Browsing by Author "Topuz, Mehmet"

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Al-5cu/B4cp Composites: the Combined Effect of Artificially Aging (T6) and Particle Volume Fractions on the Corrosion Behaviour
(Elsevier, 2020) Tozkoparan, Burak; Dikici, Burak; Topuz, Mehmet; Bedir, Fevzi; Gavgali, Mehmet
In this study, the Al-5Cu matrix composites reinforced with different boron carbide (B4C) particle volume fractions have been successfully produced by the hot-pressing method. Then, the artificially aging (T6) was applied to the composites for increasing their mechanical properties. The combined effect of the T6 heat treating and the B4C particle volume fraction on the corrosion behaviour of the composites were investigated by potentiodynamic scanning (PDS) technique under aerated and deaerated 3.5% NaCl marine environments. The effect of the T6 treating on the hardness and corrosion susceptibilities of the composites were also evaluated microstructurally to contribute to their industrial use and production processes. The microstructural characterization of the composites was carried out by using a scanning electron microscope (SEM) with an attached energy dispersive spectrum (EDS) and X-ray diffraction (XRD). It was found that the corrosion susceptibilities of the composite have been interestingly decreased with increasing the B4C particle volume fraction in the matrix while the T6 treatment enhances the pitting susceptibility of the composites. The reason of the behaviour has been discussed in details the text. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.
Cytotoxicity and Antibacterial Activity of Polyhedral Oligomeric Silsesquioxane Modified Ti3c2tx Mxene Films
(Nature Portfolio, 2025) Akinay, Yuksel; Karatas, Erkan; Ruzgar, Damla; Akbari, Ali; Baskin, Dilges; Cetin, Tayfun; Topuz, Mehmet
Bioactive antimicrobial films play important roles in various fields, such as biodegradable interfaces, tissue regeneration, and biomedical applications where preventing infection, biocompatibility, and immune rejection are important. In the present study, bioactive POSS-doped Ti3C2Tx MXene filled PLA composite film was prepared using the solution casting method for biomedical applications. The contact angle tests were investigated to reveal the usability of the thin films in biomedical applications. The angle decreased from 85.92 degrees degrees in pure PLA thin films to 72.23 degrees on POSS-doped Ti3C2Tx MXene films. The antibacterial performance, cytotoxicity and cell viability assessments of the prepared films have also been thoroughly investigated. Antibacterial tests revealed that the POSS-doped Ti3C2Tx MXene films effectively inhibited the growth of E. coli and S. aureus by 65.93% and 80.63%, respectively, within 4 h. These inhibition rates were observed as 58.32% and 54.97% for E. coli and S. aureus, respectively, after 24 h. Cytotoxicity assessments demonstrated that PMPs consistently showed higher cell viability due to the combination of POSS and Ti3C2Tx MXene. The obtained results suggest that the POSS-doped Ti3C2Tx MXene film is a promising candidate in cases where bacterial inhibition and high biocompatibility are of critical importance.
Effect of Hydroxyapatite:zirconia Volume Fraction Ratio on Mechanical and Corrosive Properties of Ti-Matrix Composite Scaffolds
(Elsevier, 2022) Topuz, Mehmet; Dikici, Burak; Gavgali, Mehmet; Yilmazer, Yasemin
Ti-based scaffolds reinforced with zirconia and hydroxyapatite were produced successfully by a hybrid method with an eco-friendliness and low cost to obtain low elastic modulus (E) with sufficient physical, electrochemical and biological properties. The effect of simultaneous modification of the volume fraction of hydroxyapatite (HA) and zirconia (ZrO2) on scaffolds was investigated in terms of mechanical, corrosive, and antibacterial properties. Scanning electron microscopy with attached electron dispersive spectroscopy and X-ray diffraction were used for the characterization of scaffolds. Compression and electrochemical tests were performed to determine mechanical properties with detailed fracture mechanism and in-vitro corrosion susceptibility to simulated body fluid at 37 degrees C, respectively. Antibacterial tests were carried out by comparing the inhibition areas of E.coli and S.aureus bacteria. It was observed that the mechanical strength of the scaffolds decreased with increasing HA:ZrO2 volume fraction ratio. The lowest E was achieved (6.61 GPa) in 6:4 HA:ZrO2 composite scaffolds. Corrosion current density (J(corr)) values were calculated to be 21, 337, and 504 mu A/cm(2) for unreinforced Ti, 3:2 and 6:4 HA:ZrO2 reinforced scaffolds, respectively. The inhibition capacity of the 6:4 reinforced composite scaffold was found to be more effective against S.aureus bacteria than other scaffolds.
Hidroksiapatit Kaplanmış Al2024'ün Simüle Edilmiş Vücut Sıvısında İn-vitro Korozyon Performansı: Karşılaştırmalı Bir Çalışma
(2023) Topuz, Mehmet; Dikici, Burak
Bu çalışmada, hidroksiapatit (HA) kaplamaların Al-Cu-Mg alaşımları (Al2024) üzerine uygulanabilirliği elektrokimyasal tekniklerle incelenmiştir. Kaplanan tabakaların yapısal karakterizasyonları SEM, EDS ve XRD test/analizleri ile incelenmiştir. Yüzey adezyon direnci ve elektrokimyasal bozunma davranışı, sırasıyla çizilme ve potansiyodinamik tarama (PDS) testleri ile test edilmiştir. Al2024 yüzeylerinde HA kaplamanın homojen bir yapıya sahip olduğu ancak kesit görüntülerinden bazı lokal bölgelerin yeterince HA ile kaplanamadığı görülmüştür. Ayrıca kaplama yüzeyleri, HA kaplamalara özgü mikro gözenekli morfolojiye sahip olduğu tespit edilmiştir. Kaplamanın çizilme testi sonuçlarından, kritik yük direncinin (Lc1), 12N’un biyomedikal uygulamalar için yeterli olacağı öngörülmüştür. Elektrokimyasal korozyon testleri, HA kaplamanın Al2024 alaşımının korozyon akımı yoğunluğunu (Icorr) ve korozyon oranını azalttığını ortaya çıkarmıştır (HA kaplı ve kaplanmamış Al2024 alaşımı için sırasıyla 0,885 ve 5,260 µA·cm-2). Ancak HA kaplama ile elde edilen düşük Icorr değerine rağmen hem Icorr hem de pasivasyon akım yoğunluğu (Ipass) değerlerinin (HA kaplama için 3,15 µA·cm-2, farklı titanyum türleri için 0.03 ila 0.08 µA·cm-2) olduğu gözlemlenmiş olup ticari titanyum alaşımlarına kıyasla yetersiz olduğu ortaya çıkarılmıştır.
Hydroxyapatite - Al2o3 Reinforced Poly- (Lactic Acid) Hybrid Coatings on Magnesium: Characterization, Mechanical and In-Vitro Bioactivity Properties
(Elsevier, 2023) Topuz, Mehmet
Hydroxyapatite - Al2O3 reinforced poly- (lactic acid) hybrid coating was synthesized on magnesium in this research, which was carried out to obtain improved interface strength and higher corrosion properties with a lower dissolution rate of magnesium. Compared to uncoated magnesium substrates, HA and HA/Al2O3 coatings were synthesized by dissolving PLA in chloroform and adding reinforcement materials. Coatings were produced on magnesium using the spin-coating technique of the synthesized solutions. Characterization (FTIR, SEM/EDX, XRD, and contact angle analyses), mechanical (tape tests and micro-Vickers hardness), and in-vitro bioactivity (immersion tests) features of the hybrid coatings were investigated. XRD results showed that no phase trans-formation occurred in the coatings. In addition, it was determined that the PLA coating was effective in covering the surfaces of Mg substrates. With the reinforcement of HA, CaPs were formed on the surface, but the adhesion strength was reduced (2B). With the addition of HA/Al2O3, the surface properties are preserved, and the adhesion strength increased (4B). In electrochemical corrosion behavior, a decrease was observed in corrosion current density (I-corr) values with the coatings compared to the uncoated Mg alloy (249.848, 1.659, 0.246, and 0.136 mu A center dot cm(-2) for uncoated, PLA coated, PLA-HA coated, and PLA-HA/Al2O3 coated, respectively), and the corrosion resistance increased. Especially, the Icorr value obtained with the Al2O3 reinforcement was measured quite low compared to previous studies using PLA-HA composite coatings, and it was determined that the corrosion resistance was increased. As a consequence of SBF immersion tests, while more CaPs were found on the surfaces of PLA-HA coatings, deep crack formation was found on the surface. Although fewer CaPs were observed with HA/Al2O3 additive, no cracks that would increase adhesion were formed and it was predicted that the degradation rate of Mg could be controlled. In the hardness measurements, it was found that the hardness value increased from 137.7 +/- 5.7 to 268.7 +/- 3.6 HV with the addition of HA/Al2O3 so it can be applied in wear-sensitive areas. In the pH changes during the SBF immersion tests, the average of the PLA-HA/Al2O3 coatings was 7.4 during the 15-day period. It has been determined that this value will not cause any adverse reactions in tissue interaction during the use of Mg in the body. Moreover, according to H-2 evolution measurements, all coated samples have lower H-2 gas evolution than uncoated Mg. As a result, it was thought that Mg will strengthen its place in potential implant applications thanks to hybrid coating compositions such as PLA-HA/ Al2O3.
Investigation of Halloysite Nanotube Effect in Poly- (Lactic Acid)/Hydroxyapatite Coatings on Ti-6al Biomedical Alloy
(Springer, 2023) Topuz, Mehmet
Due to their biodegradable nature and enhanced adhesive strength at the interface, poly- (lactic acid) (PLA) based coatings are frequently used in biomedical alloys. But it is unable to create metal-tissue interaction because of its very hydrophobic surface feature. Researchers are therefore looking at composite coatings that are reinforced with hydroxyapatite (HA). In this study, the effect of halloysite nanotube (HNT) was investigated to hydroxyapatite (HA) reinforced PLA coatings synthesized on Ti-6Al-4V (Ti64) biomedical alloy. Investigations were conducted on the hybrid coatings' characterization such as SEM/EDS, FTIR, contact angle tests, and XRD analyses. Adhesion tests at alloy-coating interface were revealed with ASTM D3359-09 standards. In-vitro electrochemical corrosion tests (ASTM-G59) and immersion tests (ISO-23317) were conducted on coatings for reveal both biodegradability and osteoconductivity behaviours of coatings. SEM morphologies revealed that surfaces have micron-sized pores on both coatings. But HA/HNT reinforced coatings have more homogenous morphology with decreased pore size. The elemental distribution of coatings was confirmed by the EDS analyses. While FTIR research demonstrated a variation in the influence of HNT on the coating of PLA depending on the bond status, XRD results showed that there were no phase changes in the coatings. It was found that coatings with HNT reinforcement, have higher adhesion strength at the substrate-coating interface (1B for HA and 4B for HA/HNT reinforced coatings). Following in-vitro electrochemical corrosion experiments, it was discovered that the corrosion current density (I-corr) value reduced even more with the PLA/HA-HNT coating (1.784, 0.245, and 0.032 mu A cm(-1)) than it did with the PLA/HA coating alone. The results of the impedance spectroscopy (Nyquist curves) confirmed that the coatings' corrosion resistance increased as the I-corr value decreased. Possible corrosion mechanism was discussed with equivalent circuit model which consist two-constant elements. It was found that both coatings exhibited a characteristic that induced calcium phosphates (CaPs) on their surfaces after in-vitro immersion tests. The contact angle tests revealed that the high hydrophobic effects of coatings would have a positive effect on the alloy-tissue interaction in the long term due to the bioactive compounds that they have. The dense and homogeneous CaPs in the PHH coatings increased with HNT reinforcement, leading to more effective interaction with surrounding tissues during in-vitro tests. The findings led to the conclusion that the hybrid coatings produced with the reinforcement of HA/HNT will not readily delaminate during application and will improve the interaction between the alloy and the tissue under prolonged physiological conditions. [GRAPHICS] .
Processing of Ti/(ha+zro2) Biocomposite and 50% Porous Hybrid Scaffolds With Low Young's Modulus by Powder Metallurgy: Comparing of Structural, Mechanical, and Corrosion Properties
(Elsevier, 2021) Topuz, Mehmet; Dikici, Burak; Gavgali, Mehmet; Kaseem, Mosab
Processing of titanium (Ti)-based implants with improved corrosion resistance and Young's modulus close to that of cortical bone are receiving considerable attention in orthopedic and dental applications. Therefore, Ti matrix, hydroxyapatite (HA) and hydroxyapatite-zirconia (HA+ZrO2) reinforced composites were successfully produced using powder metallurgy as both bulk and 50% in vol. porous scaffold in this study. Microstructure, mechanical and corrosion properties of the bulk and scaffold composites were investigated comparatively. Scanning electron microscopy with attached an energy dispersive spectroscopy (SEM-EDS) and XRD diffraction analysis was used for the characterization of samples. Mechanical properties were determined by using micro Vickers hardness and compressive tests. Besides, the corrosion behaviours of the samples were determined in simulated body fluid (SBF) at 37 degrees C by using potentiodynamic scanning (PDS) tests. Room-temperature compression tests revealed that the bulk samples had higher values of Young's modulus and yield strength in comparison to the scaffold samples where the lowest values of Young's modulus and yield strength of 3 GPa and 6.93 MPa, respectively were obtained in the case of the Ti/(HA+ZrO2) composite scaffold. Moreover, in-vitro corrosion tests in SBF showed that the Ti/(HA+ZrO2) composite scaffold had higher corrosion resistance than the scaffold reinforced with only the HA phase. The corrosion mechanism of the bulk and scaffold samples was also elucidated by taking the microstructural analysis and phase compositional of the samples into account.
Production of Annealed Cold-Sprayed 316l Stainless Steel Coatings for Biomedical Applications and Their In-Vitro Corrosion Response
(Maik Nauka/interperiodica/springer, 2018) Dikici, Burak; Topuz, Mehmet
316L powders were successfully deposited onto Al5052 aluminium substrates by cold spray method. Annealing was treated on the coated samples at 250-1000A degrees C temperatures under Ar atmosphere. The in vitro performances of the coatings have been compared with using electrochemical corrosion test technique in the simulated body fluid (SBF) at body temperature (37A degrees C). A scanning electron microscope (SEM-EDS) and X-ray diffraction (XRD) have been used for microstructural characterization and phases identifications of the coatings, respectively. The results were shown that there are high adhesions at particle and substrate interfaces and between the particles deposited as well. Also, the increasing annealing temperature increases corrosion resistance of the cold sprayed 316L stainless steel coatings. The corrosion susceptibility of the coating annealed at 1000A degrees C was similar that of standard 316L stainless steel implant material in Ringer's solution. The microstructural observations revealed that corrosion starts between the inter-splat powders and continues throughout the surface not in-depth.
Simultaneous Effect of Welding Current With Postweld T6 Heat Treatment on Corrosion Susceptibility of Al6013 Alloy Joined by Gtaw
(2023) Topuz, Mehmet
Al6013 base metals were joined successfully with ER4047 weld metal by using the GTAW method under different welding currents. Post-weld T6 heat treatment effects on corrosion properties were investigated in terms of open circuit potential (OCP), potentiodynamic polarization (PDS), and electrochemical impedance spectroscopy (EIS) tests. It was determined that corrosion resistance of the post-weld samples increased with increasing welding current, while T6 heat-treatment only effective on 110A and 140A welding current samples (3.61 to 2.08, 2.95 to 2.40, and 1.38 to 2.15 µA·cm-2 for 110, 140, and 170A welding current before and after T6 heat-treatment). The characteristics of the oxide films on the surfaces are revealed with EIS analysis by a two-constant equivalent circuit model which observed that while the passive film originating from Al is formed on the surfaces, on the other hand, it contains a pittings on the surface. It was determined that the pitting resistance of the T6 heat-treated 110A samples increased (3075 to 4562 Ω). Post-corrosion SEM surface morphologies showed that low welding currents lead to more damage with increased exposure to corrosion.
Sustainable Walnut Shell-Filled Polylactic Acid-Hydroxyapatite Hybrid Coatings for Enhanced Corrosion Resistance and Bioactivity of Magnesium Biomaterials
(Wiley, 2025) Topuz, Mehmet; Topuz, Fatma Coskun; Dikici, Burak; Seifzadeh, Davod
Due to the high corrosion rate and limited biocompatibility of commonly used magnesium (Mg) and its alloys, current studies have focused on surface modification techniques. In this study, which is aimed at overcoming these obstacles in biomedical applications, hybrid coatings of PLA-HA-Walnut shell (Wshell) were successfully applied to Mg substrates. The presence of micropores on the surfaces of the hybrid coatings was detected using SEM surface morphology, and the elemental composition and structural characterization of the coatings were confirmed through analyses. With a higher Wshell fraction, the corrosion current density decreased significantly compared to uncoated Mg and PLA-coated Mg, increasing the electrochemical corrosion resistance of Mg. The adhesion strength between the coatings and the Mg substrates increased to grade 3B with Wshell-filled hybrid coatings. Moreover, the contact angle of PLA-coated Mg decreased as the Wshell fraction increased, indicating enhanced surface wettability. Wshell hybrid coatings exhibit fibrous morphology and the formation of Ca- and P-rich layers. These results, along with the filling of Wshell, suggest that PLA-HA-Wshell hybrid coatings could be a promising additive material for potential next-generation low-cost and sustainable biomedical coatings to enhance the corrosion resistance and bioactivity of Mg.
Synthesis of Biphasic Calcium Phosphate (Bcp) Coatings on Β-Type Titanium Alloys Reinforced With Rutile-Tio2 Compounds: Adhesion Resistance and In-Vitro Corrosion
(Springer, 2018) Dikici, Burak; Niinomi, Mitsuo; Topuz, Mehmet; Koc, Serap Gungor; Nakai, Masaaki
In this study, beta( )type Ti-29Nb-13Ta-4.6Zr alloys coated with biphasic calcium phosphate (BCP) reinforced with rutile-TiO2 compounds by sol-gel technique to evaluate its possible usage in biomaterial science. Calcium nitrate tetrahydrate (Ca(NO3)(2)center dot 4H(2)O), di-ammonium hydrogen phosphate (NH4)(2)HPO4), ammonium hydroxide (NH4OH), and titanium (IV) propoxide (Ti(OC3H7)(4)) (Merck, Germany) were used as precursors for producing the BCP-only and BCP/TiO2 composite coatings. Synthesis and coating procedure, surface morphology, adhesion strength, and corrosion results of the coated samples have been investigated in details. XRD technique has been used in order to characterization of BCP phases. The morphological observations of coatings were determined by using a scanning electron microscopy (SEM). In-vitro corrosion behaviors of the coatings have been determined with polarization method in Ringer's electrolyte at body temperature. It was found that the BCP/TiO2 coating synthesized on TNTZ alloy has higher scratch resistance than BCP-only coating due to its containing rutile-TiO2 compounds. In addition, it can be said that the BCP/TiO2 coated sample was less susceptibility to corrosion than the BCP-only coatings and uncoated TNTZ sample in simulated body fluid. [GRAPHICS] .
Ti 3 C 2 T X Mxene-Functionalized Hydroxyapatite/Halloysite Nanotube Filled Poly- (Lactic Acid) Coatings on Magnesium: in Vitro and Antibacterial Applications
(Keai Publishing Ltd, 2024) Topuz, Mehmet; Akinay, Yuksel; Karatas, Erkan; Cetin, Tayfun
Magnesium (Mg) stands out in temporary biomaterial applications due to its biocompatibility, biodegradability, and low Young's modulus. However, controlling its corrosion through next-generation polymer-based functional coatings is crucial due to the rapid degradation behavior of Mg. In this study, the function of 2D lamellar Ti3 C2 Tx (MXene) in Hydroxyapatite (HA) and Halloysite nanotube (HNT) hybrid coatings in biodegradable poly- (lactic acid) (PLA) was investigated. The morphological and structural characterizations of the coatings on Mg were revealed through HRTEM, XPS, SEM-EDX, XRD, FTIR, and contact angle analyses/tests. Electrochemical in vitro corrosion tests (OCP, PDS, and EIS-Nyquist) were conducted for evaluate corrosion resistance under simulated body fluid (SBF) conditions. The bioactivity of the coatings in SBF have been revealed in accordance with the ISO 23,317 standard. Finally, antibacterial disk diffusion tests were conducted to investigate the functional effect of MXene in coatings. It has been determined that the presence of MXene in the coating increased not only surface wettability (131 degrees, 85 degrees, 77 degrees, and 74 degrees for uncoated, pH, PHH, and PHH/MXene coatings, respectively) but also increased corrosion resistance (1857.850, 42.357, 1.593, and 0.085 x 10-6 , A/cm2 for uncoated, pH, PHH, and PHH/MXene coatings, respectively). It has been proven that the in vitro bioactivity of PLA-HA coatings is further enhanced by adding HNT and MXene, along with SEM morphologies after SBF. Finally, 2D lamellar MXene-filled coating exhibits antibacterial behavior against both E. coli and S. aureus bacteria. (c) 2024 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ ) Peer review under responsibility of Chongqing University
Ti2ntx Mxene Materials Derived From Ti2aln Max Phases: Their Characterization and Electrocatalytic Activity Toward Hydrazine Electrooxidation
(Pergamon-elsevier Science Ltd, 2024) Ulas, Berdan; Cetin, Tayfun; Topuz, Mehmet; Akinay, Yuksel
Nitride-based MXenes materials are promising for advancing technological developments, especially in popular scientific fields such as energy storage and conversion. This study successfully synthesized 2D lamellar Ti2NTx 2 NTx MXenes via selective etching of Al from the Ti2AlN 2 AlN MAX phase. Synthesized Ti2NTx 2 NT x MXene was characterized by field emission scanning electron microscope with energy-dispersive X-Ray spectroscopy attachment (FESEMEDX), X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) analyses techniques in details. 2D lamellar morphology of MXene phase was observed with FESEM, while distinctive diffraction peaks were confirmed with XRD analyses. While the BET surface area of the MAX phase was 0.5375 m2/g, 2 /g, it was measured as 2.0867 m2/g 2 /g with Ti2NTx 2 NT x MXene which increased by 3.88 times. Ti-O-N, Ti-N, and surface functional groups (Tx: x : OH, -F, -O) of Ti2NTx 2 NT x MXenes were revealed with XPS analyses. (112) crystal plane associated interplanar d-space (0.243 nm) was observed with HRTEM results. The electrocatalytic activity of synthesized Ti2NTx 2 NT x MXene was investigated by hydrazine electrooxidation. The Ti2NTx 2 NT x electrocatalyst exhibited a specific activity of 2.739 mA/cm2 2 and mass activity of 44.1 mA/mg for hydrazine electrooxidation. Ti2N 2 N also showed long-term stability compared to Ti2AlN. 2 AlN.
Titanium-Based Composite Scaffolds Reinforced With Hydroxyapatite-Zirconia: Production, Mechanical and In-Vitro Characterization
(Elsevier, 2021) Topuz, Mehmet; Dikici, Burak; Gavgali, Mehmet
In this study, titanium (Ti)-based composite scaffolds reinforced with hydroxyapatite-zirconia (HA-ZrO2) were successfully produced with powder metallurgy and atmosphere-controlled sintering processes. The scaffolds structures were theoretically selected as 40% and 60% porosity, and fabricated with approximately 1.47 and 4.02 std dev values, respectively. The porosity of the scaffolds was verified by Archimedes? measurements. The scaffolds were characterized by DTA, SEM/EDS, XRD analyses. The mechanical behaviors of the scaffolds were evaluated by compression and hardness tests. Besides, the electrochemical corrosion behaviors of the structures were compared with potentiodynamic scanning (PDS) measurements in simulated body fluids (SBF) at 37 ? 1 ?C. It has been observed that all scaffolds have a bimodal porous structure as they contain varying proportions of micropores as well as macropores in desired dimensions. Biocompatible phases such as TixPy, Ca3(PO4)2 and CaTiO3, respectively, were found in the microstructure after sintering. In compression tests, 40% porous Ti had the highest strength with 37.98 MPa, interestingly, the lowest strength was seen in Ti/HA-ZrO2 scaffold with 60% porosity with 3.80 MPa. Young?s modulus values of all scaffolds vary between 1.67 - 7.20 GPa, due to the bimodal pore structure and composition effect. However, in-vitro corrosion resistance of scaffolds decreased with HA reinforcement, while increased with ZrO2 additive to HA.