WorldWideScience

Sample records for electronic property modifications

  1. Electronic properties of prismatic modifications of single-wall carbon nanotubes

    Science.gov (United States)

    Tomilin, O. B.; Muryumin, E. E.; Rodionova, E. V.; Ryskina, N. P.

    2018-01-01

    The article shows the possibility of target modifying the prismatic single-walled carbon nanotubes (SWCNTs) by regular chemisorption of fluorine atoms in the graphene surface. It is shown that the electronic properties of prismatic SWCNT modifications are determined by the interaction of π- and ρ(in-plane)-electron conjugation in the carbon-conjugated subsystems (tracks) formed in the faces. The contributions of π- and ρ(in-plane)-electron conjugation depend on the structural characteristics of the tracks. It was found that the minimum of degree deviation of the track from the plane of the prism face and the maximum of the track width ensure the maximum contribution of the π-electron conjugation, and the band gap of the prismatic modifications of the SWCNT tends to the band gap of the hydrocarbon analog of the carbon track. It is established that the maximum of degree deviation of the track from the plane of the prism face and the maximum of track width ensure the maximum contribution of the ρ(in-plane) electron interface, and the band gap of the prismatic modifications of the SWCNT tends to the band gap of the unmodified carbon nanotube. The calculation of the model systems has been carried out using an ab initio Hartree-Fock method in the 3-21G basis.

  2. Electronic excitation induced modifications of optical and morphological properties of PCBM thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, T. [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Singhal, R., E-mail: rsinghal.phy@mnit.ac.in [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Vishnoi, R. [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Department of Physics, Vardhman (P.G.) College, Bijnor 246701, U.P. (India); Sharma, P. [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Patra, A.; Chand, S. [National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Lakshmi, G.B.V.S. [Inter University Accelerator Centre, Post Box No. 10502, New Delhi 110067 (India); Biswas, S.K. [Department of Metallurgical and Materials Engineering, Malaviya National Institute of Technology, Jaipur 302017 (India)

    2016-07-15

    Highlights: • Spin casted PCBM thin films are irradiated by 90 MeV Ni{sup 7+} ion beam. • The decrease in band gap was found after irradiation. • There is a decomposition of molecular bond due to ion irradiation. • Roughness is also found to be dependent on incident ion fluence. - Abstract: Phenyl C{sub 61} butyric acid methyl ester (PCBM) is a fullerene derivative and most commonly used in organic photovoltaic devices both as electron acceptor and transporting material due to high electron mobility. PCBM is easy to spin caste on some substrate as it is soluble in chlorobenzene. In this study, the spin coated thin films of PCBM (on two different substrate, glass and double sided silicon) were irradiated using 90 MeV Ni{sup 7+} swift heavy ion beam at low fluences ranging from 1 × 10{sup 9} to 1 × 10{sup 11} ions/cm{sup 2} to study the effect of ion beam irradiation. The pristine and irradiated PCBM thin films were characterized by UV–visible absorption spectroscopy and fourier transform infrared spectroscopy (FTIR) to investigate the optical properties before and after irradiation. These thin films were further analyzed using atomic force microscopy (AFM) to investigate the morphological modifications which are induced by energetic ions. The variation in optical band gap after irradiation was measured using Tauc’s relation from UV–visible absorption spectra. A considerable change was observed with increasing fluence in optical band gap of irradiated thin films of PCBM with respect to the pristine film. The decrease in FTIR band intensity of C{sub 60} cage reveals the polymerization reaction due to high energy ion impact. The roughness is also found to be dependent on incident fluences. This study throws light for the application of PCBM in organic solar cells in form of ion irradiation induced nanowires of PCBM for efficient charge carrier transportation in active layer.

  3. Electronic excitation induced modifications of optical and morphological properties of PCBM thin films

    Science.gov (United States)

    Sharma, T.; Singhal, R.; Vishnoi, R.; Sharma, P.; Patra, A.; Chand, S.; Lakshmi, G. B. V. S.; Biswas, S. K.

    2016-07-01

    Phenyl C61 butyric acid methyl ester (PCBM) is a fullerene derivative and most commonly used in organic photovoltaic devices both as electron acceptor and transporting material due to high electron mobility. PCBM is easy to spin caste on some substrate as it is soluble in chlorobenzene. In this study, the spin coated thin films of PCBM (on two different substrate, glass and double sided silicon) were irradiated using 90 MeV Ni7+ swift heavy ion beam at low fluences ranging from 1 × 109 to 1 × 1011 ions/cm2 to study the effect of ion beam irradiation. The pristine and irradiated PCBM thin films were characterized by UV-visible absorption spectroscopy and fourier transform infrared spectroscopy (FTIR) to investigate the optical properties before and after irradiation. These thin films were further analyzed using atomic force microscopy (AFM) to investigate the morphological modifications which are induced by energetic ions. The variation in optical band gap after irradiation was measured using Tauc's relation from UV-visible absorption spectra. A considerable change was observed with increasing fluence in optical band gap of irradiated thin films of PCBM with respect to the pristine film. The decrease in FTIR band intensity of C60 cage reveals the polymerization reaction due to high energy ion impact. The roughness is also found to be dependent on incident fluences. This study throws light for the application of PCBM in organic solar cells in form of ion irradiation induced nanowires of PCBM for efficient charge carrier transportation in active layer.

  4. Electron beam induced modifications in flexible biaxially oriented polyethylene terephthalate sheets: Improved mechanical and electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhary, N. [Accelerator & Pulse Power Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Koiry, S.P. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Singh, A., E-mail: asb_barc@yahoo.com [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Tillu, A.R. [Accelerator & Pulse Power Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Jha, P.; Samanta, S.; Debnath, A.K. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Aswal, D.K., E-mail: dkaswal@yahoo.com [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Mondal, R.K. [Radiation Technology Development Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Acharya, S.; Mittal, K.C. [Accelerator & Pulse Power Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India)

    2017-03-01

    In the present work, we have studied the effects of electron beam irradiation (with dose ranging from 2 to 32 kGy) on mechanical and electrical properties of biaxially oriented polyethylene terephthalate (BOPET) sheets. The sol-gel analysis, Fourier transformation infra-red (FTIR), X-ray photoelectron spectroscopy (XPS) characterizations of the irradiated BOPET sheets suggest partial cross-linking of PET chains through the diethylene glycol (DEG). The mechanical properties of BOPET, such as, tensile strength, Young's modulus and electrical resistivity shows improvement with increasing dose and saturate for doses >10 kGy. The improved mechanical properties and high electrical resistivity of electron beam modified BOPET sheets may have additional advantages in applications, such as, packaging materials for food irradiation, medical product sterilization and electronic industries. - Graphical abstract: Irradiation of BOPET by electron beam leads to the formation of diethylene glycol that crosslink's the PET chains, resulting in improved mechanical properties and enhanced electrical resistivity. - Highlights: • BOPET exhibit improved tensile strength/Young's modulus after e-beam exposure. • Electrical resistivity of BOPET increases after e-beam exposure. • Cross-linking of PET chains through diethylene glycol was observed after e-beam exposure.

  5. Role of strain and ligand effects in the modification of the electronic and chemical properties of bimetallic surfaces

    DEFF Research Database (Denmark)

    Kitchin, J.R.; Nørskov, Jens Kehlet; Barteau, M.A.

    2004-01-01

    Periodic density functional calculations are used to illustrate how the combination of strain and ligand effects modify the electronic and surface chemical properties of Ni, Pd, and Pt monolayers supported on other transition metals. Strain and the ligand effects are shown to change the width...... of the surface d band, which subsequently moves up or down in energy to maintain a constant band filling. Chemical properties such as the dissociative adsorption energy of hydrogen are controlled by changes induced in the average energy of the d band by modification of the d-band width....

  6. Modification of the surface electronic and chemical properties of Pt(111) by subsurface 3d transition metals

    DEFF Research Database (Denmark)

    Kitchin, J. R.; Nørskov, Jens Kehlet; Barteau, M. A.

    2004-01-01

    The modification of the electronic and chemical properties of Pt(111) surfaces by subsurface 3d transition metals was studied using density-functional theory. In each case investigated, the Pt surface d-band was broadened and lowered in energy by interactions with the subsurface 3d metals......, resulting in weaker dissociative adsorption energies of hydrogen and oxygen on these surfaces. The magnitude of the decrease in adsorption energy was largest for the early 3d transition metals and smallest for the late 3d transition metals. In some cases, dissociative adsorption was calculated...

  7. Improving the electronic and optical properties of Carbz-PAHTDDT-based dyes through chemical modifications

    CERN Document Server

    Mohammadi, Narges

    2013-01-01

    To investigate geometric and electronic structure, a theoretical study is performed on the Carbz-PAHTDDT (S9) organic dye sensitizer. This dye has a reported promising efficiency when coupled with ferrocene-based electrolyte composition. The present study indicated that the long-range correction to the theoretical model in the time-dependent density functional theory is important to produce accurate absorption wavelengths. In the present study, the chemical structure of the original Carbz-PAHTDDT dye on the {\\pi}-conjugated bridge is also rationally changed to produce new dyes aiming at enhancing the spectral response as a desirable property of organic dyes in DSSC application. The theoretical studies on the new dyes have shown a significant red-shifting and broadening of their absorption spectra.

  8. Modification of graphene electronic properties via controllable gas-phase doping with copper chloride

    Science.gov (United States)

    Rybin, Maxim G.; Islamova, Vera R.; Obraztsova, Ekaterina A.; Obraztsova, Elena D.

    2018-01-01

    Molecular doping is an efficient, non-destructive, and simple method for changing the electronic structure of materials. Here, we present a simple air ambient vapor deposition method for functionalization of pristine graphene with a strong electron acceptor: copper chloride. The doped graphene was characterized by Raman spectroscopy, UV-vis-NIR optical absorption spectroscopy, scanning electron microscopy, and electro-physical measurements performed using the 4-probe method. The effect of charge transfer from graphene to a dopant results in shifting the Fermi level in doped graphene. The change of the electronic structure of doped graphene was confirmed by the tangential Raman peak (G-peak) shift and by the appearance of the gap in the UV-vis-NIR spectrum after doping. Moreover, the charge transfer resulted in a substantial decrease in electrical sheet resistance depending on the doping level. At the highest concentration of copper chloride, a Fermi level shift into the valence band up to 0.64 eV and a decrease in the sheet resistance value by 2.36 times were observed (from 888 Ω/sq to 376 Ω/sq for a single graphene layer with 97% of transparency).

  9. Modification of the electronic properties of Au/molecule/Pd junctions by adsorbed hydrogen: a DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Kucera, Jan; Gross, Axel [Institut fuer Theoretische Chemie, Universitaet Ulm, D-89069 Ulm (Germany)

    2011-07-01

    Metal-molecule-metal contacts assembled from a Pd monolayer deposited on a Au-supported self-assembled monolayer (SAM) of 4-mercaptopyridine or 4-aminothiophenol were recently achieved by means of an electrochemical approach. Subsequent photoelectron spectroscopy showed a strongly reduced Pd density of states (DOS) at the Fermi energy. This phenomenon is still not fully comprehended, however, its understanding is crucial for the use of the sandwich design as a platform for future nanoelectronics. Periodic density functional theory (DFT) calculation revealed that the dehydrogenation of the amino group and the subsequent strong bonding of the remaining nitrogen atom to the Pd layer could explain the observed modification of the DOS. We have now extended this study in order to clarify the role of hydrogen atoms for the electronic properties of the Pd layers. In equilibrium, these layers should always show a considerable hydrogen coverage in an aqueous environment. Our calculations demonstrate that indeed the adsorbed hydrogen atoms significantly modify the electronic structure of the Pd layers.

  10. Defined-size DNA triple crossover construct for molecular electronics: modification, positioning and conductance properties

    Energy Technology Data Exchange (ETDEWEB)

    Linko, Veikko; Paasonen, Seppo-Tapio; Jussi Toppari, J [Nanoscience Center, Department of Physics, University of Jyvaeskylae, PO Box 35, FIN-40014 (Finland); Leppiniemi, Jenni; Hytoenen, Vesa P, E-mail: veikko.linko@jyu.fi [Institute of Biomedical Technology, University of Tampere and Tampere University Hospital, FIN-33014 (Finland)

    2011-07-08

    We present a novel, defined-size, small and rigid DNA template, a so-called B-A-B complex, based on DNA triple crossover motifs (TX tiles), which can be utilized in molecular scale patterning for nanoelectronics, plasmonics and sensing applications. The feasibility of the designed construct is demonstrated by functionalizing the TX tiles with one biotin-triethylene glycol (TEG) and efficiently decorating them with streptavidin, and furthermore by positioning and anchoring single thiol-modified B-A-B complexes to certain locations on a chip via dielectrophoretic trapping. Finally, we characterize the conductance properties of the non-functionalized construct, first by measuring DC conductivity and second by utilizing AC impedance spectroscopy in order to describe the conductivity mechanism of a single B-A-B complex using a detailed equivalent circuit model. This analysis also reveals further information about the conductivity of DNA structures in general.

  11. Towards Applications of Quantum Dots: Surface Modification and Novel Electronic Properties

    Energy Technology Data Exchange (ETDEWEB)

    Hope-Weeks, L; Foxx, G; Taylor, B

    2003-04-18

    The possibility of quantum confinement causing the intense visible luminescence seen in porous Si, first mentioned by Canham in 1991, led to enormous interest in that material. The large blue-shift in the band gap and increase in luminescent efficiency attributed to quantum confinement in porous Si, while still controversial, continues to fuel research on colloidal Si nanoparticles prepared by sonicating porous Si, and by solution chemistry. This interest continues, and has led naturally to an interest in colloidal Ge nanoparticles, since the elements are both indirect gap semiconductors, and the exciton of Ge has a larger Bohr radius. The earliest preparation of Ge nanoparticles by a colloidal chemistry method started as a continuation of the previous work on Si, but required either high temperatures and pressures, or laser annealing to produce crystalline nanoparticles. There has been only limited work on colloidal Ge nanoparticles prepared by sonicating porous Ge, with interest instead focused primarily on solution preparation of colloidal Ge nanoparticles. The reaction between Mg{sub 2}T and TCl{sub 4} in refluxing diglyme produced silicon and germanium nanoparticles in high yields, and the surface of these nanoparticles may be terminated using Grignard reagents. Since the particles produced by the initial metathesis reaction are from 2-10 nm in diameter, from 10-30% of their atoms are on the surface. With such a large proportion of atoms at the surface, its termination is vital to controlling their properties. Surface termination with Grignard reagents forms a robust protective layer at the surface of the nanoparticle, and provides an opportunity for further chemical manipulation. Though a considerable amount of work remains, chemically manipulating the surface of the nanoparticles may provide the ability to further tailor their properties and incorporate them into composite materials or devices. The ability to chemically change the surface of the

  12. pH-Induced Surface Modification of Atomically Precise Silver Nanoclusters: An Approach for Tunable Optical and Electronic Properties

    KAUST Repository

    AbdulHalim, Lina G.

    2016-10-24

    Noble metal nanoclusters (NCs) play a pivotal role in bridging the gap between molecules and quantum dots. Fundamental understanding of the evolution of the structural, optical, and electronic properties of these materials in various environments is of paramount importance for many applications. Using state-of-the-art spectroscopy, we provide the first decisive experimental evidence that the structural, electronic, and optical properties of Ag-44(MNBA)(30) NCs can now be tailored by controlling the chemical environment. Infrared and photoelectron spectroscopies clearly indicate that there is a dimerization between two adjacent ligands capping the NCs that takes place upon lowering the pH from 13 to 7.

  13. Properties and modification of two-dimensional electronic states on noble metals; Eigenschaften und Modifikation zweidimensionaler Elektronenzustaende auf Edelmetallen

    Energy Technology Data Exchange (ETDEWEB)

    Forster, F.

    2007-07-06

    In this thesis investigations on two-dimensional electronic structures of (111)-noble metal surfaces and the influence of various adsorbates upon them is presented. It chiefly focuses on the surface-localized Shockley states of Cu, Ag and Au and their band dispersion (binding energy, band mass, and spin-orbit splitting) which turns out to be a sensitive probe for surface modifications induced by adsorption processes. Angular resolved photoelectron spectroscopy enables the observation of even subtle changes in the electronic band structure of these two dimensional systems. Different mechanisms taking place at surfaces and the substrate/adsorbate interfaces influence the Shockley state in a different manner and will be analyzed using suitable adsorbate model systems. The experimental results are matched with appropriate theoretical models like the phase accumulation model and the nearly-free electron model and - if possible - with ab initio calculations based on density functional theory. This allows for the integration of the results into a stringent overall picture. The influence of sub-monolayer adsorption of Na upon the surface state regarding the significant change in surface work function is determined. A systematic study of the physisorption of noble gases shows the effect of the repulsive adsorbate-substrate interaction upon the electrons of the surface state. A step-by-step coverage of the Cu and Au(111) surfaces by monolayers of Ag creates a gradual change in the surface potential and causes the surface state to become increasingly Ag-like. For N=7 ML thick and layer-by-layer growing Ag films on Au(111), new two-dimensional electronic structures can be observed, which are attributed to the quantum well states of the Ag adsorbate. The question whether they are localized within the Ag-layer or substantially within the substrate is resolved by the investigation of their energetic and spatial evolution with increasing Ag-film thicknesses N. For this, beside the

  14. Tuning the electronic properties by width and length modifications of narrow-diameter carbon nanotubes for nanomedicine

    KAUST Repository

    Poater, Albert

    2012-10-01

    The distinctive characteristics of nanoparticles, resulting from properties that arise at the nano-scale, underlie their potential applications in the biomedical sector. However, the very same characteristics also result in widespread concerns about the potentially toxic effects of nanoparticles. Given the large number of nanoparticles that are being developed for possible biomedical use, there is a need to develop rapid screening methods based on in silico methods. This study illustrates the application of conceptual Density Functional Theory (DFT) to some carbon nanotubes (CNTs) optimized by means of static DFT calculations. The computational efforts are focused on the geometry of a family of packed narrow-diameter carbon nanotubes (CNTs) formed by units from four to twelve carbons evaluating the strength of the C-C bonds by means of Mayer Bond Orders (MBO). Thus, width and length are geometrical features that might be used to tune the electronic properties of the CNTs. At infinite length, partial semi-conductor characteristics are expected. © 2012 Bentham Science Publishers.

  15. Electronic excitation induced modifications of structural, electrical and optical properties of Cu-C60 nanocomposite thin films

    Science.gov (United States)

    Inani, H.; Singhal, R.; Sharma, P.; Vishnoi, R.; Ojha, S.; Chand, S.; Sharma, G. D.

    2017-09-01

    High energy ion irradiation significantly affects the size and shape of nanoparticles in composites. Low concentration metal fraction embedded in fullerene matrix in form of nanocomposites was synthesized by thermal co-evaporation method. Swift heavy ion irradiation was performed with 120 MeV Au ion beam on Cu-C60 nanocomposites at different fluences 1 × 1012, 3 × 1012, 6 × 1012, 1 × 1013 and 3 × 1013 ions/cm2. Absorption spectra demonstrated that absorption intensity of nanocomposite thin film was increased whereas absorption modes of fullerene C60 were diminished with fluence. Rutherford backscattering spectroscopy was also performed to estimate the thickness of the film and atomic metal fraction in matrix and found to be 45 nm and 3%, respectively. Transmission electron microscopy was performed for structural and particle size evaluation of Cu nanoparticles (NPs) in fullerene C60 matrix. A growth of Cu nanoparticles is observed at a fluence of 3 × 1013 ions/cm2 with a bi-modal distribution in fullerene C60. Structural evolution of fullerene C60 matrix with increasing fluence of 120 MeV Au ion beam is studied by Raman spectroscopy which shows the amorphization of matrix (fullerene C60) at lower fluence. The growth of Cu nanoparticles is explained using the phenomena of Ostwald ripening.

  16. Donor–Acceptor Copolymers of Relevance for Organic Photovoltaics: A Theoretical Investigation of the Impact of Chemical Structure Modifications on the Electronic and Optical Properties

    KAUST Repository

    Pandey, Laxman

    2012-08-28

    We systematically investigate at the density functional theory level how changes to the chemical structure of donor-acceptor copolymers used in a number of organic electronics applications influences the intrinsic geometric, electronic, and optical properties. We consider the combination of two distinct donors, where a central five-membered ring is fused on both sides by either a thiophene or a benzene ring, with 12 different acceptors linked to the donor either directly or through thienyl linkages. The interplay between the electron richness/deficiency of the subunits as well as the evolution of the frontier electronic levels of the isolated donors/acceptors plays a significant role in determining the electronic and optical properties of the copolymers. © 2012 American Chemical Society.

  17. Wettability Modification of Nanomaterials by Low-Energy Electron Flux

    Directory of Open Access Journals (Sweden)

    Torchinsky I

    2009-01-01

    Full Text Available Abstract Controllable modification of surface free energy and related properties (wettability, hygroscopicity, agglomeration, etc. of powders allows both understanding of fine physical mechanism acting on nanoparticle surfaces and improvement of their key characteristics in a number of nanotechnology applications. In this work, we report on the method we developed for electron-induced surface energy and modification of basic, related properties of powders of quite different physical origins such as diamond and ZnO. The applied technique has afforded gradual tuning of the surface free energy, resulting in a wide range of wettability modulation. In ZnO nanomaterial, the wettability has been strongly modified, while for the diamond particles identical electron treatment leads to a weak variation of the same property. Detailed investigation into electron-modified wettability properties has been performed by the use of capillary rise method using a few probing liquids. Basic thermodynamic approaches have been applied to calculations of components of solid–liquid interaction energy. We show that defect-free, low-energy electron treatment technique strongly varies elementary interface interactions and may be used for the development of new technology in the field of nanomaterials.

  18. Electron beam modification of vanadium dioxide oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Belyaev, Maksim; Velichko, Andrey; Putrolaynen, Vadim; Perminov, Valentin; Pergament, Alexander [Petrozavodsk State University, Petrozavodsk (Russian Federation)

    2017-03-15

    The paper presents the results of a study of electron-beam modification (EBM) of VO{sub 2}-switch I-V curve threshold parameters and the self-oscillation frequency of a circuit containing such a switching device. EBM in vacuum is reversible and the parameters are restored when exposed to air at pressure of 150 Pa. At EBM with a dose of 3 C cm{sup -2}, the voltages of switching-on (V{sub th}) and off (V{sub h}), as well as the OFF-state resistance R{sub off}, decrease down to 50% of the initial values, and the oscillation frequency increases by 30% at a dose of 0.7 C cm{sup -2}. Features of physics of EBM of an oscillator are outlined considering the contribution of the metal and semiconductor phases of the switching channel. Controlled modification allows EBM forming of switches with preset parameters. Also, it might be used in artificial oscillatory neural networks for pattern recognition based on frequency shift keying. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Structural modification of nanocrystalline diamond films via positive/negative bias enhanced nucleation and growth processes for improving their electron field emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, A.; Huang, B. R. [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Sankaran, K. J.; Tai, N. H. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Keiser, G. [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Kurian, J.; Lin, I. N., E-mail: inanlin@mail.tku.edu.tw [Department of Physics, Tamkang University, Tamsui 251, Taiwan (China)

    2015-06-07

    Electron field emission (EFE) properties of nanocrystalline diamond (NCD) films synthesized by the bias-enhanced growth (beg) process under different bias voltages were investigated. The induction of the nanographitic phases is presumed to be the prime factor in enhancing the EFE properties of negative biased NCD films. Transmission electron microscopic investigations reveal that a negative bias voltage of −300 V increases the rate of growth for NCD films with the size of the grains changing from nano to ultranano size. This effect also is accompanied by the induction of nanographitic filaments in the grain boundaries of the films. The turn-on field (E{sub 0}) for the EFE process then effectively gets reduced. The EFE process of the beg-NCD{sub −300V} films can be turned on at E{sub 0} = 3.86 V/μm, and the EFE current density achieved is 1.49 mA/cm{sup 2} at an applied field of 7.85 V/μm. On the other hand, though a positive-bias beg process (+200 V) results in the reduction of grain size, it does not induce sufficient nanographitic phases to lower the E{sub 0} value of the EFE process. Moreover, the optical emission spectroscopic investigation indicates that one of the primary causes that changes the granular structure of the NCD films is the increase in the proportion of C{sub 2} and CH species induced in the growing plasma. The polarity of the bias voltage is of less importance in the microstructural evolution of the films.

  20. Radiation modification of the properties of polypropylene ...

    Indian Academy of Sciences (India)

    Polypropylene (PP)/carboxymethyl cellulose (CMC) blend films were prepared by changing content of CMC in the range of 0–20 wt%. Different analytical techniques such as thermogravimetric analysis (TGA), mechanicaltest and scanning electron microscopy (SEM) were used to investigate some selected properties such ...

  1. Modification of Biodegradable Polyesters Using Electron Beam

    Directory of Open Access Journals (Sweden)

    M. Suhartini

    2013-12-01

    Full Text Available Poly(4-Hydroxybutirat P4HB, Poly(butylene succinate-co-adipate PBSA and Poly(-caprolactone PCL were electron beam (EB-irradiated. Poly(4-Hydroxybutirat was irradiated without any polyfunctional monomers (PFM. While PBSA and PCL were irradiated in the presence of polyfunctional monomers such as Trimethallyl isocyanurate (TMAIC, Polyethyleneglycol dimethacrylate (2G, 4G, Trimethylolpropane trimethacrylate (TMPT and Tetramethylolmethane tetraacrylate (A-TMMT at ambient temperature. Aim of the study is to improve the properties of biodegradable polyester. It was pointed out that crosslinking yield of P4HB (6.39% gel was formed at dose of 90 kGy irradiated in vacuum conditions. Radiation degradation promoted, when P4HB was irradiated in air. The optimum crosslinking yield of PCL and PBSA respectively, were formed in the presence of 1% TMAIC at dose of 50 kGy. The biodegradability of the crosslinked PBSA evaluated by soil burial test is slightly retarded by increasing crosslinking yields.

  2. Modification of Biodegradable Polyesters Using Electron Beam

    OpenAIRE

    M. Suhartini

    2013-01-01

    Poly(4-Hydroxybutirat) P4HB, Poly(butylene succinate-co-adipate) PBSA and Poly(-caprolactone) PCL were electron beam (EB)-irradiated. Poly(4-Hydroxybutirat) was irradiated without any polyfunctional monomers (PFM). While PBSA and PCL were irradiated in the presence of polyfunctional monomers such as Trimethallyl isocyanurate (TMAIC), Polyethyleneglycol dimethacrylate (2G, 4G), Trimethylolpropane trimethacrylate (TMPT) and Tetramethylolmethane tetraacrylate (A-TMMT) at ambient temperature. Ai...

  3. Modification of Biodegradable Polyesters Using Electron Beam

    OpenAIRE

    M. Suhartini

    2013-01-01

    Poly(4-Hydroxybutirat)p4hb, Poly(butylene succinate-co-adipate) PBSA and Poly(e-caprolactone) PCL were electron beam (EB)-irradiated. Poly(4-Hydroxybutirat) was irradiated without any polyfunctional monomers (PFM). While PBSA and PCL were irradiated in the presence of polyfunctional monomers such asTrimethallyl isocyanurate (TMAIC), Polyethyleneglycol dimethacrylate (2G, 4G), Trimethylolpropane trimethacrylate (TMPT) and Tetramethylolmethane tetraacrylate (A-TMMT) at ambient temperature. Ai...

  4. Modification of The Electronic and The Adsorption Properties of Epitaxial Delafossite CuFeO2 thin films by The Substitution of Fe by Ga

    Science.gov (United States)

    Rojas, S.; Wheatley, R.; Joshi, T.; Lederman, D.; Cabrera, A. L.

    We studied the chemisorption properties of CuFeO2 and CuFe1-xGaxO2 delafossite thin film samples with respect to H2O and CO2 using thermal programmed desorption. Adsorption of CO2 and H2O was observed on both surfaces by X-Ray photoelectron spectroscopy. Substituting Fe by Ga in CuFeO2 leads to reduced amount of adsorbed H2O with respect to CO2. Additionally, NIR-Vis Transmittance and Reflectance spectroscopies were used to show changes in sample surface optical absorption properties in response to CO2/H2O exposure using a pressure range 0-90 kPa. This work was supported by FONDECyT 1130372 and Proyecto Anillo ACT1409 at PUC and supported in part by the WV Higher Education Policy Commission (Grant HEPC.dsr.12.29) and by FAME sponsored by MARCO and DARPA (contract # 2013-MA-2382).

  5. 77 FR 27612 - Modifications to Definition of United States Property

    Science.gov (United States)

    2012-05-11

    ... Internal Revenue Service 26 CFR Part 1 RIN 1545-BK11 Modifications to Definition of United States Property... or clearing agency do not constitute United States property. These regulations affect United States...)) that invests certain earnings and profits in United States property (U.S. property) ``on the grounds...

  6. Effective modification of particle surface properties using ultrasonic water mist

    DEFF Research Database (Denmark)

    Genina, Natalja; Räikkönen, Heikki; Heinämäki, Jyrki

    2009-01-01

    The goal of the present study was to design a new technique to modify particle surface properties and, through that, to improve flowability of poorly flowing drug thiamine hydrochloride and pharmaceutical sugar lactose monohydrate of two different grades. The powdered particles were supplied...... by a vibratory feeder and exposed to an instantaneous effect of water mist generated from an ultrasound nebulizer. The processed and original powders were evaluated with respect to morphology (scanning electron microscopy, atomic force microscopy, and spatial filtering technique), flow, and solid state...... increment in particle size. The changes in thiamine powder flow were mainly due to narrowing in particle size distribution where the tendency for better flow of finer lactose was related to surface and size modifications. The aqueous mist application did not cause any alteration of the crystal structures...

  7. Substituents' effect in electron attachment to epigenetic modifications of cytosine

    Science.gov (United States)

    Nunes, Fernanda B.; Bettega, Márcio H. F.; Sanchez, Sergio d'Almeida

    2017-06-01

    Epigenetic modifications of cytosine have been found to influence differently in many processes in biological systems. In order to investigate the differences in electron attachment to different epigenetic modifications of cytosine, we reported the A″ component of the integral cross section of electron scattering by cytosine (C) and its epigenetic modifications 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). Our results were obtained with the Schwinger multichannel method with pseudopotentials in the static-exchange (SE) and static-exchange plus polarization (SEP) approximations. In addition to the scattering results, we present electron attachment energies obtained through an empirical scaling relation for the five molecules. We observed three π* resonances for C, 5mC, and 5hmC and four for 5fC and 5caC, in both SE and SEP approximations. The cross sections show that the π* resonances of 5mC and 5hmC are located at higher energies than the resonances of C, while the resonances of 5fC and 5caC are located at lower energies. In order to investigate this shift in the resonances' positions, we analyzed the π* lowest-lying orbitals and the electronic density over the molecules. Using the inductive and mesomeric effects, we were able to analyze the influence of each substituent over the molecule and on the resonances' positions.

  8. 77 FR 27669 - Modifications to Definition of United States Property

    Science.gov (United States)

    2012-05-11

    ... Internal Revenue Service 26 CFR Part 1 RIN 1545-BK10 Modifications to Definition of United States Property... clearing agency do not constitute United States property. The text of the temporary regulations also serves... Federal Register establish an exception to the definition of United States property (within the meaning of...

  9. Radiation modification of the properties of polypropylene ...

    Indian Academy of Sciences (India)

    Radiation; PP/CMC blend film; packaging; biodegradability. 1. Introduction. Polypropylene (PP) is a versatile, low cost, chemically stable and light weight polymer, which offers attractive mechan- ical, electrical and thermal properties due to its relatively high degree of crystallinity. This is used in many applica- tions such as ...

  10. 78 FR 14835 - Investigations: Terminations, Modifications and Rulings: Certain Consumer Electronics and Display...

    Science.gov (United States)

    2013-03-07

    ... COMMISSION Investigations: Terminations, Modifications and Rulings: Certain Consumer Electronics and Display... electronics devices and display devices and products containing same, by reason of infringement of various... America, Inc. of Bellevue, Washington; LG Electronics, Inc. of Seoul, South Korea; LG Electronics...

  11. Electronic properties of physisorbed helium

    Energy Technology Data Exchange (ETDEWEB)

    Kossler, Sarah

    2011-09-22

    This thesis deals with electronic excitations of helium physisorbed on metal substrates. It is studied to what extent the electronic properties change compared to the gas phase due to the increased helium density and the proximity of the metal. Furthermore, the influence of different substrate materials is investigated systematically. To this end, up to two helium layers were adsorbed onto Ru (001), Pt (111), Cu (111), and Ag (111) surfaces in a custom-made cryostat. These samples were studied spectroscopically using synchrotron radiation and a time-of-flight detector. The experimental results were then analyzed in comparison with extensive theoretical model calculations.

  12. Modification of electrical properties of topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Peter Anand

    2017-08-29

    Ion implantation or deposition can be used to modify the bulk electrical properties of topological insulators. More particularly, ion implantation or deposition can be used to compensate for the non-zero bulk conductivity due to extrinsic charge carriers. The direct implantation of deposition/annealing of dopants allows better control over carrier concentrations for the purposes of achieving low bulk conductivity. Ion implantation or deposition enables the fabrication of inhomogeneously doped structures, enabling new types of device designs.

  13. Nitrogen induced modifications of MANOS memory properties

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaou, N., E-mail: n.nikolaou@inn.demokritos.gr [Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, 153 10 Athens (Greece); Department of Physics, University of Patras, 265 04 Patras (Greece); Ioannou-Sougleridis, V.; Dimitrakis, P.; Normand, P. [Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, 153 10 Athens (Greece); Skarlatos, D. [Department of Physics, University of Patras, 265 04 Patras (Greece); Giannakopoulos, K. [Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, 153 10 Athens (Greece); Ladas, S. [Department of Chemical Engineering, University of Patras, 265 04 Patras (Greece); Pecassou, B.; BenAssayag, G. [CEMES-CNRS, Toulouse (France); Kukli, K. [Department of Chemistry, University of Helsinki, FI-00014 Helsinki (Finland); Institute of Physics, University of Tartu, Ravila 14c, EE-50411 Tartu (Estonia); Niinistö, J.; Ritala, M.; Leskelä, M. [Department of Chemistry, University of Helsinki, FI-00014 Helsinki (Finland)

    2015-12-15

    In this work we examine the structural and electrical properties including the memory performance of Al{sub 2}O{sub 3}/Si{sub 3}N{sub 4}/SiO{sub 2} dielectric stacks implanted with low-energy nitrogen ions and subsequently thermal annealed at 850 or 1050 °C for 15 min. X-ray photoelectron spectroscopy reveals that the concentration and the chemical state of the nitrogen atoms within the Al{sub 2}O{sub 3} layer depends on the post-implantation annealing (PIA) temperature. Memory testing, performed on platinum gate capacitors, shows that charge retention of the programmed states is significantly improved for the high-temperature PIA samples as compared to the non-implanted samples. While such an improvement is not detected for the low-temperature PIA samples, the latter exhibit enhanced hole charging and thus, increased erase efficiency. Overall, our results suggest that the transport properties which control the erase and the retention characteristics of the blocking Al{sub 2}O{sub 3} layer can be tailored by nitrogen implantation and the PIA conditions and can be used for memory performance optimization.

  14. Modification of meson properties in the vicinty of nuclei

    Directory of Open Access Journals (Sweden)

    Filip Peter

    2014-01-01

    Full Text Available We suggest that modification of meson properties (lifetimes and branching ratios can occur due to the interaction of constituent quark magnetic moments with strong magnetic fields present in the close vicinity of nuclei. A superposition of (J =0 and (J =1, mz =0 particle-antiparticle quantum states (as observed for ortho-Positronium may occur also in the case of quarkonium states J/Ψ, ηc ϒ, ηb in heavy ion collisions. We speculate on possible modification of η(548 meson properties (related to C parity and CP violation in strong magnetic fields which are present in the vicinity of nuclei.

  15. Elaboration by ion implantation of cobalt nano-particles in silica layers and modifications of their properties by electron and swift heavy ion irradiations; Elaboration par implantation ionique de nanoparticules de cobalt dans la silice et modifications de leurs proprietes sous irradiation d'electrons et d'ions de haute energie

    Energy Technology Data Exchange (ETDEWEB)

    D' Orleans, C

    2003-07-15

    This work aims to investigate the capability of ion irradiations to elaborate magnetic nano-particles in silica layers, and to modify their properties. Co{sup +} ions have been implanted at 160 keV at fluences of 2.10{sup 16}, 5.10{sup 16} and 10{sup 17} at/cm{sup 2}, and at temperatures of 77, 295 and 873 K. The dependence of the particle size on the implantation fluence, and more significantly on the implantation temperature has been shown. TEM (transmission electronic microscopy) observations have shown a mean diameter varying from 1 nm for implantations at 2.10{sup 16} Co{sup +}/cm{sup 2} at 77 K, to 9.7 nm at 10{sup 17} Co{sup +}/cm{sup 2} at 873 K. For high temperature implantations, two regions of particles appear. Simulations based on a kinetic 3-dimensional lattice Monte Carlo method reproduce quantitatively the features observed for implantations. Thermal treatments induce the ripening of the particles. Electron irradiations at 873 K induce an important increase in mean particle sizes. Swift heavy ion irradiations also induce the ripening of the particles for low fluences, and an elongation of the particles in the incident beam direction for high fluences, resulting in a magnetic anisotropy. Mechanisms invoked in thermal spike model could also explain this anisotropic growth. (author)

  16. Electronic Properties of Semiconductor Interfaces.

    Science.gov (United States)

    1983-02-01

    AD-A130 745 ELECTRONIC PROPERTIES OF SEMICONDUCTOR INTERFACES(U) /; UNIVERSIDAD AUfONOMA DE MADRID (SPAIN) DEPT DE FISICA DEL ESTADO SOLIDO F FLORES...Estado Solido 6.11.02A Universidad Autonoma Cantoblanco, Madrid 34. Spain 1T161102BH57-03 11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE...different supe4layeru formed by the superlayers (0,1), (2,3), (4,5),... and so on. Note that the number of super - layers defined inside each 6upettayer

  17. EFFECT OF PVA MODIFICATION ON PROPERTIES OF CEMENT COMPOSITES

    Directory of Open Access Journals (Sweden)

    Jaroslav Topič

    2015-02-01

    Full Text Available Polymers are used for modification of the cement-based composites and others building materials since the thirties of 20th century. Based on the conclusions of recent studies, it is assumed that even water soluble polymers could be used as an admixture for such modification. Currently, there exist and are exploited several possibilities for polymer modification of mortars, wood-based products or bituminous asphalts. Various options differ in the way of modification, which can be basically applied to the entire volume or just a surface, but also in the form of the polymer used – either in the form of solution or fibers. The aim of our study was to investigate the influence of volume modification by the water soluble polymers, such as polyvinyl alcohol (PVA, on the properties of cement paste and find an optimum additive. It turned out that the addition of PVA solution into fresh cement paste results in an increase of porosity and therefore a stiffness and compressive strength reduction. On the other hand, the bending strength of PVA-rich specimens was significantly higher and their water absorption decreased, which may consequently result in enhanced frost resistance.

  18. Electronic properties of complex nanostructures

    Science.gov (United States)

    Zhu, Zhen

    Nanostructured materials have brought an unprecedented opportunity for advancement in many fields of human endeavor and in applications. Nanostructures are a new research field which may revolutionize people's everyday life. In the Thesis, I have used theoretical methods including density functional theory (DFT), molecular dynamic simulations (MD) and tight-binding methods to explore the structural, mechanical and electronic properties of various nanomaterials. In all this, I also paid attention to potential applications of these findings. First, I will briefly introduce the scientific background of this Thesis, including the motivation for the study of a boron enriched aluminum surface, novel carbon foam structures and my research interest in 2D electronics. Then I will review the computational techniques I used in the study, mostly DFT methods. In Chapter 3, I introduce an effective way to enhance surface hardness of aluminum by boron nanoparticle implantation. Using boron dimers to represent the nanoparticles, the process of boron implantation is modeled in a molecular dynamics simulation of bombarding the aluminum surface by energetic B 2 molecules. Possible metastable structures of boron-coated aluminum surface are identified. Within these structures, I find that boron atoms prefer to stay in the subsurface region of aluminum. By modeling the Rockwell indentation process, boron enriched aluminum surface is found to be harder than the pristine aluminum surface by at least 15%. In Chapter 4, I discuss novel carbon structures, including 3D carbon foam and related 2D slab structures. Carbon foam contains both sp 2 and sp3 hybridized carbon atoms. It forms a 3D honeycomb lattice with a comparable stability to fullerenes, suggesting possible existence of such carbon foam structures. Although the bulk 3D foam structure is semiconducting, an sp2 terminated carbon surface could maintain a conducting channel even when passivated by hydrogen. To promote the experimental

  19. Azaporphyrin phosphorus(v) complexes: synthesis, structure, and modification of optical properties.

    Science.gov (United States)

    Furuyama, Taniyuki; Kobayashi, Nagao

    2017-06-21

    Azaporphyrinoids, such as phthalocyanines (Pcs), tetraazaporphyrins (TAPs), and tetrabenzotriazacorroles (TBCs), are some of the most well-known and successful artificial dyes and pigments in modern material chemistry. Modifications of the macrocyclic core, periphery, and central element have attracted a great deal of interest in materials sciences due to generation of unique optical and electronic properties. However, the synthesis of most azaporphyrinoids with novel physical properties generally needs long, tedious procedures. On the other hand, the introduction of a phosphorus(v) atom into simple (known) azaporphyrin macrocycles is not necessarily difficult and can generate changes in the structural and optical properties. This paper provides an overview of the recent development of azaporphyrin phosphorus(v) complexes with unique structural and optical properties. Optical properties are discussed based on a combination of experimental absorption spectra, electrochemical properties, and theoretical molecular orbital calculations. These complexes are relatively easy to synthesize, are robust and free from transition metals, and have predictable properties.

  20. Structures, properties, modifications, and uses of oat starch.

    Science.gov (United States)

    Zhu, Fan

    2017-08-15

    There has been increasing interest to utilise oats and their components to formulate healthy food products. Starch is the major component of oat kernels and may account up to 60% of the dry weight. Starch properties may greatly determine the product quality. As a by-product of oat processing and fractionation, the starch may also be utilised for food and non-food applications. This mini-review updates the recent advances in the isolation, chemical and granular structures, physicochemical properties, chemical and physical modifications, and food and non-food uses of oat starch. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Adsorbate-induced modification of electronic band structure of epitaxial Bi(111) films

    Energy Technology Data Exchange (ETDEWEB)

    Matetskiy, A.V., E-mail: mateckij@iacp.dvo.ru [Institute of Automation and Control Processes FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); Bondarenko, L.V.; Tupchaya, A.Y.; Gruznev, D.V. [Institute of Automation and Control Processes FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); Eremeev, S.V. [Institute of Strength Physics and Materials Science, 634021 Tomsk (Russian Federation); Tomsk State University, 634050 Tomsk (Russian Federation); Zotov, A.V. [Institute of Automation and Control Processes FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); School of Natural Sciences, Far Eastern Federal University, 690950 Vladivostok (Russian Federation); Department of Electronics, Vladivostok State University of Economics and Service, 690600 Vladivostok (Russian Federation); Saranin, A.A. [Institute of Automation and Control Processes FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); School of Natural Sciences, Far Eastern Federal University, 690950 Vladivostok (Russian Federation)

    2017-06-01

    Highlights: • Modification of electronic properties of ultrathin Bi films by adsorbates is demonstrated. • Due to electron doping from Cs adatoms, surface-state bands shift to higher binding energies. • As a result, only electron pockets are left in the Fermi map. • Tin acts as an acceptor dopant for Bi, shifting Fermi level upward. • As a result, only hole pockets are left in the Fermi map. - Abstract: Changes of the electronic band structure of Bi(111) films on Si(111) induced by Cs and Sn adsorption have been studied using angle-resolved photoemission spectroscopy and density functional theory calculations. It has been found that small amounts of Cs when it presents at the surface in a form of the adatom gas leads to shifting of the surface and quantum well states to the higher binding energies due to the electron donation from adsorbate to the Bi film. In contrast, adsorbed Sn dissolves into the Bi film bulk upon heating and acts as an acceptor dopant, that results in shifting of the surface and quantum well states upward to the lower binding energies. These results pave the way to manipulate with the Bi thin film electron band structure allowing to achieve a certain type of conductivity (electron or hole) with a single spin channel at the Fermi level making the adsorbate-modified Bi a reliable base for prospective spintronics applications.

  2. Electron transport and electrocatalytic properties of MWCNT/nickel nanocomposites: hydrazine and diethylaminoethanethiol as analytical probes

    CSIR Research Space (South Africa)

    Adekunle, AS

    2010-06-01

    Full Text Available This work describes the electron transport and electrocatalytic properties of chemically-synthesized nickel (Ni) and nickel oxide (NiO) nanoparticles supported on multi-walled carbon nanotubes (MWCNT) platforms. Successful modification...

  3. Growth, modification and integration of carbon nanotubes into molecular electronics

    Science.gov (United States)

    Moscatello, Jason P.

    Molecules are the smallest possible elements for electronic devices, with active elements for such devices typically a few Angstroms in footprint area. Owing to the possibility of producing ultra-high density devices, tremendous effort has been invested in producing electronic junctions by using various types of molecules. The major issues for molecular electronics include (1) developing an effective scheme to connect molecules with the present micro- and nano-technology, (2) increasing the lifetime and stabilities of the devices, and (3) increasing their performance in comparison to the state-of-the-art devices. In this work, we attempt to use carbon nanotubes (CNTs) as the interconnecting nanoelectrodes between molecules and microelectrodes. The ultimate goal is to use two individual CNTs to sandwich molecules in a cross-bar configuration while having these CNTs connected with microelectrodes such that the junction displays the electronic character of the molecule chosen. We have successfully developed an effective scheme to connect molecules with CNTs, which is scalable to arrays of molecular electronic devices. To realize this far reaching goal, the following technical topics have been investigated. (1) Synthesis of multi-walled carbon nanotubes (MWCNTs) by thermal chemical vapor deposition (T-CVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques (Chapter 3). We have evaluated the potential use of tubular and bamboo-like MWCNTs grown by T-CVD and PE-CVD in terms of their structural properties. (2) Horizontal dispersion of MWCNTs with and without surfactants, and the integration of MWCNTs to microelectrodes using deposition by dielectrophoresis (DEP) (Chapter 4). We have systematically studied the use of surfactant molecules to disperse and horizontally align MWCNTs on substrates. In addition, DEP is shown to produce impurityfree placement of MWCNTs, forming connections between microelectrodes. We demonstrate the deposition density is tunable by

  4. Modeling Electronic Properties of Complex Oxides

    Science.gov (United States)

    Krishnaswamy, Karthik

    Complex oxides are a class of materials that have recently emerged as potential candidates for electronic applications owing to their interesting electronic properties. The goal of this dissertation is to develop a fundamental understanding of these electronic properties using a combination of first-principles approaches based on density functional theory (DFT), and Schr odinger-Poisson (SP) simulation (Abstract shortened by ProQuest.

  5. Effect of Aminosilane Modification on Nanocrystalline Cellulose Properties

    Directory of Open Access Journals (Sweden)

    Nurul Hanisah Mohd

    2016-01-01

    Full Text Available The application of renewable nanomaterials, like nanocrystalline cellulose (NCC, has recently been widely studied by many researchers. NCC has many benefits such as high aspect ratio, biodegradability, and high number of hydroxyl groups which offer great opportunities for modification. In this study, the NCC derived from empty fruit bunches (EFB was modified with aminosilane, 3-(2-aminoethylaminopropyl-dimethoxymethylsilane (AEAPDMS, and the characterization was performed to investigate the potential as carbon dioxide (CO2 capture. Modification of NCC with AEAPDMS was carried out in water/ethanol solvent (80/20 (v/v with a ratio of NCC to aminosilane of 1 : 1, 1 : 2, 1 : 3, and 1 : 4 w/w%. The effects of AEAPDMS on NCC were characterized using Fourier transform infrared (FTIR spectroscopy, thermogravimetric analysis (TGA, X-ray diffraction (XRD analysis, elemental analysis (CHNS, and transmission electron microscopy (TEM. The existence of AEAPDMS onto NCC was confirmed by ATR-FTIR spectroscopy as the new peaks of NH2 were bending and wagging, and Si-CH3 appeared. The thermal stability of NCC increased after modification due to the interaction with AEAPDMS. The elemental analysis result showed that the nitrogen content increased with an enhancement ratio of the modifiers. The XRD indicated that the crystallinity decreased while the rod-like geometry of NCC was maintained after amorphous AEAPDMS grafted on the NCC. Since AEAPDMS can be grafted on the NCC, the sample is applicable as CO2 capture.

  6. A study on the die steel surface modification by electron beam

    CERN Document Server

    Wu Ai Min; Zou Jian Xin; Hao Sheng Zhi; Dong Chuang; Zhang Ai Ming; Xu Tao

    2002-01-01

    A new surface modification technology-high current pulsed electron beam treatment method was applied to the surface of die steel to improve its properties. It has been shown that as a result of the HCPEB treatment, the most pronounced changes of the structure-phase state occur in the near-surface layers quenched from the liquid state, where the crystallization front velocity reaches its maximum. In these layers partial or complete dissolving of second phases and formation of over saturated solid solutions and ordered nano-sized structures may take place. This makes it possible to improve substantially the electrochemical and strength properties of the surface layer. The authors found that the thickness of remelt layer is about 10 mu m, and the sectional microhardness increased accompanied by the enhancement of the wear resistance of the material. After modification, the relative wear resistance of D2 steel have increased 5.63 times and that of H13 steel increased 11.76 times

  7. Medium Modifications of Hadron Properties and Partonic Processes

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, W. K.; Strauch, S.; Tsushima, K.

    2011-06-01

    Chiral symmetry is one of the most fundamental symmetries in QCD. It is closely connected to hadron properties in the nuclear medium via the reduction of the quark condensate , manifesting the partial restoration of chiral symmetry. To better understand this important issue, a number of Jefferson Lab experiments over the past decade have focused on understanding properties of mesons and nucleons in the nuclear medium, often benefiting from the high polarization and luminosity of the CEBAF accelerator. In particular, a novel, accurate, polarization transfer measurement technique revealed for the first time a strong indication that the bound proton electromagnetic form factors in 4He may be modified compared to those in the vacuum. Second, the photoproduction of vector mesons on various nuclei has been measured via their decay to e+e- to study possible in-medium effects on the properties of the rho meson. In this experiment, no significant mass shift and some broadening consistent with expected collisional broadening for the rho meson has been observed, providing tight constraints on model calculations. Finally, processes involving in-medium parton propagation have been studied. The medium modifications of the quark fragmentation functions have been extracted with much higher statistical accuracy than previously possible.

  8. Modification of the electrostatic sheath by secondary emission of electrons

    Energy Technology Data Exchange (ETDEWEB)

    Hall, L. S.; Bernstein, I.

    1976-10-14

    The potential distribution at the surface of a rectilinear one-dimensional plasma in the presence of wall-emitting secondary electrons is computed as a function of the secondary emission coefficient under a variety of plasma conditions.

  9. The electronic properties of a Fibonacci chain

    Directory of Open Access Journals (Sweden)

    S. A. Ketabi

    2004-12-01

    Full Text Available  Using a tight-binding model and transfer-matrix technique, as well as Lanczos algorithm, we numerically investigate the nature of the electronic states and electron transmission in site, bond and mixing Fibonacci model chains. We rely on the Landauer formalism as the basis for studying the conduction properties of these systems. Calculating the Lyapunov exponent, we also study the localization properties of electronic eigenstates in the Fibonacci chains. The focus is on the significance of the relationship between the transmission spectra and the nature of the electronic states. Our results show that, in contrast to Anderson’s localization theorem, in the Fibonacci chains the electronic states are non-localized and the transparent states occurr near the Fermi level.

  10. 76 FR 73677 - Investigations: Terminations, Modifications and Rulings: Certain Electronic Devices With Image...

    Science.gov (United States)

    2011-11-29

    ... COMMISSION Investigations: Terminations, Modifications and Rulings: Certain Electronic Devices With Image... this investigation may be viewed on the Commission's electronic docket (EDIS) at http://edis.usitc.gov... entirety. On September 15, 2011, non-parties Advanced Micro Devices, Inc. (``AMD'') and its subsidiaries...

  11. Rotary bending fatigue properties of Inconel 718 alloys by ultrasonic nanocrystal surface modification technique

    Directory of Open Access Journals (Sweden)

    Jun-Hyong Kim

    2015-08-01

    Full Text Available This study investigates the influence of ultrasonic nanocrystal surface modification (UNSM technique on fatigue properties of SAE AMS 5662 (solution treatment of Inconel 718 alloys. The fatigue properties of the specimens were investigated using a rotary bending fatigue tester. Results revealed that the UNSM-treated specimens showed longer fatigue life in comparison with those of the untreated specimens. The improvement in fatigue life of the UNSM-treated specimens is attributed mainly to the induced compressive residual stress, increased hardness, reduced roughness and refined grains at the top surface. Fractured surfaces were analysed using a scanning electron microscopy (SEM in order to give insight into the effectiveness of UNSM technique on fracture mechanisms and fatigue life.

  12. Effect of hierarchical porosity and phosphorus modification on the catalytic properties of zeolite Y

    Science.gov (United States)

    Li, Wenlin; Zheng, Jinyu; Luo, Yibin; Da, Zhijian

    2016-09-01

    The zeolite Y is considered as a leading catalyst for FCC industry. The acidity and porosity modification play important roles in determining the final catalytic properties of zeolite Y. The alkaline treatment of zeolite Y by dealumination and alkaline treatment with NaOH and NaOH&TBPH was investigated. The zeolites were characterized by X-ray diffraction, low-temperature adsorption of nitrogen, transmission electron microscope, NMR, NH3-TPD and IR study of acidity. Accordingly, the hierarchical porosity and acidity property were discussed systematically. Finally, the catalytic performance of the zeolites Y was evaluated in the cracking of 1,3,5-TIPB. It was found that desilication with NaOH&TBPH ensured the more uniform intracrystalline mesoporosity with higher microporosity, while preserving higher B/L ratio and moderate Brønsted acidities resulting in catalysts with the most appropriated acidity and then with better catalytic performance.

  13. Electronic properties of organic/metal interfaces

    CERN Document Server

    Koch, N

    2000-01-01

    Conjugated organic materials are the promising class of materials for the application in new electronic and opto-electronic devices. The successful realization of highly efficient organic light emitting devices with oligomers and polymers as active electroluminescent layers has lead to a large number of investigations on such systems, the key point being to find means of increasing efficiency and performance of the devices. Intrinsically present in light emitting devices are interfaces, and it appears that the structural and electronic properties of those are of uttermost importance for the device quality. In the present work, ultraviolet and X-ray photoelectron spectroscopy, plus related surface sensitive experimental methods, were used to investigate the electronic properties of interfaces between conjugated organic materials (based on para-phenylene) and various metals. The observed interactions between the two different kinds of materials ranged from physisorption (aluminum and samarium), to the formation...

  14. Modification to the MAPS interview process and electronic form

    CERN Multimedia

    HR Department

    2006-01-01

    Based on the first year of experience with e-MAPS and the feedback from departmental users, a number of modifications to the MAPS interview process and form have been introduced for the 2006 exercise. Definition of signatories The top of the form now also shows the name of the Group Leader and Department Head. This is especially useful in cases of detachment. Corrections can be made via the MAPS Coordinator. 'Send back' facility The possibility to send the MAPS report one step backwards, i.e. from Group Leader to supervisor, from Staff Member to Group Leader, and from Group Leader to Staff Member is only available to the MAPS coordinators. The form should only be sent back to correct factual errors or oversights, and any send- backs will be recorded. Link between 'training' part and 'training' application When entering a training objective for 2006, a search menu allows selection from various CERN internal training courses or from conferences. It is still important, however, to first read the descri...

  15. Modification to the MAPS interview process and electronic form

    CERN Multimedia

    HR Department

    2006-01-01

    Based on the first year of experience with e-MAPS and the feedback from departmental users, a number of modifications to the MAPS interview process and the form have been introduced for the 2006 exercise. Definition of signatories The top of the form now also shows the name of the group leader and department head. This is especially useful in cases of detachment. Corrections can be made via the MAPS Coordinator. 'Send back' facility The possibility to send the MAPS report one step backwards is only available to the MAPS coordinators, i.e., from group leader to supervisor, from staff member to group leader, and from group leader to staff member. The form should only be sent back to correct factual errors or oversights, and any send backs will be tracked. Link 'training' part to 'training' application When entering a training objective for 2006, a search menu allows selection from various CERN internal training courses or from conferences. It remains important however to first read the description of the...

  16. Chemical Modification Effect on the Mechanical Properties of Coir Fiber

    Directory of Open Access Journals (Sweden)

    Samia Sultana Mir

    2012-04-01

    Full Text Available Natural fiber has a vital role as a reinforcing agent due to its renewable, low cost, biodegradable, less abrasive and eco-friendly nature. Whereas synthetic fibers like glass, boron, carbon, metallic, ceramic and inorganic fibers are expensive and not eco-friendly. Coir is one of the natural fibers easily available in Bangladesh and cheap. It is derived from the husk of the coconut (Cocos nucifera. Coir has one of the highest concentrations of lignin, which makes it stronger. In recent years, wide range of research has been carried out on fiber reinforced polymer composites [4-13].The aim of the present research is to characterize brown single coir fiber for manufacturing polymer composites reinforced with characterized fibers. Adhesion between the fiber and polymer is one of factors affecting the strength of manufactured composites. In order to increase the adhesion, the coir fiber was chemically treated separately in single stage (with Cr2(SO43•12(H2O and double stages (with CrSO4 and NaHCO3. Both the raw and treated fibers were characterized by tensile testing, Fourier transform infrared (FTIR spectroscopic analysis, scanning electron microscopic analysis. The result showed that the Young’s modulus increased, while tensile strength and strain to failure decreased with increase in span length. Tensile properties of chemically treated coir fiber was found higher than raw coir fiber, while the double stage treated coir fiber had better mechanical properties compared to the single stage treated coir fiber. Scanning electron micrographs showed rougher surface in case of the raw coir fiber. The surface was found clean and smooth in case of the treated coir fiber. Thus the performance of coir fiber composites in industrial application can be improved by chemical treatment.

  17. Modification of infarct material properties limits adverse ventricular remodeling.

    Science.gov (United States)

    Morita, Masato; Eckert, Chad E; Matsuzaki, Kanji; Noma, Mio; Ryan, Liam P; Burdick, Jason A; Jackson, Benjamin M; Gorman, Joseph H; Sacks, Michael S; Gorman, Robert C

    2011-08-01

    Infarct expansion after myocardial infarction (MI) is an important phenomenon that initiates and sustains adverse left ventricular (LV) remodeling. We tested the hypothesis that infarct modification by material-induced infarct stiffening and thickening limits infarct expansion and LV remodeling. Anteroapical infarction was induced in 21 sheep. Sheep were randomized to injection of saline (2.6 mL) or tissue filler material (2.6 mL) into the infarct within 3 hours of MI. Animals were monitored for 8 weeks with echocardiography to assess infarct expansion and global LV remodeling. Morphometric measurements were performed of excised hearts to quantify infarct thickness. Regional blood flow was assessed with colored microspheres. Infarct material properties were measured using biaxial tensile testing. Compared with controls at 8 weeks, treatment animals had less infarct expansion, reduced LV dilatation (LV systolic volumes: 60.8±4.3 vs 80.3±6.9 mL; p<0.05), greater ejection fraction (0.310±0.026 vs 0.276±0.013; p<0.05), thicker infarcts (5.5±0.2 vs 2.2±0.3 mm; p<0.05), and greater infarct blood flow (0.22±0.04 vs 0.11±0.03 mL/min/g; p<0.05). The longitudinal peak strain in the treatment group was less (0.05014±0.0141) than the control group (0.1024±0.0101), indicating increased stiffness of the treated infarcts. Durable infarct thickening and stiffening can be achieved by infarct biomaterial injection, resulting in the amelioration of infarct expansion and global LV remodeling. Further material optimization will allow for clinical translation of this novel treatment paradigm. Copyright © 2011 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  18. Effect of chemical modification on properties of hybrid fibre biocomposites

    CSIR Research Space (South Africa)

    Jacob John, Maya

    2008-02-01

    Full Text Available The effects of chemical modification of fiber surface in sisal–oil palm reinforced natural rubber green composites have been studied. Composites were prepared using fibers treated with varying concentrations of sodium hydroxide solution...

  19. Impact of electron beam irradiation on fish gelatin film properties.

    Science.gov (United States)

    Benbettaïeb, Nasreddine; Karbowiak, Thomas; Brachais, Claire-Hélène; Debeaufort, Frédéric

    2016-03-15

    The objective of this work was to display the effect of electron beam accelerator doses on properties of plasticized fish gelatin film. Electron spin resonance indicates free radical formation during irradiation, which might induce intermolecular cross-linking. Tensile strength for gelatin film significantly increases after irradiation (improved by 30% for 60 kGy). The vapour permeability is weakly affected by irradiation. Surface tension and its polar component increase significantly and are in accordance with the increase of wettability. So, irradiation may change the orientation of polar groups of gelatin at the film surface and crosslink the hydrophobic amino acids. No modification of the crystallinity of the film is observed. These findings suggest that if structure changes, it only occurs in the amorphous phase of the gelatin matrix. It is also observed that irradiation enhances the thermal stability of the gelatin film, by increasing the glass transition temperature and the degradation temperature. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Effect of hierarchical porosity and phosphorus modification on the catalytic properties of zeolite Y

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wenlin; Zheng, Jinyu; Luo, Yibin; Da, Zhijian, E-mail: dazhijian.ripp@sinopec.com

    2016-09-30

    Highlights: • Hierarchical zeolite Y was prepared by citric acid treatment and alkaline treatment with NaOH&TBPH. • The addition of TBPH during desilication process transferred the bridge bonded OH− to the terminal P−OH group. • Moderate Brønsted acid sites could be created with phosphorus modification. • Zeolite with hierarchical porosity and appropriated acidities favored high conversion of 1,3,5-TIPB. - Abstract: The zeolite Y is considered as a leading catalyst for FCC industry. The acidity and porosity modification play important roles in determining the final catalytic properties of zeolite Y. The alkaline treatment of zeolite Y by dealumination and alkaline treatment with NaOH and NaOH&TBPH was investigated. The zeolites were characterized by X-ray diffraction, low-temperature adsorption of nitrogen, transmission electron microscope, NMR, NH{sub 3}-TPD and IR study of acidity. Accordingly, the hierarchical porosity and acidity property were discussed systematically. Finally, the catalytic performance of the zeolites Y was evaluated in the cracking of 1,3,5-TIPB. It was found that desilication with NaOH&TBPH ensured the more uniform intracrystalline mesoporosity with higher microporosity, while preserving higher B/L ratio and moderate Brønsted acidities resulting in catalysts with the most appropriated acidity and then with better catalytic performance.

  1. Electronic properties with and without electron-phonon coupling

    Science.gov (United States)

    Allen, Philip

    To decent approximation, electronic properties P of solids have a temperature dependence of the type ΔP(T) = Σ (dP/dωi) [ni(T) +1/2], where ωi is the frequency of the ith vibrational normal mode, and ni is the Bose-Einstein equilibrium occupation of the mode. The coupling constant (dP/dωi) comes from electron-phonon interactions. At T =0, the ``1/2'' gives the zero-point electron-phonon renormalization of the property P, and at T>ΘD, the total shift ΔP becomes linear in T, extrapolating toward ΔP =0 at T =0. This form of T-dependence arises from the adiabatic or Born-Oppenheimer approximation, where electrons essentially ``don't notice'' the time-dependence of thermal lattice fluctuations. In other words, the leading order theory for P is ΔP(T) = Σ (d2P/duiduj), responding to the thermal average mean square lattice displacement, as if it were static. There are two situations where non-adiabatic effects alter things. (1) In metals at low T, the thermal smearing kBT of the sharp Fermi edge gets small (ωi insulators with polar phonons, Froehlich polaron effects enter, and k-integrals diverge unless phonon energies are kept. Most non-adiabatic effects become unimportant by room temperature, but the low T consequences can be very interesting (e.g. superconductivity.) This talk will discuss the confusing history and predict some future developments in this field. invited session: ''Predictive Modeling of Electron-Phonon Coupling in Condensed-Matter Physics'' My talk will be coordinated with that of Xavier Gonze. It would be best to schedule them back-to-back.

  2. Electronic properties of graphene antidot lattices

    DEFF Research Database (Denmark)

    Fürst, Joachim Alexander; Pedersen, Jesper Goor; Flindt, C.

    2009-01-01

    into a semiconductor. We calculate the electronic band structure of graphene antidot lattices using three numerical approaches with different levels of computational complexity, efficiency and accuracy. Fast finite-element solutions of the Dirac equation capture qualitative features of the band structure, while full......Graphene antidot lattices constitute a novel class of nano-engineered graphene devices with controllable electronic and optical properties. An antidot lattice consists of a periodic array of holes that causes a band gap to open up around the Fermi level, turning graphene from a semimetal...

  3. 78 FR 4438 - Investigations: Terminations, Modifications and Rulings: Certain Electronic Devices With Graphics...

    Science.gov (United States)

    2013-01-22

    ... COMMISSION Investigations: Terminations, Modifications and Rulings: Certain Electronic Devices With Graphics... instituted this investigation on November 14, 2011, based on a complaint filed by S3 Graphics Co., Ltd., of Grand Cayman Islands, British West Indies, and S3 Graphics, Inc., of Fremont, California (collectively...

  4. Oxides Surfaces and Novel Electronic Properties

    Science.gov (United States)

    Koirala, Pratik

    The scope of this thesis extends to the study of surface structures and electronic properties in a number of complex oxides. The c(6x2) surface reconstruction on SrTiO3 (001) was solved using a combination of plan view transmission electron microscopy imaging, atomic resolution secondary electron imaging, and density functional theory calculations. This work provided fundamental insights on the effects of dielectric screening in secondary electron generation. A thorough analysis on the limitation and functionality of transmission plan view imaging showed that the kinematical approximations used in the separation of top and bottom surfaces is only valid in thin samples (˜5 nm or less for SrTiO3). The presence of an inversion center in the surface structure also made separation of the top and bottom surfaces more robust. Surface studies of two other oxides, KTaO3 and NdGaO3, provided understanding on the mechanism of surface heterogeneity and segregation. In the case of KTaO3, selective ion sputtering and the loss of K resulted in large stoichiometric variations at the surface. Annealing of such samples led to the formation of a potassium deficient tetragonal phase (K 6Ta10.8O30) on the surface. A similar phenomenon was also observed in NdGaO3. Exploratory surface studies of the rare earth scandates (ReScO3 , Re = Gd, Tb, Dy) led to the observation of large flexoelectric bending inside an electron microscope. Thin rods of these scandates bent by up to 90 degree under a focused electron beam; the bending was fully reversible. Ex-situ measurements of flexoelectric coe cient performed by an- other graduate student, Christopher Mizzi, confirmed that the scandates have a large flexocoupling voltage (˜42 V). Electronic structure of the lanthanide scandates was studied using temperature depen- dent X-ray photoelectron spectroscopy and hybrid density functional theory calculations. The amount of charging under X-ray illumination was greatly reduced with increasing

  5. Influence of DC plasma modification on the selected properties and the geometrical surface structure of polylactide prior to autocatalytic metallization

    Energy Technology Data Exchange (ETDEWEB)

    Moraczewski, Krzysztof, E-mail: kmm@ukw.edu.pl [Kazimierz Wielki University, Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Rytlewski, Piotr [Kazimierz Wielki University, Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Malinowski, Rafał [Institute for Engineering of Polymer Materials and Dyes, Marii Skłodowskiej-Curie 55, 87-100 Toruń (Poland); Tracz, Adam [Centre for Molecular and Macromolecular Studies of the Polish Academy of Sciences, Sienkiewicza 112, 90-363 Łódź (Poland); Żenkiewicz, Marian [Institute for Engineering of Polymer Materials and Dyes, Marii Skłodowskiej-Curie 55, 87-100 Toruń (Poland)

    2015-03-01

    The paper presents the results of studies to determine the applicability of plasma modification in the process of polylactide (PLA) surface preparation prior to the autocatalytic metallization. The polylactide plasma modification was carried out in an oxygen or nitrogen chemistry. The samples were tested with the following methods: scanning electron microscopy (SEM), atomic force microscopy (AFM), goniometry and electron spectrophotometry (XPS). Scanning electron microscopy and atomic force microscopy images were demonstrated. The results of surface free energy calculations, performed based on the results of the contact angle measurements have been presented. The results of the qualitative (degree of oxidation or nitridation) and quantitative analysis of the chemical composition of the polylactide surface layer have also been described. The results of the studies show that the DC plasma modification performed in the proposed condition is a suitable as a method of surface preparation for the polylactide metallization. - Highlights: • We modified polylactide surface layer with plasma generated in oxygen or nitrogen. • We tested selected properties and surface structure of modified samples. • DC plasma modification can be used to prepare the PLA surface for metallization. • For better results metallization should be preceded by sonication process.

  6. Influence of plasma modification on hygienic properties of textile fabrics with nonporous membrane coating

    Science.gov (United States)

    Voznesensky, E. F.; Ibragimov, R. G.; Vishnevskaya, O. V.; Sisoev, V. A.; Lutfullina, G. G.; Tihonova, N. V.

    2017-11-01

    The work investigated the possibility of using plasma modification to improve the hygienic properties of textile materials with nonporous membrane coating to improve vapor-, air-permeability and water-resistant. Determined that, after plasma modification changes degree of supramolecular orderliness of the polymers nonporous membrane coating and the base fabric.

  7. Influence of Polylactide Modification with Blowing Agents on Selected Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Aneta Tor-Świątek

    2017-12-01

    Full Text Available Article presents research of modification of PLA with four types of chemical blowing agents with a different decomposition characteristic. The modification was done both cellular extrusion and injection molding processes. Obtained results shows that dosing blowing agents have the influence on mechanical properties and structure morphology of PLA. The differences in obtained results are also visible and significant between cellular processes.

  8. Tuning photoluminescence properties of ZnO nanorods via surface modification

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xin [National Center for Nanoscience and Technology, Beijing 100190 China (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xia, Yujing [National Center for Nanoscience and Technology, Beijing 100190 China (China); He, Tao, E-mail: het@nanoctr.cn [National Center for Nanoscience and Technology, Beijing 100190 China (China)

    2012-12-14

    Zinc oxide (ZnO) is a versatile material that has been used in photocatalysis, solar cells, chemical sensors, and piezoelectric transducers. All these are directly related to its surface properties. Here ZnO nanorod arrays were successfully synthesized by electrochemical deposition method, the surface of which was modified by dopamine, a robust anchor. Compared with pristine ZnO sample, the surface modification can greatly enhance the ultraviolet and visible-light photoluminescence. This is due to the formation of polydopamine on the nanorod surface, which may act as a dye that can be photoexcited. The resultant photogenerated electrons can inject into the conduction band of ZnO and take part in the luminescent process. These results may provide a foundation for real applications of ZnO nanomaterials in optoelectronic devices and, especially, for the applications in biological field as both the dopamine and ZnO are biocompatible materials. -- Highlights: Black-Right-Pointing-Pointer ZnO nanorod arrays are prepared via a simple electrochemical deposition method. Black-Right-Pointing-Pointer Photoluminescence of ZnO nanorods can be greatly enhanced via dopamine treatment. Black-Right-Pointing-Pointer Dye-like polydopamine can be formed on the nanorod surface upon dopamine treatment. Black-Right-Pointing-Pointer Photogenerated electrons in polydopamine can inject into conduction band of ZnO. Black-Right-Pointing-Pointer Enhanced photoluminescence is because more electrons can contribute to it.

  9. Influence of electron beam irradiation on physicochemical properties of poly(trimethylene carbonate)

    NARCIS (Netherlands)

    Jozwiakowska, Joanna; Wach, Radoslaw A.; Rokita, Bozena; Ulanski, Piotr; Nalawade, Sameer P.; Grijpma, Dirk W.; Feijen, Jan; Rosiak, Janusz M.

    Electron beam (EB) irradiation of poly(trimethylene carbonate) (PTMC), an amorphous, biodegradable polymer used in the field of biomaterials, results in predominant cross-linking and finally in the formation of gel fraction, thus enabling modification of physicochemical properties of this material

  10. Effect of mechanochemical modification on the surfactant and structural properties of humic and himatomelanic acids

    Science.gov (United States)

    Mal'tseva, E. V.; Shekhovtsova, N. S.; Shilyaeva, L. P.; Yudina, N. V.

    2017-07-01

    The structural properties of humic and himatomelanic acids are studied by means of 1H NMR spectroscopy and differential thermal analysis after mechanochemical modification of peat. The relationship between the structural modification of humic and himatomelanic acids and their surfactant properties in aqueous solutions is established. It is shown that the critical micelle concentration of transformed himatomelanic acids is halved in comparison to the initial sample, while the adsorption equilibrium constant grows by 9 times.

  11. The Influence of Biochemical Modification on the Properties of Adhesive Compounds

    Directory of Open Access Journals (Sweden)

    Anna Rudawska

    2016-12-01

    Full Text Available The main objective of this study was to determine the effect of biochemical modification of epoxy adhesive compounds on the mechanical properties of a cured adhesive exposed to various climatic factors. The epoxy adhesive was modified by lyophilized fungal metabolites and prepared by three methods. Additionally, the adhesive compound specimens were seasoned for two months at a temperature of 50 °C and 50% humidity in a climate test chamber, Espec SH 661. The tensile strength tests of the adhesive compounds were performed using a Zwick/Roell Z150 testing machine in compliance with the DIN EN ISO 527-1 standard. The examination of the adhesive specimens was performed using two microscopes: a LEO 912AB transmission electron microscope equipped with Quantax 200 for EDS X-ray spectroscopy and a Zeiss 510 META confocal microscope coupled to an AxioVert 200M. The experiments involved the use of a CT Skyscan 1172 tomograph. The results revealed that some mechanical properties of the modified adhesives were significantly affected by both the method of preparation of the adhesive compound and the content of the modifying agent. In addition, it was found that seasoning of the modified adhesives does not lead to a decrease in some of their mechanical properties.

  12. Electronic properties of 8 -Pmmn borophene

    Science.gov (United States)

    Lopez-Bezanilla, Alejandro; Littlewood, Peter B.

    2016-06-01

    First-principles calculations on monolayer 8-Pmmn borophene are reported to reveal unprecedented electronic properties in a two-dimensional material. Based on a Born effective charge analysis, 8-Pmmn borophene is the first single-element-based monolayered material exhibiting two sublattices with substantial ionic features. The observed Dirac cones are actually formed by the pz orbitals of one of the inequivalent sublattices composed of uniquely four atoms, yielding an underlying hexagonal network topologically equivalent to distorted graphene. A significant physical outcome of this effect includes the possibility of converting metallic 8-Pmmn borophene into an indirect band gap semiconductor by means of external shear stress. The stability of the strained structures are supported by a phonon frequency analysis. The Dirac cones are sensitive to the formation of vacancies only in the inequivalent sublattice electronically active at the Fermi level.

  13. Electronic transport properties of (fluorinated) metal phthalocyanine

    KAUST Repository

    Fadlallah, M M

    2015-12-21

    The magnetic and transport properties of the metal phthalocyanine (MPc) and F16MPc (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Ag) families of molecules in contact with S–Au wires are investigated by density functional theory within the local density approximation, including local electronic correlations on the central metal atom. The magnetic moments are found to be considerably modified under fluorination. In addition, they do not depend exclusively on the configuration of the outer electronic shell of the central metal atom (as in isolated MPc and F16MPc) but also on the interaction with the leads. Good agreement between the calculated conductance and experimental results is obtained. For M = Ag, a high spin filter efficiency and conductance is observed, giving rise to a potentially high sensitivity for chemical sensor applications.

  14. Electronic and optical properties of lead iodide

    DEFF Research Database (Denmark)

    Ahuja, R.; Arwin, H.; Ferreira da Silva, A.

    2002-01-01

    The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising...... detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given. ©2002 American Institute of Physics....

  15. Characterization of neurohistone variants and post-translational modifications by electron capture dissociation mass spectrometry

    Science.gov (United States)

    Garcia, Benjamin A.; Siuti, Nertila; Thomas, C. Eric; Mizzen, Craig A.; Kelleher, Neil L.

    2007-01-01

    Post-translational modifications (PTMs) of histones are intimately involved in chromatin structure and thus have roles in cellular processes through their impact on gene activation or repression. At the forefront in histone PTM analysis are mass spectrometry-based techniques, which have capabilities to produce improved views of processes affected by chromatin remodeling via histone modifications. In this report, we take the first mass spectrometric look at histone variant expression and post-translational modifications from histones isolated from rat brain tissue. Analyses of whole rat brain identified specific histone H2A and H2B gene family members and several H4 and H3 post-translational modification sites by electron capture dissociation (ECD) mass spectrometry. We subsequently compared these results to selected rat brain regions. Major differences in the expression profiles of H2A and H2B gene family members or in the post-translational modifications on histone H4 were not observed from the different brain regions using a Top Down approach. However, "Middle Down" mass spectrometry facilitating improved characterization of the histone H3 tail (1-50 residues), revealed an enrichment of trimethylation on Lys9 from cerebellum tissue compared to H3 extracted from whole brain, cerebral cortex or hypothalamus tissue. We forward this study in honor of Professor Donald F. Hunt, whose pioneering efforts in protein and PTM analyses have spawned new eras and numerous careers, many exemplified in this special issue.

  16. The functional properties, modification and utilization of whey proteins

    Directory of Open Access Journals (Sweden)

    B. G. Venter

    1986-03-01

    Full Text Available Whey protein has an excellent nutritional value and exhibits a functional potential. In comparison with certain other food proteins, the whey protein content of essential amino acids is extremely favourable for human consumption. Depending on the heat-treatment history thereof, soluble whey proteins with utilizable functional properties, apart from high biological value, true digestibility, protein efficiency ratio and nett protein utilization, can be recovered. Various technological and chemical recovery processes have been designed. Chemically and enzymatically modified whey protein is manufactured to obtain technological and functional advantages. The important functional properties of whey proteins, namely hydration, gelation, emulsifying and foaming properties, are reviewed.

  17. Optical, electronic and transport properties of tetrahedrites

    Science.gov (United States)

    Kohl, Simon; Vielma, Jason; Foster, David; Schneider, Guenter

    2014-03-01

    Doped Tetrahedrites Cu12-xTMxSb4S13 (TM=Fe,Mn,Zn) have recently attracted interest as thermoelectric materials. We present an ab-initio study based on density functional theory of the optical, electronic and transport properties of these materials. We find in Cu12-xZnxSb~4S13: 1. the band-gap can be tuned through chalcogenide substitution and the optical absorption is very large making tetrahedrites attractive also as solar absorber materials. A point defect study of the Zn rich tetrahedrite (x=2) based on supercell calculations indicates p-type conductivity and Cu-Zn antisite defects are the dominant acceptor defect with Cu-vacancies also contributing. The calculated hole concentration is much larger than what is expected from conductivity measurements. We discuss these results in the context of the observed unusual, variable range hoping like electronic transport properties. Finally we present results of thermopower calculations based on semiclassical Boltzmann theory and discuss the applicability of these approach for tetrahedrites.

  18. Precision shape modification of nanodevices with a low-energy electron beam

    Science.gov (United States)

    Zettl, Alex; Yuzvinsky, Thomas David; Fennimore, Adam

    2010-03-09

    Methods of shape modifying a nanodevice by contacting it with a low-energy focused electron beam are disclosed here. In one embodiment, a nanodevice may be permanently reformed to a different geometry through an application of a deforming force and a low-energy focused electron beam. With the addition of an assist gas, material may be removed from the nanodevice through application of the low-energy focused electron beam. The independent methods of shape modification and material removal may be used either individually or simultaneously. Precision cuts with accuracies as high as 10 nm may be achieved through the use of precision low-energy Scanning Electron Microscope scan beams. These methods may be used in an automated system to produce nanodevices of very precise dimensions. These methods may be used to produce nanodevices of carbon-based, silicon-based, or other compositions by varying the assist gas.

  19. Electronic and transport properties of kinked graphene

    DEFF Research Database (Denmark)

    Rasmussen, Jesper Toft; Gunst, Tue; Bøggild, Peter

    2013-01-01

    Local curvature, or bending, of a graphene sheet is known to increase the chemical reactivity presenting an opportunity for templated chemical functionalisation. Using first-principles calculations based on density functional theory (DFT), we investigate the reaction barrier reduction for the ads......Local curvature, or bending, of a graphene sheet is known to increase the chemical reactivity presenting an opportunity for templated chemical functionalisation. Using first-principles calculations based on density functional theory (DFT), we investigate the reaction barrier reduction...... for the adsorption of atomic hydrogen at linear bends in graphene. We find a significant barrier lowering (≈15%) for realistic radii of curvature (≈20 Å) and that adsorption along the linear bend leads to a stable linear kink. We compute the electronic transport properties of individual and multiple kink lines......, and demonstrate how these act as efficient barriers for electron transport. In particular, two parallel kink lines form a graphene pseudo-nanoribbon structure with a semimetallic/semiconducting electronic structure closely related to the corresponding isolated ribbons; the ribbon band gap translates...

  20. Selective Modification of Chitosan to Enable the Formation of Chitosan-DNA Condensates by Electron Donator Stabilization

    Directory of Open Access Journals (Sweden)

    Karl E. Kador

    2011-01-01

    Full Text Available Chitosan, a polyaminosaccharide, has been investigated for its use in the field of drug-delivery and biomaterial applications because of its natural biocompatibility and polycationic properties. Chemical modifications of chitosan have been attempted in an effort to increase the transfection efficiency with respect to gene delivery applications; however, it is unknown how these modifications affect the formation of the condensates. This study attempts to determine the effects of modification of the cationic center of chitosan on the ability to condense DNA. Specifically, electron-donating or -withdrawing groups were used as modifiers of the cationic charge on the chitosan backbone to stabilize the protonated form of chitosan, which is necessary to form condensates and increase the efficiency of the polymer to condense DNA by yielding condensates at a lower nitrogen to phosphorous (N : P ratio. While an N : P ratio of 7 is needed to condense DNA with unmodified chitosan, phthalate-modified chitosan yielded condensates were obtained at an N : P ratio of 1.0.

  1. Effects of surface atomistic modification on mechanical properties of gold nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiao-Yu [AML and CNMM, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan 430072 (China); Xu, Yuanjie [Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan 430072 (China); Wang, Gang-Feng [Department of Engineering Mechanics, Xi' an Jiaotong University, Xi' an 710049 (China); Gu, Yuantong [School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology, Brisbane 4001 (Australia); Feng, Xi-Qiao, E-mail: fengxq@tsinghua.edu.cn [AML and CNMM, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

    2015-09-18

    Highlights: • Molecular dynamics simulations of surface modification effect of Au nanowires. • Surface modification can greatly affect the mechanical properties of nanowires. • Core–shell model is used to elucidate the effect of residual surface stress. - Abstract: Modulation of the physical and mechanical properties of nanowires is a challenging issue for their technological applications. In this paper, we investigate the effects of surface modification on the mechanical properties of gold nanowires by performing molecular dynamics simulations. It is found that by modifying a small density of silver atoms to the surface of a gold nanowire, the residual surface stress state can be altered, rendering a great improvement of its plastic yield strength. This finding is in good agreement with experimental measurements. The underlying physical mechanisms are analyzed by a core–shell nanowire model. The results are helpful for the design and optimization of advanced nanomaterial with superior mechanical properties.

  2. Modification of strength properties of soil-aggregate system on ...

    African Journals Online (AJOL)

    varying doses of cement is checked by conducting wetting and drying test. 2. Material and Methods. Stabilization in a broad sense includes various methods incorporated for modifying the properties of a soil to enhance its performance. It is being used for a variety of engineering works, the most common application being in ...

  3. Modification of strength properties of lime-stabilized laterites with ...

    African Journals Online (AJOL)

    The potential of sawdust ash as a stabilizer for lateritic soils was investigated to determine the modifying effects on strength properties required for road construction. Three laterite samples, A, B and C were collected respect- ively from Akoda, Osogbo and Ile-Ife (Nigeria). Atterberg limits and strength tests were performed on ...

  4. Soil physical and hydraulic properties modification under Arachis ...

    African Journals Online (AJOL)

    Conservation of soil moisture is one of the major limiting factors to crop production. Improvement of soil physical properties could enhance soil moisture conservation, improve crop productivity and reduce food insecurity in sub Saharan Africa. A field study was carried out to determine the effects of 3 plant densities (33333, ...

  5. Alteration of human serum albumin binding properties induced by modifications: A review

    Science.gov (United States)

    Maciążek-Jurczyk, Małgorzata; Szkudlarek, Agnieszka; Chudzik, Mariola; Pożycka, Jadwiga; Sułkowska, Anna

    2018-01-01

    Albumin, a major transporting protein in the blood, is the main target of modification that affects the binding of drugs to Sudlow's site I and II. These modification of serum protein moderates its physiological function, and works as a biomarker of some diseases. The main goal of the paper was to explain the possible alteration of human serum albumin binding properties induced by modifications such as glycation, oxidation and ageing, their origin, methods of evaluation and positive and negative meaning described by significant researchers.

  6. Electronic and conformational properties of 2,3-benzodiazepine derivates

    Energy Technology Data Exchange (ETDEWEB)

    Pelaggi, M.; Girlanda, R. [Messina Univ. (Italy). Dip. di Fisica della Materia e Fisica dell`Ambiente; Chimirri, A.; Gitto, R. [Messina Univ. (Italy). Dip. Farmaco-Chimico

    1996-04-01

    The molecular geometric and electronic structures of 2,3-benzodiazepine derivates have been studied by means of the MNDO-PM3 method. A number of electronic properties have been computed and examined in order to find indication of the role of the electronic characteristics of the different molecules and their pharmacological properties. Theoretical data indicate that both electronic and structural properties appear responsible for the varying degree of anticonvulsant activity exhibited by compounds 1-4.

  7. Effects of Surface Modification of MWCNT on the Mechanical and Electrical Properties of Fluoro Elastomer/MWCNT Nanocomposites

    Directory of Open Access Journals (Sweden)

    Tao Xu

    2012-01-01

    Full Text Available Surface modification is a good way to improve the surface activity and interfacial strength of multiwalled carbon nanotubes (MWCNTs when used as fillers in the polymer composites. Among the reported methods for nanotube modification, mixed acid oxidation and plasma treatment is often used by introducing polar groups to the sidewall of MWCNT successfully. The purpose of this study is to evaluate the effect of different surface modification of MWCNT on the mechanical property and electrical conductivity of Fluoro-elastomer (FE/MWCNT nanocomposites. MWCNTs were surface modified by mixed oxidation and CF4 plasma treatment and then used to reinforce the fluoro elastomer (FE, a copolymer of trifluorochloroethylene and polyvinylidene fluoride. FE/MWCNT composite films were prepared from mixture solutions of ethylacetate and butylacetate, using untreated CNTs (UCNTs, acid-modified CNTs (ACNTs, and CF4 plasma-modified CNT (FCNTs. In each case, MWCNT content was 0.01 wt%, 0.05 wt%, 0.1 wt%, and 0.2 wt% with respect to the polymer. Morphology and mechanical properties were characterized by using scanning electron microscopy (SEM, Raman spectroscopy, as well as dynamic mechanical tests. The SEM results indicated that dispersion of ACNTs and especially FCNTs in FE was better than that of UCNTs. DMA indicated mechanical properties of FCNT composites were improved over ACNT and UCNT filled FE. The resulting electrical properties of the composites ranged from dielectric behavior to bulk conductivities of 10-2 Sm-1 and were found to depend strongly on the surface modification methods of MWCNTs.

  8. Laser surface modification of Ti6Al4V-Cu for improved microhardness and wear resistance properties

    CSIR Research Space (South Africa)

    Erinosho, MF

    2017-06-01

    Full Text Available sample was etched for 10 -15 seconds, cleaned with ethanol, rinsed under running water and dried off prior to Scanning Electron Microscope (SEM) and optical microscopic (OM) observations. The SEM was conducted on the samples using the TESCAN...Laser Surface Modification of Ti6Al4V-Cu for Improved Microhardness and Wear Resistance Properties The microstructures of the selected Ti6Al4V-3Cu and Ti6Al4V-5Cu alloys observed by SEM and Optical microscope (OM) are presented Figure 5. The SEM...

  9. Electronic processes in organic electronics bridging nanostructure, electronic states and device properties

    CERN Document Server

    Kudo, Kazuhiro; Nakayama, Takashi; Ueno, Nobuo

    2015-01-01

    The book covers a variety of studies of organic semiconductors, from fundamental electronic states to device applications, including theoretical studies. Furthermore, innovative experimental techniques, e.g., ultrahigh sensitivity photoelectron spectroscopy, photoelectron yield spectroscopy, spin-resolved scanning tunneling microscopy (STM), and a material processing method with optical-vortex and polarization-vortex lasers, are introduced. As this book is intended to serve as a textbook for a graduate level course or as reference material for researchers in organic electronics and nanoscience from electronic states, fundamental science that is necessary to understand the research is described. It does not duplicate the books already written on organic electronics, but focuses mainly on electronic properties that arise from the nature of organic semiconductors (molecular solids). The new experimental methods introduced in this book are applicable to various materials (e.g., metals, inorganic and organic mater...

  10. Surface modification and antimicrobial properties of cellulose nanocrystals

    Science.gov (United States)

    Bespalova, Yulia A.

    Surface modification of cellulose nanocrystals (CNC) was performed by acetylation and subsequent reaction with various tertiary amines with different lengths of alkyl groups. Chloroacetic anhydride (95%) was used for acetylation. The acetylation of CNC was confirmed using IR spectroscopy. The bands associated with C=0 stretching (1740 cm-1) and C-Cl stretching (793 cm -1) was present in the acetylated CNC but they were absent in the neat CNC. It has been suggested that the primary hydroxyl groups of CNC are substituted by chloro acetyl groups during acetylation reaction. Subsequent reaction of chloro acetylated CNC with N, N - Dimethyl ethylamine, N, N - Dimethyl hexylamine, N, N - Dimethyl dodecylamine, N, N - Dimethyl hexadecylamine and N, N - Dimethyl decylamine formed quaternary ammonium salts. These quaternary ammonium salts were characterized by FTIR and solid state13C NMR spectroscopy. FTIR spectra of five types of quaternary ammonium salts of CNC are similar and they showed infrared bands at 2905 -1 and 2850 cm-1, attributed to symmetrical and unsymmetrical C-H stretching vibration. The absence of C-Cl band at 793 cm-1 proves that quaternary salt formation was successful. The 13C NMR spectrum of quaternary ammonium modified CNC with N, N - Dimethyl dodecylamine shows several additional resonances ranging from 14.5 ppm to 58.0 ppm when compared to 13C NMR spectrum of pure CNC. This evidence proves that long alkyl chains have been added to the pure CNC. The disc diffusion method confirmed that quaternary ammonium modified CNCs with a chain longer than ten carbons are effective antimicrobial agents against Staphylococcus aureus and E. coli bacteria. Pure CNC and quaternary ammonium modified CNCs with an alkyl chain length of ten or less were not able to inhibit bacteria growth.

  11. [Related research on mechanical property of valve membrane in transcatheter bioprosthesis valve based on the chemical modification and cutting technology].

    Science.gov (United States)

    Chen, Dakai; Li, Yu; Luo, Qiyi; Liu, Baolin; Chen, Kangmin

    2014-08-01

    The aim of this research is to investigate the preparation method of valve membrane in transcatheter bio- prosthetic valve, and to study the effect of chemical modification and cutting technology to tensile property and suture force property of valve membrane. We carried out a series of processes to perform the tests, such as firstly to test the crosslinking degree of valve membrane using ninhydrin method, then to test the tensile property and suture force property by using Instron's biomechanicAl testing equipment, and then to observe the collagen fiber orientation in valve membrane using Instron's biomechanical testing equipment and using field emission scanning electron microscopy. The study indicated that after the chemical modification, the crosslinking degree, tensile strength and suture force strength increasing rate of valve membrane were 93.78% ± 3. 2%, (8.24 ± 0.79) MPa, 102%, respectively. The valve membrane had a better biomechanical property and would be expected to become valve membrane in transcatheter bioprosthesis valve.

  12. Genetic and environmental modification of the mechanical properties of wood

    Science.gov (United States)

    Sederoff, R.; Allona, I.; Whetten, R.

    1996-02-01

    Wood is one of the nation's leading raw materials and is used for a wide variety of products, either directly as wood, or as derived materials in pulp and paper. Wood is a biological material and evolved to provide mechanical support and water transport to the early plants that conquered the land. Wood is a tissue that results from the differentiation and programmed cell death of cells that derive from a tissue known as the vascular cambium. The vascular cambium is a thin cylinder of undifferentiated tissue in plant stems and roots that gives rise to several different cell types. Cells that differentiate on the internal side of the cambium form xylem, a tissue composed in major part, of long thin cells that die leaving a network of interconnected cell walls that serve to transport water and to provide mechanical support for the woody plant. The shape and chemical composition of the cells in xylem are well suited for these functions. The structure of cells in xylem determines the mechanical properties of the wood because of the strength derived from the reinforced matrix of the wall. The hydrophobic phenolic surface of the inside of the cell walls is essential to maintain surface tension upon which water transport is based and to resist decay caused by microorganisms. The properties of wood derived from the function of xylem also determine its structural and chemical properties as wood and paper products. Therefore, the physical and chemical properties of wood and paper products also depend on the morphology and composition of the cells from which they are derived. Wood (xylem cell walls) is an anisotropic material, a composite of lignocellulose. It is a matrix of cellulose microfibrils, complexed with hemicelluloses, (carbohydrate polymers which contain sugars other than glucose, both pentoses and hexoses), embedded together in a phenolic matrix of lignin. The high tensile strength of wood in the longitudinal direction, is due to the structure of cellulose and the

  13. Effect of alcohol-acid modification on physicochemical, rheological and morphological properties of glutinous rice starch.

    Science.gov (United States)

    Gope, Sangeeta; Samyor, Duyi; Paul, Atanu Kumar; Das, Amit Baran

    2016-12-01

    In the present study chemical modification of glutinous rice starch was carried out using 1-Buatnol-hydrochloric acid with varying time and temperature. The changes in physico-chemical, dynamic rheological and morphological properties of starch during hydrolysis was investigated. There was a significant increase in water solubility of starch due to modification; however, swelling and sedimentation value decrease after modification. The peak, hold and final viscosity of modified starches were decreased significantly as compared to native starch. Thermal properties and dynamic rheological properties of rice starch were changed with the change in time and temperature during modification. The storage (G') modulus, loss (G″) modulus, dynamic viscosity (η') and complex viscosity (η*) of modified starches were varied significantly. Analysis of microstructure revealed that the hydrolysis altered morphology of starch granules. The hydrolysis was affected the surface properties and granule size of rice starch. These results suggested that 1-butanol-HCl hydrolysis of glutinous rice starch can be a preferred way of modification. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Modification of sensing properties of metallophthalocyanine by an ECR plasma

    Energy Technology Data Exchange (ETDEWEB)

    Naddaf, M.; Chakane, S.; Jain, S.; Bhoraskar, S.V. E-mail: svb@physics.unipune.ernet.in; Mandale, A.B

    2002-07-01

    Lead Phthalocyanine (PC) tetracarboxylic acid prepared by chemical reaction from phthalic anhydride and urea was used as sensor element for sensing humidity and alcohol vapors. The surface was treated with electron cyclotron resonance (ECR) plasma consisting of 25% H{sub 2} and 75% N{sub 2}. Remarkable improvement in the selectivity with respect to ethyl alcohol and reduction in the sensitivity for humidity was observed after this treatment. The response and recovery time for resistive sensing were of the order of 50 and 30 s respectively. X-ray photoelectron spectroscopy and Fourier transformation infra red studies showed that the increased cross-linking of PC is responsible for the creation of new functional groups which have imparted the sensing of alcohol vapor through extrinsic doping.

  15. Two-chamber configuration of Bio-Nano electron cyclotron resonance ion source for fullerene modification

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, T., E-mail: uchida-t@toyo.jp [Bio-Nano Electronics Research Centre, Toyo University, Kawagoe 350-8585 (Japan); Graduate School of Interdisciplinary New Science, Toyo University, Kawagoe 350-8585 (Japan); Rácz, R.; Biri, S. [Institute for Nuclear Research (Atomki), Hungarian Academy of Sciences, Bem tér 18/C, H-4026 Debrecen (Hungary); Muramatsu, M.; Kitagawa, A. [National Institute of Radiological Sciences (NIRS), Chiba 263-8555 (Japan); Kato, Y. [Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan); Yoshida, Y. [Bio-Nano Electronics Research Centre, Toyo University, Kawagoe 350-8585 (Japan); Faculty of Science and Engineering, Toyo University, Kawagoe 350-8585 (Japan)

    2016-02-15

    We report on the modification of fullerenes with iron and chlorine using two individually controllable plasmas in the Bio-Nano electron cyclotron resonance ion source (ECRIS). One of the plasmas is composed of fullerene and the other one is composed of iron and chlorine. The online ion beam analysis allows one to investigate the rate of the vapor-phase collisional modification process in the ECRIS, while the offline analyses (e.g., liquid chromatography-mass spectrometry) of the materials deposited on the plasma chamber can give information on the surface-type process. Both analytical methods show the presence of modified fullerenes such as fullerene-chlorine, fullerene-iron, and fullerene-chlorine-iron.

  16. Two-chamber configuration of Bio-Nano electron cyclotron resonance ion source for fullerene modification.

    Science.gov (United States)

    Uchida, T; Rácz, R; Muramatsu, M; Kato, Y; Kitagawa, A; Biri, S; Yoshida, Y

    2016-02-01

    We report on the modification of fullerenes with iron and chlorine using two individually controllable plasmas in the Bio-Nano electron cyclotron resonance ion source (ECRIS). One of the plasmas is composed of fullerene and the other one is composed of iron and chlorine. The online ion beam analysis allows one to investigate the rate of the vapor-phase collisional modification process in the ECRIS, while the offline analyses (e.g., liquid chromatography-mass spectrometry) of the materials deposited on the plasma chamber can give information on the surface-type process. Both analytical methods show the presence of modified fullerenes such as fullerene-chlorine, fullerene-iron, and fullerene-chlorine-iron.

  17. Modification of gas diffusion layers properties to improve water management

    Directory of Open Access Journals (Sweden)

    Martin Tomas

    2017-09-01

    Full Text Available Abstract In this paper we report an approach to improve water management of commercial GDLs by introducing hydrophobicity patterns. Specifically, line and grid patterns have been created in the MPL side by laser radiation. For an in-depth investigation of these modified GDLs the current density distribution was monitored during fuel cell operation. Additionally, the physical properties of these materials were investigated by a number of ex situ methods such as Fourier transform infrared microscopy, electrochemical impedance spectroscopy and water vapor sorption. Furthermore, a comparison of the physical properties of the patterned GDLs with chemically modified GDLs (treated in H2SO4 and H2O2 is provided. Our results show a clearly improved homogeneity of current density distribution of the patterned GDLs compared to untreated GDLs. This observation is likely due to a reduced local hydrophobicity which facilitates water diffusion along the flow field of the fuel cell. However, performance of the fuel cell was not affected by the MPL irradiation. Graphical Abstract

  18. TANNED LEATHERS PROPERTIES MODIFICATION AS A RESULT OF ARTIFICIAL AGEING

    Directory of Open Access Journals (Sweden)

    ROŞU Dan

    2017-05-01

    Full Text Available Leather is a high tech material with different application fields, such as automotive, manufacturing of leatherwear articles or clothing and footwear. Leather is a biomaterial obtained by processing animal skins. Unfortunately, raw animal hides are practically inutilizable, due to their microbiological instability and are affected by rotting. Microbiological stability is achieved by tanning, when the protein is crosslinked, followed by drying. After crosslinking and drying, the new material shows the required properties of sustainability, availability and an esthetically pleasing aspect to the touch, making it available across its entire range of applications. From a structural point of view the animal skins are constituted of collagen, which is a fibrilar protein with a high degree of supramolecular organization in triple helix form that endows softness, elasticity and mechanical strength. High quality standards and lack of toxicity are required in all cases. Leather colour changes during exposure to light radiations are considered a consequence of the presence of some products with weak photochemical resistance during fabrication. The study aims to compare changes in properties of leathers obtained using mineral tanning agents such as Cr III salts and those obtained with the more environment-friendly technology using acid hydrolysis. Accelerated aging studies were conducted on tanned leathers by exposing the samples to UV radiation with different irradiation doses and two wavelengths (254 and 365 nm under controlled humidity and temperature conditions. Structural changes caused by irradiation were studied by FTIR. Colour changes on the sample surfaces were assessed during irradiation with the CIEL a*b* system. The colour parameters variation (L*, a*, b* and colour differences have been discussed in correlation with structural changes, tanning method and irradiation conditions.

  19. The Tuning of Optical Properties of Nanoscale MOFs-Based Thin Film through Post-Modification.

    Science.gov (United States)

    Yin, Wenchang; Tao, Cheng-An; Zou, Xiaorong; Wang, Fang; Qu, Tianlian; Wang, Jianfang

    2017-08-29

    Optical properties, which determine the application of optical devices in different fields, are the most significant properties of optical thin films. In recent years, Metal-organic framework (MOF)-based optical thin films have attracted increasing attention because of their novel optical properties and important potential applications in optical and photoelectric devices, especially optical thin films with tunable optical properties. This study reports the first example of tuning the optical properties of a MOF-based optical thin film via post-modification. The MOF-based optical thin film was composed of NH₂-MIL-53(Al) nanorods (NRs) (MIL: Materials from Institute Lavoisier), and was constructed via a spin-coating method. Three aldehydes with different lengths of carbon chains were chosen to modify the MOF optical thin film to tune their optical properties. After post-modification, the structural color of the NH₂-MIL-53(Al) thin film showed an obvious change from purple to bluish violet and cyan. The reflection spectrum and the reflectivity also altered in different degrees. The effective refractive index (neff) of MOFs thin film can also be tuned from 1.292 to 1.424 at a wavelength of 750 nm. The success of tuning of the optical properties of MOFs thin films through post-modification will make MOFs optical thin films meet different needs of optical properties in various optical and optoelectronic devices.

  20. Fatigue Properties of SUS304 Stainless Steel after Ultrasonic Nanocrystal Surface Modification (unsm)

    Science.gov (United States)

    Zhang, K. Y.; Pyoun, Y. S.; Cao, X. J.; Wu, B.; Murakami, R.

    The changing of materials surface properties method always was taken into improving the fatigue strength. In this paper, an ultrasonic nanocrystal surface modification(UNSM) technique was used on the SUS 304 stainless steel to form a nanostructured surface layer with different static load(70N, 90N, 110N, 130N) and the vibration strike number was about 20,000times/mm2. The untreated and different condition specimens fatigue strength was all tested by a dual-spindle rotating bending fatigue test machine. SPring-8(a large synchrotron radiation facility) was used to test the surface nanocrystallization components. The X-ray diffraction (XRD), the scanning electron microscopy (SEM), optical microscope and a micro-Vickers hardness tester (MVK-E3, Akashi) were separately used to get the surface residual stresses, fracture surface after fatigue testing, metallographic structure and the microhardness of the nanostructured surface layer. The result showed that martensite transformation took place on the surface of specimens, the surface residual stresses had only a small increase and some cracks occurred between the martensite layer and the austenite layer, but the fatigue strength of 90N improved 81%.

  1. Modification of PLGA Nanofibrous Mats by Electron Beam Irradiation for Soft Tissue Regeneration

    Directory of Open Access Journals (Sweden)

    Jae Baek Lee

    2015-01-01

    Full Text Available Biodegradable poly(lactide-co-glycolide (PLGA has found widespread use in modern medical practice. However, the degradation rate of PLGA should be adjusted for specific biomedical applications such as tissue engineering, drug delivery, and surgical implantation. This study focused on the effect of electron beam radiation on nanofibrous PLGA mats in terms of physical properties and degradation behavior with cell proliferation. PLGA nanofiber mats were prepared by electrospinning, and electron beam was irradiated at doses of 50, 100, 150, 200, 250, and 300 kGy. PLGA mats showed dimensional integrity after electron beam irradiation without change of fiber diameter. The degradation behavior of a control PLGA nanofiber (0 kGy and electron beam-irradiated PLGA nanofibers was analyzed by measuring the molecular weight, weight loss, change of chemical structure, and fibrous morphology. The molecular weight of the PLGA nanofibers decreased with increasing electron beam radiation dose. The mechanical properties of the PLGA nanofibrous mats were decreased with increasing electron beam irradiation dose. Cell proliferation behavior on all electron beam irradiated PLGA mats was similar to the control PLGA mats. Electron beam irradiation of PLGA nanofibrous mats is a potentially useful approach for modulating the biodegradation rate of tissue-specific nonwoven nanofibrous scaffolds, specifically for soft tissue engineering applications.

  2. Modification of polyvinyl alcohol surface properties by ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Pukhova, I.V., E-mail: ivpuhova@mail.ru [National Research Tomsk State University, 36 Lenin Ave, Tomsk 634050 (Russian Federation); Institute of High Current Electronics, 2/3 Akademichesky Ave, Tomsk 634055 (Russian Federation); Kurzina, I.A. [National Research Tomsk State University, 36 Lenin Ave, Tomsk 634050 (Russian Federation); Savkin, K.P. [Institute of High Current Electronics, 2/3 Akademichesky Ave, Tomsk 634055 (Russian Federation); Laput, O.A. [National Research Tomsk Polytechnic University, 30 Lenin Ave, Tomsk 634050 (Russian Federation); Oks, E.M. [Institute of High Current Electronics, 2/3 Akademichesky Ave, Tomsk 634055 (Russian Federation)

    2017-05-15

    We describe our investigations of the surface physicochemical properties of polyvinyl alcohol modified by silver, argon and carbon ion implantation to doses of 1 × 10{sup 14}, 1 × 10{sup 15} and 1 × 10{sup 16} ion/cm{sup 2} and energies of 20 keV (for C and Ar) and 40 keV (for Ag). Infrared spectroscopy (IRS) indicates that destructive processes accompanied by chemical bond (−C=O) generation are induced by implantation, and X-ray photoelectron spectroscopy (XPS) analysis indicates that the implanted silver is in a metallic Ag3d state without stable chemical bond formation with polymer chains. Ion implantation is found to affect the surface energy: the polar component increases while the dispersion part decreases with increasing implantation dose. Surface roughness is greater after ion implantation and the hydrophobicity increases with increasing dose, for all ion species. We find that ion implantation of Ag, Ar and C leads to a reduction in the polymer microhardness by a factor of five, while the surface electrical resistivity declines modestly.

  3. Influence of titanium dioxide modification on the antibacterial properties

    Directory of Open Access Journals (Sweden)

    Rokicka Paulina

    2016-12-01

    Full Text Available Antibacterial properties of 15 titania photocatalysts, mono- and dual-modified with nitrogen and carbon were examined. Amorphous TiO2, supplied by Azoty Group Chemical Factory Police S.A., was used as titania source (Ar-TiO2, C-TiO2, N-TiO2 and N,C-TiO2 calcined at 300°C, 400°C, 500°C, 600°C, 700°C. The disinfection ability was examined against Escherichia coli K12 under irradiation with UV and artificial sunlight and in dark conditions. It has been found the development of new photocatalysts with enhanced interaction ability with microorganisms might be a useful strategy to improve disinfection method conducted under artificial sunlight irradiation. The efficiency of disinfection process conducted under artificial sunlight irradiation with carbon (C-TiO2 and carbon/nitrogen (N,C-TiO2 photocatalysts was similar as obtained under UV irradiation. Furthermore, during dark incubation, any toxicity of the photocatalyst was noted.

  4. Modification of the electronic transport in Au by prototypical impurities and interlayers

    KAUST Repository

    Fadlallah, Majida M.

    2010-02-01

    Electronic transport calculations for metallic interfaces based on density functional theory and a scattering theory on the Landauer-Büttiker level are presented. We study the modifications of the transport through Au due to prototypical impurities and interlayers. Our results show that the influence of S and Si impurities is well described in terms of simple vacancies. Metallic impurities and interlayers, on the other hand, have even more drastic effects, in particular when the Au s-d hybrid states at the Fermi energy are perturbed. The effects of a possible interface alloy formation are discussed in detail. © 2010 EPLA.

  5. Surface electronic excitations and dynamic spectral properties of adsorbates

    Science.gov (United States)

    Gumhalter, B.

    Many-body aspects of screening and relaxation mechanisms encountered in spectroscopic studies of the electronic structure of adsorbates have recently attracted considerable attention from both experimental and theoretical physicists. Interest in these phenomena has also been augmented by the rapid improvement of experimental techniques which have enabled better resolution and analysis of various subtile components of the adsorbate spectra. Many of these spectral features have until recently been ascribed to purely chemical and initial state effects. One of the first major advances of the theoretical development in this field was to seek and attribute the origin of these structures to the many-body properties of adsorption systems and, secondly, to predict how the many-body effects would manifest themselves in surface spectroscopies. We start with a rather detailed description of the formalism of the surface electronic response and discuss the properties of the surface excitation spectrum of idealized and real metals. This formalism is then successively applied to set up a model of screening firstly in the nonbonding levels of mainly physisorbed adsorbates and later in the core and valence levels of chemisorbed species. Various modifications of the model enable a dynamic description of the final state relaxation and shake-up effects typical of spectroscopic measurements. To treat the particularly complicated problem of dynamic relaxation in the adsorbate valence levels a special perturbational approach based on Mayer's cluster expansion is developed in §5. The characteristics, and some limitations of this approach, which may also prove useful in other physical problems, are described in detail and discussed within the context of the interaction of localized adsorbate charge fluctuations with bosonic surface excitations. Experimental support for the presented theoretical framework and its applications has been very important. A qualitative comparison with the

  6. Base Release and Modification in Solid-Phase DNA Exposed to Low-Energy Electrons.

    Science.gov (United States)

    Choofong, Surakarn; Cloutier, Pierre; Sanche, Léon; Wagner, J Richard

    2016-11-01

    Ionization generates a large number of secondary low-energy electrons (LEEs) with a most probable energy of approximately 10 eV, which can break DNA bonds by dissociative electron attachment (DEA) and lead to DNA damage. In this study, we investigated radiation damage to dry DNA induced by X rays (1.5 keV) alone on a glass substrate or X rays combined with extra LEEs (average energy of 5.8 eV) emitted from a tantalum (Ta) substrate under an atmosphere of N2 and standard ambient conditions of temperature and pressure. The targets included calf-thymus DNA and double-stranded synthetic oligonucleotides. We developed analytical methods to measure the release of non-modified DNA bases from DNA and the formation of several base modifications by LC-MS/MS with isotopic dilution for precise quantification. The results show that the yield of non-modified bases as well as base modifications increase by 20-30% when DNA is deposited on a Ta substrate compared to that on a glass substrate. The order of base release (Gua > Ade > Thy ∼ Cyt) agrees well with several theoretical studies indicating that Gua is the most susceptible site toward sugar-phosphate cleavage. The formation of DNA damage by LEEs is explained by DEA leading to the release of non-modified bases involving the initial cleavage of N1-C1', C3'-O3' or C5'-O5' bonds. The yield of base modifications was lower than the release of non-modified bases. The main LEE-induced base modifications include 5,6-dihydrothymine (5,6-dHT), 5,6-dihydrouracil (5-dHU), 5-hydroxymethyluracil (5-HmU) and 5-formyluracil (5-ForU). The formation of base modifications by LEEs can be explained by DEA and cleavage of the C-H bond of the methyl group of Thy (giving 5-HmU and 5-ForU) and by secondary reactions of H atoms and hydride anions that are generated by primary LEE reactions followed by subsequent reaction with Cyt and Thy (giving 5,6-dHU and 5,6-dHT).

  7. Simultaneous Top and Bottom Perovskite Interface Engineering by Fullerene Surface Modification of Titanium Dioxide as Electron Transport Layer.

    Science.gov (United States)

    Ciro, John; Mesa, Santiago; Montoya, Juan Felipe; Uribe, José Ignacio; Betancur, Rafael; Jaramillo, Franklin

    2017-09-06

    Optimization of the interface between the electron transport layer (ETL) and the hybrid perovskite is crucial to achieve high-performance perovskite solar cell (PSC) devices. Fullerene-based compounds have attracted attention as modifiers on the surface properties of TiO 2 , the archetypal ETL in regular n-i-p PSCs. However, the partial solubility of fullerenes in the aprotic solvents used for perovskite deposition hinders its application to low-temperature solution-processed PSCs. In this work, we introduce a new method for fullerene modification of TiO 2 layers derived from nanoparticles (NPs) inks. Atomic force microscopy characterization reveals that the resulting ETL is a network of TiO 2 -NPs interconnected by fullerenes. Interestingly, this surface modification enhances the bottom interface of the perovskite by improving the charge transfer as well as the top perovskite interface by reducing surface trap states enhancing the contact with the p-type buffer layer. As a result, rigid PSCs reached a 17.2% power conversion efficiency (PCE), while flexible PSCs exhibited a remarkable stabilized PCE of 12.2% demonstrating the potential application of this approach for further scale-up of PSC devices.

  8. Electronic excitation induced structural and optical modifications in InGaN/GaN quantum well structures grown by MOCVD

    Science.gov (United States)

    Prabakaran, K.; Ramesh, R.; Jayasakthi, M.; Surender, S.; Pradeep, S.; Balaji, M.; Asokan, K.; Baskar, K.

    2017-03-01

    The present study focuses on the electronic excitation induced structural and optical properties of InGaN/GaN quantum well (QW) structures grown by metal organic chemical vapor deposition technique. These excitations were produced using Au7+ ion irradiation with 100 MeV energy. The X-ray rocking curves intensity and full width at half-maximum values corresponding to the planes of (0 0 0 2) and (1 0 -1 5) of the irradiated QW structures show the modifications in the screw and edge-type dislocation densities vary with the ion fluences. The structural characteristics using the reciprocal space mapping indicate the intermixing effects in InGaN/GaN QW structures. Atomic force microscopy images confirmed the presence of nanostructures and the surface modification due to heavy ion irradiation. The irradiated QW structures exhibited degraded photoluminescence intensity and a subsequent decrease in the yellow luminescence band intensity with the fluences of 1 × 1011 and 5 × 1012 ions/cm2 compared to the pristine QW structures.

  9. Electronic properties of asymmetrical quantum dots dressed by laser field

    Energy Technology Data Exchange (ETDEWEB)

    Kibis, O.V. [Department of Applied and Theoretical Physics, Novosibirsk State Technical University, Karl Marx Avenue 20, 630092 Novosibirsk (Russian Federation); Slepyan, G.Ya.; Maksimenko, S.A. [Institute for Nuclear Problems, Belarus State University, Bobruyskaya St. 11, 220050 Minsk (Belarus); Hoffmann, A. [Institut fuer Festkoerperphysik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)

    2012-05-15

    In the present paper, we demonstrate theoretically that the strong non-resonant interaction between asymmetrical quantum dots (QDs) and a laser field results in harmonic oscillations of their band gap. It is shown that such oscillations change the spectrum of elementary electron excitations in QDs: in the absence of the laser pumping there is only one resonant electron frequency, but QDs dressed by the laser field have a set of electron resonant frequencies. One expects that this modification of elementary electron excitations in QDs can be observable in optical experiments. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Surface Modification and Alloying of Aluminum and Titanium Alloys with Low-Energy, High-Current Electron Beams

    Directory of Open Access Journals (Sweden)

    V. P. Rotshtein

    2011-01-01

    Full Text Available The paper reviews the results of investigations of surface modification and alloying of Al, Ti, and its alloys with a low-energy (up to ~40 keV, high-current (up to 25 J/cm2 electron beams of microsecond duration under systematically varied conditions. The microstructural evolution of the surface layers of Al alloys (Al2024 and Al6061 and Ti-6Al-4V alloy subjected to pulsed melting as well as changes in surface-sensitive properties of these alloys are considered. Phase formation and properties of Al-based and Ti-based surface alloys, synthesized by liquid-phase mixing of multilayer film-substrate systems in wide range of solid solubility, including [Al/Si]/Al, [Al/C]/Al, [Zr/Ti]/Ti-6Al-4V, and Al/Ti, are studied. In case of Ti-based substrates, this method allows to fabricate the single-phase nanocrystalline α-(TiZr surface alloy, free of Al and V, as well as nanosized and ultrafine grain TiAl/Ti3Al-based surface alloys of thickness ≥3 μm with enhanced mechanical properties.

  11. Surface modification of silica particles and its effects on cure and mechanical properties of the natural rubber composites

    Energy Technology Data Exchange (ETDEWEB)

    Theppradit, Thawinan [Program in Petrochemistry and Polymer Science, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Prasassarakich, Pattarapan [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Poompradub, Sirilux, E-mail: sirilux.p@chula.ac.th [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand)

    2014-12-15

    The efficiency of modified silica (SiO{sub 2}) particles in the reinforcement of natural rubber (NR) vulcanizates was evaluated. The SiO{sub 2} particles were synthesized via a sol–gel reaction using tetraethyl orthosilicate as the precursor, and then the formed SiO{sub 2} particles were modified with methyl, vinyl or aminopropyl groups using methyltriethoxysilane, vinyltriethoxysilane or aminopropyltrimethoxysilane, respectively. Fourier transform infrared spectroscopy and elemental analysis confirmed the successful modification of the surface of the silica particles. The water contact angle measurement revealed the greater hydrophobicity of the three modified silica preparations compared to the unmodified SiO{sub 2}. NR vulcanizates filled with modified SiO{sub 2} particles were prepared and the mechanical, thermal and dynamic mechanical properties of composites were investigated. The morphology of composite materials was also investigated by scanning electron microscopy. The modified SiO{sub 2} particles were well dispersed in the NR matrix leading to the good compatibility between the rubber and filler, and so an improved cure, mechanical, thermal and dynamic mechanical properties of the composite vulcanizate materials. - Highlights: • Modification of SiO{sub 2} particles by MTES, VTES and APTES. • Improvement of hydrophobicity of SiO{sub 2} particle and compatibility between SiO{sub 2} and rubbery matrix. • Improvement of cure, mechanical, thermal, dynamic mechanical properties of NR vulcanizates.

  12. [Research on surface modification and bio-tribological properties of artificial joint].

    Science.gov (United States)

    Pan, Yusong; Wang, Jing; Ding, Guoxin

    2012-06-01

    The bio-tribological properties of an artificial joint can be obviously improved by surface modification technologies. In this paper, the benefits and disadvantages of various surface modification methods-such as surface coating, plasma treatment, surface texture and surface grafting modification-are discussed. The aim of surface coating and/or plasma treatment is to improve the surface hardness of the materials, thus enhancing the wear resistance of artificial joints. However, these technologies do not effectively alleviate stress concentration of material in the short times in which artificial joints bear physiological impact load, resulting in easy fracture. Surface texture serves mainly to improve the lubrication properties through micro-concavities on the material surface for storage lubricant. Surface texturing can realize improvements in bio-tribological properties, but it does not enhance the impact resistance of the joint. Surface grafting modification is implemented mainly by grafting hydrophilic or other specific functional groups to improve the surface hydrophilicity and wetability, thus enhancing lubricating performance and reducing the coefficient of friction.

  13. Modification of optical and electrical properties of chemical bath deposited CdS using plasma treatments

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, G. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Krishnan, B. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Avellaneda, D.; Castillo, G. Alan; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Shaji, S., E-mail: sshajis@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

    2011-08-31

    Cadmium sulphide (CdS) is a well known n-type semiconductor that is widely used in solar cells. Here we report preparation and characterization of chemical bath deposited CdS thin films and modification of their optical and electrical properties using plasma treatments. CdS thin films were prepared from a chemical bath containing Cadmium chloride, Triethanolamine and Thiourea under various deposition conditions. Good quality thin films were obtained during deposition times of 5, 10 and 15 min. CdS thin films prepared for 10 min. were treated using a glow discharge plasma having nitrogen and argon carrier gases. The changes in morphology, optical and electrical properties of these plasma treated CdS thin films were analyzed in detail. The results obtained show that plasma treatment is an effective technique in modification of the optical and electrical properties of chemical bath deposited CdS thin films.

  14. Electron impact phenomena and the properties of gaseous ions

    CERN Document Server

    Field, F H; Massey, H S W; Brueckner, Keith A

    1970-01-01

    Electron Impact Phenomena and the Properties of Gaseous Ions, Revised Edition deals with data pertaining to electron impact and to molecular gaseous ionic phenomena. This book discusses electron impact phenomena in gases at low pressure that involve low-energy electrons, which result in ion formation. The text also describes the use of mass spectrometers in electron impact studies and the degree of accuracy obtained when measuring electron impact energies. This book also reviews relatively low speed electrons and the transitions that result in the ionization of the atomic system. This text the

  15. Structural and electronic properties of non-magnetic intermetallic ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 1. Structural and electronic properties of non-magnetic intermetallic YAuX (X = Ge and Si) in ... The calculated lattice parameters were in good agreement with experiment. Also, the structural and electronic properties of the non-magnetic half-Heusler YAuPb ...

  16. Opto-electronic properties of charged conjugated molecules

    NARCIS (Netherlands)

    Fratiloiu, S.

    2007-01-01

    The aim of this thesis is to provide fundamental insight into the nature and opto-electronic properties of charge carriers on conjugated oligomers and polymers. Electronic structure, optical absorption properties and distribution of charge carriers along the chains of different conjugated materials

  17. Ab initio electronic properties of dual phosphorus monolayers in silicon

    DEFF Research Database (Denmark)

    Drumm, Daniel W.; Per, Manolo C.; Budi, Akin

    2014-01-01

    , investigating the fundamental electronic properties of monolayer pairs. Quantitative band splittings and the electronic density are presented, along with effects of the layers’ relative alignment and comments on disordered systems, and for the first time, the effective electronic widths of such device...

  18. Exploiting the dynamic properties of covalent modification cycle for the design of synthetic analog biomolecular circuitry.

    Science.gov (United States)

    Foo, Mathias; Sawlekar, Rucha; Bates, Declan G

    2016-01-01

    Cycles of covalent modification are ubiquitous motifs in cellular signalling. Although such signalling cycles are implemented via a highly concise set of chemical reactions, they have been shown to be capable of producing multiple distinct input-output mapping behaviours - ultrasensitive, hyperbolic, signal-transducing and threshold-hyperbolic. In this paper, we show how the set of chemical reactions underlying covalent modification cycles can be exploited for the design of synthetic analog biomolecular circuitry. We show that biomolecular circuits based on the dynamics of covalent modification cycles allow (a) the computation of nonlinear operators using far fewer chemical reactions than purely abstract designs based on chemical reaction network theory, and (b) the design of nonlinear feedback controllers with strong performance and robustness properties. Our designs provide a more efficient route for translation of complex circuits and systems from chemical reactions to DNA strand displacement-based chemistry, thus facilitating their experimental implementation in future Synthetic Biology applications.

  19. Modification of titanium alloys surface properties by plasma electrolytic oxidation (PEO) and influence on biological response.

    Science.gov (United States)

    Echeverry-Rendón, Mónica; Galvis, Oscar; Aguirre, Robinson; Robledo, Sara; Castaño, Juan Guillermo; Echeverría, Félix

    2017-09-27

    Surface characteristics can mediate biological interaction improving or affecting the tissue integration after implantation of a biomaterial. Features such as topography, wettability, surface energy and chemistry can be key determinants for interactions between cells and materials. Plasma electrolytic oxidation (PEO) is a technique used to control this kind of parameters by the addition of chemical species and the production of different morphologies on the surfaces of titanium and its alloys. With the purpose to improve the biological response, surfaces of c.p titanium and Ti6Al4V were modified by using PEO. Different electrolytes, voltages, current densities and anodizing times were tested in order to obtain surfaces with different characteristics. The obtained materials were characterized by different techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and glow discharge optical emission spectroscopy (GDOES). Wettability of the obtained surfaces were measured and the corresponding surface energies were calculated. Superhydrophilic surfaces with contact angles of about 0 degrees were obtained without any other treatment but PEO and this condition in some cases remains stable after several weeks of anodizing; crystal phase composition (anatase-rutile) of the anodic surface appears to be critical for obtaining this property. Finally, in order to verify the biological effect of these surfaces, osteoblast were seeded on the samples. It was found that cell behavior improves as SFE (surface free energy) and coating porosity increases whereas it is affected negatively by roughness. Techniques for surface modification allow changes in the coatings such as surface energy, roughness and porosity. As a consequence of this, biological response can be altered. In this paper, surfaces of c.p Ti and Ti6Al4V were modified by using plasma electrolytic oxidation (PEO) in order to accelerate the cell adhesion process.

  20. Effects of deformation on the electronic properties of B-C-N nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Azevedo, S., E-mail: sazevedo@fisica.ufpb.br [Departamento de Fisica, Universidade Federal da Paraiba, Caixa Postal 5008, 58059-900 Joao Pessoa-PB (Brazil); Rosas, A. [Departamento de Fisica, Universidade Federal da Paraiba, Caixa Postal 5008, 58059-900 Joao Pessoa-PB (Brazil); Machado, M. [Departamento de Fisica, Universidade Federal de Pelotas, Caixa Postal 354, 96010-900 Pelotas-RS (Brazil); Kaschny, J.R. [Instituto Federal da Bahia-Campus Vitoria da Conquista, Av. Amazonas 3150, 45030-220 Vitoria da Conquista-BA (Brazil); Chacham, H. [Departamento de Fisica, ICEX, Universidade Federal de Minas Gerais, Caixa Postal 702, 30123-970 Belo Horizonte-MG (Brazil)

    2013-01-15

    We apply first-principles methods, using density functional theory, to investigate the effects of flattening deformation on the electronic properties of BC{sub 2}N and C-doped BNNTs. Four different types of BC{sub 2}N structures are considered. Two of them are semiconductors, and the radial compression produces a significant reduction of the energy band gap. The other two types of structures are metallic, and the effect of radial compression is quite distinct. For one of them it is found the opening of a small band gap, and for the other one no changes are observed. For C-doped tubes, it is also found that the electronic properties undergo significant modifications when subjected to radial compression. - Graphical Abstract: We apply first-principles methods, using density functional theory, to investigate the effects of flattening deformation on the electronic properties of BC{sub 2}N and C-doped BNNTs. Four different types of BC{sub 2}N structures are considered. Two of them are semiconductors, and the radial compression produces a significant reduction of the energy band gap. The other two types of structures are metallic, and the effect of radial compression is quite distinct. For one of them it is found the opening of a small band gap, and for the other one no changes are observed. For C-doped tubes, it is also found that the electronic properties undergo significant modifications when subjected to radial compression. Highlights: Black-Right-Pointing-Pointer We investigated electronic properties of flattened BC{sub 2}N nanotubes. Black-Right-Pointing-Pointer The electronic states depend strongly on compression. Black-Right-Pointing-Pointer It is studied flattened BN nanotubes doped with a carbon atom. Black-Right-Pointing-Pointer The flattened C-doped structures, presents a significant reduction of the gap.

  1. Plant cytoplasmic GAPDH: redox post-translational modifications and moonlighting properties

    Directory of Open Access Journals (Sweden)

    Mirko eZaffagnini

    2013-11-01

    Full Text Available Glyceraldehyde-3-phosphate dehydrogenase (GAPDH is a ubiquitous enzyme involved in glycolysis and shown, particularly in animal cells, to play additional roles in several unrelated non-metabolic processes such as control of gene expression and apoptosis. This functional versatility is regulated, in part at least, by redox post-translational modifications that alter GAPDH catalytic activity and influence the subcellular localization of the enzyme. In spite of the well established moonlighting (multifunctional properties of animal GAPDH, little is known about non-metabolic roles of GAPDH in plants. Plant cells contain several GAPDH isoforms with different catalytic and regulatory properties, located both in the cytoplasm and in plastids, and participating in glycolysis and the Calvin-Benson cycle. A general feature of all GAPDH proteins is the presence of an acidic catalytic cysteine in the active site that is overly sensitive to oxidative modifications, including glutathionylation and S-nitrosylation. In Arabidopsis, oxidatively-modified cytoplasmic GAPDH has been successfully used as a tool to investigate the role of reduced glutathione, thioredoxins and glutaredoxins in the control of different types of redox post-translational modifications. Oxidative modifications inhibit GAPDH activity, but might enable additional functions in plant cells. Mounting evidence support the concept that plant cytoplasmic GAPDH may fulfill alternative, non-metabolic functions that are triggered by redox post-translational modifications of the protein under stress conditions. The aim of this review is to detail the molecular mechanisms underlying the redox regulation of plant cytoplasmic GAPDH in the light of its crystal structure, and to provide a brief inventory of the well known redox-dependent multi-facetted properties of animal GAPDH, together with the emerging roles of oxidatively-modified GAPDH in stress signaling pathways in plants.

  2. Surface modification of additive manufactured metal products by an intense electron beam

    Science.gov (United States)

    Teresov, A. D.; Koval, N. N.; Ivanov, Yu F.; Petrikova, E. A.; Krysina, O. V.

    2017-11-01

    On the example of VT6 titanium alloy it is shown that successive surface modification of additive manufactured metal specimens in vacuum at an argon pressure of 3.5·10–2 by ten pulses with 200 μs, 45 J/cm2 and then by three pulses with 50 μm, 20 J/cm2 provides a considerable decrease in their porosity and surface roughness (20 times for Ra) while their surface microhardness, friction coefficient, and wear level remain almost unchanged. After electron beam irradiation, the ultimate tensile strength of the material increases 1.33 times, and its tensile strain 1.18 times. For specimens obtained by conventional metallurgy and irradiated in the same modes, no such effects are observed.

  3. Modification of static bending strength properties of Eucalyptus grandis heat-treated wood

    Directory of Open Access Journals (Sweden)

    Pedro Henrique Gonzalez de Cademartori

    2012-12-01

    Full Text Available The present study describes the effect of thermal rectification on physical and mechanical properties of Eucalyptus grandis wood at different levels of temperature and time. Samples of Eucalyptus grandis wood (10 × 10 × 200 mm were heat-treated at 180, 200, 220 and 240 °C during 4 and 8 hours. The mechanical properties of heat-treated and untreated samples were determined by static bending tests. The physical properties were determined by weight loss and swelling tests. The results showed that modulus of elasticity, modulus of rupture, weight loss, volumetric swelling and linear swelling were affected significantly by the thermal rectification. However, the length of exposure influenced just weight loss, while the temperature influenced all the studied properties of heat-treated wood. More significant modifications with treatments at a temperature of 200 °C or higher were found in the properties of heat-treated wood.

  4. Structure Modification toward Applicability Domain of a QSAR/QSPR Model Considering Activity/Property.

    Science.gov (United States)

    Ochi, Shoki; Miyao, Tomoyuki; Funatsu, Kimito

    2017-12-01

    In drug and material design, the activity and property values of the designed chemical structures can be predicted by quantitative structure-activity and structure-property relationship (QSAR/QSPR) models. When a QSAR/QSPR model is applied to chemical structures, its applicability domain (AD) must be considered. The predicted activity/property values are only reliable for chemical structures inside the AD. Chemical structures outside the AD are usually neglected, as the predicted values are unreliable. The purpose of this study is to develop a methodology for obtaining novel chemical structures with the desired activity or property based on a QSAR/QSPR model by making use of the neglected structures. We propose a structure modification strategy for the AD that considers the activity and property simultaneously. The AD is defined by a one-class support vector machine and the structure modification is guided by a partial derivative of the AD model and matched molecular pairs analysis. Three proof-of-concept case studies generate novel chemical structures inside the AD that exhibit preferable activity/property values according to the QSAR/QSPR model. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Surface Modification of Carbon Nanotubes with Conjugated Polyelectrolytes: Fundamental Interactions and Applications in Composite Materials, Nanofibers, Electronics, and Photovoltaics

    KAUST Repository

    Ezzeddine, Alaa

    2015-10-01

    Ever since their discovery, Carbon nanotubes (CNTs) have been renowned to be potential candidates for a variety of applications. Nevertheless, the difficulties accompanied with their dispersion and poor solubility in various solvents have hindered CNTs potential applications. As a result, studies have been developed to address the dispersion problem. The solution is in modifying the surfaces of the nanotubes covalently or non-covalently with a desired dispersant. Various materials have been employed for this purpose out of which polymers are the most common. Non-covalent functionalization of CNTs via polymer wrapping represents an attractive method to obtain a stable and homogenous CNTs dispersion. This method is able to change the surface properties of the nanotubes without destroying their intrinsic structure and preserving their properties. This thesis explores and studies the surface modification and solublization of pristine single and multiwalled carbon nanotubes via a simple solution mixing technique through non-covalent interactions of CNTs with various anionic and cationic conjugated polyelectrolytes (CPEs). The work includes studying the interaction of various poly(phenylene ethynylene) electrolytes with MWCNTs and an imidazolium functionalized poly(3-hexylthiophene) with SWCNTs. Our work here focuses on the noncovalent modifications of carbon nanotubes using novel CPEs in order to use these resulting CPE/CNT complexes in various applications. Upon modifying the CNTs with the CPEs, the resulting CPE/CNT complex has been proven to be easily dispersed in various organic and aqueous solution with excellent homogeneity and stability for several months. This complex was then used as a nanofiller and was dispersed in another polymer matrix (poly(methyl methacrylate), PMMA). The PMMA/CPE/CNT composite materials were cast or electrospun depending on their desired application. The presence of the CPE modified CNTs in the polymer matrix has been proven to enhance

  6. The effects of high electronic energy loss on the chemical modification of polyimide

    CERN Document Server

    SunYouMei; Jin Yun Fan; Liu Chang Long; LiuJie; Wang Zhi Guang; Zhang Qi; Zhu Zhi Yong

    2002-01-01

    In order to observe the role of electronic energy loss (dE/dX) sub e on chemical modification of polyimide (PI), the multi-layer stacks (corresponding to different dE/dX) were irradiated by different swift heavy ions (1.37 GeV Ar sup 4 sup 0 , 1.98 GeV Kr sup 8 sup 4 , 1.755 GeV Xe sup 1 sup 3 sup 6 and 2.636 GeV U sup 2 sup 3 sup 8) under vacuum and room temperature. The chemical changes of modified PI films were studied by Fourier transform infrared (FTIR) and ultraviolet/visible (UV/Vis) absorption spectroscopy. The degradation of PI was investigated in the fluence range from 1x10 sup 1 sup 0 to 5.5x10 sup 1 sup 2 ions/cm sup 2 and different electronic energy loss from 0.77 to 11.5 keV/nm. The FTIR results show the absorbance of the typical function group decrease exponentially as a function of fluence. The alkyne end group was found after irradiation and its formation radii were 5.6 and 5.9 nm corresponding to 8.8 and 11.5 keV/nm Xe irradiation respectively. UV/Vis analysis indicates the radiation induced...

  7. Optical and electrical properties of vanadium pentoxide xerogel films: modification in electric field and the role of ion transport

    Energy Technology Data Exchange (ETDEWEB)

    Pergament, A.L.; Kazakova, E.L.; Stefanovich, G.B. [Petrozavodsk State University, Petrozavodsk (Russian Federation)

    2002-09-07

    Reversible modification of the optical and electrical properties of V{sub 2}O{sub 5}xnH{sub 2}O gel films under the action of an electric field is studied. It is shown that under cathodic polarization (I=10{sup -6}-10{sup -5} A, t{approx}10min, film thickness {approx}10 {mu}m), the films turn from brownish-yellow to red. This internal electrochromic (EC) effect is caused by the redistribution of hydrogen ions inside the film, instead of insertion from the outside (from an electrolyte). A local increase in the hydrogen concentration occurs near the cathode, and this in turn results in modification of the optical properties. The rise of transmittance in the long-wavelength region of the spectrum, as well as the shift of the absorption edge near h{nu}{approx}2.5eV towards longer wavelengths, is observed. In addition, according to the infrared data, some increase in water content also contributes to the process of colouration. The change in the optical properties is accompanied by a change in the electrical properties, namely, an increase in ionic conductivity from {approx}4x10{sup -5} to 10{sup -4}{omega}{sup -1} cm{sup -1}. At higher currents, electroforming resulting from the transport of oxygen ions occurs. This process leads to the formation of a channel consisting of vanadium dioxide due to reduction of V{sub 2}O{sub 5} to VO{sub 2}. Electrical switching with the S-type negative resistance, associated with an electrothermally driven metal-insulator transition in the channel, is observed in the sandwich M/V{sub 2}O{sub 5}xnH{sub 2}O/M devices (unlike the planar devices described in the literature). Finally, applied potentialities of these phenomena for micro- and opto-electronics (EC devices, sensors) are discussed. (author)

  8. Modulating the electronic and optical properties of monolayer arsenene phases by organic molecular doping

    Science.gov (United States)

    Singh, Deobrat; Gupta, Sanjeev K.; Sonvane, Yogesh; Sahoo, Satyaprakash

    2017-12-01

    Recently, arsenene monolayer structure of the arsenic with two phases has displayed semiconducting behavior. We have systematically investigated the electronic and optical properties of single-layer arsenene with two types of functionalized organic molecules; an electrophilic molecule [tetracyanoquinodimethane (TCNQ)] and a nucleophilic molecule [tetrathiafulvalene (TTF)], as an electron acceptor and electron donor, respectively. The interfacial charge transfer between the arsenene monolayer and TCNQ/TTF molecules extensively reduces the band gap of arsenene and accordingly resulted in a p- or n-type semiconducting behavior, respectively. We have also performed the interfacial charge transfer from organic molecules to monolayer arsenene and vice versa. The interfacial surface molecular modification has established an efficient way to develop the light harvesting of arsenene in different polarization directions. Our theoretical investigation suggests that such n- and p-type arsenene semiconductors would broaden the applications in the field of nanoelectronic and optoelectronic devices such as photodiodes and it is also useful for constructing functional electronic systems.

  9. Electronic properties of magnetically doped nanotubes

    Indian Academy of Sciences (India)

    Unknown

    body of publications since their discovery in 1991 (Iijima. 1991). Recent experimental (Lee et al 1997; Rao et al. 1997; Grigorian et al 1998a, b) and theoretical (Miya- moto et al 1995; Esfarjani et al 1999) studies on doping nanotubes focused on doping by alkali metal or halogene elements as electron donors or acceptors, ...

  10. Electronic properties of magnetically doped nanotubes

    Indian Academy of Sciences (India)

    Effect of doping of carbon nanotubes by magnetic transition metal atoms has been considered in this paper. In the case of semiconducting tubes, it was found that the system has zero magnetization, whereas in metallic tubes the valence electrons of the tube screen the magnetization of the dopants: the coupling to the tube ...

  11. Nanofiller Modification and Incorporation into Fluoropolymer Nanocomposites and the Properties thereof

    Science.gov (United States)

    Khajehpour, Maryam

    Polymer nanocomposites (PNC) are of great interest owing to the many potential property enhancements possible via introducing different types of nanofillers in polymer matrices. In recent decades, increasing attention has being paid to PNCs due to their light weight, low cost, and ease of processability compared to metal alternatives and due to their novel capability to tune properties. Depending on the end-use application, certain PNCs properties are targeted and the PNC formulation and processing can be manipulated to achieve the desired properties. In this PhD thesis, different PNC properties have been improved by employing different strategies: (1) modification of nanofillers, (2) synthesis of novel nanofillers, (3) implementation of hybrid fillers, and (4) amendment of PNC production methods. For nanofiller modification, chemical treatment of nanoclay, multiwall carbon nanotube (MWCNT) and graphene nanoribbon (GNR) were performed. For the second strategy, GNR was synthesized from parent MWCNT to benefit from higher surface area and interaction of the novel nanofillers with the polymer chains. The main objective of these two strategies is to improve the affinity and dispersion of nanofillers in the host polymer to enhance PNC properties. Utilizing a secondary filler to further enhance the desired properties was the third strategy and was accomplished via a hybrid filler PNC consisting of MWCNT and nanoclay. Finally, the fourth strategy was to develop optimized PNC production methods. The aim of the last two strategies was to obtain an improved morphology for the nanocomposite and it is well known that nanocomposite structure can be used to control the final PNC properties.

  12. Modification of the Selectivity Properties of Tubular Ceramic Membranes after Alkaline Treatment

    Directory of Open Access Journals (Sweden)

    Patrick Dutournié

    2017-11-01

    Full Text Available This work focuses on the selectivity modification of ceramic membranes after a mild alkaline treatment. Filtration of pure salt-water solutions was carried out with commercial titania membranes before and after the treatment. After treatment, the rejection of NaF significantly decreased, while the rejection of NaCl and NaBr increased. Additionally, NaI and Na2SO4 remained close to zero. Pore size and electrical charge being almost unchanged, only significant modifications in the dielectric effects can explain this modification of selectivity. Therefore, the surface chemistry and the interaction (nature and magnitude with the solvent and with the species present in the solution appear to be modified by the alkaline treatment. This trend is also illustrated by discussing the electric and the dielectric properties that were numerically identified before and after treatment. The alkaline treatment significantly decreased the apparent dielectric constant of NaCl-water solution in the pore, highlighting the rejection of sodium chloride. Contrariwise, the modification of the surface chemistry increased the apparent dielectric constant of NaF-water solution by promoting fluoride transmission.

  13. Size-dependent electronic properties of metal nanostructures

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Size-dependent electronic properties of metal nanostructures. G.U. Kulkarni. Chemistry and Physics of Materials Unit. Jawaharlal Nehru Centre for Advanced Scientific Research. Bangalore, India. kulkarni@jncasr.ac.in.

  14. Electronic excitation induced modification in fullerene C{sub 70} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Pooja [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Singhal, R., E-mail: rsinghal.phy@mnit.ac.in [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Banerjee, M.K. [Department of Metallurgical & Materials Engineering, Malaviya National Institute of Technology, Jaipur 302017 (India); Vishnoi, R. [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Department of Physics, Vardhman - PG College, Bijnor 246701, UP (India); Kaushik, R. [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Department of Physics, Shri K.K. Jain - PG College, Khatauli, UP (India); Singh, F. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2016-07-15

    Fullerene C{sub 70} thin films were deposited by resistive heating on glass substrates and the thickness were approximated to be 150 nm. The effect of energy deposition by 55 MeV Si ions on the optical and structural properties of the prepared thin film samples is investigated. The samples were irradiated with 55 MeV Si ions within fluence range from 1 × 10{sup 12} to 3 × 10{sup 13} ions/cm{sup 2}. For optical studies, the pristine and the Si ion irradiated samples are examined by UV–visible absorption spectroscopy and Raman spectroscopy. UV–visible absorption studies reveal that the absorption peaks of irradiated samples decrease with a decrease in the band gap of the thin films. The damage cross-section (σ) and radius of damaged cylindrical zone (r) are determined as ∼0.6 × 10{sup −13} cm{sup 2} and ∼1.41 nm, respectively from the Raman spectra. Raman studies also suggest that at higher fluence (up to 3 × 10{sup 13} ions/cm{sup 2}), the damage caused by the SHI results in partial amorphization of fullerene C{sub 70} thin film. Modification in the surface properties has been investigated by atomic force microscopy; it has revealed that the roughness decreases and average particle size increases with the increase in fluences.

  15. Electron self-exchange and self-amplified posttranslational modification in the hemoglobins from Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002.

    Science.gov (United States)

    Preimesberger, Matthew R; Pond, Matthew P; Majumdar, Ananya; Lecomte, Juliette T J

    2012-04-01

    Many heme proteins undergo covalent attachment of the heme group to a protein side chain. Such posttranslational modifications alter the thermodynamic and chemical properties of the holoprotein. Their importance in biological processes makes them attractive targets for mechanistic studies. We have proposed a reductively driven mechanism for the covalent heme attachment in the monomeric hemoglobins produced by the cyanobacteria Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803 (GlbN) (Nothnagel et al. in J Biol Inorg Chem 16:539-552, 2011). These GlbNs coordinate the heme iron with two axial histidines, a feature that distinguishes them from most hemoglobins and conditions their redox properties. Here, we uncovered evidence for an electron exchange chain reaction leading to complete heme modification upon substoichiometric reduction of GlbN prepared in the ferric state. The GlbN electron self-exchange rate constants measured by NMR spectroscopy were on the order of 10(2)-10(3) M(-1) s(-1) and were consistent with the proposed autocatalytic process. NMR data on ferrous and ferric Synechococcus GlbN in solution indicated little dependence of the structure on the redox state of the iron or cross-link status of the heme group. This allowed the determination of lower bounds to the cross-exchange rate constants according to Marcus theory. The observations illustrate the ability of bishistidine hemoglobins to undergo facile interprotein electron transfer and the chemical relevance of such transfer for covalent heme attachment. © SBIC 2012

  16. Modification of optical and electrical properties of chemical bath deposited SnS using O{sub 2} plasma treatments

    Energy Technology Data Exchange (ETDEWEB)

    Gómez, A. [Facultad de Ciencias, Universidad Autónoma del Estado de México, Estado de México, México (Mexico); Martínez, H., E-mail: hm@fis.unam.mx [Instituto de Ciencias Fisicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251, Cuernavaca, Morelos (Mexico); Calixto-Rodríguez, M. [Centro de Investigación en Energía, Universidad Autónoma del Estado de México, Estado de México, México (Mexico); Avellaneda, D. [Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, México (Mexico); Reyes, P.G. [Facultad de Ciencias, Universidad Autónoma del Estado de México, Estado de México, México (Mexico); Flores, O. [Instituto de Ciencias Fisicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251, Cuernavaca, Morelos (Mexico)

    2013-06-15

    In this paper, we report modifications of structural and optical, electrical properties that occur in tin sulphide (SnS) treated in O{sub 2} plasma. The SnS thin films were deposited by chemical bath deposition technique. The samples were treated in an O{sub 2} plasma discharge at 3 Torr of pressure discharge, a discharge voltage of 2.5 kV and 20 mA of discharge current. The prepared and treated thin films were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The photoconductivity and electrical effects of SnS have been studied. The SnS thin films had an orthorhombic crystalline structure. With the plasma treatment the optical gap and electrical properties of the SnS films changed from 1.61 to 1.84 eV, for 3.9 × 10{sup 5} to 10.42 Ω cm, respectively. These changes can be attributed to an increase in electron density, percolation effects due to porosity, surface degradation/etching that is an increase in surface roughness, where some structural changes related to crystallinity occurs like a high grain size as revealed by SEM images.

  17. Electron heat capacity and lattice properties of Americium

    Science.gov (United States)

    Povzner, A. A.; Filanovich, A. N.; Os'kina, V. A.; Volkov, A. G.

    2013-12-01

    The temperature dependence of the electron heat capacity of americium is calculated using the concepts on the electronic structure and magnetic properties of this element. The Debye temperature, the thermal expansion coefficient, and the bulk modulus of americium are determined on the basis of the results of calculations and experimental data on heat capacity.

  18. Transport properties of copper phthalocyanine based organic electronic divices

    OpenAIRE

    Opitz, Andreas

    2010-01-01

    Transport properties of copper phthalocyanine based organic electronic divices / W. Brütting ... - In: Cooperative phenomena in solids with electronic correlations / Ed. by: U. Eckern ... - Les Ulis : EDP Sciences, 2010. - S. 117-134. - (The European physical journal : special topics ; 180)

  19. Electronic structure and properties of Cu2O

    OpenAIRE

    Ruiz Sabín, Eliseo; Álvarez, Santiago (Álvarez Reverter); Alemany i Cahner, Pere; Evarestov, R. A. (Robert Aleksandrovich)

    1997-01-01

    The structural and electronic properties of Cu2O have been investigated using the periodic Hartree-Fock method and a posteriori density-functional corrections. The lattice parameter, bulk modulus, and elastic constants have been calculated. The electronic structure of and bonding in Cu2O are analyzed and compared with x-ray photoelectron spectroscopy spectra, showing a good agreement for the valence-band states. To check the quality of the calculated electron density, static structure factors...

  20. Effect of thermal modification on the physical properties of juvenile and mature woods of Eucalyptus grandis

    Directory of Open Access Journals (Sweden)

    Fred Willians Calonego

    Full Text Available This study aimed to evaluate the effect of thermal treatment on the physical properties of juvenile and mature woods of Eucalyptus grandis. Boards were taken from 30-year-old E. grandis trees. The boards were thermally modified at 180 °C in the Laboratory of Wood Drying and Preservation at UNESP, Botucatu, Sao Paulo state, Brazil. The results showed that thermal modification caused: (1 decrease of 6.8% in the density at 0% equilibrium moisture content of mature wood; (2 significant decreases of 14.7% and 35.6% in the maximum volumetric swellings of juvenile and mature woods, respectively; (3 significant decreases of 13.7% and 21.3% in the equilibrium moisture content of juvenile and mature woods, respectively. The influence of thermal modification in juvenile wood was lower than in mature wood and caused greater uniformity in the physical variations between these types of wood in E. grandis.

  1. Electronic Properties of Quantum Wire Networks

    OpenAIRE

    Kuzmenko, Igor

    2005-01-01

    Quantum wire networks (``quantum crossbars'', QCB) represent a 2D grid formed by superimposed crossing arrays of parallel conducting quantum wires, molecular chains or metallic single-wall carbon nanotubes. QCB coupled only by capacitive interaction in the crosses have similar low-energy, long-wave properties characterized as a crossed sliding Luttinger liquid (CSLL) phase. In this Thesis we develop a theory of interacting Bose excitations (plasmons) in QCB. We analyze spectrum of boson field...

  2. State equations and properties of various polymorphous modifications of silicon and germanium

    Science.gov (United States)

    Magomedov, M. N.

    2017-06-01

    The state equations and the pressure dependences of the lattice properties have been obtained for various polymorphous modifications of silicon and germanium using the Mie-Lennard-Jones pair interatomic potential and the Einstein crystal model. It is shown that the elastic-type interatomic potential gives the best results for the semiconductor phase and the plastic-type interatomic potential for the metalized phases whose potential well depth is significantly smaller. The pressure dependences of the lattice properties are calculated along isotherm 300 K and the jumps of the properties during the phase transition from the diamond structure to the β-Sn phase are evaluated for both silicon and germanium. The calculated results agree well with the experimental data.

  3. Structure and thermodynamic properties of relativistic electron gases.

    Science.gov (United States)

    Liu, Yu; Wu, Jianzhong

    2014-07-01

    Relativistic effect is important in many quantum systems but theoretically complicated from both fundamental and practical perspectives. Herein we introduce an efficient computational procedure to predict the structure and energetic properties of relativistic quantum systems by mapping the Pauli principle into an effective pairwise-additive potential such that the properties of relativistic nonquantum systems can be readily predicted from conventional liquid-state methods. We applied our theoretical procedure to relativistic uniform electron gases and compared the pair correlation functions with those for systems of nonrelativistic electrons. A simple analytical expression has been developed to correlate the exchange-correlation free energy of relativistic uniform electron systems.

  4. Optical properties of phosphor-in-glass through modification of pore properties for LED packaging

    Science.gov (United States)

    Kim, Sunil; Kim, Hyungsun

    2018-01-01

    The volume and size of the voids present between the frit and the phosphor particles used before sintering determine the pore properties of the resulting phosphor-in-glass (PIG). The pores formed from the voids influence the path of the incident light, thus changing the optical properties of the PIG. Therefore, the trends observed for the shrinkage and the green and sintered densities of the PIG were investigated using SiO2-B2O3-ZnO-K2O glass frit of four sizes to understand the tendency for the pore size, porosity, and optical properties of PIG. It has been demonstrated that variation in the pore properties according to the particle size influences parameters defining the light scattering phenomenon, such as the scattering angle of the light and the scattering coefficient, as well as the color rendering index, correlated color temperature, and package efficacy. The results obtained for the variation in the optical properties with the frit size can be used as a reference to select the appropriate glass frit size to achieve the required optical properties for a light-emitting diode (LED) package.

  5. Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

    Energy Technology Data Exchange (ETDEWEB)

    Harnisch, Jennifer Anne [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic performance both in conventional liquid chromatographic columns and EMLC columns. Additionally, one may also exploit the creation of aryl films to by electroreduction of arenediazonium salts in the creation of nanostructured materials. The formation of mercaptobenzene film on the surface of a GC electrode provides a linking platform for the chemisorption of gold nanoparticles. After deposition of nanoparticles, the surface chemistry of the gold can be further altered by self-assembled monolayer (SAM) formation via the chemisorption of a second thiol species. Finally, the properties of gold films can be altered such that they display carbon-like behavior through the formation of benzenehexathiol (BHT) SAMs. BHT chemisorbs to the gold surface in a previously unprecedented planar fashion. Carbon and gold substrates can be chemically altered by several methodologies resulting in new surface properties. The development of modification protocols and their application in the analytical arena is considered herein.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaev, A.G., E-mail: nik@opee.hcei.tsc.ru [High Current Electronics Institute, Siberian Branch of the Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Yushkov, G.Yu.; Oks, E.M. [High Current Electronics Institute, Siberian Branch of the Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Oztarhan, A. [Izmir University, Izmir 35140 (Turkey); Akpek, A.; Hames-Kocabas, E.; Urkac, E.S. [Bioengineering Department, Ege University, Bornova 35100, Izmir (Turkey); Brown, I.G. [Lawrence Berkeley National Laboratory, Berkeley, CA 94708 (United States)

    2014-08-15

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

  7. Electronic properties of doped gapped graphene

    Energy Technology Data Exchange (ETDEWEB)

    Mousavi, Hamze, E-mail: hamze.mousavi@gmail.com [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Nano Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of)

    2013-04-01

    One of the carbon atoms in each Bravais lattice unit cell of pristine graphene plane is substituted by a foreign atom leading to a band gap in the density of states of the system. Then, the gapped graphene is randomly doped by another impurity. The density of states, electronic heat capacity and electrical conductivity of the gapped and doped gapped graphene are investigated within random tight-binding Hamiltonian model and Green's function formalism. The results show that by presence of impurities in the gapped graphene the band gap moves towards lower (higher) values of energy when dopants act as acceptors (donors). The heat capacity decreases (increases) before (after) the Schottky anomaly as well. It is also found that the electrical conductivity of the doped gapped graphene reduces on all ranges of temperature.

  8. Improvement of vibroacoustic properties of toothed gears through constructional modifications of gear teeth

    Directory of Open Access Journals (Sweden)

    Andrzej WIECZOREK

    2009-01-01

    Full Text Available The paper draws attention to methods of minimizing values of vibroacoustic factors by reducing the sources. In the case of toothed gears such causes include, first of all, deviations in workmanship, excitations generated when teeth move in and out of mesh, as well as mesh stiffness variations. The paper presents results of experimental research on vibroacoustic properties of gear wheels with modified and non-modified high-profile teeth. Basing on these results, it was determined that the best results in counteracting vibrations and noise are obtained by using jointly an increased gear contact ratio and a tooth profile modification.

  9. Modification of Surface Properties of Ultrahigh-Molecular – Weight Polyethylene Films by DC Discharge

    Science.gov (United States)

    Piskarev, M.; Gilman, A.; Kuznetsov, A.; Ozerin, A.

    2017-11-01

    The methods of surface modification of ultrahigh-molecular-weight polyethylene (UHMPE) by the low-temperature plasma are considered. Installations for treatment of polymers with various types electric discharges as well as the methods for studying the changes occurring on the polymer surface are described. The experimental results are given concerning properties of 100 μm UHMWPE film before and after treatment by the low pressure air dc discharge. The film samples were placed at the anode. The measurements of the peel resistance (T-test according to ASTM 1876-01) of adhesion joint of modified UHMWPE with polyimide and polytetrafluoroethylene films were obtained using polyurethane adhesive.

  10. Electronic Stopping of Slow Protons in Oxides: Scaling Properties.

    Science.gov (United States)

    Roth, D; Bruckner, B; Undeutsch, G; Paneta, V; Mardare, A I; McGahan, C L; Dosmailov, M; Juaristi, J I; Alducin, M; Pedarnig, J D; Haglund, R F; Primetzhofer, D; Bauer, P

    2017-10-20

    Electronic stopping of slow protons in ZnO, VO_{2} (metal and semiconductor phases), HfO_{2}, and Ta_{2}O_{5} was investigated experimentally. As a comparison of the resulting stopping cross sections (SCS) to data for Al_{2}O_{3} and SiO_{2} reveals, electronic stopping of slow protons does not correlate with electronic properties of the specific material such as band gap energies. Instead, the oxygen 2p states are decisive, as corroborated by density functional theory calculations of the electronic densities of states. Hence, at low ion velocities the SCS of an oxide primarily scales with its oxygen density.

  11. Ion beam modification of two-dimensional materials: Characterization, properties, and applications

    Science.gov (United States)

    Li, Ziqi; Chen, Feng

    2017-03-01

    The layered two-dimensional (2D) materials, e.g., the well-known graphene, transition metal dichalcogenides, and topological insulators, have attracted great interest of researchers from fundamental research as well as industries owing to their intriguing properties in a number of aspects. In practical applications, the efficient modification of the features of 2D materials is compelling and essential to achieve desired functionalities. Ion implantation has been successfully applied to synthesize graphene. The most exotic advantage of ion beam technology is that it offers distinct options of energetic beams, which has recently shown the unique capability to modify and tailor the properties of versatile 2D materials. To name a few, the energetic ion beams could implement the surface morphology or layer-to-layer structural engineering of 2D materials. At the microcosmic level, the introduction of ion beam induced defects and intentional doping of specific ions are the basis of tailoring properties of 2D materials. By manipulating the parameters of ion beams (energies, species, fluences, incident angles, etc.), the modified 2D materials may possess novel properties, which are unprecedented in pristine ones. Promising applications based on these 2D materials with ion beam tailored features have been realized in a broad range of fields. In this work, we systematically review the latest research progress on the deployed techniques and property modifications of graphene and other 2D materials under the treatment of various ion beams. A few selected applications are presented to indicate the practical potentials of ion beam modified 2D materials in distinct areas. Perspectives on future developments are also provided by focusing on several promising topics.

  12. Design of poly(vinylidene fluoride)-g-p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) membrane via surface modification for enhanced fouling resistance and release property

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Guili [Nanyang Environment and Water Research Institute, Interdisciplinary Graduate School, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141 (Singapore); Advanced Environmental Biotechnology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141 (Singapore); School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459 (Singapore); Chen, Wei Ning, E-mail: WNChen@ntu.edu.sg [School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459 (Singapore)

    2017-03-15

    Highlights: • PVDF modified membranes were designed by grafting PNIPAAm, PHEMA and their copolymer. • Fouling resistance and release property of membrane were both improved after modification. • Bacterial attachment and detachment were investigated to evaluate fouling release property. • Improvement of the antifouling property was justified by surface property analysis. • The copolymer modified membrane exhibited higher performance to release foulant. - Abstract: Thermo-sensitive polymer poly(N-isopropylacrylamide) (PNIPAAm), hydrophilic polymer poly(hydroxyethyl methacrylate) (PHEMA) and copolymer p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) [P(HEMA-co-NIPAAm)] were synthesized onto poly(vinylidene fluoride) (PVDF) membrane via atom transfer radical polymerization (ATRP) in order to improve not only fouling resistance but also fouling release property. The physicochemical properties of membranes including hydrophilicity, morphology and roughness were examined by contact angle analyzer, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The antifouling property of membranes was improved remarkably after surface modification according to protein and bacterial adhesion testing, and filtration experiment. Minimum protein adsorption and bacterial adhesion were both obtained on PVDF-g-P(HEMA-co-NIPAAm) membrane, with reduction by 44% and 71% respectively compared to the pristine membrane. The minimum bacterial cells after detachment at 25 °C were observed on the PVDF-g-P(HEMA-co-NIPAAm) membrane with the detachment rate of 77%, indicating high fouling release property. The filtration testing indicated that the copolymer modified membrane exhibited high resistance to protein fouling and the foulant on the surface was released and removed easily by washing, suggesting high fouling release and easy-cleaning capacity. This study provides useful insight in the combined “fouling resistance” and “fouling release

  13. Structure and electronic properties of lead-selenide nanocrystal solids

    Science.gov (United States)

    Whitham, Kevin

    Recent advances in the controlled formation of nanocrystal superlattices have potential for creating materials with properties by design. The ability to tune nanocrystal size, shape and composition as well as symmetry of the superlattice opens routes to new materials. Calculations of such materials predict interesting electronic phenomena including topological states and Dirac cones, however experimental support is lacking. We have investigated electron localization in nanocrystal superlattices using a combination of advanced structural characterization techniques and charge transport measurements. Recent experimental efforts to improve the electronic properties of nanocrystal solids have focused on increasing inter-dot coupling. However, this approach only leads to electronic bands if the coupling energy can overcome energetic and translational disorder. We have investigated oriented-attachment as a method to create nanocrystal superlattices with increased coupling and translational order. We show that epitaxially connected superlattices form by a coherent phase transformation that is sensitive to structural defects and ligand length. In order to measure intrinsic electronic properties we demonstrate control over electronic defects by tailoring surface chemistry and device architecture. To probe charge transport in these structures we performed variable temperature field-effect measurements. By integrating structure analysis, surface chemistry, and transport measurements we find that carriers are localized to a few superlattice constants due to disorder. Importantly, our analysis shows that greater delocalization is possible by optimizing dot-to-dot bonding, thus providing a path forward to create quantum dot solids in which theoretically predicted properties can be realized.

  14. Ultrasmall Carbide Nanospheres - Formation and Electronic Properties

    Science.gov (United States)

    Reinke, Petra; Monazami, Ehsan; McClimon, John

    2015-03-01

    Metallic nanoparticles are highly coveted but are subject to rapid Ostwald ripening even at moderate temperatures limiting study of their properties. Ultrasmall transition metal carbide ``nanospheres'' are synthesized by a solid-state reaction between fullerene as carbon scaffold, and a W surface. This produces nanospheres with a narrow size distribution below 2.5 nm diameter. The nanosphere shape is defined by the scaffold and densely packed arrays can be achieved. The metal-fullerene reaction is temperature driven and progresses through an intermediate semiconducting phase until the fully metallic nanospheres are created at about 350 C. The reaction sequence is observed with STM, and STS maps yield the local density of states. The reaction presumably progresses by stepwise introduction of W-atoms in the carbon scaffold. The results of high resolution STM/STS in combination with DFT calculations are used to unravel the reaction mechanism. We will discuss the transfer of this specific reaction mechanism to other transition metal carbides. The nanospheres are an excellent testbed for the physics and chemistry of highly curved surfaces.

  15. Effects of the Nanostructured Fe-V-Nb Modificators on the Microstructure and Mechanical Properties of Si-Mn Steel

    Directory of Open Access Journals (Sweden)

    Tiebao Wang

    2012-01-01

    Full Text Available The nanostructured Fe-V-Nb master alloy was prepared in vacuum rapid quenching furnace and then was added in the steel melts as modificators before casting. Next, the effects of the nanostructured Fe-V-Nb modificators on the microstructure and mechanical properties of the steel were studied. The results show that the grain size of the steel has been effectively refined, which is mainly because the dispersed nanoscale particles can produce more nucleation sites during the solidification of the liquid steel. Tensile properties and fracture morphology reveal that the yield strength and toughness of the steel modified by nanostructured Fe-V-Nb modificators are better than that of the microalloyed steel. TEM analysis shows that vanadium and niobium in the modificators exist in the form of (V, Nb C which effectively increases the nucleation rate and leads to better mechanical properties of the steel.

  16. Influence of Carbide Modifications on the Mechanical Properties of Ultra-High-Strength Stainless Steels

    Science.gov (United States)

    Seo, Joo-Young; Park, Soo-Keun; Kwon, Hoon; Cho, Ki-Sub

    2017-10-01

    The mechanical properties of ultra-high-strength secondary hardened stainless steels with varying Co, V, and C contents have been studied. A reduced-Co alloy based on the chemical composition of Ferrium S53 was made by increasing the V and C content. This changed the M2C-strengthened microstructure to a MC plus M2C-strengthened microstructure, and no deteriorative effects were observed for peak-aged and over-aged samples despite the large reduction in Co content from 14 to 7 wt pct. The mechanical properties according to alloying modification were associated with carbide precipitation kinetics, which was clearly outlined by combining analytical tools including small-angle neutron scattering (SANS) as well as an analytical TEM with computational simulation.

  17. The influence of modification and squeeze casting on properties of AlSi11 alloy castings

    Directory of Open Access Journals (Sweden)

    A. Zyska

    2011-04-01

    Full Text Available The results of structural examinations and tests of mechanical properties of AlSi11 alloy, either gravity or squeeze cast, have beenpresented. The investigations have been carried out for both the non-modified silumin and the alloy modified with AlSr10 strontiummaster alloy. The measurements have been carried out for the cast plates of dimensions 200×100×25 mm. It has been found out that themodification combined with squeeze casting provides an advantageous set of strength and plastic properties (RBmB ≈ 270 MPa, AB5B ≈ 16%.The metallographic examination has revealed a significant refinement of both the primary α-phase dendrites and the silicon eutectics,however being dependent on the method of modification and casting. It has been found that the refinement of the primary crystals resultsfrom the influence of external pressure exerted on the solidifying casting, while the refinement observed for silicon eutectics is an effect of combined influence of modification and squeeze casting.

  18. Influence of electronic energy deposition on the structural modification of swift heavy-ion-irradiated amorphous germanium layers

    Science.gov (United States)

    Steinbach, T.; Schnohr, C. S.; Kluth, P.; Giulian, R.; Araujo, L. L.; Sprouster, D. J.; Ridgway, M. C.; Wesch, W.

    2011-02-01

    Swift heavy-ion (SHI) irradiation of amorphous germanium (a-Ge) layers leads to a strong volume expansion accompanied by a nonsaturating irreversible plastic deformation (ion hammering), which are consequences of the high local electronic energy deposition within the region of the a-Ge layer. We present a detailed study of the influence of SHI irradiation parameters on the effect of plastic deformation and structural modification. Specially prepared a-Ge layers were irradiated using two SHI energies and different angles of incidence, thus resulting in a variation of the electronic energy deposition per depth ɛe between 14.0 and 38.6 keV nm-1. For all irradiation parameters used a strong swelling of the irradiated material was observed, which is caused by the formation and growth of randomly distributed voids, leading to a gradual transformation of the amorphous layer into a sponge-like porous structure as established by cross-section scanning electron microscopy investigations. The swelling depends linearly on the ion fluence and on the value of ɛe, thus clearly demonstrating that the structural changes are determined solely by the electronic energy deposited within the amorphous layer. Plastic deformation shows a superlinear dependence on the ion fluence due to the simultaneous volume expansion. This influence of structural modification on plastic deformation is described by a simple approach, thus allowing estimation of the deformation yield. With these results the threshold values of the electronic energy deposition for the onset of both structural modification and plastic deformation due to SHI irradiation are determined. Furthermore, based on these results, the longstanding question concerning the reason for the structural modification observed in SHI-irradiated crystalline Ge is answered.

  19. Structural and electronic properties of dense liquid and amorphous nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Boates, B; Bonev, S A

    2011-02-11

    We present first-principles calculations of the structural and electronic properties of liquid nitrogen in the pressure-temperature range of 0-200 GPa and 2000-6000 K. The molecular-polymerization and molecular-atomic liquid phase boundaries have been mapped over this region. We find the polymeric liquid to be metallic, similar to what has been reported for the higher-temperature atomic fluid. An explanation of the electronic properties is given based on the structure and bonding character of the transformed liquids. We discuss the structural and bonding differences between the polymeric liquid and insulating solid cubic-gauche nitrogen to explain the differences in their electronic properties. Furthermore, we discuss the mechanism responsible for charge transport in polymeric nitrogen systems to explain the conductivity of the polymeric fluid and the semi-conducting nature of low-temperature amorphous nitrogen.

  20. Properties of Whistler Waves in Warm Electron Plasmas

    Science.gov (United States)

    Zhao, Jinsong

    2017-11-01

    Dispersion relation and electromagnetic properties of obliquely propagating whistler waves are investigated on the basis of a warm electron fluid model. The magnetic field of whistler waves is nearly circularly polarized with respect to the wave vector in a plasma where the electron plasma frequency {{{Ω }}}{pe} is much larger than the electron cyclotron frequency {{{Ω }}}{ce}, and the magnetic field polarization can become elliptical, or even linear, polarization as {{{Ω }}}{pe}≲ {{{Ω }}}{ce}. In the plasmas with {{{Ω }}}{pe}wave approximates a quasi-magnetostatic mode, not a quasi-electrostatic mode in the cold electron plasmas. Moreover, the detailed mode properties are given in Earth’s magnetosphere, the solar active region, and Jupiter’s polar cap. Furthermore, the study proposes that the ratio of the electrostatic to electromagnetic component of the electric field can be used to distinguish the whistler mode from the Z-mode in the frequency range of {{{Ω }}}{pe}polar cap.

  1. One-Electron Theory of Metals. Cohesive and Structural Properties

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt

    by means of the Linear Muffin-Tin Orbital (LMTO) method. It has been the goal of the work to establish how well this one-electron approach describes physical properties such as the crystal structures of the transition metals, the structural phase transitions in the alkali, alkaline earth, and rare earth...... metals, and the localization of 3d, 4f, and 5f electrons in the 3d metal monoxides, the light lanthanides, and the actinides, respectively, as well as the cohesive properties of metals in general.!......The work described in the report r.nd the 16 accompanying publications is based upon a one-electron theory obtained within the local approximation to density-functional theory, and deals with the ground state of metals as obtained from selfconsistent electronic-structure calculations performed...

  2. Extreme electronic bandgap modification in laser-crystallized silicon optical fibres.

    Science.gov (United States)

    Healy, Noel; Mailis, Sakellaris; Bulgakova, Nadezhda M; Sazio, Pier J A; Day, Todd D; Sparks, Justin R; Cheng, Hiu Y; Badding, John V; Peacock, Anna C

    2014-12-01

    For decades now, silicon has been the workhorse of the microelectronics revolution and a key enabler of the information age. Owing to its excellent optical properties in the near- and mid-infrared, silicon is now promising to have a similar impact on photonics. The ability to incorporate both optical and electronic functionality in a single material offers the tantalizing prospect of amplifying, modulating and detecting light within a monolithic platform. However, a direct consequence of silicon's transparency is that it cannot be used to detect light at telecommunications wavelengths. Here, we report on a laser processing technique developed for our silicon fibre technology through which we can modify the electronic band structure of the semiconductor material as it is crystallized. The unique fibre geometry in which the silicon core is confined within a silica cladding allows large anisotropic stresses to be set into the crystalline material so that the size of the bandgap can be engineered. We demonstrate extreme bandgap reductions from 1.11 eV down to 0.59 eV, enabling optical detection out to 2,100 nm.

  3. Extreme electronic bandgap modification in laser-crystallized silicon optical fibres

    Science.gov (United States)

    Healy, Noel; Mailis, Sakellaris; Bulgakova, Nadezhda M.; Sazio, Pier J. A.; Day, Todd D.; Sparks, Justin R.; Cheng, Hiu Y.; Badding, John V.; Peacock, Anna C.

    2014-12-01

    For decades now, silicon has been the workhorse of the microelectronics revolution and a key enabler of the information age. Owing to its excellent optical properties in the near- and mid-infrared, silicon is now promising to have a similar impact on photonics. The ability to incorporate both optical and electronic functionality in a single material offers the tantalizing prospect of amplifying, modulating and detecting light within a monolithic platform. However, a direct consequence of silicon’s transparency is that it cannot be used to detect light at telecommunications wavelengths. Here, we report on a laser processing technique developed for our silicon fibre technology through which we can modify the electronic band structure of the semiconductor material as it is crystallized. The unique fibre geometry in which the silicon core is confined within a silica cladding allows large anisotropic stresses to be set into the crystalline material so that the size of the bandgap can be engineered. We demonstrate extreme bandgap reductions from 1.11 eV down to 0.59 eV, enabling optical detection out to 2,100 nm.

  4. The potential of electron beam radiation for simultaneous surface modification and bioresorption control of PLLA.

    Science.gov (United States)

    Cairns, Marie-Louise; Dickson, Glenn R; Orr, John F; Farrar, David; Hardacre, Christopher; Sa, Jacinto; Lemoine, Patrick; Mughal, Muhammad Zeeshan; Buchanan, Fraser J

    2012-09-01

    Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment. Copyright © 2012 Wiley Periodicals, Inc.

  5. Annealing-Induced Modifications in Physicochemical and Optoelectronic Properties of Ag-Doped Nanostructured CdS Thin Films

    Directory of Open Access Journals (Sweden)

    Vidya S. Taur

    2012-01-01

    Full Text Available The Ag-doped nanostructured CdS thin films are grown by simple, cost effective chemical ion exchange technique at room temperature on ITO-coated glass substrate. These as grown thin films are annealed at 100, 200, 300, and 400°C in air atmosphere for 1 hour. To study the effect of annealing on physicochemical and optoelectronic properties, these as grown and annealed thin films are characterized for structural, compositional, morphological, optical, and electrical properties. X-ray diffraction (XRD pattern reveals polycrystalline nature of these thin films with increase in crystallite size from 6.4 to 11.2 nm, from XRD the direct identification of Ag doping in CdS thin films cannot be judged, while shift in characteristics peak position of CdS is observed. The Raman spectrum represents increase in full width at half maxima and intensity of characteristic peak, confirming the material modification upon annealing treatment. Presence of Cd, Ag, and S in energy dispersive X-ray analysis spectra (EDAX confirms expected elemental composition in thin films. Scanning electron microscopy (SEM images represent grain growth and agglomeration upon annealing. Red shift in optical absorbance strength and energy band gap values from 2.28 to 2.14 eV is obtained. I-V response obtained from as grown and annealed thin films shows an enhancement in photosensitivity from 72% to 96% upon illumination to 100 mW/cm2 light source.

  6. Effect of Ultrasonic Nanocrystal Surface Modification on Properties of Electrodeposited Ni and Ni-SiC Composite Coatings

    Science.gov (United States)

    Gyawali, Gobinda; Joshi, Bhupendra; Tripathi, Khagendra; Lee, Soo Wohn

    2017-09-01

    In this study, pure nickel and Ni-SiC composite coatings were prepared by the conventional electrodeposition technique from nickel sulfamate electrolytic bath containing dispersed SiC particles. The samples obtained after the electrodeposition were subjected to the ultrasonic nanocrystal surface modification (UNSM) technique to improve the surface- and interface-related properties of the coatings. The surface morphology, elemental composition, surface roughness, microstructure, and crystallinity were observed and analyzed by using scanning electron microscope, energy-dispersive x-ray spectroscopy, roughness tester, and x-ray diffraction techniques, respectively. Electrochemical corrosion behavior of the obtained samples was evaluated in 3.5 wt.% NaCl solution by using three electrodes configuration. XRD result revealed the enhanced crystallinity of the UNSM-treated samples. A significant improvement in surface morphology, Vickers microhardness, wear and coefficient of friction, and anti-corrosion property was observed in the UNSM-treated nickel and Ni-SiC coatings compared to the UNSM-untreated samples.

  7. Effect of vanadium and titanium modification on the microstructure and mechanical properties of a microalloyed HSLA steel

    Energy Technology Data Exchange (ETDEWEB)

    Show, B.K., E-mail: bijay_show@rediffmail.com [Defence Metallurgical Research Laboratory, Kanchanbagh P.O., Hyderabad 500058, Andhra Pradesh (India); Veerababu, R., E-mail: veeru_met@yahoo.com [Defence Metallurgical Research Laboratory, Kanchanbagh P.O., Hyderabad 500058, Andhra Pradesh (India); Balamuralikrishnan, R., E-mail: bmk_pgh@yahoo.com [Defence Metallurgical Research Laboratory, Kanchanbagh P.O., Hyderabad 500058, Andhra Pradesh (India); Malakondaiah, G., E-mail: director@dmrl.drdo.in [Defence Metallurgical Research Laboratory, Kanchanbagh P.O., Hyderabad 500058, Andhra Pradesh (India)

    2010-03-15

    DMR-249A is a low carbon microalloyed high-strength low-alloy (HSLA) steel. While DMR-249A plates of thickness less than 18 mm meet the specified room temperature yield strength (390 MPa) and Charpy impact toughness (78J at -60 deg. C) in the as-rolled condition, thicker plates require water quenching and tempering. Elimination of the quenching and tempering treatment can result in significant cost and energy savings besides offering increased productivity. Therefore, in the present work, modifications to the base DMR-249A steel composition have been investigated with the objective of producing thicker gage plates (24 mm) capable of meeting the specified properties in the normalized condition. Plates from three modified compositions i.e., containing 0.015 wt.% titanium and 0.06, 0.09 and 0.12 wt.% vanadium respectively and one composition with 0.10 wt.% vanadium, and without any titanium were investigated over a range of normalizing temperatures (875-1000 deg. C). In all cases, only the steel without titanium met the specified properties in the normalized condition. Microstructural investigations using scanning and transmission electron microscopy, as well as support evidence from calculations performed using ThermoCalc software, suggest that this is due to the presence of nanoscale vanadium rich carbonitride particles distributed throughout the matrix. These particles were absent in the titanium-containing steel at a similar vanadium level.

  8. Microstructural evolution and surface properties of nanostructured Cu-based alloy by ultrasonic nanocrystalline surface modification technique

    Science.gov (United States)

    Amanov, Auezhan; Cho, In-Sik; Pyun, Young-Sik

    2016-12-01

    A nanostructured surface layer with a thickness of about 180 μm was successfully produced in Cu-based alloy using an ultrasonic nanocrystalline surface modification (UNSM) technique. Cu-based alloy was sintered onto low carbon steel using a powder metallurgy (P/M) method. Transmission electron microscope (TEM) characterization revealed that the severe plastic deformation introduced by UNSM technique resulted in nano-sized grains in the topmost surface layer and deformation twins. It was also found by atomic force microscope (AFM) observations that the UNSM technique provides a significant reduction in number of interconnected pores. The effectiveness of nanostructured surface layer on the tribological and micro-scratch properties of Cu-based alloy specimens was investigated using a ball-on-disk tribometer and micro-scratch tester, respectively. Results exhibited that the UNSM-treated specimen led to an improvement in tribological and micro-scratch properties compared to that of the sintered specimen, which may be attributed to the presence of nanostructured surface layer having an increase in surface hardness and reduction in surface roughness. The findings from this study are expected to be implemented to the automotive industry, in particular connected rod bearings and bushings in order to increase the efficiency and performance of internal combustion engines (ICEs).

  9. Properties of Trapped Electron Bunches in a Plasma Wakefield Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, Neil; /SLAC

    2009-10-30

    Plasma-based accelerators use the propagation of a drive bunch through plasma to create large electric fields. Recent plasma wakefield accelerator (PWFA) experiments, carried out at the Stanford Linear Accelerator Center (SLAC), successfully doubled the energy for some of the 42 GeV drive bunch electrons in less than a meter; this feat would have required 3 km in the SLAC linac. This dissertation covers one phenomenon associated with the PWFA, electron trapping. Recently it was shown that PWFAs, operated in the nonlinear bubble regime, can trap electrons that are released by ionization inside the plasma wake and accelerate them to high energies. These trapped electrons occupy and can degrade the accelerating portion of the plasma wake, so it is important to understand their origins and how to remove them. Here, the onset of electron trapping is connected to the drive bunch properties. Additionally, the trapped electron bunches are observed with normalized transverse emittance divided by peak current, {epsilon}{sub N,x}/I{sub t}, below the level of 0.2 {micro}m/kA. A theoretical model of the trapped electron emittance, developed here, indicates that the emittance scales inversely with the square root of the plasma density in the non-linear 'bubble' regime of the PWFA. This model and simulations indicate that the observed values of {epsilon}{sub N,x}/I{sub t} result from multi-GeV trapped electron bunches with emittances of a few {micro}m and multi-kA peak currents. These properties make the trapped electrons a possible particle source for next generation light sources. This dissertation is organized as follows. The first chapter is an overview of the PWFA, which includes a review of the accelerating and focusing fields and a survey of the remaining issues for a plasma-based particle collider. Then, the second chapter examines the physics of electron trapping in the PWFA. The third chapter uses theory and simulations to analyze the properties of the trapped

  10. Optical properties modification of gold doped glass induced by nanosecond laser radiation and annealing

    Science.gov (United States)

    Nedyalkov, N.; Stankova, N. E.; Koleva, M. E.; Nikov, R.; Grozeva, M.; Iordanova, E.; Yankov, G.; Aleksandrov, L.; Iordanova, R.; Karashanova, D.

    2018-01-01

    In this work the effects of laser radiation and annealing process on the change of the optical properties of gold doped borosilicate glass are presented. The glass is fabricated by conventional melt quenching method as samples with three different concentrations of gold are produced. The laser irradiation is performed by a Nd:YAG system that generates nanosecond pulses at wavelengths of 1064, 532, 355, and 266 nm. The optical properties of the glass samples are studied on the basis of their transmission spectra in the UV- near IR spectral range. The results indicate that irradiation at wavelength of 266 nm induces color changes assigned to formation of defects (color centers). Annealing of the samples results in formation of red colored zones which positions correspond to the irradiated ones. The optical properties and TEM observation indicate that this effect is related to formation of gold nanoparticles. The optical spectra of the areas irradiated by laser pulses and annealed are studied for different processing parameters - pulse number, laser fluence, annealing temperature, annealing time, and the gold concentration in the glass. Processing parameters that ensure efficient tuning of the optical spectra are defined. The presented study can be a basis for a method for surface modification of glass samples that can lead to formation of nanoparticle composed layer with tunable optical properties for applications as novel optical elements.

  11. Electronic properties of bromine-doped carbon nanotubes

    CERN Document Server

    Jhi, S H; Cohen, M L

    2002-01-01

    Intercalation of bromine molecules (Br2) into single-wall carbon nanotube (SWNT) ropes is studied using the ab initio pseudopotential density functional method. Electronic and vibrational properties of the SWNT and Br2 are studied for various bromine concentrations. A drastic change in the charge transfer, bromine stretching-mode, and bromine bond-length is observed when the bromine-bromine distance decreases. Calculated electronic structures show that, at high bromine concentrations, the bromine ppsigma level broadens due to the interbromine interaction. These states overlap with the electronic bands of the SWNT near the Fermi level which results in a substantial charge transfer from carbon to bromine.

  12. Specific heat properties of electrons in generalized Fibonacci quasicrystals

    Science.gov (United States)

    Mauriz, P. W.; Vasconcelos, M. S.; Albuquerque, E. L.

    2003-11-01

    The purpose of this paper is to investigate the specific heat properties of electrons in one-dimensional quasiperiodic potentials, arranged in accordance with the generalized Fibonacci sequence. The electronic energy spectra are calculated using the one-dimensional Schrödinger equation in a tight-binding approximation. Both analytical and numerical results on the temperature dependence of the electron's specific heat associated with their multiscale fractal energy spectra are presented. We compare our numerical results with those found for the ordinary Fibonacci structure. A rich and varied behavior is found for the specific heat oscillations when T→0, with interesting physical consequences.

  13. Electron spectroscopic study of electronic and morphological modifications of the WSe{sub 2} surface induced by Rb adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Buck, Jens

    2010-07-20

    The rubidium-covered surface of the semiconducting transition metal dichalcogenide tungsten diselenide (WSe{sub 2}) is examined using photoelectron spectroscopy (PES) and photoemission electron microscopy (PEEM). Adsorbed Rb is known to induce a variety of effects in this system concerning electronic, structural, and mechanical properties. In this work, the surface potential created by charge transfer upon Rb deposition is examined in thermal equilibrium (band bending) and stationary non-equilibrium (surface photovoltage (SPV) effect), which is induced by the absorption of light. It is shown that combined measurements and numerical simulations of the SPV effect as a function of the photon flux can be exploited for the estimation of many material parameters of the system, especially of the unoccupied adsorbate state. Issues of extending a conventional photoelectron spectrometer setup by a secondary light source will be discussed in the context of simulations and calibration measurements. The customization of an existing theoretical model of the SPV effect for the WSe{sub 2}: Rb system is introduced, and a comprehensive validation of the obtained predictions is given in the context of experimental data. In addition, the self-organized formation of Rb domains at room temperature was examined by application of spatially resolved XPS spectroscopy using the PEEM setup at the end station of beamline UE49/PGMa at the BESSY II synchrotron facility. From the obtained results, the arrangement of Rb in surface lattices can be concluded. Furthermore, an X-Ray absorption study of self-organized nanostructure networks, aiming at the chemical characterization, is presented. Based on the interpretation of the examined structures as tension-induced cracks, a statistical approach to analyzing large-scale features was pursued. First accordance with the predictions made by a primitive, mechanical model of crack creation developed here gives gives some evidence for the validity of the

  14. Co-substitution driven electronic structure modifications in Zn{sub 1−x}Co{sub x}O

    Energy Technology Data Exchange (ETDEWEB)

    Vagadia, Megha; Ravalia, Ashish; Katba, Savan; Solanki, P.S. [Department of Physics, Saurashtra University, Rajkot 360 005 (India); Bapna, Komal; Kumar, Manish; Choudhary, R.J.; Phase, D.M. [UGC DAE Consortium for Scientific Research, Khandwa Road, Indore 01 (India); Kuberkar, D.G., E-mail: dgkuberkar@rediffmail.com [Department of Physics, Saurashtra University, Rajkot 360 005 (India)

    2014-10-15

    Highlights: • Sol–gel grown polycrystalline single phasic Zn{sub 1−x}Co{sub x}O system is synthesized. • X-ray Photoemission spectroscopy reveals that, Co-substitution results in the E{sub F} shift and chemical shift in ZnO. • Co-substitution induced electronic structure and valence band modifications in Zn{sub 1−x}Co{sub x}O (x = 0, 0.5 and 0.15) samples. • Co 3d states around 3.4 eV show resonance at ∼62 eV and are hybridized with O 2p bonding states. - Abstract: We report, the studies on the electronic structure and valence band modifications in sol–gel grown Zn{sub 1−x}Co{sub x}O (x = 0, 0.5 and 0.15) samples, obtained using X-ray photoelectron spectroscopy (XPS) measurements. Structural studies confirm the single phasic hexagonal wurtzite structure having space group P6{sub 3}mc. XPS measurements of Co 2p core level indicate that, Co-ions are in +2 state in ZnO. Using valence band spectroscopy (VBS) and resonant photoemission spectroscopy (RPES) measurements, modifications in the electronic structure of Co-doped ZnO have been understood in the context of increment in the occupation of Co-3d states with Co-content which extends the VB maxima edge.

  15. Characterization and Modification of Natural Zeolite and Its Cracking Properties on Petroleum Fraction

    Directory of Open Access Journals (Sweden)

    Mukhamad Nurhadi

    2010-06-01

    Full Text Available Preparation of natural zeolite catalyst consist of dealumination using acid (HF 1% (v/v, HCI 1M, steaming at calcination temperature and both treatments ware carried out. The modification of the zeolite catalyst was done by loading a small amount of chromium (3% b/b on the zeolite by ion exchange method. Ion exchange was processed by immersing the zeolite in 0.115 M chromium nitrate solution, followed by oxidation with oxygen gas and reduction by hydrogen gas. The characterization of the zeolite catalyst by mean of Si/AI ratio, acidity, metal contents (Na, K, Ca, Fe and Cr and surface area including pore size distribution were determined by gravimetric method, ammonia adsorption, Atomic Adsorption Spectroscopy (AAS and nitrogen gas sorption analyzer (NOVA-1000, respectively. The result of characterization showed that dealumination process increased the Si/AI ratio, acidity and decreased the metal content. The result of cracking process showed that modification of the natural zeolite catalyst enhanced the catalysis property, it showed relatively high cracking activity of petroleum fraction and low kokass formation.

  16. Structural, energetic and electronic properties of intercalated boron ...

    Indian Academy of Sciences (India)

    Abstract. The effects of chirality and the intercalation of transitional metal atoms inside single walled BN nano- tubes on structural, energetic and electronic properties have been considered in this paper. The thermodynamic stability of BN nanotubes can be improved by the intercalation of cobalt or nickel. BN nanotubes can ...

  17. Understanding the structure and electronic properties of N-doped ...

    Indian Academy of Sciences (India)

    Structures and electronic properties of zigzag graphene nanoribbon (ZGNR) with pyridine (3NVZGNR) functionalized by Scandium (Sc) at the edge were studied through quantum chemical calculations in the formalism of density-functional theory (DFT). Pyridine-like nitrogen defects is very crucial for enhancing the Sc atom ...

  18. Electronic structure and optical properties of prominent phases of ...

    Indian Academy of Sciences (India)

    2017-06-19

    Jun 19, 2017 ... Home; Journals; Pramana – Journal of Physics; Volume 89; Issue 1. Electronic structure and optical properties of prominent phases of ... SINGH1 MADHVENDRA NATH TRIPATHI1. Department of Pure and Applied Physics, Guru Ghasidas Vishwavidyalaya (Central University), Koni, Bilaspur 495 009, India ...

  19. Electronic properties of organic monolayers and molecular devices

    Indian Academy of Sciences (India)

    Then, we move from monomers to oligomers: terthiophene and quaterthiophene and to fused oligoacenes: anthracene and pyrene. Our motivations are to establish a relationship between the electrical properties (electronic structure) of the starting π molecules first in vacuum, then when chemisorbed on the silicon substrate ...

  20. Effect of alloying on the electronic structure and magnetic properties ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. We use the self-consistent, augmented space recursion technique to study the electronic structure and magnetic properties of alloys of the transition metals, Fe, Co and Ni with the noble metals, Ag and Au. We analyse the effect of local environment and the hybridization between the constituent bands on the elec-.

  1. Structural, electronic and magnetic properties of MnB2

    Indian Academy of Sciences (India)

    The self-consistent ab-initio calculations, based on density functional theory approach and using the full potential linear augmented plane wave method, are performed to investigate both electronic and magnetic properties of the MnB2 compounds. Polarized spin and spin–orbit coupling are included in calculations within ...

  2. Structural, energetic and electronic properties of intercalated boron ...

    Indian Academy of Sciences (India)

    The effects of chirality and the intercalation of transitional metal atoms inside single walled BN nanotubes on structural, energetic and electronic properties have been considered in this paper. The thermodynamic stability of BN nanotubes can be improved by the intercalation of cobalt or nickel. BN nanotubes can behave ...

  3. Understanding the structure and electronic properties of N-doped ...

    Indian Academy of Sciences (India)

    2014-11-12

    Nov 12, 2014 ... cut into rectangular slices, namely, graphene nanorib- bons (GNRs), depending on crystallographic orienta- tion of cutting edge of the nanoribbons they can become one-dimensional (1D) semiconductors. Graphene and nanoribbons due to its unique and unusual electronic properties1–8 opens up new ...

  4. Properties of Commercial PVC Films with Respect to Electron Dosimetry

    DEFF Research Database (Denmark)

    Miller, Arne; Liqing, Xie

    The properties of three commercially available polyvinyl chloride (PVC) film supplies and one made without additives were tested with respect to their application as routine dose monitors at electron accelerators. Dose fractionation was found to increase the response and the post-irradiation heat...

  5. Electronic and optical properties of spodumene gemstone: A theoretical study

    Science.gov (United States)

    de Lima, A. F.; Souza, S. O.; Lalic, M. V.

    2008-03-01

    The spodumene (LiAlSi 2O 6) is a natural silicate with monoclinic structure, interesting for a jewel industry and possible application as a scintillator. In this paper we present the electronic structure and some of the basic optical properties of the pure spodumene crystal, as calculated by the first-principles, density functional based, full potential linear augmented plane wave method.

  6. Influence of electron injection on electron cyclotron resonance plasma properties and reflected mode electrons (abstract)

    Science.gov (United States)

    Ovsyannikov, V. P.; Ullmann, F.; Zschornack, G.

    2000-02-01

    The injection of an additional strong focused electron beam from a special designed electron gun into a magnetic electron cyclotron resonance (ECR) confinement field is studied. The electron gun uses a cathode with a long lifetime and resistiveness providing high emission current densities with electron currents up to 50 mA and voltages up to 4 keV. A sequence of aluminum foils is used to investigate the trajectories of the electrons in the magnetic field without plasma. The high density electron beam passes through the foils, welds them, and prints its image into the foils. Details of this technique are described in Ref. 1. Using this technique we see that before the electrons enter the sextupole region the beam moves along the magnetic straight lines preserving its structure. Only a central beam passes through the sextupole region, thereby changing its form due to the interaction with radial components of the magnetic field. A new operation method at our 14.5 GHz ECR ion source is based on so-called reflection mode electrons (RMEs) analogous to a known electron beam ion source operation regime.2 The basic idea is that electrons, which traveling from the cathode in a strong axial field, meet an anticathode potential, are reflected from it, move back to the cathode, and will be reflected again and so on. It can be supposed that the electrons will make reflections up to the moment when the anode aperture of the gun is fulfilled and the electrons will be collected on the anode electrode. Investigations are performed extracting nitrogen ions using the RME beam. As a result we got a clear increase in the beam current of the extracted ions (e.g., at 10 mA electron injection an increase of the current of N5+ ions up to 400%) and a shift of the measured ion charge state distribution to higher mean ionization stages. Measured x-ray spectra from a neon loaded plasma show for the case of RME operation increasing energy shifts to the high energy side of the spectra, i.e., the

  7. The electronic properties of superatom states of hollow molecules.

    Science.gov (United States)

    Feng, Min; Zhao, Jin; Huang, Tian; Zhu, Xiaoyang; Petek, Hrvoje

    2011-05-17

    Electronic and optical properties of molecules and molecular solids are traditionally considered from the perspective of the frontier orbitals and their intermolecular interactions. How molecules condense into crystalline solids, however, is mainly attributed to the long-range polarization interaction. In this Account, we show that long-range polarization also introduces a distinctive set of diffuse molecular electronic states, which in quantum structures or solids can combine into nearly-free-electron (NFE) bands. These NFE properties, which are usually associated with good metals, are vividly evident in sp(2) hybridized carbon materials, specifically graphene and its derivatives. The polarization interaction is primarily manifested in the screening of an external charge at a solid/vacuum interface. It is responsible for the universal image potential and the associated unoccupied image potential (IP) states, which are observed even at the He liquid/vacuum interface. The molecular electronic properties that we describe are derived from the IP states of graphene, which float above and below the molecular plane and undergo free motion parallel to it. Rolling or wrapping a graphene sheet into a nanotube or a fullerene transforms the IP states into diffuse atom-like orbitals that are bound primarily to hollow molecular cores, rather than the component atoms. Therefore, we named them the superatom molecular orbitals (SAMOs). Like the excitonic states of semiconductor nanostructures or the plasmonic resonances of metallic nanoparticles, SAMOs of fullerene molecules, separated by their van der Waals distance, can combine to form diatomic molecule-like orbitals of C(60) dimers. For larger aggregates, they form NFE bands of superatomic quantum structures and solids. The overlap of the diffuse SAMO wavefunctions in van der Waals solids provides a different paradigm for band formation than the valence or conduction bands formed by interaction of the more tightly bound

  8. Modification of the structural and optical properties of commercial ZnO powder by mechanical activation

    Directory of Open Access Journals (Sweden)

    Šćepanović M.

    2006-01-01

    Full Text Available Mechanical activation was used as a method for modification of the structural and optical properties of commercial ZnO powder. For this purpose zinc oxide powder was mechanically treated by grinding in a high-energy vibro-mill in a continual regime in air up to 300 minutes. Starting and modified ZnO samples were characterized using XRD, BET and TEM measurements. Optical properties of these samples were investigated by Raman and photoluminescence (PL spectroscopy. The color of commercial ZnO powder was white while mechanically activated ZnO powder was dark yellow, indicating the presence of nonstoichiometry. In the Raman spectra of non-activated sample Raman modes of bulk ZnO were observed, while the spectra of modified samples point out structural and stoichiometric changes. The PL spectra of modified samples excited by 325 and 442 nm lines of a He-Cd laser show great difference with respect to the spectra of the original sample. This study confirms that change in the defect structure of the ZnO crystal lattice introduced by mechanical activation affects the optical properties of this material.

  9. Microstructure and Property Modifications of Cold Rolled IF Steel by Local Laser Annealing

    Science.gov (United States)

    Hallberg, Håkan; Adamski, Frédéric; Baïz, Sarah; Castelnau, Olivier

    2017-10-01

    Laser annealing experiments are performed on cold rolled IF steel whereby highly localized microstructure and property modification are achieved. The microstructure is seen to develop by strongly heterogeneous recrystallization to provide steep gradients, across the submillimeter scale, of grain size and crystallographic texture. Hardness mapping by microindentation is used to reveal the corresponding gradients in macroscopic properties. A 2D level set model of the microstructure development is established as a tool to further optimize the method and to investigate, for example, the development of grain size variations due to the strong and transient thermal gradient. Particular focus is given to the evolution of the beneficial γ-fiber texture during laser annealing. The simulations indicate that the influence of selective growth based on anisotropic grain boundary properties only has a minor effect on texture evolution compared to heterogeneous stored energy, temperature variations, and nucleation conditions. It is also shown that although the α-fiber has an initial frequency advantage, the higher probability of γ-nucleation, in combination with a higher stored energy driving force in this fiber, promotes a stronger presence of the γ-fiber as also observed in experiments.

  10. Improving permanent magnetic properties of rapidly solidified nanophase RE-TM-B alloys by compositional modification

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Z.W. [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD (United Kingdom)], E-mail: zwliu@scut.edu.cn; Liu, Yan; Deheri, P.K.; Ramanujan, R.V. [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Davies, H.A. [Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2009-08-15

    Rapid solidification is one of the most important techniques to produce nanocrystalline rare-earth-transition metal-boron (RE-TM-B) hard magnetic materials. To achieve high performance on these NdFeB-based alloys, compositional modification and microstructure optimization have been frequently employed. In this short review, various substitutions and doping elements have been discussed regarding to their behaviors in adjusting the individual or combined hard magnetic properties as well as the microstructure based on our recent results. It has been demonstrated that Pr and Dy enhance coercivity {sub j}H{sub C}, whereas Sm reduces {sub j}H{sub C} due to their effects on intrinsic properties. Co improves the thermal stability as well as the microstructure. Introducing Fe{sub 65}Co{sub 35} is a possible approach to enhance the magnetization and maximum energy product (BH){sub max}. As a doping element, Ta was found to play an important role to obtain an appropriate combination of magnetic properties for this type of alloys.

  11. Chemical modification of New Zealand hoki (Macruronus novaezelandiae) skin gelatin and its properties.

    Science.gov (United States)

    Mohtar, Nor Fazliyana; Perera, Conrad O; Hemar, Yacine

    2014-07-15

    Chemical modifications of gelatin from New Zealand hoki (Macruronus novaezelandiae) skins were carried out using three different cross-linking agents, namely, genipin, glutaraldehyde and caffeic acid, at different concentrations. The chemically modified gelatins exhibited better physical properties, such as higher gel strength, melting point, and rheological properties than did the uncross-linked gelatin. Gelatin cross-linked with glutaraldehyde had higher gel strength and melting point (231 g, 21.9°C) than those cross-linked with caffeic acid (229 g, 21.6°C) and genipin (211 g, 20.5°C) at concentrations of 0.133, 0.111, and 0.044M, respectively. The elastic modulus (G') and the loss modulus (G″) of chemically cross-linked gelatins were higher than those of the uncross-linked ones. These improved physicochemical properties of gelatin could lead to the development of products in the food industry that meet consumer demands. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Influence of dielectric surface modification on growth, structure and transport properties of perylene films

    Energy Technology Data Exchange (ETDEWEB)

    Effertz, Christian; Beigmohamadi, Maryam; Niyamakom, Phenwisa; Schulz, Philip; Wuttig, Matthias [Institute of Physics (IA), RWTH Aachen University, 52064 Aachen (Germany)

    2008-05-15

    In this study the properties of organic thin film transistors (OTFTs) based on perylene films have been investigated. To tailor the film properties, the dielectric layer on which the perylene films were deposited on was modified by different chemical treatments. Both film properties and the device efficiency have been studied employing a range of techniques including atomic force microscopy, X-ray diffraction and a drop shape analysis for the determination of the surface free energy. A clear correlation between the adhesion energy with the dielectric surface modification is found. The change in adhesion energy influences the thin-film growth on the modified substrate and therefore the film morphology and structure. This in turn has a profound impact on the transistors performance as the charge carrier mobility and the on-to-off current ratio are effected. Hence by tailoring of the dielectric surface for the growth of perylene films, the thin-film transistor performance can be optimized. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Machine learning of molecular electronic properties in chemical compound space

    Science.gov (United States)

    Montavon, Grégoire; Rupp, Matthias; Gobre, Vivekanand; Vazquez-Mayagoitia, Alvaro; Hansen, Katja; Tkatchenko, Alexandre; Müller, Klaus-Robert; Anatole von Lilienfeld, O.

    2013-09-01

    The combination of modern scientific computing with electronic structure theory can lead to an unprecedented amount of data amenable to intelligent data analysis for the identification of meaningful, novel and predictive structure-property relationships. Such relationships enable high-throughput screening for relevant properties in an exponentially growing pool of virtual compounds that are synthetically accessible. Here, we present a machine learning model, trained on a database of ab initio calculation results for thousands of organic molecules, that simultaneously predicts multiple electronic ground- and excited-state properties. The properties include atomization energy, polarizability, frontier orbital eigenvalues, ionization potential, electron affinity and excitation energies. The machine learning model is based on a deep multi-task artificial neural network, exploiting the underlying correlations between various molecular properties. The input is identical to ab initio methods, i.e. nuclear charges and Cartesian coordinates of all atoms. For small organic molecules, the accuracy of such a ‘quantum machine’ is similar, and sometimes superior, to modern quantum-chemical methods—at negligible computational cost.

  14. Effects of initial saturation on properties modification and displacement of tetrachloroethene with aqueous isobutanol.

    Science.gov (United States)

    Boyd, Glen R; Ocampo-Gómez, Ana M; Li, Minghua; Husserl, Johana

    2006-11-20

    Packed column experiments were conducted to study effects of initial saturation of tetrachloroethene (PCE) in the range of 1.0-14% pore volume (PV) on mobilization and downward migration of the non-aqueous phase liquid (NAPL) product upon contact with aqueous isobutanol ( approximately 10 vol.%). This study focused on the consequences of swelling beyond residual saturation. Columns were packed with mixtures of neat PCE, water and glass beads and waterflooded to establish a desired homogeneous residual saturation, and then flooded with aqueous isobutanol under controlled hydraulic conditions. Results showed a critical saturation of approximately 8% PV for these packed column experimental conditions. At low initial PCE saturations (8% PV), results showed NAPL-product mobilization and downward migration which was attributed to interfacial tension (IFT) reduction, swelling of the NAPL-product, and reduced density modification. Packed column results were compared with good agreement to theoretical predictions of NAPL-product mobilization using the total trapping number, N(T). In addition to the packed column study, preliminary batch experiments were conducted to study the effects of PCE volumetric fraction in the range of 0.5-20% on density, viscosity, and IFT modification as a function of time following contact with aqueous isobutanol ( approximately 10 vol.%). Modified NAPL-product fluid properties approached equilibrium within approximately 2 h of contact for density and viscosity. IFT reduction occurred immediately as expected. Measured fluid properties were compared with good agreement to theoretical equilibrium predictions based on UNIQUAC. Overall, this study demonstrates the importance of initial DNAPL saturation, and the associated risk of downward NAPL-product migration, in applying alcohol flooding for remediation of DNAPL contaminated ground water sites.

  15. Intellectual property in consumer electronics, software and technology startups

    CERN Document Server

    Halt, Jr , Gerald B; Stiles, Amber R; Fesnak, Robert

    2014-01-01

    This book provides a comprehensive guide to procuring, utilizing and monetizing intellectual property rights, tailored for readers in the high-tech consumer electronics and software industries, as well as technology startups.  Numerous, real examples, case studies and scenarios are incorporated throughout the book to illustrate the topics discussed.  Readers will learn what to consider throughout the various creative phases of a product’s lifespan from initial research and development initiatives through post-production.  Readers will gain an understanding of the intellectual property protections afforded to U.S. corporations, methods to pro-actively reduce potential problems, and guidelines for future considerations to reduce legal spending, prevent IP theft, and allow for greater profitability from corporate innovation and inventiveness. • Offers a comprehensive guide to intellectual property for readers in high-tech consumer electronics, software and technology startups; • Uses real case studies...

  16. Activating "Invisible" Glue: Using Electron Beam for Enhancement of Interfacial Properties of Graphene-Metal Contact.

    Science.gov (United States)

    Kim, Songkil; Russell, Michael; Kulkarni, Dhaval D; Henry, Mathias; Kim, Steve; Naik, Rajesh R; Voevodin, Andrey A; Jang, Seung Soon; Tsukruk, Vladimir V; Fedorov, Andrei G

    2016-01-26

    Interfacial contact of two-dimensional graphene with three-dimensional metal electrodes is crucial to engineering high-performance graphene-based nanodevices with superior performance. Here, we report on the development of a rapid "nanowelding" method for enhancing properties of interface to graphene buried under metal electrodes using a focused electron beam induced deposition (FEBID). High energy electron irradiation activates two-dimensional graphene structure by generation of structural defects at the interface to metal contacts with subsequent strong bonding via FEBID of an atomically thin graphitic interlayer formed by low energy secondary electron-assisted dissociation of entrapped hydrocarbon contaminants. Comprehensive investigation is conducted to demonstrate formation of the FEBID graphitic interlayer and its impact on contact properties of graphene devices achieved via strong electromechanical coupling at graphene-metal interfaces. Reduction of the device electrical resistance by ∼50% at a Dirac point and by ∼30% at the gate voltage far from the Dirac point is obtained with concurrent improvement in thermomechanical reliability of the contact interface. Importantly, the process is rapid and has an excellent insertion potential into a conventional fabrication workflow of graphene-based nanodevices through single-step postprocessing modification of interfacial properties at the buried heterogeneous contact.

  17. EFFECT OF TEMPERATURE AND pH OF MODIFICATION PROCESS ON THE PHYSICAL-MECHANICAL PROPERTIES OF MODIFIED CASSAVA STARCH

    Directory of Open Access Journals (Sweden)

    Yudi Wicaksono

    2016-11-01

    Full Text Available The use of cassava starch for excipient in the manufacturing of the tablet has some problems, especially on physical-mechanical properties. The purpose of this study was to determine the effect of the differentness of temperature and pH in the process of modification on the physical-mechanical properties of modified cassava starch. Modifications were performed by suspending cassava starch into a solution of 3 % (w/v PVP K30. The effect of the difference of temperature was observed at temperatures of 25; 45 and 65 0C, while the effect of the difference of pH was observed at pH of 4.0; 7.0 and 12.0. The results showed that the temperature and pH did not affect the physical-mechanical properties of the modified cassava starch. Modification of cassava starch at pH and temperature of 7.0 and 45 0C was produced modified cassava starch with the most excellent solubility, while the best swelling power were formed by the modification process at pH and temperature of 7.0 and 25 0C. Overall, the most excellent compression properties of modified cassava starch resulted from the modification process at pH 12.

  18. Low-Temperature Modification of ZnO Nanoparticles Film for Electron-Transport Layers in Perovskite Solar Cells.

    Science.gov (United States)

    Han, Gill Sang; Shim, Hyun-Woo; Lee, Seongha; Duff, Matthew L; Lee, Jung-Kun

    2017-06-09

    An electron-transport layer (ETL) that selectively collects photogenerated electrons is an important constituent of halide perovskite solar cells (PSCs). Although TiO 2 films are widely used as ETL of PSCs, the processing of TiO 2 films with high electron mobility requires high-temperature annealing and TiO 2 dissociates the perovskite layer through a photocatalytic reaction. Here, we report an effective surface-modification method of a room-temperature processed ZnO nanoparticles (NPs) layer as an alternative to the TiO 2 ETL. A combination of simple UV exposure and nitric acid treatment effectively removes the hydroxyl group and passivates surface defects in ZnO NPs. The surface modification of ZnO NPs increases the power conversion efficiency (PCE) of PSCs to 14 % and decreases the aging of PSCs under light soaking. These results suggest that the surface-modified ZnO film can be a good ETL of PSCs and provide a path toward low-temperature processing of efficient and stable PSCs that are compatible with flexible electronics. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Modification of magicity toward the dripline and its impact on electron-capture rates for stellar core collapse

    Science.gov (United States)

    Raduta, Ad. R.; Gulminelli, F.; Oertel, M.

    2016-02-01

    The importance of microphysical inputs from laboratory nuclear experiments and theoretical nuclear structure calculations in the understanding of core-collapse dynamics and the subsequent supernova explosion is largely recognized in the recent literature. In this work, we analyze the impact of the masses of very neutron-rich nuclei on the matter composition during collapse and the corresponding electron-capture rate. To this end, we introduce an empirical modification of the popular Duflo-Zuker mass model to account for possible shell quenching far from stability. We study the effect of this quenching on the average electron-capture rate. We show that the pre-eminence of the closed shells with N =50 and N =82 in the collapse dynamics is considerably decreased if the shell gaps are reduced in the region of 78Ni and beyond. As a consequence, local modifications of the overall electron-capture rate of up to 30% can be expected, depending on the strength of magicity quenching. This finding has potentially important consequences on the entropy generation, the neutrino emissivity, and the mass of the core at bounce. Our work underlines the importance of new experimental measurements in this region of the nuclear chart, the most crucial information being the nuclear mass and the Gamow-Teller strength. Reliable microscopic calculations of the associated elementary rate, in a wide range of temperatures and electron densities, optimized on these new empirical information, will be additionally needed to get quantitative predictions of the collapse dynamics.

  20. Measurements of Electrical and Electron Emission Properties of Highly Insulating Materials

    Science.gov (United States)

    Dennison, J. R.; Brunson, Jerilyn; Hoffman, Ryan; Abbott, Jonathon; Thomson, Clint; Sim, Alec

    2005-01-01

    Highly insulating materials often acquire significant charges when subjected to fluxes of electrons, ions, or photons. This charge can significantly modify the materials properties of the materials and have profound effects on the functionality of the materials in a variety of applications. These include charging of spacecraft materials due to interactions with the severe space environment, enhanced contamination due to charging in Lunar of Martian environments, high power arching of cables and sources, modification of tethers and ion thrusters for propulsion, and scanning electron microscopy, to name but a few examples. This paper describes new techniques and measurements of the electron emission properties and resistivity of highly insulating materials. Electron yields are a measure of the number of electrons emitted from a material per incident particle (electron, ion or photon). Electron yields depend on incident species, energy and angle, and on the material. They determine the net charge acquired by a material subject to a give incident flu. New pulsed-beam techniques will be described that allow accurate measurement of the yields for uncharged insulators and measurements of how the yields are modified as charge builds up in the insulator. A key parameter in modeling charge dissipation is the resistivity of insulating materials. This determines how charge will accumulate and redistribute across an insulator, as well as the time scale for charge transport and dissipation. Comparison of new long term constant-voltage methods and charge storage methods for measuring resistivity of highly insulating materials will be compared to more commonly used, but less accurate methods.

  1. Machine Learning for Silver Nanoparticle Electron Transfer Property Prediction.

    Science.gov (United States)

    Sun, Baichuan; Fernandez, Michael; Barnard, Amanda S

    2017-10-23

    Nanoparticles exhibit diverse structural and morphological features that are often interconnected, making the correlation of structure/property relationships challenging. In this study a multi-structure/single-property relationship of silver nanoparticles is developed for the energy of Fermi level, which can be tuned to improve the transfer of electrons in a variety of applications. By combining different machine learning analytical algorithms, including k-mean, logistic regression, and random forest with electronic structure simulations, we find that the degree of twinning (characterized by the fraction of hexagonal closed packed atoms) and the population of the {111} facet (characterized by a surface coordination number of nine) are strongly correlated to the Fermi energy of silver nanoparticles. A concise three layer artificial neural network together with principal component analysis is built to predict this property, with reduced geometrical, structural, and topological features, making the method ideal for efficient and accurate high-throughput screening of large-scale virtual nanoparticle libraries and the creation of single-structure/single-property, multi-structure/single-property, and single-structure/multi-property relationships in the near future.

  2. Electron Density Determination, Bonding and Properties of Tetragonal Ferromagnetic Intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Wiezorek, Jorg [Univ. of Pittsburgh, PA (United States)

    2016-09-01

    The project developed quantitative convergent-beam electron diffraction (QCBED) methods by energy-filtered transmission electron microscopy (EFTEM) and used them in combination with density functional theory (DFT) calculations to study the electron density distribution in metallic and intermetallic phases with different cubic and non-cubic crystal structures that comprise elements with d-electron shells. The experimental methods developed here focus on the bonding charge distribution as one of the quantum mechanical characteristics central for understanding of intrinsic properties and validation of DFT calculations. Multiple structure and temperature factors have been measured simultaneously from nano-scale volumes of high-quality crystal with sufficient accuracy and precision for comparison with electron density distribution calculations by DFT. The often anisotropic temperature factors for the different atoms and atom sites in chemically ordered phases can differ significantly from those known for relevant pure element crystals due to bonding effects. Thus they have been measured from the same crystal volumes from which the structure factors have been determined. The ferromagnetic ordered intermetallic phases FePd and FePt are selected as model systems for 3d-4d and 3d-5d electron interactions, while the intermetallic phases NiAl and TiAl are used to probe 3d-3p electron interactions. Additionally, pure transition metal elements with d-electrons have been studied. FCC metals exhibit well defined delocalized bonding charge in tetrahedral sites, while less directional, more distributed bonding charge attains in BCC metals. Agreement between DFT calculated and QCBED results degrades as d-electron levels fill in the elements, and for intermetallics as d-d interactions become prominent over p-d interactions. Utilizing the LDA+U approach enabled inclusion of onsite Coulomb-repulsion effects in DFT calculations, which can afford improved agreements with QCBED results

  3. An investigation of effects of modification processes on physical properties and mechanism of drug release for sustaining drug release from modified rice

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, Vuong Duy; Luu, Thinh Duc; Van Vo, Toi [Pharmaceutical Engineering Laboratory, Biomedical Engineering Department, International University, Vietnam National University, Ho Chi Minh City (Viet Nam); Tran, Van-Thanh [Faculty of Pharmacy, University of Medicine and Pharmacy, Ho Chi Minh City (Viet Nam); Duan, Wei [School of Medicine, Deakin University, Pigdons Road, Waurn Ponds, Victoria (Australia); Tran, Phuong Ha-Lien, E-mail: phuong.tran1@deakin.edu.au [School of Medicine, Deakin University, Pigdons Road, Waurn Ponds, Victoria (Australia); Tran, Thao Truong-Dinh, E-mail: ttdthao@hcmiu.edu.vn [Pharmaceutical Engineering Laboratory, Biomedical Engineering Department, International University, Vietnam National University, Ho Chi Minh City (Viet Nam)

    2016-10-01

    The aim of this study was to investigate the effect of modification processes on physical properties and explain the mechanism of sustained drug release from modified rice (MR). Various types of Vietnamese rice were introduced in the study as the matrices of sustained release dosage form. Rice was thermally modified in water for a determined temperature at different times with a simple process. Then tablets containing MR and isradipine, the model drug, were prepared to investigate the capability of sustained drug release. Scanning electron microscopy (SEM) was used to determine different morphologies between MR formulations. Flow property of MR was analyzed by Hausner ratio and Carr's indices. The dissolution rate and swelling/erosion behaviors of tablets were evaluated at pH 1.2 and pH 6.8 at 37 ± 0.5 °C. The matrix tablet containing MR showed a sustained release as compared to the control. The SEM analyses and swelling/erosion studies indicated that the morphology as well as swelling/erosion rate of MR were modulated by modification time, drying method and incubation. It was found that the modification process was crucial because it could highly affect the granule morphologies and hence, leading to the change of flowability and swelling/erosion capacity for sustained release of drug. - Highlights: • Modification process affected granule morphologies and flowability of modified rice. • Modification process affected swelling/erosion capacity for drug sustained release. • Freeze-drying could decrease the erosion as well as increase the swelling rate.

  4. Correlation of geometrical and electronic properties in metallic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Pfnuer, H.; Tegenkamp, C.; Czubanowski, M.; Luekermann, D.; Roenspies, J.; Wiessell, S. [Institut fuer Festkoerperphysik, Abteilung Atomare und Molekulare Strukturen, Leibniz Universitaet Hannover (Germany)

    2010-10-15

    The structure on the atomic scale was found to be directly correlated with the electronic and transport properties of ultra-thin metallic wires. We present examples of both self-organized and artificially structured nanowires in the system Pb/Si(557). We demonstrate that artificial structuring on the nanoscale allows identification and determination of the electrical transport properties of atomic size defects, using Si(557) as a quasi-insulating substrate and a Si double step in a monolayer high Pb nanowire as an example. One-dimensional (1D) properties with strong electron correlation and various instabilities in metallic chains or ribbons generated by metal adsorption of sub-monolayers on insulating substrates like Si(111) or Si(557) turn out to always be modified by the unavoidable coupling to 2D and 3D. The wealth of new and partly unexpected phenomena is exemplified here again in monolayers of Pb on Si(557), which forms wire-like arrays. We identify structural self-stabilization as the origin of 1D electronic transport and show that a new 1D state is generated by step decoration. Magnetoconductance measurements yield even deeper insight into mechanisms of electronic transport, as also exemplified in this specific system. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  5. Electronic and optical properties of pristine and oxidized borophene

    Science.gov (United States)

    Lherbier, Aurélien; Botello-Méndez, Andrés Rafael; Charlier, Jean-Christophe

    2016-12-01

    Borophene, a two-dimensional monolayer of boron atoms, was recently synthesized experimentally and was shown to exhibit polymorphism. In its closed-packed triangular form, borophene is expected to exhibit anisotropic metallic character with relatively high electron velocities. At the same time, very low optical conductivities in the infrared-visible light region were predicted. Based on its promising electronic transport properties and its high transparency, borophene could become a genuine lego piece in the 2D materials assembling game known as the van der Waals heterocrystal approach. However, borophene is naturally degraded in ambient conditions and it is therefore important to assess the mechanisms and the effects of oxidation on borophene monolayers. Optical and electronic properties of pristine and oxidized borophene are here investigated by first-principles approaches. The transparent and conductive properties of borophene are elucidated by analyzing the electronic structure and its interplay with light. Optical response of borophene is found to be strongly affected by oxidation, suggesting that optical measurements can serve as an efficient probe for borophene surface contamination.

  6. Immunobiological properties of sesquiterpene lactones obtained by chemically transformed structural modifications of trilobolide.

    Science.gov (United States)

    Harmatha, Juraj; Vokáč, Karel; Buděšínský, Miloš; Zídek, Zdeněk; Kmoníčková, Eva

    2015-12-01

    Our previous research on immunostimulatory properties of trilobolide and its structurally related natural analogues isolated from Laser trilobum (L.) Borkh., encouraged us to investigate structurally related guaianolides belonging to a specific group of sesquiterpene lactones with characteristic glycol moiety attached to the lactone ring. Ever increasing attention has been paid to certain guaianolides such as thapsigargin and trilobolide for their promising anti-inflammatory, anticancer, anti-infectious and SERCA inhibitory activities. However, due to their alkylation capabilities, they might be cytotoxic. Search for compounds with preserved immunobiological properties and decreased cytotoxicity led us to transform some of their structural features, particularly those related to their side chain functionality. For this reason, we prepared a series of over 20 various deacylated, acyl modified, or relactonized derivatives of trilobolide. The immunobiological effects were screened in vitro using the rat peritoneal cells primed with lipopolysaccharide. Secretion of interferon-γ (IFN-γ), interleukins (IL) IL-1β, IL-6 and tumour necrosis factor-α (TNF-α) were determined by ELISA, and nitric oxide (NO) production by Griess reagent. Relation between the molecular structure and immunobiological activity was investigated. Acetylation at 7-OH and 11-OH positions of the lactone ring, or acyl modification of the guaianolide functionalities (including relactonization) of trilobolide, led to inability to stimulate secretion of cytokines and production of NO. Interestingly, minor structural changes achieved by catalytic hydrogenation or hydrogenolysis retained the original immunoactivity of trilobolide. It can be concluded that several new chemically transformed sesquiterpene lactones resembling the immunobiological properties of trilobolide or thapsigargin were prepared and identified. The implication of the lactone vicinal diol (glycol) moiety, combined with other structure

  7. Structural and electronic properties of arsenic nitrogen monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Pei; Nie, Yao-zhuang, E-mail: yznie@csu.edu.cn; Xia, Qing-lin; Guo, Guang-hua, E-mail: guogh@mail.csu.edu.cn

    2017-03-26

    We present our first-principles calculations of a new two-dimensional material, arsenic nitrogen monolayer. The structural, electronic, and mechanical properties are investigated in detail by means of density functional theory computations. The calculated binding energy and the phonon spectra demonstrate that the AsN can form stable monolayer in puckered honeycomb structure. It is a semiconductor with indirect band gap of 0.73 eV, and displays highly anisotropic mechanical properties. Strain has obvious influence on the electronic properties of AsN monolayer. It is found that in the armchair direction, a moderate compression strain (−12%) can trigger an indirect to direct band gap transition and a tensile strain of 18% can make the AsN becoming a stable metal. In the zigzag direction, a rather smaller strain than armchair direction (12% for compression and 8% for stretch) can induce the indirect band gap to metal transition. - Highlights: • A new two-dimensional material, arsenic nitrogen monolayer is predicated by first-principles calculations. • Arsenic nitrogen monolayer displays highly anisotropic mechanical properties. • Electronic structures of arsenic nitrogen monolayer can be effectively manipulated by applied strains.

  8. Influence of organic modification on the structure and properties of polyurethane/sepiolite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Chen Hongxiang, E-mail: chenhx_916@hotmail.com [Hubei Key Laboratory of Coal Conversion and New Carbon Material, College of Chemical Engineering and Technology, Wuhan University of Science and Technology, 947 Heping Road, 430081 Wuhan, Hubei (China); Zeng Danlin [Hubei Key Laboratory of Coal Conversion and New Carbon Material, College of Chemical Engineering and Technology, Wuhan University of Science and Technology, 947 Heping Road, 430081 Wuhan, Hubei (China); Xiao Xiaoqin [College of Machinery and Automation, Wuhan University of Science and Technology, 430081 Wuhan (China); Zheng Maosheng [Institute of Condensed Physics and Materials, Northwest University, 710069 Xi' an (China); Ke Changmei; Li Yanjun [Hubei Key Laboratory of Coal Conversion and New Carbon Material, College of Chemical Engineering and Technology, Wuhan University of Science and Technology, 947 Heping Road, 430081 Wuhan, Hubei (China)

    2011-01-25

    Research highlights: {yields} KH550 was the best among the three organic modifiers by comparing tensile properties, water resistance and swelling rate. {yields} FTIR revealed the strong interaction between KH550-Sp and the PU matrix. {yields} TEM revealed the compatibility of KH550-Sp and PU was improved. {yields} SEM confirmed the good dispersion of KH550-Sp in PU matrix. - Abstract: The polyurethane (PU) nanocomposites were prepared using organomodified sepiolite (organo-Sp) by in situ polymerization method. The clay was modified with three different organic modifiers such as {gamma}-aminopropyltriethoxylsilane (KH550), hexadecyltrimethylammonium bromide (CTAB) and lauric acid (LA). The morphology and the dispersion of organo-Sp in polyurethane were characterized by scanning electron microscope, transmission electron microscope and Fourier transform infrared spectroscopy. The influence of organo-Sp on the tensile properties, water resistance and swelling rate of polyurethane composites was studied. The results showed the properties and structure of polyurethane nanocomposites were related to the kind of organic modifier.

  9. Hydridic and electrocatalytic properties of hypo-hyper-d-electronic combinations of transition metal intermetallic phases

    Energy Technology Data Exchange (ETDEWEB)

    Jaksic, J.M. [University of Belgrade (Yugoslavia). Dept. of Chemistry; Krstajic, N.V.; rgur, B.N.; Jaksic, M.M. [University of Belgrade (Yugoslavia). Faculty of Technology and Metallurgy

    1998-12-01

    Hydridic and electrocatalytic properties of hypo-hyper-d-electronic combinations of transition metals in their intermetallic phases and alloys for the hydrogen storage, hydridic batteries and its electrode reactions (HELR) have been considered in the light of Fermi dynamics (or the electronic density of states), work function and the Brewer or Miedema intermetallic bonding theory (structural factors). It has been pointed out that such an intermetallic hypo-hyper-d-electronic interaction of transition metals (or the doped effect of a hyper-d- upon the bulk or surface of a hypo-d-electronic metal, or vice versa), which leads to the defined optimal mutual (bulk or surface) electronic density of states for both hydridic storage and/or electrocatalytic reaction (cathodic evolution (HER) and/or anodic oxidation (HOR) of hydrogen), imposes the same catalytic effect as the Non-Faradaic promotion by induced polarization, or the so-called NEMCA effect (Non-Faradaic Electrochemical Modification of Catalytic Activity). The main impact has been imposed on the most promising hydridic battery system (Ti-Ni crystalline and sintered), as well as on typical electrocatalytic issues (Mo-Co, Mo-Ni, Zr-Ni). (author)

  10. Research on the Fracture Properties and Modification Mechanism of Polyester Fiber and SBR Latex Modified Cement Concrete

    Directory of Open Access Journals (Sweden)

    Mingkai Zhou

    2016-01-01

    Full Text Available Polyester fiber and SBR latex cement concrete is prepared as pavement surface material; its fracture properties including fracture toughness, fracture energy, CMOD, and flexural strength are studied comparing with those of normal concrete (NC, polyester fiber modified concrete (FMC, SBR polymer modified concrete (SMC, and the combination of polyester fiber and SBR polymer modified concrete (FSMC. The modification mechanism of the latex and fiber on the concrete was also studied by the methods including X-ray test, chemically combined water, heat of hydration, water loss, and scanning electron microscope. Results indicated that the concrete modified by latex and polyester fiber has flexural strength, fracture toughness, and fracture energy of 44.4%, 397.0%, and 462.8% higher than the reference normal concrete, the polymer retarded the hydration process and reduced the hydration degree of cement at early age, while the hydration degree is promoted by the polymer film for its excellent water resistance after 28 d, and the bond between the fiber and cement paste is improved by the latex.

  11. Polymeric Thin Films for Organic Electronics: Properties and Adaptive Structures

    Directory of Open Access Journals (Sweden)

    Bruno Pignataro

    2013-03-01

    Full Text Available This review deals with the correlation between morphology, structure and performance of organic electronic devices including thin film transistors and solar cells. In particular, we report on solution processed devices going into the role of the 3D supramolecular organization in determining their electronic properties. A selection of case studies from recent literature are reviewed, relying on solution methods for organic thin-film deposition which allow fine control of the supramolecular aggregation of polymers confined at surfaces in nanoscopic layers. A special focus is given to issues exploiting morphological structures stemming from the intrinsic polymeric dynamic adaptation under non-equilibrium conditions.

  12. Visualization of electronic properties of molecules in chemical reactions.

    Science.gov (United States)

    Wei, S; Famini, G R

    1995-10-01

    Modern computational methods allow for the tracking of entire chemical reactions, ranging from initial reactants, through transition states, and to the final products. They also permit the computation of a variety of properties that can change as the reaction proceeds from start to finish. Visualization of these reactions is often difficult and usually limited to static displays of specific steps along the reaction paths. This article describes a program, Reaction Viewer, that we have developed to visualize a chemical reaction dynamically. The article also describes the use of this program to see the movement of electrons and other electronic effects, as well as steric ramifications during the reaction.

  13. Electronic properties of lithiated SnO-based anode materials

    Science.gov (United States)

    Bauer, Dominik; Bunjaku, Teutë; Pedersen, Andreas; Luisier, Mathieu

    2017-08-01

    In this paper, we use an ab-initio quantum transport approach to study the electron current flowing through lithiated SnO anodes for potential applications in Li-ion batteries. By investigating a set of lithiated structures with varying lithium concentrations, it is revealed that Lix SnO can be a good conductor, with values comparable to bulk β-Sn and Li. A deeper insight into the current distribution indicates that electrons preferably follow specific trajectories, which offer superior conducting properties than others. These channels have been identified and it is shown here how they can enhance or deteriorate the current flow in lithiated anode materials.

  14. Effect of Cross-Linking and Enzymatic Hydrolysis Composite Modification on the Properties of Rice Starches

    Directory of Open Access Journals (Sweden)

    Gao-Qiang Liu

    2012-07-01

    Full Text Available Native rice starch lacks the versatility necessary to function adequately under rigorous industrial processing, so modified starches are needed to meet the functional properties required in food products. This work investigated the impact of enzymatic hydrolysis and cross-linking composite modification on the properties of rice starches. Rice starch was cross-linked with epichlorohydrin (EPI with different concentrations (0.5%, 0.7%, 0.9% w/w, on a dry starch basis, affording cross-linked rice starches with the three different levels of cross-linking that were named R1, R2, and R3, respectively. The cross-linked rice starches were hydrolyzed by α-amylase and native, hydrolyzed, and hydrolyzed cross-linked rice starches were comparatively studied. It was found that hydrolyzed cross-linked rice starches showed a lower the degree of amylase hydrolysis compared with hydrolyzed rice starch. The higher the degree of cross-linking, the higher the capacity to resist enzyme hydrolysis. Hydrolyzed cross-linked rice starches further increased the adsorptive capacities of starches for liquids and decreased the trend of retrogradation, and it also strengthened the capacity to resist shear compared to native and hydrolyzed rice starches.

  15. Modification mechanism of sesbania gum, and preparation, property, adsorption of dialdehyde cross-linked sesbania gum.

    Science.gov (United States)

    Tang, Hongbo; Gao, Shiqi; Li, Yanping; Dong, Siqing

    2016-09-20

    This paper studied the modification mechanism of Sesbania gum (SG) by means of the variations in the numbers of surface hydroxyl groups on the granules, Schiff's agent coloration of aldehyde groups, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), energy dispersive spectrum (EDS), etc., and also examined the preparation, property and adsorption of dialdehyde cross-linked sesbania gum (DCLSG). The results showed that the surface hydroxyl numbers of cross-linked sesbania gum (CLSG) decreased with increasing the cross-linking degree. The distribution of the aldehyde groups on the DCLSG particles was nonuniform because most of aldehyde groups mainly located on the edge of particles. The cross-linking occurred only on the surface of SG particles. The oxidization occurred not only on the surface of SG particles, but also in the interior of particles. The cross-linking or oxidization changed the thermal properties, and reduced the swelling power, viscosity, alkali and acid resistance of SG. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Structural electronic and phonon properties of some transition metal aluminides

    Science.gov (United States)

    Fatima, Bushra; Pandit, Premlata; Sanyal, Sankar P.

    2012-06-01

    The structural and electronic properties of some Transition metal Aluminides (TMAl) namely ruthenium aluminide (RuAl), nickel aluminide (NiAl) and cobalt aluminide (CoAl) have been studied using plane wave pseudopotential method (PWSCF) within the local density approximation (LDA). The three TMAl's crystallizes in the CsCl-type structure (B2 phase). From the analysis of band structure and density of state, we found that these TMAl's are metallic in nature. The vibrational properties in terms of phonon dispersion curves and density of state have also been reported for RuAl using density functional perturbation theory (DFPT).

  17. Electronic properties of a molecular system with Platinum

    Science.gov (United States)

    Ojeda, J. H.; Medina, F. G.; Becerra-Alonso, David

    2017-10-01

    The electronic properties are studied using a finite homogeneous molecule called Trans-platinum-linked oligo(tetraethenylethenes). This system is composed of individual molecules such as benzene rings, platinum, Phosphore and Sulfur. The mechanism for the study of the electron transport through this system is based on placing the molecule between metal contacts to control the current through the molecular system. We study this molecule based on the tight-binding approach for the calculation of the transport properties using the Landauer-Büttiker formalism and the Fischer-Lee relationship, based on a semi-analytic Green's function method within a real-space renormalization approach. Our results show a significant agreement with experimental measurements.

  18. Structural and electronic properties of InPBi alloys

    Science.gov (United States)

    Zhang, Xianlong; Lu, Pengfei; Han, Lihong; Yu, Zhongyuan; Chen, Jun; Wang, Shumin

    2014-06-01

    First-principle calculations have been performed to systematically investigate structural and electronic properties of InPBi alloys. The formation energy of seven different configurations is studied. The strength of covalent bonding largely depends on the strong s-p hybridization among In-5s, P-3p and Bi-6p states. The band gap of InPBi shrinks clearly with the increasing Bi concentration and the band edge shifts when spin-orbit coupling (SOC) is considered. The insertion of Bi atom leads to hybridization of In/P/Bi p states which contributes a lot around Fermi level. In addition, our results show that the biaxial strain is an effective method to tune the electronic properties of the system.

  19. Microscopical Studies of Structural and Electronic Properties of Semiconductors

    CERN Multimedia

    2002-01-01

    The electronic and structural properties of point defects in semiconductors, e.g. radiation defects, impurities or passivating defects can excellently be studied by the hyperfine technique of Perturbed Angular Correlation (PAC). The serious limitation of this method, the small number of chemically different radioactive PAC probe atoms can be widely overcome by means of ISOLDE. Providing shortliving isotopes, which represent common dopants as well as suitable PAC probe atoms, the ISOLDE facility enables a much broader application of PAC to problems in semiconductor physics.\\\\ Using the probe atom $^{111m}$ Cd , the whole class of III-V compounds becomes accessible for PAC investigations. First successful experiments in GaAs, InP and GaP have been performed, concerning impurity complex formation and plasma induced defects. In Si and Ge, the electronic properties~-~especially their influence on acceptor-donor interaction~-~could be exemplarily st...

  20. Effects of strain on mechanical and electronic properties of borophene

    Science.gov (United States)

    Shao, Li; Li, Yan; Yuan, Qingxin; Li, Mingyu; Du, Yinxiao; Zeng, Fanguang; Ding, Pei; Ye, Honggang

    2017-04-01

    We reported a first-principles study on the geometric, mechanical, and electronic properties of two structures of borophene (B1 and B2) under three types of strain. Our results show that the mechanical and electronic properties of B1 and B2 are both highly anisotropic. The Young’s modulus are calculated to be 354 and 145 N m-1 (147 and 123 N m-1) along two different directions for B1 (B2). Although B1 under different strains has similar metallic band structures, its pseudogaps at Γ point decrease linearly with compressive and tensile strain. The pseudogaps of B2 are non-monotonic when both uniaxial compressive strain along b direction and biaxial compressive strain increase from  -0.05 to  -0.08 for the deformation of the lattice structure in the c direction.

  1. Elastic properties and electron transport in InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Migunov, Vadim

    2013-02-22

    The electron transport and elastic properties of InAs nanowires grown by chemical vapor deposition on InAs (001) substrate were studied experimentally, in-situ in a transmission electron microscope (TEM). A TEM holder allowing the measurement of a nanoforce while simultaneous imaging nanowire bending was used. Diffraction images from local areas of the wire were recorded to correlate elastic properties with the atomic structure of the nanowires. Another TEM holder allowing the application of electrical bias between the nanowire and an apex of a metallic needle while simultaneous imaging the nanowire in TEM or performing electron holography was used to detect mechanical vibrations in mechanical study or holographical observation of the nanowire inner potential in the electron transport studies. The combination of the scanning probe methods with TEM allows to correlate the measured electric and elastic properties of the nanowires with direct identification of their atomic structure. It was found that the nanowires have different atomic structures and different stacking fault defect densities that impacts critically on the elastic properties and electric transport. The unique methods, that were applied in this work, allowed to obtain dependencies of resistivity and Young's modulus of left angle 111 right angle -oriented InAs nanowires on defect density and diameter. It was found that the higher is the defect density the higher are the resistivity and the Young's modulus. Regarding the resistivity, it was deduced that the stacking faults increase the scattering of the electrons in the nanowire. These findings are consistent with the literature, however, the effect described by the other groups is not so pronounced. This difference can be attributed to the significant incompleteness of the physical models used for the data analysis. Regarding the elastic modulus, there are several mechanisms affecting the elasticity of the nanowires discussed in the thesis. It

  2. Structural, elastic, electronic and optical properties of bi-alkali ...

    Indian Academy of Sciences (India)

    The structural parameters, elastic constants, electronic and optical properties of the bi-alkali antimonides (Na 2 KSb, Na 2 RbSb, Na 2 CsSb, K 2 RbSb, K 2 CsSb and Rb 2 CsSb) were calculated using state-of-the-art density functional theory. Different exchange-correlation potentials were adopted to predict the physical ...

  3. Electronic, adsorption, and transport properties of diamondoid-based complexes

    OpenAIRE

    Adhikari, Bibek

    2017-01-01

    Quantum simulation is an invaluable tool to researchers from various fields of scientific research. It allows the investigation of various complex condensed matter in the regimes of physics, chemistry, and biology. In this work, we focused our attention in unraveling the physical, chemical, electronic, transport, and optical properties of diamondoids and their complexes through quantum simulations. We have implemented a bottom-up approach where we move from the doping and functionalization of...

  4. Structural and electronic properties of hydrosilylated silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Baumer, A.

    2005-11-15

    The structural and electronic properties of alkyl-terminated Si surfaces prepared by thermallyinduced hydrosilylation have been studied in detail in the preceding chapters. Various surfaces have been used for the functionalization ranging from crystalline Si over amorphous hydrogenated Si to nanoscaled materials such as Si nanowires and nanoparticles. In each case, the alkyl-terminated surfaces have been compared to the native oxidized and H-terminated surfaces. (orig.)

  5. Potential of New-Generation Electron Beam Technology in Interface Modification of Cold and HVOF Sprayed MCrAlY Bond Coats

    Directory of Open Access Journals (Sweden)

    J. Cizek

    2016-01-01

    Full Text Available Electron beam (EB technology treatment was carried out on CoNiCrAlY bond coats deposited on Inconel substrates via cold spray and HVOF techniques in dissimilar thicknesses. Such treatment was carried out with regard to the final materials microstructure, composition, surface roughness, and the quality of the coating-substrate interface. Following a multiple-step optimization of the processing parameters (such as beam pattern configuration, accelerating voltage, longitudinal speed, and multiple beam incidence, two final EB modifications were carried out on both coating types. It was found that the optimized EB treatment could lead to a significant alteration of the interface from a distinctive divide into smooth chemical and structural transition between the materials, significant decrease in surface roughness and porosity, and changes in mechanical properties (increase in Young’s modulus and decrease in hardness of the coating.

  6. Modification And Reengineering Of Electronic Fish Aggregating Device AS A Fishing Tools Based On Led Illuminance

    OpenAIRE

    Baswantara, Arif; Jaya, Indra; Yusfiandayani, Roza

    2017-01-01

    Fish Aggregating Devices (FADs) is generally made from foliage like a leaf of coconut, palm and nut, but with the development of marine and fishing technology, the FADs could be made electronic ally. Electronic FADs had been developed by using light and sound as an attractor, and was able to aggregate fish but the catch harvest was still relatively low compared with lift net lamp. In this paper we describe the recent development of electronic FADs. The new electronic FADs has 120 watts total...

  7. Electron and phonon properties and gas storage in carbon honeycomb

    CERN Document Server

    Gao, Yan; Zhong, Chengyong; Zhang, Zhongwei; Xie, Yuee; Zhang, Shengbai

    2016-01-01

    A new kind of three-dimensional carbon allotropes, termed carbon honeycomb (CHC), has recently been synthesized [PRL 116, 055501 (2016)]. Based on the experimental results, a family of graphene networks are constructed, and their electronic and phonon properties are calculated by using first principles methods. All networks are porous metal with two types of electron transport channels along the honeycomb axis and they are isolated from each other: one type of channels is originated from the orbital interactions of the carbon zigzag chains and is topologically protected, while the other type of channels is from the straight lines of the carbon atoms that link the zigzag chains and is topologically trivial. The velocity of the electrons can reach ~106 m/s. Phonon transport in these allotropes is strongly anisotropic, and the thermal conductivities can be very low when compared with graphite by at least a factor of 15. Our calculations further indicate that these porous carbon networks possess high storage capa...

  8. Electronic and magnetic properties of pristine and hydrogenated borophene nanoribbons

    Science.gov (United States)

    Meng, Fanchen; Chen, Xiangnan; Sun, Songsong; He, Jian

    2017-07-01

    The groundbreaking works in graphene and graphene nanoribbons (GNRs) over the past decade, and the very recent discovery of borophene naturally draw attention to the yet-to-be-explored borophene nanoribbons (BNRs). We herein report a density functional theory (DFT) study of the electronic and magnetic properties of BNRs. The foci are the impact of orientation (denoted as BxNRs and ByNRs with their respective periodic orientations along x- and y-axis), ribbon width (Nx, Ny=4-15), and hydrogenation effects on the geometric, electronic and magnetic properties of BNRs. We found that the anisotropic quasi-planar geometric structure of BNR and the edge states largely govern its electronic and magnetic properties. In particular, pristine ByNRs adopt a magnetic ground state, either anti-ferromagnetic (AFM) or ferromagnetic (FM) depending on the ribbon width, while pristine BxNRs are non-magnetic (NM). Upon hydrogenation, all BNRs exhibit NM. Interestingly, both pristine and hydrogenated ByNRs undergo a metal-semiconductor-metal transition at Ny=7, while all BxNRs remain metallic.

  9. Microstructural evolution and surface properties of nanostructured Cu-based alloy by ultrasonic nanocrystalline surface modification technique

    Energy Technology Data Exchange (ETDEWEB)

    Amanov, Auezhan, E-mail: amanov_a@yahoo.com [Department of Mechanical Engineering, Sun Moon University, Asan 336-708 (Korea, Republic of); Cho, In-Sik [R& D Group, Mbrosia Co., Ltd., Asan 336-708 (Korea, Republic of); Pyun, Young-Sik [Department of Mechanical Engineering, Sun Moon University, Asan 336-708 (Korea, Republic of)

    2016-12-01

    Graphical abstract: - Highlights: • A nanostructured surface was produced by UNSM technique. • Porosities were eliminated from the surface by UNSM technique. • Extremely high hardness obtained at the top surface after UNSM treatment. • Friction and wear behavior was improved by UNSM technique. • Resistance to scratch behavior was improved by UNSM technique. - Abstract: A nanostructured surface layer with a thickness of about 180 μm was successfully produced in Cu-based alloy using an ultrasonic nanocrystalline surface modification (UNSM) technique. Cu-based alloy was sintered onto low carbon steel using a powder metallurgy (P/M) method. Transmission electron microscope (TEM) characterization revealed that the severe plastic deformation introduced by UNSM technique resulted in nano-sized grains in the topmost surface layer and deformation twins. It was also found by atomic force microscope (AFM) observations that the UNSM technique provides a significant reduction in number of interconnected pores. The effectiveness of nanostructured surface layer on the tribological and micro-scratch properties of Cu-based alloy specimens was investigated using a ball-on-disk tribometer and micro-scratch tester, respectively. Results exhibited that the UNSM-treated specimen led to an improvement in tribological and micro-scratch properties compared to that of the sintered specimen, which may be attributed to the presence of nanostructured surface layer having an increase in surface hardness and reduction in surface roughness. The findings from this study are expected to be implemented to the automotive industry, in particular connected rod bearings and bushings in order to increase the efficiency and performance of internal combustion engines (ICEs).

  10. Sheared graphene: Electronic properties shaped by a mechanical instability

    Science.gov (United States)

    Concha, Andres; Cheng, Shengfeng; Covaci, Lucian; Mahadevan, L.

    2015-03-01

    We explore the effects of shearing graphene ribbons on its geometry, and electronic properties. Inspired by macroscopic experiments, we show that spontaneous patterns appear when a wide ribbon is subject to shear. We compared this pattern and different regimes obtained via MD simulations with macroscopic experiments, and find good agreement between them. Beyond the low shear regime a second generation of wrinkles emerge when the system relaxes trying to keep the bond lengths as close to the relaxed length as possible. Remarkably, for all shear ratios the induced superlattice generates a momentum kick when electronic excitations enter the deformed region, an effective pseudo-magnetic superlattice, and a strong Fermi velocity renormalization. These effects modify electronic properties and suggest a simple route to engineer electronic waveguides and switches at the nanoscale. Our proposal is a concrete realization of a quantum device that takes full advantage of an elastic instability that spans from the nano to macro -scales. AC was partially supported by Conicyt Grant 79112004, and Fondecyt under Grant 11130075. LC acknowledges individual support from FWO-Vlaanderen.

  11. Electronic and magnetic properties of Mn-doped ZnO: Total-energy calculations

    Energy Technology Data Exchange (ETDEWEB)

    AlGhamdi, Ghadah S [King Abdulaziz University Physics Department Faculty of Science PO Box 80203 Jeddah 21589 (Saudi Arabia); AlZahrani, A.Z., E-mail: azalzahrani@kau.edu.sa [King Abdulaziz University Physics Department Faculty of Science PO Box 80203 Jeddah 21589 (Saudi Arabia)

    2012-10-01

    Based on the spin generalized gradient approximation ({sigma}GGA) of the density functional theory (DFT), the structural, magnetic, and electronic properties of Mn-doped ZnO structure have thoroughly been investigated. It is found that the Mn atom prefers to substitute one of the Zn atoms, producing the energetically most stable configuration for the Mn-doped ZnO structure. Employing the Hubbard potential within the calculations suggests various changes and modifications to the structural, magnetic and electronic properties of the Mn-doped ZnO. Our calculations reveal that the local magnetic moment at the Mn site using the ordinary {sigma}GGA functional is 4.84 {mu}{sub B}/Mn, which is smaller than that evaluated by including the Hubbard potential of 5.04 {mu}{sub B}/Mn. Overall, the electronic band structure of the system, within the {sigma}GGA+U, is half-metallic, with metallic nature for the majority state and semiconducting nature for the minority state. Simulated scanning tunneling microscopy (STM) images for both unoccupied and occupied states indicate siginficant brightness on both Zn and Mn atoms and much brighter protrusions around the O atoms, respectively.

  12. Optical and electronic properties of pyrite nanocrystal thin films: the role of ligands.

    Science.gov (United States)

    Li, Wei; Dittrich, Thomas; Jäckel, Frank; Feldmann, Jochen

    2014-03-26

    Pyrite nanocrystals are currently considered as a promising material for large scale photovoltaic applications due to their non-toxicity and large abundance. While scalable synthetic routes for phase-pure and shape controlled colloidal pyrite nanocrystals have been reported, their use in solar cells has been hampered by the detrimental effects of their surface defects. Here, we report a systematic study of optical and electronic properties of pyrite nanocrystal thin films employing a series of different ligands varying both the anchor and bridging group. The effect of the ligands on the optical and electronic properties is investigated by UV-vis/NIR absorption spectroscopy, current voltage characteristic measurements and surface photovoltage spectroscopy. We find that the optical absorption is mainly determined by the anchor group. The absorption onset in the thin films shifts up to ∼100 meV to the red. This is attributed to changes in the dielectric environment induced by different anchors. The conductivity and photoconductivity, on the other hand, are determined by combined effects of anchor and bridging group, which modify the effective hopping barrier. Employing different ligands, the differential conductance varies over four orders of magnitude. The largest redshift and differential conductance are observed for ammonium sulfides and thiolated aromatic linkers. Pyridine and long chain amines, on the other hand, lead to smaller modifications. Our findings highlight the importance of surface functionalization and interparticle electronic coupling in the use of pyrite nanocrystals for photovoltaic devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Electronic properties of corrugated graphene: the Heisenberg principle and wormhole geometry in the solid state.

    Science.gov (United States)

    Atanasov, Victor; Saxena, Avadh

    2011-05-04

    Adopting a purely two-dimensional relativistic equation for graphene's carriers contradicts the Heisenberg uncertainty principle since it requires setting the off-the-surface coordinate of a three-dimensional wavefunction to zero. Here we present a theoretical framework for describing graphene's massless relativistic carriers in accordance with this most fundamental of all quantum principles. A gradual confining procedure is used to restrict the dynamics onto a surface and normal to the surface parts, and in the process the embedding of this surface into the three-dimensional world is accounted for. As a result an invariant geometric potential arises in the surface part which scales linearly with the mean curvature and shifts the Fermi energy of the material proportional to bending. Strain induced modification of the electronic properties or 'straintronics' is clearly an important field of study in graphene. This opens an avenue to producing electronic devices: micro- and nano-electromechanical systems (MEMS and NEMS), where the electronic properties are controlled by geometric means and no additional alteration of graphene is necessary. The appearance of this geometric potential also provides us with clues as to how quantum dynamics looks in the curved space-time of general relativity. In this context we explore a two-dimensional cross-section of the wormhole geometry, realized with graphene as a solid state thought experiment. © 2011 IOP Publishing Ltd

  14. Investigations on the optical, thermal and surface modifications of electron irradiated L-threonine single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ramesh Kumar, G.; Gokul Raj, S. [Department of Physics, Presidency College, Chepauk, Chennai 600005 (India); Bogle, K.A.; Dhole, S.D.; Bhoraskar, V.N. [Department of Physics, University of Pune, Pune 411007 (India); Mohan, R. [Department of Physics, Presidency College, Chepauk, Chennai 600005 (India)], E-mail: professormohan@yahoo.co.in

    2008-06-15

    L-Threonine single crystals have been irradiated by 6 MeV electrons. Irradiated crystals at various electron fluences were subjected to various techniques such as UV-vis-NIR, atomic force microscopy (AFM) and thermomechanical analyses. Thermal strength of the irradiated crystals has also been studied through differential scanning calorimetry (DSC) measurements. The results have been discussed in detail.

  15. First-principles study of electronic and optical properties of solid-solution ZnO1-xSx

    Science.gov (United States)

    Jani, Margi; Ray, Abhijit

    2017-09-01

    We investigated the electronic and optical properties of ZnO under the circumstances of isovalent anionic doping by sulfur. A pseudopotential implementation of density functional theory is applied within the local density approximation to examine the modification of band structure in wurtzite ZnO by sulfur substitution. Although Fermi level position does not change, a strong localization of Zn-3d orbital is found by S-doping. Optical properties and constants are found to strongly depend on the sulfur content at low photon energies.

  16. Electronic properties of transition metal doped silicon clusters

    Energy Technology Data Exchange (ETDEWEB)

    Rittmann, Jochen; Langenberg, Andreas; Lau, Tobias [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Institut fuer Methoden und Instrumentierung der Synchrotronstrahlung, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Hirsch, Konstantin; Kasigkeit, Christian; Klar, Philipp; Lofink, Fabian; Probst, Juergen; Vogel, Marlene; Wittich, Joerg; Zamudio-Bayer, Vicente; Moeller, Thomas [Technische Universitaet Berlin, Institut fuer Optik und Atomare Physik, Hardenbergstr. 36, 10623 Berlin (Germany); Issendorff, Bernd von [Universitaet Freiburg, Fakultaet fuer Physik, Stefan-Meier-Str. 21, 79104 Freiburg (Germany)

    2010-07-01

    Size selected transition metal doped silicon clusters have been studied with resonant 2p x-ray absorption spectroscopy. Despite the different number of valence electrons, nearly identical local electronic structures are found at the dopant atoms in TiSi{sub 16}{sup +}, VSi{sub 16}{sup +}, and CrSi{sub 16}{sup +}. Additional measurements of the direct 2p photoionization as well as spectroscopy on the valence electrons of MSi{sub n}{sup +} clusters, (M=V,Ti,Cr; n=15-17) allow us to determine the band gap, which is predicted to be exceptional high for the very symmetric MSi{sub 16}{sup +} clusters (M=V,Ti,Cr). The experimental data can be understood in the spherical potential model. The data indicate strongly interlinked electronic and geometric properties: While the transition metal atoms impose a geometric rearrangement on the silicon cluster, the interaction with the highly symmetric silicon cage determines the electronic structure of the transition metal dopants.

  17. Manganites in Perovskite Superlattices: Structural and Electronic Properties

    KAUST Repository

    Jilili, Jiwuer

    2016-07-13

    Perovskite oxides have the general chemical formula ABO3, where A is a rare-earth or alkali-metal cation and B is a transition metal cation. Perovskite oxides can be formed with a variety of constituent elements and exhibit a wide range of properties ranging from insulators, metals to even superconductors. With the development of growth and characterization techniques, more information on their physical and chemical properties has been revealed, which diversified their technological applications. Perovskite manganites are widely investigated compounds due to the discovery of the colossal magnetoresistance effect in 1994. They have a broad range of structural, electronic, magnetic properties and potential device applications in sensors and spintronics. There is not only the technological importance but also the need to understand the fundamental mechanisms of the unusual magnetic and transport properties that drive enormous attention. Manganites combined with other perovskite oxides are gaining interest due to novel properties especially at the interface, such as interfacial ferromagnetism, exchange bias, interfacial conductivity. Doped manganites exhibit diverse electrical properties as compared to the parent compounds. For instance, hole doped La0.7Sr0.3MnO3 is a ferromagnetic metal, whereas LaMnO3 is an antiferromagnetic insulator. Since manganites are strongly correlated systems, heterojunctions composed of manganites and other perovskite oxides are sunject to complex coupling of the spin, orbit, charge, and lattice degrees of freedom and exhibit unique electronic, magnetic, and transport properties. Electronic reconstructions, O defects, doping, intersite disorder, magnetic proximity, magnetic exchange, and polar catastrophe are some effects to explain these interfacial phenomena. In our work we use first-principles calculations to study the structural, electronic, and magnetic properties of manganite based superlattices. Firstly, we investigate the electronic

  18. Mask-assisted electron radiation grafting for localized through-volume modification of porous substrates: influence of electron energy on spatial resolution

    Science.gov (United States)

    Forner-Cuenca, A.; Manzi-Orezzoli, V.; Kristiansen, P. M.; Gubler, L.; Schmidt, T. J.; Boillat, P.

    2017-06-01

    The spatial resolution aspects of the local modification of porous materials by electron induced graft-polymerization were studied by a combination of experiments and numerical simulations. Using blocking masks, only selected regions of the material were exposed to radiation and subsequently grafted. The main focus of this study is the application to gas diffusion layers, a carbonaceous 200 μm thick porous substrate widely used in fuel cells, with the goal of improving water management by locally tuning the wettability. The comparison of experiments performed with different electron energies and corresponding simulations shows good agreement, identifying the energy threshold necessary to graft through the material to be approximately 150 keV. The impact of electron energy on spatial resolution was studied, showing that the blurring effects due to electron scattering reach a maximum at around 200 keV and are reduced at higher electron energies. Finally, the numerical simulations were used to define the conditions necessary to selectively graft only parts of bi-layer fuel cell materials.

  19. A New Approach for the Modification of Paper Surface Properties Using Polyoxometalates

    Science.gov (United States)

    Saraiva, Mikhail S.; Gamelas, José A. F.; Mendes de Sousa, António P.; Reis, Bruno M.; Amaral, José L.; Ferreira, Paulo J.

    2010-01-01

    A new approach for the chemical modification of the surface of paper based on the application of colloidal mixtures containing cationic starch and polyoxometalates on uncoated base paper is presented. Polyoxometalates with the Keggin-type structure and physical properties similar to those presented by coating pigments, namely H3PW12O40·23H2O, H4SiW12O40·24H2O, and K7PW11O39·9H2O, have been used in order to improve the quality of inkjet printing. The analysis of the different samples by FTIR-ATR spectroscopy showed the presence of the polyoxometalates (and the cationic starch) on the top surface of the paper. In addition, the determination of surface energy parameters, namely the polar component (σsp) and the dispersive component (σsd) of the surface energy, by contact angle measurements revealed that, for the new samples, the polar component level was much higher than that of the uncoated base paper. The quality of inkjet printing, evaluated by parameters such as the gamut area and the optical density, was considerably improved by these surface treatments.

  20. Properties of acid polysaccharides and their chemical modification; Sansei tato no seijo to kagaku shushoku

    Energy Technology Data Exchange (ETDEWEB)

    Kogamo, A. [Kitasato Univ., Tokyo (Japan)

    1997-03-25

    Polysaccharides are in presence throughout the kingdoms of animals, vegetables, and microbes, participating in biotic activities. It has been disclosed of late that they are closely related to biotic functions, and complex saccharides, such as glycosaminoglycan (CAG), which constitute the sugar chain are attracting attention above all. This report centers on CAG and discusses the properties of acid polysaccharides, their chemical modification, and applications. CAG in organisms combines with proteins such as collagen for the formation of connective tissues, and also combines in quantities in covalent bond with proteins that constitute thin and long high-molecular cores for the formation of gigantic molecules called proteoglycan. It is an acid sugar chain in which uronic acid and amino sugar having amino groups intertwine each other. The basic reactions to be utilized for the production of highly active saccharides on the basis of this structure are the lowering of molecular weight and sulfation. Activity against HIV (Human Immunodeficiency Virus) is observed in marine alga saccharide carageenan, and studies are under way for variously modifying it for development into medicine. 6 refs., 6 figs.

  1. 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

  2. Modification of Co/Cu nanoferrites properties via Gd3+/Er3+doping

    Science.gov (United States)

    Ateia, Ebtesam E.; Soliman, Fatma S.

    2017-05-01

    Pure nanoparticles of the rare earth-substituted cobalt and copper ferrites with general formula Me Gd0.025 Er0.05 Fe1.925 O4 (Me = Co, Cu) were prepared by the chemical citrate method. X-ray diffraction, field emission scanning electron microscopy, BET analysis are utilized to study the effect of rare earth substitution and its impact on the physical properties of the investigated samples. Rare earth-doped cobalt shows type IV isotherm suggesting mesopore structure with its hysteresis loop. The estimated crystallite sizes are found in the range of 21.49 and 36.11 nm for the doped Co and Cu samples, respectively. The magnetic properties of rare earth-substituted cobalt and copper ferrites showed a definite hysteresis loop at room temperature. An increase in coercivity and a decrease in saturation magnetization were detected. This can be explained in view of weaker nature of the Re3+-Fe3+ interaction compared to Fe3+-Fe3+ interaction. Greater than 1.13-fold increase in coercivity (Hc = 2184 Oe) was observed in doped cobalt nanoferrite samples compared to copper (Hc = 1936 Oe). It was found that the decreasing in temperature leads to great improvement in the magnetic properties of the investigated samples. As the magnetic recording performance of the magnetic samples is improved for well-crystallized samples with nano-structural, the effect of rare earth substitution seems to be particularly valuable in this regard.

  3. Local Electronic And Dielectric Properties at Nanosized Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bonnell, Dawn A. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    2015-02-23

    Final Report to the Department of Energy for period 6/1/2000 to 11/30/2014 for Grant # DE-FG02-00ER45813-A000 to the University of Pennsylvania Local Electronic And Dielectric Properties at Nanosized Interfaces PI: Dawn Bonnell The behavior of grain boundaries and interfaces has been a focus of fundamental research for decades because variations of structure and composition at interfaces dictate mechanical, electrical, optical and dielectric properties in solids. Similarly, the consequence of atomic and electronic structures of surfaces to chemical and physical interactions are critical due to their implications to catalysis and device fabrication. Increasing fundamental understanding of surfaces and interfaces has materially advanced technologies that directly bear on energy considerations. Currently, exciting developments in materials processing are enabling creative new electrical, optical and chemical device configurations. Controlled synthesis of nanoparticles, semiconducting nanowires and nanorods, optical quantum dots, etc. along with a range of strategies for assembling and patterning nanostructures portend the viability of new devices that have the potential to significantly impact the energy landscape. As devices become smaller the impact of interfaces and surfaces grows geometrically. As with other nanoscale phenomena, small interfaces do not exhibit the same properties as do large interfaces. The size dependence of interface properties had not been explored and understanding at the most fundamental level is necessary to the advancement of nanostructured devices. An equally important factor in the behavior of interfaces in devices is the ability to examine the interfaces under realistic conditions. For example, interfaces and boundaries dictate the behavior of oxide fuel cells which operate at extremely high temperatures in dynamic high pressure chemical environments. These conditions preclude the characterization of local properties during fuel cell

  4. Modification to an Auger Electron Spectroscopy system for measuring segregation in a bi-crystal

    CSIR Research Space (South Africa)

    Jafta, CJ

    2013-03-01

    Full Text Available to the scanning control unit of the AES electron beam to eliminate the difference in experimental parameters and specialized written software to automate the data acquisition process. This makes direct comparison of segregation parameters on two different...

  5. In-situ investigation of laser surface modifications of WC-Co hard metals inside a scanning electron microscope

    Science.gov (United States)

    Mueller, H.; Wetzig, K.; Schultrich, B.; Pompe, Wolfgang; Chapliev, N. I.; Konov, Vitaly I.; Pimenov, S. M.; Prokhorov, Alexander M.

    1989-05-01

    The investigation of laser interaction with solid surfaces and of the resulting mechanism of surface modification are of technical interest to optimize technological processes, and they are also of fundamental scientific importance. Most instructive indormation is available with the ail of the in-situ techniques. For instance, measuring of the photon emission of the irradiated surface ane the plasma torch (if it is produced) simultaneously to laser action, makes it possible to gain a global characterization of the laser-solid interaction. In order to obtain additional information about surface and structure modifications in microscopic detail , a laser and scanning electron microscope were combined in to a tandem equipment (LASEM). Inside this eqiipment the microscopic observation is carried out directly at the laser irradiated area without any displacement of the sample. In this way, the stepwise development of surface modification during multipulse irradiation is visible in microscopic details and much more reliable information about the surface modification process is obtainable in comparison to an external laser irradiation. Such kind of equipments were realized simultaneously and independently in the Institut of General Physics (Moscow) and the Central Institute of Solid State Physics and Material Research (Dresden) using a CO2 and a LTd-glass-laser, respectively. In the following the advantages and possibilities of a LASEM shall be demonstrated by some selected investigations of WC-CO hardmeta. The results were obtained in collaboration by both groups with the aid of the pulsed CO2-laser. The TEA CO2 laser was transmitted through a ZnSe-window into the sample chamber of the SEM and focused ofAo tfte sample surface. It was operated in TEM - oo mode with a repetition rate of about 1 pulse per second. A peak power density of about 160 MW/cm2 was achieved in front of the sample surface.

  6. Design of materials configurations for enhanced phononic and electronic properties

    Science.gov (United States)

    Daraio, Chiara

    The discovery of novel nonlinear dynamic and electronic phenomena is presented for the specific cases of granular materials and carbon nanotubes. This research was conducted for designing and constructing optimized macro-, micro- and nano-scale structural configurations of materials, and for studying their phononic and electronic behavior. Variation of composite arrangements of granular elements with different elastic properties in a linear chain-of-sphere, Y-junction or 3-D configurations led to a variety of novel phononic phenomena and interesting physical properties, which can be potentially useful for security, communications, mechanical and biomedical engineering applications. Mechanical and electronic properties of carbon nanotubes with different atomic arrangements and microstructures were also investigated. Electronic properties of Y-junction configured carbon nanotubes exhibit an exciting transistor switch behavior which is not seen in linear configuration nanotubes. Strongly nonlinear materials were designed and fabricated using novel and innovative concepts. Due to their unique strongly nonlinear and anisotropic nature, novel wave phenomena have been discovered. Specifically, violations of Snell's law were detected and a new mechanism of wave interaction with interfaces between NTPCs (Nonlinear Tunable Phononic Crystals) was established. Polymer-based systems were tested for the first time, and the tunability of the solitary waves speed was demonstrated. New materials with transformed signal propagation speed in the manageable range of 10-100 m/s and signal amplitude typical for audible speech have been developed. The enhancing of the mitigation of solitary and shock waves in 1-D chains were demonstrated and a new protective medium was designed for practical applications. 1-D, 2-D and 3-D strongly nonlinear system have been investigated providing a broad impact on the whole area of strongly nonlinear wave dynamics and creating experimental basis for new

  7. Electronic structure and physicochemical properties of selected penicillins

    Science.gov (United States)

    Soriano-Correa, Catalina; Ruiz, Juan F. Sánchez; Raya, A.; Esquivel, Rodolfo O.

    Traditionally, penicillins have been used as antibacterial agents due to their characteristics and widespread applications with few collateral effects, which have motivated several theoretical and experimental studies. Despite the latter, their mechanism of biological action has not been completely elucidated. We present a theoretical study at the Hartree-Fock and density functional theory (DFT) levels of theory of a selected group of penicillins such as the penicillin-G, amoxicillin, ampicillin, dicloxacillin, and carbenicillin molecules, to systematically determine the electron structure of full ?-lactam antibiotics. Our results allow us to analyze the electronic properties of the pharmacophore group, the aminoacyl side-chain, and the influence of the substituents (R and X) attached to the aminoacyl side-chain at 6? (in contrast with previous studies focused at the 3? substituents), and to corroborate the results of previous studies performed at the semiempirical level, solely on the ?-lactam ring of penicillins. Besides, several density descriptors are determined with the purpose of analyzing their link to the antibacterial activity of these penicillin compounds. Our results for the atomic charges (fitted to the electrostatic potential), the bond orders, and several global reactivity descriptors, such as the dipole moments, ionization potential, hardness, and the electrophilicity index, led us to characterize: the active sites, the effect of the electron-attracting substituent properties and their physicochemical features, which altogether, might be important to understand the biological activity of these type of molecules.

  8. Physical characterization of functionalized spider silk: electronic and sensing properties

    Directory of Open Access Journals (Sweden)

    Eden Steven, Jin Gyu Park, Anant Paravastu, Elsa Branco Lopes, James S Brooks, Ongi Englander, Theo Siegrist, Papatya Kaner and Rufina G Alamo

    2011-01-01

    Full Text Available This work explores functional, fundamental and applied aspects of naturally harvested spider silk fibers. Natural silk is a protein polymer where different amino acids control the physical properties of fibroin bundles, producing, for example, combinations of β-sheet (crystalline and amorphous (helical structural regions. This complexity presents opportunities for functional modification to obtain new types of material properties. Electrical conductivity is the starting point of this investigation, where the insulating nature of neat silk under ambient conditions is described first. Modification of the conductivity by humidity, exposure to polar solvents, iodine doping, pyrolization and deposition of a thin metallic film are explored next. The conductivity increases exponentially with relative humidity and/or solvent, whereas only an incremental increase occurs after iodine doping. In contrast, iodine doping, optimal at 70 °C, has a strong effect on the morphology of silk bundles (increasing their size, on the process of pyrolization (suppressing mass loss rates and on the resulting carbonized fiber structure (that becomes more robust against bending and strain. The effects of iodine doping and other functional parameters (vacuum and thin film coating motivated an investigation with magic angle spinning nuclear magnetic resonance (MAS-NMR to monitor doping-induced changes in the amino acid-protein backbone signature. MAS-NMR revealed a moderate effect of iodine on the helical and β-sheet structures, and a lesser effect of gold sputtering. The effects of iodine doping were further probed by Fourier transform infrared (FTIR spectroscopy, revealing a partial transformation of β-sheet-to-amorphous constituency. A model is proposed, based on the findings from the MAS-NMR and FTIR, which involves iodine-induced changes in the silk fibroin bundle environment that can account for the altered physical properties. Finally, proof

  9. Physical characterization of functionalized spider silk: electronic and sensing properties

    Energy Technology Data Exchange (ETDEWEB)

    Steven, Eden; Brooks, James S [Department of Physics and National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac, Tallahassee, FL 32310 (United States); Park, Jin Gyu [FAMU-FSU Department of Industrial and Manufacturing Engineering, High-Performance Materials Institute, Florida State University, 2005 Levy Ave., Tallahassee, FL 32310 (United States); Paravastu, Anant; Siegrist, Theo; Kaner, Papatya; Alamo, Rufina G [FAMU-FSU Department of Chemical and Biomedical Engineering and National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac, Tallahassee, FL 32310 (United States); Branco Lopes, Elsa [Departamento de Quimica, Instituto Tecnologico e Nuclear/CFMC-UL, P-2686-953 Sacavem (Portugal); Englander, Ongi, E-mail: esteven@magnet.fsu.edu [FAMU-FSU Department of Mechanical Engineering and National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac, Tallahassee, Florida 32310 (United States)

    2011-10-15

    This work explores functional, fundamental and applied aspects of naturally harvested spider silk fibers. Natural silk is a protein polymer where different amino acids control the physical properties of fibroin bundles, producing, for example, combinations of {beta}-sheet (crystalline) and amorphous (helical) structural regions. This complexity presents opportunities for functional modification to obtain new types of material properties. Electrical conductivity is the starting point of this investigation, where the insulating nature of neat silk under ambient conditions is described first. Modification of the conductivity by humidity, exposure to polar solvents, iodine doping, pyrolization and deposition of a thin metallic film are explored next. The conductivity increases exponentially with relative humidity and/or solvent, whereas only an incremental increase occurs after iodine doping. In contrast, iodine doping, optimal at 70 deg. C, has a strong effect on the morphology of silk bundles (increasing their size), on the process of pyrolization (suppressing mass loss rates) and on the resulting carbonized fiber structure (that becomes more robust against bending and strain). The effects of iodine doping and other functional parameters (vacuum and thin film coating) motivated an investigation with magic angle spinning nuclear magnetic resonance (MAS-NMR) to monitor doping-induced changes in the amino acid-protein backbone signature. MAS-NMR revealed a moderate effect of iodine on the helical and {beta}-sheet structures, and a lesser effect of gold sputtering. The effects of iodine doping were further probed by Fourier transform infrared (FTIR) spectroscopy, revealing a partial transformation of {beta}-sheet-to-amorphous constituency. A model is proposed, based on the findings from the MAS-NMR and FTIR, which involves iodine-induced changes in the silk fibroin bundle environment that can account for the altered physical properties. Finally, proof

  10. Structural and electronic properties of copper-doped chalcogenide glasses

    Science.gov (United States)

    Guzman, David M.; Strachan, Alejandro

    2017-10-01

    Using ab initio molecular dynamics based on density functional theory, we study the atomic and electronic structure, and transport properties of copper-doped germanium-based chalcogenide glasses. These mixed ionic-electronic conductor materials exhibit resistance or threshold switching under external electric field depending on slight variations of chemical composition. Understanding the origin of the transport character is essential for the functionalization of glassy chalcogenides for nanoelectronics applications. To this end, we generated atomic structures for GeX3 and GeX6 (X = S, Se, Te) at different copper concentrations and characterized the atomic origin of electronic states responsible for transport and the tendency of copper clustering as a function of metal concentration. Our results show that copper dissolution energies explain the tendency of copper to agglomerate in telluride glasses, consistent with filamentary conduction. In contrast, copper is less prone to cluster in sulfides and selenides leading to hysteresisless threshold switching where the nature of transport is dominated by electronic midgap defects derived from polar chalcogen bonds and copper atoms. Simulated I -V curves show that at least 35% by weight of copper is required to achieve the current demands of threshold-based devices for memory applications.

  11. Structural and electronic properties of monolayer group III monochalcogenides

    Science.gov (United States)

    Demirci, S.; Avazlı, N.; Durgun, E.; Cahangirov, S.

    2017-03-01

    We investigate the structural, mechanical, and electronic properties of the two-dimensional hexagonal structure of group III-VI binary monolayers, M X (M =B , Al, Ga, In and X =O , S, Se, Te) using first-principles calculations based on the density functional theory. The structural optimization calculations and phonon spectrum analysis indicate that all of the 16 possible binary compounds are thermally stable. In-plane stiffness values cover a range depending on the element types and can be as high as that of graphene, while the calculated bending rigidity is found to be an order of magnitude higher than that of graphene. The obtained electronic band structures show that M X monolayers are indirect band-gap semiconductors. The calculated band gaps span a wide optical spectrum from deep ultraviolet to near infrared. The electronic structure of oxides (M O ) is different from the rest because of the high electronegativity of oxygen atoms. The dispersions of the electronic band edges and the nature of bonding between atoms can also be correlated with electronegativities of constituent elements. The unique characteristics of group III-VI binary monolayers can be suitable for high-performance device applications in nanoelectronics and optics.

  12. Two-Dimensional Vlasov Simulations of Fast Stochastic Electron Heating in Ionospheric Modification Experiments

    Science.gov (United States)

    Speirs, David Carruthers; Eliasson, Bengt; Daldorff, Lars K. S.

    2017-10-01

    Ionospheric heating experiments using high-frequency ordinary (O)-mode electromagnetic waves have shown the induced formation of magnetic field-aligned density striations in the ionospheric F region, in association with lower hybrid (LH) and upper hybrid (UH) turbulence. In recent experiments using high-power transmitters, the creation of new plasma regions and the formation of descending artificial ionospheric layers (DAILs) have been observed. These are attributed to suprathermal electrons ionizing the neutral gas, so that the O-mode reflection point and associated turbulence is moving to a progressively lower altitude. We present the results of two-dimensional (2-D) Vlasov simulations used to study the mode conversion of an O-mode pump wave to trapped UH waves in a small-scale density striation of circular cross section. Subsequent multiwave parametric decays lead to UH and LH turbulence and to the excitation of electron Bernstein (EB) waves. Large-amplitude EB waves result in rapid stochastic electron heating when the wave amplitude exceeds a threshold value. For typical experimental parameters, the electron temperature is observed to rise from 1,500 K to about 8,000 K in a fraction of a millisecond, much faster than Ohmic heating due to collisions which occurs on a timescale of an order of a second. This initial heating could then lead to further acceleration due to Langmuir turbulence near the critical layer. Stochastic electron heating therefore represents an important potential mechanism for the formation of DAILs.

  13. Study of optical and electronic properties of nickel from reflection electron energy loss spectra

    Science.gov (United States)

    Xu, H.; Yang, L. H.; Da, B.; Tóth, J.; Tőkési, K.; Ding, Z. J.

    2017-09-01

    We use the classical Monte Carlo transport model of electrons moving near the surface and inside solids to reproduce the measured reflection electron energy-loss spectroscopy (REELS) spectra. With the combination of the classical transport model and the Markov chain Monte Carlo (MCMC) sampling of oscillator parameters the so-called reverse Monte Carlo (RMC) method was developed, and used to obtain optical constants of Ni in this work. A systematic study of the electronic and optical properties of Ni has been performed in an energy loss range of 0-200 eV from the measured REELS spectra at primary energies of 1000 eV, 2000 eV and 3000 eV. The reliability of our method was tested by comparing our results with the previous data. Moreover, the accuracy of our optical data has been confirmed by applying oscillator strength-sum rule and perfect-screening-sum rule.

  14. Electronic properties of boron and nitrogen doped graphene nanoribbons and its application for graphene electronics

    Energy Technology Data Exchange (ETDEWEB)

    Huang Bing, E-mail: Bing.Huang@nrel.go [Department of Physics, Tsinghua University, Beijing 100084 (China)

    2011-01-24

    On the basis of density functional theory calculations, we have systematically investigated the electronic properties of armchair-edge graphene nanoribbons (GNRs) doped with boron (B) and nitrogen (N) atoms. B (N) atoms could effectively introduce holes (electrons) to GNRs and the system exhibits p- (n-) type semiconducting behavior after B (N) doping. According to the electronic structure calculations, Z-shape GNR-based field effect transistors (FETs) is constructed by selective doping with B or N atoms. Using first-principles quantum transport calculations, we demonstrate that the B-doped p-type GNR-FETs can exhibit high levels of performance, with high ON/OFF ratios and low subthreshold swing. Furthermore, the performance parameters of GNR-FETs could be controlled by the p-type semiconducting channel length.

  15. Electronic transport properties of carbon nanotube metal-semiconductor-metal

    Directory of Open Access Journals (Sweden)

    F Khoeini

    2008-07-01

    Full Text Available  In this work, we study electronic transport properties of a quasi-one dimensional pure semi-conducting Zigzag Carbon Nanotube (CNT attached to semi-infinite clean metallic Zigzag CNT leads, taking into account the influence of topological defect in junctions. This structure may behave like a field effect transistor. The calculations are based on the tight-binding model and Green’s function method, in which the local density of states(LDOS in the metallic section to semi-conducting section, and muli-channel conductance of the system are calculated in the coherent and linear response regime, numerically. Also we have introduced a circuit model for the system and investigated its current. The theoretical results obtained, can be a base, for developments in designing nano-electronic devices.

  16. Multi-scale defect engineering and interface modification for enhancement of thermoelectric properties in nanostructured bulk materials

    Science.gov (United States)

    Puneet, Pooja

    Firstly, the effects of extrinsic point defects, such as rattlers (Ce, In, Ba, Yb), dopants (Co, Ni) and secondary phases on FeSb 3 and CoSb3 based p-type skutterudites on the transport and magnetic properties is studied. 'Phonon glass and electron crystal' like behavior was observed in Ni-doped skutterudites. Interestingly, we found that the addition of In facilitated the formation of secondary phases with various morphologies upon surpassing the filling fraction limits. Such in-situ secondary phases were in fact found to be beneficial to the system altering their electrical transport properties, and thereby increasing the ZT of the system as compared to that of the parent compound. The highest ZT value of 0.9 at 650 K was reported for p-type skutterudite sample with nominal composition In0.1Ce0.9Fe3.5 Ni0.5Sb12. In the low temperature regime (T effects due to the splitting of ground state of Ce (4f level) in presence of cubic crystalline field were observed to dictate the magnetic properties below 100 K. Further, our magnetic susceptibility data is consistent with a crystal field splitting gap of ˜39 meV (˜450 K). The intrinsic surface or interfacial defects in elemental Bismuth were introduced by controlling the surface-to-volume ratio using a combination of high energy ballmilling and spark plasma sintering (SPS) processes. The obtained ball-milled powders were SPS processed with different ON-OFF time ratios of the DC current pulses to further modify the nature and extent of these surfaces. The 'double decoupling' (simultaneous optimization of the thermopower, electrical conductivity and thermal conductivity) in single element polycrystalline Bi was observed via a combination of an increase in the surface-to-volume ratio achieved by ball milling process and an interface (or grain boundary) modification by the SPS process. As a result, a greater than six-fold improvement in the PF, and hence ZT, was achieved in polycrystalline bulk Bi samples. Our detailed

  17. Electronic, magnetic, and magnetocrystalline anisotropy properties of light lanthanides

    Science.gov (United States)

    Hackett, Timothy A.; Baldwin, D. J.; Paudyal, D.

    2017-11-01

    Theoretical understanding of interactions between localized and mobile electrons and the crystal environment in light lanthanides is important because of their key role in much needed magnetic anisotropy in permanent magnet materials that have a great impact in automobile and wind turbine applications. We report electronic, magnetic, and magnetocrystalline properties of these basic light lanthanide elements studied from advanced density functional theory (DFT) calculations. We find that the inclusion of onsite 4f electron correlation and spin orbit coupling within the full-potential band structure is needed to understand the unique magnetocrystalline properties of these light lanthanides. The onsite electron correlation, spin orbit coupling, and full potential for the asphericity of charge densities must be taken into account for the proper treatment of 4f states. We find the variation of total energy as a function of lattice constants that indicate multiple structural phases in Ce contrasting to a single stable structure obtained in other light lanthanides. The 4f orbital magnetic moments are partially quenched as a result of crystalline electric field splitting that leads to magnetocrystalline anisotropy. The charge density plots have similar asphericity and environment in Pr and Nd indicating similar magnetic anisotropy. However, Ce and Sm show completely different asphericity and environment as both orbital moments are significantly quenched. In addition, the Fermi surface structures exemplified in Nd indicate structural stability and unravel a cause of anisotropy. The calculated magnetocrystalline anisotropy energy (MAE) reveals competing c-axis and in-plane anisotropies, and also predicts possibilities of unusual structural deformations in light lanthanides. The uniaxial magnetic anisotropy is obtained in the double hexagonal closed pack structures of the most of the light lanthanides, however, the anisotropy is reduced or turned to planar in the low symmetry

  18. Stability and electronic properties of silicene on WSe2

    KAUST Repository

    Zhu, Jiajie

    2015-03-17

    Many semiconducting substrates, such as GaS and MgBr2, have been explored for silicene. However, large lattice mismatches, complicated control of terminal layers and small band gaps are critical limiting factors. First-principles results on the stability and electronic properties of silicene on WSe2 show that the energy barriers for lateral translation between the two subsystems are very small due to weak van der Waals interactions. For the same reason, the Dirac physics of silicene is preserved. It turns out that the induced band gap is sufficient to withstand thermal fluctuations. This journal is © The Royal Society of Chemistry 2015.

  19. Quantum theory of the optical and electronic properties of semiconductors

    CERN Document Server

    Haug, Hartmut

    1990-01-01

    The current technological revolution in the development of computing devices has created a demand for a textbook on the quantum theory of the electronic and optical properties of semiconductors and semiconductor devices. This book successfully fulfills this need. Based on lectures given by the authors, it is a comprehensive introduction for researchers or graduate-level students to the subject. Certain sections can also serve as a graduate-level textbook for use in solid state physics courses or for more specialized courses. The final chapters establish a direct link to current research in sem

  20. Study of electronic transport properties of doped 8AGNR

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Uma Shankar, E-mail: umashankar-rjit@yahoo.co.in [Rustamji Institute of Technology, BSF Academy Tekanpur, Gwalior-475005 (India); Srivastava, Anurag [Advanced Materials Research Group, Computational Nanoscience and Technology Lab, ABV-Indian Institute of Information Technology and Management Gwalior-474015 (India); Verma, U. P. [School of Studies in Physics, Jiwaji University, Gwalior-474011 (India)

    2014-04-24

    The electronic and transport properties of 8-armchair graphene nanoribbon (8AGNR) with defect at different sites are investigated by performing first-principles calculations based on density functional theory (DFT). The calculated results show that the 8AGNR are semiconductor. The introduction of 3d transition metals, creates the nondegenerate states in the conduction band, makes 8AGNR metallic. The computed transmission spectrum confirms that AGNR are semiconducting in nature and their band gap remain unchanged and localized states appear when there is vacancy in their structures, and the conductance decreases due to defects compared with the pristine nanoribbon.

  1. Electronic properties of semiconducting silicides: fundamentals and recent predictions

    Energy Technology Data Exchange (ETDEWEB)

    Ivanenko, L.I.; Shaposhnikov, V.L.; Filonov, A.B.; Krivosheeva, A.V.; Borisenko, V.E.; Migas, D.B.; Miglio, L.; Behr, G.; Schumann, J

    2004-08-02

    This review emphasizes progress in theoretical simulation and experiments that have been performed in the past years for semiconducting silicides. New fundamental electronic and optical properties of Ca{sub 2}Si and BaSi{sub 2}, recently found RuSi{sub 2} phase, ternaries in Fe-Os-Si and Ru-Os-Si systems, {beta}-FeSi{sub 2}, Mg{sub 2}Si and CrSi{sub 2} with stretched and compressed lattices as well as transport properties of {beta}-FeSi{sub 2}, ReSi{sub 1.75}, Ru{sub 2}Si{sub 3} are presented. Prospects for practical applications of semiconducting silicides are discussed.

  2. Theory of electronic and optical properties of nanostructures

    Science.gov (United States)

    Hewageegana, Prabath S.

    "There is plenty of room at the bottom." This bold and prophetic statement from Nobel laureate Richard Feynman back in 1950s at Cal Tech launched the Nano Age and predicted, quite accurately, the explosion in nanoscience and nanotechnology. Now this is a fast developing area in both science and technology. Many think this would bring the greatest technological revolution in the history of mankind. To understand electronic and optical properties of nanostructures, the following problems have been studied. In particular, intensity of mid-infrared light transmitted through a metallic diffraction grating has been theoretically studied. It has been shown that for s-polarized light the enhancement of the transmitted light is much stronger than for p-polarized light. By tuning the parameters of the diffraction grating enhancement can be increased by a few orders of magnitude. The spatial distribution of the transmitted light is highly nonuniform with very sharp peaks, which have the spatial widths about 10 nm. Furthermore, under the ultra fast response in nanostructures, the following two related goals have been proved: (a) the two-photon coherent control allows one to dynamically control electron emission from randomly rough surfaces, which is localized within a few nanometers. (b) the photoelectron emission from metal nanostructures in the strong-field (quasistationary) regime allows coherent control with extremely high contrast, suitable for nanoelectronics applications. To investigate the electron transport properties of two dimensional carbon called graphene, a localization of an electron in a graphene quantum dot with a sharp boundary has been considered. It has been found that if the parameters of the confinement potential satisfy a special condition then the electron can be strongly localized in such quantum dot. Also the energy spectra of an electron in a graphene quantum ring has been analyzed. Furthermore, it has been shown that in a double dot system some

  3. Modification of Functional Properties of Whey Protein Isolate Nanocomposite Films and Coatings with Nanoclays

    Directory of Open Access Journals (Sweden)

    Kerstin Müller

    2017-01-01

    Full Text Available Whey protein based films have received considerable attention to be used for environment friendly packaging applications. However, such biopolymers are prevented for use in commercial packaging due to their limited mechanical and barrier performance. The addition of nanofillers is a common method to overcome those drawbacks of biopolymers. Whey protein isolate (WPI based nanocomposite cast films and coatings were produced using montmorillonite and vermiculite clay as nanofiller in different concentrations. Uniform distribution of filler within the polymeric matrix was confirmed by scanning electron microscopy. Mechanical properties such as tensile strength as well as Young’s modulus were increased after increasing the filler content, while elongation at break values decreased. All samples showed weak barrier potential against water vapor. Nanoclay incorporation, however, reduced water vapor transmission rates by approximately 50%. The oxygen barrier performance was improved for all nanocomposites. Results also indicated proportionality with the filler ratio according to applied models. The highest barrier improvement factors (BIF were greater than five for the cast films and even greater than sixteen for the coatings. Developed WPI-based composites depicted nanoenhanced material properties representing a promising alternative to fossil-based packaging films.

  4. Influence of carbon nanoparticle modification on the mechanical and electrical properties of epoxy in small volumes.

    Science.gov (United States)

    Leopold, Christian; Augustin, Till; Schwebler, Thomas; Lehmann, Jonas; Liebig, Wilfried V; Fiedler, Bodo

    2017-11-15

    The influence of nanoparticle morphology and filler content on the mechanical and electrical properties of carbon nanoparticle modified epoxy is investigated regarding small volumes. Three types of particles, representing spherical, tubular and layered morphologies are used. A clear size effect of increasing true failure strength with decreasing volume is found for neat and carbon black modified epoxy. Carbon nanotube (CNT) modified epoxy exhibits high potential for strength increase, but dispersion and purity are critical. In few layer graphene modified epoxy, particles are larger than statistically distributed defects and initiate cracks, counteracting any size effect. Different toughness increasing mechanisms on the nano- and micro-scale depending on particle morphology are discussed based on scanning electron microscopy images. Electrical percolation thresholds in the small volume fibres are significantly higher compared to bulk volume, with CNT being found to be the most suitable morphology to form electrical conductive paths. Good correlation between electrical resistance change and stress strain behaviour under tensile loads is observed. The results show the possibility to detect internal damage in small volumes by measuring electrical resistance and therefore indicate to the high potential for using CNT modified polymers in fibre reinforced plastics as a multifunctional, self-monitoring material with improved mechanical properties. Copyright © 2017. Published by Elsevier Inc.

  5. Modification of the Absorption Edge of GaAs Arising from Hot-Electron Effects

    DEFF Research Database (Denmark)

    McGroddy, J. C.; Christensen, Ove

    1973-01-01

    We have observed a large enhancement of the electric-field-induced optical absorption arising from hot-electron effects in n-type GaAs at 77 K. The magnitude and field dependence of the enhancement can be approximately accounted for by a theory attributing the effect to broadening of the final...

  6. Localized Electron Trap Modification as a Result of Space Weather Exposure in Highly Disordered Insulating Materials

    Science.gov (United States)

    2017-03-06

    Chemistry that Drives Them) Due to Exposure to High Energy GEO-like Electrons Conference Proceeding Advanced Maui Optical and Space Surveillance...distribution is unlimited. 28 References 1. Awaja, F., et al., Surface molecular degradation of selected high performance polymer composites under low...6 2.3. Material Chemistry

  7. Stability and electronic properties of low-dimensional nanostructures

    Science.gov (United States)

    Guan, Jie

    As the devices used in daily life become smaller and more concentrated, traditional three-dimensional (3D) bulk materials have reached their limit in size. Low-dimensional nanomaterials have been attracting more attention in research and getting widely applied in many industrial fields because of their atomic-level size, unique advanced properties, and varied nanostructures. In this thesis, I have studied the stability and mechanical and electronic properties of zero-dimensional (0D) structures including carbon fullerenes, nanotori, metallofullerenes and phosphorus fullerenes, one-dimensional (1D) structures including carbon nanotubes and phosphorus nanotubes, as well as two-dimensional (2D) structures including layered transition metal dichalcogenides (TMDs), phosphorene and phosphorus carbide (PC). I first briefly introduce the scientific background and the motivation of all the work in this thesis. Then the computational techniques, mainly density functional theory (DFT), are reviewed in Chapter 2. In Chapter 3, I investigate the stability and electronic structure of endohedral rare-earth metallofullerene La C60 and the trifluoromethylized La C60(CF3)n with n ≤ 5. Odd n is preferred due to the closed-shell electronic configuration or large HOMO-LUMO gap, which is also meaningful for the separation of C 60-based metallofullerenes. Mechanical and electronic properties of layered materials including TMDs and black phosphorus are studied in Chapter 4 and 5. In Chapter 4, a metallic NbSe2/semiconducting WSe2 bilayer is investigated and besides a rigid band shift associated with charge transfer, the presence of NbSe2 does not modify the electronic structure of WSe2. Structural similarity and small lattice mismatch results in the heterojunction being capable of efficiently transferring charge acrossthe interface. In Chapter 5, I investigate the dependence of stability and electronic band structure on the in-layer strain in bulk black phosphorus. In Chapters 6, 7 and

  8. Modification of NSSC pulp broke fibers using layering method and investigating its effect on paper properties

    Directory of Open Access Journals (Sweden)

    hamidreza rudi

    2016-12-01

    Full Text Available In the current study, modification of NSSC pulp broke fibers was done by forming starch polymeric multilayers, using Layer-by-Layer (LbL layering method. After fiber slushing and preparation of pulp suspension with 0.5% consistency and conductivity formation of about 437 µS/cm, adding water solution of 1 mM NaCl, the experiments of fibers treatment were conducted to build the polymeric layers (up to 5 consecutive layers. Afterward, water retention value (WRV of fibers was calculated in samples to evaluate the influence of this method on fibers hydrophilicity. The fibers were then used to prepare standard handsheets (60±3g/m2 and the physical and strength properties of sheets were evaluated as a function of the number of layers deposited on the fibers. The results showed that the WRV index of the fibers was improved by the LbL treatment of NSSC broke pulp fibers, due to the increase in starch electrostatic absorption. Successive variation in paper apparent density increase and paper thickness decrease confirmed the construction of starch multilayers on the surface of broke fibers. Formation of such multilayers on broke fibers has led to considerable improvement in tensile index (from 13.21 N.m/g to 30.65 N.m/g and burst index (from 1.23 kPa.m2/g to 2.36 kPa.m2/g. Also, the prepared SEM micrographs approve the sheet web compaction and paper mechanical improvement resulted due to an increase in inter-fiber bonding.

  9. Enhanced Physicochemical and Biological Properties of Ion-Implanted Titanium Using Electron Cyclotron Resonance Ion Sources

    Directory of Open Access Journals (Sweden)

    Csaba Hegedűs

    2016-01-01

    Full Text Available The surface properties of metallic implants play an important role in their clinical success. Improving upon the inherent shortcomings of Ti implants, such as poor bioactivity, is imperative for achieving clinical use. In this study, we have developed a Ti implant modified with Ca or dual Ca + Si ions on the surface using an electron cyclotron resonance ion source (ECRIS. The physicochemical and biological properties of ion-implanted Ti surfaces were analyzed using various analytical techniques, such as surface analyses, potentiodynamic polarization and cell culture. Experimental results indicated that a rough morphology was observed on the Ti substrate surface modified by ECRIS plasma ions. The in vitro electrochemical measurement results also indicated that the Ca + Si ion-implanted surface had a more beneficial and desired behavior than the pristine Ti substrate. Compared to the pristine Ti substrate, all ion-implanted samples had a lower hemolysis ratio. MG63 cells cultured on the high Ca and dual Ca + Si ion-implanted surfaces revealed significantly greater cell viability in comparison to the pristine Ti substrate. In conclusion, surface modification by electron cyclotron resonance Ca and Si ion sources could be an effective method for Ti implants.

  10. First-principles analysis of structural and opto-electronic properties of indium tin oxide

    Science.gov (United States)

    Tripathi, Madhvendra Nath; Shida, Kazuhito; Sahara, Ryoji; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2012-05-01

    Density functional theory (DFT) and DFT + U (DFT with on-site Coulomb repulsion corrections) calculations have been carried out to study the structural and opto-electronic properties of indium tin oxide (ITO) for both the oxidized and reduced environment conditions. Some of the results obtained by DFT calculations differ from the experimental observations, such as uncertain indication for the site preference of tin atom to replace indium atom at b-site or d-site, underestimation of local inward relaxation in the first oxygen polyhedra around tin atom, and also the improper estimation of electronic density of states and hence resulting in an inappropriate optical spectra of ITO. These discrepancies of theoretical outcomes with experimental observations in ITO arise mainly due to the underestimation of the cationic 4d levels within standard DFT calculations. Henceforth, the inclusion of on-site corrections within DFT + U framework significantly modifies the theoretical results in better agreement to the experimental observations. Within this framework, our calculations show that the indium b-site is preferential site over d-site for tin atom substitution in indium oxide under both the oxidized and reduced conditions. Moreover, the calculated average inward relaxation value of 0.16 Å around tin atom is in good agreement with the experimental value of 0.18 Å. Furthermore, DFT + U significantly modify the electronic structure and consequently induce modifications in the calculated optical spectra of ITO.

  11. Mechanical properties and electronic structures of Fe-Al intermetallic

    Energy Technology Data Exchange (ETDEWEB)

    Liu, YaHui; Chong, XiaoYu; Jiang, YeHua, E-mail: jiangyehua@kmust.edu.cn; Zhou, Rong; Feng, Jing, E-mail: jingfeng@kmust.edu.cn

    2017-02-01

    Using the first-principles calculations, the elastic properties, anisotropy properties, electronic structures, Debye temperature and stability of Fe-Al (Fe{sub 3}Al, FeAl, FeAl{sub 2}, Fe{sub 2}Al{sub 5} and FeAl{sub 3}) binary compounds were calculated. The formation enthalpy and cohesive energy of these Fe-Al compounds are negative, and show they are thermodynamically stable structures. Fe{sub 2}Al{sub 5} has the lowest formation enthalpy, which shows the Fe{sub 2}Al{sub 5} is the most stable of Fe-Al binary compounds. These Fe-Al compounds display disparate anisotropy due to the calculated different shape of the 3D curved surface of the Young’s modulus and anisotropic index. Fe{sub 3}Al has the biggest bulk modulus with the value 233.2 GPa. FeAl has the biggest Yong’s modulus and shear modulus with the value 296.2 GPa and 119.8 GPa, respectively. The partial density of states, total density of states and electron density distribution maps of the binary Fe-Al binary compounds are analyzed. The bonding characteristics of these Fe-Al binary compounds are mainly combination by covalent bond and metallic bonds. Meanwhile, also exist anti-bond effect. Moreover, the Debye temperatures and sound velocity of these Fe-Al compounds are explored.

  12. Van der Waals trilayers and superlattices: Modification of electronic structures of MoS2 by intercalation

    OpenAIRE

    Lu, N.; Guo, H. Y.; Wang, L.; Wu, X. J.; Zeng, X. C.

    2014-01-01

    We perform a comprehensive first-principles study of the electronic properties of van der Waals (vdW) trilayers via intercalating a two-dimensional (2D) monolayer (ML = BN, MoSe2, WS2, or WSe2) between MoS2 bilayer to form various MoS2/ML/MoS2 sandwich trilayers. We find that the BN monolayer is the most effective sheet to decouple the interlayer vdW coupling of the MoS2 bilayer, and the resulting sandwich trilayer can recover the electronic structures of the MoS2 monolayer, particularly the ...

  13. Electronic properties of Fibonacci and random Si-Ge chains

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcelos, M S [Escola de Ciencias e Tecnologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN (Brazil); Azevedo, David L; Hadad, A [Departamento de Fisica, Universidade Federal do Maranhao 65080-040, Sao LuIs-MA (Brazil); Galvao, D S, E-mail: mvasconcelos@ect.ufrn.br [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas CP 6165, 13083-970 Campinas, SP (Brazil)

    2011-10-12

    In this paper we address a theoretical calculation of the electronic spectra of an Si-Ge atomic chain that is arranged in a Fibonacci quasi-periodic sequence, by using a semi-empirical quantum method based on the Hueckel extended model. We apply the Fibonacci substitutional sequences in the atomic building blocks A(Si) and B(Ge) through the inflation rule or a recursion relation. In our ab initio calculations we use only a single point, which is sufficient for considering all the orbitals and charge distribution across the entire system. Although the calculations presented here are more complete than the models adopted in the literature which take into account the electronic interaction only up to the second and third neighbors, an interesting property remains in their electronic spectra: the fractality (which is the main signature of this kind of system). We discuss this fractality of the spectra and we compare them with the random arrangement of the Si-Ge atomic chain, and with previous results based on the tight-binding approximation of the Schroedinger equation considering up to the nearest neighbor. (paper)

  14. Superconducting properties of niobium after electron beam welding

    Directory of Open Access Journals (Sweden)

    Prakash N. Potukuchi

    2011-12-01

    Full Text Available One of the major criteria for designing superconducting niobium resonant cavities is to minimize the peak surface electric and magnetic fields to maximize the achievable accelerating electric gradient. Even after addressing the extrinsic effects adequately, a large number of cavities perform below the theoretical gradient limit. The peak magnetic field for the first flux-line penetration in the superconducting state of niobium, which either severely degrades the cavity quality factor or results in complete thermal breakdown, is an important limitation. The flux-line penetration is known to depend on the microstructural properties of niobium which may get altered in the process of cavity fabrication. The most common technique of fabricating niobium cavities is to form their components using standard sheet metal techniques and join them by electron beam welding in vacuum. We present results of a study on the superconducting response through magnetization measurements in the electron beam welded region of niobium to understand the limitations (if any posed by the welding in achieving the highest gradient. We also present and discuss results on the performance of niobium quarter wave resonators incorporating such electron beam welds in the high magnetic field region.

  15. Structural and electronic properties of SnO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Akgul, Funda Aksoy, E-mail: fundaaksoy01@gmail.com [Physics Department, Nigde University, 51240 Nigde (Turkey); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Gumus, Cebrail, E-mail: cgumus@cu.edu.tr [Physics Department, Cukurova University, 01330 Adana (Turkey); Er, Ali O. [Department of Chemistry, University of California, Irvine, CA 92612 (United States); Farha, Ashraf H. [Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23529 (United States); Physics Department, Ain Shams University, Cairo 11566 (Egypt); Akgul, Guvenc [Bor Vocational School, Nigde University, 51700 Nigde (Turkey); Ufuktepe, Yuksel [Physics Department, Cukurova University, 01330 Adana (Turkey); Liu, Zhi [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2013-12-05

    Highlights: •Structural and electronic properties of SnO{sub 2} films were determined. •Oxidation states of the SnO{sub 2} thin films were confirmed by XPS analysis. •Chemical component is non-stoichiometric and ratio of oxygen to tin was 1.85. -- Abstract: Highly transparent polycrystalline thin film of SnO{sub 2} (tin dioxide) was deposited using a simple and low cost spray pyrolysis method. The film was prepared from an aqueous solution of tin tetrachloride (stannic chloride) onto glass substrates at 400 °C. A range of diagnostic techniques including X-ray diffraction (XRD), UV–visible absorption, atomic force microscopy (AFM), scanning electron microscopy (SEM), and synchrotron-based X-ray photoelectron spectroscopy (XPS) were used to investigate structural, optical, and electronic properties of the resulting film. Deposited film was found to be polycrystalline. A mixture of SnO and SnO{sub 2} phases was observed. The average crystallite size of ∼21.3 nm for SnO{sub 2} was calculated by Rietveld method using XRD data. The oxidation states of the SnO{sub 2} thin film were confirmed by the shape analysis of corresponding XPS O 1s, Sn 3d, and Sn 4d peaks using the decomposition procedure. The analysis of the XPS core level peaks showed that the chemical component is non-stoichiometric and the ratio of oxygen to tin (O/Sn) is 1.85 which is slightly under stoichiometry.

  16. Imaging nanostructural modifications induced by electronic metal-support interaction effects at Au||cerium-based oxide nanointerfaces.

    Science.gov (United States)

    López-Haro, Miguel; Cíes, José M; Trasobares, Susana; Pérez-Omil, José A; Delgado, Juan J; Bernal, Serafín; Bayle-Guillemaud, Pascale; Stéphan, Odile; Yoshida, Kenta; Boyes, Edward D; Gai, Pratibha L; Calvino, José J

    2012-08-28

    A variety of advanced (scanning) transmission electron microscopy experiments, carried out in aberration-corrected equipment, provide direct evidence about subtle structural changes taking place at nanometer-sized Au||ceria oxide interfaces, which agrees with the occurrence of charge transfer effects between the reduced support and supported gold nanoparticles suggested by macroscopic techniques. Tighter binding of the gold nanoparticles onto the ceria oxide support when this is reduced is revealed by the structural analysis. This structural modification is accompanied by parallel deactivation of the CO chemisorption capacity of the gold nanoparticles, which is interpreted in exact quantitative terms as due to deactivation of the gold atoms at the perimeter of the Au||cerium oxide interface.

  17. Modification of Polymer Network Properties through the Addition of Functional Nanogel Particles

    Science.gov (United States)

    Liu, JianCheng

    Multifunctional acrylic and methacrylic monomers have been widely applied in many photopolymerization applications to produce crosslinked polymers with advantages such as rapid curing, broad choices of commercially available monomers and desirable physical and mechanical properties. However, there still remain critical challenges for these materials during polymerization including limited conversion and early onset of gelation as well as the generation of significant polymerization shrinkage and stress. This thesis explores the effects of network property modification through the addition of polymeric nanoparticles or nanogels. In order to understand the relationship between nanogel structure and composite material properties, nanogels with different architectures and functionalities were studied during polymerization in terms of kinetics, shrinkage and stress reduction, mechanical performance and reaction mechanisms. Nanogel composite formulations were evaluated to understand the interaction between nanogel structure with the resin matrix during polymerization through adjustment of nanogel branching densities and reactivity of polymer chain ends. It was found that both the chemical crosslinking from reactive chain ends and physical entanglements of high branching density nanogels with the resin matrix dramatically could improve final material mechanical strength. The reductions in overall volumetric shrinkage and shrinkage stress were found to follow at least proportional behavior with respect to nanogel loading concentration while maintaining similar final conversion and modulus results compared with the control resin. Nanogels containing unique functionalities were designed in order to modify reaction mechanism during secondary polymerization. A nanogel containing an integrated photoinitiator and active chain-end RAFT groups was able to initiate secondary polymerization from the nanogel phase so that localized polymerization was achieved from the beginning of

  18. Efficient Density Functional Approximation for Electronic Properties of Conjugated Systems

    Science.gov (United States)

    Caldas, Marília J.; Pinheiro, José Maximiano, Jr.; Blum, Volker; Rinke, Patrick

    2014-03-01

    There is on-going discussion about reliable prediction of electronic properties of conjugated oligomers and polymers, such as ionization potential IP and energy gap. Several exchange-correlation (XC) functionals are being used by the density functional theory community, with different success for different properties. In this work we follow a recent proposal: a fraction α of exact exchange is added to the semi-local PBE XC aiming consistency, for a given property, with the results obtained by many-body perturbation theory within the G0W0 approximation. We focus the IP, taken as the negative of the highest occupied molecular orbital energy. We choose α from a study of the prototype family trans-acetylene, and apply this same α to a set of oligomers for which there is experimental data available (acenes, phenylenes and others). Our results indicate we can have excellent estimates, within 0,2eV mean ave. dev. from the experimental values, better than through complete EN - 1 -EN calculations from the starting PBE functional. We also obtain good estimates for the electrical gap and orbital energies close to the band edge. Work supported by FAPESP, CNPq, and CAPES, Brazil, and DAAD, Germany.

  19. Organic/metal interfaces. Electronic and structural properties

    Energy Technology Data Exchange (ETDEWEB)

    Duhm, Steffen

    2008-07-17

    This work addresses several important topics of the field of organic electronics. The focus lies on organic/metal interfaces, which exist in all organic electronic devices. Physical properties of such interfaces are crucial for device performance. Four main topics have been covered: (i) the impact of molecular orientation on the energy levels, (ii) energy level tuning with strong electron acceptors, (iii) the role of thermodynamic equilibrium at organic/ organic homo-interfaces and (iv) the correlation of interfacial electronic structure and bonding distance. To address these issues a broad experimental approach was necessary: mainly ultraviolet photoelectron spectroscopy was used, supported by X-ray photoelectron spectroscopy, metastable atom electron spectroscopy, X-ray diffraction and X-ray standing waves, to examine vacuum sublimed thin films of conjugated organic molecules (COMs) in ultrahigh vacuum. (i) A novel approach is presented to explain the phenomenon that the ionization energy in molecular assemblies is orientation dependent. It is demonstrated that this is due to a macroscopic impact of intramolecular dipoles on the ionization energy in molecular assemblies. Furthermore, the correlation of molecular orientation and conformation has been studied in detail for COMs on various substrates. (ii) A new approach was developed to tune hole injection barriers ({delta}{sub h}) at organic/metal interfaces by adsorbing a (sub-) monolayer of an organic electron acceptor on the metal electrode. Charge transfer from the metal to the acceptor leads to a chemisorbed layer, which reduces {delta}{sub h} to the COM overlayer. This concept was tested with three acceptors and a lowering of {delta}{sub h} of up to 1.2 eV could be observed. (iii) A transition from vacuum-level alignment to molecular level pinning at the homo-interface between a lying monolayer and standing multilayers of a COM was observed, which depended on the amount of a pre-deposited acceptor. The

  20. Electronic properties of antiferromagnetic UBi2 metal by exact exchange for correlated electrons method

    Directory of Open Access Journals (Sweden)

    E Ghasemikhah

    2012-03-01

    Full Text Available This study investigated the electronic properties of antiferromagnetic UBi2 metal by using ab initio calculations based on the density functional theory (DFT, employing the augmented plane waves plus local orbital method. We used the exact exchange for correlated electrons (EECE method to calculate the exchange-correlation energy under a variety of hybrid functionals. Electric field gradients (EFGs at the uranium site in UBi2 compound were calculated and compared with the experiment. The EFGs were predicted experimentally at the U site to be very small in this compound. The EFG calculated by the EECE functional are in agreement with the experiment. The densities of states (DOSs show that 5f U orbital is hybrided with the other orbitals. The plotted Fermi surfaces show that there are two kinds of charges on Fermi surface of this compound.

  1. Surface Modification of Light Alloys by Low-Energy High-Current Pulsed Electron Beam

    Directory of Open Access Journals (Sweden)

    X. D. Zhang

    2012-01-01

    Full Text Available This paper reviews results obtained by the research groups developing the low-energy high-current pulsed electron beam (LEHCPEB in Dalian (China and Metz (France on the surface treatment of light alloys. The pulsed electron irradiation induces an ultra-fast thermal cycle at the surface combined with the formation of thermal stress and shock waves. As illustrated for Mg alloys and Ti, this results in deep subsurface hardening (over several 100 μm which improves the wear resistance. The analysis of the top surface melted surface of light alloys also often witnesses evaporation and condensation of chemical species. This phenomenon can significantly modify the melt chemistry and was also suggested to lead to the development of specific solidification textures in the rapidly solidified layer. The potential use of the LEHCPEB technique for producing thermomechanical treatments under the so-called heating mode and, thus, modify the surface crystallographic texture, and enhance solid-state diffusion is also demonstrated in the case of the FeAl intermetallic compound.

  2. Modifications in optical and structural properties of PMMA/PCTFE blend films as a function of PCTFE concentration

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, J., E-mail: jtripathi00@gmail.com [Dept. of Physics, ISLE, IPS Academy, Indore (India); Sharma, A. [Dept. of Physics, Manipal University Jaipur, Jaipur (India); Tripathi, S. [UGC-DAE Consortium for Scientific Research, Indore (India); Bisen, R. [Dept. of Physics, ISLE, IPS Academy, Indore (India); Agrawal, A. [Dept. of Elect. and Commun., Global Engineering College, Jabalpur (India)

    2017-06-15

    The poly (methyl methacrylate) (PMMA) polymer blend films were prepared by solution casting method with varying PolyChloroTriFluoroEthylene (PCTFE) concentrations (1–5 wt %). The crystallinity, bonding behavior and disorder in the films were investigated with X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible and ellipsometry techniques, while surface morphology was studied using Atomic force microscopy (AFM). The nanocrystalline nature of PMMA is seen to be preserved in the blends although there are clear indications of bond modifications. The addition of PCTFE results in the improvement of overall crystallinity of the films via the interaction among PMMA and degraded PCTFE molecules when the films are casted from diluted solutions. In agreement, corresponding disorder in terms of Urbach energy shows a decreasing trend upon inclusion of more and more PCTFE molecules. Micro-Raman spectra are dominated by fluorescence background, which is proposed as arising from degraded PCTFE. Supporting this, FTIR spectra also shows modifications in bonding as a function of PCTFE percentage, but this bond modification is not enough to produce refractive index variation in the sample, which is dominated by the host PMMA contribution for all the PCTFE concentrations. The study suggests the useful range of PCTFE concentration in which PMMA host properties can be modified for optimizing optical and structural properties without much degradation of PCTFE. - Highlights: • PMMA blend films with varying PCTFE concentrations (1–5 wt%) were prepared. • Nanocrystalline nature of PMMA is preserved in spite of bond modifications. • Addition of PCTFE results in improvement of overall crystallinity of the films. • Urbach energy shows a decreasing Disorder upon inclusion of more PCTFE molecules. • FTIR spectra show bond modifications without changing refractive index.

  3. Synthesis Properties and Electron Spin Resonance Properties of Titanic Materials (abstract)

    Science.gov (United States)

    Cho, Jung Min; Lee, Jun; Kim, Tak Hee; Sun, Min Ho; Jang, Young Bae; Cho, Sung June

    2009-04-01

    Titanic materials were synthesized by hydrothermal method of TiO2 anatase in 10M LiOH, 10M NaOH, and 14M KOH at 130° C for 30 hours. Alkaline media were removed from the synthesized products using 0.1N HCl aqueous solution. The as-prepared samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, Brunauer-Emmett-Teller isotherm, and electron spin resonance. Different shapes of synthesized products were observed through the typical electron microscope and indicated that the formation of the different morphologies depends on the treatment conditions of highly alkaline media. Many micropores were observed in the cubic or octahedral type of TiO2 samples through the typical electron microscope and Langmuir adsorption-desorption isotherm of liquid nitrogen at 77° K. Electron spin resonance studies have also been carried out to verify the existence of paramagnetic sites such as oxygen vacancies on the titania samples. The effect of alkali metal ions on the morphologies and physicochemical properties of nanoscale titania are discussed.

  4. Electronic properties of semiconductor surfaces and metal/semiconductor interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tallarida, M.

    2005-05-15

    This thesis reports investigations of the electronic properties of a semiconductor surface (silicon carbide), a reactive metal/semiconductor interface (manganese/silicon) and a non-reactive metal/semiconductor interface (aluminum-magnesium alloy/silicon). The (2 x 1) reconstruction of the 6H-SiC(0001) surface has been obtained by cleaving the sample along the (0001) direction. This reconstruction has not been observed up to now for this compound, and has been compared with those of similar elemental semiconductors of the fourth group of the periodic table. This comparison has been carried out by making use of photoemission spectroscopy, analyzing the core level shifts of both Si 2p and C 1s core levels in terms of charge transfer between atoms of both elements and in different chemical environments. From this comparison, a difference between the reconstruction on the Si-terminated and the C-terminated surface was established, due to the ionic nature of the Si-C bond. The growth of manganese films on Si(111) in the 1-5 ML thickness range has been studied by means of LEED, STM and photoemission spectroscopy. By the complementary use of these surface science techniques, two different phases have been observed for two thickness regimes (<1 ML and >1 ML), which exhibit a different electronic character. The two reconstructions, the (1 x 1)-phase and the ({radical}3 x {radical}3)R30 -phase, are due to silicide formation, as observed in core level spectroscopy. The growth proceeds via island formation in the monolayer regime, while the thicker films show flat layers interrupted by deep holes. On the basis of STM investigations, this growth mode has been attributed to strain due to lattice mismatch between the substrate and the silicide. Co-deposition of Al and Mg onto a Si(111) substrate at low temperature (100K) resulted in the formation of thin alloy films. By varying the relative content of both elements, the thin films exhibited different electronic properties

  5. Influence of ECR-RF plasma modification on surface and thermal properties of polyester copolymer

    Directory of Open Access Journals (Sweden)

    Fray Miroslawa El

    2015-12-01

    Full Text Available In this paper we report a study on influence of radio-frequency (RF plasma induced with electron cyclotron resonance (ECR on multiblock copolymer containing butylene terephthalate hard segments (PBT and butylene dilinoleate (BDLA soft segments. The changes in thermal properties were studied by DSC. The changes in wettability of PBT-BDLA surfaces were studied by water contact angle (WCA. We found that ECR-RF plasma surface treatment for 60 s led to decrease of WCA, while prolonged exposure of plasma led to increase of WCA after N2 and N2O2 treatment up to 70°–80°. The O2 reduced the WCA to 50°–56°. IR measurements confirmed that the N2O2 plasma led to formation of polar groups. SEM investigations showed that plasma treatment led to minor surfaces changes. Collectively, plasma treatment, especially O2, induced surface hydrophilicity what could be beneficial for increased cell adhesion in future biomedical applications of these materials.

  6. SHI induced modification in structural, optical, dielectric and thermal properties of poly ethylene oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Gnansagar B.; Bhavsar, Shilpa [Department of Physics, The M.S. University of Baroda, Vadodara 390002 (India); Singh, N.L., E-mail: nl.singh-phy@msubaroda.ac.in [Department of Physics, The M.S. University of Baroda, Vadodara 390002 (India); Singh, F.; Kulriya, P.K. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2016-07-15

    Poly ethylene oxide (PEO) films were synthesized by solution cast method. These self-standing films were exposed with 60 MeV C{sup +5} ion and 100 MeV Ni{sup +7} ion at different fluences. SHI induced effect was investigated by employing various techniques. The crystalline size decreased upon irradiation as observed from XRD analysis. FTIR analysis reveals the decrement in the peak intensity upon irradiation. Tauc’s method was used to determine the optical band gap (E{sub g}), which shows decreasing trends with increase of fluence. The dielectric properties were investigated in the frequency range 10 Hz to 10 MHz for unirradiated and irradiated films. The dielectric constant remains same for the broad-spectrum of frequency and increases at lower frequency. The dielectric loss also moderately influence as a function of frequency due to irradiation. DSC analysis validated the results of XRD. Scanning electron microscopy (SEM) reveals that there is significant change in the surface morphology due to irradiation.

  7. Dramatic Modification of Coupled-Plasmon Resonances Following Exposure to Electron Beams.

    Science.gov (United States)

    Leng, Haixu; Szychowski, Brian; Daniel, Marie-Christine; Pelton, Matthew

    2017-08-03

    Studies of the plasmon resonances in individual and coupled metal nanoparticles often involve imaging of the nanostructures of interest in an electron microscope. We show that this process can dramatically modify the optical spectra of coupled plasmonic nanoparticles, illustrated here with the case of gold nanorod-nanosphere dimers. The spectral changes are due to the thin, partially conductive carbonaceous layer that deposits onto the particles during imaging. These changes are particularly significant for coupled nanoparticles with subnanometer interparticle gaps but have largely been neglected in previous studies of such structures, including studies intended to probe quantum-mechanical effects in plasmon coupling. Accounting for the effects of the carbonaceous layer will lead to a more accurate understanding of such systems.

  8. Distinct Properties Underlie Flavin-Based Electron Bifurcation in a Novel Electron Transfer Flavoprotein FixAB from Rhodopseudomonas palustris

    Energy Technology Data Exchange (ETDEWEB)

    King, Paul W [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Lubner, Carolyn E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Duan, H. Diessel [University of Kentucky; Tokmina-Lukaszewska, Monika [Montana State University; Gauss, George H. [Montana State University; Bothner, Brian [Montana State University; Peters, John W. [Washington State University; Miller, Anne-Frances [University of Kentucky

    2018-02-09

    A newly-recognized third fundamental mechanism of energy conservation in biology, electron bifurcation, uses free energy from exergonic redox reactions to drive endergonic redox reactions. Flavin-based electron bifurcation furnishes low potential electrons to demanding chemical reactions such as reduction of dinitrogen to ammonia. We employed the heterodimeric flavoenzyme FixAB from the diazotrophic bacterium Rhodopseudomonas palustris to elucidate unique properties that underpin flavin-based electron bifurcation.

  9. Modification of Electrical Properties of Thin La0.67Ca0.33MnO3 Films by Pulsed Thermocycling

    Directory of Open Access Journals (Sweden)

    Fiodoras ANISIMOVAS

    2012-09-01

    Full Text Available Highly resistive states were formed in nonhomogeneous thin La0.67Ca0.33MnO3 films at 80 K temperature after resistance switching induced by the pulsed thermocycling. Heating up to room temperature does not destroy the resistive states. They demonstrate high values of electroresistance at applied pulsed electric field. It was registered formation of novel highly resistive state by resistance switching at 130 K in Tm region. We suppose that local temperature increase in the film is responsible for the formation of the resistive states in both cases and present a plausible explanation of the obtained results. The method of cyclic nanosecond temperature increase and decrease can be useful for modification of material properties having strongly correlated electron system and of ferroelectrics. Questions of practical realization of proposed method are discussed.DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2427

  10. Electronic Properties of Graphene–PtSe2 Contacts

    KAUST Repository

    Sattar, Shahid

    2017-04-26

    In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe2 and a p-type Schottky contact with bilayer PtSe2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

  11. Growth-induced electronic properties of epitaxial graphene

    Science.gov (United States)

    First, Phillip

    2012-02-01

    The growth of epitaxial graphene on silicon carbide is challenging to understand and control, yet rife with scientific and technological opportunities. This is due in part to different growth-induced structures such as the ``moire'' alignment of graphene layers in multilayer epitaxial graphene on SiC(0001) and the formation of sidewall ribbons at natural and lithographically-defined SiC(0001) step-bunches (nanofacets). We apply scanning tunneling microscopy (STM) and spectroscopy (STS) to probe the local energy bands of such growth-induced structures. STS at cryogenic temperatures and large magnetic fields creates a comb of discrete Landau level energies that we use to quantitatively characterize the local electronic properties.

  12. Electronic transport properties of a quinone-based molecular switch

    Science.gov (United States)

    Zheng, Ya-Peng; Bian, Bao-An; Yuan, Pei-Pei

    2016-09-01

    In this paper, we carried out first-principles calculations based on density functional theory and non-equilibrium Green's function to investigate the electronic transport properties of a quinone-based molecule sandwiched between two Au electrodes. The molecular switch can be reversibly switched between the reduced hydroquinone (HQ) and oxidized quinone (Q) states via redox reactions. The switching behavior of two forms is analyzed through their I- V curves, transmission spectra and molecular projected self-consistent Hamiltonian at zero bias. Then we discuss the transmission spectra of the HQ and Q forms at different bias, and explain the oscillation of current according to the transmission eigenstates of LUMO energy level for Q form. The results suggest that this kind of a quinone-based molecule is usable as one of the good candidates for redox-controlled molecular switches.

  13. Effects of electron beam irradiation on tribological and physico-chemical properties of Polyoxymethylene copolymer (POM-C)

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Md. Shahinur; Shaislamov, Ulugbek; Yang, Jong-Keun [Nuclear Fusion and Plasma Applications Laboratory, Department of Nuclear and Energy Engineering, Jeju National University, 102 Jejudaehak-ro, Jeju-si, Jeju 63243 (Korea, Republic of); Kim, Jong-Kuk [Plasma Processing Laboratory, Division of Surface Technology, Korea Institute of Materials Science, 797 Changwondaero, Sungsan-Gu, Changwon, Kyungnam 641-010 (Korea, Republic of); Yu, Young Hun [Department of Physics, Jeju National University, 102 Jejudaehak-ro, Jeju-si, Jeju 63243 (Korea, Republic of); Choi, Sooseok [Nuclear Fusion and Plasma Applications Laboratory, Department of Nuclear and Energy Engineering, Jeju National University, 102 Jejudaehak-ro, Jeju-si, Jeju 63243 (Korea, Republic of); Lee, Heon-Ju, E-mail: hjlee@jejunu.ac.kr [Nuclear Fusion and Plasma Applications Laboratory, Department of Nuclear and Energy Engineering, Jeju National University, 102 Jejudaehak-ro, Jeju-si, Jeju 63243 (Korea, Republic of)

    2016-11-15

    Highlights: • Electron beam dose irradiation effect on tribology of POM-C was investigated. • Raman and FTIR-ATR spectra confirm the chemical structural modification. • 1 MeV, 100 kGy dose irradiation induced well suited carbonization and hydrophobicity. • Well suited carbonization and hydrophobicity reduced friction coefficient. - Abstract: Polyoxymethylene copolymer (POM-C) is an attractive and widely used engineering thermoplastic across many industrial sectors owing to outstanding physical, mechanical, self-lubricating and chemical properties. In this research work, the POM-C blocks were irradiated with 1 MeV electron beam energy in five doses (100, 200, 300, 500 and 700 kGy) in vacuum condition at room temperature. The tribological and physico-chemical properties of electron beam irradiated POM-C blocks have been analyzed using pin on disk tribometer, Raman spectroscopy, FTIR-ATR, gel content analysis, SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy), surface profiler and contact angle analyzer. Electron beam irradiation at a dose of 100 kGy resulted in decrease of the friction coefficient of POM-C block due to well suited carbonization, cross-linking, free radicals formation and partial physical modification. It also showed the lowest surface roughness and highest water contact angle among all unirradiated and irradiated POM-C blocks. The irradiation dose at 200 kGy resulted in increase of friction coefficient due to less effective cross-linking, but the irradiation doses at 300, 500 and 700 kGy resulted in increase of the friction coefficient as compared to unirradiated POM-C block due to severe chain scission, chemical and physical structural degradation. The degree of improvement for tribological attribute relies on the electron beam surface dose delivered (energy and dose rate).

  14. Examination and Mitigation of Electron Interception Processes in Dye-sensitized Solar Cells through Redox Shuttle and Photoelectrode Modification

    Science.gov (United States)

    Hoffeditz, William Lawrence

    With the dual challenges of meeting global energy demand and mitigating anthropogenic climate change, significant effort is being applied to generating power from renewable sources. The dye-sensitized solar cell (DSC) is a photovoltaic technology capable of generating electricity from sunlight, but suffers losses in efficiency due to deleterious electron transfer processes. Controlling these processes is essential if DSCs are to continue to advance, and this dissertation focuses on isolation, interrogation, and mitigation of these processes via controllable inorganic redox/coordination chemistry and atomic layer deposition (ALD). The redox shuttle is often the subject of innovation in DSCs, the goal being to increase obtainable photovoltage without sacrificing photocurrent. A copper redox shuttle with a favorable (II/I) redox potential for DSC use and intriguing inner-sphere reorganization energy was investigated. The shuttle completely replaces its tetradentate coordinating ligand upon oxidation with multiple pyridine molecules. This new species displays markedly slower electron interception, necessitating fabrication of a new counter electrode in order for the shuttle to function. Upon reduction, the tetradentate ligand re-coordinates, creating a dual-species shuttle that outperforms either species as a Cu(II/I) shuttle in isolation. Photoelectrode modification is also the subject of innovation in DSCs. ALD is ideally suited for this type of innovation as it can coat high aspect surfaces with metal-oxide films of uniform thickness. The ALD post-treatment technique is described and used to deposit Al2O3 around a TiO2 adsorbed zinc-porphyrin dye. This technique is shown to prevent dye degradation from ambient air and/or light. Additionally, the architecture allows the study of dye-influenced electron interception processes. It was found that the presence of dye increased interception, which was attributed to dye-mediated electron hopping and/or superexchange

  15. Electronic transport properties of copper and gold at atomic scale

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadzadeh, Saeideh

    2010-11-23

    The factors governing electronic transport properties of copper and gold atomic-size contacts are theoretically examined in the present work. A two-terminal conductor using crystalline electrodes is adopted. The non-equilibrium Green's function combined with the density functional tight-binding method is employed via gDFTB simulation tool to calculate the transport at both equilibrium and non-equilibrium conditions. The crystalline orientation, length, and arrangement of electrodes have very weak influence on the electronic characteristics of the considered atomic wires. The wire width is found to be the most effective geometric aspect determining the number of conduction channels. The obtained conductance oscillation and linear current-voltage curves are interpreted. To analyze the conduction mechanism in detail, the transmission channels and their decomposition to the atomic orbitals are calculated in copper and gold single point contacts. The presented results offer a possible explanation for the relation between conduction and geometric structure. Furthermore, the results are in good agreement with available experimental and theoretical studies. (orig.)

  16. Optical properties of Dirac electrons in a parabolic well.

    Science.gov (United States)

    Kim, S C; Lee, J W; Yang, S-R Eric

    2013-09-01

    A single electron transitor may be fabricated using qunatum dots. A good model for the confinement potential of a quantum dot is a parabolic well. Here we consider such a parabolic dot made of graphene. Recently, we found counter intuitively that resonant quasi-boundstates of both positive and negative energies exist in the energy spectrum. The presence of resonant quasi-boundstates of negative energies is a unique property of massless Dirac fermions. As magnetic field B gets smaller the energy width of these states become broader and for sufficiently weak value of B resonant quasi-bound states disappear into a quasi-continuum. In the limit of small B resonant and nonresonant states transform into discrete anomalous states with a narrow probability density peak inside the well and another broad peak under the potential barrier. In this paper we compute the optical strength between resonant quasi-bound states as a function of B, and investigate how the signature of resonant quasi-bound states of Dirac electrons may appear in optical measurements.

  17. Optical and electronic properties of semiconducting Sn2S3

    Science.gov (United States)

    Singh, David J.

    2016-07-01

    We report the electronic and optical properties of Sn2S3 as obtained from first principles calculations with the modified Becke-Johnson potential. The electronic structure shows that Sn occurs in both divalent and tetravalent forms. The fundamental band gap of 0.82 eV is indirect. The direct gap is 0.97 eV, but the onset of strong optical absorption is much higher at ˜1.75 eV. This is as a consequence of the Sn2+ s and Sn4+ s characters of the valence and conduction band extrema, respectively. We also find strong and different anisotropies for conduction in p- and n-type Sn2S3. This should be taken into account in device structures in order to obtain efficient charge collection. The thermopowers are reasonably high for both p- and n-type materials. p-type Sn2S3 shows complex corrugated isosurface sections, while the n-type material shows multiple band extrema.

  18. Energetic Electrons in Dipolarization Events: Spatial Properties and Anisotropy

    Science.gov (United States)

    Birn, J.; Runov, A.; Hesse, M.

    2014-01-01

    Using the electromagnetic fields of an MHD simulation of magnetotail reconnection, flow bursts, and dipolarization, we further investigate the acceleration of electrons to suprathermal energies. Particular emphasis is on spatial properties and anisotropies as functions of energy and time. The simulation results are compared with Time History of Events and Macroscale Interactions during Substorms observations. The test particle approach successfully reproduces several observed injection features and puts them into a context of spatial maps of the injection region(s): a dominance of perpendicular anisotropies farther down the tail and closer to the equatorial plane, an increasing importance of parallel anisotropy closer to Earth and at higher latitudes, a drop in energy fluxes at energies below approximately 10 keV, coinciding with the plasma density drop, together with increases at higher energy, a triple peak structure of flux increases near 0 deg, 90 deg, and 180 deg, and a tendency of flux increases to extend to higher energy closer to Earth and at lower latitudes. We identified the plasma sheet boundary layers and adjacent lobes as a main source region for both increased and decreased energetic electron fluxes, related to the different effects of adiabatic acceleration at high and low energies. The simulated anisotropies tend to exceed the observed ones, particularly for perpendicular fluxes at high energies. The most plausible reason is that the MHD simulation lacks the effects of anisotropy-driven microinstabilities and waves, which would reduce anisotropies.

  19. Wettability modification of human tooth surface by water and UV and electron-beam radiation

    Energy Technology Data Exchange (ETDEWEB)

    Tiznado-Orozco, Gaby E., E-mail: gab0409@gmail.com [UMET, Bâtiment C6, Université de Lille 1, Sciences et Technologies, 59650 Villeneuve d' Ascq (France); Unidad Académica de Odontología, Universidad Autónoma de Nayarit, Edificio E7, Ciudad de la Cultura “Amado Nervo”, C.P. 63190 Tepic, Nayarit (Mexico); Reyes-Gasga, José, E-mail: jreyes@fisica.unam.mx [UMET, Bâtiment C6, Université de Lille 1, Sciences et Technologies, 59650 Villeneuve d' Ascq (France); Instituto de Física, UNAM, Circuito de la Investigación s/n, Ciudad Universitaria, 04510 Coyoacan, México, D.F. (Mexico); Elefterie, Florina, E-mail: elefterie_florina@yahoo.com [UMET, Bâtiment C6, Université de Lille 1, Sciences et Technologies, 59650 Villeneuve d' Ascq (France); Beyens, Christophe, E-mail: christophe.beyens@ed.univ-lille1.fr [UMET, Bâtiment C6, Université de Lille 1, Sciences et Technologies, 59650 Villeneuve d' Ascq (France); Maschke, Ulrich, E-mail: Ulrich.Maschke@univ-lille1.fr [UMET, Bâtiment C6, Université de Lille 1, Sciences et Technologies, 59650 Villeneuve d' Ascq (France); Brès, Etienne F., E-mail: etienne.bres@univ-lille1.fr [UMET, Bâtiment C6, Université de Lille 1, Sciences et Technologies, 59650 Villeneuve d' Ascq (France)

    2015-12-01

    The wettability of the human tooth enamel and dentin was analyzed by measuring the contact angles of a drop of distilled water deposited on the surface. The samples were cut along the transverse and longitudinal directions, and their surfaces were subjected to metallographic mirror-finish polishing. Some samples were also acid etched until their microstructure became exposed. Wettability measurements of the samples were done in dry and wet conditions and after ultraviolet (UV) and electron beam (EB) irradiations. The results indicate that water by itself was able to increase the hydrophobicity of these materials. The UV irradiation momentarily reduced the contact angle values, but they recovered after a short time. EB irradiation raised the contact angle and maintained it for a long time. Both enamel and dentin surfaces showed a wide range of contact angles, from approximately 10° (hydrophilic) to 90° (hydrophobic), although the contact angle showed more variability on enamel than on dentin surfaces. Whether the sample's surface had been polished or etched did not influence the contact angle value in wet conditions. - Highlights: • Human tooth surface wettability changes in dry/wet and UV/EB radiation conditions. • More variability in contact angle is observed on enamel than on dentin surfaces. • Water by itself increases the hydrophobicity of the human tooth surface. • UV irradiation reduces momentarily the human tooth surface hydrophobicity. • EB irradiation increases and maintains the hydrophobicity for a long time.

  20. Modification of Electronic Surface States by Graphene Islands on Cu(111)

    Science.gov (United States)

    Gambrel, Grady; Hollen, Shawna; Tjung, Steven; Santagata, Nancy; Johnston-Halperin, Ezekiel; Gupta, Jay

    The interaction of graphene with copper is of interest for graphene applications due to the frequent use of copper in the chemical vapor deposition (CVD) growth of graphene. We grew pristine graphene islands on Cu(111) by dissociating ethylene gas in an ultra high vacuum environment. In situ low-temperature scanning tunneling microscopy (STM) was used to measure the physical and electronic structure of the surface with atomic resolution, enabling us to compare the graphene-covered regions to bare Cu(111). We observed a shift of the Rydberg-like series of images potential states (IPS) to lower energies and a decrease in linewidth in graphene-covered regions, indicating a decrease in local work function and reduced coupling to the copper bulk states. In some cases, the first of these states were split, which may correspond to the dual Rydberg series which has been predicted for graphene. By measuring the dispersion of the Shockley surface state, we found that the band edge and effective mass are influenced by the graphene layer. We will extend these findings [SM Hollen, et al. Phys. Rev B 91, 195425 (2015)] to our study of in situ graphene devices and present preliminary STM and transport data with respect to gate voltage. Funding for this research was provided by the Center for Emergent Materials: an NSF MRSEC under Award Number DMR-0820414.

  1. Modification of argon impurity transport by electron cyclotron heating in KSTAR H-mode plasmas

    Science.gov (United States)

    Hong, Joohwan; Henderson, S. S.; Kim, Kimin; Seon, C. R.; Song, Inwoo; Lee, H. Y.; Jang, Juhyeok; Park, Jae Sun; Lee, S. G.; Lee, J. H.; Lee, Seung Hun; Hong, Suk-Ho; Choe, Wonho

    2017-03-01

    Experiments with a small amount of Ar gas injection as a trace impurity were conducted in the Korea Superconducting Tokamak Advanced Research (KSTAR) H-mode plasma ({{B}\\text{T}}   =  2.8 T, {{I}\\text{P}}   =  0.6 MA, and {{P}\\text{NBI}}   =  4.0 MW). 170 GHz electron cyclotron resonance heating (ECH) at 600 and 800 kW was focused along the mid-plane with a fixed major radial position of R   =  1.66 m. The emissivity of the Ar16+ (3.949 {\\mathring{\\text{A}}} ) and Ar15+ (353.860 {\\mathring{\\text{A}}} ) spectral lines were measured by x-ray imaging crystal spectroscopy (XICS) and a vacuum UV (VUV) spectrometer, respectively. ECH reduces the peak Ar15+ emission and increases the Ar16+ emission, an effect largest with 800 kW. The ADAS-SANCO impurity transport code was used to evaluate the Ar transport coefficients. It was found that the inward convective velocity found in the plasma core without ECH was decreased with ECH, while diffusion remained approximately constant resulting in a less-peaked Ar density profile. Theoretical results from the NEO code suggest that neoclassical transport is not responsible for the change in transport, while the microstability analysis using GKW predicts a dominant ITG mode during both ECH and non-ECH plasmas.

  2. Influence of Physicochemical Properties and PEG Modification of Magnetic Liposomes on Their Interaction with Intestinal Epithelial Caco-2 Cells.

    Science.gov (United States)

    Kono, Yusuke; Jinzai, Hitomi; Kotera, Yota; Fujita, Takuya

    2017-12-01

    The present study aimed to investigate the effect of particle size (100, 500 nm), surface charge (cationic, neutral and anionic) and polyethylene glycol (PEG) modification of magnetic liposomes on their interaction with the human intestinal epithelial cell line, Caco-2. The cellular associated amount of all the magnetic liposomes was significantly increased by the presence of a magnetic field. The highest association and internalization into Caco-2 cells was observed with magnetic cationic liposomes. Moreover, small magnetic liposomes were more efficiently associated and taken up into the cells, than large ones. In contrast, PEG modification significantly attenuated the enhancing effect of the magnetic field on the cellular association of magnetic liposomes. We also found that magnetic cationic liposomes had the highest retention properties to Caco-2 cells. Moreover, the retention of large magnetic liposomes to the cells was much longer than that of small ones. In addition, magnetic cationic and neutral liposomes had relatively high stability in Caco-2 cells, whereas magnetic anionic liposomes rapidly degraded. These results indicate that the physicochemical properties and PEG modification of magnetic liposomes greatly influences their intestinal epithelial transport.

  3. Electronic, mechanical, and thermodynamic properties of americium dioxide

    Science.gov (United States)

    Lu, Yong; Yang, Yu; Zheng, Fawei; Wang, Bao-Tian; Zhang, Ping

    2013-10-01

    By performing density functional theory (DFT) +U calculations, we systematically study the electronic, mechanical, tensile, and thermodynamic properties of AmO2. It is found that the chemical bonding character in AmO2 is similar to that in PuO2, with smaller charge transfer and stronger covalent interactions between americium and oxygen atoms. The stress-strain relationship of AmO2 is examined along the three low-index directions, showing that the [1 0 0] and [1 1 1] directions are the strongest and weakest tensile directions, respectively, but the theoretical tensile strengths of AmO2 are smaller than those of PuO2. The phonon dispersion curves of AmO2 are calculated and the heat capacities as well as lattice expansion curve are subsequently determined. The lattice thermal conductivity of AmO2 is further evaluated and compared with attainable experiments. Our present work integrally reveals various physical properties of AmO2 and can be referenced for technological applications of AmO2 based materials.

  4. Structural, electronic, vibrational and optical properties of Bin clusters

    Science.gov (United States)

    Liang, Dan; Shen, Wanting; Zhang, Chunfang; Lu, Pengfei; Wang, Shumin

    2017-10-01

    The neutral, anionic and cationic bismuth clusters with the size n up to 14 are investigated by using B3LYP functional within the regime of density functional theory and the LAN2DZ basis set. By analysis of the geometries of the Bin (n = 2-14) clusters, where cationic and anionic bismuth clusters are largely similar to those of neutral ones, a periodic effect by adding units with one to four atoms into smaller cluster to form larger cluster is drawn for the stable structures of bismuth clusters. An even-odd alteration is shown for the properties of the clusters, such as the calculated binding energies and dissociation energies, as well as frontier orbital energies, electron affinities, ionization energies. All the properties indicate that the Bi4 cluster is the most possible existence in bismuth-containing materials, which supports the most recent experiment. The orbital compositions, infrared and Raman activities and the ultraviolet absorption of the most possible tetramer bismuth cluster are given in detail to reveal the periodic tendency of adding bismuth atoms and the stability of tetramer bismuth cluster.

  5. Magnetic and electronic properties of porphyrin-based molecular nanowires

    Directory of Open Access Journals (Sweden)

    Jia-Jia Zheng

    2016-01-01

    Full Text Available Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn. Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  6. Magnetic and electronic properties of porphyrin-based molecular nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jia-Jia; Li, Qiao-Zhi; Dang, Jing-Shuang; Zhao, Xiang, E-mail: xzhao@mail.xjtu.edu.cn [Institute for Chemical Physics & Department of Chemistry, MOE Key Laboratory for Non-equilibrium Condensed Matter and Quantum Engineering, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Wei-Wei [Research Center for Computational Science, Institute for Molecular Science, Okazaki, Aichi 444-8585 (Japan)

    2016-01-15

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  7. Stability and electronic properties of Gex(BN)y monolayers

    Science.gov (United States)

    Freitas, A.; Machado, L. D.; Tromer, R. M.; Bezerra, C. G.; Azevedo, S.

    2017-10-01

    In this work, we employ ab initio simulations to propose a new class of monolayers with stoichiometry Gex(BN)y . These monolayers belong to a family of 2D materials combining B, N and group IV atoms, such as BxCyNz and SixByNz . We calculated the formation energy for ten atomic arrangements, and found that it increases when the number of Bsbnd Ge and Nsbnd Ge bonds increases, and decreases when the number of Bsbnd N and Gesbnd Ge bonds increases. We found that the lowest energy monolayer presented a Ge2 BN stoichiometry, and maximized the number of Bsbnd N and Gesbnd Ge bonds. This structure also presented mixed sp2 and sp3 bonds and out-of-plane buckling. Moreover, it remained stable in our ab initio molecular dynamics simulations carried out at T = 300 K. The calculated electronic properties revealed that Gex(BN)y monolayers might present conductor or semiconductor behavior, with band gaps ranging from 0.0 to 0.74 eV, depending on atomic arrangement. Tunable values of band gap can be useful in applications. In optoelectronics, for instance, this property might be employed to control absorbed light wavelengths. Our calculations add a new class of monolayers to the increasing library of 2D materials.

  8. Modifications of a calcium phosphate cement with biomolecules--influence on nanostructure, material, and biological properties.

    Science.gov (United States)

    Vater, Corina; Lode, Anja; Bernhardt, Anne; Reinstorf, Antje; Nies, Berthold; Gelinsky, Michael

    2010-12-01

    Calcium phosphate cements (CPC), forming hydroxyapatite during the setting reaction, are characterized by good biocompatibility and osteoconductivity, however, their remodeling into native bone tissue is slow. One strategy to improve remodeling and bone regeneration is the directed modification of their nanostructure. In this study, a CPC was set in the presence of cocarboxylase, glucuronic acid, tartaric acid, α-glucose-1-phosphate, L-arginine, L-aspartic acid, and L-lysine, respectively, with the aim to influence formation and growth of hydroxyapatite crystals through the functional groups of these biomolecules. Except for glucuronic acid, all these modifications resulted in the formation of smaller and more agglomerated hydroxyapatite particles which had a positive impact on the biological performance indicated by first experiments with the human osteoblast cell line hFOB 1.19. Moreover, adhesion, proliferation, and osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSC) as well as binding of the growth factors BMP-2 and VEGF was investigated on CPC modified with cocarboxylase, arginine, and aspartic acid. Initial adhesion of hBMSC was improved on these three modifications and proliferation was enhanced on CPC modified with cocarboxylase and arginine whereas osteogenic differentiation remained unaffected. Modification of the CPC with arginine and aspartic acid, but not with cocarboxylase, led to a higher BMP-2 binding. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.

  9. Modification with alkyl chains and the influence on thermal and mechanical properties of aromatic hyperbranched polyesters

    NARCIS (Netherlands)

    Schmaljohann, Dirk; Häußler, Liane; Pötschke, Petra; Voit, Brigitte I.; Loontjens, Ton J.A.

    2000-01-01

    All-aromatic hyperbranched polyesters with hydroxy endgroups were functionalized with aliphatic n-alkyl carboxylic acids. The length of the n-alkyl chain as well as the degree of modification were varied and the resulting, partially amphiphilic polymers were characterized by differential scanning

  10. Modification of infant hypothyroidism and phenylketonuria screening program using electronic tools.

    Science.gov (United States)

    Taheri, Behjat; Haddadpoor, Asefeh; Mirkhalafzadeh, Mahmood; Mazroei, Fariba; Aghdak, Pezhman; Nasri, Mehran; Bahrami, Gholamreza

    2017-01-01

    Congenital hypothyroidism and phenylketonuria (PKU) are the most common cause for preventable mental retardation in infants worldwide. Timely diagnosis and treatment of these disorders can have lasting effects on the mental development of newborns. However, there are several problems at different stages of screening programs that along with imposing heavy costs can reduce the precision of the screening, increasing the chance of undiagnosed cases which in turn can have damaging consequences for the society. Therefore, given these problems and the importance of information systems in facilitating the management and improving the quality of health care the aim of this study was to improve the screening process of hypothyroidism and PKU in infants with the help of electronic resources. The current study is a qualitative, action research designed to improve the quality of screening, services, performance, implementation effectiveness, and management of hypothyroidism and PKU screening program in Isfahan province. To this end, web-based software was designed. Programming was carried out using Delphi.net software and used SQL Server 2008 for database management. Given the weaknesses, problems, and limitations of hypothyroidism and PKU screening program, and the importance of these diseases in a national scale, this study resulted in design of hypothyroidism and PKU screening software for infants in Isfahan province. The inputs and outputs of the software were designed in three levels including Health Care Centers in charge of the screening program, provincial reference lab, and health and treatment network of Isfahan province. Immediate registration of sample data at the time and location of sampling, providing the provincial reference Laboratory and Health Centers of different eparchies with the ability to instantly observe, monitor, and follow-up on the samples at any moment, online verification of samples by reference lab, creating a daily schedule for reference lab

  11. Electron beam irradiation and addition of poly(vinyl alcohol) affect gelatin based-films properties

    Energy Technology Data Exchange (ETDEWEB)

    Inamura, Patricia Y.; Mastro, Nelida L. del, E-mail: pinamura@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Gelatin is a mixture of high molecular weight polypeptides, product of denaturation, and partial structural degradation of collagen, and one of the first materials employed as biomaterials. Aqueous solutions of gelatin (10%), glycerin as plasticizer and poly(vinyl alcohol) (PVA) up to 10% were prepared in a water bath at 70 deg C under constant stirring. Films were irradiated with 10 and 20 kGy using an electron beam accelerator, dose rate of 22.4 kGy s{sup -1}, energy 1.407 MeV, at room temperature, in the presence of air. After irradiation, mechanical properties, color measurements, water absorption, moisture and film solubility were analyzed. The films showed an improvement in maximum force to rupture the film with increase of the irradiation dose. The higher the puncture force to rupture the lower the elongation at break. Colorimetric tests showed significant differences between samples, and also differences depending of the applied radiation dose, and analyzed color parameter. In water absorption tests a decrease of absorption percentage was found with the increase of the dose for PVA free and 5% PVA samples. The addition of PVA increased the water absorption for all applied doses. The modifications in gelatin colloids can be appointed to radiation-induced crosslinking. Also, the PVA concentration in the samples influenced the resultant material properties. (author)

  12. Electronic, Optical, and Thermal Properties of Reduced-Dimensional Semiconductors

    Science.gov (United States)

    Huang, Shouting

    Reduced-dimensional materials have attracted tremendous attention because of their new physics and exotic properties, which are of great interests for fundamental science. More importantly, the manipulation and engineering of matter on an atomic scale yield promising applications for many fields including nanoelectronics, nanobiotechnology, environments, and renewable energy. Because of the unusual quantum confinement and enhanced surface effect of reduced-dimensional materials, traditional empirical models suffer from necessary but unreliable parameters extracted from previously-studied bulk materials. In this sense, quantitative, parameter-free approaches are highly useful for understanding properties of reduced-dimensional materials and, furthermore, predicting their novel applications. The first-principles density functional theory (DFT) is proven to be a reliable and convenient tool. In particular, recent progress in many-body perturbation theory (MBPT) makes it possible to calculate excited-state properties, e.g., quasiparticle (QP) band gap and optical excitations, by the first-principles approach based on DFT. Therefore, during my PhD study, I employed first-principles calculations based on DFT and MBPT to systematically study fundamental properties of typical reduced-dimensional semiconductors, i.e., the electronic structure, phonons, and optical excitations of core-shell nanowires (NWs) and graphene-like two-dimensional (2D) structures of current interests. First, I present first-principles studies on how to engineer band alignments of nano-sized radial heterojunctions, Si/Ge core-shell NWs. Our calculation reveals that band offsets in these one-dimensional (1D) nanostructures can be tailored by applying axial strain or varying core-shell sizes. In particular, the valence band offset can be efficiently tuned across a wide range and even be diminished via applied strain. Two mechanisms contribute to this tuning of band offsets. Furthermore, varying the

  13. Influence of Low-Frequency Vibration and Modification on Solidification and Mechanical Properties of Al-Si Casting Alloy

    Directory of Open Access Journals (Sweden)

    Vadim Selivorstov

    2017-05-01

    Full Text Available One of the major aims of the modern materials foundry industry is the achievement of advanced mechanical properties of metals, especially of light non-ferrous alloys such as aluminum. Usually an alloying process is applied to obtain the required properties of aluminum alloys. However, the presented work describes an alternative approach through the application of vibration treatment, modification by ultrafine powder and a combination of these two methods. Microstructural studies followed by image analysis revealed the refinement of α-Al grains with an increase in the Si network area around them. As evidence, the improvement of the mechanical properties of Al casting alloy was detected. It was found that the alloys subjected to the vibration treatment displayed an increase in tensile and yield strengths by 20% and 10%, respectively.

  14. Effect of thermal and chemical modifications on the mechanical and release properties of paracetamol tablet formulations containing corn, cassava and sweet potato starches as filler-binders

    Directory of Open Access Journals (Sweden)

    Mariam Vbamiunomhene Lawal

    2015-07-01

    Conclusions: Modification of the experimental starches improved the mechanical and release properties of directly compressed paracetamol tablet formulations. Thus, they can be developed for use as pharmaceutical excipients in specific formulations.

  15. Changes in Structural-Mechanical Properties and Degradability of Collagen during Aging-associated Modifications.

    Science.gov (United States)

    Panwar, Preety; Lamour, Guillaume; Mackenzie, Neil C W; Yang, Heejae; Ko, Frank; Li, Hongbin; Brömme, Dieter

    2015-09-18

    During aging, changes occur in the collagen network that contribute to various pathological phenotypes in the skeletal, vascular, and pulmonary systems. The aim of this study was to investigate the consequences of age-related modifications on the mechanical stability and in vitro proteolytic degradation of type I collagen. Analyzing mouse tail and bovine bone collagen, we found that collagen at both fibril and fiber levels varies in rigidity and Young's modulus due to different physiological changes, which correlate with changes in cathepsin K (CatK)-mediated degradation. A decreased susceptibility to CatK-mediated hydrolysis of fibrillar collagen was observed following mineralization and advanced glycation end product-associated modification. However, aging of bone increased CatK-mediated osteoclastic resorption by ∼27%, and negligible resorption was observed when osteoclasts were cultured on mineral-deficient bone. We observed significant differences in the excavations generated by osteoclasts and C-terminal telopeptide release during bone resorption under distinct conditions. Our data indicate that modification of collagen compromises its biomechanical integrity and affects CatK-mediated degradation both in bone and tissue, thus contributing to our understanding of extracellular matrix aging. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  16. Changes in Structural-Mechanical Properties and Degradability of Collagen during Aging-associated Modifications*

    Science.gov (United States)

    Panwar, Preety; Lamour, Guillaume; Mackenzie, Neil C. W.; Yang, Heejae; Ko, Frank; Li, Hongbin; Brömme, Dieter

    2015-01-01

    During aging, changes occur in the collagen network that contribute to various pathological phenotypes in the skeletal, vascular, and pulmonary systems. The aim of this study was to investigate the consequences of age-related modifications on the mechanical stability and in vitro proteolytic degradation of type I collagen. Analyzing mouse tail and bovine bone collagen, we found that collagen at both fibril and fiber levels varies in rigidity and Young's modulus due to different physiological changes, which correlate with changes in cathepsin K (CatK)-mediated degradation. A decreased susceptibility to CatK-mediated hydrolysis of fibrillar collagen was observed following mineralization and advanced glycation end product-associated modification. However, aging of bone increased CatK-mediated osteoclastic resorption by ∼27%, and negligible resorption was observed when osteoclasts were cultured on mineral-deficient bone. We observed significant differences in the excavations generated by osteoclasts and C-terminal telopeptide release during bone resorption under distinct conditions. Our data indicate that modification of collagen compromises its biomechanical integrity and affects CatK-mediated degradation both in bone and tissue, thus contributing to our understanding of extracellular matrix aging. PMID:26224630

  17. Electronic and Thermal Properties of Puckered Orthorhombic Materials

    Science.gov (United States)

    Fei, Ruixiang

    Puckered orthorhombic crystals, such as black phosphorus and group IV monochalcogenides, are attracting tremendous attention because of their new exotic properties, which are of great interests for fundamental science and novel applications. Unlike those well studied layered hexagonal materials such as graphene and transition metal dichalcogenides, the puckered orthorhombic crystals possess highly asymmetrical in-plane crystal structures. Understanding the unique properties emerginge from their low symmetries is an intriguing and useful process, which gives insight into experimental observation and sheds light on manipulating their properties. In this thesis, we study and predict various properties of orthorhombic materials by using appropriate theoretical techniques such as first-principles calculations, Monte-Carlo simulations, and k · p models. In the first part of the thesis, we deal with the anisotropic electric and thermal properties of a typical puckered orthorhombic crystal, black phosphorus. We first study the electric properties in monolayer and few-layer black phosphorus, where the unique, anisotropic electrical conductance is founded. Furthermore, we find that the anisotropy of the electrical conductance can be rotated by 90° through applying appropriate uniaxial or biaxial strain. Beyond electrical conductance, we, for the first time, predict that the thermal conductance of black phosphorus is also anisotropic and, particularly, the preferred conducting direction is perpendicular to the preferred electrical conducting direction. Within the reasonable estimation regime, the thermoelectric figure of merit (ZT) ultimately reaches 1 at room temperature using only moderate doping. The second part of this thesis focuses on the electronic polarization of non-centrosymmetric puckered materials-group IV monochalcogenide. We propose that monolayer group IV monochalcogenides are a new class of two-dimensional (2D) ferroelectric materials with spontaneous in

  18. Laser Surface Modification of Ti6Al4V-Cu for Improved Microhardness and Wear Resistance Properties

    OpenAIRE

    Erinosho, Mutiu Folorunsho; Akinlabi, Esther Titilayo; Pityana, Sisa; Owolabi, Gbadebo

    2017-01-01

    To modify the properties of Ti6Al4V alloy, Cu has been added to host an antimicrobial effect in the revised alloy for marine application. The Laser Metal Deposition (LMD) process on the Ti6Al4V alloy and Cu was been investigated for surface modification in order to combat the problem of biofouling in the marine industry. The investigations focused on the microstructural observations, micro-hardness measurements and dry sliding wear in the presence of 3 and 5 weight percents of Cu. The microst...

  19. Structure and electronic properties of a benzene-water solution.

    Science.gov (United States)

    Mateus, Margarida P S; Galamba, Nuno; Cabral, Benedito J Costa

    2012-01-07

    Electronic properties of benzene in water were investigated by a sequential quantum mechanical/molecular dynamics approach. Emphasis was placed on the analysis of the structure, polarization effects, and ionization spectrum. By adopting a polarizable model for both benzene and water the structure of the benzene-water solution is in good agreement with data from first principles molecular dynamics. Further, strong evidence that water molecules acquire enhanced orientational order near the benzene molecule is found. Upon hydration, the quadrupole moment of benzene is not significantly changed in comparison with the gas-phase value. We are also reporting results for the dynamic polarizability of benzene in water. Our results indicate that the low energy behaviour of the dynamic polarizability of gas-phase and hydrated benzene is quite similar. Outer valence Green's function calculations for benzene in liquid water show a splitting of the gas-phase energy levels associated with the 1e(1g)(π), 2e(2g), and 2e(1u) orbitals upon hydration. Lifting of the orbitals degeneracy and redshift of the outer valence bands is related to symmetry breaking of the benzene structure in solution and polarization effects from the surrounding water molecules.

  20. Phonon spectra, electronic, and thermodynamic properties of WS2nanotubes.

    Science.gov (United States)

    Evarestov, Robert A; Bandura, Andrei V; Porsev, Vitaly V; Kovalenko, Alexey V

    2017-11-15

    Hybrid density functional theory calculations are performed for the first time on the phonon dispersion and thermodynamic properties of WS 2 -based single-wall nanotubes. Symmetry analysis is presented for phonon modes in nanotubes using the standard (crystallographic) factorization for line groups. Symmetry and the number of infra-red and Raman active modes in achiral WS 2 nanotubes are given for armchair and zigzag chiralities. It is demonstrated that a number of infrared and Raman active modes is independent on the nanotube diameter. The zone-folding approach is applied to find out an impact of curvature on electron and phonon band structure of nanotubes rolled up from the monolayer. Phonon frequencies obtained both for layers and nanotubes are used to compute the thermal contributions to their thermodynamic functions. The temperature dependences of energy, entropy, and heat capacity of nanotubes are estimated with respect to those of the monolayer. The role of phonons in the stability estimation of nanotubes is discussed based on Helmholtz free energy calculations. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  1. Magnetostructural, mechanical and electronic properties of manganese tetraboride

    Directory of Open Access Journals (Sweden)

    Yongcheng Liang

    2015-11-01

    Full Text Available Magnetostructural stabilities, mechanical behaviors and electronic structures of various phases of manganese tetraboride (MnB4 have been investigated systematically by density functional theory (DFT based first-principles methods. It is found that MnB4 undergoes temperature-induced phase transitions from the nonmagnetic (NM monoclinic mP20 structure to the ferromagnetic (FM orthorhombic oP10 structure at 438 K, then to the antiferromagnetic (AFM orthorhombic oP10 structure at 824 K. We reveal that the NM insulating mP20 phase stabilizes by the Peierls distortion breaking the structural degeneracy, while the FM and AFM metallic oP10 phases stabilize by the Stoner magnetism lifting the spin degeneracy. Furthermore, the calculated mechanical properties show that the NM mP20, FM oP10, and AFM oP10 phases exhibit low compressibility and high hardness, which originate from their three-dimensional covalent boron networks. Therefore, this unique temperature-assisted insulator-metal transition, strong stiffness and high hardness suggest that MnB4 may find promising technological applications as thermoelectric switches and field effect transistors at the extreme conditions.

  2. Ab-intitio studies of electronic properties of chalcogenide spinels.

    Science.gov (United States)

    Chshiev, Mairbek; Wang, Y.-H. A.; Gupta, Arunava; Bettinger, Joanna; Suzuki, Yuri; Butler, William H.

    2007-03-01

    CuCr2Se4 is a normal chalcogenide spinel which exhibits ferromagnetic properties including a relatively high Curie temperature of 450 K [1] which makes it a promising candidate for use in spintronics devices. Another chalcogenide spinel of enhanced interest for spintronics is CdCr2Se4 which seems to be a promising ferromagnetic semiconductor for electrical spin injection into III-V device heterostructures [2]. We report first principles calculations of the electronic structure of substoichiometric CuCr2Se4-x and CuxCd1-xCrSe4 spinels. The calculations were performed using the Vienna ab-initio simulation program (VASP) within the Generalized Gradient Approximation (GGA) of Density Functional Theory (DFT). Our calculations indicate that both Se deficient CuCr2Se4-x as well as CuxCd1-xCrSe4 show half-metallic behavior over a wide range of x with a gap around the Fermi level in the minority density of states. [1] F.K. Lotgering, Solid State Commun. 2 (1964) 55 [2] G. Kioseoglou et al., Nature Materials 3 (2004) 799

  3. Magnetostructural, mechanical and electronic properties of manganese tetraboride

    Science.gov (United States)

    Liang, Yongcheng; Wu, Zhaobing; Wang, Shiming

    2015-11-01

    Magnetostructural stabilities, mechanical behaviors and electronic structures of various phases of manganese tetraboride (MnB4) have been investigated systematically by density functional theory (DFT) based first-principles methods. It is found that MnB4 undergoes temperature-induced phase transitions from the nonmagnetic (NM) monoclinic mP20 structure to the ferromagnetic (FM) orthorhombic oP10 structure at 438 K, then to the antiferromagnetic (AFM) orthorhombic oP10 structure at 824 K. We reveal that the NM insulating mP20 phase stabilizes by the Peierls distortion breaking the structural degeneracy, while the FM and AFM metallic oP10 phases stabilize by the Stoner magnetism lifting the spin degeneracy. Furthermore, the calculated mechanical properties show that the NM mP20, FM oP10, and AFM oP10 phases exhibit low compressibility and high hardness, which originate from their three-dimensional covalent boron networks. Therefore, this unique temperature-assisted insulator-metal transition, strong stiffness and high hardness suggest that MnB4 may find promising technological applications as thermoelectric switches and field effect transistors at the extreme conditions.

  4. Electronic modification of Pt via Ti and Se as tolerant cathodes in air-breathing methanol microfluidic fuel cells.

    Science.gov (United States)

    Ma, Jiwei; Habrioux, Aurélien; Morais, Cláudia; Alonso-Vante, Nicolas

    2014-07-21

    We reported herein on the use of tolerant cathode catalysts such as carbon supported Pt(x)Ti(y) and/or Pt(x)Se(y) nanomaterials in an air-breathing methanol microfluidic fuel cell. In order to show the improvement of mixed-reactant fuel cell (MRFC) performances obtained with the developed tolerant catalysts, a classical Pt/C nanomaterial was used for comparison. Using 5 M methanol concentration in a situation where the fuel crossover is 100% (MRFC-mixed reactant fuel cell application), the maximum power density of the fuel cell with a Pt/C cathodic catalyst decreased by 80% in comparison with what is observed in the laminar flow fuel cell (LFFC) configuration. With Pt(x)Ti(y)/C and Pt(x)Se(y)/C cathode nanomaterials, the performance loss was only 55% and 20%, respectively. The evaluation of the tolerant cathode catalysts in an air-breathing microfluidic fuel cell suggests the development of a novel nanometric system that will not be size restricted. These interesting results are the consequence of the high methanol tolerance of these advanced electrocatalysts via surface electronic modification of Pt. Herein we used X-ray photoelectron and in situ FTIR spectroscopies to investigate the origin of the high methanol tolerance on modified Pt catalysts.

  5. Effects of Surface Modification on the Mechanical Properties of Flax/β-Polypropylene Composites.

    Science.gov (United States)

    Wu, Chang-Mou; Lai, Wen-You; Wang, Chen-Yu

    2016-04-27

    The effects of surface treatment of flax fibers featuring vinyltrimethoxy silane (VTMO) and maleic anhydride-polypropylene (MAPP) on the mechanical properties of flax/PP composites were investigated. α-polypropylene (α-PP) and β-polypropylene (β-PP) were used as matrices for measuring the mechanical properties of the flax fiber/polypropylene (flax/PP) composites. Flax/PP composites composed of double-covered uncommingled yarn (DCUY) were prepared using a film-stacking technique. The influence of surface treatment on the tensile, flexural, impact, and water uptake properties of Flax/PP composites were investigated. MAPP treatment was suitable for flax/PP composites in terms of superior tensile and impact properties. VTMO treatment showed superior flexural properties and less influence on the impact properties after moisture absorption.

  6. Effects of Surface Modification on the Mechanical Properties of Flax/β-Polypropylene Composites

    Directory of Open Access Journals (Sweden)

    Chang-Mou Wu

    2016-04-01

    Full Text Available The effects of surface treatment of flax fibers featuring vinyltrimethoxy silane (VTMO and maleic anhydride-polypropylene (MAPP on the mechanical properties of flax/PP composites were investigated. α-polypropylene (α-PP and β-polypropylene (β-PP were used as matrices for measuring the mechanical properties of the flax fiber/polypropylene (flax/PP composites. Flax/PP composites composed of double-covered uncommingled yarn (DCUY were prepared using a film-stacking technique. The influence of surface treatment on the tensile, flexural, impact, and water uptake properties of Flax/PP composites were investigated. MAPP treatment was suitable for flax/PP composites in terms of superior tensile and impact properties. VTMO treatment showed superior flexural properties and less influence on the impact properties after moisture absorption.

  7. Structure-Processing-Property Relationships at the Fiber-Matrix Interface in Electron-Beam Cured Composite Materials

    Energy Technology Data Exchange (ETDEWEB)

    Janke, C.J.

    1998-11-01

    The objective of this project was to characterize the properties of the resin and the fiber- resin interface in electron beam cured materials by evaluating several structural and processing parameters. The Oak Ridge National Laboratory (ORNL) has recently determined that the interlaminar shear strength properties of electron beam cured composites were 19-28% lower than for autoclave cured composites. Low interlaminar shear strength is widely acknowledged as the key barrier to the successfid acceptance and implementation of electron beam cured composites in industry. In this project we found that simple resin modification and process improvements are unlikely to substantially improve the interlaminar shear strength properties of electron beam cured composites. However, sizings and coatings were shown to improve these properties and there appears to be significant potential for further improvement. In this work we determined that the application of epoxy-based, electron beam compatible sizings or coatings onto surface- treated, unsized carbon fibers improved the composite interlaminar shear strength by as much as 55% compared to composites fabricated from surface-treated, unsized carbon fibers and 11 YO compared to composites made from surface-treated, GP sized carbon fibers. This work has identified many promising pathways for increasing the interlaminar shear strength of electron beam cured composites. As a result of these promising developments we have recently submitted a U.S. Department of Energy-Energy Research (DOE-ER) sponsored Laboratory Technical Research-Cooperative Research and Development Agreement (LTR- CRADA) proposal entitled, "Interracial Properties of Electron Beam Cured Composites", to continue this work. If funded, ORNL will lead a 3-year, $2.6 million effort involving eight industrial partners, NASA-Langley, and the U.S. Air Force. The principal objective of this CRADA is to significantly improve the interracial properties of carbon

  8. Electronic properties of interfaces produced by silicon wafer hydrophilic bonding

    Energy Technology Data Exchange (ETDEWEB)

    Trushin, Maxim

    2011-07-15

    The thesis presents the results of the investigations of electronic properties and defect states of dislocation networks (DNs) in silicon produced by wafers direct bonding technique. A new insight into the understanding of their very attractive properties was succeeded due to the usage of a new, recently developed silicon wafer direct bonding technique, allowing to create regular dislocation networks with predefined dislocation types and densities. Samples for the investigations were prepared by hydrophilic bonding of p-type Si (100) wafers with same small misorientation tilt angle ({proportional_to}0.5 ), but with four different twist misorientation angles Atw (being of < , 3 , 6 and 30 , respectively), thus giving rise to the different DN microstructure on every particular sample. The main experimental approach of this work was the measurements of current and capacitance of Schottky diodes prepared on the samples which contained the dislocation network at a depth that allowed one to realize all capabilities of different methods of space charge region spectroscopy (such as CV/IV, DLTS, ITS, etc.). The key tasks for the investigations were specified as the exploration of the DN-related gap states, their variations with gradually increasing twist angle Atw, investigation of the electrical field impact on the carrier emission from the dislocation-related states, as well as the establishing of the correlation between the electrical (DLTS), optical (photoluminescence PL) and structural (TEM) properties of DNs. The most important conclusions drawn from the experimental investigations and theoretical calculations can be formulated as follows: - DLTS measurements have revealed a great difference in the electronic structure of small-angle (SA) and large-angle (LA) bonded interfaces: dominating shallow level and a set of 6-7 deep levels were found in SA-samples with Atw of 1 and 3 , whereas the prevalent deep levels - in LA-samples with Atw of 6 and 30 . The critical twist

  9. Impact of electronic modification of the chelating benzylidene ligand in cis-dichloro-configured second-generation olefin metathesis catalysts on their activity

    KAUST Repository

    Pump, Eva

    2014-06-09

    A series of electronically modified second-generation cis-dichloro ruthenium ester chelating benzylidene complexes was prepared, characterized, and benchmarked in a typical ring-opening metathesis polymerization (ROMP) experiment. The electronic tuning of the parent chelating benzylidene ligand (2-ethyl ester benzylidene) was achieved by substitution at the 4- and 5-positions with electron-withdrawing nitro or electron-donating methoxy groups. The effect of the electronic tuning on the cis-trans isomerization process was studied experimentally and theoretically. Density functional theory calculations clearly revealed the influence of electronic modification on the relative stability between the cis and trans isomers, which is decisive for the activity of the studied compounds as initiators in ROMP. © 2014 American Chemical Society.

  10. How modification of accessible lysines to phenylalanine modulates the structural and functional properties of horseradish peroxidase: a simulation study.

    Directory of Open Access Journals (Sweden)

    Leila Navapour

    Full Text Available Horseradish Peroxidase (HRP is one of the most studied peroxidases and a great number of chemical modifications and genetic manipulations have been carried out on its surface accessible residues to improve its stability and catalytic efficiency necessary for biotechnological applications. Most of the stabilized derivatives of HRP reported to date have involved chemical or genetic modifications of three surface-exposed lysines (K174, K232 and K241. In this computational study, we altered these lysines to phenylalanine residues to model those chemical modifications or genetic manipulations in which these positively charged lysines are converted to aromatic hydrophobic residues. Simulation results implied that upon these substitutions, the protein structure becomes less flexible. Stability gains are likely to be achieved due to the increased number of stable hydrogen bonds, improved heme-protein interactions and more integrated proximal Ca2+ binding pocket. We also found a new persistent hydrogen bond between the protein moiety (F174 and the heme prosthetic group as well as two stitching hydrogen bonds between the connecting loops GH and F'F″ in mutated HRP. However, detailed analysis of functionally related structural properties and dynamical features suggests reduced reactivity of the enzyme toward its substrates. Molecular dynamics simulations showed that substitutions narrow the bottle neck entry of peroxide substrate access channel and reduce the surface accessibility of the distal histidine (H42 and heme prosthetic group to the peroxide and aromatic substrates, respectively. Results also demonstrated that the area and volume of the aromatic-substrate binding pocket are significantly decreased upon modifications. Moreover, the hydrophobic patch functioning as a binding site or trap for reducing aromatic substrates is shrunk in mutated enzyme. Together, the results of this simulation study could provide possible structural clues to explain

  11. The Modification of Sodium Polyacrylate Water Solution Cooling Properties by AL2O3

    OpenAIRE

    Wojciech Gęstwa; Małgorzata Przyłęcka

    2010-01-01

    This paper presents a preliminary examination of water cooling ability as a result of its modification by the addition of sodium polyacrylate and AL2O3 nanoparticles. (AL2O3) alumina oxide was present in gamma phase as a form of nanopowder whose particle size was less than 50 nm. Cooling curves in the temperature-time system were marked for the three cooling media: water, 10% water solution of sodium polyacrylate, and 10% water solution of sodium polyacrylate with 1% addition of AL2O3 nanopar...

  12. Quasiparticle properties of a coupled quantum-wire electron-phonon system

    DEFF Research Database (Denmark)

    Hwang, E. H.; Hu, Ben Yu-Kuang; Sarma, S. Das

    1996-01-01

    We study leading-order many-body effects of longitudinal-optical phonons on electronic properties of one-dimensional quantum-wire systems. We calculate the quasiparticle properties of a weakly polar one-dimensional electron gas in the presence of both electron-phonon and electron-electron...... interactions, The leading-order dynamical screening approximation (GW approximation) is used to obtain the electron self-energy, the quasiparticle spectral function, and the quasiparticle damping rate in our calculation by treating electrons and phonons on an equal footing. Our theory includes effects (within...... the random-phase approximation) of Fermi statistics, Landau damping, plasmon-phonon mode coupling, phonon renormalization, dynamical screening, and impurity scattering. In general, electron-electron and electron-phonon many-body renormalization effects are found to be nonmultiplicative and nonadditive in our...

  13. Research of the Electron Cyclotron Emission with Vortex Property excited by high power high frequency Gyrotron

    Science.gov (United States)

    Goto, Yuki; Kubo, Shin; Tsujimura, Tohru; Takubo, Hidenori

    2017-10-01

    Recently, it has been shown that the radiation from a single electron in cyclotron motion has vortex property. Although the cyclotron emission exists universally in nature, the vortex property has not been featured because this property is normally cancelled out due to the randomness in gyro-phase of electrons and the development of detection of the vortex property has not been well motivated. In this research, we are developing a method to generate the vortex radiation from electrons in cyclotron motion with controlled gyro-phase. Electron that rotates around the uniform static magnetic field is accelerated by right-hand circular polarized (RHCP) radiation resonantly when the cyclotron frequency coincides with the applied RHCP radiation frequency. A large number of electrons can be coherently accelerated in gyro-phase by a RHCP high power radiation so that these electrons can radiate coherent emission with vortex feature. We will show that vortex radiation created by purely rotating electrons for the first time.

  14. Studies on Solid Wood. II. The Influence of Chemical Modifications on Viscoelastic Properties

    DEFF Research Database (Denmark)

    Bjørkmann, Anders; Salmén, Lennart

    2000-01-01

    The relation between the properties of wood polymers and those of the composite material of wood is a subject that has been of interest for a long time. In order to increase oar knowledge in this matter, changes of wood properties have been studied on samples of spruce and birch, subjected to var...

  15. Electron-beam processed corn starch: evaluation of physicochemical and structural properties and technical-economic aspects of the processing

    Directory of Open Access Journals (Sweden)

    M. Braşoveanu

    2013-12-01

    Full Text Available The properties of starch can be modified by a variety of methods in order to meet desirable technological needs. Electron beam irradiation is able to induce changes in starch properties. The paper deals with investigation of physicochemical and structural modifications of corn starch processed by electron beam up to 50 kGy and evaluation of the technical-economic aspects of starch processing. Paste viscosity, pasting and peak temperatures decreased in a dose-dependent manner, indicating degradation of the macromolecule. Small circular perforations on the granule surface were observed for 50-kGy irradiated sample. Spectral characteristics suffered minor changes, suggesting that the inter- and intramolecular hydrogen bond stability was affected by the electron beam. These modified starches could find applications in foodstuffs requiring low-viscosity starch. A cost estimate of the electron beam processing of corn starch with an average absorbed dose of 30 kGy showed an increase of corn starch price by 16%.

  16. Modifications in physico-chemical properties of 100 MeV oxygen ions irradiated polyimide Kapton-H polymer

    Science.gov (United States)

    Gupta, Sanjeev Kumar; Gupta, Rashi; Singh, Paramjit; Kumar, Vikas; Jaiswal, Manoj Kumar; Chakarvarti, S. K.; Kumar, Rajesh

    2017-09-01

    The optical, structural and chemical properties of polyimide Kapton-H polymer thin film samples were modified by irradiation with 100 MeV O7+ ions (in the fluence range of 1 × 1011 to 5 × 1012 ions/cm2) and the modifications of these properties were observed by UV-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy respectively. The band gap energy of the polymer decreased considerably with discrete increment of the ion fluence (different fluence for each sample) and effective change for the sample irradiated at a fluence of 5 × 1012 ions/cm2 was observed from that of pristine sample. The amorphous nature of the polymer was observed to be decreased with increase of ion fluence. The vibrations of Ctbnd C appeared at mid fluences but the stretching vibrations of Osbnd H bond disappeared at these fluences due to the high LET of the oxygen ions.

  17. Surface Property Modification of Silver Nanoparticles with Dopamine-Functionalized Poly(pentafluorostyrene via RAFT Polymerization

    Directory of Open Access Journals (Sweden)

    Ka Wai Fan

    2016-03-01

    Full Text Available This research aims to synthesize a dopamine-functionalized macromolecular anchor to perform surface modification on the target nanostructures. A molecular anchor, 3,4-dichloro-1-[2-(3,4-dihydroxyphenylethyl]-1H-pyrrole-2,5-dione, was successfully synthesized from dopamine and 2,3-dichloromaleic anhydride. The anchor acted as a linkage to couple the chains of poly(pentafluorostyrene (PPFS which were synthesized via reversible addition fragmentation chain transfer (RAFT polymerization. Modification was successfully performed to silver nanoparticles (AgNPs by deposition of the dopamine-functionalized coupled PPFS onto the surface of the particles. The modified AgNPs had demonstrated improved dispersibility in organic solvent due to the hydrophobic nature of PPFS. To modify the surface chemistry of the nanoparticles further, thioglucose was grafted onto the structure of the coupled PPFS via thiol-fluoro nucleophilic substitution at the para-position of the pentafluorophenyl groups on the monomer units. The presence of sugar moieties on the coupled PPFS increased its hydrophilicity, which allowed the modified AgNPs to be readily dispersed in aqueous solvent.

  18. Effects of modification and incorporation techniques on disintegrant properties of wheat (Triticum aestivum) starch in metronidazole tablet formulations.

    Science.gov (United States)

    Odeniyi, Michael Ayodele; Ayorinde, John O

    2014-01-01

    Natural polymers serve as cheap, non-toxic, biocompatible excipients in drug delivery. Starch from wheat (Triticum aestivum) was investigated as a disintegrant in metronidazole tablet formulations in comparison with sodium starch glycolate (SSG), a standard, synthetic but relatively more expensive disintegrant. Native wheat starch (NAS) was modified by pregelatinization (PGS) and microwave irradiation (MCW). The starches were characterized using swelling capacity, angle of repose, density measurements, Carr's index and Hausner's ratio. Metronidazole tablet formulations were made with the starches incorporated by intragranular (IG), extra-granular (EG) or intra/extragranular (IG/EG) methods. Tablet properties of crushing strength, disintegration time and dissolution tests were determined. Native wheat starch had better hydration capacity than the modified starches, with PGS having a higher swelling capacity than the MCW. Modified starches formed better compacts than both NAS and SSG as indicated by the higher crushing strength of tablets containing modified starches. Intragranular incorporation gave a higher crushing strength than both EG and IG/EG methods. The ranking for disintegration time of tablets was IG/EG > IG > EG among the incorporation methods and SSG > PGS > MCW > NAS among the starches (EG > IG/EG). The difference between IG/EG and EG was significant (p SSG > PGS). Native and modified wheat starches exhibited better disintegrant properties than sodium starch glycolate in metronidazole tablet formulations. The mode of disintegrant incorporation and modification of wheat starch had different effects on tablet properties of metronidazole formulations. The modification technique and method of disintegrant incorporation should be determined based on desired tablet properties.

  19. Surface modification of Sylgard 184 polydimethylsiloxane by 254 nm excimer radiation and characterization by contact angle goniometry, infrared spectroscopy, atomic force and scanning electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Waddell, Emanuel A. [University of Alabama in Huntsville, Huntsville, AL (United States)], E-mail: ewaddell@chemistry.uah.edu; Shreeves, Stephen [University of Alabama in Huntsville, Huntsville, AL (United States); Carrell, Holly; Perry, Christopher [Oakwood College, Huntsville, AL (United States); Reid, Branden A. [Morgan State University, Baltimore, MD (United States); McKee, James [University of Alabama in Birmingham, Birmingham, AL (United States)

    2008-06-30

    The modification of polydimethylsiloxane (PDMS) by narrow band 254 nm excimer radiation under a nitrogen atmosphere was characterized by contact angle goniometry, attenuated total reflectance infrared spectroscopy, atomic force and scanning electron microscopy. UV irradiation results in the formation of the carboxylic acids that influences the wettability of the surface. Continued exposure results in the formation of an inorganic surface (SiO{sub x} (1 < x < 2)) which hinders the ability to continually increase the wettability. The continuity of this inorganic layer is disrupted by the formation of surface cracks. These results have implications in the fabrication and chemical modification of microfluidic or micro-electro-mechanical systems.

  20. Surface modification of Sylgard 184 polydimethylsiloxane by 254 nm excimer radiation and characterization by contact angle goniometry, infrared spectroscopy, atomic force and scanning electron microscopy

    Science.gov (United States)

    Waddell, Emanuel A.; Shreeves, Stephen; Carrell, Holly; Perry, Christopher; Reid, Branden A.; McKee, James

    2008-06-01

    The modification of polydimethylsiloxane (PDMS) by narrow band 254 nm excimer radiation under a nitrogen atmosphere was characterized by contact angle goniometry, attenuated total reflectance infrared spectroscopy, atomic force and scanning electron microscopy. UV irradiation results in the formation of the carboxylic acids that influences the wettability of the surface. Continued exposure results in the formation of an inorganic surface (SiO x (1 < x < 2)) which hinders the ability to continually increase the wettability. The continuity of this inorganic layer is disrupted by the formation of surface cracks. These results have implications in the fabrication and chemical modification of microfluidic or micro-electro-mechanical systems.

  1. The Influence of Pet Fibres Surface Enzymatic Modification on the Selected Properties

    Directory of Open Access Journals (Sweden)

    Kardas Iwona

    2014-09-01

    Full Text Available The effect of changes in the surface structure of glossy polyester filaments from poly(ethylene terephthalate in terms of its micro-topography, molecular and supermolecular structure of the fibre surface layers on selected fibre surface and volumetric properties has been assessed. The performed tests and measurements have shown that the change in the general surface characteristics of PET fibres (micro-topography and hydrophilicity results in very beneficial changes in both their volumetric (dyeability and surface properties (wettability, pilling, oil-soil removal and electric properties.

  2. Electronic properties of electron-doped [6,6]-phenyl-C61-butyric acid methyl ester and silylmethylfullerene

    Science.gov (United States)

    Furutani, Sho; Okada, Susumu

    2017-06-01

    Electronic properties of electron-doped chemically decorated C60 fullerenes, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and silylmethylfullerene (SIMEF), by a planar electrode were studied using density functional theory combined with the effective screening medium method to simulate the heterointerface between the chemically decorated C60 and cationic counter materials. We find that the distribution of accumulated electrons and induced electric field depend on the molecular arrangement with respect to the external electric field of the electrode. We also show that the quantum capacitance of the molecule is sensitive to molecular arrangement owing to the asymmetric distribution of the accumulated electrons.

  3. Synthesis, electronic and optical properties of Si nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Dinh, L.N.

    1996-09-01

    Silicon and silicon oxide nanostructures have been deposited on solid substrates, in an ultra high vacuum (UHV) chamber, by laser ablation or thermal vaporization. Laser ablation followed by substrate post annealing produced Si clusters with average size of a few nanometers, on highly oriented pyrolytic graphite (HOPG) surfaces. This technique, which is based on surface diffusion, is limited to the production of less than one layer of clusters on a given surface. The low coverage of Si clusters and the possibility of nonradiative decay of excitation in the Si cores to the HOPG substrates in these samples rendered them unsuitable for many optical measurements. Thermal vaporization of Si in an Ar buffer gas, on the contrary, yielded multilayer coverage of Si nanoclusters with a fairly narrow size distribution of about 2 nm, full width at half maximum (FWHM). As a result, further study was performed only on Si nanoclusters synthesized by thermal vaporization in a buffer gas. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) revealed that these nanoclusters were crystalline. However, during synthesis, if oxygen was the buffer gas, a network of amorphous Si oxide nanostructures (an-SiO{sub x}) with occasional embedded Si dots was formed. All samples showed strong infrared and/or visible photoluminescence (PL) with varying decay times from nanoseconds to microseconds depending on synthesis conditions. There were differences in PL spectra for hydrogen and oxygen passivated nc-Si, while many common PL properties between oxygen passivated nc-Si and an SiO{sub x} were observed. The observed experimental results can be best explained by a model involving absorption between quantum confined states in the Si cores and emission for which the decay times are very sensitive to surface and/or interface states.

  4. Modification of Rule of Mixtures for Estimation of the Mechanical Properties of Dual-Phase Steels

    Science.gov (United States)

    Alibeyki, Mohammad; Mirzadeh, Hamed; Najafi, Mostafa; Kalhor, Alireza

    2017-04-01

    The mechanical properties of dual-phase (DP) steels were correlated with the amount of martensite and its carbon content. The application of rule of mixtures for predicting the mechanical properties was critically discussed. Subsequently, a modified rule of mixtures was developed to estimate the mechanical properties of DP steels, which accounts for the variation of carbon content in martensite as a function of its volume fraction. The proposed model was able to predict the observed trends and values of hardness, yield stress, and tensile strength in a DP steel with 0.1 wt.% C. Then, its applicability was also verified for a DP steel with 0.2 wt.% C to cover the usual range of carbon content in DP steels. As a result, this simple and effective approach is anticipated to find application in estimating the properties of DP steels.

  5. Studies on Solid Wood. II. The Influence of Chemical Modifications on Viscoelastic Properties

    DEFF Research Database (Denmark)

    Bjørkmann, Anders; Salmén, Lennart

    2000-01-01

    The relation between the properties of wood polymers and those of the composite material of wood is a subject that has been of interest for a long time. In order to increase oar knowledge in this matter, changes of wood properties have been studied on samples of spruce and birch, subjected...... to various chemical treatments. Three properties were measured on completely dry samples: stiffness, creep and axial compression strength, using previously developed methods, tailored to slim axial samples, which allow complete impregnation with liquids. On native and treated samples, fully saturated...... with water, the glass transition was measured by applying sinusoidal vibrations with frequencies of 0.05-20 Hz, giving a transition for each frequency and an apparent activation energy of frequency changes. In wet wood, these quantities characterise the influence of a certain treatment on the properties...

  6. Accuracy of the FY 1999 Additions, Deletions, and Modifications to the Military Departments' Real Property Databases

    National Research Council Canada - National Science Library

    Lane, F

    2000-01-01

    This report is the third in a series of reports on accounting for property, plant, and equipment, and was performed in support of the Chief Financial Officers Act of 1990, as amended by the Federal...

  7. Effects of Surface Modification on the Mechanical Properties of Flax/?-Polypropylene Composites

    OpenAIRE

    Chang-Mou Wu; Wen-You Lai; Chen-Yu Wang

    2016-01-01

    The effects of surface treatment of flax fibers featuring vinyltrimethoxy silane (VTMO) and maleic anhydride-polypropylene (MAPP) on the mechanical properties of flax/PP composites were investigated. α-polypropylene (α-PP) and β-polypropylene (β-PP) were used as matrices for measuring the mechanical properties of the flax fiber/polypropylene (flax/PP) composites. Flax/PP composites composed of double-covered uncommingled yarn (DCUY) were prepared using a film-stacking technique. The influence...

  8. Impact of Enzymatic and Microbial Bioprocessing on Protein Modification and Nutritional Properties of Wheat Bran.

    Science.gov (United States)

    Arte, Elisa; Rizzello, Carlo G; Verni, Michela; Nordlund, Emilia; Katina, Kati; Coda, Rossana

    2015-10-07

    Besides providing dietary fiber, wheat bran is a recognized source of protein and is considered a very valuable substitute for other protein-rich sources in the food and feed industry. Nonetheless, several factors affect protein bioavailability, including bran's layered structure. This study showed the influence on the release and protein modification of wheat bran of different bioprocessing methods involving the activation of endogenous enzymes of bran, the addition of an enzyme mixture having carbohydrase activity, and microbial fermentation. Bioprocessing in acidic conditions significantly enhanced the solubilization of protein from wheat bran, reaching the highest value in the treatment where the sole endogenous protease activity was activated. Bioprocessing through controlled fermentation allowed a more intense proteolysis and strongly impacted the in vitro digestibility of proteins. The combined use of starter cultures and cell-wall-degrading enzymes was characterized by the highest increase of phytase activity and total phenols.

  9. Microwave Assisted Synthesis, Modification With Platinum And Photocatalytical Properties of TiO2 Nanofibers

    Directory of Open Access Journals (Sweden)

    Reinis DRUNKA

    2016-05-01

    Full Text Available In the present work formation of active TiO2 nanoparticles in microwave synthesis and their modification with platinum were studied. Anatase nanopowder and 10 M KOH solution were used as raw materials. Microwave assisted synthesis method permited to obtain TiO2 nanofibres and nanowires with a diameter of 10 nm and a specific surface area in the range of 70 – 150 m2/g. In order to modify TiO2 nanofibers with platinum it was stirred in H2PtCl6 solution under UV irradiation. Photocatalytic activity was determined by degradation of the methylene blue (MB solution under UV and visible light irradiation. The obtained samples showed higher photocatalytic activity with respect to pure TiO2 nanofibers. The doped TiO2 nanofibers were appropriate for degradation of harmful organic compounds as well as for hydrogen production by water splitting.

  10. Electronic Structure and Optical Properties Of EuIn2P2

    KAUST Repository

    Singh, Nirpendra

    2011-10-25

    The electronic structures and, optical and magneto‐optical properties of a newly found Zintl compound EuIn2P2 have been investigated within the density‐functional theory using the highly precise full‐potential linear‐augmented‐plane‐wave method. Results of detailed investigation of the electronic structure and related properties are reported.

  11. Enhanced methylarginine characterization by post-translational modification-specific targeted data acquisition and electron-transfer dissociation mass spectrometry.

    Science.gov (United States)

    Hart-Smith, Gene; Low, Jason K K; Erce, Melissa A; Wilkins, Marc R

    2012-08-01

    When localizing protein post-translational modifications (PTMs) using liquid-chromatography (LC)-tandem mass spectrometry (MS/MS), existing implementations are limited by inefficient selection of PTM-carrying peptides for MS/MS, particularly when PTM site occupancy is sub-stoichiometric. The present contribution describes a method by which peptides carrying specific PTMs of interest-in this study, methylarginines-may be selectively targeted for MS/MS: peptide features are extracted from high mass accuracy single-stage MS data, searched against theoretical PTM-carrying peptide masses, and matching features are subjected to targeted data acquisition LC-MS/MS. Using trypsin digested Saccharomyces cerevisiae Npl3, in which evidence is presented for 18 methylarginine sites-17 of which fall within a glycine-arginine-rich (GAR) domain spanning <120 amino acids-it is shown that this approach outperforms conventional data dependent acquisition (DDA): when applied to a complex protein mixture featuring in vivo methylated Npl3, 95% more (P=0.030) methylarginine-carrying peptides are selected for MS/MS than DDA, leading to an 86% increase (P=0.044) in the number of methylated peptides producing Mascot ion scores ≥20 following electron-transfer dissociation (ETD). Notably, significantly more low abundance arginine methylated peptides (maximum ion intensities <6×10(4) cps) are selected for MS/MS using this approach relative to DDA (50% more in a digest of purified in vitro methylated Npl3). It is also demonstrated that relative to collision-induced dissociation (CID), ETD facilitates a 586% increase (P=0.016) in average Mascot ion scores of methylarginine-carrying peptides. The present PTM-specific targeted data acquisition approach, though described using methylarginine, is applicable to any ionizable PTM of known mass.

  12. Chlorine-induced modifications in the electronic structure of Ag surfaces: a metastable deexcitation spectroscopy and photoemission comparative study

    CERN Document Server

    Pasquali, L; Canepa, M; Staicu-Casagrande, E M; Esaulov, V A

    2003-01-01

    Surface-sensitive spectroscopic techniques, namely metastable deexcitation spectroscopy (MDS) and ultraviolet photoemission (UPS), have been applied to investigate the effects of chlorine chemisorption on the electronic properties (surface density of states and charge density) of Ag(100), Ag(110) and Ag(111) surfaces. Initial stages of chemisorption, up to the formation of a saturated Cl overlayer, have been examined. In particular, MDS permitted us to observe at low Cl gas exposure a progressive depletion of the Ag (5s) charge due to transfer and bonding with Cl atoms. From both MDS and UPS it was possible to observe the development of Cl (3p) bonding and anti-bonding states, the amount of their splitting increasing with coverage. Differences between chemisorption at the three surfaces have been noticed and they have been justified in terms of the different adatom packing and possible formation of small AgCl clusters (especially for the Ag(111) surface).

  13. Deducing Electron Properties from Hard X-Ray Observations

    Science.gov (United States)

    Kontar, E. P.; Brown, J. C.; Emslie, A. G.; Hajdas, W.; Holman, G. D.; Hurford, G. J.; Kasparova, J.; Mallik, P. C. V.; Massone, A. M.; McConnell, M. L.; hide

    2011-01-01

    X-radiation from energetic electrons is the prime diagnostic of flare-accelerated electrons. The observed X-ray flux (and polarization state) is fundamentally a convolution of the cross-section for the hard X-ray emission process(es) in question with the electron distribution function, which is in turn a function of energy, direction, spatial location and time. To address the problems of particle propagation and acceleration one needs to infer as much information as possible on this electron distribution function, through a deconvolution of this fundamental relationship. This review presents recent progress toward this goal using spectroscopic, imaging and polarization measurements, primarily from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Previous conclusions regarding the energy, angular (pitch angle) and spatial distributions of energetic electrons in solar flares are critically reviewed. We discuss the role and the observational evidence of several radiation processes: free-free electron-ion, free-free electron-electron, free-bound electron-ion, photoelectric absorption and Compton backscatter (albedo), using both spectroscopic and imaging techniques. This unprecedented quality of data allows for the first time inference of the angular distributions of the X-ray-emitting electrons and improved model-independent inference of electron energy spectra and emission measures of thermal plasma. Moreover, imaging spectroscopy has revealed hitherto unknown details of solar flare morphology and detailed spectroscopy of coronal, footpoint and extended sources in flaring regions. Additional attempts to measure hard X-ray polarization were not sufficient to put constraints on the degree of anisotropy of electrons, but point to the importance of obtaining good quality polarization data in the future.

  14. The Effect of HCWA-PFA Hybrid Geopolymer Modification on the Properties of Soil

    Directory of Open Access Journals (Sweden)

    Hassian F.F.

    2014-01-01

    Full Text Available This study investigated the performance of the properties of foamed concrete when replacing volumes of cement of 10%, 15% and 20% by weight. A control unit of foamed concrete mixture made with Ordinary Portland Cement (OPC as well as samples containing 10%, 15% and 20% silica fume were prepared. Three mechanical property parameters of foamed concrete containing different percentages of silica fume were studied: compressive strength, flexural strength and splitting tensile strength. Silica fume is commonly used to increase the mechanical properties of concrete materials as well as for economic concerns. The foamed concrete in this study was cured at a relative humidity of 70% and a temperature of ±28°C. Improvements in the mechanical properties of foamed concrete were due to a significant densification in the microstructure of the cement paste matrix in the presence of silica fume hybrid supplementary binder as observed from micrographs obtained in the study. The overall results showed that silica fume has great potential to be utilized in foamed concrete as there was a noticeable enhancement in thermal and mechanical properties with the addition of silica fume.

  15. Electronic properties of Mn-phthalocyanine–C{sub 60} bulk heterojunctions: Combining photoemission and electron energy-loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roth, Friedrich [Center for Free-Electron Laser Science/DESY, Notkestraße 85, D-22607 Hamburg (Germany); Herzig, Melanie; Knupfer, Martin [FW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Lupulescu, Cosmin [Institute of Optics and Atomic Physics, TU Berlin, Straße des 17. Juni 135, D-10623 Berlin (Germany); Darlatt, Erik; Gottwald, Alexander [Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, D-10587 Berlin (Germany); Eberhardt, Wolfgang [Center for Free-Electron Laser Science/DESY, Notkestraße 85, D-22607 Hamburg (Germany); Institute of Optics and Atomic Physics, TU Berlin, Straße des 17. Juni 135, D-10623 Berlin (Germany)

    2015-11-14

    The electronic properties of co-evaporated mixtures (blends) of manganese phthalocyanine and the fullerene C{sub 60} (MnPc:C{sub 60}) have been studied as a function of the concentration of the two constituents using two supplementary electron spectroscopic methods, photoemission spectroscopy (PES) and electron energy-loss spectroscopy (EELS) in transmission. Our PES measurements provide a detailed picture of the electronic structure measured with different excitation energies as well as different mixing ratios between MnPc and C{sub 60}. Besides a relative energy shift, the occupied electronic states of the two materials remain essentially unchanged. The observed energy level alignment is different compared to that of the related CuPc:C{sub 60} bulk heterojunction. Moreover, the results from our EELS investigations show that, despite the rather small interface interaction, the MnPc related electronic excitation spectrum changes significantly by admixing C{sub 60} to MnPc thin films.

  16. Electronic and magnetic properties of UPdSn: the itinerant 5f electrons approach

    CERN Document Server

    Sandratskii, L M

    1997-01-01

    Density functional theory, modified to include spin-orbit coupling and an effective orbital field to simulate Hound's second rule, is applied to investigate the magnetic structure and electronic properties of the compound Upends. Our theoretical results are in overall good agreement with experiment. Thus both theory and experiment find the magnetic structure of Upends to be non collinear, the calculated magnetic U-moments being in very good agreement with the measurements. Also, the calculated density of states is found to simulate closely the photoemission spectrum and the very low experimental value of 5 mJ mol sup - sup 1 K sup - sup 2 for the specific heat gamma is reproduced reasonably well by the calculated value of 7.5 mJ mol sup - sup 1 K sup - sup 2. Furthermore, the interconnection of the magnetic structure with the crystal structure is investigated. Here theory and experiment agree concerning the planar non collinear antiferromagnetic configuration in the orthorhombic crystal structure and for the ...

  17. Structures and electronic properties of germanium-doped Ni n clusters, n = 13-23

    Science.gov (United States)

    Song, Wei; Li, Hua-qiang; He, Chao-zheng; Zhang, Wei

    2017-11-01

    The magnetic property and electronic properties such as binding energy, charge transfer, ionization potential and electron affinity of the Ni n-1Ge ( n = 13-23) neutral and ionic clusters have been studied using the density functional theory calculations with the PBE exchange-correlation energy functional. The calculated total magnetic moments decrease with the addition of Ge atom. Both the calculated ionization potential and electron affinity exhibit an oscillating behavior as the cluster size increases.

  18. Modification of Grout Properties in Prepacked Aggregate Concrete Incorporating Palm Oil Fuel Ash

    Directory of Open Access Journals (Sweden)

    Reza Hodjati

    2015-01-01

    Full Text Available Prepacked aggregate concrete (PAC is a type of concrete that is placed in two stages where the coarse aggregates are first placed inside the formworks and then the grout is pumped from underneath through a manual pump. Grout properties including density, grout consistency, bleeding, and compressive strength are of great importance in PAC. Such properties could be improved by application of pozzolanic materials like palm oil fuel ash. This paper is aimed at finding the most optimum percentage of POFA replacement by weight of cement. It was concluded that 30% POFA replacement yielded the most optimum results.

  19. Effect of water glass modification with nanoparticles of zinc oxide on selected physical and chemical properties of binder and mechanical properties of sand mixture

    Directory of Open Access Journals (Sweden)

    A. Kmita

    2012-12-01

    Full Text Available In this paper, an attempt was made to use the ZnO nanoparticles as a modifier of foundry binder - water glass. The modifier was a colloidal suspension of the ZnO zinc oxide nanoparticles in propanol. A thermal method to obtain metal oxide nanoparticles was adopted. The modifier was product of the thermal decomposition of the basic zinc carbonate ([ZnCO3]2•[Zn(OH2]3, and was introduced into the water glass in an amount of 1 and 3 wt%. To determine the interfacial reactions taking place in a quartz - modified water glass system, the binder wettability of the quartz grains was measured. The effect of water glass modification on the mechanical properties of moulding sands was verified by testing the tensile strength Rm u of moulding sands with the modified binders. Water glass modification with the colloidal solution of ZnO nanoparticles in propanol confirmed the effect of modifier on the water glass wettability of sand grains and on the mechanical properties of the sand mixtures with this additive.

  20. Electronic structure and optical properties of thorium monopnictides

    Indian Academy of Sciences (India)

    We have calculated the electronic density of states (DOS) and dielectric function for the ThX (X = P, As and Sb) using the linear muffin tin orbital method within atomic sphere approximation (LMTO–ASA) including the combined correction terms. The calculated electronic DOS of ThSb has been compared with the available ...

  1. Electronic structure and equilibrium properties of hcp titanium and ...

    Indian Academy of Sciences (India)

    The electronic structures of hexagonal-close-packed divalent titanium (3-d) and zirconium (4-d) transition metals are studied by using a non-local model potential method. From the present calculation of energy bands, Fermi energy, density of states and the electronic heat capacity of these two metals are determined and ...

  2. Electronic and Magnetic Properties of Trans-Polyacetylene

    Science.gov (United States)

    Cruz-Cruz, Luis R.

    In the first part of this work we present a study of the stability of soliton and polaron excitations in a single strand of trans-polyacetylene. We proceed by first solving exactly the continuum version of the SSH Hamiltonian for the single particle states that arise when n-doped electrons are added to a single polymer chain. The role of on-site (U), nearest-neighbor (V), and bond repulsion (W) Coulomb interactions are obtained from a first-order perturbative calculation with the exact single-particle states. By minimizing the total energy we show that, at a fixed doping level, a polaron lattice is favored over a soliton configuration provided that U and V exceed critical values. However, as the doping level is increased, we show that these critical values increase beyond experimentally -accepted estimates. Our work then supports the view of a soliton lattice that persists into the metallic phase of polyacetylene. In addition, we show that the bound state soliton levels merge to fill the gap sufficiently that the magnetic susceptibility becomes non-zero and comparable to the corresponding experimental values. This picture also accounts for the onset of a Pauli susceptibility at a doping level of 6% in terms of the rate of closure of the gap. In the second part, the transport properties in the highly doped regime are analyzed considering the density of states of an impurity in the chain. It is calculated as a function of the atomic impurity level and the hybridization energy. The inclusion of a gap in the spectrum of the chain takes into account the remaining charge alternation pattern observed in this high doping regime. It is shown that a Kondo-like resonance exists at the top of the gap and that a logT behavior should be exhibited in the resistivity of the sample, as experiments have revealed. It is shown that in order to observe the Kondo resonance, the gap must be smaller than the Kondo Temperature of the system without the gap. (Copies available exclusively

  3. Stability and properties of electron-driven fishbones in tokamaks

    Science.gov (United States)

    Merle, Antoine

    2013-01-01

    In tokamaks, the stability of magneto-hydrodynamic modes can be modified by populations of energetic particles. In ITER-type fusion reactors, such populations can be generated by fusion reactions or auxiliary heating. The electron-driven fishbone mode results from the resonant interaction of the internal kink mode with the slow toroidal precessional motion of energetic electrons and is frequently observed in present-day tokamaks with Electron Cyclotron Resonance Heating or Lower Hybrid Current Drive. In Tore Supra, electron-driven fishbones are observed during LHCD-powered discharges in which a high-energy tail of the electronic distribution function is created. Although the destabilization of those modes is related to the existence of a fast particle population, the modes are observed at a frequency that is lower than expected. The linear stability analysis of electron-driven fishbone modes is the main focus of this thesis. The fishbone dispersion relation is derived in a form that accounts for the contribution of the parallel motion of passing particles to the resonance condition. The MIKE code is developed to compute and solve the dispersion relation of electron-driven fishbones. The code is successfully benchmarked against theory using simple analytical distributions. Using the code MIKE with parametric distributions and equilibria, we show that both barely trapped and barely passing electrons resonate with the mode and can drive it unstable. More deeply trapped and passing electrons have a non-resonant effect on the mode that is, respectively, stabilizing and destabilizing. MIKE simulations using complete ECRH-like distribution functions show that energetic barely passing electrons can contribute to drive a mode unstable at a relatively low frequency. This observation could provide some insight to the understanding of Tore Supra experiments.

  4. Enhanced understanding of the relationship between chemical modification and mechanical properties of wood

    Science.gov (United States)

    Charles R. Frihart; Daniel J. Yelle; John Ralph; Robert J. Moon; Donald S. Stone; Joseph E. Jakes

    2008-01-01

    Chemical additions to wood often change its bulk properties, which can be determined using conventional macroscopic mechanical tests. However, the controlling interactions between chemicals and wood take place at and below the scale of individual cells and cell walls. To better understand the effects of chemical additions to wood, we have adapted and extended two...

  5. Modification of EPDM with Alkylphenol Polysulfide for Use in Tire Sidewalls, 1 – Mechanical Properties

    NARCIS (Netherlands)

    Zhang, Hongmei; Datta, Rabin; Talma, Auke; Noordermeer, Jacobus W.M.

    2009-01-01

    APPS has been used to modify EPDM in order to solve the cure incompatibility and heterogeneous filler distribution of NR/BR/EPDM blends for tire sidewall applications. The physical properties of the NR/BR/APPS-EPDM blends are compared with an NR/BR/EPDM blend and a conventional NR/BR tire sidewall.

  6. Effect of Sb-Modification on the Microstructure and Mechanical Properties of Secondary Alloy 319

    Directory of Open Access Journals (Sweden)

    Medlen D.

    2016-06-01

    Full Text Available 319 alloy has been selected for the study in the present work due to its wide use in many applications. 319 alloy is used in automotive and aerospace industry for the complicated castings which must comply high strength requirements. In practice, the most common elements with the modifying effect are strontium, sodium and antimony. The addition of these elements leads to a change in the shape of eutectic silicon, resulting in an increase of the mechanical characteristics and the microstructure. An experimental program has been undertaken to explore the effect of antimony on chosen mechanical properties and the microstructure of investigated alloy. An analysis of the results of these experimental works is made in order to determine an optimum Sb (Al-10% Sb addition to produce material exhibiting desirable properties. Experimental works have showed that the addition of the Al-10% Sb results in similar or even higher mechanical properties than the conventional 319 alloy. Based on the carried out experiments the best combination of mechanical properties has been achieved by the addition of 2 000 ppm Al-10% Sb.

  7. Modifications of coking coal and metallurgical coke properties induced by coal weathering

    Energy Technology Data Exchange (ETDEWEB)

    Casal, M.D.; Gonzalez, A.I.; Canga, C.S.; Barriocanal, C.; Pis, J.J.; Alvarez, R.; Diez, M.A. [Instituto Nacional del Carbon (INCAR), CSIC, Apartado 73, Oviedo 33080 (Spain)

    2003-11-15

    Chemical changes in the structure of organic matter of coking coals during storage modify their thermoplastic properties and behaviour during carbonization. As a result, the anisotropic carbon structure of the metallurgical cokes produced and their physical properties are altered. In this work, the weathering behaviour of 10 bituminous coals of different geographic origin, rank and thermoplastic properties, used as components in the preparation of industrial coking blends for coke manufacture, was studied by means of Gieseler plastometry and Fourier transform infrared (FTIR) spectroscopy. These coking coals were stored in piles at the Instituto Nacional del Carbon (INCAR) open stockyard for a period of time of up to 7 months. Special attention was paid to the relationship between the relative amount and type of aliphatic hydrogen (semi-quantitatively evaluated by FTIR), and thermoplastic properties. Depending on the nature of the coking coal, a different response to natural weathering can be expected. Thus, the results showed that there is a direct link between a decrease in methylene groups and a loss of fluidity in the weathered coals, resulting in a decrease in anisotropic carbon of the resultant cokes with weathering time. In addition, the rate of anisotropic carbon loss induced by weathering could be associated with the rank parameters of the initial coals.

  8. Particle properties and their modification in mechanically activated realgar As4S4

    Directory of Open Access Journals (Sweden)

    Peter Baláž

    2011-12-01

    Full Text Available In this work mechanical activation of realgar As4S4 was studied. The addition of sodium chloride NaCl as a solid diluent intothe milling process substantially improved solid state properties of the obtained fines. However, the polymorphous transformationof

  9. Laccase modification of the physical properties of bark and pulp of loblolly pine and spruce pulp

    Science.gov (United States)

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

    2004-01-01

    Pine bark, pine pulp, and spruce pulp were reacted with laccase in the presence of phenolic laccase substrates to modify the fiber surface properties. The acid-base and dispersive characteristics of these modified steam-treated thermomechanical loblolly pine pulps were determined by inverse gas chromatography. Different combinations of substrates with laccase modified...

  10. Effects of high pressure modification on conformation and gelation properties of myofibrillar protein.

    Science.gov (United States)

    Zhang, Ziye; Yang, Yuling; Zhou, Peng; Zhang, Xing; Wang, Jingyu

    2017-02-15

    The effects of high pressure (HP) treatment (100-500MPa) on conformation and gelation properties of myofibrillar protein (MP) were investigated. As pressure increased (0.1-500MPa), α-helix and β-sheet changed into random coil and β-turn, proteins unfolded to expose interior hydrophobic and sulfhydryl groups, therefore surface hydrophobicity and formation of disulfide bonds were strengthened. At 200MPa, protein solubility and gel hardness reached their maximum value, particle size had minimum value, and gel microstructure was dense and uniform. DSC data showed that actin and myosin completely denatured at 300MPa and 400MPa, respectively. Rheological modulus (G' and G″) of HP-treated MP decreased as pressure increased during thermal gelation. Moderate HP treatment (≦200MPa) strengthened gelation properties of MP, while stronger HP treatment (⩾300MPa) weakened the gelation properties. 200MPa was the optimum pressure level for modifying MP conformation to improve its gelation properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Optical, electronic and magnetic properties of Cr:GaN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Majid, Abdul, E-mail: abdulmajid40@yahoo.com [Department of Physics, University of Gujrat, Gujrat (Pakistan); Dar, Amna; Nabi, Azeem [Department of Physics, University of Gujrat, Gujrat (Pakistan); Shakoor, Abdul [Department of Physics, Bahauddin Zkariya University, Multan (Pakistan); Hassan, Najmul [Department of Physics, Hazara University, Mansehra (Pakistan); Junjua, Arshad [NILOP, Pakistan Institute of Nuclear Sciences and Technology, Islamabad (Pakistan); Jianjun, Zhu [Nano Fabrication Facility, Suzhou Institute of Nano-tech and Nano-Bionics, CAS (China)

    2012-10-15

    Modifications in optical and electronic properties of wurtzite GaN induced by Cr doping were studied using various experimental techniques and Density Functional Theory (DFT) based calculations. Metal Oxide Chemical Vapor Deposited grown GaN/sapphire thin film samples were implanted by Cr ions at 300 keV to achieve three different doses of 5 Multiplication-Sign 10{sup 14}, 5 Multiplication-Sign 10{sup 15} and 5 Multiplication-Sign 10{sup 16} cm{sup -2}. X-ray diffraction, Atomic force microscopy, Spectroscopy ellipsometry, UV-vis spectrophotometery, Hall and Vibrating Sample Magnetometery measurements were carried out to study structural, optical, electrical and magnetic properties of as-grown, annealed as-grown and annealed implanted GaN samples. A dose dependent decrease in band gap of the material was observed in implanted samples. Complex refractive index, dielectric constants, energy band gap and carrier concentration based on these measurements are reported for the materials. Moreover, the results indicated substitution of Cr in host GaN lattice. Results of band structure (BS) based on DFT calculations using GGA for pure and Cr doped wurtzite GaN are also reported and discussed here. The results indicated that GaCrN is a potential material for optoelectronic and spintronics devices. -- Highlights: Black-Right-Pointing-Pointer MOCVD grown GaN/sapphire thin films were implanted by Cr ions. Black-Right-Pointing-Pointer Experimental and Density Functional Theory based results are reported. Black-Right-Pointing-Pointer Four up and five down 3d states are weekly hybridized with N (2p) states in GaCrN. Black-Right-Pointing-Pointer This 1/3 filling of t{sub 2g} level in up-spin band leads to magnetic moment of 3{mu}{sub B}. Black-Right-Pointing-Pointer GaCrN appeared half metallic ferromagnetic material.

  12. Assessment of antibacterial properties of polyvinylamine (PVAm) with different charge densities and hydrophobic modifications.

    Science.gov (United States)

    Westman, Eva-Helena; Ek, Monica; Enarsson, Lars-Erik; Wågberg, Lars

    2009-06-08

    Hydrophobically modified and unmodified polyvinylamines (PVAm), including a total of five polymers, were tested against both gram-negative ( Escherichia coli ) and gram-positive ( Bacillus subtilis ) bacteria for antimicrobial activity. The assessment of PVAm in solution against bacteria is described, and the influence of the charge density and of the hydrophobic modification of the polyelectrolyte is discussed. The antimicrobial activity was found to depend upon the concentration of PVAm and also on the type of bacteria used. The results also indicated that no direct relationship exists between antimicrobial activity and charge density of the different PVAms. It was, however, observed that an alkyl chain length of six or eight alkane units had a substantial effect on the bacteria investigated. The best combined antibacterial activity for the two bacteria tested was achieved for PVAm with a C(6) alkane substituent (PVAm C(6)). To evaluate the antimicrobial activity on a solid substrate, PVAm C(6) was further studied after being deposited onto a glass slide and the results show a large reduction in bacterial infection.

  13. Surface and chemical properties of surface-modified UHMWPE powder and mechanical and thermal properties of its impregnated PMMA bone cement, IV: effect of MMA/accelerator on the surface modification of UHMWPE powder.

    Science.gov (United States)

    Yang, Dae Hyeok; Ko, Jong Tae; Kim, Yong Sik; Kim, Moon Suk; Shin, Hyung Sik; Rhee, John M; Khang, Gilson; Lee, Hai Bang

    2006-01-01

    In our previous study, we manufactured a reinforced poly(methylmethacrylate) (PMMA) bone cement with 3 wt% of the surface-modified ultra high molecular weight polyethylene (UHMWPE) powder to improve its poor mechanical and thermal properties resulting from unreacted methylmethacrylate (MMA), the generation of bubble and shrinkage, and high curing temperature. In the present study, the effect of ratios of MMA and N,N'-dimethyl-p-toluidine (DMPT) solutions in redox polymerization system was investigated for the surface modification of UHMWPE powder. We characterized physical and chemical properties of surface-modified UHMWPE powder and reinforced bone cements by a scanning electron microscope, ultimate tensile strength (UTS) and curing temperature (Tmax). It was found that UTSs (41.3-51.3 MPa) of the reinforced PMMA bone cements were similar to those (44.5 MPa) of conventional PMMA bone cement (control), as well as significantly higher (P redox polymerization system using MMA/DMPT solution was better than that of radical system using MMA/xylene solution. Also, Tmax of the reinforced PMMA bone cements decreased from 103 to 72-84 degrees C. From these results, we confirmed that the surface-modified UHMWPE powder can be used as reinforcing agent to improve the mechanical and thermal properties of conventional PMMA bone cement.

  14. Structure/Property Relations in "Giant" Semiconductor Nanocrystals: Opportunities in Photonics and Electronics.

    Science.gov (United States)

    Navarro-Pardo, Fabiola; Zhao, Haiguang; Wang, Zhiming M; Rosei, Federico

    2017-12-20

    Semiconductor nanocrystals exhibit size-tunable absorption and emission ranging from the ultraviolet (UV) to the near-infrared (NIR) spectral range, high absorption coefficient, and high photoluminescence quantum yield. Effective surface passivation of these so-called quantum dots (QDs) may be achieved by growing a shell of another semiconductor material. The resulting core/shell QDs can be considered as a model system to study and optimize structure/property relations. A special case consists in growing thick shells (1.5 up to few tens of nanometers) to produce "giant" QDs (g-QDs). Tailoring the chemical composition and structure of CdSe/CdS and PbS/CdS g-QDs is a promising approach to widen the spectral separation of absorption and emission spectra (i.e., the Stokes shift), improve the isolation of photogenerated carriers from surface defects and enhance charge carrier lifetime and mobility. However, most stable systems are limited by a thick CdS shell, which strongly absorbs radiation below 500 nm, covering the UV and part of the visible range. Modification of the interfacial region between the core and shell of g-QDs or tuning their doping with narrow band gap semiconductors are effective approaches to circumvent this challenge. In addition, the synthesis of g-QDs composed of environmentally friendly elements (e.g., CuInSe2/CuInS2) represents an alternative to extend their absorption into the NIR range. Additionally, the band gap and band alignment of g-QDs can be engineered by proper selection of the constituents according to their band edge positions and by tuning their stoichiometry during wet chemical synthesis. In most cases, the quasi-type II localization regime of electrons and holes is achieved. In this type of g-QDs, electrons can leak into the shell region, while the holes remain confined within the core region. This electron-hole spatial distribution is advantageous for optoelectronic devices, resulting in efficient electron-hole separation while

  15. MODIFICATION OF SURFACE AND TRIBOLOGICAL PROPERTIES OF DLC FILMS BY ADDING SILVER CONTENT

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hanshen S.; Endrino, Jose L.; Anders, Andre

    2008-06-12

    The incorporation of silver into the diamond-like carbon (DLC) coatings has shown excellent potential in various applications; therefore the surface and tribological properties of silver-containing DLC thin films deserve to be investigated. In this study we have deposited silver-containing hydrogenated and hydrogen-free DLC coatings by plasma immersion ion implantation and deposition (PIII-D) methods. Atomic force microscopy (AFM) and nano-scratch tests were used to study the surface and tribological properties. The silver incorporation had only slight effects on hydrogenated DLC coatings. However, the incorporation of silver has significant effect on hydrogen-free DLC of smoothing the surface and increasing the surface energy. Those effects have been illustrated and explained in the context of experimental results.

  16. [Electrochemical properties of biocompatible material hardness modifications on titanium and steel under mechanical loads].

    Science.gov (United States)

    Braun, W; Walter, U; Holbein, R; Thull, R

    2005-04-01

    Friction corrosion may appear between different implant components or between implant and hard tissue. The sliding micro movements induce fretting wear corrosion and have been recently reported as a cause of joint prostheses failure. A surface coating is desirable, that retains the mechanical properties of the substrate, offers good biocompatibility and improves the fretting corrosion resistance. In this study it could be demonstrated that tantalum and niobium coatings fulfill the requirements. On titanium substrates the coating decreases the abrasion against PMMA, an orthopedic relevant material. Furthermore, in the case of medical steel substrates the biocompatibility and the corrosion properties are improved. The better abrasion-resistance is minimizing the release of allergological critical particles like nickel and chromium.

  17. Laser Induced Modification of the Optical Properties of Nano-ZnO Doped PVC Films

    Directory of Open Access Journals (Sweden)

    Tagreed K. Hamad

    2014-01-01

    Full Text Available The effect of continuous CO2 laser radiation on the optical properties of pure polyvinyl chloride and doped of ZnO nanoparticles with two different concentrations (10, 15% has been investigated. All samples were prepared using casting method at room temperature. Optical properties (absorption, transmission, absorption coefficient, extinction coefficient, refractive index, and optical conductivity of all films after CO2 laser irradiated have been studied as a function of the wavelength in the range (200–800 nm for three energies (300, 400 and 500 mJ. It has been found that the transmission, energy gap, and refractive index increase with increasing laser energy. The values of absorption, Urbach energy, absorption coefficient, extinction coefficient, and optical conductivity were decreased.

  18. MODIFICATION OF RESIN EDT-69N FOR THE PURPOSE OF MECHANICAL PROPERTIES OF PLASTICS

    Directory of Open Access Journals (Sweden)

    В. Краля

    2012-04-01

    Full Text Available The epoxy matrix EDT-69N it is one of license matrix which applies by aviation industry in theCommonwealth of Independent States. This matrix created according to the standards NLGS-3 with a glanceto requirements of a self-damping. A self-damping achieved by a mixing of resin UP-631 in a recipe of amatrix EDT-69N. It led to a increasing of matrix cost and a decreasing of the physical-mechanical properties.According to current standards AP-25 the matrix EDT-69N does not ensure the compliances by requirementsof combustibility, fume evolution and toxicity of combustion products. That is why a pressing problem ofmodification of matrix EDT-69N appears for the purpose of increasing of the physical-mechanical andtechnologic properties in the prejudice of requirement of combustibility.

  19. Property modification of nafion via polymer blending with polyimide (Conference Presentation)

    Science.gov (United States)

    Hwang, Taeseon; Nam, Jungsoo; Lee, Dong-Chan; Kim, Kwang Jin

    2017-04-01

    The blended ion exchange membrane between Nafion and Polyimide (PI) was used for fabrication of the ionic polymer-metal composite (IPMC) not only to redeem inherent drawbacks of Nafion such as high cost or environment-unfriendliness but also to enhance mechanical properties of Nafion. PI solution was blended in Nafion solution by a volume ratio and membranes were prepared through solution casting method. The prepared blended Nafion membranes can be fabricated IPMCs with electroless plating of platinum electrode onto its surface. The surface resistance of all prepared IPMCs is measured through 2-point probe. This study investigated the chemical structure and mechanical properties of prepared blended membranes. Moreover, we characterized the cross-section morphology and studied the electromechanical performances (displacement and blocking force) of prepared IPMC actuators. The prepared IPMC actuators with blended Nafion membranes were demonstrated comparable electromechanical performance by significantly reducing the content of Nafion.

  20. Influence of fiber structure modification on the mechanical properties of flax fiber-epoxy composites

    Science.gov (United States)

    Gassan, J.; Mildner, I.; Bledzki, A. K.

    1999-09-01

    The mechanical characteristics of flax fibers were optimized by using the NaOH treatment process to improve the properties of composite materials. Shrinkage of the fibers during this treatment had a significant effect on the structure and, as a result, on the mechanical properties of the fibers and the composites based on them. Due to the higher mechanical strength and stiffness of flax fibers after NaOH treatment under isometric conditions, the strength and stiffness of composites in general increase. Further, NaOH treatment leads to a rougher surface morphology, as shown, e.g., for jute fibers, compared with the surface of untreated fibers without improved fiber/matrix adhesion.

  1. Stability, electronic and thermodynamic properties of aluminene from first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Junhui [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Yu, Niannian [School of Science, Wuhan University of Technology, Wuhan, Hubei 430070 (China); Xue, Kanhao, E-mail: xkh@hust.edu.cn [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Miao, Xiangshui [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2017-07-01

    Highlights: • We have predicted two NEW stable phases of atomic layer aluminum, buckled and 8-Pmmn aluminene. • We have revealed the electronic structures and bonding characteristics of aluminene. • Thermodynamic properties of aluminene were investigated based on phonon properties. - Abstract: Using first-principles calculations based on density functional theory (DFT), we have investigated the structure stability and electronic properties of both buckled and 8-Pmmn phase aluminene. Phonon dispersion analysis reveals that the buckled and 8-Pmmn aluminene are dynamically stable. The band structure shows that both the buckled and 8-Pmmn aluminene exhibit metallic behavior. Finally, the thermodynamic properties are investigated based on phonon properties.

  2. Modification of microstructure and micromagnetic properties in Gd-Fe thin films by rapid thermal processing

    OpenAIRE

    Talapatraa, A.; Chelvane, J. Arout; Satpati, B.; Kumar, S.; Mohanty, J.

    2017-01-01

    Impact of rapid thermal processing (RTP) on microstructure and magnetic properties of Gd-Fe thin films have been investigated with a special emphasis to magnetic microstructure. 100 nm thick amorphous Gd-Fe film shows elongated stripe domains with characteristic feature size of 122 nm, which signifies the development of perpendicular magnetic anisotropy (PMA) in this system. RTP at 550^oC for different time intervals viz. 5, 10, 15, 20 minutes induces the crystallization of Fe over the amorph...

  3. Aluminum surface modification with fluoroalkyl methacrylate-based copolymers to attain superhydrophobic properties

    Science.gov (United States)

    Bryuzgin, Evgeny V.; Klimov, Victor V.; Repin, Sergey A.; Navrotskiy, Alexander V.; Novakov, Ivan A.

    2017-10-01

    We propose a novel approach to create a superhydrophobic coating on an aluminum surface by attaching random copolymers that are based on glycidyl methacrylate and a number of fluoroalkyl methacrylates that contain 3-7 fluorine atoms in their monomer units. To texture the aluminum surface, short-term etching with hydrochloric acid solutions was used. The coatings that are based on glycidyl methacrylate and fluoroalkyl methacrylate copolymers maintain superhydrophobic properties for longer than 40 h under saturated vapor conditions.

  4. Electrochemical synthesis and one step modification of PMProDot nanotubes and their enhanced electrochemical properties.

    Science.gov (United States)

    Nguyen, Thao M; Cho, Seungil; Varongchayakul, Nitinun; Yoon, Daehyun; Seog, Joonil; Zong, Kyukwan; Lee, Sang Bok

    2012-03-11

    Poly (3,4-(2-methylene)propylenedioxythiophene) (PMProDot) nanotubes were synthesized within the pores of polycarbonate and were further modified with styrene and vinylcarbazole by a one step electrochemical method through the methylene functional group. The enhanced electrochemical and electrochromic properties of composite nanotubes were investigated using FTIR, UV/Vis absorbance spectroscopy, and AFM. This journal is © The Royal Society of Chemistry 2012

  5. Effect of Terminal Modification on the Molecular Assembly and Mechanical Properties of Protein-Based Block Copolymers.

    Science.gov (United States)

    Jacobsen, Matthew M; Tokareva, Olena S; Ebrahimi, Davoud; Huang, Wenwen; Ling, Shengjie; Dinjaski, Nina; Li, David; Simon, Marc; Staii, Cristian; Buehler, Markus J; Kaplan, David L; Wong, Joyce Y

    2017-09-01

    Accurate prediction and validation of the assembly of bioinspired peptide sequences into fibers with defined mechanical characteristics would aid significantly in designing and creating materials with desired properties. This process may also be utilized to provide insight into how the molecular architecture of many natural protein fibers is assembled. In this work, computational modeling and experimentation are used in tandem to determine how peptide terminal modification affects a fiber-forming core domain. Modeling shows that increased terminal molecular weight and hydrophilicity improve peptide chain alignment under shearing conditions and promote consolidation of semicrystalline domains. Mechanical analysis shows acute improvements to strength and elasticity, but significantly reduced extensibility and overall toughness. These results highlight an important entropic function that terminal domains of fiber-forming peptides exhibit as chain alignment promoters, which ultimately has notable consequences on the mechanical behavior of the final fiber products. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. The usage of plastic waste as a secondary raw material for the modification of sandcrete properties

    Science.gov (United States)

    Klovas, A.; Daukšys, M.; Venčkauskas, L.

    2015-03-01

    Recently the usage of various industry wastes as a secondary raw material tends to increase its relevancy. One of possible options to decrease the amount of waste is to use them to produce new products or materials. The operation of various secondary raw materials (tire rubber, tire cord, ground glass shards, ground ceramic waste products) during the concrete mixture preparation allows to change its as well as cured concrete properties. Recently polymer and steel fibers are used for concrete reinforcement. This study analyses the usage possibility of plastic shavings for the reinforcement of concrete. The technological properties of cement slurry (sand, fraction of 0/4 and 10 kg/m3, 15 kg/m3 and 20 kg/m3 of plastic shavings) as well as mechanical, physical and porosity properties of cured sandcrete were established during the experimental research. The geometric characteristics of mill-shredded plastic shavings were established. Experimental results revealed that the usage of plastic shavings decreased slurry slump and density. The minor decrease of cured sandcrete density (~2200 kg/m3) was noticed with the addition of plastic shavings within the limits of 10 - 20 kg/m3. The flexural strength of cured sandcrete increased from 36 % to 57 % compared with reference specimen (without plastic shavings). The dependence of flexural force and deflection was obtained. Study revealed that the residual strength after crack opening is bigger with the usage of plastic shavings as a secondary raw material compared with reference specimen.

  7. The effect of build orientation and surface modification on mechanical properties of high speed sintered parts

    Science.gov (United States)

    Ellis, Adam; Brown, Ryan; Hopkinson, Neil

    2015-09-01

    High speed sintering is a novel additive manufacturing technology that uses inkjet printing and infra-red energy to selectively sinter polymeric powder. The research presented here investigates the effect of build orientation on dimensional accuracy, density, mechanical properties and surface roughness of high speed sintered parts. Tensile specimens were built through seven different angles between and including the XY (horizontal) and ZY (vertical) planes and analysed. The effect of the PUSh™ process was also investigated across this range of build orientations. The results show that build orientation does infuence the properties of the parts. A number of mechanical properties showed a relationship with build orientation. Density was seen to decrease as the angle increased from XY towards ZY. This increase in angle was shown to increase surface roughness while ultimate tensile strength and elongation at break decreased. At all build orientations, the PUSh™ process significantly reduces surface roughness, mildly increases part density and had a small effect on ultimate tensile strength whilst showing a small but consistent increase in elongation at break.

  8. Electronic and optical properties of radiated oxide films on valve metals

    Energy Technology Data Exchange (ETDEWEB)

    Schultze, J.W.; Elfenthal, L.; Hansen, G.; Patzelt, T.; Siemensmeyer, B.; Thietke, J. (Duesseldorf Univ. (Germany, F.R.). Inst. fuer Physikalische Chemie und Elektrochemie)

    1990-01-01

    The electronic and optical properties of passive films are changed by radiation in different ways. Nuclear and electronic interaction must be discussed for heavy particles but only electronic interaction for {beta}- and {gamma}-radiation. Nuclear interaction means defect production and amorphization of the solid which can be detected by measurements of capacity, electron transfer reactions, photocurrents, UPS and XPS and reflection spectra. Various electrode reactions are enhanced which change the passive behavior. The electronic effect of radiation can be simulated by a focussed laser beam. Electron hole pairs are generated and separated in the electric field. Hole accumulation near the surface causes radiation induced oxide growth. (author).

  9. Influence of the substitution on the electronic properties of perylene ...

    African Journals Online (AJOL)

    dicarboximides): density functional theory study. ... Taking into account the calculated electron affinities (EA), the air stability and ambipolar behavior of the materials under study can be expected. KEY WORDS: Organic field effect transistors, ...

  10. Surface modification of MnFe₂O₄ nanoparticles to impart intrinsic multiple fluorescence and novel photocatalytic properties.

    Science.gov (United States)

    Pal, Monalisa; Rakshit, Rupali; Mandal, Kalyan

    2014-04-09

    The MnFe2O4 nanoparticle has been among the most frequently chosen systems due to its diverse applications in the fields ranging from medical diagnostics to magnetic hyperthermia and site-specific drug delivery. Although numerous efforts have been directed in the synthesis of monodisperse MnFe2O4 nanocrystals, unfortunately, however, studies regarding the tuning of surface property of the synthesized nanocrystals through functionalization are sparse in the existing literature. Herein, we demonstrate the emergence of intrinsic multicolor fluorescence in MnFe2O4 nanoparticles from blue, cyan, and green to red, upon functionalization and further surface modification with a small organic ligand, Na-tartrate. Moreover, we have found an unprecedented photocatalytic property of the functionalized MnFe2O4 nanoparticles in the degradation of a model water contaminant. Detailed characterization through XRD, TEM, and FTIR confirms the very small size and functionalization of MnFe2O4 nanoparticles with a biocompatible ligand. Proper investigation through UV-visible absorption, steady-state and time-resolved photoluminescence study reveals that ligand-to-metal charge-transfer transition from the tartrate ligand to the lowest unoccupied energy level of Mn(2+/3+)or Fe(3+) of the NPs and Jahn-Teller distorted d-d transitions centered over Mn(3+) ions in the NPs play the key role behind the generation of multiple fluorescence from the ligand-functionalized MnFe2O4 nanoparticles. VSM measurements indicates that the superparamagnetic nature of MnFe2O4 nanoparticles remains unchanged even after surface modification. We believe that the developed superparamagnetic, multicolor fluorescent MnFe2O4 nanopaticles would open up new opportunities as well as enhance their beneficial activities toward diverse applications.

  11. Enhanced Electronic Properties of SnO2 via Electron Transfer from Graphene Quantum Dots for Efficient Perovskite Solar Cells.

    Science.gov (United States)

    Xie, Jiangsheng; Huang, Kun; Yu, Xuegong; Yang, Zhengrui; Xiao, Ke; Qiang, Yaping; Zhu, Xiaodong; Xu, Lingbo; Wang, Peng; Cui, Can; Yang, Deren

    2017-09-26

    Tin dioxide (SnO2) has been demonstrated as an effective electron-transporting layer (ETL) for attaining high-performance perovskite solar cells (PSCs). However, the numerous trap states in low-temperature solution processed SnO2 will reduce the PSCs performance and result in serious hysteresis. Here, we report a strategy to improve the electronic properties in SnO2 through a facile treatment of the films with adding a small amount of graphene quantum dots (GQDs). We demonstrate that the photogenerated electrons in GQDs can transfer to the conduction band of SnO2. The transferred electrons from the GQDs will effectively fill the electron traps as well as improve the conductivity of SnO2, which is beneficial for improving the electron extraction efficiency and reducing the recombination at the ETLs/perovskite interface. The device fabricated with SnO2:GQDs could reach an average power conversion efficiency (PCE) of 19.2 ± 1.0% and a highest steady-state PCE of 20.23% with very little hysteresis. Our study provides an effective way to enhance the performance of perovskite solar cells through improving the electronic properties of SnO2.

  12. Effect of hydrostatic pressure on the structural and electronic properties of Cd0.75Cr0.25S

    Science.gov (United States)

    Rani, Anita; Kaur, Kulwinder; Dhiman, Shobna; Kumar, Ranjan

    2016-05-01

    In this paper we present the results obtained from first principle calculations of the effect of hydrostatic pressure on the structural and electronic properties of Cd1-xCrxS diluted magnetic semiconductor in Zinc Blende (B3) phase at x=0.25. High pressure behavior of Cd1-xCrxS has been investigated between 0 GPa to100 GPa The calculations have been performed using Density functional theory as implemented in the Spanish Initiative for Electronic Simulations with Thousands of Atoms code using local density approximation as exchange-correlation (XC) potential. Calculated electronic band structures of Cd1-xCrxS are discussed in terms of contribution of Cr 3d5 4s1, Cd 4d10 5s2, S 3s2 3p4 orbital's. Study of band structures shows half-metallic ferromagnetic nature of Cd0.75Cr0.25S with 100% spin polarization. Under application of external pressure, the valence band and conduction band are shifted upward which leads to modification of electronic structure

  13. Strain Effect on the Electronic and Optical Properties of CdSe Nanowires.

    Science.gov (United States)

    Huan, Hao; Chen, Li; Ye, Xiang

    2017-12-01

    First-principles density functional theory (DFT) simulations were carried out to study the strain dependence on the electronic and optical properties of cadmium selenide (CdSe) nanowires (NWs). The band structures, effective masses of electron and holes, dielectric properties, and other optical properties (such as extinction coefficient, optical reflectivity, and absorption coefficient) were calculated under both compressive and tensile uniaxial strains. Size-dependence was also discussed by comparing results among CdSe wires with various diameters. Simulation results show that an interesting band-switch behavior occurs at the valence bands regardless of size. The cause and the consequences of such band-switch behavior were also studied. Further strain dependence on corresponding electronic and optical properties were examined as well. Our results provide insights to possible mechanical tuning via strain on the electronic and optical properties of CdSe NWs.

  14. Electronic and plasmonic properties of nano-sized gold/strontium titanate interface

    Science.gov (United States)

    Hou, Jiechang

    In this thesis, nano-sized metal/oxide interfaces are fabricated to determine the size dependence of electronic and resistive switching properties, effect of atomic structure on the orientation dependence of electronic properties, and mechanisms of plasmon-induced current enhancement. A combination of drop-casting and high temperature annealing enables orientation control over nano-sized metal/oxide interfaces. To examine the electronic properties, individual Au nanoparticle/SrTiO3 interfaces with sizes ranging from 20 to 150 nm are characterized via conductive atomic force microscopy, for two distinct interface orientations. Current-voltage characterization enables the determination of dominant electron transport mechanisms. The development of a depletion region results in the transition of electron transport mechanism from edge-effect-induced tunneling to inhomogeneity-induced statistical variations, as the interface decreases below a critical size. The resultant size-dependent Schottky properties dictate the size dependence of interface-controlled resistive switching behaviors, in addition to geometrical scaling of resistance. The effect of atomic structure on electronic properties is also investigated, via correlation of atomic structure characterized by high resolution transmission electron microscopy, electronic structure probed by electron energy loss spectroscopy, and measured electronic properties. The observed orientation dependence of reverse tunneling is attributed to interface defects induced by different atomic structures. Nanofabrication procedures are optimized to develop Au nano-antenna arrays on SrTiO3 substrate, to determine the photocurrent dependence on illumination condition and mechanisms of hot electron effect. Device design is assisted by finite-difference time-domain simulation of optical properties, targeted at near-infrared working range. Plasmon resonance frequency and intensity are demonstrated to be systematically tunable by varying

  15. Modifications of Carbonate Fracture Hydrodynamic Properties by CO 2 -Acidified Brine Flow

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Hang; Ellis, Brian R.; Peters, Catherine A.; Fitts, Jeffrey P.; Crandall, Dustin; Bromhal, Grant S.

    2013-08-15

    Acidic reactive flow in fractures is relevant in subsurface activities such as CO{sub 2} geological storage and hydraulic fracturing. Understanding reaction-induced changes in fracture hydrodynamic properties is essential for predicting subsurface flows such as leakage, injectability, and fluid production. In this study, x-ray computed tomography scans of a fractured carbonate caprock were used to create three dimensional reconstructions of the fracture before and after reaction with CO{sub 2}-acidified brine (Ellis et al., 2011, Greenhouse Gases: Sci. Technol., 1:248-260). As expected, mechanical apertures were found to increase substantially, doubling and even tripling in some places. However, the surface geometry evolved in complex ways including ‘comb-tooth’ structures created from preferential dissolution of calcite in transverse sedimentary bands, and the creation of degraded zones, i.e. porous calcite-depleted areas on reacted fracture surfaces. These geometric alterations resulted in increased fracture roughness, as measured by surface Z{sub 2} parameters and fractal dimensions D{sub f}. Computational fluid dynamics (CFD) simulations were conducted to quantify the changes in hydraulic aperture, fracture transmissivity and permeability. The results show that the effective hydraulic apertures are smaller than the mechanical apertures, and the changes in hydraulic apertures are nonlinear. Overestimation of flow rate by a factor of two or more would be introduced if fracture hydrodynamic properties were based on mechanical apertures, or if hydraulic aperture is assumed to change proportionally with mechanical aperture. The differences can be attributed, in part, to the increase in roughness after reaction, and is likely affected by contiguous transverse sedimentary features. Hydraulic apertures estimated by the 1D statistical model and 2D local cubic law (LCL) model are consistently larger than those calculated from the CFD simulations. In addition, a novel

  16. Modification of aluminum alloy surface properties by wave-long laser texturing

    Directory of Open Access Journals (Sweden)

    Batishcheva Kseniya

    2017-01-01

    Full Text Available Change of the static contact angle (SCA of 10 μL distilled water droplet on laser textured aluminium alloy (AMG-6 substrates was studied. The texture was deposited by a laser system based on a fiber laser. An increase in the power of laser radiation is found to lead to a decrease in the SCA measured on the first day after texturing. Change of dispersion and polar surface energy components of textured substrates is determined. Under the influence of the environment, the surface properties of AMG-6 change with time. SCA increased and reached stable state on the twentieth day after texturing.

  17. Characterization of sperm plasma membrane properties after cholesterol modification: consequences for cryopreservation of rainbow trout spermatozoa.

    Science.gov (United States)

    Müller, Karin; Müller, Peter; Pincemy, Gwenaëlle; Kurz, Anke; Labbe, Catherine

    2008-03-01

    During cryopreservation, the cell plasma membrane faces severe perils, including lipid phase separation, solute effects, and osmotic stresses associated with ice crystallization. How the initial biophysical properties of the plasma membrane can be modulated before cryopreservation in order to influence cellular resistance to the freeze-thaw stress is addressed in this study. Rainbow trout (Oncorhynchus mykiss) spermatozoa were chosen because the lack of an acrosome in this species suppresses potential interactions of cryopreservation with capacitation. Methyl-beta cyclodextrin-induced modulation of membrane cholesterol revealed the presence of a significant cholesterol exchangeable pool in the trout sperm plasma membrane, as membrane cholesterol content could be halved or doubled with respect to the basic composition of the cell without impairing fresh sperm motility and fertilizing ability. Biophysical properties of the sperm plasma membrane were affected by cholesterol changes: membrane resistance to a hypo-osmotic stress increased linearly with membrane cholesterol whereas membrane fluidity, assessed with DPH (1,6-diphenyl-1,3,5-hexatriene) and with several spin-labeled analogues of membrane lipids, decreased. Phosphatidyl serine translocation between the bilayers was slowed at high cholesterol content. The increased cohesion of fresh trout sperm plasma membrane as cholesterol increased did not improve the fertilizing ability of frozen-thawed sperm whereas the lowest cholesterol contents impaired this parameter of sperm quality. Our study demonstrated that cholesterol induced a stabilization of the plasma membrane in rainbow trout spermatozoa, but this stabilization before cryopreservation brought no improvement to the poor freezability of this cell.

  18. Modifications on Microporosity and Physical Properties of Cement Mortar Caused by Carbonation: Comparison of Experimental Methods

    Directory of Open Access Journals (Sweden)

    Son Tung Pham

    2013-01-01

    Full Text Available The influence of carbonation on the microstructure of normalised CEM II mortar was studied using nitrogen adsorption and porosity accessible to water. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity, and 20% CO2 concentration. Conflicts in results were observed because while the pore size distributions calculated by BJH method from nitrogen adsorption provided evolution of the micro- and mesopores during carbonation, the porosity accessible to water showed changes in all three porous domains: macro-, meso- and micropores. Furthermore, the porous domains explored by water and nitrogen molecules are not the same because of the difference in the molecular sizes. These two techniques are therefore different and help to complementarily evaluate the effects of carbonation. We also examined the evolution of macrophysical properties such as the solid phase volume using helium pycnometry, gas permeability, thermal conductivity, thermal diffusivity, and longitudinal and transverse ultrasonic velocities. This is a multiscale study where results on microstructural changes can help to explain the evolution of macro physical properties.

  19. Enhanced organic photovoltaic properties via structural modifications in PEDOT:PSS due to graphene oxide doping

    Energy Technology Data Exchange (ETDEWEB)

    Goutham, Raj P.; Sandhya, Rani V.; Kanwat, Anil; Jang, Jin, E-mail: jjang@khu.ac.kr

    2016-02-15

    Highlights: • Graphene oxide(GO) blended with PEDOT:PSS is used as HTL for PTB7:PCBM BHJ solar cells. • Increase in conductivity due to structural alterations in PEDOT:PSS by GO addition. • The structural alterations are reaveled under Raman spectroscopy, XPS and AFM. • PEDOT:PSS changed to extended coil due to addition of GO to PEDOT:PSS. • Enhanced conductivity after GO addition to PEDOT:PSS resulted in enhanced PCE. - Abstract: Poly(3,4-thylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS is a well-known conductive polymer for hole transport in organic devices, the properties of which can be enhanced by doping. Common dopants are metal oxides and nanoparticles. In this study, addition of graphene oxide (GO) to PEDOT:PSS as a dopant is addressed in organic photovoltaics (OPVs). With GO doping, electrical conductivity and transport properties of PEDOT:PSS increases due to structural alterations in the presence of −COOH and −OH functional groups in GO. These structural alterations have been revealed under detailed study of Raman spectra, X-ray photoelectron spectroscopy (XPS) analysis, Topographical and conductive Atom force microscopy (AFM/C-AFM) mapping. OPVs fabricated using PEDOT:PSS: GO (5:1) as a hole transport layer (HTL) exhibited a power conversion efficiency (PCE) of 7.68%, which was higher than the 7.01% that was obtained for the OPVs using pristine PEDOT:PSS.

  20. Effect of Surface Modification of Nanosilica on the Viscoelastic Properties of Its Polystyrene Nanocomposite

    Directory of Open Access Journals (Sweden)

    M. Mortezaei

    2008-12-01

    Full Text Available The preparation and characterization of the vinyltriethoxysilane-modified silica nanoparticles were investigated. Also the surface tension of polystyrene, native (hydrophilic silica and silane-modified (hydrophobic silica were determined. Two kinds of polystyrene/silica (treated and non-treated nanocomposites were prepared with different filler loadings by solution method. Their viscoelastic properties were studied by dynamic stress controlled rotary shear rheometer. Solid-like response of polystyrene/native silica nanocomposites were observed in the terminal zone. Solid inclusionsincrease the storage modulus more than the loss modulus, hence decrease the material damping. By increasing filler volume fraction, the particles tend to agglomerate and build clusters. The presence of clusters increases the viscosity, the moduli and the viscoelastic non-linearity of the composites.Treating the filler surface reduces its tendency to agglomerate as well as the adhesion between the particles and the polystyrene, leading to lower viscosity and interfacial slippage. Also the loss modulus peak is affected significantly by the particle surface area and its surface property in silica-filled polystyrene, which corresponds to its glass transition.

  1. Quantum mechanical computation of structural, electronic, and thermoelectric properties of AgSbSe2

    Directory of Open Access Journals (Sweden)

    M Salimi

    2015-07-01

    Full Text Available In this work, density functional calculations and Boltzmann semiclassical theory of transport are used to investigate structural, electronic, and thermoelectric properties of AgSbSe2 crystal. According to the published experimental measurements, five more likely structures of this compound are considered and their structural and electronic properties are calculated and compared together. Then, thermoelectric properties (electrical conductivity, electronic contribution to the thermal conductivity, power factor, and Seebeck coefficient of three more stable structures are investigated in the constant relaxation time approximation. Finally, the calculated temperature dependence of Seebeck coefficient is compared with the corresponding experimental measurements of others.

  2. DFT study of bridged oligo(bithiophene)s. Conformational analysis and opto-electronic properties

    OpenAIRE

    Si Mohamed Bouzzine; Mohamed Hamidi; Mohammed Bouachrine

    2009-01-01

    In this paper, we have studied the conformational and opto-electronic properties of several oligomers of bridged oligo(bithiophene)s (BTX)n , n=1 to 4 with (X: CH2, SiH2, C=O, C=S and C=C(CN)2). The conformational analysis shows that the most stable conformation is anti-planar conformation. The opto-electronic properties of the octamer (OTX) lead us to suggest that this oligomer is a good model to reflect opto-electronic properties for the parent polymer.

  3. DFT study of bridged oligo(bithiophenes. Conformational analysis and opto-electronic properties

    Directory of Open Access Journals (Sweden)

    Si Mohamed Bouzzine

    2009-08-01

    Full Text Available In this paper, we have studied the conformational and opto-electronic properties of several oligomers of bridged oligo(bithiophenes (BTXn , n=1 to 4 with (X: CH2, SiH2, C=O, C=S and C=C(CN2. The conformational analysis shows that the most stable conformation is anti-planar conformation. The opto-electronic properties of the octamer (OTX lead us to suggest that this oligomer is a good model to reflect opto-electronic properties for the parent polymer.

  4. Improvement of thermal and mechanical properties of composite based on polylactic acid and microfibrillated cellulose through chemical modification

    Science.gov (United States)

    Suryanegara, L.; Nugraha, R. A.; Achmadi, S. S.

    2017-07-01

    Polylactic acid (PLA) is the most representative sustainable and bio-based polymer environmentally friendly that has a great potential to replace petroleum-based plastics. However, brittleness, low heat resistance, and slow crystallization limit the wide application of PLA. One of strategies to improve PLA properties is by reinforcing with microfibrillated cellulose (MFC). Unfortunately, the hydrophilic properties of MFC make it difficult to attain good dispersion in a hydrophobic PLA matrix. Therefore, modification of MFC was needed to increase its compatibility with PLA in the composite formation. In this experiment, MFC was modified with partial acetylation (degree of substitution: 1) and further grafted with lactide monomers through ring-opening polymerization using Sn(Oct)2 catalyst. The result of acetylation and grafting were verified by infrared spectra. Composites were prepared by mixing PLA (molecular weight of 200,000) and the modified MFC at 9:1 ratio through organic solvent method. Followed by 8 min-kneading and hot pressing at 180°C, the resulted composites were evaluated for their mechanical and thermal properties. Thermal characterization carried out using differential scanning calorimetry measurements showed that the presence of modified MFC increased the temperature of glass transition and accelerated the crystallization of PLA. Mechanical properties measurement showed that the presence of modified MFC enhanced the elongation at break (1.1 to 1.8%), tensile strength (14.9 to 25.7 MPa), and modulus of elasticity (1.7 to 2.1 GPa). These results demonstrated that the modified MFC could extend the application of PLA in industry.

  5. Enhancement of nonlinear optical (NLO) properties of indigo through modification of auxiliary donor, donor and acceptor

    Science.gov (United States)

    Mahmood, Asif; Abdullah, Muhammad Imran; Khan, Salah Ud-Din

    2015-03-01

    In this study, indigo based dyes with high non-linear optical response have been investigated. Density functional theory (DFT) was used to study non-linear optical properties of indigo and newly designed dyes (IM-Dye-0, IM-Dye-1, IM-Dye-2 and IM-Dye-3). The time dependant density functional theory (TDDFT) was used to calculate the excitation energies. The HOMO-LUMO energy gaps of newly designed dyes were smaller as compare with indigo dye. Absorption maxima of newly designed dyes strongly red shifted as compare with indigo dye. High non-linear optical (NLO) response of newly designed dyes revealed that these materials would be excellent for NLO applications. This theoretical approach of designing will pave the way for experimentalists to synthesize high response NLO compound.

  6. Tribological Properties of Aluminum Alloy treated by Fine Particle Peening/DLC Hybrid Surface Modification

    Directory of Open Access Journals (Sweden)

    Nanbu H.

    2010-06-01

    Full Text Available In order to improve the adhesiveness of the DLC coating, Fine Particle Peening (FPP treatment was employed as pre-treatment of the DLC coating process. FPP treatment was performed using SiC shot particles, and then AA6061-T6 aluminum alloy was DLC-coated. A SiC-rich layer was formed around the surface of the aluminum alloy by the FPP treatment because small chips of shot particles were embedded into the substrate surface. Reciprocating sliding tests were conducted to measure the friction coefficients. While the DLC coated specimen without FPP treatment showed a sudden increase in friction coefficient at the early stage of the wear cycles, the FPP/DLC hybrid treated specimen maintained a low friction coefficient value during the test period. Further investigation revealed that the tribological properties of the substrate after the DLC coating were improved with an increase in the amount of Si at the surface.

  7. Effects of structural modifications on physicochemical and bile acid-binding properties of psyllium.

    Science.gov (United States)

    Niu, Yuge; Xie, Zhuohong; Zhang, Hua; Sheng, Yi; Yu, Liangli Lucy

    2013-01-23

    The effects of sulfation, hydroxypropylation, and succinylation on gelling, water uptake, swelling, and bile acid-binding capacities of psyllium were examined and compared at the same molar substitution degree. Sulfated, hydroxypropylated, and succinylated psyllium were prepared with substitution levels of 1.02, 0.88, and 0.79, respectively, and their structures were characterized using FT-IR, SEM, and ζ-potential determination. All three derivatization methods reduced the gelling and swelling capacities of psyllium and increased the water uptake and bile acid-binding capacities compared to the original psyllium. Interestingly, it was observed for the first time that introduction of a stronger negatively charged group into the molecule might more effectively enhance the bile acid-binding capacity of psyllium. On the other hand, the steric effect of the substitution groups seemed to be more critical in altering the gelling and swelling properties of psyllium.

  8. Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Vostrikov, Alexander [Fermilab; Checchin, Mattia [Fermilab; Grassellino, Anna [Fermilab; Kim, Young-Kee [U. Chicago (main); Romanenko, Alexander [Fermilab

    2015-06-01

    A study is presented on the superconducting properties of niobium used for the fabrication of the SRF cavities after treating by recently discovered nitrogen doping methods. Cylindrical niobium samples have been subjected to the standard surface treatments applied to the cavities (electro-polishing, l 20°C bake) and compared with samples treated by additional nitrogen doping recipes routinely used to reach ultra-high quality factor values (>3· 1010 at 2 K, 16 MV/m). The DC magnetization curves and the complex magnetic AC susceptibility have been measured. Evidence for the lowered field of first flux penetration after nitrogen doping is found suggesting a correlation with the lowered quench fields. Superconducting critical temperatures Tc = 9.25 K are found to be in agreement with previous measurements, and no strong effect on the critical surface field (Bd) from nitrogen doping was found.

  9. Surface Properties of Titanium dioxide and its Structural Modifications by Reactions with Transition Metals

    Science.gov (United States)

    Halpegamage, Sandamali

    Surfaces of metal oxides play a vital role in many technologically important applications. The surfaces of titanium dioxide, in particular, show quite promising properties that can be utilized in solid-state gas sensing and photocatalysis applications. In the first part of this dissertation we investigate these properties of TiO2 surfaces through a vigorous surface scientific approach. In the second part, we investigate the possibilities of modifying the TiO2 surfaces by depositing multi-component transition metal oxide monolayers so that the properties of bare TiO2 surface can be influenced in a beneficial way. For instance, via formation of new surface sites or cations that have different valance states, the chemisorption and catalytic properties can be modified. We use sophisticated experimental surface science techniques that are compatible with ultra-high vacuum technology for surface characterization. All the experimental results, except for the photocatalysis experiments, were compared to and verified by supporting DFT-based theoretical results produced by our theory collaborators. TiO2 based solid-state gas sensors have been used before for detecting trace amounts of explosives such as 2,4-dinitrololuene (DNT), a toxic decomposition product of the explosive 2,4,6-trinitrotoluene (TNT) that have very low vapor pressure. However, the adsorption, desorption and reaction mechanism were not well- understood. Here, we investigate 2,4-DNT adsorption on rutile-TiO2(110) surface in order to gain insight about these mechanisms in an atomistic level and we propose an efficient way of desorbing DNT from the surface through UV-light induced photoreactions. TiO2 exists in different polymorphs and the photocatalytic activity differs from one polymorph to another. Rutile and anatase are the most famous forms of TiO2 in photocatalysis and anatase is known to show higher activity than rutile. The photoactivity also varies depending on the surface orientation for the same

  10. Tuning the Casimir force via modification of interface properties of three-dimensional topological insulators

    Science.gov (United States)

    Martinez, J. C.; Jalil, M. B. A.

    2013-05-01

    The axion coupling in topological insulators (TI), which couples electric polarization (magnetization) with the magnetic (electric) field, is known to support a small-distance Casimir repulsion and a large-distance Casimir attraction with a zero-force stable equilibrium between TI plates. By enhancing the reflection properties of the TI interface through mirrors that introduce multiple reflections, we show that it is possible to maintain these trends while tuning the position of the zero-force point and its binding energy: the former by an order of magnitude and latter by over four orders. Moreover, surface charge on the TI allows for intermediate tuning of the zero-force point between coarse settings determined by the axion coupling.

  11. Modification of ferrierite through post-synthesis treatments. Acidic and catalytic properties

    Science.gov (United States)

    Brylewska, Kamila; Tarach, Karolina A.; Mozgawa, Włodzimierz; Olejniczak, Zbigniew; Filek, Urszula; Góra-Marek, Kinga

    2016-12-01

    The main emphasis of this work was placed on a detailed characterization of structural, textural and acidic properties of FER zeolites with different Si/Al ratios in terms of their activity in ethanol dehydration reaction. Subsequent dealumination and desilication procedures were found to be an efficient methods of a secondary system of mesopore generation in the ferrierite crystals with preservation of their microporous characteristics. Through ethanol dehydration both the acidic and the textural features have a significant influence on catalytic performance of hierarchical ferrierites. It was shown that higher catalytic activity and selectivity to ethylene is ensured by zeolites with highly preserved microporous characteristic, i.e. well-developed micropore area and intrinsic acidity.

  12. Modification of natural sorbent for providing it with bactericidal and bacteriostatic properties

    Directory of Open Access Journals (Sweden)

    Martemianova Irina

    2016-01-01

    Full Text Available Currently, the problem of water purification from chemical and microbiological contaminations is very important. Sorption technologies are one of the effective and easy-to-use water purification techniques. To prevent the growth of microbiological contaminations on the surface of investigated sorbents, the surface of the investigated sorbents was treated by aqueous solution of copper sulphate with the further study of bactericidal and bacteriostatic activity. The results of sorption efficiency of original and modified zeolite samples of Kholinsk deposit are presented in this paper. These results were obtained, when Zn2+ and Pb2+ ions were removed from the simulated solutions. It was concluded that it is possible to provide natural zeolites with bactericidal and bacteriostatic properties.

  13. Electronic transport properties of graphene doped by gallium

    Science.gov (United States)

    Mach, J.; Procházka, P.; Bartošík, M.; Nezval, D.; Piastek, J.; Hulva, J.; Švarc, V.; Konečný, M.; Kormoš, L.; Šikola, T.

    2017-10-01

    In this work we present the effect of low dose gallium (Ga) deposition (graphene grown by chemical vapor deposition. In situ graphene transport measurements performed with a graphene field-effect transistor structure show that at low Ga coverages a graphene layer tends to be strongly n-doped with an efficiency of 0.64 electrons per one Ga atom, while the further deposition and Ga cluster formation results in removing electrons from graphene (less n-doping). The experimental results are supported by the density functional theory calculations and explained as a consequence of distinct interaction between graphene and Ga atoms in case of individual atoms, layers, or clusters.

  14. Shape dependent electronic properties of wurzite GaN nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Pankaj, E-mail: pankajs@iiitm.ac.in; Kumar, Avaneesh, E-mail: avaneeshk7@ymail.com; Sharma, Varun, E-mail: sunny2013@gmail.com [Nanomaterials Research Group, ABV-Indian Institute of Information Technology and Management (IIITM), Gwalior-474015 (India); Jaiswal, Neeraj K., E-mail: neerajkumar.phd@gmail.com [Discipline of Physics, PDPM-Indian Institute of Information Technology, Design and Manufacturing (IIITDM), Jabalpur-482005 (India)

    2016-05-06

    In the present work, energetic stability and electronic behavior of triangular and square shaped wurzite GaN NW oriented along [1100] and [11 2 0] direction has been investigated by employing ab-initio DFT calculation. Structural analysis suggests that triangular shaped NW undergoes strong surface reconstruction compared to square shaped NW. However, binding energy reveals that square shaped NW is energetically more feasible than triangular NW. Further, from electronic band structure we observe that both structures are metallic with higher metallicity for triangular shaped NW.

  15. Effect of platinum-nanodendrite modification on the glucose-sensing properties of a zinc-oxide-nanorod electrode

    Science.gov (United States)

    Abdul Razak, Khairunisak; Neoh, Soo Huan; Ridhuan, N. S.; Mohamad Nor, Noorhashimah

    2016-09-01

    The properties of ZnO nanorods (ZnONRs) decorated with platinum nanodendrites (PtNDs) were studied. Various sizes of PtNDs were synthesized and spin coated onto ZnONRs, which were grown on indium-titanium-oxide (ITO) substrates through a low-temperature hydrothermal method. Scanning electron microscopy and X-ray diffraction analyses were conducted to analyze the morphology and structural properties of the electrodes. The effects of PtND size, glucose concentration, and Nafion amount on glucose-sensing properties were investigated. The glucose-sensing properties of electrodes with immobilized glucose oxidase (GOx) were measured using cyclic voltammetry. The bio-electrochemical properties of Nafion/GOx/42 nm PtNDs/ZnONRs/ITO glucose sensor was observed with linear range within 1-18 mM, with a sensitivity value of 5.85 μA/mM and a limit of detection of 1.56 mM. The results of this study indicate that PtNDs/ZnONRs/ITO has potential in glucose sensor applications.

  16. Electronic structure and physical properties of 13C carbon composite

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

    This review is devoted to the application of graphite and graphite composites in science and technology. Structure and electrical properties, as so technological aspects of producing of high-strength artificial graphite and dynamics of its destruction are considered. These type of graphite are traditionally used in the nuclear industry. Author was focused on the properties of graphite composites based on carbon isotope 13C. Generally, the review relies on the original results and concentrates...

  17. Modifications in optical and electrical properties of selenium nanowire arrays using ion beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Narinder [Chaudhary Devi Lal University, Department of Physics, Sirsa (India); Haryana College of Technology and Management, Department of Physics, Kaithal (India); Kumar, Rajesh [RN College of Engineering and Technology, Department of Physics, Madlauda (India); Kumar, Sushil [Chaudhary Devi Lal University, Department of Physics, Sirsa (India); Chakarvarti, S.K. [Manav Rachana International University, Research and Development, Faridabad (India)

    2015-11-15

    In the present paper, 80 MeV Si{sup 7+} ion beam-induced changes in selenium nanowire arrays, fabricated on copper substrates, have been examined. The nanowire arrays were electrodeposited into polymer membranes using template method. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV-visible spectroscopy have been used to study the ion-induced effects in fabricated nanowire arrays. The XRD and FESEM results confirmed the formation of selenium nanowire arrays with trigonal structures. An intensity variation in the XRD peaks is observed for irradiated nanowires at different ion fluences. The band gap energy of the irradiated nanowire arrays was found to reduce compared with the pristine case. The irradiation of semiconducting selenium nanowires enhances the electrical conductivity. The current-voltage characterizations also confirm an enhancement in electrical conductivity of selenium nanowire arrays with an increase in ion fluence. This study is anticipated to greatly facilitate the design and development of nanodevices-based semiconductor nanowires which can be utilized even in the harsh environment. (orig.)

  18. Granular size of potato starch affects structural properties, octenylsuccinic anhydride modification and flowability.

    Science.gov (United States)

    Wang, Chan; Tang, Chuan-He; Fu, Xiong; Huang, Qiang; Zhang, Bin

    2016-12-01

    Native potato starch (PS) granules were separated into three size fractions: larger than 30μm (P-L), 15-30μm (P-M), and smaller than 15μm (P-S). The morphological and crystalline structure of fractionated potato starches were investigated by light and scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The P-L fraction showed ellipsoidal shape and B-type X-ray pattern, whereas the P-S fraction had spherical shape and A-type pattern. The fluorophore-assisted capillary electrophoresis data showed that the P-L fraction had more B2 chains and less short A and B1 chains than the P-S counterparts. Smaller granules with larger specific surface area had higher degree of substitution when reacted with octenylsuccinic anhydride (OSA), and showed more uniform distribution of octenylsuccinate substituents. Both OSA modified and unmodified P-S samples showed higher flowability compared with the P-L counterparts. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Noncovalent Intermolecular Interactions in Organic Electronic Materials: Implications for the Molecular Packing vs Electronic Properties of Acenes

    KAUST Repository

    Sutton, Christopher

    2015-10-30

    Noncovalent intermolecular interactions, which can be tuned through the toolbox of synthetic chemistry, determine not only the molecular packing but also the resulting electronic, optical, and mechanical properties of materials derived from π-conjugated molecules, oligomers, and polymers. Here, we provide an overview of the theoretical underpinnings of noncovalent intermolecular interactions and briefly discuss the computational chemistry approaches used to understand the magnitude of these interactions. These methodologies are then exploited to illustrate how noncovalent intermolecular interactions impact important electronic properties-such as the electronic coupling between adjacent molecules, a key parameter for charge-carrier transport-through a comparison between the prototype organic semiconductor pentacene with a series of N-substituted heteropentacenes. Incorporating an understanding of these interactions into the design of organic semiconductors can assist in developing novel materials systems from this fascinating molecular class. © 2015 American Chemical Society.

  20. Modification of structural and magnetic properties of soft magnetic multi-component metallic glass by 80 MeV {sup 16}O{sup 6+} ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Kane, S.N., E-mail: kane_sn@yahoo.com [School of Physics, D.A. University, Khandwa Road Campus, Indore 452001 (India); Shah, M.; Satalkar, M.; Gehlot, K. [School of Physics, D.A. University, Khandwa Road Campus, Indore 452001 (India); Kulriya, P.K.; Avasthi, D.K. [Inter-University Accelerator Centre, P.O. Box No. 10502, Aruna Asaf Ali Marg, New Delhi 110067 (India); Sinha, A.K. [Raja Ramanna Centre for Advanced Technology, P.O. CAT, Indore 452013 (India); Modak, S.S. [Physics Department, Jaypee University of Eng. & Tech., A-B Road, Raghogarh, Guna 473226 (India); Ghodke, N.L.; Reddy, V.R. [UGC-DAE CSR, University Campus, Khandwa Road, Indore 452001 (India); Varga, L.K. [RISSPO, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary)

    2016-07-15

    Effect of 80 MeV {sup 16}O{sup 6+} ion irradiation in amorphous Fe{sub 77}P{sub 8}Si{sub 3}C{sub 5}Al{sub 2}Ga{sub 1}B{sub 4} alloy is reported. Electronic energy loss induced modifications in the structural and, magnetic properties were monitored by synchrotron X-ray diffraction (SXRD), Mössbauer and, magnetic measurements. Broad amorphous hump seen in SXRD patterns reveals the amorphous nature of the studied specimens. Mössbauer measurements suggest that: (a) alignment of atomic spins within ribbon plane, (b) changes in average hyperfine field suggests radiation-induced decrease in the inter atomic distance around Mössbauer (Fe) atom, (c) hyperfine field distribution confirms the presence of non-magnetic elements (e.g. – B, P, C) in the first near-neighbor shell of the Fe atom, thus reducing its magnetic moment, and (d) changes in isomer shift suggests variation in average number of the metalloid near neighbors and their distances. Minor changes in soft magnetic behavior – watt loss and, coercivity after an irradiation dose of 2 × 10{sup 13} ions/cm{sup 2} suggests prospective application of Fe{sub 77}P{sub 8}Si{sub 3}C{sub 5}Al{sub 2}Ga{sub 1}B{sub 4} alloy as core material in accelerators (radio frequency cavities).

  1. Effect of modification degree of nanohydroxyapatite on biocompatibility and mechanical property of injectable poly(methyl methacrylate)-based bone cement.

    Science.gov (United States)

    Quan, Changyun; Tang, Yong; Liu, Zhenzhen; Rao, Minyu; Zhang, Wei; Liang, Peiqing; Wu, Nan; Zhang, Chao; Shen, Huiyong; Jiang, Qing

    2016-04-01

    The objective of this study is to prepare a biocompatible nanohydroxyapatite/poly(methyl methacrylate) (HA/PMMA) composite bone cement, which has good mechanical property and can be used for vertebroplasty. Up to 40 wt % of nanohydroxyapatite (nano-HA) in the power, which was surface modified with poly(methylmethacrylate-co-γ-methacryloxypropyl timethoxysilane) [P(MMA-co-MPS)] copolymer, was incorporated into the composite bone cement. The content of P(MMA-co-MPS) on the surface of nano-HA (18.7%, 22.8%, and 26%) was determined through thermogravimetric analysis (TGA). The morphology of biomineralized surface of composite bone cement was observed under scanning electron microscope (SEM). The mechanical measurements of the composite cements implied that the interfacial interaction between the HA and PMMA matrix may be greatly enhanced after surface modification of HA. Biochemical assays indicated that the HA/PMMA bone cement had no cytotoxicity and induced no hemolysis. The cell adhesion and alkaline phosphatase (ALP) activity assays indicated that the biocompatibility of HA/PMMA bone cement could be promoted, demonstrating that it can be used as an ideal weight-bearing bone repair materials on clinical application. © 2015 Wiley Periodicals, Inc.

  2. Innovation and development of exhibition electronic-commerce based on the properties of electronic-commerce

    Science.gov (United States)

    Zhang, Jiankang

    2017-06-01

    There are two roadmaps of accomplishing exhibition electronic-commerce innovation and development. The first roadmap is that the exhibition organizers should seek mutual benefit cooperation with professional electronic-commerce platform of correspondent area with exhibition projects, thus help exhibitors realize their market object. The second roadmap is to promote innovation and development of electronic-commerce (Business-to-Customer) between both exhibitors and purchasers. Exhibition electronic-commerce must focus on innovative development in the following functions: market research and information service; advertising and business negotiation; online trading and online payment. With the aid of electronic-commerce, exhibition enterprise could have distinctive strengths such as transactions with virtualization, transparency, high efficiency and low cost, enhancing market link during enterprise research and development, promoting the efficiency of internal team collaboration and the individuation of external service, and optimizing resource allocation.

  3. Evaluation of Corneal Biomechanical Properties Modification after Small Incision Lenticule Extraction Using Scheimpflug-Based Noncontact Tonometer

    Directory of Open Access Journals (Sweden)

    Leonardo Mastropasqua

    2014-01-01

    Full Text Available Purpose. To quantify the effect of small incision lenticule extraction (SMILE on the corneal biomechanics using Scheimpflug noncontact tonometer (Corvis ST. Methods. Twenty eyes of twenty patients, evaluated as eligible for surgery, with high myopia and/or moderate myopic astigmatism, underwent small incision lenticule extraction (SMILE. All patients underwent Corvis ST preoperatively and postoperatively after 1 week, and 1 and 3 months to observe alterations of corneal biomechanical properties. The main outcome measures were Deformation Amplitude, 1st-AT, and 2nd-AT. The relationship between the amount of stroma removed and the percentage variation of the measured parameters from baseline was evaluated with generalized linear model from each time point. For completeness also intraocular pressure (IOP, central corneal thickness (CCT, and their variations after surgery were evaluated. Results. The ratio between the amount of removed refractive error and, respectively, changes of Deformation Amplitude, 1st-AT, and 2nd-AT were significantly modified at the 1st week after surgery (P=0.005; P=0.001; P=0.024. At 1 and 3 months these values did not show statistically significant alterations. Intraocular pressure and central corneal thickness showed statistically significant changes during follow-up. Conclusions. No significant modifications in biomechanical properties were observed after SMILE so this procedure could induce only minimal transient alterations of corneal biomechanics.

  4. Structure and electronic properties of amorphous WO3

    NARCIS (Netherlands)

    Wijs, G.A. de; Groot, R.A. de

    1999-01-01

    The structure and electronic structure of amorphous WO3 were studied with first-principles density-functional calculations. Upon amorphization, a large increase of the band gap is observed. The empty states exhibit a tendency towards localization. We studied the filling of these states as induced by

  5. Thermal and optical properties of electron beam irradiated cellulose triacetate

    Science.gov (United States)

    Nouh, S. A.; Mohamed, Amal; El Hussieny, H. M.

    2009-06-01

    Samples from Cellulose triacetate (CTA) sheets were irradiated with electron beam in the dose range 10-200 kGy. Non-isothermal studies were carried out using thermogravimetric analysis (TGA) to obtain the activation energy of thermal decomposition for CTA polymer. The CTA samples decompose in one main break down stage. The results indicate that the irradiation by electron beam in the dose range 80-200 kGy increases the thermal stability of the polymer samples. Also, the variation of melting temperatures with the electron dose has been determined using differential thermal analysis (DTA). The CTA polymer is characterized by the appearance of one endothermic peak due to melting. It is found that the irradiation in the dose range 10-80 kGy causes defects generation that splits the crystals depressing the melting temperature, while at higher doses (80-200 kGy), the thickness of crystalline structure (lamellae) is increased, thus the melting temperature increases. In addition, the transmission of these samples in the wavelength range 200-2500 nm, as well as any color changes, were studied. The color intensity Δ E* was greatly increased on increasing the electron beam dose, and accompanied by a significant increase in the blue color component.

  6. Electronic and Magnetic Properties of High Temperature Electrolytes.

    Science.gov (United States)

    Measurements are reported on the electrical conductance in the Cs-CsCl and Rb- RbCl molten systems as a function of composition and temperature. The...in salt are evaluated from freezing point data, and are large and positive for the Cs-CsCl and Rb- RbCl systems. Electron spin resonance has been

  7. DFT study on structure, electronic properties, and reactivity of cis ...

    Indian Academy of Sciences (India)

    DFT global chemical reactivity descriptors (chemical hardness, total energy, electronic chemical potential, and electrophilicity) are calculated for the isomers and used to predict their relative stability and reactivity. The chemical reactivity indices are found to be related to the bond angle defined by the cis carbonyls and the ...

  8. Electronic structure and equilibrium properties of hcp titanium and ...

    Indian Academy of Sciences (India)

    -d) and zirco- nium (4-d) transition metals are studied by using a non-local model potential method. From the present calculation of energy bands, Fermi energy, density of states and the electronic heat capacity of these two metals are ...

  9. Molecular fingerprints in the electronic properties of crystalline organic semiconductors

    DEFF Research Database (Denmark)

    Ciuchi, S.; Hatch, R.C.; Höchst, H.

    2012-01-01

    By comparing photoemission spectroscopy with a non-perturbative dynamical mean field theory extension to many-body ab initio calculations, we show in the prominent case of pentacene crystals that an excellent agreement with experiment for the bandwidth, dispersion and lifetime of the hole carrier...... of electronic interactions cannot reproduce the experimental photoemission data in this important class of materials....

  10. Electronic properties and Compton profiles of silver iodide

    Indian Academy of Sciences (India)

    calculations is listed in table 1. In the present calculations, all-electron basis sets of Gaussian-type orbitals. (GTOs) for Ag and I have been taken from ref. [34]. These basis sets were opti- mized using BILLY software. For a faster convergence of self-consistent-field (SCF) cycles, the BROYDEN scheme [35] was applied for all ...

  11. Thermoelectric performance and electronic properties of transition metal monosilicides

    Science.gov (United States)

    Ou-Yang, T. Y.; Shu, G. J.; Fuh, H. R.

    2017-10-01

    We have performed a comprehensive series of lattice structure, band structure, electrical transport, and thermoelectric performances measurements for MnSi, FeSi, and CoSi single crystals. The band structure of this family of compounds demonstrates significant changes across the Fermi level as the number of 3d-electron is increased with transition metal substitution. In particular, a crossover from metal to semiconductor and back to semimetal has been observed in this series of compounds. Practical measurements (electrical transport and thermoelectric performances) are combined with theoretical calculations to qualify the reliability of band structures. By means of standard thermal activation simulations of electrical resistivity for FeSi, we identify a narrow band gap ∼57 meV, which is well consistent with our band calculation result. A double sign reversal of the Seebeck coefficient for FeSi suggests that both electrons and holes are contributed to electrical transport, indicating that the electronic structure of FeSi is substantially influenced by hole-doped (MnSi) and electron-doped (CoSi) effects.

  12. Mechanical and electronic-structure properties of compressed CdSetetrapod nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Schrier, Joshua; Lee, Byounghak; Wang, Lin-Wang

    2007-01-18

    The coupling of mechanical and optical properties insemiconductor nanostructures can potentially lead to new types ofdevices. This work describes our theoretical examination of themechanical properties of CdSe tetrapods under directional forces, such asmay be induced by AFM tips. In addition to studying the general behaviorof the mechanical properties under modifications of geometry,nanocrystal-substrate interaction, and dimensional scaling, ourcalculations indicate that mechanical deformations do not lead to largechanges in the band-edge state eigenenergies, and have only a weak effecton the oscillator strengths of the lowest energy transitions.

  13. Modification of thermal and oxidative properties of biodiesel produced from vegetable oils

    Energy Technology Data Exchange (ETDEWEB)

    El Diwani, G.; El Rafie, S. [National Research Center, Cairo (Egypt). Chemical Engineering and Pilot Plant Dept.

    2008-07-01

    Although biodiesel cannot entirely replace petroleum based diesel fuels, there are at least five reasons that justify its development. It provides a market for excess production of vegetable oils, it decreases the dependence on imported petroleum, it does not contribute to global warming due to its closed carbon cycle, the exhaust emissions of carbon monoxide, unburned hydrocarbons, and particulate emissions from biodiesel are lower than with regular diesel fuel, when added to regular diesel fuel in an amount up to 20% it can convert fuel into an acceptable fuel. Transesterification reaction is the most commonly applied technique to produce biodiesel. Transesterification of three vegetable oils, sunflower oil, linseed oil and mixed oils as; sunflower-soyabean and olein were carried out using methanol, and potasium hydroxide as catalyst. The methyl esters of the corresponding oils were separated from the crude glycerol and characterized by physical-chemical methods to evaluate their thermal properties. This methods are determination of densities, cloud points, pour points, flash points, kinematic viscosities, hydrogen/carbon ratios, sulfur contents, ash contents and triglycerides. The physico-chemical characteristic of biodiesel treated with ozone showed improvement of pour point and flash point indicating higher degree of safety for fuel. Methyl esters mixed with their corresponding ozonated oil were subjected to comparison and evaluation for their thermal properties by the thermo gravimetric analysis differential thermal analysis from which the calculated heat of enthalpy and comparison with the heat of conventional diesel. The results showed that the oxygen content of biodiesel samples treated with ozone increased weight % and resulted in more extensive chemical reaction, promoted combustion characteristics and less carbon residue was produced. Gas chromatography appeared more suitable to address the problem of determining/verifying biodiesel methyl ester and

  14. The Influence of Green Surface Modification of Oil Palm Mesocarp Fiber by Superheated Steam on the Mechanical Properties and Dimensional Stability of Oil Palm Mesocarp Fiber/Poly(butylene succinate Biocomposite

    Directory of Open Access Journals (Sweden)

    Yoon Yee Then

    2014-08-01

    Full Text Available In this paper, superheated steam (SHS was used as cost effective and green processing technique to modify oil palm mesocarp fiber (OPMF for biocomposite applications. The purpose of this modification was to promote the adhesion between fiber and thermoplastic. The modification was carried out in a SHS oven at various temperature (200–230 °C and time (30–120 min under normal atmospheric pressure. The biocomposites from SHS-treated OPMFs and poly(butylene succinate (PBS at a weight ratio of 70:30 were prepared by melt blending technique. The mechanical properties and dimensional stability of the biocomposites were evaluated. This study showed that the SHS treatment increased the roughness of the fiber surface due to the removal of surface impurities and hemicellulose. The tensile, flexural and impact properties, as well as dimensional stability of the biocomposites were markedly enhanced by the presence of SHS-treated OPMF. Scanning electron microscopy analysis showed improvement of interfacial adhesion between PBS and SHS-treated OPMF. This work demonstrated that SHS could be used as an eco-friendly and sustainable processing method for modification of OPMF in biocomposite fabrication.

  15. Ab-initio investigations of the electronic properties of bulk wurtzite Beryllia and its derived nanofilms

    KAUST Repository

    Goumri-Said, Souraya

    2010-08-01

    In this Letter we investigate the electronic properties of the bulk and the nanofilm BeO in wurtzite structure. We performed a first-principles pseudo-potential method within the generalized gradient approximation. We will give more importance to the changes in band structure and density of states between the bulk structure and its derived nanofilms. The bonding characterization will be investigated via the analysis Mulliken population and charge density contours. It is found that the nanofilm retains the same properties as its bulk structure with slight changes in electronic properties and band structure which may offer some unusual transport properties. © 2010 Elsevier B.V. All rights reserved.

  16. Super heavy element Copernicium: Cohesive and electronic properties revisited

    Science.gov (United States)

    Gyanchandani, Jyoti; Mishra, Vinayak; Dey, G. K.; Sikka, S. K.

    2018-01-01

    First principles scalar relativistic (SR) calculations with and without including the spin orbit (SO) interactions have been performed for solid Copernicium (Cn) to determine its ground state equilibrium structure, volume, bulk modulus, pressure derivative of the bulk modulus, density of states and band structure. Both SR and SR+SO calculations have been performed with 6p levels treated as part of core electrons and also as part of valence electrons. These calculations have been performed for the rhombohedral, BCT, FCC, HCP, BCC and SC structures. Results have been compared with the results for Hg which is lighter homologue of Cn in the periodic table. We find hcp to be the stable crystal structure at SR level of theory and also at SR+SO level of theory when the 6p electrons are treated as part of core electrons. With 6p as part of valence electrons, SR+SO level of computations, however, yield bcc structure to be the most stable structure. Equilibrium volume (V0) of the most stable crystal structure at SR level of theory viz. hcp structure is 188.66 a.u.3whereas its value for the bcc structure, the equilibrium ground state structure at SR+SO level of theory is 165.71 a.u.3 i.e a large change due to relativistic effects is seen. The density of states at Fermi level is much smaller in Cn than in Hg, making it a poorer metal than mercury. In addition the cohesive energy of Cn is computed to be almost two times that of Hg for SR+SO case.

  17. Effect of fish collagen modification on its thermal and rheological properties.

    Science.gov (United States)

    Safandowska, Marta; Pietrucha, Krystyna

    2013-02-01

    This report describes the effects of different methods of silver carp collagen crosslinking on its properties, particularly their thermal, mechanical viscoelastic and biological behavior. Enzymatic analyses and determination of the degree of crosslinking showed the stabilizing effect of both dehydrothermal (DHT) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) treatments on fish collagen. The results of the thermal (DSC) measurements demonstrated that collagen crosslinked by EDC/NHS ensured a high thermal stability compared with collagen crosslinked dehydrothermally. The denaturation temperature (T(d)) of unmodified collagen samples increased from 77 to 80°C and 88°C for DHT- and EDC/NHS-treated collagen, respectively. The influence of DHT or EDC/NHS crosslinking on the viscoelastic behavior of fish collagen was elaborated by a shift of the tan δ(max) peak toward higher temperatures resulting in higher thermostability of the modified collagen samples. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Optical properties of PLT films with various composition on quartz and modifications of their surfaces

    CERN Document Server

    Yoon, Y S; Koh, S K; Jung, H J

    1999-01-01

    (Pb sub 1 sub - sub x La sub x)TiO sub 3 (PLT) films with various compositions of La were deposited by using the sol-gel process on quartz substrates in order to study their optical properties. X-ray patterns indicated that the pseudocubic phase of the PLT film dominated with increased La concentration due to a decrease in the lattice constant of the c-axis. Three-dimensional atomic force microscopy images revealed that the grain size and root mean square (r.m.s) surface roughness were decreased by adding of La. The optical band gap of the as-deposited films became wider when Pb was replaced with La, which could be calculated from the transmittance of an UV-visible spectrometer. The addition of La increased the transparency of the PbTiO sub 3 film and shifted the threshold to shorter wavelengths for initiation of absorption. In addition, we modified the surfaces of the PLT films with La concentrations of 5 % by using an oxygen-ion beam with an oxygen-ion energy of 1 kV at different doses. The optical band gap...

  19. Practical background modification fermented beverage technology for the formation of defined functional properties

    Directory of Open Access Journals (Sweden)

    V. V. Botvinnikova

    2016-01-01

    Full Text Available The problem of provision of population with dairy products is escalating due to the fact that today, throughout the world, particularly in Russia, there is a shortage of milk as raw material, increasing every year. In the future, the consumption of milk and dairy products will continue to outpace growth in milk production is solid. To solve this problem, domestic producers need to find new ways to increase production of raw milk and improve the consumer and functional properties of fermented dairy products. The work was proposed the use of acoustic effects of ultrasound, triggered by the ultrasound, the technological model UTA ABOUT, 4/22 OM (frequency mechanical vibrations 22 ± 1,65 kHz. The main factors determining consumer characteristics, were taken physico-chemical parameters, structural and mechanical characteristics and the accumulation of minor biologically active substances – kefiran. In the study was obtained results confirming the necessity of using ultrasonic impact (RAS in the production technology of dairy products.

  20. Different chemical groups modification on the surface of chitosan nonwoven dressing and the hemostatic properties.

    Science.gov (United States)

    Yan, Dong; Hu, Shihao; Zhou, Zhongzheng; Zeenat, Shah; Cheng, Feng; Li, Yang; Feng, Chao; Cheng, Xiaojie; Chen, Xiguang

    2018-02-01

    The hemostatic properties of surface modified chitosan nonwoven had been investigated. The succinyl groups, carboxymethyl groups and quaternary ammonium groups were introduced into the surface of chitosan nonwoven (obtained NSCS, CMCS and TMCS nonwoven, respectively). For blood clotting, absorbance value (0.105±0.03) of NSCS1 nonwoven was the smallest (CS 0.307±0.002, NSCS2 0.148±0.002, CMCS1 0.195±0.02, CMCS2 0.233±0.001, TMCS1 0.191±0.002, TMCS2 0.345±0.002), which indicated the stronger hemostatic potential. For platelet aggregation, adenosine diphosphate agonist was added to induce the nonwoven to adhered platelets. The aggregation of platelet with TMCS2 nonwoven was highest (10.97±0.16%). Further research of blood coagulation mechanism was discussed, which indicated NSCS and CMCS nonwoven could activate the intrinsic pathway of coagulation to accelerate blood coagulation. NSCS1 nonwoven showed the shortest hemostatic time (147±3.7s) and the lowest blood loss (0.23±0.05g) in a rabbit ear artery injury model. These results demonstrated that these surface modified chitosan nonwoven dressings could use as a promising hemostatic intervention, especially NSCS nonwoven dressing. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Dual ion beam irradiation of polymeric materials for the modification of optical properties with improved adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jae-Won, E-mail: pjw@kaeri.re.kr [Korea Atomic Energy Research Institute, 1045 Deadeock-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); Lee, Eal H.; Lee, Jae-Sang [Korea Atomic Energy Research Institute, 1045 Deadeock-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); Lee, Byung-hoon; Kim, Min-kyu [Shinki Intermobile Co. Ltd., 69-4 Junam-Dong, Yangsan-City, Kyungnam (Korea, Republic of); Lee, Chan-Young [Korea Atomic Energy Research Institute, 1045 Deadeock-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); Kim, Hyung-jin [Korea Atomic Energy Research Institute, 1045 Deadeock-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); Shinki Intermobile Co. Ltd., 69-4 Junam-Dong, Yangsan-City, Kyungnam (Korea, Republic of); Choi, Byung-Ho [Korea Atomic Energy Research Institute, 1045 Deadeock-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of)

    2012-06-15

    Metallic (chromium) coating has often been applied on the surface of polymeric components, mainly to improve their appearance with a metallic luster and to protect from degradation under UV and visible light. However, the toxic nature of hexavalent chromium and delamination problems are an increasing concern in the plating industry. A similar metallic luster and the UV-visible light protection can be achieved by treating the surface of polymers by ion beams. However, a degradation by weathering including cracks, loss of glossiness, blistering, and eventual delamination have been problematic for ion beam processed polymers, particularly with a single ion beam irradiation. The main cause of adhesion failure is the abrupt change in material properties at the interface between coating and polymer or ion beam treated surface and the underlying untreated bulk polymer. In this work, therefore, a method is developed that improves adhesion by producing a graded interface by employing a dual ion beam processing. For demonstration purposes in this work, polycarbonate/acrylonitrile butadiene styrene blends were irradiated first with nitrogen ions followed by helium ions, achieving the desired metallic luster with improved adhesion. The experimental findings are explained in light of the stopping range of ions in materials and their interaction mechanisms with polymeric materials.

  2. Silicon-germanium (Sige) nanostructures production, properties and applications in electronics

    CERN Document Server

    Usami, N

    2011-01-01

    Nanostructured silicon-germanium (SiGe) provides the prospect of novel and enhanced electronic device performance. This book reviews the materials science and technology of SiGe nanostructures, including crystal growth, fabrication of nanostructures, material properties and applications in electronics.$bNanostructured silicon-germanium (SiGe) opens up the prospects of novel and enhanced electronic device performance, especially for semiconductor devices. Silicon-germanium (SiGe) nanostructures reviews the materials science of nanostructures and their properties and applications in different electronic devices. The introductory part one covers the structural properties of SiGe nanostructures, with a further chapter discussing electronic band structures of SiGe alloys. Part two concentrates on the formation of SiGe nanostructures, with chapters on different methods of crystal growth such as molecular beam epitaxy and chemical vapour deposition. This part also includes chapters covering strain engineering and mo...

  3. Rational modification of a dendrimeric peptide with antimicrobial activity: consequences on membrane-binding and biological properties.

    Science.gov (United States)

    Batoni, Giovanna; Casu, Mariano; Giuliani, Andrea; Luca, Vincenzo; Maisetta, Giuseppantonio; Mangoni, Maria Luisa; Manzo, Giorgia; Pintus, Manuela; Pirri, Giovanna; Rinaldi, Andrea C; Scorciapino, Mariano A; Serra, Ilaria; Ulrich, Anne S; Wadhwani, Parvesh

    2016-03-01

    Peptide-based antibiotics might help containing the rising tide of antimicrobial resistance. We developed SB056, a semi-synthetic peptide with a dimeric dendrimer scaffold, active against both Gram-negative and Gram-positive bacteria. Being the mechanism of SB056 attributed to disruption of bacterial membranes, we enhanced the amphiphilic profile of the original, empirically derived sequence [WKKIRVRLSA-NH2] by interchanging the first two residues [KWKIRVRLSA-NH2], and explored the effects of this modification on the interaction of peptide, both in linear and dimeric forms, with model membranes and on antimicrobial activity. Results obtained against Escherichia coli and Staphylococcus aureus planktonic strains, with or without salts at physiological concentrations, confirmed the added value of dendrimeric structure over the linear one, especially at physiological ionic strength, and the impact of the higher amphipathicity obtained through sequence modification on enhancing peptide performances. SB056 peptides also displayed intriguing antibiofilm properties. Staphylococcus epidermidis was the most susceptible strain in sessile form, notably to optimized linear analog lin-SB056-1 and the wild-type dendrimer den-SB056. Membrane affinity of all peptides increased with the percentage of negatively charged lipids and was less influenced by the presence of salt in the case of dendrimeric peptides. The analog lin-SB056-1 displayed the highest overall affinity, even for zwitterionic PC bilayers. Thus, in addition to electrostatics, distribution of charged/polar and hydrophobic residues along the sequence might have a significant role in driving peptide-lipid interaction. Supporting this view, dendrimeric analog den-SB056-1 retained greater membrane affinity in the presence of salt than den-SB056, despite the fact that they bear exactly the same net positive charge.

  4. Electronic structures and optical properties for Ag-N-codoped ZnO nanotubes

    National Research Council Canada - National Science Library

    Feng, Xian-Yang; Zhang, Chang-Wen; Xu, Xi-Jin; Wang, Pei-Ji

    2013-01-01

    The structural and electronic/optical properties of pure and Ag-N-codoped (8,0) ZnO nanotubes have been studied using first-principles calculations in the framework of the local spin density approximation...

  5. 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.

  6. Influence of defect luminescence and structural modification on the electrical properties of Magnesium Doped Zinc Oxide Nanorods

    Science.gov (United States)

    Santoshkumar, B.; Biswas, Amrita; Kalyanaraman, S.; Thangavel, R.; Udayabhanu, G.; Annadurai, G.; Velumani, S.

    2017-06-01

    Magnesium doped zinc oxide nanorod arrays on zinc oxide seed layers were grown by hydrothermal method. X-ray diffraction (XRD) patterns revealed the growth orientation along the preferential (002) direction. The hexagonal morphology was revealed from the field emission scanning electron microscope (FESEM) images. The elemental composition of the samples was confirmed by energy dispersive x-ray analysis spectra (EDS) and mapping dots. Carrier concentration, resistivity and mobility of the samples were obtained by Hall measurements. I-V characteristic curve confirmed the increase in resistivity upon doping. Photoluminescence (PL) spectra exposed the characteristic of UV emission along with defect mediated visible emission in the samples. Electrochemical impedance spectroscopy and cyclic voltammetry were undertaken to study the charge transport property. Owing to the change in the structural parameters and defect concentration the electrical properties of the doped samples were altered.

  7. Modification and development of electrical and magnetic properties of PVA/PEO incorporated with MnCl{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Elashmawi, I.S., E-mail: islam_shukri2000@yahoo.com [Department of Spectroscopy, Physics Division, National Research Center, Giza (Egypt); Department of Physics, Faculty of Science, Al-Ula, Taibah University, Madina (Saudi Arabia); Abdelrazek, E.M. [Department of Physics, Faculty of Science, Mansoura University, Mansoura (Egypt); Hezma, A.M. [Department of Spectroscopy, Physics Division, National Research Center, Giza (Egypt); Rajeh, A. [Department of Physics, Faculty of Science, Mansoura University, Mansoura (Egypt)

    2014-02-01

    The electrical and magnetic properties PVA/PEO films incorporated with different weight percentage of MnCl{sub 2} prepared by casting technique were studied. The Magnetic properties were investigated by electron spin resonance (ESR) and vibrating sample magnetometer (VSM). The electrical conductivity was enhanced depends on both frequencies and temperatures indicate the existence of charge carriers transported by hopping through defect sites attributed to increase in the number of mobile charge carriers of Mn{sup +2}. The AC conduction mechanism and conduction parameters have been calculated according to the Correlated barrier hopping (CBH) model. ESR spectra reveals aggregated forms of Mn{sup 2+} ions are formed at higher concentration and isolated forms at lower concentration. VSM shows paramagnetic nature for pure MnCl{sub 2} and anti-ferromagnetic nature for doped samples due to overlapping of Mn d-states with valence band.

  8. Modification of fiber properties through grafting of acrylonitrile to rayon by chemical and radiation methods

    Directory of Open Access Journals (Sweden)

    Inderjeet Kaur

    2013-11-01

    Full Text Available Fibrous properties of rayon has been modified through synthesis of graft copolymers of rayon with acrylonitrile (AN by chemical method using ceric ammonium nitrate (CAN/HNO3 as a redox initiator and gamma radiation mutual method. Percentage of grafting (Pg was determined as a function of initiator concentration, monomer concentration, irradiation dose, temperature, time of reaction and the amount of water. Maximum percentage of grafting (160.01% using CAN/HNO3 was obtained at [CAN] = 22.80 × 10−3 mol/L, [HNO3] = 112.68 × 10−2 mol/L and [AN] = 114.49 × 10−2 mol/L in 20 mL of water at 45 °C within 120 min while in case of gamma radiation method, maximum Pg (90.24% was obtained at an optimum concentration of AN of 76.32 × 10−2 mol/L using 10 mL of water at room temperature with total dose exposure of 3.456 kGy/h. The grafted fiber was characterized by FTIR, SEM, TGA and XRD studies. Swelling behavior of grafted rayon in different solvents such as water, methanol, ethanol, DMF and acetone was studied and compared with the unmodified rayon. Dyeing behavior of the grafted fiber was also investigated.

  9. The Swedish P-CAT: modification and exploration of psychometric properties of two different versions.

    Science.gov (United States)

    Selan, Denis; Jakobsson, Ulf; Condelius, Anna

    2017-09-01

    The aim of this study was to further investigate the psychometric properties (with focus on construct validity and scale function) of the Swedish version of the Person-centred Care Assessment Tool (P-CAT) in a sample consisting of staff working in elderly care units (N = 142). The aim was also to further develop and psychometrically test a modified, noncontext-specific version of the instrument (mP-CAT) in a sample consisting of staff working in primary health care or within home care for older people (N = 182). Principal component analysis with varimax rotation initially suggested a three-factor solution for the P-CAT, explaining 55.96% of variance. Item 13 solely represented one factor wherefore this solution was rejected. A final 2-factor solution, without item 13, had a cumulative explained variance of 50.03%. All communalities were satisfactory (>0.3), and alpha values for both first factor (items 1-6, 11) and second factor (items 7-10, 12) were found to be acceptable. Principal component analysis with varimax rotation suggested a final 2-factor solution for the mP-CAT explaining 46.15% of the total variance with communalities ranging from 0.263 to 0.712. Cronbach's α for both factors was found to be acceptable (>0.7). This study suggests a 2-factor structure for the P-CAT and an exclusion of item 13. The results indicated that the modified noncontext-specific version, mP-CAT, seems to be a valid measure. Further psychometric testing of the mP-CAT is however needed in order to establish the instrument's validity and reliability in various contexts. © 2016 Nordic College of Caring Science.

  10. Plasmonic modification of electron-longitudinal-optical phonon coupling in Ag-nanoparticle embedded InGaN/GaN quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Llopis, Antonio; Neogi, Arup, E-mail: arup@unt.edu [Department of Physics, University of North Texas, Denton, Texas 76203 (United States); Pereira, Sérgio M. S. [Department of Physics, CICECO, Universidade de Aveiro, 3810-193 Aveiro (Portugal); Watson, Ian M. [Institute of Photonics, University of Strathclyde, Wolfson Centre, 106 Rottenrow East, Glasgow G4 0NW (United Kingdom)

    2014-09-01

    Surface plasmon enhanced GaN and InGaN quantum wells (QWs) show promise for use as room-temperature light emitters. The effectiveness of the plasmon enhancement, however, is limited by the strong electron/hole and longitudinal optical phonon coupling found in the III-V nitrides. The electron-phonon coupling within semiconductor QWs has been modified using silver nanoparticles embedded within the QWs. Direct evidence is provided for this change via confocal Raman spectroscopy of the samples. This evidence is augmented by Angle-dependent photoluminescence experiments which show the alteration of the electron-phonon coupling strength through measurement of the emitted phonon replicas. Together these demonstrate a direct modification of carrier-phonon interactions within the system, opening up the possibility of controlling the coupling strength to produce high-efficiency room-temperature light emitters.

  11. Inelastic Scattering in STEM for Studying Structural and Electronic Properties of Chalcogenide-Based Semiconductor Nanocrystals

    Science.gov (United States)

    Gunawan, Aloysius Andhika

    Transmission electron microscopy (TEM) relies upon elastic and inelastic scattering signals to perform imaging and analysis of materials. TEM images typically contain contributions from both types of scattering. The ability to separate the contributions from elastic and inelastic processes individually through energy filter or electron energy loss spectroscopy (EELS) allows unique analysis that is otherwise unachievable. Two prominent types of inelastic scattering probed by EELS, namely plasmon and core-loss excitations, are useful for elucidating structural and electronic properties of chalcogenide-based semiconductor nanocrystals. The elastic scattering, however, is still a critical part of the analysis and used in conjunction with the separated inelastic scattering signals. The capability of TEM operated in scanning mode (STEM) to perform localized atomic length scale analysis also permits the understanding of the nanocrystals unattainable by other techniques. Despite the pivotal role of inelastic scatterings, their contributions for STEM imaging, particularly high-angle annular dark field STEM (HAADF-STEM), are not completely understood. This is not surprising since it is currently impossible to experimentally separate the inelastic signals contributing to HAADF-STEM images although images obtained under bright-field TEM mode can be analyzed separately from their scattering contributions using energy-filtering devices. In order to circumvent such problem, analysis based on simulation was done. The existing TEM image simulation algorithm called Multislice method, however, only accounts for elastic scattering. The existing Multislice algorithm was modified to incorporate (bulk or volume) plasmon inelastic scattering. The results were verified based on data from convergent-beam electron diffraction (CBED), electron energy loss spectroscopy (EELS), and HAADF-STEM imaging as well as comparison to experimental data. Dopant atoms are crucial factors which control

  12. Electronic Structure and Optical Properties of the Lonsdaleite Phase of Si, Ge and diamond

    OpenAIRE

    De, Amrit; Pryor, Craig E.

    2012-01-01

    Crystalline semiconductors may exist in different polytypic phases with significantly different electronic and optical properties. In this paper, we calculate the electronic structure and optical properties of diamond, Si and Ge in the lonsdaleite (hexagonal-diamond) phase. We use an empirical pseudopotentials method based on transferable model potentials, including spin-orbit interactions. We obtain band structures, densities of states and complex dielectric functions calculated in the dipol...

  13. Electronic Properties of Antiperovskite Materials from State-of-the-Art Density Functional Theory

    OpenAIRE

    Bilal, M.; Jalali-Asadabadi, S.; Ahmad, Rashid; Ahmad, Iftikhar

    2015-01-01

    We present a review on the research developments on the theoretical electronic properties of the antiperovskite materials. The antiperovskite materials have perovskite type structure with the positions of cations and anions interchanged. The electronic structures are used to explain different physical properties of materials; therefore it is crucial to understand band structures and densities of states of materials for their effective use in technology. The theoretical results of ...

  14. Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide

    Science.gov (United States)

    2015-06-01

    of Boron Suboxide by Amol B Rahane, Jennifer S Dunn, and Vijay Kumar Approved for public release; distribution unlimited...Laboratory Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide by Amol B Rahane and Vijay Kumar Dr...SUBTITLE Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  15. A comparative computational study of the electronic properties of planar and buckled silicene

    OpenAIRE

    Behera, Harihar; Mukhopadhyay, Gautam

    2012-01-01

    Using full potential density functional calculations within local density approximation (LDA), we report our investigation of the structural electronic properties of silicene (the graphene analogue of silicon), the strips of which has been synthesized recently on Ag(110) and Ag(100) surfaces. An assumed planar and an optimized buckled two dimensional (2D) hexagonal structures have been considered for comparisons of their electronic properties. Planar silicene shows a gapless band structure an...

  16. Protonated serotonin: Geometry, electronic structures and photophysical properties

    Science.gov (United States)

    Omidyan, Reza; Amanollahi, Zohreh; Azimi, Gholamhassan

    2017-07-01

    The geometry and electronic structures of protonated serotonin have been investigated by the aim of MP2 and CC2 methods. The relative stabilities, transition energies and geometry of sixteen different protonated isomers of serotonin have been presented. It has been predicted that protonation does not exhibit essential alteration on the S1 ← S0 electronic transition energy of serotonin. Instead, more complicated photophysical nature in respect to its neutral analogue is suggested for protonated system owing to radiative and non-radiative deactivation pathways. In addition to hydrogen detachment (HD), hydrogen/proton transfer (H/PT) processes from ammonium to indole ring along the NH+⋯ π hydrogen bond have been predicted as the most important photophysical consequences of SERH+ at S1 excited state. The PT processes is suggested to be responsible for fluorescence of SERH+ while the HD driving coordinate is proposed for elucidation of its nonradiative deactivation mechanism.

  17. Determination of electronic properties of nanostructures using reflection electron energy loss spectroscopy: Nano-metalized polymer as case study

    Energy Technology Data Exchange (ETDEWEB)

    Deris, Jamileh [Department of Physics, Yasouj University, Yasouj 75918-74831 (Iran, Islamic Republic of); Hajati, Shaaker, E-mail: Hajati@mail.yu.ac.ir [Department of Physics, Yasouj University, Yasouj 75918-74831 (Iran, Islamic Republic of); Tougaard, Sven [Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, 5230 Odense M (Denmark); Zaporojtchenko, Vladimir [Lehrstuhl fur Materialverbunde, Technische Fakultat der CAU, Kaiserstr 2, D-24143 Kiel (Germany)

    2016-07-30

    Highlights: • Application of reflection electron energy loss spectroscopy. • Determination of electron inelastic cross section of Nano-metalized Polymer. • Determination of energy loss function of Nano-metalized Polymer. • Determination of electron inelastic mean free path of Nano-metalized Polymer. • Determination of surface excitation parameters of Nano-metalized Polymer. - Abstract: In this work, Au was deposited with nominal effective thickness of 0.8 nm on polystyrene (PS) at room temperature. According to previous study, using XPS peak shape analysis [S. Hajati, V. Zaporojtchenko, F. Faupel, S. Tougaard, Surf. Sci. 601 (2007) 3261–3267], Au nanoparticles (Au-NPs) of sizes 5.5 nm were formed corresponding to such effective thickness (0.8 nm). Then the sample was annealed to 200 °C, which is far above the glass transition of PS. At this temperature, the Au-NPs were diffused within the depth 0.5 nm–6.5 nm as found using nondestructive XPS peak shape analysis. Electrons with primary energy 500 eV were used because the electronic properties will then be probed in utmost surface (∼1 IMFP range of depths that is 1.8 nm for PS). By using QUEELS software, theoretical and experimental electron inelastic cross section, energy loss function, electron inelastic mean free path and surface excitation parameters were obtained for the sample. The information obtained here, does not rely on any previously known information on the sample. This means that the method, applied here, is suitable for the determination of the electronic properties of new and unknown composite nanostructures.

  18. influence of the substitution on the electronic properties of perylene ...

    African Journals Online (AJOL)

    Preferred Customer

    ABSTRACT. Geometries of the substituted perylene-3,4:9,10-bis(dicarboximides) (PDI) and their radical anions have been optimized at the B3LYP/6-31G** level of theory. The adiabatic and vertical electron affinities have been computed at the B3LYP/6-31+G*//B3LYP/6-31G** level. Substitution of the PDI with COOCF3.

  19. Electronic structure and optical properties of thorium monopnictides

    Indian Academy of Sciences (India)

    Unknown

    ASA) including the combined correction terms. The calculated electronic DOS of ThSb has been compared with the available experimental data and we find a good agreement. The calculated optical conductivity for. ThP and ThAs is increasing monotonically, while for ThSb a sharp peak has been found at 6⋅⋅5 eV. Unfortu ...

  20. Local electronic properties of graphene flakes on noble metal surfaces

    OpenAIRE

    Leicht, Philipp

    2015-01-01

    This thesis examines possible routes for the preparation of graphene nanostructures on metal substrates and performs structural and electronic characterizations using scanning tunneling microcopy and spectroscopy. Investigations of graphene nanostructures necessitate the use of a suitable graphene-substrate combination, which allows for a controlled in situ preparation of small and well-shaped graphene nanostructures. The choice of a graphene-substrate combination with weak interaction in or...

  1. Electronic and chemical properties of graphene-based structures:

    DEFF Research Database (Denmark)

    Vanin, Marco

    In the present thesis several aspects of graphene-based structures have been investigated using density functional theory calculations to solve the electronic structure problem. A review of the implementation of a localized basis-set within the projector augmented wave method - the way of describ......In the present thesis several aspects of graphene-based structures have been investigated using density functional theory calculations to solve the electronic structure problem. A review of the implementation of a localized basis-set within the projector augmented wave method - the way...... of describing the core electrons employed - is also presented. The investigation of the binding of graphene on metallic model surfaces is presented comparing the results from traditional exchange and correlation functionals to the results obtained with a new type of non-local functional, which includes van der...... are easier to remove and therefore only zigzag edges are left. Finally, functionalized graphene has been investigated as catalyst for the electrochemical reduction of CO2 to chemical fuels and comparisons are made with traditional transition-metal surfaces. The investigated porphyrin-like structures...

  2. TECHNIQUES FOR THE STUDY OF THE ELECTRONIC PROPERTIES.

    Energy Technology Data Exchange (ETDEWEB)

    FERNANDEZ-GARCIA, M.; RODRIGUEZ, J.A.

    2006-06-30

    The electronic structure of a solid is affected by size and altered from the continuous electronic levels forming a band, characteristic of bulk or microsized solids, to discrete-like or quantized levels. This is drastically observed when the particle size goes down to the nano-meter range and is the origin of the so-called ''quantum confinement'' terminology referring to this phenomenon. From a solid state point of view, electronic states of confined materials can be considered as being a superposition of bulk-like states with a concomitant increase of the oscillator strength. The valence/conduction band-width and position observables of a solid oxide are functions of the crystal potential and this, in turn, is perturbed by effect of the size in two ways; a short-range effect induced by the presence of ions with a different coordination number and bond distance, and a large-range one, induced by changes in the Madelung potential of the oxide. Theoretical analyses for oxides show a redistribution of charge when going from large periodic structures to small clusters which is roughly considered small for ionic solids and significantly important for covalent ones. Chapter 1 of this book describes the most recent theoretical frameworks employed to deal with these physical phenomena while here we will describe their influence in physico-chemical observables obtained by spectroscopical techniques.

  3. Effect of platinum-nanodendrite modification on the glucose-sensing properties of a zinc-oxide-nanorod electrode

    Energy Technology Data Exchange (ETDEWEB)

    Abdul Razak, Khairunisak, E-mail: khairunisak@usm.my [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); NanoBiotechnology Research & Innovation (NanoBRI), INFORMM, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Neoh, Soo Huan; Ridhuan, N.S.; Mohamad Nor, Noorhashimah [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

    2016-09-01

    Highlights: • Effect of PtNDs on ZnONRs/ITO glucose sensor was studied. • Well-defined PtNDs synthesis using 20 mM K{sub 2}PtCl{sub 4} produced good dispersion between nanodendrites with uniform particle size. • Nafion coating significantly improved the catalytic oxidation of glucose sensor. • Nafion/GO{sub x}/PtNDs/ZnONRs/ITO demonstrated better properties compared with Nafion/GO{sub x}/PtNDs/ITO and Nafion/GO{sub x}/ZnONRs/ITO electrodes. - Abstract: The properties of ZnO nanorods (ZnONRs) decorated with platinum nanodendrites (PtNDs) were studied. Various sizes of PtNDs were synthesized and spin coated onto ZnONRs, which were grown on indium–titanium–oxide (ITO) substrates through a low-temperature hydrothermal method. Scanning electron microscopy and X-ray diffraction analyses were conducted to analyze the morphology and structural properties of the electrodes. The effects of PtND size, glucose concentration, and Nafion amount on glucose-sensing properties were investigated. The glucose-sensing properties of electrodes with immobilized glucose oxidase (GO{sub x}) were measured using cyclic voltammetry. The bio-electrochemical properties of Nafion/GO{sub x}/42 nm PtNDs/ZnONRs/ITO glucose sensor was observed with linear range within 1–18 mM, with a sensitivity value of 5.85 μA/mM and a limit of detection of 1.56 mM. The results of this study indicate that PtNDs/ZnONRs/ITO has potential in glucose sensor applications.

  4. Structural and electronic properties of non-magnetic intermetallic ...

    Indian Academy of Sciences (India)

    heavy Fermion behaviour [3,4], half-metallic properties [5,6], mixed valent behaviour in Eu, Yb and Ce compounds [7–12], giant magnetoresistance [13] superconductivity [8,14], etc. Approximately 50 hexagonal RETX compounds crystal- lize in the LiGaGe structure, which can be thought of as a. REn+ ion stuffing a wurtzite ...

  5. DFT study on structure, electronic properties, and reactivity of cis ...

    Indian Academy of Sciences (India)

    bases (HSAB) principle. HSAB principle states that,. 'hard acids prefer to coordinate with hard bases and soft acids prefer to coordinate with soft bases for both their thermodynamic and kinetic properties'.24,25. The relationship between OC–Fe–CO bond angles and backbonding to CO for the isomers discussed above.

  6. Density functional study of : Electronic and optical properties

    Indian Academy of Sciences (India)

    K C Bhamu

    2017-06-20

    Jun 20, 2017 ... the refractive index in zero frequency limits is 2.42. The absorption coefficient predicts the applicability of AgScO2 in solar cells and flat panel liquid crystal display as a transparent top window layer. Keywords. Density functional theory; band structure; optical properties. PACS Nos 71.15.Mb; 71.20.−b; 78.20.

  7. Frustrated Magnetism and Electronic Properties of Hollandite Oxide Materials

    Science.gov (United States)

    Larson, Amber Marie

    Microporous transition metal oxides with the hollandite structure type have been prepared by standard solid-state techniques with varying compositions. With a nominal formula of Ax M8O16 and a framework of edge and corner-sharing MO6 octahedra, hollandites feature a pseudo-one dimensional tunnel occupied loosely by cation A. The metastability of these open-framework materials, combined with the ability of accommodating a variety of redox-active transition metals leads to unique and indispensable properties. Inherent to the triangular connectivity of the M cations in the hollandite framework, these materials frequently exhibit frustrated magnetic behavior. This thesis demonstrates that it is possible to significantly affect the magnetic and transport properties of these microporous materials through tuning of their chemical compositions. We have shown that it is possible to synthesize polycrystalline and single crystal hollandite materials under ambient conditions utilizing salt flux techniques. Our efforts to characterize the structure-property relationships provide some of the first magnetic structure determinations of these complex frameworks. The interesting behavior of these materials is a result of the interplay between charge, orbital, and spin degrees of freedom. This work shows that the hollandite framework is quite versatile, leading to the real possibility of tuning the material properties to achieve desired effects and opening up many potential applications for these microporous oxides.

  8. Electronic absorption spectra and nonlinear optical properties of ...

    Indian Academy of Sciences (India)

    Administrator

    New Chemistry Unit,. Jawaharlal Nehru Center for Advanced Scientific Research Jakkur Campus, Bangalore 560 064 e-mail: pati@jncasr.ac.in. Abstract. We have investigated the structural aspects of several carbon dioxide molecular aggregates and their spectroscopic and nonlinear optical properties within the quantum ...

  9. The intriguing electronic and optical properties modulation of hydrogen and fluorine codecorated silicene layers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Qun; Tan, Chunjian [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Opto-Electronic Engineering, Chongqing University, 400044 Chongqing (China); Meng, Ruishen; Jiang, Junke; Liang, Qiuhua; Sun, Xiang [Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Opto-Electronic Engineering, Chongqing University, 400044 Chongqing (China); Yang, Daoguo [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Chen, Xianping, E-mail: xianpingchen@cqu.edu.cn [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Opto-Electronic Engineering, Chongqing University, 400044 Chongqing (China)

    2017-03-15

    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.

  10. The Modification of Sodium Polyacrylate Water Solution Cooling Properties by AL2O3

    Directory of Open Access Journals (Sweden)

    Wojciech Gęstwa

    2010-01-01

    results allowus to conclude that by the addition of solid nanoparticles to water based quenching media their cooling properties which are not inferior to mineral oils and polymer water solutions can be shaped.

  11. Lorentz Covariance of Dirac Electrons in Solids: Dielectric and Diamagnetic Properties

    Science.gov (United States)

    Maebashi, Hideaki; Ogata, Masao; Fukuyama, Hidetoshi

    2017-08-01

    We study the electrodynamics of Dirac electrons in solids (e.g., bismuth) by comparing it with quantum electrodynamics (QED). It is shown that Lorentz covariance associated with the Dirac electrons in solids results in a remarkable correlation between the dielectric and diamagnetic properties, leading to a significant enhancement in the permittivity directly linked to the well-known phenomenon of large diamagnetism.

  12. Electronic properties of diphenyl-s-tetrazine and some related oligomers. An spectroscopic and theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Moral, Monica; Garcia, Gregorio [Departamento de Quimica Fisica y Analitica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain); Penas, Antonio [Departamento de Quimica Inorganica y Organica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain); Garzon, Andres; Granadino-Roldan, Jose M. [Departamento de Quimica Fisica y Analitica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain); Melguizo, Manuel [Departamento de Quimica Inorganica y Organica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain); Fernandez-Gomez, Manuel, E-mail: mfg@ujaen.es [Departamento de Quimica Fisica y Analitica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain)

    2012-10-26

    Highlights: Black-Right-Pointing-Pointer We study properties of Ph{sub 2}Tz and (PhTz){sub n}Ph as candidates for organic electronics. Black-Right-Pointing-Pointer The synthesis of Ph{sub 2}Tz was performed through a modified Pinner-type reaction. Black-Right-Pointing-Pointer IR/Raman spectra allowed to conclude that Ph{sub 2}Tz is nearly planar in liquid phase. Black-Right-Pointing-Pointer Electronic structure was studied by UV-Vis/TD-DFT methods in different solvents. Black-Right-Pointing-Pointer Bandgap, E{sub LUMO}, electron mobility predict some n-type character for limit polymer. -- Abstract: This work presents a theoretical and spectroscopic study on the electronic and structural properties of the diphenyl-s-tetrazine molecule (Ph{sub 2}Tz) and some oligomeric derivatives. Ph{sub 2}Tz was synthesized through a variation of Pinner-type reaction which uses N-acetylcysteine as catalyst. Insight into the structure and electronic properties of the title compound was obtained through IR, Raman, UV-Vis spectra in different solvents, and theoretical calculations. Theoretical studies have been extended to different n-mers derivatives up to an ideal molecular wire through the oligomeric approximation, predicting this way electronic properties such as LUMO energy levels, electron affinity and reorganization energy in order to assess their possible applications in molecular electronics.

  13. Electronic properties and orbital-filling mechanism in Rb-intercalated copper phthalocyanine

    NARCIS (Netherlands)

    Evangelista, F.; Gotter, R.; Mahne, N.; Nannarone, S.; Ruocco, A.; Rudolf, P.

    2008-01-01

    The evolution of the electronic properties of a thin film of copper phthalocyanine deposited on Al(100) and progressively intercalated with rubidium atoms was followed by photoemission and X-ray absorption spectroscopies. Electron donation from the Rb atoms to the C32H16N8Cu molecules results in the

  14. Electronic structure and magnetic properties of selected lanthanide and actinide intermetallic Laves-phase alloys

    DEFF Research Database (Denmark)

    Eriksson, Olle; Johansson, Börje; Brooks, M. S. S.

    1989-01-01

    The electronic structure and magnetic properties of some yttrium and uranium Laves-phase pseudobinary alloys with 3d elements have been calculated. The calculations were done by simulating the electronic structure of the alloy by that of an ordered compound with the same stoichiometry. In general...

  15. Mechanical properties and the electronic structure of transition metal alloys. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Arsenault, R.J.; Drew, H.D.

    1977-01-01

    This interdiscipline research program was undertaken in an effort to investigate the relationship between the mechanical strength of Mo-based alloys with their electronic structure. Electronic properties of these alloys were examined through optical studies, and the classical solid solution strengthening mechanisms were considered, based on size and molecular differences to determine if these mechanisms could explain the hardness data.

  16. Mechanical properties and the electronic structure of transition of metal alloys

    Science.gov (United States)

    Arsenault, R. J.; Drew, H. D.

    1977-01-01

    This interdiscipline research program was undertaken in an effort to investigate the relationship between the mechanical strength of Mo based alloys with their electronic structure. Electronic properties of these alloys were examined through optical studies, and the classical solid solution strengthening mechanisms were considered, based on size and molecular differences to determine if these mechanisms could explain the hardness data.

  17. Electron irradiation-induced mechanical property changes in reactor pressure vessel alloys

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, D.E.; Rehn, L.E. [Argonne National Lab., IL (United States); Odette, G.R.; Lucas, G.E. [California Univ., Santa Barbara, CA (United States). Dept. of Mechanical Engineering

    1995-11-01

    High-energy electrons were used to study tensile property changes in simple Fe-Cu and Fe-Cu-Mn alloys irradiated at 288C. A comparison was made with neutron irradiation data on the same alloys. An apparent effect of alloy chemistry was observed in which the presence of Mn affected embrittlement differently for electron and neutron irradiation. Comparison of previous experimental studies with the present experimental results indicates that electrons may be more efficient than fast neutrons at producing embrittlement.

  18. Effect of Holstein phonons on the electronic properties of graphene

    Energy Technology Data Exchange (ETDEWEB)

    Stauber, T [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); Peres, N M R [Center of Physics and Department of Physics, University of Minho, P-4710-057, Braga (Portugal)

    2008-02-06

    We obtain the self-energy of the electronic propagator due to the presence of Holstein polarons within the first Born approximation. This leads to a renormalization of the Fermi velocity of 1%. We further compute the optical conductivity of the system at the Dirac point and at finite doping within the Kubo formula. We argue that the effects due to Holstein phonons are negligible and that the Boltzmann approach, which does not include inter-band transitions and can thus not treat optical phonons due to their high energy of {Dirac_h}{omega}{sub 0} {approx} 0.1-0.2 eV, remains valid.

  19. Vacuum ultraviolet electronic properties of liquids. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Painter, L.R.

    1980-06-01

    A program to study the electronic structure of liquids over the energy range from 2 to 25 eV was carried out from November, 1968 to October 1980. These studies basically consisted of measuring the reflectance, transmittance, photoionization, and photoemission of liquids in the vacuum ultraviolet spectral region as a function of angle of incidence and photon energy. Such measurements are analyzed to yield the optical and dielectric functions of the liquid as functions of photon energy. A summary of the progress in the program is presented. (GHT)

  20. Electric field gradient and electronic properties of crown thioether compounds

    Energy Technology Data Exchange (ETDEWEB)

    Camargo Dalmatti Alves Lima, Filipe, E-mail: flima@if.usp.br; Rodrigues do Nascimento, Rafael; Brown Goncalves, Marcos [Universidade de Sao Paulo, Instituto de Fisica (Brazil); Cottenier, Stefaan [Ghent University, Center for Molecular Modeling (Belgium); Caldas, Marilia Junqueira; Petrilli, Helena Maria [Universidade de Sao Paulo, Instituto de Fisica (Brazil)

    2010-04-15

    We compare published TDPAC experiments on {sup 111}Cd in the crown thioether C{sub 6}H{sub 12}S{sub 3}AgCl with ab-initio electronic structure calculations performed within the framework of the Density Functional Theory using the Projector Augmented Wave method. We conclude from this comparison that the Cd atom at the very moment of the TDPAC experiment is positively charged, and we point out to a methodological difference between reproducing experimental electric-field gradients in molecules versus solid metals.

  1. Microstructure Modifications and Associated Corrosion Improvements in GH4169 Superalloy Treated by High Current Pulsed Electron Beam

    OpenAIRE

    Su, Yichang; Li, Guangyu; Niu, Liyuan; Yang, Shengzhi; Cai, Jie; Guan, Qingfeng

    2015-01-01

    The surface of the nickel-based superalloy GH4169 was subjected to high-current pulsed electron beam (HCPEB) treatment. The microstructural morphologies of the material were analysed by means of optical microscope (OP), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results reveal that the irradiated surface was remelted and many craters were formed. The density of craters decreased with the increment of HCPEB pulses. After 20-pulsed HCPEB irradiation, nan...

  2. Density functional study of AgScO 2: Electronic and optical properties

    Indian Academy of Sciences (India)

    2017-06-20

    Jun 20, 2017 ... Electronic properties deal with energy bands and density of states (DOSs), while optical properties describe refractive index and absorption coefficient.The energy bands are interpreted in terms of DOSs. The computed value of band gap is in agreement with that reported in the literature. Our results predict ...

  3. Theory of the electronic and structural properties of solid state oxides

    Energy Technology Data Exchange (ETDEWEB)

    Chelikowsky, J.R.

    1990-01-01

    Studies on electronic and structural properties of solid state oxides continued. This quarter, studies have concentrated on silica. Progress is discussed in the following sections: interatomic potentials and the structural properties of silica; chemical reactivity and covalent/metallic bonding on Si clusters; and surface and thermodynamic interatomic forces fields for silicon. 64 refs., 20 figs., 5 tabs. (CBS)

  4. Electronic properties of core-shell nanowire resonant tunneling diodes

    Science.gov (United States)

    2014-01-01

    The electronic sub-band structure of InAs/InP/InAs/InP/InAs core-shell nanowire resonant tunneling diodes has been investigated in the effective mass approximation by varying the core radius and the thickness of the InP barriers and InAs shells. A top-hat, double-barrier potential profile and optimal energy configuration are obtained for core radii and surface shells >10 nm, InAs middle shells barriers. In this case, two sub-bands exist above the Fermi level in the InAs middle shell which belongs to the m = 0 and m = 1 ladder of states that have similar wave functions and energies. On the other hand, the lowest m = 0 sub-band in the core falls below the Fermi level but the m = 1 states do not contribute to the current transport since they reside energetically well above the Fermi level. We compare the case of GaAs/AlGaAs/GaAs/AlGaAs/GaAs which may conduct current with smaller applied voltages due to the larger effective mass of electrons in GaAs and discuss the need for doping. PMID:25288912

  5. Mn/Cu(111): alloying, electronic and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kralj, Marko; Krajinovic, Sanja; Pervan, Petar [Institute of Physics, Bijenicka 46, HR-10000 Zagreb (Croatia); Breinlich, Christian; Becker, Conrad; Wandelt, Klaus [Institut fuer Physikalische und Theoretische Chemie, Universitaet Bonn, Wegelerstr. 12, 53115 Bonn (Germany)

    2008-07-01

    Spin-split two-dimensional (2D) states which can, for instance, be realized in magnetically stabilized surface alloys, are of immense technological interest for new spintronic devices. For example, Mn/Cu(100)-c(2 x 2) is considered as a prototypical 2D magnetic alloy. We have studied the interaction of manganese with a Cu(111) surface using different surface sensitive techniques. While the electronic structure and perfectness of a periodic root-3 alloy were characterized by ARPES and LEED, the electronic characteristics of the surface occupied by single Mn atoms were studied by STM and STS. STS at low temperature indicates no observable Kondo-effect for single Mn atoms. Increasing the temperature, leads to incorporation of Mn atoms into and below the surface layer and the appearance of very specific surface defect structures. Formation of this surface alloy first leads to the quenching of the Cu(111) surface state. Only after annealing higher than 500 K, when Mn atoms are incorporated several layers deep, leading to complex changes in the LEED pattern, ARPES indicates the appearance of a modified surface state. All this seems to indicate none or very weak magnetic and spin-splitting effects for Mn/Cu(111).

  6. Influence of electron irradiation on the structural and thermal properties of silk fibroin films

    Energy Technology Data Exchange (ETDEWEB)

    Asha, S.; Sangappa,; Sanjeev, Ganesh, E-mail: ganeshanjeev@rediffmail.com [Department of Studies in Physics, Mangalore University, Mangalagangotri, Mangalore - 574 199 (India)

    2015-06-24

    Radiation-induced changes in Bombyx mori silk fibroin (SF) films under electron irradiation were investigated and correlated with dose. SF films were irradiated in air at room temperature using 8 MeV electron beam in the range 0-150 kGy. Various properties of the irradiated SF films were studied using X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Electron irradiation was found to induce changes in the physical and thermal properties, depending on the radiation dose.

  7. The effect of electron induced hydrogenation of graphene on its electrical transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Sung Oh [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); Teizer, Winfried [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); WPI-Advanced Institute for Materials Research, Tohoku University, Sendai (Japan)

    2013-07-22

    We report a deterioration of the electrical transport properties of a graphene field effect transistor due to energetic electron irradiation on a stack of Poly Methyl Methacrylate (PMMA) on graphene (PMMA/graphene bilayer). Prior to electron irradiation, we observed that the PMMA layer on graphene does not deteriorate the carrier transport of graphene but improves its electrical properties instead. As a result of the electron irradiation on the PMMA/graphene bilayer, the Raman “D” band appears after removal of PMMA. We argue that the degradation of the transport behavior originates from the binding of hydrogen generated during the PMMA backbone secession process.

  8. Computation and analysis of the electron transport properties for nitrogen and air inductively-coupled plasmas

    Science.gov (United States)

    Yu, Minghao; Kihara, Hisashi; Abe, Ken-ichi; Takahashi, Yusuke

    2015-06-01

    A relatively simple method for calculating accurately the third-order electron transport properties of nitrogen and air thermal plasmas is presented. The electron transport properties, such as the electrical conductivity and the electron thermal conductivity, were computed with the best and latest available collision cross-section data in the temperature and pressure ranges of T = 300 - 15000 K and p = 0.01 - 1.0 atm, respectively. The results obtained under the atmospheric pressure condition showed good agreements with the experimental and the high-accuracy theoretical results. The presently-introduced method has good application potential in numerical simulations of nitrogen and air inductively-coupled plasmas.

  9. Modification of wheat starch with succinic acid/acetic anhydride and azelaic acid/acetic anhydride mixtures I. Thermophysical and pasting properties.

    Science.gov (United States)

    Subarić, Drago; Ačkar, Durđica; Babić, Jurislav; Sakač, Nikola; Jozinović, Antun

    2014-10-01

    The aim of this research was to investigate the influence of modification with succinic acid/acetic anhydride and azelaic acid/acetic anhydride mixtures on thermophysical and pasting properties of wheat starch. Starch was isolated from two wheat varieties and modified with mixtures of succinic acid and acetic anhydride, and azelaic acid and acetic anhydride in 4, 6 and 8 % (w/w). Thermophysical, pasting properties, swelling power, solubility and amylose content of modified starches were determined. The results showed that modifications with mixtures of afore mentioned dicarboxylic acids with acetic anhydride decreased gelatinisation and pasting temperatures. Gelatinisation enthalpy of Golubica starch increased, while of Srpanjka starch decreased by modifications. Retrogradation after 7 and 14 day-storage at 4 °C decreased after modifications of both starches. Maximum, hot and cold paste viscosity of both starches increased, while stability during shearing at high temperatures decreased. % setback of starches modified with azelaic acid/acetic anhydride mixture decreased. Swelling power and solubility of both starches increased by both modifications.

  10. Electronic and optical properties of 2D graphene-like ZnS: DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Lashgari, Hamed [Department of Physics, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Boochani, Arash, E-mail: arash_bch@yahoo.com [Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Shekaari, Ashkan [Department of Physics, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Solaymani, Shahram [Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Sartipi, Elmira [Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Mendi, Rohollah Taghavi [Department of Physics, Mashhad Branch, Islamic Azad University, Mashhad (Iran, Islamic Republic of)

    2016-04-30

    Graphical abstract: - Highlights: • DFT has been applied to investigate the optical properties of 2D-ZnS and 3D-ZnS. • The electronic and the optical properties of 3D-ZnS and 2D-ZnS are compared. • At visible range of energies the transparency of 2D-ZnS is more than the 3D. - Abstract: Density-functional theory has been applied to investigate the electronic and optical properties of graphene-like two-dimensional ZnS in the (0001) direction of its Wurtzite phase. A comparison with 3D-ZnS has been carried out within the PBE- and EV-GGA. The electronic properties of 2D- and 3D-ZnS have been derived by the examination of the electronic band structures and density of states. The optical properties have been determined through the study of the dielectric function, reflectivity, electron loss function, refractive and extinction indices, the absorption index and optical conductivity. It is found that the transparency of 2D-ZnS is greater than the 3D over the visible range. A thorough study of the dielectric function has been performed so that the peaks and the transition bands have been specified. The electron loss function demonstrates that the plasmonic frequency for 2D- and 3D-ZnS is accrued at 11.22 and 19.93 eV within the PBE-GGA, respectively.

  11. Controlling the electronic properties of the graphene nanoflakes by BN impurities

    Science.gov (United States)

    Mohammed, Mohammed H.

    2018-01-01

    Electronic properties of the graphene nanoflakes (GNFs) can be controlled by using chemical doping method. First-principle of the density functional theory (DFT) method, which is implemented in the Gaussian 09W program are used to investigate the electronic properties, such as electronic band gap, DOS, total energy, dipole moment, HOMO, and LOMO energies of the GNFs with and without various concentrations of the BN impurities in various sites. There are very significant results. My founding results show that these properties of the GNFs depend on the concentrations of BN impurities and the geometrical pattern of the BN impurities in the GNFs. By increasing the distance between these impurities, the electronic band gap and the shape of the DOS are reduced and altered, respectively. So, the results offer that the electronic band gap value depends on the concentrations of BN impurities and sites of these impurities in the GNFs. The electronic dipole moments value is increased by increased the concentrations of the BN impurities. All structures became more stable due to the total energy is increased, excepted B, BN and B2N impurities, which is reduced and make GNFs structure unstable. Then, GNFs can be used in various applications because the electronic properties of the GNFs are controlled and modified with BN impurities.

  12. Information Functional Theory: Electronic Properties as Functionals of Information for Atoms and Molecules.

    Science.gov (United States)

    Zhou, Xia-Yu; Rong, Chunying; Lu, Tian; Zhou, Panpan; Liu, Shubin

    2016-05-26

    How to accurately predict electronic properties of a Columbic system with the electron density obtained from experiments such as X-ray crystallography is still an unresolved problem. The information-theoretic approach recently developed in the framework of density functional reactivity theory is one of the efforts to address the issue. In this work, using 27 atoms and 41 molecules as illustrative examples, we present a study to demonstrate that one is able to satisfactorily describe such electronic properties as the total energy and its components with information-theoretic quantities like Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, and Onicescu information energy. Closely related to the earlier attempt of expanding density functionals using simple homogeneous functionals, this work not only confirms Nagy's proof that Shannon entropy alone should contain all the information needed to adequately describe an electronic system but also provides a feasible pathway to map the relationship between the experimentally available electron density and various electronic properties for Columbic systems such as atoms and molecules. Extensions to other electronic properties are straightforward.

  13. Study on the Electronic Transport Properties of Zigzag GaN Nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Li Enling; Wang Xiqiang; Hou Liping; Zhao Danna; Dai Yuanbin [Sciences School, Xi' an University of Technology, Xi' an, China 710054 (China); Wang Xuewen [Electronic Information Science and Technology, Northwest University, Xi' an, China 710068 (China)

    2011-02-01

    The electronic transport properties of zigzag GaN nanotubes (n, 0) (4 {<=} n {<=} 9) have been calculated using the density functional theory and non-equilibrium Green's functions method. Firstly, the density functional theory (DFT) is used to optimize and calculate the electronic structure of GaNNTs (n, 0) (4{<=}n{<=}9). Secondly, DFT and non-equilibrium Green function (NEGF) method are also used to predict the electronic transport properties of GaNNTs two-probe system. The results showed: there is a corresponding relation between the electronic transport properties and the valley of state density of each GaNNT. In addition, the volt-ampere curve of GaNNT is approximately linear.

  14. Towards Liquid Chromatography Time-Scale Peptide Sequencing and Characterization of Post-Translational Modifications in the Negative-Ion Mode Using Electron Detachment Dissociation Tandem Mass Spectrometry

    DEFF Research Database (Denmark)

    Kjeldsen, Frank; Hørning, Ole B; Jensen, Søren S

    2008-01-01

    Electron detachment dissociation (EDD) of peptide poly-anions is gentle towards post-translational modifications (PTMs) and produces predictable and interpretable fragment ion types (a., x ions). However, EDD is considered an inefficient fragmentation technique and has not yet been implemented...... in large-scale peptide characterization strategies. We successfully increased the EDD fragmentation efficiency (up to 9%), and demonstrate for the first time the utility of EDD-MS/MS in liquid chromatography time-scale experiments. Peptides and phosphopeptides were analyzed in both positive- and negative...

  15. Localization of Post-Translational Modifications in Peptide Mixtures via High-Resolution Differential Ion Mobility Separations Followed by Electron Transfer Dissociation

    Science.gov (United States)

    Baird, Matthew A.; Shvartsburg, Alexandre A.

    2016-12-01

    Precise localization of post-translational modifications (PTMs) on proteins and peptides is an outstanding challenge in proteomics. While electron transfer dissociation (ETD) has dramatically advanced PTM analyses, mixtures of localization variants that commonly coexist in cells often require prior separation. Although differential or field asymmetric waveform ion mobility spectrometry (FAIMS) achieves broad variant resolution, the need for standards to identify the features has limited the utility of approach. Here we demonstrate full a priori characterization of variant mixtures by high-resolution FAIMS coupled to ETD and the procedures to systematically extract the FAIMS spectra for all variants from such data.

  16. Numerical analysis of the morphological and phase changes in the TiN/Al2O3 coating under high current electron beam modification

    Directory of Open Access Journals (Sweden)

    A.D. Pogrebnjak

    2013-01-01

    Full Text Available The modification of the surface structure of the hybrid coating TiN/Al2O3 with a low-energy high-current electron beam (NCEB is performed. The surface roughness is considered as a function of beam current. Surfaces of the obtained samples are investigated within the two-dimensional multifractal detrended fluctuation analysis (MF-DFA. The multifractal spectrum of the surface is calculated as a quantitative parameter of the roughness. It is shown that with the increase of the beam energy, the surface become more regular and uniform.

  17. Experimental Investigation of Charging Properties of Interstellar Type Silica Dust Grains by Secondary Electron Emissions

    Science.gov (United States)

    Tankosic, D.; Abbas, M. M.

    2013-01-01

    The dust charging by electron impact is an important dust charging processes in astrophysical and planetary environments. Incident low energy electrons are reflected or stick to the grains charging the dust grains negatively. At sufficiently high energies electrons penetrate the grains, leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Available classical theoretical models for calculations of SEE yields are generally applicable for neutral, planar, or bulk surfaces. These models, however, are not valid for calculations of the electron impact charging properties of electrostatically charged micron/submicron-size dust grains in astrophysical environments. Rigorous quantum mechanical models are not yet available, and the SEE yields have to be determined experimentally for development of more accurate models for charging of individual dust grains. At the present time, very limited experimental data are available for charging of individual micron-size dust grains, particularly for low energy electron impact. The experimental results on individual, positively charged, micron-size lunar dust grains levitated carried out by us in a unique facility at NASA-MSFC, based on an electrodynamic balance, indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (Abbas et al, 2010, 2012). In this paper, we discuss SEE charging properties of individual micron-size silica microspheres that are believed to be analogs of a class of interstellar dust grains. The measurements indicate charging of the 0.2m silica particles when exposed to 25 eV electron beams and discharging when exposed to higher energy electron beams. Relatively large size silica particles (5.2-6.82m) generally discharge to lower equilibrium potentials at both electron energies

  18. Structure and Electronic Properties of Transition Metal Doped Kaolinite Nanoclay

    Science.gov (United States)

    Fu, Liangjie; Yang, Huaming

    2017-06-01

    In this work, a series of transition metal (Cr, Mn, Fe, and Co) doped kaolinite nanoclays were investigated by density functional theory (DFT) calculations. The influence of metal doping on geometric structure and electronic structure of kaolinite was analyzed. The ferromagnetic (FM), antiferromagnetic (AFM), and nonmagnetic (NM) states of transition metal (TM) doped kaolinite structures were studied. The crystal volume, lattice parameters, bond length, charge, and spin were calculated by dispersion-corrected density functional theory (DFT-D2). The results indicated that Cr3+ and Fe3+ dopants showed more stable under AFM state, while Mn3+ preferred both AFM and FM states, and Co3+ dopant preferred NM state. Also, the transition metal doping could induce lattice volume expansion and some dopant states in the band gap.

  19. Electronic and magnetic properties of 3D transition-metal atom adsorbed arsenene

    Science.gov (United States)

    Liu, Ming-Yang; Chen, Qing-Yuan; Huang, Yang; Li, Ze-Yu; Cao, Chao; He, Yao

    2018-03-01

    To utilize arsenene as the electronic and spintronic material, it is important to enrich its electronic properties and induce useful magnetic properties in it. In this paper, we theoretically studied the electronic and magnetic properties of arsenene functionalized by 3D transition-metal (TM) atoms (TM@As). Although pristine arsenene is a nonmagnetic material, the dilute magnetism can be produced upon TM atoms chemisorption, where the magnetism mainly originates from TM adatoms. We find that the magnetic properties can be tuned by a moderate external strain. The chemisorption of 3D TM atoms also enriches the electronic properties of arsenene, such as metallic, half-metallic, and semiconducting features. Interestingly, we can classify the semiconducting feature into three types according to the band-gap contribution of spin channels. On the other hand, the chemisorption properties can be modified by introducing monovacancy defect in arsenene. Present results suggest that TM-adsorbed arsenene may be a promising candidate for electronic and spintronic applications.

  20. Substrate Effects on Electronic Properties of Atomic Chains

    Science.gov (United States)

    Yamada, Toshishige; Saini, Subhash (Technical Monitor)

    1998-01-01

    When the device size is reduced down to 0.07 micrometers, the number of dopant atoms in the channel will no longer be macroscopic, typically less than a hundred. A spatial distribution of these dopant atoms will fluctuate statistically from device to device even in identically designed devices, and this places a serious limitation for integration. It is, however, impractical to control dopant positions within atomic dimension. One fundamental solution to this problem is to create electronics with atomically precise, but preferably simple structures. Atomic chains, precise structures of adatoms created on an atomically regulated surface, are candidates for constituent components in future electronics. All the adatoms will be placed at designated positions on the substrate, and all the device structures will be precise, free from any deviations. It was predicted using the tight-binding calculation with universal parameters that silicon chains were metallic and magnesium chains were semiconducting regardless of the lattice spacing, and a possible doping method was also proposed. In these treatments, the substrate was assumed to serve as a non-interacting template holding the adatoms without a formation of chemical bonding with substrate atoms. However, this scheme may not be easy to implement experimentally. Adatoms will have to be fixed with a van der Waals force on the substrate, but the force is generally weak and an extremely low temperature environment has to be prepared to suppress their unwanted thermal displacement. It may be logical to seek a scheme to allow the adatoms to form chemical bonding with the substrate atoms and secure their positions. The substrate effects are studied in detail.