-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0 10 20 30 40 50Time, h

Pot

entia

l, V

(S

CE

)

Figure 1. Open circuit potential variation as a function of immersion time for the Ti-13Nb-

13Zr alloy immersed in MEM at 37 °C.

-1.0

0.0

1.0

2.0

3.0

4.0

1E-10 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4

Current density, A/cm2

Pot

entia

l, V

(SC

E)

MEM-15 daysMEM-125 days

15 days

125 days

(a)

-1.0

0.0

1.0

2.0

3.0

4.0

1.0E-10 1.0E-9 1.0E-8 1.0E-7 1.0E-6 1.0E-5 1.0E-4

Current density, A/cm2

Pot

entia

l, V

(SC

E)

MEM + H2O2 15 daysMEM + H2O2 125 days

125 days

15 days

(b)

-1.0

0.0

1.0

2.0

3.0

4.0

1E-10 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4

Current density, A/cm2

Pot

entia

l, V

(SC

E)

MEM-125 daysMEM+H2O2-125 days

MEM+H2O2

MEM

(c) Figure 2. Potentiodynamic polarisation curves of Ti-13Nb-13Zr alloy after: (a) 15 days or 125

days of immersion in MEM, (b) 15 days or 125 days of immersion in MEM+H2O2 and (c) 125

days of immersion in MEM or MEM + H2O2. Scan rate: 0.1 mV/s.

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

-2 -1 0 1 2 3 4 5

Log f(Hz)

|Z|

cm

2-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

(d

egre

es)

MEM-15 days- experim.MEM-125 days-experim.MEM-15 days-simulatedMEM-125 days-simulated

(a)

0.0E+0

4.0E+5

8.0E+5

0.0E+0 4.0E+5 8.0E+5

Z real (.cm2)

-Z im

ag (

.cm

2 )

MEM-15 days-exp.MEM-125 days -exp.MEM-15 days-simulatedMEM-125 days-simuated

10 mHZ

(b)

Figure 3. Experimental and simulated EIS diagrams for Ti-13Nb-13Zr alloy obtained after 15

days or 125 days of immersion in MEM: (a) Bode and (b) Nyquist diagrams.

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

-2 -1 0 1 2 3 4 5

Log f(Hz)

|Z|

cm

2-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

(d

egre

es)

MEM+H2O2-15 days-experim.MEM+H2O2-125 days-experim.MEM+H2O2-15 days-simulatedMEM+H2O2-125 days-simulated

(a)

0.0E+0

4.0E+5

8.0E+5

0.0E+0 4.0E+5 8.0E+5

Z real (.cm2)

-Z im

ag (

.cm

2 )

MEM+H2O2-15 days-exp.MEM+H2O2-125 days -exp.MEM+H2O2-15 days-simulatedMEM+H2O2-125 days-simuated

10 mHz

(b)

Figure 4. Experimental and simulated EIS diagrams for Ti-13Nb-13Zr alloy obtained after 15

days or 125 days of immersion in MEM+100 mM H2O2: (a) Bode and (b) Nyquist diagrams.

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

-2 -1 0 1 2 3 4 5

Log f (Hz)

|Z| (

.cm

2)

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

(d

egre

es)

MEM+H2O2-125 daysMEM-125 days

(a)

0.0E+0

4.0E+5

8.0E+5

0.0E+0 4.0E+5 8.0E+5

Z real (cm2)

-Z im

ag (

cm2 )

MEM+H2O2-125 daysMEM-125 days

10 mHz

(b)

Figure 5. Experimental and simulated EIS diagrams for Ti-13Nb-13Zr alloy obtained after 125

days of immersion in MEM or MEM+100 mM H2O2: (a) Bode and (b) Nyquist diagrams.

Rs

CPEp

Rp

CPEb

Rb

Figure 6. Equivalent electric circuit used for fitting the experimental EIS data obtained for the

Ti-13Nb-13Zr alloy in MEM or MEM+H2O2 solutions.

(a)

1

2

3

4

5

6

7

275280285290295

Binding Energy (eV)

C1s

Ref (15)MEM (8)MEM 4V 30min (16)MEM + H2O2 (2)MEM + H2O2 4V 30min (12)

Ref

MEM

MEM 4V 30min

MEM + H2O2

MEM + H2O2 4V 30min

(a) C1sC 1s

(b)

(c)

1

2

3

4

5

6

7

525530535540

Binding Energy (eV)

O1s

Ref (15)MEM (8)MEM 4V 30min (16)MEM + H2O2 (2)MEM + H2O2 4V 30min (12)

(c)

Ref.

MEM

MEM 4V 30min

MEM + H2O2

MEM + H2O2 4V 30min

O 1s

1

2

3

4

5

6

7

450460470

Binding Energy (eV)

Ti2p

REF (15)MEM (8)MEM 4V 30 min (16)MEM + H2O2 (2)MEM + H2O2 4V 30 min (12)

MEM + H2O2 4V 30min

MEM + H2O2

MEM 4V 30min

MEM

Ref

(b) Ti 2p

(d) Figure 7. XPS spectra for the Ti-13Nb-13Zr alloy after different exposures: (a) C 1s; (b) Ti 2p; (c) O 1s; (d) N 1s.

1

2

3

4

5

6

7

390392394396398400402404406408

Binding Energy (eV)

N1s

Ref (15)MEM (8)MEM 4V 30min (16)MEM + H2O2 (2)MEM + H2O2 4V 30min (12)

Ref

MEM

MEM 4V 30min

MEM + H2O2

MEM + H2O2 4V 30min

(d) N1sN 1s

Figure 8. XPS spectra for the Ti-13Nb-13Zr alloy (a) Ca 2p peak for the sample immersed for 72 hours in MEM + H2O2; (b) P 2p peak for the sample immersed for 72 hours in MEM + H2O2; (c) Nb 3d peak for the as-received sample; (d) Zr 3d peak for the as-received sample.

(a) Ca 2p (b) P 2p

(c) Nb 3d (d) Zr 3d

Figure 9. Peak fitted Ti 2p region for the as-received Ti-13Nb-13Zr alloy.

10000

12000

14000

16000

18000

20000

22000

24000

26000

28000

30000

450452454456458460462464466468

Cou

nts

/ s

Binding Energy (eV)

Ti2p - ref (15)

Ti 2p

Ti (O) Ti (2+)

Ti (3+)

Ti (4+)

(a)

(b)

80000

100000

120000

140000

160000

180000

525526527528529530531532533534535536537

Cou

nts

/ s

Binding Energy (eV)

O1s - MEM (8)

O 1s O2-

OH-

H2O

(b)

20000

25000

30000

35000

40000

525526527528529530531532533534535536537

Cou

nts

/ s

Binding Energy (eV)

O1s - ref (15)

O 1s O2-

OH-

H2O

(a)

(c) Figure 10. Peak fitted O 1s region for the Ti-13Nb-13Zr alloy (a) as-received; (b) immersed in MEM solution for 72 hours; (c) immersed in MEM + H2O2 solution for 72 hours.

30000

40000

50000

60000

70000

80000

525526527528529530531532533534535536537538

Cou

nts

/ s

Binding Energy (eV)

O1s - MEM + H2O2 (2)

O 1s

OH-/PO42-

H2O O2-

(c)

(a)

(b)

Figure 11. SEM micrographs of Ti-13Nb-13Zr alloy after 125 days immersion in MEM: (a) without H2O2, (b) with 100 mM H2O2.

10 100

0

20

40

60

80

100

120

IC50%

Ti-13Nb-13Zr Negative control Positive control

Cel

ular

via

bilit

y %

Extract concentrations %

Figure 12. Colony suppression curve of the cytotoxicity test for Ti-13Nb-13Zr alloy.

Figure 13. Schematic diagram of the proposed surface structure which develops on the Ti-

13Nb-13Zr alloy after 72 hours immersion in MEM and MEM + H2O2

Ti-13Nb-13Zr Ti-13Nb-13Zr

MEM MEM + H2O2

passive film (barrier layer)

hydrated titanium oxide (porous)

hydroxyapatite (porous)

amino acids