**1.3.7 Effect of cathodic-electrodeposition time on surface morphology**

Figure 1-29 shows the optical microscope morphologies of the cathodically-electrodeposited samples at current density of 20mA/cm2 for different times. It can be seen from the figure that after deposited for 3min, obviously the Ti-O film began to emerge on the surface of TiNi SMA, fine, close and even, but there were some holes, which might be caused by the gas produced on the sample surface when cathodically-electrodeposited at the high current density. After deposited for 5min, the film thickness of the sample surface got increased apparently, but there were some big cracks emerging, adhered lumpily on the sample surface. After deposited for 7min, the Ti-O film fluffily adhered to the sample surface, bonding closely, with less cracks relatively, but uneven. The difference between the morphology of the sample deposited for 9min and that of the one for 7min was not great, fluffily adhered to the sample surface the same. Apparently, the surface of the sample deposited for 2h was different from that of the ones for short times, and its surface had no thicker fluffy Ti-O film, but with some holes. Similarly, the sample deposited for 12h had no fluffy Ti-O film emerging on the surface, but with some small cracks and porosities in different sizes and deepnesses. This is because of that at beginning of depositing, the Ti-O film nucleated and grew quickly on the sample surface, and its thickness increased quickly too. At the same time, with the increase of the thickness in the process of nucleation and growth, the Ti-O film on TiNi SMA surface continuously dissolved and peeled off, besides a lot of gas produced on the sample surface, that brought about uneven stress emerging internal Ti-O film, thus causing distributing lumpily. Because current density was higher, Ti-O film continuously formed and peeled off with time, thus gradually forming the fluffy distribution, and uneven very much. When to a certain time, because of reduction of Ti4+ in electrolyte, that made the level of Ti-O film peeling off far higher than that of forming, until the fluffy film disappearing completely, so some porosities in different sizes and deepnesses emerging. The cracks emerged in figure 1-27f might be caused by long time depositing, when drying, under the uneven stress, thus producing cracks. In short, at current density of 20 mA/cm2, Ti-O film was a growth process of "thickeningcracking-lumping-peeling off-cracking again".

Ti-O Film Cathodically-Electrodeposited on

the Surface of TiNi SMA and Its Bioactivity and Blood Compatibility 27

area, but not even, there were some places where undeposited or deposited very thin. The surface Ti-O film of the sample deposited for 2min had been very even, and adhered to the substrate's surface in large area. The surface Ti-O film of the sample deposited for 3min got thickening, distributed well laminally, there were a lot of fine holes and cracks in disorder. On the surface of the sample deposited for 4min, the lamina Ti-O film(s) combined and grew with each other, that made the holes number reduce, and fine cracks in disorder get long. Deposited for 5min, surface Ti-O film(s) continuously combined with each other, and thickened, with long surface cracks, Ti-O film adhered in large laminas to substrate surface. The surface Ti-O film of the sample deposited for 6min continued to thicken, and emerge big cracks and distributed not well lumpily on the substrate's surface. The big cracks in the Ti-O film of the sample deposited for 7min began to get less, fine and shallow, and there were some fine cracks emerging within the Ti-O film in big lumps. The surface cracks of the sample deposited for 8min got more and fine, and Ti-O film in big lumps got smaller. The surface Ti-O film of the sample deposited for 30min distributed well on the substrate surface in fine particles was big relatively. From the change of the surface morphology of Ti-O film in the figure of view, that was a process of "forming-evening-cracking-aggregating-cracking again". It can be seen that the particles of sample cathodically-electrodeposited at low current density were fine and even. This is because of that the drying force for nucleation of Ti-O film at low current density was not so great, the film would slowly nucleate on the substrate surface, besides at low current density, the gas produced on the sample surface was not strongly, so that made the Ti-O film adhere evenly to the substrate surface. Among the samples, the Ti-O film of the sample

deposited at 5mA/cm2 for 4min had the best levels of evenness and thickness.

a 1min b 2min

c 3min d 4min

c 7min d 9min

Figure 1-30 shows the optical microscope morphologies of cathodic-electrodeposition at low current density (5mA/cm2) for different times. It can be seen from the figure that at low current density, the Ti-O film deposited on the sample surface for 1min had formed in large

a 3min b 5min

c 7min d 9min

e 2h f 12h Fig. 1-29. Optical microscope result of sample by current 20mA/cm2 for different times (1000×)

Figure 1-30 shows the optical microscope morphologies of cathodic-electrodeposition at low current density (5mA/cm2) for different times. It can be seen from the figure that at low current density, the Ti-O film deposited on the sample surface for 1min had formed in large

area, but not even, there were some places where undeposited or deposited very thin. The surface Ti-O film of the sample deposited for 2min had been very even, and adhered to the substrate's surface in large area. The surface Ti-O film of the sample deposited for 3min got thickening, distributed well laminally, there were a lot of fine holes and cracks in disorder. On the surface of the sample deposited for 4min, the lamina Ti-O film(s) combined and grew with each other, that made the holes number reduce, and fine cracks in disorder get long. Deposited for 5min, surface Ti-O film(s) continuously combined with each other, and thickened, with long surface cracks, Ti-O film adhered in large laminas to substrate surface. The surface Ti-O film of the sample deposited for 6min continued to thicken, and emerge big cracks and distributed not well lumpily on the substrate's surface. The big cracks in the Ti-O film of the sample deposited for 7min began to get less, fine and shallow, and there were some fine cracks emerging within the Ti-O film in big lumps. The surface cracks of the sample deposited for 8min got more and fine, and Ti-O film in big lumps got smaller. The surface Ti-O film of the sample deposited for 30min distributed well on the substrate surface in fine particles was big relatively. From the change of the surface morphology of Ti-O film in the figure of view, that was a process of "forming-evening-cracking-aggregating-cracking again". It can be seen that the particles of sample cathodically-electrodeposited at low current density were fine and even. This is because of that the drying force for nucleation of Ti-O film at low current density was not so great, the film would slowly nucleate on the substrate surface, besides at low current density, the gas produced on the sample surface was not strongly, so that made the Ti-O film adhere evenly to the substrate surface. Among the samples, the Ti-O film of the sample deposited at 5mA/cm2 for 4min had the best levels of evenness and thickness.

Ti-O Film Cathodically-Electrodeposited on



value, adding in enough NO3

concentration (1000×)

reduced to OH-


within a shorter time. So, electrolyte PH value and NO3

in the process of TiNi SMA cathodic-electrodeposition.

there was no NO3

amount of NO3

OH-

the Surface of TiNi SMA and Its Bioactivity and Blood Compatibility 29

that there was an obvious Ti-O film produced. This because of that when PH value increased, Ti gel could be formed within a short time. It can be seen from figure 1-29c that there was less Ti-O film formed. This is because of that under the circumstance of higher PH value, although

which could form less Ti gel within a short time. But at low current density, even if small

can be seen from figure 1-29d and e. It can be seen from figure 1-29e that under higher PH

a b

c d

e f

Fig. 1-31. Optical microscope of sample in electrolyte of different PH value and NO3

was added in, it was not enough to form a Ti gel within a shorter time, this


yet, at driving of high current density, H2O was reduced to

, it could form fine and close Ti-O film at low current density

concentration have played a vital role


### **1.3.8 Effect of electrolyte PH value and NO3 concentration on cathodicelectrodeposition**

Figure 1-31 and table 1-2 are the optical microscope morphologies, technical parameters and results affected by cathodic-electrodeposition in different PH values of electrolyte and NO3 concentrations. It can be seen from the figure 1-29a that there was no obvious Ti-O film existing on the sample surface. This is because of that acidity of the solution was too high, although OH produced on the cathodic sample surface, then quickly dissolved, it did not form a Ti gel to adhere to the sample surface within a short time. It can be seen from figure 1-29b

e 5min f 6min

g 7min h 8min

i 30min Fig. 1-30. Optical microscope result of samples by current 5mA/cm2 for different times (1000×)

**-**

Figure 1-31 and table 1-2 are the optical microscope morphologies, technical parameters and results affected by cathodic-electrodeposition in different PH values of electrolyte and NO3

concentrations. It can be seen from the figure 1-29a that there was no obvious Ti-O film existing on the sample surface. This is because of that acidity of the solution was too high,

a Ti gel to adhere to the sample surface within a short time. It can be seen from figure 1-29b

produced on the cathodic sample surface, then quickly dissolved, it did not form

 **concentration on cathodic-**


**1.3.8 Effect of electrolyte PH value and NO3**

**electrodeposition** 

although OH-

that there was an obvious Ti-O film produced. This because of that when PH value increased, Ti gel could be formed within a short time. It can be seen from figure 1-29c that there was less Ti-O film formed. This is because of that under the circumstance of higher PH value, although there was no NO3 reduced to OH yet, at driving of high current density, H2O was reduced to OH which could form less Ti gel within a short time. But at low current density, even if small amount of NO3 was added in, it was not enough to form a Ti gel within a shorter time, this can be seen from figure 1-29d and e. It can be seen from figure 1-29e that under higher PH value, adding in enough NO3 - , it could form fine and close Ti-O film at low current density within a shorter time. So, electrolyte PH value and NO3 concentration have played a vital role in the process of TiNi SMA cathodic-electrodeposition.

Fig. 1-31. Optical microscope of sample in electrolyte of different PH value and NO3 concentration (1000×)

Ti-O Film Cathodically-Electrodeposited on

9. The electrolyte's PH value and NO3-

**2. Chapter II 2.1 Preface** 

diphosphate)[11].

been made a great progress recent years.

experimentally carried out in following two aspects[14]:

the Surface of TiNi SMA and Its Bioactivity and Blood Compatibility 31

of "forming-evening-cracking-agglomerating-cracking again".

patient's injured site(s) recover the functions early, and alleviate suffering[10].

agglomerating-peel off-cracking again". At that of 5mA/cm2, the change was a process

TiNi SMA cathodic-electrodeposition. Only under PH1-3 and about 0.2M of NO3 concentration, a better effectiveness of cathodic-electrodeposition could be obtained.

The key, for a plant material to bonding surface, is that the material must be with excellent bioactivity, that is, the biomaterial should have capability of closely bonding with surrounding living tissue under physiological fluid environment[9]. The bioactive bonding called, is that after a bone plant is planted into human body, there will be a layer of bioactive hydroxyapatite (HA) forming on the material's surface. HA is a main inorganic substance, occupying about 69%, and about 41.8% in volumetric fraction of human bone. Through HA thin layer, chemical bonding at a molecular level is formed. After planting into human body for 3-6 months, the interface strength of the bioactive bonding is equal to or higher than that of surrounding bone tissue[9]. Under the circumstance of guaranteeing other properties, promoting coating's bioactivity will be helpful to shorten osseointegration period, make

Blood compatibility includes quite wide content. There are the reactions at cell level, such as thrombosis (platelet adhesiveness, agglomerating, and deformation) when connecting with material, haemolysis and leucopenia; there are the reactions at plasma protein level, such as coagulation system and fibrinolytic system activation; and there are the reactions at molecular level, such as immune ingredient change, platelet receptor and ADP (adenosine

When a material connects to blood, a competitive protein adsorption will come about first to form a complex protein adsorption layer, then blood cell and platelet adhesiveness, and then thrombosis, if which can not be repaired or cured, it is easy to bring about coagulating. So, avoiding thrombosis and preventing coagulation are the most important factors of a biomaterial's blood compatibility. Approach a mechanism of thrombosis to promote material's blood compatibility is a research hot point in the academic circle[12,13], and it has

In this chapter, evaluations for the biomaterials' blood compatibility in vitro have been

1. Haemolysis rate test For a plant apparatus directly connected to blood, it is necessary to carry out the experiment on haemolysis rate in vitro. Under normal circumstance, the average life of erythrocyte is 120d. Under the same reason, the life of erythrocyte shortens, it is called that a haemolysis process comes about. Through haemolysis rate experiment the rank of toxicity produced by erythrocyte in blood connecting to material can be evaluated, the erythrocyte in blood will be damaged in varying degrees because of the toxic substance(s) of the material, to release hemoglobin, and to bring about haemolysis. By testing the amount of hemoglobin released from the material, the haemolysis rate for the material can be obtained. Generally speaking, the concentration

concentration played a vital role in the process of


Table 1-2. Processing parameter and electrodeposition result in electrolyte of different PH values and NO3- concentrations
