Measurements Of Bulk Properties Research Articles

Magnetic properties of tapiolite (FeTa2O6); a quasi two-dimensional (2D) antiferromagnet

The possibilities of two-dimensional (2D) short-range magnetic correlations and frustration effects in the mineral tapiolite are investigated using bulk-property measurements and neutron Laue diffraction. In this study of the magnetic properties of synthetic single-crystals of tapiolite, we find that single crystals of FeTa2O6 order antiferromagnetically at TN = 7.95 ± 0.05 K, with extensive two-dimensional correlations existing up to at least 40 K. Although we find no evidence that FeTa2O6 is magnetically frustrated, hallmarks of two-dimensional magnetism observed in our single-crystal data include: (i) broadening of the susceptibility maximum due to short-range correlations, (ii) a spin-flop transition and (iii) lambda anomalies in the heat capacity and d(χT)/dT. Complementary neutron Laue diffraction measurements reveal 1D magnetic diffuse scattering extending along the c* direction perpendicular to the magnetic planes. This magnetic diffuse scattering, observed for the first time using the neutron Laue technique by VIVALDI, arises directly as a result of 2D short-range spin correlations.

Systematic characterization of petroleum residua based on SFEF

Supercritical fluid extraction and fractionation (SFEF) has been used to separate a variety of petroleum residua and other heavy oils into narrow-cut fractions with total yields up to 75–90%. Any insoluble material, or end-cut, corresponds to the asphaltene fraction in the parent oil. The narrow-cut fractions were analyzed comprehensively and separated into the solubility classes of saturate, aromatic, resin, and asphaltene fractions. The boiling points were measured up to 700 °C and correlations were established with the key factors such as density and molecular weight. This allows extrapolation of boiling points of residue fractions up to 1000 °C. Unlike bulk property measurements, the narrow-cut characterization data show increasing concentrations of key contaminants as the fractions become heavier. The solubility parameter for each narrow-cut fraction was measured using high-pressure fluid phase equilibrium with propane. The corresponding values for the end-cuts were obtained by the conventional precipitation method. The distribution and reactivity of sulfur species were determined by XPS in the bitumen pitch fractions and the corresponding residua produced during thermocracking and hydrocracking. The average structures for the narrow-cuts were constructed from molecular weight and elemental analyses together with FTIR, 1H-NMR and 13C-NMR data. The results were used to develop a generalized feedstock characteristic index, K R. This index shows good correlation with feedstock hydrocarbon constituents and can be used to assess feedstock reactivity and processability. Downstream refiners can use the narrow-cut data and K R values for process optimization by either cutting deeper into residua bottoms to increase yield or by selecting the most appropriate process units for the various residue fractions. This information can also be used by upstream operators to determine the economic feasibility of utilizing the end-cut onsite.

Feedstock characteristic index and critical properties of heavy crudes and petroleum residua

Supercritical fluid extraction and fractionation was used to prepare narrow-cuts from a variety of petroleum vacuum residua. The narrow-cuts were subjected to comprehensive characterization and solubility class separation into saturates, aromatics, resins and asphaltenes fractions. Unlike the bulk property measurements, the narrow-cut characterization data show uneven distribution of key contaminants (with the concentration increasing) as the fraction becomes heavier. Narrow-cut data were used to develop a generalized feedstock characteristic index, K R, that correlates well with the feedstock hydrocarbon constituents and can be used to assess feedstock reactivity and process capability. Downstream refiners can use the narrow-cut data and K R index for process optimization by either cutting deep into the bottom of residua to increase yield or selecting appropriate process units for various residue fractions. Narrow-cut data were also used to develop critical properties of residue fractions, which can be used as input parameters for simulation studies in designing process units for heavy crude and residua.

A new model for the crystal field and the quadrupolar phase transitions of UPd3

The double-hexagonal close-packed localized moment 5f system UPd3exhibits four phase transitions below 8 K. We present newmeasurements of the magnetic susceptibility of UPd3single crystals. The phase transitions are attributed to a sequenceof antiferroquadrupolar ordered structures of the U 5f electrons onthe quasi-cubic sites.From a comprehensive analysis of the neutronscattering, x-ray scattering, and bulk property measurements of thissystem, we have deduced a new crystal field model for UPd3.This model, which has a doublet ground state on the quasi-cubic sites with a firstexcited singlet some 4 meV above it, provides a qualitative understanding of thesuccession of quadrupolar phase transitions and order parameters of UPd3.Moreover, the new model also explains the excitationsobserved, by inelastic neutron scattering, in UPd3at 2 K.

Understanding the origin of non-Fermi liquid behaviour in doped Kondoinsulators

We have made inelastic neutron scattering measurements on the doped Kondo insulators Ce(Rh0.8Pd0.2)Sband (Ce0.7Th0.3)RhSb.Previous bulk property measurements showed non-Fermi liquid (NFL) behaviour forboth compositions. In our inelastic neutron scattering data these two compounds alsoshow E/Tscaling behaviour in the dynamical spin susceptibility with different exponents,which is considered a characteristic feature of NFL systems. We discuss howthese two different exponents might be related to different microscopicmechanisms of the NFL behaviour in the bulk properties as well as theE/Tscaling behaviour seen in the dynamical susceptibility.

Synthesis, physical properties and preliminary investigation of hemocompatibility of polyurethanes from aliphatic resources with castor oil participation.

The synthesis of polyurethanes (PURs) from oligoetherdiol, two low molecular diols, castor oil and 4,4'-Methylenebis(cyclohexylisocyanate) is described. These polymers are characterized by measurements of the mechanical bulk and surface properties, preliminary investigation of compatibility with human blood and calcification in static conditions. The critical surface energy of synthesized PURs is similar to the critical surface energy of natural surfaces. Material-induced hemolysis and the changes of platelet counts in blood samples after contact with PURs are very low. Static seven-weeks-calcification testing in a synthetic calcification fluid did not indicate calcification by optical density measurements and by visual inspection and computer image processing of the X-ray films for PURs with and without castor oil.

Physical properties of skutterudites , M = Fe, Co, Rh, Ir

A series of compounds YbxM4Sb12, were synthesised by reaction sintering. From Rietveld refinements isotypism was determined in all cases with the LaFe4P12-(skutterudite)-type, space group $${\mathop{\rm Im}\nolimits} \overline 3 $$ - No. 204. These refinements also served to derive the Yb-content in the samples. There is a systematic trend for the Yb-occupancy in the parent lattice M4Sb12, revealing a gradual decrease of the Yb-content from x =0.8 (M=Fe), x =0.5 (FeCo), x =0.2 (Co), x =0.1 (Rh) to $$x \approx 0.02$$ (Ir). This dependency seems to correlate with the thermal stability of the ternary compounds: a true ternary compound forms for M =Fe, whilst for M = Co stable binary skutterudite compounds MSb3 already exist. Measurements of various bulk properties revealed the absence of any long range magnetic order in this series of compounds. While the samples rich in Yb behave metallic like, the Rh and Ir based skutterudites show a semiconducting-like resistivity which at lower temperatures is characterised by variable range hopping in the presence of strong Coulomb interaction. Although Yb0.1Rh4Sb12 exhibits a Seebeck coefficient up to about 150 μV/K, figures of merit ZT generally are below 0.1 near room temperature, primarily due to the large resistivities of the sintered material.

Inverse bounds for microstructural parameters of composite media derived from complex permittivity measurements

Bounds on the volume fraction of the constituents in a two-component mixture are derived from measurements of the effective complex permittivity of the mixture, using the analyticity of the effective property. First-order inverse bounds for general anisotropic materials, as well as second-order bounds for isotropic mixtures, are obtained. By exploiting an analytic representation of the effective complex permittivity, the problem of estimating the structural parameters is reduced to a problem of evaluating the moments and support of a measure containing information about the geometrical structure of the material. Rigorous bounds on the volume fraction are found by inverting first- and second-order (Hashin–Shtrikman) forward bounds on the complex permittivity. The inverse bounds are applied to measurements of the effective complex permittivity of sea ice, which is a three-component mixture of ice, brine and air. The sea ice is treated via the two-component theory applied to a mixture of brine and an ice/air composite. The bounds on the brine volume of sea ice derived from the effective permittivity measurements are in excellent agreement with data from experiments. The inversion of forward bounds on the complex permittivity of composite media provides a basis for a theory of inverse homogenization for recovering microstructural parameters from bulk property measurements. Such results are applicable to problems in remote sensing, medical imaging and non-destructive testing of materials.

Random fields and phase transitions in model magnetic systems

Random fields occur in a wide variety of physical systems varying from type II superconductors to two-component fluids in a random medium. However, only in model magnetic systems have systematic studies as a function of both temperature and random-field strength been possible. In this article we review recent neutron and magnetic X-ray scattering studies of the magnetic ordering processes in the antiferromagnets Mn 0.75Zn 0.25F 2, Fe 0.5Zn 0.5F 2 and Fe 0.75Co 0.25TiO 3 in an applied magnetic field. These systems should all represent realizations of the three-dimensional random-field Ising model which is the simplest version of the random-field problem in models with discrete symmetry. In all cases on field cooling (FC) the systems evolve continuously from a high-temperature paramagnetic state to a low-temperature antiferromagnetic domain state. However, on cooling to low temperatures in zero field and then applying a field (ZFC) long-range order (LRO) is obtained. On subsequent heating in the three systems the LRO vanishes continuously with a rounded power-law behavior which has been labelled trompe l'oeil critical behavior. The width of the transition region scales as H 2. Reconsideration of indirect ZFC specific-heat measurements shows that the observed peaks, previously attributed to equilibrium critical fluctuations, instead arise entirely from a LRO contribution, scaling like dM s 2/dT , to the measured quantity. Here M s is the staggered magnetization. These results thus reconcile scattering and bulk property measurements of random-field Ising systems.

Surface and bulk analyses of the oxidation of polyolefins

The non-uniformity of oxidation across polypropylene and polyethylene films has been measured by a combination of X-ray photoelectron spectroscopy (XPS), internal reflection infrared spectroscopy and bulk property measurements. Films were photo-oxidized or γ-irradiated in air. Photo-oxidized film showed detectable oxidation at a very early stage in the outermost 70 Å of the film thickness (as measured by XPS). Oxidation advanced into the films as exposure level increased. Although γ-irradiated films also showed enhanced surface oxidation, this was attributed to the reaction of the polymer surfaces with short-lived species such as ozone from the radiolysis of the moist air atmosphere. When films were γ-irradiated and oxidized under conditions which precluded these reactions, oxidation proceeded uniformly throughout the film cross-section.

Diffusion of chlorine in fluid-bearing quartzite: effects of fluid composition and total porosity

To assess further the role of pore fluids in enhancing mass transport in deep-seated rocks, bulk diffusion coefficients (D-values) for chlorine have been measured at 1.0 GPa and 1000°C in texturally-equilibrated quartzites containing varying amounts (0.3–2.8 vol%) of H2O or a CO2−H2O mixture (X CO2=0.4). Experiments were used to monitor transport predominantly through the fluid phase by employing a chemical tracer dissolved in the fluid (chlorine) that is virtually insoluble in the rock matrix (quartzite) but is somewhat soluble in a small fraction of dispersed indicator minerals (fluorapatite). For diffusion in H2O-bearing quartzite, experiments with ≥ 1 vol.% fluid exhibit a continuous decrease in D-values with decreasing porosity whereas an abrupt drop in the diffusion coefficient is indicated by the experiments with 0.3 vol.% fluid. At a given total porosity, diffusion coefficients obtained from quartzites containing the CO2−H2O fluid range from ∼80x to > 3000x lower than those from H2O-bearing experiments. Bulk transport measurements were correlated with textural observations and the observed reduction in bulk D-values for quartzites containing the CO2−H2O fluid reflects the overall isolated nature of porosity in such samples. The drop in the bulk D-value for quartzites with 0.3 vol.% H2O probably arises from the elimination of interconnected porosity owing to the presence of a sufficient number of dry grain edges. Textural observations, combined with transport measurements, are consistent with the pore structure predicted by dihedral angle measurements. However, due to anisotropy in the interfacial energy of quartz, long-range fluid connectivity is dramatically reduced in quartzites with low H2O contents, despite a median dihedral angle of less than (but near) 60°. Observed variations in chlorine D-values in samples with connected and non-connected porosity are found to be consistent with previous bulk property measurements on texturally-equilibrated, fluid-bearing rocks. Results of this study, combined with prior bulk diffusion measurements for oxygen, provides a general assessment of the effect of small amounts of fluid on the enhancement of mass transport in quartzose lithologies over a range of crustal P and T. At conditions of textural equilibrium, it is expected that the fluid phase provides little or no contribution to the long-range diffusive flux of solutes in quartz-rich rocks containing small amounts of H2O or CO2−H2O mixtures.

RotorRing Measurement of Fiber Cohesion and Bulk Properties of Staple Fibers

Fiber cohesion and bulk properties and their consistency have a significant influence on yarn manufacturing processes and yarn quality. These critical properties depend on several staple fiber properties, including staple length, finish type and level, fiber geometries, crimp type and level, fiber additives, degree of fiber entanglements, and surface roughness. In order to ensure high processing performance and good yarn quality, it is necessary to understand how various staple fiber properties affect fiber cohesion and bulk. A method has been developed using a modified RotorRing instrument to monitor changes in staple fiber cohesion and bulk. The modified RotorRing yields three measurements, fiber-to-metal and fiber-to-fiber opening energy and the bandwidth of the ribbon formed inside the rotor. The method successfully and accurately detects differences in selected nylon and polyester fibers with different crimp/bulk levels, and the correlations between the modified RotorRing and traditional crimp measurements are examined. In addition, differences in crimp/bulk properties induced during the nylon staple processing operation are detected by the modified RotorRing responses. The results indicate that different crimp variables influence the three RotorRing measurements differently, and these independent responses show that the modified RotorRing method is indeed a potential tool for understanding the total effect of crimp variables on fiber cohesion and crimp/bulk and for monitoring the resulting yarn's properties and quality.

Canadian ceramic breeder sphere-pac technology: capability and recent results

Sphere-pac ceramic breeders have been under development in Canada for several years. The goal is to fabricate and characterize these materials for use in engineering test reactors and subsequent fusion power reactors. Practical application of sphere-pac beds requires close consideration of both properties and fabrication. The present emphasis of the program is on 1–3 mm diameter Li 2ZrO 3 spheres, with the future development of binary beds planned. Litre quantities have been produced by methods that are applicable to high production rates. These spheres are being tested for measurement of bulk properties (e.g., thermal conductivity, gas permeability, packing density, tritium release, specific heat) and long-term irradiation exposure. This paper summarizes the status of the work.

Performance criteria for quantitative ultrasonology and image parameterisation

For the purpose of assessing and comparing the practical performance of various specific approaches to quantitative tissue characterisation, three sets of performance criteria are proposed, relating respectively to contrast resolution, spatial resolution, and speed of presentation. In each case numerical performance targets are suggested: in particular that spatial resolution should preferably be within a linear factor of three of the best achievable anatomical resolution of the associated imaging techniques and that presentation speed should be 'real time' (i.e. about 10 Hz). In the light of these criteria and performance targets the main existing approaches to ultrasonic tissue characterisation are then considered. These are classified in two groups: first those approaches based on measurements of bulk properties of tissues and secondly those related to parameters of the structural organisation of tissues. Examination of available evidence suggests that the latter group are more promising than the former. Finally it is argued that ultrasonic methods of tissue characterisation have substantial practical potential but that the realisation of such potential is contingent on achieving consensus on choice of a single, optimised and generally applicable approach that would carry with it the linked benefits of industrial standardisation and broad sharing of clinical experience.

Structural and magnetic properties of Fe impurities in YBa 2Cu 3O 7−δ

Samples having the general composition YBa 2(Cu 1−xFe x) 3O 7−δ have been investigated using x-ray and neutron diffraction, Mossbauer spectroscopy and bulk property measurements. X-ray and neutron data show that samples having x ≥ 0.04 are tetragonal. Neutron diffraction shows that this structure is very similar to that found for undoped YBa 2Cu 3O 7−δ when the oxygen concentration is low, although, in the present case, the total oxygen content is found to be ≥7 for all concentrations. Contrary to the common statement that Fe substitutes onto the Cu sites, it is found from neutron diffraction that the Cu1 site is not occupied, and that Fe appears to have a substantial substitution for Ba. Both Mossbauer spectroscopy and heat capacity measurements show the presence of magnetic transitions at temperatures well below the superconducting transition temperature, with evidence for a large variation in magnetic transition temperatures.

Bulk property measurements for studying solid state reactions

We describe the application of bulk property measurements to the study of the solid state reaction. We show how to use a concentration profile and a set of results obtained from amorphous alloys (either experimentally or theoretically) to simulate average measurements. We illustrate the procedure with the example of X-ray absorption spectroscopy, and we show how we implemented the procedure for studying the solid state reaction in Ce Ni multilayers.

Variation in nitroxide probe chain flexibility within sodium dodecyl sulfate hemimicelles

Three nitroxide spin probes (5-, 12-, and 16-doxylstearic acid) were used to investigate the structure of sodium dodecyl sulfate (SDS) micelles and the interfacial layer between water and alumina formed by SDS (hemimicelles of SDS). It was found that whereas the rotational correlation times of the three probes differ in SDS micelles, the effective microviscosities of the probes are the same. In contrast, the microviscosity within the SDS hemimicelles varies according to the distance from the alumina surface: the nitroxide sees a more ordered environment as it is placed closer to the alumina. This represents the first report of variations in flexibility (microviscosity) within a hemimicelle. The science of the water-solid interfacial layer formed by adsorbed long-chain surfactants on solids has been studied extensively for its value in the fields of enhanced oil recovery,2 fl~tation,~ detergen~y,~ l ~brication,~ and microelectronics.6 Considerable experimental evidence is consistent with the postulate that such surfactants form localized aggregates (termed hemimicelles) on the solid surface.’ The evidence for hemimicelles has generally been indirect, and hemimicelle structure and dynamics have been inferred from measurements of bulk properties using such techniques as adsorption isotherms, {potentials, particle wettability, and heats of adsorption.8 Recently we reported the use of two types of molecular probes for use in spectroscopic investigations of the hemimicelle microstructure formed by sodium dodecyl sulfate (SDS) adsorbed on alumina. The first involved studies of pyrene and dinaphthylpropane fl~orescence,~ while the second involved the spin probe 16-doxylstearic acid (l), a stable nitroxide radical, for use with ESR spectroscopy.i0 The carboxylate functionality of this latter probe adsorbs on the positively charged alumina surface. Our results indicated that at pH 6.5 this probe aggregates mostly by itself on the surface at low SDS concentrations and forms cohemimicelles with the SDS at higher SDS concentrations. The relative anisotropy observed in an ESR spectrum is directly related to the rotational mobility of the probe, a term that can be correlated with the probe’s microviscosity.” Using this correlation, we were able to deduce that the environment within the SDS hemimicelle is relatively viscous. In both these studies of the microenvironment of the SDS hemimicelle, the data reported represent a single probe position within the hemimicelle (or a time average of many depths from the surface). Spin probes have been used extensively to study the microviscosity and micropolarity of membranes, multilayers, and micelles.12 In particular, doxylstearic acid spin probes have been useful in determining these parameters for different probe depths within phospholipid bilayers and micelles. Such studies have provided information on the orientation of the probes within the systems as well as information on the microenvironmental differences within the bilayer or micelle. In this communication, we wish to report the use of three doxylstearic acid derivatives, 16-, 12-, and 5-doxylstearic acids (1, 2, and 3, respectively) in

Invariance of Curie temperature of iron for heating rates up to 10 000 Ks−1

Abstract We have shown that the Curie temperature of Fe is unaffected by heating rates up to 10000 Ks−1. This appears to be the first direct evidence, from measurement of bulk properties, that magnetization responds very rapidly to change of temperature through the ferromagnetic—paramagnetic phase transition.

Scattering of thermal He beams by crossed atomic and molecular beams. V. Anisotropic intermolecular potentials for He+CO2, N2O, C2N2

Experimentally measured differential cross sections are presented for the interactions of He with the linear molecules CO2,N2O, and C2N2. These data show pronounced dampening of the diffraction oscillations, and provide an indication that the intermolecular potentials have large anisotropies. Indeed, central-field analyses of the experimental data, even in terms of very flexible models, are shown to be inadequate. However, an anisotropic analysis using the infinite-order sudden approximation yields physically reasonable intermolecular potentials, and provides excellent fits to the scattering data. Neither the spherical averages of these empirical anisotropic potentials, nor the spherically symmetric potentials obtained by the central-field analyses, reproduce the experimental differential cross sections. For He+CO2, the anisotropic potential is extended to highly repulsive interactions, to which the present data are insensitive, by combining theoretical calculations and measurements of gas-phase bulk properties. Estimates for the reliability of the fitted anisotropic potentials are given, and convenient parametrizations are recommended.

Measurements of surface and bulk properties for the interaction of hydrogen with inconel 600

The permeation of hydrogen through an Inconel 600-membrane has been measured in order to determine the bulk properties (diffusivity D, solubility K s ) and the surface constants for the solubilisation ( σk s ) and for the release ( σk r ). After a brief introduction into the theoretical relations, the experimental apparatus and the prehandling procedure of the membrane are described. The temperature of the membrane has been varied between 150°C and 400°C. Experimental data for hydrogen and deuterium are presented as Arrhenius relations and discussed.