Biodegradable ceramics consisting of hydroxyapatite for orthopaedic implants

This study aims to analyze hydroxyapatite (HAP) coatings enriched with Mg and Ti prepared by a magnetron sputtering technique on Ti6Al4V substrate. For preparation of the coatings, three magnetron targets (HAP, MgO and TiO2) were simultaneously co-worked. The concentration of Mg added was varied by modifying the power applied to the MgO target. In all coatings, the Ti concentration was maintained constant by keeping the same cathode power fed during the whole deposition. The influence of different Mg dopant contents on the formation of phase, microstructure and morphology of the obtained Ti-doped HAP coatings were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Moreover, the effects of Mg addition upon corrosion, mechanical and biological properties were also investigated. Mg- and Ti-doped HAP coating obtained at low radio-frequency (RF) power fed to the MgO target provided material with high corrosion resistance compared to other coatings and bare alloy. A slight decrease in hardness of the coatings was found after the Mg addition, from 8.8 to 5.7 GPa. Also, the values of elastic modulus were decreased from 87 to 53 GPa, this being an advantage for biomedical applications. The coatings with low Mg concentration proved to have good deformation to yielding and higher plastic properties. Biological test results showed that the novel surfaces exhibited excellent properties for the adhesion and growth of bone cells. Moreover, early adherent vital cell numbers were significantly higher on both coatings compared to Ti6Al4V, suggesting that Mg ions may accelerate initial osteoblast adhesion and proliferation

Sol-jel yöntemiyle 316L paslanmaz çelik üzerine hidroksiapatit kaplamanın üretilmesi ve korozyon özellikleri

Ortopedik ve diş protezlerinde geniş bir kullanım alanına sahip olan hidroksiapatit (HAP) kaplamalar, sol-jel tekniği yardımıyla, kalsiyum ve fosfor başlangıç kimyasalı olarak sırasıyla Ca(NO3)2.4H2O ve C6H15O3P sol çözeltileri kullanılarak 316L paslanmaz çelik altlıklar üzerinde üretilmiştir. Çalışmada, altlık yüzeyine biyoaktif HAP tabakasının oluşumunu teşvik etmek için alkali ve asit işlemi ve electroçöktürme yöntemi ile CaP esaslı çekirdeklerle yüzeyin aşılanması olarak isimlendirilen yüzey işlemleri uygulanmıştır. Hazırlanan sol çözeltisinin yaşlanma zamanı ve pH etkisinin sol-jel kaplamaları özelliklerine etkisi incelenmiş ve HAP fazı üretimi için başarıyla optimize edilmiştir. Ayrıca, sol çözeltisine yapılan kimyasal katkıların kaplama faz yapısına ve morfolojisine etkisi incelenmiştir. Sonuçlar, elektroçöktürme yöntemi ile gerçekleştirilen yüzey modifikasyonunun kaplama kalitesini iyileştirdiğini çatlaksız ve gözenekli yapıya sahip kaplamanın, pH'ı 2,25 olarak ayarlanmış ve 24h yaşlandırma işlemine tabi tutulmuş sol çözeltisi kullanılarak elde edildiğini göstermiştir. Ayrıca, sol çözeltisine silika katkısı uygulamasının da kaplama kalitesinde olumlu bir etki gösterdiği görülmüştür. Üretilen kaplamaların etkinliği, yüzde 0,9 NaCl içeren fizyolojik tuzlu çözelti içerisinde polarizasyon ve elektrokimyasal empedans spektroskopisi çalışmaları ile belirlenmiştir. Elde edilen HAP kaplamaların, kaplanmamış 316L paslanmaz çelik altlığa göre daha iyi korozyon performansı gösterdiği bulunmuştur. Gözenekli yapıdaki kaplamanın düşük korozyon performansı göstermesinden kaplamanın korozyon performansı ile gözeneklilik arasında ters ilişki olduğu sonucuna varılmıştır. Hydroxyapatite (HAP) coatings which are widely used for orthopedic and dental prosthesis were produced on 316L stainless steel substrates via sol-gel technique by using sol solution containing Ca(NO3)2.4H2O and C6H15O3P as calcium and phosphorus precursors, respectively. In the study, surface modifications processes named as alkali and acid treatment, and formation of CaP seed by the electrodeposition technique were applied to the substrate so as to establish and induce a bioactive HAP layer on the surface of substrates. Effect of aging time and pH of the sol solution on the properties of sol-gel coating were investigated and successfully optimized for HAP phase formation. Besides, effect of chemical additives to the sol solution on the coating morphology and phase structure was studied. Results revealed that surface modification via electrodeposition route has improved the coating quality and provided coating with a porous and crack free structure derived from the sol solution with pH adjusted to 2.25 and subjected to aging process for 24h. It was also observed that silica addition into the sol solution has provided affirmative effect on the coating quality. Corrosion efficiencies of the coatings produced were determined in the physiological saline solution (0.9 percent NaCl) by means of polarization and electrochemical impedance spectroscopy studies. Obtained HAP coatings were found to show better corrosion performance compared to the uncoated 316L stainless steel substrate. It was concluded that there was an inverse relation between corrosion performance of the coating and porosity, that is the lower corrosion performance of the coating corresponds to increasing porosity

Production of HAP Coating on 316L Stainless Steel Substrates by Sol-gel Technique

In recent years, synthetic hydroxyapatite (HAP) has attracted much interest because of the quest for new generation implants able to promote rapid osteointegration and having longer lifetimes. HAP a major inorganic component of bone, has been increasingly used as a bioceramic coating for load-bearing implants to improve fixation to natural bone tissue. In this study, HAP coating was synthesized using a sol-gel processing on 316L stainless steel substrate and heat treated at different calcination temperatures. The formation of HAP and other compounds were identified and characterized using X-ray diffraction spectroscopy (XRD), Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). It was found that crystallinity, structure and morphology of the coatings varied depending on calcination temperature of the layer. The surface morphology of the HAP coating calcined at 500 degrees C displayed porous and crack free structure

Improvement of nickel nanocomposite coatings by combining zinc-doped TiO2 nanoparticles

Pure nickel and compound of nickel coatings (Ni-TiO2 and Ni-Zn/TiO2) were coated on the steel material using Watts bath with the electrodeposition conditions. Effect of the nanoparticle type and current density on the coating structure, surface morphology of the coating, hardness of the coating, and the corrosion properties of the coatings are presented. Phase and elemental analysis of the coatings were carried out by XRD and EDS techniques, respectively. SEM was used to investigate the surface morphology of the coatings, and Vickers microhardness values were measured to determine the hardness variation of the coatings. NaCl solution (3.5 wt%) was used to evaluate the corrosion properties of the coatings by the potentiodynamic polarization tests. Corrosion current density of 2.890 mu A/cm(2) for pure nickel coating was improved to 0.379 mu A/cm(2) by the coating of Zn-doped TiO2 nanoparticles at the 7A/dm(2) current density. Microhardness of the Zn-doped TiO2 coating was improved compared to the pure Ni coating