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All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Reaction of amorphous Ni-W and Ni-N-W films with substrate silicon

Wiley et al. (1982) have studied sputtered amorphous films of Nb-Ni, Mo-Ni, Si-W, and Si-Mo. Kung et al. (1984) have found that amorphous Ni-Mo films as diffusion barriers between multilayer metallizations on silicon demonstrate good electrical and thermal stability. In the present investigation, the Ni-W system was selected because it is similar to the Ni-Mo system. However, W has a higher silicide formation temperature than Mo. Attention is given to aspects of sample preparation, sample characterization, the interaction between amorphous Ni-W films and Si, the crystallization of amorphous Ni(36)W(64) films on SiO2, amorphous Ni-N-W films, silicide formation and phase separation, and the crystallization of amorphous Ni(36)W(64) and Ni(30)N(21)W(49) layers.

Zhu, M. F.↗
NASA NTRS1993

Tungsten solution kinetics and amorphization of nickel in mechanically alloyed Ni-W alloys

The kinetics of solution of W, and the subsequent amorphization of Ni, in mechanically alloyed Ni-W alloys has been investigated. As W is a highly abrasive material in the energy intensive devices used for mechanical alloying, we studied the above reactions in different mills. One used hardened steel balls as the grinding media, and the other Al2O3. Abrasion is common to both mills, but Fe wear debris from the hardened steel enters into solution in the Ni rich phases whereas Al2O3 debris is present as small dispersoids. The kinetics of W solution and those of subsequent amorphization do not appear strongly affected by the Fe in solution or the Al2O3 dispersoid. Tungsten dissolves in crystalline Ni in amounts in excess of the equilibrium solubility during alloying. Amorphization of the Ni phase occurs if the W content in this phase exceeds ca. 28 at. pct.

Aning, A. O.↗
NASA NTRS1974

A study of the diffusional behavior of a two-phase metal matrix composite exposed to a high temperature environment

The progress of diffusion-controlled filament-matrix interaction in a metal matrix composite where the filaments and matrix comprise a two-phase binary alloy system was studied by mathematically modeling compositional changes resulting from prolonged elevated temperature exposure. The analysis treats a finite, diffusion-controlled, two-phase moving-interface problem by means of a variable-grid finite-difference technique. The Ni-W system was selected as an example system. Modeling was carried out for the 1000 to 1200 C temperature range for unidirectional composites containing from 6 to 40 volume percent tungsten filaments in a Ni matrix. The results are displayed to show both the change in filament diameter and matrix composition as a function of exposure time. Compositional profiles produced between first and second nearest neighbor filaments were calculated by superposition of finite-difference solutions of the diffusion equations.

Tenney, D. R.↗
DOE OSTI2020

Materials Data on Ni4W by Materials Project

Ni4W crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. W is bonded to twelve Ni atoms to form WNi12 cuboctahedra that share corners with twelve NiNi9W3 cuboctahedra, edges with eight equivalent WNi12 cuboctahedra, edges with sixteen NiNi9W3 cuboctahedra, faces with two equivalent WNi12 cuboctahedra, and faces with sixteen NiNi9W3 cuboctahedra. There are eight shorter (2.54 Å) and four longer (2.57 Å) W–Ni bond lengths. There are three inequivalent Ni sites. In the first Ni site, Ni is bonded to three equivalent W and nine Ni atoms to form distorted NiNi9W3 cuboctahedra that share corners with three equivalent WNi12 cuboctahedra, corners with nine NiNi9W3 cuboctahedra, edges with four equivalent WNi12 cuboctahedra, edges with twenty NiNi9W3 cuboctahedra, faces with four equivalent WNi12 cuboctahedra, and faces with fourteen NiNi9W3 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.53–2.57 Å. In the second Ni site, Ni is bonded to three equivalent W and nine Ni atoms to form distorted NiNi9W3 cuboctahedra that share corners with three equivalent WNi12 cuboctahedra, corners with nine equivalent NiNi9W3 cuboctahedra, edges with four equivalent WNi12 cuboctahedra, edges with twenty NiNi9W3 cuboctahedra, faces with four equivalent WNi12 cuboctahedra, and faces with fourteen NiNi9W3 cuboctahedra. All Ni–Ni bond lengths are 2.53 Å. In the third Ni site, Ni is bonded to three equivalent W and nine Ni atoms to form distorted NiNi9W3 cuboctahedra that share corners with three equivalent WNi12 cuboctahedra, corners with nine NiNi9W3 cuboctahedra, edges with four equivalent WNi12 cuboctahedra, edges with twenty NiNi9W3 cuboctahedra, faces with four equivalent WNi12 cuboctahedra, and faces with fourteen NiNi9W3 cuboctahedra.

36 MATERIALS SCIENCE↗