Chromium-Based Anode Splitter Plate for SOFC Thermal Stress Reduction

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Solution Overview

Problem

In high-temperature fuel cell systems, a mismatch in the coefficient of thermal expansion (CTE) between the materials used for anode splitter plates (ASP) and other components leads to internal stresses during thermal cycling, causing physical damage to SOFC components, such as cracking of electrolytes and damage to glass seals, which hinders the structural integrity and operation of the fuel cell stack.

Innovation Solution

A reactant feed and return assembly, including an anode splitter plate made from a chromium-based alloy with a CTE that closely matches the end plates of the fuel cell stacks, minimizing stress buildup. This assembly features a chromium-iron alloy with a composition of approximately 94-96% chromium and 4-6% iron, and is fabricated using powder metallurgy techniques, with brazing used to secure the components together, ensuring a secure bond and reducing CTE mismatch issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional materials are used for anode splitter plates, then manufacturing is easier, but CTE mismatch causes internal stresses and physical damage during thermal cycling

Engineering Contradiction:

Improvestructural integrityVSAvoidmaterial selection

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter (CTE) of the anode splitter plate by selecting a chromium-based alloy with specific composition (20-30% Cr, 65-75% Fe, 2-10% Ni) to match the CTE of electrolyte and seal materials, thereby reducing thermal stress and preventing physical damage during thermal cycling

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite material approach by using a multi-component chromium-iron-nickel alloy that combines the desirable properties of each element: chromium for oxidation resistance, iron for mechanical strength, and nickel for ductility and CTE adjustment, creating a material that simultaneously satisfies multiple requirements

Inventive Principle:

Principle #40Composite materials

2Reliability

If chromium-based alloy is used to minimize CTE mismatch, then stress buildup is reduced, but manufacturing complexity increases due to powder metallurgy and brazing processes

Engineering Contradiction:

Improvestress resistanceVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-forming the anode splitter plate components using powder metallurgy to achieve the desired complex geometry and material composition before assembly, and by pre-brazing the chromium-based alloy plates to the electrolyte and seal materials to ensure proper thermal and mechanical coupling before stack operation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses brazing material as an intermediary substance to join the chromium-based alloy anode splitter plate with the electrolyte and seal materials, allowing for reliable bonding while accommodating slight dimensional variations and ensuring good thermal contact without direct metal-to-ceramic bonding

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The use of a chromium-based alloy for the reactant feed and return assembly minimizes CTE mismatch, reducing stress buildup and maintaining the structural integrity of the fuel cell stack during thermal cycles, thereby enhancing the operational reliability and longevity of the SOFC system.

Implementation Method 1

a chromium-iron alloy with a composition of approximately 94-96% chromium and 4-6% iron, and is fabricated using powder metallurgy techniques

Methodology Applied

Scientific EffectCoefficient of thermal expansion (CTE): Thermal Expansion

Implementation Method 2

bonding the first portion of the reactant feed and return assembly to at least one second portion of the reactant feed and return assembly using a brazing material

Methodology Applied

Scientific EffectBrazing: Brazing

Implementation Method 3

sintering the metal powder in the preform shape

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS10511047B2Anode splitter plate and methods for making the same

Publication Date: 2019.12.17 BLOOM ENERGY CORP

AI summary

Various embodiments of a reactant feed and return assembly, such as an anode splitter plate (ASP), are provided for facilitating reactant feed and exhaust flow in a solid oxide fuel cell (SOFC) stack system. Embodiments include a reactant feed and return assembly including at least a first portion formed of a chromium-based alloy, such as a chromium-iron alloy, having a similar coefficient of thermal expansion as other SOFC components and may therefore reduce internal stress in an SOFC stack. Methods for making an a reactant feed and return assembly comprising a chromium-based alloy are also provided.