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A review on fundamentals and applications
of electrophoretic deposition (EPD)
Laxmidhar Besraa,*,Meilin Liub
Progress in Materials Science 52 (2007) 1–61
指導教授：王聖璋
演講者：黃俊嘉
2009/12/16
Outline
• Definition
• Factors influencing
– the suspension
– the process
•
•
•
•
•
Role of polymer binders in EPD
Practical considerations
Water-based & Non-aqueous EPD
Results and discussion
Conclusion
Definition
Property
Electroplating
EPD
Moving species
Ions
Solid particles
Charge transfer on
deposition
Ion
None
Reduction conductance of
liquid medium
High
Low
Preferred liquid
Water
Organic
Factors influencing
Hamaker equation
ω
(ω) the deposit yield
(
) the particle mass concentration in the suspension
(
) the permittivity of vacuum
(
) the relative permittivity of the solvent
(
) the zeta potential of the particles
(
) the viscosity of the solvent
(
) the applied potential
(
) the distance between the electrodes
(
) the deposition time
C‧E‧t
parameters related to the suspension
Particle size
SEM images of YBCO film electrophoretically deposited on silver
electrode from its suspension in acetone at 10 V for 180 s
(film A: mean particle size = 3 μm;
film B: mean particle size = 0.06 μm).
The films were calcined at 945°C for 1 h and annealed at 500°C for 6 h.
For crack formation smaller particle is better than larger particles
because for larger particles the mobility of particles
electrophoresis must be higher than that gravity
Physical properties of solvents
Dielectric constant of liquid can affect the particle dissociative power,
with too low a dielectric constant, deposition fails because of
insufficient dissociative power, whilst with a high dielectric constant,
the ionic concentration in the liquid must remain low .
1
EP
Dielectric constant
electric field
low viscosity, high dielectric constant and low conductivity
Zeta potential
(1) stabilization of the suspension by determining the intensity of
repulsive interaction between particles
(2) determining the direction and migration velocity of particle during
EPD
2.2
(3) determining the green density of the deposit
high electrostatic repulsion can be avoid particle agglomeration，
If the particle charge is low, the particles would coagulate even for
relative large inter-particle distances, leading to porous, spongepacking density
like deposits. particle charge
Parameters related to the process
Effect of deposition time
Relationship between deposit
thickness and time of deposition for
ZnO coatings on copper electrode
at different applied potential
Current density versus deposition time
for deposition of hydroxyapatite at
different applied voltages:
(a) 50 V; (b) 100 V; (c) 200 V
Applied voltage
Weight of deposited hydroxyapatite
on Ti6Al4V substrate versus applied
voltage for different deposition
durations: (a) 30 s and (b) 120 s
Stability of current density of
n-propanol for different applied
voltages
particles move so fast that they cannot find enough time to sit
in their best positions to form a close-packed structure.
the unstable current density influences the quality of deposition
morphology.
A is constant-current and constant-suspension concentration
B is constant-current but decreasing suspension concentration
C is constant-voltage and constant-suspension concentration
D is constant-voltage but decreasing suspension concentration
• Role of polymer binders in EPD
– obtain adherent deposits and prevent cracks
and the adsorbed polymer can provide steric
stabilization of suspension of ceramic
particles and reduce viscosity of the
suspension.
• Practical considerations
– how to avoid cracking in the ceramic coating
during drying and sintering
– 10–15% linear shrinkage.
– moderate control on drying
– liquid phase sintering
– SOFC
Water-based & Non-aqueous EPD
water
organic
low
higher
higher
low
chemical stability
bad
good
density
low
higher
flammability
no
yes
toxicity
no
yes
cost
low
higher
Applied voltage
conductivity
乙基丙酮
丁酮
甲苯+乙醇
electrical double layer
電位
吸附面
表面應力
電位
德拜長度
吸附層
擴散層
DLVO theory
Vt = VR+VA
靜電斥力
能障
次小總位能
凡德瓦力
最小總位能
穩定狀態
團聚狀態
沉降狀態
Results and discussion
• Deposit yield proportional particle mass
concentration in the suspension、 applied
potential、 deposition time.
• For crack formation smaller particle is better than
larger particles
• low viscosity, high dielectric constant and low
conductivity for suspension
• Zeta potential suspension would affect the
stability of the direction and rate of
electrophoretic particles, deposition density
• Film thickness is proportional to deposition time,
applied voltage
• add polymer binders
–
–
–
–
obtain adherent deposits
prevent cracks
stabilization of suspension of ceramic particles
reduce viscosity of the suspension.
• moderate on drying may avoid the formation of drying
cracks.
• the organic liquids has higher density ,good chemical
stability,low conductivity
defect is higher voltages ,the cost, toxicity and
flammability
Ethyl alcohol–acetylacetone、Methyl ethyl ketone
(MEK) 、Toluene-ethyl alcohol

Conclusion



EPD 為近年來生產製造技術上，一種先進的製程，
其製程簡單、操作簡單和具有成本效益的沉積方法。
EPD製程的重點在於要選擇對的溶劑(低黏度、高介
電常數和低電導率)、粉末的選擇小顆粒優於大顆粒、
調整pH值來使zeta電位遠離等電位，膠體便可以穩
定分散、添加適度的黏結劑可以提昇裂紋的產生、
穩定懸浮液和降低懸浮液的黏度。
發展水性電泳沉積將有助於減少成本，也可以減少
非水性電泳沉積對環境的破壞