Synthesis Of Nanocrystalline Hydroxyapatite Research Articles

Facile solution-based synthesis of impurity-free hydroxyapatite nanocrystals at ambient conditions

Synthesis of nanocrystalline hydroxyapatite with high degree of crystallinity results in improved bioactivity responses due to its high specific surface area and low ion release. Therefore, the innovative methods resulting in these qualities are of significant importance especially for 3D printing of biomaterials and biocomponents made by hydroxyapatite. Addressing the qualities essential for bioperformance of hydroxyapatite, a new method was developed in this work, which is able to prepare impurity-free hydroxyapatite nanocrystals at ambient conditions. Characterization of role of processing conditions and their successive optimization resulted in a facile cost-effective process in contrast to the literature. Stoichiometric nanoscale hydroxyapatite free from by-products, unwanted materials (unwanted phase formation) and impurities was obtained by the approach. It was found that the longer drying time increases the crystallinity of the as-washed precipitate; however, to reach a high degree of crystallinity, application of a heat treatment process is essential. The designed short time heat treatment was able to enhance the crystallinity of the dried precipitate while its structure remained nanoscale after heat treatment. Keeping the nanoscale structure of the samples even after heat treatment allows using its benefits for improvement of biocompatibility, osteoconductivity and tissue in-growth of the biomaterials made by these nanoscale hydroxyapatite powder products. The results showed that the amino acid (glycine) has a significant effect on the crystallinity of the hydroxyapatite due to its effect on kinetic of hydroxyapatite crystallization (nucleation of new crystals) by enhancing the surface diffusion mechanism in the precipitate. In contrast, the glycine also controlled the growth process of the nucleated crystals by its adsorption on the growing surfaces and/or by introducing the strain to the growing crystals. These stresses controlled the growth of the nanocrystals and induced directional growth and morphological changes in the hydroxyapatite powder products.

Hydrothermal synthesis of nanocrystalline hydroxyapatite\u2013graphene nanosheet on Ti-6Al-7Nb: mechanical and in vitro corrosion performance

The hybrid coatings containing the graphene nano-sheet (GNS) and nano-hydroxyapatite (nHA) phases have been successfully synthesized on Ti6Al7Nb alloys by a one-step hydrothermal method. The hydrothermal reaction was carried out for 24 h at 200 °C. The GNS ratio has been altered as 1, 3, 5 and 7 wt.% in the coatings and, the results have compared with non- GNS containing coatings. The effect of the GNS ratio on the microstructure, hardness, and in vitro corrosion responses has been investigated in detail. The characterizations of the coatings were carried out by SEM, EDS, AFM, XRD and, FTIR. The corrosion behavior of the hybrid coatings was compared in Kokubo’s solution at 37 °C by using potentiodynamic polarization tests. The results showed that the hydroxyapatite phases were deposed on the graphene layers with nano-size nucleation with its Ca/P stoichiometric ratio. The best hydrophilicity (~52°) property has been obtained in nHA/3GNS coatings. In addition, the corrosion rates of coatings increased in the following order: nHA/3GNS < nHA/1GNS < nHA/7GNS < nHA/5GNS < only nHA.

Experimental Investigation on Synthesis of Nanocrystalline Hydroxyapatite by the Mechanochemical Method

Mechanochemical synthesis is a simple and effective method to prepare ceramic compounds with nanosize. The present work was aimed at investigating the application of the mechanochemical method to synthesize nanocrystalline hydroxyapatite (HA). The shortest milling time required for synthesizing HA, using Ca (OH)2 and (NH4)2HPO4 as precursor materials was also established. The synthesized samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) to determine the phases evolved, functional groups present and to assess the size and morphology of the particles, respectively. Further, the thermal stability of the synthesized powders was investigated by heating to a temperature of 900 °C with a dwell time of 2 h. The broadening of the XRD peaks was used to find out the crystallite size and Williamson-Hall plots were used to estimate the lattice strain. The XRD and FTIR results demonstrated that the complete formation of the HA phase by mechanochemical method has started within a milling time of 30 min using Ca (OH)2 and (NH4)2HPO4 as precursors and the Ca/P ratio of the HA increased with increasing milling time. The TEM micrographs demonstrated that the HA particles are nanosized, non-spherical and highly agglomerated.

Microwave Synthesis of Nanocrystalline Hydroxyapatite and the Application in Bio-Composite

This research synthesized nanocrystalline hydroxyapatite (HA) via microwave assisted heating method. The morphology and crystallinity of nanocrystalline hydroxyapatite were affected by heating power and pH of the mixed solution. Nanocrystalline HA was best obtained when synthesized at pH = 11. Crystal size increased and crystal shape changed from spherical to rod and plate-like when the microwave power was increased from 320 to 800 watts. The synthesized nano-HA could be fabricated into bio-composite films using poly lactic acid (PLA) as the matrix and solvent casting method was utilized. In-vitro study for bioactivity was carried out in the SBF solution which formed hydroxyl-carbonate apatite (HCA) layer on the PLA/nano HA composite surface. The layer thickness increased in the background with increasing soaking time in the SBF.

Effect of trace elements on the sintering effect of fish scale derived hydroxyapatite and its bioactivity

Synthesis of nano-crystalline hydroxyapatite (HAp) from fish scale (Catla catla) was carried out by calcining of raw fish scale between 200 °C and 1200 °C. The synthesized powders were characterized using thermogravimetry – differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The crystallinity, crystallite size, strain and cell parameters of fish scale derived calcined powders and chemically synthesized HAp (S-HAp) powders were estimated from XRD data. The average crystallite size of fish scale derived HAp powder increased with increasing calcination temperature. The fish scale derived HAp (FSH800) and S-HAp, calcined at 800 °C, showed crystallite size of 30 nm and 60 nm, respectively. ICP-AES analysis revealed that the fish scale derived HAp powder calcined at 1200 °C (FSH1200) contain significantly high amount of magnesium and strontium ions compared to S-HAp. After sintering at 1200 °C for 1 h, the relative density of FSH1200 was 20% higher than that of S-HAp due to better sinterability as a result of its small crystallite size and the presence of trace elements. In vitro cytotoxicity studies performed using human osteoblast-like cells (MG63) and mouse osteoblast cell line (MC3T3-E1) demonstrated that fish scale derived HAp (FSH1200) is non-toxic.

Ethanol-based sol-gel synthesis of nano-crystalline hydroxyapatite with different calcium phosphorus ratios (Ca/P)

Ethanol-based sol-gel synthesis of nano-crystalline hydroxyapatite with different calcium phosphorus ratios (Ca/P)

Synthesis of Nanocrystalline Hydroxyapatite Using Eggshell and Trimethyl Phosphate

Background: Recently, the use of synthetic bone graft substitutes has garnered attention and become more popular than tradi- tional methods for reconstructing osseous defects in the fields of orthopedics and maxillofacial surgery. Commercially available hydroxyapatites (HAs) have been widely reported to be eective bone graft substitutes. Unfortunately, they are expensive to pro- duce. Thus, there is a need to develop methods of producing HA bone graft substitutes from inexpensive sources. Objectives: To synthesize nanocrystalline HA using recycled eggshell and trimethyl phosphate. Until date, several phosphate solu- tions have been utilized for this purpose. However, this is for the first time to the best of our knowledge that trimethyl phosphate is used as a source of phosphate to synthesize eggshell-derived HA. Methods: To produce HA, calcined hen's eggshell was used as a source of calcium, and trimethyl phosphate was used as a source of phosphate in a sol-gel method at a controlled temperature. The results were estimated using scanning electron microscopy (SEM) observantion to evaluate surface morphology, X-ray diraction (XRD) to analyze phase composition, and transmission electron mi- croscopy (TEM) to evaluate the shape and size of prepared HA. Micro-chemical analysis was conducted using energy-dispersive X-ray spectroscopy (EDX). Fourier transform infrared spectroscopy (FTIR) was employed to identify the functional groups of the prepared HA. Results: XRD evaluation showed that high-purity synthetic HA powder was obtained. The results of the SEM, XRD, TEM, EDX, and FTIR analyses demonstrated that the synthesis yielded nanostructured HA. Conclusions: A complete synthesis of nanocrystalline HA was obtained by using trimethyl phosphate and eggshells in a sol-gel method at a controlled temperature. A spherical particle morphology and particle size ranged 19 - 41 nm were achieved. Eggshell waste material is inexpensive and can be considered a viable choice for high-volume HA powder production, based on the present results.

Synthesis of Nanocrystalline Hydroxyapatite by Natural Biopolymers Based Sol-Gel Technique

Nanocrystalline hydroxyapatite (HAp) powders were successfully synthesized by natural biopolymers based sol-gel technique. The biopolymers were extracted from the leaves of Yanang (Tiliacora triandra), Krueo Ma Noy (Cissampelos pareira) and Konjac (Amorphophallus konjac). To obtain HAp powders, the prepared precursors were calcined in air at 600, 700, and 800 °C for 2 h. The phase composition of the calcined samples was studied by X-ray diffraction (XRD) technique. The XRD results confirmed the formation of HAp phase with a small trace of β-tricalcium phosphate (β-TCP). The crystalline sizes of the samples were found to be 20-50 nm as evaluated by the XRD line broadening method. TEM investigation revealed that the synthesized HAp samples consisted of nanoparticles with a particle size in the range of 50-100 nm in diameter. The corresponding selected area electron diffraction (SAED) analysis further confirmed the formation of hexagonal structure of HAp.

Mechanochemical synthesis of nanocrystalline hydroxyapatite via mechanical alloying

Hydroxyapatite (HA) nanostructure powder was successfully synthesised by ball milling. Effect of starting materials, milling time and annealing temperature were investigated. Formation of HA during milling and annealing was studied by X-ray diffraction. Morphology and microstructure were monitored by SEM and TEM, respectively. The Reitveld refinement method was used for calculation of mean grain size and microstrain. Results showed that the HA was synthesised in COP and COC series after 5 h milling. There is no reaction in CCP and CCPH after 80 h milling. The synthesised HA partially transformed to TCP during annealing at 1000°C in COP and COC series. In all series, a nanostructure powder was obtained after milling. The minimum mean grain sizes of 25, 33, 44 and 39 nm were obtained for COP, COC, CCP and CCPH respectively, at the end of milling on the basis of Reitveld refinement analysis that is in consistent with TEM images. The significant grain growth and strain release took place during annealing. The maximum mean grain sizes of 115, 104, 79 and 116 nm were procured for COP, COC, CCP and CCPH respectively after annealing.

Synthesis of nanocrystalline hydroxyapatite by precipitation using hen's eggshell

Hydroxyapatite (HAP) is a substance that is most actively used in orthopedia and dentistry as a biocoating of implants in order to improve its osteointegration with bone tissue. HAP was synthesized by precipitation technique with the use of the biological source — hen's eggshell. X-ray diffraction (XRD) investigations, IR-spectroscopy, scanning electron microscopy (SEM) demonstrate that the obtained powder-like material in the form of globules from 4 to 5 μm in size is single-phase, thermally stable up to 900 °C and morphologically uniform. The globules consist of nanocrystals with the average size of about 30 nm.

Synthesis of nano-crystalline hydroxyapatite and ammonium sulfate from phosphogypsum waste

Phosphogypsum (PG) waste which is derived from phosphoric acid manufacture by using wet method was converted into hydroxyapatite (HAP) and ammonium sulfate. Very simple method was applied by reacting PG with phosphoric acid in alkaline medium with adjusting pH using ammonia solution. The obtained nano-HAP was dried at 80°C and calcined at 600°C and 900°C for 2h. Both of HAP and ammonium sulfate were characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR) to study the structural evolution. The thermal behavior of nano-HAP was studied; the particle size and morphology were estimated by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). All the results showed that HAP nano-crystalline and ammonium sulfate can successfully be produced from phosphogypsum waste.

Synthesis of nanocrystalline hydroxyapatite from Ca(OH) 2 and H 3PO 4 assisted by ultrasonic irradiation

This work is focused on the synthesis of hydroxyapatite powders by precipitation assisted by a tip ultrasonic irradiation (UI) from Ca(OH) 2 and H 3PO 4. The effect of UI time, applied UI power during the synthesis, initial Ca 2+ concentration and ageing time of the mixture on phase composition, morphology and specific surface area of the obtained powders was analysed. Particles obtained from the precipitation method using UI or mechanical agitation were compared with a nanosized hydroxyapatite of reference in terms of crystal size, phase composition and thermal stability. This study revealed the feasibility to produce hydroxyapatite powders with controlled crystal size between 31.7 and 70.6 nm by ultrasonic assisted precipitation method. Hydroxyapatite powder with similar surface area to the reference material can be obtained adjusting experimental conditions. The used method allowed us to synthesise hydroxyapatite powders with thermal stability up to 1100 °C.

Influence of microwave power, irradiation time and polymeric additions on synthesis of nanocrystalline hydroxyapatite

Synthetic hydroxyapatite (HA) has been extensively used as an implant material owing to its excellent osteoconductive properties. The preparation of nanocrystalline HA is of paramount importance as the large surface area of the diminutive crystals makes them very active and consequently strongly affects the properties of it. In this paper, to study the effect of microwave irradiation power and time, nanocrystalline HA was synthesised at different microwave irradiation times (15, 45, 120, 240 and 600 min) and with different microwave powers (800 and 1100 W). This study also investigated the crystallisation of HA in the presence of sodium alginate and alginic acid at different addition levels (5, 10 and 15 wt-% to the final HA). It was found that crystallinity of the HA increases with increasing microwave irradiation time and/or power. Sodium alginate or alginic acid addition during crystallisation of HA decreases the crystal size and crystallinity of the precipitated HA.

Synthesis of nanocrystalline hydroxyapatite by using precipitation method

In this investigation, hydroxyapatite powder has been synthesized from the calcium nitrate hydrated and di-ammonium hydrogen phosphate solution by precipitation method and heat treatment of hydroxyapatite powders. In order to study the structural evolution, the Fourier transform infrared spectroscopy (FTIR), the X-ray diffraction (XRD) and simultaneous thermal analysis (STA) were used. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to estimate the particle size of the powder and observe the morphology and agglomeration state of the powder. Results show that hydroxyapatite nanocrystalline can successfully be produced by precipitation technique from raw materials. Hydroxyapatite grain gradually increased in size when temperature increased from 100 to 1200 °C, and the hydroxyapatite hexagonal-dipyramidal phase was not transformed to the other calcium phosphates phases up to 1200 °C.