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Influence of carbon coatings origin on the properties important for biomedical application
ELSEVIER
Diamond and Related Materials 5 (1996) 1185-1188
DIAMOND AND RELATED MATERIALS
Influence of carbon coatings origin on the properties important for biomedical application 1 Stanislaw Mitura a Piotr Niedzielski a Dariusz Jachowicz a Malgorzata Langer ~
Jan Marciniak b, Andrew Stanishevsky c, Eduard Tochitsky c, Petr Louda d, Patrice Couvrat e, Michel Denis e, Pierre Lourdin e a Institute of Materials Science and Engineering, Lodz Technical University, Stefanowskiego 1, 90-924 Lodz, Poland b Institute of Metals, Silesian University of Technology, Gli~vice,Poland ° Plasmoteg Engineering Center; BeIarus Academy of Sciences, Zhodinskaya Str.I-3, Minsk, 220141, Belarus a Institute of Materials Science, Technical University ofLiberec, HaIkova 6, 46-117 Liberec, Czech Republic e Ecole CathoIique d'Arts et Mtiers ECAM, 40, montee Saint-Barthelemy, 69321 Lyon Cedex 05, France
Received 20 September; accepted in final form 23 January 1996
Abstract The purpose of the present study was to investigate the properties of a carbon layer depending of the origin of applied methods. Quasiamorphous carbon coatings prepared by ion beam methane decomposition by RF dense plasma and vacuum pulsed arc deposition were applied to stainless steel implants used in surgery. The studies of carbon rilms as coatings for implants in surgery were aimed on the investigations of biological resistance of implants, histopathologicaI investigations using laboratory animals, tests of corrosion resistance, measurements of mechanical properties and a breakdown test in Tyrod solution. The comparison of the properties of the coating produced by these methods shows very good biotolerance and biocompatibility of all of the coatings. They are not corroded in physiological fluids. From the other side they have different properties, especially electrical and optical, and are not influenced on medical applications. The obtained results prove that the implants coated by all the methods mentioned are a very good material for medical use.
Key~vords: Carbon coatings; Plasma assisted CVD; Biomaterials
1. Introduction Biomaterials as material used in the human body, should satisfy the following requirements [-1-3]: (1) they must not initiate reactions in the tissues surrounding an implant; (2) biotolerance (sometimes biocompatibility), means the ability of the human body to endure the coated implants without destruction of the tissue; (3) a specific system of mechanical properties (especially adhesion [-2-7]). Possibilities of using carbon as an implant material appeared when a method for low-pressure synthesis of diamond and diamond-like carbon layers were developed [4]. 1 Paper presented at the 6th European Conference on Diamond, Diamond-like and Related Materials, Barcelona, Spain 10-15 September 1995. 0925-9635/96/$15.00 © i996 ElsevierScience S.A. All rights reserved PII S0925-9635 (96) 00531-6
Attempts of its application for implants appeared to be successful [-8-12]. Thanks to the highest biocompatibility of carbon resulting from the presence of this element in the human body, it appears to be a potentially new biomaterial [-2,3]. In our previous paper we showed the properties of the layers deposited onto AISI 316L stainless steel and their applications in medicine [13,14]. The purpose of the present study was to investigate the properties of a carbon layer depending on the origin of applied methods.
2. Experimental details In this paper we present the results of experimental studies concerning the manufacture and characterization of amorphous carbon coatings obtained by the following methods: radio frequency plasma chemical vapour
1186
S. Mitura et al./Diamond and Related Materials 5 (1996) 1185-1188
deposition (RF PCVD); vacuum pulse arc deposition (VPAD), and ion beam. Characterizations of obtained coatings are provided by the following methods: tribological investigations (microhardness, adhesion by scratch test); corrosion resistance; biotolerance, and breakdown test.
, 7
T
=
~ =
-
.
.
.
.
I carb0n
.
.
?
.
.
.
.
.
.
.
.
Layer]
2.i. RF PCVD method The substrates were coated with superfine crystalline diamond deposited by the method of dense plasma [ 15]. The idea of this method was to excite a plasma in methane with nitrogen or other hydrocarbons with nitrogen in an RF electric field at a relatively high gas pressure that equals about 20 to 400 Pa. The experimental details and the main parameters for the RF dense methane plasma CVD process are given in Table 1. A schematic diagram of the apparatus is shown in Fig. 1. The substrates were placed on an RF-powered negatively self-biased electrode. The carbon films are amorphous. One should note that these films are chemically homogeneous. Specificity of the layers consisting first in very good adhesion to steel is explained by the authors on the basis of investigations carried out by Auger electron spectroscopy (AES) [14,16]. On the basis of the research mentioned above a diagrammatic model of hard carbon coatings onto metal substrate containing Cr or Ti, shown in Fig. 2, was suggested. The surface layer which was several thousand angstroms thick, consists of carbon. The carbon film passes smoothly into a thick layer ( g micron) consisting of metal carbides of metals which are Table 1 The growth conditions for the RF dense methane plasma CVD process Substrates Gas Pressure RF generator Negative self-biasvoltage of RF-powered electrode
AISI 316L, Ti Methane with nitrogen 100-200 Pa 27.12 MHz, 2 kW 600-1000 V
1
~ac
Fig. 1. The apparatus for amorphous carbon film synthesis by RF decomposition of methane method. RF, 27.12 MHz generator; GFMC, gas feeder with a microcomputer control; G, vacuum gauge; Vac, vacuum unit.
substrate
]
Fig. 2. A diagrammatic modeI of hard carbon coating onto titanium or chromium containing substrate (AISI 316L, Ti...). Metal carbides: CrC or TiC.
included in steel (Fig. 2). Such a structure of the coatings ensures a higher mechanical strength. Therefore, the coatings are also a good protection for metal against corrosion.
2.2. Vacuumpulse arc deposition (VPAD) method Method is based on the evaporation of coating material under pulsed arc discharge between eroded cathode and anode of a plasma source [171. The main parameters for the VPAD process are given in Table 2. A schematic diagram of the apparatus is shown in Fig. 3. VPAD carbon films were prepared at the integral substrate temperature less than 80 °C, and the average deposition rate was 5-20 nm min -1, Substrates were rotated with planetary motion. Film thickness was up to 1 ~tm. No bias was applied during experiments.
2.3. Ion beam (IB) method Ion-beam deposition films were prepared at the substrate temperature of less than 100 °C and deposition rate of 20-30 nm min -1. The starting gas was benzene. The main parameters for the IB method are given in Table 3. A schematic diagram of the apparatus is shown in Fig. 2. Carbon films prepared by VPAD and IB methods have good adhesion and are quite amorphous (near-ordering area less than 1 nm) with embedded crystalline carbon particles [ 181. Table 2 The growth conditions for the VPAD method Substrates Electrode (starting material) Pressure Pulsed discharge power Duration of impulse Repetition rate of impulse The average deposition rate
AISI 316L high purity gaphite i0-3-10 -4 Pa 5-10J 50-2500 gs 0.1-50 Hz 5-20 nm min- t
S. Mitura et al./Diamond and Related Materials 5 (1995) 1185-1188 Piilsed arc
r
plat~etary
SO ~ r ¢ ¢
1187
[0 I1 -b e ~ l 501~ rcg
substrales
I
P, o t a l e d
Iiolder
)
Fig. 3, The apparatus for amorphous carbon film synthesis by VPAD and IB methods.
Table 3 The growth conditions for the IB method Substrates Gas Pressure The average deposition rate Substrate temperature
AISI 316L Benzene 10-~-10 Pa 20-30 nm rain -~ less than 100 °C
2.4. Characterization of obtained coatings 2.4.1. Tribological investigations Tribotogical investigations were provided by the method of microhardness and adhesion, via a scratch test. 2.4.2. Corrosion resistance Both groups of coated specimens had been tested to find their resistance to acids. The tests of corrosion resistance of steel AISI 316L coated with superfine diamond layer were carried out in Tyrod solution according to ASTM STP 684 standard. The Tyrod solution simulates fluids present in the human body. 2.4.3. BiotoIerance The investigation of biotolerance was made with stainless steel AISI 316L implants passivated and coated with a carbon layer in laboratory animals. The aim of the research was to reveal toxic and allergic reactions occurring after placing implants in animal tissue. The research was carried out according to ASTM 981-86 standard. In the investigations Guinea pigs were used as animals reacting to toxicological and allergic factors similarly to man. Implants in the form of disks 5.0 mm in diameter and 1.0 mm thick of weight 0.750 g were investigated. The disks were implanted into chest muscles, subcutaneously between shoulder blades and into the tibia bone. The investigations were carried out for 52 weeks.
2.4.4. Breakdown test One of the parameters which makes it possible to state a coating applicability in medicine is the breakdown voltage in Tyrode's solution I2,3]. Tyrode's solution is water with the addition of salt, with similar properties to that in the human body. The value of the voltage allows us to estimate the corrosion resistance inside the human body. The breakdown voltage in Tyrode's solution for the uncoated steel oscillates between 340 and 420 mV [3]. Traditional electrolytic polishing and passiviting of AISI 316L steel implants increase the breakdown voltage to 600 mV.
3. Results
3.1. Tribological investigations Results of tribological investigations are presented in Table 3. Differences between properties of DLC layers obtained by the dense plasma RF method and that applied by VPAD and IB should be stressed. 3.2. Tests of corrosion resistance The tests of corrosion resistance of steel AISI 316L coated with superfine diamond layer were carried out in Tyrod solution according to ASTM STP 684 standard. Samples stored in the Tyrod fluid at temperatures of 277, 310, 337 and 355 K did not reveal the least traces of surface degradation. The SEM observations were made after a week, a month and three months. The investigations are continuing. 3.3. Breakdown test The breakdown voltage was measured in the Tyrod fluid. The value of this potential V= 1300 mV shows that the DLC layers produced by all the mentioned methods can be an efficient protection against galvanic processes in a human organism.
1188
S. Mitura et aL /Diamond and Related Materials 5 (1996) 1185-1188
Table 4 Results of tribological investigations of AISI 316L steel implants coated with carbon by RF PCVD, VPAD and IB methods Parameter
Microhardness GPa Adhesion-scratch test (critical load) N Density gcm -3
Deposition method RF-plasma CVD V P A D
Ion-beam
> 60 50 _+5
18-30 30 _+5
> 70 40 _+5
~3
2.6+3.2
Acknowledgments
1.8+2.2
TabIe 5 Qualitative comparison of the properties of carbon films produced by different methods Characterization
The manufacturing of amorphous carbon layers obtained by the methods of RF plasma CVD and VPAD seems to be the most convenient for the production of implants coating used in medicine. The properties of the coatings make possible apply them in medicine to fabricate good biomaterials.
Deposition method
The work was partly financed by Grant Manufacturing of nanocrystalline diamond - - biomatefial for medical applications no 7 S201 016 07 and C/3605/94 from the Polish State Committee for Scientific Research and by Project ATP of French Government I04/94 Couches minces diamantes.
RF-plasma CVD VPAD Ion-beam Tribological investigations Corrosion resistance Biotolerance Breakdown test
++ ++ ++ ++
+ + + +
+++ ++ +++ +++
+ ++ +++ ++
3.4. Investigation o f biotolerance
The histopathological investigation showed a very good biotolerance of the implants coated with the mentioned layers. The coating protects efficiently against corrosion and metalosis. G o o d results were received for carbon films coated surgical scalpels, needles and guide wires for mouth cavity surgery I-191. No remarkable difference was found between biotolerance test results for films prepared by RF PCVD, VPAD and ion-beam methods. It may just be connected with similarity of quasiamorphous films structure. The results mentioned above are shown in the Tables 4 and 5.
4. Conclusions The comparison of test results shows practice suitability of RF-plasma and VPAD methods for the hard carbon films preparation on medical implants and surgical instruments. These methods have an advantage with regard to ion-beam methods in sense of higher adhesion, hardness and wear-resistance. Each method has definite opportunities for medical application. For example, the advantage of the VPAD method is to prepare carbon films onto polymeric substrates and other materials with low temperature of phase transformations. RF PCVD provides broad intermediate diffusion layers of hard solution and carbides; it gives good adhesion of films.
References [11 D.F. Williams and R. Roar, Implants in Surgery, Saunders, London, 1973. [2] P. Couvrat, M. Denis, P. Louda, M. Langer, S. Mitura, P. Niedzielski and J. Marciniak, Diamond Relat. Mater., 4 (i995) 1251. [31 J. Marciniak, Biomaterialy w ehirurgii kostnej, Polit. Slaska, Gliwice, 1992. [4] J. Angus, P. Koidl and S. Domitz, Carbon thin films,in J. Mort and F. Jansen (eds.), Plasma Deposited Thin Fihns, CRC Press, Boca Raton, 1986. [5] R. Wei, P.J. Wilbur and M.-J. Liston, Diamond Relat. Mater., 2 (1994) 898. [6] A. Gril and V. Patel, Diamond Relat. Mater., 2 (1994) 597. [7] C.V. Cooper, C.P. Beetz, B.W. Buehholtz, P.J. Wilbur and R. Wei, Diamond Relat. Mater., 3 (1994) 534. [8] S. Mitura, Z. Has and V. Gorokhovsky,Surf. Coat. Teehnol., 47 (1991) 106. [9] A.H. Lettington and S. Smith, Diamond Relat. Mater., I (1992) 805. [101 D.M. Grant, I.R. MeColl, M.A. GoIozar, J.V. Wood and N.St.J. Braithwaite, Diamond Relat. Mater., 1 (1992) 727. [11"1 R. Butter, M. Alien, L. Chandra, A.H. Lettington and N. Rushton, Diamond Relat. Mater., 4 (1994) 857. [12] L. Chandra, M. Alien, R. Butter, N. Rushton, A.H. Letfington and T.W. CIyne,Diamond Relat. Mater., 4 (1994) 852. [13] E. Mitura, S. Mitura, P. Niedzielski, Z. Has, R. Wolowiec, A. Jakubowski, J. Szmidt, A. Sokolowska, P. Louda, J. Marciniak and B. Koczy,Diamond Relat. Mater., 3 (1994) 896. [14"] A. Olborska, M. Swider, R. Wolowiec,P. Niedzielski, A. Rylski and S. Mitura, Diamond Relat. Mater., 3 (1994) 899. [15] S. Mitura, P. Niedzielski, A. Rylski, M. Denis, P. Couvrat, P. Louda, J. Szmidt, A. Jakubowski and A. Sokolowska, in P. Vinzenzini (ed.), Advances in Science and Technology, vol. 6; Proc. 8th CIMTEC World CeramicCongress & Forum on New Materials; New Diamond and Diamond-LikeFilms, TECHNA srl., Faenza 1995, p. 273. [16] S. Mitura, E. Mitura and A. Mitura, Diamond Relat. Mater., 4 (1995) 302. [17] E.I. Tochitsky, O.V. Selifanov,A.V.Stanishevsky,V.V. Akulich and I.A. Kapustin, Surf. Coat. Teehnol., 47 (1991) 522. [18] E.I. Tochitsky, A.V. Stanishevsky,I.A. Kapustin, V.V. Akulich and O.V. Selifanov,Swf. Coat. Teetmol., 47 (1991) 292. [i9"1 A.K. Kcholodny, personal communication, Institute for re-qualification of physisians, Minsk, 1995.
Diamond and Related Materials 5 (1996) 1185-1188
DIAMOND AND RELATED MATERIALS
Influence of carbon coatings origin on the properties important for biomedical application 1 Stanislaw Mitura a Piotr Niedzielski a Dariusz Jachowicz a Malgorzata Langer ~
Jan Marciniak b, Andrew Stanishevsky c, Eduard Tochitsky c, Petr Louda d, Patrice Couvrat e, Michel Denis e, Pierre Lourdin e a Institute of Materials Science and Engineering, Lodz Technical University, Stefanowskiego 1, 90-924 Lodz, Poland b Institute of Metals, Silesian University of Technology, Gli~vice,Poland ° Plasmoteg Engineering Center; BeIarus Academy of Sciences, Zhodinskaya Str.I-3, Minsk, 220141, Belarus a Institute of Materials Science, Technical University ofLiberec, HaIkova 6, 46-117 Liberec, Czech Republic e Ecole CathoIique d'Arts et Mtiers ECAM, 40, montee Saint-Barthelemy, 69321 Lyon Cedex 05, France
Received 20 September; accepted in final form 23 January 1996
Abstract The purpose of the present study was to investigate the properties of a carbon layer depending of the origin of applied methods. Quasiamorphous carbon coatings prepared by ion beam methane decomposition by RF dense plasma and vacuum pulsed arc deposition were applied to stainless steel implants used in surgery. The studies of carbon rilms as coatings for implants in surgery were aimed on the investigations of biological resistance of implants, histopathologicaI investigations using laboratory animals, tests of corrosion resistance, measurements of mechanical properties and a breakdown test in Tyrod solution. The comparison of the properties of the coating produced by these methods shows very good biotolerance and biocompatibility of all of the coatings. They are not corroded in physiological fluids. From the other side they have different properties, especially electrical and optical, and are not influenced on medical applications. The obtained results prove that the implants coated by all the methods mentioned are a very good material for medical use.
Key~vords: Carbon coatings; Plasma assisted CVD; Biomaterials
1. Introduction Biomaterials as material used in the human body, should satisfy the following requirements [-1-3]: (1) they must not initiate reactions in the tissues surrounding an implant; (2) biotolerance (sometimes biocompatibility), means the ability of the human body to endure the coated implants without destruction of the tissue; (3) a specific system of mechanical properties (especially adhesion [-2-7]). Possibilities of using carbon as an implant material appeared when a method for low-pressure synthesis of diamond and diamond-like carbon layers were developed [4]. 1 Paper presented at the 6th European Conference on Diamond, Diamond-like and Related Materials, Barcelona, Spain 10-15 September 1995. 0925-9635/96/$15.00 © i996 ElsevierScience S.A. All rights reserved PII S0925-9635 (96) 00531-6
Attempts of its application for implants appeared to be successful [-8-12]. Thanks to the highest biocompatibility of carbon resulting from the presence of this element in the human body, it appears to be a potentially new biomaterial [-2,3]. In our previous paper we showed the properties of the layers deposited onto AISI 316L stainless steel and their applications in medicine [13,14]. The purpose of the present study was to investigate the properties of a carbon layer depending on the origin of applied methods.
2. Experimental details In this paper we present the results of experimental studies concerning the manufacture and characterization of amorphous carbon coatings obtained by the following methods: radio frequency plasma chemical vapour
1186
S. Mitura et al./Diamond and Related Materials 5 (1996) 1185-1188
deposition (RF PCVD); vacuum pulse arc deposition (VPAD), and ion beam. Characterizations of obtained coatings are provided by the following methods: tribological investigations (microhardness, adhesion by scratch test); corrosion resistance; biotolerance, and breakdown test.
, 7
T
=
~ =
-
.
.
.
.
I carb0n
.
.
?
.
.
.
.
.
.
.
.
Layer]
2.i. RF PCVD method The substrates were coated with superfine crystalline diamond deposited by the method of dense plasma [ 15]. The idea of this method was to excite a plasma in methane with nitrogen or other hydrocarbons with nitrogen in an RF electric field at a relatively high gas pressure that equals about 20 to 400 Pa. The experimental details and the main parameters for the RF dense methane plasma CVD process are given in Table 1. A schematic diagram of the apparatus is shown in Fig. 1. The substrates were placed on an RF-powered negatively self-biased electrode. The carbon films are amorphous. One should note that these films are chemically homogeneous. Specificity of the layers consisting first in very good adhesion to steel is explained by the authors on the basis of investigations carried out by Auger electron spectroscopy (AES) [14,16]. On the basis of the research mentioned above a diagrammatic model of hard carbon coatings onto metal substrate containing Cr or Ti, shown in Fig. 2, was suggested. The surface layer which was several thousand angstroms thick, consists of carbon. The carbon film passes smoothly into a thick layer ( g micron) consisting of metal carbides of metals which are Table 1 The growth conditions for the RF dense methane plasma CVD process Substrates Gas Pressure RF generator Negative self-biasvoltage of RF-powered electrode
AISI 316L, Ti Methane with nitrogen 100-200 Pa 27.12 MHz, 2 kW 600-1000 V
1
~ac
Fig. 1. The apparatus for amorphous carbon film synthesis by RF decomposition of methane method. RF, 27.12 MHz generator; GFMC, gas feeder with a microcomputer control; G, vacuum gauge; Vac, vacuum unit.
substrate
]
Fig. 2. A diagrammatic modeI of hard carbon coating onto titanium or chromium containing substrate (AISI 316L, Ti...). Metal carbides: CrC or TiC.
included in steel (Fig. 2). Such a structure of the coatings ensures a higher mechanical strength. Therefore, the coatings are also a good protection for metal against corrosion.
2.2. Vacuumpulse arc deposition (VPAD) method Method is based on the evaporation of coating material under pulsed arc discharge between eroded cathode and anode of a plasma source [171. The main parameters for the VPAD process are given in Table 2. A schematic diagram of the apparatus is shown in Fig. 3. VPAD carbon films were prepared at the integral substrate temperature less than 80 °C, and the average deposition rate was 5-20 nm min -1, Substrates were rotated with planetary motion. Film thickness was up to 1 ~tm. No bias was applied during experiments.
2.3. Ion beam (IB) method Ion-beam deposition films were prepared at the substrate temperature of less than 100 °C and deposition rate of 20-30 nm min -1. The starting gas was benzene. The main parameters for the IB method are given in Table 3. A schematic diagram of the apparatus is shown in Fig. 2. Carbon films prepared by VPAD and IB methods have good adhesion and are quite amorphous (near-ordering area less than 1 nm) with embedded crystalline carbon particles [ 181. Table 2 The growth conditions for the VPAD method Substrates Electrode (starting material) Pressure Pulsed discharge power Duration of impulse Repetition rate of impulse The average deposition rate
AISI 316L high purity gaphite i0-3-10 -4 Pa 5-10J 50-2500 gs 0.1-50 Hz 5-20 nm min- t
S. Mitura et al./Diamond and Related Materials 5 (1995) 1185-1188 Piilsed arc
r
plat~etary
SO ~ r ¢ ¢
1187
[0 I1 -b e ~ l 501~ rcg
substrales
I
P, o t a l e d
Iiolder
)
Fig. 3, The apparatus for amorphous carbon film synthesis by VPAD and IB methods.
Table 3 The growth conditions for the IB method Substrates Gas Pressure The average deposition rate Substrate temperature
AISI 316L Benzene 10-~-10 Pa 20-30 nm rain -~ less than 100 °C
2.4. Characterization of obtained coatings 2.4.1. Tribological investigations Tribotogical investigations were provided by the method of microhardness and adhesion, via a scratch test. 2.4.2. Corrosion resistance Both groups of coated specimens had been tested to find their resistance to acids. The tests of corrosion resistance of steel AISI 316L coated with superfine diamond layer were carried out in Tyrod solution according to ASTM STP 684 standard. The Tyrod solution simulates fluids present in the human body. 2.4.3. BiotoIerance The investigation of biotolerance was made with stainless steel AISI 316L implants passivated and coated with a carbon layer in laboratory animals. The aim of the research was to reveal toxic and allergic reactions occurring after placing implants in animal tissue. The research was carried out according to ASTM 981-86 standard. In the investigations Guinea pigs were used as animals reacting to toxicological and allergic factors similarly to man. Implants in the form of disks 5.0 mm in diameter and 1.0 mm thick of weight 0.750 g were investigated. The disks were implanted into chest muscles, subcutaneously between shoulder blades and into the tibia bone. The investigations were carried out for 52 weeks.
2.4.4. Breakdown test One of the parameters which makes it possible to state a coating applicability in medicine is the breakdown voltage in Tyrode's solution I2,3]. Tyrode's solution is water with the addition of salt, with similar properties to that in the human body. The value of the voltage allows us to estimate the corrosion resistance inside the human body. The breakdown voltage in Tyrode's solution for the uncoated steel oscillates between 340 and 420 mV [3]. Traditional electrolytic polishing and passiviting of AISI 316L steel implants increase the breakdown voltage to 600 mV.
3. Results
3.1. Tribological investigations Results of tribological investigations are presented in Table 3. Differences between properties of DLC layers obtained by the dense plasma RF method and that applied by VPAD and IB should be stressed. 3.2. Tests of corrosion resistance The tests of corrosion resistance of steel AISI 316L coated with superfine diamond layer were carried out in Tyrod solution according to ASTM STP 684 standard. Samples stored in the Tyrod fluid at temperatures of 277, 310, 337 and 355 K did not reveal the least traces of surface degradation. The SEM observations were made after a week, a month and three months. The investigations are continuing. 3.3. Breakdown test The breakdown voltage was measured in the Tyrod fluid. The value of this potential V= 1300 mV shows that the DLC layers produced by all the mentioned methods can be an efficient protection against galvanic processes in a human organism.
1188
S. Mitura et aL /Diamond and Related Materials 5 (1996) 1185-1188
Table 4 Results of tribological investigations of AISI 316L steel implants coated with carbon by RF PCVD, VPAD and IB methods Parameter
Microhardness GPa Adhesion-scratch test (critical load) N Density gcm -3
Deposition method RF-plasma CVD V P A D
Ion-beam
> 60 50 _+5
18-30 30 _+5
> 70 40 _+5
~3
2.6+3.2
Acknowledgments
1.8+2.2
TabIe 5 Qualitative comparison of the properties of carbon films produced by different methods Characterization
The manufacturing of amorphous carbon layers obtained by the methods of RF plasma CVD and VPAD seems to be the most convenient for the production of implants coating used in medicine. The properties of the coatings make possible apply them in medicine to fabricate good biomaterials.
Deposition method
The work was partly financed by Grant Manufacturing of nanocrystalline diamond - - biomatefial for medical applications no 7 S201 016 07 and C/3605/94 from the Polish State Committee for Scientific Research and by Project ATP of French Government I04/94 Couches minces diamantes.
RF-plasma CVD VPAD Ion-beam Tribological investigations Corrosion resistance Biotolerance Breakdown test
++ ++ ++ ++
+ + + +
+++ ++ +++ +++
+ ++ +++ ++
3.4. Investigation o f biotolerance
The histopathological investigation showed a very good biotolerance of the implants coated with the mentioned layers. The coating protects efficiently against corrosion and metalosis. G o o d results were received for carbon films coated surgical scalpels, needles and guide wires for mouth cavity surgery I-191. No remarkable difference was found between biotolerance test results for films prepared by RF PCVD, VPAD and ion-beam methods. It may just be connected with similarity of quasiamorphous films structure. The results mentioned above are shown in the Tables 4 and 5.
4. Conclusions The comparison of test results shows practice suitability of RF-plasma and VPAD methods for the hard carbon films preparation on medical implants and surgical instruments. These methods have an advantage with regard to ion-beam methods in sense of higher adhesion, hardness and wear-resistance. Each method has definite opportunities for medical application. For example, the advantage of the VPAD method is to prepare carbon films onto polymeric substrates and other materials with low temperature of phase transformations. RF PCVD provides broad intermediate diffusion layers of hard solution and carbides; it gives good adhesion of films.
References [11 D.F. Williams and R. Roar, Implants in Surgery, Saunders, London, 1973. [2] P. Couvrat, M. Denis, P. Louda, M. Langer, S. Mitura, P. Niedzielski and J. Marciniak, Diamond Relat. Mater., 4 (i995) 1251. [31 J. Marciniak, Biomaterialy w ehirurgii kostnej, Polit. Slaska, Gliwice, 1992. [4] J. Angus, P. Koidl and S. Domitz, Carbon thin films,in J. Mort and F. Jansen (eds.), Plasma Deposited Thin Fihns, CRC Press, Boca Raton, 1986. [5] R. Wei, P.J. Wilbur and M.-J. Liston, Diamond Relat. Mater., 2 (1994) 898. [6] A. Gril and V. Patel, Diamond Relat. Mater., 2 (1994) 597. [7] C.V. Cooper, C.P. Beetz, B.W. Buehholtz, P.J. Wilbur and R. Wei, Diamond Relat. Mater., 3 (1994) 534. [8] S. Mitura, Z. Has and V. Gorokhovsky,Surf. Coat. Teehnol., 47 (1991) 106. [9] A.H. Lettington and S. Smith, Diamond Relat. Mater., I (1992) 805. [101 D.M. Grant, I.R. MeColl, M.A. GoIozar, J.V. Wood and N.St.J. Braithwaite, Diamond Relat. Mater., 1 (1992) 727. [11"1 R. Butter, M. Alien, L. Chandra, A.H. Lettington and N. Rushton, Diamond Relat. Mater., 4 (1994) 857. [12] L. Chandra, M. Alien, R. Butter, N. Rushton, A.H. Letfington and T.W. CIyne,Diamond Relat. Mater., 4 (1994) 852. [13] E. Mitura, S. Mitura, P. Niedzielski, Z. Has, R. Wolowiec, A. Jakubowski, J. Szmidt, A. Sokolowska, P. Louda, J. Marciniak and B. Koczy,Diamond Relat. Mater., 3 (1994) 896. [14"] A. Olborska, M. Swider, R. Wolowiec,P. Niedzielski, A. Rylski and S. Mitura, Diamond Relat. Mater., 3 (1994) 899. [15] S. Mitura, P. Niedzielski, A. Rylski, M. Denis, P. Couvrat, P. Louda, J. Szmidt, A. Jakubowski and A. Sokolowska, in P. Vinzenzini (ed.), Advances in Science and Technology, vol. 6; Proc. 8th CIMTEC World CeramicCongress & Forum on New Materials; New Diamond and Diamond-LikeFilms, TECHNA srl., Faenza 1995, p. 273. [16] S. Mitura, E. Mitura and A. Mitura, Diamond Relat. Mater., 4 (1995) 302. [17] E.I. Tochitsky, O.V. Selifanov,A.V.Stanishevsky,V.V. Akulich and I.A. Kapustin, Surf. Coat. Teehnol., 47 (1991) 522. [18] E.I. Tochitsky, A.V. Stanishevsky,I.A. Kapustin, V.V. Akulich and O.V. Selifanov,Swf. Coat. Teetmol., 47 (1991) 292. [i9"1 A.K. Kcholodny, personal communication, Institute for re-qualification of physisians, Minsk, 1995.