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7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

First Principles Evaluation of Phase Stability in the In-Sn Binary System

Abstract The In-Sn binary alloy system exhibits several unusual features that challenge crystallographic and thermodynamic expectations. We combine first principles total energy calculation with simple thermodynamic modeling to address two key points. First, we evaluate energies along the Bain path to interpret the discontinuous transition between the phases α-In (Pearson type tI2) and β-In 3 Sn (also Pearson type tI2) that are identical in symmetry. Second, we demonstrate that the solid solution phases β-In 3 Sn and γ-InSn 4 (Pearson type hP1) exist at high temperatures only, and they exhibit eutectoid decompositions at low temperatures.

Chemistry↗
NASA NTRS1982

Long term variability of transmission of thin In-Sn and Sn-C films for EUV instrumentation

The transmission variability is reported for two filters in the EUV, where the filters were supported on an 80% transmission nickel mesh and fabricated by means of a vacuum deposition technique. The first film consisted of 2500 A-thick indium, deposited on 500 A-thick tin, and had its primary bandpass in the 740-960 A range. The second consisted of 1800 A-thick tin and 2000 A-thick carbon, with a bandpass of 500-750 A. At the end of 10 months, the transmission of both filters was measured to check variations. It is demonstrated that the EUV transmission of such filters can change over the typical lifetime of satellite missions, and that such variation depends on the storage environment. The use of vacuum, rather than dry nitrogen storage is recommended.

Chakrabarti, S.↗
NASA NTRS1988

Oxidation and protection of fiberglass-epoxy composite masts for photovoltaic arrays in the low earth orbital environment

The extent of degradation of fiberglass-epoxy composite masts of the Space Station solar array panel, when these are exposed to atomic oxygen environment of the low-earth orbit, was investigated in ground testing of fiberglass-epoxy composites in an RF plasma asher. In addition, several methods of protecting the composite structures were evaluated, including an aluminum braid covering, an In-Sn eutectic, and a silicone based paint. It was found that, during exposure, the epoxy at the surface of the composite was oxidized, exposing individual glass fibers which could easily be removed. The results of mass measurements and SEM examination carried out after thermal cycling and flexing of exposed composite samples indicated that coatings such as In-Sn eutectic may provide adequate protection by containing the glass fibers, even though mass loss still occurs.

Rutledge, Sharon K.↗
NASA NTRS1988

Oxidation and protection of fiberglass-epoxy composite masts for photovoltaic arrays in the low Earth orbital environment

Fiberglass-epoxy composites are considered for use as structural members for the mast of the space station solar array panel. The low Earth orbital environment in which space station is to operate is composed mainly of atomic oxygen, which has been shown to cause erosion of many organic materials and some metals. Ground based testing in a plasma asher was performed to determine the extent of degradation of fiberglass-epoxy composites when exposed to a simulated atomic oxygen environment. During exposure, the epoxy at the surface of the composite was oxidized, exposing individual glass fibers which could easily be removed. Several methods of protecting the composite were evaluated in an atomic oxygen environment and with thermal cycling and flexing. The protection techniques evaluated to date include an aluminum braid covering, an indium-tin eutectic and a silicone based paint. The open aluminum braid offered little protection while the CV-1144 coating offered some initial protection against atomic oxygen, but appears to develop cracks which accelerate degradation when flexed. Coatings such as the In-Sn eutectic may provide adequate protection by containing the glass fibers even though mass loss still occurs.

Rutledge, Sharon K.↗
NASA NTRS1996

Microstructural Development during Directional Solidification of Peritectic Alloys

A thorough understanding of the microstructures produced through solidification in peritectic systems has yet to be achieved, even though a large number of industrially and scientifically significant materials are in this class. One type of microstructure frequently observed during directional solidification consists of alternating layers of primary solid and peritectic solid oriented perpendicular to the growth direction. This layer formation is usually reported for alloy compositions within the two-phase region of the peritectic isotherm and for temperature gradient and growth rate conditions that result in a planar solid-liquid interface. Layered growth in peritectic alloys has not previously been characterized on a quantitative basis, nor has a mechanism for its formation been verified. The mechanisms that have been proposed for layer formation can be categorized as either extrinsic or intrinsic to the alloy system. The extrinsic mechanisms rely on externally induced perturbations to the system for layer formation, such as temperature oscillations, growth velocity variations, or vibrations. The intrinsic mechanisms approach layer formation as an alternative type of two phase growth that is inherent for certain peritectic systems and solidification conditions. Convective mixing of the liquid is an additional variable which can strongly influence the development and appearance of layers due to the requisite slow growth rate. The first quantitative description of layer formation is a model recently developed by Trivedi based on the intrinsic mechanism of cyclic accumulation and depiction of solute in the liquid ahead of the interface, linked to repeated nucleation events in the absence of convection. The objective of this research is to characterize the layered microstructures developed during ground-based experiments in which external influences have been minimized as much as possible and to compare these results to the current the model. Also, the differences between intrinsic and externally influenced layer formation were explored. The choice of alloy system is critical to a study of the formation of layered microstructures. The ideal system would have a well-characterized phase diagram, equal densities of both elements in the liquid state to minimize compositionally-driven convective flows, a low peritectic temperature to simplify directional solidification and the achievement of a high temperature gradient in the liquid, a broad composition range for the peritectic reaction, and a reasonable hardness at room temperature to facilitate handling and metallographic preparation. The In-Sn system was selected initially due to a very low peritectic temperature and the nearly equal densities of In and Sn in the liquid state. Since the In-rich peritectic reaction had apparently not been utilized previously for solidification research, experiments were conducted to check the phase diagram in the region of interest. The alloys in this system proved to be difficult to handle and prepare in bulk form with the equipment available, so experiments were initiated with the Sn-Cd system. Layered microstructures had been observed previously in Sn-Cd.

Lograsso, Thomas A.↗
DOE OSTI2020

Materials Data on In3Sn by Materials Project

In3Sn is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. In is bonded to eight equivalent In and four equivalent Sn atoms to form InIn8Sn4 cuboctahedra that share corners with twelve equivalent InIn8Sn4 cuboctahedra, edges with eight equivalent SnIn12 cuboctahedra, edges with sixteen equivalent InIn8Sn4 cuboctahedra, faces with four equivalent SnIn12 cuboctahedra, and faces with fourteen equivalent InIn8Sn4 cuboctahedra. All In–In bond lengths are 3.39 Å. All In–Sn bond lengths are 3.39 Å. Sn is bonded to twelve equivalent In atoms to form SnIn12 cuboctahedra that share corners with twelve equivalent SnIn12 cuboctahedra, edges with twenty-four equivalent InIn8Sn4 cuboctahedra, faces with six equivalent SnIn12 cuboctahedra, and faces with twelve equivalent InIn8Sn4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSn4 by Materials Project

InSn4 is Hg_xSn-derived structured and crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. In is bonded to four equivalent In and four Sn atoms to form InIn4Sn4 hexagonal bipyramids that share corners with four equivalent InIn4Sn4 hexagonal bipyramids, corners with four SnSn8 hexagonal bipyramids, edges with six equivalent InIn4Sn4 hexagonal bipyramids, and edges with eighteen SnIn2Sn6 hexagonal bipyramids. There are two shorter (3.05 Å) and two longer (3.19 Å) In–In bond lengths. All In–Sn bond lengths are 3.32 Å. There are seven inequivalent Sn sites. In the first Sn site, Sn is bonded to two equivalent In and six Sn atoms to form SnIn2Sn6 hexagonal bipyramids that share corners with eight SnIn2Sn6 hexagonal bipyramids, edges with eight equivalent InIn4Sn4 hexagonal bipyramids, and edges with sixteen SnIn2Sn6 hexagonal bipyramids. There are a spread of Sn–Sn bond distances ranging from 3.05–3.30 Å. In the second Sn site, Sn is bonded to eight Sn atoms to form SnSn8 hexagonal bipyramids that share corners with two equivalent InIn4Sn4 hexagonal bipyramids, corners with six SnSn8 hexagonal bipyramids, an edgeedge with one InIn4Sn4 hexagonal bipyramid, and edges with twenty-three SnIn2Sn6 hexagonal bipyramids. There are a spread of Sn–Sn bond distances ranging from 3.05–3.31 Å. In the third Sn site, Sn is bonded to eight Sn atoms to form SnSn8 hexagonal bipyramids that share corners with two equivalent InIn4Sn4 hexagonal bipyramids, corners with six SnIn2Sn6 hexagonal bipyramids, an edgeedge with one InIn4Sn4 hexagonal bipyramid, and edges with twenty-three SnIn2Sn6 hexagonal bipyramids. There are a spread of Sn–Sn bond distances ranging from 3.05–3.30 Å. In the fourth Sn site, Sn is bonded to two equivalent In and six Sn atoms to form SnIn2Sn6 hexagonal bipyramids that share corners with eight SnSn8 hexagonal bipyramids, edges with eight equivalent InIn4Sn4 hexagonal bipyramids, and edges with sixteen SnSn8 hexagonal bipyramids. Both Sn–In bond lengths are 3.32 Å. There are two shorter (3.05 Å) and two longer (3.19 Å) Sn–Sn bond lengths. In the fifth Sn site, Sn is bonded to two equivalent In and six Sn atoms to form SnIn2Sn6 hexagonal bipyramids that share corners with eight SnIn2Sn6 hexagonal bipyramids, edges with eight equivalent InIn4Sn4 hexagonal bipyramids, and edges with sixteen SnIn2Sn6 hexagonal bipyramids. Both Sn–In bond lengths are 3.32 Å. There are a spread of Sn–Sn bond distances ranging from 3.05–3.30 Å. In the sixth Sn site, Sn is bonded to eight Sn atoms to form SnSn8 hexagonal bipyramids that share corners with two equivalent InIn4Sn4 hexagonal bipyramids, corners with six SnIn2Sn6 hexagonal bipyramids, an edgeedge with one InIn4Sn4 hexagonal bipyramid, and edges with twenty-three SnIn2Sn6 hexagonal bipyramids. There are a spread of Sn–Sn bond distances ranging from 3.05–3.31 Å. In the seventh Sn site, Sn is bonded to two equivalent In and six Sn atoms to form SnIn2Sn6 hexagonal bipyramids that share corners with eight SnIn2Sn6 hexagonal bipyramids, edges with eight equivalent InIn4Sn4 hexagonal bipyramids, and edges with sixteen SnIn2Sn6 hexagonal bipyramids. There are a spread of Sn–Sn bond distances ranging from 3.05–3.30 Å.

36 MATERIALS SCIENCE↗