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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54 JUNE 2016 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 55, NO. 6 MATERIALS SELECTION & DESIGN O Ceramics are preferred over metallic alloys for hard tissue replacements because of their inertness, corrosion resistance, and biocompatibility prop- erties. A new technique called ion beam mixing for surface modifcation has been developed to improve the bioactivity of the ceramic by deposit- ing a hydroxyapatite (HAP) coating on an alumina substrate. HAP thin flms were grown on alumina using sol-gel, and were ion beam mixed with 1.4 MeV Argon (Ar + ) ions at different ion doses: 5 × 10 14 ions/cm 2 , 1 × 10 15 ions/ cm 2 , 5 × 10 15 ions/cm 2 , and 1 × 10 16 ions/ cm 2 . Improvement in corrosion resis- tance in Ringer solution and throm- bogenic behavior are discussed. Osteoporosis is a leading disease that causes bone fractures and it affects both males and females. Other bone disorders, such as osteogenesis, rickets, and osteoma- lacia, also have adverse influences on bone structure, strength, and density that subse- quently lead to bone fractures. Orthopedic implants are often required to repair or replace damaged bone tissue. 1 Hydroxyapatite (HAP) [Ca 10 (PO 4 ) 6 (OH) 2 ] is used as a bony material replacement be- cause of its osteoconductive nature. It has excellent biocompatibility and tissue bio- activity with various kinds of cells and tis- sue, which makes it ideal for orthopedic implants, tissue engineering, and dental applications. 2 However, the brittle nature of the HAP restricts its clinical use in load- bearing applications. In the past decade, synthetic biomateri- als have not served as satisfactory implants. It is important to discover a better implant material for orthopedic applications. In most applications, blood compatibil- ity (i.e., no effect on blood coagulation) is required. Promotion of blood coagulation is desirable for some applications, however, such as hemorrhage control in trauma and surgical injuries. The compatibility of blood with biomaterials (hemocompatibility) is a critical assessment when evaluating a po- tential biomaterial for clinical applica- tion. 3-5 A thrombus (blood clot) is formed as a combination of activated coagulation factors, particularly fibrinogen combined with activated platelets (Figure 1). To improve the blood biocompatibility of the implanted materials, surface modifi- cation has been considered as one possible path. A number of novel methods have been proposed for applying HAP ceramic coatings that offer the potential for better control of film structure. 6 Methods that have been widely studied include hot iso- static pressing, f lame spraying, ion beam deposition, laser ablation, sol-gel coating, electrochemical deposition, and plasma spraying. Over the last two decades, the preparation of single and mixed oxides via the sol-gel process has increased. 7-8 One ceramic, alumina (Al 2 O 3 ), is the most cost-effective and well-established structural engineering material. 9 Its prop- erties, including reasonable corrosion re- Corrosion and Thrombogenicity of Argon-Implanted HAP/Alumina md. Shahid, d. ShiKha, and S.K. Sinha, Birla Institute of Technology, Mesra, Ranchi, India

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