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Title: Engineered high expansion glass-ceramics having near linear thermal strain and methods thereof

Abstract

The present invention relates to glass-ceramic compositions, as well as methods for forming such composition. In particular, the compositions include various polymorphs of silica that provide beneficial thermal expansion characteristics (e.g., a near linear thermal strain). Also described are methods of forming such compositions, as well as connectors including hermetic seals containing such compositions.

Inventors:
; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1418988
Patent Number(s):
9,878,944
Application Number:
14/834,616
Assignee:
National Technology & Engineering Solutions of Sandia, LLC (Albuquerque, NM) SNL-A
DOE Contract Number:
AC04-94AL85000
Resource Type:
Patent
Resource Relation:
Patent File Date: 2015 Aug 25
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Dai, Steve Xunhu, Rodriguez, Mark A., and Lyon, Nathanael L. Engineered high expansion glass-ceramics having near linear thermal strain and methods thereof. United States: N. p., 2018. Web.
Dai, Steve Xunhu, Rodriguez, Mark A., & Lyon, Nathanael L. Engineered high expansion glass-ceramics having near linear thermal strain and methods thereof. United States.
Dai, Steve Xunhu, Rodriguez, Mark A., and Lyon, Nathanael L. 2018. "Engineered high expansion glass-ceramics having near linear thermal strain and methods thereof". United States. doi:. https://www.osti.gov/servlets/purl/1418988.
@article{osti_1418988,
title = {Engineered high expansion glass-ceramics having near linear thermal strain and methods thereof},
author = {Dai, Steve Xunhu and Rodriguez, Mark A. and Lyon, Nathanael L.},
abstractNote = {The present invention relates to glass-ceramic compositions, as well as methods for forming such composition. In particular, the compositions include various polymorphs of silica that provide beneficial thermal expansion characteristics (e.g., a near linear thermal strain). Also described are methods of forming such compositions, as well as connectors including hermetic seals containing such compositions.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2018,
month = 1
}

Patent:

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  • Thermal mechanical stresses of glass-ceramic to stainless steel (GCtSS) seals are analyzed using finite element modeling over a temperature cycle from a set temperature (T set) 500°C to -55°C, and then back to 600°C. There are two glass-ceramics that have an identical coefficient of thermal expansion (CTE) at ~16 ppm/°C but have very different linearity of thermal strains, designated as near-linear NL16 and step-like SL16, and were formed from the same parent glass using different crystallization processes. Stress modeling reveals much higher plastic strain in the stainless steel using SL16 glass-ceramic when the GCtSS seal cools from T set. Uponmore » heating tensile stresses start to develop at the GC-SS interface before the temperature reaches T set. On the other hand, the much lower plastic deformation in stainless steel accumulated during cooling using NL16 glass-ceramic allows for radially compressive stress at the GC-SS interface to remain present when the seal is heated back to T set. Finally, the qualitative stress comparison suggests that with a better match of thermal strain rate to that of stainless steel, the NL16 glass-ceramic not only improves the hermeticity of the GCtSS seals, but would also improve the reliability of the seals exposed to high-temperature and/or high-pressure abnormal environments.« less
  • Here, the sequence of crystallization in a re-crystallizable lithium silicate sealing glass-ceramic Li 2O-SiO 2-Al 2O 3-K 2O-B 2O 3-P 2O 5-ZnO was analyzed by in situ high temperature X-ray diffraction (HTXRD). Glass-ceramic specimens have been subjected to a 2-stage heat treatment schedule, including rapid cooling from sealing temperature to a 1st hold temperature 650 °C, following by heating to a 2nd hold temperature of 810 °C. Notable growth and saturation of Quartz was observed at 650 °C (1st hold).
  • Here, a widely adopted approach to form matched seals in metals having high coefficient of thermal expansion (CTE), e.g. stainless steel, is the use of high CTE glass-ceramics. With the nucleation and growth of Cristobalite as the main high-expansion crystalline phase, the CTE of recrystallizable lithium silicate Li 2O-SiO 2-Al 2O 3-K 2O-B 2O 3-P 2O 5-ZnO glass-ceramic can approach 18 ppm/°C, matching closely to the 18 ~ 20 ppm/°C CTE of 304L stainless steel.
  • A widely adopted approach to form matched seals in metals having high coefficient of thermal expansion (CTE), e.g. stainless steel, is the use of high CTE glass-ceramics. With the nucleation and growth of Cristobalite as the main high-expansion crystalline phase, the CTE of recrystallizable lithium silicate Li 2O–SiO 2–Al 2O 3–K 2O–B 2O 3–P 2O 5–ZnO glass-ceramic can approach 18 ppm/°C, matching closely to the 18 ppm/°C–20 ppm/°C CTE of 304L stainless steel. However, a large volume change induced by the α-β inversion between the low- and high- Cristobalite, a 1 st order displacive phase transition, results in a nonlinearmore » step-like change in the thermal strain of glass-ceramics. The sudden change in the thermal strain causes a substantial transient mismatch between the glass-ceramic and stainless steel. In this study, we developed new thermal profiles based on the SiO2 phase diagram to crystallize both Quartz and Cristobalite as high expansion crystalline phases in the glass-ceramics. A key step in the thermal profile is the rapid cooling of glass-ceramic from the peak sealing temperature to suppress crystallization of Cristobalite. The rapid cooling of the glass-ceramic to an initial lower hold temperature is conducive to Quartz crystallization. After Quartz formation, a subsequent crystallization of Cristobalite is performed at a higher hold temperature. Quantitative X-ray diffraction analysis of a series of quenched glass-ceramic samples clearly revealed the sequence of crystallization in the new thermal profile. In conclusion, the coexistence of two significantly reduced volume changes, one at ~220°C from Cristobalite inversion and the other at ~470°C from Quartz inversion, greatly improves the linearity of the thermal strains of the glass-ceramics, and is expected to improve the thermal strain match between glass-ceramics and stainless steel over the sealing cycle.« less