Materials Literature
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Understanding the size-dependent electronic, structural and chemical properties of metal clusters on oxide supports is an important aspect of heterogeneous catalysis. Recently model oxide-supported metal catalysts have been prepared by vapour deposition of catalytically relevant metals onto ultra-thin oxide films grow…
The magnetocaloric effect that originates from the martensitic transition in the ferromagnetic Ni-Mn-Ga shape-memory alloy is studied. We show that this effect is controlled by the magnetostructural coupling at both the martensitic variant and magnetic domain length scales. A large entropy change induced by moderate m…
Purification and enhanced processability of carbon nanotubes have previously been achieved through interaction with a conjugated polymer. In particular, microscopy and Raman spectroscopy indicate a selective interaction between single-walled carbon nanotubes and a conjugated polymer. Until now, there has been no exten…
A direct measurement of the length scale of dynamic heterogeneity in supercooled d -sorbitol has been performed using a multidimensional 13 C solid-state NMR experiment. Several models predict that the growth of this length scale is linked to the slowing of dynamics as the glass transition is approached from above. At…
A series of first-principles calculations were performed for ferromagnetic Ni 2 MnGa using density functional theory and PAW potentials. Theoretically, a tetragonal crystal structure homogeneous lattice-distortive strain is stabilized around c / a = 0.94 with respect to the L2 1 structure when, in addition, modulation…
We report a theoretical and experimental investigation of Cr-doped AlN. Density functional calculations predict that the isolated Cr t2 defect level in AlN is 1/3 full, falls approximately at midgap, and broadens into an impurity band for concentrations over 5%. Substitutional Al1-xCrxN random alloys with 0.05 <= x <=…
We show that the electron-phonon coupling in the transition-metal diborides NbB2 and TaB2 is dominated by the longitudinal acoustical (LA) mode, in contrast to the optical E_{2g} mode dominated coupling in MgB2. Our ab initio results, described in terms of phonon dispersion, linewidth, and partial electron-phonon coup…
Theory of current hysteresis for tunneling through a molecular quantum dot (MQD) with strong electron-vibron interactions and attractive electron-electron correlations is developed. The dot is modeled as a d-fold degenerate energy level weakly coupled to the leads. The effective attractive interaction between polarons…
We present a study of the magnetic properties of the electron doped manganites Ca 1− x Y x MnO 3 (for 0 ≤ x ≤ 0.25) in the paramagnetic regime. For the less doped samples ( x ≤ 0.1) the magnetic susceptibility, χ( T ), follows a Curie–Weiss (CW) law only for T > 450 K and, below this temperature, χ −1 ( T ) shows a fe…
A great number of the existing data for electrical transport, the Altshuler Aronov Spivak and Aharonov Bohm effects, as well as the tunneling spectra of individual carbon nanotubes can be well explained by theories of the quantum phase slips in quasi-one-dimensional superconductors. The existing data consistently sugg…
Detailed analyses are made on previously published data for multi-walled carbon nanotubes. The field dependence of the Hall voltage, the temperature dependence of the Hall coefficient, and the magnetoresistance effect (Phys. Rev. Lett. 72, 697 (1994)) can all be consistently explained in terms of the coexistence of ph…
Mineral-bound Fe(II) species represent important natural reductants of pollutants in the anaerobic subsurface. At clay minerals, three types of Fe(II) species in fundamentally different chemical environments may be present simultaneously, i.e., structural Fe(II), Fe(II) complexed by surface hydroxyl groups, and Fe(II)…
The photocurrents generated by a monolayer consisting of a CdS nanoparticles/acetylcholine esterase hybrid system associated with an electrode are controlled by the enzyme inhibitors.
The TSC spectroscopy was applied to investigate an influence of structural change and interfacial state on the electrical properties of epoxy composites cured with acid-anhydride. A addition of over abundant hardener and inorganic filler separated a /spl beta/ peak near 10[/spl deg/C] into two peaks of /spl beta//sub…
We present the conditions in which a toroidal type, line frequency, power transformer can yield reduced stray magnetic field, reduced weight and size, and improved efficiency over an E-I laminate transformer in single phase linear power supplies. These benefits must be considered in relation to the disadvantages of sl…
The time stability of the surface potential of PTFE and silicon dioxide electrets at room temperature are similar: after an initial small decay the potential is practically constant during a time interval that decreases as humidity increases and then drastically drops. The time stability of the surface is correlated w…
The development of ferroelectric memory devices requires an understanding of the fatigue properties of ferroelectric thin films. PZT thin films by sol-gel method on Pt/Ti with residual polarization reduced by continuous polarization reversal about 10/sup 8/ cycles. In this paper, we regard Ir, IrO/sub 2/ and these lay…
We demonstrate a novel solid-state three-dimensional display using rare earth doped heavy metal fluoride glass as the active medium. In this device, two laser beams intersect inside a bulk glass at room temperature to address a pixel in three-dimensional space. The two-step resonant upconversion process requires two d…
Undoped barium titanate ceramics exhibiting a distinct positive temperature coefficient of resistivity (PTCR) effect have been produced by sintering high-purity barium titanate powder compacts in the temperature range 1300-1400/spl deg/C in air. The formation of core-shell type duplex microstructures in the materials…
The influence of /spl gamma/-ray irradiation on the phase transition temperature in (NH/sub 2/(C/sub 2/H/sub 5/)/sub 2/)/sub 2/CuCl/sub 4/ crystals was investigated. It has been ascertained that irradiation at room temperature leads to increase of transition temperature T/sub 1/. Contrary to this, irradiation just bel…