X. Zhao, A.G. Cook, H. Assender, C. Johnston, M. Johnson1 andPatrick Grant

Department of Materials, Oxford University.

1School of Electrical & Electronic Engineering, Nottingham University.

Novel High Energy Density, High Reliability Capacitors

IeMRC award 774613 and DSTL award RD020-013644, further supported by Rolls-Royce, Norfolk Capacitors, Scott Bader and Nanion

Outline

The more electric airframe

Power capacitors

Nanocomposite dielectrics

Progress

Conclusions and future directions

Rudder

ElevatorsLoads

Load

Generator

Power control

Load centre

Transmission

Transmission& Distribution

Galleys

Avionics

TE flaps

Spoilers

Ailerons

Gear

LoadsLights

Loads

Cabinservices

ECScompressor

Loads

Lights

APU generator

powerconverter

Fuelpump

250kW generator

LE flaps

LightsAnti-ice

Loads

250kW generator

More electric aircraftFeatures

Electrical startingElectro-hydraulic actuators / Electro-mechanical actuatorsElectrical anti-iceModified cabin environmental systemSimplified engine-airframe interface

DeletingThree major hydraulic systemsRam-air turbineCabin-air bleedsPneumatic anti-ice

ECScompressor

More electric aircraft

For a 200 passenger B767-type aircraft:10% reduction in aircraft empty weight

13% reduction in required engine thrust

9% reduction in fuel burn

significant reduction in emissions[NASA]

“Global electrical optimisation is the only way to achieve meaningful improvements in the total airframe package”

M.J. Provost, Advanced Propulsion Systems Design, Rolls-Royce, Proc Int. Conf. IEE Power Electronics, Bath, 2002

Power capacitors

Increased electrical power generation – 1MWIncreased power conditioning Current high value capacitors based on electrolytics or polymer filmsHeavy (~40% of converter), temperature limited (~70°C), catastrophic failure modes ⇒ the “weakest link”Combining a high permittivity nanoscale ceramic powder with a high temperature polymer film to produce a high performance dielectric nanocomposite

Nanocomposite dielectric materials

Ceramic particles in polymersAdd nanoparticles to increase dielectric constant to 30-50 (Cα ε)

ButThin films (C α 1/t)Do not undermine breakdown strength (u α E2)Do not compromise processability into large areasDo not increase density more than necessary

Properties up to 200ºCDevelop a scaleable manufacturing technology

Objectives

To investigate the manufacturability of polymer based nanocomposite films for power capacitor applications at the laboratory and near industrial scale.To undertake performance and reliability testing and to relate performance to processing and microstructural features.

Manufacturing technology

Spray deposition Web coating

Lab-scaleProof of concept

Lab-scaleProof of concept

Intermediate scale Near industrial scale

Industrial collaborators

Manufacturing technology

Pre-heated table

Syringe pumps with nano suspensions

Hypodermic needle(s)

Compressed air

X-Y manipulator linear drives

Sputtercathode

Evaporation

E-beam

Monomerdelivery

Rotatingdrum

Roll-to-roll

Spray deposition

Spray nozzle

Compressed air

Hypodermic needle

TPGDA/BaTiO3/MEK:EtOH suspension

Syringe

Syringe pump

Atomized droplet spray

xy

Pre-metallizedglass substrate

Heated plate moving in x-y

Spray nozzle

Compressed air

Hypodermic needle

TPGDA/BaTiO3/MEK:EtOH suspension

Syringe

Syringe pump

Atomized droplet spray

xy

Pre-metallizedglass substrate

Heated plate moving in x-y

Acrylate-BaTiO3 films

SEM micrograph of PTPGDA-30vol%BaTiO3 film at an accelerating voltage of 2.0 kV.

Acrylate-BaTiO3 films

Dielectric constant and dissipation factor (tan δ) of spray deposited PTPGDA-BaTiO3 nano-composites at 25°C as a function of frequency for various volume fractions of BaTiO3.

Acrylate-BaTiO3 films

Comparison of experimental data and theoretical predictions of ε for PTPGDA-BaTiO3 nanocomposites

Spray deposition of polymer nanocomposite films for dielectric applications, X. Zhao et al, Mat. Sci. Eng. B. in the press.

Perfluoro alkoxy CNT films

SEM micrographs of as-grown aligned arrays of(a) 100μm x 50nm multi-wall carbon nanotubes (MWNT-1),(b) 500μm x 50nm (MWNT-2), and(c) and (d) after sonication.

PFA-CNT films

Dependence of dielectric permittivity and AC conductivity of:(a) PFA-MWNT-1 films, and(b) PFA-MWNT-2 films on MWNT volume fraction at 10kHz.Insets show best of AC conductivity to percolation theory.

Manufacturing technology

Spray deposition Web coating

Lab-scaleProof of concept

Lab-scaleProof of concept

Intermediate scale Near industrial scale

Industrial collaborators

Web coating – lab unit up and running

Rotatingdrum

Monomerdelivery

Evaporationsource

Sputtercathode

E-beamMelamine +

TiO2-np film?

Conclusions

Nanoparticle-polymer filmsNew process routeExciting propertiesScale up

CNT-polymer filmsReproduced (exceeded?) best results from literatureShows “platform” nature of processOther industrial uses

Mini web coaterFirst good results obtained but need to show reproducibilityMigrate to large web coater in the next year

IeMRC investment effectively geared with other funds