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

Synthesis of HAP coating on galvanostatically treated stainless steel substrates by sol-gel method

Producing bioactive hydroxyapatite coatings on metallic implant materials combines the mechanical advantages of implant materials and biological affinity of the hydroxyapatite surface to the natural tissue. In this work, hydroxyapatite was synthesized on 316L stainless steel substrates via sol-gel method by using Ca(NO3)(2)center dot 4H(2)O and C6H15O3P. In order to improve adherence of the coatings produced, the surface of the substrate was initially modified by electrodepositing nucleus of calcium phosphate compounds. Effect of aging time for preparation of the sol solution and coating characteristics were investigated. The phase compositions and structures of the coatings were characterized by X-ray diffractometry, and scanning electron microscopy was used to determine morphological characteristics of the coatings. Adhesion between the hydroxyapatite coating and the substrate was investigated by using scanning scratch tester. The coating produced on the modified surface by the sol solution aged for 24 h was found to prove better morphological and adhesion properties

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