Anomalous Thermal Behavior Research Articles

Preparation of single crystal of Ca 2CuO 3 by TSFZ method

A bulky (7×3×3 mm 3) single crystal fo Ca 2CuO 3 has been successfully prepared by the traveling-solvent-floating-zone (TSFZ) method using CuO excess solvent. An optimum solvent composition for growth of the titled compound was found to be around 9 in CuO/CaO molar ratio R under 0.1 MPa oxygen partial pressure. The obtained R value considerably deviates from the estimated one based on the reported equilibrium phase diagrams. Anisotropic magnetic susceptibilities of the prepared single crystal were observed. In particular an anomalous thermal behaviour of the susceptibility under the magnetic field along [001] and [010] indicates an appearance of three-dimensional antiferromagnetic order below around 8 K.

Anomalous thermal expansion behavior of the YBaCuO superconductor. Indirect evidence of polaron formation

A simple-minded semiclassical method is used to study the thermal expansion data of YBa 2Cu 3O 7−δ ( δ = 0.15) both in the normal and superconducting phases. It is shown that there is an anomaly in the temperature variation of the thermal expansion which begins to show up at a temperature somewhat higher than T c. We argue that this anomaly can be attributed to the phenomenon of polaron formation. This might give an indirect support to the bipolaronic mechanism of high-temperature superconductivity.

Evidence of strong correlations between anomalous lattice parameters and transport properties in Ce 16Ru 9

The new phase Ce 16 Ru 9 (R 3m, α  13.645 A ̊ and c  22.742 A ̊ ) was examined via the temperature dependences of the lattice parameters (10–300 K), magnetic susceptibility (1.5–300 K) and electrical resistivity (0.3–300 K). Different Ce valences (+4 and +3) for different crystallographic sites are proposed from magnetic data and are supported by previous structural results. No magnetic order is observed down to 0.3 K. Highly anisotropic stresses observed in the electrical resistivity temperature dependence are attributed to the anomalous thermal behaviour of the lattice parameter c.

High temperature structural stability of chemically vapor-deposited silicon carbide filaments

The structural stability of SCS-6 filament was investigated in the temperature interval 1000–1600 °C by differential scanning calorimetry (DSC) and in situ X-ray diffraction techniques. It was found that this filament is composed mostly of the cubic β polytype of SiC and of graphite, and that these phases are stable in the temperature interval studied. The lattice parameter for β-SiC was determined between room temperature and 1600°C, and the calculated average linear thermal expansion of the lattice in this temperature interval (5.24 × 10−6 °C−1 is in agreement with macroscopic thermal expansion measurements on single filaments. Thermal events observed by DSC occur at 1380 °C on heating and at 1300°C on cooling, and are suggested as being related to the melting and solidification, respectively, of excess silicon. These results are analysed in relation to the anomalous thermal expansion behavior exhibited by this filament.

On the origin of the low-frequency excitations in glassy selenium

The microscopic low-frequency dynamics of glassy selenium is investigated by means of the concurrent use of neutron inelastic scattering and computer simulations. A separation of the dynamic response in terms of intra-and interchain processes is achieved from the analysis of the simulation results. The low-frequency peak in the dynamic structure factor S(Q,E) as well as the tail of the vibrational density of states Z(E) are then shown to be originated mostly by interchain interactions. The implications of these findings for the anomalous thermal behaviour of glasses are finally discussed.

Retention of Implanted Gases and Enhanced Thermal Expansion of Mica

Helium and xenon gases implanted into muscovite micas increase the reversible thermal expansion perpendicular to the silicate layers by one or two orders of magnitude. The gas‐mica composite behaves like a gas within an elastic membrane, and this can be developed into a thermal actuator or heat sensor. Helium gas is implanted into muscovite mica to simulate the anomalous thermal expansion behavior of water in phlogopite. The implanted Xe gas has been studied by Rutherford backscattering and by counting and measuring gas bubble radii. Helium gas appears to diffuse out of the structure, since the anomalous thermal expansion decreases slowly over a period of several months. All of the implanted Xe is found to remain within the mica structure.

EPR linewidth of local magnetic moments diluted in Ce intermediate-valence compounds.

Anomalous thermal behavior on the EPR linewidths has been observed for Gd impurities diluted in ${\mathrm{Ce}}_{\mathit{x}}$${\mathit{A}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathit{B}}_{\mathit{n}}$ (A=La,Y, B=Ir,Os,Rh,Pd) intermediate-valence compounds. In this work we show that the exchange interaction between the local magnetic moments and the intermediate-valence host ions has an important contribution to the relaxation rates of the local moments. We calculated the relaxation, using the Redfield formalism and the ideas contained in the interconfigurational fluctuation model of Hirst. We show that the exchange interaction contribution has an exponential dependence on the excitation energy of the intermediate-valence ions.

Anomalous thermal behaviour and hydrogen bond in VOPO 4·2H 2O

An anomalous thermal behaviour of the vanadyl phosphate dihydrate has been found by means of X-ray powder diffraction. In the tetragonal layered structure of VOPO 4.2H 2O the monotonie decrease of the c-parameter with increasing temperature in the 3–42°C range has been observed, whereas the a-parameter remains constant at a = 6.2098(21) Å. The upper and lower limits of the c-parameter for the tetragonal phase of VOPO 4.2H 2O are c = 7.4593(25) Å at 3°C and c = 7.3907(25) Å at 42°C. Based on the temperature dependence of the lattice parameters and diffraction line profiles, the structural changes with variation of the temperature have been derived and the mechanism of the topotactic dehydration proposed. It is evident that the interlayer hydrogen bonds play the key role in the observed effects. This implies that the present study confirms certain common structural features of ices and hydrates and illustrates the influence of the crystalline environment on the behaviour of the water-water dimer.

Structural investigation of the silica-titania gel/glass transition

Vitreous silica containing titania has received considerable attention due to its anomalous thermal expansion behaviour, together with high optical quality. The effect and the role of TiO2 in the properties of glass are directly correlated with the structural position of titanium; thus several attempts have been made to elucidate the structural aspects of gels and glasses containing titania. Several SiO2-TiO2 gels containing up to 30 mol% TiO2 prepared using (i) normal drying; (ii) supercritical drying in alcohol; (iii) supercritical drying in CO2 were studied in this work. The aim of this work is to establish the titanium coordination during thermal treatments during the gel/glass system evolution. X-ray diffraction (XRD) and dilatometric analysis have been used to detect the presence of a crystal phase of TiO2 (anatase) in gel/glass samples. The crystal size of anatase was evaluated using the Scherrer relation from XRD patterns. Infrared and diffuse reflectance spectroscopy in the UV-visible region have been used to elucidate the structural aspects and the electronic transitions due to different titanium coordination. These results indicate that drying conditions strongly influence the silicon-oxygen-titanium structure.

POSSIBLE CORRELATION OF THE ANOMALOUS THERMAL BEHAVIOR OF NbSe3 TO MOBILE DEFECTS

The model of quasi-regular impurity (defect) distribution driven by CDW is used to suggest a possible explanation of the anomalous thermal behavior (thermal hysteresis, latent heats, etc.) found at the CDW transitions in the linear chain compound NbSe 3.

Depth dependence of the anomalous thermal behavior of Cu(110)

We report the results of a mirror electron microscope low energy electron diffraction (MEM-LEED) study of anomalous thermal behavior caused by enhanced thermal vibrational motion on a clean Cu(110) surface. The enhanced vibrational amplitudes cause diffracted intensities to deviate from simple Debye-Waller behavior. These deviations become apparent between 550 K and 600 K; i.e. at about 0.45 of the bulk melting temperature. Because of the finite penetration of low energy electrons, LEED intensities contain information about both surface and subsurface order. Our LEED results are analyzed to extract this information using a kinematical model in which the electron attenuation and the depth and temperature dependent vibrational amplitudes are parametrized. For a large range of model parameters, we conclude that by 850 K large anharmonic vibrations are present in several layers and at least two subsurface layers may have melted.

Structures and anomalous thermal behaviour of CF 2Cl 2 monolayers physisorbed on graphite

Monolayers of the methane deriva te CF 2Cl 2 physisorbed on graphite have been studied by X-ray diffraction. The coverage-temperature phase diagram includes a commensurate 4√3× 4√3 and two incommensurate solid phases. The high-temperature incommensurate phase shows an anomalous thermal behaviour.

Raman microprobe spectroscopic studies on thermal shock fracture of ZrO2-based ceramics

~t/a3b = [1/2(m + 1)2] '/m (4) by using the value of Weibull modulus of m = 10 and three-point bending strength, O'3b , of each ceramic material. As expected from Equation 3, the observed values of ATo were generally greater than R0. Since yttria-doped tetragonal zirconia (Y-TZP)-based ceramics possess extensively high fracture strength [4, 5] and large R0, they are expected to show excellent thermal shock resistance. However, the observed values of AT c for Y-TZP-based ceramics were significantly smaller than R0. The results of anomalous thermal shock fracture behaviour for Y-TZP-based ceramics indicated that the thermal shock fracture of Y-TZP was caused by a thermal stress smaller than the original fracture stress. Therefore, it is thought that the toughening mechanism of zirconia by the stress-induced phase transformation did not function sufficiently against thermal stress fracture of Y-TZP-based ceramics, but the details have not yet been clarified. In the present study the tetragonal-to-monoclinic phase transformation behaviour of zirconia ceramics around cracks introduced by both mechanical stress and thermal stress was investigated by using Raman microprobe spectroscopy. TZP-doped 2 mol % Y2 03 (2Y-TZP) and (2Y-TZP)40 wt % A1203 composite sintered at 1500 ° C for 3 h in air and then hot isostatically pressed at 1450°C and 150 MPa for 1 h in argon atmosphere and magnesiadoped partially stabilized zirconia (Mg-PSZ) were used as test samples. The samples were cut into bars (5ram x 2mm x 15mm) and then ground and polished with successively finer diamond paste to parallel mirror-like planes. After keeping the samples at 400 ° C the cracks were introduced to the sample by quenching into water at 0°C or by making 20kg Vickers hardness indents on the surface, and then the Raman microprobe spectra around both cracks were

LITERATURE ABSTRACTS

GENERAL PRINCIPLES: Wall Slip Corrections for Couette and Parallel Disk Viscometers. A. Yoshimura and R. K. Prud'HommeGENERAL PRINCIPLES: Foam Rheology: III. Measurement of Shear Flow Properties. S. A. Khan, C. A. Schnepper and R. C ArmstrongGENERAL PRINCIPLES: Stability of Bovine Muscle Connective Tissues. V. M. Bernal and D. W. StanleyGENERAL PRINCIPLES: Application of Reaction Kinetics to the Denaturation of Whey Proteins in Heated Milk. F. Dannenberg and H. G. KesslerGENERAL PRINCIPLES: Rheological Properties of Ultrafiltered Skim Milk. M. Hallström and P. DejmekGENERAL PRINCIPLES: Mechanical Studies of Sol‐Gel Transition: Universal Behavior of Elastic Modulus. Masayuki Tokita and Kunio HikichiGENERAL PRINCIPLES: Rheological and Thermal Properties of Carrageenan Gels. Effect of Sulfate Content. Mineo Watase and Katsuyoshi NishinariGENERAL PRINCIPLES: Dymanic Viscoelasticity and Anomalous Thermal Behaviour of Concentrated Agarose Gels. Mineo Watase and Katsuyoshi NishinariGENERAL PRINCIPLES: Foaming Properties of Protein Solutions: Comparison of Large‐Scale Whipping and Conductimetric Methods. David J. Wright and John W. HemmantFACTORS AFFECTING TEXTURE: Responses of CA‐stored Bramley's Seedling and Cox's Orange Pippin Apples to Modified Atmosphere Retail Packaging. J. D. Geeson, S. M. Smith, Helen P. Everson, Pia M. Genge and K. M. BrowneFACTORS AFFECTING TEXTURE: Restructured Pork with Texture Variation. N. G. Marriott, S. K. Phelps, C. A. Costello and P. P. GrahamFACTORS AFFECTING TEXTURE: Texture Changes in White Bread: Effects of Processing and Storage. U. Stollman and B. LundgrenFACTORS AFFECTING TEXTURE: Chemical Composition and Rheological Behaviour of Strawberry Jams Relation with Fruit Content. E. Costell, E. Carbonell and L. DuranFACTORS AFFECTING TEXTURE: Influence of Sugar and Cyanide Concentrations and Paste Viscosities of Cassava Flour on Fried Cassava Chip Quality. A. M. AlmazanFACTORS AFFECTING TEXTURE: Influence of Hot and Cold Boning on the Palatability, Textural and Economic Traits of Restructured Beef Steaks. D. L. Seman, W. G. Moody, J. D. Fox and N. GayFACTORS AFFECTING TEXTURE: Influence of Soy Protein and NaCl on the Rheological Properties of Beef, Pork or Chicken Muscle Homogenates. M. A. Bianchi, A. M. R. Rilosof and G. B. BartholomaiFACTORS AFFECTING TEXTURE: Relationship of Water Content to Textural Characteristics, Water Activity and Thermal Conductivity of Some Commercial Sausages. G. R. Ziegler, S. S. H. Rizvi and J. C. ActonFACTORS AFFECTING TEXTURE: Texture of Cooked Mantle of Squid Ilex argentinus as Influenced by Specimen Characteristics and Treatments. I. Kolodziejska, Z. E. Sikorski and M. SadowskaFACTORS AFFECTING TEXTURE: Relationship Between Pectic Composition and the Softening of the Texture of Japanese Radish Roots During Cooking. M. FuchigamiFACTORS AFFECTING TEXTURE: Intrinsic Viscosity of Tomato Serum as Affected by Methods of Determination and Methods of Processing Concentrates. T. Tanglertpaibul and M. A. RaoFACTORS AFFECTING TEXTURE: Rheological Properties and Conformation of Tomato Paste Pectins, Citrus and Apple Pectins. T. D. Chou and J. L KokiniFACTORS AFFECTING TEXTURE: Effect of Aging and Mustard Flour on Rheological Properties of Model O/W Emulsion. R. Fischbach and J. L. KokiniFACTORS AFFECTING TEXTURE: Cold Shock in Fish: Its Characteristics in Bighead. R. W. H. Parry, M. V. Alcasid and E. B. PanggatFACTORS AFFECTING TEXTURE: Continuous Emulsification and Gelation of Dairy Ingredients by HTST Extrusion Cooking: Production of Processed Cheeses. F. Zuber, D. Megard and J. C. CheftelFACTORS AFFECTING TEXTURE: The Effect of Fermentation Temperature, Flour Type, and Starter on the Properties of Sour Wheat Bread. H. Salovaara and T. ValjakkaFACTORS AFFECTING TEXTURE: Rheological Properties of Ultrafiltered Skim Milk. I. Effects of pH, Temperature and Heat Treatment. M. Hallstrom and P. Dejmek.FACTORS AFFECTING TEXTURE: Improvement of Quality of Whipping Cream by Adding Carrageenan and Milk Constituents. II. Influence of Additives on the Physical Properties of Whipped Cream. D. Precht, K.‐H. Peters, and J. PetersenFACTORS AFFECTING TEXTURE: The Effects of Salt Concentration and pH Upon Water‐Binding, Water‐Holding and Protein Extractability of Turkey Meat. R. I. Richardson and J. M. JonesSENSORY EVALUATIONS: Sensory Profiling and Multidimensional Scaling of Selected Finnish Raye Breads. U. Hellemann, H. Tuorila, H. Salovaara and L. TarkkonenSENSORY EVALUATIONS: Texture and Sensory Evaluation of Frankfurters Made with Different Formulations and Processes. C. M. Lee, R. C. Whiting and R. K. JenkinsINSTRUMENTATION AND METHODOLOGY: Adaptation of the Instron to Determine the Surface Tension of Ice Cream Mix. S. A. Wittinger and D. E. SmithINSTRUMENTATION AND METHODOLOGY: Double Direct Shear Test for Potato Texture. D. R. McComber, R. A. Lohnes and E. M. OsmanINSTRUMENTATION AND METHODOLOGY: Computer Simulation of the Attrition Patterns of Particulated and Agglomerated Foods. M. Peleg and M. D. NormandINSTRUMENTATION AND METHODOLOGY: A Rapid Method for the Evaluation of Emulsion Stability of Non‐Dairy Creamers. R. M. Tran and M. A. EinersonINSTRUMENTATION AND METHODOLOGY: Elongational Viscosity Measurements of Melting American Process Cheese. O. H. Campanella, L. M. Popplewell, J. R. Rosenau and M. Peleg

Electronic and microstructural properties of disorder-induced gap states at compound semiconductor–insulator interfaces

In order to clarify the structure and properties of the disordered semiconductor layer which forms the basis of the recently proposed disorder-induced gap state (DIGS) model, the electronic and microstructural properties of the compound semiconductor insulator–semiconductor interfaces (InP, GaAs, AlGaAs, InGaAs) are studied using C–V, isothermal capacitance transient spectroscopy, photocapacitance transient spectroscopy, cross-sectional transmission electron microscopy, Rutherford backscattering spectrometry, and x-ray and ultraviolet photoemission spectroscopy techniques. Based on the experimental results, a detailed model of the disordered layer which consists of a disordered crystal region and a graded amorphous region is presented. In these two regions, DIGS are distributed both in energy and space. The model can reproduce the observed hysteresis behavior remarkably well, and can explain the observed anomalous thermal and optical transient behavior. The measured location of the charge neutrality point EHO of DIGS continuum with respect to the valence-band maximum agrees well with the theoretical locations of the hybrid orbital energy based on sp3s* tight binding theory for various semiconductors.

Lattice images of inert gas bubbles in aluminium

Recent electron diffraction studies of a number of fcc metals implanted with inert gas ions have revealed that argon, krypton and xenon form room-temperature, solid, fcc precipitates (referred to as bubbles) epitaxial with the metal. We report on the use of high-resolution, phase contrast electron microscopy to produce one and two dimensional lattice images of room temperature solid argon and xenon in ion implanted aluminium. The images reveal clearly a high degree of crystalline perfection in many bubbles with a lattice parameter of 5.16 Å for the argon and 6.04 Å for the xenon. In the case of the Ar/AI system we also report on the anomalous thermal behaviour of the bubbles as deduced from diffraction measurements over the range ~80 to 800 K.

Structural Mechanisms of Anomalous Thermal Expansion of Cordierite‐Beryl and Other Framework Silicates

The structural mechanisms controlling the anomalous thermal expansion behavior of the cordierite‐beryl type structure and other framework silicates are discussed. The expansion of a particular silicate framework depends on the temperature response of the framework itself involving T–O–T and O–T–O angular changes, the expansion coefficient(s) of the nontetrahedral bonds, if present, and the interplay between these two factors. For cordierite, beryl, and β‐eucryptite, expanding nontetrahedral bonds play a critical role in driving the anomalous thermal expansion observed. For β‐spodumene and the feldspars, the thermal response of the framework dominates the expansion mechanism. The effects of channel constituents on the thermal expansion of the cordierite‐beryl framework are also discussed.

Pantolactone as a plastic crystal.

D-Pantolactone crystals showed anomalous thermal behavior, that is, two endothermic peaks (62.0 and 91.6°C) were observed in the differential scanning calorimetry curves. The entropy change of the first transition was calculated as 44.4 JK-1 mol-1 and that of the second transition was 9.20 JK-1 mol-1. The powder X-ray diffraction patterns of D-pantolactone differed significantly before and after the transition (62.0°C) and only one sharp peak at 2θ=17.4° was observed at 75°C. At 75°C, carbon-13 nuclear magnetic resonance chemical shifts of D-pantolactone were clearly observed by the pulse Fourier-transform technique.It was concluded that D- and L-pantolactone showed a stable plastic crystal phase between 62.0 and 91.6°C, and that DL-pantolactone is in a plastic crystal phase at room temperature.

An Interphasic Region between Nitrocellulose and Nitroguanidine in triple base propellant

AbstractEvidence for the existence of an interphasic region in the nitroglycerin‐nitrocellulose matrix immediately surrounding the crystalline nitroguanidine filler in triple base propellant is presented for the first time. This interphasic region displays anomalous thermal expansion and mechanical relaxation behaviour compared to the bulk nitroglycerin‐nitrocellulose matrix in the propellant. The interphasic region accounts for the highly unusual thermal expansion behaviour of triple base propellants containing long needlelike nitroguanidine crystals. An interphasic region does not occur in similar propellant when the nitroguanidine filler is replaced by crystalline RDX. Thus the interphase region is thought to be a manifestation of a significant bindernitroguanidine interaction. Implications for munition survivability stemming from the existence of a separate polymeric interphase are discussed in terms of the thermal and relaxation behaviour of the interphasic binder‐crystalline filler interface.

Thermal conductivity of pure fluids in the critical region

A generalized approach has been made to find the parameters strongly influencing the anomalous thermal conductivity behavior in the critical point region. For an analysis of the mathematical character of the critical anomaly, the two commonly used thermodynamic variables, temperature and density, and the two characteristic parameters, critical compressibility factor, Zc, and De Boer quantum parameter, Λ*, have been adopted.