# Presentation: 081199

##  Braze Sealing Technology for Gas Separation Membranes 

**Advances in Air Brazing**

**K. S. Weil, J. Y. Kim, and J. S. Hardy**
**Pacific Northwest National Laboratory**
**Richland, WA 99352   **
**USA**

**U.S. Department of Energy, Office of Fossil Energy, Advanced Research Materials Program**
**20****th**** Annual Conference on Fossil Energy Materials**
**June 14 – 16, 2006**

## “Develop coal as a potential source of clean hydrogen fuel for use in fuel cells, turbines and various process applications.”

**“****Develop coal as a potential source of clean hydrogen fuel for use in fuel cells, turbines and various process applications.”**

## Applications

**Applications**

## Collaborations

_**Washington State University**_**: studying the underlying effects of joint microstructure on joint strength**
_**Alfred University**_**: investigating brazing techniques to join ORNL’s microporous membrane substrates to the gas manifold material**
_**Aachen University**_**: employing the new brazing technique in joining large tubular oxygen separation membranes to metallic gas manifolds**
_**Delphi Corporation**_**: demonstrating the use of a new binary braze filler metal in joining solid oxide fuel cell components**
_**Battelle Memorial Institute**_**: demonstrating the use of the binary braze filler metal in joining oxygen concentrators**
_**Bechtel Bettis Inc.**_**: developing a new braze filler metal alloy for use in YSZ electrochemical probes to be employed in pressurized water reactor applications**
_**Corning Inc.**_**: demonstrating the use of a new ternary braze filler metal in joining solid oxide fuel cell components**

## Objectives and Approach

**Identify and develop a viable joining strategy for electrochemical devices**
**The use of air-based joining processes minimizes potential degradation to the separation membrane materials **
**Seals formed in air typically offer more effective protection against later environmental degradation during use**
**Compliance improves the thermal cycling performance of the seal**
**Conduct joint characterization and use the results to optimize the sealing materials/process**
**Develop field joining techniques**
**Conduct prototypic exposure testing**
**Demonstrate use in prototype devices/equipment**

## Hermeticity is key

**Technical Challenges**

**Hermeticity is key**
**CTE mismatch is inherent in joining dissimilar materials**
**Resistance to degradation at high temperature/extended exposure time**
**Resistance to thermal cycling/thermal shock degradation**
**Retention of mechanical robustness in the joint and device**

## Review: Glass-Ceramic Sealing

**Hermetic**
**Good stability in air and H****2**** environments**
**Good wetting on stainless steel and ceramics such as Al****2****O****3**** and YSZ**

**Poor thermal shock characteristics**
**Long-term CTE not stable – problems with thermal cycling**

**KD Meinhardt, DS Kim, ZG Yang, and KS Weil, *****J. Non-Cryst. Sol.*****, in review**

## Review: Commercial Braze Sealing

**Original Braze Position**

_**MIEC Oxide Decomposition**_

**Decomposition:**

**LaFeO****3****  ****→  1⁄2 La****2****O****3****  +  ****1⁄2 ****Fe****2****O****3**

**La(OH)****3**

**(spallation)**

_**Braze Oxidation**_

**YSZ**

**430 SS**

**Au ABA**

**(Cr,Fe)****2****O****3**** scale formation after 200hrs air exposure at 700****°****C**

**(H****2****O vapor)**

**KS Weil and JP Rice, Scr. Mater*****.*****, 52 (2005) 1081**

## New Approach: Air Brazing

**Shao et al, *****J. Am. Ceram. Soc*****. [1993] 2663**

**A new method of ceramic-to-ceramic and ceramic-to-metal joining**
**Uses a unique filler metal system: a soluble metal oxide dissolved in a noble metal – e.g. CuO in Ag**
**Is conducted in open air (i.e. in a simple muffle or continuous belt furnace)**
**Does not require fluxing or the use of inert cover gas**
**Confers oxidation resistance to the joint**

**Ag-CuO Phase Diagram**

**Typical air brazed joint**

## Previous Work: Wetting Studies

## KS Weil, JS Hardy, JP Rice, and JY Kim, Fuel, 85 (2006) 156 

**KS Weil, JS Hardy, JP Rice, and JY Kim, *****Fuel*****, 85 (2006) 156**

**Previous Work: Wetting Studies**

## Scientific Studies

## Critical Point Wetting Theory

_**Critical Point Wetting Theory**_

**JW Cahn, *****J. Chem. Phys*****., 66, 5667 (1977)**
**JM Douillard et al., *****J. Coll. Interf. Sci*****., 106, 146 (1985)**

**Wetting: Absorption Phenomenon**

## Pre-Wetting Line in Ag-CuO

**3 mol% CuO**

**5 mol% CuO**

**1 mol% CuO**

**1.8 mol% CuO**

_**Pre-Wetting Line in Ag-CuO**_

**KS Weil, JY Kim, and JT Darsell, *****Acta Mater.*****, in review**

**Wetting: Absorption Phenomenon**

## 4-pt Bend Test Results

_**4-pt Bend Test Results**_

**YSZ samples brazed at 1000°C**

**JY Kim, JS Hardy, and KS Weil, *****J. Mater. Res.*****, 20 (2005) 636**

**Absorption Phenomenon: Strength Effects**

## Fracture Analysis

**1% CuO in Ag**

**2% CuO in Ag**

**8% CuO in Ag**

**1% - poor adhesion, fails by peeling**
**2% - good adhesion, ductile failure**
**8% - good adhesion, but brittle failure**

**All samples brazed at 1000****o****C for 15min**

**JY Kim, JS Hardy, and KS Weil, *****J. Mater. Res.*****, 20 (2005) 636**

**Absorption Phenomenon: Strength Effects**

## Engineering Studies

## Engineering Tests: Rupture Strength

**Engineering Tests: Rupture Strength**

**KS Weil, JE Deibler, JS Hardy, DS Kim, GG Xia, LA Chick, and CA Coyle, *****J. Mater. Eng. Perf.*****, 13 (2004) 316**

## Aging in Air

_**Aging in Air**_

**KS Weil, CA Coyle, JT Darsell, GG Xia, and JS Hardy, *****J. Power Sources*****, 152 (2005) 97**

**Engineering Tests: Aging**

## Thermal Cycling in Air (75oC/min from RT to 750°C)

_**Thermal Cycling in Air (75**__**o**__**C/min from RT to 750**__**°**__**C)**_

**KS Weil, CA Coyle, JT Darsell, GG Xia, and JS Hardy, *****J. Power Sources*****, 152 (2005) 97**

**Engineering Tests: Thermal Cycling**

## Application: SOFCs

**Application: SOFCs**

**Over1200hrs of operation with no loss in hermeticity**
***(Delphi-Battelle Phase 1 SECA Project)***

## Recent Work

## Filler Metal Compositional Effects

**Filler Metal Compositional Effects**

**YSZ coated 430SS/YSZ**

_**Issue: Need for Improved Wetting**_

## Ag-CuO-TiO2

**Ag-CuO-TiO****2**

**KS Weil, JY Kim, JS Hardy, and JT Darsell, *****Scr. Mater.*****, 54 (2006) 1071**

**Addition of TiO****2****: Improved Wetting**

## Issue: Increased Operational Temperature

_**Issue: Increased Operational Temperature**_

**Pd-Ag-CuO**

**JT Darsell and KS Weil, *****J. Alloys & Compounds*****, in press**

**Addition of Pd: Increased T****use**

## Addition of Pd: Pd-Ag-CuO Phase Equilibria

- _0%Pd_

- _5%Pd_

- _15%Pd_

- _25%Pd_

**Addition of Pd: Pd-Ag-CuO Phase Equilibria**

## Addition of Pd: Wetting Behavior

**JT Darsell and KS Weil, *****J. Alloys & Compounds*****, in press**

**Addition of Pd: Wetting Behavior**

## Examine the interfacial microstructures of the Ag-CuO-TiO2 specimens to understand the mechanisms of wetting improvement  

**Examine the interfacial microstructures of the Ag-CuO-TiO****2**** specimens to understand the mechanisms of wetting improvement  **
**Study the effects of Pd and TiO****2**** additions on joint strength in a model system (either YSZ or Al****2****O****3****)**
**Investigate the Cahn absorption effect in the Pd-Ag-TiO****2**** system to determine if the correlation between the pre-wetting line and optimized joint strength exists for this family of filler metals**
**Explore the quaternary Pd-Ag-CuO-TiO****2**** system to determine if both T****use**** and wettability can be simultaneously optimized**

## Corrosion Testing: Coal Gas Exposure

_**Issue: Degradation behavior and long-term hermeticity in coal gas**_

**Clamshell Furnace**

**Dual atmosphere containment**

**H****2**

**Simulated coal gas**

## Primary test variables: time of exposure, coal gas composition (particularly the concentration of H2S), temperature of exposure, and substrate compositions

**Primary test variables: time of exposure, coal gas composition (particularly the concentration of H****2****S), temperature of exposure, and substrate compositions**
**Initial study: Al****2****O****3****/Fecralloy joint;** **650****°****C in H****2****/simulated coal gas (composition TBD) **
**Measure hermeticity via pressure decay technique**
**Examine joint microstructure as a function of exposure time (100, 500, 1000, 2000 hrs)**
**Subsequent testing: focus on the effects of exposure temperature and coal gas composition**

**Corrosion Testing: Future Work**

## New Investigation: In-situ Heat Source

**New Investigation: In-situ Heat Source**

**Coal Gas**

**Hydrogen**

**Gas separator tube bank**

**Easier means of brazing, lower residual stress**

## In-situ Heat Source: Development

**In-situ Heat Source: Development**

## In-situ Heat Source: Development

**In-situ Heat Source: Development**

## Re-design the thickness and number of diyad layers in order to tune the exothermic film for Ag-CuO melting

**Re-design the thickness and number of diyad layers in order to tune the exothermic film for Ag-CuO melting**
**Demonstrate the exothermic film in braze joining  **
**Conduct hermeticity and joint strength testing and microstructural analysis on initial joining specimens**

## Summary

**Ag-CuO based air brazing**

**Fab**

**Alloying**

**Wetting**

**Performance Testing**

**H****2****/O****2**** Sep**

**SOFC**

**Thermal Cycling**

**Aging Effects**

## PNNL: Eric Mast, Gordon Xia, Jim Coleman, Nat Saenz, and Shelly Carlson

**Washington State University: Professor Amit Bandyopadhyay and Jens Darsell (Doctoral Candidate)**
**Alfred University: Professor Alan Meier and Veruska Malave (Master’s Candidate)**
**Support:****	**** U. S. DOE, Office of Fossil Energy, ARM program**

**The Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the U.S. DOE under Contract DE-AC06-76RLO 1830 **

**Acknowledgements**