Materials Performance

JUN 2016

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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56 JUNE 2016 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 55, NO. 6 Results and Discussion Argon ions were chosen because they provide improved corrosion resistance and thrombogenicity. As the ions enter the ma- terial, they lose energy via two processes: nuclear and electronic collision. The target atoms are mainly displaced due to nuclear collision; however, electronic collision in- duces ionization only. 12-13 The GRXD results in Figure 2 show the compound formation of HAP before and after coating the alumina. Clear peaks of HAP are observed, confirming the forma- tion of HAP on alumina. Figure 3 shows the RBS spectrum along with simulated plots. Simulation was carried out using Ruther- ford back-scattering spectra (RUMP † ) soft- ware. The calcium and phosphorous peaks are clearly resolved. The thickness of HAP measured during the simulation was 100 nm. From the simulation of the spectra, the Ca:P ratio was 10:6, which is close to the stoichiometric value of the Ca/P ratio at 1.67. At this ratio, HAP forms strong bonds with the surrounding tissue. Figure 4 shows the EIS spectra of all the samples, known as Bode plots. Logarithms of the impedance modulus |Z| and phase angle φ are plotted as a function of the loga- rithm of the ω. The Bode plots show that there is maximum polarization resistance for the 1 × 10 15 ions/cm 2 dose-implanted sample, which implies the greatest corro- sion resistance. Another surface property of ceramics that may be effectively modified through ion implantation is thrombogenicity. 14-15 Thrombogenic materials are clot-produc- ing materials. The imperative requirement for blood-interfacing implants is blood compatibility. The implant should not damage prot eins, enzym es, or form ed blood elements (red blood cells, white blood cell s, and platelets). Som etim es thrombogenic materials with rough sur- faces are used to promote clotting in po- rous interstices to prevent initial leaking of blood and to allow later tissue ingrowth through the pores of vascular implants. The size of the clot is inversely proportional to the absorbance value, as shown in Figure 5. This graph shows that clotting will be slightly less than with pure alumina. Clot- ting increases with the increase in ion dose. FIGURE 2 Compound formation observed using GXRD. FIGURE 3 RBS spectrum of unimplanted HAP/alumina and its simulation. MATERIALS SELECTION & DESIGN

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