WorldWideScience

Sample records for thermal composite supernova

  1. Evolution of supernova remnants. III. Thermal waves

    International Nuclear Information System (INIS)

    Chevalier, R.A.

    1975-01-01

    The effect of heat conduction on the evolution of supernova remnants is investigated. A thermal wave, or electron conduction front, can travel more rapidly than a shock wave during the first thousand years of the remnant's evolution. A self-similar solution describing this phase has been found by Barenblatt. Numerical computations verify the solution and give the evolution past the thermal wave phase. While shell formation is not impeded, the interior density and temperature profiles are smoothed by the action of conduction

  2. Supernovae

    International Nuclear Information System (INIS)

    Petschek, A.

    1990-01-01

    This book offers papers incorporating the latest results and understanding about supernovae, including SN1987A. There are several chapters reviewing all the radio through infrared, visible, and ultraviolet to X-rays and gamma-rays but also neutrinos. Other chapters deal with the classification of supernovae, depending on their spectra and light curves. Three chapters treat supernovae theory, including an idea of a fractal burning front and another on the behavior of neutron stars

  3. Systematic thermal reduction of neutronization in core-collapse supernovae

    International Nuclear Information System (INIS)

    Fantina, A.F.; Donati, P.; Pizzochero, P.M.

    2009-01-01

    We investigate to what extent the temperature dependence of the nuclear symmetry energy can affect the neutronization of the stellar core prior to neutrino trapping during gravitational collapse. To this end, we implement a one-zone simulation to follow the collapse until β-equilibrium is reached and the lepton fraction remains constant. Since the strength of electron capture on the neutron-rich nuclei associated to the supernova scenario is still an open issue, we keep it as a free parameter. We find that the temperature dependence of the symmetry energy consistently yields a small reduction of deleptonization, which corresponds to a systematic effect on the shock wave energetics: the gain in dissociation energy of the shock has a small yet non-negligible value of about 0.4 foe (1 foe=10 51 erg) and this result is almost independent from the strength of nuclear electron capture. The presence of such a systematic effect and its robustness under changes of the parameters of the one-zone model are significant enough to justify further investigations with detailed numerical simulations of supernova explosions.

  4. Thermal Conductivity of Diamond Composites

    Directory of Open Access Journals (Sweden)

    Fedor M. Shakhov

    2009-12-01

    Full Text Available A major problem challenging specialists in present-day materials sciences is the development of compact, cheap to fabricate heat sinks for electronic devices, primarily for computer processors, semiconductor lasers, high-power microchips, and electronics components. The materials currently used for heat sinks of such devices are aluminum and copper, with thermal conductivities of about 250 W/(m·K and 400 W/(m·K, respectively. Significantly, the thermal expansion coefficient of metals differs markedly from those of the materials employed in semiconductor electronics (mostly silicon; one should add here the low electrical resistivity metals possess. By contrast, natural single-crystal diamond is known to feature the highest thermal conductivity of all the bulk materials studied thus far, as high as 2,200 W/(m·K. Needless to say, it cannot be applied in heat removal technology because of high cost. Recently, SiC- and AlN-based ceramics have started enjoying wide use as heat sink materials; the thermal conductivity of such composites, however, is inferior to that of metals by nearly a factor two. This prompts a challenging scientific problem to develop diamond-based composites with thermal characteristics superior to those of aluminum and copper, adjustable thermal expansion coefficient, low electrical conductivity and a moderate cost, below that of the natural single-crystal diamond. The present review addresses this problem and appraises the results reached by now in studying the possibility of developing composites in diamond-containing systems with a view of obtaining materials with a high thermal conductivity.

  5. Supernova neutrinos

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    In the first part of his in-depth article on the 1987 supernova, David Schramm of the University of Chicago and the NASA/Fermilab Astrophysics Centre reviewed the background to supernovae, the composition of massive stars and the optical history of SN 1987A, and speculated on what the 1987 remnant might be. In such a Type II supernova, gravitational pressure crushes the atoms of the star's interior producing neutron matter, or even a black hole, and releasing an intense burst of neutrinos. 1987 was the first time that physicists were equipped (but not entirely ready!) to intercept these particles, and in the second part of his article, David Schramm covers the remarkable new insights from the science of supernova neutrino astronomy, born on 23 February 1987

  6. Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. I: spectrum and chemical composition

    International Nuclear Information System (INIS)

    Blasi, Pasquale; Amato, Elena

    2012-01-01

    In this paper we investigate the effect of stochasticity in the spatial and temporal distribution of supernova remnants on the spectrum and chemical composition of cosmic rays observed at Earth. The calculations are carried out for different choices of the diffusion coefficient D(E) experienced by cosmic rays during propagation in the Galaxy. In particular, at high energies we assume that D(E)∝E δ , with δ = 1/3 and δ = 0.6 being the reference scenarios. The large scale distribution of supernova remnants in the Galaxy is modeled following the distribution of pulsars, with and without accounting for the spiral structure of the Galaxy. We find that the stochastic fluctuations induced by the spatial and temporal distribution of supernovae, together with the effect of spallation of nuclei, lead to mild but sensible violations of the simple, leaky-box-inspired rule that the spectrum observed at Earth is N(E)∝E −α with α = γ+δ, where γ is the slope of the cosmic ray injection spectrum at the sources. Spallation of nuclei, even with the small rates appropriate for He, may account for small differences in spectral slopes between different nuclei, possibly providing an explanation for the recent CREAM observations. For δ = 1/3 we find that the slope of the proton and helium spectra are ∼ 2.67 and ∼ 2.6 respectively (with fluctuations depending on the realization of source distribution) at energies around ∼ 1 TeV (to be compared with the measured values of 2.66±0.02 and 2.58±0.02). For δ = 0.6 the hardening of the He spectra is not observed. The stochastic effects discussed above cannot be found in ordinary propagation calculations, such as GALPROP, where these effects and the point like nature of the sources are not taken into account. We also comment on the effect of time dependence of the escape of cosmic rays from supernova remnants, and of a possible clustering of the sources in superbubbles. In a second paper we will discuss the implications of

  7. Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. I: spectrum and chemical composition

    Energy Technology Data Exchange (ETDEWEB)

    Blasi, Pasquale; Amato, Elena, E-mail: blasi@arcetri.astro.it, E-mail: amato@arcetri.astro.it [INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5 — 50125 Firenze (Italy)

    2012-01-01

    In this paper we investigate the effect of stochasticity in the spatial and temporal distribution of supernova remnants on the spectrum and chemical composition of cosmic rays observed at Earth. The calculations are carried out for different choices of the diffusion coefficient D(E) experienced by cosmic rays during propagation in the Galaxy. In particular, at high energies we assume that D(E)∝E{sup δ}, with δ = 1/3 and δ = 0.6 being the reference scenarios. The large scale distribution of supernova remnants in the Galaxy is modeled following the distribution of pulsars, with and without accounting for the spiral structure of the Galaxy. We find that the stochastic fluctuations induced by the spatial and temporal distribution of supernovae, together with the effect of spallation of nuclei, lead to mild but sensible violations of the simple, leaky-box-inspired rule that the spectrum observed at Earth is N(E)∝E{sup −α} with α = γ+δ, where γ is the slope of the cosmic ray injection spectrum at the sources. Spallation of nuclei, even with the small rates appropriate for He, may account for small differences in spectral slopes between different nuclei, possibly providing an explanation for the recent CREAM observations. For δ = 1/3 we find that the slope of the proton and helium spectra are ∼ 2.67 and ∼ 2.6 respectively (with fluctuations depending on the realization of source distribution) at energies around ∼ 1 TeV (to be compared with the measured values of 2.66±0.02 and 2.58±0.02). For δ = 0.6 the hardening of the He spectra is not observed. The stochastic effects discussed above cannot be found in ordinary propagation calculations, such as GALPROP, where these effects and the point like nature of the sources are not taken into account. We also comment on the effect of time dependence of the escape of cosmic rays from supernova remnants, and of a possible clustering of the sources in superbubbles. In a second paper we will discuss the

  8. Thermal conductivity of tungsten–copper composites

    International Nuclear Information System (INIS)

    Lee, Sang Hyun; Kwon, Su Yong; Ham, Hye Jeong

    2012-01-01

    Highlights: ► We present the temperature dependence of the thermophysical properties for tungsten–copper composite from room temperature to 400 °C. The powders of tungsten–copper were produced by the spray conversion method and the W–Cu alloys were fabricated by the metal injection molding. Thermal conductivity and thermal expansion of tungsten–copper composite was controllable by volume fraction copper. - Abstract: As the speed and degree of integration of semiconductor devices increases, more heat is generated, and the performance and lifetime of semiconductor devices depend on the dissipation of the generated heat. Tungsten–copper alloys have high electrical and thermal conductivities, low contact resistances, and low coefficients of thermal expansion, thus allowing them to be used as a shielding material for microwave packages, and heat sinks for high power integrated circuits (ICs). In this study, the thermal conductivity and thermal expansion of several types of tungsten–copper (W–Cu) composites are investigated, using compositions of 5–30 wt.% copper balanced with tungsten. The tungsten–copper powders were produced using the spray conversion method, and the W–Cu alloys were fabricated via the metal injection molding. The tungsten–copper composite particles were nanosized, and the thermal conductivity of the W–Cu alloys gradually decreases with temperature increases. The thermal conductivity of the W–30 wt.% Cu composite was 238 W/(m K) at room temperature.

  9. Thermal stress relaxation in magnesium composites during thermal cycling

    Energy Technology Data Exchange (ETDEWEB)

    Trojanova, Z.; Lukac, P. (Karlova Univ., Prague (Czech Republic)); Kiehn, J.; Kainer, K.U.; Mordike, B.L. (Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany))

    1998-01-01

    It has been shown that the internal friction of Mg - Saffil metal matrix composites can be influenced by thermal stresses, if MMCc are submitted to thermal cycling between room temperature and an upper temperature of cycling. These stresses can be accommodated by generation and motion of dislocations giving the formation of the microplastic zones. The thermal stress relaxation depends on the upper temperature of cycling, the volume fraction of reinforcement and the matrix composition and can result in plastic deformation and strain hardening of the matrix without applied stress. The internal friction measurements can be used for non destructive investigation of processes which influence the mechanical properties. (orig.)

  10. Thermal instability of helium-burning shell in stars evolving toward carbon-detonation supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, D; Nomoto, K [Tokyo Univ. (Japan). Coll. of General Education

    1975-07-01

    Artificially suppressing the occurrence of thermal pulses, evolution in the phase of a growing carbon-oxygen core was computed through the ignition of carbon burning. From this computation we chose two models with the core masses of 1.074 and 1.393 Msub(solar mass). Starting from these models, we followed by numerical computation the occurrence of thermal pulses in the helium-burning shell. We have found the following. More than 4000 thermal pulses take place through the evolutionary phase. The peak energy generation rate is 10/sup 7/Lsub(solar) at most, a rate too small to induce any major dynamical effect. After each pulse the convective envelope penetrates into the helium zone, and the products of helium burning, which contain carbon and s-process elements, are mixed into the convective envelope, which thereby develops composition characteristics of carbon stars.

  11. Thermal Analysis of Filler Reinforced Polymeric Composites

    Science.gov (United States)

    Ghadge, Mahesh Devidas

    Improving heat dissipating property of composite materials is becoming increasingly important in domains ranging from the automotive industry, electronic devices to aeronautical industry. Effective heat dissipation is required especially in aircraft and racing tires to guarantee high performance and good service life [1]. The present study is focused on improving the thermal conductivity of Emulsion-styrene butadiene rubber (ESBR) which is a cheap alternative to other rubber composites. The disadvantages of ESBR are low thermal conductivity and high heat generation. Adding fillers with high thermal conductivity to ESBR is proposed as a technique for improving the thermal conductivity of ESBR. The purpose of the research is to predict the thermal conductivity of ESBR when filled with fillers of much higher thermal conductivity and also to find out to what extent the filler properties affect the heat transfer capabilities of the composite matrix. The influence of different filler shapes i.e. spherical, cylindrical and platelets on the overall thermal capability of composite matrix is studied, the finite element modelings are conducted using Abaqus. Three-dimensional and two-dimensional models are created in Abaqus to simulate the microstructure of the composite matrix filled with fillers. Results indicate that the overall thermal conductivity increases with increasing filler loading i.e. for a filler volume fraction of 0.27, the conductivity increased by around 50%. Filler shapes, orientation angle, and aspect ratio of the fillers significantly influences the thermal conductivity. Conductivity increases with increasing aspect ratio (length/diameter) of the cylindrical fillers since longer conductive chains are able to form at the same volume percentage as compared to spherical fillers. The composite matrix reaches maximum thermal conductivity when the cylindrical fillers are oriented in the direction of heat flow. The heat conductivity predicted by FEM for ESBR is

  12. High Thermal Conductivity Composite Structures

    National Research Council Canada - National Science Library

    Bootle, John

    1999-01-01

    ... applications and space based radiators. The advantage of this material compared to competing materials that it can be used to fabricate high strength, high thermal conductivity, relatively thin structures less than 0.050" thick...

  13. LATE-TIME EVOLUTION OF COMPOSITE SUPERNOVA REMNANTS: DEEP CHANDRA OBSERVATIONS AND HYDRODYNAMICAL MODELING OF A CRUSHED PULSAR WIND NEBULA IN SNR G327.1-1.1

    Energy Technology Data Exchange (ETDEWEB)

    Temim, Tea [Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Slane, Patrick [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kolb, Christopher; Blondin, John [North Carolina State University, 421 Riddick Hall, Raleigh, NC 27695 (United States); Hughes, John P. [Rutgers University, 57 US Highway 1, New Brunswick, NJ 08901 (United States); Bucciantini, Niccoló [INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze Italy (Italy)

    2015-07-20

    In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology: a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the origin of the PWN structures, while enhanced abundances in the PWN region provide evidence for a mixing of supernova ejecta with PWN material. The overall morphology and spectral properties of the SNR suggest that the PWN has undergone an asymmetric interaction with the SNR reverse shock (RS), whichcan occur as a result of a density gradient in the ambient medium and/or a moving pulsar that displaces the PWN from the center of the remnant. We present hydrodynamical simulations of G327.1-1.1 that show that its morphology and evolution can be described by a ∼17,000-year-old composite SNR that expanded into a density gradient with an orientation perpendicular to the pulsar’s motion. We also show that the RS/PWN interaction scenario can reproduce the broadband spectrum of the PWN from radio to γ-ray wavelengths. The analysis and modeling presented in this work have important implications for our general understanding of the structure and evolution of composite SNRs.

  14. Late-Time Evolution of Composite Supernova Remnants: Deep Chandra Observations and Hydrodynamical Modeling of a Crushed Pulsar Wind Nebula in SNR G327.1-1.1

    Science.gov (United States)

    Temim, Tea; Slane, Patrick; Kolb, Christopher; Blondin, John; Hughes, John P.; Bucciantini, Niccolo

    2015-01-01

    In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 ks Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology; a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the origin of the PWN structures, while enhanced abundances in the PWN region provide evidence for mixing of supernova ejecta with PWN material. The overall morphology and spectral properties of the SNR suggest that the PWN has undergone an asymmetric interaction with the SNR reverse shock(RS) that can occur as a result of a density gradient in the ambient medium and or a moving pulsar that displaces the PWN from the center of the remnant. We present hydrodynamical simulations of G327.1-1.1 that show that its morphology and evolution can be described by a approx. 17,000 yr old composite SNR that expanded into a density gradient with an orientation perpendicular to the pulsar's motion. We also show that the RSPWN interaction scenario can reproduce the broadband spectrum of the PWN from radio to gamma-ray wavelengths. The analysis and modeling presented in this work have important implications for our general understanding of the structure and evolution of composite SNRs.

  15. Thermal cycling in multifilamentary superconducting composites

    International Nuclear Information System (INIS)

    Aragao, E.E.A. de.

    1984-01-01

    NbTi-Cu multifilamentary superconducting composites were embedded, polished, characterized by microscopic techniques, and analyzed in a qualitative and semiquantitative way by energy dispersion technique. The superconductors were submitted to thermal cycling between the ambient temperature and the boiling point of helium (4.2K), for different number of cycles. The aims were to study the correlation between the possible microstructural damages due to thermal stresses arising in the composite during cycling and the variation of properties of the material with the number of cycles as well as to verify the validity of an elastic model for thermal stresses for low temperature cycles. (author)

  16. Young supernova remnants and INTEGRAL: "4"4Ti lines and non-thermal emission

    International Nuclear Information System (INIS)

    Renaud, M.

    2006-10-01

    This thesis deals with the search for and the study of young galactic supernova remnants using the observations performed by IBIS/ISGRI, one of the two main coded-mask instruments onboard the european gamma-ray satellite INTEGRAL. This research is based on i) the study of gamma-ray lines coming from the radioactive decay of "4"4Ti, a short-lived nucleus (τ∼ 86 y) exclusively produced during the first stages of stellar explosions, and ii) the study of the nonthermal continuum mechanisms which take place inside the young supernova remnants. I separate the manuscript in four main parts. The first one presents an overview of supernovae from an observational and theoretical point of view. The second part describes the INTEGRAL satellite with its instruments, the techniques used for analyzing the data collected by IBIS/ISGRI, and my personal investigations concerning different developments such as: the spectral calibration of the IBIS/ISGRI instrument, the correction of noisy pixels on the camera, the creation of background maps, and the development of an alternative pipeline useful for dealing with a large amount of data. I also present a method for imaging extended sources with a coded-mask instrument such as IBIS/ISGRI, and its first application on the Coma Cluster. The results obtained on historical supernova remnants like Cas A, Tycho, RXJ0852-4622 (Vela Junior) are presented in the third part. The first chapter of the last part is devoted to the study of the detectability of supernovae in the optical domain with a model of the interstellar extinction. The second chapter reports on the search for missing and hidden young supernova remnants in the Milky Way with the IBIS/ISGRI galactic plane survey through the "4"4Sc gamma-ray lines as well as with a multi-wavelength approach, from the radio domain (VLA) to the new observational window at TeV energies (HESS). I also discuss the constraints on the supernova rate and the "4"4Ti production in core-collapse supernovae

  17. Thermal conductivity of glass copper-composite

    International Nuclear Information System (INIS)

    Kinoshita, Makoto; Terai, Ryohei; Haidai, Haruki

    1980-01-01

    Glass-metal composites are to be one of the answers for promoting thermal conduction in the glassy solids containing high-level radioactive wastes. In order to investigate the effect of metal addition on thermal conductivity of glasses, glass-copper composites were selected, and the conductivities of the composites were measured and discussed in regards to copper content and microstructure. Fully densified composites were successfully prepared by pressure sintering of the powder mixtures of glass and copper at temperatures above the yield points of the constituent glasses if the copper content was not so much. The conductivity was measured by means of a comparative method, in which the thermal gradient of the specimen was compared with that of quartz glass as standard under thermally steady state. Measurements were carried out at around 50 0 C. The thermal conductivity increased with increasing content of copper depending on the kind of copper powder used. The conductivities of the composites of the same copper content differed considerably each another. Fine copper powder was effective on increasing conductivity, and the conductivity became about threefold of that of glass by mixing the fine copper powder about 10 vol%. For the composites containing the fine copper powder less than 5 vol%, the conductivity obeyed so-called logarithmic rule, one of the mixture rules of conductivity, whereas for composites containing more than 5 vol%, the conductivity remarkably increased apart from the rule. This fact suggests that copper becomes continuous in the composite when the copper content increased beyond 5 vol%. For the composites containing coarse copper powder, the conductivity was increased not significantly, and obeyed an equation derived from the model in which conductive material dispersed in less conductive one. (author)

  18. Non-thermal emission from young supernova remnants: Implications on cosmic ray acceleration

    Science.gov (United States)

    Araya-Arguedas, Miguel A.

    For a long time, supernova remnants have been thought to constitute the main source of galactic cosmic rays. Plausible mechanisms have been proposed through which these objects would be able to transfer some of their energy to charged particles. Detailed studies of SNRs, particularly allowed by the spectral and spatial resolution obtained with telescopes such as the Chandra X-Ray Observatory , have permitted us to understand some of the properties of high-energy particles within these objects and their interactions with their environment. In the first part of this work, the basic concepts of particle acceleration in SNRs are outlined, and the main observational tools available today for studying high-energy phenomena in astrophysics are mentioned briefly. In the second part, a study of non-thermal emission from the young SNR Cassiopeia A is presented. Through the use of a very deep one million-second Chandra observation of this remnant, the spectral evolution across non-thermal filaments near the forward shock was studied. A consistent hardening of the spectrum towards the exterior of the remnant was found and explained via a model developed that takes into account particle diffusion, plasma advection and radiation losses. The role of particle diffusion was studied and its effect on the photon spectral index quantified. In the model, the diffusion is included as a fraction of Bohm-type diffusion, which is consistent with the data. The model also allowed an estimation of the electron distribution, the magnetic field and its orientation, as well as the level of magnetic turbulence. In the third part, a multi-wavelength study of two young SNRs is presented. Multi-wavelength modeling of spectral energy distributions (SED) may hold the key to disentangle the nature and content of cosmic rays within these objects. The first model shown presents state of the art measurements gathered for Cassiopeia A, and the modeling is based partly on the results presented in the second

  19. Fiber Optic Thermal Health Monitoring of Composites

    Science.gov (United States)

    Wu, Meng-Chou; Winfree, William P.; Moore, Jason P.

    2010-01-01

    A recently developed technique is presented for thermographic detection of flaws in composite materials by performing temperature measurements with fiber optic Bragg gratings. Individual optical fibers with multiple Bragg gratings employed as surface temperature sensors were bonded to the surfaces of composites with subsurface defects. The investigated structures included a 10-ply composite specimen with subsurface delaminations of various sizes and depths. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The data obtained from grating sensors were analyzed with thermal modeling techniques of conventional thermography to reveal particular characteristics of the interested areas. Results were compared with the calculations using numerical simulation techniques. Methods and limitations for performing in-situ structural health monitoring are discussed.

  20. Fiber Optic Thermal Detection of Composite Delaminations

    Science.gov (United States)

    Wu, Meng-Chou; Winfree, William P.

    2011-01-01

    A recently developed technique is presented for thermographic detection of delaminations in composites by performing temperature measurements with fiber optic Bragg gratings. A single optical fiber with multiple Bragg gratings employed as surface temperature sensors was bonded to the surface of a composite with subsurface defects. The investigated structure was a 10-ply composite specimen with prefabricated delaminations of various sizes and depths. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The data obtained from grating sensors were analyzed with thermal modeling techniques of conventional thermography to reveal particular characteristics of the interested areas. Results were compared and found to be consistent with the calculations using numerical simulation techniques. Also discussed are methods including various heating sources and patterns, and their limitations for performing in-situ structural health monitoring.

  1. Thermally Conductive Structural 2D Composite Materials

    Science.gov (United States)

    2012-08-14

    Dimensional Pitch Polyimide Composite Micrographs ........ 27 Figure 23. 4-Ply Silver Polyimide Laminate ...through-thickness thermal conductivity of up to 20 W/m.K. This novel structural prepreg material will be developed through engineering of an optimal fiber...with an EPON 862/Epikure W epoxy resin system to form unidirectional prepreg tapes. Each prepreg was then cut to 6 inch by 6 inch plies and

  2. Thermal expansion of fibre-reinforced composites

    International Nuclear Information System (INIS)

    Schneider, B.

    1991-07-01

    The integral thermal expansion and the coefficient of thermal expansion (CTE) of carbon and Kevlar fibre-reinforced composites were measured with high accuracy from 5 K to room temperature. For this, a laser dilatometer and a sophisticated measuring procedure were used. CTE dependence on the orientation angle ω of angle-ply laminates was determined for samples with 5 different fibre alignments (UD 0deg, +/-30deg, +/-45deg, +/-60deg and UD 90deg). A high variability of the CTE with the orientation angle was shown. At angles of approximately +/-30deg even negative CTEs were found. With suitable reinforcing fibres being selected, their absolute values rose up to 30-100% of the positive CTEs of metals. Hence, composites of this type would be suitable as compensating materials in metal constructions where little thermal expansion is desired. To check the lamination theory, theoretical computations of the CTE- ω -dependence were compared with the measured values. An excellent agreement was found. Using the lamination theory, predictions about the expansion behaviour of angle-ply laminates can be made now, if the thermal and mechanical properties of the unidirectional (UD) laminate are known. Furthermore, it is possible to carry out simulation computations aimed at investigating the influence of a single parameter of the UD-laminate (e.g. shear modulus) on the expansion of the angle-ply laminate. (orig.) [de

  3. Thermal stress effects in intermetallic matrix composites

    Science.gov (United States)

    Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

    1993-01-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  4. A SYSTEMATIC STUDY OF THE THERMAL AND NONTHERMAL EMISSION IN THE SUPERNOVA REMNANT RCW 86 WITH SUZAKU

    International Nuclear Information System (INIS)

    Tsubone, Yoshio; Sawada, Makoto; Bamba, Aya; Katsuda, Satoru; Vink, Jacco

    2017-01-01

    Diffusive shock acceleration by the shockwaves in supernova remnants (SNRs) is widely accepted as the dominant source for Galactic cosmic rays. However, it is unknown what determines the maximum energy of accelerated particles. The surrounding environment could be one of the key parameters. The SNR RCW 86 shows both thermal and nonthermal X-ray emission with different spatial morphologies. These emission originate from the shock-heated plasma and accelerated electrons respectively, and their intensities reflect their density distributions. Thus, the remnant provides a suitable laboratory to test possible association between the acceleration efficiency and the environment. In this paper, we present results of spatially resolved spectroscopy of the entire remnant with Suzaku . The spacially resolved spectra are well reproduced with a combination of a power-law for synchrotron emission and a two-component optically thin thermal plasma, corresponding to the shocked interstellar medium (ISM) with kT of 0.3–0.6 keV and Fe-dominated ejecta. It is discovered that the photon index of the nonthermal component becomes smaller when decreasing the emission measure of the shocked ISM, where the shock speed has remained high. This result implies that the maximum energy of accelerated electrons in RCW 86 is higher in the low-density and higher shock speed regions.

  5. Thermal Diffusivity and Thermal Conductivity of Dispersed Glass Sphere Composites Over a Range of Volume Fractions

    Science.gov (United States)

    Carson, James K.

    2018-06-01

    Glass spheres are often used as filler materials for composites. Comparatively few articles in the literature have been devoted to the measurement or modelling of thermal properties of composites containing glass spheres, and there does not appear to be any reported data on the measurement of thermal diffusivities over a range of filler volume fractions. In this study, the thermal diffusivities of guar-gel/glass sphere composites were measured using a transient comparative method. The addition of the glass beads to the gel increased the thermal diffusivity of the composite, more than doubling the thermal diffusivity of the composite relative to the diffusivity of the gel at the maximum glass volume fraction of approximately 0.57. Thermal conductivities of the composites were derived from the thermal diffusivity measurements, measured densities and estimated specific heat capacities of the composites. Two approaches to modelling the effective thermal diffusivity were considered.

  6. Composite Materials for Thermal Energy Storage: Enhancing Performance through Microstructures

    Science.gov (United States)

    Ge, Zhiwei; Ye, Feng; Ding, Yulong

    2014-01-01

    Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. PMID:24591286

  7. Composite materials for thermal energy storage: enhancing performance through microstructures.

    Science.gov (United States)

    Ge, Zhiwei; Ye, Feng; Ding, Yulong

    2014-05-01

    Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Thermal conductivity of microPCMs-filled epoxy matrix composites

    OpenAIRE

    Su, J.F.; Wang, X.Y; Huang, Z.; Zhao, Y.H.; Yuan, X.Y.

    2011-01-01

    Microencapsulated phase change materials (microPCMs) have been widely applied in solid matrix as thermal-storage or temperature-controlling functional composites. The thermal conductivity of these microPCMs/matrix composites is an important property need to be considered. In this study, a series of microPCMs have been fabricated using the in situ polymerization with various core/shell ratio and average diameter; the thermal conductivity of microPCMs/epoxy composites were investigated in detai...

  9. Supernova VLBI

    Science.gov (United States)

    Bartel, N.

    2009-08-01

    We review VLBI observations of supernovae over the last quarter century and discuss the prospect of imaging future supernovae with space VLBI in the context of VSOP-2. From thousands of discovered supernovae, most of them at cosmological distances, ˜50 have been detected at radio wavelengths, most of them in relatively nearby galaxies. All of the radio supernovae are Type II or Ib/c, which originate from the explosion of massive progenitor stars. Of these, 12 were observed with VLBI and four of them, SN 1979C, SN 1986J, SN 1993J, and SN 1987A, could be imaged in detail, the former three with VLBI. In addition, supernovae or young supernova remnants were discovered at radio wavelengths in highly dust-obscured galaxies, such as M82, Arp 299, and Arp 220, and some of them could also be imaged in detail. Four of the supernovae so far observed were sufficiently bright to be detectable with VSOP-2. With VSOP-2 the expansion of supernovae can be monitored and investigated with unsurpassed angular resolution, starting as early as the time of the supernova's transition from its opaque to transparent stage. Such studies can reveal, in a movie, the aftermath of a supernova explosion shortly after shock break out.

  10. Supernova explosions

    CERN Document Server

    Branch, David

    2017-01-01

    Targeting advanced students of astronomy and physics, as well as astronomers and physicists contemplating research on supernovae or related fields, David Branch and J. Craig Wheeler offer a modern account of the nature, causes and consequences of supernovae, as well as of issues that remain to be resolved. Owing especially to (1) the appearance of supernova 1987A in the nearby Large Magellanic Cloud, (2) the spectacularly successful use of supernovae as distance indicators for cosmology, (3) the association of some supernovae with the enigmatic cosmic gamma-ray bursts, and (4) the discovery of a class of superluminous supernovae, the pace of supernova research has been increasing sharply. This monograph serves as a broad survey of modern supernova research and a guide to the current literature. The book’s emphasis is on the explosive phases of supernovae. Part 1 is devoted to a survey of the kinds of observations that inform us about supernovae, some basic interpreta tions of such data, and an overview of t...

  11. Thermal Degradation of Lead Monoxide Filled Polymer Composite Radiation Shields

    International Nuclear Information System (INIS)

    Harish, V.; Nagaiah, N.

    2011-01-01

    Lead monoxide filled Isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the thermo gravimetric analysis of the composites done to understand their thermal properties especially the effect of filler concentration on the thermal stability and degradation rate of composites. Pristine polymer exhibits single stage degradation whereas filled composites exhibit two stage degradation processes. Further, the IDT values as well as degradation rates decrease with the increased filler content in the composite.

  12. Aspherical supernovae

    International Nuclear Information System (INIS)

    Kasen, Daniel Nathan

    2004-01-01

    Although we know that many supernovae are aspherical, the exact nature of their geometry is undetermined. Because all the supernovae we observe are too distant to be resolved, the ejecta structure can't be directly imaged, and asymmetry must be inferred from signatures in the spectral features and polarization of the supernova light. The empirical interpretation of this data, however, is rather limited--to learn more about the detailed supernova geometry, theoretical modeling must been undertaken. One expects the geometry to be closely tied to the explosion mechanism and the progenitor star system, both of which are still under debate. Studying the 3-dimensional structure of supernovae should therefore provide new break throughs in our understanding. The goal of this thesis is to advance new techniques for calculating radiative transfer in 3-dimensional expanding atmospheres, and use them to study the flux and polarization signatures of aspherical supernovae. We develop a 3-D Monte Carlo transfer code and use it to directly fit recent spectropolarimetric observations, as well as calculate the observable properties of detailed multi-dimensional hydrodynamical explosion simulations. While previous theoretical efforts have been restricted to ellipsoidal models, we study several more complicated configurations that are tied to specific physical scenarios. We explore clumpy and toroidal geometries in fitting the spectropolarimetry of the Type Ia supernova SN 2001el. We then calculate the observable consequences of a supernova that has been rendered asymmetric by crashing into a nearby companion star. Finally, we fit the spectrum of a peculiar and extraordinarily luminous Type Ic supernova. The results are brought to bear on three broader astrophysical questions: (1) What are the progenitors and the explosion processes of Type Ia supernovae? (2) What effect does asymmetry have on the observational diversity of Type Ia supernovae, and hence their use in cosmology? (3) And

  13. Smoking supernovae

    OpenAIRE

    Gomez, Haley Louise; Eales, Stephen Anthony; Dunne, L.

    2007-01-01

    The question ‘Are supernovae important sources of dust?’ is a contentious one. Observations with the Infrared Astronomical Satellite (IRAS) and the Infrared Space Observatory (ISO) only detected very small amounts of hot dust in supernova remnants. Here, we review observations of two young Galactic remnants with the Submillimetre Common User Bolometer Array (SCUBA), which imply that large quantities of dust are produced by supernovae. The association of dust with the Cassiopeia A remnant is i...

  14. Flexible composite material with phase change thermal storage

    Science.gov (United States)

    Buckley, Theresa M. (Inventor)

    2001-01-01

    A highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The composite material can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The composite may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the PCM composite also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, ,gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

  15. Estimation of effective thermal conductivity tensor from composite microstructure images

    International Nuclear Information System (INIS)

    Thomas, M; Boyard, N; Jarny, Y; Delaunay, D

    2008-01-01

    The determination of the effective thermal properties of inhomogeneous materials is a long-standing problem of continuously interest. The impressive number of methods developed to measure or estimate the thermal properties of composite materials clearly exhibits the importance given to their knowledge. Homogenization models are a cheap way to determine or predict them. Many different approaches of homogenization were developed, but the last advances are credited to numerical methods. In this study, a new computational model is developed to estimate the 2D thermal conductivity tensor and the thermal main directions of a pure carbon/epoxy unidirectional composite. This tool is based on real composite microstructure.

  16. Nucleosynthesis in Supernovae

    Science.gov (United States)

    Thielemann, Friedrich-Karl; Isern, Jordi; Perego, Albino; von Ballmoos, Peter

    2018-04-01

    We present the status and open problems of nucleosynthesis in supernova explosions of both types, responsible for the production of the intermediate mass, Fe-group and heavier elements (with the exception of the main s-process). Constraints from observations can be provided through individual supernovae (SNe) or their remnants (e.g. via spectra and gamma-rays of decaying unstable isotopes) and through surface abundances of stars which witness the composition of the interstellar gas at their formation. With a changing fraction of elements heavier than He in these stars (known as metallicity) the evolution of the nucleosynthesis in galaxies over time can be determined. A complementary way, related to gamma-rays from radioactive decays, is the observation of positrons released in β+-decays, as e.g. from ^{26}Al, ^{44}Ti, ^{56,57}Ni and possibly further isotopes of their decay chains (in competition with the production of e+e- pairs in acceleration shocks from SN remnants, pulsars, magnetars or even of particle physics origin). We discuss (a) the role of the core-collapse supernova explosion mechanism for the composition of intermediate mass, Fe-group (and heavier?) ejecta, (b) the transition from neutron stars to black holes as the final result of the collapse of massive stars, and the relation of the latter to supernovae, faint supernovae, and gamma-ray bursts/hypernovae, (c) Type Ia supernovae and their nucleosynthesis (e.g. addressing the ^{55}Mn puzzle), plus (d) further constraints from galactic evolution, γ-ray and positron observations. This is complemented by the role of rare magneto-rotational supernovae (related to magnetars) in comparison with the nucleosynthesis of compact binary mergers, especially with respect to forming the heaviest r-process elements in galactic evolution.

  17. Composite materials for thermal energy storage

    Science.gov (United States)

    Benson, D. K.; Burrows, R. W.; Shinton, Y. D.

    1985-01-01

    A composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations are discussed. These PCM's do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

  18. Composite materials for thermal energy storage

    Science.gov (United States)

    Benson, D.K.; Burrows, R.W.; Shinton, Y.D.

    1985-01-04

    A composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These PCM's do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

  19. Neutrinos in supernovae

    International Nuclear Information System (INIS)

    Cooperstein, J.

    1986-10-01

    The role of neutrinos in Type II supernovae is discussed. An overall view of the neutrino luminosity as expected theoretically is presented. The different weak interactions involved are assessed from the standpoint of how they exchange energy, momentum, and lepton number. Particular attention is paid to entropy generation and the path to thermal and chemical equilibration, and to the phenomenon of trapping. Various methods used to calculate the neutrino flows are considered. These include trapping and leakage schemes, distribution-averaged transfer, and multi-energy group methods. The information obtained from the neutrinos caught from Supernova 1987a is briefly evaluated. 55 refs., 7 figs

  20. supernovae: Photometric classification of supernovae

    Science.gov (United States)

    Charnock, Tom; Moss, Adam

    2017-05-01

    Supernovae classifies supernovae using their light curves directly as inputs to a deep recurrent neural network, which learns information from the sequence of observations. Observational time and filter fluxes are used as inputs; since the inputs are agnostic, additional data such as host galaxy information can also be included.

  1. Thermal Properties of Anionic Polyurethane Composition for Leather Finishing

    Directory of Open Access Journals (Sweden)

    Olga KOVTUNENKO

    2016-09-01

    Full Text Available Thermal properties of anionic polyurethane composition mixed with collagen product and hydrophilic sodium form of montmorillonite for use in the finishing of leather were studied by thermogravimetric method. The thermal indices of processes of thermal and thermo-oxidative destruction depending on the polyurethane composition were determined. The influence of anionic polyurethane composition on thermal behavior of chromium tanned gelatin films that imitate the leather were studied. APU composition with natural compounds increases their thermal stability both in air and in nitrogen atmosphere due to the formation of additional bonds between active groups of APU, protein and chrome tanning agent as the result of chemical reactions between organic and inorganic parts with the new structure formation.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.10043

  2. Thermal Properties of Carbon Nanotube–Copper Composites for Thermal Management Applications

    Directory of Open Access Journals (Sweden)

    Jia Chengchang

    2010-01-01

    Full Text Available Abstract Carbon nanotube–copper (CNT/Cu composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications.

  3. Supernova cosmology

    International Nuclear Information System (INIS)

    Leibundgut, B.

    2005-01-01

    Supernovae have developed into a versatile tool for cosmology. Their impact on the cosmological model has been profound and led to the discovery of the accelerated expansion. The current status of the cosmological model as perceived through supernova observations will be presented. Supernovae are currently the only astrophysical objects that can measure the dynamics of the cosmic expansion during the past eight billion years. Ongoing experiments are trying to determine the characteristics of the accelerated expansion and give insight into what might be the physical explanation for the acceleration. (author)

  4. Supernova models

    International Nuclear Information System (INIS)

    Woosley, S.E.; Weaver, T.A.

    1980-01-01

    Recent progress in understanding the observed properties of Type I supernovae as a consequence of the thermonuclear detonation of white dwarf stars and the ensuing decay of the 56 Ni produced therein is reviewed. Within the context of this model for Type I explosions and the 1978 model for Type II explosions, the expected nucleosynthesis and gamma-line spectra from both kinds of supernovae are presented. Finally, a qualitatively new approach to the problem of massive star death and Type II supernovae based upon a combination of rotation and thermonuclear burning is discussed

  5. Residual stress of particulate polymer composites with reduced thermal expansion

    International Nuclear Information System (INIS)

    Nishino, T; Kotera, M; Sugiura, Y

    2009-01-01

    Thermal expansion behavior was investigated for tangusten zirconium phosphate (Zr 2 (WO 4 )(PO 4 ) 2 (ZWP)) particulate filled poly(ether ether ketone) (PEEK) composite. ZWP is known as ceramic filler with a negative thermal expansion. By incorporating ZWP with 40 volume %, the linear thermal expansion coefficient of the PEEK composite was reduced to almost same value (2.53 X 10 -5 K -1 ) with that of aluminum. This decrease was found to be quite effective for the decrease of the residual stress at the interface between aluminum plate and the composite.

  6. Anisotropic thermal conductivity in epoxy-bonded magnetocaloric composites

    Science.gov (United States)

    Weise, Bruno; Sellschopp, Kai; Bierdel, Marius; Funk, Alexander; Bobeth, Manfred; Krautz, Maria; Waske, Anja

    2016-09-01

    Thermal management is one of the crucial issues in the development of magnetocaloric refrigeration technology for application. In order to ensure optimal exploitation of the materials "primary" properties, such as entropy change and temperature lift, thermal properties (and other "secondary" properties) play an important role. In magnetocaloric composites, which show an increased cycling stability in comparison to their bulk counterparts, thermal properties are strongly determined by the geometric arrangement of the corresponding components. In the first part of this paper, the inner structure of a polymer-bonded La(Fe, Co, Si)13-composite was studied by X-ray computed tomography. Based on this 3D data, a numerical study along all three spatial directions revealed anisotropic thermal conductivity of the composite: Due to the preparation process, the long-axis of the magnetocaloric particles is aligned along the xy plane which is why the in-plane thermal conductivity is larger than the thermal conductivity along the z-axis. Further, the study is expanded to a second aspect devoted to the influence of particle distribution and alignment within the polymer matrix. Based on an equivalent ellipsoids model to describe the inner structure of the composite, numerical simulation of the thermal conductivity in different particle arrangements and orientation distributions were performed. This paper evaluates the possibilities of microstructural design for inducing and adjusting anisotropic thermal conductivity in magnetocaloric composites.

  7. Thermal conductivity of polymer composites with oriented boron nitride

    International Nuclear Information System (INIS)

    Ahn, Hong Jun; Eoh, Young Jun; Park, Sung Dae; Kim, Eung Soo

    2014-01-01

    Highlights: • Thermal conductivity depended on the orientation of BN in the polymer matrices. • Hexagonal boron nitride (BN) particles were treated by C 27 H 27 N 3 O 2 and C 14 H 6 O 8 . • Amphiphilic-agent-treated BN particles are more easily oriented in the composite. • BN/PVA composites with C 14 H 6 O 8 -treated BN showed the highest thermal conductivity. • Thermal conductivity of the composites was compared with several theoretical models. - Abstract: Thermal conductivity of boron nitride (BN) with polyvinyl alcohol (PVA) and/or polyvinyl butyral (PVB) was investigated as a function of the degree of BN orientation, the numbers of hydroxyl groups in the polymer matrices and the amphiphilic agents used. The composites with in-plane orientation of BN showed a higher thermal conductivity than the composites with out-of-plane orientation of BN due to the increase of thermal pathway. For a given BN content, the composites with in-plane orientation of BN/PVA showed higher thermal conductivity than the composites with in-plane orientation of BN/PVB. This result could be attributed to the improved degree of orientation of BN, caused by a larger number of hydroxyl groups being present. Those treated with C 14 H 6 O 8 amphiphilic agent demonstrated a higher thermal conductivity than those treated by C 27 H 27 N 3 O 2 . The measured thermal conductivity of the composites was compared with that predicted by the several theoretical models

  8. The diversity of neutron stars: Nearby thermally emitting neutron stars and the compact central objects in supernova remnants

    Science.gov (United States)

    Kaplan, David L.

    Neutron stars are invaluable tools for exploring stellar death, the physics of ultra-dense matter, and the effects of extremely strong magnetic fields. The observed population of neutron stars is dominated by the > 1000 radio pulsars, but there are distinct sub-populations that, while fewer in number, can have significant impact on our understanding of the issues mentioned above. These populations are the nearby isolated neutron stars discovered by ROSAT, and the central compact objects in supernova remnants. The studies of both of these populations have been greatly accelerated in recent years through observations with the Chandra X-ray Observatory and the XMM-Newton telescope. First, we discuss radio, optical, and X-ray observations of the nearby neutron stars aimed at determining their relation to the Galactic neutron star population and at unraveling their complex physical processes by determining the basic astronomical parameters that define the population -- instances, ages, and magnetic fields -- the uncertainties in which limit any attempt to derive basic physical parameters for these objects. We conclude that these sources are 10^6 year-old cooling neutron stars with magnetic fields above 10^13 G. Second, we describe the hollow supernova remnant problem: why many of the supernova remnants in the Galaxy have no indication central neutron stars. We have undertaken an X-ray census of neutron stars in a volume-limited sample of Galactic supernova remnants, and from it conclude that either many supernovae do not produce neutron stars contrary to expectation, or that neutron stars can have a wide range in cooling behavior that makes many sources disappear from the X-ray sky.

  9. Thermal stability of polyvinyl alcohol/nanocrystalline cellulose composites.

    Science.gov (United States)

    Voronova, Marina I; Surov, Oleg V; Guseinov, Sabir S; Barannikov, Vladimir P; Zakharov, Anatoly G

    2015-10-05

    Thermal stability of polyvinyl alcohol/cellulose nanocrystals (PVA/CNCs) composites prepared with solution casting technique was studied. The PVA/CNCs composites were characterized by Fourier transform infrared spectrometry, X-ray diffraction, differential scanning calorimeter (DSC) and thermogravimetric (TG) analysis. Due to the presence of CNCs nanoparticles, thermal degradation of the composites occurs at much higher temperatures compared to that of the neat PVA. Thermal stability of the PVA/CNCs composites is maximally enhanced with CNCs content of 8-12 wt%. Some thermal degradation products of the PVA/CNCs composites were identified by mass spectrometric analysis. TG measurements with synchronous recording of mass spectra revealed that the thermal degradation of both CNCs and PVA in the composites with CNCs content of 8-12 wt% occurs simultaneously at a much higher temperature than that of CNCs or the neat PVA. However, with increasing CNCs content more than 12 wt% the thermal stability of the composites decreases. In this case, the degradation of CNCs comes first followed by the degradation of PVA. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Interacting supernovae and supernova impostors

    Science.gov (United States)

    Tartaglia, Leonardo

    2016-02-01

    Massive stars are thought to end their lives with spectacular explosions triggered by the gravitational collapse of their cores. Interacting supernovae are generally attributed to supernova explosions occurring in dense circumstellar media, generated through mass-loss which characterisie the late phases of the life of their progenitors. In the last two decades, several observational evidences revealed that mass-loss in massive stars may be related to violent eruptions involving their outer layers, such as the luminous blue variables. Giant eruptions of extragalactic luminous blue variables, similar to that observed in Eta Car in the 19th century, are usually labelled 'SN impostors', since they mimic the behaviour of genuine SNe, but are not the final act of the life of the progenitor stars. The mechanisms producing these outbursts are still not understood, although the increasing number of observed cases triggered the efforts of the astronomical community to find possible theoretical interpretations. More recently, a number of observational evidences suggested that also lower-mass stars can experience pre-supernova outbursts, hence becoming supernova impostors. Even more interestingly, there is growing evidence of a connection among massive stars, their outbursts and interacting supernovae. All of this inspired this research, which has been focused in particular on the characterisation of supernova impostors and the observational criteria that may allow us to safely discriminate them from interacting supernovae. Moreover, the discovery of peculiar transients, motivated us to explore the lowest range of stellar masses that may experience violent outbursts. Finally, the quest for the link among massive stars, their giant eruptions and interacting supernovae, led us to study the interacting supernova LSQ13zm, which possibly exploded a very short time after an LBV-like major outburst.

  11. The Analysis of the Possible Thermal Emission at Radio Frequencies from an Evolved Supernova Remnant HB 3 (G132.7+1.3: Revisited

    Directory of Open Access Journals (Sweden)

    Onić, D.

    2008-12-01

    Full Text Available It has recently been reported that some of the flux density values for an evolved supernova remnant (SNR HB 3 (G132.7$+$1.3 are not accurate enough. In this work we therefore revised the analysis of the possible thermal emission at radio frequencies from this SNR using the recently published, corrected flux density values. A model including the sum of non-thermal (purely synchrotron and thermal (bremsstrahlung components is applied to fit the integrated radio spectrum of this SNR. The contribution of thermal component to the total volume emissivity at $1 mathrm{GHz}$ is estimated to be $approx37 \\%$. The ambient density is also estimated to be $napprox 9 mathrm{cm}^{-3}$ for $mathrm{T}=10^{4} mathrm{K}$. Again we obtained a relatively significant presence of thermal emission at radio frequencies from the SNR, which can support interaction between SNR HB 3 and adjacent molecular cloud associated with the mbox{H,{sc ii}} region W3. Our model estimates for thermal component contribution to total volume emissivity at $1 mathrm{GHz}$ and ambient density are similar to those obtained earlier ($approx40 \\%$, $approx10 mathrm{cm^{-3}}$. It is thus obvious that the corrected flux density values do not affect the basic conclusions.

  12. Study on thermal conductive BN/novolac resin composites

    International Nuclear Information System (INIS)

    Li, Shasha; Qi, Shuhua; Liu, Nailiang; Cao, Peng

    2011-01-01

    Highlights: → Boron nitride (BN) particles were used to modify novolac resin. → BN particles were pretreated by γ-aminopropyltriethoxysilane. → The thermal conductivity trend of composite almost agrees with the predicted data from the Maxwell-Eucken model. → At BN concentration of 80 wt.%, thermal conductivity value of composite is 4.5 times that of pure novolac resin. → Combined use of the larger and smaller particles with a mass ratio of 1:2 provides the composites with the maximum thermal conductivity among the testing systems. → The composite thermal property also increases with an increase in the BN concentration. - Abstract: In this study, γ-aminopropyltriethoxysilane-treated boron nitride (BN) particles were used to modify novolac resin. The effect of varying the BN concentration, particle size, and hybrid BN fillers with the binary particle size distribution on the thermal conductivity of the composites was investigated. Scanning electron microscopy (SEM) imaging showed homogeneously dispersed treated BN particles in the matrix. Furthermore, the thermal conductivity increased as the BN concentration was increased. This behavior was also observed when the filler size was increased. Experimentally obtained thermal conductivity values agree with the predicted data from the Maxwell-Eucken model well at less than 70 wt.% BN loading. A larger particle size BN-filled novolac resin exhibits a higher thermal conductivity than a smaller particle size BN-filled one. The combined use of 0.5 and 15 μm particles with a mass ratio of 2:1 achieved the maximum thermal conductivity among the testing systems. The thermal resistance properties of the composites were also studied.

  13. Electrical and thermal properties of graphite/polyaniline composites

    Energy Technology Data Exchange (ETDEWEB)

    Bourdo, Shawn E., E-mail: sxbourdo@ualr.edu [Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204 (United States); Warford, Brock A.; Viswanathan, Tito [Department of Chemistry, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204 (United States)

    2012-12-15

    A composite of a carbon allotrope (graphite) and an inherently conducting polymer, polyaniline (PANI), has been prepared that exhibits an electrical conductivity greater than either of the two components. An almost 2-fold increase in the bulk conductivity occurs when only a small mass fraction of polyaniline exists in the composite (91% graphite/ 9% polyaniline, by mass). This increase in dc electrical conductivity is curious since in most cases a composite material will exhibit a conductivity somewhere between the two individual components, unless a modification to the electronic nature of the material occurs. In order to elucidate the fundamental electrical properties of the composite we have performed variable temperature conductivity measurements to better understand the nature of conduction in these materials. The results from these studies suggest a change in the mechanism of conduction as the amount of polyaniline is increased in the composite. Along with superior electrical properties, the composites exhibit an increase in thermal stability as compared to the graphite. - Graphical abstract: (Left) Room temperature electrical conductivity of G-PANI composites at different mass ratios. (Right) Electrical conductivity of G-PANI composites at temperatures from 5 K to 300 K. Highlights: Black-Right-Pointing-Pointer Composites of graphite and polyaniline have been synthesized with unique electrical and thermal properties. Black-Right-Pointing-Pointer Certain G-PANI composites are more conductive and more thermally stable than graphite alone. Black-Right-Pointing-Pointer G-PANI composites exhibit a larger conductivity ratio with respect to temperature than graphite alone.

  14. Thermal Conductivity of Polymer Composite poypropilene-Sand

    International Nuclear Information System (INIS)

    Betha; Mashuri; Sudirman; Karo Karo, Aloma

    2001-01-01

    Thermal conductivity composite materials polypropylene (PP)-sand have been investigated. PP composite with sand to increase thermal conductivity from the polymer. The composite in this observation is done by mixing matrix (PP melt flow 2/10)and filler sand)by means tool labo plastomil. The result of thermal conductivity is composite of PP-sand which is obtained increase and followed by the raising of filler particle volume fraction. The analysis of thermal conductivity based on the model Cheng and Vachon, model Lewis and Nielsen where this model has the function to support experiment finding. It is proved that Lewis' and Nielsen's model almost approach experiment result. And then thermal conductivity raising will be analyzed by the model of pararel-series conductive with the two (2)phases system. It is showed that sand in PP MF 2 composite have the big role to increase the thermal conductivity than sand in PP MF 10 composition, but it is not easy to shape conductive medium

  15. Effect of thermal processing methods on the proximate composition ...

    African Journals Online (AJOL)

    The nutritive value of raw and thermal processed castor oil seed (Ricinus communis) was investigated using the following parameters; proximate composition, gross energy, mineral constituents and ricin content. Three thermal processing methods; toasting, boiling and soaking-and-boiling were used in the processing of the ...

  16. Thermally conductive, dielectric PCM-boron nitride nanosheet composites for efficient electronic system thermal management.

    Science.gov (United States)

    Yang, Zhi; Zhou, Lihui; Luo, Wei; Wan, Jiayu; Dai, Jiaqi; Han, Xiaogang; Fu, Kun; Henderson, Doug; Yang, Bao; Hu, Liangbing

    2016-11-24

    Phase change materials (PCMs) possessing ideal properties, such as superior mass specific heat of fusion, low cost, light weight, excellent thermal stability as well as isothermal phase change behavior, have drawn considerable attention for thermal management systems. Currently, the low thermal conductivity of PCMs (usually less than 1 W mK -1 ) greatly limits their heat dissipation performance in thermal management applications. Hexagonal boron nitride (h-BN) is a two-dimensional material known for its excellent thermally conductive and electrically insulating properties, which make it a promising candidate to be used in electronic systems for thermal management. In this work, a composite, consisting of h-BN nanosheets (BNNSs) and commercialized paraffin wax was developed, which inherits high thermally conductive and electrically insulating properties from BNNSs and substantial heat of fusion from paraffin wax. With the help of BNNSs, the thermal conductivity of wax-BNNS composites reaches 3.47 W mK -1 , which exhibits a 12-time enhancement compared to that of pristine wax (0.29 W mK -1 ). Moreover, an 11.3-13.3 MV m -1 breakdown voltage of wax-BNNS composites was achieved, which shows further improved electrical insulating properties. Simultaneously enhanced thermally conductive and electrically insulating properties of wax-BNNS composites demonstrate their promising application for thermal management in electronic systems.

  17. Thermal contraction effects in epoxy resin composites at low temperatures

    International Nuclear Information System (INIS)

    Evans, D.; Morgan, J.T.

    1979-10-01

    Because of their electrical and thermal insulation characteristics, high strength fibreglass/epoxy composites are widely used in the construction of bubble chamber and other cryogenic equipment. Thermal contraction effects on cooling to operating temperature present problems which need to be taken into account at the design stage. This paper gives results of thermal contraction tests carried out on fibreglass/epoxy composites including the somewhat anomalous results obtained with rings and tubes. Also considered are some of the problems associated with the use of these materials at temperatures in the region of 20K. (author)

  18. The great supernova of 1987

    International Nuclear Information System (INIS)

    Woosley, S.E.

    1989-01-01

    Seven hundred day after the explosion of the brightest supernova in four centuries, astronomers continue to be both excited and perplexed by its behavior. By now, the supernova has received considerably attention in the literature. This paper emphasizes several aspects of the supernova that continue to be of special interest. These include: the evolution of the presupernova star, why it was blue, what its composition and core structure were; the iron core mass, explosion mechanism, and certain aspects of the neutrino burst; the detailed isotopic composition of the ejecta; the light curve and the requirement for mixing; the expected continued evolution of the supernova at all wavelengths given both the presence of several radioactivities as well as a central collapsed object as a power source; and late breaking news regarding the pulsar

  19. Methods and compositions for rapid thermal cycling

    Energy Technology Data Exchange (ETDEWEB)

    Beer, Neil Reginald; Benett, William J.; Frank, James M.; Deotte, Joshua R.; Spadaccini, Christopher

    2018-04-10

    The rapid thermal cycling of a material is targeted. A microfluidic heat exchanger with an internal porous medium is coupled to tanks containing cold fluid and hot fluid. Fluid flows alternately from the cold tank and the hot tank into the porous medium, cooling and heating samples contained in the microfluidic heat exchanger's sample wells. A valve may be coupled to the tanks and a pump, and switching the position of the valve may switch the source and direction of fluid flowing through the porous medium. A controller may control the switching of valve positions based on the temperature of the samples and determined temperature thresholds. A sample tray for containing samples to be thermally cycled may be used in conjunction with the thermal cycling system. A surface or internal electrical heater may aid in heating the samples, or may replace the necessity for the hot tank.

  20. Solar-thermal conversion and thermal energy storage of graphene foam-based composite

    KAUST Repository

    Zhang, Lianbin

    2016-07-11

    Among various utilizations of solar energy, solar-thermal conversion has recently gained renewed research interest due to its extremely high energy efficiency. However, one limiting factor common to all solar-based energy conversion technologies is the intermittent nature of solar irradiation, which makes them unable to stand-alone to satisfy continuous energy need. Herein, we report a three-dimensional (3D) graphene foam and phase change material (PCM) composite for the seamlessly combined solar-thermal conversion and thermal storage for sustained energy release. The composite is obtained by infiltrating the 3D graphene foam with a commonly used PCM, paraffin wax. The high macroporosity and low density of the graphene foam allow for high weight fraction of the PCM to be incorporated, which enhances heat storage capacity of the composite. The interconnected graphene sheets in the composite provide (1) the solar-thermal conversion capability, (2) high thermal conductivity and (3) form stability of the composite. Under light irradiation, the composite effectively collects and converts the light energy into thermal energy, and the converted thermal energy is stored in the PCM and released in an elongated period of time for sustained utilization. This study provides a promising route for sustainable utilization of solar energy.

  1. Solar-thermal conversion and thermal energy storage of graphene foam-based composites.

    Science.gov (United States)

    Zhang, Lianbin; Li, Renyuan; Tang, Bo; Wang, Peng

    2016-08-14

    Among various utilizations of solar energy, solar-thermal conversion has recently gained renewed research interest due to its extremely high energy efficiency. However, one limiting factor common to all solar-based energy conversion technologies is the intermittent nature of solar irradiation, which makes them unable to stand-alone to satisfy the continuous energy need. Herein, we report a three-dimensional (3D) graphene foam and phase change material (PCM) composite for the seamlessly combined solar-thermal conversion and thermal storage for sustained energy release. The composite is obtained by infiltrating the 3D graphene foam with a commonly used PCM, paraffin wax. The high macroporosity and low density of the graphene foam allow for high weight fraction of the PCM to be incorporated, which enhances the heat storage capacity of the composite. The interconnected graphene sheets in the composite provide (1) the solar-thermal conversion capability, (2) high thermal conductivity and (3) form stability of the composite. Under light irradiation, the composite effectively collects and converts the light energy into thermal energy, and the converted thermal energy is stored in the PCM and released in an elongated period of time for sustained utilization. This study provides a promising route for sustainable utilization of solar energy.

  2. Dielectric, thermal and mechanical properties of ADP doped PVA composites

    Science.gov (United States)

    Naik, Jagadish; Bhajantri, R. F.; Ravindrachary, V.; Rathod, Sunil G.; Sheela, T.; Naik, Ishwar

    2015-06-01

    Polymer composites of poly(vinyl alcohol) (PVA), doped with different concentrations of ammonium dihydrogen phosphate (ADP) has been prepared by solution casting. The formation of complexation between ADP and PVA was confirmed with the help of Fourier transforms infrared (FTIR) spectroscopy. Thermogravimetric analysis (TGA) shows thermal stability of the prepared composites. Impedance analyzer study revealed the increase in dielectric constant and loss with increase the ADP concentration and the strain rate of the prepared composites decreases with ADP concentration.

  3. Thermal analysis of compositionally modulated Fe/Y films

    International Nuclear Information System (INIS)

    Kajiura, M.; Morishita, T.; Togami, Y.; Tsushima, K.

    1987-01-01

    Structures of compositionally modulated Fe/Y films were studied by thermal analysis. The exothermic peak found in the DSC curve of (Fe 12 A/Y 12 A) most probably corresponds to crystallization of an amorphous material. SEM analysis suggested that the composition of crystallized (Fe 12 A/Y 12 A) was YFe2. It is concluded that a compositionally modulated (Fe 12 A/Y 12 A) is amorphous in structure as well as in magnetic properties

  4. Experimental Investigations on Thermal Conductivity of Fenugreek and Banana Composites

    Science.gov (United States)

    Pujari, Satish; Venkatesh, Talari; Seeli, Hepsiba

    2018-04-01

    The use of composite materials in manufacturing has significantly increased in the past decade. Research is being done to identify natural fibers that can be used as composites. Several natural fibers are already being used in the industry as composites. The appealing advantages of using natural fibers are reflected in lower density when compared to synthetic fibers and also in saving costs. This research paper highlights the experiment that analyses the use of biodegradable fenugreek composite as natural fiber and concludes that fenugreek natural fibers are an excellent substitute to the synthetic fibers in terms of reinforcement properties for the polymers. These fenugreek fibers are naturally sourced, renewable, cost effective and bio-friendly. In thermal energy storage systems as well as in air conditioning systems, thermal insulators are predominantly used to enhance the storage properties. An experiment was created to investigate the thermal properties of fenugreek banana composites for different fiber concentrations. The experimental results showed that the thermal conductivity of the composites decrease with an increase in the fiber content. The experimental results were compared with the theoretical models to describe the variation of thermal conductivity with the volume fraction of the fiber. Good agreement between theoretical and experimental results was observed.

  5. Process for fabricating composite material having high thermal conductivity

    Science.gov (United States)

    Colella, Nicholas J.; Davidson, Howard L.; Kerns, John A.; Makowiecki, Daniel M.

    2001-01-01

    A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

  6. Thermally Conductive Metal-Tube/Carbon-Composite Joints

    Science.gov (United States)

    Copeland, Robert J.

    2004-01-01

    An improved method of fabricating joints between metal and carbon-fiber-based composite materials in lightweight radiators and heat sinks has been devised. Carbon-fiber-based composite materials have been used in such heat-transfer devices because they offer a combination of high thermal conductivity and low mass density. Metal tubes are typically used to carry heat-transfer fluids to and from such heat-transfer devices. The present fabrication method helps to ensure that the joints between the metal tubes and the composite-material parts in such heat-transfer devices have both (1) the relatively high thermal conductances needed for efficient transfer of heat and (2) the flexibility needed to accommodate differences among thermal expansions of dissimilar materials in operation over wide temperature ranges. Techniques used previously to join metal tubes with carbon-fiber-based composite parts have included press fitting and bonding with epoxy. Both of these prior techniques have been found to yield joints characterized by relatively high thermal resistances. The present method involves the use of a solder (63 percent Sn, 37 percent Pb) to form a highly thermally conductive joint between a metal tube and a carbon-fiber-based composite structure. Ordinarily, the large differences among the coefficients of thermal expansion of the metal tube, solder, and carbon-fiber-based composite would cause the solder to pull away from the composite upon post-fabrication cooldown from the molten state. In the present method, the structure of the solder is modified (see figure) to enable it to deform readily to accommodate the differential thermal expansion.

  7. Viscous and thermal modelling of thermoplastic composites forming process

    Science.gov (United States)

    Guzman, Eduardo; Liang, Biao; Hamila, Nahiene; Boisse, Philippe

    2016-10-01

    Thermoforming thermoplastic prepregs is a fast manufacturing process. It is suitable for automotive composite parts manufacturing. The simulation of thermoplastic prepreg forming is achieved by alternate thermal and mechanical analyses. The thermal properties are obtained from a mesoscopic analysis and a homogenization procedure. The forming simulation is based on a viscous-hyperelastic approach. The thermal simulations define the coefficients of the mechanical model that depend on the temperature. The forming simulations modify the boundary conditions and the internal geometry of the thermal analyses. The comparison of the simulation with an experimental thermoforming of a part representative of automotive applications shows the efficiency of the approach.

  8. Enhancing composite durability : using thermal treatments

    Science.gov (United States)

    Jerrold E. Winandy; W. Ramsay Smith

    2007-01-01

    The use of thermal treatments to enhance the moisture resistance and aboveground durability of solid wood materials has been studied for years. Much work was done at the Forest Products Laboratory in the last 15 years on the fundamental process of both short-and long-term exposure to heat on wood materials and its interaction with various treatment chemicals. This work...

  9. Thermal conductivity of the pine-biocarbon-preform/copper composite

    Science.gov (United States)

    Parfen'eva, L. S.; Orlova, T. S.; Smirnov, B. I.; Smirnov, I. A.; Misiorek, H.; Jezowski, A.; Faber, K. T.

    2010-07-01

    The thermal conductivity of composites of a new type prepared by infiltration under vacuum of melted copper into empty sap channels (aligned with the sample length) of high-porosity biocarbon preforms of white pine tree wood has been studied in the temperature range 5-300 K. The biocarbon preforms have been prepared by pyrolysis of tree wood in an argon flow at two carbonization temperatures of 1000 and 2400°C. From the experimental values of the composite thermal conductivities, the fraction due to the thermal conductivity of the embedded copper is isolated and found to be substantially lower than that of the original copper used in preparation of the composites. The decrease in the thermal conductivity of copper in the composite is assigned to defects in its structure, namely, breaks in the copper filling the sap channels, as well as the radial ones, also filled by copper. A possibility of decreasing the thermal conductivity of copper in a composite due to its doping by the impurities present in the carbon preform is discussed.

  10. Transverse thermal expansion of carbon fiber/epoxy matrix composites

    Science.gov (United States)

    Helmer, J. F.; Diefendorf, R. J.

    1983-01-01

    Thermal expansion coefficients and moduli of elasticity have been determined experimentally for a series of epoxy-matrix composites reinforced with carbon and Kevlar fibers. It is found that in the transverse direction the difference between the properties of the fiber and the matrix is not as pronounced as in the longitudinal direction, where the composite properties are fiber-dominated. Therefore, the pattern of fiber packing tends to affect transverse composite properties. The transverse properties of the composites tested are examined from the standpoint of the concept of homogeneity defined as the variation of packing (or lack thereof) throughout a sample.

  11. New acrylic resin composite with improved thermal diffusivity.

    Science.gov (United States)

    Messersmith, P B; Obrez, A; Lindberg, S

    1998-03-01

    Studies have shown that physical characteristics of denture base materials may affect patient acceptance of denture prostheses by altering sensory experience of food during mastication. Thermal diffusivity is one material property that has been cited as being important in determining gustatory response, with denture base acrylic resins having low thermal diffusivity compared with denture base metal alloys. This study prepared and characterized experimental acrylic resin composite material with increased thermal diffusivity. Sapphire (Al2O3) whiskers were added to conventional denture base acrylic resin during processing to achieve loadings of 9.35% and 15% by volume. Cylindrical test specimens containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 degree to 70 degrees C). Thermal diffusivities of the sapphire containing composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the volume percentage of sapphire filler, which suggested that the high aspect ratio ceramic particles formed a pathway for heat conduction through the insulating polymer matrix. The thermal diffusivity of denture base acrylic resin was increased by the addition of thermally conducting sapphire whiskers.

  12. Thermal shock behavior of rare earth modified alumina ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Junlong; Liu, Changxia [Ludong Univ., Yantai (China). School of Transportation

    2017-05-15

    Alumina matrix ceramic composites toughened by AlTiC master alloys, diopside and rare earths were fabricated by hot-pressing and their thermal shock behavior was investigated and compared with that of monolithic alumina. Results showed that the critical thermal shock temperature (ΔT) of monolithic alumina was 400 C. However, it decreased to 300 C for alumina incorporating only AlTiC master alloys, and increased with further addition of diopside and rare earths. Improvement of thermal shock resistance was obtained for alumina ceramic composites containing 9.5 wt.% AlTiC master alloys and 0.5 wt.% rare earth additions, which was mainly attributed to the formation of elongated grains in the composites.

  13. Peculiar Supernovae

    Science.gov (United States)

    Milisavljevic, Dan; Margutti, Raffaella

    2018-06-01

    What makes a supernova truly "peculiar?" In this review we attempt to address this question by tracing the history of the use of "peculiar" as a descriptor of non-standard supernovae back to the original binary spectroscopic classification of Type I vs. Type II proposed by Minkowski (Publ. Astron. Soc. Pac., 53:224, 1941). A handful of noteworthy examples are highlighted to illustrate a general theme: classes of supernovae that were once thought to be peculiar are later seen as logical branches of standard events. This is not always the case, however, and we discuss ASASSN-15lh as an example of a transient with an origin that remains contentious. We remark on how late-time observations at all wavelengths (radio-through-X-ray) that probe 1) the kinematic and chemical properties of the supernova ejecta and 2) the progenitor star system's mass loss in the terminal phases preceding the explosion, have often been critical in understanding the nature of seemingly unusual events.

  14. Thermal Conductivities of Some Polymers and Composites

    Science.gov (United States)

    2018-02-01

    conductivities (Kt) of epoxies, polyurethanes, and hydrocarbons of interest to the Army. The study explores the effects of different curing agents...obtained. 4.12 p-DCPD P-DCPD is currently of interest for composite armor applications because of its unusual ballistic properties and its high TG...the matrix, and recalling that Kt for the fiber does not dominate in the simple model above, a reasonable upper bound for Kt for a 50 volume

  15. Thermal properties of composite materials with a complex fractal structure

    International Nuclear Information System (INIS)

    Cervantes-Álvarez, F; Reyes-Salgado, J J; Dossetti, V; Carrillo, J L

    2014-01-01

    In this work, we report the thermal characterization of platelike composite samples made of polyester resin and magnetite inclusions. By means of photoacoustic spectroscopy and thermal relaxation, the thermal diffusivity, conductivity and volumetric heat capacity of the samples were experimentally measured. The volume fraction of the inclusions was systematically varied in order to study the changes in the effective thermal conductivity of the composites. For some samples, a static magnetic field was applied during the polymerization process, resulting in anisotropic inclusion distributions. Our results show a decrease in the thermal conductivity of some of the anisotropic samples, compared to the isotropic randomly distributed ones. Our analysis indicates that the development of elongated inclusion structures leads to the formation of magnetite and resin domains, causing this effect. We correlate the complexity of the inclusion structure with the observed thermal response through a multifractal and lacunarity analysis. All the experimental data are contrasted with the well known Maxwell–Garnett effective media approximation for composite materials. (paper)

  16. Thermal Stress Effect on Density Changes of Hemp Hurds Composites

    Science.gov (United States)

    Schwarzova, Ivana; Cigasova, Julia; Stevulova, Nadezda

    2016-12-01

    The aim of this article is to study the behavior of prepared biocomposites based on hemp hurds as a filling agent in composite system. In addition to the filler and water, an alternative binder, called MgO-cement was used. For this objective were prepared three types of samples; samples based on untreated hemp hurds as a referential material and samples based on chemically (with NaOH solution) and physically (by ultrasonic procedure) treated hemp hurds. The thermal stress effect on bulk density changes of hemp hurds composites was monitored. Gradual increase in temperature led to composites density reduction of 30-40 %. This process is connected with mass loss of the adsorbed moisture and physically bound water and also with degradation of organic compounds present in hemp hurds aggregates such as pectin, hemicelluloses and cellulose. Therefore the changes in the chemical composition of treated hemp hurds in comparison to original sample and its thermal decomposition were also studied.

  17. An experimental study on thermal properties of composite insulation

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Gyoung-Seok [Building and Urban Research Department, Korea Institute of Construction Technology, 2311 Daehwa-Dong, Ilsanseo-Gu, Goyang-Si, Gyeonggi-Do 411-712 (Korea); College of Architecture, Hanyang University, 17, Hangdang-Dong, Sungdong-Gu, Seoul 133-791 (Korea); Kang, Jae-Sik; Jeong, Young-Sun; Lee, Seung-Eon [Building and Urban Research Department, Korea Institute of Construction Technology, 2311 Daehwa-Dong, Ilsanseo-Gu, Goyang-Si, Gyeonggi-Do 411-712 (Korea); Sohn, Jang-Yeul [College of Architecture, Hanyang University, 17, Hangdang-Dong, Sungdong-Gu, Seoul 133-791 (Korea)

    2007-04-01

    In accordance with the insulation standards reinforced since 2001 and the compulsory standards on floor impact sound insulation that have been enforced since 2004, insulation materials for actual buildings have been converted to composite materials and new insulation materials have been released in the market. However, Korea is lagging behind the world in fundamental experimental studies and resources. In case of some composite insulation materials, there also have been problems of distorted performance occurring as a result of tests being conducted without having verification and evaluation on the accuracy and inaccuracy of such tests. Therefore, this study grasped the thermal properties of composite insulation materials using thermal conductivity test equipment by heat flux method, and performed quantitative evaluation on the measurement precision and uncertainty of composite materials. (author)

  18. Simulating Supernova Light Curves

    International Nuclear Information System (INIS)

    Even, Wesley Paul; Dolence, Joshua C.

    2016-01-01

    This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth's atmosphere.

  19. Simulating Supernova Light Curves

    Energy Technology Data Exchange (ETDEWEB)

    Even, Wesley Paul [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dolence, Joshua C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-05

    This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth’s atmosphere.

  20. Thermal Oxidation Resistance of Rare Earth-Containing Composite Elastomer

    Institute of Scientific and Technical Information of China (English)

    邱关明; 张明; 周兰香; 中北里志; 井上真一; 冈本弘

    2001-01-01

    The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.

  1. Measurement and model on thermal properties of sintered diamond composites

    International Nuclear Information System (INIS)

    Moussa, Tala; Garnier, Bertrand; Peerhossaini, Hassan

    2013-01-01

    Highlights: ► Thermal properties of sintered diamond used for grinding is studied. ► Flash method with infrared temperature measurement is used to investigate. ► Thermal conductivity increases with the amount of diamond. ► It is very sensitive to binder conductivity. ► Results agree with models assuming imperfect contact between matrix and particles. - Abstract: A prelude to the thermal management of grinding processes is measurement of the thermal properties of working materials. Indeed, tool materials must be chosen not only for their mechanical properties (abrasion performance, lifetime…) but also for thermal concerns (thermal conductivity) for efficient cooling that avoids excessive temperatures in the tool and workpiece. Sintered diamond is currently used for grinding tools since it yields higher performances and longer lifetimes than conventional materials (mineral or silicon carbide abrasives), but its thermal properties are not yet well known. Here the thermal conductivity, heat capacity and density of sintered diamond are measured as functions of the diamond content in composites and for two types of metallic binders: hard tungsten-based and soft cobalt-based binders. The measurement technique for thermal conductivity is derived from the flash method. After pulse heating, the temperature of the rear of the sample is measured with a noncontact method (infrared camera). A parameter estimation method associated with a three-layer nonstationary thermal model is used to obtain sample thermal conductivity, heat transfer coefficient and absorbed energy. With the hard metallic binder, the thermal conductivity of sintered diamond increased by up to 64% for a diamond content increasing from 0 to 25%. The increase is much less for the soft binder: 35% for diamond volumes up to 25%. In addition, experimental data were found that were far below the value predicted by conventional analytical models for effective thermal conductivity. A possible explanation

  2. Strength and thermal stability of fiber reinforced plastic composites ...

    African Journals Online (AJOL)

    Therefore, the strength properties and thermal stability of plastic composites reinforced with rattan fibers were investigated in this work. Particles of rattan species (Eremospatha macrocarpa (EM) and Laccosperma secundiflorum (LS)) were blended with High-Density Polyethylene (HDPE) to produce fiber reinforced plastic ...

  3. Dust in Supernovae and Supernova Remnants II: Processing and Survival

    Science.gov (United States)

    Micelotta, E. R.; Matsuura, M.; Sarangi, A.

    2018-03-01

    Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations.

  4. Supernova models

    International Nuclear Information System (INIS)

    Woosley, S.E.; California, University, Livermore, CA); Weaver, T.A.

    1981-01-01

    Recent progress in understanding the observed properties of type I supernovae as a consequence of the thermonuclear detonation of white dwarf stars and the ensuing decay of the Ni-56 produced therein is reviewed. The expected nucleosynthesis and gamma-line spectra for this model of type I explosions and a model for type II explosions are presented. Finally, a qualitatively new approach to the problem of massive star death and type II supernovae based upon a combination of rotation and thermonuclear burning is discussed. While the theoretical results of existing models are predicated upon the assumption of a successful core bounce calculation and the neglect of such two-dimensional effects as rotation and magnetic fields the new model suggests an entirely different scenario in which a considerable portion of the energy carried by an equatorially ejected blob is deposited in the red giant envelope overlying the mantle of the star

  5. Supernova neutrinos

    International Nuclear Information System (INIS)

    John Beacom

    2003-01-01

    We propose that neutrino-proton elastic scattering, ν + p → ν + p, can be used for the detection of supernova neutrinos. Though the proton recoil kinetic energy spectrum is soft, with T p ≅ 2E ν 2 /M p , and the scintillation light output from slow, heavily ionizing protons is quenched, the yield above a realistic threshold is nearly as large as that from (bar ν) e + p → e + + n. In addition, the measured proton spectrum is related to the incident neutrino spectrum, which solves a long-standing problem of how to separately measure the total energy release and temperature of ν μ , ν τ , (bar ν) μ , and (bar ν) τ . The ability to detect this signal would give detectors like KamLAND and Borexino a crucial and unique role in the quest to detect supernova neutrinos

  6. Lamb Wave Assessment of Fatigue and Thermal Damage in Composites

    Science.gov (United States)

    Seale, Michael D.; Smith, Barry T.; Prosser, W. H.

    2004-01-01

    Among the various techniques available, ultrasonic Lamb waves offer a convenient method of evaluating composite materials. Since the Lamb wave velocity depends on the elastic properties of a structure, an effective tool exists to monitor damage in composites by measuring the velocity of these waves. Lamb wave measurements can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper describes two studies which monitor fatigue damage and two studies which monitor thermal damage in composites using Lamb waves. In the fatigue studies, the Lamb wave velocity is compared to modulus measurements obtained using strain gage measurements in the first experiment and the velocity is monitored along with the crack density in the second. In the thermal damage studies, one examines samples which were exposed to varying temperatures for a three minute duration and the second includes rapid thermal damage in composites by intense laser beams. In all studies, the Lamb wave velocity is demonstrated to be an excellent method to monitor damage in composites.

  7. Using lamb waves tomonitor moisture absorption thermally fatigues composite laminates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Sun; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

    2016-06-15

    Nondestructive evaluation for material health monitoring is important in aerospace industries. Composite laminates are exposed to heat cyclic loading and humid environment depending on flight conditions. Cyclic heat loading and moisture absorption may lead to material degradation such as matrix breaking, debonding, and delamination. In this paper, the moisture absorption ratio was investigated by measuring the Lamb wave velocity. The composite laminates were manufactured and subjected to different thermal aging cycles and moisture absorption. For various conditions of these cycles, not only changes in weight and also ultrasonic wave velocity were measured, and the Lamb wave velocity at various levels of moisture on a carbon-epoxy plate was investigated. Results from the experiment show a linear correlation between moisture absorption ratio and Lamb wave velocity at different thermal fatigue stages. The presented method can be applied as an alternative solution in the online monitoring of composite laminate moisture levels in commercial flights.

  8. Novel Magnetic-to-Thermal Conversion and Thermal Energy Management Composite Phase Change Material

    Directory of Open Access Journals (Sweden)

    Xiaoqiao Fan

    2018-05-01

    Full Text Available Superparamagnetic materials have elicited increasing interest due to their high-efficiency magnetothermal conversion. However, it is difficult to effectively manage the magnetothermal energy due to the continuous magnetothermal effect at present. In this study, we designed and synthesized a novel Fe3O4/PEG/SiO2 composite phase change material (PCM that can simultaneously realize magnetic-to-thermal conversion and thermal energy management because of outstanding thermal energy storage ability of PCM. The composite was fabricated by in situ doping of superparamagnetic Fe3O4 nanoclusters through a simple sol–gel method. The synthesized Fe3O4/PEG/SiO2 PCM exhibited good thermal stability, high phase change enthalpy, and excellent shape-stabilized property. This study provides an additional promising route for application of the magnetothermal effect.

  9. A novel phase-change cement composite for thermal energy storage: Fabrication, thermal and mechanical properties

    International Nuclear Information System (INIS)

    Zhang, He; Xing, Feng; Cui, Hong-Zhi; Chen, Da-Zhu; Ouyang, Xing; Xu, Su-Zhen; Wang, Jia-Xin; Huang, Yi-Tian; Zuo, Jian-Dong; Tang, Jiao-Ning

    2016-01-01

    Highlights: • A novel flaky graphite-doped phase-change microcapsule (FGD-MPCM) was prepared. • FGD-MPCM has substantial latent heat storage capacity (135.8 J/g). • FGD-MPCMs/cement composite is capable of reducing indoor temperature fluctuation. • Compressive strength of cement composite with 30% FGD-MPCMs can reach to 14.2 MPa. - Abstract: Facing upon the increasingly severe energy crisis, one of the key issues for reducing the building energy consumption is to pursue high-performance thermal energy storage technologies based on phase-change materials. In this study, a novel cement composite incorporated with flaky graphite-doped microencapsulated phase-change materials (FGD-MPCMs) was developed. Various techniques, such as field emission-scanning electron microscopy (FE-SEM), optical microscopy (OM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to analyse the composite structure and thermal performances. The results indicate that the spherical microcapsules are well dispersed in the cement matrix. When combined within the cement, the thermal stability of the microcapsules was highly improved, and the inclusion of greater amounts of FGD-MPCMs further increased the latent heat of the composite. The mechanical properties of the cement composites were affected with the increase of FGD-MPCMs dosage and the porosity of the composites. In spite of this, the compressive strength and flexural strength of the cement composite with 30% FGD-MPCM could still reach to as high as 14.2 MPa and 4.1 MPa, respectively. Results from the infrared thermography and the model room test suggested that the composite filled with FGD-MPCMs is capable of reducing indoor temperature fluctuation and exhibits good potential for application in buildings to enhance energy savings and thermal comfort.

  10. Thermal Conductivity and Erosion Durability of Composite Two-Phase Air Plasma Sprayed Thermal Barrier Coatings

    Science.gov (United States)

    Schmitt, Michael P.; Rai, Amarendra K.; Zhu, Dongming; Dorfman, Mitchell R.; Wolfe, Douglas E.

    2015-01-01

    To enhance efficiency of gas turbines, new thermal barrier coatings (TBCs) must be designed which improve upon the thermal stability limit of 7 wt% yttria stabilized zirconia (7YSZ), approximately 1200 C. This tenant has led to the development of new TBC materials and microstructures capable of improved high temperature performance. This study focused on increasing the erosion durability of cubic zirconia based TBCs, traditionally less durable than the metastable t' zirconia based TBCs. Composite TBC microstructures composed of a low thermal conductivity/high temperature stable cubic Low-k matrix phase and a durable t' Low-k secondary phase were deposited via APS. Monolithic coatings composed of cubic Low-k and t' Low-k were also deposited, in addition to a 7YSZ benchmark. The thermal conductivity and erosion durability were then measured and it was found that both of the Low-k materials have significantly reduced thermal conductivities, with monolithic t' Low-k and cubic Low-k improving upon 7YSZ by approximately 13 and approximately 25%, respectively. The 40 wt% t' Low-k composite (40 wt% t' Low-k - 60 wt% cubic Low-k) showed a approximately 22% reduction in thermal conductivity over 7YSZ, indicating even at high levels, the t' Low-k secondary phase had a minimal impact on thermal in the composite coating. It was observed that a mere 20 wt% t' Low-k phase addition can reduce the erosion of a cubic Low-k matrix phase composite coating by over 37%. Various mixing rules were then investigated to assess this non-linear composite behavior and suggestions were made to further improve erosion durability.

  11. Polyimide-Foam/Aerogel Composites for Thermal Insulation

    Science.gov (United States)

    Williams, Martha; Fesmire, James; Sass, Jared; Smith, Trent; Weoser. Erol

    2009-01-01

    Composites of specific types of polymer foams and aerogel particles or blankets have been proposed to obtain thermal insulation performance superior to those of the neat polyimide foams. These composites have potential to also provide enhanced properties for vibration dampening or acoustic attenuation. The specific type of polymer foam is denoted "TEEK-H", signifying a series, denoted H, within a family of polyimide foams that were developed at NASA s Langley Research Center and are collectively denoted TEEK (an acronym of the inventors names). The specific types of aerogels include Nanogel aerogel particles from Cabot Corporation in Billerica, MA. and of Spaceloft aerogel blanket from Aspen Aerogels in Northborough, MA. The composites are inherently flame-retardant and exceptionally thermally stable. There are numerous potential uses for these composites, at temperatures from cryogenic to high temperatures, in diverse applications that include aerospace vehicles, aircraft, ocean vessels, buildings, and industrial process equipment. Some low-temperature applications, for example, include cryogenic storage and transfer or the transport of foods, medicines, and chemicals. Because of thermal cycling, aging, and weathering most polymer foams do not perform well at cryogenic temperatures and will undergo further cracking over time. The TEEK polyimides are among the few exceptions to this pattern, and the proposed composites are intended to have all the desirable properties of TEEK-H foams, plus improved thermal performance along with enhanced vibration or acoustic-attenuation performance. A composite panel as proposed would be fabricated by adding an appropriate amount of TEEK friable balloons into a mold to form a bottom layer. A piece of flexible aerogel blanket material, cut to the desired size and shape, would then be placed on the bottom TEEK layer and sandwiched between another top layer of polyimide friable balloons so that the aerogel blanket would become

  12. Study of Physical Properties of SiCw/Al Composites During Unloaded Thermal Cycling

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xin-ming; TIAN zhi-gang; CHENG hua; ZHU Xiao-gang; CHEN Wen-li

    2004-01-01

    The thermal expansion coefficient of SiCw/Al composites squeeze cast during unloaded thermal cycling was determined and analyzed. The study had shown that the thermal expansion coefficient of SiCw/Al composites reduced greatly with temperature raising. The thermal expansion coefficient of artificial ageing treatment SiCw/Al composites during unloaded thermal cycling reduced gradually, while the thermal expansion coefficient of squeezing SiCw/Al composites increased gradually. In addition, the thermal expansion coefficient of SiCw/Al composites reduced drastically with fiber fraction increasing.

  13. Lauric Acid Hybridizing Fly Ash Composite for Thermal Energy Storage

    Directory of Open Access Journals (Sweden)

    Dawei Xu

    2018-04-01

    Full Text Available Fly ash includes different mineral phases. This paper reported on the preparation of a novel lauric acid (LA/fly ash (FA composite by vacuum impregnation as a form-stable phase change material (PCM for thermal energy, and especially investigated the effect of the hydrochloric acid-treated fly ash (FAh on the thermal energy storage performance of the composites. The morphology, crystalline structure, and porous textures of the samples were characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD, Brunauer–Emmett–Teller (BET, X-ray fluorescence (XRF, and differential scanning calorimetry (DSC. The results indicated that hydrochloric acid treatment was beneficial to the increase of loading capacity and crystallinity of LA in the LA/FAh composite, which caused an enhanced thermal storage capacity with latent heats for melting and freezing of LA/FAh (80.94 and 77.39 J/g, higher than those of LA/FA (34.09 and 32.97 J/g, respectively. Furthermore, the mechanism of enhanced thermal storage properties was investigated in detail.

  14. Adaptive implicit method for thermal compositional reservoir simulation

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, A.; Tchelepi, H.A. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Stanford Univ., Palo Alto (United States)

    2008-10-15

    As the global demand for oil increases, thermal enhanced oil recovery techniques are becoming increasingly important. Numerical reservoir simulation of thermal methods such as steam assisted gravity drainage (SAGD) is complex and requires a solution of nonlinear mass and energy conservation equations on a fine reservoir grid. The most currently used technique for solving these equations is the fully IMplicit (FIM) method which is unconditionally stable, allowing for large timesteps in simulation. However, it is computationally expensive. On the other hand, the method known as IMplicit pressure explicit saturations, temperature and compositions (IMPEST) is computationally inexpensive, but it is only conditionally stable and restricts the timestep size. To improve the balance between the timestep size and computational cost, the thermal adaptive IMplicit (TAIM) method uses stability criteria and a switching algorithm, where some simulation variables such as pressure, saturations, temperature, compositions are treated implicitly while others are treated with explicit schemes. This presentation described ongoing research on TAIM with particular reference to thermal displacement processes such as the stability criteria that dictate the maximum allowed timestep size for simulation based on the von Neumann linear stability analysis method; the switching algorithm that adapts labeling of reservoir variables as implicit or explicit as a function of space and time; and, complex physical behaviors such as heat and fluid convection, thermal conduction and compressibility. Key numerical results obtained by enhancing Stanford's General Purpose Research Simulator (GPRS) were also presented along with a list of research challenges. 14 refs., 2 tabs., 11 figs., 1 appendix.

  15. Nanobioceramic Composites: A Study of Mechanical, Morphological, and Thermal Properties

    Directory of Open Access Journals (Sweden)

    Sivabalan Sasthiryar

    2013-12-01

    Full Text Available The aim of this study was to explore the incorporation of biomass carbon nanofillers (CNF into advanced ceramic. Biomass from bamboo, bagasse (remains of sugarcane after pressing, and oil palm ash was used as the predecessor for producing carbon black nanofillers. Furnace pyrolysis was carried out at 1000 °C and was followed by ball-mill processing to obtain carbon nanofillers in the range of 50 nm to 100 nm. CNFs were added to alumina in varying weight fractions and the resulting mixture was subjected to vacuum sintering at 1400 °C to produce nanobioceramic composites. The ceramic composites were characterized for mechanical, thermal, and morphological properties. A high-resolution Charge-coupled device (CCD camera was used to study the fracture impact and the failure mechanism. An increase in the loading percentage of CNFs in the alumna decreased the specific gravity, vickers hardness (HV, and fracture toughness values of the composite materials. Furthermore, the thermal conductivity and the thermal stability of the ceramic composite increased as compared to the pristine alumina.

  16. On composition and thermal degradation of basic zirconium sulfates

    Energy Technology Data Exchange (ETDEWEB)

    Grizik, A A; Nekhamkin, L G; Kondrashova, I A; Serebrennikov, E L; Kerina, V P

    1988-02-01

    Methods of potentiometric titration, conductometry and thermal gravimetric analysis are used to study composition and properties of basic zirconium sulfates (BZS) obtained under different conditions of precipitation from aqueous solutions. Three X-ray amorphous phases of BZR with mole ratio SO/sub 4//sup 2-/:Zr, being 0.60+-0.03; 0.37+-0.04 and 0.176+-0.005, are identified. Different character of thermal decomposition of these phases in the process of zirconium dioxide preparation from BZS is confirmed.

  17. On composition and thermal degradation of basic zirconium sulfates

    International Nuclear Information System (INIS)

    Grizik, A.A.; Nekhamkin, L.G.; Kondrashova, I.A.; Serebrennikov, E.L.; Kerina, V.P.

    1988-01-01

    Methods of potentiometric titration, conductometry and thermal gravimetric analysis are used to study composition and properties of basic zirconium sulfates (BZS) obtained under different conditions of precipitation from aqueous solutions. Three X-ray amorphous phases of BZR with mole ratio SO 4 2- :Zr, being 0.60±0.03; 0.37±0.04 and 0.176±0.005, are identified. Different character of thermal decomposition of these phases in the process of zirconium dioxide preparation from BZS is confirmed

  18. Thermal stresses in composite tubes using complementary virtual work

    Science.gov (United States)

    Hyer, M. W.; Cooper, D. E.

    1988-01-01

    This paper addresses the computation of thermally induced stresses in layered, fiber-reinforced composite tubes subjected to a circumferential gradient. The paper focuses on using the principle of complementary virtual work, in conjunction with a Ritz approximation to the stress field, to study the influence on the predicted stresses of including temperature-dependent material properties. Results indicate that the computed values of stress are sensitive to the temperature dependence of the matrix-direction compliance and matrix-direction thermal expansion in the plane of the lamina. There is less sensitivity to the temperature dependence of the other material properties.

  19. Modeling of composite synthesis in conditions of controlled thermal explosion

    Science.gov (United States)

    Kukta, Yaroslav; Knyazeva, Anna

    2017-12-01

    The paper proposes the model for the titanium-based composite synthesis from powders of titanium and carbon of non-stoichiometric composition. The model takes into account the mixture heating from chamber walls, the dependence of liquidus and solidus temperatures on the composition of reacting mixture and the formation of possible irreversible phases. The reaction retardation by the reaction product is taken into consideration in kinetic laws. As an example, the results of temperature and conversion level calculation are presented for the system Ti-C with the summary reaction for different temperatures of chamber walls heating. It was revealed that the reaction retardation being the reaction product can be the cause of incomplete conversion in the thermal explosion conditions. Non-stoichiometric composition leads to the conditions of degenerated mode when some additional heating is necessary to complete the reaction.

  20. Development of Composite for Thermal Barriers Reinforced by Ceramic Fibers

    Directory of Open Access Journals (Sweden)

    Ondřej Holčapek

    2018-01-01

    Full Text Available The paper introduces the development process of fiber-reinforced composite with increased resistance to elevated temperatures, which could be additionally increased by the hydrothermal curing. However, production of these composites is extremely energy intensive, and that is why the process of the design reflects environmental aspects by incorporation of waste material—fine ceramic powder applied as cement replacement. Studied composite materials consisted of the basalt aggregate, ceramic fibers applied up to 8% by volume, calcium-aluminous cement (CAC, ceramic powder up to 25% by mass (by 5% as cement replacement, plasticizer, and water. All studied mixtures were subjected to thermal loading on three thermal levels: 105°C, 600°C, and 1000°C. Experimental assessment was performed in terms of both initial and residual material properties; flow test of fresh mixtures, bulk density, compressive strength, flexural strength, fracture energy, and dynamic modulus of elasticity were investigated to find out an optimal dosage of ceramic fibers. Resulting set of composites containing 4% of ceramic fibers with various modifications by ceramic powder was cured under specific hydrothermal condition and again subjected to elevated temperatures. One of the most valuable benefits of additional hydrothermal curing of the composites lies in the higher residual mechanical properties, what allows successful utilization of cured composite as a thermal barrier in civil engineering. Mixtures containing ceramic powder as cement substitute exhibited after hydrothermal curing increase of residual flexural strength about 35%; on the other hand, pure mixture exhibited increase up to 10% even higher absolute values.

  1. Thermal expansion of epoxy-fiberglass composite specimens

    International Nuclear Information System (INIS)

    McElroy, D.L.; Weaver, F.J.; Bridgman, C.

    1986-01-01

    The thermal expansion behavior of three epoxy-fiberglass composite specimens was measured from 20 to 120 0 C (70 to 250 0 F) using a fused quartz push-rod dilatometer. Billets produced by vacuum impregnating layers of two types of fiberglass cloth with an epoxy resin were core-drilled to produce cylindrical specimens. These were used to study expansion perpendicular and parallel to the fiberglass layers. The dilatometer is held at a preselected temperature until steady-state is indicated by stable length and temperature data. Before testing the composite specimens, a reliability check of the dilatometer was performed using a copper secondary standard. This indicated thermal expansion coefficient (α) values within +-2% of expected values from 20 to 200 0 C

  2. Thermal stability of poly(3-hydroxybutyrate)/vegetable fiber composites

    Science.gov (United States)

    Cipriano, Pâmela Bento; de Sá, Mayelli Dantas; Andrade, André L. Simões; de Carvalho, Laura Hecker; Canedo, Eduardo Luis

    2015-05-01

    The present work deals with the thermal stability during and after processing of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermoplastic obtained from renewable resources through low-impact biotechnological process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB/babassu composites with 0, 5, 10 and 20% w/w load were prepared in a laboratory internal mixer. Two fractions of the mesocarp of babassu with different particle sizes were compounded with PHB and test specimens molded by compression. The effect of loading level and processing conditions on torque, temperature and mechanical energy dissipation were studied using a new engineering model. It was found that PHB degrades during processing at temperatures slightly above the melting point. To minimize thermal degradation stabilizer and chain extender additives were incorporated, with mixed results. These findings were confirmed by the dependence of the melt flow rate on the processing temperature.

  3. Hard thermal loops, static response, and the composite effective action

    International Nuclear Information System (INIS)

    Jackiw, R.; Liu, Q.; Lucchesi, C.

    1994-01-01

    First, we investigate the static non-Abelian Kubo equation. We prove that it does not possess finite energy solutions; thereby we establish that gauge theories do not support hard thermal solitons. This general result is verified by a numerical solution of the equations. A similar argument shows that ''static'' instantons are absent. In addition, we note that the static equations reproduce the expected screening of the non-Abelian electric field by a gauge-invariant Debye mass m=gT √(N+N F /2)/3 . Second, we derive the non-Abelian Kubo equation from the composite effective action. This is achieved by showing that the requirement of stationarity of the composite effective action is equivalent, within a kinematical approximation scheme, to the condition of gauge invariance for the generating functional of hard thermal loops

  4. Diurnal thermal analysis of microencapsulated PCM-concrete composite walls

    International Nuclear Information System (INIS)

    Thiele, Alexander M.; Sant, Gaurav; Pilon, Laurent

    2015-01-01

    Highlights: • Transient heat conduction across microencapsulated PCM-concrete walls was simulated. • Equivalent homogeneous wall with effective thermal properties was rigorously derived. • Adding PCM to the wall increases daily energy savings and delays peak thermal load. • Energy savings is maximum when PCM melting temperature equals indoor temperature. • Energy savings are limited in extreme climates but time delay can be large. - Abstract: This paper examines the benefits of adding microencapsulated phase change material (PCM) to concrete used in building envelopes to reduce energy consumption and costs. First, it establishes that the time-dependent thermal behavior of microencapsulated PCM-concrete composite walls can be accurately predicted by an equivalent homogeneous wall with appropriate effective thermal properties. The results demonstrate that adding microencapsulated PCM to concrete resulted in a reduction and a time-shift in the maximum heat flux through the composite wall subjected to diurnal sinusoidal outdoor temperature and solar radiation heat flux. The effects of the PCM volume fraction, latent heat of fusion, phase change temperature and temperature window, and outdoor temperature were evaluated. Several design rules were established including (i) increasing the PCM volume fraction and/or enthalpy of phase change increased the energy flux reduction and the time delay, (ii) the energy flux reduction was maximized when the PCM phase change temperature was close to the desired indoor temperature, (iii) the optimum phase change temperature to maximize the time delay increased with increasing average outdoor temperature, (iv) in extremely hot or cold climates, the thermal load could be delayed even though the reduction in daily energy flux was small, and (v) the choice of phase change temperature window had little effect on the energy flux reduction and on the time delay. This analysis can serve as a framework to design PCM composite walls

  5. Thermal transformations of pitch and its compositions with thermoanthracite

    Energy Technology Data Exchange (ETDEWEB)

    Belkina, T.V.; Ulanovskii, M.L.; Krysin, V.P.

    1983-01-01

    Derivatogrphy is used to investigate the character of thermal transformations of hard coal pitch in compositions with thermoanthracite. It was shown that losses in mass during thermal transformations of hard coal pitch in the temperature interval 200-1000 C occur in two stages, at a varying rate in the 200-600 C range and at a constant rate in the 600-1000 C range. The rate of loss in the 200-600 C range is determined primarily by the rate of diffusion of volatile components and products of pitch conversion and in the 600-1000 C range mainly by the rate of the elemental chemical event. The thermal transformation is essentially unchanged in the presence of thermoanthracite. Silica intensifies the synthesis and increases the solid residue yield. Increasing the rate of heating of the pitch-thermoanthracite brings about incomplete separation of volatile products and a corresponding increase in the solid residue yield. (9 refs.)

  6. A DETAILED STUDY OF NON-THERMAL X-RAY PROPERTIES AND INTERSTELLAR GAS TOWARD THE γ-RAY SUPERNOVA REMNANT RX J1713.7–3946

    Energy Technology Data Exchange (ETDEWEB)

    Sano, H.; Fukuda, T.; Yoshiike, S.; Sato, J.; Horachi, H.; Kuwahara, T.; Torii, K.; Hayakawa, T.; Matsumoto, H.; Inutsuka, S.; Yamamoto, H.; Tachihara, K. [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Tanaka, T. [Department of Physics, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Inoue, T.; Kawamura, A.; Okuda, T.; Mizuno, N. [National Astronomical Observatory of Japan, Mitaka 181-8588 (Japan); Yamazaki, R. [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Chuou-ku, Sagamihara 252-5258 (Japan); Onishi, T. [Department of Astrophysics, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531 (Japan); Mizuno, A., E-mail: sano@a.phys.nagoya-u.ac.jp [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); and others

    2015-02-01

    We have carried out a spectral analysis of the Suzaku X-ray data in the 0.4-12 keV range toward the shell-type very high-energy γ-ray supernova remnant (SNR) RX J1713.7–3946. The aims of this analysis are to estimate detailed X-rays spectral properties at a high angular resolution up to 2 arcmin and to compare them with the interstellar gas. The X-ray spectrum is non-thermal and used to calculate absorbing column density, photon index, and absorption-corrected X-ray flux. The photon index varies significantly from 2.1 to 2.9. It is shown that the X-ray intensity is well correlated with the photon index, especially in the west region, with a correlation coefficient of 0.81. The X-ray intensity tends to increase with the averaged interstellar gas density while the dispersion is relatively large. The hardest spectra, with photon indexes of less than 2.4, are found outside of the central 10 arcmin of the SNR, from the north to the southeast (∼430 arcmin{sup 2}) and from the southwest to the northwest (∼150 arcmin{sup 2}). The former region shows low interstellar gas density, while the latter shows high interstellar gas density. We present a discussion of possible scenarios that explain the distribution of the photon index and its relationship with the interstellar gas.

  7. Thermal Protective Coating for High Temperature Polymer Composites

    Science.gov (United States)

    Barron, Andrew R.

    1999-01-01

    The central theme of this research is the application of carboxylate-alumoxane nanoparticles as precursors to thermally protective coatings for high temperature polymer composites. In addition, we will investigate the application of carboxylate-alumoxane nanoparticle as a component to polymer composites. The objective of this research was the high temperature protection of polymer composites via novel chemistry. The significance of this research is the development of a low cost and highly flexible synthetic methodology, with a compatible processing technique, for the fabrication of high temperature polymer composites. We proposed to accomplish this broad goal through the use of a class of ceramic precursor material, alumoxanes. Alumoxanes are nano-particles with a boehmite-like structure and an organic periphery. The technical goals of this program are to prepare and evaluate water soluble carboxylate-alumoxane for the preparation of ceramic coatings on polymer substrates. Our proposed approach is attractive since proof of concept has been demonstrated under the NRA 96-LeRC-1 Technology for Advanced High Temperature Gas Turbine Engines, HITEMP Program. For example, carbon and Kevlar(tm) fibers and matting have been successfully coated with ceramic thermally protective layers.

  8. Thermal characterization of magnetically aligned carbonyl iron/agar composites.

    Science.gov (United States)

    Diaz-Bleis, D; Vales-Pinzón, C; Freile-Pelegrín, Y; Alvarado-Gil, J J

    2014-01-01

    Composites of magnetic particles into polymeric matrices have received increasing research interest due to their capacity to respond to external magnetic or electromagnetic fields. In this study, agar from Gelidium robustum has been chosen as natural biocompatible polymer to build the matrix of the magnetic carbonyl iron particles (CIP) for their uses in biomedical fields. Heat transfer behavior of the CIP-agar composites containing different concentrations (5, 10, 15, 20, 25 and 30% w/w) of magnetically aligned and non-aligned CIP in the agar matrix was studied using photothermal radiometry (PTR) in the back-propagation emission configuration. The morphology of the CIP-agar composites with aligned and non-aligned CIP under magnetic field was also evaluated by scanning electron microscopy (SEM). The results revealed a dominant effect of CIP concentration over the alignment patterns induced by the magnetic field, which agrees with the behavior of the thermal diffusivity and thermal conductivity. Agar served as a perfect matrix to be used with CIP, and CIP-agar composites magnetically aligned at 20% CIP concentration can be considered as promising 'smart' material for hyperthermia treatments in the biomedical field. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Thermal expansion behaviour of high performance PEEK matrix composites

    International Nuclear Information System (INIS)

    Goyal, R K; Mulik, U P; Tiwari, A N; Negi, Y S

    2008-01-01

    The thermal expansion behaviour of high performance poly(ether-ether-ketone) (PEEK) composites reinforced with micro- (8 μm) and nano- (39 nm) sized Al 2 O 3 particles was studied. The distribution of Al 2 O 3 in the PEEK matrix was studied by scanning electron microscopy and transmission electron microscopy. The coefficient of thermal expansion (CTE) was reduced from 58 x 10 -6 deg. C -1 for pure PEEK to 22 x 10 -6 deg. C -1 at 43 vol% micro-Al 2 O 3 and to 23 x 10 -6 deg. C -1 at 12 vol% nano-Al 2 O 3 composites. For a given volume fraction, nano-Al 2 O 3 particles are more effective in reducing the CTE of composites than that of micro-Al 2 O 3 particles. This may be attributed to the much higher interfacial area or volume of nanocomposites than that of microcomposites. The upper limit and lower limit of the Schapery model separately fit closely the CTE of the micro- and nano-composites, respectively. Other models such as the rule of mixture and Kerner and Turner models were also correlated with the data

  10. Thermal Stress Effect on Density Changes of Hemp Hurds Composites

    Directory of Open Access Journals (Sweden)

    Schwarzova Ivana

    2016-12-01

    Full Text Available The aim of this article is to study the behavior of prepared biocomposites based on hemp hurds as a filling agent in composite system. In addition to the filler and water, an alternative binder, called MgO-cement was used. For this objective were prepared three types of samples; samples based on untreated hemp hurds as a referential material and samples based on chemically (with NaOH solution and physically (by ultrasonic procedure treated hemp hurds. The thermal stress effect on bulk density changes of hemp hurds composites was monitored. Gradual increase in temperature led to composites density reduction of 30-40 %. This process is connected with mass loss of the adsorbed moisture and physically bound water and also with degradation of organic compounds present in hemp hurds aggregates such as pectin, hemicelluloses and cellulose. Therefore the changes in the chemical composition of treated hemp hurds in comparison to original sample and its thermal decomposition were also studied.

  11. Surface properties of thermally treated composite wood panels

    Science.gov (United States)

    Croitoru, Catalin; Spirchez, Cosmin; Lunguleasa, Aurel; Cristea, Daniel; Roata, Ionut Claudiu; Pop, Mihai Alin; Bedo, Tibor; Stanciu, Elena Manuela; Pascu, Alexandru

    2018-04-01

    Composite finger-jointed spruce and oak wood panels have been thermally treated under standard pressure and oxygen content conditions at two different temperatures, 180 °C and respectively 200 °C for short time periods (3 and 5 h). Due to the thermally-aided chemical restructuration of the wood components, a decrease in water uptake and volumetric swelling values with up to 45% for spruce and 35% for oak have been registered, comparing to the reference samples. In relation to water resistance, a 15% increase of the dispersive component of the surface energy has been registered for the thermal-treated spruce panels, which impedes water spreading on the surface. The thermal-treated wood presents superior resistance to accelerated UV exposure and subsequently, with up to 10% higher Brinell hardness values than reference wood. The proposed thermal treatment improves the durability of the finger-jointed wood through a more economically and environmental friendly method than traditional impregnation, with minimal degradative impact on the structural components of wood.

  12. Atomistic Modeling of Thermal Conductivity of Epoxy Nanotube Composites

    Science.gov (United States)

    Fasanella, Nicholas A.; Sundararaghavan, Veera

    2016-05-01

    The Green-Kubo method was used to investigate the thermal conductivity as a function of temperature for epoxy/single wall carbon nanotube (SWNT) nanocomposites. An epoxy network of DGEBA-DDS was built using the `dendrimer' growth approach, and conductivity was computed by taking into account long-range Coulombic forces via a k-space approach. Thermal conductivity was calculated in the direction perpendicular to, and along the SWNT axis for functionalized and pristine SWNT/epoxy nanocomposites. Inefficient phonon transport at the ends of nanotubes is an important factor in the thermal conductivity of the nanocomposites, and for this reason discontinuous nanotubes were modeled in addition to long nanotubes. The thermal conductivity of the long, pristine SWNT/epoxy system is equivalent to that of an isolated SWNT along its axis, but there was a 27% reduction perpendicular to the nanotube axis. The functionalized, long SWNT/epoxy system had a very large increase in thermal conductivity along the nanotube axis (~700%), as well as the directions perpendicular to the nanotube (64%). The discontinuous nanotubes displayed an increased thermal conductivity along the SWNT axis compared to neat epoxy (103-115% for the pristine SWNT/epoxy, and 91-103% for functionalized SWNT/epoxy system). The functionalized system also showed a 42% improvement perpendicular to the nanotube, while the pristine SWNT/epoxy system had no improvement over epoxy. The thermal conductivity tensor is averaged over all possible orientations to see the effects of randomly orientated nanotubes, and allow for experimental comparison. Excellent agreement is seen for the discontinuous, pristine SWNT/epoxy nanocomposite. These simulations demonstrate there exists a threshold of the SWNT length where the best improvement for a composite system with randomly oriented nanotubes would transition from pristine SWNTs to functionalized SWNTs.

  13. Expansion and Brightness Changes in the Pulsar-wind Nebula in the Composite Supernova Remnant Kes 75

    Science.gov (United States)

    Reynolds, Stephen P.; Borkowski, Kazimierz J.; Gwynne, Peter H.

    2018-04-01

    We report new Chandra X-ray observations of the shell supernova remnant Kes 75 (G29.7‑0.3) containing a pulsar and pulsar-wind nebula (PWN). Expansion of the PWN is apparent across four epochs—2000, 2006, 2009, and 2016. We find an expansion rate between 2000 and 2016 of the northwest edge of the PWN of 0.249% ± 0.023% yr‑1, for an expansion age R/(dR/dt) of 400 ± 40 yr and an expansion velocity of about 1000 km s‑1. We suggest that the PWN is expanding into an asymmetric nickel bubble in a conventional Type IIP supernova. Some acceleration of the PWN expansion is likely, giving a true age of 480 ± 50 yr. The pulsar’s birth luminosity was larger than the current value by a factor of 3–8, while the initial period was within a factor of 2 of its current value. We confirm directly that Kes 75 contains the youngest known PWN, and hence the youngest known pulsar. The pulsar PSR J1846‑0258 has a spindown-inferred magnetic field of 5 × 1013 G; in 2006, it emitted five magnetar-like short X-ray bursts, but its spindown luminosity has not changed significantly. However, the flux of the PWN has decreased by about 10% between 2009 and 2016, almost entirely in the northern half. A bright knot has declined by 30% since 2006. During this time, the photon indices of the power-law models did not change. This flux change is too rapid to be due to normal PWN evolution in one-zone models.

  14. Supernova hydrodynamics

    International Nuclear Information System (INIS)

    Colgate, S.A.

    1981-01-01

    The explosion of a star supernova occurs at the end of its evolution when the nuclear fuel in its core is almost, or completely, consumed. The star may explode due to a small residual thermonuclear detonation, type I SN or it may collapse, type I and type II SN leaving a neutron star remnant. The type I progenitor should be thought to be an old accreting white dwarf, 1.4 M/sub theta/, with a close companion star. A type II SN is thought to be a massive young star 6 to 10 M/sub theta/. The mechanism of explosion is still a challenge to our ability to model the most extreme conditions of matter and hydrodynamics that occur presently and excessively in the universe. 39 references

  15. Highly thermal conductive carbon fiber/boron carbide composite material

    International Nuclear Information System (INIS)

    Chiba, Akio; Suzuki, Yasutaka; Goto, Sumitaka; Saito, Yukio; Jinbo, Ryutaro; Ogiwara, Norio; Saido, Masahiro.

    1996-01-01

    In a composite member for use in walls of a thermonuclear reactor, if carbon fibers and boron carbide are mixed, since they are brought into contact with each other directly, boron is reacted with the carbon fibers to form boron carbide to lower thermal conductivity of the carbon fibers. Then, in the present invention, graphite or amorphous carbon is filled between the carbon fibers to provide a fiber bundle of not less than 500 carbon fibers. Further, the surface of the fiber bundle is coated with graphite or amorphous carbon to suppress diffusion or solid solubilization of boron to carbon fibers or reaction of them. Then, lowering of thermal conductivity of the carbon fibers is prevented, as well as the mixing amount of the carbon fiber bundles with boron carbide, a sintering temperature and orientation of carbon fiber bundles are optimized to provide a highly thermal conductive carbon fiber/boron carbide composite material. In addition, carbide or boride type short fibers, spherical graphite, and amorphous carbon are mixed in the boron carbide to prevent development of cracks. Diffusion or solid solubilization of boron to carbon fibers is reduced or reaction of them if the carbon fibers are bundled. (N.H.)

  16. Thermal properties of poly(3-hydroxybutyrate)/vegetable fiber composites

    Science.gov (United States)

    Vitorino, Maria B. C.; Reul, Lízzia T. A.; Carvalho, Laura H.; Canedo, Eduardo L.

    2015-05-01

    The present work studies the thermal properties of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermo-plastic obtained from renewable resources through low-impact biotechno-logical process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB is a highly crystalline resin and this characteristic leads to suboptimal properties in some cases. Consequently, thermal properties, in particular those associated with the crystallization of the matrix, are important to judge the suitability of the compounds for specific applications. PHB/babassu composites with 0-50% load were prepared in an internal mixer. Two different types of babassu fibers with two different particle size ranges were compounded with PHB and test specimens molded by compression. Melting and crystallization behavior were studied by differential scanning calorimetry (DSC) at heating/cooling rates between 2 and 30°C/min. Several parameters, including melting point, crystallization temperature, crystallinity, and rate of crystallization, were estimated as functions of load and heating/cooling rates. Results indicate that fibers do not affect the melting process, but facilitate crystallization from the melt. Crystallization temperatures are 30 to 40°C higher for the compounds compared with the neat resin. However, the amount of fiber added has little effect on crystallinity and the degree of crystallinity is hardly affected by the load. Fiber type and initial particle size do not have a significant effect on thermal properties.

  17. The thermal transformations of pitch and its compositions with thermoanthracite

    Energy Technology Data Exchange (ETDEWEB)

    Belkina, T.V.; Krysin, V.P.; Ulanovskii, M.L.

    1983-01-01

    The loss of mass in the thermal transformations of a hard-coal pitch and its compositions with thermoanthracite in the temperature interval of 200-1000/sup 0/C takes place in two main stages: with a variable rate in the 200-600/sup 0/C interval and at a constant rate in the 600-1000/sup 0/C interval. The rate of the mass loss process in the 200-600/sup 0/C interval is determined mainly by the rate of diffusion of the volatile components and also of the light products of the thermal transformations of the pitch from the bulk to the phase separation boundary, and in the 600-1000/sup 0/C interval predominantly by the rate of the actual elementary chemical reaction. In the presence of thermoanthracite, the nature of the thermal transformations of the pitch does not change appreciably, while in the presence of silica synthetic reactions are intensified, which leads to an increase in the yield of solid residue by approximately 4 mass %. (A rise in the rate of heating of pitch-thermoanthracite compositions leads to the incomplete elimination of volatile products in the first stage, which has a favorable action on the increase in the yield of solid residue.)

  18. Type II supernovae modelisation: neutrinos transport simulation

    International Nuclear Information System (INIS)

    Mellor, P.

    1988-10-01

    A modelisation of neutrino transport in type II supernovae is presented. The first part is a description of hydrodynamics and radiative processes responsible of supernovae explosions. Macroscopic aspects of these are displayed in part two. Neutrino transport theory and usual numerical methods are also developed. A new technic of coherent scattering of neutrinos on nuclei or free nucleons is proposed in the frame work of the Lorentz bifluid approximation. This method deals with all numerical artifices (flux limiting schemes, closure relationship of Eddington moments) and allows a complete and consistent determination of the time-dependent neutrino distribution function for any value of the opacity, gradient of opacity and for all (relativistic) velocity fields of the diffusive medium. Part three is dedicated to microscopic phenomena (electronic capture, chimical composition, etc) which rule neutrinos emission-absorption mechanisms. The numerical treatments of those are presented, and some applications are useful for their parametrization. Finally, an extension of the method to inelastic scattering on light particules (electrons) is described in view to study neutrinos thermalization mechanism [fr

  19. THERMAL COMPOSITE COATINGS IMPROVING QUALITY OF TECHNICAL MEANS OF TRANSPORT

    Directory of Open Access Journals (Sweden)

    Andrzej POSMYK

    2015-06-01

    Full Text Available The paper presents the thermal properties of composite insulating material designed for producing of technical means of transport. This material can be coated on most of engineering materials. The matrix of this material is an acrylic resin ant non porous ceramic microspheres made of alumina are the reinforcing phase. Thanks to that into the spheres almost vacuum (0,13 Pa dominants and a big amount of spheres pro thickness unit is it possible to achieve low thermal conductivity. Usage of these coatings for producing of cooling cabins on vehicles let us to reduce of fuel for maintain of given temperature. Usage of these coatings in planes flying on high altitudes (temperature up to -60 allows to reduce of fuel consumption for heating. It has an important influence on transport quality and quality costs.

  20. Masses of supernova progenitors

    International Nuclear Information System (INIS)

    Tinsley, B.M.

    1977-01-01

    The possible nature and masses of supernovae progenitors, and the bearing of empirical results on some unsolved theoretical problems concerning the origin of supernovae, are discussed. The author concentrates on two main questions: what is the lower mass limit for stars to die explosively and what stars initiate type I supernovae. The evidence considered includes local supernova rates, empirical estimates of msub(w) (the upper mass limit for death as a white dwarf), the distributions of supernovae among stellar populations in galaxies and the colors of supernova producing galaxies. (B.D.)

  1. GALAXY OUTFLOWS WITHOUT SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Sur, Sharanya [Indian Institute of Astrophysics, 2nd Block, Koramangala, Bangalore 560034 (India); Scannapieco, Evan [School of Earth and Space Exploration, Arizona State University, P.O. Box 876004, Tempe-85287 (United States); Ostriker, Eve C., E-mail: sharanya.sur@iiap.res.in, E-mail: sharanya.sur@asu.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2016-02-10

    High surface density, rapidly star-forming galaxies are observed to have ≈50–100 km s{sup −1} line of sight velocity dispersions, which are much higher than expected from supernova driving alone, but may arise from large-scale gravitational instabilities. Using three-dimensional simulations of local regions of the interstellar medium, we explore the impact of high velocity dispersions that arise from these disk instabilities. Parametrizing disks by their surface densities and epicyclic frequencies, we conduct a series of simulations that probe a broad range of conditions. Turbulence is driven purely horizontally and on large scales, neglecting any energy input from supernovae. We find that such motions lead to strong global outflows in the highly compact disks that were common at high redshifts, but weak or negligible mass loss in the more diffuse disks that are prevalent today. Substantial outflows are generated if the one-dimensional horizontal velocity dispersion exceeds ≈35 km s{sup −1}, as occurs in the dense disks that have star-formation rate (SFR) densities above ≈0.1 M{sub ⊙} yr{sup −1} kpc{sup −2}. These outflows are triggered by a thermal runaway, arising from the inefficient cooling of hot material coupled with successive heating from turbulent driving. Thus, even in the absence of stellar feedback, a critical value of the SFR density for outflow generation can arise due to a turbulent heating instability. This suggests that in strongly self-gravitating disks, outflows may be enhanced by, but need not caused by, energy input from supernovae.

  2. Cosmological and supernova neutrinos

    Science.gov (United States)

    Kajino, T.; Aoki, W.; Balantekin, A. B.; Cheoun, M.-K.; Hayakawa, T.; Hidaka, J.; Hirai, Y.; Kusakabe, M.; Mathews, G. J.; Nakamura, K.; Pehlivan, Y.; Shibagaki, S.; Suzuki, T.

    2014-06-01

    The Big Bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) anisotropies are the pillars of modern cosmology. It has recently been suggested that axion which is a dark matter candidate in the framework of the standard model could condensate in the early universe and induce photon cooling before the epoch of the photon last scattering. Although this may render a solution to the overproduction problem of primordial 7Li abundance, there arises another serious difficulty of overproducing D abundance. We propose a hybrid dark matter model with both axions and relic supersymmetric (SUSY) particles to solve both overproduction problems of the primordial D and 7Li abundances simultaneously. The BBN also serves to constrain the nature of neutrinos. Considering non-thermal photons produced in the decay of the heavy sterile neutrinos due to the magnetic moment, we explore the cosmological constraint on the strength of neutrino magnetic moment consistent with the observed light element abundances. Core-collapse supernovae eject huge flux of energetic neutrinos which affect explosive nucleosynthesis of rare isotopes like 7Li, 11B, 92Nb, 138La and 180Ta and r-process elements. Several isotopes depend strongly on the neutrino flavor oscillation due to the Mikheyev-Smirnov-Wolfenstein (MSW) effect. Combining the recent experimental constraints on θ13 with predicted and observed supernova-produced abundance ratio 11B/7Li encapsulated in the presolar grains from the Murchison meteorite, we show a marginal preference for an inverted neutrino mass hierarchy. We also discuss supernova relic neutrinos (SRN) that may indicate the softness of the equation of state (EoS) of nuclear matter and adiabatic conditions of the neutrino oscillation.

  3. Cosmological and supernova neutrinos

    Energy Technology Data Exchange (ETDEWEB)

    Kajino, T. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Department of Astronomy, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Aoki, W. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Balantekin, A. B. [Department of Physics, University of Wisconsin - Madison, Wisconsin 53706 (United States); Cheoun, M.-K. [Department of Physics, Soongsil University, Seoul 156-743 (Korea, Republic of); Hayakawa, T. [Japan Atomic Energy Agency, Shirakara-Shirane 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); Hidaka, J. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Hirai, Y.; Shibagaki, S. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan and Department of Astronomy, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Kusakabe, M. [School of Liberal Arts and Science, Korea Aerospace University, Goyang 412-791 (Korea, Republic of); Mathews, G. J. [Department of Physics, University of Notre Dame, IN 46556 (United States); Nakamura, K. [Waseda University, Ohkubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan); Pehlivan, Y. [Mimar Sinan GSÜ, Department of Physics, Şişli, İstanbul 34380 (Turkey); Suzuki, T. [Nihon University, Sakurajosui 3-25-40, Setagaya-ku, Tokyo 156-8550 (Japan)

    2014-06-24

    The Big Bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) anisotropies are the pillars of modern cosmology. It has recently been suggested that axion which is a dark matter candidate in the framework of the standard model could condensate in the early universe and induce photon cooling before the epoch of the photon last scattering. Although this may render a solution to the overproduction problem of primordial {sup 7}Li abundance, there arises another serious difficulty of overproducing D abundance. We propose a hybrid dark matter model with both axions and relic supersymmetric (SUSY) particles to solve both overproduction problems of the primordial D and {sup 7}Li abundances simultaneously. The BBN also serves to constrain the nature of neutrinos. Considering non-thermal photons produced in the decay of the heavy sterile neutrinos due to the magnetic moment, we explore the cosmological constraint on the strength of neutrino magnetic moment consistent with the observed light element abundances. Core-collapse supernovae eject huge flux of energetic neutrinos which affect explosive nucleosynthesis of rare isotopes like {sup 7}Li, {sup 11}B, {sup 92}Nb, {sup 138}La and {sup 180}Ta and r-process elements. Several isotopes depend strongly on the neutrino flavor oscillation due to the Mikheyev-Smirnov-Wolfenstein (MSW) effect. Combining the recent experimental constraints on θ{sub 13} with predicted and observed supernova-produced abundance ratio {sup 11}B/{sup 7}Li encapsulated in the presolar grains from the Murchison meteorite, we show a marginal preference for an inverted neutrino mass hierarchy. We also discuss supernova relic neutrinos (SRN) that may indicate the softness of the equation of state (EoS) of nuclear matter and adiabatic conditions of the neutrino oscillation.

  4. Constitutional equations of thermal stresses of particle-reinforced composite

    International Nuclear Information System (INIS)

    Asakawa, Atsushi; Noda, Naotake; Tohgo, Keiichiro; Tsuji, Tomoaki.

    1994-01-01

    Functionally gradient materials (FGM) have been developed as ultrahigh-heat-resistant materials in aircraft, space engineering and nuclear fields. In the heat-resistant FGM which contain particles (ceramics) in the matrix (metal), the matrix will be subjected to plastic deformation, particles will be debonded, and finally cracks will be generated. The constitutive equations of FGM which take into account the damage process and change in temperature are necessary in order to solve these phenomena. In this paper, the constitutive equations of particle-reinforced composites with consideration of the damage process and change in temperature are estimated by the equivalent inclusion method in terms of elastoplasticity. The stress-strain relations and the coefficients of linear thermal expansion of the composites (Al-PSZ and Ti-PSZ) are calculated in ultrahigh temperature. (author)

  5. The effect of water on thermal stresses in polymer composites

    Science.gov (United States)

    Sullivan, Roy M.

    1994-01-01

    The fundamentals of the thermodynamic theory of mixtures and continuum thermochemistry are reviewed for a mixture of condensed water and polymer. A specific mixture which is mechanically elastic with temperature and water concentration gradients present is considered. An expression for the partial pressure of water in the mixture is obtained based on certain assumptions regarding the thermodynamic state of the water in the mixture. Along with a simple diffusion equation, this partial pressure expression may be used to simulate the thermostructural behavior of polymer composite materials due to water in the free volumes of the polymer. These equations are applied to a specific polymer composite material during isothermal heating conditions. The thermal stresses obtained by the application of the theory are compared to measured results to verify the accuracy of the approach.

  6. Thermal fatigue of refractory metal / graphite composites for fusion applications

    International Nuclear Information System (INIS)

    Smid, I.; Nickel, H.

    1989-01-01

    Reactor grade graphite and molybdenum (TZM) were brazed with different high temperature brazes. The resulting composite tiles had a size of 50 mm x 50 mm with a graphite thickness of 10 mm and a TZM thickness of 5mm. The brazed composites have been tested in electron beam simulation for their thermal fatigue properties. The parameters of these tests were chosen to match NET design specifications for normal operation and 'slow' peak energy deposition. The resulting damages and microstructural changes on the graphites and the brazes are discussed. Additional information is supplied on X-ray diffraction data proving the presence of different phases in the brazes. Finally the influence of a hydrogen plasma on the adaptability of the investigated brazes in fusion devices is discussed. 12 refs., 4 tabs., 4 figs. (Author)

  7. Thermal characteristics of expanded perlite/paraffin composite phase change material with enhanced thermal conductivity using carbon nanotubes

    International Nuclear Information System (INIS)

    Karaipekli, Ali; Biçer, Alper; Sarı, Ahmet; Tyagi, Vineet Veer

    2017-01-01

    Highlights: • Expanded perlite/n-eicosane composite for thermal energy storage was prepared. • Addition of CNTs increases considerably the thermal conductivity of the composite. • The composite PCM including 1 wt% CNTs is promising material. - Abstract: Paraffins constitute a class of solid-liquid organic phase change materials (PCMs). However, low thermal conductivity limits their feasibility in thermal energy storage (TES) applications. Carbon nano tubes (CNTs) are one of the best materials to increase the thermal conductivity of paraffins. In this regard, the present study is focus on the preparation, characterization, and improvement of thermal conductivity using CNTs as well as determination of TES properties of expanded perlite (ExP)/n-eicosane (C20) composite as a novel type of form-stable composite PCM (F-SCPCM). It was found that the ExP could retain C20 at weight fraction of 60% without leakage. The SEM and FTIR analyses were carried out to characterize the microstructure and chemical properties of the composite PCM. The TES properties of the prepared F-SCPCM were determined using DSC and TG analyses. The analysis results showed that the components of the composite are in good compatibleness and C20 used as PCM are well-infiltrated into the structure of ExP/CNTs matrix. The DSC analysis indicated that the ExP/C20/CNTs (1 wt%) composite has a melting point of 36.12 °C and latent heat of 157.43 J/g. The TG analysis indicated that the F-SCPCM has better thermal durability compared with pure C20 and also it has good long term-TES reliability. In addition, the effects of CNTs on the thermal conductivity of the composite PCM were investigated. Compared to ExP/C20 composite, the use of CNTs has apparent improving effect for the thermal conductivity without considerably affecting the compatibility of components, TES properties, and thermal stability.

  8. Effect of copper content on the thermal conductivity and thermal expansion of Al–Cu/diamond composites

    International Nuclear Information System (INIS)

    Wu, Jianhua; Zhang, Hailong; Zhang, Yang; Li, Jianwei; Wang, Xitao

    2012-01-01

    Highlights: ► Al–Cu/diamond composites have been produced by a squeeze casting method. ► Cu alloying is an effective approach to promoting interface bonding between metal matrix and diamond. ► Alloying Cu to Al matrix improves thermal conductivity and reduces coefficient of thermal expansion of the composites. -- Abstract: Al–Cu matrix composites reinforced with diamond particles (Al–Cu/diamond composites) have been produced by a squeeze casting method. Cu content added to Al matrix was varied from 0 to 3.0 wt.% to detect the effect on thermal conductivity and thermal expansion behavior of the resultant Al–Cu/diamond composites. The measured thermal conductivity for the Al–Cu/diamond composites increased from 210 to 330 W/m/K with increasing Cu content from 0 to 3.0 wt.%. Accordingly, the coefficient of thermal expansion (CTE) was tailored from 13 × 10 −6 to 6 × 10 −6 /K, which is compatible with the CTE of semiconductors in electronic packaging applications. The enhanced thermal conductivity and reduced coefficient of thermal expansion were ascribed to strong interface bonding in the Al–Cu/diamond composites. Cu addition has lowered the melting point and resulted in the formation of Al 2 Cu phase in Al matrix. This is the underlying mechanism responsible for the strengthening of Al–Cu/diamond interface. The results show that Cu alloying is an effective approach to promoting interface bonding between Al and diamond.

  9. Preparation and thermal conductivity enhancement of composite phase change materials for electronic thermal management

    International Nuclear Information System (INIS)

    Wu, Weixiong; Zhang, Guoqing; Ke, Xiufang; Yang, Xiaoqing; Wang, Ziyuan; Liu, Chenzhen

    2015-01-01

    Highlights: • A kind of composite phase change material board (PCMB) is prepared and tested. • PCMB presents a large thermal storage capacity and enhanced thermal conductivity. • PCMB displays much better cooling effect in comparison to natural air cooling. • PCMB presents different cooling characteristics in comparison to ribbed radiator. - Abstract: A kind of phase change material board (PCMB) was prepared for use in the thermal management of electronics, with paraffin and expanded graphite as the phase change material and matrix, respectively. The as-prepared PCMB presented a large thermal storage capacity of 141.74 J/g and enhanced thermal conductivity of 7.654 W/(m K). As a result, PCMB displayed much better cooling effect in comparison to natural air cooling, i.e., much lower heating rate and better uniformity of temperature distribution. On the other hand, compared with ribbed radiator technology, PCMB also presented different cooling characteristics, demonstrating that they were suitable for different practical application

  10. Electrically conductive carbon nanofiber/paraffin wax composites for electric thermal storage

    International Nuclear Information System (INIS)

    Zhang Kun; Han Baoguo; Yu Xun

    2012-01-01

    Highlights: ► Carbon nanofiber (CNF)/paraffin wax composite is found to be a promising electric thermal storage material. ► The thermal storage capacity of CNF/paraffin wax composite is five times of traditional electric thermal storage material. ► CNF is shown to be an effective conductive filler for the composite. - Abstract: The research of electric thermal storage (ETS) has attracted a lot of attention recently, which converts off-peak electrical energy into thermal energy and release it later at peak hours. In this study, new electric thermal storage composites are developed by employing paraffin wax as thermal storage media and carbon nanofiber (CNF) as conductive fillers. Electric heating and thermal energy release performances of the CNF/paraffin wax composites are experimentally investigated. Experimental results show that, when the composites are heated to about 70 °C, the developed electrically conductive CNF/paraffin wax composites present a thermal storage capacity of about 280 kJ/kg, which is five times of that of traditional thermal storage medium such as ceramic bricks (54 kJ/kg). The CNF/paraffin wax composites can also effectively store the thermal energy and release the thermal energy in later hours.

  11. Simple method of calculating the transient thermal performance of composite material and its applicable condition

    Institute of Scientific and Technical Information of China (English)

    张寅平; 梁新刚; 江忆; 狄洪发; 宁志军

    2000-01-01

    Degree of mixing of composite material is defined and the condition of using the effective thermal diffusivity for calculating the transient thermal performance of composite material is studied. The analytical result shows that for a prescribed precision of temperature, there is a condition under which the transient temperature distribution in composite material can be calculated by using the effective thermal diffusivity. As illustration, for the composite material whose temperatures of both ends are constant, the condition is presented and the factors affecting the relative error of calculated temperature of composite materials by using effective thermal diffusivity are discussed.

  12. Prompt effects of supernovae

    International Nuclear Information System (INIS)

    Colgate, S.A.

    1975-01-01

    Conflicting theories on the mechanisms of supernova production are examined. Supernova as sources of other phenomena such as comic rays, gamma rays, x-rays, and electromagnetic pulses are considered. 32 references

  13. [FeII] as a tracer supernova rate

    International Nuclear Information System (INIS)

    Rosenberg, M J F; Van der Werf, P P; Israel, F P

    2012-01-01

    Supernovae play an integral role in the feedback of processed material into the ISM of galaxies and are responsible for most of the chemical enrichment of the universe. The rate of supernovae can also reveal the star formation histories. Supernova rate is usually measured through the non-thermal radio continuum luminosity, but in this paper we establish a quantitative relationship between the [FeII] 1.26 luminosity and supernova rate in a sample of 11 near-by starburst galaxies. SINFONI data cubes are used to perform a pixel pixel analysis of this correlation. Using Bry equivalent width and luminosity as the only observational inputs into Starburst 99, the supernova rate is derived at each pixel and a map of supernova rate is created. This is then compared morphologically and quantitatively to [FeII] 1.26 luminosity map. We find a strong linear and morphological correlation between supernova rate and [FeII] 1.26 on a pixel-pixel basis. The Starburst 99 derived supernova rates are also in good agreement with the radio derived supernova rates, which further demonstrates the strength of [FeII] as a tracer of supernova rate. With the strong correlation found in this sample of galaxies, we now qualitatively use [FeII] 1.26 to derive supernova rate on either a pixel-pixel or integrated galactic basis.

  14. Stress analysis in curved composites due to thermal loading

    Science.gov (United States)

    Polk, Jared Cornelius

    Many structures in aircraft, cars, trucks, ships, machines, tools, bridges, and buildings, consist of curved sections. These sections vary from straight line segments that have curvature at either one or both ends, segments with compound curvatures, segments with two mutually perpendicular curvatures or Gaussian curvatures, and segments with a simple curvature. With the advancements made in multi-purpose composites over the past 60 years, composites slowly but steadily have been appearing in these various vehicles, compound structures, and buildings. These composite sections provide added benefits over isotropic, polymeric, and ceramic materials by generally having a higher specific strength, higher specific stiffnesses, longer fatigue life, lower density, possibilities in reduction of life cycle and/or acquisition cost, and greater adaptability to intended function of structure via material composition and geometry. To be able to design and manufacture a safe composite laminate or structure, it is imperative that the stress distributions, their causes, and effects are thoroughly understood in order to successfully accomplish mission objectives and manufacture a safe and reliable composite. The objective of the thesis work is to expand upon the knowledge of simply curved composite structures by exploring and ascertaining all pertinent parameters, phenomenon, and trends in stress variations in curved laminates due to thermal loading. The simply curved composites consist of composites with one radius of curvature throughout the span of the specimen about only one axis. Analytical beam theory, classical lamination theory, and finite element analysis were used to ascertain stress variations in a flat, isotropic beam. An analytical method was developed to ascertain the stress variations in an isotropic, simply curved beam under thermal loading that is under both free-free and fixed-fixed constraint conditions. This is the first such solution to Author's best knowledge

  15. Fiber/matrix interfacial thermal conductance effect on the thermal conductivity of SiC/SiC composites

    International Nuclear Information System (INIS)

    Nguyen, Ba Nghiep; Henager, Charles H.

    2013-01-01

    SiC/SiC composites used in fusion reactor applications are subjected to high heat fluxes and require knowledge and tailoring of their in-service thermal conductivity. Accurately predicting the thermal conductivity of SiC/SiC composites as a function of temperature will guide the design of these materials for their intended use, which will eventually include the effects of 14-MeV neutron irradiations. This paper applies an Eshelby–Mori–Tanaka approach (EMTA) to compute the thermal conductivity of unirradiated SiC/SiC composites. The homogenization procedure includes three steps. In the first step EMTA computes the homogenized thermal conductivity of the unidirectional (UD) SiC fiber embraced by its coating layer. The second step computes the thermal conductivity of the UD composite formed by the equivalent SiC fibers embedded in a SiC matrix, and finally the thermal conductivity of the as-formed SiC/SiC composite is obtained by averaging the solution for the UD composite over all possible fiber orientations using the second-order fiber orientation tensor. The EMTA predictions for the transverse thermal conductivity of several types of SiC/SiC composites with different fiber types and interfaces are compared to the predicted and experimental results by Youngblood et al. [J. Nucl. Mater. 307–311 (2002) 1120–1125, Fusion Sci. Technol. 45 (2004) 583–591, Compos. Sci. Technol. 62 (2002) 1127–1139.

  16. Thermal shock fatigue behavior of TiC/Al2O3 composite ceramics

    Institute of Scientific and Technical Information of China (English)

    SI Tingzhi; LIU Ning; ZHANG Qingan; YOU Xianqing

    2008-01-01

    The thermal shock fatigue behaviors of pure hot-pressed alumina and 30 wt. % TiC/Al2O3 composites were studied. The effect of TiC and Al2O3 starting particle size on the mechanical properties of the composites was discussed. Indentation-quench test was conducted to evaluate the effect of thermal fatigue temperature difference (ΔT) and number of thermal cycles (N) on fatigue crack growth (Δα). The mechanical properties and thermal fatigue resistance of TiC/Al2O3 composites are remarkably improved by the addition of TiC. The thermal shock fatigue of monolithic alumina and TiC/Al2O3 composites is due to a "true" cycling effect (thermal fatigue). Crack deflection and bridging are the predominant reasons for the improvement of thermal shock fatigue resistance of the composites.

  17. Environmental/Thermal Barrier Coatings for Ceramic Matrix Composites: Thermal Tradeoff Studies

    Science.gov (United States)

    Murthy, Pappu L. M.; Brewer, David; Shah, Ashwin R.

    2007-01-01

    Recent interest in environmental/thermal barrier coatings (EBC/TBCs) has prompted research to develop life-prediction methodologies for the coating systems of advanced high-temperature ceramic matrix composites (CMCs). Heat-transfer analysis of EBC/TBCs for CMCs is an essential part of the effort. It helps establish the resulting thermal profile through the thickness of the CMC that is protected by the EBC/TBC system. This report documents the results of a one-dimensional analysis of an advanced high-temperature CMC system protected with an EBC/TBC system. The one-dimensional analysis was used for tradeoff studies involving parametric variation of the conductivity; the thickness of the EBC/TBCs, bond coat, and CMC substrate; and the cooling requirements. The insight gained from the results will be used to configure a viable EBC/TBC system for CMC liners that meet the desired hot surface, cold surface, and substrate temperature requirements.

  18. Neutrinos from type-II supernovae and the neutrino-driven supernova mechanism

    International Nuclear Information System (INIS)

    Janka, H.T.

    1996-01-01

    Supernova 1987A has confirmed fundamental aspects of our theoretical view of type-II supernovae: Type-II supernovae are a consequence of the collapse of the iron core of a massive evolved star and lead to the formation of a neutron star or black hole. This picture is most strongly supported by the detection of electron antineutrinos in the IMB and Kamiokande II experiments in connection with SN 1987A. However, the mechanism causing the supernova explosion is not yet satisfactorily understood. In this paper the properties of the neutrino emission from supernovae and protoneutron stars will be reviewed; analytical estimates will be derived and results of numerical simulations will be shown. It will be demonstrated that the spectral distributions of the emitted neutrinos show clear and systematic discrepancies compared with thermal (black body-type) emission. This must be taken into account when neutrino observations from supernovae are to be interpreted, or when implications of the neutrino emission on nucleosynthesis processes in mantle and envelope of the progenitor star are to be investigated. Furthermore, the influence of neutrinos on the supernova dynamics will be discussed, in particular their crucial role in causing the explosion by Wilson's neutrino-driven delayed mechanism. Possible implications of convection inside the newly born neutron star and between surface and the supernova shock will be addressed and results of multi-dimensional simulations will be presented. (author) 7 figs., 1 tab., refs

  19. Neutrinos from type-II supernovae and the neutrino-driven supernova mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Janka, H T [Max-Planck-Institut fuer Astrophysik, Garching (Germany)

    1996-11-01

    Supernova 1987A has confirmed fundamental aspects of our theoretical view of type-II supernovae: Type-II supernovae are a consequence of the collapse of the iron core of a massive evolved star and lead to the formation of a neutron star or black hole. This picture is most strongly supported by the detection of electron antineutrinos in the IMB and Kamiokande II experiments in connection with SN 1987A. However, the mechanism causing the supernova explosion is not yet satisfactorily understood. In this paper the properties of the neutrino emission from supernovae and protoneutron stars will be reviewed; analytical estimates will be derived and results of numerical simulations will be shown. It will be demonstrated that the spectral distributions of the emitted neutrinos show clear and systematic discrepancies compared with thermal (black body-type) emission. This must be taken into account when neutrino observations from supernovae are to be interpreted, or when implications of the neutrino emission on nucleosynthesis processes in mantle and envelope of the progenitor star are to be investigated. Furthermore, the influence of neutrinos on the supernova dynamics will be discussed, in particular their crucial role in causing the explosion by Wilson`s neutrino-driven delayed mechanism. Possible implications of convection inside the newly born neutron star and between surface and the supernova shock will be addressed and results of multi-dimensional simulations will be presented. (author) 7 figs., 1 tab., refs.

  20. Thermal energy storage characteristics of bentonite-based composite PCMs with enhanced thermal conductivity as novel thermal storage building materials

    International Nuclear Information System (INIS)

    Sarı, Ahmet

    2016-01-01

    Graphical abstract: In this work, novel bentonite-based and form-stable composite phase change materials (Bb-FSPCMs) were produced for LHTES in buildings by impregnation of CA, PEG600, DD and HD with bentonite clay. The microstructures of the compatibility of the Bb-FSPCMs were by using SEM and FT-IR techniques. The DSC results indicated that the produced Bb-FSPCMs composites had suitable phase change temperature of 4–30 °C and good latent heat capacity between 38 and 74 J/g. The TG results demonstrated that all of the fabricated Bb-FSPCMs had good thermal resistance. The Bb-FSPCMs maintained their LHTES properties even after 1000 heating–cooling cycling. The total heating times of the prepared Bb-FSPCMs were reduced noticeably due to their enhanced thermal conductivity after EG (5 wt%) addition. - Highlights: • Bb-FSPCMs were produced by impregnation of CA, PEG600, DD and HD with bentonite. • DSC analysis indicated that Bb-FSPCMs had melting temperature in range of 4–30 °C. • DSC analysis also showed that Bb-FSPCMs had latent heat between 38 and 74 J/g. • The TG analysis demonstrated that Bb-FSPCMs had good thermal resistance. • Thermal conductivity of Bb-FSPCMs were enhanced noticeably with EG (5 wt%) addition. - Abstract: In this work, for latent heat thermal energy storage (LHTES) applications in buildings, bentonite-based form-stable composite phase change materials (Bb-FSPCMs) were produced by impregnation of capric acid (CA), polyethylene glycol (PEG600), dodecanol (DD) and heptadecane (HD) into bentonite clay. The morphological characterization results obtained by scanning electron microscopy (SEM) showed that the bentonite acted as good structural barrier for the organic PCMs homogenously dispersed onto its surface and interlayers. The chemical investigations made by using fourier transform infrared (FT-IR) technique revealed that the attractions between the components of the composites was physical in nature and thus the PCMs were hold

  1. Novel Formulations of Phase Change Materials—Epoxy Composites for Thermal Energy Storage

    OpenAIRE

    Maria Elena Arce; Miguel Angel Alvarez Feijoo; Andres Suarez Garcia; Claudia C. Luhrs

    2018-01-01

    This research aimed to evaluate the thermal properties of new formulations of phase change materials (PCMs)-epoxy composites, containing a thickening agent and a thermally conductive phase. The composite specimens produced consisted of composites fabricated using (a) inorganic PCMs (hydrated salts), epoxy resins and aluminum particulates or (b) organic PCM (paraffin), epoxy resins, and copper particles. Differential Scanning Calorimetry (DSC) was used to analyze the thermal behavior of the sa...

  2. Study of Selected Composites Copper Concentrate-Plastic Waste Using Thermal Analysis

    Science.gov (United States)

    Szyszka, Danuta

    2017-12-01

    The paper presents thermal analysis of selected composites (copper concentrate, plastic waste) in two stages. The first stage consisted in thermogravimetric analysis and differential thermal analysis on the applied plastic waste and copper concentrate, and subsequently, a comparative study has been carried out on products obtained, constituting composites of those materials. As a result of analyses, it was found that up to ca. 400 °C composites show high thermal stability, whereas above that temperature, a thermal decomposition of the composite occurs, resulting in emissions of organic compounds, i.e. hydrocarbon compounds and organic oxygenate derivatives.

  3. Handbook of supernovae

    CERN Document Server

    Murdin, Paul

    2017-01-01

    This reference work gathers all of the latest research in the supernova field areas to create a definitive source book on supernovae, their remnants and related topics. It includes each distinct subdiscipline, including stellar types, progenitors, stellar evolution, nucleosynthesis of elements, supernova types, neutron stars and pulsars, black holes, swept up interstellar matter, cosmic rays, neutrinos from supernovae, supernova observations in different wavelengths, interstellar molecules and dust. While there is a great deal of primary and specialist literature on supernovae, with a great many scientific groups around the world focusing on the phenomenon and related subdisciplines, nothing else presents an overall survey. This handbook closes that gap at last. As a comprehensive and balanced collection that presents the current state of knowledge in the broad field of supernovae, this is to be used as a basis for further work and study by graduate students, astronomers and astrophysicists working in close/r...

  4. X-rays characterisation of thermal sprayed bioceramics and composites

    International Nuclear Information System (INIS)

    Khor, K.A.; Cheang, P.; White, T.

    2000-01-01

    Materials characterization using x-rays plays an important role in the ongoing endeavour to develop superior materials for biomedical devices. Current emphasis on biomaterials worldwide has highlighted the prominence of materials in successful implementation of implants to improve the quality of human lives. A clear example can be seen in the artificial hip implant where a layer of bioactive material, hydroxyapatite (HA), drastically aids the pain during the post-operation recovery process. Thermal spray is a process whereby powders are injected into a high temperature flame. Instantaneous melting takes place and the molten droplets are projected at a very high velocities onto a suitably prepared substrate. The adoption of this process by most biomedical companies manufacturing artificial hip implants is based on the efficacy of the process and the economic benefits such as high production rate and relatively low installation cost. However, material decomposition often occurs in the high temperature environment of thermal spray. Subsequent development of proper process parameters, customised powder characteristics and better process control nonetheless help mitigate this effect. A constant demand in the escalating usage of biomaterials in human body is reliability. Implants should preferably remain in the body for at least 5-10 years with minimal occurrences of revision. To ensure an acceptable level of reliability, materials characterisation is needed at practically every stage of its development and manufacture. The role that x-rays play in biomaterials development can be categorised as: (1) phase identification and structural determination and (2) chemical analysis. This paper will present the characterisation of biomaterials using x-rays in the development of new generation of biomaterials and composites that posses superior properties than the present group of materials. Specifically, this paper will highlight the problems encountered in phase identification

  5. Preparation and thermal properties of polyacrylonitrile/hexagonal boron nitride composites

    International Nuclear Information System (INIS)

    Madakbaş, Seyfullah; Çakmakçı, Emrah; Kahraman, Memet Vezir

    2013-01-01

    Highlights: ► PAN/h-BN composites with improved thermal stability were prepared. ► Thermal properties of composites were analysed by TGA and DSC. ► Flame retardancy of the composites increased up to 27%. - Abstract: Polyacrylonitrile is a thermoplastic polymer with unique properties and it has several uses. However its flammability is a major drawback for certain applications. In this study it was aimed to prepare polyacrylonitrile (PAN)/hexagonal boron nitride (h-BN) composites with improved flame retardancy and thermal stability. Chemical structures of the composites were characterized by FTIR analysis. Thermal properties of these novel composites were analysed by TGA and DSC measurements. Glass transition temperatures and char yields increased with increasing h-BN percentage. Flame retardancy of the PAN composite materials improved with the addition of h-BN and the LOI value reached to 27% from 18%. Furthermore, the surface morphology of the composites was investigated by SEM analysis.

  6. Effect of thermal-treatment sequence on sound absorbing and mechanical properties of porous sound-absorbing/thermal-insulating composites

    Directory of Open Access Journals (Sweden)

    Huang Chen-Hung

    2016-01-01

    Full Text Available Due to recent rapid commercial and industrial development, mechanical equipment is supplemented massively in the factory and thus mechanical operation causes noise which distresses living at home. In livelihood, neighborhood, transportation equipment, jobsite construction noises impact on quality of life not only factory noise. This study aims to preparation technique and property evaluation of porous sound-absorbing/thermal-insulating composites. Hollow three-dimensional crimp PET fibers blended with low-melting PET fibers were fabricated into hollow PET/low-melting PET nonwoven after opening, blending, carding, lapping and needle-bonding process. Then, hollow PET/low-melting PET nonwovens were laminated into sound-absorbing/thermal-insulating composites by changing sequence of needle-bonding and thermal-treatment. The optimal thermal-treated sequence was found by tensile strength, tearing strength, sound-absorbing coefficient and thermal conductivity coefficient tests of porous composites.

  7. Thermal Conductivity and Thermal Gradient Cyclic Behavior of Refractory Silicate Coatings on SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

    2001-01-01

    Plasma-sprayed mullite and BSAS coatings have been developed to protect SiC/SiC ceramic matrix composites from high temperature environmental attack. In this study, thermal conductivity and thermal barrier functions of these coating systems are evaluated using a laser high-heat-flux test rig. The effects of water vapor on coating thermal conductivity and durability are studied by using alternating furnace and laser thermal gradient cyclic tests. The influence of laser high thermal-gradient cycling on coating failure modes is also investigated.

  8. Materials Compositions for Lithium Ion Batteries with Extended Thermal Stability

    Science.gov (United States)

    Kalaga, Kaushik

    Advancements in portable electronics have generated a pronounced demand for rechargeable energy storage devices with superior capacity and reliability. Lithium ion batteries (LIBs) have evolved as the primary choice of portable power for several such applications. While multiple variations have been developed, safety concerns of commercial technologies limit them to atmospheric temperature operability. With several niche markets such as aerospace, defense and oil & gas demanding energy storage at elevated temperatures, there is a renewed interest in developing rechargeable batteries that could survive temperatures beyond 100°C. Instability of critical battery components towards extreme thermal and electrochemical conditions limit their usability at high temperatures. This study deals with developing material configurations for LIB components to stabilize them at such temperatures. Flammable organic solvent based electrolytes and low melting polymer based separators have been identified as the primary bottleneck for LIBs to survive increasing temperature. Furthermore, thermally activated degradation processes in oxide based electrodes have been identified as the reason for their limited lifetime. A quasi-solid composite comprising of room temperature ionic liquids (RTILs) and Clay was developed as an electrolyte/separator hybrid and tested to be stable up to 120°C. These composites facilitate complete reversible Li intercalation in lithium titanate (LTO) with a stable capacity of 120 mAh g-1 for several cycles of charge and discharge while simultaneously resisting severe thermal conditions. Modified phosphate based electrodes were introduced as a reliable alternative for operability at high temperatures in this study. These systems were shown to deliver stable reversible capacity for numerous charge/discharge cycles at elevated temperatures. Higher lithium intercalation potential of the developed cathode materials makes them interesting candidates for high voltage

  9. Microcracking in composite laminates under thermal and mechanical loading. Thesis

    Science.gov (United States)

    Maddocks, Jason R.

    1995-01-01

    Composites used in space structures are exposed to both extremes in temperature and applied mechanical loads. Cracks in the matrix form, changing the laminate thermoelastic properties. The goal of the present investigation is to develop a predictive methodology to quantify microcracking in general composite laminates under both thermal and mechanical loading. This objective is successfully met through a combination of analytical modeling and experimental investigation. In the analysis, the stress and displacement distributions in the vicinity of a crack are determined using a shear lag model. These are incorporated into an energy based cracking criterion to determine the favorability of crack formation. A progressive damage algorithm allows the inclusion of material softening effects and temperature-dependent material properties. The analysis is implemented by a computer code which gives predicted crack density and degraded laminate properties as functions of any thermomechanical load history. Extensive experimentation provides verification of the analysis. AS4/3501-6 graphite/epoxy laminates are manufactured with three different layups to investigate ply thickness and orientation effects. Thermal specimens are cooled to progressively lower temperatures down to -184 C. After conditioning the specimens to each temperature, cracks are counted on their edges using optical microscopy and in their interiors by sanding to incremental depths. Tensile coupons are loaded monotonically to progressively higher loads until failure. Cracks are counted on the coupon edges after each loading. A data fit to all available results provides input parameters for the analysis and shows them to be material properties, independent of geometry and loading. Correlation between experiment and analysis is generally very good under both thermal and mechanical loading, showing the methodology to be a powerful, unified tool. Delayed crack initiation observed in a few cases is attributed to a

  10. Thermal degradation and tensile strength of sansevieria trifasciata-polypropylene composites

    Science.gov (United States)

    Abral, H.; Kenedy, E.

    2015-07-01

    The paper exhibits thermal degradation and tensile strength of Sansevieria Trifasciata (ST) fibers and polypropylene (PP) composites. Thermal degradation of ST fibers PP composites was conducted by using thermogravimetry (TGA) instrument, meanwhile tensile strength of the composite was done by using tensile equipment. The results show that the thermal resistance of ST fibers PP composites was higher than that of virgin PP only. Increases in volume fraction of fibers in the composites enhance the tensile strength. Scanning Electron Microscope (SEM) observation exhibits good interface bonding between ST fibers and PP matrix.

  11. Thermal degradation and tensile strength of sansevieria trifasciata-polypropylene composites

    International Nuclear Information System (INIS)

    Abral, H; Kenedy, E

    2015-01-01

    The paper exhibits thermal degradation and tensile strength of Sansevieria Trifasciata (ST) fibers and polypropylene (PP) composites. Thermal degradation of ST fibers PP composites was conducted by using thermogravimetry (TGA) instrument, meanwhile tensile strength of the composite was done by using tensile equipment. The results show that the thermal resistance of ST fibers PP composites was higher than that of virgin PP only. Increases in volume fraction of fibers in the composites enhance the tensile strength. Scanning Electron Microscope (SEM) observation exhibits good interface bonding between ST fibers and PP matrix. (paper)

  12. [Effect of thermal cycling on surface microstructure of different light-curing composite resins].

    Science.gov (United States)

    Lv, Da; Liu, Kai-Lei; Yao, Yao; Zhang, Wei-Sheng; Liao, Chu-Hong; Jiang, Hong

    2015-04-01

    To evaluate the effect of thermal cycling on surface microstructure of different light-curing composite resins. A nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum, and AP-X) were fabricated from lateral to center to form cubic specimens. The lateral surfaces were abrased and polished before water storage and 40 000 thermal cycles (5/55 degrees celsius;). The mean surface roughness (Ra) were measured and compared before and after thermal cycling, and the changes of microstructure were observed under scanning electron microscope (SEM). Significant decreases of Ra were observed in the composites, especially in Spectrum (from 0.164±0.024 µm to 0.140±0.017 µm, Presins, and fissures occurred on Z350 following the thermal cycling. Water storage and thermal cycling may produce polishing effect on composite resins and cause fissures on nanofilled composite resins.

  13. Thermal compatibility of Sodium Nitrate/Expanded Perlite composite phase change materials

    International Nuclear Information System (INIS)

    Li, Ruguang; Zhu, Jiaoqun; Zhou, Weibing; Cheng, Xiaomin; Li, Yuanyuan

    2016-01-01

    Highlights: • Expanded Perlite/Sodium Nitrate composites hardly reported in thermal storage fields. • The thermal compatibility and adsorption of Expanded Perlite were investigated. • The thermo physic properties of composites were determined. • The thermal stability and long term enthalpy changes of composites were investigated. - Abstract: The present work focused on the preparation and characterization of a new thermal storage material applied in thermal energy management. X-ray diffraction (XRD) results showed that Expanded Perlite (EP) has a good thermal stability varying from 300 °C to 900 °C. Morphology of scanning electron microscopy (SEM) revealed that sodium nitrate is uniformly encapsulated and embedded in the three-dimensional network structure of EP. Fourier transform infrared (FT-IR) spectroscopy indicated that the EP is physically combined with the nitrate salt. Thermo-gravimetric analysis (TGA) and differential Scanning Calorimeter (DSC) indicated that the composites have good thermal stability. The adsorption capacity of loose EP was 213.21%. When the EP mass fraction varying from 10% to 60%, thermal conductivity decreased with the content of EP increased, and the highest thermal conductivity is 1.14 W (m K)"−"1 at 300 °C. SEM revealed the network structure of EP provided thermal conduction paths which enhanced the thermal conductivity of the composites. All results indicated that EP could be a good adsorption material to be applied in the thermal storage fields.

  14. Study of Thermal Fatigue Resistance of a Composite Coating Made by a Vacuum Fusion Sintering Method

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Thermal fatigue behavior of a Ni-base alloy chromium carbide composite coating made by a vacuum fusion sintering method are discussed. Results show that thermal fatigue behavior is associated with cyclic upper temperature and coating thickness. As the thickness of the coating decreases, the thermal fatigue resistance increases. The thermal fatigue resistance cuts down with the thermal cyclic upper temperature rising. The crack growth rate decreases with the increase in cyclic number until crack arrests. Thermal fatigue failure was not found along the interface of the coating/matrix. The tract of thermal fatigue crack cracks along the interfaces of phases.

  15. Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity

    Science.gov (United States)

    Oddone, Valerio; Boerner, Benji; Reich, Stephanie

    2017-12-01

    High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal-graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied.

  16. Improvement of Thermal and Electrical Conductivity of Epoxy/boron Nitride/silver Nanoparticle Composite

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seungyong; Lim, Soonho [Korea Institute of Science and Technology, Wanju (Korea, Republic of)

    2017-06-15

    In this study, we investigated the effect of BN (boron nitride) on the thermal and the electrical conductivity of composites. In case of epoxy/BN composites, the thermal conductivity was increased as the BN contents were increased. Epoxy/AgNP (Ag nanoparticle) nanocomposites exhibited a slight change of thermal conductivity and showed a electrical percolation threshold at 20 vol% of Ag nanoparticles. At the fixed Ag nanoparticle content below the electrical percolation threshold, increasing the amount of BN enhanced the electrical conductivity as well as thermal conductivity for the epoxy/AgNP/BN composites.

  17. Why type 2 supernovae do not explode in irregular galaxies

    International Nuclear Information System (INIS)

    Shklovskij, I.S.

    1984-01-01

    The conclusion is drawn that reason for an absence of type 2 supernovae explosions in irregular galaxies is their peculiar chemical composition. The observed lack of stellar wind from massive hot giants is due to relatively low heavy element abundance. For this reason evolving massive stars do not form an extended dense envelopes that is a necessary condition for the type 2 supernova phenomenon

  18. Development of AlN/Epoxy Composites with Enhanced Thermal Conductivity.

    Science.gov (United States)

    Xu, Yonggang; Yang, Chi; Li, Jun; Mao, Xiaojian; Zhang, Hailong; Hu, Song; Wang, Shiwei

    2017-12-18

    AlN/epoxy composites with high thermal conductivity were successfully prepared by infiltrating epoxy into AlN porous ceramics which were fabricated by gelcasting of foaming method. The microstructure, mechanical, and thermal properties of the resulting composites were investigated. The compressive strengths of the AlN/epoxy composites were enhanced compared with the pure epoxy. The AlN/epoxy composites demonstrate much higher thermal conductivity, up to 19.0 W/(m·K), compared with those by the traditional particles filling method, because of continuous thermal channels formed by the walls and struts of AlN porous ceramics. This study demonstrates a potential route to manufacture epoxy-based composites with extremely high thermal conductivity.

  19. Development of AlN/Epoxy Composites with Enhanced Thermal Conductivity

    Science.gov (United States)

    Xu, Yonggang; Yang, Chi; Li, Jun; Zhang, Hailong; Hu, Song; Wang, Shiwei

    2017-01-01

    AlN/epoxy composites with high thermal conductivity were successfully prepared by infiltrating epoxy into AlN porous ceramics which were fabricated by gelcasting of foaming method. The microstructure, mechanical, and thermal properties of the resulting composites were investigated. The compressive strengths of the AlN/epoxy composites were enhanced compared with the pure epoxy. The AlN/epoxy composites demonstrate much higher thermal conductivity, up to 19.0 W/(m·K), compared with those by the traditional particles filling method, because of continuous thermal channels formed by the walls and struts of AlN porous ceramics. This study demonstrates a potential route to manufacture epoxy-based composites with extremely high thermal conductivity. PMID:29258277

  20. Thermal shock resistances of a bonding material of C/C composite and copper

    International Nuclear Information System (INIS)

    Kurumada, Akira; Oku, Tatsuo; Kawamata, Kiyohiro; Motojima, Osamu; Noda, Nobuaki; McEnaney, B.

    1997-01-01

    The purpose of this study is to contribute to the development and the safety design of plasma facing components for fusion reactor devices. We evaluated the thermal shock resistance and the thermal shock fracture toughness of a bonding material which was jointed a carbon-fiber-reinforced carbon composite (C/C composite) to oxygen-free copper. We also examined the microstructures of the bonding layers using a scanning electron microscope before and after thermal shock tests. The bonding material did not fracture during thermal shock tests. However, thermal cracks and delamination cracks were observed in the bonding layers. (author)

  1. Effect of filler geometry on coefficient of thermal expansion in carbon nanofiber reinforced epoxy composites.

    Science.gov (United States)

    Cho, M; Jang, J; Suhr, J

    2011-02-01

    This study involves the investigation of the geometry effect of nano-fillers on thermally induced dimensional stability of epoxy composites by experimentally evaluating the linear coefficient of thermal expansion (CTE). Carbon nanofibers (CNF) were chosen as the filler in epoxy matrix to investigate the effect of an aspect ratio on the CTE of the nanocomposites at three different volume fractions of 0.5, 1, and 2% of the nano-filler. The composites were fabricated using a mechanical mixing method. The CTE values were evaluated by measuring thermal strains of the composites and also compared with a micromechanics model. It was observed that the composites with short CNF (average L/d = 10) show better thermal stability than one of the composites with long CNF (average L/d = 70), and the thermal stability of the composites was proportional to the volume fraction of the filler in each composite. In addition, the CTE of mutliwalled carbon nanotubes (MWNT) reinforced epoxy composites was evaluated and compared with the CTE of the CNF reinforced composites. Interestingly, the MWNT reinforced composites show the greatest thermal stability with an 11.5% reduction in the CTE over the pure epoxy. The experimental data was compared with micromechanics model.

  2. Type Ia Supernova Cosmology

    Science.gov (United States)

    Leibundgut, B.; Sullivan, M.

    2018-03-01

    The primary agent for Type Ia supernova cosmology is the uniformity of their appearance. We present the current status, achievements and uncertainties. The Hubble constant and the expansion history of the universe are key measurements provided by Type Ia supernovae. They were also instrumental in showing time dilation, which is a direct observational signature of expansion. Connections to explosion physics are made in the context of potential improvements of the quality of Type Ia supernovae as distance indicators. The coming years will see large efforts to use Type Ia supernovae to characterise dark energy.

  3. The historical supernovae

    CERN Document Server

    Clark, David H

    1977-01-01

    The Historical Supernovae is an interdisciplinary study of the historical records of supernova. This book is composed of 12 chapters that particularly highlight the history of the Far East. The opening chapter briefly describes the features of nova and supernova, stars which spontaneously explode with a spectacular and rapid increase in brightness. The succeeding chapter deals with the search for the historical records of supernova from Medieval European monastic chronicles, Arabic chronicles, astrological works etc., post renaissance European scientific writings, and Far Eastern histories and

  4. Surface Composition of Trojan Asteroids from Thermal-Infrared Spectroscopy

    Science.gov (United States)

    Martin, A.; Emery, J. P.; Lindsay, S. S.

    2017-12-01

    Asteroid origins provide an effective means of constraining the events that dynamically shaped the solar system. Jupiter Trojan asteroids (hereafter Trojans) may help in determining the extent of radial mixing that occurred during giant planet migration. Previous studies aimed at characterizing surface composition show that Trojans have low albedo surfaces and fall into two distinct spectral groups the near infrared (NIR). Though, featureless in this spectral region, NIR spectra of Trojans either exhibit a red or less-red slope. Typically, red-sloped spectra are associated with organics, but it has been shown that Trojans are not host to much, if any, organic material. Instead, the red slope is likely due to anhydrous silicates. The thermal infrared (TIR) wavelength range has advantages for detecting silicates on low albedo asteroids such as Trojans. The 10 µm region exhibits strong features due to the Si-O fundamental molecular vibrations. We hypothesize that the two Trojan spectral groups have different compositions (silicate mineralogy). With TIR spectra from the Spitzer Space Telescope, we identify mineralogical features from the surface of 11 Trojan asteroids, five red and six less-red. Preliminary results from analysis of the 10 µm region indicate red-sloped Trojans have a higher spectral contrast compared to less-red-sloped Trojans. Fine-grain mixtures of crystalline pyroxene and olivine exhibit a 10 µm feature with sharp cutoffs between about 9 µm and 12 µm, which create a broad flat plateau. Amorphous phases, when present, smooth the sharp emission features, resulting in a dome-like shape. Further spectral analysis in the 10 µm, 18 µm, and 30 µm band region will be performed for a more robust analysis. If all Trojans come from the same region, it is expected that they share spectral and compositional characteristics. Therefore, if spectral analysis in the TIR reinforce the NIR spectral slope dichotomy, it is likely that Trojans were sourced from

  5. Studies on Enhancing Transverse Thermal Conductivity Carbon/Carbon Composites

    National Research Council Canada - National Science Library

    Manocha, Lalit M; Manocha, Satish M; Roy, Ajit

    2007-01-01

    The structure derived potential properties of Graphite such as high stiffness coupled with high thermal conductivity and low coefficient of thermal expansion have been better achieved in Carbon fibers...

  6. Matching Supernovae to Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2016-12-01

    One of the major challenges for modern supernova surveys is identifying the galaxy that hosted each explosion. Is there an accurate and efficient way to do this that avoids investing significant human resources?Why Identify Hosts?One problem in host galaxy identification. Here, the supernova lies between two galaxies but though the centroid of the galaxy on the right is closer in angular separation, this may be a distant background galaxy that is not actually near the supernova. [Gupta et al. 2016]Supernovae are a critical tool for making cosmological predictions that help us to understand our universe. But supernova cosmology relies on accurately identifying the properties of the supernovae including their redshifts. Since spectroscopic followup of supernova detections often isnt possible, we rely on observations of the supernova host galaxies to obtain redshifts.But how do we identify which galaxy hosted a supernova? This seems like a simple problem, but there are many complicating factors a seemingly nearby galaxy could be a distant background galaxy, for instance, or a supernovas host could be too faint to spot.The authors algorithm takes into account confusion, a measure of how likely the supernova is to be mismatched. In these illustrations of low (left) and high (right) confusion, the supernova is represented by a blue star, and the green circles represent possible host galaxies. [Gupta et al. 2016]Turning to AutomationBefore the era of large supernovae surveys, searching for host galaxies was done primarily by visual inspection. But current projects like the Dark Energy Surveys Supernova Program is finding supernovae by the thousands, and the upcoming Large Synoptic Survey Telescope will likely discover hundreds of thousands. Visual inspection will not be possible in the face of this volume of data so an accurate and efficient automated method is clearly needed!To this end, a team of scientists led by Ravi Gupta (Argonne National Laboratory) has recently

  7. Thermal Properties of Cement-Based Composites for Geothermal Energy Applications

    Science.gov (United States)

    Bao, Xiaohua; Memon, Shazim Ali; Yang, Haibin; Dong, Zhijun; Cui, Hongzhi

    2017-01-01

    Geothermal energy piles are a quite recent renewable energy technique where geothermal energy in the foundation of a building is used to transport and store geothermal energy. In this paper, a structural–functional integrated cement-based composite, which can be used for energy piles, was developed using expanded graphite and graphite nanoplatelet-based composite phase change materials (CPCMs). Its mechanical properties, thermal-regulatory performance, and heat of hydration were evaluated. Test results showed that the compressive strength of GNP-Paraffin cement-based composites at 28 days was more than 25 MPa. The flexural strength and density of thermal energy storage cement paste composite decreased with increases in the percentage of CPCM in the cement paste. The infrared thermal image analysis results showed superior thermal control capability of cement based materials with CPCMs. Hence, the carbon-based CPCMs are promising thermal energy storage materials and can be used to improve the durability of energy piles. PMID:28772823

  8. Thermal Properties of Cement-Based Composites for Geothermal Energy Applications.

    Science.gov (United States)

    Bao, Xiaohua; Memon, Shazim Ali; Yang, Haibin; Dong, Zhijun; Cui, Hongzhi

    2017-04-27

    Geothermal energy piles are a quite recent renewable energy technique where geothermal energy in the foundation of a building is used to transport and store geothermal energy. In this paper, a structural-functional integrated cement-based composite, which can be used for energy piles, was developed using expanded graphite and graphite nanoplatelet-based composite phase change materials (CPCMs). Its mechanical properties, thermal-regulatory performance, and heat of hydration were evaluated. Test results showed that the compressive strength of GNP-Paraffin cement-based composites at 28 days was more than 25 MPa. The flexural strength and density of thermal energy storage cement paste composite decreased with increases in the percentage of CPCM in the cement paste. The infrared thermal image analysis results showed superior thermal control capability of cement based materials with CPCMs. Hence, the carbon-based CPCMs are promising thermal energy storage materials and can be used to improve the durability of energy piles.

  9. Mechanical Properties and Thermal Shock Resistance Analysis of BNNT/Si3N4 Composites

    Science.gov (United States)

    Wang, Shouren; Wang, Gaoqi; Wen, Daosheng; Yang, Xuefeng; Yang, Liying; Guo, Peiquan

    2018-04-01

    BNNT/Si3N4 ceramic composites with different weight amount of BNNT fabricated by hot isostatic pressing were introduced. The mechanical properties and thermal shock resistance of the composites were investigated. The results showed that BNNT-added ceramic composites have a finer and more uniform microstructure than that of BNNT-free Si3N4 ceramic because of the retarding effect of BNNT on Si3N4 grain growth. The addition of 1.5 wt.% BNNT results in simultaneous increase in flexural strength, fracture toughness, and thermal shock resistance. The analysis of the results indicates that BNNT brings many thermal transport channels in the microstructure, increasing the efficiency of thermal transport, therefore results in increase of thermal shock resistance. In addition, BNNT improves the residual flexural strength of composites by crack deflection, bridging, branching and pinning, which increase the crack propagation resistance.

  10. Multiscale Modeling of Carbon/Phenolic Composite Thermal Protection Materials: Atomistic to Effective Properties

    Science.gov (United States)

    Arnold, Steven M.; Murthy, Pappu L.; Bednarcyk, Brett A.; Lawson, John W.; Monk, Joshua D.; Bauschlicher, Charles W., Jr.

    2016-01-01

    Next generation ablative thermal protection systems are expected to consist of 3D woven composite architectures. It is well known that composites can be tailored to achieve desired mechanical and thermal properties in various directions and thus can be made fit-for-purpose if the proper combination of constituent materials and microstructures can be realized. In the present work, the first, multiscale, atomistically-informed, computational analysis of mechanical and thermal properties of a present day - Carbon/Phenolic composite Thermal Protection System (TPS) material is conducted. Model results are compared to measured in-plane and out-of-plane mechanical and thermal properties to validate the computational approach. Results indicate that given sufficient microstructural fidelity, along with lowerscale, constituent properties derived from molecular dynamics simulations, accurate composite level (effective) thermo-elastic properties can be obtained. This suggests that next generation TPS properties can be accurately estimated via atomistically informed multiscale analysis.

  11. Thermal conductivity of an organic phase change material/expanded graphite composite across the phase change temperature range and a novel thermal conductivity model

    International Nuclear Information System (INIS)

    Ling, Ziye; Chen, Jiajie; Xu, Tao; Fang, Xiaoming; Gao, Xuenong; Zhang, Zhengguo

    2015-01-01

    Highlights: • Expanded graphite can improve thermal conductivity of RT44HC by 20–60 times. • Thermal conductivity of PCM/EG composites keeps constant before/after melting. • Thermal conductivity of PCMs nearly doubled during phase changing. • Thermal conductivity of composite PCM increases with density and percentage of EG. • The simple model predicts thermal conductivity of EG-based composites accurately. - Abstract: This work studies factors that affect the thermal conductivity of an organic phase change material (PCM), RT44HC/expanded graphite (EG) composite, which include: EG mass fraction, composite PCM density and temperature. The increase of EG mass fraction and bulk density will both enhance thermal conductivity of composite PCMs, by up to 60 times. Thermal conductivity of RT44HC/EG composites remains independent on temperature outside the phase change range (40–45 °C), but nearly doubles during the phase change. The narrow temperature change during the phase change allows the maximum heat flux or minimum temperature for heat source if attaching PCMs to a first (constant temperature) or second (constant heat flux) thermal boundary. At last, a simple thermal conductivity model for EG-based composites is put forward, based on only two parameters: mass fraction of EG and bulk density of the composite. This model is validated with experiment data presented in this paper and in literature, showing this model has general applicability to any composite of EG and poor thermal conductive materials

  12. Evolution of Supernova Remnants

    Science.gov (United States)

    Arbutina, B.

    2017-12-01

    This book, both a monograph and a graduate textbook, is based on my original research and partly on the materials prepared earlier for the 2007 and 2008 IARS Astrophysics Summer School in Istanbul, AstroMundus course 'Supernovae and Their Remnants' that was held for the first time in 2011 at the Department of Astronomy, Faculty of Mathematics, University of Belgrade, and a graduate course 'Evolution of Supernova Remnants' that I teach at the aforementioned university. The first part Supernovae (introduction, thermonuclear supernovae, core-collapse supernovae) provides introductory information and explains the classification and physics of supernova explosions, while the second part Supernova remnants (introduction, shock waves, cosmic rays and particle acceleration, magnetic fields, synchrotron radiation, hydrodynamic and radio evolution of supernova remnants), which is the field I work in, is more detailed in scope i.e. technical/mathematical. Special attention is paid to details of mathematical derivations that often cannot be found in original works or available literature. Therefore, I believe it can be useful to both, graduate students and researchers interested in the field.

  13. Nurseries of Supernovae

    DEFF Research Database (Denmark)

    Frederiksen, Teddy

    Type Ia supernovae (SNe) have long been the gold standard for precision cosmology and after several decades of intense research the supernova (SN) community was in 2011 honored by giving the Nobel Prize in physics for the discovery of Dark Energy to the leaders of the two big SN collaborations: S...

  14. Gravitational collapse and supernovae

    International Nuclear Information System (INIS)

    Lattimer, J.M.

    1989-01-01

    The collapse of the core of a massive star and the subsequent birth of a neutron star in a supernova explosion are discussed, and a model of the supernova mechanism is developed. The basic theory is then compared with the particular case of SN1987A, whose emitted neutrinos permitted the first direct test of the model. (author)

  15. Investigation on Thermal Properties of Kenaf Fibre Reinforced Polyurethane Bio-Composites

    Science.gov (United States)

    Athmalingam, Mathan; Vicki, W. V.

    2018-01-01

    This research focuses on the effect of Kenaf fibre on thermal properties of Polyurethane (PU) reinforced kenaf bio-composites. The samples were prepared using the polymer casting method with different percentages of kenaf fibre content (5 wt%, 10 wt%, 15 wt%). The thermal properties of Kenaf/PU bio-composite are determined through the Thermogravimetric Analysis and Differential Scanning Calorimeter test. The TGA results revealed that 10 wt% Kenaf/PU bio-composite appeared to be more stable. DSC results show that the glass transition temperature (Tg) value of 10 wt% Kenaf/PU composite is significant to pure polyurethane. It can be said that the thermal stability of 10 wt% Kenaf/PU bio-composite exhibits higher thermal stability compared to other samples.

  16. Supernova 1604, Kepler’s Supernova, and Its Remnant

    NARCIS (Netherlands)

    Vink, J.; Alsabti, A.W.; Murdin, P.

    2016-01-01

    Supernova 1604 is the last galactic supernova for which historical records exist. Johannes Kepler’s name is attached to it, as he published a detailed account of the observations made by himself and European colleagues. Supernova 1604 was very likely a type Ia supernova, which exploded 350–750 pc

  17. Palmitic acid/polypyrrole composites as form-stable phase change materials for thermal energy storage

    International Nuclear Information System (INIS)

    Silakhori, Mahyar; Metselaar, Hendrik Simon Cornelis; Mahlia, Teuku Meurah Indra; Fauzi, Hadi; Baradaran, Saeid; Naghavi, Mohammad Sajad

    2014-01-01

    Highlights: • A novel phase change composite of palmitic acid–polypyrrole(PA–PPy) was fabricated. • Thermal properties of PA–PPy are characterized in different mass ratios of PA–PPy. • Thermal cycling test showed that form stable PCM had a favorable thermal reliability. - Abstract: In this study a novel palmitic acid (PA)/polypyrrole (PPy) form-stable PCMs were readily prepared by in situ polymerization method. PA was used as thermal energy storage material and PPy was operated as supporting material. Form-stable PCMs were investigated by SEM (scanning electron microscopy) and FTIR (Fourier transform infrared spectrometer) analysis that illustrated PA Particles were wrapped by PPy particles. XRD (X-ray diffractometer) was used for crystalline phase of PA/PPy composites. Thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) were used for investigating Thermal stability and thermal energy storage properties of prepared form-stable PCMs. According to the obtained results the form stable PCMs exhibited favorable thermal stability in terms of their phase change temperature. The form-stable PCMs (79.9 wt% loading of PA) were considered as the highest loading PCM with desirable latent heat storage of 166.3 J/g and good thermal stability. Accelerated thermal cycling tests also showed that form stable PCM had an acceptable thermal reliability. As a consequence of acceptable thermal properties, thermal stability and chemical stability, we can consider the new kind of form stable PCMs for low temperature solar thermal energy storage applications

  18. Effect of Filler Concentration on Thermal Stability of Vinyl Copolymer Elastomer (VCE) Composites

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Dali [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hubbard, Kevin Mark [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Devlin, David James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Henderson, Kevin C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Pacheco, Robin Montoya [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-06

    To study the thermal stability of vinyl copolymer elastomer (VCE) in its composite form, systematic TGA characterizations were conducted in both nonisothermal and isothermal modes. The effects of filler concentration on the aging behaviors of the VCE/filler composites were investigated under nitroplasticizer (NP) environment. FTIR characterization was used to probe the structural changes in the VCE polymer before and after the thermal treatments. This study suggests that the filler concentration significantly deteriorates the thermal stability of NP at a moderate temperature (< 70 °C). The degradation of NP, in turn, accelerates the aging process of the VCE polymer in its composite form.

  19. Mineralogical and Thermal Properties of Poly(methyl methacrylate) Alite Composite

    International Nuclear Information System (INIS)

    Ismail, M.R.; El-Fass, M.M.; Abd-El-Rahman, H.A.; El-Miligy, A.A.

    1999-01-01

    The X-ray diffraction (XRD) characteristics and thermal stability of PMMA alite composite have been studied. The dried alite samples were impregnated by methyl methacrylate monomer and then subjected to gamma irradiation. The mineralogical and thermal properties of the PMMA alite composite materials were investigated by using XRD, DTA, and TGA techniques. The results indicate that, a markedly reduction of the peaks intensities of XRD for tricalcium silicate and calcium hydroxide. TGA data showed that PMMA alite composite has a high thermal stability as compared to PMMA

  20. Random walks in nanotube composites: Improved algorithms and the role of thermal boundary resistance

    International Nuclear Information System (INIS)

    Duong, Hai M.; Papavassiliou, Dimitrios V.; Lee, Lloyd L.; Mullen, Kieran J.

    2005-01-01

    Random walk simulations of thermal walkers are used to study the effect of interfacial resistance on heat flow in randomly dispersed carbon nanotube composites. The adopted algorithm effectively makes the thermal conductivity of the nanotubes themselves infinite. The probability that a walker colliding with a matrix-nanotube interface reflects back into the matrix phase or crosses into the carbon nanotube phase is determined by the thermal boundary (Kapitza) resistance. The use of 'cold' and 'hot' walkers produces a steady state temperature profile that allows accurate determination of the thermal conductivity. The effects of the carbon nanotube orientation, aspect ratio, volume fraction, and Kapitza resistance on the composite effective conductivity are quantified

  1. Thermal Properties of Polymethyl Methacrylate Composite Containing Copper Nanoparticles.

    Science.gov (United States)

    Yu, Wei; Xie, Huaqing; Xin, Sha; Yin, Junshan; Jiang, Yitong; Wang, Mingzhu

    2015-04-01

    Thermal functional Materials have wide applications in thermal management fields, and inserting highly thermal conductive materials is effective in enhancing thermal conductivity of matrix. In this paper, copper nanoparticles were selected as the additive to prepare polymethyl methacrylate (PMMA) based nanocomposite with enhanced thermal properties. Uniform copper nanoparticles with pure face-centered lattice were prepared by liquid phase reduction method. Then, they were added into PMMA/N, N-Dimethylmethanamide (DMF) solution according to the different mass fraction for uniform dispersion. After DMF was evaporated, Cu-PMMA nanocomposites were gained. The thermal analysis measurement results showed that the decomposition temperature of nanocomposites decreased gradually with the increasing particle loadings. The thermal conductivity of the Cu-PMMA nanocomposites rose with the increasing contents of copper nanoparticles. With a 20 vol.% addition, the thermal conductivity was up to 1.2 W/m · K, a 380.5% increase compared to the pure PMMA. The results demonstrate that copper nanoparticles have great potential in enhancing thermal transport properties of polymer.

  2. Enhanced thermal conductance of polymer composites through embeddingaligned carbon nanofibers

    Directory of Open Access Journals (Sweden)

    Dale K. Hensley

    2016-07-01

    Full Text Available The focus of this work is to find a more efficient method of enhancing the thermal conductance of polymer thin films. This work compares polymer thin films embedded with randomly oriented carbon nanotubes to those with vertically aligned carbon nanofibers. Thin films embedded with carbon nanofibers demonstrated a similar thermal conductance between 40–60 μm and a higher thermal conductance between 25–40 μm than films embedded with carbon nanotubes with similar volume fractions even though carbon nanotubes have a higher thermal conductivity than carbon nanofibers.

  3. Non-thermal X-rays and interstellar gas toward the γ-ray supernova remnant RX J1713.7–3946: evidence for X-ray enhancement around CO and H I clumps

    Energy Technology Data Exchange (ETDEWEB)

    Sano, H.; Torii, K.; Fukuda, T.; Yoshiike, S.; Sato, J.; Horachi, H.; Kuwahara, T.; Hayakawa, T.; Matsumoto, H.; Inutsuka, S.; Kawamura, A.; Tachihara, K.; Yamamoto, H.; Okuda, T.; Mizuno, N.; Onishi, T. [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Tanaka, T. [Department of Physics, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Inoue, T.; Yamazaki, R. [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Chuou-ku, Sagamihara 252-5258 (Japan); Mizuno, A., E-mail: sano@a.phys.nagoya-u.ac.jp [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); and others

    2013-11-20

    RX J1713.7–3946 is the most remarkable very high energy γ-ray supernova remnant that emits synchrotron X-rays without thermal features. We made a comparative study of CO, H I, and X-rays in order to better understand the relationship between the X-rays, and the molecular and atomic gas. The results indicate that the X-rays are enhanced around the CO and H I clumps on a pc scale, but are decreased inside the clumps on a 0.1 pc scale. Magnetohydrodynamic numerical simulations of the shock interaction with molecular and atomic gas indicate that the interaction between the shock waves and the clumps excite turbulence, which amplifies the magnetic field around the clumps. We suggest that the amplified magnetic field around the CO and H I clumps enhances the synchrotron X-rays and possibly the acceleration of cosmic-ray electrons.

  4. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    Science.gov (United States)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-12-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  5. Effect of boron compounds on the thermal and combustion properties of wood-plastic composites

    OpenAIRE

    Altuntaş, Ertuğrul; Karaoğul, Eyyup; Alma, Mehmet Hakkı

    2017-01-01

    In this study, the thermal properties and fire resistancesof the wood plastic composites produced with waste lignocellulosic materialswere investigated. For this purpose, lignocellulosic waste, high densitypolyethylene, (HDPE) sodium borate (borax) and boric acid was used to producethe wood-plastic composites. A twin-screw extruder was used during theproduction of the wood plastic composites. The produced composite granule waspressed at 175 °C hot press. The effects of boric acid and borax ad...

  6. Ceramic/Metal Composites with Positive Temperature Dependence of Thermal Conductivity

    International Nuclear Information System (INIS)

    Li Jianhui; Yu Qi; Sun Wei; Zhang Rui; Wang Ke; Li Jingfeng; Ichigozaki, Daisuke

    2013-01-01

    Most materials show decreasing thermal conductivity with increasing temperature, but an opposite temperature dependence of thermal conductivity is required for some industrial applications. The present work was conducted with a motivation to develop composite materials with a positive temperature dependence of thermal conductivity. ZrO 2 / stainless steel powders (304L) composite, with 3% stearic acid, was prepared by normal sintering under the protecting of Ar after mixing by mechanical ball milling technique. With the 304L content increasing from 10% to 20%, the thermal conductivity values increased. For all samples, the thermal conductivity in the temperature range of room temperature to 700 °C decreased with temperature below 300 °C, and then began to increase. The increasing thermal conductivity of the composites (within the high temperature range was attributed to the difference of the thermal conductivity and thermal expansion coefficient between ZrO 2 ceramic and 304L stainless steel powders. Two simple models were also used to estimate the thermal conductivity of the composites, which were in good agreement with the experiment results.

  7. Preparation and thermal energy storage properties of paraffin/expanded graphite composite phase change material

    International Nuclear Information System (INIS)

    Zhang, Zhengguo; Zhang, Ni; Peng, Jing; Fang, Xiaoming; Gao, Xuenong; Fang, Yutang

    2012-01-01

    Highlights: ► EG was obtained by microwave irradiation to prepare the paraffin/EG composite PCM. ► Composite PCM was characterized by XRD to investigate the chemical compatibility. ► Temperature profiles of the composite PCM were obtained during thermal energy storage. -- Abstract: The paraffin/expanded graphite (EG) composite phase change material (PCM) was prepared by absorbing liquid paraffin into EG, in which paraffin was chosen as the PCM. EG was produced by microwave irradiation performed at room temperature. It was found that the EG prepared at 800 W irradiation power for 10 s exhibited the maximum sorption capacity of 92 wt% for paraffin. Scanning electron microscopy images showed that paraffin was uniformly dispersed in the pores of EG. Differential scanning calorimeter analysis indicated that the melting temperature of the composite PCM was close to that of paraffin, and its latent heat was equivalent to the calculated value based on the mass fraction of paraffin in the composite. X-ray diffraction analysis showed that the composite PCM was just a combination of paraffin with EG, and no new substance was produced. Thermal energy storage performance of the composite PCM was tested in a latent thermal energy storage (LTES) system. Transients of axial and radial temperature profiles were obtained in the LTES for the composite PCM and paraffin. The thermal energy storage charging duration for the composite PCM was reduced obviously compared to paraffin.

  8. Thermal Conductivity on the Nanofluid of Graphene and Silver Nanoparticles Composite Material.

    Science.gov (United States)

    Myekhlai, Munkhshur; Lee, Taejin; Baatar, Battsengel; Chung, Hanshik; Jeong, Hyomin

    2016-02-01

    The composite material consisted of graphene (GN) and silver nanoparticles (AgNPs) has been essential topic in science and industry due to its unique thermal, electrical and antibacterial proper- ties. However, there are scarcity studies based on their thermal properties of nanofluids. Therefore, GN-AgNPs composite material was synthesized using facile and environment friendly method and further nanofluids were prepared by ultrasonication in this study. The morphological and structural investigations were carried out using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD) as well as ultra violet (UV)-visible spectroscopy. Furthermore, thermal conductivity measurements were performed for as-prepared nanofluids. As a result of thermal conductivity study, GN-AgNPs composite material was considerably enhanced the thermal conductivity of base fluid (water) by to 6.59% for the nanofluid (0.2 wt% GN and 0.4 wt% AgNPs).

  9. Thermal Conductivity Performance of Polypropylene Composites Filled with Polydopamine-Functionalized Hexagonal Boron Nitride.

    Science.gov (United States)

    Chen, Lin; Xu, Hong-Fei; He, Shao-Jian; Du, Yi-Hang; Yu, Nan-Jie; Du, Xiao-Ze; Lin, Jun; Nazarenko, Sergei

    2017-01-01

    Mussel-inspired approach was attempted to non-covalently functionalize the surfaces of boron nitride (BN) with self-polymerized dopamine coatings in order to reduce the interfacial thermal barrier and enhance the thermal conductivity of BN-containing composites. Compared to the polypropylene (PP) composites filled with pristine BN at the same filler content, thermal conductivity was much higher for those filled with both functionalized BN (f-BN) and maleic anhydride grafted PP (PP-g-ma) due to the improved filler dispersion and better interfacial filler-matrix compatibility, which facilitated the development of more thermal paths. Theoretical models were also applied to predict the composite thermal conductivity in which the Nielsen model was found to fit well with the experimental results, and the estimated effective aspect ratio of fillers well corresponded to the degree of filler aggregation as observed in the morphological study.

  10. Modeling of Thermal Conductivity of CVI-Densified Composites at Fiber and Bundle Level

    Science.gov (United States)

    Guan, Kang; Wu, Jianqing; Cheng, Laifei

    2016-01-01

    The evolution of the thermal conductivities of the unidirectional, 2D woven and 3D braided composites during the CVI (chemical vapor infiltration) process have been numerically studied by the finite element method. The results show that the dual-scale pores play an important role in the thermal conduction of the CVI-densified composites. According to our results, two thermal conductivity models applicable for CVI process have been developed. The sensitivity analysis demonstrates the parameter with the most influence on the CVI-densified composites’ thermal conductivity is matrix cracking’s density, followed by volume fraction of the bundle and thermal conductance of the matrix cracks, finally by micro-porosity inside the bundles and macro-porosity between the bundles. The obtained results are well consistent with the reported data, thus our models could be useful for designing the processing and performance of the CVI-densified composites. PMID:28774130

  11. Supernovae and neutrinos

    International Nuclear Information System (INIS)

    Totsuka, Y.

    1991-01-01

    On February 25, 1987, a sheet of telefax came to us from S. A. Bludman, saying Supernova went off in Large Magellanic Clouds. Can you see it? This is what we have been waiting 350 years for exclamation point In few hours, more information arrived. But it was still too early to definitely identify the supernova as type I or type II. This paper reports that the type I supernova is an explosion of a complete star due to uncontrolled nuclear fusion, while the type II supernova is triggered by gravitational collapse of the Fe core of a massive star (≥8 solar mass). It is this type II supernova that would leave a neutron star or a black hole after the liberation of an enormous amount of energy (3 x 10 53 erg) in the form of neutrinos. Therefore only the type II supernova is a relevant place to look for neutrino signals. It was also frustrating that the time when the stellar collapse actually took place was not definitely determined, because it was believed that the supernova brightened up about a day after the collapse and there was an ambiguity in a time lag of the optical observation. There was a possibility that it had happened well before February 24

  12. Carbon nanotube/paraffin/montmorillonite composite phase change material for thermal energy storage.

    Science.gov (United States)

    Li, Min; Guo, Qiangang; Nutt, Steven

    2017-04-01

    A composite phase change material (PCM) comprised of organic montmorillonite (OMMT)/paraffin/grafted multi-walled nanotube (MWNT) is synthesized via ultrasonic dispersion and liquid intercalation. The microstructure of the composite PCM has been characterized to determine the phase distribution, and thermal properties (latent heat and thermal conductivity) have been measured by differential scanning calorimetry (DSC) and a thermal constant analyzer. The results show that paraffin molecules are intercalated in the montmorillonite layers and the grafted MWNTs are dispersed in the montmorillonite layers. The latent heat is 47.1 J/g, and the thermal conductivity of the OMMT/paraffin/grafted MWNT composites is 34% higher than that of the OMMT/paraffin composites and 65% higher than that of paraffin.

  13. Derivation of governing equation for predicting thermal conductivity of composites with spherical inclusions and its applications

    International Nuclear Information System (INIS)

    Lee, Jae-Kon; Kim, Jin-Gon

    2011-01-01

    A governing differential equation for predicting the effective thermal conductivity of composites with spherical inclusions is shown to be simply derived by using the result of the generalized self-consistent model. By applying the equation to composites including spherical inclusions such as graded spherical inclusions, microballoons, mutiply-coated spheres, and spherical inclusions with an interphase, their effective thermal conductivities are easily predicted. The results are compared with those in the literatures to be consistent. It can be stated from the investigations that the effective thermal conductivity of composites with spherical inclusions can be estimated as long as their conductivities are expressed as a function of their radius. -- Highlights: → We derive equation for predicting the effective thermal conductivity of composites. → The equation is derived using the results of the generalized self-consistent model. → The inclusions are graded sphere, microballoons, and mutiply-coated spheres.

  14. Fatty acid esters-based composite phase change materials for thermal energy storage in buildings

    International Nuclear Information System (INIS)

    Sarı, Ahmet; Karaipekli, Ali

    2012-01-01

    In this study, fatty acid esters-based composite phase change materials (PCMs) for thermal energy storage were prepared by blending erythritol tetrapalmitate (ETP) and erythritol tetrastearate (ETS) with diatomite and expanded perlite (EP). The maximum incorporation percentage for ETP and ETS into diatomite and EP was found to be 57 wt% and 62 wt%, respectively without melted PCM seepage from the composites. The morphologies and compatibilities of the composite PCMs were structurally characterized using scanning electron microscope (SEM) and Fourier transformation infrared (FT–IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by differential scanning calorimetry (DSC) analysis. The DSC analyses results indicated that the composite PCMs were good candidates for building applications in terms of their large latent heat values and suitable phase change temperatures. The thermal cycling test including 1000 melting and freezing cycling showed that composite PCMs had good thermal reliability and chemical stability. TG analysis revealed that the composite PCMs had good thermal durability above their working temperature ranges. Moreover, in order to improve the thermal conductivity of the composite PCMs, the expanded graphite (EG) was added to them at different mass fractions (2%, 5%, and 10%). The best results were obtained for the composite PCMs including 5wt% EG content in terms of the increase in thermal conductivity values and the decrease amount in latent heat capacity. The improvement in thermal conductivity values of ETP/Diatomite, ETS/Diatomite, ETP/EP and ETS/EP were found to be about 68%, 57%, 73% and 75%, respectively. Highlights: ► Fatty acid esters-based composite PCMs were prepared by blending ETP and ETS with diatomite and expanded perlite. ► The composite PCMs were characterized by using SEM, FT–IR, DSC and TG analysis methods. ► The DSC results indicated that the composites PCMs had good thermal

  15. Mechanical and thermal properties of sisal fiber-reinforced rubber seed oil-based polyurethane composites

    International Nuclear Information System (INIS)

    Bakare, I.O.; Okieimen, F.E.; Pavithran, C.; Abdul Khalil, H.P.S.; Brahmakumar, M.

    2010-01-01

    The development of high-performance composite materials from locally sourced and renewable materials was investigated. Rubber seed oil polyurethane resin synthesized using rubber seed monoglyceride derived from glycerolysis of the oil was used as matrix in the composite samples. Rubber seed oil-based polyurethane composite reinforced with unidirectional sisal fibers were prepared and characterized. Results showed that the properties of unidirectional fiber-reinforced rubber seed oil-based polyurethane composites gave good thermal and mechanical properties. Also, the values of tensile strengths and flexural moduli of the polyurethane composites were more than tenfold and about twofold higher than un-reinforced rubber seed oil-based polyurethane. The improved thermal stability and the scanning electron micrographs of the fracture surface of the composites were attributed to good fiber-matrix interaction. These results indicate that high-performance 'all natural products' composite materials can be developed from resources that are readily available locally.

  16. Thermal degradation kinetics and lifetime estimation for polycarbonate/polymethylphenylsilsesquioxane composite

    Institute of Scientific and Technical Information of China (English)

    Jiangbo WANG; Zhong XIN

    2009-01-01

    The thermal degradation behaviors of poly-carbonate/polymethylphenylsilsesquioxane (FRPC) composites were investigated by thermogravimetric analysis (TGA) under isothermal conditions in nitrogen atmosphere. The isothermal kinetics equation was used to describe the thermal degradation process. The results showed that activation energy (E), in the case of isothermal degradation, was a quick increasing function of conversion (a) for polycarbonate (PC) but was a strong and decreasing function of conversion for FRPC. Under the isothermal condition, the addition of polymethylphenylsilsesquioxane (PMPSQ) retardanted the thermal degradation and enhanced the thermal stability of PC during the early and middle stages of thermal degradation. It also indicated a possible existence of a difference in nucleation, nuclei growth, and gas diffusion mechanism in the thermal degradation process between PC and FRPC. Meanwhile, the addition of PMPSQ influenced the lifetime of PC, but the composite still met the demand in manufacturing and application.

  17. Improved thermal stability and wettability behavior of thermoplastic polyurethane / barium metaborate composites

    International Nuclear Information System (INIS)

    Baştürka, Emre; Madakbaş, Seyfullah; Kahraman, Memet Vezir

    2016-01-01

    In this paper, it was targeted to the enhance thermal stability and wettability behavior of thermoplastic polyurethane (TPU) by adding barium metaborate. TPU-Barium metaborate composites were prepared by adding various proportions of barium metaborate to TPU. The chemical structures of the composites were characterised by fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. All prepared composites have extremely high Tg and thermal stability as determined from DSC and TGA analysis. All composite materials have the Tg ranging from 15 to 35 °C. The surface morphologies of the composites were investigated by a scanning electron microscopy. Mechanical properties of the samples were characterized with stress-strain test. Hydrophobicity of the samples was determined by the contact angle measurements. The obtained results proved that thermal, hydrophobic and mechanical properties were improved. (author)

  18. Improved thermal stability and wettability behavior of thermoplastic polyurethane / barium metaborate composites

    Energy Technology Data Exchange (ETDEWEB)

    Baştürka, Emre; Madakbaş, Seyfullah; Kahraman, Memet Vezir, E-mail: smadakbas@marmara.edu.tr [Department of Chemistry, Marmara University, Istanbul (Turkey)

    2016-03-15

    In this paper, it was targeted to the enhance thermal stability and wettability behavior of thermoplastic polyurethane (TPU) by adding barium metaborate. TPU-Barium metaborate composites were prepared by adding various proportions of barium metaborate to TPU. The chemical structures of the composites were characterised by fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. All prepared composites have extremely high Tg and thermal stability as determined from DSC and TGA analysis. All composite materials have the Tg ranging from 15 to 35 °C. The surface morphologies of the composites were investigated by a scanning electron microscopy. Mechanical properties of the samples were characterized with stress-strain test. Hydrophobicity of the samples was determined by the contact angle measurements. The obtained results proved that thermal, hydrophobic and mechanical properties were improved. (author)

  19. Iridescent cellulose nanocrystal/polyethylene oxide composite films with low coefficient of thermal expansion

    Science.gov (United States)

    Jairo A. Diaz; Julia L. Braun; Robert J. Moon; Jeffrey P. Youngblood

    2015-01-01

    Simultaneous control over optical and thermal properties is particularly challenging and highly desired in fields like organic electronics. Here we incorporated cellulose nanocrystals (CNCs) into polyethylene oxide (PEO) in an attempt to preserve the iridescent CNC optical reflection given by their chiral nematic organisation, while reducing the composite thermal...

  20. Thermal, Thermophysical, and Compositional Properties of the Moon Revealed by the Diviner Lunar Radiometer

    Science.gov (United States)

    Greenhagen, B. T.; Paige, D. A.

    2012-01-01

    The Diviner Lunar Radiometer is the first multispectral thermal instrument to globally map the surface of the Moon. After over three years in operation, this unprecedented dataset has revealed the extreme nature of the Moon's thermal environment, thermophysical properties, and surface composition.

  1. Effect of thermal interface on heat flow in carbon nanofiber composites.

    Science.gov (United States)

    Gardea, F; Naraghi, M; Lagoudas, D

    2014-01-22

    The thermal transport process in carbon nanofiber (CNF)/epoxy composites is addressed through combined micromechanics and finite element modeling, guided by experiments. The heat exchange between CNF constituents and matrix is studied by explicitly accounting for interface thermal resistance between the CNFs and the epoxy matrix. The effects of nanofiber orientation and discontinuity on heat flow and thermal conductivity of nanocomposites are investigated through simulation of the laser flash experiment technique and Fourier's model of heat conduction. Our results indicate that when continuous CNFs are misoriented with respect to the average temperature gradient, the presence of interfacial resistance does not affect the thermal conductivity of the nanocomposites, as most of the heat flow will be through CNFs; however, interface thermal resistance can significantly alter the patterns of heat flow within the nanocomposite. It was found that very high interface resistance leads to heat entrapment at the interface near to the heat source, which can promote interface thermal degradation. The magnitude of heat entrapment, quantified via the peak transient temperature rise at the interface, in the case of high thermal resistance interfaces becomes an order of magnitude more intense as compared to the case of low thermal resistance interfaces. Moreover, high interface thermal resistance in the case of discontinuous fibers leads to a nearly complete thermal isolation of the fibers from the matrix, which will marginalize the contribution of the CNF thermal conductivity to the heat transfer in the composite.

  2. Effect of severely thermal shocked MWCNT enhanced glass fiber reinforced polymer composite: An emphasis on tensile and thermal responses

    Science.gov (United States)

    Mahato, K. K.; Fulmali, A. O.; Kattaguri, R.; Dutta, K.; Prusty, R. K.; Ray, B. C.

    2018-03-01

    Fiber reinforced polymeric (FRP) composite materials are exposed to diverse changing environmental temperatures during their in-service period. Current investigation is aimed to investigate the influence of thermal-shock exposure on the mechanical behavior of multiwalled carbon nanotube (MWCNT) enhanced glass fiber reinforced polymeric (GFRP) composites. The samples were exposed to +70°C for 36 hrs followed by further exposure to ‑ 60°C for the similar interval of time. Tensile tests were conducted in order to evaluate the results of thermal-shock on the mechanical behavior of the neat and conditioned samples at 1 mm/min loading rate. The polymer phase i.e. epoxy was modified with various MWCNT content. The ultimate tensile strength (UTS) was raised by 15.11 % with increase in the 0.1 % MWCNT content GFRP as related to the thermal-shocked neat GFRP conditioned samples. The possible reason may be attributed to the variation in the coefficients of thermal expansion at the time of conditioning. Also, upto some extent the pre-existing residual stresses allows uniform distribution of stress and hence the reason in enhanced mechanical properties of GFRP and MWCNT filled composites. In order to access the modifications in the glass transition temperature (Tg) due to the addition of MWCNT in GFRP composite and also due to the thermal shock temperature modulated differential scanning calorimeter (TMDSC) measurements are carried out. Scanning electron microscopy(SEM) was carried out to identify different modes of failures and strengthening morphology in the composites.

  3. Thermal Conduction in Vertically Aligned Copper Nanowire Arrays and Composites.

    Science.gov (United States)

    Barako, Michael T; Roy-Panzer, Shilpi; English, Timothy S; Kodama, Takashi; Asheghi, Mehdi; Kenny, Thomas W; Goodson, Kenneth E

    2015-09-02

    The ability to efficiently and reliably transfer heat between sources and sinks is often a bottleneck in the thermal management of modern energy conversion technologies ranging from microelectronics to thermoelectric power generation. These interfaces contribute parasitic thermal resistances that reduce device performance and are subjected to thermomechanical stresses that degrade device lifetime. Dense arrays of vertically aligned metal nanowires (NWs) offer the unique combination of thermal conductance from the constituent metal and mechanical compliance from the high aspect ratio geometry to increase interfacial heat transfer and device reliability. In the present work, we synthesize copper NW arrays directly onto substrates via templated electrodeposition and extend this technique through the use of a sacrificial overplating layer to achieve improved uniformity. Furthermore, we infiltrate the array with an organic phase change material and demonstrate the preservation of thermal properties. We use the 3ω method to measure the axial thermal conductivity of freestanding copper NW arrays to be as high as 70 W m(-1) K(-1), which is more than an order of magnitude larger than most commercial interface materials and enhanced-conductivity nanocomposites reported in the literature. These arrays are highly anisotropic, and the lateral thermal conductivity is found to be only 1-2 W m(-1) K(-1). We use these measured properties to elucidate the governing array-scale transport mechanisms, which include the effects of morphology and energy carrier scattering from size effects and grain boundaries.

  4. Thermal properties of poly (lactic acid)/milkweed composites

    Science.gov (United States)

    Currently, most polymer composites utilize petroleum-based materials that are non-degradable and difficult to recycle or incur substantial cost for disposal. Green composites can be used in nondurable limited applications. In order to determine the degree of compatibility between Poly (lactic Acid...

  5. Mechanisms for supernova explosions

    International Nuclear Information System (INIS)

    Epstein, R.I.

    1977-01-01

    This report discusses some of the recent developments in the study of one supernova mechanism, the neutrino transport mechanism, and indicates what future developments are needed before this model can be adequately understood. (Auth.)

  6. Automated search for supernovae

    International Nuclear Information System (INIS)

    Kare, J.T.

    1984-01-01

    This thesis describes the design, development, and testing of a search system for supernovae, based on the use of current computer and detector technology. This search uses a computer-controlled telescope and charge coupled device (CCD) detector to collect images of hundreds of galaxies per night of observation, and a dedicated minicomputer to process these images in real time. The system is now collecting test images of up to several hundred fields per night, with a sensitivity corresponding to a limiting magnitude (visual) of 17. At full speed and sensitivity, the search will examine some 6000 galaxies every three nights, with a limiting magnitude of 18 or fainter, yielding roughly two supernovae per week (assuming one supernova per galaxy per 50 years) at 5 to 50 percent of maximum light. An additional 500 nearby galaxies will be searched every night, to locate about 10 supernovae per year at one or two percent of maximum light, within hours of the initial explosion

  7. Berkeley automated supernova search

    Energy Technology Data Exchange (ETDEWEB)

    Kare, J.T.; Pennypacker, C.R.; Muller, R.A.; Mast, T.S.; Crawford, F.S.; Burns, M.S.

    1981-01-01

    The Berkeley automated supernova search employs a computer controlled 36-inch telescope and charge coupled device (CCD) detector to image 2500 galaxies per night. A dedicated minicomputer compares each galaxy image with stored reference data to identify supernovae in real time. The threshold for detection is m/sub v/ = 18.8. We plan to monitor roughly 500 galaxies in Virgo and closer every night, and an additional 6000 galaxies out to 70 Mpc on a three night cycle. This should yield very early detection of several supernovae per year for detailed study, and reliable premaximum detection of roughly 100 supernovae per year for statistical studies. The search should be operational in mid-1982.

  8. Automated search for supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Kare, J.T.

    1984-11-15

    This thesis describes the design, development, and testing of a search system for supernovae, based on the use of current computer and detector technology. This search uses a computer-controlled telescope and charge coupled device (CCD) detector to collect images of hundreds of galaxies per night of observation, and a dedicated minicomputer to process these images in real time. The system is now collecting test images of up to several hundred fields per night, with a sensitivity corresponding to a limiting magnitude (visual) of 17. At full speed and sensitivity, the search will examine some 6000 galaxies every three nights, with a limiting magnitude of 18 or fainter, yielding roughly two supernovae per week (assuming one supernova per galaxy per 50 years) at 5 to 50 percent of maximum light. An additional 500 nearby galaxies will be searched every night, to locate about 10 supernovae per year at one or two percent of maximum light, within hours of the initial explosion.

  9. Berkeley automated supernova search

    International Nuclear Information System (INIS)

    Kare, J.T.; Pennypacker, C.R.; Muller, R.A.; Mast, T.S.

    1981-01-01

    The Berkeley automated supernova search employs a computer controlled 36-inch telescope and charge coupled device (CCD) detector to image 2500 galaxies per night. A dedicated minicomputer compares each galaxy image with stored reference data to identify supernovae in real time. The threshold for detection is m/sub v/ = 18.8. We plan to monitor roughly 500 galaxies in Virgo and closer every night, and an additional 6000 galaxies out to 70 Mpc on a three night cycle. This should yield very early detection of several supernovae per year for detailed study, and reliable premaximum detection of roughly 100 supernovae per year for statistical studies. The search should be operational in mid-1982

  10. Mechanical and Thermal Properties of Bamboo Pulp Fiber Reinforced Polyethylene Composites

    Directory of Open Access Journals (Sweden)

    Wenhan Ren

    2014-05-01

    Full Text Available The purpose of this study was to investigate the mechanical and thermal properties of high-density polyethylene (HDPE composites reinforced by bamboo pulp fibers (BPF. Using a twin-screw extruder, polymer composites were fabricated using BPF and bamboo flour (BF as the reinforcement and HDPE as the matrix. Tensile and flexural tests of the HDPE composites were performed to determine the mechanical properties under different conditions. The thermal properties of HDPE composites were characterized by thermogravimetric analysis (TGA and dynamic mechanical analysis (DMA. The results showed that BPF improved the mechanical and thermal properties of the polymer composites more than did BF. The tensile and flexural strength of composites with 30 wt% BPF were increased by 61.46% and 22.94%, respectively, while the tensile and flexural modulus were increased by 84.52% and 27.30%, respectively. Compared to composites with 50 wt% BF, the T5% of composites with 50 wt% BPF increased by 20.18 °C. As the BPF content increased, the storage modulus (E’ and loss modulus (E” initially increased, followed by a decrease. Compared to the BF/HDPE composites, BPF/HDPE composites reinforced at 30 wt% had a higher storage modulus (E’ and loss modulus (E” and lower damping parameter (tanδ.

  11. Effect of magnesium aluminum silicate glass on the thermal shock resistance of BN matrix composite ceramics

    NARCIS (Netherlands)

    Cai, Delong; Jia, Dechang; Yang, Zhihua; Zhu, Qishuai; Ocelik, Vaclav; Vainchtein, Ilia D.; De Hosson, Jeff Th M.; Zhou, Yu

    The effects of magnesium aluminum silicate (MAS) glass on the thermal shock resistance and the oxidation behavior of h-BN matrix composites were systematically investigated at temperature differences from 600 degrees C up to 1400 degrees C. The retained strength rate of the composites rose with the

  12. Thermal recycling and re-manufacturing of glass fibre thermosetting composites

    DEFF Research Database (Denmark)

    Fraisse, Anthony; Beauson, Justine; Brøndsted, Povl

    2016-01-01

    The impact of using thermally recycled glass fibre in re-manufactured composites was investigated. A unidirectional glass fibre thermosetting composite laminate was manufactured. The matrix in one part of the laminate was burnt off to recover the glass fibres. These recycled glass fibres were used...

  13. Study on paraffin/expanded graphite composite phase change thermal energy storage material

    International Nuclear Information System (INIS)

    Zhang Zhengguo; Fang Xiaoming

    2006-01-01

    A paraffin/expanded graphite composite phase change thermal energy storage material was prepared by absorbing the paraffin into an expanded graphite that has an excellent absorbability. In such a composite, the paraffin serves as a latent heat storage material and the expanded graphite acts as the supporting material, which prevents leakage of the melted paraffin from its porous structure due to the capillary and surface tension forces. The inherent structure of the expanded graphite did not change in the composite material. The solid-liquid phase change temperature of the composite PCM was the same as that of the paraffin, and the latent heat of the paraffin/expanded graphite composite material was equivalent to the calculated value based on the mass ratio of the paraffin in the composite. The heat transfer rate of the paraffin/expanded graphite composite was obviously higher than that of the paraffin due to the combination with the expanded graphite that had a high thermal conductivity. The prepared paraffin/expanded graphite composite phase change material had a large thermal storage capacity and improved thermal conductivity and did not experience liquid leakage during its solid-liquid phase change

  14. Thermal shock properties of 2D-SiCf/SiC composites

    International Nuclear Information System (INIS)

    Lee, Sang Pill; Lee, Jin Kyung; Son, In Soo; Bae, Dong Su; Kohyama, Akira

    2012-01-01

    This paper dealt with the thermal shock properties of SiC f /SiC composites reinforced with two dimensional SiC fabrics. SiC f /SiC composites were fabricated by a liquid phase sintering process, using a commercial nano-size SiC powder and oxide additive materials. An Al 2 O 3 –Y 2 O 3 –SiO 2 powder mixture was used as a sintering additive for the consolidation of SiC matrix region. In this composite system, Tyranno SA SiC fabrics were also utilized as a reinforcing material. The thermal shock test for SiC f /SiC composites was carried out at the elevated temperature. Both mechanical strength and microstructure of SiC f /SiC composites were investigated by means of optical microscopy, SEM and three point bending test. SiC f /SiC composites represented a dense morphology with a porosity of about 8.2% and a flexural strength of about 160 MPs. The characterization of SiC f /SiC composites was greatly affected by the history of cyclic thermal shock. Especially, SiC f /SiC composites represented a reduction of flexural strength at the thermal shock temperature difference higher than 800 °C.

  15. Effect of Thermal Stresses on the Failure Criteria of Fiber Composites

    DEFF Research Database (Denmark)

    Leong, Martin Klitgaard; Sankar, Bhavani V.

    2010-01-01

    , the latter, called micro-thermal stresses, has not been given much attention. In this paper the Direct Micromechanics Method is used to investigate the effects of micro-thermal stresses on the failure envelope of composites. Using FEA the unit-cell of the composite is analyzed. Assuming the failure criteria...... for the fiber and matrix are known, the exact failure envelope is developed. Using the micromechanics results, the Tsai-Wu failure envelope is modified to account for the micro-thermal stresses. The approach is demonstrated using two example structures at cryogenic temperature....

  16. Thermomechanical and Environmental Durability of Environmental Barrier Coated Ceramic Matrix Composites Under Thermal Gradients

    Science.gov (United States)

    Zhu, Dongming; Bhatt, Ramakrishna T.; Harder, Bryan

    2016-01-01

    This paper presents the developments of thermo-mechanical testing approaches and durability performance of environmental barrier coatings (EBCs) and EBC coated SiCSiC ceramic matrix composites (CMCs). Critical testing aspects of the CMCs will be described, including state of the art instrumentations such as temperature, thermal gradient, and full field strain measurements; materials thermal conductivity evolutions and thermal stress resistance; NDE methods; thermo-mechanical stress and environment interactions associated damage accumulations. Examples are also given for testing ceramic matrix composite sub-elements and small airfoils to help better understand the critical and complex CMC and EBC properties in engine relevant testing environments.

  17. Physics of supernovae

    International Nuclear Information System (INIS)

    Woosley, S.E.; Weaver, T.A.

    1985-01-01

    Presupernova models of massive stars are presented and their explosion by ''delayed neutrino transport'' examined. A new form of long duration Type II supernova model is also explored based upon repeated encounter with the electron-positron pair instability in stars heavier than about 60 Msub solar. Carbon deflagration in white dwarfs is discussed as the probable explanation of Type I supernovae and special attention is paid to the physical processes whereby a nuclear flame propagates through degenerate carbon. 89 refs., 12 figs

  18. High thermal conductivity SiC/SiC composites for fusion applications -- 2

    International Nuclear Information System (INIS)

    Kowbel, W.; Tsou, K.T.; Withers, J.C.; Youngblood, G.E.

    1998-01-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion Structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23--24, 1997. An unirradiated SiC/SiC composite made with MER-developed CVR SiC fiber and a hybrid PIP/CVI SiC matrix exhibited room temperature transverse thermal conductivity of 45 W/mK. An unirradiated SiC/SiC composite made from C/C composite totally CVR-converted to a SiC/SiC composite exhibited transverse thermal conductivity values of 75 and 35 W/mK at 25 and 1000 C, respectively. Both types of SiC/SiC composites exhibited non-brittle failure in flexure testing

  19. Thermal Dissipation Efficiency in a Micro-Processor Using Carbon Nanotubes Based Composite

    Science.gov (United States)

    Thang, Bui Hung; Van Quang, Cao; Nghia, Van Trong; Hong, Phan Ngoc; Van Chuc, Nguyen; Tam, Ngo Thi Thanh; Quang, Le Dinh; Khang, Dao Duc; Khoi, Phan Hong; Minh, Phan Ngoc

    2009-09-01

    Modern electronic and optoelectronic devices such as μ-processor, light emitting diode, semiconductor laser issued a challenge in the thermal dissipation problem. Finding an effective way for thermal dissipation therefore becomes a very important issue. It is known that carbon nanotubes (CNTs) is one of the most valuable materials with high thermal conductivity (2000 W/m.K compared to thermal conductivity of Ag 419 W/m.K). This suggested an approach in applying the CNTs as an essential component for thermal dissipation media to improve the performance of computer processor and other high power electronic devices. In this work multi walled carbon nanotubes (MWCNTs) based composites were utilized as the thermal dissipation media in a micro processor of a personal computer. The MWCNTs of different concentrations were added into polyaniline, commercial silicon thermal paste and commercial silver thermal paste by mechanical methods. A personal computer with configuration: Intel Pentium IV 3.066 GHz, 512 MB of RAM and Windows XP Service Pack 2 Operating System was employed. The thermal dissipation efficiency of the system was evaluated by directly measure the temperature of the μ-processor during the operation of the computer in different CPU speeds. The measured results showed that the CNTs based composite could reduce the temperature of the u-processor more than 5° C, and the time for increasing the temperature of the μ-processor was three times longer than that when using commercial thermal paste.

  20. High thermal conductivity of graphite fiber silicon carbide composites for fusion reactor application

    International Nuclear Information System (INIS)

    Snead, L.L.; Balden, M.; Causey, R.A.; Atsumi, H.

    2002-01-01

    The benefits of using CVI SiC/graphite fiber composites as low tritium retaining, high thermal conductivity composites for fusion applications are presented. Three-dimensional woven composites have been chemically vapor infiltrated with SiC and their thermophysical properties measured. One material used an intermediate grade graphite fiber in all directions (Amoco P55) while a second material used very high thermal conductive fiber (Amoco K-1100) in the high fiber density direction. The overall void was less than 20%. Strength as measured by four-point bending was comparable to those of SiC/SiC composite. The room temperature thermal conductivity in the high conductivity direction was impressive for both materials, with values >70 W/m K for the P-55 and >420 W/m K for the K-1100 variant. The thermal conductivity was measured as a function of temperature and exceeds the highest thermal conductivity of CVD SiC currently available at fusion relevant temperatures (>600 deg. C). Limited data on the irradiation-induced degradation in thermal conductivity is consistent with carbon fiber composite literature

  1. Preparation and characterization of stearic acid/expanded graphite composites as thermal energy storage materials

    International Nuclear Information System (INIS)

    Fang, Guiyin; Li, Hui; Chen, Zhi; Liu, Xu

    2010-01-01

    Stearic acid/expanded graphite composites with different mass ratios were prepared by absorbing liquid stearic acid into the expanded graphite. In the composite materials, the stearic acid was used as the phase change material for thermal energy storage, and the expanded graphite acted as the supporting material. Fourier transformation infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermal diffusivity measurement were used to determine the chemical structure, crystalline phase, microstructure and thermal diffusivity of the composites, respectively. The thermal properties and thermal stability were investigated by differential scanning calorimetry and thermogravimetric analysis. The thermal analysis results indicated that the materials exhibited the same phase transition characteristics as the stearic acid and their latent heats were approximately the same as the values calculated based on the weight fraction of the stearic acid in the composites. The microstructural analysis results showed that the stearic acid was well absorbed in the porous network of the expanded graphite, and there was no leakage of the stearic acid from the composites even when it was in the molten state.

  2. Thermal buffering performance of composite phase change materials applied in low-temperature protective garments

    Science.gov (United States)

    Yang, Kai; Jiao, Mingli; Yu, Yuanyuan; Zhu, Xueying; Liu, Rangtong; Cao, Jian

    2017-07-01

    Phase change material (PCM) is increasingly being applied in the manufacturing of functional thermo-regulated textiles and garments. This paper investigated the thermal buffering performance of different composite PCMs which are suitable for the application in functional low-temperature protective garments. First, according to the criteria selecting PCM for functional textiles/garments, three kinds of pure PCM were selected as samples, which were n-hexadecane, n-octadecane and n-eicosane. To get the adjustable phase change temperature range and higher phase change enthalpy, three kinds of composite PCM were prepared using the above pure PCM. To evaluate the thermal buffering performance of different composite PCM samples, the simulated low-temperature experiments were performed in the climate chamber, and the skin temperature variation curves in three different low temperature conditions were obtained. Finally composite PCM samples’ thermal buffering time, thermal buffering capacity and thermal buffering efficiency were calculated. Results show that the comprehensive thermal buffering performance of n-octadecane and n-eicosane composite PCM is the best.

  3. Thermal performance enhancement of erythritol/carbon foam composites via surface modification of carbon foam

    Science.gov (United States)

    Li, Junfeng; Lu, Wu; Luo, Zhengping; Zeng, Yibing

    2017-03-01

    The thermal performance of the erythritol/carbon foam composites, including thermal diffusivity, thermal capacity, thermal conductivity and latent heat, were investigated via surface modification of carbon foam using hydrogen peroxide as oxider. It was found that the surface modification enhanced the wetting ability of carbon foam surface to the liquid erythritol of the carbon foam surface and promoted the increase of erythritol content in the erythritol/carbon foam composites. The dense interfaces were formed between erythritol and carbon foam, which is due to that the formation of oxygen functional groups C=O and C-OH on the carbon surface increased the surface polarity and reduced the interface resistance of carbon foam surface to the liquid erythritol. The latent heat of the erythritol/carbon foam composites increased from 202.0 to 217.2 J/g through surface modification of carbon foam. The thermal conductivity of the erythritol/carbon foam composite before and after surface modification further increased from 40.35 to 51.05 W/(m·K). The supercooling degree of erythritol also had a large decrease from 97 to 54 °C. Additionally, the simple and effective surface modification method of carbon foam provided an extendable way to enhance the thermal performances of the composites composed of carbon foams and PCMs.

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

    Science.gov (United States)

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

    2017-11-01

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

  5. Anisotropic thermal expansion behaviors of copper matrix in β-eucryptite/copper composite

    International Nuclear Information System (INIS)

    Wang Lidong; Xue Zongwei; Qiao Yingjie; Fei, W.D.

    2012-01-01

    Highlights: ► The thermal expansion behaviors of Cu matrix were studied by in situ XRD. ► The expansion of Cu{1 1 1} plane is linear, that of Cu{2 0 0} is nonlinear. ► The anisotropic thermal expansion of Cu is related to the twinning of Cu matrix. ► The twinning of Cu matrix makes the CTE of the composite increasing. - Abstract: A β-eucryptite/copper composite was fabricated by spark plasma sintering process. The thermal expansion behaviors of Cu matrix of the composite were studied by in situ X-ray diffraction during heating process. The results show that Cu matrix exhibits anisotropic thermal expansion behaviors for different crystallographic directions, the expansion of Cu{1 1 1} plane is linear in the temperature range from 20 °C to 300 °C and the expansion of Cu{2 0 0} is nonlinear with a inflection at about 180 °C. The microstructures of Cu matrix before and after thermal expansion testing were investigated using transmission electronic microscope. The anisotropic thermal expansion behavior is related to the deformation twinning formed in the matrix during heating process. At the same time, the deformation twinning of Cu matrix makes the average coefficient of thermal expansion of the composite increase.

  6. Synthesis and characterization of conducting composites of polyaniline and carbon black with high thermal stability

    Directory of Open Access Journals (Sweden)

    Fabio R. Simões

    2009-01-01

    Full Text Available In this work, a detailed chemical route to prepare thermally stable polyaniline (PANI/carbon black (CB composites is described. The syntheses were performed by chemical polymerization of aniline over CB particles, using different PANI/CB mass ratios. The thermal and electrical properties were characterized. Composites with mass ratio up to 65:35 (PANI:CB showed excellent thermal stability maintaining their conducting properties when thermally treated at 230 °C for two hours, which is adequate to process these materials. Moreover, the results showed an important reduction in the surface area of the composites which have a good relationship with the improvement of the rheological properties in melt processing.

  7. Study of thermal properties and the dispersion state of nano composites epoxy/clay

    International Nuclear Information System (INIS)

    Paz, Juliana D.; Bertholdi, Jonas; Toledo, Tais C.; Folgueras, Marilena V.; Pezzin, Sergio H.; Coelho, Luiz A.F.

    2011-01-01

    This work investigates an exfoliation/intercalation of nano clays in an epoxy resin by means of x-rays diffraction, scanning electronic microscopy, thermal gravimetric analysis and dilatometric analysis. A comparison of two techniques for preparing nano composites is addressed: mechanical stirring and sonication. X-rays analysis showed that an exfoliation/intercalation is occurring in some samples. TG analysis indicated and increase in thermal stability of the nano composites compared to the neat resin. Finally, dilatometric analysis indicates and increase in Tg for nano composites compared to the neat resin. (author)

  8. Mechanical and thermal properties of water glass coated sisal fibre-reinforced polypropylene composite

    CSIR Research Space (South Africa)

    Phiri, G

    2012-10-01

    Full Text Available ?C). Figure 1 shows the processing steps followed to produce composite samples. Up to 15% fibre loading could be achieved and the sisal fibres were coated with water glass to improve fire resistance. In order to improve the adhesion between sisal... preparation process: (A) WG coated fibre, (B) High speed granulator, (C) Composite granules, (D) Single screw extruder, (E) Injection moulder and (F) Composite samples (dumbbells) Mechanical and thermal properties of water glass coated sisal fi bre...

  9. An emerging alternative to thermal curing: Electron curing of fiber-reinforced composites

    International Nuclear Information System (INIS)

    Singh, A.; Saunders, C.B.; Lopata, V.J.; Kremers, W.; Chung, M.

    1995-01-01

    Electron curing of fiber-reinforced composites to produce materials with good mechanical properties has been demonstrated by the authors' work, and by Aerospatiale. The attractions of this technology are the technical and processing advantages offered over thermal curing, and the projected cost benefits. Though the work so far has focused on the higher value composites for the aircraft and aerospace industries, the technology can also be used to produce composites for the higher volume industries, such as transportation and automotive

  10. Efficacy of Thermally Conditioned Sisal FRP Composite on the Shear Characteristics of Reinforced Concrete Beams

    OpenAIRE

    Sen, Tara; Reddy, H. N. Jagannatha

    2013-01-01

    The development of commercially viable composites based on natural resources for a wide range of applications is on the rise. Efforts include new methods of production and the utilization of natural reinforcements to make biodegradable composites with lignocellulosic fibers, for various engineering applications. In this work, thermal conditioning of woven sisal fibre was carried out, followed by the development of woven sisal fibre reinforced polymer composite system, and its tensile and flex...

  11. Construction of 3D Skeleton for Polymer Composites Achieving a High Thermal Conductivity.

    Science.gov (United States)

    Yao, Yimin; Sun, Jiajia; Zeng, Xiaoliang; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

    2018-03-01

    Owing to the growing heat removal issue in modern electronic devices, electrically insulating polymer composites with high thermal conductivity have drawn much attention during the past decade. However, the conventional method to improve through-plane thermal conductivity of these polymer composites usually yields an undesired value (below 3.0 Wm -1 K -1 ). Here, construction of a 3D phonon skeleton is reported composed of stacked boron nitride (BN) platelets reinforced with reduced graphene oxide (rGO) for epoxy composites by the combination of ice-templated and infiltrating methods. At a low filler loading of 13.16 vol%, the resulting 3D BN-rGO/epoxy composites exhibit an ultrahigh through-plane thermal conductivity of 5.05 Wm -1 K -1 as the best thermal-conduction performance reported so far for BN sheet-based composites. Theoretical models qualitatively demonstrate that this enhancement results from the formation of phonon-matching 3D BN-rGO networks, leading to high rates of phonon transport. The strong potential application for thermal management has been demonstrated by the surface temperature variations of the composites with time during heating and cooling. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Thermal-mechanical behavior of high precision composite mirrors

    Science.gov (United States)

    Kuo, C. P.; Lou, M. C.; Rapp, D.

    1993-01-01

    Composite mirror panels were designed, constructed, analyzed, and tested in the framework of a NASA precision segmented reflector task. The deformations of the reflector surface during the exposure to space enviroments were predicted using a finite element model. The composite mirror panels have graphite-epoxy or graphite-cyanate facesheets, separated by an aluminum or a composite honeycomb core. It is pointed out that in order to carry out detailed modeling of composite mirrors with high accuracy, it is necessary to have temperature dependent properties of the materials involved and the type and magnitude of manufacturing errors and material nonuniformities. The structural modeling and analysis efforts addressed the impact of key design and materials parameters on the performance of mirrors.

  13. Thermal-mechanical behavior of high precision composite mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, C.P.; Lou, M.C.; Rapp, D.

    1993-01-01

    Composite mirror panels were designed, constructed, analyzed, and tested in the framework of a NASA precision segmented reflector task. The deformations of the reflector surface during the exposure to space enviroments were predicted using a finite element model. The composite mirror panels have graphite-epoxy or graphite-cyanate facesheets, separated by an aluminum or a composite honeycomb core. It is pointed out that in order to carry out detailed modeling of composite mirrors with high accuracy, it is necessary to have temperature dependent properties of the materials involved and the type and magnitude of manufacturing errors and material nonuniformities. The structural modeling and analysis efforts addressed the impact of key design and materials parameters on the performance of mirrors. 4 refs.

  14. Agave nonwovens in polypropylene composites: mechanical and thermal studies

    CSIR Research Space (South Africa)

    John, MJ

    2015-03-01

    Full Text Available Blends of agave fibres with wool waste, pineapple leaf fibres and polypropylene fibres were manufactured by needle-punching technique. Composites were prepared with polypropylene matrix by the process of compression moulding. The effects of blend...

  15. Thermal shock effect on Mechanical and Physical properties of pre-moisture treated GRE composite

    Science.gov (United States)

    Chakraverty, A. P.; Panda, A. B.; Mohanty, U. K.; Mishra, S. C.; Biswal, B. B.

    2018-03-01

    Many practical situations may be encountered under which a GFRP (Glass fibre reinforced polymer) composite, during its service life, is exposed to the severities of sudden temperature fluctuations. Moisture absorption of GRE (Glass fibre reinforced epoxy) composites followed by various gradients of temperature fluctuations may cause thermo- mechanical degradation. It is on this context, the hand layed GRE composite samples are exposed to up-thermal shock (-40°C to +50°C) and down-thermal shock (+50°C to -40°C) for various time interval after several periods of moisture (hydrothermal/hygrothermal) conditioning. The thermally shocked GRE specimens are put to 3-point bend test to divulge inter laminar shear strength (ILSS). Least ILSS values are recorded for the samples with maximum period of moisture treatments under with both up-thermal and down-thermal shock conditions. Lower glass transition temperature (Tg) values, as revealed through the low temperature DSC test, are exhibited at maximum durations of both up-thermal and down-thermal shock for the samples with higher periods of hygrothermal/hydrothermal treatments. SEM fractographs of representative GRE specimens after optimum period of moisture treatments and thermal shock show the various modes of failures.

  16. Detection of thermal fatigue in composites by second harmonic Lamb waves

    International Nuclear Information System (INIS)

    Li, Weibin; Cho, Younho; Achenbach, Jan D

    2012-01-01

    Composite materials which are widely used in the aerospace industry, are usually subjected to frequent variation of temperature. Thermal cyclic loading may induce material degradation. Considering the long-term service of aircraft composites and the importance of safety in the aircraft industry, even a little damage that may be accumulative via thermal fatigue is often of great concern. Therefore, there is a demand to develop non-destructive approaches to evaluate thermal fatigue damage in an early stage. Due to the sensitivity of acoustic nonlinearity to micro-damage, the nonlinear ultrasonic technique has been explored as a promising tool for early detection of micro-damage. This paper investigates an experimental scheme for characterizing thermal fatigue damage in composite laminates using second harmonic Lamb waves. The present results show a monotonic increase of acoustic nonlinearity with respect to thermal fatigue cycles. The experimental observation of the correlation between the acoustic nonlinearity and thermal fatigue cycles in carbon/epoxy laminates verifies that nonlinear Lamb waves can be used to assess thermal fatigue damage rendering improved sensitivity over conventional linear feature based non-destructive evaluation techniques. Velocity and attenuation based ultrasonic studies are carried out for comparison with the nonlinear ultrasonic approach and it is found that nonlinear acoustic parameters are more promising indicators of thermal fatigue damage than linear ones. (paper)

  17. Comprehensive NMR analysis of compositional changes of black garlic during thermal processing.

    Science.gov (United States)

    Liang, Tingfu; Wei, Feifei; Lu, Yi; Kodani, Yoshinori; Nakada, Mitsuhiko; Miyakawa, Takuya; Tanokura, Masaru

    2015-01-21

    Black garlic is a processed food product obtained by subjecting whole raw garlic to thermal processing that causes chemical reactions, such as the Maillard reaction, which change the composition of the garlic. In this paper, we report a nuclear magnetic resonance (NMR)-based comprehensive analysis of raw garlic and black garlic extracts to determine the compositional changes resulting from thermal processing. (1)H NMR spectra with a detailed signal assignment showed that 38 components were altered by thermal processing of raw garlic. For example, the contents of 11 l-amino acids increased during the first step of thermal processing over 5 days and then decreased. Multivariate data analysis revealed changes in the contents of fructose, glucose, acetic acid, formic acid, pyroglutamic acid, cycloalliin, and 5-(hydroxymethyl)furfural (5-HMF). Our results provide comprehensive information on changes in NMR-detectable components during thermal processing of whole garlic.

  18. PCM/wood composite to store thermal energy in passive building envelopes

    Science.gov (United States)

    Barreneche, C.; Vecstaudza, J.; Bajare, D.; Fernandez, A. I.

    2017-10-01

    The development of new materials to store thermal energy in a passive building system is a must to improve the thermal efficiency by thermal-regulating the indoor temperatures. This fact will deal with the reduction of the gap between energy supply and energy demand to achieve thermal comfort in building indoors. The aim of this work was to test properties of novel PCM/wood composite materials developed at Riga Technical University. Impregnation of PCM (phase change material) in wood increases its thermal mass and regulates temperature fluctuations during day and night. The PCM used are paraffin waxes (RT-21 and RT-27 from Rubitherm) and the wood used was black alder, the most common wood in Latvia. The PCM distribution inside wood sample has been studied as well as its thermophysical, mechanical and fire reaction properties. Developed composite materials are promising in the field of energy saving in buildings.

  19. The monolithic carbon aerogels and aerogel composites for electronics and thermal protection applications

    Science.gov (United States)

    Lu, Sheng; Guo, Hui; Zhou, Yugui; Liu, Yuanyuan; Jin, Zhaoguo; Liu, Bin; Zhao, Yingmin

    2017-09-01

    Monolithic carbon aerogels have been prepared by condensation polymerization and high temperature pyrolysis. The morphology of carbon aerogels are characterized by SEM. The pore structure is characterized by N2 adsorption-desorption technique. Monolithic carbon aerogels are mesoporous nanomaterials. Carbon fiber reinforced carbon aerogel composites are prepared by in-situ sol-gel process. Fiber reinforced carbon aerogel composites are of high mechanical strength. The thermal response of the fiber reinforced aerogel composite samples are tested in an arc plasma wind tunnel. Carbon aerogel composites show good thermal insulation capability and high temperature resistance in inert atmosphere even at ultrahigh temperature up to 1800 °C. The results show that they are suitable for applications in electrodes for supercapacitors/ Lithium-ion batteries and aerospace thermal protection area.

  20. Composite material having high thermal conductivity and process for fabricating same

    Science.gov (United States)

    Colella, Nicholas J.; Davidson, Howard L.; Kerns, John A.; Makowiecki, Daniel M.

    1998-01-01

    A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

  1. Thermal properties of silica-filled high density polyethylene composites compatibilized with glut palmitate

    Science.gov (United States)

    Samsudin, Dalina; Ismail, Hanafi; Othman, Nadras; Hamid, Zuratul Ain Abdul

    2017-07-01

    A study of thermal properties resulting from the utilization of Glut Palmitate (GP) on the silica filled high density polyethylene (HDPE) composites was carried out. The composites with the incorporation of GP at 0.5, 1.0, 2.0 and 3.0 phr were prepared by using an internal mixer at the temperature 180 °C and the rotor speed of 50 rpm. The thermal behaviours of the composites were then investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was found that the crystallinity and the thermal stability of the composites increased with the incorporation of GP. The highest crystallinity contents and decomposition temperatures were observed at the 1 phr GP loading.

  2. Neutrinos and supernova collapse

    International Nuclear Information System (INIS)

    Colgate, S.A.; Petschek, A.G.

    1980-01-01

    The neutrino emission resulting from stellar collapse and supernova formation is reviewed. The electron capture and consequent neutronization of the collapsing stellar matter at the end of evolution determines both the initial adiabat of core collapse as well as the trapped lepton fraction. The initial lepton fraction, Y/sub l/ = .48 supplies the pressure for neutral support of the star at the Chandrasekhar limit. High trapping values, Y/sub l/ = .4, lead to soft core collapses; low values to harder collapses. The value of Y/sub l/ is presently in dispute. The neutrino emission from initial electron capture is relatively small. A strong core-bounce shock releases both electron neutrino as well as thermal muon and tau neutrinos. Subsequent neutrino emission and cooling can sometimes lead to an unstable buoyancy gradient in the core in which case unstable core overturn is expected. Calculations have already shown the importance of the largest possible eddy or equivalently the lowest mode of overturn. Present models of low lepton trapping ratio lead to high entropy creation by the reflected shock and the stabilization of the core matter against overturn. In such cases the exterior matter must cool below an entropy of approximately s/k approx. = 2 to become unstable. This may require too long a time approximately one second for neutrino cooling from a neutrinosphere at rho approx. = 2 x 10 12 g cm -3 . On the other hand, high values of Y/sub l/ such as .4 lead to softer bounces at lower density and values of the critical stabilizing entropy of 3 or higher. Under such circumstances, core overturn can still occur

  3. Development of Thermally Actuated, High Temperature Composite Morphing Concepts

    Science.gov (United States)

    2016-03-31

    set of applications exists in gas turbine engines, which stand to benefit greatly from aerodynamic control in their combustors, turbines, and nozzles...Modelling Development 27 3.1 Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.1.1 Achieving Snap-Through Behaviour ...Fabrication of Hybrid Laminate Shell and Strip Specimens . . . . . . 35 3.3.2 Measurement of Thermal Curvatures and Snap-Through Behaviour of Hybrid

  4. Development of Thermally Actuated, High-Temperature Composite Morphing Concepts

    Science.gov (United States)

    2016-05-11

    set of applications exists in gas turbine engines, which stand to benefit greatly from aerodynamic control in their combustors, turbines, and nozzles...Modelling Development 27 3.1 Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.1.1 Achieving Snap-Through Behaviour ...Fabrication of Hybrid Laminate Shell and Strip Specimens . . . . . . 35 3.3.2 Measurement of Thermal Curvatures and Snap-Through Behaviour of Hybrid

  5. Investigations on Thermal Conductivities of Jute and Banana Fiber Reinforced Epoxy Composites

    Science.gov (United States)

    Pujari, Satish; Ramakrishna, Avasarala; Balaram Padal, Korabu Tulasi

    2017-04-01

    The Jute and Banana fibers are used as reinforcement in epoxy resin matrix for making partially green biodegradable material composite via hand lay-up technique. The thermal conductivity of the jute fiber epoxy composites and banana fiber epoxy composites at different volume fraction of the fiber is determined experimentally by using guarded heat flow meter method. The experimental results had shown that thermal conductivity of the composites decrease with an increase in the fiber content. Experimental results are compared with theoretical models (Series model, Hashin model and Maxwell model) to describe the variation of the thermal conductivity versus the volume fraction of the fiber. Good agreement between theoretical and experimental results is observed. Thermal conductivity of Banana fiber composite is less when compared to that of Jute composite which indicates banana is a good insulator and also the developed composites can be used as insulating materials in building, automotive industry and in steam pipes to save energy by reducing rate of heat transfer.

  6. MECHANICAL AND THERMAL PROPERTIES OF COMPOSITES FROM UNSATURATED POLYESTER FILLED WITH OIL PALM ASH

    Directory of Open Access Journals (Sweden)

    M.S. Ibrahim

    2012-06-01

    Full Text Available Oil palm ash (OPA is available in abundance, is renewable, can be obtained at no cost and shows good performance at high thermal conditions. Combinations of the unsaturated polyester with natural fillers have been reported to improve the mechanical and thermal properties of composites. Utilisation of oil palm ash as a filler in the manufacture of polymer composites can significantly reduce the requirement for other binders or matrixes of composite materials. This research uses oil palm ash as a filler to form composites through the investigation of the effect of different contents of filler on the properties of OPA-filled unsaturated polyester (UP/OPA composites. The effect of different volume fractions, i.e., 0, 10, 20 and 30 vol.% of oil palm ash introduced into 100, 90, 80 and 70 vol.% of an unsaturated polyester matrix on the composite mechanical properties, i.e., tensile and flexural, has been studied, together with thermal gravimetric analysis (TGA and differential scanning calorimetric (DSC. Specimens were prepared using compression moulding techniques based on the ASTM D790 and D5083 standards for flexural and tensile tests, respectively. The tensile and flexural mechanical properties of UP/OPA composites were improved in modulus by increasing the filler content. Thermal stability of the composites increased as the OPA filler content was increased, which was a logical consequence because of the high thermal stability of the silica compound of the OPA filler compared with that of the UP matrix. The results from the surface electron microscope (SEM analysis were the extension of mechanical and thermal tests.

  7. Preparation and properties of highly conductive palmitic acid/graphene oxide composites as thermal energy storage materials

    International Nuclear Information System (INIS)

    Mehrali, Mohammad; Latibari, Sara Tahan; Mehrali, Mehdi; Indra Mahlia, Teuku Meurah; Cornelis Metselaar, Hendrik Simon

    2013-01-01

    PA/GO (palmitic acid/graphene oxide) as PCMs (phase change materials) prepared by vacuum impregnation method, have high thermal conductivity. The GO (graphene oxide) composite was used as supporting material to improve thermal conductivity and shape stabilization of composite PCM (phase change material). SEM (Scanning electronic microscope), FT-IR (Fourier transformation infrared spectroscope) and XRD (X-ray diffractometer) were applied to determine microstructure, chemical structure and crystalloid phase of palmitic acid/GO composites, respectively. DSC (Differential scanning calorimeter) test was done to investigate thermal properties which include melting and solidifying temperatures and latent heat. FT-IR analysis represented that the composite instruction of porous palmitic acid and GO were physical. The temperatures of melting, freezing and latent heats of the composite measured through DSC analysis were 60.45, 60.05 °C, 101.23 and 101.49 kJ/kg, respectively. Thermal cycling test showed that the form-stable composite PCM has good thermal reliability and chemical stability. Thermal conductivity of the composite PCM was improved by more than three times from 0.21 to 1.02. As a result, due to their acceptable thermal properties, good thermal reliability, chemical stability and great thermal conductivities, we can consider the prepared form-stable composites as highly conductive PCMs for thermal energy storage applications. - Highlights: • Novel composite PCM with high thermal conductivity and latent heat storage. • New thermal cycling test for thermal reliability of composite PCMs. • Increasing thermal conductivity of composite PCM with graphene oxide. • Increasing thermal stability of phase change material by adding graphene oxide

  8. Phase Stability and Thermal Conductivity of Composite Environmental Barrier Coatings on SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Benkel, Samantha; Zhu, Dongming

    2011-01-01

    Advanced environmental barrier coatings are being developed to protect SiC/SiC ceramic matrix composites in harsh combustion environments. The current coating development emphasis has been placed on the significantly improved cyclic durability and combustion environment stability in high-heat-flux and high velocity gas turbine engine environments. Environmental barrier coating systems based on hafnia (HfO2) and ytterbium silicate, HfO2-Si nano-composite bond coat systems have been processed and their stability and thermal conductivity behavior have been evaluated in simulated turbine environments. The incorporation of Silicon Carbide Nanotubes (SiCNT) into high stability (HfO2) and/or HfO2-silicon composite bond coats, along with ZrO2, HfO2 and rare earth silicate composite top coat systems, showed promise as excellent environmental barriers to protect the SiC/SiC ceramic matrix composites.

  9. Fabrication, thermal and electrical properties of polyphenylene sulphide/copper composites

    International Nuclear Information System (INIS)

    Goyal, R.K.; Kambale, K.R.; Nene, S.S.; Selukar, B.S.; Arbuj, S.; Mulik, U.P.

    2011-01-01

    Highlights: → Polyphenylene sulphide/copper composites show a low percolation threshold, i.e., about 6 vol% Cu. → Both pre- and post- glass transition coefficient of thermal expansion (CTE) of composites decreased significantly. → The microhardness was increased by more than 50% compared to pure PPS matrix. → The electrical conductivity was increased by about eight orders of magnitude for 18 vol% Cu composite. → Dielectric constant and dissipation factor of composites measured at MHz was increased to about 6-fold and 70-fold compared to PPS matrix. - Abstract: The thermal and electrical properties of high performance poly(phenylene sulphide) (PPS) composites reinforced up to 31 vol% Cu particles were investigated to be used as materials for electronic applications. The thermal stability and char yield of the composites increased significantly. Both pre- and post- glass transition coefficient of thermal expansion (CTE) of composites decreased significantly. The microhardness was increased by more than 50% compared to pure PPS matrix. Microhardness and CTE of composites correlated well with the rule of mixtures. A percolation threshold about 6 vol% Cu was obtained. The electrical conductivity was increased by about eight orders of magnitude for 18 vol% composite. Dielectric constant and dissipation factor of composites at 1 MHz was increased by about 6-fold and 70-fold compared to matrix, respectively. They decreased gradually with increasing frequency up to 1 MHz and thereafter, there was insignificant change. The scanning electron microscope showed almost uniform distribution of Cu particles in the matrix. Owing to better dimensional stability and good electrical properties, these composites are very promising for electronic applications.

  10. Thermal Insulation System for Non-Vacuum Applications Including a Multilayer Composite

    Science.gov (United States)

    Fesmire, James E. (Inventor)

    2017-01-01

    The thermal insulation system of the present invention is for non-vacuum applications and is specifically tailored to the ambient pressure environment with any level of humidity or moisture. The thermal insulation system includes a multilayered composite including i) at least one thermal insulation layer and at least one compressible barrier layer provided as alternating, successive layers, and ii) at least one reflective film provided on at least one surface of the thermal insulation layer and/or said compressible barrier layer. The different layers and materials and their combinations are designed to provide low effective thermal conductivity for the system by managing all modes of heat transfer. The thermal insulation system includes an optional outer casing surrounding the multilayered composite. The thermal insulation system is particularly suited for use in any sub-ambient temperature environment where moisture or its adverse effects are a concern. The thermal insulation system provides physical resilience against damaging mechanical effects including compression, flexure, impact, vibration, and thermal expansion/contraction.

  11. Influence of Hybrid Fillers on Thermal Conductivity of Nylon-6/Graphene Composites

    Directory of Open Access Journals (Sweden)

    SONG Na

    2018-03-01

    Full Text Available The thermal insulating properties of polymer greatly restrict the application of polymer as the thermal conductivity materials in industry. Multilayer graphene was chosen as a filler due to its unique thermal transfer property. The effect of alumina oxide (Al2O3 and silicon carbide (SiC with graphene as hybrid fillers on thermal conductivity of polymers was also explored. The thermal conductivity of the composites enhances 161% with 3%(mass fraction graphene content compared to pure nylon-6(PA6. The thermal conductivity of PA6 composites is within 0.653-4.307W·m-1·K-1 by adjusting hybrid fillers content and the ratio of graphene with Al2O3 and SiC. The best thermal conductivity is 20 times higher than the pure PA6. It is no doubt that the exploration can provide valuable experimental basis for extending the utilization of graphene as thermal conductivity filler and the application of PA6 thermal conductivity materials in industry.

  12. PROGENITORS OF RECOMBINING SUPERNOVA REMNANTS

    Energy Technology Data Exchange (ETDEWEB)

    Moriya, Takashi J., E-mail: takashi.moriya@ipmu.jp [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8583 (Japan)

    2012-05-01

    Usual supernova remnants have either ionizing plasma or plasma in collisional ionization equilibrium, i.e., the ionization temperature is lower than or equal to the electron temperature. However, the existence of recombining supernova remnants, i.e., supernova remnants with ionization temperature higher than the electron temperature, has been recently confirmed. One suggested way to have recombining plasma in a supernova remnant is to have a dense circumstellar medium at the time of the supernova explosion. If the circumstellar medium is dense enough, collisional ionization equilibrium can be established in the early stage of the evolution of the supernova remnant and subsequent adiabatic cooling, which occurs after the shock wave gets out of the dense circumstellar medium, makes the electron temperature lower than the ionization temperature. We study the circumstellar medium around several supernova progenitors and show which supernova progenitors can have a circumstellar medium dense enough to establish collisional ionization equilibrium soon after the explosion. We find that the circumstellar medium around red supergiants (especially massive ones) and the circumstellar medium dense enough to make Type IIn supernovae can establish collisional ionization equilibrium soon after the explosion and can evolve to become recombining supernova remnants. Wolf-Rayet stars and white dwarfs have the possibility to be recombining supernova remnants but the fraction is expected to be very small. As the occurrence rate of the explosions of red supergiants is much higher than that of Type IIn supernovae, the major progenitors of recombining supernova remnants are likely to be red supergiants.

  13. Thermal conductivity analysis of SiC ceramics and fully ceramic microencapsulated fuel composites

    International Nuclear Information System (INIS)

    Lee, Hyeon-Geun; Kim, Daejong; Lee, Seung Jae; Park, Ji Yeon; Kim, Weon-Ju

    2017-01-01

    Highlights: • Thermal conductivity of SiC ceramics and FCM pellets was measured and discussed. • Thermal conductivity of FCM pellets was analyzed by the Maxwell-Eucken equation. • Effective thermal conductivity of TRISO particles applied in this study was assumed. - Abstract: The thermal conductivity of SiC ceramics and FCM fuel composites, consisting of a SiC matrix and TRISO coated particles, was measured and analyzed. SiC ceramics and FCM pellets were fabricated by hot press sintering with Al_2O_3 and Y_2O_3 sintering additives. Several factors that influence thermal conductivity, specifically the content of sintering additives for SiC ceramics and the volume fraction of TRISO particles and the matrix thermal conductivity of FCM pellets, were investigated. The thermal conductivity values of samples were analyzed on the basis of their microstructure and the arrangement of TRISO particles. The thermal conductivity of the FCM pellets was compared to that predicted by the Maxwell-Eucken equation and the thermal conductivity of TRISO coated particles was calculated. The thermal conductivity of FCM pellets in various sintering conditions was in close agreement to that predicted by the Maxwell-Eucken equation with the fitted thermal conductivity value of TRISO particles.

  14. Thermal and Electrical Properties of Polyaniline-glycine Composites

    Science.gov (United States)

    Mathavan, T.; Umapathy, S.; Jothirajan, M. A.; Vivekanandam, T. S.; Okram, G. S.

    2011-07-01

    Polymer-amino acid composites were prepared by combining the synthesized polyaniline and glycine in solid state. The samples were characterized by modulated DSC and AFM. Modulated DSC thermogram showed the structural changes occurred while composite formation. D.C electrical conductivity measurements were carried out on the samples in the temperature range of 310 K-85 K by using two-probe method. Analysis of D.C conductivity results revealed that the conductivity was governed by Mott's 2-dimensional variable range hopping.

  15. Thermal conductivity of wood ash diatomite composites using the transient hot strip method

    International Nuclear Information System (INIS)

    Muia, L.M.; Gaitho, F.

    2003-08-01

    The transient Hot Strip method (THS) was used to determine the thermal conductivities of pure Wood Ash (WA), two kinds of diatomite i.e., DB and DF, and their composites. The effects of grain size and temperature on the thermal conductivities of the three systems and their composites were also determined. The lowest thermal conductivities of 0.02x10 -2 Wm -1 K -1 for wood ash and ∼ 3x10 -2 Wm -1 K -1 for the diatomites are found in the particle size range 60 -80μm. The thermal conductivities of the various composites range between 1.3x10 -3 and 6.8x10 -2 Wm -1 K -1 . These values are a factor of 10 lower than those of the pure materials. The thermal conductivity of the three composites is independent of temperature in the range 26-350 deg. C, in contrast to those pure materials which increase with temperature. Generally, the thermal conductivites of the pure materials which increase as their porosity or moisture contents are increased. (author)

  16. Effect of graphene nanoplatelets on coefficient of thermal expansion of polyetherimide composite

    International Nuclear Information System (INIS)

    Wu, Huang; Drzal, Lawrence T.

    2014-01-01

    Thermal expansion is one of the major concerns for polymer composites. In this research, graphene nanoplatelets (GNPs) were added to polyetherimide (PEId) thermoplastic polymer in order to reduce the coefficient of thermal expansion (CTE) of the injection molded composite. First, the coefficient of linear thermal expansion (LTE) was measured in three directions in the anisotropic coupon: 0°, 90° and the out of plane Z direction. It is found that the GNP particles are very effective in terms of reducing the LTE in 0° direction due to high degree of alignment. After annealing above glass transition temperature, significant increase of 0° LTE and decrease of Z° LTE were observed. The bulk CTE was calculated by adding up the LTEs in all three directions and is found to be independent of annealing. Second, several models were applied to predict both CTE and LTE. It is found that Schapery's lower limit model fits the experimental CTE very well. Chow's model was applied for LTEs in three directions. The behavior of GNP-5/PEId composites is explained by the combination of Chow's model and morphology obtained by scanning electron microscope (SEM). - Highlights: • Coefficient of thermal expansion (CTE) of polymer composite is characterized. • Reduction of linear thermal expansion depends on filler orientation. • Filler orientation is characterized based on the location of the specimen. • Filler orientation is changed by annealing, causing subsequent change in CTE. • CTE and linear thermal expansion coefficient are modeled

  17. Thermal Conductivity of Epoxy Resin Composites Filled with Combustion Synthesized h-BN Particles

    Directory of Open Access Journals (Sweden)

    Shyan-Lung Chung

    2016-05-01

    Full Text Available The thermal conductivity of epoxy resin composites filled with combustion-synthesized hexagonal boron nitride (h-BN particles was investigated. The mixing of the composite constituents was carried out by either a dry method (involving no use of solvent for low filler loadings or a solvent method (using acetone as solvent for higher filler loadings. It was found that surface treatment of the h-BN particles using the silane 3-glycidoxypropyltrimethoxysilane (GPTMS increases the thermal conductivity of the resultant composites in a lesser amount compared to the values reported by other studies. This was explained by the fact that the combustion synthesized h-BN particles contain less –OH or active sites on the surface, thus adsorbing less amounts of GPTMS. However, the thermal conductivity of the composites filled with the combustion synthesized h-BN was found to be comparable to that with commercially available h-BN reported in other studies. The thermal conductivity of the composites was found to be higher when larger h-BN particles were used. The thermal conductivity was also found to increase with increasing filler content to a maximum and then begin to decrease with further increases in this content. In addition to the effect of higher porosity at higher filler contents, more horizontally oriented h-BN particles formed at higher filler loadings (perhaps due to pressing during formation of the composites were suggested to be a factor causing this decrease of the thermal conductivity. The measured thermal conductivities were compared to theoretical predictions based on the Nielsen and Lewis theory. The theoretical predictions were found to be lower than the experimental values at low filler contents (< 60 vol % and became increasing higher than the experimental values at high filler contents (> 60 vol %.

  18. Thermal Conductivity of Epoxy Resin Composites Filled with Combustion Synthesized h-BN Particles.

    Science.gov (United States)

    Chung, Shyan-Lung; Lin, Jeng-Shung

    2016-05-20

    The thermal conductivity of epoxy resin composites filled with combustion-synthesized hexagonal boron nitride (h-BN) particles was investigated. The mixing of the composite constituents was carried out by either a dry method (involving no use of solvent) for low filler loadings or a solvent method (using acetone as solvent) for higher filler loadings. It was found that surface treatment of the h-BN particles using the silane 3-glycidoxypropyltrimethoxysilane (GPTMS) increases the thermal conductivity of the resultant composites in a lesser amount compared to the values reported by other studies. This was explained by the fact that the combustion synthesized h-BN particles contain less -OH or active sites on the surface, thus adsorbing less amounts of GPTMS. However, the thermal conductivity of the composites filled with the combustion synthesized h-BN was found to be comparable to that with commercially available h-BN reported in other studies. The thermal conductivity of the composites was found to be higher when larger h-BN particles were used. The thermal conductivity was also found to increase with increasing filler content to a maximum and then begin to decrease with further increases in this content. In addition to the effect of higher porosity at higher filler contents, more horizontally oriented h-BN particles formed at higher filler loadings (perhaps due to pressing during formation of the composites) were suggested to be a factor causing this decrease of the thermal conductivity. The measured thermal conductivities were compared to theoretical predictions based on the Nielsen and Lewis theory. The theoretical predictions were found to be lower than the experimental values at low filler contents ( 60 vol %).

  19. Thermal characterization of polymer matrix composites containing microencapsulated paraffin in solid or liquid state

    International Nuclear Information System (INIS)

    Sari-Bey, Sana; Fois, Magali; Krupa, Igor; Ibos, Laurent; Benyoucef, Boumédiène

    2014-01-01

    Highlights: • Thermal characterization of PCL/Micronal composites. • Melting enthalpy and heat capacity measured by DSC. • Interest: have measured thermal properties at different temperatures. • Thermophysical properties measurement temperatures chosen outside phase changes. • Characteristics useful to model composites heat transfer for LHTES applications. - Abstract: This work focuses on the study of heat transfer mechanisms in composites materials which may be used for Latent Heat Thermal Energy Storage applications. These composites contain phase change material (PCM) which can absorb and release energy during thermal cycling. PCM’s used here are paraffins microencapsulated in poly(methylmethacrylate); microencapsulation avoids the flow of paraffin when it is in the liquid state. Samples with different paraffin weight fractions and particles shape and distribution were studied in this work. Scanning Electron Microscopy and Differential Scanning Calorimetry were used to determine morphology and perform measurements of phase changes temperatures, enthalpies and heat capacity respectively. Further, a periodic method (DICO) allowed measuring thermal conductivity (λ) and diffusivity (a) of the composites at temperatures below and above of the paraffin phase change from crystalline solid to isotropic liquid

  20. Dense Vertically Aligned Copper Nanowire Composites as High Performance Thermal Interface Materials.

    Science.gov (United States)

    Barako, Michael T; Isaacson, Scott G; Lian, Feifei; Pop, Eric; Dauskardt, Reinhold H; Goodson, Kenneth E; Tice, Jesse

    2017-12-06

    Thermal interface materials (TIMs) are essential for managing heat in modern electronics, and nanocomposite TIMs can offer critical improvements. Here, we demonstrate thermally conductive, mechanically compliant TIMs based on dense, vertically aligned copper nanowires (CuNWs) embedded into polymer matrices. We evaluate the thermal and mechanical characteristics of 20-25% dense CuNW arrays with and without polydimethylsiloxane infiltration. The thermal resistance achieved is below 5 mm 2 K W -1 , over an order of magnitude lower than commercial heat sink compounds. Nanoindentation reveals that the nonlinear deformation mechanics of this TIM are influenced by both the CuNW morphology and the polymer matrix. We also implement a flip-chip bonding protocol to directly attach CuNW composites to copper surfaces, as required in many thermal architectures. Thus, we demonstrate a rational design strategy for nanocomposite TIMs that simultaneously retain the high thermal conductivity of aligned CuNWs and the mechanical compliance of a polymer.

  1. Solidification behavior and thermal conductivity of bulk sodium acetate trihydrate composites with thickening agents and graphite

    DEFF Research Database (Denmark)

    Dannemand, Mark; Johansen, Jakob Berg; Furbo, Simon

    2016-01-01

    Sodium acetate trihydrate is a promising phase change material for long term storage of solar thermal energy if supercooling is actively utilized. Well performing thermal energy storages need to be able to charge and discharge energy at a high rate. The relatively low thermal conductivity....... Investigations of the solidification behavior, the formation of cavities and thermal conductivity of composites based on sodium acetate trihydrate crystalizing with or without supercooling are presented in this paper. The thermal conductivity was measured with an ISOMET hot disc surface measurement probe....... Samples that crystalized without supercooling tended to form solid crystals near the heat transfer surface and cavities away from the heat transfer surface. The measured thermal conductivity was up to 0.7 W/m K in solid sodium acetate trihydrate. Samples that crystalized from supercooled state formed...

  2. Non linear thermal behaviour induced by damage of ceramic matrix composite

    International Nuclear Information System (INIS)

    El-Yagoubi, J.

    2011-10-01

    In this work the relationship between the evolution of damage and the loss of thermal properties of Ceramic Matrix Composites is investigated by a multi-scale approach. Research are conducted both experimentally and theoretically. The implemented approach is to consider two significant scales (micro and meso) where different damage mechanisms are operating and then assess the effect on the effective thermal properties by homogenization techniques. Particular attention has been given to the development of a thorough experimental work combining various characterization tools (mechanical, thermal and microstructural). At the two aforementioned scales, an experimental setup was designed to perform thermal measurements on CMC under tensile test. Thermal diffusivity of mini-composites is estimated using Lock-in thermography. Also, transverse diffusivity mapping as well as global in-plane diffusivity of woven CMC are determined by suitable rear face flash methods. The evolution of damage is then derived from acoustic emission activity along with postmortem microstructural observations. Experimental results are systematically compared to simulations. At microscale, a micromechanical-based model is used to simulate the loss of thermal conductivity of a mini-composite under tensile test. At mesoscale, a multi-scale Finite Element Model is proposed to compute the effect of damage on thermal properties of woven CMC. (author) [fr

  3. Preparation and thermal properties characterization of carbonate salt/carbon nanomaterial composite phase change material

    International Nuclear Information System (INIS)

    Tao, Y.B.; Lin, C.H.; He, Y.L.

    2015-01-01

    Highlights: • Nanocomposite phase change materials were prepared and characterized. • Larger specific surface area is more efficient to enhance specific heat. • Columnar structure is more efficient to enhance thermal conductivity. • Thermal conductivity enhancement is the key. • Single walled carbon nanotube is the optimal nanomaterial additive. - Abstract: To enhance the performance of high temperature salt phase change material, four kinds of carbon nanomaterials with different microstructures were mixed into binary carbonate eutectic salts to prepare carbonate salt/nanomaterial composite phase change material. The microstructures of the nanomaterial and composite phase change material were characterized by scanning electron microscope. The thermal properties such as melting point, melting enthalpy, specific heat, thermal conductivity and total thermal energy storage capacity were characterized. The results show that the nanomaterial microstructure has great effects on composite phase change material thermal properties. The sheet structure Graphene is the best additive to enhance specific heat, which could be enhanced up to 18.57%. The single walled carbon nanotube with columnar structure is the best additive to enhance thermal conductivity, which could be enhanced up to 56.98%. Melting point increases but melting enthalpy decreases with nanomaterial specific surface area increase. Although the additives decrease the melting enthalpy of composite phase change material, they also enhance the specific heat. As a combined result, the additives have little effects on thermal energy storage capacity. So, for phase change material performance enhancement, more emphasis should be placed on thermal conductivity enhancement and single walled carbon nanotube is the optimal nanomaterial additive

  4. Thermal stability relationships between PMR-15 resin and its composites

    Science.gov (United States)

    Bowles, Kenneth J.; Jayne, Douglas; Leonhardt, Todd A.; Bors, Dennis

    1993-01-01

    A study was conducted to investigate the relationship between the thermo-oxidative stability of PMR-15 matrix resin and the stability of graphite-fiber-reinforced composites that contain this resin as the matrix material. Three areas were investigated. The first was the effect of fiber/matrix interfacial bond strength on the isothermal aging weight loss of composites. By using type-A graphite fibers produced by Hercules, it was possible to study composites reinforced with fibers that were processed to receive different surface treatments. One of the fibers was untreated, a second fiber was treated by oxidation to enhance fiber/matrix bonding, and the third type of fiber was coated with an epoxy sizing. These treatments produced three significantly different interfacial bond strengths. The epoxy sizing on the third fiber was quickly oxidized from the bare fiber surfaces at 288, 316, and 343 C. The weight loss due to the removal of the sizing was constant at 1.5 percent. This initial weight loss was not observed in thermo-oxidative stability studies of composites. The PMR-15 matrix satisfactorily protected the reinforcemnt at all three temperatures.

  5. Shape-stabilized phase change materials with high thermal conductivity based on paraffin/graphene oxide composite

    International Nuclear Information System (INIS)

    Mehrali, Mohammad; Latibari, Sara Tahan; Mehrali, Mehdi; Metselaar, Hendrik Simon Cornelis; Silakhori, Mahyar

    2013-01-01

    Highlights: ► The composite PCM was prepared with impregnation method. ► Shapes stabilized phase change material made with paraffin and GO composite. ► Determine effects of GO composite on shape stabilized PCM properties. ► The composite PCM has good thermal stability and form-stability. ► The composite PCM has much higher thermal conductivity than that of paraffin. - Abstract: This paper mainly focuses on the preparation, characterization, thermal properties and thermal stability and reliability of new form-stable composite phase change materials (PCMs) prepared by vacuum impregnation of paraffin within graphene oxide (GO) sheets. SEM and FT-IR techniques and TGA and DSC analysis are used for characterization of material and thermal properties. The composite PCM contained 48.3 wt.% of paraffin without leakage of melted PCM and therefore this composite found to be a form-stable composite PCM. SEM results indicate that the paraffin bounded into the pores of GO. FT-IR analysis showed there was no chemical reaction between paraffin and GO. Temperatures of melting and freezing and latent heats of the composite were 53.57 and 44.59 °C and 63.76 and 64.89 kJ/kg, respectively. Thermal cycling tests were done by 2500 melting/freezing cycling for verification of the form-stable composite PCM in terms of thermal reliability and chemical stability. Thermal conductivity of the composite PCM was highly improved from 0.305 to 0.985 (W/mk). As a result, the prepared paraffin/GO composite is appropriate PCM for thermal energy storage applications because of their acceptable thermal properties, good thermal reliability, chemical stability and thermal conductivities

  6. The effect of reinforcement volume ratio on porosity and thermal conductivity in Al-Mgo composites

    Directory of Open Access Journals (Sweden)

    Recep Calin

    2012-12-01

    Full Text Available In this study, the effects of reinforcement volume ratios (RVR on composite structure and thermal conductivity were examined in Al-MgO reinforced metal matrix composites (MMCs of 5%, 10% and 15% RVR produced by melt stirring. In the production of composites, EN AW 1050A aluminum alloy was used as the matrix material and MgO powders with particle size of -105 µm were used as the reinforcement material. For every composite specimen was produced at 500 rev/min stirring speed, at 750 °C liquid matrix temperature and 4 minutes stirring time. Composite samples were cooled under normal atmosphere. Then, microstructures of the samples were determined and evaluated by using Scanning Electron Microscope (SEM and Energy Dispersive X-ray Spectroscopy (EDS analysis. In general, it was observed that the reinforcement exhibited a homogeneous distribution. Furthermore, it was determined that the increase in the RVR increased porosity. From the Scanning Electron Microscope images, a thermal Ansys model was generated to determine effective thermal conductivity. Effective thermal conductivity of Al-MgO composites increased with the decrease in reinforcement volume ratio.

  7. Presupernova models and supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, D [Tokyo Univ. (Japan). Dept. of Earth Science and Astronomy; Nomoto, K I [Ibaraki Univ., Mito (Japan). Dept. of Physics

    1980-02-01

    Present status of the theories for presupernova evolution and triggering mechanisms of supernova explosions are summarized and discussed from the standpoint of the theory of stellar structure and evolution. It is not intended to collect every detail of numerical results thus far obtained, but to extract physically clear-cut understanding from complexities of the numerical stellar models. For this purpose the evolution of stellar cores is discussed in a generalized fashion. The following types of the supernova explosions are discussed. The carbon deflagration supernova of intermediate mass star which results in the total disruption of the star. Massive star evolves into a supernova triggered by photo-dissociation of iron nuclei which results in a formation of a neutron star or a black hole depending on its mass. These two are typical types of the supernova. Between them there remains a range of mass for which collapse of the stellar core is triggered by electron captures, which has been recently shown to leave a neutron star despite oxygen deflagration competing with the electron captures. Also discussed are combustion and detonation of helium or carbon which take place in accreting white dwarfs, and the collapse which is triggered by electron-pair creation in very massive stars.

  8. X-Ray Emission Properties of Supernova Remnants

    NARCIS (Netherlands)

    Vink, J.; Alsabti, A.W.; Murdin, P.

    2016-01-01

    X-ray emission from supernova remnants can be broadly divided into thermal X-ray emission from the shock-heated plasmas and in nonthermal (synchrotron) emission caused by very high-energy (10–100 TeV) electrons moving in the magnetic fields of the hot plasmas. The thermal X-ray emission of young

  9. Mechanical and Thermal Properties of Epoxy Composites Containing Zirconia-Impregnated Halloysite Nanotubes with Different Loadings.

    Science.gov (United States)

    Kim, Suhyun; Kim, Moon Il; Shon, Minyoung; Seo, Bongkuk; Lim, Choongsun

    2018-09-01

    Epoxy resins are widely used in various industrial fields due to their low cost, good workability, heat resistance, and good mechanical strength. However, they suffer from brittleness, an issue that must be addressed for further applications. To solve this problem, additional fillers are needed to improve the mechanical and thermal properties of the resins; zirconia is one such filler. However, it has been reported that aggregation may occur in the epoxy composites as the amount of zirconia increases, preventing enhancement of the mechanical strength of the epoxy composites. Herein, to reduce the aggregation, zirconia was well dispersed on halloysite nanotubes (HNTs), which have high thermal and mechanical strength, by a conventional wet impregnation method. The HNTs were impregnated with zirconia at different loadings using zirconyl chloride octahydrate as a precursor. The mechanical and thermal strengths of the epoxy composites with these fillers were investigated. The zirconia-impregnated HNTs (Zr/HNT) were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and tunneling electron microscopy (TEM). The hardening conditions of the epoxy composites were analyzed by differential scanning calorimetry (DSC). The thermal strength of the epoxy composites was studied by thermomechanical analysis (TMA) and micro-calorimetry and the mechanical strength of the epoxy composites (flexural strength and tensile strength) was studied by using a universal testing machine (UTM). The mechanical and thermal strengths of the epoxy composites with Zr/HNT were improved compared to those of the epoxy composite with HNT, and also increased as the zirconia loading on HNT increased.

  10. Thermal modeling of the ceramic composite fuel for light water reactors

    International Nuclear Information System (INIS)

    Revankar, S.T.; Latta, R.; Solomon, A.A.

    2005-01-01

    Full text of publication follows: Composite fuel designs capable of providing improved thermal performance are of great interest in advanced reactor designs where high efficiency and long fuel cycles are desired. Thermal modeling of the composite fuel consisting of continuous second phase in a ceramic (uranium oxide) matrix has been carried out with detailed examination of the microstructure of the composite and the interface. Assuming that constituent phases are arranged as slabs, upper and lower bounds for the thermal conductivity of the composite are derived analytically. Bounding calculations on the thermal conductivity of the composite were performed for SiC dispersed in the UO 2 matrix. It is found that with 10% SiC, the thermal conductivity increases from 5.8 to 9.8 W/m.deg. K at 500 K, or an increase of 69% was observed in UO 2 matrix. The finite element analysis computer program ANSYS was used to create composite fuel geometries with set boundary conditions to produce accurate thermal conductivity predictions. A model developed also accounts for SiC-matrix interface resistance and the addition of coatings or interaction barriers. The first set of calculations using the code was to model simple series and parallel fuel slab geometries, and then advance to inter-connected parallel pathways. The analytical calculations were compared with the ANSYS results. The geometry of the model was set up as a 1 cm long by 400 micron wide rectangle. This rectangle was then divided into one hundred sections with the first ninety percent of a single section being UO 2 and the remaining ten percent consisting of SiC. The model was then meshed using triangular type elements. The boundary conditions were set with the sides of the rectangle being adiabatic and having an assigned temperature at the end of the rectangle. A heat flux was then applied to one end of the model producing a temperature gradient. The effective thermal conductivity was then calculated using the geometry

  11. Physical and thermal behavior of cement composites reinforced with recycled waste paper fibers

    Science.gov (United States)

    Hospodarova, Viola; Stevulova, Nadezda; Vaclavik, Vojtech; Dvorsky, Tomas

    2017-07-01

    In this study, three types of recycled waste paper fibers were used to manufacture cement composites reinforced with recycled cellulosic fibers. Waste cellulosic fibers in quantity of 0.2, 0.3, and 0.5 wt.% were added to cement mixtures. Physical properties such as density, water capillarity, water absorbability and thermal conductivity of fiber cement composites were studied after 28 days of hardening. However, durability of composites was tested after their water storage up to 90 days. Final results of tested properties of fiber cement composites were compared with cement reference sample without cellulosic fibers.

  12. Thermal shock behavior of nano-sized SiC particulate reinforced AlON composites

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, X.J. [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Ru, H.Q., E-mail: ruhq@smm.neu.edu.cn [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Chen, D.L., E-mail: dchen@ryerson.ca [Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Zhang, N.; Liang, B. [Key Laboratory of Advanced Materials Manufacturing Technology of Liaoning Province, Shenyang University, Shenyang, Liaoning 110044 (China)

    2012-03-25

    Highlights: Black-Right-Pointing-Pointer Addition of nano-SiC particles enhances residual strength and critical temperature. Black-Right-Pointing-Pointer Young's modulus decreases with increasing quenching temperature. Black-Right-Pointing-Pointer Linear relationship between residual strength and thermal shock times is obtained. Black-Right-Pointing-Pointer Rougher fracture surfaces in the SiC-AlON composites are observed. - Abstract: Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications. Thermal shock resistance is a major concern and an important performance index of high-temperature ceramics. While silicon carbide (SiC) particles have been proven to improve mechanical properties of AlON ceramic, the high-temperature thermal shock behavior was unknown. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of AlON ceramic and 8 wt% SiC-AlON composites over a temperature range between 175 Degree-Sign C and 275 Degree-Sign C. The residual strength and Young's modulus after thermal shock decreased with increasing quenching temperature and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. A linear relationship between the residual strength and thermal shock times was observed in both pure AlON and SiC-AlON composites. The addition of nano-sized SiC particles increased both residual strength and critical temperature from 200 Degree-Sign C in the monolithic AlON to 225 Degree-Sign C in the SiC-AlON composites due to the toughening effect, the lower coefficient of thermal expansion and higher thermal conductivity of SiC. The enhancement of the thermal shock resistance in the SiC-AlON composites was directly related to the change of fracture mode from intergranular cracking along with cleavage-type fracture in the AlON to a rougher fracture surface with ridge

  13. Finite Element Modeling of Thermal Cycling Induced Microcracking in Carbon/Epoxy Triaxial Braided Composites

    Science.gov (United States)

    Zhang, Chao; Binienda, Wieslaw K.; Morscher, Gregory; Martin, Richard E.

    2012-01-01

    The microcrack distribution and mass change in PR520/T700s and 3502/T700s carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between -55 C and 120 C. Transverse microcrack morphology was investigated using X-ray Computed Tomography. Different performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied. Keywords: Thermal cycles; Microcrack; Finite Element Model; Braided Composite

  14. Mechanical and thermal properties of polypropylene composites with curaua fibre irradiated with gamma radiation

    International Nuclear Information System (INIS)

    Egute, Nayara S.; Forster, Pedro L.; Parra, Duclerc F.; Fermino, Danilo M.; Santana, Sebastiao; Lugao, Ademar B.

    2009-01-01

    Thermal and mechanical behavior of polypropylene with curaua fibre composites were investigated. The treatment of the curaua fibres was processed in alkaline solution (10% wt NaOH). A coupling agent was used (maleic anhydride) to increase the adhesion of the fibre/matrix interface. This composite was irradiated with gamma source in the doses of 5, 15 and 30 kGy and the adhesion between the fibres and the polymeric matrix was monitored to observe probable changes. The thermal behavior was evaluated using differential scanning calorimetry (DSC) and Thermogravimetry (TGA). The mechanical behavior was evaluated using tensile strength in comparison with non-reinforced polypropylene resin. The morphology of the composite fracture surface was observed using scanning electron microscopy (SEM). There were no significant changes in the thermal properties neither in the adhesion of irradiated fibres at doses of 5, 15 and 30 kGy of gamma radiation. (author)

  15. Finite Element Model Characterization Of Nano-Composite Thermal And Environmental Barrier Coatings

    Science.gov (United States)

    Yamada, Yoshiki; Zhu, Dongming

    2011-01-01

    Thermal and environmental barrier coatings have been applied for protecting Si based ceramic matrix composite components from high temperature environment in advanced gas turbine engines. It has been found that the delamination and lifetime of T/EBC systems generally depend on the initiation and propagation of surface cracks induced by the axial mechanical load in addition to severe thermal loads. In order to prevent T/EBC systems from surface cracking and subsequent delamination due to mechanical and thermal stresses, T/EBC systems reinforced with nano-composite architectures have showed promise to improve mechanical properties and provide a potential crack shielding mechanism such as crack bridging. In this study, a finite element model (FEM) was established to understand the potential beneficial effects of nano-composites systems such as SiC nanotube-reinforced oxide T/EBC systems.

  16. Porosity Effect on Thermal Properties of Al-12 wt % Si/Graphite Composites

    Directory of Open Access Journals (Sweden)

    José-Miguel Molina

    2017-02-01

    Full Text Available The effect of porosity on the thermal conductivity and the coefficient of thermal expansion of composites obtained by infiltration of Al-12 wt % Si alloy into graphite particulate preforms has been determined. Highly irregular graphite particles were used to fabricate the preforms. The thermal conductivity of these composites gradually increases with the applied infiltration pressure given the inherent reduction in porosity. A simple application of the Hasselman-Johnson model in a two-step procedure (that accounts for the presence of both graphite particles and voids randomly dispersed in a metallic matrix offers a good estimation of the experimental results. As concerns the coefficient of thermal expansion, the results show a slight increase with saturation being approximately in the range 14.6–15.2 × 10−6 K−1 for a saturation varying from 86% up to 100%. Results lie within the standard Hashin-Strikman bounds.

  17. Porosity Effect on Thermal Properties of Al-12 wt % Si/Graphite Composites.

    Science.gov (United States)

    Molina, José-Miguel; Rodríguez-Guerrero, Alejandro; Louis, Enrique; Rodríguez-Reinoso, Francisco; Narciso, Javier

    2017-02-14

    The effect of porosity on the thermal conductivity and the coefficient of thermal expansion of composites obtained by infiltration of Al-12 wt % Si alloy into graphite particulate preforms has been determined. Highly irregular graphite particles were used to fabricate the preforms. The thermal conductivity of these composites gradually increases with the applied infiltration pressure given the inherent reduction in porosity. A simple application of the Hasselman-Johnson model in a two-step procedure (that accounts for the presence of both graphite particles and voids randomly dispersed in a metallic matrix) offers a good estimation of the experimental results. As concerns the coefficient of thermal expansion, the results show a slight increase with saturation being approximately in the range 14.6-15.2 × 10 -6 K -1 for a saturation varying from 86% up to 100%. Results lie within the standard Hashin-Strikman bounds.

  18. Rheological and Thermal Behavior of Polypropylene-Kaolin Composites

    International Nuclear Information System (INIS)

    Teng, S.T.; Nor Azura Abdul Rahim; Lan, D.N.U

    2014-01-01

    Kaolins effect on rheological behaviour of polypropylene-kaolin composites was investigated. The research found that not only the kaolin content influence the rheological behaviour but also the compounding using internal mixer and twin screw extruder. In details, viscosity and shear stress increased with addition of kaolin content. These characteristics also exhibited higher in polypropylene-kaolin composite suspensions compounded using twin screw extruder than using internal mixer. Chain scission was assumed to occur and affect the melt properties. Further justification characterized by Differential Scanning Calorimeter (DSC) showed that the effect of kaolin and loading content were more evident on the onset melting temperature and crystallinity. Besides, due to the different cooling operation in both processes, the effect of compounding on melting characteristic was conspicuous. (author)

  19. Boride ceramics covalent functionalization and its effect on the thermal conductivity of epoxy composites

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Zhi-Qiang, E-mail: yuzhiqiang@fudan.edu.cn [Department of Materials Science, Fudan University, 200433 Shanghai (China); Wu, Yicheng [Department of Materials Science, Fudan University, 200433 Shanghai (China); Wei, Bin; Baier, Horst [Institute of Lightweight Structures, Technical University Munich (TUM), Boltzmannstr. 15, D-85747 Garching (Germany)

    2015-08-15

    Zirconium diboride/aluminium oxide (ZrB{sub 2}/Al{sub 2}O{sub 3}) composite particles were functionalized with epoxide functionalized γ-glycidoxypropyltrimethoxysilane by the covalent bonding approach to improve the interfacial compatibility of composite particles in epoxy matrix. The composites of epoxy resin filled with functionalized ZrB{sub 2}/Al{sub 2}O{sub 3} were prepared by in situ bulk condensation polymerization of bisphenol A and epichlorohydrin in the presence of ZrB{sub 2}/Al{sub 2}O{sub 3}. The heat-conducting properties of composites were investigated by the finite element method (FEM) and the thermal conductivity test. The finite-element program ANSYS was used for this numerical analysis, and three-dimensional spheres-in-cube lattice array models were built to simulate the microstructure of composite materials for different filler contents. The thermal conductivity of composites was determined by laser flash method (LFA447 Nanoflash), using the measured heat capacity and thermal diffusivity, with separately entered density data. The results show that the effective chemical bonds are formed between ZrB{sub 2}/Al{sub 2}O{sub 3} and γ-glycidoxypropyltrimethoxysilane after the surface functionalization. The interfacial compatibility and bonding of modified particles with the epoxy matrix are improved. The thermal conductivities of functionalized composites with 3 vol% and 5 vol% loading are increased by 8.3% and 12.5% relative to the unmodified composites, respectively. Comparison of experimental values and calculated values of the thermal conductivity, the average relative differences are under 5%. The predictive values of thermal conductivity of epoxy composites are in reasonable agreement with the experimental values. - Highlights: • The surfaces of ZrB{sub 2}/Al{sub 2}O{sub 3} were functionalized by silane coupling agents. • The thermal conductivity (TC) of modified epoxy composites is improved significantly. • The FEM values of TC are in

  20. NiTi-polyimide composites prepared using thermal imidization process

    Czech Academy of Sciences Publication Activity Database

    Vokoun, David; Sysel, P.; Heller, Luděk; Kadeřávek, L.; Svatuška, Michal; Goryczka, T.; Kafka, Vratislav; Šittner, Petr

    2016-01-01

    Roč. 25, č. 5 (2016), 1993-1999 ISSN 1059-9495 R&D Projects: GA ČR GC15-13174J; GA ČR GA14-15264S Institutional support: RVO:68378271 ; RVO:68378297 Keywords : actuator * composite * model * NiTi * polyimide * residual * stress Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.331, year: 2016

  1. Nearby supernova factory announces 34 supernovae in one year'; best Rookie year ever for supernova search

    CERN Multimedia

    2003-01-01

    The Nearby Supernova Factory (SNfactory), an international collaboration based at Lawrence Berkeley National Laboratory, announced that it had discovered 34 supernovae during the first year of the prototype system's operation (2 pages).

  2. High Density Polyethylene Composites Reinforced with Hybrid Inorganic Fillers: Morphology, Mechanical and Thermal Expansion Performance

    Directory of Open Access Journals (Sweden)

    Birm-June Kim

    2013-09-01

    Full Text Available The effect of individual and combined talc and glass fibers (GFs on mechanical and thermal expansion performance of the filled high density polyethylene (HDPE composites was studied. Several published models were adapted to fit the measured tensile modulus and strength of various composite systems. It was shown that the use of silane-modified GFs had a much larger effect in improving mechanical properties and in reducing linear coefficient of thermal expansion (LCTE values of filled composites, compared with the use of un-modified talc particles due to enhanced bonding to the matrix, larger aspect ratio, and fiber alignment for GFs. Mechanical properties and LCTE values of composites with combined talc and GF fillers varied with talc and GF ratio at a given total filler loading level. The use of a larger portion of GFs in the mix can lead to better composite performance, while the use of talc can help lower the composite costs and increase its recyclability. The use of 30 wt % combined filler seems necessary to control LCTE values of filled HDPE in the data value range generally reported for commercial wood plastic composites. Tensile modulus for talc-filled composite can be predicted with rule of mixture, while a PPA-based model can be used to predict the modulus and strength of GF-filled composites.

  3. High Density Polyethylene Composites Reinforced with Hybrid Inorganic Fillers: Morphology, Mechanical and Thermal Expansion Performance.

    Science.gov (United States)

    Huang, Runzhou; Xu, Xinwu; Lee, Sunyoung; Zhang, Yang; Kim, Birm-June; Wu, Qinglin

    2013-09-17

    The effect of individual and combined talc and glass fibers (GFs) on mechanical and thermal expansion performance of the filled high density polyethylene (HDPE) composites was studied. Several published models were adapted to fit the measured tensile modulus and strength of various composite systems. It was shown that the use of silane-modified GFs had a much larger effect in improving mechanical properties and in reducing linear coefficient of thermal expansion (LCTE) values of filled composites, compared with the use of un-modified talc particles due to enhanced bonding to the matrix, larger aspect ratio, and fiber alignment for GFs. Mechanical properties and LCTE values of composites with combined talc and GF fillers varied with talc and GF ratio at a given total filler loading level. The use of a larger portion of GFs in the mix can lead to better composite performance, while the use of talc can help lower the composite costs and increase its recyclability. The use of 30 wt % combined filler seems necessary to control LCTE values of filled HDPE in the data value range generally reported for commercial wood plastic composites. Tensile modulus for talc-filled composite can be predicted with rule of mixture, while a PPA-based model can be used to predict the modulus and strength of GF-filled composites.

  4. Numerical Investigation of Thermal and Thermo-mechanical Effective Properties for Short Fibre Reinforced Composite

    Science.gov (United States)

    Ioannou, Ioannis; Hodzic, Alma; Gitman, Inna M.

    2017-10-01

    This study aims to investigate the thermal conductivity and the linear coefficient of thermal expansion for short fibre reinforced composites. The study combines numerical and statistical analyses in order to primarily examine the representative size and the effective properties of the volume element. Effects of various micromechanical parameters, such as fibre's aspect ratio and fibre's orientation, on the minimum representative size are discussed. The numerically acquired effective properties, obtained for the representative size, are presented and compared with analytical models.

  5. High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner For Advanced Rocket Engines

    Science.gov (United States)

    Bhat, Biliyar N.; Ellis, David; Singh, Jogender

    2014-01-01

    Advanced high thermal conductivity materials research conducted at NASA Marshall Space Flight Center (MSFC) with state of the art combustion chamber liner material NARloy-Z showed that its thermal conductivity can be increased significantly by adding diamond particles and sintering it at high temperatures. For instance, NARloy-Z containing 40 vol. percent diamond particles, sintered at 975C to full density by using the Field assisted Sintering Technology (FAST) showed 69 percent higher thermal conductivity than baseline NARloy-Z. Furthermore, NARloy-Z-40vol. percent D is 30 percent lighter than NARloy-Z and hence the density normalized thermal conductivity is 140 percent better. These attributes will improve the performance and life of the advanced rocket engines significantly. By one estimate, increased thermal conductivity will directly translate into increased turbopump power up to 2X and increased chamber pressure for improved thrust and ISP, resulting in an expected 20 percent improvement in engine performance. Follow on research is now being conducted to demonstrate the benefits of this high thermal conductivity NARloy-Z-D composite for combustion chamber liner applications in advanced rocket engines. The work consists of a) Optimizing the chemistry and heat treatment for NARloy-Z-D composite, b) Developing design properties (thermal and mechanical) for the optimized NARloy-Z-D, c) Fabrication of net shape subscale combustion chamber liner, and d) Hot fire testing of the liner for performance. FAST is used for consolidating and sintering NARlo-Z-D. The subscale cylindrical liner with built in channels for coolant flow is also fabricated near net shape using the FAST process. The liner will be assembled into a test rig and hot fire tested in the MSFC test facility to determine performance. This paper describes the development of this novel high thermal conductivity NARloy-Z-D composite material, and the advanced net shape technology to fabricate the combustion

  6. Influence of Thermal Preparation Method on Mineral Composition of Mussels

    Directory of Open Access Journals (Sweden)

    Gheorghe Valentin GORAN

    2018-02-01

    Full Text Available This study focuses on evaluation of the effects of 3 different thermal preparation methods (boiling, roasting, microwaving on mineral concentrations of mussels from Bucharest market. The mineral content in raw and cooked mussel samples was evaluated by ICP-OES and relative humidity of raw and cooked mussels by thermogravimetry. Se level in microwaved samples was significantly decreased compared to raw and the other 2 cooked mussel samples. Zn concentration in raw samples was not significantly different compared to those in roasted samples. Fe level was insignificantly different between boiled and roasted samples and significantly lowers in microwaved samples. Ni, Pb, and Se levels were significantly higher in boiled samples, and Cd levels were insignificantly different reported to cooking method. The percentage of water loss during roasting was lower than the other 2 thermal preparation methods. Potassium concentrations in cooked mussels were higher compared to raw ones. Mineral concentrations were highest in roasted samples and heavy metal concentrations in boiled mussels.

  7. Thermal Properties of Cement-Based Composites for Geothermal Energy Applications

    Directory of Open Access Journals (Sweden)

    Xiaohua Bao

    2017-04-01

    Full Text Available Geothermal energy piles are a quite recent renewable energy technique where geothermal energy in the foundation of a building is used to transport and store geothermal energy. In this paper, a structural–functional integrated cement-based composite, which can be used for energy piles, was developed using expanded graphite and graphite nanoplatelet-based composite phase change materials (CPCMs. Its mechanical properties, thermal-regulatory performance, and heat of hydration were evaluated. Test results showed that the compressive strength of GNP-Paraffin cement-based composites at 28 days was more than 25 MPa. The flexural strength and density of thermal energy storage cement paste composite decreased with increases in the percentage of CPCM in the cement paste. The infrared thermal image analysis results showed superior thermal control capability of cement based materials with CPCMs. Hence, the carbon-based CPCMs are promising thermal energy storage materials and can be used to improve the durability of energy piles.

  8. A Study on Accelerated Thermal Aging of High Modulus Carbon/Epoxy Composite Material

    Directory of Open Access Journals (Sweden)

    Ju Min Kyung

    2015-01-01

    Full Text Available Composite materials have been used increasingly for various space applications due to the favorable characteristic of high modulus to density ratio and potential for near-zero coefficient of thermal expansion. In composite system, depending on the orientation of fibers, strength and stiffness can be changed so that the optimum structure can be accomplished. This is because the coefficient of thermal expansion (CTE of carbon fibers is negative. For spacecraft and orbiting space structure, which are thermally cycled by moving through the earth' shadow for at least 5 years, it is necessary to investigate the change of properties of the material over time. In this study, thermal aging of epoxy matrix/high modulus carbon fiber composite materials are accelerated to predict the long term creep property. Specimens are tested at various temperatures of 100~140°C with dynamic mechanical analysis to obtain creep compliances that are functions of time and temperature. Using Time Temperature Superposition method, creep compliance curves at each temperature are shifted to the reference temperature by shift factor and a master curve is generated at the reference temperature. This information is useful to predict the long term thermal aging of high modulus composite material for spacecraft application.

  9. Enhancement of thermal conductive pathway of boron nitride coated polymethylsilsesquioxane composite.

    Science.gov (United States)

    Kim, Gyungbok; Ryu, Seung Han; Lee, Jun-Tae; Seong, Ki-Hun; Lee, Jae Eun; Yoon, Phil-Joong; Kim, Bum-Sung; Hussain, Manwar; Choa, Yong-Ho

    2013-11-01

    We report here in the fabrication of enhanced thermal conductive pathway nanocomposites of boron nitride (BN)-coated polymethylsilsesquioxane (PMSQ) composite beads using isopropyl alcohol (IPA) as a mixing medium. Exfoliated and size-reduced boron nitride particles were successfully coated on the PMSQ beads and explained by surface charge differences. A homogeneous dispersion and coating of BN on the PMSQ beads using IPA medium was confirmed by SEM. Each condition of the composite powder was carried into the stainless still mould and then hot pressed in an electrically heated hot press machine. Three-dimensional percolation networks and conductive pathways created by exfoliated BN were precisely formed in the nanocomposites. The thermal conductivity of nanocomposites was measured by multiplying specific gravity, specific heat, and thermal diffusivity, based upon the laser flash method. Densification of the composite resulted in better thermal properties. For an epoxy reinforced composite with 30 vol% BN and PMSQ, a thermal conductivity of nine times higher than that of pristine PMSQ was observed.

  10. THERMAL INSULATION PROPERTIES RESEARCH OF THE COMPOSITE MATERIAL WATER GLASS–GRAPHITE MICROPARTICLES

    Directory of Open Access Journals (Sweden)

    V. A. Gostev

    2014-05-01

    Full Text Available Research results for the composite material (CM water glass–graphite microparticles with high thermal stability and thermal insulation properties are given. A composition consisting of graphite (42 % by weight, water glass Na2O(SiO2n (50% by weight and the hardener - sodium silicofluoric Na2SiF6 (8% by weight. Technology of such composition receipt is suggested. Experimental samples of the CM with filler particles (graphite and a few microns in size were obtained. This is confirmed by a study of samples by X-ray diffraction and electron microscopy. The qualitative and quantitative phase analysis of the CM structure is done. Load limit values leading to the destruction of CM are identified. The character of the rupture surface is detected. Numerical values of specific heat and thermal conductivity are defined. Dependence of the specific heat capacity and thermal conductivity on temperature at monotonic heating is obtained experimentally. Studies have confirmed the increased thermal insulation properties of the proposed composition. CM with such characteristics can be recommended as a coating designed to reduce heat losses and resistant to high temperatures. Due to accessibility and low cost of its components the proposed material can be produced on an industrial scale.

  11. Thermal Analysis of NR Composite with MWCNTs Aligned in a Magnetic Field

    Directory of Open Access Journals (Sweden)

    Jin Xu

    2015-01-01

    Full Text Available We got the aligned carbon tube in the rubber matrix through magnetic field. TEM shows that Fe3O4 is symmetrically coated on the outer surface of MWCNTs. Diffraction peaks corresponding to Fe3O4 cubic crystal also appeared in the X-ray diffraction spectra. Thermal conductivity of composites increases by filling the appropriate content of carbon tube. If the magnetic field is larger and the direction time is longer, a greater thermal conductivity of composites can be obtained.

  12. Effect of Microstructure on the Thermal Properties of Sintered Iron-copper Composites

    OpenAIRE

    Ugarteche, Caroline Velasques; Furlan, Kaline Pagnan; Pereira, Rafaela do Vale; Trindade, Gabriel; Binder, Roberto; Binder, Cristiano; Klein, Aloisio Nelmo

    2015-01-01

    Copper is a well know material for use as heat sink or heat exchanger. However, copper has a considerable low tensile strength and temperature limit. A material that has a good thermal conductivity, low cost, but also resistance is the desired. Effects of copper on the sintering and thermal properties of iron-copper composites produced by powder metallurgy and Fe on copper-iron composites have been investigated. Copper and iron were varied from 20 to 80 vol.% in the samples, alternating the c...

  13. Compositional dependence thermal and optical properties of a novel germanate glass

    International Nuclear Information System (INIS)

    El-Rabaie, S.; Taha, T.A.; Higazy, A.A.

    2014-01-01

    A series of zinc lithium germanate glasses of the composition (45−x)Li 2 O–xZnO–55GeO 2 have been synthesized via melt quenching technique. Dependencies of their thermal and optical properties on composition were investigated. It is found that the gradual replacement of Li 2 O by ZnO, decreases the glass transition temperature from 430 to 280 °C and increases the thermal stability (ΔT) of the studied glasses. The optical band gap E opt also decreases from 2.31 to 1.40 eV with increasing the mole content of ZnO

  14. Structural and thermal properties of silk fibroin - Silver nanoparticles composite films

    Science.gov (United States)

    Shivananda, C. S.; Rao B, B. Lakshmeesha; Shetty, G. Rajesh; Sangappa, Y.

    2018-05-01

    In this work, silk fibroin-silver nanoparticles (SF-AgNPs) composite films have been prepared by simple solution casting method. The composite films were examined for structural and thermal properties using X-ray diffraction (XRD), thermogravimatric (TGA) and differential scanning calorimetry (DSC) analysis. The XRD results showed that with the introduction of AgNPs in the silk fibroin matrix the amorphous nature of the silk fibroin decreases with increasing nanoparticles concentration. The silk fibroin films possess good thermal stability with the presence of AgNPs.

  15. Porous composite with negative thermal expansion obtained by photopolymer additive manufacturing

    Directory of Open Access Journals (Sweden)

    Akihiro Takezawa

    2015-07-01

    Full Text Available Additive manufacturing (AM could be a novel method of fabricating composite and porous materials having various effective performances based on mechanisms of their internal geometries. Materials fabricated by AM could rapidly be used in industrial application since they could easily be embedded in the target part employing the same AM process used for the bulk material. Furthermore, multi-material AM has greater potential than usual single-material AM in producing materials with effective properties. Negative thermal expansion is a representative effective material property realized by designing a composite made of two materials with different coefficients of thermal expansion. In this study, we developed a porous composite having planar negative thermal expansion by employing multi-material photopolymer AM. After measurement of the physical properties of bulk photopolymers, the internal geometry was designed by topology optimization, which is the most effective structural optimization in terms of both minimizing thermal stress and maximizing stiffness. The designed structure was converted to a three-dimensional stereolithography (STL model, which is a native digital format of AM, and assembled as a test piece. The thermal expansions of the specimens were measured using a laser scanning dilatometer. Negative thermal expansion corresponding to less than −1 × 10−4 K−1 was observed for each test piece of the N = 3 experiment.

  16. Aqueous preparation of polyethylene glycol/sulfonated graphene phase change composite with enhanced thermal performance

    International Nuclear Information System (INIS)

    Li, Hairong; Jiang, Ming; Li, Qi; Li, Denian; Chen, Zongyi; Hu, Waping; Huang, Jing; Xu, Xizhe; Dong, Lijie; Xie, Haian; Xiong, Chuanxi

    2013-01-01

    Highlights: • We report an aqueous preparation technique of PEG/graphene phase change composite. • Hydrophilic sulfonated graphene (SG) nanosheets were synthesized. • Large increase in thermal conductivity is attained at low SG loading. • High latent heat is retained due to the low filler loading. • Affinity between SG and PEG contributes to the enhanced thermal performance. - Abstract: A polyethylene glycol (PEG)/sulfonated graphene (SG) phase change composite with enhanced thermal performance was prepared by solution processing in aqueous medium. It is remarkable that the addition of only 4 wt.% of SG to PEG could lead to a four times higher increase in thermal conductivity and a slight decrease in the phase change enthalpy, which is attributed to the formation of efficient thermal conductive network within the PEG matrix relevant to the excellent thermal property and unique 2-dimensional morphology of graphene as well as strong interface affinity between PEG matrix and SG nanosheets. The aqueous preparation technique is expected to pioneer a new way to prepare environment friendly organic phase change materials, and the production of PEG/SG composites is potentially scalable due to the facile fabricating process

  17. Carriers' localization and thermal redistribution in post growth voluntarily tuned quantum dashes' size/composition distribution

    International Nuclear Information System (INIS)

    Alouane, M.H. Hadj; Helali, A.; Morris, D.; Maaref, H.; Aimez, V.; Salem, B.; Gendry, M.

    2014-01-01

    This paper treats the impact of post growth tuned InAs/InP quantum dashes' (QDas) size/composition distribution on carriers' localization and thermal redistribution. The spread of this distribution depends on the experimental conditions used for the phosphorus ion implantation enhanced intermixing process. Atypical temperature-dependent luminescence properties have been observed and found to be strongly dependent on the amount of QDas size/composition dispersion. The experimental results have been reproduced by a model that takes into account the width of the QDas localized states distribution and consequent thermally induced carriers' redistribution. This model gives critical temperature values marking the beginning and the end of carriers delocalization and thermal transfer processes via an intermixing induced carrier's transfer channel located below the wetting layer states. -- Highlights: • We examine optical properties of post growth tuned QDas size/composition distribution. • Carriers' localization and thermal redistribution within inhomogeneously intermixed QDas are the origin of the atypical temperature-dependent luminescence properties. • Localized states ensemble's model is successively used to interpret the experimental results. • The carriers thermal transfer processes occur via an intermixing induced channel located below the wetting layer states. • Intermixing degree strongly influence the critical temperatures marking the beginning and the end of the carriers thermal transfer processes

  18. Enhanced Thermal Conductivity of Polyimide Composites Filled with Modified h-BN and Nanodiamond Hybrid Filler.

    Science.gov (United States)

    Yang, Xi; Yu, Xiaoyan; Naito, Kimiyoshi; Ding, Huili; Qu, Xiongwei; Zhang, Qingxin

    2018-05-01

    A new thermally conductive and electrically insulative polyimide were prepared by filling different amounts of hexagonal boron nitride (h-BN) particles, and the thermal conductivity of Polyimide (PI) composites were improved with the increasing h-BN content. Based on this, two methods were applied to improve thermal conductivity furtherly at limited filler loading in this paper. One is modifying the h-BN to improve interface interaction, another is fabricating a nano-micro hybrid filler with 2-D h-BN and 0-D nano-scale nanodiamond (ND) to build more effective conductive network. Both surface modification and hybrid system have a positive effect on thermal conductivity. The composites introducing 40 wt% hybrid filler (the weight ratio of ND/modified BN was 1/10) showed the highest thermal conductivity, being up to 0.98 W/(m K) (5.2 times that of PI). In addition, the composites exhibits excellent electrical insulation, thermal stability properties etc.

  19. Exploring Cosmology with Supernovae

    DEFF Research Database (Denmark)

    Li, Xue

    distribution of strong gravitational lensing is developed. For Type Ia supernova (SNe Ia), the rate is lower than core-collapse supernovae (CC SNe). The rate of SNe Ia declines beyond z 1:5. Based on these reasons, we investigate a potential candidate to measure cosmological distance: GRB......-SNe. They are a subclass of CC SNe. Light curves of GRB-SNe are obtained and their properties are studied. We ascertain that the properties of GRB-SNe make them another candidate for standardizable candles in measuring the cosmic distance. Cosmological parameters M and are constrained with the help of GRB-SNe. The first...

  20. Type I supernova models

    International Nuclear Information System (INIS)

    Canal, Ramon; Labay, Javier; Isern, Jordi

    1987-01-01

    We briefly describe the characteristics of Type I supernova outbursts and we present the theoretical models so far advanced to explain them. We especially insist on models based on the thermonuclear explosion of a white dwarf in a close binary system, even regarding the recent division of Type I supernovae into the Ia and Ib subtypes. Together with models assuming explosive thermonuclear burning in a fluid interior, we consider in some detail those based on partially solid interiors. We finally discuss models that incorporate nonthermonuclear energy contributions, suggested in order to explain Type Ib outbursts. (Author)

  1. Thermal Stability and Flammability of Styrene-Butadiene Rubber-Based (SBR Ceramifiable Composites

    Directory of Open Access Journals (Sweden)

    Rafał Anyszka

    2016-07-01

    Full Text Available Ceramifiable styrene-butadiene (SBR-based composites containing low-softening-point-temperature glassy frit promoting ceramification, precipitated silica, one of four thermally stable refractory fillers (halloysite, calcined kaolin, mica or wollastonite and a sulfur-based curing system were prepared. Kinetics of vulcanization and basic mechanical properties were analyzed and added as Supplementary Materials. Combustibility of the composites was measured by means of cone calorimetry. Their thermal properties were analyzed by means of thermogravimetry and specific heat capacity determination. Activation energy of thermal decomposition was calculated using the Flynn-Wall-Ozawa method. Finally, compression strength of the composites after ceramification was measured and their micromorphology was studied by scanning electron microscopy. The addition of a ceramification-facilitating system resulted in the lowering of combustibility and significant improvement of the thermal stability of the composites. Moreover, the compression strength of the mineral structure formed after ceramification is considerably high. The most promising refractory fillers for SBR-based ceramifiable composites are mica and halloysite.

  2. General Approach for Composite Thermoelectric Systems with Thermal Coupling: The Case of a Dual Thermoelectric Cooler

    Directory of Open Access Journals (Sweden)

    Cuautli Yanehowi Flores-Niño

    2015-06-01

    Full Text Available In this work, we show a general approach for inhomogeneous composite thermoelectric systems, and as an illustrative case, we consider a dual thermoelectric cooler. This composite cooler consists of two thermoelectric modules (TEMs connected thermally in parallel and electrically in series. Each TEM has different thermoelectric (TE properties, namely thermal conductance, electrical resistance and the Seebeck coefficient. The system is coupled by thermal conductances to heat reservoirs. The proposed approach consists of derivation of the dimensionless thermoelectric properties for the whole system. Thus, we obtain an equivalent figure of merit whose impact and meaning is discussed. We make use of dimensionless equations to study the impact of the thermal conductance matching on the cooling capacity and the coefficient of the performance of the system. The equivalent thermoelectric properties derived with our formalism include the external conductances and all intrinsic thermoelectric properties of each component of the system. Our proposed approach permits us changing the thermoelectric parameters of the TEMs and the working conditions of the composite system. Furthermore, our analysis shows the effect of the number of thermocouples on the system. These considerations are very useful for the design of thermoelectric composite systems. We reproduce the qualitative behavior of a commercial composite TEM connected electrically in series.

  3. The Electrical and Thermal Conductivity of Woven Pristine and Intercalated Graphite Fiber-Polymer Composites

    Science.gov (United States)

    Gaier, James R.; Vandenburg, Yvonne Yoder; Berkebile, Steven; Stueben, Heather; Balagadde, Frederick

    2002-01-01

    A series of woven fabric laminar composite plates and narrow strips were fabricated from a variety of pitch-based pristine and bromine intercalated graphite fibers in an attempt to determine the influence of the weave on the electrical and thermal conduction. It was found generally that these materials can be treated as if they are homogeneous plates. The rule of mixtures describes the resistivity of the composite fairly well if it is realized that only the component of the fibers normal to the equipotential surface will conduct current. When the composite is narrow with respect to the fiber weave, however, there is a marked angular dependence of the resistance which was well modeled by assuming that the current follows only along the fibers (and not across them in a transverse direction), and that the contact resistance among the fibers in the composite is negligible. The thermal conductivity of composites made from less conductive fibers more closely followed the rule of mixtures than that of the high conductivity fibers, though this is thought to be an artifact of the measurement technique. Electrical and thermal anisotropy could be induced in a particular region of the structure by weaving together high and low conductivity fibers in different directions, though this must be done throughout all of the layers of the structure as interlaminar conduction precludes having only the top layer carry the anisotropy. The anisotropy in the thermal conductivity is considerably less than either that predicted by the rule of mixtures or the electrical resistivity.

  4. Effect of electron beam irradiation on thermal and mechanical properties of aluminum based epoxy composites

    Science.gov (United States)

    Visakh, P. M.; Nazarenko, O. B.; Sarath Chandran, C.; Melnikova, T. V.; Nazarenko, S. Yu.; Kim, J.-C.

    2017-07-01

    The epoxy resins are widely used in nuclear and aerospace industries. The certain properties of epoxy resins as well as the resistance to radiation can be improved by the incorporation of different fillers. This study examines the effect of electron beam irradiation on the thermal and mechanical properties of the epoxy composites filled with aluminum nanoparticles at percentage of 0.35 wt%. The epoxy composites were exposed to the irradiation doses of 30, 100 and 300 kGy using electron beam generated by the linear electron accelerator ELU-4. The effects of the doses on thermal and mechanical properties of the aluminum based epoxy composites were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The results revealed that the studied epoxy composites showed good radiation resistance. The thermal and mechanical properties of the aluminum based epoxy composites increased with increasing the irradiation dose up to 100 kGy and decreased with further increasing the dose.

  5. Average thermal stress in the Al+SiC composite due to its manufacturing process

    International Nuclear Information System (INIS)

    Miranda, Carlos A.J.; Libardi, Rosani M.P.; Marcelino, Sergio; Boari, Zoroastro M.

    2013-01-01

    The numerical analyses framework to obtain the average thermal stress in the Al+SiC Composite due to its manufacturing process is presented along with the obtained results. The mixing of Aluminum and SiC powders is done at elevated temperature and the usage is at room temperature. A thermal stress state arises in the composite due to the different thermal expansion coefficients of the materials. Due to the particles size and randomness in the SiC distribution, some sets of models were analyzed and a statistical procedure used to evaluate the average stress state in the composite. In each model the particles position, form and size are randomly generated considering a volumetric ratio (VR) between 20% and 25%, close to an actual composite. The obtained stress field is represented by a certain number of iso stress curves, each one weighted by the area it represents. Systematically it was investigated the influence of: (a) the material behavior: linear x non-linear; (b) the carbide particles form: circular x quadrilateral; (c) the number of iso stress curves considered in each analysis; and (e) the model size (the number of particles). Each of above analyzed condition produced conclusions to guide the next step. Considering a confidence level of 95%, the average thermal stress value in the studied composite (20% ≤ VR ≤ 25%) is 175 MPa with a standard deviation of 10 MPa. Depending on its usage, this value should be taken into account when evaluating the material strength. (author)

  6. Thermal, spectral, and surface properties of LED light-polymerized bulk fill resin composites.

    Science.gov (United States)

    Pişkin, Mehmet Burçin; Atalı, Pınar Yılmaz; Figen, Aysel Kantürk

    2015-02-01

    The aim of this study was to evaluate the thermal, spectral, and surface properties of four different bulk fill materials – SureFil SDR (SDR, Dentsplay DETREY), QuixFil (QF, Dentsplay DETREY), X-tra base (XB, Voco) X-tra fil (XF, Voco) – polymerized by light-emitting diode (LED). Resin matrix, filler type, size and amount, and photoinitiator types influence the degree of conversion. LED-cured bulk fill composites achieved sufficient polymerization. Scanning electron microscope (SEM) analysis revealed different patterns of surface roughness, depending on the composite material. Bulk fill materials showed surface characteristics similar to those of nanohybrid composites. Based on the thermal analysis results, glass transition (T(g)) and initial degradation (T(i)) temperatures changed depending on the bulk fill resin composites.

  7. Seawater infiltration effect on thermal degradation of fiber reinforced epoxy composites

    Science.gov (United States)

    Ibrahim, Mohd Haziq Izzuddin bin; Hassan, Mohamad Zaki bin; Ibrahim, Ikhwan; Rashidi, Ahmad Hadi Mohamed; Nor, Siti Fadzilah M.; Daud, Mohd Yusof Md

    2018-05-01

    Seawater salinity has been associated with the reduction of polymer structure durability. The aim of this study is to investigate the change in thermal degradation of fiber reinforced epoxy composite due to the presence of seawater. Carbon fiber, carbon/kevlar, fiberglass, and jute that reinforced with epoxy resin was laminated through hand-layup technique. Initially, these specimen was sectioned to 5×5 mm dimension, then immersed in seawater and distilled water at room temperature until it has thoroughly saturated. Following, the thermal degradation analysis using Differential Scanning Calorimetry (DSC), the thermic changes due to seawater infiltration was defined. The finding shows that moisture absorption reduces the glass transition temperature (Tg) of fiber reinforced epoxy composite. However, the glass transition temperature (Tg) of seawater infiltrated laminate composite is compareable with distilled water infiltrated laminate composite. The carbon fiber reinfored epoxy has the highest glass transition temperature out of all specimen.

  8. Composition dependent thermal annealing behaviour of ion tracks in apatite

    Energy Technology Data Exchange (ETDEWEB)

    Nadzri, A., E-mail: allina.nadzri@anu.edu.au [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601 (Australia); Schauries, D.; Mota-Santiago, P.; Muradoglu, S. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601 (Australia); Trautmann, C. [GSI Helmholtz Centre for Heavy Ion Research, Planckstrasse 1, 64291 Darmstadt (Germany); Technische Universität Darmstadt, 64287 Darmstadt (Germany); Gleadow, A.J.W. [School of Earth Science, University of Melbourne, Melbourne, VIC 3010 (Australia); Hawley, A. [Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168 (Australia); Kluth, P. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601 (Australia)

    2016-07-15

    Natural apatite samples with different F/Cl content from a variety of geological locations (Durango, Mexico; Mud Tank, Australia; and Snarum, Norway) were irradiated with swift heavy ions to simulate fission tracks. The annealing kinetics of the resulting ion tracks was investigated using synchrotron-based small-angle X-ray scattering (SAXS) combined with ex situ annealing. The activation energies for track recrystallization were extracted and consistent with previous studies using track-etching, tracks in the chlorine-rich Snarum apatite are more resistant to annealing than in the other compositions.

  9. Thermal characteristic investigation of eutectic composite fatty acid as heat storage material for solar heating and cooling application

    Science.gov (United States)

    Thaib, R.; Fauzi, H.; Ong, H. C.; Rizal, S.; Mahlia, T. M. I.; Riza, M.

    2018-03-01

    A composite phase change material (CPCM) of myristic acid/palmitic acid/sodium myristate (MA/PA/SM) and of myristic acid/palmitic acid/sodium laurate (MA/PA/SL) were impregnated with purified damar gum as called Shorea Javanica (SJ) to improve the thermal conductivity of CPCM. The thermal properties, thermal conductivity, and thermal stability of both CPCM have investigated by using a Differential Scanning Calorimetry (DSC) thermal analysis, hot disc thermal conductivity analyzer, and Simultaneous Thermal Analyzer (STA), simultaneously. However, a chemical compatibility between both fatty acid eutectic mixtures and SJ in composite mixtures measured by Fourier Transform Infra-Red (FT-IR) spectrophotometer. The results were obtained that the thermal conductivity of MA/PA/SM/SJ and MA/PA/SL/SJ eutectic composite phase change material (CPCM) were improved by addition 3 wt.% and 2 wt.% of Shorea javanica (SJ), respectively, without occur a significant change on thermal properties of CPCM. Moreover, the absorbance spectrum of FT-IR shows the good compatibility of SJ with both MA/PA/SM and MA/PA/SL eutectic mixtures, the composite PCM also present good thermal performance and good thermal stability. Therefore, it can be noted that the purified Shorea Javanica proposed, the as high conductive material in this study was able to improve the thermal conductivity of eutectic PCM without any significant reduction on its thermo-physical and chemical properties and can be recommended as novelty composite phase change material for thermal energy storage application.

  10. Thermal Analysis of Copper-Titanium-Multiwall Carbon Nanotube Composites.

    Science.gov (United States)

    Hamamda, Smail; Jari, Ahmed; Revo, S; Ivanenko, K; Jari, Youcef; Avramenko, T

    2017-12-01

    The aim of this research is the thermostructural study of Cu-Ti, Cu-Ti 1 vol% multiwall carbon nanotubes (MWCNTs) and Cu-Ti 3 vol% MWCNTs. Several investigation techniques were used to achieve this objective. Dilatometric data show that the coefficient of thermal expansion of the nanocomposite containing less multiwall carbon nanotubes is linear and small. The same nanocomposite exhibits regular heat transfer and weak mass exchange with the environment. Raman spectroscopy shows that the nanocomposite with more MWCNTs contains more defects. This implies that the carbon nanotubes have better dispersion in Cu-Ti 1 vol% MWCNTs. Infrared spectroscopy reveals that Cu-Ti 1 vol% MWCNTs has better crystallinity than Cu-Ti 3 vol% MWCNTs.

  11. Influence of Thermal Preparation Method on Mineral Composition of Shrimps

    Directory of Open Access Journals (Sweden)

    Gheorghe Valentin GORAN

    2017-11-01

    Full Text Available This study goal was to evaluate the effects of 3 different cooking methods (boiling, roasting, and microwaving on mineral concentrations of shrimps from the Bucharest market. Mineral content in shrimp samples was evaluated by ICP-OES, and relative humidity was assessed by thermogravimetry. Cooking method insignificantly influenced the level of Fe. Ca and K levels were higher in cooked samples compared to raw shrimps, independent of cooking method. Essential (Cu, Se, and Zn, and non-essential and toxic (Al, Cd, Ni, and Pb elements levels were significantly increased in boiled shrimps, compared to raw and the other 2 types of cooked samples. Generally, after cooking the lowest values of essential trace elements concentration was registered in roasted samples. The highest percentage of water loss was found in boiled samples. In general, thermal preparation increased mineral concentrations in cooked samples compared to raw shrimps.

  12. Study of the thermal conductivity of ZnO nanowires/PMMA composites

    International Nuclear Information System (INIS)

    Igamberdiev, Kh. T.; Yuldashev, Sh. U.; Cho, H. D.; Kang, T. W.; Rakhimova, Sh. M.; Akhmedov, T. Kh.

    2012-01-01

    From thermal conductivity measurements on ZnO nanowires (NWs)/poly(methyl methacrylate) PMMA composites, the thermal conductivities of the ZnO nanowires were determined. The thermal conductivity of a ZnO NW decreases considerably with decreasing nanowire diameter, and for a ZnO nanowire with a diameter of 250 nm, the thermal conductivity at room temperature is approximately two times lower than that of bulk ZnO at the same temperature. The results of this study show that the thermal conductivity of a ZnO NW is mainly determined by increased phonon-surface boundary scattering. These results could be useful for the design of ZnO-nanowire-based devices.

  13. Effect of irradiation on thermal expansion of SiCf/SiC composites

    International Nuclear Information System (INIS)

    Senor, D.J.; Trimble, D.J.; Woods, J.J.

    1996-06-01

    Linear thermal expansion was measured on five different SiC-fiber-reinforced/SiC-matrix (SiC f /SiC) composite types in the unirradiated and irradiated conditions. Two matrices were studied in combination with Nicalon CG reinforcement and a 150 nm PyC fiber/matrix interface: chemical vapor infiltrated (CVI) SiC and liquid-phase polymer impregnated precursor (PIP) SiC. Composites of PIP SiC with Tyranno and HPZ fiber reinforcement and a 150 nm PyC interface were also tested, as were PIP SiC composites with Nicalon CG reinforcement and a 150 nm BN fiber/matrix interface. The irradiation was conducted in the Experimental Breeder Reactor-II at a nominal temperature of 1,000 C to doses of either 33 or 43 dpa-SiC. Irradiation caused complete fiber/matrix debonding in the CVI SiC composites due to a dimensional stability mismatch between fiber and matrix, while the PIP SiC composites partially retained their fiber/matrix interface after irradiation. However, the thermal expansion of all the materials tested was found to be primarily dependent on the matrix and independent of either the fiber or the fiber/matrix interface. Further, irradiation had no significant effect on thermal expansion for either the CVI SiC or PIP SiC composites. In general, the thermal expansion of the CVI SiC composites exceeded that of the PIP SiC composites, particularly at elevated temperatures, but the expansion of both matrix types was less than chemical vapor deposited (CVD) β-SiC at all temperatures

  14. Effect of Thermally Reduced Graphene Oxide on Mechanical Properties of Woven Carbon Fiber/Epoxy Composite

    OpenAIRE

    Nitai Chandra Adak; Suman Chhetri; Naresh Chandra Murmu; Pranab Samanta; Tapas Kuila

    2018-01-01

    Thermally reduced graphene oxide (TRGO) was incorporated as a reinforcing filler in the epoxy resin to investigate the effect on the mechanical properties of carbon fiber (CF)/epoxy composites. At first, the epoxy matrix was modified by adding different wt % of TRGO from 0.05 to 0.4 wt % followed by the preparation of TRGO/CF/epoxy composites througha vacuum-assisted resin transfer molding process. The prepared TRGO was characterized by using Fourier transform infrared spectroscopy, Raman Spe...

  15. Thermal conductivity of bulk boron nitride nanotube sheets and their epoxy-impregnated composites

    International Nuclear Information System (INIS)

    Jakubinek, Michael B.; Kim, Keun Su; Simard, Benoit; Niven, John F.; Johnson, Michel B.; Ashrafi, Behnam; White, Mary Anne

    2016-01-01

    The thermal conductivity of bulk, self-supporting boron nitride nanotube (BNNT) sheets composed of nominally 100% BNNTs oriented randomly in-plane was measured by a steady-state, parallel thermal conductance method. The sheets were either collected directly during synthesis or produced by dispersion and filtration. Differences between the effective thermal conductivities of filtration-produced BNNT buckypaper (∝1.5 W m -1 K -1 ) and lower-density as-synthesized sheets (∝0.75 W m -1 K -1 ), which are both porous materials, were primarily due to their density. The measured results indicate similar thermal conductivity, in the range of 7-12 W m -1 K -1 , for the BNNT network in these sheets. High BNNT-content composites (∝30 wt.% BNNTs) produced by epoxy impregnation of the porous BNNT network gave 2-3 W m -1 K -1 , more than 10 x the baseline epoxy. The combination of manufacturability, thermal conductivity, and electrical insulation offers exciting potential for electrically insulating, thermally conductive coatings and packaging. Thermal conductivity of free-standing BNNT buckypaper, buckypaper composites, and related materials at room temperature. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Thermal conductivity of bulk boron nitride nanotube sheets and their epoxy-impregnated composites

    Energy Technology Data Exchange (ETDEWEB)

    Jakubinek, Michael B.; Kim, Keun Su; Simard, Benoit [Security and Disruptive Technologies, Division of Emerging Technologies, National Research Council Canada, Ottawa, ON (Canada); Niven, John F. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS (Canada); Johnson, Michel B. [Institute for Research in Materials, Dalhousie University, Halifax, NS (Canada); Ashrafi, Behnam [Aerospace, Division of Engineering, National Research Council Canada, Montreal, QC (Canada); White, Mary Anne [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS (Canada); Institute for Research in Materials, Dalhousie University, Halifax, NS (Canada); Department of Chemistry, Dalhousie University, Halifax, NS (Canada)

    2016-08-15

    The thermal conductivity of bulk, self-supporting boron nitride nanotube (BNNT) sheets composed of nominally 100% BNNTs oriented randomly in-plane was measured by a steady-state, parallel thermal conductance method. The sheets were either collected directly during synthesis or produced by dispersion and filtration. Differences between the effective thermal conductivities of filtration-produced BNNT buckypaper (∝1.5 W m{sup -1} K{sup -1}) and lower-density as-synthesized sheets (∝0.75 W m{sup -1} K{sup -1}), which are both porous materials, were primarily due to their density. The measured results indicate similar thermal conductivity, in the range of 7-12 W m{sup -1} K{sup -1}, for the BNNT network in these sheets. High BNNT-content composites (∝30 wt.% BNNTs) produced by epoxy impregnation of the porous BNNT network gave 2-3 W m{sup -1} K{sup -1}, more than 10 x the baseline epoxy. The combination of manufacturability, thermal conductivity, and electrical insulation offers exciting potential for electrically insulating, thermally conductive coatings and packaging. Thermal conductivity of free-standing BNNT buckypaper, buckypaper composites, and related materials at room temperature. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Analysis of Sensory/Active Piezoelectric Composite Structures in Thermal Environments

    Science.gov (United States)

    Lee, Ho-Jun; Saravanos, Dimitris A.

    1996-01-01

    Although there has been extensive development of analytical methods for modeling the behavior of piezoelectric structures, only a limited amount of research has been performed concerning the implications of thermal effects on both the active and sensory response of smart structures. Thermal effects become important when the piezoelectric structure has to operate in either extremely hot or cold temperature environments. Consequently, the purpose of this paper is to extend the previously developed discrete layer formulation of Saravanos and Heyliger to account for the coupled mechanical, electrical, and thermal response in modern smart composite beams. The mechanics accounts for thermal effects which may arise in the elastic and piezoelectric media at the material level through the constitutive equations. The displacements, electric potentials, and temperatures are introduced as state variables, allowing them to be modeled as variable fields through the laminate thickness. This unified representation leads to an inherent capability to model both the active compensation of thermal distortions in smart structures and the resultant sensory voltage when thermal loads are applied. The corresponding finite element formulation is developed and numerical results demonstrate the ability to model both the active and sensory modes of composite beams with heterogeneous plies with attached piezoelectric layers under thermal loadings.

  18. Thermal Aging of Unsaturated Polyester Composite Reinforced with E-Glass Nonwoven Mat

    Directory of Open Access Journals (Sweden)

    Hossain Milon

    2017-12-01

    Full Text Available An experiment was carried out using glass fiber (GF as reinforcing materials with unsaturated polyester matrix to fabricate composite by hand layup technique. Four layers of GF were impregnated by polyester resin and pressed under a load of 5 kg for 20 hours. The prepared composite samples were treated by prolonged exposure to heat for 1 hour at 60-150°C and compared with untreated GF-polyester composite. Different mechanical test of the fabricated composite were investigated. The experiment depicted significant improvement in the mechanical properties of the fabricated composite resulted from the heat treatment. The maximum tensile strength of 200.6 MPa is found for 90°C heat-treated sample. The mechanical properties of the composite do seem to be very affected negatively above 100°C. Water uptake of the composite was carried out and thermal stability of the composite was investigated by thermogravimetric analysis, and it was found that the composite is stable up to 600°C. Fourier transform infrared spectroscopy shows the characteristic bond in the composite. Finally, the excellent elevated heat resistant capacity of glass-fiber-reinforced polymeric composite shows the suitability of its application to heat exposure areas such as kitchen furniture materials, marine, and electric board.

  19. Mechanical and thermal properties of date palm leaf fiber reinforced recycled poly (ethylene terephthalate) composites

    International Nuclear Information System (INIS)

    Dehghani, Alireza; Madadi Ardekani, Sara; Al-Maadeed, Mariam A.; Hassan, Azman; Wahit, Mat Uzir

    2013-01-01

    Highlights: • A novel natural fiber reinforced recycled poly (ethylene terephthalate) composite was prepared. • Mechanical performance and thermal behavior of the composites were investigated. • Composites with improved toughness and strength were achieved. - Abstract: Development of a recycled poly (ethylene terephthalate) (PETr) reinforced with surface treated date palm leaf fiber (DPLF) composites with enhanced mechanical properties have been studied. Surface modified date palm leaf fiber reinforced PETr composites were prepared using twin-screw extruder followed by injection molding and the influence of the DPLF content on the mechanical and thermal behavior of the PETr matrix was evaluated. Upon the addition of fibers, remarkable enhancements in the mechanical properties of the composites were observed. Scanning electron microscopy (SEM) images taken from DPLF fibers showed significant enhancements in the fiber’s surface topography after the surface treatment process. Dynamic mechanical analysis (DMA) indicated that the addition of DPLF to PETr matrix increased the composites toughness. The crystallization behavior of the samples, analyzed by differential scanning calorimetry (DSC) indicated an increase in the onset crystallization temperature and showed a higher degree of crystallinity of the composites as compared to PETr, demonstrating that DPLF particles could act as nucleating agents. The results point to the composite’s potential in wider indoor applications

  20. Preparation, Mechanical and Thermal Properties of Cement Board with Expanded Perlite Based Composite Phase Change Material for Improving Buildings Thermal Behavior

    Directory of Open Access Journals (Sweden)

    Rongda Ye

    2015-11-01

    Full Text Available Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28/expanded perlite (EP composite phase change materials (PCMs. The composite PCMs were prepared by adsorbing RT28 into the pores of EP, in which the mass fraction of RT28 should be limited to be no more than 40 wt %. The adsorbed RT28 is observed to be uniformly confined into the pores of EP. The phase change temperatures of the RT28/EP composite PCMs are very close to that of the pure RT28. The apparent density and compression strength of the composite cubes increase linearly with the mass fraction of RT28. Compared with the thermal conductivity of the boards composed of cement and EP, the thermal conductivities of the composite boards containing RT28 increase by 15%–35% with the mass fraction increasing of RT28. The cubic test rooms that consist of six boards were built to evaluate the thermal energy storage performance, it is found that the maximum temperature different between the outside surface of the top board with the indoor temperature using the composite boards is 13.3 °C higher than that of the boards containing no RT28. The thermal mass increase of the built environment due to the application of composite boards can contribute to improving the indoor thermal comfort and reducing the energy consumption in the buildings.

  1. Preparation, Mechanical and Thermal Properties of Cement Board with Expanded Perlite Based Composite Phase Change Material for Improving Buildings Thermal Behavior.

    Science.gov (United States)

    Ye, Rongda; Fang, Xiaoming; Zhang, Zhengguo; Gao, Xuenong

    2015-11-13

    Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28)/expanded perlite (EP) composite phase change materials (PCMs). The composite PCMs were prepared by adsorbing RT28 into the pores of EP, in which the mass fraction of RT28 should be limited to be no more than 40 wt %. The adsorbed RT28 is observed to be uniformly confined into the pores of EP. The phase change temperatures of the RT28/EP composite PCMs are very close to that of the pure RT28. The apparent density and compression strength of the composite cubes increase linearly with the mass fraction of RT28. Compared with the thermal conductivity of the boards composed of cement and EP, the thermal conductivities of the composite boards containing RT28 increase by 15%-35% with the mass fraction increasing of RT28. The cubic test rooms that consist of six boards were built to evaluate the thermal energy storage performance, it is found that the maximum temperature different between the outside surface of the top board with the indoor temperature using the composite boards is 13.3 °C higher than that of the boards containing no RT28. The thermal mass increase of the built environment due to the application of composite boards can contribute to improving the indoor thermal comfort and reducing the energy consumption in the buildings.

  2. Thermal modelling of extrusion based additive manufacturing of composite materials

    DEFF Research Database (Denmark)

    Jensen, Mathias Laustsen; Sonne, Mads Rostgaard; Hattel, Jesper Henri

    One of the hottest topics regarding manufacturing these years is additive manufacturing (AM). AM is a young branch of manufacturing techniques, which by nature is disruptive due to its completely different manufacturing approach, wherein material is added instead of removed. By adding material...... layer by layer, mould and customised tooling requirements from the conventional manufacturing are reduced or removed, which leads to increased customisation options and enables new part complexities without increasing the manufacturing cost. AM hence enables customised small volume productions...... of composite parts not feasible by conventional manufacturing techniques. This sets up new requirements to the part verification and validation, while conventional destructive tests become too expensive. This initial study aims to investigate alternative options to this destructive testing by increasing...

  3. The viscoelastic behavior of a composite in a thermal environment

    Science.gov (United States)

    Morris, D. H.; Brinson, H. F.; Griffith, W. I.; Yeow, Y. T.

    1979-01-01

    A proposed method for the accelerated predictions of modulus and life times for time dependent polymer matrix composite laminates is presented. The method, based on the time temperature superposition principle and lamination theory, is described in detail. Unidirectional reciprocal of compliance master curves and the shift functions needed are presented and discussed. Master curves for arbitrarily oriented unidirectional laminates are predicted and compared with experimantal results obtained from master curves generated from 15 minute tests and with 25 hour tests. Good agreement is shown. Predicted 30 deg and 60 deg unidirectional strength master curves are presented and compared to results of creep rupture tests. Reasonable agreement is demonstrated. In addition, creep rupture results for a (90 deg + or - 60 deg/90 deg) sub 2s laminate are presented.

  4. Fabrication and properties of polyimide composites filled with zirconium tungsten phosphate of negative thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Shi, XinWei, E-mail: Shixw@zzu.edu.cn [School of Physical Science & Engineering, Zhengzhou University, 100th Science Road, Zhengzhou 450001 (China); Lian, Hong; Yan, XiaoSheng; Qi, Ruiqiong; Yao, Ning [School of Physical Science & Engineering, Zhengzhou University, 100th Science Road, Zhengzhou 450001 (China); Li, Tao [Department of Technology & Physics, Zhengzhou University of Lightindustry, 5th Dongfeng Road, Zhengzhou 450002 (China)

    2016-08-15

    Negative thermal expansion Zr{sub 2}WP{sub 2}O{sub 12} (ZWP) powder prepared by hydrothermal method was used as fillers to tailor the thermal expansion coefficient (TEC) of the polyimide (PI)-based composites. A series of PI-based composites containing different loading (0–40 wt% or 0–19.6 vol%) of ZWP powder were fabricated by the in-situ polymerization technique. Their structures and properties were characterized by Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Impedance meter, Thermal mechanical analysis (TMA) and Thermogravimetric analysis (TGA). The additions of ZWP steadily reduced the TEC of the PI matrix at all loadings studied. A 40 wt% (19.6 vol%) ZWP loading gives a 32.5% (about 15 × 10{sup −6}/K) reduction of TEC. The thermal stability of the ZWP/PI composites can be enhanced with the increment of ZWP powder. The independence of the dielectric constant on frequency is improved by introduction of ZWP particles to PIs. The dielectric loss displays good stability, which indicates that the ZWP/PI composites show potential applications in microelectronic and aerospace industries. - Graphical abstract: With increasing of ZWP in the composites, the CTEs of the ZWP/PI were reduced. A 40 wt% (19.6 vol%) ZWP loading gives a 32.5% (about 15 × 10{sup −6}/K) reduction of CTE of the composite. - Highlights: • Zr{sub 2}P{sub 2}WO{sub 12} was firstly used as filler to tune the TEC of polyimides. • The TECs of polyimides were reduced by introduction of Zr{sub 2}P{sub 2}WO{sub 12} powders. • Polyimides with reduced TECs have favorable thermal and dielectric properties.

  5. Thermal cycling effects on adhesion of resin-bovine enamel junction among different composite resins.

    Science.gov (United States)

    Chen, Wen-Cheng; Ko, Chia-Ling; Wu, Hui-Yu; Lai, Pei-Ling; Shih, Chi-Jen

    2014-10-01

    Thermal cycling is used to mimic the changes in oral cavity temperature experienced by composite resins when used clinically. The purpose of this study is to assess the thermal cycling effects of in-house produced composite resin on bonding strength. The dicalcium phosphate anhydrous filler surfaces are modified using nanocrystals and silanization (w/NP/Si). The resin is compared with commercially available composite resins Filtek Z250, Z350, and glass ionomer restorative material GIC Fuji-II LC (control). Different composite resins were filled into the dental enamel of bovine teeth. The bond force and resin-enamel junction graphical structures of the samples were determined after thermal cycling between 5 and 55°C in deionized water for 600 cycles. After thermal cycling, the w/NP/Si 30wt%, 50wt% and Filtek Z250, Z350 groups showed higher shear forces than glass ionomer GIC, and w/NP/Si 50wt% had the highest shear force. Through SEM observations, more of the fillings with w/NP/Si 30wt% and w/NP/Si 50wt% groups flowed into the enamel tubule, forming closed tubules with the composite resins. The push-out force is proportional to the resin flow depth and uniformity. The push-out tubule pore and resin shear pattern is the most uniform and consistent in the w/NP/Si 50wt% group. Accordingly, this developed composite resin maintains great mechanical properties after thermal cycling. Thus, it has the potential to be used in a clinical setting when restoring non-carious cervical lesions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Supernova Photometric Lightcurve Classification

    Science.gov (United States)

    Zaidi, Tayeb; Narayan, Gautham

    2016-01-01

    This is a preliminary report on photometric supernova classification. We first explore the properties of supernova light curves, and attempt to restructure the unevenly sampled and sparse data from assorted datasets to allow for processing and classification. The data was primarily drawn from the Dark Energy Survey (DES) simulated data, created for the Supernova Photometric Classification Challenge. This poster shows a method for producing a non-parametric representation of the light curve data, and applying a Random Forest classifier algorithm to distinguish between supernovae types. We examine the impact of Principal Component Analysis to reduce the dimensionality of the dataset, for future classification work. The classification code will be used in a stage of the ANTARES pipeline, created for use on the Large Synoptic Survey Telescope alert data and other wide-field surveys. The final figure-of-merit for the DES data in the r band was 60% for binary classification (Type I vs II).Zaidi was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  7. Theoretical models for supernovae

    International Nuclear Information System (INIS)

    Woosley, S.E.; Weaver, T.A.

    1981-01-01

    The results of recent numerical simulations of supernova explosions are presented and a variety of topics discussed. Particular emphasis is given to (i) the nucleosynthesis expected from intermediate mass (10sub solar less than or equal to M less than or equal to 100 Msub solar) Type II supernovae and detonating white dwarf models for Type I supernovae, (ii) a realistic estimate of the γ-line fluxes expected from this nucleosynthesis, (iii) the continued evolution, in one and two dimensions, of intermediate mass stars wherein iron core collapse does not lead to a strong, mass-ejecting shock wave, and (iv) the evolution and explosion of vary massive stars M greater than or equal to 100 Msub solar of both Population I and III. In one dimension, nuclear burning following a failed core bounce does not appear likely to lead to a supernova explosion although, in two dimensions, a combination of rotation and nuclear burning may do so. Near solar proportions of elements from neon to calcium and very brilliant optical displays may be created by hypernovae, the explosions of stars in the mass range 100 M/sub solar/ to 300 M/sub solar/. Above approx. 300 M/sub solar/ a black hole is created by stellar collapse following carbon ignition. Still more massive stars may be copious producers of 4 He and 14 N prior to their collapse on the pair instability

  8. Supernova neutrino detection

    International Nuclear Information System (INIS)

    Selvi, M.

    2005-01-01

    Neutrinos emitted during a supernova core collapse represent a unique feature to study both stellar and neutrino properties. After discussing the details of the neutrino emission in the star and the effect of neutrino oscillations on the expected neutrino fluxes at Earth, a review of the detection techniques is presented in this paper, with particular attention to the problem of electron neutrino detection

  9. Supernova Cosmology Project

    Science.gov (United States)

    , i.e. with the cosmology hidden. Looking Beyond Lambda with the Union Supernova Compilation by Rubin et Matrix Description Covariance Matrix with Systematics Description Full Table of All SNe Description Beyond Lambda Figures Updated 11-18-11 Contact: drubin at physics dot fsu dot edu, saul at lbl dot gov

  10. Decays of supernova neutrinos

    International Nuclear Information System (INIS)

    Lindner, Manfred; Ohlsson, Tommy; Winter, Walter

    2002-01-01

    Supernova neutrinos could be well-suited for probing neutrino decay, since decay may be observed even for very small decay rates or coupling constants. We will introduce an effective operator framework for the combined description of neutrino decay and neutrino oscillations for supernova neutrinos, which can especially take into account two properties: one is the radially symmetric neutrino flux, allowing a decay product to be re-directed towards the observer even if the parent neutrino had a different original direction of propagation. The other is decoherence because of the long baselines for coherently produced neutrinos. We will demonstrate how to use this effective theory to calculate the time-dependent fluxes at the detector. In addition, we will show the implications of a Majoron-like decay model. As a result, we will demonstrate that for certain parameter values one may observe some effects which could also mimic signals similar to the ones expected from supernova models, making it in general harder to separate neutrino and supernova properties

  11. Neutrino Emission from Supernovae

    Science.gov (United States)

    Janka, Hans-Thomas

    Supernovae are the most powerful cosmic sources of MeV neutrinos. These elementary particles play a crucial role when the evolution of a massive star is terminated by the collapse of its core to a neutron star or a black hole and the star explodes as supernova. The release of electron neutrinos, which are abundantly produced by electron captures, accelerates the catastrophic infall and causes a gradual neutronization of the stellar plasma by converting protons to neutrons as dominant constituents of neutron star matter. The emission of neutrinos and antineutrinos of all flavors carries away the gravitational binding energy of the compact remnant and drives its evolution from the hot initial to the cold final state. The absorption of electron neutrinos and antineutrinos in the surroundings of the newly formed neutron star can power the supernova explosion and determines the conditions in the innermost supernova ejecta, making them an interesting site for the nucleosynthesis of iron-group elements and trans-iron nuclei.

  12. SUPERNOVA LIGHT CURVES POWERED BY FALLBACK ACCRETION

    Energy Technology Data Exchange (ETDEWEB)

    Dexter, Jason; Kasen, Daniel, E-mail: jdexter@berkeley.edu [Departments of Physics and Astronomy, University of California, Berkeley, CA 94720 (United States)

    2013-07-20

    Some fraction of the material ejected in a core collapse supernova explosion may remain bound to the compact remnant, and eventually turn around and fall back. We show that the late time ({approx}>days) power potentially associated with the accretion of this 'fallback' material could significantly affect the optical light curve, in some cases producing super-luminous or otherwise peculiar supernovae. We use spherically symmetric hydrodynamical models to estimate the accretion rate at late times for a range of progenitor masses and radii and explosion energies. The accretion rate onto the proto-neutron star or black hole decreases as M-dot {proportional_to}t{sup -5/3} at late times, but its normalization can be significantly enhanced at low explosion energies, in very massive stars, or if a strong reverse shock wave forms at the helium/hydrogen interface in the progenitor. If the resulting super-Eddington accretion drives an outflow which thermalizes in the outgoing ejecta, the supernova debris will be re-energized at a time when photons can diffuse out efficiently. The resulting light curves are different and more diverse than previous fallback supernova models which ignored the input of accretion power and produced short-lived, dim transients. The possible outcomes when fallback accretion power is significant include super-luminous ({approx}> 10{sup 44} erg s{sup -1}) Type II events of both short and long durations, as well as luminous Type I events from compact stars that may have experienced significant mass loss. Accretion power may unbind the remaining infalling material, causing a sudden decrease in the brightness of some long duration Type II events. This scenario may be relevant for explaining some of the recently discovered classes of peculiar and rare supernovae.

  13. Thermal transfer performance of a spherical encapsulated PEG 6000-based composite for thermal energy storage

    Czech Academy of Sciences Publication Activity Database

    Anghel, E.M.; Pavel, P.M.; Constantinescu, M.; Petrescu, S.; Atkinson, I.; Buixaderas, Elena

    2017-01-01

    Roč. 208, Sep (2017), s. 1222-1231 ISSN 0306-2619 Grant - others:AV ČR(CZ) AR-17-02 Program:Bilaterální spolupráce Institutional support: RVO:68378271 Keywords : phase change materials * thermal energy storage * modeling Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 7.182, year: 2016

  14. Thermal Properties of Wood-Plastic Composites Prepared from Hemicellulose-extracted Wood Flour

    Directory of Open Access Journals (Sweden)

    A.A. Enayati

    2013-01-01

    Full Text Available Hemicellulose of Southern Yellow Pine wood spices was extracted by pressurized hot water at three different temperatures: 140°C, 155°C and 170°C. Compounding with PP (polypropylene was performed by extrusion after preparing wood flour and sieving to determine its mesh size. The ratio of wood to polymer was 50:50 based on oven-dry weight of wood flour. All extraction treatments and control samples were compounded under two sets of conditions, without and with 2% MAPP as coupling agent. Injection molding was used to make tensile test samples (dogbone from the pellets made by extrusion. Thermal properties of wood-plastic composites were studied by TGA and DSC while the thermal stability of pretreated wood flours, PP and MAPP were studied by TGA as well. The greater weight loss of wood materials was an indication that higher treatment temperature increases the extractability of hemicellulose. The removal of hemicellulose by extraction improves thermal stability of wood flour, especially for extraction at 170°C. Wood-plastic composites made from extracted fibers at 170°C showed the highest thermal stability. Coupling agent did not have a significant effect on thermal stability but it improved the degree of crystallinity of the composites.Surface roughness of wood fiber increased after treatment. Extraction of hemicellulose increased the degree of crystallinity but it was not significant except for samples from treated wood flour at 170°C and with MAPP.

  15. Finite Element Analysis of Interfacial Debonding in Copper/Diamond Composites for Thermal Management Applications.

    Science.gov (United States)

    Zain-Ul-Abdein, Muhammad; Ijaz, Hassan; Saleem, Waqas; Raza, Kabeer; Mahfouz, Abdullah Salmeen Bin; Mabrouki, Tarek

    2017-07-02

    Copper/diamond (Cu/D) composites are famous in thermal management applications for their high thermal conductivity values. They, however, offer some interface related problems like high thermal boundary resistance and excessive debonding. This paper investigates interfacial debonding in Cu/D composites subjected to steady-state and transient thermal cyclic loading. A micro-scale finite element (FE) model was developed from a SEM image of the Cu/20 vol % D composite sample. Several test cases were assumed with respect to the direction of heat flow and the boundary interactions between Cu/uncoated diamonds and Cu/Cr-coated diamonds. It was observed that the debonding behavior varied as a result of the differences in the coefficients of thermal expansions (CTEs) among Cu, diamond, and Cr. Moreover, the separation of interfaces had a direct influence upon the equivalent stress state of the Cu-matrix, since diamond particles only deformed elastically. It was revealed through a fully coupled thermo-mechanical FE analysis that repeated heating and cooling cycles resulted in an extremely high stress state within the Cu-matrix along the diamond interface. Since these stresses lead to interfacial debonding, their computation through numerical means may help in determining the service life of heat sinks for a given application beforehand.

  16. Graphite-high density polyethylene laminated composites with high thermal conductivity made by filament winding

    Directory of Open Access Journals (Sweden)

    W. Lv

    2018-03-01

    Full Text Available The low thermal conductivity of polymers limits their use in numerous applications, where heat transfer is important. The two primary approaches to overcome this limitation, are to mix in other materials with high thermal conductivity, or mechanically stretch the polymers to increase their intrinsic thermal conductivity. Progress along both of these pathways has been stifled by issues associated with thermal interface resistance and manufacturing scalability respectively. Here, we report a novel polymer composite architecture that is enabled by employing typical composites manufacturing method such as filament winding with the twist that the polymer is in fiber form and the filler in form of sheets. The resulting novel architecture enables accession of the idealized effective medium composite behavior as it minimizes the interfacial resistance. The process results in neat polymer and 50 vol% graphite/polymer plates with thermal conductivity of 42 W·m–1·K–1 (similar to steel and 130 W·m–1·K–1 respectively.

  17. MECHANICAL, ELECTRICAL, AND THERMAL PROPERTIES OF MALEIC ANHYDRIDE MODIFIED RICE HUSK FILLED PVC COMPOSITES

    OpenAIRE

    Navin Chand; Bhajan Das Jhod

    2008-01-01

    Unmodified and modified rice husk powder filled PVC composites were prepared having different amounts of rice husk powder. Mechanical, thermal, and electrical properties of these composites were determined. The tensile strength of rice husk powder PVC composites having 0, 10, 20, 30, and 40 weight percent of rice husk powder was found to be 33.9, 19.4, 18.1, 14.6, and 9.5 MPa, respectively. Adding of maleic anhydride- modified rice husk powder improved the tensile strength of rice husk powder...

  18. Effects of thermal residual stresses and fiber packing on deformation of metal-matrix composites

    International Nuclear Information System (INIS)

    Nakamura, T.; Suresh, S.

    1993-01-01

    The combined effects of thermal residual stresses and fiber spatial distribution on the deformation of a 6061 aluminum alloy containing a fixed concentration unidirectional boron fibers have been analyzed using detailed finite element models. The geometrical structure includes perfectly periodic, uniformly space fiber arrangements in square and hexagonal cells, as well as different cells in which either 30 or 60 fibers are randomly placed in the ductile matrix. The model involves an elastic-plastic matrix, elastic fibers, and mechanically bonded interfaces. The results indicate that both fiber packing and thermal residual stresses can have a significant effect on the stress-strain characteristics of the composite. The thermal residual stresses cause pronounced matrix yielding which also influences the apparent overall stiffness of the composite during the initial stages of subsequent far-field loading along the axial and transverse direction. Furthermore, the thermal residual stresses apparently elevate the flow stress of the composite during transverse tension. Such effects can be traced back to the level of constraint imposed on the matrix by local fiber spacing. The implications of the present results to the processing of the composites are also briefly addressed

  19. Gas storage cylinder formed from a composition containing thermally exfoliated graphite

    Science.gov (United States)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2012-01-01

    A gas storage cylinder or gas storage cylinder liner, formed from a polymer composite, containing at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m(exp 2)/g to 2600 m(exp 2)2/g.

  20. Humidity Effects on Soluble Core Mechanical and Thermal Properties (Polyvinyl Alcohol/Microballoon Composite)

    Science.gov (United States)

    1993-01-01

    This document constitutes the final report for the study of humidity effects and loading rate on soluble core (PVA/MB composite material) mechanical and thermal properties. This report describes test results, procedures employed, and any unusual occurrences or specific observations associated with this test program.

  1. Review of data of oxygen and hydrogen isotope composition in thermal waters in China

    International Nuclear Information System (INIS)

    Fan Zhicheng; Wang Jiyang

    1988-01-01

    Based on the data of δD and δ 18 O content from more than 600 water samples, this paper reviews the stable isotope composition of thermal waters in China. Data to be used in this paper were mostly collected from published literatures with a few by authors. 9 figs, 2 tabs

  2. Improving the thermal dimensional stability of flexible polymer composite backing materials for ultrasound transducers

    NARCIS (Netherlands)

    State, M.; Brands, P.J.; Vosse, van de F.N.

    2010-01-01

    Novel ultrasound backing materials based on polymer composites with improved dimensional stability and low coefficient of thermal expansion are being developed and analyzed. For this purpose a filled epoxy resin (Stycast1265), a commonly used backing material, was considered reference material and

  3. Bio-composites based on polypropylene reinforced with Almond Shells particles: Mechanical and thermal properties

    International Nuclear Information System (INIS)

    Essabir, H.; Nekhlaoui, S.; Malha, M.; Bensalah, M.O.; Arrakhiz, F.Z.; Qaiss, A.; Bouhfid, R.

    2013-01-01

    Highlights: • Almond Shells (ASs) particles have been used as reinforcement in polypropylene matrix. • The SEBS-g-MA has been used to improve the adhesion between matrix and particles. • The mechanical and thermal properties of the composite have been improved by the AS. - Abstract: In this work, Almond Shells (ASs) particles are used as reinforcement in a thermoplastic matrix as polypropylene (PP). Composites containing Almond Shells (ASs) particles with and without compatibilizer (maleic anhydride grafted polypropylene; SEBS-g-MA) for various particle content (5, 10, 15, 20, 25, 30 wt.%) was investigated by means of studying their mechanical, thermal and rheological properties. The composites were prepared in a twin-screw extruder and assessed by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), tensile testing and Dynamic Mechanical Analysis (DMA). Results show a clear improvement in mechanical and rheological properties from the use of Almond Shells particles in the matrix without and with maleic anhydride compatibilizer, corresponding to a gain in Young’s modulus of 56.2% and 35% respectively, at 30 wt.% particle loading. Thermal analysis revealed that incorporation of particle in the composites resulted in increase in the initial thermal decomposition temperatures

  4. Simulation of the structure and calculation of the thermal conductivity of napped composites

    International Nuclear Information System (INIS)

    Berezko, S.N.; Zarichnyak, Yu.P.; Korenev, P.A.

    1995-01-01

    We propose a model of the structure of a napped composite. Characteristic trends in the structure of the material are delineated, and the effective thermal conductivity of the model structure is calculated for these trends with allowance for conduction and radiation

  5. Tribological Properties of Ti(Al,O)/Al2O3 Composite Coating by Thermal Spraying

    Science.gov (United States)

    Salman, Asma; Gabbitas, Brian; Cao, Peng; Zhang, Deliang

    The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity air fuel (HVAF) thermally sprayed wear resistant Ti(Al,O)/Al2O3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting and dummy blocks aluminium extrusion. A feedstock of Ti(Al,O)/Al2O3 composite powder was produced from a mixture of Al and TiO2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity air-fuel (HVAF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The wear resistance of the coating was investigated by a tribometer using a spherical ended alumina pin as a counter body under dry and lubricating conditions. The results showed that composite coating has lower wear rate at high temperature than at room temperature without using lubricant. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

  6. Solar-thermal conversion and thermal energy storage of graphene foam-based composite

    KAUST Repository

    Zhang, Lianbin; Li, Renyuan; Tang, Bo; Wang, Peng

    2016-01-01

    is the intermittent nature of solar irradiation, which makes them unable to stand-alone to satisfy continuous energy need. Herein, we report a three-dimensional (3D) graphene foam and phase change material (PCM) composite for the seamlessly combined solar

  7. Thermal shock resistance of ceramic fibre composites characterized by non-destructive methods

    Directory of Open Access Journals (Sweden)

    M. Dimitrijević

    2008-12-01

    Full Text Available Alumina based ceramic fibres and alumina based ceramic were used to produce composite material. Behaviour of composite ceramics after thermal shock treatments was investigated. Thermal shock of the samples was evaluated using water quench test. Surface deterioration level of samples was monitored by image analysis before and after a number of quenching cycles. Ultrasonic measurements were done on samples after quench tests. Dynamic Young modulus of elasticity and strength degradation were calculated using measured values of ultrasonic velocities. Strengths deterioration was calculated using the non-destructive measurements and correlated to degradation of surface area and number of quenches. The addition of small amount of ceramic fibres improves the strengths and diminishes the loss of mechanical properties of samples during thermal shock experiments.

  8. Three-dimensional temperature field model of thermally decomposing resin composite irradiated by laser

    International Nuclear Information System (INIS)

    Chen Minsun; Jiang Houman; Liu Zejin

    2011-01-01

    Fundamental equations governing the temperature field of thermally decomposing resin composite irradiated by laser are derived from mass and energy conservation laws with the control Janume method. The thermal decomposition of resin is described by a multi-step model. An assumption is proposed that the flow of pyrolysis gas is one-dimensional, which makes it possible to consider the influence of pyrolysis gas convective transport and realize the closure of the three-dimensional model without introducing mechanical quantities. In view of the anisotropy of resin composite, expressions of the thermal conductivities of partially pyrolyzed material are deduced, as well as the computing formula for the laser absorption coefficient of partially pyrolyzed material. The energy conservation equation is consistent with reference under some simplifications. (authors)

  9. Stone-ground wood pulp-reinforced polypropylene composites: Water uptake and thermal properties

    Directory of Open Access Journals (Sweden)

    Joan Pere López

    2012-11-01

    Full Text Available Two of the drawbacks of using natural-based composites in industrial applications are thermal instability and water uptake capacity. In this work, mechanical wood pulp was used to reinforce polypropylene at a level of 20 to 50 wt. %. Composites were mixed by means of a Brabender internal mixer for both non-coupled and coupled formulations. Differential scanning calorimetry (DSC and thermogravimetric analysis (TGA were used to determine the thermal properties of the composites. The water uptake behavior was evaluated by immersion of the composites in water until an equilibrium state was reached. Results of water absorption tests revealed that the amount of water absorption was clearly dependent upon the fiber content. The coupled composites showed lower water absorption compared to the uncoupled composites. The incorporation of mechanical wood pulp into the polypropylene matrix produced a clear nucleating effect by increasing the crystallinity degree of the polymer and also increasing the temperature of polymer degradation. The maximum degradation temperature for stone ground wood pulp–reinforced composites was in the range of 330 to 345 ºC.

  10. Thermal analysis and microstructure of hexaperrite based magnet composite with natural rubber matrix

    International Nuclear Information System (INIS)

    Sudirman; Ridwan; Jamilah; Trijono, Waluyo

    2000-01-01

    Thermal and microstructure analyse of hexa ferrite based on composite magnets with natural rubber matrix have been done to investigate their performance. Such magnets play an important role in the toy and house-hold industries because of their suitable magnetic properties, low cost, lightness and flexibility. The composite magnets were synthesized by blending the ferrite powder and natural rubber at composition 30%-70% rubber volume. The microstructure and thermal behaviour of the composite were examined by using SEM and OTA/TGA. The result show that the natural rubber swelling is optimally at 181,17 o C, which is the recommended top condition for blending. The performance magnet composite is limited by the change of natural rubber properties which decompose at temperature around 400 o C. In the decomposition process, the natural rubber molecule trapped in a composite system based on BaM is more difficult are more compared to the composite system based on SrM because the BaM system particle microstructure and its distribution more homogeneous

  11. Thermal characterization of tubular SiC/SiC composite structures for nuclear applications

    International Nuclear Information System (INIS)

    Duquesne, Loys

    2015-01-01

    Researches on the development on SiCf/SiC refractory composites for generation IV nuclear fuel cladding led the CEA to focus on the thermal behavior of these materials. In particular, knowledge of the thermal properties is essential for designing the components. Regarding the development of the 'sandwich' cladding concept, for which the complexity and the geometry differ from the conventionally used flat tubes, usual measurement methods are unsuitable. This study reports on the characterization and modeling of the thermal behavior of these structures. The first part deals with the identification of the global thermal parameters for the different layers of a 'sandwich' cladding. For this purpose, a flash method is used and an experimental device suitable for tubular geometries was developed. A new estimation method based on the combination of both collected signals in front and rear faces allows the identification of the thermal diffusivity of tubular composites using infrared thermography. The second part focuses on a virtual material approach, established to describe the thermal behavior of a 'sandwich' cladding, starting from the measured properties of the elementary components (fibers and matrix). They are then used as input data for the heat transfer modeling. Confrontations between experimental measurements and numerical results finally allow us to understand the importance of the various key parameters governing the heat transfer. (author) [fr

  12. Novel Formulations of Phase Change Materials—Epoxy Composites for Thermal Energy Storage

    Directory of Open Access Journals (Sweden)

    Maria Elena Arce

    2018-01-01

    Full Text Available This research aimed to evaluate the thermal properties of new formulations of phase change materials (PCMs-epoxy composites, containing a thickening agent and a thermally conductive phase. The composite specimens produced consisted of composites fabricated using (a inorganic PCMs (hydrated salts, epoxy resins and aluminum particulates or (b organic PCM (paraffin, epoxy resins, and copper particles. Differential Scanning Calorimetry (DSC was used to analyze the thermal behavior of the samples, while hardness measurements were used to determine changes in mechanical properties at diverse PCM and conductive phase loading values. The results indicate that the epoxy matrix can act as a container for the PCM phase without hindering the heat-absorbing behavior of the PCMs employed. Organic PCMs presented reversible phase transformations over multiple cycles, an advantage that was lacking in their inorganic counterparts. The enthalpy of the organic PCM-epoxy specimens increased linearly with the PCM content in the matrix. The use of thickening agents prevented phase segregation issues and allowed the fabrication of specimens containing up to 40% PCM, a loading significantly higher than others reported. The conductive phase seemed to improve the heat transfer and the mechanical properties of the composites when present in low percentages (<10 wt %; however, given its mass, the enthalpy detected in the composites was reduced as their loading further increased. The conductive phase combination (PCM + epoxy resin + hardener + thickening agent presents great potential as a heat-absorbing material at the temperatures employed.

  13. Stress and reliability analyses of multilayered composite cylinder under thermal and mechanical loads

    Science.gov (United States)

    Wang, Xiaohua

    The coupling resulting from the mutual influence of material thermal and mechanical parameters is examined in the thermal stress analysis of a multilayered isotropic composite cylinder subjected to sudden axisymmetric external and internal temperature. The method of complex frequency response functions together with the Fourier transform technique is utilized. Because the coupling parameters for some composite materials, such as carbon-carbon, are very small, the effect of coupling is neglected in the orthotropic thermal stress analysis. The stress distributions in multilayered orthotropic cylinders subjected to sudden axisymmetric temperature loading combined with dynamic pressure as well as asymmetric temperature loading are also obtained. The method of Fourier series together with the Laplace transform is utilized in solving the heat conduction equation and thermal stress analysis. For brittle materials, like carbon-carbon composites, the strength variability is represented by two or three parameter Weibull distributions. The 'weakest link' principle which takes into account both the carbon-carbon composite cylinders. The complex frequency response analysis is performed on a multilayered orthotropic cylinder under asymmetrical thermal load. Both deterministic and random thermal stress and reliability analyses can be based on the results of this frequency response analysis. The stress and displacement distributions and reliability of rocket motors under static or dynamic line loads are analyzed by an elasticity approach. Rocket motors are modeled as long hollow multilayered cylinders with an air core, a thick isotropic propellant inner layer and a thin orthotropic kevlar-epoxy case. The case is treated as a single orthotropic layer or a ten layered orthotropic structure. Five material properties and the load are treated as random variable with normal distributions when the reliability of the rocket motor is analyzed by the first-order, second-moment method (FOSM).

  14. Exploring biomass based carbon black as filler in epoxy composites: Flexural and thermal properties

    International Nuclear Information System (INIS)

    Abdul Khalil, H.P.S.; Firoozian, P.; Bakare, I.O.; Akil, Hazizan Md.; Noor, Ahmad Md.

    2010-01-01

    Carbon blacks (CB), derived from bamboo stem (BS-CB), coconut shells (CNS-CB) and oil palm empty fiber bunch (EFB-CB), were obtained by pyrolysis of fibers at 700 o C, characterized and used as filler in epoxy composites. The results obtained showed that the prepared carbon black possessed well-developed porosities and are predominantly made up of micropores. The BS-CB, CNS-CB and EFB-CB filled composites were prepared and characterized using scanning electron microscope (SEM) and thermogravimetric analyzer (TGA). The SEM showed that the fractured surface of the composite indicates its high resistance to fracture. The CBs-epoxy composites exhibited better flexural properties than the neat epoxy, which was attributed to better adhesion between the CBs and the epoxy resin. TGA showed that there was improvement in thermal stability of the carbon black filled composites compared to the neat epoxy resin.

  15. The Study on Thermal Expansion of Ceramic Composites with Addition of ZrW[2]O]8

    OpenAIRE

    Dedova, Elena Sergeevna; Shadrin, V. S.; Petrushina, M. Y.; Kulkov, Sergey Nikolaevich

    2016-01-01

    The studies on structure, phase composition and thermal properties of (Al[2]O[3] - 20 wt% ZrO[2]) - ZrW[2]O[8] ceramic composites obtained using nanosized, initial powders were conducted. Homogeneously distributed white particles on the polished surface of composites were observed. Phase composition of the composites was represented with corundum, monoclinic ZrO[2] and two modifications of ZrW[2]O[8] (tetragonal and cubic). Linear thermal expansion coefficient values of the composites were de...

  16. Mechanical, thermal, rheological and morphological behaviour of irradiated PP/HA composites

    International Nuclear Information System (INIS)

    Ramirez, C.; Albano, C.; Karam, A.; Dominguez, N.; Sanchez, Y.; Gonzalez, G.

    2005-01-01

    Hydroxyapatite (HA) reinforced polypropylene (PP) composites are being developed as bone graft materials. In this research, the effect of γ irradiation on mechanical, rheological, thermal and morphological behaviour of PP-HA composites was studied. The melt flow index of polymer increased markedly when it was exposed to radiation. This is indicative of chain scission reaction as the predominant process. During the tensile testing, the composites exhibited brittle behaviour, showing no fluency point. Elongation at break showed a tendency to decrease with the increase in radiation dose while stress at break did not show significant variation with radiation dose. High HA content (>20%) and radiation dose (25 kGy) had significant influence on thermal stability

  17. Factors influencing the thermally-induced strength degradation of B/Al composites

    Science.gov (United States)

    Dicarlo, J. A.

    1983-01-01

    Literature data related to the thermally-induced strength degradation of B/Al composites were examined in the light of fracture theories based on reaction-controlled fiber weakening. Under the assumption of a parabolic time-dependent growth for the interfacial reaction product, a Griffith-type fracture model was found to yield simple equations whose predictions were in good agreement with data for boron fiber average strength and for B/Al axial fracture strain. The only variables in these equations were the time and temperature of the thermal exposure and an empirical factor related to fiber surface smoothness prior to composite consolidation. Such variables as fiber diameter and aluminum alloy composition were found to have little influence. The basic and practical implications of the fracture model equations are discussed. Previously announced in STAR as N82-24297

  18. Topological and thermal properties of polypropylene composites based on oil palm biomass

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, A. H., E-mail: aamir.bhat@petronas.com.my, E-mail: anie-yal88@yahoo.com; Dasan, Y. K., E-mail: aamir.bhat@petronas.com.my, E-mail: anie-yal88@yahoo.com [Department of Fundamental and Applied Sciences, Universiti Teknologi Petronas, 31750 Perak (Malaysia)

    2014-10-24

    Roughness on pristine and polymer composite surfaces is of enormous practical importance for polymer applications. This study deals with the use of varying quantity of oil palm ash as a nanofiller in a polypropylene based matrix. The oil palm ash sample was preprocessed to break the particles into small diameter by using ultra sonication before using microfluidizer for further deduction in size and homogenization. The oil palm ash was made to undergo many passes through the microfluidizer for fine distribution of particles. Polypropylene based composites containing different loading percentage oil palm ash was granulated by twin screw extruder and then injection molded. The surface morphology of the OPA passed through microfluidizer was analyzed by Tapping Mode - Atomic Force Microscopy (TMAFM). Thermal analysis results showed an increase in the activation energy values. The thermal stability of the composite samples showed improvement as compared to the virgin polymer as corroborated by the on-set degradation temperatures and the temperatures at which 50% degradation occurred.

  19. Factors influencing the thermally-induced strength degradation of B/Al composites

    International Nuclear Information System (INIS)

    Dicarlo, J.A.

    1983-01-01

    Literature data related to the thermally-induced strength degradation of B/Al composites were examined in the light of fracture theories based on reaction-controlled fiber weakening. Under the assumption of a parabolic time-dependent growth for the interfacial reaction product, a Griffith-type fracture model was found to yield simple equations whose predictions were in good agreement with data for boron fiber average strength and for B/Al axial fracture strain. The only variables in these equations were the time and temperature of the thermal exposure and an empirical factor related to fiber surface smoothness prior to composite consolidation. Such variables as fiber diameter and aluminum alloy composition were found to have little influence. The basic and practical implications of the fracture model equations are discussed

  20. Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique

    Directory of Open Access Journals (Sweden)

    Chmielewski Marcin

    2017-01-01

    Full Text Available The presented paper investigates the relationship between the microstructure and thermal properties of copper-silicon carbide composites obtained through hot pressing (HP and spark plasma sintering (SPS techniques. The microstructural analysis showed a better densification in the case of composites sintered in the SPS process. TEM investigations revealed the presence of silicon in the area of metallic matrix in the region close to metal-ceramic boundary. It is the product of silicon dissolving process in copper occurring at an elevated temperature. The Cu-SiC interface is significantly defected in composites obtained through the hot pressing method, which has a major influence on the thermal conductivity of materials.

  1. Topological and thermal properties of polypropylene composites based on oil palm biomass

    International Nuclear Information System (INIS)

    Bhat, A. H.; Dasan, Y. K.

    2014-01-01

    Roughness on pristine and polymer composite surfaces is of enormous practical importance for polymer applications. This study deals with the use of varying quantity of oil palm ash as a nanofiller in a polypropylene based matrix. The oil palm ash sample was preprocessed to break the particles into small diameter by using ultra sonication before using microfluidizer for further deduction in size and homogenization. The oil palm ash was made to undergo many passes through the microfluidizer for fine distribution of particles. Polypropylene based composites containing different loading percentage oil palm ash was granulated by twin screw extruder and then injection molded. The surface morphology of the OPA passed through microfluidizer was analyzed by Tapping Mode - Atomic Force Microscopy (TMAFM). Thermal analysis results showed an increase in the activation energy values. The thermal stability of the composite samples showed improvement as compared to the virgin polymer as corroborated by the on-set degradation temperatures and the temperatures at which 50% degradation occurred

  2. Evaluation of the thermal properties of polypropylene reinforced with palm fibers composites

    International Nuclear Information System (INIS)

    Capri, M.R.; Santana, L.C.; Mulinari, D.R.

    2016-01-01

    The aim of this study was to characterize polypropylene reinforced with palm composites. Of this form, it was studied physical and chemical modifications of the in nature fibers, washed with hot water and mercerized. The composites of polypropylene reinforced with 5%, 10% and 20% (wt /wt) in nature fibers and mercerized were evaluated thermally. The fibers were characterized by SEM XRD and TGA / DSC techniques. Results revealed that the mercerized fibers presented higher crystallinity when compared to others, as well as increased roughness, facilitating interlacing with the reinforcement matrix. Thermal studies of the fibers showed that the mercerization caused displacement curves paragraph higher temperatures. The composites reinforced with treated fibers presented largest temperatures and enthalpies of degradation. The content of fiber influenced in enthalpy degradation and reduction in fusion temperature. (author)

  3. Analysis of Thermo-Acoustic Emission from Damage in Composite Laminates under Thermal Cyclic Loading

    International Nuclear Information System (INIS)

    Kim, Young Bok; Min, Dae Hong; Lee, Deok Bo; Choi, Nak Sam

    2001-01-01

    An investigation on nondestructive evaluation of thermal stress-reduced damage in the composite laminates (3mm in thickness and [+45 6 /-45 6 ] S lay-up angles) has been performed using the thermo-acoustic emission technique. Reduction of thermo-AE events due to repetitive thermal load cycles showed a Kaiser effect. An analysis of the thermo-AE behavior determined the stress free temperature of composite laminates. Fiber fracture and matrix cracks were observed using the optical microscopy, scanning electron microscopy and ultrasonic C-sean. Short-Time Fourier Transform of thermo-AE signals offered the time-frequency characteristics which might classify the thermo-AE as three different types to estimate the damage processes of the composites

  4. Foam/Aerogel Composite Materials for Thermal and Acoustic Insulation and Cryogen Storage

    Science.gov (United States)

    Williams, Martha K. (Inventor); Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Weiser, Erik S. (Inventor); Sass, Jared P. (Inventor)

    2011-01-01

    The invention involves composite materials containing a polymer foam and an aerogel. The composite materials have improved thermal insulation ability, good acoustic insulation, and excellent physical mechanical properties. The composite materials can be used, for instance, for heat and acoustic insulation on aircraft, spacecraft, and maritime ships in place of currently used foam panels and other foam products. The materials of the invention can also be used in building construction with their combination of light weight, strength, elasticity, ability to be formed into desired shapes, and superior thermal and acoustic insulation power. The materials have also been found to have utility for storage of cryogens. A cryogenic liquid or gas, such as N.sub.2 or H.sub.2, adsorbs to the surfaces in aerogel particles. Thus, another embodiment of the invention provides a storage vessel for a cryogen.

  5. Thermal and mechanical behavior of metal matrix and ceramic matrix composites

    Science.gov (United States)

    Kennedy, John M. (Editor); Moeller, Helen H. (Editor); Johnson, W. S. (Editor)

    1990-01-01

    The present conference discusses local stresses in metal-matrix composites (MMCs) subjected to thermal and mechanical loads, the computational simulation of high-temperature MMCs' cyclic behavior, an analysis of a ceramic-matrix composite (CMC) flexure specimen, and a plasticity analysis of fibrous composite laminates under thermomechanical loads. Also discussed are a comparison of methods for determining the fiber-matrix interface frictional stresses of CMCs, the monotonic and cyclic behavior of an SiC/calcium aluminosilicate CMC, the mechanical and thermal properties of an SiC particle-reinforced Al alloy MMC, the temperature-dependent tensile and shear response of a graphite-reinforced 6061 Al-alloy MMC, the fiber/matrix interface bonding strength of MMCs, and fatigue crack growth in an Al2O3 short fiber-reinforced Al-2Mg matrix MMC.

  6. Electrical and thermal conductivities of Stycast 1266 epoxy/graphite composites

    International Nuclear Information System (INIS)

    Tien, Hoang; Park, Joonkyu; Han, Sanga; Ahmad, Muneer; Seo, Yongho; Shin, Koo

    2011-01-01

    Nanocomposites composed of graphene flakes and epoxy resin (Stycast 1266) were produced with different concentrations of graphene in the range of 0 to 15 wt.%. The direct-current conductivity of the composites complied with percolation behavior. The percolation threshold concentration pc from the conductivity measurement was estimated as 8 wt.%, and the critical exponent as t = 1.85 ± 0.23. The alternating-current conductivity of the composite increased monotonically as the frequency was increased in the range from 1 to 10 MHz. The thermal conductivity k also exhibited a similar percolation behavior, with highest value of k = 0.73 W/m·K for the 12-wt.% composite, which corresponds to a 350% enhancement of the thermal conductivity.

  7. Thermal load histories for North American roof assembles using various cladding materials including wood-thermoplastic composite shingles

    Science.gov (United States)

    J. E. Winandy

    2006-01-01

    Since 1991, thermal load histories for various roof cladding types have been monitored in outdoor attic structures that simulate classic North American light-framed construction. In this paper, the 2005 thermal loads for wood-based composite roof sheathing, wood rafters, and attics under wood-plastic composite shingles are compared to common North American roof...

  8. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    International Nuclear Information System (INIS)

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1996-06-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation of irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD β-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination

  9. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    International Nuclear Information System (INIS)

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1997-05-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation after irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD β-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination

  10. Impacto ambiental de los remanentes de supernova

    Science.gov (United States)

    Dubner, G. M.

    2015-08-01

    The explosion of a supernovae (SN) represents the sudden injection of about ergs of thermal and mechanical energy in a small region of space, causing the formation of powerful shock waves that propagate through the interstellar medium at speeds of several thousands of km/s. These waves sweep, compress and heat the interstellar material that they encounter, forming the supernova remnants. Their evolution over thousands of years change forever, irreversibly, not only the physical but also the chemical properties of a vast region of space that can span hundreds of parsecs. This contribution briefly analyzes the impact of these explosions, discussing the relevance of some phenomena usually associated with SNe and their remnants in the light of recent theoretical and observational results.

  11. Effect of composition ratio on the thermal and physical properties of semicrystalline PLA/PHB-HHx composites.

    Science.gov (United States)

    Lim, Jung Seop; Park, Ku-il; Chung, Gun Soo; Kim, Jong Hoon

    2013-05-01

    In this study, composites of semicrystalline, biodegradable polylactide (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx) were prepared by direct melt compounding. The physical and thermal properties of the composites were investigated as a function of the composition ratio. Differential scanning calorimetry analysis indicated that PLA and PHB-HHx formed immiscible composites over the observed range of composition. The crystallization of PLA was gradually suppressed by increasing proportions of PHB-HHx. Dynamic mechanical analysis results confirmed that the innate ductility of PHB-HHX and its inhibiting effect on PLA crystallization improved the stiffness of the composite compared to those of neat PLA. The infrared spectra of the immiscible PLA/PHB-HHx composites at two crystallization temperatures (30 °C, 130 °C) were obtained and presented. At 30 °C, PHB-HHx existed as crystalline domains in the PLA matrix, while, amorphous phase of molten PHB-HHx was diffused within the crystalline phase of PLA at 130 °C. The interaction between PHB-HHX and PLA could not be elucidated from the temperature data. Mechanical tests showed that the addition of PHB-HHx improves ductility of PLA/PHB-HHx composite. Morphological analysis revealed that small proportions of PHB-HHx exhibited less tendency to aggregate, which resulted in greater plastic deformation and improved toughness. From this study, PLA blended with small portions of PHB-HHx may further expand the use of bio-friendly resources in a variety of applications such as flexible films, food packaging and something like that. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Detection and quantification of defects in composite material by using thermal wave method

    International Nuclear Information System (INIS)

    Ranjit, Shrestha; Kim, Won Tae

    2015-01-01

    This paper explored the results of experimental investigation on carbon fiber reinforced polymer (CFRP) composite sample with thermal wave technique. The thermal wave technique combines the advantages of both conventional thermal wave measurement and thermography using a commercial Infrared camera. The sample comprises the artificial inclusions of foreign material to simulate defects of different shape and size at different depths. Lock-in thermography is employed for the detection of defects. The temperature field of the front surface of sample was observed and analysed at several excitation frequencies ranging from 0.562 Hz down to 0.032 Hz. Four-point methodology was applied to extract the amplitude and phase of thermal wave's harmonic component. The phase images are analyzed to find qualitative and quantitative information about the defects

  13. Examination of coagulant additives on qualitative composition of selected thermal waters

    Science.gov (United States)

    Łukasiewicz, Ewelina; Rząsa, Mariusz

    2017-10-01

    On the territory of Poland occur rich deposits of thermal waters. Although the utilisation of these waters is continuously extending, Poland is not exploiting their full geothermal potential due to high investment costs. Thermal waters industry in Poland to date indicates operations within mainly balneology as well as recreation objectives. Higher temperature values of these waters foster a washout in the surrounding rocks resulting in a high concentration of diluted substances which must be often removed. The following study investigates thermal waters from three intakes for which coagulation processes were conducted. Research clearly shows that coagulant additives not impact on the qualitative composition of thermal water, what is very important according to medicinal properties of water. The study results may be further applied as a valuable piece of information for further exploitation in balneology or within the heating sector and other installations.

  14. Dynamic measurement of coal thermal properties and elemental composition of volatile matter during coal pyrolysis

    Directory of Open Access Journals (Sweden)

    Rohan Stanger

    2014-01-01

    Full Text Available A new technique that allows dynamic measurement of thermal properties, expansion and the elemental chemistry of the volatile matter being evolved as coal is pyrolysed is described. The thermal and other properties are measured dynamically as a function of temperature of the coal without the need for equilibration at temperature. In particular, the technique allows for continuous elemental characterisation of tars as they are evolved during pyrolysis and afterwards as a function of boiling point. The technique is demonstrated by measuring the properties of maceral concentrates from a coal. The variation in heats of reaction, thermal conductivity and expansion as a function of maceral composition is described. Combined with the elemental analysis, the results aid in the interpretation of the chemical processes contributing to the physical and thermal behaviour of the coal during pyrolysis. Potential applications in cokemaking studies are discussed.

  15. High Thermal Conductivity of Copper Matrix Composite Coatings with Highly-Aligned Graphite Nanoplatelets

    Science.gov (United States)

    Tagliaferri, Vincenzo; Ucciardello, Nadia

    2017-01-01

    Nanocomposite coatings with highly-aligned graphite nanoplatelets in a copper matrix were successfully fabricated by electrodeposition. For the first time, the disposition and thermal conductivity of the nanofiller has been evaluated. The degree of alignment and inclination of the filling materials has been quantitatively evaluated by polarized micro-Raman spectroscopy. The room temperature values of the thermal conductivity were extracted for the graphite nanoplatelets by the dependence of the Raman G-peak frequency on the laser power excitation. Temperature dependency of the G-peak shift has been also measured. Most remarkable is the global thermal conductivity of 640 ± 20 W·m−1·K−1 (+57% of copper) obtained for the composite coating by the flash method. Our experimental results are accounted for by an effective medium approximation (EMA) model that considers the influence of filler geometry, orientation, and thermal conductivity inside a copper matrix. PMID:29068424

  16. Detection and quantification of defects in composite material by using thermal wave method

    Energy Technology Data Exchange (ETDEWEB)

    Ranjit, Shrestha; Kim, Won Tae [Dept. of Mechanical Engineering, Kongju National University, Cheonan (Korea, Republic of)

    2015-12-15

    This paper explored the results of experimental investigation on carbon fiber reinforced polymer (CFRP) composite sample with thermal wave technique. The thermal wave technique combines the advantages of both conventional thermal wave measurement and thermography using a commercial Infrared camera. The sample comprises the artificial inclusions of foreign material to simulate defects of different shape and size at different depths. Lock-in thermography is employed for the detection of defects. The temperature field of the front surface of sample was observed and analysed at several excitation frequencies ranging from 0.562 Hz down to 0.032 Hz. Four-point methodology was applied to extract the amplitude and phase of thermal wave's harmonic component. The phase images are analyzed to find qualitative and quantitative information about the defects.

  17. A facile strategy for the reduction of graphene oxide and its effect on thermal conductivity of epoxy based composites

    Directory of Open Access Journals (Sweden)

    F. Xie

    2016-06-01

    Full Text Available A facile and efficient approach to reduce graphene oxide with Al particles and potassium hydroxide was developed at moderate temperature and the graphene/epoxy composite was prepared by mould casting method. The as-prepared graphene has been confirmed by Transmission electron microscopy, Fourier transform infrared spectrometer, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Thermal gravimetric analysis. This provides a new green way to synthesize graphene with high surface area and opens another opportunity for the production of graphene. Effects of graphene on thermal conductivity, thermal stability and microstructures of the epoxy-based composite were also investigated. The results showed that thermal conductivity of the composite exhibited a remarkable improvement with increasing content of graphene and thermal conductivity could reach 1.192 W/(m*K when filled with 3 wt% graphene. Moreover, graphene/epoxy composite exhibits good thermal stability with 3 wt% graphene.

  18. Structural, thermal and electrical characterizations of multiwalled carbon nanotubes and polyaniline composite

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Kamal, E-mail: singhkamal204@gmail.com; Garg, Leena; Singh, Jaspal [Department of Applied Sciences, Chandigarh University, Gharuan, Mohali (India); Kumar, Sanjeev [Applied Sciences Department, PEC University of Technology, Chandigarh (India); Sharma, Amit L. [Central Scientific Instrumentation Organization, Sector 30, Chandigarh (India)

    2016-05-06

    The undoped and doped composite of MWNTs (Multiwalled Carbon Nanotubes) with PANI (/Polyaniline) was prepared by chemical oxidative polymerization. The MWNTs/PANI composites have been characterized by using various techniques like Thermogravometric Analysis (TGA), Fourier transform infrared (FT-IR) spectrometer and Field emission scanning electron microscope (FE-SEM) and conductivity measurement by using two probe method. TGA results has shown that thermal stability followed the pattern undoped MWNTs/PANI composite < doped MWNTs/PANI composite. FE-SEM micrographs demonstrated the morphological changes on the surface of MWNTs as a result of composite formation. Fourier transformed infrared (FT-IR) spectra ascertained the formation of the composite. Study of electrical characteristics demonstrated that the doped MWNTs/PANI composite (1.2 × 10{sup 1} Scm{sup −1}) have better conductivity than the undoped MWNTs/PANI composite (10{sup −4} Scm{sup −1}). These CNTs based polymeric composites are of great importance in developing new nano-scale devices for future chemical, mechanical and electronic applications.

  19. Mechanical, Morphological, and Thermal Properties of Nutshell and Microcrystalline Cellulose Filled High-Density Polyethylene Composites

    Directory of Open Access Journals (Sweden)

    Sevda Boran

    2016-01-01

    Full Text Available Effects of nutshell fiber loadings of 30 wt.% and MCC loadings up to 15 wt.% on some properties of high-density polyethylene composites (HDPE were investigated. The composites were manufactured by a single screw extruder and injection molding. The experimental composite samples were tested for their mechanical performance including tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength. Thermal and morphological properties of the composites were tested by differential scanning calorimetry-DSC and scanning electron microscopy (SEM, respectively. The maximum tensile strength was obtained from the MCC-filled composites, whereas the maximum flexural strength was achieved with the MCC-nutshell filled composites. The tensile and flexural moduli of the composites were significantly improved with increasing MCC content and the presence of nutshell fibers in polymer matrix. Impact strength decreased using MCC and nutshell fiber in the polymer matrix. Based on the DSC results, there was no remarkable change in the melting point for all composites. The results showed that the incorporation of nutshell fibers and MCC in the polymer matrix had brought about some positive effect on mechanical properties of HDPE composites.

  20. SHOCK BREAKOUT FROM TYPE Ia SUPERNOVA

    International Nuclear Information System (INIS)

    Piro, Anthony L.; Chang, Philip; Weinberg, Nevin N.

    2010-01-01

    The mode of explosive burning in Type Ia supernovae (SNe Ia) remains an outstanding problem. It is generally thought to begin as a subsonic deflagration, but this may transition into a supersonic detonation (the delayed detonation transition, DDT). We argue that this transition leads to a breakout shock, which would provide the first unambiguous evidence that DDTs occur. Its main features are a hard X-ray flash (∼20 keV) lasting ∼10 -2 s with a total radiated energy of ∼10 40 erg, followed by a cooling tail. This creates a distinct feature in the visual light curve, which is separate from the nickel decay. This cooling tail has a maximum absolute visual magnitude of M V ∼ -9 to -10 at ∼1 day, which depends most sensitively on the white dwarf radius at the time of the DDT. As the thermal diffusion wave moves in, the composition of these surface layers may be imprinted as spectral features, which would help to discern between SN Ia progenitor models. Since this feature should accompany every SNe Ia, future deep surveys (e.g., m = 24) will see it out to a distance of ∼80 Mpc, giving a maximum rate of ∼60 yr -1 . Archival data sets can also be used to study the early rise dictated by the shock heating (at ∼20 days before maximum B-band light). A similar and slightly brighter event may also accompany core bounce during the accretion-induced collapse to a neutron star, but with a lower occurrence rate.

  1. Low-temperature densification and excellent thermal properties of W–Cu thermal-management composites prepared from copper-coated tungsten powders

    International Nuclear Information System (INIS)

    Zhang, Lianmeng; Chen, Wenshu; Luo, Guoqiang; Chen, Pingan; Shen, Qiang; Wang, Chuanbin

    2014-01-01

    Highlights: • High-density (98.4%) W–20 wt.%Cu composites were low-temperature fabricated. • A highly pure Cu network and a homogenous microstructure formed in the composites. • The interfaces between W and Cu are well bonded with no spaces. • The composites have excellent thermal properties. -- Abstract: High-density W–20 wt.%Cu composites containing a Cu-network structure and exhibiting good thermal properties were fabricated by low-temperature hot-press sintering from high-purity copper-coated tungsten powders. The relative density of W–20 wt.%Cu composites sintered at 950 °C–100 MPa–2 h was 98.4%. The low-temperature densification of W–Cu composites occurs because the sintering mode of the coated particles involves only sintering of Cu to Cu, rather than both Cu to W and Cu to Cu, as required for conventional powder particles. The microstructure shows that a network of high-purity Cu extends throughout the composites, and that the W is distributed homogeneously; the interfaces between W and Cu show good contact. The composites have excellent thermal conductivity (239 W/(m K)) and a relatively low coefficient of thermal expansion (7.4 × 10 −6 /K), giving them some of the best properties reported to date for thermal-management materials. The excellent performance is mainly because of their structure, which arises from the characteristics of the high-purity copper-coated tungsten powders

  2. Transient Thermal Response of Lightweight Cementitious Composites Made with Polyurethane Foam Waste

    Science.gov (United States)

    Kismi, M.; Poullain, P.; Mounanga, P.

    2012-07-01

    The development of low-cost lightweight aggregate (LWA) mortars and concretes presents many advantages, especially in terms of lightness and thermal insulation performances of structures. Low-cost LWA mainly comes from the recovery of vegetal or plastic wastes. This article focuses on the characterization of the thermal conductivity of innovative lightweight cementitious composites made with fine particles of rigid polyurethane (PU) foam waste. Five mortars were prepared with various mass substitution rates of cement with PU-foam particles. Their thermal conductivity was measured with two transient methods: the heating-film method and the hot-disk method. The incorporation of PU-foam particles causes a reduction of up to 18 % of the mortar density, accompanied by a significant improvement of the thermal insulating performance. The effect of segregation on the thermal properties of LWA mortars due to the differences of density among the cementitious matrix, sand, and LWA has also been quantified. The application of the hot-disk method reveals a gradient of thermal conductivity along the thickness of the specimens, which could be explained by a non-uniform repartition of fine PU-foam particles and mineral aggregates within the mortars. The results show a spatial variation of the thermal conductivity of the LWA mortars, ranging from 9 % to 19 %. However, this variation remains close to or even lower than that observed on a normal weight aggregate mortar. Finally, a self-consistent approach is proposed to estimate the thermal conductivity of PU-foam cement-based composites.

  3. Improvement of thermal conductivity of ceramic matrix composites for 4. generation nuclear reactors

    International Nuclear Information System (INIS)

    Cabrero, J.

    2009-11-01

    This study deals with thermal conductivity improvement of SiCf/SiC ceramic matrix composites materials to be used as cladding material in 4. generation nuclear reactor. The purpose of the study is to develop a composite for which both the temperature and irradiation effect is less pronounced on thermal conductivity of material than for SiC. This material will be used as matrix in CMC with SiC fibers. Some TiC-SiC composites with different SiC volume contents were prepared by spark plasma sintering (SPS). The sintering process enables to fabricate specimens very fast, with a very fine microstructure and without any sintering aids. Neutron irradiation has been simulated using heavy ions, at room temperature and at 500 C. Evolution of the thermal properties of irradiated materials is measured using modulated photothermal IR radiometry experiment and was related to structural evolution as function of dose and temperature. It appears that such approach is reliable to evaluate TiC potentiality as matrix in CMC. Finally, CMC with TiC matrix and SiC fibers were fabricated and both mechanical and thermal properties were measured and compare to SiCf/SiC CMC. (author)

  4. Electrical resistivity and thermal properties of compatibilized multi-walled carbon nanotube/polypropylene composites

    Directory of Open Access Journals (Sweden)

    A. Szentes

    2012-06-01

    Full Text Available The electrical resistivity and thermal properties of multi-walled carbon nanotube/polypropylene (MWCNT/PP composites have been investigated in the presence of coupling agents applied for improving the compatibility between the nanotubes and the polymer. A novel olefin-maleic-anhydride copolymer and an olefin-maleic-anhydride copolymer based derivative have been used as compatibilizers to achieve better dispersion of MWCNTs in the polymer matrix. The composites have been produced by extrusion followed by injection moulding. They contained different amounts of MWCNTs (0.5, 2, 3 and 5 wt% and coupling agent to enhance the interactions between the carbon nanotubes and the polymer. The electrical resistivity of the composites has been investigated by impedance spectroscopy, whereas their thermal properties have been determined using a thermal analyzer operating on the basis of the periodic thermal perturbation method. Rheological properties, BET-area and adsorption-desorption isotherms have been determined. Dispersion of MWCNTs in the polymer has been studied by scanning electron microscopy (SEM.

  5. The relationship between fatty acid compositions and thermal stability of extra virgin olive oils

    Directory of Open Access Journals (Sweden)

    Fayegh Moulodi

    2014-11-01

    Full Text Available Background: Fatty acids are one of the most important compounds in edible oils. Further, the stability of oils depends on the composition of fatty acids. So, this study was conducted to investigate the effect of fatty acid composition on the oxidative stability of extra virgin olive oils during the heating process. Methods: In total, eight samples of extra virgin olive oil were studied. To evaluate their thermal stability, the oils were heated at 120 ° C for 4 h and sampling was carried out in 2-hour intervals. Then, fatty acid composition, peroxide value, anisidine value and totox value were evaluated according to Iranian national standards. Results: Results showed a significantly direct correlation between Palmitoleic acid and Totox index in the second (r=0.786 and fourth hours (r=0.762, and between linoleic and Totox index in the second (r=0.643 and fourth hours (r=0.786. However, there was a significantly inverse relationship between oleic acid and Totox index in the fourth hour (r=-0.833. Conclusion: Result indicated that linoleic and Palmitoleic acids had a reducing effect on thermal stability of extra virgin olive oil after the second hour. But, Oleic acid caused a positive effect on thermal stability after the fourth hour. Thus, it is concluded that unsaturated fatty acids especially oleic acid affect the thermal stability at final hours.

  6. Numerical study on the thermal behavior of graphene nanoplatelets/epoxy composites

    Science.gov (United States)

    Xiao, Wenkai; Zhai, Xian; Ma, Pengfei; Fan, Taotao; Li, Xiaotuo

    2018-06-01

    A three-dimensional computational model was developed using the finite element method (FEM) to evaluate the thermal behavior of graphene nanoplatelets (GNPs)/epoxy composites based on continuum mechanics. The model was validated with experimental data. The effects of the ratio of radius to thickness (Rrt) of GNPs, the interfacial thermal conductivity between GNPs and the matrix (Cgm), the contact thermal conductivity between GNPs (Cgg) and the agglomeration degree of GNPs on the thermal conductivity of composites (Kc) were quantified using this model. The results show that a larger Rrt is beneficial to Kc. GNPs could increase Kc only when the Cgm is greater than a critical value. A percolation phenomenon will occur when Cgg is larger than 1.0E8 W/(m2k) in randomly distributed GNPs/epoxy composites. The percolation effects become more obvious with the increase of Cgg and the volume fraction of GNPs. The agglomeration of GNPs has negative effects on the Kc. The higher the agglomeration degree of GNPs is, the lower Kc is. This is attributed to less beneficial interfacial areas, more inefficient contact areas, smaller Rrt and less effective connection/contact between GNPs.

  7. Theoretical Estimation of Thermal Effects in Drilling of Woven Carbon Fiber Composite

    Directory of Open Access Journals (Sweden)

    José Díaz-Álvarez

    2014-06-01

    Full Text Available Carbon Fiber Reinforced Polymer (CFRPs composites are extensively used in structural applications due to their attractive properties. Although the components are usually made near net shape, machining processes are needed to achieve dimensional tolerance and assembly requirements. Drilling is a common operation required for further mechanical joining of the components. CFRPs are vulnerable to processing induced damage; mainly delamination, fiber pull-out, and thermal degradation, drilling induced defects being one of the main causes of component rejection during manufacturing processes. Despite the importance of analyzing thermal phenomena involved in the machining of composites, only few authors have focused their attention on this problem, most of them using an experimental approach. The temperature at the workpiece could affect surface quality of the component and its measurement during processing is difficult. The estimation of the amount of heat generated during drilling is important; however, numerical modeling of drilling processes involves a high computational cost. This paper presents a combined approach to thermal analysis of composite drilling, using both an analytical estimation of heat generated during drilling and numerical modeling for heat propagation. Promising results for indirect detection of risk of thermal damage, through the measurement of thrust force and cutting torque, are obtained.

  8. Thermal Performance Study of Composite Phase Change Material with Polyacrylicand Conformal Coating.

    Science.gov (United States)

    Kee, Shin Yiing; Munusamy, Yamuna; Ong, Kok Seng; Cornelis Metselaar, Hendrik Simon; Chee, Swee Yong; Lai, Koon Chun

    2017-07-28

    The composite PCM was prepared by blending polymethyl methacrylate (PMMA) and myristic acid (MA) in different weight percentages. The MA and PMMA were selected as PCM and supporting material, respectively. As liquid MA may leak out during the phase transition, this study proposes the use of two coatings, namely a polyacrylic coating and a conformal coating to overcome the leakage problem. Both coatings were studied in terms of the leakage test, chemical compatibility, thermal stability, morphology, and reliability. No leakage was found in the PCMs with coatings compared to those without under the same proportions of MA/PMMA, thus justifying the use of coatings in the present study. The chemically compatibility was confirmed by FTIR spectra: the functional groups of PCMs were in accordance with those of coatings. DSC showed that the coatings did not significantly change the melting and freezing temperatures, however, they improved the thermal stability of composite PCMs as seen in TGA analysis. Furthermore, the composite PCMs demonstrated good thermal reliability after 1000 times thermal cycling. The latent heat of melting reduced by only 0.16% and 1.02% for the PCMs coated with conformal coating and polyacrylic coating, respectively. Therefore, the proposed coatings can be considered in preparing fatty acid/PMMA blends attributed to the good stability, compatibility and leakage prevention.

  9. Learning from Natural Nacre: Constructing Layered Polymer Composites with High Thermal Conductivity.

    Science.gov (United States)

    Pan, Guiran; Yao, Yimin; Zeng, Xiaoliang; Sun, Jiajia; Hu, Jiantao; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

    2017-09-27

    Inspired by the microstructures of naturally layered and highly oriented materials, such as natural nacre, we report a thermally conductive polymer composite that consists of epoxy resin and Al 2 O 3 platelets deposited with silver nanoparticles (AgNPs). Owing to their unique two-dimensional structure, Al 2 O 3 platelets are stacked together via a hot-pressing technique, resulting in a brick-and-mortar structure, which is similar to the one of natural nacre. Moreover, the AgNPs deposited on the surfaces of the Al 2 O 3 platelets act as bridges that link the adjacent Al 2 O 3 platelets due to the reduced melting point of the AgNPs. As a result, the polymer composite with 50 wt % filler achieves a maximum thermal conductivity of 6.71 W m -1 K -1 . In addition, the small addition of AgNPs (0.6 wt %) minimally affects the electrical insulation of the composites. Our bioinspired approach will find uses in the design and fabrication of thermally conductive materials for thermal management in modern electronics.

  10. Novel thermally stable poly(vinyl chloride) composites for sulfate removal

    Energy Technology Data Exchange (ETDEWEB)

    Nadagouda, Mallikarjuna N., E-mail: Nadagouda.mallikarjuna@epa.gov [Water Supply and Water Resources Division, National Risk Management Research Laboratory U.S. Environmental Protection Agency, 26 W. Martin Luther King Drive Cincinnati, Ohio 45268 (United States); Pressman, Jonathan; White, Colin; Speth, Thomas F.; McCurry, Daniel L. [Water Supply and Water Resources Division, National Risk Management Research Laboratory U.S. Environmental Protection Agency, 26 W. Martin Luther King Drive Cincinnati, Ohio 45268 (United States)

    2011-04-15

    Graphical abstract: Barium carbonate and/or barium carbonate-loaded silica aero-gels dispersed polyvinyl chloride (PVC) composites were prepared by dissolving PVC in tetrahydrofuran (THF), dispersing BaCO{sub 3} and/or BaCO{sub 3}-loaded silica aero-gels, re-precipitating the PVC with water at room temperature. The PVC composites were then characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray mapping, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. The obtained composites had better thermal properties than the control PVC. The composites were tested for sulfate removal and found to significantly reduce sulfate when compared with control PVC. - Abstract: BaCO{sub 3} dispersed PVC composites were prepared through a polymer re-precipitation method. The composites were tested for sulfate removal using rapid small scale column test (RSSCT) and found to significantly reduce sulfate concentration. The method was extended to synthesize barium carbonate-loaded silica aero-gels-polyvinyl chloride (PVC) polymer composites. The PVC composites were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray mapping, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. The method has advantages over conventional sulfate precipitation (sulfate removal process) using BaCO{sub 3} wherein clogging of the filter can be avoided. The method is environmentally friendly and does not interfere with natural organic matter as the conventional resin does. Some of the composites were thermally more stable as compared with the pure PVC discussed in the literature.

  11. Novel thermally stable poly(vinyl chloride) composites for sulfate removal

    International Nuclear Information System (INIS)

    Nadagouda, Mallikarjuna N.; Pressman, Jonathan; White, Colin; Speth, Thomas F.; McCurry, Daniel L.

    2011-01-01

    Graphical abstract: Barium carbonate and/or barium carbonate-loaded silica aero-gels dispersed polyvinyl chloride (PVC) composites were prepared by dissolving PVC in tetrahydrofuran (THF), dispersing BaCO 3 and/or BaCO 3 -loaded silica aero-gels, re-precipitating the PVC with water at room temperature. The PVC composites were then characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray mapping, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. The obtained composites had better thermal properties than the control PVC. The composites were tested for sulfate removal and found to significantly reduce sulfate when compared with control PVC. - Abstract: BaCO 3 dispersed PVC composites were prepared through a polymer re-precipitation method. The composites were tested for sulfate removal using rapid small scale column test (RSSCT) and found to significantly reduce sulfate concentration. The method was extended to synthesize barium carbonate-loaded silica aero-gels-polyvinyl chloride (PVC) polymer composites. The PVC composites were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray mapping, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. The method has advantages over conventional sulfate precipitation (sulfate removal process) using BaCO 3 wherein clogging of the filter can be avoided. The method is environmentally friendly and does not interfere with natural organic matter as the conventional resin does. Some of the composites were thermally more stable as compared with the pure PVC discussed in the literature.

  12. High Thermal Conductivity NARloy-Z-Diamond Composite Liner for Advanced Rocket Engines

    Science.gov (United States)

    Bhat, Biliyar; Greene, Sandra

    2015-01-01

    NARloy-Z (Cu-3Ag-0.5Zr) alloy is state-of-the-art combustion chamber liner material used in liquid propulsion engines such as the RS-68 and RS-25. The performance of future liquid propulsion systems can be improved significantly by increasing the heat transfer through the combustion chamber liner. Prior work1 done at NASA Marshall Space Flight Center (MSFC) has shown that the thermal conductivity of NARloy-Z alloy can be improved significantly by embedding high thermal conductivity diamond particles in the alloy matrix to form NARloy-Z-diamond composite (fig. 1). NARloy-Z-diamond composite containing 40vol% diamond showed 69% higher thermal conductivity than NARloy-Z. It is 24% lighter than NARloy-Z and hence the density normalized thermal conductivity is 120% better. These attributes will improve the performance and life of the advanced rocket engines significantly. The research work consists of (a) developing design properties (thermal and mechanical) of NARloy-Z-D composite, (b) fabrication of net shape subscale combustion chamber liner, and (c) hot-fire testing of the liner to test performance. Initially, NARloy-Z-D composite slabs were made using the Field Assisted Sintering Technology (FAST) for the purpose of determining design properties. In the next step, a cylindrical shape was fabricated to demonstrate feasibility (fig. 3). The liner consists of six cylinders which are sintered separately and then stacked and diffusion bonded to make the liner (fig. 4). The liner will be heat treated, finish-machined, and assembled into a combustion chamber and hot-fire tested in the MSFC test facility (TF 115) to determine perform.

  13. Melamine-formaldehyde microcapsules filled sappan dye modified polypropylene composites: encapsulation and thermal properties

    Science.gov (United States)

    Phanyawong, Suphitcha; Siengchin, Suchart; Parameswaranpillai, Jyotishkumar; Asawapirom, Udom; Polpanich, Duangporn

    2018-01-01

    Sappan dye, a natural dye extracted from sappan wood is widely used in cosmetics, textile dyeing and as food additives. However, it was recognized that natural dyes cannot withstand high temperature. In this study, a protective coating of melamine-formaldehyde shell material was applied over the sappan dye to improve its thermal stability. The percentage of sappan dye used in the microencapsulation was 30, 40, 50, 60 and 70 wt%. The color, shape, size, and thermal stability of sappan dye microcapsules were investigated. It was found that increasing amount of sappan dye content in the microcapsules decreased the particle size. Thermal analysis reveals that the melamine-formaldehyde resin served as an efficient protective shell for sappan dye. Besides, 30 wt% sappan dye microcapsules with different weight percent (1, 3 and 5 wt%) of sappan dye was used as modifier for polypropylene (PP). All the prepared composites are red in color which supports the thermal stability of the microcapsules. The changes in crystallinity and melting behavior of PP by the addition of microcapsules were studied in detail by differential scanning calorimetry. Thermogravimetric studies showed that the thermal stability of PP composites increased by the addition of microcapsules.

  14. Thermal dewetting behavior of polystyrene composite thin films with organic-modified inorganic nanoparticles.

    Science.gov (United States)

    Kubo, Masaki; Takahashi, Yosuke; Fujii, Takeshi; Liu, Yang; Sugioka, Ken-ichi; Tsukada, Takao; Minami, Kimitaka; Adschiri, Tadafumi

    2014-07-29

    The thermal dewetting of polystyrene composite thin films with oleic acid-modified CeO2 nanoparticles prepared by the supercritical hydrothermal synthesis method was investigated, varying the nanoparticle concentration (0-30 wt %), film thickness (approximately 50 and 100 nm), and surface energy of silanized silicon substrates on which the composite films were coated. The dewetting behavior of the composite thin films during thermal annealing was observed by an optical microscope. The presence of nanoparticles in the films affected the morphology of dewetting holes, and moreover suppressed the dewetting itself when the concentration was relatively high. It was revealed that there was a critical value of the surface energy of the substrate at which the dewetting occurred. In addition, the spatial distributions of nanoparticles in the composite thin films before thermal annealing were investigated using AFM and TEM. As a result, we found that most of nanoparticles segregated to the surface of the film, and that such distributions of nanoparticles contribute to the stabilization of the films, by calculating the interfacial potential of the films with nanoparticles.

  15. A Novel Composite PMMA-based Bone Cement with Reduced Potential for Thermal Necrosis.

    Science.gov (United States)

    Lv, Yang; Li, Ailing; Zhou, Fang; Pan, Xiaoyu; Liang, Fuxin; Qu, Xiaozhong; Qiu, Dong; Yang, Zhenzhong

    2015-06-03

    Percutaneous vertebroplasty (VP) and balloon kyphoplasty (BKP) are now widely used to treat patients who suffer painful vertebral compression fractures. In each of these treatments, a bone cement paste is injected into the fractured vertebral body/bodies, and the cement of choice is a poly(methyl methacrylate) (PMMA) bone cement. One drawback of this cement is the very high exothermic temperature, which, it has been suggested, causes thermal necrosis of surrounding tissue. In the present work, we prepared novel composite PMMA bone cement where microcapsules containing a phase change material (paraffin) (PCMc) were mixed with the powder of the cement. A PCM absorbs generated heat and, as such, its presence in the cement may lead to reduction in thermal necrosis. We determined a number of properties of the composite cement. Compared to the values for a control cement (a commercially available PMMA cement used in VP and BKP), each composite cement was found to have significantly lower maximum exothermic temperature, increased setting time, significantly lower compressive strength, significantly lower compressive modulus, comparable biocompatibility, and significantly smaller thermal necrosis zone. Composite cement containing 20% PCMc may be suitable for use in VP and BKP and thus deserves further evaluation.

  16. Thermal properties of highly structured composite and aluminium sheets in an aerodynamic tunnel

    Science.gov (United States)

    Kulhavy, Petr; Egert, Josef

    This article deals with the thermodynamic behaviour of heat shields - structured metal and composite plates. Experiments have been carried out in a wind tunnel with an additional heating, which simulates the heat source from engine or exhaust pipe and simultaneously the airflow generated during a car movement. The tested sheets with hexagonal structure were a standard commercial made of aluminium and a second manufactured by replication (lamination, diffusion) from glass fabric. The airflow in a parallel way along the sheets was analysed experimentally in order to determine the heat transfer efficiency between surfaces of sheets and surrounding airflow. The temperature on the sheets was chosen to observe the effects of different sheets material, various heat power and airflow velocity. During the experiment a thermal input below the sheets and airflow velocity through the tunnel have been changed. The thermal field distribution on the metal sheet is different than in case of composite sheet. For the composite material the thermal field distribution was more homogeneous. This article describe briefly also methods of obtaining real composite geometry based on scanned data and their reconstruction for using in some future numerical models.

  17. Novel Formulations of Phase Change Materials—Epoxy Composites for Thermal Energy Storage

    Science.gov (United States)

    Alvarez Feijoo, Miguel Angel

    2018-01-01

    This research aimed to evaluate the thermal properties of new formulations of phase change materials (PCMs)-epoxy composites, containing a thickening agent and a thermally conductive phase. The composite specimens produced consisted of composites fabricated using (a) inorganic PCMs (hydrated salts), epoxy resins and aluminum particulates or (b) organic PCM (paraffin), epoxy resins, and copper particles. Differential Scanning Calorimetry (DSC) was used to analyze the thermal behavior of the samples, while hardness measurements were used to determine changes in mechanical properties at diverse PCM and conductive phase loading values. The results indicate that the epoxy matrix can act as a container for the PCM phase without hindering the heat-absorbing behavior of the PCMs employed. Organic PCMs presented reversible phase transformations over multiple cycles, an advantage that was lacking in their inorganic counterparts. The enthalpy of the organic PCM-epoxy specimens increased linearly with the PCM content in the matrix. The use of thickening agents prevented phase segregation issues and allowed the fabrication of specimens containing up to 40% PCM, a loading significantly higher than others reported. The conductive phase seemed to improve the heat transfer and the mechanical properties of the composites when present in low percentages (phase combination (PCM + epoxy resin + hardener + thickening agent) presents great potential as a heat-absorbing material at the temperatures employed. PMID:29373538

  18. Novel Formulations of Phase Change Materials-Epoxy Composites for Thermal Energy Storage.

    Science.gov (United States)

    Arce, Maria Elena; Alvarez Feijoo, Miguel Angel; Suarez Garcia, Andres; Luhrs, Claudia C

    2018-01-26

    This research aimed to evaluate the thermal properties of new formulations of phase change materials (PCMs)-epoxy composites, containing a thickening agent and a thermally conductive phase. The composite specimens produced consisted of composites fabricated using (a) inorganic PCMs (hydrated salts), epoxy resins and aluminum particulates or (b) organic PCM (paraffin), epoxy resins, and copper particles. Differential Scanning Calorimetry (DSC) was used to analyze the thermal behavior of the samples, while hardness measurements were used to determine changes in mechanical properties at diverse PCM and conductive phase loading values. The results indicate that the epoxy matrix can act as a container for the PCM phase without hindering the heat-absorbing behavior of the PCMs employed. Organic PCMs presented reversible phase transformations over multiple cycles, an advantage that was lacking in their inorganic counterparts. The enthalpy of the organic PCM-epoxy specimens increased linearly with the PCM content in the matrix. The use of thickening agents prevented phase segregation issues and allowed the fabrication of specimens containing up to 40% PCM, a loading significantly higher than others reported. The conductive phase seemed to improve the heat transfer and the mechanical properties of the composites when present in low percentages (material at the temperatures employed.

  19. Thermal properties of highly structured composite and aluminium sheets in an aerodynamic tunnel

    Directory of Open Access Journals (Sweden)

    Kulhavy Petr

    2017-01-01

    Full Text Available This article deals with the thermodynamic behaviour of heat shields - structured metal and composite plates. Experiments have been carried out in a wind tunnel with an additional heating, which simulates the heat source from engine or exhaust pipe and simultaneously the airflow generated during a car movement. The tested sheets with hexagonal structure were a standard commercial made of aluminium and a second manufactured by replication (lamination, diffusion from glass fabric. The airflow in a parallel way along the sheets was analysed experimentally in order to determine the heat transfer efficiency between surfaces of sheets and surrounding airflow. The temperature on the sheets was chosen to observe the effects of different sheets material, various heat power and airflow velocity. During the experiment a thermal input below the sheets and airflow velocity through the tunnel have been changed. The thermal field distribution on the metal sheet is different than in case of composite sheet. For the composite material the thermal field distribution was more homogeneous. This article describe briefly also methods of obtaining real composite geometry based on scanned data and their reconstruction for using in some future numerical models.

  20. Binary progenitors of supernovae

    Science.gov (United States)

    Trimble, V.

    1984-12-01

    Among the massive stars that are expected to produce Type II, hydrogen-rich supernovae, the presence of a close companion can increase the main sequence mass needed to yield a collapsing core. In addition, due to mass transfer from the primary to the secondary, the companion enhances the stripping of the stellar hydrogen envelope produced by single star winds and thereby makes it harder for the star to give rise to a typical SN II light curve. Among the less massive stars that may be the basis for Type I, hydrogen-free supernovae, a close companion could be an innocent bystander to carbon detonation/deflagration in the primary. It may alternatively be a vital participant which transfers material to a white dwarf primary and drives it to explosive conditions.

  1. Supernova research with VLBI

    Science.gov (United States)

    Bartel, Norbert; Bietenholz, Michael F.

    2016-06-01

    Core-collapse supernovae have been monitored with VLBI from shortly after the explosion to many years thereafter. Radio emission is produced as the ejecta hit the stellar wind left over from the dyingstar. Images show the details of the interaction as the shock front expands into the circumstellar medium. Measurements of the velocity and deceleration of the expansion provide information on both the ejecta and the circumstellar medium. VLBI observations can also search for the stellar remnant of the explosion, a neutron star or a black hole. Combining the transverse expansion rate with the radial expansion rate from optical spectra allows a geometric determination of the distance to the host galaxy. We will present results from recent VLBI observations, focus on their interpretations, and show updated movies of supernovae from soon after their explosion to the present.

  2. STRESS Counting Supernovae

    Science.gov (United States)

    Botticella, M. T.; Cappellaro, E.; Riello, M.; Greggio, L.; Benetti, S.; Patat, F.; Turatto, M.; Altavilla, G.; Pastorello, A.; Valenti, S.; Zampieri, L.; Harutyunyan, A.; Pignata, G.; Taubenberger, S.

    2008-12-01

    The rate of occurrence of supernovae (SNe) is linked to some of the basic ingredients of galaxy evolution, such as the star formation rate, the chemical enrichment and feedback processes. SN rates at intermediate redshift and their dependence on specific galaxy properties have been investigated in the Southern inTermediate Redshift ESO Supernova Search (STRESS). The rate of core collapse SNe (CC SNe) at a redshift of around 0.25 is found to be a factor two higher than the local value, whereas the SNe Ia rate remains almost constant. SN rates in red and blue galaxies were also measured and it was found that the SNe Ia rate seems to be constant in galaxies of different colour, whereas the CC SN rate seems to peak in blue galaxies, as in the local Universe.

  3. Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid Green Composites during Thermal Cycling

    Directory of Open Access Journals (Sweden)

    Hideaki Katogi

    2016-07-01

    Full Text Available This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid (PLA during thermal cycling. Temperature ranges of thermal cycling tests were 35–45 °C and 35–55 °C. The maximum number of cycles was 103 cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35–45 °C, tensile strength of composite at 103 cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35–55 °C, tensile strength and Young’s modulus of composite at 103 cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 103 cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin.

  4. Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid) Green Composites during Thermal Cycling.

    Science.gov (United States)

    Katogi, Hideaki; Takemura, Kenichi; Akiyama, Motoki

    2016-07-14

    This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid) (PLA) during thermal cycling. Temperature ranges of thermal cycling tests were 35-45 °C and 35-55 °C. The maximum number of cycles was 10³ cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35-45 °C, tensile strength of composite at 10³ cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35-55 °C, tensile strength and Young's modulus of composite at 10³ cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 10³ cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin.

  5. Tribological properties of thermally sprayed TiAl-Al2O3 composite coating

    Science.gov (United States)

    Salman, A.; Gabbitas, B.; Li, J.; Zhang, D.

    2009-08-01

    The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity oxy fuel (HVOF) thermally sprayed wear resistant TiAl/Al2O3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting. A feedstock of TiAl/Al2O3 composite powder was produced from a mixture of Al and TiO2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity oxy-fuel (HVOF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The results showed that the composite coating has lower wear rate at high temperature (700°C) than the uncoated H13 sample. At Room temperature without using lubricant there is no much significant difference between the wear rate of the coated and uncoated samples. The experimental results showed that the composite coating has great potential for high temperature application due to its lower wear rate at high temperature in comparison with the uncoated sample at the same temperature. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

  6. Tribological properties of thermally sprayed TiAl-Al2O3 composite coating

    International Nuclear Information System (INIS)

    Salman, A; Gabbitas, B; Zhang, D; Li, J

    2009-01-01

    The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity oxy fuel (HVOF) thermally sprayed wear resistant TiAl/Al 2 O 3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting. A feedstock of TiAl/Al 2 O 3 composite powder was produced from a mixture of Al and TiO 2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity oxy-fuel (HVOF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700 deg. C). The results showed that the composite coating has lower wear rate at high temperature (700deg. C) than the uncoated H13 sample. At Room temperature without using lubricant there is no much significant difference between the wear rate of the coated and uncoated samples. The experimental results showed that the composite coating has great potential for high temperature application due to its lower wear rate at high temperature in comparison with the uncoated sample at the same temperature. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

  7. Hot interstellar tunnels. I. Simulation of interacting supernova remnants

    International Nuclear Information System (INIS)

    Smith, B.W.

    1977-01-01

    Reexamining a suggestion of Cox and Smith, we find that intersecting supernova remnants can indeed generate and maintain hot interstellar regions with napproximately-less-than10 -2 cm -3 and Tapprox.10 6 K. These regions are likely to occupy at least 30% of the volume of a spiral arm near the midplane of the gaseous disk if the local supernova rate there is greater than 1.5 x 10 -7 Myr -1 pc -3 . Their presence in the interstellar medium is supported by observations of the soft X-ray background. The theory required to build a numerical simulation of interacting supernova remnants is developed. The hot cavities within a population of remnants will become connected for a variety of assumed conditions in the outer shells of old remnants. Extensive hot cavity regions or tunnels are built and enlarged by supernovae occurring in relatively dense gas which produce connections, but tunnels are kept hot primarily by supernovae occurring within the tunnels. The latter supernovae initiate fast shock waves which apparently reheat tunnels faster than they are destroyed by thermal conduction in a galactic magnetic field or by radiative cooling. However, the dispersal of these rejuvenating shocks over a wide volume is inhibited by motions of cooler interstellar gas in the interval between shocks. These motions disrupt the contiguity of the component cavities of a tunnel and may cause its death.The Monte Carlo simulations indicate that a quasi-equilibrium is reached within 10 7 years of the first supernova in a spiral arm. This equilibrium is characterized by a constant average filling fraction for cavities in the interstellar volume. Aspects of the equilibrium are discussed for a range of supernova rates. Two predictions of Cox and Smith are not confirmed within this range: critical growth of hot regions to encompass the entire medium, and the efficient quenching of a remnant's expansion by interaction with other cavities

  8. Supernovae and neutrinos

    International Nuclear Information System (INIS)

    John F. Beacom

    2002-01-01

    A long-standing problem in supernova physics is how to measure the total energy and temperature of ν μ , ν τ , (bar ν) μ , and (bar ν) τ . While of the highest importance, this is very difficult because these flavors only have neutral-current detector interactions. We propose that neutrino-proton elastic scattering, ν + p → ν + p, can be used for the detection of supernova neutrinos in scintillator detectors. It should be emphasized immediately that the dominant signal is on free protons. Though the proton recoil kinetic energy spectrum is soft, with T p ≅ 2E ν 2 /M p , and the scintillation light output from slow, heavily ionizing protons is quenched, the yield above a realistic threshold is nearly as large as that from (bar ν) e + p → e + + n. In addition, the measured proton spectrum is related to the incident neutrino spectrum. The ability to detect this signal would give detectors like KamLAND and Borexino a crucial and unique role in the quest to detect supernova neutrinos

  9. Thermal behavior of La2O3/Nio composite prepared by sol-gel method

    International Nuclear Information System (INIS)

    Sakallioglu, M.

    2005-01-01

    The La 2 O 3 /NiO composite was prepared by sol-gel method by using transition metal oxides (La 2 O 3 /NiO). The variation of specific heat capacity Cp with temperature for La2O3/NiO composite was investigated by DSC. The heat capacity curve was taken with a heating rate of 20 degrees/min between 0-100 degrees. The variation of specific heat capacity was found by PKI Muse Standard Analysis Program. The thermal stability of the La 2 O 3 /NiO composite was investigated by thermogravimetric analysis (TG) in air atmosphere at a heating rate of 20 degrees/min. The weight loss of La 2 O 3 /NiO composite was determined by the variation of temperature

  10. Effect of organo clay addition on thermal properties of poly lactide/ polycaprolactone (PLA/ PCL) nano composites

    International Nuclear Information System (INIS)

    Siti Zulaiha Hairaldin; Wan Md Zin Wan Yunus; Norazoma Ibrahim

    2010-01-01

    In this study, melt blending technique was applied to prepare poly lactide/polycaprolactone (PLA/ PCL) nano composites with various blends. Montmorillonite (MMT) was used as an addition to the matrix. In this study, melt blending technique was applied to prepare poly lactide/polycaprolactone (PLA/ PCL) nano composites. Montmorillonite (MMT) was used as an addition to the matrix with various percentages. The other one is modified clay prepared by modifying the nature of montmorillonite with octadecylamine (ODA) to improve the characteristic of PLA/ PCL blends. X-ray diffraction (XRD) results indicated intercalation of the PLA/ PCL into silicate nano size interlayers galleries of the nano composites. The presence of modified clays in nano composite was confirmed by FTIR spectrum. TGA and DTG results show addition of MMT and modified clay ODA-MMT improved the thermal stability of the PLA/ PCL blends. (author)

  11. Flammability and thermal properties studies of nonwoven flax reinforced acrylic based polyester composites

    Science.gov (United States)

    Rasyid, M. F. Ahmad; Salim, M. S.; Akil, H. M.; Ishak, Z. A. Mohd.

    2017-12-01

    In the pursuit of green and more sustainable product, natural fibre reinforced composites originating from renewable resources has gained interest in recent years. These natural fibres exhibit good mechanical properties, low production costs, and good environmental properties. However, one of the disadvantages of natural fibre reinforced composites is their high flammability that limits their application in many fields. Within this research, the effect of sodium silicate on the flammability and thermal properties of flax reinforced acrylic based polyester composites has been investigated. Sodium silicate is applied as binder and flame retardant system in impregnation process of the natural flax fiber mats. The addition of sodium silicate significantly improved the flame retardant efficiency but reduced the degree of crosslinking of the composites.

  12. Mechanical and thermal properties of short-coirfiber-reinforced natural rubber/polyethylene composites

    Science.gov (United States)

    Xu, Zh. H.; Kong, Zh. N.

    2014-07-01

    Natural rubber (NR) and polyethylene (PE) composites were compounded with chemically treated coir fibers by using a heated two-roll mill. Two chemical treatments of the fibers — by silane and sodium hydroxide — were carried out to improve the interfacial adhesion between them and the polyethylene matrix. The mechanical properties of the composites obtained were evaluated and compared with those made from a neat polymer and untreated fibers. The mechanical properties of the composites, such as the tensile strength, Young's modulus, and the elongation at break, were examined, and their shrinkage and flame retardant characteristics were measured. From these experiments, the effect of plasma treatment on the mechanical-physical behavior of coconut-fiberreinforced NR/PE composites was identified. In addition, their thermal characteristics were evaluated, and the results showed a slight decrease in them with increasing content of coir fibers.

  13. Thermogravimetric analysis and thermal degradation behaviour of advanced PMR-X carbon fiber composites

    International Nuclear Information System (INIS)

    Rngie, M.

    2003-01-01

    Thermal degradation behavior of sized and unsized carbon fibers in polyimide matrix was investigated. Degradation of neat resin and unidirectional laminates were investigated by thermogravimetric analysis technique at temperatures between 470 d ig C -650 d ig C and up to 250 h rs. Isothermal ageing of the PMR-X composite samples under different test conditions (i. e. different temperatures and prolonged aging times), showed that oxidation and degradation occurs in stage three different rates. Thermogravimetric analysis showed that the cured PMR-X composite panels are more stable in an inert atmosphere (nitrogen atmosphere)than in air and the degradation of neat resin is much higher than the composite samples. However, the rate of degradation of the unsized untreated carbon fibers in nitrogen environment is much higher than that for the PMR-X composites containing sized fibers

  14. Synthesis and Thermal Conductivity of Exfoliated Hexagonal Boron Nitride/Alumina Ceramic Composite

    Science.gov (United States)

    Hung, Ching-cheh; Hurst, Janet; Santiago, Diana; Lizcano, Maricela; Kelly, Marisabel

    2017-01-01

    Exfoliated hexagonal boron nitride (hBN)/alumina composite can be fabricated by following the process of (1) heating a mixture of hBN, AlCl3, and NaF in nitrogen for intercalation; (2) heating the intercalated product in air for exfoliation and at the same time converting the intercalate (AlCl3) into Al2O3, (3) rinsing the oxidized product, (4) coating individual exfoliated hBN platelets that contain Al2O3 with new layers of aluminum oxide, and finally, (5) hot pressing the product into the composite. The composite thus obtained has a composition of approximately 60 percent by weight hBN and 40 percent by weight alumina. Its in-plane and through-plane thermal conductivity were measured to be 86 and 18 watts per meter Kelvin, respectively, at room temperature.

  15. Thermal and mechanical behaviour of sub micron sized fly ash reinforced polyester resin composite

    Science.gov (United States)

    Nantha Kumar, P.; Rajadurai, A.; Muthuramalingam, T.

    2018-04-01

    The utilization of particles reinforced resin matrix composites is being increased owing to its lower density and high strength to weight ratio. In the present study, an attempt has been made to synthesize fly ash particles reinforced polyester resin composite for engine cowling application. The thermal stability and mechanical behaviours such as hardness and flexural strength of the composite with 2, 3 and 4 weight % of reinforcement is studied and analyzed. The thermo gravimetric analysis indicates that the higher addition of reinforcement increases the decomposition temperature due to its refractory nature. It is also observed that the hardness increases with higher filler addition owing to the resistance of FA particles towards penetration. The flexural strength is found to increase up to the addition of 3% of FA particles, whereas the polyester resin composite prepared with 4% FA particles addition is observed to have low flexural strength owing to agglomeration of particles.

  16. Enhanced thermal and mechanical properties of epoxy composites by mixing thermotropic liquid crystalline epoxy grafted graphene oxide

    Directory of Open Access Journals (Sweden)

    B. Qi

    2014-07-01

    Full Text Available Graphene oxide (GO sheets were chemically grafted with thermotropic liquid crystalline epoxy (TLCP. Then we fabricated composites using TLCP-g-GO as reinforcing filler. The mechanical properties and thermal properties of composites were systematically investigated. It is found that the thermal and mechanical properties of the composites are enhanced effectively by the addition of fillers. For instance, the composites containing 1.0 wt% of TLCP-g-GO present impact strength of 51.43 kJ/m2, the tensile strength of composites increase from 55.43 to 80.85 MPa, the flexural modulus of the composites increase by more than 48%. Furthermore, the incorporation of fillers is effective to improve the glass transition temperature and thermal stability of the composites. Therefore, the presence of the TLCP-g-GO in the epoxy matrix could make epoxy not only stronger but also tougher.

  17. Thermal and Electrical Characterization of the Carbon Nanofibers Based Cement Composites

    Directory of Open Access Journals (Sweden)

    Agnieszka ŚLOSARCZYK

    2017-08-01

    Full Text Available The paper describes the influence of chemical modification of vapor grown carbon nanofibers (VGCnFs on the thermal and electrical properties of the cement composites. The surface modification of nanofibers was performed by means of ozone and nitric acid treatments. It was shown that the oxidized carbon nanofibers surface plays an important role in shaping the mechanical and especially electrical properties of cement composite. For cement matrix modified with carbon nanofibers subjected to oxidized treatment, the slightly increase of cement paste resistivity was observed. It confirms the better adhesion of carbon nanofibers to cement paste. However, independently of carbon nanofibers modification, the occurrence of VGCnFs in cement paste increased the electrical conductivity of the composite in comparison to the cement paste without fibers. The obtained values of electrical resistivity were comparable with values of cement composites modified with 4 mm long carbon fibers. Moreover, it was shown that the chemical modification of carbon nanofibers surface does not influence on the thermal properties of cement composites. In case of cement paste with unmodified and modified carbon nanofibers, the Seebeck voltage was proportional to the temperature difference and was independent of the oxidation degree of carbon nanofibers.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.14993

  18. Date palm biochar-polymer composites: An investigation of electrical, mechanical, thermal and rheological characteristics.

    Science.gov (United States)

    Poulose, Anesh Manjaly; Elnour, Ahmed Yagoub; Anis, Arfat; Shaikh, Hamid; Al-Zahrani, S M; George, Justin; Al-Wabel, Mohammad I; Usman, Adel R; Ok, Yong Sik; Tsang, Daniel C W; Sarmah, Ajit K

    2018-04-01

    The application of biochar (BC) as a filler in polymers can be viewed as a sustainable approach that incorporates pyrolysed waste based value-added material and simultaneously mitigate bio-waste in a smart way. The overarching aim of this work was to investigate the electrical, mechanical, thermal and rheological properties of biocomposite developed by utilizing date palm waste-derived BC for the reinforcing of polypropylene (PP) matrix. Date palm waste derived BC prepared at (700 and 900°C) were blended at different proportions with polypropylene and the resultant composites (BC/PP) were characterized using an array of techniques (scanning electron microscope, energy-dispersive X-ray spectroscopy and Fourier transform infra-red spectroscopy). Additionally the thermal, mechanical, electrical and rheological properties of the BC/PP composites were evaluated at different loading of BC content (from 0 to15% w/w). The mechanical properties of BC/PP composites showed an improvement in the tensile modulus while that of electrical characterization revealed an enhanced electrical conductivity with increased BC loading. Although the BC incorporation into the PP matrix has significantly reduced the total crystallinity of the resulted composites, however; a positive effect on the crystallization temperature (T c ) was observed. The rheological characterization of BC/PP composites revealed that the addition of BC had minimal effect on the storage modulus (G') compared to the neat (PP). Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Efficacy of Thermally Conditioned Sisal FRP Composite on the Shear Characteristics of Reinforced Concrete Beams

    Directory of Open Access Journals (Sweden)

    Tara Sen

    2013-01-01

    Full Text Available The development of commercially viable composites based on natural resources for a wide range of applications is on the rise. Efforts include new methods of production and the utilization of natural reinforcements to make biodegradable composites with lignocellulosic fibers, for various engineering applications. In this work, thermal conditioning of woven sisal fibre was carried out, followed by the development of woven sisal fibre reinforced polymer composite system, and its tensile and flexural behaviour was characterized. It was observed that thermal conditioning improved the tensile strength and the flexural strength of the woven sisal fibre composites, which were observed to bear superior values than those in the untreated ones. Then, the efficacy of woven sisal fibre reinforced polymer composite for shear strengthening of reinforced concrete beams was evaluated using two types of techniques: full and strip wrapping techniques. Detailed analysis of the load deflection behaviour and fracture study of reinforced concrete beams strengthened with woven sisal under shearing load were carried out, and it was concluded that woven sisal FRP strengthened beams, underwent very ductile nature of failure, without any delamination or debonding of sisal FRP, and also increased the shear strength and the first crack load of the reinforced concrete beams.

  20. Thermal conductivity and latent heat thermal energy storage properties of LDPE/wax as a shape-stabilized composite phase change material

    International Nuclear Information System (INIS)

    Trigui, Abdelwaheb; Karkri, Mustapha; Krupa, Igor

    2014-01-01

    Highlights: • This study deals with the comparison of experimental results for different PCM composite to be used in passive solar walls. • This paper reports on the successful use of a specific experimental method in order to characterize the phase change effects. • The results have shown that most important thermal properties of these composites at the solid and liquid states. • Results indicate the thermal effectiveness of phase change material and significant amount of energy saving can be achieved. • Heat flux measurements are a very interesting experimental source of data which comes to complete the calorimetric device (DSC). - Abstract: Phase change material (PCM) composites based on low-density polyethylene (LDPE) with paraffin waxes were investigated in this study. The composites were prepared using a meltmixing method with a Brabender-Plastograph. The LDPE as the supporting matrix kept the molten waxes in compact shape during its phase transition from solid to liquid. Immiscibility of the PCMs (waxes) and the supporting matrix (LDPE) is a necessary property for effective energy storage. Therefore, this type paraffin can be used in a latent heat storage system without encapsulation. The objective of this research is to use PCM composite as integrated components in a passive solar wall. The proposed composite TROMBE wall allows daily storage of the solar energy in a building envelope and restitution in the evening, with a possible control of the air flux in a ventilated air layer. An experimental set-up was built to determine the thermal response of these composites to thermal solicitations. In addition, a DSC analysis was carried out. The results have shown that most important thermal properties of these composites at the solid and liquid states, like the “apparent” thermal conductivity, the heat storage capacity and the latent heat of fusion. Results indicate the performance of the proposed system is affected by the thermal effectiveness of

  1. Operating modes of high-Tc composite superconductors and thermal runaway conditions under current charging

    International Nuclear Information System (INIS)

    Romanovskii, V R; Watanabe, K

    2006-01-01

    The operating thermal and electric modes of a high-T c superconducting composite in partially and fully penetrated states induced by the charging current are investigated. They were studied under conditions in which the current charging rate, the volume fraction of the superconductor in a composite or the temperature of the cooling bath were changed. The transient behaviour of the voltage-current dependence, which is characteristic during stable and unstable increases in electric field inside the composite under a continuous current charging, is discussed. Simulations were done using zero- and one-dimensional steady and unsteady thermoelectric models with a power equation describing the virgin voltage-current characteristic of a superconductor. It is found that some thermoelectric trends underlie the shape of the voltage-current characteristic of the high-T c superconducting composite. These have to be considered during experiments in which the critical or quench currents are defined. First, in the initial stage of the fully penetrated regime (in the low voltage range), the electric field distribution does not have a uniform character. These states depend on the volume fraction of the superconductor and the current charging rate: the higher these quantities, the higher the heterogeneity of the electric field. Second, during the stable over-critical regime (in the high voltage range) occurring in complete penetration modes, the evolution of the electric field may depend on the relevant temperature increase of a composite according to the corresponding increase in its temperature-dependent heat capacity. Consequently, the shape of the voltage-current characteristic of a composite high-T c superconductor during continuous current charging, both before and after thermal runaway, has only a positive slope. Moreover, it is proved that the growth of the fully penetrated part of the voltage-current characteristic becomes less intensive when the current charging rate or the

  2. The relationship between fatty acid compositions and thermal stability of extra virgin olive oils

    OpenAIRE

    Fayegh Moulodi; Peyman Qajarbeigi; Ashraf Haj Hosseini Babaei; Asghar Mohammadpoor Asl

    2014-01-01

    Background: Fatty acids are one of the most important compounds in edible oils. Further, the stability of oils depends on the composition of fatty acids. So, this study was conducted to investigate the effect of fatty acid composition on the oxidative stability of extra virgin olive oils during the heating process. Methods: In total, eight samples of extra virgin olive oil were studied. To evaluate their thermal stability, the oils were heated at 120 ° C for 4 h and sampling was carried o...

  3. Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

    Science.gov (United States)

    Geohegan, David B [Knoxville, TN; Ivanov, Ilya N [Knoxville, TN; Puretzky, Alexander A [Knoxville, TN

    2010-07-27

    Methods and apparatus are described for fabrication of high thermal conductivity arrays of carbon nanotubes and their composites. A composition includes a vertically aligned nanotube array including a plurality of nanotubes characterized by a property across substantially all of the vertically aligned nanotube array. A method includes depositing a vertically aligned nanotube array that includes a plurality of nanotubes; and controlling a deposition rate of the vertically aligned nanotubes array as a function of an in situ monitored property of the plurality of nanotubes.

  4. THE INFLUENCE OF ECOLOGICAL MATERIALS EMBEDDED INTO COMPOSITES UPON THE THERMAL INSULATING CAPACITY

    Directory of Open Access Journals (Sweden)

    Luminiţa-Maria BRENCI

    2014-12-01

    Full Text Available The paper presents the results of a research performed in order to design and manufacture composites that embed in their structure ecological raw materials, such as wood chips and hemp hurds. The thermal conductivity was determined for a temperature difference (ΔT of 200 C between the cold plate and warm plate and the measurements were done in eight points. The results showed that the best insulating composite material was obtained for the structure containing equal shares of wood chips and chopped hemp

  5. RESEARCH ON THE THERMAL CONDUCTIVITY OF COMPOSITES MADE OF ECOLOGICAL FIBERS

    Directory of Open Access Journals (Sweden)

    Maria-Luminita BRENCI, Camelia COSEREANU, Adriana FOTIN, Alexandru VASILACHE

    2013-09-01

    Full Text Available The paper presents the results of the researchconducted to obtain new ecological composites thatcould be used for thermal insulation of buildings. Theobtained panels are made of ecological materials thatdo not affect the human health (wood chips andfibers, host of hemp, textile fibers, wool and reed.The testing was performed in eight points, for aninternal temperature of T=200C and an outdoortemperature situated in the range of -200C÷200C. Asthe tests conducted, the results showed that the bestinsulating capacity belonged to a composite whichhas wood fiber and wool in its structure, followed acomposite which has wood chips, hemp particles andwool in its structure.

  6. Concurrent design of composite materials and structures considering thermal conductivity constraints

    Science.gov (United States)

    Jia, J.; Cheng, W.; Long, K.

    2017-08-01

    This article introduces thermal conductivity constraints into concurrent design. The influence of thermal conductivity on macrostructure and orthotropic composite material is extensively investigated using the minimum mean compliance as the objective function. To simultaneously control the amounts of different phase materials, a given mass fraction is applied in the optimization algorithm. Two phase materials are assumed to compete with each other to be distributed during the process of maximizing stiffness and thermal conductivity when the mass fraction constraint is small, where phase 1 has superior stiffness and thermal conductivity whereas phase 2 has a superior ratio of stiffness to density. The effective properties of the material microstructure are computed by a numerical homogenization technique, in which the effective elasticity matrix is applied to macrostructural analyses and the effective thermal conductivity matrix is applied to the thermal conductivity constraint. To validate the effectiveness of the proposed optimization algorithm, several three-dimensional illustrative examples are provided and the features under different boundary conditions are analysed.

  7. Control of internal and external short circuits in lithium batteries using a composite thermal switch

    Science.gov (United States)

    Mcdonald, Robert C.; Pickett, Jerome; Goebel, Franz

    1991-01-01

    A composite material has been developed, consisting of a blend of metal and fluorocarbon particles, which behaves as an electronic conductor at room temperature and which abruptly becomes an insulator at a predetermined temperature. This switching behavior results from the difference in thermal expansion coefficients between the conductive and non-conductive portions of the composite. This material was applied as a thin film between the carbon cathode in Li/SOCl2 cells, and the metallic cathode current collector. Using test articles incorporating this feature it was shown that lithium cells externally heated or internally heated during a short circuit lost rate capability and the ability to overheat well below the melting point of lithium (180 C). Thus, during an internal or external cell short circuit, the potential for thermal runaway involving reactions of molten lithium is avoided.

  8. Enhanced thermal and mechanical properties of PVA composites formed with filamentous nanocellulose fibrils.

    Science.gov (United States)

    Li, Wei; Wu, Qiong; Zhao, Xin; Huang, Zhanhua; Cao, Jun; Li, Jian; Liu, Shouxin

    2014-11-26

    Long filamentous nanocellulose fibrils (NCFs) were prepared from chemical-thermomechanical pulps (CTMP) using ultrasonication. Their contribution to enhancements in thermal stability and mechanical properties of poly(vinyl alcohol) films were investigated. The unique chemical pretreatment and mechanical effects of CTMP loosen and unfold fibers during the pulping process, which enables further chemical purification and subsequent ultrasound treatment for formation of NCFs. The NCFs exhibited higher crystallinity (72.9%) compared with that of CTMP (61.5%), and had diameters ranging from 50 to 120 nm. A NCF content of 6 wt% was found to yield the best thermal stability, light transmittance, and mechanical properties in the PVA/NCF composites. The composites also exhibited a visible light transmittance of 73.7%, and the tensile strength and Young's modulus were significantly improved, with values 2.8 and 2.4 times larger, respectively, than that of neat PVA. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Preparation and thermal energy storage properties of paraffin/calcined diatomite composites as form-stable phase change materials

    International Nuclear Information System (INIS)

    Sun, Zhiming; Zhang, Yuzhong; Zheng, Shuilin; Park, Yuri; Frost, Ray L.

    2013-01-01

    Highlights: ► Composite phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite. ► The optimum mixed proportion was obtained through differential scanning calorimetry. ► Thermal energy storage properties of the composite PCMs were determined by DSC. ► Thermal cycling test showed that the prepared PCMs are thermally reliable and chemically stable. - Abstract: A composite paraffin-based phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite through the fusion adsorption method. In this study, raw diatomite was purified by thermal treatment in order to improve the adsorption capacity of diatomite, which acted as a carrier material to prepare shape-stabilized PCMs. Two forms of paraffin (paraffin waxes and liquid paraffin) with different melting points were blended together by the fusion method, and the optimum mixed proportion with a suitable phase-transition temperature was obtained through differential scanning calorimetry (DSC) analysis. Then the prepared composite paraffin was adsorbed in calcined diatomite. The prepared paraffin/calcined diatomite composites were characterized by the scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by DSC method. DSC results showed that there was an optimum adsorption ratio between composite paraffin and calcined diatomite and the phase-transition temperature and the latent heat of the composite PCMs were 33.04 °C and 89.54 J/g, respectively. Thermal cycling test of composite PCMs showed that the prepared material is thermally reliable and chemically stable. The obtained paraffin/calcined diatomite composites have proper latent heat and melting temperatures, and show practical significance and good potential application value

  10. Preparation and thermal energy storage properties of paraffin/calcined diatomite composites as form-stable phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Zhiming [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia); Zhang, Yuzhong [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Zheng, Shuilin, E-mail: shuilinzh@yahoo.com.cn [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Park, Yuri [Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia); Frost, Ray L., E-mail: r.frost@qut.edu.au [Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia)

    2013-04-20

    Highlights: ► Composite phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite. ► The optimum mixed proportion was obtained through differential scanning calorimetry. ► Thermal energy storage properties of the composite PCMs were determined by DSC. ► Thermal cycling test showed that the prepared PCMs are thermally reliable and chemically stable. - Abstract: A composite paraffin-based phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite through the fusion adsorption method. In this study, raw diatomite was purified by thermal treatment in order to improve the adsorption capacity of diatomite, which acted as a carrier material to prepare shape-stabilized PCMs. Two forms of paraffin (paraffin waxes and liquid paraffin) with different melting points were blended together by the fusion method, and the optimum mixed proportion with a suitable phase-transition temperature was obtained through differential scanning calorimetry (DSC) analysis. Then the prepared composite paraffin was adsorbed in calcined diatomite. The prepared paraffin/calcined diatomite composites were characterized by the scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by DSC method. DSC results showed that there was an optimum adsorption ratio between composite paraffin and calcined diatomite and the phase-transition temperature and the latent heat of the composite PCMs were 33.04 °C and 89.54 J/g, respectively. Thermal cycling test of composite PCMs showed that the prepared material is thermally reliable and chemically stable. The obtained paraffin/calcined diatomite composites have proper latent heat and melting temperatures, and show practical significance and good potential application value.

  11. Controlled High Filler Loading of Functionalized Al2O3-Filled Epoxy Composites for LED Thermal Management

    Science.gov (United States)

    Permal, Anithambigai; Devarajan, Mutharasu; Hung, Huong Ling; Zahner, Thomas; Lacey, David; Ibrahim, Kamarulazizi

    2018-03-01

    Thermal management in light-emitting diode (LED) has been extensively researched recently. This study is intended to develop an effective thermally conductive epoxy composite as thermal interface material (TIM) for headlamp LEDs. Silane-functionalized aluminum oxide (Al2O3) powder of different average particle sizes (44 and 10 µm) was studied for its feasibility as filler at its maximum loading. A detailed comparison of three different methods of particle dispersions, hand-mix, speed-mix and calendaring process (3-roll mill), has been reported. The dispersion of Al2O3 particles, the thermal conductivity and thermal degradation characteristics of the composites were investigated and explained in detail. At 75 wt.% filler loading, 10 and 44 µm Al2O3 achieved composite thermal conductivities of 1.13 and 2.08 W/mK, respectively, which is approximately 528 and 1055% of enhancement with respect to neat epoxy. The package-level thermal performance of the LED employing the Al2O3-filled TIMs was carried out using thermal transient analysis. The experimental junction-to-ambient thermal resistances ( R thJ-A) achieved were 6.65, 7.24, and 8.63 K/W for Al2O3_44µm, Al2O3_10µm and neat epoxy, respectively. The results revealed that the Al2O3_44µm fillers-filled composite performed better in both material-level and package-level thermal characteristics.

  12. New composites graphite/salt for high temperature thermal energy storage: From elaboration to development of thermal characterization methods for orthotropic conductive materials

    International Nuclear Information System (INIS)

    Acem, Zoubir

    2007-01-01

    This PhD is carried out within the framework of DISTOR (European) and HTPSTOCK (French) projects, which have for objective to conceive and study new graphite/salt composites dedicated to high temperature energy storage (>200 deg. C). She is split into two distinct part. The first one focused mainly on works linked with elaboration and thermal characterisation of these new composites. The different composites ways of elaboration (Dispersion, uniaxial compression, isostatic) associated to the different kind of graphite (Natural expanded graphite (ENG), synthetic graphite) investigated during the PhD are presented. The results of the thermal characterization campaign of these composites are also presented and permit to highlight the impact of graphite in the thermal behaviour of studied materials. Based on these results, modelling studies of the evolution of the thermal conductivity have been undertaken to deepen the understanding of the effect of graphite (quantity, size of particles) on the effective conductivity composites. The second one describes the thermal characterization devices and associated thermo-kinetics models which had to be developed and adapted to the specificities of newly developed materials. This concerns mainly the materials prepared by compression, which present orthotropic properties and are difficult to reproduce. So, the characterization of this kind of material is very difficult and tedious. That is why we are committed to develop and adapt existing methods of characterization to allow the complete thermal characterisation of an orthotropic conductive material from a single experimentation on a single sample. (author) [fr

  13. A reconstruction of Maxwell model for effective thermal conductivity of composite materials

    International Nuclear Information System (INIS)

    Xu, J.Z.; Gao, B.Z.; Kang, F.Y.

    2016-01-01

    Highlights: • Deficiencies were found in classical Maxwell model for effective thermal conductivity. • Maxwell model was reconstructed based on potential mean-field theory. • Reconstructed Maxwell model was extended with particle–particle contact resistance. • Predictions by reconstructed Maxwell model agree excellently with experimental data. - Abstract: Composite materials consisting of high thermal conductive fillers and polymer matrix are often used as thermal interface materials to dissipate heat generated from mechanical and electronic devices. The prediction of effective thermal conductivity of composites remains as a critical issue due to its dependence on considerably factors. Most models for prediction are based on the analog between electric potential and temperature that satisfy the Laplace equation under steady condition. Maxwell was the first to derive the effective electric resistivity of composites by examining the far-field spherical harmonic solution of Laplace equation perturbed by a sphere of different resistivity, and his model was considered as classical. However, a close review of Maxwell’s derivation reveals that there exist several controversial issues (deficiencies) inherent in his model. In this study, we reconstruct the Maxwell model based on a potential mean-field theory to resolve these issues. For composites made of continuum matrix and particle fillers, the contact resistance among particles was introduced in the reconstruction of Maxwell model. The newly reconstructed Maxwell model with contact resistivity as a fitting parameter is shown to fit excellently to experimental data over wide ranges of particle concentration and mean particle diameter. The scope of applicability of the reconstructed Maxwell model is also discussed using the contact resistivity as a parameter.

  14. Lamb Wave Stiffness Characterization of Composites Undergoing Thermal-Mechanical Aging

    Science.gov (United States)

    Seale, Michael D.; Madaras, Eric I.

    2004-01-01

    The introduction of new, advanced composite materials into aviation systems requires a thorough understanding of the long term effects of combined thermal and mechanical loading upon those materials. Analytical methods investigating the effects of intense thermal heating combined with mechanical loading have been investigated. The damage mechanisms and fatigue lives were dependent on test parameters as well as stress levels. Castelli, et al. identified matrix dominated failure modes for out-of-phase cycling and fiber dominated damage modes for in-phase cycling. In recent years, ultrasonic methods have been developed that can measure the mechanical stiffness of composites. To help evaluate the effect of aging, a suitably designed Lamb wave measurement system is being used to obtain bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system works by exciting an antisymmetric Lamb wave and calculating the velocity at each frequency from the known transducer separation and the measured time-of-flight. The same peak in the waveforms received at various distances is used to measure the time difference between the signals. The velocity measurements are accurate and repeatable to within 1% resulting in reconstructed stiffness values repeatable to within 4%. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. A mechanical scanner is used to move the sensors over the surface to map the time-of-flight, velocity, or stiffnesses of the entire specimen. Access to only one side of the material is required and no immersion or couplants are required because the sensors are dry coupled to the surface of the plate. In this study, the elastic stiffnesses D(sub 11), D(sub 22), A(sub 44), and A(sub 55) as well as time-of-flight measurements for composite samples that have undergone combined thermal and mechanical aging for

  15. Electro-Thermal Transport in Nanotube Based Composites for Macroelectronic Applications

    OpenAIRE

    Kumar, Satish

    2007-01-01

    Dispersions of particles of different shapes and sizes in fluids or solids modify the transport properties of the underlying matrix. A remarkable enhancement in the electrical, thermal and other transport properties of the matrix due to the long aspect ratio dispersions like nanotube/nanowires has been observed my many research groups. This has motivated tremendous research to explore these composites for various macro-electronic and micro-electronic applications in the last decade. Carbon na...

  16. Lasing and thermal characteristics of Yb:YAG/YAG composite with atomic diffusion bonding

    Czech Academy of Sciences Publication Activity Database

    Nagisetty, Siva S.; Severová, Patricie; Miura, Taisuke; Smrž, Martin; Kon, H.; Uomoto, M.; Shimatsu, T.; Kawasaki, M.; Higashiguchi, T.; Endo, Akira; Mocek, Tomáš

    2017-01-01

    Roč. 14, č. 1 (2017), 1-6, č. článku 015001. ISSN 1612-2011 R&D Projects: GA MŠk LM2015086; GA MŠk LO1602 Institutional support: RVO:68378271 Keywords : composite Yb:YAG ceramic * atomic diffusion bonding * thermal effects Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 2.537, year: 2016

  17. Productivity and species composition of algal mat communities exposed to a fluctuating thermal regime

    International Nuclear Information System (INIS)

    Tison, D.L.; Wilde, E.W.; Pope, D.H.; Fliermans, C.B.

    1981-01-01

    Algal mat communities growing in thermal effluents of production nuclear reactors at the Savannah River Plant, near Aiken, SC, are exposed to large temperature fluctuations resulting from reactor operations. Rates of primary production and species composition were monitored at 4 sites along a thermal gradient in a trough microcosm to determine how these large temperature fluctuations affected productivity and algal community structure. Blue-green algae (cyanobacteria) were the only phototrophic primary producers growing in water above 45 0 C. These thermophiles were able to survive and apparently adapt to ambient temperatures when the reactor was shut down. The algal mat communities exposed to 14 C-labeled dissolved organic compounds and a decrease in primary production were observed during periods of thermal fluctuation. The results show that the dominant phototrophs in this artificially heated aquatic habitat have been selected for their abiity to survive large temperature fluctuations and are similar to those of natural hot springs

  18. Mechanical and thermal properties of basalt fiber reinforced poly(butylene succinate) composites

    International Nuclear Information System (INIS)

    Zhang Yihe; Yu Chunxiao; Chu, Paul K.; Lv Fengzhu; Zhang Changan; Ji Junhui; Zhang Rui; Wang Heli

    2012-01-01

    Highlights: ► Novel basalt fiber-reinforced biodegradable poly(butylene succinate) composites have been successfully fabricated with various fiber loadings. ► The tensile and flexural properties of the PBS matrix resin are improved significantly by increasing the fiber loading in the composites. ► The impact strength of the BF/PBS composite decreases with the addition fibers primarily and increases with increasing fiber loading due to energy dissipation when the fibers are pulled out. ► Heat deflection temperature tests clearly show that the HDT of the basalt fiber reinforced PBS composites is significantly higher than the HDT of the PBS resin. - Abstract: Basalt fiber (BF) reinforced poly(butylene succinate) (PBS) composites have been fabricated with different fiber contents by a injection molding method and their tensile, flexural and impact properties, as well as thermal stability have been investigated. The tensile and flexural properties of the PBS matrix resin are improved markedly by increasing the fiber contents in the composites. The values are relatively higher than the natural fiber/PP systems reported earlier by other research groups. The heat deflection temperature (HDT) and Vicat softening temperature (VST) of the composites are significantly higher than those of the neat PBS resin. Scanning electron microscopy (SEM) conducted on the fracture surfaces of the composites reveals superior interfacial linkage between the basalt fibers and PBS matrix. The results suggest that the BF/PBS composites may be a potential candidate of PP or PP composites to manufacturing some daily commodities to solve the “white pollution” in environmental management.

  19. Flexural behavior and design of steel-plate composite (SC) walls for accident thermal loading

    Energy Technology Data Exchange (ETDEWEB)

    Booth, Peter N., E-mail: boothpn@purdue.edu [Lyles School of Civil Engineering, Purdue University, West Lafayette, IN (United States); Varma, Amit H., E-mail: ahvarma@purdue.edu [Lyles School of Civil Engineering, Purdue University, West Lafayette, IN (United States); Sener, Kadir C., E-mail: ksener@purdue.edu [Lyles School of Civil Engineering, Purdue University, West Lafayette, IN (United States); Malushte, Sanjeev R. [Bechtel Corp., Frederick, MD (United States)

    2015-12-15

    Modular steel-plate composite (SC) safety-related nuclear power plant structures must be designed to resist accident thermal and mechanical loads. The design accident thermal load represents the condition where high pressure and temperature steam is released as result of a mechanical failure and applied against the surfaces of power plant structural walls. The effect of heating and pressure can have both short and long term effects on the mechanical integrity of SC structures including degradation and cracking of concrete infill, residual stresses, and out-of-plane deformations. The purpose of this research is to study the effects of thermal and mechanical loads on the out-of-plane flexural response of SC walls and to develop simplified equations that can be used to predict behavior. Four experimental beam tests are reported that represent full-scale cross-sections of SC walls subjected to combinations of mechanical and thermal loads. The study determined that thermal loads reduce the out-of-plane flexural stiffness of SC walls. For the ambient condition, the flexural stiffness closely matches a conventional elastic cracked-transformed model, and at elevated temperatures, the stiffness is reduced to a fully-cracked flexural stiffness that only takes into account the stiffness of the steel faceplates. A method is presented for estimating the thermal curvature, ϕ{sub th}, and thermal moment, M{sub th}, resulting from unequal heating of opposing faces of an SC wall. Based on the tests in this study, the application of accident thermal loads did not result in a reduction of the flexural strength of the SC section.

  20. Thermal and Nonthermal Emissions of a Composite Flare Derived from NoRH and SDO Observations

    Science.gov (United States)

    Lee, Jeongwoo; White, Stephen M.; Jing, Ju; Liu, Chang; Masuda, Satoshi; Chae, Jongchul

    2017-12-01

    Differential emission measure (DEM) derived from the extreme ultraviolet (EUV) lines of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory is used in the analysis of a solar flare observed by the Nobeyama Radioheliograph (NoRH). The target was a composite event consisting of an impulsive flare, SOL2015-06-21T01:42 (GOES class M2.0), and a gradual flare, SOL2015-06-21T02:36 (M2.6), for which separation of thermal plasma heating from nonthermal particle acceleration was of major interest. We have calculated the thermal free-free intensity maps with the AIA-derived DEM and compared them against the observed NoRH maps to attribute the difference to the nonthermal component. In this way, we were able to locate three distinct sources: the major source with thermal and nonthermal components mixed, a nonthermal source devoid of thermal particles, and a thermal source lacking microwave emission. Both the first and the second nonthermal sources produced impulsively rising 17 GHz intensities and moved away from the local magnetic polarization inversion lines in correlation with the flare radiation. In contrast, the thermal sources stay in fixed locations and show temporal variations of the temperature and emission measure uncorrelated with the flare radiation. We interpret these distinct properties as indicating that nonthermal sources are powered by magnetic reconnection and thermal sources passively receive energy from the nonthermal donor. The finding of these distinct properties between thermal and nonthermal sources demonstrates the microwave and EUV emission measure combined diagnostics.

  1. Thermal Conductivity of Structural Glass/Fibre Epoxy Composite as a Function of Fibre Orientation

    CERN Document Server

    Cugnet, D; Kuijper, A; Parma, Vittorio; Vandoni, Giovanna

    2002-01-01

    The LHC, the new superconducting particle accelerator presently under construction at CERN, makes use of some 1200 dipole magnets for orbit bending and 500 quadrupole magnets for focusing/defocusing of the circulating high-energy proton beams. Two or three column-type support posts sustain each cryomagnet. The choice of a convenient material for these supports is critical, because of the required high positioning accuracy of the magnets in their cryostats and stringent thermal budget requirements imposed by the LHC cryogenic system. A glass-fibre/epoxy resin composite has been chosen for its good combination of high stiffness and low thermal conductivity over the 2-293 K temperature range. Plies of long glass-fibres are stacked optimally yielding the best mechanical behaviour. However, heat leaks from the supports are influenced by the thermal characteristics of the composite, which in turn depend on the orientation of the fibres. To study the dependence of the thermal conductivity on fibre's orientation, we ...

  2. Correlation between thermal behavior of clays and their chemical and mineralogical composition: a review

    Science.gov (United States)

    Dwi Yanti, Evi; Pratiwi, I.

    2018-02-01

    Clay's abundance has been widely used as industrial raw materials, especially ceramic and tile industries. Utilization of these minerals needs a thermal process for producing ceramic products. Two studies conducted by Septawander et al. and Chin C et al., showed the relationship between thermal behavior of clays and their chemical and mineralogical composition. Clays are characterized by XRD analysis and thermal analysis, ranging from 1100°C to 1200°C room temperature. Specimen of raw materials of clay which is used for the thermal treatment is taken from different geological conditions and formation. In raw material, Quartz is almost present in all samples. Halloysite, montmorillonite, and feldspar are present in Tanjung Morawa raw clay. KC and MC similar kaolinite and illite are present in the samples. The research illustrates the interrelationships of clay minerals and chemical composition with their heat behavior. As the temperature of combustion increases, the sample reduces a significant weight. The minerals which have undergone a transformation phase became mullite, cristobalite or illite and quartz. Under SEM analysis, the microstructures of the samples showed irregularity in shape; changes occurred due the increase of heat.

  3. Thermal transport in binary colloidal glasses: Composition dependence and percolation assessment

    Science.gov (United States)

    Ruckdeschel, Pia; Philipp, Alexandra; Kopera, Bernd A. F.; Bitterlich, Flora; Dulle, Martin; Pech-May, Nelson W.; Retsch, Markus

    2018-02-01

    The combination of various types of materials is often used to create superior composites that outperform the pure phase components. For any rational design, the thermal conductivity of the composite as a function of the volume fraction of the filler component needs to be known. When approaching the nanoscale, the homogeneous mixture of various components poses an additional challenge. Here, we investigate binary nanocomposite materials based on polymer latex beads and hollow silica nanoparticles. These form randomly mixed colloidal glasses on a sub-μ m scale. We focus on the heat transport properties through such binary assembly structures. The thermal conductivity can be well described by the effective medium theory. However, film formation of the soft polymer component leads to phase segregation and a mismatch between existing mixing models. We confirm our experimental data by finite element modeling. This additionally allowed us to assess the onset of thermal transport percolation in such random particulate structures. Our study contributes to a better understanding of thermal transport through heterostructured particulate assemblies.

  4. Effect of composition on thermal conductivity of MgO–Nd2Zr2O7 composites for inert matrix materials

    International Nuclear Information System (INIS)

    Nelson, A.T.; Giachino, M.M.; Nino, J.C.; McClellan, K.J.

    2014-01-01

    Inert matrix fuels based on magnesium oxide (MgO) as the inert phase have been of historic interest due to its high thermal conductivity. Minor actinide-bearing phases possessing an A 2 B 2 O 7 pyrochlore structure are also believed to contain a range of favorable attributes, suggesting a possible pairing with MgO to yield a high performance inert matrix fuel. The thermal diffusivity, heat capacity, and thermal expansion of MgO–Nd 2 Zr 2 O 7 composites were measured from room temperature to 1273 K, where the MgO phase content was varied from 40 to 70 volume percent. The thermal conductivity of each composition was calculated using these results and then compared to widely employed methods to approximate the thermal conductivity of composite materials based upon the properties of the constituent phases. Results suggest that use of either a rule of mixtures or geometric mean approximation for the thermal conductivity of composite systems such as this one would be subject to significant uncertainties when the constituent properties widely differ. A sigmoidal average of the upper and lower Hashin–Shtrikman bounds was found to be in good agreement with the thermal conductivity of the composites as determined experimentally

  5. Influence of thermal cycling on flexural properties of composites reinforced with unidirectional silica-glass fibers.

    Science.gov (United States)

    Meriç, Gökçe; Ruyter, I Eystein

    2008-08-01

    The purpose was to investigate the effect of water storage and thermal cycling on the flexural properties of differently sized unidirectional fiber-reinforced composites (FRCs) containing different quantities of fibers. The effect of fiber orientation on the thermal expansion of FRCs as well as how the stresses in the composites can be affected was considered. An experimental polymeric base material was reinforced with silica-glass fibers. The cleaned and silanized fibers were sized with either linear PBMA-size or crosslinked PMMA-size. For the determination of flexural properties and water uptake, specimens were processed with various quantities of differently sized unidirectional fibers. Water uptake of FRC was measured. Water immersed specimens were thermally cycled for 500 and 12,000 cycles (5 degrees C/55 degrees C). Flexural properties of "dry" and wet specimens with and without thermal cycling were determined by a three-point bending test. The linear coefficients of thermal expansion (LCTE) for FRC samples with different fiber orientations were determined using a thermomechanical analyzer. Water uptake of the FRC specimens increased with a decrease in fiber content of the FRC. Flexural properties of FRCs improved with increasing fiber content, whereas the flexural properties were not influenced significantly by water and thermal cycling. Fiber orientation had different effects on LCTE of FRCs. Unidirectional FRCs had two different LCTE in longitudinal and transverse directions whereas bidirectional FRCs had similar LCTE in two directions and a higher one in the third direction. The results of the study suggest that the surface-treated unidirectional silica-glass FRC can be used for long-term clinical applications in the oral cavity.

  6. Nucleosynthesis in Core-Collapse Supernovae

    Science.gov (United States)

    Stevenson, Taylor Shannon; Viktoria Ohstrom, Eva; Harris, James Austin; Hix, William R.

    2018-01-01

    The nucleosynthesis which occurs in core-collapse supernovae (CCSN) is one of the most important sources of elements in the universe. Elements from Oxygen through Iron come predominantly from supernovae, and contributions of heavier elements are also possible through processes like the weak r-process, the gamma process and the light element primary process. The composition of the ejecta depends on the mechanism of the explosion, thus simulations of high physical fidelity are needed to explore what elements and isotopes CCSN can contribute to Galactic Chemical Evolution. We will analyze the nucleosynthesis results from self-consistent CCSN simulations performed with CHIMERA, a multi-dimensional neutrino radiation-hydrodynamics code. Much of our understanding of CCSN nucleosynthesis comes from parameterized models, but unlike CHIMERA these fail to address essential physics, including turbulent flow/instability and neutrino-matter interaction. We will present nucleosynthesis predictions for the explosion of a 9.6 solar mass first generation star, relying both on results of the 160 species nuclear reaction network used in CHIMERA within this model and on post-processing with a more extensive network. The lowest mass iron core-collapse supernovae, like this model, are distinct from their more massive brethren, with their explosion mechanism and nucleosynthesis being more like electron capture supernovae resulting from Oxygen-Neon white dwarves. We will highlight the differences between the nucleosynthesis in this model and more massive supernovae. The inline 160 species network is a feature unique to CHIMERA, making this the most sophisticated model to date for a star of this type. We will discuss the need and mechanism to extrapolate the post-processing to times post-simulation and analyze the uncertainties this introduces for supernova nucleosynthesis. We will also compare the results from the inline 160 species network to the post-processing results to study further

  7. New kinds of energy-storing building composite PCMs for thermal energy storage

    International Nuclear Information System (INIS)

    Biçer, Alper; Sarı, Ahmet

    2013-01-01

    Graphical abstract: In this work, 10 new kinds of BCPCMs were prepared by blending of liquid xylitol pentalaurate (XPL) and xylitol pentamyristate (XPM) esters into gypsum, cement, diatomite, perlite and vermiculite. DSC results showed that the melting temperatures and energy storage capacities of the prepared BCPCMs are in range of about 40–55 °C and 31–126 J/g, respectively. TG investigations and thermal cycling test showed that the BCPCMs had good thermal endurance and thermal reliability. It can be also concluded that among the prepared 10 kinds materials, especially the BCPCMs including perlite, vermiculite, diatomite were found to better candidates for thermal energy storage applications in buildings due to the fact that they have relatively high heat storage ability. Highlights: ► New kinds BCPCMs were prepared by blending of liquid XPL and XPM esters with some building materials. ► The BCPCMs had suitable melting temperatures and energy storage capacities. ► Especially, the BCPCMs including perlite, vermiculite, diatomite were found to better candidates for thermal energy storage. - Abstract: Energy storing-composite phase change materials (PCMs) are significant means of thermal energy storage in buildings. Although several building composite PCMs (BCPCMs) have been developed in recent years, the additional investigations are still required to enrich the diversity of BCPCMs for solar heating and energy conservation applications in buildings. For this purpose, the present work is focused the preparation, characterization and determination of 10 new kinds of BCPCMs. The BCPCMs were prepared by blending of liquid xylitol pentalaurate (XPL) and xylitol pentamyristate (XPM) esters with gypsum, cement, diatomite, perlite and vermiculite as supporting matrices. The scanning electron microscopy (SEM) and Fourier Transform Infrared (FT-IR) analysis showed that the ester compounds were adsorbed uniformly into the building materials due to capillary forces

  8. Supernova will continue to glow

    International Nuclear Information System (INIS)

    Anon.

    1987-01-01

    On the night of 23/24 February 1987 a new supernova called SN 1987A, was discovered. Within a few hours of the announcement of the discovery, the South African Astronomical Observatory (SAAO) began a series of observations. In this article, the importance of supernovae-exploding stars, and what the SAAO has discovered so far from SN 1987A are discussed

  9. Disturbance Ecology from nearby Supernovae

    OpenAIRE

    Hartmann, D. H.; Kretschmer, K.; Diehl, R.

    2002-01-01

    Monte Carlo simulations of Galactic Supernovae are carried out to study the rate of nearby events, which may have a direct effect on Earth's ecology though ionizing radiation and cosmic ray bombardment. A nearby supernova may have left a radioactive imprint (60Fe) in recent galactic history.

  10. X-ray haloes around supernova remnants

    International Nuclear Information System (INIS)

    Morfill, G.E.; Aschenbach, B.

    1984-01-01

    Recent observations of the Cas-A supernova remnant have shown X-ray emissions not only from the interior, but also from a fainter 'halo' extending beyond what is normally regarded as the outer boundary, or shock front. The authors suggest that this may be due to the diffusion of energetic, charged particles out of the remnant giving rise to precursor structure of the type predicted by the theory of diffusive shock acceleration. If this is the case we are seeing thermal emission from ambient gas heated by compression and wave dissipation. (author)

  11. X-ray haloes around supernova remnants

    Energy Technology Data Exchange (ETDEWEB)

    Morfill, G.E.; Aschenbach, B. (Max-Planck-Institut fuer Physik und Astrophysik, Garching (Germany, F.R.). Inst. fuer Extraterrestrische Physik); Drury, L.O' C. (Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany, F.R.))

    1984-09-27

    Recent observations of the Cas-A supernova remnant have shown X-ray emissions not only from the interior, but also from a fainter 'halo' extending beyond what is normally regarded as the outer boundary, or shock front. The authors suggest that this may be due to the diffusion of energetic charged particles out of the remnant giving rise to precursor structure of the type predicted by the theory of diffusive shock acceleration. If this is the case we are seeing thermal emission from ambient gas heated by compression and wave dissipation.

  12. Effects of neutrino trapping on supernova explosions

    International Nuclear Information System (INIS)

    Takahara, Mariko; Sato, Katsuhiko

    1982-01-01

    Effects of neutrino trapping on the mass ejection from the stellar cores are investigated with the aid of a simplified equation of state under the assumption of adiabatic collapse. It is found that mass ejection becomes violent only if the ratio of the trapped leptons to baryons, Y sub(L), lies in an appropriate range. If the value of Y sub(L) lies out of this range, mass ejection is difficult. It is also shown that as the thermal stiffness of the shocked matter increases, the range necessary for the violent mass ejection becomes wider. Possibilities of supernova explosion are discussed on the basis of these results. (author)

  13. Mechanical and thermal properties of polypropylene (PP) composites filled with modified shell waste

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Z.T., E-mail: sxyzt@126.com [College of Materials Science and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Chen, T. [Department of Ocean Science and Engineering, Zhejiang University, Hangzhou 310058 (China); Li, H.Y. [Zhoushan Ocean Research Institute, Zhejiang University, Zhoushan 316021 (China); Xia, M.S., E-mail: msxia@zju.edu.cn [Department of Ocean Science and Engineering, Zhejiang University, Hangzhou 310058 (China); Ye, Y.; Zheng, H. [Department of Ocean Science and Engineering, Zhejiang University, Hangzhou 310058 (China)

    2013-11-15

    Highlights: • Adding modified shell powder could significantly increase the properties of PP. • The modified shell powder could act as a nucleating agent in PP matrix. • The modified shell powder has a potential to be used as a bio-filler. -- Abstract: Shell waste, with its high content of calcium carbonate (CaCO{sub 3}) plus organic matrix, has a potential to be used as a bio-filler. In this work, shell waste was modified by furfural and then incorporated to reinforce polypropylene (PP). The shell waste and modified powder were characterized by means of X-ray diffraction (XRD), scanning electron microscopy equipped with an energy dispersive spectrometer (SEM-EDS), X-ray photoelectronic spectroscopy (XPS), and Fourier transformed infrared spectroscopy (FTIR). The mechanical and thermal properties of neat PP and PP composites were investigated as well. Thermal gravimetric (TG) analyses confirmed the reinforcing role of modified powder in PP composites. The mechanical properties studied showed that adding modified powder could significantly increase the impact strength, elongation at break point and flexural modulus of composites. The maximum incorporation content could reach 15 wt.% with a good balance between toughness and stiffness of PP composites. Differential scanning calorimetry (DSC) results showed that the modified powder could act as a nucleating agent and thus increase the crystallization temperature of PP. Polarized optical microscopy (POM) observation also indicated that the introduction of modified powder could promote the heterogeneous nucleation of PP matrix.

  14. Microstructural Improvement of Hydroxyapatite-ZrO2 Composite Ceramics via Thermal Precipitation Techniques.

    Science.gov (United States)

    Sangmala, A.; Limsuwan, P.; Kaewwiset, W.; Naemchanthara, K.

    2017-09-01

    Hydroxyapatite-ZrO2 composite ceramic were synthesized using a thermal precipitation techniques. The chemical precursors were prepared from di-ammonium hydrogen orthophosphate, calcium oxide (CaO) derived from chicken eggshell, zirconium dioxide (ZrO2) and distilled water. The mixture were heated at the various temperatures from 100 to 700 °C in the furnace with an incremental temperature of 100 °C. The ZrO2 contents in the composite ceramic were varied from 0 to 15 percent weight of CaO. The prepared composites were then annealed at 300, 600 and 700 °C for 4 h in air. The crystal structure, function group and morphology of all samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and universal testing machine (UTM), respectively. The results indicated that the undoped-ZrO2 samples hydroxyapatite phase with a hexagonal structure. However, the hydroxyapatite was transformed to the tri-calcium phosphate after thermal treatment at 700 °C. For the doped-ZrO2 samples, the hydroxyapatite and ZrO2 phases were found. Moreover, the result showed that the compressive strength of hydroxyapatite-ZrO2 composite ceramic increased with increasing the ZrO2 content.

  15. Preparation, Characterization and Thermal Degradation of Polyimide (4-APS/BTDA/SiO2 Composite Films

    Directory of Open Access Journals (Sweden)

    Arash Dehzangi

    2012-04-01

    Full Text Available Polyimide/SiO2 composite films were prepared from tetraethoxysilane (TEOS and poly(amic acid (PAA based on aromatic diamine (4-aminophenyl sulfone (4-APS and aromatic dianhydride (3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA via a sol-gel process in N-methyl-2-pyrrolidinone (NMP. The prepared polyimide/SiO2 composite films were characterized using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, scanning electron microscope (SEM and thermogravimetric analysis (TGA. The FTIR results confirmed the synthesis of polyimide (4-APS/BTDA and the formation of SiO2 particles in the polyimide matrix. Meanwhile, the SEM images showed that the SiO2 particles were well dispersed in the polyimide matrix. Thermal stability and kinetic parameters of the degradation processes for the prepared polyimide/SiO2 composite films were investigated using TGA in N2 atmosphere. The activation energy of the solid-state process was calculated using Flynn–Wall–Ozawa’s method without the knowledge of the reaction mechanism. The results indicated that thermal stability and the values of the calculated activation energies increased with the increase of the TEOS loading and the activation energy also varied with the percentage of weight loss for all compositions.

  16. THERMAL DECOMPOSITION AND FLAMMABILITY OF ACRYLONITRILE-BUTADIENE-STYRENE/MULTI-WALLED CARBON NANOTUBES COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    Li-fang Tong; Hai-yun Ma; Zheng-ping Fang

    2008-01-01

    Thermal and flammability properties of acrylonitrile-butadiene-styrene copolymer (ABS) with the addition of multi-walled carbon nanotubes (MWNTs) were studied. ABS/MWNTs composites were prepared via melt blending with the MWNTs content varied from 0.2% to 4.0% by mass. Thermogravimetry results showed that the addition of MWNTs accelerated the degradation of ABS during the whole process under air atmosphere, and both onset and maximum degradation temperature were lower than those of pure ABS. The destabilization effect of MWNTs on the thermal stability of the composites became unobvious under nitrogen, and the addition of MWNTs could improve the maximum degradation temperature. The heat release rate and time of ignition (tign) for the composites reduced greatly with the addition of MWNTs especially when the concentration of nanotubes was higher than 1.0%. The accumulation of carbon nanotubes with a network structure was observed and the char layer became thicker with increasing nanotubes concentration. Results from Raman spectra showed a higher degree of graphitization for the residues of ABS/MWNTs composites.

  17. Microstructural and thermal study of Al-Si-Mg/melon shell ash particulate composite

    Directory of Open Access Journals (Sweden)

    M. Abdulwahab

    Full Text Available The microstructural study via scanning electron microscope (SEM and thermal study via differential scanning calorimetric (DSC study of Al-7%Si-0.3Mg/melon shell ash particulate composite has been carried out. The melon shell ash was used in the production of MMC ranging from 5% to 20% at interval of 5% addition using stir casting method. The melon shell ash was characterized using X-ray fluorescent (XRF that reveal the presence of CaO, SiO2, Al2O3, MgO, and TiO2 as major compounds. The composite was machined and subjected to heat treatment. Microstructural analyses of the composite produced were done using scanning electron microscope (SEM. The microstructure obtained reveals a dark ceramic (reinforcer and white metallic phase. Equally, the 5 wt% DSC result gives better thermal conductivity than other proportions (10 wt%, 15 wt%, and 20 wt%. These results showed that an improved property of Al-Si-Mg alloy was achieved using melon shell ash particles as reinforcement up to a maximum of 20 wt% for microstructural and 5% wt DSC respectively. Keywords: Microstructural analysis, Melon shell ash, Stir casting, X-ray fluorescent, Reinforcement, Composite

  18. Pore structure modified diatomite-supported PEG composites for thermal energy storage.

    Science.gov (United States)

    Qian, Tingting; Li, Jinhong; Deng, Yong

    2016-09-01

    A series of novel composite phase change materials (PCMs) were tailored by blending PEG and five kinds of diatomite via a vacuum impregnation method. To enlarge its pore size and specific surface area, different modification approaches including calcination, acid treatment, alkali leaching and nano-silica decoration on the microstructure of diatomite were outlined. Among them, 8 min of 5 wt% NaOH dissolution at 70 °C has been proven to be the most effective and facile. While PEG melted during phase transformation, the maximum load of PEG could reach 70 wt.%, which was 46% higher than that of the raw diatomite. The apparent activation energy of PEG in the composite was 1031.85 kJ·mol(-1), which was twice higher than that of the pristine PEG. Moreover, using the nano-silica decorated diatomite as carrier, the maximum PEG load was 66 wt%. The composite PCM was stable in terms of thermal and chemical manners even after 200 cycles of melting and freezing. All results indicated that the obtained composite PCMs were promising candidate materials for building applications due to its large latent heat, suitable phase change temperature, excellent chemical compatibility, improved supercooling extent, high thermal stability and long-term reliability.

  19. Mechanical and Thermal Stability Properties of Modified Rice Straw Fiber Blend with Polycaprolactone Composite

    Directory of Open Access Journals (Sweden)

    Roshanak Khandanlou

    2014-01-01

    Full Text Available The goal of this study was to investigate the effect of modified rice straw (ORS on the mechanical and thermal properties of modified rice straw/polycaprolactone composites (ORS/PCL-Cs. The composites (Cs of polycaprolactone (PCL with ORS were successfully synthesized using the solution-casting method. The RS modified with octadecylamine (ODA as an organic modifier. The prepared composites were characterized by using powder X-ray diffraction (XRD, thermogravimetric analysis (TGA, scanning electron microscopy (SEM, and Fourier transforms infrared spectroscopy (FT-IR, and mechanical properties were investigated. Composites of ORS/PCL showed superior mechanical properties due to greater compatibility of ORS with PCL. The XRD results showed that the intensity of the peaks decreased with the increase of ORS content from 1.0 to 7.0 wt.% in comparison with PCL peaks. Tensile measurement showed an increase in tensile modulus but a decrease in tensile strength and elongation at break as the ORS contents are increased from 1.0 to 7.0 wt.%; on the other hand, tensile strength was improved with the addition of 5.0 wt.% of ORS. Thermal stability was decreased with the increase of ORS contents. SEM micrograph indicated good dispersion of ORS into the matrix, and FT-IR spectroscopy showed that the interaction between PCL and ORS is physical interaction.

  20. Pore structure modified diatomite-supported PEG composites for thermal energy storage

    Science.gov (United States)

    Qian, Tingting; Li, Jinhong; Deng, Yong

    2016-09-01

    A series of novel composite phase change materials (PCMs) were tailored by blending PEG and five kinds of diatomite via a vacuum impregnation method. To enlarge its pore size and specific surface area, different modification approaches including calcination, acid treatment, alkali leaching and nano-silica decoration on the microstructure of diatomite were outlined. Among them, 8 min of 5 wt% NaOH dissolution at 70 °C has been proven to be the most effective and facile. While PEG melted during phase transformation, the maximum load of PEG could reach 70 wt.%, which was 46% higher than that of the raw diatomite. The apparent activation energy of PEG in the composite was 1031.85 kJ·mol-1, which was twice higher than that of the pristine PEG. Moreover, using the nano-silica decorated diatomite as carrier, the maximum PEG load was 66 wt%. The composite PCM was stable in terms of thermal and chemical manners even after 200 cycles of melting and freezing. All results indicated that the obtained composite PCMs were promising candidate materials for building applications due to its large latent heat, suitable phase change temperature, excellent chemical compatibility, improved supercooling extent, high thermal stability and long-term reliability.

  1. Preparation and characterization of silicon nitride (Si−N)-coated carbon fibers and their effects on thermal properties in composites

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyeon-Hye [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of); Nano& Advanced Materials Engineering, Jeonju University, Jeonju 560-759 (Korea, Republic of); Han, Woong [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of); Lee, Hae-seong [Nano& Advanced Materials Engineering, Jeonju University, Jeonju 560-759 (Korea, Republic of); Min, Byung-Gak [Department of Polymer Science & Engineering, Korea National University of Transportation, Chungju 380-702 (Korea, Republic of); Kim, Byung-Joo, E-mail: ap2-kbj@hanmail.net [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of)

    2015-10-15

    Graphical abstract: We report preparation and characterization of silicon nitride (Si−N)-coated carbon fibers and their effects on thermal properties in composites. Thermally composites showed enhanced thermal conductivity increasing from up to 59% by the thermal network. - Highlights: • A new method of Si−N coating on carbon fibers was reported. • Silane layer were successfully converted to Si−N layer on carbon fiber surface. • Si−N formation was confirmed by FT-IR, XPS, and EDX. • Thermal conductivity of Si−N coated CF composites were enhanced to 0.59 W/mK. - Abstract: This study investigates the effect of silicon nitride (Si−N)-coated carbon fibers on the thermal conductivity of carbon-fiber-reinforced epoxy composite. The surface properties of the Si−N-coated carbon fibers (SiNCFs) were observe using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy, and the thermal stability was analyzed using thermogravimetric analysis. SiNCFs were fabricated through the wet thermal treatment of carbon fibers (Step 1: silane finishing of the carbon fibers; Step 2: high-temperature thermal treatment in a N{sub 2}/NH{sub 3} environment). As a result, the Si−N belt was exhibited by SEM. The average thickness of the belt were 450–500 nm. The composition of Si−N was the mixture of Si−N, Si−O, and C−Si−N as confirmed by XPS. Thermal residue of the SiNCFs in air was enhanced from 3% to 50%. Thermal conductivity of the composites increased from 0.35 to 0.59 W/mK after Si−N coating on carbon surfaces.

  2. Synthesis and thermal properties of the MA/HDPE composites with nano-additives as form-stable PCM with improved thermal conductivity

    International Nuclear Information System (INIS)

    Tang, Yaojie; Su, Di; Huang, Xiang; Alva, Guruprasad; Liu, Lingkun; Fang, Guiyin

    2016-01-01

    Highlights: • MA/HDPE composites with nano-additives were prepared for thermal conductivity enhancement. • Microstructure and chemical structure of the FSPCM were analyzed. • Thermal properties and thermal reliability of the FSPCM were investigated. • Thermal conductivity of the FSPCM can be enhanced by adding NAO and NG. - Abstract: For the purpose of improving the thermal conductivity of the form–stable phase change materials (FSPCM), two types of nano–powders with high thermal conductivity were added into the samples. In the modified FSPCM, myristic acid (MA) was used as a solid–liquid phase change material (PCM), high density polyethylene (HDPE) acted as supporting material to prevent the leakage of the melted MA. Nano–Al 2 O 3 (NAO) and nano–graphite (NG) were the additives for thermal conductivity enhancement. Scanning electronic microscope (SEM), Fourier transformation infrared spectroscope (FT–IR) and X-ray diffractometer (XRD) were used to analyze the microstructure, chemical structure and crystalline phase of the samples, respectively. Furthermore, the specific latent heat and phase transition temperature, thermal conductivity and thermal reliability were investigated using differential scanning calorimeter (DSC), thermal conductivity meter and thermo–gravimetric analyzer (TGA). The results showed that the MA was uniformly absorbed in the HDPE matrices and there was no leakage during the melting process when the mass fraction of the MA in the MA/HDPE composite was less than 70%. The DSC results revealed that the modified FSPCM have a constant phase change temperature and high specific latent heat. The thermal conductivity of the FSPCM was measured in the solid (30 °C) and liquid (60 °C) states of the MA. When the mass fraction of nano–powder additives is 12%, the thermal conductivities of the FSPCM increase by 95% (NAO) and 121% (NG) at 30 °C. It is anticipated that the FSPCM possess a potential application for thermal energy

  3. Thermal Gradient Cyclic Behavior of a Thermal/Environmental Barrier Coating System on SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

    2002-01-01

    Thermal barrier and environmental barrier coatings (TBCs and EBCs) will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability of the ceramic matrix composite (CMC) engine components in harsh combustion environments. In order to develop high performance, robust coating systems for effective thermal and environmental protection of the engine components, appropriate test approaches for evaluating the critical coating properties must be established. In this paper, a laser high-heat-flux, thermal gradient approach for testing the coatings will be described. Thermal cyclic behavior of plasma-sprayed coating systems, consisting of ZrO2-8wt%Y2O3 thermal barrier and NASA Enabling Propulsion Materials (EPM) Program developed mullite+BSAS/Si type environmental barrier coatings on SiC/SiC ceramic matrix composites, was investigated under thermal gradients using the laser heat-flux rig in conjunction with the furnace thermal cyclic tests in water-vapor environments. The coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after the tests. The coating failure mechanisms are discussed based on the cyclic test results and are correlated to the sintering, creep, and thermal stress behavior under simulated engine temperature and heat flux conditions.

  4. Thermal decomposition of poly(ethylene terephthalate)/mesoporous molecular sieve composites

    Institute of Scientific and Technical Information of China (English)

    RUN Mingtao; ZHANG Dayu; WU Sizhu; WU Gang

    2007-01-01

    The nonisothermal and isothermal degradation processesofpoly(ethyleneterephthalate)/mesoporous molecular sieve (PET/MMS) composites synthesized by insitu polymerization were studied by using thermogravimetric analysis in nitrogen.The nonisothermal degradation of the composite is found to be the first-order reaction.An isoconversional procedure developed by Ozawa is used to calculate the apparent activation energy (E),which is an average value of about 260 kJ/mol with the weight conversion from 0% to 30%,and is higher than that of neat PET.Isothermal degradation results are confirmed with the nonisothermal process,in which PET/MMS showed higher thermal stability than neat PET.The polymer in mesoporous channels has more stability due to the protection of the inorganic pore-wall.These results indicate that mesoporous MMS in PET/MMS composites improve the stability of the polymer.

  5. Thermal Decomposition Behaviors and Burning Characteristics of AN/Nitramine-Based Composite Propellant

    Science.gov (United States)

    Naya, Tomoki; Kohga, Makoto

    2015-04-01

    Ammonium nitrate (AN) has attracted much attention due to its clean burning nature as an oxidizer. However, an AN-based composite propellant has the disadvantages of low burning rate and poor ignitability. In this study, we added nitramine of cyclotrimethylene trinitramine (RDX) or cyclotetramethylene tetranitramine (HMX) as a high-energy material to AN propellants to overcome these disadvantages. The thermal decomposition and burning rate characteristics of the prepared propellants were examined as the ratio of AN and nitramine was varied. In the thermal decomposition process, AN/RDX propellants showed unique mass loss peaks in the lower temperature range that were not observed for AN or RDX propellants alone. AN and RDX decomposed continuously as an almost single oxidizer in the AN/RDX propellant. In contrast, AN/HMX propellants exhibited thermal decomposition characteristics similar to those of AN and HMX, which decomposed almost separately in the thermal decomposition of the AN/HMX propellant. The ignitability was improved and the burning rate increased by the addition of nitramine for both AN/RDX and AN/HMX propellants. The increased burning rates of AN/RDX propellants were greater than those of AN/HMX. The difference in the thermal decomposition and burning characteristics was caused by the interaction between AN and RDX.

  6. Controlling thermal deformation by using composite materials having variable fiber volume fraction

    International Nuclear Information System (INIS)

    Bouremana, M.; Tounsi, A.; Kaci, A.; Mechab, I.

    2009-01-01

    In application, many thin structural components such as beams, plates and shells experience a through-thickness temperature variation. This temperature variation can produce both an in-plane expansion and an out-of-plane (bending) curvature. Given that these thin components interact with or connect to other components, we often wish to minimize the thermal deformation or match the thermal deformation of another component. This is accomplished by using a composite whose fibers have a negative axial thermal expansion coefficient. By varying the fiber volume fraction within a symmetric laminated beam to create a functionally graded material (FGM), certain thermal deformations can be controlled or tailored. Specifically, a beam can be designed which does not curve under a steady-state through-thickness temperature variation. Continuous gradation of the fiber volume fraction in the FGM layer is modelled in the form of a mth power polynomial of the coordinate axis in thickness direction of the beam. The beam results are independent of the actual temperature values, within the limitations of steady-state heat transfer and constant material properties. The influence of volume fiber fraction distributions are studied to match or eliminate an in-plane expansion coefficient, or to match a desired axial stiffness. Combining two fiber types to create a hybrid FGM can offer desirable increase in axial and bending stiffness while still retaining the useful thermal deformation behavior.

  7. Experimental Characterization of a Composite Morphing Radiator Prototype in a Relevant Thermal Environment

    Science.gov (United States)

    Bertagne, Christopher L.; Chong, Jorge B.; Whitcomb, John D.; Hartl, Darren J.; Erickson, Lisa R.

    2017-01-01

    For future long duration space missions, crewed vehicles will require advanced thermal control systems to maintain a desired internal environment temperature in spite of a large range of internal and external heat loads. Current radiators are only able to achieve turndown ratios (i.e. the ratio between the radiator's maximum and minimum heat rejection rates) of approximately 3:1. Upcoming missions will require radiators capable of 12:1 turndown ratios. A radiator with the ability to alter shape could significantly increase turndown capacity. Shape memory alloys (SMAs) offer promising qualities for this endeavor, namely their temperature-dependent phase change and capacity for work. In 2015, the first ever morphing radiator prototype was constructed in which SMA actuators passively altered the radiator shape in response to a thermal load. This work describes a follow-on endeavor to demonstrate a similar concept using highly thermally conductive composite materials. Numerous versions of this new concept were tested in a thermal vacuum environment and successfully demonstrated morphing behavior and variable heat rejection, achieving a turndown ratio of 4.84:1. A summary of these thermal experiments and their results are provided herein.

  8. Nuclear astrophysics of supernovae

    International Nuclear Information System (INIS)

    Cooperstein, J.

    1988-01-01

    In this paper, I'll give a general introduction to Supernova Theory, beginning with the presupernova evolution and ending with the later stages of the explosion. This will be distilled from a colloquium type of talk. It is necessary to have the whole supernova picture in one's mind's eye when diving into some of its nooks and crannies, as it is quite a mess of contradictory ingredients. We will have some discussion of supernova 1987a, but will keep our discussion more general. Second, we'll look at the infall and bounce of the star, seeing why it goes unstable, what dynamics it follows as it collapses, and how and why it bounces back. From there, we will go on to look at the equation of state (EOS) in more detail. We'll consider the cases T = 0 and T > 0. We'll focus on /rho/ 0 , and then /rho/ > /rho/ 0 and the EOS of neutron stars, and whether or not they contain cores of strange matter. There are many things we could discuss here and not enough time. If I had more lectures, the remaining time would focus on two more questions of special interest to nuclear physicists: the electron capture reactions and neutrino transport. If time permitted, we'd have some discussion of the nucleosynthetic reactions in the explosion's debris as well. However, we cannot cover such material adequately, and I have chosen these topics because they are analytically tractable, pedagogically useful, and rather important. 23 refs., 14 figs., 3 tabs

  9. Supernovae Discovery Efficiency

    Science.gov (United States)

    John, Colin

    2018-01-01

    Abstract:We present supernovae (SN) search efficiency measurements for recent Hubble Space Telescope (HST) surveys. Efficiency is a key component to any search, and is important parameter as a correction factor for SN rates. To achieve an accurate value for efficiency, many supernovae need to be discoverable in surveys. This cannot be achieved from real SN only, due to their scarcity, so fake SN are planted. These fake supernovae—with a goal of realism in mind—yield an understanding of efficiency based on position related to other celestial objects, and brightness. To improve realism, we built a more accurate model of supernovae using a point-spread function. The next improvement to realism is planting these objects close to galaxies and of various parameters of brightness, magnitude, local galactic brightness and redshift. Once these are planted, a very accurate SN is visible and discoverable by the searcher. It is very important to find factors that affect this discovery efficiency. Exploring the factors that effect detection yields a more accurate correction factor. Further inquires into efficiency give us a better understanding of image processing, searching techniques and survey strategies, and result in an overall higher likelihood to find these events in future surveys with Hubble, James Webb, and WFIRST telescopes. After efficiency is discovered and refined with many unique surveys, it factors into measurements of SN rates versus redshift. By comparing SN rates vs redshift against the star formation rate we can test models to determine how long star systems take from the point of inception to explosion (delay time distribution). This delay time distribution is compared to SN progenitors models to get an accurate idea of what these stars were like before their deaths.

  10. Thermal Protection of Carbon Fiber-Reinforced Composites by Ceramic Particles

    Directory of Open Access Journals (Sweden)

    Baljinder Kandola

    2016-06-01

    Full Text Available The thermal barrier efficiency of two types of ceramic particle, glass flakes and aluminum titanate, dispersed on the surface of carbon-fiber epoxy composites, has been evaluated using a cone calorimeter at 35 and 50 kW/m2, in addition to temperature gradients through the samples’ thicknesses, measured by inserting thermocouples on the exposed and back surfaces during the cone tests. Two techniques of dispersing ceramic particles on the surface have been employed, one where particles were dispersed on semi-cured laminate and the other where their dispersion in a phenolic resin was applied on the laminate surface, using the same method as used previously for glass fiber composites. The morphology and durability of the coatings to water absorption, peeling, impact and flexural tension were also studied and compared with those previously reported for glass-fiber epoxy composites. With both methods, uniform coatings could be achieved, which were durable to peeling or water absorption with a minimal adverse effect on the mechanical properties of composites. While all these properties were comparable to those previously observed for glass fiber composites, the ceramic particles have seen to be more effective on this less flammable, carbon fiber composite substrate.

  11. Thermal Degradation, Mechanical Properties and Morphology of Wheat Straw Flour Filled Recycled Thermoplastic Composites

    Directory of Open Access Journals (Sweden)

    Kadir Karakus

    2008-01-01

    Full Text Available Thermal behaviors of wheat straw flour (WF filled thermoplastic compositeswere measured applying the thermogravimetric analysis and differential scanningcalorimetry. Morphology and mechanical properties were also studied using scanningelectron microscope and universal testing machine, respectively. Presence of WF inthermoplastic matrix reduced the degradation temperature of the composites. One for WFand one for thermoplastics, two main decomposition peaks were observed. Morphologicalstudy showed that addition of coupling agent improved the compatibility between WFs andthermoplastic. WFs were embedded into the thermoplastic matrix indicating improvedadhesion. However, the bonding was not perfect because some debonding can also be seenon the interface of WFs and thermoplastic matrix. In the case of mechanical properties ofWF filled recycled thermoplastic, HDPE and PP based composites provided similar tensileand flexural properties. The addition of coupling agents improved the properties ofthermoplastic composites. MAPE coupling agents performed better in HDPE while MAPPcoupling agents were superior in PP based composites. The composites produced with thecombination of 50-percent mixture of recycled HDPE and PP performed similar with theuse of both coupling agents. All produced composites provided flexural properties requiredby the ASTM standard for polyolefin-based plastic lumber decking boards.

  12. Thermal and mechanical interfacial properties of epoxy composites based on functionalized carbon nanotubes

    International Nuclear Information System (INIS)

    Jin Fanlong; Ma Changjie; Park, Soo-Jin

    2011-01-01

    Highlights: → CNTs were functionalized by acid and amine treatments. → Epoxy resin/CNT composites were prepared. → T g of the composites increased by about 10 deg. C compared to neat epoxy resins. → Toughness of the composites was significantly improved by the addition of functionalized CNTs. - Abstract: Carbon nanotubes (CNTs) were treated by a mixture of acid and functionalized subsequently by amine treatment to improve interfacial interactions and dispersion of CNTs in epoxy matrix. The thermal stabilities and mechanical interfacial properties of epoxy/CNT composites were investigated using several techniques. The dispersion state of CNTs in the epoxy matrix was observed by scanning electron microscope (SEM) and transmission electron microscopy (TEM). As a result, the glass transition temperature of epoxy/CNT composites increased by about 11 deg. C compared to neat epoxy resins. The mechanical interfacial property of the composites was significantly increased by the addition of amine treated CNTs. The SEM and TEM results showed that the separation and uniform dispersion of CNTs in the epoxy matrix.

  13. Effect of Thermally Reduced Graphene Oxide on Mechanical Properties of Woven Carbon Fiber/Epoxy Composite

    Directory of Open Access Journals (Sweden)

    Nitai Chandra Adak

    2018-02-01

    Full Text Available Thermally reduced graphene oxide (TRGO was incorporated as a reinforcing filler in the epoxy resin to investigate the effect on the mechanical properties of carbon fiber (CF/epoxy composites. At first, the epoxy matrix was modified by adding different wt % of TRGO from 0.05 to 0.4 wt % followed by the preparation of TRGO/CF/epoxy composites througha vacuum-assisted resin transfer molding process. The prepared TRGO was characterized by using Fourier transform infrared spectroscopy, Raman Spectroscopy and field emission scanning electron microscopy (FE-SEM techniques. It was observed that the wrinkled structure of synthesized TRGO may be helpful to interlock with the epoxy resin and CF.The inter-laminar shear strength, in-plane fracture toughness and impact strength increased by ~67%, 62% and 93% at 0.2 wt % of TRGO loading in the CF/epoxy composites as compared to the CF reinforced epoxy. The mechanical properties of the hybrid composites decreased beyond the 0.2 wt % of TRGO incorporation in the epoxy resin. The fracture surfaces of the hybrid composites were studied by FE-SEM image analysis to investigate the synergistic effect of TRGO in the CF/epoxy composite. This study suggested that TRGO could be used asgood nanofiller to resist the matrix and fiber fracture.

  14. Radio Emission from Supernovae

    International Nuclear Information System (INIS)

    Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; Van Dyk, Schuyler D.; Williams, Christopher L.; Stockdale, Christopher J.; Kelley, Matthew T.

    2009-01-01

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect dumpiness of the circumstellar material.

  15. Preparation of shape-stabilized co-crystallized poly (ethylene glycol) composites as thermal energy storage materials

    International Nuclear Information System (INIS)

    Qian, Yong; Wei, Ping; Jiang, Pingkai; Li, Zhi; Yan, Yonggang; Ji, Kejian; Deng, Weihua

    2013-01-01

    Highlights: • Shape-stabilized PEG composites were prepared by sol–gel process. • The increased energy storage ability of composite was from cocrystallization effect. • Diammonium phosphate improved flame retardancy properties of PEG composite. • PEG composites had potential to be used as thermal energy storage materials. - Abstract: Shape-stabilized co-crystallized poly (ethylene glycol) (PEG) composites were prepared by sol–gel process. Tetraethoxysilane was utilized as supporting matrix precursor. The crystallization property as well as thermal energy storage properties of PEG was influenced by silica network. The combination of PEG 2k and PEG 10k with suitable ratio (3:1 by weight) led to synergistically increased fusion enthalpy attributed to cocrystallization effect. Furthermore, halogen-free flame retarded PEG composites were obtained using diammonium phosphate as flame retardant. With suitable composition, the latent heat value of flame retarded PEG composite was 96.7 kJ/kg accompanied with good thermal stability and improved flame retardancy properties. Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), polarized optical microscope (POM) and scanning electron microscope (SEM) were used to characterize the structure of PEG composites. Thermal stability properties of PEG composites were investigated by thermogravimetric analyzer (TGA). Char residue obtained from muffle furnace of PEG composites was analyzed by SEM and FT-IR. Flame retardancy properties of PEG composites were estimated by pyrolysis combustion flow calorimeter. Results showed that it was potential for shape-stabilized halogen-free flame retarded PEG composite to be applied in thermal energy storage field

  16. Fabrication of mesoporous silica/polymer composites through solvent evaporation process and investigation of their excellent low thermal expansion property.

    Science.gov (United States)

    Suzuki, Norihiro; Kiba, Shosuke; Yamauchi, Yusuke

    2011-03-21

    We fabricate mesoporous silica/epoxy polymer composites through a solvent evaporation process. The easy penetration of the epoxy polymers into mesopores is achieved by using a diluted polymer solution including a volatile organic solvent. After the complete solvent evaporation, around 90% of the mesopores are estimated to be filled with the epoxy polymer chains. Here we carefully investigate the thermal expansion behavior of the obtained mesoporous silica/polymer composites. Thermal mechanical analysis (TMA) charts revealed that coefficient of linear thermal expansion (CTE) gradually decreases, as the amount of the doped mesoporous silica increases. Compared with spherical silica particle without mesopores, mesoporous silica particles show a greater effect on lowering the CTE values. Interestingly, it is found that the CTE values are proportionally decreased with the decrease of the total amount of the polymers outside the mesopores. These data demonstrate that polymers embedded inside the mesopores become thermally stable, and do not greatly contribute to the thermal expansion behavior of the composites.

  17. Fabrication of epoxy composites with large-pore sized mesoporous silica and investigation of their thermal expansion.

    Science.gov (United States)

    Suzuki, Norihiro; Kiba, Shosuke; Yamauchi, Yusuke

    2012-02-01

    We fabricate epoxy composites with low thermal expansion by using mesoporous silica particles with a large pore diameter (around 10 nm) as inorganic fillers. From a simple calculation, almost all the mesopores are estimated to be completely filled with the epoxy polymer. The coefficient of linear thermal expansion (CTE) values of the obtained epoxy composites proportionally decrease with the increase of the mesoporous silica content.

  18. Evaluation of Ultrasonic and Thermal Nondestructive Evaluation for the Characterization of Aging Degradation in Braided Composite Materials

    Science.gov (United States)

    Martin, Richard E.

    2010-01-01

    This paper examines the ability of traditional nondestructive evaluation (NDE) techniques to measure the degradation of braided polymer composite materials subjected to thermal-humidity cycling to simulate aging. A series of braided composite coupons were examined using immersion ultrasonic and pulsed thermography techniques in the as received condition. These same specimens were then examined following extended thermal-humidity cycling. Results of this examination did not show a significant change in the resulting (NDE) signals.

  19. The nearby supernova factory

    International Nuclear Information System (INIS)

    Wood-Vasey, W.M.; Aldering, G.; Lee, B.C.; Loken, S.; Nugent, P.; Perlmutter, S.; Siegrist, J.; Wang, L.; Antilogus, P.; Astier, P.; Hardin, D.; Pain, R.; Copin, Y.; Smadja, G.; Gangler, E.; Castera, A.; Adam, G.; Bacon, R.; Lemonnier, J.-P.; Pecontal, A.; Pecontal, E.; Kessler, R.

    2004-01-01

    The Nearby Supernova Factory (SNfactory) is an ambitious project to find and study in detail approximately 300 nearby Type Ia supernovae (SNe Ia) at redshifts 0.03 < z < 0.08. This program will provide an exceptional data set of well-studied SNe in the nearby smooth Hubble flow that can be used as calibration for the current and future programs designed to use SNe to measure the cosmological parameters. The first key ingredient for this program is a reliable supply of Hubble-flow SNe systematically discovered in unprecedented numbers using the same techniques as those used in distant SNe searches. In 2002, 35 SNe were found using our test-bed pipeline for automated SN search and discovery. The pipeline uses images from the asteroid search conducted by the Near Earth Asteroid Tracking group at JPL. Improvements in our subtraction techniques and analysis have allowed us to increase our effective SN discovery rate to ∼12 SNe/month in 2003

  20. Automated Supernova Discovery (Abstract)

    Science.gov (United States)

    Post, R. S.

    2015-12-01

    (Abstract only) We are developing a system of robotic telescopes for automatic recognition of Supernovas as well as other transient events in collaboration with the Puckett Supernova Search Team. At the SAS2014 meeting, the discovery program, SNARE, was first described. Since then, it has been continuously improved to handle searches under a wide variety of atmospheric conditions. Currently, two telescopes are used to build a reference library while searching for PSN with a partial library. Since data is taken every night without clouds, we must deal with varying atmospheric and high background illumination from the moon. Software is configured to identify a PSN, reshoot for verification with options to change the run plan to acquire photometric or spectrographic data. The telescopes are 24-inch CDK24, with Alta U230 cameras, one in CA and one in NM. Images and run plans are sent between sites so the CA telescope can search while photometry is done in NM. Our goal is to find bright PSNs with magnitude 17.5 or less which is the limit of our planned spectroscopy. We present results from our first automated PSN discoveries and plans for PSN data acquisition.

  1. Thermal Edge-Effects Model for Automated Tape Placement of Thermoplastic Composites

    Science.gov (United States)

    Costen, Robert C.

    2000-01-01

    Two-dimensional thermal models for automated tape placement (ATP) of thermoplastic composites neglect the diffusive heat transport that occurs between the newly placed tape and the cool substrate beside it. Such lateral transport can cool the tape edges prematurely and weaken the bond. The three-dimensional, steady state, thermal transport equation is solved by the Green's function method for a tape of finite width being placed on an infinitely wide substrate. The isotherm for the glass transition temperature on the weld interface is used to determine the distance inward from the tape edge that is prematurely cooled, called the cooling incursion Delta a. For the Langley ATP robot, Delta a = 0.4 mm for a unidirectional lay-up of PEEK/carbon fiber composite, and Delta a = 1.2 mm for an isotropic lay-up. A formula for Delta a is developed and applied to a wide range of operating conditions. A surprise finding is that Delta a need not decrease as the Peclet number Pe becomes very large, where Pe is the dimensionless ratio of inertial to diffusive heat transport. Conformable rollers that increase the consolidation length would also increase Delta a, unless other changes are made, such as proportionally increasing the material speed. To compensate for premature edge cooling, the thermal input could be extended past the tape edges by the amount Delta a. This method should help achieve uniform weld strength and crystallinity across the width of the tape.

  2. Thermal and Ablative Properties of Ipns and Composites of High Ortho Resole Resin and Difurfurylidene Acetone

    Directory of Open Access Journals (Sweden)

    Tariq S. NAJIM

    2008-12-01

    Full Text Available High ortho resole resin was prepared by condensation of phenol with excess of formaldehyde in the presence of magnesium oxide as catalyst. Reaction of furfuraldehyde with acetone in basic medium led to difurfurylidene acetone (DFA. Their interpenetrating polymer network (IPNS were obtained by the reaction of predetermined quantities of difurfurylidene acetone and high ortho resole using p-toluene sulphonic acid (PTSA as curing agent. The thermal behavior of the resins was studied using thermogravimetry (TG under ambient and nitrogen atmospheres over a temperature range of (25-1000 Cº. It was observed that the IPN of 20% DFA – 80% resole has higher thermal stability than that of resole alone and the decomposition temperature was higher by 80 Cº. This behavior was attributed to highly cross linked structure and thermally stable backbone of ploy difurfurylidene acetone due to formation of ladder structure.Impregnation of chopped fiber glass type (E with the polymeric solutions was used to prepare their composites, and the ablative properties were investigated according to ASTM E-285 –80. It was observed that the IPN of (DFA- resol perform better than the resole composite alone.

  3. Preparations and thermal properties of micro- and nano-BN dispersed HDPE composites

    International Nuclear Information System (INIS)

    Jung, Jinwoo; Kim, Jaewoo; Uhm, Young Rang; Jeon, Jae-Kyun; Lee, Sol; Lee, Hi Min; Rhee, Chang Kyu

    2010-01-01

    The thermal properties of micro-sized boron nitride (BN) and nano-sized BN dispersed high density polyethylene (HDPE) composites were investigated by means of differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Nano-BN powder was prepared by using a ball mill process before it was mixed in HDPE. To enhance the dispersivity of nano-BN in the polymer matrix, the surfaces of the nano-particles were treated with low density polyethylene (LDPE) which was dissolved in the cyclohexane solvent. The average particle sizes of micro-BN powder and LDPE coated nano-BN powder were ∼10 μm and ∼100 nm respectively. Dispersion and distribution of 5 wt% and 20 wt% of micro-BN and nano-BN respectively mixed in HDPE were observed by using the scanning electron microscope (SEM). According to the thermal analyses of pure HDPE, micro-BN/HDPE, and nano-BN/HDPE, 20 wt% nano-BN/HDPE composite shows the lowest enthalpy of fusion (ΔH m ) and better thermal conductive characteristics compared to the others.

  4. Quantitative measurement of carbon nanotubes released from their composites using thermal carbon analysis

    International Nuclear Information System (INIS)

    Ogura, I; Honda, K; Shigeta, M; Kotake, M; Uejima, M

    2015-01-01

    The ability of thermal carbon analysis to determine CNTs was evaluated in the presence of a polymer (Polystyrene, PS). Samples placed in an Au (Pt) foil boat were measured using a thermal-carbon analyzer, and the results were compared with gravimetric measurements of sample masses obtained using an ultra-microbalance. First, debris from the polymer without CNTs (i.e., PS debris) was analyzed. The amount of PS debris detected in the organic carbon (OC) fraction was found to be in good agreement with the gravimetrically measured mass of the PS debris, while the amount of pyrolyticallygenerated carbon soot detected in the elemental carbon (EC) fraction was negligible. Next, single-wall CNT (AIST/TASC Super-Growth) powder was analyzed, and the amount of the CNT powder detected in the EC fraction was found to be 95-96% of the gravimetrically measured mass of the CNT powder. Subsequently, a mixture of the PS debris and the CNT powder was analyzed, and the amounts of detected OC and EC were found to be comparable to the gravimetrically measured masses of the PS debris and the CNT powder, respectively. Finally, debris from 5 wt% CNT-PS composites was analyzed, and amounts of OC and EC detected were found to be approximately comparable to the estimated masses of the PS and the CNTs in the debris of CNT-PS composite, respectively. The results therefore indicate thermal carbon analysis is capable of determining CNTs in the presence of PS. (paper)

  5. Needle-Bonded Electromagnetic Shielding Thermally Insulating Nonwoven Composite Boards: Property Evaluations

    Directory of Open Access Journals (Sweden)

    Jia-Horng Lin

    2016-10-01

    Full Text Available Complicated environmental problems inevitably arise when technology advances. One major environmental problem is the presence of electromagnetic radiation. Long-term exposure to electromagnetic radiation can damage people’s health in many ways. Therefore, this study proposes producing composite boards with electromagnetic shielding effectiveness and thermal insulation by utilizing the structures and properties of materials. Different combinations of flame-retardant polyester fiber (FR fiber, recycled far-infrared polyester fiber (FI fiber, and 4D low-melting-point fibers (LM fiber were made into flame-retardant and thermally insulating matrices. The matrices and carbon fiber (CF woven fabric in a sandwich-structure were needle-punched in order to be tightly compact, and then circularly heat dried in order to have a heat set and reinforced structure. The test results indicate that Polyester (PET/CF composite boards are mechanically strong and have thermal insulation and electromagnetic shielding effectiveness at a frequency between 0.6 MHz and 3 GHz.

  6. Continuous Carbon Nanotube-Ultrathin Graphite Hybrid Foams for Increased Thermal Conductivity and Suppressed Subcooling in Composite Phase Change Materials.

    Science.gov (United States)

    Kholmanov, Iskandar; Kim, Jaehyun; Ou, Eric; Ruoff, Rodney S; Shi, Li

    2015-12-22

    Continuous ultrathin graphite foams (UGFs) have been actively researched recently to obtain composite materials with increased thermal conductivities. However, the large pore size of these graphitic foams has resulted in large thermal resistance values for heat conduction from inside the pore to the high thermal conductivity graphitic struts. Here, we demonstrate that the effective thermal conductivity of these UGF composites can be increased further by growing long CNT networks directly from the graphite struts of UGFs into the pore space. When erythritol, a phase change material for thermal energy storage, is used to fill the pores of UGF-CNT hybrids, the thermal conductivity of the UGF-CNT/erythritol composite was found to increase by as much as a factor of 1.8 compared to that of a UGF/erythritol composite, whereas breaking the UGF-CNT bonding in the hybrid composite resulted in a drop in the effective room-temperature thermal conductivity from about 4.1 ± 0.3 W m(-1) K(-1) to about 2.9 ± 0.2 W m(-1) K(-1) for the same UGF and CNT loadings of about 1.8 and 0.8 wt %, respectively. Moreover, we discovered that the hybrid structure strongly suppresses subcooling of erythritol due to the heterogeneous nucleation of erythritol at interfaces with the graphitic structures.

  7. Dielectric and thermal properties of isotactic polypropylene/hexagonal boron nitride composites for high-frequency applications

    International Nuclear Information System (INIS)

    Takahashi, Susumu; Imai, Yusuke; Kan, Akinori; Hotta, Yuji; Ogawa, Hirotaka

    2014-01-01

    Highlights: • The degree of orientation of the hBN could be controlled by the fabrication process. • The dielectric constants of composites ranged between 2.25 and 3.39. • The dielectric loss of composites was on the order of 10 −4 for all compositions. • The thermal conductivity were improved by controlling orientation of hBN. - Abstract: Dielectric composites aimed for high frequency applications were prepared by using anisotropic hexagonal boron nitride (hBN) particles as a fillers and isotactic polypropylene (iPP) as polymer matrix. Dielectric and thermal properties of the composites were studied, focusing on the filler orientation in the plate-shape specimens and filler concentration up to 40 vol%. The degree of orientation of the filler was controlled by the composite fabrication process. Hot-pressing gave relatively random orientation of the filler in the matrix, while injection molding induced a high orientation. Dielectric constant (ε r ) of the composites ranged between 2.25 and 3.39. The estimation of ε r based on the Bruggeman mixing model agreed well with the measured value. Low dielectric losses (tan δ) at microwave frequencies, on the order of 10 −4 , were obtained for all the compositions. Through-thickness thermal conductivity (k) of the hot-pressed samples showed a drastic increase with increasing the filler concentration, reaching up to 2.1 W/m K at 40 vol% of hBN. The filler concentration dependence of k was less significant for the injection molded composites. In-plane thermal expansion was almost independent on the filler orientation, while the coefficient of thermal expansion for the thickness direction of the hot-pressed sample was reduced to approximately half of the injection molded counterpart. These differences in thermal conductivity and thermal expansion are thought to arise from the difference in hBN filler orientation

  8. SiC fiber and yttria-stabilized zirconia composite thick thermal barrier coatings fabricated by plasma spray

    Science.gov (United States)

    Ma, Rongbin; Cheng, Xudong; Ye, Weiping

    2015-12-01

    Approximately 4 mm-thick SiC fiber/yttria-stabilized zirconia (YSZ) composite thermal barrier coatings (TBCs) were prepared by atmospheric plasma spray (APS). The composite coatings have a 'reinforced concrete frame structure', which can protect the coating from failure caused by increasing thickness of coating. The SiC fiber plays an important role in reducing the residual stress level of the composite coatings. The thermal conductivity (TC) value of the composite coatings is 0.632 W/m K, which is about 50% reduction compared to that of typical APS YSZ TBCs. And the composite coatings have higher fracture toughness and better thermal shock resistance than the YSZ TBCs.

  9. Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

    Science.gov (United States)

    Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

    2016-05-11

    The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

  10. Aliphatic polycarbonate-based polyurethane nanostructured materials. The influence of the composition on thermal stability and degradation

    Czech Academy of Sciences Publication Activity Database

    Poreba, Rafal; Špírková, Milena; Pavličević, J.; Budinski-Simendic, J.; Mészáros Szécsényi, K.; Hollo, B.

    2014-01-01

    Roč. 58, March (2014), s. 496-501 ISSN 1359-8368 R&D Projects: GA ČR GAP108/10/0195 Institutional support: RVO:61389013 Keywords : polymer-matrix composites (PMCs) * thermal properties * thermal analysis Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.983, year: 2014

  11. Enhanced thermal diffusivity of copperbased composites using copper-RGO sheets

    Science.gov (United States)

    Kim, Sangwoo; Kwon, Hyouk-Chon; Lee, Dohyung; Lee, Hyo-Soo

    2017-11-01

    The synthesis of copper-reduced graphene oxide (RGO) sheets was investigated in order to control the agglutination of interfaces and develop a manufacturing process for copper-based composite materials based on spark plasma sintering. To this end, copper-GO (graphene oxide) composites were synthesized using a hydrothermal method, while the copper-reduced graphene oxide composites were made by hydrogen reduction. Graphene oxide-copper oxide was hydrothermally synthesized at 80 °C for 5 h, and then annealed at 800 °C for 5 h in argon and hydrazine rate 9:1 to obtain copper-RGO flakes. The morphology and structure of these copper-RGO sheets were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. After vibratory mixing of the synthesized copper-RGO composites (0-2 wt%) with copper powder, they were sintered at 600 °C for 5 min under100 MPa of pressure by spark plasma sintering process. The thermal diffusivity of the resulting sintered composite was characterized by the laser flash method at 150 °C.

  12. Dynamic Mechanical and Thermal Properties of Bagasse/Glass Fiber/Polypropylene Hybrid Composites

    Directory of Open Access Journals (Sweden)

    Mehdi Roohani

    2016-06-01

    Full Text Available This work aims to evaluate the thermal and dynamic mechanical properties of bagasse/glass fiber/polypropylene hybrid composites. Composites were prepared by the melt compounding method and their properties were characterized by differential scanning calorimetry (DSC and dynamic mechanical analysis (DMA. DSC results found that with incorporation of bagasse and glass fiber the melting temperature (Tm and the crystallisation temperature (Tc shift to higher temperatures and the degree of crystallinity (Xc increase. These findings suggest that the fibers played the role of a nucleating agent in composites. Dynamic mechanical analysis indicated that by the incorporation of bagasse and glass fiber into polypropylene, the storage modulus ( and the loss modulus ( increase whereas the mechanical loss factor (tanδ decrease. To assess the effect of reinforcement with increasing temperature, the effectiveness coefficient C was calculated at different temperature ranges and revealed that, at the elevated temperatures, improvement of mechanical properties due to the presence of fibers was more noticeable. The fiber-matrix adhesion efficiency determined by calculating of adhesion factor A in terms of the relative damping of the composite (tan δc and the polymer (tan δpand volume fraction of the fibers (Фf. Calculated adhesion factor A values indicated that by adding glass fiber to bagasse/polypropylene system, the fiber-matrix adhesion improve. Hybrid composite containing 25% bagasse and 15% glass fiber showed better fiber-matrix adhesion.

  13. Thermal analysis and in vitro bioactivity of bioactive glass-alumina composites

    Energy Technology Data Exchange (ETDEWEB)

    Chatzistavrou, Xanthippi, E-mail: x.chatzistavrou@imperial.ac.uk [Solid State Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kantiranis, Nikolaos, E-mail: kantira@geo.auth.gr [School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kontonasaki, Eleana, E-mail: kont@dent.auth.gr [School of Dentistry, Department of Fixed Prosthesis and Implant Prosthodontics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Chrissafis, Konstantinos, E-mail: hrisafis@physics.auth.gr [Solid State Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Papadopoulou, Labrini, E-mail: lambrini@geo.auth.gr [School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Koidis, Petros, E-mail: pkoidis@dent.auth.gr [School of Dentistry, Department of Fixed Prosthesis and Implant Prosthodontics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Boccaccini, Aldo R., E-mail: a.boccaccini@imperial.ac.uk [Department of Materials, Faculty of Engineering, Imperial College, SW7 2AZ London (United Kingdom); Paraskevopoulos, Konstantinos M., E-mail: kpar@auth.gr [Solid State Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2011-01-15

    Bioactive glass-alumina composite (BA) pellets were fabricated in the range 95/5-60/40 wt.% respectively and were heat-treated under a specific thermal treatment up to 950 {sup o}C. Control (unheated) and heat-treated pellets were immersed in Simulated Body Fluid (SBF) for bioactivity testing. All pellets before and after immersion in SBF were studied by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM-EDS) and X-ray Diffraction (XRD) analysis. All composite pellets presented bioactive response. On the surface of the heat-treated pellets the development of a rich biological hydroxyapatite (HAp) layer was delayed for one day, compared to the respective control pellets. Independent of the proportion of the two components, all composites of each group (control and heat-treated) presented the same bioactive response as a function of immersion time in SBF. It was found that by the applied methodology, Al{sub 2}O{sub 3} can be successfully applied in bioactive glass composites without obstructing their bioactive response. - Research Highlights: {yields} Isostatically pressed glass-alumina composites presented apatite-forming ability. {yields} The interaction with SBF resulted in an aluminium phosphate phase formation. {yields} The formation of an aluminium phosphate phase enhanced the in vitro apatite growth.

  14. Mechanical and Thermal Properties and Morphology of Thermoplastic Polyurethane (TPU/Clay Composites

    Directory of Open Access Journals (Sweden)

    Leandro Pizzatto

    2015-11-01

    Full Text Available In this study, thermoplastic polyurethane (TPU composites were prepared with different nanoclay contents (1, 3 and 10 wt%. The nanoclay Cloisite ®30B (C30B was dispersed in the TPU matrix by melt processing using a twin-screw extruder. The synthesis method of TPU involved the two-step bulk polymerization of polyesterpolyol and 4,4’ diphenylmethanediisocyanate with butane-1,4-diol as the chain extender. The dispersion of the nanoclay particles and its effect on the mechanical and thermal properties of the composites was investigated. The characterization of TPU/nanoclay composites was carried out by means of scanning electron microscopy, energy dispersion microanalysis and X ray diffraction. The mechanical characterization was performed through determination of the tensile strength. The TPU 3 wt% composite showed the best improvement with increases in stress and tensile at break (28% and 35%, respectively, compared to the neat TPU (sample without nanoclay. The differential scanning calorimetry and thermogravimetry analyses for composites indicated that the nanoclay did not affect significantly the glass transition, melt, and degradation temperatures of the polymeric matrix, but reduces the molecular mobility.

  15. Thermal performance study of form-stable composite phase change material with polyacrylic

    Science.gov (United States)

    Kee, Shin Yiing; Munusamy, Yamuna; Ong, Kok Seng; Chee, Swee Yong; Sanmuggam, Shimalaa

    2017-04-01

    Phase change material (PCM) is one of the most popular and widely used as thermal energy storage material because it is able to absorb and release a large amount of latent heat during a phase change process over a narrow temperature range. In this work, the form-stable composite PCM was prepared by blending of PMMA and myristic acid in different weight percentage. PMMA was used as a supporting material while myristic acid was used as PCM. Theoretically, PCM can be encapsulated in the support material after blending. However, a small amount of liquid PCMs can leak out from supporting material due to the volume change in phase change process. Therefore, a form-stable composite PCM with polyacrylic coating was studied. Leakage test was carried out to determine the leakage percentage of the form-stable composite PCM. Fourier transform infrared spectroscopy (FTIR) was used to characterize the chemical compatibility of the form-stable PCM composite while differential scanning calorimetry (DSC) was used to study the melting, freezing point and the latent heat of melting and freezing for the form-stable composite PCM.

  16. X-rays from supernova 1987A

    International Nuclear Information System (INIS)

    Xu, Y.; Sutherland, P.; Mccray, R.; Ross, R.R.

    1988-01-01

    Detailed calculations of the development of the X-ray spectrum of 1987A are presented using more realistic models for the supernova composition and density structure provided by Woosley. It is shown how the emergence of the X-ray spectrum depends on the parameters of the model and the nature of its central energy source. It is shown that the soft X-ray spectrum should be dominated by a 6.4 keV Fe K(alpha) emission line that could be observed by a sensitive X-ray telescope. 28 references

  17. Form-stable paraffin/high density polyethylene composites as solid-liquid phase change material for thermal energy storage: preparation and thermal properties

    International Nuclear Information System (INIS)

    Sari, Ahmet

    2004-01-01

    This paper deals with the preparation of paraffin/high density polyethylene (HDPE) composites as form-stable, solid-liquid phase change material (PCM) for thermal energy storage and with determination of their thermal properties. In such a composite, the paraffin (P) serves as a latent heat storage material and the HDPE acts as a supporting material, which prevents leakage of the melted paraffin because of providing structural strength. Therefore, it is named form-stable composite PCM. In this study, two kinds of paraffins with melting temperatures of 42-44 deg. C (type P1) and 56-58 deg. C (type P2) and latent heats of 192.8 and 212.4 J g -1 were used. The maximum weight percentage for both paraffin types in the PCM composites without any seepage of the paraffin in the melted state were found as high as 77%. It is observed that the paraffin is dispersed into the network of the solid HDPE by investigation of the structure of the composite PCMs using a scanning electronic microscope (SEM). The melting temperatures and latent heats of the form-stable P1/HDPE and P2/HDPE composite PCMs were determined as 37.8 and 55.7 deg. C, and 147.6 and 162.2 J g -1 , respectively, by the technique of differential scanning calorimetry (DSC). Furthermore, to improve the thermal conductivity of the form-stable P/HDPE composite PCMs, expanded and exfoliated graphite (EG) by heat treatment was added to the samples in the ratio of 3 wt.%. Thereby, the thermal conductivity was increased about 14% for the form-stable P1/HDPE and about 24% for the P2/HDPE composite PCMs. Based on the results, it is concluded that the prepared form-stable P/HDPE blends as composite type PCM have great potential for thermal energy storage applications in terms of their satisfactory thermal properties and improved thermal conductivity. Furthermore, these composite PCMs added with EG can be considered cost effective latent heat storage materials since they do not require encapsulation and extra cost to enhance

  18. Mechanical, Thermal Degradation, and Flammability Studies on Surface Modified Sisal Fiber Reinforced Recycled Polypropylene Composites

    Directory of Open Access Journals (Sweden)

    Arun Kumar Gupta

    2012-01-01

    Full Text Available The effect of surface treated sisal fiber on the mechanical, thermal, flammability, and morphological properties of sisal fiber (SF reinforced recycled polypropylene (RPP composites was investigated. The surface of sisal fiber was modified with different chemical reagent such as silane, glycidyl methacrylate (GMA, and O-hydroxybenzene diazonium chloride (OBDC to improve the compatibility with the matrix polymer. The experimental results revealed an improvement in the tensile strength to 11%, 20%, and 31.36% and impact strength to 78.72%, 77%, and 81% for silane, GMA, and OBDC treated sisal fiber reinforced recycled Polypropylene (RPP/SF co