progress report on sequential-fab plasma-sprayed sofc components

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Progress Report on Sequential-Fab Plasma-Sprayed

SOFC Components

Rob S. Hui, H. Zhang, X. Ma, J. Roth, J. Broadhead, D. Xiao, and D. Reisner

US Nanocorp, Inc.

Fuel cells 2003 The Third Annual BCC Conference

Stamford, CT


Outline

• Motivation

• Brief Review of Previous Work

• Progress Report

• Summary

2/23


• Thermal Sprayed Electrodes / Electrolytes for Batteries and Fuel Cells

• Fuzzy Logic Modeling Methods to Manage Batteries and Fuel Cells

2002 D&T Connecticut Technology Fast 50 Award

3/23

2002 Deloitte & Touche Technology Fast 500 Award

US Nanocorp


Solid Oxide Fuel Cells (SOFCs)

Features:

4/23

• Higher efficiency• More flexible fuels• All solid components

Applications:

Power plant Residential Transportation Military


YSZ

Ni-YSZ

LSM

Air

Fuel

Loa

d

Low temperature SOFCs (< 850oC)

Alternative materials Appropriate cell design Manufacturing routes

High temperature SOFCs (~ 1000oC)

Materials constraints High stress of differential thermal expansion Long term stability poor Precludes nanomaterials High cost of operation

Research Motivation

5/23


USN’s Enabling SOFC Technology

Nanostructured electrode materials Enable low Temperature Operation High activity (high interfacial surface area) Expect Improved cell performance

Plasma Spray Integrated fabrication of membrane-type SOFC

New materials with high performance Sr1-1.5xYxTiO3 (“SYT”) replaces Ni/YSZ MIEC has more reaction sites than Ni-cermet LSGM has four-time higher ionic conductivity than YSZ

6/23


USN’s SOFC Strategy Reduce cell operating temperature

Thin film LSGM electrolyte (high conductivity)

Nanostructured electrodes (many grain boundaries -> large interface)

SYT anode material is a MIEC working at 600 – 800 oC

Increase fuel cell operating efficiency SYT could directly catalyze hydrocarbon fuel SYT has more reaction sites than Ni-cermet

Drive down fuel cell manufacturing cost using APS Inexpensive, Universal (Metco 9MB) Sequential fabrication of cell components Possibility of elimination of reforming unit

7/23


Plasma Processing

• Brief (on the order of 1 ms) particle residence time

• Rapid heating

• Steep gradients in HVOF and plasma flow fields

8/23


Thermal Spray GunNanocoated Component

Nanomaterial Feedstock Substrate

Advantages of Plasma Spray

Rapid and sequential fabrication Nanostructured materials Accurately controlled Thickness Potential low cost (automation) Robotic continuous operation

Graded porosity & composition Excellent interfacial contact Large area and free geometry Unlimited substrates (@RT) No high temperature sintering

9/23


20m

5 - 20 nmparticles

reconstituted sprayable form

5 - 20 nmparticles

non-agglomerated

5 - 20 nm particles

loosely agglomerated

hollow shell agglomerates

30 mm

Feedstock Reconstitution

10/23


Microstructure of Feedstock

0

2

4

6

8

10

12

14

9 12 18 27 36 40 45 49 53 58 62 78

Feedstock size (um)

Fe

ed

sto

ck

nu

mb

er

100m

10 m

11/23


Free standing plasma sprayed SOFC single cells

Anode electrode

Cathode electrode

Electrolyte

USN’s Planar SOFC Systems

12/23


LDC40 + Ni

SWPC tube

LSGM

LDC40

Anode: Nano LDC40 + Ni Interlayer: LDC40 Electrolyte: La0.8Sr0.2Ga0.8Mg0.2O3

Cathode: SWPC proprietary tube

USN’s Tubular SOFC Systems

13/23


50 m LSM

SYT

LSGM

Requirements for Sprayed Components

14/23

Porous electrodes

Dense electrolyte

Right chemical phase and composition

Compatible electrochemical properties


SEM Images of LSGM

LSGM feedstock

100m(b) 100m(b)LSGM 30 m

LSGM

LSM

As-sprayed LSGM on LSM 15/23


Open-Circuit Voltage

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50 60

Time hourV

olta

ge V

700oC

0

0.2

0.4

0.6

0.8

1

1.2

250 350 450 550 650 750

Temperature /oC

Vol

tage

/V

3oC/min

16/23


As-sprayed LSGM

20 30 40 50 60 70 80

LSGM as sprayed

Inte

nsity

(arb

. unit

)

2

LSGM feedstock

0 500 1000 1500 2000 2500 3000 3500 40000

500

1000

1500

2000

2500

3000

3500

4000

4500

650oC

700oC

750oC

800oC

-ZI

ZR

0.0 0.5 1.0 1.5 2.0 2.50.0

0.5

1.0

1.5

2.0

2.5

-ZI

ZR

Ac Impedance measurementX-ray diffraction spectra17/23


Heat-treatment of Sprayed LSGM

30 40 50 60 70 80

900oC

800oC

700oC

Inten

sity (

arb.

unit)

2

500oC

0 2 4 6 8 10 120

2

4

6

8

10

12

650oC

700oC

750oC

800oC

-ZI

ZR

Change of ac Impedance spectra Chang of XRD pattern

18/23


0.0 0.5 1.0 1.50.0

0.5

1.0

1.5

pressed sprayed

-ZI

ZR

Sintered & Sprayed LSGM

0 1 2 3 40

1

2

3

4 650oC

700oC

750oC

800oC

-ZI

ZR

Pressed / Sintered LSGM Sintered vs Sprayed LSGM

19/23


Pump

Tungsten Anode

Tungsten Cathode

Atomizing Nozzle

Work pieceYSZ Liquid Feed Stock

+

+-

Gas

Gas

Plasma

Solution Feedstock Plasma Spray

20/23


Advantages of SPS Electrode

Forms 3-D porous structure, leading to high fuel gas permeability for anode

Forms nanostructured anode, increases surface area of fuel – solid interaction

Enables thin layer coating formation

Higher thermal shock resistance21/23


Nanostructured SOFC was proposed based on the materials selection and fabrication technique

Planar SOFCs have been successful fabricated by plasma spray technique with dense electrolyte and porous electrodes

Thick film LSGM has been sprayed and characterized. Sprayed layer has same electrochemical properties with sintered one

Improvement of electrode structure and characterization of fuel cell performance are needed in the future

22/23

Summary


Acknowledgement

This work was supported by the Department of Energy:

(1)with Dr. Keqin Huang at Siemens Westinghouse Power Corp. under DOE Prime Contract No. DE-FC26-99FT40709

(2)under a DOE SBIR Grant No. DE-FG 02-01ER83340.

23/23

progress report on sequential-fab plasma-sprayed sofc components

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