the sheet resistance down to 414.1 Ω/sq. The high optical transmittance (ca. 84%) in the visible region in combination with the low sheet resistance of the Tetracyanoethylene-doped bilayer graphene stack opens up the possibility of making transparent conducting electrodes for practical applications.

  11. Study on the optical and electrical properties of tetracyanoethylene doped bilayer graphene stack for transparent conducting electrodes

    Directory of Open Access Journals (Sweden)

    Tej B. Limbu

    2016-03-01

    Full Text Available We report the optical and electrical properties of chemically-doped bilayer graphene stack by tetracyanoethylene, a strong electron acceptor. The Tetracyanoethylene doping on the bilayer graphene via charge transfer was confirmed by Raman spectroscopy and Infrared Fourier transform spectroscopy. Doped graphene shows a significant increase in the sheet carrier concentration of up to 1.520 × 1013 cm−2 with a concomitant reduction of the sheet resistance down to 414.1 Ω/sq. The high optical transmittance (ca. 84% in the visible region in combination with the low sheet resistance of the Tetracyanoethylene-doped bilayer graphene stack opens up the possibility of making transparent conducting electrodes for practical applications.

  12. Interface coupling and magnetic properties of exchange-coupled Ni81Fe19/Ir22Mn78 bilayers

    CERN Document Server

    Xi, H; Mao, S; Kief, M T; White, R M

    2003-01-01

    Hysteresis loop measurements using magnetooptic Kerr effect magnetometry in the low frequency region and magnetization dynamics measurements using high frequency permeametry are carried out to study the exchange anisotropy in Ni sub 8 sub 1 Fe sub 1 sub 9 /Ir sub 2 sub 2 Mn sub 7 sub 8 bilayers. These two measurement techniques provide different exchange anisotropies for bilayers with thin Ir sub 2 sub 2 Mn sub 7 sub 8 films. The observations can be understood by assuming that the AF grains break into domains due to the interface random field. By analysing the results from these two techniques, the interface coupling strength and the magnetic properties of the bilayers can be quantitatively determined.

  13. Optical and water repellant properties of Ag/SnO2 bilayer thin films

    Directory of Open Access Journals (Sweden)

    Ravipati Praveena

    2016-02-01

    Full Text Available The optical and water repellant properties of single layer and bilayer films of Ag and SnO2 deposited on glass substrates by thermal evaporation have been reported. Ag/SnO2 bilayers were deposited in two sequences wherein the deposition of SnO2 layer was followed by Ag deposition and vice versa. X-ray diffraction studies show that the Ag films crystallize in the FCC structure and SnO2 is amorphous, while atomic force microscopy images indicate the formation of large clusters of the order of 12 nm. The single layer Ag films exhibit localized surface plasmon resonance (LSPR that shifts from visible region to the infrared with increase in thickness from 5 to 12 nm. It is observed that, only the Ag films of thickness ≤ 8 nm exhibits LSPR peak whereas the critical thickness is 5 nm for Ag/SnO2 films. A blue shift is observed in the LSPR peak position when the SnO2 layer caps the Ag film. Whereas, the LSPR of Ag is suppressed significantly when the SnO2 layer is introduced between the glass and the Ag film and also when Ag and SnO2 were co-evaporated. Water repellant properties indicate that the pure Ag film has an average contact angle of 104o which decreases to 100o when SnO2 caps the Ag layer and 97o when Ag is deposited on top of the SnO2 buffer layer. Co-evaporated Ag-SnO2 films show a contact angle of 93o.

  14. Electromechanical oscillations in bilayer graphene

    Science.gov (United States)

    Benameur, Muhammed M.; Gargiulo, Fernando; Manzeli, Sajedeh; Autès, Gabriel; Tosun, Mahmut; Yazyev, Oleg V.; Kis, Andras

    2015-10-01

    Nanoelectromechanical systems constitute a class of devices lying at the interface between fundamental research and technological applications. Realizing nanoelectromechanical devices based on novel materials such as graphene allows studying their mechanical and electromechanical characteristics at the nanoscale and addressing fundamental questions such as electron-phonon interaction and bandgap engineering. In this work, we realize electromechanical devices using single and bilayer graphene and probe the interplay between their mechanical and electrical properties. We show that the deflection of monolayer graphene nanoribbons results in a linear increase in their electrical resistance. Surprisingly, we observe oscillations in the electromechanical response of bilayer graphene. The proposed theoretical model suggests that these oscillations arise from quantum mechanical interference in the transition region induced by sliding of individual graphene layers with respect to each other. Our work shows that bilayer graphene conceals unexpectedly rich and novel physics with promising potential in applications based on nanoelectromechanical systems.

  15. The effect of calcium on the properties of charged phospholipid bilayers

    DEFF Research Database (Denmark)

    Pedersen, U.R.; Leidy, Chad; Westh, P.

    2006-01-01

    We have performed molecular dynamics simulations to investigate the structure and dynamics of charged bilayers as well as the distribution of counterions at the bilayer interface. For this, we have considered the negatively charged di-myristoyl-phosphatidyl-glycerol (DMPG) and di-myristoyl-phosph......We have performed molecular dynamics simulations to investigate the structure and dynamics of charged bilayers as well as the distribution of counterions at the bilayer interface. For this, we have considered the negatively charged di-myristoyl-phosphatidyl-glycerol (DMPG) and di...

  16. Strain and electric field co-modulation of electronic properties of bilayer boronitrene.

    Science.gov (United States)

    Wang, Rui-Ning; Yang, Ming; Dong, Guo-Yi; Wang, Shu-Fang; Fu, Guang-Sheng; Wang, Jiang-Long

    2016-02-10

    The electronic properties of bilayer strained boronitrenes are investigated under an external electric field using density functional methods. Our result is just the same as the previous conclusion: ie, that the electric field will reduce their band gaps. Except for the decrease of their band gaps, the degeneracy of π valence bands at K points will be lifted and the degenerate gap will increase with the electric field increasing. Moreover, the widths of π valence bands are nearly robust and increase a little. In addition, a simple tight-binding model, where different electrostatic potentials are applied to boronitrene layers, can be sufficient to describe the variations of their band gaps. It is found that the interlayer hopping interaction increases while the intralayer hopping parameter changes little with increasing the electric field. Furthermore, a band gap phase diagram is determined within the in-plane strain [-0.2, 0.2] and the interlayer bias [0, 10] V nm(-1). The strain could make the bottom of conduction bands shift from K to M, then to Γ in the Brillouin zone, while the top of valence bands shifts from K to Γ. Thus, a direct-gap semiconductor at K points is changed into an indirect-gap semiconductor, and then a semiconductor with the direct band gap at Γ points. When bilayer boronitrene is a semiconductor with a direct gap at K points, the electric field and strain are inverse proportional relationships. Particularly, when the compressive strain exceeds  -0.194, there is an insulator-metal transition and the system becomes metallic with sizable pocket Fermi surfaces.

  17. Optical properties of advanced materials

    CERN Document Server

    Kajikawa, Kotaro

    2013-01-01

    In the last decade, optically functionalized materials have developed rapidly, from bulk matters to structured forms. Now we have a rich variety of attractive advanced materials. They are applied to optical and electrical devices that support the information communication technology in the mid 21-th century. Accordingly, it is quite important to have a broad knowledge of the optical properties of advanced materials for students, scientists and engineers working in optics and related fields. This book is designed to teach fundamental optical properties of such advanced materials effectively. These materials have their own peculiarities which are very interesting in modern optical physics and also for applications because the concepts of optical properties are quite different from those in conventional optical materials. Hence each chapter starts to review the basic concepts of the materials briefly and proceeds to the practical use. The important topics covered in this book include:  quantum structures of sem...

  18. Properties of the chalcogenide–carbon nano tubes and graphene composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Abhay Kumar, E-mail: abhaysngh@rediffmail.com [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Department of Electronics Engineering, Incheon National University, Incheon 406-772 (Korea, Republic of); Department of Physics, Incheon National University, Incheon 406-772 (Korea, Republic of); Kim, JunHo [Department of Physics, Incheon National University, Incheon 406-772 (Korea, Republic of); Park, Jong Tae [Department of Electronics Engineering, Incheon National University, Incheon 406-772 (Korea, Republic of); Sangunni, K.S. [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)

    2015-04-05

    Highlights: • Chalcogenides. • Melt quenched. • Composite materials. • Multi walled carbon nano tubes. • Bilayer graphene. - Abstract: Composite can deliver more than the individual elemental property of the material. Specifically chalcogenide- multi walled carbon nano tubes and chalcogenide- bilayer graphene composite materials could be interesting for the investigation, which have been less covered by the investigators. We describe micro structural properties of Se{sub 55}Te{sub 25}Ge{sub 20,} Se{sub 55}Te{sub 25}Ge{sub 20} + 0.025% multi walled carbon nano tubes and Se{sub 55}Te{sub 25}Ge{sub 20} + 0.025% bilayer graphene materials. This gives realization of the alloying constituents inclusion/or diffusion inside the multi walled carbon nano tubes and bilayer graphene under the homogeneous parent alloy configuration. Raman spectroscopy, X-ray photoelectron spectroscopy, UV/Visible spectroscopy and Fourier transmission infrared spectroscopy have also been carried out under the discussion. A considerable core energy levels peak shifts have been noticed for the composite materials by the X-ray photoelectron spectroscopy. The optical energy band gaps are measured to be varied in between 1.2 and 1.3 eV. In comparison to parent (Se{sub 55}Te{sub 25}Ge{sub 20}) alloy a higher infrared transmission has been observed for the composite materials. Subsequently, variation in physical properties has been explained on the basis of bond formation in solids.

  19. Tribological and Corrosion Properties of Nickel/TiC Bilayered Coatings Produced by Electroless Deposition and PACVD

    Science.gov (United States)

    Shanaghi, Ali; Chu, Paul K.

    2016-11-01

    Ni/TiC bilayered coatings are deposited on hot-working steel (H11) by plasma-assisted chemical vapor deposition and electroless technique. The TiC layer is deposited at 490 °C using a gas mixture of TiCl4, CH4, H2, and Ar, and a dense nanostructured TiC coating with minimum excessive carbon phases and low chlorine concentration is produced. The effects of the Ni intermediate layer on the microstructure, tribology, and corrosion behavior of the nanostructured TiC coating are investigated. The friction coefficient of the Ni/TiC bilayered coating (Ni thickness = 4 µm) at 500 cycles is much smaller than that of the coating without the Ni intermediate layer. The smallest friction coefficient is about 0.2, and the hardness values of the Ni/TiC bilayered samples with three different Ni layer thicknesses of 2, 4, and 6 µm are 2534, 3070, and 2008 Hv, respectively. The wear mechanism of the Ni/TiC bilayered coatings is abrasive induced by plastic deformation and fatigue during the sliding process. The smaller groove width on the 4-µm electroless nickel-Ni3P/TiC bilayered coating correlates with the larger H/ E ratio and the 4-µm nickel/TiC bilayered sample shows the better wear resistance. The polarization resistance of the 6-µm electroless nickel-Ni3P/TiC coating in 0.05 M NaCl and 0.5 M H2SO4 increases by about 8 and 15 times, respectively. The Ni intermediate layer increases the toughness of the coating and adhesion between the hard coating and steel substrate thereby enhancing the tribological properties and corrosion resistance.

  20. Tribological and Corrosion Properties of Nickel/TiC Bilayered Coatings Produced by Electroless Deposition and PACVD

    Science.gov (United States)

    Shanaghi, Ali; Chu, Paul K.

    2016-10-01

    Ni/TiC bilayered coatings are deposited on hot-working steel (H11) by plasma-assisted chemical vapor deposition and electroless technique. The TiC layer is deposited at 490 °C using a gas mixture of TiCl4, CH4, H2, and Ar, and a dense nanostructured TiC coating with minimum excessive carbon phases and low chlorine concentration is produced. The effects of the Ni intermediate layer on the microstructure, tribology, and corrosion behavior of the nanostructured TiC coating are investigated. The friction coefficient of the Ni/TiC bilayered coating (Ni thickness = 4 µm) at 500 cycles is much smaller than that of the coating without the Ni intermediate layer. The smallest friction coefficient is about 0.2, and the hardness values of the Ni/TiC bilayered samples with three different Ni layer thicknesses of 2, 4, and 6 µm are 2534, 3070, and 2008 Hv, respectively. The wear mechanism of the Ni/TiC bilayered coatings is abrasive induced by plastic deformation and fatigue during the sliding process. The smaller groove width on the 4-µm electroless nickel-Ni3P/TiC bilayered coating correlates with the larger H/E ratio and the 4-µm nickel/TiC bilayered sample shows the better wear resistance. The polarization resistance of the 6-µm electroless nickel-Ni3P/TiC coating in 0.05 M NaCl and 0.5 M H2SO4 increases by about 8 and 15 times, respectively. The Ni intermediate layer increases the toughness of the coating and adhesion between the hard coating and steel substrate thereby enhancing the tribological properties and corrosion resistance.

  1. Comparison of the mechanical properties of NiTi/Cu bilayer by nanoindentation and tensile test: molecular dynamics simulation

    Science.gov (United States)

    Fazeli, Sara; Vahedpour, Morteza; Khatiboleslam Sadrnezhaad, Sayed

    2016-12-01

    Molecular dynamics simulation was used to study of mechanical properties of NiTi/Cu bilayer by nanoindentation and tensile testing. A comparison has been made among mechanical properties measured and plastic deformation process at different copper thickness during nanoindnetation and tensile test of the samples. Embedded atom method potentials for describing of inter-atomic interaction and Nose-Hoover thermostat and barostat are employed in the simulation at 400 K. The results showed that as the copper film thickness decreased, the maximum load and hardness values increased during nanoindetation. Saha and Nix model is used to describe reduced young’s modulus behaviour of the bilayer system through nanoindentation. A good agreement among calculated reduced elastic modulus by nanoindentation test and young’s modulus behaviour via tensile test have been obtained. The ‘incoherent interface’ in both of nanoindentation test and tensile testing is one of the governing factors for the dislocation propagation, which resulted in significant strengthening of the bilayer. It was observed that during tensile test, only copper layers were necked and fractured in all of samples. However, the present study seeks to examine the effect of film thickness on the free energy values that is obtained using Jarzynski’s equality during nanoindentation. As the copper film thickness was decreased, the free energy difference increased. According to both techniques, the thin film copper thickness provides lower number of nucleation locations resulting in the higher value of yield strength, hardness and free energy difference during nanoindenation. Mechanical properties of bilayer systems are improved with decreasing of copper film thickness. However, it specifies that strengths of all bilayer systems have prominent increase in young’s modulus in compared to the pure NiTi.

  2. X-Ray Kinematography of Temperature-Jump Relaxation Probes the Elastic Properties of Fluid Bilayers

    CERN Document Server

    Pabst, G; Amenitsch, H; Bernstorff, S; Laggner, P; Pabst, Georg; Rappolt, Michael; Amenitsch, Heinz; Bernstorff, Sigrid; Laggner, Peter

    2000-01-01

    The response kinetics of liquid crystalline phosphatidylcholine bilayerstacks to rapid, IR-laser induced temperature jumps has been studied bymillisecond time-resolved x-ray diffraction. The system reacts on the fasttemperature change by a discrete bilayer compression normal to its surface anda lateral bilayer expansion. Since water cannot diffuse from the excess phaseinto the interbilayer water region within the 2 ms duration of the laser pulse,the water layer has to follow the bilayer expansion, by an anomalous thinning.Structural analysis of a 20 ms diffraction pattern from the intermediate phaseindicates that the bilayer thickness remains within the limits of isothermalequilibrium values. Both, the intermediate structure and its relaxation intothe original equilibrium L_(alpha)-phase, depend on the visco-elasticproperties of the bilayer/water system. We present an analysis of therelaxation process by an overdamped one-dimensional oscillation model revealingthe concepts of Hooke's law for phospholipid bila...

  3. Porous Materials - Structure and Properties

    DEFF Research Database (Denmark)

    Nielsen, Anders

    1997-01-01

    The paper presents some viewpoints on the description of the pore structure and the modelling of the properties of the porous building materials. Two examples are given , where it has been possible to connect the pore structure to the properties: Shrinkage of autoclaved aerated concrete and the p......The paper presents some viewpoints on the description of the pore structure and the modelling of the properties of the porous building materials. Two examples are given , where it has been possible to connect the pore structure to the properties: Shrinkage of autoclaved aerated concrete...

  4. Dental materials with antibiofilm properties.

    Science.gov (United States)

    Wang, Zhejun; Shen, Ya; Haapasalo, Markus

    2014-02-01

    Oral bacteria have evolved to form biofilms on hard tooth surfaces and dental materials. The antibiofilm effect of materials used for the restoration of oral function affects oral health. In this review we describe the features involved in the formation of oral biofilms on different surfaces in the oral cavity and the antibiofilm properties of dental materials. An electronic search of scientific papers from 1987 to 2013 was performed with PubMed, ScienceDirect and Google search engines using the following search terms: antibiofilm, dental material, dental hard tissue, endodontic material, implant material, oral biofilm, and restorative material. Selected inclusion criteria resulted in 179 citations from the scientific, peer-reviewed literature. Oral biofilms form not only on dental hard tissue, but also on a wide range of dental materials used in cariology, endodontics, restorative dentistry and periodontology, resulting in destruction of dental hard tissue and even infection. Therefore, there has been a continuous effort to develop the antibiofilm properties of dental materials used for different purposes. Specific antimicrobial design in the composition and application of new materials (e.g. bioceramic sealer, resin composite, implant coating) demonstrates an improvement of the antibiofilm properties of these materials compared to earlier generations. A significant number of dental materials have been shown to affect biofilm growth by inhibiting the adhesion of bacteria, limiting their growth or killing microbes in the biofilms formed in vitro. Incorporation of an appropriate amount of antibacterial agent could provide dental materials with antibiofilm activity without significantly influencing their mechanical properties. However, more randomized and double-blind clinical studies of sufficient length with these materials are needed to confirm long term success following their use in the dental clinic. Copyright © 2013 Academy of Dental Materials. Published by

  5. Phospholipid bilayer-perturbing properties underlying lysis induced by pH-sensitive cationic lysine-based surfactants in biomembranes.

    Science.gov (United States)

    Nogueira, Daniele Rubert; Mitjans, Montserrat; Busquets, M Antonia; Pérez, Lourdes; Vinardell, M Pilar

    2012-08-14

    Amino acid-based surfactants constitute an important class of natural surface-active biomolecules with an unpredictable number of industrial applications. To gain a better mechanistic understanding of surfactant-induced membrane destabilization, we assessed the phospholipid bilayer-perturbing properties of new cationic lysine-based surfactants. We used erythrocytes as biomembrane models to study the hemolytic activity of surfactants and their effects on cells' osmotic resistance and morphology, as well as on membrane fluidity and membrane protein profile with varying pH. The antihemolytic capacity of amphiphiles correlated negatively with the length of the alkyl chain. Anisotropy measurements showed that the pH-sensitive surfactants, with the positive charge on the α-amino group of lysine, significantly increased membrane fluidity at acidic conditions. SDS-PAGE analysis revealed that surfactants induced significant degradation of membrane proteins in hypo-osmotic medium and at pH 5.4. By scanning electron microscopy examinations, we corroborated the interaction of surfactants with lipid bilayer. We found that varying the surfactant chemical structure is a way to modulate the positioning of the molecule inside bilayer and, thus, the overall effect on the membrane. Our work showed that pH-sensitive lysine-based surfactants significantly disturb the lipid bilayer of biomembranes especially at acidic conditions, which suggests that these compounds are promising as a new class of multifunctional bioactive excipients for active intracellular drug delivery.

  6. Effect of the HIV-1 fusion peptide on the mechanical properties and leaflet coupling of lipid bilayers

    Science.gov (United States)

    Shchelokovskyy, P.; Tristram-Nagle, S.; Dimova, R.

    2011-02-01

    The fusion peptide (FP) of the human immunodeficiency virus (HIV) is part of the N-terminus of the viral envelope glycoprotein gp41 and is believed to play an important role in the viral entry process. To understand the immediate effect of this peptide on the cell membrane, we have studied the influence of the synthetic FP sequence FP23 on the mechanical properties of model lipid bilayers. For this purpose, giant unilamellar vesicles were prepared from the unsaturated lipid dioleoylphosphatidylcholine mixed in various molar ratios with FP23. The bending stiffness of the vesicles was measured with two different methods: fluctuation analysis and aspiration with micropipettes. The data obtained from both of these approaches show that the bending stiffness of the membrane decreases gradually with increasing concentration of the FP23 in the bilayer. Low concentrations of only a few mol% FP23 are sufficient to decrease the bending stiffness of the lipid bilayer by about a factor of 2. Finally, data obtained for the stretching elasticity modulus of the membrane suggest that the peptide insertion decreases the coupling between the two leaflets of the bilayer.

  7. Effect of the HIV-1 fusion peptide on the mechanical properties and leaflet coupling of lipid bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Shchelokovskyy, P; Dimova, R [Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam (Germany); Tristram-Nagle, S, E-mail: rumiana.dimova@mpikg.mpg.de [Carnegie Mellon University, Pittsburgh, PA (United States)

    2011-02-15

    The fusion peptide (FP) of the human immunodeficiency virus (HIV) is part of the N-terminus of the viral envelope glycoprotein gp41 and is believed to play an important role in the viral entry process. To understand the immediate effect of this peptide on the cell membrane, we have studied the influence of the synthetic FP sequence FP23 on the mechanical properties of model lipid bilayers. For this purpose, giant unilamellar vesicles were prepared from the unsaturated lipid dioleoylphosphatidylcholine mixed in various molar ratios with FP23. The bending stiffness of the vesicles was measured with two different methods: fluctuation analysis and aspiration with micropipettes. The data obtained from both of these approaches show that the bending stiffness of the membrane decreases gradually with increasing concentration of the FP23 in the bilayer. Low concentrations of only a few mol% FP23 are sufficient to decrease the bending stiffness of the lipid bilayer by about a factor of 2. Finally, data obtained for the stretching elasticity modulus of the membrane suggest that the peptide insertion decreases the coupling between the two leaflets of the bilayer.

  8. Magnetoelectric properties of particulate and bi-layer PMN-PT/CoFe{sub 2}O{sub 4} composites

    Energy Technology Data Exchange (ETDEWEB)

    Mathe, V.L., E-mail: vlmathe@physics.unipune.ernet.in [Novel Materials Research Laboratory, Department of Physics, University of Pune, Pune, 411 007 Maharastra (India); Sheikh, A.D. [Novel Materials Research Laboratory, Department of Physics, University of Pune, Pune, 411 007 Maharastra (India); Srinivasan, G. [Physics Department, Oakland University, Rochester, MI 48309 (United States)

    2012-03-15

    Our studies comprise electrical dielectric and magnetoelectric properties of CoFe{sub 2}O{sub 4} (CFO) and Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.67}Ti{sub 0.33}O{sub 3} [PMN-PT] magnetoelectric composites. The individual phases were prepared by conventional ceramic method. The particulate composites of ferrite and ferroelectric phases were prepared in ferroelectric rich region. Presence of both the phases in the composites was confirmed using X-ray diffraction techniques. The scanning electron microscopic images recorded in backscattered mode were used to study the microstructure of composites. Lattice constant, dielectric constant, electrical resistivity, ferroelectric, and magnetic properties of individual as well as particulate composites were studied. Further the bi-layer composites were made using the discs obtained from the powders of individual phases where hot press technique was employed to obtain disc of individual phases. CFO phase used in bi-layer composites was obtained using chemical co-precipitation technique. Magnetoelectric (ME) measurements were carried out on both, particulate and layered magnetoelectric composites. Comparison of ME signal obtained from particulate and layered composites revealed that the layered composites gives superior magnetoelectric signal. ME data obtained for layered composites show good agreement with the theoretical model. - Highlights: Black-Right-Pointing-Pointer Study on dielectric, electrical, ferroelectric, and magnetic properties of particulate magnetoelectric composite of PMN-PT/CFO. Black-Right-Pointing-Pointer These properties are correlated with the magnetoelectric effect in particulate composites. Black-Right-Pointing-Pointer Magnetoelectric properties of particulate composites are compared with bilayer magnetoelectric composites of PMN-PT/CFO. Black-Right-Pointing-Pointer Magnetoelectric signal obtain for bilayer composites show good agreement with theoretical model suggested by Bichurin et al.

  9. Material Properties at Low Temperature

    CERN Document Server

    Duthil, P

    2014-01-01

    From ambient down to cryogenic temperatures, the behaviour of materials changes greatly. Mechanisms leading to variations in electrical, thermal, mechanical, and magnetic properties in pure metals, alloys, and insulators are briefly introduced from a general engineering standpoint. Data sets are provided for materials commonly used in cryogenic systems for design purposes.

  10. Mechanical Properties of Materials

    CERN Document Server

    Pelleg, Joshua

    2013-01-01

    The subject of mechanical behavior has been in the front line of basic studies in engineering curricula for many years.  This textbook was written for engineering students with the aim of presenting, in a relatively simple manner, the basic concepts of mechanical behavior in solid materials. A second aim of the book is to guide students in their laboratory experiments by helping them to understand their observations in parallel with the lectures of their various courses; therefore the first chapter of the book is devoted to mechanical testing. Another aim of the book is to provide practicing engineers with basic help to bridge the gap of time that has passed from their graduation up to their actual involvement in engineering work. The book also serves as the basis for more advanced studies and seminars when pursuing courses on a graduate level. The content of this textbook and the topics discussed correspond to courses that are usually taught in universities and colleges all over the world, but with a differ...

  11. Modulating effect of lipid bilayer-carotenoid interactions on the property of liposome encapsulation.

    Science.gov (United States)

    Xia, Shuqin; Tan, Chen; Zhang, Yating; Abbas, Shabbar; Feng, Biao; Zhang, Xiaoming; Qin, Fang

    2015-04-01

    Liposomes have become an attractive alternative to encapsulate carotenoids to improve their solubility, stability and bioavailability. The interaction mechanism of carotenoid with lipid bilayer is one of the major concerns in improving the delivery efficiency of liposomes. In this study, the microstructure and carotenoid encapsulation efficiency of liposomes composed of native phospholipid (egg yolk phosphatidylcholine, EYPC) and nonionic surfactant Tween 80 were investigated by atomic force microscopy, dynamic light scattering, and Raman spectroscopy, respectively. Subsequently, the effects of carotenoid incorporation on the physical properties of liposomal membrane were performed by Raman spectroscopy, fluorescence polarization, and electron paramagnetic resonance. Results showed that the incorporation of carotenoids affected the liposomes morphology, size and size distribution to various extents. Analysis on the Raman characteristic peaks of carotenoids revealed that lutein exhibited the strongest incorporating ability into liposomes, followed by β-carotene, lycopene, and canthaxanthin. Furthermore, it was demonstrated that carotenoids modulated the dynamics, structure and hydrophobicity of liposomal membrane, highly depending on their molecular structures and incorporated concentration. These modulations were closely correlated with the stabilization of liposomes, including mediating particle aggregation and fusion. These findings should guide the rationale designing for liposomal encapsulation technology to efficiently deliver carotenoids in pharmaceutics, nutraceuticals and functional foods.

  12. Temperature-induced assembly of semiconductor nanocrystals into fractal architectures and thermoelectric power properties in Au/Ge bilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Li Quanbao; Wang Jian; Jiao Zheng [Shanghai Applied Radiation Institute, Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China); Wu Minghong, E-mail: mhwu@staff.shu.edu.cn [Shanghai Applied Radiation Institute, Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China); Shek, Chan-Hung; Lawrence Wu, C.M.; Lai, Joseph K.L. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Chen Zhiwen, E-mail: cnzwchen@yahoo.com.cn [Shanghai Applied Radiation Institute, Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)

    2011-08-15

    Highlights: > Ge fractal architectures were achieved by temperature-induced assembly. > The appearance of fractal architectures influences the thermoelectric power. > But it has little effect on the resistivity. > The values of the superlocalization exponent were within 1.22 {<=} {xi} {<=} 1.29. > It was higher than expected for two-dimension fractal system. - Abstract: Fractal architectures of semiconductor nanocrystals were successfully achieved by temperature-induced assembly of semiconductor nanocrystals in gold/germanium (Au/Ge) bilayer films. New assessment strategies of fractal architectures are of fundamental importance in the development of micro/nano-devices. Temperature-dependent properties including resistivity and thermoelectric power (TEP) of Au/Ge bilayer films with self-similar fractal patterns were investigated in detail. Experimental results indicated that the microstructure of Au film plays an important role in the characteristics of Au/Ge bilayer films after annealing and the crystallization processes of amorphous Ge accompany by fractal formation of Ge nanocrystals via temperature-induced assembly. The appearance of fractal architectures has significantly influence on the TEP but little effect on the resistivity of the annealed bilayer film. By analysis of the data, we found that the values of superlocalization exponent are within 1.22 {<=} {xi} {<=} 1.29, which are higher than expected for two-dimension fractal systems. The results provided possible evidence for the superlocalization on fractal architectures in Au/Ge bilayer films. The TEP measurements are considered a more effective method than the conductivity for investigating superlocalization in a percolating system.

  13. Dynamics, Surface Electrostatics and Phase Properties of Nanoscale Curved Lipid Bilayers

    Science.gov (United States)

    Koolivand, Amir

    Surface electrostatic potential of a lipid bilayer governs many vital functions of living cells. Several classes of proteins are known of exhibiting strong binding preferences to curved lipid bilayer surfaces. In this project we employed electron paramagnetic resonance (EPR) of a recently introduced phospholipid (IMTSL-PTE) bearing a pH-sensitive nitroxide covalently attached to the lipid head group to measure the surface electrostatics of the lipid membrane and nanopore-confined lipid bilayers as a function of the bilayer curvature. The pKa of the ionizable group of this lipid-based spin probe is reporting on the bilayer surface electrostatics potential by changes in the EPR spectra. Specifically, both rotational dynamics and magnetic parameters of the nitroxide are affected by the probe protonation. Effect of curvature on the surface electrostatic potential and dynamics of lipid bilayer was studied for POPG and DMPG unilamellar vesicles (ULVs). It was found that the magnitude of the negative surface electrostatic potential increased upon decrease in the vesicle diameter for the bilayers in the fluid phase; however, no significant changes were observed for DMPG ULVs in a gel phase. We speculate that biologically relevant fluid bilayer phase allows for a larger variability in the lipid packing density in the lipid polar head group region than a more ordered gel phase and it is likely that the lipid flip-flop is responsible for pH equilibration of IMTSL-PTE. The kinetic EPR study of nitroxide reduction showed that the rate of flip-flop is in the order of 10-5 s-1. The flip-flop rate constant increases when vesicle size deceases. Oxygen permeability measured by X-ban EPR decreases in higher curved vesicles---an observation that is consistent with a tighter packing in smaller vesicles. Partitioning of a small nitroxide molecule TEMPO into ULVs was measured by X-band (9 GHz) and W-band (95 GHz) EPR spectroscopy. The partitioning coefficient of this probe in the lipid

  14. The Effect of Bilayer Graphene Nanoribbon Geometry on Schottky-Barrier Diode Performance

    OpenAIRE

    Meisam Rahmani; Razali Ismail; Mohammad Taghi Ahmadi; Mohammad Javad Kiani; Mehdi Saeidmanesh; F. A. Hediyeh Karimi; Elnaz Akbari; Komeil Rahmani

    2013-01-01

    Bilayer graphene nanoribbon is a promising material with outstanding physical and electrical properties that offers a wide range of opportunities for advanced applications in future nanoelectronics. In this study, the application of bilayer graphene nanoribbon in schottky-barrier diode is explored due to its different stacking arrangements. In other words, bilayer graphene nanoribbon schottky-barrier diode is proposed as a result of contact between a semiconductor (AB stacking) and metal (AA ...

  15. Microstructures and properties of Cr-Cu/W-Cu bi-layer composite coatings prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jiaping; Feng, Xiaomei; Shen, Yifu; Chen, Cheng; Duan, Cuiyuan [Nanjing Univ. of Aeronautics and Astronautics (China). Dept. of Materials Science and Technology

    2016-06-15

    Cr-Cu/W-Cu bi-layer coatings with composite structures were fabricated by means of mechanical alloying. The Cr-Cu layer and the W-Cu layer were deposited successively and the as-synthesized bi-layer coating was made up of an inner Cr-Cu layer and an outer W-Cu layer. Microstructures, chemical and phase compositions of the as-prepared coatings were characterized. The results indicated that the bonding between the inner coating and the substrate was improved with the increase of Cu in the raw powder. The annealing treatment of the inner Cr-Cu layer was beneficial to the bonding between the inner Cr-Cu coating and the outer W-Cu coating layer. Mechanical properties such as microhardness, friction and wear resistance were tested. The as-synthesized coating could effectively improve the hardness and wear resistance of the Cu substrate.

  16. Monte Carlo simulation of magnetic properties of a nano-graphene bilayer in a longitudinal magnetic field

    Science.gov (United States)

    Wang, Wei; Liu, Ruijia; Lv, Dan; Luo, Xiaohong

    2016-10-01

    Monte Carlo simulation has been used to study the magnetic properties of a nano-graphene bilayer which consists of the upper layer A with spin-3/2 and the bottom layer B with spin-5/2. The effects of the single-ion anisotropy, the intralayer exchange coupling and the longitudinal magnetic field on the magnetization, the susceptibility, the blocking temperature and hysteresis loops of the mixed-spin nano-graphene bilayer system have been examined detailedly. In particular, the variations of the blocking temperature with different intralayer exchange couplings, single-ion anisotropies, and the longitudinal magnetic field are obtained for the present system. Many multiple hysteresis loop behaviors have also been found, depending on the combinations of both the upper and bottom layer magnetizations in the longitudinal magnetic field. Through a comparison, our results obtained are according well with other theoretical researches and experimental results.

  17. Material properties in complement activation

    DEFF Research Database (Denmark)

    Moghimi, S. Moein; Andersen, Alina Joukainen; Ahmadvand, Davoud

    2011-01-01

    -immune performance’ relationship studies in nanomedicine research at many fronts. The interaction between nanomaterials and the complement system is complex and regulated by inter-related factors that include nanoscale size, morphology and surface characteristics. Each of these parameters may affect complement...... activation differently and through different sensing molecules and initiation pathways. The importance of material properties in triggering complement is considered and mechanistic aspects discussed. Mechanistic understanding of complement events could provide rational approaches for improved material design...

  18. Fundamental Studies of Assembly and Mechanical Properties of Lipid Bilayer Membranes and Unilamellar Vesicles

    Science.gov (United States)

    Wang, Xi

    This dissertation work focuses on: (i) obtaining a phospholipid bilayer membrane (LBM)/conducting electrode system with low defect density and optimized rigidity; (ii) investigating vesicle stability and mechanical properties. LBM is a simplified yet representative cell membrane model. LBMs assembled on conductive surfaces can probe protein-LBM interactions activities electrochemically. Sterically stabilized vesicles could be used as cell models or for drug delivery. The main challenges for LBM assembly on gold are vesicles do not spontaneously rupture to form LBMs on gold and the roughness of the gold substrate has considerable influence on molecular film defect density. In this study, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) vesicles were functionalized with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine- N-poly(ethylene glycol)-2000-N-[3-(2-pyridyldithio)propionate] (DSPE-PEG-PDP) to yield stable LBMs on gold without surface modification. A template-stripping method was used to obtain atomically flat and pristine gold surfaces. The critical force to initiate vesicle rupture decreases with increasing DSPE-PEG-PDP concentration, indicating that gold-thiolate bonding between DSPE-PEG-PDP and gold substrates promotes LBM formation. Mechanical properties of LBMs and vesicles were investigated as a function of DSPE-PEG-PDP concentration via Atomic Force Microscopy. The elastic moduli of LBMs were determined with DSPE-PEG-PDP concentration ranging from 0mol% to 24mol% and were found to depend on PEG chain conformation. Incorporating DSPE-PEG-PDP molecules with PEG in mushroom conformation results in a decrease of LBM rigidity, while incorporating PEG in brush conformation leads to LBM stiffening. Contrarily, mechanical properties of functionalized vesicles did not vary significantly by varying DSPE-PEG-PDP concentration. LBM with tunable rigidity by adjusting DSPE-PEG-PDP concentration provides a versatile cell membrane model for studying protein or

  19. Microstructural characterization, optical and photocatalytic properties of bilayered CuO and ZnO based thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sáenz-Trevizo, A.; Amézaga-Madrid, P.; Pizá-Ruiz, P.; Solís-Canto, O.; Ornelas-Gutiérrez, C.; Pérez-García, S.; Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx

    2014-12-05

    Highlights: • High quality bilayered Zn–Cu oxide thin films were deposited by aerosol assisted CVD. • Detailed microstructural characterization was performed by XRD and electron microscopy. • Absorbance of bilayered films shows a shift of absorption edge toward visible region. • Optical band gap or nearly 3.2 and 2 eV was determined for ZnO and Cu oxide. • High photocatalytic activity around 90% was obtained for bilayered samples. - Abstract: In this work, it is presented the synthesis, microstructural characterization and photocatalytic properties of bilayered CuO–ZnO/ZnO thin films onto borosilicate glass and fused silica substrates. The films were deposited by aerosol assisted chemical vapor deposition, using an experimental setup reported elsewhere. Deposition conditions were optimized to get high quality films; i.e. they were structurally uniform, highly transparent, non-light scattering, homogeneous, and well adhered to the substrate. Different Cu/Zn atomic ratios were tried for the upper layer. The microstructure of the films was characterized by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy. GIXRD results indicate the presence of ZnO Wurzite and Cu oxide phases. Results of SEM and HRTEM analysis of the cross sectional microstructure showed that the films were composed of compact and dense layers with no visible evidence of an interfacial boundary or porosity. Optical absorbance of the bilayered films showed a clear shift of the absorption toward the visible range. Optical band gap was determined roughly at 3.2 and 2 eV for ZnO and Cu oxide, respectively. Photocatalytic activity of the samples, for the degradation of a 10{sup −5} mol dm{sup −3} solution of methylene blue (MB), was determined after 120 and 240 min of irradiation with an UV-A source. Around 90% of MB degradation was reached by bilayered films with

  20. Structural and superconducting properties of ion beam sputtered Nb thin films and Nb/Cu bilayers

    Science.gov (United States)

    Nath, S. K.; Dhawan, R.; Rai, S.; Lodha, G. S.; Sokhey, K. J. S.

    2012-01-01

    We present the results of a study of structural and superconducting properties of polycrystalline Nb thin films (200 Å, 300 Å, 400 Å, 700 Å and 1000 Å) and Nb/Cu bilayers (300 Å/300 Å and 400 Å/300 Å) prepared on Si substrates by ion beam sputtering at room temperature. The thicknesses, roughnesses at the surfaces and interfaces were determined by X-ray reflectivity whereas the grain sizes were determined from grazing incidence X-ray diffraction and transmission electron microscopic studies. The superconducting transition temperature ( T C) of Nb thin films are smaller than T C of bulk Nb. The Nb-200 Å sample does not show T C down to 2.3 K. The average size of the grains varies from 42 Å for Nb-200 Å sample to 69 Å for Nb-1000 Å sample. Our results show that the T C in these polycrystalline films is not only limited by its thickness but also by the size of the grains. The Nb films deposited in situ on the Cu layer (Nb/Cu) show a marginal increase in average sizes of the grains as compare to their respective values in Nb films of same thicknesses. As a result a marginal increase in T C of these films is also observed. The maximum decrease in T C due to oxygen intake during deposition should be about 0.5 K from its bulk value (9.28 K). We have attributed the large decrease in T C in our case on the basis of decrease in the Debye temperature and density of states at the Fermi level for Nb thin films as compared to their respective values for bulk Nb.

  1. Spectral properties of doped bilayer cuprates at finite temperatures

    Indian Academy of Sciences (India)

    Amit Pratap; Ratan Lal; Govinda; S K Joshi

    2002-05-01

    Recently, angle-resolved photoemission spectroscopy measurements on Bi2Sr2CaCu2O8+, which possesses two CuO2 layers in the same unit cell, have yielded very interesting results. For the overdoped samples, these results show a splitting of electronic states near = (,0) point of Brillioun zone. On the other hand, no splitting is observed in the underdoped samples. In view of this, the detailed studies including the doping and temperature dependence of the spectral properties become desirable. In this paper, we consider cuprates possessing two CuO2 layers per unit cell. Each layer in the system is described by the -'- model and the two layers are coupled via an intrabilayer hopping term (⊥) and an intrabilayer exchange coupling (⊥). A self-consistent perturbation approach is used to calculate the electronic spectral function for different values of hole density, hole momentum and temperature. We find that the imaginary part of the self energy is strongly momentum dependent which contradicts the suggestion that the Fermi surface of cuprates may be described by marginal Fermi liquid theory. We have calculated the spectral function for various values of intrabilayer parameters ⊥ and ⊥. For larger values of intrabilayer interactions we observe the splitting in the quasi-particle peak at = (,0) which is in agreement with the recent observations. The splitting is also found to be sensitive to the hole concentration as well as the temperature of the system. We have also discussed the reasons why the splitting is absent in underdoped bilayer cuprates at low temperature.

  2. Mechanical Properties of Composite Materials

    Directory of Open Access Journals (Sweden)

    Mitsuhiro Okayasu

    2014-10-01

    Full Text Available An examination has been made of the mechanical and failure properties of several composite materials, such as a short and a long carbon fiber reinforced plastic (short- and long-CFRP and metal based composite material. The short CFRP materials were used for a recycled CFRP which fabricated by the following process: the CFRP, consisting of epoxy resin with carbon fiber, is injected to a rectangular plate cavity after mixing with acrylonitrile butadiene styrene resin with different weight fractions of CFRP. The fatigue and ultimate tensile strength (UTS increased with increasing CFRP content. These correlations, however, break down, especially for tensile strength, as the CFPR content becomes more than 70%. Influence of sample temperature on the bending strength of the long-CFRP was investigated, and it appears that the strength slightly decreases with increasing the temperature, due to the weakness in the matrix. Broken fiber and pull-out or debonding between the fiber and matrix were related to the main failure of the short- and long-CFRP samples. Mechanical properties of metal based composite materials have been also investigated, where fiber-like high hardness CuAl2 structure is formed in aluminum matrix. Excellent mechanical properties were obtained in this alloy, e.g., the higher strength and the higher ductility, compared tothe same alloy without the fiber-like structure. There are strong anisotropic effects on the mechanical properties due to the fiber-like metal composite in a soft Al based matrix.

  3. Structure and properties of phosphorene-like IV-VI 2D materials

    Science.gov (United States)

    Ma, Zhinan; Wang, Bo; Ou, Liangkai; Zhang, Yan; Zhang, Xu; Zhou, Zhen

    2016-10-01

    Because of the excellent physical and chemical properties of phosphorene, phosphorene and phosphorene-like materials have attracted extensive attention. Since phosphorus belongs to group V, some group IV-VI compounds could also form phosphorene-like configurations. In this work, GeO, SnO, GeS, and SnS monolayers were constructed to investigate the structural and electronic properties by employing first-principles computations. Phonon spectra suggest that these monolayers are dynamically stable and could be realized in experiments. These monolayers are all semiconductors with the band gaps of 2.26 ∼ 4.13 eV. Based on the monolayers, GeO, SnO, GeS, and SnS bilayers were also constructed. The band gaps of these bilayers are smaller than those of the corresponding monolayers. Moreover, the optical properties of these monolayers and bilayers were calculated, and the results indicate that the SnO, GeS and SnS bilayers exhibit obvious optical absorption in the visible spectrum. All the results suggest that phosphorene-like IV-VI materials are promising candidates for electronic and optical devices.

  4. Satellite material contaminant optical properties

    Science.gov (United States)

    Wood, B. E.; Bertrand, W. T.; Seiber, B. L.; Kiech, E. L.; Falco, P. M.; Holt, J. D.

    1990-03-01

    The Air Force Wright Research and Development Center and the Arnold Engineering Development Center are continuing a program for measuring optical effects of satellite material outgassing products on cryo-optic surfaces. Presented here are infrared (4000 to 700 cm(-1)) transmittance data for contaminant films condensed on a 77 K germanium window. From the transmittance data, the contaminant film refractive and absorptive indices (n, k) were derived using an analytical thin-film interference model with a nonlinear least-squares algorithm. To date 19 materials have been studied with the optical contents determined for 13 of those. The materials include adhesives, paints, composites, films, and lubricants. This program is continuing and properties for other materials will be available in the future.

  5. Kinetics properties of voltage induced colicin Ia channels into a lipid bilayer

    CERN Document Server

    Cassia-Moura, R

    1998-01-01

    The activation kinetics of the ion channels formed by colicin Ia incorporated into a planar bilayer lipid membrane (BLM) was investigated by the voltage clamp technique using different step voltage stimuli. The temporal behaviour of ion channels put in evidence a gain or a loss of memory, revealed by a specific sequence of electrical pulses used for stimulation.

  6. Effects of core-to-dentin thickness ratio on the biaxial flexural strength, reliability, and fracture mode of bilayered materials of zirconia core (Y-TZP) and veneer indirect composite resins.

    Science.gov (United States)

    Su, Naichuan; Liao, Yunmao; Zhang, Hai; Yue, Li; Lu, Xiaowen; Shen, Jiefei; Wang, Hang

    2017-01-01

    Indirect composite resins (ICR) are promising alternatives as veneering materials for zirconia frameworks. The effects of core-to-dentin thickness ratio (C/Dtr) on the mechanical property of bilayered veneer ICR/yttria-tetragonal zirconia polycrystalline (Y-TZP) core disks have not been previously studied. The purpose of this in vitro study was to assess the effects of C/Dtr on the biaxial flexural strength, reliability, and fracture mode of bilayered veneer ICR/ Y-TZP core disks. A total of 180 bilayered 0.6-mm-thick composite resin disks in core material and C/Dtr of 2:1, 1:1, and 1:2 were tested with either core material placed up or placed down for piston-on-3-ball biaxial flexural strength. The mean biaxial flexural strength, Weibull modulus, and fracture mode were measured to evaluate the variation trend of the biaxial flexural strength, reliability, and fracture mode of the bilayered disks with various C/Dtr. One-way analysis of variance (ANOVA) and chi-square tests were used to evaluate the variation tendency of fracture mode with the C/Dtr or material placed down during testing (α=.05). Light microscopy was used to identify the fracture mode. The mean biaxial flexural strength and reliability improved with the increase in C/Dtr when specimens were tested with the core material either up and down, and depended on the materials that were placed down during testing. The rates of delamination, Hertzian cone cracks, subcritical radial cracks, and number of fracture fragments partially depended on the C/Dtr and the materials that were placed down during testing. The biaxial flexural strength, reliability, and fracture mode in bilayered structures of Y-TZP core and veneer ICR depend on both the C/Dtr and the material that was placed down during testing. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  7. Ferroelectric, Dielectric, Ferromagnetic, and Magnetoelectric Properties of BNF-NZF Bilayer Nanofilms Prepared via Sol-Gel Process.

    Science.gov (United States)

    Guo, Kaixin; Zhang, Rongfen; Mou, Qingfeng; Cui, Ruirui; Deng, Chaoyong

    2016-12-01

    Bilayer magnetoelectric (ME) nanofilms composed of Bi0.9Nd0.1FeO3 (BNF) and Ni0.55Zn0.45Fe2O4 (NZF) were fabricated on the Pt(111)/Ti/SiO2/Si(100) substrates via sol-gel and a subsequent rapid thermal process with different growth sequences of BNF and NZF forming the following layered structures: BNF/NZF and NZF/BNF. The phase composition, microstructure, and ferroelectric, dielectric, ferromagnetic, and ME coupling properties of the composites were investigated at room temperature. Structural characterization by X-ray diffraction and scanning electron microscopy showed that there are no other impurity phases but BNF and NZF, and the nucleation barrier caused that it is easier for NZF and BNF to grow on each other rather than on the surface of Pt/Ti/SiO2/Si. The tests of the physical properties indicated that such heterostructures present both good ferroelectric, ferromagnetic, and dielectric properties and the in-plane ME coupling coefficient α E at room temperature but some discrepancies also exist, which can be attributed to an interfacial effect, in other words, the deposition sequences of the constituent phases have a great influence on the properties of bilayer films.

  8. Assessment of measurement techniques to determine the interfacial properties of bilayer dental ceramics

    Science.gov (United States)

    Anunmana, Chuchai

    The clinical success of all-ceramic dental restorations depends on the quality of interfacial bonding between ceramic layers. In addition, the residual stress in the structure that developed during ceramic processing is one of the important factors that contributes to the quality of the bond. Because all-ceramic restorations are usually fabricated as bilayer or trilayer structures and failures of all-ceramic restorations have been frequently reported as chipping or delamination of the veneer layers, the interfacial quality of bilayer dental ceramic restorations was investigated. However, most of the published bond test data reflect strength values that are inversely related to cross-sectional areas and failure locations are frequently disregarded or bond strength values are misinterpreted. In addition, residual tensile stresses that develop in the structures because of thermal expansion/contraction mismatches may also adversely affect interfacial fracture resistance. The first objective of this study was to determine the interfacial toughness of bonded bilayer ceramics using two different approaches. The results indicate that the short-bar chevron-notch test and a controlled-flaw microtensile test can induce interfacial failure that represents true bonding quality. The second objective of this study was to test the hypothesis that residual stresses estimated from an indentation technique are not significantly different from residual stresses that are calculated based on fractography and flexural strength. The indentation technique may be useful as a simplified method to determine residual stresses in bilayer dental ceramics. The results of this study demonstrate that there is no significant difference in mean residual stresses determined from the two techniques. Because of relationship between residual stresses and apparent interfacial toughness, estimates of residual stresses can now be estimated more rapidly by measuring the apparent interfacial toughness of

  9. Theoretical Investigation of Influence of Mechanical Stress on Magnetic Properties of Ferromagnetic/Antiferromagnetic Bilayers Deposited on Flexible Substrates

    Institute of Scientific and Technical Information of China (English)

    Yu-Hao Bai; Xia Wang; Lin-Ping Mu; Xiao-Hong Xu

    2016-01-01

    Effect of mechanical stress on magnetic properties of an exchange-biased ferromagnetic/antiferromagnetic bilayer deposited on a flexible substrate is investigated.The hysteresis loops with different magnitudes and orientations of the stress can be classified into three types.The corresponding physical conditions for each type of the loop are deduced based on the principle of minimal energy.The equation of the critical stress is derived,which can judge whether the loops show hysteresis or not.Numerical calculations suggest that except for the magnitude of the mechanical stress,the relative orientation of the stress is also an important factor to tune the exchange bias effect.

  10. Relation between interfacial structure and mechanical properties in AlN/TiN bilayers investigated by EXAFS

    Energy Technology Data Exchange (ETDEWEB)

    Ersen, O. [Equipe de Recherche Mecanique, Materiaux et Procedes de Fabrication, 61, rue Albert Camus, F-68093 Mulhouse (France)]. E-mail: ovidiu.ersen@ipcms.u-strasbg.fr; Tuilier, M.-H. [Equipe de Recherche Mecanique, Materiaux et Procedes de Fabrication, 61, rue Albert Camus, F-68093 Mulhouse (France); Thobor-Keck, A. [Centre de Recherche sur les Ecoulements les Surfaces et les Transferts (UMR CNRS 6000), ITSFC, 4, place Tharradin, BP 71427, F-25211 Montbeliard (France); Rousselot, C. [Centre de Recherche sur les Ecoulements les Surfaces et les Transferts (UMR CNRS 6000), ITSFC, 4, place Tharradin, BP 71427, F-25211 Montbeliard (France); Cortes, R. [Laboratoire de Physique de la Matiere Condensee (UMR CNRS 7643), Ecole Polytechnique, F-91128 Palaiseau cedex (France)

    2005-06-01

    The relation between the mechanical properties and the structure of AlN/TiN bilayers prepared by reactive magnetron sputtering in the 600 nm range is investigated. Al and Ti K-edge extended X-ray absorption fine structure is used in order to determine the local order around Al and Ti by comparison with 300 nm thick AlN and TiN single layers. The use of this powerful local probe allows the evidence of intermixing between AlN and TiN deposited layers, which is suggested by glow discharge optical emission spectroscopy experiments. The effect of ionic bombardment applied at various steps of the deposition process is studied. The ionic bombardment applied during the deposit induces substantial changes in the absorption spectra that are assigned to a decrease of intermixing and an improvement of local order. Simulations of (Al, Ti)N ternary alloys Al and Ti K-edge absorption spectra for increasing mean occupation factors C {sub Ti} (C {sub Al}) of Ti(Al) substituting Al(Ti) in hexagonal AlN (cubic TiN) lattice are performed in order to determine the initial parameters for the fit of the experimental data. The refinements performed by using FEFFIT software demonstrate that an ionic bombardment applied during the deposition phase results in a significant reduction of the number of Al-Ti pairs within the bilayer and an improvement of the local order around Ti and Al, which is quantified by a decrease of the Debye-Waller parameters. This structural evolution is tentatively correlated with the improvement of mechanical properties of the bilayers.

  11. Fractal butterflies of chiral fermions in bilayer graphene: Phase transitions and emergent properties

    Science.gov (United States)

    Ghazaryan, Areg; Chakraborty, Tapash

    2015-12-01

    We have studied the influence of electron-electron interaction on the fractal butterfly spectrum of Dirac fermions in biased bilayer graphene in the fractional quantum Hall effect (FQHE) regime. We demonstrate that the butterfly spectrum exhibits remarkable phase transitions between the FQHE gap and the butterfly gap for chiral electrons in bilayer graphene, when the periodic potential strength or the bias voltage is varied. We also find that, in addition to those phase transitions, by varying the bias voltage one can effectively control the periodic potential strength experienced by the electrons. The electron-electron interaction causes the butterfly spectrum to exhibit new gaps inside the Bloch sub-bands not found in the single-particle case. We expect that both the observed phase transition and other new features in the butterfly spectrum of interacting Dirac fermions will be of great interest to researchers from diverse fields.

  12. Magnetic properties dependence on the coupled effects of magnetic fields on the microstructure of as-deposited and post-annealed Co/Ni bilayer thin films

    Energy Technology Data Exchange (ETDEWEB)

    Franczak, Agnieszka [LISM, Universite de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France); Department of Materials Science, Katholieke Universiteit Leuven, 3001 Leuven (Belgium); Levesque, Alexandra, E-mail: alexandra.levesque@univ-reims.fr [LISM, Universite de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France); Coïsson, Marco [Electromagnetism Division, Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Li, Donggang [LISM, Universite de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France); Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, 110004 Shenyang (China); Barrera, Gabriele [Electromagnetism Division, Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Università di Torino, Dipartimento di Chimica, 10125 Torino (Italy); Celegato, Federica [Electromagnetism Division, Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Wang, Qiang [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, 110004 Shenyang (China); Tiberto, Paola [Electromagnetism Division, Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Chopart, Jean-Paul [LISM, Universite de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2 (France)

    2014-12-15

    Magnetic films and multilayers are the focus of much attention motivated mainly by their wide range of applications, such as magnetic data storage devices and sensors. The magnetic multilayer structures are normally prepared through physical means of deposition, as molecular beam epitaxy (MBE) or sputtering. However, there are already examples of materials produced by electrochemical routes, which share with the other deposition techniques a high sensitivity of magnetic and transport properties of the samples on their crystallographic and chemical structure. In addition, electrochemical deposition allows growing structures with high aspect ratio, which are not possible to obtain by MBE deposition followed by lithographic processes. The present work investigates the Co/Ni bilayered nanocrystalline films produced through the temperature-elevated electrochemical deposition, and modified by annealing carried out also under an external magnetic field. The results indicate an increase of the coercive field of deposited Co/Ni bilayers, when the electrodeposition process was conducted under magnetic field of 1 T. The annealing processing caused further remarkable increase of the coercive field of as-prepared bilayers that has been preserved under magnetic annealing conditions. The magnetic properties are discussed in terms of samples microstructure. In as-prepared samples the in-plane magnetization was observed, while high temperature treatment, causing microstructural changes in the film, resulted also in appearance of a small component of magnetization oriented perpendicularly to the films’ plane that could have been observed by MFM analysis. The induced perpendicular magnetization component in the post-annealed samples was a result of the magnetic field applied in the perpendicular direction to the samples’ surface during annealing treatment. - Highlights: • Co deposits were obtained at high electrolyte temperature under applied B-field. • The

  13. Transport properties of monolayer and bilayer graphene supported by hexagonal boron nitride

    Science.gov (United States)

    Li, Jing; Zou, Ke; Seiwell, Donald; Zhu, Jun

    2013-03-01

    We present transport studies on hexagonal boron nitride (h-BN) supported monolayer and bilayer graphene. Following the method introduced by Dean et al, we first exfoliate thin sheets of h-BN (15-20 nm) to SiO2/Si substrate then align and transfer exfoliated graphene flakes onto the h-BN sheets. E-beam lithography is used to process the samples into Hall bar devices. We find that current annealing at low temperature can increase the mobility of as-fabricated devices but often introduces large density inhomogeneity at the same time. AFM images of annealed devices reveal the limitations of this technique. In comparison, thermal annealing is much more reliable in improving the sample quality. Bilayer devices annealed in a flow of Ar/H2 at 450C for 5 hours show high mobility of 30,000 cm2/Vs at low temperature. We observe high-quality Shubnikov-de Hass (SdH) oscillations and degeneracy-lifted Landau levels in these samples. We extend existing measurements of the electron and hole effective mass in bilayer graphene to lower carrier density regimes and discuss the implications of the results. Department of Applied Physics, Yale University

  14. Comparative Study of Monolayer and Bilayer Epitaxial Graphene Field-Effect Transistors on SiC Substrates

    Institute of Scientific and Technical Information of China (English)

    Ze-Zhao He; Ke-Wu Yang; Cui Yu; Qing-Bin Liu; Jing-Jing Wang; Xu-Bo Song; Ting-Ting Han

    2016-01-01

    Monolayer and bilayer graphenes have generated tremendous excitement as the potentially useful electronic materials due to their unique features.We report on monolayer and bilayer epitaxial graphene field-effect transistors (GFETs) fabricated on SiC substrates.Compared with monolayer GFETs,the bilayer GFETs exhibit a significant improvement in dc characteristics,including increasing current density IDS,improved transconductance gm,reduced sheet resistance Ron,and current saturation.The improved electrical properties and tunable bandgap in the bilayer graphene lead to the excellent dc performance of the bilayer GFETs.Furthermore,the improved dc characteristics enhance a better rf performance for bilayer graphene devices,demonstrating that the quasifree-standing bilayer graphene on SiC substrates has a great application potential for the future graphene-based electronics.

  15. Transition metal chalcogenides: ultrathin inorganic materials with tunable electronic properties.

    Science.gov (United States)

    Heine, Thomas

    2015-01-20

    CONSPECTUS: After the discovery of graphene and the development of powerful exfoliation techniques, experimental preparation of two-dimensional (2D) crystals can be expected for any layered material that is known to chemistry. Besides graphene and hexagonal boron nitride (h-BN), transition metal chalcogenides (TMC) are among the most studied ultrathin materials. In particular, single-layer MoS2, a direct band gap semiconductor with ∼1.9 eV energy gap, is popular in physics and nanoelectronics, because it nicely complements semimetallic graphene and insulating h-BN monolayer as a construction component for flexible 2D electronics and because it was already successfully applied in the laboratory as basis material for transistors and other electronic and optoelectronic devices. Two-dimensional crystals are subject to significant quantum confinement: compared with their parent layered 3D material, they show different structural, electronic, and optical properties, such as spontaneous rippling as free-standing monolayer, significant changes of the electronic band structure, giant spin-orbit splitting, and enhanced photoluminescence. Most of those properties are intrinsic for the monolayer and already absent for two-layer stacks of the same 2D crystal. For example, single-layer MoS2 is a direct band gap semiconductor with spin-orbit splitting of 150 meV in the valence band, while the bilayer of the same material is an indirect band gap semiconductor without observable spin-orbit splitting. All these properties have been observed experimentally and are in excellent agreement with calculations based on density-functional theory. This Account reports theoretical studies of a subgroup of transition metal dichalcogenides with the composition MX2, with M = Mo, or W and X = Se or S, also referred to as "MoWSeS materials". Results on the electronic structure, quantum confinement, spin-orbit coupling, spontaneous monolayer rippling, and change of electronic properties in the

  16. Synthesis and microstructural studies of annealed Cu(2)O/Cu(x)S bilayer as transparent electrode material for photovoltaic and energy storage devices.

    Science.gov (United States)

    Taleatu, B A; Arbab, E A A; Omotoso, E; Mola, G T

    2014-10-01

    Cu2 O thin film and a transparent bilayer have been fabricated by electrodeposition method. The growths were obtained in potentiostatic mode with gradual degradation of anodic current. X-ray diffraction (XRD) study showed that the bilayer is polycrystalline and it possesses mixture of different crystallite phases of copper oxides. Surface morphology of the films was investigated by scanning electron microscopy (SEM). The SEM images revealed that the films were uniformly distributed and the starting material (Cu2 O) had cubical structure. Grains agglomeration and crystallinity were enhanced by annealing. Optical studies indicated that all the samples have direct allowed transition. Energy band gap of the bilayer film was reduced by annealing treatment thus corroborating quantum confinement upshot. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

  17. The use of virtual ground to control transmembrane voltages and measure bilayer currents in serial arrays of droplet interface bilayers

    Science.gov (United States)

    Sarles, Stephen A.

    2013-09-01

    The droplet interface bilayer (DIB) is a simple technique for constructing a stable lipid bilayer at the interface of two lipid-encased water droplets submerged in oil. Networks of DIBs formed by connecting more than two droplets constitute a new form of modular biomolecular smart material, where the transduction properties of a single lipid bilayer can affect the actions performed at other interface bilayers in the network via diffusion through the aqueous environments of shared droplet connections. The passive electrical properties of a lipid bilayer and the arrangement of droplets that determine the paths for transport in the network require specific electrical control to stimulate and interrogate each bilayer. Here, we explore the use of virtual ground for electrodes inserted into specific droplets in the network and employ a multichannel patch clamp amplifier to characterize bilayer formation and ion-channel activity in a serial DIB array. Analysis of serial connections of DIBs is discussed to understand how assigning electrode connections to the measurement device can be used to measure activity across all lipid membranes within a network. Serial arrays of DIBs are assembled using the regulated attachment method within a multi-compartment flexible substrate, and wire-type electrodes inserted into each droplet compartment of the substrate enable the application of voltage and measurement of current in each droplet in the array.

  18. Failure modes and fracture origins of porcelain veneers on bilayer dental crowns.

    Science.gov (United States)

    Liu, Yihong; Liu, Guanghua; Wang, Yong; Shen, James Zhijian; Feng, Hailan

    2014-01-01

    The aims of this study were to determine the fracture origins and crack paths in the porcelain of clinically failed bilayer ceramic restorations and to reveal the correlation between the porcelain failures and material properties. Three clinically failed crowns of each material (bilayer zirconia crowns, galvano-ceramic crowns, and porcelain-fused-to-metal crowns) were collected and underwent failure analysis. The fractures found in porcelain veneers showed several characteristics including wear, Hertzian cone crack, chipping off, and delamination. The results indicated that the fracture origins and features of the porcelain in bilayer ceramic restorations might be affected by the rigidity of core materials and thickness of copings.

  19. Hydrogenated bilayer wurtzite SiC nanofilms: a two-dimensional bipolar magnetic semiconductor material.

    Science.gov (United States)

    Yuan, Long; Li, Zhenyu; Yang, Jinlong

    2013-01-14

    Recently, a new kind of spintronics material, bipolar magnetic semiconductors (BMS), has been proposed. The spin polarization of BMS can be conveniently controlled by a gate voltage, which makes it very attractive in device engineering. Now, the main challenge is finding more BMS materials. In this article, we propose that hydrogenated wurtzite SiC nanofilm is a two-dimensional BMS material. Its BMS character is very robust under the effect of strain, substrate or even a strong electric field. The proposed two-dimensional BMS material paves the way to use this promising new material in an integrated circuit.

  20. Electronic, Vibrational and Thermoelectric Properties of Two-Dimensional Materials

    Science.gov (United States)

    Wickramaratne, Darshana

    The discovery of graphene's unique electronic and thermal properties has motivated the search for new two-dimensional materials. Examples of these materials include the layered two-dimensional transition metal dichalcogenides (TMDC) and metal mono-chalcogenides. The properties of the TMDCs (eg. MoS 2, WS2, TaS2, TaSe2) and the metal mono-chalcogenides (eg. GaSe, InSe, SnS) are diverse - ranging from semiconducting, semi-metallic and metallic. Many of these materials exhibit strongly correlated phenomena and exotic collective states such as exciton condensates, charge density waves, Lifshitz transitions and superconductivity. These properties change as the film thickness is reduced down to a few monolayers. We use first-principles simulations to discuss changes in the electronic and the vibrational properties of these materials as the film thickness evolves from a single atomic monolayer to the bulk limit. In the semiconducting TMDCs (MoS2, MoSe2, WS2 and WSe2) and monochalcogenides (GaS, GaSe, InS and InSe) we show confining these materials to their monolayer limit introduces large band degeneracies or non-parabolic features in the electronic structure. These changes in the electronic structure results in increases in the density of states and the number of conducting modes. Our first-principles simulations combined with a Landauer approach show these changes can lead to large enhancements up to an order of magnitude in the thermoelectric performance of these materials when compared to their bulk structure. Few monolayers of the TMDCs can be misoriented with respect to each other due to the weak van-der-Waals (vdW) force at the interface of two monolayers. Misorientation of the bilayer semiconducting TMDCs increases the interlayer van-der-Waals gap distance, reduces the interlayer coupling and leads to an increase in the magnitude of the indirect bandgap by up to 100 meV compared to the registered bilayer. In the semi-metallic and metallic TMDC compounds (TiSe2, Ta

  1. Modification of photosensing property of CdS–Bi{sub 2}S{sub 3} bi-layer by thermal annealing and swift heavy ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shaikh, Shaheed U.; Siddiqui, Farha Y. [Thin Film and Nanotechnology Laboratory, Department of Physics (India); Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (India); Singh, Fouran; Kulriya, Pawan K. [Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110 067 (India); Phase, D.M. [UGC DAE Consortium for Scientific Research, Khandwa Road, Indore 452017 (India); Sharma, Ramphal, E-mail: ramphalsharma@yahoo.com [Thin Film and Nanotechnology Laboratory, Department of Physics (India); Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (India)

    2016-02-01

    The CdS–Bi{sub 2}S{sub 3} bi-layer thin films have been deposited on Indium Tin Oxide (ITO) glass substrates at room temperature by Chemical Bath Deposition Technique (CBD) and bi-layer thin films were annealed in air atmosphere for 1 h at 250 {sup °}C. The air annealed sample was irradiated using Au{sup 9+} ions at the fluence 5 × 10{sup 11} ion/cm{sup 2} with 120 MeV energy. Effects of Swift Heavy Ion (SHI) irradiation on CdS–Bi{sub 2}S{sub 3} bi-layer thin films were studied. The results are explained on the basis annealing and high electronic excitation, using X-ray diffraction (XRD), Selective Electron Area Diffraction (SEAD), Atomic Force Microscopy (AFM), Raman Spectroscopy, UV spectroscopy and I–V characteristics. The photosensing property after illumination of visible light over the samples is studied. These as-deposited, annealed and irradiated bi-layer thin films are used to sense visible light at room temperature. - Graphical abstract: Schematic illustration of CdS–Bi{sub 2}S{sub 3} bi-layer thin film (a) As-deposited (b) Annealed (c) irradiated sample respectively (d) Model of bi-layer photosensor device (e) Graph of illumination intensity verses photosensitivity. - Highlights: • CdS–Bi{sub 2}S{sub 3} bi-layer thin film prepared at room temperature. • Irradiated using Au{sup 9+} ions at the fluence of 5 × 10{sup 11} ion/cm{sup 2} with 120 MeV energy. • Study of modification induced by irradiations. • Study of Photosensitivity after annealing and irradiation.

  2. Molecular Dynamics of Lipid Bilayers

    Science.gov (United States)

    1989-08-09

    The aim of this work is to study, by molecular dynamics simulations, the properties of lipid bilayers. We have applied the vectorizable, order-N...fast angle-dependent force/potential algorithms to treat angle bending and torsion. Keywords: Molecular dynamics , Lipid bilayers.

  3. Influence of an Fe cap layer on the structural and magnetic properties of Fe49Pt51/Fe bi-layers

    Institute of Scientific and Technical Information of China (English)

    Duan Chao-Yang; Ma Bin; Wei Fu-Lin; Zhang zong-Zhi; Jin Qing-Yuan

    2009-01-01

    The influences of an Fe cap layer on the structural and magnetic properties of FePt/Fe bi-layers are investigated.Compared with single FePt alloy films, a thin Fe layer can affect the crystalline orientation and improve the chemical ordering of L10 FePt films. Moreover, the coercivity increases when a thin Fe layer covers the FePt layer. Beyond a critical thickness, however, the Fe cover layer quickens the magnetization reversal of Fe49Pt51/Fe bi-layers by their exchange coupling.

  4. Nanoscale magnetism and novel electronic properties of a bilayer bismuth(111) film with vacancies and chemical doping.

    Science.gov (United States)

    Sahoo, M P K; Zhang, Yajun; Wang, Jie

    2016-07-27

    Magnetically doped topological insulators (TIs) exhibit several exotic phenomena including the magnetoelectric effect and quantum anomalous Hall effect. However, from an experimental perspective, incorporation of spin moment into 3D TIs is still challenging. Thus, instead of 3D TIs, the 2D form of TIs may open up new opportunities to induce magnetism. Based on first principles calculations, we demonstrate a novel strategy to realize robust magnetism and exotic electronic properties in a 2D TI [bilayer Bi(111) film: abbreviated as Bi(111)]. We examine the magnetic and electronic properties of Bi(111) with defects such as bismuth monovacancies (MVs) and divacancies (DVs), and these defects decorated with 3d transition metals (TMs). It has been observed that the MV in Bi(111) can induce novel half metallicity with a net magnetic moment of 1 μB. The origin of half metallicity and magnetism in MV/Bi(111) is further explained by the passivation of the σ-dangling bonds near the defect site. Furthermore, in spite of the nonmagnetic nature of DVs, the TMs (V, Cr, Mn, and Fe) trapped at the 5/8/5 defect structure of DVs can not only yield a much higher spin moment than those trapped at the MVs but also display intriguing electronic properties such as metallic, semiconducting and spin gapless semiconducting properties. The predicted magnetic and electronic properties of TM/DV/Bi(111) systems are explained through density of states, spin density distribution and Bader charge analysis.

  5. Electrical properties of bilayer graphene synthesized using surface wave microwave plasma techniques at low temperature

    Science.gov (United States)

    Yamada, Takatoshi; Kato, Hiromitsu; Okigawa, Yuki; Ishihara, Masatou; Hasegawa, Masataka

    2017-01-01

    Bilayer graphene was synthesized at low temperature using surface wave microwave plasma techniques where poly(methyl metacrylate) (PMMA) and methane (CH4) were used as carbon sources. Temperature-dependent Hall effect measurements were carried out in a helium atmosphere. Sheet resistance, sheet carrier density and mobility showed weak temperature dependence for graphene from PMMA, and the highest carrier mobility is 740 cm2 V-1 s-1. For graphene from CH4, tunneling of the domain boundary limited carrier transport. The difference in average domain size was determined by Raman signal maps. In addition, residuals of PMMA were detected on graphene from PMMA. The low sheet resistances of graphene synthesized at a temperature of 280 °C using plasma techniques were explained by the PMMA related residuals rather than the domain sizes.

  6. Optical stretching as a tool to investigate the mechanical properties of lipid bilayers.

    Science.gov (United States)

    Solmaz, Mehmet E; Sankhagowit, Shalene; Biswas, Roshni; Mejia, Camilo A; Povinelli, Michelle L; Malmstadt, Noah

    2013-10-07

    Measurements of lipid bilayer bending modulus by various techniques produce widely divergent results. We attempt to resolve some of this ambiguity by measuring bending modulus in a system that can rapidly process large numbers of samples, yielding population statistics. This system is based on optical stretching of giant unilamellar vesicles (GUVs) in a microfluidic dual-beam optical trap (DBOT). The microfluidic DBOT system is used here to measure three populations of GUVs with distinct lipid compositions. We find that gel-phase membranes are significantly stiffer than liquid-phase membranes, consistent with previous reports. We also find that the addition of cholesterol does not alter the bending modulus of membranes composed of a monounsaturated phospholipid.

  7. Fundamentals of semiconductors physics and materials properties

    CERN Document Server

    Yu, Peter Y

    2005-01-01

    Provides detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors. This textbook emphasizes understanding the physical properties of Si and similar tetrahedrally coordinated semiconductors and features an extensive collection of tables of material parameters, figures, and problems.

  8. Properties of easy-plane/perpendicular magnetic anisotropy bilayers with varied interlayer exchange coupling

    Science.gov (United States)

    Fallarino, Lorenzo; Sluka, Volker; Kardasz, Bartek; Pinarbasi, Mustafa; Kent, Andrew D.

    We explore the possibility of an easy-cone ground state in coupled easy plane/easy axis magnetic bilayers. The samples consist of a Co/Ni multilayer with perpendicular magnetic anisotropy and a CoFe layer with easy-plane anisotropy separated by a variable thickness Ru layer. Using ferromagnetic resonance spectroscopy, we characterize the magnetic behavior of the coupled thin films for different Ru thicknesses by determining the resonance fields for both the acoustic and optical FMR modes. In particular, we observe a gap in the resonance field opening up between the two modes in angular-dependent FMR, which is direct evidence for the presence of interlayer coupling. Quantitative comparisons with a theoretical model indicate that by varying the Ru thickness the coupling strength can be tuned continuously from ferromagnetic to the anti-ferromagnetic. These results are consistent with a canted magnetic ground state in zero field, a state of interest for applications in spin-torque devices, such as current tunable spin-torque oscillators. Supported by NSF-DMR1309202 and Spin-Transfer Technologies Inc.

  9. FRACTURE OF AMORPHOUS BILAYER RIBBON

    NARCIS (Netherlands)

    Ocelik, Vaclav; DUHAJ, P; CSACH, K; MISKUF, J; BENGUS, VZ

    On the basis of measuring the mechanical properties and observing the fracture surface of an amorphous bilayer ribbon some partial conclusions on the mechanical quality of the bimetal boundary were drawn.

  10. Structural impact of cations on lipid bilayer models: nanomechanical properties by AFM-force spectroscopy.

    Science.gov (United States)

    Redondo-Morata, Lorena; Giannotti, Marina I; Sanz, Fausto

    2014-02-01

    Atomic Force Microscopy (AFM) has become an invaluable tool for studying the micro- and nanoworlds. As a stand-alone, high-resolution imaging technique and force transducer, it defies most other surface instrumentation in ease of use, sensitivity and versatility. The main strength of AFM relies on the possibility to operate in an aqueous environment on a wide variety of biological samples, from single molecules - DNA or proteins - to macromolecular assemblies like biological membranes. Understanding the effect of mechanical stress on membranes is of primary importance in biophysics, since cells are known to perform their function under a complex combination of forces. In the later years, AFM-based Force-Spectroscopy (AFM-FS) has provided a new vista on membrane mechanics in a confined area within the nanometer realm, where most of the specific molecular interactions take place. Lipid membranes are electrostatically charged entities that physiologically coexist with electrolyte solutions. Thus, specific interactions with ions are a matter of considerable interest. The distribution of ions in the solution and their interaction with the membranes are factors that substantially modify the structure and dynamics of the cell membranes. Furthermore, signaling processes are modified by the membrane capability of retaining ions. Supported Lipid Bilayers (SLBs) are a versatile tool to investigate phospholipid membranes mimicking biological surfaces. In the present contribution, we review selected experiments on the mechanical stability of SLBs as models of lipid membranes by means of AFM-FS, with special focus on the effect of cations and ionic strength in the overall nanomechanical stability.

  11. Membrane fluidity and the surface properties of the lipid bilayer: ESR experiment and computer simulation.

    Science.gov (United States)

    Man, Dariusz; Olchawa, Ryszard; Kubica, Krystian

    2010-09-01

    Penetration of the liposome membranes formed in the gel phase from DPPC (DPPC liposomes) and in the liquid-crystalline phase from egg yolk lecithin (EYL liposomes) by the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and 16 DOXYL (2-ethyl-2-(15-methoxy-oxopentadecyl)-4,4-dimethyl-3-oxazolidinyloxy) spin probes has been investigated. The penetration process was followed by 120 hours at 24(0)C, using the electron spin resonance (ESR) method. The investigation of the kinetics of the TEMPO probe building into the membranes of both types of liposomes revealed differences appearing 30 minutes after the start of the experiment. The number of TEMPO particles built into the EYL liposome membranes began to clearly rise, aiming asymptotically to a constant value after about 100 minutes, whereas the number of the TEMPO particles built into the DPPC liposome membranes was almost constant in time. The interpretation of the obtained experimental results was enriched with those of computer simulation, following the behavior of the polar heads (dipoles) of the lipid particles forming a lipid layer due to the change in the value of the model parameter, k, determining the mobility of the dipoles. The possibility of the formation of an irregular ordering of the polar part of lipid membranes was proved, which leads to the appearance of spaces filled with of water for k > 0.4. The appearance of these defects enables the penetration of the bilayer by the TEMPO particles. The limited mobility of lipid polar heads (k < 0.2) prevents the appearance of such areas facilitating the penetration of the lipid membrane by alien particles in the gel phase.

  12. Specific heat of twisted bilayer graphene: Engineering phonons by atomic plane rotations

    Energy Technology Data Exchange (ETDEWEB)

    Nika, Denis L. [E. Pokatilov Laboratory of Physics and Engineering of Nanomaterials, Department of Physics and Engineering, Moldova State University, Chisinau MD-2009, Republic of Moldova (Moldova, Republic of); Nano-Device Laboratory, Department of Electrical Engineering and Materials Science and Engineering Program, Bourns College of Engineering, University of California—Riverside, Riverside, California, 92521 (United States); Cocemasov, Alexandr I. [E. Pokatilov Laboratory of Physics and Engineering of Nanomaterials, Department of Physics and Engineering, Moldova State University, Chisinau MD-2009, Republic of Moldova (Moldova, Republic of); Balandin, Alexander A., E-mail: balandin@ee.ucr.edu [Nano-Device Laboratory, Department of Electrical Engineering and Materials Science and Engineering Program, Bourns College of Engineering, University of California—Riverside, Riverside, California, 92521 (United States)

    2014-07-21

    We have studied the phonon specific heat in single-layer, bilayer, and twisted bilayer graphene. The calculations were performed using the Born-von Karman model of lattice dynamics for intralayer atomic interactions and spherically symmetric interatomic potential for interlayer interactions. We found that at temperature T < 15 K, specific heat varies with temperature as T{sup n}, where n = 1 for graphene, n = 1.6 for bilayer graphene, and n = 1.3 for the twisted bilayer graphene. The phonon specific heat reveals an intriguing dependence on the twist angle in bilayer graphene, which is particularly pronounced at low temperature. The results suggest a possibility of phonon engineering of thermal properties of layered materials by twisting the atomic planes.

  13. Magnetic and electrical properties of CuFe2O4/BaTiO3 bilayer thin films

    Science.gov (United States)

    Yoon, Dong Jin; Hwang, Sung-Ok; Koo, Chang Young; Lee, Jai-Yeoul; Lee, Hee Young; Ryu, Jungho

    2013-04-01

    The magnetic and the electrical properties of CuFe2O4/BaTiO3 thin films grown on highly-textured Pt(111)/TiO2/SiO2/Si(100) substrates were studied. Sintered BaTiO3 and CuFe2O4 pellets prepared by the conventional mixed oxide process were used as targets during deposition by using the ion-beam sputtering and the pulsed laser deposition techniques. The film structure is of a bilayer type, where the BaTiO3 layer lies underneath the CuFe2O4 layer. The CuFe2O4/BaTiO3 film stack was then annealed at a temperature between 700 and 750 °C, followed by either FC (fast-cooling) or SC (slow-cooling) treatment. The ferroelectric and the electrical properties were measured using a ferroelectric test system, a digital multimeter, and an impedance analyzer. The Magnetic hysteresis (M-H) behavior at room temperature was measured using a vibration sample magnetometer (VSM), and the maximum saturation magnetization ( M s ) and coercivity ( H c ) values were 700 emu/cm3 and 325 Oe, respectively.

  14. Control of the optical and crystalline properties of TiO{sub 2} in visible-light active TiO{sub 2}/TiN bi-layer thin-film stacks

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Wilson; Fakhouri, Houssam; Pulpytel, Jerome; Arefi-Khonsari, Farzaneh [Laboratoire de Genie des Procedes Plasma et Traitement de Surface, Universite Pierre et Marie Curie, 11 Rue Pierre et Marie Curie, Paris 75231 (France)

    2012-01-15

    Multi-layered thin films of TiO{sub 2} and TiN were created by rf reactive magnetron sputtering, and their crystalline, optical, and photoelectrochemical properties were measured. The overall composition of the films (TiO{sub 2}-to-TiN ratio) was kept constant with the height of each film. The number of layers and thickness of each layer was controlled to create bi-layer thin films that were composed of: 9 bi-layers, 18 bi-layers, 27 bi-layers, 36 bi-layers, and 45 bi-layers. XRD patterns were observed for each film after annealing to measure the grain size and composition of anatase and rutile as a function of temperature. It was found that the phase-transition temperature is able to be substantially controlled (between 550 deg. C and 850 deg. C) for the anatase to rutile transition by varying the number of layers/thickness of each layer. In addition, bi-layer stacking significantly affected the film's optical properties by lowering the bandgap into the visible-light region, and also showed up to three times the improvement in photoelectrochemical performance under uv and visible irradiation. Overall, bi-layer stacking of TiO{sub 2}/TiN films has shown a unique and highly desirable control over several important physical characteristics that can be beneficial for many applications, such as high-temperature sensors and optoelectronic devices.

  15. Nanoparticle-lipid bilayer interactions studied with lipid bilayer arrays

    Science.gov (United States)

    Lu, Bin; Smith, Tyler; Schmidt, Jacob J.

    2015-04-01

    The widespread environmental presence and commercial use of nanoparticles have raised significant health concerns as a result of many in vitro and in vivo assays indicating toxicity of a wide range of nanoparticle species. Many of these assays have identified the ability of nanoparticles to damage cell membranes. These interactions can be studied in detail using artificial lipid bilayers, which can provide insight into the nature of the particle-membrane interaction through variation of membrane and solution properties not possible with cell-based assays. However, the scope of these studies can be limited because of the low throughput characteristic of lipid bilayer platforms. We have recently described an easy to use, parallel lipid bilayer platform which we have used to electrically investigate the activity of 60 nm diameter amine and carboxyl modified polystyrene nanoparticles (NH2-NP and COOH-NP) with over 1000 lipid bilayers while varying lipid composition, bilayer charge, ionic strength, pH, voltage, serum, particle concentration, and particle charge. Our results confirm recent studies finding activity of NH2-NP but not COOH-NP. Detailed analysis shows that NH2-NP formed pores 0.3-2.3 nm in radius, dependent on bilayer and solution composition. These interactions appear to be electrostatic, as they are regulated by NH2-NP surface charge, solution ionic strength, and bilayer charge. The ability to rapidly measure a large number of nanoparticle and membrane parameters indicates strong potential of this bilayer array platform for additional nanoparticle bilayer studies.The widespread environmental presence and commercial use of nanoparticles have raised significant health concerns as a result of many in vitro and in vivo assays indicating toxicity of a wide range of nanoparticle species. Many of these assays have identified the ability of nanoparticles to damage cell membranes. These interactions can be studied in detail using artificial lipid bilayers, which

  16. Spin-crossover materials properties and applications

    CERN Document Server

    Halcrow, Malcolm A

    2013-01-01

    The phenomenon of spin-crossover has a large impact on the physical properties of a solid material, including its colour, magnetic moment, and electrical resistance. Some materials also show a structural phase change during the transition. Several practical applications of spin-crossover materials have been demonstrated including display and memory devices, electrical and electroluminescent devices, and MRI contrast agents. Switchable liquid crystals, nanoparticles, and thin films of spin-crossover materials have also been achieved. Spin-Crossover Materials: Properties and Applicat

  17. Transport properties of AB stacked (Bernal) bilayer graphene on and without substrate within 2- and 4-band approximations

    Energy Technology Data Exchange (ETDEWEB)

    Gusynin, V. P., E-mail: vgusynin@bitp.kiev.ua; Sharapov, S. G., E-mail: sharapov@bitp.kiev.ua [Bogolyubov Institute for Theoretical Physics, Kiev, 03680 Ukraine (Ukraine); Reshetnyak, A. A., E-mail: reshet@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

    2015-10-27

    We present the results of the calculations of longitudinal and Hall conductivities of AB-stacked bilayer graphene as a function of frequency, finite chemical potential, temperature both with and without magnetic fields on a base of 2- and 4-band effective models. The limited cases of the conductivities for direct current are derived. The relations being important for optoelectronic among Hall conductivities and Faraday, Kerr angles in the AB-bilayers samples in the electric and magnetic fields when the radiation passes across bilayer sheets on different kinds a substrate are obtained.

  18. Tailoring of epoxy material properties

    NARCIS (Netherlands)

    Nakka, J.S.

    2010-01-01

    This research work is aimed to understand the effect of resin chemistry on the physical properties (e.g. moduli, viscoelasticity, moisture uptake, coefficient of thermal expansion) of cured aromatic epoxy-amine thermoset resins. This understanding will result into a good first approximation of the f

  19. Fundamental properties of semiconductor materials, and material performance in detectors

    Science.gov (United States)

    Casper, K. J.

    1973-01-01

    Procedures for determining fundamental properties of semiconductor materials, their performance as radiation detectors, and their service life as such detectors are given. Relationships were established between the minority carrier lifetime in the bulk of the material and the charge collection efficiency of the detector.

  20. Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations.

    Science.gov (United States)

    Zhong, Hongxia; Quhe, Ruge; Wang, Yangyang; Ni, Zeyuan; Ye, Meng; Song, Zhigang; Pan, Yuanyuan; Yang, Jinbo; Yang, Li; Lei, Ming; Shi, Junjie; Lu, Jing

    2016-01-01

    Although many prototype devices based on two-dimensional (2D) MoS2 have been fabricated and wafer scale growth of 2D MoS2 has been realized, the fundamental nature of 2D MoS2-metal contacts has not been well understood yet. We provide a comprehensive ab initio study of the interfacial properties of a series of monolayer (ML) and bilayer (BL) MoS2-metal contacts (metal = Sc, Ti, Ag, Pt, Ni, and Au). A comparison between the calculated and observed Schottky barrier heights (SBHs) suggests that many-electron effects are strongly suppressed in channel 2D MoS2 due to a charge transfer. The extensively adopted energy band calculation scheme fails to reproduce the observed SBHs in 2D MoS2-Sc interface. By contrast, an ab initio quantum transport device simulation better reproduces the observed SBH in 2D MoS2-Sc interface and highlights the importance of a higher level theoretical approach beyond the energy band calculation in the interface study. BL MoS2-metal contacts generally have a reduced SBH than ML MoS2-metal contacts due to the interlayer coupling and thus have a higher electron injection efficiency.

  1. Properties and characterization of modern materials

    CERN Document Server

    Altenbach, Holm

    2017-01-01

    This book focuses on robust characterization and prediction methods for materials in technical applications as well as the materials’ safety features during operation. In particular, it presents methods for reliably predicting material properties, an aspect that is becoming increasingly important as engineering materials are pushed closer and closer to their limits to boost the performance of machines and structures. To increase their engineering value, components are now designed under the consideration of their multiphysical properties and functions, which requires much more intensive investigation and characterization of these materials. The materials covered in this monograph range from metal-based groups such as lightweight alloys, to advanced high-strength steels and modern titanium alloys. Furthermore, a wide range of polymers and composite materials (e.g. with micro- and nanoparticles or fibres) is covered. The book explores methods for property prediction from classical mechanical characterization-...

  2. Design of materials with prescribed nonlinear properties

    DEFF Research Database (Denmark)

    Wang, Fengwen; Sigmund, Ole; Jensen, Jakob Søndergaard

    2014-01-01

    We systematically design materials using topology optimization to achieve prescribed nonlinear properties under finite deformation. Instead of a formal homogenization procedure, a numerical experiment is proposed to evaluate the material performance in longitudinal and transverse tensile tests un....... The numerical examples illustrate optimized materials with rubber-like behavior and also optimized materials with extreme strain-independent Poisson's ratio for axial strain intervals of εi ∈ [0.00,0.30]. © 2014 Elsevier Ltd. All rights reserved....... under finite deformation, i.e. stress-strain relations and Poisson's ratio. By minimizing errors between actual and prescribed properties, materials are tailored to achieve the target. Both two dimensional (2D) truss-based and continuum materials are designed with various prescribed nonlinear properties...

  3. Learning targeted materials properties from data

    Science.gov (United States)

    Lookman, Turab; Balachandran, Prasanna V.; Dezhen, Xue; Theiler, James; Hogden, John

    We compare several strategies using a data set of 223 M2AX family of compounds for which the elastic properties [bulk (B), shear (G), and Young's (E) modulus] have been computed using density functional theory. The strategy is decomposed into two steps: a regressor is trained to predict elastic properties in terms of elementary orbital radii of the individual components of the materials; and a selector uses these predictions to choose the next material to investigate. The ultimate goal is to obtain a material with desired elastic properties. We examine how the choice of data set size, regressor and selector impact the results.

  4. Dynamic properties of ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Grady, D.E. [Sandia National Labs., Albuquerque, NM (United States). Experimental Impact Physics Dept.

    1995-02-01

    The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis of shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.

  5. Bilayer polymer/oxide coating for electroluminescent organic semiconductors

    DEFF Research Database (Denmark)

    Tavares, Luciana

    Organic materials have been given much attention due to their intriguing properties that can be tailored via synthetic chemistry for specific applications combined with their low price and fairly straight-forward large-scale synthesis. Para-hexaphenylene (p6P) nanofibers emit polarized light...... of the fibers with oxygen. We have developed a bilayer coating that does not change significantly the p6P spectrum but strongly reduces bleaching. This bilayer coating consists of a first layer of a stable polymer (PMMA) on top of the organic nanofibers as a protecting layer for avoiding modifications of the p6...

  6. Electronic and thermoelectric properties of van der Waals materials with ring-shaped valence bands

    Science.gov (United States)

    Wickramaratne, Darshana; Zahid, Ferdows; Lake, Roger K.

    2015-08-01

    The valence band of a variety of few-layer, two-dimensional materials consist of a ring of states in the Brillouin zone. The energy-momentum relation has the form of a "Mexican hat" or a Rashba dispersion. The two-dimensional density of states is singular at or near the band edge, and the band-edge density of modes turns on nearly abruptly as a step function. The large band-edge density of modes enhances the Seebeck coefficient, the power factor, and the thermoelectric figure of merit ZT. Electronic and thermoelectric properties are determined from ab initio calculations for few-layer III-VI materials GaS, GaSe, InS, InSe, for Bi2Se3, for monolayer Bi, and for bilayer graphene as a function of vertical field. The effect of interlayer coupling on these properties in few-layer III-VI materials and Bi2Se3 is described. Analytical models provide insight into the layer dependent trends that are relatively consistent for all of these few-layer materials. Vertically biased bilayer graphene could serve as an experimental test-bed for measuring these effects.

  7. Electronic and thermoelectric properties of van der Waals materials with ring-shaped valence bands

    Energy Technology Data Exchange (ETDEWEB)

    Wickramaratne, Darshana, E-mail: darshanaw@engineering.ucsb.edu, E-mail: rlake@ece.ucr.edu; Lake, Roger K., E-mail: darshanaw@engineering.ucsb.edu, E-mail: rlake@ece.ucr.edu [Laboratory for Terahertz and Terascale Electronics, Department of Electrical and Computer Engineering, University of California, Riverside, California 92521 (United States); Zahid, Ferdows [Department of Physics and the Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China)

    2015-08-21

    The valence band of a variety of few-layer, two-dimensional materials consist of a ring of states in the Brillouin zone. The energy-momentum relation has the form of a “Mexican hat” or a Rashba dispersion. The two-dimensional density of states is singular at or near the band edge, and the band-edge density of modes turns on nearly abruptly as a step function. The large band-edge density of modes enhances the Seebeck coefficient, the power factor, and the thermoelectric figure of merit ZT. Electronic and thermoelectric properties are determined from ab initio calculations for few-layer III–VI materials GaS, GaSe, InS, InSe, for Bi{sub 2}Se{sub 3}, for monolayer Bi, and for bilayer graphene as a function of vertical field. The effect of interlayer coupling on these properties in few-layer III–VI materials and Bi{sub 2}Se{sub 3} is described. Analytical models provide insight into the layer dependent trends that are relatively consistent for all of these few-layer materials. Vertically biased bilayer graphene could serve as an experimental test-bed for measuring these effects.

  8. Magnetic materials fundamentals, products, properties, applications

    CERN Document Server

    Hilzinger, Rainer

    2013-01-01

    At a practical level, this compendium reviews the basics of soft and hard magnetic materials, discusses the advantages of the different processing routes for the exploitation of the magnetic properties and hence assists in proper, fail-safe and economic application of magnetic materials. Essential guidelines and formulas for the calculation of the magnetic and electrical properties, temperature and long-term stability of permanent magnets, of inductive components and magnetic shielding are compiled. Selected fields of application and case studies illustrate the large diversity of technical applications. Application engineers will appreciate the comprehensive compilation of the properties and detailed characteristic curves of modern soft and hard magnetic materials. Materials scientists will enjoy the presentation of the different processing routes and their impact on the magnetic properties and students will profit from the survey from the basics of magnetism down to the applications in inductive components, ...

  9. Measurement of thermal properties of PCM materials

    Energy Technology Data Exchange (ETDEWEB)

    Domanski, R.; Jaworski, M. [Warsaw Univ. of Technology (Poland). Inst. of Heat Engineering

    1994-12-31

    In the article results of measurements of thermal properties of PCM (phase change materials) and their stability are presented. These include specific heat, temperature of phase change, latent heat and enthalpy as a function of temperature. Different kind of materials were considered, especially some waxes, n-alkanes and salt hydrates. Measurements of thermal capacity of materials were performed using two techniques - standard DSC (for small samples and pure materials) and simple thermal analysis based on the measurement of temperature field in relatively big samples (about 20-50 g). Stability of thermal properties in many cycles of melting and solidification for some materials obtained in special set-up (for fast cycling) are presented. On the base of measurements mathematical formulas describing enthalpy vs. temperature for some materials were developed. These are very useful in computer simulation of thermal storage systems with PCM. (orig.)

  10. Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Rizwan Ali

    2015-05-01

    Full Text Available We investigate the optical and thermo-optical properties of amorphous TiO\\(_2\\–Al\\(_2\\O\\(_3\\ thin-film bilayers fabricated by atomic layer deposition (ALD. Seven samples of TiO\\(_2\\–Al\\(_2\\O\\(_3\\ bilayers are fabricated by growing Al\\(_2\\O\\(_3\\ films of different thicknesses on the surface of TiO\\(_2\\ films of constant thickness (100 nm. Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE\\textsuperscript{\\textregistered}. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO\\(_2\\ films. The effects of TiO\\(_2\\ surface defects on the films' thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al\\(_2\\O\\(_3\\ diffusion barrier layers. Increasing the ALD-Al\\(_2\\O\\(_3\\ thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO\\(_2\\. The thermo-optic coefficients of the 100 nm-thick ALD-TiO\\(_2\\ film and 30 nm-thick ALD-Al\\(_2\\O\\(_3\\ film in a bilayer are (0.048 \\(\\pm\\ 0.134 \\(\\times 10 ^{-4} {^\\circ}\\mathrm {C}^{-1}\\ and (0.680 \\(\\pm\\ 0.313 \\(\\times 10^{-4} {^\\circ} \\mathrm {C}^{-1}\\, respectively, at a temperature \\(T = 62 ^\\circ \\mathrm{C}\\.

  11. Optical properties of low-dimensional materials

    CERN Document Server

    Ogawa, T

    1998-01-01

    This book surveys recent theoretical and experimental studies of optical properties of low-dimensional materials. As an extended version of Optical Properties of Low-Dimensional Materials (Volume 1, published in 1995 by World Scientific), Volume 2 covers a wide range of interesting low-dimensional materials including both inorganic and organic systems, such as disordered polymers, deformable molecular crystals, dilute magnetic semiconductors, SiGe/Si short-period superlattices, GaAs quantum wires, semiconductor microcavities, and photonic crystals. There are excellent review articles by promis

  12. Design and properties of maxillofacial prosthetic materials.

    Science.gov (United States)

    Andreopoulos, A G; Theophanides, T

    1993-11-01

    Maxillofacial reconstruction by prosthetic means is a valuable contribution that medicine offers to the public. Materials design and properties are the main problems faced by scientists in this field. Materials used for intraoral prostheses are not ideal, but they have been perfected to the point of practical use. Denture resins, gold, chromium-cobalt alloys, and porcelain are widely used and produce acceptable results in the oral cavity. In this review, the properties and performance of some polymeric materials used in maxillofacial prosthetics are discussed, and new trends in research and development are also reported.

  13. Bioactive glasses materials, properties and applications

    CERN Document Server

    Ylänen, Heimo

    2011-01-01

    Due to their biocompatibility and bioactivity, bioactive glasses are used as highly effective implant materials throughout the human body to replace or repair damaged tissue. As a result, they have been in continuous use since shortly after their invention in the late 1960s and are the subject of extensive research worldwide.Bioactive glasses provides readers with a detailed review of the current status of this unique material, its properties, technologies and applications. Chapters in part one deal with the materials and mechanical properties of bioactive glass, examining topics such

  14. Synergistic effect of temperature and point defect on the mechanical properties of single layer and bi-layer graphene

    Science.gov (United States)

    Debroy, Sanghamitra; Pavan Kumar, V.; Vijaya Sekhar, K.; Acharyya, Swati Ghosh; Acharyya, Amit

    2017-10-01

    The present study reports a comprehensive molecular dynamics simulation of the effect of a) temperature (300-1073 K at intervals of every 100 K) and b) point defect on the mechanical behaviour of single (armchair and zigzag direction) and bilayer layer graphene (AA and AB stacking). Adaptive intermolecular reactive bond order (AIREBO) potential function was used to describe the many-body short-range interatomic interactions for the single layer graphene sheet. Moreover, Lennard Jones model was considered for bilayer graphene to incorporate the van der Waals interactions among the interlayers of graphene. The effect of temperature on the strain energy of single layer and bilayer graphene was studied in order to understand the difference in mechanical behaviour of the two systems. The strength of the pristine single layer graphene was found to be higher as compared to bilayer AA stacked graphene at all temperatures. It was observed at 1073 K and in the presence of vacancy defect the strength for single layer armchair sheet falls by 30% and for bilayer armchair sheet by 33% as compared to the pristine sheets at 300 K. The AB stacked graphene sheet was found to have a two-step rupture process. The strength of pristine AB sheet was found to decrease by 22% on increase of temperature from 300 K to 1073 K.

  15. Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties

    Directory of Open Access Journals (Sweden)

    Emma Werz

    2015-06-01

    Full Text Available A series of six cyanine-5-labeled oligonucleotides (LONs 10–15, each terminally lipophilized with different nucleolipid head groups, were synthesized using the recently prepared phosphoramidites 4b–9b. The insertion of the LONs within an artificial lipid bilayer, composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE, was studied by single molecule fluorescence spectroscopy and microscopy with the help of an optically transparent microfluidic sample carrier with perfusion capabilities. The incorporation of the lipo-oligonucleotides into the bilayer was studied with respect to efficiency (maximal bilayer brightness as well as stability against perfusion (final stable bilayer brightness. Attempts to correlate these parameters with the log P values of the corresponding nucleolipid head groups failed, a result which clearly demonstrates that not only the lipophilicity but mainly the chemical structure and topology of the head group is of decisive importance for the optimal interaction of a lipo-oligonucleotide with an artificial lipid bilayer. Moreover, fluorescence half-live and diffusion time values were measured to determine the diffusion coefficients of the lipo-oligonucleotides.

  16. From Microstructures to Predict Properties of Materials

    Science.gov (United States)

    Wang, Ke-Gang

    2010-03-01

    Understanding the precise and fundamental manner in which materials structures (nanostructures or microstructures) and their evolution influences properties and service lifetimes of advanced materials profoundly impacts material design and today materials design plays an increasingly important rôle in many engineering applications. Linking structures to properties and predicting properties of materials is fundamental step for materials design. First, a framework of applications of multiscale modeling to property prediction of advanced materials will be briefly presented. As an example, a methodology will be shown to link micro-scale to the continuum scale, integrating microstructure modeling with the large Thermo-Calc^ database. This paradigm was successfully applied to the case of Fe-12Ni-6Mn maraging steel. Next, methodology for integrating first-principle calculation into simulations of microstructure evolution will be reviewed. Our methods are sufficiently reliable to permit control and fabrication of quantum-dots structures, nanocrystals, and particle-reinforced nanocomposites, as well as assist in the predictive behavior of macro-scale colloids, aerosols, and other soft matter systems.

  17. Role of substrate induced electron-phonon interactions in biased graphitic bilayers

    Science.gov (United States)

    Davenport, A. R.; Hague, J. P.

    2016-08-01

    Bilayers of graphitic materials have potential applications in field effect transistors (FETs). A potential difference applied between certain ionic bilayers made from insulating graphitic materials such as BN, ZnO and AlN could reduce gap sizes, turning them into useful semiconductors. On the other hand, opening of a small semiconducting gap occurs in graphene bilayers under applied field. The aim here is to investigate to what extent substrate induced electron-phonon interactions (EPIs) modify this gap change. We examine EPIs in several lattice configurations of graphitic bilayers, using a perturbative approach. The typical effect of EPIs on the ionic bilayers is an undesirable gap widening. The size of this gap change varies considerably with lattice structure and the magnitude of the bias. When bias is larger than the non-interacting gap size, EPIs have the smallest effect on the bandgap, especially in configurations with A{{A}\\prime} and AB structures. Thus careful selection of substrate, lattice configuration and bias strength to minimise the effects of EPIs could be important for optimising the properties of electronic devices. We use parameters related to BN in this article. In practice, the results presented here are broadly applicable to other graphitic bilayers, and are likely to be qualitatively similar in metal dichalcogenide bilayers such as MoS2, which are already of high interest for their use in FETs.

  18. Exploring the Local Elastic Properties of Bilayer Membranes Using Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Pieffet, Gilles; Botero, Alonso; Peters, Günther H.J.;

    2014-01-01

    of mean force (PMF) allowed us to dissect the elastic contribution. With this information, we calculated an effective linear spring constant of 44 +/- 4 kJ.nm-2.mol-1 for the DOPC membrane, in agreement with experimental estimates. The membrane deformation profile was determined independently during...... the stretching process in molecular detail, allowing us to fit this profile to a previously proposed continuum elastic model. Through this approach, we calculated an effective membrane spring constant of 42 kJ-2.mol-1, which is in good agreement with the PMF calculation. Furthermore, the solvation energy we...... derived from the data is shown to match the solvation energy estimated from critical micelle formation constants. This methodology can be used to determine how changes in lipid composition or the presence of membrane modifiers can affect the elastic properties of a membrane at a local level....

  19. Thermal protection materials: Thermophysical property data

    Science.gov (United States)

    Williams, S. D.; Curry, Donald M.

    1992-01-01

    This publication presents a thermophysical property survey on materials that could potentially be used for future spacecraft thermal protection systems (TPS). This includes data that was reported in the 1960's as well as more current information reported through the 1980's. An attempt was made to cite the manufacturers as well as the data source in the bibliography. This volume represents an attempt to provide in a single source a complete set of thermophysical data on a large variety of materials used in spacecraft TPS analysis. The property data is divided into two categories: ablative and reusable. The ablative materials have been compiled into twelve categories that are descriptive of the material composition. An attempt was made to define the Arrhenius equation for each material although this data may not be available for some materials. In a similar manner, char data may not be available for some of the ablative materials. The reusable materials have been divided into three basic categories: thermal protection materials (such as insulators), adhesives, and structural materials.

  20. Two-step preparation of laser-textured Ni/FTO bilayer composite films with high photoelectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bao-jia, E-mail: li_bjia@126.com [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Jiangsu Provincial Key Laboratory for Science and Technology of Photon Manufacturing, Jiangsu University, Zhenjiang 212013 (China); Huang, Li-jing [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Jiangsu Provincial Key Laboratory for Science and Technology of Photon Manufacturing, Jiangsu University, Zhenjiang 212013 (China); Ren, Nai-fei [Jiangsu Provincial Key Laboratory for Science and Technology of Photon Manufacturing, Jiangsu University, Zhenjiang 212013 (China); School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Kong, Xia; Cai, Yun-long; Zhang, Jie-lu [Jiangsu Tailong Reduction Box Co. Ltd, Taixing 225400 (China)

    2015-08-15

    Highlights: • A two-step strategy was proposed to prepare laser-textured Ni/FTO composite films. • Ni/FTO film with a 10-nm-thick Ni layer (Ni{sub 10}/FTO film) had the best performance. • The Ni{sub 10}/FTO film underwent magnetic-field-assisted and -free laser irradiations. • All the magnetic laser-irradiated (MLI-NF) films were textured and annealed. • The MLI-NF film using a fluence of 1.0 J/cm{sup 2} showed the highest figure of merit. - Abstract: A two-step strategy, i.e. sputtering Ni layers on FTO glass combined with magnetic-field-assisted laser irradiation, was proposed to prepare laser-textured Ni/FTO bilayer composite films. By analyzing surface morphology, crystal structure and photoelectric properties of Ni/FTO films with different Ni layer thicknesses, the Ni/FTO film with a 10-nm-thick Ni layer (Ni{sub 10}/FTO film), which had the best overall photoelectric property, was chosen to undergo magnetic-field-assisted laser irradiation with different laser fluences. Magnetic-field-free laser irradiation of the Ni{sub 10}/FTO film was also carried out for comparison purpose. It was found that magnetic-field-assisted laser irradiation using a fluence of 1.0 J/cm{sup 2} was more effective for simultaneously achieving texturing and annealing, resulting in formation of ideal grating textures and significantly increased grain size. The corresponding film (MLI-NF1.0 film) showed the highest figure of merit of 22.8 × 10{sup −3} Ω{sup −1} compared to 13.1 × 10{sup −3} Ω{sup −1} of the FTO glass and 1.4 × 10{sup −3} Ω{sup −1} of the Ni{sub 10}/FTO film, suggesting that the two-step strategy is excellent for preparing textured Ni/FTO films with high photoelectric properties.

  1. Multifunctional Polycrystalline Ferroelectric Materials Processing and Properties

    CERN Document Server

    Pardo, Lorena

    2011-01-01

    This book presents selected topics on processing and properties of ferroelectric materials that are currently the focus of attention in scientific and technical research. Ferro-piezoelectric ceramics are key materials in devices for many applications, such as automotive, healthcare and non-destructive testing. As they are polycrystalline, non-centrosymmetric materials, their piezoelectricity is induced by the so-called poling process. This is based on the principle of polarization reversal by the action of an electric field that characterizes the ferroelectric materials. This book was born with the aim of increasing the awareness of the multifunctionality of ferroelectric materials among different communities, such as researchers, electronic engineers, end-users and manufacturers, working on and with ferro-piezoelectric ceramic materials and devices which are based on them. The initiative to write this book comes from a well-established group of researchers at the Laboratories of Ferroelectric Materials, Mate...

  2. Synthesis, structural and optical properties of a novel bilayered organic-inorganic perovskite C{sub 5}Pb{sub 2}I{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Elleuch, S., E-mail: slimlpa@yahoo.f [Laboratoire de Physique Appliquee, Faculte des Sciences de Sfax, 3000, BP 1171, Sfax (Tunisia); Dammak, T.; Abid, Y. [Laboratoire de Physique Appliquee, Faculte des Sciences de Sfax, 3000, BP 1171, Sfax (Tunisia); Mlayah, A. [Centre d' Elaboration de Materiaux et d' Etudes Structurales, CNRS-Universite Paul Sabatier, 29 Rue Jeanne Marvig, Toulouse 31055 (France); Boughzala, H. [Laboratoire de Materiaux et Cristallochimie, Institut Preparatoire aux etudes Ingenieur de Nabeul, 8000 Mrezga, Nabeul (Tunisia)

    2010-04-15

    Single crystals of [C{sub 5}H{sub 11}NH{sub 3}]Pb{sub 2}I{sub 5}, abbreviated C{sub 5}Pb{sub 2}I{sub 5}, have been prepared. This compound is a new member of the family of the bilayered organic-inorganic lead-iodide based perovskites. Its crystal structure has been determined by X-ray diffraction. The inorganic sub-lattice consists of periodic bilayers of iodoplumbate octahedra. Each PbI{sub 6} octahedra exhibits both edge- and corner-sharing with adjacent octahedra. The vibrational properties of this compound have been studied by Raman scattering spectroscopy. Optical absorption, photoluminescence and diffuse reflectance measurements have been performed. The room-temperature bandgap and free exciton absorption bands are observed at 2.46 and 2.23 eV, respectively. The exciton binding energy is 230 meV which is the largest value ever reported till date for the bilayered PbI based perovskites. Calculations assuming Wannier-type quasi-two-dimensional excitons and taking into account the image potential of the exciton charges showed that nearly 64% of the exciton binding energy is due to the dielectric confinement effect.

  3. Multiscale Modeling of Supported Lipid Bilayers

    Science.gov (United States)

    Hoopes, Matthew I.; Xing, Chenyue; Faller, Roland

    Cell membranes consist of a multitude of lipid molecules that serve as a framework for the even greater variety of membrane associated proteins [1-4]. As this highly complex (nonequilibrium) system cannot easily be understood and studied in a controlled way, a wide variety of model systems have been devised to understand the dynamics, structure, and thermodynamics in biological membranes. One such model system is a supported lipid bilayer (SLB), a two-dimensional membrane suspended on a surface. SLBs have been realized to be manageable experimentally while reproducing many of the key features of real biological membranes [5,6]. One of the main advantages of supported bilayers is the physical stability due to the solid support that enables a wide range of surface characterization techniques not available to free or unsupported membranes. As SLBs maintain some of the crucial structural and dynamic properties of biological membranes, they provide an important bridge to natural systems. In order to mimic cell membranes reliably, certain structural and dynamic features have to be reliably reproduced in the artificially constructed lipid bilayers. SLBs should display lateral mobility as in living cells, because many membrane activities involve transport, recruitment, or assembly of specific components. It is also critical for membranes to exhibit the correct thermodynamic phase, namely, a fluid lipid bilayer, to respond to environmental stress such as temperature and pressure changes [7]. There are several ways to fabricate supported lipid bilayers (SLBs) on planar substrates. One can use vesicle fusion on solid substrates [5,8-10] as well as Langmuir-Blodgett deposition [11,12]. Proteoliposome adsorption and subsequent membrane formation on a mica surface was first demonstrated by Brian and McConnell [13]. Because of its simplicity and reproducibility, this is one of the most common approaches to prepare supported membranes. A diverse range of different solid substrates

  4. Horizontal Bilayer for Electrical and Optical Recordings

    Directory of Open Access Journals (Sweden)

    Alf Honigmann

    2012-12-01

    Full Text Available Artificial bilayer containing reconstituted ion channels, transporters and pumps serve as a well-defined model system for electrophysiological investigations of membrane protein structure–function relationship. Appropriately constructed microchips containing horizontally oriented bilayers with easy solution access to both sides provide, in addition, the possibility to investigate these model bilayer membranes and the membrane proteins therein with high resolution fluorescence techniques up to the single-molecule level. Here, we describe a bilayer microchip system in which long-term stable horizontal free-standing and hydrogel-supported bilayers can be formed and demonstrate its prospects particularly for single-molecule fluorescence spectroscopy and high resolution fluorescence microscopy in probing the physicochemical properties like phase behavior of the bilayer-forming lipids, as well as in functional studies of membrane proteins.

  5. Growth and magnetic properties of ultrathin epitaxial FeO films and Fe/FeO bilayers on MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Kozioł-Rachwał, A., E-mail: akoziol@agh.edu.pl [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Ślęzak, T. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Nozaki, T.; Yuasa, S. [National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Korecki, J. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków (Poland)

    2016-01-25

    Ultrathin FeO(001) films were grown via molecular beam epitaxy on MgO(001) using reactive deposition of Fe. The growth conditions were adjusted toward stabilization of the wüstite phase, the existence of which was confirmed by means of conversion electron Mössbauer spectroscopy. It was shown how the metallic Fe overlayer modified the chemical state and the magnetic properties of the FeO oxide. Finally, we observed the exchange bias for an epitaxial Fe/FeO bilayer grown on MgO(001)

  6. Interface Properties in Extruded FRC-Materials

    DEFF Research Database (Denmark)

    Stang, Henrik

    1997-01-01

    In a research and development project recently carried out at Department of Structural Engineering and Materials, Technical University of Denmark a new extrusion process for HPFRCC-materials was demonstrated.It is shown that superior interfacial properties are obtained in a polypropylene fiber...... reinforced cementitious material extruded by the developed process. It is further more shown that the fiber-matrix bond is highly dependent on the relative slip at the interface and a bond-slip relationship is suggested for the extruded material. The observed very high fiber-matrix bond is explained...... by the densification of the interfacial matrix material which has taken place during the consolidation process and which can be observed in the thin-section analysis....

  7. Mechanical properties of wet granular materials

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, Z; Geromichalos, D; Herminghaus, S; Kohonen, M M; Mugele, F; Scheel, M; Schulz, M; Schulz, B; Schier, Ch; Seemann, R; Skudelny, A

    2005-03-09

    We elaborate on the impact of liquids upon the mechanical properties of granular materials. We find that most of the experimental and simulation results may be accounted for by a simple model assuming frictionless, spherical grains, with a hysteretic attractive interaction between neighbouring grains due to capillary forces.

  8. DNA nanotechnology: Bringing lipid bilayers into shape

    Science.gov (United States)

    Howorka, Stefan

    2017-07-01

    Lipid bilayers form the thin and floppy membranes that define the boundary of compartments such as cells. Now, a method to control the shape and size of bilayers using DNA nanoscaffolds has been developed. Such designer materials advance synthetic biology and could find use in membrane research.

  9. Capacitance Variation of Electrolyte-Gated Bilayer Graphene Based Transistors

    OpenAIRE

    Hediyeh Karimi; Rubiyah Yusof; Mohammad Taghi Ahmadi; Mehdi Saeidmanesh; Meisam Rahmani; Elnaz Akbari; Wong King Kiat

    2013-01-01

    Quantum capacitance of electrolyte-gated bilayer graphene field-effect transistors is investigated in this paper. Bilayer graphene has received huge attention due to the fact that an energy gap could be opened by chemical doping or by applying external perpendicular electric field. So, this extraordinary property can be exploited to use bilayer graphene as a channel in electrolyte-gated field-effect transistors. The quantum capacitance of bi-layer graphene with an equivalent circuit is presen...

  10. Superconducting and ferromagnetic properties of NbN/NiCu and NbTiN/NiCu bilayer nanostructures for photon detection

    Science.gov (United States)

    Klimov, A.; Puźniak, R.; Aichner, B.; Lang, W.; Joon, E.; Stern, R.; Słysz, W.; Guziewicz, M.; Juchniewicz, M.; Borysiewicz, M. A.; Kruszka, R.; Wegrzecki, M.; Łaszcz, A.; Czerwinski, A.; Sobolewski, Roman

    2015-05-01

    Performance of superconducting single-photon detectors based on resistive hotspot formation in nanostripes upon optical photon absorption depends strongly on the critical current density JC of the fabricated nanostructure. Utilization of an ultrathin, weak-ferromagnet cap layer on the top of a superconducting film enhances of the structure's JC due to an extra flux pinning. We have fabricated a number of both NbN/NiCu and NbTiN/NiCu superconductor/ferromagnet (S/F) ultrathin bilayers and microbridges. NbN and NbTiN underlayers with thicknesses varying from 4 to 7 nm were grown using dc-magnetron sputtering on chemically cleaned sapphire single-crystal substrates. After rapid thermal annealing at high temperatures, the S films were coated with Ni0.54Cu0.46 overlayers with thicknesses of about 6 nm, using cosputtering. Compositions of the deposited films were confirmed by EDX spectroscopy analysis, while TEM studies demonstrated excellent epitaxial quality of our S layers with ~2-nm-thick F/S transition layer and atomically-sharp S/substrate interface. Magnetic properties of bilayers were studied using both the SQUID and Vibrating Sample Magnetometer techniques in low and high magnetic fields. Low-temperature tests confirmed that in all cases NiCu films were ferromagnetic with the Curie temperature of above 30 K. Below the bilayer critical temperature of approx. 12-13 K, the structures were fully proximitized with the strong superconducting signal. For superconducting transport properties characterization, we used bilayers patterned into 40-μm-long microbridges with the width varying from 0.4 μm to 2 μm. The same S/F nanostructures were also used to study their superconducting fluctuations. The temperature dependence of magnetoresistance demonstrated highly 2-dimensional character with an unusual negative region that extended almost to room temperature. In the S/F sample, the fluctuations were observed to be substantially below theoretical expectations.

  11. Optical properties of photochromic and thermochromic materials

    Science.gov (United States)

    Mo, Yeon-Gon

    The optical properties of some thin film materials can be altered by an external stimulus. Photochromic and thermochromic materials, including inorganic and organic substances, have optical properties that can be changed in a reversible manner by irradiation and temperature respectively. These materials can be used in applications such as radiation or thermal sensors, information storage devices and smart window applications in buildings and cars. In this work, major effort was concentrated on passive thermal control coatings based on photochromic and thermochromic materials. The inorganic photochromic materials were based on tungsten and molybdenum oxide films and the organic photochromic materials included spiropyrans and spirooxazines. In addition, photochromic composite organic-inorganic films and thermochromic vanadium oxide films were prepared. The samples were synthesized using sputtering, sol-gel process, and thermal oxidation. The optical properties were investigated for the first time by ultraviolet/visible/infrared (UV/VIS/IR) spectroscopic ellipsometry, attenuated total reflection (ATR) infrared ellipsometry, spectrophotometry, and X-ray diffraction (XRD). For amorphous oxide films, the oxygen deficiency was important in determining the photochromic properties of the films. In the mid-infrared region, no photochromism was observed for the films. The optical properties of organic-inorganic composite films changed in the VIS/NIR wavelength region markedly in a reversible process, with UV irradiation. The composite films containing tungsten heteropolyoxometalate (HPOM) showed faster coloration and bleaching than pure tungsten oxide films. The composite films with molybdenum HPOM showed faster coloration and much slower bleaching than tungsten HPOM. The spiropyran and spirooxazine doped polymeric films were investigated for the first time using infrared and ATR ellipsometry. The infrared optical functions obtained by ATR measurements were a little smaller

  12. Comparison on mechanical properties of single layered and bilayered chitosan-gelatin coated porous hydroxyapatite scaffold prepared through freeze drying method

    Science.gov (United States)

    Effendi, M. D.; Gustiono, D.; Lukmana; Ayu, D.; Kurniawati, F.

    2017-02-01

    Biopolymer coated porous hydroxyapatite (HA) scaffolds were prepared for tissue engineering trough freeze drying method and impregnation. in this study, to mimic the mineral and organic component of natural bone, synthetic hydroxapatite (HA) scaffolds coated by polymer were prepared. Highly porous Hap scaffolds, fabricated by synthetic HA impregnation method on polyurethane foam, were coated with polymer coating solution, consisting of chitosan, Gelatin, and bilayered chitosan-gelatin prepared by aging and impregnating technique. For the purpose of comparison, The bare scaffolds without polymer coating layer were investigated. The Bare scaffolds were highly porous and interconnected with a pore size of around 150 µm–714 µm, has porosity at around 67,7% -85,7%, and has mechanical strength at around 0.06 Mpa - 0.071 Mpa, which is suitable for osteoblast cell Proliferation. Chitosan coated porous HA scaffold and gelatin coated porous HA scaffold had mechanical strength at around 0.81-0.85 Mpa, and 1.32-1.34 Mpa, respectively, with weight ratio of biopolymer and Hap was around 18%-22%. To compare these results, the coating on the bare scaffold with gelatin and chitosan had been conducted. Based on the result of FTIR, it could be concluded that coating procedure applied on porous hydroxy apatite (HA) coated by gelatin, chitosan coated HA scaffold, and bilayered Gelatin-chitosan coated porous HA scaffold, confirming that for allsampleshad no significant chemical effect on the coating structure. The compressive strength of bilayered Gelatin-chitosan coated HA scaffold had middle values between the rest, at around 1,06-1.2 Mpa for the samples at the same weight ratio of biopolymer: HA (around 18% - 22%). These results also confirming that coating by gelatin on porous hydroxyapatite was highest compresive strength and can be applied to improve mechanical properties of porous hydroxyapatite bare scaffold

  13. Properties of nanoclay PVA composites materials

    Directory of Open Access Journals (Sweden)

    Mohamed H. M. Ali

    2012-03-01

    Full Text Available Polyvinyl alcohol (PVA/ Na-rich Montmorillonite (MMT nanocomposites were prepared using solution method to create polymer-clay nanocomposite (PCN material. The PCN material was studied using X-ray diffraction (XRD, demonstrating polymer-clay intercalation that has a high d-spacing (lower diffraction angles in the PCN XRD pattern, compared to the pure MMT clay XRD pattern, which has a low d-spacing (high diffraction angles. The nano-scanning electron microscope (NSEM was used to study the morphological image of the PVA, MMT and PCN materials. The results showed that intercalation that took place between the PVA and MMT produced the PCN material. The mechanical properties of the pure PVA and the intercalated polymer material were studied. It was found that the small amount of MMT clay made the tensile modulus and percentage of the total elongation of the nano-composite significantly higher than the pure PVA polymer value, due to polymer-clay intercalation. The thermal stability of the intercalated polymer has been studied using thermal analytical techniques such as thermogravimetric analysis (TGA and differential scanning calorimetry (DSC. The results showed that the PCN material is more thermally stable than the pure PVA polymer.

  14. On Structure and Properties of Amorphous Materials

    Directory of Open Access Journals (Sweden)

    Zbigniew H. Stachurski

    2011-09-01

    Full Text Available Mechanical, optical, magnetic and electronic properties of amorphous materials hold great promise towards current and emergent technologies. We distinguish at least four categories of amorphous (glassy materials: (i metallic; (ii thin films; (iii organic and inorganic thermoplastics; and (iv amorphous permanent networks. Some fundamental questions about the atomic arrangements remain unresolved. This paper focuses on the models of atomic arrangements in amorphous materials. The earliest ideas of Bernal on the structure of liquids were followed by experiments and computer models for the packing of spheres. Modern approach is to carry out computer simulations with prediction that can be tested by experiments. A geometrical concept of an ideal amorphous solid is presented as a novel contribution to the understanding of atomic arrangements in amorphous solids.

  15. Measuring Interlayer Shear Stress in Bilayer Graphene

    Science.gov (United States)

    Wang, Guorui; Dai, Zhaohe; Wang, Yanlei; Tan, PingHeng; Liu, Luqi; Xu, Zhiping; Wei, Yueguang; Huang, Rui; Zhang, Zhong

    2017-07-01

    Monolayer two-dimensional (2D) crystals exhibit a host of intriguing properties, but the most exciting applications may come from stacking them into multilayer structures. Interlayer and interfacial shear interactions could play a crucial role in the performance and reliability of these applications, but little is known about the key parameters controlling shear deformation across the layers and interfaces between 2D materials. Herein, we report the first measurement of the interlayer shear stress of bilayer graphene based on pressurized microscale bubble loading devices. We demonstrate continuous growth of an interlayer shear zone outside the bubble edge and extract an interlayer shear stress of 40 kPa based on a membrane analysis for bilayer graphene bubbles. Meanwhile, a much higher interfacial shear stress of 1.64 MPa was determined for monolayer graphene on a silicon oxide substrate. Our results not only provide insights into the interfacial shear responses of the thinnest structures possible, but also establish an experimental method for characterizing the fundamental interlayer shear properties of the emerging 2D materials for potential applications in multilayer systems.

  16. The Influence of New Hydrophobic Silica Nanoparticles on the Surface Properties of the Films Obtained from Bilayer Hybrids

    Science.gov (United States)

    Petcu, Cristian; Purcar, Violeta; Spătaru, Cătălin-Ilie; Alexandrescu, Elvira; Şomoghi, Raluca; Trică, Bogdan; Niţu, Sabina Georgiana; Panaitescu, Denis Mihaela; Donescu, Dan; Jecu, Maria-Luiza

    2017-01-01

    Ultra-hydrophobic bilayer coatings on a glass surface were fabricated by sol–gel process using hexadecyltrimethoxysilane (C16TMS) and tetramethoxysilane (TMOS) (1:4 molar ratio) as precursors. After coating, silica nanoparticles (SiO2 NPs) functionalized with different mono-alkoxy derivatives (methoxytrimethylsilane, TMeMS; ethoxydimethylvinylsilane, DMeVES; ethoxydimethylphenylsilane, DMePhES; and methoxydimethyloctylsilane, DMeC8MS) were added, assuring the microscale roughness on the glass surface. Influences of the functionalized SiO2 NPs and surface morphology on the hydrophobicity of the hybrid films were discussed. The successful functionalization of SiO2 NPs with hydrophobic alkyl groups were confirmed by Fourier transform infrared spectroscopy (FTIR). The thermal stability of hydrophobic SiO2 NPs showed that the degradation of the alkyl groups takes place in the 200–400 °C range. Bilayer coating with C16TMS/TMOS and SiO2 NPs modified with alkoxysilane substituted with C8 alkyl chain (SiO2 NP-C8) has micro/nano structure. Hydrophobicity of functionalized SiO2 NPs-C8 and its higher degree of nanometer-scale roughness gave rise to ultra-hydrophobicity performance for bilayer coating C16TMS/TMOS + SiO2 NPs-C8 (145°), compared to other similar hybrid structures. Our synthesis method for the functionalization of SiO2 NPs is useful for the modification of surface polarity and roughness.

  17. TiB{sub 2}/TiSi{sub 2} bilayer fabrication by various techniques: Structure and contact properties

    Energy Technology Data Exchange (ETDEWEB)

    Pelleg, Joshua [Department of Materials Engineering, Ben Gurion University of the Negev, Ben Gurion Str. 84105, Beer Sheva (Israel)]. E-mail: pelleg@bgumail.bgu.ac.il; Sade, G. [Department of Materials Engineering, Ben Gurion University of the Negev, Ben Gurion Str. 84105, Beer Sheva (Israel)

    2006-01-15

    TiB{sub 2}/TiSi{sub 2} films were produced by several techniques in an attempt to evaluate the most appropriate method to fabricate this system. Analysis by X-ray diffraction, Auger electron spectroscopy, transmission and high-resolution transmission electron microscopy indicate that the best method to obtain the above system is by sequential cosputtering of the layers without exposure to air between the two cosputtering sequences. Post-deposition annealing was performed to obtain a low resistive bilayer. Schottky diodes fabricated by this method provided an average barrier height of {approx}0.68 V with an ideality factor in the range of 1.0-1.04 (excluding the as-deposited specimen). In specimens fabricated by silicidation of TiB{sub 2}/Ti films formation of TiSi{sub 2} was Ti thickness dependent [G. Sade, Ph.D. Thesis, Ben Gurion University of the Negev, Beer Sheva, Israel, 1999]. Small amounts of Ti{sub 5}Si{sub 3} were observed at 1123 K. The attempts to obtain a TiB{sub 2}/TiSi{sub 2} bilayer from (Ti+B) enriched with Ti at 1073 K resulted in the formation of small amounts of Ti{sub 5}Si{sub 3}, and some crystallization of the amorphous TiB{sub 2} also occurred. Diodes fabricated by this technique showed Ohmic rather than rectifying character. The shift from rectifying to Ohmic behavior is the result of B out-diffusion to the Si and the consequent change of the substrate from an n- to a p-type Si. The results place the Fermi level of TiB{sub 2} about 0.9 eV below the silicon conduction band. A remedy to this problem could result in a challenging method of fabricating a TiB{sub 2}/TiSi{sub 2} bilayer structure in a one-step process.

  18. The Influence of New Hydrophobic Silica Nanoparticles on the Surface Properties of the Films Obtained from Bilayer Hybrids

    Directory of Open Access Journals (Sweden)

    Cristian Petcu

    2017-02-01

    Full Text Available Ultra-hydrophobic bilayer coatings on a glass surface were fabricated by sol–gel process using hexadecyltrimethoxysilane (C16TMS and tetramethoxysilane (TMOS (1:4 molar ratio as precursors. After coating, silica nanoparticles (SiO2 NPs functionalized with different mono-alkoxy derivatives (methoxytrimethylsilane, TMeMS; ethoxydimethylvinylsilane, DMeVES; ethoxydimethylphenylsilane, DMePhES; and methoxydimethyloctylsilane, DMeC8MS were added, assuring the microscale roughness on the glass surface. Influences of the functionalized SiO2 NPs and surface morphology on the hydrophobicity of the hybrid films were discussed. The successful functionalization of SiO2 NPs with hydrophobic alkyl groups were confirmed by Fourier transform infrared spectroscopy (FTIR. The thermal stability of hydrophobic SiO2 NPs showed that the degradation of the alkyl groups takes place in the 200–400 °C range. Bilayer coating with C16TMS/TMOS and SiO2 NPs modified with alkoxysilane substituted with C8 alkyl chain (SiO2 NP-C8 has micro/nano structure. Hydrophobicity of functionalized SiO2 NPs-C8 and its higher degree of nanometer-scale roughness gave rise to ultra-hydrophobicity performance for bilayer coating C16TMS/TMOS + SiO2 NPs-C8 (145°, compared to other similar hybrid structures. Our synthesis method for the functionalization of SiO2 NPs is useful for the modification of surface polarity and roughness.

  19. AGC 2 Irradiated Material Properties Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Rohrbaugh, David Thomas [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2017-05-01

    The Advanced Reactor Technologies Graphite Research and Development Program is conducting an extensive graphite irradiation experiment to provide data for licensing of a high temperature reactor (HTR) design. In past applications, graphite has been used effectively as a structural and moderator material in both research and commercial high temperature gas cooled reactor designs. , Nuclear graphite H 451, used previously in the United States for nuclear reactor graphite components, is no longer available. New nuclear graphite grades have been developed and are considered suitable candidates for new HTR reactor designs. To support the design and licensing of HTR core components within a commercial reactor, a complete properties database must be developed for these current grades of graphite. Quantitative data on in service material performance are required for the physical, mechanical, and thermal properties of each graphite grade, with a specific emphasis on data accounting for the life limiting effects of irradiation creep on key physical properties of the HTR candidate graphite grades. Further details on the research and development activities and associated rationale required to qualify nuclear grade graphite for use within the HTR are documented in the graphite technology research and development plan.

  20. Synthesis of new materials with properties ameliorated

    Science.gov (United States)

    Baira, F.; Benfarhi, S.; Zidani, S.

    2012-09-01

    Cellulose is the most abundant polymer in nature. It is used mainly for the production of paper bet also as a reinforcement in the polymer matrixes[1]. The modification of this polysaccharide presents a great interest, for it is the main constituent of agricultural wastes. It is well known that the microcrystalline cellulose gives, after chemical modification, new biodegradable materials[2], which may be used, for instance, for packaging. The esterification of cellulose necessitates an acid pretreatment which makes hydroxyl groups more accessible by breaking hydrogen bonds. X-rays diffraction analysis showed a feeble diminution of the treated samples cristallinity[3]. Cellulose, activated in this way, is esterified in a classic way in DMF, in the presence of triethylamine, LiCl and acid chloride at 60C° for 24 hours[4]. The obtained ester is precipitated in MeOH. The residue, dissolved in CHCl3, gives after evaporation in the open air, a plastic film surface. The water drop test has shown the hydrophobe properties of the plastic film surface. Our work is the study of the preparation of composite materials from the basis of their derivatives. Well as the study of the photopolymerisation kinetic, and the chemical degradation. The obtained films were analyzed by IR-TF, and the volumetrie[5,6]. As a conclusion, we have prepared composite materials with improved properties with reference to the matrix alone.

  1. Wear Property of Cast Steel Wheel Material in Rail Truck

    Institute of Scientific and Technical Information of China (English)

    MI Guo-fa; LIU Yan-lei; ZHANG Bin; FU Xiu-qin; ZHANG Hong; SONG Guo-xiang

    2009-01-01

    Wear property of material plays a key role in the service time of workpiece.A major objective in the development of new wheel materials is to improve the wear performance.The wear property of B and B+ grade cast steel materials was reported.The results showed that B+ grade cast steel material exhibited better wear property than the B grade material.Carbon content related to the hardness match was the principal factor affecting the wear properties.

  2. Materials with complex behaviour II properties, non-classical materials and new technologies

    CERN Document Server

    Oechsner, Andreas

    2012-01-01

    This book reviews developments and trends in advanced materials and their properties; modeling and simulation of non-classical materials and new technologies for joining materials. Offers tools for characterizing and predicting properties and behavior.

  3. Fundamentals of semiconductors physics and materials properties

    CERN Document Server

    Yu, Peter Y

    1996-01-01

    Fundamentals of Semiconductors attempts to fill the gap between a general solid-state physics textbook and research articles by providing detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors The approach is physical and intuitive rather than formal and pedantic Theories are presented to explain experimental results This textbook has been written with both students and researchers in mind Its emphasis is on understanding the physical properties of Si and similar tetrahedrally coordinated semiconductors The explanations are based on physical insights Each chapter is enriched by an extensive collection of tables of material parameters, figures and problems Many of these problems 'lead the student by the hand' to arrive at the results

  4. Fundamentals of semiconductors physics and materials properties

    CERN Document Server

    Yu, Peter Y

    2010-01-01

    This fourth edition of the well-established Fundamentals of Semiconductors serves to fill the gap between a general solid-state physics textbook and research articles by providing detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors. The approach is physical and intuitive rather than formal and pedantic. Theories are presented to explain experimental results. This textbook has been written with both students and researchers in mind. Its emphasis is on understanding the physical properties of Si and similar tetrahedrally coordinated semiconductors. The explanations are based on physical insights. Each chapter is enriched by an extensive collection of tables of material parameters, figures, and problems. Many of these problems "lead the student by the hand" to arrive at the results. The major changes made in the fourth edition include: an extensive appendix about the important and by now well-established deep center known as the DX center, additional problems...

  5. Thermal Radiative Properties of Xonotlite Insulation Material

    Institute of Scientific and Technical Information of China (English)

    Xinxin ZHANG; Gaosheng WEI; Fan YU

    2005-01-01

    This paper presents experimental results of thermal radiative properties of xonotlite-type calcium silicate insulation material. Transmittance spectra were first taken using Fourier transform infrared spectrometer (FTIR)for the samples with ρ = 234 kg/m3. Specific extinction coefficient spectra were then obtained by applying Beer's law.Finally,by using the diffusion approximation,the specific Rossland mean extinction coefficients and radiative thermal conductivities were obtained for various temperatures. The results show that the specific spectral extinction coefficient of xonotlite is larger than 7 m2/kg in the whole measured spectra, and diffusion approximation equation is a reasonable description of radiative heat transfer in xonotlite insulation material. The specific Rossland mean extinction coefficient of xonotlite has a maximum ualue at 400 K and the radiative thermal conductivity is almost proportional to the cube of temperature.

  6. Photorefractive optics materials, properties, and applications

    CERN Document Server

    Yu, Francis T S

    1999-01-01

    The advances of photorefractive optics have demonstrated many useful and practical applications, which include the development of photorefractive optic devices for computer communication needs. To name a couple significant applications: the large capacity optical memory, which can greatly improve the accessible high-speed CD-ROM and the dynamic photorefractive gratings, which can be used for all-optic switches for high-speed fiber optic networks. This book is an important reference both for technical and non-technical staffs who are interested in this field. * Covers the recent development in materials, phenomena, and applications * Includes growth, characterization, dynamic gratings, and liquid crystal PR effect * Includes applications to photonic devices such as large capacity optical memory, 3-D interconnections, and dynamic holograms * Provides the recent overall picture of current trends in photorefractive optics * Includes optical and electronic properties of the materials as applied to dynamic photoref...

  7. Material properties of the plantar aponeurosis.

    Science.gov (United States)

    Kitaoka, H B; Luo, Z P; Growney, E S; Berglund, L J; An, K N

    1994-10-01

    Material properties of the plantar aponeurosis were determined by a two-dimensional video tracking method to simultaneously measure the aponeurosis deformation. Failure loads averaged 1189 +/- 244 N and were higher in men. Average stiffness of the intact fascia was 203.7 +/- 50.5 N/mm at a loading rate of 11.12 N/sec and it did not vary significantly for the loading rates of 11.12 to 1112 N/sec. The high tensile loads required for failure were consistent with clinical and biomechanical studies and indicated the importance of the aponeurosis in foot function and arch stability.

  8. Photon correlation spectroscopy of bilayer lipid membranes.

    Science.gov (United States)

    Crilly, J F; Earnshaw, J C

    1983-02-01

    Light scattering by thermal fluctuations on simple monoglyceride bilayer membranes has been used to investigate the viscoelastic properties of these structures. Spectroscopic analysis of these fluctuations (capillary waves) permits the nonperturbative measurement of the interfacial tension and a shear interfacial viscosity acting normal to the membrane plane. The methods were established by studies of solvent and nonsolvent bilayers of glycerol monooleate (GMO). Changes in the tension of GMO/n-decane membranes induced by altering the composition of the parent solution were detected and quantified. In a test of the reliability of the technique controlled variations of the viscosity of the aqueous bathing solution were accurately monitored. The technique was applied to solvent-free bilayers formed from dispersions of GMO in squalane. The lower tensions observed attested to the comparative absence of solvent in such bilayers. In contrast to the solvent case, the solvent-free membranes exhibited a significant transverse shear viscosity, indicative of the enhanced intermolecular interactions within the bilayer.

  9. Lipid bilayers and interfaces

    NARCIS (Netherlands)

    Kik, R.A.

    2007-01-01

    In biological systems lipid bilayers are subject to many different interactions with other entities. These can range from proteins that are attached to the hydrophilic region of the bilayer or transmembrane proteins that interact with the hydrophobic region of the lipid bilayer. Interaction between

  10. Magnetic and electronic properties of La{sub 0.7}Ca{sub 0.3}MnO{sub 3}/h-YMnO{sub 3} bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Manish; Choudhary, R. J.; Phase, D. M., E-mail: dmphase@csr.res.in [UGC-DAE Consortium for Scientific Research, Indore 452001 (India)

    2016-03-15

    La{sub 0.7}Ca{sub 0.3}MnO{sub 3}/h-YMnO{sub 3} (h ∼ hexagonal) bilayer thin films are grown using pulsed laser deposition technique and magnetic/band-offset measurements are performed to explore the magnetic/electronic properties. The bilayer displays the signatures of the ferromagnetic (FM) La{sub 0.7}Ca{sub 0.3}MnO{sub 3} layer and antiferromagnetic (AFM) h-YMnO{sub 3} layer. The uncompensated spins at the interface of FM/AFM layers caused exchange bias effect. The vertical and horizontal shift in field cooled isothermal magnetization curves below the AFM transition temperature shows dependence on the sign of the cooling magnetic field. Type-II band alignment at the interface of bilayer is realized through valence band offset and conduction band offset values estimated from the photoemission results.

  11. Emission properties of heterostructures with a (GaAsSb-InGaAs)/GaAs bilayer quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Zvonkov, B. N.; Nekorkin, S. M.; Vikhrova, O. V.; Dikareva, N. V., E-mail: dikareva@nifti.unn.ru [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation)

    2013-09-15

    The specific features of the emission characteristics of GaAs-based heterostructures with a GaAs{sub 1-x}Sb{sub x}-In{sub y}Ga{sub 1-y}As bilayer quantum well are studied. The heterostructures are grown by metal-organic chemical vapor deposition (MOCVD). With an analysis of previously reported data on the MOCVD growth process taken into account, the temperature range (560-580 Degree-Sign C), the relation between the fluxes emitted by the sources of Group-V and -III elements ( Less-Than-Or-Equivalent-To 1), and the order of layer growth for the production of the active region of a GaAs/InGaP laser heterostructure are determined experimentally. The active region is a GaAs{sub 0.75}Sb{sub 0.25}-In{sub 0.2}Ga{sub 0.8}As bilayer quantum well. For the structure, a 1075-nm electroluminescence signal attributed to indirect transitions between the valence band of the GaAs{sub 0.75}Sb{sub 0.25} layer and the conduction band of the In{sub 0.2}Ga{sub 0.8}As layer is observed. An increase in the continuous-wave pump current yields a decrease in the 1075-nm emission intensity and initiates stable lasing at a wavelength of 1022 nm at a threshold current density of 1.4 kA cm{sup -2} at room temperature. Lasing occurs at transitions direct in coordinate space.

  12. Engineering Lipid Bilayer Membranes for Protein Studies

    Directory of Open Access Journals (Sweden)

    Muhammad Shuja Khan

    2013-10-01

    Full Text Available Lipid membranes regulate the flow of nutrients and communication signaling between cells and protect the sub-cellular structures. Recent attempts to fabricate artificial systems using nanostructures that mimic the physiological properties of natural lipid bilayer membranes (LBM fused with transmembrane proteins have helped demonstrate the importance of temperature, pH, ionic strength, adsorption behavior, conformational reorientation and surface density in cellular membranes which all affect the incorporation of proteins on solid surfaces. Much of this work is performed on artificial templates made of polymer sponges or porous materials based on alumina, mica, and porous silicon (PSi surfaces. For example, porous silicon materials have high biocompatibility, biodegradability, and photoluminescence, which allow them to be used both as a support structure for lipid bilayers or a template to measure the electrochemical functionality of living cells grown over the surface as in vivo. The variety of these media, coupled with the complex physiological conditions present in living systems, warrant a summary and prospectus detailing which artificial systems provide the most promise for different biological conditions. This study summarizes the use of electrochemical impedance spectroscopy (EIS data on artificial biological membranes that are closely matched with previously published biological systems using both black lipid membrane and patch clamp techniques.

  13. Structural Phase Transition and Material Properties of Few-Layer Monochalcogenides

    Science.gov (United States)

    Mehboudi, Mehrshad; Fregoso, Benjamin M.; Yang, Yurong; Zhu, Wenjuan; van der Zande, Arend; Ferrer, Jaime; Bellaiche, L.; Kumar, Pradeep; Barraza-Lopez, Salvador

    2016-12-01

    GeSe and SnSe monochalcogenide monolayers and bilayers undergo a two-dimensional phase transition from a rectangular unit cell to a square unit cell at a critical temperature Tc well below the melting point. Its consequences on material properties are studied within the framework of Car-Parrinello molecular dynamics and density-functional theory. No in-gap states develop as the structural transition takes place, so that these phase-change materials remain semiconducting below and above Tc. As the in-plane lattice transforms from a rectangle into a square at Tc, the electronic, spin, optical, and piezoelectric properties dramatically depart from earlier predictions. Indeed, the Y and X points in the Brillouin zone become effectively equivalent at Tc, leading to a symmetric electronic structure. The spin polarization at the conduction valley edge vanishes, and the hole conductivity must display an anomalous thermal increase at Tc. The linear optical absorption band edge must change its polarization as well, making this structural and electronic evolution verifiable by optical means. Much excitement is drawn by theoretical predictions of giant piezoelectricity and ferroelectricity in these materials, and we estimate a pyroelectric response of about 3 ×10-12 C /K m here. These results uncover the fundamental role of temperature as a control knob for the physical properties of few-layer group-IV monochalcogenides.

  14. Large-signal model of the bilayer graphene field-effect transistor targeting radio-frequency applications: Theory versus experiment

    Energy Technology Data Exchange (ETDEWEB)

    Pasadas, Francisco, E-mail: Francisco.Pasadas@uab.cat; Jiménez, David [Departament d' Enginyeria Electrònica, Escola d' Enginyeria, Universitat Autònoma de Barcelona, 08193 Bellaterra (Spain)

    2015-12-28

    Bilayer graphene is a promising material for radio-frequency transistors because its energy gap might result in a better current saturation than the monolayer graphene. Because the great deal of interest in this technology, especially for flexible radio-frequency applications, gaining control of it requires the formulation of appropriate models for the drain current, charge, and capacitance. In this work, we have developed them for a dual-gated bilayer graphene field-effect transistor. A drift-diffusion mechanism for the carrier transport has been considered coupled with an appropriate field-effect model taking into account the electronic properties of the bilayer graphene. Extrinsic resistances have been included considering the formation of a Schottky barrier at the metal-bilayer graphene interface. The proposed model has been benchmarked against experimental prototype transistors, discussing the main figures of merit targeting radio-frequency applications.

  15. Interdisciplinary research on the nature and properties of ceramic materials

    Science.gov (United States)

    1980-01-01

    The advancement of material performance and design methodology as related to brittle materials was investigated. The processing and properties of ceramic materials as related to design requirements was also studied.

  16. Thermophysical Properties of Selected Aerospace Materials. Part 2. Thermophysical Properties of Seven Materials

    Science.gov (United States)

    1977-01-01

    Determining Thermal Conductivity of Solids from 20 to 600 K," Cryogenics, 5( 1), 17-20, 1965. 11. Garth, R.C. and Sailer , V.L., "Thermal Conductivity of...34Thermal Property Data Utilized for Asset Materials," McDonnell Aircraft Corp. Rept. A656, 45 pp., 1964. [AD 480 414] 23. Makarounls, O., " Solar

  17. Properties of Sealing Materials in Groundwater Wells

    DEFF Research Database (Denmark)

    Köser, Claus

    on the maximum swelling pressure; i) the bulk density of the sample, and ii) whether the sample is sorted or unsorted. CT scans (Computed Tomography) have been used to evaluate certain properties of bentonite seals in a limited volume. In this context, a set of algorithms to convert CT numbers (HU unit......) into densities for clay/water systems has been developed. This method has successfully been used to evaluate e.g., macroporosity, homogenization of the bentonite seal during the hydration of water, hydraulic conductivity and the creation of channels in the bentonite seals. Based on the results obtained...... in this Ph.D. thesis, a number of recommendations has been offered; i) a change regarding the production of pellets and ii) how sealing material must be treated in the actual construction of groundwater wells....

  18. Bone Material Properties in Osteogenesis Imperfecta.

    Science.gov (United States)

    Bishop, Nick

    2016-04-01

    Osteogenesis imperfecta entrains changes at every level in bone tissue, from the disorganization of the collagen molecules and mineral platelets within and between collagen fibrils to the macroarchitecture of the whole skeleton. Investigations using an array of sophisticated instruments at multiple scale levels have now determined many aspects of the effect of the disease on the material properties of bone tissue. The brittle nature of bone in osteogenesis imperfecta reflects both increased bone mineralization density-the quantity of mineral in relation to the quantity of matrix within a specific bone volume-and altered matrix-matrix and matrix mineral interactions. Contributions to fracture resistance at multiple scale lengths are discussed, comparing normal and brittle bone. Integrating the available information provides both a better understanding of the effect of current approaches to treatment-largely improved architecture and possibly some macroscale toughening-and indicates potential opportunities for alternative strategies that can influence fracture resistance at longer-length scales.

  19. Spacecraft dielectric material properties and spacecraft charging

    Science.gov (United States)

    Frederickson, A. R.; Wall, J. A.; Cotts, D. B.; Bouquet, F. L.

    1986-01-01

    The physics of spacecraft charging is reviewed, and criteria for selecting and testing semiinsulating polymers (SIPs) to avoid charging are discussed and illustrated. Chapters are devoted to the required properties of dielectric materials, the charging process, discharge-pulse phenomena, design for minimum pulse size, design to prevent pulses, conduction in polymers, evaluation of SIPs that might prevent spacecraft charging, and the general response of dielectrics to space radiation. SIPs characterized include polyimides, fluorocarbons, thermoplastic polyesters, poly(alkanes), vinyl polymers and acrylates, polymers containing phthalocyanine, polyacene quinones, coordination polymers containing metal ions, conjugated-backbone polymers, and 'metallic' conducting polymers. Tables summarizing the results of SIP radiation tests (such as those performed for the NASA Galileo Project) are included.

  20. High-k ZrO2/Al2O3 bilayer on hydrogenated diamond: Band configuration, breakdown field, and electrical properties of field-effect transistors

    Science.gov (United States)

    Liu, J. W.; Liao, M. Y.; Imura, M.; Koide, Y.

    2016-09-01

    A band configuration of a high-k ZrO2/Al2O3 bilayer on hydrogenated diamond (H-diamond), a breakdown field (EB) of the ZrO2/Al2O3 bilayer, and an effect of gate-drain distance (dG-D) on electrical properties of ZrO2/Al2O3/H-diamond metal-insulator-semiconductor field-effect transistors (MISFETs) have been investigated. The Al2O3 and ZrO2 layers are successively deposited on H-diamond by atomic layer deposition (ALD) and sputtering-deposition (SD) techniques, respectively. The thin ALD-Al2O3 buffer layer with 4.0 nm thickness plays a role in protecting the H-diamond surface from being damaged by the plasma discharge during SD-ZrO2 deposition. The ZrO2/Al2O3 heterojunction has a type I band structure with valence and conduction band offsets of 0.6 ± 0.2 and 1.0 ± 0.2 eV, respectively. The valence band offset between ZrO2 and H-diamond is deduced to be 2.3 ± 0.2 eV. The EB of the ZrO2/Al2O3 bilayer is measured to be 5.2 MV cm-1, which is larger than that of the single ZrO2 layer due to the existence of the ALD-Al2O3 buffer layer. The dependence of dG-D on drain-source current maximum (IDS,max), on-resistance (RON), threshold voltage (VTH), and extrinsic transconductance maximum (gm,max) of the MISFETs has been investigated. With increasing dG-D from 4 to 18 μm, the absolute IDS,max decreases from 72.7 to 40.1 mA mm-1, and the RON increases linearly from 83.3 ± 5 to 158.7 ± 5 Ω mm. Variation of VTH values of around 1.0 V is observed, and the gm,max is in the range between 8.0 ± 0.1 and 13.1 ± 0.1 mS mm-1.

  1. Berry phase transition in twisted bilayer graphene

    Science.gov (United States)

    Rode, Johannes C.; Smirnov, Dmitri; Schmidt, Hennrik; Haug, Rolf J.

    2016-09-01

    The electronic dispersion of a graphene bilayer is highly dependent on rotational mismatch between layers and can be further manipulated by electrical gating. This allows for an unprecedented control over electronic properties and opens up the possibility of flexible band structure engineering. Here we present novel magnetotransport data in a twisted bilayer, crossing the energetic border between decoupled monolayers and coupled bilayer. In addition a transition in Berry phase between π and 2π is observed at intermediate magnetic fields. Analysis of Fermi velocities and gate induced charge carrier densities suggests an important role of strong layer asymmetry for the observed phenomena.

  2. Mechanical properties of low dimensional materials

    Science.gov (United States)

    Saini, Deepika

    Recent advances in low dimensional materials (LDMs) have paved the way for unprecedented technological advancements. The drive to reduce the dimensions of electronics has compelled researchers to devise newer techniques to not only synthesize novel materials, but also tailor their properties. Although micro and nanomaterials have shown phenomenal electronic properties, their mechanical robustness and a thorough understanding of their structure-property relationship are critical for their use in practical applications. However, the challenges in probing these mechanical properties dramatically increase as their dimensions shrink, rendering the commonly used techniques inadequate. This dissertation focuses on developing techniques for accurate determination of elastic modulus of LDMs and their mechanical responses under tensile and shear stresses. Fibers with micron-sized diameters continuously undergo tensile and shear deformations through many phases of their processing and applications. Significant attention has been given to their tensile response and their structure-tensile properties relations are well understood, but the same cannot be said about their shear responses or the structure-shear properties. This is partly due to the lack of appropriate instruments that are capable of performing direct shear measurements. In an attempt to fill this void, this dissertation describes the design of an inexpensive tabletop instrument, referred to as the twister, which can measure the shear modulus (G) and other longitudinal shear properties of micron-sized individual fibers. An automated system applies a pre-determined twist to the fiber sample and measures the resulting torque using a sensitive optical detector. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers. Two industrially important fibers, IM7 carbon fiber and KevlarRTM 119, were found to have G = 17 and 2.4 GPa, respectively. In addition to measuring the shear

  3. Studies on the pyroelectric properties of ferroelectric bilayer film%铁电薄膜热释电性质的研究

    Institute of Scientific and Technical Information of China (English)

    张芹; 董亚男; 陈红

    2013-01-01

    Using Ginzburg-Landau-Devonshire theory, a ferroelectric bilayer film consisting of two different ferroelectric constituent films with the transition layer within each constituent film is considered. Introduced a parameter,which described the differences of physical properties between two constituent films, to investigate the temperature dependence of the pyroelectric coefficient of the bilayer film. It is shown that one or two peaks can be obtained in the pyroelectric curve by the adjustment of parameter Q. The modification of ferroelectric interfacial coupling cofficient,parameter a and surficial transition layer parameter leads to the peaks of the pyroelectric curve shifting to the higher or lower temperature region.%利用Ginzburg-Landau-Devonshire (GLD)热力学唯象理论,对由2种不同铁电材料构成的含有表面过渡层的铁电双层膜体系进行了探讨.通过引入一个描述2种铁电材料物理性能差异大小的物理参量α,并考虑2种铁电材料物理性能的差异,研究了铁电双层膜的热释电性质.结果表明:通过控制参量α的大小,热释电曲线上会呈现1个或2个峰;改变铁电界面耦合系数、参量α以及表面过渡层参量的大小,热释电曲线的峰位向高温区或低温区移动.

  4. Thermoelectric Power in Bilayer Graphene Device with Ionic Liquid Gating.

    Science.gov (United States)

    Chien, Yung-Yu; Yuan, Hongtao; Wang, Chang-Ran; Lee, Wei-Li

    2016-01-01

    The quest for materials showing large thermoelectric power has long been one of the important subjects in material science and technology. Such materials have great potential for thermoelectric cooling and also high figure of merit ZT thermoelectric applications. We have fabricated bilayer graphene devices with ionic-liquid gating in order to tune its band gap via application of a perpendicular electric field on a bilayer graphene. By keeping the Fermi level at charge neutral point during the cool-down, we found that the charge puddles effect can be greatly reduced and thus largely improve the transport properties at low T in graphene-based devices using ionic liquid gating. At (Vig, Vbg) = (-1 V, +23 V), a band gap of about 36.6 ± 3 meV forms, and a nearly 40% enhancement of thermoelectric power at T = 120 K is clearly observed. Our works demonstrate the feasibility of band gap tuning in a bilayer graphene using ionic liquid gating. We also remark on the significant influence of the charge puddles effect in ionic-liquid-based devices.

  5. Amphiphile regulation of ion channel function by changes in the bilayer spring constant

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Koeppe, R.E.; Andersen, Oluf Sten

    2010-01-01

    be predicted from measurements of isolated changes in such properties. Thus, the bilayer contribution to the promiscuous regulation of membrane proteins by drugs and other amphiphiles remains unknown. To overcome this problem, we use gramicidin A (gA) channels as molecular force probes to measure the net......Many drugs are amphiphiles that, in addition to binding to a particular target protein, adsorb to cell membrane lipid bilayers and alter intrinsic bilayer physical properties (e. g., bilayer thickness, monolayer curvature, and elastic moduli). Such changes can modulate membrane protein function...... by altering the energetic cost (Delta G(bilayer)) of bilayer deformations associated with protein conformational changes that involve the protein-bilayer interface. But amphiphiles have complex effects on the physical properties of lipid bilayers, meaning that the net change in Delta G(bilayer) cannot...

  6. WO3 Nanoparticles or Nanorods Incorporating Cs2CO3/PCBM Buffer Bilayer as Carriers Transporting Materials for Perovskite Solar Cells

    Science.gov (United States)

    Chen, Chih-Ming; Lin, Zheng-Kun; Huang, Wei-Jie; Yang, Sheng-Hsiung

    2016-10-01

    In this work, we demonstrate a novel carrier transporting combination made of tungsten trioxide (WO3) nanomaterials and Cs2CO3/PCBM buffer bilayer for the fabrication of perovskite solar cells (PSCs). Two different types of WO3, including nanoparticles and nanorods, were prepared by sol-gel process and hydrothermal method, respectively. Cs2CO3/PCBM buffer bilayer was inserted between WO3 and perovskite layers to improve charge transfer efficiency and formation of pinhole-free perovskite layer. Besides, the leakage current of the devices containing Cs2CO3/PCBM buffer bilayer was significantly suppressed. The optimized device based on WO3 nanoparticles and Cs2CO3/PCBM bilayer showed an open-circuit voltage of 0.84 V, a short-circuit current density of 20.40 mA/cm2, a fill factor of 0.61, and a power conversion efficiency of 10.49 %, which were significantly higher than those of PSCs without Cs2CO3/PCBM buffer bilayer. The results revealed that the combination of WO3 nanomaterials and Cs2CO3/PCBM bilayer provides an effective solution for improving performances of PSCs.

  7. Biotechnology Applications of Tethered Lipid Bilayer Membranes

    Directory of Open Access Journals (Sweden)

    Joshua A. Jackman

    2012-12-01

    Full Text Available The importance of cell membranes in biological systems has prompted the development of model membrane platforms that recapitulate fundamental aspects of membrane biology, especially the lipid bilayer environment. Tethered lipid bilayers represent one of the most promising classes of model membranes and are based on the immobilization of a planar lipid bilayer on a solid support that enables characterization by a wide range of surface-sensitive analytical techniques. Moreover, as the result of molecular engineering inspired by biology, tethered bilayers are increasingly able to mimic fundamental properties of natural cell membranes, including fluidity, electrical sealing and hosting transmembrane proteins. At the same time, new methods have been employed to improve the durability of tethered bilayers, with shelf-lives now reaching the order of weeks and months. Taken together, the capabilities of tethered lipid bilayers have opened the door to biotechnology applications in healthcare, environmental monitoring and energy storage. In this review, several examples of such applications are presented. Beyond the particulars of each example, the focus of this review is on the emerging design and characterization strategies that made these applications possible. By drawing connections between these strategies and promising research results, future opportunities for tethered lipid bilayers within the biotechnology field are discussed.

  8. Evaluation of the performance characteristics of bilayer tablets: Part II. Impact of environmental conditions on the strength of bilayer tablets.

    Science.gov (United States)

    Kottala, Niranjan; Abebe, Admassu; Sprockel, Omar; Bergum, James; Nikfar, Faranak; Cuitiño, Alberto M

    2012-12-01

    Ambient air humidity and temperature are known to influence the mechanical strength of tablets. The objective of this work is to understand the influence of processing parameters and environmental conditions (humidity and temperature) on the strength of bilayer tablets. As part of this study, bilayer tablets were compressed with different layer ratios, dwell times, layer sequences, material properties (plastic and brittle), first and second layer forces, and lubricant concentrations. Compressed tablets were stored in stability chambers controlled at predetermined conditions (40C/45%RH, 40C/75%RH) for 1, 3, and 5 days. The axial strength of the stored tablets was measured and a statistical model was developed to determine the effects of the aforementioned factors on the strength of bilayer tablets. As part of this endeavor, a full 3 × 2(4) factorial design was executed. Responses of the experiments were analyzed using PROC GLM of SAS (SAS Institute Inc, Cary, North Carolina, USA). A model was fit using all the responses to determine the significant interactions (p < 0.05). Results of this study indicated that storage conditions and storage time have significant impact on the strength of bilayer tablets. For Avicel-lactose and lactose-Avicel tablets, tablet strength decreased with the increasing humidity and storage time. But for lactose-lactose tablets, due to the formation of solid bridges upon storage, an increase in tablet strength was observed. Significant interactions were observed between processing parameters and storage conditions on the strength of bilayer tablets.

  9. Numerical study of the influence of interfacial roughness on the exchange bias properties of ferromagnetic/antiferromagnetic bilayers

    Science.gov (United States)

    Moritz, J.; Bacher, P.; Dieny, B.

    2016-09-01

    Exchange bias and coercivity are both studied numerically in antiferromagnetic/ferromagnetic (AFM/FM) bilayers in the presence of a rough interface. The roughness is modeled by an AFM atomic mesa of variable width, in a periodic bidimensional system. Unlike the flat interface case, roughness can favor the presence of magnetic interfacial frustration or the formation of sharp magnetic domain walls pinned within the first AFM planes, inside the AFM mesa, in a Peierls potential well. We demonstrate by using athermal steepest-descent calculations that irreversible processes can occur during the hysteresis loops, when the AFM mesa width is less than half of the system period. In this case, the depinning of the domain wall from the Peierls potential well during the descending branch is not followed by its rewinding in a certain range of the AFM anisotropy. This leads to a large increase of both exchange bias and coercivity at low temperature and to an athermal training effect. When the thermal activation is taken into account by using Monte Carlo simulations, we show that a random walk of the domain wall occurs within the AFM layer. These processes induce changes in the AFM spin configuration when the system is cycled several times and produce a thermally activated training effect. Our simulations, interpreted in the context of periodic Peierls potential, provide an explanation for two important features of the exchange bias phenomenon, i.e., the thermal variation of its characteristic fields and the different contributions giving rise to the training effect (AFM bulk vs interface). More generally, the presence of interfacial atomic roughness reduces both exchange bias and coercivity with respect to the perfect interface case.

  10. Bursting Bubbles and Bilayers

    Directory of Open Access Journals (Sweden)

    Steven P. Wrenn, Stephen M. Dicker, Eleanor F. Small, Nily R. Dan, Michał Mleczko, Georg Schmitz, Peter A. Lewin

    2012-01-01

    Full Text Available This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol (PEG - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented

  11. Interfacial characterization of ceramic core materials with veneering porcelain for all-ceramic bi-layered restorative systems.

    Science.gov (United States)

    Tagmatarchis, Alexander; Tripodakis, Aris-Petros; Filippatos, Gerasimos; Zinelis, Spiros; Eliades, George

    2014-01-01

    The aim of the study was to characterize the elemental distribution at the interface between all-ceramic core and veneering porcelain materials. Three groups of all-ceramic cores were selected: A) Glass-ceramics (Cergo, IPS Empress, IPS Empress 2, e-max Press, Finesse); B) Glass-infiltrated ceramics (Celay Alumina, Celay Zirconia) and C) Densely sintered ceramics (Cercon, Procera Alumina, ZirCAD, Noritake Zirconia). The cores were combined with compatible veneering porcelains and three flat square test specimens were produced for each system. The core-veneer interfaces were examined by scanning electron microscopy and energy dispersive x-ray microanalysis. The glass-ceramic systems showed interfacial zones reach in Si and O, with the presence of K, Ca, Al in core and Ca, Ce, Na, Mg or Al in veneer material, depending on the system tested. IPS Empress and IPS Empress 2 demonstrated distinct transitional phases at the core-veneer interface. In the glassinfiltrated systems, intermixing of core (Ce, La) with veneer (Na, Si) elements occurred, whereas an abrupt drop of the core-veneer elemental concentration was documented at the interfaces of all densely sintered ceramics. The results of the study provided no evidence of elemental interdiffusion at the core-veneer interfaces in densely sintered ceramics, which implies lack of primary chemical bonding. For the glass-containing systems (glassceramics and glass-infiltrated ceramics) interdiffusion of the glass-phase seems to play a critical role in establishing a primary bonding condition between ceramic core and veneering porcelain.

  12. Electronic properties of MoS{sub 2} on monolayer, bilayer and bulk SiC: A density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Zan, Wenyan; Geng, Wei [State Key Laboratory of Applied Organic Chemistry, Department of Chemistry, Lanzhou University, Lanzhou 730000 (China); Liu, Huanxiang [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Yao, Xiaojun, E-mail: xjyao@lzu.edu.cn [State Key Laboratory of Applied Organic Chemistry, Department of Chemistry, Lanzhou University, Lanzhou 730000 (China)

    2016-05-05

    The structure and electronic properties of MoS{sub 2} and SiC (single-layer SiC, double layer SiC, C-terminated SiC and Si-terminated SiC) composites were investigated by using density functional theory calculations. The calculation results show that the electronic properties of MoS{sub 2} are modified at different levels by combining with different thickness of SiC. The heterostructures (MoS{sub 2}/C-terminated SiC and MoS{sub 2}/Si-terminated SiC) possess larger binding energies than MoS{sub 2}/single-layer SiC and MoS{sub 2}/bilayer SiC, suggesting the higher stability for MoS{sub 2}/C-terminated SiC and MoS{sub 2}/Si-terminated SiC composites. It is found that charge transfer is from SiC to MoS{sub 2} in these heterostructures. MoS{sub 2}/single-layer SiC, MoS{sub 2}/double-layer SiC and MoS{sub 2}/C-terminated SiC are semiconductors, whereas MoS{sub 2}/Si-terminated SiC has no gap. - Highlights: • The structure and electronic properties of MoS{sub 2}/SiC composites were investigated. • The electronic property of MoS{sub 2} can be modulated by SiC with different thickness. • The MoS{sub 2}/Si-terminated SiC has higher stability than MoS{sub 2}/C-terminated SiC.

  13. Hybrid matrix method for stable numerical analysis of the propagation of Dirac electrons in gapless bilayer graphene superlattices

    Science.gov (United States)

    Briones-Torres, J. A.; Pernas-Salomón, R.; Pérez-Álvarez, R.; Rodríguez-Vargas, I.

    2016-05-01

    Gapless bilayer graphene (GBG), like monolayer graphene, is a material system with unique properties, such as anti-Klein tunneling and intrinsic Fano resonances. These properties rely on the gapless parabolic dispersion relation and the chiral nature of bilayer graphene electrons. In addition, propagating and evanescent electron states coexist inherently in this material, giving rise to these exotic properties. In this sense, bilayer graphene is unique, since in most material systems in which Fano resonance phenomena are manifested an external source that provides extended states is required. However, from a numerical standpoint, the presence of evanescent-divergent states in the eigenfunctions linear superposition representing the Dirac spinors, leads to a numerical degradation (the so called Ωd problem) in the practical applications of the standard Coefficient Transfer Matrix (K) method used to study charge transport properties in Bilayer Graphene based multi-barrier systems. We present here a straightforward procedure based in the hybrid compliance-stiffness matrix method (H) that can overcome this numerical degradation. Our results show that in contrast to standard matrix method, the proposed H method is suitable to study the transmission and transport properties of electrons in GBG superlattice since it remains numerically stable regardless the size of the superlattice and the range of values taken by the input parameters: the energy and angle of the incident electrons, the barrier height and the thickness and number of barriers. We show that the matrix determinant can be used as a test of the numerical accuracy in real calculations.

  14. Equilibrium insertion of nanoscale objects into phospholipid bilayers

    CERN Document Server

    Pogodin, Sergey

    2011-01-01

    Certain membrane proteins, peptides, nanoparticles and nanotubes have rigid structure and fixed shape. They are often viewed as spheres and cylinders with certain surface properties. Single Chain Mean Field theory is used to model the equilibrium insertion of nanoscale spheres and rods into the phospholipid bilayer. The equilibrium structures and the resulting free energies of the nano-objects in the bilayer allow to distinguish different orientations in the bilayer and estimate the energy barrier of insertion.

  15. Structure and properties of layered inorganic materials

    Institute of Scientific and Technical Information of China (English)

    Xue Duan

    2010-01-01

    @@ Inorganic layered materials are a class of advanced functional materials that have attracted considerable attention by virtue of their practical applications in a wide variety of fields. Sys-tematic studies of structure, design, synthesis, and fabrication processing may extend the range of practical utility of inor-ganic layered functional materials, in areas such as food industry,chemical industry, energy engineering, environmental engineer-ing, drug and gene delivery, electronics technology, and materials protection.

  16. Bilayer Effects of Antimalarial Compounds.

    Directory of Open Access Journals (Sweden)

    Nicole B Ramsey

    Full Text Available Because of the perpetual development of resistance to current therapies for malaria, the Medicines for Malaria Venture developed the Malaria Box to facilitate the drug development process. We tested the 80 most potent compounds from the box for bilayer-mediated effects on membrane protein conformational changes (a measure of likely toxicity in a gramicidin-based stopped flow fluorescence assay. Among the Malaria Box compounds tested, four compounds altered membrane properties (p< 0.05; MMV007384 stood out as a potent bilayer-perturbing compound that is toxic in many cell-based assays, suggesting that testing for membrane perturbation could help identify toxic compounds. In any case, MMV007384 should be approached with caution, if at all.

  17. Feeling the hidden mechanical forces in lipid bilayer is an original sense.

    Science.gov (United States)

    Anishkin, Andriy; Loukin, Stephen H; Teng, Jinfeng; Kung, Ching

    2014-06-03

    Life's origin entails enclosing a compartment to hoard material, energy, and information. The envelope necessarily comprises amphipaths, such as prebiotic fatty acids, to partition the two aqueous domains. The self-assembled lipid bilayer comes with a set of properties including its strong anisotropic internal forces that are chemically or physically malleable. Added bilayer stretch can alter force vectors on embedded proteins to effect conformational change. The force-from-lipid principle was demonstrated 25 y ago when stretches opened purified Escherichia coli MscL channels reconstituted into artificial bilayers. This reductionistic exercise has rigorously been recapitulated recently with two vertebrate mechanosensitive K(+) channels (TREK1 and TRAAK). Membrane stretches have also been known to activate various voltage-, ligand-, or Ca(2+)-gated channels. Careful analyses showed that Kv, the canonical voltage-gated channel, is in fact exquisitely sensitive even to very small tension. In an unexpected context, the canonical transient-receptor-potential channels in the Drosophila eye, long presumed to open by ligand binding, is apparently opened by membrane force due to PIP2 hydrolysis-induced changes in bilayer strain. Being the intimate medium, lipids govern membrane proteins by physics as well as chemistry. This principle should not be a surprise because it parallels water's paramount role in the structure and function of soluble proteins. Today, overt or covert mechanical forces govern cell biological processes and produce sensations. At the genesis, a bilayer's response to osmotic force is likely among the first senses to deal with the capricious primordial sea.

  18. The Effect of Bilayer Graphene Nanoribbon Geometry on Schottky-Barrier Diode Performance

    Directory of Open Access Journals (Sweden)

    Meisam Rahmani

    2013-01-01

    Full Text Available Bilayer graphene nanoribbon is a promising material with outstanding physical and electrical properties that offers a wide range of opportunities for advanced applications in future nanoelectronics. In this study, the application of bilayer graphene nanoribbon in schottky-barrier diode is explored due to its different stacking arrangements. In other words, bilayer graphene nanoribbon schottky-barrier diode is proposed as a result of contact between a semiconductor (AB stacking and metal (AA stacking layers. To this end, an analytical model joint with numerical solution of carrier concentration for bilayer graphene nanoribbon in the degenerate and nondegenerate regimes is presented. Moreover, to determine the proposed diode performance, the carrier concentration model is adopted to derive the current-voltage characteristic of the device. The simulated results indicate a strong bilayer graphene nanoribbon geometry and temperature dependence of current-voltage characteristic showing that the forward current of the diode rises by increasing of width. In addition, the lower value of turn-on voltage appears as the more temperature increases. Finally, comparative study indicates that the proposed diode has a better performance compared to the silicon schottky diode, graphene nanoribbon homo-junction contact, and graphene-silicon schottky diode in terms of electrical parameters such as turn-on voltage and forward current.

  19. Effect of methanol on the phase-transition properties of glycerol-monopalmitate lipid bilayers investigated using molecular dynamics simulations: in quest of the biphasic effect.

    Science.gov (United States)

    Laner, Monika; Hünenberger, Philippe H

    2015-02-01

    The effect of methanol on the phase and phase-transition properties of a 2×8×8 glycerol-1-monopalmitate bilayer patch is investigated using a series of 239 molecular dynamics simulations on the 180 ns timescale, considering methanol concentrations cM and temperatures T in the ranges 0-12.3M and 302-338 K, respectively. The results in the form of hysteresis-corrected transition temperatures Tm are compatible with the expected features of the biphasic effect, with a reversal concentration crev of about 5.2 M. Below this concentration, the main transition is between the liquid crystal (LC) and gel (GL) phases, and Tm decreases upon increasing cM. Above this concentration, the interdigitated (ID) phase is the stable ordered phase instead, and Tm slightly increases upon increasing T up to about 10 M. The analysis of the structural and dynamical properties also reveals very different sensitivities and responses of the three phases to changes in cM. In particular, the properties of the GL phase are insensitive to cM, whereas those of the LC and ID phases are altered via an increase of the area per lipid. For the LC phase, increasing cM promotes disorder and fluidity. For the ID phase, in contrast, increasing cM up to about 10 M slightly increases the ordering and rigidity. Two side issues are also addressed, concerning: (i) the occurrence tilt-precession motions in the GL and ID phases; (ii) the influence of the pressure coupling scheme employed in the simulations, semi- or fully-anisotropic, on the simulation results.

  20. Theoretic insights into the Ag doping in monolayer and bilayer ZnO armchair nanoribbons: edge effect and position-dependent properties

    Energy Technology Data Exchange (ETDEWEB)

    Li Yanlu [Shandong University, Department of Chemistry and Chemical Engineering (China); Zhao Xian; Cheng Xiufeng [Shandong University, State Key Laboratory of Crystal Materials (China); Fan Weiliu, E-mail: fwl@sdu.edu.cn [Shandong University, Department of Chemistry and Chemical Engineering (China)

    2012-10-15

    One-dimensional nanoribbons, thickness of which is smaller than width, exhibit special confinement and edge effects far from uniform in the cross-section. By means of density functional theory, we investigated the influence of the edges and doping positions on the electronic structure of Ag-doped ZnO armchair nanoribbons (ZnOANRs). Ag doping in monolayer and bilayer ZnOANRs (m- and b-ZnOANRs) have all been examined. The results indicated that there is no significant difference on the stability of Ag doping in different positions of both m- and b-ZnOANRs, but exhibits very different electronic properties directly related to the different doping positions. The depth of the acceptor states has essential relationship with the interaction between host O 2p and Ag 4d states in the acceptor. Ag substituting Zn atoms at the inner region of m-ZnOANRs could create shallow acceptors with small hole effective masses, benefit for p-type conduction. Ag doping in the inner region of b-ZnOANRs would create shallow acceptors but larger hole effective masses. The difficulty of hole mobility could be improved by increasing the Ag doping concentration in b-ZnOANRs. The discussion about the mechanism and the suggestion about the achievement in the experiment are interesting and timely.

  1. Finite-size effects on electronic structure and local properties in passivated AA-stacked bilayer armchair-edge graphene nanoribbons

    Science.gov (United States)

    Chen, Xiongwen; Shi, Zhengang; Xiang, Shaohua; Song, Kehui; Zhou, Guanghui

    2017-03-01

    Based on the tight-binding model and dual-probe scanning tunneling microscopy technology, we theoretically investigate the electronic structure and local property in the passivated AA-stacked bilayer armchair-edge graphene nanoribbons (AABLAGNRs). We show that they are highly sensitive to the size of the ribbons, which is evidently different from the single-layer armchair-edge graphene nanoribbons. The ‘3p’ rule only applies to the narrow AABLGNRs. Namely, in the passivated 3p- and (3p  +  1)-AABLGNRs, the narrow ribbons are semiconducting while the medium and wide ribbons are metallic. Although the passivated (3p  +  2)-AABLGNRs are metallic, the ‘3j’ rule only applies to the narrow and medium ribbons. Namely, electrons are in the semiconducting states at sites of line 3j while they are in the metallic states at other sites. This induces a series of parallel and discrete metallic channels, consisting of lines 3j  -  1 and 3j  -  2, for the low-energy electronic transports. In the passivated wide (3p  +  2)-AABLGNRs, all electrons are in the metallic states. Additionally, the ‘3p’ and ‘3j’ rules are controllable to disappear and reappear by applying an external perpendicular electric field. Resultantly, an electric filed-driven current switch can be realized in the passivated narrow and medium (3p  +  2)-AABLGNRs.

  2. Engineering amorphous-crystalline interfaces in TiO2-x/TiO2-y-based bilayer structures for enhanced resistive switching and synaptic properties

    Science.gov (United States)

    Bousoulas, P.; Asenov, P.; Karageorgiou, I.; Sakellaropoulos, D.; Stathopoulos, S.; Tsoukalas, D.

    2016-10-01

    The operating principle of resistive random access memories (RRAMs) relies on the distribution of ionic species and their influence on the electron transport. Taking into account that formation and annihilation of conducting filaments (CFs) is the driving mechanism for the switching effect, it is very important to control the regions where these filaments will evolve. Thus, homolayers of titanium oxide with different oxygen contents were fabricated in order to tune the local electrical and thermal properties of the CFs and narrow down the potential percolation paths. We show that the oxygen content in the top layer of the TiO2-x/TiO2-y bilayer memristors can directly influence the morphology of the layers which affect the diffusion barrier and consequently the diffusivity and drift velocity of oxygen vacancies, yielding in important enhancement of switching characteristics, in terms of spatial uniformity (σ/μ < 0.2), enlarged switching ratio (˜104), and synaptic learning. In order to address the experimental data, a physical model was applied, divulging the crucial role of temperature, electric potential and oxygen vacancy density on the switching effect and offering physical insights to the SET/RESET transitions and the analog switching. The forming free nature of all the devices in conjunction with the self-rectifying behavior, should also be regarded as important assets towards RRAM device optimization.

  3. Two-component membrane material properties and domain formation from dissipative particle dynamics.

    Science.gov (United States)

    Illya, G; Lipowsky, R; Shillcock, J C

    2006-09-21

    The material parameters (area stretch modulus and bending rigidity) of two-component amphiphilic membranes are determined from dissipative particle dynamics simulations. The preferred area per molecule for each species is varied so as to produce homogeneous mixtures or nonhomogeneous mixtures that form domains. If the latter mixtures are composed of amphiphiles with the same tail length, but different preferred areas per molecule, their material parameters increase monotonically as a function of composition. By contrast, mixtures of amphiphiles that differ in both tail length and preferred area per molecule form both homogeneous and nonhomogeneous mixtures that both exhibit smaller values of their material properties compared to the corresponding pure systems. When the same nonhomogeneous mixtures of amphiphiles are assembled into planar membrane patches and vesicles, the resulting domain shapes are different when the bending rigidities of the domains are sufficiently different. Additionally, both bilayer and monolayer domains are observed in vesicles. We conclude that the evolution of the domain shapes is influenced by the high curvature of the vesicles in the simulation, a result that may be relevant for biological vesicle membranes.

  4. Cytocompatibility and Antibacterial Properties of Capping Materials

    Science.gov (United States)

    Arciola, Carla Renata; Monaco, Annachiara; Lombardini, Marco

    2014-01-01

    The aim of this study was to evaluate and compare the antimicrobial activity and cytocompatibility of six different pulp-capping materials: Dycal (Dentsply), Calcicur (Voco), Calcimol LC (Voco), TheraCal LC (Bisco), MTA Angelus (Angelus), and Biodentine (Septodont). To evaluate antimicrobial activity, materials were challenged in vitro with Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguis in the agar disc diffusion test. Cytocompatibility of the assayed materials towards rat MDPC-23 cells was evaluated at different times by both MTT and apoptosis assays. Results significantly differed among the different materials tested. Both bacterial growth inhibition halos and cytocompatibility performances were significantly different among materials with different composition. MTA-based products showed lower cytotoxicity and valuable antibacterial activity, different from calcium hydroxide-based materials, which exhibited not only higher antibacterial activity but also higher cytotoxicity. PMID:24959601

  5. Cytocompatibility and Antibacterial Properties of Capping Materials

    Directory of Open Access Journals (Sweden)

    Claudio Poggio

    2014-01-01

    Full Text Available The aim of this study was to evaluate and compare the antimicrobial activity and cytocompatibility of six different pulp-capping materials: Dycal (Dentsply, Calcicur (Voco, Calcimol LC (Voco, TheraCal LC (Bisco, MTA Angelus (Angelus, and Biodentine (Septodont. To evaluate antimicrobial activity, materials were challenged in vitro with Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguis in the agar disc diffusion test. Cytocompatibility of the assayed materials towards rat MDPC-23 cells was evaluated at different times by both MTT and apoptosis assays. Results significantly differed among the different materials tested. Both bacterial growth inhibition halos and cytocompatibility performances were significantly different among materials with different composition. MTA-based products showed lower cytotoxicity and valuable antibacterial activity, different from calcium hydroxide-based materials, which exhibited not only higher antibacterial activity but also higher cytotoxicity.

  6. Metallurgy and properties of plasma spray formed materials

    Science.gov (United States)

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

    1992-01-01

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

  7. Absorption properties of waste matrix materials

    Energy Technology Data Exchange (ETDEWEB)

    Briggs, J.B. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1997-06-01

    This paper very briefly discusses the need for studies of the limiting critical concentration of radioactive waste matrix materials. Calculated limiting critical concentration values for some common waste materials are listed. However, for systems containing large quantities of waste materials, differences up to 10% in calculated k{sub eff} values are obtained by changing cross section data sets. Therefore, experimental results are needed to compare with calculation results for resolving these differences and establishing realistic biases.

  8. Cytocompatibility and Antibacterial Properties of Capping Materials

    OpenAIRE

    Claudio Poggio; Carla Renata Arciola; Riccardo Beltrami; Annachiara Monaco; Alberto Dagna; Marco Lombardini; Livia Visai

    2014-01-01

    The aim of this study was to evaluate and compare the antimicrobial activity and cytocompatibility of six different pulp-capping materials: Dycal (Dentsply), Calcicur (Voco), Calcimol LC (Voco), TheraCal LC (Bisco), MTA Angelus (Angelus), and Biodentine (Septodont). To evaluate antimicrobial activity, materials were challenged in vitro with Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguis in the agar disc diffusion test. Cytocompatibility of the assayed materials towa...

  9. Studies of molecular properties of polymeric materials

    Science.gov (United States)

    Harries, W. L.; Long, Sheila Ann T.; Long, Edward R., Jr.

    1990-01-01

    Aerospace environment effects (high energy electrons, thermal cycling, atomic oxygen, and aircraft fluids) on polymeric and composite materials considered for structural use in spacecraft and advanced aircraft are examined. These materials include Mylar, Ultem, and Kapton. In addition to providing information on the behavior of the materials, attempts are made to relate the measurements to the molecular processes occurring in the material. A summary and overview of the technical aspects are given along with a list of the papers that resulted from the studies. The actual papers are included in the appendices and a glossary of technical terms and definitions is included in the front matter.

  10. New elastoplastic materials with performance properties

    OpenAIRE

    Sanda VISAN,; Virginia CIOBOTARU; Florica IONESCU; Anca ANGELESCU

    2009-01-01

    The fabrication of high performance materials using EPDM rubber and polyethylene mixtures with a low cost, nonpolluting and minimum investment technology is studied. These new materials can be used for obtaining a lot of goods for the economy, sport and private life..

  11. New elastoplastic materials with performance properties

    Directory of Open Access Journals (Sweden)

    Sanda VISAN,

    2009-06-01

    Full Text Available The fabrication of high performance materials using EPDM rubber and polyethylene mixtures with a low cost, nonpolluting and minimum investment technology is studied. These new materials can be used for obtaining a lot of goods for the economy, sport and private life.

  12. Textile materials for lightweight constructions technologies, methods, materials, properties

    CERN Document Server

    2016-01-01

    In this book, experts on textile technologies convey both general and specific informa­tion on various aspects of textile engineering, ready-made technologies, and textile chemistry. They describe the entire process chain from fiber materials to various yarn constructions, 2D and 3D textile constructions, preforms, and interface layer design. In addition, the authors introduce testing methods, shaping and simulation techniques for the characterization of and structural mechanics calculations on anisotropic, pliable high-performance textiles, including specific examples from the fields of fiber plastic composites, textile concrete, and textile membranes. Readers will also be familiarized with the potential offered by increasingly popular textile structures, for instance in the fields of composite technology, construction technology, security technology, and membrane technology. Textile materials and semi-finished products have widely varied potential characteristics, and are commonly used as essential element...

  13. Elastic properties of superconductors and materials with weakly correlated spins.

    Science.gov (United States)

    Binek, Christian

    2017-07-07

    It is shown that in the ergodic regime, the temperature dependence of Young's modulus is solely determined by the magnetic properties of a material. For the large class of materials with paramagnetic or diamagnetic response, simple functional forms of the temperature derivative of Young's modulus are derived and compared with experimental data and empirical results. Superconducting materials in the Meissner phase are ideal diamagnets. As such, they display remarkable elastic properties. Constant diamagnetic susceptibility gives rise to a temperature independent elastic modulus for ceramic and single crystalline superconductors alike. The thermodynamic approach established in this report, paves the way to tailor elastic material parameters through the design of magnetic properties.

  14. Optimization of Structure and Material Properties for Solids Composed of Softening Material

    DEFF Research Database (Denmark)

    Bendsøe, Martin P.; Guedes, J.M.; J.M., Plaxton;

    1996-01-01

    Recent results on the design of material properties in the context of global structural optimization provide, in analytical form, a prediction of the optimal material tensor distributions for two or three dimensional continuum structures. The model developed for that purpose is extended here...... to cover the design of a structure and associated material properties for a system composed of a generic form of nonlinear softening material. As was established in the earlier study on design with linear materials, the formulation for combined 'material and structure' design with softening materials can...

  15. Superconductivity and magnetism: Materials properties and developments

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, N.H.; Bay, N.; Grivel, J.C. (eds.) [and others

    2003-07-01

    The 24th Risoe International Symposium on Materials Science focuses on development of new materials, devices and applications, as well as experimental and theoretical studies of novel and unexplained phenomena in superconductivity and magnetism, e.g. within high.T{sub c} superconductivity, magnetic superconductors, MgB{sub 2}, CMR materials, nanomagnetism and spin-tronics. The aim is to stimulate exchange of ideas and establish new collaborations between leading Danish and international scientists. The topics are addressed by presentations from 24 invited speakers and by 41 contributed papers. (ln)

  16. Fundamental Material Properties Underlying Solid Oxide Electrochemistry

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Hansen, Karin Vels; Holtappels, Peter

    2012-01-01

    and electronic conductor (MIEC) the electrode is. Selected examples of literature studies of specific electrodes in solid oxide cells (SOC) are discussed. The reported effects of impurities - both impurities in the electrode materials and in the gases – point to high reactivity and mobility of materials...... in the TPB region. Also, segregations to the surfaces and interfaces of the electrode materials, which may affect the electrode reaction mechanism, are very dependent on the exact history of fabrication and operation. The positive effects of even small concentrations of nanoparticles in the electrodes may...

  17. Fundamental Material Properties Underlying Solid Oxide Electrochemistry

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Hansen, Karin Vels; Holtappels, Peter

    2012-01-01

    and electronic conductor (MIEC) the electrode is. Selected examples of literature studies of specific electrodes in solid oxide cells (SOC) are discussed. The reported effects of impurities - both impurities in the electrode materials and in the gases – point to high reactivity and mobility of materials...... place. The length of the TPB is a key factor even though the width and depth of the zone, in which the rate limiting reactions take place, may vary depending of the degree of the electrode materials ability to conduct both electrons and ions, i.e. the TPB zone volume depends on how good a mixed ionic...... in the TPB region. Also, segregations to the surfaces and interfaces of the electrode materials, which may affect the electrode reaction mechanism, are very dependent on the exact history of fabrication and operation. The positive effects of even small concentrations of nanoparticles in the electrodes may...

  18. Optical properties of active photonic materials

    OpenAIRE

    Zeng, Yong

    2007-01-01

    Because of the generation of polaritons, which are quasiparticles possessing the characteristics of both photonics and electronics, active photonic materials offer a possible solution to transfer electromagnetic energy below the diffraction limit and further increase the density of photonic integrated circuits. A theoretical investigation of these exciting materials is, therefore, very important for practical applications. Four different kinds of polaritons have been studied in this thesis, (...

  19. Elastic properties of superconductors and materials with weakly correlated spins

    OpenAIRE

    Binek, Christian

    2017-01-01

    It is shown that in the ergodic regime, the temperature dependence of Young?s modulus is solely determined by the magnetic properties of a material. For the large class of materials with paramagnetic or diamagnetic response, simple functional forms of the temperature derivative of Young?s modulus are derived and compared with experimental data and empirical results. Superconducting materials in the Meissner phase are ideal diamagnets. As such, they display remarkable elastic properties. Const...

  20. Effect of Undulations on Surface Tension in Simulated Bilayers

    NARCIS (Netherlands)

    Marrink, S.J.; Mark, A.E.

    2001-01-01

    To understand the effect of the finite size of simulation cells on the equilibrium properties of bilayers, an extensive series of glycerolmonoolein bilayer molecular dynamics simulations in which the surface area and system size were systematically changed have been conducted. Systems ranging from

  1. Dielectric properties of materials at microwave frequencies

    Directory of Open Access Journals (Sweden)

    Ivo Křivánek

    2008-01-01

    Full Text Available The paper introduces the review of the present state of art in the measurement of the interaction of electromagnetic waves with different kinds of materials. It is analysis of the possibilities of the mea­surement of the interaction of high frequencies waves (microwaves with materials and proposal of the experimental method for the studies mentioned above.The electromagnetic field consists of two components: electric and magnetic field. The influence of these components on materials is different. The influence of the magnetic field is negligible and it has no impact on practical use. The influence of the electric field is strong as the interaction between them results in the creation of electric currents in the material (Křivánek and Buchar, 1993.Experiments focused on the evaluation of the complex dielectric permitivity of different materials have been performed. The permitivity of solid material is also measurable by phasemethod, when the specimen is a part of transmission sub-circuit. Microwave instrument for complex permittivity measurement works in X frequency band (8.2–12.5 GHz, the frequency 10.1 GHz was used for all the measurement in the laboratory of physics, Mendel University in Brno. The extensive number of experimental data have been obtained for different materials. The length of the square side of the ae­rial open end was 50 mm and internal dimensions of waveguides were 23 mm × 10 mm. The samples have form of the plate shape with dimensions 150 mm × 150 mm × 4 mm.

  2. Test Methods for Measuring Material Properties of Composite Materials in all Three Material Axes

    Science.gov (United States)

    2012-01-24

    conducted using ASTM D 6641/D 6641M “Standard Test Method for Determining the Compressive Properties of Polymer Matrix Composite Laminates Using a Combined...D 7291/D 7291M “Standard Test Method for Through-Thickness “Flatwise” Tensile Strength and Elastic Modulus of a Fiber- Reinforced Polymer Matrix Composite Material...34Flatwise" Tensile Strength and Elastic Modulus of a Fiber-Reinforced Polymer Matrix Composite Material”. West Conshohocken, PA, 2005, DOI: 10.1520/D7291

  3. Tribological Property of Polyimide Porous Materials

    Institute of Scientific and Technical Information of China (English)

    PU Yu-ping; L(U) Guang-shu; LI Xiao-jun; XIAO Han-cheng

    2006-01-01

    The friction performance of the polyimide (PI) porous composite materials made by moulding method with MoS2 or polytetrafluoroethylene (PTFE) appended are disserted. The result shows that all the PI-based porous composites have the performance of transfer lubrication in the friction process, and the transfer film is built between the counter friction bodies; with the increasing of the MoS2 a mount from 0 to 20%, the friction coefficient trends toward decrease, and the tr ansfer lubricate phenomenon become more obvious; when adding PTFE as synergist t o the porous PI+MoS2 composite material, the synergistic effect happens, which can improve the friction performance of the material effectively.

  4. The effect of depolarization fields on the electronic properties of two-dimensional materials

    Science.gov (United States)

    Shin, Young-Han; Kim, Hye Jung; Noor-A-Alam, Mohammad

    2015-03-01

    Graphene is a two-dimensional semimetal with a zero band gap. By weakening the sp2 covalent bonding of graphene with additional elements such as hydrogen or fluorine, however, it is possible to make it insulating. We can expect that the band gap converges to that of a three-dimensional analogue by repeating such two-dimensional layers along the normal to the layer. If we control the position of additional elements to make a dipole monolayer, the system will have an intrinsic internal field decreases as the number of layers increases. But, for two-dimensional bilayers, depolarization field is so strong that its electronic properties can be much different from its monolayer analogue. In this presentation, we show that the internal fields induced by dipole moments can change electronic properties of two-dimensional materials such as graphene-like structures and complex metal oxides. This work was supported by the National Research Foundation of Korea Grant by the Ministry of Education, Science, and Technology (2009-0093818, 2012-014007, 2014M3A7B4049367)

  5. Structure and Properties of Energetic Materials

    Science.gov (United States)

    1992-12-02

    7.76 9.11 30 Gurney energy (MJ/kg) 1.1 1.6 30 Heat of detonation (MJ/kg) -5.02 -6.78 30 In Table 2 we compare the properties of TATB and...velocity of HMX is some 17% greater than that of TATB, the Gurney energy 45% greater, and the heat of detonation 35% greater One reason that TATB...MJ/kg) 1.1 1.6 30 Heat of detonation (MJ/kg) -5.02 -6.78 30 In Table 2 we compare the properties of TATB and cyclotetramethylenetetranitramine (HMX

  6. Adsorption Properties of Chalk Reservoir Materials

    DEFF Research Database (Denmark)

    Okhrimenko, Denis

    Understanding adsorption energetics and wetting properties of calcium carbonate surfaces is essential for developing remediation strategies for aquifers, improving oil recovery, minimising risk in CO2 storage and optimising industrial processes. This PhD was focussed on comparing the vapour....../gas adsorption properties of synthetic calcium carbonate phases (calcite, vaterite and aragonite) with chalk, which is composed of biogenic calcite (>98%). In combination with data from nanotechniques, the results demonstrate the complexity of chalk behavior and the role of nanoscale clay particles. The results...

  7. Interlayer thermal conductance within a phosphorene and graphene bilayer.

    Science.gov (United States)

    Hong, Yang; Zhang, Jingchao; Zeng, Xiao Cheng

    2016-11-24

    Monolayer graphene possesses unusual thermal properties, and is often considered as a prototype system for the study of thermal physics of low-dimensional electronic/thermal materials, despite the absence of a direct bandgap. Another two-dimensional (2D) atomic layered material, phosphorene, is a natural p-type semiconductor and it has attracted growing interest in recent years. When a graphene monolayer is overlaid on phosphorene, the hybrid van der Waals (vdW) bilayer becomes a potential candidate for high-performance thermal/electronic applications, owing to the combination of the direct-bandgap properties of phosphorene with the exceptional thermal properties of graphene. In this work, the interlayer thermal conductance at the phosphorene/graphene interface is systematically investigated using classical molecular dynamics (MD) simulation. The transient pump-probe heating method is employed to compute the interfacial thermal resistance (R) of the bilayer. The predicted R value at the phosphorene/graphene interface is 8.41 × 10(-8) K m(2) W(-1) at room temperature. Different external and internal conditions, i.e., temperature, contact pressure, vacancy defect, and chemical functionalization, can all effectively reduce R at the interface. Numerical results of R reduction as a function of temperature, interfacial coupling strength, defect ratio, or hydrogen coverage are reported with the most R reduction amounting to 56.5%, 70.4%, 34.8% and 84.5%, respectively.

  8. Organic materials with nonlinear optical properties

    Science.gov (United States)

    Stupp, Samuel I.; Son, Sehwan; Lin, Hong-Cheu

    1995-01-01

    The present invention is directed to organic materials that have the ability to double or triple the frequency of light that is directed through the materials. Particularly, the present invention is directed to the compound 4-[4-(2R)-2-cyano-7-(4'-pentyloxy-4-biphenylcarbonyloxy)phenylheptylidene) phenylcarbonyloxy]benzaldehyde, which can double the frequency of light that is directed through the compound. The invention is also directed to the compound (12-hydroxy-5,7-dodecadiynyl) 4'-[(4'-pentyloxy-4-biphenyl)carbonyloxy]-4-biphenylcarboxylate, and its polymeric form. The polymeric form can triple the frequency of light directed through it.

  9. Finite Element Method for Analysis of Material Properties

    DEFF Research Database (Denmark)

    Rauhe, Jens Christian

    description of the material microstructure the finite element models must contain a large number of elements and this problem is solved by using the preconditioned conjugated gradient solver with an Element-By-Element preconditioner. Finite element analysis provides the volume averaged stresses and strains...... and the finite element method. The material microstructure of the heterogeneous material is non-destructively determined using X-ray microtomography. A software program has been generated which uses the X-ray tomographic data as an input for the mesh generation of the material microstructure. To obtain a proper...... which are used for the determination of the effective properties of the heterogeneous material. Generally, the properties determined using the finite element method coupled with X-ray microtomography are in good agreement with both experimentally determined properties and properties determined using...

  10. Handbook of the Properties of Optical Materials

    Science.gov (United States)

    1984-01-01

    EFFECTIVE MASS - - MOBILITY - - A-2 ARSEWIC SELENIOE (As2 Se3 ) OPTICAL PROPERTIES TRANSMISSION RANGE: 9 - 11n Optical Absorption Coefficient = 0.079...of 55 KRS-5 as a function of wavelength. A-2120 ZINC SELENIOE ZnSe 0 STRUCTURE CRYSTALLINE SYMMETRY = Cubic, 43m LATTICE CONSTANTS (A) = a = 5.667

  11. Adsorption Properties of Chalk Reservoir Materials

    DEFF Research Database (Denmark)

    Okhrimenko, Denis

    Understanding adsorption energetics and wetting properties of calcium carbonate surfaces is essential for developing remediation strategies for aquifers, improving oil recovery, minimising risk in CO2 storage and optimising industrial processes. This PhD was focussed on comparing the vapour...

  12. Dynamic Deformation Properties of Energetic Composite Materials

    Science.gov (United States)

    2005-04-01

    properties are close to that of pure beryllium ( Silversmith and Averbach 1970), but as far as we know no-one has acted on this suggestion. According to...J.L. (1998) "Analysis of load oscillations in instrumented impact testing" Engng Fract. Mech. 60 437-446 Silversmith , D.J. and Averbach, B.L. (1970

  13. Material properties under intensive dynamic loading

    CERN Document Server

    Cherne, Frank J; Zhernokletov, Mikhail V; Glushak, B L; Zocher, Marvin A

    2007-01-01

    Understanding the physical and thermomechanical response of materials subjected to intensive dynamic loading is a challenge of great significance in engineering today. This volume assumes the task of gathering both experimental and diagnostic methods in one place, since not much information has been previously disseminated in the scientific literature.

  14. Displacement sensor based on an amorphous bilayer including a magnetostrictive component

    Energy Technology Data Exchange (ETDEWEB)

    Mehnen, L. E-mail: mehnen@gte.tuwien.ac.at; Svec, P.; Pfuetzner, H.; Duhaj, P

    2003-01-01

    The present study concerns a novel type of bilayer material for displacement sensors based on the detection of curvature changes through the magnetoelastic effect. For increased bilayer stability, attempts were made to use a double-nozzle melt spinning technique (DNT) for direct flow-cast of bilayers. Compared to an agglutination technique, DNT yielded much lower sensitivity but improved long-term stability.

  15. Modification of Textile Materials' Surface Properties Using Chemical Softener

    Directory of Open Access Journals (Sweden)

    Jurgita KOŽENIAUSKIENĖ

    2011-03-01

    Full Text Available In the present study the effect of technological treatment involving the processes of washing or washing and softening with chemical cationic softener "Surcase" produced in Great Britain on the surface properties of cellulosic textile materials manufactured from cotton, bamboo and viscose spun yarns was investigated. The changes in textile materials surface properties were evaluated using KTU-Griff-Tester device and FEI Quanta 200 FEG scanning electron microscope (SEM. It was observed that the worst hand properties and the higher surface roughness are observed of cotton materials if compared with those of bamboo and viscose materials. Also, it was shown that depending on the material structure the handle parameters of knitted materials are the better than the ones of woven fabrics.http://dx.doi.org/10.5755/j01.ms.17.1.249

  16. Size-Dependent Materials Properties Toward a Universal Equation

    Directory of Open Access Journals (Sweden)

    Guisbiers G

    2010-01-01

    Full Text Available Abstract Due to the lack of experimental values concerning some material properties at the nanoscale, it is interesting to evaluate this theoretically. Through a “top–down” approach, a universal equation is developed here which is particularly helpful when experiments are difficult to lead on a specific material property. It only requires the knowledge of the surface area to volume ratio of the nanomaterial, its size as well as the statistic (Fermi–Dirac or Bose–Einstein followed by the particles involved in the considered material property. Comparison between different existing theoretical models and the proposed equation is done.

  17. Broadband optical characterization of material properties

    DEFF Research Database (Denmark)

    Nielsen, Otto Højager Attermann

    , as well as details of the absorption spectrum which relate to chemical composition. The thesis focuses on two production process from the food industry. The first process is from the dairy industry where discrimination between chemical and structural properties is of importance. To explore...... inspection system for spectrallyresolved Static Light Scattering (SLS). (II) Photon Time-of-Flight (PToF) spectroscopy, which is a state of the art technique for characterization of turbid media. (III) A new hyperspectral imaging system based on full-field illumination by diffuse laser light. This thesis...... the fermentation process. It has also been shown that the optical inspection methods sense changes to structural properties before any are detected by traditional mechanical rheology. Finally, the developed hyperspectral imaging system was used to quantify the content of astaxanthin in fish feed, and performed...

  18. Mechanical Properties of Infrared Transmitting Materials

    Science.gov (United States)

    1978-01-01

    Theory of the Elasticity," 4th Edition, Dover Publ. Co., New York, N.Y., 1944. Marriott, J. B., and G. Rowden, "The Erosion of a Cobalt - Chromium Alloy...alumina (A1203), spinel (magnesium aluminate ), magnesia (MgO), yttria (Y203), as well as chemical vapor deposition (CVD) silicon carbide, CVD...known to be a problem. Because of their thermal and mechanical properties, alumina and magnesium aluminate (spinel) show, or can show, erosion

  19. Study of the influence of semiconductor material parameters on acoustic wave propagation modes in GaSb/AlSb bi-layered structures by Legendre polynomial method

    Science.gov (United States)

    Othmani, Cherif; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi

    2016-09-01

    The propagation of Rayleigh-Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh-Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.

  20. Study of the influence of semiconductor material parameters on acoustic wave propagation modes in GaSb/AlSb bi-layered structures by Legendre polynomial method

    Energy Technology Data Exchange (ETDEWEB)

    Othmani, Cherif, E-mail: othmanicheriffss@gmail.com; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi

    2016-09-01

    The propagation of Rayleigh–Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh–Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.

  1. Permittivity spectroscopy - an insight into materials properties.

    Science.gov (United States)

    Stoynov, Zdravko; Mladenova, Emiliya; Levi, Daniela; Vladikova, Daria

    2014-01-01

    Permittivity Spectroscopy is a branch of the Impedance Spectroscopy specially tuned for measurements and analyses of dielectrics permittivity properties. The present paper presents experimental results on permittivity properties of composite objects in which a polarizable dielectric is distributed in a fine non-polarizable matrix (solid or liquid) measured in frequency range 1 MHz down to 0.01 Hz. Two types of objects are studied - water in porous functional ceramics and lubricating oils. In both systems gigantic enhancement of the effective capacitance is observed. The first series of experiments was performed on porous membranes of yttrium doped barium cerate, which is a proton conducting ceramics with hydrophilic properties. At a given level of watering the measured capacitance is sharply increasing (3 to 5 orders of magnitude) in the lower frequency range. The second example covers permittivity study of lubricating oils, where the increase is 2-3 orders of magnitude. The phenomenon of gigantic enhancement of the effective capacitance could be related to a formation of dipole volume structures induced by the external alternating electrical field.

  2. Thermal and Electrical Properties of Nanocomposites, Including Material Properties

    NARCIS (Netherlands)

    Kochetov, R.

    2012-01-01

    The research described in this thesis is part of a state-funded IOP-EMVT project in cooperation with industrial companies, aiming at the design, assessment and implementation of new, environmental friendly (e.g. oil and SF6 - free) solid dielectric materials. A large disadvantage of solid polymer di

  3. Thermal and Electrical Properties of Nanocomposites, Including Material Properties

    NARCIS (Netherlands)

    Kochetov, R.

    2012-01-01

    The research described in this thesis is part of a state-funded IOP-EMVT project in cooperation with industrial companies, aiming at the design, assessment and implementation of new, environmental friendly (e.g. oil and SF6 - free) solid dielectric materials. A large disadvantage of solid polymer

  4. Probabilistic Modeling of Graded Timber Material Properties

    DEFF Research Database (Denmark)

    Faber, M. H.; Köhler, J.; Sørensen, John Dalsgaard

    2004-01-01

    The probabilistic modeling of timber material characteristics is considered with special emphasis to the modeling of the effect of different quality control and selection procedures used as means for quality grading in the production line. It is shown how statistical models may be established...... an important role in the overall probabilistic modeling. Therefore a scheme for estimating the parameters of probability distribution parameters focusing on the tail behavior has been established using a censored Maximum Likelihood estimation technique. The proposed probabilistic models have been formulated...

  5. Direct in situ measurement of specific capacitance, monolayer tension, and bilayer tension in a droplet interface bilayer.

    Science.gov (United States)

    Taylor, Graham J; Venkatesan, Guru A; Collier, C Patrick; Sarles, Stephen A

    2015-10-14

    Thickness and tension are important physical parameters of model cell membranes. However, traditional methods to measure these quantities require multiple experiments using separate equipment. This work introduces a new multi-step procedure for directly accessing in situ multiple physical properties of droplet interface bilayers (DIB), including specific capacitance (related to thickness), lipid monolayer tension in the Plateau-Gibbs border, and bilayer tension. The procedure employs a combination of mechanical manipulation of bilayer area followed by electrowetting of the capacitive interface to examine the sensitivities of bilayer capacitance to area and contact angle to voltage, respectively. These data allow for determining the specific capacitance of the membrane and surface tension of the lipid monolayer, which are then used to compute bilayer thickness and tension, respectively. The use of DIBs affords accurate optical imaging of the connected droplets in addition to electrical measurements of bilayer capacitance, and it allows for reversibly varying bilayer area. After validating the accuracy of the technique with diphytanoyl phosphatidylcholine (DPhPC) DIBs in hexadecane, the method is applied herein to quantify separately the effects on membrane thickness and tension caused by varying the solvent in which the DIB is formed and introducing cholesterol into the bilayer. Because the technique relies only on capacitance measurements and optical images to determine both thickness and tension, this approach is specifically well-suited for studying the effects of peptides, biomolecules, natural and synthetic nanoparticles, and other species that accumulate within membranes without altering bilayer conductance.

  6. Spectroscopic properties of rare earths in optical materials

    CERN Document Server

    Parisi, Jürgen; Osgood, R; Warlimont, Hans; Liu, Guokui; Jacquier, Bernard

    2005-01-01

    Aimed at researchers and graduate students, this book provides up-to-date information for understanding electronic interactions that impact the optical properties of rare earth ions in solids. Its goal is to establish a connection between fundamental principles and the materials properties of rare-earth activated luminescent and laser optical materials. The theoretical survey and introduction to spectroscopic properties include electronic energy level structure, intensities of optical transitions, ion-phonon interactions, line broadening, and energy transfer and up-conversion. An important aspect of the book lies in its deep and detailed discussions on materials properties and the potential of new applications such as optical storage, information processing, nanophotonics, and molecular probes that have been identified in recent experimental studies. This volume will be a valuable reference book on advanced topics of rare earth spectroscopy and materials science.

  7. Interdisciplinary research concerning the nature and properties of ceramic materials

    Science.gov (United States)

    1975-01-01

    The nature and properties of ceramic materials as they relate to solid state physics and metallurgy are studied. Special attention was given to the applications of ceramics to NASA programs and national needs.

  8. Outgassing Properties of Chemically Polished Titanium Materials

    Science.gov (United States)

    Kurisu, Hiroki; Kimoto, Gou; Fujii, Hiroaki; Tanaka, Kazuhiko; Yamamoto, Setsuo; Matsuura, Mitsuru; Ishizawa, Katsunobu; Nomura, Takeru; Murashige, Nobuyuki

    We developed a chemical polishing (CP) for titanium materials applicable to ultrahigh vacuum (UHV) and extremely high vacuum (XHV) systems. The surface roughness, Ra, of the chemically polished titanium is obtained to be 25 nm by the atomic force microscopy measurement. This value is smaller than those of the base metal (BM) and the buff-polished (BP) samples. The thickness of the surface oxide layer of CP sample is estimated to be 7 nm by the cross section of transmission electron micrograph. Amount of desorption gas of CP sample obtained by the thermal desorption measurement is smaller than those of BM and BP sample, and is the same as that of the mechanochemically polished (MCP) sample. The outgassing rate of CP sample after baking at 150°C×20 h is obtained to be 7×10-13 Pa•m•s-1. This value is lower than that of standard vacuum materials by two orders of magnitude after the ordinary baking.

  9. Transport properties of colossal magnetoresistive materials

    CERN Document Server

    Yates, K A

    2002-01-01

    A microwave technique was developed in order to test the validity of the hypothesis that the microwave transport of polycrystalline, optimally doped, colossal magnetoresistive materials was dominated by intragranular material. The microwave surface resistance at 9GHz was compared with dc resistivity and magnetisation to study the influence of yttrium doping on the grain boundary regions of bulk polycrystalline samples of La sub 0 sub . sub 7 sub - sub x Y sub x Ca sub 0 sub . sub 3 MnO sub 3. It was found that, within the grains, the addition of yttrium causes the activation energy above T sub p to increase. A phenomenological model was introduced to explain the data in terms of the difference in structure between the grain and grain boundary regions. The technique was also used to study the influence of deoxygenation on the grain boundary regions of bulk, polycrystalline, La sub 0 sub . sub 6 sub 7 Ca sub 0 sub . sub 3 sub 3 MnO sub 3. For samples interconnected porosity, low temperature (600 deg C), short a...

  10. MIDAS (Material Implementation, Database, and Analysis Source): A comprehensive resource of material properties

    Energy Technology Data Exchange (ETDEWEB)

    Tang, M; Norquist, P; Barton, N; Durrenberger, K; Florando, J; Attia, A

    2010-12-13

    MIDAS is aimed to be an easy-to-use and comprehensive common source for material properties including both experimental data and models and their parameters. At LLNL, we will develop MIDAS to be the central repository for material strength related data and models with the long-term goal to encompass other material properties. MIDAS will allow the users to upload experimental data and updated models, to view and read materials data and references, to manipulate models and their parameters, and to serve as the central location for the application codes to access the continuously growing model source codes. MIDAS contains a suite of interoperable tools and utilizes components already existing at LLNL: MSD (material strength database), MatProp (database of materials properties files), and MSlib (library of material model source codes). MIDAS requires significant development of the computer science framework for the interfaces between different components. We present the current status of MIDAS and its future development in this paper.

  11. A Reference Guide for Cryogenic Properties of Materials

    Energy Technology Data Exchange (ETDEWEB)

    Weisend, John G

    2003-09-16

    A thorough knowledge of the behavior of materials at cryogenic temperatures is critical for the design of successful cryogenic systems. Over the past 50 years, a tremendous amount of material properties at cryogenic temperatures have been measured and published. This guide lists resources for finding these properties. It covers online databases, computer codes, conference proceedings, journals, handbooks, overviews and monographs. It includes references for finding reports issued by government laboratories and agencies. Most common solids and fluids used in cryogenics are covered.

  12. Cellular and Porous Materials Thermal Properties Simulation and Prediction

    CERN Document Server

    Öchsner, Andreas; de Lemos, Marcelo J S

    2008-01-01

    Providing the reader with a solid understanding of the fundamentals as well as an awareness of recent advances in properties and applications of cellular and porous materials, this handbook and ready reference covers all important analytical and numerical methods for characterizing and predicting thermal properties. In so doing it directly addresses the special characteristics of foam-like and hole-riddled materials, combining theoretical and experimental aspects for characterization purposes.

  13. INVESTIGATION OF TRIBOLOGICAL PROPERTIES CuSn10 BEARING MATERIAL

    OpenAIRE

    2005-01-01

    Bronzes which copper based alloys is widely used because of properties physical, thermal and tribological as journal bearing material. This material that has tribological performance good conclusions gives at journal bearings. In this study, CuSn10 bronze that were manufactured journal bearings friction and wear properties has been examined and compared. SAE 1050 steel shaft has been used as counter abrader. Experiments have been carried out 10 N and 20 N loads, 750 and 1500 rpm, dry and lubr...

  14. Magnetic Properties of Nanoparticles of Antiferromagnetic Materials

    DEFF Research Database (Denmark)

    Mørup, Steen; Frandsen, Cathrine; Bødker, Franz

    2003-01-01

    The magnetic properties of antiferromagnetic nanoparticles have been studied by Mossbauer spectroscopy and neutron scattering. Temperature series of Mossbauer spectra of non-interacting, superparamagnetic hematite nanoparticles were fitted by use of the Blume-Tjon relaxation model. It has been...... found that the magnetic anisotropy energy constant increases significantly with decreasing particle size. Neutron scattering experiments on similar samples give new information on both superparamagnetic relaxation and collective magnetic excitations. There is good agreement between the values...... of the parameters obtained from Mossbauer spectroscopy and neutron scattering. In samples of interacting hematite nanoparticles, the relaxation was significantly suppressed. The Mossbauer data for these samples are in accordance with a mean field model for an ordered state of strongly interacting particles. Mixing...

  15. Surface properties of copper based cermet materials

    Energy Technology Data Exchange (ETDEWEB)

    Voinea, M. [The Centre: Product Design for Sustainable Development, Transilvania University of Brasov, Eroilor 29, 500036 (Romania)], E-mail: m.voinea@unitbv.ro; Vladuta, C.; Bogatu, C.; Duta, A. [The Centre: Product Design for Sustainable Development, Transilvania University of Brasov, Eroilor 29, 500036 (Romania)

    2008-08-25

    The paper presents the characterization of the surface properties of copper based cermets obtained by two different techniques: spray pyrolysis deposition (SPD) and electrodeposition. Copper acetate was used as precursor of Cu/CuO{sub x} cermet. The surface morphology was tailored by adding copolymers of maleic anhydride with controlled hydrophobia. The films morphology of Cu/CuO{sub x} was assessed using contact angle measurements and AFM analysis. The porous structures obtained via SPD lead to higher liquid adsorption rate than the electrodeposited films. A highly polar liquid - water is recommended as testing liquid in contact angle measurements, for estimating the porosity of copper based cermets, while glycerol can be used to distinguish among ionic and metal predominant structures. Thus, contact angle measurements can be used for a primary evaluation of the films morphology and, on the other hand, of the ratio between the cermet components.

  16. Novel thermal properties of nanostructured materials.

    Energy Technology Data Exchange (ETDEWEB)

    Eastman, J. A.

    1999-01-13

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

  17. Analytic Thermoelectric Couple Modeling: Variable Material Properties and Transient Operation

    Science.gov (United States)

    Mackey, Jonathan A.; Sehirlioglu, Alp; Dynys, Fred

    2015-01-01

    To gain a deeper understanding of the operation of a thermoelectric couple a set of analytic solutions have been derived for a variable material property couple and a transient couple. Using an analytic approach, as opposed to commonly used numerical techniques, results in a set of useful design guidelines. These guidelines can serve as useful starting conditions for further numerical studies, or can serve as design rules for lab built couples. The analytic modeling considers two cases and accounts for 1) material properties which vary with temperature and 2) transient operation of a couple. The variable material property case was handled by means of an asymptotic expansion, which allows for insight into the influence of temperature dependence on different material properties. The variable property work demonstrated the important fact that materials with identical average Figure of Merits can lead to different conversion efficiencies due to temperature dependence of the properties. The transient couple was investigated through a Greens function approach; several transient boundary conditions were investigated. The transient work introduces several new design considerations which are not captured by the classic steady state analysis. The work helps to assist in designing couples for optimal performance, and also helps assist in material selection.

  18. Solder joint technology materials, properties, and reliability

    CERN Document Server

    Tu, King-Ning

    2007-01-01

    Solder joints are ubiquitous in electronic consumer products. The European Union has a directive to ban the use of Pb-based solders in these products on July 1st, 2006. There is an urgent need for an increase in the research and development of Pb-free solders in electronic manufacturing. For example, spontaneous Sn whisker growth and electromigration induced failure in solder joints are serious issues. These reliability issues are quite complicated due to the combined effect of electrical, mechanical, chemical, and thermal forces on solder joints. To improve solder joint reliability, the science of solder joint behavior under various driving forces must be understood. In this book, the advanced materials reliability issues related to copper-tin reaction and electromigration in solder joints are emphasized and methods to prevent these reliability problems are discussed.

  19. Liquid Crystalline Semiconductors Materials, properties and applications

    CERN Document Server

    Kelly, Stephen; O'Neill, Mary

    2013-01-01

    This is an exciting stage in the development of organic electronics. It is no longer an area of purely academic interest as increasingly real applications are being developed, some of which are beginning to come on-stream. Areas that have already been commercially developed or which are under intensive development include organic light emitting diodes (for flat panel displays and solid state lighting), organic photovoltaic cells, organic thin film transistors (for smart tags and flat panel displays) and sensors. Within the family of organic electronic materials, liquid crystals are relative newcomers. The first electronically conducting liquid crystals were reported in 1988 but already a substantial literature has developed. The advantage of liquid crystalline semiconductors is that they have the easy processability of amorphous and polymeric semiconductors but they usually have higher charge carrier mobilities. Their mobilities do not reach the levels seen in crystalline organics but they circumvent all of t...

  20. Confinement of charge carriers in bilayer graphene

    NARCIS (Netherlands)

    Goossens, A.M.

    2013-01-01

    In this thesis we investigate the fundamental properties of electronic transport in bilayer graphene. We do this by confining electrons to narrow constrictions and small islands. Our key result is the fabrication and measurement of nanoscale devices that permit confinement with electric fields in b

  1. Confinement of charge carriers in bilayer graphene

    NARCIS (Netherlands)

    Goossens, A.M.

    2013-01-01

    In this thesis we investigate the fundamental properties of electronic transport in bilayer graphene. We do this by confining electrons to narrow constrictions and small islands. Our key result is the fabrication and measurement of nanoscale devices that permit confinement with electric fields in b

  2. The design and modeling of periodic materials with novel properties

    Science.gov (United States)

    Berger, Jonathan Bernard

    Cellular materials are ubiquitous in our world being found in natural and engineered systems as structural materials, sound and energy absorbers, heat insulators and more. Stochastic foams made of polymers, metals and even ceramics find wide use due to their novel properties when compared to monolithic materials. Properties of these so called hybrid materials, those that combine materials or materials and space, are derived from the localization of thermomechanical stresses and strains on the mesoscale as a function of cell topology. The effects of localization can only be generalized in stochastic materials arising from their inherent potential complexity, possessing variations in local chemistry, microstructural inhomogeneity and topological variations. Ordered cellular materials on the other hand, such as lattices and honeycombs, make for much easier study, often requiring analysis of only a single unit-cell. Theoretical bounds predict that hybrid materials have the potential to push design envelopes offering lighter stiffer and stronger materials. Hybrid materials can achieve very low and even negative coefficients of thermal expansion (CTE) while retaining a relatively high stiffness -- properties completely unmatched by monolithic materials. In the first chapter of this thesis a two-dimensional lattice is detailed that possess near maximum stiffness, relative to the tightest theoretical bound, and low, zero and even appreciably negative thermal expansion. Its CTE and stiffness are given in closed form as a function of geometric parameters and the material properties. This result is confirmed with finite elements (FE) and experiment. In the second chapter the compressive stiffness of three-dimensional ordered foams, both closed and open cell, are predicted with FE and the results placed in property space in terms of stiffness and density. A novel structure is identified that effectively achieves theoretical bounds for Young's, shear and bulk modulus

  3. Materials Selection, Synthesis, and Dielectrical Properties of PVC Nanocomposites

    OpenAIRE

    Youssef Mobarak; Bassyouni, M.; Almutawa, M.

    2013-01-01

    Materials selection process for electrical insulation application was carried out using Cambridge Engineering Selector (CES) program. Melt mixing technique was applied to prepare polyvinyl-chloride- (PVC-) nanofumed silica and nanomontmorillonite clay composites. Surface analysis and particles dispersibility were examined using scanning electron microscope. Dielectrical properties were assessed using Hipot tester. An experimental work for dielectric loss of the nanocomposite materials has bee...

  4. Understanding Materials Science History · Properties · Applications

    CERN Document Server

    Hummel, Rolf E

    2005-01-01

    This introduction to materials science both for students of engineering and physics and for the interested general public examines not only the physical and engineering properties of virtually all kinds of materials, but also their history, uses, development, and some of the implications of resource depletion and recycling. It covers all topics on materials from an entirely novel perspective: the role materials have played throughout history in the development of humankind and technologies. Specifically, it shows the connection between the technical and the cultural, economic, ecological, and societal aspects of materials science. It aims to whet the appetite of its readers and inspire them to further explore the properties and applications of metals, alloys, ceramics, plastics, and electronic materials by presenting easily understandable explanations and entertaining historical facts. It is also intended to raise the reader’s awareness of their obligations to society as practicing engineers and scientists....

  5. Finite Element Method for Analysis of Material Properties

    DEFF Research Database (Denmark)

    Rauhe, Jens Christian

    The use of cellular and composite materials have in recent years become more and more common in all kinds of structural components and accurate knowledge of the effective properties is therefore essential. In this wok the effective properties are determined using the real material microstructure...... and the finite element method. The material microstructure of the heterogeneous material is non-destructively determined using X-ray microtomography. A software program has been generated which uses the X-ray tomographic data as an input for the mesh generation of the material microstructure. To obtain a proper...... description of the material microstructure the finite element models must contain a large number of elements and this problem is solved by using the preconditioned conjugated gradient solver with an Element-By-Element preconditioner. Finite element analysis provides the volume averaged stresses and strains...

  6. OM85. Basic Properties of Optical Materials Summaries of Papers.

    Science.gov (United States)

    1985-05-01

    Optical Properties of Solids (Academic, New York, 1972) Ch.3. 7. D.B. Tanner, A.J...12, (1973). 6. T. Fleisch and R. Abermann, Thin Solid FilffF-42, 255-263 (1977). 7. F. Wooten, Optical Properties of Solids (Academic Press, New York...resolve cp structure. Such mea- surements are still lacking for many common semiconducting materials. REFERENCES 1. D.E. Aspnes, in Optical Properties of Solids :

  7. Piezoelectricity in asymmetrically strained bilayer graphene

    Science.gov (United States)

    Van der Donck, M.; De Beule, C.; Partoens, B.; Peeters, F. M.; Van Duppen, B.

    2016-09-01

    We study the electronic properties of commensurate faulted bilayer graphene by diagonalizing the one-particle Hamiltonian of the bilayer system in a complete basis of Bloch states of the individual graphene layers. Our novel approach is very general and can be easily extended to any commensurate graphene-based heterostructure. Here, we consider three cases: (i) twisted bilayer graphene, (ii) bilayer graphene where triaxial stress is applied to one layer and (iii) bilayer graphene where uniaxial stress is applied to one layer. We show that the resulting superstructures can be divided into distinct classes, depending on the twist angle or the magnitude of the induced strain. The different classes are distinguished from each other by the interlayer coupling mechanism, resulting in fundamentally different low-energy physics. For the cases of triaxial and uniaxial stress, the individual graphene layers tend to decouple and we find significant charge transfer between the layers. In addition, this piezoelectric effect can be tuned by applying a perpendicular electric field. Finally, we show how our approach can be generalized to multilayer systems.

  8. Residual stresses in bilayer dental ceramics.

    Science.gov (United States)

    Taskonak, Burak; Mecholsky, John J; Anusavice, Kenneth J

    2005-06-01

    It is clinically observed that lithia-disilicate-based all-ceramic fixed partial dentures (FPD) can fail because of the fragmentation of the veneering material. The hypothesis of this study is that the global residual stresses within the surface of those veneered FPDs may be responsible for partial fragmentation of the veneering ceramic. Bilayer and monolithic ceramic composites were prepared using a lithia disilicate based (Li2OSiO2) glass-ceramic core and a glass veneer. A four-step fracture mechanics approach was used to analyze residual stress in bilayered all-ceramic FPDs. We found a statistically significant increase in the mean flexural strengths of bilayer specimens compared with monolithic glass specimens (p < or = 0.05). There was a statistically significant difference between the mean longitudinal and transverse indentation-induced crack sizes in bilayer specimens (p < or = 0.05), which indicates the existence of residual stress. Global residual stresses in the veneer layer, calculated using a fracture mechanics equation, were determined to be responsible for the increased strength and observed chipping, i.e., spallation in bilayer ceramic composites.

  9. Grain size dependent mechanical properties in nanophase materials

    Energy Technology Data Exchange (ETDEWEB)

    Siegel, R.W. [Argonne National Lab., IL (United States); Fougere, G.E. [Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering

    1995-02-01

    It has become possible in recent years to synthesize metals and ceramics under well controlled conditions with constituent grain structures on a manometer size scale (below 100 nm). These new materials have mechanical properties that are strongly grain-size dependent and often significantly different than those of their coarser grained counterparts. Nanophase metals tend to become stronger and ceramics are more easily deformed as grain size is reduced. The observed mechanical property changes appear to be related primarily to grain size limitations and the large percentage of atoms in grain boundary environments. A brief overview of our present knowledge about the grain-size dependent mechanical properties of nanophase materials is presented.

  10. Tunneling properties of electromagnetic wave in slab superconducting material

    Institute of Scientific and Technical Information of China (English)

    Khem B. Thapa; Sanjay Srivastava; Alka Vishwakarma; S. P. Ojha

    2011-01-01

    When the electromagnetic wave propagates through a slab superconducting material in microwave ranges, tunneling properties of the electromagnetic wave at critical temperature are investigated theoretically. The transmittance and the reflectance of the slab superconducting material vary with the thickness of material as well as the refractive index of substrates.The high transmittance is found for thin superconductor at low wavelength region.However, optical properties are strongly dependent upon temperature and incidence wavelength. The electromagnetic wave is totally transmitted without loss for incidence wavelength (λ = 5000 nm) due to the zero refractive index and infinite penetration depth of the superconductor at the critical temperature.

  11. Compact rock material gas permeability properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huanling, E-mail: whl_hm@163.com [Key Laboratory of Coastal Disaster and Defence, Ministry of Education, Hohai University, Nanjing 210098 (China); LML, University of Lille, Cite Scientifique, 59655 Villeneuve d’Ascq (France); Xu, Weiya; Zuo, Jing [Institutes of Geotechnical Engineering, Hohai University, Nanjing 210098 (China)

    2014-09-15

    Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO{sub 2,} shale gas, and radioactive waste because they have extremely low permeabilities and high mechanical strengths. Using the inert gas argon as the fluid medium, the stress-dependent permeability and porosity of monzonitic granite and granite gneiss from an underground oil storage depot were measured using a permeability and porosity measurement system. Based on the test results, models for describing the relationships among the permeability, porosity, and confining pressure of rock specimens were analyzed and are discussed. A power law is suggested to describe the relationship between the stress-dependent porosity and permeability; for the monzonitic granite and granite gneiss (for monzonitic granite (A-2), the initial porosity is approximately 4.05%, and the permeability is approximately 10{sup −19} m{sup 2}; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10{sup −17} m{sup 2}; and the porosity-sensitivity exponents that link porosity and permeability are 0.98 and 3.11, respectively). Compared with moderate-porosity and high-porosity rocks, for which φ > 15%, low-porosity rock permeability has a relatively lower sensitivity to stress, but the porosity is more sensitive to stress, and different types of rocks show similar trends. From the test results, it can be inferred that the test rock specimens’ permeability evolution is related to the relative particle movements and microcrack closure.

  12. SEWABILITY PROPERTIES OF GARMENT LEATHERS TANNED WITH VARIOUS TANNING MATERIALS

    Directory of Open Access Journals (Sweden)

    ORK Nilay

    2016-05-01

    Full Text Available Chromium tannage is the most used technology in processing of garment leathers. Due to environmental requirements and demands on natural products there is an increasing interest on alternatives to chromium tannage especially on vegetable tanned leathers. Leather properties vary in a very wide range depending on the animal type it is obtained from and the process type and chemicals used in the manufacturing. In this study, the effect of various tanning materials to the sewability of garment leathers was investigated. For this purpose, vegetable, chromium and chromium-vegetable combination tanned garment leathers from the same animal origin were supplied from a garment leather manufacturing factory. Needle penetration force and the sewability values of these leathers were determined by using L&M Sewability Tester. It was found that material properties and sewing properties showed differences regarding to the tanning material used even in same type of raw material. Chromium tanned leathers had sewability values of 13.4% horizontal and 14.2% vertical which are considered good to fair. Vegetable tanned leathers and chromium-vegetable tanned leathers had sewability values of 38.2% horizontal, 49.2% vertical and 98% horizontal, 98.5% vertical respectively which are considered poor. The results of the study conclude that, there is a big difference in material properties when the tanning technology and material is changed which also affects the sewing properties.

  13. High Temperature Thermoelectric Properties of ZnO Based Materials

    DEFF Research Database (Denmark)

    Han, Li

    This thesis investigated the high temperature thermoelectric properties of ZnO based materials. The investigation first focused on the doping mechanisms of Al-doped ZnO, and then the influence of spark plasma sintering conditions on the thermoelectric properties of Al, Ga-dually doped ZnO....... Following that, the nanostructuring effect for Al-doped ZnO was systematically investigated using samples with different microstructure morphologies. At last, the newly developed ZnCdO materials with superior thermoelectric properties and thermal stability were introduced as promising substitutions...... for conventional ZnO materials. For Al-doped ZnO, α- and γ-Al2O3 were selectively used as dopants in order to understand the doping mechanism of each phase and their effects on the thermoelectric properties. The samples were prepared by the spark plasma sintering technique from precursors calcined at various...

  14. Understanding and Predicting the Properties of Complex Materials

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Mauro, John C.; Yue, Yuanzheng

    Predicting the properties of new materials prior to manufacturing is a topic attracting great industrial and scientific interest. Mechanical properties are currently of particular interest given the increasing demand for stronger, thinner, and more flexible materials in recent years. Property...... prediction for ceramic materials is facilitated by the periodic short- and long-range order of crystals. Based on J.C. Phillips’s theory for the ionicity of chemical bonding from ~1970, a method for predicting the hardness of covalent crystals was developed in the 2000s, which is now widely applied...... for the design of new superhard ceramic materials. It took another 10 years before the same predictions became possible for glassy systems, in which the lack of long-range order and the long time scales for relaxation greatly complicate the traditional modeling efforts. The key for making progress was to extract...

  15. Bilayer-thickness-mediated interactions between integral membrane proteins.

    Science.gov (United States)

    Kahraman, Osman; Koch, Peter D; Klug, William S; Haselwandter, Christoph A

    2016-04-01

    Hydrophobic thickness mismatch between integral membrane proteins and the surrounding lipid bilayer can produce lipid bilayer thickness deformations. Experiment and theory have shown that protein-induced lipid bilayer thickness deformations can yield energetically favorable bilayer-mediated interactions between integral membrane proteins, and large-scale organization of integral membrane proteins into protein clusters in cell membranes. Within the continuum elasticity theory of membranes, the energy cost of protein-induced bilayer thickness deformations can be captured by considering compression and expansion of the bilayer hydrophobic core, membrane tension, and bilayer bending, resulting in biharmonic equilibrium equations describing the shape of lipid bilayers for a given set of bilayer-protein boundary conditions. Here we develop a combined analytic and numerical methodology for the solution of the equilibrium elastic equations associated with protein-induced lipid bilayer deformations. Our methodology allows accurate prediction of thickness-mediated protein interactions for arbitrary protein symmetries at arbitrary protein separations and relative orientations. We provide exact analytic solutions for cylindrical integral membrane proteins with constant and varying hydrophobic thickness, and develop perturbative analytic solutions for noncylindrical protein shapes. We complement these analytic solutions, and assess their accuracy, by developing both finite element and finite difference numerical solution schemes. We provide error estimates of our numerical solution schemes and systematically assess their convergence properties. Taken together, the work presented here puts into place an analytic and numerical framework which allows calculation of bilayer-mediated elastic interactions between integral membrane proteins for the complicated protein shapes suggested by structural biology and at the small protein separations most relevant for the crowded membrane

  16. Edge effects on band gap energy in bilayer 2H-MoS{sub 2} under uniaxial strain

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Liang; Wang, Jin; Dongare, Avinash M., E-mail: dongare@uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Namburu, Raju [Computational and Information Sciences Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); O' Regan, Terrance P.; Dubey, Madan [Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland 20783 (United States)

    2015-06-28

    The potential of ultrathin MoS{sub 2} nanostructures for applications in electronic and optoelectronic devices requires a fundamental understanding in their electronic structure as a function of strain. Previous experimental and theoretical studies assume that an identical strain and/or stress state is always maintained in the top and bottom layers of a bilayer MoS{sub 2} film. In this study, a bilayer MoS{sub 2} supercell is constructed differently from the prototypical unit cell in order to investigate the layer-dependent electronic band gap energy in a bilayer MoS{sub 2} film under uniaxial mechanical deformations. The supercell contains an MoS{sub 2} bottom layer and a relatively narrower top layer (nanoribbon with free edges) as a simplified model to simulate the as-grown bilayer MoS{sub 2} flakes with free edges observed experimentally. Our results show that the two layers have different band gap energies under a tensile uniaxial strain, although they remain mutually interacting by van der Waals interactions. The deviation in their band gap energies grows from 0 to 0.42 eV as the uniaxial strain increases from 0% to 6% under both uniaxial strain and stress conditions. The deviation, however, disappears if a compressive uniaxial strain is applied. These results demonstrate that tensile uniaxial strains applied to bilayer MoS{sub 2} films can result in distinct band gap energies in the bilayer structures. Such variations need to be accounted for when analyzing strain effects on electronic properties of bilayer or multilayered 2D materials using experimental methods or in continuum models.

  17. Nanostructured antireflective bilayers: Optical design and preparation

    Energy Technology Data Exchange (ETDEWEB)

    Detrich, Ádám [Budapest University of Technology and Economics, Department of Physical Chemistry and Materials Science, Centre for Colloid Chemistry, H-1521 Budapest (Hungary); Nagy, Norbert [Research Centre for Natural Sciences (MTA TTK), Institute for Technical Physics and Materials Science (MFA), P.O. Box 49, H-1525 Budapest (Hungary); Nyári, Mária; Albert, Emőke; Zámbó, Dániel [Budapest University of Technology and Economics, Department of Physical Chemistry and Materials Science, Centre for Colloid Chemistry, H-1521 Budapest (Hungary); Hórvölgyi, Zoltán, E-mail: zhorvolgyi@mail.bme.hu [Budapest University of Technology and Economics, Department of Physical Chemistry and Materials Science, Centre for Colloid Chemistry, H-1521 Budapest (Hungary)

    2014-05-01

    We show different methods for tailoring and fabrication of various cost-effective antireflective nanocoatings on transparent and non-transparent substrates. The main purpose was to prepare coatings with decreased reflectance in the full visible wavelength range using simple wet layer deposition techniques. Structure of coatings was designed by optical simulations applying simplified calculations. The refractive index of substrates was also considered for the calculations. The advantageous optical properties were achieved by bilayered structures combining compact and porous sol–gel derived oxide layers and nanoparticulate films. The bilayered structures enhance the flexibility of design by not only the selection of the layer thicknesses but also by different ways of adjusting the effective refractive index of the layers. Furthermore, chemical stability of the coatings was also investigated. The optical and structural properties of prepared films and bilayered coatings were studied by UV–vis spectroscopy and scanning electron microscopy, respectively. The transmittance of coated glass substrates was above 97.5%, while the reflectance of coated silicon substrates was below 4% between 450 nm and 900 nm. - Highlights: • Designed antireflective bilayered coatings on glass and silicon. • Simple, colloid chemical approaches to preparation. • Favorable optical properties by combining compact and porous oxide layers. • Different ways for adjusting the effective refractive index. • Strong chemical resistance against acidic effects.

  18. Dielectric properties of tissues and biological materials: a critical review.

    Science.gov (United States)

    Foster, K R; Schwan, H P

    1989-01-01

    We critically review bulk electrical properties of tissues and other biological materials, from DC to 20 GHz, with emphasis on the underlying mechanisms responsible for the properties. We summarize the classical principles behind dielectric relaxation and critically review recent developments in this field. Special topics include a summary of the significant recent advances in theories of counterion polarization effects, dielectric properties of cancer vs. normal tissues, properties of low-water-content tissues, and macroscopic field-coupling considerations. Finally, the dielectric properties of tissues are summarized as empirical correlations with tissue water content in other compositional variables; in addition, a comprehensive table is presented of dielectric properties. The bulk electrical properties of tissues are needed for many bioengineering applications of electric fields or currents, and they provide insight into the basic mechanisms that govern the interaction of electric fields with tissue.

  19. Regulation of sodium channel function by bilayer elasticity

    DEFF Research Database (Denmark)

    Lundbaek, Jens A; Birn, Pia; Hansen, Anker J

    2004-01-01

    be a general mechanism regulating membrane protein function, we examined whether voltage-dependent skeletal-muscle sodium channels, expressed in HEK293 cells, are regulated by bilayer elasticity, as monitored using gramicidin A (gA) channels. Nonphysiological amphiphiles (beta-octyl-glucoside, Genapol X-100......, Triton X-100, and reduced Triton X-100) that make lipid bilayers less "stiff", as measured using gA channels, shift the voltage dependence of sodium channel inactivation toward more hyperpolarized potentials. At low amphiphile concentration, the magnitude of the shift is linearly correlated to the change...... in gA channel lifetime. Cholesterol-depletion, which also reduces bilayer stiffness, causes a similar shift in sodium channel inactivation. These results provide strong support for the notion that bilayer-protein hydrophobic coupling allows the bilayer elastic properties to regulate membrane protein...

  20. Asymmetric heat transfer from nanoparticles in lipid bilayers

    Science.gov (United States)

    Potdar, Dipti; Sammalkorpi, Maria

    2015-12-01

    Here, we use molecular dynamics simulations to characterize the heat transfer properties of lipid bilayer - gold nanoparticle systems in which the nanoparticle acts as a heat source. The focus is on dipalmitoylphosphatidylcholine (DPPC) lipid bilayers and thiolated alcohol and alkyl functionalized nanoparticles as prototype hydrophilic and hydrophobic nanoparticles. We find hydrophilic nanoparticles which are partly in contact with the surrounding water environment are more efficient in transferring heat to the system than hydrophobic ones which reside surrounded by the membrane. This is because of the hydrogen bonding capability of the hydroxy pentanethiol and the more efficient heat conductivity through water than the lipid bilayer. Additionally, we find the heat conductance is strongly asymmetric and has a discontinuity between the bilayer leaflets. In total, the findings provide understanding on heat transport from localized heat sources in lipid bilayers and could bear significance, e.g., in engineering and controlling photoactivated triggering of liposomal systems.

  1. Investigation of thermal properties of raw materials of asphalt mixtures

    Science.gov (United States)

    Géber, R.; Simon, A.; Kocserha, I.

    2017-02-01

    Asphalt mixtures are composite materials, which are made of different grades of mineral aggregates and bitumen. During the mixing process mineral materials were blended with bitumen at relatively high temperature (∼200 °C). As the binding process come off in these higher temperature range, thermal properties of asphaltic materials are important. The aim of this project is to reveal the thermal properties of raw materials. During our research two types of mineral aggregates were tested (limestone and dolomite) by different methods. Differential thermal analysis, thermal expansion and thermal conductivity were investigated at technologically important temperatures. The results showed that the structure of mineral materials did not change at elevated temperatures, expansion of samples was neglible, while thermal conductivity changed by temperature.

  2. A Summary of the Fatigue Properties of Wind Turbine Materials

    Energy Technology Data Exchange (ETDEWEB)

    SUTHERLAND, HERBERT J.

    1999-10-07

    Modern wind turbines are fatigue critical machines that are typically used to produce electrical power from the wind. The materials used to construct these machines are subjected to a unique loading spectrum that contains several orders of magnitude more cycles than other fatigue critical structures, e.g., an airplane. To facilitate fatigue designs, a large database of material properties has been generated over the past several years that is specialized to materials typically used in wind turbines. In this paper, I review these fatigue data. Major sections are devoted to the properties developed for wood, metals (primarily aluminum) and fiberglass. Special emphasis is placed on the fiberglass discussion because this material is current the material of choice for wind turbine blades. The paper focuses on the data developed in the U.S., but cites European references that provide important insights.

  3. Thermal properties of graphene and nanostructured carbon materials

    Science.gov (United States)

    Balandin, Alexander A.

    2011-08-01

    Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. Carbon allotropes and their derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range -- of over five orders of magnitude -- from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. Here, I review the thermal properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. Special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe the prospects of applications of graphene and carbon materials for thermal management of electronics.

  4. Properties of structural materials in liquid metal environment. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Borgstedt, H.U. [ed.

    1991-12-15

    The International Working Group on Fast Reactors (IWGFR) Specialists Meeting on Properties of Structural Materials in Liquid Metal Environment was held during June 18 to June 20, 1991, at the Nuclear Research Centre (Kernforschungszentrum) in Karlsruhe, Germany. The Specialists Meeting was divided into five technical sessions which addressed topics as follows: Creep-Rupture Behaviour of Structural Materials in Liquid Metal Environment; Behaviour of Materials in Liquid Metal Environments under Off-Normal Conditions;Fatigue and Creep-Fatigue of Structural Materials in Liquid Metal Environment; Crack Propagation in Liquid Sodium; and Conclusions and recommendations. Individual papers have been cataloged separately.

  5. MPOD: A Material Property Open Database linked to structural information

    Science.gov (United States)

    Pepponi, Giancarlo; Gražulis, Saulius; Chateigner, Daniel

    2012-08-01

    Inspired by the Crystallography Open Database (COD), the Material Properties Open Database (MPOD) was given birth. MPOD aims at collecting and making publicly available at no charge tensorial properties (including scalar properties) of phases and linking such properties to structural information of the COD when available. MPOD files are written with the STAR file syntax, used and developed for the Crystallographic Information Files. A dictionary containing new definitions has been written according to the Dictionary Definition Language 1, although some tricks were adopted to allow for multiple entries still avoiding ambiguousness. The initial set includes mechanical properties, elastic stiffness and compliance, internal friction; electrical properties, resistivity, dielectric permittivity and stiffness, thermodynamic properties, heat capacity, thermal conductivity, diffusivity and expansion; electromechanical properties, piezoelectricity, electrostriction, electromechanical coupling; optical properties; piezooptic and photoelastic properties; superconducting properties, critical fields, penetration and coherence lengths. Properties are reported in MPOD files where the original published paper containing the data is cited and structural and experimental information is also given. One MPOD file contains information relative to only one publication and one phase. The files and the information contained therein can also be consulted on-line at http://www.materialproperties.org.

  6. Development and Demonstration of Material Properties Database and Software for the Simulation of Flow Properties in Cementitious Materials

    Energy Technology Data Exchange (ETDEWEB)

    Smith, F. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Flach, G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-03-30

    This report describes work performed by the Savannah River National Laboratory (SRNL) in fiscal year 2014 to develop a new Cementitious Barriers Project (CBP) software module designated as FLOExcel. FLOExcel incorporates a uniform database to capture material characterization data and a GoldSim model to define flow properties for both intact and fractured cementitious materials and estimate Darcy velocity based on specified hydraulic head gradient and matric tension. The software module includes hydraulic parameters for intact cementitious and granular materials in the database and a standalone GoldSim framework to manipulate the data. The database will be updated with new data as it comes available. The software module will later be integrated into the next release of the CBP Toolbox, Version 3.0. This report documents the development efforts for this software module. The FY14 activities described in this report focused on the following two items that form the FLOExcel package; 1) Development of a uniform database to capture CBP data for cementitious materials. In particular, the inclusion and use of hydraulic properties of the materials are emphasized; and 2) Development of algorithms and a GoldSim User Interface to calculate hydraulic flow properties of degraded and fractured cementitious materials. Hydraulic properties are required in a simulation of flow through cementitious materials such as Saltstone, waste tank fill grout, and concrete barriers. At SRNL these simulations have been performed using the PORFLOW code as part of Performance Assessments for salt waste disposal and waste tank closure.

  7. Quantum anomalous Hall phase and half-metallic phase in ferromagnetic (111) bilayers of 4 d and 5 d transition metal perovskites

    Science.gov (United States)

    Chandra, Hirak Kumar; Guo, Guang-Yu

    2017-04-01

    Extraordinary electronic phases can form in artificial oxide heterostructures, which will provide a fertile ground for new physics and also give rise to novel device functions. Based on a systematic first-principles density functional theory study of the magnetic and electronic properties of the (111) superlattices (ABO3) 2/(AB'O3)10 of 4 d and 5 d transition metal perovskite (B = Ru, Rh, Ag, Re, Os, Ir, Au; AB'O3=LaAlO3 , SrTiO3) , we demonstrate that due to quantum confinement, bilayers (LaBO3)2 (B = Ru, Re, Os) and (SrBO3)2 (B = Rh, Os, Ir) are ferromagnetic with ordering temperatures up to room temperature. In particular, bilayer (LaOsO3)2 is an exotic spin-polarized quantum anomalous Hall insulator, while the other ferromagnetic bilayers are metallic with large Hall conductances comparable to the conductance quantum. Furthermore, bilayers (LaRuO3)2 and (SrRhO3)2 are half metallic, while the bilayer (SrIrO3)2 exhibits a peculiar colossal magnetic anisotropy. Our findings thus show that 4 d and 5 d metal perovskite (111) bilayers are a class of quasi-two-dimensional materials for exploring exotic quantum phases and also for advanced applications such as low-power nanoelectronics and oxide spintronics.

  8. Electronic and optical studies of pulse laser deposited ZnO/NiO bilayer film

    Science.gov (United States)

    Baraskar, P.; Dar, T. A.; Choudhary, R. J.; Sen, P. K.; Sen, P.

    2016-10-01

    We report the structural, optical and electronic properties of polycrystalline ZnO and NiO thin films and amorphous ZnO/NiO bilayer film, prepared by pulsed laser deposition technique. Despite of the presence of both Zn and Ni in +2 state in the bilayer film, the grown bilayer shows no reflections (in XRD) corresponding to ZnO or NiO. The difference in crystal structure of ZnO and NiO leads to the strain in the grown bilayer film. An increase in the band gap has been observed in bilayer film which can be attributed to the amorphous nature of the structure.

  9. Polyvinyl siloxane impression materials: a review of properties and techniques.

    Science.gov (United States)

    Chee, W W; Donovan, T E

    1992-11-01

    Polyvinyl siloxane impression materials have been shown to have excellent properties as impression materials; however, they are sensitive to manipulative variables. Several methods of using very high viscosity (putty) materials to form "trays" to obtain uniform bulk of the wash impression are described, and the disadvantages of each of these techniques is pointed out. It is recommended that for best results acrylic resin custom trays should be used routinely. The interaction of polyvinyl siloxane materials with latex products is also discussed and problems that this inhibition can cause are stated. Suggestions to avoid this interaction are outlined. One of the disadvantages of the impression materials is that it has a relatively short working time. Refrigerating the material will increase working time without affecting accuracy.

  10. Standard Guide for Identification of Fibers, Fillers, and Core Materials in Computerized Material Property Databases

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1992-01-01

    1.1 This guide establishes the essential and desirable elements of data required for the identification in computerized material property databases of fibers, fillers, and core materials used in composite materials. A recommended format for entry of these fields into a computerized database is provided. Examples of the application of this guide are also included. 1.2 The recommended format described in this guide is suggested for use in recording data in a database, which is different from contractural reporting of actual test results. The latter type of information is described in materials specifications shown in business transactions and is subject to agreement between vendor and purchaser. 1.3 The materials covered by this guide include fibers, both continuous and discontinuous, and fillers of various geometries which are used as reinforcements in composite materials, as well as core materials used in sandwich composites. Cores may be foam, honeycomb, or naturally occurring materials such as balsa wood....

  11. Frequency-dependent dynamic effective properties of porous materials

    Institute of Scientific and Technical Information of China (English)

    Peijun Wei; Zhuping Huang

    2005-01-01

    The frequency-dependent dynamic effective properties (phase velocity, attenuation and elastic modulus) of porous materials are studied numerically. The coherent plane longitudinal and shear wave equations, which are obtained by averaging on the multiple scattering fields, are used to evaluate the frequency-dependent dynamic effective properties of a porous material. It is found that the prediction of the dynamic effective properties includes the size effects of voids which are not included in most prediction of the traditional static effective properties. The prediction of the dynamic effective elastic modulus at a relatively low frequency range is compared with that of the traditional static effective elastic modulus, and the dynamic effective elastic modulus is found to be very close to the Hashin-Shtrikman upper bound.

  12. Handbook on dielectric and thermal properties of microwaveable materials

    CERN Document Server

    Komarov, Vyacheslav V

    2012-01-01

    The application of microwave energy for thermal processing of different materials and substances is a rapidly growing trend in modern science and engineering. In fact, optimal design work involving microwaves is impossible without solid knowledge of the properties of these materials. Here s a practical reference that collects essential data on the dielectric and thermal properties of microwaveable materials, saving you countless hours on projects in a wide range of areas, including microwave design and heating, applied electrodynamics, food science, and medical technology. This unique book provides hard-to-find information on complex dielectric permittivity of media at industrial, scientific, and medical frequencies (430 MHz, 915MHz, 2.45GHz, 5.8 GHz, and 24.125GHz). Written by a leading expert in the field, this authoritative book does an exceptional job at presenting critical data on various materials and explaining what their key characteristics are concerning microwaves.

  13. Fabrication, properties, and tritium recovery from solid breeder materials

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, C.E. (Argonne National Lab., IL (USA)); Kondo, T. (Japan Atomic Energy Research Inst., Tokyo (Japan)); Roux, N. (CEA Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)); Tanaka, S. (Tokyo Univ. (Japan)); Vollath, D. (Kernforschungszentrum Karlsruhe GmbH (Germany, F.R.))

    1991-01-01

    The breeding blanket is a key component of the fusion reactor because it directly involves tritium breeding and energy extraction, both of which are critical to development of fusion power. The lithium ceramics continue to show promise as candidate breeder materials. This promise was recognized by the International Thermonuclear Experimental Reactor (ITER) design team in its selection of ceramics as the first option for the ITER breeder material. Blanket design studies have indicated properties in the candidate materials data base that need further investigation. Current studies are focusing on tritium release behavior at high burnup, changes in thermophysical properties with burnup, compatibility between the ceramic breeder and beryllium multiplier, and phase changes with burnup. Laboratory and in-reactor tests, some as part of an international collaboration for development of ceramic breeder materials, are underway. 133 refs., 1 fig.

  14. Reflector and Shield Material Properties for Project Prometheus

    Energy Technology Data Exchange (ETDEWEB)

    J. Nash

    2005-11-02

    This letter provides updated reflector and shield preliminary material property information to support reactor design efforts. The information provided herein supersedes the applicable portions of Revision 1 to the Space Power Program Preliminary Reactor Design Basis (Reference (a)). This letter partially answers the request in Reference (b) to provide unirradiated and irradiated material properties for beryllium, beryllium oxide, isotopically enriched boron carbide ({sup 11}B{sub 4}C) and lithium hydride. With the exception of {sup 11}B{sub 4}C, the information is provided in Attachments 1 and 2. At the time of issuance of this document, {sup 11}B{sub 4}C had not been studied.

  15. Material Property Characterization of AS4/VRM-34 Textile Laminates

    Science.gov (United States)

    Grenoble, Ray W.; Johnston, William M

    2013-01-01

    Several material properties (modulus, strengths, and fracture toughness) of a textile composite have been evaluated to provide input data to analytical models of Pultruded Rod Stiffened Efficient Unitized Structure (PRSEUS). The material system is based on warp-knitted preforms of AS4 carbon fibers and VRM-34 epoxy resin, which have been processed via resin infusion and oven curing. Tensile, compressive, shear, and fracture toughness properties have been measured at ambient and elevated temperatures. All specimens were tested in as-fabricated (dry) condition. Specimens were tested with and without through-thickness stitching.

  16. Synthesis, Properties and Mineralogy of Important Inorganic Materials

    CERN Document Server

    Warner, Terence E

    2010-01-01

    Intended as a textbook for courses involving preparative solid-state chemistry, this book offers clear and detailed descriptions on how to prepare a selection of inorganic materials that exhibit important optical, magnetic and electrical properties, on a laboratory scale. The text covers a wide range of preparative methods and can be read as separate, independent chapters or as a unified coherent body of work. Discussions of various chemical systems reveal how the properties of a material can often be influenced by modifications to the preparative procedure, and vice versa. References to miner

  17. Direct Imaging of Anisotropic Material Properties using Photorefractive Laser Ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Telschow, Kenneth Louis; Deason, Vance Albert; Schley, Robert Scott; Watson, Scott Marshall

    1999-07-01

    Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous excitation is employed and the data is recorded and displayed in all directions simultaneously at video camera frame rates. Fourier transform of the data produces an image of the wave slowness in all planar directions. The results demonstrate imaging of microstructural isotropy and anisotropy and stress induced ansiotropy in plates.

  18. Direct Imaging of Anisotropic Material Properties using Photorefractive Laser Ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    K.L. Telschow; R.S. Schley; S.M. Watson; V.A. Deason

    1999-06-01

    Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous excitation is employed and the data is recorded and displayed in all directions simultaneously at video camera frame rates. Fourier transform of the data produces an image of the wave slowness in all planar directions. The results demonstrate imaging of microstructural isotropy and anisotropy and stress induced ansiotropy in plates.

  19. INVESTIGATION OF TRIBOLOGICAL PROPERTIES CuSn10 BEARING MATERIAL

    Directory of Open Access Journals (Sweden)

    Bekir Sadık ÜNLÜ

    2005-01-01

    Full Text Available Bronzes which copper based alloys is widely used because of properties physical, thermal and tribological as journal bearing material. This material that has tribological performance good conclusions gives at journal bearings. In this study, CuSn10 bronze that were manufactured journal bearings friction and wear properties has been examined and compared. SAE 1050 steel shaft has been used as counter abrader. Experiments have been carried out 10 N and 20 N loads, 750 and 1500 rpm, dry and lubricated conditions by using radial journal bearing wear test rig. As a results, high friction coefficient and weigh loss have been obtained at dry condition more than lubricated condition.

  20. Polymers for electricity and electronics materials, properties, and applications

    CERN Document Server

    Drobny, Jiri George

    2011-01-01

    The comprehensive, practical book that explores the principles, properties, and applications of electrical polymers The electrical properties of polymers present almost limitless possibilities for industrial research and development, and this book provides an in-depth look at these remarkable molecules. In addition to traditional applications in insulating materials, wires, and cables, electrical polymers are increasingly being used in a range of emerging technologies. Presenting a comprehensive overview of how electrical polymers function and how they can be applied in the elec

  1. Mechanical properties of some polymer materials used for tooth positioners.

    Science.gov (United States)

    Collett, A R; Cook, W D; West, V C

    1994-10-01

    The chemical composition, thermal behaviour and mechanical properties of three tooth positioner materials, Urethane P1 (P1), White Rubber (WR) and Elastocryl (EL) were investigated. Infra-red spectrophotometry indicated the P1 polyurethane material to be of the polyether type, and EL to be a blend of poly(ethyl methacrylate) and poly(methyl methacrylate) while WR appeared to be filled cis-poly (isoprene) (natural rubber). The glass transition temperature (Tg) for EL was determined as approximately 10 degrees C, and for both P1 and WR the Tg was less than -50 degrees C. The stress relaxation behaviour was assessed in compression by measuring the stress variation with time. The results for all three materials conformed to the superelastic theory of rubber elasticity. EL exhibited both a more rapid rate and higher degree of stress relaxation than did P1 and WR. Recovery from deformation was assessed by compressing cylinders for given periods of time and then measuring the level of reduced residual strain of the material with time. All three materials exhibited significant residual strain (epsilon(t)) over 'clinically relevant' time periods, and the reduced residual strain (epsilon(t)/epsilon(O)) following deformation was greater for EL than P1 or WR. There was some indication that the three materials have some permanent set following deformation. It was concluded that, in considering desirable mechanical properties of tooth positioner materials, EL is the least suitable of the three examined, with none of the materials being ideal.

  2. Characterization of mechanical properties of materials using ultrasound broadband spectroscopy.

    Science.gov (United States)

    Agrawal, Megha; Prasad, Abhinav; Bellare, Jayesh R; Seshia, Ashwin A

    2016-01-01

    This article explores the characterization of homogenous materials (metals, alloys, glass and polymers) by a simple broadband ultrasonic interrogation method. The novelty lies in the use of ultrasound in a continuous way with very low input power (0 dBm or less) and analysis of the transmitted acoustic wave spectrum for material property characterization like speed of sound, density and dimensions of a material. Measurements were conducted on various thicknesses of samples immersed in liquid where continuous-wave, frequency swept ultrasonic energy was incident normal to the sample surface. The electro-acoustic transmission response is analyzed in the frequency domain with respect to a specifically constructed multi-layered analytical model. From the acoustic signature of the sample materials, material properties such as speed of sound and acoustic impedance can be calculated with experimentally derived values found to be in general agreement with the literature and with pulse-echo technique establishing the basis for a non-contact and non-destructive technique for material characterization. Further, by looking at the frequency spacing of the peaks of water when the sample is immersed, the thickness of the sample can be calculated independently from the acoustic response. This technique can prove to be an effective non-contact, non-destructive and fast material characterization technique for a wide variety of materials.

  3. Multiscale modeling of droplet interface bilayer membrane networks.

    Science.gov (United States)

    Freeman, Eric C; Farimani, Amir B; Aluru, Narayana R; Philen, Michael K

    2015-11-01

    Droplet interface bilayer (DIB) networks are considered for the development of stimuli-responsive membrane-based materials inspired by cellular mechanics. These DIB networks are often modeled as combinations of electrical circuit analogues, creating complex networks of capacitors and resistors that mimic the biomolecular structures. These empirical models are capable of replicating data from electrophysiology experiments, but these models do not accurately capture the underlying physical phenomena and consequently do not allow for simulations of material functionalities beyond the voltage-clamp or current-clamp conditions. The work presented here provides a more robust description of DIB network behavior through the development of a hierarchical multiscale model, recognizing that the macroscopic network properties are functions of their underlying molecular structure. The result of this research is a modeling methodology based on controlled exchanges across the interfaces of neighboring droplets. This methodology is validated against experimental data, and an extension case is provided to demonstrate possible future applications of droplet interface bilayer networks.

  4. Electron paramagnetic resonance of material properties and processes

    Energy Technology Data Exchange (ETDEWEB)

    Brower, K. L.

    1980-01-01

    This paper demonstrates, primarily for the non-specialist and within the context of new and recent achievements, the diagnostic value of electron paramagnetic resonance (EPR) in the study of material properties and processes. I have selected three EPR studies which demonstrate the elegance and uniqueness of EPR in atomic defect studies and exemplify unusual achievements through the use of new techniques for material measurement and preparation. A brief introduction into the origin, interaction, and detection of unpaired electrons is included.

  5. Thermomechanical Properties of Corundum—Mullite—Zirconia Materials

    Institute of Scientific and Technical Information of China (English)

    ZHONGXiangchong; SUNGengcheng

    1998-01-01

    The mechanical properties at elevated tempera-tures of corundum-mullite materials and the effects of zirconia and titania additions have been investi-gated.The results are correlated with changes in microstructure,Based on the results of these investi-gations ,reaction-sintered corundum-mullite-zirco-nia materials with improved hot strength and ther-mal shock resistance have been developed for refractor-ries usage.

  6. The synthesis and properties of nanoscale ionic materials

    KAUST Repository

    Rodriguez, Robert Salgado

    2010-02-17

    In this article we discuss the effect of constituents on structure, flow, and thermal properties of nanoscale ionic materials (NIMs). NIMs are a new class of nanohybrids consisting of a nanometer-sized core, a charged corona covalently attached to the core, and an oppositely charged canopy. The hybrid nature of NIMs allows for their properties to be engineered by selectively varying their components. The unique properties associated with these systems can help overcome some of the issues facing the implementation of nanohybrids to various commercial applications, including carbon dioxide capture,water desalinization and as lubricants. Copyright © 2010 John Wiley & Sons, Ltd.

  7. Evaluation of Water Resistance and Diffusion Properties of Paint Materials

    Directory of Open Access Journals (Sweden)

    J. Drchalová

    2001-01-01

    Full Text Available A simple method is presented for evaluating the water-proofness quality of paints on lining materials. The method is based on measuring the integral capillarity in dependence on time, and then comparing this value to the value determined for the basic lining material. Measurements of the effective water vapor permeability then provide information on the risk of condensation which may increase after applying the paint. A practical application of the method is performed with four Karlocolor paints on glass concrete substrates. All the Karlocolor paints are found to be very effective materials for driven rain protection. The diffusion properties of all the paints are found to be excellent.

  8. Determination of replicate composite bone material properties using modal analysis.

    Science.gov (United States)

    Leuridan, Steven; Goossens, Quentin; Pastrav, Leonard; Roosen, Jorg; Mulier, Michiel; Denis, Kathleen; Desmet, Wim; Sloten, Jos Vander

    2017-02-01

    Replicate composite bones are used extensively for in vitro testing of new orthopedic devices. Contrary to tests with cadaveric bone material, which inherently exhibits large variability, they offer a standardized alternative with limited variability. Accurate knowledge of the composite's material properties is important when interpreting in vitro test results and when using them in FE models of biomechanical constructs. The cortical bone analogue material properties of three different fourth-generation composite bone models were determined by updating FE bone models using experimental and numerical modal analyses results. The influence of the cortical bone analogue material model (isotropic or transversely isotropic) and the inter- and intra-specimen variability were assessed. Isotropic cortical bone analogue material models failed to represent the experimental behavior in a satisfactory way even after updating the elastic material constants. When transversely isotropic material models were used, the updating procedure resulted in a reduction of the longitudinal Young's modulus from 16.00GPa before updating to an average of 13.96 GPa after updating. The shear modulus was increased from 3.30GPa to an average value of 3.92GPa. The transverse Young's modulus was lowered from an initial value of 10.00GPa to 9.89GPa. Low inter- and intra-specimen variability was found. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Research of properties of modern heat-insulation materials

    Directory of Open Access Journals (Sweden)

    A. S. Shcherbak

    2013-04-01

    Full Text Available Purpose. To study the modern heat-insulating materials presented at the market of Ukraine and to estimate the efficiency of their application. Methodology. Research and analysis of heat-insulating materials presented at the market of Ukraine, according to the existing standards. Findings. To ensure the energy efficiency in buildings and constructions it is necessary to apply the domestic heat-insulating material, which possesses the given thermo technical characteristics, reduced indexes of water absorption, flammability and toxicity, as well as durability and relatively low self–cost. Originality. Basic heat-insulating materials, which are most widely used in construction are systematized, the researches of their properties are conducted and the foam glass is chosen as the most effective heat-insulating material. It is characterized by high thermo technical characteristics and possesses the best ecological indexes, as well as the sturdiness for aggressive factors influence. Practical value. Special attention deserves the insulating material foam glass, which is a synthetic silicate material with evenly placed pores (0.1 ... 5.0 mm separated by thin septa with a vitreous substance possesses the necessary properties and by aforesaid may be accepted for studies aimed its improvement (modification. The results of researches can be applied in the foam glass production, which is used for heat-insulation of buildings and constructions, equipment, pipelines etc.

  10. Lipid bilayer regulation of membrane protein function: gramicidin channels as molecular force probes

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Collingwood, S.A.; Ingolfsson, H.I.

    2010-01-01

    physical properties. This advance is because of the introduction of new tools for studying lipid bilayer regulation of protein function. The present review provides an introduction to the regulation of membrane protein function by the bilayer physical properties. We further describe the use of gramicidin...... channels as molecular force probes for studying this mechanism, with a unique ability to discriminate between consequences of changes in monolayer curvature and bilayer elastic moduli....

  11. Mechanics of advanced materials analysis of properties and performance

    CERN Document Server

    Matveenko, Valery

    2015-01-01

    The last decades have seen a large extension of types of materials employed in various applications. In many cases these materials demonstrate mechanical properties and performance that vary significantly from those of their traditional counterparts. Such uniqueness is sought – or even specially manufactured – to meet increased requirements on modern components and structures related to their specific use. As a result, mechanical behaviors of these materials under different loading and environmental conditions are outside the boundaries of traditional mechanics of materials, presupposing development of new characterization techniques, theoretical descriptions and numerical tools. The book presents interesting examples of recent developments in this area. Among the studied materials are bulk metallic glasses, metamaterials, special composites, piezoelectric smart structures, nonwovens, etc.

  12. Comparison of shrinkage related properties of various patch repair materials

    Science.gov (United States)

    Kristiawan, S. A.; Fitrianto, R. S.

    2017-02-01

    A patch repair material has been developed in the form of unsaturated polyester resin (UPR)-mortar. The performance and durability of this material are governed by its compatibility with the concrete being repaired. One of the compatibility issue that should be tackled is the dimensional compatibility as a result of differential shrinkage between the repair material and the concrete substrate. This research aims to evaluate such shrinkage related properties of UPR-mortar and to compare with those of other patch repair materials. The investigation includes the following aspects: free shrinkage, resistance to delamination and cracking. The results indicate that UPR-mortar poses a lower free shrinkage, lower risk of both delamination and cracking tendency in comparison to other repair materials.

  13. Surface effects on the mechanical properties of nanoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Xia Re [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China); Li Xide; Feng Xiqiao [AML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Qin Qinghua [School of Engineering, Australian National University, Canberra, ACT 0200 (Australia); Liu Jianlin, E-mail: fengxq@tsinghua.edu.cn [Department of Engineering Mechanics, China University of Petroleum, Qingdao 266555 (China)

    2011-07-01

    Using the theory of surface elasticity, we investigate the mechanical properties of nanoporous materials. The classical theory of porous materials is modified to account for surface effects, which become increasingly important as the characteristic sizes of microstructures shrink to nanometers. First, a refined Timoshenko beam model is presented to predict the effective elastic modulus of nanoporous materials. Then the surface effects on the elastic microstructural buckling behavior of nanoporous materials are examined. In particular, nanoporous gold is taken as an example to illustrate the application of the proposed model. The results reveal that both the elastic modulus and the critical buckling behavior of nanoporous materials exhibit a distinct dependence on the characteristic sizes of microstructures, e.g. the average ligament width.

  14. Bone strength and material properties of the glenoid

    DEFF Research Database (Denmark)

    Frich, Lars Henrik; Jensen, N.C.; Odgaard, A.;

    1997-01-01

    The quality of the glenoid bone is important to a successful total shoulder replacement. Finite element models have been used to model the response of the glenoid bone to an implanted prosthesis. Because very little is known about the bone strength and the material properties at the glenoid, thes...

  15. Food material properties and early hominin processing techniques.

    Science.gov (United States)

    Zink, Katherine D; Lieberman, Daniel E; Lucas, Peter W

    2014-12-01

    Although early Homo is hypothesized to have used tools more than australopiths to process foods prior to consumption, it is unknown how much the food processing techniques they used altered the material properties of foods, and therefore the masticatory forces they generated, and how well they were able to comminute foods. This study presents experimental data on changes to food material properties caused by mechanical tenderization (pounding with a stone tool) and cooking (dry roasting) of two foods likely to have been important components of the hominin diet: meat and tubers. Mechanical tenderization significantly decreased tuber toughness by 42%, but had no effect on meat toughness. Roasting significantly decreased several material properties of tubers correlated with masticatory effort including toughness (49%), fracture stress (28%) and elastic modulus (45%), but increased the toughness (77%), fracture stress (50%-222%), and elastic modulus of muscle fibers in meat (308%). Despite increasing many material properties of meat associated with higher masticatory forces, roasting also decreased measured energy loss by 28%, which likely makes it easier to chew. These results suggest that the use of food processing techniques by early Homo probably differed for meat and tubers, but together would have reduced masticatory effort, helping to relax selection to maintain large, robust faces and large, thickly enameled teeth.

  16. Tailoring material properties of a nanofibrous extracellular matrix derived hydrogel

    Science.gov (United States)

    Johnson, Todd D.; Lin, Stephen Y.; Christman, Karen L.

    2011-12-01

    In the native tissue, the interaction between cells and the extracellular matrix (ECM) is essential for cell migration, proliferation, differentiation, mechanical stability, and signaling. It has been shown that decellularized ECMs can be processed into injectable formulations, thereby allowing for minimally invasive delivery. Upon injection and increase in temperature, these materials self-assemble into porous gels forming a complex network of fibers with nanoscale structure. In this study we aimed to examine and tailor the material properties of a self-assembling ECM hydrogel derived from porcine myocardial tissue, which was developed as a tissue specific injectable scaffold for cardiac tissue engineering. The impact of gelation parameters on ECM hydrogels has not previously been explored. We examined how modulating pH, temperature, ionic strength, and concentration affected the nanoscale architecture, mechanical properties, and gelation kinetics. These material characteristics were assessed using scanning electron microscopy, rheometry, and spectrophotometry, respectively. Since the main component of the myocardial matrix is collagen, many similarities between the ECM hydrogel and collagen gels were observed in terms of the nanofibrous structure and modulation of properties by altering ionic strength. However, variation from collagen gels was noted for the gelation temperature along with varied times and rates of gelation. These discrepancies when compared to collagen are likely due to the presence of other ECM components in the decellularized ECM based hydrogel. These results demonstrate how the material properties of ECM hydrogels could be tailored for future in vitro and in vivo applications.

  17. Thermal properties of hemp fibre non-woven materials

    Science.gov (United States)

    Freivalde, Liga; Kukle, Silvija; Russell, Stephen

    2013-12-01

    This review considers the thermal properties analysis of hemp fiber non-woven materials made by three different manufacturing technologies - thermal bonding, needle-punching and hydro-entanglement. For non-wovens development two hemp fibers cultivars grown in Latvia were used - Purini and Bialobrzeskie. Thermal resistance, conductivity and the effects of several parameters on thermal performance are revised.

  18. Investigation of Effective Material Properties of Stony Meteorites

    Science.gov (United States)

    Agrawal, Parul; Carlozzi, Alex; Bryson, Kathryn

    2016-01-01

    To assess the threat posed by an asteroid entering Earth's atmosphere, one must predict if, when, and how it fragments during entry. A comprehensive understanding of the Asteroid material properties is needed to achieve this objective. At present, the meteorite material found on Earth are the only objects from an entering asteroid that can be used as representative material and be tested inside a laboratory setting. Therefore, unit cell models are developed to determine the effective material properties of stony meteorites and in turn deduce the properties of asteroids. The unit cell is representative volume that accounts for diverse minerals, porosity, and matrix composition inside a meteorite. The various classes under investigation includes H-class, L-class, and LL-class chondrites. The effective mechanical properties such as Young's Modulus and Poisson's Ratio of the unit cell are calculated by performing several hundreds of Monte-Carlo simulations. Terrestrial analogs such as Basalt and Gabbro are being used to validate the unit cell methodology.

  19. I. The metabolic properties of plutonium and allied materials

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, J.G.

    1948-05-24

    This report on the metabolic properties of plutonium and related radioactive materials presents experimental information in the following areas: radioautographic studies; tracer studies (with tables of accumulation in tissues) of actinium, radio-zirconium, technetium, radio-rubidium, radio-germanium, beryllium, and cadmium; decontamination and bone metabolism studies; and radio-chemical isolation.

  20. Material and Flexural Properties of Fiber-reinforced Rubber Concrete

    Science.gov (United States)

    Helminger, Nicholas P.

    The purpose of this research is to determine the material properties of rubber concrete with the addition of fibers, and to determine optimal mixture dosages of rubber and fiber in concrete for structural applications. Fiber-reinforced concrete and rubberized concrete have been researched separately extensively, but this research intends to combine both rubber and fiber in a concrete matrix in order to create a composite material, fiber-reinforced rubber concrete (FRRC). Sustainability has long been important in engineering design, but much of the previous research performed on sustainable concrete does not result in a material that can be used for practical purposes. While still achieving a material that can be used for structural applications, economical considerations were given when choosing the proportions and types of constituents in the concrete mix. Concrete mixtures were designed, placed, and tested in accordance with common procedures and standards, with an emphasis on practicality. Properties that were investigated include compressive strength, tensile strength, modulus of elasticity, toughness, and ductility. The basis for determining the optimal concrete mixture is one that is economical, practical, and exhibits ductile properties with a significant strength. Results show that increasing percentages of rubber tend to decrease workability, unit weight, compressive strength, split tensile strength, and modulus of elasticity while the toughness is increased. The addition of steel needle fibers to rubber concrete increases unit weight, compressive strength, split tensile strength, modulus of elasticity, toughness, and ductility of the composite material.

  1. Experimental analysis of electrical properties of composite materials

    Science.gov (United States)

    Fiala, L.; Rovnaník, P.; Černý, R.

    2017-02-01

    Dry cement-based composites are electrically non-conductive materials that behave in electric field like dielectrics. However, a relatively low amount of electrically conductive admixture significantly increases the electrical conductivity which extends applicability of such materials in practice. Therefore, they can be used as self-monitoring sensors controlling development of cracks; as sensors monitoring moisture content or when treated by an external electrical voltage as heat sources used for deicing of material's surface layer. Alkali-activated aluminosilicates (AAA), as competing materials to cement-based materials, are intensively investigated in the present due to their superior durability and environmental impact. Whereas the electrical properties of AAA are similar to those cement-based, they can be enhanced in the same way. In both cases, it is crucial to find a reasonable amount of electrically conductive phase to design composites with a sufficient electrical conductivity at an affordable price. In this paper, electrical properties of composites based on AAA binder and electrically conductive admixture represented by carbon nanotubes (CNT) are investigated. Measurements of electrical properties are carried out by means of 2-probes DC technique on nine types of samples; reference sample without the conductive phase and samples with CNT admixture in amount of 0.1 % - 2.5 % by vol. A significant increase of the electrical conductivity starts from the amount of 0.5 % CNT admixture and in case of 2.5 % CNT is about three orders of magnitude higher compared to the reference sample.

  2. Development and Analysis of Synthetic Composite Materials Emulating Patient AAA Wall Material Properties

    Science.gov (United States)

    Margossian, Christa M.

    Abdominal Aortic Aneurysm (AAA) rupture accounts for 14,000 deaths a year in the United States. Since the number of ruptures has not decreased significantly in recent years despite improvements in imaging and surgical procedures, there is a need for an accurate, noninvasive technique capable of establishing rupture risk for specific patients and discriminating lesions at high risk. In this project, synthetic composite materials replicating patient-specific wall stiffness and strength were developed and their material properties evaluated. Composites utilizing various fibers were developed to give a range of stiffness from 1825.75 kPa up through 8187.64 kPa with one base material, Sylgard 170. A range of strength from 631.12 kPa to 1083 kPa with the same base material was also found. By evaluating various base materials and various reinforcing fibers, a catalogue of stiffnesses and strengths was started to allow for adaptation to specific patient properties. Three specific patient properties were well-matched with two composites fabricated: silk thread-reinforced Sylgard 170 and silk thread-reinforced Dragon Skin 20. The composites showed similar stiffnesses to the specific patients while reaching target stresses at particular strains. Not all patients were matched with composites as of yet, but recommendations for future matches are able to be determined. These composites will allow for the future evaluation of flow-induced wall stresses in models replicating patient material properties and geometries.

  3. Preparation and Properties of Carbon Fiber Chiral Materials

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ping; HUANG Zhixin; WANG Guoqing

    2008-01-01

    The chiral materials were prepared by using the carbon fiber helices as chiral inclusions,and the composite of Fe3O4 and polyaniline as matrix.The electromagnetic properties,including the rotation angles,the axial ratios and the complex chirality parameters,were measured by using a circular waveguide method in the 8.5-11.0 GHz frequency range.The dependence of these electromagnetic properties on the frequency and the concentration of the Fe3O4 in the composite matrix were analyzed.The results show that an appropriate concentration of Fe3O4 in the matrix is useful in improving the electromagnetic properties of the chiral material.

  4. Identification of material properties of sandwich structure with piezoelectric patches

    Directory of Open Access Journals (Sweden)

    Zemčík R.

    2008-11-01

    Full Text Available The work focuses on light-weight sandwich structures made of carbon-epoxy skins and foam core which have unique bending stiffness compared to conventional materials. The skins are manufactured by vacuum autoclave technology from unidirectional prepregs and the sandwich is then glued together. The resulting material properties of the structure usually differ from those provided by manufacturer or even those obtained from experimental tests on separate materials, which makes computational models unreliable. Therefore, the properties are identified using the combination of experimental analysis of the sandwich with attached piezoelectric transducer and corresponding static and modal finite element analyses. Simple mathematical optimization with repetitive finite element solution is used. The model is then verified by transient analysis when the piezoelectric patch is excited by harmonic signals covering the first two eigen-frequencies and the induced oscillations are measured by laser sensor.

  5. Effects of Material Properties on Bacterial Adhesion and Biofilm Formation.

    Science.gov (United States)

    Song, F; Koo, H; Ren, D

    2015-08-01

    Adhesion of microbes, such as bacteria and fungi, to surfaces and the subsequent formation of biofilms cause multidrug-tolerant infections in humans and fouling of medical devices. To address these challenges, it is important to understand how material properties affect microbe-surface interactions and engineer better nonfouling materials. Here we review the recent progresses in this field and discuss the main challenges and opportunities. In particular, we focus on bacterial biofilms and review the effects of surface energy, charge, topography, and stiffness of substratum material on bacterial adhesion. We summarize how these surface properties influence oral biofilm formation, and we discuss the important findings from nondental systems that have potential applications in dental medicine. © International & American Associations for Dental Research 2015.

  6. Structure-property relationships in silica-siloxane nanocomposite materials

    Energy Technology Data Exchange (ETDEWEB)

    Ulibarri, T.A.; Derzon, D.K.; Wang, L.C.

    1997-03-01

    The simultaneous formation of a filler phase and a polymer matrix via in situ sol-gel techniques provides silica-siloxane nanocomposite materials of high strength. This study concentrates on the effects of temperature and relative humidity on a trimodal polymer system in an attempt to accelerate the reaction as well as evaluate subtle process- structure-property relations. It was found that successful process acceleration is only viable for high humidity systems when using the tin(IV) catalyst dibutyltin dilaurate. Processes involving low humidity were found to be very temperature and time dependent. Bimodal systems were investigated and demonstrated that the presence of a short-chain component led to enhanced material strength. This part of the study also revealed a link between the particle size and population density and the optimization of material properties.

  7. Tethered and Polymer Supported Bilayer Lipid Membranes: Structure and Function

    Directory of Open Access Journals (Sweden)

    Jakob Andersson

    2016-05-01

    Full Text Available Solid supported bilayer lipid membranes are model systems to mimic natural cell membranes in order to understand structural and functional properties of such systems. The use of a model system allows for the use of a wide variety of analytical tools including atomic force microscopy, impedance spectroscopy, neutron reflectometry, and surface plasmon resonance spectroscopy. Among the large number of different types of model membranes polymer-supported and tethered lipid bilayers have been shown to be versatile and useful systems. Both systems consist of a lipid bilayer, which is de-coupled from an underlying support by a spacer cushion. Both systems will be reviewed, with an emphasis on the effect that the spacer moiety has on the bilayer properties.

  8. Active Bilayer PE/PCL Films for Food Packaging Modified with Zinc Oxide and Casein

    Directory of Open Access Journals (Sweden)

    Ana Rešček

    2015-12-01

    Full Text Available This paper studies the properties of active polymer food packaging bilayer polyethylene/polycaprolactone (PE/PCL films. Such packaging material consists of primary PE layer coated with thin film of PCL coating modified with active component (zinc oxide or zinc oxide/casein complex with intention to extend the shelf life of food and to maintain the quality and health safety. The influence of additives as active components on barrier, mechanical, thermal and antimicrobial properties of such materials was studied. The results show that, in comparison to the neat PE and PE/PCL films, some of PE/PCL bilayer films with additives exhibit improved barrier properties i.e. decreased water vapour permeability. Higher thermal stability of modified PE/PCL material is obtained due to a modified mechanism of thermal degradation. The samples with the additive nanoparticles homogeneously dispersed in the polymer matrix showed good mechanical properties. Addition of higher ZnO content contributes to the enhanced antibacterial activity of a material.

  9. Millimeter wave and terahertz dielectric properties of biological materials

    Science.gov (United States)

    Khan, Usman Ansar

    Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to

  10. Material Properties Analysis of Structural Members in Pumpkin Balloons

    Science.gov (United States)

    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

  11. Properties of granular analogue model materials: A community wide survey

    Science.gov (United States)

    Klinkmüller, M.; Schreurs, G.; Rosenau, M.; Kemnitz, H.

    2016-08-01

    We report the material properties of 26 granular analogue materials used in 14 analogue modelling laboratories. We determined physical characteristics such as bulk density, grain size distribution, and grain shape, and performed ring shear tests to determine friction angles and cohesion, and uniaxial compression tests to evaluate the compaction behaviour. Mean grain size of the materials varied between c. 100 and 400 μm. Analysis of grain shape factors shows that the four different classes of granular materials (14 quartz sands, 5 dyed quartz sands, 4 heavy mineral sands and 3 size fractions of glass beads) can be broadly divided into two groups consisting of 12 angular and 14 rounded materials. Grain shape has an influence on friction angles, with most angular materials having higher internal friction angles (between c. 35° and 40°) than rounded materials, whereas well-rounded glass beads have the lowest internal friction angles (between c. 25° and 30°). We interpret this as an effect of intergranular sliding versus rolling. Most angular materials have also higher basal friction angles (tested for a specific foil) than more rounded materials, suggesting that angular grains scratch and wear the foil. Most materials have an internal cohesion in the order of 20-100 Pa except for well-rounded glass beads, which show a trend towards a quasi-cohesionless (C < 20 Pa) Coulomb-type material. The uniaxial confined compression tests reveal that rounded grains generally show less compaction than angular grains. We interpret this to be related to the initial packing density after sifting, which is higher for rounded grains than for angular grains. Ring-shear test data show that angular grains undergo a longer strain-hardening phase than more rounded materials. This might explain why analogue models consisting of angular grains accommodate deformation in a more distributed manner prior to strain localisation than models consisting of rounded grains.

  12. Effects of Dimethyl Sulfoxide on Surface Water near Phospholipid Bilayers.

    Science.gov (United States)

    Lee, Yuno; Pincus, Philip A; Hyeon, Changbong

    2016-12-06

    Despite much effort to probe the properties of dimethyl sulfoxide (DMSO) solution, the effects of DMSO on water, especially near plasma membrane surfaces, still remain elusive. By performing molecular dynamics simulations at varying DMSO concentrations (XDMSO), we study how DMSO affects structural and dynamical properties of water in the vicinity of phospholipid bilayers. As proposed by a number of experiments, our simulations confirm that DMSO induces dehydration from bilayer surfaces and disrupts the H-bond structure of water. However, DMSO-enhanced water diffusivity at solvent-bilayer interfaces, an intriguing discovery reported by a spin-label measurement, is not confirmed in our simulations. To resolve this discrepancy, we examine the location of the spin label (Tempo) relative to the solvent-bilayer interface. In accord with the evidence in the literature, our simulations, which explicitly model Tempo-phosphatidylcholine, find that the Tempo moiety is equilibrated at ∼8-10 Å below the bilayer surface. Furthermore, the DMSO-enhanced surface-water diffusion is confirmed only when water diffusion is analyzed around the Tempo moiety that is immersed below the bilayer surface, which implies that the experimentally detected signal of water using Tempo stems from the interior of bilayers, not from the interface. Our analysis finds that the increase of water diffusion below the bilayer surface is coupled to the increase of area per lipid with an increasing XDMSO(≲10mol%). Underscoring the hydrophobic nature of the Tempo moiety, our study calls for careful re-evaluation of the use of Tempo in measurements on lipid bilayer surfaces. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  13. How to determine composite material properties using numerical homogenization

    DEFF Research Database (Denmark)

    Andreassen, Erik; Andreasen, Casper Schousboe

    2014-01-01

    Numerical homogenization is an efficient way to determine effective macroscopic properties, such as the elasticity tensor, of a periodic composite material. In this paper an educational description of the method is provided based on a short, self-contained Matlab implementation. It is shown how t...... cell of the periodic material can take the shape of a square, rectangle, or parallelogram, allowing for all kinds of 2D periodicities. © 2013 Elsevier B.V. All rights reserved.......Numerical homogenization is an efficient way to determine effective macroscopic properties, such as the elasticity tensor, of a periodic composite material. In this paper an educational description of the method is provided based on a short, self-contained Matlab implementation. It is shown how...... the basic code, which computes the effective elasticity tensor of a two material composite, where one material could be void, is easily extended to include more materials. Furthermore, extensions to homogenization of conductivity, thermal expansion, and fluid permeability are described in detail. The unit...

  14. Capillary wrinkling of thin bilayer polymeric sheets

    Science.gov (United States)

    Chang, Jooyoung; Menon, Narayanan; Russell, Thomas

    We have investigated capillary force induced wrinkling on a floated polymeric bilayer thin sheet. The origin of the wrinkle pattern is compressional hoop stress caused by the capillary force of a water droplet placed on the floated polymeric thin sheet afore investigated. Herein, we study the effect of the differences of surface energy arising from the hydrophobicity of Polystyrene (PS Mw: 97 K, Contact Angle: 88 º) and the hydrophilicity of Poly(methylmethacrylate) (PMMA Mw: 99K, Contact Angle: 68 º) on two sides of a bilayer film. We measure the number and the length of the wrinkles by broadly varying the range of thicknesses of top (9 nm to 550 nm) and bottom layer (25 nm to 330 nm). At the same, there is only a small contrast in mechanical properties of the two layers (PS E = 3.4 GPa, and PMMA E = 3 GPa). The number of the wrinkles is not strongly affected by the composition (PS(Top)/PMMA(Bottom) or PMMA(Top)/PS(Bottom)) and the thickness of each and overall bilayer system. However, the length of the wrinkle is governed by the contact angle of the drop on the top layer of bilayer system. We also compare this to the wrinkle pattern obtained in monolayer systems over a wide range of thickness from PS and PMMA (7 nm to 1 μm). W.M. Keck Foundation.

  15. Bifurcation of self-folded polygonal bilayers

    Science.gov (United States)

    Abdullah, Arif M.; Braun, Paul V.; Hsia, K. Jimmy

    2017-09-01

    Motivated by the self-assembly of natural systems, researchers have investigated the stimulus-responsive curving of thin-shell structures, which is also known as self-folding. Self-folding strategies not only offer possibilities to realize complicated shapes but also promise actuation at small length scales. Biaxial mismatch strain driven self-folding bilayers demonstrate bifurcation of equilibrium shapes (from quasi-axisymmetric doubly curved to approximately singly curved) during their stimulus-responsive morphing behavior. Being a structurally instable, bifurcation could be used to tune the self-folding behavior, and hence, a detailed understanding of this phenomenon is appealing from both fundamental and practical perspectives. In this work, we investigated the bifurcation behavior of self-folding bilayer polygons. For the mechanistic understanding, we developed finite element models of planar bilayers (consisting of a stimulus-responsive and a passive layer of material) that transform into 3D curved configurations. Our experiments with cross-linked Polydimethylsiloxane samples that change shapes in organic solvents confirmed our model predictions. Finally, we explored a design scheme to generate gripper-like architectures by avoiding the bifurcation of stimulus-responsive bilayers. Our research contributes to the broad field of self-assembly as the findings could motivate functional devices across multiple disciplines such as robotics, artificial muscles, therapeutic cargos, and reconfigurable biomedical devices.

  16. Biologic properties of surgical scaffold materials derived from dermal ECM.

    Science.gov (United States)

    Kulig, Katherine M; Luo, Xiao; Finkelstein, Eric B; Liu, Xiang-Hong; Goldman, Scott M; Sundback, Cathryn A; Vacanti, Joseph P; Neville, Craig M

    2013-07-01

    Surgical scaffold materials manufactured from donor human or animal tissue are increasingly being used to promote soft tissue repair and regeneration. The clinical product consists of the residual extracellular matrix remaining after a rigorous decellularization process. Optimally, the material provides both structural support during the repair period and cell guidance cues for effective incorporation into the regenerating tissue. Surgical scaffold materials are available from several companies and are unique products manufactured by proprietary methodology. A significant need exists for a more thorough understanding of scaffold properties that impact the early steps of host cell recruitment and infiltration. In this study, a panel of in vitro assays was used to make direct comparisons of several similar, commercially-available materials: Alloderm, Medeor Matrix, Permacol, and Strattice. Differences in the materials were detected for both cell signaling and scaffold architecture-dependent cell invasion. Material-conditioned media studies found Medeor Matrix to have the greatest positive effect upon cell proliferation and induction of migration. Strattice provided the greatest chemotaxis signaling and best suppressed apoptotic induction. Among assays measuring structure-dependent properties, Medeor Matrix was superior for cell attachment, followed by Permacol. Only Alloderm and Medeor Matrix supported chemotaxis-driven cell invasion beyond the most superficial zone. Medeor Matrix was the only material in the chorioallantoic membrane assay to support substantial cell invasion. These results indicate that both biologic and structural properties need to be carefully assessed in the considerable ongoing efforts to develop new uses and products in this important class of biomaterials. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Temporal properties of material categorization and material rating: visual vs non-visual material features.

    Science.gov (United States)

    Nagai, Takehiro; Matsushima, Toshiki; Koida, Kowa; Tani, Yusuke; Kitazaki, Michiteru; Nakauchi, Shigeki

    2015-10-01

    Humans can visually recognize material categories of objects, such as glass, stone, and plastic, easily. However, little is known about the kinds of surface quality features that contribute to such material class recognition. In this paper, we examine the relationship between perceptual surface features and material category discrimination performance for pictures of materials, focusing on temporal aspects, including reaction time and effects of stimulus duration. The stimuli were pictures of objects with an identical shape but made of different materials that could be categorized into seven classes (glass, plastic, metal, stone, wood, leather, and fabric). In a pre-experiment, observers rated the pictures on nine surface features, including visual (e.g., glossiness and transparency) and non-visual features (e.g., heaviness and warmness), on a 7-point scale. In the main experiments, observers judged whether two simultaneously presented pictures were classified as the same or different material category. Reaction times and effects of stimulus duration were measured. The results showed that visual feature ratings were correlated with material discrimination performance for short reaction times or short stimulus durations, while non-visual feature ratings were correlated only with performance for long reaction times or long stimulus durations. These results suggest that the mechanisms underlying visual and non-visual feature processing may differ in terms of processing time, although the cause is unclear. Visual surface features may mainly contribute to material recognition in daily life, while non-visual features may contribute only weakly, if at all.

  18. Atomistic Simulations of Material Properties under Extreme Conditions

    Science.gov (United States)

    An, Qi

    Extreme conditions involve low or high temperatures (> 1500 K), high pressures (> 30 MPa), high strains or strain rates, high radiation fluxes (> 100 dpa), and high electromagnetic fields (> 15T). Material properties under extreme conditions can be extremely different from those under normal conditions. Understanding material properties and performance under extreme conditions, including their dynamic evolution over time, plays an essential role in improving material properties and developing novel materials with desired properties. To understand material properties under extreme conditions, we use molecular dynamics (MD) simulations with recently developed reactive force fields (ReaxFF) and traditional embedded atom methods (EAM) potentials to examine various materials (e.g., energetic materials and binary liquids) and processes. The key results from the simulations are summarized below. Anisotropic sensitivity of RDX crystals: Based on the compress-and-shear reactive dynamics (CS-RD) simulations of cyclotrimethylene trinitramine (RDX) crystals, we predict that for mechanical shocks between 3 and 7 GPa, RDX is the most sensitive to shocks perpendicular to the (100) and (210) planes, while it is insensitive to those perpendicular to the (120), (111), and (110) planes. The simulations demonstrate that the molecular origin of anisotropic shock sensitivity is the steric hindrance to shearing of adjacent slip planes. Mechanisms of hotspot formation in polymer bonded explosives (PBXs): The simulations of a realistic model of PBXs reveal that hotspots may form at the nonplanar interfaces where shear relaxation leads to a dramatic temperature increase that persists long after the shock front has passed the interface. For energetic materials this temperature increase is coupled to chemical reactions that eventually lead to detonation. We show that decreasing the density of the binder eliminates the hotspots or reduces the sensitivity. Cavitation in binary metallic liquids

  19. Quantitative optical microscopy and micromanipulation studies on the lipid bilayer membranes of giant unilamellar vesicles

    DEFF Research Database (Denmark)

    Bagatolli, Luis; Needham, David

    2014-01-01

    some of their most important contributions to our understanding of lipid bilayer membranes; and (iii) outline studies that would utilize both techniques simultaneously on the same vesicle thus bringing the ability to characterize structure and strain responses together with the direct application......This manuscript discusses basic methodological aspects of optical microscopy and micromanipulation methods to study membranes and reviews methods to generate giant unilamellar vesicles (GUVs). In particular, we focus on the use of fluorescence microscopy and micropipette manipulation techniques...... to study composition-structure-property materials relationships of free-standing lipid bilayer membranes. Because their size (~5 to 100 m diameter) that is well above the resolution limit of regular light microscopes, GUVs are suitable membrane models for optical microscopy and micromanipulation...

  20. Tunable Fermi surface topology and Lifshitz transition in bilayer graphene

    OpenAIRE

    Varlet, Anastasia; Mucha-Kruczyński, Marcin; Bischoff, Dominik; Simonet, Pauline; Taniguchi, Takashi; Watanabe, Kenji; Fal'ko, Vladimir; Ihn, Thomas; Ensslin, Klaus

    2015-01-01

    Bilayer graphene is a highly tunable material: not only can one tune the Fermi energy using standard gates, as in single-layer graphene, but the band structure can also be modified by external perturbations such as transverse electric fields or strain. We review the theoretical basics of the band structure of bilayer graphene and study the evolution of the band structure under the influence of these two external parameters. We highlight their key role concerning the ease to experimentally pro...

  1. Microstructure characterization and magnetic properties of nano structured materials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, X.C

    2000-07-01

    The present thesis deals with the unique microstructural properties and their novel magnetic properties of core-shell Ni-Ce nano composite particles, carbon encapsulated Fe, Co, and Ni nanoparticles and the nano crystallization behavior of typical ferromagnetic Fe{sub 78}Si{sub 9}B{sub 13} ribbons. These properties have intensively been investigated by high resolution transmission electron microscopy (HREM), X-ray diffraction (XRD), scanning electron microscopy (Sem), X-ray energy dispersive spectroscopy [eds.]; selected area electron diffraction pattern (SAED), Ft-IR, differential scanning calorimeter (DSC). In addition, magnetic moments measurements at different temperatures and applied fields have been performed by transmission Moessbauer spectroscopy, superconducting quantum interference device magnetometer (SQUID), and vibrating sample magnetometer (VSM). The present studies may provide the insights for the better understanding of the correlation between the unique microstructure and novel magnetic properties for several magnetic nano structured materials. (Author)

  2. Material Properties of High-Speed Steel Rolls

    Directory of Open Access Journals (Sweden)

    Shaohua Wu

    2017-03-01

    Full Text Available Recently, it has been required to improve the material properties of high-speed steel (HSS rolls, because of the low wear resistance and low mechanical properties. To improve them, several new steels have been proposed, which have high wear resistance as well as excellent mechanical properties, e.g., hardness and tensile properties, where additional elements (V, Cr and W were employed. However, their steels may have still technical issues, as the roll surfaces become roughened during the production process. The reason for this problem is found to be affected by the oxidation of the HSS surface. In this work, we have provided the suggestions to make high wear resistance of the HSS rolls

  3. Homogenization for Periodic Heterogeneous Materials with Arbitrary Position-Dependent Material Properties

    Institute of Scientific and Technical Information of China (English)

    徐志杰

    2012-01-01

    We present a rigorous homogenization approach for elcient computation of a class of physical problems in a one-dimensional periodic heterogeneous material. This material is represented by a spatially periodic array of unit cells with a length of More specifically, the method is applied to the diffusion, heat conduction, and wave propagation problems. Heterogeneous materials can have arbitrary position-dependent continuous or discontinuous materials properties (for example heat conductivity) within the unit cell. The final effective model includes both effective properties at the leading order and high-order contributions due to the microscopic heterogeneity. A dimensionless heterogeneity parameter ~ is defined to represent high-order contributions, shown to be in the range of [-1/12, 0], and has a universal expression for all three problems. Both effective properties and heterogeneity parameter 13 are independent oft, the microscopic scale of heterogeneity. The homogenized solution describing macroscopic variations can be obtained from the effective model. Solution with sub-unit-cell accuracy can be constructed based on the homogenized solution and its spatial derivatives. The paper represents a general approach to obtain the effective model for arbitrary periodic heterogeneous materials with position-dependent properties.

  4. Rectangular waveguide material characterization: anisotropic property extraction and measurement validation

    Science.gov (United States)

    Crowgey, Benjamin Reid

    for characterization of a sample filling the cross-section of a waveguide. Due to the rectangular nature of the waveguide, typically three different samples are manufactured from the same material in order to characterize the six complex material parameters. The second technique for measuring the electromagnetic properties of a biaxially anisotropic material sample uses a reduced-aperture waveguide sample holder designed to accommodate a cubical sample. All the tensor material parameters can then be determined by measuring the reflection and transmission coefficients of a single sample placed into several orientations. The parameters are obtained using a root-searching algorithm by comparing theoretically computed and measured reflection and transmission coefficients. The theoretical coefficients are determined using a mode matching technique. The first technique for characterizing the electromagnetic properties of gyromagnetic materials considers requires filling the cross-section of a waveguide. The material parameters are extracted from the measured reflection and transmission coefficients. Since the cross-sectional dimensions of waveguides become prohibitively large at low frequencies, and it is at these frequencies that the gyromagnetic properties are most pronounced, sufficiently large samples may not be available. Therefore, the second technique uses a reduced-aperture sample holder that does not require the sample to fill the entire cross section of the guide. The theoretical reflection and transmission coefficients for both methods are determined using a mode matching technique. A nonlinear least squares method is employed to extract the gyromagnetic material parameters. Finally, this dissertation introduces a waveguide standard that acts as a surrogate material with both electric and magnetic properties and is useful for verifying systems designed to characterize engineered materials using the NRW technique. A genetic algorithm is used to optimize the all

  5. Further developments in material properties determined by vibration analysis

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang; Andreasen, Lotte; Seifert, Mette

    1997-01-01

    have been studied by testing a number of building materials. The method has been PC-integrated with the Brüel & Kjær's type 3550 vibration equipment - and special user menus have been developed to facilitate handling of the method in practice. Limits on range of test frequencies applied are discussed...... with respect to configurations of vibration equipment and shapes of test specimens used. Sensitivity studies have been made to identify sources of errors which may disturb the reliability of the method used in practice. Practical aspects with respect to test set-ups are considered in these studies - as well......A method was described in Materialnyt 1 (1995) on "Material properties determined by vibration analysis". This new method of materials testing has been further developed as the result of research at the Building Materials Laboratory, Technical University of Denmark.Practical aspects of the method...

  6. Correlation of macroscopic material properties with microscopic nuclear data

    Energy Technology Data Exchange (ETDEWEB)

    Simons, R.L.

    1981-12-18

    Two primary irradiation-induced changes occur during neutron irradiation: the displacement of atoms forming crystal defects and the transmutation of atoms into either gaseous or solid products. The material scientist studying irradiation damage to material by fusion-produced neutrons is faced with several questions: Is the nature of high-energy (14-MeV) displacement damage the same as or different from that caused by fission neutrons (< 2 MeV). How do the high helium concentrations expected in a fusion environment affect the material properties. What effects do solid transmutation products have on the behavior of the irradiated materials. In the past few years, much work has been done to answer these questions. This paper reviews recent work in this area.

  7. Thermal property of insulation material for HTS power cable

    Science.gov (United States)

    Choi, Yeon Suk; Kim, D. L.; Shin, D. W.; Hwang, S. D.

    2012-06-01

    The thermal property of insulation material is essential in developing a high temperature superconductor (HTS) power cable operating at around liquid nitrogen temperature. The accurate estimate of the heat flux is difficult in the nonmetallic materials because nonmetallic materials have a high thermal resistance and low temperature gradient along the specimen. The objective of the present work is to develop a precise instrument for measuring the thermal conductivity of insulating materials over a temperature range of 30 K to approximately the room temperature by using a cryocooler. The thermal conductivity of Teflon is measured and the accuracy confirmation is carried out by comparing published data. In addition, the experimental results of apparent thermal conductivity of polypropylene laminated paper (PPLP) are presented and the temperature dependency is also discussed

  8. Alkali-activated cementitious materials: Mechanisms, microstructure and properties

    Science.gov (United States)

    Jiang, Weimin

    The goal of this study was to examine the activation reaction, microstructure, properties, identify the mechanisms of activation, and achieve an enhanced understanding of activation processes occurring during the synthesis of alkali activated cementitious materials (AAC). The discussions classify the following categories. (1) alkali activated slag cement; (2) alkali activated portland-slag cement; (3) alkali activated fly ash-slag cement; (4) alkali activated pozzolana-lime cement; (5) alkali activated pozzolana cement. The activators involved are NaOH, KOH; Nasb2SOsb4;\\ Nasb2COsb3;\\ CaSOsb4, and soluble silicate of sodium and potassium. The effect of alkali activation on the microstructure of these materials were analyzed at the micro-nanometer scale by SEM, EDS, ESEM, and TEM. Also sp{29}Si and sp{27}Al MAS-NMR, IR, Raman, TGA, and DTA were performed to characterize the phase in these systems. Slag, fly ash, silica fume, as well as blended cements containing mixtures of these and other components were characterized. A set of ordinary portland cement paste samples served as a control. This study confirmed that AAC materials have great potential because they could generate very early high strength, greater durability and high performance. Among the benefits to be derived from this research is a better understanding of the factors that control concrete properties when using AAC materials, and by controlling the chemistry and processing to produce desired microstructures and properties, as well as their durability.

  9. Mechanical Properties of Calcium Fluoride-Based Composite Materials

    Science.gov (United States)

    Kleczewska, Joanna; Pryliński, Mariusz; Podlewska, Magdalena; Sokołowski, Jerzy; Łapińska, Barbara

    2016-01-01

    Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM) and one commercially available flowable light-curing composite material (FA) that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA), unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties. PMID:28004001

  10. Mechanical Properties of Calcium Fluoride-Based Composite Materials

    Directory of Open Access Journals (Sweden)

    Monika Łukomska-Szymańska

    2016-01-01

    Full Text Available Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM and one commercially available flowable light-curing composite material (FA that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM and Energy Dispersive Spectroscopy (EDS. Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA, unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties.

  11. Estimating Energy Conversion Efficiency of Thermoelectric Materials: Constant Property Versus Average Property Models

    Science.gov (United States)

    Armstrong, Hannah; Boese, Matthew; Carmichael, Cody; Dimich, Hannah; Seay, Dylan; Sheppard, Nathan; Beekman, Matt

    2017-01-01

    Maximum thermoelectric energy conversion efficiencies are calculated using the conventional "constant property" model and the recently proposed "cumulative/average property" model (Kim et al. in Proc Natl Acad Sci USA 112:8205, 2015) for 18 high-performance thermoelectric materials. We find that the constant property model generally predicts higher energy conversion efficiency for nearly all materials and temperature differences studied. Although significant deviations are observed in some cases, on average the constant property model predicts an efficiency that is a factor of 1.16 larger than that predicted by the average property model, with even lower deviations for temperature differences typical of energy harvesting applications. Based on our analysis, we conclude that the conventional dimensionless figure of merit ZT obtained from the constant property model, while not applicable for some materials with strongly temperature-dependent thermoelectric properties, remains a simple yet useful metric for initial evaluation and/or comparison of thermoelectric materials, provided the ZT at the average temperature of projected operation, not the peak ZT, is used.

  12. Electronic and Vibrational Properties of Low-Dimensional Heterogeneous Systems: Materials and Device Perspectives

    Science.gov (United States)

    Neupane, Mahesh Raj

    Due to the aggressive miniaturization of memory and logic devices, the current technologies based on silicon have nearly reached their ultimate size limit. One method to maintain the trend in device scaling observed by Moore's law is to create a heterostructure from existing materials and utilize the underlying electronic and optical properties. Another radical approach is the conceptualization of a new device design paradigm. The central objective of this thesis is to use both of these approaches to address issues associated with the aggressive scaling of memory and logic devices such as leakage current, leakage power, and minimizing gate oxide thickness and threshold voltage. In the first part of the dissertation, an atomistic, empirical tight binding method was used to perform a systematic investigation of the effect of physical (shape and size), and material dependent (heterogenity and strain) properties on the device related electronic and optical properties of the Germanium (Ge)/Silicon (Si) nanocrystal (NC) or quantum dot (QD). The device parameters pertaining to Ge-core/Si-shell NC-based floating gate memory and optical devices such as confinement energy, retention lifetimes and optical intensities are captured and analyzed. For both the memory and optical device applications, regardless of the shape and size, the Ge-core is found to play an important role in modifying the confinement energy and carrier dynamics. However, the variation in the thickness of outer Si-shell layer had no or minimal effect on the overall device parameters. In the second part of the dissertation, we present a systematic study of the effect of atomistic heterogeneity on the vibrational properties of quasi-2D systems and recently discovered 2D materials such as graphene, while investigating their applicabilities in future devices applications. At first, we investigate the vibrational properties of an experimentally observed misoriented bilayer graphene (MBG) system, a

  13. Elastic therapeutic tape: do they have the same material properties?

    Science.gov (United States)

    Boonkerd, Chuanpis; Limroongreungrat, Weerawat

    2016-01-01

    [Purpose] Elastic therapeutic tape has been widely used for rehabilitation and treatment of sports injuries. Tapes with different elastic properties serve different treatment purposes with inappropriate tension reducing tape effectiveness. Many tapes are available in the market, but studies on tape properties are limited. The aim of this study was to examine the material properties of elastic therapeutic tape. [Subjects and Methods] Brands of elastic therapeutic tape included KinesioTex®, ATex, Mueller, 3M, and ThaiTape. The Material Testing System Insight® 1 Electromechanical Testing Systems was used to apply a tensile force on elastic therapeutic tape. Ten specimens of each brand were tested. Stress, load, and Young’s modulus at 25%, 50%, 75%, 100%, and maximum point were collected. One-way analysis of variance with post hoc testing was used to analyze tape parameters. [Results] Maximum elongation and Young’s modulus at all percentages were significantly different between brands. There were no differences in maximum load and maximum stress. [Conclusion] Mechanical properties are different for commercial elastic therapeutic tapes. Physiotherapists and other clinicians should be aware of mechanical tape properties to correctly apply kinesio tape. PMID:27190472

  14. Elastic therapeutic tape: do they have the same material properties?

    Science.gov (United States)

    Boonkerd, Chuanpis; Limroongreungrat, Weerawat

    2016-04-01

    [Purpose] Elastic therapeutic tape has been widely used for rehabilitation and treatment of sports injuries. Tapes with different elastic properties serve different treatment purposes with inappropriate tension reducing tape effectiveness. Many tapes are available in the market, but studies on tape properties are limited. The aim of this study was to examine the material properties of elastic therapeutic tape. [Subjects and Methods] Brands of elastic therapeutic tape included KinesioTex(®), ATex, Mueller, 3M, and ThaiTape. The Material Testing System Insight(®) 1 Electromechanical Testing Systems was used to apply a tensile force on elastic therapeutic tape. Ten specimens of each brand were tested. Stress, load, and Young's modulus at 25%, 50%, 75%, 100%, and maximum point were collected. One-way analysis of variance with post hoc testing was used to analyze tape parameters. [Results] Maximum elongation and Young's modulus at all percentages were significantly different between brands. There were no differences in maximum load and maximum stress. [Conclusion] Mechanical properties are different for commercial elastic therapeutic tapes. Physiotherapists and other clinicians should be aware of mechanical tape properties to correctly apply kinesio tape.

  15. Analysis of Mechanical Properties of Fabrics of Different Raw Material

    Directory of Open Access Journals (Sweden)

    Aušra ADOMAITIENĖ

    2011-07-01

    Full Text Available The study analyzes dependence of mechanical properties (breaking force, elongation at break, static friction force and static friction coefficient on integrated fabric structure factor j and raw material density r, among the fabrics of different raw material (cotton, wool, polypropylene, polyester and polyacrylnitrile and woven in different conditions. The received results demonstrate that sometimes strong dependences exist (wool, polypropylene and polyacrylnitrile, whereas in some cases (cotton and polyester there is no correlation. It was also discovered that the breaking force and elongation at break in the direction of weft increase, when fabric structure becomes more rigid. In the meantime variations of the curves in the direction of warp are insignificant. Regarding static friction force and static friction coefficient (found in two cases, when fabrics were rubbing against leather and materials, it was discovered that consistency of the curves is irregular, i. e. they either increase or decrease, when integrated fabric structure factor j growth. It was also identified that some dependences are not strong and relationship between explored and analyzed factors does not exist. Variation of all these mechanical properties with respect to material density r enables to conclude that increase of material density r results in poor dependences or they are whatsoever non-existent.http://dx.doi.org/10.5755/j01.ms.17.2.487

  16. Preparation and Properties of Orthogonal Piezoelectric Composite Materials

    Institute of Scientific and Technical Information of China (English)

    Liu Jun; Lu Ying; Zhang Xingguo; Shen Yi; Chen Chun

    2004-01-01

    . PZT piezoelectric ceramic with La2O3, SrCO3, BaO and Sb2O5 was prepared. It has high value of the piezoelectric strain constant d33 ( -681 PC/N) and high value of-d33/d31 (2.65). Orthogonal piezoelectric composite materials was designed and prepared by PZT, DAD- 40 electric conductive adhesive and E51 epoxy resin. The OPCM shows obvious orthogonal anisotropy. The matching property of the interface between piezoelectric ceramic and polymer of OPCM relies on the defects of interface. The proper conductive mid-layer could improve the matching property of the interface.

  17. Thermophysical properties of new materials; Proprietes thermophysiques des materiaux nouveaux

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-31

    This conference day was organized by the `thermo-kinetics` section of the French association of thermal engineers. This book of proceedings contains 5 papers entitled: `characterization of thermal properties using periodical methods at the Odeillo test centre: developments and applications`; `measurement of the distribution of local thermophysical properties by IR images processing and averaging technique`; `extension of shock probes to the characterization of multi-layers - development of a simple device for the characterization of insulating materials or shear fluids`; `thermal local diffusivity of constituents of carbon/carbon composites`; `new method for the thermal diffusivity measurement of thermo-hardenable resins during polymerization`. (J.S.)

  18. Structure/property relationships in non-linear optical materials

    Energy Technology Data Exchange (ETDEWEB)

    Cole, J.M. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)]|[Durham Univ. (United Kingdom); Howard, J.A.K. [Durham Univ. (United Kingdom); McIntyre, G.J. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    The application of neutrons to the study of structure/property relationships in organic non-linear optical materials (NLOs) is described. In particular, charge-transfer effects and intermolecular interactions are investigated. Charge-transfer effects are studied by charge-density analysis and an example of one such investigation is given. The study of intermolecular interactions concentrates on the effects of hydrogen-bonding and an example is given of two structurally similar molecules with very disparate NLO properties, as a result of different types of hydrogen-bonding. (author). 3 refs.

  19. Simulated Analysis of Dielectric Properties of Heterogeneous Materials

    Directory of Open Access Journals (Sweden)

    Yang Biao

    2016-01-01

    Full Text Available The present paper reports the results of a numerical analysis of two phases lossless heterogeneous materials based on a three dimensional (3-D random dielectric mixture. The effective permittivity of a 3-D dielectric materials is calculated by the S-parameter retrieval method and finite element method. The calculated effective permittivity is in good agreement with theoretical models by compared with Bruggeman formula and Coherent potential formula, showing that the volume fraction of inclusions is increasing, the effective permittivity increases with radiation frequency and appear an imaginary part taking on the dielectric loss properties.

  20. Relationships between fracture toughness and other material properties. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Perra, M.; Finnie, I.

    1974-01-01

    The key experimental and analytical studies which have led to our present understanding of the mechanisms of ductile fracture are reviewed. It is concluded that insufficient progress has been made in the quantitative description of ductile separation mechanisms on a microscale to allow the realistic prediction of fracture toughness from material properties and microstructure. An experimental study of ductile fracture is underway which has the aim of determining the growth rate of voids in known plastic deformation fields as a function of triaxiality of stress and material work-hardening. Novel specimens of particularly well characterized microstructure are utilized.

  1. One-dimensional Topological Edge States of Bismuth Bilayers

    Science.gov (United States)

    Drozdov, Ilya; Alexandradinata, Aris; Jeon, Sangjun; Nadj-Perge, Stevan; Ji, Huiwen; Cava, Robert; Bernevig, B. Andrei; Yazdani, Ali

    2014-03-01

    The hallmark of a time-reversal symmetry protected topologically insulating state of matter in two-dimensions (2D) is the existence of chiral edge modes propagating along the perimeter of the sample. Bilayers of bismuth (Bi), an elemental system theoretically predicted to be a Quantum Spin Hall (QSH) insulator1, has been studied with Scanning Tunneling Microscopy (STM) and the electronic structure of its bulk and edge modes has been experimentally investigated. Spectroscopic mapping with STM reveals the presence of the state bound to the edges of the Bi-bilayer. By visualizing quantum interference of the edge state quasi-particles in confined geometries we characterize their dispersion and demonstrate that their properties are consistent with the absence of backscattering. Hybridization of the edge modes to the underlying substrate will be discussed. [1] Shuichi Murakami, Phys. Rev. Lett. 97, 236805 (2006). The work at Princeton and the Princeton Nanoscale Microscopy Laboratory was supported by ARO MURI program W911NF-12-1-0461, DARPA-SPWAR Meso program N6601-11-1-4110, NSF-DMR1104612, and NSF-MRSEC programs through the Princeton Center for Complex Materials (DMR-0819860)

  2. Optical and structural investigations of self-assembled Ge/Si bi-layer containing Ge QDs

    Energy Technology Data Exchange (ETDEWEB)

    Samavati, Alireza, E-mail: alireza.samavati@yahoo.com [Ibn Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Othaman, Z., E-mail: zulothaman@gmail.com [Ibn Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Ghoshal, S.K.; Dousti, M.R. [Advanced Optical Material Research Group, Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

    2014-10-15

    We report the influence of Si spacer thickness variation (10–40 nm) on structural and optical properties of Ge quantum dots (QDs) in Ge/Si(1 0 0) bi-layer grown by radio frequency magnetron sputtering. AFM images reveal the spacer dependent width, height, root mean square roughness and number density of QDs vary in the range of ∼12–25 nm, ∼2–6 nm, ∼1.95–1.05 nm and ∼0.55×10{sup 11}–2.1×10{sup 11} cm{sup −2}, respectively. XRD patterns exhibit the presence of poly-oriented structures of Ge with preferred growth along (1 1 1) direction accompanied by a reduction in strain from 4.9% to 1.2% (estimated from Williamson–Hall plot) due to bi-layering. The room temperature luminescence displays strong blue–violet peak associated with a blue shift as much as 0.05 eV upon increasing the thickness of Si spacer. This shift is attributed to the quantum size effect, the material intermixing and the strain mediation. Raman spectra for both mono and bi-layer samples show intense Ge–Ge optical phonon mode that is shifted towards higher frequency. Furthermore, the first order features of Raman spectra affirm the occurrence of interfacial intermixing and phase formation during deposition. The excellent features of the results suggest that our systematic method may constitute a basis for the tunable growth of Ge QDs suitable in nanophotonics. - Highlights: • High quality bilayered hetero-structure Ge/Si using economic and easy rf magnetron sputtering fabrication method. • The role of phonon-confinement and strain relaxation mechanisms. • Influence of bilayering on evolutionary growth dynamics. • Band gap shift of visible PL upon bilayering.

  3. Effective Materials Property Information Management for the 21st Century

    Science.gov (United States)

    Ren, Weiju; Cebon, David; Arnold, Steve

    2009-01-01

    This paper discusses key principles for the development of materials property information management software systems. There are growing needs for automated materials information management in various organizations. In part these are fueled by the demands for higher efficiency in material testing, product design and engineering analysis. But equally important, organizations are being driven by the need for consistency, quality and traceability of data, as well as control of access to sensitive information such as proprietary data. Further, the use of increasingly sophisticated nonlinear, anisotropic and multi-scale engineering analyses requires both processing of large volumes of test data for development of constitutive models and complex materials data input for Computer-Aided Engineering (CAE) software. And finally, the globalization of economy often generates great needs for sharing a single "gold source" of materials information between members of global engineering teams in extended supply chains. Fortunately, material property management systems have kept pace with the growing user demands and evolved to versatile data management systems that can be customized to specific user needs. The more sophisticated of these provide facilities for: (i) data management functions such as access, version, and quality controls; (ii) a wide range of data import, export and analysis capabilities; (iii) data "pedigree" traceability mechanisms; (iv) data searching, reporting and viewing tools; and (v) access to the information via a wide range of interfaces. In this paper the important requirements for advanced material data management systems, future challenges and opportunities such as automated error checking, data quality characterization, identification of gaps in datasets, as well as functionalities and business models to fuel database growth and maintenance are discussed.

  4. Effective Materials Property Information Management for the 21st Century

    Science.gov (United States)

    Ren, Weiju; Cebon, David; Arnold, Steve

    2009-01-01

    This paper discusses key principles for the development of materials property information management software systems. There are growing needs for automated materials information management in various organizations. In part these are fueled by the demands for higher efficiency in material testing, product design and engineering analysis. But equally important, organizations are being driven by the need for consistency, quality and traceability of data, as well as control of access to sensitive information such as proprietary data. Further, the use of increasingly sophisticated nonlinear, anisotropic and multi-scale engineering analyses requires both processing of large volumes of test data for development of constitutive models and complex materials data input for Computer-Aided Engineering (CAE) software. And finally, the globalization of economy often generates great needs for sharing a single "gold source" of materials information between members of global engineering teams in extended supply chains. Fortunately, material property management systems have kept pace with the growing user demands and evolved to versatile data management systems that can be customized to specific user needs. The more sophisticated of these provide facilities for: (i) data management functions such as access, version, and quality controls; (ii) a wide range of data import, export and analysis capabilities; (iii) data "pedigree" traceability mechanisms; (iv) data searching, reporting and viewing tools; and (v) access to the information via a wide range of interfaces. In this paper the important requirements for advanced material data management systems, future challenges and opportunities such as automated error checking, data quality characterization, identification of gaps in datasets, as well as functionalities and business models to fuel database growth and maintenance are discussed.

  5. Effective Materials Property Information Management for the 21st Century

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Weiju [ORNL; Cebon, David [Cambridge University; Barabash, Oleg M [ORNL

    2011-01-01

    This paper discusses key principles for the development of materials property information management software systems. There are growing needs for automated materials information management in various organizations. In part these are fuelled by the demands for higher efficiency in material testing, product design and engineering analysis. But equally important, organizations are being driven by the needs for consistency, quality and traceability of data, as well as control of access to proprietary or sensitive information. Further, the use of increasingly sophisticated nonlinear, anisotropic and multi-scale engineering analyses requires both processing of large volumes of test data for development of constitutive models and complex materials data input for Computer-Aided Engineering (CAE) software. And finally, the globalization of economy often generates great needs for sharing a single gold source of materials information between members of global engineering teams in extended supply-chains. Fortunately material property management systems have kept pace with the growing user demands and evolved to versatile data management systems that can be customized to specific user needs. The more sophisticated of these provide facilities for: (i) data management functions such as access, version, and quality controls; (ii) a wide range of data import, export and analysis capabilities; (iii) data pedigree traceability mechanisms; (iv) data searching, reporting and viewing tools; and (v) access to the information via a wide range of interfaces. In this paper the important requirements for advanced material data management systems, future challenges and opportunities such as automated error checking, data quality characterization, identification of gaps in datasets, as well as functionalities and business models to fuel database growth and maintenance are discussed.

  6. Finite amplitude effects on drop levitation for material properties measurement

    Science.gov (United States)

    Ansari Hosseinzadeh, Vahideh; Holt, R. Glynn

    2017-05-01

    The method of exciting shape oscillation of drops to extract material properties has a long history, which is most often coupled with the technique of acoustic levitation to achieve non-contact manipulation of the drop sample. We revisit this method with application to the inference of bulk shear viscosity and surface tension. The literature is replete with references to a "10% oscillation amplitude" as a sufficient condition for the application of Lamb's analytical expressions for the shape oscillations of viscous liquids. Our results show that even a 10% oscillation amplitude leads to dynamic effects which render Lamb's results inapplicable. By comparison with samples of known viscosity and surface tension, we illustrate the complicating finite-amplitude effects (mode-splitting and excess dissipation associated with vorticity) that can occur and then show that sufficiently small oscillations allow us to recover the correct material properties using Lamb's formula.

  7. Mechanical Properties of Materials with Nanometer Scale Microstructures

    Energy Technology Data Exchange (ETDEWEB)

    William D. Nix

    2004-10-31

    We have been engaged in research on the mechanical properties of materials with nanometer-scale microstructural dimensions. Our attention has been focused on studying the mechanical properties of thin films and interfaces and very small volumes of material. Because the dimensions of thin film samples are small (typically 1 mm in thickness, or less), specialized mechanical testing techniques based on nanoindentation, microbeam bending and dynamic vibration of micromachined structures have been developed and used. Here we report briefly on some of the results we have obtained over the past three years. We also give a summary of all of the dissertations, talks and publications completed on this grant during the past 15 years.

  8. Optical properties of glazing materials at normal incidence

    Energy Technology Data Exchange (ETDEWEB)

    Rubin, M.; Powles, R.

    2001-10-01

    Measurements of spectral transmittance T and reflectance R at normal incidence continue to be the most common and accurate source of energy performance data for glazing materials. Prediction of these radiometric properties from more fundamental materials data is often confounded by the complexity and uncertainty of coating structures. Angle-dependent radiometric properties of coated glazing will probably be predicted from normal-incidence data rather than being measured at many angles. The general error level demonstrated in round-robin tests is on the order 1-2%; it is often necessary to achieve better levels of performance. Based on results obtained following the round-robin tests, it is expected that accuracy of better than 0.5% can be generally achieved. A new type of absolute standard reference is described and tested with promising results.

  9. New Technique for Evaluating Adhesion Properties between Soft Materials

    Science.gov (United States)

    Sato, Takaya; Goto, Motoaki; Nakano, Ken; Suzuki, Atsushi

    2005-11-01

    A new, simple apparatus for measuring the surface adhesion properties of soft materials was designed, where the adhesion force of a point contact between soft materials and the total energy required to separate the contact can be measured using the springs of phosphor-bronze thin plates with strain gauges. The adhesion between swollen hydrogels was studied here by this simple technique in air at room temperature. The gels used in the present preliminary experiments were poly(sodium acrylate) hydrogels physically cross-linked by aluminum ions. The adhesion force and the separation energy showed a power-law increase with separation velocity. The apparatus was applied to evaluate the adhesion properties of seven anti-inflammatory analgesic cataplasms on the market. It was found that the easiness to separate (rank of adhesion force and the separation energy) was consistent with the results of those obtained by organoleptic evaluations.

  10. Textile Materials with New Properties Used for Confections Manufacturing

    Directory of Open Access Journals (Sweden)

    Neacşu A. N.

    2009-12-01

    Full Text Available The quality of textile clothing depends on the quality of prime materials and also on the technology used; this must ensure a balance between transferred heat, resulted humidity and human and environmental thermal demands, all this bringing about physiological comfort. In order to meet consumers’ demands regarding the production of products which are easy to maintain and have high hygiene properties, new prime materials are searched, with a view to ensuring a wide range of clothing. Taking into consideration the acceleration of changes and the global inter-connections, a company must develop its capacity of innovation in order to bring products with new properties on the market before others do.

  11. Determination of thermal properties of composting bulking materials.

    Science.gov (United States)

    Ahn, H K; Sauer, T J; Richard, T L; Glanville, T D

    2009-09-01

    Thermal properties of compost bulking materials affect temperature and biodegradation during the composting process. Well determined thermal properties of compost feedstocks will therefore contribute to practical thermodynamic approaches. Thermal conductivity, thermal diffusivity, and volumetric heat capacity of 12 compost bulking materials were determined in this study. Thermal properties were determined at varying bulk densities (1, 1.3, 1.7, 2.5, and 5 times uncompacted bulk density), particle sizes (ground and bulk), and water contents (0, 20, 50, 80% of water holding capacity and saturated condition). For the water content at 80% of water holding capacity, saw dust, soil compost blend, beef manure, and turkey litter showed the highest thermal conductivity (K) and volumetric heat capacity (C) (K: 0.12-0.81 W/m degrees C and C: 1.36-4.08 MJ/m(3) degrees C). Silage showed medium values at the same water content (K: 0.09-0.47 W/m degrees C and C: 0.93-3.09 MJ/m(3) degrees C). Wheat straw, oat straw, soybean straw, cornstalks, alfalfa hay, and wood shavings produced the lowest K and C values (K: 0.03-0.30 W/m degrees C and C: 0.26-3.45 MJ/m(3) degrees C). Thermal conductivity and volumetric heat capacity showed a linear relationship with moisture content and bulk density, while thermal diffusivity showed a nonlinear relationship. Since the water, air, and solid materials have their own specific thermal property values, thermal properties of compost bulking materials vary with the rate of those three components by changing water content, bulk density, and particle size. The degree of saturation was used to represent the interaction between volumes of water, air, and solids under the various combinations of moisture content, bulk density, and particle size. The first order regression models developed in this paper represent the relationship between degree of saturation and volumetric heat capacity (r=0.95-0.99) and thermal conductivity (r=0.84-0.99) well. Improved

  12. Tensile Properties of Fiber Materials under Different Strain Rates

    Institute of Scientific and Technical Information of China (English)

    XIONG Jie; GU Bo-hong; WANG Shan-yuan

    2002-01-01

    The quasi-static and dynamic tensile tests of aranid and high strength PVA fiber bundles are carried out under a wider range of strain rate by use of MTS (Materials Testing System) and bar-bar tensile impact apparatus.The influences of strain rate on mechanical properties of aramid and high strength polyvinyl alcohol fibers ar estudied. Micro failure mechanisms of fibers at different strain rates are examined by means of SEM.

  13. Models for acoustical properties of green roof materials

    OpenAIRE

    2011-01-01

    To predict the acoustical effects of green roof structures it is necessary to be able to model the acoustical properties of their materials including gravel. For time domain calculations it is convenient to use the phenomenological model due to Zwikker and Kosten. However this phenomenological model is related to a low frequency/high flow resistivity approximation of more ‘exact’ identical pore models. The results of fitting predictions to short range level difference data and to impedance da...

  14. Measurement of Mechanical Properties of Cantilever Shaped Materials

    Directory of Open Access Journals (Sweden)

    Thomas Thundat

    2008-05-01

    Full Text Available Microcantilevers were first introduced as imaging probes in Atomic Force Microscopy (AFM due to their extremely high sensitivity in measuring surface forces. The versatility of these probes, however, allows the sensing and measurement of a host of mechanical properties of various materials. Sensor parameters such as resonance frequency, quality factor, amplitude of vibration and bending due to a differential stress can all be simultaneously determined for a cantilever. When measuring the mechanical properties of materials, identifying and discerning the most influential parameters responsible for the observed changes in the cantilever response are important. We will, therefore, discuss the effects of various force fields such as those induced by mass loading, residual stress, internal friction of the material, and other changes in the mechanical properties of the microcantilevers. Methods to measure variations in temperature, pressure, or molecular adsorption of water molecules are also discussed. Often these effects occur simultaneously, increasing the number of parameters that need to be concurrently measured to ensure the reliability of the sensors. We therefore systematically investigate the geometric and environmental effects on cantilever measurements including the chemical nature of the underlying interactions. To address the geometric effects we have considered cantilevers with a rectangular or circular cross section. The chemical nature is addressed by using cantilevers fabricated with metals and/or dielectrics. Selective chemical etching, swelling or changes in Young’s modulus of the surface were investigated by means of polymeric and inorganic coatings. Finally to address the effect of the environment in which the cantilever operates, the Knudsen number was determined to characterize the molecule-cantilever collisions. Also bimaterial cantilevers with high thermal sensitivity were used to discern the effect of temperature

  15. Ocean acidification alters the material properties of Mytilus edulis shells.

    Science.gov (United States)

    Fitzer, Susan C; Zhu, Wenzhong; Tanner, K Elizabeth; Phoenix, Vernon R; Kamenos, Nicholas A; Cusack, Maggie

    2015-02-01

    Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening the formation of calcium carbonate shells and exoskeletons of marine organisms. The production of biominerals in such organisms relies on the availability of carbonate and the ability of the organism to biomineralize in changing environments. To understand how biomineralizers will respond to OA the common blue mussel, Mytilus edulis, was cultured at projected levels of pCO2 (380, 550, 750, 1000 µatm) and increased temperatures (ambient, ambient plus 2°C). Nanoindentation (a single mussel shell) and microhardness testing were used to assess the material properties of the shells. Young's modulus (E), hardness (H) and toughness (KIC) were measured in mussel shells grown in multiple stressor conditions. OA caused mussels to produce shell calcite that is stiffer (higher modulus of elasticity) and harder than shells grown in control conditions. The outer shell (calcite) is more brittle in OA conditions while the inner shell (aragonite) is softer and less stiff in shells grown under OA conditions. Combining increasing ocean pCO2 and temperatures as projected for future global ocean appears to reduce the impact of increasing pCO2 on the material properties of the mussel shell. OA may cause changes in shell material properties that could prove problematic under predation scenarios for the mussels; however, this may be partially mitigated by increasing temperature.

  16. Characterization of ion-exchange membrane materials: properties vs structure.

    Science.gov (United States)

    Berezina, N P; Kononenko, N A; Dyomina, O A; Gnusin, N P

    2008-06-22

    This review focuses on the preparation, structure and applications of ion-exchange membranes formed from various materials and exhibiting various functions (electrodialytic, perfluorinated sulphocation-exchange and novel laboratory-tested membranes). A number of experimental techniques for measuring electrotransport properties as well as the general procedure for membrane testing are also described. The review emphasizes the relationships between membrane structures, physical and chemical properties and mechanisms of electrochemical processes that occur in charged membrane materials. The water content in membranes is considered to be a key factor in the ion and water transfer and in polarization processes in electromembrane systems. We suggest the theoretical approach, which makes it possible to model and characterize the electrochemical properties of heterogeneous membranes using several transport-structural parameters. These parameters are extracted from the experimental dependences of specific electroconductivity and diffusion permeability on concentration. The review covers the most significant experimental and theoretical research on ion-exchange membranes that have been carried out in the Membrane Materials Laboratory of the Kuban State University. These results have been discussed at the conferences "Membrane Electrochemistry", Krasnodar, Russia for many years and were published mainly in Russian scientific sources.

  17. Thermophysical Properties of Automotive Metallic Brake Disk Materials

    Science.gov (United States)

    Kim, S. W.; Park, K.; Lee, S. H.; Kang, K. H.; Lim, K. T.

    2008-12-01

    The temperature distribution, the thermal deformation, and the thermal stress of automotive brake disks have quite close relations with car safety; therefore, much research in this field has been performed. However, successful and satisfactory results have not been obtained because the temperature-dependent thermophysical properties of brake disk materials are not sufficiently known. In this study, the thermophysical properties (thermal diffusivity, the specific heat, and the coefficient of thermal expansion) of three kinds of iron alloy series brake disk materials, FC250, FC170, and FCD50, and two kinds of aluminum alloy series brake disk materials, Al MMC and A356, were measured in the temperature range from room temperature to 500 °C, and the thermal conductivity was calculated using the measured thermal diffusivity, specific heat capacity, and density. As expected, the results show that the two series have significant differences in respect of the thermophysical properties, and to reduce the thermal deformation of the brake disk, the aluminum alloys with a high thermal conductivity and the iron alloys with low thermal expansion are recommended.

  18. Filter properties of seam material from paved urban soils

    Directory of Open Access Journals (Sweden)

    T. Nehls

    2007-08-01

    Full Text Available We studied pavement seam material. This is the soil substrate in joints of pervious pavements in urban areas. It is mostly 1 cm thick and develops from the original seam filling by depositions of all kinds of urban residues, including anthropogenic organic substances. It was investigated, how this unique form of organic matter influences the filter properties of seam material and how the seam material influences heavy metal transport through the pavement. The seam material is characterised by a darker munsell colour, higher organic carbon content, higher surface areas, higher cation exchange capacities, but a lower fraction of high adsorption energy sites compared to the original seam filling. The deposited anthropogenic organic matter itself could be characterised as particulate and non-polar. Compared to natural soils, it has a small surface area and a low surface charge density resulting in a small cation exchange capacity of only 75 cmol(+ kg−1C. The seam material shows stronger sorption of Pb and Cd compared to the original construction sand. The retardation capacity of seam material towards Pb is similar, towards Cd it is much smaller compared to natural soils. The simulated long term displacement scenarios for a street in Berlin do not indicate an acute contamination risk for Pb. For Cd the infiltration from ponds can lead to a displacement of Cd during only one decade.

  19. Material Properties of Wire for the Fabrication of Knotted Fences

    Directory of Open Access Journals (Sweden)

    Dirk J. Pons

    2014-01-01

    Full Text Available This paper describes the materials properties of galvanised fencing wire, as used in the fabrication of knotted wire fences. A range of physical properties are investigated: tensile strength, ductility in tension, Young’s modulus, three-point bending, and bending span. A range of commercially available wire products were tested. The results show that most, but not all, high tensile wire samples met the minimum tensile and ductility requirements. Young’s modulus results failed to provide any meaningful insights into wire quality. Flexural modulus results also failed to provide any insight into wire quality issues, with no statistically significant differences existing between acceptable and problematic wire batches. The implications are that premature fence failures are unlikely to be caused solely by reduced tensile properties. Existing test methods, including tensile strength and ductility, are somewhat incomplete, perhaps even unreliable, as measures of wire quality.

  20. Regional material properties of the human hip joint capsule ligaments.

    Science.gov (United States)

    Hewitt, J; Guilak, F; Glisson, R; Vail, T P

    2001-05-01

    The hip joint capsule functions to constrain translation between the femur and acetabulum while allowing rotational and planar movements. Despite the crucial role it plays in the pathogenesis of hip instability, little is known about its biomechanical properties. The goal of this study was to determine the regional material properties of the iliofemoral and ischiofemoral ligaments of the capsule. Ten human cadaveric specimens of each ligament were tested to failure in tension. The stress at failure, strain at failure, strain energy density at failure, toe- and linear-region elastic moduli, and the Poisson's ratio were measured for each ligament. The strain to failure was greatest in the ischiofemoral ligament, while no significant difference was noted in failure stress by region or ligament. The Young's moduli of elasticity ranged from 76.1 to 285.8 MPa among the different ligaments, and were generally consistent with properties previously reported for the shoulder capsule. The elastic moduli and strain energy density at failure differed by region. No significant differences in Poisson's ratio were found by region or ligament. The average Poisson's ratio was approximately 1.4, consistent with anisotropic behavior of ligamentous tissues. Understanding the material properties of the hip capsule may help the orthopaedic surgeon better understand normal ligament function, and thereby choose a surgical approach or strategy of repair. Furthermore, knowledge of the normal mechanical function of the hip capsule ligaments could assist in the evaluation of the success of a repair.

  1. Space-Time Transfinite Interpolation of Volumetric Material Properties.

    Science.gov (United States)

    Sanchez, Mathieu; Fryazinov, Oleg; Adzhiev, Valery; Comninos, Peter; Pasko, Alexander

    2015-02-01

    The paper presents a novel technique based on extension of a general mathematical method of transfinite interpolation to solve an actual problem in the context of a heterogeneous volume modelling area. It deals with time-dependent changes to the volumetric material properties (material density, colour, and others) as a transformation of the volumetric material distributions in space-time accompanying geometric shape transformations such as metamorphosis. The main idea is to represent the geometry of both objects by scalar fields with distance properties, to establish in a higher-dimensional space a time gap during which the geometric transformation takes place, and to use these scalar fields to apply the new space-time transfinite interpolation to volumetric material attributes within this time gap. The proposed solution is analytical in its nature, does not require heavy numerical computations and can be used in real-time applications. Applications of this technique also include texturing and displacement mapping of time-variant surfaces, and parametric design of volumetric microstructures.

  2. Static Magnetic Properties of AL800 Garnet Material

    Energy Technology Data Exchange (ETDEWEB)

    Kuharik, J. [Fermilab; Madrak, R. [Fermilab; Makarov, A. [Fermilab; Pellico, W. [Fermilab; Sun, S. [Fermilab; Tan, C. Y. [Fermilab; Terechkine, I. [Fermilab

    2017-05-17

    A second harmonic tunable RF cavity is being devel-oped for the Fermilab Booster. This device, which prom-ises reduction of the particle beam loss at the injection, transition, and extraction stages, employs perpendicularly biased garnet material for frequency tuning. The required range of the tuning is significantly wider than in previously built and tested tunable RF devices. As a result, the mag-netic field in the garnet comes fairly close to the gyromag-netic resonance line at the lower end of the frequency range. The chosen design concept of a tuner for the cavity cannot ensure uniform magnetic field in the garnet mate-rial; thus, it is important to know the static magnetic prop-erties of the material to avoid significant increase in the lo-cal RF loss power density. This report summarizes studies performed at Fermilab to understand variations in the mag-netic properties of the AL800 garnet material used to build the tuner of the cavity.

  3. Capacitance Variation of Electrolyte-Gated Bilayer Graphene Based Transistors

    Directory of Open Access Journals (Sweden)

    Hediyeh Karimi

    2013-01-01

    Full Text Available Quantum capacitance of electrolyte-gated bilayer graphene field-effect transistors is investigated in this paper. Bilayer graphene has received huge attention due to the fact that an energy gap could be opened by chemical doping or by applying external perpendicular electric field. So, this extraordinary property can be exploited to use bilayer graphene as a channel in electrolyte-gated field-effect transistors. The quantum capacitance of bi-layer graphene with an equivalent circuit is presented, and also based on the analytical model a numerical solution is reported. We begin by modeling the DOS, followed by carrier concentration as a function V in degenerate and nondegenerate regimes. To further confirm this viewpoint, the presented analytical model is compared with experimental data, and acceptable agreement is reported.

  4. Bilayer fractal structure with multiband left-handed characteristics.

    Science.gov (United States)

    Du, Qiujiao; Liu, Jinsong; Yang, Hongwu; Yi, Xunong

    2011-08-20

    We present a bilayer fractal structure for the realization of multiband left-handed metamaterial at terahertz frequencies. The structure is composed of metallic H-fractal pairs separated by a dielectric layer. The electromagnetic properties of periodic H-fractal pairs have been investigated by numerical simulation. The period in the propagation direction is extremely small as compared to the wavelength at the operational frequency. Under the electromagnetic wave normal incidence, the material exhibits negative refraction simultaneously around the frequencies of 0.10 and 0.15 THz for parallel polarization, and around the frequencies of 0.19 and 0.38 THz for perpendicular polarization. The design provides a left-handed metamaterial suitable for multiband and compact devices at terahertz frequencies.

  5. Preparation and properties on hollow nano-structured smoke material

    Science.gov (United States)

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

    2013-09-01

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

  6. Scanning Probe Evaluation of Electronic, Mechanical and Structural Material Properties

    Science.gov (United States)

    Virwani, Kumar

    2011-03-01

    We present atomic force microscopy (AFM) studies of a range of properties from three different classes of materials: mixed ionic electronic conductors, low-k dielectrics, and polymer-coated magnetic nanoparticles. (1) Mixed ionic electronic conductors are being investigated as novel diodes to drive phase-change memory elements. Their current-voltage characteristics are measured with direct-current and pulsed-mode conductive AFM (C-AFM). The challenges to reliability of the C-AFM method include the electrical integrity of the probe, the sample and the contacts, and the minimization of path capacitance. The role of C-AFM in the optimization of these electro-active materials will be presented. (2) Low dielectric constant (low-k) materials are used in microprocessors as interlayer insulators, a role directly affected by their mechanical performance. The mechanical properties of nanoporous silicate low-k thin films are investigated in a comparative study of nanomechanics measured by AFM and by traditional nanoindentation. Both methods are still undergoing refinement as reliable analytical tools for determining nanomechanical properties. We will focus on AFM, the faster of the two methods, and its developmental challenges of probe shape, cantilever force constant, machine compliance and calibration standards. (3) Magnetic nanoparticles are being explored for their use in patterned media for magnetic storage. Current methods for visualizing the core-shell structure of polymer-coated magnetic nanoparticles include dye-staining the polymer shell to provide contrast in transmission electron microscopy. AFM-based fast force-volume measurements provide direct visualization of the hard metal oxide core within the soft polymer shell based on structural property differences. In particular, the monitoring of adhesion and deformation between the AFM tip and the nanoparticle, particle-by-particle, provides a reliable qualitative tool to visualize core-shell contrast without the use

  7. Synthesis, processing and properties of materials for SOFCs

    Energy Technology Data Exchange (ETDEWEB)

    Bates, J.L.; Armstrong, T.A.; Kingsley, J.J.; Pederson, L.R.

    1994-03-01

    The synthesis and processing methods of complex oxide materials can significantly influence use in solid oxide fuel cells (SOFCs). This paper discusses (1) effects of powder synthesis and conditioning on fabrication, i.e., sintering, where close, reproducible control of composition and structure are required, and (2) influences on electrical, mechanical, structural and electrochemical properties that can influence SOFC performance. Examples are given for chromites, manganites and related oxides used as interconnections and electrodes in SOFCs. Materials, from source to incorporation into the fuel cell and generator, is a major issue in the development of solid oxide fuel cells (SOFCs). An integral part of this is the synthesis from chemicals and other virgin materials, generally as an oxide or metal powder, which can become a SOFC component. In some instances, such as with electrochemical vapor deposition, the component is formed directly from the chemicals. The synthesized materials are then conditioned and processes prior to fabrication into the fuel cell component, either separately or in conjunction with other material components.

  8. Properties of Residue from Olive Oil Extraction as a Raw Material for Sustainable Construction Materials. Part I: Physical Properties

    Directory of Open Access Journals (Sweden)

    Almudena Díaz-García

    2017-01-01

    Full Text Available Action on climate, the environment, and the efficient use of raw materials and resources are important challenges facing our society. Against this backdrop, the construction industry must adapt to new trends and environmentally sustainable construction systems, thus requiring lines of research aimed at keeping energy consumption in new buildings as low as possible. One of the main goals of this research is to efficiently contribute to reducing the amount of residue from olive oil extraction using a two-phase method. This can be achieved by producing alternative structural materials to be used in the construction industry by means of a circular economy. The technical feasibility of adding said residue to ceramic paste was proven by analyzing the changes produced in the physical properties of the paste, which were then compared to the properties of the reference materials manufactured with clay without residue. Results obtained show that the heating value of wet pomace can contribute to the thermal needs of the sintering process, contributing 30% of energy in pieces containing 3% of said material. Likewise, adding larger amounts of wet pomace to the clay body causes a significant decrease in bulk density values.

  9. Structure of twisted and buckled bilayer graphene

    Science.gov (United States)

    Jain, Sandeep K.; Juričić, Vladimir; Barkema, Gerard T.

    2017-03-01

    We study the atomic structure of twisted bilayer graphene, with very small mismatch angles (θ ∼ {0.28}0), a topic of intense recent interest. We use simulations, in which we combine a recently presented semi-empirical potential for single-layer graphene, with a new term for out-of-plane deformations, (Jain et al 2015 J. Phys. Chem. C 119 9646) and an often-used interlayer potential (Kolmogorov et al 2005 Phys. Rev. B 71 235415). This combination of potentials is computationally cheap but accurate and precise at the same time, allowing us to study very large samples, which is necessary to reach very small mismatch angles in periodic samples. By performing large scale atomistic simulations, we show that the vortices appearing in the Moiré pattern in the twisted bilayer graphene samples converge to a constant size in the thermodynamic limit. Furthermore, the well known sinusoidal behavior of energy no longer persists once the misorientation angle becomes very small (θ \\lt {1}0). We also show that there is a significant buckling after the relaxation in the samples, with the buckling height proportional to the system size. These structural properties have direct consequences on the electronic and optical properties of bilayer graphene.

  10. Material properties of bovine intervertebral discs across strain rates.

    Science.gov (United States)

    Newell, Nicolas; Grigoriadis, Grigorios; Christou, Alexandros; Carpanen, Diagarajen; Masouros, Spyros D

    2017-01-01

    The intervertebral disc (IVD) is a complex structure responsible for distributing compressive loading to adjacent vertebrae and allowing the vertebral column to bend and twist. To study the mechanical behaviour of individual components of the IVD, it is common for specimens to be dissected away from their surrounding tissues for mechanical testing. However, disrupting the continuity of the IVD to obtain material properties of each component separately may result in erroneous values. In this study, an inverse finite element (FE) modelling optimisation algorithm has been used to obtain material properties of the IVD across strain rates, therefore bypassing the need to harvest individual samples of each component. Uniaxial compression was applied to ten fresh-frozen bovine intervertebral discs at strain rates of 10(-3)-1/s. The experimental data were fed into the inverse FE optimisation algorithm and each experiment was simulated using the subject specific FE model of the respective specimen. A sensitivity analysis revealed that the IVD's response was most dependent upon the Young's modulus (YM) of the fibre bundles and therefore this was chosen to be the parameter to optimise. Based on the obtained YM values for each test corresponding to a different strain rate (ε̇), the following relationship was derived:YM=35.5lnε̇+527.5. These properties can be used in finite element models of the IVD that aim to simulate spinal biomechanics across loading rates. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  11. Tooth and bone deformation: structure and material properties by ESPI

    Science.gov (United States)

    Zaslansky, Paul; Shahar, Ron; Barak, Meir M.; Friesem, Asher A.; Weiner, Steve

    2006-08-01

    In order to understand complex-hierarchical biomaterials such as bones and teeth, it is necessary to relate their structure and mechanical-properties. We have adapted electronic speckle pattern-correlation interferometry (ESPI) to make measurements of deformation of small water-immersed specimens of teeth and bones. By combining full-field ESPI with precision mechanical loading we mapped sub-micron displacements and determined material-properties of the samples. By gradually and elastically compressing the samples, we compensate for poor S/N-ratios and displacement differences of about 100nm were reliably determined along samples just 2~3mm long. We produced stress-strain curves well within the elastic performance range of these materials under biologically relevant conditions. For human tooth-dentin, Young's modulus in inter-dental areas of the root is 40% higher than on the outer sides. For cubic equine bone samples the compression modulus of axial orientations is about double the modulus of radial and tangential orientations (20 GPa versus 10 GPa respectively). Furthermore, we measured and reproduced a surprisingly low Poisson's ratio, which averaged about 0.1. Thus the non-contact and non-destructive measurements by ESPI produce high sensitivity analyses of mechanical properties of mineralized tissues. This paves the way for mapping deformation-differences of various regions of bones, teeth and other biomaterials.

  12. Materials Selection, Synthesis, and Dielectrical Properties of PVC Nanocomposites

    Directory of Open Access Journals (Sweden)

    Youssef Mobarak

    2013-01-01

    Full Text Available Materials selection process for electrical insulation application was carried out using Cambridge Engineering Selector (CES program. Melt mixing technique was applied to prepare polyvinyl-chloride- (PVC- nanofumed silica and nanomontmorillonite clay composites. Surface analysis and particles dispersibility were examined using scanning electron microscope. Dielectrical properties were assessed using Hipot tester. An experimental work for dielectric loss of the nanocomposite materials has been investigated in a frequency range of 10 Hz–50 kHz. The initial results using CES program showed that microparticles of silica and clay can improve electrical insulation properties and modulus of elasticity of PVC. Nano-montmorillonite clay composites were synthesized and characterized. Experimental analyses displayed that trapping properties of matrix are highly modified by the presence of nanofillers. The nanofumed silica and nanoclay particles were dispersed homogenously in PVC up to 10% wt/wt. Dielectric loss tangent constant of PVC-nanoclay composites was decreased successfully from 0.57 to 0.5 at 100 Hz using fillers loading from 1% to 10% wt/wt, respectively. Nano-fumed silica showed a significant influence on the electrical resistivity of PVC by enhancing it up to 1 × 1011 Ohm·m.

  13. Oxide Thermoelectric Materials: A Structure-Property Relationship

    Science.gov (United States)

    Nag, Abanti; Shubha, V.

    2014-04-01

    Recent demand for thermoelectric materials for power harvesting from automobile and industrial waste heat requires oxide materials because of their potential advantages over intermetallic alloys in terms of chemical and thermal stability at high temperatures. Achievement of thermoelectric figure of merit equivalent to unity ( ZT ≈ 1) for transition-metal oxides necessitates a second look at the fundamental theory on the basis of the structure-property relationship giving rise to electron correlation accompanied by spin fluctuation. Promising transition-metal oxides based on wide-bandgap semiconductors, perovskite and layered oxides have been studied as potential candidate n- and p-type materials. This paper reviews the correlation between the crystal structure and thermoelectric properties of transition-metal oxides. The crystal-site-dependent electronic configuration and spin degeneracy to control the thermopower and electron-phonon interaction leading to polaron hopping to control electrical conductivity is discussed. Crystal structure tailoring leading to phonon scattering at interfaces and nanograin domains to achieve low thermal conductivity is also highlighted.

  14. The Study of the Thermoelectric Properties of Phase Change Materials

    Science.gov (United States)

    Yin, Ming; Abdi, Mohammed; Noimande, Zibusisu; Mbamalu, Godwin; Alameeri, Dheyaa; Datta, Timir

    We study thermoelectric property that is electrical phenomena occurring in conjunction with the flow of heat of phase-change materials (PCM) in particular GeSbTe (GST225). From given sets of material parameters, COMSOL Multiphysics heat-transfer module is used to compute maps of temperature and voltage distribution in the PCM samples. These results are used to design an apparatus including the variable temperature sample holder set up. An Arbitrary/ Function generator and a circuit setup is also designed to control the alternation of heaters embedded on the sample holder in order to ensure sequential back and forward flow of heat current from both sides of the sample. Accurate values of potential differences and temperature distribution profiles are obtained in order to compute the Seebeck coefficient of the sample. The results of elemental analysis and imaging studies such as XRD, UV-VIS, EDEX and SEM of the sample are obtained. Factors affecting the thermoelectric properties of phase change memory are also discussed. NNSA/ DOD Consortium for Materials and Energy Studies.

  15. 双层单负材料结构的古斯-亨兴位移调控%Control of Goos-Hanchen Displacement on Bilayer Structure Composed of Single Negative Materials

    Institute of Scientific and Technical Information of China (English)

    张曦; 许静平; 羊亚平

    2011-01-01

    运用反射相位法和高斯光束峰值位移判断法研究了由电单负材料(ENM)和磁单负材料(MNM)组成的双层结构的古斯-亨兴位移现象.首先利用传输矩阵计算结构的反射系数,通过对反射系数的相位分析,发现对于单层的电单负材料和单层的磁单负材料,反射高斯光束的古斯-亨兴位移方向相反,同时位移的大小与材料厚度存在一定的联系.进一步对双层材料传输矩阵进行解析分析,发现由电磁参数互为相反数的电单负材料和磁单负材料组合而成的双层材料,可以便捷地通过改变某一层材料的厚度来调控古斯-亨兴位移的大小和方向.%Goos-Hcinchen effect which occurs on the surface of bilayer composed of electric-negative-material (ENM) slab and magnetic-negative-material (MNM) slab is analyzed by using the reflective-phase method and the Gaussianbeam peak-shift criterion. And by using the transfer matrix, it is found that the directions of Goos-Hanchendisplacement are different between the situation when the beams reflect from the ENM and the situation that happen on MNM. It also shows that the Goos-H(a)nchen displacement of such bilayer can be controlled expediently by adjusting the thickness of one layer as the indices of ENM slab are opposite to those of MNM slab.

  16. Acoustic Properties of Innovative Material from Date Palm Fibre

    Directory of Open Access Journals (Sweden)

    Lamyaa Abd AL-Rahman

    2012-01-01

    Full Text Available Problem statement: An organic material is one of the major requirements to improve living environment and the invention of materials need to consider for the best solution. This study presents an experimental investigation on pure porous from Date Palm Fibre (DPF. The effectiveness of sound absorbers depends on structural architecture of this material. This study was conducted to examine the potential of using date palm fibre as sound absorber. The effects of porous layer thicknesses, densities and compression on Acoustic Absorption Coefficient (AAC of sound absorber using date palm fibre were studied. Approach: Rigid frame Johnson-Allard Model for various sample thicknesses was used in this study. The measurements were conducted in impedance tube on normal incidence acoustic absorption. The date palm fibre was mixed with latex which used for physical treatment on this material. Acoustic absorption behaviour of a porous material with different thicknesses was studied as well as samples with same thickness but different densities. In addition, samples with same properties but different period of compression time were inspected. The tests were in accordance to ISO 10534-2 and ASTM E1050-98 international standards for Acoustic Absorption Coefficient (AAC. Results: The experimental data indicates that two peak values of AAC is 0.93 at 1356Hz for sample with 50 mm thickness, also the AAC at high frequency for same thickness is 0.99 at 4200-4353 Hz that means able to improve acoustic absorption coefficient at low and high frequencies with significant increasing. Meanwhile, another experimental results were acquired for AAC of date palm fibre, with samples thicknesses of 35 mm at different densities .The results show that denser sample (11 Kg m-3 has higher AAC value of 0.83 at 1934- 2250 Hz as compared to less dense sample (9.92 Kg m-3 with AAC value 0.84 at 2443-2587 Hz . Conclusion: Acoustic absorption coefficient AAC of date palm fibre was

  17. Saturation properties of a supercritical gas sorbed in nanoporous materials.

    Science.gov (United States)

    Poirier, Eric; Dailly, Anne

    2012-12-28

    The description of experimental gas adsorption data in terms of an accurate model is key to understand the adsorption mechanism and its limits. As a basic feature such a model should predict correctly the conditions under which saturation occurs. However, in the absence of bulk condensation properties for a supercritical adsorbate this matter remains open to discussions. In this study, the decreasing region of excess hydrogen adsorption isotherms measured down to 50 K is used to determine the adsorbed phase volume, density and pressure corresponding to saturation. The experimental method developed for these key measurements addresses the challenges of very low temperature adsorption measurements at high pressure. Therefore, the modifications specially made to a cryostat used in conjunction with a Sievert apparatus to reach high temperature stability (±10 mK) down to 40 K are presented. The approach is implemented on the novel nanoporous materials UMCM-1 and NOTT-112 over 50-77 K and 0-40 bar. The derived hydrogen saturation properties are found to be consistent with a Dubinin-Astakhov model. Importantly, the measured adsorbed hydrogen phase volume also compares well with the pore volume obtained from Ar porosimetry. The found saturation properties provide a physical basis to calculate consistent absolute adsorption isotherms and enthalpies, and to project the ultimate adsorption capacity of a conceptual material with a maximized specific surface area. The present findings provide additional evidence that the common view on supercritical adsorption, in which it is assumed that no liquid is formed and that the only possible mechanism involves monolayer coverage, does not hold in many nanoporous materials.

  18. Magnetomechanical Properties Of Composite Materials With Giant Magnetostriction

    Directory of Open Access Journals (Sweden)

    Tomiczek A.E.

    2015-09-01

    Full Text Available The aim of this work was to observe the changes in the magnetomechanical properties of composite materials with different Tb0.3Dy0.7Fe1.9 (Terfenol-D powder particle-size distributions and varying volume fractions in the polyurethane matrix. The results show a direct relationship between the properties and the particle size of the Tb0.3Dy0.7Fe1.9 powder: the increases in the particle-size distribution of the Tb0.3Dy0.7Fe1.9 powder in the matrix amplify the magnetostrictive responses and the compressive modulus values. Moreover, it was found that the key role in efficiency of the transformation of magnetic energy into mechanical plays the initial compressing pre-stress.

  19. Research on lunar materials. [optical, chemical, and electrical properties

    Science.gov (United States)

    Gold, T.

    1978-01-01

    Abstracts of 14 research reports relating to investigations of lunar samples are presented. The principal topics covered include: (1) optical properties of surface and core samples; (2) chemical composition of the surface layers of lunar grains: Auger electron spectroscopy of lunar soil and ground rock samples; (3) high frequency electrical properties of lunar soil and rock samples and their relevance for the interpretation of lunar radar observations; (4) the electrostatic dust transport process; (5) secondary electron emission characteristics of lunar soil samples and their relevance to the dust transportation process; (6) grain size distribution in surface soil and core samples; and (7) the optical and chemical effects of simulated solar wind (2keV proton and a particle radiation) on lunar material.

  20. Development and mechanical properties of structural materials from lunar simulants

    Science.gov (United States)

    Desai, Chandra S.; Girdner, K.; Saadatmanesh, H.; Allen, T.

    1991-01-01

    Development of the technologies for manufacture of structural and construction materials on the Moon, utilizing local lunar soil (regolith), without the use of water, is an important element for habitats and explorations in space. Here, it is vital that the mechanical behavior such as strength and flexural properties, fracture toughness, ductility and deformation characteristics be defined toward establishment of the ranges of engineering applications of the materials developed. The objective is to describe the research results in two areas for the above goal: (1) liquefaction of lunar simulant (at about 100 C) with different additives (fibers, powders, etc.); and (2) development and use of a new triaxial test device in which lunar simulants are first compressed under cycles of loading, and then tested with different vacuums and initial confining or in situ stress.

  1. Dosimetric properties of natural quartz grains extracted from fired materials

    DEFF Research Database (Denmark)

    Bluszcz, A.; Bøtter-Jensen, L.

    1995-01-01

    The paper describes an examination of the dosimetric properties of natural quartz grains extracted from ancient fired materials. Eleven samples of different origin were tested for their TL and GLSL (green light stimulated luminescence) sensitivities within the mGy dose range. Very promising results...... were obtained showing the possibility of measuring the doses of around 10 mGy with 1% precision using GLSL or TL and using the single aliquot technique for natural quartz as a dosimeter. The lowest detectable dose was estimated to be lower than 500 mu Gy. The results obtained indicate that natural...... quartz grains from selected materials could be used for the dosimetry of environmental gamma radiation for the purposes of paleodosimetric dating methods as well as for accident dosimetry....

  2. Pulsed power experiments in hydrodynamics and material properties

    CERN Document Server

    Reinovsky, R E

    1999-01-01

    A new application for high performance pulsed power program, the production of high energy density environments in materials for the study of material properties and hydrodynamics in complex geometries, has joined family of radiation source applications in the Stockpile Stewardship. The principle tool for producing high energy density environments is the high precision, magnetically imploded, near-solid density liner. The most attractive pulsed power system for driving such experiments is an ultra-high current, low impedance, microsecond time scale source that is economical both to build and operate. The 25-MJ Atlas capacitor bank system currently under construction at Los Alamos is the first system of its scale specifically designed to drive high precision solid liners. Delivering 30 MA, Atlas will provide liner velocities 12-15 km/sec and kinetic energies of 1-2 MJ /cm with extensive diagnostics and excellent reproducibility. Explosive flux compressor technology provides access to currents exceeding 100 MA ...

  3. Structure and Property Characterization of Oyster Shell Cementing Material

    Institute of Scientific and Technical Information of China (English)

    钟彬杨; 周强; 单昌锋; 于岩

    2012-01-01

    Oyster shell powder was used as the admixture of ordinary portland cement.The effects of different addition amounts and grinding ways on the strength and stability of cement mortar were discussed and proper addition amount of oyster shell powder was determined.The structure and property changes of cementing samples with different oyster shell powder contents were tested by XRD and SEM means.The results revealed that compressive and rupture strengths of the sample with 10% oyster shell powder was close to those of the original one without addition.Stability experiment showed that the sample prepared by pat method had smooth surface without crack and significant expansion or shrinkage after pre-curing and boiling,which indicated that cementing material dosed with oyster shell powder had fine stability.XRD and SEM observation showed that oyster shell independently exists in the cementing material.

  4. Comparison of Electrical Properties between Fluoroapatite and Hydroxyapatite Materials

    Science.gov (United States)

    Laghzizil, A.; El Herch, N.; Bouhaouss, A.; Lorente, G.; Macquete, J.

    2001-01-01

    By appropriate modifications of existing precipitation methods, apatite samples of formula M10(PO4)6X2 (M=Ca, Pb, Ba and X=F, OH) were prepared at 80°C. Samples were characterized using X-ray diffraction, infrared, 31P NMR, SEM, and chemical analysis. By comparing the effect of fluoride and hydroxide ions on ionic conductivity measurements, it was concluded that the fluorinated materials (MFAp) were better conductors than other hydroxyapatites (MHAp). The F- and H+ ions are the main charge carriers, respectively, in fluoroapatite and in hydroxyapatite compounds. The most pronounced effect on the conduction properties was observed in the lead apatite material. These results should provide important physico-chemical information for ionic diffusion of the roles played by fluoride in inhibiting dental caries.

  5. Properties and processing of nanocrystalline materials. Quarterly report

    Energy Technology Data Exchange (ETDEWEB)

    Valiev, R.Z.

    1996-01-22

    The present Report completes the investigations in the frame of the project for the first year. It is important to estimate our achievements in the investigation of properties of nanocrystalline materials obtained by severe plastic deformation and their production. We think that the main results obtained can be summarized as follows: (1) We performed an improvement of the die-set for equal channel (ECA) pressing and torsion under high pressure with the aim to increase dimensions of the samples produced and to conduct processing of low ductile materials. (2) It was established that in pure metals severe plastic deformation led to the formation of an ultra fine-grained structure with a mean grain size of 100-200 nm, while in alloys due to severe plastic deformation and/or special methods of treatment (a decrease in the temperature of deformation, an increase of the pressure applied etc.) the grain size could be decreased down to a few tens of manometers.

  6. Relaxor behavior and electrical properties of high dielectric constant materials

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Several typical high dielectric constant materials are reviewed to study the electrical properties and relaxation mechanism. It is found that a Lorenz-type law can be used to describe the dielectric permit- tivity of either the normal ferroelectrics with or without diffuse phase transitions (DPT) or the typical ferroelectric relaxors. The ferroelectric DPT can be well described by just one fitting process using the Lorenz-type law, while the relaxor ferroelectric transition needs two independent fitting processes. The Lorenz-type law fails at the low temperature side of the dielectric maximum of a first-order ferroelectric phase transition. Above the transition temperature, the dielectric curves of all the studied materials can be well described by a Lorenz-type law.

  7. Relaxor behavior and electrical properties of high dielectric constant materials

    Institute of Scientific and Technical Information of China (English)

    FAN HuiQing; KE ShanMing

    2009-01-01

    Several typical high dielectric constant materials are reviewed to study the electrical properties and relaxation mechanism.It is found that a Lorenz-type law can be used to describe the dielectric permitUvity of either the normal ferroelectrics with or without diffuse phase transitions(DPT)or the typical ferroelectric relaxors.The ferroelectric DPT can be well described by just one fitting process using the Lorenz-type law,while the relaxor ferroelectric transition needs two independent fitting processes.The Lorenz-type law fails at the low temperature side of the dielectric maximum of a first-order ferroelectric phase transition.Above the transition temperature,the dielectric curves of all the studied materials can be well described by a Lorenz-type law.

  8. Optimization of the magnetic properties of materials for fluxgate sensors

    Directory of Open Access Journals (Sweden)

    Luiz Carlos de Carvalho Benyosef

    2008-06-01

    Full Text Available A study was made of the variation of the magnetic properties of cobalt-based alloys using different compositions of CoFeSiB and CoFeSiBCr systems, which were produced by the melt-spinning technique and some of them subjected to a stress annealing treatment. A comparative study of core geometry and supporting material was also performed in order to obtain low noise fluxgate sensor core using amorphous magnetic ribbons of these alloys. The best alloy was a stress annealed Co67.5Fe3.5Si17.4B11.6 sample, which yielded fluxgate sensors with lower noise levels than those of commercial crystalline materials.

  9. Fabrication of nanoscale to macroscale nickel-multiwall carbon nanotube hybrid materials with tunable material properties

    Science.gov (United States)

    Abdalla, Ahmed M.; Majdi, Tahereh; Ghosh, Suvojit; Puri, Ishwar K.

    2016-12-01

    To utilize their superior properties, multiwall carbon nanotubes (MWNTs) must be manipulated and aligned end-to-end. We describe a nondestructive method to magnetize MWNTs and provide a means to remotely manipulate them through the electroless deposition of magnetic nickel nanoparticles on their surfaces. The noncovalent bonds between Ni nanoparticles and MWNTs produce a Ni-MWNT hybrid material (NiCH) that is electrically conductive and has an enhanced magnetic susceptibility and elastic modulus. Our experiments show that MWNTs can be plated with Ni for Ni:MWNT weight ratios of γ = 1, 7, 14 and 30, to control the material properties. The phase, atom-level, and morphological information from x-ray diffraction, energy dispersive x-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, dark field STEM, and atomic force microscopy clarify the plating process and reveal the mechanical properties of the synthesized material. Ni metalizes at the surface of the Pd catalyst, forming a continuous wavy layer that encapsulates the MWNT surfaces. Subsequently, Ni acts as an autocatalyst, allowing the plating to continue even after the original Pd catalyst has been completely covered. Raising γ increases the coating layer thickness from 10 to 150 nm, which influences the NiCH magnetic properties and tunes its elastic modulus from 12.5 to 58.7 GPa. The NiCH was used to fabricate Ni-MWNT macrostructures and tune their morphologies by changing the direction of an applied magnetic field. Leveraging the hydrophilic Ni-MWNT outer surface, a water-based conductive ink was created and used to print a conductive path that had an electrical resistivity of 5.9 Ω m, illustrating the potential of this material for printing electronic circuits.

  10. Hygrothermal Simulation of Foundations: Part 1 - Soil Material Properties

    Energy Technology Data Exchange (ETDEWEB)

    Kehrer, Manfred [ORNL; Pallin, Simon B [ORNL

    2012-10-01

    The hygrothermal performance of soils coupled to buildings is a complicated process. A computational approach for heat transfer through the ground has been well defined (EN ISO 13370:2007, 2007), and simplified methods have been developed (Staszczuk, Radon, and Holm 2010). However, these approaches generally ignore the transfer of soil moisture, which is not negligible (Janssen, Carmeliet, and Hens 2004). This study is divided into several parts. The intention of the first part is to gather, comprehend and adapt soil properties from Soil Science. The obtained information must be applicable to related tasks in Building Science and validated with hygrothermal calculation tools. Future parts of this study will focus on the validation aspect of the soil properties to be implemented. Basic changes in the software code may be requested at this time. Different types of basement construction will be created with a hygrothermal calculation tool, WUFI. Simulations from WUFI will be compared with existing or ongoing measurements. The intentions of the first part of this study have been fulfilled. The soil properties of interest in Building Science have been defined for 12 different soil textures. These properties will serve as input parameters when performing hygrothermal calculations of building constructions coupled to soil materials. The reliability of the soil parameters will be further evaluated with measurements in Part 2.

  11. Material properties of the heel fat pad across strain rates.

    Science.gov (United States)

    Grigoriadis, Grigoris; Newell, Nicolas; Carpanen, Diagarajen; Christou, Alexandros; Bull, Anthony M J; Masouros, Spyros D

    2017-01-01

    The complex structural and material behaviour of the human heel fat pad determines the transmission of plantar loading to the lower limb across a wide range of loading scenarios; from locomotion to injurious incidents. The aim of this study was to quantify the hyper-viscoelastic material properties of the human heel fat pad across strains and strain rates. An inverse finite element (FE) optimisation algorithm was developed and used, in conjunction with quasi-static and dynamic tests performed to five cadaveric heel specimens, to derive specimen-specific and mean hyper-viscoelastic material models able to predict accurately the response of the tissue at compressive loading of strain rates up to 150s(-1). The mean behaviour was expressed by the quasi-linear viscoelastic (QLV) material formulation, combining the Yeoh material model (C10=0.1MPa, C30=7MPa, K=2GPa) and Prony׳s terms (A1=0.06, A2=0.77, A3=0.02 for τ1=1ms, τ2=10ms, τ3=10s). These new data help to understand better the functional anatomy and pathophysiology of the foot and ankle, develop biomimetic materials for tissue reconstruction, design of shoe, insole, and foot and ankle orthoses, and improve the predictive ability of computational models of the foot and ankle used to simulate daily activities or predict injuries at high rate injurious incidents such as road traffic accidents and underbody blast. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Anticoagulation property and security of artificial heart valve material

    Institute of Scientific and Technical Information of China (English)

    WANG Xianghui; XU Jingfang; LIU Xianghuai; ZHANG Feng; LI Changrong; YU Liujiang; ZHENG Zhihong; WANG Xi; JIANG Zhenbin; CHEN Anqing

    2005-01-01

    Heart valve diseases threaten human health. One reliable way to save lives of such patients is to replace the pathologically changed heart valves by artificial ones. Over 2 million patients have received LTI-carbon heart valve's implantation. However, the thrombosis after the implantation is one of the difficulties that need to be solved. In order to improve the blood compatibility and security of mechanical heart valves, ion beam technology was used to modify the surface properties of the materials. The investigation results have been summarized in this paper.

  13. Measurement of Thermal Properties of Biosourced Building Materials

    Science.gov (United States)

    Pierre, Thomas; Colinart, Thibaut; Glouannec, Patrick

    2014-10-01

    This paper presents both experimental and theoretical works concerning the evaluation of the thermal conductivity and thermal diffusivity of hemp concrete. Experimental measurements of thermal properties are performed using a hot-strip technique for temperatures ranging from 3 to 30 and relative humidities ranging from 0 % to 95 %, thus creating a large database for this material. These experimental thermal conductivities are then compared with the results from the Krischer theoretical predictive model. The comparison shows good agreement, and a predictive analytical relation between the hemp concrete thermal conductivity, temperature, and relative humidity is determined.

  14. Mechanical Properties of Heat Exchanger Tube Materials at Elevated Temperatures

    Science.gov (United States)

    Kahl, Sören; Zajac, Jozefa; Ekström, Hans-Erik

    Since automotive heat exchangers are operated at elevated temperatures and under varying pressures, both static and dynamic mechanical properties should be known at the relevant temperatures. We have collected elevated-temperature tensile test data, elevated-temperature stress amplitude-fatigue life data, and creep-rupture data in a systematic fashion over the past years. For thin, soft, and braze-simulated heat exchanger tube materials tested inside closed furnaces, none of the well-established methods for crack detection and observation can be applied. In our contribution, we present a simple statistical method to estimate the time required for crack initiation.

  15. Preparation and properties of antimony thin film anode materials

    Institute of Scientific and Technical Information of China (English)

    SU Shufa; CAO Gaoshao; ZHAO Xinbing

    2004-01-01

    Metallic antimony thin films were deposited by magnetron sputtering and electrodeposition. Electrochemical properties of the thin film as anode materials for lithium-ion batteries were investigated and compared with those of antimony powder. It was found that both magnetron sputtering and electrodeposition are easily controllable processes to deposit antimony films with fiat charge/discharge potential plateaus. The electrochemical performances of antimony thin films, especially those prepared with magnetron sputtering, are better than those of antimony powder. The reversible capacities of the magnetron sputtered antimony thin film are above 400 mA h g-1 in the first 15 cycles.

  16. Electromagnetic properties in ferroelectric materials; Proprietes electromagnetiques des materiaux ferroelectriques

    Energy Technology Data Exchange (ETDEWEB)

    Ravez, J.; Elissalde, C. [Institut de Chimie de la Matiere Condensee, 33 - Pessac (France); Miane, J.L. [ENSCPB, 33 - Talence (France)

    1996-12-31

    The recent development of network analyzers has allowed electromagnetic property studies in perovskite-type ferroelectric materials in a large frequency range ({approx} 10{sup 2}-10{sup 10} Hz). A high frequency ({approx} 10{sup 7}-10{sup 10} Hz) relaxation has been evidenced. The origin of the relaxation process has been determined: it is an intrinsic mechanism directly related to the crystal lattice. In the light of the obtained results, physical-chemistry laws can be used to modulate the relaxation frequency using appropriate ionic substitutions. (authors). 13 refs., 6 figs., 1 tab.

  17. Mechanical properties of new dental pulp-capping materials.

    Science.gov (United States)

    Nielsen, Matthew J; Casey, Jeffery A; VanderWeele, Richard A; Vandewalle, Kraig S

    2016-01-01

    The mechanical properties of pulp-capping materials may affect their resistance to fracture during placement of a final restorative material or while supporting an overlying restoration over time. The purpose of this study was to compare the compressive strength, flexural strength, and flexural modulus of 2 new pulp-capping materials (TheraCal LC and Biodentine), mineral trioxide aggregate (MTA), and calcium hydroxide over time. Specimens were created in molds and tested to failure in a universal testing machine after 15 minutes, 3 hours, and 24 hours. The MTA specimens did not set at 15 minutes. At all time periods, TheraCal LC had the greatest compressive and flexural strengths. After 3 and 24 hours, Biodentine had the greatest flexural modulus. TheraCal LC had greater early strength to potentially resist fracture during immediate placement of a final restorative material. Biodentine had greater stiffness after 3 hours to potentially provide better support of an overlying restoration under function over time.

  18. Mechanical properties of gangue-containing aluminosilicate based cementitious materials

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials.The gangue was calcined at 500℃.The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent.The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM.The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt.For 28-day curing time, the compressive strength of the sample with a mass proportion of 2:1:1 (gangue: slag: fly ash) is 58.9 MPa, while the compressive strength of the sample containing 80wt%gangue can still be up to 52.3 MPa.The larger K+ favors the formation of large silicate oligomers with which Al(OH)4- prefers to bind.Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator.The reasons for this were found through IR and NMR analysis.Glauber's salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.

  19. Mechanisms Responsible for Microwave Properties in High Performance Dielectric Materials

    Science.gov (United States)

    Zhang, Shengke

    Microwave properties of low-loss commercial dielectric materials are optimized by adding transition-metal dopants or alloying agents (i.e. Ni, Co, Mn) to tune the temperature coefficient of resonant frequency (tau f) to zero. This occurs as a result of the temperature dependence of dielectric constant offsetting the thermal expansion. At cryogenic temperatures, the microwave loss in these dielectric materials is dominated by electron paramagnetic resonance (EPR) loss, which results from the spin-excitations of d-shell electron spins in exchange-coupled clusters. We show that the origin of the observed magnetically-induced shifts in the dielectric resonator frequency originates from the same mechanism, as described by the Kramers-Kronig relations. The temperature coefficient of resonator frequency, tauf, is related to three material parameters according to the equation, tau f = - (½ tauepsilon + ½ taumu + alphaL), where tauepsilon, taumu , and alphaL are the temperature coefficient of dielectric constant, magnetic permeability, and lattice constant, respectively. Each of these parameters for dielectric materials of interest are measured experimentally. These results, in combination with density functional simulations, developed a much improved understanding of the fundamental mechanisms responsible for tau f. The same experimental methods have been used to characterize in-situ the physical nature and concentration of performance-degrading point defects in the dielectrics of superconducting planar microwave resonators.

  20. Molecular-dynamics simulation of a ceramide bilayer

    Science.gov (United States)

    Pandit, Sagar A.; Scott, H. Larry

    2006-01-01

    Ceramide is the simplest lipid in the biologically important class of glycosphingolipids. Ceramide is an important signaling molecule and a major component of the strateum corneum layer in the skin. In order to begin to understand the biophysical properties of ceramide, we have carried out a molecular-dynamics simulation of a hydrated 16:0 ceramide lipid bilayer at 368K (5° above the main phase transition). In this paper we describe the simulation and present the resulting properties of the bilayer. We compare the properties of the simulated ceramide bilayer to an earlier simulation of 18:0 sphingomyelin, and we discuss the results as they relate to experimental data for ceramide and other sphingolipids. The most significant differences arise at the lipid/water interface, where the lack of a large ceramide polar group leads to a different electron density and a different electrostatic potential but, surprisingly, not a different overall "dipole potential," when ceramide is compared to sphingomyelin.

  1. The effects of interfacial interactions between Fe–O and Fe–Si induced by ion-beam bombardment on the magnetic properties of Si-oxide/Fe bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Li, X. [Department of Electrical and Electronic Engineering, The University of Hong Kong (Hong Kong); Lin, K.-W., E-mail: kwlin@dragon.nchu.edu.tw [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan (China); Liang, H.-T.; Hsu, H.-F. [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan (China); Galkin, N.G. [Institute of Automation & Control Processes, FEB RAS, Radio Str. 5, 690041 Vladivostok (Russian Federation); Wroczynskyj, Y. [Department of Physics and Astronomy, University of Manitoba, Winnipeg R3T 2N2 (Canada); Lierop, J. van, E-mail: johan@physics.umanitoba.ca [Department of Physics and Astronomy, University of Manitoba, Winnipeg R3T 2N2 (Canada); Pong, P.W.T., E-mail: ppong@eee.hku.hk [Department of Electrical and Electronic Engineering, The University of Hong Kong (Hong Kong)

    2015-12-15

    Highlights: • Si capping layer was deposited on Fe layer with O{sub 2}/Ar ion beam bombardment. • Structure deformation and grain re-orientation was observed after bombardment. • FeO, Fe{sub 2}O{sub 3}, SiO{sub 2}, and FeSi were formed in the interface, as proved by XPS. • The interface layer resulted in magnetic coercivity enhancement at low temperature. • Fe–O changed to antiferromagnetic at 10 K, establishing exchange coupling with Fe. - Abstract: Si/Fe and SiO{sub 2}/Fe thin-film heterostructures are commonly seen in magnetic multilayer devices, whose magnetic properties are strongly influenced by intermixing at the interfaces. In this paper, Si-oxide/Fe bilayers were formed by depositing Si on Fe with in situ O{sub 2}/Ar ion-beam bombardment during the Si deposition. The surface oxidation conditions were altered by applying different O{sub 2}/Ar ratios (0–41%) in the ion-beam. The surface and cross-sectional morphologies, and the crystalline structures were characterized by transmission electron microscopy. The formation of Fe–O, Fe–Si and Si–O bonds at the interface of the O{sub 2}/Ar ion-beam bombarded Si-oxide/Fe bilayers was evidenced by X-ray photoemission spectra. FeO, Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} at the interface resulted in a marked increase in the magnetic coercivity at low temperatures, as characterized by magnetometry.

  2. Robustly Engineering Thermal Conductivity of Bilayer Graphene by Interlayer Bonding.

    Science.gov (United States)

    Zhang, Xiaoliang; Gao, Yufei; Chen, Yuli; Hu, Ming

    2016-02-25

    Graphene and its bilayer structure are the two-dimensional crystalline form of carbon, whose extraordinary electron mobility and other unique features hold great promise for nanoscale electronics and photonics. Their realistic applications in emerging nanoelectronics usually call for thermal transport manipulation in a controllable and precise manner. In this paper we systematically studied the effect of interlayer covalent bonding, in particular different interlay bonding arrangement, on the thermal conductivity of bilayer graphene using equilibrium molecular dynamics simulations. It is revealed that, the thermal conductivity of randomly bonded bilayer graphene decreases monotonically with the increase of interlayer bonding density, however, for the regularly bonded bilayer graphene structure the thermal conductivity possesses unexpectedly non-monotonic dependence on the interlayer bonding density. The results suggest that the thermal conductivity of bilayer graphene depends not only on the interlayer bonding density, but also on the detailed topological configuration of the interlayer bonding. The underlying mechanism for this abnormal phenomenon is identified by means of phonon spectral energy density, participation ratio and mode weight factor analysis. The large tunability of thermal conductivity of bilayer graphene through rational interlayer bonding arrangement paves the way to achieve other desired properties for potential nanoelectronics applications involving graphene layers.

  3. Experimental Study on the Comparison of the Material Properties of Glass Wool Used as Building Materials

    Directory of Open Access Journals (Sweden)

    Kyoung-Woo KIM

    2014-04-01

    Full Text Available Artificial mineral fibers such as glass wool or stone wool are commonly used in building walls, ceilings and floors as a major insulation material for buildings. Among the material properties of building materials, thermal conductivity, the sound absorption coefficient, compressibility, and dynamic stiffness are regarded as important performance requirements since they directly affect the thermal and acoustic properties of the building. This study measured the changes of the thermal and acoustical performances of glass wool that was actually installed for a long time to the outer wall of a building as an insulation material through a comparison with recently produced glass wool. The results showed that the measured thermal conductivities of the old and the new specimens both rise with an increase of temperature, showing quite similar results in both specimens over temperature ranges of (0 – 20 ºC. The noise reduction coefficient decreased by 0.1 in the old specimen and the difference of the compressibilities in both specimens was shown to be 7.32 mm. The dynamic stiffness of the old specimen was found to be 1.28 MN/m3 higher than that of the new specimen.DOI: http://dx.doi.org/10.5755/j01.ms.20.1.3714

  4. Molecular Dynamics of a Water-Lipid Bilayer Interface

    Science.gov (United States)

    Wilson, Michael A.; Pohorille, Andrew

    1994-01-01

    We present results of molecular dynamics simulations of a glycerol 1-monooleate bilayer in water. The total length of analyzed trajectories is 5ns. The calculated width of the bilayer agrees well with the experimentally measured value. The interior of the membrane is in a highly disordered fluid state. Atomic density profile, orientational and conformational distribution functions, and order parameters indicate that disorder increases toward the center of the bilayer. Analysis of out-of-plane thermal fluctuations of the bilayer surfaces occurring at the time scale of the present calculations reveals that the distribution of modes agrees with predictions of the capillary wave model. Fluctuations of both bilayer surfaces are uncorrelated, yielding Gaussian distribution of instantaneous widths of the membrane. Fluctuations of the width produce transient thinning defects in the bilayer which occasionally span almost half of the membrane. The leading mechanism of these fluctuations is the orientational and conformational motion of head groups rather than vertical motion of the whole molecules. Water considerably penetrates the head group region of the bilayer but not its hydrocarbon core. The total net excess dipole moment of the interfacial water points toward the aqueous phase, but the water polarization profile is non-monotonic. Both water and head groups significantly contribute to the surface potential across the interface. The calculated sign of the surface potential is in agreement with that from experimental measurements, but the value is markedly overestimated. The structural and electrical properties of the water-bilayer system are discussed in relation to membrane functions, in particular transport of ions and nonelectrolytes across membranes.

  5. Molecular Dynamics of a Water-Lipid Bilayer Interface

    Science.gov (United States)

    Wilson, Michael A.; Pohorille, Andrew

    1994-01-01

    We present results of molecular dynamics simulations of a glycerol 1-monooleate bilayer in water. The total length of analyzed trajectories is 5ns. The calculated width of the bilayer agrees well with the experimentally measured value. The interior of the membrane is in a highly disordered fluid state. Atomic density profile, orientational and conformational distribution functions, and order parameters indicate that disorder increases toward the center of the bilayer. Analysis of out-of-plane thermal fluctuations of the bilayer surfaces occurring at the time scale of the present calculations reveals that the distribution of modes agrees with predictions of the capillary wave model. Fluctuations of both bilayer surfaces are uncorrelated, yielding Gaussian distribution of instantaneous widths of the membrane. Fluctuations of the width produce transient thinning defects in the bilayer which occasionally span almost half of the membrane. The leading mechanism of these fluctuations is the orientational and conformational motion of head groups rather than vertical motion of the whole molecules. Water considerably penetrates the head group region of the bilayer but not its hydrocarbon core. The total net excess dipole moment of the interfacial water points toward the aqueous phase, but the water polarization profile is non-monotonic. Both water and head groups significantly contribute to the surface potential across the interface. The calculated sign of the surface potential is in agreement with that from experimental measurements, but the value is markedly overestimated. The structural and electrical properties of the water-bilayer system are discussed in relation to membrane functions, in particular transport of ions and nonelectrolytes across membranes.

  6. Transport properties of damaged materials. Cementitious barriers partnership

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-11-01

    The objective of the Cementitious Barriers Partnership (CBP) project is to develop tools to improve understanding and prediction of the long-term structural, hydraulic, and chemical performance of cementitious barriers used in low-level waste storage applications. One key concern for the long-term durability of concrete is the degradation of the cementitious matrix, which occurs as a result of aggressive chemical species entering the material or leaching out in the environment, depending on the exposure conditions. The objective of the experimental study described in this report is to provide experimental data relating damage in cementitious materials to changes in transport properties, which can eventually be used to support predictive model development. In order to get results within a reasonable timeframe and to induce as much as possible uniform damage level in materials, concrete samples were exposed to freezing and thawing (F/T) cycles. The methodology consisted in exposing samples to F/T cycles and monitoring damage level with ultrasonic pulse velocity measurements. Upon reaching pre-selected damage levels, samples were tested to evaluate changes in transport properties. Material selection for the study was motivated by the need to get results rapidly, in order to assess the relevance of the methodology. Consequently, samples already available at SIMCO from past studies were used. They consisted in three different concrete mixtures cured for five years in wet conditions. The mixtures had water-to-cement ratios of 0.5, 0.65 and 0.75 and were prepared with ASTM Type I cement only. The results showed that porosity is not a good indicator for damage caused by the formation of microcracks. Some materials exhibited little variations in porosity even for high damage levels. On the other hand, significant variations in tortuosity were measured in all materials. This implies that damage caused by internal pressure does not necessarily create additional pore space in

  7. Cementitious barriers partnership transport properties of damaged materials

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-11-01

    The objective of the Cementitious Barriers Partnership (CBP) project is to develop tools to improve understanding and prediction of the long-term structural, hydraulic, and chemical performance of cementitious barriers used in low level waste storage applications. One key concern for the long-term durability of concrete is the degradation of the cementitious matrix, which occurs as a result of aggressive chemical species entering the material or leaching out in the environment, depending on the exposure conditions. The objective of the experimental study described in this report is to provide experimental data relating damage in cementitious materials to changes in transport properties, which can eventually be used to support predictive model development. In order to get results within a reasonable timeframe and to induce as much as possible uniform damage level in materials, concrete samples were exposed to freezing and thawing (F/T) cycles. The methodology consisted in exposing samples to F/T cycles and monitoring damage level with ultrasonic pulse velocity measurements. Upon reaching pre-selected damage levels, samples were tested to evaluate changes in transport properties. Material selection for the study was motivated by the need to get results rapidly, in order to assess the relevance of the methodology. Consequently, samples already available at SIMCO from past studies were used. They consisted in three different concrete mixtures cured for five years in wet conditions. The mixtures had water-to-cement ratios of 0.5, 0.65 and 0.75 and were prepared with ASTM Type I cement only. The results showed that porosity is not a good indicator for damage caused by the formation of microcracks. Some materials exhibited little variations in porosity even for high damage levels. On the other hand, significant variations in tortuosity were measured in all materials. This implies that damage caused by internal pressure do not necessarily creates additional pore space in

  8. Elucidating the role of interfacial materials properties in microfluidic packages.

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, Thayne L.

    2013-01-01

    The purpose of this work was to discover a method to investigate the properties of interfaces as described by a numerical physical model. The model used was adopted from literature and applied to a commercially available multiphysics software package. By doing this the internal properties of simple structures could be elucidated and then readily applied to more complex structures such as valves and pumps in laminate microfluidic structures. A numerical finite element multi-scale model of a cohesive interface comprised of heterogeneous material properties was used to elucidate irreversible damage from applied strain energy. An unknown internal state variable was applied to characterize the damage process. Using a constrained blister test, this unknown internal state variable could be determined for an adherend/adhesive/adherend body. This is particularly interesting for laminate systems with microfluidic and microstructures contained within the body. A laminate structure was designed and fabricated that could accommodate a variety of binary systems joined using nearly any technique such as adhesive, welding (solvent, laser, ultrasonic, RF, etc.), or thermal. The adhesive method was the most successful and easy to implement but also one of the more difficult to understand, especially over long periods of time. Welding methods are meant to achieve a bond that is similar to bulk properties and so are easier to predict. However, methods of welding often produce defects in the bonds.. Examples of the test structures used to elucidate the internal properties of the model were shown and demonstrated. The real life examples used this research to improve upon current designs and aided in creating complex structures for sensor and other applications.

  9. Ultrafast control and monitoring of material properties using terahertz pulses

    Energy Technology Data Exchange (ETDEWEB)

    Bowlan, Pamela Renee [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Lab. for Ultrafast Materials Optical Science (LUMOS)

    2016-05-02

    These are a set of slides on ultrafast control and monitoring of material properties using terahertz pulses. A few of the topics covered in these slides are: How fast is a femtosecond (fs), Different frequencies probe different properties of molecules or solids, What can a THz pulse do to a material, Ultrafast spectroscopy, Generating and measuring ultrashort THz pulses, Tracking ultrafast spin dynamics in antiferromagnets through spin wave resonances, Coherent two-dimensional THz spectroscopy, and Probing vibrational dynamics at a surface. Conclusions are: Coherent two-dimensional THz spectroscopy: a powerful approach for studying coherence and dynamics of low energy resonances. Applying this to graphene we investigated the very strong THz light mater interaction which dominates over scattering. Useful for studying coupled excitations in multiferroics and monitoring chemical reactions. Also, THz-pump, SHG-probe spectoscopy: an ultrafast, surface sensitive probe of atomic-scale symmetry changes and nonlinear phonon dymanics. We are using this in Bi2Se3 to investigate the nonlinear surface phonon dynamics. This is potentially very useful for studying catalysis.

  10. Development of Thermoelectric Power Generation and Peltier Cooling Properties of Materials for Thermoelectric Cryocooling Devices

    Science.gov (United States)

    2015-05-12

    Distribution Unlimited Final Report: Development of Thermoelectric Power Generation and Peltier Cooling Properties of Materials for Thermoelectric...Thermoelectric Power Generation and Peltier Cooling Properties of Materials for Thermoelectric Cryocooling Devices Report Title The research

  11. Recommended Best Practices for the Characterization of Storage Properties of Hydrogen Storage Materials

    Energy Technology Data Exchange (ETDEWEB)

    None

    2010-03-01

    This is a reference guide to common methodologies and protocols for measuring critical performance properties of advanced hydrogen storage materials. It helps users to communicate clearly the relevant performance properties of new materials as they are discovered and tested.

  12. The intriguing electronic and optical properties modulation of hydrogen and fluorine codecorated silicene layers

    Science.gov (United States)

    Yang, Qun; Tan, Chunjian; Meng, Ruishen; Jiang, Junke; Liang, Qiuhua; Sun, Xiang; Yang, Daoguo; Chen, Xianping

    2017-03-01

    First-principles calculations based on density-functional theory reveal some superior physical properties of hydrogen and fluorine co-decorated silicene (HSiF) monolayer and bilayer. Our simulated results reveal that the HSiF monolayer is a large direct band gap semiconductor greatly differing from the gapless semi-metallic silicene. There exists strong interlayer coupling in HSiF bilayer, leading to the good stabilities of HSiF bilayer even beyond bilayer graphene. The proposed HSiF bilayer exhibits a moderate direct band gap of 0.296 eV which is much lower than that of HSiF monolayer. Encouragingly, HSiF layers all have a direct band gap nature, irrespective of stacking pattern, thickness and external electric fields, which is an advantage over MoS2 layers. Furthermore, an out-of-plane electric field has an evident impact on the band structures of the HSiF monolayer and bilayer. Especially, the band gap of HSiF bilayer can be effectively tuned by external electric field, even a semiconductor-metal transition occurs. More importantly, the HSiF bilayer exhibits a significant improved visible light adsorption peak with respect to that of HSiF monolayer, and the superior optical properties is robust, independent of stacking pattern. The complete electron-hole separation also enhances the photocatalytic efficiency of HSiF bilayer. In a word, the moderate band gap, effective band gap modification by external electric field, robust direct band gap nature, suitable band edge positions, electron-hole separation, and fascinating visible light adsorption, which enable HSiF bilayer to have great potential applications in the field of solar energy conversion, high performance photocatalysis and nanoelectronic devices, and we call for more concern over this kind of 2D Janus materials which possesses excellent properties.

  13. Thermal and Thermoelectric Properties of Nanostructured Materials and Interfaces

    Science.gov (United States)

    Liao, Hao-Hsiang

    Many modern technologies are enabled by the use of thin films and/or nanostructured composite materials. For example, many thermoelectric devices, solar cells, power electronics, thermal barrier coatings, and hard disk drives contain nanostructured materials where the thermal conductivity of the material is a critical parameter for the device performance. At the nanoscale, the mean free path and wavelength of heat carriers may become comparable to or smaller than the size of a nanostructured material and/or device. For nanostructured materials made from semiconductors and insulators, the additional phonon scattering mechanisms associated with the high density of interfaces and boundaries introduces additional resistances that can significantly change the thermal conductivity of the material as compared to a macroscale counterpart. Thus, better understanding and control of nanoscale heat conduction in solids is important scientifically and for the engineering applications mentioned above. In this dissertation, I discuss my work in two areas dealing with nanoscale thermal transport: (1) I describe my development and advancement of important thermal characterization tools for measurements of thermal and thermoelectric properties of a variety of materials from thin films to nanostructured bulk systems, and (2) I discuss my measurements on several materials systems done with these characterization tools. First, I describe the development, assembly, and modification of a time-domain thermoreflectance (TDTR) system that we use to measure the thermal conductivity and the interface thermal conductance of a variety of samples including nanocrystalline alloys of Ni-Fe and Co-P, bulk metallic glasses, and other thin films. Next, a unique thermoelectric measurement system was designed and assembled for measurements of electrical resistivity and thermopower of thermoelectric materials in the temperature range of 20 to 350 °C. Finally, a commercial Anter Flashline 3000 thermal

  14. Self-folding graphene-polymer bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Tao [Institute of Microelectronics, Tsinghua University, Beijing 100084 (China); Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Yoon, ChangKyu [Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Jin, Qianru [Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Li, Mingen [Department of Physics, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Liu, Zewen [Institute of Microelectronics, Tsinghua University, Beijing 100084 (China); Gracias, David H., E-mail: dgracias@jhu.edu [Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

    2015-05-18

    In order to incorporate the extraordinary intrinsic thermal, electrical, mechanical, and optical properties of graphene with three dimensional (3D) flexible substrates, we introduce a solvent-driven self-folding approach using graphene-polymer bilayers. A polymer (SU-8) film was spin coated atop chemically vapor deposited graphene films on wafer substrates and graphene-polymer bilayers were patterned with or without metal electrodes using photolithography, thin film deposition, and etching. After patterning, the bilayers were released from the substrates and they self-folded to form fully integrated, curved, and folded structures. In contrast to planar graphene sensors on rigid substrates, we assembled curved and folded sensors that are flexible and they feature smaller form factors due to their 3D geometry and large surface areas due to their multiple rolled architectures. We believe that this approach could be used to assemble a range of high performance 3D electronic and optical devices of relevance to sensing, diagnostics, wearables, and energy harvesting.

  15. Self-folding graphene-polymer bilayers

    Science.gov (United States)

    Deng, Tao; Yoon, ChangKyu; Jin, Qianru; Li, Mingen; Liu, Zewen; Gracias, David H.

    2015-05-01

    In order to incorporate the extraordinary intrinsic thermal, electrical, mechanical, and optical properties of graphene with three dimensional (3D) flexible substrates, we introduce a solvent-driven self-folding approach using graphene-polymer bilayers. A polymer (SU-8) film was spin coated atop chemically vapor deposited graphene films on wafer substrates and graphene-polymer bilayers were patterned with or without metal electrodes using photolithography, thin film deposition, and etching. After patterning, the bilayers were released from the substrates and they self-folded to form fully integrated, curved, and folded structures. In contrast to planar graphene sensors on rigid substrates, we assembled curved and folded sensors that are flexible and they feature smaller form factors due to their 3D geometry and large surface areas due to their multiple rolled architectures. We believe that this approach could be used to assemble a range of high performance 3D electronic and optical devices of relevance to sensing, diagnostics, wearables, and energy harvesting.

  16. Organoapatites: materials for artificial bone. II. Hardening reactions and properties.

    Science.gov (United States)

    Stupp, S I; Mejicano, G C; Hanson, J A

    1993-03-01

    This article reports on chemical reactions and the properties they generated in artificial bone materials termed "organoapatites." These materials are synthesized using methodology we reported in the previous article of this series. Two different processes were studied here for the transition from organoapatite particles to implants suitable for the restoration of the skeletal system. One process involved the hardening of powder compacts by beams of blue light derived from a lamp or a laser and the other involved pressure-induced interdiffusion of polymers. In both cases, the hardening reaction involved the formation of a polyion complex between two polyelectrolytes. In the photo-induced reaction an anionic electrolyte polymerizes to form the coulombic network and in the pressure-induced one, pressure forms the complex by interdiffusion of two polyions. Model reactions were studied using various polycations. Based on these results the organoapatite selected for the study was that containing dispersed poly(L-lysine) and sodium acrylate as the anionic monomer. The organomineral particles can be pressed at room temperature into objects of great physical integrity and hydrolytic stability relative to anorganic controls. The remarkable fact about these objects is that intimate molecular dispersion of only 2-3% by weight organic material provides integrity to the mineral network in an aqueous medium and also doubles its tensile strength. This integrity is essentially nonexistent in "anorganic" samples prepared by the same methodology used in organoapatite synthesis. The improvement in properties was most effectively produced by molecular bridges formed by photopolymerization. The photopolymerization leads to the "hardening" of pellets prepared by pressing of organoapatite powders. The reaction was found to be more facile in the microstructure of the organomineral, and it is potentially useful in the surgical application of organoapatites as artificial bone.

  17. ABINIT: First-principles approach to material and nanosystem properties

    Science.gov (United States)

    Gonze, X.; Amadon, B.; Anglade, P.-M.; Beuken, J.-M.; Bottin, F.; Boulanger, P.; Bruneval, F.; Caliste, D.; Caracas, R.; Côté, M.; Deutsch, T.; Genovese, L.; Ghosez, Ph.; Giantomassi, M.; Goedecker, S.; Hamann, D. R.; Hermet, P.; Jollet, F.; Jomard, G.; Leroux, S.; Mancini, M.; Mazevet, S.; Oliveira, M. J. T.; Onida, G.; Pouillon, Y.; Rangel, T.; Rignanese, G.-M.; Sangalli, D.; Shaltaf, R.; Torrent, M.; Verstraete, M. J.; Zerah, G.; Zwanziger, J. W.

    2009-12-01

    ABINIT [ http://www.abinit.org] allows one to study, from first-principles, systems made of electrons and nuclei (e.g. periodic solids, molecules, nanostructures, etc.), on the basis of Density-Functional Theory (DFT) and Many-Body Perturbation Theory. Beyond the computation of the total energy, charge density and electronic structure of such systems, ABINIT also implements many dynamical, dielectric, thermodynamical, mechanical, or electronic properties, at different levels of approximation. The present paper provides an exhaustive account of the capabilities of ABINIT. It should be helpful to scientists that are not familiarized with ABINIT, as well as to already regular users. First, we give a broad overview of ABINIT, including the list of the capabilities and how to access them. Then, we present in more details the recent, advanced, developments of ABINIT, with adequate references to the underlying theory, as well as the relevant input variables, tests and, if available, ABINIT tutorials. Program summaryProgram title: ABINIT Catalogue identifier: AEEU_v1_0 Distribution format: tar.gz Journal reference: Comput. Phys. Comm. Programming language: Fortran95, PERL scripts, Python scripts Computer: All systems with a Fortran95 compiler Operating system: All systems with a Fortran95 compiler Has the code been vectorized or parallelized?: Sequential, or parallel with proven speed-up up to one thousand processors. RAM: Ranges from a few Mbytes to several hundred Gbytes, depending on the input file. Classification: 7.3, 7.8 External routines: (all optional) BigDFT [1], ETSF IO [2], libxc [3], NetCDF [4], MPI [5], Wannier90 [6] Nature of problem: This package has the purpose of computing accurately material and nanostructure properties: electronic structure, bond lengths, bond angles, primitive cell size, cohesive energy, dielectric properties, vibrational properties, elastic properties, optical properties, magnetic properties, non-linear couplings, electronic and

  18. Lifelong modelling of properties for materials with technological memory

    Science.gov (United States)

    Falaleev, AP; Meshkov, VV; Vetrogon, AA; Ogrizkov, SV; Shymchenko, AV

    2016-10-01

    An investigation of real automobile parts produced from dual phase steel during standard periods of life cycle is presented, which considers such processes as stamping, exploitation, automobile accident, and further repair. The development of the phenomenological model of the mechanical properties of such parts was based on the two surface plastic theory of Chaboche. As a consequence of the composite structure of dual phase steel, it was shown that local mechanical properties of parts produced from this material change significantly their during their life cycle, depending on accumulated plastic deformations and thermal treatments. Such mechanical property changes have a considerable impact on the accuracy of the computer modelling of automobile behaviour. The most significant errors of modelling were obtained at the critical operating conditions, such as crashes and accidents. The model developed takes into account the kinematics (Bauschinger effect), isotropic hardening, non-linear elastic steel behaviour and changes caused by the thermal treatment. Using finite element analysis, the model allows the evaluation of the passive safety of a repaired car body, and enables increased restoration accuracy following an accident. The model was confirmed experimentally for parts produced from dual phase steel DP780.

  19. Composition, structure and mechanical properties of several natural cellular materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The stem piths of sunflower, kaoliang and corn are natural cellular materials. In this paper, the contents of the compositions of these piths are determined and their cell shapes and structures are examined through scanning electron microscope (SEM) and optical microscope. Further research is conducted in the effects of the compositions and structures of the piths on the mechanical properties after testing the partial mechanical properties. The results show that the total cellulose, hemicelluloses and lignin content of each sample approaches 75% of the dry mass of its primary cell walls. With the fall of R value, a parameter relative to the contents of the main compositions, the flexibilities of the cellular piths descend while their stresses and rigidities increase. The basic cell shape making up the sunflower pith is approximately a tetrakaidehedron. The stem piths of kaoliang and corn are made up of cells close to hexangular prisms and a few tubular ones which can observably reinforce their mechanical properties in the axial directions.

  20. Electron Transport Materials: Synthesis, Properties and Device Performance

    Energy Technology Data Exchange (ETDEWEB)

    Cosimbescu, Lelia; Wang, Liang; Helm, Monte L.; Polikarpov, Evgueni; Swensen, James S.; Padmaperuma, Asanga B.

    2012-06-01

    We report the design, synthesis and characterization, thermal and photophysical properties of two silane based electron transport materials, dibenzo[b,d]thiophen-2-yltriphenylsilane (Si{phi}87) and (dibenzo[b,d]thiophen-2-yl)diphenylsilane (Si{phi}88) and their performance in blue organic light emitting devices (OLEDs). The utility of these materials in blue OLEDs with iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C']picolinate (Firpic) as the phosphorescent emitter was demonstrated. Using the silane Si{phi}87 as the electron transport material (ETm) an EQE of 18.2% was obtained, with a power efficiency of 24.3 lm/W (5.8V at 1mA/cm{sup 2}), in a heterostructure. When Si{phi}88 is used, the EQE is 18.5% with a power efficiency of 26.0 lm/W (5.5V at 1mA/cm{sup 2}).

  1. Designing functionally graded materials with superior load-bearing properties.

    Science.gov (United States)

    Zhang, Yu; Sun, Ming-Jie; Zhang, Denzil

    2012-03-01

    Ceramic prostheses often fail from fracture and wear. We hypothesize that these failures may be substantially mitigated by an appropriate grading of elastic modulus at the ceramic surface. In this study, we elucidate the effect of elastic modulus profile on the flexural damage resistance of functionally graded materials (FGMs), providing theoretical guidelines for designing FGMs with superior load-bearing property. The Young's modulus of the graded structure is assumed to vary in a power-law relation with a scaling exponent n; this is in accordance with experimental observations from our laboratory and elsewhere. Based on the theory for bending of graded beams, we examine the effect of n value and bulk-to-surface modulus ratio (E(b)/E(s)) on stress distribution through the graded layer. Theory predicts that a low exponent (0.15graded materials with various n values and E(b)/E(s) ratios can be fabricated by infiltrating alumina and zirconia with a low-modulus glass. Flexural tests show that graded alumina and zirconia with suitable values of these parameters exhibit superior load-bearing capacity, 20-50% higher than their homogeneous counterparts. Improving load-bearing capacity of ceramic materials could have broad impacts on biomedical, civil, structural, and an array of other engineering applications.

  2. Interfacial properties and design of functional energy materials.

    Science.gov (United States)

    Sumpter, Bobby G; Liang, Liangbo; Nicolaï, Adrien; Meunier, Vincent

    2014-11-18

    CONSPECTUS: The vital importance of energy to society continues to demand a relentless pursuit of energy responsive materials that can bridge fundamental chemical structures at the molecular level and achieve improved functionality and performance. This demand can potentially be realized by harnessing the power of self-assembly, a spontaneous process where molecules or much larger entities form ordered aggregates as a consequence of predominately noncovalent (weak) interactions. Self-assembly is the key to bottom-up design of molecular devices, because the nearly atomic-level control is very difficult to realize in a top-down, for example, lithographic, approach. However, while function in simple systems such as single crystals can often be evaluated a priori, predicting the function of the great variety of self-assembled molecular architectures is complicated by the lack of understanding and control over nanoscale interactions, mesoscale architectures, and macroscale order. To establish a foundation toward delivering practical solutions, it is critical to develop an understanding of the chemical and physical mechanisms responsible for the self-assembly of molecular and hybrid materials on various support substrates. Typical molecular self-assembly involves noncovalent intermolecular and substrate-molecule interactions. These interactions remain poorly understood, due to the combination of many-body interactions compounded by local or collective influences from the substrate atomic lattice and electronic structure. Progress toward unraveling the underlying physicochemical processes that control the structure and macroscopic physical, chemical, mechanical, electrical, and transport properties of materials increasingly requires tight integration of theory, modeling, and simulation with precision synthesis, advanced experimental characterization, and device measurements. Theory, modeling, and simulation can accelerate the process of materials understanding and design

  3. Lipid bilayers on nano-templates

    Science.gov (United States)

    Noy, Aleksandr; Artyukhin, Alexander B.; Bakajin, Olgica; Stoeve, Pieter

    2009-08-04

    A lipid bilayer on a nano-template comprising a nanotube or nanowire and a lipid bilayer around the nanotube or nanowire. One embodiment provides a method of fabricating a lipid bilayer on a nano-template comprising the steps of providing a nanotube or nanowire and forming a lipid bilayer around the polymer cushion. One embodiment provides a protein pore in the lipid bilayer. In one embodiment the protein pore is sensitive to specific agents

  4. Filter properties of seam material from paved urban soils

    Directory of Open Access Journals (Sweden)

    T. Nehls

    2008-04-01

    Full Text Available Depositions of all kinds of urban dirt and dust including anthropogenic organic substances like soot change the filter properties of the seam filling material of pervious pavements and lead to the formation of a new soil substrate called seam material.

    In this study, the impact of the particular urban form of organic matter (OM on the seam materials CECpot, the specific surface area (As, the surface charge density (SCD, the adsorption energies (Ea and the adsorption of Cd and Pb were assessed. The Cd and Pb displacement through the pavement system has been simulated in order to assess the risk of soil and groundwater contamination from infiltration of rainwater in paved urban soils.

    As, Ea and SCD derived from water vapor adsorption isotherms, CECpot, Pb and Cd adsorption isotherms where analyzed from adsorption experiments. The seam material is characterized by a darker munsell-color and a higher Corg (12 to 48g kg-1 compared to the original seam filling. Although, the increased Corg leads to higher As (16m2g-1 and higher CECpot (0.7 to 4.8cmolckg-1, with 78cmolckg-1C its specific CECpot is low compared to OM of non-urban soils. This can be explained by a low SCD of 1.2×10-6molc m-2 and a low fraction of high adsorption energy sites which is likely caused by the non-polar character of the accumulated urban OM in the seam material.

    The seam material shows stronger sorption of Pb and Cd compared to the original construction sand. The retardation capacity of seam material for Pb is similar, for Cd it is much smaller compared to natural sandy soils with similar Corg concentrations

  5. Electric-field-induced destruction of quasi-Landau levels in bilayer graphene nanoribbons.

    Science.gov (United States)

    Chung, Hsien-Ching; Su, Wu-Pei; Lin, Ming-Fa

    2013-01-21

    The magneto-electronic properties of bilayer zigzag graphene nanoribbons are investigated by the Peierls tight-binding method. In the presence of magnetic fields, Landau quantization leads to the formation of Landau subbands. For the bilayer nanoribbons, these subbands are partially dispersionless in k-space and are called quasi-Landau levels (QLLs). Perpendicular electric fields, serving as the top gate, push the QLLs to higher state energy and split the flat subbands. From the evidence of band structure and density of states, the QLLs remain dispersionless and the corresponding peaks are still the main structure of density of states, which means that the material properties related to the QLLs are unchanged. However, the wave functions present a totally different evidence that the Landau wave functions are severely mixed, and the corresponding material properties would be strongly affected or destroyed. The wave functions provide an effective way to comprehend the characteristics of the flat subbands and Landau subbands. The energy spectra, density of states, and wave functions are discussed in detail.

  6. Quantitative property-structural relation modeling on polymeric dielectric materials

    Science.gov (United States)

    Wu, Ke

    Nowadays, polymeric materials have attracted more and more attention in dielectric applications. But searching for a material with desired properties is still largely based on trial and error. To facilitate the development of new polymeric materials, heuristic models built using the Quantitative Structure Property Relationships (QSPR) techniques can provide reliable "working solutions". In this thesis, the application of QSPR on polymeric materials is studied from two angles: descriptors and algorithms. A novel set of descriptors, called infinite chain descriptors (ICD), are developed to encode the chemical features of pure polymers. ICD is designed to eliminate the uncertainty of polymer conformations and inconsistency of molecular representation of polymers. Models for the dielectric constant, band gap, dielectric loss tangent and glass transition temperatures of organic polymers are built with high prediction accuracy. Two new algorithms, the physics-enlightened learning method (PELM) and multi-mechanism detection, are designed to deal with two typical challenges in material QSPR. PELM is a meta-algorithm that utilizes the classic physical theory as guidance to construct the candidate learning function. It shows better out-of-domain prediction accuracy compared to the classic machine learning algorithm (support vector machine). Multi-mechanism detection is built based on a cluster-weighted mixing model similar to a Gaussian mixture model. The idea is to separate the data into subsets where each subset can be modeled by a much simpler model. The case study on glass transition temperature shows that this method can provide better overall prediction accuracy even though less data is available for each subset model. In addition, the techniques developed in this work are also applied to polymer nanocomposites (PNC). PNC are new materials with outstanding dielectric properties. As a key factor in determining the dispersion state of nanoparticles in the polymer matrix

  7. Composite Materials with Magnetically Aligned Carbon Nanoparticles Having Enhanced Electrical Properties and Methods of Preparation

    Science.gov (United States)

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

    2016-01-01

    Magnetically aligned carbon nanoparticle composites have enhanced electrical properties. The composites comprise carbon nanoparticles, a host material, magnetically sensitive nanoparticles and a surfactant. In addition to enhanced electrical properties, the composites can have enhanced mechanical and thermal properties.

  8. Quantitative measurement of nanomechanical properties in composite materials

    Science.gov (United States)

    Zhao, Wei

    results significantly, and new, power-law body of revolution models of the probe tip geometry have been applied. Due to the low yield strength of polymers compared with other engineering materials, elastic-plastic contact is considered to better represent the epoxy surface response and was used to acquire more accurate quantitative measurements. Visco-elastic contact response was introduced in the boundary condition of the AFAM cantilever vibration model, due to the creep nature of epoxy, to determine time-dependent effects. These methods have direct impact on the quantitative measurement capabilities of near-filler interphase regions in polymers and composites and the long-term influence of environmental conditions on composites. In addition, quantitative AFAM scans were made on distal surfaces of human bicuspids and molars, to determine the microstructural and spatial variation in nanomechanical properties of the enamel biocomposite. Single point AFAM measurements were performed on individual enamel prism and sheath locations to determine spatial elastic modulus. Mechanical property variation of enamel is associated to the differences in the mineral to organic content and the apatite crystal orientations within the enamel microstructure. Also, variation in the elastic modulus of the enamel ultrastructure was observed in measurements at the outer enamel versus near the dentine enamel junction (DEJ).

  9. Extended liner performance for hydrodynamics and material properties experiments

    CERN Document Server

    Reinovsky, R E

    2001-01-01

    Summary form only given, as follows. Over the last few years a new application for high performance pulsed power, the production of high energy density environments for the study of material properties under extreme conditions and hydrodynamics in complex geometries has joined the traditional family of radiation source applications. The newly commissioned Atlas pulsed power system at Los Alamos has replaced its predecessor, Pegasus, and joined the Shiva Star system at AFRL, Albuquerque and a variety of flux compression systems, principally at the All Russian Scientific Research Institute of Experimental Physics (VNIIEF) as ultra high current drivers for the high precision, magnetically imploded, near-solid density liner that is used to create the needed environments. Three families of experiments: the production of ultra strong shocks (>10 Mbar), the production of strongly coupled plasmas by liner compression of an initially dense plasma of a few eV temperature, and the compression of a magnetized plasma for ...

  10. Optimal Reconstruction of Material Properties in Complex Multiphysics Phenomena

    CERN Document Server

    Bukshtynov, Vladislav

    2013-01-01

    We develop an optimization-based approach to the problem of reconstructing temperature-dependent material properties in complex thermo-fluid systems described by the equations for the conservation of mass, momentum and energy. Our goal is to estimate the temperature dependence of the viscosity coefficient in the momentum equation based on some noisy temperature measurements, where the temperature is governed by a separate energy equation. We show that an elegant and computationally efficient solution of this inverse problem is obtained by formulating it as a PDE-constrained optimization problem which can be solved with a gradient-based descent method. A key element of the proposed approach, the cost functional gradients are characterized by mathematical structure quite different than in typical problems of PDE-constrained optimization and are expressed in terms of integrals defined over the level sets of the temperature field. Advanced techniques of integration on manifolds are required to evaluate numericall...

  11. Piezoelectric properties of rhombohedral ferroelectric materials with phase transition

    Science.gov (United States)

    Zhao, Xiaofang; Soh, A. K.

    2015-12-01

    The temporal evolution of domain structure and its piezoelectric behavior of ferroelectric material BaTiO3 during the transition process from rhombohedral to tetragonal phase under an applied electric field have been studied by employing Landau-Ginzburg theory and the phase-field method. The results obtained show that, during the transformation process, the intermediate phase was monoclinic MA phase, and several peak values of piezoelectric coefficient appeared at the stage where obvious change of domain pattern occurred. In addition, by comparing the cases of applied electric field with different frequencies, it was found that the maximum piezoelectric coefficient obtained decreased with increasing frequency value. These results are of great significance in tuning the properties of engineering domains in ferroelectrics, and could provide more fundamentals to the design of ferroelectric devices.

  12. Basis Function Sampling: A New Paradigm for Material Property Computation

    Science.gov (United States)

    Whitmer, Jonathan K.; Chiu, Chi-cheng; Joshi, Abhijeet A.; de Pablo, Juan J.

    2014-11-01

    Wang-Landau sampling, and the associated class of flat histogram simulation methods have been remarkably helpful for calculations of the free energy in a wide variety of physical systems. Practically, convergence of these calculations to a target free energy surface is hampered by reliance on parameters which are unknown a priori. Here, we derive and implement a method built upon orthogonal functions which is fast, parameter-free, and (importantly) geometrically robust. The method is shown to be highly effective in achieving convergence. An important feature of this method is its ability to attain arbitrary levels of description for the free energy. It is thus ideally suited to in silico measurement of elastic moduli and other material properties related to free energy perturbations. We demonstrate the utility of such applications by applying our method to calculate the Frank elastic constants of the Lebwohl-Lasher model of liquid crystals.

  13. Preliminary Material Properties Handbook. Volume 2: SI Units

    Science.gov (United States)

    2000-07-01

    Aluminium 4.8 5.3 Titanium 1.6 2.0 Tungsten 5.2 5.9 Niobium 2.4 2.8 Hafnium 0.1 0.4 Zirconium — 0.015 Magnesium — 0.02 Boron — 0.015 Cerium — 0.01...alloy MA754 EP741NP (Russian Powder Material) Cobalt-Base Alloys Other Alloys C-103 (Niobium- Hafnium -Titanium) HEAT-RESISTANT ALLOYS Heat-resistant... HAFNIUM -TITANIUM) 6.5.1.0 Comments and Properties — C-103 is a Niobium-based alloy (Nb-10Hf-0.7 to1.3Ti) used for elevated temperature applications with

  14. Amplified Spontaneous Emission Properties of Semiconducting Organic Materials

    Directory of Open Access Journals (Sweden)

    Eva M. Calzado

    2010-06-01

    Full Text Available This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N´-bis(3-methylphenyl-N,N´-diphenylbenzidine (TPD, several perilenediimide derivatives (PDIs, as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature.

  15. Amplified spontaneous emission properties of semiconducting organic materials.

    Science.gov (United States)

    Calzado, Eva M; Boj, Pedro G; Díaz-García, María A

    2010-06-18

    This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature.

  16. Viscoelastic effective properties of two types of heterogeneous materials.

    Science.gov (United States)

    Cornet, Jan; Dabrowski, Marcin; Schmid, Daniel

    2015-04-01

    In the past, a lot of efforts have been put to describe two end cases of rock behaviors: elasticity and viscosity. In recent years, more focus has been brought on the intermediate viscoelastic cases which describe better the rheology of rocks such as shales. Shales are typically heterogeneous and the question arises as to how to derive their effective properties so that they can be approximated as homogeneous media. This question has already been dealt with at the elastic and viscous limit but still remains for some cases in between. Using MILAMIN, a fast finite element solver for large problems, we numerically investigate different approaches to derive the effective properties of several viscoelastic media. Two types of geometries are considered: layered and inclusion based media. We focus on two dimensional plane strain problems considering two phase composites deformed under pure shear. We start by investigating the case of transversely isotropic layered media made of two Maxwell materials. Using the Backus averaging method we discuss the degree of relevance of this averaging by considering some parameters as: layer periodicity, layer thickness and layer interface roughness. Other averaging methods are also discussed which provide a broader perspective on the performances of Backus averaging. In a second part we move on to inclusion based models. The advantage of these models compared to the previous one is that they provide a better approximation to real microstructures in rocks. The setup we consider in this part is the following: some viscous circular inclusions are embedded in an elastic matrix. Both the inclusions and the matrix are homogeneous but the inclusions are purely isotropic while the matrix can also be anisotropic. In order to derive the effective viscoelastic properties of the medium we use two approaches: the self-consistent averaging and the differential effective medium theory. The idea behind self-consistency is to assume that the inclusions

  17. The OpenPicoAmp : an open-source planar lipid bilayer amplifier for hands-on learning of neuroscience

    CERN Document Server

    Shlyonsky, Vadim; Gall, David

    2014-01-01

    Neuroscience education can be promoted by the availability of low cost and engaging teaching materials. To address this, we developed an open-source lipid bilayer amplifier, the OpenPicoAmp, which is appropriate for use in introductory courses in biophysics or neurosciences concerning the electrical properties of the cell membrane. The amplifier is designed using the common lithographic printed circuit board fabrication process and off-the-shelf electronic components. In addition, we propose a specific design for experimental chambers allowing the insertion of a commercially available polytetrafluoroethylene film. This experimental setup can be used in simple experiments in which students monitor the bilayer formation by capacitance measurement and record unitary currents produced by ionophores like gramicidin A. Used in combination with a low-cost data acquisition board this system provides a complete solution for hands-on lessons, therefore improving the effectiveness in teaching basic neurosciences or biop...

  18. GaAs-based long-wavelength InAs bilayer quantum dots grown by molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Zhu Yan; Li Mifeng; He Jifang; Yu Ying; Ni Haiqiao; Xu Yingqiang; Wang Juan; He Zhenhong; Niu Zhichuan

    2011-01-01

    Molecular beam epitaxy growth ofa bilayer stacked InAs/GaAs quantum dot structure on a pure GaAs matrix has been systemically investigated.The influence of growth temperature and the InAs deposition of both layers on the optical properties and morphologies of the bilayer quantum dot (BQD) structures is discussed.By optimizing the growth parameters,InAs BQD emission at 1.436μm at room temperature with a narrower FWHM of 27 meV was demonstrated.The density of QDs in the second layer is around 9 × 109 to 1.4 × 1010 cm-2.The BQD structure provides a useful way to extend the emission wavelength of GaAs-based material for quantum functional devices.

  19. Hygrothermal Material Properties for Soils in Building Science

    Energy Technology Data Exchange (ETDEWEB)

    Kehrer, Manfred [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pallin, Simon B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-01-01

    Hygrothermal performance of soils coupled to buildings is complicated because of the dearth of information on soil properties. However they are important when numerical simulation of coupled heat and moisture transport for below-grade building components are performed as their temperature and moisture content has an influence on the durability of the below-grade building component. Soils can be classified by soil texture. According to the Unified Soil Classification System (USCA), 12 different soils can be defined on the basis of three soil components: clay, sand, and silt. This study shows how existing material properties for typical American soils can be transferred and used for the calculation of the coupled heat and moisture transport of building components in contact with soil. Furthermore a thermal validation with field measurements under known boundary conditions is part of this study, too. Field measurements for soil temperature and moisture content for two specified soils are carried out right now under known boundary conditions. As these field measurements are not finished yet, the full hygrothermal validation is still missing

  20. Material simulation of charge carrier transport properties of polymer dielectrics

    Science.gov (United States)

    Unge, Mikael; Christen, Thomas; Törnkvist, Christer; ABB Corporate Research Team

    To understand electron and hole transport in solid material requires to know its electronic properties, i.e. the density of states (DOS) and whether the states are spatially localized or delocalized. The states closest to the band edges may be localized, states further away can be delocalized. This transition from localized to delocalized states determines the mobility edge, above the mobility edge the mobility is expected to be high. A real polymer is never perfect; it contains a number of oxidative states, bonding defects and molecular impurities. These imperfections yield electronic states that can appear in the band gap of the polymer, traps. Traps can be shallow, i.e. close to the band edges, from these states the charge carrier easily can jump to a state in the band edge or another shallow state. Other traps can be deep, in these states it is likely that the charge carrier remains and become immobile. All these properties related to the electronic structure of the polymer, including its defects, affects the conductivity of the polymer. Linear scaling Density Functional Theory has been applied to calculate electronic structure of amorphous polyethylene. In particular DOS, trap levels and mobility edges are studied.

  1. Analysis of nonlinear optical properties in donor–acceptor materials

    Energy Technology Data Exchange (ETDEWEB)

    Day, Paul N. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States); General Dynamics Information Technology, Inc., Dayton, Ohio 45431 (United States); Pachter, Ruth [Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States); Nguyen, Kiet A. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States); UES, Inc., Dayton, Ohio 45432 (United States)

    2014-05-14

    Time-dependent density functional theory has been used to calculate nonlinear optical (NLO) properties, including the first and second hyperpolarizabilities as well as the two-photon absorption cross-section, for the donor-acceptor molecules p-nitroaniline and dimethylamino nitrostilbene, and for respective materials attached to a gold dimer. The CAMB3LYP, B3LYP, PBE0, and PBE exchange-correlation functionals all had fair but variable performance when compared to higher-level theory and to experiment. The CAMB3LYP functional had the best performance on these compounds of the functionals tested. However, our comprehensive analysis has shown that quantitative prediction of hyperpolarizabilities is still a challenge, hampered by inadequate functionals, basis sets, and solvation models, requiring further experimental characterization. Attachment of the Au{sub 2}S group to molecules already known for their relatively large NLO properties was found to further enhance the response. While our calculations show a modest enhancement for the first hyperpolarizability, the enhancement of the second hyperpolarizability is predicted to be more than an order of magnitude.

  2. Assessment of the material properties of a fire damaged building

    Directory of Open Access Journals (Sweden)

    Oladipupo OLOMO

    2012-12-01

    Full Text Available This study identifies a process for assessing the material properties of a fire damaged building so as to determine whether the remains can be utilized in construction or be demolished. Physical and chemical analysis were carried out on concrete and steel samples taken from various elements of the building after thorough visual inspection of the entire building had been conducted. The physical (non-destructive tests included the Schmidt hammer and ultrasonic pulse velocity tests on the concrete samples, tensile strength test on the steel samples and chemical tests involving the assessment of the quantities of cement, sulphates and chloride concentrations in the samples. A redesign of the building elements was also carried out and the results were compared with the existing design. The non-destructive test results indicated compressive strengths as low as 9.9 N/mm2, the tensile strength test indicated a maximum strength of 397.48 N/mm2 and the chemical test indicated chloride contents as high as 0.534 g per gramme of concrete. These properties deviated significantly from standard requirements. Based on these results, it was concluded that the remains of the building should be demolished.

  3. Electrical and optoelectronic properties of two-dimensional materials

    Science.gov (United States)

    Wang, Qiaoming

    Electrical and optoelectronic properties of bulk semiconductor materials have been extensively explored in last century. However, when reduced to one-dimensional and two-dimensional, many semiconductors start to show unique electrical and optoelectronic behaviors. In this dissertation, electrical and optoelectronic properties of one-dimensional (nanowires) and two-dimensional semiconductor materials are investigated by various techniques, including scanning photocurrent microscopy, scanning Kelvin probe microscopy, Raman spectroscopy, photoluminescence, and finite-element simulations. In our work, gate-tunable photocurrent in ZnO nanowires has been observed under optical excitation in the visible regime, which originates from the nanowire/substrate interface states. This gate tunability in the visible regime can be used to enhance the photon absorption efficiency, and suppress the undesirable visible-light photodetection in ZnO-based solar cells. The power conversion efficiency of CuInSe2/CdS core-shell nanowire solar cells has been investigated. The highest power conversion efficiency per unit area/volume is achieved with core diameter of 50 nm and the thinnest shell thickness. The existence of the optimal geometrical parameters is due to a combined effect of optical resonances and carrier transport/dynamics. Significant current crowding in two-dimensional black phosphorus field-effect transistors has been found, which has been significantly underestimated by the commonly used transmission-line model. This current crowding can lead to Joule heating close to the contacts. New van der Waals metal-semiconductor junctions have been mechanically constructed and systematically studied. The photocurrent on junction area has been demonstrated to originate from the photothermal effect rather than the photovoltaic effect. Our findings suggest that a reasonable control of interface/surface state properties can enable new and beneficial functionalities in nanostructures. We

  4. Computational evaluation of optoelectronic properties for organic/carbon materials.

    Science.gov (United States)

    Shuai, Zhigang; Wang, Dong; Peng, Qian; Geng, Hua

    2014-11-18

    CONSPECTUS: Organic optoelectronic materials are used in a variety of devices, including light-emitting diodes, field-effect transistors, photovoltaics, thermoelectrics, spintronics, and chemico- and biosensors. The processes that determine the intrinsic optoelectronic properties occur either in the photoexcited states or within the electron-pumped charged species, and computations that predict these optical and electrical properties would help researchers design new materials. In this Account, we describe recent advances in related density functional theory (DFT) methods and present case studies that examine the efficiency of light emission, carrier mobility, and thermoelectric figures of merit by calculation of the electron-vibration couplings. First we present a unified vibrational correlation function formalism to evaluate the excited-state radiative decay rate constant kr, the nonradiative decay rate constant knr, the intersystem crossing rate constant kISC, and the optical spectra. The molecular parameters that appear in the formalism, such as the electronic excited-state energy, vibrational modes, and vibronic couplings, require extensive DFT calculations. We used experiments for anthracene at both low and ambient temperatures to benchmark the calculated photophysical parameters. In the framework of Fermi's golden rule, we incorporated the non-adiabatic coupling and the spin-orbit coupling to evaluate the phosphorescence efficiency and emission spectrum. Both of these are in good agreement with experimental results for anthracene and iridium compounds. Band electron scattering and relaxation processes within Boltzmann theory can describe charge transport in two-dimensional carbon materials and closely packed organic solids. For simplicity, we considered only the acoustic phonon scattering as modeled by the deformation potential approximation coupled with extensive DFT calculations for band structures. We then related the carrier mobility to the band

  5. Characterization of electrical and optical properties of silicon based materials

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Guobin

    2009-12-04

    In this work, the electrical and luminescence properties of a series of silicon based materials used for photovoltaics, microelectronics and nanoelectronics have been investigated by means of electron beam induced current (EBIC), cathodoluminescence (CL), photoluminescence (PL) and electroluminescence (EL) methods. Photovoltaic materials produced by block casting have been investigated by EBIC on wafers sliced from different parts of the ingot. Various solar cell processings have been compared in parallel wafers by means of EBIC collection efficiency measurements and contrast-temperature C(T) behaviors of the extended defects, i. e. dislocations and grain boundaries (GBs). It was found that the solar cell processing with phosphorus diffusion gettering (PDG) followed with a SiN firing greatly reduces the recombination activity of extended defects at room temperature, and improves the bulk property simultaneously. A remaining activity of the dislocations indicates the limitation of the PDG at extended defects. Abnormal behavior of the dislocation activity after certain solar cell processes was also observed in the region with high dislocation density, the dislocations are activated after certain solar cell processings. In order to evaluate the properties of a thin polycrystalline silicon layer prepared by Al-induced layer exchange (Alile) technique, epitaxially layer grown on silicon substrate with different orientations was used as a model system to investigate the impact by the process temperature and the substrates. EBIC energy dependent collection efficiency measurements reveal an improvement of the epilayer quality with increasing substrate temperature during the growth from 450 C to 650 C, and a decrease of epilayer quality at 700 C. PL measurements on the epitaxially grown Si layer on silicon substrates revealed no characteristic dislocation-related luminescence (DRL) lines at room temperature and 77 K, while in the samples prepared by Alile process, intense

  6. Rich Polymorphic Behavior of Wigner Bilayers

    Science.gov (United States)

    Antlanger, Moritz; Kahl, Gerhard; Mazars, Martial; Šamaj, Ladislav; Trizac, Emmanuel

    2016-09-01

    Self-assembly into target structures is an efficient material design strategy. Combining analytical calculations and computational techniques of evolutionary and Monte Carlo types, we report about a remarkable structural variability of Wigner bilayer ground states, when charges are confined between parallel charged plates. Changing the interlayer separation, or the plate charge asymmetry, a cascade of ordered patterns emerges. At variance with the symmetric case phenomenology, the competition between commensurability features and charge neutralization leads to long range attraction, appearance of macroscopic charges, exotic phases, and nonconventional phase transitions with distinct critical indices, offering the possibility of a subtle, but precise and convenient control over patterns.

  7. Recommended reference materials for realization of physicochemical properties pressure-volume-temperature relationships

    CERN Document Server

    Herington, E F G

    1977-01-01

    Recommended Reference Materials for Realization of Physicochemical Properties presents recommendations of reference materials for use in measurements involving physicochemical properties, namely, vapor pressure; liquid-vapor critical temperature and critical pressure; orthobaric volumes of liquid and vapor; pressure-volume-temperature properties of the unsaturated vapor or gas; and pressure-volume-temperature properties of the compressed liquid. This monograph focuses on reference materials for vapor pressures at temperatures up to 770 K, as well as critical temperatures and critical pressures

  8. Anisotropic local physical properties of human dental enamel in comparison to properties of some common dental filling materials.

    Science.gov (United States)

    Raue, Lars; Hartmann, Christiane D; Rödiger, Matthias; Bürgers, Ralf; Gersdorff, Nikolaus

    2014-11-01

    A major aspect in evaluating the quality of dental materials is their physical properties. Their properties should be a best fit of the ones of dental hard tissues. Manufacturers give data sheets for each material. The properties listed are characterized by a specific value. This assumes (but does not prove) that there is no direction dependence of the properties. However, dental enamel has direction-dependent properties which additionally vary with location in the tooth. The aim of this paper is to show the local direction dependence of physical properties like the elastic modulus or the thermal expansion in dental hard tissues. With this knowledge the 'perfect filling/dental material' could be characterized. Enamel sections of ∼400-500 μm thickness have been cut with a diamond saw from labial/buccal to palatal/lingual (canine, premolar and molar) and parallel to labial (incisor). Crystallite arrangements have been measured in over 400 data points on all types of teeth with x-ray scattering techniques, known from materials science. X-ray scattering measurements show impressively that dental enamel has a strong direction dependence of its physical properties which also varies with location within the tooth. Dental materials possess only little or no property direction dependence. Therefore, a mismatch was found between enamel and dental materials properties. Since dental materials should possess equal (direction depending) properties, worthwhile properties could be characterized by transferring the directional properties of enamel into a property 'wish list' which future dental materials should fulfil. Hereby the 'perfect dental material' can be characterized.

  9. 29 CFR 779.336 - Sales of building materials for commercial property construction.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Sales of building materials for commercial property... construction, maintenance or repair of commercial property or any other property not excepted in section 3(n... business for the construction, maintenance or repair of commercial property or any other property...

  10. Alginate based bilayer hydrocolloid films as potential slow-release modern wound dressing.

    Science.gov (United States)

    Thu, Hnin-Ei; Zulfakar, Mohd Hanif; Ng, Shiow-Fern

    2012-09-15

    The aims of this research were to develop a novel bilayer hydrocolloid film based on alginate and to investigate its potential as slow-release wound healing vehicle. The bilayer is composed of an upper layer impregnated with model drug (ibuprofen) and a drug-free lower layer, which acted as a rate-controlling membrane. The thickness uniformity, solvent loss, moisture vapour transmission rate (MVTR), hydration rate, morphology, rheology, mechanical properties, in vitro drug release and in vivo wound healing profiles were investigated. A smooth bilayer film with two homogenous distinct layers was produced. The characterisation results showed that bilayer has superior mechanical and rheological properties than the single layer films. The bilayers also showed low MVTR, slower hydration rate and lower drug flux in vitro compared to single layer inferring that bilayer may be useful for treating low suppurating wounds and suitable for slow release application on wound surfaces. The bilayers also provided a significant higher healing rate in vivo, with well-formed epidermis with faster granulation tissue formation when compared to the controls. In conclusions, a novel alginate-based bilayer hydrocolloid film was developed and results suggested that they can be exploited as slow-release wound dressings.

  11. PREPARATION AND IN VITRO AND IN VIVO EVALUATION OF BUCCOADHESIVE BILAYERED TABLETS OF DILTIAZEM HYDROCHLORIDE

    Directory of Open Access Journals (Sweden)

    D’souza A

    2012-08-01

    Full Text Available In this study buccoadhesive bilayered tablets of Diltiazem HCl (DTZ were prepared in order to improve the bioavailability by the avoidance of hepatic first-pass metabolism, and to prevent frequent administration. Bilayered Tablets containing fixed amount of Diltiazem HCl (DTZ were prepared by direct compression method using polymers like hydroxyl propyl methyl cellulose (HPMC K4M, HPMC K15M, HPMC K100M in combination with backing layer of ethyl cellulose and evaluated for physicochemical properties, swelling, bioadhesive strength, in vitro permeation studies, in vitro drug release and possible interaction between ingredients. The physicochemical properties, swelling index, surface pH, bioadhesive strength, in vitro drug release and in vitro permeation studies were found to be dependent on the grade and proportion of buccoadhesive material used. The dissolution of Diltiazem HCl from all the prepared tablets into phosphate buffer (pH 6.8 was controlled for 6 hrs and followed non-Fickian release mechanism. Lower release rates were observed for formulations containing higher concentration of higher viscosity grade of HPMC. FTIR and DSC studies revealed the absence of significant interaction between DTZ and the selected bioadhesive materials. In vivo studies of selected formulation in rabbits demonstrated significant enhancement in bioavailability of DTZ relative to orally administered drug.

  12. Material properties of zooplankton and nekton from the California current

    Science.gov (United States)

    Becker, Kaylyn

    This study measured the material properties of zooplankton, Pacific hake (Merluccius productus), Humboldt squid (Dosidicus gigas), and two species of myctophids (Symbolophorus californiensis and Diaphus theta) collected from the California Current ecosystem. The density contrast (g) was measured for euphausiids, decapods (Sergestes similis), amphipods (Primno macropa, Phronima sp., and Hyperiid spp.), siphonophore bracts, chaetognaths, larval fish, crab megalopae, larval squid, and medusae. Morphometric data (length, width, and height) were collected for these taxa. Density contrasts varied within and between zooplankton taxa. The mean and standard deviation for euphausiid density contrast were 1.059 +/- 0.009. Relationships between zooplankton density contrast and morphometric measurements, geographic location, and environmental conditions were investigated. Site had a significant effect on euphausiid density contrast. Density contrasts of euphausiids collected in the same geographic area approximately 4-10 days apart were significantly higher (p < 0.001). Sound speed contrast (h) was measured for euphausiids and pelagic decapods (S. similis) and it varied between taxa. The mean and standard deviation for euphausiid sound speed were 1.019 +/- 0.009. Euphausiid mass was calculated from density measurements and volume, and a relationship between euphausiid mass and length was produced. We determined that euphausiid from volumes could be accurately estimated two dimensional measurements of animal body shape, and that biomass (or biovolume) could be accurately calculated from digital photographs of animals. Density contrast (g) was measured for zooplankton, pieces of hake flesh, myctophid flesh, and of the following Humboldt squid body parts: mantle, arms, tentacle, braincase, eyes, pen, and beak. The density contrasts varied within and between fish taxa, as well as among squid body parts. Effects of animal length and environmental conditions on nekton density

  13. Hyperelastic Material Properties of Mouse Skin under Compression.

    Directory of Open Access Journals (Sweden)

    Yuxiang Wang

    Full Text Available The skin is a dynamic organ whose complex material properties are capable of withstanding continuous mechanical stress while accommodating insults and organism growth. Moreover, synchronized hair cycles, comprising waves of hair growth, regression and rest, are accompanied by dramatic fluctuations in skin thickness in mice. Whether such structural changes alter skin mechanics is unknown. Mouse models are extensively used to study skin biology and pathophysiology, including aging, UV-induced skin damage and somatosensory signaling. As the skin serves a pivotal role in the transfer function from sensory stimuli to neuronal signaling, we sought to define the mechanical properties of mouse skin over a range of normal physiological states. Skin thickness, stiffness and modulus were quantitatively surveyed in adult, female mice (Mus musculus. These measures were analyzed under uniaxial compression, which is relevant for touch reception and compression injuries, rather than tension, which is typically used to analyze skin mechanics. Compression tests were performed with 105 full-thickness, freshly isolated specimens from the hairy skin of the hind limb. Physiological variables included body weight, hair-cycle stage, maturity level, skin site and individual animal differences. Skin thickness and stiffness were dominated by hair-cycle stage at young (6-10 weeks and intermediate (13-19 weeks adult ages but by body weight in mature mice (26-34 weeks. Interestingly, stiffness varied inversely with thickness so that hyperelastic modulus was consistent across hair-cycle stages and body weights. By contrast, the mechanics of hairy skin differs markedly with anatomical location. In particular, skin containing fascial structures such as nerves and blood vessels showed significantly greater modulus than adjacent sites. Collectively, this systematic survey indicates that, although its structure changes dramatically throughout adult life, mouse skin at a given

  14. Property Evaluation Method Using Spherical Indentation for High-Yield Strength Materials

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Youngsick; Marimuthu, Karuppasamy Pandian; Lee, Hyungyil [Sogang Univ., Seoul (Korea, Republic of); Lee, Jin Haeng [KAERI, Daejeon (Korea, Republic of)

    2015-11-15

    In this paper, we propose a method to evaluate the material properties of high-yield strength materials exceeding 10GPa from spherical indentation. Using a regression equation considering four indentation variables, we map the load displacement relation into a stress-strain relation. To calculate the properties of high-strength materials, we then write a program that produces material properties using the loading / unloading data from the indentation test. The errors in material properties computed by the program are within 0.3, 0.8, and 6.4 for the elastic modulus, yield strength, and hardening coefficient, respectively.

  15. Property evaluation method using spherical indentation for high-yield strength materials

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Young Sick; Marimuthu, Karuppasamy Pandian; Lee, Hyung Yil [Dept. of Mechanical Engineering, Sogang University, Seoul (Korea, Republic of); Lee, Jin Haeng [Reactor Mechanical Engineering Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-11-15

    In this paper, we propose a method to evaluate the material properties of high-yield strength materials exceeding 10 GPa from spherical indentation. Using a regression equation considering four indentation variables, we map the load displacement relation into a stress-strain relation. To calculate the properties of high-strength materials, we then write a program that produces material properties using the loading / unloading data from the indentation test. The errors in material properties computed by the program are within 0.3, 0.8, and 6.4 for the elastic modulus, yield strength, and hardening coefficient, respectively.

  16. Sensitivity analysis of bi-layered ceramic dental restorations.

    Science.gov (United States)

    Zhang, Zhongpu; Zhou, Shiwei; Li, Qing; Li, Wei; Swain, Michael V

    2012-02-01

    The reliability and longevity of ceramic prostheses have become a major concern. The existing studies have focused on some critical issues from clinical perspectives, but more researches are needed to address fundamental sciences and fabrication issues to ensure the longevity and durability of ceramic prostheses. The aim of this paper was to explore how "sensitive" the thermal and mechanical responses, in terms of changes in temperature and thermal residual stress of the bi-layered ceramic systems and crown models will be with respect to the perturbation of the design variables chosen (e.g. layer thickness and heat transfer coefficient) in a quantitative way. In this study, three bi-layered ceramic models with different geometries are considered: (i) a simple bi-layered plate, (ii) a simple bi-layer triangle, and (iii) an axisymmetric bi-layered crown. The layer thickness and convective heat transfer coefficient (or cooling rate) seem to be more sensitive for the porcelain fused on zirconia substrate models. The resultant sensitivities indicate a critical importance of the heat transfer coefficient and thickness ratio of core to veneer on the temperature distributions and residual stresses in each model. The findings provide a quantitative basis for assessing the effects of fabrication uncertainties and optimizing the design of ceramic prostheses. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. Laurdan fluorescence senses mechanical strain in the lipid bilayer membrane.

    Science.gov (United States)

    Zhang, Yan-Liang; Frangos, John A; Chachisvilis, Mirianas

    2006-09-01

    The precise molecular mechanisms by which cells transduce a mechanical stimulus into an intracellular biochemical response have not yet been established. Here, we show for the first time that the fluorescence emission of an environment-sensitive membrane probe Laurdan is modulated by mechanical strain of the lipid bilayer membrane. We have measured fluorescence emission of Laurdan in phospholipid vesicles of 30, 50, and 100 nm diameter to show that osmotically induced membrane tension leads to an increase in polarity (hydration depth) of the phospholipid bilayer interior. Our data indicate that the general polarization of Laurdan emission is linearly dependent on membrane tension. We also show that higher membrane curvature leads to higher hydration levels. We anticipate that the proposed method will facilitate future studies of mechanically induced changes in physical properties of lipid bilayer environment both in vitro and in vivo.

  18. Manipulating interface states in monolayer-bilayer graphene planar junctions

    Science.gov (United States)

    Zhao, Fang; Xu, Lei; Zhang, Jun

    2016-05-01

    We report on transport properties of monolayer-bilayer graphene planar junctions in a magnetic field. Due to its unique geometry, the edge and interface states can be independently manipulated by either interlayer potential or Zeeman field, and the conductance exhibits interesting quantized behaviors. In the hybrid graphene junction, the quantum Hall (QH) conductance is no longer antisymmetric with respect to the charge neutrality point. When the Zeeman field is considered, a quantum spin Hall (QSH) phase is found in the monolayer region while the weak-QSH phase stays in the bilayer region. In the presence of both interlayer potential and Zeeman field, the bilayer region hosts a QSH phase, whereas the monolayer region is still in a QH phase, leading to a spin-polarized current in the interface. In particular, the QSH phase remains robust against the disorder.

  19. Electro-absorption of silicene and bilayer graphene quantum dots

    Science.gov (United States)

    Abdelsalam, Hazem; Talaat, Mohamed H.; Lukyanchuk, Igor; Portnoi, M. E.; Saroka, V. A.

    2016-07-01

    We study numerically the optical properties of low-buckled silicene and AB-stacked bilayer graphene quantum dots subjected to an external electric field, which is normal to their surface. Within the tight-binding model, the optical absorption is calculated for quantum dots, of triangular and hexagonal shapes, with zigzag and armchair edge terminations. We show that in triangular silicene clusters with zigzag edges a rich and widely tunable infrared absorption peak structure originates from transitions involving zero energy states. The edge of absorption in silicene quantum dots undergoes red shift in the external electric field for triangular clusters, whereas blue shift takes place for hexagonal ones. In small clusters of bilayer graphene with zigzag edges the edge of absorption undergoes blue/red shift for triangular/hexagonal geometry. In armchair clusters of silicene blue shift of the absorption edge takes place for both cluster shapes, while red shift is inherent for both shapes of the bilayer graphene quantum dots.

  20. Method and apparatus for measuring properties of particle beams using thermo-resistive material properties

    Science.gov (United States)

    Degtiarenko, Pavel V.; Dotson, Danny Wayne

    2007-10-09

    A beam position detector for measuring the properties of a charged particle beam, including the beam's position, size, shape, and intensity. One or more absorbers are constructed of thermo-resistive material and positioned to intercept and absorb a portion of the incoming beam power, thereby causing local heating of each absorber. The local temperature increase distribution across the absorber, or the distribution between different absorbers, will depend on the intensity, size, and position of the beam. The absorbers are constructed of a material having a strong dependence of electrical resistivity on temperature. The beam position detector has no moving parts in the vicinity of the beam and is especially suited to beam areas having high ionizing radiation dose rates or poor beam quality, including beams dispersed in the transverse direction and in their time radio frequency structure.