1. Electrochemical Surface Treatment of Carbon Fiber

2. Basics_Electrolysis Anodizing_priciple Electroplating_process
Extraction of sodium
Electrolysis of aqueous solutions
Purification of copper

3. Basics_Electrolysis Anode 2H2O → 4H+ + O2 + 4e- 4OH-  2H2O + O2 + 4e-
The positive electrode. It is positively charged because electrons are drawn away from it.
2H2O → 4H+ + O2 + 4e-
4OH-  2H2O + O2 + 4e-
Cathode
The negative electrode. It is negatively charged because an excess of electrons move towards it.

4. Basics_Electrolyte(USP4,839,006)
Electrolyte 5 % aqueous solution pH
Electric conductivity of solution
(m·mho/cm)
Phosphoric acid
1.6
27.5
Nitric acid
0.9
184.5
Sulfuric acid
0.8
216.2
Potassium tertiary phosphate
12.4
47.0
Potassium secondary phosphate
8.8
32.5
Potassium primary phosphate
4.3
28.1
Sodium tertiary phosphate
12.3
25.3
Sodium secondary phosphate
9.1
17.7
Sodium primary phosphate
17.8
Ammonium tertiary phosphate
30.3
Ammonium secondary phosphate
8.0
42.4
Ammonium primary phosphate
4.1
30.7
Potassium nitrate
5.5
49.7
Sodium nitrate
5.4
50.5
Ammonium nitrate
4.8
48.1
Potassium sulfate
6.4
52.7
Sodium sulfate
5.9
Ammonium sulfate
5.3
62.5
Sodium hydroxide
12.8
142.0
Potassium hydroxide
13.2
144.2
Ammonium carbonate
8.5
32.7
Ammonium hydrogencarbonate
7.5
34.3
Barium hydroxide (3%)
12.7

5. Basics_Anodising of Aluminium
Equations of the anode reactions
Al → Al3+ + 3e- (1)
2Al3+ + 3O2- → Al2O3 (2)
2Al3+ + 3OH- → Al2O3 + 3H + (3)
For which the overall process is:
2Al + 3H2O → Al2O3 + 6H+ + 6e- (4)

6. Basics_Anodising of Aluminium
Sulphuric acid begins to decompose, the hydrogen ions moving to the cathode where they are reduced to hydrogen gas. Simultaneously, negatively charged anions, i.e. hydroxide, sulphate and maybe oxide ions move to the anode. The electrical charge in the circuit causes positively charged aluminium ions(Al3+) to be generated in the anode and in turn move toward the cathode.
At the anode surface they react with the oxide/hydroxide ions to form aluminium oxide.
The sulphate ions also play some part as the oxide coating contains % sulphate ions. It is suggested that the sulphate ions facilitate the movement of hydrogen ions reducing the cell voltages required.

7. Basics_Electroplating
Similar Process

8. Basics_Electroplating
Process Development

9. Examples

10. Basics_Calculations
The quantity of electricity flowing through an electrolysis cell is measured in coulombs (C). If one ampere (A) is passed for one second, the quantity of electricity is said to be 1 coulomb.
In the purification of copper you saw that copper was deposited at the cathode. The electrode equation is:
This equation tells us that 1 mole of copper (II) ions combines with 2 moles of electrons to produce 1 mole of copper metal atoms (63.5 g).
A mole of electrons is called a faraday.
From accurate electrolysis experiments it has been found that:
1 faraday = coulombs
Therefore, the quantity of electricity required to deposit 1 mole of copper atoms (63.5 g) is: 2 × = coulombs (2 faradays)

11. Electrolytic Oxidation of Carbon(Graphite)
Chemical Effect : Chemical modification of carbon fiber surface

12. Physical Effect :
Peel off defected skin
Removal of surface flaw
Wave shaped surface
Improvement of tensile strength

13. Current flow(Current density)
The treatment current for a specific fiber type can be specified in coulombs/meter(C/m). The total coulomb(C) flowing in 1 h would be 3600 X I (C/h). m is the total length of all fiber processed in 1 h with n tows running through the bath at a speed of s (m/h).
C/m is specific to a particular d’tex tow and C/m should be adjusted to compensate for any change in the surface area of the tow.
HM fiber needs about 10 ~ 20 times the treatment level used for a HT(high strength) fiber.

14. Parameters HT or HM Current density : greater than 1 A/m2
Voltage : greater than electrolyte decomposition V
Speed : depend on carbonization
Electrolyte selection: ammonium carbonate compound
Distance between CF and Cathode : < 50 mm
Anode contact design
Electrolyte solution flow rate

15. HT or HM 1,000℃ 1,500℃ 2,500℃ High strength Carbon fiber
(Easy oxidation)
1,500℃
High modulus
Carbon fiber
(Hard oxidation)
2,500℃

16. Current density !! Constant current density !! : greater than 1 A/m2
The fineness ↓  C.D. ↑
Running speed ↑  C.D. ↑
HM fiber > HT fiber

17. Voltage Greater than electrolyte decomposition V
Depends on the type of electrolyte
on the distance between Fiber and Cathode

18. Electrolyte Ammonium bicarbonate NH4HCO3  NH3 ↑ + CO2 ↑ + H2O
Easy removal by heating
Neutral pH(not acidic and alkaline)
But Bad smell
Relatively low conductivity

19. Distance between CF and Cathode

20. Anode contact design
Contact or Noncontact
Uniform current transfer

21. Electrolyte solution flow rate
Maintain constant electrolyte concentration
Prevent chemical polarization
Remove air bubble on electrode surface
(O2 and H2  flammable and explosive)

23. Example Electrolyte NH4HCO3 Conc. 10, 20, 30, 40 % Voltage 2V
Current density
0.01
Time
60sec

24. Example