Search

Possible applications for dipolar magnetic nanorods in the fields of perpendicular storage media and ferrofluids are highlighted. Magnetic-field-assisted self-assembly of magnetic-dipole moment carrying aerosol-grown iron nanoparticles on a nonmagnetic substrate results in the formation of magnetic nanoscale rods and bundles thereof.

A study was conducted to analyze the grain size-dependent electrical characteristics of nanocrystalline ZnO. ZnO was chosen as the model system because of its semiconductive characteristics. Results indicated that a small amount of Bi dopant had no significant effect on the electrical characteristics in the small grin size range. However, it promoted a higher specimen resistance in the large grain size range.

X-ray diffraction and thermal analysis of solid-state reactions in nanometer-sized Cu Zr and Ni Zr binary mixtures indicate that the Ni(x)Za(1-x) mixture undergoes amorphization. Ball-milled samples of Cu Zr mixtures show amorphization, implying the importance of external driving forces for solid-state amorphization. Inert-gas condensation and in situ compaction help prepare these particles, whose behavior is in conjunction with that of multilayered samples.

Calorimetric measurements were used to investigate enthalpy release during the heating of nanocrystalline platinum samples. The results showed that50% of the excess enthalpy was released during a primary relaxation phase with no observed change in the grain size. Grain growth activity caused a second relaxation process. The excess grain boundary enthalpy was measured by analyzing the isothermal heat release of the grain growth.

Nickel nanorods with an average length of 250-420 nm and diameter of 20-26 nm were prepared by pulsed current electrodeposition into porous aluminum oxide templates and dispersed as colloidal probes in water-based viscoelastic matrices. The ferromagnetic single domain nanorods were driven to rotational motion by an oscillating magnetic field. Nanorod rotation was detected using optical transmission of linearly polarized light providing a frequency-dependent complex magneto-optical response function. Quantitative data analysis was derived for the two most basic mechanical equivalents to viscoelastic materials, the Voigt-Kelvin and Maxwell model, respectively, and demonstrated by means of two examples. The transition from a viscous fluid towards a viscoelastic hydrogel with static shear elasticity was monitored by analyzing an isothermal series of magneto-optical measurements of a gelatin sol after temperature quench in terms of the Voigt-Kelvin model. Maxwell-type relaxation was investigated using CTAC/NaSal giant wormlike micellar solution as matrix. The viscosities and shear moduli retrieved from magneto-optical measurements were compared with macroscopic values obtained by conventional shear rheometry. Characteristic features for each model system were found in the rheological properties at both length scales, yet with quantitative differences caused by the small size of the nanorod probe particles. [ABSTRACT FROM AUTHOR]

Aqueous dispersions of nickel nanorods, ≈13 nm in diameter and 40–160 nm in length, were synthesized using ac electrodeposition into porous alumina templates. The nanorods in suspension can be aligned by modest magnetic fields, which leads to a change in the optical transmittance of the dispersion. Optical transmission measurements with polarized and unpolarized light as a function of magnetic field were performed on suspensions of different particle concentration and varying aspect ratio of the nanoparticles. The experimental results were compared with a theoretical model in which the optical absorption of the nanorods is calculated from the polarizability of prolate ellipsoids in the quasistatic approximation. The magnetic field dependence is introduced in terms of the static orientational distribution function of magnetic moments in an external field. In addition, the relaxation dynamics of the optical transmission was studied, which allowed us to determine the rotational diffusion coefficient of the nanorods in suspension. [ABSTRACT FROM AUTHOR]