Proceedings of the 5th International Conference on Integrity Reliability Failure, Porto/Portugal 24 28 July 2016 Editors J.F. Silva Gomes and S.A. Meguid Publ. INEGI/FEUP (2016)
PAPER REF: 6306
THE PREDICTION OF FRACTURE TOUGHNESS PROPERTIES OF BIOCERAMIC MATERIALS BY CRACK GROWTH SIMULATION USING FINITE ELEMENT METHOD AND MORPHOLOGICAL ANALYSIS
Dariush Firouzi, Amirsalar Khandan (*) , Neriman Ozada Mech. Eng. Dept., Eastern Mediterranean University, North Cyprus, Gazimağusa, TRNC, Mersin, Turkey (*) Email: [email protected]
ABSTRACT Various types of hydroxyapatite (HA) structures have received great attention of scientific researcher in biomaterials field. Also, it is common that HA is the essential inorganic materials in human hard tissue such as bone or teeth. Fracture toughness and micro hardness properties are the important parameters required for the prediction of the mechanical performance of biomaterials structures before failures. The indentation micro fracture method, which yields for the mode is critical stress intensity factor, KIC , is particularly useful when applied to brittle materials with low K IC . As fracture toughness is easy, fast technique and needs small testing equipments and area, here we represent the enhancement in hardness and toughness which is possible due to attain nano crystalline size for HA powder using in powder, bulk or coating form, suitable sintering and variable composition. It is obvious that the HA hardness have close relationship with fracture toughness. Also, materials properties as the size of grain changes/reduced from micron to nano meters influence the mechanical behaviour of biomaterials. As the current observation of papers illustrates, the HA toughness rise up to about 70% with compositing with other beneficial additives like Al 2O3, polyethylene, fluorine, diopside, zircon, akermanite, bioglass (BG), tungsten carbide (WC), carbon nanotube (NC), etc. Secondly, sintering improve the fracture toughness of the HA particles and other biomaterials as well. Also, one can say that sintering procedure effect the microstructure mechanisms for simultaneous enhancements in the hardness and fracture toughness of the bio ceramics. In the current paper we predict the fracture toughness value changes to greater value with the morphology of the powder less in the case of amorphous materials like zircon. We consider the prediction method with Finite element analysis and gather data from other literatures.
Keywords: Fracture toughness, sintered, non sintered, powder, bulk, coating, biomaterials.
INTRODUCTION The aim with the current paper was studying several literature regarding to fracture mechanics relates to the mechanism of products, geometry of materials, load application of bio ceramics. It has been well recognized that bio ceramics like hydroxyapatite (HA) is the basic inorganic materials human bone structure [1]. Research observation on in vitro test represented, it has the natural capacity to advance bone development [2]. Biomedical applications of bio ceramic as well as in artificial bones implant are recently being clinically investigated. Various procedures (sintering, grain size, composition) have been examined in endeavors to enhance
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the mechanical properties for coating case and other specific applications [3 4]. This ability can be further improved by arranging of additive (various ions) into HA structure gradually by the encompassing bone showing cells which produced novel structured product [4]. As the second materials (phase) added to advanced biomaterial structure, other properties like mechanical behaviour like fracture toughness, micro hardness, and thermal behaviour could be enhanced due to different synthesis technique and materials fabrications methods like mechanical activation (MA) [3, 7, 15], mechanochemical (MC) [4], sol gel, precipitation, etc [4 6]. Strength properties of Ca 10 (PO 4)6(OH) 2 have been well investigated in several literature [6 10]. Because pure HA is very brittle compared to other ceramic, which is enough strong under compression test, however the materials properties is weak under tensile examination, micro hardness and shear stresses sample test [9]. However, high applications have been encountered with some limitation to non load bearing conditions because of its low mechanical properties, high dissolution rate and particularly low fracture toughness (low K IC ) [11 12]. In this literature, we investigate fracture toughness of HA in the form of powder composite and bulk dense materials. We present the materials and techniques that are possible to upgrade and improve these types of unique materials. Many experimental methods have been proposed to estimate roughness and fracture toughness of the coatings [12 13]. The 1/2 fracture toughness of HA is less than K IC <1 MPa m which is a principle disadvantage of this materials limits for bearing orthopaedic and clinical applications [14]. The indentation micro fracture method, which yields for the different three mode like tensile force (mode I), shear force (mode II), and torsional force (mode III) is critical stress intensity parameter, KIC. It is particularly useful when applied to brittle materials with low K IC . In addition, the biological evaluation of bio ceramic shows that i n vitro and in vivo studies have close correlation with fracture toughness as mechanical behaviour [15]. Bioactivity and biocompatibility evaluation supporting a human cell reaction on synthesized materials and results showed that composites demonstrated no deleterious defect on some antigen expressions that play a vital role in the integrity fracture toughness (K IC ) was determined by an indentation technique as proposed by Laugier [16] and Evans [17]. The densification behaviour and mechanical properties of sintered and non sintered HA effects on biological reaction as the several literature review illustrates [18 21]. As the HA biocompability and bioactivity proves with several characterization technique like cell culture and simulated body fluid (SBF) solution test, the mechanical characterization of HA is still a interesting topic in the recent years [9, 12]. Applying of calcium phosphates (CaPs) as artificial organ in human’s body has been constrained by low quality and low crack durability in the implant coating using in dental and orthopaedic prosthesis [3]. Furthermore, nanostructured bredigite (Ca 7MgSi 4O16 ) [22], fluorine [4], nanostructured diopside (CaMgSi 2O6) [3, 9], poly caprolactone, nanostructured akermanite (Ca 2MgSi 2O7) [1 3], polyethylene, Al 2O3, and tungsten carbide (WC), have discharge at a controlled rate to strength the HA arrangement for better mechanical reaction/behaviour. The crack durability and KIC for tungsten carbide (WC) is 6 MPa m 1/2 is accomplished with the SPS procedure. Additionally, some polymers like poly imides have been composited and sintered to enhanced mechanical properties of primary and pure material [3]. Their outcomes also demonstrated that the mechanical and biological properties of the composites were better than those delivered by cold isostatic pressing (CIP) and conventional sintering. In every case study with proper fracture toughness, mechanical properties were observed that enhanced by compositions and sintering [6, 17]. Another factor which influence the fracture toughness of HA materials is the term of temperature which changes in higher heat condition between 800 1300°C for different biomaterials [1 3]. Applying these parameters like sintering, change in morphology, grain size, composition allows the HA to be utilize for suitable artificial organs under high load bearing situation [3,
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12]. Here we illustrate a valuable reference data to predict enhanced mechanical blends of HA at high temperatures with different particle size. Such composites plan to hold their valuable bioactive properties whilst giving more suitable mechanical properties to specific applications. In addition, the improved fracture toughness is connected with the microstructure of the compacts. The objective of the current report was to investigate the fracture toughness HA added with some reinforcement and different sintering temperature and condition.
EXPERIMENTAL PROCEDURE (FRACTURE TOUGHNESS)
Fracture toughness (K IC ) play a vital role in the integrity mechanical reaction was determined by an indentation technique as proposed by Laugier and Evans [16] as following Eq. 1.
2/3 KIC = 0.015( ( Eq. (1) ) ) √ Where c is the crack length, a, the half of the diagonal indention, E, the Young’s modulus, H, the hardness, P, the load applied and y is a polynomial function of c . A standout amongst the most imperative controlling parameter that must be considered a amid the preparing of hydroxyapatite is the determination of suitable powder solidification/sintering system to get a strong, high thickness HA body that is portrayed by having fine microstructure. The most ordinarily utilized union strategy is the traditional sintering technique. In any case, this strategy frequently requires long sintering calendar, ordinarily above 18–24 h which thus bring about coarse grained microstructure and low mechanical properties. Thus, a more quick method, for example, microwave handling has been accounted for to create a thick sintered HA body that had fine microstructure combined with enhanced mechanical attributes. Sintering by microwave since heat is created inside of the material as opposed to being transmitted from outside the body as in routine sintering. The goal of the present work was to contemplate the impact of sintering on the densification and mechanical properties (fracture toughness) of nanocrystalline HA powder, bulk and coating arranged through a synthetic methodology.
Effect of sintering of ceramics (Fracture Toughness) Densification and mechanical properties of biomaterials that mixed showed a quick decrease in the crystallite size and improve the strength as shown in ref [3]. The decrease in crystallite size and synchronize strong arrangement of particles in the structure is obtained by suitable sintering system. At lower surface region for the powder may have been various charges phase transformation, the higher surface region for biomaterials powder my influence on lower mechanical and chemical stability of element [1 3]. Densification amid sintering is managed by mass exchange through instruments, for example, evaporation–condensation, surface dispersion, volume dissemination and grain limit dissemination [1, 4].
Finite element analysis (FEA) Applying finite element analysis to investigate distribution of stress in the contact area is useful technique. This comparison reveals that the shear testing consequences with the FEA records have a close correlation between the failure patterns and the stress distribution identified by the FEA [23].
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Fig. 1 Both the three point bending (1) test specimens (3×3×22 mm 3) and the symmetrical biomaterial (2) test specimens (2×6×20 mm 3) were tested at a load rate of 1mm/min [23]
In the work presented by other researchers with FEA study, a case study was conducted with an experimental work, Toparli and Aksoy [23] discover the validity of the fracture toughness and adhesive bond toughness of composite made of dentin resin interfaces from a fracture mechanics standpoint [figure 1 (1 2)]. The result of the work deal with fracture toughness (K IC ) and fracture energy (J IC ) range of two different composite by using single edge notch (SEN) specimens loaded in three point bending (Fig. 1 1). The result indicated the fracture loads in tension of bonded composite–dentin specimens (Fig. 1 2). The result for their work was not trustable for K IC values with the bonded samples, due to the crack occurred at interface of part [23].
Fig. 2 Concentration of stress in at elliptical defect, a=3b in Cartesian coordinate system [23].
According to the Inglis’ report [23] stress analyses of elliptical defects reveal their impact (Fig. 2). The ơ xx stress which is perpendicular to ơ yy , increase from zero to a sharp peak within a small distance from the flaw tip and subsequently drops toward zero with the same tendency as ơ yy as shown in figure 1 [23].
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Definition of fracture energy and toughness
Fracture energy (G) and fracture toughness (K IC ) are defined as important parameters which represent a fundamental introduction in fracture mechanics researches. A report released by Griffith [23] presented that K IC happens as enough mechanical energy is released from a stress field, type of energy that is required to create a fracture surface in the propagate of crack. This type of energy which released received from potential energy of the loading system. Recent work by Irwin declares that the stress field in the sharp crack in a linear elastic material could be uniquely defined by a parameter named the stress intensity factor, K [23]. According to Inglis’ analysis, the level of these stresses near to an elliptical crack in a bulk material (in tension) can be written as following:
a 1/2 σij =σ0( ) fij (θ) Eq. (2) 2r
where σij is the parts of the stress tensor at a certain area, ij , σ0 is the total level of applied stress, r and θ the polar coordinates of point i and j using the crack tip as the origin, and a shows half the length of the crack ( . These modified equations by ) Irwin are represented like equation 3:
K σij = ) fij (θ) Eq. (3) √ 2πr) Where K was represent as stress intensity factor. K relates to the magnitude of the stress intensity locally adjacent to the crack tip in terms of the applied loading and depends on crack geometry where it placed. As a result, for a crack occurred in the central region, above two equations can be mixed into one following equation 4:
1/2 K K= (aπ) Eq. (4) σ0 fij (θ)= fij (θ) or σ0 √2πr 1/2 where K = σ0(aπ) shows the fracture toughness of central crack. The following situation is connected with tension of the sample. Although, three various types of load conditions are available which leads to the initiate the cracks or propagate. The various three load conditions are denoted modes I, II and III as shown in figure 3.
Fig. 3 Failure modes in three load conditions. (A) Tensile force shows in mode I, (B) Shows shear force mode II, and (C) Shows torsional force mode III [23].
Also, one can say, crack propagates with three different load conditions denoted modes I, II and –III (Fig. 3) [23].
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Mechanical characteristic of sintered materials The sintered compacts created in authors work display a more noteworthy thickness and littler grain size than different reports [20]. It may be credited to processing of the calcined materials in ethanol which is isolates the crystallites and avoids agglomeration that generally happens because of the hygroscopic way of HA particles. The little size of grain extent in the sintered compacts recommends little impact on microhardness [9]. By considering the decreasing fractures toughness of mentioned is due to amorphous properties of zircon and it structured. In the case of when 15 wt% zircon was added to the HA under the same condition, the K IC average became 91 MPa. Difference is proper result in to find with the vicinity of the ZrO 2–Al 2O3 crystals safeguarded in the HA framework. As more increment in the containing of Zr powders, both the twisting quality and the crack strength disappeared. As the zircon increase into composite it shows that porosity starts to be increased. To solve this issue Al 2O3 can be added to ZrO 2 to decrease its negative results and improve the fracture toughness. Along these lines, Al 2O3 and ZrO 2 both influence quality and strength of HA composite. The compositional, thermal, mechanical and properties of HA/phosphate glass composites are connected with structural behaviour of particles which can be determined by various techniques like BET, PSA, SEM instruments [21]. As the reviews shows fabrication of composites bio ceramics glass increases the mechanical behaviour of product with simultaneous enhancements in hardness and toughness within 10 wt.% to the best potential average because of their close compositional similar to osseoconductive and reaction of biomaterials.
Toughness of sintered HA bodies The toughness result for sintered HA is represented that toughness has close relation with crystal diameter. The graph introduced that the HA toughness rise up, as the grain size of the materials decreased. The data shows the indentation toughness for the sample sintered at the 850°C have a grain size about 67 nm and toughness of 1.06 ±0.16 MPa m 1/2 which is 73.8% higher than the indentation toughness (0.61±0.04 MPam 1/2 ) of the 1200 °C sintered HA with an average grain size of 732 nm. Moreover, most of the toughness increase takes place in the range of grain sizes smaller than 141 nm above which the toughness appears to be independent of grain sizes. Reviewing substitution fluorine into HA show that manufactured FHA have improved structured for mechanical reaction like fracture toughness. The methodology used for the producing FHA and these types of CaPs is really influence the mechanical powder of powders. Constrained data on the impact of fluoride substitution for HA shows an improved the mechanical properties of HA in mechanical behaviour by adding second phase to HA. Crack durability is enhanced with fluorine consolidation into the cross section and achieves a crest of 1.8 for a 95% thick sintered pellet with a 60% fluoride substitution, trailed by a quick abatement at higher fluoride fixations [4]. High fluoride levels are unfavorable from a mechanical point of view, are not suggested for biomaterials, and can prompt a higher frequency of break where sodium fluorine, for treatment of osteoporosis, may create an exceptionally FHA [4].
Impact of sintering temperature The impact of sintering temperature of incorporated nanocrystalline HA was researched. The beginning powder was incorporated by means of a novel wet substance course [1 4]. HA compacts were arranged and sintered in climatic situation at different temperatures running from 900–1300 C. The outcomes reveals that fracture toughness reaches to 1.17MPa m 1/2 and °
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Young's modulus of above 110 GPa were acquired for HA sintered at temperature as low as 1050 C. According the fact that the Young's modulus expanded with expanding mass ° thickness, the hardness and crack fracture of the sintered material began to decay when the temperature was increase from 1000–1050°C in spite of displaying high densities 498% of hypothetical quality.
Sintering or non- sintering Although several recent studies show that there is a possible improvement in the hardness and toughness of HA with decreasing the grain size, but in some cases researchers illustrate some other result which is in contrast with the previous research or some other report there is no changes [3].
Table 1 Changing of fracture toughness at different temperature and value of hardness and fracture toughness of biomaterials in various research papers [1 4, 8 9, 20]. Powder type Temperature (°C) Young’s Hardness Fracture Toughness Ref. Modulus (GPa) (MPa m 1/2 ) Sintered Conventional 1100 87±4 508±40HV 0.77±0.12 [8],[9] HA HA+CaPO 4+ZrO 2 1100 130±6 5.5±0.5 GPa 1.60±0.21 [2] HA+CaPO 4 1100 103±9 5.7±0.3 GPa 1.17±0.11 HA 850 47 110 0.6 1 [1, 3] Diopside 1350 170 300 1.8 2.4 [9] Dense Bone 2 12 [20] sponge Bone Not observed [20] Magnesium 41 45 GPa 15 40 [22] Dentin 1.0–4.0 Ti-6Al-4V 110 117 55 115 [3] Co-Cr alloy 230 N/A [3] Stainless steel 189 205 50 200 [2] HA+CaP+ZrO 2 1100 108±4 5.2±0.2 GPa 1.41±0.11 [2]
Reported analysis that considers the sintering process in various temperatures (900 °C and 1200°C) for HA. It is obvious that at 900°C fewer cracks propagate and have a higher crack growth resistance more than the sample sintered at 1200°C. The reason for this phenomenon is the crack with a shorter length is created at 900°C sintered HA [3 5].
RESULTS Geometry of as-splashed powders and sintered Fig. 4 demonstrates the surface morphology of the as splashed particles. It is apparent that the particles are almost circular fit as a fiddle and the diopside particles (brilliant dabs) are consistently disseminated in the CaPs grid all through the volume of the powder particles.
Fracture toughness HA looks to be an important bio ceramic for biomaterials application like dentin and bones with proper biological behaviour. However the mechanical behaviour of HA in pure form is 1/2 weak and not able to have excellent fracture toughness (K IC ) more than 1.0 MPA m compared with authentic bone which is 2 12 MPa m 1/2 . The application of these types of powders, coatings, and low loaded porous implants are not enough strong. Due to improve the properties of HA ceramics, various reinforcements and additives have been developed (ceramic, metallic, or polymer). Pure HA and dense HA ceramics has K IC in the range
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amount of 0.8–1.2 MPa m 1/2 with an average of 1.0 MPa m 1/2 . As the porosity increases the KIC begins to decrease linearly.
A case study performed in powder sample A case study is performed in our previous works including powder preparation [1], coating [2 3], bulk materials [4]. Fatty calf bones are bought; the bones are boiled with hot water for several hours. The boiled bones were heated with direct heat. The result of heated bones (black ash) is milled with milling process to reach pure and homogeneous powder. The outcome is black bone ash was heated for 3 h at 750°C, 850 °C and 950 °C, Figure 4.
Fig. 4 Effect of sintering on the powder sample with various in HA microstructure heated for 3 h at 850 °C and composited with diopside powder
Table 2 Values crystallite size average at any given heat treatment [1]. Sintering heat (°°°C) and time (h) Length of particle (nm) 750 for 3 29 850 for 3 43 950 for 3 51 850 for 2 33 850 for 1 34
XRD patterns in figure 6 show a gradual sharpness peaks when the temperature increases, that showing the crystal grow of HAs. Relatively gradual decrease in β. Cosθ and almost increase in L values L = (const /. β .Cos θ ) is observed with the increase of 2θ. This is equivalent to ln β = .4 8149 (ln /1 Cos θ ) + ln Kλ / L . It is interesting to notice that although variations exist in lnβ values, but the intercept systematically changes as 5.1196, 5.5542, 5.6054 and 5.6276 respectively for 600, 700, 900 and 1100 °C [1 4]. The result of temperature versus length of the particle is represented in table 3 [1, 2].
Table 3 Treatment of linear plots to obtain nano size of crystallites [1 3].
kλ ln Temp ( °°°C) e L L (nm) − .5 1196 750 e = .0 006 24 800 e− .5 5542 = .0 00387 36 850 e− .5 6054 = .0 00368 38 1000 e − .5 16276 = .0 0036 39
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A case study performed in coated sample As the case of coated samples consideration to discover implant coating effect with EPD or plasma spray technique and effect of voltage on the surface modification, also a case study is conducted in which the specimen with different percentages of diopside (as a second phase) synthesized with mechanical activation process. The observation of were done by considering the cross section of scan electron microscopy (SEM) images after sintering the coated sample at 850°C. The results illustrate that sample which is coated with 50V were crack free although the sample with 40 V has a great crack (Figure 5) due to improper voltage and heavy particles in the ceramic solution [3, 9]. Data after this observation gathered and a clear results show that the optimum values for temperature are is 850°C in order to have surface without crack. The SEM micrograph reveals that particle size of the materials has a close correlation with temperature (sintering) which creating a crack in the coated sample [3]. It is obvious that with particles with the size of less than 1 µm have proper distribution in the ceramic solution for the sample composed of 30 wt% Di powder that has coated on the Ti alloy [3, 9].
Fig. 5 Effect of sintering on the coated sample with various % of diopside in HA microstructure in the paper published in ceramic international journal [1 3].
As mentioned above the maximum range for K IC is dedicated to fibers made of ceramic reinforced HA. However, there are several problems happened to coat ceramic powder to metallic implants, because of wear corrosion and other negative reaction. Most of the dental and orthopaedic implants are encapsulated by hard fibrous tissue which avoid suitable changes in stresses distribution and became one of implant loosening reason [3 6]. Also, the 1/2 vicinity of β TCP with K IC = 1.3 MPa m become more strong than HA, and would have been supporting to enhancing the typical fracture toughness. As the literature by other authors indicates little amount of bioactive glass (BG) are mixed to HA powder leads to enhance the solidification and improved the fracture toughness for pure HA. K IC factor for bio ceramics is a certain amount with minimum of 1.0 1.7 MPa m 1/2 . In some case, as the fracture toughness increases the strength has been increases. Typically, addition of BG powder enhances decomposition of HA in great percentages. Nanocomposite HA with polyethylene additive show brittle/ductile transition at a HA volume content of about 40–45% [8]. Compared with cortical bone these nanobio composites have shown an excellent K IC for HA lower than 40% and same K IC in the range of 45–50%. Young’s modulus of these types of additives is in the range of 1–8 GPa, which is quite close to the Young’s modulus of bone. However, such additive like polyethylene’s which reinforced HA are not biodegradable [8]. Moreover, the presence of bio inert polyethylene decreases the ability to bond to the bone [8]. Also, other drawback is for coated metals implant with polyethylenes and load bearing approaches in
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comparison with polymeric biomaterials causes to their adding of higher strength and K IC . These days, it is recommended for bio metallic such as stainless steels (SS 316 L), titanium (Ti 6Al 4V) and cobalt–chromium based alloys to coat with these types of bio ceramic with high fracture toughness properties. However, these bio metallic have some problem like possible release of toxic metallic ions and subsequently wear resistance and negative corrosion which may influence to solve by coating. To summarize the influence of composition and sintering on fracture toughness of HA structure, it is shown that the toughness and durability of the sintered HA at 1200°C is close to the other researcher reports by various agents for high sintered HA is about 0.6 MPa m 1/2 and sintered HA fracture toughness about ≤ 0.73 MPa m 1/2 . Reports indicated that process of spark plasma sintering (SPS) of HA is about 1.0–1.4 MPa m 1/2 [20] and 1.15–1.25 MPa m 1/2 . A similar pattern is discovered, that shows correlations between SPS process and higher strength of materials especially fracture toughness more than other technique like conventional sintering and hot pressing sintering. The grain size average of materials starts to decrease to 50 nm for HA and 1/2 leads to K IC 1.52 MPa m . These averages reach us to the conclusion that the strength of HA increments with diminishing grain size in the nano meter range is higher.
CONCLUSION Biomaterial fracture toughness behaviour To understand better definition of fracture toughness the following aspect should be considered: Local stress and growth of crack occurred as a fracture toughness in the case of fracture mechanics. Also, one can say a part does not damage or ruin instantaneously; it destroys as a local area start to create a crack and propagate. Basic description of fracture mechanics describes that internal properties of biomaterials like porosity, Gc, Kc can be measured and evaluate to discover different materials reaction. From these parameters is correlate with thermodynamic approach. Several modes of failure are happens in fracture mechanics of materials. When the crack propagates in near to an interface, the various failure modes can contribute to crack propagation.
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[4] Khandan, A., Karamian, E., & Bonakdarchian, M. (2014). Mechanochemical synthesis evaluation of nanocrystalline bone derived bioceramic powder using for bone tissue engineering. Dental Hypotheses, 5(4), 155. [5] Fathi, M. H., & Hanifi, A. (2007). Evaluation and characterization of nanostructure hydroxyapatite powder prepared by simple sol–gel method.Materials letters, 61(18), 3978 3983. [6] Lopes, M. A., Monteiro, F. J., & Santos, J. D. (1999). Glass reinforced hydroxyapatite composites: fracture toughness and hardness dependence on microstructural characteristics. Biomaterials, 20(21), 2085 2090. [7] Abdellahi, M., & Bahmanpour, M. (2014). A novel technology for minimizing the synthesis time of nanostructured powders in planetary mills. Materials Research, 17(3), 781 791. [8] Bonfield, W. (1988). Hydroxyapatite‐Reinforced Polyethylene as an Analogous Material for Bone Replacementa. Annals of the New York academy of sciences, 523(1), 173 177. [9] Khandan, A., Abdellahi, M., Ozada, N., & Ghayour, H. (2015). Study of the bioactivity, wettability and hardness behaviour of the bovine hydroxyapatite diopside bio nanocomposite coating. Journal of the Taiwan Institute of Chemical Engineers. [10] Choe, H., Inaba, Y., Kobayashi, N., Miyamae, Y., Ike, H., & Saito, T. (2015). Clinical utility of antibiotic loaded hydroxyapatite block for treatment of intractable periprosthetic joint infection and septic arthritis of the hip. Modern Rheumatology, (0), 1 6. [11] Tan, C. Y., Singh, R., Teh, Y. C., Tan, Y. M., & Yap, B. K. (2015). The Effects of Calcium‐to‐Phosphorus Ratio on the Densification and Mechanical Properties of Hydroxyapatite Ceramic. International Journal of Applied Ceramic Technology, 12(1), 223 227. [12] Karamian, E., Khandan, A., Kalantar Motamedi, M. R., & Mirmohammadi, H. (2014). Surface characteristics and bioactivity of a novel natural HA/zircon nanocomposite coated on dental implants. BioMed research international, 2014. [13] Singh, S., Kumar, R. M., Kuntal, K. K., Gupta, P., Das, S., Jayaganthan, R., ... & Lahiri, D. (2015). Sol–Gel Derived Hydroxyapatite Coating on Mg 3Zn Alloy for Orthopedic Application. JOM, 67(4), 702 712. [14] Niakan, A., Ramesh, S., Ganesan, P., Tan, C. Y., Purbolaksono, J., Chandran, H., & Teng, W. D. (2015). Sintering behaviour of natural porous hydroxyapatite derived from bovine bone. Ceramics International, 41(2), 3024 3029. [15] Abdellahi, M. (2013). A new predictive model for calculating the hardness of metal matrix nanocomposites produced by mechanical alloying. Journal of Materials Research, 28(23), 3270 3278. [16] Laugier, M. T. (1987). New formula for indentation toughness in ceramics.Journal of materials science letters, 6(3), 355 356. [16] Evans, A. G. (1979). Fracture toughness: the role of indentation techniques.Fracture mechanics applied to brittle materials, 678, 112. [17] Suzuki, O. (2010). Octacalcium phosphate: osteoconductivity and crystal chemistry. Acta biomaterialia, 6(9), 3379 3387.
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[18] Grandjean Laquerriere, A., Laquerriere, P., Laurent Maquin, D., Guenounou, M., & Phillips, T. M. (2004). The effect of the physical characteristics of hydroxyapatite particles on human monocytes IL 18 production in vitro.Biomaterials, 25(28), 5921 5927. [19] Khandan, A., Karamian, E., Mehdikhani Nahrkhalaji, M., Mirmohammadi, H., Farzadi, A., Ozada, N., ... & Zamani, K. (2015). Influence of Spark Plasma Sintering and Baghdadite Powder on Mechanical Properties of Hydroxyapatite.Procedia Materials Science, 11, 183 189. [20] Khandan, A., Ozada, N., & Karamian, E. (2015). Novel Microstructure Mechanical Activated Nano Composites for Tissue Engineering Applications. J Bioengineer & Biomedical Sci, 5(143), 2. [21] Razavi, M., Fathi, M., Savabi, O., Razavi, S. M., Beni, B. H., Vashaee, D., & Tayebi, L. (2013). Surface modification of magnesium alloy implants by nanostructured bredigite coating. Materials Letters, 113, 174 178. [22] Mobasherpour, I., Hashjin, M. S., Toosi, S. R., & Kamachali, R. D. (2009). Effect of the addition ZrO2–Al2O3 on nanocrystalline hydroxyapatite bending strength and fracture toughness. Ceramics International, 35(4), 1569 1574.
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