Structural and Mechanical properties of Ti–Si–C–ON for biomedical applications

S uc u al and Mechanical p ope ies o Ti–Si–C–ON o biomedical applica ions F eddy Guima ães a , C is ina Oli ei a a , Elsa Sequei os a , Ma a To es a , M. Susano b , M. Hen iques b , R. Oli ei a b , R. Escoba Galindo c , S. Ca alho a, ⁎, N.M.G. Pa ei a d ,F.Vaz a , A. Ca alei o d a Dep . Física, Uni e sidade do Minho, Campus de Azu ém, 4800-058 Guima ães, Po ugal b IBB—Ins i u e o Bio echnology and Bioenginee ing Cen e o Biological Enginee ing, Uni e sidade do Minho, Campus de Gual a , 4700-057, Po ugal c Ins i u o de Ciencia de Ma e iales de Mad id (ICMM-CSIC), Can oblanco, 28049, Mad id, Spain d ICEMS—Fac. de Ciências e Tecnologia da Uni e sidade de Coimb a, 3030-788 Coimb a, Po ugal A ailable online 4 Sep embe 2007 Abs ac Ti–Si–C–ON ilms we e deposi ed by DC eac i e magne on spu e ing using di e en pa ial p essu e o oxygen (p O2 ) and ni ogen (p N2 ) a io. Composi ional analysis e ealed he exis ence o wo di e en g ow h zones o he ilms; one zone deposi ed unde low p O2 /p N2 and ano he zone deposi ed unde high p O2 /p N2 . The ilms p oduced unde low p O2 /p N2 we e deposi ed a a lowe a e and p esen ed a cc s uc u e, as well as, dense and ea u eless mo phologies. The ilms deposi ed wi h high p O2 /p N2, consequen ly highe oxygen con en , we e deposi ed a a highe a e and de eloped an amo phous s uc u e. The s uc u al changes a e consis en wi h he ha dness and Young's modulus e olu ion, as seen by he signi ican educ ion o he ha dness and in luence on he Young's modulus by inc easing p O2 /p N2. © 2007 Else ie B.V. All igh s ese ed. Keywo ds: Ti–Si–C–ON; Mechanical; S uc u al; Bioma e ials 1. In oduc ion Signi ican de elopmen o nano echnology in ma e ial science and enginee ing has aken place in he las decade. The ecen in e es in he so-called mul i unc ional-coa ing ma e ials is o majo impo ance, om bo h he undamen al scien i ic iewpoin and in e ms o indus ial applica ions. Mo e speci ically nowadays, as he endency in implan science is o subs i u e he o al hip eplacemen , usually a a ie y o ma e ials, such as me als, ce amics, polyme s and composi es by ma e ials coa ed wi h p o ec i e hin- ilms [1]. Clinical esul s show ha excessi e wea and wea deb is a e he p ima y cause o ailu e implan s o ul a high molecula weigh polye hylene—UHMWPE o me al [2]. Mo eo e , in ec ions caused by commensal mic o ganisms a e also a cause o implan ailu e. Fo example, S aphylococcus epide midis and o he coagulase-nega i e s aphylococci (CoNS) a e amongs he majo culp i s o hese in ec ions [3,4]. This is ela ed, in pa , o hei abili y o adhe e o implan ed medical de ices and o m bio ilms. Despi e se e al e o s o ind medical he apies o ea bio ilm in ec ions [5], he physical emo al o an in ec ed medical de ice is o en necessa y wi h i s associa ed incon enience and addi ional economic cos . The e is conside - able in e es in inc easing he li e ime o implan s h ough he inhibi ion o bio ilm o ma ion and he use o mo e wea - esis an biocompa ible coa ings. The pu pose o his wo k is o s a o in es iga e he easibili y o a ious Ti–Si–C–ON ilms o load-bea ing medical de ices. F om known esul s i is widely accep ed ha is possible o achie e supe ha dness by Si inco po a ion in TiN [6] and a dec ease in he Young's modulus is obse ed by addi ion o oxygen [7]. Also, wo k has shown ha he co osion esis ance ends o be sligh ly imp o ed by oxygen inco po a- ion [8]. Recen published wo ks showed ha Ti–Si–Cisa p omising sys em because o i s pa icula s uc u e, as well as, i s ex ao dina y mechanical and ibological p ope ies [9]. A ailable online a www.sciencedi ec .com Su ace & Coa ings Technology 202 (2008) 2403–2407 www.else ie .com/loca e/su coa ⁎Co esponding au ho . E-mail add ess: [email p o ec ed] (S. Ca alho). 0257-8972/$ - see on ma e © 2007 Else ie B.V. All igh s ese ed. doi:10.1016/j.su coa .2007.08.056 Taking his in o conside a ion, he main ask o his pape is ocussed on he s udy o he s uc u al and mechanical p ope ies o Ti–Si–C–ON ilms wi h di e en O/N a ios. 2. Expe imen al de ails The Ti–Si–C–ON samples we e deposi ed by d.c. eac i e magne on spu e ing om wo opposed high pu i y (99.6%) Ti a ge s (20×10 cm 2 ); one Ti a ge wi h some inc us ed Si pelle s (he ea e designa ed as he TiSi a ge ) and he o he wi h ca bon pelle s (designa ed as he TiC a ge ), placed in p e e en ial e oded zone. The a ea occupied by he pelle s was close o 11 cm 2 in each a ge . Deposi ions we e ca ied ou unde an A +(N 2 +O 2 ) a mosphe e in an Alca el SCM 650 appa a us. Du ing he deposi ions he subs a es (s eel and silicon) we e o a ed 70 mm abo e he a ge a cons an speed o 7 pm. The base p essu e in he chambe was abou 10 −4 Pa and ose 4.5× 10 −1 Pa du ing he deposi ions. In o de o change he amoun o oxygen, he samples we e g own wi h a a ia ion in he N 2 +O 2 low (changing he N 2 om 6.5 o 0 sccm and he O 2 om 0 o 5.25 sccm), while main aining he A low cons an a 60 sccm. The subs a e bias ol age and he empe a u e we e kep cons an a −50 V and 200 °C, espec i ely. The cu en densi y applied o he TiC a ge was 5 mA/cm 2 and ha o he TiSi a ge was 6 mA/cm 2 . Elec on P obe Mic oAnalysis (EMPA) and Glow Discha ge Op ical Emission Spec oscopy (GDOES) we e used o he de e mina ion o he chemical composi ion o he coa ings and we e ca ied ou using a Cameca SX-50 elec on p obe mic oanalysis appa a us and a Jobin Y on RF GD P o ile , espec i ely. The c oss-sec ional mo phology was examined using a con en ional SEM on ac u ed samples. The s uc u e and phase composi ion o he coa ings we e assessed by XRD, using a con en ional Philips PW 1710 di ac ome e , ope a ing wi h CuK α adia ion, in a B agg-B en ano con igu a ion. The ha dness (H) and he Young's modulus (E), we e e alua ed by dep h-sensing inden a ion, using a Fishe scope H100 appa a us a maximum load o 30 mN. Co ec ion o he geome ical de ec s in he ip o he inden e , he mal d i o he equipmen and unce ain y o he ini ial con ac was also pe o med in ag eemen wi h wha is p oposed on [10,11]. I should be poin ed ou ha any co ec ion due o esidual s esses was done. The Residual s esses, σ , we e ob ained by he de lec ion me hod om S oney's equa ion [12], using subs a e cu a u e adii, bo h be o e and a e coa ing deposi ion [13]. 3. Resul s and discussion 3.1. Composi ion mo phology analysis The chemical analysis o he ilms was ob ained using GDOES and EPMA measu emen s. Fo he deposi ed samples he esul s o an a e age o hese analyses as unc ion o he oxygen pa ial p essu e and he ni ogen pa ial p essu e a io (p O2 /p N2 ) a e shown in Fig. 1. I is isible ha he Si and C con en emains almos cons an o all coa ings independen o p O2 /p N2 and he alue is e y low (b10 a .%). As expec ed, he ni ogen con en dec eased om 54 o 2 a . % and he oxygen inc eased om 2.9 o 34.7 a . % on inc easing he p O2 /p N2 om 0.046 o 20. Also an inc ease in Ti con en was obse ed as p O2 / p N2 inc eased. In ac , due o he high amoun o ni ogen in he coa ing deposi ed wi h lowe p O2 /p N2 (NN50 a .%), i is possible ha he a ge s a e al eady poisoned; his would also explain he low deposi ion a e o his coa ing (as can be seen in Fig. 2). By inc easing he oxygen low, he oxygen beha iou is no linea , o lowe low a es dissocia ion o he oxy- gen molecules can occu , which inc eases he eac i i y o he sys em and hus he deposi ion a e (seen in Fig. 2). A he same ime some ni ogen a oms a e eplaced by oxygen (p O2 /p N2 =0.6) and in a second phase, he eac ion be ween he oxygen in he a ge commences. This eac ion s a s in a monolaye o med by chemiso p ion and o each oxygen a om inco po a ed in he a ge , wo o ni ogen a e eed, due o he o ma ion o a TiN laye o he o ma ion o a TiO 2 laye . This will inc ease he pa ial p essu e o ni ogen in he eac i e a mosphe e, which can explain he lowe oxygen con en o he coa ing deposi ed a p O2 /p N2 =0.8, keeping in mind ha , he low o eac i e gas is always he same and so, he numbe o molecules o O 2 +N 2 is cons an . To educe oxygen poisoning, Fig. 1. Va ia ion o he concen a ion o Ti, C, Si, O and N as a unc ion o p O2 / p N2 . Fig. 2. Va ia ion o he deposi ion a e as a unc ion o p O2 /p N2 . 2404 F. Guima ães e al. / Su ace & Coa ings Technology 202 (2008) 2403–2407 i is equi ed o double he numbe o a oms in compa ison o ha o ni ogen. This will inc ease o he non-poisoned ac ion o he a ge , acco ding he Be g's Model, and should inc ease in he numbe o he spu e ed Ti a oms, leading o an inc ease in Ti composi ion. Fo he coa ings deposi ed wi h a high p O2 /p N2 a io, he con inua ion o he p e iously desc ibed phenomenon occu s, bu because o he dec ease o he ni ogen low, he amoun o ni ogen in he coa ing educes, while a he same ime he oxygen low is inc eased, which will p omo e an inc ease o he oxygen in he coa ing. The amoun o oxygen added o he eac i e a mosphe e is no enough o each he s oichiome ic composi ion TiO 2 , see composi ion o he coa ing deposi ed wi h p O2 /p N2 =20, his is an e idence o a non-poisoned a ge , du ing he deposi ion wi h high amoun o oxygen, and his is he explana ion o he high deposi ion a e o his coa ing, as is seen in Fig. 2. The mo phology o he coa ings is disclosed by c oss-sec ional SEM mic og aphs o ac u ed samples, shown in Fig. 3. Conside ing he esul s o samples ep esen ing he g oup deposi ed wi h low p O2 /p N2 (Fig. 3a), all ilms show dense and e y compac ea u eless mo phologies. The dec ease in he deposi ion a e can induce his compac mo phology. The mic os uc u e o single-phase ilms is quali a i ely well desc ibed by he s uc u al zone models de eloped by Mo chan and Demchishin [14] and Tho n on [15]. These models, howe e , change ma kedly when impu i ies o selec ed addi i es a e inco po a ed in he ilms [16]. Impu i ies o addi i es (like oxygen in ou case) s op he g ain g ow h and s imula e a enuclea ion o g ains, which esul s in a globula mo phology. The sample deposi ed wi h p O2 /p N2 =1.76 (Fig. 3b) p esen s his ype o mo phology. As he p O2 /p N2 is u he inc eased he coa ings p esen mo phologies wi h a la ge numbe o oids wi hin shaped c ys alli es (Fig. 3c), as a esul o he highe deposi ion a e. 3.2. S uc u e cha ac e iza ion The di e ences in he composi ion a e well co ela ed wi h he di e ences obse ed in he de eloped s uc u e. The X- ay di ac og ams o he as-deposi ed samples a e illus a ed in Fig. 4. In e na ional Cen e o Di ac ion Da a (ICDD) o α—Ti (ICDD ca d n . 44-1294), TiN (ICDD ca d n . 38-1420, TiC (ICDD ca d n . 01-071-6256), and TiC 0.2 N 0.8 (ICDD ca d n . 01-076-2484) we e also included a he op o Fig. 4.The abo e-men ioned egimes changes (low p O2 /p N2 a io and high p O2 /p N2 a io) a e also e iden in he s uc u al ea u es e ealed by he XRD esul s. Fo he samples deposi ed unde low p O2 /p N2 i is possible o iden i y a cc ype s uc u e and he e is a endency o an inc ease in he peak in ensi y a io I (111) /(I (111) +I (200) wi h inc ease in p O2 /p N2 , indica ing a p e e en ial c ys alline g ow h change. I is di icul o unequi ocally iden i y which phases a e o med. E.V. Shalae a e al. [17] s a ed o Ti–Si–N–O ilms ha a a silicon con en o 10 a . %, he ilms had nea ly single- phase c ys alline s uc u e TiSiN(O) wi h minimum g ain size 1.5–2 nm. Al hough, a ha momen , wi h he di ac ion analysis, he e is no e idence ha silicon is pa ially dissol ed in a cubic solid solu ion TiSiN(O). Ca bon and oxygen subs i u ion o egula ni ogen posi ions o o med cc Ti(C,O,N) phase, once he ni ogen con en dec eases, could be possible. The samples ha we e deposi ed a high p O2 /p N2 p esen ed a signi ican loss o c ys allini y, wi h he sample wi h highes oxygen con en ound o be amo phous. Fo his g oup he inc ease in he deposi ion a e (as men ioned be o e) and he a ailable oxygen ha is in- co po a ed in he la ice, educes he possibili y o c ys alliza ion. The ex ended de o ma ion o he cc s uc u e esul ing om he Fig. 3. C oss-sec ional mic og aphs o Ti–Si–C–ON coa ings o di e en p O2 /p N2 a) 0.046 b) 1.73 c) 20. Fig. 4. XRD pa e ns o di e en Ti–Si–C–ON ilms. 2405F. Guima ães e al. / Su ace & Coa ings Technology 202 (2008) 2403–2407 inco po a ion o oxygen p obably inc eases he numbe o de ec s, which acili a es he o ma ion o he amo phous s uc u e. The obse ed changes in ilm s uc u e and o ien a ion as a unc ion o p O2 /p N2 , can be desc ibed in h ee s eps: - Fi s a low p O2 /p N2 , he oxygen is p obably inco po a ed in o he g ain bounda ies and con inues o accumula e du ing GB mig a ion, esul ing in a ex u e wi h low deg ee o p e e ed o ien a ion and wi h low g ain size (Fig. 4); - Second wi h sligh ly highe p O2 /p N2 coa sening du ing coalescence is se e ely supp essed. The compe i i e g ow h which ollows is go e ned by aniso opic c ys allog aphic e ec s since he oxygen is inco po a ed in o he la ice, as desc ibed in [18]. The ilm is composed o globula g ains (Fig. 3b) wi h andom o ien a ion (Fig. 4); - Thi d as he p O2 /p N2 is u he inc eased, wi h inc easing oxygen concen a ion, he g ain size dec eased. The p esence o oxide phases inhibi s GB mig a ion in he bulk o he ilm, p e en ing g ain coa sening, becoming he ilm g ow h, a e y high p O2 /p N2 , amo phous. 3.3. Mechanical p ope ies The e olu ion o ha dness and Young's modulus as a unc ion o he p O2 /p N2 is illus a ed in Fig. 5. The s uc u al changes a e consis en wi h he e olu ion o he ha dness, as i can be seen by he signi ican educ ion o he ha dness by inc easing p O2 /p N2 , a ying om ypical TiN (23 GPa) ilm o he lowes p O2 /p N2 o hose o TiO x amo phous phase o highes concen a ion o oxygen (≈15 GPa) [19]. The eplace- men o ni ogen by ca bon a oms and he addi ion o Si in he coa ings leads o a dis o ion in he NaCl la ice ype s uc u e, which usually esul s in he inc ease o ha dness [20,21]. This is no obse ed in ou coa ings p obably due o he amoun o oxygen, as i is known ha he oxygen ac ing as an impu i y dec eases he ha dness o he coa ings [22]. A isible dec ease in Young's modulus was ound, wi h inc easing p O2 /p N2 and ela es o an inc ease on he de ec densi y and also he dec ease o he bonding ene gy, due o he inc ease dis ance be ween he a oms Ti, N and O, as he s uc u e changes o an amo phous ype. Fig. 6 shows he e olu ion o esidual s ess as unc ion o p O2 /p N2 . F om his g aph i is clea ha all coa ings a e in he comp essi e s ess s a e. This esul should be expec ed because o he low wo king p essu e (b0.45 Pa). Unde hese condi ions, spu e ed a oms o e lec ed A neu als could induce he well- known a omic peening e ec , which p omo es he comp essi e esidual s ess s a e [12,23]. Rega ding he e olu ion o he comp essi e s esses wi h inc easing p O2 /p N2 , i is possible o see ha he e is a dependence o he esidual s ess on he p O2 / p N2 . I is also no iceable a co ela ion be ween he comp essi e s esses and he measu ed ha dness. Fi s he ha des samples (deposi ed wi h low p O2 /p N2 ) p esen ed he highes esidual s ess alues, which we belie e is due o ilm densi ica ion and he p esence o la ice de ec s in he ilm's s uc u e, which ac as an obs acle o disloca ion mo ion. Secondly, o he ilms deposi ed wi h a high p O2 /p N2 which p esen ed e y low ha dness alues and de eloped a po ous columna g ow h is obse ed a s ong endency o s ess educ ion. Fu he mo e, as he oxygen inc eases he dis o ion in he c ys alline la ice inc eases, leading o a endency o ilm o become amo phous, as can be seen om he di ac ion pa e ns. As a esul o his highe deg ee o amo phous s uc u e, he ilms enhance hei capaci y o accommoda e he s ess, leading o a educ ion o i s alue. Fo he highes oxygen con en , eached o highes p O2 /p N2 , he coa ing is amo phous and he e o e he esidual s esses and ha dness a e e y low. In he li e a u e, Pa ei a e al. [12] as well as Vaz e al. [19] ha e s udied he in luence o he oxygen ac ion in he esidual s esses and ha dness o W–O–N, Ti–O–N coa ings, espec i ely. Globally, also hei case, he ha dness and esidual s ess dec eased wi h inc easing oxygen ac ion. 4. Conclusions Ti–Si–C–ON hin ilms we e deposi ed by eac i e mag- ne on spu e ing wi h di e en p O2 /p N2 . The ilms deposi ed unde low p O2 /p N2 p esen ed a dense and compac mo phology, a cc—c is alline s uc u e, ha dness highe han 20 GPa, highe Fig. 6. Comp essi e esidual s esses o spu e ed Ti–Si–C–ON as a unc ion o p O2 /p N2 . Fig. 5. Ha dness o spu e ed Ti–Si–C–ON as a unc ion o p O2 /p N2 . 2406 F. Guima ães e al. / Su ace & Coa ings Technology 202 (2008) 2403–2407 comp essi e esidual s ess. The ilms ha we e deposi ed wi h highe p O2 /p N2 p esen ed a po ous mo phology and a e amo phous. These samples exhibi ed low ha dness and e y low comp essi e esidual s ess. Tanking accoun he applica ion o hese coa ings (biomedical applica ion), p elimina y esul s showed, ha samples deposi ed wi h highe a ios o p O2 /p N2 p esen ed lowe alues o bio ilm o ma ion, indica ing ha he inc ease o oxygen leads o bioma e ials less suscep ible o be colonized by S. epide midis. Howe e , hese bioassays will be p esen ed by he au ho s in a u u e publica ion. Re e ences [1] D.V. S ansky, D.V. Le asho , N.B. Glushanko a, N.B. D'yakono a, e al., Su . Coa . Technol. 182 (1) (2004) 101. [2] Kalpana S. Ka i, Colloids Su . B Bioin e aces 39 (2004) 133. [3] Nuno Ce ca, Síl ia Ma ins, Ge a d B. Pie , Rosá io Oli ei a, Joana Aze edo, Res. Mic obiol. 156 (2005) 650. [4] M. Hen iques, J. Aze edo, R. Oli ei a, B . J. Biomed. Sci. 63 (1) (2006) 5. [5] B. Jansen, K. K is insson, S. Jansen, G. Pe e s, G. Pul e e , J. An imic ob. Chemo he . 30 (1992) 135. [6] S. Vep ěk, A. Niode ho e , K. Mo o, e al., Su . Coa . Technol. 133–134 (2000) 152. [7] F. Vaz, P. Ce quei a, L.Rebou a, S.M.C. 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