Browsing by Author "Bastan F.E."

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    Investigation of bond strength of spray dried hydroxyapatite-wollastonite composite powder after plasma spray
    (Springer Verlag, 2016) Bastan F.E.; Karaarslan O.; Erdogan G.; Ustel F.
    Hydroxyapatite (HA) is one of the most significant calcium phosphate bio-ceramic which is used commercially in biomedical application due to its similar structure with natural bone, bioactivity, and stability in body fluid. HA has excellent biological properties, while plasma sprayed HA coatings have poor bond strength which makes it difficult to use HA coated implants under mechanical stress. Wollastonite (CS) is a calcium silicate based bioactive ceramic which is used in thermal spraying due to its higher bond strength than HA coatings, however it dissolves quicker than HA in simulated body fluid (SBF). The aim of this work is to produce HA-CS composite powder in order to increase bond strength of the coating. In this study, commercial CS and precipitated HA mixture suspension which involved wt.20% CS was prepared for spray drying (SD) application. HA-CS composite microspheres were granulated by spray drying to supply homogeneity of coating and carry powders to the plasma easily. Afterwards, HA and HA-CS composite microspheres were coated by plasma spraying on carbon steel. Results showed that HA-CS composite coatings have higher adhesion strength, while it decomposes easier to other calcium phosphates than pure HA coating. Additionally, HA-CS coating has higher rate of porosity and un-melted particles. © Springer Science+Business Media Singapore 2016.
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    Spray drying of hydroxyapatite powders: The effect of spray drying parameters and heat treatment on the particle size and morphology
    (Elsevier Ltd, 2017) Bastan F.E.; Erdogan G.; Moskalewicz T.; Ustel F.
    The physical and chemical properties of spray dried hydroxyapatite (SD-HA) are significantly depended on precipitation and spray drying (SD) process parameters. This study presents the effects of precipitation pH, solid content, slurry feed rate, atomization pressure, hot air temperature and hot air flow rate on the particle size distribution of SD-HA. Moreover, the physical and chemical properties of SD-HAs and heat treated micro-granules depending on the precipitation pH were investigated. Taguchi Experimental Design (DoE) was employed to optimize the parameters and to determine the significant factors. The physical properties of SD-HA and heat treated micro-granules were analyzed via particle size analyzer, SEM and TEM. RAMAN and FTIR were carried out to examine the chemical properties. Increasing of the precipitation pH led to slightly increase of the median particle size and the high temperature stability of the SD-HA. DoE results demonstrated the most significant SD parameters as atomization pressure and slurry feed rate. The increases in heat treatment temperature decreased the specific surface area, pore volume and particle size of SD-HA, while increased the crystallinity and powder density. SD-HA were stable up to 1250 °C and decomposed at approximately 1450 °C. © 2017 Elsevier B.V.