Materials Literature
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Subdomain size superparamagnetic particles of Mn-Zn ferrites, having a narrow particle size distribution (peaked around 10 nm) were prepared under mild hydrothermal conditions. High densities (≳99.5%) have been obtained upon sintering these green ferrite powders at relatively low temperatures (∼1000 °C), without the u…
The corrosion mechanism of Nd-Fe-B sintered magnets has been investigated. A correlation between the lifetime of epoxy-coated magnets in a humidity test (80 °C, 90% RH) and the rate of weight loss (ΔW/Δt) of the bare magnets in the pressure cooker test (PCT: 125 °C; 85% RH; 2 atm) has been established. In this system,…
The power loss of Mn-Zn ferrites and its dependency on the microstructural factors have been investigated. The power loss was found to be lowered due to the formation of a high-electrical-resistive boundary layers, which is accomplished by an addition of specific refractory oxides, which are concentrated on the grain…
The photovoltaic characteristics of optimized iodine-doped thin-film sandwich cells of the structure Al/Al2O3/magnesium tetraphenylporphyrin/Au, fabricated and tested under high vacuum, are reported. The action spectra of the short-circuit photocurrent show that only light absorbed near the Al-Al2O3 electrode, to a de…
Chemical and electronic properties of polypyrrole films are investigated for different doping levels using x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy, and high-resolution electron-energy-loss spectroscopy. The XPS results give evidence for instabilities in perchlorate-doped polypyrr…
The influence of an attractive interparticle potential on the rheology of a sterically stabilized silica dispersion was investigated. Using a marginal solvent, there was an effective attraction between the particles which depended on the temperature. Three experiments in which different properties of the dispersion we…
The chemical nature of the nitrogens corresponding to various intrinsic redox states of polypyrrole (PPY) and polyaniline (PAN) has been critically compared using x-ray photoelectron spectroscopy (XPS) as a primary tool. Proton modifications of nitrogens in PPY give rise to a number of intrinsic redox states analogous…
Amorphous transition-metal boron (TM-B) alloy particles can be prepared by chemical reduction of TM ions by borohydride in aqueous solutions. ln the last few years systematic studies of the parameters which control the composition, and, in turn, many of the properties of the alloy particles, have been performed and ar…
Femtosecond response and relaxation of the third-order optical nonlinearity in a newly developed poly (p-phenylene vinylene)/sol-gel silica composite are investigated by time-resolved forward wave degenerate four-wave mixing, Kerr gate, and transient absorption techniques using 60 fs pulses at 620 nm. Using a theoreti…
The nature of media recording noise in metallic, quasiparticulate thin films is principally related to the grain size, crystallographic orientation, and intergranular exchange and magnetostatic coupling in the films. In this study the results of a magnetic evaluation of magnetostatic interactions in CoNiCr thin films…
Nd-Fe-B permanent magnets prepared by rapid solidification have been extensively characterized by transmission electron microscopy at all stages of their development. Grains in the as-spun ribbons range in size up to several micrometers in their largest dimension. Excess Nd is trapped within some of the larger grains…
Magnetic susceptibility measurements of high purity MgO single crystals (<50-wt. ppm transition metals) by means of a vibrating-sample magnetometer shows an anomaly at 800 K. At the same temperature the electric conductivity increases anomalously, the static dielectric constant epsilon increases from 9 to approximatel…
Magnetization, magnetic susceptibility, and crystal structure are investigated on the ternary chromium arsenides CrM′As (M′=Ru,Rh,Pd) and ternary manganese phosphides and arsenides MnM′P(M′=Rh,Pd) and MnM′As(M′=Ru,Pd). MnRhP, MnRuAs, and MnPdAs are ferromagnets with a Curie temperature of Tc=401, 496, and 210 K, respe…
Anisotropic Nd-Fe-B magnets are produced from melt-spun ribbons by hot working technique. The processing is facilitated by improved workability. In order to obtain a sound magnet, it is important to suppress the crack initiation and growth. An investigation was carried out to study the deformation mechanism of the all…
We have succeeded in forming single-phase MnBi in its two ferromagnetic phases, the low-temperature phase (LTP) and the quenched high-temperature phase (QHTP). The formation process involves rapid solidification into the amorphous state followed by thermal annealing. The crystallization of the amorphous material invol…
Experimental results concerning the reduction of the amplitude nonuniformity of a Metglas 2605SC magnetostrictive delay line (MDL) after stress relief and current annealing under stress are reported. Nonuniformity is defined here as the fluctuation of the peak voltage V0 received by a coil around the MDL at a fixed po…
The influences of varying cerium, neodymium, cobalt, and silicon concentrations on the magnetic properties of Ce-Fe-B type magnets were investigated. The results indicated that magnets containing 13.5 at.% of cerium exhibits superior magnetic properties to those exhibited by magnets with higher rare-earth element comp…
From magnetization (M) and magnetostriction (λ) measurements as a function of magnetic field and stress, the temperatures of anisotropy compensation, Tm, for technologically important TbxDy1−x(Fe1−yTy)1.9 [T=Co,Mn (0.3≤x≤0.5) (0≤y≤0.3)] were determined. Measurements of M and λ encompassing Tm were made under compressi…
Using frequency-dependent dielectric susceptibility, we have studied three different types of relaxation phenomena, namely primary (\ensuremath{\alpha}), secondary (\ensuremath{\beta}), and conductivity (c) relaxation, in a sample of 25 vol % benzyl chloride in toluene. The measurement covers ten decades of frequency:…
Neutron diffraction, in conjuction with substitution of deuterium (D) for hydrogen (H), has been used to determine the structure of interlayer water in sodium- and nickel-substituted vermiculites. We have measured the intensities of the (00l) Bragg reflections as a function of relative humidity and H/D content, up to…