Search

Nanowhiskers of biphasic calcium phosphates composed of monetite/hydroxyapatite were fabricated using a cost-effective reflux hydrothermal approach from calcium nitrate and ammonium hydrogen phosphate precursors in presence of urea. The produced nanowhiskers were characterized using, FT-IR-spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron micrograph (TEM) and BET surface area determination. The major phase in Biphasic was (monetite, CaHPO4.) and their grown crystals were morphologically formed with irregular sizes of well defined rod or whiskers crystal structure. The specific surface area of these fabricated nanowhiskers was found to be 8.48 m2/g according to BET studies. The N2 adsorption/desorption isotherm of the as prepared monetite calcium phosphate is of type IV indicating that this material has a mesoporous structure. The produced nanowhiskers had 80% of monetite and 20% is hydroxyapatite. By controlling the parameters of the reflux approach it is possible to manipulate the composition and the size of these produced nanowhiskers.

In this paper, we reported a novel continuous microwave assisted flow synthesis (CMFS) of nanosized manganese substituted hydroxyapatite particles by using calcium nitrate and diammonium hydrogen phosphate precursor solutions in only 7 min retention time at pH 9. The identification of nanoproduct was made by using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Dynamic light scattering (DLS), Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. The results indicated that nanosized manganese substituted hydroxyapatite particles were synthesized successfully in a shorter time period. The degree of crystallinity of the nanoproduct decreased with increasing manganese contents from 0% to 4%. At such conditions, variations in particles’ size and morphology from larger rod shaped particles (~110 nm) to smaller semispherical form (~75 nm) was observed. Thus the use of continuous microwave assisted flow synthesis procedure facilitated faster production of manganese substituted hydroxyapatite nanoparticles suitable for bone replacement applications.

In this study, single-phase hardystonite (Ca 2 ZnSi 2 O 6 ) nanopowder was synthesized by combustion synthesis method from aqueous solution of Calcium nitrate, Zinc nitrate and Tetraethyl orthosilicate. In order to characterize the obtained powders, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used. The effect of sucrose concentration on the purity and morphology of the obtained hardystonite powder, and its initial annealing temperature was investigated. The optimum sucrose to metal ratio was found to be 2:1. The average particle size and the maximum crystallite size of the produced hardystonite nanopowder were 220 and 40 nm, respectively.

A successful electrodeposition method for preparing silver and zinc modified bioactive calcium phosphate layers onto surgical grade titanium alloy material (Ti6Al4V) was developed. The coatings were deposited on the Ti6Al4V surface by pulse current at 70 °C from an electrolyte containing adequate amounts of calcium nitrate, ammonium dihydrogen phosphate, zinc nitrate and silver nitrate. The corrosion resistivity of the bioceramic coatings was assessed in conventional Ringer׳s solution in a three electrode open cell by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results revealed the pure bioactive calcium phosphate (CaP) coated implant materials to possess the highest resistivity to corrosion, while the silver and zinc doped CaP layer showed at least one order of magnitude lower corrosion resistance. These modified CaP coatings can be further considered as antimicrobial coatings with enhanced biocompatibility. The morphology and structure of the coatings were characterized by Scanning electron microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDX) and X-ray diffraction (XRD) that confirmed the pulse current deposited CaP layer to consist of a mixture of different calcium phosphate phases such as hydroxyapatite (HAp), monetite (dicalcium phosphate, CaHPO4) as well as other Ca-containing components, portlandite (Ca(OH)2) and parascholzite (CaZn2(PO4)2(H2O)2).

Calcium silicates have proven to be potential candidates for biomedical applications because of their osteogenic properties. Sol–gel methods are typically used for the preparation of calcium silicate powders. However, in the sol–gel route, an acid or base and ethanol are used to catalyze the precursors. From the perspective of green chemistry, it is better to avoid the use of organic solvents. The objective of this study was to prepare calcium silicate powders using a green synthesis route (hydrothermal method) without organic solvents. The powders were also prepared via the sol–gel process using tetraethoxysilane (TEOS) and calcium nitrate as the raw materials for the purpose of comparison. The powders were sintered at temperatures ranging from 600 to 1000 °C after the application of both methods. To understand the feasibility of using the resulting materials in medical applications for bone repair, the powders were mixed with water to form cements. The results indicated that the powder composition was not significantly affected by the different techniques but was dependent on the Ca:Si ratio of the precursors and on the sintering temperature. The different techniques produced no differences in powder morphology. In addition, the setting times of the powder-derived cements were found to be independent of the sintering temperature and synthesis technique, but it was affected by the Ca:Si ratio of the precursors. The mechanical strength of the cements was similar. These encouraging results suggest that the hydrothermal method is a potentially beneficial alternative to the sol–gel route for the production of calcium silicate powders.

The present work involved solution combustion synthesis of high alumina cements from their metal nitrate precursors, using urea as an organic fuel. Combusted aluminium nitrate, calcium nitrate and urea complexes leads to formation of high alumina cement at temperature as low as 800 °C. The prime cementing phases observed were CA, CA 2 and C 12 A 7 . The second stage of work evaluates, the role of this high alumina cement (HAC) on bauxite based low cement castables. The effect of micro-fine Cr 2 O 3 and MgO additions on the sinterability and thermo-mechanical strength of these castables was also investigated. Phase identification and microstructural evaluation of the sintered castables confirms spinel and corundum phase formation. Addition of nano structured cements in refractory castables improved the thermo-mechanical properties to a significant extent.

Nano-sized calcium hydroxyapatite, [Ca10(PO4)6(OH)2] has been synthesized by the sol–gel combustion method using calcium nitrate and di-ammonium hydrogen phosphate as precursors in the aqueous medium. Triethyl phosphite was used as a phosphate precursor for alcohol mediated combustion. The aqueous and alcohol media were employed for the investigation of combustion synthesis in the presence of various fuels such as urea, glycine, alanine, hydrazine and hexamine. The metal-to-fuel ratio in the synthesis was maintained at 1 to facilitate complete combustion and the Ca/P ratio was maintained at 1.67 to aid the stoichiometric formation of hydroxyapatite. The combustion products were calcined at 800 °C for 10 h and were characterized by powder XRD, FT-IR, HR-SEM and HR-TEM techniques. All the five fuels used under the alcohol mediated combustion, resulted in forming phase pure hydroxyapatite; whereas the aqueous mediated combustion method yielded biphasic calcium phosphate containing Ca10(PO4)6(OH)2 and β-TCP depending on the nature of the fuel.

Hydroxyapatite-like (apatitic) calcium phosphate (Ap-CaP) powders are usually synthesized in stirred solutions containing the highly soluble salts of calcium, such as calcium nitrate, calcium acetate and calcium chloride as the Ca-source. The current study tested the ideas of simultaneously using (i) precipitated calcite (CaCO3) powders as the Ca-source and (ii) non-stirred, static solutions for synthesizing carbonated, Na+- and Mg2+-doped apatitic calcium phosphate (Ap-CaP) powders. 0.5 M phosphate buffer (non-saline) solutions were used as the sole phosphate source. The synthesized Ap-CaP powders were found to consist of micron-size carnation-like crystalline particles. Samples were characterized by FE-SEM, XRD, FTIR, ICP-AES, dynamic light scattering (DLS), carbon percentage and BET surface area analyses.

Calcium phosphate based bioceramics have been synthesized by a modified combustion synthetic route using both citric acid and succinic acid separately and in mixture as fuels and nitrate and nitric acid as oxidants. Calcium nitrate and diammonium hydrogen phosphate were used as calcium and phosphate sources. The effects of citric acid to succinic acid ratio on the phase formation have been investigated. The precursors and the calcined products have been characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. Succinic acid has been used as a fuel for the first time to synthesize hydroxyapatite. Hydroxyapatite phase is formed when either citric acid or succinic acid is used as a fuel and β-tricalcium phosphate phase is formed when a mixture of citric acid and succinic acid is used as a fuel as revealed by powder X-ray diffraction. The average crystallite size of the synthesized powder determined by Debye–Scherrer formula is found to be in the range of 55–65 nm. Surface morphology of the samples was imaged using scanning electron microscope. Chemical analysis shows that the Ca:P ratio in synthesized ceramics is 1.67. Results are discussed in terms of the phases present in the precursors formed during single and mixed fuel approaches and also its carbonate content present in hydroxyapatite products.

A polymeric combustion synthesis is described for the preparation of calcium phosphate compounds. The polymeric gel containing calcium and phosphate ions were synthesised by concentrating a solution of calcium nitrate and ethyl phosphate. When the above gel was introduced to a furnace kept at 500 °C, a self combustion reaction was observed, leaving behind a calcium phosphate precursor powder. The above powder on heat treatment at 1000 °C resulted in β-TCP, HAP or a mixture of the two phases depending on the CaP ratio in the gel. Dependence of CaP ratio on the composition of the calcium phosphate phase was studied by XRD. The morphological features of the precursor as well as the heat treated compounds were studied by SEM. The method offers an easy route for the preparation of β-TCP or HAP in the powder or in the porous form.