Materials Literature
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The temperature dependence of the static magnetic susceptibility (5 to 700 K) and that of the electron paramagnetic resonance linewidth (300 to 700 K) measured at 9.25 GHz is reported for bulk polycrystalline samples of and with negative giant magnetoresistance. For both systems, and the product increase linearly with…
By solving a viscoelastic model of polymer solutions in two dimensions, we demonstrate that polymer-rich regions can form a spongelike network in deeply quenched cases. In late stages the velocity field is suppressed because the network supports stress and is rigid. As a result the domain size grows as ${t}^{1/3}$. In…
The negative thermal expansion recently observed over a wide range of temperatures in may be attributed to the existence of low-frequency phonon modes which can propagate with no distortions of the tetrahedra and octahedra, the so-called `rigid unit modes'. Using methods developed for the study of similar modes in sil…
Introduction to Carbon Materials, M.S. Dresselhaus, G. Dresselhaus, P.C. Eklund, R. Saito, and M. Endo From Carbon Fibers to Nanotubes, M. Endo, R. Saito, M.S. Dresselhaus, and G. Dresselhaus Structure and Morphology of Carbon Nanotubes, P.M. Ajayan Production and Purification of Carbon Nanotubes, T.W. Ebbesen Growth…
The Mg(3s3dπ 3DJ)⋅Ar(3Π), Mg(3s3dδ 3DJ)⋅Ar(3Δ), and Mg(3s4pπ 3PJ)⋅Ar(3Π) excited states have been characterized via resonance enhanced two-photon ionization (R2PI) spectroscopy of transitions from the long-lived Mg(3s3pπ 3PJ)⋅Ar(3Π0+,0−) metastable states of the MgAr van der Waals molecule. Because the outer excited M…
Information obtained from optical absorption, excitation, and emission experiments on erbium doped crystalline CsCdBr3 is analyzed, using a semiempirical Hamiltonian, to calculate atomic and crystal-field interaction parameters and electronic state wave functions. A majority of the Er3+ ions substitute at a Cd2+ site…
We use x-ray scattering at small angles (SAXS) to study interparticle interactions in dilute dispersions of CdSe nanocrystallite particles. In particular, we probe the dependence of these interactions on a few key parameters, including the nature of the cap molecules attached to the surface of the particles and the so…
Magnetoresistance is an effect in which the electrical resistance of a material changes in a magnetic field. This phenomenon is of great importance in magnetic data recording, where a magnetoresistive sensor detects the patterns of bits on magnetic storage media. In his Perspective, Goldman discusses results reported…
We present a new approach to the evaluation of the on-site repulsion energy U for use in the LDA+U method of Anisimov and collaborators. Our objectives are to make the method more firmly based, to concentrate primarily on ground state properties rather than spectra, and to test the method in cases where only modest ch…
The current-perpendicular-to-plane magnetoresistance (CPP-MR) has been investigated for the layered manganite, La2-2xSr1+2xMn2O7 (x = 0.3), which is composed of the ferromagnetic-metallic MnO2 bilayers separated by nonmagnetic insulating block layers. The CPP-MR is extremely large (10(4) percent at 50 kilo-oersted) at…
Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned…
A study of the interaction of fatty foods with rigid PVC packages was undertaken, using fatty acid esters CH3(CH2)n−2COOR (8 ≤ n ≤ 18; R = Me, Et) as food simulants. Determination at 50°C of weight uptaken by PVC and of depth of penetration of the simulant into the material allowed us to define the time required to re…
The effect of processing temperature on the low-speed tensile and high-speed impact properties of novel ABS/PET blends was investigated. In agreement with the conclusions from related studies of ABS/PC blends, it appears that catalytic impurities in the ABS accentuate the propensity of PET for chain scission. Due to t…
Novel blends of PET and ABS were prepared by extrusion and injection molding. DSC and DMTA studies show that PET and ABS are immiscible and that the blends consist of four phases: SAN, grafted polybutadiene, amorphous PET, and minor amounts of crystalline PET. The morphology was investigated by transmission electron m…
Toughening mechanism of polypropylene (PP) blended with ethylene–propylene–diene rubber (EPDM) following selective crosslinking was examined in comparison with that of blends of PP before crosslinking. The yield stress, strength of craze, and density of void which are dominant factors for enhancing toughness in PP ble…
Measurements were made on a series of cotton/polyester blends having different compositions. The results showed that the time to ignition increased as the polyester contents of the fabric were increased. An explanation of this observation is given. Both the orientation of the fabric and the temperature of the furnace…
Incorporation of hard clay causes improvement in most of the physical properties of zinc-sulfonated EPDM of high ethylene content. Zinc stearate reduces the melt viscosity of the clay-filled zinc-sulfonated EPDM during high-temperature processing, but does not adversely affect the physical properties at ambient temper…
Based on a successful description of II-VI ternary alloys, which introduces an empirical bowing parameter to the widely used virtual crystal approximation, we set up a tight-binding Hamiltonian to describe the Zn_{1-y}Cd_ySe_{1-x}Te_x and Zn_{.9}Cd_{.1}S_{.07}Se_{.93} quaternary alloys. We just use a formula that can…
The intersection volume of two independent 2-level cut Gaussian random fields is proposed to model the open-cell microstructure of organic aerogels. The experimentally measured X-ray scattering intensity, surface area and solid thermal conductivity of both polymeric and colloidal organic aerogels can be accounted for…
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