WorldWideScience

Sample records for thermal expansion studies

  1. Thermal expansion and magnetostriction studies on iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liran

    2010-09-19

    In this work, a 3-terminal capacitance dilatometer was set up and used for measurements of the thermal expansion and magnetostriction of novel superconducting iron pinictides and related materials. In particular, RFeAsO with R = La, Ce, Pr, Sm, Gd, LaFeASO{sub 1-x}F{sub x} and Ca(F{sub 1-c}Co{sub x}){sub 2}As{sub 2} have been investigated. The data on polycrystalline LaFeAsO{sub 1-x} are the first published thermal expansion data on this material. The lattice effects at the structural and the magnetic phase transition have been investigated and the phase diagram upon F-doping has been studied. A main result is the observation of a previously unknown fluctuation regime for the doping level x ≤ 0.04 over a large T range above the structural transition temperature T{sub S}. The absence of any structural anomalies in the normal state of the superconducting LaFeAlO{sub 1-x}F{sub x} samples with x ≥ 0.05 corroborates the discontinuous character of the phase boundary not only for the magnetism but also for the structural degrees of freedom. Similarly, the presence of high-temperature fluctuations is found for all RFeAsO undoped materials under study. The discussion of the probable origin of the fluctuations as well as the definition of the structural transition temperature T{sub S} are done. The low temperature features shown by the thermal expansion data for RFeAsO are caused by the onset of long range magnetic order of the 4f-moments and their different configurations. In particular, PrFeAsO, which has a very pronounced anomaly associated with Pr-ordering exhibits a large magnetostriction at low temperatures. By discussing this effect along with the magnetization, resistivity and other measurements, it is found that this large magneto-elastic effect may originate from the correlations between the momentum from Fe{sup 3+} and Pr{sup 3+}. Last, the thermal expansion of Ca(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} 122 single crystals is investigated. Ca(Fe{sub 1-x}Co{sub x

  2. Molecular dynamics study of the thermal expansion coefficient of silicon

    Science.gov (United States)

    Nejat Pishkenari, Hossein; Mohagheghian, Erfan; Rasouli, Ali

    2016-12-01

    Due to the growing applications of silicon in nano-scale systems, a molecular dynamics approach is employed to investigate thermal properties of silicon. Since simulation results rely upon interatomic potentials, thermal expansion coefficient (TEC) and lattice constant of bulk silicon have been obtained using different potentials (SW, Tersoff, MEAM, and EDIP) and results indicate that SW has a better agreement with the experimental observations. To investigate effect of size on TEC of silicon nanowires, further simulations are performed using SW potential. To this end, silicon nanowires of different sizes are examined and their TEC is calculated by averaging in different directions ([100], [110], [111], and [112]) and various temperatures. Results show that as the size increases, due to the decrease of the surface effects, TEC approaches its bulk value.

  3. Thermal Expansion Studies of Selected High Temperature Thermoelectric Materials

    Science.gov (United States)

    Ravi, Vilupanur; Firdosy, Samad; Caillat, Thierry; Brandon, Erik; Van Der Walde, Keith; Maricic, Lina; Sayir, Ali

    2008-01-01

    Radioisotope thermoelectric generators (RTGs) generate electrical power by converting the heat released from the nuclear decay of radioactive isotopes (typically plutonium-238) into electricity using a thermoelectric converter. RTGs have been successfully used to power a number of space missions and have demonstrated their reliability over an extended period of time (tens of years) and are compact, rugged, radiation resistant, scalable, and produce no noise, vibration or torque during operation. System conversion efficiency for state-of-practice RTGs is about 6% and specific power less than or equal to 5.1 W/kg. Higher specific power would result in more on-board power for the same RTG mass, or less RTG mass for the same on-board power. The Jet Propulsion Laboratory has been leading, under the advanced thermoelectric converter (ATEC) project, the development of new high-temperature thermoelectric materials and components for integration into advanced, more efficient RTGs. Thermoelectric materials investigated to date include skutterudites, the Yb14MnSb11 compound, and SiGe alloys. The development of long-lived thermoelectric couples based on some of these materials has been initiated and is assisted by a thermo-mechanical stress analysis to ensure that all stresses under both fabrication and operation conditions will be within yield limits for those materials. Several physical parameters are needed as input to this analysis. Among those parameters, the coefficient of thermal expansion (CTE) is critically important. Thermal expansion coefficient measurements of several thermoelectric materials under consideration for ATEC are described in this paper. The stress response at the interfaces in material stacks subjected to changes in temperature is discussed, drawing on work from the literature and project-specific tools developed here. The degree of CTE mismatch and the associated effect on the formation of stress is highlighted.

  4. Molecular dynamics study of the thermal expansion coefficient of silicon

    Energy Technology Data Exchange (ETDEWEB)

    Nejat Pishkenari, Hossein, E-mail: nejat@sharif.edu; Mohagheghian, Erfan; Rasouli, Ali

    2016-12-16

    Due to the growing applications of silicon in nano-scale systems, a molecular dynamics approach is employed to investigate thermal properties of silicon. Since simulation results rely upon interatomic potentials, thermal expansion coefficient (TEC) and lattice constant of bulk silicon have been obtained using different potentials (SW, Tersoff, MEAM, and EDIP) and results indicate that SW has a better agreement with the experimental observations. To investigate effect of size on TEC of silicon nanowires, further simulations are performed using SW potential. To this end, silicon nanowires of different sizes are examined and their TEC is calculated by averaging in different directions ([100], [110], [111], and [112]) and various temperatures. Results show that as the size increases, due to the decrease of the surface effects, TEC approaches its bulk value. - Highlights: • MD simulations of TEC and lattice constant of bulk silicon. • Effects of four potentials on the results. • Comparison to experimental data. • Investigating size effect on TEC of silicon nanowires.

  5. Fundamentals of Thermal Expansion and Thermal Contraction

    OpenAIRE

    Liu, Zi-Kui; Shang, Shun-Li; Wang, Yi

    2017-01-01

    Thermal expansion is an important property of substances. Its theoretical prediction has been challenging, particularly in cases the volume decreases with temperature, i.e., thermal contraction or negative thermal expansion at high temperatures. In this paper, a new theory recently developed by the authors has been reviewed and further examined in the framework of fundamental thermodynamics and statistical mechanics. Its applications to cerium with colossal thermal expansion and Fe3Pt with th...

  6. Negative thermal expansion properties in tetragonal NbPO5 from the first principles studies

    Directory of Open Access Journals (Sweden)

    Tao Li

    2017-03-01

    Full Text Available By using the first-principles calculations based on density functional theory combined with quasi-harmonic approximation, we have studied the geometric structural, thermal properties, and the negative thermal expansion (NTE properties of tetrahedral NbPO5. The variations of cell parameter and cell volume of tetrahedral NbPO5 with temperature show that it displays NTE behavior in the range of 473-800 K along a-axis and the corresponding average coefficient of thermal expansion (CTE is approximately -0.766 ×10−6 K−1, while the c cell parameter and the cell volume display positive thermal expansion behaviors. These results are in consistent well with the experiment observations. Further vibrational modes analysis, together with Grüneisen parameters calculations, revealed that the transverse vibration of O corner atoms accompanying the rocking motions of corner-shared NbO6 octahedron and PO4 tetrahedron dominate the negative thermal properties of tetrahedral NbPO5. Our findings will provide an understanding for the underlying mechanisms of the NTE in oxides materials.

  7. Study on radial core thermal expansion for MOX fuelled large LMFBRS

    Energy Technology Data Exchange (ETDEWEB)

    Ohkubo, Y. [Mitsubishi Heavy Industries, Yokohama (Japan); Watanabe, O. [Advanced Reactor Technology, Tokyo (Japan); Nakagawa, M. [Toshiba Co., Kawasaki (Japan); Fujimura, K. [Hitachi, Ltd., Ibarakiken (Japan); Ishida, M. [FBR Engineering Co., Ltd., Tokyo (Japan); Kotake, S. [The Japan Atomic Power Com., Tokyo (Japan)

    1998-07-01

    A study has been performed to evaluate radial core thermal expansion characteristics in ULOF (Unprotected Loss Of Flow) events of large LMFBRs with MOX fuel, which are expected as a passive safety feature of LMFBRs. The mechanism of radial core expansion is so complicated that the precise evaluation of its reactivity effect needs a sophisticated analytical tool system. An analytical code system has been developed in order to determine the best-estimate reactivity due to core radial expansion. The code system consists of the 3-D core thermal hydraulic transient analysis code with point kinetics, the 3-D core deflection analysis code and the 3-D core bowing reactivity analysis code. The core radial expansion reactivity in ULOF events of a large FBR with electric power of 1500MWe has been evaluated by iteration procedures among the three codes in order to study the negative reactivity insertion mechanism. It has been concluded that the core radial expansion reactivity feedback is not sufficient to prevent the coolant boiling in ULOF event of the MOX fuelled large LMFBR by itself but is considered to assist other passive safety measures to settle the core in a stable shutdown state by delaying the coolant boiling inception.

  8. TOPICAL REVIEW: Negative thermal expansion

    Science.gov (United States)

    Barrera, G. D.; Bruno, J. A. O.; Barron, T. H. K.; Allan, N. L.

    2005-02-01

    There has been substantial renewed interest in negative thermal expansion following the discovery that cubic ZrW2O8 contracts over a temperature range in excess of 1000 K. Substances of many different kinds show negative thermal expansion, especially at low temperatures. In this article we review the underlying thermodynamics, emphasizing the roles of thermal stress and elasticity. We also discuss vibrational and non-vibrational mechanisms operating on the atomic scale that are responsible for negative expansion, both isotropic and anisotropic, in a wide range of materials.

  9. Thermal Expansion of Polyurethane Foam

    Science.gov (United States)

    Lerch, Bradley A.; Sullivan, Roy M.

    2006-01-01

    Closed cell foams are often used for thermal insulation. In the case of the Space Shuttle, the External Tank uses several thermal protection systems to maintain the temperature of the cryogenic fuels. A few of these systems are polyurethane, closed cell foams. In an attempt to better understand the foam behavior on the tank, we are in the process of developing and improving thermal-mechanical models for the foams. These models will start at the microstructural level and progress to the overall structural behavior of the foams on the tank. One of the key properties for model characterization and verification is thermal expansion. Since the foam is not a material, but a structure, the modeling of the expansion is complex. It is also exacerbated by the anisoptropy of the material. During the spraying and foaming process, the cells become elongated in the rise direction and this imparts different properties in the rise direction than in the transverse directions. Our approach is to treat the foam as a two part structure consisting of the polymeric cell structure and the gas inside the cells. The polymeric skeleton has a thermal expansion of its own which is derived from the basic polymer chemistry. However, a major contributor to the thermal expansion is the volume change associated with the gas inside of the closed cells. As this gas expands it exerts pressure on the cell walls and changes the shape and size of the cells. The amount that this occurs depends on the elastic and viscoplastic properties of the polymer skeleton. The more compliant the polymeric skeleton, the more influence the gas pressure has on the expansion. An additional influence on the expansion process is that the polymeric skeleton begins to breakdown at elevated temperatures and releases additional gas species into the cell interiors, adding to the gas pressure. The fact that this is such a complex process makes thermal expansion ideal for testing the models. This report focuses on the thermal

  10. The Study on Thermal Expansion of Ceramic Composites with Addition of ZrW2O8

    Science.gov (United States)

    Dedova, E. S.; Shadrin, V. S.; Petrushina, M. Y.; Kulkov, S. N.

    2016-02-01

    The studies on structure, phase composition and thermal properties of (Al2O3 - 20 wt% ZrO2) - ZrW2O8 ceramic composites obtained using nanosized, initial powders were conducted. Homogeneously distributed white particles on the polished surface of composites were observed. Phase composition of the composites was represented with corundum, monoclinic ZrO2 and two modifications of ZrW2O8 (tetragonal and cubic). Linear thermal expansion coefficient values of the composites were determined. The difference in experimental and calculated coefficient of thermal expansion values for composites obtained may be attributed to phase transformations, features of the structure, internal stresses due to thermal expansion mismatch, which contribute significantly to thermal expansion of the ceramic composites.

  11. Low thermal expansion glass ceramics

    CERN Document Server

    1995-01-01

    This book is one of a series reporting on international research and development activities conducted by the Schott group of companies With the series, Schott aims to provide an overview of its activities for scientists, engineers, and managers from all branches of industry worldwide where glasses and glass ceramics are of interest Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subjects treated This volume describes the fundamental principles, the manufacturing process, and applications of low thermal expansion glass ceramics The composition, structure, and stability of polycrystalline materials having a low thermal expansion are described, and it is shown how low thermal expansion glass ceramics can be manufactured from appropriately chosen glass compositions Examples illustrate the formation of this type of glass ceramic by utilizing normal production processes together with controlled crystallization Thus glass ceramics with thermal c...

  12. Low Thermal Expansion Glass Ceramics

    CERN Document Server

    Bach, Hans

    2005-01-01

    This book appears in the authoritative series reporting the international research and development activities conducted by the Schott group of companies. This series provides an overview of Schott's activities for scientists, engineers, and managers from all branches of industry worldwide in which glasses and glass ceramics are of interest. Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subjects treated. This new extended edition describes the fundamental principles, the manufacturing process, and applications of low thermal expansion glass ceramics. The composition, structure, and stability of polycrystalline materials having a low thermal expansion are described, and it is shown how low thermal expansion glass ceramics can be manufactured from appropriately chosen glass compositions. Examples illustrate the formation of this type of glass ceramic by utilizing normal production processes together with controlled crystallization. Thus g...

  13. Contribution of thermal expansion and

    Directory of Open Access Journals (Sweden)

    O.I.Pursky

    2007-01-01

    Full Text Available A theoretical model is developed to describe the experimental results obtained for the isobaric thermal conductivity of rare gas solids (RGS. The isobaric thermal conductivity of RGS has been analysed within Debye approximation with regard to the effect of thermal expansion. The suggested model takes into consideration the fact that thermal conductivity is determined by U-processes while above the phonon mobility edge it is determined by "diffusive" modes migrating randomly from site to site. The mobility edge ω0 is determined from the condition that the phonon mean-free path restricted by the U-processes cannot be smaller than half of the phonon wavelength.

  14. Low-thermal expansion infrared glass ceramics

    Science.gov (United States)

    Lam, Philip

    2009-05-01

    L2 Tech, Inc. is in development of an innovative infrared-transparent glass ceramic material with low-thermal expansion (ZrW2O8) which has Negative Thermal Expansion (NTE). The glass phase is the infrared-transparent germanate glass which has positive thermal expansion (PTE). Then glass ceramic material has a balanced thermal expansion of near zero. The crystal structure is cubic and the thermal expansion of the glass ceramic is isotropic or equal in all directions.

  15. Thermal expansion of doped lanthanum gallates

    Indian Academy of Sciences (India)

    Thermal expansion of several compositions of Sr and Mg-doped LaGaO3 including an -site deficient composition (La0.9Sr0.1)0.98(Ga0.8Mg0.2)O2.821 were measured in the temperature range from 298 to 1273 K. The effect of doping on thermal expansion was studied by varying the composition at one site of the ...

  16. Negative thermal expansion in framework compounds

    Indian Academy of Sciences (India)

    2015-11-27

    Nov 27, 2015 ... We have studied negative thermal expansion (NTE) compounds with chemi- cal compositions of NX2O8 and NX2O7 (N=Zr, Hf and X=W, Mo, V) and M2O (M=Cu, Ag) using the techniques of inelastic neutron scattering and lattice dynamics. There is a large variation in the negative thermal expansion ...

  17. Thermal Expansion of Hafnium Carbide

    Science.gov (United States)

    Grisaffe, Salvatore J.

    1960-01-01

    Since hafnium carbide (HfC) has a melting point of 7029 deg. F, it may have many high-temperature applications. A literature search uncovered very little information about the properties of HfC, and so a program was initiated at the Lewis Research Center to determine some of the physical properties of this material. This note presents the results of the thermal expansion investigation. The thermal-expansion measurements were made with a Gaertner dilatation interferometer calibrated to an accuracy of +/- 1 deg. F. This device indicates expansion by the movement of fringes produced by the cancellation and reinforcement of fixed wave-length light rays which are reflected from the surfaces of two parallel quartz glass disks. The test specimens which separate these disks are three small cones, each approximately 0.20 in. high.

  18. A study of the coefficient of thermal expansion of nuclear graphites

    Energy Technology Data Exchange (ETDEWEB)

    Hacker, P.J

    2001-02-01

    This thesis presents the results of a study of the Coefficient of Thermal Expansion (CTE) of two grades of nuclear graphite that are used as the moderator in the Magnox and Advanced Gas-Cooled reactors operated in the UK. This work has two main aims, the first is to characterise those elements of the graphite microstructure that control CTE within these materials and to relate these to the effects induced within the reactor. The second is to develop a microstructural model, of general applicability, that can initially be applied to model the CTE changes within the graphites under reactor conditions (neutron irradiation and radiolytic oxidation). These aims have been met by study in three interlinked areas, theoretical, experimental and modelling. Previous to this study, a loose assembly of single crystals together with changes in small scale nanometric porosity (Mrozowski cracks) were used to describe CTE behaviour of nuclear graphite both as-received and under reactor conditions. Within the experimental part of this thesis the graphite nanostructure was studied using, primarily, Transmission Electron Microscopy (TEM). This work concluded that structure on this scale was complex and that the loose assembly of single crystals was a poor microstructural approximation for modelling the CTE of these materials. Other experimental programmes measured the CTE of highly oxidised samples and simulated the effects of irradiation. The former discovered that CTE remained largely unaffected to high weight losses. This insensitivity was explained by ''The Continuous Network Hypothesis'' that was also related to classical percolation theory. The final part of the thesis modelled an abstraction of the key microstructural features identified in the previous parts of the thesis. This approach has been applied to AGR moderator graphite where it has successfully modelled the thermal expansion behaviour of the as-received, irradiated and oxidised material. (author)

  19. Ultra-low thermal expansion realized in giant negative thermal expansion materials through self-compensation

    Science.gov (United States)

    Shen, Fei-Ran; Kuang, Hao; Hu, Feng-Xia; Wu, Hui; Huang, Qing-Zhen; Liang, Fei-Xiang; Qiao, Kai-Ming; Li, Jia; Wang, Jing; Liu, Yao; Zhang, Lei; He, Min; Zhang, Ying; Zuo, Wen-Liang; Sun, Ji-Rong; Shen, Bao-Gen

    2017-10-01

    Materials with zero thermal expansion (ZTE) or precisely tailored thermal expansion are in urgent demand of modern industries. However, the overwhelming majority of materials show positive thermal expansion. To develop ZTE or negative thermal expansion (NTE) materials as compensators has become an important challenge. Here, we present the evidence for the realization of ultra-low thermal expansion in Mn-Co-Ge-In particles. The bulk with the Ni2In-type hexagonal structure undergoes giant NTE owing to a martensitic magnetostructural transition. The major finding is that the thermal expansion behavior can be totally controlled by modulating the crystallinity degree and phase transition from atomic scale. Self-compensation effect leads to ultra-low thermal expansion with a linear expansion coefficient as small as +0.68 × 10-6/K over a wide temperature range around room temperature. The present study opens an avenue to reach ZTE particularly from the large class of giant NTE materials based on phase transition.

  20. High-pressure study on borides, nanocrystals and negative thermal expansion materials

    Science.gov (United States)

    Chen, Bin

    2001-07-01

    By the use of Mao-Bell diamond anvil cell, employed with x-ray diffraction, optical absorption, Raman and Fourier Transform Infrared (FTIR) spectroscopy, iron borides, nanocrystalline Ni, Fe, Ni3Fe, Al2O 3, Negative Thermal Expansion (NTE) materials such as HfW2O 8, ZrW2O8, ZrMo2O8 have been studied under high pressure. The results of a synchrotron x-ray diffraction study of Fe2B under quasi-hydrostatic conditions from 0 to 50 GPa are reported. Over this pressure range, no phase change or disproportionation has been observed. A value of the bulk modulus, K, of 192 +/- 14 GPa and the first pressure derivative of the bulk modulus, K', of 2.6 +/- 0.6, are obtained. The compression is found to be anisotropic, with the a-axis being more incompressible than the c-axis. X-ray diffraction data of nanocrystalline Ni, Fe and Ni3Fe, using a synchrotron source, was collected under nonhydrostatic and quasi-hydrostatic conditions up to 60 GPa. The bulk moduli, of 185.4 +/- 10 GPa, 171 +/- 5 GPa, 179.4 +/- 8.1 GPa, 168.3 +/- 2.6 GPa, are determined from quasi-hydrostatic compression data of nanocrystalline Ni, alpha-Fe, epsilon-Fe and Ni3Fe, respectively, which are found similar to those of large-grained counterparts. Their phase transformations are studied and compared with their bulk counterparts. A new phase of Al2O3 formed by compression of the nanocrystalline gamma-phase has been detected. This high-pressure phase is metastable upon decompression to ambient pressure, and has a bulk modulus of 251 +/- 10 GPa for Al2O3 of 67 nm. From hydrostatic compression, bulk moduli of K67 = 238 +/- 3 GPa and K37 = 172 +/- 3 GPa are obtained for the 67 nm and 37 nm gamma-Al2O3 particles, respectively, which are significantly higher than that found in a previous study of smaller sized nanocrystals of gamma-alumina (K20 = 162 +/- 14 GPa for 20 nm crystallites). High pressure optical absorption, Raman and FTIR measurements are carried out on negative thermal expansion materials: HfW2O8, ZrW2O

  1. Negative thermal expansion in framework compounds

    Indian Academy of Sciences (India)

    electron microscopy, EXAFS and differential scanning calorimetry have been used to study structural properties as a function of temperature for these compounds. In this paper we report the results obtained from our study [14–20] of negative thermal expansion (NTE) compounds with chemical compositions of NX2O8 and.

  2. Anisotropic Thermal Expansion of Zirconium Diboride: An Energy-Dispersive X-Ray Diffraction Study

    Directory of Open Access Journals (Sweden)

    William A. Paxton

    2016-01-01

    Full Text Available Zirconium diboride (ZrB2 is an attractive material due to its thermal and electrical properties. In recent years, ZrB2 has been investigated as a superior replacement for sapphire when used as a substrate for gallium nitride devices. Like sapphire, ZrB2 has an anisotropic hexagonal structure which defines its directionally dependent properties. However, the anisotropic behavior of ZrB2 is not well understood. In this paper, we use energy-dispersive synchrotron X-ray diffraction to measure the thermal expansion of polycrystalline ZrB2 powder from 300 to 1150 K. Nine Bragg reflections are fit using Pseudo-Voigt peak profiles and used to compute the a and c lattice parameters using a nonlinear least-squares approximation. The temperature-dependent instantaneous thermal expansion coefficients are determined for each a-axis and c-axis direction and are described by the following equations: αa = (4.1507×10-6 + 5.1086 × 10-9(T-293.15/(1+4.1507 × 10-6(T-293.15 + 2.5543×10-9(T-293.152 and αc = (4.5374×10-6 + 4.3004×10-9(T-293.15/(1+4.5374×10-6(T-293.15 + 2.1502×10-9(T-293.152. Our results are within range of previously reported values but describe the temperature anisotropy in more detail. We show that anisotropic expansion coefficients converge to the same value at about 780 K and diverge at higher temperatures. Results are compared with other reported values.

  3. Anomalous thermal expansion in rare-earth gallium perovskites: a comprehensive powder diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Senyshyn, A; Trots, D M; Engel, J M; Ehrenberg, H; Fuess, H [Institute for Materials Science, Darmstadt University of Technology, D-64287 Darmstadt (Germany); Vasylechko, L [Lviv Polytechnic National University, 12 Bandera Street, 79013 Lviv (Ukraine); Hansen, T [Institut Max von Laue-Paul Langevin, 38042 Grenoble Cedex 9 (France); Berkowski, M [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw (Poland)

    2009-04-08

    Crystal structures of rare-earth gallium perovskites LaGaO{sub 3}, PrGaO{sub 3}, NdGaO{sub 3} and Pr{sub 1-x}Nd{sub x}GaO{sub 3} (x = 0.25, 0.50, 0.75) solid solutions were investigated in the temperature range 12-300 K by high-resolution powder diffraction using synchrotron or neutron radiation. The previously reported negative thermal expansion in the b direction of the PrGaO{sub 3} lattice has been found to be persistent in Pr{sub 1-x}Nd{sub x}GaO{sub 3} solid solutions and its magnitude has been revealed as proportional to the amount of praseodymium. Evaluation of the obtained temperature evolution of cell dimensions indicated a weak anomalous behaviour of the b lattice parameter in NdGaO{sub 3}, and its origin is supposed to be the same as in PrGaO{sub 3}, i.e. a coupling of the crystal electric field levels with phonon excitations of about 23-25 meV energy. The performed bond length analysis revealed an anomalous behaviour of both LnO{sub 12} (Ln-rare-earth) and GaO{sub 6} coordination polyhedra, which can be a structural manifestation of anomalous thermal expansion in the considered compounds.

  4. Thermal expansion and decomposition of jarosite: a high-temperature neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hongwu [Los Alamos National Laboratory; Zhao, Yusheng [Los Alamos National Laboratory; Vogel, Sven C [Los Alamos National Laboratory; Hickmott, Donald D [Los Alamos National Laboratory; Daemen, Luke L [Los Alamos National Laboratory; Hartl, Monika A [Los Alamos National Laboratory

    2009-01-01

    The structure of deuterated jarosite, KFe{sub 3}(SO{sub 4}){sub 2}(OD){sub 6}, was investigated using time-of-flight neutron diffraction up to its dehydroxylation temperature. Rietveld analysis reveals that with increasing temperature, its c dimension expands at a rate {approx}10 times greater than that for a. This anisotropy of thermal expansion is due to rapid increase in the thickness of the (001) sheet of [Fe(O,OH){sub 6}] octahedra and [SO{sub 4}] tetrahedra with increasing temperature. Fitting of the measured cell volumes yields a coefficient of thermal expansion, a = a{sub 0} + a{sub 1} T, where a{sub 0} = 1.01 x 10{sup -4} K{sup -1} and a{sub 1} = -1.15 x 10{sup -7} K{sup -2}. On heating, the hydrogen bonds, O1{hor_ellipsis}D-O3, through which the (001) octahedral-tetrahedral sheets are held together, become weakened, as reflected by an increase in the D{hor_ellipsis}O1 distance and a concomitant decrease in the O3-D distance with increasing temperature. On further heating to 575 K, jarosite starts to decompose into nanocrystalline yavapaiite and hematite (as well as water vapor), a direct result of the breaking of the hydrogen bonds that hold the jarosite structure together.

  5. Pressurized electrolysis stack with thermal expansion capability

    Science.gov (United States)

    Bourgeois, Richard Scott

    2015-07-14

    The present techniques provide systems and methods for mounting an electrolyzer stack in an outer shell so as to allow for differential thermal expansion of the electrolyzer stack and shell. Generally, an electrolyzer stack may be formed from a material with a high coefficient of thermal expansion, while the shell may be formed from a material having a lower coefficient of thermal expansion. The differences between the coefficients of thermal expansion may lead to damage to the electrolyzer stack as the shell may restrain the thermal expansion of the electrolyzer stack. To allow for the differences in thermal expansion, the electrolyzer stack may be mounted within the shell leaving a space between the electrolyzer stack and shell. The space between the electrolyzer stack and the shell may be filled with a non-conductive fluid to further equalize pressure inside and outside of the electrolyzer stack.

  6. Structure and thermal expansion of liquid bismuth

    Directory of Open Access Journals (Sweden)

    Mudry S.

    2015-12-01

    Full Text Available Experimental structural data for liquid Bi were used for estimation of the main structure parameters as well as the thermal expansion coefficient both in supercooled and superheated temperature ranges. It was shown that the equilibrium melt had a positive thermal expansion coefficient within a temperature range upon melting and a negative one at higher temperatures. The former was related to structure changes upon melting, whereas the latter with topologic disordering upon further heating. It was found that the superheated melt had a negative thermal expansion coefficient. The results obtained from structural data were compared with the thermal expansion coefficient calculated from the data of density for liquid Bi.

  7. Effect of prolonged thermal cycling on microleakage around Class V cavities restored with glass-ceramic inserts with different coefficients of thermal expansion: an in vitro study.

    Science.gov (United States)

    Santini, Ario; Ivanovic, Vladimir; Tan, Chuei Luan; Ibbetson, Richard

    2006-10-01

    The purpose of this in vitro study was to evaluate microleakage around Class V glass-ceramic restorations of different coefficients of thermal expansion after prolonged thermal cycling. One hundred and twenty noncarious extracted human premolars (patient age range 12-20 years) were randomly assigned to three groups. Standard Class V preparations were cut in the buccal surface using customised Cerana burs, size no. 3. Glass-ceramic inserts from two manufacturers (Cerana, Nordiska Dental AB, Helsingborg, Sweden; Beta-Quartz, Hager & Werken GmbH, Duisburg, Germany) were used to restore the cavities and were luted with a hybrid, high-viscous composite (Tetric Ceram, Ivoclar Vivadent, Schaan, Liechtenstein) and a bonding agent (Excite, Ivoclar Vivadent, Schaan, Liechtenstein). A control group, without inserts, was bulk-filled with the same composite used as the luting agent. In accordance with American Dental Association guidelines, half of the preparation was in enamel, half in dentine/cementum and had a mesio-distal width of 3 mm, an occluso-gingival height of 3 mm, and a depth of 2 mm. All margins had butt joints. Sixty teeth, selected at random, were not thermal cycled; the remaining 60 teeth were thermal cycled 4000 times between water baths held at 5 degrees C and 55 degrees C and the specimens prepared and examined for microleakage using 2.0% Procion Red (ICI, Slough, UK) dye, buffered at pH7, as a marker. The results were analysed using the Kruskal-Wallis test (ANOVA) at a 95% significance level. At the occlusal margins there was no significant difference in microleakage between the three groups (P>0.5) without thermal cycling. After thermal cycling, microleakage at the occlusal margins was significantly less around cavities restored with Cerana glass-ceramic inserts versus Beta-Quartz and Tetric Ceram (Pmicroleakge between the groups before thermal cycling (P>0.5). After thermal cycling, there was significantly less microleakage between Cerana inserts and

  8. Impact of size and temperature on thermal expansion of nanomaterials

    Indian Academy of Sciences (India)

    A theoretical method has been discussed to study the size dependency of thermal expansion of nanomaterials at higher temperature by considering the surface effect. A thermodynamical analysis of the equation of state (EoS) is studied from the knowledge of thermal expansion of nano-materials based on theoretical ...

  9. Micro-architected Composite Lattices with Tunable Negative Thermal Expansions

    Science.gov (United States)

    Wang, Qiming

    Solid materials with minimum or negative thermal expansion (NTE) have broad applications, from dental fillings to thermal-sensitive precision instruments. Previous studies on NTE structures were mostly focused on theoretically design and 2D experimental demonstrations. Here, aided with multimaterial projection micro-stereolithography, we experimentally fabricate multi-material composite lattices that exhibit significant negative thermal expansion in three directions and over a large range of temperature variations. The negative thermal expansion is induced by the structural interaction of material components with distinct thermal expansion coefficients. The NTE performance can be tuned over a large range by varying the thermal expansion coefficient difference between constituent beams and geometrical arrangement. Our experimental results match qualitatively with a simple scaling law and quantitatively consistently with computational models.

  10. Frequency dependent thermal expansion in binary viscoelasticcomposites

    Energy Technology Data Exchange (ETDEWEB)

    Berryman, James G.

    2007-12-01

    The effective thermal expansion coefficient beta* of abinary viscoelastic composite is shown to be frequency dependent even ifthe thermal expansion coefficients beta A and beta B of both constituentsare themselves frequency independent. Exact calculations for binaryviscoelastic systems show that beta* is related to constituent valuesbeta A, beta B, volume fractions, and bulk moduli KA, KB, as well as tothe overall bulk modulus K* of the composite system. Then, beta* isdetermined for isotropic systems by first bounding (or measuring) K* andtherefore beta*. For anisotropic systems with hexagonal symmetry, theprincipal values of the thermal expansion beta*perp and beta*para can bedetermined exactly when the constituents form a layered system. In allthe examples studied, it is shown explicitly that the eigenvectors of thethermoviscoelastic system possess non-negative dissipation -- despite thecomplicated analytical behavior of the frequency dependent thermalexpansivities themselves. Methods presented have a variety ofapplications from fluid-fluid mixtures to fluid-solid suspensions, andfrom fluid-saturated porous media to viscoelastic solid-solidcomposites.

  11. Thermal expansion of L-ascorbic acid

    Science.gov (United States)

    Nicolaï, B.; Barrio, M.; Tamarit, J.-Ll.; Céolin, R.; Rietveld, I. B.

    2017-04-01

    The specific volume of vitamin C has been investigated by X-ray powder diffraction as a function of temperature from 110 K up to complete degradation around 440 K. Its thermal expansion is relatively small in comparison with other organic compounds with an expansivity α v of 1.2(3) × 10-4 K-1. The structure consists of strongly bound molecules in the ac plane through a dense network of hydrogen bonds. The thermal expansion is anisotropic. Along the b axis, the expansion has most leeway and is about 10 times larger than in the other directions.

  12. Giant negative thermal expansion in magnetic nanocrystals

    Science.gov (United States)

    Zheng, X. G.; Kubozono, H.; Yamada, H.; Kato, K.; Ishiwata, Y.; Xu, C. N.

    2008-12-01

    Most solids expand when they are heated, but a property known as negative thermal expansion has been observed in a number of materials, including the oxide ZrW2O8 (ref. 1) and the framework material ZnxCd1-x(CN)2 (refs 2,3). This unusual behaviour can be understood in terms of low-energy phonons, while the colossal values of both positive and negative thermal expansion recently observed in another framework material, Ag3[Co(CN)6], have been explained in terms of the geometric flexibility of its metal-cyanide-metal linkages. Thermal expansion can also be stopped in some magnetic transition metal alloys below their magnetic ordering temperature, a phenomenon known as the Invar effect, and the possibility of exploiting materials with tuneable positive or negative thermal expansion in industrial applications has led to intense interest in both the Invar effect and negative thermal expansion. Here we report the results of thermal expansion experiments on three magnetic nanocrystals-CuO, MnF2 and NiO-and find evidence for negative thermal expansion in both CuO and MnF2 below their magnetic ordering temperatures, but not in NiO. Larger particles of CuO and MnF2 also show prominent magnetostriction (that is, they change shape in response to an applied magnetic field), which results in significantly reduced thermal expansion below their magnetic ordering temperatures; this behaviour is not observed in NiO. We propose that the negative thermal expansion effect in CuO (which is four times larger than that observed in ZrW2O8) and MnF2 is a general property of nanoparticles in which there is strong coupling between magnetism and the crystal lattice.

  13. Thermal expansion: Metallic elements and alloys. [Handbook

    Science.gov (United States)

    Touloukian, Y. S.; Kirby, R. K.; Taylor, R. E.; Desai, P. D.

    1975-01-01

    The introductory sections of the work are devoted to the theory of thermal expansion of solids and to methods for the measurement of the linear thermal expansion of solids (X-ray methods, high speed methods, interferometry, push-rod dilatometry, etc.). The bulk of the work is devoted to numerical data on the thermal linear expansion of all the metallic elements, a large number of intermetallics, and a large number of binary alloy systems and multiple alloy systems. A comprehensive bibliography is provided along with an index to the materials examined.

  14. Spontaneous thermal expansion of nematic elastomers

    Science.gov (United States)

    Tajbakhsh, A. R.; Terentjev, E. M.

    2001-10-01

    We study the monodomain (single-crystal) nematic elastomer materials, all side-chain siloxane polymers with the same mesogenic groups and crosslinking density, but differing in the type of crosslinking. Increasing the proportion of long di-functional segments of main-chain nematic polymer, acting as network crosslinking, results in dramatic changes in the uniaxial equilibrium thermal expansion on cooling from the isotropic phase. At higher concentration of main chains their behaviour dominates the elastomer properties. At low concentration of main-chain material, we detect two distinct transitions at different temperatures, one attributed to the main-chain, the other to the side-chain component. The effective uniaxial anisotropy of nematic rubber, r(T)=ell_{allel}/ell_{bot} proportional to the effective nematic order parameter Q(T), is given by an average of the two components and thus reflects the two-transition nature of thermal expansion. The experimental data is compared with the theoretical model of ideal nematic elastomers; applications in high-amplitude thermal actuators are discussed in the end.

  15. Negative thermal expansion materials: technological key for control of thermal expansion

    Directory of Open Access Journals (Sweden)

    Koshi Takenaka

    2012-01-01

    Full Text Available Most materials expand upon heating. However, although rare, some materials contract upon heating. Such negative thermal expansion (NTE materials have enormous industrial merit because they can control the thermal expansion of materials. Recent progress in materials research enables us to obtain materials exhibiting negative coefficients of linear thermal expansion over −30 ppm K−1. Such giant NTE is opening a new phase of control of thermal expansion in composites. Specifically examining practical aspects, this review briefly summarizes materials and mechanisms of NTE as well as composites containing NTE materials, based mainly on activities of the last decade.

  16. Controlling Thermal Expansion: A Metal–Organic Frameworks Route

    Science.gov (United States)

    2016-01-01

    Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal–organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application. MOF-5 has been selected as model material, along with three molecules of similar size and known differences in terms of the nature of host–guest interactions. It has been shown that adsorbate molecules can control, in a colligative way, the thermal expansion of the solid, so that changing the adsorbate molecules induces the solid to display positive, zero, or negative thermal expansion. We analyze in depth the distortion mechanisms, beyond the ligand metal junction, to cover the ligand distortions, and the energetic and entropic effect on the thermo-structural behavior. We provide an unprecedented atomistic insight on the effect of adsorbates on the thermal expansion of MOFs as a basic tool toward controlling the thermal expansion. PMID:28190918

  17. Controlling Thermal Expansion: A Metal-Organic Frameworks Route.

    Science.gov (United States)

    Balestra, Salvador R G; Bueno-Perez, Rocio; Hamad, Said; Dubbeldam, David; Ruiz-Salvador, A Rabdel; Calero, Sofia

    2016-11-22

    Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal-organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application. MOF-5 has been selected as model material, along with three molecules of similar size and known differences in terms of the nature of host-guest interactions. It has been shown that adsorbate molecules can control, in a colligative way, the thermal expansion of the solid, so that changing the adsorbate molecules induces the solid to display positive, zero, or negative thermal expansion. We analyze in depth the distortion mechanisms, beyond the ligand metal junction, to cover the ligand distortions, and the energetic and entropic effect on the thermo-structural behavior. We provide an unprecedented atomistic insight on the effect of adsorbates on the thermal expansion of MOFs as a basic tool toward controlling the thermal expansion.

  18. Anisotropic thermal expansion in flexible materials

    Science.gov (United States)

    Romao, Carl P.

    2017-10-01

    A definition of the Grüneisen parameters for anisotropic materials is derived based on the response of phonon frequencies to uniaxial stress perturbations. This Grüneisen model relates the thermal expansion in a given direction (αi i) to one element of the elastic compliance tensor, which corresponds to the Young's modulus in that direction (Yi i). The model is tested through ab initio prediction of thermal expansion in zinc, graphite, and calcite using density functional perturbation theory, indicating that it could lead to increased accuracy for structurally complex systems. The direct dependence of αi i on Yi i suggests that materials which are flexible along their principal axes but rigid in other directions will generally display both positive and negative thermal expansion.

  19. Thermal expansion behaviour of granites

    Czech Academy of Sciences Publication Activity Database

    Plevová, Eva; Vaculíková, Lenka; Kožušníková, Alena; Ritz, M.; Simha Martynková, G.

    2016-01-01

    Roč. 123, č. 2 (2016), s. 1555-1561 ISSN 1388-6150 R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : thermomechanical analysis * differential thermal analysis * granites Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.953, year: 2016 http://link.springer.com/article/10.1007/s10973-015-4996-z

  20. Soft Manifold Dynamics behind Negative Thermal Expansion

    Science.gov (United States)

    Schlesinger, Z.; Rosen, J. A.; Hancock, J. N.; Ramirez, A. P.

    2008-07-01

    Minimal models are developed to examine the origin of large negative thermal expansion in underconstrained systems. The dynamics of these models reveals how underconstraint can organize a thermodynamically extensive manifold of low-energy modes which not only drives negative thermal expansion but extends across the Brillioun zone. Mixing of twist and translation in the eigenvectors of these modes, for which in ZrW2O8 there is evidence from infrared and neutron scattering measurements, emerges naturally in our model as a signature of the dynamics of underconstraint.

  1. Negative thermal expansion near two structural quantum phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Occhialini, Connor A.; Handunkanda, Sahan U.; Said, Ayman; Trivedi, Sudhir; Guzmán-Verri, G. G.; Hancock, Jason N.

    2017-12-01

    Recent experimental work has revealed that the unusually strong, isotropic structural negative thermal expansion in cubic perovskite ionic insulator ScF3 occurs in excited states above a ground state tuned very near a structural quantum phase transition, posing a question of fundamental interest as to whether this special circumstance is related to the anomalous behavior. To test this hypothesis, we report an elastic and inelastic x-ray scattering study of a second system Hg2I2 also tuned near a structural quantum phase transition while retaining stoichiometric composition and high crystallinity. We find similar behavior and significant negative thermal expansion below 100 K for dimensions along the body-centered-tetragonal c axis, bolstering the connection between negative thermal expansion and zero-temperature structural transitions.We identify the common traits between these systems and propose a set of materials design principles that can guide discovery of newmaterials exhibiting negative thermal expansion

  2. Impact of size and temperature on thermal expansion of nanomaterials

    Indian Academy of Sciences (India)

    Abstract. A theoretical method has been discussed to study the size dependency of thermal expan- sion of nanomaterials at higher temperature by considering the surface effect. A thermodynamical analysis of the equation of state (EoS) is studied from the knowledge of thermal expansion of nano- materials based on ...

  3. Negative thermal expansion in cubic ZrMo2 O8 : Inelastic neutron scattering and lattice dynamical studies

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Schober, H.; Kolesnikov, A. I.; Loong, C.-K.; Lind, C.; Wilkinson, A. P.

    2004-12-01

    Disordered cubic ZrMo2O8(Pa3¯,Z=4) is known to display isotropic negative thermal expansion (NTE) below 600 K. We report high-pressure inelastic neutron scattering experiments up to 2.5 kbar in this material using the IN6 spectrometer at Institut Laue-Langevin. The observed phonon softening of about 0.1-0.3 meV for phonons below 8 meV is able to account for the NTE below 100 K. The phonon spectrum in the entire energy range up to 150 meV has been measured using the HRMECS spectrometer at Argonne National Laboratory. The ordered phase (space group P213 ) of cubic ZrMo2O8 has not yet been synthesized. However, we have calculated the phonon spectrum and thermal expansion in this phase for comparison with the known ordered phase of cubic ZrW2O8 .

  4. Strong anisotropic thermal expansion in cristobalite-type BPO 4

    Science.gov (United States)

    Achary, S. N.; Tyagi, A. K.

    2004-11-01

    In this communication, the thermal expansion behavior of cristobalite-type BPO 4, determined from high-temperature X-ray diffraction studies, is being reported. BPO 4 crystallizes in tetragonal lattice, with space group I-4 (No. 82) at room temperature, with unit cell parameters: a=4.3447(2), c=6.6415(5) Å and V=125.37(1) Å 3. The tetragonal unit cell parameters at 900 °C are: a=4.3939(2), c=6.6539(6) Å and V=128.46(1) Å 3. The results show a very strong anisotropic expansion in the lattice, with the typical thermal expansion coefficients along a- and c-axis 12.9×10 -6 and 2.1×10 -6/°C, respectively. The volume thermal expansion coefficient of the lattice is 28.2×10 -6/°C in the temperature range of 25-900 °C. The variation of the crystal structure with temperature and the thermal expansion behavior are explained in this manuscript. The role of inter-polyhedral angle on the thermal expansion behavior has also been established.

  5. Thermal Expansion Behavior of Hot-Pressed Engineered Matrices

    Science.gov (United States)

    Raj, S. V.

    2016-01-01

    Advanced engineered matrix composites (EMCs) require that the coefficient of thermal expansion (CTE) of the engineered matrix (EM) matches those of the fiber reinforcements as closely as possible in order to reduce thermal compatibility strains during heating and cooling of the composites. The present paper proposes a general concept for designing suitable matrices for long fiber reinforced composites using a rule of mixtures (ROM) approach to minimize the global differences in the thermal expansion mismatches between the fibers and the engineered matrix. Proof-of-concept studies were conducted to demonstrate the validity of the concept.

  6. Frostless heat pump having thermal expansion valves

    Science.gov (United States)

    Chen, Fang C [Knoxville, TN; Mei, Viung C [Oak Ridge, TN

    2002-10-22

    A heat pump system having an operable relationship for transferring heat between an exterior atmosphere and an interior atmosphere via a fluid refrigerant and further having a compressor, an interior heat exchanger, an exterior heat exchanger, a heat pump reversing valve, an accumulator, a thermal expansion valve having a remote sensing bulb disposed in heat transferable contact with the refrigerant piping section between said accumulator and said reversing valve, an outdoor temperature sensor, and a first means for heating said remote sensing bulb in response to said outdoor temperature sensor thereby opening said thermal expansion valve to raise suction pressure in order to mitigate defrosting of said exterior heat exchanger wherein said heat pump continues to operate in a heating mode.

  7. Thin metastructures with engineered thermal expansion

    Science.gov (United States)

    Gdoutos, Eleftherios E.

    The geometry and constituent materials of metastructures can be used to engineer the thermal expansion coefficient. In this thesis, we design, fabricate, and test thin thermally stable metastructures consisting of bi-metallic unit cells and show how the coefficient of thermal expansion (CTE) of these metastructures can be finely and coarsely tuned by varying the CTE of the constituent materials and the unit cell geometry. Planar and three-dimensional finite element method modeling is used to drive the design and inform experiments, and predict the response of these metastructures. We demonstrate computationally the significance of out-of-plane effects in the metastructure response. We develop an experimental setup using digital image correlation and an infrared camera to experimentally measure full displacement and temperature fields during testing and accurately measure the metastructures' CTE. We experimentally demonstrate high aspect ratio metastructures of Ti/Al and Kovar/Al which exhibit near-zero and negative CTE, respectively. We demonstrate robust fabrication procedures for thermally stable samples with high aspect ratios in thin foil and thin film scales. We investigate the lattice structure and mechanical properties of thin films comprising a near-zero CTE metastructure. The mechanics developed in this work can be used to engineer metastructures of arbitrary CTE and can be extended to three dimensions.

  8. The effect of leucite crystallization and thermal history on thermal expansion measurement of dental porcelains

    Science.gov (United States)

    Khajotia, Sharukh Soli

    1997-12-01

    Objectives. Measurement of thermal expansion in glassy materials is complicated by thermal history effects. The purpose of this research was to determine whether the occurrence of structural relaxation in glassy materials, such as dental porcelains, and changes in porcelain leucite content could interfere with the accurate measurement of the coefficient of thermal expansion during the thermal expansion measurement itself. Methods. In a randomized design, thermal expansion specimens were fabricated using six commercial body porcelains and the leucite-containing Component No. 1 frit (Weinstein et al. patent, 1962), and subjected to one of the following heat treatments: a single heating run at 3sp°C/min in a conventional dilatometer followed by air quenching; three successive low-rate heating and cooling thermal expansion runs at 3sp°C/min in a conventional dilatometer; or three successive high-rate heating and cooling thermal expansion runs at 600sp°C/min in a laser dilatometer. The remaining specimens were left untreated and served as controls. Potential changes in porcelain leucite content were monitored via quantitative X-ray diffraction. Thermal expansion data for each run over a temperature range of 25-500sp°C and the leucite content of all specimens were subjected to repeated measures analysis of variance. Results. The thermal expansion coefficient measured on first slow heating was significantly lower than the values for succeeding low-rate heating and cooling runs in all materials (p $ 0.05). No significant effect of dilatometer thermal treatments on leucite content (p >$ 0.05) was shown for all materials studied using both dilatometers. Significance. The crystallization of additional amounts of leucite during thermal expansion runs can be ruled out as a possible interference in the determination of the thermal expansion coefficient of dental porcelain. Conventional dilatometer measurements exhibited structural relaxation during the first heating run, as

  9. Correlated atomic motions in the negative thermal expansion material ZrW2O8: A local structure study

    Science.gov (United States)

    Cao, D.; Bridges, F.; Kowach, G. R.; Ramirez, A. P.

    2003-07-01

    Recent studies of zirconium tungstate, ZrW2O8, show an isotropic negative thermal expansion (NTE) over a wide temperature range. It has been proposed that the low-energy phonon vibrational modes, observed in both specific heat and phonon density-of-states measurements, are responsible for this unusual NTE. We have carried out x-ray-absorption fine-structure (XAFS) experiments at both the W LIII edge and Zr K edge to study the detailed local structure in ZrW2O8. Our XAFS results show a very small temperature dependence of the broadening parameter, σ, for the W-Zr atom pair and the W-O-Zr linkage; consequently, the displacements of the W, O, and Zr atoms must be correlated. The data show a much larger temperature dependence of σ for the nearest W1-W2 pair as well as for the nearest Zr-Zr pair. These combined results indicate that it is the correlated motion of a WO4 tetrahedron and its three nearest ZrO6 octahedra that leads to the NTE effect in this material instead of primarily transverse vibrations of the middle O atom in the W-O-Zr linkage. The data for both W-W and Zr-Zr atom pairs also indicate a hardening of the effective spring constant near 100 K, which is consistent with the shift of the lowest mode with T in the phonon density of states. A simple model is developed to explain the NTE in terms of the local structure results; it also provides a natural explanation for the lack of a soft-mode phase transition.

  10. Thermal expansion method for lining tantalum alloy tubing with tungsten

    Science.gov (United States)

    Watson, G. K.; Whittenberger, J. D.; Mattson, W. F.

    1973-01-01

    A differential-thermal expansion method was developed to line T-111 (tantalum - 8 percent tungsten - 2 percent hafnium) tubing with a tungsten diffusion barrier as part of a fuel element fabrication study for a space power nuclear reactor concept. This method uses a steel mandrel, which has a larger thermal expansion than T-111, to force the tungsten against the inside of the T-111 tube. Variables investigated include lining temperature, initial assembly gas size, and tube length. Linear integrity increased with increasing lining temperature and decreasing gap size. The method should have more general applicability where cylinders must be lined with a thin layer of a second material.

  11. 6th International Symposium on Thermal Expansion

    CERN Document Server

    1978-01-01

    This 6th International Symposium on Thermal Expansion, the first outside the USA, was held on August 29-31, 1977 at the Gull Harbour Resort on Hecla Island, Manitoba, Canada. Symposium Chairman was Ian D. Peggs, Atomic Energy of Canada Limited, and our continuing sponsor was CINDAS/Purdue University. We made considerable efforts to broaden the base this year to include more users of expansion data but with little success. We were successful, however, in establishing a session on liquids, an area which is receiving more attention as a logical extension to the high-speed thermophysical property measurements on materials at temperatures close to their melting points. The Symposium had good international representation but the overall attendance was, disappointingly, relatively low. Neverthe­ less, this enhanced the informal atmosphere throughout the meeting with a resultant frank exchange of information and ideas which all attendees appreciated. A totally new item this year was the presentation of a bursary to ...

  12. Glass ceramics for sealing to high-thermal-expansion metals

    Energy Technology Data Exchange (ETDEWEB)

    Wilder, Jr., J. A.

    1980-10-01

    Glass ceramics were studied, formulated in the Na/sub 2/O CaO.P/sub 2/O/sub 5/, Na/sub 2/O.BaOP/sub 2/O/sub 5/, Na/sub 2/O.Al/sub 2/O/sub 3/.P/sub 2/O/sub 5/, and Li/sub 2/O.BaO.P/sub 2/O/sub 5/ systems to establish their suitability for sealing to high thermal expansion metals, e.g. aluminum, copper, and 300 series stainless steels. Glass ceramics in Na/sub 2/O.CaO.P/sub 2/O/sub 5/ and Na/sub 2/O.BaO.P/sub 2/O/sub 5/ systems have coefficients of thermal expansion in the range 140 x 10/sup -1/ per /sup 0/C less than or equal to ..cap alpha.. less than or equal to 225 x 10/sup -7/ per /sup 0/C and fracture toughness values generally greater than those of phosphate glasses; they are suitable for fabricating seals to high thermal expansion metals. Crystal phases include NaPo/sub 3/, (NaPO/sub 3/)/sub 3/, NaBa(PO/sub 3/)/sub 3/, and NaCa(PO/sub 3/)/sub 3/. Glass ceramics formed in the Na/sub 2/O.Al/sub 2/O/sub 3/.P/sub 2/O/sub 5/ systems have coefficients of thermal expansion greater than 240 x 10/sup -7/ per /sup 0/C, but they have extensive microcracking. Due to their low thermal expansion values (..cap alpha.. less than or equal to 120 x 10/sup -7/ per /sup 0/C), glass ceramics in the Li/sub 2/O.BaO.P/sub 2/O/sub 5/ system are unsuitable for sealing to high thermal expansion metals.

  13. Effect of high thermal expansion glass infiltration on mechanical ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high.

  14. Anisotropic thermal expansion in crystals of different categories

    Science.gov (United States)

    Zamkovskaya, A.; Maksimova, E.

    2015-12-01

    The three-dimensional (3D) indicatory surfaces of thermal expansion in crystals of different categories were constructed in program MathCad. Indicatory surface of thermal expansion is a sphere, spheroid, ellipsoid or surface of multiple parts, depending on the category of the crystal symmetry. The symmetry elements of thermal expansion include the symmetry elements of the point group of the crystal according Neumann's Principle.

  15. Thermal expansion of CuInSe{sub 2} in the 11-1,073 K range: an X-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Paszkowicz, W.; Minikayev, R.; Wojciechowski, T. [Institute of Physics PAS, Warsaw (Poland); Piszora, P. [A. Mickiewicz University, Faculty of Chemistry, Poznan (Poland); Trots, D. [Universitaet Bayreuth, Bayerisches Geoinstitut, Bayreuth (Germany); Knapp, M. [Institute for Applied Materials-Energy Storage Systems, Karlsruhe Institute of Technology, Karlsruhe (Germany); Bacewicz, R. [Warsaw University of Technology, Faculty of Physics, Warsaw (Poland)

    2014-08-15

    Structural and elastic properties of chalcopyrite-type CuInSe{sub 2} are determined in almost full stability range of temperature from 11 to 1,073 K, by in situ X-ray diffraction, employing a synchrotron-radiation source. The studied polycrystalline sample was prepared from a stoichiometric single crystal. Phase analysis reveals the formation of a trace amount of indium oxide impurity phase at the highest temperatures studied. From the obtained smooth lattice-parameter dependencies on temperature, the temperature dependencies of thermal expansion coefficients are derived. These coefficients are found to follow the trends previously reported for narrow temperature intervals. The present results provide a clear experimental evidence that the linear expansion coefficient is slightly negative below 47 K in both, a and c, directions; this temperature limit is in between the previously reported theoretical value (35 K) and the experimental ones (60 and 80 K) of such limit. (orig.)

  16. Origin of the colossal positive and negative thermal expansion in Ag{sub 3}[Co(CN){sub 6}]: an ab initio density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Calleja, Mark [Cambridge eScience Centre, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Goodwin, Andrew L; Dove, Martin T [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)], E-mail: mtd10@cam.ac.uk

    2008-06-25

    DFT calculations have been used to provide insights into the origin of the colossal positive and negative thermal expansion in Ag{sub 3}[Co(CN){sub 6}]. The results confirm that the positive expansion within the trigonal basal plane and the negative expansion in the orthogonal direction are coupled due to the existence of a network defined by nearly rigid bonds within the chains of Co-C-N-Ag-N-C-Co linkages. The origin of the colossal values of the coefficients of thermal expansion arise from an extremely shallow energy surface that allows a flexing of the structure with small energy cost. The thermal expansion can be achieved with a modest value of the overall Grueneisen parameter. The energy surface is so shallow that we need to incorporate a small empirical dispersive interaction to give ground-state lattice parameters that match experimental values at low temperature. We compare the results with DFT calculations on two isostructural systems: H{sub 3}[Co(CN){sub 6}], which is known to have much smaller values of the coefficients of thermal expansion, and Au{sub 3}[Co(CN){sub 6}], which has not yet been synthesized but which is predicted by our calculations to be another candidate material for showing colossal positive and negative thermal expansion.

  17. Study of negative thermal expansion and shift in phase transition temperature in Ti4+- and Sn4+-substituted ZrW2O8 materials.

    Science.gov (United States)

    Buysser, Klaartje De; Driessche, Isabel Van; Putte, Bart Vande; Vanhee, Paul; Schaubroeck, Joseph; Hoste, Serge

    2008-01-21

    The negative-thermal-expansion material ZrW(2)O(8) is known to undergo an order-disorder phase transition which affects its expansion behavior. In this study, Ti(4+) and Sn(4+) are examined as possible substituting ions for the Zr(4+) position in ZrW(2)O(8). This substitution leads to a decrease in cell parameters, as the ionic radii of the substituents are smaller than the Zr(4+) ionic radius. A remarkable decrease in transition temperature is noticed. DSC is used to quantify the enthalpy and entropy changes during the phase transition in order to reveal the mechanisms behind this decrease. It is shown that the strength of the M-O bond plays an important role, as it is a partner in the rigid unit mode motion and the order-disorder transition mechanism.

  18. Seal assembly for materials with different coefficients of thermal expansion

    Science.gov (United States)

    Minford, Eric [Laurys Station, PA

    2009-09-01

    Seal assembly comprising (a) two or more seal elements, each element having having a coefficient of thermal expansion; and (b) a clamping element having a first segment, a second segment, and a connecting segment between and attached to the first and second segments, wherein the two or more seal elements are disposed between the first and second segments of the clamping element. The connecting segment has a central portion extending between the first segment of the clamping element and the second segment of the clamping element, and the connecting segment is made of a material having a coefficient of thermal expansion. The coefficient of thermal expansion of the material of the connecting segment is intermediate the largest and smallest of the coefficients of thermal expansion of the materials of the two or more seal elements.

  19. Effectively control negative thermal expansion of single-phase ferroelectrics of PbTiO3-(Bi,La)FeO3 over a giant range.

    Science.gov (United States)

    Chen, Jun; Wang, Fangfang; Huang, Qingzhen; Hu, Lei; Song, Xiping; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

    2013-01-01

    Control of negative thermal expansion is a fundamentally interesting topic in the negative thermal expansion materials in order for the future applications. However, it is a challenge to control the negative thermal expansion in individual pure materials over a large scale. Here, we report an effective way to control the coefficient of thermal expansion from a giant negative to a near zero thermal expansion by means of adjusting the spontaneous volume ferroelectrostriction (SVFS) in the system of PbTiO3-(Bi,La)FeO3 ferroelectrics. The adjustable range of thermal expansion contains most negative thermal expansion materials. The abnormal property of negative or zero thermal expansion previously observed in ferroelectrics is well understood according to the present new concept of spontaneous volume ferroelectrostriction. The present studies could be useful to control of thermal expansion of ferroelectrics, and could be extended to multiferroic materials whose properties of both ferroelectricity and magnetism are coupled with thermal expansion.

  20. Thermal expansion of spinel-type Si3N4

    DEFF Research Database (Denmark)

    Paszkowics, W.; Minkikayev, R.; Piszora, P.

    2004-01-01

    The lattice parameter and thermal expansion coefficient (TEC) for the spinel-type Si3N4 phase prepared under high-pressure and high-temperature conditions are determined for 14 K......The lattice parameter and thermal expansion coefficient (TEC) for the spinel-type Si3N4 phase prepared under high-pressure and high-temperature conditions are determined for 14 K...

  1. Thermal expansion behavior of fluor-chlorapatite crystalline solutions

    Science.gov (United States)

    Hovis, G.; Harlov, D.; Gottschalk, M.; Hudacek, W.; Wildermuth, S.

    2009-04-01

    the fluor-chlorapatite series is little affected by composition. This contrasts with relationships in alkali feldspars (Hovis and coworkers, 1997, 1999), which show that K-rich feldspars expand less than Na-rich feldspars. It contrasts also with the behavior of additional AlSi3 feldspars (Hovis and others, 2008), in which room-temperature chemical expansion limits the degree to which the structure can expand thermally. It also differs from expansion in kalsilite crystalline solutions (Hovis and coworkers, 2003, 2006), which depends on K:Na ratio. Among the minerals we have studied previously, only nepheline displays expansion behavior similar to that of fluor-chlorapatite crystalline solutions in that thermal expansion shows little sensitivity to composition. In AlSi3 feldspars and kalsilite one observes a single crystallographically distinct alkali site and a dominating SiO4 tetrahedral framework that limits the vibrational characteristics of the alkali-site occupant(s). Fluor-chlorapatite crystalline solutions have no such structural framework. Moreover, the anion site in the latter changes structural character in the transition from fluorapatite to chlorapatite. This flexibility apparently allows anion vibrational characteristics, coupled with those of Ca polyhedral components, to change continuously and in a compensating manner across the series. The thermal expansion data also imply that volumes of F-Cl mixing in fluor-chlorapatite are constant from room temperature to 1000 °C. References: Cherniak, D.J. (2000) Rare earth element diffusion in apatite. Geochimica et Cosmochimica Acta 64, 3871-3885. Harlov, D.E. and Förster, H-J. (2002) High grade fluid metasomatism on both a local and regional Scale: the Seward Peninsula, Alaska and the Ivrea-Verbano Zone, Northern Italy Part II: phosphate mineral chemistry. Journal of Petrology 43, 801-824. Holland, T.J.B. and Redfern, S.A.T. (1997) Unit-cell refinement: Changing the dependent variable, and use of regression

  2. Exploring the thermal expansion of fluorides and oxyfluorides with rhenium trioxide-type structures: From negative to positive thermal expansion

    Science.gov (United States)

    Greve, Benjamin K.

    This thesis explores the thermal expansion and high pressure behavior of some materials with the ReO3 structure type. This structure is simple and has, in principle, all of the features necessary for negative thermal expansion (NTE) arising from the transverse thermal motion of the bridging anions and the coupled rotation of rigid units; however, ReO 3 itself only exhibits mild NTE across a narrow temperature range at low temperatures. ReO3 is metallic because of a delocalized d-electron, and this may contribute to the lack of NTE in this material. The materials examined in this thesis are all based on d 0 metal ions so that the observed thermal expansion behavior should arise from vibrational, rather than electronic, effects. In Chapter 2, the thermal expansion of scandium fluoride, ScF3 , is examined using a combination of in situ synchrotron X-ray and neutron variable temperature diffraction. ScF3 retains the cubic ReO3 structure across the entire temperature range examined (10 - 1600 K) and exhibits pronounced negative thermal expansion at low temperatures. The magnitude of NTE in this material is comparable to that of cubic ZrW2O8, which is perhaps the most widely studied NTE material, at room temperature and below. This is the first report of NTE in an ReO3 type structure across a wide temperature range. Chapter 3 presents a comparison between titanium oxyfluoride, TiOF 2, and a vacancy-containing titanium hydroxyoxyfluoride, Ti x(O/OH/F)3. TiOF2 was originally reported to adopt the cubic ReO3 structure type under ambient conditions, therefore the initial goal for this study was to examine the thermal expansion of this material and determine if it displayed interesting behavior such as NTE. During the course of the study, it was discovered that the original synthetic method resulted in Tix(O/OH/F)3, which does adopt the cubic ReO3 structure type. The chemical composition of the hydroxyoxyfluoride is highly dependent upon synthesis conditions and subsequent

  3. Development of Low Thermal Expansion Tungsten UO 2 Cermet Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Marlowe, M O; Kaznoff, A I

    1970-03-31

    An attempt was made to develop a tungsten-uranium dioxide cermet of high fue 1 loading with thermal expansion approaching that of tungsten and with good dimensional stability on thermal cycling. These goals were sought through the use of tungsten-coated uranium dioxide particles with sufficient locally available void volume to accommodate the difference in thermal expansion between the uranium dioxide and the tungsten matrix and through limitation of plastic deformation in the particles during fabrication to avoid mechanical keying of the particles and the matrix. The particles were vibratorily compacted prior to hot pressing. The thermal expansion of the cermets was determined and they were thermal cycle tested. The thermal expansion of the cermets was considerably closer to that of tungsten than was observed with previously reported specimens of similar composition. However, the thermal cycling of the cermets resulted in intolerable growth. This growth could be accounted for by the agglomeration of gases trapped in the uranium dioxide particles during deposition of the tungsten coating.

  4. Effective Thermal Expansion Property of Consolidated Granular Materials.

    Science.gov (United States)

    Küçük, Gülşad; Gonzalez, Marcial; Cuitiño, Alberto M

    2017-11-09

    Thermally-assisted compaction of granular materials is of keen interest in many engineering applications. A proper estimation of the material behavior of compacted granular materials is contingent upon the knowledge of microstructure formation, which is highly dependent on the bulk material properties and processing conditions, during the deformation stage. Originating from the pair interactions between particles, the macroscopic properties are obtained using various homogenization techniques and postulating continuum constitutive laws. While pioneers in this field have laid fundamental groundwork regarding effective medium descriptions, there exists a discrepancy between discrete and continuum level solutions. In our previous work, we elaborated a Particle Mechanics Approach (PMA) that integrates thermal contact and Hertzian deformation models to understand the thermo-mechanically-coupled consolidation problem. We also considered the analogous problem from the perspective of the conventional Continuum Mechanics Approach (CMA). In this study, following the multi-scale modeling framework, we propose an effective thermal expansion coefficient for the thermally-assisted compaction of granular materials.

  5. Thermal expansion investigation of tourmaline-group minerals

    Science.gov (United States)

    Hovis, G.; Scott, B.; Altomare, C.; Tomaino, G.

    2012-04-01

    In recent years one aim of this laboratory has been the characterization of thermal expansion in various mineral groups with an eye toward evaluation of the extent to which chemical composition affects expansion behaviour. We have undertaken studies on various mineral series including alkali feldspar, plagioclase, Ba/K-feldspar, Rb/K feldspar, nepheline/kalsilite minerals of various excess Si contents, and F/Cl/OH apatite. We turn our attention now to the tourmaline mineral system, which is of interest because of its wide variation in chemical composition, as well as its structural complexity. We have obtained multiple chemically-characterized tourmaline specimens from the U.S. National Museum of Natural History and also from George Rossman. Six specimens have been investigated so far, including elbaite, rossmanite, uvite, buergerite, schorl, and foitite. High-temperature X-ray powder diffraction measurements have been made from room temperature to 1000 °C at 75° intervals. X-ray peak positions were corrected utilizing NIST SRM 640a silicon as an internal standard. Peaks were indexed manually based on data in the literature; unit-cell dimensions were computed utilizing the software of Holland and Redfern (1997, Mineralogical Magazine). V-T relationships are generally linear, or close to it, up to the breakdown temperatures of all specimens. Coefficients of thermal expansion have been computed as (ΔV/ΔT)*(1/V0C), where V0C is the extrapolated volume intercept at 0 °C based on the various linear V-T relationships. Among the six specimens, all except foitite give thermal expansion coefficients between 23 and 26 x 10-6 deg-1. Foitite has a flatter V-T slope and thus expands less, giving a thermal expansion coefficient of 18 x 10-6. Based on the initial data, the relative uniformity of expansion behaviour in this system implies that any volumes of mixing in this system will be essentially constant with temperature, recognizing that this conclusion is based on the

  6. Zirconium titanate: stability and thermal expansion; Titanato de circonio: estabilidad termodinamica y expansion termica

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Lopez, E.; Moreno, R.; Baudin, C.

    2011-07-01

    Zirconium titanate is a well known compound in the field of electro ceramics, although it has also been used in catalyst and sensors applications. The crystallographic thermal expansion anisotropy of this compound makes it a potential candidate as constituent of structural components. In general, to assure the structural integrity and microstructural homogeneity of a ceramic piece, relatively low cooling rates from the fabrication temperature are required. This requirement is essential for zirconium titanate because thermal expansion as well as phase distribution is affected by small variations in the composition and cooling rate. This work reviews the available data on the phase equilibrium relationships in the systems ZrO{sub 2}-TiO{sub 2} and ZrO{sub 2}-TiO{sub 2}-Y{sub 2}O{sub 3}. The main discrepancies as well as the possible origins of them are discussed. Additionally, the crystallographic thermal expansion data in the current literature are reviewed. (Author) 56 refs.

  7. DYN3D thermal expansion models for SFR applications

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, Evgeny; Fridman, Emil [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Reactor Safety

    2016-07-01

    The nodal diffusion code DYN3D is under extension for SFR applications. As a part of the extension a new model for axial thermal expansion of fuel rods was developed. The new model provides a flexible way of handling the axial fuel rod expansion, because each sub-assembly and node can be treated independently. The performance of the model was tested on a large oxide SFR core, and the results were compared to the reference full core Serpent solution. The test results indicated that the proposed model can accurately account for the axial expansion effects on full core level.

  8. Symmetry Switching of Negative Thermal Expansion by Chemical Control.

    Science.gov (United States)

    Senn, Mark S; Murray, Claire A; Luo, Xuan; Wang, Lihai; Huang, Fei-Ting; Cheong, Sang-Wook; Bombardi, Alessandro; Ablitt, Chris; Mostofi, Arash A; Bristowe, Nicholas C

    2016-05-04

    The layered perovskite Ca3-xSrxMn2O7 is shown to exhibit a switching from a material exhibiting uniaxial negative to positive thermal expansion as a function of x. The switching is shown to be related to two closely competing phases with different symmetries. The negative thermal expansion (NTE) effect is maximized when the solid solution is tuned closest to this region of phase space but is switched off suddenly on passing though the transition. Our results show for the first time that, by understanding the symmetry of the competing phases alone, one may achieve unprecedented chemical control of this unusual property.

  9. Theory of low-temperature thermal expansion of glasses

    Science.gov (United States)

    Galperin, Yu. M.; Gurevich, V. L.; Parshin, D. A.

    1985-11-01

    We have developed a theory of low-temperature thermal expansion of glasses explaining a number of existing experimental data. We assume that thermal expansion, like many other low-temperature properties of glasses, is determined by associated two-level systems (TLS's) this concept has been introduced to explain these properties by Anderson, Halperin, and Varma and by Phillips. Our theory is based on the Karpov-Klinger-Ignat'ev model of two-level systems in glasses. The deformation potential of the TLS's is calculated. We have shown that it consists of two parts: The larger part (of the order of 0.3 eV) is responsible for the observed transport properties of glasses; however, it does not contribute to the thermal expansion of glasses. The latter is caused by a relatively small second part of the deformation potential which is, within logarithmic accuracy, proportional to the TLS's interlevel spacing E. This is why at low temperatures the coefficient of thermal expansion of glasses is approximately a linear function of the temperature. Its sign is determined by a microscopic structure of the TLS. We have calculated the Grüneisen parameter Γ. It appears to be of the order of (scrEa/ħωD)2/3~=100, where scrEa is an energy of the order of 30 eV and ωD is the Debye frequency. Such large values of Γ are connected with the softness of local anharmonic potentials that produce the TLS's in glasses. Our principal result is the dependence of the coefficient of thermal expansion α on the time of experiment, τexpt. It is shown that if α<0, then after heating glass it is at first contracted and afterwards, after the time about 10-8 sec (at T=0.3 K), a slow expansion begins. At τexpt~=1 sec the parameter Γ can have the absolute value of about (1/3) of that at τexpt~=10-8 sec. Such behavior of the thermal expansion coefficient is due to the fact that the contribution of the TLS's with large relative tunnel splitting (Δ0/E~=1) is negative while that of the TLS's with

  10. Quantum elasticity of graphene: Thermal expansion coefficient and specific heat

    NARCIS (Netherlands)

    Burmistrov, I.S.; Gornyi, I.V.; Kachorovskii, V.Y.; Katsnelson, M.I.; Mirlin, A.D.

    2016-01-01

    We explore thermodynamics of a quantum membrane, with a particular application to suspended graphene membrane and with a particular focus on the thermal expansion coefficient. We show that an interplay between quantum and classical anharmonicity-controlled fluctuations leads to unusual elastic

  11. Thermal expansion behaviour of barium and strontium zirconium ...

    Indian Academy of Sciences (India)

    Unknown

    Thermal expansion behaviour of barium and strontium zirconium phosphates. P SRIKARI TANTRI, K GEETHA†, A M UMARJI† and SHEELA K RAMASESHA*. Materials Science Division, National Aerospace Laboratories, Bangalore 560 017, India. †Materials Research Centre, Indian Institute of Science, Bangalore 560 ...

  12. Thermal Expansion and Aging Effects in Neuromorphic Signal Processor

    NARCIS (Netherlands)

    Zjajo, A.; van Leuken, T.G.R.M.

    2016-01-01

    In this paper, we propose an efficient methodology based on a real-time estimator and predictor-corrector scheme for accurate thermal expansion profile and aging evaluation of a neuromorphic signal processor circuit components. As the experimental results indicate, for comparable mesh size, the

  13. The role of static disorder in negative thermal expansion in ReO3

    Science.gov (United States)

    Rodriguez, Efrain E.; Llobet, Anna; Proffen, Thomas; Melot, Brent C.; Seshadri, Ram; Littlewood, Peter B.; Cheetham, Anthony K.

    2009-06-01

    Time-of-flight neutron powder diffraction and specific heat measurements were used to study the nature of thermal expansion in rhenium trioxide, an electrically conducting oxide with cubic symmetry. The temperature evolution of the lattice parameters shows that ReO3 can exhibit negative thermal expansion below room temperature and that the transition from negative to positive thermal expansion depends on sample preparation; the single crystal sample demonstrated the highest transition temperature, 294(19) K, and largest negative value for the coefficient of thermal expansion, α =-10(1)×10-7 K-1. For the oxygen atoms, the atomic displacement parameters are strongly anisotropic even at 15 K, indicative of a large contribution of static disorder to the displacement parameters. Further inspection of the temperature evolution of the oxygen displacement parameters for different samples reveals that the static disorder contribution is greater for the samples with diminished negative thermal expansion (NTE) behavior. In addition, specific heat measurements show that ReO3 lacks the low energy Einstein-type modes seen in other NTE oxides such as ZrW2O8. The thermal expansion behavior in other NTE materials such as ZrW2O8, cuprite-type oxides, and the Prussian blue cyanides are discussed and compared with that of our ReO3 samples.

  14. The mechanism of the area negative thermal expansion in KBe{sub 2}BO{sub 3}F{sub 2} family crystals: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Xingxing [Center for Crystal Research and Development, Key Lab of Functional Crystals and Laser Technology of Chinese Academy of Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Molokeev, Maxim S. [Laboratory of Crystal Physics, Kirensky Institute of Physics, SB RAS, Krasnoyarsk 660036 (Russian Federation); Department of Physics, Far Eastern State Transport University, Khabarovsk 680021 (Russian Federation); Li, Wei [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Wu, Shaofan [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Lin, Zheshuai, E-mail: zslin@mail.ipc.ac.cn; Wu, Yicheng; Chen, Chuangtian [Center for Crystal Research and Development, Key Lab of Functional Crystals and Laser Technology of Chinese Academy of Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2016-02-07

    A very recent study demonstrated that the KBe{sub 2}BO{sub 3}F{sub 2} (KBBF) family of crystals, including KBBF, RbBe{sub 2}BO{sub 3}F{sub 2}, and CsBe{sub 2}BO{sub 3}F{sub 2}, are the only known borates exhibiting a rarely occurring isotropic area negative thermal expansion (NTE) behavior, over a very large temperature range. In the present work, the NTE mechanism in these crystals is comprehensively investigated using the first-principles calculations. It is revealed that the area NTE behavior mainly originates from the concerted distortion of [BeO{sub 3}F] tetrahedra in the two-dimensional [Be{sub 2}BO{sub 3}F{sub 2}]{sub ∞} framework with respect to temperature, while the [BO{sub 3}] triangles remain almost rigid. Moreover, the different magnitude of NTE effect in the three crystals is attributed to the interaction difference between the alkali metal atoms (K, Rb, or Cs) and the [Be{sub 2}BO{sub 3}F{sub 2}]{sub ∞} layer.

  15. The Origin of High Thermal Conductivity and Ultralow Thermal Expansion in Copper-Graphite Composites.

    Science.gov (United States)

    Firkowska, Izabela; Boden, André; Boerner, Benji; Reich, Stephanie

    2015-07-08

    We developed a nanocomposite with highly aligned graphite platelets in a copper matrix. Spark plasma sintering ensured an excellent copper-graphite interface for transmitting heat and stress. The resulting composite has superior thermal conductivity (500 W m(-1) K(-1), 140% of copper), which is in excellent agreement with modeling based on the effective medium approximation. The thermal expansion perpendicular to the graphite platelets drops dramatically from ∼20 ppm K(-1) for graphite and copper separately to 2 ppm K(-1) for the combined structure. We show that this originates from the layered, highly anisotropic structure of graphite combined with residual stress under ambient conditions, that is, strain-engineering of the thermal expansion. Combining excellent thermal conductivity with ultralow thermal expansion results in ideal materials for heat sinks and other devices for thermal management.

  16. Compressibility and thermal expansion of cubic silicon nitride

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Lindelov, H.; Gerward, Leif

    2002-01-01

    The compressibility and thermal expansion of the cubic silicon nitride (c-Si3N4) phase have been investigated by performing in situ x-ray powder-diffraction measurements using synchrotron radiation, complemented with computer simulations by means of first-principles calculations. The bulk...... compressibility of the c-Si3N4 phase originates from the average of both Si-N tetrahedral and octahedral compressibilities where the octahedral polyhedra are less compressible than the tetrahedral ones. The origin of the unit cell expansion is revealed to be due to the increase of the octahedral Si-N and N-N bond...

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

    Science.gov (United States)

    Takezawa, Akihiro; Kobashi, Makoto; Kitamura, Mitsuru

    2015-07-01

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

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

    Directory of Open Access Journals (Sweden)

    Akihiro Takezawa

    2015-07-01

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

  19. The Elusive Coefficients of Thermal Expansion in PBX 9502

    Energy Technology Data Exchange (ETDEWEB)

    C.B. Skidmore; T.A. Butler; C.W. Sandoval

    2003-05-01

    PBX 9502 has been in war reserve service for over two decades. Ninety-five percent of the solid phase of this insensitive high explosive is composed of energetic crystallites designated as TATB (1,3,5-triamino-2,4,6-trinitrobenzene), held together by the remaining solid fraction--an inert, polymeric binder named Kel-F 800. The unusual combination of extreme insensitivity and adequate performance characteristics is not the only enigmatic feature of such TATB-based materials. In this report, we describe the difficulty and progress to date in reliably determining the coefficients of thermal expansion for consolidated components of PBX 9502. We provide bulk linear coefficient of thermal expansion (CTE) values for PBX 9502 consolidated to a density of approximately 1.890 g/cm{sup 3} and offer a simple set of equations for calculating dimensional changes for temperatures from 218 to 347 K (-55 C to 74 C).

  20. Effect of particle size on the thermal expansion of nanostructured lead sulfide films

    Energy Technology Data Exchange (ETDEWEB)

    Sadovnikov, S.I.; Gusev, A.I., E-mail: gusev@ihim.uran.ru

    2014-10-15

    Highlights: • PbS nanofilms prepared by chemical deposition have a D0{sub 3}-type crystal structure. • Thermal expansion coefficient α of PbS nanofilm is twice as large as that of bulk PbS. • Large difference in the coefficients α is due to the small particle size in PbS film. • Small size of particles in PbS film increases the anharmonicity of atomic vibrations. - Abstract: The effect of particle size on the thermal expansion of nanostructured lead sulfide films produced by hydrochemical deposition has been studied. The coherent scattering region size and thermal expansion coefficients of PbS nanofilm have been measured depending on the annealing temperature in the interval 293–473 K and on the duration of annealing at a constant temperature of 423 K. It is found that the thermal expansion coefficient α of nanostructured PbS film is nearly twice as large as that of bulk lead sulfide. It is shown that the observed large difference in the coefficients α is due to the small size of PbS particles in the film that leads to the change of the phonon spectrum boundaries and to the growth of anharmonicity of atomic vibrations. The additional contribution to the thermal expansion coefficient caused by the small particle size in PbS nanofilm is estimated theoretically.

  1. Copper-based conductive composites with tailored thermal expansion.

    Science.gov (United States)

    Della Gaspera, Enrico; Tucker, Ryan; Star, Kurt; Lan, Esther H; Ju, Yongho Sungtaek; Dunn, Bruce

    2013-11-13

    We have devised a moderate temperature hot-pressing route for preparing metal-matrix composites which possess tunable thermal expansion coefficients in combination with high electrical and thermal conductivities. The composites are based on incorporating ZrW2O8, a material with a negative coefficient of thermal expansion (CTE), within a continuous copper matrix. The ZrW2O8 enables us to tune the CTE in a predictable manner, while the copper phase is responsible for the electrical and thermal conductivity properties. An important consideration in the processing of these materials is to avoid the decomposition of the ZrW2O8 phase. This is accomplished by using relatively mild hot-pressing conditions of 500 °C for 1 h at 40 MPa. To ensure that these conditions enable sintering of the copper, we developed a synthesis route for the preparation of Cu nanoparticles (NPs) based on the reduction of a common copper salt in aqueous solution in the presence of a size control agent. Upon hot pressing these nanoparticles at 500 °C, we are able to achieve 92-93% of the theoretical density of copper. The resulting materials exhibit a CTE which can be tuned between the value of pure copper (16.5 ppm/°C) and less than 1 ppm/°C. Thus, by adjusting the relative amount of the two components, the properties of the composite can be designed so that a material with high electrical conductivity and a CTE that matches the relatively low CTE values of semiconductor or thermoelectric materials can be achieved. This unique combination of electrical and thermal properties enables these Cu-based metal-matrix composites to be used as electrical contacts to a variety of semiconductor and thermoelectric devices which offer stable operation under thermal cycling conditions.

  2. Anion-mediated negative thermal expansion in lanthanum hexaboride

    Science.gov (United States)

    Mattox, Tracy M.; Groome, Chloe; Doran, Andrew; Beavers, Christine M.; Urban, Jeffrey J.

    2017-10-01

    Lanthanum hexaboride (LaB6) is well known for its thermionic emission, mechanical hardness, and intriguing optical properties. Though this material has been studied for decades, it is difficult to design LaB6 to meet application needs because little is understood about the mechanistic details of the synthesis. The ability to observe lattice formation during the reaction through in-situ x-ray diffraction is helping improve our knowledge. We report here the strong influence of anion size of the lanthanum precursor in the solid state reaction of LaX3 (X = Cl or I) and NaBH4. The Cl atom of the precursor remains within LaB6 post-synthesis and causes negative thermal expansion when the lattice is heated. Replacing Cl with the larger I atom has a larger impact on crystal growth; however, I does not remain within the lattice post-synthesis. These results suggest subtle new synthetic knobs may be available to optimize the synthesis of LaB6 that have previously gone unexplored.

  3. Coefficient of Thermal Expansion of Pressed PETN Pellets

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Darla Graff [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); DeLuca, Racci [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-11

    The PETN single crystal coefficient of thermal expansion (CTE) values were measured and reported by Cady in 1972 [1] over the temperature range of -160 to 100°C. Measurements were made in the (001) and (100) crystallographic directions, see Figure 1 (a replicate of Figure 1 from the Cady paper). Cady used his single-crystal data to calculate the linear CTE for a randomly-oriented multi-crystal pressing of PETN, and his values ranged from 76.5 με/°C (at 20°C) to 89.9 5 με/°C (at 90°C).

  4. Modulus of Elasticity and Thermal Expansion Coefficient of ITO Film

    Energy Technology Data Exchange (ETDEWEB)

    Carter, Austin D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Elhadj, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-06-24

    The purpose of this experiment was to determine the modulus of elasticity (E) and thermal expansion coefficient (α) of RF sputtered Indium Tin Oxide (ITO) as a function of temperature (T), and to collect ITO film stress data. In order to accomplish that goal, the Toho FLX-2320-S thin film stress measurement machine was used to collect both single stress and stress-temperature data for ITO coated fused silica and sapphire substrates. The stress measurement function of the FLX-2320-S cannot be used to calculate the elastic modulus of the film because the Stoney formula incorporates the elastic modulus of the substrate, rather than of the film itself.

  5. Deformation analysis considering thermal expansion of injection mold

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jun Hyung; Yi, Dae Eun; Jang, Jeong Hui; Lee, Min Seok [Samsung Electronics Co., LTD., Seoul (Korea, Republic of)

    2015-09-15

    In the design of injection molds, the temperature distribution and deformation of the mold is one of the most important parameters that affect the flow characteristics, flash generation, and surface appearance, etc. Plastic injection analyses have been carried out to predict the temperature distribution of the mold and the pressure distribution on the cavity surface. As the input loads, we transfer the temperature and pressure results to the structural analysis. We compare the structural analysis results with the thermal expansion effect using the actual flash and step size of a smartphone cover part. To reduce the flash problem, we proposed a new mold design, and verified the results by performing simulations.

  6. Negative Thermal Expansion Coefficient of Graphene Measured by Raman Spectroscopy

    OpenAIRE

    Yoon, Duhee; Son, Young-Woo; Cheong, Heonsik

    2011-01-01

    The thermal expansion coefficient (TEC) of single-layer graphene is estimated with temperature-dependent Raman spectroscopy in the temperature range between 200 and 400 K. It is found to be strongly dependent on temperature but remains negative in the whole temperature range, with a room temperature value of -8.0x10^{-6} K^{-1}. The strain caused by the TEC mismatch between graphene and the substrate plays a crucial role in determining the physical properties of graphene, and hence its effect...

  7. Negative thermal expansion coefficient of graphene measured by Raman spectroscopy.

    Science.gov (United States)

    Yoon, Duhee; Son, Young-Woo; Cheong, Hyeonsik

    2011-08-10

    The thermal expansion coefficient (TEC) of single-layer graphene is estimated with temperature-dependent Raman spectroscopy in the temperature range between 200 and 400 K. It is found to be strongly dependent on temperature but remains negative in the whole temperature range with a room temperature value of (-8.0 ± 0.7) × 10(-6) K(-1). The strain caused by the TEC mismatch between graphene and the substrate plays a crucial role in determining the physical properties of graphene, and hence its effect must be accounted for in the interpretation of experimental data taken at cryogenic or elevated temperatures.

  8. Negative thermal expansion and its relation to high pressures

    Science.gov (United States)

    Sikka, S. K.

    2004-04-01

    Most materials expand when heated. However, many exceptions are now known. Recently, interest in this has been revived with the discovery of isotropic negative thermal expansion (NTE) in ZrW2O8. From equation of state considerations, one can relate NTE to negative Grüneisen parameters (thermal or electronic). Under pressure, these lead to equation of state anomalies with the pressure derivative of the bulk modules being small or negative. Many of these materials undergo pressure-induced amorphization. This in some of them can be understood on the steric constraint model. It is also argued that NTE in most materials may be understood from the fact that these materials have two degenerate or nearly degenerate energy states. On increase of temperature, the material then samples the lower volume state, leading to NTE.

  9. Negative Thermal Expansion and Ferroelectric Oxides in Electronic Device Composites

    Science.gov (United States)

    Trujillo, Joy Elizabeth

    Electronic devices increasingly pervade our daily lives, driving the need to develop components which have material properties that can be designed to target a specific need. The principle motive of this thesis is to investigate the effects of particle size and composition on three oxides which possess electronic and thermal properties essential to designing improved ceramic composites for more efficient, high energy storage devices. A metal matrix composite project used the negative thermal expansion oxide, ZrW2O 8, to offset the high thermal expansion of the metal matrix without sacrificing high thermal conductivity. Composite preparation employed a powder mixing technique to achieve easy composition control and homogenous phase distribution in order to build composites which target a specific coefficient of thermal expansion (CTE). A tailorable CTE material is desirable for overcoming thermomechanical failure in heat sinks or device casings. This thesis also considers the particle size effect on dielectric properties in a common ferroelectric perovskite, Ba1-xSrxTiO 3. By varying the Ba:Sr ratio, the Curie temperature can be adjusted and by reducing the particle size, the dielectric constant can be increased and hysteresis decreased. These conditions could yield anonymously large dielectric constants near room temperature. However, the ferroelectric behavior has been observed to cease below a minimum size of a few tens of nanometers in bulk or thin film materials. Using a new particle slurry approach, electrochemical impedance spectroscopy allows dielectric properties to be determined for nanoparticles, as opposed to conventional methods which measure only bulk or thin film dielectric properties. In this manner, Ba1-xSrxTiO3 was investigated in a new size regime, extending the theory on the ferroelectric behavior to < 10 nm diameter. This knowledge will improve the potential to incorporate high dielectric constant, low loss ferroelectric nanoparticles in many

  10. Thermal expansion of vitrified blood vessels permeated with DP6 and synthetic ice modulators.

    Science.gov (United States)

    Eisenberg, David P; Taylor, Michael J; Jimenez-Rios, Jorge L; Rabin, Yoed

    2014-06-01

    This study provides thermal expansion data for blood vessels permeated with the cryoprotective cocktail DP6, when combined with selected synthetic ice modulators (SIMs): 12% polyethylene glycol 400, 6% 1,3-cyclohexanediol, and 6% 2,3-butanediol. The general classification of SIMs includes molecules that modulate ice nucleation and growth, or possess properties of stabilizing the amorphous state, by virtue of their chemical structure and at concentrations that are not explained on a purely colligative basis. The current study is part of an ongoing effort to characterize thermo-mechanical effects on structural integrity of cryopreserved materials, where thermal expansion is the driving mechanism to thermo-mechanical stress. This study focuses on the lower part of the cryogenic temperature range, where the cryoprotective agent (CPA) behaves as a solid for all practical applications. By combining results obtained in the current study with literature data on the thermal expansion in the upper part of the cryogenic temperature range, unified thermal expansion curves are presented. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Lattice thermal expansion and anisotropic displacements in -sulfur from diffraction experiments and first-principles theory.

    Science.gov (United States)

    George, Janine; Deringer, Volker L; Wang, Ai; Müller, Paul; Englert, Ulli; Dronskowski, Richard

    2016-12-21

    Thermal properties of solid-state materials are a fundamental topic of study with important practical implications. For example, anisotropic displacement parameters (ADPs) are routinely used in physics, chemistry, and crystallography to quantify the thermal motion of atoms in crystals. ADPs are commonly derived from diffraction experiments, but recent developments have also enabled their first-principles prediction using periodic density-functional theory (DFT). Here, we combine experiments and dispersion-corrected DFT to quantify lattice thermal expansion and ADPs in crystalline α-sulfur (S8), a prototypical elemental solid that is controlled by the interplay of covalent and van der Waals interactions. We begin by reporting on single-crystal and powder X-ray diffraction measurements that provide new and improved reference data from 10 K up to room temperature. We then use several popular dispersion-corrected DFT methods to predict vibrational and thermal properties of α-sulfur, including the anisotropic lattice thermal expansion. Hereafter, ADPs are derived in the commonly used harmonic approximation (in the computed zero-Kelvin structure) and also in the quasi-harmonic approximation (QHA) which takes the predicted lattice thermal expansion into account. At the PPBE+D3(BJ) level, the QHA leads to excellent agreement with experiments. Finally, more general implications of this study for theory and experiment are discussed.

  12. The origin of uniaxial negative thermal expansion in layered perovskites

    Science.gov (United States)

    Ablitt, Chris; Craddock, Sarah; Senn, Mark S.; Mostofi, Arash A.; Bristowe, Nicholas C.

    2017-10-01

    Why is it that ABO3 perovskites generally do not exhibit negative thermal expansion (NTE) over a wide temperature range, whereas layered perovskites of the same chemical family often do? It is generally accepted that there are two key ingredients that determine the extent of NTE: the presence of soft phonon modes that drive contraction (have negative Grüneisen parameters); and anisotropic elastic compliance that predisposes the material to the deformations required for NTE along a specific axis. This difference in thermal expansion properties is surprising since both ABO3 and layered perovskites often possess these ingredients in equal measure in their high-symmetry phases. Using first principles calculations and symmetry analysis, we show that in layered perovskites there is a significant enhancement of elastic anisotropy due to symmetry breaking that results from the combined effect of layering and condensed rotations of oxygen octahedra. This feature, unique to layered perovskites of certain symmetry, is what allows uniaxial NTE to persist over a large temperature range. This fundamental insight means that symmetry and the elastic tensor can be used as descriptors in high-throughput screening and to direct materials design.

  13. Lithium aluminosilicate reinforced with carbon nanofiber and alumina for controlled-thermal-expansion materials

    Directory of Open Access Journals (Sweden)

    Amparo Borrell, Olga García-Moreno, Ramón Torrecillas, Victoria García-Rocha and Adolfo Fernández

    2012-01-01

    Full Text Available Materials with a very low or tailored thermal expansion have many applications ranging from cookware to the aerospace industry. Among others, lithium aluminosilicates (LAS are the most studied family with low and negative thermal expansion coefficients. However, LAS materials are electrical insulators and have poor mechanical properties. Nanocomposites using LAS as a matrix are promising in many applications where special properties are achieved by the addition of one or two more phases. The main scope of this work is to study the sinterability of carbon nanofiber (CNFs/LAS and CNFs/alumina/LAS nanocomposites, and to adjust the ratio among components for obtaining a near-zero or tailored thermal expansion. Spark plasma sintering of nanocomposites, consisting of commercial CNFs and alumina powders and an ad hoc synthesized β-eucryptite phase, is proposed as a solution to improving mechanical and electrical properties compared with the LAS ceramics obtained under the same conditions. X-ray diffraction results on phase compositions and microstructure are discussed together with dilatometry data obtained in a wide temperature range (−150 to 450 °C. The use of a ceramic LAS phase makes it possible to design a nanocomposite with a very low or tailored thermal expansion coefficient and exceptional electrical and mechanical properties.

  14. How important is thermal expansion for predicting molecular crystal structures and thermochemistry at finite temperatures?

    Science.gov (United States)

    Heit, Yonaton N; Beran, Gregory J O

    2016-08-01

    Molecular crystals expand appreciably upon heating due to both zero-point and thermal vibrational motion, yet this expansion is often neglected in molecular crystal modeling studies. Here, a quasi-harmonic approximation is coupled with fragment-based hybrid many-body interaction calculations to predict thermal expansion and finite-temperature thermochemical properties in crystalline carbon dioxide, ice Ih, acetic acid and imidazole. Fragment-based second-order Möller-Plesset perturbation theory (MP2) and coupled cluster theory with singles, doubles and perturbative triples [CCSD(T)] predict the thermal expansion and the temperature dependence of the enthalpies, entropies and Gibbs free energies of sublimation in good agreement with experiment. The errors introduced by neglecting thermal expansion in the enthalpy and entropy cancel somewhat in the Gibbs free energy. The resulting ∼ 1-2 kJ mol(-1) errors in the free energy near room temperature are comparable to or smaller than the errors expected from the electronic structure treatment, but they may be sufficiently large to affect free-energy rankings among energetically close polymorphs.

  15. Isotropic Zero Thermal Expansion and Local Vibrational Dynamics in (Sc,Fe)F3.

    Science.gov (United States)

    Qin, Feiyu; Chen, Jun; Aydemir, Umut; Sanson, Andrea; Wang, Lu; Pan, Zhao; Xu, Jiale; Sun, Chengjun; Ren, Yang; Deng, Jinxia; Yu, Ranbo; Hu, Lei; Snyder, G Jeffrey; Xing, Xianran

    2017-09-18

    Scandium fluoride (ScF3) exhibits a pronounced negative thermal expansion (NTE), which can be suppressed and ultimately transformed into an isotropic zero thermal expansion (ZTE) by partially substituting Sc with Fe in (Sc0.8Fe0.2)F3 (Fe20). The latter displays a rather small coefficient of thermal expansion of -0.17 × 10(-6)/K from 300 to 700 K. Synchrotron X-ray and neutron pair distribution functions confirm that the Sc/Fe-F bond has positive thermal expansion (PTE). Local vibrational dynamics based on extended X-ray absorption fine structure indicates a decreased anisotropy of relative vibration in the Sc/Fe-F bond. Combined analysis proposes a delicate balance between the counteracting effects of the chemical bond PTE and NTE from transverse vibration. The present study extends the scope of isotropic ZTE compounds and, more significantly, provides a complete local vibrational dynamics to shed light on the ZTE mechanism in chemically tailored NTE compounds.

  16. Thermal Expansion of Fluorapatite-Chlorapatite Solid Solutions

    Science.gov (United States)

    Hovis, Guy; Abraham, Tony; Hudacek, William; Wildermuth, Sarah; Scott, Brian; Altomare, Caitlin; Medford, Aaron; Conlon, Maricate; Morris, Matthew; Leaman, Amanda; Almer, Christine; Tomaino, Gary; Harlov, Daniel

    2015-04-01

    X-ray powder diffraction experiments have been performed on fifteen fluorapatite-chlorapatite solid solutions synthesized and chemically characterized at the GeoForschungsZentrum - Potsdam (Hovis and Harlov, 2010; Schettler, Gottschalk, and Harlov, 2011), as well as two natural near-end-member samples, from room temperature to ~900 °C at 50 to 75 °C intervals. NIST 640a Si was employed as an internal standard; data from Parrish (1953) were used to determine Si peak positions at elevated temperatures. Unit-cell parameters calculated using the software of Holland and Redfern (1997) result in volume-temperature (V-T) plots that are linear or slightly concave up (V plotted as the vertical axis) over the T range investigated. Relations for the "a" and "c" unit-cell dimensions with T for these hexagonal minerals are nearly linear, but as with V, commonly improved by quadratic fits to the data. Coefficients of thermal expansion for volume (αV ), calculated as (1/V0°C) x (ΔV/ΔT) based on linear V-T relationships, mostly fall within the range 42 ± 2 x 10-6 deg-1 and show no obvious dependence on composition. Thermal expansion coefficients for individual unit-cell axes, however, do show clear relationships to composition, αa increasing from ~9.5 to ~13.5 x 10-6 deg-1 and αc decreasing from ~19.5 to ~13 x 10-6 deg-1 from the Cl to the F end member. Clearly, a compensating structural relationship accounts for the observed relationships. Such compositional dependence was not seen in the thermal expansion data for F-OH apatite solid solutions (Hovis, Scott, Altomare, Leaman, Morris, and Tomaino, American Mineralogist, in press). This difference can be explained by the similar sizes of F- and (OH)- versus the much greater size contrast between F- and Cl-. Sincere thanks to the National Science Foundation for support of this work, which has provided numerous research experiences for Lafayette College undergraduates. Thanks also to the Earth Sciences Department, University

  17. Glass-ceramic hermetic seals to high thermal expansion metals

    Science.gov (United States)

    Kramer, D.P.; Massey, R.T.

    1987-04-28

    A process for forming glass-ceramic materials from an alkaline silica-lithia glass composition comprising 60-72 mole-% SiO/sub 2/, 18-27 mole-% Li/sub 2/O, 0-5 mole-% Al/sub 2/O/sub 3/, 0-6 mole-% K/sub 2/O, 0-3 mole-% B/sub 2/O/sub 3/, and 0.5-2.5 mole-% P/sub 2/O/sub 5/, which comprises heating said glass composition at a first temperature within the 950-1050/degree/C range for 5-60 minutes, and then at a devitrification temperature within the 700-900/degree/C range for about 5-300 minutes to obtain a glass-ceramic having a thermal expansion coefficient of up to 210 x 10/sup /minus/7///degree/C. These ceramics form strong, hermetic seals with high expansion metals such as stainless steel alloys. An intermediate nucleation heating step conducted at a temperature within the range of 675-750/degree/C for 10-120 minutes may be employed between the first stage and the devitrification stage. 1 fig., 2 tabs.

  18. Investigation of the relationship between negative thermal expansion and other thermal properties of framework oxides

    Science.gov (United States)

    Kennedy, Catherine Anne

    2005-07-01

    Several framework solids exhibit negative thermal expansion (NTE) over a wide temperature range, e.g. ZrW2O 8 exhibits NTE from 0.3 to 1050 K. Although NTE is observed in other materials, it occurs over much smaller temperature ranges. NTE in ZrW 2O8 is associated with the low-energy modes corresponding to the correlated vibrations of the [WO4]2- tetrahedra and their three nearest [ZrO6]8- octahedra. This involves translation as well as libration, and low-energy optic modes play a central role. Thermal expansion and resistance to heat flow both originate in the anharmonic terms of the lattice dynamics. The influence of NTE in these framework materials on thermal conductivity was investigated by measuring thermal properties (thermal conductivity, kappa, from ca. 2 to 390 K and heat capacity, CP, from ca. 0.4 to 300 K) of ZrW2O8 and HfMo2O8. Literature values of the CP of ZrW2 O8 showed more disagreement than one might expect. In this research, it was found that the discrepancy could be due to low thermal conductivity of ZrW2O8. The CP of HfMo 2O8 is reported here for the first time. Analysis of CP reveals low-frequency modes that are not present in the binary oxides. A calculation of CP of HfMo 2O8 from HfMo2O8, ZrW2O 8, and ZrMo2O8 fits experimental C P of HfMo2O8 better since each AB 2O8 compound exhibits NTE and therefore has the low-frequency modes attributed to NTE. The thermodynamic calculations of the production of ZrW2O8 and HfMo2O8 from the appropriate oxides confirm that both are thermodynamically unstable with respect to the oxides. The kappa values of both ZrW2O8 and HfMo 2O8 are exceptionally low: kappadense(ZrW 2O8) is 0.91 W m-1 K-1 and kappadense(HfMo2O8) is 0.64 W m-1 K-1 at T = 300 K. Temperature-dependent kappa values of ZrW2O8 and HfMo2O8 are glass-like, despite polycrystalline morphology. Through consideration of the CP, phonon mean free path, and Gruneisen parameter, the kappa behavior is attributed to the low-frequency modes which are also

  19. Thermal expansion in the orthorhombic γ phase of ZrW2O8

    Science.gov (United States)

    Evans, J. S. O.; Jorgensen, J. D.; Short, S.; David, W. I. F.; Ibberson, R. M.; Sleight, A. W.

    1999-12-01

    The thermal expansion of the orthorhombic γ phase of ZrW2O8 has been measured using neutron powder diffraction from 4.6 to 410 K, where it transforms to the cubic α phase. At low temperature, γ-ZrW2O8 has a negative thermal expansion, but the thermal expansion becomes less negative with increasing temperature and is slightly positive at room temperature. This behavior can be explained in terms of the contributing phonon modes: At low temperature, the vibrational modes lead to a negative thermal expansion, but additional modes that become active upon increasing temperature add positive contributions. Above room temperature, the a and b axes increase more sharply while the c axis reverses its behavior and decreases with increasing temperature. This unusual behavior can be explained in terms of a thermally activated process, presumed to result from oxygen-atom migration, that makes an additional contribution to the thermal expansion.

  20. With respect to coefficient of linear thermal expansion, bacterial vegetative cells and spores resemble plastics and metals, respectively

    Science.gov (United States)

    2013-01-01

    Background If a fixed stress is applied to the three-dimensional z-axis of a solid material, followed by heating, the amount of thermal expansion increases according to a fixed coefficient of thermal expansion. When expansion is plotted against temperature, the transition temperature at which the physical properties of the material change is at the apex of the curve. The composition of a microbial cell depends on the species and condition of the cell; consequently, the rate of thermal expansion and the transition temperature also depend on the species and condition of the cell. We have developed a method for measuring the coefficient of thermal expansion and the transition temperature of cells using a nano thermal analysis system in order to study the physical nature of the cells. Results The tendency was seen that among vegetative cells, the Gram-negative Escherichia coli and Pseudomonas aeruginosa have higher coefficients of linear expansion and lower transition temperatures than the Gram-positive Staphylococcus aureus and Bacillus subtilis. On the other hand, spores, which have low water content, overall showed lower coefficients of linear expansion and higher transition temperatures than vegetative cells. Comparing these trends to non-microbial materials, vegetative cells showed phenomenon similar to plastics and spores showed behaviour similar to metals with regards to the coefficient of liner thermal expansion. Conclusions We show that vegetative cells occur phenomenon of similar to plastics and spores to metals with regard to the coefficient of liner thermal expansion. Cells may be characterized by the coefficient of linear expansion as a physical index; the coefficient of linear expansion may also characterize cells structurally since it relates to volumetric changes, surface area changes, the degree of expansion of water contained within the cell, and the intensity of the internal stress on the cellular membrane. The coefficient of linear expansion holds

  1. Thermal expansion behaviour and phase stability of AFe2As2 (A ...

    Indian Academy of Sciences (India)

    The lattice parameter in the tetragonal phase (AT) of CaFe 2 As 2 contracts with increasing temperature, whereas CT expands. The rate of contraction in AT is lower than the rate of expansion in CT. Other compounds show normal thermal expansion behaviour along both a- and c-axes. In-plane expansion (i.e., along the ...

  2. Negative thermal expansion materials related to cubic zirconium tungstate

    Science.gov (United States)

    Lind, Cora

    2001-12-01

    A non-hydrolytic sol-gel method for the preparation of ZrW2O 8 was developed. A new trigonal polymorph was discovered, which is structurally related to trigonal ZrMO2O8 and MnRe2O 8 as evidenced by powder x-ray diffraction and EXAFS studies. Seeding of the starting mixtures with cubic ZrW2O8 promoted crystallization of the cubic phase instead of trigonal material. Dehydration of ZrW2O7(OH)2·2H 2O gave cubic ZrW2O8 at 650°C, and a modification of this route led to the discovery of the new NTE materials cubic ZrMo 2O8 and HfMo2O8. These compounds crystallize in the same temperature range as the more stable trigonal AMo2O 8 polymorphs. To facilitate preparation of phase pure cubic molybdates, the influence of precursor chemistry on the crystallization behavior was investigated. The synthesis was extended to the solid solution system ZrxHf 1-xMoyW2-yO8 (0 ≤ x ≤ 1, 0 ≤ y ≤ 2). All compounds showed negative thermal expansion between 77 and 573 K. High-pressure in situ diffraction experiments were conducted on several AM2O8 polymorphs. With the exception of monoclinic ZrMo2O8, all materials underwent at least one pressure induced phase transition. Quasi-hydrostatic experiments on cubic AMo 2O8 led to a reversible transition to a new high-pressure structure, while low-pressure amorphization was observed under non-hydrostatic conditions. Isothermal kinetic studies of the cubic to trigonal transformation for ZrMo2O8 were carried out on four samples. Apparent activation energies of 170--290 kJ/mol were obtained using an Avrami model in combination with an Arrhenius analysis. This corresponds to 5% conversion levels after one year at temperatures between 220 and 315°C. Ex situ studies showed that the conversion at lower temperatures was considerably slower than what would be expected from extrapolation of the kinetic data. Drop solution calorimetry was carried out on several polymorphs of ZrMo 2O8, HfMo2O8 and ZrW2O 8. Only monoclinic ZrMo2O8 was enthalpically

  3. Measurement of the thermal expansion coefficient of AISI 420 stainless steel between 20 and 293 K

    Science.gov (United States)

    Martelli, Valentina; Bianchini, Giovanni; Ventura, Guglielmo

    2014-07-01

    The accurate measurement of thermal expansion coefficient at low temperatures is fundamental in applications where a high mechanical stability is required over the complete procedure of cooling. Here we report on our measurement of thermal expansion of AISI 420 between 20 and 293 K, measured by an interferometric dilatometer.

  4. Dendritic solidification and thermal expansion of refractory Nb-Zr alloys investigated by electrostatic levitation

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S.J.; Hu, L.; Wang, L.; Wei, B. [Northwestern Polytechnical University, Department of Applied Physics, Xi' an (China)

    2017-05-15

    The dendritic growth and thermal expansion of isomorphous refractory Nb-5%Zr, Nb-10%Zr, and Nb-15%Zr alloys were studied by electrostatic levitation technique. The obtained maximum undercoolings for the three alloys were 534 (0.2T{sub L}), 498 (0.19T{sub L}), and 483 K (0.18T{sub L}), respectively. Within these undercooling ranges, the dendritic growth velocities of the three alloys all exhibited power laws, and achieved 38.5, 34.0, and 27.1 m s{sup -1} at each maximum undercooling. The microstructures were characterized by coarse dendrites at small undercooling, while they transformed into refined dendrites under large undercooling condition. In addition, the measured thermal expansion coefficients of solid Nb-Zr alloys increased linearly with temperature. The values at liquid state were more than double of those at solid state, which also displayed linear dependence on temperature. (orig.)

  5. Removal properties of low-thermal-expansion materials with rotating-sphere elastic emission machining

    Directory of Open Access Journals (Sweden)

    Masahiko Kanaoka et al

    2007-01-01

    Full Text Available Optical mirrors used in extreme ultraviolet lithography systems require a figure accuracy and a roughness of about 0.1 nm rms. In addition, mirror substrates must be low-thermal-expansion materials. Thus, in this study, we processed two low-thermal-expansion materials, ULE [K. Hrdina, B. Hanson, P. Fenn, R. Sabia, Proc. SPIE 4688 (2002 454.] (Corning Inc. and Zerodur [I. Mitra, M.J. Davis, J. Alkemper, Rolf Müller, H. Kohlmann, L. Aschke, E. Mörsen, S. Ritter, H. Hack, W. Pannhorst, Proc. SPIE 4688 (2002 462.] (SCHOTT AG, with elastic emission machining (EEM in order to evaluate the removal properties. Consequently, we successfully calculated the respective removal rates, because removal volumes were found to be proportional to process times in EEM. Moreover, we demonstrated that the surface roughness of Zerodur is reduced to 0.1 nm rms in the spatial wavelength range from 100 μm to 1 mm.

  6. Colossal Positive and Negative Thermal Expansion in the Framework Material Ag3[Co(CN)6

    Science.gov (United States)

    Goodwin, Andrew L.; Calleja, Mark; Conterio, Michael J.; Dove, Martin T.; Evans, John S. O.; Keen, David A.; Peters, Lars; Tucker, Matthew G.

    2008-02-01

    We show that silver(I) hexacyanocobaltate(III), Ag3[Co(CN)6], exhibits positive and negative thermal expansion an order of magnitude greater than that seen in other crystalline materials. This framework material expands along one set of directions at a rate comparable to the most weakly bound solids known. By flexing like lattice fencing, the framework couples this to a contraction along a perpendicular direction. This gives negative thermal expansion that is 14 times larger than in ZrW2O8. Density functional theory calculations quantify both the low energy associated with this flexibility and the role of argentophilic (Ag+...Ag+) interactions. This study illustrates how the mechanical properties of a van der Waals solid might be engineered into a rigid, useable framework.

  7. Uniaxial Negative Thermal Expansion and Mechanical Properties of a Zinc-Formate Framework

    Directory of Open Access Journals (Sweden)

    Hongqiang Gao

    2017-02-01

    Full Text Available The thermal expansion behavior of a metal-formate framework, Zn(HCOO2·2(H2O (1, has been systematically studied via variable temperature single-crystal X-ray diffraction. Our results demonstrate that this formate exhibits significant negative thermal expansion (NTE, −26(2 MK−1 along its c-axis. Detailed structural analyses reveal that the large NTE response is attributed to the ‘hinge-strut’ like framework motion. In addition, the fundamental mechanical properties of framework 1 have been explored via nanoindentation experiments. The measured elastic modulus and hardness properties on the (00-2/(100/(110 facets are 35.5/35.0/27.1 and 2.04/1.83/0.47 GPa, respectively. The stiffness and hardness anisotropy can be correlated well with the underlying framework structure, like its thermoelastic behavior.

  8. Analysis of the thermal expansivity near the tricritical point in dilute chromium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yurtseven, H., E-mail: hamit@metu.edu.tr [Department of Physics, Middle East Technical University, 06531 Ankara-TURKEY (Turkey); Tari, Ö., E-mail: ozlemilgin@arel.edu.tr [Department of Mathematics and Computer Science, Istanbul Arel University, 34537 Büyükçekmece, Istanbul-TURKEY (Turkey)

    2016-03-25

    Chromium (Cr) undergoes a first order Neel transition as an antiferromagnetic material. When V, Mo and Mn atoms are substituted in the Cr lattice, a weak first order Neel transition in pure Cr changes toward a second order transition and a possible tricritical point in CrV occurs close to 0.2 at %V, as observed experimentally from the measurements of the thermal expansivity at various temperatures. In this study, we analyze the experimental data for the thermal expansivity from the literature as a function of temperature using the power - law formula for Cr alloys (Cr - 0.1V, 0.2V, 0.5V and Cr - 0.1Mn, Cr - 0.2Mo, 0.3Mo, 0.4Mo). Our results are interpreted near the tricritical point in dilute chromium alloys.

  9. Giant extrinsic negative thermal expansion in vanadium pentoxide nanocrystalline films

    Energy Technology Data Exchange (ETDEWEB)

    Bahgat, A.A. [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); Department of Physics, Faculty of Science, Al-Azhar University, Nasr City 11884, Cairo (Egypt); Al-Hajry, A. [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); El-Desoky, M.M. [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); Department of Physics, Faculty of Education, Suez Canal University, Al-Arish (Egypt)

    2006-06-15

    Vanadium pentoxide gels, V{sub 2}O{sub 5}.1.6H{sub 2}O, give rise to xerogel layers that exhibit a preferred orientation. X-ray diffraction of this xerogel displays the 00l peaks typical of a turbostratic stacking of the V{sub 2}O{sub 5} ribbons along a direction parallel to the substrate. The distance along the c-axis is observed from the interlayer spacing to decrease continuously with increasing temperature up to 180 C, as observed by high-temperature X-ray diffraction. This contraction may be described by an extrinsic mechanism of negative thermal expansion (NTE). The coefficient of NTE as large as -1.5 x 10{sup -3} K{sup -1} was observed. Full recovery of the interlayer spacing is obtained after cooling the sample to room temperature in open air, where water molecules are reabsorbed, indicating that the process is reversible and the heating process can be repeated without losing NTE. The structure of the xerogel was explored further using differential scanning calorimetry as well as infrared spectroscopy. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Thermal stability, thermal expansion and grain-growth in exchange-coupled Fe-Pt-Ag-B bulk nanocomposite magnets

    Energy Technology Data Exchange (ETDEWEB)

    Nicula, R., E-mail: radu.nicula@empa.ch [Empa, Swiss Federal Laboratories for Materials Science and Technology, Advanced Materials Processing, Feuerwerkerstr. 39, CH-3602 Thun (Switzerland); Crisan, O.; Crisan, A.D.; Mercioniu, I. [National Institute for Materials Physics, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Stir, M. [University of Berne, Department of Chemistry and Biochemistry, Freiestrasse 3, CH-3012 Berne (Switzerland); Vasiliu, F. [National Institute for Materials Physics, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania)

    2015-02-15

    Highlights: • Formation of the L10 FePt hard-magnetic phase (>90%) directly in the as-cast state. • Specific alternating hard/soft nanostructure is stable to 600 °C without grain growth. • Anisotropic and non-linear thermal expansion effects. • The FePtAgB alloy behaves like a single magnetic phase (full exchange coupling). - Abstract: Rare-earth free (RE-free) exchange coupling nanocomposite magnets are intensively studied nowadays due to their potential use in applications demanding stable high-temperature operation and corrosion resistance. In this respect, the FePt alloy system is one of the most actively addressed potential permanent magnet solutions. In FePt alloys, promising magnetic features arise from the co-existence of hard magnetic L1{sub 0} FePt and soft magnetic L1{sub 2} Fe{sub 3}Pt phases emerged from the same metastable precursor. The present work deals with an in-situ temperature-resolved synchrotron radiation study of the thermal stability, thermal expansion and microstructure evolution in exchange-coupled FePtAgB alloys. The as-cast microstructural state as well as the optimized magnetic behavior are given as reference and correlated to the observed microstructural evolution with temperature. The melt-spun Fe{sub 48}Pt{sub 28}Ag{sub 6}B{sub 18} alloy ribbons were examined in situ by synchrotron X-ray powder diffraction from ambient temperature up to 600 °C. The FePt-Fe{sub 3}Pt exchange-coupled microstructure achieved by rapid solidification is not significantly altered during the high temperature exposure. The thermal expansion of the FePt L1{sub 0} unit cell has been found to be strongly anisotropic, being essentially an in-plane expansion which may be seen as an anisotropic invar effect. For the FePt L1{sub 0} phase, a significant deviation from linear thermal expansion is observed at the Curie temperature T{sub C} = 477 °C. This non-linear behavior above T{sub C} is tentatively linked to a diffusion/segregation mechanism of Ag

  11. Glass-Transition Temperature Profile Measured in a Wood Cell Wall Using Scanning Thermal Expansion Microscope (SThEM)

    Science.gov (United States)

    Antoniow, J. S.; Maigret, J.-E.; Jensen, C.; Trannoy, N.; Chirtoc, M.; Beaugrand, J.

    2012-11-01

    This study aims to assess the in situ spatial distribution of glass-transition temperatures ( T g) of the main lignocellulosic biopolymers of plant cell walls. Studies are conducted using scanning thermal expansion microscopy to analyze the cross-section of the cell wall of poplar. The surface topography is mapped over a range of probe-tip temperatures to capture the change of thermal expansion on the sample surface versus temperature. For different temperature values chosen between 20 °C and 250 °C, several quantitative mappings were made to show the spatial variation of the thermal expansion. As the glass transition affects the thermal expansion coefficient and elastic modulus considerably, the same data line of each topography image was extracted to identify specific thermal events in their topographic evolution as a function of temperature. In particular, it is shown that the thermal expansion of the contact surface is not uniform across the cell wall and a profile of the glass-transition temperature could thus be evidenced and quantified corresponding to the mobility of lignocellulosic polymers having a role in the organization of the cell wall structures.

  12. Thermal expansion of PBX 9501 and PBX 9502 plastic-bonded explosives

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Darla Graff [Los Alamos National Laboratory; Brown, Geoff W [Los Alamos National Laboratory; Deluca, Racci [Los Alamos National Laboratory; Giambra, Anna [Los Alamos National Laboratory; Sandstrom, Mary [Los Alamos National Laboratory

    2009-01-01

    Two applications of thermal expansion measurements on plastic-bonded explosive (PBX) composites are described. In the first dilatometer application, thermal expansion properties of HMX-based PBX 9501 are measured over a broad thermal range that includes glass and domain-restructuring transitions in the polymeric binder. Results are consistent with other thermal measurements and analyses performed on the composite, as well as on the binder itself. The second application used the dilatometer to distinguish the reversible and irreversible components of thermal expansion in PBX 9502, a TATB-based explosive. Irreversible expansion of the composite is believed to derive from the highly-anisotropic coefficient of thermal expansion (CTE) values measured on single T A TB crystals, although the mechanism is not well understood. Effects of specimen density, thermal ramp rate, and thermal range variation (warm first or cold first) were explored, and the results are presented and discussed. Dilatometer measurements are ongoing towards gaining insight into the mechanism(s) responsible for PBX 9502 irreversible thermal expansion.

  13. Controllable rectification of the axial expansion in the thermally driven artificial muscle

    Science.gov (United States)

    Yue, Donghua; Zhang, Xingyi; Yong, Huadong; Zhou, Jun; Zhou, You-He

    2015-09-01

    At present, the concept of artificial muscle twisted by polymers or fibers has become a hot issue in the field of intelligent material research according to its distinguishing advantages, e.g., high energy density, large-stroke, non-hysteresis, and inexpensive. The axial thermal expansion coefficient is an important parameter which can affect its demanding applications. In this letter, a device with high accuracy capacitive sensor is constructed to measure the axial thermal expansion coefficient of the twisted carbon fibers and yarns of Kevlar, and a theoretical model based on the thermal elasticity and the geometrical features of the twisted structure are also presented to predict the axial expansion coefficient. It is found that the calculated results take good agreements with the experimental data. According to the present experiment and analyses, a method to control the axial thermal expansion coefficient of artificial muscle is proposed. Moreover, the mechanism of this kind of thermally driven artificial muscle is discussed.

  14. Tuning of a cavity in a silicon photonic crystal by thermal expansion of an elastomeric infill

    NARCIS (Netherlands)

    Erdamar, A.K.; Van Leest, M.M.; Picken, S.J.; Caro, J.

    2011-01-01

    We use an elastomer as infill material for a photonic crystal. As a result of the thermal-expansion-induced strongly negative thermal optical coefficient, this material is highly suitable for thermal tuning of the transmission of a cavity. This is demonstrated by global infilling of a hole-type

  15. Stopping, heating, thermalization and expansion at SPS energies

    CERN Document Server

    Gaardhoje, J J

    1997-01-01

    The Pb beam at 158AGeV from the CERN SPS accelerator which was taken into use in the fall of 1994 has opened a new dimension in the study of highly excited nuclear matter in heavy ion reactions. It has now become possible to form reasonably large volumes (containing more than 300 nucleons) in central collisions between heavy ions, with energy and matter densities in some parts of the volume exceeding those expected for the phase transition from hadronic matter to deconfined quark and gluon matter. In this talk we discuss some features of the expansion of the hot and compressed system that may be learned by analysing the single particle spectra of baryons and mesons with emphasis on data from the NA44 experiment.

  16. Effect of Microstructure Scale on Negative Thermal Expansion of Antiperovskite Manganese Nitride

    National Research Council Canada - National Science Library

    Zhonghua Sun Xiaoyan Song

    The negative thermal expansion (NTE) properties of the antiperovskite manganese nitrides with micron-scale, submicron-scale and nanometer-scale microstructures, respectively, were investigated using...

  17. Absolute thermal expansion of copper and aluminum between 5 K and 330 K

    Energy Technology Data Exchange (ETDEWEB)

    Kroeger, F.R. Jr.

    1976-02-01

    Theoretical and experimental results of experiments on thermal expansion of Al and Cu are presented. Experimental apparatus and procedures are described. Results are presented in graphs and plots and discussed. (JRD)

  18. Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design : research project capsule.

    Science.gov (United States)

    2009-01-01

    PROBLEM: The coefficient of thermal expansion (CTE) is a fundamental property of construction : materials such as steel and concrete. Although the CTE of steel is a well-defined : constant, the CTE of concrete varies substantially with aggregate type...

  19. Thermal expansion of solutions of deuteromethane in fullerite C60 at low temperatures. Isotopic effect

    Science.gov (United States)

    Dolbin, A. V.; Vinnikov, N. A.; Gavrilko, V. G.; Esel'Son, V. B.; Manzheliĭ, V. G.; Gadd, G. E.; Moricca, S.; Cassidy, D.; Sundqvist, B.

    2009-03-01

    The thermal expansion of CD4 solutions in the orientational glass C60 with molar concentration of deuteromethane 20 and 50% has been investigated in the temperature range 2.5-23K. The orientational glass CD4-C60 undergoes a first-order phase transition in the temperature interval 4.5-55K. This transition is manifested as hysteresis of the linear thermal expansion coefficient α as well as maxima in the temperature dependences α(T ) and τ1(T), where τ1 is the characteristic thermalization time of the experimental samples. The characteristic re-orientation times of the C60 molecules and the characteristic phase transformations occurring in the experimental solutions are determined. The results of the present study are compared with the results of a similar study of the solution CH4-C60. It is concluded that tunneling rotation of the CH4 and CD4 molecules occupying interstitial positions in the fullerite C60 lattice occurs.

  20. Rapid replacement of bridge deck expansion joints study - phase I.

    Science.gov (United States)

    2014-12-01

    Bridge deck expansion joints are used to allow for movement of the bridge deck due to thermal expansion, dynamics loading, and : other factors. More recently, expansion joints have also been utilized to prevent the passage of winter de-icing chemical...

  1. Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites

    OpenAIRE

    Wei, Chenyu; Srivastava, Deepak; Cho, Kyeongjae

    2002-01-01

    Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and Van der Waals forces for polymer-nanotube interfaces are used to invetigate the thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Additions of carbon nanotubes to polymer matrix are found to increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. These findings could have implic...

  2. Synthesis and characterization of some low and negative thermal expansion materials

    Science.gov (United States)

    Varga, Tamas

    2005-12-01

    The high-pressure behavior of several negative thermal expansion materials was studied by different methods. In-situ high-pressure x-ray and neutron diffraction studies on several compounds of the orthorhombic Sc 2W3O12 structure revealed an unusual "bulk modulus collapse" at the orthorhombic to monoclinic phase transition. In some members of the A2M3O12 family, a second phase transition and/or pressure-induced amorphization were also seen at higher pressure. The mechanism for volume contraction on compression is different from that on heating. A combined in-situ high pressure x-ray diffraction and absorption spectroscopic study has been carried out for the first time. The pressure-induced amorphization in cubic ZrW2O8 and ZrMo 2O8 was studied by following the changes in the local coordination environments of the metals. A significant change in the average tungsten coordination was found in ZrW2O8, and a less pronounced change in the molybdenum coordination in ZrMo2O8 on amorphization. A kinetically frustrated phase transition to a high-pressure crystalline phase or a kinetically hindered decomposition, are likely driving forces of the amorphization. A complementary ex-situ study confirmed the greater distortion of the framework tetrahedra in ZrW2O8, and revealed a similar distortion of the octahedra in both compounds. The possibility of stabilizing the low thermal expansion high-temperature structure in AM2O7 compounds to lower temperatures through stuffing of ZrP2O7 was explored. Although the phase transition temperature was suppressed in MIxZr 1-xMIIIxP2O7 compositions, the chemical modification employed was not successful in stabilizing the high-temperature structure to around room temperature. An attempt has been made to control the thermal expansion properties in materials of the (MIII0.5MV 0.5)P2O7-type through the choice of the metal cations and through manipulating the ordering of the cations by different heat treatment conditions. Although controlled heat

  3. Origin of the Giant Negative Thermal Expansion in Mn3(Cu0.5Ge0.5N

    Directory of Open Access Journals (Sweden)

    B. Y. Qu

    2012-01-01

    Full Text Available The giant negative thermal expansion in the Ge-doped antiperovskite Mn3CuN compound is theoretically studied by using the first principles calculations. We propose that such a negative thermal expansion property is essentially attributed to the magnetic phase transition, rather than to the lattice vibration of the Ge-doped compound. Furthermore, we found that the doped Ge atoms in the compound significantly enhance the antiferromagnetic couplings between the nearest neighboring Mn ions, which effectively stabilizes the magnetic ground states. In addition, the nature of the temperature-dependent changes in the volume of the Ge-doped compound was revealed.

  4. ZrO2-ZrW2O8 Composites with tailor-made thermal expansion

    Directory of Open Access Journals (Sweden)

    K. De Buysser

    2004-12-01

    Full Text Available Most of the materials expand upon heating. There are a few families of materials which exhibit negative thermal expansion (NTE. ZrW2O8 is an example which gained a lot of interest in international literature recently. This cubic material has an exceptionally large and isotropic negative thermal expansion over its entire stability range (0.5 to 1050 K. At 430 K a phase transition occurs from a-ZrW2O8 (a = -9.1 x 10-6 K-1 to b-ZrW2O8 (b = -5.4 x 10-6 K-1. At high pressures an orthorhombic phase is formed, g-ZrW2O8, which possesses a small negative expansion coefficient. A broad range of applications have been suggested for these NTE materials. In composites, their thermal expansion coefficient can be tailor-made by combining a NTE material with a positive expansion material. Adjusting the volume fraction of the different phases results in a positive, negative or even zero thermal expansion. The ZrW2O8 - ZrO2 - composites studied in this paper were prepared in two ways. The first synthesis method applied, started from off-stoichiometry mixtures of the pure oxide powders of ZrO2 and WO3. This novel in situ process included a heating step up to 1450 K which combines the formation and sintering of ZrW2O8. In the conventional synthesis the starting materials were ZrO2 and ZrW2O8. ZrW2O8 was first obtained using an optimised spray drying technique. Obviously, our "in situ" method does not require such an additional step. The crystal structure, morphology, thermal expansion behaviour and mechanical properties of these composites were tested and compared.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huang, E-mail: huang.wu.84@gmail.com [Composite Materials and Structures Center, Michigan State University, East Lansing, MI 48864 (United States); Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48864 (United States); Drzal, Lawrence T. [Composite Materials and Structures Center, Michigan State University, East Lansing, MI 48864 (United States); Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48864 (United States)

    2014-07-01

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

  6. Zirconium tungstate/epoxy nanocomposites: effect of nanoparticle morphology and negative thermal expansivity.

    Science.gov (United States)

    Wu, Hongchao; Rogalski, Mark; Kessler, Michael R

    2013-10-09

    The ability to tailor the coefficient of thermal expansion (CTE) of a polymer is essential for mitigating thermal residual stress and reducing microcracks caused by CTE mismatch of different components in electronic applications. This work studies the effect of morphology and thermal expansivity of zirconium tungstate nanoparticles on the rheological, thermo-mechanical, dynamic-mechanical, and dielectric properties of ZrW2O8/epoxy nanocomposites. Three types of ZrW2O8 nanoparticles were synthesized under different hydrothermal conditions and their distinct properties were characterized, including morphology, particle size, aspect ratio, surface area, and CTE. Nanoparticles with a smaller particle size and larger surface area led to a more significant reduction in gel-time and glass transition temperature of the epoxy nanocomposites, while a higher initial viscosity and significant shear thinning behavior was found in prepolymer suspensions containing ZrW2O8 with larger particle sizes and aspect ratios. The thermo- and dynamic-mechanical properties of epoxy-based nanocomposites improved with increasing loadings of the three types of ZrW2O8 nanoparticles. In addition, the introduced ZrW2O8 nanoparticles did not negatively affect the dielectric constant or the breakdown strength of the epoxy resin, suggesting potential applications of ZrW2O8/epoxy nanocomposites in the microelectronic insulation industry.

  7. Negative thermal expansion in crystals with the delafossite structure: An extended x-ray absorption fine structure study of CuScO2 and CuLaO2

    Science.gov (United States)

    Ahmed, S. I.; Dalba, G.; Fornasini, P.; Vaccari, M.; Rocca, F.; Sanson, A.; Li, J.; Sleight, A. W.

    2009-03-01

    Extended x-ray absorption fine structure has been measured at the K edge of copper in CuScO2 and CuLaO2 to investigate the local origin of negative thermal expansion (NTE) along the c axis. A positive expansion of the Cu-O bond has been measured within the entire temperature interval to be contrasted with the negative expansion of the distance between average atomic positions measured by diffraction; the inadequacy of the riding correction to diffraction data has been evidenced. The weak temperature dependence of the parallel mean-square relative displacement (MSRD) indicates a rather stiff Cu-O bond, while the large perpendicular MSRD measures an intense relative motion of copper with respect to oxygen atoms perpendicular to the c axis. The comparison between the two compounds enlightens the relevance of the correlation of perpendicular motion to quantitatively explain the apparent NTE of the Cu-O bond.

  8. Polyglutamine expansion in Drosophila: thermal stress and Hsp70 ...

    Indian Academy of Sciences (India)

    2007-03-15

    Mar 15, 2007 ... Repetitive DNA sequences that encode polyglutamine tracts are prone to expansion and cause highly deleterious phenotypes of neurodegeneration. Despite this tendency, polyglutamine tracts (``polyQs”) are conserved features of eukaryotic genomes. PolyQs are the most frequent protein-coding ...

  9. Engineered high expansion glass-ceramics having near linear thermal strain and methods thereof

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Steve Xunhu; Rodriguez, Mark A.; Lyon, Nathanael L.

    2018-01-30

    The present invention relates to glass-ceramic compositions, as well as methods for forming such composition. In particular, the compositions include various polymorphs of silica that provide beneficial thermal expansion characteristics (e.g., a near linear thermal strain). Also described are methods of forming such compositions, as well as connectors including hermetic seals containing such compositions.

  10. Description of the RHIC p(perpendicular) spectra in a thermal model with expansion.

    Science.gov (United States)

    Broniowski, W; Florkowski, W

    2001-12-31

    The assumption of simultaneous chemical and thermal freeze-outs of the hadron gas leads to a surprisingly accurate, albeit entirely conventional, explanation of the recently measured RHIC p(perpendicular) spectra. The original thermal spectra are supplied with secondaries from cascade decays of all resonances, and subsequently folded with a suitably parametrized expansion involving longitudinal and transverse flow. The predictions of this thermal approach, with various parametrizations for the expansion, are in a striking quantitative agreement with the data in the whole available range of 0 < or = p(perpendicular) < or = 3.5 GeV.

  11. Lattice thermal expansion and anisotropic displacements in 𝜶-sulfur from diffraction experiments and first-principles theory

    Science.gov (United States)

    George, Janine; Deringer, Volker L.; Wang, Ai; Müller, Paul; Englert, Ulli; Dronskowski, Richard

    2016-12-01

    Thermal properties of solid-state materials are a fundamental topic of study with important practical implications. For example, anisotropic displacement parameters (ADPs) are routinely used in physics, chemistry, and crystallography to quantify the thermal motion of atoms in crystals. ADPs are commonly derived from diffraction experiments, but recent developments have also enabled their first-principles prediction using periodic density-functional theory (DFT). Here, we combine experiments and dispersion-corrected DFT to quantify lattice thermal expansion and ADPs in crystalline α-sulfur (S8), a prototypical elemental solid that is controlled by the interplay of covalent and van der Waals interactions. We begin by reporting on single-crystal and powder X-ray diffraction measurements that provide new and improved reference data from 10 K up to room temperature. We then use several popular dispersion-corrected DFT methods to predict vibrational and thermal properties of α-sulfur, including the anisotropic lattice thermal expansion. Hereafter, ADPs are derived in the commonly used harmonic approximation (in the computed zero-Kelvin structure) and also in the quasi-harmonic approximation (QHA) which takes the predicted lattice thermal expansion into account. At the PPBE+D3(BJ) level, the QHA leads to excellent agreement with experiments. Finally, more general implications of this study for theory and experiment are discussed.

  12. Switching Between Giant Positive and Negative Thermal Expansions of a YFe(CN)6 -based Prussian Blue Analogue Induced by Guest Species.

    Science.gov (United States)

    Gao, Qilong; Chen, Jun; Sun, Qiang; Chang, Dahu; Huang, Qingzhen; Wu, Hui; Sanson, Andrea; Milazzo, Ruggero; Zhu, He; Li, Qiang; Liu, Zhanning; Deng, Jinxia; Xing, Xianran

    2017-07-24

    The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K(+) ) and molecules (H2 O) can substantially switch thermal expansion of YFe(CN)6 from negative (αv =-33.67×10(-6)  K(-1) ) to positive (αv =+42.72×10(-6)  K(-1) )-a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Fabrication of low thermal expansion SiC/ZrW2O8 porous ceramics

    Science.gov (United States)

    Poowancum, A.; Matsumaru, K.; Juárez-Ramírez, I.; Torres-Martínez, L. M.; Fu, Z. Y.; Lee, S. W.; Ishizaki, K.

    2011-03-01

    Low or zero thermal expansion porous ceramics are required for several applications. In this work near zero thermal expansion porous ceramics were fabricated by using SiC and ZrW2O8 as positive and negative thermal expansion materials, respectively, bonded by soda lime glass. The mixture of SiC, ZrW2O8 and soda lime glass was sintered by Pulsed Electric Current Sintering (PECS, or sometimes called Spark Plasma Sintering, SPS) at 700 °C. Sintered samples with ZrW2O8 particle size smaller than 25 μm have high thermal expansion coefficient, because ZrW2O8 has the reaction with soda lime glass to form Na2ZrW3O12 during sintering process. The reaction between soda lime glass and ZrW2O8 is reduced by increasing particle size of ZrW2O8. Sintered sample with ZrW2O8 particle size 45-90 μm shows near zero thermal expansion.

  14. Pressure-dependence of the phase transitions and thermal expansion in zirconium and hafnium pyrovanadate

    Energy Technology Data Exchange (ETDEWEB)

    Gallington, Leighanne C.; Hester, Brett R.; Kaplan, Benjamin S.; Wilkinson, Angus P. (GIT)

    2017-05-01

    Low or negative thermal expansion (NTE) has been previously observed in members of the ZrP2O7 family at temperatures higher than their order-disorder phase transitions. The thermoelastic properties and phase behavior of the low temperature superstructure and high temperature negative thermal expansion phases of ZrV2O7 and HfV2O7 were explored via in situ variable temperature/pressure powder x-ray diffraction measurements. The phase transition temperatures of ZrV2O7 and HfV2O7 exhibited a very strong dependence on pressure (~700 K GPa), with moderate compression suppressing the formation of their NTE phases below 513 K. Compression also reduced the magnitude of the coefficients of thermal expansion in both the positive and negative thermal expansion phases. Additionally, the high temperature NTE phase of ZrV2O7 was found to be twice as stiff as the low temperature positive thermal expansion superstructure (24 and 12 GPa respectively).

  15. Influence of soil consolidation and thermal expansion effects on height and gravity variations

    Science.gov (United States)

    Romagnoli, C.; Zerbini, S.; Lago, L.; Richter, B.; Simon, D.; Domenichini, F.; Elmi, C.; Ghirotti, M.

    2003-07-01

    The daily GPS height series of the Medicina station were analyzed for the period July 1996-September 2001. The station is located in the middle Po Plain on fine-grained alluvial deposits. A seasonal oscillation in the order of 18 mm (peak-to-peak amplitude) is present in the data. This crustal deformation has been modeled by including variations in the atmospheric, oceanic and hydrologic mass. The vertical positions can also be affected significantly by soil consolidation. Geotechnical parameters derived by in situ tests and laboratory analyses of the clayey soil collected at Medicina allowed the estimate of the soil settlement relevant to the seasonal oscillation of the surficial water table. Thermal expansion of the geodetic monument has to be taken into account in the case of high-precision vertical positioning. In this work models both for the soil consolidation and the thermal expansion effects are provided. The continuous gravity observations collected at Medicina by means of a superconducting gravimeter also exhibit a marked seasonal oscillation, which has been interpreted as the sum of loading and Newtonian attraction effects, as well as of the contribution due to soil consolidation. Especially the study concerning the soil consolidation effect has allowed a better insight on the seasonal vertical movements occurring at the Medicina station by providing quantitative information on soil behavior due to change of effective pressures. The results can be applied to those stations characterized by similar fine-grained soils and surficial hydrogeology.

  16. Modeling the thermal deformation of TATB-based explosives. Part 1: Thermal expansion of “neat-pressed” polycrystalline TATB

    Energy Technology Data Exchange (ETDEWEB)

    Luscher, Darby J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-05-08

    We detail a modeling approach to simulate the anisotropic thermal expansion of polycrystalline (1,3,5-triamino-2,4,6-trinitrobenzene) TATB-based explosives that utilizes microstructural information including porosity, crystal aspect ratio, and processing-induced texture. This report, the first in a series, focuses on nonlinear thermal expansion of “neat-pressed” polycrystalline TATB specimens which do not contain any binder; additional complexities related to polymeric binder and irreversible ratcheting behavior are briefly discussed, however detailed investigation of these aspects are deferred to subsequent reports. In this work we have, for the first time, developed a mesoscale continuum model relating the thermal expansion of polycrystal TATB specimens to their microstructural characteristics. A self-consistent homogenization procedure is used to relate macroscopic thermoelastic response to the constitutive behavior of single-crystal TATB. The model includes a representation of grain aspect ratio, porosity, and crystallographic texture attributed to the consolidation process. A quantitative model is proposed to describe the evolution of preferred orientation of graphitic planes in TATB during consolidation and an algorithm constructed to develop a discrete representation of the associated orientation distribution function. Analytical and numerical solutions using this model are shown to produce textures consistent with previous measurements and characterization for isostatic and uniaxial “die-pressed” specimens. Predicted thermal strain versus temperature for textured specimens are shown to be in agreement with corresponding experimental measurements. Using the developed modeling approach, several simulations have been run to investigate the influence of microstructure on macroscopic thermal expansion behavior. Results from these simulations are used to identify qualitative trends. Implications of the identified trends are discussed in the context of

  17. Transient evolution of inter vessel gap pressure due to relative thermal expansion between two vessels

    Science.gov (United States)

    Natesan, K.; Selvaraj, P.; Chellapandi, P.; Chetal, S. C.

    2002-08-01

    In a typical liquid metal cooled fast breeder reactor (LMFBR), a cylindrical sodium filled main vessel, which carries the internals such as reactor core, pumps, intermediate heat exchangers etc. is surrounded by another vessel called safety vessel. The inter vessel gap is filled with nitrogen. During a thermal transient in the pool sodium, because of the relative delay involved in the thermal diffusion between MV and SV, they are subjected to relative thermal expansion or contraction between them. This in turn results in pressurisation and depressurisation of inter vessel gap nitrogen respectively. In order to obtain the external pressurization for the buckling design of MV, transient thermal models for obtaining the evolutions of MV, SV and inter gap nitrogen temperatures and hence their relative thermal expansion and inter vessel gap pressure have been developed. This paper gives the details of the mathematical model, assumptions made in the calculation and the results of the analysis.

  18. Two Decades of Negative Thermal Expansion Research: Where Do We Stand?

    Directory of Open Access Journals (Sweden)

    Cora Lind

    2012-06-01

    Full Text Available Negative thermal expansion (NTE materials have become a rapidly growing area of research over the past two decades. The initial discovery of materials displaying NTE over a large temperature range, combined with elucidation of the mechanism behind this unusual property, was followed by predictions that these materials will find use in various applications through controlled thermal expansion composites. While some patents have been filed and devices built, a number of obstacles have prevented the widespread implementation of NTE materials to date. This paper reviews NTE materials that contract due to transverse atomic vibrations, their potential for use in controlled thermal expansion composites, and known problems that could interfere with such applications.

  19. Pressure-induced amorphization and negative thermal expansion in ZrW2O8

    Science.gov (United States)

    Perottoni; Jornada

    1998-05-08

    It has recently been shown that zirconium tungstate (ZrW2O8) exhibits isotropic negative thermal expansion over its entire temperature range of stability. This rather unusual behavior makes this compound particularly suitable for testing model predictions of a connection between negative thermal expansion and pressure-induced amorphization. High-pressure x-ray diffraction and Raman scattering experiments showed that ZrW2O8 becomes progressively amorphous from 1.5 to 3.5 gigapascals. The amorphous phase was retained after pressure release, but the original crystalline phase returned after annealing at 923 kelvin. The results indicate a general trend between negative thermal expansion and pressure-induced amorphization in highly flexible framework structures.

  20. Anisotropic thermal expansion of Ni, Pd and Pt germanides and silicides

    Science.gov (United States)

    Geenen, F. A.; Knaepen, W.; Moens, F.; Brondeel, L.; Leenaers, A.; Van den Berghe, S.; Detavernier, C.

    2016-07-01

    Silicon or germanium-based transistors are nowadays used in direct contact with silicide or germanide crystalline alloys for semiconductor device applications. Since these compounds are formed at elevated temperatures, accurate knowledge of the thermal expansion of both substrate and the contact is important to address temperature depending effects such as thermal stress. Here we report the linear coefficients of thermal expansion of Ni-, Pd- and Pt-based mono-germanides, mono-silicides and di-metal-silicides as determined by powder-based x-ray diffraction between 300 and 1225 K. The investigated mono-metallic compounds, all sharing the MnP crystal structure, as well as Pd2Si and Pt2Si exhibit anisotropic expansion. By consequence, this anisotropic behaviour should be taken into account for evaluating the crystal unit’s cell at elevated temperatures.

  1. Application of double modulation for measurement of the thermal expansion coefficient of liquid metals

    Energy Technology Data Exchange (ETDEWEB)

    Blagonravov, L A; Karchevskiy, O O; Ivannikov, P V; Soboleva, A V [M. V. Lomonosov Moscow State University, Faculty of Physics, Lenin Hills, 1-2, GSP-2, Moscow, 119991 (Russian Federation)], E-mail: blagonravovla@mail.ru

    2008-02-15

    The first results of the thermal expansion coefficient measurement obtained for liquid conductors using a new modulation method are presented. The method is based on a superposition of two periodical influences on a liquid metal. The thermal expansion coefficient {alpha}{sub P} is determined by means of measuring the amplitudes of oscillations of electric current power w{sub {approx}} and pressure p{sub {approx}}. In the present work the K-Na alloy of the eutectic composition was used as a sample. Distinction of the experimental data obtained by authors from the literature data is 30 to 40%. Such a difference is in the range of error of determination of {alpha}{sub P} from the density data of K-Na alloy. The method allows direct determination of the thermal expansion coefficient of liquid conductors in absolute units.

  2. Dynamic thermal expansivity of liquids near the glass transition

    DEFF Research Database (Denmark)

    Niss, Kristine; Gundermann, Ditte; Christensen, Tage Emil

    2012-01-01

    ) in the ultraviscous regime. Compared to the method of Bauer et al., the dynamical range has been extended by making time-domain experiments and by making very small and fast temperature steps. The modeling of the experiment presented in this paper includes the situation in which the capacitor is not full because......Based on previous works on polymers by Bauer et al. [ Phys. Rev. E 61 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704...... the liquid contracts when cooling from room temperature down to around the glass-transition temperature, which is relevant when measuring on a molecular liquid rather than a polymer....

  3. The crystallization behavior and thermal expansion properties of {beta}-eucryptite prepared by sol-gel route

    Energy Technology Data Exchange (ETDEWEB)

    Xia Long [School of Material Science and Engineering, Harbin Institute of Technology at Weihai, 2 Wenhua West Road, Weihai 264209 (China); Wen Guangwu, E-mail: wgw@hitwh.edu.cn [School of Material Science and Engineering, Harbin Institute of Technology at Weihai, 2 Wenhua West Road, Weihai 264209 (China); Song Liang; Wang Xinyu [School of Material Science and Engineering, Harbin Institute of Technology at Weihai, 2 Wenhua West Road, Weihai 264209 (China)

    2010-02-15

    Lithium-aluminosilicate glass-ceramics in the form of eucryptite were synthesized through sol-gel technique by mixing boehmite sol, silica sol and lithium salt and sintering at different temperatures for further analysis. Thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), IR analysis and dilatometry were done to study sintering characteristics, phase transformation and thermal expansion behavior on the sintered specimens. XRD and FTIR results confirmed that crystallization of {beta}-eucryptite took place at about 600 deg. C, substantial increase of {beta}-eucryptite was observed in the specimens sintered at temperatures from 800 to 1300 deg. C. Trace amount of cristobalite also emerged at 600 deg. C and disappeared at 1300 deg. C. The thermal expansion behavior characteristics were found to be strongly influenced by crystalline phases in the specimens which depended on the sintering temperatures.

  4. Non-contact measurement of the coefficient of thermal expansion of Al 6061-T6 with fiber Bragg grating sensors

    Energy Technology Data Exchange (ETDEWEB)

    Hayat, Khazar; Ha, Sung Kyu [Hanyang University, Ansan (Korea, Republic of)

    2014-02-15

    An experimental study describing the non-contact measurement of the coefficient of thermal expansion of an aluminum (Al-6061-T6) specimen with two fiber Bragg grating sensors using a pair of C-lens collimators was carried out. The collimators were used for the free space coupling between the fiber Bragg sensors and the optical sensing interrogator. During the experiment, the wavelength distortion of the optical signals was observed. Consequently, the measured thermal strains were corrected using an estimated collimator correction factor of 0.8466. The coefficient of thermal expansion of the specimen was then calculated to be (22.0 ± 0.1)X10{sup -60} C{sup -1} for every 5 .deg. C step in the range 35 .deg. C ∼ 75 .deg. C, which was in good agreement with the typical value of 23.6X10{sup -60}C{sup -1} for aluminum.

  5. About Utilization Efficiency Evaluation of Gas-Expansion and Generator Units at Thermal Power Stations

    Directory of Open Access Journals (Sweden)

    S. A. Kachan

    2007-01-01

    Full Text Available The paper considers methods for determination of gas-expansion and generator unit indices when they are applied at a thermal power station. It is shown, that while relating the effect of additional power-and-heat generation output due to heat taking-off from steam turbines to gas-expansion and generator unit to the operation of this unit a specific fuel consumption of power supply from gas-expansion and generator unit can be lower than fuel equivalent of kilowatt-hour.

  6. Anomalous thermal expansion of InSe layered semiconductors in the low-temperature region

    Energy Technology Data Exchange (ETDEWEB)

    Krynetskii, I. B.; Kulbachinskii, V. A. [Moscow State University (Russian Federation); Shabanova, N. P., E-mail: shaban@sci.lebedev.ru; Tsikunov, A. V.; Kovalenko, R. I.; Rodin, V. V.; Gavrilkin, S. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2013-05-15

    The temperature dependence of the linear thermal expansion coefficient (TEC) of an InSe single crystal in the (001) plane is measured in the temperature range 7-50 K. A peak in the thermal expansion is detected near T = 10 K, after which the sample shrinks upon heating. The effect of an external magnetic field of up to 6 T, which is parallel to the (001) plane, on the TEC is investigated. The observed partial suppression of the peak and crystal compression by the field indicates the relation of these anomalies to possible electron ordering in InSe layers.

  7. Measurements on thermal expansion with strain gauge; yugami geji wo mochiita gokuteion netsubochoritsu no keisoku

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, T.; Sato, A. [National Research Inst. for Metals, Tokyo (Japan); Arai, O.; Okuda, Y. [Tokyo Inst. of Tech., Tokyo (Japan)

    1999-11-10

    As the part of very low temperature thermophysical property measurement technique standardization by the intelligent basis promotion system, very low temperature coefficient of thermal expansion measurement method using the strain gauge was examined. Here, DyVO4 that that it has the unique temperature dependency as a sample for the test at 20K or less was expected was taken up. The strain gauge, which constituted bridge circuit using strain sensor of 4 used by fatigue test of very low temperature, was produced, and the measurement of coefficient of thermal expansion was tried. (NEDO)

  8. Effect of Aggregate Mineralogy and Concrete Microstructure on Thermal Expansion and Strength Properties of Concrete

    Directory of Open Access Journals (Sweden)

    Jinwoo An

    2017-12-01

    Full Text Available Aggregate type and mineralogy are critical factors that influence the engineering properties of concrete. Temperature variations result in internal volume changes could potentially cause a network of micro-cracks leading to a reduction in the concrete’s compressive strength. The study specifically studied the effect of the type and mineralogy of fine and coarse aggregates in the normal strength concrete properties. As performance measures, the coefficient of thermal expansion (CTE and compressive strength were tested with concrete specimens containing different types of fine aggregates (manufactured and natural sands and coarse aggregates (dolomite and granite. Petrographic examinations were then performed to determine the mineralogical characteristics of the aggregate and to examine the aggregate and concrete microstructure. The test results indicate the concrete CTE increases with the silicon (Si volume content in the aggregate. For the concrete specimens with higher CTE, the micro-crack density in the interfacial transition zone (ITZ tended to be higher. The width of ITZ in one of the concrete specimens with a high CTE displayed the widest core ITZ (approx. 11 µm while the concrete specimens with a low CTE showed the narrowest core ITZ (approx. 3.5 µm. This was attributed to early-age thermal cracking. Specimens with higher CTE are more susceptible to thermal stress.

  9. Hybrid Composites from Wheat Straw, Inorganic Filler, and Recycled Polypropylene: Morphology and Mechanical and Thermal Expansion Performance

    National Research Council Canada - National Science Library

    Yu, Min; Huang, Runzhou; He, Chunxia; Wu, Qinglin; Zhao, Xueni

    2016-01-01

    .... The effects of individual filler (WS) and combined fillers (WS and inorganic filler) on morphological, mechanical, and thermal expansion and water absorption properties of hybrid composites were investigated...

  10. Lattice thermal expansion and anisotropic displacements in urea, bromomalonic aldehyde, pentachloropyridine, and naphthalene

    Science.gov (United States)

    George, Janine; Wang, Ruimin; Englert, Ulli; Dronskowski, Richard

    2017-08-01

    Anisotropic displacement parameters (ADPs) are commonly used in crystallography, chemistry, and related fields to describe and quantify thermal motion of atoms. Within the very recent years, these ADPs have become predictable by lattice dynamics in combination with first-principles theory. Here, we study four very different molecular crystals, namely, urea, bromomalonic aldehyde, pentachloropyridine, and naphthalene, by first-principles theory to assess the quality of ADPs calculated in the quasi-harmonic approximation. In addition, we predict both the thermal expansion and thermal motion within the quasi-harmonic approximation and compare the predictions with the experimental data. Very reliable ADPs are calculated within the quasi-harmonic approximation for all four cases up to at least 200 K, and they turn out to be in better agreement with the experiment than those calculated within the harmonic approximation. In one particular case, ADPs can even reliably be predicted up to room temperature. Our results also hint at the importance of normal-mode anharmonicity in the calculation of ADPs.

  11. Thermal niche evolution and geographical range expansion in a species complex of western Mediterranean diving beetles.

    Science.gov (United States)

    Hidalgo-Galiana, Amparo; Sánchez-Fernández, David; Bilton, David T; Cieslak, Alexandra; Ribera, Ignacio

    2014-09-04

    Species thermal requirements are one of the principal determinants of their ecology and biogeography, although our understanding of the interplay between these factors is limited by the paucity of integrative empirical studies. Here we use empirically collected thermal tolerance data in combination with molecular phylogenetics/phylogeography and ecological niche modelling to study the evolution of a clade of three western Mediterranean diving beetles, the Agabus brunneus complex. The preferred mitochondrial DNA topology recovered A. ramblae (North Africa, east Iberia and Balearic islands) as paraphyletic, with A. brunneus (widespread in the southwestern Mediterranean) and A. rufulus (Corsica and Sardinia) nested within it, with an estimated origin between 0.60-0.25 Ma. All three species were, however, recovered as monophyletic using nuclear DNA markers. A Bayesian skyline plot suggested demographic expansion in the clade at the onset of the last glacial cycle. The species thermal tolerances differ significantly, with A. brunneus able to tolerate lower temperatures than the other taxa. The climatic niche of the three species also differs, with A. ramblae occupying more arid and seasonal areas, with a higher minimum temperature in the coldest month. The estimated potential distribution for both A. brunneus and A. ramblae was most restricted in the last interglacial, becoming increasingly wider through the last glacial and the Holocene. The A. brunneus complex diversified in the late Pleistocene, most likely in south Iberia after colonization from Morocco. Insular forms did not differentiate substantially in morphology or ecology, but A. brunneus evolved a wider tolerance to cold, which appeared to have facilitated its geographic expansion. Both A. brunneus and A. ramblae expanded their ranges during the last glacial, although they have not occupied areas beyond their LGM potential distribution except for isolated populations of A. brunneus in France and England. On

  12. Non-adiabatic effects within a single thermally averaged potential energy surface: thermal expansion and reaction rates of small molecules.

    Science.gov (United States)

    Alonso, J L; Castro, A; Clemente-Gallardo, J; Echenique, P; Mazo, J J; Polo, V; Rubio, A; Zueco, D

    2012-12-14

    At non-zero temperature and when a system has low-lying excited electronic states, the ground-state Born-Oppenheimer approximation breaks down and the low-lying electronic states are involved in any chemical process. In this work, we use a temperature-dependent effective potential for the nuclei which can accommodate the influence of an arbitrary number of electronic states in a simple way, while at the same time producing the correct Boltzmann equilibrium distribution for the electronic part. With the help of this effective potential, we show that thermally activated low-lying electronic states can have a significant effect in molecular properties for which electronic excitations are oftentimes ignored. We study the thermal expansion of the Manganese dimer, Mn(2), where we find that the average bond length experiences a change larger than the present experimental accuracy upon the inclusion of the excited states into the picture. We also show that, when these states are taken into account, reaction-rate constants are modified. In particular, we study the opening of the ozone molecule, O(3), and show that in this case the rate is modified as much as a 20% with respect to the ground-state Born-Oppenheimer prediction.

  13. Effect of dynamic and thermal prehistory on aerodynamic characteristics and heat transfer behind a sudden expansion in a round tube

    Science.gov (United States)

    Terekhov, V. I.; Bogatko, T. V.

    2017-03-01

    The results of a numerical study of the influence of the thicknesses of dynamic and thermal boundary layers on turbulent separation and heat transfer in a tube with sudden expansion are presented. The first part of this work studies the influence of the thickness of the dynamic boundary layer, which was varied by changing the length of the stabilization area within the maximal extent possible: from zero to half of the tube diameter. In the second part of the study, the flow before separation was hydrodynamically stabilized and the thermal layer before the expansion could simultaneously change its thickness from 0 to D1/2. The Reynolds number was varied in the range of {Re}_{{{{D}}1 }} = 6.7 \\cdot 103 {{to}} 1.33 \\cdot 105, and the degree of tube expansion remained constant at ER = ( D 2/ D 1)2 = 1.78. A significant effect of the thickness of the separated boundary layer on both dynamic and thermal characteristics of the flow is shown. In particular, it was found out that with an increase in the thickness of the boundary layer the recirculation zone increases and the maximal Nusselt number decreases. It was determined that the growth of the heat layer thickness does not affect the hydrodynamic characteristics of the flow after separation but does lead to a reduction of heat transfer intensity in the separation area and removal of the coordinates of maximal heat transfer from the point of tube expansion. The generalizing dependence for the maximal Nusselt number at various thermal layer thicknesses is given. Comparison with experimental data confirmed the main trends in the behavior of heat and mass transfer processes in separated flows behind a step with different thermal prehistories.

  14. Biomedical photoacoustics beyond thermal expansion using triggered nanodroplet vaporization for contrast-enhanced imaging.

    Science.gov (United States)

    Wilson, Katheryne; Homan, Kimberly; Emelianov, Stanislav

    2012-01-10

    Since being discovered by Alexander Bell, photoacoustics may again be seeing major resurgence in biomedical imaging. Photoacoustics is a non-ionizing, functional imaging modality capable of high contrast images of optical absorption at depths significantly greater than traditional optical imaging techniques. Optical contrast agents have been used to extend photoacoustics to molecular imaging. Here we introduce an exogenous contrast agent that utilizes vaporization for photoacoustic signal generation, providing significantly higher signal amplitude than that from the traditionally used mechanism, thermal expansion. Our agent consists of liquid perfluorocarbon nanodroplets with encapsulated plasmonic nanoparticles, entitled photoacoustic nanodroplets. Upon pulsed laser irradiation, liquid perfluorocarbon undergoes a liquid-to-gas phase transition generating giant photoacoustic transients from these dwarf nanoparticles. Once triggered, the gaseous phase provides ultrasound contrast enhancement. We demonstrate in phantom and animal studies that photoacoustic nanodroplets act as dual-contrast agents for both photoacoustic and ultrasound imaging through optically triggered vaporization.

  15. Comparison of High Temperature Crystal Lattice and Bulk Thermal Expansion Measurements of LGT Single Crystal

    Energy Technology Data Exchange (ETDEWEB)

    Beaucage, Timothy R [University of Maine; Beenfeldt, Eric P [University of Maine; Speakman, Scott A [ORNL; Porter, Wallace D [ORNL; Payzant, E Andrew [ORNL; Pereira da Cunha, Mauricio [University of Maine

    2006-01-01

    Among the langasite family of crystals (LGX), the three most popular materials are langasite (LGS, La3Ga5SiO14), langatate (LGT, La3Ga5.5Ta0.5O14) and langanite (LGN, La3Ga5.5Nb0.5O14). The LGX crystals have received significant attention for acoustic wave (AW) device applications due to several properties, which include: (1) piezoelectric constants about two and a half times those of quartz, thus allowing the design of larger bandwidth filters; (2) existence of temperature compensated orientations; (3) high density, with potential for reduced vibration and acceleration sensitivity; and (4) possibility of operation at high temperatures, since the LGX crystals do not present phase changes up to their melting point above 1400degC. The LGX crystals' capability to operate at elevated temperatures calls for an investigation on the growth quality and the consistency of these materials' properties at high temperature. One of the fundamental crystal properties is the thermal expansion coefficients in the entire temperature range where the material is operational. This work focuses on the measurement of the LGT thermal expansion coefficients from room temperature (25degC) to 1200degC. Two methods of extracting the thermal expansion coefficients have been used and compared: (a) dual push-rod dilatometry, which provides the bulk expansion; and (b) x-ray powder diffraction, which provides the lattice expansion. Both methods were performed over the entire temperature range and considered multiple samples taken from <001> Czochralski grown LGT material. The thermal coefficients of expansion were extracted by approximating each expansion data set to a third order polynomial fit over three temperature ranges reported in this work: 25degC to 400degC, 400degC to 900degC, 900degC to 1200degC. An accuracy of fit better than 35ppm for the bulk expansion and better than 10ppm for the lattice expansion have been obtained with the aforementioned polynomial fitting. The

  16. Copper-zirconium tungstate composites exhibiting low and negative thermal expansion influenced by reinforcement phase transformations

    Science.gov (United States)

    Balch, Dorian K.; Dunand, David C.

    2004-03-01

    A fully-dense Cu-75 vol pct ZrW2O8 metal matrix composite was fabricated by hot isostatic pressing of Cu-coated ZrW2O8 particles. A small amount of the high-pressure γ-ZrW2O8 phase was created during the cooldown and depressurization following densification; near complete transformation to γ-ZrW2O8 was achieved by subsequent cold isostatic pressing. The thermal expansion behavior of the composite between 25°C and 325°C was altered by the cold isostatic pressing treatment, and also depended on the length of time that had passed between thermal cycles. The measured thermal expansion coefficients within specific temperature ranges varied from -6·10-6 K-1 to far above the thermal expansion coefficient of the copper matrix. The complex temperature-dependent expansion/contraction behavior could be justified by considering the evolution of phase transformations taking place in the ZrW2O8 phase, which were observed by in-situ synchrotron X-ray diffraction measurements.

  17. 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 therma...

  18. XRD- and infrared-probed anisotropic thermal expansion properties of an organic semiconducting single crystal.

    Science.gov (United States)

    Mohanraj, J; Capria, E; Benevoli, L; Perucchi, A; Demitri, N; Fraleoni-Morgera, A

    2018-01-17

    The anisotropic thermal expansion properties of an organic semiconducting single crystal constituted by 4-hydroxycyanobenzene (4HCB) have been probed by XRD in the range 120-300 K. The anisotropic thermal expansion coefficients for the three crystallographic axes and for the crystal volume have been determined. A careful analysis of the crystal structure revealed that the two different H-bonds stemming from the two independent, differently oriented 4HCB molecules composing the unit cell have different rearrangement patterns upon temperature variations, in terms of both bond length and bond angle. Linearly Polarized Mid InfraRed (LP-MIR) measurements carried out in the same temperature range, focused on the O-H bond spectral region, confirm this finding. The same LP-MIR measurements, on the basis of a semi-empirical relation and of geometrical considerations and assumptions, allowed calculation of the -CNH-O- hydrogen bond length along the a and b axes of the crystal. In turn, the so-calculated -CNH-O- bond lengths were used to derive the thermal expansion coefficients along the corresponding crystal axes, as well as the volumetric one, using just the LP-MIR data. Reasonable to good agreement with the same values obtained from XRD measurements was obtained. This proof-of-principle opens interesting perspectives about the possible development of a rapid, low cost and industry-friendly assessment of the thermal expansion properties of organic semiconducting single crystals (OSSCs) involving hydrogen bonds.

  19. Thermal Expansion and Swelling of Cured Epoxy Resin Used in Graphite/Epoxy Composite

    Science.gov (United States)

    Adamson, M. J.

    1979-01-01

    The thermal expansion and swelling of resin material as influenced by variations in temperature during moisture absorption is discussed. Comparison measurements using composites constructed of graphite fibers and each of two epoxy resin matrices are included. Polymer theory relative to these findings is discussed and modifications are proposed.

  20. Mantle dynamics with pressure- and temperature-dependent thermal expansivity and conductivity

    Science.gov (United States)

    Tosi, Nicola; Yuen, David A.; de Koker, Nico; Wentzcovitch, Renata M.

    2013-04-01

    In numerical simulations of mantle convection it is commonly assumed that the coefficients of thermal expansion α and thermal conduction k are either constant or pressure-dependent. Pressure changes are generally computed using parametrizations that rely on extrapolations of low-pressure data for a single upper-mantle phase. Here we collect data for both the pressure and temperature dependence of α from a database of first-principles calculations, and of k from recent experimental studies. We use these data-sets to construct analytical parametrizations of α and k for the major upper- and lower-mantle phases that can be easily incorporated into exisiting convection codes. We then analyze the impact of such parametrizations on Earth's mantle dynamics by employing two-dimensional numerical models of thermal convection. When α is the only variable parameter, both its temperature and pressure dependence enhance hot plumes and tend to inhibit the descent of cold downwellings. Taking into account a variable k leads to a strong increase of the bulk mantle temperature, which reduces the buoyancy available to amplify bottom boundary layer instabilities and causes mantle flow to be driven primarily by the instability of cold plates whose surface velocity also tends to rise. When both parameters are considered together, we observe an increased propensity to local layering which favors slab stagnation in the transition zone and subsequent thickening in the lower mantle. Furthermore, the values of k near the core-mantle boundary ultimately control the effect of this physical property on convection, which stresses the importance of determining the thermal conductivity of the post-perovskite phase.

  1. Waste Package Outer Barrier Stress Due to Thermal Expansion with Various Barrier Gap Sizes

    Energy Technology Data Exchange (ETDEWEB)

    M. M. Lewis

    2001-11-27

    The objective of this activity is to determine the tangential stresses of the outer shell, due to uneven thermal expansion of the inner and outer shells of the current waste package (WP) designs. Based on the results of the calculation ''Waste Package Barrier Stresses Due to Thermal Expansion'', CAL-EBS-ME-000008 (ref. 10), only tangential stresses are considered for this calculation. The tangential stresses are significantly larger than the radial stresses associated with thermal expansion, and at the WP outer surface the radial stresses are equal to zero. The scope of this activity is limited to determining the tangential stresses the waste package outer shell is subject to due to the interference fit, produced by having two different shell coefficients of thermal expansions. The inner shell has a greater coefficient of thermal expansion than the outer shell, producing a pressure between the two shells. This calculation is associated with Waste Package Project. The calculations are performed for the 21-PWR (pressurized water reactor), 44-BWR (boiling water reactor), 24-BWR, 12-PWR Long, 5 DHLW/DOE SNF - Short (defense high-level waste/Department of Energy spent nuclear fuel), 2-MCO/2-DHLW (multi-canister overpack), and Naval SNF Long WP designs. The information provided by the sketches attached to this calculation is that of the potential design for the types of WPs considered in this calculation. This calculation is performed in accordance with the ''Technical Work Plan for: Waste Package Design Description for SR (Ref.7). The calculation is documented, reviewed, and approved in accordance with AP-3.12Q, Calculations (Ref.1).

  2. Mechanical stability of the LHC dipole-dipole 50-75K thermal shield interconnect "floating" expansion joint concept

    CERN Document Server

    Skoczen, Blazej

    1998-01-01

    The LHC dipole cryostats are equipped with thermal shields carrying super-insulation. A cold helium transfer line equipped with expansion joints is integrated into the shield carrying trays (aluminium profiles supported on three composite feet). The stainless steel (316 L) expansion joints compensate for thermal contraction/expansion of the aluminium panels as well as for their misalignment. Design of the LHC thermal shield interconnect is based on the "floating" expansion joint concept (distance between the supports is of around 5 m). The present paper is dedicated to the analysis of mechanical stability of this large span system working at room and at cryogenic temperatures.

  3. Comparison of the Thermal Expansion Behavior of Several Intermetallic Silicide Alloys Between 293 and 1523 K

    Science.gov (United States)

    Raj, S. V.

    2015-03-01

    Thermal expansion measurements were conducted on hot-pressed CrSi2, TiSi2, WSi2 and a two-phase Cr-Mo-Si intermetallic alloy between 303 and 1523 K during three heat-cool cycles. The corrected thermal expansion, (Δ L/ L 0)thermal, varied with the absolute temperature, T, as where, A, B, C, and D are regression constants. Excellent reproducibility was observed for most of the materials after the first heat-up cycle. In some cases, the data from first heat-up cycle deviated from those determined in the subsequent cycles. This deviation was attributed to the presence of residual stresses developed during processing, which are relieved after the first heat-up cycle.

  4. High flux expansion divertor studies in NSTX

    Energy Technology Data Exchange (ETDEWEB)

    Soukhanovskii, V A; Maingi, R; Bell, R E; Gates, D A; Kaita, R; Kugel, H W; LeBlanc, B P; Maqueda, R; Menard, J E; Mueller, D; Paul, S F; Raman, R; Roquemore, A L

    2009-06-29

    Projections for high-performance H-mode scenarios in spherical torus (ST)-based devices assume low electron collisionality for increased efficiency of the neutral beam current drive. At lower collisionality (lower density), the mitigation techniques based on induced divertor volumetric power and momentum losses may not be capable of reducing heat and material erosion to acceptable levels in a compact ST divertor. Divertor geometry can also be used to reduce high peak heat and particle fluxes by flaring a scrape-off layer (SOL) flux tube at the divertor plate, and by optimizing the angle at which the flux tube intersects the divertor plate, or reduce heat flow to the divertor by increasing the length of the flux tube. The recently proposed advanced divertor concepts [1, 2] take advantage of these geometry effects. In a high triangularity ST plasma configuration, the magnetic flux expansion at the divertor strike point (SP) is inherently high, leading to a reduction of heat and particle fluxes and a facilitated access to the outer SP detachment, as has been demonstrated recently in NSTX [3]. The natural synergy of the highly-shaped high-performance ST plasmas with beneficial divertor properties motivated a further systematic study of the high flux expansion divertor. The National Spherical Torus Experiment (NSTX) is a mid-sized device with the aspect ratio A = 1.3-1.5 [4]. In NSTX, the graphite tile divertor has an open horizontal plate geometry. The divertor magnetic configuration geometry was systematically changed in an experiment by either (1) changing the distance between the lower divertor X-point and the divertor plate (X-point height h{sub X}), or by (2) keeping the X-point height constant and increasing the outer SP radius. An initial analysis of the former experiment is presented below. Since in the divertor the poloidal field B{sub {theta}} strength is proportional to h{sub X}, the X-point height variation changed the divertor plasma wetted area due to

  5. Local Chemical Ordering and Negative Thermal Expansion in PtNi Alloy Nanoparticles.

    Science.gov (United States)

    Li, Qiang; Zhu, He; Zheng, Lirong; Fan, Longlong; Wang, Na; Rong, Yangchun; Ren, Yang; Chen, Jun; Deng, Jinxia; Xing, Xianran

    2017-12-13

    An atomic insight into the local chemical ordering and lattice strain is particular interesting to recent emerging bimetallic nanocatalysts such as PtNi alloys. Here, we reported the atomic distribution, chemical environment, and lattice thermal evolution in full-scale structural description of PtNi alloy nanoparticles (NPs). The different segregation of elements in the well-faceted PtNi nanoparticles is convinced by extended X-ray absorption fine structure (EXAFS). Atomic pair distribution function (PDF) study evidences the coexistence of the face-centered cubic and tetragonal ordering parts in the local environment of PtNi nanoparticles. Further reverse Monte Carlo (RMC) simulation with PDF data obviously exposed the segregation as Ni and Pt in the centers of {111} and {001} facets, respectively. Layer-by-layer statistical analysis up to 6 nm for the local atomic pairs revealed the distribution of local tetragonal ordering on the surface. This local coordination environment facilitates the distribution of heteroatomic Pt-Ni pairs, which plays an important role in the negative thermal expansion of Pt41Ni59 NPs. The present study on PtNi alloy NPs from local short-range coordination to long-range average lattice provides a new perspective on tailoring physical properties in nanomaterials.

  6. Evaluating the coefficient of thermal expansion using time periods of minimal thermal gradient for a temperature driven structural health monitoring

    Science.gov (United States)

    Reilly, J.; Abdel-Jaber, H.; Yarnold, M.; Glisic, B.

    2017-04-01

    Structural Health Monitoring aims to characterize the performance of a structure from a combination of recorded sensor data and analytic techniques. Many methods are concerned with quantifying the elastic response of the structure, treating temperature changes as noise in the analysis. While these elastic profiles do demonstrate a portion of structural behavior, thermal loads on a structure can induce comparable strains to elastic loads. Understanding this relationship between the temperature of the structure and the resultant strain and displacement can provide in depth knowledge of the structural condition. A necessary parameter for this form of analysis is the Coefficient of Thermal Expansion (CTE). The CTE of a material relates the amount of expansion or contraction a material undergoes per degree change in temperature, and can be determined from temperature-strain relationship given that the thermal strain can be isolated. Many times with concrete, the actual amount of expansion with temperature in situ varies from the given values for the CTE due to thermally generated elastic strain, which complicates evaluation of the CTE. To accurately characterize the relationship between temperature and strain on a structure, the actual thermal behavior of the structure needs to be analyzed. This rate can vary for different parts of a structure, depending on boundary conditions. In a case of unrestrained structures, the strain in the structure should be linearly related to the temperature change. Thermal gradients in a structure can affect this relationship, as they induce curvature and deplanations in the cross section. This paper proposes a method that addresses these challenges in evaluating the CTE.

  7. Measurements of thermal conductivity and the coefficient of thermal expansion for polysilicon thin films by using double-clamped beams

    Science.gov (United States)

    Liu, Haiyun; Wang, Lei

    2018-01-01

    In this paper, a test structure for simultaneously determining thermal conductivity and the coefficient of thermal expansion (CTE) of polysilicon thin film is proposed. The test structure consists of two double-clamped beams with different lengths. A theoretical model for extracting thermal conductivity and CTE based on electrothermal analysis and resonance frequency approach is developed. Both flat and buckled beams are considered in the theoretical model. The model is confirmed by finite element software ANSYS. The test structures are fabricated by surface micromachined fabrication process. Experiments are carried out in our atmosphere. Thermal conductivity and CTE of polysilicon thin film are obtained to be (29.96  ±  0.92) W · m · K‑1 and (2.65  ±  0.03)  ×  10‑6 K‑1, respectively, with temperature ranging from 300–400 K.

  8. Thermal expansion and the heat capacity of nanocrystalline and coarse-crystalline silver sulfide Ag2S

    Science.gov (United States)

    Sadovnikov, S. I.; Gusev, A. I.

    2017-09-01

    The thermal expansion and the heat capacity of coarse-crystalline and nanocrystalline silver sulfide Ag2S were studied by dilatometry and differential scanning calorimentry for the first time in the temperature range 290-970 K. It is found that the thermal expansion coefficient and the heat capacity of nanocrystalline silver sulfide in this temperature range are higher than those in the case of the coarse-crystalline sulfide. It is revealed that the transformation of α-Ag2S acanthite to β-Ag2S argentite and β-Ag2S argentite to γ-Ag2S phase are the first-order phase transitions; the temperatures and the enthalpies of these transformations have been determined.

  9. Unusual Low-Energy Phonon Dynamics in the Negative Thermal Expansion Compound ZrW2O8

    Science.gov (United States)

    Hancock, Jason N.; Turpen, Chandra; Schlesinger, Zack; Kowach, Glen R.; Ramirez, Arthur P.

    2004-11-01

    An infrared study of the phonon spectra of ZrW2O8 as a function of temperature which includes the low-energy (2 10meV) region relevant to negative thermal expansion is reported and discussed in the context of specific heat and neutron density of state results. The prevalence of infrared active phonons at low energy and their observed temperature dependence are highly unusual and indicative of exotic low-energy lattice dynamics. Eigenvector calculations indicate a mixing of librational and translational motion within each low-frequency IR mode. The role of the underconstrained structure in establishing the nature of these modes and the relationship between the IR spectra and the large negative thermal expansion in ZrW2O8 are discussed.

  10. The fabrication and thermal expansion properties of 4H-Ag nanowire arrays in porous anodic alumina templates.

    Science.gov (United States)

    Zhou, Ye; Fei, Guang Tao; Cui, Ping; Wu, Bing; Wang, Biao; Zhang, Li De

    2008-07-16

    Hexagonal silver nanowire (4H-Ag NW) arrays with preferred orientation are fabricated into the holes of porous anodic alumina membranes (AAMs) by direct current electrodeposition. The addition of tartaric acid and low deposition temperature are crucial conditions for the growth of 4H-Ag NWs. The thermal expansion properties of the as-prepared and annealed 4H-Ag NWs are studied by in situ x-ray diffraction in the temperature range from room temperature to 800 °C. The axial thermal expansion coefficient (TEC) of the as-prepared sample decreases initially and increases subsequently, while that of the annealed sample consistently increases during the whole measuring process.

  11. The fabrication and thermal expansion properties of 4H-Ag nanowire arrays in porous anodic alumina templates

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Ye; Fei Guangtao; Cui Ping; Wu Bing; Wang Biao; Zhang Lide [Key Laboratory of Materials Physics and Anhui Key Laboratory of Nanomaterials and Nanostructures, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, PO Box 1129, Hefei, 230031 (China)], E-mail: gtfei@issp.ac.cn

    2008-07-16

    Hexagonal silver nanowire (4H-Ag NW) arrays with preferred orientation are fabricated into the holes of porous anodic alumina membranes (AAMs) by direct current electrodeposition. The addition of tartaric acid and low deposition temperature are crucial conditions for the growth of 4H-Ag NWs. The thermal expansion properties of the as-prepared and annealed 4H-Ag NWs are studied by in situ x-ray diffraction in the temperature range from room temperature to 800 deg. C. The axial thermal expansion coefficient (TEC) of the as-prepared sample decreases initially and increases subsequently, while that of the annealed sample consistently increases during the whole measuring process.

  12. Unusual compressibility in the negative-thermal-expansion material ZrW2O8

    Science.gov (United States)

    Migliori, Albert; Pantea, C.; Ledbetter, H.; Zhao, Y.; Kimura, T.; Littlewood, Peter B.; van Duijn, J.; Kowach, G. R.

    2006-03-01

    The negative thermal expansion (NTE) compound ZrW2O8 has been well-studied because it remains cubic with a nearly constant, isotropic NTE coefficient over a broad temperature range. However, its elastic constants seem just as strange as its volume because NTE makes temperature acts as positive pressure, decreasing volume on warming and, unlike most materials, the thermally-compressed solidsoftens. Does ZrW2O8 also soften when pressure alone is applied? Using pulse-echo ultrasound in a hydrostatic SiC anvil cell, we determine the elastic tensor of monocrystalline ZrW2O8 near 300 K as a function of pressure. We indeed find an unusual decrease in bulk modulus with pressure. Our results are inconsistent with conventional lattice dynamics, but do show that the thermodynamically-complete constrained-lattice model can relate NTE to elastic softening as increases in either temperature or pressure reduce volume, establishing the predictive power of the model, and making it an important concept in condensed-matter physics.

  13. Investigation of Thermal Expansion Properties of Single Walled Carbon Nanotubes by Raman Spectroscopy and Molecular Dynamics Simulation

    Science.gov (United States)

    Casimir, Daniel

    The mechanical properties of nano-sized materials seem to differ significantly from the predicted behavior of their bulk macroscopic counterparts (Smart, 2014, 16). The former tend to be stronger, more malleable and exhibit greater flexibility. The thermal properties of materials have also been shown to be altered significantly after having been shrunken to nanometer dimensions. The nano material that exhibits this peculiar behavior that is studied in this dissertation are single walled carbon nanotubes. Single walled carbon nanotubes are hollow cylindrical tubes that are one atomic layer in thickness and made up of sp2 hybridized carbon atoms. The majority of samples have diameters on the order 1 nm, with lengths ranging from 1 micron to sometimes a centimeter (Tomanek, 2008, v). The thermo-mechanical quantity that I specifically examine in this research is the linear and volume thermal expansion coefficients of SWCNTs. The mean linear thermal expansion coefficient is the ratio of the change in unit length in response to a 1 degree Celsius rise in temperature. The "true" value of this quantity is obtained in the theoretical limit of a vanishing temperature range DeltaT in the ratio stated above. However, this simply stated thermo-mechanical quantity for Carbon Nanotubes still remains a controversial topic, with widespread discrepancies among results of certain magnitudes - such as the temperature at the occurrence of maximum contraction, and at the transition from contraction to expansion. In conclusion, there is much incentive in examining the somewhat controversial variation in the behavior and quoted values of the thermal expansion of these quasi one-dimensional objects. In this study, I examine this important property of single walled carbon nanotubes using Resonant Raman Spectroscopy and Molecular Dynamics Simulation based on the Adaptive Intermolecular Reactive Empirical Bond Order potential. The latter is a well established potential that is well-suited to

  14. Thermophysical Properties of Matter - the TPRC Data Series. Volume 13. Thermal Expansion - Nonmetallic Solids

    Science.gov (United States)

    1977-01-01

    to a high enough the near-zero expansivity of vitreous silica that makes temperature it will crystallize in the cristobalite it so useful. Methods for...John Wiley, 1961. 33. Matthias, B.T., Geballe, T.H., Corenzwit, E., Andres, K., and Hall, G.W., "Superconductivity of Beta -Uranium," Science, 151, 985...Thermal Expansion Coefficients of Beta -MnOt,ŕ J. Electro- chem. Soc., 109(7), 651, 1962. 125 52255 Mistler, R. E., Ploetz, G. L., and Smith, J. A

  15. Two-level systems and negative thermal expansion of lutetium borides

    Science.gov (United States)

    Novikov, V. V.; Mitroshenkov, N. V.; Kornev, B. I.; Matovnikov, A. V.

    2017-05-01

    The heat capacity Cv(T) and unit cell volume V(T) temperature dependencies of lutetium borides LuB2 and LuB4 in the region of 2-300 K were analysed in the Debye-Einstein approximation. The characteristic temperatures of the Debye and Einstein components of boride heat capacity and thermal expansion were found. The anomalous contribution to the borides' thermal characteristics was revealed. This contribution was attributed to the influence of two-level systems (TLS), formed in the subsystem of lutetium ions due to asymmetry in the way they are surrounded by the boron atoms in the boride crystal structure. The TLS influence is revealed on heat capacity temperature dependencies by the Schottky-type maxima at Tmax LuB2 =13.8 K, Tmax LuB4 =22.7 K, as well as by the negative contribution to the borides' thermal expansion. The borides' Grüneisen parameters corresponding to the heat capacity and thermal expansion TLS anomalies are negative, and amount to several 10 s of units.

  16. Role of bond strength on the lattice thermal expansion and oxide ion conductivity in quaternary pyrochlore solid solutions.

    Science.gov (United States)

    Radhakrishnan, A N; Prabhakar Rao, P; Mahesh, S K; Thampi, D S Vaisakhan; Koshy, Peter

    2012-02-20

    Quaternary pyrochlore-type solid solutions, CaGdZrNb(1-x)Ta(x)O(7) (x = 0, 0.2, 0.4, 0.6, 0.8, 1), were prepared by a high-temperature ceramic route. The pyrochlore phases of the compounds were confirmed by powder X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. The crystallographic parameters of the pyrochlore compounds were accurately determined by Rietveld analysis of the powder XRD data. The isovalent substitution of Ta in place of Nb at the B site can reveal the effect of chemical bonding on lattice thermal expansion and oxide ion conductivity because both Nb and Ta have the same ionic radius (0.64 Å). Lattice thermal expansion coefficients of the samples were calculated from high-temperature XRD measurements, and it was found that the thermal expansion coefficient decreases with substitution of Ta. Oxide ion conductivity measured by a two-probe method also shows the same trend with substitution of Ta, and this can be attributed to the high bond strength of the Ta-O bond compared to that of the Nb-O bond. Microstructural characterization using scanning electron microscopy proves that the size of the grains has a small effect on the oxide ion conductivity. Our studies established the role of chemical bonding in deciding the conductivity of pyrochlore oxides and confirmed that the 48f-48f mechanism of oxide ion conduction is dominant in pyrochlore oxides.

  17. Synthesis, Structure, and Rigid Unit Mode-like Anisotropic Thermal Expansion of BaIr2In9.

    Science.gov (United States)

    Calta, Nicholas P; Han, Fei; Kanatzidis, Mercouri G

    2015-09-08

    This Article reports the synthesis of large single crystals of BaIr2In9 using In flux and their characterization by variable-temperature single-crystal and synchrotron powder X-ray diffraction, resistivity, and magnetization measurements. The title compound adopts the BaFe2Al9-type structure in the space group P6/mmm with room temperature unit cell parameters a = 8.8548(6) Å and c = 4.2696(4) Å. BaIr2In9 exhibits anisotropic thermal expansion behavior with linear expansion along the c axis more than 3 times larger than expansion in the ab plane between 90 and 400 K. This anisotropic expansion originates from a rigid unit mode-like mechanism similar to the mechanism of zero and negative thermal expansion observed in many anomalous thermal expansion materials such as ZrW2O8 and ScF3.

  18. Sound velocity of high-strength polymer with negative thermal expansion coefficient

    Science.gov (United States)

    Nomura, R.; Ueno, M.; Okuda, Y.; Burmistrov, S.; Yamanaka, A.

    2003-05-01

    Sound velocities of fiber reinforced plastics (FRPs) were measured along the fiber axis at temperatures between 360 and 77 K. We used two kinds of the high-strength crystalline polymer fibers, polyethylene (Dyneema) and polybenzobisoxazole (Zylon), which have negative thermal expansion coefficients. They also have high thermal conductivities and high resistances for flash over voltage, and are expected as new materials for coil bobbins or spacers at cryogenic temperatures. They have very large sound velocities of about 9000 (m/s) at 77 K, which are 4.5 times larger than that of the ordinary polyethylene fiber.

  19. HAYNES 244 alloy – a new 760 ∘C capable low thermal expansion alloy

    OpenAIRE

    Fahrmann Michael G.; Srivastava S. Krishna; Pike Lee M.

    2014-01-01

    HAYNES® 244TM alloy is a new 760∘C capable, high strength low thermal expansion (CTE) alloy. Its nominal chemical composition in weight percent is Ni – 8 Cr – 22.5 Mo – 6 W. Recently, a first mill-scale heat of 244 alloy was melted by Haynes International, and processed to various product forms such as re-forge billet, plate, and sheet. This paper presents key attributes of this new alloy (CTE, strength, low-cycle fatigue performance, oxidation resistance, thermal stability) as they pertain t...

  20. HAYNES 244 alloy – a new 760 ∘C capable low thermal expansion alloy

    Directory of Open Access Journals (Sweden)

    Fahrmann Michael G.

    2014-01-01

    Full Text Available HAYNES® 244TM alloy is a new 760∘C capable, high strength low thermal expansion (CTE alloy. Its nominal chemical composition in weight percent is Ni – 8 Cr – 22.5 Mo – 6 W. Recently, a first mill-scale heat of 244 alloy was melted by Haynes International, and processed to various product forms such as re-forge billet, plate, and sheet. This paper presents key attributes of this new alloy (CTE, strength, low-cycle fatigue performance, oxidation resistance, thermal stability as they pertain to the intended use in rings and seals of advanced gas turbines.

  1. Thermal expansion and magnetostriction of superconducting URu{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    van Dijk, N.H.; de Visser, A.; Franse, J.J.M.; Menovsky, A.A. [Van der Waals-Zeeman Laboratory, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)

    1995-05-01

    Dilatation measurements have been performed on a single-crystalline sample of the heavy-fermion superconductor URu{sub 2}Si{sub 2} ({ital T}{sub {ital c}}=1.2 K). Thermal-expansion measurements in combination with specific-heat data reveal a thermal electronic Grueneisen parameter of {Gamma}{sub {ital T}}=27. A comparison with the magnetic electronic Grueneisen parameter derived from the magnetostriction, {Gamma}{sub {ital B}}=26, points to a single energy scale. The measured magnetostriction is strongly anisotropic with a peculiar hysteresis. Close to the upper critical field, a change of sign in the magnetostrictive hysteresis is observed.

  2. Metal-Matrix Nanocomposites with Tailored Coefficients of Thermal Expansion for Improved Thermomechanical Reliability

    Science.gov (United States)

    Trujillo, J. E.; Kim, J. W.; Lan, E. H.; Sharratt, S.; Ju, Y. S.; Dunn, B.

    2012-06-01

    Ensuring the thermomechanical reliability of various interfaces in thermoelectric (TE) devices during manufacture and operation is challenging, especially for those incorporating TE materials with small coefficients of thermal expansion (CTEs). In this paper, we describe our recent progress in the development of metal-matrix nanocomposites with tailorable CTEs, for use as electrodes or as interfacial bonding layers for creating segmented TE elements. The composites incorporate ceramic nanoscale fillers with isotropic negative thermal expansion (NTE) to effectively offset the high CTE of the metal phase. The NTE fillers, synthesized using a sol-gel route, were mixed with metal powders and hot pressed to yield nanocomposites having CTE values decreasing approximately linearly with filler volume fraction. Composites with 54/46 v/v Ag/zirconium tungstate (ZrW2O8) achieved average CTE of 7.2 ppm/K, with electrical and thermal conductivities approximately 50% of that of Ag nanopowders hot pressed under identical conditions. X-ray diffraction (XRD) analyses suggest that the composites are thermally stable at temperatures as high as 920 K. This research provides a foundation upon which to investigate alternative electrode and interface materials with tailored CTEs for achieving improved thermomechanical reliability of TE modules and other thermal and electronic devices.

  3. Thermal expansions in wurtzite AlN, GaN, and InN: First-principle phonon calculations

    Science.gov (United States)

    Xu, Li-Chun; Wang, Ru-Zhi; Yang, Xiaodong; Yan, Hui

    2011-08-01

    Using the first-principle phonon calculations under the quasiharmonic approximation, thermal expansions in III-nitrides with wurtzite AlN, GaN, and InN are reported. The results showed that it is different for each thermal expansion of three III-nitrides at low temperatures, which is consistent with their Grüneisen parameters as the function of temperature. Below 50 K, negative thermal expansions occur in InN, while GaN and AlN follow the rule of positive thermal expansion. To seek the origin of positive/negative thermal expansion distinction, the mode Grüneisen parameters and the phonon spectra are investigated. They indicate that different low-frequency phonon vibration modes correspond to the change of thermal expansions. Below 5 THz, the significant weighted negative values of mode Grüneisen parameters, caused by the weakening of mixing-mode constituted with two transverse acoustic (TA) modes and a small overlapped part of optical modes, directly lead to the negative thermal expansion at low temperatures.

  4. Thermal expansion in UO 2 determined by high-energy X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Guthrie, M.; Benmore, C. J.; Skinner, L. B.; Alderman, O. L. G.; Weber, J. K. R.; Parise, J. B.; Williamson, M.

    2016-10-01

    Here we present crystallographic analyses of high-energy X-ray diffraction data on polycrystalline UO2 up to the melting temperature. The Rietveld refinements of our X-ray data are in agreement with previous measurements, but are systematically located around the upper bound of their uncertainty, indicating a slightly steeper trend of thermal expansion compared to established values. This observation is consistent with recent first principles calculations.

  5. Coefficient of thermal expansion (CTE) in EUV lithography: LER and adhesion improvement

    Science.gov (United States)

    Higgins, Craig; Settens, Charles; Wolfe, Patricia; Petrillo, Karen; Auger, Robert; Matyi, Richard; Brainard, Robert

    2011-04-01

    Spin-on underlayers are currently being employed by the lithographic industry to improve the imaging performance of EUV resists. In this work, multiple examples have shown improved line-edge roughness (LER) of an open-source resist using new open-source underlayers in comparison to a primed silicon substrate. Additionally, several experiments demonstrate better resist adhesion on underlayers that have lower coefficients of thermal expansion (CTE). Both organic and inorganic underlayers provide better resist LER when their CTE is lower.

  6. A Noncontact Measurement Technique for the Density and Thermal Expansion Coefficient of Solid and Liquid Materials

    Science.gov (United States)

    Chung, Sang K.; Thiessen, David B.; Rhim, Won-Kyu

    1996-01-01

    A noncontact measurement technique for the density and the thermal expansion refractory materials in their molten as well as solid phases is presented. This technique is based on the video image processing of a levitated sample. Experiments were performed using the high-temperature electrostatic levitator (HTESL) at the Jet Propulsion Laboratory in which 2-3 mm diameter samples can be levitated, melted, and radiatively cooled in a vacuum. Due to the axisymmetric nature of the molten samples when levitated in the HTESL, a rather simple digital image analysis can be employed to accurately measure the volumetric change as a function of temperature. Density and the thermal expansion coefficient measurements were made on a pure nickel sample to test the accuracy of the technique in the temperature range of 1045-1565 C. The result for the liquid phase density can be expressed by p = 8.848 + (6.730 x 10(exp -4)) x T (degC) g/cu cm within 0.8% accuracy, and the corresponding thermal expansion coefficient can be expressed by Beta=(9.419 x 10(exp -5)) - (7.165 x 10(exp -9) x T (degC)/K within 0.2% accuracy.

  7. Phase behaviour, thermal expansion and compressibility of SnMo 2 O 8

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Luiza R.; Gallington, Leighanne C.; Wilkinson, Angus P.; Evans, John S. O.

    2018-02-01

    The phase behaviour and thermoelastic properties of SnMo2O8, derived from variable temperature and pressure synchrotron powder diffraction data, are reported. SnMo2O8 is a member of the AM2O8 family of negative thermal expansion (NTE) materials, but unexpectedly, has positive thermal expansion. Over the P-T space explored (298–513 K, ambient to 310 MPa) four different forms of SnMo2O8 are observed: α, β, γ and γ'. The γ to β transition is temperature-, pressure-, and time-dependent. SnMo2O8 is a much softer material (α and γ form have BT = 29 and 26 GPa at 298 K) than other members of the AM2O8 family. Counter-intuitively, its high temperature β phase becomes stiffer with increasing temperature (BT ~36 GPa at 490 K). The pressure dependence of the thermal expansion for each phase is reported.

  8. Novel quantum criticality in CeRu2Si2 near absolute zero observed by thermal expansion and magnetostriction.

    Science.gov (United States)

    Yoshida, J; Abe, S; Takahashi, D; Segawa, Y; Komai, Y; Tsujii, H; Matsumoto, K; Suzuki, H; Onuki, Y

    2008-12-19

    We report linear thermal expansion and magnetostriction measurements for CeRu2Si2 in magnetic fields up to 52.6 mT and at temperatures down to 1 mK. At high temperatures, this compound showed Landau-Fermi-liquid behavior: The linear thermal expansion coefficient and the magnetostriction coefficient were proportional to the temperature and magnetic field, respectively. In contrast, a pronounced non-Fermi-liquid effect was found below 50 mK. The negative contribution of thermal expansion and magnetostriction suggests the existence of an additional quantum critical point.

  9. Experimental Study on the Tensile Strength and Linear Expansion Coefficient of Air Tunnel Terrazzo Surface

    Directory of Open Access Journals (Sweden)

    Boping Li

    2015-01-01

    Full Text Available At present, studies on the surface tension of air tunnel terrazzo under wind load and how regularly it is affected by temperature are relatively less, and the measured results of the thermal expansion coefficient of terrazzo have not yet been given. In this paper, based on the top terrazzo surface structure of the inner wall of the wind tunnel, the tensile performance tests of terrazzo surface layer are conducted, while the thermal expansion coefficient of the six terrazzo test blocks were tested. The tests and analysis show that the construction of terrazzo surface, based on the proposed construction process, can effectively guarantee the reliable cement performance for the binding layer between mortar and concrete base layer, terrazzo surface layer and the cement mortar layer. And the thermal expansion coefficient of terrazzo can be valued at 1.06e-5/ºC.

  10. Gene expression under thermal stress varies across a geographical range expansion front.

    Science.gov (United States)

    Lancaster, Lesley T; Dudaniec, Rachael Y; Chauhan, Pallavi; Wellenreuther, Maren; Svensson, Erik I; Hansson, Bengt

    2016-03-01

    Many ectothermic species are currently expanding their distributions polewards due to anthropogenic global warming. Molecular genetic mechanisms facilitating range expansion under these conditions are largely unknown, but understanding these could help mitigate expanding pests and disease vectors, or help explain why some species fail to track changing climates. Here, using RNA-seq data, we examine genomewide changes in gene expression under heat and cold stress in the range-expanding damselfly Ischnura elegans in northern Europe. We find that both the number of genes involved and levels of gene expression under heat stress have become attenuated during the expansion, consistent with a previously reported release from selection on heat tolerances as species move polewards. Genes upregulated under cold stress differed between core and edge populations, corroborating previously reported rapid adaptation to cooler climates at the expansion front. Expression of sixty-nine genes exhibited a region x treatment effect; these were primarily upregulated in response to heat stress in core populations but in response to cold stress at the range edge, suggesting that some cellular responses originally adapted to heat stress may switch to cold-stress functionality upon encountering novel thermal selection regimes during range expansion. Transcriptional responses to thermal stress involving heat-shock and neural function genes were largely geographically conserved, while retrotransposon, regulatory, muscle function and defence gene expression patterns were more variable. Flexible mechanisms of cold-stress response and the ability of some genes to shift their function between heat and cold stress might be key mechanisms facilitating rapid poleward expansion in insects. © 2016 John Wiley & Sons Ltd.

  11. Jupiter's North Equatorial Belt expansion and thermal wave activity ahead of Juno's arrival

    Science.gov (United States)

    Fletcher, L. N.; Orton, G. S.; Sinclair, J. A.; Donnelly, P.; Melin, H.; Rogers, J. H.; Greathouse, T. K.; Kasaba, Y.; Fujiyoshi, T.; Sato, T. M.; Fernandes, J.; Irwin, P. G. J.; Giles, R. S.; Simon, A. A.; Wong, M. H.; Vedovato, M.

    2017-07-01

    The dark colors of Jupiter's North Equatorial Belt (NEB, 7-17°N) appeared to expand northward into the neighboring zone in 2015, consistent with a 3-5 year cycle. Inversions of thermal-IR imaging from the Very Large Telescope revealed a moderate warming and reduction of aerosol opacity at the cloud tops at 17-20°N, suggesting subsidence and drying in the expanded sector. Two new thermal waves were identified during this period: (i) an upper tropospheric thermal wave (wave number 16-17, amplitude 2.5 K at 170 mbar) in the mid-NEB that was anticorrelated with haze reflectivity; and (ii) a stratospheric wave (wave number 13-14, amplitude 7.3 K at 5 mbar) at 20-30°N. Both were quasi-stationary, confined to regions of eastward zonal flow, and are morphologically similar to waves observed during previous expansion events.

  12. [The measurement of thermal expansion coefficient of Co-Cr alloy fabricated by selective laser melting].

    Science.gov (United States)

    Tian, Xiao-mei; Zeng, Li; Wei, Bin; Huang, Yi-feng

    2015-12-01

    To investigate the thermal expansion coefficient of different processing parameters upon the Co-Cr alloy prepared by selective laser melting (SLM) technique, in order to provide technical support for clinical application of SLM technology. The heating curve of self-made Co-Cr alloy was protracted from room temperature to 980°C centigrade with DIL402PC thermal analysis instrument, keeping temperature rise rate and cooling rate at 5 K/min, and then the thermal expansion coefficient of 9 groups of Co-Cr alloy was measured from 20°C centigrade to 500°C centigrade and 600°C centigrade. The 9 groups thermal expansion coefficient values of Co-Cr alloy heated from 20°C centigrade to 500°C centigrade were 13.9×10(-6)/K,13.6×10(-6)/K,13.9×10(-6)/K,13.7×10(-6)/K,13.5×10(-6)/K,13.8×10(-6)/K,13.7×10(-6)/K,13.7×10(-6)/K,and 13.9×10(-6)/K, respectively; when heated from 20°C centigrade to 600°C centigrade, they were 14.2×10(-6)/K,13.9×10(-6)/K,13.8×10(-6)/K,14.0×10(-6)/K,14.1×10(-6)/K,14.1×10(-6)/K,13.9×10(-6)/K,14.2×10(-6)/K, and 13.7×10(-6)/K, respectively. The results showed that the Co-Cr alloy has good matching with the VITA VMK 95 porcelain powder and can meet the requirement of clinic use.

  13. Structural investigation of the negative thermal expansion in yttrium and rare earth molybdates

    Energy Technology Data Exchange (ETDEWEB)

    Guzman-Afonso, Candelaria; Torres, Manuel Eulalio; Sabalisck, Nanci; Sanchez-Fajardo, VIctor [Departamento de Fisica Basica, Universidad de La Laguna, Tenerife (Spain); Gonzalez-Silgo, Cristina; Gonzalez-Platas, Javier [Departamento de Fisica Fundamental II, Universidad de La Laguna, Tenerife (Spain); Lozano-GorrIn, Antonio Diego [Servicio Integrado de Difraccion de Rayos X, Universidad de La Laguna, Tenerife (Spain); Campo, Javier [Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza (Spain); RodrIguez-Carvajal, Juan, E-mail: csilgo@ull.es [Institut Laue-Langevin, Grenoble (France)

    2011-08-17

    The Sc{sub 2}(WO{sub 4}){sub 3}-type phase (Pbcn) of Y{sub 2}(MoO{sub 4}){sub 3}, Er{sub 2}(MoO{sub 4}){sub 3} and Lu{sub 2}(MoO{sub 4}){sub 3} has been prepared by the conventional solid-state synthesis with preheated oxides and the negative thermal expansion (NTE) has been investigated along with an exhaustive structural study, after water loss. Their crystal structures have been refined using the neutron and x-ray powder diffraction data of dehydrated samples from 150 to 400 K. The multi-pattern Rietveld method, using atomic displacements with respect to a known structure as parameters to refine, has been applied to facilitate the interpretation of the NTE behavior. Polyhedral distortions, transverse vibrations of A{center_dot}{center_dot}{center_dot}O-Mo (A = Y and rare earths) binding oxygen atoms, non-bonded distances A{center_dot}{center_dot}{center_dot}Mo and atomic displacements from the high temperature structure, have been evaluated as a function of the temperature and the ionic radii.

  14. Thermal expansion and magnetic properties of benzoquinone-bridged dinuclear rare-earth complexes.

    Science.gov (United States)

    Moilanen, Jani O; Mansikkamäki, Akseli; Lahtinen, Manu; Guo, Fu-Sheng; Kalenius, Elina; Layfield, Richard A; Chibotaru, Liviu F

    2017-10-10

    The synthesis and structural characterization of two benzoquinone-bridged dinuclear rare-earth complexes [BQ(MCl2·THF3)2] (BQ = 2,5-bisoxide-1,4-benzoquinone; M = Y (1), Dy (2)) are described. Of these reported metal complexes, the dysprosium analogue 2 is the first discrete bridged dinuclear lanthanide complex in which both metal centres reside in pentagonal bipyramidal environments. Interestingly, both complexes undergo significant thermal expansion upon heating from 120 K to 293 K as illustrated by single-crystal X-ray and powder diffraction experiments. AC magnetic susceptibility measurements reveal that 2 does not show the slow relation of magnetization in zero dc field. The absent of single-molecule behaviour in 2 arises from the rotation of the principal magnetic axis as compared to the pseudo-C5 axis of the pentagonal bipyramidal environment as suggested by ab initio calculations. The cyclic voltammetry and chemical reduction experiments demonstrated that complexes 1 and 2 can be reduced to radical species containing [BQ(3)˙(-)]. This study establishes efficient synthetic strategy to make bridged redox-active multinuclear lanthanide complexes with a pentagonal bipyramidal coordination environment that are potential precursors for single-molecule magnets.

  15. Effect of space exposure of some epoxy matrix composites on their thermal expansion and mechanical properties (A0138-8)

    Science.gov (United States)

    Jabs, Heinrich

    1992-01-01

    Assessments of the behavior of the carbon/epoxy composites in space conditions are described. After an exposure of five years, the mechanical characteristics and the coefficient of thermal expansion are measured and compared to reference values.

  16. Anharmonic phonon quasiparticle theory of zero-point and thermal shifts in insulators: Heat capacity, bulk modulus, and thermal expansion

    Science.gov (United States)

    Allen, Philip B.

    2015-08-01

    The quasiharmonic (QH) approximation uses harmonic vibrational frequencies ωQ ,H(V ) computed at volumes V near V0 where the Born-Oppenheimer (BO) energy Eel(V ) is minimum. When this is used in the harmonic free energy, QH approximation gives a good zeroth order theory of thermal expansion and first-order theory of bulk modulus, where nth-order means smaller than the leading term by ɛn, where ɛ =ℏ ωvib/Eel or kBT /Eel , and Eel is an electronic energy scale, typically 2 to 10 eV. Experiment often shows evidence for next-order corrections. When such corrections are needed, anharmonic interactions must be included. The most accessible measure of anharmonicity is the quasiparticle (QP) energy ωQ(V ,T ) seen experimentally by vibrational spectroscopy. However, this cannot just be inserted into the harmonic free energy FH. In this paper, a free energy is found that corrects the double-counting of anharmonic interactions that is made when F is approximated by FH( ωQ(V ,T ) ) . The term "QP thermodynamics" is used for this way of treating anharmonicity. It enables (n +1 ) -order corrections if QH theory is accurate to order n . This procedure is used to give corrections to the specific heat and volume thermal expansion. The QH formulas for isothermal (BT) and adiabatic (BS) bulk moduli are clarified, and the route to higher-order corrections is indicated.

  17. Parallel calculations of vibrational properties in complex materials: negative thermal expansion and elastic inhomogeneity

    Science.gov (United States)

    Vila, F. D.; Rehr, J. J.

    Effects of thermal vibrations are essential to obtain a more complete understanding of the properties of complex materials. For example, they are important in the analysis and simulation of x-ray absorption spectra (XAS). In previous work we introduced an ab initio approach for a variety of vibrational effects, such as crystallographic and XAS Debye-Waller factors, Debye and Einstein temperatures, and thermal expansion coefficients. This approach uses theoretical dynamical matrices from which the locally-projected vibrational densities of states are obtained using a Lanczos recursion algorithm. In this talk I present recent improvements to our implementation, which permit simulations of more complex materials with up to two orders of magnitude larger simulation cells. The method takes advantage of parallelization in calculations of the dynamical matrix with VASP. To illustrate these capabilities we discuss two problems of considerable interest: negative thermal expansion in ZrW2O8; and local inhomogeneities in the elastic properties of supported metal nanoparticles. Both cases highlight the importance of a local treatment of vibrational properties. Supported by DOE Grant DE-FG02-03ER15476, with computer support from DOE-NERSC.

  18. Thermal expansion and swelling of cured epoxy resin used in graphite/epoxy composite materials

    Science.gov (United States)

    Adamson, M. J.

    1980-01-01

    The paper presents results of experiments in which the thermal expansion and swelling behavior of an epoxy resin system and two graphite/epoxy composite systems exposed to water were measured. It was found that the cured epoxy resin swells by an amount slightly less than the volume of the absorbed water and that the swelling efficiency of the water varies with the moisture content of the polymer. Additionally, the thermal expansion of cured epoxy resin that is saturated with water is observed to be more than twice that of dry resin. Results also indicate that cured resin that is saturated with 7.1% water at 95 C will rapidly increase in moisture content to 8.5% when placed in 1 C water. The mechanism for this phenomenon, termed reverse thermal effect, is described in terms of a slightly modified free-volume theory in conjunction with the theory of polar molecule interaction. Nearly identical behavior was observed in two graphite/epoxy composite systems, thus establishing that this behavior may be common to all cured epoxy resins.

  19. Diffraction phase microscopy imaging and multi-physics modeling of the nanoscale thermal expansion of a suspended resistor.

    Science.gov (United States)

    Wang, Xiaozhen; Lu, Tianjian; Yu, Xin; Jin, Jian-Ming; Goddard, Lynford L

    2017-07-04

    We studied the nanoscale thermal expansion of a suspended resistor both theoretically and experimentally and obtained consistent results. In the theoretical analysis, we used a three-dimensional coupled electrical-thermal-mechanical simulation and obtained the temperature and displacement field of the suspended resistor under a direct current (DC) input voltage. In the experiment, we recorded a sequence of images of the axial thermal expansion of the central bridge region of the suspended resistor at a rate of 1.8 frames/s by using epi-illumination diffraction phase microscopy (epi-DPM). This method accurately measured nanometer level relative height changes of the resistor in a temporally and spatially resolved manner. Upon application of a 2 V step in voltage, the resistor exhibited a steady-state increase in resistance of 1.14 Ω and in relative height of 3.5 nm, which agreed reasonably well with the predicted values of 1.08 Ω and 4.4 nm, respectively.

  20. Investigation of the thermal expansion of the refractory materials at high temperatures

    Science.gov (United States)

    Kostanovskiy, A.; Kostanovskaya, M.; Zeodinov, M.; Pronkin, A.

    2017-11-01

    We present the experimental investigation of the relative elongation and the coefficient of linear thermal expansion for monocrystaline alumina Al2O3 (1200 K – 1860 K), zirconia ZrO2 (1200 K – 2730 K) and siliconized silicon carbide SiC+Si (1150 K – 2500 K) in the specified range of temperatures. The following approach is used to measure the relative elongation: the through-cylindrical-marks located in the centre of isothermal part of the sample, and the measurement of temperature by two blackbody models, taken out of the area of the sample where the relative elongation is measured.

  1. Novel Materials through Non-Hydrolytic Sol-Gel Processing: Negative Thermal Expansion Oxides and Beyond

    Directory of Open Access Journals (Sweden)

    Cora Lind

    2010-04-01

    Full Text Available Low temperature methods have been applied to the synthesis of many advanced materials. Non-hydrolytic sol-gel (NHSG processes offer an elegant route to stable and metastable phases at low temperatures. Excellent atomic level homogeneity gives access to polymorphs that are difficult or impossible to obtain by other methods. The NHSG approach is most commonly applied to the preparation of metal oxides, but can be easily extended to metal sulfides. Exploration of experimental variables allows control over product stoichiometry and crystal structure. This paper reviews the application of NHSG chemistry to the synthesis of negative thermal expansion oxides and selected metal sulfides.

  2. Frustrated Soft Modes and Negative Thermal Expansion in ZrW2O8

    Science.gov (United States)

    Cao, D.; Bridges, F.; Kowach, G. R.; Ramirez, A. P.

    2002-11-01

    Negative thermal expansion (NTE) in cubic ZrW2O8 has generated much interest due to its large, isotropic, and temperature independent behavior. Here, x-ray absorption fine structure data are presented for various atom pairs, providing evidence that the low-energy modes causing NTE correspond to the correlated vibrations of a WO4 tetrahedron and its three nearest ZrO6 octahedra. This involves translations of the WO4 as a rigid unit along each of the four axes. The interconnectivity of these modes prevents an anisotropic soft mode from developing, a new geometrical phenomenon that we call the ``frustrated soft mode.''

  3. Complex oxide with negative thermal expansion for producing ceramic matrix composites with invar effect

    Science.gov (United States)

    Dedova, Elena S.; Pertushina, Mariya U.; Kondratenko, Anton I.; Gorev, Mikhail V.; Kulkov, Sergei N.

    2016-11-01

    The article investigates the phase composition of (Al2O3-20 wt % ZrO2)-ZrW2O8 ceramic composites obtained by cold-pressing and sintering processes. Using X-ray analysis it has been shown that composites mainly have monoclinic modification of zirconium dioxide and orthorhombic phase of aluminum oxide. After adding zirconium tungstate the phase composition of sintered ceramics changes, followed by the formation of tungsten-aluminates spinel such as Alx(WOy)z. It has been shown that thermal expansion coefficient of material decreases approximatly by 30%, as compared with initial ceramics.

  4. Effect of Inclusion Morphology on the Coefficient of Thermal Expansion in Filled Epoxy Matrix (Preprint)

    Science.gov (United States)

    2006-04-01

    Aeronautics and Astronautics 6 F. Effect of Inclusion Shape on Effective CTE There has been tremendous interest in Zirconium Tungstate ( ZrW2O8 ), a ceramic...with a strongly negative coefficient of thermal expansion (CTE). In contrast to most other ceramics exhibiting negative CTE, the CTE of ZrW2O8 is...unusual properties suggest the incorporation of ZrW2O8 into a polymeric matrix, to create a composite with very low CTE. The objective of the

  5. Control of biaxial strain in single-layer Molybdenite using local thermal expansion of the substrate

    OpenAIRE

    Plechinger, G.; Castellanos-Gomez, A.; Buscema, M.; van der Zant, H. S. J.; Steele, G. A.; Kuc, A.; Heine, T; Schüller, C.; Korn, T.

    2015-01-01

    Single-layer MoS2 is a direct-gap semiconductor whose electronic band structure strongly depends on the strain applied to its crystal lattice. While uniaxial strain can be easily applied in a controlled way, e.g., by bending of a flexible substrate with the atomically thin MoS2 layer on top, experimental realization of biaxial strain is more challenging. Here, we exploit the large mismatch between the thermal expansion coefficients of MoS2 and a silicone-based substrate to apply a controllabl...

  6. Negative coefficient of thermal expansion in (epoxy resin)/(zirconium tungstate) nanocomposites

    Science.gov (United States)

    See, Erich; Kochergin, Vladimir; Neely, Lauren; Zayetnikov, Madrakhim; Ciovati, Gianluigi; Robinson, Hans

    2011-10-01

    The α-phase of zirconium tungstate (ZrW2O8) has the remarkable property that its coefficient of thermal expansion (CTE) takes on a nearly constant negative value throughout its entire range of thermal stability (0 -- 1050 K). Composites of ZrW2O8 nanoparticles and polymer resins have a reduced CTE compared to the pure polymer, but previous work has been restricted to measurements near room temperature. We show that the CTE of such composites can take on increasingly negative values as the temperature is lowered to cryogenic values. We used this phenomenon to fabricate a metal-free all-optical cryogenic temperature sensor by coating a fiber optic Bragg grating with the nanocomposite. This sensor has a sensitivity at 2 K that is at least six time better than any previous fiber-optic temperature sensor at this temperature.

  7. Internal Thermal Control System Hose Heat Transfer Fluid Thermal Expansion Evaluation Test Report

    Science.gov (United States)

    Wieland, P. O.; Hawk, H. D.

    2001-01-01

    During assembly of the International Space Station, the Internal Thermal Control Systems in adjacent modules are connected by jumper hoses referred to as integrated hose assemblies (IHAs). A test of an IHA has been performed at the Marshall Space Flight Center to determine whether the pressure in an IHA filled with heat transfer fluid would exceed the maximum design pressure when subjected to elevated temperatures (up to 60 C (140 F)) that may be experienced during storage or transportation. The results of the test show that the pressure in the IHA remains below 227 kPa (33 psia) (well below the 689 kPa (100 psia) maximum design pressure) even at a temperature of 71 C (160 F), with no indication of leakage or damage to the hose. Therefore, based on the results of this test, the IHA can safely be filled with coolant prior to launch. The test and results are documented in this Technical Memorandum.

  8. Bond thermal expansion and effective pair potential in crystals: the case of cadmium selenide.

    Science.gov (United States)

    Sanson, Andrea

    2011-08-10

    The local dynamics of cadmium selenide (CdSe) with wurtzite structure has been investigated by molecular dynamics simulations, using a many-body Tersoff potential. The radial distribution functions (i.e., the effective pair potentials) of the first seven coordination shells have been determined as a function of temperature, as well as their parallel and perpendicular mean-square relative atomic displacements. The bond thermal expansion of the first coordination shell is mainly due to the asymmetry of the effective pair potential. In contrast, the bond thermal expansion of the outer shells is mostly due to a rigid shift of the effective pair potential. This behavior, recently observed also in simple cubic monoatomic crystals, can be generalized and related to the correlation of atomic motion. Finally, a shift toward lower values of the first Se-Cd effective pair potential has been observed when increasing the temperature, confirming previous findings by extended x-ray absorption fine-structure measurements. Differently from superionic conductors like AgI and CuBr, in which this anomalous negative shift was tentatively explained by cluster distortion and cation diffusion, the negative shift of CdSe is related to the peculiar properties of the crystalline potential.

  9. A Micro-Test Structure for the Thermal Expansion Coefficient of Metal Materials

    Directory of Open Access Journals (Sweden)

    Qingying Ren

    2017-02-01

    Full Text Available An innovative micro-test structure for detecting the thermal expansion coefficient (TEC of metal materials is presented in this work. Throughout this method, a whole temperature sensing moveable structures are supported by four groups of cascaded chevrons beams and packed together. Thermal expansion of the metal material causes the deflection of the cascaded chevrons, which leads to the capacitance variation. By detecting the capacitance value at different temperatures, the TEC value of the metal materials can be calculated. A finite element model has been established to verify the relationship between the TEC of the material and the displacement of the structure on horizontal and vertical directions, thus a function of temperature for different values of TEC can be deduced. In order to verify the analytical model, a suspended-capacitive micro-test structure has been fabricated by MetalMUMPs process and tested in a climate chamber. Test results show that in the temperature range from 30 °C to 80 °C, the TEC of the test material is 13.4 × 10−6 °C−1 with a maximum relative error of 0.8% compared with the given curve of relationship between displacement and temperature.

  10. TEV—A Program for the Determination of the Thermal Expansion Tensor from Diffraction Data

    Directory of Open Access Journals (Sweden)

    Thomas Langreiter

    2015-02-01

    Full Text Available TEV (Thermal Expansion Visualizing is a user-friendly program for the calculation of the thermal expansion tensor αij from diffraction data. Unit cell parameters determined from temperature dependent data collections can be provided as input. An intuitive graphical user interface enables fitting of the evolution of individual lattice parameters to polynomials up to fifth order. Alternatively, polynomial representations obtained from other fitting programs or from the literature can be entered. The polynomials and their derivatives are employed for the calculation of the tensor components of αij in the infinitesimal limit. The tensor components, eigenvalues, eigenvectors and their angles with the crystallographic axes can be evaluated for individual temperatures or for temperature ranges. Values of the tensor in directions parallel to either [uvw]’s of the crystal lattice or vectors (hkl of reciprocal space can be calculated. Finally, the 3-D representation surface for the second rank tensor and pre- or user-defined 2-D sections can be plotted and saved in a bitmap format. TEV is written in JAVA. The distribution contains an EXE-file for Windows users and a system independent JAR-file for running the software under Linux and Mac OS X. The program can be downloaded from the following link: http://www.uibk.ac.at/mineralogie/downloads/TEV.html (Institute of Mineralogy and Petrography, University of Innsbruck, Innsbruck, Austria

  11. Bond thermal expansion and effective pair potential in crystals: the case of cadmium selenide

    Energy Technology Data Exchange (ETDEWEB)

    Sanson, Andrea, E-mail: andrea.sanson@unipd.it [Dipartimento di Fisica, Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy)

    2011-08-10

    The local dynamics of cadmium selenide (CdSe) with wurtzite structure has been investigated by molecular dynamics simulations, using a many-body Tersoff potential. The radial distribution functions (i.e., the effective pair potentials) of the first seven coordination shells have been determined as a function of temperature, as well as their parallel and perpendicular mean-square relative atomic displacements. The bond thermal expansion of the first coordination shell is mainly due to the asymmetry of the effective pair potential. In contrast, the bond thermal expansion of the outer shells is mostly due to a rigid shift of the effective pair potential. This behavior, recently observed also in simple cubic monoatomic crystals, can be generalized and related to the correlation of atomic motion. Finally, a shift toward lower values of the first Se-Cd effective pair potential has been observed when increasing the temperature, confirming previous findings by extended x-ray absorption fine-structure measurements. Differently from superionic conductors like AgI and CuBr, in which this anomalous negative shift was tentatively explained by cluster distortion and cation diffusion, the negative shift of CdSe is related to the peculiar properties of the crystalline potential.

  12. Matrix-filler interfaces and physical properties of metal matrix composites with negative thermal expansion manganese nitride

    Science.gov (United States)

    Takenaka, Koshi; Kuzuoka, Kota; Sugimoto, Norihiro

    2015-08-01

    Copper matrix composites containing antiperovskite manganese nitrides with negative thermal expansion (NTE) were formed using pulsed electric current sintering. Energy dispersive X-ray spectroscopy revealed that the chemically reacted region extends over 10 μm around the matrix-filler interfaces. The small-size filler was chemically deteriorated during formation of composites and it lost the NTE property. Therefore, we produced the composites using only the nitride particles having diameter larger than 50 μm. The large-size filler effectively suppressed the thermal expansion of copper and improved the conductivity of the composites to the level of pure aluminum. The present composites, having high thermal conductivity and low thermal expansion, are suitable for practical applications such as a heat radiation substrate for semiconductor devices.

  13. Matrix-filler interfaces and physical properties of metal matrix composites with negative thermal expansion manganese nitride

    Energy Technology Data Exchange (ETDEWEB)

    Takenaka, Koshi, E-mail: takenaka@nuap.nagoya-u.ac.jp [Department of Applied Physics, Nagoya University, Nagoya 464-8603 (Japan); Department of Crystalline Materials Science, Nagoya University, Nagoya 464-8603 (Japan); Kuzuoka, Kota [Department of Applied Physics, Nagoya University, Nagoya 464-8603 (Japan); Sugimoto, Norihiro [Department of Crystalline Materials Science, Nagoya University, Nagoya 464-8603 (Japan)

    2015-08-28

    Copper matrix composites containing antiperovskite manganese nitrides with negative thermal expansion (NTE) were formed using pulsed electric current sintering. Energy dispersive X-ray spectroscopy revealed that the chemically reacted region extends over 10 μm around the matrix–filler interfaces. The small-size filler was chemically deteriorated during formation of composites and it lost the NTE property. Therefore, we produced the composites using only the nitride particles having diameter larger than 50 μm. The large-size filler effectively suppressed the thermal expansion of copper and improved the conductivity of the composites to the level of pure aluminum. The present composites, having high thermal conductivity and low thermal expansion, are suitable for practical applications such as a heat radiation substrate for semiconductor devices.

  14. Studies of Expansive Learning: Foundations, Findings and Future Challenges

    Directory of Open Access Journals (Sweden)

    Yrjö Engeström

    2013-07-01

    Full Text Available The paper examines studies based on the theory of expansive learning, formulated in 1987. In recent years the theory has been used in a wide variety of studies and interventions. The theory builds on foundational ideas put forward by Vygotsky, Leont’ev, Il’enkov, and Davydov, key figures in the Russian school of cultural-historical activity theory. Studies based on the theory are reviewed in six sections: expansive learning as transformation of the object, expansive learning as movement in the zone of proximal development, expansive learning as cycles of learning actions, expansive learning as boundary crossing and network building, expansive learning as distributed and discontinuous movement, and formative interventions.A separate section is devoted to critiques of expansive learning. It is concluded that the ultimate test of learning theories is how they help practitioners to generate learning that grasps pressing issues the humankind is facing. The theory of expansive learning currently expands its analyses both up and down, outward and inward. Moving up and outward, it tackles learning in fields or networks of interconnected activity systems with their partially shared and often contested objects. Moving down and inward, it tackles issues of subjectivity, experiencing, personal sense, emotion, embodiment, identity, and moral commitment.

  15. Molecular modeling of nanotube composite materials: Interface formation, interfacial strength, and thermal expansion

    Science.gov (United States)

    Marietta-Tondin, Olivier

    present in this resin system, such as molecular wrapping around the SWNTs. Second, existing MD simulation models of nanotube pullout are analyzed and modified to examine the energy of certain material systems more correctly, and to characterize interfacial shear strength in SWNT/polymer composites. The interfacial bonding and load transfer behaviors between the different SWNTs' configurations (open end, capped end, functionalized end) and three different matrices (polystyrene, polyethylene and Epon862) were examined using the modified models. The results of the modified models effectively reveal the effects of different tube configurations and resin matrices on the interfacial strength during a simulated pullout. Finally, we use MD simulation to investigate the coefficient of thermal expansion (CTE) of individual SWNTs, SWNT ropes, as well as SWNT nanocomposites. Experiments were also carried out in order to gain further insight in the results. It is found that, while the CTE of individual nanotubes is of low negative value, the CTE of the same tubes within a rope or a nanocomposite can significantly change. We also find that SWNTs can be utilized to tailor the CTE of the Epon862 resin system, depending on the functionalization of the SWNTs prior to their introduction in the resin. Finally, a new twisting vibration mode was revealed in SWNT ropes that should prove critical in further SWNT rope studies utilizing MD simulation.

  16. Low-temperature abnormal thermal expansion property of Mn doped cubic NaZn13-type La(Fe, Al)13 compounds

    Science.gov (United States)

    Zhao, Yuqiang; Huang, Rongjin; Shan, Yi; Wang, Wei; Li, Jiangtao; Li, Laifeng

    2017-09-01

    Low-temperature abnormal thermal expansion (ATE) materials have been recently developed because of their significant applications for cryogenic engineering. However, the challenge still remains for the control of ATE effect at cryogenic temperature and adjustable ATE is of fundamental interest. In this paper, we report the isotropic ATE in La(Fe, Al)13 compounds over a wide adjusting temperature range by partially substituting Fe by Mn. It is found that all samples crystallize in the cubic NaZn13-type structure with the Fm\\bar{3}c space group. The introduction of nonmagnetic Mn atoms reduces the Fe-Fe exchange interaction, therefore, the itinerant electron system needs less energy to break the magnetic order in ferromagnetic (FM) state at low temperature. The negative thermal expansion (NTE) operation-temperature window moves towards lower temperatures accompanied with the decrease of Curie temperature (T C) by increasing Mn elements. Moreover, the composite combining Mn 0 and Mn 57 broadens the zero thermal expansion (ZTE) behavior occurring in the whole tested temperature range. The present studies could be useful to control the thermal expansion, and indicate the potential applications of ATE materials in cryogenic engineering.

  17. Composite Laminate With Coefficient of Thermal Expansion Matching D263 Glass

    Science.gov (United States)

    Robinson, David; Rodini, Benjamin

    2012-01-01

    The International X-ray Observatory project seeks to make an X-ray telescope assembly with 14,000 flexible glass segments. The glass used is commercially available SCHOTT D263 glass. Thermal expansion causes the mirror to distort out of alignment. A housing material is needed that has a matching coefficient of thermal expansion (CTE) so that when temperatures change in the X-ray mirror assembly, the glass and housing pieces expand equally, thus reducing or eliminating distortion. Desirable characteristics of this material include a high stiffness/weight ratio, and low density. Some metal alloys show promise in matching the CTE of D263 glass, but their density is high compared to aluminum, and their stiffness/weight ratio is not favorable. A laminate made from carbon fiber reinforced plastic (CFRP) should provide more favorable characteristics, but there has not been any made with the CTE matching D263 Glass. It is common to create CFRP laminates of various CTEs by stacking layers of prepreg material at various angles. However, the CTE of D263 glass is 6.3 ppm/ C at 20 C, which is quite high, and actually unachievable solely with carbon fiber and resin. A composite laminate has been developed that has a coefficient of thermal expansion identical to that of SCHOTT D263 glass. The laminate is made of a combination of T300 carbon fiber, Eglass, and RS3C resin. The laminate has 50% uni-T300 plies and 50% uni-E-glass plies, with each fiber-layer type laid up in a quasi-isotropic laminate for a total of 16 plies. The fiber volume (percent of fiber compared to the resin) controls the CTE to a great extent. Tests have confirmed that a fiber volume around 48% gives a CTE of 6.3 ppm/ C. This is a fairly simple composite laminate, following well established industry procedures. The unique feature of this laminate is a somewhat unusual combination of carbon fiber with E-glass (fiberglass). The advantage is that the resulting CTE comes out to 6.3 ppm/ C at 20 C, which matches D

  18. Implications of Thermal Diffusity being Inversely Proportional to Temperature Times Thermal Expansivity on Lower Mantle Heat Transport

    Science.gov (United States)

    Hofmeister, A.

    2010-12-01

    Many measurements and models of heat transport in lower mantle candidate phases contain systematic errors: (1) conventional methods of insulators involve thermal losses that are pressure (P) and temperature (T) dependent due to physical contact with metal thermocouples, (2) measurements frequently contain unwanted ballistic radiative transfer which hugely increases with T, (3) spectroscopic measurements of dense samples in diamond anvil cells involve strong refraction by which has not been accounted for in analyzing transmission data, (4) the role of grain boundary scattering in impeding heat and light transfer has largely been overlooked, and (5) essentially harmonic physical properties have been used to predict anharmonic behavior. Improving our understanding of the physics of heat transport requires accurate data, especially as a function of temperature, where anharmonicity is the key factor. My laboratory provides thermal diffusivity (D) at T from laser flash analysis, which lacks the above experimental errors. Measuring a plethora of chemical compositions in diverse dense structures (most recently, perovskites, B1, B2, and glasses) as a function of temperature provides a firm basis for understanding microscopic behavior. Given accurate measurements for all quantities: (1) D is inversely proportional to [T x alpha(T)] from ~0 K to melting, where alpha is thermal expansivity, and (2) the damped harmonic oscillator model matches measured D(T), using only two parameters (average infrared dielectric peak width and compressional velocity), both acquired at temperature. These discoveries pertain to the anharmonic aspects of heat transport. I have previously discussed the easily understood quasi-harmonic pressure dependence of D. Universal behavior makes application to the Earth straightforward: due to the stiffness and slow motions of the plates and interior, and present-day, slow planetary cooling rates, Earth can be approximated as being in quasi

  19. The P-T conditions of garnet inclusion formation in diamond: thermal expansion of synthetic end-member pyrope

    Science.gov (United States)

    Milani, Sula; Mazzucchelli, Matteo; Nestola, Fabrizio; Alvaro, Matteo; Angel, Ross J.; Geiger, Charles A.; Domeneghetti, Chiara

    2013-04-01

    Pyrope, Mg3Al2Si3O12, due to the abundance of garnet in Earths's upper mantle, has been studied many times. A number of different investigations have measured its physical and thermodynamic properties at high temperature or pressure and, even more recently, under simultaneous high P-T conditions (e.g. Zou et al., 2012). This abstract reports thermal expansion results on pyrope, as part of a much wider project on the determination of the physical properties of garnet, in order to obtain geobarometric information on the formation conditions of its inclusion in diamond. Our experimental approach is based on the elastic method (e.g. Izraeli et al., 1999; Howell et al., 2010; Nestola et al., 2011; Howell et al., 2012), which takes into account the thermoelastic properties of both diamond and any tiny solid phase inclusion within it. The method requires accurate and precise knowledge of thermal expansion and compressibility behavior in order to calculate precisely the pressure and temperature formation conditions of the diamond-inclusion pair. Thus, in order to do this, we measured the thermal expansion of an end-member synthetic single crystal of pyrope up to 1100 K at 52 different temperatures. This was done by measuring the ao unit-cell edge with high precision and accuracy under heating and cooling conditions. This allows excellent experimental reproducibility, which is also checked by monitoring any diffraction peak broadening over the entire range of temperatures. Fitting the temperature-volume data to the thermal expansion equation of Berman (1988), we obtained a room temperature volume-thermal expansion coefficient equal to 2.72(2)×10-5K-1. Using the same pyrope crystal, in situ high-pressure measurements are now in progress in order to determine its isothermal bulk modulus. The use of our results, along with the dK/dT data of Zou et al ( 2012), we plan to calculate the pressure of formation of diamonds containing pyrope-rich garnet inclusions. References Berman

  20. Vendor Capability for Low Thermal Expansion Mask Substrates for EUV Lithography

    Energy Technology Data Exchange (ETDEWEB)

    Blaedel, K L; Taylor, J S; Hector, S D; Yan, P Y; Ramamoorthy, A; Brooker, P D

    2002-04-12

    Development of manufacturing infrastructure is required to ensure a commercial source of mask substrates for the timely introduction of EUVL. Improvements to the low thermal expansion materials that compose the substrate have been made, but need to be scaled to production quantities. We have been evaluating three challenging substrate characteristics to determine the state of the infrastructure for the finishing of substrates. First, surface roughness is on track and little risk is associated with achieving the roughness requirement as an independent specification. Second, with new flatness-measuring equipment just coming on line, the vendors are poised for improvement toward the SEMI P37 flatness specification. Third, significant acceleration is needed in the reduction of defect levels on substrates. The lack of high-sensitivity defect metrology at the vendors' sites is limiting progress in developing substrates for EWL.

  1. Controlled thermal expansion printed wiring boards based on liquid crystal polymer dielectrics

    Science.gov (United States)

    Knoll, Thomas E.; Blizard, Kent; Jayaraj, K.; Rubin, Leslie S.

    1994-04-01

    Dielectric materials based on innovative Liquid Crystal Polymers (LCP's) have been used to fabricate surface mount printed wiring boards (PWB's) with a coefficient of thermal expansion matched to leadless ceramic chip carriers. Proprietary and patented polymer processing technology has resulted in self reinforcing material with balanced in-plane mechanical properties. In addition, LCP's possess excellent electrical properties, including a low dielectric constant (less than 2.9) and very low moisture absorption (less than 0.02%). LCP-based multilayer boards processed with conventional drilling and plating processes show improved performance over other materials because they eliminate the surface flatness problems of glass or aramid reinforcements. Laser drilling of blind vias in the LCP dielectric provides a very high density for use in direct chip attach and area array packages. The material is ideally suited for MCM-L and PCMCIA applications fabricated with very thin dielectric layers of the liquid crystal polymer.

  2. Local Vibrations and Negative Thermal Expansion in ZrW2O8

    Science.gov (United States)

    Bridges, F.; Keiber, T.; Juhas, P.; Billinge, S. J. L.; Sutton, L.; Wilde, J.; Kowach, Glen R.

    2014-01-01

    We present an x-ray pair distribution function (XPDF) analysis and extended x-ray absorption fine structure (EXAFS) data for ZrW2O8 (10-500 K) with a focus on the stiffness of the Zr-O-W linkage. The XPDF is highly sensitive to W-Zr and W-W correlations, but much less so to O-O or W-O correlations. The Zr-W peak in the XPDF data has a weak temperature dependence and, hence, this linkage is relatively stiff and does not permit bending of the Zr-O-W link. We propose that the low energy vibrational modes that lead to negative thermal expansion involve correlated rotations of ZrO6 octahedra that produce large ⟨111⟩ translations of the WO4 tetrahedra, rather than a transverse motion of O atoms that imply a flexible Zr-O-W linkage.

  3. Negative-thermal-expansion ZrW2O8. Elasticity and pressure

    Science.gov (United States)

    Pantea, Cristian; Migliori, Albert; Littlewood, Peter; Zhao, Yusheng; Ledbetter, Hassel; Lashley, Jason; Kimura, Tsuyoshi; van Duijn, Joost; Kowach, Glen

    2007-03-01

    The elasticity of the negative thermal expansion (NTE) compound ZrW2O8 is rather strange: the solid softens as its volume decreases on warming. Does ZrW2O8 also soften when pressure alone is applied? Using pulse-echo ultrasound in a large-volume moissanite anvil cell, we find an unusual decrease in bulk modulus with pressure at 300K. Our results are inconsistent with conventional lattice dynamics, but a framework-solid-based non-linear model with many degrees of freedom predicts elastic softening as increases in either temperature or pressure reduce volume. The pressure-induced phase transition from α-ZrW2O8 (cubic) to γ-ZrW2O8 (orthorhombic) is found to take place at 0.5 GPa, result confirmed by Raman spectroscopy.

  4. Negative thermal expansion and low-frequency modes in cyanide-bridged framework materials

    Science.gov (United States)

    Goodwin, Andrew L.; Kepert, Cameron J.

    2005-04-01

    We analyze the intrinsic geometric flexibility of framework structures incorporating linear metal-cyanide-metal (M-CN-M') linkages using a reciprocal-space dynamical matrix approach. We find that this structural motif is capable of imparting a significant negative thermal expansion (NTE) effect upon such materials. In particular, we show that the topologies of a number of simple cyanide-containing framework materials support a very large number of low-energy rigid-unit phonon modes, all of which give rise to NTE behavior. We support our analysis by presenting experimental verification of this behavior in the family of compounds ZnxCd1-x(CN)2 , which we show to exhibit a NTE effect over the temperature range 25-375K more than double that of materials such as ZrW2O8 .

  5. Measurement of phonon dispersion relation in negative thermal expansion compound ZrW2O8

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Pintschovius, L.; Achary, S. N.; Kowach, G. R.

    2007-12-01

    Isotropic negative thermal expansion (NTE) is found in cubic AX2O8(A = Zr, Hf: X=W, Mo) up to high temperatures (1050 K). Anharmonicity of low energy phonon modes plays an important role in leading to the NTE behaviour. Earlier we verified our predictions of large phonon softening for low energy phonons (below 8 meV) through high-pressure inelastic neutron scattering measurements on powder samples at ILL, France. Now we have measured the phonon dispersion relation from a single crystal of ZrW2O8. The measurements are useful to verify our prediction of highly anharmonic nature of specific phonon branches, in particular the transverse acoustic branch, and other branches up to 10 meV. These modes below 10 meV mainly contribute to the NTE in ZrW2O8.

  6. Acute plasma volume expansion alters cardiovascular but not thermal function during moderate intensity prolonged exercise.

    Science.gov (United States)

    Roy, B D; Green, H J; Grant, S M; Tarnopolsky, M A

    2000-03-01

    To investigate the hypothesis that the increase in plasma volume (PV) that typically occurs with training results in improved cardiovascular and thermal regulation during prolonged exercise, eight untrained males (V(O2)peak = 3.52 +/- 0.12 L x min(-1)) performed 90 min of cycle ergometry at 62% V(O2)peak before and after acute PV expansion. Subjects were infused with a PV-expanding solution (dextran (6%) or Pentaspan (10%)) equivalent to 6.7 mL x kg(-1) body mass (PVX) or acted as their own control (CON) in a randomized order. PVX resulted in a calculated 15.8% increase in resting PV, which relative to CON, was maintained throughout the exercise (P performance without affecting the thermoregulatory response to prolonged cycle exercise.

  7. 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

    that optimizes an objective function (e.g. thermoelastic properties) subject to certain constraints, such as elastic symmetry or volume fractions of the constituent phases, within a periodic base cell. The effective properties of the material structures are found using the numerical homogenization method based......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...... microstructures that realize the bounds. For three phases, the optimal microstructures are also compared with new rigorous bounds and again it is shown that the method yields designed materials with thermoelastic properties that are close to the bounds. The three-phase design method is illustrated by designing...

  8. Determination of Coefficient of Thermal Expansion (CTE) of 20MPa Mass Concrete Using Granite Aggregate

    Science.gov (United States)

    Chee Siang, GO

    2017-07-01

    Experimental test was carried out to determine the coefficient of thermal expansion (CTE) value of 20MPa mass concrete using granite aggregate. The CTE value was established using procedure proposed by Kada et al. 2002 in determining the magnitude of early-ages CTE through laboratory test which is a rather accurate way by eliminating any possible superimposed effect of others early-age thermal deformation shrinkages such as autogenous, carbonation, plastic and drying shrinkage. This was done by submitting granite concrete block samples instrumented with ST4 vibrating wire extensometers to thermal shocks. The response of the concrete samples to this shock results in a nearly instantaneous deformation, which are measured by the sensor. These deformations, as well as the temperature signal, are used to calculate the CTE. By repeating heat cycles, the variation in the early-ages of concrete CTE over time was monitored and assessed for a period of upto 7 days. The developed CTE value facilitating the verification and validation of actual maximum permissible critical temperature differential limit (rather than arbitrarily follow published value) of cracking potential. For thick sections, internal restraint is dominant and this is governed by differentials mainly. Of the required physical properties for thermal modelling, CTE is of paramount importance that with given appropriate internal restraint factor the condition of cracking due to internal restraint is governs by equation, ΔTmax= 3.663ɛctu / αc. Thus, it can be appreciated that an increase in CTE will lower the maximum allowable differential for cracking avoidance in mass concrete while an increase of tensile strain capacity will increase the maximum allowable temperature differential.

  9. New wrought Ni-based superalloys with low thermal expansion for 700C steam turbines

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, R.; Kadoya, Y. [Takasago Research and Development Center, Mitsubishi Heavy Industries, Ltd., Takasago, Hyogo (Japan); Kawai, H.; Magoshi, R. [Takasago Machinery Works, Mitsubishi Heavy Industries, Ltd., Takasago, Hyogo (Japan); Noda, T.; Hamano, S.; Ueta, S.; Isobe, S. [Research and Development Lab., Daido Steel Co., Ltd., Minamiku, Nagoya (Japan)

    2002-07-01

    Advanced 700C class steam turbines require austenitic alloys to replace conventional ferritic 12Cr steels, which lose creep strength and oxidation resistance above 650C. The austenitic alloys, however, possess a higher thermal expansion coefficient than ferritic 12Cr steels. Therefore, Ni-based superalloys were tailored to reduce their coefficients to the level of 12Cr steels. A regression analysis of commercial superalloys proves that Ti, Mo and Al decrease the coefficient quantitatively in this order, while Cr increases it so significantly that Cr should be limited to 12wt% to secure oxidation resistance. The newly designed Ni-18Mo-12Cr-1.1Ti-0.9Al alloy is strengthened by gamma-prime [Ni{sub 3}(Al,Ti)] and also Laves [Ni{sub 2}(Mo,Cr)] phase precipitates. It bears a RT/700C mean expansion coefficient equivalent to that of 12Cr steels and far lower than that of low-alloyed heat resistant steels. It surpasses a current turbine alloy, Refractaloy 26, in tensile strength at RT to 700C and SCC life in 330C deaerated pure water. Its creep rupture life at 700C is equivalent to that of Refractaloy 26. The developed alloy will be suitable for fasteners and/or blades in steam turbines at present and future USC power plants. (orig.)

  10. The Origin of Uni-axial Negative Thermal Expansion in a Layered Perovskite

    Science.gov (United States)

    Ablitt, Chris; Craddock, Sarah; Senn, Mark; Mostofi, Arash; Bristowe, Nicholas

    Using first-principles calculations within the quasi-harmonic approximation (QHA), we explain the origin of experimentally observed uni-axial negative thermal expansion (NTE) in a layered perovskite: the Ruddlesden-Popper (RP) oxide Ca2MnO4, which has anti-ferromagnetic ordering at low temperatures and is closely related to Ca3Mn2O7, which exhibits hybrid improper ferroelectricity and uni-axial NTE in competing phases. Dynamic tilts of MnO6 octahedra, common in many complex oxides, drive the expansion of the a axis and contraction of the c axis of the tetragonal NTE phase. We find that ferroelastic RP phases with a frozen octahedral rotation are unusually compliant to particular combinations of strains along different axes. The atomic mechanism responsible is characteristic of the perovskite/rock-salt interfaces present in the RP structure. We show that the contribution from this anisotropic elasticity must be taken into account in order to accurately predict NTE over the temperature range observed in experiment. A similar compliance to cooperative strains is found in other systems with uni-axial NTE. The development of this mechanistic understanding of NTE in complex oxides may pave the way for designing tunable multifunctional materials. The authors would like to acknowledge support from the EPSRC and the Centre for Doctoral Training in Theory and Simulation of Materials.

  11. Investigation of the Negative Thermal Expansion of ZrW2O8

    Science.gov (United States)

    Ulbrich, N.; Tröger, W.; Butz, T.; Blaha, P.

    2000-02-01

    The negative thermal expansion in ZrW2O8 was investigated on a microscopic scale by temperature dependent measurements of the electric field gradients at the nuclear probe 187W(β-) 187Re using time differential perturbed angular correlation spectroscopy. Two distinct nuclear quadrupole interactions I VzzRe1 l= 18.92(4) • 10 21 V/m2 , ηRe1 = 0.0 and I VzzRe1 l = 4.55(2) • 1021 V/m2 , ηRe1 = 0.053(3) were observed at 295 K, which are assigned to the two crystallographically distinct W0 4 tetrahedra of the room temperature structure. Ab initio calculations of electron densities and electric field gradients with 1:7 Re-impurities using the full potential linearized augmented plane wave package WIEN97 yield the electric field gradients VzzRe1 = 12.63 • 10 21 V/m2 , ηRe1 = 0.0 and VzzRe2 =4.90 • 10 21 V/m2 , ηRe2 =0.0. The observed temperature dependence of the nuclear quadrupole interactions agrees well with the structural phase transition at 428 K observed by neutron and x-ray diffraction. Our experiments corroborate the suggested mechanism of coupled librations of rigid ZrO6 octahedra and WO4 tetrahedra, which is an alternative description of transverse vibrations of oxygen atoms in Zr-O-W bonds, for the negative thermal expansion in ZrW2 O8

  12. The Thermal Expansion and Tensile Properties of Nanofiber-ZrW2O8 Reinforced Epoxy Resin Nanocomposites

    Science.gov (United States)

    Shan, Xinran; Huang, Chuanjun; Yang, Huihui; Wu, Zhixiong; Li, Jingwen; Huang, Rongjin; Li, Laifeng

    Zirconium tungstate/epoxy (ZrW2O8/EP) nanocomposites were prepared and their thermal expansion properties were investigated within the temperature range of 4-300 K. Compared to unmodified epoxy resin, zirconium tungstate/epoxy composites lowers the thermal expansion coefficient (CTEs). The tensile strength was investigated at room temperature (300 K) and liquid nitrogen temperature (77 K). The fracture surfaces were examined by scanning electron microscopy (SEM). Results showed that the tensile strength and elongation at break increases with the increasing ZrW2O8 content.

  13. Negative thermal expansion behavior in single crystal and ceramic of Nb{sub 2}O{sub 5}-based compositions.

    Energy Technology Data Exchange (ETDEWEB)

    Choosuwan, H.; Guo, R.; Bhalla, A. S.; Balachandran, U.; Energy Technology; Pennsylvania State Univ.

    2002-04-15

    The thermal expansion coefficients of a single crystal and ceramic of Nb{sub 2}O{sub 5} are measured in the temperature range of -200-500 C by the dilatometer technique. Both single crystals and ceramics of Nb{sub 2}O{sub 5} and Nb{sub 2}O{sub 5}(1-x):xTiO{sub 2} show negative thermal expansion in this temperature range. Some contribution to the result could be due to the presence of the Magneli phases. The main phase transition temperature, which also matches with the dielectric anomaly, occurs at {approx}150 C.

  14. A model to estimate volume change due to radiolytic gas bubbles and thermal expansion in solution reactors

    Energy Technology Data Exchange (ETDEWEB)

    Souto, F.J. [NIS-6: Advanced Nuclear Technology, Los Alamos National Lab., Los Alamos, NM (United States); Heger, A.S. [ESA-EA: Engineering Sciences and Application, Los Alamos National Lab., Los Alamos, NM (United States)

    2001-07-01

    To investigate the effects of radiolytic gas bubbles and thermal expansion on the steady-state operation of solution reactors at the power level required for the production of medical isotopes, a calculational model has been developed. To validate this model, including its principal hypotheses, specific experiments at the Los Alamos National Laboratory SHEBA uranyl fluoride solution reactor were conducted. The following sections describe radiolytic gas generation in solution reactors, the equations to estimate the fuel solution volume change due to radiolytic gas bubbles and thermal expansion, the experiments conducted at SHEBA, and the comparison of experimental results and model calculations. (author)

  15. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Science.gov (United States)

    Sekine, N.; Tada, S.; Higuchi, T.; Furumura, Y.; Takao, T.; Yamanaka, A.

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema® fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon® fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  16. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Energy Technology Data Exchange (ETDEWEB)

    Sekine, N. [Tsukamoto Laboratory, Faculty of Engineering, Yokohama National University, 79-5, Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan)]. E-mail: n-sekine@tsukalab.dnj.ynu.ac.jp; Tada, S. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Higuchi, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Furumura, Y. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Takao, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Yamanaka, A. [Research Center, Toyobo, Co., Ltd, 2-1-1, Katata, Otsu, Shiga 520-0292 (Japan)

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema[reg] fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon[reg] fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  17. Coprecipitation synthesis and negative thermal expansion of NbVO5.

    Science.gov (United States)

    Wang, Jinrui; Deng, Jinxia; Yu, Ranbo; Chen, Jun; Xing, Xianran

    2011-04-07

    We develop a coprecipitation synthesis route to prepare NbVO(5) with simple oxide Nb(2)O(5) and NH(4)VO(3) as starting materials. No metal alkoxide or organometallic substance was used in the process. Nano-crystal NbVO(5) was obtained by calcination of the coprecipitates at 550 °C for 2 h. DSC/TG and XRD investigations indicate that the target compound NbVO(5) is completely formed up to 504.5 °C and is thermally stable below 658 °C. Rietveld XRD refinements give an orthorhombic structure with space group Pnma and lattice parameters, a=11.8453(2), b=5.5126(3) and c=6.9212(2) Å, respectively. In particular, HTXRD determinations show a negative thermal expansion in NbVO(5) with a TEC of -6.63 × 10(-6) °C(-1) in the temperature range of RT-600 °C. This fact is ascribed to the tilting of NbO(6) octahedra and VO(4) tetrahedra in the flexible framework structure. The present synthesis route is facile and easy to be extended to prepare analogues such as TaVO(5), etc. © The Royal Society of Chemistry 2011

  18. Thermal expansion of the cryoprotectant cocktail DP6 combined with synthetic ice modulators in presence and absence of biological tissues.

    Science.gov (United States)

    Eisenberg, David P; Taylor, Michael J; Rabin, Yoed

    2012-10-01

    This study explores physical effects associated with the application of cryopreservation via vitrification using a class of compounds which are defined here as synthetic ice modulators (SIMs). The general classification of SIMs includes molecules that modulate ice nucleation and growth, or possess properties of stabilizing the amorphous state, by virtue of their chemical structure and at concentrations that are not explained on a purely colligative basis. A sub-category of SIMs, referred to in the literature as synthetic ice blockers (SIBs), are compounds that interact directly with ice nuclei or crystals to modify their structure and/or rate of growth. The current study is part of an ongoing effort to characterize thermo-mechanical effects during vitrification, with emphasis on measuring the physical property of thermal expansion-the driving mechanism to thermo-mechanical stress. Materials under investigation are the cryoprotective agent (CPA) cocktail DP6 in combination with one of the following SIMs: 12% polyethylene glycol 400, 6% 1,3 cyclohexanediol, and 6% 2,3 butanediol. Results are presented for the CPA-SIM cocktail in the absence and presence of bovine muscle and goat artery specimens. This study focuses on the upper part of the cryogenic temperature range, where the CPA behaves as a fluid for all practical applications. Results of this study indicate that the addition of SIMs to DP6 allows lower cooling rates to ensure vitrification and extends the range of measurements. It is demonstrated that the combination of SIM with DP6 increases the thermal expansion of the cocktail, with implications for the likelihood of fracture formation-the most dramatic outcome of thermo-mechanical stress. Copyright © 2012 Elsevier Inc. All rights reserved.

  19. Synthesis and thermal expansion hysteresis of Ca1–xSrxZr4P6O24

    Indian Academy of Sciences (India)

    Unknown

    and Roy 1984; Lenain et al 1984; Roy et al 1984), controlled lattice thermal expansion anisotropy (Oota and ... hexagonal lattice with structural holes that are partially or fully, depending upon the composition, occupied ..... Wurst J C and Nelson J A 1972 J. Am. Ceram. Soc. 55. 109. Yamai I and Ota T 1985 J. Am. Ceram.

  20. Thermal Expansion of ZrO2-ZrW2O8 Composites Prepared Using Co-Precipitation Route

    Science.gov (United States)

    Liu, Hongfei; Zhang, Zhiping; Cheng, Xiaonong; Yang, Juan

    In this work, a series of ZrO2/ZrW2O8 ceramic composites with different amounts of ZrW2O8 were successfully prepared by calcining the precursors synthesized using co-precipitation route at 1150°C for 3 h. The X-ray diffraction (XRD) data confirmed that the composites only consisted of α-ZrW2O8 phase and m-ZrO2 phase. The scanning electron microscopy (SEM) analysis of the synthesized ZrO2/ZrW2O8 composites showed that the specimens had good mixed-uniformities. In addition, the thermal expansion coefficients of the composites decreased with increased amounts of negative thermal expansion ZrW2O8, specimen with 26wt% ZrW2O8 shows almost zero thermal expansion and its average thermal expansion coefficient is -0.5897×10-6K-1 in the temperature range from 30°C to 600°C.

  1. First-Principles Mode Gruneisen Parameters and Negative Thermal Expansion in α-ZrW2O8

    Science.gov (United States)

    Gava, V.; Martinotto, A. L.; Perottoni, C. A.

    2012-11-01

    Mode Grüneisen parameters were estimated for α-ZrW2O8 zone-center modes by means of density functional theory calculations and the temperature dependence of the coefficient of thermal expansion was obtained according to the Debye-Einstein model of the quasiharmonic approximation. The lowest energy optic modes were identified at 45 and 46cm-1, and were shown to be the main modes responsible for negative thermal expansion at low temperature. Experimental evidence of the lowest energy, triply degenerated infrared active optic mode, was also found in the far infrared spectrum of α-ZrW2O8. Upon increasing temperature, other optic modes with E<25meV (particularly at 96, 100, 133, 161, and 164cm-1) also contribute significantly to the coefficient of thermal expansion near room temperature. An analysis was made of selected zone-center modes in light of previously proposed models for explaining negative thermal expansion in open framework materials.

  2. A MODEL TO ESTIMATE VOLUME CHANGE DUE TO RADIOLYTIC GAS BUBBLES AND THERMAL EXPANSION IN SOLUTION REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    F. SOUTO; A HEGER

    2001-02-01

    Aqueous homogeneous solution reactors have been proposed for the production of medical isotopes. However, the reactivity effects of fuel solution volume change, due to formation of radiolytic gas bubbles and thermal expansion, have to be mitigated to allow steady-state operation of solution reactors. The results of the free run experiments analyzed indicate that the proposed model to estimate the void volume due to radiolytic gas bubbles and thermal expansion in solution reactors can accurately describe the observed behavior during the experiments. This void volume due to radiolytic gas bubbles and fuel solution thermal expansion can then be used in the investigation of reactivity effects in fissile solutions. In addition, these experiments confirm that the radiolytic gas bubbles are formed at a higher temperature than the fuel solution temperature. These experiments also indicate that the mole-weighted average for the radiolytic gas bubbles in uranyl fluoride solutions is about 1 {micro}m. Finally, it should be noted that another model, currently under development, would simulate the power behavior during the transient given the initial fuel solution level and density. The model is based on Monte Carlo simulation with the MCNP computer code [Briesmeister, 1997] to obtain the reactor reactivity as a function of the fuel solution density, which, in turn, changes due to thermal expansion and radiolytic gas bubble formation.

  3. FEM Simulation of the Effect of Coefficient of Thermal Expansion and Heat Capacity on Prediction of Residual Stresses of Compression Molded Glass Lenses

    Science.gov (United States)

    Tao, Bo; Yuan, Ye

    2017-11-01

    In this research, the effects of the coefficient of thermal expansion (CTE) and heat capacity on the prediction of residual stresses in BK7 compression molded glass lenses were studied. Three different groups of CTE and two different kinds of heat capacity, which are constant and proportional to temperature, were chosen to investigate the impacts of residual stresses. The simulation results show a big difference and suggest that the properties of glass materials determine the residual stresses and should be measured carefully.

  4. TiO2 films annealing temperature-dependent properties in terms of the Amlouk-Boubaker opto-thermal expansivity ψAB

    Science.gov (United States)

    Amlouk, A.; Boubaker, K.; El Mir, L.; Amlouk, M.

    2011-02-01

    In this study, TiO2 films were grown at room temperature by sol-gel process using titanium (IV)-isopropylat as precursor. XRD, EDS and MEB analyses proved that an eventual annealing treatment caused the TiO2 amorphous phase to shift to a crystalline anatase phase. Optical measurements were carried out via absorbance spectra in 500-2500 nm wavelength domain. From these optical measurements, the temperature-dependent conjoint optical and thermal properties were deduced using the Amlouk-Boubaker opto-thermal expansivity ψAB.

  5. Structural investigation of the negative-thermal-expansion material ZrW2O8.

    Science.gov (United States)

    Evans; David; Sleight

    1999-06-01

    High-resolution powder diffraction data have been recorded on cubic ZrW(2)O(8) [a = 9.18000 (3) Å at 2 K] at 260 temperatures from 2 to 520 K in 2 K steps. These data have confirmed that alpha-ZrW(2)O(8) has a negative coefficient of thermal expansion, alpha = -9.07 x 10(-6) K(-1) (2-350 K). A 'parametric' approach to Rietveld refinement is adopted and it is demonstrated that a full anisotropic refinement can be performed at each temperature, despite using a data collection time of only 5 min. Examination of the resulting structural parameters suggests that the origin of the contraction with increasing temperature can be traced straightforwardly to the rigid-body transverse librations of bridging O atoms. alpha-ZrW(2)O(8) undergoes a phase transition from P2(1)3 to Pa3; at 448 K that is associated with the onset of considerable oxygen mobility. The phase transition can be described in terms of a simple cubic three-dimensional Ising model. Unusual kinetics are associated with this phase transition. Hysteresis in the cell parameter through the phase transition is the opposite of that normally observed.

  6. Control of biaxial strain in single-layer molybdenite using local thermal expansion of the substrate

    Science.gov (United States)

    Plechinger, Gerd; Castellanos-Gomez, Andres; Buscema, Michele; van der Zant, Herre S. J.; Steele, Gary A.; Kuc, Agnieszka; Heine, Thomas; Schüller, Christian; Korn, Tobias

    2015-03-01

    Single-layer MoS2 is a direct-gap semiconductor whose electronic band structure strongly depends on the strain applied to its crystal lattice. While uniaxial strain can be easily applied in a controlled way, e.g., by bending of a flexible substrate with the atomically thin MoS2 layer on top, experimental realization of biaxial strain is more challenging. Here, we exploit the large mismatch between the thermal expansion coefficients of MoS2 and a silicone-based substrate to apply a controllable biaxial tensile strain by heating the substrate with a focused laser. The effect of this biaxial strain is directly observable in optical spectroscopy as a redshift of the MoS2 photoluminescence. We also demonstrate the potential of this method to engineer more complex strain patterns by employing highly absorptive features on the substrate to achieve non-uniform heat profiles. By comparison of the observed redshift to strain-dependent band structure calculations, we estimate the biaxial strain applied by the silicone-based substrate to be up to 0.2%, corresponding to a band gap modulation of 105 meV per percentage of biaxial tensile strain.

  7. Giant negative thermal expansion covering room temperature in nanocrystalline GaNxMn3

    Science.gov (United States)

    Lin, J. C.; Tong, P.; Zhou, X. J.; Lin, H.; Ding, Y. W.; Bai, Y. X.; Chen, L.; Guo, X. G.; Yang, C.; Song, B.; Wu, Y.; Lin, S.; Song, W. H.; Sun, Y. P.

    2015-09-01

    Nanocrystalline antiperovskite GaNxMn3 powders were prepared by mechanically milling. The micrograin GaNxMn3 exhibits an abrupt volume contraction at the antiferromagnetic (AFM) to paramagnetic (PM) (AFM-PM) transition. The temperature window of volume contraction (ΔT) is broadened to 50 K as the average grain size (⟨D⟩) is reduced to ˜30 nm. The corresponding coefficient of linear thermal expansion (α) reaches ˜ -70 ppm/K, which are comparable to those of giant NTE materials. Further reducing ⟨D⟩ to ˜10 nm, ΔT exceeds 100 K and α remains as large as -30 ppm/K (-21 ppm/K) for x = 1.0 (x = 0.9). Excess atomic displacements together with the reduced structural coherence, revealed by high-energy X-ray pair distribution functions, are suggested to delay the AFM-PM transition. By controlling ⟨D⟩, giant NTE may also be achievable in other materials with large lattice contraction due to electronic or magnetic phase transitions.

  8. Thermal expansion and magnetostriction measurements on PrIr{sub 2}Zn{sub 20}

    Energy Technology Data Exchange (ETDEWEB)

    Woerl, Andreas; Stingl, Christian; Sakai, Akito; Gegenwart, Philipp [Experimentalphysics VI, Center for Electronic Correlations and Magnetism, University of Augsburg (Germany); Matsumoto, Keisuke T.; Onimaru, Takahiro [Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima (Japan); Takabatake, Toshiro [Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima (Japan); Institute for Advanced Materials Research, Hiroshima University, Higashi-Hiroshima (Japan)

    2016-07-01

    Strong hybridization between electric quadrupole moments and conduction electrons gives rise to interesting physical phenomena such as new quantum phases and novel metallic properties. Non-fermi-liquid behavior based on the two channel Kondo effect is predicted by theory. PrIr{sub 2}Zn{sub 20} crystallizes in the CeCr{sub 2}Al{sub 20}-type structure, where the Pr{sup 3+} ions are surrounded by the highly symmetric cubic crystal field of 16 Zn atoms. The ground state is the non-magnetic Γ{sub 3} doublet and carries only electric quadrupole and a magnetic octupole moment. At T{sub Q}=0.11 K the electric quadrupole moments order in a antiferroquadrupolar way. A superconducting transition occurs at T{sub c}=0.05 K. The phase transition at T{sub Q}=0.11 K can be suppressed by high magnetic fields parallel to the [100] direction. We investigate the thermal expansion and magnetostriction at low temperatures. By applying high magnetic fields the system is tuned towards a quadrupolar quantum critical point. Furthermore the reaction of the system on breaking the cubic symmetry by compressive stress is explored.

  9. Coefficient of Thermal Expansion of the Beta and Delta Polymorphs of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Weese, R K; Burnham, A K

    2005-01-11

    Dimensional changes related to temperature cycling of the {beta} and {delta} polymorphs of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are important for a variety of applications. The coefficient of thermal expansion (CTE) of the {beta} and {delta} phases are measured over a temperature range of -20 C to 215 C by thermo-mechanical analysis (TMA). Dimensional changes associated with the phase transition were also measured, and the time-temperature dependence of the dimensional change is consistent with phase transition kinetics measured earlier by differential scanning calorimetry (DSC). One HMX sample measured by TMA during its initial heating and again three days later during a second heating showed the {beta}-to-{delta} phase transition a second time, thereby indicating back conversion from {delta}-to-{beta} phase HMX during those three days. DSC was used to measure kinetics of the {delta}-to-{beta} back conversion. The most successful approach was to first heat the material to create the {delta} phase, then after a given period at room temperature, measure the heat absorbed during a second pass through the {beta}-to-{delta} phase transition. Back conversion at room temperature follows nucleation-growth kinetics.

  10. Coefficient of Thermal Expansion of the Beta and Delta Polymorphs of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Weese, R K; Burnham, A K; Maienschein, J L

    2004-08-05

    Dimensional changes related to temperature cycling of the beta and delta polymorphs of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are important for a variety of applications. The coefficient of thermal expansion (CTE) of the beta and delta phases are measured and reported in this work over a temperature range of -20 C to 215 C. In addition, dimensional changes associated with the phase transition were measured, both through the transition and back down. Initially, differential scanning calorimetry (DSC) was used to investigate back conversion of the delta phase to the beta phase polymorph. The most successful approach was first to measure the amount of the beta to delta conversion, then after a given cooling period a repeat analysis, to measure the heat consumed by a second pass through the beta to delta phase transition. In addition, TMA is used to measure the dimensional change of a 0.20-gram sample of HMX during its initial heating and then three days later during a 2nd heating. This HMX shows the beta to delta phase transition a second time, thereby confirming the back conversion from delta to beta phase HMX.

  11. Effects of cation substitution on thermal expansion and electrical properties of lanthanum chromites

    Energy Technology Data Exchange (ETDEWEB)

    Ding Xifeng [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu, 210009 (China); Liu Yingjia [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu, 210009 (China); Gao Ling [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu, 210009 (China); Guo Lucun [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu, 210009 (China)]. E-mail: lc-guo@163.com

    2006-11-30

    The effects of cation substitution on the sintering characteristics, thermal expansion and electrical conductivity properties of La(AE)Cr(M)O{sub 3} (AE=Mg, Ca, Sr, M=Ni, Cu, Co) were investigated. The sinterability of alkaline metal earth (AE)-doped LaCrO{sub 3} increased with AE contents in a sequence of Ca > Sr > Mg. Sr-doped LaCrO{sub 3} sample had a TEC compatible with that of 8YSZ electrolyte. The transition metals of Ni, Co and Cu substituted in Cr-site further optimized the sinterability of La{sub 0.85}Sr{sub 0.15}CrO{sub 3} in air. Ni and Co could effectively enhance the electrical conductivity from room temperature to 1123 K though the concomitant increase in TEC was distinctively large with Co doping. The TEC was controlled by co-doping Ni and Co in Cr-site, and La{sub 0.85}Sr{sub 0.15}Cr{sub 0.95}Ni{sub 0.02}Co{sub 0.02}O{sub 3} exhibited a TEC of 10.9 x 10{sup -6}/K, which was matched with that of 8YSZ, indicating that it could be suitable to be used as an SOFC interconnect material.

  12. Anisotropic properties of high-temperature polyimide thin films: Dielectric and thermal-expansion behaviors

    Science.gov (United States)

    Ree, M.; Chen, K.-J.; Kirby, D. P.; Katzenellenbogen, N.; Grischkowsky, D.

    1992-09-01

    Multilayer poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide films of 172 μm total thickness (11.4 μm per layer) were prepared from the poly(amic acid) precursor solution through repetition of a spin-coat/softbake/cure process. Wide-angle x-ray diffraction results indicate that the polyimide molecules in the multilayer films are highly ordered along the chain axes as well as in the lateral direction and furthermore are highly oriented in the film plane as observed in a single-layer film of 11.4 μm thickness. The multilayer films showed the same dynamic mechanical properties and glass transition behavior (Tg = 330 °C) as a single-layer film. For the multilayer films both the in-plane dielectric constant (ɛ'XY) and out-of-plane thermal-expansion coefficient (αZ) were measured using time-domain spectroscopy and conventional thermal mechanical analysis, respectively. The ɛ'XY at room temperature was 3.69 (±0.08) over a frequency range of 0.35-2.50 THz. A similar ɛ'XY is predicted at frequencies of ≤0.35 THz. In contrast to the ɛ'XY, a relatively lower out-of-plane dielectric constant (ɛ'Z) was observed: ɛ'Z = 2.96-3.03 (±0.02) at 1 MHz, depending on moisture content in the film. The dielectric loss ɛ`Z at 1 MHz was 0.011-0.014 (±0.001), depending on moisture content. The measured αZ was 74 ppm/°C over the temperature range of 25-150 °C, which was much higher than αXY = 2.6-5 ppm/°C. Consequently, large anisotropic ɛ' and α have been observed in the in plane and out of plane of the thermally imidized BPDA-PDA films. The anisotropic ɛ' and α were caused by high in-plane orientation of the polyimide molecules highly ordered along the chain axes in the films.

  13. Effects of thermal expansion of the crystal lattice on x-ray crystal spectrometers used for fusion research

    Science.gov (United States)

    Delgado-Aparicio, L.; Bitter, M.; Podpaly, Y.; Rice, J.; Burke, W.; Sanchez del Rio, M.; Beiersdorfer, P.; Bell, R.; Feder, R.; Gao, C.; Hill, K.; Johnson, D.; Lee, S. G.; Marmar, E.; Pablant, N.; Reinke, M. L.; Scott, S.; Wilson, R.

    2013-12-01

    X-ray imaging crystal spectrometers with high spectral and spatial resolution are currently being used on magnetically confined fusion devices to infer the time history profiles of ion and electron temperatures as well as plasma flow velocities. The absolute measurement of flow velocities is important for optimizing various discharge scenarios and evaluating the radial electric field in tokamak and stellarator plasmas. Recent studies indicate that the crystal temperature must be kept constant to within a fraction of a degree to avoid changes of the interplanar 2d-spacing by thermal expansion that cause changes in the Bragg angle, which could be misinterpreted as Doppler shifts. For the instrumental parameters of the x-ray crystal spectrometer on Alcator C-Mod, where those thermal effects were investigated, a change of the crystal temperature by 1 °C causes a change of the lattice spacing of the order of Δd = 1 × 10-5 Å introducing a fictitious velocity drift of the order of ˜3 km s-1. This effect must be considered for x-ray imaging crystals spectrometers installed on LHD, KSTAR, EAST, J-TEXT, NSTX and, in the future, W7-X and ITER.

  14. Non-adiabatic effects within a single thermally-averaged potential energy surface: Thermal expansion and reaction rates of small molecules

    CERN Document Server

    Alonso, J L; Clemente-Gallardo, J; Echenique, P; Mazo, J J; Polo, V; Rubio, A; Zueco, D

    2012-01-01

    At non-zero temperature and when a system has low-lying excited electronic states, the ground-state Born--Oppenheimer approximation breaks down and the low-lying electronic states are involved in any chemical process. In this work, we use a temperature-dependent effective potential for the nuclei which can accomodate the influence of an arbitrary number of electronic states in a simple way, while at the same time producing the correct Boltzmann equibrium distribution for the electronic part. With the help of this effective potential, we show that thermally-activated low-lying electronic states can have a significant effect in molecular properties for which electronic excitations are oftentimes ignored. We study the thermal expansion of the Manganese dimer, Mn$_2$, where we find that the average bond length experiences a change larger than the present experimental accuracy upon the inclusion of the excited states into the picture. We also show that, when these states are taken into account, reaction rate const...

  15. Carbon fiber-reinforced cyanate ester/nano-ZrW2O8 composites with tailored thermal expansion.

    Science.gov (United States)

    Badrinarayanan, Prashanth; Rogalski, Mark K; Kessler, Michael R

    2012-02-01

    Fiber-reinforced composites are widely used in the design and fabrication of a variety of high performance aerospace components. The mismatch in coefficient of thermal expansion (CTE) between the high CTE polymer matrix and low CTE fiber reinforcements in such composite systems can lead to dimensional instability and deterioration of material lifetimes due to development of residual thermal stresses. The magnitude of thermally induced residual stresses in fiber-reinforced composite systems can be minimized by replacement of conventional polymer matrices with a low CTE, polymer nanocomposite matrix. Zirconium tungstate (ZrW(2)O(8)) is a unique ceramic material that exhibits isotropic negative thermal expansion and has excellent potential as a filler for development of low CTE polymer nanocomposites. In this paper, we report the fabrication and thermal characterization of novel, multiscale, macro-nano hybrid composite laminates comprising bisphenol E cyanate ester (BECy)/ZrW(2)O(8) nanocomposite matrices reinforced with unidirectional carbon fibers. The results reveal that incorporation of nanoparticles facilitates a reduction in CTE of the composite systems, which in turn results in a reduction in panel warpage and curvature after the cure because of mitigation of thermally induced residual stresses.

  16. Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

    Science.gov (United States)

    Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

    2016-12-28

    Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

  17. Zero thermal expansion and ferromagnetism in cubic Sc(1-x)M(x)F3 (M = Ga, Fe) over a wide temperature range.

    Science.gov (United States)

    Hu, Lei; Chen, Jun; Fan, Longlong; Ren, Yang; Rong, Yangchun; Pan, Zhao; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

    2014-10-01

    The rare physical property of zero thermal expansion (ZTE) is intriguing because neither expansion nor contraction occurs with temperature fluctuations. Most ZTE, however, occurs below room temperature. It is a great challenge to achieve isotropic ZTE at high temperatures. Here we report the unconventional isotropic ZTE in the cubic (Sc1-xMx)F3 (M = Ga, Fe) over a wide temperature range (linear coefficient of thermal expansion (CTE), αl = 2.34 × 10(-7) K(-1), 300-900 K). Such a broad temperature range with a considerably negligible CTE has rarely been documented. The present ZTE property has been designed using the introduction of local distortions in the macroscopic cubic lattice by heterogeneous cation substitution for the Sc site. Even though the macroscopic crystallographic structure of (Sc0.85Ga0.05Fe0.1)F3 adheres to the cubic system (Pm3̅m) according to the results of X-ray diffraction, the local structure exhibits a slight rhombohedral distortion. This is confirmed by pair distribution function analysis of synchrotron radiation X-ray total scattering. This local distortion may weaken the contribution from the transverse thermal vibration of fluorine atoms to negative thermal expansion, and thus may presumably be responsible for the ZTE. In addition, the present ZTE compounds of (Sc1-xMx)F3 can be functionalized to exhibit high-Tc ferromagnetism and a narrow-gap semiconductor feature. The present study shows the possibility of obtaining ZTE materials with multifunctionality in future work.

  18. Origin of Negative Thermal Expansion in Cubic ZrW2O8 Revealed by High Pressure Inelastic Neutron Scattering

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Schober, H.; Mary, T. A.

    2001-05-01

    Isotropic negative thermal expansion has been reported in cubic ZrW2O8 over a wide range of temperatures (0-1050 K). Here we report the direct experimental determination of the Grüneisen parameters of phonon modes as a function of their energy, averaged over the whole Brillouin zone, by means of high pressure inelastic neutron scattering measurements. We observe a pronounced softening of the phonon spectrum at P = 1.7 kbar compared to that at ambient pressure by about 0.1-0.2 meV for phonons of energy below 8 meV. This unusual phonon softening on compression, corresponding to large negative Grüneisen parameters, is able to account for the observed large negative thermal expansion.

  19. Linear thermal expansion data for tuffs from the unsaturated zone at Yucca Mountain, Nevada; Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, B.M.; Chocas, C.S.

    1992-07-01

    Experiment results are presented for linear thermal expansion measurements on tuffaceous rocks from the unsaturated thermal expansion measurements could not be determined.

  20. An alternative empirical model for the relationship between the bond valence and the thermal expansion rate of chemical bonds.

    Science.gov (United States)

    Sidey, Vasyl

    2015-08-01

    The relationship between the bond valence s and the thermal expansion rate of chemical bonds (dr/dT) has been closely approximated by using the alternative three-parameter empirical model (dr/dT) = (u + vs)(-1/w), where u, v and w are the refinable parameters. Unlike the s-(dr/dT) model developed by Brown et al. [(1997), Acta Cryst. B53, 750-761], this alternative model can be optimized for particular s-(dr/dT) datasets in the least-squares refinement procedure. For routine calculations of the thermal expansion rates of chemical bonds, the alternative model with the parameters u = -63.9, v = 2581.0 and w = 0.647 can be recommended.

  1. End plate for e.g. solid oxide fuel cell stack, sets thermal expansion coefficient of material to predetermined value

    DEFF Research Database (Denmark)

    2011-01-01

    .05-0.3 mm. USE - End plate for solid oxide fuel cell stack (claimed). Can also be used in polymer electrolyte fuel cell stack and direct methanol fuel cell stack. ADVANTAGE - The robustness of the end plate is improved. The structure of the end plate is simplified. The risk of delamination of the stack......NOVELTY - The end plate is made of material whose thermal expansion coefficient is corresponding to that of material of a cell (103). The thermal expansion coefficient of material is 9asterisk10-6 K-1 to 14asterisk10-6 K11. The thickness of the end plate is within the range of 0.001-1 mm and 0...

  2. Effect of micro-cracking on the thermal conductivity and thermal expansion of tialite (Al2TiO5 ceramics

    Directory of Open Access Journals (Sweden)

    Ramanathan Papitha

    2013-09-01

    Full Text Available The pure and magnesium silicate (Mg2+/Si4+ doped tialite ceramics were prepared from the homogenized mixture of alumina and titania by uniaxial pressing and pressure-less sintering at 1550 °C in air. Thermal conductivity and thermal expansion of the doped and undoped tialite ceramics were measured from 30 to 700 °C. The identical trend in the behaviour of these thermal properties most probably is influenced by the population, size and shape of microcracks present throughout the grain and grain boundaries as complemented by the microstructural observations. The observed decrease in thermal properties of the doped in comparison to the pure tialite can be attributed to the substitutional Mg2+ and Si4+ at Al3+ site in Al2TiO5 which promotes the phonon scattering and causes modifications in micro-crack density and the morphology of the cracks.

  3. The infrared camera application for calculating the impact of the feed screw thermal expansion on machining accuracy

    Science.gov (United States)

    Matras, A.

    2017-08-01

    The paper discusses the impact of the feed screw heating on the machining accuracy. The test stand was built based on HASS Mini Mill 2 CNC milling machine and a Flir SC620 infrared camera. Measurements of workpiece were performed on Talysurf Intra 50 Taylor Hobson profilometer. The research proved that the intensive work of the milling machine lasted 60 minutes, causing thermal expansion of the feed screw what influence on the dimension error of the workpiece.

  4. Thermal expansion of LaFeAsO1-xFx: evidence for high temperature fluctuations

    NARCIS (Netherlands)

    Wang, L.; Köhler, U.; Leps, N.; Kondrat, A.; Nale, M.; Gasparini, A.; de Visser, A.; Behr, G.; Hess, C.; Klingeler, R.; Büchner, B.

    2009-01-01

    We present measurements of the thermal expansion coefficient α of polycrystalline LaFeAsO1−xFx (x≤0.1). The magnetic and structural transitions of the samples with x≤0.04 give rise to large anomalies in α(T) while the onset of superconductivity in the crystals with x≥0.05 is not resolved. Above the

  5. Determination of the coefficient of thermal expansion of jp-4 fuels. Interim report, April 1983-July 1985

    Energy Technology Data Exchange (ETDEWEB)

    Duvall, D.S.; Hale, M.D.; Lewis, D.J.; Snyder, A.D.

    1985-12-01

    Precise density determinations were made on 100 JP-4 jet fuels using a Mettler/Paar Model ADS-55 density-measuring system. Statistical analysis of the density measurements was performed using a computerized nonlinear regression technique; and coefficient of thermal expansion values were calculated for each fuel at 60 F. A majortiy of the fuels (88 out of 100) were consistent with the API published volume series correction for crude oils.

  6. Crystal structure, electrical conductivity and thermal expansion of Ni and Nb co-doped LaCoO3.

    Science.gov (United States)

    Øygarden, Vegar; Grande, Tor

    2013-02-28

    The effect of co-doping LaCoO(3) with Ni and Nb has been investigated in the two solid solution series (1 - x)LaCoO(3)-xLaNi(2/3)Nb(1/3)O(3) and (1 - y)LaCo(2/3)Ni(1/3)O(3)-yLaNi(2/3)Nb(1/3)O(3). The materials were shown to be stoichiometric with respect to oxygen. The compositional effect on the evolution of the crystal structure, thermal expansion and electrical conductivity is reported. The chemical stability of LaCoO(3) in a reducing atmosphere was improved and the thermal expansion was suppressed at higher levels of Nb-substitution. The materials with mixed oxidation states on the B-site possessed superior electrical transport properties compared to solid solutions with cations in mainly isovalent oxidation states. The evolution of the electronic conductivity, thermal expansion and crystal structural is discussed with emphasis on the oxidation states of Ni and Co, and the spin transitions of Co.

  7. Inelastic neutron scattering and lattice dynamical calculation of negative thermal expansion in HfW2O8

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Kolesnikov, A. I.; Loong, C.-K.; Mary, T. A.

    2003-08-01

    The compounds ZrW2O8 and HfW2O8 undergo large isotropic negative thermal expansion (NTE) over a wide range of temperatures up to 1443 K and 1050 K, respectively. We have showed previously that large softening of low-energy phonons in ZrW2O8 is responsible for its anomalous thermal expansion behavior. In order to understand the effect of replacing Zr by Hf on NTE behavior we report lattice dynamical calculations and neutron time-of-flight spectroscopic measurements of the phonon density of states for cubic HfW2O8. The calculated phonon spectrum for cubic HfW2O8 is in fair agreement with the experimental data. The phonon spectra in the Zr and Hf compounds differ at low energies largely due to the mass difference. The calculated negative thermal expansion for HfW2O8 is in good agreement with experimental data from the literature. We further report a calculation of the pressure dependence of the detailed phonon dispersion relation which reveals large softening of several phonon branches on compression associated with the NTE.

  8. Analysis of the Effect of Construction and Operation of Thermal Expansion System Compounds on Steam Turbines Reliability

    Science.gov (United States)

    Murmansky, B. E.; Sosnovsky, A. Yu.; Brodov, Yu. M.

    2017-11-01

    The inspection results are presented of turbines of different types and capacity, showing the influence of various factors (such as increased frictional forces on the mating surfaces, clearance changes in the joints elements, TES elements design, state of the thermal expansions compensation system of pipelines) on the operation both of thermal expansion system and of the turbine as a whole. The data are presented on the effectiveness of various measures aimed to eliminate the causes of the turbine thermal expansion system deviations from its normal operation. The results are shown of the influence simulation of various factors (such as flanges and piping warming, ratio of clearance changes in the elements) on the probability of turbine TES hindrance. It is shown that clearance ratios employed in most turbines do not provide the stability of turbine TES against the external action of connected pipes. The simulation results permit to explain the bearing housings turns observed during inspections, resulting in a jam on the longitudinal keys, in temperature distribution changes on the thrust bearing pads, and in some cases in false readings of instruments rotor axial displacement.

  9. MATERIALS THAT SHRINK ON HEATING: PRESSURE-INDUCED PHASE TRANSITIONS IN NEGATIVE THERMAL EXPANSION MATERIALS, AND THEIR ENERGETICS

    Energy Technology Data Exchange (ETDEWEB)

    Varga, Tamas

    2011-09-01

    Despite the fact that all chemical bonds expand on heating, a small class of materials shrinks when heated. These, so called negative thermal expansion (NTE) materials, are a unique class of materials with some exotic properties. The present chapter offers insight into the structural aspects of pressure- (or temperature-) induced phase transformations, and the energetics of those changes in these fascinating materials, in particular NTE compound cubic ZrW2O8, orthorhombic Sc2W3O12 and Sc2Mo3O12, as well as other members of the 'scandium tungstate family'. In subsequent sections, (i) combined in situ high-pressure synchrotron XRD and XAS studies of NTE material ZrW2O8; (ii) an in situ high-pressure synchrotron XRD study of Sc2W3O12, Sc2Mo3O12, and Al2W3O12; and (iii) thermochemical studies of the above materials are presented and discussed. In all of these studies, chemical bonds change, sometimes break and new ones form. Correlations between structure, chemistry, and energetics are revealed. It is also shown that (iv) NTE materials are good candidates as precursors to make novel solid state materials, such as the conducting Sc0.67WO4, using high-pressure, high-temperature synthesis, through modification of bonding and electronic structure, and thus provide vast opportunities for scientific exploration.

  10. Numerical study of laminar flow in a sudden expansion obstacled channel

    Directory of Open Access Journals (Sweden)

    Mushatet Khudheyer S.

    2015-01-01

    Full Text Available In the present work, a numerical study has been conducted to investigate the flow heat transfer through an obstacled sudden expansion channel. Rectangular adiabatic obstacles mounted behind the expansion region on the upper and lower wall of the channel used. The effects of obstacles length, obstacles thickness and number of obstacles on flow and thermal fields for different Reynolds number and expansion ratio examined. Three values of expansion ratio (ER equal to 1.5, 1.75 and 2 were used. The choice of values of Reynolds number takes in consideration the symmetry state. The governing equations of continuity, momentum and energy discretized by using the finite difference formulation and the resulting algebraic equations solved by using Gauss-Seidle iteration method. The obtained results show that the obstacles have a considerable effect on dynamics of the flow and enhancement of heat transfer. In addition, it is found that the heat transfer is enhanced more as the obstacles thickness increases and this trend is decreased as the obstacles length increases.

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

    National Research Council Canada - National Science Library

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

    2007-01-01

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

  12. Real-space distribution of local WO4 ordering in negative thermal expansive ZrW2O8.

    Science.gov (United States)

    Sato, Yukio; Yamamura, Yasuhisa; Saito, Kazuya; Ikuhara, Yuichi

    2012-08-29

    Solids usually expand when they are heated. This is quite common behavior of solids; however, there are some exceptions. Zirconium tungstate (ZrW(2)O(8)) is a prototype material among them, because it has the highest degree of negative thermal expansion (NTE) over broad temperature range. Intensive investigation of NTE mechanisms has suggested the importance of metal-oxygen polyhedra. However, most of the studies have been done with volume-averaged techniques, and microscopic information has been lacking. Here, our electron microscopy observations have unraveled the real-space distribution of local WO(4) tetrahedra ordering for the first time. We have found that (i) the WO(4) ordering is partly inverted; (ii) WO(4) is disordered on the nanoscale; and (iii) doping with scandium enhances the WO(4) disordering. These findings led to construction of a microstructure model for ZrW(2)O(8), providing a new structural perspective for better understanding of local structure and its role in phase transitions.

  13. An Ag based brazing system with a tunable thermal expansion for the use as sealant for solid oxide cells

    DEFF Research Database (Denmark)

    Kiebach, Wolff-Ragnar; Engelbrecht, Kurt; Grahl-Madsen, Laila

    2016-01-01

    An Ag-Al2TiO5 composite braze was developed and successfully tested as seal for solid oxide cells. The thermo-mechanical properties of the Ag-Al2TiO5 system and the chemical compatibility between this composite braze and relevant materials used in stacks were characterized and the leak rates...... as a function of the operation temperature were measured. The thermal expansion coefficient in the Ag-Al2TiO5 system can be tailored by varying the amount of the ceramic filler. The brazing process can be carried out in air, the joining partners showed a good chemical stability and sufficient low leak rates...... were demonstrated. Furthermore, the long-term stability of the Ag-Al2TiO5 composite braze was studied under relevant SOFC and SOEC conditions. The stability of brazed Crofer/Ag-Al2TiO5/NiO-YSZ assemblies in reducing atmosphere and in pure oxygen was investigated over 500 h at 850 °C. Additionally...

  14. The world's smallest capacitive dilatometer, for high-resolution thermal expansion and magnetostriction in high magnetic fields.

    Science.gov (United States)

    Küchler, R; Wörl, A; Gegenwart, P; Berben, M; Bryant, B; Wiedmann, S

    2017-08-01

    For the characterization of novel quantum phases of matter, it is often required to study materials under multi-extreme conditions, in particular down to very low temperatures and in very high magnetic fields. We developed the world's smallest high-resolution capacitive dilatometer suitable for temperatures down to 10 mK and usage in high magnetic fields up to 37.5 T. Despite the extreme miniaturization, the capacitive dilatometer can resolve length changes down to 0.01 Å. This is an unprecedented resolution in a capacitive dilatometer of this compact size. Many cryogenic devices have limited space. Due to the extremely reduced cell size (3 cm3, 12 g), implementation or new applications in many of these sample space lacking devices are now possible. As an important example, the minute device can now be rotated in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system. The present super compact design provides also for high resolution thermal expansion and magnetostriction measurements in a 15.2 mm diameter tube, enabling its use in the 32 mm bore, 37.5 T Bitter magnet at the High Field Magnet Laboratory in Nijmegen down to a temperature of 300 mK.

  15. Calcium pyroxenes at Mercurian surface temperatures: investigation of in-situ emissivity spectra and thermal expansion

    Science.gov (United States)

    Ferrari, S.; Nestola, F.; Helbert, J.; Maturilli, A.; D'Amore, M.; Alvaro, M.; Domeneghetti, M.; Massironi, M.; Hiesinger, H.

    2013-12-01

    The European Space Agency and Japan Aerospace Agency mission to Mercury, named BepiColombo, will carry on board the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) that will be able to provide surface Thermal Infra-Red (TIR) emissivity spectra from 7 to 14 μm. This range of wavelengths is very useful to identify the fine-scale structural properties of several silicates. For mineral families as pyroxenes, the emissivity peak positions are good indicators of the composition. A complication in the interpretation of MERTIS data could arise from the extreme daily surface temperature range of Mercury (70 to 725 K) that significantly affects the crystal structure and density of minerals and consequently should affect the TIR spectral signature of each single mineral present on the surface of the planet. In preparation for the MERTIS data analysis, we are extensively investigating at high temperatures conditions several mineral phases potentially detectable on the surface of Mercury. Two C2/c augitic pyroxenes, with constant calcium content and very different magnesium to iron ratio, were studied by in situ high-temperature thermal infrared spectroscopy (up to 750 K) and in situ high-temperature single-crystal X-ray diffraction (up to 770 K). The emissivity spectra of the two samples show similar band center shifts of the main three bands toward lower wavenumbers with increasing temperature. Our results indicate that the center position of bands 1 and 2 is strictly dependent on temperature, whereas the center position of band 3 is a strong function of the composition regardless the temperature. These data suggest that MERTIS spectra will be able to provide indications of C2/c augitic pyroxene with different magnesium contents and will allow a correct interpretation independently on the spectra acquisition temperature.

  16. Study on durability for thermal cycle of planar SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Ando, Motoo; Nakata, Kei-ichi; Wakayama, Sin-ichi [Tonen Corp., Saitama (Japan)] [and others

    1996-12-31

    TONEN CORPORATION has developed planar type SOFC since 1986. We demonstrated the output of 1.3 kW in 1991 and 5.1 kW in 1995. Simultaneously we have studied how to raise electric efficiency and reliability utilizing hydrogen and propane as fuel. Durability for thermal cycle is one of the most important problems of planar SOFC to make it more practical. The planar type SOFC is made up of separator, zirconia electrolyte and glass sealant. The thermal expansion of these components are expected to be the same value, however, they still possess small differences. In this situation, a thermal cycle causes a thermal stress due to the difference of the cell components and is often followed by a rupture in cell components, therefore, the analysis of the thermal stress should give us much useful information. The thermal cycle process consists of a heating up and cooling down procedure. Zirconia electrolyte is not bonded to the separator under the condition of the initial heating up procedure, and glass sealant becomes soft or melts and glass seals spaces between the zirconia and separator. The glass sealant becomes harder with the cooling down procedure. Moreover, zirconia is tightly bonded with separator below a temperature which is defined as a constraint temperature and thermal stress also occurs. This indicates that the heating up process relaxes the thermal stress and the cooling down increases it. In this paper, we simulated dependence of the stress on the sealing configuration, thermal expansion of sealant and constraint temperature of sealant glass. Furthermore, we presented SOFC electrical properties after a thermal cycle.

  17. Mode Grüneisen parameters and negative thermal expansion of cubic ZrW2O8 and ZrMo2O8

    Science.gov (United States)

    Wang, Kai; Reeber, Robert R.

    2000-04-01

    Thermal expansion for ZrW2O8 and ZrMo2O8 is analyzed by a multifrequency Einstein model. Vibrational modes that contribute significantly to the thermal expansion are empirically identified. For ZrW2O8, a negative Grüneisen parameter mode is consistent with the observed Raman spectral peak of 40 cm-1. Experimental confirmation of the results is proposed.

  18. Shape forming by thermal expansion mismatch and shape memory locking in polymer/elastomer laminates

    Science.gov (United States)

    Yuan, Chao; Ding, Zhen; Wang, T. J.; Dunn, Martin L.; Qi, H. Jerry

    2017-10-01

    This paper studies a novel method to fabricate three-dimensional (3D) structure from 2D thermo-responsive shape memory polymer (SMP)/elastomer bilayer laminate. In this method, the shape change is actuated by the thermal mismatch strain between the SMP and the elastomer layers upon heating. However, the glass transition behavior of the SMP locks the material into a new 3D shape that is stable even upon cooling. Therefore, the second shape becomes a new permanent shape of the laminate. A theoretical model that accounts for the temperature-dependent thermomechanical behavior of the SMP material and thermal mismatch strain between the two layers is developed to better understand the underlying physics. Model predictions and experiments show good agreement and indicate that the theoretical model can well predict the bending behavior of the bilayer laminate. The model is then used in the optimal design of geometrical configuration and material selection. The latter also illustrates the requirement of thermomechanical behaviors of the SMP to lock the shape. Based on the fundamental understandings, several self-folding structures are demonstrated by the bilayer laminate design.

  19. An anisotropic linear thermo-viscoelastic constitutive law - Elastic relaxation and thermal expansion creep in the time domain

    Science.gov (United States)

    Pettermann, Heinz E.; DeSimone, Antonio

    2017-09-01

    A constitutive material law for linear thermo-viscoelasticity in the time domain is presented. The time-dependent relaxation formulation is given for full anisotropy, i.e., both the elastic and the viscous properties are anisotropic. Thereby, each element of the relaxation tensor is described by its own and independent Prony series expansion. Exceeding common viscoelasticity, time-dependent thermal expansion relaxation/creep is treated as inherent material behavior. The pertinent equations are derived and an incremental, implicit time integration scheme is presented. The developments are implemented into an implicit FEM software for orthotropic material symmetry under plane stress assumption. Even if this is a reduced problem, all essential features are present and allow for the entire verification and validation of the approach. Various simulations on isotropic and orthotropic problems are carried out to demonstrate the material behavior under investigation.

  20. Laser ablation in CdZnTe crystal due to thermal self-focusing: Secondary phase hydrodynamic expansion

    Energy Technology Data Exchange (ETDEWEB)

    Medvid’, A., E-mail: mychko@latnet.lv [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia); Mychko, A.; Dauksta, E. [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia); Kosyak, V. [Sumy State University, 2, Rymskogo-Korsakova St., 40007 Sumy (Ukraine); Grase, L. [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia)

    2016-06-30

    Highlights: • We found two laser induced threshold intensity for CdZnTe crystal. • The laser beam self-focusing lead to increase of intensity of laser radiation at exit surface. • Laser ablation is a result of Te inclusion hydrodynamic expansion. - Abstract: The present paper deals with the laser ablation in CdZnTe crystal irradiated by pulsed infrared laser. Two values of threshold intensities of the laser ablation were determined, namely of about 8.5 and 6.2 MW/cm{sup 2} for the incident and the rear surfaces, correspondingly. Lower intensity of the laser ablation for the rear surface is explained by thermal self-focusing of the laser beam in the CdZnTe crystal due to heating of Te inclusions with a following hydrodynamic expansion.

  1. High pressure studies of A{sub 2}Mo{sub 3}O{sub 12} negative thermal expansion materials (A{sub 2}=Al{sub 2}, Fe{sub 2}, FeAl, AlGa)

    Energy Technology Data Exchange (ETDEWEB)

    Young, Lindsay; Gadient, Jennifer; Gao, Xiaodong; Lind, Cora, E-mail: cora.lind@utoledo.edu

    2016-05-15

    High pressure powder X-ray diffraction studies of several A{sub 2}Mo{sub 3}O{sub 12} materials (A{sub 2}=Al{sub 2}, Fe{sub 2}, FeAl, and AlGa) were conducted up to 6–7 GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversible on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga{sub 2}Mo{sub 3}O{sub 12} suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations. - Graphical abstract: Overlay of variable pressure X-ray diffraction data of Al{sub 2}Mo{sub 3}O{sub 12} collected in a diamond anvil cell. Both subtle and discontinuous phase transitions are clearly observed. - Highlights: • The high pressure behavior of A{sub 2}Mo{sub 3}O{sub 12} (A=Al, Fe, (AlGa), (AlFe)) was studied. • All compounds undergo the same sequence of pressure-induced phase transitions. • The phase transition pressures correlate with the average size of the A-site cation. • All transitions were reversible with hysteresis. • Previously studied Ga{sub 2}Mo{sub 3}O{sub 12} undergoes the same sequence of transitions.

  2. Thermal expansion and specific heat of a superior IR-SOFC cathode material Sr1-xCexCoO3-δ

    Science.gov (United States)

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2017-05-01

    We present the specific heat (Cv) and thermal expansion (α) of lightly doped Sr1-xCexCoO3-δ (x=0.0-0.15) using Modified Rigid Ion Model (MRIM) and a novel atomistic approach of Atom in Molecules(AIM) theory. We partial replaced the A-site Strontium cation by other element (Cerium) of different size, valence and mass. The effect of Cerium doping on lattice specific heat (Cv)lat, thermal expansion(α) of Sr1-xCexCoO3-δ (x = 0.0-0.15) as a function of temperature (20K≤T≤ 1000K) is reported probably for the first time. The results indicate better thermal compatibility of Sr0.95Ce0.05CoO3 with Samaria doped Ceria (SDC) electrolyte than other studied compounds. The Debye temperature of these perovskite material as cathode for Intermediate Range Solid Oxide Fuel Cell (IR-SOFC) is also predicted.

  3. Magnetic structure and local lattice distortion in giant negative thermal expansion material Mn{sub 3}Cu{sub 1-x}Ge{sub x}N

    Energy Technology Data Exchange (ETDEWEB)

    Iikubo, S; Kodama, K; Takenaka, K; Takagi, H; Shamoto, S, E-mail: iikubo@life.kyutech.ac.jp

    2010-11-01

    Magnetic and local structures in an antiperovskite system, Mn{sub 3}Cu{sub 1-x}Ge{sub x}N, with a giant negative thermal expansion have been studied by neutron powder diffraction measurement. We discuss (1) an importance of an averaged cubic crystal structure and a {Gamma}G{sup 5g} antiferromagnetic spin structure for the large magneto-volume effect (MVE) in this itinerant electron system, (2) an unique role of a local lattice distortion well described by the low temperature tetragonal structure of Mn{sub 3}GeN for the broadening of MVE.

  4. Preparation and properties of negative thermal expansion zirconium tungstate thin films deposited by radio frequency magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hong-Fei; Cheng, Xiao-Nong; Zhang, Zhi-Ping [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China)

    2008-11-15

    Zirconium tungstate (ZrW{sub 2}O{sub 8}) thin films were deposited on quartz substrates by radio frequency magnetron sputtering followed by annealing at various temperatures. The effects of post-deposition annealing temperature on the phase, morphology and negative thermal expansion properties of the ZrW{sub 2}O{sub 8} thin films were investigated. X-ray diffraction data confirmed that the as-deposited ZrW{sub 2}O{sub 8} films were amorphous, and crystalline ZrW{sub 2}O{sub 8} films could be obtained at high annealing temperature. Trigonal ZrW{sub 2}O{sub 8} films could be prepared at 740 C and cubic ZrW{sub 2}O{sub 8} films could be prepared at 1200 C. The surface morphologies of the ZrW{sub 2}O{sub 8} thin films were evaluated using scanning electron microscopy. The results indicated that amorphous ZrW{sub 2}O{sub 8} films were uniform and dense, and the grain size of the crystalline ZrW{sub 2}O{sub 8} films became larger with increasing annealing temperature. The resulting cubic ZrW{sub 2}O{sub 8} films showed negative thermal expansion, the average value of thermal expansion coefficient being -8.18 x 10{sup -6} K{sup -1} in the temperature range 15-700 C. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Surgically assisted maxillary expansion in adults: prospective study.

    Science.gov (United States)

    de Freitas, R R; Gonçalves, A J; Moniz, N J; Maciel, F A

    2008-09-01

    The purpose of this research was to carry out a prospective clinical study of patients with transverse maxillary deficiency, orthopaedically expanded after minimum osteotomies of the zygomatic pillars and the median palatine suture, with quantitative assessment of the stability of the transverse dimensions of the maxilla. The distance between the superior canines and the first superior molars was measured six times during the clinical experiment. The desired expansion was achieved by 15 days postoperatively for all patients. After one year of follow-up, clinical measurements showed a relapse rate of 23% in the superior canine area and 18% in the superior first molar area.

  6. Thermal expansion measurements by x-ray scattering and breakdown of Ehrenfest's relation in alloy liquids

    Energy Technology Data Exchange (ETDEWEB)

    Gangopadhyay, A. K.; Blodgett, M. E.; Johnson, M. L.; Vogt, A. J.; Mauro, N. A.; Kelton, K. F. [Department of Physics and Institute of Materials Science and Engineering, Washington University in St. Louis, St. Louis, Missouri 63130 (United States)

    2014-05-12

    Measurements of sharp diffraction peaks as a function of temperature are routinely used to obtain precise linear expansion coefficients of crystalline solids. In this case, the relation between temperature dependent changes in peak position in momentum transfer (q{sub 1}) and volume expansion is straightforward (Ehrenfest's relation: q{sub 1} = K(2π/d), where K is a constant and d is the interatomic spacing) and the data obtained are usually in close agreement with more direct measurements. With high intensity synchrotron x-ray and spallation neutron sources, it is also possible to accurately measure the positions of the much broader peaks for liquids and glasses. This has led to a debate on whether linear expansion coefficients derived from these data are an accurate representation of the volume expansion coefficients. We present here volume thermal expansion and x-ray diffraction data for a large number of glass-forming alloy liquids acquired in a containerless environment using the beamline electrostatic levitation technique. The data show a large difference in the values obtained from the two different techniques. Moreover, the position of the first peak (q{sub 1}) in the scattered intensity in the structure factor (S(q)) and the atomic volume v for all liquids follow a simple relationship, v∝(q{sub 1}){sup −ε}. The exponent, ε = 2.28 (±0.11), is much different from the expected value of 3 from Ehrenfest's relation and shows no temperature dependence over the temperature range of the data collected.

  7. Magnetic transition broadening and local lattice distortion in the negative thermal expansion antiperovskite Cu1-xSnxNMn3

    Science.gov (United States)

    Tong, P.; Louca, Despina; King, Graham; Llobet, Anna; Lin, J. C.; Sun, Y. P.

    2013-01-01

    The local distortion indicated by the split of the Cu/Sn-Mn bonds for the negative thermal expansion (NTE) materials Cu1-xSnxNMn3 (x = 0.1 and 0.5) was observed using neutron pair distribution function. The distribution of Cu/Sn-Mn bonds upon Sn doping is suggested to be attributable to the fluctuation in the hybridization of Mn d with Sn p orbitals. Accordingly, the antiferromagnetic (AFM) coupling mediated by the p-d hybridization fluctuates in strength. Consequently, the AFM transition closely coupled with the volume change is broadened, leading to the NTE.

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

    Science.gov (United States)

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

    2015-01-01

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

  9. Analysis of thermal expansivity of iron (Fe) metal at ultra high ...

    Indian Academy of Sciences (India)

    Abstract. In the present investigation we have explained the thermal and compression properties of HCP iron (Fe) at high pressure with variable temperature (isobars) and at high temperature with variable pressure (isotherm). The usual Tait equation of state is modified by incorporating the effect of thermal pressure.

  10. Seal accommodating thermal expansion between adjacent casings in gas turbine engine

    Science.gov (United States)

    Marra, John J. (Inventor)

    1992-01-01

    A casing around a turbine and a casing around discharge nozzles have a concentrically arranged shell portion. The seal contains internal pressure while accommodating eccentric, expansion and axial travel. Arcuate seal segments have one leg sealing against a radial surface extending from the inner shell and the other leg against the outer shell. A linkage guides travel of the segments.

  11. Hybrid Composites from Wheat Straw, Inorganic Filler, and Recycled Polypropylene: Morphology and Mechanical and Thermal Expansion Performance

    Directory of Open Access Journals (Sweden)

    Min Yu

    2016-01-01

    Full Text Available Reinforcing effect of hybrid filler including wheat straw (WS and inorganic filler (heavy calcium carbonate, silicon dioxide, and fly ash in recycled polypropylene (R-PP has been investigated. The effects of individual filler (WS and combined fillers (WS and inorganic filler on morphological, mechanical, and thermal expansion and water absorption properties of hybrid composites were investigated. The flexural modulus and flexural strength were both reduced when reinforced with three kinds of inorganic fillers, respectively, which was possibly due to the poor interphase adhesion as observed in SEM. The high surface energy of heavy calcium carbonate due to its high acidic character provides an opportunity of better PP-heavy calcium carbonate interfacial interactions compared to PP-straw, PP-fly ash, and PP-SiO2 interface. The water absorption at saturation increased markedly by introduction of WS in it. The hybrid composites from WS and inorganic fillers showed better water absorption compared to those WS/PP composites. The thermal expansion of composites decreased with the increase of WS loading. Heavy calcium and SiO2 can obviously reduce the LCTE value of composite. At the 25% inorganic filler content, composites had the smallest LCTE values.

  12. An Investigation of the Thermal Expansion Coefficient for Resin Concrete with ZrW2O8

    Directory of Open Access Journals (Sweden)

    Kuangzhe Lin

    2015-08-01

    Full Text Available This paper presents a novel resin concrete obtained by adding cubic zirconium tungstate (ZrW2O8 as filler. A prediction algorithm on the thermal expansion coefficient (CTE of resin concrete (including filler was established on the basis of the meso-mechanics method and a three-phase model for concrete. The concept of twice mixing was also proposed for prediction accuracy. Then, a 2D and 3D irregular polygon aggregate particles packing model was set up by Matlab and the properties of the packing model were simulated by finite element analysis. Finally, resin concrete samples were made and their CTE were measured. Mix proportion and addition of ZrW2O8 as influencing factors were considered in this experiment. The CTE of resin concrete was verified by comparing results of the prediction model, simulation model and experiment. The optimum CTE obtained from the experiment was 1.504 × 10−6/K. Compared with 6.817 × 10−6/K without ZrW2O8, it was found that the addition of ZrW2O8 to resin concrete can make it perform significantly better in thermal expansion.

  13. New Nanocomposite Materials with Improved Mechanical Strength and Tailored Coefficient of Thermal Expansion for Electro-Packaging Applications

    Directory of Open Access Journals (Sweden)

    Abdollah Saboori

    2017-12-01

    Full Text Available In this research, copper nanocomposites reinforced by graphene nanoplatelets (GNPs were fabricated using a wet mixing method followed by a classical powder metallurgy route. In order to find the best dispersion technique, ball milling and wet mixing were chosen. Qualitative evaluation of the structure of the graphene after mixing indicated that the wet mixing is an appropriate technique to disperse the GNPs. Thereafter, the influence of graphene content on microstructure, density, hardness, elastic modulus, and thermal expansion coefficient of composites was investigated. It was shown that by increasing the graphene content the aggregation of graphene is more obvious and, thus, these agglomerates affect the final properties adversely. In comparison with the unreinforced Cu, Cu–GNP composites were lighter, and their hardness and Young’s modulus were higher as a consequence of graphene addition. According to the microstructural observation of pure copper and its composites after sintering, it was concluded that grain refinement is the main mechanism of strengthening in this research. Apart from the mechanical characteristics, the coefficient of thermal expansion of composites decreased remarkably and the combination of this feature with appropriate mechanical properties can make them a promising candidate for use in electronic packaging applications.

  14. ZrW2O8-doped epoxy as low thermal expansion insulating materials for superconducting feeder system

    Science.gov (United States)

    Chu, Xinxin; Wu, Zhixiong; Huang, Chuanjun; Huang, Rongjin; Zhou, Yuan; Li, Laifeng

    2012-12-01

    Epoxy resin insulating materials used in superconducting feeder system of fusion device are required to be low thermal expansion coefficient (TEC). In this paper, negative thermal expansion (NTE) material ZrW2O8 filled epoxy resins were fabricated. To improve the dispersion of fillers in epoxy matrix, plasma polymerization was performed on the surface of ZrW2O8 powders. Transmission electron microscope (TEM) and surface wettability analysis were performed before and after the surface modification of ZrW2O8 powders. The TEC of ZrW2O8/epoxy composites were measured from 77 K to room temperature. The results show the doping of ZrW2O8 can significantly reduce the TEC of epoxy resins. The sedimentation rate of ZrW2O8 before and after modified in epoxy was compared by density measurement. It can be seen that the ZrW2O8 surface modified by plasma polymerization can enhance its dispersion properties in epoxy matrix.

  15. Spin-glass-like behavior and negative thermal expansion in antiperovskite Mn3Ni1-xCuxN compounds

    Science.gov (United States)

    Ding, Lei; Wang, Cong; Sun, Ying; Colin, Claire V.; Chu, Lihua

    2015-06-01

    The Cu-doping effect on the lattice and magnetic properties in Mn3Ni1-xCuxN (x = 0, 0.3, 0.5, 0.7, 1.0) was extensively investigated. We observed that the Cu-doping at the Ni site complicated the magnetic ground states, which induced the competition of antiferromagnetic and ferromagnetic interactions. Spin-glass-like behavior, arising from possible site-randomness and competing interactions of magnetism, was observed in compounds with x = 0.3, 0.5, and 0.7, and typically discussed by means of the measurement of ac magnetic susceptibility for x = 0.7. The negative thermal expansion (NTE) behavior, due to the magnetic ordering transition, was observed in Mn3Ni1-xCuxN compounds using variable temperature x-ray diffraction. It reveals that the introduction of Cu effectively broadens the temperature range displaying negative thermal expansion. The relationship between the local lattice distortion and the competing magnetic ground states might play an important role in broadening the NTE temperature range in this antiperovskite compound.

  16. Density and anomalous thermal expansion of deeply cooled water confined in mesoporous silica investigated by synchrotron X-ray diffraction.

    Science.gov (United States)

    Liu, Kao-Hsiang; Zhang, Yang; Lee, Jey-Jau; Chen, Chia-Cheng; Yeh, Yi-Qi; Chen, Sow-Hsin; Mou, Chung-Yuan

    2013-08-14

    A synchrotron X-ray diffraction method was used to measure the average density of water (H2O) confined in mesoporous silica materials MCM-41-S-15 and MCM-41-S-24. The average density versus temperature at atmospheric pressure of deeply cooled water is obtained by monitoring the intensity change of the MCM-41-S Bragg peaks, which is directly related to the scattering length density contrast between the silica matrix and the confined water. Within MCM-41-S-15, the pore size is small enough to prevent the crystallization at least down to 130 K. Besides the well-known density maximum at 277 K, a density minimum is observed at 200 K for the confined water, below which a regular thermal expansion behavior is restored. Within MCM-41-S-24 of larger pore size, water freezes at 220.5 K. The average water/ice density measurement in MCM-41-S-24 validated the diffraction method. The anomalous thermal expansion coefficient (αp) is calculated. The temperature at which the αp reaches maximum is found to be pore size independent, but the peak height of the αp maximum is linearly dependent on the pore size. The obtained data are critical to verify available theoretical and computational models of water.

  17. Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients

    Science.gov (United States)

    Aktas, Guliz; Sahin, Erdal; Vallittu, Pekka; Özcan, Mutlu; Lassila, Lippo

    2013-01-01

    This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients (TECs), when zirconia ceramics were coloured at green stage. Zirconia blocks (N=240; 6 mm×7 mm×7 mm) were manufactured from two materials namely, ICE Zirconia (Group 1) and Prettau Zirconia (Group 2). In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid (shade A2). Three different veneering ceramics with different TEC (ICE Ceramic, GC Initial Zr and IPS e.max Ceram) were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys (Esteticor Plus) veneered with ceramic (VM 13) (n=16) acted as the control group. Core–veneer interface of the specimens were subjected to shear force in the Universal Testing Machine (0.5 mm⋅min−1). Neither the zirconia core material (P=0.318) nor colouring (P=0.188) significantly affected the results (three-way analysis of variance, Tukey's test). But the results were significantly affected by the veneering ceramic (P=0.000). Control group exhibited significantly higher mean bond strength values (45.7±8) MPa than all other tested groups ((27.1±4.1)−(39.7±4.7) and (27.4±5.6)−(35.9±4.7) MPa with and without colouring, respectively) (Pzirconia–veneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering 1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core–veneer adhesion. Metal–ceramic adhesion was more reliable than all zirconia–veneer ceramics tested. PMID:24158142

  18. An Ag based brazing system with a tunable thermal expansion for the use as sealant for solid oxide cells

    Science.gov (United States)

    Kiebach, Ragnar; Engelbrecht, Kurt; Grahl-Madsen, Laila; Sieborg, Bertil; Chen, Ming; Hjelm, Johan; Norrman, Kion; Chatzichristodoulou, Christodoulos; Hendriksen, Peter Vang

    2016-05-01

    An Ag-Al2TiO5 composite braze was developed and successfully tested as seal for solid oxide cells. The thermo-mechanical properties of the Ag-Al2TiO5 system and the chemical compatibility between this composite braze and relevant materials used in stacks were characterized and the leak rates as a function of the operation temperature were measured. The thermal expansion coefficient in the Ag-Al2TiO5 system can be tailored by varying the amount of the ceramic filler. The brazing process can be carried out in air, the joining partners showed a good chemical stability and sufficient low leak rates were demonstrated. Furthermore, the long-term stability of the Ag-Al2TiO5 composite braze was studied under relevant SOFC and SOEC conditions. The stability of brazed Crofer/Ag-Al2TiO5/NiO-YSZ assemblies in reducing atmosphere and in pure oxygen was investigated over 500 h at 850 °C. Additionally, a cell component test was performed to investigate the durability of the Ag-Al2TiO5 seal when exposed to dual atmosphere. The seals performed well over 900 h under electrolysis operation conditions (-0.5 A cm2, 850 °C), and no cell degradation related to the Ag-Al2TiO5 sealing was found, indicating that the developed braze system is applicable for the use in SOFC/SOEC stacks.

  19. Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients.

    Science.gov (United States)

    Aktas, Guliz; Sahin, Erdal; Vallittu, Pekka; Ozcan, Mutlu; Lassila, Lippo

    2013-12-01

    This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients (TECs), when zirconia ceramics were coloured at green stage. Zirconia blocks (N=240; 6 mm×7 mm×7 mm) were manufactured from two materials namely, ICE Zirconia (Group 1) and Prettau Zirconia (Group 2). In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid (shade A2). Three different veneering ceramics with different TEC (ICE Ceramic, GC Initial Zr and IPS e.max Ceram) were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys (Esteticor Plus) veneered with ceramic (VM 13) (n=16) acted as the control group. Core-veneer interface of the specimens were subjected to shear force in the Universal Testing Machine (0.5 mm⋅min(-1)). Neither the zirconia core material (P=0.318) nor colouring (P=0.188) significantly affected the results (three-way analysis of variance, Tukey's test). But the results were significantly affected by the veneering ceramic (P=0.000). Control group exhibited significantly higher mean bond strength values (45.7±8) MPa than all other tested groups ((27.1±4.1)-(39.7±4.7) and (27.4±5.6)-(35.9±4.7) MPa with and without colouring, respectively) (Pveneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering veneering ceramic was left adhered >1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core-veneer adhesion. Metal-ceramic adhesion was more reliable than all zirconia-veneer ceramics tested.

  20. Influence of thermal expansion mismatch on residual stress profile in veneering ceramic layered on zirconia: Measurement by hole-drilling.

    Science.gov (United States)

    Mainjot, Amélie K; Najjar, Achref; Jakubowicz-Kohen, Boris D; Sadoun, Michaël J

    2015-09-01

    Mismatch in thermal expansion coefficient between core and veneering ceramic (Δα=αcore-αveneer, ppm/°C) is reported as a crucial parameter influencing veneer fractures with Yttria-tetragonal-zirconia-polycrystal (Y-TZP) prostheses, which still constitutes a misunderstood problem. However, the common positive Δα concept remains empirical. The objective of this study is to investigate the Δα dependence of residual stress profiles in veneering ceramic layered on Y-TZP frameworks. The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 0.7mm thick Y-TZP framework and a 1.5mm thick veneer layer. 3 commercial and 4 experimental veneering ceramics (n=3 per group) were used to obtain different Δα varying from -1.3ppm/°C to +3.2ppm/°C, which were determined by dilatometric analyses. Veneer fractures were observed in samples with Δα≥+2.3 or ≤-0.3ppm/°C. Residual stress profiles measured in other groups showed compressive stresses in the surface, these stresses decreasing with depth and then becoming more compressive again near the interface. Small Δα variations were shown to induce significant changes in residual stress profiles. Compressive stress near the framework was found to decrease inversely to Δα. Veneer CTE close to Y-TZP (+0.2ppm/°C Δα) gived the most favorable stress profile. Yet, near the framework, Δα-induced residual stress varied inversely to predictions. This could be explained by the hypothesis of structural changes occurrence within the Y-TZP surface. Consequently, the optimum Δα value cannot be determined before understanding Y-TZP's particular behavior when veneered. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  1. Optical temperature sensor and thermal expansion measurement using a femtosecond micromachined grating in 6H-SiC.

    Science.gov (United States)

    DesAutels, G Logan; Powers, Peter; Brewer, Chris; Walker, Mark; Burky, Mark; Anderson, Gregg

    2008-07-20

    An optical temperature sensor was created using a femtosecond micromachined diffraction grating inside transparent bulk 6H-SiC, and to the best of our knowledge, this is a novel technique of measuring temperature. Other methods of measuring temperature using fiber Bragg gratings have been devised by other groups such as Zhang and Kahrizi [in MEMS, NANO, and Smart Systems (IEEE, 2005)]. This temperature sensor was, to the best of our knowledge, also used for a novel method of measuring the linear and nonlinear coefficients of the thermal expansion of transparent and nontransparent materials by means of the grating first-order diffracted beam. Furthermore the coefficient of thermal expansion of 6H-SiC was measured using this new technique. A He-Ne laser beam was used with the SiC grating to produce a first-order diffracted beam where the change in deflection height was measured as a function of temperature. The grating was micromachined with a 20 microm spacing and has dimensions of approximately 500 microm x 500 microm (l x w) and is roughly 0.5 microm deep into the 6H-SiC bulk. A minimum temperature of 26.7 degrees C and a maximum temperature of 399 degrees C were measured, which gives a DeltaT of 372.3 degrees C. The sensitivity of the technique is DeltaT=5 degrees C. A maximum deflection angle of 1.81 degrees was measured in the first-order diffracted beam. The trend of the deflection with increasing temperature is a nonlinear polynomial of the second-order. This optical SiC thermal sensor has many high-temperature electronic applications such as aircraft turbine and gas tank monitoring for commercial and military applications.

  2. Using Charged Particle Imaging to Study Ultracold Plasma Expansion

    Science.gov (United States)

    Zhang, X. L.; Fletcher, R. S.; Rolston, S. L.

    2009-03-01

    We develop a projection imaging technique to study ultracold plasma dynamics. We image the charged particle spatial distributions by extraction with a high-voltage pulse onto a position-sensitive detector. Measuring the 2D width of the ion image at later times (the ion image size in the first 20 μs is dominated by the Coulomb explosion of the dense ion cloud), we extract the plasma expansion velocity. These velocities at different initial electron temperatures match earlier results obtained by measuring the plasma oscillation frequency. The electron image size slowly decreases during the plasma lifetime because of the strong Coulomb force of the ion cloud on the electrons, electron loss and Coulomb explosion effects.

  3. Effects of waste eggshells and SiC addition on specific strength and thermal expansion of hybrid green metal matrix composite.

    Science.gov (United States)

    Sharma, Satpal; Dwivedi, Shashi Prakash

    2017-07-05

    Chicken eggshell waste is an industrial byproduct, and its disposal constitutes a serious environmental hazard. Chicken eggshell can be used in commercial products to produce new materials with low cost and density. Low density material which can sustain at higher temperature is a remarkable area of research. Keeping these facts in the mind, the present investigation aims to study the physical behaviour, specific strength and thermal expansion of AA2014/SiC/carbonized eggshell hybrid green metal matrix composites. Microstructure of hybrid green metal matrix shows that the reinforcement particles (SiC particulates and carbonized eggshells particles) are uniformly distributed in the matrix AA2014 alloy. Specific strength for the composites containing 2.5wt.% SiC and up to 7.5wt.% carbonized eggshell was observed to be higher than that of the other selected composites. While for the same composition (AA2014/2.5% SiC/7.5% carbonized eggshell composites), porosity was observed lower than other selected composites. The results revealed that sample of AA2014/2.5% SiC/7.5% carbonized eggshell showed minimum cross sectional area reduction after the thermal expansion at 450°C among all the selected samples. Overall costs of hybrid metal matrix composites were also calculated. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Spatial variability in the coefficient of thermal expansion induces pre-service stresses in computer models of virgin Gilsocarbon bricks

    Energy Technology Data Exchange (ETDEWEB)

    Arregui-Mena, José David, E-mail: jose.arreguimena@postgrad.manchester.ac.uk [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Margetts, Lee, E-mail: lee.margetts@manchester.ac.uk [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Griffiths, D.V., E-mail: d.v.griffiths@mines.edu [Colorado School of Mines, 1500 Illinois St, Golden, CO 80401 (United States); Lever, Louise, E-mail: louise.lever@manchester.ac.uk [Research Computing, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Hall, Graham, E-mail: graham.n.hall@manchester.ac.uk [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Mummery, Paul M., E-mail: paul.m.mummery@manchester.ac.uk [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2015-10-15

    In this paper, the authors test the hypothesis that tiny spatial variations in material properties may lead to significant pre-service stresses in virgin graphite bricks. To do this, they have customised ParaFEM, an open source parallel finite element package, adding support for stochastic thermo-mechanical analysis using the Monte Carlo Simulation method. For an Advanced Gas-cooled Reactor brick, three heating cases have been examined: a uniform temperature change; a uniform temperature gradient applied through the thickness of the brick and a simulated temperature profile from an operating reactor. Results are compared for mean and stochastic properties. These show that, for the proof-of-concept analyses carried out, the pre-service von Mises stress is around twenty times higher when spatial variability of material properties is introduced. The paper demonstrates that thermal gradients coupled with material incompatibilities may be important in the generation of stress in nuclear graphite reactor bricks. Tiny spatial variations in coefficient of thermal expansion (CTE) and Young's modulus can lead to the presence of thermal stresses in bricks that are free to expand. - Highlights: • Open source software has been modified to include random variability in CTE and Young's modulus. • The new software closely agrees with analytical solutions and commercial software. • Spatial variations in CTE and Young's modulus produce stresses that do not occur with mean values. • Material variability may induce pre-service stress in virgin graphite.

  5. Influence of sodalite zeolite infiltration on the coefficient of thermal expansion and bond strength of all-ceramic dental prostheses.

    Science.gov (United States)

    Naji, Ghassan Abdul-Hamid; Omar, Ros Anita; Yahya, Rosiyah

    2017-03-01

    In all-ceramic systems, a high incidence of veneer chip-off has been reported in clinical studies. Coefficient of thermal expansion (CTE) behaviour is one of the factors that may increase residual stress in the interface and influence the veneer/core bond strength. Therefore, this study aimed to evaluate the effect of sodalite zeolite-infiltration on the CTE behaviour and bond strength of different all-ceramic prostheses. The case-study groups were synthesized sodalite zeolite-infiltrated alumina (IA-SOD) and synthesized sodalite zeolite-infiltrated zirconia-toughened alumina (ZTA) (IZ-SOD), while the control groups were glass-infiltrated alumina (IA-glass) and glass-infiltrated ZTA (IZ-glass). Forty cylindrical-shaped samples measuring 5 mm in diameter and 10 mm in height were tested for CTE using a thermo-mechanical analyser machine, and forty disc-shaped ceramic samples measuring 12 mm in diameter and 1.2 ± 0.2 mm in thickness were prepared using specially designed stainless steel split mould and veneered by cylinder-shaped (2 mm high × 2 mm diameter) low-fusing porcelain (Vita VM7). The veneer/core samples were sintered and tested for shear bond strength using a high precision universal testing machine. Scanning electron microscope, stereo microscope, atomic force microscope, and energy-dispersive X-ray spectroscopy were used to investigate the structural characteristics of samples at the fracture surface. The collected data were analyzed with a one-way ANOVA and Tukey HSD test (α=.05). IZ-SOD revealed highest CTE and shear bond strength values, while the IA-glass revealed the lowest values than the other groups. There was no significant difference in CTE and bond strength among IZ-SOD, IA-SOD and IZ-glass samples (p>0.05). The experimental SOD zeolite-infiltrated samples revealed higher CTE mismatch and bond strength along with a more favourable mode of failure than did the commercial glass-infiltrated samples. Sandblast technique is considered as effective

  6. Negative Thermal Expansion in ZrW2O8: Mechanisms, Rigid Unit Modes, and Neutron Total Scattering

    Science.gov (United States)

    Tucker, Matthew G.; Goodwin, Andrew L.; Dove, Martin T.; Keen, David A.; Wells, Stephen A.; Evans, John S. O.

    2005-12-01

    The local structure of the low-temperature ordered phase of the negative thermal expansion (NTE) material ZrW2O8 has been investigated by reverse Monte Carlo (RMC) modeling of neutron total scattering data. We obtain, for the first time, quantitative measurements of the extent to which the WO4 and ZrO6 polyhedra move as rigid units, and we show that these values are consistent with the predictions of rigid unit mode theory. We suggest that rigid unit modes are associated with the NTE. Our results do not support a recent interpretation of x-ray-absorption fine structure spectroscopy data in terms of a larger rigid structural component involving the Zr-O-W linkage.

  7. Local lattice distortion in the giant negative thermal expansion material Mn3Cu1-xGexN.

    Science.gov (United States)

    Iikubo, S; Kodama, K; Takenaka, K; Takagi, H; Takigawa, M; Shamoto, S

    2008-11-14

    Giant negative thermal expansion is achieved in antiperovskite manganese nitrides when the sharp volume change associated with magnetic ordering is broadened by substitution. In this Letter, we address the unique role of the ''magic" element, Ge, for such broadening in Mn3Cu1-xGexN. We present evidence for a local lattice distortion well described by the low-temperature tetragonal (T4) structure of Mn3GeN for a range of x, where the overall structure remains cubic. This structural instability shows a strong correlation with the broadness of the growth of the ordered magnetic moment and, hence, is considered to trigger the broadening of the volume change.

  8. The evolution of magnetic transitions, negative thermal expansion and unusual electronic transport properties in Mn3AgxMnyN

    Science.gov (United States)

    Deng, Sihao; Sun, Ying; Yan, Jun; Shi, Zaixing; Shi, Kewen; Wang, Lei; Hu, Pengwei; Malik, Muhammad Imran; Wang, Cong

    2015-11-01

    The antiperovskite compounds Mn3AgxMnyN with Ag vacancies and Mn doping at Ag site were synthesized and investigated. The introduction of Ag vacancies has a very small influence on magnetic transitions. However, the magnetic transitions at TN (Néel temperature) and Tt (transition at lower temperature) gradually overlap with Mn doping accompanied by broadening of negative thermal expansion behavior. We also observed the nearly zero temperature coefficient of resistivity (NZ-TCR) behavior above magnetic order-disorder transition. The tunable TCR values from positive to negative could be achieved in Mn3AgxMnyN by reducing the contribution of (electron-phonon) e-p scattering in resistivity. Our results reveal the significance of e-p scattering for the evolution of TCR values, which could enrich the understanding of NZ-TCR behavior in antiperovskite manganese nitrides.

  9. An Adaptive Neuro-Fuzzy Inference System for Sea Level Prediction Considering Tide-Generating Forces and Oceanic Thermal Expansion

    Directory of Open Access Journals (Sweden)

    Li-Ching Lin Hsien-Kuo Chang

    2008-01-01

    Full Text Available The paper presents an adaptive neuro fuzzy inference system for predicting sea level considering tide-generating forces and oceanic thermal expansion assuming a model of sea level dependence on sea surface temperature. The proposed model named TGFT-FN (Tide-Generating Forces considering sea surface Temperature and Fuzzy Neuro-network system is applied to predict tides at five tide gauge sites located in Taiwan and has the root mean square of error of about 7.3 - 15.0 cm. The capability of TGFT-FN model is superior in sea level prediction than the previous TGF-NN model developed by Chang and Lin (2006 that considers the tide-generating forces only. The TGFT-FN model is employed to train and predict the sea level of Hua-Lien station, and is also appropriate for the same prediction at the tide gauge sites next to Hua-Lien station.

  10. Geographic Expansion Strategic Model in Iran: A Qualitative Study

    Directory of Open Access Journals (Sweden)

    Shahram Yazdani

    2016-12-01

    Conclusion: For promotion of community health and improvement of the national and international position of Iran’s medical universities and HE centers, policymakers should consider the diverse factors that influence HE expansion in our developed model.

  11. Gateway Arch Circulator Conceptual Feasibility Study : Jefferson National Expansion Memorial

    Science.gov (United States)

    2015-03-01

    The Jefferson National Expansion Memorial (JEFF) is undergoing major design changes as part of the City Arch River 2015 project (CAR) that will impact access for park visitors. The park and stakeholders are considering a circulator system to facilita...

  12. Potassium lithium carbonate, KLiCO{sub 3}: single-crystal X-ray structure analysis and thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Kirfel, A.; Euler, H.; Barbier, H.; Haegele, E.; Klapper, H. [Bonn Univ. (Germany). Mineralogisch-Petrologisches Inst. und Museum

    2000-07-01

    Single crystals of KLiCO{sub 3}, the intermediate compound in the eutectic system K{sub 2}CO{sub 3}-Li{sub 2}CO{sub 3}, were synthesized from the melt and the crystal structure was redetermined at room temperature by single-crystal X-ray diffraction: a = 7.232(1) A, b = 7.085(2) A, c = 6.579(1) A, {beta} = 113.40(1) , space group P2{sub 1}/n (No 14), Z = 4. Earlier literature results obtained by neutron time-of-flight powder diffraction are corroborated. The structure is composed of distorted face and edge sharing LiO{sub 5} and KO{sub 9} coordination polyhedra which are arranged in a layered manner and are connected by distorted but planar carbonate anions. In addition to the structure analysis, the thermal expansion of the crystal was measured and analyzed up to melting at 504.5 C. It exhibits a significant anisotropy with a maximum in direction c{sup *} about three times as large as the almost equal expansions in the a, b plane. This anisotropy is clearly understood from the distribution of bonds in the structure rather than from its layered nature. (orig.)

  13. Thermal expansion, thermal conductivity, and heat capacity measurements for boreholes UE25 NRG-4, UE25 NRG-5, USW NRG-6, and USW NRG-7/7A

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, N.S.; Riggins, M. [Sandia National Labs., Albuquerque, NM (United States); Connolly, J. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology and Inst. of Meteoritics; Ricci, P. [Holometrix, Inc., Bedford, MA (United States)

    1997-09-01

    Specimens were tested from four thermal-mechanical units, namely Tiva Canyon (TCw), Paintbrush Tuff (PTn), and two Topopah Spring units (TSw1 and TSw2), and from two lithologies, i.e., welded devitrified (TCw, TSw1, TSw2) and nonwelded vitric tuff (PTn). Thermal conductivities in W(mk){sup {minus}1} averaged over all boreholes, ranged (depending upon temperature and saturation state) from 1.2 to 1.9 for TCw, from 0.4 to 0.9 for PTn, from 1.0 to 1.7 for TSw1, and from 1.5 to 2.3 for TSw2. Mean coefficients of thermal expansion were highly temperature dependent and values, averaged over all boreholes, ranged (depending upon temperature and saturation state) from 6.6 {times} 10{sup {minus}6} to 49 {times} 10{sup {minus}6} C{sup {minus}1} for TCw, from the negative range to 16 {times} 10{sup {minus}6} {center_dot} {degree}C{sup {minus}1} for PTn, from 6.3 {times} 10{sup {minus}6} to 44 {times} 10{sup {minus}6} C{sup {minus}1} for TSw1, and from 6.7 {times} 10{sup {minus}6} to 37 {times} 10{sup {minus}6} {center_dot} {degree}C{sup {minus}1} for TSw2. Mean values of thermal capacitance in J/cm{sup 3}K (averaged overall specimens) ranged from 1.6 J to 2.1 for TSw1 and from 1.8 to 2.5 for TSw2. In general, the lithostratigraphic classifications of rock assigned by the USGS are consistent with the mineralogical data presented in this report.

  14. Combustion synthesis and thermal expansion measurements of the rare earth-uranium ternary oxides RE 6UO 12 (RE=La, Nd and Sm)

    Science.gov (United States)

    Jena, Hrudananda; Asuvathraman, R.; Govindan Kutty, K. V.

    2000-08-01

    Rare earth-uranium ternary oxides were synthesized by a solution combustion route. The starting materials were the corresponding metal nitrates and urea. In these preparations, the metal nitrates act as oxidizer and urea as fuel. Highly exothermic decomposition of the metal nitrate-urea complexes on heating at about 500 K leads to a combustion process yielding RE 6UO 12 fine powders. Thermal expansion measurements of these compounds were carried out in the temperature range of 298-1173 K by high temperature X-ray powder diffractometry. The observed axial thermal expansion behaviour is explained on the basis of the crystal chemistry of the compounds.

  15. A longitudinal study of incremental expansion using a mandibular lip bumper.

    Science.gov (United States)

    Murphy, C Chris; Magness, W Bonham; English, Jeryl D; Frazier-Bowers, Sylvia A; Salas, Anna Maria

    2003-08-01

    A retrospective study using models was performed to evaluate the incremental expansion that occurred during mandibular lip bumper therapy in 44 adolescent patients. The purpose was to determine whether expansion occurs evenly between appointments or whether it attenuates with treatment time. Dental cast measurements were made for arch width and arch length. Treatment duration was broken into near-equal time segments and compared. Results showed that about 50% of the total expansion achieved occurred within about the first 100 days. Forty percent of the total amount of expansion occurred during the next 200 days, with only about 10% of the total expansion occurring after the first 300 days. It is unnecessary to have the appliance in place for longer than 300 days. The percentage of expansion that occurred at each time segment was not related to whether the patient had concomitant maxillary expansion.

  16. Zambia : long-term generation expansion study - executive summary.

    Energy Technology Data Exchange (ETDEWEB)

    Conzelmann, G.; Koritarov, V.; Buehring, W.; Veselka, T.; Decision and Information Sciences

    2008-02-28

    The objective of this study is to analyze possible long-term development options of the Zambian electric power system in the period up to 2015. The analysis involved the hydro operations studies of the Zambezi river basin and the systems planning studies for the least-cost generation expansion planning. Two well-known and widely accepted computer models were used in the analysis: PC-VALORAGUA model for the hydro operations and optimization studies and the WASP-III Plus model for the optimization of long-term system development. The WASP-III Plus model is a part of the Argonne National Laboratory's Energy and Power Evaluation Model (ENPEP). The analysis was conducted in close collaboration with the Zambia Electricity Supply Corporation (ZESCO). On the initiative from The World Bank, the sponsor of the study, ZESCO formed a team of experts that participated in the analysis and were trained in the use of computer models. Both models were transferred to ZESCO free of charge and installed on several computers in the ZESCO corporate offices in Lusaka. In September-October 1995, two members of the ZESCO National Team participated in a 4-week training course at Argonne National Laboratory near Chicago, U.S.A., focusing on the long-term system expansion planning using the WASP and VALORAGUA models. The hydropower operations studies were performed for the whole Zambezi river basin, including the full installation of the Kariba power station, and the Cahora Bassa hydro power station in Mozambique. The analysis also included possible future projects such as Itezhi-Tezhi, Kafue Gorge Lower, and Batoka Gorge power stations. As hydropower operations studies served to determine the operational characteristics of the existing and future hydro power plants, it was necessary to simulate the whole Zambezi river basin in order to take into account all interactions and mutual influences between the hydro power plants. In addition, it allowed for the optimization of reservoir

  17. Zirconium tungstate/epoxy resin nanocomposites with negative coefficient of thermal expansion for all-dielectric cryogenic temperature sensors

    Science.gov (United States)

    See, Erich; Kochergin, Vladimir; Neely, Lauren; Zayetnikov, Madrakhim; Ciovati, Gianluigi; Robinson, Hans

    2012-02-01

    The α-phase of zirconium tungstate (ZrW2O8) has the remarkable property that its coefficient of thermal expansion (CTE) is negative over its entire range of thermal stability (0-1050K), and through this range it has a nearly constant negative CTE. When ZrW2O8 nanoparticles are mixed into a polymer resin, the resulting composite has a reduced CTE when compared with that of the pure polymer. However, previous research on such composites has occurred only near room temperature. We show that at cryogenic temperatures, it is possible to make ZrW2O8/resin nanocomposites with negative CTE. By coating a fiber-optic Bragg grating with such a composite, we were able to create an all-optical temperature sensor without the use of metals, which would be of particular use in superconducting RF cavities. The sensor has sensitivity down to at least 2 K, six times lower than previous fiber-optic temperature sensors.

  18. Disentangling random thermal motion of particles and collective expansion of source from transverse momentum spectra in high energy collisions

    Science.gov (United States)

    Wei, Hua-Rong; Liu, Fu-Hu; Lacey, Roy A.

    2016-12-01

    In the framework of a multisource thermal model, we describe experimental results of the transverse momentum spectra of final-state light flavor particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead (p-Pb), and proton-proton (p -p) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, by using the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein), Tsallis, and two- or three-component standard distributions which can be in fact regarded as different types of ‘thermometers’ or ‘thermometric scales’ and ‘speedometers’. A central parameter in the three distributions is the effective temperature which contains information on the kinetic freeze-out temperature of the emitting source and reflects the effects of random thermal motion of particles as well as collective expansion of the source. To disentangle both effects, we extract the kinetic freeze-out temperature from the intercept of the effective temperature (T) curve as a function of particle’s rest mass (m 0) when plotting T versus m 0, and the mean transverse flow velocity from the slope of the mean transverse momentum ( ) curve as a function of mean moving mass (\\overline{m}) when plotting versus \\overline{m}.

  19. Cryogenic Refractive Index and Coefficient of Thermal Expansion for the S-TIH1 Glass

    Science.gov (United States)

    Quijada, Manuel A.; Leviton, Douglas; Content, David

    2013-01-01

    Using the CHARMS facility at NASA GSFC, we have measured the cryogenic refractive index of the Ohara S-TIH1 glass from 0.40 to 2.53 micrometers and from 120 to 300 K. We have also examined the spectral dispersion and thermo-optic coefficients (dn/dT). We also derived temperature-dependent Sellmeier models from which refractive index may be calculated for any wavelength and temperature within the stated ranges of each model. The S-TIH1 glass we tested exhibited unusual behavior in the thermo-optic coefficient. We found that for delta glass in order to understand its thermal properties. The CTE showed a monotonic change with a decrease in temperature.

  20. Merchant electricity transmission expansion: A European case study

    Energy Technology Data Exchange (ETDEWEB)

    Kristiansen, T. [RBS Sempra Commodities, 155 Bishopsgate, London EC2M3TZ (United Kingdom); Rosellon, J. [Centro de Investigacion y Docencia Economicas (CIDE), Division de Economia, Carretera Mexico-Toluca 3655, Lomas de Santa Fe, 01210 Mexico D.F. (Mexico); German Institute for Economic Research (DIW Berlin), Mohrenstrasse 58, 10117, Berlin (Germany)

    2010-10-15

    We apply a merchant transmission model to the trilateral market coupling (TLC) arrangement among the Netherlands, Belgium and France as an example, and note that it could further be applied to other market splitting or coupling of Europe's different national power markets. In this merchant framework the system operator allocates financial transmission rights (FTRs) to investors in transmission expansion based upon their preferences, and revenue adequacy. The independent system operator (ISO) preserves some proxy FTRs to manage potential negative externalities that may result from expansion projects. This scheme could help European market coupling arrangements attract additional investment. (author)

  1. Langmuir probe study of plasma expansion in pulsed laser ablation

    DEFF Research Database (Denmark)

    Hansen, T.N.; Schou, Jørgen; Lunney, J.G.

    1999-01-01

    Langmuir probes were used to monitor the asymptotic expansion of the plasma produced by the laser ablation of a silver target in a vacuum. The measured angular and temporal distributions of the ion flux and electron temperature were found to be in good agreement with the self-similar isentropic a...... and adiabatic solution of the gas dynamics equations describing the expansion. The value of the adiabatic index gamma was about 1.25, consistent with the ablation plume being a low temperature plasma....

  2. Possible Phonon Density of States of High-Temperature Phase Structure of the Negative Thermal Expansion Compound ZrW2O8

    Science.gov (United States)

    Yamamura, Yasuhisa; Saito, Kazuya

    2007-12-01

    To study the phonon properties of β-ZrW2O8 showing the negative thermal expansion (NTE), the heat capacities of Zr1-xMxW2O8-y (M = Sc, Lu; x = 0.02, 0.04) at low temperatures were measured and analyzed. The analysis presents the effective phonon density of states (DOS) of β-ZrW2O8, showing a rounded form around 5 meV. The rounded phonon DOS of β-ZrW2O8 is in marked contrast to that of the low-temperature phase of ZrW2O8, and their distinction is consistent with the difference in NTE nature between two structures.

  3. Near zero thermal expansion properties in antiperovskite Mn3Cu0.6Ge0.4N prepared by spark plasma sintering

    Science.gov (United States)

    Tan, Jie; Huang, Rongjin; Li, Wen; Huang, Chuangjun; Han, Yemao; Li, Laifeng

    2014-09-01

    Antiperovskite manganese nitride Mn3Cu0.6Ge0.4N was fabricated by spark plasma sintering (SPS) at different temperatures and its negative thermal expansion behavior was investigated. It is observed that the width of negative thermal expansion (NTE) operation-temperature window becomes broader when the sintering temperature decreases. Moreover, it is significantly larger than that of other Mn3CuN-based antiperovskite manganese nitrides prepared by solid-state reaction. More interestingly, the Mn3Cu0.6Ge0.4N sintered at 650 °C shows near zero thermal expansion (ZTE) behavior in the temperature range of 220-170 K. The average linear coefficient of thermal expansion (CTE) is estimated to be -0.9 × 10-6 K-1. Magnetic measurement shows that the process of the magnetic transition becomes slow when the sintering temperature decreases. This antiperovskite manganese nitride Mn3Cu0.6Ge0.4N with ZTE behavior is much useful for applications in the fields of cryogenics and applied superconductivity.

  4. Contrast Enhanced Microscopy Digital Image Correlation: A General Method to Contact-Free Coefficient of Thermal Expansion Measurement of Polymer Films

    Science.gov (United States)

    Jairo A. Diaz; Robert J. Moon; Jeffrey P. Youngblood

    2014-01-01

    Thermal expansion represents a vital indicator of the processing history and dimensional stability of materials. Solvent-sensitive, thin, and compliant samples are particularly challenging to test. Here we describe how textures highlighted by contrast enhanced optical microscopy modes (i.e., polarized light (PL), phase contrast (PC)) and bright field (BF) can be used...

  5. LED phototherapy on midpalatal suture after rapid maxilla expansion: a Raman spectroscopic study

    Science.gov (United States)

    Rosa, Cristiane B.; Habib, Fernando Antonio L.; de Araújo, Telma M.; dos Santos, Jean N.; Cangussu, Maria Cristina T.; Barbosa, Artur Felipe S.; de Castro, Isabele Cardoso V.; Soares, Luiz Guilherme P.; Pinheiro, Antonio L. B.

    2015-03-01

    A quick bone formation after maxillary expansion would reduce treatment timeand the biomodulating effects of LED light could contribute for it. The aim of this study was to analyze the effect of LED phototherapy on the acceleration of bone formation at the midpalatal suture after maxilla expansion. Thirty rats divided into 6 groups were used on the study at 2 time points - 7 days: Control; Expansion; and Expansion + LED; and 14 days: Expansion; Expansion + LED in the first week; Expansion and LED in the first and second weeks. LED irradiation occurred at every 48 h during 2 weeks. Expansion was accomplished using a spatula and maintained with a triple helicoid of 0.020" stainless steel orthodontic wire. A LED light (λ850 ± 10nm, 150mW ± 10mW, spot of 0.5cm2, t=120 sec, SAEF of 18J/cm2) was applied in one point in the midpalatal suture immediately behind the upper incisors. Near infrared Raman spectroscopic analysis of the suture region was carried and data submitted to statistical analyzes (p≤0.05). Raman spectrum analysis demonstrated that irradiation increased hydroxyapatite in the midpalatal suture after expansion. The results of this indicate that LED irradiation; have a positive biomodulation contributing to the acceleration of bone formation in the midpalatal suture after expansion procedure.

  6. Large pyroelectric and thermal expansion coefficients in the [(CH3)2NH2]Mn (HCOO)3 metal-organic framework

    Science.gov (United States)

    Ma, Yinina; Cong, Junzhuang; Chai, Yisheng; Yan, Liqin; Shang, Dashan; Sun, Young

    2017-07-01

    The [(CH3)2NH2]Mn(HCOO)3 perovskite metal-organic framework exhibits a first-order ferroelectric phase transition with a high polarization at Tc ˜ 192 K, induced by the order-disorder transition of hydrogen bonds. Accompanying this sharp phase transition, a huge pyroelectric coefficient with a peak value of 5.16 × 10-2 C/m2 K is detected. In addition, there is a large lattice expansion along the [012] direction at Tc, resulting in a giant linear thermal expansion coefficient as high as 35 000 ppm/K. These striking results indicate that ferroelectric metal-organic frameworks combing both merits of inorganic and organic compounds hold a great potential in generating superior pyroelectric and thermal expansion properties.

  7. A prospective study of lip adaptation during six months of simulated mandibular dental arch expansion.

    Science.gov (United States)

    Shellhart, W C; Moawad, M I; Matheny, J; Paterson, R L; Hicks, E P

    1997-01-01

    The stability of dental arch expansion with conventional orthodontic treatments is disappointing. An increase in labial soft tissue pressure resulting from the expansion may contribute to this instability. An 8-month study of lip pressure changes resulting from lip bumper wear has been conducted, but no long-term studies have been conducted on pressure changes resulting from conventional expansion using fixed appliances. The purpose of the current study was to investigate changes in labial soft tissue pressures when conventional expansion was simulated. Twenty-two subjects wore a stent simulating mandibular dental arch expansion. They were instructed to wear the stent full-time. Lip pressure was recorded initially at 1 week, and monthly for 6 months. A repeated measures ANOVA was used for statistical analysis. A statistically significant (P < or = 0.05) increase in pressure was documented after initial insertion of the expansion-simulating stent. The increase was not maintained, suggesting an adaptation of the labial soft tissues.

  8. Improved Compressive, Damping and Coefficient of Thermal Expansion Response of Mg–3Al–2.5La Alloy Using Y2O3 Nano Reinforcement

    Directory of Open Access Journals (Sweden)

    Amit Kumar

    2017-03-01

    Full Text Available In the present study, the effects of the addition of Y2O3 nanoparticles on Mg–3Al–2.5La alloy were investigated. Materials were synthesized using a disintegrated melt deposition technique followed by hot extrusion. The samples were then characterized for microstructure, compression properties, damping properties, CTE (coefficient of thermal expansion and fracture morphology. The grain size of Mg–3Al–2.5La was significantly reduced by the addition of the Y2O3 nano-sized reinforcement (~3.6 μm, 43% of Mg–3Al–2.5La grain size. SEM and X-ray studies revealed that the size of uniformly distributed intermetallic phases, Al 11 La 3 , Al 2 La , and Al 2.12 La 0.88 reduced by the addition of Y2O3 to Mg–3Al–2.5La alloy. The coefficient of thermal expansion (CTE was slightly improved by the addition of nanoparticles. The results of the damping measurement revealed that the damping capacity of the Mg–3Al–2.5La alloy increased due to the presence of Y2O3. The compression results showed that the addition of Y2O3 to Mg–3Al–2.5La improved the compressive yield strength (from ~141 MPa to ~156 MPa and the ultimate compressive strength (from ~456 MPa to ~520 MPa, which are superior than those of the Mg–3Al alloy (Compressive Yield Strength, CYS ~154 MPa and Ultimate Compressive Strength, UCS ~481 MPa. The results further revealed that there is no significant effect on the fracture strain value of Mg–3Al–2.5La due to the addition of Y2O3.

  9. Spectroscopic, thermal and biological studies of coordination ...

    Indian Academy of Sciences (India)

    , thermal and biological studies of coordination compounds of sulfasalazine drug: Mn(II), Hg(II), Cr(III), ZrO(II), VO(II) and Y(III) transition metal complexes. M G Abd El-Wahed M S Refat S M El-Megharbel. Thermal Studies Volume 32 Issue 2 ...

  10. Structural and controllable thermal expansion properties of Sc{sub 2−x}Al{sub x}Mo{sub 3}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Meimei, E-mail: mmwu@ciae.ac.cn [China Institute of Atomic Energy, Beijing 102413 (China); Peng, Jie [Experimental Physics Center, Institute of High Energy Physics, CAS, Beijing 100049 (China); Cheng, Yingzhi [College of Chemical Engineering, Shandong University of Technology, Zibo 255049 (China); Xiao, Xiaoling [College of Materials and Photoelectric Technology, Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Chen, Dongfeng, E-mail: dongfeng@ciae.ac.cn [China Institute of Atomic Energy, Beijing 102413 (China); Hu, Zhongbo [College of Materials and Photoelectric Technology, Graduate University of Chinese Academy of Sciences, Beijing 100049 (China)

    2013-11-15

    Highlights: •Monophasic solid solutions Sc{sub 2−x}Al{sub x}Mo{sub 3}O{sub 12} have been prepared in the whole composition range. •The cell parameters decrease with increasing Al content. •Fe substitution induces the thermal expansion property of Sc{sub 2−x}Al{sub x}Mo{sub 3}O{sub 12} controllable. •Sc{sub 1.7}Al{sub 0.3}Mo{sub 3}O{sub 12} exhibits zero thermal expansion in 600–800 °C temperature range. -- Abstract: The crystal structure and thermal expansion properties of solid solutions Sc{sub 2−x}Al{sub x}Mo{sub 3}O{sub 12} (x = 0.0–2.0) are systematically investigated by X-ray diffraction. Rietveld refinement results indicate that samples with x ⩽ 1.3 crystallize in a Sc{sub 2}Mo{sub 3}O{sub 12}-type orthorhombic (Pnca) structure, whereas others have an Al{sub 2}Mo{sub 3}O{sub 12}-type monoclinic (P2{sub 1}/a) structure. Substitution of 15% Al{sup 3+} for Sc{sup 3+} leads to a rapid change in linear thermal expansion coefficient from −2.334 × 10{sup −6} °C{sup −1} to −0.732 × 10{sup −6} °C{sup −1}. The thermal expansion coefficients of Sc{sub 2−x}Al{sub x}Mo{sub 3}O{sub 12} monotonously increase with increased Al{sup 3+} content.

  11. Uranium hexafluoride liquid thermal expansion, elusive eutectic with hydrogen fluoride, and very first production using chlorine trifluoride

    Energy Technology Data Exchange (ETDEWEB)

    Rutledge, G.P. [Central Environmental, Inc., Anchorage, AK (United States)

    1991-12-31

    Three unusual incidents and case histories involving uranium hexafluoride in the enrichment facilities of the USA in the late 1940`s and early 1950`s are presented. The history of the measurements of the thermal expansion of liquids containing fluorine atoms within the molecule is reviewed with special emphasis upon uranium hexafluoride. A comparison is made between fluorinated esters, fluorocarbons, and uranium hexafluoride. The quantitative relationship between the thermal expansion coefficient, a, of liquids and the critical temperature, T{sub c} is presented. Uranium hexafluoride has an a that is very high in a temperature range that is used by laboratory and production workers - much higher than any other liquid measured. This physical property of UF{sub 6} has resulted in accidents involving filling the UF{sub 6} containers too full and then heating with a resulting rupture of the container. Such an incident at a uranium gaseous diffusion plant is presented. Production workers seldom {open_quotes}see{close_quotes} uranium hexafluoride. The movement of UF{sub 6} from one container to another is usually trailed by weight, not sight. Even laboratory scientists seldom {open_quotes}see{close_quotes} solid or liquid UF{sub 6} and this can be a problem at times. This inability to {open_quotes}see{close_quotes} the UF{sub 6}-HF mixtures in the 61.2{degrees}C to 101{degrees}C temperature range caused a delay in the understanding of the phase diagram of UF{sub 6}-HF which has a liquid - liquid immiscible region that made the eutectic composition somewhat elusive. Transparent fluorothene tubes solved the problem both for the UF{sub 6}-HF phase diagram as well as the UF{sub 6}-HF-CIF{sub 3} phase diagram with a miscibility gap starting at 53{degrees}C. The historical background leading to the first use of CIF{sub 3} to produce UF{sub 6} in both the laboratory and plant at K-25 is presented.

  12. The Spatiotemporal Pattern of Urban Expansion in China: A Comparison Study of Three Urban Megaregions

    OpenAIRE

    Wenjuan Yu; Weiqi Zhou

    2017-01-01

    Urban megaregions have emerged as a new urbanized form. However, previous studies mostly focused on urban expansion at the city scale, particularly for large cities. Understanding urban expansion at the regional scale including cities having different sizes is important for extending current knowledge of urban growth and its environmental and ecological impacts. Here, we addressed two questions: (1) How do the extent, rate, and morphological model of urban expansion vary at both the regional ...

  13. Heat capacity, lattice dynamics, and thermodynamic stability of the negative thermal expansion material HfMo2O8

    Science.gov (United States)

    Kennedy, Catherine A.; White, Mary Anne; Wilkinson, Angus P.; Varga, Tamas

    2007-06-01

    We explore the lattice dynamics of the negative thermal expansion material, cubic HfMo2O8 , through analysis of its heat capacity (measured from 0.5to300K ) and its room-temperature Raman spectrum. Its heat capacity is quantitatively very similar to that of ZrW2O8 , as is its Raman spectrum. The heat capacity of HfMo2O8 can be well represented by the present lattice dynamical assignment and by CP(HfW2O8)-CP(ZrW2O8)+CP(ZrMo2O8) , but not by CP(HfO2)+2CP(MoO3) , likely because the AB2O8 compounds have low-frequency optic modes, not present in HfO2 and MoO3 . The present thermodynamic data also allow an analysis of the thermodynamic stability of cubic HfMo2O8 , and it is shown to be unstable with respect to MoO3 and HfO2 at room temperature.

  14. Giant negative thermal expansion covering room temperature in nanocrystalline GaN{sub x}Mn{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Lin, J. C.; Tong, P., E-mail: tongpeng@issp.ac.cn; Chen, L.; Guo, X. G.; Yang, C.; Song, B.; Wu, Y.; Lin, S.; Song, W. H. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhou, X. J.; Lin, H., E-mail: linhe@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 200120 (China); Ding, Y. W.; Bai, Y. X. [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026 (China); Sun, Y. P., E-mail: ypsun@issp.ac.cn [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-09-28

    Nanocrystalline antiperovskite GaN{sub x}Mn{sub 3} powders were prepared by mechanically milling. The micrograin GaN{sub x}Mn{sub 3} exhibits an abrupt volume contraction at the antiferromagnetic (AFM) to paramagnetic (PM) (AFM-PM) transition. The temperature window of volume contraction (ΔT) is broadened to 50 K as the average grain size (〈D〉) is reduced to ∼30 nm. The corresponding coefficient of linear thermal expansion (α) reaches ∼ −70 ppm/K, which are comparable to those of giant NTE materials. Further reducing 〈D〉 to ∼10 nm, ΔT exceeds 100 K and α remains as large as −30 ppm/K (−21 ppm/K) for x = 1.0 (x = 0.9). Excess atomic displacements together with the reduced structural coherence, revealed by high-energy X-ray pair distribution functions, are suggested to delay the AFM-PM transition. By controlling 〈D〉, giant NTE may also be achievable in other materials with large lattice contraction due to electronic or magnetic phase transitions.

  15. Fuel cell integral bundle assembly including ceramic open end seal and vertical and horizontal thermal expansion control

    Science.gov (United States)

    Zafred, Paolo R [Murrysville, PA; Gillett, James E [Greensburg, PA

    2012-04-24

    A plurality of integral bundle assemblies contain a top portion with an inlet fuel plenum and a bottom portion containing a base support, the base supports a dense, ceramic air exhaust manifold having four supporting legs, the manifold is below and connects to air feed tubes located in a recuperator zone, the air feed tubes passing into the center of inverted, tubular, elongated, hollow electrically connected solid oxide fuel cells having an open end above a combustion zone into which the air feed tubes pass and a closed end near the inlet fuel plenum, where the open end of the fuel cells rest upon and within a separate combination ceramic seal and bundle support contained in a ceramic support casting, where at least one flexible cushion ceramic band seal located between the recuperator and fuel cells protects and controls horizontal thermal expansion, and where the fuel cells operate in the fuel cell mode and where the base support and bottom ceramic air exhaust manifolds carry from 85% to all of the weight of the generator.

  16. Thermal Expansion, Elastic and Magnetic Properties of FeCoNiCu-Based High-Entropy Alloys Using First-Principle Theory

    Science.gov (United States)

    Huang, Shuo; Vida, Ádám; Heczel, Anita; Holmström, Erik; Vitos, Levente

    2017-11-01

    The effects of V, Cr, and Mn on the magnetic, elastic, and thermal properties of FeCoNiCu high-entropy alloy are studied by using the exact muffin-tin orbitals method in combination with the coherent potential approximation. The calculated lattice parameters and Curie temperatures in the face-centered-cubic structure are in line with the available experimental and theoretical data. A significant change in the magnetic behavior is revealed when adding equimolar V, Cr, and Mn to the host composition. The three independent single-crystal elastic constants are computed using a finite strain technique, and the polycrystalline elasticity parameters including shear modulus, Young's modulus, Pugh ratio, Poisson's ratio, and elastic anisotropy are derived and discussed. The effects of temperature on the structural parameters are determined by making use of the Debye-Grüneisen model. It is found that FeCoNiCuCr possesses a slightly larger thermal expansion coefficient than do the other alloys considered here.

  17. Joining of silicon carbide using interlayer with matching coefficient of thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Perham, T. [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering]|[Lawrence Berkeley National Lab., CA (United States)

    1996-11-01

    The primary objective of this study is to develop a technique for joining a commercially available Silicon Carbide that gives good room temperature strength and the potential for good high temperature strength. One secondary objective is that the joining technique be adaptable to SiC{sub f}/SiC composites and/or Nickel based superalloys, and another secondary objective is that the materials provide good neutron irradiation resistance and low activation for potential application inside nuclear fusion reactors. The joining techniques studied here are: (1) reaction bonding with Al-Si/Si/SiC/C; (2) reaction/infiltration with calcium aluminum silicate; (3) ion exchange mechanism to form calcium hexaluminate (a refractory cement); and (4) oxide frit brazing with cordierite.

  18. Thermophysical Properties of Matter - the TPRC Data Series. Volume 12. Thermal Expansion Metallic Elements and Alloys

    Science.gov (United States)

    1975-01-01

    34Crystallographic Study and Self-irradiation Effects of Plutonium at Low Temperature," Paris University, France, Ph.D. Thesis, 57 pp., 1965; USAEC Rapt. CEA -R...Stabilization of Mixed Carbides of Uranium-Plutonium by Zirconium. Part I. Uranium Carbide with Small Additions of Zirconium, ", NASA Rapt. CEA -R...Magnesium-Tin System 884 MN. Pt, a 594 Magnesium-Uranium System 889 MDR 591 Magnsium + in +Oo121: , 894Magesum Znc+2209, Manganese-Silver System 893 1213

  19. Distortions and stresses in thin shells due to anisotropic thermal expansion

    Science.gov (United States)

    Koenig, Manfred

    1992-10-01

    The considerable interest in the application of refractory anisotropic materials to the design of shell components, which are used in the very hot regions of future hypersonic flight and reusable reentry vehicle structures, is discussed. These materials are often homogeneous in the macroscopic scale but anisotropic. Typical examples are pyrolytic graphite (obtained by vapor deposition) and more recently, carbon fiber reinforced carbon (C/C) and carbon fiber reinforced silicon carbide (C/SiC). The carbon fiber reinforcement of C/C and C/SiC often consists of layers of fabrics (0/90 deg), resulting in a behavior that is nearly isotropic in the plane of the shell but differs in the perpendicular (thickness) direction. The study focuses on such transversely isotropic materials and deals with distortions and residual stresses in shells made of such materials and resulting from uniform temperature changes.

  20. In Situ Diffraction from Levitated Solids Under Extreme Conditions-Structure and Thermal Expansion in the Eu 2 O 3 -ZrO 2 System

    Energy Technology Data Exchange (ETDEWEB)

    Maram, Pardha S. [Peter A. Rock Thermochemistry Laboratory and Neat ORU, University of California, Davis, One Shields Avenue 4415 Chemistry Annex Davis California 95616; Ushakov, Sergey V. [Peter A. Rock Thermochemistry Laboratory and Neat ORU, University of California, Davis, One Shields Avenue 4415 Chemistry Annex Davis California 95616; Weber, Richard J. K. [Materials Development, Inc., 3090 Daniels Court Arlington Heights Illinois 60004; X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue Lemont Illinois 60439; Benmore, Chris J. [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue Lemont Illinois 60439; Navrotsky, Alexandra [Peter A. Rock Thermochemistry Laboratory and Neat ORU, University of California, Davis, One Shields Avenue 4415 Chemistry Annex Davis California 95616; Raveau, B.

    2014-12-31

    The accurate determination of structure and thermal expansion of refractory materials at temperatures above 1500 degrees C is challenging. Here, for the first time, we demonstrate the ability to reliably refine the structure and thermal expansion coefficient of oxides at temperatures to 2200 degrees C using in situ synchrotron diffraction coupled with aerodynamic levitation. Solid solutions in the Eu2O3-ZrO2 binary system were investigated, including the high-temperature order-disorder transformation in Eu2Zr2O7. The disordered fluorite phase is found to be stable above 1900 degrees C, and a reversible phase transition to the pyrochlore phase is noticed during cooling. Site occupancies in Eu2Zr2O7 show a gradual increase in disorder on both cation and anion sublattices with increasing temperature. The thermal expansion coefficients of all cubic solid solutions are relatively similar, falling in the range 8.6-12.0x10(-6)C(-1). These studies open new vistas for in situ exploration of complex structural changes in high-temperature materials.

  1. Two satellite study of substorm expansion near geosynchronous orbit

    Directory of Open Access Journals (Sweden)

    Ø. Holter

    2004-12-01

    Full Text Available During several time intervals in 1979–1980 the satellites GEOS-2 and SCATHA were situated relatively close on the nightside of the Earth at geosynchronous distances. Several substorm events were identified during these periods. The event considered in this paper was recorded on 22 May 1979, when the satellites were separated by less than 30min in local time around 21:00 LT. The observed 45 to 60 s delay of magnetic signatures observed at the two s/c indicates a westward expansion of ~7.7°/min. At the two s/c, the magnetic signatures are, in particular for the azimuthal magnetic field components, quite different. At GEOS-2, being close to the magnetic equator, the dominant feature is a dipolarization with a weak field-aligned current signature corresponding to a symmetric current which cancels at the equator. On SCATHA, however, being close to the current sheet boundary, the azimuthal magnetic field indicates a strong field-aligned Birkeland current structure. On both s/c the first indication of an approaching substorm was an increase in the high energy ion flux followed by a reduction in the flux intensity of energetic electrons and a further tailward stretching of the magnetic field, starting ~2min before the onset of the magnetic field dipolarization. The tailward stretching, the observed variations of the magnetic field components, and the subsequent dipolarization are interpreted in terms of an azimuthally tilted field-aligned current system passing the s/c on the tailward side from east to west. The westward expansion and dipolarization observed at the two s/c are consistent with the propagation of a Rayleigh-Taylor type instability. The increased radial ion flux corresponds to the ExB-drift due to the substorm associated electric field.

    Key words. Magnetospheric physics (storms and substorms; plasma waves and instabilities; current systems

  2. Two satellite study of substorm expansion near geosynchronous orbit

    Directory of Open Access Journals (Sweden)

    Ø. Holter

    2004-12-01

    Full Text Available During several time intervals in 1979–1980 the satellites GEOS-2 and SCATHA were situated relatively close on the nightside of the Earth at geosynchronous distances. Several substorm events were identified during these periods. The event considered in this paper was recorded on 22 May 1979, when the satellites were separated by less than 30min in local time around 21:00 LT. The observed 45 to 60 s delay of magnetic signatures observed at the two s/c indicates a westward expansion of ~7.7°/min. At the two s/c, the magnetic signatures are, in particular for the azimuthal magnetic field components, quite different. At GEOS-2, being close to the magnetic equator, the dominant feature is a dipolarization with a weak field-aligned current signature corresponding to a symmetric current which cancels at the equator. On SCATHA, however, being close to the current sheet boundary, the azimuthal magnetic field indicates a strong field-aligned Birkeland current structure. On both s/c the first indication of an approaching substorm was an increase in the high energy ion flux followed by a reduction in the flux intensity of energetic electrons and a further tailward stretching of the magnetic field, starting ~2min before the onset of the magnetic field dipolarization. The tailward stretching, the observed variations of the magnetic field components, and the subsequent dipolarization are interpreted in terms of an azimuthally tilted field-aligned current system passing the s/c on the tailward side from east to west. The westward expansion and dipolarization observed at the two s/c are consistent with the propagation of a Rayleigh-Taylor type instability. The increased radial ion flux corresponds to the ExB-drift due to the substorm associated electric field. Key words. Magnetospheric physics (storms and substorms; plasma waves and instabilities; current systems

  3. Crystalline electric field and lattice contributions to thermodynamic properties of PrGaO{sub 3}: specific heat and thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Senyshyn, A [Materialwissenschaft, Technische Universitaet Darmstadt, Petersenstrasse 23, 64287 Darmstadt (Germany); Schnelle, W [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Strasse 40, 01187 Dresden (Germany); Vasylechko, L [Semiconductor Electronics Department, Lviv Polytechnic National University, 12 Bandera St, 79013 Lviv (Ukraine); Ehrenberg, H [Materialwissenschaft, Technische Universitaet Darmstadt, Petersenstrasse 23, 64287 Darmstadt (Germany); Berkowski, M [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw (Poland)

    2007-04-16

    The low-temperature heat capacity of perovskite-type PrGaO{sub 3} has been measured in the temperature range from 2 to 320 K. Thermodynamic standard values at 298.15 K are reported. An initial Debye temperature {theta}{sub D}(0) (480 {+-} 10) K was determined by fitting the calculated lattice heat capacity. The entropy of the derived Debye temperature functions agrees well with values calculated from thermal displacement parameters and from atomistic simulations. The thermal expansion and the Grueneisen parameter, arising from a coupling of crystal field states of Pr{sup 3+} ion and phonon modes at low temperature, were analysed.

  4. Robust high pressure stability and negative thermal expansion in sodium-rich antiperovskites Na{sub 3}OBr and Na{sub 4}OI{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yonggang, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154 (United States); Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou, Henan 450006 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Wen, Ting [Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou, Henan 450006 (China); Park, Changyong; Kenney-Benson, Curtis [High Pressure Collaborative Access Team (HPCAT), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Pravica, Michael; Zhao, Yusheng, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154 (United States); Yang, Wenge, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China)

    2016-01-14

    The structure stability under high pressure and thermal expansion behavior of Na{sub 3}OBr and Na{sub 4}OI{sub 2}, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na{sub 3}OBr and Na{sub 4}OI{sub 2}, respectively. The cubic Na{sub 3}OBr structure and tetragonal Na{sub 4}OI{sub 2} with intergrowth K{sub 2}NiF{sub 4} structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na{sub 4}OI{sub 2} exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20–80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.

  5. Robust high pressure stability and negative thermal expansion in sodium-rich antiperovskites Na3OBr and Na4OI2

    Science.gov (United States)

    Wang, Yonggang; Wen, Ting; Park, Changyong; Kenney-Benson, Curtis; Pravica, Michael; Yang, Wenge; Zhao, Yusheng

    2016-01-01

    The structure stability under high pressure and thermal expansion behavior of Na3OBr and Na4OI2, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na3OBr and Na4OI2, respectively. The cubic Na3OBr structure and tetragonal Na4OI2 with intergrowth K2NiF4 structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na4OI2 exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20-80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.

  6. Thermal Expansion Measurements in Fresh and Saline Ice Using Fiber Optic Strain Gauges and Multipoint Temperature Sensors Based on Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Aleksey Marchenko

    2016-01-01

    Full Text Available This paper describes the use of Fiber Bragg Grating (FBG sensors to investigate the thermomechanical properties of saline ice. FBG sensors allowed laboratory measurements of thermal expansion of ice samples with a range of different sizes and geometries. The high sampling frequency, accuracy, and resolution of the FBG sensors provide good quality data across a temperature range from 0°C to −20°C. Negative values of the effective coefficient of thermal expansion were observed in ice samples with salinities 6 ppt, 8 ppt, and 9.4 ppt. A model is formulated under which structural transformations in the ice, caused by temperature changes, can lead to brine transfer from closed pockets to permeable channels, and vice versa. This model is compared to experimental data. Further, in experiments with confined floating ice, heating as well as thermal expansion due to vertical migration of liquid brine, caused by under-ice water pressure, was observed.

  7. Internal damping due to dislocation movements induced by thermal expansion mismatch between matrix and particles in metal matrix composites. [Al/SiC

    Energy Technology Data Exchange (ETDEWEB)

    Girand, C.; Lormand, G.; Fougeres, R.; Vincent, A. (GEMPPM, Villeurbanne (France))

    1993-05-01

    In metal matrix composites (MMCs), the mechanical 1 of the reinforcement-matrix interface is an important parameter because it governs the load transfer from matrix to particles, from which the mechanical properties of these materials are derived. Therefore, it would be useful to set out an experimental method able to characterize the interface and the adjacent matrix behaviors. Thus, a study has been undertaken by means of internal damping (I.D.) measurements, which are well known to be very sensitive for studying irreversible displacements at the atomic scale. More especially, this investigation is based on the fact that, during cooling of MMC's, stress concentrations originating from differences in coefficients of thermal expansion (C.T.E.) of matrix and particles should induce dislocation movements in the matrix surrounding the reinforcement; that is, local microplastic strains occur. Therefore, during I.D. measurements vs temperature these movements should contribute to MMCs I.D. in a process similar to those involved around first order phase transitions in solids. The aim of this paper is to present, in the case of Al/SiC particulate composites, new developments of this approach that has previously led to promising results in the case of Al-Si alloys.

  8. Effect of a rapid maxillary expansion on snoring and sleep in children: a pilot study.

    Science.gov (United States)

    Giannasi, Lilian Chrystiane; Santos, Israel Reis; Alfaya, Thays Almeida; Bussadori, Sandra Kalil; Leitão-Filho, Fernando Studart; de Oliveira, Luis Vicente Franco

    2015-07-01

    The aim of this study was to assess the efficacy of the McNamara rapid palatal expansion device for the treatment of sleep disorders in children. The sample enrolled 12 children aged 4-11 years. Children with snoring and bruxism whose parents did not agree to tonsil surgery were included in the study. During the initial evaluation, a questionnaire addressing sleep was administered, and plaster models were made for the construction of the McNamara rapid maxillary expansion device. The expansion period was 7-15 days, and the McNamara device was removed after 6-8 months. The same questionnaire was administered again after 30 days of use of the orthopedic appliance. The data were analyzed using the McNemar test, with the level of significance set to 5% (Pmaxillary expansion, can be an effective treatment for snoring and other undesirable sleep behaviors in children.

  9. The influence of the relative thermal expansion and electric permittivity on phase transitions in the perovskite-type bidimensional layered NH3(CH2)3NH3CdBr4 compound

    Science.gov (United States)

    Staśkiewicz, Beata; Staśkiewicz, Anna

    2017-07-01

    Hydrothermal method has been used to synthesized the layered hybrid compound NH3(CH2)3NH3CdBr4 of perovskite architecture. Structural, dielectric and dilatometric properties of the compound have been analyzed. Negative thermal expansion (NTE) effect in the direction perpendicular to the perovskite plane as well as an unusual phase sequence have been reported based on X-ray diffraction analysis. Electric permittivity measurements evidenced the phase transitions at Tc1=326/328 K and Tc2=368/369 K. Relative linear expansion measurements almost confirmed these temperatures of phase transitions. Anomalies of electric permittivity and expansion behavior connected with the phase transitions are detected at practically the same temperatures as those observed earlier in differential scanning calorimetry (DSC), infrared (IR), far infrared (FIR) and Raman spectroscopy studies. Mechanism of the phase transitions is explained. Relative linear expansion study was prototype to estimate critical exponent value β for continuous phase transition at Tc1. It has been inferred that there is a strong interplay between the distortion of the inorganic network, those hydrogen bonds and the intermolecular interactions of the organic component.

  10. Study of thermal behavior of phytic acid

    Directory of Open Access Journals (Sweden)

    André Luis Máximo Daneluti

    2013-06-01

    Full Text Available Phytic acid is a natural compound widely used as depigmenting agent in galenic cosmetic emulsions. However, we have observed experimentally that phytic acid, when heated to 150 ºC for around one hour, shows evidence of thermal decomposition. Few studies investigating this substance alone with regard to its stability are available in the literature. This fact prompted the present study to characterize this species and its thermal behavior using thermal analysis (TG/DTG and DSC and to associate the results of these techniques with those obtained by elemental analysis (EA and absorption spectroscopy in the infrared region. The TG/DTG and DSC curves allowed evaluation of the thermal behavior of the sample of phytic acid and enabled use of the non-isothermal thermogravimetric method to study the kinetics of the three main mass-loss events: dehydration I, dehydration II and thermal decomposition. The combination of infrared absorption spectroscopy and elemental analysis techniques allowed evaluation of the intermediate products of the thermal decomposition of phytic acid. The infrared spectra of samples taken during the heating process revealed a reduction in the intensity of the absorption band related to O-H stretching as a result of the dehydration process. Furthermore, elemental analysis results showed an increase in the carbon content and a decrease in the hydrogen content at temperatures of 95, 150, 263 and 380 °C. Visually, darkening of the material was observed at 150 °C, indicating that the thermal decomposition of the material started at this temperature. At a temperature of 380 °C, thermal decomposition progressed, leading to a decrease in carbon and hydrogen. The results of thermogravimetry coupled with those of elemental analysis allow us to conclude that there was agreement between the percentages of phytic acid found in aqueous solution. The kinetic study by the non-isothermal thermogravimetric method showed that the dehydration

  11. Measurements on thermal expansion with strain gauge 2; Yugami geji wo mochiita gokuteion netsu bochoritsu no keisoku 2

    Energy Technology Data Exchange (ETDEWEB)

    Arai, O.; Numazawa, T.; Sato, A. [National Research Inst. of Metals, Tokyo (Japan); Okuda, Y. [Tokyo Inst. of Tech., Tokyo (Japan)

    2000-05-29

    As the part of very low temperature thermophysical property measurement technique standardization by the intelligent basis promotion system, it examined very low temperature coefficient of linear expansion measurement method using the strain gauge. It produced the clip, which constituted the bridge circuit using strain sensor of 4 used by fatigue test of very low temperature, and it tried the measurement of convenient and quick coefficient of linear expansion from low temperature over high temperature. (NEDO)

  12. Direct observation of a transverse vibrational mechanism for negative thermal expansion in Zn(CN)2: an atomic pair distribution function analysis.

    Science.gov (United States)

    Chapman, Karena W; Chupas, Peter J; Kepert, Cameron J

    2005-11-09

    The instantaneous structure of the cyanide-bridged negative thermal expansion (NTE) material Zn(CN)(2) has been probed using atomic pair distribution function (PDF) analysis of high energy X-ray scattering data (100-400 K). The temperature dependence of the atomic separations extracted from the PDFs indicates an increase of the average transverse displacement of the cyanide bridge from the line connecting the Zn(II) centers with increasing temperature. This allows the contraction of non-nearest-neighbor Zn...Zn' and Zn...C/N distances despite the observed expansion of the individual direct Zn-C/N and C-N bonds. Thus, this analysis provides definitive structural confirmation that an increase in the average displacement of bridging atoms is the origin of the NTE behavior. The lattice parameters reveal a slight reduction in the NTE behavior at high temperature from a minimum coefficient of thermal expansion (alpha = dl/ldT) of -19.8 x 10(-6) K(-1) below 180 K, which is attributed to interaction between the doubly interpenetrated frameworks that comprise the structure.

  13. Preparation, spectral and thermal studies of pyrazinecarboxylic ...

    Indian Academy of Sciences (India)

    Unknown

    carboxylic acid) have been prepared by neutralization of aqueous hydrazine hydrate with the respective acids in appropriate molar ratios. The free acids and their hydrazinium salts have been characterized by analytical, IR spectroscopic and thermal studies. IR spectra of all the salts show N–N stretching frequencies of the ...

  14. imide, crystal structure, thermal and dielectric studies

    Indian Academy of Sciences (India)

    IR and Raman spectroscopies and its crystal structure is confirmed by single crystal X-ray diffraction method. The X-ray studies on ... Di-cationic ionic liquids; crystal structure; dielectric; thermal properties. 1. Introduction. The chemistry of ionic ... exposed in various emerging areas as solvents of high tem- perature organic ...

  15. Lattice dynamical calculation of negative thermal expansion in ZrV2O7 and HfV2O7

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.

    2008-11-01

    We report lattice dynamics calculations of negative thermal-expansion (NTE) behavior of ZrV2O7 family, extending our previous work on the ZrW2O8 family. The two families of compounds differ in terms of the oxygen coordination around the V/W atoms leading to differences in the nature of soft phonons under compression that are responsible for the NTE. Our calculations quantitatively reproduce the negative expansion over a range of temperatures. We also discuss the relation of the soft phonons with the phase transitions observed in the ZrV2O7 family. Especially, the calculations show a soft-phonon mode at a wave vector of 0.31⟨1,1,0⟩ , which is in excellent agreement with the known incommensurate modulation in ZrV2O7 below 375 K.

  16. The protein amide ¹H(N) chemical shift temperature coefficient reflects thermal expansion of the N-H···O=C hydrogen bond.

    Science.gov (United States)

    Hong, Jingbo; Jing, Qingqing; Yao, Lishan

    2013-01-01

    The protein amide (1)H(N) chemical shift temperature coefficient can be determined with high accuracy by recording spectra at different temperatures, but the physical mechanism responsible for this temperature dependence is not well understood. In this work, we find that this coefficient strongly correlates with the temperature coefficient of the through-hydrogen-bond coupling, (3h)J(NC'), based on NMR measurements of protein GB3. Parallel tempering molecular dynamics simulation suggests that the hydrogen bond distance variation at different temperatures/replicas is largely responsible for the (1)H(N) chemical shift temperature dependence, from which an empirical equation is proposed to predict the hydrogen bond thermal expansion coefficient, revealing responses of individual hydrogen bonds to temperature changes. Different expansion patterns have been observed for various networks formed by β strands.

  17. Expansive waves of arts festivals. Approaches in impact studies

    OpenAIRE

    Colombo Alba

    2009-01-01

    Having examined the conceptualisation of economic impact studies as well as the underlying methodological aspects, this paper analyses the following three economic impact studies of arts festivals: European Capital of Culture Salamanca 2002 (Spain), XI Festival de Flamenco de Jerez (Spain), and Glastonbury Music Festival (UK). The analysed data are mainly derived from the studies carried out by various researchers and institutions, as well as from several conceptualisation reviews. The paper ...

  18. Measurement method of compressibility and thermal expansion coefficients for density standard liquid at 2329 kg/m3 based on hydrostatic suspension principle

    Science.gov (United States)

    Wang, Jintao; Liu, Ziyong; Xu, Changhong; Li, Zhanhong

    2014-07-01

    The accurate measurement on the compressibility and thermal expansion coefficients of density standard liquid at 2329kg/m3 (DSL-2329) plays an important role in the quality control for silicon single crystal manufacturing. A new method is developed based on hydrostatic suspension principle in order to determine the two coefficients with high measurement accuracy. Two silicon single crystal samples with known density are immersed into a sealed vessel full of DSL-2329. The density of liquid is adjusted with varying liquid temperature and static pressure, so that the hydrostatic suspension of two silicon single crystal samples is achieved. The compression and thermal expansion coefficients are then calculated by using the data of temperature and static pressure at the suspension state. One silicon single crystal sample can be suspended at different state, as long as the liquid temperature and static pressure function linearly according to a certain mathematical relationship. A hydrostatic suspension experimental system is devised with the maximal temperature control error ±50 μK; Silicon single crystal samples can be suspended by adapting the pressure following the PID method. By using the method based on hydrostatic suspension principle, the two key coefficients can be measured at the same time, and measurement precision can be improved due to avoiding the influence of liquid surface tension. This method was further validated experimentally, where the mixture of 1, 2, 3-tribromopropane and 1,2-dibromoethane is used as DSL-2329. The compressibility and thermal expansion coefficients were measured, as 8.5×10-4 K-1 and 5.4×1010 Pa-1, respectively.

  19. Studies on the expansion characteristics of the granular bed present ...

    African Journals Online (AJOL)

    Zaki equation (1954) have been investigated. The settling velocity study shows that the mean settling velocity of the granules is in accordance with the Allen formula because the settling process falls within the intermediate flow regime range (1

  20. Development of reduced-variable master curves for estimating tensile stresses of encapsulated solar cells caused by module deflection or thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Cuddihy, E.F.

    1981-10-01

    Complex computer programs are being used by Spectrolab, Inc., to achieve encapsulation engineering optimization of photovoltaic modules. Optimization involves structural adequacy, electrical isolation (safety), maximum optical transmission, and minimum module temperature, at the lowest life-cycle energy cost. A goal of this activity is the generation, where possible, of encapsulation engineering generalities, principles, and design aids (tables or graphs) that would permit a ready, desktop capability of an engineering evaluation of encapsulation options involving materials or designs. The first efforts to generate reduced-variable mater curves for thermal expansion and deflection stress to serve as structural-analysis design aids are reported.

  1. A comparison of skin expansion and contraction between one expander and two expanders: a preliminary study.

    Science.gov (United States)

    Zhang, Gan-lin; Zhang, Jin-ming; Ji, Chen-yang; Meng, Hong; Huang, Jian-hua; Luo, He-yuan; Zhang, Hua-sheng; Liu, Xiao-tao; Hong, Xiao-fang

    2013-12-01

    This study aimed to compare the difference between the skin expansion and contraction rates for an expanded flap with one versus two expanders. The study cohort comprised 24 cases of two overlapping expanders and 15 cases of a single implanted expander involving 22 patients. The method of "wet-cloth sampling" was applied to measure the expanded flap area and the initial unexpanded area and to calculate the skin expansion rate. Two points 5 cm apart in the center of the expanded flap were selected before the second surgical stage. After removal of the expander, the distance between the two fixed points was measured and recorded. The contraction rate of the expanded flap then was calculated. During the same period of expansion in the two groups (p = 0.06, >0.01), the skin expansion rate was 3.5 ± 0.9 % in the group with two overlapping expanders and 2.6 ± 0.6 % in the control group. The difference between the two groups was statistically significant (p = 0.002, 0.05). We fitted a linear regression model that was Y = 0.533 − 0.003X, where Y was the contraction rate of the expanded flap and X was the period of expansion. The contraction rate of the expanded flap was negatively correlated with the period of expansion. Compared with the traditional method of implanting a single expander, the new method of overlapping two expanders in a single cavity increased the skin expansion rate. The instantly expanded flap contraction rate did not differ significantly between the two groups, so the amount of expanded skin area absolutely increased. The clinical application of the new method is worth promoting. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

  2. Development of Solution-Processable, Optically Transparent Polyimides with Ultra-Low Linear Coefficients of Thermal Expansion

    Directory of Open Access Journals (Sweden)

    Masatoshi Hasegawa

    2017-10-01

    Full Text Available This paper reviews the development of new high-temperature polymeric materials applicable to plastic substrates in image display devices with a focus on our previous results. Novel solution-processable colorless polyimides (PIs with ultra-low linear coefficients of thermal expansion (CTE are proposed in this paper. First, the principles of the coloration of PI films are briefly discussed, including the influence of the processing conditions on the film coloration, as well as the chemical and physical factors dominating the low CTE characteristics of the resultant PI films to clarify the challenges in simultaneously achieving excellent optical transparency, a very high Tg, a very low CTE, and excellent film toughness. A possible approach of achieving these target properties is to use semi-cycloaliphatic PI systems consisting of linear chain structures. However, semi-cycloaliphatic PIs obtained using cycloaliphatic diamines suffer various problems during precursor polymerization, cyclodehydration (imidization, and film preparation. In particular, when using trans-1,4-cyclohexanediamine (t-CHDA as the cycloaliphatic diamine, a serious problem emerges: salt formation in the initial stages of the precursor polymerization, which terminates the polymerization in some cases or significantly extends the reaction period. The system derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA and t-CHDA can be polymerized by a controlled heating method and leads to a PI film with relatively good properties, i.e., excellent light transmittance at 400 nm (T400 = ~80%, a high Tg (>300 °C, and a very low CTE (10 ppm·K−1. However, this PI film is somewhat brittle (the maximum elongation at break, εb max is about 10%. On the other hand, the combination of cycloaliphatic tetracarboxylic dianhydrides and aromatic diamines does not result in salt formation. The steric structures of cycloaliphatic tetracarboxylic dianhydrides significantly influence

  3. Thermal transpiration: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    T, Joe Francis [Computational Nanotechnology Laboratory, School of Nano Science and Technology, National Institute of Technology Calicut, Kozhikode (India); Sathian, Sarith P. [Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai (India)

    2014-12-09

    Thermal transpiration is a phenomenon where fluid molecules move from the cold end towards the hot end of a channel under the influence of longitudinal temperature gradient alone. Although the phenomenon of thermal transpiration is observed at rarefied gas conditions in macro systems, the phenomenon can occur at atmospheric pressure if the characteristic dimensions of the channel is less than 100 nm. The flow through these nanosized channels is characterized by the free molecular flow regimes and continuum theory is inadequate to describe the flow. Thus a non-continuum method like molecular dynamics (MD) is necessary to study such phenomenon. In the present work, MD simulations were carried out to investigate the occurance of thermal transpiration in copper and platinum nanochannels at atmospheric pressure conditions. The mean pressure of argon gas confined inside the nano channels was maintained around 1 bar. The channel height is maintained at 2nm. The argon atoms interact with each other and with the wall atoms through the Lennard-Jones potential. The wall atoms are modelled using an EAM potential. Further, separate simulations were carried out where a Harmonic potential is used for the atom-atom interaction in the platinum channel. A thermally insulating wall was introduced between the low and high temperature regions and those wall atoms interact with fluid atoms through a repulsive potential. A reduced cut off radius were used to achieve this. Thermal creep is induced by applying a temperature gradient along the channel wall. It was found that flow developed in the direction of the increasing temperature gradient of the wall. An increase in the volumetric flux was observed as the length of the cold and the hot regions of the wall were increased. The effect of temperature gradient and the wall-fluid interaction strength on the flow parameters have been studied to understand the phenomenon better.

  4. Composite material having controlled coefficient of thermal expansion with oxidic ceramics and procedure for the obtainment thereof

    OpenAIRE

    Torrecillas, Ramón; García Moreno, Olga; Fernández, Adolfo

    2009-01-01

    [EN] The present invention relates to a composite material comprising a ceramic component, characterized in having a negative coefficient of thennal expansion, and oxidic ceramic particles, to the procedure for the obtainment thereof, and to the uses thereof in microelectronics, precision optics, aeronautics and aerospace.

  5. Maxillary Expansion

    OpenAIRE

    Agarwal, Anirudh; Mathur, Rinku

    2010-01-01

    ABSTRACT Maxillary transverse discrepancy usually requires expansion of the palate by a combination of orthopedic and orthodontic tooth movements. Three expansion treatment modalities are used today: rapid maxillary expansion, slow maxillary expansion and surgically assisted maxillary expansion.This article aims to review the maxillary expansion by all the three modalities and a brief on commonly used appliances.

  6. Relapse and stability of surgically assisted rapid maxillary expansion, an anatomical biomechanical study

    NARCIS (Netherlands)

    Koudstaal, M.J.; Smeets, J.B.J.; Kleinrensink, G.J.; Schulten, A.J.M.; van der Wal, K.G.H.

    2009-01-01

    Purpose: This anatomic biomechanical study was undertaken to gain insight into the underlining mechanism of tipping of the maxillary segments during transverse expansion using tooth-borne and bone-borne distraction devices. Materials and Methods: An anatomic biomechanical study was performed on 10

  7. Anomalous Thermal Expansion of HoCo0.5Cr0.5O3 Probed by X-ray Synchrotron Powder Diffraction

    Science.gov (United States)

    Hreb, Vasyl; Vasylechko, Leonid; Mykhalichko, Vitaliya; Prots, Yurii

    2017-07-01

    Mixed holmium cobaltite-chromite HoCo0.5Cr0.5O3 with orthorhombic perovskite structure (structure type GdFeO3, space group Pbnm) was obtained by solid state reaction of corresponding oxides in air at 1373 K. Room- and high-temperature structural parameters were derived from high-resolution X-ray synchrotron powder diffraction data collected in situ in the temperature range of 300-1140 K. Analysis of the results obtained revealed anomalous thermal expansion of HoCo0.5Cr0.5O3, which is reflected in a sigmoidal temperature dependence of the unit cell parameters and in abnormal increase of the thermal expansion coefficients with a broad maxima near 900 K. Pronounced anomalies are also observed for interatomic distances and angles within Co/CrO6 octahedra, tilt angles of octahedra and atomic displacement parameters. The observed anomalies are associated with the changes of spin state of Co3+ ions and insulator-metal transition occurring in HoCo0.5Cr0.5O3.

  8. Spin-glass-like behavior and negative thermal expansion in antiperovskite Mn{sub 3}Ni{sub 1−x}Cu{sub x}N compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Lei [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, 100191 Beijing (China); Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble (France); CNRS, Inst NEEL, F-38000 Grenoble (France); Wang, Cong, E-mail: congwang@buaa.edu.cn; Sun, Ying [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, 100191 Beijing (China); Colin, Claire V. [Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble (France); CNRS, Inst NEEL, F-38000 Grenoble (France); Chu, Lihua [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, School of Renewable Energy, North China Electric Power University, Beijing 102206 (China)

    2015-06-07

    The Cu-doping effect on the lattice and magnetic properties in Mn{sub 3}Ni{sub 1−x}Cu{sub x}N (x = 0, 0.3, 0.5, 0.7, 1.0) was extensively investigated. We observed that the Cu-doping at the Ni site complicated the magnetic ground states, which induced the competition of antiferromagnetic and ferromagnetic interactions. Spin-glass-like behavior, arising from possible site-randomness and competing interactions of magnetism, was observed in compounds with x = 0.3, 0.5, and 0.7, and typically discussed by means of the measurement of ac magnetic susceptibility for x = 0.7. The negative thermal expansion (NTE) behavior, due to the magnetic ordering transition, was observed in Mn{sub 3}Ni{sub 1−x}Cu{sub x}N compounds using variable temperature x-ray diffraction. It reveals that the introduction of Cu effectively broadens the temperature range displaying negative thermal expansion. The relationship between the local lattice distortion and the competing magnetic ground states might play an important role in broadening the NTE temperature range in this antiperovskite compound.

  9. Magnetically driven negative thermal expansion in antiperovskite Ga1-xMnxN0.8Mn3 (0.1 ≤ x ≤ 0.3)

    Science.gov (United States)

    Guo, X. G.; Lin, J. C.; Tong, P.; Wang, M.; Wu, Y.; Yang, C.; Song, B.; Lin, S.; Song, W. H.; Sun, Y. P.

    2015-11-01

    Negative thermal expansion (NTE) was investigated for Ga1-xMnxN0.8Mn3 (0.1 ≤ x ≤ 0.3). As x increases, the temperature range where lattice contracts upon heating becomes broad and shifts to lower temperatures. The coefficient of linear thermal expansion beyond -40 ppm/K with a temperature interval of ˜50 K was obtained around room temperature in x = 0.2 and 0.25. Local lattice distortion which was thought to be intimately related to NTE is invisible in the X-ray pair distribution function of x = 0.3. Furthermore, a zero-field-cooling exchange bias was observed as a result of competing ferromagnetic (FM) and antiferromagnetic (AFM) orders. The concomitant FM order serves as an impediment to the growth of the AFM order, and thus broadens the temperature range of NTE. Our result suggests that NTE can be achieved in antiperovskite manganese nitrides by manipulating the magnetic orders without distorting the local structure.

  10. Trends in negative thermal expansion behavior for AMO 2 ( A=Cu or Ag; M=Al, Sc, In, or La) compounds with the delafossite structure

    Science.gov (United States)

    Li, J.; Sleight, A. W.; Jones, C. Y.; Toby, B. H.

    2005-01-01

    Powder neutron diffraction data were obtained from 30 to 600 K for CuAlO 2, CuInO 2, CuLaO 2, 2H CuScO 2, 3R CuScO 2, and AgInO 2. Rietveld refinements of these data showed negative thermal expansion (NTE) of the O-Cu-O linkage in all cases. This behavior was especially strong for CuLaO 2 and CuScO 2, where it persisted up to our maximum measuring temperature of 600 K. This NTE in turn caused NTE of the c cell edge, which was moderated by the positive thermal expansion of the M-O bonds. The NTE behavior increases in the Cu MO 2 series as the size of M increases. No NTE behavior was found for the O-Ag-O linkage in AgInO 2; nonetheless, this compound did exhibit NTE for the c cell edge at low temperatures. For CuLaO 2 there is NTE for both the a and c cell edges at low temperatures. Structural trends for compounds with the delafossite structure are discussed with respect to both composition and temperature.

  11. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part I: atmospheric expansion and thermal escape.

    Science.gov (United States)

    Erkaev, Nikolai V; Lammer, Helmut; Odert, Petra; Kulikov, Yuri N; Kislyakova, Kristina G; Khodachenko, Maxim L; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

    2013-11-01

    The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H₂O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 R(Earth) and a mass of 10 M(Earth). We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general.

  12. A study of uniform stars using 1/d-expansions and numerical methods

    Science.gov (United States)

    Gaunt, D. S.; Yu, T. C.

    2000-02-01

    We study a lattice model of an interacting uniform self-avoiding star polymer with f branches. A 1/d -expansion for the limiting reduced free energy is derived through order 1/d for general f and, for f = 3, to order 1/d 2 . The terms in the expansion are independent of f and agree term by term with the corresponding expansion for interacting self-avoiding walks. We also present a miscellany of numerical results obtained by more conventional series and Monte Carlo techniques. All our results, both past and present, support the conjecture that the limiting reduced free energies of f -stars, walks and polygons are identical for all values of the interaction parameter icons/Journals/Common/beta" ALT="beta" ALIGN="TOP"/> .

  13. Study of variation of thermal diffusivity of advanced composite ...

    Indian Academy of Sciences (India)

    Administrator

    Modified Angstrom method is applied to study the variation of thermal diffusivity of plain woven fabric composite in closed ... Keywords. Thermal diffusivity; composite material; cryogenic temperature; phase difference; modified Ang- strom method. .... where D is the thermal diffusivity, k the heat conductivity and ρ the thermal ...

  14. Clonal expansion under the microscope: studying lymphocyte activation and differentiation using live-cell imaging.

    Science.gov (United States)

    Polonsky, Michal; Chain, Benjamin; Friedman, Nir

    2016-03-01

    Clonal expansion of lymphocytes is a hallmark of vertebrate adaptive immunity. A small number of precursor cells that recognize a specific antigen proliferate into expanded clones, differentiate and acquire various effector and memory phenotypes, which promote effective immune responses. Recent studies establish a large degree of heterogeneity in the level of expansion and in cell state between and within expanding clones. Studying these processes in vivo, while providing insightful information on the level of heterogeneity, is challenging due to the complex microenvironment and the inability to continuously track individual cells over extended periods of time. Live cell imaging of ex vivo cultures within micro fabricated arrays provides an attractive methodology for studying clonal expansion. These experiments facilitate continuous acquisition of a large number of parameters on cell number, proliferation, death and differentiation state, with single-cell resolution on thousands of expanding clones that grow within controlled environments. Such data can reveal stochastic and instructive mechanisms that contribute to observed heterogeneity and elucidate the sequential order of differentiation events. Intercellular interactions can also be studied within these arrays by following responses of a controlled number of interacting cells, all trapped within the same microwell. Here we describe implementations of live-cell imaging within microwell arrays for studies of lymphocyte clonal expansion, portray insights already gained from these experiments and outline directions for future research. These tools, together with in vivo experiments tracking single-cell responses, will expand our understanding of adaptive immunity and the ways by which it can be manipulated.

  15. Plume expansion of a laser-induced plasma studied with the particle-in-cell method

    DEFF Research Database (Denmark)

    Ellegaard, Ole; Nedela, T; Urbassek, H

    2002-01-01

     The initial stage of laser-induced plasma plume expansion from a solid in vacuum and the effect of the Coulomb field have been studied. We have performed a one-dimensional numerical calculation by mapping the charge on a computational grid according to the particle-in-cell (PIC) method of Birdsall...

  16. Plume expansion of a laser-induced plasma studied with the particle-in-cell method

    DEFF Research Database (Denmark)

    Ellegaard, O.; Nedelea, T.; Schou, Jørgen

    2002-01-01

    The initial stage of laser-induced plasma plume expansion from a solid in vacuum and the effect of the Coulomb field have been studied. We have performed a one-dimensional numerical calculation by mapping the charge on a computational grid according to the particle-in-cell (PIC) method of Birdsall...

  17. 76 FR 55732 - Public Listening Sessions Regarding the Maritime Administration's Panama Canal Expansion Study...

    Science.gov (United States)

    2011-09-08

    ... Maritime Administration Public Listening Sessions Regarding the Maritime Administration's Panama Canal Expansion Study and the America's Marine Highway Program AGENCY: Maritime Administration, DOT. ACTION: Notice. SUMMARY: The purpose of this notice is to announce a series of public listening sessions and...

  18. Plasma volume expansion by medium molecular weight hydroxyethyl starch in neonates: a pilot study.

    Science.gov (United States)

    Liet, Jean-Michel; Bellouin, Anne-Sophie; Boscher, Cécile; Lejus, Corinne; Rozé, Jean-Christophe

    2003-07-01

    To study the renal effects (measured by creatininemia) of plasma volume expansion with a medium molecular weight hydroxyethyl starch in the newborn. A prospective, randomized, double-blinded, pilot study. The study included 26 neonates weighing 690-4030 g (gestational age, 26-40 wks), without cardiac or renal failure or major hemostasis abnormalities and requiring a peripherally inserted central catheter for parenteral nutrition. Pediatric and neonatal intensive care unit of a university-affiliated hospital. Plasma volume expansion was performed to facilitate insertion of the central catheter. After parental consent, neonates were randomly allocated to receive intravenous infusions at 10 mL.kg(-1) of 5% albumin or 6% hydroxyethyl starch 200/0.5. Sample size was calculated to detect an increase in mean creatininemia of >20 micromol.L(-1) (with alpha = 0.05, beta = 0.80). No clinically or statistically significant differences were found between the two groups 6 hrs, 24 hrs, 48 hrs, and 7 days after plasma volume expansion. The study could detect an increase in creatininemia > or =20 micromol.L(-1) with a power of 80%. In 13 healthy neonates, plasma volume expansion with 10 mL.kg(-1) of 6% hydroxyethyl starch 200/0.5 does not increase creatininemia.

  19. Influence of disorder-to-order transition on lattice thermal expansion and oxide ion conductivity in (Ca(x)Gd(1-x))(2)(Zr(1-x)M(x))2O7 pyrochlore solid solutions.

    Science.gov (United States)

    Radhakrishnan, A N; Rao, P Prabhakar; Linsa, K S Mary; Deepa, M; Koshy, Peter

    2011-04-21

    The effect of simultaneous substitutions of Ca at A site and Nb or Ta at B site in pyrochlore-type solid solutions: (Ca(x)Gd(1-x))(2)(Zr(1-x)M(x))(2)O(7) (x = 0.1, 0.2, 0.3, 0.4, 0.5 and M = Nb or Ta) were studied by powder X-ray diffraction (XRD), FT NIR Raman spectroscopic techniques and transmission electron microscopy. The solid solutions were prepared by the conventional high-temperature ceramic route. The XRD results and Rietveld analysis revealed that the defect fluorite structure of Gd(2)Zr(2)O(7) progressively changed to a more ordered pyrochlore phase by simultaneous substitutions at A and B sites. Raman spectroscopy reveals the progressive ordering in the anion sublattice with simultaneous doping. High-resolution images and selected-area electron diffraction patterns obtained from TEM confirms the XRD and Raman spectroscopic results. High-temperature XRD studies show that the lattice expansion coefficient in these pyrochlore oxides is of the order of 10(-6) K(-1). Lattice thermal expansion coefficient increases with increase of disorder in pyrochlore oxides, and hence the variation of thermal expansion coefficient with composition is also a good indicator of disordering in pyrochlore-type oxides. The ionic conducting properties of the samples were characterised by impedance spectroscopy, and it was found that Nb-doped compositions show a considerable change in conductivity near the phase boundary of disordered pyrochlore and defect fluorite phases.

  20. Solar thermal electric power information user study

    Energy Technology Data Exchange (ETDEWEB)

    Belew, W.W.; Wood, B.L.; Marle, T.L.; Reinhardt, C.L.

    1981-02-01

    The results of a series of telephone interviews with groups of users of information on solar thermal electric power are described. These results, part of a larger study on many different solar technologies, identify types of information each group needed and the best ways to get information to each group. The report is 1 of 10 discussing study results. The overall study provides baseline data about information needs in the solar community. An earlier study identified the information user groups in the solar community and the priority (to accelerate solar energy commercialization) of getting information to each group. In the current study only high-priority groups were examined. Results from five solar thermal electric power groups of respondents are analyzed: DOE-Funded Researchers, Non-DOE-Funded Researchers, Representatives of Utilities, Electric Power Engineers, and Educators. The data will be used as input to the determination of information products and services the Solar Energy Research Institute, the Solar Energy Information Data Bank Network, and the entire information outreach community should be preparing and disseminating.

  1. Thermal expansion, internal stresses and porosity distribution in AlSiCp MMC; Thermische Ausdehnung, innere Spannungen und Porenverteilung in AlSiCp Metallmatrixverbundwerkstoffen

    Energy Technology Data Exchange (ETDEWEB)

    Requena, G.; Degischer, H.P.; Kaminski, H. [TU Wien, Institut fuer Werkstoffwissenschaft und Werkstofftechnologie (Austria); Buslaps, T.; Di Michiel, M. [Europ. Synchrotron-Strahlungsquelle (ESRF), Grenoble (France); Schoebel, M.

    2007-11-15

    AlSi7Mg/SiC/70p (AlSiC) is used for heat sinks because of its good thermal conductivity combined with a low coefficient of thermal expansion (CTE). These properties are important for power electronic devices where heat sinks have to provide efficient heat transfer to a cooling device. A low CTE is essential for a good surface bonding of the heat sink material to the isolating ceramics. Otherwise mismatch in thermal expansion would lead to damage of the bonding degrading the thermal contact within the electronic package. Therefore AlSiC replaces increasingly copper heat sinks. The CTE mismatch between isolation and a conventional metallic heat sink is transferred into the metal matrix composite (MMC). The stability of the external and internal interface bonding is essential for the heat sink function of AlSiC. In situ thermal cycling (RT - 400 C) measurements of an AlSi7Mg/SiC/70p MMC are reported yielding the pore volume fraction and internal stresses between the matrix and the reinforcements in function of temperature. The changes in pore volume fractions are determined by synchrotron tomography and residual stresses by synchrotron diffraction at ESRF-ID15A. The measurements show a relationship between thermal expansion, residual stresses and pore formation in the MMC. The results obtained from the in situ measurements reveal a thermo elastic range with inversion of the dominant tensile stresses in the matrix into compressive up to 200 C followed by plastic matrix deformation reducing the volume of pores during heating. A reverse process takes place during cooling from 500 C starting with elastic matrix strains converting into tensile stresses increasing the pore volume fraction again. Below 200 C, the CTE behaves again according to thermo elastic calculations. Damage like in low cycle fatigue could be observed after multiple extreme cooling-heating cycles between -100 C and +400 C, which increase the volume fraction and the size of the voids. (Abstract Copyright

  2. Pressure-induced cubic-to-orthorhombic phase transformation in the negative thermal expansion material HfW2O8

    Science.gov (United States)

    Jorgensen, J. D.; Hu, Z.; Short, S.; Sleight, A. W.; Evans, J. S. O.

    2001-03-01

    The effect of pressure on the crystal structure of HfW2O8 has been investigated by neutron powder diffraction. At a hydrostatic pressure of 0.62 GPa at room temperature the cubic material transforms, with a 5% reduction in volume, to the same orthorhombic phase that is seen in the isostructural compound ZrW2O8 above 0.21 GPa. The transformation is sluggish, requiring about 24 h to complete at constant pressure. Once formed, the orthorhombic phase is retained upon release of pressure. Upon heating to 360 K, the metastable orthorhombic phase transforms back to the cubic phase. The substantially higher pressure for the cubic-to-orthorhombic transition in HfW2O8, compared to ZrW2O8, may be important for the application of this material in composites with controlled thermal expansion because rather large local pressures can occur in such composites.

  3. Dielectric and thermal studies on gel grown strontium tartrate ...

    Indian Academy of Sciences (India)

    /fulltext/boms/033/04/0377-0382. Keywords. Permittivity; polarization effects; strontium tartrate; thermal properties; dielectric properties. Abstract. Results of dielectric and thermal studies on strontium tartrate pentahydrate crystals are described.

  4. Quartz: structural and thermodynamic analyses across the α ↔ β transition with origin of negative thermal expansion (NTE) in β quartz and calcite

    Energy Technology Data Exchange (ETDEWEB)

    Antao, Sytle M.

    2016-04-01

    The temperature variation,T, of the crystal structure of quartz, SiO2, from 298 to 1235 K was obtained with synchrotron powder X-ray diffraction data and Rietveld structure refinements. The polymorphic transformation fromP3221 (low-T, α quartz) toP6222 (high-T, β quartz) occurs at a transition temperature,Ttr= 847 K. TheTvariations of spontaneous strains and several structural parameters are fitted to an order parameter,Q, using Landau theory. The change in Si atom coordinate, Six, givesTtr-Tc= 0.49 K, which indicates an α ↔ β transition that is weakly first order and nearly tricritical in character (Q4T). Strains give higherTtr-Tcvalues (≃ 7 K). Other fitted parameters are the oxygen Ozcoordinate, Si—Si distance, Si—O—Si and φ angles, and intensity of the (111) reflection,I111. In α quartz, the Si—Si distance increases withTbecause of cation repulsion, so the Si—O—Si angle increases (and φ decreases) and causes the thermal expansion of the framework structure that consists of corner-sharing distorted rigid SiO4tetrahedra. The Si—Si distances contract withTand cause negative thermal expansion (NTE) in β quartz because of increasing thermal librations of the O atom in the Si—O—Si linkage that occur nearly perpendicular to the Si—Si contraction. In calcite, CaCO3, the short Ca—Ca distance expands withT, but the next-nearest Ca—Ca distance, which is of equal length to theaaxis, contracts withTand causes NTE along

  5. Phase equilibria, crystal structure, oxygen nonstoichiometry and thermal expansion of complex oxides in the Nd2O3 - SrO - Fe2O3 system

    Science.gov (United States)

    Aksenova, T. V.; Vakhromeeva, A. E.; Elkalashy, Sh. I.; Urusova, A. S.; Cherepanov, V. A.

    2017-07-01

    The phase equilibria in the ½ Nd2O3 - SrO - ½ Fe2O3 system were systematically studied at 1373 K in air. The homogeneity ranges and crystal structure of the solid solutions Nd1-xSrxFeO3-δ with 0.0≤x≤0.6 (sp. gr. Pbnm) and with 0.7≤x≤0.9 (sp. gr. Pm3m), Sr2-yNdyFeO4-δ with 0.7≤y≤0.9 (sp. gr. I4/mmm), Sr3-zNdzFe2O7-δ with 0.0≤z≤0.4 and 1.8≤z≤1.9 (sp. gr. I4/mmm) and Sr4-uNduFe3O10-δ with 0.7≤u≤0.9 (sp. gr. I4/mmm) were determined by X-ray diffraction analysis of quenched samples. The structural parameters of single-phase oxides were refined by the Rietveld profile method. The changes of oxygen content in the solid solutions Nd1-xSrxFeO3-δ (0.2≤x≤0.9), Sr3-zNdzFe2O7-δ (0.0≤z≤0.4 and z=1.9) and Sr4-uNduFe3O10-δ (0.7≤u≤0.9) versus temperature in air were determined by thermogravimetric analysis. Gradual substitution of neodymium by strontium leads to the decrease of the oxygen content. The average thermal expansion coefficients for the Nd1-xSrxFeO3-δ (0.6≤x≤0.8) samples were calculated within the temperature range 298-1373 K in air. The project of isothermal-isobaric phase diagram for the Nd-Sr-Fe-O system to the compositional triangle of metallic components was presented.

  6. A new isotropic cell for studying the thermo-mechanical behavior of unsaturated expansive clays

    OpenAIRE

    Tang, Anh Minh; Cui, Yu-Jun; Barnel, Nathalie

    2007-01-01

    International audience; This paper presents a new suction-temperature controlled isotropic cell that can be used to study the thermo-mechanical behavior of unsaturated expansive clays. The vapor equilibrium technique is used to control the soil suction; the temperature of the cell is controlled using a thermostat bath. The isotropic pressure is applied using a volume/pressure controller that is also used to monitor the volume change of soil specimen. Preliminary experimental results showed go...

  7. Greenhouse automation, illumination and expansion study for mars desert research station

    OpenAIRE

    Poulet, Lucie; Doule, Ondrej

    2014-01-01

    A partially or fully autonomous food production facility is one of the most important elements in any extraterrestrial settlement. The GreenHab, the greenhouse of the Mars Desert Research Station (MDRS), provides an excellent opportunity for an expansion study, considering it both as an experimental facility for crop growth but also as a food provider for the crew. The current GreenHab is a basic horizontal cylindrical structure divided into two parts. The larger part is used for vegetables g...

  8. Influence of sodium dodecyl benzene sulfonate (SDBS) on the morphology and negative thermal expansion property of ZrW{sub 2}O{sub 8} powders synthesized by hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Sun Xiujuan; Yang Juan; Liu Qinqin [School of Materials Science and Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, Jiangsu (China); Cheng Xiaonong [School of Materials Science and Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, Jiangsu (China)], E-mail: xncheng@ujs.edu.cn

    2009-07-29

    ZrW{sub 2}O{sub 8} powders were prepared by hydrothermal thermal method using sodium dodecyl benzene sulfonate (SDBS) as surfactant. The products were investigated by X-ray diffraction (XRD) method, scanning electron microscopy (SEM), thermogravimetric and differential scanning calorimetry (TG-DSC) and Fourier transform infrared (FTIR) absorption spectra. Results indicate that the resulting powders are single cubic phase with high crystallinity. With increasing the amount of SDBS, morphology and particle size change from rod-like with an average dimension of 1.2 {mu}m x 1.2 {mu}m x 10 {mu}m to layered column with an average diameter of 0.4 {mu}m. ZrW{sub 2}O{sub 8} powders exhibit negative thermal expansion property. And the amount of SDBS is not influence on the average thermal expansion coefficients. The thermal expansion coefficients are about similar with an average value of -5.8 x 10{sup -6} deg. C{sup -1} from room temperature to 500 deg. C. However, the morphology has some effect on the thermal expansion coefficient of {alpha}-ZrW{sub 2}O{sub 8}.

  9. Changes in graphite coefficient of thermal expansion due to fast neutron irradiation and applied stress in the temperature range 300C-1200C

    Energy Technology Data Exchange (ETDEWEB)

    Marsden, B.J. [AEA Technology Plc, Risley, Warrington, Cheshire (United Kingdom); Arai, Taketoshi [Oarai Research Establishment, Japan Atomic Energy Research Institute JAERI, Ibaraki-ken (Japan); McLachlan, N. [Nuclear Electric Ltd, Edinburgh, Scotland (United Kingdom)

    1998-09-01

    Changes in coefficient of thermal expansion (CTE) in nuclear graphite are important because they are related to dimensional change and the thermal stressing of graphite moderated reactor graphite components. The CTE of nuclear graphite can be modified by fast neutron irradiation, stress and creep strain. Various theories exist which relate the CTE of the individual graphite crystallite to the CTE of the polycrystalline graphite through a structure factor. This structure factor is a function of the graphite crystal orientation and the accommodation available due to local crystal porosity. The porosity can be taken up by raising the temperature of the graphite, which causes the lattice `c` spacing to expand, or by fast neutron irradiation induced crystal dimensional changes. It is also proposed that this porosity can be taken up by stressing unirradiated graphite, although there appears to be some evidence from Japan that the anisotropy of graphite is also altered by pre-stress. Annealing of creep strain specimens has shown that not all of irradiation induced creep strain is responsible for modifying CTE. 12 refs.

  10. Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

    Science.gov (United States)

    Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.; Medina, A. N.; Baesso, M. L.; Astrath, N. G. C.; Astrath, F. B. G.; Santos, A. D.; Moraes, J. C. S.; Bento, A. C.

    2013-11-01

    The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (˜7 min) and with similar thermal expansion (˜12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its application in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10-3 cm2/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s0.5/cm2 K and volume heat capacity (5.2 ± 0.7) J/cm3 K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water).

  11. Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

    Energy Technology Data Exchange (ETDEWEB)

    Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.; Medina, A. N.; Baesso, M. L.; Astrath, N. G. C.; Astrath, F. B. G.; Bento, A. C., E-mail: acbento@uem.br [Departamento de Física, Grupo de Espectroscopia Fotoacústica e Fototérmica, Universidade Estadual de Maringá – UEM, Av. Colombo 5790, 87020-900 Maringá, Paraná (Brazil); Santos, A. D.; Moraes, J. C. S. [Departamento de Física e Química, Universidade Estadual Paulista Júlio de Mesquita Filho – UNESP, Av. Brasil 56, 15385-000 Ilha Solteira, SP (Brazil)

    2013-11-21

    The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (∼7 min) and with similar thermal expansion (∼12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its application in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10{sup −3} cm{sup 2}/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s{sup 0.5}/cm{sup 2} K and volume heat capacity (5.2 ± 0.7) J/cm{sup 3} K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water)

  12. Magnetostriction and thermal expansion of high T c magnetic superconductors REBa 2Cu 3O 7- x ( RE = Eu, Sm, Gd, Dy, Ho, Er, TmandY) Gd, Dy, Ho, Er, Tm and Y)

    Science.gov (United States)

    Del Moral, A.; Ibarra, M. R.; Arnaudas, J. I.; Algarabel, P. A.; Marquina, C.; Morán, E.; Alario, M. A.

    1988-12-01

    Thermal expansion and magnetostriction measurements for REBa 2Cu 3O 7 -x superconductors are reported, up to 2.4 T and down to 3.8 K. Anisotropic striction is negligible, except for Dy and Ho compounds where is of single-ion origin. Volume striction displays similar order of magnitude and thermal variation, and it is weak (except for Dy compound) pointing to a "host" diamagnetic lattice origin.

  13. Role of graphene layers on the radiation resistance of copper-graphene nanocomposite: Inhibiting the expansion of thermal spike

    Science.gov (United States)

    Huang, Hai; Tang, Xiaobin; Chen, Feida; Liu, Jian; Chen, Da

    2017-09-01

    Metal-graphene nanocomposites are expected to have excellent radiation resistance. The intrinsic role of the graphene layers (GrLs) in their performance has not been fully understood. Five copper-graphene nanocomposite (CGNC) systems were used to investigate the detailed mechanisms underpinning this behaviour by atomistic simulation. Results showed that GrLs can reduce the formation, growth, and intensity of the thermal spike of CGNC; this effect became more evident with the increasing number of layers of graphene. The role of the GrLs can be explained by three mechanisms: first, the ultra-strength C-C bonds of graphene hindered the penetration of high-energy atoms, second, the number of recoiled atoms decreased with the increasing number of layers of graphene, and third, the energy dissipation along the graphene planes also indirectly weakened the damage caused to the entire system. These mechanisms may provide a pathway to prevent material degradation in extreme radiation environments.

  14. SPECTROSCOPIC STUDIES AND THERMAL ANALYSIS OF LEAD ...

    African Journals Online (AJOL)

    a

    KEY WORDS: Lead, Tin, Schiff base, Infrared spectra, Thermal analysis. INTRODUCTION ... elemental analysis, infrared spectra as well as by their thermal analysis (DTA and TG). Analysis results are reported in Table 1. The percentage of lead and tin metals were determined using ..... PbO + 5C + 10C2H2 + N2 + CO.

  15. High-Temperature Oxidation-Resistant and Low Coefficient of Thermal Expansion NiAl-Base Bond Coat Developed for a Turbine Blade Application

    Science.gov (United States)

    2003-01-01

    Many critical gas turbine engine components are currently made from Ni-base superalloys that are coated with a thermal barrier coating (TBC). The TBC consists of a ZrO2-based top coat and a bond coat that is used to enhance the bonding between the superalloy substrate and the top coat. MCrAlY alloys (CoCrAlY and NiCrAlY) are currently used as bond coats and are chosen for their very good oxidation resistance. TBC life is frequently limited by the oxidation resistance of the bond coat, along with a thermal expansion mismatch between the metallic bond coat and the ceramic top coat. The aim of this investigation at the NASA Glenn Research Center was to develop a new longer life, higher temperature bond coat by improving both the oxidation resistance and the thermal expansion characteristics of the bond coat. Nickel aluminide (NiAl) has excellent high-temperature oxidation resistance and can sustain a protective Al2O3 scale to longer times and higher temperatures in comparison to MCrAlY alloys. Cryomilling of NiAl results in aluminum nitride (AlN) formation that reduces the coefficient of thermal expansion (CTE) of the alloy and enhances creep strength. Thus, additions of cryomilled NiAl-AlN to CoCrAlY were examined as a potential bond coat. In this work, the composite alloy was investigated as a stand-alone substrate to demonstrate its feasibility prior to actual use as a coating. About 85 percent of prealloyed NiAl and 15 percent of standard commercial CoCrAlY alloys were mixed and cryomilled in an attritor with stainless steel balls used as grinding media. The milling was carried out in the presence of liquid nitrogen. The milled powder was consolidated by hot extrusion or by hot isostatic pressing. From the consolidated material, oxidation coupons, four-point bend, CTE, and tensile specimens were machined. The CTE measurements were made between room temperature and 1000 C in an argon atmosphere. It is shown that the CTE of the NiAl-AlN-CoCrAlY composite bond coat

  16. Rapid Urban Expansion and Its Implications on Geomorphology: A Remote Sensing and GIS Based Study

    Directory of Open Access Journals (Sweden)

    S. N. Mohapatra

    2014-01-01

    Full Text Available Topography, vegetation, climate, water table, and even the anthropogenic activities all are affected by urban growth through diverse mechanisms. The present study focuses on the implications of urban expansion on geomorphology in the historical city of Gwalior in central India. The expansion of urban area has been quantified by deriving data for four decades (1972–2013 from the Landsat images. The results show that the urban built-up area has increased by 08.48 sq. km during the first eighteen years (1972–1990 which has increased to 16.28 sq. km during the next sixteen years (1990–2006. The built-up area has gone up to 23.19 sq. km in the next seven years (2006–2013. Overall during the last 40 years the growth of the urban built-up is nearly three times of the built-up areas in 1972. The average decadal growth rate of population is 27.28 percent while that of built-up land is 36.29 percent. The construction activities have affected important geomorphic features such pediplain, buried pediplain, residual hills, and denudational hills. It was concluded that, instead of shortsighted urban development, proper measures should be taken in accordance with scientific planning for the urban expansion of the city in the future.

  17. Enhancement of Tissue Expansion by Calcium Channel Blocker: A preliminary study

    Directory of Open Access Journals (Sweden)

    Aktas Alper

    2003-10-01

    Full Text Available Abstract Background Reconstruction of the defects after surgical resection of tumors is one of the important issues in surgical oncology. It is essential that the defect should be covered with a tissue quite similar to the original one and is best achieved by harvesting tissue from an area adjacent to the defect. Tissue expansion is one of the most frequently used reconstructive techniques. A number of studies evaluated blood circulation, capsule formation, tissue tolerance, histomorphological changes and complications of expander placement. However, only a few attempted to enhance tissue expansion. This study we aimed to evaluate verapamil, a calcium channel blocker, to enhance tissue expansion. Material and method Twelve New Zealand rabbits weighing between 900 gm and 1200 gm were assigned into study and control groups. High volume expanders (100, 200 or 300 cc were placed into the subcutaneous tissue. Rabbits in the study group received verapamil. Expanders in the control group were inflated every three days to achieve same pressure as the study group. The size of the flaps was assessed by applying pressure on tip of the flap to demonstrate the contraction. Histopathological examinations were performed. Results By administering liquid earlier and more quickly less flap retraction was observed in the study group. In the control group expanders were exposed in two rabbits while no complication occurred in the study group. Following extraction of the expanders, the flaps were elevated and less retraction was observed in the study group compared to controls. Conclusion Verapamil is safe when used topically and provides less retracted flaps. It can be suggested that verapamil acts on the myofibroblasts in the capsule around tissue expanders and thus increases efficiency of the expanders.

  18. Thermal Stress Awareness, Self-Study #18649

    Energy Technology Data Exchange (ETDEWEB)

    Chochoms, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-15

    Thermal stresses can expose individuals to a variety of health hazards at work, home, and play. Every year thermal stresses cause severe injuries and death to a large range of people, from elderly people in cities during summer heat waves to young people engaged in winter mountaineering. Awareness is the key to preventing the health hazards associated with thermal stresses. This course is designed for personnel at Los Alamos National Laboratory (LANL). It addresses both heat and cold stresses and discusses their factors, signs and symptoms, treatments, and controls.

  19. Thermal conductivity of penta-graphene from molecular dynamics study.

    Science.gov (United States)

    Xu, Wen; Zhang, Gang; Li, Baowen

    2015-10-21

    Using classical equilibrium molecular dynamics simulations and applying the original Tersoff interatomic potential, we study the thermal transport property of the latest two dimensional carbon allotrope, penta-graphene. It is predicted that its room-temperature thermal conductivity is about 167 W/mK, which is much lower than that of graphene. With normal mode decomposition, the accumulated thermal conductivity with respect to phonon frequency and mean free path is analyzed. It is found that the acoustic phonons make a contribution of about 90% to the thermal conductivity, and phonons with mean free paths larger than 100 nm make a contribution over 50%. We demonstrate that the remarkably lower thermal conductivity of penta-graphene compared with graphene results from the lower phonon group velocities and fewer collective phonon excitations. Our study highlights the importance of structure-property relationship and provides better understanding of thermal transport property and valuable insight into thermal management of penta-graphene.

  20. Three-dimensional assessment of buccal alveolar bone after rapid and slow maxillary expansion: a clinical trial study.

    Science.gov (United States)

    Brunetto, Mauricio; Andriani, Juliana da Silva Pereira; Ribeiro, Gerson Luiz Ulema; Locks, Arno; Correa, Marcio; Correa, Letícia Ruhland

    2013-05-01

    The purposes of this study were to analyze and compare the immediate effects of rapid and slow maxillary expansion protocols, accomplished by Haas-type palatal expanders activated in different frequencies of activation on the positioning of the maxillary first permanent molars and on the buccal alveolar bones of these teeth with cone-beam computerized tomography. The sample consisted of 33 children (18 girls, 15 boys; mean age, 9 years) randomly distributed into 2 groups: rapid maxillary expansion (n = 17) and slow maxillary expansion (n = 16). Patients in the rapid maxillary expansion group received 2 turns of activation (0.4 mm) per day, and those in the slow maxillary expansion group received 2 turns of activation (0.4 mm) per week until 8 mm of expansion was achieved in both groups. Cone-beam computerized tomography images were taken before treatment and after stabilization of the jackscrews. Data were gathered through a standardized analysis of cone-beam computerized tomography images. Intragroup statistical analysis was accomplished with the Wilcoxon matched-pairs test, and intergroup statistical analysis was accomplished with analysis of variance. Linear relationships, among all variables, were determined by Spearman correlation. Both protocols caused buccal displacement of the maxillary first permanent molars, which had more bodily displacement in the slow maxillary expansion group, whereas more inclination was observed in the rapid maxillary expansion group. Vertical and horizontal bone losses were found in both groups; however, the slow maxillary expansion group had major bone loss. Periodontal modifications in both groups should be carefully considered because of the reduction of spatial resolution in the cone-beam computerized tomography examinations after stabilization of the jackscrews. Modifications in the frequency of activation of the palatal expander might influence the dental and periodontal effects of palatal expansion. Copyright © 2013

  1. Rehabilitation of a Distressed Single Storied Building Founded on Expansive Soil: A Case Study

    Science.gov (United States)

    Pakrashi, Somdev

    2017-12-01

    A single storied building was constructed on strip foundation system—on a subsoil, with high expansivity, without taking necessary precautions and it suffered extensive cracks and damages in roof slab, beams, columns and brick walls, subsidence /upheavals in floors etc. within 2/3 years of its construction and consequently it had to be abandoned. The study examines the reasons for the severe damages, cracks etc. and also suggests remediation by ground improvement and other necessary measures that were actually taken up, to rehabilitate the highly distressed and abandoned building within a reasonably short period of time—at a reasonable cost.

  2. Rehabilitation of a Distressed Single Storied Building Founded on Expansive Soil: A Case Study

    Science.gov (United States)

    Pakrashi, Somdev

    2017-10-01

    A single storied building was constructed on strip foundation system—on a subsoil, with high expansivity, without taking necessary precautions and it suffered extensive cracks and damages in roof slab, beams, columns and brick walls, subsidence/upheavals in floors etc. within 2/3 years of its construction and consequently it had to be abandoned. The study examines the reasons for the severe damages, cracks etc. and also suggests remediation by ground improvement and other necessary measures that were actually taken up, to rehabilitate the highly distressed and abandoned building within a reasonably short period of time—at a reasonable cost.

  3. A STUDY ON DEF-RELATED EXPANSION IN HEAT-CURED CONCRETE

    Science.gov (United States)

    Kawabata, Yuichiro; Matsushita, Hiromichi

    This paper reports the requirements for deleterious expansion due to delayed ettringite formation (DEF) based on field experience. In recent years, the delete rious expansion of concrete have been reported. The concrete have been characterized by expansion and cracking after several years of service in environments exposed in wet conditions. In many cases, the concrete consists of white cement, limestone and copper slag and it has been manufactured at elevated temperatures for early shipment. From detailed analysis, it was made clear that the cause of deleterious expansion was DEF. The gaps which are featured in DEF-damaged concrete were observed around limest one aggregate. There was a possibility that use of limestone aggregate affects DEF-related expansion while the condition of steam curing was the most effective factor for DEF-related expansion. Based on experimental data, the mechanism of DEF-related expansion and the methodology of diagnosing DEF-deterior ated concrete structures were discussed in this paper.

  4. Experimental study of rotating Hagen-Poiseuille flow discharging into a 1:8 sudden expansion

    Science.gov (United States)

    Miranda-Barea, A.; Martínez-Arias, B.; Parras, L.; Burgos, M. A.; del Pino, C.

    2015-03-01

    In this paper, we present experimental evidence for the five different states that result from rotating Hagen-Poiseuille flow when it discharges into a 1:8 sudden expansion, namely: stable, convectively unstable, unstable shear layer, stable and unstable vortex breakdowns. Sanmiguel-Rojas et al. ["Three-dimensional structure of confined swirling jets at moderately large Reynolds numbers," Phys. Fluids 20, 044104 (2008)] numerically predicted four of these five states and mapped the transition from one state to another. Our main objective is to study the onset of instabilities and vortex breakdown in these states experimentally. For this purpose, we visualize the flow at the inlet of the expansion for several values of moderately large Reynolds numbers, Re, and of swirl parameters, S. We analyze the inner region of the state that corresponds to the unstable shear layer in the sudden expansion and find two different states that share the same character, although they have different non-dimensional frequencies. The first relates to an oscillating structure near the axis, which arises at a small value of the swirl parameter, as well as to a generation of vortices that move downstream. The second shows, for greater values of the swirl parameter, vortices interacting with the boundary layer located on the wall of the static container that is perpendicular to the flow direction. In addition, we find a transition from stable to unstable vortex breakdown when perturbations become absolutely unstable inside the rotating pipe flow. Therefore, the most remarkable experimental finding is a new state, namely, unstable or transient vortex breakdown that takes place for the same pair of values (Rea, Sa) at which the onset of the absolute instability curve appears and intersects the region of stable vortex breakdown.

  5. Numerical evaluation of the coefficients of thermal expansion of fibers in composite materials using a lamina-scale cost function with quasi-analytical gradients

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jae Hyuk [Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Charpentier, Jean Baptiste [École Nationale Supérieur des Mines de Saint-Étienne, Saint-Étienne (France); Sohn, Dong Woo [Korea Maritime and Ocean University, Busan (Korea, Republic of)

    2015-03-15

    In this work, the coefficients of thermal expansion (CTEs) of fibers in composite materials that contain microstructures are numerically evaluated using a lamina-scale cost function with quasi-analytical gradients. To consider the effects of fiber arrangements and local defects, such as interface debonding and voids, a variety of representative volume elements are modeled with a number of finite element meshes. Then, the CTEs of fibers are evaluated by minimizing a lamina-scale cost function that represents the difference between the measured CTEs and the computed CTEs by means of a computational homogenization scheme for the composite lamina. The descent direction of the cost function is obtained using quasi-analytical gradients that take partial derivatives from prediction models, such as the Schapery model and Hashin model defined in an explicit manner, which accelerates the minimization procedure. To verify the performance of the proposed scheme in terms of accuracy and efficiency, the CTEs of constituents calculated using the proposed scheme in a unidirectional composite lamina are compared with experimental values reported in the literature. Furthermore, the convergence behavior of the proposed scheme with quasi-analytical gradients is also investigated and compared with other minimization methods.

  6. Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion

    Directory of Open Access Journals (Sweden)

    Omar Rodriguez

    2016-12-01

    Full Text Available Silica-based and borate-based glass series, with increasing amounts of TiO2 incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion closer to the substrate’s (Ti6Al4V CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO2 in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO2 to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO2 incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass® and Pyrex.

  7. Negative thermal expansion in cubic ZrW2O8: Role of phonons in the entire Brillouin zone from ab initio calculations

    Science.gov (United States)

    Gupta, M. K.; Mittal, R.; Chaplot, S. L.

    2013-07-01

    We report the ab initio density functional theory calculation of phonons in the cubic phase of ZrW2O8 in the entire Brillouin zone and identify specific anharmonic phonons that are responsible for large negative thermal expansion (NTE) in terms of the translation, rotation, and distortion of WO4 and ZrO6. We have used density functional calculations to interpret the experimental phonon spectra as a function of pressure and temperature as reported in literature. We discover that the phonons showing anharmonicity with temperature are not necessarily the same as those showing anharmonicity with pressure although both are of similar frequencies. Only the latter phonons are associated with NTE. Therefore, the cubic and/or quadratic anharmonicity of phonons is not relevant to NTE but just the volume dependence of frequencies. The calculations are able to reproduce the observed anomalous trends, namely, the softening of the low-frequency peak at about 4 meV in the phonon spectra with pressure and its hardening with temperature, whereas, both changes involve a compression of the lattice.

  8. Measurement of anharmonicity of phonons in the negative thermal expansion compound Zn(CN)2 by high pressure inelastic neutron scattering

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Schober, H.

    2009-11-01

    Zn(CN)2 is known to have an isotropic negative thermal expansion (NTE) coefficient (about -51×10-6 K-1) over 10-370 K that is twice as large as that of ZrW2O8. We have measured the pressure dependence of the phonon spectra up to 30 meV from a polycrystalline sample of Zn(CN)2 at pressures of 0, 0.3, 1.9, and 2.8 kbar at temperatures of 165 and 225 K. The measurements enabled us to estimate the energy dependence of the ratios Γi/B (Γi are Grüneisen parameters as a function of phonon energy Ei at ambient pressure and B is the bulk modulus), which reflect the anharmonicity of phonons. We conclude that the phonon modes of low energy below 15 meV play an important role in the understanding of the NTE behavior in Zn(CN)2 and the measured anharmonicity can quantitatively explain the NTE.

  9. Synthesis of Defect Perovskites (He2-x□x)(CaZr)F6 by Inserting Helium into the Negative Thermal Expansion Material CaZrF6.

    Science.gov (United States)

    Hester, Brett R; Dos Santos, António M; Molaison, Jamie J; Hancock, Justin C; Wilkinson, Angus P

    2017-09-27

    Defect perovskites (He2-x□x)(CaZr)F6 can be prepared by inserting helium into CaZrF6 at high pressure. They can be recovered to ambient pressure at low temperature. There are no prior examples of perovskites with noble gases on the A-sites. The insertion of helium gas into CaZrF6 both elastically stiffens the material and reduces the magnitude of its negative thermal expansion. It also suppresses the onset of structural disorder, which is seen on compression in other media. Measurements of the gas released on warming to room temperature and Rietveld analyses of neutron diffraction data at low temperature indicate that exposure to helium gas at 500 MPa leads to a stoichiometry close to (He1□1)(CaZr)F6. Helium has a much higher solubility in CaZrF6 than silica glass or crystobalite. An analogue with composition (H2)2(CaZr)F6 would have a volumetric hydrogen storage capacity greater than current US DOE targets. We anticipate that other hybrid perovskites with small neutral molecules on the A-site can also be prepared and that they will display a rich structural chemistry.

  10. Genetic Code Expansion as a Tool to Study Regulatory Processes of Transcription

    Science.gov (United States)

    Schmidt, Moritz; Summerer, Daniel

    2014-02-01

    The expansion of the genetic code with noncanonical amino acids (ncAA) enables the chemical and biophysical properties of proteins to be tailored, inside cells, with a previously unattainable level of precision. A wide range of ncAA with functions not found in canonical amino acids have been genetically encoded in recent years and have delivered insights into biological processes that would be difficult to access with traditional approaches of molecular biology. A major field for the development and application of novel ncAA-functions has been transcription and its regulation. This is particularly attractive, since advanced DNA sequencing- and proteomics-techniques continue to deliver vast information on these processes on a global level, but complementing methodologies to study them on a detailed, molecular level and in living cells have been comparably scarce. In a growing number of studies, genetic code expansion has now been applied to precisely control the chemical properties of transcription factors, RNA polymerases and histones, and this has enabled new insights into their interactions, conformational changes, cellular localizations and the functional roles of posttranslational modifications.

  11. The two-stage clonal expansion model in occupational cancer epidemiology: results from three cohort studies.

    Science.gov (United States)

    Zeka, Ariana; Gore, Rebecca; Kriebel, David

    2011-08-01

    The objective of this work was to apply the two-stage clonal expansion model, with the intention to expand the literature on epidemiological applications of the model and demonstrate the feasibility of incorporating biologically based modelling methods into the widely used retrospective cohort study. The authors fitted the two-stage clonal expansion model model to three occupational cohort studies: (1) a cohort of textile workers exposed to asbestos and followed for lung cancer mortality; (2) a cohort of diatomaceous earth workers exposed to silica and also followed for lung cancer mortality; and (3) a cohort of automotive manufacturing workers exposed to straight metalworking fluid (MWF) and followed for larynx cancer incidence. The model allowed the authors to estimate exposure effects in three stages: cancer initiation (early effects), promotion or malignant transformation (late effects). In the first cohort, the authors found strong evidence for an early effect of asbestos on lung cancer risk. Findings from analyses of the second cohort suggested early and less evidently late effects of silica on lung cancer risk. In the MWF (third) cohort, there was only weak evidence of straight MWF exposure effects on both early and late stages. The authors also observed a late birth cohort effect on larynx cancer risk. The findings for asbestos and silica were essentially confirmatory, supporting evidence for their early effects on lung cancer from a large body of literature. The effect of straight MWF on larynx cancer was less clear.

  12. Preliminary Findings of the South Africa Power System Capacity Expansion and Operational Modelling Study

    Energy Technology Data Exchange (ETDEWEB)

    Reber, Timothy J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Chartan, Erol Kevin [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Brinkman, Gregory L [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-01-01

    Wind and solar power contract prices have recently become cheaper than many conventional new-build alternatives in South Africa and trends suggest a continued increase in the share of variable renewable energy (vRE) on South Africa's power system with coal technology seeing the greatest reduction in capacity, see 'Figure 6: Percentage share by Installed Capacity (MW)' in [1]. Hence it is essential to perform a state-of-the-art grid integration study examining the effects of these high penetrations of vRE on South Africa's power system. Under the 21st Century Power Partnership (21CPP), funded by the U.S. Department of Energy, the National Renewable Energy Laboratory (NREL) has significantly augmented existing models of the South African power system to investigate future vRE scenarios. NREL, in collaboration with Eskom's Planning Department, further developed, tested and ran a combined capacity expansion and operational model of the South African power system including spatially disaggregated detail and geographical representation of system resources. New software to visualize and interpret modelling outputs has been developed, and scenario analysis of stepwise vRE build targets reveals new insight into associated planning and operational impacts and costs. The model, built using PLEXOS, is split into two components, firstly a capacity expansion model and secondly a unit commitment and economic dispatch model. The capacity expansion model optimizes new generation decisions to achieve the lowest cost, with a full understanding of capital cost and an approximated understanding of operational costs. The operational model has a greater set of detailed operational constraints and is run at daily resolutions. Both are run from 2017 through 2050. This investigation suggests that running both models in tandem may be the most effective means to plan the least cost South African power system as build plans seen to be more expensive than optimal by the

  13. Spectroscopic, thermal and biological studies of coordination ...

    Indian Academy of Sciences (India)

    Administrator

    (Cl)(H2O)3]⋅xH2O (M = Cr(III) and Y(III), x = 5 and 6, respectively) were obtained and characterized by physicochemical and spectroscopic methods. The IR spectra of the complexes suggest that the sulfasalazine behaves as a monoanionic bidentate ligand. The thermal decomposition of the complexes as well as ...

  14. Synthesis, spectroscopy, thermal studies and supramolecular ...

    Indian Academy of Sciences (India)

    The chains thus formed are further cross-linked with the aid of H-donor bonds from both the free as well as the coordinated Im. Both 1 and 2 exhibit - stacking interactions. Complex 1 is thermally more stable as compared to 2, and both complexes can be dehydrated to the corresponding anhydrous complexes by heating ...

  15. Thermally stimulated luminescence studies in combustion ...

    Indian Academy of Sciences (India)

    Wintec

    Photoluminescence; thermoluminescence; gamma irradiation; colour centres. 1. Introduction. Thermally stimulated luminescence (TSL), also called thermoluminescence (TL), is extensively used as a techni- que in dosimetry. The energy absorbed by a phosphor on being exposed to some ionizing radiation is released as.

  16. Synthesis, Photophysical, Electrochemical and Thermal Studies of ...

    Indian Academy of Sciences (India)

    solutions in toluene, CH2Cl2 and CHCl3 in a 1 cm path length quartz cuvette as well as thermally deposited thin solid films, on SHIMADZU UV–2401PC at room temperature. The excitation and emission spec- tra were recorded on a Perkin Elmer LS 55 Fluores- cence spectrophotometer. Fluorescence quantum yield.

  17. Tribological Studies of Dynamic Thermal Seal Materials

    Science.gov (United States)

    DeMange, Jeffrey J.; Taylor, Shawn C.

    2016-01-01

    Thermal seals are required on high-speed vehicles in many dynamic applications such as variable inlets in propulsion systems and control surfaces. These seals, often referred to as dynamic thermal seals, must not only mitigate inboard heat transfer, but must also exhibit sufficient durability when scrubbed against mating surfaces. For high-temperature high-speed vehicle applications, the mating surfaces are often made from thermal protection system (TPS) materials, which are typically rougher and more abrasive than TPS materials used at lower temperatures. The high-temperature TPS materials used can include non-ablative (e.g., lightweight porous oxides, ceramic matrix composites) andor ablative systems (e.g., phenolic systems). Due to the increased need for durable high-temperature dynamic seals, researchers working with the NASA Glenn Research Center embarked on an effort to (a) characterize the tribological performance of state-of-the-art thermal seal materials against a variety of TPS materials and (b) develop approaches for improved wear resistance. Tests were conducted using a recently upgraded high-temperature tribometer to assess wear resistance for a variety of tribopairs under multiple conditions. This data will begin to frame the challenges of using these materials and eventually permit an improved ability to design and implement these critical TPS components.

  18. Effect of hygroscopic expansion of resin filling on interfacial gap and sealing: a confocal microscopy study.

    Science.gov (United States)

    Rosales-Leal, Juan I; Castillo-Salmerón, Ramón Del; Molino-Serrano, María A; González-Moreira, Humberto; Cabrerizo-Vílchez, Miguel A

    2013-10-01

    To measure dimensional changes due to hygroscopic expansion and their effect on interface gaps and sealing in four light-cured restorative materials using an original confocal microscopic methodology. The materials tested were an ormocer (Admira [Voco]), a compomer (Dyract AP [Dentsply]), a hybrid composite (Spectrum [Dentsply]), and a nanohybrid composite (Esthet·X [Dentsply]). Water sorption was evaluated by weighing material disks after immersion. Hygroscopic expansion was measured from volumetric variations of material fillings in cylindrical cavities in dentin slices; the interfacial gap size was obtained from the same cavities using a novel confocal microscopic method. Microleakage was evaluated in cavities prepared in extracted third molars. Measurements followed water immersion for 24 h, 1 week, 4 weeks, and 8 weeks. A factorial ANOVA, the Student Newman Keuls test for post-hoc comparisons, the Student's t-test, and the Pearson test were used for the statistical analysis (p hygroscopic expansion, and sealing. Hygroscopic expansion reduced post-polymerization interfacial gaps and improved cavity sealing. Dyract AP and Admira showed the highest water sorption, hygroscopic expansion, and gap size reduction. 1. The proposed methodology is valid to measure hygroscopic expansion and interfacial gap. 2. Water sorption and hygroscopic expansion are positively correlated, and hygroscopic expansion, gap size, and sealing are also positively correlated. 3. The adhesive influences the interfacial gap size and its variation after hygroscopic expansion. 4. Hygroscopic expansion reduces the interfacial gaps generated by polymerization shrinkage and improves cavity sealing.

  19. On skin expansion.

    Science.gov (United States)

    Pamplona, Djenane C; Velloso, Raquel Q; Radwanski, Henrique N

    2014-01-01

    This article discusses skin expansion without considering cellular growth of the skin. An in vivo analysis was carried out that involved expansion at three different sites on one patient, allowing for the observation of the relaxation process. Those measurements were used to characterize the human skin of the thorax during the surgical process of skin expansion. A comparison between the in vivo results and the numerical finite elements model of the expansion was used to identify the material elastic parameters of the skin of the thorax of that patient. Delfino's constitutive equation was chosen to model the in vivo results. The skin is considered to be an isotropic, homogeneous, hyperelastic, and incompressible membrane. When the skin is extended, such as with expanders, the collagen fibers are also extended and cause stiffening in the skin, which results in increasing resistance to expansion or further stretching. We observed this phenomenon as an increase in the parameters as subsequent expansions continued. The number and shape of the skin expanders used in expansions were also studied, both mathematically and experimentally. The choice of the site where the expansion should be performed is discussed to enlighten problems that can lead to frustrated skin expansions. These results are very encouraging and provide insight into our understanding of the behavior of stretched skin by expansion. To our knowledge, this study has provided results that considerably improve our understanding of the behavior of human skin under expansion. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. A Study of Solar Thermal Propulsion System Enhancement via Thermal Storage and Thermal-electric Conversion

    Science.gov (United States)

    2010-03-24

    material. Molybdenum has a thermal conductivity of 138 W/mK, while rheniums is much lower at 39.6 W/mK 2 . Zirconium Boride (ZrB2) and Hafnium Boride ...14,000 Iridium 77 2739 213 147 $42,000 Niobium 41 2750 323 53.7 $170 Molybdenum 42 2896 390 138 $100 The materials listed in Table 1 do not...this paper, several materials with melting points above 3000 K are boride compounds and several of those that are not borides contain elements which

  1. Characterization and thermal expansion of Sr2FexMo2− xO6 double ...

    Indian Academy of Sciences (India)

    SFMO) of different compositions were prepared by sol–gel growth followed by annealing under reducing atmosphere conditions of H2/Ar flow. X-ray powder diffraction studies revealed that the crystal structure of the samples changes from tetragonal ...

  2. a Study on the Thermal Vibration Analysis of the Graphite Disk Under Thermal Shock

    Science.gov (United States)

    Lee, Young-Shin; Kim, Jae-Hoon; Kim, Hyun-Soo; Kim, Duck-Hoi; Ku, Seong-Hoi; Moon, Soon-Il

    Graphite is applied to structural material of the high temperature reactor and nozzle of high energy rocket engine. The excessive vibration and stress field can be occurred for this material due to the severe thermal condition. In this study, the thermal stress and vibration characteristics of ATJ graphite under high temperature condition are investigated by finite element analysis (FEA). The specimen is designed as a disk shape in order to simulate the rocket nozzle combustion condition. The experiment of thermal heat is also conducted using by CO2 laser.

  3. A thermal study of an encapsulated electrical transformer

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, A. [Unidad Geotermia, Temixco (Mexico). Instituto de Investigaciones Electricas; Espinosa-Paredes, G. [Universidad Autonoma Metropolitana, Vicentina (Mexico). Dpto. de Ingenieria de Procesos e Hidraulica; Hernandez, I. [Centro de Sistemas de Manufactura, Nuevo Leon (Mexico). Instituto Tecnologico y de Estudios Superiores de Monterrey

    2002-11-01

    A thermal study of a 45 KVA-prototype encapsulated transformer is described. Casting resin systems were used as insulating systems for encapsulated electric transformers. Normal transformer operation is at full load and, thus the conductor and insulating system becomes hot owing to current circulation through the winding. To determine the various temperature distributions throughout the transformer, the thermal properties of the insulating system and boundary conditions must be known, so that hot spots are located via numerical modelling and maximum permissible temperatures are not attained. Results presented herein include thermal conductivity, thermal diffusivity, and specific heat capacity. Thermal conductivity was obtained experimentally by means of the line-source technique at various temperatures, between room temperature and 155{sup o}C which is the thermal limit of class F insulators. The thermal diffusivity was obtained by parameter estimation by fitting an approximate analytical model to the temperature-time data of the thermal conductivity experiment. Specific heat capacity was obtained from the definition of thermal diffusivity and the insulating-system density. In order to improve the electrical performance of the transformer criteria, a numerical simulation of the different dielectric structures was made using computer program. The boundary conditions for the thermal simulation stage were also determined experimentally from temperature test runs. Finally, in order to obtain data for thermal design, a numerical simulation of the high tension winding was carried out. The thermal simulation stage was performed at different current densities in the conductor with and without electrostatic shields to determine the temperature field and maximum attainable temperatures. Maximum transformer temperature were found to be 15-20{sup o}C below its thermal limit and a correlation of maximum temperature as function of circulating current was developed for design

  4. Composition-thermal expandability relations and oxidation processes in tourmaline studied by in situ Raman spectroscopy

    Science.gov (United States)

    Watenphul, Anke; Malcherek, Thomas; Wilke, Franziska D. H.; Schlüter, Jochen; Mihailova, Boriana

    2017-11-01

    The crystal chemistry of tourmaline, XY3Z6(T6O18)(BO3)3V3W, has a strong influence on the structure and physical properties. Since tourmalines occur in a wide range of geological settings and have large temperature and pressure stability fields, the understanding of the relation between the tourmaline chemistry and thermal expansion allows for better thermodynamic modeling of geological processes. Here, we report dynamic and static thermal expansions as well as mode Grüneisen parameters studied by Raman spectroscopy and single-crystal X-ray diffraction data on several tourmaline species. In addition, oxidation processes in fluor-schorl and Fe2+-bearing elbaite were followed by Raman spectroscopy. Our results emphasize the role of Y-/Z-site occupancy disorder to reduce the local strains and demonstrate that small-size octahedrally coordinated cations perturb the topology of the SiO4 rings, which in turn seems to enhance the anisotropic thermal-expansion response. In addition, it is shown that the temperature-dependent behavior of the VOH modes primarily depends on the occupancy of the Y site, whereas that of the WOH modes depends on the occupancy of the X site. High-temperature Raman experiments in air allowed to follow the oxidation of Fe2+ to Fe3+ in fluor-schorl by analyzing both the framework and OH-stretching phonon modes. It is further demonstrated that under the same conditions, no oxidation of iron is observed for Fe2+-bearing elbaite, which implies that at high oxygen fugacity, iron is only oxidized in tourmaline species with prevalent divalent cations at the Y site.

  5. Periodontal and dental effects of surgically assisted rapid maxillary expansion, assessed by using digital study models

    Directory of Open Access Journals (Sweden)

    Danilo Furquim Siqueira

    2015-06-01

    Full Text Available OBJECTIVE: The present study assessed the maxillary dental arch changes produced by surgically assisted rapid maxillary expansion (SARME. METHODS: Dental casts from 18 patients (mean age of 23.3 years were obtained at treatment onset (T1, three months after SARME (T2 and 6 months after expansion (T3. The casts were scanned in a 3D scanner (D-250, 3Shape, Copenhagen, Denmark. Maxillary dental arch width, dental crown tipping and height were measured and assessed by ANOVA and Tukey's test. RESULTS: Increased transversal widths from T1 and T2 and the maintenance of these values from T2 and T3 were observed. Buccal teeth tipping also showed statistically significant differences, with an increase in all teeth from T1 to T2 and a decrease from T2 to T3. No statistically significant difference was found for dental crown height, except for left first and second molars, although clinically irrelevant. CONCLUSION: SARME proved to be an effective and stable procedure, with minimum periodontal hazards.

  6. Growth Type and Functional Trajectories: An Empirical Study of Urban Expansion in Nanjing, China

    Science.gov (United States)

    Yuan, Feng

    2016-01-01

    Drawing upon the Landsat satellite images of Nanjing from 1985, 1995, 2001, 2007, and 2013, this paper integrates the convex hull analysis and common edge analysis at double scales, and develops a comprehensive matrix analysis to distinguish the different types of urban land expansion. The results show that Nanjing experienced rapid urban expansion, dominated by a mix of residential and manufacturing land from 1985 to 2013, which in turn has promoted Nanjing’s shift from a compact mononuclear city to a polycentric one. Spatial patterns of three specific types of growth, namely infilling, extension, and enclave were quite different in four consecutive periods. These patterns result primarily from the existing topographic constraints, as well as government-oriented urban planning and policies. By intersecting the function maps, we also reveal the functional evolution of newly-developed urban land. Moreover, both self-enhancing and mutual promotion of the newly developed functions are surveyed over the last decade. Our study confirms that the integration of a multi-scale method and multi-perspective analysis, such as the spatiotemporal patterns and functional evolution, helps us to better understand the rapid urban growth in China. PMID:26845155

  7. A Rapid Compression Expansion Machine (RCEM) for studying chemical kinetics: Experimental principle and first applications

    CERN Document Server

    Werler, Marc; Maas, Ulrich

    2016-01-01

    A novel extension of a rapid compression machine (RCM), namely a Rapid Compression Expansion Machine (RCEM), is described and its use for studying chemical kinetics is demonstrated. Like conventional RCMs, the RCEM quickly compresses a fuel/air mixture by pushing a piston into a cylinder; the resulting high temperatures and pressures initiate chemical reactions. In addition, the machine can rapidly expand the compressed gas in a controlled way by pulling the piston outwards again. This freezes chemical activity after a pre-defined reaction duration, and therefore allows a convenient probe sampling and ex-situ gas analysis of stable species. The RCEM therefore is a promising instrument for studying chemical kinetics, including also partially reacted fuel/air mixtures. The setup of the RCEM, its experimental characteristics and its use for studying chemical reactions are outlined in detail. To allow comparisons of RCEM results with predictions of chemical reaction mechanisms, a simple numerical model of the RCE...

  8. Thermal conductivity and thermal rectification in graphene nanoribbons: a molecular dynamics study.

    Science.gov (United States)

    Hu, Jiuning; Ruan, Xiulin; Chen, Yong P

    2009-07-01

    We have used molecular dynamics to calculate the thermal conductivity of symmetric and asymmetric graphene nanoribbons (GNRs) of several nanometers in size (up to approximately 4 nm wide and approximately 10 nm long). For symmetric nanoribbons, the calculated thermal conductivity (e.g., approximately 2000 W/m-K at 400 K for a 1.5 nm x 5.7 nm zigzag GNR) is on the similar order of magnitude of the experimentally measured value for graphene. We have investigated the effects of edge chirality and found that nanoribbons with zigzag edges have appreciably larger thermal conductivity than nanoribbons with armchair edges. For asymmetric nanoribbons, we have found significant thermal rectification. Among various triangularly shaped GNRs we investigated, the GNR with armchair bottom edge and a vertex angle of 30 degrees gives the maximal thermal rectification. We also studied the effect of defects and found that vacancies and edge roughness in the nanoribbons can significantly decrease the thermal conductivity. However, substantial thermal rectification is observed even in the presence of edge roughness.

  9. Thermal expansion in BaRuO3 perovskites - an unusual case of bond strengthening at high temperatures.

    Science.gov (United States)

    Kayser, Paula; Injac, Sean; Kennedy, Brendan J; Menezes de Oliveira, Andre L; Shirako, Yuichi; Hasegawa, Masashi

    2017-02-28

    The temperature dependences of the structures of three polytypes of BaRuO3 have been investigated between room temperature and 1000 °C using high resolution synchrotron X-ray diffraction. The structural studies reveal a systematic decrease of the Ru-Ru distance as the pressure required to prepare the polytype increases. The O-O distance across the shared face increases as the Ru-Ru separation decreases. The 9R and 4H polytypes undergo unexceptional changes with increasing temperature. In 6H-BaRuO3 there is an apparent increase in the Ru-Ru interaction at around 650 °C and a concurrent reduction in the O-O distance, indicating an anomalous strengthening of the Ru-Ru interactions upon heating.

  10. Study of thermal destruction of lignin

    Energy Technology Data Exchange (ETDEWEB)

    Reti, M.; Hojnos, J.

    1979-01-01

    Using thermofractography, infra- and mass-spectrometry and other techniques thermal destruction of lignin was investigated at a temp. range of 200 to 500/sup 0/C. At temp. from 225 to 330/sup 0/C first of all splitting of ..beta..-aryil- and benzyl-ether binds between principal phenylpropane links of lignin, thus forming derivative phenols, vinyl guaiacol, coinferyl alcohol and aldehyde and respective syringic derivatives. At temp. of 350/sup 0/C splitting of C-C connections occurs in the lateral chain, forming guaiacol, 2,6-dimetoxiphenol and their saturated 4-alkyl derivatives. With a speeded up pyrolysis process, thermal destruction of lignin occurs at temp. of greater than or equal to 400/sup 0/C, with 62% of overall quantity derived at 500-550/sup 0/C with an overall tar release of about 30.

  11. Thermal conduction study of warm dense aluminum by proton differential heating

    Science.gov (United States)

    Ping, Y.; Kemp, G.; McKelvey, A.; Fernandez-Panella, A.; Shepherd, R.; Collins, G.; Sio, H.; King, J.; Freeman, R.; Hua, R.; McGuffey, C.; Kim, J.; Beg, F.

    2016-10-01

    A differential heating platform has been developed for thermal conduction study (Ping et al. PoP 2015), where a temperature gradient is induced and subsequent heat flow is probed by time-resolved diagnostics. An experiment using proton differential heating has been carried out at Titan laser for Au/Al targets. Two single-shot time-resolved diagnostics are employed, SOP (streaked optical pyrometry) for surface temperature and FDI (Fourier Domain Interferometry) for surface expansion. Hydrodynamic simulations show that after 15ps, absorption in underdense plasma needs to be taken into account to correctly interpret SOP data. Comparison between simulations with different thermal conductivity models and a set of data with varying target thickness will be presented. This work was performed under DOE contract DE-AC52-07NA27344 with support from OFES Early Career program and LLNL LDRD program.

  12. A Robust Single Primate Neuroepithelial Cell Clonal Expansion System for Neural Tube Development and Disease Studies

    Directory of Open Access Journals (Sweden)

    Xiaoqing Zhu

    2016-02-01

    Full Text Available Developing a model of primate neural tube (NT development is important to promote many NT disorder studies in model organisms. Here, we report a robust and stable system to allow for clonal expansion of single monkey neuroepithelial stem cells (NESCs to develop into miniature NT-like structures. Single NESCs can produce functional neurons in vitro, survive, and extensively regenerate neuron axons in monkey brain. NT formation and NESC maintenance depend on high metabolism activity and Wnt signaling. NESCs are regionally restricted to a telencephalic fate. Moreover, single NESCs can turn into radial glial progenitors (RGPCs. The transition is accurately regulated by Wnt signaling through regulation of Notch signaling and adhesion molecules. Finally, using the “NESC-TO-NTs” system, we model the functions of folic acid (FA on NT closure and demonstrate that FA can regulate multiple mechanisms to prevent NT defects. Our system is ideal for studying NT development and diseases.

  13. Comparative study of thermal insulation boards from leaf and bark ...

    African Journals Online (AJOL)

    The aim of this study was to compare the performance of insulation boards made from leave and bark fibres of Pilios tigma thonningii L.in terms of density, water absorption, apparent thermal conductivity, specific heat and thermal diffusivity. The leave and the bark fibres were prepared in form of squared boards of 200 mm x ...

  14. Thermal Decompositon Studies Of Pre-Irradiated Nickel (II) Azides ...

    African Journals Online (AJOL)

    The effect of pre-irradiation on the thermal decomposition of three samples of nickel (II) azide was studied. It was found that the rates of thermal decomposition of Ni(OH)N3 increased substantially with increase in pre-irradiation dosage. The initial reaction rates change from time-dependant nucleation law for the unirradiated ...

  15. Thermal and IR studies on copper doped polyvinyl alcohol

    Indian Academy of Sciences (India)

    5 mol% PVA : mol% Cu2+ polymer films were prepared by casting process. Thermal transitions and thermal degradation of samples with respect to copper concentration were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Increase in glass transition temperature as ...

  16. An experimental study of arch perimeter and arch width increase with mandibular expansion: a finite element method.

    Science.gov (United States)

    Baswaraj; Hemanth, M; Jayasudha; Patil, Chandrashekhargouda; Sunilkumar, P; Raghuveer, H P; Chandralekha, B

    2013-01-01

    The objective of this study was to estimate the increase in arch perimeter associated with mandibular lateral expansion, To estimate the increase in intermolar width with mandibular lateral expansion and to find out the changes of tooth inclination with mandibular expansion. The mandibular bone with dentition of indian skeletal specimen was obtained. The computer tomogram (CT) slices of the mandible were taken. Finite element model (FEM): Numerical representation of the geometry was created by dividing the geometry into finite number of elements and the elements were connected together with nodes at the junction. The result of the study showed when 10° of lateral expansion was applied to the lower buccal segment at the center of rotation found at 4.3 mm below the root apex of first molar, a space of 1.3 mm between the canine and first premolar, and thus an increase in arch perimeter of 2.6 mm. The tip of the mesiolingual cusp of the first molar moved 4.2 mm laterally, resulting in a change in intermolar width by 8.4 mm. Three-dimensional simulation showed that 1 mm of intermolar expansion increased the arch perimeter by 0.30 mm. As the finite element method evolves and scientists are able to more clearly define physical properties of biological tissues, more accurate information can be generated at the level that other analytical methods cannot fully provide data.This result would be of value clinically for prediction of the effects of mandibular expansion.

  17. Controlled Thermal Expansion Alloys Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This first part of this effort investigated the iron-nickel binary system with varying nickel content over a range of CTE from 0.6ppm/°C to 10.0ppm/°C. ...

  18. Synthesis, thermal expansion and high-temperature electrical conductivity of Co-doped (Y,Ca)FeO{sub 3−δ} with orthorhombic perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Kalyuzhnaya, A.S.; Drozhzhin, O.A. [M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Istomin, S.Ya., E-mail: istomin@icr.chem.msu.ru [M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Gippius, A.A.; Kazakov, S.M. [M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Lyskov, N.V. [Institute of Problems of Chemical Physics RAS, Academician Semenov Av. 1, Chernogolovka, Moscow District 142432 (Russian Federation); Rozova, M.G.; Antipov, E.V. [M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation)

    2015-06-15

    Highlights: • (Y,Ca)(Fe,Co)O{sub 3−δ} was prepared via citrate-based route with annealing at 1150–1200 °C. • Y{sub 0.9}Ca{sub 0.1}Fe{sub 0.8}Co{sub 0.2}O{sub 3−δ} demonstrates low thermal expansion coefficient of 11.9 ppm K{sup −1}. • Oxides do not react with YSZ and GDC up to 1000 °C and 1100 °C, respectively. • Compounds demonstrate higher electrical conductivity in comparison with Y{sub 0.9}Ca{sub 0.1}FeO{sub 3}. • Pr-doped (Y,Ca)(Fe,Co)O{sub 3−δ} demonstrate both higher electrical conductivity and TEC. - Abstract: Orthorhombic perovskites Y{sub 1−x}Ca{sub x}Fe{sub 1−y}Co{sub y}O{sub 3−δ} (0.1 ≤ x ≤ 0.2, 0.1 ≤ y ≤ 0.2 and x = 0.1, y = 0.3) were synthesized in air by the citrate route at 1150–1300 °C. High-temperature X-ray powder diffraction (HT XRPD) data for Y{sub 0.9}Ca{sub 0.1}Fe{sub 0.8}Co{sub 0.2}O{sub 3−δ} at 25–800 °C showed no phase transition with calculated thermal expansion coefficient (TEC) of 11.9 ppm K{sup −1}. High-temperature electrical conductivity measurements revealed almost composition independent conductivity values of 22–27 S/cm at 900 °C. No chemical interaction of Y{sub 0.8}Ca{sub 0.2}Fe{sub 0.9}Co{sub 0.1}O{sub 3−δ} with (Zr,Y)O{sub 2−x} (YSZ) or (Ce,Gd)O{sub 2−x} (GDC) was observed up to 1000 °C and 1100 °C, respectively. Partial replacement of Y by Pr according to formula Y{sub 0.8−z}Pr{sub z}Ca{sub 0.2}Fe{sub 0.7}Co{sub 0.3}O{sub 3−δ}, 0.1 ≤ z ≤ 0.35, leads to an increase of both electrical conductivity up to 50 S/cm (z = 0.3) at 900 °C and dilatometry measured TEC up to 15.1 ppm K{sup −1}. Moderate values of electrical conductivity in combination with low TEC and stability towards chemical interaction with typical SOFC electrolytes make Co-doped Y{sub 1−x}Ca{sub x}FeO{sub 3−δ} promissing cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC)

  19. A Study on Evaluation Method of Equipment Expansion in Power System under Competitive Environment

    Science.gov (United States)

    Nakajima, Takuya; Oyama, Tsutomu

    The supply reliability of the power system strongly depends on the system planning and operation. Under the competitive environment, system planning and operation become more complicated and difficult due to the new uncertainties that have not been considered so far. Which may also results in the enlargement of difficulties in forecast in the planning stage, and causes the deterioration of supply reliability. In the competitive environment, the transmission network must be planned and operated with the economical rationality and fairness. However, it is difficult to realize the system planning and operation considering the economical rationality and fairness because of the uncertainties. Then, the high flexibility and robustness against the uncertainties are required for the system planning and operation. This paper evaluates the performance of system expansion planning from two points of views: the probabilistic supply reliability and transmission margin in power system. As indices, the Expected Energy Not Supplied (EENS) and Available Transmission Capability (ATC) are used in this study.

  20. Quality evaluation of spaceborne SiC mirrors (I): analytical examination of the effects on mirror accuracy by variation in the thermal expansion property of the mirror surface.

    Science.gov (United States)

    Kotani, Masaki; Imai, Tadashi; Katayama, Haruyoshi; Yui, Yukari; Tange, Yoshio; Kaneda, Hidehiro; Nakagawa, Takao; Enya, Keigo

    2013-07-10

    The Japan Aerospace Exploration Agency has studied a large-scale lightweight mirror constructed of reaction-bonded silicon carbide-based material as a key technology in future astronomical and earth observation missions. The authors selected silicon carbide as the promising candidate due to excellent characteristics of specific stiffness and thermal stability. One of the most important technical issues for large-scale ceramic components is the uniformity of the material's property, depending on part and processing. It might influence mirror accuracy due to uneven thermal deformation. The authors conducted systematic case studies for the conditions of CTE by finite element analysis to know the typical influence of material property nonuniformity on mirror accuracy and consequently derived a comprehensive empirical equation for the series of CTE's main factors. In addition, the authors computationally reproduced the mirror accuracy profile of a small prototype mirror shown in cryogenic testing and hereby verified wide-range practical computational evaluation technology of mirror accuracy.

  1. Tunable negative thermal expansion related with the gradual evolution of antiferromagnetic ordering in antiperovskite manganese nitrides Ag1-xNMn3+x (0 ≤ x ≤ 0.6)

    Science.gov (United States)

    Lin, J. C.; Tong, P.; Tong, W.; Lin, S.; Wang, B. S.; Song, W. H.; Zou, Y. M.; Sun, Y. P.

    2015-02-01

    The thermal expansion and magnetic properties of antiperovskite manganese nitrides Ag1-xNMn3+x were reported. The substitution of Mn for Ag effectively broadens the temperature range of negative thermal expansion and drives it to cryogenic temperatures. As x increases, the paramagnetic (PM) to antiferromagnetic (AFM) phase transition temperature decreases. At x ˜ 0.2, the PM-AFM transition overlaps with the AFM to glass-like state transition. Above x = 0.2, two new distinct magnetic transitions were observed: One occurs above room temperature from PM to ferromagnetic (FM), and the other one evolves at a lower temperature (T*) below which both AFM and FM orderings are involved. Further, electron spin resonance measurement suggests that the broadened volume change near T* is closely related with the evolution of Γ5g AFM ordering.

  2. Tunable negative thermal expansion related with the gradual evolution of antiferromagnetic ordering in antiperovskite manganese nitrides Ag{sub 1−x}NMn{sub 3+x} (0 ≤ x ≤ 0.6)

    Energy Technology Data Exchange (ETDEWEB)

    Lin, J. C.; Tong, P., E-mail: tongpeng@issp.ac.cn; Lin, S.; Wang, B. S.; Song, W. H. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Tong, W.; Zou, Y. M. [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Sun, Y. P., E-mail: ypsun@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-02-23

    The thermal expansion and magnetic properties of antiperovskite manganese nitrides Ag{sub 1−x}NMn{sub 3+x} were reported. The substitution of Mn for Ag effectively broadens the temperature range of negative thermal expansion and drives it to cryogenic temperatures. As x increases, the paramagnetic (PM) to antiferromagnetic (AFM) phase transition temperature decreases. At x ∼ 0.2, the PM-AFM transition overlaps with the AFM to glass-like state transition. Above x = 0.2, two new distinct magnetic transitions were observed: One occurs above room temperature from PM to ferromagnetic (FM), and the other one evolves at a lower temperature (T{sup *}) below which both AFM and FM orderings are involved. Further, electron spin resonance measurement suggests that the broadened volume change near T{sup *} is closely related with the evolution of Γ{sup 5g} AFM ordering.

  3. Mechanical properties and coefficient of thermal expansion of β-eucryptite sintered by microwave technique; Propiedades mecanicas y coeficiente de dilatacion termica de la β-eucriptita sinterizada por la tecnica de microondas

    Energy Technology Data Exchange (ETDEWEB)

    Benavente, R.; Borrell, A.; Salvador, M. D.; Garcia-Moreno, O.; Penaranda-Foix, F. L.; Catala-Civera, J. M.

    2014-10-01

    Microwave non-conventional sintering technique allows obtaining fully dense glass-free β-eucryptite bulk material (∼99 %). A considerable difference in the densification, microstructure, coefficient of thermal expansion behaviour and mechanical properties, between conventional and non-conventional sintered specimens was observed. The hardness and Young's modulus values obtained by microwaves at 1200 degree centigrade-5min have been relatively high, 6.8 GPa and 101 GPa, respectively, compared to conventional sintering (3.9 GPa and 58 GPa, respectively). Very low thermal expansion materials have been obtained in a wide temperature range including cryogenic temperatures (from -150 degree centigrade to 150 degree centigrade). The high heating rate along with the lower energy consumption makes microwave technique a clear alternative to other types of sintering methods. (Author)

  4. The structure, thermal expansion and phase transition properties of Ho{sub 2}Mo{sub 3−x}W{sub x}O{sub 12} (x = 0, 1.0, 2.0) solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X.Z.; Hao, L.J.; Wu, M.M.; Ma, X.B.; Chen, D.F.; Liu, Y.T., E-mail: ytliu@ciae.ac.cn

    2015-10-15

    Graphical abstract: A polymorph with Gd{sub 2}Mo{sub 3}O{sub 12}-type structure (space group: Pba2) for negative thermal expansion material Ho{sub 2}Mo{sub 3}O{sub 12} is observed above 700 °C, this polymorphism could be effectively supressed by W-substiution for Mo, the give the temperature dependence of Pba2 phase contents for Ho{sub 2}Mo{sub 3−x}W{sub x}O{sub 12} (x = 0.0, 1.0, 2.0). - Highlights: • The solid solution Ho{sub 2}Mo{sub 3−x}W{sub x}O{sub 12} was investigated by in situ X-ray diffraction. • It is found that the substitution slightly influence thermal expansion property. • A polymorph of Ho{sub 2}Mo{sub 3}O{sub 12} with Pba2 space group was observed above 700 °C. • The W-substitution for Mo effectively suppresses this transformation. - Abstract: Three solid solutions of Ho{sub 2}Mo{sub 3−x}W{sub x}O{sub 12}(x = 0, 1.0, 2.0) were prepared by solid state reaction method, the temperature dependent in-situ X-ray diffraction and thermal analysis were performed to investigate their structure and thermal expansion. All samples have orthorhombic structure(space group Pbcn# 60) with negative thermal expansion at the room temperature. the substitution of W for Mo enlarges the lattice constant and slightly influences the negative thermal expansion. An irreversible phase transformation to the Pba2 phase(Tb{sub 2}Mo{sub 3}O{sub 12} structure) was observed at high temperature for Mo-rich samples. This ploymorphism could be effectively suppressed by the W-substitution for Mo, this phenomenon could be explained by the lower electronegativity of W{sup 6+} than Mo{sup 6+}.

  5. Synthesis, microstructure and thermal expansion studies on Ca0·5+ ...

    Indian Academy of Sciences (India)

    2009-01-19

    Jan 19, 2009 ... The binder burn out was carried out through a slow heating process up to 550. ◦. C. The final sintering of the pellets was carried out at 1250. ◦. C for 24 h. The phase identification of the samples was carried out by room temperature X-ray diffractometry (XRD) using Scintag. X-ray diffractometer with CuKα ...

  6. Optothermal Raman Studies of Thermal Properties of Graphene Based Films

    Science.gov (United States)

    Malekpour, Hoda

    Efficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene's unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives and their applications in thermal management. The dissertation consists of three parts. In the first part, I investigated thermal conductivity of graphene laminate films deposited on thermally insulating polyethylene terephthalate substrates. Graphene laminate is made of chemically derived graphene and few layer graphene flakes packed in overlapping structure. Two types of graphene laminate were studied: as deposited and compressed. The thermal conductivity of the laminate was found to be in the range from 40 W/mK to 90 W/mK at room temperature. It was established that the average size and the alignment of graphene flakes are parameters dominating the heat conduction. In the second part of this dissertation, I investigated thermal conductivity of chemically reduced freestanding graphene oxide films. It was found that the in-plane thermal conductivity of graphene oxide can be increased significantly using chemical reduction and temperature treatment. Finally, I studied the effect of defects on thermal conductivity of suspended graphene. The knowledge of the thermal conductivity dependence on the concentration of defects can shed light on the strength of the phonon - point defect scattering in two-dimensional materials. The defects were introduced to graphene in a controllable way using the low-energy electron beam irradiation. It was determined that as the defect density increases the thermal conductivity decreases down to about 400 W/mK, and then reveal saturation type behavior

  7. Thermal Comfort Studies in Naturally Ventilated Buildings in Jakarta, Indonesia

    OpenAIRE

    Karyono, Tri; Sri, Elita; Sulistiawan, Jevi; Triswanti, Yenny

    2015-01-01

    Many thermal comfort studies have been conducted in offices, classrooms and dwellings, but few in public buildings such as cathedrals, museums and markets. A recent thermal comfort study has been conducted in three naturally ventilated (NV) buildings, a cathedral, a museum and a market, in Jakarta, between March and April 2014. There is a curiosity as to whether people doing slightly different activities with slightly different clothing insulation values, in different building types, might ha...

  8. Rapid replacement of bridge deck expansion joints study - phase I : [tech transfer summary].

    Science.gov (United States)

    2014-12-01

    This initial research phase focused on documenting the current : means and methods of bridge expansion joint deterioration, : maintenance, and replacement and on identifying improvements : through all of the input gathered.

  9. Parametric study of closed wet cooling tower thermal performance

    Science.gov (United States)

    Qasim, S. M.; Hayder, M. J.

    2017-08-01

    The present study involves experimental and theoretical analysis to evaluate the thermal performance of modified Closed Wet Cooling Tower (CWCT). The experimental study includes: design, manufacture and testing prototype of a modified counter flow forced draft CWCT. The modification based on addition packing to the conventional CWCT. A series of experiments was carried out at different operational parameters. In view of energy analysis, the thermal performance parameters of the tower are: cooling range, tower approach, cooling capacity, thermal efficiency, heat and mass transfer coefficients. The theoretical study included develops Artificial Neural Network (ANN) models to predicting various thermal performance parameters of the tower. Utilizing experimental data for training and testing, the models simulated by multi-layer back propagation algorithm for varying all operational parameters stated in experimental test.

  10. Quantitative study on the hygroscopic expansion of spurr resin to obtain a high-resolution atlas of the mouse brain.

    Science.gov (United States)

    Wang, Qingdi; Li, Anan; Gong, Hui; Xu, Dongli; Luo, Qingming

    2012-10-01

    Ultra-thin section-based microscopic imaging is considered one of the most realistic techniques for determining fine architectures of a brain-wide neural network. In this kind of method, the sample is usually embedded in resin and then immersed in water for sectioning and imaging. The effect of resin hygroscopic expansion on data accuracy and integrity is important as it may lead to inconsistent image qualities or degeneration of sectioning properties. But few studies have been conducted on this issue. Here, we have used surface profile measurements combined with sectioning and imaging by micro-optical sectioning tomography (MOST) to quantitatively study the sectioned surface expansion of spurr resin blocks as a result of water immersion for a short time period. The expansion effect on MOST imaging is also presented. The results revealed significant differences in the surface expansion of pure resin blocks with different immersion time durations (P hygroscopic expansion properties of resin materials for maintaining the accuracy and integrity of whole brain atlas data.

  11. Expansion Thoracoplasty Affects Lung Growth and Morphology in a Rabbit Model: A Pilot Study

    OpenAIRE

    Mehta, Hemal P.; Olson, J. Casey; Kurek, Kyle Christopher; Matthew L Warman; Snyder, Brian Dale

    2011-01-01

    Background Thoracic insufficiency syndrome represents a novel form of postnatal restrictive respiratory disease occurring in children with early-onset scoliosis and chest wall anomalies. Expansion thoracoplasty improves lung volumes in children with thoracic insufficiency syndrome; however, how it affects lung development is unknown. Questions/purposes Using a rabbit model of thoracic insufficiency syndrome, we evaluated the effect of expansion thoracoplasty on the response of biologic mechan...

  12. Study of thermal degradation of vanadium and titanium acetylacetonate derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Dyagileva, L.M.; Tsyganova, E.I.; Mar' in, V.P.; Aleksandrov, Yu.A. (Gor' kovskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Khimii)

    1982-09-01

    Kinetics and products of vanadium (+3), vanadyl (+3) and titanium (+3) acetylacetonates thermal degradation have been studied in vapor phase in the closed system at 300-470 deg C. Gaseous composition of pyrolysis has been determined at different levels of decomposition. It is supposed that vanadium and metal vanadium mixed oxides become vanadium (+3) pyrolysis products. It is shown that metal oxidation level does not affect the thermal degradation rate. Central atom substitution leads to the change in thermal stability. Titanium (+3) acetylacetate derivatives are less stable than vanadium (+3) ones.

  13. A Study of Thermal Analyses and Fundamental Combustion Characteristics for Thermal Utility with Biomass Volatile Matter

    Science.gov (United States)

    Ida, Tamio; Namba, Kunihiko; Sano, Hiroshi

    Based on un-use biomass utilities, Carbonized technology is noticed as material utilities and solid fuel. Therefore, this technology is tackling by national project as large-scale utilities. But, this technology is dehydrated volatiles matter during carbonized from biomass. Especially, Woody tar into one of volatile matter has vicious handling to get into trouble in carbonized equipment. In this study, we propose to get fundamental knowledge for effective thermal utility through thermal decompositions and fundamental combustion properties on experimental results. Woody tar has high caloric value (approximately 30MJ/kg) and high carbon ration. On the other hand, a woody vinegar liquid has thermal decomposition property close to water property with heat absorption as evaporation latent heat of water. In fundamental combustion experimental result, a woody tar has fl ammable combustion and surface combustion. Especially, a total combustion and ignition time properties has hyperbola relation to environment temperatures in furnace.

  14. Using TOPEX Satellite El Niño Altimetry Data to Introduce Thermal Expansion and Heat Capacity Concepts in Chemistry Courses

    Science.gov (United States)

    Blanck, Harvey F.

    1999-12-01

    extremely complex system. The Gaussian model proposed for the cross section of a warm-water ridge requires more study, but it is a useful visual model of the warm-water bump above the normal surface and its subsurface warm-water wedge. I believe students will enjoy these relevant calculations and learn a bit about density, thermal expansion, and heat capacity in the process. I have tried to present sufficient data and detail to allow teachers to pick and choose calculations appropriate to the level of their students. It is evident that dimensional analysis is a distinct advantage in using these equations. I have also tried to include enough descriptive detail of the TOPEX data and El Niño to answer many of the questions students may ask. The Web sites mentioned are very informative with both text and graphics. Figure 2. General appearance of the cross section of a warm water ridge of excess sea surface height and the subsurface warm water. The subsurface curve is the warm water/thermocline boundary. Because of a large difference between the size of the warm water portion above and below the normal surface, two different scales have been used. Acknowledgments The data for the cells and the pictorial representation of the relative TOPEX altimetry data of the Pacific basin were very kindly provided by the TOPEX/Poseidon Project conducted by the Jet Propulsion Laboratory of the California Institute of Technology under contract with NASA. I wish to specifically thank JPL scientists Akiko Hayashi and Lee-Lueng Fu for providing data and I especially thank JPL scientist Victor Zlotnicki for helpful comments and suggestions. Several reviewers made helpful suggestions, which were very much appreciated. Literature Cited 1. NOAA's Pacific Marine Environmental Laboratory (PMEL) Web site; http://www.pmel.noaa.gov and especially http://www.pmel.noaa.gov/toga-tao/realtime.html (accessed Sep 1999). 2. Chambers, D.P.; Tapley, B. D.; Stewart, R. H. J. Geophys. Res. 1997, 102C, 10525-10533. 3

  15. Study the Possibility for Manufacturing a Conical Pipe Thread by Expansion

    Directory of Open Access Journals (Sweden)

    S. A. Evsyukov

    2014-01-01

    Full Text Available The experience of operating oil wells showed that the weak point of tubing is a connecting thread.Currently, the pipe thread of the specified class is made using the technology of cutting. The process of cutting a thread leads to waste metal chips and cutting fibers. Therefore the idea arose to make a thread by the method of pressure shaping.The aim was to study the possibility for full filling of the threaded matrix profile.The study was conducted by means of mathematical modeling in the software complex DEFORM. The impact of technological and geometrical factors on the process of form change was in detail analyzed. Thus, a work-piece material was specified to be continuous, isotropic, homogeneous, viscous-plastic and a tool material was set as a hard one. The friction was speci-fied according to Prandtl-Siebel law with the friction factor of 0.3. The thread profile has been replaced by the annular grooves of the similar profile. The task was considered to be axisymmetric.Scientific novelty of received results consists in revealed regularities of the plastic de-formation process of the work-piece when forming a profile of the conical thread on the pipe in the process of its expansion with a conical punch.The simulation allowed us to obtain information about the stress-strain state of the work-piece and tool, about the nature of the metal flow during deformation, and about the strength parameters of the process.In particular, it was found that the work-piece metal is displaced along the pipe axis both in punch movement direction and in the opposite one. Thus, a mechanical end burr is formed. The article shows that to remove a mechanical end burr requires insertion of extra limit stop housing. The article also analyses distribution of stresses arising in the matrix at the final moment of deformation. It was proved that the highest stresses occur in the hollows of the threaded part of matrix. Thus, their absolute value does not exceed 470 MPa that

  16. Scenario Analysis on Climate Change Impacts of Urban Land Expansion under Different Urbanization Patterns: A Case Study of Wuhan Metropolitan

    Directory of Open Access Journals (Sweden)

    Xinli Ke

    2013-01-01

    Full Text Available Urban land expansion plays an important role in climate change. It is significant to select a reasonable urban expansion pattern to mitigate the impact of urban land expansion on the regional climate in the rapid urbanization process. In this paper, taking Wuhan metropolitan as the case study area, and three urbanization patterns scenarios are designed to simulate spatial patterns of urban land expansion in the future using the Partitioned and Asynchronous Cellular Automata Model. Then, simulation results of land use are adjusted and inputted into WRF (Weather Research and Forecast model to simulate regional climate change. The results show that: (1 warming effect is strongest under centralized urbanization while it is on the opposite under decentralized scenario; (2 the warming effect is stronger and wider in centralized urbanization scenario than in decentralized urbanization scenario; (3 the impact trends of urban land use expansion on precipitation are basically the same under different scenarios; (4 and spatial distribution of rainfall was more concentrated under centralized urbanization scenario, and there is a rainfall center of wider scope, greater intensity. Accordingly, it can be concluded that decentralized urbanization is a reasonable urbanization pattern to mitigate climate change in rapid urbanization period.

  17. Thermal Management Tools for Propulsion System Trade Studies and Analysis

    Science.gov (United States)

    McCarthy, Kevin; Hodge, Ernie

    2011-01-01

    Energy-related subsystems in modern aircraft are more tightly coupled with less design margin. These subsystems include thermal management subsystems, vehicle electric power generation and distribution, aircraft engines, and flight control. Tighter coupling, lower design margins, and higher system complexity all make preliminary trade studies difficult. A suite of thermal management analysis tools has been developed to facilitate trade studies during preliminary design of air-vehicle propulsion systems. Simulink blocksets (from MathWorks) for developing quasi-steady-state and transient system models of aircraft thermal management systems and related energy systems have been developed. These blocksets extend the Simulink modeling environment in the thermal sciences and aircraft systems disciplines. The blocksets include blocks for modeling aircraft system heat loads, heat exchangers, pumps, reservoirs, fuel tanks, and other components at varying levels of model fidelity. The blocksets have been applied in a first-principles, physics-based modeling and simulation architecture for rapid prototyping of aircraft thermal management and related systems. They have been applied in representative modern aircraft thermal management system studies. The modeling and simulation architecture has also been used to conduct trade studies in a vehicle level model that incorporates coupling effects among the aircraft mission, engine cycle, fuel, and multi-phase heat-transfer materials.

  18. Urban area thermal monitoring: Liepaja case study using satellite and aerial thermal data

    Science.gov (United States)

    Gulbe, Linda; Caune, Vairis; Korats, Gundars

    2017-12-01

    The aim of this study is to explore large (60 m/pixel) and small scale (individual building level) temperature distribution patterns from thermal remote sensing data and to conclude what kind of information could be extracted from thermal remote sensing on regular basis. Landsat program provides frequent large scale thermal images useful for analysis of city temperature patterns. During the study correlation between temperature patterns and vegetation content based on NDVI and building coverage based on OpenStreetMap data was studied. Landsat based temperature patterns were independent from the season, negatively correlated with vegetation content and positively correlated with building coverage. Small scale analysis included spatial and raster descriptor analysis for polygons corresponding to roofs of individual buildings for evaluating insulation of roofs. Remote sensing and spatial descriptors are poorly related to heat consumption data, however, thermal aerial data median and entropy can help to identify poorly insulated roofs. Automated quantitative roof analysis has high potential for acquiring city wide information about roof insulation, but quality is limited by reference data quality and information on building types, and roof materials would be crucial for further studies.

  19. Dental arch changes associated with rapid maxillary expansion: A retrospective model analysis study

    Directory of Open Access Journals (Sweden)

    Ivor M D′Souza

    2015-01-01

    Full Text Available Introduction: Transverse deficiency of the maxilla is a common clinical problem in orthodontics and dentofacial orthopedics. Transverse maxillary deficiency, isolated or associated with other dentofacial deformities, results in esthetic and functional impairment giving rise to several clinical manifestations such as asymmetrical facial growth, positional and functional mandibular deviations, altered dentofacial esthetics, adverse periodontal responses, unstable dental tipping, and other functional problems. Orthopedic maxillary expansion is the preferred treatment approach to increase the maxillary transverse dimension in young patients by splitting of the mid palatal suture. This orthopedic procedure has lately been subject of renewed interest in orthodontic treatment mechanics because of its potential for increasing arch perimeter to alleviate crowding in the maxillary arch without adversely affecting facial profile. Hence, the present investigation was conducted to establish a correlation between transverse expansion and changes in the arch perimeter, arch width and arch length. Methods: For this purpose, 10 subjects (five males, five females were selected who had been treated by rapid maxillary expansion (RME using hyrax rapid palatal expander followed by fixed mechanotherapy (PEA. Pretreatment (T1, postexpansion (T2, and posttreatment (T3 dental models were compared for dental changes brought about by RME treatment and its stability at the end of fixed mechanotherapy. After model measurements were made, the changes between T1-T2, T2-T3 and T1-T3 were determined for each patient. The mean difference between T1-T2, T2-T3 and T1-T3 were compared to assess the effects of RME on dental arch measurements. Results are expressed as mean ± standard deviation and are compared by repeated measures analysis of variance followed by a post-hoc test. Arch perimeter changes are correlated with changes in arch widths at the canine, premolar and molar

  20. A Thermal Test System for Helmet Cooling Studies

    Directory of Open Access Journals (Sweden)

    Shaun Fitzgerald

    2018-02-01

    Full Text Available One of the primary causes of discomfort to both irregular and elite cyclists is heat entrapment by a helmet resulting in overheating and excessive sweating of the head. To accurately assess the cooling effectiveness of bicycle helmets, a heated plastic thermal headform has been developed. The construction consists of a 3D-printed headform of low thermal conductivity with an internal layer of high thermal mass that is heated to a constant uniform temperature by an electrical heating element. Testing is conducted in a wind tunnel where the heater power remains constant and the resulting surface temperature distribution is directly measured by 36 K-type thermocouples embedded within the surface of the head in conjunction with a thermal imaging camera. Using this new test system, four bicycle helmets were studied in order to measure their cooling abilities and to identify ‘hot spots’ where cooling performance is poor.

  1. Maxillary expansion in Class II correction with orthopedic cervical headgear. A posteroanterior cephalometric study.

    Science.gov (United States)

    Kirjavainen, Mirja; Kirjavainen, Turkka

    2003-06-01

    Class-II, division-1 malocclusion appears to be associated with a narrow maxilla. A Class-II malocclusion may be corrected to a Class-I relationship in children using a cervical headgear provided that the narrow maxilla is expanded. This expansion is possible using headgear by dental cast analysis, but this has not been confirmed by cephalometry. We studied the effects of orthopedic cervical headgear on dental and skeletal facial widths in 40 children aged 9.1 (7.2-11.5) who had Class-II, division-I malocclusions. The headgear consisted of a long outer bow bent 15 degrees upward and a large inner bow expanded by 10 mm. Posteroanterior cephalographs and dental casts were taken before and after treatment. The results were compared with the control values presented in the literature. The malocclusion was treated to a Class-I relationship in all children. The average treatment time was 1.6 (0.3-3.1) years. The maxilla was widened significantly (P headgear therapy with Class-II malocclusions, a widening of maxilla and nasal cavity may be obtained.

  2. Multi-Criteria Analyses of Urban Planning for City Expansion: A Case Study of Zamora, Spain

    Directory of Open Access Journals (Sweden)

    Marco Criado

    2017-10-01

    Full Text Available This study has established a methodology to determine the most environmentally suitable area for the expansion of Zamora (Spain using geographic information system (GIS technology. The objective was to develop a GIS-based methodology for the identification of urban peripheral areas that are suitable for the accommodation of new buildings and services, that are compliant with environmental criteria, and that guarantee an adequate quality of life for the future population such that extra construction costs are avoided. The methodological core is based on two multi-criteria analyses (MCAs: MCA-1 determines areas suitable for building—the most environmentally sustainable areas that do not present risks or discomforts to the population—by analyzing the restrictive factors; MCA-2 takes the sectors that received a favorable evaluation in MCA-1, determines which of those have a lower economic overhead for construction, and analyzes the different conditioning criteria related to their pre-existing infrastructures. Finally, the location of the sectors is determined by a decision factor that satisfies some strategic need of the municipality.

  3. From intent to action: A case study for the expansion of tiger conservation from southern India

    Directory of Open Access Journals (Sweden)

    Sanjay Gubbi

    2017-01-01

    Full Text Available To conserve a large, wide-ranging carnivore like the tiger, it is critical not only to maintain populations at key habitat sites, but also to enable the persistence of the species across much larger landscapes. To do this, it is important to establish well-linked habitat networks where sites for survival and reproduction of tigers are complemented by opportunities for dispersal and colonization. On the ground, expanding protection to areas with a potential for tiger recovery still remains the means of operationalizing the landscape approach. Yet, while the gazetting of protected areas is necessary to enable this, it is not sufficient. It is essential to benchmark and monitor the process by which establishment of protected areas must necessarily be followed by management changes that enable a recovery of tigers, their prey and their habitats. In this paper, we report a case study from the Cauvery and Malai Mahadeshwara Hills Wildlife Sanctuaries of southern India, where we document the infrastructural and institutional changes that ensued after an unprecedented expansion of protected areas in this landscape. Further, we establish ecological benchmarks of the abundance and distribution of tigers, the relative abundance of their prey, and the status of their habitats, against which the recovery of tigers in this area of vast conservation potential may be assessed over time.

  4. Personality traits in Huntington's disease: An exploratory study of gene expansion carriers and non-carriers.

    Science.gov (United States)

    Larsen, Ida Unmack; Mortensen, Erik Lykke; Vinther-Jensen, Tua; Nielsen, Jørgen Erik; Knudsen, Gitte Moos; Vogel, Asmus

    2016-12-01

    Huntington's disease (HD) is associated with risk for developing psychiatric symptoms. Vulnerability or resilience to psychiatric symptoms may be associated with personality traits. This exploratory study, aimed to investigate personality traits in a large cohort of HD carriers and at risk gene-expansion negative individuals (HD non-carriers), exploring whether carrying the HD gene or growing up in an HD family influences personality traits. Forty-seven HD carriers, Thirty-nine HD non-carriers, and 121 healthy controls answered the Danish version of the revised NEO personality inventory. Comparisons between HD carriers and HD non-carriers were mostly non-significant but the combined group of HD carriers and non-carriers showed significantly higher scores on the facets: "hostility," "assertiveness," and "activity" and on the trait "Conscientiousness" relative to controls, "Conscientiousness" have been associated with resilience to psychiatric symptoms. Twelve HD carriers and non-carriers were classified as depressed and showed significantly lower scores on "Extraversion" and "Conscientiousness" and significantly higher scores on "Neuroticism," which are associated with vulnerability to psychiatric symptoms. Our findings suggest that, there is no direct effect of the HD gene on personality traits, but that personality assessment may be relevant to use when identifying individuals from HD families who are vulnerable to develop psychiatric symptoms. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  5. Expansion thoracoplasty affects lung growth and morphology in a rabbit model: a pilot study.

    Science.gov (United States)

    Olson, J Casey; Kurek, Kyle C; Mehta, Hemal P; Warman, Matt L; Snyder, Brian D

    2011-05-01

    Thoracic insufficiency syndrome represents a novel form of postnatal restrictive respiratory disease occurring in children with early-onset scoliosis and chest wall anomalies. Expansion thoracoplasty improves lung volumes in children with thoracic insufficiency syndrome; however, how it affects lung development is unknown. Using a rabbit model of thoracic insufficiency syndrome, we evaluated the effect of expansion thoracoplasty on the response of biologic mechanisms in the alveolar microstructure. Using archived material from a previous experiment, 10 4-week-old New Zealand rabbits were divided into three groups: normal (n = 3), disease (n = 3), and treated (n = 4). Left ribs four to eight were tethered in seven rabbits at age 5 weeks to induce hypoplasia of the left hemithorax (disease). At age 10 weeks, four of these rabbits were treated by expansion thoracoplasty (treated). At age 24 weeks, lungs were excised and processed. Alveolar density and parenchymal airspace were measured on histologic sections. Immunohistochemistry was performed for vascular endothelial growth factor receptor 2 (angiogenesis), KI-67 (cell proliferation), and RAM-11 (macrophages). Alveolar walls were poorly perfused and airspace fraction was larger (emphysematous) in disease rabbits than normal or treated rabbits. Immunohistochemistry provided inconclusive evidence to support the concept that pulmonary hypoplasia is induced by thoracic insufficiency syndrome and controlled by expansion thoracoplasty. Treatment of thoracic insufficiency syndrome by expansion thoracoplasty may prevent emphysematous changes in the alveolar microstructure, thereby enhancing gas exchange.

  6. Impacts of impervious surface expansion on soil organic carbon--a spatially explicit study.

    Science.gov (United States)

    Yan, Yan; Kuang, Wenhui; Zhang, Chi; Chen, Chunbo

    2015-12-08

    The rapid expansion of impervious surface areas (ISA) threatens soil organic carbon (SOC) pools in urbanized areas globally. The paucity of field observations on SOC under ISA (SOCISA), especially in dryland areas has limited our ability to assess the ecological impacts of ISA expansion. Based on systematically measured SOCISA (0-80 cm depth) of a dryland city, and land-use and land-cover change data derived from remotely sensed data, we investigated the magnitude and vertical/horizontal patterns of SOCISA and mapped the impact of ISA expansion on SOC storage. The mean SOCISA in the city was 5.36 ± 0.51 kg C m(-2), lower than that observed in humid cities but much higher than that assumed in many regional carbon assessments. SOCISA decreased linearly as the soil depth or the horizontal distance from the open area increased. SOCISA accounted for over half of the city's SOC stock, which decreased by 16% (primarily in the converted croplands) because of ISA expansion from 1990 to 2010. The impacts of the ISA expansion varied spatially, depending on the land- use and converted land-cover type.

  7. Integrated thermal treatment system study -- Phase 2 results. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Feizollahi, F.; Quapp, W.J.

    1996-02-01

    This report presents the second phase of a study on thermal treatment technologies. The study consists of a systematic assessment of nineteen thermal treatment alternatives for the contact-handled mixed low-level waste (MLLW) currently stored in the US Department of Energy complex. The treatment alternatives consist of widely varying technologies for safely destroying the hazardous organic components, reducing the volume, and preparing for final disposal of the MLLW. The alternatives considered in Phase 2 were innovative thermal treatments with nine types of primary processing units. Other variations in the study examined the effect of combustion gas, air pollution control system design, and stabilization technology for the treatment residues. The Phase 1 study examined ten initial thermal treatment alternatives. The Phase 2 systems were evaluated in essentially the same manner as the Phase 1 systems. The alternatives evaluated were: rotary kiln, slagging kiln, plasma furnace, plasma gasification, molten salt oxidation, molten metal waste destruction, steam gasification, Joule-heated vitrification, thermal desorption and mediated electrochemical oxidation, and thermal desorption and supercritical water oxidation. The quantities, and physical and chemical compositions, of the input waste used in the Phase 2 systems differ from those in the Phase 1 systems, which were based on a preliminary waste input database developed at the onset of the Integrated Thermal Treatment System study. The inventory database used in the Phase 2 study incorporates the latest US Department of Energy information. All systems, both primary treatment systems and subsystem inputs, have now been evaluated using the same waste input (2,927 lb/hr). 28 refs., 88 figs., 41 tabs.

  8. Thermal loading study for FY 1996. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-11-08

    The primary objective of this study was to provide recommendations for Mined Geologic Disposal System requirements affected by thermal loading that will provide sufficient definition to facilitate development of design concepts and support life cycle cost determinations. The study reevaluated and/or redefined selected thermal goals used for design and are currently contained in the requirements documents or the Controlled Design Assumption Document. The study provided recommendations as to what, if any, actions (such as edge loading and limiting of the heat variability between waste packages) are needed and must be accommodated in the design. Additionally, the study provided recommendations as to what alternative thermal loads should be maintained for continued flexibility. Section 1 provides the study objective, background, scope, and organization of the report. Section 2 documents the requirements and standards to include quality assurance (QA) requirements, any requirements used or evaluated, and the inputs and assumptions considered. Section 3 provides the analysis and recommendations for the thermal goals reevaluation. Section 4 discusses the evaluation of edge loading and provides conclusions. Section 5 provides the analyses done to establish recommendations as to what requirements need to be implemented to either limit or manage the amount of heat output variability that may occur. Section 6 discusses alternate thermal loadings; Section 7 provides the study conclusions and recommendations; Section 8 provides the references, standards, and regulations; and Section 9 contains the acronym list.

  9. Study of query expansion techniques and their application in the biomedical information retrieval.

    Science.gov (United States)

    Rivas, A R; Iglesias, E L; Borrajo, L

    2014-01-01

    Information Retrieval focuses on finding documents whose content matches with a user query from a large document collection. As formulating well-designed queries is difficult for most users, it is necessary to use query expansion to retrieve relevant information. Query expansion techniques are widely applied for improving the efficiency of the textual information retrieval systems. These techniques help to overcome vocabulary mismatch issues by expanding the original query with additional relevant terms and reweighting the terms in the expanded query. In this paper, different text preprocessing and query expansion approaches are combined to improve the documents initially retrieved by a query in a scientific documental database. A corpus belonging to MEDLINE, called Cystic Fibrosis, is used as a knowledge source. Experimental results show that the proposed combinations of techniques greatly enhance the efficiency obtained by traditional queries.

  10. Study of Query Expansion Techniques and Their Application in the Biomedical Information Retrieval

    Science.gov (United States)

    Rivas, A. R.; Iglesias, E. L.; Borrajo, L.

    2014-01-01

    Information Retrieval focuses on finding documents whose content matches with a user query from a large document collection. As formulating well-designed queries is difficult for most users, it is necessary to use query expansion to retrieve relevant information. Query expansion techniques are widely applied for improving the efficiency of the textual information retrieval systems. These techniques help to overcome vocabulary mismatch issues by expanding the original query with additional relevant terms and reweighting the terms in the expanded query. In this paper, different text preprocessing and query expansion approaches are combined to improve the documents initially retrieved by a query in a scientific documental database. A corpus belonging to MEDLINE, called Cystic Fibrosis, is used as a knowledge source. Experimental results show that the proposed combinations of techniques greatly enhance the efficiency obtained by traditional queries. PMID:24723793

  11. Rose bush leaf and internode expansion dynamics: analysis and development of a model capturing interplant variability

    Directory of Open Access Journals (Sweden)

    Sabine eDemotes-Mainard

    2013-10-01

    Full Text Available Bush rose architecture, among other factors, such as plant health, determines plant visual quality. The commercial product is the individual plant and interplant variability may be high within a crop. Thus, both mean plant architecture and interplant variability should be studied. Expansion is an important feature of architecture, but it has been little studied at the level of individual organs in bush roses. We investigated the expansion kinetics of primary shoot organs, to develop a model reproducing the organ expansion of real crops from non destructive input variables. We took interplant variability in expansion kinetics and the model’s ability to simulate this variability into account. Changes in leaflet and internode dimensions over thermal time were recorded for primary shoot expansion, on 83 plants from three crops grown in different climatic conditions and densities. An empirical model was developed, to reproduce organ expansion kinetics for individual plants of a real crop of bush rose primary shoots. Leaflet or internode length was simulated as a logistic function of thermal time. The model was evaluated by cross-validation. We found that differences in leaflet or internode expansion kinetics between phytomer positions and between plants at a given phytomer position were due mostly to large differences in time of organ expansion and expansion rate, rather than differences in expansion duration. Thus, in the model, the parameters linked to expansion duration were predicted by values common to all plants, whereas variability in final size and organ expansion time was captured by input data. The model accurately simulated leaflet and internode expansion for individual plants (RMSEP = 7.3% and 10.2% of final length, respectively. Thus, this study defines the measurements required to simulate expansion and provides the first model simulating organ expansion in rosebush to capture interplant variability.

  12. Heat exchange studies on coconut oil cells as thermal energy storage for room thermal conditioning

    Science.gov (United States)

    Sutjahja, I. M.; Putri, Widya A.; Fahmi, Z.; Wonorahardjo, S.; Kurnia, D.

    2017-07-01

    As reported by many thermal environment experts, room air conditioning might be controlled by thermal mass system. In this paper we discuss the performance of coconut oil cells as room thermal energy storage. The heat exchange mechanism of coconut oil (CO) which is one of potential organic Phase Change Material (PCM) is studied based on the results of temperature measurements in the perimeter and core parts of cells. We found that the heat exchange performance, i.e. heat absorption and heat release processes of CO cells are dominated by heat conduction in the sensible solid from the higher temperature perimeter part to the lower temperature core part and heat convection during the solid-liquid phase transition and sensible liquid phase. The capability of heat absorption as measured by the reduction of air temperature is not influenced by CO cell size. Besides that, the application of CO as the thermal mass has to be accompanied by air circulation to get the cool sensation of the room’s occupants.

  13. Integrated thermal treatment systems study. Internal review panel report

    Energy Technology Data Exchange (ETDEWEB)

    Cudahy, J.; Escarda, T.; Gimpel, R. [and others

    1995-04-01

    The U.S. Department of Energy (DOE) Office of Technology Development (OTD) commissioned two studies to evaluate nineteen thermal treatment technologies for treatment of DOE mixed low-level waste. These studies were called the Integrated Thermal Treatment System (ITTS) Phase I and Phase II. With the help of the DOE Office of Environmental Management (EM) Mixed Waste Focus Group, OTD formed an ITTS Internal Review Panel to review and comment on the ITTS studies. This Panel was composed of scientists and engineers from throughout the DOE complex, the U.S. Environmental Protection Agency, the California EPA, and private experts. The Panel met from November 15-18, 1994 to review the ITTS studies and to make recommendations on the most promising thermal treatment systems for DOE mixed low-level wastes and on research and development necessary to prove the performance of the technologies. This report describes the findings and presents the recommendations of the Panel.

  14. [Study on the thermal radiation polarization characteristics of ice].

    Science.gov (United States)

    Wang, Ting-Ting; Zhao, Yun-Sheng; Zhang, Hong-Yan; Zhang, Xia; Zhang, Li-Li

    2014-03-01

    As an important parameter of the global energy balance, climate, hydrological and ecological model, ice directly affects the energy balance of the earth-atmosphere system, weather and climate. It is of great significance to use the thermal infrared polarization technology to study ice thermal radiation. For the ice monitoring and the impact of global climate change on the ice, studies on ice thermal radiation polarization characteristics were conducted based on the wavelength, detection angle and azimuth angle. The results show that the wavelength has an obvious impact on the ice thermal radiation polarization properties. The polarized radiance of four bands shows that L(CH1) > L(CH3) > L(CH4) > L(CH2) while the polarization brightness temperature shows that T(CH4) > T(CH1) > TCH2 > TCH3. It's better to use the brightness temperature of the third channel than the radiance to study the thermal radiation polarization. The detection angle affects the ice thermal radiation polarization characteristics greatly and there are some differences between the polarization angles. The brightness temperature of ice is the lowest in the detection angle of 10 degrees and the polarization angle of 30 degrees, which are non-accidental factors. These was closely related to ice physical and chemical properties. The degree of ice polarization performance shows that P0 thermal radiation polarization characteristics was not significant. And it is affected by the roughness of the surface, organizational structure and other factors which are direct results of ice emitted radiation at different azimuth angles.

  15. Nanoscale studies of thermal transport: R-matrix theory and thermal transport in strained graphene nanoribbons

    Science.gov (United States)

    Gunawardana, K. G. S. H.

    The rapid development of nanotechnology has enabled the fabrication of structures much smaller than the mean free path of electrons and phonons. In modern electronics, miniaturization is desired to increase the transistor density and the clock speed. Electronic transport on the nanoscale has been studied for over three decades and fascinating quantum effects have been observed. Phonon transport on this scale is of significant interest because of the increased power dissipation in nanoelectronics, which undermines the correct functionality of devices and limits their lifetime. Apart from the effort to minimize heat generation, an efficient heat management scheme is necessary. Historically, thermal transport in bulk materials was described by the Fourier's law, in which the thermal conductivity is an intrinsic property of the material. Later a more descriptive model, the Boltzmann approach for thermal transport, was developed and could explain the thermal conductivity down to a 100 nm length scale at high temperatures. At low temperatures and in structures smaller than roughly 100 nm, thermal transport is described by the fully quantum mechanical Landauer- Butticker formalism. In this context, accurate calculation of phonon transmission probabilities is very important. In this dissertation, I develop a continuum model to calculate phonon transmission probabilities between media, which have high contrast in the elastic properties. In this work, we include an interface transition layer between the two media and look for interface properties that improve thermal transport. Secondly, I develop a new theoretical tool based on the R-Matrix theory to calculate phonon transmission probabilities on the atomic scale. R-matrix theory is a well developed theoretical approach commonly used in nuclear and atomic physics to solve scattering problems. Recently, this approach has been successfully developed to calculate electronic scattering in mesoscopic quantum devices. The key

  16. THERMAL EXPANSION BEHAVIOR OF THE Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF WITH Sm0.2Ce0.8O1.9

    Directory of Open Access Journals (Sweden)

    M. AHMADREZAEI

    2014-03-01

    Full Text Available Nanostructured perovskite oxides of Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF were synthesized through the co-precipitation method. The thermal decomposition, phase formation and thermal expansion behavior of BSCF were characterized by thermogravimetric analysis, X-ray diffraction (XRD, and dilatometry, respectively. XRD peaks were indexed to a cubic perovskite structure with a Pm3m (221 space group. All the combined oxides produced the desired perovskite-phase BSCF. The microstructures were characterized by scanning electron microscopy (SEM and transmission electron microscopy (TEM. The TEM analysis showed that BSCF powders had uniform nanoparticle sizes and high homogeneity. The cross-sectional SEM micrograph of BSCF exhibited a continuous and no delaminated layer from the electrolyte-supported cell. The thermal expansion coefficient (TEC of BSCF was 16.2×10-6 K-1 at a temperature range of 600°C to 800°C. Additional experiments showed that the TEC of BSCF is comparable to that of Sm0.2Ce0.8O1.9 (SDC within the same temperature range. The results demonstrate that BSFC is a promising cathode material for intermediate-temperature solid-oxide fuel cells.

  17. Mitsui model with diagonal strains: A unified description of external pressure effect and thermal expansion of Rochelle salt NaKC4H4O6·4H2O

    Directory of Open Access Journals (Sweden)

    I.R. Zachek

    2011-12-01

    Full Text Available We elaborate a modification of the deformable two-sublattice Mitsui model of [Levitskii R.R. et al., Phys. Rev. B. 2003, Vol. 67, 174112] and [Levitskii R.R. et al., Condens. Matter Phys., 2005, Vol. 8, 881] that consistently takes into account diagonal components of the strain tensor, arising either due to external pressures or due to thermal expansion. We calculate the related to those strains thermal, piezoelectric, and elastic characteristics of the system. Using the developed fitting procedure, a set of the model parameters is found for the case of Rochelle salt crystals, providing a satisfactory agreement with the available experimental data for the hydrostatic and uniaxial pressure dependences of the Curie temperatures, temperature dependences of spontaneous diagonal strains, linear thermal expansion coefficients, elastic constants cijE and ci4E, piezoelectric coefficients d1i and g1i (i=1,2,3. The hydrostatic pressure variation of dielectric permittivity is described using a derived expression for the permittivity of a partially clamped crystal. The dipole moments and the asymmetry parameter of Rochelle salt are found to increase with hydrostatic pressure.

  18. Compressive Sensing Cluster Expansion Studies of Lithium Intercalation and Phase Transformation in MoS2 for Energy Storage

    Science.gov (United States)

    Liu, Chi-Ping; Zhou, Fei; Ozolins, Vidvuds; University of California, Los Angeles Collaboration; Lawrence livermore national laboratory Collaboration

    2015-03-01

    Bulk molybdenum disulfide (MoS2) is a good electrode material candidate for energy storage applications, such as lithium ion batteries and supercapacitors due to its high theoretical energy and power density. First-principles density-functional theory (DFT) calculations combined with cluster expansion are an effective method to study thermodynamic and kinetic properties of electrode materials. In order to construct accurate models for cluster expansion, it is important to effectively choose clusters with significant contributions. In this work, we employ a compressive sensing based technique to select relevant clusters in order to build an accurate Hamiltonian for cluster expansion, enabling the study of Li intercalation in MoS2. We find that the 2H MoS2 structure is only stable at low Li content while 1T MoS2 is the preferred phase at high Li content. The results show that the 2H MoS2 phase transforms into the disordered 1T phase and the disordered 1T structure remains after the first Li insertion/deinsertion cycle suggesting that disordered 1T MoS2 is stable even at dilute Li content. This work also highlights that cluster expansion treated with compressive sensing is an effective and powerful tool for model construction and can be applied to advanced battery and supercapacitor electrode materials.

  19. Impacts of road network expansion on landscape ecological risk in a megacity, China: A case study of Beijing.

    Science.gov (United States)

    Mo, Wenbo; Wang, Yong; Zhang, Yingxue; Zhuang, Dafang

    2017-01-01

    Road networks affect the spatial structure of urban landscapes, and with continuous expansion, it will also exert more widespread influences on the regional ecological environment. With the support of geographic information system (GIS) technology, based on the application of various spatial analysis methods, this study analyzed the spatiotemporal changes of road networks and landscape ecological risk in the research area of Beijing to explore the impacts of road network expansion on ecological risk in the urban landscape. The results showed the following: 1) In the dynamic processes of change in the overall landscape pattern, the changing differences in landscape indices of various landscape types were obvious and were primarily related to land-use type. 2) For the changes in a time series, the expansion of the road kernel area was consistent with the extension of the sub-low-risk area in the urban center, but some differences were observed during different stages of development. 3) For the spatial position, the expanding changes in the road kernel area were consistent with the grade changes of the urban central ecological risk, primarily because both had a certain spatial correlation with the expressways. 4) The influence of road network expansion on the ecological risk in the study area had obvious spatial differences, which may be closely associated with the distribution of ecosystem types. Copyright © 2016 Office national des forêts. Published by Elsevier B.V. All rights reserved.

  20. Effective potential of the three-dimensional Ising model: The pseudo-ϵ expansion study

    Directory of Open Access Journals (Sweden)

    A.I. Sokolov

    2017-08-01

    Full Text Available The ratios R2k of renormalized coupling constants g2k that enter the effective potential and small-field equation of state acquire the universal values at criticality. They are calculated for the three-dimensional scalar λϕ4 field theory (3D Ising model within the pseudo-ϵ expansion approach. Pseudo-ϵ expansions for the critical values of g6, g8, g10, R6=g6/g42, R8=g8/g43 and R10=g10/g44 originating from the five-loop renormalization group (RG series are derived. Pseudo-ϵ expansions for the sextic coupling have rapidly diminishing coefficients, so addressing Padé approximants yields proper numerical results. Use of Padé–Borel–Leroy and conformal mapping resummation techniques further improves the accuracy leading to the values R6⁎=1.6488 and R6⁎=1.6490 which are in a brilliant agreement with the result of advanced lattice calculations. For the octic coupling the numerical structure of the pseudo-ϵ expansions is less favorable. Nevertheless, the conform-Borel resummation gives R8⁎=0.868, the number being close to the lattice estimate R8⁎=0.871 and compatible with the result of 3D RG analysis R8⁎=0.857. Pseudo-ϵ expansions for R10⁎ and g10⁎ are also found to have much smaller coefficients than those of the original RG series. They remain, however, fast growing and big enough to prevent obtaining fair numerical estimates.

  1. Effective potential of the three-dimensional Ising model: The pseudo-ɛ expansion study

    Science.gov (United States)

    Sokolov, A. I.; Kudlis, A.; Nikitina, M. A.

    2017-08-01

    The ratios R2k of renormalized coupling constants g2k that enter the effective potential and small-field equation of state acquire the universal values at criticality. They are calculated for the three-dimensional scalar λϕ4 field theory (3D Ising model) within the pseudo-ɛ expansion approach. Pseudo-ɛ expansions for the critical values of g6, g8, g10, R6 =g6 / g42 , R8 =g8 / g43 and R10 =g10 / g44 originating from the five-loop renormalization group (RG) series are derived. Pseudo-ɛ expansions for the sextic coupling have rapidly diminishing coefficients, so addressing Padé approximants yields proper numerical results. Use of Padé-Borel-Leroy and conformal mapping resummation techniques further improves the accuracy leading to the values R6* = 1.6488 and R6* = 1.6490 which are in a brilliant agreement with the result of advanced lattice calculations. For the octic coupling the numerical structure of the pseudo-ɛ expansions is less favorable. Nevertheless, the conform-Borel resummation gives R8* = 0.868, the number being close to the lattice estimate R8* = 0.871 and compatible with the result of 3D RG analysis R8* = 0.857. Pseudo-ɛ expansions for R10* and g10* are also found to have much smaller coefficients than those of the original RG series. They remain, however, fast growing and big enough to prevent obtaining fair numerical estimates.

  2. Asymmetric rapid maxillary expansion in true unilateral crossbite malocclusion: a prospective controlled clinical study.

    Science.gov (United States)

    Ileri, Zehra; Basciftci, Faruk Ayhan

    2015-03-01

    To investigate the short-term effects of the asymmetric rapid maxillary (ARME) appliance on the vertical, sagittal, and transverse planes in patients with true unilateral posterior crossbite. Subjects were divided into two groups. The treatment group was comprised of 21 patients with unilateral posterior crossbite (mean age  =  13.3 ± 2.1 years). Members of this group were treated with the ARME appliance. The control group was comprised of 17 patients with Angle Class I who were kept under observation (mean age  =  12.3 ± 0.8 years). Lateral and frontal cephalograms were taken before the expansion (T1), immediately after expansion (T2), and at postexpansion retention (T3) in the treatment group and at preobservation (T1) and postobservation (T2) in the control group. A total of 34 measurements were assessed on cephalograms. For statistical analysis, the Wilcoxon test and analysis of covariance were used. The ARME appliance produced significant increases in nasal, maxillary base, upper arch, and lower arch dimensions (P ARME appliance created asymmetric increments in the transversal dimensions of the nose, maxilla, and upper arch in the short term. Asymmetric expansion therapy for subjects with unilateral maxillary deficiency may provide satisfactory outcomes in adolescents, with the exception of mandibular arch expansion. The triangular pattern of expansion caused clockwise rotation of the mandible and the occlusal plane and produced significant alterations in the vertical facial dimensions, whereas it created no displacement in maxilla in the sagittal plane.

  3. Review of the integrated thermal and nonthermal treatment system studies

    Energy Technology Data Exchange (ETDEWEB)

    Durrani, H.A.; Schmidt, L.J.; Erickson, T.A.; Sondreal, E.A.; Erjavec, J.; Steadman, E.N.; Fabrycky, W.J.; Wilson, J.S.; Musich, M.A.

    1996-07-01

    This report analyzes three systems engineering (SE) studies performed on integrated thermal treatment systems (ITTSs) and integrated nonthermal treatment systems (INTSs) for the remediation of mixed low-level waste (MLLW) stored throughout the US Department of Energy (DOE) weapons complex. The review was performed by an independent team of nine researchers from the Energy and Environmental Research Center (EERC), Science Applications International Corporation (SAIC), the Waste Policy Institute (WPI), and Virginia Tech (VT). The three studies reviewed were as follows: Integrated Thermal Treatment System Study, Phase 1--issued July 1994; Integrated Thermal Treatment System Study, Phase 2--issued February 1996; and Integrated Nonthermal Treatment System Study--drafted March 1996. The purpose of this review was to (1) determine whether the assumptions taken in the studies might bias the resulting economic evaluations of both thermal and nonthermal systems, (2) identify the critical areas of the studies that would benefit from further investigation, and (3) develop a standard template that could be used in future studies to produce sound SE applications.

  4. Review of the integrated thermal and nonthermal treatment system studies

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    This report contains a review and evaluation of three systems analysis studies performed by LITCO on integrated thermal treatment systems and integrated nonthermal treatment systems for the remediation of mixed low-level waste stored throughout the US Department of Energy weapons complex. The review was performed by an independent team of nine researchers from the Energy and Environmental Research Center, Science Applications International Corporation, the Waste Policy Institute, and Virginia Tech. The three studies reviewed were as follows: Integrated Thermal Treatment System Study, Phase 1--issued July 1994; Integrated Thermal Treatment System Study, Phase 2--issued February 1996; and Integrated Nonthermal Treatment System Study--drafted March 1996. The purpose of this review was to (1) determine whether the assumptions of the studies were adequate to produce an unbiased review of both thermal and nonthermal systems, (2) to identify the critical areas of the studies that would benefit from further investigation, and (3) to develop a standard template that could be used in future studies to assure a sound application of systems engineering.

  5. A Novel SOFC/SOEC Sealing Glass with a Low SiO2 Content and a High Thermal Expansion Coefficient

    DEFF Research Database (Denmark)

    Kiebach, Wolff-Ragnar; Agersted, Karsten; Zielke, Philipp

    2017-01-01

    behavior of the glass were studied under SOFC and SOEC relevant conditions. The glass-ceramic sealant performed well over 400 h, and no cell degradation or leakage related to the seal was found, indicating that the developed glass system is applicable for the use in SOFC/SOEC stacks.......Solid oxide cells require seals that can function in harsh, elevated temperature environments. In addition, a low Si content can be advantageous, since Si impurities from the glass sealant can be transported to the active fuel electrode and poison the Ni-YSZ triple phase boundaries. To reduce...... the amount of Si emission, a low Si containing sealing glass (chemical composition: 50 mol% CaO, 20 mol% ZnO, 20 mol% B2O3 and 10 mol% SiO2) was developed at DTU. In this work, the results from thermal characterization, the crystallization behavior of the glass and the long-term stability and adhesion...

  6. Thermal-decomposition studies of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Kolb, J.R.; Garza, R.G.

    1981-10-20

    We have investigated the rates of decomposition as functions of time and temperature on a combined thermogravimetric analyzer-residual gas analyzer (TGA-RGA). This technique also allows us to identify decomposition products generated as the original HMX begins to decompose. The temperature range studied was 50 to 200/sup 0/C. The decomposition process and the nature of decomposition products as functions of HMX polymorphs and conformations of the organic ring systems and possible reactive intermediates are discussed. 7 figures, 3 tables.

  7. Thermal-structural combined loads design criteria study

    Science.gov (United States)

    Deriugin, V.; Brogren, E. W.; Jaeck, C. L.; Brown, A. L.; Clingan, B. E.

    1972-01-01

    A study was conducted to determine methodology for combining thermal structural loads and assessing the effects of the combined loads on the design of a thermal protection system and a hot structure of a high cross range delta wing space shuttle orbiter vehicle. The study presents guidelines for establishing a basis for predicting thermal and pressure environments and for determining limit and ultimate design loads on the vehicle during reentry. Limit trajectories were determined by using dispersions on a representative nominal mission and system parameters expected during the life of the vehicle. Nine chosen locations on the vehicle surface having TPS or hot structures were examined, and weight sensitivity analyses were performed for each location.

  8. expansion method

    Indian Academy of Sciences (India)

    In this paper, we shall apply the (G /G)-expansion method to obtain the exact travelling wave solution of the two-dimensional ... In §3, we apply our method to the mentioned equations. In §4, some conclusions are ..... The exact solution obtained by this method can be used to check computer codes or as initial condition for ...

  9. Experimental study on surface wrinkling of silicon monoxide film on compliant substrate under thermally induced loads

    Science.gov (United States)

    Li, Chuanwei; Kong, Yingxiao; Jiang, Wenchong; Wang, Zhiyong; Li, Linan; Wang, Shibin

    2017-06-01

    The wrinkling of a silicon monoxide thin film on a compliant poly(dimethylsiloxane) (PDMS) substrate structure was experimentally investigated in this study. The self-expansion effect of PDMS during film deposition was utilized to impose a pretensile strain on the structure through a specially made fixture. A laser scanning confocal microscope (LSCM) system with an in situ heating stage was employed for the real-time measurement. The Young’s modulus of the silicon monoxide thin film as well as the PDMS substrate was measured on the basis of the elasticity theory. Moreover, the effects of temperature variations on geometric parameters in the postbuckling state, such as wavelength and amplitude, were analyzed. It was proved that wavelength is relatively immune to thermal loads, while amplitude is much more sensitive.

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

    Science.gov (United States)

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

    2007-01-01

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

  11. Using high pressure to study thermal transport and phonon scattering mechanisms

    Science.gov (United States)

    Hohensee, Gregory Thomas

    The aerospace industry studies nanocomposites for heat dissipation and moderation of thermal expansion, and the semiconductor industry faces a Joule heating barrier in devices with high power density. My primary experimental tools are the diamond anvil cell (DAC) coupled with time-domain thermoreflectance (TDTR). TDTR is a precise optical method well-suited to measuring thermal conductivities and conductances at the nanoscale and across interfaces. The DAC-TDTR method yields thermal property data as a function of pressure, rather than temperature. This relatively unexplored independent variable can separate the components of thermal conductance and serve as an independent test for phonon-defect scattering models. I studied the effect of non-equilibrium thermal transport at the aluminum-coated surface of an exotic cuprate material Ca9La5Cu 24O41, which boasts a tenfold enhanced thermal conductivity along one crystalline axis where two-leg copper-oxygen spin-ladder structures carry heat in the form of thermalized magnetic excitations. Highly anisotropic materials are of interest for controlled thermal management applications, and the spin-ladder magnetic heat carriers ("magnons") are not well understood. I found that below room temperature, the apparent thermal conductivity of Ca9La5Cu24O41 depends on the frequency of the applied surface heating in TDTR. This occurs because the thermal penetration depth in the TDTR experiment is comparable to the length-scale for the equilibration of the magnons that are the dominant channel for heat conduction and the phonons that dominate the heat capacity. I applied a two-temperature model to analyze the TDTR data and extracted an effective volumetric magnon-phonon coupling parameter g for Ca9La5Cu24O 41 at temperatures from 75 K to 300 K; g varies by approximately two orders of magnitude over this range of temperature and has the value g = 1015 W m-3 K-1 near the peak of the thermal conductivity at T ≈ 180 K. To examine

  12. Experimental Study of Thermal Field Evolution in the Short-Impending Stage Before Earthquakes

    Science.gov (United States)

    Ren, Yaqiong; Ma, Jin; Liu, Peixun; Chen, Shunyun

    2017-08-01

    Phenomena at critical points are vital for identifying the short-impending stage prior to earthquakes. The peak stress is a critical point when stress is converted from predominantly accumulation to predominantly release. We call the duration between the peak stress and instability "the meta-instability stage", which refers to the short-impending stage of earthquakes. The meta-instability stage consists of a steady releasing quasi-static stage and an accelerated releasing quasi-dynamic stage. The turning point of the above two stages is the remaining critical point. To identify the two critical points in the field, it is necessary to study the characteristic phenomena of various physical fields in the meta-instability stage in the laboratory, and the strain and displacement variations were studied. Considering that stress and relative displacement can be detected by thermal variations and peculiarities in the full-field observations, we employed a cooled thermal infrared imaging system to record thermal variations in the meta-instability stage of stick slip events generated along a simulated, precut planer strike slip fault in a granodiorite block on a horizontally bilateral servo-controlled press machine. The experimental results demonstrate the following: (1) a large area of decreasing temperatures in wall rocks and increasing temperatures in sporadic sections of the fault indicate entrance into the meta-instability stage. (2) The rapid expansion of regions of increasing temperatures on the fault and the enhancement of temperature increase amplitude correspond to the turning point from the quasi-static stage to the quasi-dynamic stage. Our results reveal thermal indicators for the critical points prior to earthquakes that provide clues for identifying the short-impending stage of earthquakes.

  13. Study on the influences of interaction behaviors between multiple combustion-gas jets on expansion characteristics of Taylor cavities

    Science.gov (United States)

    Xue, Xiaochun; Yu, Yonggang; Zhang, Qi

    2015-10-01

    The purpose of this study is to investigate means of controlling the interior ballistic stability of a bulk-loaded propellant gun (BLPG). Experiments on the interaction of twin combustion gas jets and liquid medium in a cylindrical stepped-wall combustion chamber are conducted in detail to obtain time series processes of jet expansion, and a numerical simulation under the same working conditions is also conducted to verify the reliability of the numerical method by comparing numerical results and experimental results. From this, numerical simulations on mutual interference and expansion characteristics of multiple combustion gas jets (four, six, and eight jets) in liquid medium are carried out, and the distribution characteristic of pressure, velocity, temperature, and evolutionary processes of Taylor cavities and streamlines of jet flow field are obtained in detail. The results of numerical simulations show that when different numbers of combustion gas jets expand in liquid medium, there are two different types of vortices in the jet flow field, including corner vortices of liquid phase near the step and backflow vortices of gas phase within Taylor cavities. Because of these two types of vortices, the radial expansion characteristic of the jets is increased, while changing numbers of combustion gas jets can restrain Kelvin-Helmholtz instability to a certain degree in jet expansion processes, which can at last realize the goal of controlling the interior ballistic stability of a BLPG. The optimum method for both suppressing Kelvin-Helmholtz instability and promoting radial expansion of Taylor cavities can be determined by analyzing the change of characteristic parameters in a jet flow field.

  14. Study on Thermal Insulation Zeolite by Coal Fly Ash

    OpenAIRE

    Huiping Song; Nan Zheng; Fangbin Xue; Fangqin Cheng

    2014-01-01

    This paper takes the coal fly ash as the material and makes zeolite with low thermal conductivity under a two-step synthesis for the purpose of thermal insulation. It studies main factors affecting zeolite such as the different concentration of NaOH, the solid-liquid ratio, the silica-alumina ratio, and the crystallization temperature. The optimal conditions were obtained that the NaOH concentration was 3 mol/L, the solid-liquid ratio was 10 : 1, the silica-alumina ratio was 2, and the crysta...

  15. Positron annihilation studies on reactor irradiated and thermal annealed ferrocene

    Energy Technology Data Exchange (ETDEWEB)

    Marques Netto, A. [Laboratorio de Espectroscopia de Aniquilacao de Positrons-LEAP, Depto. de Quimica, ICEX, Univ. Federal de Minas Gerais-UFMG, Belo Horizonte, MG (Brazil); Carvalho, R.S. [Laboratorio de Espectroscopia de Aniquilacao de Positrons-LEAP, Depto. de Quimica, ICEX, Univ. Federal de Minas Gerais-UFMG, Belo Horizonte, MG (Brazil); Magalhaes, W.F. [Laboratorio de Espectroscopia de Aniquilacao de Positrons-LEAP, Depto. de Quimica, ICEX, Univ. Federal de Minas Gerais-UFMG, Belo Horizonte, MG (Brazil); Sinisterra, R.D. [Laboratorio de Espectroscopia de Aniquilacao de Positrons-LEAP, Depto. de Quimica, ICEX, Univ. Federal de Minas Gerais-UFMG, Belo Horizonte, MG (Brazil)

    1996-10-01

    Retention and thermal annealing following (n, {gamma}) reaction in solid ferrocene, Fe(C{sub 5}H{sub 5}){sub 2}, were studied by positron annihilation lifetime spectroscopy (PAL). Positronium (Ps) formation was observed in the non-irradiated compound with a probability or intensity (I{sub 3}) of 30%. Upon irradiation of the compound with thermal neutrons in a nuclear reactor, I{sub 3} decreases with increasing irradiation time. Thermal treatment again increases I{sub 3} values from 16% to 25%, revealing an important proportion of molecular reformation without variation of the ortho-positronium lifetime ({tau}{sub 3}). These results point out the major influence of the electronic structure as determining the Ps yields in the pure complex. In the irradiated and non irradiated complexes the results are satisfactorily explained on the basis of the spur model. (orig.)

  16. Inverse thermal analysis method to study solidification in cast iron

    DEFF Research Database (Denmark)

    Dioszegi, Atilla; Hattel, Jesper

    2004-01-01

    Solidification modelling of cast metals is widely used to predict final properties in cast components. Accurate models necessitate good knowledge of the solidification behaviour. The present study includes a re-examination of the Fourier thermal analysis method. This involves an inverse numerical...... solution of a 1-dimensional heat transfer problem connected to solidification of cast alloys. In the analysis, the relation between the thermal state and the fraction solid of the metal is evaluated by a numerical method. This method contains an iteration algorithm controlled by an under relaxation term...... was developed in order to investigate the thermal behaviour of the solidifying metal. Three cylindrically shaped cast samples surrounded by different cooling materials were introduced in the same mould allowing a common metallurgical background for samples solidifying at different cooling rates. The proposed...

  17. Study of the observational compatibility of an inhomogeneous cosmology with linear expansion according to SNe Ia

    Science.gov (United States)

    Monjo, R.

    2017-11-01

    Most of current cosmological theories are built combining an isotropic and homogeneous manifold with a scale factor that depends on time. If one supposes a hyperconical universe with linear expansion, an inhomogeneous metric can be obtained by an appropriate transformation that preserves the proper time. This model locally tends to a flat Friedman-Robertson-Walker metric with linear expansion. The objective of this work is to analyze the observational compatibility of the inhomogeneous metric considered. For this purpose, the corresponding luminosity distance was obtained and was compared with the observations of 580 SNe Ia, taken from the Supernova Cosmology Project. The best fit of the hyperconical model obtains χ02=562 , the same value as the standard Λ CDM model. Finally, a possible relationship is found between both theories.

  18. Marketing Strategic Change in Expansionof Disneyland : Cases Study of Disneyland's Overseas Expansion in Shanghai

    OpenAIRE

    Zhu, Li; Xu, Dan

    2010-01-01

    Problem: The international theme park industry is growing but is also facing a series of bottleneck problems. Disneyland as one of the most famous theme parks, is trying to expand its kingdom to China. With the success and failure of the three previous oversea Disneyland, marketing strategic changes are becoming crucial and critical in the expansion of theme parks. Recognizing the elements that lead to strategic changes and generate proper strategies are preconditions of any successful expans...

  19. Comparative study of the thermal performance and emission levels ...

    African Journals Online (AJOL)

    Comparative study of the thermal performance and emission levels of an existing and modified coal/biomass burning stove. ... The stove was charged with jive (5) selected wood species and a number of parameters, such as temperature projile amI flue gas composition were measured. Experimental evidence points to an ...

  20. Thermally stimulated discharge conductivity study of zinc oxide ...

    Indian Academy of Sciences (India)

    The present work deals with transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermally stimulated discharge current (TSDC) study of inorganic metal oxide (ZnO) nanoparticles and its thermoelectrets. The thermoelectrets were prepared by applying different electric ...