Advanced Electronic Ceramics I (2004)

Two-Phase Colloid System

Continuous phaseGasGasGasLiquidLiquidLiquid

SolidSolidSolid

Dispersed phaseGasLiquidSolidGasLiquidSolid

GasLiquidSolid

Descriptive namesImpossibleFog, mist, aerosolSmoke, aerosol, tear gasFoamEmulsionSol, colloidal solution, gel, suspension

Solid foamGel, solid emulsionAlloy

Paul C. Hiemenz, “Principles of colloid and surface,”

Advanced Electronic Ceramics I (2004)

Electrostatic interaction between particles

Www.zeta-meter.com

Advanced Electronic Ceramics I (2004)

Potential Determining Ion 1

1. Potential determiningions : [Ag+], [I-]

2. Indifferent Ions:[NO3-], [K+]

Advanced Electronic Ceramics I (2004)

Potential Determining Ion 2

Advanced Electronic Ceramics I (2004)

Potential Determining Ion in oxide

Advanced Electronic Ceramics I (2004)

Iso-electric points in oxide

Materials

SiO2

TiO2

Fe2O3

Al2O3

MgOCa5(PO4) 2(OH) [Hap]

Iso-electric point(pH)

1-367-8912.59.5

For AgI, the point of zero charge should be given bypAg = -log [Ag+] = -log (3 X 10-6) = 5.6

Advanced Electronic Ceramics I (2004)

Electric Double Layer

Advanced Electronic Ceramics I (2004)

Poisson equation

Advanced Electronic Ceramics I (2004)

Debye-Hückel approximation

Advanced Electronic Ceramics I (2004)

Debye-Hückel approximation

Advanced Electronic Ceramics I (2004)

Example

Advanced Electronic Ceramics I (2004)

Example

Advanced Electronic Ceramics I (2004)

The meaning of double layer thickness

Advanced Electronic Ceramics I (2004)

The meaning of double layer thicknessϕ = ϕ0 exp (-κx)at x= 1/κ (double layer thickness)ϕ = ϕ0/e

the double layer thickness: the distance over which significant potential exist

as double layer thickness ↓→ repulsive force ↓→ coagulation ↑

Advanced Electronic Ceramics I (2004)http://www.ness.co.kr/

Ultracapacitor (Supercapacitor) for pulse power

- All-weather quick start applications- Load-leveling and Uninterruptible Power Systems (UPS)- No Maintenance applications - Peak pulse power applications - Quick charge applications - Memory back-up applications - Automotive applications and Electric Vehicles

Double-Layer Capacitor (no redox)Pseudo Capacitor (redox)

Advantages- No limit in cyclic charging - High Power densityDisadvantage- Low energy density

Advanced Electronic Ceramics I (2004)http://www.chipcenter.com/eexpert/akruger/akruger008.html

Ultracapacitor & Batteries

Advanced Electronic Ceramics I (2004)Figures are from http://www.elna-america.com/PDF/DLC-chart(270,274).pdf

Materials Issues in EDLC and Pseudocapacitor

EDLC- The sophisticated design of the activated carbon• Too small pore : slow energy input and output• Too large pore and particle sizes : low capacitance- well-designed nano carbon (particle or tube containing nano-sized pore)

Pseudocapacitor- Preparation of nano-sized RuO2- High cost due to RuO2

Charging

Discharging

Advanced Electronic Ceramics I (2004)http://www.ec-central.org/magazine/PDF/art_1_jul_aug_01.pdf

Why EDLC?