Prof. Mieczysław JURCZYK, M.Sc.(Eng.) Katarzyna NIESPODZIANA Institute of Materials Science and Engineering, Poznań University of Technology, Poznań
Dentist Karolina JURCZYK
Department of Conservative Dentistry and Periodontology, Poznań University of Medical Sciences, Poznań
Novel Ti-based nanocomposites
for medical applications
Nanokompozyty tytanowe do zastosowań w medycynie
AbstractTitanium and titanium alloys possess favorable properties, such as relatively low modulus, low density, high strength. Apart from that, these alloys are generally regarded to have good biocompatibility and high corrosion resistance, but cannot directly bond to the bone. In addition, metal implants may loose and even separate from surrounding tissues during implantation. One of the methods that allow the change of bio-logical properties of Ti alloys is to produce a composite, which will exhibit the favorable mechanical prop-erties of titanium and excellent biocompatibility and bioactivity of ceramic.
Recently, at Poznan University of Technology, mechanical alloying method (MA) and powder metallurgy process for the fabrication of novel titanium-ceramic nanocomposites with a unique microstructure has been developed. This process permits the control of microstructural properties such as the size of pore openings, surfaces properties, and the nature of the base metal/alloy. In our work, the structure, mechanical, corrosion properties and biocompatibility of titanium-ceramic nanocomposites were studied. For example, the Ti-HA nanocomposites mainly consist of different apatite or calcium particles, respectively, reinforced with titanium matrix. The existence of Ti can promote decomposition of HA, however no reactions form between HA and Ti. Different phase constitutions have significant influence on the mechanical and corro-sion properties of sintered materials. The biocompatibility was investigated studying the behaviour of Nor-mal Human Osteoblast (NHOst) cells, as well. Ti-ceramic nanocomposites posses better mechanical and cor-rosion properties than microcrystalline titanium. For this reason, they are promising biomaterial for use as medical implants.
Streszczenie
Tytan i stopy tytanu charakteryzują szeregiem korzystnych własności takich jak niski moduł spręŜystości, mała gęstość, wysoka wytrzymałość. Powszechnie uwaŜa się, Ŝe stopy te maja dobrą biokompatybilność i odporność korozyjną lecz nie mogą bezpośrednio łączyć się z kością. JednakŜe, implanty metalowe w cza-sie uŜytkowania mogą się obluzowywać a nawet oddzielać od otaczającej tkanki. Jedną z metod, pozwala-jącą na zmianę własności biologicznych stopów tytanu, jest wytwarzanie kompozytów, które będą łączyć korzystne własności wytrzymałościowe tytanu z doskonałą biokompatybilnością i bioaktywnością ceramiki. Ostatnio, w Instytucie InŜynierii Materiałowej Politechniki Poznańskiej opracowano technologię wytwa-rzania nowych nanokompozytów tytanowo-ceramicznych metodą mechanicznej syntezy i metalurgii prosz-ków. Procesy te umoŜliwiają kontrolę własności mikrostruktury takich jak wielkość por i własności po-wierzchni. W niniejszej pracy zbadano własności strukturalne, mechaniczne, korozyjne i biokompatybilność kompozytów tytanowo-ceramicznych. Przykładowo, nanokompozyty typu Ti-HA zbudowane są głównie z cząstek róŜnego rodzaju apatytów i wapnia rozłoŜonych w osnowie tytanowej. Obecność tytanu moŜe powodować rozkład HA, jednakŜe reakcja pomiędzy HA i Ti nie jest obserwowana. RóŜna budowa fazowa syntetyzowanych materiałów ma znaczący wpływ na ich własności mechaniczne i odporność korozyjną. Zbadano równieŜ biokompatybilność kompozytów w hodowli komórek ludzkich osteoblastów. Wytworzone nanokompozyty tytanowo-ceramiczne posiadają lepsze własności mechaniczne i korozyjne w porównaniu do mikrokrystalicznego tytanu. Z tego względu mogą stać się perspektywicznymi biomateriałami do zasto-sowań na implanty medyczne.
Key words:nanotechnology, nanocomposites, titanium, hydroxyapatite, biocompatibility, mechanical alloying
1. INTRODUCTION
The present work aims to fabricate Ti-based porous scaffolds to promote bone or tissue ingrowth into pores and provide bio-logical anchorage. Several factors have shown their influence on bone ingrowth into porous implants, such as porous structure (pore size, pore shape, porosity and interconnecting pore size) of the implant, duration of implantation, biocompatibility, implant stiffness, micromo-tion between the implant and adjacent bone etc. The architecture of a porous implant has been suggested to have a great effect on implant integration by newly grown bone [1, 2].
Generally, porous metallic scaffolds are fabricated using a variety of processes to pro-vide a high degree of interconnected porosity to allow bone ingrowth. Fabrication technologies include chemical vapour infiltration to deposit tantalum onto vitreous carbon foams, solid freeform fabrication, self-propagating high-temperature synthesis, and powder metallurgy [1-7]. While these porous metals have been successful at encouraging bone ingrowth both
in vivo and in clinical trials, the range of
mate-rials and microstructures available is still rather limited.
Because titanium (Ti) and Ti-based alloys have excellent mechanical, anti-corrosive and biocompatible properties, they are widely used for orthopaedic and dental implant materials. The Ti metal spontaneously forms a compact and protective oxide layer (mainly as TiO2) under the atmospheric environment, that pos-sesses ideal anti-corrosive properties. When a Ti implant is inserted into the human body, the surrounding tissue contacts directly with the Ti–O layer on the implant surface. Therefore, the properties, including structure, chemical composition and morphology, of the Ti–O layer determine the biocompatibility of the Ti implant. Although Ti is widely used for clinical purposes, some unresolved issues still remain. The clinical failure rate for implant materials occurs in the range from a few to over 10% [8]. It is important to use appropriate surface modi-fication to increase the anti-corrosive and bio-compatible properties of Ti implants for long-term clinical applications.
Various methodologies are being used in an effort to improve the interfacial properties be-tween the biological tissues and the existing implants, e.g., Ti and Ti-based alloy. The elec-trochemical technique, a more simple and fast method, can be used as a potential alternative for producing porous Ti-based metals for medical implants. Good corrosion resistance of the titanium is provided by the passive titanium oxide film on the surface. This layer is impor-tant for the good biocompatibility. The native oxide has thickness of few nanometers. In the case of anodic oxidation the oxide thickness can be multiplied up to micrometer range. The structure and thickness of the grown oxide de-pends on the electrochemical etching condi-tions, for example: current density, voltage, electrolyte composition. In the electrochemical etching of titanium are used electrolytes con-taining H3PO4, CH3COOH, H2SO4. In the Ti anodization, the dissolution is enhanced by HF- or NH4F-containing electrolytes, which results in pore or nanotubes formation. The current density in this case is much higher than in elec-trolyte without HF or NH4F [9]. Fluoride ions form soluble [TiF6]2- complexes resulting in dissolution of the titanium oxides. In this way the dissolution process limits the thickness of the porous layer.
Porous implants layer has lower density than respective bulk and good mechanical strength is provided by bulk substrate. Hence that material is attractive with respect to bulk titanium alloys. The porous layer on the Ti substrate is necessary to osseointegration with bones which is not normally provided by native oxide [3, 4].
On the other hand, Ti and its alloys possess favourable properties, such as relatively low modulus, low density and high strength. Apart from that, these alloys are generally regarded to have good biocompatibility and high corrosion resistance, but cannot directly bond to the bone. In addition, metal implants may loose and even separate from surrounding tissues during im-plantation. Titanium and titanium based alloys have relatively poor tribological properties be-cause of their low hardness. One of the meth-ods that allow the change of biological proper-ties of Ti alloys is to produce a nanocomposite,
which will exhibit the favourable mechanical properties of titanium and excellent biocom-patibility and bioactivity of ceramic. The most commonly ceramics, used in medicine are hy-droxyapatite, bioglass or Al2O3 [3, 10, 11].
Over the past years, nanoscale metallic and ceramic materials, also called nanomaterials have attracted enormous amounts of interest from researchers. Nanomaterials demonstrate novel properties compared to conventional (microcrystalline) materials due to their nano-scale features [3, 11-14]. Recently, mechanical alloying method and powder metallurgy proc-ess for the fabrication of metal/alloy-ceramic nanocomposites with a unique microstructure has been developed at Poznan University of Technology [3, 6, 14-16]. The process permits the control of microstructural properties such as the size of pore openings, surfaces proper-ties, and the nature of the base metal/alloy. For example, Ti-based nanocomposites reinforced with hydroxyapatite particles were fabricated by the optimal technical condition of hot press-ing technique.
The paper reviews research at Poznan Univer-sity of Technology, on the synthesis of nano-scale metallic and composite biomaterials. Ex-amples of the materials include a titanium-ceramic Ti-HA (3, 10, 20 vol%) and Ti-SiO2 (3, 10 vol%) nanocomposites, prepared by me-chanical alloying and powder metallurgical process. Aim of the research is to develop a new generation of titanium-ceramic bionano-composites by producing the porous structures with a strictly specified chemical and phase compositions, and such that show high hard-ness, high resistance to biological corrosion and good biocompatibility with human tis-sues.As the continuation of the previous work, in this paper the corrosion behaviour in Ringer’s solution and cytotoxicity tests were performed.
2. EXPERIMENTAL DETAILS
The titanium-ceramic nanocomposite ma-terials with different content of hydroxyapatite or silica were prepared by mechanical alloying and powder metallurgical process. The mixture of Ti-HA (3, 10, 20 vol%) and Ti-SiO2 (3, 10
vol%) powders were first ball milled for 44 and 20 hours, respectively and then compacted at 830 MPa. Finally green compacts were heat treated at 1150ºC for 2 h under a gas atmos-phere composed of 95% Ar and 5% H2 to form ordered phases.
The powders were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) with an energy-dispersive X-ray microanalysis system (EDS). XRD was performed using an X-ray powder diffractometer with Co Kα radiation, at various stages during milling, prior to annealing and after annealing. The TEM images and selected area electron diffraction (SAED) patterns were recorded with a Philips CM 20 Super Twin microscope, which provides a 0.24 nm resolu-tion at acceleraresolu-tion voltage of 200 kV.
Microhardness measurements were carried out in Vickers method with the load of 200 g. The micrographs were obtained using an optical microscope. The corrosion resistance in Ringer’s solution was measurement using in vitro potentiodynamic corrosion test. The com-position of Ringer solution was NaCl 9.0 g/l, KCl 0.42 g/l, CaCl2 0.48 g/l and NaHCO3 0.2 g/l. The corrosion test was performed at 37 ± 1°C. The counter electrode consisted of two graphite rods and saturate calomel solution was used as the reference electrode. The surface area exposed to the electrolyte was 0.78 cm2. The polarization curves were obtained for each specimen. Corrosion potentials (EC) and corro-sion current densities (IC) were determined by Tafel extrapolation methods. The corrosion rate, CR (rate of metal dissolution), in millimeters per year, was estimated with the following equation: CR = ρ ⋅ ⋅ F EW IC
were IC is a corrosion current density (µA/cm2), EW is an equivalent weight of the corroding species in grams (11,975 g), ρ is the density of the corroding species (g/cm3) and F is the Faraday constant (96500 C/mol).
Two types of cytotoxicity tests were per-formed, in static and dynamic conditions [17]. For these tests the discs of Ti-HAp nanocompo-sites (diameter 10 mm and thickness of 2 mm) and microcrystalline Ti (prepared from
com-mercial titanium cylinder as the diameter of 10 mm by slicing into the disks with the thickness of 2 mm) were polished with 800 SiC paper in water and ultrasonically rinsed with acetone. Then, these disks were sterilised by autoclaving at 120oC for 15 min and were separately located at the bottom of 24-well (NUNC #144530) mi-croplates. Normal Human Osteoblast (NHOst) cells from Cambrex (CC-2538) in static condi-tion were cultured onto each disk at the concen-tration of 5000 cells/well in 1 ml culture me-dium. The cells were cultured at 37oC in 5% CO2 incubator for 1, 7 and 14 days. The stained cells were observed by atomic force microscope (AFM) and their images were captured. In dy-namic conditions, the disks were rotated in extracting medium with SiO2 balls at 37°C for 14 days, and the collected extracting medium was added into CC-2538 culture to examine its inhibitive effect on cell growth. Relative viabil-ity of the cells (RVC) was calculated by the following equation: RVC (%) = [(a-b)/(c-b)]×100, where a was the absor-bance of the sample well, b was the absorbance of the blank well, and c was the absorbance of the control well at 595 nm.
The quantification of metallic elements in each extract of studied samples was performed by inductively coupled plasma optical emission spectrometry (ICP-OES); (Thermo Jarrell Ash, USA). Quantification was performed for five elements such as Ca, Cr, Ni, P and Ti under the optimum condition for each element.
3. RESULTS AND DISCUSSION
X-ray diffraction was also employed to study the effect of mechanical alloying on Ti-HA composites. The typical XRD patterns of titanium and hydroxyapatite before mechanical alloying are shown in Fig. 1 a, b. During MA process the original sharp diffraction lines of the sintering powders gradually become broader and their intensity decreases with mill-ing time (Fig. 1c). The peak broadenmill-ing repre-sents a reduction in the crystallite size and in-crease in the internal strain in the mechanically alloyed materials. After 44 h of MA, the amor-phous phase forms directly from the starting
mixture, without formation of other phases (Fig. 1d).
Fig. 1. XRD spectra of Ti and HA (10 vol%) powders mechanically alloyed for different times: (a) Ti - 0 h, (b) HA - 0 h, (c) 10 h, (d) 44 h, (e) after annealing
at 1150°C for 2 h
Rys. 1. Dyfraktogramy rentgenowskie mielonych prosz-ków Ti-10% HA dla róŜnych czasów trwania procesu
MA: (a) Ti – 0 h, (b) HA – 0 h, (c) 10 h, (d) 44 h, (e) po obróbce cieplnej 1150°C/2h
Fig. 2. TEM micrographs and electron diffraction patterns (insets) of the milled Ti-10 vol% HA sample
for 44h: (a) typical amorphous fragment, (b) same fine- crystalline phase, (c) crystalline grain
Rys. 2. Mikrofotografie TEM kompozytu Ti-10 % HA po 44 h procesu MA: (a) amorficzny fragment próbki, (b) drobnokrystaliczny fragment próbki, (c) duŜy kryształ
The microstructure of milled titanium and hydroxyapatite powder was also studied by TEM. The sample milled for 44 h was mostly amorphous (broad rings in the SEAD pattern) as appears from high resolution image (Fig. 2a). Apart from prevailing amorphous phase, there is small amount of fine-crystalline (Fig. 2b) and crystalline phases (Fig. 2c). Lack of any sharp reflections in the XRD pattern sug-gests that the amount of the crystalline phase is very low and/or it forms during in TEM
obser-vation. During TEM studies, it has been found that the amorphous powders was unstable upon exposure to electron beam and underwent some crystallization.
During MA process of Ti-silica (10 wt%), the intensity of diffraction line of titanium de-creases and after 20 h of milling has trans-formed completely to an amorphous phase, without formation of any other phases. TEM results shows that the powder milled for 20 h was mostly amorphous.
Formation of the bulk nanocomposites were achieved by annealing of the amorphous materials in high purity gas atmosphere com-posed of 95% Ar and 5% H2 at 1150ºC for 2 h (Fig. 1e). XRD analysis of Ti-10 vol% SiO2 showed the presence of α-Ti type structure with cell parameters a = 2.972 Å, c = 4.774 Å. The formation of crystalline SiO2 phase was not observed. In the XRD patters from the Ti-10 vol% HA composite after thermal treatment, there is present α-Ti (with cell parameters a = 2.774 Å, c = 4.494 Å) and apatite peaks. In this diagram, there is a shift of the titanium peaks towards larger angles. According to the Scherrer method of XRD profiles, the average size of heat treated Ti-HA and Ti-SiO2 nano-composites is about 30-40 and 40-50 nm, re-spectively.
The results of EDS analysis and scanning electron micrograph of the surface of sintered Ti-HA and Ti-SiO2 nanocomposites mechani-cally are shown in Fig. 3. The phase constitu-tion of Ti-10 vol% HA nanocomposite consists of titanium matrix with calcium and titanium matrix with apatite, which Ca/P ratio was 1.07, a value similar to the Ca/P ratio in Ca2P2O7. The presence of secondary HA phases are the result of cooling from a high temperature. Be-sides, the existence of Ti can degrade the struc-tural stability of HA crystal and promote its decomposition [18, 19].The existence of sec-ond phase of HA in the composites can influ-ence the final properties of sintered Ti-HA nanocomposites.
EDS results indicate that the predominant phase in Ti-SiO2 composites is titanium with content of silica or silicon particles. The pre-sence of some amount of iron atoms in the sin-tered nanocomposites, could be explained by
Fe impurities trapped in the MA powders from erosion of the milling media [20].
Fig. 3. EDS spectra of surface of: ( top) Ti-10 vol% HA, (bottom) Ti-10 vol% SiO2 nanocomposites mechanically
alloyed for 44h and heat treated at 1150˚C for 2h
Rys. 3. Mikroanaliza rentgenowska powierzchni nano-kompozytów Ti–10% HA (góra) i Ti-10% SiO2 (dół)
otrzymanych metodą MA (44h) i obrobionych cieplnie w temp. 1150°C w czasie 2h
Change of processing parameters, like me-chanical alloying and annealing times, as well as the chemical compositions and microstruc-ture of titanium-ceramic nanocomposites leads also to a distribution of the properties [3]. The Vickers’ microhardness of the sintered nano-composites exhibit various distribution corre-sponding to constitutional change and in-creased with the rise of ceramic contents. The Vickers’ hardness strongly increases for Ti-10 vol% HA nanocomposites (1500 HV0,2) and is six times higher than of pure microcrystalline Ti metal (250 HV0,2); see Fig. 4.
Fig. 4. Hardness of studied Ti-based nanocomposites
Rys. 4. Twardość otrzymanych nanokompozytów tytanowych
Fig. 5. Potentiodynamic polarization curves of: (a) Ti-3 vol% HA, (b) Ti-10 vol% HA, (c) Ti-20 vol%
HA composites in Ringer’s solution at 37oC
Rys. 5. Potencjodynamiczne krzywe polaryzacji otrzymane dla kompozytów: (a) Ti-3% HA, (b) Ti-10%
HA i (c) Ti-20% HA w płynie Ringera w temperaturze 37oC
Table 1. Vicker’s hardness, mean values of corrosion current densities, corrosion potentials and corrosion rate
at Ringers solution of studied Ti-HA and Ti-SiO2
nanocomposites and microcrystalline titanium (T=37oC)
Tablica 1. Twardość Vickersa, średnia wartość gęstości prądów korozyjnych, potencjałów korozyjnych |oraz stopnia korozji w płynie Ringera (T = 37oC) dla badanych nanomateriałów typu Ti-HA i Ti-SiO2,
i mikrokrystalicznego tytanu
sample HV0.2 IC [Amp/cm2] EC [V] CR [mm/y]
Ti-3 vol% HA 480 9.06 · 10-8 -0.34 0.003
Ti-10 vol % HA 1500 1.19 · 10-7 -0.41 0.004
Ti-20 vol% HA 1030 7.5 · 10-7 -0.55 0.025
Ti-3 vol% SiO2 550 − − −
Ti-10 vol % SiO2 670 3.74 · 10-8 -0.44 0.001
Ti
(microcrystal-line) 250 1.31 · 10-5 -0.36 0.363 The polarization data obtained for sintered composites and microcrystalline titanium, in-cluding corrosion potentials (EC), corrosion cur-rent densities (IC) and corrosion rate (CR) values
are summarized in Table 1 (see Fig. 5). Tita-nium composites with silica have better corro-sion resistance than that with hydroxyapatite. From Table 1 it is possible to observe low val-ues of corrosion rate, especially for Ti-10 vol% SiO2 nanocomposite. Titanium composite with 10 vol% of HA or SiO2 ceramic were more corrosion resistance (Ic= 1.19·10-7 Amp/cm2, Ec = -0.41 V; Ic = 3.74·10-8 Amp/cm2, Ec = -0.44 V, respectively) than microcrystalline titanium (Ic = 1.31·10-5 Amp/cm2, Ec= -0.36 V).
a)
b)
c)
Fig. 6. AFM images of the cells cultured on microcrys-talline Ti (a), Ti-10 vol% HA (b) and Ti-20 vol% HA (c)
disks sterilised by autoclaving for 14 days
Rys. 6. Zdjęcia AFM komórek ludzkich osteoblastów na powierzchni mikrokrystalicznego Ti (a), Ti-10% HA (b) i Ti-20% HA (c) po 14 dniach hodowli
Application of Ti-HA nanocomposites fo-cused also our attention on the biocompatibility of synthesized bulk materials. For example, the AFM images of the cells cultured on micro-crystalline Ti and Ti-10 and 20 vol% HA disks
sterilised by autoclaving for 14 days are shown in Fig. 6. After 1 day incubation, the cells were observed as scattered black dots because of the dye while the cells grew spread to cover almost all surface of the disks after 7 day incubation. There is a big difference in number of cells in studied samples. Two factors may influence cell growth on the disks. They can be: adsorbing protein onto the disks and released metal ions from the disks.
Cytotoxicity tests of the extracts of studied materials under wear conditions are shown in Fig. 7. The relative viability of the cells (RVC) decreases when fraction increases. It is impor-tant to note that the RVC of nanoscale Ti-HA is higher in comparison with microcrystalline titanium. The wear and fretting accelerates the corrosion of the studied samples in a biological environment such as cell culture medium. The same behaviour was observed also in the case of Ti-SiO2 nanocomposites.
The quantification of metallic elements in each extract of studied samples was performed for five elements such as Ca, Cr, Ni, P and Ti under the optimum condition for each element and the results are shown in Table 2. In the extract of microcrystalline Ti and nanocompo-site Ti-20 vol% HA nickel was detected at the concentration of 0.19±0.03 mg/l and 0.32±0.04 mg/l, respectively. It is important to note, that the preferential release of Ni was also reported on Ti–6Al–4V as impurity at the concentration less than 0.01 mass% [17]. Additionally, in all extracts of Ti, Ti-20 vol% HA and Ti-10 vol% SiO2 chromium was detected at the concentra-tion of 4.4±0.7, 4.1±0.6 and 4.0±0.5 mg/l, re-spectively. Chromium is one of the essential elements for human, so slight amount of this element may contribute to cell proliferation, resulting in higher cell growth [18, 21]. In all studied extracts of Ti, 20 vol% HA and Ti-10 vol% SiO2 calcium was present at the con-centration of 64±8, 82±11 and 78±10 mg/l, respectively. The existence of Ca could pro-mote the formation of apatite. On the other hand, titanium element was cannot be detected. These results indicate that Ti-ceramic (HA and SiO2) nanocomposites have superior cyto-compatibility than the conventional microcrys-talline Ti. Based on the above results
Ti-ceramic nanocomposites have a high possibil-ity for the application in biomedical field.
0 10 20 30 40 50 60 70 50% 25% 12.50% 6.25% extract fraction R V C (% ) a b c
Fig. 7. Cytotoxicity tests of the extracts of studied samples: (a) Ti-10 vol% HA, (b) Ti-20 vol%HA and (c) microcrystalline titanium in dynamic conditions
(see text for details)
Rys. 7. śywotności komórek ludzkich osteoblastów dla badanych nanokompozytów:
(a) Ti-10% HA, (b) Ti-20% HA i (c) mikrokrystalicznego Ti w warunkach dynamicznych (szczegóły w tekście)
Table 2. Quantifications of metallic elements in the extracts (<DL – concentration below
detection level)
Tablica 2. Zawartości metali we frakcjach (<DL – stęŜenie poniŜej granicy wykrywalności)
4. CONCLUSION
In this work, the structure, mechanical, corrosion properties and biocompatibility of Ti-ceramic nanocomposites synthesized by mechanical alloying and powder metallurgical process were studied. Different phase constitu-tions have significant influence on the me-chanical and corrosion properties of sintered materials. The Ti-HA and Ti-SiO2 nanocompo-sites mainly consist of different apatite or silica and silicon particles, respectively, reinforced with titanium matrix. Ti-10 vol% HA or SiO2 nanocomposites possesses better mechanical
sample element microcrystalline Ti
[mg/l] Ti-20 vol% HA [mg/l] Ti-10 vol% SiO[mg/l] 2
Ca 64±8 82±11 78±10
Cr 4.4±0.7 4.1±0.6 4.0±0.5
Ni 0.19±0.03 0.32±0.04 0.31±0.04
P 0 0 0
and corrosion properties than microcrystalline titanium. This is due to the structure refinement and the transformation into nanostructured material, achieved by very cheap and succe-ssive mechanical alloying process.
The studies lead to the following conclu-sions:
- the final mechanical properties of the bulk sintered nanocomposites are the function of the mechanical alloying parameters as well as sintering temperature and time,
- Vickers’ hardness of Ti-ceramic nanocompo-sites are about 3-5 times higher than of pure microcrystalline Ti metal,
- the Ti-ceramic nanocomposites are more corrosion resistant than the microcrystalline titanium,
- the relative viability of the cells (RVC) of nanocomposite Ti-20 vol% HA is higher in comparrison with Ti-10 vol% HA and microcrystalline Ti,
- cytotoxicity tests showed that Ti-ceramic nanocomposites have superior cytocompa-tibility compared to conventional titanium.
With regard to microcrystalline Ti it could help to obtain better medical implants with better mechanical properties, corrosion resistance and biocompatibility. The processing of these nanomaterials and their upscaling to enable industrial use has many challenges. This research will be the gateway for traditional industry to nanotechnology and knowledge-based materials, with positive effects on the environmental and health issues.
Acknowledgements
The financial support of the Polish Ministry of Education and Science under the contract No N507 071 32/2092 is gratefully acknow-ledged.
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