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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ti5Si3 by Materials Project

Ti5Si3 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. there are two inequivalent Ti+2.40+ sites. In the first Ti+2.40+ site, Ti+2.40+ is bonded in a 6-coordinate geometry to six equivalent Si4- atoms. All Ti–Si bond lengths are 2.64 Å. In the second Ti+2.40+ site, Ti+2.40+ is bonded to five equivalent Si4- atoms to form a mixture of distorted edge and corner-sharing TiSi5 trigonal bipyramids. There are a spread of Ti–Si bond distances ranging from 2.57–2.78 Å. Si4- is bonded in a 9-coordinate geometry to nine Ti+2.40+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti5Si3C by Materials Project

Ti5Si3(C) crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. there are two inequivalent Ti+3.20+ sites. In the first Ti+3.20+ site, Ti+3.20+ is bonded to six equivalent Si4- atoms to form a mixture of distorted edge, face, and corner-sharing TiSi6 octahedra. The corner-sharing octahedral tilt angles are 31°. All Ti–Si bond lengths are 2.61 Å. In the second Ti+3.20+ site, Ti+3.20+ is bonded in a 7-coordinate geometry to five equivalent Si4- and two equivalent C4- atoms. There are a spread of Ti–Si bond distances ranging from 2.64–2.90 Å. Both Ti–C bond lengths are 2.16 Å. Si4- is bonded in a 9-coordinate geometry to nine Ti+3.20+ atoms. C4- is bonded to six equivalent Ti+3.20+ atoms to form face-sharing CTi6 octahedra.

36 MATERIALS SCIENCE↗
NASA NTRS1979

Interfacial reactions in borsic/Ti-3Al-2-1/2V composite

The paper provides a detailed X-ray characterization of a borsic/Ti-3Al-2-1/2V composite, and to correlate the relative intensities of the reaction products with the mechanical properties. Based on X-ray integrated intensity data two stages of interface reactions were identified: during the first stage there is a simultaneous interdiffusion of Si, C, and Ti atoms at the filament/matrix interface resulting in the formation of Ti5Si3, TiSi and small amounts of TiSi2 and TiC. The second stage is associated with considerable TiSi2 and boride formation. It appears that the alpha-phase of Ti is more reactive in forming silicides and borides than the beta-phase. The silicide intensities and the reaction zone thicknesses are shown to be directly related to the reduction of the ultimate tensile strength by thermal degradation, and the results indicate that silicide reaction products are as detrimental to strength as the borides.

Rao, V. B.↗
NASA NTRS2010

Microstructural and Mechanical Evaluation of a Cu-Based Active Braze Alloy to Join Silicon Nitride Ceramics

Self-joining of St. Gobain Si3N4 (NT-154) using a ductile Cu-Al-Si-Ti active braze (Cu-ABA) was demonstrated. A reaction zone approx.2.5-3.5 microns thick) developed at the interface after 30 min brazing at 1317 K. The interface was enriched in Ti and Si. The room temperature compressive shear strengths of Si3N4/Si3N4 and Inconel/Inconel joints (the latter created to access baseline data for use with the proposed Si3N4/Inconel joints) were 140+/-49MPa and 207+/-12MPa, respectively. High-temperature shear tests were performed at 1023K and 1073 K, and the strength of the Si3N4/Si3N4 and Inconel/Inconel joints were determined. The joints were metallurgically well-bonded for temperatures above 2/3 of the braze solidus. Scanning and transmission electron microscopy studies revealed a fine grain microstructure in the reaction layer, and large grains in the inner part of the joint with interfaces being crack-free. The observed formation of Ti5Si3 and AlN at the joint interface during brazing is discussed.

Singh, M.↗