Materials Literature
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We report that a Au/Ge/Pd layered structure can result in low contact resistivities (∼10−6 Ω cm2) to n-GaAs processed in three temperature ranges (175–200, 340–350, and 425–450 °C). The contacts processed below the Au–Ge eutectic temperature (361 °C) show good surface and interface morphology, thermal stability, Au wi…
Magnets with a nominal composition of Nd14.5Fe79.5B6 have been prepared by the conventional powder metallurgy technique. Precursor alloy powders with average particle sizes of 2.5, 3.0, 3.5, and 4.2 μm were included in this study. Average particle size and oxygen content were effectively manipulated to control the ave…
Direct current hysteresis loops of 49%Co–2%V–Fe alloy have been measured at temperatures up to 800 °C. Two phase structure is evident in the B–H loops between 580 and 730 °C. This alloy cannot be reliably operated above 580 °C. The second magnetic phase is believed to result from the nucleation and growth of disordere…
The result of spin-polarized band calculation for Fe16N2 is presented. The most distant Fe atoms from N is found to have the largest magnetic moment. The major role of the N atom is to expand the Fe lattice, leading to the enhancement of the magnetic moments. Quantitatively speaking, the calculated moment of Fe16N2 is…
Experimental inelastic electron-scattering cross sections of Si and Fe determined from reflection-electron-energy-loss spectroscopy (REELS) experiments are presented. Three primary energies of the electrons (300, 800, and 2000 eV) and three experimental geometries have been considered. The cross sections have been com…
Ni–Co ferrite has been studied with Mössbauer spectroscopy and x-ray diffraction. The crystal structure for this system is spinel, and the lattice constant is in accord with Vegard’s law. The Mössbauer spectra consist of two six-line patterns corresponding to Fe3+ at the tetrahedral (A) and octahedral (B) sites. The N…
A thin electromagnetic wave absorber has been investigated; it is composed of hexagonal ferrite and retains high permeability even in the gigahertz-range. The grid-type wave absorber composed of the hexagonal ferrite was examined to broaden the bandwidth in a gigahertz-range by introducing free space in the direction…
Anisotropic Nd–Fe–B magnet powders can be produced by the hydrogenationdecomposition-desorption-recombination (HDDR) process from Nd–Fe–B–Co–M (M=Ga, Zr, Nb, Hf, and Ta) alloys. The present status of those HDDR powders and the bonded magnets made from them are reviewed with regards to the powder particle size dependen…
The microstructure and electrical properties of tin-doped indium oxide thin films crystallized under the action of a temperature gradient are compared with those of films prepared under uniform temperature. This zone-confining process, coupled with slow deposition rates, causes preferential segregation of dopants from…
The dissolution mechanism of rubbery polymers was analyzed by dividing the penetrant concentration field into three regimes that delineate three distinctly different transport processes. The solvent penetration into the rubbery polymer was assumed to be Fickian. The mode of mobility of the polymer chains was shown to…
Field emission of electrons from boron- and nitrogen-doped diamond is compared. Emission from boron-doped diamond requires vacuum electric fields of 20–50 V μm−1, while nitrogen-doped, type Ib diamond requires fields of 0–1 V μm−1. Since boron-doped diamond is very conductive, very little voltage drop occurs in the di…
Modifications of the magnetic properties of a nonoriented 3% SiFe alloy with plastic strains are reported. The samples have been tested along rolling and transverse directions lying in the sheet plane by means of a suitable experimental system of measurements using a 50 Hz sinusoidal magnetic field. The magnetic prope…
Optical absorption curves for nominally pure and Ce 3+ doped single crystals of Y 3 Al 5 O 12 (YAG) have been measured in the region of 5 eV–7 eV at 292 K, 78 K and 10 K. The parameters of the Urbach rule have been determined referring to those optical absorption curves which are believed to be the fundamental absorpt…
The Jiles–Atherton theory is based on considerations of the dependence of energy dissipation within a magnetic material resulting from changes in its magnetization. The algorithm based on the theory yields five computed model parameters, MS, a, α, k, and c, which represent the saturation magnetization, the effective d…
Various processing routes for making permanent magnets based on interstitially modified Sm2Fe17 have been recently developed. Zn bonding of coarse grained Sm2Fe17N3 gives coercivities μ0JHc as high as 2.2 T. Effective methods to prepare highly coercive Sm2Fe17N3 powders for polymer bonding are mechanical alloying and…
The molecular characteristics which determine the melting points of high polymer crystals are considered, and it is shown that the properties of monomeric crystals often throw light on those of the polymers. The principal factors controlling melting points appear to be molar cohesion energy (of the whole molecule for…
The combination of chemical composition and microstructure of cast alloy has been found to be critical to the performance of NdFeB sintered magnets. Maximizing the amount of Nd2Fe14B phase (or minimizing the amount of secondary phase) by reducing the Nd content more closely to the stoichiometric composition appears to…
Resonant photoelectron spectroscopy studies have been performed on the NiO valence band at photon energies corresponding to the Ni $2p$,$3p$,and O $1s$ absorption thresholds. Strong resonances are seen in the vicinity of the Ni $2p$ threshold, which confirm earlier conclusions from the weaker resonances seen at the Ni…
Diffusion of penetrants through polymers often does not follow the standard Fickian model. Such anomalous behavior can cause difficulty when designing polymer networks for specific uses. One type of non-Fickian behavior that results is so-called case II diffusion, where Fickian-like fronts initially move like √t with…
A model for the radiation-induced production of defects in amorphous insulators is proposed. It is shown that an irreversible creation of defects from network sites follows power law kinetics, and a reversible activation of precursor sites follows Kohlrausch kinetics. Electron spin resonance was used to measure the co…