Effect of precursor concentration and spray pyrolysis temperature upon hydroxyapatite particle size and density

Abstract

In the synthesis of hydroxyapatite powders by spray pyrolysis, control of the particle size was investigated by varying the initial concentration of the precursor solution and the pyrolysis temperature. Calcium phosphate solutions (Ca/P ratio of 1.67) with a range of concentrations from 0.1 to 2.0 mol/L were prepared by dissolving calcium nitrate tetrahydrate and diammonium hydrogen phosphate in deionized water and subsequently adding nitric acid. Hydroxyapatite powders were then synthesized by spray pyrolysis at 900°C and at 1500°C, using these calcium phosphate precursor solutions, under the fixed carrier gas flow rate of 10 L/min. The particle size decreased as the precursor concentration decreased and the spray pyrolysis temperature increased. Sinterability tests conducted at 1100°C for 1 h showed that the smaller and denser the particles were, the higher the relative densities were of sintered hydroxyapatite disks formed from these particles. The practical implication of these results is that highly sinterable small and dense hydroxyapatite particles can be synthesized by means of spray pyrolysis using a low-concentration precursor solution and a high pyrolysis temperature under a fixed carrier gas flow rate.

A brief review on hydroxyapatite production and use in biomedicine

“…According to the method, reagents and variables adopted, it is possible to obtain materials based on CaP with different phases, which results in materials with diverse characteristics and properties, such as crystalline defects, high surface area, organic material affinity found in physiological medium and so on [46]. HAp can be synthesized by a variety of techniques that can be broadly grouped into six sets of methods: i) dry methods: involve solid state and mechanochemical reactions [63][64][65][66][67]; ii) wet methods: based on low-temperature chemical precipitation [68], co-precipitation [66,69,70], sol-gel route [71][72][73][74][75][76] and hydrolysis [77,78]; iii) hydrothermal methods: use aqueous solutions of high temperature and high voltage, as hydrothermal [79][80][81], emulsion and microemulsion [82,83], and sonochemical [84]; iv) high temperature processes: include combustion [85,86] and pyrolysis [87,88]; v) synthesis based on biogenic sources: can be extracted from fish bones [89], shells [90], eggshells [91,92], bovine bones [93,94], in the presence of biomolecules [95][96][97] or biomembranes [98]; and vi) combination of the aforementioned methods. All methods used for synthesizing HAp particles have different processing characteristics and can result ...…”

“…In spray pyrolysis synthesis, particles are formed through the aerosol process that atomizes a solution and heats the droplets to produce solid particles with no addition of fuel. The precursor solution is sprayed in a flame or in a hot zone of an electric oven by an ultrasonic spray generator [87,88]. Cho et al [87] synthesized HAp powders via spray-pyrolysis and observed that the reduction of precursor concentration and an increase in the spray pyrolysis temperature caused a decrease in particle sizes.…”

The effect of simulating body fluid on the structural properties of hydroxyapatite synthesized in the presence of citric acid

“…Therefore, many studies have been published on HAp preparation and investigation of its major properties. Namely, synthetic HAp can be successfully prepared using various experimental techniques, such as sol–gel (Sanosh et al 2009 ), spray pyrolysis (Cho et al 2016 ), solution combustion (Pratihar et al 2006 ), hydrothermal (Manafi and Rahimipour 2011 ), microwave (Ruban Kumar et al 2010 ), precipitation (Mobasherpour et al 2007 ) and extraction from natural resources (Akram et al 2014 ). Among them, sol–gel is an inexpensive method for preparing of the nano-sized HAp, having high crystallinity and purity, at low temperatures (Kalita et al 2007 ; Kaygili and Tatar 2012 ).…”

Introductory Chapter: The Testament of Hydroxyapatite: New Prospects in Regenerative Medicinal Treatments

“…zone of an electric furnace [32,33] a. Solvothermal process b. Spray pyrolysis Table 1. Shows the key methods for the synthesis of hydroxyapatite (HAp).…”