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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Low Temperature Magnetic Properties of Amorphous Ferromagnetic Fe–Si–B Glass-Coated and Glass Removed Microwire

This work presents results of investigations of low temperature magnetic properties of microwires, fabricated by the Ulitovsky–Taylor method from Fe–Si–B alloy. Influence of the glass coating presence on the magnetostatic properties was shown at room temperature and at 2 K. Conclusions about the peculiarities of temperature dependence of the magnetic moment, measured in low and high magnetic fields (10 Oe–5 kOe) in the temperature range from 2 to 300 K for a sample with partially reduced fabricated processinduced stress by removing the glass, were made.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Double Hard Axes of Hysteresis Loop in Wide-Angle Obliquely Sputtered CoFeB Amorphous Films

Soft magnetic Co{sub 40}Fe{sub 40}B{sub 20} films with different tilt angle were successfully deposited on silicon substrates by using oblique sputtering technique. Different oblique angles are achieved by controlling the position of samples. The corresponding static magnetic properties of these samples were then systematically investigated. Interestingly, with the oblique angle increasing from 38° to 55°, the MOKE hysteresis loop of the thin films displays a unique and special performance with double hard axes. Meanwhile, despite of the measurement magnetic field along PR or AR direction, both of the hysteresis loops have two-stage magnetization reversal that means there are two comparably strong anisotropies in the CoFeB films. Moreover, rotating samples from in-plane to out-of-plane, the hysteresis loops demonstrate the perpendicular anisotropy exist in CoFeB films. The cross-section SEM characterizations further verify that the residual field from the magnetic cylinder will strongly impact the microstructures of thin film.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Relation between carriers hopping rate and structural constants in amorphous carbon nickel films with different nickel nanoparticles distributions

In this paper, the films were prepared by radio frequency magnetron co-sputtering technique. The effect of different mosaic targets made of nickel strips and graphite pure on the dielectric relaxation time, the carriers hopping rate, the fractal dimensions and the optical loss of films were studied. The values of the optical band gap of films using the cross-point between the tangent of the plot of lower and higher values of the photon energy were calculated. The films deposited at 4.64% have maximum hopping rate of about 8.6 × 10{sup 12} S{sup −1}. It can be seen that the films deposited at 3.92% have minimum value of fractal dimension of 2.27. With increasing Ni content of films a nonmetal–metal transition is observed which it is explainable by the power law of percolation theory. Critical metal content and the critical exponent of films were 87.25% and 1, respectively. With increasing Ni content, the carriers effective mass of films decreased and average lattice separation values of films increased. Films deposited at 3.92% have minimum value of Debye frequency ν{sub D} of about 1.09 × 10{sup 12} Hz. The value of energy loss by free charge carriers when traversing the bulk and surface of films at 3.92% has maximum value and it has an increasing function behavior with energy.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Determination of melt processing conditions for high performance amorphous thermoplastics for large format additive manufacturing

As the application space for large-scale 3D printed components continues to grow, it is necessary to identify appropriate processing conditions for high-performance thermoplastics on large format Additive Manufacturing (LFAM) systems. This study compares the rheological behavior of a high-performance thermoplastic, polyphenylsulfone (PPSU), with that of a commonly used low-temperature polymer, acrylonitrile butadiene styrene (ABS), to identify suitable processing conditions for large format AM systems. The linear viscoelastic properties (complex viscosity, storage modulus, loss modulus, and tan delta) of these materials are evaluated as a function of temperature, angular frequency, and carbon fiber content. Over the range of frequencies of interest to LFAM (10–100 rad/s), ABS behaves more like an elastic solid whereas PPSU behaves more like a viscous liquid. Here, the addition of 20–35% by weight of carbon fiber increased the shear thinning effect of both thermoplastics, showing a potential variation of 2–3 x over the range of expected LFAM extrusion shear rates (10–100 s –1 ).

36 MATERIALS SCIENCE↗