WorldWideScience

Sample records for chevrel phase materials

  1. Hydrodesulfurization catalysis by Chevrel phase compounds

    Science.gov (United States)

    McCarty, Kevin F.; Schrader, Glenn L.

    1985-12-24

    A process is disclosed for the hydrodesulfurization of sulfur-containing hydrocarbon fuel with reduced ternary molybdenum sulfides, known as Chevrel phase compounds. Chevrel phase compounds of the general composition M.sub.x Mo.sub.6 S.sub.8, with M being Ho, Pb, Sn, Ag, In, Cu, Fe, Ni, or Co, were found to have hydrodesulfurization activities comparable to model unpromoted and cobalt-promoted MoS.sub.2 catalysts. The most active catalysts were the "large" cation compounds (Ho, Pb, Sn), and the least active catalysts were the "small" cation compounds (Cu, Fe, Ni, Co.).

  2. Electronic structure of Chevrel-phase high-critical-field superconductors

    DEFF Research Database (Denmark)

    Andersen, Ole Krogh; Klose, W.; Nohl, H.

    1978-01-01

    Using muffin-tin orbitals and the atomic-sphere approximation, we have studied the band structures of Chevrel-phase molybdenum chalcogenides, MmMo6X8-x. Generally, these compounds exist for a broad variety of elements, M=Pb,Sn,Ag,Cu and X=S,Se,Te. m may be between 0 and 2, depending on the elemen...

  3. Chevrel Phase Grain Flocculated Films Linked by Chemical Cross-Linking

    Science.gov (United States)

    Obara, Kozo; Ogushi, Tetuya

    1984-08-01

    A new method of forming superconducting grain flocculated films is presented. Chevrel phase compounds are used as superconducting grains, and these are combined with organic barriers. The barriers are formed by catalytic reaction on the grain surface, and are useful for Chevrel phase compound Josephson junctions. The grain flocculated film is composed of Josephson coupled grains. The importance of the orthokinetic flocculation and the mechanical syneresis for the flocculation process is shown. The temperature dependence of dV/dI is measured from 300 K to 4.2 K, and the magnetic field dependence of dV/dI is measured up to 1 kG. Below Tc, the I-V curve shows current steps up to n{=}3, with a voltage interval of approximately 45 mV. These current steps are proof that at least twenty junctions connected in series act coherently.

  4. Express and low-cost microwave synthesis of the ternary Chevrel phase Cu2Mo6S8 for application in rechargeable magnesium batteries

    Science.gov (United States)

    Murgia, Fabrizio; Antitomaso, Philippe; Stievano, Lorenzo; Monconduit, Laure; Berthelot, Romain

    2016-10-01

    The ternary Chevrel phase Cu2Mo6S8 was successfully synthetized using a simple and cost-effective solid-state microwave-assisted reaction. While solid-state routes require days of high-temperature treatment under inert atmosphere, highly pure and crystalline Cu2Mo6S8 could be obtained in only 400 s from this precursor, the Chevrel binary phase Mo6S8 was then obtained by copper removal through acidic leaching, and was evaluated as a positive electrode material for Mg-battery. The electrochemical performance in half-cell configuration shows reversible capacity exceeding 80 mAh/g, which is comparable to previous works carried out with materials synthesized by conventional high-temperature solid-state routes.

  5. Highly Reversible Zinc-ion Intercalation with Chevrel Phase Mo6S8 Nanocubes and Applications for Advanced Zinc-ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Yingwen; Luo, Langli; Zhong, Li; Chen, Junzheng; Li, Bin; Wang, Wei; Mao, Scott X.; Wang, Chong M.; Sprenkle, Vincent L.; Li, Guosheng; Liu, Jun

    2016-05-16

    We demonstrate the application of the Chevrel phase Mo6S8 nanocubes as the anode material for rechargeable Zn-ion batteries. Mo6S8 can host Zn2+ ions reversibility both in aqueous and nonaqueous electrolytes with specific capacities around 90 mAh/g and exhibited remarkable intercalation kinetics as well as stability. Furthermore, we assembled full cells by integrating Mo6S8 anode with zinc-polyiodide (I-/I3-) based catholytes, and demonstrated that such fuel cells was also able to deliver outstanding rate performance and cyclic stability. This first demonstration of zinc intercalating anode could inspire the design of advanced Zn ion batteries.

  6. Thermoelectric and structural properties of a new Chevrel phase: Ti 0.3Mo 5RuSe 8

    Science.gov (United States)

    McGuire, Michael A.; Schmidt, Anneliese M.; Gascoin, Franck; Jeffrey Snyder, G.; DiSalvo, Francis J.

    2006-07-01

    The new Chevrel phase Ti 0.3Mo 5RuSe 8 has been synthesized and characterized by quantitative microprobe analysis, powder X-ray diffraction, and high-temperature thermoelectric properties measurements. The thermoelectric properties of this compound are compared to the previously reported data for other related Chevrel phases. We report also the results of Rietveld analysis of powder X-ray diffraction data for Ti 0.3Mo 5RuSe 8. This compound adopts the rhombohedral Chevrel phase structure (space group R3¯, Z=3) with hexagonal lattice constants a=9.75430(25) Å and c=10.79064(40) Å. The low level of incorporation and low scattering power of Ti precluded the identification of the Ti positions, and Rietveld refinement was carried out only for the Mo 5RuSe 8 framework of Ti 0.3Mo 5RuSe 8 ( Rp=10.5%, Rwp=14.6%). Rietveld analysis was also used to refine the structure of the unfilled phase Mo 5RuSe 8 ( R3¯, Z=3, a=9.63994(8) Å, c=10.97191(11) Å, Rp=8.0%, Rwp=10.5%). Comparisons between the two structures are made.

  7. Relations de phases et cristallogenèse de phases de Chevrel séliniées TRMo_{6Se8} (TR = Terre rare) : premiers résultats sur monocristal

    Science.gov (United States)

    Maho, F.; Le Berre, F.; Penã, O.; Horyń, R.; Wojakowski, A.

    1995-01-01

    An approach to grow single crystals of chosen RE-Mo-Se Chevrel phase materials from a liquid phase was done. To reduce the effects of compositional shifts due to incongruent melting (at 1 650-1 750 ^{circ}C), off-stoichiometric selenium-rich compositions were used. Prior to this, a detailed study of phase relations at 1 200 ^{circ}C was done and extended to 1 700 ^{circ}C. First preliminary magnetic and superconducting measurements were done on crystals containing RE = Gd, Ho, Er and Yb. La cristallogenèse de phases de Chevrel séléniés à base de terres rares (TRMo{6}Se{8}) a été réalisée avec succès pour TR = Gd, Ho, Er et Yb. La technique consiste en la fusion (non congruente) des compositions riches en terres rares et en sélénium, dans des nacelles hermétiques, à 1 650-1 750 ^{circ}C. Une étude des relations de phases à 1 200 ^{circ}C et son extension à 1 700 ^{circ}C ont dû être préalablement effectuées. Les mesures préliminaires de propriétés magnétiques et supraconductrices de ces cristaux ont été effectuées.

  8. Electrochemical determination of the diffusion coefficient of cations into Chevrel phase-based electrochemical transfer junction by potential step chronoamperometry and impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Seghir, S.; Stein, N. [Institut Jean Lamour - Electrochimie des Materiaux, Nancy-Universite, Universite Paul Verlaine Metz, CNRS, 1 Bd. Arago, F-57078 Metz (France); Boulanger, C., E-mail: clotilde.boulanger@univ-metz.f [Institut Jean Lamour - Electrochimie des Materiaux, Nancy-Universite, Universite Paul Verlaine Metz, CNRS, 1 Bd. Arago, F-57078 Metz (France); Lecuire, J.-M. [Institut Jean Lamour - Electrochimie des Materiaux, Nancy-Universite, Universite Paul Verlaine Metz, CNRS, 1 Bd. Arago, F-57078 Metz (France)

    2011-02-15

    The molybdenum chalcogenides Mo{sub 6}X{sub 8} (X = S, Se) offer the possibility of intercalation/de-intercalation processes by chemical or electrochemical way. Besides the different applications of so-called Chevrel phases, we have proposed an electrochemical transfer junction for selective recovery of metallic cations in the perspective of recycling of industrial liquid mineral wastes. Thus, the knowledge of the diffusion properties of cations in the Chevrel phases is essential. Here we report on the electrochemical determination of diffusion coefficients of Co{sup 2+}, Ni{sup 2+}, Fe{sup 2+}, Cd{sup 2+}, Zn{sup 2+}, Mn{sup 2+} and Cu{sup 2+} for Mo{sub 6}S{sub 8} and Mo{sub 6}Se{sub 8} matrices. Experiments were realized on samples with compactness of 50% and 96-98%. They point out that the lower compactness is unfavorable to the mobility of the cobalt ions. From potential step chronoamperometry and electrochemical impedance spectroscopy, the diffusion coefficients were found around 10{sup -9} cm{sup 2} s{sup -1}, even 10{sup -6} cm{sup 2} s{sup -1} for copper. These results confirm the high mobility of transition metal ions in studied phases and complete the data for Co, Fe or Mn-Mo{sub 6}S{sub 8} system and Mn-Mo{sub 6}Se{sub 8} system. For the sulfide phase, the following sequence for D-tilde is observed Ni < Co < Fe < Cd < Zn < Mn << Cu and can be explained in regards with structural considerations and repulsion effects for copper.

  9. Chevrel-phase solid solution Mo 6Se 8- xTe x. Study of its superconducting, magnetic and NMR properties

    Science.gov (United States)

    Hamard1a, C.; Auffret, V.; Peña, O.; Le Floch, M.; Nowak, B.; Wojakowski, A.

    2000-09-01

    The Chevrel-phase solid solution Mo 6Se 8-Mo 6Te 8 was studied by X-ray diffraction, AC and DC magnetic susceptibility and 77Se and 125Te NMR spectroscopy. From the smooth evolution of the lattice parameters and superconducting critical temperatures, a progressive substitution of selenium atoms by tellurium is shown, on the whole range of composition 0⩽ x⩽8, in the formulation Mo 6Se 8- xTe x: the unit-cell volume increases linearly because of the larger ionic size of tellurium, while Tc decreases rapidly (from 6.45 down to 0 K) because of the different formal oxidation states of the anions and a probable evolution of the Fermi level in the density of states. Results of magnetic susceptibility support this model and suggest the inhibition of the intrinsic metallic behavior with increasing x. The NMR spectra of the binaries Mo 6Se 8 and Mo 6Te 8 reveal two significant features, attributed to two different chalcogen positions in the R 3¯ symmetry. At low Se contents in Mo 6Se 8- xTe x ( x=7.5, 7 and 6), selenium first fills the two X(2) sites along the three-fold axis (2c positions), and then it becomes statistically distributed over the general 6f positions, leading to broad 77Se NMR lines. On the other hand, substitution of Te atoms in Mo 6Se 8 seems to occur in a random way, creating large perturbations on the 125Te NMR spectra, over the whole range of x. Theoretical analysis based on the presence of two anisotropic lines (of axial and non-axial symmetries, respectively) allowed us to estimate their anisotropy factors and to perfectly simulate the frequency response of both Mo 6Se 8 and Mo 6Te 8 binaries. Analysis of the Knight shift anisotropy leads us to conclude about the importance of the molybdenum z 2 molecular orbital contribution which controls the Mo-X dipolar interactions.

  10. The Chevrel phase HgMo6S8

    Directory of Open Access Journals (Sweden)

    Michel Potel

    2009-05-01

    Full Text Available The crystal structure of HgMo6S8, mercury(II hexamolybdenum octasulfide, is based on (Mo6S8S6 cluster units (overline{3} symmetry interconnected through interunit Mo—S bonds. The Hg2+ cations occupy large voids between the different cluster units and are covalently bonded to two S atoms. The Hg atoms and one S atom lie on sites with crystallographic overline{3} and 3 symmetry, respectively. Refinement of the occupancy factor of the Hg atom led to the composition Hg0.973 (3Mo6S8.

  11. Nanoscale phase change memory materials.

    Science.gov (United States)

    Caldwell, Marissa A; Jeyasingh, Rakesh Gnana David; Wong, H-S Philip; Milliron, Delia J

    2012-08-01

    Phase change memory materials store information through their reversible transitions between crystalline and amorphous states. For typical metal chalcogenide compounds, their phase transition properties directly impact critical memory characteristics and the manipulation of these is a major focus in the field. Here, we discuss recent work that explores the tuning of such properties by scaling the materials to nanoscale dimensions, including fabrication and synthetic strategies used to produce nanoscale phase change memory materials. The trends that emerge are relevant to understanding how such memory technologies will function as they scale to ever smaller dimensions and also suggest new approaches to designing materials for phase change applications. Finally, the challenges and opportunities raised by integrating nanoscale phase change materials into switching devices are discussed.

  12. Polymers in phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, M.C.; Brites, M.J.; Alexandre, J.H. [National Lab. for Energy and Geology, Lisbon (Portugal)

    2010-07-01

    Phase Change Materials (PCMs) which are the core of latent heat thermal energy storage systems are currently an area of investigation of increasing interest. Several substances differing in physical and chemical characteristics as well as in thermal behavior have been studied as PCMS{sup 1-3}. In order to meet the requisites of particular systems, auxiliary materials are often used with specific functions. This bibliographic survey shows that polymeric materials have been proposed either as the PCM itself in solid-liquid or solid-solid transitions or to perform auxiliary functions of shape stabilisation and microencapsulation for solid-liquid PCMs. The PCMs have an operating temperature ranging from around 0 C (for the system water/polyacrilamid) to around 127 C (for crosslinked HDPE). (orig.)

  13. PCM Concrete. [Phase Change Materials

    Energy Technology Data Exchange (ETDEWEB)

    Juul Andersen, T. [Danish Technological Institute, Taastrup (Denmark); Poulsen, H.-H. [BASF A/S, Roedekro (Denmark); Passov, F. [Spaencom A/S, Hedehusene (Denmark); Heiselberg, P. [Aalborg Univ..Aalborg (Denmark)

    2013-04-01

    PCM-Concrete was a research and development project launched in 2009 and finished in 2012. The project, which was funded by The Danish National Advanced Technology Foundation, had a total budget of 1.7 million Euros and included 4 partners: Danish Technological Institute (project manager), Aalborg University, BASF A/S and Spaencom A/S. The overall vision of the project was to reduce energy consumption for heating and cooling in buildings by developing high-performance concrete structures microencapsulated Phase Change Materials (PCM). The PCM used in the project was Micronal produced by BASF A/S. Micronal is small capsules with an acrylic shell and inside a wax with a melting point at approx. 23 deg. C equal to a comfortable indoor temperature. During the melting process thermal energy is transferred to chemical reaction (melting/solidification) depending on PCM being heated up or cooled down. Adding Micronal to concrete would theoretically increase the thermal mass of the concrete and improve the diurnal heat capacity which is the amount of energy that can be stored and released during 24 hours. Nevertheless, it is a relatively new technology that has not received much attention, yet. In the PCM-Concrete project 5 main investigations were carried out: 1) Development of concrete mix design with PCM. 2) Investigation of thermal properties of the PCM concrete: thermal conductivity, specific heat capacity, density. 3) Up-scaling the research to industrial production of PCM-concrete structures. 4) Testing energy efficiency in full scale. 5) Confronting aesthetic and acoustic barriers to full exploitation of the potential of PCM-concrete structures. The results from the test program showed: 1) That the diurnal heat storage capacity is higher for all 4 hollow core decks with tiles attached compared to the reference hollow core deck. 2) The hollow core decks with concrete tiles without PCM performs slightly better than the tiles with PCM. 3) That is was impossible to

  14. Research on microcapsules of phase change materials

    Institute of Scientific and Technical Information of China (English)

    DAI Xia; SHEN Xiaodong

    2006-01-01

    Microcapsule technology is a kind of technology wrapping the solid or liquid into minute-sized particles within the field of micrometer or millimeter with film forming materials. This thesis introduces microcapsule technology of phase change materials and its main functions and the structural composition, preparation methods and characterization technology of microcapsule of phase change materials. The microcapsule of phase change materials is small in size and its temperature remains unchanged during the process of heat absorption and heat release. It is of great value in research and application prospect due to these characteristics.

  15. Nuclear Concrete Materials Database Phase I Development

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Weiju [ORNL; Naus, Dan J [ORNL

    2012-05-01

    The FY 2011 accomplishments in Phase I development of the Nuclear Concrete Materials Database to support the Light Water Reactor Sustainability Program are summarized. The database has been developed using the ORNL materials database infrastructure established for the Gen IV Materials Handbook to achieve cost reduction and development efficiency. In this Phase I development, the database has been successfully designed and constructed to manage documents in the Portable Document Format generated from the Structural Materials Handbook that contains nuclear concrete materials data and related information. The completion of the Phase I database has established a solid foundation for Phase II development, in which a digital database will be designed and constructed to manage nuclear concrete materials data in various digitized formats to facilitate electronic and mathematical processing for analysis, modeling, and design applications.

  16. Heat transfer in multi-phase materials

    CERN Document Server

    Öchsner, Andreas

    2011-01-01

    This book provides a profound understanding, which physical processes and mechanisms cause the heat transfer in composite and cellular materials. It shows models for all important classes of composite materials and introduces into the latest advances. In three parts, the book covers Composite Materials (Part A), Porous and Cellular Materials (Part B) and the appearance of a conjoint solid phase and fluid aggregate (Part C).

  17. Phase transformations, stability, and materials interactions

    Energy Technology Data Exchange (ETDEWEB)

    Morris, J.W. Jr.; Brewer, L.; Cost, J.R.; Shewmon, P.

    1977-07-01

    The proceedings of the Materials Sciences Workshop on Phase Transformations, Stability, and Materials Interactions are divided into sections according to the following topics: (I) workshop scope and priorities; (II) study group reports--ERDA mission needs; (III) study group reports--technical area research priorities. (SDF)

  18. Thermal Energy Storage with Phase Change Material

    Directory of Open Access Journals (Sweden)

    Lavinia Gabriela SOCACIU

    2012-08-01

    Full Text Available Thermal energy storage (TES systems provide several alternatives for efficient energy use and conservation. Phase change materials (PCMs for TES are materials supplying thermal regulation at particular phase change temperatures by absorbing and emitting the heat of the medium. TES in general and PCMs in particular, have been a main topic in research for the last 30 years, but although the information is quantitatively enormous, it is also spread widely in the literature, and difficult to find. PCMs absorb energy during the heating process as phase change takes place and release energy to the environment in the phase change range during a reverse cooling process. PCMs possesses the ability of latent thermal energy change their state with a certain temperature. PCMs for TES are generally solid-liquid phase change materials and therefore they need encapsulation. TES systems using PCMs as a storage medium offers advantages such as high TES capacity, small unit size and isothermal behaviour during charging and discharging when compared to the sensible TES.

  19. Caloric materials near ferroic phase transitions

    Science.gov (United States)

    Moya, X.; Kar-Narayan, S.; Mathur, N. D.

    2014-05-01

    A magnetically, electrically or mechanically responsive material can undergo significant thermal changes near a ferroic phase transition when its order parameter is modified by the conjugate applied field. The resulting magnetocaloric, electrocaloric and mechanocaloric (elastocaloric or barocaloric) effects are compared here in terms of history, experimental method, performance and prospective cooling applications.

  20. Magnetocaloric materials and first order phase transitions

    DEFF Research Database (Denmark)

    Neves Bez, Henrique

    of the properties of such materials.The experimental characterization of these materials is done through various different methods, such as X-ray diffraction, magnetometry, calorimetry, direct measurements of entropy change, capacitance dilatometry, scanning electron microscopy,energy-dispersive X-ray spectrometry......This thesis studies the first order phase transitions of the magnetocaloric materials La0.67Ca0.33MnO3 and La(Fe,Mn,Si)13Hz trying to overcome challenges that these materials face when applied in active magnetic regenerators. The study is done through experimental characterization and modelling...... and magnetocaloric regenerative tests. The magnetic, thermal and structural properties obtained from such measurements are then evaluated through different models, i.e. the Curie-Weiss law, the Bean-Rodbell model, the free electron model and the Debye model.The measured magnetocaloric properties of La0.67Ca0.33MnO3...

  1. Transitional Phenomena on Phase Change Materials

    Directory of Open Access Journals (Sweden)

    Wójcik Tadeusz M.

    2014-03-01

    Full Text Available One of the most significant problem with technology development is transferring of large heat fluxes, which requires constant heat transfer temperature (in the specified temperature range. This problem concern mainly the nuclear energetics, space technologies, military technologies and most of all electronics containing integrated circuits with very large scale of integrations. Intensive heat transfer and thermal energy storage are possible by the use of phase change materials (PCMs. In the paper there are presented preliminary results of research on the use of liquid-gas (L-G PCMs and solid-solid phase change materials (S-S PCMs. For L-G PCMs the boiling characteristics were determined by increasing and decreasing the heat flux, which for certain sets of structural parameters of the heating surface and the physical properties of the liquid induce a variety of forms of transitional phenomena. Thermal energy storage is much more effective when using PCMs than sensible heat.

  2. NMR in Chevrel-phase solid solution Mo 6Se 8- xTe x

    Science.gov (United States)

    Hamard, C.; Le Floch, M.; Peña, O.; Wojakowski, A.

    1999-01-01

    The Mo 6Se 8-Mo 6Te 8 solid solution was studied by X-ray diffraction, magnetic susceptibility and 77Se and 125Te NMR. Dynamic studies show that substitution occurs differently when Se replaces Te in Mo 6Te 8 than when Te replaces Se in Mo 6Se 8. Selenium first fills the high-symmetry sites and then it becomes statistically distributed on the 6f positions of the R3¯ symmetry. In the second case, Te occupies randomly the 8 X sites of the Mo 6X 8 structure, creating large perturbations of the 125Te NMR spectra over the whole range of x.

  3. Phase change material thermal capacitor clothing

    Science.gov (United States)

    Buckley, Theresa M. (Inventor)

    2005-01-01

    An apparatus and method for metabolic cooling and insulation of a user in a cold environment. In its preferred embodiment the apparatus is a highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The apparatus 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 apparatus 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 apparatus 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.

  4. Electrical transport in crystalline phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Woda, Michael

    2012-01-06

    In this thesis, the electrical transport properties of crystalline phase change materials are discussed. Phase change materials (PCM) are a special class of semiconducting and metallic thin film alloys, typically with a high amount of the group five element antimony or the group six element tellurium, such as Ge{sub 2}Sb{sub 2}Te{sub 5}. The unique property portfolio of this material class makes it suitable for memory applications. PCMs reveal fast switching between two stable room-temperature phases (amorphous and crystalline) realized by optical laser or electrical current pulses in memory devices. Additionally, a pronounced property contrast in form of optical reflectivity and electrical conductivity between the amorphous and crystalline phase is the characteristic fingerprint of PCMs. The emerging electrical solid state memory PCRAM is a very promising candidate to replace Flash memory in the near future or to even become a universal memory, which is non-volatile and shows the speed and cyclability of DRAM. One of the main technological challenges is the switching process into the amorphous state, which is the most power demanding step. In order to reduce the switching power, the crystalline resistivity needs to be increased at a given voltage. Thus understanding and tayloring of this property is mandatory. In this work, first the technological relevance, i.e. optical and electrical memory concepts based on PCMs are introduced. Subsequently a description of the physical properties of PCMs in four categories is given. Namely, structure, kinetics, optical properties and electrical properties are discussed. Then important recent developments such as the identification of resonant bonding in crystalline PCMs and a property predicting coordination scheme are briefly reviewed. The following chapter deals with the theoretical background of electrical transport, while the next chapter introduces the experimental techniques: Sputtering, XRR, XRD, DSC, thermal annealing

  5. Material Engineering for Phase Change Memory

    Science.gov (United States)

    Cabrera, David M.

    As semiconductor devices continue to scale downward, and portable consumer electronics become more prevalent there is a need to develop memory technology that will scale with devices and use less energy, while maintaining performance. One of the leading prototypical memories that is being investigated is phase change memory. Phase change memory (PCM) is a non-volatile memory composed of 1 transistor and 1 resistor. The resistive structure includes a memory material alloy which can change between amorphous and crystalline states repeatedly using current/voltage pulses of different lengths and magnitudes. The most widely studied PCM materials are chalcogenides - Germanium-Antimony-Tellerium (GST) with Ge2Sb2Te3 and Germanium-Tellerium (GeTe) being some of the most popular stochiometries. As these cells are scaled downward, the current/voltage needed to switch these materials becomes comparable to the voltage needed to sense the cell's state. The International Roadmap for Semiconductors aims to raise the threshold field of these devices from 66.6 V/mum to be at least 375 V/mum for the year 2024. These cells are also prone to resistance drift between states, leading to bit corruption and memory loss. Phase change material properties are known to influence PCM device performance such as crystallization temperature having an effect on data retention and litetime, while resistivity values in the amorphous and crystalline phases have an effect on the current/voltage needed to write/erase the cell. Addition of dopants is also known to modify the phase change material parameters. The materials G2S2T5, GeTe, with dopants - nitrogen, silicon, titanium, and aluminum oxide and undoped Gallium-Antimonide (GaSb) are studied for these desired characteristics. Thin films of these compositions are deposited via physical vapor deposition at IBM Watson Research Center. Crystallization temperatures are investigated using time resolved x-ray diffraction at Brookhaven National Laboratory

  6. Phase Change Material Thermal Power Generator

    Science.gov (United States)

    Jones, Jack A.

    2013-01-01

    An innovative modification has been made to a previously patented design for the Phase Change Material (PCM) Thermal Generator, which works in water where ocean temperature alternatively melts wax in canisters, or allows the wax to re-solidify, causing high-pressure oil to flow through a hydraulic generator, thus creating electricity to charge a battery that powers the vehicle. In this modification, a similar thermal PCM device has been created that is heated and cooled by the air and solar radiation instead of using ocean temperature differences to change the PCM from solid to liquid. This innovation allows the device to use thermal energy to generate electricity on land, instead of just in the ocean.

  7. Phase Change Material Heat Exchanger Life Test

    Science.gov (United States)

    Lillibridge, Sean; Stephan, Ryan

    2009-01-01

    Low Lunar Orbit (LLO) poses unique thermal challenges for the orbiting space craft, particularly regarding the performance of the radiators. The IR environment of the space craft varies drastically from the light side to the dark side of the moon. The result is a situation where a radiator sized for the maximal heat load in the most adverse situation is subject to freezing on the dark side of the orbit. One solution to this problem is to implement Phase Change Material (PCM) Heat Exchangers. PCM Heat Exchangers act as a "thermal capacitor," storing thermal energy when there is too much being produced by the space craft to reject to space, and then feeding that energy back into the thermal loop when conditions are more favorable. Because they do not use an expendable resource, such as the feed water used by sublimators and evaporators, PCM Heat Exchangers are ideal for long duration LLO missions. In order to validate the performance of PCM Heat Exchangers, a life test is being conducted on four n-Pentadecane, carbon filament heat exchangers. Fluid loop performance, repeatability, and measurement of performance degradation over 2500 melt-freeze cycles will be performed.

  8. NMR study of the influence of iodine substitution in the Chevrel compounds Mo 6Te 8- xI x and Mo 6Se 8- xI x

    Science.gov (United States)

    Knoll, R.; Goren, S. D.; Korn, C.; Shames, A.; Perrin, C.; Privalov, A.; Vieth, H. M.

    2002-11-01

    We have obtained the 125Te and 77Se nuclear magnetic resonance spectra of the Chevrel type compounds Mo 6Te 8- xI x ( x=0,1,2) at room temperature and Mo 6Se 8- xI x ( x=0,0.5,1.0,1.5,2.0) over the temperature range 70-300 K, in order to study the effect of I doping in these materials. The spectra consisted of the superposition of two separate anisotropic Knight shifts corresponding to the two different crystallographic sites of the Se and Te nuclei within their respective compounds. The distinction between the two lines became more blurred with the increase of the iodine concentration. Analysis of the results tends to favor the supposition that in the case of the Se compound, the iodine favors the replacement of the Se ternary sites, although some temperature dependence on the choice of site was discerned. In the case of the Te compounds, the experimental evidence showed that even for x=2, both the ternary and the non-ternery sites were occupied. An abrupt change in the NMR parameters for Mo 6Se 8 near T=100 K was found.

  9. Energy efficiency of buildings with phase-change materials

    Directory of Open Access Journals (Sweden)

    Lukić Predrag

    2012-01-01

    Full Text Available The construction of energy efficient buildings using innovative building materials such as phase change materials, in addition to improving indoor comfort, energy savings and costs, can be achieved by increasing their market value. Because of its ability to absorb and release energy at predictable temperatures, phase change materials are effective in controlling and maintaining the thermal environment in the building. The use of phase changing materials, materials stored latent energy storage is an effective form of heat. [Projekat Ministarstva nauke Republike Srbije, br. TR36016: Experimental and theoretical investigation of frames and plates with semi-rigid connections from the view of the second order theory and stability analysis

  10. PHASE CHANGE MATERIALS IN FLOOR TILES FOR THERMAL ENERGY STORAGE

    Energy Technology Data Exchange (ETDEWEB)

    Douglas C. Hittle

    2002-10-01

    Passive solar systems integrated into residential structures significantly reduce heating energy consumption. Taking advantage of latent heat storage has further increased energy savings. This is accomplished by the incorporation of phase change materials into building materials used in passive applications. Trombe walls, ceilings and floors can all be enhanced with phase change materials. Increasing the thermal storage of floor tile by the addition of encapsulated paraffin wax is the proposed topic of research. Latent heat storage of a phase change material (PCM) is obtained during a change in phase. Typical materials use the latent heat released when the material changes from a liquid to a solid. Paraffin wax and salt hydrates are examples of such materials. Other PCMs that have been recently investigated undergo a phase transition from one solid form to another. During this process they will release heat. These are known as solid-state phase change materials. All have large latent heats, which makes them ideal for passive solar applications. Easy incorporation into various building materials is must for these materials. This proposal will address the advantages and disadvantages of using these materials in floor tile. Prototype tile will be made from a mixture of quartz, binder and phase change material. The thermal and structural properties of the prototype tiles will be tested fully. It is expected that with the addition of the phase change material the structural properties will be compromised to some extent. The ratio of phase change material in the tile will have to be varied to determine the best mixture to provide significant thermal storage, while maintaining structural properties that meet the industry standards for floor tile.

  11. Stress-Induced Phase Transformation in Incompressible Materials and Stability of Multi-Phase Deformation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The stress-induced phase transformation in incompressible materials and the interfacial stability of multi-phase deformation were studied. The existence of multi-phase deformation was determined through exploring whether the material would lose the strong ellipticity at some deformation gradient.Then, according to the stability criterion which is based on a quasi-static approach, the stability of the multi-phase deformation in incompressible materials was investigated by studying the growth/decay behaviour of the interface in the undeformed configuration when it is perturbed. At last, the way to define multi-phase deformation in incompressible materials was concluded and testified by a corresponding numerical example.

  12. A New Kind of Shape-stabilized Phase Change Materials

    Institute of Scientific and Technical Information of China (English)

    XIAO Liguang; DING Rui; SUN Hao; WANG Fujun

    2011-01-01

    Based on the lowest melting point and Schroeder's theoretical calculation formula, nanomodified organic composite phase change materials (PCMs) were prepared. The phase transition temperature and the latent heat of the materials were 24 ℃ and 172 J/g, respectively. A new shape-stabilized phase change materials were prepared, using high density polyethylene as supporting material. The PCM kept the shape when temperature was higher than melting point. Thus, it can directly contact with heat transfer media. The structure,morphology and thermal behavior of PCM were analyzed by FTIR, SEM and DSC.

  13. Phase stress measurements in composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Akiniwa, Yoshiaki; Tanaka, Keisuke [Nagoya Univ. (Japan). School of Engineering

    1997-06-01

    Using an aluminum alloy composite containing 20 wt.% of SiC powder and an aluminum alloy itself, a phase stress under monoaxial tensile load was tested using x-ray and neutron methods, to compare both of them. For specimens, a 20 vol.% SiC powder reinforced aluminum alloy and an aluminum alloy itself were used. As a result, the following results could be obtained. Young`s modulus and Poisson ratio of the aluminum alloy itself using x-ray method were E=74.5 GPa and {nu}=0.312, respectively, and those using neutron method were E=75.3 GPa and {nu}=0.384, respectively. A relationship between loading stress and lattice strain of the aluminum alloy itself using neutron method was possible to approximate linearly by containing macroscopic plastic deformation region. The lattice strain of each phase in the composite increased proportionally with loading stress in its elastic region, but when remarkably increasing plastic deformation, the lattice strain decreased proportionally in aluminum phase and increased in SiC phase. (G.K.)

  14. Nonminimum Phase Behavior of Laser Material Processing

    NARCIS (Netherlands)

    Römer, G.R.B.E.; Weerkamp, N.P.; Meijer, J.; Postma, S.

    2001-01-01

    Optical sensors are increasingly applied in laser material processing to monitor and control the lasermaterial interaction zone. Dynamic models, relating the sensor signals (e.g. as temperature or molten area) to the process inputs (e.g. laser power or beam velocity), provide the basis for the desig

  15. Thin Film Composite Materials, Phase 2

    Science.gov (United States)

    1987-01-01

    were Kevlar coated with silicone, EPDM , or neoprene rubber, with the following results: 1. Tensile testing of coated Kevlar fabric is very difficult...materials. 2. A method was developed for measuring water vapor permeability. Neoprene and EPDM are promising as coatings with good water resistance; however...control the folding of the fabric, since the diameters of the spiral channel will be fixed. Because of the stability imparted by the channel, it is

  16. Confined crystals of the smallest phase-change material.

    Science.gov (United States)

    Giusca, Cristina E; Stolojan, Vlad; Sloan, Jeremy; Börrnert, Felix; Shiozawa, Hidetsugu; Sader, Kasim; Rümmeli, Mark H; Büchner, Bernd; Silva, S Ravi P

    2013-09-11

    The demand for high-density memory in tandem with limitations imposed by the minimum feature size of current storage devices has created a need for new materials that can store information in smaller volumes than currently possible. Successfully employed in commercial optical data storage products, phase-change materials, that can reversibly and rapidly change from an amorphous phase to a crystalline phase when subject to heating or cooling have been identified for the development of the next generation electronic memories. There are limitations to the miniaturization of these devices due to current synthesis and theoretical considerations that place a lower limit of 2 nm on the minimum bit size, below which the material does not transform in the structural phase. We show here that by using carbon nanotubes of less than 2 nm diameter as templates phase-change nanowires confined to their smallest conceivable scale are obtained. Contrary to previous experimental evidence and theoretical expectations, the nanowires are found to crystallize at this scale and display amorphous-to-crystalline phase changes, fulfilling an important prerequisite of a memory element. We show evidence for the smallest phase-change material, extending thus the size limit to explore phase-change memory devices at extreme scales.

  17. Perhydroazulene-based liquid-crystalline materials with smectic phases.

    Science.gov (United States)

    Hussain, Zakir; Hopf, Henning; Eichhorn, S Holger

    2012-01-01

    New liquid-crystalline materials with a perhydroazulene core were synthesized and the stereochemistry of these compounds was investigated. The mesomorphic properties of the new LC compounds were investigated by differential scanning colorimetry, polarizing optical microscopy and X-ray diffraction. We report here on the LC properties of nonchiral materials, which predominantly exhibit smectic phases and display nematic phases only within narrow temperature ranges. The dependence of the mesogenic behavior of the new materials on the stereochemistry of the core system was also investigated. All newly synthesized compounds were fully characterized by the usual spectroscopic and analytical methods.

  18. Perhydroazulene-based liquid-crystalline materials with smectic phases

    Directory of Open Access Journals (Sweden)

    Zakir Hussain

    2012-03-01

    Full Text Available New liquid-crystalline materials with a perhydroazulene core were synthesized and the stereochemistry of these compounds was investigated. The mesomorphic properties of the new LC compounds were investigated by differential scanning colorimetry, polarizing optical microscopy and X-ray diffraction. We report here on the LC properties of nonchiral materials, which predominantly exhibit smectic phases and display nematic phases only within narrow temperature ranges. The dependence of the mesogenic behavior of the new materials on the stereochemistry of the core system was also investigated. All newly synthesized compounds were fully characterized by the usual spectroscopic and analytical methods.

  19. Unconventional phase field simulations of transforming materials with evolving microstructures

    Institute of Scientific and Technical Information of China (English)

    Jiang-Yu Li; Chi-Hou Lei; Liang-Jun Li; Yi-Chung Shu; Yun-Ya Liu

    2012-01-01

    Transforming materials with evolving microstructures is one of the most important classes of smart materials that have many potential technological applications,and an unconventional phase field approach based on the characteristic functions of transforming variants has been developed to simulate the formation and evolution of their microstructures.This approach is advantageous in its explicit material symmetry and energy well structure,minimal number of material coefficients,and easiness in coupling multiple physical processes and order parameters,and has been applied successfully to study the microstructures and macroscopic properties of shape memory alloys,ferroelectrics,ferromagnetic shape memory alloys,and multiferroic magnetoelectric crystals and films with increased complexity.In this topical review,the formulation of this unconventional phase field approach will be introduced in details,and its applications to various transforming materials will be discussed.Some examples of specific microstructures will also be presented.

  20. Thermodynamics and Kinetics of Phase Transformations in Hydrogen Storage Materials

    Energy Technology Data Exchange (ETDEWEB)

    Ceder, Gerbrand; Marzari, Nicola

    2011-08-31

    The aim of this project is to develop and apply computational materials science tools to determine and predict critical properties of hydrogen storage materials. By better understanding the absorption/desorption mechanisms and characterizing their physical properties it is possible to explore and evaluate new directions for hydrogen storage materials. Particular emphasis is on the determination of the structure and thermodynamics of hydrogen storage materials, the investigation of microscopic mechanisms of hydrogen uptake and release in various materials and the role of catalysts in this process. As a team we have decided to focus on a single material, NaAlH{sub 4}, in order to fully be able to study the many aspects of hydrogen storage. We have focused on phase stability, mass transport and size-dependent reaction mechanisms in this material.

  1. Thermal energy storage using phase change materials fundamentals and applications

    CERN Document Server

    Fleischer, Amy S

    2015-01-01

    This book presents a comprehensive introduction to the use of solid‐liquid phase change materials to store significant amounts of energy in the latent heat of fusion. The proper selection of materials for different applications is covered in detail, as is the use of high conductivity additives to enhance thermal diffusivity. Dr. Fleischer explores how applications of PCMS have expanded over the past 10 years to include the development of high efficiency building materials to reduce heating and cooling needs, smart material design for clothing, portable electronic systems thermal management, solar thermal power plant design and many others. Additional future research directions and challenges are also discussed.

  2. Thermal Performance of Microencapsulated Phase Change Material Survey

    Science.gov (United States)

    2008-03-01

    ER D C TR -0 8 -4 Basic Research/Military Construction Thermal Performance of Microencapsulated Phase Change Material Slurry Jorge L...distribution is unlimited. Basic Research/Military Construction ERDC TR-08-4 March 2008 Thermal Performance of Microencapsulated Phase Change... microencapsulated PCM (MPCM) slurries is enhanced significantly, even when using low volume fractions. MPCM slurries have potential to decrease costs and improve

  3. Thermal Performance of Microencapsulated Phase Change Material Slurry

    Science.gov (United States)

    2008-03-01

    ER D C TR -0 8 -4 Basic Research/Military Construction Thermal Performance of Microencapsulated Phase Change Material Slurry Jorge L...distribution is unlimited. Basic Research/Military Construction ERDC TR-08-4 March 2008 Thermal Performance of Microencapsulated Phase Change... microencapsulated PCM (MPCM) slurries is enhanced significantly, even when using low volume fractions. MPCM slurries have potential to decrease costs and improve

  4. Subthreshold electrical transport in amorphous phase-change materials

    Science.gov (United States)

    Le Gallo, Manuel; Kaes, Matthias; Sebastian, Abu; Krebs, Daniel

    2015-09-01

    Chalcogenide-based phase-change materials play a prominent role in information technology. In spite of decades of research, the details of electrical transport in these materials are still debated. In this article, we present a unified model based on multiple-trapping transport together with 3D Poole-Frenkel emission from a two-center Coulomb potential. With this model, we are able to explain electrical transport both in as-deposited phase-change material thin films, similar to experimental conditions in early work dating back to the 1970s, and in melt-quenched phase-change materials in nanometer-scale phase-change memory devices typically used in recent studies. Experimental measurements on two widely different device platforms show remarkable agreement with the proposed mechanism over a wide range of temperatures and electric fields. In addition, the proposed model is able to seamlessly capture the temporal evolution of the transport properties of the melt-quenched phase upon structural relaxation.

  5. Lightweight Phase-Change Material For Solar Power

    Science.gov (United States)

    Stark, Philip

    1993-01-01

    Lightweight panels containing phase-change materials developed for use as heat-storage elements of compact, lightweight, advanced solar dynamic power system. During high insolation, heat stored in panels via latent heat of fusion of phase-change material; during low insolation, heat withdrawn from panels. Storage elements consist mainly of porous carbon-fiber structures imbued with germanium. Developed for use aboard space station in orbit around Earth, also adapted to lightweight, compact, portable solar-power systems for use on Earth.

  6. Optimization of a phase change material wallboard for building use

    Energy Technology Data Exchange (ETDEWEB)

    Kuznik, Frederic; Virgone, Joseph [Thermal Sciences Center of Lyon, CNRS, UMR 5008, INSA de Lyon, Universite Lyon 1, Bat Freyssinet, 40 Rue des Arts, 69621 Villeurbanne Cedex (France); Noel, Jean [Free-lance Scientific Software Developer, 15 Place Carnot, 69002 Lyon (France)

    2008-08-15

    In construction, the use of phase change materials (PCM) allows the storage/release of energy from the solar radiation and/or internal loads. The application of such materials for lightweight construction (e.g., a wood house) makes it possible to improve thermal comfort and reduce energy consumption. A wallboard composed of a new PCM material is investigated in this paper to enhance the thermal behavior of a lightweight internal partition wall. The paper focuses on the optimization of phase change material thickness. The in-house software CODYMUR is used to optimize the PCM wallboard by the means of numerical simulations. The results show that an optimal PCM thickness exists. The optimal PCM thickness value is then calculated for use in construction. (author)

  7. Temperature reduction due to the application of phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Voelker, Conrad; Kornadt, Oliver [Department of Building Physics, Bauhaus-University Weimar, Coudraystrasse 11a, 99423 Weimar (Germany); Ostry, Milan [Faculty of Civil Engineering, Brno University of Technology, Department of Building Structures, Veveri 95, 602 00 Brno (Czech Republic)

    2008-07-01

    Overheating is a major problem in many modern buildings due to the utilization of lightweight constructions with low heat storing capacity. A possible answer to this problem is the emplacement of phase change materials (PCM), thereby increasing the thermal mass of a building. These materials change their state of aggregation within a defined temperature range. Useful PCM for buildings show a phase transition from solid to liquid and vice versa. The thermal mass of the materials is increased by the latent heat. A modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction. For realistic investigations, test rooms were erected where measurements were carried out under different conditions such as temporary air change, alternate internal heat gains or clouding. The experimental data was finally reproduced by dint of a mathematical model. (author)

  8. A Gibbs Formulation for Reactive Materials with Phase Change

    Science.gov (United States)

    Stewart, D. Scott

    2015-11-01

    A large class of applications have pure, condensed phase constituents that come into contact, chemically react and simultaneously undergo phase change. Phase change in a given molecular material has often been considered to be separate from chemical reaction. Continuum modelers of phase change often use a phase field model whereby an indicator function is allowed to change from one value to another in regions of phase change, governed by evolutionary (Ginzburg-Landau) equations, whereas classic chemical kinetics literally count species concentrations and derive kinetics evolution equations based on species mass transport. We argue the latter is fundamental and is the same as the former, if all species, phase or chemical are treated as distinct chemical species. We pose a self-consistent continuum, thermo-mechanical model to account for significant energetic quantities with correct molecular and continuum limits in the mixture. A single stress tensor, and a single temperature is assumed for the mixture with specified Gibbs potentials for all relevant species, and interaction energies. We discuss recent examples of complex reactive material modeling, drawn from thermitic and propellant combustion that use this new model. DSS supported by DTRA, ONR and AFOSR.

  9. Phase change materials and the perception of wetness

    NARCIS (Netherlands)

    Bergmann Tiest, W.M.; Kosters, N.D.; Kappers, A.M.L.; Daanen, H.A.M.

    2012-01-01

    Phase change materials (PCMs) are increasingly incorporated in textiles in order to serve as a thermal buffer when humans change from a hot to a cold environment and the reverse. Due to the absence of wetness sensors in the skin, cooling of the skin may be perceived as a sensation of wetness instead

  10. Preparation of Firefighting Hood for Cooling for Phase Change Materials

    Directory of Open Access Journals (Sweden)

    Shu Hwa Lin

    2016-10-01

    Full Text Available There are two types of Phase Change Materials (PCMs which have been developed and adopted in textiles: heat (energy released and cool (energy absorbed. This paper discusses current PCM applications and explores future applications in firefighting gear. Phase change materials are considered latent heat storage units because as they change phase from solid to liquid, liquid to gas and vice versa, energy in the form of heat is absorbed or released. The goal of PCM textiles is to create reusable energy to maintain body temperature, as well as to optimize the performance of protective wear such as hoods. When the wearer’s body temperature increases or decreases, the PCMs applied to the fabric will change state helping to regulate the wearer’s body temperature by providing warmth or cooling. Maintaining a stable body temperature can improve working conditions and comfort.

  11. Preparation of Firefighting Hood for Cooling For Phase Change Materials

    Directory of Open Access Journals (Sweden)

    Shu Hwa Lin

    2016-10-01

    Full Text Available There are two types of Phase Change Materials (PCMs which have been developed and adopted in textiles: heat (energy released and cool (energy absorbed. This paper discusses current PCM applications and explores future applications in firefighting gear. Phase change materials are considered latent heat storage units because as they change phase from solid to liquid, liquid to gas and vice versa, energy in the form of heat is absorbed or released. The goal of PCM textiles is to create reusable energy to maintain body temperature, as well as to optimize the performance of protective wear such as hoods. When the wearer’s body temperature increases or decreases, the PCMs applied to the fabric will change state helping to regulate the wearer’s body temperature by providing warmth or cooling. Maintaining a stable body temperature can improve working conditions and comfort.

  12. Ultrafast response of phase-change memory materials

    Science.gov (United States)

    Lindenberg, Aaron

    2015-03-01

    We describe recent experiments probing the first steps in the amorphous-to-crystalline transition that underlies the behavior of phase-change materials, examining both electric-field-driven and optically-driven responses in GeSbTe and AgInSbTe alloys. First measurements using femtosecond x-ray pulses at the Linac Coherent Light Source will be described which enable direct snapshots of these transitions and associated intermediate states. We will also describe studies using single-cycle terahertz pulses as an all-optical means of biasing phase-change materials on femtosecond time-scales in order to examine the threshold-switching response on microscopically relevant time-scales. These studies indicate nonlinear scaling with the applied electric field and field-induced crystallization as evidenced by ultrafast optical reflectivity and conductivity measurements, from which a mechanistic understanding of these phase transitions can be obtained.

  13. Development of Latent Heat Storage Phase Change Material Containing Plaster

    Directory of Open Access Journals (Sweden)

    Diana BAJARE

    2016-05-01

    Full Text Available This paper reviews the development of latent heat storage Phase Change Material (PCM containing plaster as in passive application. Due to the phase change, these materials can store higher amounts of thermal energy than traditional building materials and can be used to add thermal inertia to lightweight constructions. It was shown that the use of PCMs have advantages stabilizing the room temperature variations during summer days, provided sufficient night ventilation is allowed. Another advantage of PCM usage is stabilized indoor temperature on the heating season. The goal of this study is to develop cement and lime based plaster containing microencapsulated PCM. The plaster is expected to be used for passive indoor applications and enhance the thermal properties of building envelope. The plaster was investigated under Scanning Electron Microscope and the mechanical, physical and thermal properties of created plaster samples were determined.

  14. Round-Robin Test of Paraffin Phase-Change Material

    Science.gov (United States)

    Vidi, S.; Mehling, H.; Hemberger, F.; Haussmann, Th.; Laube, A.

    2015-11-01

    A round-robin test between three institutes was performed on a paraffin phase-change material (PCM) in the context of the German quality association for phase-change materials. The aim of the quality association is to define quality and test specifications for PCMs and to award certificates for successfully tested materials. To ensure the reproducibility and comparability of the measurements performed at different institutes using different measuring methods, a round-robin test was performed. The sample was unknown. The four methods used by the three participating institutes in the round-robin test were differential scanning calorimetry, Calvet calorimetry and three-layer calorimetry. Additionally, T-history measurements were made. The aim of the measurements was the determination of the enthalpy as a function of temperature. The results achieved following defined test specifications are in excellent agreement.

  15. Piezoelectric properties of rhombohedral ferroelectric materials with phase transition

    Science.gov (United States)

    Zhao, Xiaofang; Soh, A. K.

    2015-12-01

    The temporal evolution of domain structure and its piezoelectric behavior of ferroelectric material BaTiO3 during the transition process from rhombohedral to tetragonal phase under an applied electric field have been studied by employing Landau-Ginzburg theory and the phase-field method. The results obtained show that, during the transformation process, the intermediate phase was monoclinic MA phase, and several peak values of piezoelectric coefficient appeared at the stage where obvious change of domain pattern occurred. In addition, by comparing the cases of applied electric field with different frequencies, it was found that the maximum piezoelectric coefficient obtained decreased with increasing frequency value. These results are of great significance in tuning the properties of engineering domains in ferroelectrics, and could provide more fundamentals to the design of ferroelectric devices.

  16. Vibration damping and heat transfer using material phase changes

    Science.gov (United States)

    Kloucek, Petr (Inventor); Reynolds, Daniel R. (Inventor)

    2009-01-01

    A method and apparatus wherein phase changes in a material can dampen vibrational energy, dampen noise and facilitate heat transfer. One embodiment includes a method for damping vibrational energy in a body. The method comprises attaching a material to the body, wherein the material comprises a substrate, a shape memory alloy layer, and a plurality of temperature change elements. The method further comprises sensing vibrations in the body. In addition, the method comprises indicating to at least a portion of the temperature change elements to provide a temperature change in the shape memory alloy layer, wherein the temperature change is sufficient to provide a phase change in at least a portion of the shape memory alloy layer, and further wherein the phase change consumes a sufficient amount of kinetic energy to dampen at least a portion of the vibrational energy in the body. In other embodiments, the shape memory alloy layer is a thin film. Additional embodiments include a sensor connected to the material.

  17. Investigating materials formation with liquid-phase and cryogenic TEM

    Science.gov (United States)

    de Yoreo, J. J.; N. A. J. M., Sommerdijk

    2016-08-01

    The recent advent of liquid-phase transmission electron microscopy (TEM) and advances in cryogenic TEM are transforming our understanding of the physical and chemical mechanisms underlying the formation of materials in synthetic, biological and geochemical systems. These techniques have been applied to study the dynamic processes of nucleation, self-assembly, crystal growth and coarsening for metallic and semiconductor nanoparticles, (bio)minerals, electrochemical systems, macromolecular complexes, and organic and inorganic self-assembling systems. New instrumentation and methodologies that are currently on the horizon promise new opportunities for advancing the science of materials synthesis.

  18. Kinetic Processes Crystal Growth, Diffusion, and Phase Transformations in Materials

    CERN Document Server

    Jackson, Kenneth A

    2004-01-01

    The formation of solids is governed by kinetic processes, which are closely related to the macroscopic behaviour of the resulting materials. With the main focus on ease of understanding, the author begins with the basic processes at the atomic level to illustrate their connections to material properties. Diffusion processes during crystal growth and phase transformations are examined in detail. Since the underlying mathematics are very complex, approximation methods typically used in practice are the prime choice of approach. Apart from metals and alloys, the book places special emphasis on th

  19. Investigation of composite materials using SLM-based phase retrieval.

    Science.gov (United States)

    Agour, Mostafa; Falldorf, Claas; Bergmann, Ralf B

    2013-07-01

    We present a robust method to inspect a typical composite material constructed of carbon fiber reinforced plastic (CFRP). It is based on optical surface contouring using the spatial light modulator (SLM)-based phase retrieval technique. The method utilizes multiple intensity observations of the wave field, diffracted by the investigated object, captured at different planes along the optical axis to recover the phase information across the object plane. The SLM-based system allows for the recording of the required consecutive intensity measurements in various propagation states across a common recording plane. This overcomes the mechanical shifting of a camera sensor required within the capturing process. In contrast to existing phase retrieval approaches, the measuring time is considerably reduced, since the switching time of the SLM is less than 50 ms. This enables nondestructive testing under thermal load. Experimental results are presented that demonstrate the approach can be used to assess structural properties of technical components made from CFRP.

  20. Phase stability in nanoscale material systems: extension from bulk phase diagrams.

    Science.gov (United States)

    Bajaj, Saurabh; Haverty, Michael G; Arróyave, Raymundo; Goddard, William A; Shankar, Sadasivan

    2015-06-07

    Phase diagrams of multi-component systems are critical for the development and engineering of material alloys for all technological applications. At nano dimensions, surfaces (and interfaces) play a significant role in changing equilibrium thermodynamics and phase stability. In this work, it is shown that these surfaces at small dimensions affect the relative equilibrium thermodynamics of the different phases. The CALPHAD approach for material surfaces (also termed "nano-CALPHAD") is employed to investigate these changes in three binary systems by calculating their phase diagrams at nano dimensions and comparing them with their bulk counterparts. The surface energy contribution, which is the dominant factor in causing these changes, is evaluated using the spherical particle approximation. It is first validated with the Au-Si system for which experimental data on phase stability of spherical nano-sized particles is available, and then extended to calculate phase diagrams of similarly sized particles of Ge-Si and Al-Cu. Additionally, the surface energies of the associated compounds are calculated using DFT, and integrated into the thermodynamic model of the respective binary systems. In this work we found changes in miscibilities, reaction compositions of about 5 at%, and solubility temperatures ranging from 100-200 K for particles of sizes 5 nm, indicating the importance of phase equilibrium analysis at nano dimensions.

  1. A phenomenological approach of solidification of polymeric phase change materials

    Science.gov (United States)

    Bahrani, Seyed Amir; Royon, Laurent; Abou, Bérengère; Osipian, Rémy; Azzouz, Kamel; Bontemps, André

    2017-01-01

    Phase Change Materials (PCMs) are widely used in thermal energy storage and thermal management systems due to their small volume for a given stored energy and their capability for maintaining nearly constant temperatures. However, their performance is limited by their low thermal conductivity and possible leaks while in the liquid phase. One solution is to imprison the PCM inside a polymer mesh to create a Polymeric Phase Change Material (PPCM). In this work, we have studied the cooling and solidification of five PPCMs with different PCMs and polymer fractions. To understand the heat transfer mechanisms involved, we have carried out micro- and macrorheological measurements in which Brownian motion of tracers embedded in PPCMs has been depicted and viscoelastic moduli have been measured, respectively. Beyond a given polymer concentration, it was shown that the Brownian motion of the tracers is limited by the polymeric chains and that the material exhibits an elastic behavior. This would suggest that heat transfer essentially occurs by conduction, instead of convection. Experiments were conducted to measure temperature variation during cooling of the five samples, and a semi-empirical model based on a phenomenological approach was proposed as a practical tool to choose and size PPCMs.

  2. Diffraction phase microscopy: monitoring nanoscale dynamics in materials science [invited].

    Science.gov (United States)

    Edwards, Chris; Zhou, Renjie; Hwang, Suk-Won; McKeown, Steven J; Wang, Kaiyuan; Bhaduri, Basanta; Ganti, Raman; Yunker, Peter J; Yodh, Arjun G; Rogers, John A; Goddard, Lynford L; Popescu, Gabriel

    2014-09-20

    Quantitative phase imaging (QPI) utilizes the fact that the phase of an imaging field is much more sensitive than its amplitude. As fields from the source interact with the specimen, local variations in the phase front are produced, which provide structural information about the sample and can be used to reconstruct its topography with nanometer accuracy. QPI techniques do not require staining or coating of the specimen and are therefore nondestructive. Diffraction phase microscopy (DPM) combines many of the best attributes of current QPI methods; its compact configuration uses a common-path off-axis geometry which realizes the benefits of both low noise and single-shot imaging. This unique collection of features enables the DPM system to monitor, at the nanoscale, a wide variety of phenomena in their natural environments. Over the past decade, QPI techniques have become ubiquitous in biological studies and a recent effort has been made to extend QPI to materials science applications. We briefly review several recent studies which include real-time monitoring of wet etching, photochemical etching, surface wetting and evaporation, dissolution of biodegradable electronic materials, and the expansion and deformation of thin-films. We also discuss recent advances in semiconductor wafer defect detection using QPI.

  3. Scalability of Phase Change Materials in Nanostructure Template

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2015-01-01

    Full Text Available The scalability of In2Se3, one of the phase change materials, is investigated. By depositing the material onto a nanopatterned substrate, individual In2Se3 nanoclusters are confined in the nanosize pits with well-defined shape and dimension permitting the systematic study of the ultimate scaling limit of its use as a phase change memory element. In2Se3 of progressively smaller volume is heated inside a transmission electron microscope operating in diffraction mode. The volume at which the amorphous-crystalline transition can no longer be observed is taken as the ultimate scaling limit, which is approximately 5 nm3 for In2Se3. The physics for the existence of scaling limit is discussed. Using phase change memory elements in memory hierarchy is believed to reduce its energy consumption because they consume zero leakage power in memory cells. Therefore, the phase change memory applications are of great importance in terms of energy saving.

  4. Ultrafast characterization of phase-change material crystallization properties in the melt-quenched amorphous phase.

    Science.gov (United States)

    Jeyasingh, Rakesh; Fong, Scott W; Lee, Jaeho; Li, Zijian; Chang, Kuo-Wei; Mantegazza, Davide; Asheghi, Mehdi; Goodson, Kenneth E; Wong, H-S Philip

    2014-06-11

    Phase change materials are widely considered for application in nonvolatile memories because of their ability to achieve phase transformation in the nanosecond time scale. However, the knowledge of fast crystallization dynamics in these materials is limited because of the lack of fast and accurate temperature control methods. In this work, we have developed an experimental methodology that enables ultrafast characterization of phase-change dynamics on a more technologically relevant melt-quenched amorphous phase using practical device structures. We have extracted the crystallization growth velocity (U) in a functional capped phase change memory (PCM) device over 8 orders of magnitude (10(-10) programmed PCM devices at very high heating rates (>10(8) K/s), which reveals the extreme fragility of Ge2Sb2Te5 in its supercooled liquid phase. Furthermore, these crystallization properties were studied as a function of device programming cycles, and the results show degradation in the cell retention properties due to elemental segregation. The above experiments are enabled by the use of an on-chip fast heater and thermometer called as microthermal stage (MTS) integrated with a vertical phase change memory (PCM) cell. The temperature at the PCM layer can be controlled up to 600 K using MTS and with a thermal time constant of 800 ns, leading to heating rates ∼10(8) K/s that are close to the typical device operating conditions during PCM programming. The MTS allows us to independently control the electrical and thermal aspects of phase transformation (inseparable in a conventional PCM cell) and extract the temperature dependence of key material properties in real PCM devices.

  5. Phase change thermal control materials, method and apparatus

    Science.gov (United States)

    Buckley, Theresa M. (Inventor)

    2001-01-01

    An apparatus and method for metabolic cooling and insulation of a user in a cold environment. In its preferred embodiment the apparatus is a highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The apparatus 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 apparatus 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 apparatus 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.

  6. Phase classification by mean shift clustering of multispectral materials images.

    Science.gov (United States)

    Martins, Diego Schmaedech; Josa, Victor M Galván; Castellano, Gustavo; da Costa, José A T Borges

    2013-10-01

    A mean-shift clustering (MSC) algorithm is introduced as a valuable alternative to perform materials phase classification from multispectral images. As opposed to other multivariate statistical techniques, such as factor analysis or principal component analysis (PCA), clustering techniques directly assign a class label to each pixel, so that their outputs are phase segmented images, i.e., there is no need for an additional segmentation algorithm. On the other hand, as compared to other clustering procedures and classification methods, such as segmentation by thresholding of multiple spectral components, MSC has the advantages of not requiring previous knowledge of the number of data clusters and not assuming any shape for these clusters, i.e., neither the number nor the composition of the phases must be previously known. This makes MSC a particularly useful tool for exploratory research, assisting phase identification of unknown samples. Visualization and interpretation of the results are also simplified, since the information content of the output image does not depend on the particular choice of the content of the color channels.We applied MSC to the analysis of two sets of X-ray maps acquired in scanning electron microscopes equipped with energy-dispersive detection systems. Our results indicate that MSC is capable of detecting additional phases, not clearly identified through PCA or multiple thresholding, with a very low empirical reject rate.

  7. Electric-field-assisted crystallisation in phase-change materials

    Energy Technology Data Exchange (ETDEWEB)

    Kohary, Krisztian; Diosdado, Jorge A.V.; Ashwin, Peter; Wright, C. David [College of Engineering, Mathematics, and Physical Sciences, University of Exeter (United Kingdom)

    2012-10-15

    Phase-change materials are of intense research interest due mainly to their use in phase-change memory (PCM) devices that are emerging as a promising technology for future non-volatile, solid-state, electrical storage. Electrically driven transitions from the amorphous to the crystalline phase in such devices exhibit characteristic threshold switching. Several alternative electronic explanations for the origins of this characteristic behaviour have been put forward, for example Poole-Frenkel effects, delocalisation of tail states, field emission processes and space charge limited currents [for a full discussion, see Radielli et al., J. Appl. Phys. 103, 111101 (2008) and Simon et al., MRS Proc. 1251, H01-H011 (2010)]. However, an alternative to these conventional electronic models of threshold switching is based on electric field induced lowering of the system free energy, leading to the field induced nucleation of conducting crystal filaments. In this paper we investigate this alternative view. We present a detailed kinetics study of crystallisation in the presence of an electric field for the phase-change material Ge{sub 2}Sb{sub 2}Te{sub 5}. We derive quantitative crystallisation maps to show the effects of both temperature and electric field on crystallisation and we identify field ranges and parameter values where the electric field might play a significant role. Then we carry out physically realistic simulations of the threshold switching process in typical phase-change device structures, both with and without electric field dependent energy contributions to the system free energy. Our results show that threshold switching can be obtained by a mechanism driven purely by electric field induced nucleation, but the fields so required are large, of the order of 300 MV m{sup -1}, and significantly larger than the experimentally measured threshold fields. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Particle Rebound and Phase State of Secondary Organic Material

    Science.gov (United States)

    Bateman, A.; Bertram, A. K.; Martin, S. T.

    2014-12-01

    Secondary organic material (SOM) is produced in the atmosphere from the oxidation of volatile organic compounds emitted from anthropogenic and biogenic sources. Aerosol particles, composed in part of SOM, play important roles in climate and air quality by scattering/absorbing radiation and serving as cloud condensation nuclei (CCN). The magnitude of climate-relevant perturbations depends on particle chemical composition, hygroscopic growth, and phase state, among other factors. Herein, the hygroscopic influence on particle rebound and the phase state of particles composed of isoprene, toluene, and α-pinene secondary organic material (SOM) was studied. Particle rebound measurements were obtained from 5 to 95% RH using a three-arm impaction apparatus. The experimentally determined rebound fractions were compared with results from a model of the rebound process that took into account the particle kinetic energy, van der Waals forces, and RH-dependent capillary forces. Comparison of the experimental and modeled indicated particles softened due to water uptake. For low RH values, the model explained the rebound behavior for all studied SOMs. At higher RH values specific to each SOM, however, particle rebound was no longer observed, and the model did not capture this behavior. Calibration experiments using sucrose particles of variable known viscosities showed the transition from non-rebounding to rebounding particles occurred for viscosity values from 100 to 1 Pa s, corresponding to a transition from semisolid to liquid material. The implication of the differing RH-dependent behaviors among the SOMs is that each SOM has a specific and quantitatively different interaction with water. A linear correlation between rebound fraction and hygroscopic growth factor was demonstrated, implying that absorbed water volume is the governing factor of viscosity for the studied classes of SOM. The findings of this study suggest that both the chemical composition and the ambient

  9. Sb-Te Phase-change Materials under Nanoscale Confinement

    Science.gov (United States)

    Ihalawela, Chandrasiri A.

    Size, speed and efficiency are the major challenges of next generation nonvolatile memory (NVM), and phase-change memory (PCM) has captured a great attention due to its promising features. The key for PCM is rapid and reversible switching between amorphous and crystalline phases with optical or electrical excitation. The structural transition is associated with significant contrast in material properties which can be utilized in optical (CD, DVD, BD) and electronic (PCRAM) memory applications. Importantly, both the functionality and the success of PCM technology significantly depend on the core material and its properties. So investigating PC materials is crucial for the development of PCM technology to realized enhanced solutions. In regards to PC materials, Sb-Te binary plays a significant role as a basis to the well-known Ge-Sb-Te system. Unlike the conventional deposition methods (sputtering, evaporation), electrochemical deposition method is used due to its multiple advantages, such as conformality, via filling capability, etc. First, the controllable synthesis of Sb-Te thin films was studied for a wide range of compositions using this novel deposition method. Secondly, the solid electrolytic nature of stoichiometric Sb2Te3 was studied with respect to precious metals. With the understanding of 2D thin film synthesis, Sb-Te 1D nanowires (18 - 220 nm) were synthesized using templated electrodeposition, where nanoporous anodic aluminum oxide (AAO) was used as a template for the growth of nanowires. In order to gain the controllability over the deposition in high aspect ratio structures, growth mechanisms of both the thin films and nanowires were investigated. Systematic understanding gained thorough previous studies helped to formulate the ultimate goal of this dissertation. In this dissertation, the main objective is to understand the size effect of PC materials on their phase transition properties. The reduction of effective memory cell size in conjunction with

  10. Microencapsulated Phase Change Composite Materials for Energy Efficient Buildings

    Science.gov (United States)

    Thiele, Alexander

    This study aims to elucidate how phase change material (PCM)-composite materials can be leveraged to reduce the energy consumption of buildings and to provide cost savings to ratepayers. Phase change materials (PCMs) can store thermal energy in the form of latent heat when subjected to temperatures exceeding their melting point by undergoing a phase transition from solid to liquid state. Reversibly, PCMs can release this thermal energy when the system temperature falls below their solidification point. The goal in implementing composite PCM walls is to significantly reduce and time-shift the maximum thermal load on the building in order to reduce and smooth out the electricity demand for heating and cooling. This Ph.D. thesis aims to develop a set of thermal design methods and tools for exploring the use of PCM-composite building envelopes and for providing design rules for their practical implementation. First, detailed numerical simulations were used to show that the effective thermal conductivity of core-shell-matrix composites depended only on the volume fraction and thermal conductivity of the constituent materials. The effective medium approximation reported by Felske (2004) was in very good agreement with numerical predictions of the effective thermal conductivity. Second, a carefully validated transient thermal model was used to simulate microencapsulated PCM-composite walls subjected to diurnal or annual outdoor temperature and solar radiation flux. It was established that adding microencapsulated PCM to concrete walls both substantially reduced and delayed the thermal load on the building. Several design rules were established, most notably, (i) increasing the volume fraction of microencapsulated PCM within the wall increases the energy savings but at the potential expense of mechanical properties [1], (ii) the phase change temperature leading to the maximum energy and cost savings should equal the desired indoor temperature regardless of the climate

  11. Artefacts in geometric phase analysis of compound materials

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Jonathan J.P., E-mail: j.j.p.peters@warwick.ac.uk [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Beanland, Richard; Alexe, Marin [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Cockburn, John W.; Revin, Dmitry G.; Zhang, Shiyong Y. [Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Sanchez, Ana M., E-mail: a.m.sanchez@warwick.ac.uk [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom)

    2015-10-15

    The geometric phase analysis (GPA) algorithm is known as a robust and straightforward technique that can be used to measure lattice strains in high resolution transmission electron microscope (TEM) images. It is also attractive for analysis of aberration-corrected scanning TEM (ac-STEM) images that resolve every atom column, since it uses Fourier transforms and does not require real-space peak detection and assignment to appropriate sublattices. Here it is demonstrated that, in ac-STEM images of compound materials with compositionally distinct atom columns, an additional geometric phase is present in the Fourier transform. If the structure changes from one area to another in the image (e.g. across an interface), the change in this additional phase will appear as a strain in conventional GPA, even if there is no lattice strain. Strategies to avoid this pitfall are outlined. - Highlights: • GPA is shown to produce incorrect strains when applied to images of compound materials. • A mathematical description is laid out for why GPA can produce artefacts. • The artefact is demonstrated using experimental and simulated data. • A ‘rule’ is set to avoid this artefact in GPA.

  12. Study of Phase Change Materials Applied to CPV Receivers

    Directory of Open Access Journals (Sweden)

    Zun-Hao Shih

    2015-01-01

    Full Text Available There are lots of factors which can directly affect output efficiency of photovoltaic device. One of them is high temperature which would cause adverse effect to solar cell. When solar cell is operated in high temperature, the cell’s output efficiency will become low. Therefore, improving thermal spreading of solar cell is an important issue. In this study, we focused on finding new materials to enhance the thermal dispreading and keep the temperature of solar cell as low as possible. The new materials are different from conventional metal ones; they are called “phase change materials (PCMs” which are mainly applied to green buildings. We chose two kinds of PSMs to study their thermal dispreading ability and to compare them with traditional aluminum material. These two kinds of PCMs are wax and lauric acid. We made three aluminum-based cuboids as heat sinking units and two of them were designed with hollow space to fill in the PCMs. We applied electric forward bias on solar cells to simulate the heat contributed from the concentrated sunlight. Then we observed the thermal distribution of these three kinds of thermal spreading materials. Two levels of forward biases were chosen to test the samples and analyze the experiment results.

  13. The Study of the Thermoelectric Properties of Phase Change Materials

    Science.gov (United States)

    Yin, Ming; Abdi, Mohammed; Noimande, Zibusisu; Mbamalu, Godwin; Alameeri, Dheyaa; Datta, Timir

    We study thermoelectric property that is electrical phenomena occurring in conjunction with the flow of heat of phase-change materials (PCM) in particular GeSbTe (GST225). From given sets of material parameters, COMSOL Multiphysics heat-transfer module is used to compute maps of temperature and voltage distribution in the PCM samples. These results are used to design an apparatus including the variable temperature sample holder set up. An Arbitrary/ Function generator and a circuit setup is also designed to control the alternation of heaters embedded on the sample holder in order to ensure sequential back and forward flow of heat current from both sides of the sample. Accurate values of potential differences and temperature distribution profiles are obtained in order to compute the Seebeck coefficient of the sample. The results of elemental analysis and imaging studies such as XRD, UV-VIS, EDEX and SEM of the sample are obtained. Factors affecting the thermoelectric properties of phase change memory are also discussed. NNSA/ DOD Consortium for Materials and Energy Studies.

  14. Thermal performance of sodium acetate trihydrate thickened with different materials as phase change energy storage material

    Energy Technology Data Exchange (ETDEWEB)

    Cabeza, L.F. [Universitat de Lleida (Spain); Svensson, G.; Hiebler, S.; Mehling, H. [ZAE Bayern, Garching (Germany)

    2003-09-01

    The use of phase change materials (PCMs) in energy storage has the advantage of high energy density and isothermal operation. Although the use of only non-segregating PCMs is a good commercial approach, some desirable PCM melting points do not seem attainable with non-segregating salt hydrates at a reasonable price. The addition of gellants and thickeners can avoid segregation of these materials. In this paper, sodium acetate trihydrate is successfully thickened with bentonite and starch. Cellulose gives an even better thickened PCM, but temperatures higher than 65 {sup o}C give phase separation. The mixtures would show a similar thermal behavior as the salt hydrate, with the same melting point and an enthalpy decrease between 20% and 35%, depending on the type and amount of thickening material used. (Author)

  15. Design of materials with extreme thermal expansion using a three-phase topology optimization method

    DEFF Research Database (Denmark)

    Sigmund, Ole; Torquato, S.

    1997-01-01

    Composites with extremal or unusual thermal expansion coefficients are designed using a three-phase topology optimization method. The composites are made of two different material phases and a void phase. The topology optimization method consists in finding the distribution of material phases...... materials having maximum directional thermal expansion (thermal actuators), zero isotropic thermal expansion, and negative isotropic thermal expansion. It is shown that materials with effective negative thermal expansion coefficients can be obtained by mixing two phases with positive thermal expansion...

  16. Phase Change Materials for Thermal Management of IC Packages

    Directory of Open Access Journals (Sweden)

    P. Fiala

    2007-06-01

    Full Text Available This paper deals with the application of phase change materials (PCM for thermal management of integrated circuits as a viable alternative to active forced convection cooling systems. The paper presents an analytical description and solution of heat transfer, melting and freezing process in 1D which is applied to inorganic crystalline salts. There are also results of numerical simulation of a real 3D model. These results were obtained by means of the finite element method (FEM. Results of 3D numerical solutions were verified experimentally.

  17. Phase I. Lanthanum-based Start Materials for Hydride Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Gschneidner, K. A. [Ames Lab., Ames, IA (United States); Schmidt, F. A. [Ames Lab., Ames, IA (United States); Frerichs, A. E. [Ames Lab., Ames, IA (United States); Ament, K. A. [Ames Lab., Ames, IA (United States)

    2013-08-20

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La1-xRx)(Ni1-yMy)(Siz), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.

  18. Electronic transport in amorphous phase-change materials

    Energy Technology Data Exchange (ETDEWEB)

    Luckas, Jennifer Maria

    2012-09-14

    Phase change materials combine a pronounced contrast in resistivity and reflectivity between their disordered amorphous and ordered crystalline state with very fast crystallization kinetics. Due to this exceptional combination of properties phase-change materials find broad application in non-volatile optical memories such as CD, DVD or Bluray Disc. Furthermore, this class of materials demonstrates remarkable electrical transport phenomena in their disordered state, which have shown to be crucial for their application in electronic storage devices. The threshold switching phenomenon denotes the sudden decrease in resistivity beyond a critical electrical threshold field. The threshold switching phenomenon facilitates the phase transitions at practical small voltages. Below this threshold the amorphous state resistivity is thermally activated and is observed to increase with time. This effect known as resistance drift seriously hampers the development of multi-level storage devices. Hence, understanding the physical origins of threshold switching and resistance drift phenomena is crucial to improve non-volatile phase-change memories. Even though both phenomena are often attributed to localized defect states in the band gap, the defect state density in amorphous phase-change materials has remained poorly studied. Starting from a brief introduction of the physics of phase-change materials this thesis summarizes the most important models behind electrical switching and resistance drift with the aim to discuss the role of localized defect states. The centerpiece of this thesis is the investigation of defects state densities in different amorphous phase-change materials and electrical switching chalcogenides. On the basis of Modulated Photo Current (MPC) Experiments and Photothermal Deflection Spectroscopy, a sophisticated band model for the disordered phase of the binary phase-change alloy GeTe has been developed. By this direct experimental approach the band-model for a

  19. Pickering Emulsification to Mass Produce Nanoencapsulated Phase-change-material

    Science.gov (United States)

    Wang, Xuezhen; Zhang, Lecheng; Yu, Yi-Hsien; Mannan, S. Sam; Chen, Ying; Cheng, Zhengdong; Cheng's Group Team, Dr.

    2015-03-01

    Phase changing materials (PCM) have useful applications in thermal management. However, mass production of micro and nano encapsulated PCM has been a challenge. Here, we present a simple and scalable method via a two-step Pickering emulsification method. We have developed interface active nanoplates by asymmetric modification of nanoplates of layered crystal materials. Nanoencapsulated PCM is realized with exfoliated monolayer nanoplates surfactants using very little energy input for emulsification. Further chemical reactions are performed to convert the emulsions into core-shell structures. The resulted capsules are submicron in size with remarkable uniformity in size distribution. DSC characterization showed that the capsulation efficiency of NEPCM was 58.58% and were thermal stable which was characterized by the DSC data for the sample after 200 thermal cycling.

  20. Review on phase change materials for building applications

    Directory of Open Access Journals (Sweden)

    Lavinia SOCACIU

    2014-11-01

    Full Text Available In nowadays, the Phase Change Material (PCM is a viable alternative for reducing the energy consumption and for increase the thermal comfort in buildings. The use of PCM in building applications provides the potential to increase the indoor thermal comfort for occupants due to the reduced indoor temperature fluctuations and lower global energy consumption. The possibility to incorporate the PCM into the material of construction for cooling and heating the buildings gained the interest of researchers from all the world because the PCM have a high heat of fusion, meaning it is capable to storing and release large amounts of energy in the form of heat during its melting and solidifying process at a specific temperature.

  1. Research on phase-change material building mass applied in the air-conditioning field

    Institute of Scientific and Technical Information of China (English)

    YANQuanying

    2003-01-01

    Phase-change material building mass contains phase-change matenals. It can decrease air-conditioning load and indoor temperature fluctuations, and improve comfort degree in summer because of thermal storage property of phase-change material. Thereby, the scale, initial investment and operational cost of air-conditioning system decrease effectively. The indoor surroundings improve. In this paper, suitable phase-change material used in architecture and combination mode between phase change material and architectural material were studied. By considering the properties of materials, such as phase-change temperature, phase-change latent heat, thermal conductivity and expansion coefficient, phase-change materials were selected and evaluated. Combination mode between phase-change material and architectural material were provided. The influence of phase-change material structure on thermal performance in room and energy-saving effect were analyzed and compared with traditional structure without phase-change material. It is proved that phase-change material structure is feasible in the practical engineenng. These provide the basis for developing phase-change material building mass.

  2. Phase Change Material Heat Sink for an ISS Flight Experiment

    Science.gov (United States)

    Quinn, Gregory; Stieber, Jesse; Sheth, Rubik; Ahlstrom, Thomas

    2015-01-01

    A flight experiment is being constructed to utilize the persistent microgravity environment of the International Space Station (ISS) to prove out operation of a microgravity compatible phase change material (PCM) heat sink. A PCM heat sink can help to reduce the overall mass and volume of future exploration spacecraft thermal control systems (TCS). The program is characterizing a new PCM heat sink that incorporates a novel phase management approach to prevent high pressures and structural deformation that often occur with PCM heat sinks undergoing cyclic operation in microgravity. The PCM unit was made using brazed aluminum construction with paraffin wax as the fusible material. It is designed to be installed into a propylene glycol and water cooling loop, with scaling consistent with the conceptual designs for the Orion Multipurpose Crew Vehicle. This paper reports on the construction of the PCM heat sink and on initial ground test results conducted at UTC Aerospace Systems prior to delivery to NASA. The prototype will be tested later on the ground and in orbit via a self-contained experiment package developed by NASA Johnson Space Center to operate in an ISS EXPRESS rack.

  3. An investigation on phase change materials to reduce summer overheating

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, S.; Kornadt, O. [Bauhaus-University Weimar, Weimar (Germany). Dept. of Building Physics

    2006-07-01

    The overheating problem in office buildings can be partially attributed to modern architectural constructions with high glazing facades and light-weight constructions. One way to solve the problem is to use phase change materials (PCMs) which are heat accumulators that store and release heat during the phase change process. PCMs increase the thermal mass in buildings and help reduce peak temperatures during summer hot spells. This study examined the heat storing effect of PCMs and their potential use in the building sector. In particular, 2 PCMs were examined in full scale experiments at the Bauhaus-University Weimar. The study examined the effects of PCMs placed on the surface of inner partitioning, ceilings or floors that could be numerically treated as a separate layer with room-side heat transfer one side and heat conduction to the next layers on the other side. Experimental results led to the development of a numerical description of the phase change process with and without super-cooling. The numerical description was based on temperature dependent functions for heat capacity and thermal conductivity. This presentation described the validation, stability and accuracy of the model and proposed recommendations. Simulation results of PCM-plaster with micro-encapsulated paraffin show the potential of a marketable material. In addition to optimizing the melting temperature and layer thickness, an important criterion for PCM efficiency is the number of overheating hours that can be reduced. For a European climate, a 3 cm layer thick PCM plaster with optimized peak temperature can reduce overheating hours by 25 to 50 per cent. 15 refs., 1 tab., 8 figs.

  4. Electronic transport in amorphous phase-change materials

    Energy Technology Data Exchange (ETDEWEB)

    Luckas, Jennifer Maria

    2012-09-14

    Phase change materials combine a pronounced contrast in resistivity and reflectivity between their disordered amorphous and ordered crystalline state with very fast crystallization kinetics. Due to this exceptional combination of properties phase-change materials find broad application in non-volatile optical memories such as CD, DVD or Bluray Disc. Furthermore, this class of materials demonstrates remarkable electrical transport phenomena in their disordered state, which have shown to be crucial for their application in electronic storage devices. The threshold switching phenomenon denotes the sudden decrease in resistivity beyond a critical electrical threshold field. The threshold switching phenomenon facilitates the phase transitions at practical small voltages. Below this threshold the amorphous state resistivity is thermally activated and is observed to increase with time. This effect known as resistance drift seriously hampers the development of multi-level storage devices. Hence, understanding the physical origins of threshold switching and resistance drift phenomena is crucial to improve non-volatile phase-change memories. Even though both phenomena are often attributed to localized defect states in the band gap, the defect state density in amorphous phase-change materials has remained poorly studied. Starting from a brief introduction of the physics of phase-change materials this thesis summarizes the most important models behind electrical switching and resistance drift with the aim to discuss the role of localized defect states. The centerpiece of this thesis is the investigation of defects state densities in different amorphous phase-change materials and electrical switching chalcogenides. On the basis of Modulated Photo Current (MPC) Experiments and Photothermal Deflection Spectroscopy, a sophisticated band model for the disordered phase of the binary phase-change alloy GeTe has been developed. By this direct experimental approach the band-model for a

  5. Micro-encapsulated phase-change materials integrated into construction materials

    Energy Technology Data Exchange (ETDEWEB)

    Schossig, P.; Henning, H.-M.; Gschwander, S. [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany); Haussmann, T. [PSE GmbH-Forschung, Entwicklung, Marketing Solar Info Center, 79072 Freiburg (Germany)

    2005-11-15

    The idea of improving the thermal comfort of lightweight buildings by integrating phase-change materials (PCMs) into the building structure has been investigated in various research projects over several decades. Most of these attempts applied macro-capsules or direct immersion processes, which both turned out to present several drawbacks. Due to these problems, none of these PCM products was successful in the wider market. The new option to micro-encapsulate PCMs, a key technology which overcomes many of these problems, may make PCM products accessible for the building industry. This paper describes the work done at Fraunhofer ISE within a German government-funded project over the last 5 years, extending from building simulations to first measurements of full-size rooms equipped with PCM. The first products are now available on the market. (author) [Phase change material; Passive cooling; Energy efficient building; Microencapsulation].

  6. Materials Research Society Symposia Proceedings, Volume 19. Alloy Phase Diagrams Held November 1982 in Boston, Massachusetts.

    Science.gov (United States)

    Alloys, * Phase diagrams , *Symposia, Stability, Thermodynamic properties, Models, Solidification, Chemical equilibrium, Microstructure, Metallurgy, Structural analysis, Research management, Materials

  7. Structure of covalently bonded materials: From the Peierls distortion to Phase-Change Materials

    Science.gov (United States)

    Gaspard, Jean-Pierre

    2016-03-01

    The relation between electronic structure and cohesion of materials has been a permanent quest of Jacques Friedel and his school. He developed simple models that are of great value as guidelines in conjunction with ab initio calculations. His local approach of bonding has both the advantages of a large field of applications including non-crystalline materials and a common language with chemists. Along this line, we review some fascinating behaviors of covalent materials, most of them showing a Peierls (symmetry breaking) instability mechanism, even in liquid and amorphous materials. We analyze the effect of external parameters such as pressure and temperature. In some temperature ranges, the Peierls distortion disappears and a negative thermal expansion is observed. In addition, the Peierls distortion plays a central role in Phase-Change Materials, which are very promising non-volatile memories. Son approche locale de la liaison chimique s'applique à un vaste champ de systèmes, incluant les matériaux non cristallins et permis un langage commun avec les chimistes. Dans cet axe nous passons en revue quelques comportements fascinants des matériaux covalents, la plupart d'entre eux présentant un mécanisme d'instabilité de Peierls (brisure de symétrie), même les liquides et les amorphes, étonnamment. Nous analysons aussi l'effet de parame'tres externes tels que la pression et la température. Dans un certain domaine de température, la distorsion de Peierls disparaît et une dilatation thermique négative est observée. Enfin, la distorsion de Peierls joue un rôle central dans les matériaux à changement de phase (PC materials), qui sont très prometteurs pour la réalisation de mémoires non volatiles.

  8. Enhancing the performance of BICPV systems using phase change materials

    Science.gov (United States)

    Sharma, Shivangi; Sellami, Nazmi; Tahir, Asif; Reddy, K. S.; Mallick, Tapas K.

    2015-09-01

    Building Integrated Concentrated Photovoltaic (BICPV) systems have three main benefits for integration into built environments, namely, (i) generating electricity at the point of use (ii) allowing light efficacy within the building envelope and (iii) providing thermal management. In this work, to maintain solar cell operating temperature and improve its performance, a phase change material (PCM) container has been designed, developed and integrated with the BICPV system. Using highly collimated continuous light source, an indoor experiment was performed. The absolute electrical power conversion efficiency for the module without PCM cooling resulted in 7.82% while using PCM increased it to 9.07%, thus showing a relative increase by 15.9% as compared to a non- PCM system. A maximum temperature reduction of 5.2°C was also observed when the BICPV module was integrated with PCM containment as compared to the BICPV system without any PCM containment.

  9. Cooling of mobile electronic devices using phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Tan, F.L.; Tso, C.P. [Nanyang Technological University (Singapore). School of Mechanical and Production Engineering

    2004-02-01

    An experimental study is conducted on the cooling of mobile electronic devices, such as personal digital assistants (PDAs) and wearable computers, using a heat storage unit (HSU) filled with the phase change material (PCM) of n-eicosane inside the device. The high latent heat of n-eicosane in the HSU absorbs the heat dissipation from the chips and can maintain the chip temperature below the allowable service temperature of 50{sup o}C for 2 h of transient operations of the PDA. The heat dissipation of the chips inside a PDA and the orientation of the HSU are experimentally investigated in this paper. It was found that different orientation of the HSU inside the PDA could affect significantly the temperature distribution. (author)

  10. Plastic phase change material and articles made therefrom

    Science.gov (United States)

    Abhari, Ramin

    2016-04-19

    The present invention generally relates to a method for manufacturing phase change material (PCM) pellets. The method includes providing a melt composition, including paraffin and a polymer. The paraffin has a melt point of between about 10.degree. C. and about 50.degree. C., and more preferably between about 18.degree. C. and about 28.degree. C. In one embodiment, the melt composition includes various additives, such as a flame retardant. The method further includes forming the melt composition into PCM pellets. The method further may include the step of cooling the melt to increase the melt viscosity before pelletizing. Further, PCM compounds are provided having an organic PCM and a polymer. Methods are provided to convert the PCM compounds into various form-stable PCMs. A method of coating the PCMs is included to provide PCMs with substantially no paraffin seepage and with ignition resistance properties.

  11. Force law in material media, hidden momentum and quantum phases

    Energy Technology Data Exchange (ETDEWEB)

    Kholmetskii, Alexander L., E-mail: alkholmetskii@gmail.com [Belarusian State University, Minsk (Belarus); Missevitch, Oleg V. [Institute for Nuclear Problems, Belarusian State University, Minsk (Belarus); Yarman, T. [Okan University, Akfirat, Istanbul (Turkey); Savronik, Eskisehir (Turkey)

    2016-06-15

    We address to the force law in classical electrodynamics of material media, paying attention on the force term due to time variation of hidden momentum of magnetic dipoles. We highlight that the emergence of this force component is required by the general theorem, deriving zero total momentum for any static configuration of charges/currents. At the same time, we disclose the impossibility to add this force term covariantly to the Lorentz force law in material media. We further show that the adoption of the Einstein–Laub force law does not resolve the issue, because for a small electric/magnetic dipole, the density of Einstein–Laub force integrates exactly to the same equation, like the Lorentz force with the inclusion of hidden momentum contribution. Thus, none of the available expressions for the force on a moving dipole is compatible with the relativistic transformation of force, and we support this statement with a number of particular examples. In this respect, we suggest applying the Lagrangian approach to the derivation of the force law in a magnetized/polarized medium. In the framework of this approach we obtain the novel expression for the force on a small electric/magnetic dipole, with the novel expression for its generalized momentum. The latter expression implies two novel quantum effects with non-topological phases, when an electric dipole is moving in an electric field, and when a magnetic dipole is moving in a magnetic field. These phases, in general, are not related to dynamical effects, because they are not equal to zero, when the classical force on a dipole is vanishing. The implications of the obtained results are discussed.

  12. Subscale Water Based Phase Change Material Heat Exchanger Development

    Science.gov (United States)

    Sheth, Rubik; Hansen, Scott

    2016-01-01

    Supplemental heat rejection devices are required in many spacecraft as the radiators are not sized to meet the full heat rejection demand. One means of obtaining additional heat rejection is through the use of phase change material heat exchangers (PCM HX's). PCM HX's utilize phase change to store energy in unfavorable thermal environments (melting) and reject the energy in favorable environments (freezing). Traditionally, wax has been used as a PCM on spacecraft. However, water is an attractive alternative because it is capable of storing about 40% more energy per unit mass due to its higher latent heat of fusion. The significant problem in using water as a PCM is its expansion while freezing, leading to structural integrity concerns when housed in an enclosed heat exchanger volume. Significant investigation and development has taken place over the past five years to understand and overcome the problems associated with water PCM HX's. This paper reports on the final efforts by Johnson Space Center's Thermal Systems Branch to develop a water based PCM HX. The test article developed and reported on is a subscale version of the full-scale water-based PCM HX's constructed by Mezzo Technologies. The subscale unit was designed by applying prior research on freeze front propagation and previous full-scale water PCM HX development. Design modifications to the subscale unit included use of urethane bladder, decreased aspect ratio, perforated protection sheet, and use of additional mid-plates. Testing of the subscale unit was successful and 150 cycles were completed without fail.

  13. Pressure-induced phase transition in silicon nitride material

    Institute of Scientific and Technical Information of China (English)

    Chen Dong; Yu Ben-Hai

    2013-01-01

    The equilibrium crystal structures,lattice parameters,elastic constants,and elastic moduli of the polymorphs α-,β-,and γ-Si3N4,have been calculated by first-principles method.β-Si3N4 is ductile in nature and has an ionic bonding.γ-Si3N4 is found to be a brittle material and has covalent chemical bonds,especially at high pressures.The phase boundary of the β → γ transition is obtained and a positive slope is found.This indicates that at higher temperatures it requires higher pressures to synthesize γ-Si3N4.On the other hand,the α → γ phase boundary can be described as P =14.37198 + 3.27 × 10-3T-7.83911 × 10-7T2-3.13552 × 10-10T3.The phase transition from α-to γ-Si3N4 occurs at 16.1 GPa and 1700 K.Then,the dependencies of bulk modulus,heat capacity,and thermal expansion on the pressure P are obtained in the ranges of 0 GPa-30 GPa and 0 K-2000 K.Significant features in these properties are observed at high temperatures.It turns out that the thermal expansion of γ-Si3N4 is larger than that of α-Si3N4 over wide pressure and temperature ranges.The evolutions of the heat capacity with temperature for the Si3N4 polymorphs are close to each other,which are important for possible applications of Si3N4.

  14. Water Based Phase Change Material Heat Exchanger Development

    Science.gov (United States)

    Hansen, Scott W.; Sheth, Ribik B.; Atwell, Matt; Cheek, Ann; Agarwal, Muskan; Hong, Steven; Patel, Aashini,; Nguyen, Lisa; Posada, Luciano

    2014-01-01

    In a cyclical heat load environment such as low Lunar orbit, a spacecraft’s radiators are not sized to reject the full heat load requirement. Traditionally, a supplemental heat rejection device (SHReD) such as an evaporator or sublimator is used to act as a “topper” to meet the additional heat rejection demands. Utilizing a Phase Change Material (PCM) heat exchanger (HX) as a SHReD provides an attractive alternative to evaporators and sublimators as PCM HXs do not use a consumable, thereby leading to reduced launch mass and volume requirements. Studies conducted in this paper investigate utilizing water’s high latent heat of formation as a PCM, as opposed to traditional waxes, and corresponding complications surrounding freezing water in an enclosed volume. Work highlighted in this study is primarily visual and includes understanding ice formation, freeze front propagation, and the solidification process of water/ice. Various test coupons were constructed of copper to emulate the interstitial pin configuration (to aid in conduction) of the proposed water PCM HX design. Construction of a prototypic HX was also completed in which a flexible bladder material and interstitial pin configurations were tested. Additionally, a microgravity flight was conducted where three copper test articles were frozen continuously during microgravity and 2-g periods and individual water droplets were frozen during microgravity.

  15. An Overview of 2014 SBIR Phase I and Phase II Materials Structures for Extreme Environments

    Science.gov (United States)

    Nguyen, Hung D.; Steele, Gynelle C.; Morris, Jessica R.

    2015-01-01

    NASA's Small Business Innovation Research (SBIR) program focuses on technological innovation by investing in development of innovative concepts and technologies to help NASA mission directorates address critical research needs for Agency programs. This report highlights nine of the innovative SBIR 2014 Phase I and Phase II projects that emphasize one of NASA Glenn Research Center's six core competencies-Materials and Structures for Extreme Environments. The technologies cover a wide spectrum of applications such as high temperature environmental barrier coating systems, deployable space structures, solid oxide fuel cells, and self-lubricating hard coatings for extreme temperatures. Each featured technology describes an innovation, technical objective, and highlights NASA commercial and industrial applications. This report provides an opportunity for NASA engineers, researchers, and program managers to learn how NASA SBIR technologies could help their programs and projects, and lead to collaborations and partnerships between the small SBIR companies and NASA that would benefit both.

  16. High Pressure Materials Research: Novel Extended Phases of Molecular Triatomics

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, C

    2004-05-26

    Application of high pressure significantly alters the interatomic distance and thus the nature of intermolecular interaction, chemical bonding, molecular configuration, crystal structure, and stability of solid [1]. With modern advances in high-pressure technologies [2], it is feasible to achieve a large (often up to a several-fold) compression of lattice, at which condition material can be easily forced into a new physical and chemical configuration [3]. The high-pressure thus offers enhanced opportunities to discover new phases, both stable and metastable ones, and to tune exotic properties in a wide-range of atomistic length scale, substantially greater than (often being several orders of) those achieved by other thermal (varying temperatures) and chemical (varying composition or making alloys) means. Simple molecular solids like H{sub 2}, C, CO{sub 2}, N{sub 2}, O{sub 2}, H{sub 2}O, CO, NH{sub 3}, and CH{sub 4} are bounded by strong covalent intramolecular bonds, yet relatively weak intermolecular bonds of van der Waals and/or hydrogen bonds. The weak intermolecular bonds make these solids highly compressible (i.e., low bulk moduli typically less than 10 GPa), while the strong covalent bonds make them chemically inert at least initially at low pressures. Carbon-carbon single bonds, carbon-oxygen double bonds and nitrogen-nitrogen triple bonds, for example, are among the strongest. These molecular forms are, thus, often considered to remain stable in an extended region of high pressures and high temperatures. High stabilities of these covalent molecules are also the basis of which their mixtures are often presumed to be the major detonation products of energetic materials as well as the major constituents of giant planets. However, their physical/chemical stabilities are not truly understood at those extreme pressure-temperature conditions. In fact, an increasing amount of experimental evidences contradict the assumed stability of these materials at high

  17. Continued Water-Based Phase Change Material Heat Exchanger Development

    Science.gov (United States)

    Hansen, Scott W.; Sheth, Rubik B.; Poynot, Joe; Giglio, Tony; Ungar, Gene K.

    2015-01-01

    In a cyclical heat load environment such as low Lunar orbit, a spacecraft's radiators are not sized to meet the full heat rejection demands. Traditionally, a supplemental heat rejection device (SHReD) such as an evaporator or sublimator is used to act as a "topper" to meet the additional heat rejection demands. Utilizing a Phase Change Material (PCM) heat exchanger (HX) as a SHReD provides an attractive alternative to evaporators and sublimators as PCM HX's do not use a consumable, thereby leading to reduced launch mass and volume requirements. In continued pursuit of water PCM HX development two full-scale, Orion sized water-based PCM HX's were constructed by Mezzo Technologies. These HX's were designed by applying prior research on freeze front propagation to a full-scale design. Design options considered included bladder restraint and clamping mechanisms, bladder manufacturing, tube patterns, fill/drain methods, manifold dimensions, weight optimization, and midplate designs. Two units, Units A and B, were constructed and differed only in their midplate design. Both units failed multiple times during testing. This report highlights learning outcomes from these tests and are applied to a final sub-scale PCM HX which is slated to be tested on the ISS in early 2017.

  18. Experimental Investigation of Ice Phase Change Material Heat Exchangers

    Science.gov (United States)

    Leimkuehler, Thomas O.; Stephan, Ryan A.

    2012-01-01

    Phase change materials (PCM) may be useful for spacecraft thermal control systems that involve cyclical heat loads or cyclical thermal environments. Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. This can result in a decreased turndown ratio for the radiator and a reduced system mass. The use of water as a PCM rather than the more traditional paraffin wax has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. A number of ice PCM heat exchangers were fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion were investigated. This paper presents an overview of the results of this investigation from the past three years.

  19. Nano-scale spinning detonation in condensed phase energetic materials

    Science.gov (United States)

    Zhakhovsky, Vasily; Budzevich, Mikalai; Landerville, Aaron; White, Carter; Oleynik, Ivan

    2013-06-01

    Single- and multi-headed spinning detonation waves are observed in molecular dynamics simulations of a condensed phase detonation of an energetic material (EM) confined in round tubes of different radii. The EM is modeled using a modified AB Reactive Empirical Bond Order potential. The thermochemistry and reactive equation of state are varied by adjusting the barrier height for the exothermic reaction AB +B --> A +BB. This allows us to study the evolution of the detonation-wave structure as a function of physico-chemical properties of the AB explosive. The detonation wave is found to exhibit a pulsating planar front in a tube of 8 nm radius, which later collapses due to the development of longitudinal perturbations. Upon increase of the tube's radius to 16 nm, the detonation wave structure is stabilized through the development of a single-headed spinning detonation. The spinning detonation displays a four-wave configuration, including incident, oblique, transverse, and contact shock waves. The contact shock generated by a contact discontinuity is observed for the first time in our MD simulations. A multi-headed turbulent-like detonation structure develops within tubes of larger radii, and exhibit features similar to those observed in gases.

  20. Thermal analysis of a building brick containing phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Alawadhi, E.M. [Kuwait Univ., Safat (Kuwait). Dept. of Mechanical Engineering

    2008-07-01

    This paper presents the thermal analysis of a building brick containing phase change material (PCM) to be used in hot climates. The objective of using the PCM is to utilize its high latent heat of fusion to reduce the heat gain by absorbing the heat in the bricks through the melting process before it reaches the indoor space. The considered model consists of bricks with cylindrical holes filled with PCM. The problem is solved in a two-dimensional space using the finite element method. The thermal effectiveness of the proposed brick-PCM system is evaluated by comparing the heat flux at the indoor surface to a wall without the PCM during typical working hours. A paramedic study is conducted to assess the effect of different design parameters, such as the PCM's quantity, type, and location in the brick. The results indicate that the heat gain is significantly reduced when the PCM is incorporated into the brick, and increasing the quantity of the PCM has a positive effect. PCM cylinders located at the centerline of the bricks shows the best performance. (author)

  1. Free-cooling of buildings with phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Zalba, B.; Marin, J.M. [Universidad de Zaragoza Maria de Luna (Spain). Departamento de Ingenieria Mecanica; Cabeza, L.F. [Universitat de Lleida (Spain). Departamento d' Informatica i Eng. Industrial; Mehling, H. [ZAE Bayern, Abt. 1 Energy Conversion and Storage, Garching (Germany)

    2004-12-01

    In this paper, the application of phase change materials (PCM) in free-cooling systems is studied. Free-cooling is understood as a means to store outdoors coolness during the night, to supply indoors cooling during the day. The use of PCMs is suitable because of the small temperature difference between day indoors and night outdoors. An installation that allows testing the performance of PCMs in such systems was designed and constructed. The main influence parameters like ratio of energy/volume in the encapsulates, load/unload rate of the storage, and cost of the installation were determined, and experiments were performed following the design of experiments strategy. The statistical analysis showed that the effects with significant influence in the solidification process are the thickness of the encapsulation, the inlet temperature of the air, the air flow, and the interaction thickness x temperature. For the melting process the same holds, but the inlet air temperature had a higher influence than the thickness of the encapsulation. With the empirical model developed in this work, a real free-cooling system was designed and economically evaluated. (author)

  2. 40 CFR 227.32 - Liquid, suspended particulate, and solid phases of a material.

    Science.gov (United States)

    2010-07-01

    ... MATERIALS Definitions § 227.32 Liquid, suspended particulate, and solid phases of a material. (a) For the... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Liquid, suspended particulate, and solid phases of a material. 227.32 Section 227.32 Protection of Environment ENVIRONMENTAL...

  3. Phase-change material as a thermal storage media

    Energy Technology Data Exchange (ETDEWEB)

    El Chazly, Nihad M; Khattab, Nagwa M [Dokki, Cairo (Egypt)

    2000-07-01

    Heat storage based on the sensible heating of media such as water, rock and earth represent the first generation of solar energy storage subsystems and technology for their utilization. However, recently the heat storage based on the latent heat associated with a change in phase of a material offers many advantages over sensible heat storage. The most important characteristic of such a subsystem is its a sufficient storage capacity. An idealized model visualizing a thermal capacitor using a phase change material is constructed and subjected to simulated solar system environmental conditions. The proposed model is of a flat plate geometry consisting of two panels compartments forming the body of the capacitor containing the paraffin, leaving at their inner surfaces a thin passage allowing the water flow. The whole structure was assumed to be insulated to minimize heat loss. An analysis of the model is conducted using Goodman technique to generate data about the temperature distribution, the melt thickness, and the heat stored in the PCM under conditions of: ( i ) constant mass flow rate tests for various water inlet temperatures and ( ii ) constant water inlet temperature for various mass flow rate. A FORTRAN computer program was constructed to perform the analysis. It was found the water outlet temperature increases with time until it becomes nearly equals to the inlet temperature. Increasing the mass flow rate for a given inlet temperature, decreases the time required for outlet temperature to reach a given value. Increasing inlet temperature for a given mass flow rate gives a very rapid decrease in the time required for the outlet water temperature to reach a given value. Instantaneous rate of heat storage was determined from the inlet-to- exit temperature differential and measured flow rate. This rate was then integrated numerically to determine the cumulative total energy stored as a function of time. It was found that the instantaneous rate of heat storage

  4. Study of improving the thermal response of a construction material containing a phase change material

    Science.gov (United States)

    Laaouatni, A.; Martaj, N.; Bennacer, R.; Elomari, M.; El Ganaoui, M.

    2016-09-01

    The use of phase change materials (PCMs) for improving the thermal comfort in buildings has become an attractive application. This solution contributes to increasing the thermal inertia of the building envelope and reducing power consumption. A building element filled with a PCM and equipped with ventilation tubes is proposed, both for increasing inertia and contributing to refreshing building envelope. A numerical simulation is conducted by the finite element method in COMSOL Multiphysics, which aims to test the thermal behaviour of the developed solution. An experimental study is carried out on a concrete block containing a PCM with ventilation tubes. The objective is to see the effect of PCM coupled with ventilation on increasing the inertia of the block. The results show the ability of this new solution to ensure an important thermal inertia of a building.

  5. Studies of cluster-assembled materials: From gas phase to condensed phase

    Science.gov (United States)

    Gao, Lin

    . After being mass gated in a reflectron equipped time-of-flight mass spectrometer (TOF-MS) and deposited onto TEM grids, the resultant specimens can be loaded onto high-resolution TEM investigation via electron diffraction. In conclusion, soft-landing of mass selected clusters has been shown to be a successful approach to obtain structural information on Zr-Met-Car cluster-assembled materials collected from the gas phase. TEM images indicate the richness of the morphologies associated with these cluster crystals. However, passivation methods are expected to be examined further to overcome the limited stabilities of these novel clusters. From this initial study, it's shown the promising opportunity to study other Met-Cars species and more cluster-based materials. Experimental results of reactions run with a solvothermal synthesis method obtained while searching for new Zr-C cluster assembled materials, are reported. One unexpected product in single crystal form was isolated and tentatively identified by X-ray diffraction to be [Zr6i O(OH)O12·2(Bu)4], with space group P2 1/n and lattice parameters of a = 12.44 A, b = 22.06 A, c = 18.40 A, alpha = 90°, beta = 105°, gamma = 90°, V = 4875 A3 and R 1 = 3.15% for the total observed data (I ≥ 2 sigma I) and oR2 = 2.82%. This novel hexanuclear Zr(IV)-oxo-hydroxide cluster anion may be the first member in polyoxometalates class with metal atoms from the IVB group and having Oh symmetry. Alternatively, it may be the first member in {[(Zr6Z)X 12]X6}m- class with halides replaced by oxo- and hydroxyl groups and with an increased oxidation state of Zr. It is predicted to bear application potentials directed by both families. This work could suggest a direction in which the preparation of Zr-C cluster-assembled materials in a liquid environment may be eventually fulfilled. 1,3-Bis(diethylphosphino)propane (depp) protected small gold clusters are studied via multiple techniques, including Electrospray Ionization Mass Spectrometry

  6. Ductile-Phase-Toughened Tungsten for Plasma-Facing Materials

    Science.gov (United States)

    Cunningham, Kevin Hawkins

    A variety of processing approaches were employed to fabricate ductile-phase-toughened (DPT) tungsten (W) composites. Mechanical testing and analytical modeling were used to guide composite development. This work provides a basis for further development of W composites to be used in structural divertor components of future fusion reactors. W wire was tested in tension, showing significant ductility and strength. Coatings of copper (Cu) or tungsten carbide (WC) were applied to the W wire via electrodeposition and carburization, respectively. Composites were fabricated using spark plasma sintering (SPS) to consolidate W powders together with each type of coated W wire. DPT behavior, e.g. crack arrest and crack bridging, was not observed in three-point bend testing of the sintered composites. A laminate was fabricated by hot pressing W and Cu foils together with W wires, and subsequently tested in tension. This laminate was bonded via hot pressing to thick W plate as a reinforcing layer, and the composite was tested in three-point bending. Crack arrest was observed along with some fiber pullout, but significant transverse cracking in the W plate confounded further fracture toughness analysis. The fracture toughness of thin W plate was measured in three-point bending. W plates were brazed with Cu foils to form a laminate. Crack arrest and crack bridging were observed in three-point bend tests of the laminate, and fracture resistance curves were successfully calculated for this DPT composite. An analytical model of crack bridging was developed using the basis described by Chao in previous work by the group. The model uses the specimen geometry, matrix properties, and the stress-displacement function of a ductile reinforcement ("bridging law") to calculate the fracture resistance curve (R-curve) and load-displacement curve (P-D curve) for any test specimen geometry. The code was also implemented to estimate the bridging law of an arbitrary composite using R-curve data

  7. The MAX Phases: Unique New Carbide and Nitride Materials

    Science.gov (United States)

    Barsoum, Michel W.; El-Raghy, Tamer

    2001-07-01

    One of the major challenges in engineering is the need for versatile materials to serve rapidly developing technologies. For durability and high performance in extreme environments, metals seem ideal: They are electrical and thermal conductors, damage-tolerant and able to withstand high temperatures. Ceramics offer a different set of qualities, being elastically rigid, lightweight, resistant to fatigue and oxidation and even better at enduring high temperatures. An ideal high-performance structural material for, say, jet engines would have all these qualities—and a new class of materials being explored by the authors meets the test. They are fabricating layered materials combining transition metals, carbon or nitrogen and silicon or a related material. The materials form a new class of solids, the nanolaminates, which exhibits new physics along with unusual machinability.

  8. Modeling of Impact Properties of Auxetic Materials: Phase 1

    Science.gov (United States)

    2013-08-01

    underlying metal substrate from impact damage will be determined, and compared to the effect of solid polymer coatings (containing no honeycomb shaped air...higher indentation resistance, higher fracture toughness and greater resistance to impact damage . These unique features of the auxetic materials make... Elastoplasticity of auxetic materials, Computational Material Science, in press. [24] Horrigan, E.J., Smith, C.W., Scarpa, F.L., Gaspar, N., Javadi, A.A

  9. The use of lipids as phase change materials for thermal energy storage

    Science.gov (United States)

    Phase change materials (PCMs) are substances capable of absorbing and releasing large 2 amounts of thermal energy (heat or cold) as latent heat over constant temperature as they 3 undergo a change in state of matter (phase transition), commonly, between solid and 4 liquid phases. Since the late 194...

  10. Phase relationships and materials design in the Ln-Si-Al-O-N system

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Subsolidus phase relationships in the system Ln2O3-Si3N4-AlN-Al2O3, where Ln represents Nd, Sm and Dy, were summarized, with emphasis on the region involving α-sialon, β-sialon and AlN-polytypoid phases. This information is further used in designing the compatible matrix phases of sialon materials with desirable properties. Examples were provided to illustrate the advantage of such a basic approach to materials design.

  11. Materials Information for Science and Technology (MIST): Project overview: Phase 1 and 2 and general considerations

    Energy Technology Data Exchange (ETDEWEB)

    Grattidge, W.; Westbrook, J.; McCarthy, J.; Northrup, C. Jr.; Rumble, J. Jr.

    1986-11-01

    The National Bureau of Standards and the Department of Energy have embarked on a program to build a demonstration computerized materials data system called Materials Information for Science and Technology (MIST). This report documents the first two phases of the project. The emphasis of the first phase was on determining what information was needed and how it could impact user productivity. The second phase data from the Aerospace Metal Handbook on a set of alloys was digitized and incorporated in the system.

  12. Raman Mapping for the Investigation of Nano-phased Materials

    Science.gov (United States)

    Gouadec, G.; Bellot-Gurlet, L.; Baron, D.; Colomban, Ph.

    Nanosized and nanophased materials exhibit special properties. First they offer a good compromise between the high density of chemical bonds by unit volume, needed for good mechanical properties and the homogeneity of amorphous materials that prevents crack initiation. Second, interfaces are in very high concentration and they have a strong influence on many electrical and redox properties. The analysis of nanophased, low crystallinity materials is not straigtforward. The recording of Raman spectra with a geometric resolution close to 0.5 \\upmu {text{ m}^3} and the deep understanding of the Raman signature allow to locate the different nanophases and to predict the properties of the material. Case studies are discussed: advanced polymer fibres, ceramic fibres and composites, textured piezoelectric ceramics and corroded (ancient) steel.

  13. Analysis of writing and erasing behaviours in phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Hyot, B. E-mail: bhyot@cea.fr; Poupinet, L.; Gehanno, V.; Desre, P.J

    2002-09-01

    An understanding of the process involved in writing and erasing of phase-change optical recording media is vital to the development of new, and the improvement of existing, products. The present work investigates both experimental and theoretical laser-induced fast structural transformations of GeSbTe thin films. Optical and microstructural changes are correlated using both a static tester and transmission electron microscopy. In the second part of this paper we try to elucidate the physics underlying the amorphous-to-crystalline phase transformation under short-pulse laser excitation. Both thermal and thermodynamical behaviours must be taken into account to illustrate real processes.

  14. Tunable ferroelectric meta-material phase shifter embedded inside low temperature co-fired ceramics (LTCC)

    Science.gov (United States)

    Tork, Hossam S.

    This dissertation describes electrically tunable microwave devices utilizing low temperature co-fired ceramics (LTCC) and thick film via filled with the ferroelectric materials barium strontium titanate (BST) and barium zirconate titanate (BZT). Tunable ferroelectric capacitors, zero meta-material phase shifters, and tunable meta-material phase shifters are presented. Microwave phase shifters have many applications in microwave devices. They are essential components for active and passive phased array antennas and their most common use is in scanning phased array antennas. They are used in synthetic aperture radars (SAR), low earth orbit (LEO) communication satellites, collision warning radars, and intelligent vehicle highway systems (IVHS), in addition to various other applications. Tunable ferroelectric materials have been investigated, since they offer the possibility of lowering the total cost of phased arrays. Two of the most promising ferroelectric materials in microwave applications are BST and BZT. The proposed design and implementation in this research introduce new types of tunable meta-material phase shifters embedded inside LTCC, which use BST and BZT as capacitive tunable dielectric material controlled by changing the applied voltage. This phase shifter has the advantages of meta-material structures, which produce little phase error and compensation while having the simultaneous advantage of using LTCC technology for embedding passive components that improve signal integrity (several signal lines, power planes, and ground planes) by using different processes like via filling, screen printing, laminating and firing that can be produced in compact sizes at a low cost. The via filling technique was used to build tunable BST, BZT ferroelectric material capacitors to control phase shift. Finally, The use of the proposed ferroelectric meta-material phase shifter improves phase shifter performance by reducing insertion loss in both transmitting and receiving

  15. Research data supporting "Determining pressure-temperature phase diagrams of materials"

    OpenAIRE

    Baldock, Robert J.N.; Partay, Livia B.; Bartok, Albert P.; Payne, Michael C.; Csanyi, Gabor

    2016-01-01

    Pressure-temperature phase diagrams of the Lennard-Jones system, aluminium and nickel titanium as reported in the paper "Determining pressure-temperature phase diagrams of materials", together with example nested sampling output for aluminium and nickel titanium calculations. This research data supports “Determining pressure-temperature phase diagrams of materials” which has been published in “Physical Review B”. Research data supporting “Determining pressure-temperature phase diagrams...

  16. The role of vacancies and local distortions in the design of new phase-change materials.

    Science.gov (United States)

    Wuttig, Matthias; Lüsebrink, Daniel; Wamwangi, Daniel; Wełnic, Wojciech; Gillessen, Michael; Dronskowski, Richard

    2007-02-01

    Phase-change materials are of tremendous technological importance ranging from optical data storage to electronic memories. Despite this interest, many fundamental properties of phase-change materials, such as the role of vacancies, remain poorly understood. 'GeSbTe'-based phase-change materials contain vacancy concentrations around 10% in their metastable crystalline structure. By using density-functional theory, the origin of these vacancies has been clarified and we show that the most stable crystalline phases with rocksalt-like structures are characterized by large vacancy concentrations and local distortions. The ease by which vacancies are formed is explained by the need to annihilate energetically unfavourable antibonding Ge-Te and Sb-Te interactions in the highest occupied bands. Understanding how the interplay between vacancies and local distortions lowers the total energy helps to design novel phase-change materials as evidenced by new experimental data.

  17. Temperature-driven topological quantum phase transitions in a phase-change material Ge2Sb2Te5

    Science.gov (United States)

    Eremeev, S. V.; Rusinov, I. P.; Echenique, P. M.; Chulkov, E. V.

    2016-12-01

    The Ge2Sb2Te5 is a phase-change material widely used in optical memory devices and is a leading candidate for next generation non-volatile random access memory devices which are key elements of various electronics and portable systems. Despite the compound is under intense investigation its electronic structure is currently not fully understood. The present work sheds new light on the electronic structure of the Ge2Sb2Te5 crystalline phases. We demonstrate by predicting from first-principles calculations that stable crystal structures of Ge2Sb2Te5 possess different topological quantum phases: a topological insulator phase is realized in low-temperature structure and Weyl semimetal phase is a characteristic of the high-temperature structure. Since the structural phase transitions are caused by the temperature the switching between different topologically non-trivial phases can be driven by variation of the temperature. The obtained results reveal the rich physics of the Ge2Sb2Te5 compound and open previously unexplored possibility for spintronics applications of this material, substantially expanding its application potential.

  18. Emission energy control of semiconductor quantum dots using phase change material

    Science.gov (United States)

    Kanazawa, Shohei; Sato, Yu; Yamamura, Ariyoshi; Saiki, Toshiharu

    2015-03-01

    Semiconductor quantum dots have paid much attention as it is a promising candidate for quantum, optical devices, such as quantum computer and quantum dot laser. We propose a local emission energy control method of semiconductor quantum dots using applying strain by volume expansion of phase change material. Phase change material can change its phase crystalline to amorphous, and the volume expand by its phase change. This method can control energy shift direction and amount by amorphous religion and depth. Using this method, we matched emission energy of two InAs/InP quantum dots. This achievement can connect to observing superradiance phenomenon and quantum dot coupling effect.

  19. Materials for Spectral Hole Burning Research. Phase 1

    Science.gov (United States)

    1994-03-22

    furnace causing the furnace to melt. This problem occurs occassionally in the growth of other crystals . 4 Figure 2 Verneuil (Flame Fusion) I...SB1 1 ,1 11 ) Ia ght L tion r .9,Gi stributin uniitd Approved for public release; 13. ABSTRACT (Maximum 200 wordt)I Work on the crystal growth and...multiple hosts. In the work on this program, Scientific Materials Corporation grew crystals of the following compositions. Dopant Growth Method 1.0

  20. Thermal performance of a pcm [phase change material] storage unit

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, K.A.R.; Goncalves, M.M. [Depto de Engenharia Termica e de Fluidos-FEM-UNICAMP (Brazil)

    1999-10-01

    This paper presents a two-dimensional model for the phase change, conduction based heat transfer problem around a tube immersed in the pcm. The energy equation is written in the enthalpy form, and the heat and flow problems are coupled by an energy balance on the fluid element flowing inside the tube. The numerical solution is based upon the average control volume technique and the ADI finite difference representation. The results obtained show the effects of the variation of the ratio of the radius of the inner to the outer tube, Biot number, Stefan number and the working fluid inlet temperature on the solidified mass fraction, NTU and effectiveness. (author)

  1. Materials Design of Microstructure in Grain Boundary and Second Phase Particles

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A concept of microstructure design for materials or materials microstructure engineering is proposed. The argument was suggested based on literature review and some our new research work on second phase strengthening mechanisms and mechanical property modeling of a particulate reinforced metal matrix composite. Due to development of computer technology, it is possible now for us to establish the relationship between microstructures and properties systematically and quantitatively by analytical and numerical modeling in the research scope of computerization materials. Discussions and examples on intellectual optimization of microstructure are presented on two aspects:grain boundary engineering and optimal geometry of particulate reinforcements in two-phase materials.

  2. Thermophysical properties and behavioral characteristics of phase-change materials

    Energy Technology Data Exchange (ETDEWEB)

    Cantor, S

    1977-01-01

    The primary and near-term objective of the project is to compile a handbook of compounds and mixtures that melt in the range of 90 to 250/sup 0/C and which are suitable for isothermal heat storage. Organic compounds have been screened according to bulk price, thermal stability, and safety. Compounds were selected for further consideration if they cost less than $1.10/kg and if encyclopedia articles or handbooks indicated that they were reasonably stable chemically and were not toxic or otherwise hazardous. Of seven compounds thus selected, four (urea, phthalimide, adipic acid, phthalic anhydride) have been examined by DSC and other methods. The differential scanning calorimeter was used with two fairly well-characterized PCM's to test its applicability for rapidly evaluating thermal decomposition and supercooling. With Na/sub 2/SO/sub 4/ . 10H/sub 2/O, DSC data indicated (a) decrease in heat of transition with thermal cycling, and (b) considerable supercooling; with 3 to 6 percent borax added, supercooling was greatly lessened but not entirely eliminated. Measurements with paraffin wax showed that this material does not supercool nor does it degrade in thermal performance with cycling. The DSC results with these two materials confirmed (and extended) thermal performance characteristics obtained by other means. However, studies of supercooling in urea and in phthalimide suggested that DSC techniques may magnify the extent of supercooling at elevated temperatures.

  3. Microencapsulation of butyl stearate as a phase change material by interfacial polycondensation in a polyurea system

    Energy Technology Data Exchange (ETDEWEB)

    Chen Liang [College of Material Science and Engineering, Nanjing University of Technology, Nanjing 210009 (China)], E-mail: doseng_1982@hotmail.com; Xu Lingling; Shang Hongbo; Zhang Zhibin [College of Material Science and Engineering, Nanjing University of Technology, Nanjing 210009 (China)

    2009-03-15

    For the last 20 years, microencapsulated phase change materials (MicroPCMs), which combine microencapsulation technology and phase change material, have been attracted more and more interest. By overcoming some limitations of the PCMs, the MicroPCMs improve the efficiency of PCMs and make it possible to apply PCMs in many areas. In this experiment, polyurea microcapsules containing phase change materials were prepared using interfacial polycondensation method. Toluene-2,4-diisocyanate (TDI) and ethylenediamine (EDA) were chosen as monomers. Butyl stearate was employed as a core material. The MicroPCMs' properties have been characterized by dry weight analysis, differential scanning calorimetry, Fourier transform IR spectra analysis and optical microscopy. The results show that the MicroPCMs were synthesized successfully and that, the phase change temperature was about 29 deg. C, the latent heat of fusion was about 80 J g{sup -1}, the particle diameter was 20-35 {mu}m.

  4. Microencapsulation of butyl stearate as a phase change material by interfacial polycondensation in a polyurea system

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Chen; Lingling, Xu; Hongbo, Shang; Zhibin, Zhang [College of Material Science and Engineering, Nanjing University of Technology, Nanjing 210009 (China)

    2009-03-15

    For the last 20 years, microencapsulated phase change materials (MicroPCMs), which combine microencapsulation technology and phase change material, have been attracted more and more interest. By overcoming some limitations of the PCMs, the MicroPCMs improve the efficiency of PCMs and make it possible to apply PCMs in many areas. In this experiment, polyurea microcapsules containing phase change materials were prepared using interfacial polycondensation method. Toluene-2,4-diisocyanate (TDI) and ethylenediamine (EDA) were chosen as monomers. Butyl stearate was employed as a core material. The MicroPCMs' properties have been characterized by dry weight analysis, differential scanning calorimetry, Fourier transform IR spectra analysis and optical microscopy. The results show that the MicroPCMs were synthesized successfully and that, the phase change temperature was about 29 C, the latent heat of fusion was about 80 J g{sup -1}, the particle diameter was 20-35 {mu}m. (author)

  5. Novel Elastomeric Closed Cell Foam - Nonwoven Fabric Composite Material (Phase III)

    Science.gov (United States)

    2008-10-01

    AFRL-RX-TY-TR-2009-4577 NOVEL ELASTOMERIC CLOSED CELL FOAM – NONWOVEN FABRIC COMPOSITE MATERIAL (PHASE III) Davis, Stephen C...07-OCT-2009 Novel Elastomeric Closed Cell Foam - Nonwoven Fabric Composite Material (Phase III) FA4819-07-D-0001 62102F 4347 D2 4347D23A Davis...develop novel closed cell foam- nonwoven fabric composites to commercial scale evaluation. Armacell tasks focused on foam optimization for commercial

  6. Field experiments on the use of phase changing materials, insulation materials and passive solar radiation in the built environment

    NARCIS (Netherlands)

    Entrop, A.G.; Brouwers, H.J.H.; Reinders, A.H.M.E.

    2008-01-01

    This paper describes the development of an experimental research facility to assess the effectiveness of Phase Change Materials (PCM), that can be used for passive solar heating. Four test boxes are constructed representing the conventional and future Dutch building practices regarding insulation an

  7. Structural properties of the metastable state of phase change materials investigated by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Merkelbach, Philipp; Eijk, Julia van; Wuttig, Matthias [I. Phys. Institut (IA), RWTH Aachen, 52056 Aachen (Germany); Braun, Carolin [Institut fuer Anorg. Chemie, CAU Kiel, 24098 Kiel (Germany)

    2008-07-01

    Phase change alloys are among the most promising materials for novel data storage devices. Since several years Phase Change Materials based on Ge-Sb-Te- alloys have been used in optical data storage solutions like rewriteable CDs and DVDs. Recently these alloys have been explored as potential candidates for fast nonvolatile electrical data storage devices in Phase Change Random Access Memory (PCRAM). Besides attracting considerable interest from the commercial point of view phase change materials are very interesting also due to their remarkable physical properties. They have the ability to be reversibly switched within a few nanoseconds between the amorphous and the crystalline phase, while changing their physical properties such as optical reflectivity and electrical resistivity significantly. Even though the electronic properties show a drastical contrast such fast transitions can only be caused by small atomic rearrangements. This behavior calls for a deeper understanding of the structural properties of the alloys. We have performed powder diffraction measurements of the crystal phase of various GeSbTe alloys, to determine the structural similarities and differences of several alloys. Understanding the crystal structure of phase change materials is a key to a deeper insight into the properties of these promising materials.

  8. Accurate switching intensities and length scales in quasi-phase-matched materials

    DEFF Research Database (Denmark)

    Bang, Ole; Graversen, Torben Winther; Corney, Joel Frederick

    2001-01-01

    We consider unseeded typeI second-harmonic generation in quasi-phase-matched quadratic nonlinear materials and derive an accurate analytical expression for the evolution of the average intensity. The intensity- dependent nonlinear phase mismatch that is due to the cubic nonlinearity induced by qu...

  9. Effect of microencapsulated phase change material in sandwich panels

    Energy Technology Data Exchange (ETDEWEB)

    Castellon, Cecilia; Medrano, Marc; Roca, Joan; Cabeza, Luisa F. [GREA Innovacio Concurrent, Edifici CREA, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida (Spain); Navarro, Maria E.; Fernandez, Ana I. [Departamento de Ciencias de los Materiales e Ingenieria Metalurgica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Lazaro, Ana; Zalba, Belen [Instituto de Investigacion en Ingenieria de Aragon, I3A, Grupo de Ingenieria Termica y Sistemas Energeticos (GITSE), Dpto. Ingenieria Mecanica, Area de Maquinas y Motores Termicos, Universidad de Zaragoza, Campus Politecnico Rio Ebro, Edificio ' ' Agustin de Betancourt,' ' Maria de Luna s/n, 50018 Zaragoza (Spain)

    2010-10-15

    Sandwich panels are a good option as building materials, as they offer excellent characteristics in a modular system. The goal of this study was to demonstrate the feasibility of using the microencapsulated PCM (Micronal BASF) in sandwich panels to increase their thermal inertia and to reduce the energy demand of the final buildings. In this paper, to manufacture the sandwich panel with microencapsulated PCM three different methods were tested. In case 1, the PCM was added mixing the microencapsulated PCM with one of the components of the polyurethane. In the other two cases, the PCM was added either a step before (case 2) or a step after (case 3) to the addition of the polyurethane to the metal sheets. The results show that in case 1 the effect of PCM was overlapped by a possible increase in thermal conductivity, but an increase of thermal inertia was found in case 3. In case 2, different results were obtained due to the poor distribution of the PCM. Some samples showed the effect of the PCM (higher thermal inertia), and other samples results were similar to the conventional sandwich panel. In both cases (2 and 3), it is required to industrialize the process to improve the results. (author)

  10. Interface Characterization of Metals and Metal-nitrides to Phase Change Materials

    NARCIS (Netherlands)

    Roy, Deepu; Wolters, Rob A.M.

    2011-01-01

    We have investigated the interfacial contact properties of the CMOS compatible electrode materials W, TiW, Ta, TaN and TiN to doped-Sb2Te phase change material (PCM). This interface is characterized both in the amorphous and in the crystalline state of the doped-Sb2Te. The electrical nature of the i

  11. Phase field crystal study of deformation and plasticity in nanocrystalline materials.

    Science.gov (United States)

    Stefanovic, Peter; Haataja, Mikko; Provatas, Nikolas

    2009-10-01

    We introduce a modified phase field crystal (MPFC) technique that self-consistently incorporates rapid strain relaxation alongside the usual plastic deformation and multiple crystal orientations featured by the traditional phase field crystal (PFC) technique. Our MPFC formalism can be used to study a host of important phase transformation phenomena in material processing that require rapid strain relaxation. We apply the MPFC model to study elastic and plastic deformations in nanocrystalline materials, focusing on the "reverse" Hall-Petch effect. Finally, we introduce a multigrid algorithm for efficient numerical simulations of the MPFC model.

  12. Reflectance and reflection phase of photonic crystal with anisotropic left-handed materials

    Science.gov (United States)

    Kang, Yongqiang; Zhang, Chunmin; Yao, Baoli

    2016-11-01

    The reflectance and reflection phase properties of one dimensional photonic crystals with anisotropic left-handed materials is investigated by transfer matrix method. It is demonstrated that the width of zero- n band gap is influenced by the incident angle, polarization, the proportion of lattice and the ratio of thickness which is different from the zero- n band gap with isotropic left hand materials. The value of reflection phase is affected by incident angle and polarization and not affected by the proportion of lattice and the ratio of thickness. These characteristic may be useful for making photonic crystal phase compensators and the dispersion compensators.

  13. Deriving binary phase diagrams for chromonic materials in water mixtures via fluorescence spectroscopy: cromolyn and water.

    Science.gov (United States)

    Van Hecke, Gerald R; Karukstis, Kerry K; Rayermann, Scott

    2015-01-14

    We report here the first example of a new and novel method of determining the binary temperature-composition phase diagram of a chromonic material in water using its intrinsic fluorescence. Disodium cromoglycate, or cromolyn, is an anti-allergy medicine representative of a class of compounds known as the chromonics. We have discovered that cromolyn's fluorescence is very sensitive to the polarity, hence structure, of the phase it exhibits. The fluorescence signal shifts its wavelength maximum and its shape depending on whether the cromolyn is a single phase or in coexisting phases. Since the signal due to individual phases can be identified, the fluorescence signal can reveal the temperature-induced transitions between single phase and phase coexistence regions. By studying such fluorescence data for different compositions, an isobaric temperature-composition phase diagram may be constructed. We present here a phase diagram derived from fluorescence studies that is in agreement with previous determinations using other techniques. Our results suggest that the binary phase diagrams of other intrinsically fluorescent chromonic materials, such as perylene monoimide and bisimide derivatives used in organic optoelectronic devices, solar cells, and light-emitting diodes, can be studied in water using an analogous fluorescence approach.

  14. First order magneto-structural transition in functional magnetic materials: phase-coexistence and metastability

    Indian Academy of Sciences (India)

    S B Roy; M K Chattopadhyay; M A Manekar; K J S Sokhey; P Chaddah

    2006-11-01

    First order magneto-structural transition plays an important role in the functionality of various magnetic materials of current interest like manganese oxide systems showing colossal magnetoresistance, Gd5(Ge, Si)4 alloys showing giant magnetocaloric effects and magnetic shape memory alloys. The key features of this magneto-structural transition are phase-coexistence and metastability. This generality is highlighted with experimental results obtained in a particular class of materials. A generalized framework of disorder influenced first order phase transition is introduced to understand the interesting experimental results which have some bearing on the functionality of the concerned materials.

  15. Design of materials with extreme thermal expansion using a three-phase topology optimization method

    DEFF Research Database (Denmark)

    Sigmund, Ole; Torquato, S.

    1997-01-01

    We show how composites with extremal or unusual thermal expansion coefficients can be designed using a numerical topology optimization method. The composites are composed of two different material phases and void. The optimization method is illustrated by designing materials having maximum thermal...... expansion, zero thermal expansion, and negative thermal expansion. Assuming linear elasticity, it is shown that materials with effective negative thermal expansion coefficients can be obtained by mixing two phases with positive thermal expansion coefficients and void. We also show...... that there is no mechanistic relationship between negative thermal expansion and negative Poisson's ratio....

  16. Review on thermal energy storage with phase change: materials, heat transfer analysis and applications

    Energy Technology Data Exchange (ETDEWEB)

    Zalba, Belen; Marin, Jose M. [Dpto. Ingenieria Mecanica, Campus Politecnico, Universidad de Zaragoza, EUITIZ ' EDIFICIO B.3' Maria de Luna 3 (Actur), 50015, Zaragoza (Spain); Cabeza, Luisa F. [Dpt.d' Informatica i Enginyeria Industrial, Escola, Universitaria Politecnica, Universitat de Lleida, CREA, Jaurne 11,69,25001, Lleida (Spain); Mehling, Harald [ZAE Bayem, Division 1: Energy Conversion and Storage, Walther-Meissner-Str. 6, 85748, Garching (Germany)

    2003-02-01

    Thermal energy storage in general, and phase change materials (PCMs) in particular, have been a main topic in research for the last 20 years, but although the information is quantitatively enormous, it is also spread widely in the literature, and difficult to find. In this work, a review has been carried out of the history of thermal energy storage with solid-liquid phase change. Three aspects have been the focus of this review: materials, heat transfer and applications. The paper contains listed over 150 materials used in research as PCMs, and about 45 commercially available PCMs. The paper lists over 230 references. (Author)

  17. Importance of the gas phase role to the prediction of energetic material behavior: An experimental study

    Science.gov (United States)

    Ali, A. N.; Son, S. F.; Asay, B. W.; Sander, R. K.

    2005-03-01

    Various thermal (radiative, conductive, and convective) initiation experiments are performed to demonstrate the importance of the gas phase role in combustion modeling of energetic materials (EM). A previously published condensed phase model that includes a predicted critical irradiance above which ignition is not possible is compared to experimental laser ignition results for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 2,4,6-trinitrotoluene (TNT). Experimental results conflict with the predicted critical irradiance concept. The failure of the model is believed to result from a misconception about the role of the gas phase in the ignition process of energetic materials. The model assumes that ignition occurs at the surface and that evolution of gases inhibits ignition. High speed video of laser ignition, oven cook-off and hot wire ignition experiments captures the ignition of HMX and TNT in the gas phase. A laser ignition gap test is performed to further evaluate the effect of gas phase laser absorption and gas phase disruption on the ignition process. Results indicate that gas phase absorption of the laser energy is probably not the primary factor governing the gas phase ignition observations. It is discovered that a critical gap between an HMX pellet and a salt window of 6mm±0.4mm exists below which ignition by CO2 laser is not possible at the tested irradiances of 29W /cm2 and 38W/cm2 for HMX ignition. These observations demonstrate that a significant disruption of the gas phase, in certain scenarios, will inhibit ignition, independent of any condensed phase processes. These results underscore the importance of gas phase processes and illustrate that conditions can exist where simple condensed phase models are inadequate to accurately predict the behavior of energetic materials.

  18. Microstructure-property relationships in digitally generated three-dimensional, two-phase, liquid phase sintered materials

    Science.gov (United States)

    Lee, Sukbin

    In studying microstructure-property relationships, it is of great interest to reveal the effect of individual microstructural parameters on the properties of the materials in all three dimensions. However, it is not easy to obtain experimentally samples in which the individual microstructural features are independently controlled. Even though one can prepare such samples, conventional materials characterization is based on the data obtained from two-dimensional plane sections of the samples. Since many problems related to the properties of materials are three-dimensional in nature, conventional two-dimensional characterization is not always sufficient to describe the microstructure quantitatively. Also, many property experiments are destructive and therefore one needs to repeat the process many times to map the properties as a function of the microstructural parameters. Considerable effort has been made to reconstruct three-dimensional microstructures using serial sectioning in recent years in order to determine three-dimensional microstructural features of two-phase composite materials directly. While this approach yields three-dimensional data on the size, shape, and spatial correlation of particles, it demands difficult and time-consuming steps. Thus, numerical reconstruction or synthesis methods can contribute significantly to modeling three-dimensional microstructures, especially two-phase composite microstructures for this project. One objective of this project is to introduce a procedure for generating three-dimensional digital microstructures representing two-phase composite materials containing isotropically coarsened particles in the surrounding matrix phase. In order to achieve the goal, a three-dimensional, Q-state Monte Carlo Potts model of isotropic particle coarsening in a system with full wetting of particles by matrix is introduced to investigate the coarsening kinetics and microstructures associated with this process. By imposing the condition of

  19. Summary of workshop on high temperature materials based on Laves phases

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    The Offices of Fossil Energy and Basic Energy Sciences of the Department of Energy jointly sponsored the Workshop on High Temperature Materials Based on Laves Phases in conjunction with the Tenth Annual Conference on Fossil Energy Materials held at the Radisson Summit Hill Hotel in Knoxville, Tennessee on May 14-16, 1996. The objective of this workshop was to review the current status and to address critical issues in the development of new-generation high-temperature structural materials based on Laves phases. The one-day workshop included two sessions of overview presentations and a session of discussion on critical scientific and technological issues. The Laves phases represent an abundant class of intermetallic alloys with possible high-temperature structural applications. Laves phases form at or near the AB{sub 2} composition, and there are over 360 binary Laves phases. The ability of these alloys to dissolve considerable amounts of ternary alloying additions provides over 900 combined binary and ternary Laves phases. Many Laves phases have unique properties which make them attractive for high-temperature structural use. At half their homologous temperature, they retain >0.85 of their ambient yield strength, which is higher than all other intermetallics. Many of the Laves phases also have high melting temperatures, excellent creep properties, reasonably low densities, and for alloys containing Cr, Al, Si or Be, good oxidation resistance. Despite these useful properties, the tendency for low-temperature brittleness has limited the potential application of this large class of alloys.

  20. Effective anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent magnetic material

    Institute of Scientific and Technical Information of China (English)

    韩广兵; 高汝伟; 冯维存; 刘汉强; 王标; 张鹏; 陈伟; 李卫; 郭永权

    2003-01-01

    The effect of exchange-coupling interaction on the effective anisotropy and its varying tendency in nanocrystalline single-phase NdFeB permanent magnetic material have been investigated. The results show that the exchange-coupling interaction between grains makes the effective anisotropy of material, Keff, decrease with the reduction of grain size. The variation of Keff is basically the same as that of coercivity. The decrease in effective anisotropy is the main reason of the reduction of coercivity for nanocrystalline single-phase NdFeB permanent magnetic material. In order to get high anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent material, the grain size should be larger than 35 nm.

  1. Experimental data showing the thermal behavior of a flat roof with phase change material

    Directory of Open Access Journals (Sweden)

    Ayça Tokuç

    2015-12-01

    Full Text Available The selection and configuration of building materials for optimal energy efficiency in a building require some assumptions and models for the thermal behavior of the utilized materials. Although the models for many materials can be considered acceptable for simulation and calculation purposes, the work for modeling the real time behavior of phase change materials is still under development. The data given in this article shows the thermal behavior of a flat roof element with a phase change material (PCM layer. The temperature and energy given to and taken from the building element are reported. In addition the solid–liquid behavior of the PCM is tracked through images. The resulting thermal behavior of the phase change material is discussed and simulated in [1] A. Tokuç, T. Başaran, S.C. Yesügey, An experimental and numerical investigation on the use of phase change materials in building elements: the case of a flat roof in Istanbul, Build. Energy, vol. 102, 2015, pp. 91–104.

  2. Generalized thermoelastic interaction in functional graded material with fractional order three-phase lag heat transfer

    Institute of Scientific and Technical Information of China (English)

    Ibrahim A. Abbas

    2015-01-01

    The present work is concerned with the solution of a problem on thermoelastic interactions in a functional graded material due to thermal shock in the context of the fractional order three-phase lag model. The governing equations of fractional order generalized thermoelasticity with three-phase lag model for functionally graded materials (FGM) (i.e., material with spatially varying material properties) are established. The analytical solution in the transform domain is obtained by using the eigenvalue approach. The inversion of Laplace transform is done numerically. The graphical results indicate that the fractional parameter has significant effects on all the physical quantities. Thus, we can consider the theory of fractional order generalized thermoelasticity an improvement on studying elastic materials.

  3. Preparation of n-tetradecane-containing microcapsules with different shell materials by phase separation method

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Rui [Department of Chemical Engineering, Tsinghua University, Beijing (China); Zhang, Yan; Zhang, Qingwu [Department of Chemical Engineering, China University of Mining and Technology, Beijing (China); Wang, Xin; Zhang, Yinping [Department of Building Science, Tsinghua University, Beijing (China)

    2009-10-15

    Microcapsules for thermal energy storage and heat-transfer enhancement have attracted great attention. Microencapsulation of n-tetradecane with different shell materials was carried out by phase separation method in this paper. Acrylonitrile-styrene copolymer (AS), acrylonitrile-styrene-butadiene copolymer (ABS) and polycarbonate (PC) were used as the shell materials. The structures, morphologies and the thermal capacities of the microcapsules were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The ternary phase diagrams showed the potential encapsulation capabilities of the three shell materials. The effects of the shell/core ratio and the molecular weight of the shell material on the encapsulation efficiency and the thermal capacity of the microcapsules were also discussed. Microcapsules with melting enthalpy > 100 J/g, encapsulation efficiency 66-75%, particle size<1 {mu}m were obtained for all three shell materials. (author)

  4. Dead lithium phase investigation of Sn-Zn alloy as anode materials for lithium ion battery

    Institute of Scientific and Technical Information of China (English)

    HUANG ZhaoWen; HU SheJun; HOU XianHua; RU Qiang; YU HongWen; ZHAO LingZhi; LI WeiShan

    2009-01-01

    In this work, based on First-principle plane wave pseudo-potential method, we have carried out an in-depth study on the possible dead lithium phase of Sn-Zn alloy as anode materials for lithium ion batteries. Through investigation, we found that the phases LixSn4Zn4(x = 2, 4, 6, 8) contributed to reversible capacity, while the phases LixSn4Zns-(x-4)(x = 4.74, 7.72) led to capacity loss due to high formation energy, namely, they were the dead lithium phases during the charge/discharge process. And we come up with a new idea that stable lithium alloy phase with high lithiation formation energy (dead lithium phase) can also result in high loss of active lithium ion, besides the traditional expression that the formation of solid electrolyte interface film leads to high capacity loss.

  5. Compositional phase stability of strongly correlated electron materials within DFT+U

    Science.gov (United States)

    Isaacs, Eric B.; Marianetti, Chris A.

    2017-01-01

    Predicting the compositional phase stability of strongly correlated electron materials is an outstanding challenge in condensed matter physics. In this work, we employ the density functional theory plus U (DFT +U ) formalism to address the effects of local correlations due to transition metal d electrons on compositional phase stability in the prototype phase stable and separating materials LixCoO2 and olivine LixFePO4 , respectively. We introduce a spectral decomposition of the DFT +U total energy, revealing the distinct roles of the filling and ordering of the d orbital correlated subspace. The on-site interaction U drives both of these very different materials systems towards phase separation, stemming from enhanced ordering of the d orbital occupancies in the x =0 and x =1 species, whereas changes in the overall filling of the d shell contribute negligibly. We show that DFT +U formation energies are qualitatively consistent with experiments for phase stable LixCoO2 , phase separating LixFePO4 , and phase stable LixCoPO4 . However, we find that charge ordering plays a critical role in the energetics at intermediate x , strongly dampening the tendency for the Hubbard U to drive phase separation. Most relevantly, the phase stability of Li1 /2CoO2 within DFT +U is qualitatively incorrect without allowing charge ordering, which is problematic given that neither charge ordering nor the band gap that it induces are observed in experiment. We demonstrate that charge ordering arises from the correlated subspace interaction energy as opposed to the double counting. Additionally, we predict the Li order-disorder transition temperature for Li1 /2CoO2 , demonstrating that the unphysical charge ordering within DFT +U renders the method problematic, often producing unrealistically large results. Our findings motivate the need for other advanced techniques, such as DFT plus dynamical mean-field theory, for total energies in strongly correlated materials.

  6. Study on the Motion state of Powdery materials in Dense-phase Pneumatic Conveying Pipe

    Directory of Open Access Journals (Sweden)

    Lia Zhihua

    2016-01-01

    Full Text Available Using the method of computational fluid dynamics, a model is created about powdery materials flowing in the dense-phase pneumatic conveying pipe. the motion state powdery materials flowing in the horizontal and vertical pipe is simulated. It is found that in the horizontal pipe the powdery materials represent the flow of dune-like state, and continuously move forward in this form, the volume fraction of powdery materials at the pipe's bottom is large, the velocity is low; In the vertical pipe, the columnar solid-plug can form and scatter continuously, and the motion state is closer to fluidization.

  7. The solidification of two-phase heterogeneous materials: Theory versus experiment

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bin; KIM Tongbeum; LU TianJian

    2009-01-01

    The solidification behavior of two-phase heterogeneous materials such as close-celled aluminum foams was analytically studied. The proposed analytical model can precisely predict the location of solidification front as well as the full solidification time for a two-phase heterogeneous material composed of aluminum melt and non-conducting air pores. Experiments using distilled water simulating the aluminum melt to be solidified (frozen) were subsequently conducted to validate the analytical model for two selected porosities (ε), ε=0 and 0.5. Full numerical simulations with the method of finite difference were also performed to examine the influence of pore shape on solidification. The remarkable agreement between theory and experiment suggests that the delay of solidification in the two-phase heterogeneous material is mainly caused by the reduction of bulk thermal conductivity due to the presence of pores, as this is the sole mechanism accounted for by the analytical model for solidification in a porous medium.

  8. Nanocasting of Periodic Mesoporous Materials as an Effective Strategy to Prepare Mixed Phases of Titania

    Directory of Open Access Journals (Sweden)

    Luther Mahoney

    2015-12-01

    Full Text Available Mesoporous titanium dioxide materials were prepared using a nanocasting technique involving silica SBA-15 as the hard-template. At an optimal loading of titanium precursor, the hexagonal periodic array of pores in SBA-15 was retained. The phases of titanium dioxide could be easily varied by the number of impregnation cycles and the nature of titanium alkoxide employed. Low number of impregnation cycles produced mixed phases of anatase and TiO2(B. The mesoporous TiO2 materials were tested for solar hydrogen production, and the material consisting of 98% anatase and 2% TiO2(B exhibited the highest yield of hydrogen from the photocatalytic splitting of water. The periodicity of the pores was an important factor that influenced the photocatalytic activity. This study indicates that mixed phases of titania containing ordered array of pores can be prepared by using the nanocasting strategy.

  9. Sol-gel composite material characteristics caused by different dielectric constant sol-gel phases

    Science.gov (United States)

    Kimoto, Keisuke; Matsumoto, Makoto; Kaneko, Tsukasa; Kobayashi, Makiko

    2016-07-01

    Ultrasonic transducers prepared by a sol-gel composite method have been investigated in the field of nondestructive testing (NDT). Sol-gel composite materials could be ideal piezoelectric materials for ultrasonic transducer applications in the NDT field, and a new sol-gel composite with desirable characteristics has been developed. Three kinds of sol-gel composite materials composed of different dielectric constant sol-gel phases, Pb(Zr,Ti)O3 (PZT), Bi4Ti3O12 (BiT), and BaTiO3 (BT), and the same piezoelectric powder phase, PbTiO3 (PT), were fabricated and their properties were compared quantitatively. As a result, the PT/BT, sol-gel composite with the highest dielectric constant sol-gel phase showed the highest d 33 and signal strength. In addition, only PT/BT was successfully poled by room-temperature corona poling with reasonable signal strength.

  10. Green material composites from renewable resources: Polymorphic transitions and phase diagram of beeswax/rosin resin

    Energy Technology Data Exchange (ETDEWEB)

    Gaillard, Yves [Mines-ParisTech., CEMEF, UMR CNRS 7635, 1 rue Claude Daunesse 06904 Sophia Antipolis cedex (France); Mija, Alice [University of Nice-Sophia Antipolis, Thermokinetic Group, Laboratory of Chemistry of Organic and Metallic Materials C.M.O.M., 06108 Nice Cedex 2 (France); Burr, Alain; Darque-Ceretti, Evelyne; Felder, Eric [Mines-ParisTech., CEMEF, UMR CNRS 7635, 1 rue Claude Daunesse 06904 Sophia Antipolis cedex (France); Sbirrazzuoli, Nicolas, E-mail: sbirrazz@unice.fr [University of Nice-Sophia Antipolis, Thermokinetic Group, Laboratory of Chemistry of Organic and Metallic Materials C.M.O.M., 06108 Nice Cedex 2 (France)

    2011-07-10

    Highlights: {yields} Blends of Rosin and beeswax are studied by DSC, XRD, and optical microscopy. {yields} The first phase diagram beeswax/rosin is established. {yields} Polymorphic transitions are identified and appear to be highly related to rosin content. - Abstract: Rosin and beeswax are two complex natural materials presenting numerous applications in paints, adhesives, varnishes or inks. Melted, they are particularly interesting for their adhesion properties. This paper establishes the first phase diagram beeswax/rosin blends. A systematic approach using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and polarised optical microscopy (POM) has been performed in order to describe the crystallographic structure and the thermal properties of two materials, beeswax and rosin, and their blends. Indeed, melting, softening and crystallisation temperatures, polymorphic transitions but also crystalline index has been investigated. The resulting phase diagram reveals a complex behaviour in terms of phase transformation and time-dependent phenomenon mainly representative of the complex composition of beeswax.

  11. Modeling Phase Change Material in Micro-Foam Under Constant Temperature Condition (Postprint)

    Science.gov (United States)

    2014-01-01

    capture the phase change process in PCM /micro-foam systems, with the effective thermal conductivity derived from direct simulations and expressed as a...in PCM /micro-foam systems, with the effective thermal conductivity derived from direct simulations and expressed as a power law of porosity. Published...by Elsevier Ltd.1. Introduction Metal or graphite foams [1] filled with phase change materials ( PCM ) are attractive for thermal energy storage (TES

  12. Porous MgO material with ultrahigh surface area as the matrix for phase change composite

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Yonggan; Shao, Xiankun; Liu, Tongxuan [School of Materials Science and Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001 (China); Li, Benxia, E-mail: libx@mail.ustc.edu.cn [School of Materials Science and Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001 (China); Nie, Shibin, E-mail: nsb@mail.ustc.edu.cn [School of Energy Resources and Safety, Anhui University of Science and Technology, Huainan, Anhui 232001 (China)

    2015-03-20

    Highlights: • Porous MgO material with ultrahigh surface area was synthesized. • A composite PCM was prepared from PEG-1000 and the porous MgO. • The phase change temperatures and enthalpy of the composite were measured. • The composite PCM performed good shape-stabilized property. - Abstract: Mesoporous magnesium oxide (MgO) material was synthesized using an integration of the evaporation-induced surfactant assembly and magnesium nitrate pyrolysis. The as-prepared MgO material is well crystalline, and possesses three-dimensional interconnected mesopores and a surface area as high as 596 m{sup 2}/g. Using the porous MgO as a matrix and polyethylene glycol (PEG-1000) as the functional phase for heat energy storage, a shape-stabilized phase change composite of PEG/MgO was fabricated by an easy impregnation method. In the composite, mesoporous MgO material provides structural strength and prevents the leakage of the molten PEG during the phase change process. The compositions and microstructures of the PEG/MgO composite were determined by Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), scanning electronic microscope (SEM) and thermogravimetric analyzer (TGA), respectively. The phase change properties of the PEG/MgO composite were determined by differential scanning calorimeter (DSC). The high heat-energy storage capability and good thermal stability of the composite enable it extensive applications in the future.

  13. THE RATE-INDEPENDENT CONSTITUTIVE MODELING FOR POROUS AND MULTI-PHASE NANOCRYSTALLINE MATERIAL

    Institute of Scientific and Technical Information of China (English)

    Zhou Jianqiu; Li Yuanling; Zhang Zhenzhong

    2007-01-01

    To determine the time-independent constitutive modeling for porous and multiphase nanocrystalline materials and understand the effects of grain size and porosity on their mechanical behavior, each phase was treated as a mixture of grain interior and grain boundary, and pores were taken as a single phase, then Budiansky's self-consistent method was used to calculate the Young's modulus of porous, possible multi-phase, nanocrystalline materials, the prediction being in good agreement with the results in the literature. Further, the established method is extended tosimulate the constitutive relations of porous and possible multi-phase nanocrystalline materials with small plastic deformation in conjunction with the secant-moduli approach and iso-strain assumption. Comparisons between the experimental grain size and porosity dependent mechanical data and the corresponding predictions using the established model show that it appears to be capable of describing the time-independent mechanical behaviors for porous and multi-phase nanocrystalline materials in a small plastic strain range. Further discussion on the modification factor, the advantages and limitations of the model developed were present.

  14. Dynamically vulcanized biobased polylactide/natural rubber blend material with continuous cross-linked rubber phase.

    Science.gov (United States)

    Chen, Yukun; Yuan, Daosheng; Xu, Chuanhui

    2014-03-26

    We prepared a biobased material, dynamically vulcanized polylactide (PLA)/natural rubber (NR) blend in which the cross-linked NR phase owned a continuous network-like dispersion. This finding breaks the traditional concept of a sea-island morphology formed after dynamic vulcanization of the blends. The scan electron microscopy and dissolution/swell experiments provided the direct proof of the continuous cross-linked NR phase. This new biobased PLA/NR blend material with the novel structure is reported for the first time in the field of dynamic vulcanization and shows promise for development for various functional applications.

  15. Embedded binary eutectic alloy nanostructures: a new class of phase change materials.

    Science.gov (United States)

    Shin, S J; Guzman, J; Yuan, C-W; Liao, Christopher Y; Boswell-Koller, Cosima N; Stone, P R; Dubon, O D; Minor, A M; Watanabe, Masashi; Beeman, Jeffrey W; Yu, K M; Ager, J W; Chrzan, D C; Haller, E E

    2010-08-11

    Phase change materials are essential to a number of technologies ranging from optical data storage to energy storage and transport applications. This widespread interest has given rise to a substantial effort to develop bulk phase change materials well suited for desired applications. Here, we suggest a novel and complementary approach, the use of binary eutectic alloy nanoparticles embedded within a matrix. Using GeSn nanoparticles embedded in silica as an example, we establish that the presence of a nanoparticle/matrix interface enables one to stabilize both nanobicrystal and homogeneous alloy morphologies. Further, the kinetics of switching between the two morphologies can be tuned simply by altering the composition.

  16. Development of phase change materials based microencapsulated technology for buildings: A review

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, V.V.; Kaushik, S.C. [Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Tyagi, S.K. [School of Infrastructure Technology and Resource Management, Shri Mata Vaishno Devi University, Katra 182320, J and K (India); Akiyama, T. [Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo 060-86283 (Japan)

    2011-02-15

    Thermal energy storage (TES) systems using phase change material (PCM) have been recognized as one of the most advanced energy technologies in enhancing the energy efficiency and sustainability of buildings. Now the research is focus on suitable method to incorporate PCMs with building. There are several methods to use phase change materials (PCMs) in thermal energy storage (TES) for different applications. Microencapsulation is one of the well known and advanced technologies for better utilization of PCMs with building parts, such as, wall, roof and floor besides, within the building materials. Phase change materials based microencapsulation for latent heat thermal storage (LHTS) systems for building application offers a challenging option to be employed as effective thermal energy storage and a retrieval device. Since the particular interest in using microencapsulation PCMs for concrete and wall/wallboards, the specific research efforts on both subjects are reviewed separately. This paper presents an overview of the previous research work on microencapsulation technology for thermal energy storage incorporating the phase change materials (PCMs) in the building applications, along with few useful conclusive remarks concluded from the available literature. (author)

  17. Study on polyethylene glycol/epoxy resin composite as a form-stable phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Yutang; Kang, Huiying; Wang, Weilong; Liu, Hong; Gao, Xuenong [The Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, South China University of Technology, Guangzhou 510640 (China)

    2010-12-15

    Form-stable polyethylene glycol (PEG)/epoxy resin (EP) composite as a novel phase change material (PCM) was prepared using casting molding method. In this new material, PEG acts as the latent heat storage material and EP polymer serves as the supporting material, which provides structural strength and prevents the leakage of the melted PEG. The structure and morphology of the novel composite were observed using Fourier transformation infrared spectroscope (FTIR) and scanning electronic microscope (SEM). The thermo-mechanical property and transition behavior were characterized by polarizing optical microscope (POM), static thermo-mechanical analysis (TMA) and differential scanning calorimeter (DSC). The experimental results show that, as a result of the physical tangled function of the epoxy resin carrier to the PEG segment, the composite macroscopically presents the solid-solid phase change characteristic. (author)

  18. Study on polyethylene glycol/epoxy resin composite as a form-stable phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Fang Yutang, E-mail: ppytfang@scut.edu.c [Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, South China University of Technology, Guangzhou 510640 (China); Kang Huiying; Wang Weilong; Liu Hong; Gao Xuenong [Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, South China University of Technology, Guangzhou 510640 (China)

    2010-12-15

    Form-stable polyethylene glycol (PEG)/epoxy resin (EP) composite as a novel phase change material (PCM) was prepared using casting molding method. In this new material, PEG acts as the latent heat storage material and EP polymer serves as the supporting material, which provides structural strength and prevents the leakage of the melted PEG. The structure and morphology of the novel composite were observed using Fourier transformation infrared spectroscope (FTIR) and scanning electronic microscope (SEM). The thermo-mechanical property and transition behavior were characterized by polarizing optical microscope (POM), static thermo-mechanical analysis (TMA) and differential scanning calorimeter (DSC). The experimental results show that, as a result of the physical tangled function of the epoxy resin carrier to the PEG segment, the composite macroscopically presents the solid-solid phase change characteristic.

  19. Characterization of a lime-pozzolan plaster containing phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Pavlíková, Milena; Pavlík, Zbyšek; Trník, Anton; Pokorný, Jaroslav; Černý, Robert [Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague (Czech Republic)

    2015-03-10

    A PCM (Phase Change Material) modified lime-pozzolan plaster for improvement of thermal energy storage of building envelopes is studied in the paper. The investigated plaster is composed of lime hydrate, pozzolan admixture based on metakaolin and mudstone, silica sand, water and paraffin wax encapsulated in polymer capsule. The reference plaster without PCM application is studied as well. The analyzed materials are characterized by bulk density, matrix density, total open porosity, compressive strength and pore size distribution. The temperature of phase change, heat of fusion and crystallization are studied using DSC (Difference Scanning Calorimetry) analysis performed in air atmosphere. In order to get information on materials hygrothermal performance, determination of thermal and hygric properties is done in laboratory conditions. Experimental data reveal a substantial improvement of heat storage capacity of PCM-modified plaster as compared to the reference material without PCM.

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

    Science.gov (United States)

    Pinney, Nathan Douglas

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

  1. On entropy change measurements around first order phase transitions in caloric materials

    Science.gov (United States)

    Caron, Luana; Doan, Nguyen Ba; Ranno, Laurent

    2017-02-01

    In this work we discuss the measurement protocols for indirect determination of the isothermal entropy change associated with first order phase transitions in caloric materials. The magneto-structural phase transitions giving rise to giant magnetocaloric effects in Cu-doped MnAs and FeRh are used as case studies to exemplify how badly designed protocols may affect isothermal measurements and lead to incorrect entropy change estimations. Isothermal measurement protocols which allow correct assessment of the entropy change around first order phase transitions in both direct and inverse cases are presented.

  2. Nature of defects and gap states in GeTe model phase change materials

    Science.gov (United States)

    Huang, B.; Robertson, J.

    2012-03-01

    The electrical storage mechanism in GeSbTe phase change materials is discussed in terms of their gap states using GeTe as a model system. The lowest energy defect in crystalline rhombohedral GeTe phase is the Ge vacancy, because it reconstructs along the resonant bonding directions. The lowest energy in amorphous GeTe is the divalent Te atom, which creates overlapping band-tail states that pin Fermi level EF near midgap. In contrast, the lowest cost defect in disordered phase in GeSbTe superlattices is the Te interstitial whose negative correlation energy pins EF near midgap.

  3. A Review On Free Cooling Through Heat Pipe by Using Phase Change Materials

    Directory of Open Access Journals (Sweden)

    A.S.Futane ,

    2011-06-01

    Full Text Available Thermal energy storage is renewable source of energy to develop energy storage system, which minimize environmental impact such as ozone depletion and global warming. Thermal energy can be stored as latent heat which is latter use when substance changes from one phase to another phase by either freezing or melting. Now a days need of refrigeration and air conditioning has been increased, which can be achieved by free cooling, for this various substances are use, depending upon required temperature. Phase change materials are one of the substances having low temperature of melting and solidification.

  4. Intergranular and inter-phased boundaries in the materials; Joints intergranulaires et interphases dans les materiaux

    Energy Technology Data Exchange (ETDEWEB)

    Aslanides, A. [Electricite de France, Dept. CIMA, 77 - Moret sur Loing (France); Backhaus-Ricoult, M. [Centre d' Etudes de Chimie metallurgique, 94 - Vitry-sur-Seine (France); Bayle-Guillemaud, P. [CEA Grenoble, Dept. de Recherche Fondamentale sur la Matiere Condensee, 38 (France)] [and others

    2000-07-01

    This document collects the abstracts of the talks presented during the colloquium J2IM on the intergranular and inter-phased boundaries in the materials. Around the themes of the interfaces behaviour and grain boundaries defects in materials, these days dealt with the microstructure behaviour in many domains such as the interfaces in batteries, the irradiation damages and the special case of the fuel-cladding interactions, the stressed interfaces, the alumina or silicon carbides substrates. (A.L.B.)

  5. RIMS International Conference : Mathematical Challenges in a New Phase of Materials Science

    CERN Document Server

    Kotani, Motoko

    2016-01-01

    This volume comprises eight papers delivered at the RIMS International Conference "Mathematical Challenges in a New Phase of Materials Science", Kyoto, August 4–8, 2014. The contributions address subjects in defect dynamics, negatively curved carbon crystal, topological analysis of di-block copolymers, persistence modules, and fracture dynamics. These papers highlight the strong interaction between mathematics and materials science and also reflect the activity of WPI-AIMR at Tohoku University, in which collaborations between mathematicians and experimentalists are actively ongoing.

  6. Simulated Aging and Characterization of Phase Change Materials for Thermal Management of Building Envelopes

    Science.gov (United States)

    2015-09-01

    Method B). West Conshohocken, PA: ASTM International. ———. 2009. Standard Method for Surface Burning Characteristics of Building Materials. ASTM E84-09...storage in buildings : A state of art. Renewable and Sustainable Energy Reviews 11(6):1146-1166 Yu, S., S. Jeong, C. Chyoung, and S. Kim. 2014. Bio-based...Simulated Aging and Characterization of Phase Change Materials for lhermal Management of Building Envelopes Elizabeth J. Gao, Jignesh Patel, Veera M. Boddu

  7. Basic Principles and Utilization Possibilities’ of Ultrasonic Phased Array in Material Nondestructive Evaluation

    OpenAIRE

    Ivo Cap; Klara Capova; Dagmar Faktorova

    2004-01-01

    The paper deals with the basic principles of operation and with the utilization possibilities of phased array (PA) in materials nondestructive testing (NDT). The first part deals with description of PA arrangement modes, which enable to generate, focus and steer the ultrasonic beem. The second part deals with the description of electromagnetic acoustic transducer PA operation. The last part deals with the description of the utilization of PA in nondestructive testing of conductive materials a...

  8. Energy Storage Properties of Phase Change Materials Prepared from PEG/CPP

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    New kinds of solid-solid phase change materials have been prepared in our laboratory.In these materials, the rigid polymer chlorinated polypropylene is taken as skeletons and the flexible polymer polyethylene glycol 6000 and polyethylene glycol 10000 are taken as functional chains. Results show that chlorinated polypropylene grafted by polyethylene glycol 10000 has greater enthalpy than chlorinated polypropylene grafted by polyethylene glycol 6000.

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

    Science.gov (United States)

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

    2010-06-01

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

  10. PHASE I MATERIALS PROPERTY DATABASE DEVELOPMENT FOR ASME CODES AND STANDARDS

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Weiju [ORNL; Lin, Lianshan [ORNL

    2013-01-01

    To support the ASME Boiler and Pressure Vessel Codes and Standard (BPVC) in modern information era, development of a web-based materials property database is initiated under the supervision of ASME Committee on Materials. To achieve efficiency, the project heavily draws upon experience from development of the Gen IV Materials Handbook and the Nuclear System Materials Handbook. The effort is divided into two phases. Phase I is planned to deliver a materials data file warehouse that offers a depository for various files containing raw data and background information, and Phase II will provide a relational digital database that provides advanced features facilitating digital data processing and management. Population of the database will start with materials property data for nuclear applications and expand to data covering the entire ASME Code and Standards including the piping codes as the database structure is continuously optimized. The ultimate goal of the effort is to establish a sound cyber infrastructure that support ASME Codes and Standards development and maintenance.

  11. Nanoscale Phase Immiscibility in High-ZT Bulk Lead Telluride Thermoelectric Materials

    Science.gov (United States)

    Girard, Steven Neal

    Renewable energy initiatives have increased interest in thermoelectric materials as an option for inexpensive and environmentally friendly waste heat-to-power generation. Unfortunately, low efficiencies have limited their wide-scale utilization. This work describes the synthesis and characterization of bulk nanostructured thermoelectric materials wherein natural phase immiscibility is manipulated to selectively generate nanoscale inclusions of a second phase that improve their efficiency through reductions in lattice thermal conductivity. The PbTe-PbS system exhibits natural phase separation by nucleation and growth or spinodal decomposition phase transformations depending on composition and temperature treatment. Through rapid quenching, nearly ideal solid solution alloys of PbTe-PbS are observed by powder X-ray diffraction. However, characterization by solid-state NMR and IR reflectivity show that solid solutions are obtained for rapidly quenched samples within the nucleation and growth region of the phase diagram, but samples within the spinodal decomposition region exhibit very slight phase immiscibility. We report the temperatures of phase separation using high temperature powder X-ray diffraction. Microscopy reveals that phase separation in PbTe-PbS naturally produces nanoinclusions. A decrease in lattice thermal conductivity is observed as a result of the solid solution-to-nanostructured phase transformation in this materials system, increasing thermoelectric figure of merit. Sn addition to PbTe-PbS produces a pseudobinary system of PbTe-PbSnS 2. This materials system produces microscale lamellae that effectively reduce lattice thermal conductivity. Unfortunately, the PbSnS2 inclusions also scatter electrons, reducing electrical conductivity and producing only a minimal increase in thermoelectric figure of merit. We additionally investigate PbSnS2 as prepared through Bridgman crystal growth. PbTe-PbS doped with Na appears to increase the kinetic rate of

  12. Energy Saving Potentials of Phase Change Materials Applied to Lightweight Building Envelopes

    Directory of Open Access Journals (Sweden)

    Yoon-Bok Seong

    2013-10-01

    Full Text Available Phase change materials (PCMs have been considered as an innovative technology that can reduce the peak loads and heating, ventilating and air conditioning (HVAC energy consumption in buildings. Basically they are substances capable of storing or releasing thermal energy as latent heat. Because the amount of latent heat absorbed or released is much larger than the sensible heat, the application of PCMs in buildings has significant potential to reduce energy consumption. However, because each PCM has its own phase change temperature, which is the temperature at which latent heat is absorbed or released, it is important to use an appropriate PCM for the purpose of building envelope design. Therefore, this paper aims to investigate the energy saving potentials in buildings when various PCMs with different phase change temperatures are applied to a lightweight building envelope by analyzing the thermal load characteristics. As results, the annual heating load increased at every phase change temperature, but the peak heating load decreased by 3.19% with heptadecane (phase change temperature 21 °C, and the lowest indoor temperature increased by 0.86 °C with heptadecane (phase change temperature 21 °C. The annual cooling load decreased by 1.05% with dodecanol (phase change temperature 24 °C, the peak cooling load decreased by 1.30% with octadecane (phase change temperature 29 °C, and the highest indoor temperature dropped by 0.50 °C with octadecane (phase change temperature 29 °C. When the night ventilation was applied to the building HVAC system for better passive cooling performance, the annual cooling load decreased by 9.28% with dodecanol (phase change temperature 24 °C, the peak load decreased by 11.33% with octadecane (phase change temperature 29 °C, and the highest indoor temperature dropped by 0.85 °C with octadecane (phase change temperature 29 °C.

  13. LIFE Materials: Phase Formation and Transformations in Transmutation Fuel Materials for the LIFE Engine Part I - Path Forward Volume 3

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, P A; Kaufman, L; Fluss, M

    2008-12-19

    The current specifications of the LLNL fusion-fission hybrid proposal, namely LIFE, impose severe constraints on materials, and in particular on the nuclear fissile or fertile nuclear fuel and its immediate environment. This constitutes the focus of the present report with special emphasis on phase formation and phase transformations of the transmutation fuel and their consequences on particle and pebble thermal, chemical, and mechanical integrities. We first review the work that has been done in recent years to improve materials properties under the Gen-IV project, and with in particular applications to HTGR and MSR, and also under GNEP and AFCI in the USA. Our goal is to assess the nuclear fuel options that currently exist together with their issues. Among the options, it is worth mentioning TRISO, IMF, and molten salts. The later option will not be discussed in details since an entire report (Volume 8 - Molten-salt Fuels) is dedicated to it. Then, in a second part, with the specific LIFE specifications in mind, the various fuel options with their most critical issues are revisited with a path forward for each of them in terms of research, both experimental and theoretical. Since LIFE is applicable to very high burn-up of various fuels, distinctions will be made depending on the mission, i.e., energy production or incineration. Finally a few conclusions are drawn in terms of the specific needs for integrated materials modeling and the in depth knowledge on time-evolution thermo-chemistry that controls and drastically affects the performance of the nuclear materials and their immediate environment. Although LIFE demands materials that very likely have not yet been fully optimized, the challenges are not insurmountable, and a well concerted experimental-modeling effort should lead to dramatic advances that should well serve other fission programs such as Gen-IV, GNEP, AFCI as well as the international fusion program, ITER.

  14. Analysis of Phase Separation in High Performance PbTe–PbS Thermoelectric Materials

    Energy Technology Data Exchange (ETDEWEB)

    Girard, Steven N. [Northwestern University; Schmidt-Rohr, Klaus [Ames Laboratory; Chasapis, Thomas C. [Northwestern University; Hatzikraniotis, Euripides [Aristotle University of Thessaloniki; Njegic, B. [Ames Laboratory; Levin, E. M. [Ames Laboratory; Rawal, A. [Ames Laboratory; Paraskevopoulos, Konstantios M. [Aristotle University of Thessaloniki; Kanatzidis, Mercouri G. [Northwestern University

    2013-02-11

    Phase immiscibility in PbTe–based thermoelectric materials is an effective means of top-down synthesis of nanostructured composites exhibiting low lattice thermal conductivities. PbTe1-x Sx thermoelectric materials can be synthesized as metastable solid solution alloys through rapid quenching. Subsequent post-annealing induces phase separation at the nanometer scale, producing nanostructures that increase phonon scattering and reduce lattice thermal conductivity. However, there has yet to be any study investigating in detail the local chemical structure of both the solid solution and nanostructured variants of this material system. Herein, quenched and annealed (i.e., solid solution and phase-separated) samples of PbTe–PbS are analyzed by in situ high-resolution synchrotron powder X-ray diffraction, solid-state 125Te nuclear magnetic resonance (NMR), and infrared (IR) spectroscopy analysis. For high concentrations of PbS in PbTe, e.g., x >16%, NMR and IR analyses reveal that rapidly quenched samples exhibit incipient phase separation that is not detected by state-of-the-art synchrotron X-ray diffraction, providing an example of a PbTe thermoelectric “alloy” that is in fact phase inhomogeneous. Thermally-induced PbS phase separation in PbTe–PbS occurs close to 200 °C for all compositions studied, and the solubility of the PbS phase in PbTe at elevated temperatures >500 °C is reported. The findings of this study suggest that there may be a large number of thermoelectric alloy systems that are phase inhomogeneous or nanostructured despite adherence to Vegard's Law of alloys, highlighting the importance of careful chemical characterization to differentiate between thermoelectric alloys and composites.

  15. Basic Principles and Utilization Possibilities’ of Ultrasonic Phased Array in Material Nondestructive Evaluation

    Directory of Open Access Journals (Sweden)

    Dagmar Faktorova

    2004-01-01

    Full Text Available The paper deals with the basic principles of operation and with the utilization possibilities of phased array (PA in materials nondestructive testing (NDT. The first part deals with description of PA arrangement modes, which enable to generate, focus and steer the ultrasonic beem. The second part deals with the description of electromagnetic acoustic transducer PA operation. The last part deals with the description of the utilization of PA in nondestructive testing of conductive materials and the advantages of PA utilization in inhomogeneous materials NDT.

  16. The behavior of self-compacting concrete containing micro-encapsulated Phase Change Materials

    NARCIS (Netherlands)

    Hunger, M.; Entrop, A.G.; Mandilaras, I.; Brouwers, H.J.H.; Founti, M.

    2009-01-01

    In order to come to a sustainable built environment the construction industry requires new energy saving concepts. One concept is to use Phase Change Materials (PCM), which have the ability to absorb and to release thermal energy at a specific temperature. This paper presents a set of experiments us

  17. Nature of the first-order magnetic phase transition in giant-magnetocaloric materials

    NARCIS (Netherlands)

    Yibole

    2016-01-01

    This thesis reports on advanced characterizations of giant magnetocaloric materials that show a first order magnetic phase transition (FOMT). The results are of great interest not only for the design of new magnetic refrigerants, but also for a better understanding of the FOMT. This thesis paves the

  18. Optimal design variable considerations in the use of phase change materials in indirect evaporative cooling

    Science.gov (United States)

    Chilakapaty, Ankit Paul

    The demand for sustainable, energy efficient and cost effective heating and cooling solutions is exponentially increasing with the rapid advancement of computation and information technology. Use of latent heat storage materials also known as phase change materials (PCMs) for load leveling is an innovative solution to the data center cooling demands. These materials are commercially available in the form of microcapsules dispersed in water, referred to as the microencapsulated phase change slurries and have higher heat capacity than water. The composition and physical properties of phase change slurries play significant role in energy efficiency of the cooling systems designed implementing these PCM slurries. Objective of this project is to study the effect of PCM particle size, shape and volumetric concentration on overall heat transfer potential of the cooling systems designed with PCM slurries as the heat transfer fluid (HTF). In this study uniform volume heat source model is developed for the simulation of heat transfer potential using phase change materials in the form of bulk temperature difference in a fully developed flow through a circular duct. Results indicate the heat transfer potential increases with PCM volumetric concentration with gradually diminishing returns. Also, spherical PCM particles offer greater heat transfer potential when compared to cylindrical particles. Results of this project will aid in efficient design of cooling systems based on PCM slurries.

  19. Micromechanical Analyses of Debonding and Matrix Cracking in Dual-Phase Materials

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Yang, Qingda

    2016-01-01

    Failure in elastic dual-phase materials under transverse tension is studied numerically. Cohesive zones represent failure along the interface and the augmented finite element method (A-FEM) is used for matrix cracking. Matrix cracks are formed at an angle of 55 deg - 60 deg relative to the loading...

  20. Structural semiconductor-to-semimetal phase transition in two-dimensional materials induced by electrostatic gating.

    Science.gov (United States)

    Li, Yao; Duerloo, Karel-Alexander N; Wauson, Kerry; Reed, Evan J

    2016-01-01

    Dynamic control of conductivity and optical properties via atomic structure changes is of technological importance in information storage. Energy consumption considerations provide a driving force towards employing thin materials in devices. Monolayer transition metal dichalcogenides are nearly atomically thin materials that can exist in multiple crystal structures, each with distinct electrical properties. By developing new density functional-based methods, we discover that electrostatic gating device configurations have the potential to drive structural semiconductor-to-semimetal phase transitions in some monolayer transition metal dichalcogenides. Here we show that the semiconductor-to-semimetal phase transition in monolayer MoTe2 can be driven by a gate voltage of several volts with appropriate choice of dielectric. We find that the transition gate voltage can be reduced arbitrarily by alloying, for example, for Mo(x)W(1-x)Te2 monolayers. Our findings identify a new physical mechanism, not existing in bulk materials, to dynamically control structural phase transitions in two-dimensional materials, enabling potential applications in phase-change electronic devices.

  1. Non-Toxic, Non-Flammable, -80 C Phase Change Materials

    Science.gov (United States)

    Cutbirth, J. Michael

    2013-01-01

    The objective of this effort was to develop a non-toxic, non-flammable, -80 C phase change material (PCM) to be used in NASA's ICEPAC capsules for biological sample preservation in flight to and from Earth orbit. A temperature of about -68 C or lower is a critical temperature for maintaining stable cell, tissue, and cell fragment storage.

  2. X-Ray Diffraction Phase Analyses for Granulated and Sintered Ceramic Materials

    Directory of Open Access Journals (Sweden)

    Suminar Pratapa

    2007-11-01

    Full Text Available One basic problematic aspect in x-ray diffraction phase analysis is microabsorption effect which may arise from the size of the crystallite phases. Complication of the problem may intensify in sintered ceramic materials where milling of the samples is not simple. We report the Rietveld x-ray diffraction phase analysis of MgO-α-Al2O3 powder mixtures with phase content ratio of 1:1 by weight and MgO-Y2O3 sintered ceramic composites with Y2O3 contents of 10%, 20% and 30% by weight. The mixtures were pre-sintered at 1000°C for 2 hours and then milled while the composites were sintered at 1550°C for 3 hours. The phase composition analysis was done using Rietica, a non-commercial Rietveld method-based software. Relative and absolute phase compositions were examined and results showed that there was a significant amount of phase composition bias resulted from the examination. For the powder mixture, milling can reduce microabsorption effect and hence the calculation bias. For the ceramic composite where milling is almost impossible, additional of Y2O3 caused smaller crystallite size of MgO, so that composition bias is smaller in composites with higher Y2O3 content. A mathematical model is proposed to provide more acceptable phase composition results.

  3. Penn gap rule in phase-change memory materials: No clear evidence for resonance bonds

    Science.gov (United States)

    Shimakawa, K.; Střižik, L.; Wagner, T.; Frumar, M.

    2015-04-01

    Although a proposal of resonance bonds in crystalline phase-change materials based on the GeSbTe system has been provided, we do not find any clear evidence in favor of the proposal. The ellipsometric study demonstrates that a change in the high frequency dielectric constant ɛ∞ between the amorphous and crystalline phases is only scaled by the average bandgap (the Penn gap rule). Even for a pure antimony film, regarded as a prototype resonance bonding material, ɛ∞ was found to follow the Penn gap rule. Experimentally, we did not find any evidence of a significant change in the optical transition matrix element during the phase change, which is necessary to support the idea of resonance bonds.

  4. Penn gap rule in phase-change memory materials: No clear evidence for resonance bonds

    Directory of Open Access Journals (Sweden)

    K. Shimakawa

    2015-04-01

    Full Text Available Although a proposal of resonance bonds in crystalline phase-change materials based on the GeSbTe system has been provided, we do not find any clear evidence in favor of the proposal. The ellipsometric study demonstrates that a change in the high frequency dielectric constant ε∞ between the amorphous and crystalline phases is only scaled by the average bandgap (the Penn gap rule. Even for a pure antimony film, regarded as a prototype resonance bonding material, ε∞ was found to follow the Penn gap rule. Experimentally, we did not find any evidence of a significant change in the optical transition matrix element during the phase change, which is necessary to support the idea of resonance bonds.

  5. Preparation and Properties of Paraffin/TiO2/Active-carbon Composite Phase Change Materials

    Directory of Open Access Journals (Sweden)

    HAO Yong-gan

    2016-11-01

    Full Text Available A novel composite phase change materials (PCMs of paraffin/TiO2/active-carbon was prepared by a microemulsion method, where paraffin acted as a PCM and titanium dioxide (TiO2 as matrix material, and a small amount of active carbon was added to improve the thermal conductivity. The compositions, morphology and thermal properties of the paraffin/TiO2/active-carbon composite PCMs were characterized by XRD, SEM, TGA and DSC respectively. The shape stability during phase change process of this composite was also tested. The results show that paraffin is well encapsulated by TiO2 matrix, and thus exhibiting excellent shape-stabilized phase change feature. Besides, this composite PCM also presents superhydrophobic property. Therefore, these multifunctional features will endow PCMs with important application potential in energy efficient buildings.

  6. Advanced phase change materials and systems for solar passive heating and cooling of residential buildings

    Energy Technology Data Exchange (ETDEWEB)

    Salyer, I.O.; Sircar, A.K.; Dantiki, S.

    1988-01-01

    During the last three years under the sponsorship of the DOE Solar Passive Division, the University of Dayton Research Institute (UDRI) has investigated four phase change material (PCM) systems for utility in thermal energy storage for solar passive heating and cooling applications. From this research on the basis of cost, performance, containment, and environmental acceptability, we have selected as our current and most promising series of candidate phase change materials, C-15 to C-24 linear crystalline alkyl hydrocarbons. The major part of the research during this contract period was directed toward the following three objectives. Find, test, and develop low-cost effective phase change materials (PCM) that melt and freeze sharply in the comfort temperature range of 73--77{degree}F for use in solar passive heating and cooling of buildings. Define practical materials and processes for fire retarding plasterboard/PCM building products. Develop cost-effective methods for incorporating PCM into building construction materials (concrete, plasterboard, etc.) which will lead to the commercial manufacture and sale of PCM-containing products resulting in significant energy conservation.

  7. Electronic Structure and Spin Configuration Trends of Single Transition Metal Impurity in Phase Change Material

    Science.gov (United States)

    Li, H.; Pei, J.; Shi, L. P.

    2016-10-01

    Fe doped phase change material GexSbyTez has shown experimentally the ability to alter its magnetic properties by phase change. This engineered spin degree of freedom into the phase change material offers the possibility of logic devices or spintronic devices where they may enable fast manipulation of ferromagnetism by a phase change mechanism. The electronic structures and spin configurations of isolated transition metal dopant in phase change material (iTM-PCM) is important to understand the interaction between localized metal d states and the unique delocalized host states of phase change material. Identifying an impurity center that has, in isolation, a nonvanishing magnetic moment is the first step to study the collective magnetic ordering, which originates from the interaction among close enough individual impurities. Theoretical description of iTM-PCM is challenging. In this work, we use a screened exchange hybrid functional to study the single 3d transition metal impurity in crystalline GeTe and GeSb2Te4. By curing the problem of local density functional (LDA) such as over-delocalization of the 3d states, we find that Fe on the Ge/Sb site has its majority d states fully occupied while its minority d states are empty, which is different from the previously predicted electronic configuration by LDA. From early transition metal Cr to heavier Ni, the majority 3d states are gradually populated until fully occupied and then the minority 3d states begin to be filled. Interpretive orbital interaction pictures are presented for understanding the local and total magnetic moments.

  8. Microencapsulation of coco fatty acid mixture for thermal energy storage with phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Ozonur, Y.; Mazman, M.; Paksoy, H.O.; Evilya, H. [Cukurova University, Adana (Turkey). Dept. of Chemistry

    2005-07-01

    Thermal energy storage systems provide several alternatives for efficient energy use and energy conservation. Microcapsules of natural coco fatty acid mixture were prepared to be used as phase change materials for thermal energy storage. The coacervation technique was used for the microencapsulation process. Several alternatives for the capsule wall material were tried. The microcapsules were characterized according to their geometric profiles, phase transition temperatures, mean particle sizes, chemical stabilities, and their thermal cycling. The diameters of microcapsules prepared in this study were about 1 mm. Coco fatty acid mixtures have kept their geometrical profiles even after 50 thermal cycles for melting and freezing operations in temperature range from 22 to 34{sup o}C. It was found that gelatin+gum Arabic mixture was the best wall material for microencapsulating coco fatty acid mixtures. (author)

  9. Processing And Properties Of MAX Phases – Based Materials Using SHS Technique

    Directory of Open Access Journals (Sweden)

    Chlubny L.

    2015-06-01

    Full Text Available Authors present results of works on the interesting new group of advanced ceramics called MAX phases – Ti-based ternary carbides and nitrides. They have an original layered structure involved highly anisotropic properties laying between ceramics and metals, with high elastic modulus, low hardness, very high fracture toughness and high electrical and heat conductivity. Using Self-Propagating High-Temperature Synthesis (SHS in the combustion regime it is possible to prepare MAX phases-rich powders that can be used as the precursors for preparation of dense MAX polycrystals by presureless sintering or hot-pressing. Different novel Ti-based phases with layered structures, namely: Ti3AlC2 and Ti2AlC have been synthesized in a combustion regime. The possibility of controlling of combustion phenomena for obtaining near single-phase products is discussed in details as well as some of properties of the materials tested as structure and functional ceramics.

  10. Si1Sb2Te3 phase change material for chalcogenide random access memory

    Institute of Scientific and Technical Information of China (English)

    Zhang Ting; Song Zhi-Tang; Liu Bo; Liu Wei-Li; Feng Song-Lin; Chen Bomy

    2007-01-01

    This paper investigated phase change Si1Sb2Te3 material for application of chalcogenide random access memory.Current-voltage performance was conducted to determine threshold current of phase change from amorphous phase to polycrystalline phase.The film holds a threshold current about 0.155 mA,which is smaller than the value 0.31 mA of Ge2Sb2Te5 film.Amorphous Si1Sb2Te3 changes to face-centred-cubic structure at~180°C and changes to hexagonal structure at~270°C.Annealing temperature dependent electric resistivity of Si1Sb2Te3 film was studied by four-point probe method.Data retention of the films was characterized as well.

  11. A hybrid phenomenological model for ferroelectroelastic ceramics. Part I: Single phased materials

    Science.gov (United States)

    Stark, S.; Neumeister, P.; Balke, H.

    2016-10-01

    In this part I of a two part series, a rate-independent hybrid phenomenological constitutive model applicable for single phased polycrystalline ferroelectroelastic ceramics is presented. The term "hybrid" refers to the fact that features from macroscopic phenomenological models and micro-electromechanical phenomenological models are combined. In particular, functional forms for a switching function and the Helmholtz free energy are assumed as in many macroscopic phenomenological models; and the volume fractions of domain variants are used to describe the internal material state, which is a key feature of micro-electromechanical phenomenological models. The approach described in this paper is an attempt to combine the advantages of macroscopic and micro-electromechanical material models. Its potential is demonstrated by comparison with experimental data for barium titanate. Finally, it is shown that the model for single phased materials cannot reproduce the material behavior of morphotropic PZT ceramics based on a realistic choice for the material parameters. This serves as a motivation for part II of the series, which deals with the modeling of morphotropic PZT ceramics taking into account the micro-structural specifics of these materials.

  12. A Super Cooled, Non-toxic, Non-flammable Phase Change Material Thermal Pack for Portable Life Support Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The continuation of concept development and test of a water-based, advanced Phase Change Material (PCM) heat sink is proposed. Utilizing a novel material choice for...

  13. A Super Cooled, Non-toxic, Non-flammable Phase Change Material Thermal Pack for Portable Life Support Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The concept development and test of a water-based, advanced Phase Change Material (PCM) heat sink is proposed. Utilizing a novel material choice for both an...

  14. Nanoengineered materials for liquid-vapour phase-change heat transfer

    Science.gov (United States)

    Cho, H. Jeremy; Preston, Daniel J.; Zhu, Yangying; Wang, Evelyn N.

    2016-12-01

    Liquid-vapour phase change is a useful and efficient process to transfer energy in nature, as well as in numerous domestic and industrial applications. Relatively recent advances in altering surface chemistry, and in the formation of micro- and nanoscale features on surfaces, have led to exciting improvements in liquid-vapour phase-change performance and better understanding of the underlying science. In this Review, we present an overview of the surface, thermal and material science to illustrate how new materials and designs can improve boiling and condensation. There are many parallels between boiling and condensation, such as nucleation of a phase and its departure from a surface; however, the particular set of challenges associated with each phenomenon results in different material designs used in different manners. We also discuss alternative techniques, such as introducing heterogeneous surface chemistry or direct real-time manipulation of the phase-change process, which can offer further control of heat-transfer processes. Finally, long-term robustness is essential to ensure reliability and feasibility but remains a key challenge.

  15. Electrical properties of Cr-doped Sb2Te3 phase change material

    Science.gov (United States)

    Wang, Qing; Liu, Bo; Xia, Yangyang; Zheng, Yonghui; Song, Sannian; Cheng, Yan; Song, Zhitang; Feng, Songlin

    2016-10-01

    Phase Change Memory (PCM) is regarded as one of the most promising candidates for the next-generation nonvolatile memory. Its storage medium, phase change material, has attracted continuous exploration. Sb2Te3 is a high-speed phase change material matrix with low crystallization temperature. Cr-doped Sb2Te3 (CST) films with suitable composition have been studied and proved to be a promising novel phase change material with high speed and good thermal stability. In this paper, detailed Rs-T characteristics and Hall characteristics of the CST films are studied. We find that, when more parts of the film crystallizes into the ordered structure, the activation energy for electrical conduction (Eσ) decreases, indicating that the semiconductor property is weakened. And with the increase of Cr-dopants, Eσ of the As-deposited (As-de) amorphous CST films decreases, thus the thermal stability of resistance is improved. Hall results show that Sb2Te3 and CST films are all in P-type. For As-de amorphous films, with the increase of Cr-dopants, the carrier mobility decreases all along, while the carrier density decreases at first and then increases. For the crystalline films, with the increase of Cr-dopants, the carrier mobility decreases, while the carrier density increases.

  16. A new analytical model for thermal stresses in multi-phase materials and lifetime prediction methods

    Institute of Scientific and Technical Information of China (English)

    Ladislav Ceniga

    2008-01-01

    Based on the fundamental equations of the mechanics of solid continuum, the paper employs an ana-lytical model for determination of elastic thermal stresses in isotropic continuum represented by periodically distributed spherical particles with different distributions in an infinite matrix, imaginarily divided into identical cells with dimen-sions equal to inter-particle distances, containing a central spherical particle with or without a spherical envelope on the particle surface. Consequently, the multi-particle-(envelope)-matrix system, as a model system regarding the analytical modelling, is applicable to four types of multi-phase mate-rials. As functions of the particle volume fraction v, the inter-particle distances d1, d2, d3 along three mutually per-pendicular axes, and the particle and envelope radii, R1 and Re, respectively, the thermal stresses within the cell, are originated during a cooling process as a consequence of the difference in thermal expansion coefficients of phases rep-resented by the matrix, envelope and particle. Analytical-(experimental)-computational lifetime prediction methods for multi-phase materials are proposed, which can be used in engineering with appropriate values of parameters of real multi-phase materials.

  17. Effect of water-ice phase change on thermal performance of building materials

    Science.gov (United States)

    Kočí, Václav; Černý, Robert

    2016-07-01

    The effect of water ice-phase change on thermal performance of integrated building material is investigated in this paper. As a characteristic construction, simple external wall made of aerated autoclaved concrete was assumed which was exposed to dynamic climatic condition of Šerák, Czech Republic. The computational modelling of hygrothermal performance was carried out using computer codes HEMOT and SIFEL that work on the basis of finite element method. The effect of phase change was taken into account by fixed-domain method, when experimentally determined effective specific heat capacity was used as a material parameter. It comprises also the effect of heat consumption and heat release that accompany the water-ice phase change. Comparing to the results with specific heat capacity, the effect of phase change on thermal performance could be quantified. The results showed that temperature fields can differ more than 6 °C. Additionally, the amount energy transported through the wall may be higher up to 4 %. This confirmed, that the effect water-ice phase change should be included in all the relevant energy calculations.

  18. In Situ Environmental TEM in Imaging Gas and Liquid Phase Chemical Reactions for Materials Research.

    Science.gov (United States)

    Wu, Jianbo; Shan, Hao; Chen, Wenlong; Gu, Xin; Tao, Peng; Song, Chengyi; Shang, Wen; Deng, Tao

    2016-11-01

    Gas and liquid phase chemical reactions cover a broad range of research areas in materials science and engineering, including the synthesis of nanomaterials and application of nanomaterials, for example, in the areas of sensing, energy storage and conversion, catalysis, and bio-related applications. Environmental transmission electron microscopy (ETEM) provides a unique opportunity for monitoring gas and liquid phase reactions because it enables the observation of those reactions at the ultra-high spatial resolution, which is not achievable through other techniques. Here, the fundamental science and technology developments of gas and liquid phase TEM that facilitate the mechanistic study of the gas and liquid phase chemical reactions are discussed. Combined with other characterization tools integrated in TEM, unprecedented material behaviors and reaction mechanisms are observed through the use of the in situ gas and liquid phase TEM. These observations and also the recent applications in this emerging area are described. The current challenges in the imaging process are also discussed, including the imaging speed, imaging resolution, and data management.

  19. Direct observation of titanium-centered octahedra in titanium-antimony-tellurium phase-change material.

    Science.gov (United States)

    Rao, Feng; Song, Zhitang; Cheng, Yan; Liu, Xiaosong; Xia, Mengjiao; Li, Wei; Ding, Keyuan; Feng, Xuefei; Zhu, Min; Feng, Songlin

    2015-11-27

    Phase-change memory based on Ti0.4Sb2Te3 material has one order of magnitude faster Set speed and as low as one-fifth of the Reset energy compared with the conventional Ge2Sb2Te5 based device. However, the phase-transition mechanism of the Ti0.4Sb2Te3 material remains inconclusive due to the lack of direct experimental evidence. Here we report a direct atom-by-atom chemical identification of titanium-centered octahedra in crystalline Ti0.4Sb2Te3 material with a state-of-the-art atomic mapping technology. Further, by using soft X-ray absorption spectroscopy and density function theory simulations, we identify in amorphous Ti0.4Sb2Te3 the titanium atoms preferably maintain the octahedral configuration. Our work may pave the way to more thorough understanding and tailoring of the nature of the Ti-Sb-Te material, for promoting the development of dynamic random access memory-like phase-change memory as an emerging storage-class memory to reform current memory hierarchy.

  20. Phase Change Material on Augmentation of Fresh Water Production Using Pyramid Solar Still

    Directory of Open Access Journals (Sweden)

    S. Ravishankara

    2013-10-01

    Full Text Available The augmentation of fresh water and increase in the solar still efficiency of a triangular pyramid is added with phase change material (PCM on the basin. Experimental studies were conducted and the effects of production of fresh water with and without PCM were investigated. Using paraffin as the PCM material, performance of the solar still were conducted on a hot, humid climate of Chennai (13°5′ 2" North, 80°16′ 12"East, India. The use of paraffin wax increases the latent heat storage so that the energy is stored in the PCM and in the absence of solar radiation it rejects its stored heat into the basin for further evaporation of water from the basin. Temperatures of water, Tw, Temperature of phase change material, TPCM, Temperature of cover, Tc were measured using thermocouple. Results show that there is an increase of maximum 20%, in productivity of fresh water with PCM. Keywords: fresh water production; PCM; thermal energy storage; phase change material

  1. Experimental investigation of performances of microcapsule phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Li, H. [Department of Material Science and Engineering, Nanjing University, Nanjing (China); Liu, X.; Wu, S. [Department of Physics, Nanjing University, Nanjing (China); Fang, G.

    2010-02-15

    Performances of microcapsule phase change material (MPCM) for thermal energy storage are investigated. The MPCM for thermal energy storage is prepared by a complex coacervation method with gelatin and acacia as wall materials and paraffin as core material in an emulsion system. A scanning electron microscope (SEM) was used to study the microstructure of the MPCM. In thermal analysis, a differential scanning calorimeter (DSC) was employed to determine the melting temperature, melting latent heat, solidification temperature, and solidification latent heat of the MPCM for thermal energy storage. The SEM micrograph indicates that the MPCM has been successfully synthesized and that the particle size of the MPCM is about 81 {mu}m. The DSC output results show that the melting temperature of the MPCM is 52.05 C, the melting latent heat is 141.03 kJ/kg, the solidification temperature is 59.68 C, and the solidification latent heat is 121.59 kJ/kg. The results prove that the MPCM for thermal energy storage has a larger phase change latent heat and suitable phase change temperature, so it can be considered as an efficient thermal energy storage material for heat utilizing systems. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  2. From rice husk to high performance shape stabilized phase change materials for thermal energy storage

    DEFF Research Database (Denmark)

    Mehrali, Mohammad; Latibari, Sara Tahan; Rosen, Marc A.

    2016-01-01

    exceptional phase change behavior, having a desirable latent heat storage capacity of 175 kJ kg(-1). When exposed to high solar radiation intensities, the composites can absorb and store the thermal energy. An FTIR analysis of the SSPCMs indicated that there was no chemical interaction between the palmitic...... and excellent reversibility. The prepared SSPCMs with enhanced heat transfer and phase change properties provide a beneficial option for building energy conservation and solar energy applications owing to the low cost of raw materials and the simple synthetic technique....

  3. Review of Development Survey of Phase Change Material Models in Building Applications

    Directory of Open Access Journals (Sweden)

    Hussein J. Akeiber

    2014-01-01

    Full Text Available The application of phase change materials (PCMs in green buildings has been increasing rapidly. PCM applications in green buildings include several development models. This paper briefly surveys the recent research and development activities of PCM technology in building applications. Firstly, a basic description of phase change and their principles is provided; the classification and applications of PCMs are also included. Secondly, PCM models in buildings are reviewed and discussed according to the wall, roof, floor, and cooling systems. Finally, conclusions are presented based on the collected data.

  4. On the Inhibition of Linear Absorption in Opaque Materials Using Phase-Locked Harmonic Generation

    CERN Document Server

    Centini, Marco; Fazio, Eugenio; Pettazzi, Federico; Sibilia, Concita; Haus, Joseph W; Foreman, John V; Akozbek, Neset; Bloemer, Mark J; Scalora, Michael

    2008-01-01

    We theoretically predict and experimentally demonstrate inhibition of linear absorption for phase and group velocity mismatched second and third harmonic generation in strongly absorbing materials, GaAs in particular, at frequencies above the absorption edge. A 100-fs pump pulse tuned to 1300nm generates 650nm and 435nm second and third harmonic pulses that propagate across a 450 micron-thick GaAs substrate without being absorbed. We attribute this to a phase-locking mechanism that causes the pump to trap the harmonics and to impress them with its dispersive properties.

  5. Structures, phase stabilities, and electrical potentials of Li-Si battery anode materials

    KAUST Repository

    Tipton, William W.

    2013-05-28

    The Li-Si materials system holds promise for use as an anode in Li-ion battery applications. For this system, we determine the charge capacity, voltage profiles, and energy storage density solely by ab initio methods without any experimental input. We determine the energetics of the stable and metastable Li-Si phases likely to form during the charging and discharging of a battery. Ab initio molecular dynamics simulations are used to model the structure of amorphous Li-Si as a function of composition, and a genetic algorithm coupled to density-functional theory searches the Li-Si binary phase diagram for small-cell, metastable crystal structures. Calculations of the phonon densities of states using density-functional perturbation theory for selected structures determine the importance of vibrational, including zero-point, contributions to the free energies. The energetics and local structural motifs of these metastable Li-Si phases closely resemble those of the amorphous phases, making these small unit cell crystal phases good approximants of the amorphous phase for use in further studies. The charge capacity is estimated, and the electrical potential profiles and the energy density of Li-Si anodes are predicted. We find, in good agreement with experimental measurements, that the formation of amorphous Li-Si only slightly increases the anode potential. Additionally, the genetic algorithm identifies a previously unreported member of the Li-Si binary phase diagram with composition Li5Si2 which is stable at 0 K with respect to previously known phases. We discuss its relationship to the partially occupied Li7Si3 phase. © 2013 American Physical Society.

  6. Effects of Microencapsulated Phase Change Material (MPCM) on Critical Heat Flux in Pool Boiling

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sung Dae; Kim, Seong Man; Kang, Sarah; Lee, Seung Won; Seo, Han; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2011-10-15

    Thermal power is limited by critical heat flux (CHF) in the nuclear power plant. And the in-vessel retention by external reactor vessel cooling (IVR-ERVC) is applied in some nuclear power plants; AP600, AP1000, Loviisa and APR1400. The heat removal capacity of IVR-ERVC is also restricted by CHF. So, it is essential to get CHF margin to improve an economics and a safety of the plant. There are some typical approaches to enhance CHF: vibrating the heater or fluid, coating with porous media on the heater surface, applying an electric field. The recent study related to the CHF is focus on using the nanofluid. In this paper, the new approach was investigated by using the microencapsulated phase change material (MPCM). MPCM is the particles whose diameter is from 0.1{mu}m to 1000{mu}m. The MPCM consists of the core material and the shell material. The core material can be solid, liquid, gas or even the mixture. The solid paraffin is the best candidate as the core material due to its stable chemical and thermal properties. And the shell material is generally synthesized polymer of about several micrometers in thickness. The most interesting feature of the MPCM is that the latent heat associated with the solid-liquid phase change is related to the heat transfer. When the MPCM is dispersed into the carrier fluid, a kind of suspension named as microencapsulated phase change slurry (MPCS) is formed. The study on the MPCS was conducted in field of both the heat transfer fluids and energy storage media. It is inspired by the fact that the latent heat can serve distribution to the additional CHF margin. The purpose of this work is to confirm whether or not the CHF is enhanced

  7. Melting of Nanoprticle-Enhanced Phase Change Material inside Shell and Tube Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Seiyed Mohammad Javad Hosseini

    2013-01-01

    Full Text Available This paper presents a numerical study of melting of Nanoprticle-Enhanced phase change material (NEPCM inside a shell and tube heat exchanger using RT50 and copper particles as base material and nanoparticle, respectively. In this study, the effects of nanoparticles dispersion (, 0.03, and 0.05 on melting time, liquid fraction, and penetration length are investigated. The results show that the melting time decreases to 14.6% and the penetration length increases to 146% with increasing volume fraction of nanoparticle up to .

  8. IFMIF (International Fusion Materials Irradiation Facility) key element technology phase interim report

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Hiroo; Ida, Mizuho; Sugimoto, Masayoshi; Takeuchi, Hiroshi; Yutani, Toshiaki (eds.) [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2002-03-01

    Activities of International Fusion Materials Irradiation Facility (IFMIF) have been performed under an IEA collaboration since 1995. IFMIF is an accelerator-based deuteron (D{sup +})-lithium (Li) neutron source designed to produce an intense neutron field (2 MW/m{sup 2}, 20 dpa/year for Fe) in a volume of 500 cm{sup 3} for testing candidate fusion materials. In 2000, a 3 year Key Element technology Phase (KEP) of IFMIF was started to reduce the key technology risk factors. This interim report summarizes the KEP activities until mid 2001 in the major project work-breakdown areas of accelerator, target, test facilities and design integration. (author)

  9. Mathematical Modeling and Simulations of Phase Change Materials in Basic Orthogonal Coordinate Systems

    Energy Technology Data Exchange (ETDEWEB)

    Rousse, Daniel; Dutil, Yvan; Ben Salah, Nizar; Lassue, Stephane

    2010-09-15

    Energy storage components improve the energy efficiency of systems by reducing the mismatch between supply and demand. Phase change materials are attractive since they provide a high energy storage density at constant temperatures. Nevertheless, the incorporation of such materials in a particular application often calls for numerical analyses due to the non-linear nature of the problem. The review of the mathematical models will include selected results to enable one to start his/her research with an exhaustive overview of the subject. This overview also stresses the need to match experimental investigations with recent numerical analyses.

  10. Preparation and characterization of phase change material for thermal energy storage in buildings

    Science.gov (United States)

    Lo, Tommy Y.

    2016-04-01

    The paper presents the developing of novel form-stable composite phase change material (PCM) by incorporation of paraffin into lightweight aggregate through vacuum impregnation. The macro-encapsulated Paraffin-lightweight aggregate is a chemical compatible, thermal stable and thermal reliable PCM material for thermal energy storage applications in buildings. The 28 days compressive strength of NWAC using PCM-LWA is 33 - 53 MPa, which has an opportunity for structural purpose. Scanning electronic microscopic images indicated the paraffin can be held inside the porous structure of the aggregate. Thermal performance test showed that the cement paste panel with composite PCM can reduce the indoor temperature.

  11. Wettability in the liquid Cu-Ag alloy – fireproof material – gas phase system

    Directory of Open Access Journals (Sweden)

    G. Siwiec

    2013-07-01

    Full Text Available In the present paper, results of wettability studies on the liquid metal – fireproof material – gas phase system using copper and Cu-Ag alloys as well as typical fireproof materials, i.e. aluminium oxide, magnesium oxide and graphite, are presented. Contact angle measurements were conducted at 1 373–1 573 K by means of a high-temperature microscope coupled with a camera and a computer equipped with a program for recording and analysing images. For the measurements, the sessile drop method was used.

  12. Investigating Processes of Materials Formation via Liquid Phase and Cryogenic TEM

    Energy Technology Data Exchange (ETDEWEB)

    De Yoreo, James J.; Sommerdijk, Nico

    2016-06-14

    The formation of materials in solutions is a widespread phenomenon in synthetic, biological and geochemical systems, occurring through dynamic processes of nucleation, self-assembly, crystal growth, and coarsening. The recent advent of liquid phase TEM and advances in cryogenic TEM are transforming our understanding of these phenomena by providing new insights into the underlying physical and chemical mechanisms. The techniques have been applied to metallic and semiconductor nanoparticles, geochemical and biological minerals, electrochemical systems, macromolecular complexes, and selfassembling systems, both organic and inorganic. New instrumentation and methodologies currently on the horizon promise new opportunities for advancing the science of materials synthesis.

  13. Hardening in Two-Phase Materials. II. Plastic Strain and Mean Stress Hardening Rate

    DEFF Research Database (Denmark)

    Lilholt, Hans

    1977-01-01

    The strain parameters which are relevant in a tensile experiment, are analysed and related to the geometry of deformation and to the mean stress of two-phase materials. The hardening rate of the mean stress with respect to plastic strain is found to be useful in comparison between experiments and...... and theories, and it allows theories to be probed over a range of strains. Previous experiments on the fibre-reinforced material of copper-tungsten are analysed in relation to the geometry of deformation....

  14. Frequency and phase swept holograms in spectral hole-burning materials.

    Science.gov (United States)

    Bernet, S; Altner, S B; Graf, F R; Maniloff, E S; Renn, A; Wild, U P

    1995-08-01

    A new hologram type in spectral hole-burning systems is presented. During exposure, the frequency of narrow-band laser light is swept over a spectral range that corresponds to a few homogeneous linewidths of the spectrally selective recording material. Simultaneously the phase of the hologram is adjusted as a function of frequency-the phase sweep function. Because of the phase-reconstructing properties of holography, this recording technique programs the sample as a spectral amplitude and phase filter. We call this hologram type frequency and phase swept (FPS) holograms. Their properties and applications are summarized, and a straightforward theory is presented that describes all the diffraction phenomena observed to date. Thin FPS holograms show strongly asymmetric diffraction into conjugated diffraction orders, which is an unusual behavior for thin transmission holograms. Investigations demonstrate the advantages of FPS holograms with respect to conventional cw recording techniques in freq ncymultiplexed data storage. By choosing appropriate phase sweep functions, various features of holographic data storage can be optimized. Examples for cross-talk reduction, highest diffraction efficiency, and maximal readout stability are demonstrated. The properties of these FPS hologram types are deduced from theoretical considerations and confirmed by experiments.

  15. Thermal Response Of An Aerated Concrete Wall With Micro-Encapsulated Phase Change Material

    Directory of Open Access Journals (Sweden)

    Halúzová Dušana

    2015-06-01

    Full Text Available For many years Phase Change Materials (PCM have attracted attention due to their ability to store large amounts of thermal energy. This property makes them a candidate for the use of passive heat storage. In many applications, they are used to avoid the overheating of the temperature of an indoor environment. This paper describes the behavior of phase change materials that are inbuilt in aerated concrete blocks. Two building samples of an aerated concrete wall were measured in laboratory equipment called “twin-boxes”. The first box consists of a traditional aerated concrete wall; the second one has additional PCM micro-encapsulated in the wall. The heat flux through the wall was measured and compared to simulation results modeled in the ESP-r program. This experimental measurement provides a foundation for a model that can be used to analyze further building constructions.

  16. Using multi-shell phase change materials layers for cooling a lithium-ion battery

    Directory of Open Access Journals (Sweden)

    Nasehi Ramin

    2016-01-01

    Full Text Available One of the cooling methods in engineering systems is usage of phase change materials. Phase change materials or PCMs, which have high latent heats, are usually used where high energy absorption in a constant temperature is required. This work presents a numerical analysis of PCMs effects on cooling Li-ion batteries and their decrease in temperature levels during intense discharge. In this study, three PCM shells with different thermo-physical specifications located around a battery pack is examined. The results of each possible arrangement are compared together and the best arrangement leading to the lowest battery temperature during discharge is identified. In addition, the recovery time for the system which is the time required for the PCMs to refreeze is investigated.

  17. Empirical Validation of a Thermal Model of a Complex Roof Including Phase Change Materials

    CERN Document Server

    Guichard, Stéphane; Bigot, Dimitri; Malet-Damour, Bruno; Libelle, Teddy; Boyer, Harry

    2015-01-01

    This paper deals with the empirical validation of a building thermal model using a phase change material (PCM) in a complex roof. A mathematical model dedicated to phase change materials based on the heat apparent capacity method was implemented in a multi-zone building simulation code, the aim being to increase understanding of the thermal behavior of the whole building with PCM technologies. To empirically validate the model, the methodology is based both on numerical and experimental studies. A parametric sensitivity analysis was performed and a set of parameters of the thermal model have been identified for optimization. The use of a generic optimization program called GenOpt coupled to the building simulation code enabled to determine the set of adequate parameters. We first present the empirical validation methodology and main results of previous work. We then give an overview of GenOpt and its coupling with the building simulation code. Finally, once the optimization results are obtained, comparisons o...

  18. Ultrafast broadband tuning of resonant optical nanostructures using phase change materials

    CERN Document Server

    Rudé, Miquel; Cetin, Arif E; Miller, Timothy A; Carrilero, Albert; Wall, Simon; de Abajo, F Javier García; Altug, Hatice; Pruneri, Valerio

    2015-01-01

    The phenomenon of extraordinary optical transmission {EOT} through arrays of nanoholes patterned in a metallic film has emerged as a promising tool for a wide range of applications, including photovoltaics, nonlinear optics, and sensing. Designs and methods enabling the dynamic tuning of the optical resonances of these structures are essential to build efficient optical devices, including modulators, switches, filters, and biosensors. However, the efficient combination of EOT and dynamic tuning remains a challenge, mainly because of the lack of materials that can induce modulation over a broad spectral range at high speeds. Here, we demonstrate tuneable resonance wavelength shifts as large as 385 nm - an order of magnitude higher than previously reported - through the combination of phase change materials {PCMs}, which exhibit dramatic variations in optical properties upon transitions between amorphous and crystalline phases, with properly designed subwavelength nanohole metallic arrays. We further find throu...

  19. High Temperature Phase Change Materials for Thermal Energy Storage Applications: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, J.; Glatzmaier, G. C.; Starace, A.; Turchi, C.; Ortega, J.

    2011-08-01

    To store thermal energy, sensible and latent heat storage materials are widely used. Latent heat thermal energy storage (TES) systems using phase change materials (PCM) are useful because of their ability to charge and discharge a large amount of heat from a small mass at constant temperature during a phase transformation. Molten salt PCM candidates for cascaded PCMs were evaluated for the temperatures near 320 degrees C, 350 degrees C, and 380 degrees C. These temperatures were selected to fill the 300 degrees C to 400 degrees C operating range typical for parabolic trough systems, that is, as one might employ in three-PCM cascaded thermal storage. Based on the results, the best candidate for temperatures near 320 degrees C was the molten salt KNO3-4.5wt%KCl. For the 350 degrees C and 380 degrees C temperatures, the evaluated molten salts are not good candidates because of the corrosiveness and the high vapor pressure of the chlorides.

  20. Heat Transfer Modeling of Phase Change Materials in Multiple Plates Heat Exchanger

    Directory of Open Access Journals (Sweden)

    M. Alipanah

    2013-12-01

    Full Text Available Nowadays, given the increasing importance of energy sources, the possibility of energy storage in the heat exchangers through the Phase Change Materials (PCM and releasing it when needed have been extremely essential. This study seeks to model the domestic water heat system in which the paraffin is as the phase change material and it stores the solar energy. The behavior of a PCM plate was studied by writing the governing equations and solving them as the one-dimensional, implicit method and through numerical calculation of the method equations. Given the confirmed accuracy of performed modeling by the results of similar studies for the complete melting and solidification of PCM, the application of this system seems appropriate for the solar domestic water heaters.

  1. A Family of Reference Hugoniots for Two-phase Porous Materials

    Science.gov (United States)

    2015-06-01

    and strength of the material at these pressures (for detailed analysis, see [5, 6]). Nevertheless, even at low pressures the trend and behaviour of... behaviour of the Hugoniot is observed if phase temperatures are not in equilibrium and this occurs at higher pressures because the corresponding...analyse the Hugoniot behaviour , the present work employs simplest EOSs thermodynamically consistent with shock-wave compression. For the gaseous

  2. Field Testing of Low-Cost Bio-Based Phase Change Material

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Kaushik [ORNL; Childs, Phillip W [ORNL; Atchley, Jerald Allen [ORNL

    2013-03-01

    A test wall built with phase change material (PCM)-enhanced loose-fill cavity insulation was monitored for a period of about a year in the warm-humid climate of Charleston, South Carolina. The test wall was divided into various sections, one of which contained only loose-fill insulation and served as a control for comparing and evaluating the wall sections with the PCM-enhanced insulation. This report summarizes the findings of the field test.

  3. Water solar distiller productivity enhancement using concentrating solar water heater and phase change material (PCM)

    OpenAIRE

    Miqdam T. Chaichan; Hussein A. Kazem

    2015-01-01

    This paper investigates usage of thermal energy storage extracted from concentrating solar heater for water distillation. Paraffin wax selected as a suitable phase change material, and it was used for storing thermal energy in two different insulated treasurers. The paraffin wax is receiving hot water from concentrating solar dish. This solar energy stored in PCM as latent heat energy. Solar energy stored in a day time with a large quantity, and some heat retrieved for later use. Water’s temp...

  4. THERMAL ENERGY STORAGE PROPERTIES OF FORMSTABLE PARAFFIN/RECYCLE BLOCK CONCRETE COMPOSITE PHASE CHANGE MATERIAL

    Directory of Open Access Journals (Sweden)

    PATTARAPORN SUTTAPHAKDEE

    2017-01-01

    Full Text Available In this research, the form-stable composite phase change material was developed by incorporating paraffin on recycle block concrete (RB through the vacuum impregnation method. The compatibility and thermal properties of RB impregnated with paraffin ranging from 0-35 wt% were characterized by Fourier transform infrared spectroscopy (FTIR and differential scanning calorimetry (DSC. Results revealed that paraffin was uniformly absorbed in RB with a good physical compatibility. The optimum adsorption ratio of paraffin in RB was 25 wt% which produced phase transition temperature of 52.85 OC and latent heat of 30.98 J/g. The obtained form-stable paraffin/RB composite PCM had proper latent heat and phase transition temperature and can be applied for thermal energy storage applications such as solar heating and cooling in buildings.

  5. Ultrafast terahertz-induced response of GeSbTe phase-change materials

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Michael J. [Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Zalden, Peter [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Chen, Frank [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Weems, Ben [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); Chatzakis, Ioannis [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Xiong, Feng; Jeyasingh, Rakesh; Pop, Eric; Philip Wong, H.-S. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Hoffmann, Matthias C. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Wuttig, Matthias [I. Physikalisches Institut, RWTH Aachen University, 52056 Aachen (Germany); JARA–Fundamentals of Information Technology, RWTH Aachen University, 52056 Aachen (Germany); Lindenberg, Aaron M., E-mail: aaronl@stanford.edu [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)

    2014-06-23

    The time-resolved ultrafast electric field-driven response of crystalline and amorphous GeSbTe films has been measured all-optically, pumping with single-cycle terahertz pulses as a means of biasing phase-change materials on a sub-picosecond time-scale. Utilizing the near-band-gap transmission as a probe of the electronic and structural response below the switching threshold, we observe a field-induced heating of the carrier system and resolve the picosecond-time-scale energy relaxation processes and their dependence on the sample annealing condition in the crystalline phase. In the amorphous phase, an instantaneous electroabsorption response is observed, quadratic in the terahertz field, followed by field-driven lattice heating, with Ohmic behavior up to 200 kV/cm.

  6. Ultrafast terahertz-induced response of GeSbTe phase-change materials

    Science.gov (United States)

    Shu, Michael J.; Zalden, Peter; Chen, Frank; Weems, Ben; Chatzakis, Ioannis; Xiong, Feng; Jeyasingh, Rakesh; Hoffmann, Matthias C.; Pop, Eric; Philip Wong, H.-S.; Wuttig, Matthias; Lindenberg, Aaron M.

    2014-06-01

    The time-resolved ultrafast electric field-driven response of crystalline and amorphous GeSbTe films has been measured all-optically, pumping with single-cycle terahertz pulses as a means of biasing phase-change materials on a sub-picosecond time-scale. Utilizing the near-band-gap transmission as a probe of the electronic and structural response below the switching threshold, we observe a field-induced heating of the carrier system and resolve the picosecond-time-scale energy relaxation processes and their dependence on the sample annealing condition in the crystalline phase. In the amorphous phase, an instantaneous electroabsorption response is observed, quadratic in the terahertz field, followed by field-driven lattice heating, with Ohmic behavior up to 200 kV/cm.

  7. Ultrafast optical manipulation of atomic motion in multilayer Ge-Sb-Te phase change materials

    Directory of Open Access Journals (Sweden)

    Fons P.

    2013-03-01

    Full Text Available Phase change random access memory devices have evolved dramatically with the recent development of superlattice structure of Ge-Sb-Te material (GST-SL in terms of its low power consumption. The phase change in GST-SL is mainly characterized by the displacement of Ge atoms. Here we examine a new phase change method, that is the manipulation of Ge-Te bonds using linearly-polarized femtosecond near-infrared optical pulses. As a result, we found that the p-polarized pump pulse is more effective in inducing the reversible and irreversible displacement of Ge atoms along [111] direction in the local structure. This structural change would be induced by the anisotropic carrier-phonon interaction along the [111] direction created by the p-polarized pulse.

  8. Meso-Scale Modeling of Spall in a Heterogeneous Two-Phase Material

    Energy Technology Data Exchange (ETDEWEB)

    Springer, Harry Keo [Univ. of California, Davis, CA (United States)

    2008-07-11

    The influence of the heterogeneous second-phase particle structure and applied loading conditions on the ductile spall response of a model two-phase material was investigated. Quantitative metallography, three-dimensional (3D) meso-scale simulations (MSS), and small-scale spall experiments provided the foundation for this study. Nodular ductile iron (NDI) was selected as the model two-phase material for this study because it contains a large and readily identifiable second- phase particle population. Second-phase particles serve as the primary void nucleation sites in NDI and are, therefore, central to its ductile spall response. A mathematical model was developed for the NDI second-phase volume fraction that accounted for the non-uniform particle size and spacing distributions within the framework of a length-scale dependent Gaussian probability distribution function (PDF). This model was based on novel multiscale sampling measurements. A methodology was also developed for the computer generation of representative particle structures based on their mathematical description, enabling 3D MSS. MSS were used to investigate the effects of second-phase particle volume fraction and particle size, loading conditions, and physical domain size of simulation on the ductile spall response of a model two-phase material. MSS results reinforce existing model predictions, where the spall strength metric (SSM) logarithmically decreases with increasing particle volume fraction. While SSM predictions are nearly independent of applied load conditions at lower loading rates, which is consistent with previous studies, loading dependencies are observed at higher loading rates. There is also a logarithmic decrease in SSM for increasing (initial) void size, as well. A model was developed to account for the effects of loading rate, particle size, matrix sound-speed, and, in the NDI-specific case, the probabilistic particle volume fraction model. Small-scale spall experiments were designed

  9. Numerical Model and Analysis of Peak Temperature Reduction in LiFePO4 Battery Packs Using Phase Change Materials

    DEFF Research Database (Denmark)

    Coman, Paul Tiberiu; Veje, Christian

    2013-01-01

    Numerical model and analysis of peak temperature reduction in LiFePO4 battery packs using phase change materials......Numerical model and analysis of peak temperature reduction in LiFePO4 battery packs using phase change materials...

  10. Computational Design and Analysis of Core Material of Single-Phase Capacitor Run Induction Motor

    Directory of Open Access Journals (Sweden)

    Gurmeet Singh

    2014-07-01

    Full Text Available A Single-phase induction motor (SPIM has very crucial role in industrial, domestic and commercial sectors. So, the efficient SPIM is a foremost requirement of today's market. For efficient motors, many research methodologies and propositions have been given by researchers in past. Various parameters like as stator/rotor slot variation, size and shape of stator/rotor slots, stator/rotor winding configuration, choice of core material etc. have momentous impact on machine design. Core material influences the motor performance to a degree. Magnetic flux linkage and leakage preliminary depends upon the magnetic properties of core material and air gap. The analysis of effects of core material on the magnetic flux distribution and the performance of induction motor is of immense importance to meet out the desirable performance. An increase in the air gap length will result in the air gap performance characteristics deterioration and decrease in air gap length will lead to serious mechanical balancing concern. So possibility of much variation in air gap beyond the limits on both sides is not feasible. For the optimized performance of the induction motor the core material plays a significant role. Using higher magnetic flux density, reduction on a magnetizing reactance and leakage of flux can be achieved. In this thesis work the analysis of single phase induction motor has been carried out with different core materials. The four models have been simulated using Ansys Maxwell 15.0. Higher flux density selection for same machine dimensions result into huge amount of reduction in iron core losses and thereby improve the efficiency. In this paper 2% higher efficiency has been achieved with Steel_1010 as compared to the machine using conventional D23 material. Out of four models result reflected by the machine using steel_1010 and steel_1008 are found to be better.

  11. The solidification of two-phase heterogeneous materials:Theory versus experiment

    Institute of Scientific and Technical Information of China (English)

    KIM; Tongbeum

    2009-01-01

    The solidification behavior of two-phase heterogeneous materials such as close-celled aluminum foams was analytically studied.The proposed analytical model can precisely predict the location of solidification front as well as the full solidification time for a two-phase heterogeneous material composed of aluminum melt and non-conducting air pores.Experiments using distilled water simulating the aluminum melt to be solidified(frozen)were subsequently conducted to validate the analytical model for two selected porosities(ε),ε=0 and 0.5.Full numerical simulations with the method of finite difference were also performed to examine the influence of pore shape on solidification.The remarkable agreement between theory and experiment suggests that the delay of solidification in the two-phase heterogeneous material is mainly caused by the reduction of bulk thermal conductivity due to the presence of pores,as this is the sole mechanism accounted for by the analytical model for solidification in a porous medium.

  12. A review on phase-change materials: Mathematical modeling and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Dutil, Yvan; Rousse, Daniel R. [Chaire de Recherche Industrielle T3E, Ecole de technologie superieure, Universite du Quebec, 801 Boul. Mgr, Bourget Levis, QC G6V 9V6 (Canada); Salah, Nizar Ben [Laboratoire MMP, Ecole Superieure des Sciences et Techniques de Tunis, 5 Avenue Taha Hussein, BP 56, Bab Manara, Tunis (Tunisia); Lassue, Stephane; Zalewski, Laurent [LAMTI, Faculte des sciences appliquees, Universite d' Artois, Technoparc Futura, 62400 Bethune (France)

    2011-01-15

    Energy storage components improve the energy efficiency of systems by reducing the mismatch between supply and demand. For this purpose, phase-change materials are particularly attractive since they provide a high-energy storage density at a constant temperature which corresponds to the phase transition temperature of the material. Nevertheless, the incorporation of phase-change materials (PCMs) in a particular application calls for an analysis that will enable the researcher to optimize performances of systems. Due to the non-linear nature of the problem, numerical analysis is generally required to obtain appropriate solutions for the thermal behavior of systems. Therefore, a large amount of research has been carried out on PCMs behavior predictions. The review will present models based on the first law and on the second law of thermodynamics. It shows selected results for several configurations, from numerous authors so as to enable one to start his/her research with an exhaustive overview of the subject. This overview stresses the need to match experimental investigations with recent numerical analyses since in recent years, models mostly rely on other models in their validation stages. (author)

  13. High-Temperature Phase Change Materials (PCM) Candidates for Thermal Energy Storage (TES) Applications

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, J. C.

    2011-09-01

    It is clearly understood that lower overall costs are a key factor to make renewable energy technologies competitive with traditional energy sources. Energy storage technology is one path to increase the value and reduce the cost of all renewable energy supplies. Concentrating solar power (CSP) technologies have the ability to dispatch electrical output to match peak demand periods by employing thermal energy storage (TES). Energy storage technologies require efficient materials with high energy density. Latent heat TES systems using phase change material (PCM) are useful because of their ability to charge and discharge a large amount of heat from a small mass at constant temperature during a phase transformation like melting-solidification. PCM technology relies on the energy absorption/liberation of the latent heat during a physical transformation. The main objective of this report is to provide an assessment of molten salts and metallic alloys proposed as candidate PCMs for TES applications, particularly in solar parabolic trough electrical power plants at a temperature range from 300..deg..C to 500..deg.. C. The physical properties most relevant for PCMs service were reviewed from the candidate selection list. Some of the PCM candidates were characterized for: chemical stability with some container materials; phase change transformation temperatures; and latent heats.

  14. Numerical analysis of phase change materials for thermal control of power battery of high power dissipations

    Science.gov (United States)

    Xia, X.; Zhang, H. Y.; Deng, Y. C.

    2016-08-01

    Solid-fluid phase change materials have been of increasing interest in various applications due to their high latent heat with minimum volume change. In this work, numerical analysis of phase change materials is carried out for the purpose of thermal control of the cylindrical power battery cells for applications in electric vehicles. Uniform heat density is applied at the battery cell, which is surrounded by phase change material (PCM) of paraffin wax type and contained in a metal housing. A two-dimensional geometry model is considered due to the model symmetry. The effects of power densities, heat transfer coefficients and onset melting temperatures are examined for the battery temperature evolution. Temperature plateaus can be observed from the present numerical analysis for the pure PCM cases, with the temperature level depending on the power densities, heat transfer coefficients, and melting temperatures. In addition, the copper foam of high thermal conductivity is inserted into the copper foam to enhance the heat transfer. In the modeling, the local thermal non-equilibrium between the metal foam and the PCM is taken into account and the temperatures for the metal foam and PCM are obtained respectively.

  15. Application of phase diagram calculations to development of new ultra-high temperature structural materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In-situ refractory metal intermetallic composites(RMICs) based either on (Nb, Si) or (Mo, Si, B) are candidate materials for ultra-high temperature applications (> 1 400 ℃). To provide a balance of mechanical and environmental properties, Nb-Si composites are typically alloyed with Ti and Cr, and Mo-Si-B composites are alloyed with Ti. Phase diagrams of Nb-Cr-Ti-Si and Mo-Si-B-Ti, as prerequisite knowledge for advanced materials design and processing development, are critically needed. The phase diagrams in the metal-rich regions of multicomponent Nb-Cr-Ti-Si and Mo-Si-B-Ti were rapidly established using the Calphad(Calculation of phase diagram) approach coupled with key experiments. The calculated isotherms, isopleths, and solidification paths were validated by experimental work. The important heterogeneous multiphase equilibria in both quaternary systems identified will offer engineers the opportunity to develop materials with a balance of properties for high-temperature applications.

  16. Using phase information to enhance speckle noise reduction in the ultrasonic NDE of coarse grain materials

    Science.gov (United States)

    Lardner, Timothy; Li, Minghui; Gachagan, Anthony

    2014-02-01

    Materials with a coarse grain structure are becoming increasingly prevalent in industry due to their resilience to stress and corrosion. These materials are difficult to inspect with ultrasound because reflections from the grains lead to high noise levels which hinder the echoes of interest. Spatially Averaged Sub-Aperture Correlation Imaging (SASACI) is an advanced array beamforming technique that uses the cross-correlation between images from array sub-apertures to generate an image weighting matrix, in order to reduce noise levels. This paper presents a method inspired by SASACI to further improve imaging using phase information to refine focusing and reduce noise. A-scans from adjacent array elements are cross-correlated using both signal amplitude and phase to refine delay laws and minimize phase aberration. The phase-based and amplitude-based corrected images are used as inputs to a two-dimensional cross-correlation algorithm that will output a weighting matrix that can be applied to any conventional image. This approach was validated experimentally using a 5MHz array a coarse grained Inconel 625 step wedge, and compared to the Total Focusing Method (TFM). Initial results have seen SNR improvements of over 20dB compared to TFM, and a resolution that is much higher.

  17. Modeling the viscoplastic micromechanical response of two-phase materials using fast Fourier transforms

    Energy Technology Data Exchange (ETDEWEB)

    Lebensohn, Ricardo A [Los Alamos National Laboratory; Lee, Sukbin [CMU; Rollett, Anthony D [CMU

    2009-01-01

    A viscoplastic approach using the Fast Fourier Transform (FFT) method for obtaining local mechanical response is utilized to study microstructure-property relationships in composite materials. Specifically, three-dimensional, two-phase digital materials containing isotropically coarsened particles surrounded by a matrix phase, generated through a Kinetic Monte Carlo Potts model for Ostwald ripening, are used as instantiations in order to calculate the stress and strain rate fields under uniaxial tension. The effects of the morphology of the matrix phase, the volume fraction and the contiguity of particles, and the polycrystallinity of matrix phase, on the stress and strain rate fields under uniaxial tension are examined. It is found that the first moments of the stress and strain rate fields have a different dependence on the particle volume fraction and the particle contiguity from their second moments. The average stresses and average strain rates of both phases and of the overall composite have rather simple relationships with the particle volume fraction whereas their standard deviations vary strongly, especially when the particle volume fraction is high, and the contiguity of particles has a noticeable effect on the mechanical response. It is also found that the shape of stress distribution in the BCC hard particle phase evolves as the volume fraction of particles in the composite varies, such that it agrees with the stress field in the BCC polycrystal as the volume of particles approaches unity. Finally, it is observed that the stress and strain rate fields in the microstructures with a polycrystalline matrix are less sensitive to changes in volume fraction and contiguity of particles.

  18. An investigation on the effects of phase change material on material components used for high temperature thermal energy storage system

    Science.gov (United States)

    Kim, Taeil; Singh, Dileep; Zhao, Weihuan; Yua, Wenhua; France, David M.

    2016-05-01

    The latent heat thermal energy storage (LHTES) systems for concentrated solar power (CSP) plants with advanced power cycle require high temperature phase change materials (PCMs), Graphite foams with high thermal conductivity to enhance the poor thermal conductivity of PCMs. Brazing of the graphite foams to the structural metals of the LHTES system could be a method to assemble the system and a method to protect the structural metals from the molten salts. In the present study, the LHTES prototype capsules using MgCl2-graphite foam composites were assembled by brazing and welding, and tested to investigate the corrosion attack of the PCM salt on the BNi-4 braze. The microstructural analysis showed that the BNi-4 braze alloy can be used not only for the joining of structure alloy to graphite foams but also for the protecting of structure alloy from the corrosion by PCM.

  19. Novel solid – solid phase change material based on polyethylene glycol and cellulose used for temperature stabilisation

    Directory of Open Access Journals (Sweden)

    Wojda Marta

    2014-01-01

    Full Text Available Thermal management is one of crucial issues in the development of modern electronic devices. In the recent years interest in phase change materials (PCMs as alternative cooling possibility has increased significantly. Preliminary results concerning the research into possibility of the use of solid-solid phase change materials (S-S PCMs for stabilisation temperature of electronic devices has been presented in the paper. Novel solid-solid phase change material based on polyethylene glycol and cellulose has been synthesized. Attempt to improve its thermal conductivity has been taken. Material has been synthesized for the purpose of stabilisation of temperature of electronic devices.

  20. Materials information for science and technology (MIST): Project overview: Phases I and II and general considerations

    Energy Technology Data Exchange (ETDEWEB)

    Grattidge, W.; Westbrook, J.; McCarthy, J.; Northrup, C. Jr.; Rumble, J. Jr.

    1986-01-01

    This report documents the initial phases of the Materials Information for Science and Technology (MIST) project jointly supported by the Department of Energy and the National Bureau of Standards. The purpose of MIST is to demonstrate the power and utility of computer access to materials property data. The initial goals include: to exercise the concept of a computer network of materials databases and to build a demonstration of such a system suitable for use as the core of operational systems in the future. Phases I and II are described in detail herein. In addition, a discussion is given of the expected usage of the system. The primary MIST prototype project is running on an IBM 3084 under STS at the Stanford University's Information Technology Services (ITS). Users can access the Stanford system via ARPANET, TELENET, and TYMNET, as well as via commercial telephone lines. For fastest response time and use of the full screen PRISM interface, direct connection using a 2400 baud modem with the MNP error-correcting protocol over standard telephone lines gives the best results - though slower speed connections and a line-oriented interface are also available. This report gives detailed plans regarding the properties to be enterend and the materials to be entered into the system.

  1. A numerical study of latent thermal energy storage in a phase change material/carbon panel

    Science.gov (United States)

    Mekaddem, Najoua; Ali, Samia Ben; Mazioud, Atef; Hannachi, Ahmed

    2016-07-01

    To reduce the energetic dependence of building, it has become necessary to explore and develop new materials promoting energy conservation. Because of their high storage capacity, phase change materials (PCMs) are efficient to store thermal energy. In this paper, a 3D model was studied for simulation of energy storing cycles to predict the performances of PCM loaded panels. Carbon was used as supporting material for the PCM. The simulation was based on the enthalpy method using Ansys Fluent software. The panel was exposed to a daily heat flow including the effects of convection and radiation. The results show that the temperature decreased of approximately 2.5°C with a time shift about 2 hours. The steady state was reached after four cycles. Thus, after four cycles the PCM showed its effects on the temperature conditioning.

  2. A Route for Phase Control in Metal Nanoparticles: A Potential Strategy to Create Advanced Materials.

    Science.gov (United States)

    Kusada, Kohei; Kitagawa, Hiroshi

    2016-02-10

    There is untapped potential for materials whose crystal structures are unobtainable in the bulk state. Several examples of such structures have been found in nanomaterials, and these materials exhibit unique properties that arise from their unique electronic states and surface structures. Here, recent developments in the syntheses of these nanomaterials and their unique properties, such as hydrogen-storage ability and catalytic activity, are summarized. Firstly, the syntheses and properties of novel solid-solution alloy nanoparticles in immiscible alloy systems such as Ag-Rh and Pd-Ru are introduced. Following this, the crystal structure control of nanoscale Ru is discussed. These unique alloy materials show enhanced properties and highlight the potential of phase control to be a new strategy for nanomaterial development.

  3. New methodology developed for the differential scanning calorimetry analysis of polymeric matrixes incorporating phase change materials

    Science.gov (United States)

    Barreneche, Camila; Solé, Aran; Miró, Laia; Martorell, Ingrid; Inés Fernández, A.; Cabeza, Luisa F.

    2012-08-01

    Nowadays, thermal comfort needs in buildings have led to an increase in energy consumption of the residential and service sectors. For this reason, thermal energy storage is shown as an alternative to achieve reduction of this high consumption. Phase change materials (PCM) have been studied to store energy due to their high storage capacity. A polymeric material capable of macroencapsulating PCM was developed by the authors of this paper. However, difficulties were found while measuring the thermal properties of these materials by differential scanning calorimetry (DSC). The polymeric matrix interferes in the detection of PCM properties by DSC. To remove this interfering effect, a new methodology which replaces the conventional empty crucible used as a reference in the DSC analysis by crucibles composed of the polymeric matrix was developed. Thus, a clear signal from the PCM is obtained by subtracting the new full crucible signal from the sample signal.

  4. Fast Atomic-Scale Chemical Imaging of Crystalline Materials and Dynamic Phase Transformations.

    Science.gov (United States)

    Lu, Ping; Yuan, Ren Liang; Ihlefeld, Jon F; Spoerke, Erik David; Pan, Wei; Zuo, Jian Min

    2016-04-13

    Atomic-scale phenomena fundamentally influence materials form and function that makes the ability to locally probe and study these processes critical to advancing our understanding and development of materials. Atomic-scale chemical imaging by scanning transmission electron microscopy (STEM) using energy-dispersive X-ray spectroscopy (EDS) is a powerful approach to investigate solid crystal structures. Inefficient X-ray emission and collection, however, require long acquisition times (typically hundreds of seconds), making the technique incompatible with electron-beam sensitive materials and study of dynamic material phenomena. Here we describe an atomic-scale STEM-EDS chemical imaging technique that decreases the acquisition time to as little as one second, a reduction of more than 100 times. We demonstrate this new approach using LaAlO3 single crystal and study dynamic phase transformation in beam-sensitive Li[Li0.2Ni0.2Mn0.6]O2 (LNMO) lithium ion battery cathode material. By capturing a series of time-lapsed chemical maps, we show for the first time clear atomic-scale evidence of preferred Ni-mobility in LNMO transformation, revealing new kinetic mechanisms. These examples highlight the potential of this approach toward temporal, atomic-scale mapping of crystal structure and chemistry for investigating dynamic material phenomena.

  5. Time-resolved lattice measurements of shock-induced phase transitions in polycrystalline materials

    Science.gov (United States)

    Milathianaki, Despina

    The response of materials under extreme temperature and pressure conditions is a topic of great significance because of its relevance in astrophysics, geophysics, and inertial confinement fusion. In recent years, environments exceeding several hundred gigapascals in pressure have been produced in the laboratory via laser-based dynamic loading techniques. Shock-loading is of particular interest as the shock provides a fiducial for measuring time-dependent processes in the lattice such as phase transitions. Time-resolved x-ray diffraction is the only technique that offers an insight into these shock-induced processes at the relevant spatial (atomic) and temporal scales. In this study, nanosecond resolution x-ray diffraction techniques were developed and implemented towards the study of shock-induced phase transitions in polycrystalline materials. More specifically, the capability of a focusing x-ray diffraction geometry in high-resolution in situ lattice measurements was demonstrated by probing shock-compressed Cu and amorphous metallic glass samples. In addition, simultaneous lattice and free surface velocity measurements of shock-compressed Mg in the ambient hexagonal close packed (hcp) and shock-induced body centered cubic (bcc) phases between 12 and 45 GPa were performed. These measurements revealed x-ray diffraction signals consistent with a compressed bcc lattice above a shock pressure of 26.2+/-1.3 GPa, thus capturing for the first time direct lattice evidence of a shock-induced hcp to bcc phase transition in Mg. Our measurement of the hcp-bcc phase boundary in Mg was found to be consistent with the calculated boundary from generalized pseudopotential theory in the pressure and temperature region intersected by the principal shock Hugoniot. Furthermore, the subnanosecond timescale of the phase transition implied by the shock-loading conditions was in agreement with the kinetics of a martensitic transformation. In conclusion, we report on the progress and

  6. Heat Transfer Characteristics of Liquid-Gas Taylor Flows incorporating Microencapsulated Phase Change Materials

    Science.gov (United States)

    Howard, J. A.; Walsh, P. A.

    2014-07-01

    This paper presents an investigation on the heat transfer characteristics associated with liquid-gas Taylor flows in mini channels incorporating microencapsulated phase change materials (MPCM). Taylor flows have been shown to result in heat transfer enhancements due to the fluid recirculation experienced within liquid slugs which is attributable to the alternating liquid slug and gas bubble flow structure. Microencapsulated phase change materials (MPCM) also offer significant potential with increased thermal capacity due to the latent heat required to cause phase change. The primary aim of this work was to examine the overall heat transfer potential associated with combining these two novel liquid cooling technologies. By investigating the local heat transfer characteristics, the augmentation/degradation over single phase liquid cooling was quantified while examining the effects of dimensionless variables, including Reynolds number, liquid slug length and gas void fraction. An experimental test facility was developed which had a heated test section and allowed MPCM-air Taylor flows to be subjected to a constant heat flux boundary condition. Infrared thermography was used to record high resolution experimental wall temperature measurements and determine local heat transfer coefficients from the thermal entrance point. 30.2% mass particle concentration of the MPCM suspension fluid was examined as it provided the maximum latent heat for absorption. Results demonstrate a significant reduction in experimental wall temperatures associated with MPCM-air Taylor flows when compared with the Graetz solution for conventional single phase coolants. Total enhancement in the thermally developed region is observed to be a combination of the individual contributions due to recirculation within the liquid slugs and also absorption of latent heat. Overall, the study highlights the potential heat transfer enhancements that are attainable within heat exchange devices employing MPCM

  7. Influence of the pore size of reversed phase materials on peptide purification processes.

    Science.gov (United States)

    Gétaz, David; Dogan, Nihan; Forrer, Nicola; Morbidelli, Massimo

    2011-05-20

    The influence of the pore size of a chromatographic reversed phase material on the adsorption equilibria and diffusion of two industrially relevant peptides (i.e. a small synthetic peptide and insulin) has been studied using seven different reversed phase HPLC materials having pore sizes ranging from 90 Å to 300 Å. The stationary phase pore size distribution was obtained by inverse size exclusion measurement (iSEC). The effect of the pore size on the mass transfer properties of the materials was evaluated from Van Deemter experiments. It has been shown that the lumped mass transfer coefficient increases linearly with the average pore size. The Henry coefficient and the impurity selectivity were determined in diluted conditions. The saturation capacity of the main peptides was determined in overloaded conditions using the inverse method (i.e. peak fitting). It was shown that the adsorption equilibria of the peptides on the seven materials is well described by a surface-specific adsorption isotherm. Based on this a lumped kinetic model has been developed to model the elution profile of the two peptides in overloaded conditions and to simulate the purification of the peptide from its crude mixture. It has been found that the separation of insulin from its main impurity (i.e. desamido-insulin) was not affected by the pore size. On the other hand, in the case of the synthetic peptide, it was found that the adsorption of the most significant impurity decreases with the pore size. This decrease is probably due to an increase in silanol activity with decreasing pore size.

  8. X-ray phase contrast imaging of the breast: Analysis of tissue simulating materials

    Energy Technology Data Exchange (ETDEWEB)

    Vedantham, Srinivasan; Karellas, Andrew [Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655 (United States)

    2013-04-15

    Purpose: Phase contrast imaging, particularly of the breast, is being actively investigated. The purpose of this work is to investigate the x-ray phase contrast properties of breast tissues and commonly used breast tissue substitutes or phantom materials with an aim of determining the phantom materials best representative of breast tissues. Methods: Elemental compositions of breast tissues including adipose, fibroglandular, and skin were used to determine the refractive index, n= 1 -{delta}+i {beta}. The real part of the refractive index, specifically the refractive index decrement ({delta}), over the energy range of 5-50 keV were determined using XOP software (version 2.3, European Synchrotron Radiation Facility, France). Calcium oxalate and calcium hydroxyapatite were considered to represent the material compositions of microcalcifications in vivo. Nineteen tissue substitutes were considered as possible candidates to represent adipose tissue, fibroglandular tissue and skin, and four phantom materials were considered as possible candidates to represent microcalcifications. For each material, either the molecular formula, if available, or the elemental composition based on weight fraction, was used to determine {delta}. At each x-ray photon energy, the absolute percent difference in {delta} between the breast tissue and the substitute material was determined, from which three candidates were selected. From these candidate tissue substitutes, the material that minimized the absolute percent difference in linear attenuation coefficient {mu}, and hence {beta}, was considered to be best representative of that breast tissue. Results: Over the energy range of 5-50 keV, while the {delta} of CB3 and fibroglandular tissue-equivalent material were within 1% of that of fibroglandular tissue, the {mu} of fibroglandular tissue-equivalent material better approximated the fibroglandular tissue. While the {delta} of BR10 and adipose tissue-equivalent material were within 1% of

  9. Melting of a phase change material in a horizontal annulus with discrete heat sources

    Directory of Open Access Journals (Sweden)

    Mirzaei Hooshyar

    2015-01-01

    Full Text Available Phase change materials have found many industrial applications such as cooling of electronic devices and thermal energy storage. This paper investigates numerically the melting process of a phase change material in a two-dimensional horizontal annulus with different arrangements of two discrete heat sources. The sources are positioned on the inner cylinder of the annulus and assumed as constant-temperature boundary conditions. The remaining portion of the inner cylinder wall as well as the outer cylinder wall is considered to be insulated. The emphasis is mainly on the effects of the arrangement of the heat source pair on the fluid flow and heat transfer features. The governing equations are solved on a non-uniform O type mesh using a pressure-based finite volume method with an enthalpy porosity technique to trace the solid and liquid interface. The results are obtained at Ra=104 and presented in terms of streamlines, isotherms, melting phase front, liquid fraction and dimensionless heat flux. It is observed that, depending on the arrangement of heat sources, the liquid fraction increases both linearly and non-linearly with time but will slow down at the end of the melting process. It can also be concluded that proper arrangement of discrete heat sources has the great potential in improving the energy storage system. For instance, the arrangement C3 where the heat sources are located on the bottom part of the inner cylinder wall can expedite the melting process as compared to the other arrangements.

  10. Thermal analysis on organic phase change materials for heat storage applications

    Science.gov (United States)

    Lager, Daniel

    2016-07-01

    In this paper, methodologies based on thermal analysis to evaluate specific heat capacity, phase transition enthalpies, thermal cycling stability and thermal conductivity of organic phase change materials (PCMs) are discussed. Calibration routines for a disc type heat flow differential scanning calorimetry (hf-DSC) are compared and the applied heating rates are adapted due to the low thermal conductivity of the organic PCMs. An assessment of thermal conductivity measurements based on "Laser Flash Analysis" (LFA) and the "Transient Hot Bridge" method (THB) in solid and liquid state has been performed. It could be shown that a disc type hf-DSC is a useful method for measuring specific heat capacity, melting enthalpies and cycling stability of organic PCM if temperature and sensitivity calibration are adapted to the material and quantity to be measured. The LFA method shows repeatable and reproducible thermal diffusivity results in solid state and a high effort for sample preparation in comparison to THB in liquid state. Thermal conductivity results of the two applied methods show large deviations in liquid phase and have to be validated by further experiments.

  11. CONTACT MATERIALS FOR GaSb AND InSb: A PHASE DIAGRAM APPROACH

    Institute of Scientific and Technical Information of China (English)

    K.W. Richter; H. Ipser

    2002-01-01

    The development of well defined and thermally stable ohmic contacts for Ⅲ- Ⅴ semi-conductors like InSb and GaSb is still a challenging problem in semiconductor devicetechnology. As device processing usually includes the exposure to elevated tempera-tures, interface reactions often occur during metallization and further heat treatment.It is thus important to understand the respective phase equilibria of the involved el-ements. From the thermodynamic point of view, binary and ternary compounds inequilibrium with the respective compound semiconductor would be the best choice forcontact materials as these contacts will be stable even after long exposure to elevatedtemperatures. These possible candidates for contact materials may be directly obtainedfrom the phase diagrams.During the last years we investigated several phase diagrams of transition metals withGaSb and InSb. Experimental results in the systems Ga-Ni-Sb, Ga-Pd-Sb, Ga-Pt-Sb,In-Ni-Sb and In-Pd-Sb are summarized and are discussed in the context of contactchemistry.

  12. Enhanced reversibility and unusual microstructure of a phase-transforming material.

    Science.gov (United States)

    Song, Yintao; Chen, Xian; Dabade, Vivekanand; Shield, Thomas W; James, Richard D

    2013-10-01

    Materials undergoing reversible solid-to-solid martensitic phase transformations are desirable for applications in medical sensors and actuators, eco-friendly refrigerators and energy conversion devices. The ability to pass back and forth through the phase transformation many times without degradation of properties (termed 'reversibility') is critical for these applications. Materials tuned to satisfy a certain geometric compatibility condition have been shown to exhibit high reversibility, measured by low hysteresis and small migration of transformation temperature under cycling. Recently, stronger compatibility conditions called the 'cofactor conditions' have been proposed theoretically to achieve even better reversibility. Here we report the enhanced reversibility and unusual microstructure of the first martensitic material, Zn45Au30Cu25, that closely satisfies the cofactor conditions. We observe four striking properties of this material. (1) Despite a transformation strain of 8%, the transformation temperature shifts less than 0.5 °C after more than 16,000 thermal cycles. For comparison, the transformation temperature of the ubiquitous NiTi alloy shifts up to 20 °C in the first 20 cycles. (2) The hysteresis remains approximately 2 °C during this cycling. For comparison, the hysteresis of the NiTi alloy is up to 70 °C (refs 9, 12). (3) The alloy exhibits an unusual riverine microstructure of martensite not seen in other martensites. (4) Unlike that of typical polycrystal martensites, its microstructure changes drastically in consecutive transformation cycles, whereas macroscopic properties such as transformation temperature and latent heat are nearly reproducible. These results promise a concrete strategy for seeking ultra-reliable martensitic materials.

  13. Phase Formation and Transformations in Transmutation Fuel Materials for the LIFE Engine Part I - Path Forward

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, P E; Kaufman, L; Fluss, M J

    2008-11-10

    The current specifications of the LLNL fusion-fission hybrid proposal, namely LIFE, impose severe constraints on materials, and in particular on the nuclear fissile or fertile nuclear fuel and its immediate environment. This constitutes the focus of the present report with special emphasis on phase formation and phase transformations of the transmutation fuel and their consequences on particle and pebble thermal, chemical and mechanical integrities. We first review the work that has been done in recent years to improve materials properties under the Gen-IV project, and with in particular applications to HTGR and MSR, and also under GNEP and AFCI in the USA. Our goal is to assess the nuclear fuel options that currently exist together with their issues. Among the options, it is worth mentioning TRISO, IMF, and molten salts. The later option will not be discussed in details since an entire report is dedicated to it. Then, in a second part, with the specific LIFE specifications in mind, the various fuel options with their most critical issues are revisited with a path forward for each of them in terms of research, both experimental and theoretical. Since LIFE is applicable to very high burn-up of various fuels, distinctions will be made depending on the mission, i.e., energy production or incineration. Finally a few conclusions are drawn in terms of the specific needs for integrated materials modeling and the in depth knowledge on time-evolution thermochemistry that controls and drastically affects the performance of the nuclear materials and their immediate environment. Although LIFE demands materials that very likely have not yet been fully optimized, the challenge are not insurmountable and a well concerted experimental-modeling effort should lead to dramatic advances that should well serve other fission programs such as Gen-IV, GNEP, AFCI as well as the international fusion program, ITER.

  14. Multi-phase flow effect on SRM nozzle flow field and thermal protection materials

    Institute of Scientific and Technical Information of China (English)

    SHAFQAT Wahab; XIE Kan; LIU Yu

    2009-01-01

    Multi-phase flow effect generated from the combustion of aluminum based com-posite propellant was performed on the thermal protection material of solid rocket motor (SRM) nozzle. Injection of alumina (Al2O3) particles from 5% to 10% was tried on SRM nozzle flow field to see the influence of multiphase flow on heat transfer computations. A coupled, time resolved CFD (computational fluid dynamics) approach was adopted to solve the conjugate problem of multi-phase fluid flow and heat transfer in the solid rocket motor nozzle. The governing equations are discretized by using the finite volume method. Spalart-Allmaras (S-A) turbulence model was employed. The computation was executed on the dif-ferent models selected for the analysis to validate the temperature variation in the throat in-serts and baking material of SRM nozzle. Comparison for temperatures variations were also carried out at different expansion ratios of nozzle. This paper also characterized the advanced SRM nozzle composites material for their high thermo stability and their high thermo me-chanical capabilities to make it more reliable simpler and lighter.

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

    Science.gov (United States)

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

    2016-12-01

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

  16. Crystal growth of an organic non-linear optical material from the vapour phase

    CERN Document Server

    Hou, W

    1999-01-01

    Due to the potential applications of organic non-linear optical materials in the areas of optical processing and communication, the investigation of the crystal growth of new organic NLO materials has been an active field for the last 20 years. For such uses it is necessary to produce single crystals of high quality and perfection, free of strain and defects. When crystals are grown from the solution and the melt, solvent and the decomposition component in the melt can introduce impurities and imperfection to the as-grown crystals. For crystals grown from vapour phase, in the absence of the solvent, this cannot occur and the method promises to yield single crystals of higher quality. Despite this attraction, little attention has been paid to the vapour phase growth of organic NLO crystals. It was with this in mind that the following investigation was carried out. Using Methyl p-hydroxybenzoate (p-MHB), a potential organic NLO material, a comparison investigation was made of its crystal growth from both the va...

  17. Experimental and Numerical Investigations of Thermal Ignition of a Phase Changing Energetic Material

    Directory of Open Access Journals (Sweden)

    Priyanka Shukla

    2016-04-01

    Full Text Available Fortuitous exposure to high temperatures initiates reaction in energetic materials and possibilities of such event are of great concern in terms of the safe and controlled usage of explosive devices. Experimental and numerical investigations on time to explosion and location of ignition of a phase changing polymer bonded explosive material (80 per cent RDX and 20 per cent binder, contained in a metallic confinement subjected to controlled temperature build-up on its surface, are presented. An experimental setup was developed in which the polymer bonded explosive material filled in a cylindrical confinement was provided with a precise control of surface heating rate. Temperature at various radial locations was monitored till ignition. A computational model for solving two dimensional unsteady heat transfer with phase change and heat generation due to multi-step chemical reaction was developed. This model was implemented using a custom field function in the framework of a finite volume method based standard commercial solver. Numerical study could simulate the transient heat conduction, the melting pattern of the explosive within the charge and also the thermal runaway. Computed values of temperature evolution at various radial locations and the time to ignition were closely agreeing with those measured in experiment. Results are helpful both in predicting the possibility of thermal ignition during accidents as well as for the design of safety systems.

  18. Geopolymer encapsulation of a chloride salt phase change material for high temperature thermal energy storage

    Science.gov (United States)

    Jacob, Rhys; Trout, Neil; Raud, Ralf; Clarke, Stephen; Steinberg, Theodore A.; Saman, Wasim; Bruno, Frank

    2016-05-01

    In an effort to reduce the cost and increase the material compatibility of encapsulated phase change materials (EPCMs) a new encapsulated system has been proposed. In the current study a molten salt eutectic of barium chloride (53% wt.), potassium chloride (28% wt.) and sodium chloride (19% wt.) has been identified as a promising candidate for low cost EPCM storage systems. The latent heat, melting point and thermal stability of the phase change material (PCM) was determined by DSC and was found to be in good agreement with results published in the literature. To cope with the corrosive nature of the PCM, it was decided that a fly-ash based geopolymer met the thermal and economic constraints for encapsulation. The thermal stability of the geopolymer shell was also tested with several formulations proving to form a stable shell for the chosen PCM at 200°C and/or 600°C. Lastly several capsules of the geopolymer shell with a chloride PCM were fabricated using a variety of methods with several samples remaining stable after exposure to 600°C testing.

  19. Effect of DMMP on the pyrolysis products of polyurethane foam materials in the gaseous phase

    Science.gov (United States)

    Liu, W.; Li, F.; Ge, X. G.; Zhang, Z. J.; He, J.; Gao, N.

    2016-07-01

    Dimethyl methylphosphonate (DMMP) has been used as a flame retardant containing phosphorus to decrease the flammability of the polyurethane foam material (PUF). Flame retardancy and thermal degradation of PUF samples have been investigated by the LOI tests and thermal analysis. The results show that LOI values of all PUF/DMMP samples are higher than that of the neat PUF sample and the LOI value of the samples increases with both DMMP concentration and the %P value. Thermal analysis indicates that flame retardant PUF shows a dominant condensed flame retardant activity during combustion. Thermogravimetric analysis-infrared spectrometry (TG-FTIR) has been used to study the influence of DMMP on the pyrolysis products in the gaseous phase during the thermal degradation of the PUF sample. Fourier transform infrared spectrometry (FTIR) spectra of the PUF sample at the maximum evolution rates and the generated trends of water and the products containing -NCO have been examined to obtain more information about the pyrolysis product evolutions of the samples at high temperature. These results reveal that although DMMP could improve the thermal stability of PUF samples through the formation of the residual char layer between fire and the decomposed materials, the influence of DMMP on the gaseous phase can be also observed during the thermal degradation process of materials.

  20. High-field electrical transport in amorphous phase-change materials

    Science.gov (United States)

    Kaes, Matthias; Le Gallo, Manuel; Sebastian, Abu; Salinga, Martin; Krebs, Daniel

    2015-10-01

    Electrical transport in chalcogenide-based phase change materials is an active area of research owing to the prominent role played by these materials in the field of information technology. Here, we present transport measurements (IV curves) obtained on line-cells of as-deposited amorphous phase change materials (Ge2Sb2Te5, GeTe, Ag4In3Sb66Te27) over a wide voltage and temperature range (300 K to 160 K). The well defined geometry of our devices enables a description of the transport behavior in terms of conductivity vs. electric field. At higher temperatures (300 K ≥ T ≥ 220 K) and low to intermediate fields (F Poole-Frenkel emission from a two-center Coulomb potential. Based on this model, we observe a temperature dependence of the inter-trap distance, which we can relate to a temperature dependence in the occupation of the defect creating the Coulomb potential governing Poole-Frenkel emission. At higher fields and lower temperatures, the dependency of the IV curve on the electric field can be described by ln(I/I0) = (F/Fc)2. By combining this contribution with that of the Poole-Frenkel emission, we can show that the slope at high fields, Fc, is independent of temperature. We argue that models based on direct tunneling or thermally assisted tunneling from a single defect into the valence band cannot explain the observed behavior quantitatively.

  1. Review of the use of phase change materials (PCMs in buildings with reinforced concrete structures

    Directory of Open Access Journals (Sweden)

    Pons, O.

    2014-09-01

    Full Text Available Phase change materials are capable of storing and releasing energy in the form of heat in determined temperature ranges, so to increase a building’s thermal inertia, stabilize its indoor temperatures and reduce its energetic demand. Therefore, if we used these materials we could have more energetically efficient buildings. Nevertheless, are these materials most appropriate to be used in buildings? Could the incorporation of phase change materials in buildings with concrete structures be generalized? This article aims to carry out a review of these phase change materials from construction professionals’ points of view, study their applications for buildings with reinforced concrete structures and the key points for these applications, draw conclusions and provide recommendations useful for all professionals within the sector who are considering the application of these materials.Los materiales de cambio de fase son capaces de almacenar y liberar energía en forma de calor en un determinando rango de temperaturas, y así aumentar la inercia térmica de un edificio, estabilizar las temperaturas en el interior y reducir la demanda energética. En consecuencia, si utilizáramos estos materiales podríamos tener un parque de edificios más eficientes energéticamente. No obstante, ¿estos materiales son apropiados para usarse en edificios? ¿Se podría generalizar la incorporación de materiales de cambio de fase en edificios con estructuras de hormigón? Este artículo tiene como objetivos hacer una revisión del estado del arte de estos materiales de cambio de fase desde el punto de vista de los profesionales de la construcción, estudiar las aplicaciones en edificios con estructuras de hormigón armado y los puntos clave para estas aplicaciones, extraer conclusiones y recomendaciones útiles para los profesionales del sector que se planteen la utilización de estos materiales.

  2. A Preisach approach to modeling partial phase transitions in the first order magnetocaloric material MnFe(P,As)

    DEFF Research Database (Denmark)

    von Moos, Lars; Bahl, C.R.H.; Nielsen, Kaspar Kirstein;

    2014-01-01

    . Such materials are potential candidates for application in magnetic refrigeration devices. However, the first order materials often have adverse properties such as hysteresis, making actual performance troublesome to quantify, a subject not thoroughly studied within this field.Here we investigate the behavior...... of MnFe(P,As) under partial phase transitions, which is similar to what materials experience in actual magnetic refrigeration devices. Partial phase transition curves, in the absence of a magnetic field, are measured using calorimetry and the experimental results are compared to simulations......Magnetic refrigeration is an emerging technology that could provide energy efficient and environmentally friendly cooling. Magnetocaloric materials in which a structural phase transition is found concurrently with the magnetic phase transition are often termed first order magnetocaloric materials...

  3. Microstructure and electrical properties of Sb2Te phase-change material

    Science.gov (United States)

    Liu, Guangyu; Wu, Liangcai; Li, Tao; Rao, Feng; Song, Sannian; Liu, Bo; Song, Zhitang

    2016-10-01

    Phase Change Memory (PCM) has great potential for commercial applications of next generation non-volatile memory (NVM) due to its high operation speed, high endurance and low power consumption. Sb2Te (ST) is a common phase-change material and has fast crystallization speed, while thermal stability is relatively poor and its crystallization temperature is about 142°C. According to the Arrhenius law, the extrapolated failure temperature is about 55°C for ten years. When heated above the crystallization temperature while below the melting point, its structure can be transformed from amorphous phase to hexagonal phase. Due to the growth-dominated crystallization mechanism, the grain size of ST film is large and the diameter of about 300 nm is too large compared with Ge2Sb2Te5 (GST), which may deteriorate the device performance. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were employed to study the microstructures and the results indicate that the crystal plane is {110}. In addition, device cells were manufactured and their current-voltage (I-V) and resistance-voltage characteristics were tested, and the results reveal that the threshold voltage (Vth) of ST film is 0.87 V. By researching the basic properties of ST, we can understand its disadvantages and manage to improve its performance by doping or other proper methods. Finally, the improved ST can be a candidate for optical discs and PCM.

  4. Metal - Insulator Transition Driven by Vacancy Ordering in GeSbTe Phase Change Materials

    Science.gov (United States)

    Bragaglia, Valeria; Arciprete, Fabrizio; Zhang, Wei; Mio, Antonio Massimiliano; Zallo, Eugenio; Perumal, Karthick; Giussani, Alessandro; Cecchi, Stefano; Boschker, Jos Emiel; Riechert, Henning; Privitera, Stefania; Rimini, Emanuele; Mazzarello, Riccardo; Calarco, Raffaella

    2016-04-01

    Phase Change Materials (PCMs) are unique compounds employed in non-volatile random access memory thanks to the rapid and reversible transformation between the amorphous and crystalline state that display large differences in electrical and optical properties. In addition to the amorphous-to-crystalline transition, experimental results on polycrystalline GeSbTe alloys (GST) films evidenced a Metal-Insulator Transition (MIT) attributed to disorder in the crystalline phase. Here we report on a fundamental advance in the fabrication of GST with out-of-plane stacking of ordered vacancy layers by means of three distinct methods: Molecular Beam Epitaxy, thermal annealing and application of femtosecond laser pulses. We assess the degree of vacancy ordering and explicitly correlate it with the MIT. We further tune the ordering in a controlled fashion attaining a large range of resistivity. Employing ordered GST might allow the realization of cells with larger programming windows.

  5. Programming margin enlargement by material engineering for multilevel storage in phase-change memory

    Science.gov (United States)

    Yin, You; Noguchi, Tomoyuki; Ohno, Hiroki; Hosaka, Sumio

    2009-09-01

    In this work, we investigate the effect of the material engineering on programming margin in the double-layered phase-change memory, which is the most important parameter for the stability of multilevel storage. Compared with the TiN/SbTeN cell, the TiSiN/GeSbTe double-layered cell exhibits the resistance ratio of the highest to lowest resistance levels up to two to three orders of magnitude, indicating much larger programming margin and thus higher stability and/or more available levels. Our calculation results show that the resistivities of the top heating layer and the phase-change layer have a significant effect on the programming margin.

  6. Gas-driven subharmonic waves in a vibrated two-phase granular material.

    Science.gov (United States)

    Matas, J-P; Uehara, J; Behringer, R P

    2008-04-01

    Vibrated powders exhibit striking phenomena: subharmonic waves, oscillons, convection, heaping, and even bubbling. We demonstrate novel rectangular profile subharmonic waves for vibrated granular material, that occur uniquely in the two-phase case of grains, and a fluid, such as air. These waves differ substantially from those for the gas-free case, exhibit different dispersion relations, and occur for specific shaking parameters and air pressure, understandable with gas-particle flow models. These waves occur when the gas diffusively penetrates the granular layer in a time comparable to the shaker period. As the pressure is lowered towards P =0, the granular-gas system exhibits a Knudsen regime. This instability provides an opportunity to quantitatively test models of two-phase flow.

  7. Experimental Research of Electronic Devices Thermal Control Using Metallic Phase Change Materials

    Institute of Scientific and Technical Information of China (English)

    Ai-Gang Pan; Jun-Biao Wang; Xian-Jie Zhang; Xiao-Bao Cao

    2014-01-01

    A Phase-change thermal control unit ( PTCU) filled with metallic phase change material ( PCM) Bismuth alloy for electric devices thermal protection was developed and investigated experimentally. The PTCU filled with PCM was designed and manufactured. Resistance heating components ( RCHs) produced 1 W, 3 W, 5 W, 7W, and 10 W for simulating heat generation of electronic devices. At various heating power levels, the performance of PTCU were tested during heating period and one duty cycle period. The experimental results show that the PTCU delays RCH reaching the maximum operating temperature. Also, a numerical model was developed to enable interpretation of experimental results and to perform parametric studies. The results confirmed that the PTCU is suitable for electric devices thermal control.

  8. Dental materials. Amorphous intergranular phases control the properties of rodent tooth enamel.

    Science.gov (United States)

    Gordon, Lyle M; Cohen, Michael J; MacRenaris, Keith W; Pasteris, Jill D; Seda, Takele; Joester, Derk

    2015-02-13

    Dental enamel, a hierarchical material composed primarily of hydroxylapatite nanowires, is susceptible to degradation by plaque biofilm-derived acids. The solubility of enamel strongly depends on the presence of Mg(2+), F(-), and CO3(2-). However, determining the distribution of these minor ions is challenging. We show—using atom probe tomography, x-ray absorption spectroscopy, and correlative techniques—that in unpigmented rodent enamel, Mg(2+) is predominantly present at grain boundaries as an intergranular phase of Mg-substituted amorphous calcium phosphate (Mg-ACP). In the pigmented enamel, a mixture of ferrihydrite and amorphous iron-calcium phosphate replaces the more soluble Mg-ACP, rendering it both harder and more resistant to acid attack. These results demonstrate the presence of enduring amorphous phases with a dramatic influence on the physical and chemical properties of the mature mineralized tissue.

  9. Mapping of the photo-induced metastable and hidden phases in 2D electronic materials

    Science.gov (United States)

    Zhou, Faran; Sun, Tianyin; Han, Tzong-Ru; Malliakas, Christos; Duxbury, Phillip; Mahanti, Subhendra; Kanatzidis, Mercouri; Ruan, Chong-Yu; MSU Team; NU Team

    Using the ultrafast electron imaging techniques, we studied the light-induced phase transitions in transition-metal dichalcogenide materials. A succession of different phases was introduced transiently using femtosecond mid-infrared pulses and the local atomic scale charge-density-wave dynamics and morphological evolution of the long-range textured domains were in situ characterized using the ultrashort coherent electron pulses. The various metastable and hidden states emerging under the controlled nonthermal, nonadiabatic driving highlight the interaction-driven nature of these transitions with limited involvement of lattice entropy. The methodology introduced here can be generally applied to survey the complex energy landscape in strongly correlated electron systems, avoiding the difficulty of electrostatic gating or confounding effects due to defects and/or disorder. In particular, the observation of robust non-thermal switching at meso-scales and at ultrafast timescales, provides a platform for designing high-speed low-energy consumption nano-photonics and electronics devices.

  10. Formation dynamics of femtosecond laser-induced phase objects in transparent materials

    Science.gov (United States)

    Mermillod-Blondin, A.; Rosenfeld, A.; Stoian, R.; Audouard, E.

    2012-01-01

    Ultrashort pulse lasers offer the possibility to structure the bulk of transparent materials on a microscale. As a result, the optical properties of the irradiated material are locally modified in a permanent fashion. Depending on the irradiation parameters, different types of laser-induced phase objects can be expected, from uniform voxels (that can exhibit higher or lower refractive index than the bulk) to self-organized nanoplanes. We study the physical mechanisms that lead to material restructuring, with a particular emphasis on events taking place on a sub picosecond to a microsecond timescale following laser excitation. Those timescales are particularly interesting as they correspond to the temporal distances between two consecutive laser pulses when performing multiple pulse irradiation: burst microprocessing usually involves picosecond separation times and high repetition rate systems operate in the MHz range. We employ a time-resolved microscopy technique based on a phase-contrast microscope setup extended into a pump-probe scheme. This methods enables a dynamic observation of the complex refractive index in the interaction region with a time resolution better than 300 fs. In optical transmission mode, the transient absorption coefficient can be measured for different illumination wavelengths (400 nm and 800 nm). The phase-contrast mode provides qualitative information about the real part of the transient refractive index. Based on the study of those transient optical properties, we observe the onset and relaxation of the laser-generated plasma into different channels such as defect creation, sample heating, and shockwave generation. The majority of our experiments were carried out with amorphous silica, but our method can be applied to the study of all transparent media.

  11. Ferromagnetism modulation by phase change in Mn-doped GeTe chalcogenide magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Adam, Adam Abdalla Elbashir [Huazhong University of Science and Technology, School of Optical and Electronic Information, Wuhan (China); Wuhan National Laboratory for Optoelectronics, Wuhan (China); Alneelain University, Faculty of Science and Technology, Khartoum (Sudan); Cheng, Xiaomin; Guan, Xiawei; Miao, Xiangshui [Huazhong University of Science and Technology, School of Optical and Electronic Information, Wuhan (China); Wuhan National Laboratory for Optoelectronics, Wuhan (China)

    2014-12-15

    In this work, an effective method to modulate the ferromagnetic properties of Mn-doped GeTe chalcogenide-based phase change materials is presented. The microstructure of the phase change magnetic material Ge{sub 1-x} Mn{sub x} Te thin films was studied. The X-ray diffraction results demonstrate that the as-deposited films are amorphous, and the crystalline films are formed after annealing at 350 C for 10 min. Crystallographic structure investigation shows the existence of some secondary magnetic phases. The lattice parameters of Ge{sub 1-x} Mn{sub x} Te (x = 0.04, 0.12 and 0.15) thin films are found to be slightly different with changes of Mn compositions. The structural analysis clearly indicates that all the films have a stable rhombohedral face-centered cubic polycrystalline structure. The magnetic properties of the amorphous and crystalline Ge{sub 0.96}Mn{sub 0.04}Te were investigated. The measurements of magnetization (M) as a function of the magnetic field (H) show that both amorphous and crystalline phases of Ge{sub 0.96}Mn{sub 0.04}Te thin film are ferromagnetic and there is drastic variation between amorphous and crystalline states. The temperature (T) dependence of magnetizations at zero field cooling (ZFC) and field cooling (FC) conditions of the crystalline Ge{sub 0.96}Mn{sub 0.04}Te thin film under different applied magnetic fields were performed. The measured data at 100 and 300 Oe applied magnetic fields show large bifurcations in the ZFC and FC curves while on the 5,000 Oe magnetic field there is no deviation. (orig.)

  12. Random-phase approximation and its applications in computational chemistry and materials science

    Science.gov (United States)

    Ren, Xinguo; Rinke, Patrick; Joas, Christian; Scheffler, Matthias

    2012-11-01

    The random-phase approximation (RPA) as an approach for computing the electronic correlation energy is reviewed. After a brief account of its basic concept and historical development, the paper is devoted to the theoretical formulations of RPA, and its applications to realistic systems. With several illustrating applications, we discuss the implications of RPA for computational chemistry and materials science. The computational cost of RPA is also addressed which is critical for its widespread use in future applications. In addition, current correction schemes going beyond RPA and directions of further development will be discussed.

  13. Analysis of Phase Change Material in Glazing Systems in Future Zero-Energy-Buildings

    DEFF Research Database (Denmark)

    Winther, Frederik Vildbrad; Heiselberg, Per; Jensen, Rasmus Lund

    2016-01-01

    the thermal storage capacity of the glazed facade by using phase change material (PCM), in the glazing cavity, reduces the cooling demand. When wanting to use this technology under colder weather conditions, the pane can potentially reduce the heat loss of the pane thereby minimizing energy demand for heating.......When designing glazed constructions, this often results in thermally light constructions, with a low time constant. In order for these buildings to improve the redistribution of loads between night and day, solutions such as active slabs and exposed concrete cores are often used. However...

  14. Numerical computation of solar heat storage in phase change material/concrete wall

    Directory of Open Access Journals (Sweden)

    Mustapha Faraji

    2014-01-01

    Full Text Available A one-dimensional mathematical model was developed in order to analyze and optimize the latent heat storage wall. Two layers of phase change material (PCM are sandwiched within a concrete wall. The governing equations for energy transport were developed by using the enthalpy method and discretized with volume control scheme. A series of numerical investigations were conducted. The effect of the melting temperature on the possibility of increasing the energy performance of the proposed heating system was analyzed. Results are obtained for thermal gain and temperature fluctuation. The charging/discharging process was also presented and analyzed.

  15. Low-power switching of phase-change materials with carbon nanotube electrodes.

    Science.gov (United States)

    Xiong, Feng; Liao, Albert D; Estrada, David; Pop, Eric

    2011-04-29

    Phase-change materials (PCMs) are promising candidates for nonvolatile data storage and reconfigurable electronics, but high programming currents have presented a challenge to realize low-power operation. We controlled PCM bits with single-wall and small-diameter multi-wall carbon nanotubes. This configuration achieves programming currents of 0.5 microampere (set) and 5 microamperes (reset), two orders of magnitude lower than present state-of-the-art devices. Pulsed measurements enable memory switching with very low energy consumption. Analysis of over 100 devices finds that the programming voltage and energy are highly scalable and could be below 1 volt and single femtojoules per bit, respectively.

  16. Re-utilization of Industrial CO2 for Algae Production Using a Phase Change Material

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Brian

    2013-12-31

    This is the final report of a 36-month Phase II cooperative agreement. Under this project, Touchstone Research Laboratory (Touchstone) investigated the merits of incorporating a Phase Change Material (PCM) into an open-pond algae production system that can capture and re-use the CO2 from a coal-fired flue gas source located in Wooster, OH. The primary objective of the project was to design, construct, and operate a series of open algae ponds that accept a slipstream of flue gas from a coal-fired source and convert a significant portion of the CO2 to liquid biofuels, electricity, and specialty products, while demonstrating the merits of the PCM technology. Construction of the pilot facility and shakedown of the facility in Wooster, OH, was completed during the first two years, and the focus of the last year was on operations and the cultivation of algae. During this Phase II effort a large-scale algae concentration unit from OpenAlgae was installed and utilized to continuously harvest algae from indoor raceways. An Algae Lysing Unit and Oil Recovery Unit were also received and installed. Initial parameters for lysing nanochloropsis were tested. Conditions were established that showed the lysing operation was effective at killing the algae cells. Continuous harvesting activities yielded over 200 kg algae dry weight for Ponds 1, 2 and 4. Studies were conducted to determine the effect of anaerobic digestion effluent as a nutrient source and the resulting lipid productivity of the algae. Lipid content and total fatty acids were unaffected by culture system and nutrient source, indicating that open raceway ponds fed diluted anaerobic digestion effluent can obtain similar lipid productivities to open raceway ponds using commercial nutrients. Data were also collected with respect to the performance of the PCM material on the pilot-scale raceway ponds. Parameters such as evaporative water loss, temperature differences, and growth/productivity were tracked. The pond with the

  17. Simultaneous microscopic measurements of thermal and spectroscopic fields of a phase change material

    Science.gov (United States)

    Romano, M.; Ryu, M.; Morikawa, J.; Batsale, J. C.; Pradere, C.

    2016-05-01

    In this paper, simultaneous microscopic measurements of thermal and spectroscopic fields of a paraffin wax n-alkane phase change material are reported. Measurements collected using an original set-up are presented and discussed with emphasis on the ability to perform simultaneous characterization of the system when the proposed imaging process is used. Finally, this work reveals that the infrared wavelength contains two sets of important information. Furthermore, this versatile and flexible technique is well adapted to characterize many systems in which the mass and heat transfers effects are coupled.

  18. Melting of nanoparticles-enhanced phase change material (NEPCM) in vertical semicircle enclosure: numerical study

    Energy Technology Data Exchange (ETDEWEB)

    Jourabian, Mahmoud [University of Trieste, Piazzale (Italy); Farhadi, Mousa [Babol Noshirvani University of Technology, Shariati Avenue (Iran, Islamic Republic of)

    2015-09-15

    Convection melting of ice as a Phase change material (PCM) dispersed with Cu nanoparticles, which is encapsulated in a semicircle enclosure is studied numerically. The enthalpy-based Lattice Boltzmann method (LBM) combined with a Double distribution function (DDF) model is used to solve the convection-diffusion equation. The increase in solid concentration of nanoparticles results in the enhancement of thermal conductivity of PCM and the decrease in the latent heat of fusion. By enhancing solid concentration of nanoparticles, the viscosity of nanofluid increases and convective heat transfer dwindles. For all Rayleigh numbers investigated in this study, the insertion of nanoparticles in PCM has no effect on the average Nusselt number.

  19. First-principles computation of mantle materials in crystalline and amorphous phases

    Science.gov (United States)

    Karki, Bijaya B.

    2015-03-01

    First-principles methods based on density functional theory are used extensively in the investigation of the behavior and properties of mantle materials over broad ranges of pressure, temperature, and composition that are relevant. A review of computational results reported during the last couple of decades shows that essentially all properties including structure, phase transition, equation of state, thermodynamics, elasticity, alloying, conductivity, defects, interfaces, diffusivity, viscosity, and melting have been calculated from first principles. Using MgO, the second most abundant oxide of Earth's mantle, as a primary example and considering many other mantle materials in their crystalline and amorphous phases, we have found that most properties are strongly pressure dependent, sometimes varying non-monotonically and anomalously, with the effects of temperature being systematically suppressed with compression. The overall agreement with the available experimental data is excellent; it is remarkable that the early-calculated results such as shear wave velocities of two key phases, MgO and MgSiO3 perovskite, were subsequently reproduced by experimentation covering almost the entire mantle pressure regime. As covered in some detail, the defect formation and migration enthalpies of key mantle materials increase with pressure. The predicted trend is that partial MgO Schottky defects are energetically most favorable in Mg-silicates but their formation enthalpies are high. So, the diffusion in the mantle is likely to be in the extrinsic regime. Preliminary results on MgO and forsterite hint that the grain boundaries can accommodate point defects (including impurities) and enhance diffusion rates at all pressures. The structures are highly distorted in the close vicinity of the defects and at the interface with excess space. Recent simulations of MgO-SiO2 binary and other silicate melts have found that the melt self-diffusion and viscosity vary by several orders of

  20. Electro-optical properties of photochemically stable polymer-stabilized blue-phase material

    Energy Technology Data Exchange (ETDEWEB)

    Chojnowska, O., E-mail: ochojnowska@wat.edu.pl; Dąbrowski, R. [Institute of Chemistry, Military University of Technology, Warsaw 00-908 (Poland); Yan, J.; Chen, Y.; Wu, S. T. [College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States)

    2014-12-07

    Polymer-stabilized blue-phase liquid crystal (BPLC) comprising fluorinated compounds with high resistivity and photochemical stability is demonstrated. The Kerr constant, driving voltage, and response time of this BPLC are measured using an in-plane switching liquid crystal cell. At 20 °C, the measured total response time is faster than 0.7 ms and Kerr constant is 2 nm/V{sup 2}. This fluorinated BPLC material is a promising candidate for next-generation photonic and display devices, because it can be used in active matrix addressed devices.

  1. IFMIF-KEP. International fusion materials irradiation facility key element technology phase report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-03-01

    The International Fusion Materials Irradiation Facility (IFMIF) is an accelerator-based D-Li neutron source designed to produce an intense neutron field that will simulate the neutron environment of a D-T fusion reactor. IFMIF will provide a neutron flux equivalent to 2 MW/m{sup 2}, 20 dpa/y in Fe, in a volume of 500 cm{sup 3} and will be used in the development and qualification of materials for fusion systems. The design activities of IFMIF are performed under an IEA collaboration which began in 1995. In 2000, a three-year Key Element Technology Phase (KEP) of IFMIF was undertaken to reduce the key technology risk factors. This KEP report describes the results of the three-year KEP activities in the major project areas of accelerator, target, test facilities and design integration. (author)

  2. Feasibility of using phase change materials to control the heat of hydration in massive concrete structures.

    Science.gov (United States)

    Choi, Won-Chang; Khil, Bae-Soo; Chae, Young-Seok; Liang, Qi-Bo; Yun, Hyun-Do

    2014-01-01

    This paper presents experimental results that can be applied to select a possible phase change material (PCM), such as a latent heat material (LHM), to control the hydration heat in mass concrete structures. Five experimental tests (microconduction, simplified adiabatic temperature rise, heat, and compressive strength tests) were conducted to select the most desirable LHM out of seven types of inorganic PCM used in cement mortar and to determine the most suitable mix design. The results of these experimental tests were used to assess the feasibility of using PCM to reduce hydration heat in mass concrete that was examined. The experimental results show that cement mortar containing barium- [Ba(OH)2 · 8H2O] based PCM has the lowest amount of total hydration heat of the cement pastes. The barium-based PCM provides good latent heat properties that help to prevent volume change and microcracks caused by thermal stress in mass concrete.

  3. Feasibility of Using Phase Change Materials to Control the Heat of Hydration in Massive Concrete Structures

    Directory of Open Access Journals (Sweden)

    Won-Chang Choi

    2014-01-01

    Full Text Available This paper presents experimental results that can be applied to select a possible phase change material (PCM, such as a latent heat material (LHM, to control the hydration heat in mass concrete structures. Five experimental tests (microconduction, simplified adiabatic temperature rise, heat, and compressive strength tests were conducted to select the most desirable LHM out of seven types of inorganic PCM used in cement mortar and to determine the most suitable mix design. The results of these experimental tests were used to assess the feasibility of using PCM to reduce hydration heat in mass concrete that was examined. The experimental results show that cement mortar containing barium- [Ba(OH2·8H2O] based PCM has the lowest amount of total hydration heat of the cement pastes. The barium-based PCM provides good latent heat properties that help to prevent volume change and microcracks caused by thermal stress in mass concrete.

  4. Ternary mixture of fatty acids as phase change materials for thermal energy storage applications

    Directory of Open Access Journals (Sweden)

    Karunesh Kant

    2016-11-01

    Full Text Available The present study deals with the development of ternary mixtures of fatty acids for low temperature thermal energy storage applications. The commercial grade fatty acids such as Capric Acid (CA, Lauric Acid (LA, Palmitic Acid (PA and Stearic Acid (SA, have been used to prepare stable, solid–liquid phase change material (PCM for the same. In this regard, a series of ternary mixture i.e. CA–LA–SA (CLS and CA–PA–SA (CPS have been developed with different weight percentages. Thermal characteristics of these developed ternary mixture i.e. melting temperature and latent heat of fusion have been measured by using Differential Scanning Calorimeter (DSC technique. The synthesized materials are found to have melting temperature in the range of 14–21 °C (along with adequate amount of latent heat of fusion, which may be quite useful for several low temperature thermal energy storage applications.

  5. Diffusion, Thermal Properties and Chemical Compatibilities of Select MAX Phases with Materials For Advanced Nuclear Systems

    Energy Technology Data Exchange (ETDEWEB)

    Barsoum, Michel [Drexel Univ., Philadelphia, PA (United States); Bentzel, Grady [Drexel Univ., Philadelphia, PA (United States); Tallman, Darin J. [Drexel Univ., Philadelphia, PA (United States); Sindelar, Robert [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Garcia-Diaz, Brenda [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hoffman, Elizabeth [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-04-04

    The demands of Gen IV nuclear power plants for long service life under neutron irradiation at high temperature are severe. Advanced materials that would withstand high temperatures (up to 1000+ ºC) to high doses in a neutron field would be ideal for reactor internal structures and would add to the long service life and reliability of the reactors. The objective of this work is to investigate the chemical compatibility of select MAX with potential materials that are important for nuclear energy, as well as to measure the thermal transport properties as a function of neutron irradiation. The chemical counterparts chosen for this work are: pyrolytic carbon, SiC, U, Pd, FLiBe, Pb-Bi and Na, the latter 3 in the molten state. The thermal conductivities and heat capacities of non-irradiated MAX phases will be measured.

  6. Design of a Protection Thermal Energy Storage Using Phase Change Material Coupled to a Solar Receiver

    Science.gov (United States)

    Verdier, D.; Falcoz, Q.; Ferrière, A.

    2014-12-01

    Thermal Energy Storage (TES) is the key for a stable electricity production in future Concentrated Solar Power (CSP) plants. This work presents a study on the thermal protection of the central receiver of CSP plant using a tower which is subject to considerable thermal stresses in case of cloudy events. The very high temperatures, 800 °C at design point, impose the use of special materials which are able to resist at high temperature and high mechanical constraints and high level of concentrated solar flux. In this paper we investigate a TES coupling a metallic matrix drilled with tubes of Phase Change Material (PCM) in order to store a large amount of thermal energy and release it in a short time. A numerical model is developed to optimize the arrangement of tubes into the TES. Then a methodology is given, based from the need in terms of thermal capacity, in order to help the choice of the geometry.

  7. Impact-induced tensile waves in a kind of phase-transforming materials

    CERN Document Server

    Huang, Shou-Jun

    2010-01-01

    This paper concerns the global propagation of impact-induced tensile waves in a kind of phase-transforming materials. It is well-known that the governing system of partial differential equations is hyperbolic-elliptic and the initial-boundary value problem is not well-posed at all levels of loading. By making use of fully nonlinear stress-strain curve to model this material, Dai and Kong succeeded in constructing a physical solution of the above initial-boundary value problem. For the impact of intermediate range, they assumed that $\\beta<3\\alpha$ in the stress-response function for simplicity. In this paper, we revisit the impact problem and consider the propagation of impact-induced tensile waves for all values of the parameters $\\alpha$ and $\\beta$. The physical solutions for all levels of loading are obtained completely.

  8. Phase Change Material Based Accumulation Panels in Combination with Renewable Energy Sources and Thermoelectric Cooling

    Directory of Open Access Journals (Sweden)

    Jan Skovajsa

    2017-01-01

    Full Text Available The article deals with the use of modern materials and technologies that can improve the thermal comfort in buildings. The article describes the design and usage of a special accumulation device, which is composed of thermal panels based on phase change materials (PCMs. The thermal panels have an integrated tube heat exchanger and heating foils. The technology can be used as a passive or active system for heating and cooling. It is designed as a “green technology”, so it is able to use renewable energy sources, e.g., photovoltaic (PV panels, solar thermal collectors and heat pumps. Moreover, an interesting possibility is the ability to use thermoelectric coolers. In the research, measurements of the different operating modes were made, and the results are presented in the text. The measurement approves that the technology improves the thermal capacity of the building, and it is possible to use it for active heating and cooling.

  9. Phase Change Materials (PCM) fabricated in vertical structures for reconfigurable and tunable circuits

    Science.gov (United States)

    Barajas, Eduardo; Coutu, Ronald A.

    2014-03-01

    Germanium Telluride (GeTe) can be described as a non-volatile (latching state) phase change material (PCM) in memory applications. GeTe also exhibits a volatile (reversible state) region when heated and cooled between 100-180 °C. At temperatures higher than 185 °C the material crystallizes and "latches" until a temperature near to its melting point (725 °C) is reached and cooled rapidly (quenching). Germanium Antimony Telluride (GeSbTe) or also known as GST has similar characteristics as GeTe. GST also exhibits a volatile (reversible state) region when heated and cooled between 100-150 °C. GST crystallizes at 155 °C and its melting point is 600 °C. This paper demonstrates the feasibility of fabricating radio frequency (RF) devices of phase change materials (PCM) and it also presents a comparison between amorphous and crystalline PCMs in the RF spectrum. Previous work focuses on exploiting GeTe and GST as nonvolatile materials in memory applications, and also on characterizing them for their electrical and mechanical properties. The approach here focuses on fabricating RF devices and analyzing their responses. A simulation with resistor-capacitor (RC) and resistor-inductor (RL) circuits is presented to represent the response of the RF devices under testing. The fabrication process includes two-layer and four-layer devices on the Si wafer. PCMs are sputtered and the test pads are deposited using electron beam evaporation. Results show that these RF devices alone can serve as a low pass filter with a cutoff frequency of 10 MHz.

  10. Preparation of shape-stabilized phase change materials as temperature-adjusting powder

    Institute of Scientific and Technical Information of China (English)

    MIAO Chunyan; L(U) Gang; YAO Youwei; TANG Guoyi; WENG Duan

    2007-01-01

    The shape-stabilized phase change materials (PCMs)composed of paraffin wax and silica were prepared in O/W emulsion with cetyl trimethylamine bromide as emulsifier and n-pentanol as assist emulsifier.The paraffin wax(with melting temperature of 29℃,crystallizing temperature of 26℃ and latent heat of 142 J/g)served as latent heat storage material and the silica as supporting material,which prevented the leakage of the melted paraffin wax.Silica supporting material was formed in situ via hydrolysis and condensation from low-cost sodium silicate solution with chlorhydric acid and ammonium bicarbonate as neutralizing agent.The thermogravimetry(TG)curves show that the composite has a thermal stability superior to that of paraffin wax and that the content of paraffin wax in the composite is 65wt%.The maximum latent heat and its relevant melting point of composite are 95 J/g and 30℃,respectively.

  11. Polymer-coated fibrous materials as the stationary phase in packed capillary gas chromatography.

    Science.gov (United States)

    Saito, Yoshihiro; Tahara, Ai; Imaizumi, Motohiro; Takeichi, Tsutomu; Wada, Hiroo; Jinno, Kiyokatsu

    2003-10-15

    Synthetic polymer filaments have been introduced as the support material in packed capillary gas chromatography (GC). The filaments of the heat-resistant polymers, Zylon, Kevlar, Nomex, and Technora, were longitudinally packed into a short fused-silica capillary, followed by the conventional coating process for open-tubular GC columns. The separation of several test mixtures such as n-alkylbenzenes and n-alkanes was carried out with these polymer-coated fiber-packed capillary columns. With the coating by various polymeric materials on the surface of these filaments, the retentivity was significantly improved over the parent fiber-packed column (without polymer coating) as well as a conventional open-tubular capillary of the same length. The results demonstrated a good combination of Zylon as the support and poly(dimethylsiloxane)-based materials as the coating liquid-phase for the successful GC separation of n-alkanes and polycyclic aromatic hydrocarbons (PAHs), while successful applications for other separations such as poly(ethylene glycol) coating for the separation of alcohols were also obtained. From the results it has been suggested that the selectivity of the fiber-packed column could be tuned by selecting different coating materials, indicating the promising possibility for a novel usage of fine fibrous polymers as the support material that can be combined with newly synthesized coating materials specially designed for particular separations. Taking advantage of good thermal stability of the fibers, the column temperature could be elevated to higher than 350 degrees C with the combination of a short metallic capillary.

  12. Max Phase Materials And Coatings For High Temperature Heat Transfer Applications

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Rodriguez, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Garcia-Diaz, B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Olson, L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Fuentes, R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Sindelar, R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-10-19

    Molten salts have been used as heat transfer fluids in a variety of applications within proposed Gen IV nuclear designs and in advanced power system such as Concentrating Solar Power (CSP). However, operating at elevated temperatures can cause corrosion in many materials. This work developed coating technologies for MAX phase materials on Haynes-230 and characterized the corrosion of the coatings in the presence of commercial MgCl2-KCl molten salt. Cold spraying of Ti2AlC and physical vapor deposition (PVD) of Ti2AlC or Zr2AlC were tested to determine the most effective form of coating MAX phases on structural substrates. Corrosion testing at 850°C for 100 hrs showed that 3.9 μm Ti2AlC by PVD was slightly protective while 117 μm Ti2AlC by cold spray and 3.6 μm Zr2AlC by PVD were completely protective. None of the tests showed decomposition of the coating (Ti or Zr) into the salt

  13. Phase inversion of particle-stabilized materials from foams to dry water

    Science.gov (United States)

    Binks, Bernard P.; Murakami, Ryo

    2006-11-01

    Small particles attached to liquid surfaces arise in many products and processes, including crude-oil emulsions and food foams and in flotation, and there is a revival of interest in studying their behaviour. Colloidal particles of suitable wettability adsorb strongly to liquid-liquid and liquid-vapour interfaces, and can be sole stabilizers of emulsions and foams, respectively. New materials, including colloidosomes, anisotropic particles and porous solids, have been prepared by assembling particles at such interfaces. Phase inversion of particle-stabilized emulsions from oil in water to water in oil can be achieved either by variation of the particle hydrophobicity (transitional) or by variation of the oil/water ratio (catastrophic). Here we describe the phase inversion of particle-stabilized air-water systems, from air-in-water foams to water-in-air powders and vice versa. This inversion can be driven either by a progressive change in silica-particle hydrophobicity at constant air/water ratio or by changing the air/water ratio at fixed particle wettability, and has not been observed in the corresponding systems stabilized by surfactants. The simplicity of the work is that this novel inversion is achieved in a single system. The resultant materials in which either air or water become encapsulated have potential applications in the food, pharmaceutical and cosmetics industries.

  14. CFD ANALYSIS FOR HEAT TRANSFER BETWEEN COPPER ENCAPSULATED PHASE CHANGE MATERIAL AND HEAT TRANSFER FLUID

    Directory of Open Access Journals (Sweden)

    M.Premkumar

    2013-03-01

    Full Text Available Heat transfer plays an important role in the enhancement of thermal energy storage in phase change material (PCM. The effective utilization of solar thermal energy can be obtained by proper storage of that energy. There are various techniques for the enhancement solar thermal storage in phase change material such as introductionof wire brushes, honey comb structure, fins and packed bed storage. In this study the analysis of heat transfer between PCM and heat transfer fluids (HTF with Spherical and cylindrical finned encapsulations made of copper are done using computational fluid dynamic (CFD analysis software GAMBIT and Fluent 6.2. The analysis is done in two modes as charging and discharging. During the charging mode the input is given in terms of temperature to the heat transfer fluid and the amount of heat transfer inside the PCM encapsulation is taken as output. During the discharging process the output temperature in the PCM is given as input and the amount of heat transferred to the heat transfer fluid is noted. The results from CFD analysis conclude that the heat transfer is more in finned encapsulations than that of without finned encapsulations and the copper sphere with fins is considered to be the best out of all other encapsulations.

  15. Phase inversion of particle-stabilized materials from foams to dry water.

    Science.gov (United States)

    Binks, Bernard P; Murakami, Ryo

    2006-11-01

    Small particles attached to liquid surfaces arise in many products and processes, including crude-oil emulsions and food foams and in flotation, and there is a revival of interest in studying their behaviour. Colloidal particles of suitable wettability adsorb strongly to liquid-liquid and liquid-vapour interfaces, and can be sole stabilizers of emulsions and foams, respectively. New materials, including colloidosomes, anisotropic particles and porous solids, have been prepared by assembling particles at such interfaces. Phase inversion of particle-stabilized emulsions from oil in water to water in oil can be achieved either by variation of the particle hydrophobicity (transitional) or by variation of the oil/water ratio (catastrophic). Here we describe the phase inversion of particle-stabilized air-water systems, from air-in-water foams to water-in-air powders and vice versa. This inversion can be driven either by a progressive change in silica-particle hydrophobicity at constant air/water ratio or by changing the air/water ratio at fixed particle wettability, and has not been observed in the corresponding systems stabilized by surfactants. The simplicity of the work is that this novel inversion is achieved in a single system. The resultant materials in which either air or water become encapsulated have potential applications in the food, pharmaceutical and cosmetics industries.

  16. OCV Hysteresis in Li-Ion Batteries including Two-Phase Transition Materials

    Directory of Open Access Journals (Sweden)

    Michael A. Roscher

    2011-01-01

    Full Text Available The relation between batteries' state of charge (SOC and open-circuit voltage (OCV is a specific feature of electrochemical energy storage devices. Especially NiMH batteries are well known to exhibit OCV hysteresis, and also several kinds of lithium-ion batteries show OCV hysteresis, which can be critical for reliable state estimation issues. Electrode potential hysteresis is known to result from thermodynamical entropic effects, mechanical stress, and microscopic distortions within the active electrode materials which perform a two-phase transition during lithium insertion/extraction. Hence, some Li-ion cells including two-phase transition active materials show pronounced hysteresis referring to their open-circuit voltage. This work points out how macroscopic effects, that is, diffusion limitations, superimpose the latte- mentioned microscopic mechanisms and lead to a shrinkage of OCV hysteresis, if cells are loaded with high current rates. To validate the mentioned interaction, Li-ion cells' state of charge is adjusted to 50% with various current rates, beginning from the fully charged and the discharged state, respectively. As a pronounced difference remains between the OCV after charge and discharge adjustment, obviously the hysteresis vanishes as the target SOC is adjusted with very high current rate.

  17. Thermoelectric generators incorporating phase-change materials for waste heat recovery from engine exhaust

    Science.gov (United States)

    Meisner, Gregory P; Yang, Jihui

    2014-02-11

    Thermoelectric devices, intended for placement in the exhaust of a hydrocarbon fuelled combustion device and particularly suited for use in the exhaust gas stream of an internal combustion engine propelling a vehicle, are described. Exhaust gas passing through the device is in thermal communication with one side of a thermoelectric module while the other side of the thermoelectric module is in thermal communication with a lower temperature environment. The heat extracted from the exhaust gasses is converted to electrical energy by the thermoelectric module. The performance of the generator is enhanced by thermally coupling the hot and cold junctions of the thermoelectric modules to phase-change materials which transform at a temperature compatible with the preferred operating temperatures of the thermoelectric modules. In a second embodiment, a plurality of thermoelectric modules, each with a preferred operating temperature and each with a uniquely-matched phase-change material may be used to compensate for the progressive lowering of the exhaust gas temperature as it traverses the length of the exhaust pipe.

  18. Reversible optical switching of highly confined phonon-polaritons with an ultrathin phase-change material

    Science.gov (United States)

    Li, Peining; Yang, Xiaosheng; Maß, Tobias W. W.; Hanss, Julian; Lewin, Martin; Michel, Ann-Katrin U.; Wuttig, Matthias; Taubner, Thomas

    2016-08-01

    Surface phonon-polaritons (SPhPs), collective excitations of photons coupled with phonons in polar crystals, enable strong light-matter interaction and numerous infrared nanophotonic applications. However, as the lattice vibrations are determined by the crystal structure, the dynamical control of SPhPs remains challenging. Here, we realize the all-optical, non-volatile, and reversible switching of SPhPs by controlling the structural phase of a phase-change material (PCM) employed as a switchable dielectric environment. We experimentally demonstrate optical switching of an ultrathin PCM film (down to 7 nm, detect ultra-confined SPhPs (polariton wavevector kp > 70k0, k0 = 2π/λ) in quartz. Our proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods. With optimized materials and parallelized optical addressing we foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors.

  19. Preparation, characterization, and thermal properties of microencapsulated phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Alkan, Cemil; Sari, Ahmet; Karaipekli, Ali [Department of Chemistry, Gaziosmanpasa University, 60240 Tokat (Turkey); Uzun, Orhan [Department of Physics, Gaziosmanpasa University, 60240 Tokat (Turkey)

    2009-01-15

    This study is focused on the preparation, characterization, and determination of thermal properties of microencapsulated docosane with polymethylmethacrylate (PMMA) as phase change material for thermal energy storage. Microencapsulation of docosane has been carried out by emulsion polymerization. The microencapsulated phase change material (MEPCM) was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Thermal properties and thermal stability of MEPCM were measured by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC analysis indicated that the docosane in the microcapsules melts at 41.0 C and crystallizes at 40.6 C. It has latent heats of 54.6 and -48.7 J/g for melting and crystallization, respectively. TGA showed that the MEPCM degraded in three distinguishable steps and had good chemical stability. Accelerated thermal cycling tests also indicated that the MEPCM had good thermal reliability. Based on all these results, it can be concluded that the microencapsulated docosane as MEPCMs have good potential for thermal energy storage purposes such as solar space heating applications. (author)

  20. Investigation of Thermal Interface Materials Using Phase-Sensitive Transient Thermoreflectance Technique: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Feng, X.; King, C.; DeVoto, D.; Mihalic, M.; Narumanchi, S.

    2014-08-01

    With increasing power density in electronics packages/modules, thermal resistances at multiple interfaces are a bottleneck to efficient heat removal from the package. In this work, the performance of thermal interface materials such as grease, thermoplastic adhesives and diffusion-bonded interfaces are characterized using the phase-sensitive transient thermoreflectance technique. A multi-layer heat conduction model was constructed and theoretical solutions were derived to obtain the relation between phase lag and the thermal/physical properties. This technique enables simultaneous extraction of the contact resistance and bulk thermal conductivity of the TIMs. With the measurements, the bulk thermal conductivity of Dow TC-5022 thermal grease (70 to 75 um bondline thickness) was 3 to 5 W/(m-K) and the contact resistance was 5 to 10 mm2-K/W. For the Btech thermoplastic material (45 to 80 μm bondline thickness), the bulk thermal conductivity was 20 to 50 W/(m-K) and the contact resistance was 2 to 5 mm2-K/W. Measurements were also conducted to quantify the thermal performance of diffusion-bonded interface for power electronics applications. Results with the diffusion-bonded sample showed that the interfacial thermal resistance is more than one order of magnitude lower than those of traditional TIMs, suggesting potential pathways to efficient thermal management.

  1. Influence of deformation on structural-phase state of weld material in St3 steel

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, Alexander, E-mail: galvas.kem@gmail.ru; Ababkov, Nicolay, E-mail: n.ababkov@rambler.ru; Ozhiganov, Yevgeniy, E-mail: zhigan84@mail.ru [Kuzbass State Technical University, 25-54, Krasnaya Str., 650000, Kemerovo (Russian Federation); LLC “Kuzbass Center of Welding and Control”, 33/2, Lenin Str., 650055, Kemerovo (Russian Federation); Kozlov, Eduard, E-mail: kozlov@tsuab.ru [Kuzbass State Technical University, 25-54, Krasnaya Str., 650000, Kemerovo (Russian Federation); Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Popova, Natalya, E-mail: natalya-popova-44@mail.ru [Kuzbass State Technical University, 25-54, Krasnaya Str., 650000, Kemerovo (Russian Federation); Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk (Russian Federation); Nikonenko, Elena, E-mail: vilatomsk@mail.ru [Kuzbass State Technical University, 25-54, Krasnaya Str., 650000, Kemerovo (Russian Federation); Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30, Lenin Str., 634050, Tomsk (Russian Federation); Zboykova, Nadezhda, E-mail: tezaurusn@gmail.com; Koneva, Nina, E-mail: koneva@tsuab.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation)

    2016-01-15

    The structural-phase condition of the weld material subjected to the plastic deformation was investigated using the translucent diffraction electron microscopy method. The investigations were carried out near the joint of the weld and the base metal. The seam was done by the method of manual arc welding without artificial defects. The St3 steel was taken as the welded material. Influence of the plastic deformation on morphology, phase composition, defect structure and its parameters of weld metal was revealed. All investigations were done at the distance of 0.5 mm from the joint of the weld and the base metal at the deformation degrees from 0 to 5% and after destruction of a sample. It was established that deformation of the sample did not lead to qualitative changes in the structure (the structure is still presented by ferrite-pearlite mixture) but changed the quantitative parameters of the structure, namely, with the increase of plastic deformation a part of the pearlite component becomes more and more imperfect. In the beginning it turns into the destroyed pearlite then into ferrite, the volume fraction of pearlite is decreased. The polarization of dislocation structure takes place but it doesn’t lead to the internal stresses that can destroy the sample.

  2. Control over emissivity of zero-static-power thermal emitters based on phase changing material GST

    CERN Document Server

    Du, Kaikai; Lyu, Yanbiao; Ding, Jichao; Lu, Yue; Cheng, Zhiyuan; Qiu, Min

    2016-01-01

    Controlling the emissivity of a thermal emitter has attracted growing interest with a view towards a new generation of thermal emission devices. So far, all demonstrations have involved sustained external electric or thermal consumption to maintain a desired emissivity. Here control over the emissivity of a thermal emitter consisting of a phase changing material Ge2Sb2Te5 (GST) film on top of a metal film is demonstrated. This thermal emitter shows broad wavelength-selective spectral emissivity in the mid-infrared. The peak emissivity approaches the ideal blackbody maximum and a maximum extinction ratio of above 10dB is attainable by switching GST between the crystalline and amorphous phases. By controlling the intermediate phases, the emissivity can be continuously tuned. This switchable, tunable, wavelength-selective and thermally stable thermal emitter will pave the way towards the ultimate control of thermal emissivity in the field of fundamental science as well as for energy-harvesting and thermal contro...

  3. Transient Structures and Possible Limits of Data Recording in Phase-Change Materials.

    Science.gov (United States)

    Hu, Jianbo; Vanacore, Giovanni M; Yang, Zhe; Miao, Xiangshui; Zewail, Ahmed H

    2015-07-28

    Phase-change materials (PCMs) represent the leading candidates for universal data storage devices, which exploit the large difference in the physical properties of their transitional lattice structures. On a nanoscale, it is fundamental to determine their performance, which is ultimately controlled by the speed limit of transformation among the different structures involved. Here, we report observation with atomic-scale resolution of transient structures of nanofilms of crystalline germanium telluride, a prototypical PCM, using ultrafast electron crystallography. A nonthermal transformation from the initial rhombohedral phase to the cubic structure was found to occur in 12 ps. On a much longer time scale, hundreds of picoseconds, equilibrium heating of the nanofilm is reached, driving the system toward amorphization, provided that high excitation energy is invoked. These results elucidate the elementary steps defining the structural pathway in the transformation of crystalline-to-amorphous phase transitions and describe the essential atomic motions involved when driven by an ultrafast excitation. The establishment of the time scales of the different transient structures, as reported here, permits determination of the possible limit of performance, which is crucial for high-speed recording applications of PCMs.

  4. Heat Transfer of Heat Sinking Vest with Phase-change Material

    Institute of Scientific and Technical Information of China (English)

    QIU Yifen; JIANG Nan; WU Wei; ZHANG Guangwei; XIAO Baoliang

    2011-01-01

    To investigate thermal protection effects of heat sinking vest with phase-change material (PCM),human thermoregulation model is introduced,and a thermal mathematical model of heat transfer with phase change has been developed with the enthalpy method.The uniform energy equation is constructed for the whole domain,and the equation is implicitly discreted by control volume and finite difference method.Then the enthalpy in each node is solved by using chasing method to calculate the tridiagonal equations,and the inner surface temperature of PCM could be obtained.According to the human thermoregulation model of heat sinking vest,the dynamic temperature distribution and sweat of the body are solved.Calculation results indicate that the change of core temperature matches the experimental result,and the sweat difference is small.This thermal mathematical model of heat transfer with phase change is credible and appropriate.Through comparing the dynamic temperature distribution and sweat of the body wearing heat sinking vest to results of the body not wearing this clothing,it is evident that wearing heat sinking vest can reduce the body heat load significantly.

  5. Mechanism of GeSbTe phase change materials: an ab initio molecular dynamics study

    Science.gov (United States)

    Raty, Jean-Yves; Otjacques, Céline; Gaspard, Jean-Pierre; Bichara, Christophe

    2008-03-01

    Among phase change materials, Ge2Sb2Te5 (225) is one of the most successfully used in applications. Accepted models are based on EXAFS spectra and suppose a complete reorganization of bonds during amorphization, with Ge changing from sixfold to tetrahedral coordination. We perform ab initio MD simulations of the (225), (124) and (415) liquid alloys. We show that the crystalline, liquid and amorphous structure of these systems are similar, with very little sp3 hybridization around Ge atoms and a majority of p-sigma bonds. Using a set of quenched liquid configurations we reproduce the EXAFS measurements on the (225) composition and explain how the static Debye Waller factor due to the vacancies in the crystal phase leads to a cancellation of individual neighbors contribution to the EXAFS signal while in the amorphous, a larger coherence occurs, enhancing the EXAFS signal. The computed electrical conductivities of the three phases (cubic solid, liquid and amorphous) prove to be very different, accordingly with the experiment.

  6. Study on BSTO/MgO Ferroelectric Materials for Phase Shift Doped with Rare Earth Oxides

    Institute of Scientific and Technical Information of China (English)

    Yang Chunxia; Zhou Hongqing; Liu Min; Wu Hongzhong

    2005-01-01

    Barium strontium titanate/magnesia (BSTO/MgO) ferroelectric materials for phase shift were prepared by traditional ceramic process-solid phase synthesis. The effects of various rare earth oxides of 0.5% on dielectric behaviors of BSTO/MgO composites were studied in terms of permittivity, loss tangent and tunability both at low and high frequencies. The dielectric constant of Y2O3 and Er2O3 doped samples decreases from 160 to 120, and the microwave loss of La2O3 and Er2O3 doped samples decreases from 8.2×10-3 to 6.8×10-3. Only La2O3 increases the tunability of BSTO/MgO system, from 13.6% to 14.8%. For the La2O3 doped sample, the value of tunability is more than 14% with the external DC field 4000 V*mm-1 and the microwave loss at 2.47 GHz is 6.77×10-3 and, hence, it can basically meet the requirements of phase shifters working at microwave frequencies. The influence mechanism was discussed preliminarily.

  7. The ω-SQUIPT as a tool to phase-engineer Josephson topological materials

    Science.gov (United States)

    Strambini, E.; D'Ambrosio, S.; Vischi, F.; Bergeret, F. S.; Nazarov, Yu. V.; Giazotto, F.

    2016-12-01

    Multi-terminal superconducting Josephson junctions based on the proximity effect offer the opportunity to tailor non-trivial quantum states in nanoscale weak links. These structures can realize exotic topologies in several dimensions, for example, artificial topological superconductors that are able to support Majorana bound states, and pave the way to emerging quantum technologies and future quantum information schemes. Here we report the realization of a three-terminal Josephson interferometer based on a proximized nanosized weak link. Our tunnelling spectroscopy measurements reveal transitions between gapped (that is, insulating) and gapless (conducting) states that are controlled by the phase configuration of the three superconducting leads connected to the junction. We demonstrate the topological nature of these transitions: a gapless state necessarily occurs between two gapped states of different topological indices, in much the same way that the interface between two insulators of different topologies is necessarily conducting. The topological numbers that characterize such gapped states are given by superconducting phase windings over the two loops that form the Josephson interferometer. As these gapped states cannot be transformed to one another continuously without passing through a gapless condition, they are topologically protected. The same behaviour is found for all of the points of the weak link, confirming that this topology is a non-local property. Our observation of the gapless state is pivotal for enabling phase engineering of different and more sophisticated artificial topological materials.

  8. Integrity of the Pericentriolar Material Is Essential for Maintaining Centriole Association during M Phase.

    Directory of Open Access Journals (Sweden)

    Mi Young Seo

    Full Text Available A procentriole is assembled next to the mother centriole during S phase and remains associated until M phase. After functioning as a spindle pole during mitosis, the mother centriole and procentriole are separated at the end of mitosis. A close association of the centriole pair is regarded as an intrinsic block to the centriole reduplication. Therefore, deregulation of this process may cause a problem in the centriole number control, resulting in increased genomic instability. Despite its importance for faithful centriole duplication, the mechanism of centriole separation is not fully understood yet. Here, we report that centriole pairs are prematurely separated in cells whose cell cycle is arrested at M phase by STLC. Dispersal of the pericentriolar material (PCM was accompanied. This phenomenon was independent of the separase activity but needed the PLK1 activity. Nocodazole effectively inhibited centriole scattering in STLC-treated cells, possibly by reducing the microtubule pulling force around centrosomes. Inhibition of PLK1 also reduced the premature separation of centrioles and the PCM dispersal as well. These results revealed the importance of PCM integrity in centriole association. Therefore, we propose that PCM disassembly is one of the driving forces for centriole separation during mitotic exit.

  9. Designing dual phase sensing materials from polyaniline filled styrene–isoprene–styrene composites

    Energy Technology Data Exchange (ETDEWEB)

    Sadasivuni, Kishor Kumar, E-mail: kishor_kumars@yahoo.com [Centre for Advanced Materials, Qatar University, Doha (Qatar); Ponnamma, Deepalekshmi [School of Chemical Sciences, Mahatma Gandhi University, Kottayam 686560, Kerala (India); Kasak, Peter; Krupa, Igor; Ali S A Al-Maadeed, Mariam [Centre for Advanced Materials, Qatar University, Doha (Qatar)

    2014-10-15

    The demand for developing oil detectors is ever increasing since the cleanup and recovery from oil spill usually take long time. Here we propose oil sensors made of polyaniline (PANI) filled poly(styrene–isoprene–styrene) (SIS) block copolymer composite films with good uniformity and dispersion. The changes in resistivity of the samples in presence of both oil and water media reveal the good sensing ability of SIS–PANI films towards oil in water (dual phase). The morphology and chemical composition of the developed products are characterized by scanning electron microscopy and Fourier transformation infrared spectroscopy. Swelling studies are performed to correlate the sensing response to the structural variations and based on it a mechanism is derived for the dual phase sensing. Contact angle measurements confirm the behavior further. The thermal properties and crystallinity of the composites are also addressed by the thermogravimetric and differential scanning calorimetric studies. The developed oil sensor material is able to withstand extreme temperature condition as well. - Highlights: • We model a dual phase sensor capable of detecting oil in water. • A mechanism is proposed to correlate sensing with diffusion. • In situ polymerization helps in the uniform distribution of filler. • Polymer composite sensor could be used as stickers on oil pipelines.

  10. Non-von Neumann computing using plasmon particles interacting with phase change materials (Conference Presentation)

    Science.gov (United States)

    Saiki, Toshiharu

    2016-09-01

    Control of localized surface plasmon resonance (LSPR) excited on metal nanostructures has drawn attention for applications in dynamic switching of plasmonic devices. As a reversible active media for LSPR control, chalcogenide phase-change materials (PCMs) such as GeSbTe (GST) are promising for high-contrast robust plasmonic switching. Owing to the plasticity and the threshold behavior during both amorphization and crystallization of PCMs, PCM-based LSPR switching elements possess a dual functionality of memory and processing. Integration of LSPR switching elements so that they interact with each other will allow us to build non-von-Neumann computing devices. As a specific demonstration, we discuss the implementation of a cellular automata (CA) algorithm into interacting LSPR switching elements. In the model we propose, PCM cells, which can be in one of two states (amorphous and crystalline), interact with each other by being linked by a AuNR, whose LSPR peak wavelength is determined by the phase of PCM cells on the both sides. The CA program proceeds by irradiating with a light pulse train. The local rule set is defined by the temperature rise in the PCM cells induced by the LSPR of the AuNR, which is subject to the intensity and wavelength of the irradiating pulse. We also investigate the possibility of solving a problem analogous to the spin-glass problem by using a coupled dipole system, in which the individual coupling strengths can be modified to optimize the system so that the exact solution can be easily reached. For this algorithm, we propose an implementation based on an idea that coupled plasmon particles can create long-range spatial correlations, and the interaction of this with a phase-change material allows the coupling strength to be modified.

  11. Modelling of phase change materials in the Toronto SUI net zero energy house using TRNSYS

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, O.; Fung, A.; Zhang, D. [Ryerson Polytechnic Univ., Toronto, ON (Canada). Dept. of Mechanical and Industrial Engineering

    2008-08-15

    In the context of building applications, phase change materials (PCM), can be defined as any heat storage material that can absorb a large amount of thermal energy while undergoing a change in phase, such as from a solid to a liquid phase. The incorporation of PCM into the building envelope can enhance occupant comfort through the reduction of indoor temperature fluctuations. It has also been shown to cause a decrease in the overall energy consumption associated with the heating and cooling of buildings. This paper extended the analysis of the impact of using PCM, which has traditionally focused on homes of ordinary construction, to incorporate low to zero energy homes using a model of the Toronto net zero energy house developed in TRNSYS. The paper provided a description of the TRNSYS model/methodology, with reference to the wall layer used in the net zero energy house, and model of the layout of the net zero energy house in TRYNSYS. The TRYNSYS/type 204 PCM component was also presented along with the simulation results in terms of the temperature profile of the third floor of the net zero energy house on a typical winter day with varying PCM concentrations; the temperature profile of the third floor of the net zero energy house on a typical summer day with varying PCM concentrations; yearly heating/cooling load requirements of the net zero energy house for a variety of thermal mass used; temperature profile of the third floor of the net zero energy house on a typical summer day when PCM and concrete slab was used; yearly temperature profile of the third floor of the net zero energy house, illustrating the impact of using PCM; and the yearly heating/cooling load of the net zero energy house as the concentration of PCM was varied. It was concluded that the use of building integrated PCM can reduce temperature fluctuations considerably in the summer but only slightly in the winter. 16 refs., 1 tab., 8 figs.

  12. Effect of expanded graphite on the phase change materials of high density polyethylene/wax blends

    Energy Technology Data Exchange (ETDEWEB)

    AlMaadeed, M.A., E-mail: m.alali@qu.edu.qa [Center for Advanced Materials, Qatar University, 2713 Doha (Qatar); Labidi, Sami [Center for Advanced Materials, Qatar University, 2713 Doha (Qatar); Krupa, Igor [QAPCO Polymer Chair, Center for Advanced Materials, Qatar University, P.O. Box 2713, Doha (Qatar); Karkri, Mustapha [Université Paris-Est CERTES, 61 avenue du Général de Gaulle, 94010 Créteil (France)

    2015-01-20

    Highlights: • Expanded graphite (EG) and low melting point (42.3 °C) wax were added to HDPE to form phase change material. • EG was well dispersed in the composites and did not affect the melting or crystallization of the HDPE matrix. • EG increased the thermal stability of the composites by reducing chain mobility and inhibiting degradation. • The addition of a relatively small quantity of EG enhances the heat conduction in the composite. • HDPE/40% RT42 that contained up to 15% EG demonstrated excellent mechanical and thermal properties and can be used as PCM. - Abstract: Phase change materials fabricated from high density polyethylene (HDPE) blended with 40 or 50 wt% commercial wax (melting point of 43.08 °C) and up to 15 wt% expanded graphite (EG) were studied. Techniques including scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and an experimental device to measure diffusivity and conductivity (DICO) were used to determine the microstructural, mechanical and thermal properties of the composites. The composites possessed good mechanical properties. Additionally, no leaching was observed during material processing or characterization. Although the Young’s modulus increased with the addition of EG, no significant changes in tensile strength were detected. The maximum Young’s modulus achieved was 650 MPa for the HDPE/40% wax composite with 15 wt% EG. The EG was well dispersed within the composites and did not affect the melting or crystallization of the HDPE matrix. The incorporation of EG increased the thermal stability of the composites by reducing chain mobility and inhibiting degradation. The intensification of thermal conductivity occurred with increasing fractions of EG, which was attributed to the high thermal conductivity of graphite. The maximum quantity of heat stored by latent heat was found for the HDPE/40% wax composite with EG. The addition of a relatively small quantity

  13. A 4-D dataset for validation of crystal growth in a complex three-phase material, ice cream

    Science.gov (United States)

    Rockett, P.; Karagadde, S.; Guo, E.; Bent, J.; Hazekamp, J.; Kingsley, M.; Vila-Comamala, J.; Lee, P. D.

    2015-06-01

    Four dimensional (4D, or 3D plus time) X-ray tomographic imaging of phase changes in materials is quickly becoming an accepted tool for quantifying the development of microstructures to both inform and validate models. However, most of the systems studied have been relatively simple binary compositions with only two phases. In this study we present a quantitative dataset of the phase evolution in a complex three-phase material, ice cream. The microstructure of ice cream is an important parameter in terms of sensorial perception, and therefore quantification and modelling of the evolution of the microstructure with time and temperature is key to understanding its fabrication and storage. The microstructure consists of three phases, air cells, ice crystals, and unfrozen matrix. We perform in situ synchrotron X-ray imaging of ice cream samples using in-line phase contrast tomography, housed within a purpose built cold-stage (-40 to +20oC) with finely controlled variation in specimen temperature. The size and distribution of ice crystals and air cells during programmed temperature cycling are determined using 3D quantification. The microstructural evolution of three-phase materials has many other important applications ranging from biological to structural and functional material, hence this dataset can act as a validation case for numerical investigations on faceted and non-faceted crystal growth in a range of materials.

  14. Mineralogical composition and phase-to-phase relationships in natural hydraulic lime and/or natural cement - raw materials and burnt products revealed by scanning electron microscopy

    Science.gov (United States)

    Kozlovcev, Petr; Přikryl, Richard; Racek, Martin; Přikrylová, Jiřina

    2016-04-01

    In contrast to modern process of production of cement clinker, traditional burning of natural hydraulic lime below sintering temperature relied on the formation of new phases from ion migration between neighbouring mineral grains composing raw material. The importance of the mineralogical composition and spatial distribution of rock-forming minerals in impure limestones used as a raw material for natural hydraulic lime presents not well explored issue in the scientific literature. To fill this gap, the recent study focuses in detailed analysis of experimentally burnt impure limestones (mostly from Barrandian area, Bohemian Massif). The phase changes were documented by optical microscopy, X-ray diffraction, and scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS) coupled with x-ray elemental mapping. The latest allowed for visualization of distribution of elements within raw materials and burnt products. SEM/EDS study brought valuable data on the presence of transitional and/or minor phases, which were poorly detectable by other methods.

  15. Phase Change Materials (PCMs for energy storage in architecture. Use with the Magic Box prototype

    Directory of Open Access Journals (Sweden)

    Bedoya Frutos, C.

    2008-09-01

    Full Text Available The article shows an energy-accumulation system in change of phase materials, designed for a prototype dwelling used for building two bioclimatic and self-sufficient buildings. These bulidings have been built in Madrid, Washington and Beijing. The characteristics of these materials, the construction systems into which these materials were incorporated, its comparative valuation with sensitive accumulation systems, and the results of the building monitorization are included.El artículo muestra un sistema de acumulación de energía en Materiales de Cambio de Fase diseñado para un prototipo de vivienda con el que se han construido dos edificios bioclimáticos y autosuficientes. Estos edificios se han realizado en Madrid, Washington y Pekín. Se incluyen las características de estos materiales, de los sistemas constructivos donde se integraron, su valoración comparativa con los sistemas de acumulación sensibles y los resultados de la monitorización del edificio.

  16. Braze Development of Graphite Fiber for Use in Phase Change Material Heat Sinks

    Science.gov (United States)

    Quinn, Gregory; Beringer, Woody; Gleason, Brian; Stephan, Ryan

    2011-01-01

    Hamilton Sundstrand (HS), together with NASA Johnson Space Center, developed methods to metallurgically join graphite fiber to aluminum. The goal of the effort was to demonstrate improved thermal conductance, tensile strength and manufacturability compared to existing epoxy bonded techniques. These improvements have the potential to increase the performance and robustness of phase change material heat sinks that use graphite fibers as an interstitial material. Initial work focused on evaluating joining techniques from four suppliers, each consisting of a metallization step followed by brazing or soldering of one inch square blocks of Fibercore graphite fiber material to aluminum end sheets. Results matched the strength and thermal conductance of the epoxy bonded control samples, so two suppliers were down-selected for a second round of braze development. The second round of braze samples had up to a 300% increase in strength and up to a 132% increase in thermal conductance over the bonded samples. However, scalability and repeatability proved to be significant hurdles with the metallization approach. An alternative approach was pursued which used a nickel braze allow to prepare the carbon fibers for joining with aluminum. Initial results on sample blocks indicate that this approach should be repeatable and scalable with good strength and thermal conductance when compared with epoxy bonding.

  17. Water solar distiller productivity enhancement using concentrating solar water heater and phase change material (PCM

    Directory of Open Access Journals (Sweden)

    Miqdam T. Chaichan

    2015-03-01

    Full Text Available This paper investigates usage of thermal energy storage extracted from concentrating solar heater for water distillation. Paraffin wax selected as a suitable phase change material, and it was used for storing thermal energy in two different insulated treasurers. The paraffin wax is receiving hot water from concentrating solar dish. This solar energy stored in PCM as latent heat energy. Solar energy stored in a day time with a large quantity, and some heat retrieved for later use. Water’s temperature measured in a definite interval of time. Four cases were studied: using water as storage material with and without solar tracker. Also, PCM was as thermal storage material with and without solar tracker.The system working time was increased to about 5 h with sun tracker by concentrating dish and adding PCM to the system. The system concentrating efficiency, heating efficiency, and system productivity, has increased by about 64.07%, 112.87%, and 307.54%, respectively. The system working time increased to 3 h when PCM added without sun tracker. Also, the system concentrating efficiency increased by about 50.47%, and the system heating efficiency increased by about 41.63%. Moreover, the system productivity increased by about 180%.

  18. Thermophysical and Mechanical Properties of Hardened Cement Paste with Microencapsulated Phase Change Materials for Energy Storage

    Directory of Open Access Journals (Sweden)

    Hongzhi Cui

    2014-12-01

    Full Text Available In this research, structural-functional integrated cement-based materials were prepared by employing cement paste and a microencapsulated phase change material (MPCM manufactured using urea-formaldehyde resin as the shell and paraffin as the core material. The encapsulation ratio of the MPCM could reach up to 91.21 wt%. Thermal energy storage cement pastes (TESCPs incorporated with different MPCM contents (5%, 10%, 15%, 20% and 25% by weight of cement were developed, and their thermal and mechanical properties were studied. The results showed that the total energy storage capacity of the hardened cement specimens with MPCM increased by up to 3.9-times compared with that of the control cement paste. The thermal conductivity at different temperature levels (35–36 °C, 55–56 °C and 72–74 °C decreased with the increase of MPCM content, and the decrease was the highest when the temperature level was 55–56 °C. Moreover, the compressive strength, flexural strength and density of hardened cement paste decreased with the increase in MPCM content linearly. Among the evaluated properties, the compressive strength of TESCPs had a larger and faster degradation with the increase of MPCM content.

  19. Binding Materials of Dehydrated Phases of Waste Hardened Cement Paste and Pozzolanic Admixture

    Institute of Scientific and Technical Information of China (English)

    LU Linnu; HE Yongjia; HU Shuguang

    2009-01-01

    Fly ash (FA) and ground granulated blast-furnace slag (GGBFS) were added to improve the performances of regenerated binding materials (RBM) which refer to dehydrated phases with rebinding ability of waste hardened cement paste. Flowability tests, compressive strength tests,SEM, TG-DSC, and non-evaporable water content tests were employed to study the performances of the combined binding materials and the interactions between RBM, FA, and GGBFS. Results show that adding FA or GGBFS can improve the workability of RBM paste, and GGBFS has positive effects on strength of RBM. Pozzolanic reactions happen between RBM, FA, and GGBFS. And the activation effect of RBM to FA and GGBFS is superior to that of P.O grade-32.5 cement, especially at earlier ages, because of the high reactive f-CaO existing in RBM. On the advantages of the synergetic effects of RBM and pozzolanic admixtures such as FA and GGBFS, new combined binding materials can be prepared by blending them together.

  20. Processing and characterization of phase boundaries in ceramic and metallic materials

    Science.gov (United States)

    Zeng, Liang

    The goal of this dissertation work was to explore and describe advanced characterization of novel materials processing. These characterizations were carried out using scanning and transmission electron microscopy (SEM and TEM), and X-ray diffraction techniques. The materials studied included ceramics and metallic materials. The first part of this dissertation focuses on the processing, and the resulting interfacial microstructure of ceramics joined using spin-on interlayers. SEM, TEM, and indentation tests were used to investigate the interfacial microstructural and mechanical property evolution of polycrystalline zirconia bonded to glass ceramic MaCor(TM), and polycrystalline alumina to single crystal alumina. Interlayer assisted specimens were joined using a thin amorphous silica interlayer. This interlayer was produced by spin coating an organic based silica bond material precursor and curing at 200°C, followed by joining in a microwave cavity or conventional electric furnace. Experimental results indicate that in the joining of the zirconia and MaCor(TM) no significant interfacial microstructural and mechanical property differences developed between materials joined either with or without interlayers, due to the glassy nature of MaCor(TM). The bond interface was non-planar, as a result of the strong wetting of MaCor(TM) and silica and dissolution of the zirconia. However, without the aid of a silica interlayer, sapphire and 98% polycrystalline alumina failed to join under the experimental conditions under this study. A variety of interfacial morphologies have been observed, including amorphous regions, fine crystalline alumina, and intimate contact between the sapphire and polycrystalline alumina. In addition, the evolution of the joining process from the initial sputter-cure to the final joining state and joining mechanisms were characterized. The second part of this dissertation focused on the effects of working and heat treatment on microstructure, texture

  1. On consistent micromechanical estimation of macroscopic elastic energy, coherence energy and phase transformation strains for SMA materials

    Science.gov (United States)

    Ziółkowski, Andrzej

    2017-01-01

    An apparatus of micromechanics is used to isolate the key ingredients entering macroscopic Gibbs free energy function of a shape memory alloy (SMA) material. A new self-equilibrated eigenstrains influence moduli (SEIM) method is developed for consistent estimation of effective (macroscopic) thermostatic properties of solid materials, which in microscale can be regarded as amalgams of n-phase linear thermoelastic component materials with eigenstrains. The SEIM satisfy the self-consistency conditions, following from elastic reciprocity (Betti) theorem. The method allowed expressing macroscopic coherency energy and elastic complementary energy terms present in the general form of macroscopic Gibbs free energy of SMA materials in the form of semilinear and semiquadratic functions of the phase composition. Consistent SEIM estimates of elastic complementary energy, coherency energy and phase transformation strains corresponding to classical Reuss and Voigt conjectures are explicitly specified. The Voigt explicit relations served as inspiration for working out an original engineering practice-oriented semiexperimental SEIM estimates. They are especially conveniently applicable for an isotropic aggregate (composite) composed of a mixture of n isotropic phases. Using experimental data for NiTi alloy and adopting conjecture that it can be treated as an isotropic aggregate of two isotropic phases, it is shown that the NiTi coherency energy and macroscopic phase strain are practically not influenced by the difference in values of austenite and martensite elastic constants. It is shown that existence of nonzero fluctuating part of phase microeigenstrains field is responsible for building up of so-called stored energy of coherency, which is accumulated in pure martensitic phase after full completion of phase transition. Experimental data for NiTi alloy show that the stored coherency energy cannot be neglected as it considerably influences the characteristic phase transition

  2. On consistent micromechanical estimation of macroscopic elastic energy, coherence energy and phase transformation strains for SMA materials

    Science.gov (United States)

    Ziółkowski, Andrzej

    2016-09-01

    An apparatus of micromechanics is used to isolate the key ingredients entering macroscopic Gibbs free energy function of a shape memory alloy (SMA) material. A new self-equilibrated eigenstrains influence moduli (SEIM) method is developed for consistent estimation of effective (macroscopic) thermostatic properties of solid materials, which in microscale can be regarded as amalgams of n-phase linear thermoelastic component materials with eigenstrains. The SEIM satisfy the self-consistency conditions, following from elastic reciprocity (Betti) theorem. The method allowed expressing macroscopic coherency energy and elastic complementary energy terms present in the general form of macroscopic Gibbs free energy of SMA materials in the form of semilinear and semiquadratic functions of the phase composition. Consistent SEIM estimates of elastic complementary energy, coherency energy and phase transformation strains corresponding to classical Reuss and Voigt conjectures are explicitly specified. The Voigt explicit relations served as inspiration for working out an original engineering practice-oriented semiexperimental SEIM estimates. They are especially conveniently applicable for an isotropic aggregate (composite) composed of a mixture of n isotropic phases. Using experimental data for NiTi alloy and adopting conjecture that it can be treated as an isotropic aggregate of two isotropic phases, it is shown that the NiTi coherency energy and macroscopic phase strain are practically not influenced by the difference in values of austenite and martensite elastic constants. It is shown that existence of nonzero fluctuating part of phase microeigenstrains field is responsible for building up of so-called stored energy of coherency, which is accumulated in pure martensitic phase after full completion of phase transition. Experimental data for NiTi alloy show that the stored coherency energy cannot be neglected as it considerably influences the characteristic phase transition

  3. Design and Analysis of Phase Change Material based thermal energy storage for active building cooling: a Review

    Directory of Open Access Journals (Sweden)

    Nitin .D. Patil

    2012-06-01

    Full Text Available Phase Change Materials (PCMs are "latent" thermal storage materials. They use chemical bonds to store and release heat. The thermal energy transfer occurs when a material changes from a solid to a liquid orfrom a liquid to a solid form. This is called a change in state or "phase." Initially, these solid-liquid PCMs perform like conventional storage materials; their temperature rises as they absorb solar heat. Unlike conventional heat storage materials, when PCMs reach the temperature at which they change phase (their melting point, they absorb large amounts of heat without getting hotter. When the ambient temperature in the space around the PCM material drops, the Phase Change Material solidifies, releasing its stored latent heat. PCMs absorb and emit heat while maintaining a nearly constant temperature. Within the human comfort and electronic-equipment tolerance range of 20°C to 35°C, latent thermal storage materials are very effective.They can be used for equalization of day & night temperature and for transport of refrigerated products. In the proposed project heat of fusion of Cacl2. 6H2o as PCM is used for cooling water during night and this cooled water is used as circulating medium trough fan coil unit, air trough FCU will get cooled by transferring heat to water and fresh & cool air will be thrown in a room. In the proposed project FREE COOLING & ACTIVE BUILDING COOLING concepts of Thermal Energy Storage are used in combine

  4. Preparation, characterization, and thermal properties of starch microencapsulated fatty acids as phase change materials thermal energy storage applications

    Science.gov (United States)

    Stable starch-oil composites can be prepared from renewable resources by excess steam jet-cooking aqueous slurries of starch and vegetable oils or other hydrophobic materials. Fatty acids such as stearic acid are promising phase change materials (PCMs) for latent heat thermal energy storage applica...

  5. Phase field model for optimization of multi-material structural topology in two and three dimensions

    Science.gov (United States)

    Zhou, Shiwei

    The Optimization of Structural Topology (OST) is a breakthrough in product design because it can optimize size, shape and topology synchronously under different physical constraints. It has promising applications in industry ranging from automobile and aerospace engineering to micro electromechanical system. This dissertation first substitutes the nonlinear diffusion method for filter process in the optimization of structural topology. Filtering has been a major technique used in a homogenization-based method for topology optimization of structures. It plays a key role in regularizing the basic problem into a well-behaved setting. But it has a drawback of smoothing effect around the boundary of material domain. A diffusion technique is presented here as a variational approach to the regularization of the topology optimization problem. A nonlinear or anisotropic diffusion process not only leads to a suitable problem regularization but also exhibits strong "edge"-preserving characteristics. Thus, it shows that the use of the nonlinear diffusions brings desirable effects of boundary preservation and even enhancement of lower-dimensional features such as flow-like structures. The proposed diffusion techniques have a close relationship with the diffusion methods and the phase-field methods of the fields of materials and digital image processing. Then this dissertation introduces a gradient flow in the norm of H-1 for the problem of multi-material structural topology optimization in 2/3D with a generalized Cahn-Hilliard (C-H) model with elasticity. Unlike the traditional C-H model applied to spinodal separation which only has bulk energy and interface energy, the generalized model couples the macroscopic elastic energy (mean compliance) into the total free energy. As a result, the grain morphology is not random islands or zigzag web-like objects but regular truss or bar structure. Although disturbed by elastic energy, the C-H system still keeps its two most important

  6. Study of multi-layer active magnetic regenerators using magnetocaloric materials with first and second order phase transition

    DEFF Research Database (Denmark)

    Lei, Tian; Engelbrecht, Kurt; Nielsen, Kaspar Kirstein;

    2016-01-01

    Magnetocaloric materials (MCM) with a first order phase transition (FOPT) usually exhibit a large, although sharp, isothermal entropy change near their Curie temperature, compared to materials with a second order phase transition (SOPT). Experimental results of applying FOPT materials in recent...... FOPT and SOPT materials is also of fundamental interest. We present modeling results of multi-layer AMRs using FOPT and SOPT materials based on a 1D numerical model. First the impact of isothermal entropy change, adiabatic temperature change and shape factor describing the temperature dependence...... magnetocaloric refrigerators (MCR) demonstrated the great potential for these materials, but a thorough study on the impact of the moderate adiabatic temperature change and strong temperature dependence of the magnetocaloric effect (MCE) is lacking. Besides, comparing active magnetic regenerators (AMR) using...

  7. Simulation and experimental study of thermal performance of a building roof with a phase change material (PCM)

    Indian Academy of Sciences (India)

    A Mannivannan; M T Jaffarsathiq Ali

    2015-12-01

    Latent heat storage in a phase change material (PCM) is very attractive because of its high-energy storage density and its isothermal behaviour during the phase change process. Low thermal conductivity of the walls and roof reduces the heat gain at a steady state condition. Chloride hexahydrate (CaCl26H2O) as a phase change material (PCM) for a room was proposed in this paper to control the indoor air temperature for a better thermal comfort for human beings. Building concrete roof with vertical cylindrical hole of 0.5 $\\times$ 0.5 m and array of 3 $\\times$ 3 filled with phase change material (PCM) was considered for analysis. A detailed thermal analysis was carried by both simulation and experimental study. Results showed that this type of PCM room can decrease the indoor air temperature fluctuation by a maximum of 4°C.

  8. A numerical model for thermal energy storage systems utilising encapsulated phase change materials

    Science.gov (United States)

    Jacob, Rhys; Saman, Wasim; Bruno, Frank

    2016-05-01

    In an effort to reduce the cost of thermal energy storage for concentrated solar power plants, a thermocline storage concept was investigated. Two systems were investigated being a sensible-only and an encapsulated phase change system. Both systems have the potential to reduce the storage tank volume and/or reduce the cost of the filler material, thereby reducing the cost of the system when compared to current two-tank molten salt systems. The objective of the current paper is to create a numerical model capable of designing and simulating the aforementioned thermocline storage concepts in the open source programming language known as Python. The results of the current study are compared to previous numerical results and are found to be in good agreement.

  9. Controlling Pickering Emulsion Destabilisation: A Route to Fabricating New Materials by Phase Inversion

    Directory of Open Access Journals (Sweden)

    Catherine P. Whitby

    2016-07-01

    Full Text Available The aim of this paper is to review the key findings about how particle-stabilised (or Pickering emulsions respond to stress and break down. Over the last ten years, new insights have been gained into how particles attached to droplet (and bubble surfaces alter the destabilisation mechanisms in emulsions. The conditions under which chemical demulsifiers displace, or detach, particles from the interface were established. Mass transfer between drops and the continuous phase was shown to disrupt the layers of particles attached to drop surfaces. The criteria for causing coalescence by applying physical stress (shear or compression to Pickering emulsions were characterised. These findings are being used to design the structures of materials formed by breaking Pickering emulsions.

  10. Experimental Investigation of Thermal Conductivity of Concrete Containing Micro-Encapsulated Phase Change Materials

    DEFF Research Database (Denmark)

    Pomianowski, Michal Zbigniew; Heiselberg, Per; Jensen, Rasmus Lund

    2011-01-01

    The aim of increasing the building internal heat storage capacity is to be able to store excessive heat gains and by that reduce indoor high temperature peaks and at the same time shift high heat loads to the low heat loads hours and to decrease cooling energy need. The concept presented in this ......The aim of increasing the building internal heat storage capacity is to be able to store excessive heat gains and by that reduce indoor high temperature peaks and at the same time shift high heat loads to the low heat loads hours and to decrease cooling energy need. The concept presented...... in this article utilizes integration of the concrete and the microencapsulated Phase Change Material (PCM). PCM has the ability to absorb and release significant amounts of heat at a specific temperature range. As a consequence of admixing PCM to the concrete, new thermal properties like thermal conductivity...

  11. USE OF PHASE CHANGE MATERIAL (PCM FOR FROST PREVENTION IN A MODEL GREENHOUSE

    Directory of Open Access Journals (Sweden)

    Ahmet KÜRKLÜ

    1997-02-01

    Full Text Available In this study, the possibility of using phase change materials to prevent occurrance of frost in greenhouses during winter was investigated. The melting and freezing temperatures of the PCM were about 8 oC and 4 oC, respectively.The air temperature difference between the PCM and the control greenhouses was about 2oC on average during the day and night time, PCM greenhouse having the higher temperature at night and lower temperature during the day. Frost was prevented on 7 out of 9 occasions, though the temperature difference between the greenhouses was small for some of these days. Solar fraction stored by the PCM store was about 30 %.

  12. The Influence of Phase Change Materials on the Properties of Self-Compacting Concrete

    Directory of Open Access Journals (Sweden)

    Miguel Ángel Álvarez

    2013-08-01

    Full Text Available The aim of this paper is to research new thermally-efficient concrete walls, analyzing the mechanical behavior of a self-compacting concrete to manufacture an uncoated solid structural panel, with the incorporation of a micro-encapsulated phase change material as additive. Different dosages are tested and mechanical properties of the product obtained from the molding of concrete specimens are evaluated, testing mechanical compressive strength, slump flow, and density. The results reveal the optimum percentage of additive in the mixture that enables compliance with the technical specifications required by the product to be manufactured. A test is also performed for measuring the thermal conductivity for the optimal sample obtained and it evidences the reduction thereof.

  13. Thermal cycling test of few selected inorganic and organic phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Anant; Sawhney, R.L. [Thermal Energy Storage Laboratory, School of Energy and Environmental Studies, Devi Ahilya University, Takshashila Campus, Indore 452001, M.P. (India); Buddhi, D. [Green Hi-Tech Energy Pvt. Ltd., Bari Brahmmana, Adda Sarore, Jammu 180011, Jammu and Kashmir (India)

    2008-12-15

    Thermal cycling tests were performed to check the stability in thermal energy storage systems on some selected organic and inorganic phase change materials (PCMs). The possibility of using these PCMs in thermal energy storage systems were examined on the basis of thermal, chemical and kinetic criteria. Organic and inorganic PCMs were selected to check their thermal stability. Inorganic PCMs were not found suitable after some cycles while thermal cycling for organic PCMs were undertaken up to 1000 thermal cycles and has shown a gradual change in melting temperature and latent heat of fusion. The PCMs were then checked with differential scanning calorimeter (DSC) for their latent heat storage capacity and melting temperature change. (author)

  14. Dynamic thermal behavior of building using phase change materials for latent heat storage

    Directory of Open Access Journals (Sweden)

    Selka Ghouti

    2015-01-01

    Full Text Available This study presents a two-dimensional model with a real size home composed of two-storey (ground and first floor spaces separated by a slab, enveloped by a wall with rectangular section containing phase change material (PCM in order to minimize energy consumption in the buildings. The main objective of the PCM-wall system is to decrease the temperature change from outdoor space before it reaches the indoor space during the daytime. The numerical approach uses effective heat capacity Ceff model with realistic outdoor climatic conditions of Tlemcen city, Algeria. The numerical results showed that by using PCM in wall as energy storage components may reduce the room temperature by about 6 to 7°C of temperature depending on the floor level (first floor spaces or ground floor spaces.

  15. A Numerical Algorithm for the Solution of a Phase-Field Model of Polycrystalline Materials

    Energy Technology Data Exchange (ETDEWEB)

    Dorr, M R; Fattebert, J; Wickett, M E; Belak, J F; Turchi, P A

    2008-12-04

    We describe an algorithm for the numerical solution of a phase-field model (PFM) of microstructure evolution in polycrystalline materials. The PFM system of equations includes a local order parameter, a quaternion representation of local orientation and a species composition parameter. The algorithm is based on the implicit integration of a semidiscretization of the PFM system using a backward difference formula (BDF) temporal discretization combined with a Newton-Krylov algorithm to solve the nonlinear system at each time step. The BDF algorithm is combined with a coordinate projection method to maintain quaternion unit length, which is related to an important solution invariant. A key element of the Newton-Krylov algorithm is the selection of a preconditioner to accelerate the convergence of the Generalized Minimum Residual algorithm used to solve the Jacobian linear system in each Newton step. Results are presented for the application of the algorithm to 2D and 3D examples.

  16. Flow frictional characteristics of microencapsulated phase change material suspensions flowing through rectangular minichannels

    Institute of Scientific and Technical Information of China (English)

    RAO; Yu; Frank; Dammel; Peter; Stephan; LIN; Guiping

    2006-01-01

    An experimental investigation was conducted on the laminar flow frictional characteristics of suspensions with microencapsulated phase change material (MEPCM) in water flowing through rectangular copper minichannels. The MEPCM was provided at an average particle size of 4.97 μm, and was mixed with distilled water to form suspensions with various mass concentrations ranging from 0 to 20%. The experiment was performed to explore the effect of MEPCM mass concentration on friction factor and pressure drop in the minichannels. The Reynolds number ranged from 200 to 2000 to provide laminar and transitional flows. It was found that the experimental data for the suspensions with 0 and 5% concentration agree well with the existing theoretical data for an incompressible, fully developed, laminar Newtonian flow. For the suspensions with mass concentrations higher than 10%, there is an obvious increase in friction factor and pressure drop in comparison with laminar Newtonian flow.

  17. Thermal energy storage system using phase change materials: Constant heat source

    Directory of Open Access Journals (Sweden)

    Reddy Meenakshi R.

    2012-01-01

    Full Text Available The usage of phase change materials (PCM to store the heat in the form of latent heat is increased, because large quantity of thermal energy is stored in smaller volumes. In the present experimental investigation paraffin and stearic acid are employed as PCMs in thermal energy storage (TES system to store the heat as sensible and latent heat also. A constant heat source is used to supply heat transfer fluid (HTF at constant temperature to the TES system. In the TES system PCMs are stored in the form of spherical capsules of 38 mm diameter made of high density poly ethylene (HDPE. The results of the investigation are related to the charging time and recovery of stored energy from the TES system.

  18. Solar thermal charging properties of graphene oxide embedded myristic acid composites phase change material

    Science.gov (United States)

    Yadav, Apurv; Barman, Bidyut; Kumar, Vivek; Kardam, Abhishek; Narayanan, S. Shankara; Verma, Abhishek; Madhwal, Devinder; Shukla, Prashant; Jain, V. K.

    2016-05-01

    The present paper reports the heat transfer characteristics of graphene oxide (GO) embedded myristic acid based phase change material (GO-PCM) composites. By varying concentrations of GO (0.1-0.5 wt%), different GO-PCM composites were preapred. Two different experimental setups were used for investigating the heat transfer characteristics of the prepared GO-PCM composites during the melting and solidification processes: (i) conventional heating and (ii) solar illumination. The experimental observations indicated a higher heat transfer rate in the GO-PCM composites as compared to pristine PCM for both experimental setups. From the experimental results of conventional heating setup, it was observed that the melting and solidification rate for GO-PCM composites, at 0.5 wt% of GO, increased by 48% and 70%, respectively in comparison to pristine PCM. The experimental results using solar illumination setup demonstrated an ultrafast heating rate for GO-PCM composites than the conventional heating based approach.

  19. Phase change material solidification in a finned cylindrical shell thermal energy storage: An approximate analytical approach

    Directory of Open Access Journals (Sweden)

    Mosaffa Amirhossein

    2013-01-01

    Full Text Available Results are reported of an investigation of the solidification of a phase change material (PCM in a cylindrical shell thermal energy storage with radial internal fins. An approximate analytical solution is presented for two cases. In case 1, the inner wall is kept at a constant temperature and, in case 2, a constant heat flux is imposed on the inner wall. In both cases, the outer wall is insulated. The results are compared to those for a numerical approach based on an enthalpy method. The results show that the analytical model satisfactory estimates the solid-liquid interface. In addition, a comparative study is reported of the solidified fraction of encapsulated PCM for different geometric configurations of finned storage having the same volume and surface area of heat transfer.

  20. Optimizing the performance of phase-change materials in personal protective clothing systems.

    Science.gov (United States)

    Reinertsen, Randi Eidsmo; Faerevik, Hilde; Holbø, Kristine; Nesbakken, Ragnhild; Reitan, Jarl; Røyset, Arne; Suong Le Thi, Maria

    2008-01-01

    Phase-change materials (PCM) can be used to reduce thermal stress and improve thermal comfort for workers wearing protective clothing. The aim of this study was to investigate the effect of PCM in protective clothing used in simulated work situations. We hypothesized that it would be possible to optimize cooling performance with a design that focuses on careful positioning of PCM, minimizing total insulation and facilitating moisture transport. Thermal stress and thermal comfort were estimated through measurement of body heat production, body temperatures, sweat production, relative humidity in clothing and subjective ratings of thermal comfort, thermal sensitivity and perception of wetness. Experiments were carried out using 2 types of PCM, the crystalline dehydrate of sodium sulphate and microcapsules in fabrics. The results of 1 field and 2 laboratory experimental series were conclusive in that reduced thermal stress and improved thermal comfort were related to the amount and distribution of PCM, reduced sweat production and adequate transport of moisture.

  1. A new method for measuring the thermal regulatory properties of phase change material (PCM) fabrics

    Science.gov (United States)

    Wan, X.; Fan, J.

    2009-02-01

    Several methods already exist for the measurement of the thermal regulatory properties of fabrics containing phase change materials (PCMs). However, they do not adequately simulate the actual use condition; consequently the measurements may not have relevance to the performance of PCM fabrics in actual use. Here we report on the development of a new method, which better simulates the real use situation. In this method, a hot plate, simulating the human body, generates a constant amount of heat depending on the type of human activity to be simulated. The hot plate covered by the PCM fabric is then exposed to a thermal transient simulating a wearer moving from one thermal environment to another; the changes of surface temperature and heat loss of the hot plate are then recorded and used to characterize the thermal regulatory properties of the PCM fabrics.

  2. Formation and phase separation during the smelting of sulfide raw materials

    Science.gov (United States)

    Tarasov, A. V.; Paretsky, V. M.

    2009-10-01

    This paper discusses the most recent developments made at the Gintsvetmet Institute in technologies and equipment for single-stage autogenous smelting of copper sulfide raw materials to produce white metal and blister copper. In particular, the oxygen-flame smelting process and separation of highly basic calcium-containing slags are considered. This technology includes the oxygen-flame smelting process (KFP Process) to produce highly basic self-disintegrating ferrite-calcium slags with their subsequent flotation to recover copper. Also included is a sparging smelting process (FBP Process) to produce combined slags subjected to decopperizing inside the same furnace. Results of special investigations of the slag structure obtained in the KFP and FBP processes and substantiating selection of their chemical and phase composition are presented. These processes meet stringent requirements for advanced technologies with respect to energy conservation and environmental safety with different scales of production and within a wide range of specific conditions of particular operations.

  3. Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I

    Science.gov (United States)

    Thibeault, Sheila A.; Fay, Catharine C.; Lowther, Sharon E.; Earle, Kevin D.; Sauti, Godfrey; Kang, Jin Ho; Park, Cheol; McMullen, Amelia M.

    2012-01-01

    than possible with hydrogen storage; however, a systematic experimental hydrogenation study has not been reported. A combination of the two approaches may be explored to provide yet higher hydrogen content. The hydrogen containing BNNT produced in our study will be characterized for hydrogen content and thermal stability in simulated space service environments. These new materials systems will be tested for their radiation shielding effectiveness against high energy protons and high energy heavy ions at the HIMAC facility in Japan, or a comparable facility. These high energy particles simulate exposure to SEP and GCR environments. They will also be tested in the LaRC Neutron Exposure Laboratory for their neutron shielding effectiveness, an attribute that determines their capability to shield against the secondary neutrons found inside structures and on lunar and planetary surfaces. The potential significance is to produce a radiation protection enabling technology for future exploration missions. Crew on deep space human exploration missions greater than approximately 90 days cannot remain below current crew Permissible Exposure Limits without shielding and/or biological countermeasures. The intent of this research is to bring the Agency closer to extending space missions beyond the 90-day limit, with 1 year as a long-term goal. We are advocating a systems solution with a structural materials component. Our intent is to develop the best materials system for that materials component. In this Phase I study, we have shown, computationally, that hydrogen containing BNNT is effective for shielding against GCR, SEP, and neutrons over a wide range of energies. This is why we are focusing on hydrogen containing BNNT as an innovative advanced concept. In our future work, we plan to demonstrate, experimentally, that hydrogen, boron, and nitrogen based materials can provide mechanically strong, thermally stable, structural materials with effective radiation shielding against GCR

  4. Relationship between magnetic Barkhausen noise and the stresses, the hardness and the phase content of ferromagnetic materials

    Institute of Scientific and Technical Information of China (English)

    QI Xin; HOU Zhi-ling; TIAN Jian-long

    2005-01-01

    Magnetic Barkhausen Noise (MBN) is a phenomenon of electromagnetic energy emission due to the movement of magnetic domain walls inside ferromagnetic materials when they are locally magnetized by an altercoil attached to the surface of the material being magnetized and the noise carries the message of the characteristics of the material such as stresses, hardness, phase content, etc. Based on the characteristic of the noise, research about the relationship between the welding stresses in the welding assembly and the noise, the fatigue damage of the plate structure and the noise, and the influence of heat treatment and the variation of phase content to the noise are carried out in this paper.

  5. POTENTIAL USE OF PHASE CHANGE MATERIALS IN GREENHOUSES HEATING: COMPARISON WITH A TRADITIONAL SYSTEM

    Directory of Open Access Journals (Sweden)

    Claudio Caprara

    2009-09-01

    Full Text Available In order to use solar radiation as thermal energy source, heat storage equipments result necessary in each application where continuous supply is required, because of the natural unsteady intensity of radiation during the day. Thermal solar collectors are especially suitable for low temperature applications, since their efficiency decreases when an high inlet temperature of fluid flowing through them is established. On the other hand, low temperatures and low temperature gaps, above all, make very difficult to use traditional sensible heat storing units (water tanks, because of the very large amounts of material required. In this work, a traditional sensible heat storage system is compared with a latent heat storing unit based on phase change materials (PCMs. As a case study, a 840 m3 greenhouse heating application was considered with an inside constant temperature of 18°C. It is thought to be heated by using single layer plate thermal solar collectors as energy source. Inlet temperature of the collectors fluid (HTF was fixed at 35°C (little higher than melting temperature of PCMs and a constant flux of 12 l/m2 hour was established as technical usual value. At these conditions, 215m2 solar panels exposed surface resulted necessary. The sensible heat storage system considered here is a traditional water tank storing unit equipped with two pipe coils, respectively for heat exchanges with HTF from collectors and water flux for greenhouse heating. Available DT for heat exchange is estimated as the difference of minimum HTF temperature (in outlet from the collectors and the required water temperature for greenhouse heating. The latent heat storing unit is instead a series of copper rectangular plate shells which a phase change material is filled in (Na2SO4⋅10H2O. Heat transfer fluids flow through thin channels between adjacent plates, so that a large heat exchange available surface is achieved. The developed computational model (Labview software

  6. A Phase-Conjugate-Mirror Inspired Approach for Building Cloaking Structures with Left-handed Materials.

    Science.gov (United States)

    Zheng, Guoan; Heng, Xin; Yang, Changhuei

    2009-01-01

    A phase conjugate mirror (PCM) has a remarkable property of cancellation the back-scattering wave of the lossless scatterers. The similarity of a phase conjugate mirror to the interface of a matched RHM (right-handed material) and a LHM (left-handed material) prompts us to explore the potentials of using the RHM-LHM structure to achieve the anti-scattering property of the PCM. In this paper, we present two such structures. The first one is a RHM-LHM cloaking structure with a lossless arbitrary-shape scatterer imbedded in the RHM and its left-handed duplicate imbedded in the matched LHM. It is shown that such a structure is transparent to the incident electromagnetic (EM) field. As a special case of this structure, we proposed an EM tunnel that allows EM waves to spatially transport to another location in space without significant distortion and reflection. The second one is an RHM-PEC (perfect electric conductor)-LHM cloaking structure, which is composed of a symmetric conducting shell embedded in the interface junction of an RHM and the matched LHM layer. Such a structure presents an anomalously small scattering cross-section to an incident propagating EM field, and the interior of the shell can be used to shield small objects (size comparable to the wavelength) from interrogation. We report the results of 2D finite-element-method (FEM) simulations that were performed to verify our idea, and discuss the unique properties of the proposed structures as well as their limitations.

  7. A Liquid-Liquid Thermoelectric Heat Exchanger as a Heat Pump for Testing Phase Change Material Heat Exchangers

    Science.gov (United States)

    Sheth, Rubik B.; Makinen, Janice; Le, Hung V.

    2016-01-01

    The primary objective of the Phase Change HX payload on the International Space Station (ISS) is to test and demonstrate the viability and performance of Phase Change Material Heat Exchangers (PCM HX). The system was required to pump a working fluid through a PCM HX to promote the phase change material to freeze and thaw as expected on Orion's Multipurpose Crew Vehicle. Due to limitations on ISS's Internal Thermal Control System, a heat pump was needed on the Phase Change HX payload to help with reducing the working fluid's temperature to below 0degC (32degF). This paper will review the design and development of a TEC based liquid-liquid heat exchanger as a way to vary to fluid temperature for the freeze and thaw phase of the PCM HX. Specifically, the paper will review the design of custom coldplates and sizing for the required heat removal of the HX.

  8. IFMIF (International Fusion Materials Irradiation Facility) key element technology phase task description

    Energy Technology Data Exchange (ETDEWEB)

    Ida, M.; Nakamura, H.; Sugimoto, M.; Yutani, T.; Takeuchi, H. [eds.] [Japan Atomic Energy Research Inst., Tokai Research Establishment, Fusion Neutron Laboratory, Tokai, Ibaraki (Japan)

    2000-08-01

    In 2000, a 3 year Key Element technology Phase (KEP) of the International Fusion Materials Irradiation Facility (IFMIF) has been initiated to reduce the key technology risk factors needed to achieve continuous wave (CW) beam with the desired current and energy and to reach the corresponding power handling capabilities in the liquid lithium target system. In the KEP, the IFMIF team (EU, Japan, Russian Federation, US) will perform required tasks. The contents of the tasks are described in the task description sheet. As the KEP tasks, the IFMIF team have proposed 27 tasks for Test Facilities, 12 tasks for Target, 26 tasks for Accelerator and 18 tasks for Design Integration. The task description by RF is not yet available. The task items and task descriptions may be added or revised with the progress of KEP activities. These task description sheets have been compiled in this report. After 3 years KEP, the results of the KEP tasks will be reviewed. Following the KEP, 3 years Engineering Validation Phase (EVP) will continue for IFMIF construction. (author)

  9. Fourth-order strain-gradient phase mixture model for nanocrystalline fcc materials

    Science.gov (United States)

    Klusemann, Benjamin; Bargmann, Swantje; Estrin, Yuri

    2016-12-01

    The proposed modeling approach for nanocrystalline materials is an extension of the local phase mixture model introduced by Kim et al (2000 Acta Mater. 48 493-504). Local models cannot account for any non-uniformities or strain patterns, i.e. such models describe the behavior correctly only as long as it is homogeneous. In order to capture heterogeneities, the phase mixture model is augmented with gradient terms of higher order, namely second and fourth order. Different deformation mechanisms are assumed to operate in grain interior and grain boundaries concurrently. The deformation mechanism in grain boundaries is associated with diffusional mass transport along the boundaries, while in the grain interior dislocation glide as well as diffusion controlled mechanisms are considered. In particular, the mechanical response of nanostructured polycrystals is investigated. The model is capable of correctly predicting the transition of flow stress from Hall-Petch behavior in conventional grain size range to an inverse Hall-Petch relation in the nanocrystalline grain size range. The consideration of second- and fourth-order strain gradients allows non-uniformities within the strain field to represent strain patterns in combination with a regularization effect. Details of the numerical implementation are provided.

  10. Liquid phase crystallized silicon on glass: Technology, material quality and back contacted heterojunction solar cells

    Science.gov (United States)

    Haschke, Jan; Amkreutz, Daniel; Rech, Bernd

    2016-04-01

    Liquid phase crystallization has emerged as a novel approach to grow large grained polycrystalline silicon films on glass with high electronic quality. In recent years a lot of effort was conducted by different groups to determine and optimize suitable interlayer materials, enhance the crystallographic quality or to improve post crystallization treatments. In this paper, we give an overview on liquid phase crystallization and describe the necessary process steps and discuss their influence on the absorber properties. Available line sources are compared and different interlayer configurations are presented. Furthermore, we present one-dimensional numerical simulations of a rear junction device, considering silicon absorber thicknesses between 1 and 500 µm. We vary the front surface recombination velocity as well as doping density and minority carrier lifetime in the absorber. The simulations suggest that a higher absorber doping density is beneficial for layer thicknesses below 20 µm or when the minority carrier lifetime is short. Finally, we discuss possible routes for device optimization and propose a hybride cell structure to circumvent current limitations in device design.

  11. Thermal Characterization of Lauric-Stearic Acid/Expanded Graphite Eutectic Mixture as Phase Change Materials.

    Science.gov (United States)

    Zhu, Hua; Zhang, Peng; Meng, Zhaonan; Li, Ming

    2015-04-01

    The eutectic mixture of lauric acid (LA) and stearic acid (SA) is a desirable phase change material (PCM) due to the constant melting temperature and large latent heat. However, its poor thermal conductivity has hampered its broad utilization. In the present study, pure LA, SA and the mixtures with various mass fractions of LA-SA were used as the basic PCMs, and 10 wt% expanded graphite (EG) was added to enhance the thermal conductivities. The phase change behaviors, microstructural analysis, thermal conductivities and thermal stabilities of the mixtures of PCMs were investigated by differential scanning calorimetry (DSC), scanning electronic microscope (SEM), transient plane source (TPS) and thermogravimetric analysis (TGA), respectively. The results show that the LA-SA binary mixture of mixture ratio of 76.3 wt%: 23.7 wt% forms an eutectic mixture, which melts at 38.99 °C and has a latent heat of 159.94 J/g. The melted fatty acids are well absorbed by the porous network of EG and they have a good thermal stability. Furthermore, poor thermal conductivities can be well enhanced by the addition of EG.

  12. Study on the melting process of phase change materials in metal foams using lattice Boltzmann method

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A thermal lattice Boltzmann model is developed for the melting process of phase change material (PCM) embedded in open-cell metal foams. Natural convection in the melt PCM is considered. Under the condition of local thermal non-equilibrium between the metal matrix and PCM, two evolution equations of temperature distribution function are pre-sented through selecting an equilibrium distribution function and a nonlinear source term properly. The enthalpy-based method is employed to copy with phase change problem. Melting process in a cavity of the metal foams is simulated using the present model. The melting front locations and the temperature distributions in the metal foams filled with PCM are obtained by the lattice Boltzmann method. The effects of the porosity and pore size on the melting are also investigated and discussed. The re-sults indicate that the effects of foam porosity play important roles in the overall heat transfer. For the lower porosity foams, the melting rate is comparatively greater than the higher porosity foams, due to greater heat conduction from metal foam with high heat conductivity. The foam pore size has a limited effect on the melting rate due to two counteracting effects between conduction and convection heat transfer.

  13. Reducing Pumping Power in Hydronic Heating and Cooling Systems with Microencapsulated Phase Change Material Slurries

    Science.gov (United States)

    Karas, Kristoffer Jason

    Phase change materials (PCMs) are being used increasingly in a variety of thermal transfer and thermal storage applications. This thesis presents the results of a laboratory study into the feasibility of improving the performance of hydronic heating and cooling systems by adding microcapsules filled with a PCM to the water used as heat transport media in these systems. Microencapsulated PCMs (MPCMs) increase the heat carrying capacity of heat transport liquids by absorbing or releasing heat at a constant temperature through a change of phase. Three sequences of tests and their results are presented: 1) Thermal cycling tests conducted to determine the melting temperatures and extent of supercooling associated with the MPCMs tested. 2) Hydronic performance tests in which MPCM slurries were pumped through a fin-and-tube, air-to-liquid heat exchanger and their thermal transfer performance compared against that of ordinary water. 3) Mechanical stability tests in which MPCM slurries were pumped in a continuous loop in order to gauge the extent of rupture due to pumping. It is shown that slurries consisting of water and MPCMs ˜ 14-24 mum in diameter improve thermal performance and offer the potential for power savings in the form of reduced pumping requirements. In addition, it is shown that while slurries of MPCMs 2-5 mum in diameter appear to exhibit better mechanical stability than slurries of larger diameter MPCMs, the smaller MPCMs appear to reduce the thermal performance of air-to-liquid heat exchangers.

  14. Anatase-rutile phase transformation of titanium dioxide bulk material: a DFT + U approach.

    Science.gov (United States)

    Vu, Nam H; Le, Hieu V; Cao, Thi M; Pham, Viet V; Le, Hung M; Nguyen-Manh, Duc

    2012-10-10

    The anatase-rutile phase transformation of TiO(2) bulk material is investigated using a density functional theory (DFT) approach in this study. According to the calculations employing the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional with the Vanderbilt ultrasoft pseudopotential, it is suggested that the anatase phase is more energetically stable than rutile, which is in variance with the experimental observations. Consequently, the DFT + U method is employed in order to predict the correct structural stability in titania from electronic-structure-based total energy calculations. The Hubbard U term is determined by examining the band structure of rutile with various values of U from 3 to 10 eV. At U = 5 eV, a theoretical bandgap for rutile is obtained as 3.12 eV, which is in very good agreement with the reported experimental bandgap. Hence, we choose the DFT + U method (with U = 5 eV) to investigate the transformation pathway using the newly-developed solid-state nudged elastic band (ss-NEB) method, and consequently obtain an intermediate transition structure that is 9.794 eV per four-TiO(2) above the anatase phase. When the Ti-O bonds in the transition state are examined using charge density analysis, seven Ti-O bonds (out of 24 bonds in the anatase unit cell) are broken, and this result is in excellent agreement with a previous experimental study (Penn and Banfield 1999 Am. Miner. 84 871-6).

  15. Atomic structure and electronic properties of the SixSb100-x phase-change memory material

    DEFF Research Database (Denmark)

    Verma, Ashok K.; Modak, Paritosh; Svane, Axel

    2011-01-01

    The electronic and structural properties of SixSb100-x (x∼16) materials are investigated using first-principles molecular dynamics simulations. Crystalline-liquid-amorphous phase transitions are examined and remarkable changes in the local structure around the Si atoms are found. The average Si....... The electronic density of states is metal-like in both the crystalline and the liquid phases, but it exhibits a pseudogap at the Fermi level in the amorphous phase, reflecting the strong abundance of fourfold coordinated Si in the amorphous phase....

  16. Gypsum plasterboards enhanced with phase change materials: A fire safety assessment using experimental and computational techniques

    Directory of Open Access Journals (Sweden)

    Kolaitis Dionysios I.

    2013-11-01

    Full Text Available Phase Change Materials (PCM can be used for thermal energy storage, aiming to enhance building energy efficiency. Recently, gypsum plasterboards with incorporated paraffin-based PCM blends have become commercially available. In the high temperature environment developed during a fire, the paraffins, which exhibit relatively low boiling points, may evaporate and, escaping through the gypsum plasterboard's porous structure, emerge to the fire region, where they may ignite, thus adversely affecting the fire resistance characteristics of the building. Aiming to assess the fire safety behaviour of such building materials, an extensive experimental and computational analysis is performed. The fire behaviour and the main thermo-physical physical properties of PCM-enhanced gypsum plasterboards are investigated, using a variety of standard tests and devices (Scanning Electron Microscopy, Thermo Gravimetric Analysis, Cone Calorimeter. The obtained results are used to develop a dedicated numerical model, which is implemented in a CFD code. CFD simulations are validated using measurements obtained in a cone calorimeter. In addition, the CFD code is used to simulate an ISO 9705 room exposed to fire conditions, demonstrating that PCM addition may indeed adversely affect the fire safety of a gypsum plasterboard clad building.

  17. The Possibility of Phase Change Materials (PCM Usage to Increase Efficiency of the Photovoltaic Modules

    Directory of Open Access Journals (Sweden)

    Klugmann-Radziemska Ewa

    2014-01-01

    Full Text Available Solar energy is widely available, free and inexhaustible. Furthermore this source of energy is the most friendly to the environment. For direct conversion of solar energy into useful forms like of electricity and thermal energy, respectively photovoltaic cells and solar collectors are being used. Forecast indicate that the first one solution will soon have a significant part in meeting the global energy demand. Therefore it is highly important to increase their efficiency in the terms of providing better energy conversion conditions. It can be obtain by designing new devices or by modifications of existing ones. This article presents general issues of photovoltaic installations exposed to work in high temperatures and basic concepts about phase change materials (PCMs. The paper presents the possibility of PCM usage to receive heat from the photovoltaic module. Specially designed test stand, consisting of PV module covered with a layer of PCM has been build and tested. Current-voltage characteristics of the cell without PCM material and with a layer of PCM have been presented. Authors also describe the results of the electrical and thermal characteristic of a coupled PV-PCM system.

  18. An Overview of SBIR Phase 2 Materials Structures for Extreme Environments

    Science.gov (United States)

    Nguyen, Hung D.; Steele, Gynelle C.

    2015-01-01

    Technological innovation is the overall focus of NASA's Small Business Innovation Research (SBIR) program. The program invests in the development of innovative concepts and technologies to help NASA's mission directorates address critical research and development needs for agency projects. This report highlights innovative SBIR Phase II projects from 2007-2012 specifically addressing Areas in Materials and Structures for Extreme Environments which is one of six core competencies at NASA Glenn Research Center. There are twenty three technologies featured with emphasis on a wide spectrum of applications such as fine-filament superconductor wire, composite oxide cathode materials, nano-composites, high radiation solar cell, wrapped multilayer insulation, thin aerogel, and much more. Each article in this booklet describes an innovation, technical objective, and highlights NASA commercial and industrial applications. This report serves as an opportunity for NASA personnel including engineers, researchers, and program managers to learn of NASA SBIR's capabilities that might be crosscutting into this technology area. As the result, it would cause collaborations and partnerships between the small companies and NASA Programs and Projects resulting in benefit to both SBIR companies and NASA.

  19. Lauric and myristic acids eutectic mixture as phase change material for low-temperature heating applications

    Energy Technology Data Exchange (ETDEWEB)

    Keles, Sadat; Kaygusuz, Kamil [Karadeniz Technical Univ., Dept. of Chemistry, Trabzon (Turkey); Sari, Ahmet [Gaziosmanpasa Univ., Dept. of Chemistry, Tokat (Turkey)

    2005-07-01

    Lauric acid (m.p.: 42.6 deg C) and myristic acid (m.p.: 52.2 deg C) are phase change materials (PCM) having quite high melting points which can limit their use in low-temperature solar applications such as solar space heating and greenhouse heating. However, their melting temperatures can be tailored to appropriate value by preparing a eutectic mixture of lauric acid (LA) and myristic acid (MA). In the present study, the thermal analysis based on differential scanning calorimetry (DSC) technique shows that the mixture of 66.0 wt% LA forms a eutectic mixture having melting temperature of 34.2 deg C and the latent heat of fusion of 166.8 J g{sup -1} . This study also considers the experimental establishment of thermal characteristics of the eutectic PCM in a vertical concentric pipe-in-pipe heat storage system. Thermal performance of the PCM was evaluated with respect to the effect of inlet temperature and mass flow rate of the heat transfer fluid on those characteristics during the heat charging and discharging processes. The DSC thermal analysis and the experimental results indicate that the LA-MA eutectic PCM can be potential material for low-temperature solar energy storage applications in terms of its thermo-physical and thermal characteristics. (Author)

  20. An Approach to Preparing Ni-P with Different Phases for Use as Supercapacitor Electrode Materials.

    Science.gov (United States)

    Wang, Dan; Kong, Ling-Bin; Liu, Mao-Cheng; Luo, Yong-Chun; Kang, Long

    2015-12-01

    Herein, we describe a simple two-step approach to prepare nickel phosphide with different phases, such as Ni2 P and Ni5 P4 , to explain the influence of material microstructure and electrical conductivity on electrochemical performance. In this approach, we first prepared a Ni-P precursor through a ball milling process, then controlled the synthesis of either Ni2 P or Ni5 P4 by the annealing method. The as-prepared Ni2 P and Ni5 P4 are investigated as supercapacitor electrode materials for potential energy storage applications. The Ni2 P exhibits a high specific capacitance of 843.25 F g(-1) , whereas the specific capacitance of Ni5 P4 is 801.5 F g(-1) . Ni2 P possesses better cycle stability and rate capability than Ni5 P4 . In addition, the Fe2 O3 //Ni2 P supercapacitor displays a high energy density of 35.5 Wh kg(-1) at a power density of 400 W kg(-1) and long cycle stability with a specific capacitance retention rate of 96 % after 1000 cycles, whereas the Fe2 O3 //Ni5 P4 supercapacitor exhibits a high energy density of 29.8 Wh kg(-1) at a power density of 400 W kg(-1) and a specific capacitance retention rate of 86 % after 1000 cycles.

  1. 2006/07 Field Testing of Cellulose Fiber Insulation Enhanced with Phase Change Material

    Energy Technology Data Exchange (ETDEWEB)

    Kosny, Jan [ORNL; Yarbrough, David W [ORNL; Miller, William A [ORNL; Petrie, Thomas [ORNL; Childs, Phillip W [ORNL; Syed, Azam M [ORNL

    2008-12-01

    Most recent improvements in building envelope technologies suggest that in the near future, residences will be routinely constructed to operate with very low heating and cooling loads. In that light, the application of novel building materials containing active thermal components (e.g., phase change materials [PCMs,] sub-venting, radiant barriers, and integrated hydronic systems) is like a final step in achieving relatively significant heating and cooling energy savings from technological improvements in the building envelope. It is expected that optimized building envelope designs using PCMs for energy storage can effectively bring notable savings in energy consumption and reductions in peak hour power loads. During 2006/07, a research team at Oak Ridge National Laboratory (ORNL) performed a series of laboratory and field tests of several wall and roof assemblies using PCM-enhanced cellulose insulation. This report summarizes the test results from the perspective of energy performance. The ORNL team is working on both inorganic and organic PCMs; this report discusses only paraffinic PCMs. A limited economical analysis also is presented. PCMs have been tested as a thermal mass component in buildings for at least 40 years. Most of the research studies found that PCMs enhanced building energy performance. In the case of the application of organic PCMs, problems such as high initial cost and PCM leaking (surface sweating) have hampered widespread adoption. Paraffinic hydrocarbon PCMs generally performed well, with the exception that they increased the flammability of the building envelope.

  2. Progress Report 2011: Understanding compound phase transitions in Heusler alloy giant magnetocaloric materials

    Energy Technology Data Exchange (ETDEWEB)

    Stadler, Shane

    2011-12-13

    Our goal is to gain insight into the fundamental physics that is responsible for magnetocaloric effects (MCE) and related properties at the atomic level. We are currently conducting a systematic study on the effects of atomic substitutions in Ni2MnGa-based alloys, and also exploring related full- and half-Heusler alloys, for example Ni-Mn-X (X=In, Sn, Sb), that exhibit a wide variety of interesting and potentially useful physical phenomena. It is already known that the magnetocaloric effect in the Heusler alloys is fundamentally connected to other interesting phenomena such as shape-memory properties. And the large magnetic entropy change in Ni2Mn0.75Cu0.25Ga has been attributed to the coupling of the first-order, martensitic transition with the second-order ferromagnetic paramagnetic (FM-PM) transition. Our research to this point has focused on understanding the fundamental physics at the origin of these complex, compound phase transitions, and the novel properties that emerge. We synthesize the materials using a variety of techniques, and explore their material properties through structural, magnetic, transport, and thermo-magnetic measurements.

  3. Consistency of measured phase boundaries of the FFLO superconducting phase for different materials and types of probes

    Science.gov (United States)

    Agosta, Charles; Fortune, Nathanael; Hannahs, Scott; Park, Ju-Hyun; Schleuter, John; Liang, Lucy; Gao, Shuyao; Bishop-van Horn, Logan; Newman, Max; Gu, Shuyao; Liang, Lucy

    New magnetocaloric and specific heat measurements of the high field superconducting state in the organic superconductor κ-­ (BEDT­-TTF)2Cu(NCS)2 are compared to rf penetration depth, magnetic torque, and NMR measurements. The position of the phase lines separating the uniform superconducting state with the FFLO state and the normal state are mostly in good agreement with each other. The order of the phase transitions can only be determined from the calorimetric measurements and will be compared to theory. Results from other organic superconductors show that there is universal behavior. As an example, the distance between the lower and upper magnetic field phase line containing the FFLO state is proportional to the upper critical field. The position of the lower phase line, the Clogston ­Chandrasakar paramagnetic limit, will be compared to semi empirical calculations based on the specific heat for five different superconductors.

  4. Subsolidus binary phase diagram of C10Zn-C18Zn of thermotropic phase transitions materials

    Institute of Scientific and Technical Information of China (English)

    武克忠; 王新东; 刘晓地; 左萍

    2004-01-01

    The thermotropic phase transitions layer compound in the perovskite type (n-C10 H21 NH3 )2 ZnCl4 and (nC18 H37 NH3 )2 ZnCl4 were synthesized and, at the same time, a series of rnixtures C10 Zn/C18 Zn were prepared. The experimental binary phase diagram of C10 Zn/C18 Zn was established by means of differential scanning calorimetry (DSC) and X-ray diffraction. In the phase diagram, compound (n-C10 H21 NH3 ) (n-C21 H37 NH3 )ZnCl4 and two eutectoid invariants were observed; two eutectoid temperatures are about 53 ℃ and 58 ℃. Contrasting with other similar systems, there are three noticeable solid solution ranges at the left and right boundary and middle of the phase diagram.

  5. First Principles Study of structural characteristics and phase change mechanism of Ge-Sb-Te based materials

    Science.gov (United States)

    Park, Hanjin; Kim, Cheol-Woon; Lee, Hyung-June; Song, Hosin; Kwon, Young-Kyun

    Using ab initio density functional theory, we investigate the structural properties and their phase transition mechanism of the crystalline and amorphous phases of Ge-Sb-Te (GST) based phase change materials, which would be utilized for phase change random access memory. Among various stochiometries of GST, we focus on compositions along the (GeTe)n(Sb2Te3)m pseudo-binary line, denoted simply by (n , m) with integer n and m. We explore various GST materials corresponding (n , m) sets including (1,0), (0,1), (1,1), (2,1) and (1,2) by modeling their both phases. Especially, their amorphous phases can be constructed based on experimental data available or molecular dynamics (MD) simulations performing melt-quench processes. To understand the phase transition mechanism, we evaluate their coordination numbers, radial distribution functions, and angle distribution functions, which enables us to identify the characteristic local geometry representing each phase. We further investigate the thermal properties of various phases by evaluating their phonon densities of states obtained by Fourier-transforming the velocity autocorrelation functions calculated directly from our MD simulation.

  6. Chemical Complementarity between the Gas Phase of the Interstellar Medium and the Rocky Material of Our Planetary System

    CERN Document Server

    Wang, Haiyang

    2016-01-01

    We compare the elemental depletions in the gas phase of the interstellar medium (ISM) with the elemental depletions in the rocky material of our Solar System. Our analysis finds a high degree of chemical complementarity: elements depleted in the gas phase of the ISM are enriched in the rocky material of our Solar System, and vice versa. This chemical complementarity reveals the generic connections between interstellar dust and rocky planetary material. We use an inheritance model to explain the formation of primordial grains in the solar nebula. The primary dust grains inherited from the ISM, in combination with the secondary ones condensed from the solar nebula, constitute the primordial rocky material of our planetary system, from which terrestrial planets are formed through the effects of the progressive accretion and sublimation. The semi-major-axis-dependence of the chemical composition of rocky planetary material is also observed by comparing elemental depletions in the Earth, CI chondrites and other ty...

  7. Two phase modeling of the influence of plastic strain on the magnetic and magnetostrictive behaviors of ferromagnetic materials

    Science.gov (United States)

    Hubert, Olivier; Lazreg, Said

    2017-02-01

    A growing interest of automotive industry in the use of high performance steels is observed. These materials are obtained thanks to complex manufacturing processes whose parameters fluctuations lead to strong variations of microstructure and mechanical properties. The on-line magnetic non-destructive monitoring is a relevant response to this problem but it requires fast models sensitive to different parameters of the forming process. The plastic deformation is one of these important parameters. Indeed, ferromagnetic materials are known to be sensitive to stress application and especially to plastic strains. In this paper, a macroscopic approach using the kinematic hardening is proposed to model this behavior, considering a plastic strained material as a two phase system. Relationship between kinematic hardening and residual stress is defined in this framework. Since stress fields are multiaxial, an uniaxial equivalent stress is calculated and introduced inside the so-called magneto-mechanical multidomain modeling to represent the effect of plastic strain. The modeling approach is complemented by many experiments involving magnetic and magnetostrictive measurements. They are carried out with or without applied stress, using a dual-phase steel deformed at different levels. The main interest of this material is that the mechanically hard phase, soft phase and the kinematic hardening can be clearly identified thanks to simple experiments. It is shown how this model can be extended to single phase materials.

  8. Preparation, characterization, and thermal properties of the microencapsulation of a hydrated salt as phase change energy storage materials

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jin, E-mail: huangjiner@126.com [School of Materials and Energy, Guangdong University of Technology, 510006 Guangzhou (China); Wang, Tingyu; Zhu, Panpan; Xiao, Junbin [School of Materials and Energy, Guangdong University of Technology, 510006 Guangzhou (China)

    2013-04-10

    Highlights: ► Phase change point and fusion heat of samples are about 51 °Cand 150 J/g respectively. ► DSC results indicated the core material is not Na{sub 2}HPO{sub 4}·12H{sub 2}O but Na{sub 2}HPO{sub 4}·7H{sub 2}O. ► Encapsulation takes a significant role in reducing subcooling degree. - Abstract: Microcapsules loaded by disodium hydrogen phosphate heptahydrate (Na{sub 2}HPO{sub 4}·7H{sub 2}O) were prepared by means of the suspension copolymerization-solvent volatile method, with modified polymethylmethacrylate (PMMA) as coating polymer under the conditions of various organic solvents. The formation of the microencapsulated phase change materials (MEPCMs)-PMMA/Na{sub 2}HPO{sub 4}·7H{sub 2}O was investigated and analyzed. The morphology of the resultant materials was characterized by using scanning electron microscope (SEM) and phase contrast microscope. Its final composition was confirmed by the Fourier transformation infrared (FT-IR). Thermo gravimetric analyzer (TGA) and differential scanning calorimetry (DSC) were adopted to reveal its thermal stability and thermal properties. Results indicated that the materials owned improved subcooling degree and good thermal properties, enabling the materials to be one promising phase change materials for thermal energy storage.

  9. Characterization of a backfill candidate material, IBECO-RWC-BF Baclo Project - Phase 3 Laboratory tests

    Energy Technology Data Exchange (ETDEWEB)

    Johannesson, Lars-Erik; Sanden, Torbjoern; Dueck, Ann; Ohlsson, Lars (Clay Technology AB, Lund (Sweden))

    2010-01-15

    A backfill candidate material, IBECO-RWC-BF, which origin from Milos, Greece, has been investigated. The material was delivered both as granules and as pellets. The investigation described in this report aimed to characterize the material and evaluate if it can be used in a future repository. The following investigations have been done and are presented in this report: 1. Standard laboratory tests. Water content, liquid limit and swelling potential are examples on standard tests that have been performed. 2. Block manufacturing. The block compaction properties of the material have been determined. A first test was performed in laboratory but also tests in large scale have been performed. After finishing the test phase, 60 tons of blocks were manufactured at Hoeganaes Bjuf AB. The blocks will be used in large scale laboratory tests at Aespoe HRL. 3. Mechanical parameters. The compressibility of the material was investigated with oedometer tests (four tests) where the load was applied in steps after saturation. The evaluated oedometer modulus varied between 34.50 MPa. Tests were made to evaluate the elastic parameters of the material (E, nu). Altogether three tests were made on specimens with dry densities of about 1,710 kg/m3. The evaluated E-modulus and Poisson's ratio varied between 231-263 MPa and 0.16-0.19 respectively. The strength of the material, both the compressive strength and the tensile strength were measured on specimens compacted to different dry densities. The test results yielded a relation between density and the two types of strength. Furthermore, tests have been made in order to determine the compressibility of the unsaturated filling of pellets. Two tests were made where the pellets were loosely filled in a Proctor cylinder and then compressed at a constant rate of strain during continuously measurement of the applied load. 4. Swelling pressure and hydraulic conductivity. There is, as expected, a very clear influence of the dry density on the

  10. Confined-Volume Effect on the Thermal Properties of Encapsulated Phase Change Materials for Thermal Energy Storage.

    Science.gov (United States)

    De Castro, Paula F; Ahmed, Adham; Shchukin, Dmitry G

    2016-03-18

    We have encapsulated the heat exchange material, n-docosane, into polyurethane capsules of different sizes. Decreasing the size of the capsules leads to changes of the crystallinity of phase-change material as well as melting/crystallization temperature. The novelty of the paper includes 1) protection of the nanostructured energy-enriched materials against environment during storage and controlled release of the encapsulated energy on demand and 2) study of the structure and surface-to-volume properties of the energy-enriched materials dispersed in capsules of different sizes. The stability of energy nanomaterials, influence of capsule diameter on their energy capacity, homogeneity and operation lifetime are investigated.

  11. Screening of high melting point phase change materials (PCM) in solar thermal concentrating technology based on CLFR

    Energy Technology Data Exchange (ETDEWEB)

    Hoshi, Akira [Ichinoseki National College of Technology (Japan). Dept. of Mechanical Engineering; Mills, D.R.; Bittar, A. [University of Sydney (Australia). School of Physics; Saitoh, T.S. [Tohoku University, Sendai (Japan). Graduate School of Environmental Studies

    2005-09-01

    We have investigated the suitability of high melting point phase change materials for use in new, large scale solar thermal electricity plants. Candidate materials for latent heat thermal energy storage are identified and their operating parameters modeled and analysed. The mathematical characteristics of charging and discharging these storage materials are discussed. Several high melting point, high conductivity materials are shown to be suitable and advantageous for use with solar thermal electricity plants, such as Sydney University's novel, low cost CLFR and MTSA collector systems, as well as existing parabolic trough and tower technologies. (author)

  12. Preparation of Paraffin/γ-Al2O3Composites as Phase Change Energy Storage Materials%Preparation of Paraffin/γ-Al2O3 Composites as Phase Change Energy Storage Materials

    Institute of Scientific and Technical Information of China (English)

    ZHAO Liang; MARuiying; MENG Xianglan; WANG Gang; FANG Xiangchen

    2011-01-01

    Paraffin/γ-Al2O3 composites as phase change energy storage materials were prepared by absorbingparaffin in porous network of γ-Al2O3.In the composite materials,paraffin was used as a phase change material(PCM) for thermal energy storage,and γ-Al2O3 acted as supporting materials.Characterizations were conducted to evaluate the energy storage performance of the composites,and differential scanning calorimeter results showed that the PCM-3 composite has melting latent heat of 112.9 kJ/kg with a melting temperature of 62.9 ℃.Due to strong capillary force and surface tension between paraffin and γ-Al2O3,the leakage of melted paraffin from the composites can be effectively prevented.Therefore,the paraffin/γ-Al2O3 composites have a good thermal stability and can be used repeatedly.

  13. Epitaxial growth of Ge-Sb-Te based phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Perumal, Karthick

    2013-07-30

    Ge-Sb-Te based phase change materials are considered as a prime candidate for optical and electrical data storage applications. With the application of an optical or electrical pulse, they can be reversibly switched between amorphous and crystalline state, thereby exhibiting large optical and electrical contrast between the two phases, which are then stored as information in the form of binary digits. Single crystalline growth is interesting from both the academic and industrial perspective, as ordered Ge-Sb-Te based metamaterials are known to exhibit switching at reduced energies. The present study deals with the epitaxial growth and analysis of Ge-Sb-Te based thin films. The first part of the thesis deals with the epitaxial growth of GeTe. Thin films of GeTe were grown on highly mismatched Si(111) and (001) substrates. On both the substrate orientations the film grows along [111] direction with an amorphous-to-crystalline transition observed during the initial stages of growth. The amorphous-to-crystalline transition was studied in-vivo using azimuthal reflection high-energy electron diffraction scans and grazing incidence X-ray diffraction. In the second part of the thesis epitaxy and characterization of Sb{sub 2}Te{sub 3} thin films are presented. The third part of the thesis deals with the epitaxy of ternary Ge-Sb-Te alloys. The composition of the films are shown to be highly dependent on growth temperatures and vary along the pseudobinary line from Sb{sub 2}Te{sub 3} to GeTe with increase in growth temperatures. A line-of-sight quadrupole mass spectrometer was used to reliably control the GeSbTe growth temperature. Growth was performed at different Ge, Sb, Te fluxes to study the compositional variation of the films. Incommensurate peaks are observed along the [111] direction by X-ray diffraction. The possibility of superstructural vacancy ordering along the [111] direction is discussed.

  14. Combined model of strain-induced phase transformation and orthotropic damage in ductile materials at cryogenic temperatures

    CERN Document Server

    Garion, Cedric

    2003-01-01

    Ductile materials (like stainless steel or copper) show at cryogenic temperatures three principal phenomena: serrated yielding (discontinuous in terms of dsigma/depsilon), plastic strain-induced phase transformations and evolution of ductile damage. The present paper deals exclusively with the two latter cases. Thus, it is assumed that the plastic flow is perfectly smooth. Both in the case of damage evolution and for the gamma-alpha prime phase transformation, the principal mechanism is related to the formation of plastic strain fields. In the constitutive modeling of both phenomena, a crucial role is played by the accumulated plastic strain, expressed by the Odqvist parameter p. Following the general trends, both in the literature concerning the phase transformation and the ductile damage, it is assumed that the rate of transformation and the rate of damage are proportional to the accumulated plastic strain rate. The gamma-alpha prime phase transformation converts the initially homogenous material to a two-p...

  15. Study of multi-layer active magnetic regenerators using magnetocaloric materials with first and second order phase transition

    Science.gov (United States)

    Lei, T.; Engelbrecht, K.; Nielsen, K. K.; Neves Bez, H.; Bahl, C. R. H.

    2016-09-01

    Magnetocaloric materials (MCM) with a first order phase transition (FOPT) usually exhibit a large, although sharp, isothermal entropy change near their Curie temperature, compared to materials with a second order phase transition (SOPT). Experimental results of applying FOPT materials in recent magnetocaloric refrigerators (MCR) demonstrated the great potential for these materials, but a thorough study on the impact of the moderate adiabatic temperature change and strong temperature dependence of the magnetocaloric effect (MCE) is lacking. Besides, comparing active magnetic regenerators (AMR) using FOPT and SOPT materials is also of fundamental interest. We present modeling results of multi-layer AMRs using FOPT and SOPT materials based on a 1D numerical model. First the impact of isothermal entropy change, adiabatic temperature change and shape factor describing the temperature dependence of the MCE are quantified and analyzed by using artificially built magnetocaloric properties. Then, based on measured magnetocaloric properties of La(Fe,Mn,Si)13H y and Gd, an investigation on how to layer typical FOPT and SOPT materials with different temperature spans is carried out. Moreover, the sensitivity of variation in Curie temperature distribution for both groups of AMRs is investigated. Finally, a concept of mixing FOPT and SOPT materials is studied for improving the stability of layered AMRs with existing materials.

  16. Transient modelling of heat loading of phase change material for energy storage

    Directory of Open Access Journals (Sweden)

    Asyraf W.M.

    2017-01-01

    Full Text Available As the development of solar energy is getting advance from time to time, the concentration solar technology also get the similar attention from the researchers all around the globe. This technology concentrate a large amount of energy into main spot. To collect all the available energy harvest from the solar panel, a thermal energy storage is required to convert the heat energy to one of the purpose such as electrical energy. With the idea of energy storage application that can be narrow down to commercial application such as cooking stove. Using latent heat type energy storage seem to be appropriate with the usage of phase change material (PCM that can release and absorb heat energy at nearly constant temperature by changing its state. Sodium nitrate (NaNO3 and potassium nitrate (KNO3 was selected to use as PCM in this project. This paper focus on the heat loading process and the melting process of the PCM in the energy storage using a computer simulation. The model of the energy storage was created as solid three dimensional modelling using computer aided software and the geometry size of it depend on how much it can apply to boil 1 kg of water in cooking application. The materials used in the tank, heat exchanger and the heat transfer fluid are stainless steel, copper and XCELTHERM MK1, respectively. The analysis was performed using a commercial simulation software in a transient state. The simulation run on different value of velocity but kept controlled under laminar state only, then the relationship of velocity and heat distribution was studied and the melting process of the PCM also has been analyzed. On the effect of heat transfer fluid velocity, the higher the velocity resulted in higher the rate of heat transfer. The comparison between the melting percentages of the PCMs under test conditions show that NaNO3 melts quite faster than KNO3.

  17. Local Structure Analysis and Interface Layer Effect of Phase-Change Recording Material Using Actual Media

    Science.gov (United States)

    Nakai, Tsukasa; Yoshiki, Masahiko; Satoh, Yasuhiro; Ashida, Sumio

    2008-07-01

    The influences of the interface layer on crystal structure, the local atomic arrangement, and the electronic and chemical structure of a GeBiTe (GBT) phase-change recording material have been investigated using X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), and hard X-ray photoelectron spectroscopy (HX-PES) methods using actual rewritable high-speed HD DVD media without special sample processing. XRD results showed that the crystal structure of laser-crystallized GBT alloy in the actual HD DVD media is the same as that of GeSbTe (GST) alloy, which has a NaCl-type structure. No differences between samples with and without interface layers were found. The lattice constant of GBT is larger than that of GST. Bi increases the lattice constant of GST with respect to the Bi substitution ratio of Sb. According to HX-PES, the DOS of in the recording film amorphous state with an interface layer is closer to that of the crystalline state than the recording film without an interface layer. From XAFS results, clear differences between amorphous (Amo.) and crystalline states (Cry.) were observed. The interatomic distance of amorphous recording material is independent of the existence of an interface layer. On the other hand, the coordination number varied slightly due to the presence of the interface layer. Therefore, the electronic state of the recording layer changes because of the interface layer, although the local structure changes only slightly except for the coordination number. Combining these results, we conclude that the interface layer changes the electronic state of the recording layer and promotes crystallization, but only affects the local structure of the atomic arrangement slightly.

  18. Thermal properties of a novel nanoencapsulated phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Fuensanta, Mónica, E-mail: monica.fuensanta@aidico.es [AIDICO, Technological Institute of Construction, Camí de Castella, 4, 03660 Novelda, Alicante (Spain); Paiphansiri, Umaporn [Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany); Romero-Sánchez, María Dolores, E-mail: md.romero@aidico.es [AIDICO, Technological Institute of Construction, Camí de Castella, 4, 03660 Novelda, Alicante (Spain); Guillem, Celia; López-Buendía, Ángel M. [AIDICO, Technological Institute of Construction, Camí de Castella, 4, 03660 Novelda, Alicante (Spain); Landfester, Katharina [Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany)

    2013-08-10

    Highlights: • A paraffin wax RT80 was encapsulated in styrene–butyl acrylate copolymer as polymer shell using miniemulsion polymerization process to obtain a novel nanoencapsulated PCM with 80 °C melting temperature. • Nano-PCMs have high compact structure, spherical morphology and thermal stability. • The nano-PCMs have potential applications as thermal energy storage materials. - Abstract: A novel nanoencapsulation of a paraffine type phase change material, RT80, in a styrene–butyl acrylate copolymer shell using the miniemulsion polymerization process was carried out. General characteristics of the RT80 nanoparticles in terms of thermal properties, morphology, chemical composition and particle size distribution were characterized by Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Dynamic Light Scattering (DLS). The influence of different monomers (styrene, butyl acrylate) and the surfactant/paraffin mass ratios on nanoparticles properties such as thermal capacity, particle size and morphology were systematically investigated. In all cases studied, encapsulation efficiency was close to 80 wt% with a particle size distribution between 52 and 112 nm and regular spherical shape and uniform structure. The amount of encapsulated paraffin achieved was comprised between 8 and 20%. Melting and crystallization heats were found to be approximately 5–25 J g{sup −1}, mainly depending on surfactant/paraffin mass ratio. Melting temperature of RT80 nanoparticles slightly decreased (1–7 °C) respect to the raw RT80. In addition, the encapsulated RT80 nanoparticles show thermal stability even after 200 thermal (heat-cooling) cycles.

  19. Characterization of a backfill candidate material, IBECO-RWC-BF Baclo Project - Phase 3 Laboratory tests

    Energy Technology Data Exchange (ETDEWEB)

    Johannesson, Lars-Erik; Sanden, Torbjoern; Dueck, Ann; Ohlsson, Lars (Clay Technology AB, Lund (Sweden))

    2010-01-15

    A backfill candidate material, IBECO-RWC-BF, which origin from Milos, Greece, has been investigated. The material was delivered both as granules and as pellets. The investigation described in this report aimed to characterize the material and evaluate if it can be used in a future repository. The following investigations have been done and are presented in this report: 1. Standard laboratory tests. Water content, liquid limit and swelling potential are examples on standard tests that have been performed. 2. Block manufacturing. The block compaction properties of the material have been determined. A first test was performed in laboratory but also tests in large scale have been performed. After finishing the test phase, 60 tons of blocks were manufactured at Hoeganaes Bjuf AB. The blocks will be used in large scale laboratory tests at Aespoe HRL. 3. Mechanical parameters. The compressibility of the material was investigated with oedometer tests (four tests) where the load was applied in steps after saturation. The evaluated oedometer modulus varied between 34.50 MPa. Tests were made to evaluate the elastic parameters of the material (E, nu). Altogether three tests were made on specimens with dry densities of about 1,710 kg/m3. The evaluated E-modulus and Poisson's ratio varied between 231-263 MPa and 0.16-0.19 respectively. The strength of the material, both the compressive strength and the tensile strength were measured on specimens compacted to different dry densities. The test results yielded a relation between density and the two types of strength. Furthermore, tests have been made in order to determine the compressibility of the unsaturated filling of pellets. Two tests were made where the pellets were loosely filled in a Proctor cylinder and then compressed at a constant rate of strain during continuously measurement of the applied load. 4. Swelling pressure and hydraulic conductivity. There is, as expected, a very clear influence of the dry density on the

  20. Future utilization of space: Silverton Conference on material science and phase transformations in zero-gravity, summary of proceeding

    Science.gov (United States)

    Eisner, M. (Editor)

    1975-01-01

    The importance of zero gravity environment in the development and production of new and improved materials is considered along with the gravitational effects on phase changes or critical behavior in a variety of materials. Specific experiments discussed include: fine scale phase separation in zero gravity; glass formation in zero gravity; effects of gravitational perturbations on determination of critical exponents; and light scattering from long wave fluctuations in liquids in zero gravity. It is concluded that the space shuttle/spacelab system is applicable to various fields of interest.

  1. Simulation of a high temperature thermal energy storage system employing several families of phase-change storage material

    Energy Technology Data Exchange (ETDEWEB)

    Adebiyi, G.A. [Mississippi State Univ., MS (United States)

    1989-03-01

    Previous work by the author entailed modeling of the Packed Bed Thermal Energy Storage System, utilizing Phase-Change Materials, and a performance evaluation of the system based on the Second Law of thermodynamics. A principal conclusion reached is that the use of a single family of phase-change storage material may not in fact produce a thermodynamically superior system relative to one utilizing sensible heat storage material. This prompted us to modify our model so that we could investigate whether or not a significantly improved performance may be achieved via the use of multiple families of phase-change materials instead. Other factors investigated in the present work include the effect on system performance due to the thermal mass of the containment vessel wall, varying temperature and mass flow rate of the flue gas entering the packed bed during the storage process, and thermal radiation which could be a significant factor at high temperature levels. The resulting model is intended to serve as an integral part of a real-time simulation of the application of a high temperature regenerator in a periodic brick plant. This paper describes the more comprehensive model of the high temperature thermal energy storage system and presents results indicating that improved system performance could be achieved via a judicious choice of multiple families of phase-change materials.

  2. Experimental Study on Melting and Solidification of Phase Change Material Thermal Storage

    Science.gov (United States)

    Ambarita, H.; Abdullah, I.; Siregar, C. A.; Siregar, R. E. T.; Ronowikarto, A. D.

    2017-03-01

    Melting and solidification process of Phase Change Materials (PCMs) are investigated experimentally. The tested PCMs are Paraffin wax and Steric acid which typically used for solar water heater. The objective is to explore the characteristics of the PCM when it is being melted and solidified. The experiments are performed in a glass box. One side of the box wall is heated while the opposite wall is kept constant and other walls are insulated. Temperature of the heated wall are kept constant at 80°C, 85°C, and 90°C, respectively. Every experiment is carried out for 600 minutes. Temperatures are recorded and the melting and solidification processes are pictured by using camera. The results show that the melting process starts from the upper part of the thermal storage. In the solidification process, it starts from the lower part of the thermal storage. As a thermal energy storage, Paraffin wax is better than Steric acid. This is because Paraffin wax can store more energy. At heat source temperature of 90°C, thermal energy stored by Paraffin wax and Stearic acid is 61.84 kJ and 57.39 kJ, respectively. Thus it is better to used Paraffin wax in the solar water heater as thermal energy storage.

  3. Phase Change Materials-Assisted Heat Flux Reduction: Experiment and Numerical Analysis

    Directory of Open Access Journals (Sweden)

    Hussein J. Akeiber

    2016-01-01

    Full Text Available Phase change materials (PCM in the construction industry became attractive because of several interesting attributes, such as thermo-physical parameters, open air atmospheric condition usage, cost and the duty structure requirement. Thermal performance optimization of PCMs in terms of proficient storage of a large amount of heat or cold in a finite volume remains a challenging task. Implementation of PCMs in buildings to achieve thermal comfort for a specific climatic condition in Iraq is our main focus. From this standpoint, the present paper reports the experimental and numerical results on the lowering of heat flux inside a residential building using PCM, which is composed of oil (40% and wax (60%. This PCM (paraffin, being plentiful and cost-effective, is extracted locally from waste petroleum products in Iraq. Experiments are performed with two rooms of identical internal dimensions in the presence and absence of PCM. A two-dimensional numerical transient heat transfer model is developed and solved using the finite difference method. A relatively simple geometry is chosen to initially verify the numerical solution procedure by incorporating in the computer program two-dimensional elliptic flows. It is demonstrated that the heat flux inside the room containing PCM is remarkably lower than the one devoid of PCM.

  4. Energy reduction of building air-conditioner with phase change material in Thailand

    Directory of Open Access Journals (Sweden)

    Nattaporn Chaiyat

    2014-11-01

    Full Text Available In this study, a concept of using phase change material (PCM for improving cooling efficiency of an air-conditioner had been presented under Thai climate. Paraffin waxes melting point at around 20 °C was selected to evaluate the thermal performance by reducing the air temperature entering the evaporating coil. The model of PCM celluloid balls had been performed with the air-conditioner. Moreover, the mathematical model of the air-conditioner with the PCM storage was developed and verified with the testing results. From the study results, it could be seen that the simulated data agreed quite well with the experimental result at the discrepant around 2–4%. Finally, the model was used to analyze the economic result which was found that the electrical consumption of the modified air-conditioner could be decreased 3.09 kW h/d. The electrical power consumption of the modified unit was 36.27 kW h/d at the operating time 15 h/d compared with 39.36 kW h/d of the normal unit at the operating time 12 h/d. The saving cost of the PCM bed could be 9.10% or 170.03 USD and the payback period was 4.15 y.

  5. Preparation and Characterization of Microencapsulated Phase Change Materials for Use in Building Applications

    Directory of Open Access Journals (Sweden)

    Jessica Giro-Paloma

    2015-12-01

    Full Text Available A method for preparing and characterizing microencapsulated phase change materials (MPCM was developed. A comparison with a commercial MPCM is also presented. Both MPCM contained paraffin wax as PCM with acrylic shell. The melting temperature of the PCM was around 21 °C, suitable for building applications. The M-2 (our laboratory made sample and Micronal® DS 5008 X (BASF samples were characterized using SEM, DSC, nano-indentation technique, and Gas Chromatography/Mass spectrometry (GC-MS. Both samples presented a 6 μm average size and a spherical shape. Thermal energy storage (TES capacities were 111.73 J·g−1 and 99.3 J·g−1 for M-2 and Micronal® DS 5008 X, respectively. Mechanical characterization of the samples was performed by nano-indentation technique in order to determine the elastic modulus (E, load at maximum displacement (Pm, and displacement at maximum load (hm, concluding that M-2 presented slightly better mechanical properties. Finally, an important parameter for considering use in buildings is the release of volatile organic compounds (VOC’s. This characteristic was studied at 65 °C by CG-MS. Both samples showed VOC’s emission after 10 min of heating, however peaks intensity of VOC’s generated from M-2 microcapsules showed a lower concentration than Micronal® DS 5008 X.

  6. Increasing energy efficiency of HVAC systems of buildings using phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Chusak, Lee; Daiber, Jared; Agarwal, Ramesh [Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO 63130 (United States)

    2012-07-01

    Using Computational Fluid Dynamics (CFD), four different cooling systems used in contemporary office environments are modeled to compare energy consumption and thermal comfort levels. Incorporating convection and radiation technologies, full-scale models of an office room compare energy efficiency of (a) an all-air overhead system, (b) a combined all-air overhead and hydronic radiant system (chilled ceiling), (c) an all-air raised floor system (displacement ventilation), and (d) a combined displacement ventilation with a chilled ceiling. The computational domain for each model consists of one temperature varying wall (simulating the temperature of the exterior wall of the building during a 24-hour period) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations are conducted. The first set considers a glass window and plastic shade configuration for the exterior wall. The second set of computations includes a phase change material layer between the glass window and the plastic shade. Results show substantial energy savings can be accrued using the displacement ventilation and especially the displacement ventilation with a chilled ceiling over the conventional overhead mixing ventilation system. The results also show that the addition of a PCM layer to the exterior wall can significantly decrease the cooling energy requirements.

  7. An experimental and numerical simulation study of an active solar wall enhanced with phase change materials

    Directory of Open Access Journals (Sweden)

    Dionysios I. Kolaitis

    2015-06-01

    Full Text Available Solar walls can be used to increase the overall energy efficiency of a building. Phase Change Materials (PCM are capable of increasing the effective thermal mass of building elements, thus decreasing the overall energy consumption. Recently, the incorporation of PCM in a solar wall has been proposed, aiming to increase the total energy efficiency of the system. The main scope of this work is to investigate the thermal behaviour of a PCM-enhanced solar wall (PCMESW, using experimental and numerical simulation techniques. A prototype PCMESW is installed in a large-scale test facility and is exposed to dynamically changing climate conditions. A broad range of sensors, used to monitor the time-evolution of several important physical parameters, is employed to assess the dynamic response of the PCMESW. In addition, a Computational Fluid Dynamics tool is used to numerically investigate the thermal behaviour of the PCMESW prototype. Predictions of the developing flow- and thermal-field in the PCMESW’s air cavity are validated by means of comparison with the obtained measurements; in general, good levels of agreement are observed. Results of the numerical simulations may support the design optimization process of innovative PCMESW systems.  

  8. Development, Testing, and Failure Mechanisms of a Replicative Ice Phase Change Material Heat Exchanger

    Science.gov (United States)

    Leimkuehler, Thomas O.; Hansen, Scott; Stephan, Ryan A.

    2010-01-01

    Phase change materials (PCM) may be useful for thermal control systems that involve cyclical heat loads or cyclical thermal environments such as Low Earth Orbit (LEO) and Low Lunar Orbit (LLO). Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. One advantage that PCM's have over evaporators in this scenario is that they do not use a consumable. Wax PCM units have been baselined for the Orion thermal control system and also provide risk mitigation for the Altair Lander. However, the use of water as a PCM has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. An ice PCM heat exchanger that replicates the thermal energy storage capacity of an existing wax PCM unit was fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion are investigated. This paper presents the results to date of this investigation. Nomenclature

  9. Testing and Failure Mechanisms of Ice Phase Change Material Heat Exchangers

    Science.gov (United States)

    Leimkuehler, Thomas O.; Stephan, Ryan A.; Hawkins-Reynolds, Ebony

    2011-01-01

    Phase change materials (PCM) may be useful for thermal control systems that involve cyclical heat loads or cyclical thermal environments such as specific spacecraft orientations in Low Earth Orbit (LEO) and low beta angle Low Lunar Orbit (LLO). Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. One advantage that PCM s have over evaporators in this scenario is that they do not use a consumable. The use of water as a PCM rather than the more traditional paraffin wax has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. A number of ice PCM heat exchangers were fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion were investigated. This paper presents the results of testing that occurred from March through September of 2010 and builds on testing that occurred during the previous year.

  10. Method of encapsulating a phase change material with a metal oxide

    Energy Technology Data Exchange (ETDEWEB)

    Ram, Manoj Kumar; Jotshi, Chand K.; Stefanakos, Elias K.; Goswami, Dharendra Yogi

    2016-11-15

    Storage systems based on latent heat storage have high-energy storage density, which reduces the footprint of the system and the cost. However, phase change materials (PCMs), such as NaNO.sub.3, NaCl, KNO.sub.3, have very low thermal conductivities. To enhave the storage of PCMs, macroencapsulation of PCMs was performed using a metal oxide, such as SiO.sub.2 or a graphene-SiO.sub.2, over polyimide-coated or nickel-embedded, polyimide-coated pellets The macro encapsulation provides a self-supporting structure, enhances the heat transfer rate, and provides a cost effective and reliable solution for thermal energy storage for use in solar thermal power plants. NaNO.sub.3 was selected for thermal storage in a temperature range of 300.degree. C. to 500.degree. C. The PCM was encapsulated in a metal oxide cell using self-assembly reactions, hydrolysis, and simultaneous chemical oxidation at various temperatures.

  11. Phase change material for thermotherapy of Buruli ulcer: modelling as an aid to implementation.

    Science.gov (United States)

    Braxmeier, S; Hellmann, M; Beck, A; Umboock, A; Pluschke, G; Junghanss, T; Weinlaeder, H

    2009-01-01

    A mathematical model was developed and validated to predict the thermal behaviour of a heat application device based on a phase change material (pcm) for the heat treatment of Mycobacterium ulcerans infection (Buruli ulcer). The thermal model allows the prediction of skin surface temperatures and an optimization of the amount of pcm with respect to discharge time. A first prototype of such a pcm bandage was manufactured and used in a proof-of-principal trial in Cameroon. The experimental data were analysed and yielded no difference in thermoregulatory response between people living in hot or moderate climate. Short-term maximum skin surface temperatures of 42 degrees C are tolerable; the pcm bandage keeps the skin surface temperature above 40 degrees C for about four to five hours. This makes such pcm bandages an ideal device for the heat treatment of Buruli ulcer. The pcm bandage is easy to apply, cheap, and thus is well suited for use in low-resource countries.

  12. Preparation and characterization of porous carbon material-coated solid-phase microextraction metal fibers.

    Science.gov (United States)

    Zhu, Fang; Guo, Jiaming; Zeng, Feng; Fu, Ruowen; Wu, Dingcai; Luan, Tiangang; Tong, Yexiang; Lu, Tongbu; Ouyang, Gangfeng

    2010-12-10

    Two kinds of porous carbon materials, including carbon aerogels (CAs), wormhole-like mesoporous carbons (WMCs), were synthesized and used as the coatings of solid-phase microextraction (SPME) fibers. By using stainless steel wire as the supporting core, six types of fibers were prepared with sol-gel method, direct coating method and direct coating plus sol-gel method. Headspace SPME experiments indicated that the extraction efficiencies of the CA fibers are better than those of the WMC fibers, although the surface area of WMCs is much higher than that of CAs. The sol-gel-CA fiber (CA-A) exhibited excellent extraction properties for non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene), while direct-coated CA fiber (CA-B) presented the best performance in extracting polar compounds (phenols). The two CA fibers showed wide linear ranges, low detection limits (0.008-0.047μgL(-1) for BTEX, 0.15-5.7μgL(-1) for phenols) and good repeatabilities (RSDs less than 4.6% for BTEX, and less than 9.5% for phenols) and satisfying reproducibilities between fibers (RSDs less than 5.2% for BTEX, and less than 9.9% for phenols). These fibers were successfully used for the analysis of water samples from the Pearl River, which demonstrated the applicability of the home-made CA fibers.

  13. Experimental investigations on the cooling of a motorcycle helmet with phase change material (PCM

    Directory of Open Access Journals (Sweden)

    Fok S.C.

    2011-01-01

    Full Text Available The thermal comfort of motorcycle helmet during hot weather is important as it can affect the physiological and psychological condition of the rider. This paper examines the use of phase change material (PCM to cool a motorcycle helmet and presents the experimental investigations on the influences of the simulated solar radiation, wind speed, and heat generation rate on the cooling system. The result shows that the PCM-cooled helmet is able to prolong the thermal comfort period compared to a normal helmet. The findings also indicate that the heat generation from the head is the predominant factor that will affect the PCM melting time. Simulated solar radiation and ram-air due to vehicle motion under adiabatic condition can have very little influences on the PCM melting time. The results suggested that the helmet usage time would be influenced by the amount of heat generated from the head. Some major design considerations based on these findings have been included. Although this investigation focuses on the cooling of a motorcyclist helmet, the findings would also be useful for the development of PCM-cooling systems in other applications.

  14. Microencapsulated n-octacosane as phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Sari, Ahmet; Alkan, Cemil; Karaipekli, Ali [Department of Chemistry, Gaziosmanpasa University, 60240 Tokat (Turkey); Uzun, Orhan [Department of Physics, Gaziosmanpasa University, 60240 Tokat (Turkey)

    2009-10-15

    This study deals with preparation and characterization of polymethylmetracrylate (PMMA) microcapsules containing n-octacosane as phase change material for thermal energy storage. The surface morphology, particle size and particle size distribution (PSD) were studied by scanning electron microscopy (SEM). The chemical characterization of PMMA/octacosane microcapsules was made by FT-IR spectroscopy method. Thermal properties and thermal stability of microencapsulated octacosane were determined using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The melting and freezing temperatures and the latent heats of the microencapsulated octacosane as PCM were measured as 50.6 and 53.2 C, 86.4 and -88.5 J/g, respectively, by DSC analysis. TGA analysis indicated that the microencapsulated octacosane degrade in two steps and had good chemical stability. Thermal cycling test shows that the microcapsules have good thermal reliability with respect to the accelerated thermal cycling. Based on the results, it can be considered that the microencapsulated octacosane have good energy storage potential. (author)

  15. Empirical Validation of a Thermal Model of a Complex Roof Including Phase Change Materials

    Directory of Open Access Journals (Sweden)

    Stéphane Guichard

    2015-12-01

    Full Text Available This paper deals with the empirical validation of a building thermal model of a complex roof including a phase change material (PCM. A mathematical model dedicated to PCMs based on the heat apparent capacity method was implemented in a multi-zone building simulation code, the aim being to increase the understanding of the thermal behavior of the whole building with PCM technologies. In order to empirically validate the model, the methodology is based both on numerical and experimental studies. A parametric sensitivity analysis was performed and a set of parameters of the thermal model has been identified for optimization. The use of the generic optimization program called GenOpt® coupled to the building simulation code enabled to determine the set of adequate parameters. We first present the empirical validation methodology and main results of previous work. We then give an overview of GenOpt® and its coupling with the building simulation code. Finally, once the optimization results are obtained, comparisons of the thermal predictions with measurements are found to be acceptable and are presented.

  16. Thermal Vacuum Test of Ice as a Phase Change Material Integrated with a Radiator

    Science.gov (United States)

    Lee, Steve A.; Leimkuehler, Thomas O.; Stephan, Ryan; Le, Hung V.

    2010-01-01

    Water may be used as radiation shielding for Solar Particle Events (SPE) to protect crewmembers in the Lunar Electric Rover (LER). Because the water is already present for radiation protection, it could also provide a mass efficient solution to the vehicle's thermal control system. This water can be frozen by heat rejection from a radiator and used as a Phase Change Material (PC1V1) for thermal storage. Use of this water as a PCM can eliminate the need for a pumped fluid loop thermal control system as well as reduce the required size of the radiator. This paper describes the testing and analysis performed for the Rover Engineering Development Unit (REDU), a scaled-down version of a water PCM heat sink for the LER. The REDU was tested in a thermal-vacuum chamber at environmental temperatures similar to those of a horizontal radiator panel on the lunar surface. Testing included complete freeze and melt cycles along with scaled transient heat load profiles simulating a 24-hour day for the rover.

  17. Thermal Charging Study of Compressed Expanded Natural Graphite/Phase Change Material Composites

    Energy Technology Data Exchange (ETDEWEB)

    Mallow, Anne M [ORNL; Abdelaziz, Omar [ORNL; Graham, Samuel [Georgia Institute of Technology, Atlanta

    2016-01-01

    The thermal charging performance of phase change materials, specifically paraffin wax, combined with compressed expanded natural graphite foam is studied under constant heat flux and constant temperature conditions. By varying the heat flux between 0.39 W/cm2 and 1.55 W/cm2 or maintaining a boundary temperature of 60 C for four graphite foam bulk densities, the impact on the rate of thermal energy storage is discussed. Thermal charging experiments indicate that thermal conductivity of the composite is an insufficient metric to compare the influence of graphite foam on the rate of thermal energy storage of the PCM composite. By dividing the latent heat of the composite by the time to melt for various boundary conditions and graphite foam bulk densities, it is determined that bulk density selection is dependent on the applied boundary condition. A greater bulk density is advantageous for samples exposed to a constant temperature near the melting temperature as compared to constant heat flux conditions where a lower bulk density is adequate. Furthermore, the anisotropic nature of graphite foam bulk densities greater than 50 kg/m3 is shown to have an insignificant impact on the rate of thermal charging. These experimental results are used to validate a computational model for future use in the design of thermal batteries for waste heat recovery.

  18. Increasing energy efficiency of HVAC systems of buildings using phase change material

    Directory of Open Access Journals (Sweden)

    Lee Chusak, Jared Daiber, Ramesh Agarwal

    2012-01-01

    Full Text Available Using Computational Fluid Dynamics (CFD, four different cooling systems used in contemporary office environments are modeled to compare energy consumption and thermal comfort levels. Incorporating convection and radiation technologies, full-scale models of an office room compare energy efficiency of (a an all-air overhead system, (b a combined all-air overhead and hydronic radiant system (chilled ceiling, (c an all-air raised floor system (displacement ventilation, and (d a combined displacement ventilation with a chilled ceiling. The computational domain for each model consists of one temperature varying wall (simulating the temperature of the exterior wall of the building during a 24-hour period and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room. Two sets of computations are conducted. The first set considers a glass window and plastic shade configuration for the exterior wall. The second set of computations includes a phase change material layer between the glass window and the plastic shade. Results show substantial energy savings can be accrued using the displacement ventilation and especially the displacement ventilation with a chilled ceiling over the conventional overhead mixing ventilation system. The results also show that the addition of a PCM layer to the exterior wall can significantly decrease the cooling energy requirements.

  19. Modelling of solar distillation system with phase change material (PCM storage medium

    Directory of Open Access Journals (Sweden)

    Al-Hamadani Ali A.F.

    2014-01-01

    Full Text Available An experimental investigation on a passive solar still with myristic acid as phase change material (PCM is carried out to examine the effect of both the mass of PCM and basin water on the daily distillate output and efficiency of the system under indoor simulated condition. Basic energy balance equations are written to predict the water and glass temperatures, daily distillate output and instantaneous efficiency of the single slope solar distillation system with PCM. It is found that the higher mass of PCM with lower mass of water in the solar still basin significantly increases the daily yield and efficiency, but when the amount of PCM exceeds 20 kg productivity reduces. Therefore, a novel and simple of solar stills with PCM is proposed to enhance the overall productivity of the distillation system. The new solar still has increased the distillate output by 35-40%. The use of inner glass cover temperature for productivity prediction has also been investigated, and the prediction shows relatively better agreement with the experimental data.

  20. Determination of phthalates in food packing materials by electrokinetic chromatography with polymeric pseudostationary phase.

    Science.gov (United States)

    Ni, Xinjiong; Xing, Xiaoping; Cao, Yuhua; Cao, Guangqun

    2016-01-01

    Polymeric pseudostationary phase (PSP), formed by random copolymer poly (stearyl methacrylate-co-methacrylic acid) (P(SMA-co-MAA)), was used in electrokinetic chromatography (EKC) to separate 15 kinds of phthalates (PAEs). The organic solvent modifier is a key factor for the separation of PAEs. Without organic solvents, only four kinds of PAEs with smaller molecular weight could be separated in the running buffer containing 1% P(SMA-co-MAA). The other eleven kinds of PAEs with larger molecular weight could be separated within 25 min by adding 40% (v/v) methanol and 2% (v/v) 1-butanol in the running buffer. The linear ranges of 15 kinds of PAEs were between 2 and 200mg/L, and the limit of detection based on the ratio of signal to noise of 3 were between 1 and 3mg/L. The method was applied to determination of PAEs in 6 kinds of food packing materials. The recoveries were between 81% and 118% with the RSD less than 4%.

  1. Experimental Investigation on the Effect of Phase Change Materials on Compressed Air Expansion in CAES Plants

    Directory of Open Access Journals (Sweden)

    Beatrice Castellani

    2015-07-01

    Full Text Available The integration of renewable energy in the electrical grid is challenging due to the intermittent and non-programmable generated electric power and to the transmission of peak power levels. Several energy storage technologies have been studied to find a solution to these issues. In particular, compressed air energy storage (CAES plants work by pumping and storing air into a vessel or in an underground cavern; then when energy is needed, the pressurized air is expanded in an expansion turbine. Several CAES configurations have been proposed: diabatic, adiabatic and isothermal. The isothermal process seems to be the most promising to improve the overall efficiency. It differs from conventional CAES approaches as it employs near-isothermal compression and expansion. Currently, there are no commercial isothermal CAES implementations worldwide, but several methods are under investigation. In this paper, the use of phase change materials (PCM for isothermal air expansion is discussed. Air expansion tests in presence of PCM were carried out in a high-pressure vessel in order to analyze the effect of PCM on the process. Results show that in presence of PCM near isothermal expansion conditions occur and therefore they affect positively the value of the obtainable expansion work.

  2. E-beam addressed Spatial Light Modulator employing electron trapping materials. Phase 1

    Science.gov (United States)

    Lu, Xiaojing; Yang, Xiangyang; Wrigley, Charles Y.; Bradley, Richard; Meszaros, Janos

    1995-03-01

    Spatial light modulators (SLM's) play a critically important role in optical signal processing and optical computing. A novel electron beam addressed emissive SLM which combines high performance polycrystalline electron trapping (ET) materials with an advanced field-emitter array is being developed. The proposed SLM combines high resolution (greater than 100 lplmm), high SBP (greater than 1000 x 1000), high frame rate (greater than or equal 1 KHz), high contrast ratio (greater than l03:l) and low drive voltage (less than 15 V) in a single device. The additional features of the proposed SLM are its wide variety of operation modes and electrical and optical dual-addressability. Such a SLM, if successfully developed, will surely have substantial impact on optical processing technology. During the Phase-1 efforts, a review of field emitter arrays has been done to show that it has the merits of electrical-addressability, high space-bandwidth product (SBP), low drive voltage compatible with IC driving circuitry, and high update speed. The device architecture has been investigated and the design of two prototype devices has been provided.

  3. Life Cycle Assessment of the inclusion of phase change materials (PCM) in experimental buildings

    Energy Technology Data Exchange (ETDEWEB)

    de Gracia, Alvaro; Rincon, Lidia; Castell, Albert; Medrano, Marc; Cabeza, Luisa F. [GREA Innovacio concurrent, Edifici CREA, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida (Spain); Jimenez, Melanie; Boer, Dieter [Department of Mechanical Engineering, Universitat Rovira i Virgili, Av. Paisos Catalans, 26, 43007 Tarragona (Spain)

    2010-09-15

    The present work evaluates the environmental impact of including phase change materials (PCM) in a typical Mediterranean building. A Life Cycle Assessment (LCA) is developed for three monitored cubicles built in Puigverd de Lleida (Spain). It is possible to control the inner temperature of the cubicles using a domestic heat pump for cooling and an electrical radiator for heating: The energy consumption is registered to determine the energy savings achieved. The aim is to analyze if these energy savings are large enough to balance the environmental impact originated during the manufacturing of PCM. Some hypothetical scenarios, such as different systems to control the temperature different PCM types or different weather conditions are proposed and studied using LCA process to point out the critical issues. Furthermore, a parametric analysis of the lifetime of buildings is developed. Results show that the addition of PCM in the building envelope, although decreasing the energy consumption during operation, does not reduce significantly the global impact throughout the lifetime of the building. For the hypothetical scenario considering summer conditions all year around and a lifetime of the building of 100 years, the use of PCM reduces the overall impact by more than 10%. (author)

  4. Energy Efficiency Enhancement of Photovoltaics by Phase Change Materials through Thermal Energy Recovery

    Directory of Open Access Journals (Sweden)

    Ahmad Hasan

    2016-09-01

    Full Text Available Photovoltaic (PV panels convert a certain amount of incident solar radiation into electricity, while the rest is converted to heat, leading to a temperature rise in the PV. This elevated temperature deteriorates the power output and induces structural degradation, resulting in reduced PV lifespan. One potential solution entails PV thermal management employing active and passive means. The traditional passive means are found to be largely ineffective, while active means are considered to be energy intensive. A passive thermal management system using phase change materials (PCMs can effectively limit PV temperature rises. The PCM-based approach however is cost inefficient unless the stored thermal energy is recovered effectively. The current article investigates a way to utilize the thermal energy stored in the PCM behind the PV for domestic water heating applications. The system is evaluated in the winter conditions of UAE to deliver heat during water heating demand periods. The proposed system achieved a ~1.3% increase in PV electrical conversion efficiency, along with the recovery of ~41% of the thermal energy compared to the incident solar radiation.

  5. Phase change Materials (PCM) microcapsules with different shell compositions: Preparation, characterization and thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Bayes-Garcia, L.; Ventola, L.; Cordobilla, R.; Benages, R.; Calvet, T.; Cuevas-Diarte, M.A. [Departament de Cristal.lografia, Mineralogia i Diposits Minerals, Facultat de Geologia, Universitat de Barcelona, Marti i Franques s/n, E-08028 Barcelona (Spain)

    2010-07-15

    In this study, phase change materials (Rubitherm registered RT 27) microcapsules were successfully obtained by two different methods. The main difference between them remains on the shell composition, as they are composed of different coacervates (Sterilized Gelatine/Arabic Gum for the SG/AG method and Agar-Agar/Arabic Gum for the AA/AG method). Microcapsules were thermally characterized by thermo-optical microscopy and differential scanning calorimetry. Using scanning electron microscopy, their spherical morphology (sphericity factor of 0.94-0.95) and their particle size distribution were determined, obtaining an average diameter of 12 {mu}m for the SG/AG method and lower values for the AA/AG method, where nanocapsules were also observed (average diameter of 4.3 {mu}m for the microcapsules and 104 nm for the nanocapsules). The thermal stability determination was carried out by Thermogravimetric analyses (TG) and the results show a high decomposition temperature, although the process takes places in four steps for the two mentioned methods. Moreover, the microcapsules obtained by the AA/AG method decompose in a more gradual way, as in the TG results a double step, instead of one, is appreciable. On the whole, the prepared microencapsulated PCM are totally capable of developing their role in thermal energy storage. (author)

  6. A Novel Approach to Obtain GeSbTe-Based High Speed Crystallizing Materials for Phase Change Optical Recording

    Science.gov (United States)

    2001-04-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012318 TITLE: A Novel Approach to Obtain GeSbTe -Based High Speed...UNCLASSIFIED Mat. Res. Soc. Symp. Proc. Vol. 674 © 2001 Materials Research Society A Novel Approach to Obtain GeSbTe -Based High Speed Crystallizing...fast crystallizing materials based on a conventional GeSbTe alloy for rewritable phase change optical data storage. By means of co-sputtering

  7. Tunable PhoXonic Band Gap Materials from Self-Assembly of Block Copoliymers and Colloidal Nanocrystals (NBIT Phase II)

    Science.gov (United States)

    2011-05-06

    Final Report for AOARD Grant 1014069 “Tunable PhoXonic Band Gap Materials from Self-Assembly of Block Copoliymers and Colloidal Nanocrystals...NBIT Phase II)” 5 July 2011 Name of Principal Investigators: Edwin L Thomas, Dept of Materials Science and Engineering, MIT e-mail address... elt @mit.edu Institution : Massachusetts Institute of Technology Mailing Address : 77 Mass. Avenue, 6-113, Cambridge, MA 02139 Phone : 617-253-6901

  8. Nano-Phase Powder Based Exothermic Braze Repair Technology For RCC Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Phase II project will advance innovative, cost effective and reliable nano-phase exothermic RCC joining processes (ExoBrazeTM) in order to be able to reinforce...

  9. New methods and materials for solid phase extraction and high performance liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Dumont, Philip John [Iowa State Univ., Ames, IA (United States)

    1996-04-23

    This paper describes methods for solid phase extraction and high performance liquid chromatography (HPLC). The following are described: Effects of Resin Sulfonation on the Retention of Polar Organic Compounds in Solid Phase Extraction; Ion-Chromatographic Separation of Alkali Metals In Non-Aqueous Solvents; Cation-Exchange Chromatography in Non-Aqueous Solvents; and Silicalite As a Stationary Phase For HPLC.

  10. HEAT STORAGE SYSTEM WITH PHASE CHANGE MATERIALS IN COGENERATION UNITS: STUDY OF PRELIMINARY MODEL

    Directory of Open Access Journals (Sweden)

    Claudio Caprara

    2008-12-01

    Full Text Available The continuous increase in the mechanization of farm activities, the rise in fuel prices and the environmental aspects concerning gas emissions are the main driving forces behind efforts toward more effective use of renewable energy sources and cogeneration systems even in agricultural and cattle farms. Nevertheless these systems are still not very suitable for this purpose because of their little flexibility in following the changing energy demand as opposed to the extremely various farm load curves, both in daytime and during the year. In heat recovery systems, the available thermal energy supply is always linked to power production, thus it does not usually coincide in time with the heat demand. Hence some form of thermal energy storage (TES is necessary in order to reach the most effective utilization of the energy source. This study deals with the modelling of a packed bed latent heat TES unit, integrating a cogeneration system made up of a reciprocating engine. The TES unit contains phase change materials (PCMs filled in spherical capsules, which are packed in an insulated cylindrical storage tank. Water is used as heat transfer fluid (HTF to transfer heat from the tank to the final uses, and exhausts from the engine are used as thermal source. PCMs are considered especially for their large heat storage capacity and their isothermal behaviour during the phase change processes. Despite their high energy storage density, most of them have an unacceptably low thermal conductivity, hence PCMs encapsulation technique is adopted in order to improve heat transfer. The special modular configuration of heat exchange tubes and the possibility of changing water flow through them allow to obtain the right amount of thermal energy from the tank, according to the hourly demand of the day. The model permits to choose the electrical load of the engine, the dimensions of the tank and the spheres, thickness and diameter of heat exchanger and the nature of

  11. Heat storage properties of organic phase-change materials confined in the nanospace of mesoporous SBA-15 and CMK-3.

    Science.gov (United States)

    Kadoono, Tomosuke; Ogura, Masaru

    2014-03-28

    A novel type of material encapsulating phase-change materials (PCMs) is reported concerning their implication for use as thermal energy storage devices. The composites of siliceous SBA-15 or carbonaceous CMK-3 mesoporous assemblies and organic PCMs could be used to make leak-free devices that retain their capabilities over many thermal cycles for heat storage/release. A confinement effect was observed that alters the thermal properties of the encapsulated PCM, especially in CMK-3 without any similar effects in other carbon materials.

  12. 关于多相材料的研究%About the Research of Multi-phase Materials

    Institute of Scientific and Technical Information of China (English)

    郭景坤

    2000-01-01

    多相材料是材料研究发展的必然结果。提出多相材料的研究,目的是要拓宽材料研究的视野,主张模糊各类材料的界限,运用纳米材料制备技术,博采各类材料制备工艺之所长,以使用上的要求为材料研究的准则,制作出低成本和高性能稳定性的材料。还强调在考虑材料研究中的问题时,始终以满足使用要求为目标,并不一味地追求材料的高性能,务求创新。提倡用逆向思维来考虑多相材料的研完,研究对象则针对于信息、能源、生物和环保领域的应用。多相材料材料研究About the Research of Multi-phase MaterialsGuo Jingkun (Shanghai Institute of Ceramics,Chinese Academy of Sciences ,Shanghai 200050, China)%The multi-phase materials are the inevitable result of thedevelopment of material research. In this paper the research of multiphase materials is porposed,whose purpose is to widen the field of vision of mateial re search. It is advocating that the demarcation line of various materials is blurred. It is expected that the merits of the composed phase materials are able to collect in the multi-phase material. The applying nano-fabrication technology is encouraged,and absorbing the advanced processing of various materials is emphasized. The request of application is the criterion of material research and then the suitable performance as well as high stability materials with low-cost fabrication. In this paper it is suggested that the target of material research is throughout how to satisfying the request of applications ,and to pursue creation but not only the high performance. It is recommended that the converse thought is considered for the research thinking of material. The research objects are appropriate in connection to the application for information,energy,biology and ecological environment fields.

  13. Development of a poly(dimethylacrylamide) based matrix material for solid phase high density peptide array synthesis employing a laser based material transfer

    Science.gov (United States)

    Ridder, Barbara; Foertsch, Tobias C.; Welle, Alexander; Mattes, Daniela S.; von Bojnicic-Kninski, Clemens M.; Loeffler, Felix F.; Nesterov-Mueller, Alexander; Meier, Michael A. R.; Breitling, Frank

    2016-12-01

    Poly(dimethylacrylamide) (PDMA) based matrix materials were developed for laser-based in situ solid phase peptide synthesis to produce high density arrays. In this specific array synthesis approach, amino acid derivatives are embedded into a matrix material, serving as a "solid" solvent material at room temperature. Then, a laser pulse transfers this mixture to the target position on a synthesis slide, where the peptide array is synthesized. Upon heating above the glass transition temperature of the matrix material, it softens, allowing diffusion of the amino acid derivatives to the synthesis surface and serving as a solvent for peptide bond formation. Here, we synthesized PDMA six-arm star polymers, offering the desired matrix material properties, using atom transfer radical polymerization. With the synthesized polymers as matrix material, we structured and synthesized arrays with combinatorial laser transfer. With densities of up to 20,000 peptide spots per cm2, the resolution could be increased compared to the commercially available standard matrix material. Time-of-Flight Secondary Ion Mass Spectrometry experiments revealed the penetration behavior of an amino acid derivative into the prepared acceptor synthesis surface and the effectiveness of the washing protocols.

  14. Verification and Validation of EnergyPlus Conduction Finite Difference and Phase Change Material Models for Opaque Wall Assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Tabares-Velasco, Paulo Cesar [National Renewable Energy Lab. (NREL), Golden, CO (United States); Christensen, Craig [National Renewable Energy Lab. (NREL), Golden, CO (United States); Bianchi, Marcus [National Renewable Energy Lab. (NREL), Golden, CO (United States); Booten, Chuck [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2012-07-01

    Phase change materials (PCMs) represent a potential technology to reduce peak loads and HVAC energy consumption in buildings. There are few building energy simulation programs that have the capability to simulate PCM but their accuracy has not been completely tested. This report summarizes NREL efforts to develop diagnostic tests cases to obtain accurate energy simulations when PCMs are modeled in residential buildings.

  15. Modeling Temperature Development of Li-ion Battery Packs using Phase Change Materials (PCM) and Fluid Flow

    DEFF Research Database (Denmark)

    Coman, Paul Tiberiu; Veje, Christian

    2014-01-01

    This paper presents a dynamic model for simulating the heat generation and the impact of Phase Change Materials (PCMs) on the maximum temperature in LiFePO4 battery cells. The model is constructed by coupling a one-dimensional electro-chemical model with a two-dimensional thermal model and fluid...

  16. Experimental Method Development for Estimating Solid-phase Diffusion Coefficients and Material/Air Partition Coefficients of SVOCs

    Science.gov (United States)

    The solid-phase diffusion coefficient (Dm) and material-air partition coefficient (Kma) are key parameters for characterizing the sources and transport of semivolatile organic compounds (SVOCs) in the indoor environment. In this work, a new experimental method was developed to es...

  17. Novel metallic alloys as phase change materials for heat storage in direct steam generation applications

    Science.gov (United States)

    Nieto-Maestre, J.; Iparraguirre-Torres, I.; Velasco, Z. Amondarain; Kaltzakorta, I.; Zubieta, M. Merchan

    2016-05-01

    of these proposed eutectic alloys are too high for currently available DSG solar fields, for instance the Mg49-Zn51 alloy melts at 342°C requiring saturated steam pressures above 160 bar to charge the TES unit. Being aware of this, novel eutectic metallic alloys have been designed reducing the Tms to the range between 285°C and 330°C (79bar and 145bar of charging steam pressure respectively) with ΔHfs between 150 and 170 J/g, and thus achieving metallic Phase Change Materials (PCM) suitable for the available DSG technologies.

  18. Physical and mechanical characterization of gypsum boards containing phase change materials for latent heat storage

    Directory of Open Access Journals (Sweden)

    Oliver-Ramírez, A.

    2011-09-01

    Full Text Available This article describes the design and manufacture of a gypsum board which, despite its 45 % wt content of phase change materials, meets the minimum physical and mechanical requirements laid down in the legislation on gypsum plasters (Spanish and European standard UNE EN 13279 and Spanish specifications for gypsum acceptance, RY 85. Under this design, a one-metre square, 1.5-cm thick board contains 4.75 kg of PCM, much more than in any prior drylining (the maximum attained to date is 3 kg per m2. The mechanical and physical characteristics of this new composite were previously improved with two joint-action additives: polypropylene fibres and melamine formaldehyde as a dispersing agent. In the 20-30 ºC temperature range, a gypsum board 1.5 cm thick containing this percentage of PCMs can store five times more thermal energy than conventional plasterboard of the same thickness, and the same amount of energy as half-foot hollow brick masonry.

    En esta investigación se ha diseñado y fabricado un panel de escayola que incorpora un 45% en peso de material de cambio de fase, manteniendo las propiedades físicas y mecánicas exigidas en la normativa de aplicación para yesos de construcción (UNE EN 13279 y referencias a la RY 85. Así, un panel de 1,0 m2 y 1,5 cm de espesor, contiene 4,75 kg de PCM, cantidad muy superior a la conseguida hasta la fecha (3 kg/m2. Para ello se ha mejorado previamente sus prestaciones mecánicas y físicas mediante adiciones binarias: fibras de polipropileno y dispersión de melanina formaldehído. Este porcentaje es capaz de almacenar en 1,5 cm de espesor cinco veces la energía térmica de un panel de cartón yeso con el mismo espesor y la misma cantidad que una fábrica de 1/2 pie de ladrillo hueco, en el rango de temperaturas próximas a la de confort (20-30 ºC.

  19. Thermal characteristics of non-edible oils as phase change materials candidate to application of air conditioning chilled water system

    Science.gov (United States)

    Irsyad, M.; Indartono, Y. S.; Suwono, A.; Pasek, A. D.

    2015-09-01

    The addition of phase change material in the secondary refrigerant has been able to reduce the energy consumption of air conditioning systems in chilled water system. This material has a high thermal density because its energy is stored as latent heat. Based on material melting and freezing point, there are several non-edible oils that can be studied as a phase change material candidate for the application of chilled water systems. Forests and plantations in Indonesia have great potential to produce non-edible oil derived from the seeds of the plant, such as; Calophyllum inophyllum, Jatropha curcas L, and Hevea braziliensis. Based on the melting temperature, these oils can further studied to be used as material mixing in the secondary refrigerant. Thermal characteristics are obtained from the testing of T-history, Differential Scanning Calorimetric (DSC) and thermal conductivity materials. Test results showed an increase in the value of the latent heat when mixed with water with the addition of surfactant. Thermal characteristics of each material of the test results are shown completely in discussion section of this article.

  20. Light-Driven Liquid Crystalline Materials: From Photo-Induced Phase Transitions and Property Modulations to Applications.

    Science.gov (United States)

    Bisoyi, Hari Krishna; Li, Quan

    2016-12-28

    Light-driven phenomena both in living systems and nonliving materials have enabled truly fascinating and incredible dynamic architectures with terrific forms and functions. Recently, liquid crystalline materials endowed with photoresponsive capability have emerged as enticing systems. In this Review, we focus on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade. Design and synthesis of photochromic liquid crystals (LCs), photoinduced phase transitions in LC, and photoalignment and photoorientation of LCs have been covered. Photomodulation of pitch, polarization, lattice constant and handedness inversion of chiral LCs is discussed. Light-driven phenomena and properties of liquid crystalline polymers, elastomers, and networks have also been analyzed. The applications of photoinduced phase transitions, photoalignment, photomodulation of chiral LCs, and photomobile polymers have been highlighted wherever appropriate. The combination of photochromism, liquid crystallinity, and fabrication techniques has enabled some fascinating functional materials which can be driven by ultraviolet, visible, and infrared light irradiation. Nanoscale particles have been incorporated to widen and diversify the scope of the light-driven liquid crystalline materials. The developed materials possess huge potential for applications in optics, photonics, adaptive materials, nanotechnology, etc. The challenges and opportunities in this area are discussed at the end of the Review.

  1. Development of a prototype thermoelectric space cooling system using phase change material to improve the performance

    Science.gov (United States)

    Zhao, Dongliang

    The thermoelectric cooling system has advantages over conventional vapor compression cooling devices, including compact in size, light in weight, high reliability, no mechanical moving parts, no refrigerant, being powered by direct current, and easily switching between cooling and heating modes. However, it has been long suffering from its relatively high cost and low energy efficiency, which has restricted its usage to niche applications, such as space missions, portable cooling devices, scientific and medical equipment, where coefficient of performance (COP) is not as important as reliability, energy availability, and quiet operation environment. Enhancement of thermoelectric cooling system performance generally relies on two methods: improving thermoelectric material efficiency and through thermoelectric cooling system thermal design. This research has been focused on the latter one. A prototype thermoelectric cooling system integrated with phase change material (PCM) thermal energy storage unit for space cooling has been developed. The PCM thermal storage unit used for cold storage at night, functions as the thermoelectric cooling system's heat sink during daytime's cooling period and provides relatively lower hot side temperature for the thermoelectric cooling system. The experimental test of the prototype system in a reduced-scale chamber has realized an average cooling COP of 0.87, with the maximum value of 1.22. Another comparison test for efficacy of PCM thermal storage unit shows that 35.3% electrical energy has been saved from using PCM for the thermoelectric cooling system. In general, PCM faces difficulty of poor thermal conductivity at both solid and liquid phases. This system implemented a finned inner tube to increase heat transfer during PCM charging (melting) process that directly impacts thermoelectric system's performance. A simulation tool for the entire system has been developed including mathematical models for a single thermoelectric module

  2. Preparation of Composite Phase Change Material Based on Sol-Gel Method and Its Temperature-Adjustable Textile

    Institute of Scientific and Technical Information of China (English)

    YI Shi-xiong; MA Xiao-guang; ZHANG Ying; LI Hua

    2009-01-01

    In this study, the sol-gel method was introduced to prepare the composite phase change material (CPCM). The CPCM was added to fabric with coating techniques and the thermal activity of modified fabric was studied. In addition, the thermal property and the microstructure of CPCM were also discussed in detail by means of polarization microscope and differential scanning calorimeter, respectively. According to the analysis of main influencial factors of the property of CPCM, the optimal preparing technique was determined. It was proved that CPCM could exhibit a good thermal property while phase transformation process took place, and a better appearance of the fabric modified with CPCM could be obtained due to the fact that in a warm circumstance, the liquid-state phase change material could be firmly enwrapped and embedded in the three-dimensional network all the time during the phase transformation. Besides, the fabric treated with CPCM had a high phase-transition enthalpy and an appropriate phase-transition temperature. As a result, a desirable temperature-adjustable function appeared.

  3. Phase Change Materials: Technology Status and Potential Defence Applications (Review Papers

    Directory of Open Access Journals (Sweden)

    Ravindra Kumar

    2011-10-01

    Full Text Available Phase change materials (PCM are being utilised world over for energy storage and temperature smoothening applications. Defence Laboratory Jodhpur (DLJ has initiated a R&D programme to apply PCM in solving many heat related problems being faced by Indian forces during desert operations specially failure of mission-critical components. Under the programme, special organic PCM (Patent application no. 2258/DEL/2007 and low melting metal alloys have been developed well tuned to desert diurnal cycle. The PCM panels, when applied as an internal lining in buildings, structures and vehicles can moderate the extreme temperature within human tolerable range (below 40 °C without the use of any external power for cooling. The panels can also act as power saver in air conditioned buildings. A cool vest has also been developed with chargeable PCM packs to provide comfortable microenvironment to a soldier on field duty (below 30 °C for 2-3 hrs. To improve reliability of mission critical electronic instruments during desert operation, technology of absorptive PCM heat sinks is under development at DLJ. The special heat sink will absorb heat generated by component for critical mission (up to 1 hr independent of environment temperature and thus ensure smooth functioning of critical components even in extreme hot conditions. In present paper status of PCM technology world over has been reviewed along with the brief account of research on PCM at DLJ.Defence Science Journal, 2011, 61(6, pp.576-582, DOI:http://dx.doi.org/10.14429/dsj.61.363

  4. Utilization of phase change materials in solar domestic hot water systems

    Energy Technology Data Exchange (ETDEWEB)

    Mazman, Muhsin; Evliya, Hunay; Paksoy, Halime Oe. [Chemistry Dept., Art and Science Fac., Cukurova University, Balcali, Adana (Turkey); Cabeza, Luisa F.; Nogues, Miquel [Dept. Informatica i Eng. Industrial, Universitat de Lleida, Jaume II 69, 25001 Lleida (Spain); Mehling, Harald [ZAE Bayern, Division 1, Walther-Meissner-Str. 6, 85748 Garching (Germany)

    2009-06-15

    Thermal energy storage systems which keep warm and cold water separated by means of gravitational stratification have been found to be attractive in low and medium temperature thermal storage applications due to their simplicity and low cost. This effect is known as thermal stratification, and has been studied experimentally thoughtfully. This system stores sensible heat in water for short term applications. Adding PCM (phase change material) modules at the top of the water tank would give the system a higher storage density and compensate heat loss in the top layer because of the latent heat of PCM. Tests were performed under real operating conditions in a complete solar heating system that was constructed at the University of Lleida, Spain. In this work, new PCM-graphite compounds with optimized thermal properties were used, such as 80:20 weight percent ratio mixtures of paraffin and stearic acid (PS), paraffin and palmitic acid (PP), and stearic acid and myristic acid (SM). The solar domestic hot water (SDHW) tank used in the experiments had a 150 L water capacity. Three modules with a cylindrical geometry with an outer diameter of 0.176 m and a height of 0.315 m were used. In the cooling experiments, the average tank water temperature dropped below the PCM melting temperature range in about 6-12 h. During reheating experiments, the PCM could increase the temperature of 14-36 L of water at the upper part of the SDHW tank by 3-4 C. This effect took place in 10-15 min. It can be concluded that PS gave the best results for thermal performance enhancement of the SDHW tank (74% efficiency). (author)

  5. Application of phase-change materials in passive solar systems. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Sliwkowski, J.

    1979-01-01

    The Institute of Energy Conversion of the University of Delaware has designed and constructed a modular, hybrid passive solar energy collection and storage unit called the Thermal Wall Panel. The Thermal Wall Panel uses the concept of energy storage in phase change materials combined with direct solar gain. In the winter of 1977-78, the Thermal Wall Panel was tested at Solar One, the Institute's solar house and laboratory. The key results and conclusions from this testing and analysis program include the following: (1) Based on measurements, a Thermal Wall Panel with movable nighttime insulation (R = 6.80) between the storage components and the outside can retain and deliver as heat an average of 45 percent of the sun's energy which falls on it during the day. (2) Based on calculations, a 120 square foot wall can provide about 25 percent of the heating needs of a 1100 square foot house. Analysis indicates that when the Thermal Wall Panel (R = 6.00 nighttime insulation) is combined with other direct gain passive solar energy systems as large, south-facing windows, 56 percent of a home's heating needs can be provided. (3) A Thermal Wall Panel can be installed into a typical home in the Mid-Atlantic Region for an incremental cost of from $6 to $8 per square foot beyond the cost of the normal wall and pay for itself in 5 to 9 years at 1978 energy costs. Also, the Thermal Wall Panel does not require any additional foundation support. (4) A computer model has been developed for the Thermal Wall Panel which shows good agreement with predicted and measured performance. Based on these results, it is recommended that full-scale testing of the system be initiated at multiple sites in the Mid-Atlantic Region.

  6. Heat Storage Performance of the Prefabricated Hollow Core Concrete Deck Element with Integrated Microencapsulated Phase Change Material

    DEFF Research Database (Denmark)

    Pomianowski, Michal Zbigniew; Heiselberg, Per; Jensen, Rasmus Lund

    2012-01-01

    of thermal properties of standard concrete material and pure PCM. Consequently, the numerical models of the decks were updated with the experimentally determined thermal properties of PCM concrete after these two materials have been combined into one material. Finally, the heat storage of the decks......The paper presents the numerically calculated dynamic heat storage capacity of the prefabricated hollow core concrete deck element with and without microencapsulated phase change material (PCM). The reference deck is the ordinary deck made of standard concrete material and that is broadly used...... in many emerging buildings. The new concrete deck with microencapsulated PCM is the standard deck on which one more layer with PCM concrete was added and at the same time the latent heat storage was introduced to the construction. The challenge to simulate the performance of the new deck with PCM concrete...

  7. Numerical analysis of melting of nano-enhanced phase change material in latent heat thermal energy storage system

    Directory of Open Access Journals (Sweden)

    Kashani Sina

    2014-01-01

    Full Text Available The heat transfer enhancement in the latent heat thermal energy storage system through dispersion of nanoparticle is reported. The resulting nanoparticle-enhanced phase change materials exhibit enhanced thermal conductivity in comparison to the base material. Calculation is performed for nanoparticle volume fraction from 0 to 0.08. In this study rectangular and cylindrical containers are modeled numerically and the effect of containers dimensions and nano particle volume fraction are studied. It has been found that the rectangular container requires half of the melting time as for the cylindrical container of the same volume and the same heat transfer area and also, higher nano particle volume fraction result in a larger solid fraction. The increase of the heat release rate of the nanoparticle-enhanced phase change materials shows its great potential for diverse thermal energy storage application.

  8. On metallic gratings coated conformally with isotropic negative-phase-velocity materials

    Energy Technology Data Exchange (ETDEWEB)

    Inchaussandague, Marina E. [GEA-Grupo de Electromagnetismo Aplicado, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); CONICET-Consejo Nacional de Investigaciones Cientificas y Tecnicas, Rivadavia 1917, Buenos Aires (Argentina)], E-mail: mei@df.uba.ar; Lakhtakia, Akhlesh [CATMAS-Computational and Theoretical Materials Sciences Group, Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802-6812 (United States)], E-mail: akhlesh@psu.edu; Depine, Ricardo A. [GEA-Grupo de Electromagnetismo Aplicado, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); CONICET-Consejo Nacional de Investigaciones Cientificas y Tecnicas, Rivadavia 1917, Buenos Aires (Argentina)], E-mail: rdep@df.uba.ar

    2008-03-31

    Application of the differential method (also called the C method) to plane-wave diffraction by a perfectly conducting, sinusoidally corrugated metallic grating coated with a linear, homogeneous, isotropic, lossless dielectric-magnetic material shows that coating materials with negative index of refraction may deliver enhanced maximum nonspecular reflection efficiencies in comparison to coating materials with positive index of refraction.

  9. Study on preparation and thermal properties of sodium nitrate/silica composite as shape-stabilized phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Qiang [State Key Lab of Chemical Engineering, Department of Chemical Engineering Tsinghua University, Beijing 100084 (China); Postdoctoral Work Station, Shenhua Group Corporation Limited, Beijing 100011 (China); Wang, Tao, E-mail: taowang@tsinghua.edu.cn [State Key Lab of Chemical Engineering, Department of Chemical Engineering Tsinghua University, Beijing 100084 (China)

    2015-08-10

    Highlights: • The NaNO{sub 3}/SiO{sub 2} composite was prepared as shape-stabilized PCM by sol–gel process. • The composite had good thermal energy storage and release ability. • The latent heat was increased with the increase of the roasting temperature. - Abstract: A sodium nitrate (NaNO{sub 3})/silica (SiO{sub 2}) composite was prepared as a shape-stabilized phase change material by a sol–gel procedure. In this composite, NaNO{sub 3} acted as the phase change material and SiO{sub 2} was used as the supporting material. The maximal weight percentage of NaNO{sub 3} in the composite was determined to be 60 wt.%. The chemical composition, morphology, structure and thermal properties were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC) and Laser thermal conductivity meter. The DSC results indicated that the enthalpies of melting and freezing of the NaNO{sub 3}/SiO{sub 2} (60 wt.% NaNO{sub 3}) composite were 108 kJ/kg and 110 kJ/kg, and the corresponding temperatures of the phase transition were 302 °C and 300 °C, respectively. In the temperature range of lower than 500 °C the phase change enthalpy of the composite was increased with the increase of the roasting temperature.

  10. High accuracy interface characterization of three phase material systems in three dimensions

    DEFF Research Database (Denmark)

    Jørgensen, Peter Stanley; Hansen, Karin Vels; Larsen, Rasmus;

    2010-01-01

    Quantification of interface properties such as two phase boundary area and triple phase boundary length is important in the characterization ofmanymaterial microstructures, in particular for solid oxide fuel cell electrodes. Three-dimensional images of these microstructures can be obtained by tom...

  11. Asymmetric induced cubic nonlinearities in homogeneous and quasi-phase-matched quadratic materials: signature and importance

    DEFF Research Database (Denmark)

    Bang, Ole; Corney, Joel Frederick

    2001-01-01

    In continuous-wave operation asymmetric induced nonlinearities induce an intensity-dependent phase mismatch that implies a nonzero so-called separatrix intensity, the crossing of which changes the one-period phase shift of the fundamental by Pi , with obvious use in switching applications.We deri...

  12. Novel materials and methods for solid-phase extraction and liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Ambrose, Diana [Iowa State Univ., Ames, IA (United States)

    1997-06-24

    This report contains a general introduction which discusses solid-phase extraction and solid-phase micro-extraction as sample preparation techniques for high-performance liquid chromatography, which is also evaluated in the study. This report also contains the Conclusions section. Four sections have been removed and processed separately: silicalite as a sorbent for solid-phase extraction; a new, high-capacity carboxylic acid functionalized resin for solid-phase extraction; semi-micro solid-phase extraction of organic compounds from aqueous and biological samples; and the high-performance liquid chromatographic determination of drugs and metabolites in human serum and urine using direct injection and a unique molecular sieve.

  13. Research & Development of Materials/Processing Methods for Continuous Fiber Ceramic Composites (CFCC) Phase 2 Final Report.

    Energy Technology Data Exchange (ETDEWEB)

    Szweda, A.

    2001-01-01

    The Department of Energy's Continuous Fiber Ceramic Composites (CFCC) Initiative that begun in 1992 has led the way for Industry, Academia, and Government to carry out a 10 year R&D plan to develop CFCCs for these industrial applications. In Phase II of this program, Dow Corning has led a team of OEM's, composite fabricators, and Government Laboratories to develop polymer derived CFCC materials and processes for selected industrial applications. During this phase, Dow Corning carried extensive process development and representative component demonstration activities on gas turbine components, chemical pump components and heat treatment furnace components.

  14. Experimental Conditions to Obtain Photopolymerization Induced Phase Separation Process in Liquid Crystal-Photopolymer Composite Materials under Laser Exposure

    Directory of Open Access Journals (Sweden)

    Manuel Ortuño

    2014-01-01

    Full Text Available We analyze the experimental conditions necessary to obtain a photopolymerization induced phase separation process inside liquid crystal-photopolymer composite materials. Composites stored for 24 hours perform poorly in hologram recording but a good result is obtained if they are used recently prepared. We use a procedure combining heat and sonication to disarrange the liquid crystal structures formed during storage of the composite. We also propose incoherent light treatment after recording the hologram in order to evaluate if the phase separation evolved correctly during hologram recording.

  15. New nanocrystalline materials: a previously unknown simple cubic phase in the SnS binary system.

    Science.gov (United States)

    Rabkin, Alexander; Samuha, Shmuel; Abutbul, Ran E; Ezersky, Vladimir; Meshi, Louisa; Golan, Yuval

    2015-03-11

    We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due to the nanoscale size and minute amounts of these particles in the synthesis yield, the structure was exclusively solved using electron diffraction methods. The atomic model of the new phase (a = 11.7 Å, P2(1)3) was deduced and found to be associated with the rocksalt-type structure. Kramers-Kronig analysis predicted different optical and electronic properties for the new phase, as compared to α-SnS.

  16. INTERACTION OF A SCREW DISLOCATION WITH AN INTERFACIAL EDGE CRACK IN A TWO-PHASE PIEZOELECTRIC MATERIAL

    Institute of Scientific and Technical Information of China (English)

    LIU Jinxi; LIU Ai; JIANG Zhiqing

    2004-01-01

    The interaction of a screw dislocation with an interfacial edge crack in a two-phase piezoelectric medium is investigated. Closed-form solutions of the elastic and electrical fields induced by the screw dislocation are derived using the conformal mapping method in conjunction with the image principle. Based on the electroelastic fields derived, the stress and electric displacement intensity factors, the image force acting on the dislocation are given explicitly. We find that the stress and electric displacement intensity factors depend on the effective electroelastic material constants. In the case where one of two phases is purely elastic, the stress intensity factor and image force are plotted to illustrate the influences of electromechanical coupling effect, the position of the dislocation and the material properties on the interaction mechanism.

  17. Ultrasonic Phased Array Sound Field Mapping Through Large-Bore Coarse Grained Cast Austenitic Stainless Steel (CASS) Piping Materials

    Energy Technology Data Exchange (ETDEWEB)

    Cinson, Anthony D.; Crawford, Susan L.; Prowant, Matthew S.; Diaz, Aaron A.; Hathaway, John E.; Anderson, Michael T.

    2012-04-16

    A sound field beam mapping exercise was conducted to further understand the effects of coarse grained microstructures found in CASS materials on phased array ultrasonic wave propagation. Laboratory measurements were made on three CASS specimens with different microstructures; the specimens were polished and etched to reveal measurable grain sizes, shapes and orientations. Three longitudinal, phased array probes were fixed on a specimen's outside diameter with the sound field directed toward one end (face) of the pipe segment over a fixed range of angles. A point receiver was raster scanned over the surface of the specimen face generating a sound field image. A slice of CASS material was then removed from the specimen end and the beam mapping exercise repeated. The sound fields acquired were analyzed for spot size, coherency, and beam redirection. Analyses were conducted between the resulting sound fields and the microstructural characteristics of each specimen.

  18. Numerical Heat Transfer Studies of a Latent Heat Storage System Containing Nano-Enhanced Phase Change Material

    Directory of Open Access Journals (Sweden)

    S F Hosseinizadeh

    2011-01-01

    Full Text Available The heat transfer enhancement in the latent heat thermal energy storage system through dispersion of nanoparticle is reported. The resulting nanoparticle-enhanced phase change materials (NEPCM exhibit enhanced thermal conductivity in comparison to the base material. The effects of nanoparticle volume fraction and some other parameters such as natural convection are studied in terms of solid fraction and the shape of the solid-liquid phase front. It has been found that higher nanoparticle volume fraction result in a larger solid fraction. The present results illustrate that the suspended nanoparticles substantially increase the heat transfer rate and also the nanofluid heat transfer rate increases with an increase in the nanoparticles volume fraction. The increase of the heat release rate of the NEPCM shows its great potential for diverse thermal energy storage application.

  19. Graphene-Based Materials as Solid Phase Extraction Sorbent for Trace Metal Ions, Organic Compounds, and Biological Sample Preparation.

    Science.gov (United States)

    Ibrahim, Wan Aini Wan; Nodeh, Hamid Rashidi; Sanagi, Mohd Marsin

    2016-07-03

    Graphene is a new carbon-based material that is of interest in separation science. Graphene has extraordinary properties including nano size, high surface area, thermal and chemical stability, and excellent adsorption affinity to pollutants. Its adsorption mechanisms are through non-covalent interactions (π-π stacking, electrostatic interactions, and H-bonding) for organic compounds and covalent interactions for metal ions. These properties have led to graphene-based material becoming a desirable adsorbent in a popular sample preparation technique known as solid phase extraction (SPE). Numerous studies have been published on graphene applications in recent years, but few review papers have focused on its applications in analytical chemistry. This article focuses on recent preconcentration of trace elements, organic compounds, and biological species using SPE-based graphene, graphene oxide, and their modified forms. Solid phase microextraction and micro SPE (µSPE) methods based on graphene are discussed.

  20. Effects of two-phase flow on the deflagration of porous energetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Margolis, S.B. [Sandia National Labs., Livermore, CA (United States); Williams, F.A. [Univ. of California, San Diego, La Jolla, CA (United States). Dept. of Applied Mechanics and Engineering Sciences

    1994-07-01

    Theoretical analyses are developed for the multi-phase deflagration of porous energetic solids, such as degraded nitramine propellants, that experience significant gas flow in the solid preheat region and are characterized by the presence of exothermic reactions in a bubbling melt layer at their surfaces. Relative motion between the gas and condensed phases is taken into account in both regions, and expressions for the mass burning rate and other quantities of interest, such as temperature and volume-fraction profiles, are derived by activation-energy asymptotics. The model extends recent work by allowing for gas flow in the unburned solid, and by incorporating pressure effects through the gas-phase equation of state. As a consequence, it is demonstrated how most aspects of the deflagration wave, including its structure, propagation speed and final temperature, depend on the local pressure in the two-phase regions.

  1. Synthesis, phase and reaction mechanism of nonlinear optical material MnTeMoO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Chengguo; Shao, Juxiang; Yang, Junsheng; Wan, Mingjie [Yibin University, Key Laboratory of Computational Physics of Sichuan Province, Yibin (China); Yibin University, School of Physics and Electronic Engineering, Yibin (China); Luo, Huafeng [Yibin University, College of Chemistry and Chemical Engineering, Yibin (China); Huang, Xingyong [Yibin University, School of Physics and Electronic Engineering, Yibin (China); Wang, Fanhou [Yibin University, Key Laboratory of Computational Physics of Sichuan Province, Yibin (China)

    2016-09-15

    Pure polycrystalline MnTeMoO{sub 6} is highly desirable to crystal growth. Polycrystalline MnTeMoO{sub 6} has been synthesized by solid-state reaction techniques. The optimized preparation process, phase purity and reaction mechanism of polycrystalline MnTeMoO{sub 6} were investigated. The reaction will be paused if the atoms cannot pass through the grain boundary and restarted after ground intimately. A new method combined with X-ray diffraction and microscopic observation is employed to determine the phase purity of polycrystalline MnTeMoO{sub 6}. Pure polycrystalline MnTeMoO{sub 6} with gray color and single crystalline phase can be obtained after the reactant was calcined at 500 C for 20 h three times and can be used to crystal growth. This method for determining the phase purity of powder sample can be used in the synthesis of other polycrystalline powders. (orig.)

  2. Stress engineering for the design of morphotropic phase boundary in piezoelectric material

    Energy Technology Data Exchange (ETDEWEB)

    Ohno, Tomoya, E-mail: ohno@mail.kitami-it.ac.jp [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan); Yanagida, Hiroshi; Maekawa, Kentaroh [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan); Arai, Takashi; Sakamoto, Naonori; Wakiya, Naoki; Suzuki, Hisao [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561 (Japan); Satoh, Shigeo [Graduate School of Science and Engineering, Ibaragi University, 4-12-1 Nakanarusawa-cho, Hitachi, Ibaragi 316-0033 (Japan); Matsuda, Takeshi [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan)

    2015-06-30

    Alkoxide-derived lead zirconate titanate thin films having Zr/Ti = 50/50 to 60/40 compositions with different residual stress conditions were deposited on a Si wafer to clarify the effects of the residual stress on the morphotropic phase boundary shift. The residual stress condition was controlled to − 0.1 to − 0.9 GPa by the design of the buffer layer structure on the Si wafer. Results show that the maximum effective piezoelectric constant d{sub 33} was obtained at 58/42 composition under − 0.9 GPa compressive residual stress condition. Moreover, the MPB composition shifted linearly to Zr-rich phase with increasing compressive residual stress. - Highlights: • The residual stress in lead zirconate titanate film on silicon was controlled. • The maximum residual stress in lead zirconate titanate film was − 0.9 GPa. • The morphotropic phase boundary shifted to zirconium rich phase by the strain.

  3. On modeling shape memory polymers as elastic two-phase composite materials

    OpenAIRE

    Gilormini, Pierre; Diani, Julie

    2012-01-01

    International audience; A model has been proposed recently, which describes the experimentally observed mechanical behavior of some shape memory polymers. It considers a purely thermoelastic behavior, without strain rate effects, and assumes essentially that the polymer can be considered as a two-phase composite, with glassy and rubbery phases having volume fractions that depend on temperature only. Since a uniform stress hypothesis was used in the original formulation, with an inconsistency ...

  4. Molecularly imprinted polymers: New molecular recognition materials for selective solid-phase extraction of organic compounds

    OpenAIRE

    Martín Esteban, A.

    2001-01-01

    During the last few years molecularly imprinted polymers have appeared as new selective sorbents for solid-phase extraction of organic compounds in different samples. Molecular imprinting technology involves the preparation of a polymer with specific recognition sites for certain molecules. Once the polymer has been obtained, it can be used in solid-phase extraction protocols, where a careful selection of the most appropriate solvents to be used in the different steps (sample loading, washing...

  5. Performance Evaluation of Various Phase Change Materials for Thermal Energy Storage of A Solar Cooker via Numerical Simulation

    Directory of Open Access Journals (Sweden)

    Dede Tarwidi

    2016-11-01

    Full Text Available In this paper, thermal performance of various phase change materials (PCMs used as thermal energy storage in a solar cooker has been investigated numerically. Heat conduction equations in cylindrical domain are used to model heat transfer of the PCMs. Mathematical model of phase change problem in the PCM storage encompasses heat conduction equations in solid and liquid region separated by moving solid-liquid interface. The phase change problem is solved by reformulating heat conduction equations with emergence of moving boundary into an enthalpy equation. Numerical solution of the enthalpy equation is obtained by implementing Godunov method and verified by analytical solution of one-dimensional case. Stability condition of the numerical scheme is also discussed. Thermal performance of various PCMs is evaluated via the stored energy and temperature history. The simulation results show that phase change material with the best thermal performance during the first 2.5 hours of energy extraction is shown by erythritol. Moreover, magnesium chloride hexahydrate can maintain temperature of the PCM storage in the range of 110-116.7°C for more than 4 hours while magnesium nitrate hexahydrate is effective only for one hour with the PCM storage temperature around 121-128°C. Among the PCMs that have been tested, it is only erythritol that can cook 10 kg of the loaded water until it reaches 100°C for about 3.5 hours. Article History: Received June 22nd 2016; Received in revised form August 26th 2016; Accepted Sept 1st 2016; Available online How to Cite This Article: Tarwidi, D., Murdiansyah, D.T, Ginanja, N. (2016 Performance Evaluation of Various Phase Change Materials for Thermal Energy Storage of A Solar Cooker via Numerical Simulation. Int. Journal of Renewable Energy Development, 5(3, 199-210. http://dx.doi.org/10.14710/ijred.5.3.199-210

  6. Strain localization in polycrystalline material with second phase particles: Numerical modeling with application to ice mixtures

    Science.gov (United States)

    Cyprych, D.; Brune, S.; Piazolo, S.; Quinteros, J.

    2016-09-01

    We use a centimeter-scale 2-D numerical model to investigate the effect of the presence of a second phase with various volume percent, shape, and orientation on strain localization in a viscoelastic matrix. In addition, the evolution of bulk rheological behavior of aggregates during uniaxial compression is analyzed. The rheological effect of dynamic recrystallization processes in the matrix is reproduced by viscous strain softening. We show that the presence of hard particles strengthens the aggregate, but also causes strain localization and the formation of ductile shear zones in the matrix. The presence of soft particles weakens the aggregate, while strain localizes within the particles and matrix between particles. The shape and the orientation of second phases control the orientation, geometry, and connectivity of ductile shear zones. We propose an analytical scaling method that translates the bulk stress measurements of our 2-D simulations to 3-D experiments. Comparing our model to the laboratory uniaxial compression experiments on ice cylinders with hard second phases allows the analysis of transient and steady-state strain distribution in ice matrix, and strain partitioning between ice and second phases through empirical calibration of viscous softening parameters. We find that the ice matrix in two-phase aggregates accommodates more strain than the applied bulk strain, while at faster strain rates some of the load is transferred into hard particles. Our study illustrates that dynamic recrystallization processes in the matrix are markedly influenced by the presence of a second phase.

  7. Elaboration of Conductive Thermal Storage Composites Made of Phase Change Materials and Graphite for Solar Plant

    Energy Technology Data Exchange (ETDEWEB)

    Pincemin, S.; Py, X.; Olives, R.; Christ, M.; Oettinger, O.

    2006-07-01

    New thermal storage composites made of graphite and PCM have been developed for the Solar plant of Almeria TROUGH different elaboration routes. Those materials are presented with their respective properties (enhanced thermal conductivities, thermal storage capacities, stability) and compared together. Both the laboratory and industrial scales are considered and corresponding material compared. (Author)

  8. Te-free environmental materials of TixSb2.19Se applied in phase change memory

    Science.gov (United States)

    Zhu, Yueqin; Song, Sannian; Li, Le; Xie, Huaqing; Song, Zhitang; Liu, Bo; Wu, Junxing

    2016-10-01

    Environmental friendly Te-free phase change material of TixSb2.19Se was investigated for PCM application. As the important thermal properties, the crystallization temperature (Tc) and data retention for ten years for the best selected composition Ti0.34Sb2.19Se (TSS) are 234°C and 160‡C, respectively. Detection of the crystal structure of TSS by means of XRD, TEM and XPS reveals that the grains are more uniform compared with Ge2Sb2Te5 (GST). The Set and Reset operation voltages for TSS-based phase change memory devices are much lower than those of conventional GST-based ones. Remarkably, the TSS device exhibits an extremely high phase change speed of 10 ns.

  9. Hydrophilic solid-phase extraction of melamine with ampholine-modified hybrid organic-inorganic silica material.

    Science.gov (United States)

    Wang, Tingting; Zhu, Yiming; Ma, Junfeng; Xuan, Rongrong; Gao, Haoqi; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

    2015-01-01

    In this work, an ampholine-functionalized hybrid organic-inorganic silica sorbent was successfully used to extract melamine from a milk formula sample by a hydrophilic interaction solid-phase extraction protocol. Primary factors affecting the extraction efficiency of the material such as extraction solvent, elution solvent, sample loading volume, and elution volume have been thoroughly optimized. Under the optimized hydrophilic solid-phase extraction conditions, the recoveries of melamine spiked in milk formula samples ranged from 86.2 to 101.8% with relative standard deviations of 4.1-9.4% (n = 3). The limit of detection (S/N = 3) was 0.32 μg/g. The adsorption capacity toward melamine was 30 μg of melamine per grams of sorbent. Due to its simplicity, rapidity and cost effectiveness, the newly developed hydrophilic solid-phase extraction method should provide a promising tool for daily monitoring of doped melamine in milk formula.

  10. Heat transfer and parametric studies of an encapsulated phase change material based cool thermal energy storage system

    Institute of Scientific and Technical Information of China (English)

    CHERALATHAN M.; VELRAJ R.; RENGANARAYANAN S.

    2006-01-01

    This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES)system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature histories of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. The model was also used to investigate the effect of porosity, Stanton number, Stefan number and Peclet number on CTES system performance. The results showed that increase in porosity contributes to a higher rate of energy storage. However, for a given geometry and heat transfer coefficient, the mass of PCM charged in the unit decreases as the increase in porosity. The St number as well as the Ste number is also influential in the performance of the unit. The model is a convenient and more suitable method to determine the heat transfer characteristics of CTES system. The results reported are much useful for designing CTES system.

  11. Using the Analytic Hierarchy Process to Prioritize and Select Phase Change Materials for Comfort Application in Buildings

    Directory of Open Access Journals (Sweden)

    Socaciu Lavinia Gabriela

    2014-03-01

    Full Text Available Phase change materials (PCMs selection and prioritization for comfort application in buildings have a significant contribution to the improvement of latent heat storage systems. PCMs have a relatively large thermal energy storage capacity in a temperature range close to their switch point. PCMs absorb energy during the heating process as phase change takes place and release energy to the environment in the phase change range during a reverse cooling process. Thermal energy storage systems using PCMs as storage medium offer advantages such as: high heat storage capacity and store/release thermal energy at a nearly constant temperature, relative low weight, small unit size and isothermal behaviour during charging and discharging when compared to the sensible thermal energy storage. PCMs are valuable only in the range of temperature close to their phase change point, since their main thermal energy storage capacity depend on their mass and on their latent heat of fusion. Selection of the proper PCMs is a challenging task because there are lots of different materials with different characteristics. In this research paper the principles and techniques of the Analytic Hierarchy Process (AHP are presented, discussed and applied in order to prioritize and select the proper PCMs for comfort application in buildings. The AHP method is used for solving complex decisional problems and allows the decision maker to take the most suitable decisions for the problem studied. The results obtained reveal that the AHP method can be successfully applied when we want to choose a PCM for comfort application in buildings.

  12. Nano-scale gap filling and mechanism of deposit-etch-deposit process for phase-change material

    Institute of Scientific and Technical Information of China (English)

    Ren Wan-Chun; Liu Bo; Song Zhi-Tang; Xiang Yang-Hui; Wang Zong-Tao; Zhang Bei-Chao; Feng Song-Lin

    2012-01-01

    Ge2Sb2Te5 gap filling is one of the key processes for phase-change random access memory manufacture.Physical vapor deposition is the mainstream method of Ge2Sb2Te5 film deposition due to its advantages of film quality,purity,and accurate composition control.However,the conventional physical vapor deposition process cannot meet the gapfilling requirement with the critical device dimension scaling down to 90 nm or below.In this study,we find that the deposit-etch-deposit process shows better gap-filling capability and scalability than the single-step deposition process,especially at the nano-scale critical dimension.The gap-filling mechanism of the deposit-etch-deposit process was briefly discussed.We also find that re-deposition of phase-change material from via the sidewall to via the bottom by argon ion bombardment during the etch step was a key ingredient for the final good gap filling.We achieve void-free gap filling of phase-change material on the 45-nm via the two-cycle deposit-etch-deposit process.We gain a rather comprehensive insight into the mechanism of deposit-etch-deposit process and propose a potential gap-filling solution for over 45-nm technology nodes for phase-change random access memory.

  13. Novel restricted access materials combined to molecularly imprinted polymers for selective solid-phase extraction of organophosphorus pesticides from honey.

    Science.gov (United States)

    He, Juan; Song, Lixin; Chen, Si; Li, Yuanyuan; Wei, Hongliang; Zhao, Dongxin; Gu, Keren; Zhang, Shusheng

    2015-11-15

    A novel restricted access materials (RAM) combined to molecularly imprinted polymers (MIPs), using malathion as template molecule and glycidilmethacrylate (GMA) as pro-hydrophilic co-monomer, were prepared for the first time. RAM-MIPs with hydrophilic external layer were characterized by scanning electron microscopy and recognition and selectivity properties were compared with the restricted access materials-non-molecularly imprinted polymers (RAM-NIPs) and unmodified MIPs. RAM-MIPs were used as the adsorbent enclosed in solid phase extraction column and several important extraction parameters were comprehensively optimized to evaluate the extraction performance. Under the optimum extraction conditions, RAM-MIPs exhibited comparable or even higher selectivity with greater extraction capacity toward six kinds of organophosphorus pesticides (including malathion, ethoprophos, phorate, terbufos, dimethoate, and fenamiphos) compared with the MIPs and commercial solid phase extraction columns. The RAM-MIPs solid phase extraction coupled with gas chromatography was successfully applied to simultaneously determine six kinds of organophosphorus pesticides from honey sample. The new established method showed good linearity in the range of 0.01-1.0 μg mL(-1), low limits of detection (0.0005-0.0019 μg mL(-1)), acceptable reproducibility (RSD, 2.26-4.81%, n = 6), and satisfactory relative recoveries (90.9-97.6%). It was demonstrated that RAM-MIPs solid phase extraction with excellent selectivity and restricted access function was a simple, rapid, selective, and effective sample pretreatment method.

  14. 方腔内合金相变材料的熔化过程%Phase Change Process of Alloy Phase Change Material in a Rectangular

    Institute of Scientific and Technical Information of China (English)

    郭茶秀; 陈俊

    2015-01-01

    The melting process of alloy phase change material in a rectangular under temperature difference is simulated by CFD software. The simulation model is verified by the experimental result. The impacts of the natural convection on the solid-liquid interface, the temperature and the circulation speed in the melting process are analyzed. The results show that the phase change material in rectangular should to be heated from the two sides and the bottom in order to reduce heat transfer resistance and get a faster melting speed.%本文利用CFD软件对方腔内合金相变材料在温差作用下的熔化过程进行了数值模拟研究.通过与试验结果的比较,验证了本文采用的模型和算法的正确性.同时,详细研究了熔化过程中合金相变材料的固?液界面、温度及环流速度的变化规律.结果表明,为了减小传热热阻,加快合金的熔化速度,从方腔的侧面和底面加热相变材料时熔化效果最好.

  15. Reversible crystal-to-amorphous-to-crystal phase transition and a large magnetocaloric effect in a spongelike metal organic framework material.

    Science.gov (United States)

    Tian, Chong-Bin; Chen, Rui-Ping; He, Chao; Li, Wei-Jin; Wei, Qi; Zhang, Xu-Dong; Du, Shao-Wu

    2014-02-21

    Reversible crystal-to-amorphous-to-crystal phase transition accompanied by changes in magnetic and NLO properties was first observed in a rigid non-porous spongelike MOF material. The crystal phase exhibits a high magnetocaloric effect, while the amorphous phase has potential application as a magnetic DMF sensor.

  16. The electro-mechanical phase transition of Gent model dielectric elastomer tube with two material constants

    Science.gov (United States)

    Liu, Liwu; Luo, Xiaojian; Fei, Fan; Wang, Yixing; Leng, Jinsong; Liu, Yanju

    2013-04-01

    Applied to voltage, a dielectric elastomer membrane may deform into a mixture of two states under certain conditions. One of which is the flat state and the other is the wrinkled state. In the flat state, the membrane is relatively thick with a small area, while on the contrary, in the wrinkled state, the membrane is relatively thin with a large area. The coexistence of these two states may cause the electromechanical phase transition of dielectric elastomer. The phase diagram of idea dielectric elastomer membrane under unidirectional stress and voltage inspired us to think about the liquid-to-vapor phase transition of pure substance. The practical working cycle of a steam engine includes the thermodynamical process of liquid-to-vapor phase transition, the fact is that the steam engine will do the maximum work if undergoing the phase transition process. In this paper, in order to consider the influence of coexistent state of dielectric elastomer, we investigate the homogeneous deformation of the dielectric elastomer tube. The theoretical model is built and the relationship between external loads and stretch are got, we can see that the elastomer tube experiences the coexistent state before reaching the stretching limit from the diagram. We think these results can guide the design and manufacture of energy harvesting equipments.

  17. Microstructure and phase transformation behavior of Mo-MoSi2 gradient material

    Institute of Scientific and Technical Information of China (English)

    Ying-Yi Zhang; Yun-Gang Li; Yong-Hong Qi; Xue-Feng Shi

    2015-01-01

    Mo-MoSi2 gradient coating on Mo substrate was prepared by siliconizing process,using the polysilicon as silicon atoms.The gradient layer was analyzed by the experimental results,theoretical analysis,and thermodynamic calculation.The silicon,molybdenum content of gradient coating shows a gradual change regulation.The reaction between silicon and molybdenum is most likely to generate Mo5Si3,then MoSi2,finally Mo3Si,but when the silicon content is excessive,the Mo5Si3 and Mo3Si will react with silicon and generate MoSi2.The gradient layer is mainly constituted by Si and MoSi2,only about 1/10 gradient layer is constituted by Mo5Si3 and Mo3Si,and the stable existences of Mo5Si3 and Mo3Si are mainly determined by the silicon content.Along the Mo substrate to the surface of the coating,the phase compo sition of gradient coating changes as follows:Mo → transition layer,Mo (main phase) + Mo3Si + Mo5Si3 →intermediate layer,and MoSi2 (main phase)+ Mo5Si3 + Si → surface layer MoSi2 (main phase)+ Si,and the experimental temperature has no effect on phase composition of gradient coating.

  18. Improved thermal stability of N-doped Sb materials for high-speed phase change memory application

    Science.gov (United States)

    Hu, Yifeng; Zhu, Xiaoqin; Zou, Hua; Zhang, Jianhao; Yuan, Li; Xue, Jianzhong; Sui, Yongxing; Wu, Weihua; Song, Sannian; Song, Zhitang

    2016-05-01

    Compared with pure Sb, N-doped Sb material was proved to be a promising candidate for the phase change memory (PCM) use because of its higher crystallization temperature (˜250 °C), larger crystallization activation energy (3.53 eV), and better data retention ability (166 °C for 10 years). N-doping also broadened the band gap and refined grain size. The reversible resistance transition could be achieved by an electric pulse as short as 8 ns for the PCM cell based on N-doped Sb material. A lower operation power consumption (the energy for RESET operation 2.2 × 10-12 J) was obtained. In addition, N-doped Sb material showed a good endurance of 1.8 × 105 cycles.

  19. An Experimental Study on the Thermal Performance of Phase-Change Material and Wood-Plastic Composites for Building Roofs

    Directory of Open Access Journals (Sweden)

    Min Hee Chung

    2017-02-01

    Full Text Available We assessed the usefulness of phase-change material (PCM-based thermal plates fabricated from wood-plastic composites (WPCs in mitigating the urban heat island effect. The thermal performance of plates containing PCMs with two different melting temperatures and with two different albedo levels was evaluated. The results showed that the PCM with a melting temperature of 44 °C maintained lower surface and inner temperatures than the PCM with a melting temperature of 25 °C. Moreover, a higher surface albedo resulted in a lower surface temperature. However, the thermal performance of PCMs with different melting temperatures but the same surface albedo did not differ. Using PCM-based materials in roof finishing materials can reduce surface temperatures and improve thermal comfort.

  20. Preparation of urea-formaldehyde paraffin microcapsules modified by carboxymethyl cellulose as a potential phase change material

    Institute of Scientific and Technical Information of China (English)

    Zhan-hua Huang; Xin Yu; Wei Li; Shou-xin Liu

    2015-01-01

    We prepared spherical microcapsules modified by carboxymethyl cellulose (CMC) with urea-formalde-hyde (UF) resin as a shell material with a two-step process by in situ polymerization, and characterized the micro-cosmic features, chemical structure, and thermal perfor-mance of the microcapsules by SEM, FTIR, DSC, and TGA. We studied the effects of different experimental parameters of curing pH, the amounts of the emulsifier and emulsion speed. The CMC-UF microcapsules had good heat resistance and stability. The enthalpy of CMC-UF microcapsules reached 50.33 J g-1. Therefore, CMC-UF resin can be used as a potential wall material of phase change materials.

  1. Adaptive Back Sheet Material for Acoustic Liner Applications-ARMD Seedling Fund Phase I Final Report

    Science.gov (United States)

    Gerhold, Carl H.; Jones, Michael G.; Farrar, Dawnielle

    2014-01-01

    A recently developed piezo-electric composite film is evaluated for its usefulness in application in acoustic liners. Researchers at the NASA Langley Research Center Liner Technology Facility developed experiments to measure the electrical response of the material to acoustic excitation and the vibrational response of the material to electrical excitation. The robustness of the piezo-electric film was also assessed. The material's electrical response to acoustic excitation is found to be comparable to a commercial microphone in the range of frequencies from 500 to 3000 Hz. However, the vibrational response to electrical excitation in the frequency range of interest is an order of magnitude less than may be necessary for application to acoustic liners. Nevertheless, experimental results indicate that the potential exists for the material to produce a measurable change in the impedance spectrum of a liner. Work continues to improve the authority of the piezo-electric film.

  2. EXPERIMENTATION OF THREE PHASE OUTER ROTATING SWITCHED RELUCTANCE MOTOR WITH SOFT MAGNETIC COMPOSITE MATERIALS

    Directory of Open Access Journals (Sweden)

    N. C. LENIN

    2017-01-01

    Full Text Available This paper presents the application of Soft Magnetic Composite (SMC material in Outer Rotating Switched Reluctance Motor (ORSRM. The presented stator core of the Switched Reluctance Motor was made of two types of material, the classical laminated silicon steel sheet and the soft magnetic composite material. First, the stator core made of laminated steel has been analysed. The next step is to analyse the identical geometry SRM with the soft magnetic composite material, SOMALOY for its stator core. The comparisons of both cores include the calculated torque and torque ripple, magnetic conditions, simplicity of fabrication and cost. The finite element method has been used to analyse the magnetic conditions and the calculated torque. Finally, tested results shows that SMC is a better choice for SRM in terms of torque ripple and power density.

  3. Phase behaviour of macromolecular liquid crystalline materials. Computational studies at the molecular level

    CERN Document Server

    Stimson, L M

    2003-01-01

    Molecular simulations provide an increasingly useful insight into the static and dynamic characteristics of materials. In this thesis molecular simulations of macro-molecular liquid crystalline materials are reported. The first liquid crystalline material that has been investigated is a side chain liquid crystal polymer (SCLCP). In this study semi-atomistic molecular dynamics simulations have been conducted at a range of temperatures and an aligning potential has been applied to mimic the effect of a magnetic field. In cooling the SCLCP from an isotropic melt, microphase separation was observed yielding a domain structure. The application of a magnetic field to this structure aligns the domains producing a stable smectic mesophase. This is the first study in which mesophases have been observed using an off-lattice model of a SCLCP. The second material that has been investigated is a dendrimer with terminal mesogenic functionalization. Here, a multi-scale approach has been taken with Monte Carlo studies of a s...

  4. Surface Characterization of Some Novel Bonded Phase Packing Materials for HPLC Columns Using MAS-NMR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Jude Abia

    2015-03-01

    Full Text Available Information on the surface properties of three novel chemically bonded phase packing materials for High performance liquid chromatography (HPLC were obtained using spectra obtained by solid state cross-polarization (CP magic-angle spinning (MAS nuclear magnetic resonance (NMR spectroscopic experiments for the 29Si, and 13C nuclei. These packing materials were: Cogent bidentate C18 bonded to type-C silica, hybrid packing materials XTerra MS C18, and XBridge Prep. C18. The spectra obtained using cross-polarization magic angle spinning (CP-MAS on the Cogent bidentate C18 bonded to type-C silica show the surface to be densely populated with hydride groups (Si-H, with a relative surface coverage exceeding 80%. The hybrid packing materials XTerra and XBridge gave spectra that reveal the silicon atoms to be bonded to organic moieties embedded in the molecular structure of these materials with over 90% of the alkyl silicon atoms found within the completely condensed silicon environments. The hydrolytic stability of these materials were investigated in acidic aqueous solutions at pHs of 7.0 and 3.0, and it was found that while the samples of XTerra and XBridge were not affected by hydrolysis at this pH range, the sample of Cogent lost a significant proportion of its Si-H groups after five days of treatment in acidic aqueous solution.

  5. Metal-Organic Vapor Phase Epitaxial Reactor for the Deposition of Infrared Detector Materials

    Science.gov (United States)

    2015-04-09

    ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park , NC 27709-2211 Epitaxial reactor, MOCVD, Infrared Materials, CdTe and...researchers from First Solar in depositing single crystal solar cell materials. A research contract worth over $150K was awarded to RPI b First Solar based on...Administrative Support Army Contracting Command - APG Research Triangle Park Division TEL: (919) 549-4269 FAX: (919) 549-4388 Table of

  6. On grain growth kinetics in two-phase polycrystalline materials through Monte Carlo simulation

    Indian Academy of Sciences (India)

    K R Phaneesh; Anirudh Bhat; Gautam Mukherjee; K T Kashyap

    2013-08-01

    Monte Carlo Potts model simulation was carried out on a 2D square lattice for various surface fractions of second phase particles for over 50,000 iterations. The observations are in good agreement with known theoretical and experimental results with respect to both growth kinetics as well as grain size distribution. Further, the average grain size and the largest grain size were computed for various surface fractions which have indicated normal grain growth and microstructure homogeneity. The surface fraction of the second phase particles interacting with the grain boundaries (), hitherto not computed through the simulation route, is shown to vary inversely as the average grain size due to Zener pinning.

  7. Origin, secret, and application of the ideal phase-change material GeSbTe

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Noboru [Advanced Technology Research Laboratories, Panasonic Corporation, 3-4 Hikaridai, Seika-cho, Soraku-gun, 619-0237 Kyoto (Japan); Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Central 4, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8562 (Japan)

    2012-10-15

    Discovery of the GeSbTe phase-change alloy in particular along the GeTe-Sb{sub 2}Te{sub 3} tie-line took place in the mid-1980s. The amorphous alloys showed ideal properties, for example, high thermal stability at r.t. and laser-induced rapid crystallization with large optical changes. Thereafter, GeSbTe was successively applied to various optical disks such as DVDs and BDs. Through DSC and XRD analyses, the appearance of the metastable phase having a NaCl-type structure was observed over a wide compositional region. This was the ''key'' to realizing the ideal phase-change properties. During this year, the role of the constituent elements of Ge and Sb became clear by RMC modeling using AXS data at SPring-8, where the ''nucleation dominant crystallization process'' was well explained. The aspect of the latest Blu-ray Disc (BD) product of Panasonic: GeSbTe phase-change films are utilized in every recording layer. It is seen that the front-side recording layers, L1 and L2, are highly transparent. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. A compressed hydrogen gas storage system with an integrated phase change material

    DEFF Research Database (Denmark)

    Mazzucco, Andrea; Rothuizen, Erasmus Damgaard; Jørgensen, Jens Erik;

    2015-01-01

    below the critical temperature of 85 °C, while filling the hydrogen at ambient temperature. Results show that a 10-mm-thick layer of paraffin wax can absorb enough heat to reduce the adiabatic temperature by 20 K when compared to a standard Type IV tank. The heat transfer from the gas to the phase...

  9. Nondestructive material characterization of meteorites with synchrotron-based high energy x-ray phase micro-computed tomography

    Science.gov (United States)

    Liu, Huiqiang; Xiao, Tiqiao; Xie, Honglan; Fu, Yanan; Zhang, Xueliang; Fan, Xiaoxi

    2017-02-01

    Synchrotron radiation based x-ray propagation-based micro-computed tomography (SRPCT) has been widely used to nondestructively access 3D structural information in many fields in the last decade. However, for strongly absorbed objects with small density-differential compositions, conventional SRPCT technique fails in providing high-contrast images for visualization of objects characteristic information except edge-enhancements at interfaces or boundaries of samples. In this study, we successfully employed the SRPCT technique with phase retrieval, the high energy x-ray phase-attenuation-duality (PAD) algorithm, into nondestructive material characterization of invaluable meteorite samples due to the greatly enhanced phase-contrast of different bulk material areas, as compared to conventional SRPCT on equal dose basis. Our experimental results demonstrated the PAD-SRPCT technique is superior to conventional SRPCT technique to access density and structure distributions of different meteorite compositions with high density resolution, owing to the striking contrast-to-noise ratio (CNR). In addition, a new mass-density measurement method was presented to estimate the mass density of different compositions in the meteorite sample based on the calibration of the imaging system.

  10. Preparation, characterization and thermal properties of binary nitrate salts/expanded graphite as composite phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Junbing [School of Materials and Energy, Guangdong University of Technology, 510006 Guangzhou (China); Huang, Jin, E-mail: huangjiner@126.com [School of Materials and Energy, Guangdong University of Technology, 510006 Guangzhou (China); Zhu, Panpan; Wang, Changhong [School of Materials and Energy, Guangdong University of Technology, 510006 Guangzhou (China); Li, Xinxi [School of Materials and Energy, Guangdong University of Technology, 510006 Guangzhou (China); Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing (China)

    2014-07-01

    Highlights: • The expanded graphite enhanced thermal conductivity coefficient greatly. • The aqueous solution method adopting ultrasonic was utilized to disperse EG. • The combination of composite was physical without chemical reaction. • The reduction on total latent heat was slight after the adding EG. - Abstract: The binary nitrate salts/expanded graphite (EG) composite phase change material (PCM) were prepared via adding different mass rate of EG to binary nitrate salts consisting of NaNO{sub 3} and KNO{sub 3} (6:4) by aqueous solution method adopting ultrasonic. The morphology and chemical composition of EG and the composite PCM were characterized and investigated by X-ray diffraction (XRD), scan electron microscope (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM), respectively. Laser thermal conductivity instrument and differential scanning calorimeter (DSC) were employed to measure thermo physical properties. Drawing the conclusion from investigation, that EG had enhanced thermal conductivity coefficient which largely increased to 4.884 W/(m K) and reduced total latent heat by mostly 11.0%. The morphology and phase structure results indicated that EG were well dispersed into and physically combined with molten salts. In general, the prepared composite PCM could be a suitable phase change material for thermal energy storage.

  11. Formation and emissions of carbonyls during and following gas-phase ozonation of indoor materials

    DEFF Research Database (Denmark)

    Poppendieck, D.G.; Hubbard, H.F.; Weschler, Charles J.;

    2007-01-01

    from 1 to 20 mg m(-2), with most of the carbonyls being of lower molecular weight (C-1-C-4). In contrast, total BOBP mass released from wood-based products ranged from 20 to 100 mg m(-2), with a greater fraction of the BOBPs being heavier carbonyls (C-5-C-9). The total BOBP mass released during...... relatively high BOBP releases. The greatest overall BOBP mass releases were observed for three materials that building occupants might have significant contact with: paper, office partition, and medium density fiberboard, e.g., often used in office furniture. These materials also exhibited extended BOBP...

  12. Polymer composites and porous materials prepared by thermally induced phase separation and polymer-metal hybrid methods

    Science.gov (United States)

    Yoon, Joonsung

    The primary objective of this research is to investigate the morphological and mechanical properties of composite materials and porous materials prepared by thermally induced phase separation. High melting crystallizable diluents were mixed with polymers so that the phase separation would be induced by the solidification of the diluents upon cooling. Theoretical phase diagrams were calculated using Flory-Huggins solution thermodynamics which show good agreement with the experimental results. Porous materials were prepared by the extraction of the crystallized diluents after cooling the mixtures (hexamethylbenzene/polyethylene and pyrene/polyethylene). Anisotropic structures show strong dependence on the identity of the diluents and the composition of the mixtures. Anisotropic crystal growth of the diluents was studied in terms of thermodynamics and kinetics using DSC, optical microscopy and SEM. Microstructures of the porous materials were explained in terms of supercooling and dendritic solidification. Dual functionality of the crystallizable diluents for composite materials was evaluated using isotactic polypropylene (iPP) and compatible diluents that crystallize upon cooling. The selected diluents form homogeneous mixtures with iPP at high temperature and lower the viscosity (improved processability), which undergo phase separation upon cooling to form solid particles that function as a toughening agent at room temperature. Tensile properties and morphology of the composites showed that organic crystalline particles have the similar effect as rigid particles to increase toughness; de-wetting between the particle and iPP matrix occurs at the early stage of deformation, followed by unhindered plastic flow that consumes significant amount of fracture energy. The effect of the diluents, however, strongly depends on the identity of the diluents that interact with the iPP during solidification step, which was demonstrated by comparing tetrabromobisphenol-A and

  13. Electrode Materials, Thermal Annealing Sequences, and Lateral/Vertical Phase Separation of Polymer Solar Cells from Multiscale Molecular Simulations

    KAUST Repository

    Lee, Cheng-Kuang

    2014-12-10

    © 2014 American Chemical Society. The nanomorphologies of the bulk heterojunction (BHJ) layer of polymer solar cells are extremely sensitive to the electrode materials and thermal annealing conditions. In this work, the correlations of electrode materials, thermal annealing sequences, and resultant BHJ nanomorphological details of P3HT:PCBM BHJ polymer solar cell are studied by a series of large-scale, coarse-grained (CG) molecular simulations of system comprised of PEDOT:PSS/P3HT:PCBM/Al layers. Simulations are performed for various configurations of electrode materials as well as processing temperature. The complex CG molecular data are characterized using a novel extension of our graph-based framework to quantify morphology and establish a link between morphology and processing conditions. Our analysis indicates that vertical phase segregation of P3HT:PCBM blend strongly depends on the electrode material and thermal annealing schedule. A thin P3HT-rich film is formed on the top, regardless of bottom electrode material, when the BHJ layer is exposed to the free surface during thermal annealing. In addition, preferential segregation of P3HT chains and PCBM molecules toward PEDOT:PSS and Al electrodes, respectively, is observed. Detailed morphology analysis indicated that, surprisingly, vertical phase segregation does not affect the connectivity of donor/acceptor domains with respective electrodes. However, the formation of P3HT/PCBM depletion zones next to the P3HT/PCBM-rich zones can be a potential bottleneck for electron/hole transport due to increase in transport pathway length. Analysis in terms of fraction of intra- and interchain charge transports revealed that processing schedule affects the average vertical orientation of polymer chains, which may be crucial for enhanced charge transport, nongeminate recombination, and charge collection. The present study establishes a more detailed link between processing and morphology by combining multiscale molecular

  14. Diffuse Interface Methods for Multiple Phase Materials: An Energetic Variational Approach

    CERN Document Server

    Brannick, J; Qian, T; Sun, H

    2014-01-01

    In this paper, we introduce a diffuse interface model for describing the dynamics of mixtures involving multiple (two or more) phases. The coupled hydrodynamical system is derived through an energetic variational approach. The total energy of the system includes the kinetic energy and the mixing (interfacial) energies. The least action principle (or the principle of virtual work) is applied to derive the conservative part of the dynamics, with a focus on the reversible part of the stress tensor arising from the mixing energies. The dissipative part of the dynamics is then introduced through a dissipation function in the energy law, in line with the Onsager principle of least energy dissipation. The final system, formed by a set of coupled time-dependent partial differential equations, reflects a balance among various conservative and dissipative forces and governs the evolution of velocity and phase fields. To demonstrate the applicability of the proposed model, a few two-dimensional simulations have been car...

  15. Removal of Oxygen from Electronic Materials by Vapor-Phase Processes

    Science.gov (United States)

    Palosz, Witold

    1997-01-01

    Thermochemical analyses of equilibrium partial pressures over oxides with and without the presence of the respective element condensed phase, and hydrogen, chalcogens, hydrogen chalcogenides, and graphite are presented. Theoretical calculations are supplemented with experimental results on the rate of decomposition and/or sublimation/vaporization of the oxides under dynamic vacuum, and on the rate of reaction with hydrogen, graphite, and chalcogens. Procedures of removal of a number of oxides under different conditions are discussed.

  16. Controlling the near-field excitation of nano-antennas with phase-change materials

    OpenAIRE

    2013-01-01

    By utilizing the strongly induced plasmon coupling between discrete nano-antennas and quantitatively controlling the crystalline proportions of an underlying Ge2Sb2Te5 (GST) phase-change thin layer, we show that nanoscale light localizations in the immediate proximity of plasmonic nano-antennas can be spatially positioned. Isolated energy hot-spots at a subwavelength scale can be created and adjusted across the landscape of the plasmonic system at a step resolution of λ/20. These findings int...

  17. Melting of nanoparticle-enhanced phase change material inside an enclosure heated by laminar heat transfer fluid flow

    Science.gov (United States)

    Elbahjaoui, Radouane; El Qarnia, Hamid; El Ganaoui, Mohammed

    2016-05-01

    The proposed work presents a numerical investigation of the melting of a phase change material (PCM: Paraffin wax P116) dispersed with nanoparticles (Al2O3) in a latent heat storage unit (LHSU). The latter is composed of a number of vertical and identical slabs of nano-enhanced phase change material (NEPCM) separated by rectangular channels through which passes heat transfer fluid (HTF: water). A mathematical model based on the conservation equations of mass, momentum and energy has been developed. The resulting equations are discretized using the finite volume approach. The numerical model has been validated by experimental and numerical results published in literature. Numerical investigations have been conducted to evaluate the effects of the volumetric fraction of nanoparticles, HTF mass flow rate and inlet temperature on the latent heat storage unit's thermal behaviour and performance. Modelling results show that the volumetric fraction, HTF mass flow rate and inlet temperature need to be designed to achieve a significant improvement in thermal performance. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  18. Backward phase-matching for nonlinear optical generation in negative-index materials

    Science.gov (United States)

    Lan, Shoufeng; Kang, Lei; Schoen, David T.; Rodrigues, Sean P.; Cui, Yonghao; Brongersma, Mark L.; Cai, Wenshan

    2015-08-01

    Metamaterials have enabled the realization of unconventional electromagnetic properties not found in nature, which provokes us to rethink the established rules of optics in both the linear and nonlinear regimes. One of the most intriguing phenomena in nonlinear metamaterials is `backward phase-matching', which describes counter-propagating fundamental and harmonic waves in a negative-index medium. Predicted nearly a decade ago, this process is still awaiting a definitive experimental confirmation at optical frequencies. Here, we report optical measurements showing backward phase-matching by exploiting two distinct modes in a nonlinear plasmonic waveguide, where the real parts of the mode refractive indices are 3.4 and -3.4 for the fundamental and the harmonic waves respectively. The observed peak conversion efficiency at the excitation wavelength of ~780 nm indicates the fulfilment of the phase-matching condition of k2ω = 2kω and n2ω = -nω, where the coherent harmonic wave emerges along a direction opposite to that of the incoming fundamental light.

  19. Cold-rolled complex-phase steels: AHSS material with remarkable properties

    Energy Technology Data Exchange (ETDEWEB)

    Hebesberger, T.; Pichler, A.; Walch, C.; Blaimschein, M. [voestalpine Stahl GmbH, Linz (Austria); Spiradek-Hahn, K. [ARC Seibersdorf Research GmbH (Austria)

    2005-07-01

    The reduction of the body-in-white weight, in combination with stiffness and crash safety improvements is of fundamental interest in the automotive industry. Therefore, several Advanced High Strength Steel (AHSS) grades have been developed in the last several years, whereby the main focus was laid on dual-phase (DP) and TRIP steels. Recently, a new high strength steel grade - complex-phase (CP) steels - is gaining more and more interest. In contrast to DP grades of similar strength level, CP grades have a significantly higher yield strength and thus a higher yield ratio. Although, CP grades reach lower elongation values in the tensile test, they show an excellent bendability and stretch-flangeability. Due to this remarkable balance between strength, bendability and stretch-flangeability, complex-phase steels are potential candidates for roll-formed parts and parts where sharp radii and/or a good formability of punched edges are required. Therefore, the microstructure, the processing, and the formability of CP grades are discussed in detail in this work. (orig.)

  20. Hardening in Two-Phase Materials. I. Strength Contributions in Fibre-Reinforced Copper-Tungsten

    DEFF Research Database (Denmark)

    Lilholt, Hans

    1977-01-01

    Cyclic tests (Bauschinger tests) were conducted at 77 K and at room temperature on the fibre-reinforced material of single crystal Cu with long W-fibres of diameter 20 mum and volume fractions up to 4%. These tests enabled two important contributions to the total strength of the unrelaxed materia...

  1. Preparation and properties of lauric acid/silicon dioxide composites as form-stable phase change materials for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Fang Guiyin, E-mail: gyfang@nju.edu.cn [Department of Physics, Nanjing University, Hankou Road 22, Nanjing, Jiangsu 210093 (China); Li Hui [Department of Material Science and Engineering, Nanjing University, Nanjing 210093 (China); Liu Xu [Department of Physics, Nanjing University, Hankou Road 22, Nanjing, Jiangsu 210093 (China)

    2010-08-01

    Form-stable lauric acid (LA)/silicon dioxide (SiO{sub 2}) composite phase change materials were prepared using sol-gel methods. The LA was used as the phase change material for thermal energy storage, with the SiO{sub 2} acting as the supporting material. The structural analysis of these form-stable LA/SiO{sub 2} composite phase change materials was carried out using Fourier transformation infrared spectroscope (FT-IR). The microstructure of the form-stable composite phase change materials was observed by a scanning electronic microscope (SEM). The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetric analysis apparatus (TGA), respectively. The SEM results showed that the LA was well dispersed in the porous network of SiO{sub 2}. The DSC results indicated that the melting latent heat of the form-stable composite phase change material is 117.21 kJ kg{sup -1} when the mass percentage of the LA in the SiO{sub 2} is 64.8%. The results of the TGA showed that these materials have good thermal stability. The form-stable composite phase change materials can be used for thermal energy storage in waste heat recovery and solar heating systems.

  2. Numerical Simulation for Effects of Microcapsuled Phase Change Material (mpcm) Distribution on Heat and Moisture Transfer in Porous Textiles

    Science.gov (United States)

    Li, Fengzhi

    In recent years, the use of phase change materials (PCM) to improve heat and moisture transfer properties of clothing has gained considerable attention. The PCM distribution in the clothing impacts heat and moisture transfer properties of the clothing significantly. For describing the mechanisms of heat and moisture transfer in clothing with PCM and investigating the effect of the PCM distribution, a new dynamic model of coupled heat and moisture transfer in porous textiles with PCM was developed. The effect of water content on physical parameters of textiles and heat transfer with phase change in the PCM microcapsules were considered in the model. Meanwhile, the numerical predictions were compared with experimental data, and good agreement was observed between the two, indicating that the model was satisfactory. Also the effects of the PCM distribution on heat transfer in the textiles-PCM microcapsule composites were investigated by using the model.

  3. Si2Sb2Te5 phase change material studied by an atomic force microscope nano-tip

    Institute of Scientific and Technical Information of China (English)

    Liu Yanbo; Zhang Ting; Niu Xiaoming; Song Zhitang; Min Guoquan; Zhang Jing; Zhou Weimin; Wan Yongzhong; Zhang Jianping; Li Xiaoli; Feng Songlin

    2009-01-01

    The Si2Sb2Te5 phase change material has been studied by applying a nano-tip (30 nm in diameter) on an atomic force microscopy system. Memory switching from a high resistance state to a low resistance state has been achieved, with a resistance change of about 1000 times. In a typical Ⅰ-Ⅴ curve, the current increases significantly after the voltage exceeds~4.3 V. The phase transformation of a Si2Sb2Te5 film was studied in situ by means of in situ X-ray diffraction and temperature dependent resistance measurements. The thermal stability of Si2Sb2Te5 and Ge2Sb2Te5 was characterized and compared as well.

  4. Structural phase transformations in V{sub 2}O{sub 5} thin film cathode material for Li rechargeable batteries

    Energy Technology Data Exchange (ETDEWEB)

    McGraw, J.M.; Perkins, J.D.; Zhang, J.G.; Parilla, P.A.; Ciszek, T.F.; Fu, M.L.; Trickett, D.M.; Turner, J.A.; Ginley, D.S.

    1998-07-01

    The authors report on investigations of V{sub 2}O{sub 5} thin film cathodes prepared by pulsed laser deposition and the phase transformations which occur during electrochemical cycling. The experimental results on PLD-grown, textured V{sub 2}O{sub 5} crystalline films occur with reports in the literature that there is a voltage threshold above which, cycling appears to be completely reversible and below which, cycling appears to be irreversible. Crystalline films discharged beyond the threshold to 2.0 V vs. Li exhibited an immediate and continuous fade in capacity as well as a {approximately}90% decrease in XRD peak intensity and a similar decrease in Raman signal intensity in as few as 10 cycles. They have made {omega}-phase material by both electrochemically discharging virgin, crystalline V{sub 2}O{sub 5} and by further discharging previously cycled films which showed irreversible structural changes.

  5. Field dependence of the magnetic entropy change in typical materials with a second-order phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Dong Qiaoyan [State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Zhang Hongwei [State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)], E-mail: hwzhang@g203.iphy.ac.cn; Shen Juelian; Sun Jirong; Shen Baogen [State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

    2007-12-15

    Magnetic field dependence of the magnetic entropy change ({delta}S) is the key for magnetic refrigeration. For magnetic materials with a second-order phase transition, the experimental data can be well fitted by the formula of {delta}S=-kM{sub s}(0)h{sup 2/3}-S(0,0) for a practical field change from 0 to h (the reduced field), where M{sub s}(0) is the spontaneous magnetization at 0 K. The constant k is approximately equal to 1.00 T/K, and S(0,0) is interestingly found to be negative. The formula is discussed based on the renormalization group approach to scaling. The attempts have also been made using the formula for NaZn{sub 13}-type La(Fe,Si){sub 13} compounds with a magnetic first-order phase transition.

  6. Preparation and characterization of form-stable paraffin/polycaprolactone composites as phase change materials for thermal energy storage

    Directory of Open Access Journals (Sweden)

    Aludin M.S.

    2017-01-01

    Full Text Available Paraffin is Phase Change Materials (PCM that possesses desirable properties such as high thermal energy storage and thermal stability to make it suitable for thermal energy storage applications. However, paraffin has been reported to leak out during the melting process. In this study, composites were prepared by dissolving paraffin and polycaprolactone (PCL at varied mass percent compositions in chloroform and then purified through precipitation techniques. The leakage test was conducted by placing the composite samples on a set of four-layer filter papers and left in a furnace at 90°C for 1 hour. By incorporating PCL into paraffin phase, the leakage mass percentage was drastically reduced. The PCL polymer matrix in the composites may have trapped the paraffin molecules during melting process thus prevent it from leaking.

  7. Existence and regularity of solutions of a phase field model for solidification with convection of pure materials in two dimensions

    Directory of Open Access Journals (Sweden)

    Jose Luiz Boldrini

    2003-11-01

    Full Text Available We study the existence and regularity of weak solutions of a phase field type model for pure material solidification in presence of natural convection. We assume that the non-stationary solidification process occurs in a two dimensional bounded domain. The governing equations of the model are the phase field equation coupled with a nonlinear heat equation and a modified Navier-Stokes equation. These equations include buoyancy forces modelled by Boussinesq approximation and a Carman-Koseny term to model the flow in mushy regions. Since these modified Navier-Stokes equations only hold in the non-solid regions, which are not known a priori, we have a free boundary-value problem.

  8. Theory-Guided Materials Design of Multi-Phase Ti-Nb Alloys with Bone-Matching Elastic Properties

    Directory of Open Access Journals (Sweden)

    Jörg Neugebauer

    2012-10-01

    Full Text Available We present a scale-bridging approach for modeling the integral elasticresponse of polycrystalline composite that is based on a multi-disciplinary combination of(i parameter-free first-principles calculations of thermodynamic phase stability andsingle-crystal elastic stiffness; and (ii homogenization schemes developed forpolycrystalline aggregates and composites. The modeling is used as a theory-guidedbottom-up materials design strategy and applied to Ti-Nb alloys as promising candidatesfor biomedical implant applications. The theoretical results (i show an excellent agreementwith experimental data and (ii reveal a decisive influence of the multi-phase character ofthe polycrystalline composites on their integral elastic properties. The study shows thatthe results based on the density functional theory calculations at the atomistic level canbe directly used for predictions at the macroscopic scale, effectively scale-jumping severalorders of magnitude without using any empirical parameters.

  9. Solar combi system with phase-change materials; CoSyPCM. Combi-systeme avec materiaux a changement de phase

    Energy Technology Data Exchange (ETDEWEB)

    Citherlet, S.; Bony, J.

    2007-02-15

    Within the framework of Task 32 of the Solar Heating and Cooling Programme of the International Energy Agency (IEA) we studied the potential of using Phase Change Material (PCM) in a solar combi system in the form of modules placed in a storage tank. The goal was to analyze the potential of latent heat storage in a water tank of a solar installation, in order to increase the performance or to reduce the storage volume. This report describes the methodology used and the results obtained during the analysis of the heat storage potential by latent heat. The following stages were carried out: (i) Development of a simulation model: As no reliable numerical model exists, we developed a dynamic model to simulate PCM modules of various PCM types and shapes. This simulation model takes into account the hysteresis, the subcooling as well as the internal convection of the PCM in a liquid phase. This model was implemented in an existing TRNSYS Type(60). (ii) Laboratory measurements: In order to validate the digital model we tested various configurations and different types of PCM to check the agreement between simulations and experimental results. This step was focused on the time-dependent temperature distribution in the PCM and in the storage tank in order to validate the numerical model. (iii) Solar combi system: The potential relevance of the PCM was tested by using a solar combi system (Arpege) both with and without PCM. An energy balance was established on the basis of a seven days uninterrupted use of Arpege in various conditions (meteorological conditions and domestic hot water draw-off). Following the validation of the numerical model, annual simulations were carried out. (iv) Environmental impacts: A life cycle analysis of this solar combi system both with and without PCM was carried out. This analysis takes into account materials of the Arpege installation, the PCM and its container, as well as auxiliary energy used. (author)

  10. Investigation of the mineral components of porcelain raw material and their phase evolution during a firing process by using a Rietveld quantitative analysis

    Science.gov (United States)

    Kim, Jaegyeom; Heo, Eunae; Kim, Seung-Joo; Kim, Jong-Young

    2016-01-01

    A ceramic raw material for white porcelain and its phase evolution during a firing process were investigated by using Rietveld method based on powder X-ray diffraction data. The raw material was mainly composed of five mineral phases: quartz (SiO2), microcline (KAlSi3O8), albite (NaAlSi3O8), muscovite (KAl2(AlSi3O10)(OH)2), and kaolinite (Al2Si2O5(OH)4). The amount of each mineral phase could be determined by using Rietveld quantitative phase analyses. During the firing process, the microcline, albite, muscovite and kaolinite phases started to react with each other to produce the mullite phase embedded in an amorphous matrix. The amount of quartz remained nearly unchanged until a temperature above 1200 °C; then, it converted to an amorphous phase at higher temperatures.

  11. Local control of emission energy of semiconductor quantum dots using volume expansion of a phase-change material

    Science.gov (United States)

    Takahashi, Motoki; Syafawati Humam, Nurrul; Tsumori, Nobuhiro; Saiki, Toshiharu; Regreny, Philippe; Gendry, Michel

    2013-03-01

    A method is proposed to precisely control the emission energy of semiconductor quantum dots (QDs) by the application of local strain due to volume expansion of a phase-change material (GeSbTe) upon amorphization. The feasibility of the method is experimentally demonstrated using photoluminescence (PL) spectroscopy of single InAs/InP QDs on which a GeSbTe thin film is deposited. A significant red-shift of the PL peak energy upon amorphization and subsequent recovery by recrystallization with laser annealing were observed.

  12. Optical properties of opaline photonic crystals covered by phase-change material Ge$_2$Sb$_2$Te$_5$

    CERN Document Server

    Dyakov, Sergey A; Voronov, Mikhail M; Yakovlev, Sergey A; Pevtsov, Alexander B; Akimov, Ilya A; Tikhodeev, Sergei G

    2016-01-01

    Reflection spectra from 3D opaline photonic crystals covered with phase-change material Ge$_2$Sb$_2$Te$_5$ are studied for different incident angles of light both experimentally and theoretically. We demonstrate that in presence of Ge$_2$Sb$_2$Te$_5$ chalcogenide capping layer, the reflection spectra have peaks associated with resonant Wood's anomalies. The experimental reflection spectra are in a good agreement with theoretical calculations performed by the Fourier modal method in the scattering matrix form. The electromagnetic near-field distributions of incident light at resonant frequencies are calculated.

  13. Re-utilization of Industrial CO2 for Algae Production Using a Phase Change Material

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Brian [Touchstone Research Laboratory Ltd, Triadelphia, WV (United States)

    2014-03-31

    This is the final report of a 36-month Phase II cooperative agreement. Under this project, Touchstone Research Laboratory (Touchstone) investigated the merits of incorporating a Phase Change Material (PCM) into an open-pond algae production system that can capture and re-use the CO2 from a coal-fired flue gas source located in Wooster, OH. The primary objective of the project was to design, construct, and operate a series of open algae ponds that accept a slipstream of flue gas from a coal-fired source and convert a significant portion of the CO2 to liquid biofuels, electricity, and specialty products, while demonstrating the merits of the PCM technology. Construction of the pilot facility and shakedown of the facility in Wooster, OH, was completed during the first two years, and the focus of the last year was on operations and the cultivation of algae. During this Phase II effort a large-scale algae concentration unit from OpenAlgae was installed and utilized to continuously harvest algae from indoor raceways. An Algae Lysing Unit and Oil Recovery Unit were also received and installed. Initial parameters for lysing nanochloropsis were tested. Conditions were established that showed the lysing operation was effective at killing the algae cells. Continuous harvesting activities yielded over 200 kg algae dry weight for Ponds 1, 2 and 4. Studies were conducted to determine the effect of anaerobic digestion effluent as a nutrient source and the resulting lipid productivity of the algae. Lipid content and total fatty acids were unaffected by culture system and nutrient source, indicating that open raceway ponds fed diluted anaerobic digestion effluent can obtain similar lipid productivities to open raceway ponds using commercial nutrients. Data were also collected with respect to the performance of the PCM material on the pilot-scale raceway ponds. Parameters such as evaporative water loss, temperature differences, and growth/productivity were

  14. CRADA (AL-C-2009-02) Final Report: Phase I. Lanthanum-based Start Materials for Hydride Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Gschneidner, Jr., Karl [Ames Laboratory; Schmidt, Frederick [Ames Laboratory; Frerichs, A. E. [Ames Laboratory; Ament, Katherine A. [Ames Laboratory

    2013-05-01

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La{sub 1-x}R{sub x})(Ni{sub 1-y}M{sub y})(Si{sub z}), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.

  15. PCM-enhanced building components an application of phase change materials in building envelopes and internal structures

    CERN Document Server

    Kosny, Jan

    2015-01-01

    Presenting an overview of the use of Phase Change Materials (PCMs) within buildings, this book discusses the performance of PCM-enhanced building envelopes. It reviews the most common PCMs suitable for building applications, and discusses PCM encapsulation and packaging methods. In addition to this, it examines a range of PCM-enhanced building products in the process of development as well as examples of whole-building-scale field demonstrations. Further chapters discuss experimental and theoretical analyses (including available software) to determine dynamic thermal and energy performance ch

  16. Electrical explosion of a conductor in energy accumulating phase change materials with nanosized semiconducting additions

    Science.gov (United States)

    Savenkov, G. G.; Morozov, V. A.; Lukin, A. A.

    2016-11-01

    The results of experiments on the explosion of a copper conductor in paraffin and wax both without additions and with nanosized copper oxide additions are presented. The experiments provided the size of the channel formed in wax samples upon the conductor explosion and subsequent expansion of the electric discharge plasma. The obtained results testify to the influence of nanosized additions on the character of electric discharge plasma expansion in the formed channel, the strength of composite materials, and the sample fragmentation (destruction).

  17. Frequency Selective Materials for Control of Radiated Emissions and Interference Suppression, Phase 2

    Science.gov (United States)

    2006-04-01

    Figures Figure Page 1 Frequency selective Radome design 6 2 Predicted FSR performance 6 3 Ultem ® Radome 7 4 Radome/can assembly 8 5 Radome/Test Fixture...satisfactory peel strength. MRC examined many materials and coating techniques before deciding on using ULTEM ® with 20,000 angstroms of copper vapor...geometry, and determining how to impose this geometry onto the conductive ULTEM ® surface. It was decided to brute force the mapping on to the radome (a

  18. Mathematical modelling of the thermal performance of a phase-change material (PCM) store: cooling cycle

    Energy Technology Data Exchange (ETDEWEB)

    Kuerklue, A. [Akdeniz University, Faculty of Agriculture, Antalya (Turkey); Wheldon, A.; Hadley, P. [Reading Univ. (United Kingdom). Dept. of Engineering]|[Reading Univ. (United Kingdom). School of Plant Sciences

    1996-07-01

    A mathematical model for the prediction of the thermal performances of a PCM store containing 1 m long and 38 mm diameter polypropylene tube has been developed in this study. Air was utilised in the store as the heat transfer fluid. The model was based on an energy balance or the `conservation of energy principle`. The results indicate that the agreement between the predicted and observed temperature of heat transfer data is generally good. The amount of energy used in increasing the temperature of the PCM at any time during the phase- change process is predicted to be about 3.5% of the total energy stored. (Author)

  19. Novel Electro-Analytical Tools for Phase-Transformation Electrode Materials

    Science.gov (United States)

    2009-08-13

    words) We measured and compared phase transformation accommodation energy (AE) for Li4Ti5O12 and LiFePO4 with different particle size by using...larger than next cycles due to inducing of defects; Because of smaller volume difference, AE of Li4Ti5O12 was lower than that of LiFePO4 ; AE of... LiFePO4 with small particle size was lower than that of LiFePO4 with large particle size. By plugging the AE measured by GITT into mixed control

  20. Controlling the near-field excitation of nano-antennas with phase-change materials

    Directory of Open Access Journals (Sweden)

    Tsung Sheng Kao

    2013-10-01

    Full Text Available By utilizing the strongly induced plasmon coupling between discrete nano-antennas and quantitatively controlling the crystalline proportions of an underlying Ge2Sb2Te5 (GST phase-change thin layer, we show that nanoscale light localizations in the immediate proximity of plasmonic nano-antennas can be spatially positioned. Isolated energy hot-spots at a subwavelength scale can be created and adjusted across the landscape of the plasmonic system at a step resolution of λ/20. These findings introduce a new approach for nano-circuitry, bio-assay addressing and imaging applications.