Mechanical Properties Of Hydroxyapatite Research Articles

Effects of Sr and Mg doping on elastic, mechanical, and optical properties of hydroxyapatite: A first-principles study

Hydroxyapatite (HAp), with the chemical formula Ca10(PO4)6(OH)2, is a bioactive ceramic material typically used in the treatment of bone defects owing to the excellent biocompatibility and the ability to bond with bone tissues. Mechanical properties of HAp have drawn pronounced attention because of the crucial roles in the medical applications. Based on density functional theory (DFT), this work reports the structural, formation energy, mechanical, Vickers hardness, electronic properties, and optical properties of hydroxyapatite (HAp), strontium-substituted HAp (Sr-HAp), and magnesium-substituted HAp (Mg-HAp). The results reveal that the Sr2+ and Mg2+ ions mainly replace the Ca2+ ion at the Ca-1 site in HAp. Resistance to hydrostatic compression followed the order Mg-HAp > HAp > Sr-HAp. Sr-HAp has the capability to enhance thermal shock resistance and lattice thermal conductivity. In addition, the electronic properties of HAp change upon substitutional Sr2+ and Mg2+ doping. In comparison with pristine HAp, the energy gap of Sr-doped HAp relatively increases, whereas that of Mg-doped HAp decreases. Nevertheless, both Sr-HAp and Mg-HAp remain insulators. Intriguingly, Sr-HAp possesses the improved hardness by 11.31 % owing to the hybridization of the Sr (4p) and O (2p) states, which contributed to its high shear modulus and high hardness. Beyond that, we further investigate their optical properties. The presence of Mg states at approximately 10 eV in the conduction band leads to enhanced absorption within the 14 – 20 eV for Mg-doped HAp. Similarly, the presence of a deep Sr(4p) level in Sr-HAp amplifies absorption within the 20–25 eV range. These findings have raised a potential avenue for selectively boosting the optical absorption of HAp, thus improving its photocatalytic properties.

Synthesis and mechanical characterization of hydroxyapatite-based biomaterials reinforced with nickel-titanium-magnesium alloys for use in cortical bone implants

In this work, biomaterials consisting of bioactive hydroxyapatite-based ceramic and nickel-titanium-magnesium alloys were made. The biomaterials were obtained through powder techniques involving mechanical milling, uniaxial pressing and pressureless sintering. The purpose of the study was to evaluate the effect of alloys on the mechanical properties of hydroxyapatite, the alloy additions were 0, 20, 30, 40, 40, 50 and 60 wt.%. The results were compared with cortical bone samples of bovine origin. From the results, it is possible to comment that, with increasing alloy contents in the hydroxyapatite, the mechanical properties increase considerably. The behavior of the composites reinforced with 50 and 60 wt.% NiTiMg alloy is similar to that of bovine cortical bone. The microstructures of the biomaterials are fine, homogeneous, and similar to those of bovine cortical bone. From the study it can be commented that given the mechanical characteristics of the biomaterials obtained, they could be used as possible bone implants.

Bioactivity and Mechanical Properties of Hydroxyapatite on Ti6Al4V and Si(100) Surfaces by Pulsed Laser Deposition

In this study, the effects of substrate temperature and ablation wavelength/mechanism on the structural, mechanical, and bioactivity properties of hydroxyapatite (HA) coatings were investigated. HA coatings were deposited on both Si(100) and Ti6Al4V surfaces. Substrate temperature varied from room temperature to 800 °C. Depositions were performed in Ar/H2O and vacuum environments. X-ray diffraction, scanning electron microscopy, and atomic force microscopy techniques were used to analyze structural and morphological variations. The adherence of coatings to the substrates was assessed by the pull-out method. The obtained data indicated that with the temperature increase, the coatings steadily crystallized. However, temperatures above 700 °C adversely affected protein adsorption and adhesion properties. Similar trends were confirmed via pull-out testing, protein adsorption, and cell proliferation tests. The ablation mechanism was also proven to play an important role in the deposition process. Overall, this study provides further evidence that crystallinity is a vital factor in the functionality of the coatings and depends on the deposition conditions. However, all measurements directly indicated that beyond 700 °C, the morpho-structural, mechanical, and bioactivity properties degrade.

Effect of Cordierite Additions on Mechanical Properties of Hydroxyapatite Used in Medical Applications

In this study, a novel bioceramic material with improved mechanical properties was prepared to be consentient with the mechanical requirements of living bodies. Cordierite was synthesized via the sintering method at 1400 °C, based on a composition of 51.4% silica, 34.8% of alumina, and 13.8% magnesia. The composition of precursor materials was studied using wet chemical analysis. Three different compositions of the cordierite (30, 40, and 50 wt.%) were incorporated in hydroxyapatite and then sintered at 700, 900, and 1100 °C. To visualize the characteristics of all prepared materials, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were analyzed. The crystallite size was determined from XRD patterns using the Scherrer equation. Microhardness was investigated using (a digital micro hardness tester), while the compressive strength was tested using a microcomputer-controlled electronic universal testing machine (WDW-5E). The modulus of elasticity was determined from the stress-strain curve. As a result, all samples which contain cordierite powder have considerable mechanical properties as compared to the control sample. The incorporation of cordierite caused a slight increase in grain size at all sintering temperatures. Among all ratios, the second mixture, which includes 40% cordierite showed the best mechanical properties at all sintering temperatures. The percentage of 40% cordierite led to increasing the compressive strength of HA by 126.27% at 700 °C, 61.52% at 900 °C, and 123.05% at 1100 °C. On the other hand, the effect of this cordierite level on hardness increased by 94.04% at 700 °C, 141.29% at 900 °C, and 128.44% at 1100 °C. The values of elasticity modulus ranged between 15-37 GPa, i.e. consistent with that of cortical bone.

Densification behaviors of hydroxyapatite/pectin bio-ceramics

Hydroxyapatite (HA) is a popular biomaterial in making implants and bone grafts owing to its high biocompatibility and close resemblance to human bone. This study aims to determine the physiochemical and mechanical properties of HA derived from chicken bones (CHA) through calcination. Microwave irradiation-extracted pectin was ball-milled with CHA. Pure CHA and CHA added with pectin (CHAP) were sintered via conventional and two-step sintering. FTIR and XRD peaks confirmed the presence of HA and β-tricalcium phosphate in CHA and CHAP. SEM image of CHA and CHAP powder exhibited 0.5–0.625 µm rod-shaped and spherical particles, with 2–8 µm grains after sintering. Ca/P ratios of CHA and CHAP fell between 1.47 and 1.85. The highest relative density and hardness of sintered samples achieved are 96.66% and 4.76 GPa, respectively. This proves that the calcination of chicken bones can produce HA which is suitable for biomedical applications.

Resistive coupled microwave sintering of hydroxyapatite/titania nano-biocomposite and tailoring its mechanical properties

Tailoring the mechanical properties of bioceramics plays a crucial role in the fabrication of hard tissue substitutes. In this work, phase pure nanostructured hydroxyapatite and titania were synthesized using a single-step combustion technique. To study the influence of titania in the mechanical properties of hydroxyapatite, hydroxyapatite/titania (TiO2-0%, 10%, 20%, and 30%) nanocomposites were prepared. The sample containing 20% titania showed maximum sinterability and was analysed in detail. The samples were sintered by a novel resistive coupled microwave sintering to 98.9% of the theoretical density at 1020 °C for a soaking duration of 20 min. A substantial reduction in sintering temperature of ∼165 °C and a significantly low soaking duration were observed in the samples sintered using the new technique and it yielded pellets with reduced grain size compared to the samples sintered via conventional resistive heating. They have shown better microhardness of 7.7 GPa, enhanced compressive strength of 194.9 MPa, and improved elastic modulus of 136.2 GPa without compromising the cell viability, cell adhesion, differentiation, proliferation, and biomineralization. The results indicate that by varying the titania content in hydroxyapatite and by adopting a suitable low-temperature sintering strategy like resistive coupled microwave sintering, one can tailor the mechanical properties of bone implants.

3D Printability of Silk/Hydroxyapatite Composites for Microprosthetic Applications.

Micro-prosthetics requires the fabrication of mechanically robust and personalized components with sub-millimetric feature accuracy. Three-dimensional (3D) printing technologies have had a major impact on manufacturing such miniaturized devices for biomedical applications; however, biocompatibility requirements greatly constrain the choice of usable materials. Hydroxyapatite (HA) and its composites have been widely employed to fabricate bone-like structures, especially at the macroscale. In this work, we investigate the rheology, printability, and prosthetic mechanical properties of HA and HA-silk protein composites, focusing on the roles of composition and water content. We correlate key linear and nonlinear shear rheological parameters to geometric outcomes of printing and explain how silk compensates for the inherent brittleness of printed HA components. By increasing ink ductility, the inclusion of silk improves the quality of printed items through two mechanisms: (1) reducing underextrusion by lowering the required elastic modulus and, (2) reducing slumping by increasing the ink yield stress proportional to the modulus. We demonstrate that the elastic modulus and compressive strength of parts fabricated from silk-HA inks are higher than those for rheologically comparable pure-HA inks. We construct a printing map to guide the manufacturing of HA-based inks with excellent final properties, especially for use in biomedical applications for which sub-millimetric features are required.

Evolution of dynamics of physico-chemical and mechanical properties of hydroxyapatite with fluorine addition and degradation stability of new matrices

This multidisciplinary study examined sensitively the change in the dynamics of main mechanical performance, stability of crystal structure, crystallinity quality, strength, corrosion resistance, biocompatibility, resistance to structural degradation/separations and mechanical durability features of hydroxyapatite (HAp) biomedical materials based on the fluorine addition and degradation process to guide future medical and dental treatment studies. In the study, the fluorine ions were used to be the dental coating, filling and supporting material for biologically or synthetically produced bone minerals. The general characteristic properties were investigated by means of standard spectroscopic, structural and mechanical analysis methods including RAMAN, SEM-EDS, TEM, Vickers micro-indentation hardness and density measurements. A time dependent release test was performed to evaluate possible fluorine ion release after the degradation process. It was found that the fundamental characteristic properties of HAp biomedical materials are noted to improve with the increase in the fluoride level up to 2% due much more stabilization of HAp crystal system. The combination of RAMAN spectra and powder XRD analyzes indicates that 2% addition level affects positively the formation velocity of characteristic HAP phase. Besides, fluorine doped HAp materials all exhibited the main characteristic peaks after degradation process. This is attributed to the fact that the fluorine ions enabled the hydroxyapatite to enhance the structural quality and stability towards the corrosion environment. However, in case of excess dopant level of 3% the degradation rates were obtained to increase due to higher contribution rate and especially electrostatic interactions. As for the surface morphology examinations, 2% fluorine added HAp with the highest density of 3.0879 g/cm3 was determined to present the superior crystallinity quality (smallest grain size, best smooth surface, honeycomb pattern, regular shaped particles and densest particle distributions through the specimen surface). Conversely, the excess fluorine triggered to increase seriously degree of micro/macro porosity in the surface morphology and microscopic structural problems in the crystal system. Thus, the HAp doped with 3% was the most affected material from the degradation process. Additionally, the fluorine ion values read after the release process were quite far from the value that could cause toxic effects. Lastly, the optimum fluorine addition provides the positive effects on the highest durability, stiffness and mechanical fracture strength properties as a consequence of differentiation in the surface residual compressive stress regions (lattice strain fields), amplification sites and active operable slip systems in the matrix. Hence, the crack propagations prefer to proceed in the transcrystalline regions rather than the intergranular parts. Similarly, it was found that Vickers micro-indentation hardness tests showed that the microhardness parameters increased after the degradation process. All in all, the fluorine addition level of 2% was noted to be good choice to improve the fundamental characteristic properties of hydroxyapatite biomedical materials for heavy-duty musculoskeletal, orthopedic implant, biological and therapeutic applications in medicine and dentistry application fields.

Improving the Mechanical Resistance of Hydroxyapatite/Chitosan Composite Materials Made of Nanofibers with Crystalline Preferential Orientation.

The stability and mechanical properties of hydroxyapatite (HAp)/Chitosan composite materials depend on the dispersion of HAp aggregates in the chitosan matrix and on the chemical interaction between them. Therefore, hexagonal cross-sectioned HAp nanofibers were produced using a microwave-assisted hydrothermal method. Glutamic acid was used to control the HAp crystal growth; thereby, nanofibers were obtained with a preferential crystalline orientation, and they were grown along the “c” axis of HAp crystal structures. This morphology exposed the (300) and (100) crystal planes on the surface, and several phosphate groups and calcium ions were also exposed; they were able to form numerous chemical interactions with the amine, hydroxyl, and carbonyl groups of chitosan. Consequently, the final mechanical resistance of the composite materials was synergistically increased. Nanofibers were mixed with commercial chitosan using a sonotrode to improve their dispersion within the biopolymer matrix and prevent migration. The HAp nanofiber/Chitosan composite materials showed higher mechanical resistance than that observed in similar materials with the same chemical composition that were made of commercial HAp powders, which were used as reference materials. The mechanical resistance under tension of the composite materials made of nanofibers was similar to that reported for cortical bone.

Mechanical properties, microstructure, and bioactivity of β-Si3N4/HA composite ceramics for bone reconstruction

Pure hydroxyapatite (HA) as bone graft substitute has excellent osteogenic activity, but it has lower fracture toughness and its biological activity is harmed by the addition of toughening phases, which limits its clinical application. To alleviate the contradiction, columnar β-Si 3 N 4 as the toughening phase and La 3+ /Y 3+ sintering aid as active ions are used in this study to prepare β-Si 3 N 4 /HA composite biomaterials. According to the results, hardness and toughness of 10 wt% β-Si 3 N 4 /HA composite prepared by cold press sintering at 1300 °C were 6.44 GPa and 1.69 MPa m 1/2 , respectively, being 110% and 140% higher than those of pure HA. Moreover, 10 wt% β-Si 3 N 4 /HA composite exhibited better protein adsorption capacity and obviously stimulated adhesion, proliferation, and osteogenic differentiation of osteoblast. In addition, it was found that sintering aid not only facilitated the improvement of mechanical properties, but also promoted the formation of 100–200 nm nanostripe structure, which was beneficial to cell adhesion. Determination of La 3+ concentration combined with biological experiments also proved that its concentration range from 4×10 −8 M to 6 × 10 −8 M was beneficial to cell proliferation and osteogenic differentiation. In summary, β-Si 3 N 4 and sintering aids were shown to improve mechanical properties of HA at maintaining the biological activity of the latter.

Measurement of the Fracture Toughness and Mechanical Properties of Hydroxyapatite Using Vickers Indentation Technique

Measurement of the Fracture Toughness and Mechanical Properties of Hydroxyapatite Using Vickers Indentation Technique

Effects of biomimetic synthesis route and sintering temperature on physicochemical, microstructural, and mechanical properties of hydroxyapatite

Effects of biomimetic synthesis route and sintering temperature on physicochemical, microstructural, and mechanical properties of hydroxyapatite

Sinterability of Calcium Phosphate Through Rapid Sintering

Development of dense nanostructured hydroxyapatite (HA) with the major concern to enhance densification while limiting its grain growth has received great demand. This is due to inherent brittleness and lower mechanical strength of HA ceramic. A promising way to obtain this could be a fabrication of nanostructured HA materials through rapid sintering process. In this work, eggshell derived hydroxyapatite powder has been prepared via solid state route and its sinterability was investigated through microwave sintering (1000-1250 °C). The phase stability, microstructural evolution, relative density and hardness of the microwave sintered HA were reflected. The results indicate that the rapid sintering regime has been successfully employed with pure HA phase stability remained up to 1200°C and the relative density and hardness increase with increase in sintering temperature. On top of that, the result also showed good correlation of grain size and mechanical properties of HA and supported that microwave sintering did not promote extensive grain growth of HA.

Mechanical Properties of Hydroxyapatite/La Prepared by a Solid Chemical Reaction Method

Mechanical properties of Hydroxyapatite (Ca10(PO4)6(OH)2, HA, still need to be modified to improve its function as dental filler or bone implant. HA is usually substituted with other metals to increase its mechanical strength. In this study, HA from chicken eggshells was substituted with La with a concentration variation of 1-3 wt % with a solid chemical reaction at a temperature of 1100 °C for 2 hours. The structure, morphology and mechanical strength of HA/La were characterized by XRD, SEM and Vicker Hardness, respectively. All HA samples adopt the P 63/m space group. Likewise, the IR spectra are similar to each other, which shows the formation of the HA structure, indicated by the presence of the -OH and PO43- groups. HA/La with the highest hardness value of 1.85 GPa is obtained from the 3 wt % La doping. The higher the La content added, the higher the hardness of the hydroxyapatite. The doping of 3% La increased the hardness of HA 17%.

Hydroxyapatite/polyetheretherketone nanocomposites for selective laser sintering: Thermal and mechanical performances

Abstract In this article, the thermal and mechanical properties of hydroxyapatite (HA)/polyetheretherketone (PEEK) nanocomposites were investigated. The surface of the HA particles was modified by stearic acid. Subsequently, the modified HA and PEEK were ultrasonically dispersed in ethanol and then subjected to drying and ball milling treatments. By controlling the concentration of modified HA, HA/PEEK nanocomposite powders containing various amounts of modified HA were successfully prepared. The tensile strength, impact strength, and flexural strength of the nanocomposite reached maximum values at 2.5 wt% HA and were 18.5%, 38.2%, and 5.7% higher than those of the pure PEEK, respectively. Moreover, the flexural modulus of the HA/PEEK nanocomposites increased at 2.5 wt% HA and was approximately 30% higher than that of the pure PEEK. The thermal property measurements (differential scanning calorimetry and thermogravimetric analysis) showed that the nanocomposites with 2.5 wt%-modified HA exhibited enhanced thermal stability as compared to the pure PEEK, showing potential for selective laser sintering.

Elastic and mechanical properties of hydroxyapatite under pressure: A first-principles investigation

The structural, elastic, and mechanical properties of hydroxyapatite (HAp) were investigated by generalized gradient approximation (GGA) in the functional form by Perdew, Bruke, and Ernzerhof (PBE) exchange-correlation functional using density-functional theory. Our calculated equilibrium lattice parameters at ambient pressure are in good agreement with the experimental and previous theoretical results. The details of the structural, mechanical, and electrical properties such as elastic constants, bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratioν, Cauchy pressure, shear anisotropic factor A, and total density of states under pressure ranging 0 GPa to 10 GPa are studied. The lattice parameters a and c are found to be decreased with increasing pressure. Moreover, the lattice parameter a is more sensitive to external pressure than c. The calculated elastic constants of hexagonal HAp increase with increasing pressure. The elastic constants C11 and C33, which represent the elasticity in length are larger than the elasticity in shape, which represent by the elastic constants C12, C13, C44, and C66. The deformation resistances along the axial direction are stronger than the deformation resistances in shape. The calculated B/G, Poisson’s ratio ν, and Cauchy pressure show that the hexagonal HAp behaves as a ductility material at ambient pressure and has more ductile under pressure. While the calculated shear anisotropic factor A indicate that the HAp shows elastic anisotropy under pressure. Moreover, calculated total density of states (DOS) show that HAp becomes more insulator property with increasing pressure.

Statistical evaluation of nano-structured hydroxyapatite mechanical characteristics by employing the Vickers indentation technique

In this study, the mechanical characteristics of hydroxyapatite (HA) against the Vickers indenter under different loads were investigated. For this purpose, the HA powders were first synthesized by a one-pot solvothermal method. The powders were then subjected to consolidating by the spark plasma sintering (SPS) method for mechanical evaluation. Characterization methods used in this study included X-rays diffraction, field emission scanning electron microscopy, transmission electron microscopy, inductively coupled plasma, energy dispersive X-ray spectroscopy, and Vickers indentation technique. The findings of this study showed that the morphology of the synthesized powders by solvothermal method were rod-shaped and nanometer-sized. As the applied load increased to 2 N, the elastic modulus increased but the hardness did not change much. At a constant force, the contact depth increased with decreasing elastic modulus and hardness. Also, increasing contact depth increased the stiffness and contact area. The results of this study will be useful for investigating the mechanical properties of HA based materials.

Innovating Hardness Model of Bioceramics Hydroxyapatite Based on Variety of Synthetic Conditions

Hydroxyapatite is bioceramics which have conducive biocompatible property and have been widely used in bone scaffolds. Although they have potential development, there have not been any matematical model that elaborates the relation between the parameter of synthetic conditons and the mechanical properties of hydroxyapatite. That is why, this article tries to present the relation model between the hardness of hydroxyapatite based on variety of synthetic conditions and sintering temperature, relative density, and the size of particle as well. Developing hardness model is performed on the basis of its relation with the responses from each experiment factor. Validating model which was carried out through comparison between the model and the data of experiments indicates that the model proposed has a good accuracy and capable for explaining the bond between the parameter of synthetic and the hardness of hydroxyapatite.

The Sintering Behaviour and Mechanical Properties of Hydroxyapatite - Based Composites for Bone Tissue Regeneration

The developement and regeneration of healthy bone tissue is a complex process that includes the interaction of different cell types and requires a set of coordinated processes. The loss of bone tissue may occur due to various reasons: surgical removal, bone trauma (i.e., fractures) or systemic bone loss (i.e., osteoporosis). When the natural bone tissue is destroyed, the regeneration capacity of the bone is not always satisfactory. The result consists therefore in many functional and structural aberrations. In order to improve and accelerate the healing process, bone substitutes have been developed. Hydroxyapatite has been widely used in bone applications due to its excellent biocompatibility, osteoconductivity and bioactivity [1,2]. The objective of this research is to obtain a new composite biomaterial that can be used as bone substitute. In this study, bovine hydroxyapatite obtained from freshly calcined bovine femur was used. The objective of this research is to obtain a new composite biomaterial that can be used as bone substitute. The experimental composite samples were obtained using bovine hydroxyapatite as matrix and tricalcium phosphate, respectively, magnesium oxide as reinforcement materials. The synthesis process of these new biomaterial composites, the effect of chemical composition, surface structure, chemical and phase composition as well as mechanical features have been investigated.

HAp/TiO2 nanocomposites: Influence of TiO2 on microstructure and mechanical properties

Hydroxyapatite is a very attractive material for artificial implants and human tissue restorations because they accelerate bone growth around the implant. The hydroxyapatite nanocomposites (HAp/TiO2) were produced by using high energy ball milling. X-ray diffraction studies revealed the formation of HAp and TiO2 composites. Cubic-like crystals with boundary morphologies were observed; it was also found that the grain size gradually increased with the increase in TiO2 content. It was found that the mechanical properties (hardness, Young's modulus, fracture toughness, flexural strength, and compression strength)of the composites significantly improved with the addition of TiO2, which was sintered at 1200℃. These properties were then also correlated with the microstructure of the composites. This paper investigates the effect of titania (TiO2 = 0, 5, 10, 15, 20, and 25 wt%) addition on the microstructure and mechanical properties of hydroxyapatite (Ca10(PO4)6(OH)2) nanocomposites.