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Fe1-xMx (M=Ga, Ge, Si, Al, Mo and x~0.18) alloys offer an extraordinary combination of magnetoelasticity and mechanical properties. They are rare-earth-free, can be processed using conventional deformation techniques, have high magnetic permeability, low hysteresis, and low magnetic saturation fields, making them attractive for device applications such as actuators and energy harvesters. Starting with Fe-Ga as a reference and using a rigid-band-filling argument, Zhang et al. predicted that lowering the Fermi level by reducing the total number of electrons could enhance magnetoelasticity. To provide a direct experimental validation for Zhang's hypothesis, elemental additions with lower-than-Ga valence are needed. Of the possible candidates, only Be and Zn have sufficient solubility. Single crystals of bcc Fe-Ga-Zn have been grown with up to 4.6 at.% Zn in a Bridgman furnace under elevated pressure (15 bars) in order to overcome the high vapor pressure of Zn and obtain homogeneous crystals. Single-crystal measurements of magnetostriction and elastic constants allow for the direct comparison of the magnetoelastic coupling constants of Fe-Ga-Zn with those of other magnetoelastic alloys in its class. The partial substitution of Ga with Zn yields values for the magnetoelastic coupling factor, -b1, comparable to those of the binary Fe- Ga alloy. [ABSTRACT FROM AUTHOR]

Iron is a well-utilized material in structural and magnetic applications. This does not mean, however, that it is well understood, especially in the field of magnetostriction. In particular, the rhombohedral magnetostriction of iron, λ111, is anomalous in two respects: it is negative in sign, in disagreement with the prediction of first principles theory, and its magnitude decreases with increasing temperature much too rapidly to be explained by a power law dependence on magnetization. These behaviors could arise from the location of the Fermi level, which leaves a small region of the majority 3d t2g states unfilled, possibly favoring small internal displacements that split these states. If this view is correct, adding small amounts of Co to Fe fills some of these states, and the value of λ111 should increase toward a positive value, as predicted for perfect bcc Fe. We have measured the magnetostriction coefficients (λ111 and λ100) of pure Fe, Fe97Co3, and Fe94Co6 single crystals from 77K to 450 K. Resonant ultrasound spectroscopy has been used to check for anomalies in the associated elastic constants, c44 and c'. The additional electrons provided by the cobalt atoms indeed produced positive contributions to both magnetostriction constants, λ111 and λ100, exhibiting an increase of 2.8 × 10-6 per at.% Co for λ111 and 3.8×10-6 per at.% Co for λ100. [ABSTRACT FROM AUTHOR]

The stress-strain hysteresis losses of [Tb.sub.x] [Dy.sub.1-x] [Fe.sub.1.92] (x = 0.30, 0.33, 0.40, 0.45, and 0.50) were measured at a variety of magnetic fields between 0 and 1600 Oe. Stress ranges from ~0 to -10, -20, -40, and -60 MPa (the minus sign indicates compressive stresses) were used. The hysteresis loop area increased from 5.7 kJ/[m.sup.3] at x = 0.30 to 10 kJ/[m.sup.3] at x = 0.50 as the Tb concentration and the magnetic anisotropy increased. The position of the hysteresis loop shifted to larger compressive stresses as the magnetic field was increased allowing the strength of the damping to be controlled by the magnetic field. Index Terms--Hysteresis, magnetomechanical damping, Terfenol.

SiO2/SiC coatings were deposited onto ceramics disks using plasma‐enhanced chemical vapor deposition. The effects of deposition pressure and gas‐flow ratio on the refractive index, extinction coefficient, and SiC composition were studied. For the highest studied SiH4 to CH4 gas‐flow ratio of 1.5, the refractive index increased by 17% from 2.53 (at the wavelength of 845 nm) to 2.96 (at the wavelength of 400 nm). For the lowest studied SiH4 to CH4 gas‐flow ratio of 0.5, the refractive index only increased by 4% from 2.11 (at the wavelength of 845 nm) to 2.20 (at the wavelength of 400 nm). At higher deposition pressures, the variation in refractive index of the SiC coatings was significantly lower showing a slight increase from 1.93 (at a wavelength of 845 nm) to 1.96 at a wavelength of 400 nm. Except for the case of a low SiH4 to CH4 gas‐flow ratio of 0.5, for light with wavelengths ≤650 nm, the extinction coefficient of the SiC coatings increased significantly. Light with a wavelength >650 nm had an extinction coefficient near 0 in all cases. After annealing the sample at 400°C for 4 hours, hydrogen‐related bonds broke and the stress of the film was reduced from −245 to −71 MPa. By utilizing different thicknesses of SiC, the full standard dental shade guide was matched with the ΔE of each coated disk being less than 3.3 compared to the shade guide. [ABSTRACT FROM AUTHOR]

Bioglass cones acting as space fillers after removal of tooth roots delay the resorption of alveolar ridges. In 1987, 242 implants in 29 patients with a mean postimplantation interval of 19.9 months were reported by the authors. Bioglass cones had been fitted snugly at least 2 mm below the alveolar crest, and dentures were placed no sooner than 6 weeks following tooth removal; 2.9% had been lost and 3.7% developed dehiscences. The present report on 168 implants in 20 recalled patients (mean postimplantation interval of 63.2 months) revealed a loss of 14.3% of the implants and 7.7% of the implants requiring recontouring. Literature indicates highest survival rates for implants in the anterior mandible; however, the present data demonstrate a statistically significant retention rate in the anterior maxilla. With this high rate of Bioglass cone retention (85.7%) after 5 years, their placement into fresh sockets to maintain the alveolar ridge is recommended. [ABSTRACT FROM AUTHOR]

The magnetostriction ([[Lambda].sub.100]) of b.c.c. Fe is increased over 10-fold at room temperature by the substitution of ~20% gallium for Fe. [Fe.sub.1-x][Ga.sub.x] alloys with x between 0.19 and 0.214 that are quenched from 800 [degrees] C exhibit magnetostrictions ~25% higher than those furnace-cooled at 10 [degrees]/min. We propose that this great increase of magnetostriction above that of Fe in Fe-Ga alloys is not due to conventional magnetoelastic effects but due to the substitutive presence of asymmetrically shaped clusters of the Ga atoms. As the concentration of solute atoms approaches 25%, the lattice becomes relaxed with formation of a more ordered structure and the magnetostriction decreases in value. Index Terms--Actuator, iron-gallium alloys, magnetostriction, structural materials, transduction.

The magnetic and magnetostrictive properties of [Fe.sub.1-x][Ga.sub.x] and [Fe.sub.1-x-y][Ga.sub.x][Al.sub.y] (x + y [is less than] 0.3) single crystals were measured under compressive stresses up to 120 MPa and in magnetic fields up to 1 kOe. Values of [[Lambda].sub.100] exceeding 200 ppm were observed in samples of [Fe.sub.83][Ga.sub.17] from 180 K to room temperature. Only a small monotonic decrease in magnetostriction with temperature was found. On the other hand, [[Lambda].sub.111] maintained small negative values close to those of b.c.c. Fe. In all cases, no higher order magnetostrictive terms were detectable. With 15 to 20 atomic percent replacement of Fe by Ga, the magnetizations remain high ([M.sub.s] [nearly equals to] 1.8 T) and the magnetic anisotropies reduced ([K.sub.1] [nearly equals to] J/[m.sup.3]). Values of the `stiff' (high magnetic field) Young's modulus, Bulk modulus, Poison's ratio, and elastic constant [c.sub.11]-[c.sub.12] for [Fe.sub.85][Ga.sub.15] at room temperature are, respectively, 77 GPa, 111 GPa, 0.38, and 56 GPa. Index Terms--Actuator, Fe-Ga, Fe-Ga-Al, magnetostriction, structural materials, transduction.