Goto  Takashi

Narushima  Takayuki

Sato  Mitsutaka

Tu  Rong

Ueda  Kyosuke

MATERIALS TRANSACTIONS

Sato, Mitsutaka

Tu, Rong

Goto, Takashi

Ueda, Kyosuke

Narushima, Takayuki

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

Preparation behavior in a Hanks' solution onCa-P-O films prepared by laser CVD著者 Sato  Mitsutaka, Tu  Rong, Goto  Takashi, Ueda Kyosuke, Narushima  Takayukijournal orpublication titleMaterials Transactionsvolume 50number 10page range 2455-2459year 2009URL http://hdl.handle.net/10097/52139Precipitation Behavior in a Hanks’ Solutionon Ca-P-O Films Prepared by Laser CVDMitsutaka Sato1, Rong Tu2, Takashi Goto2, Kyosuke Ueda3 and Takayuki Narushima31Osaka Center for Industrial Materials Research, Tohoku University, Sakai 599-8531, Japan2Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan3Department of Materials Processing, Tohoku University, Sendai 980-8579, JapanCa-P-O films were prepared by laser CVD using Ca(dpm)2 and (C6H5O)3PO metal organic precursors. The crystal phase of Ca-P-O filmschanged depending on deposition temperature (Tdep), total pressure (Ptot), laser power (PL) and molar ratio of Ca to P (RCa/P). -TCP films in asingle phase were obtained in a P-rich and high Tdep region, while HAp films in a single phase were obtained in a Ca-rich and low Tdep region.The -TCP films had a (220) orientation with an elongated and angular roof-shaped surface texture, whereas HAp films had a (300) orientationwith a granular surface texture. Both the -TCP film and the HAp film had a dense cross section. The Ca-P-O films were immersed in a Hanks’solution for 6 h to 7 d. Particle-shaped precipitates were observed on the -TCP and HAp films after 3 d immersion. Needle-shaped precipitatescovered the whole surface of HAp film after 7 d immersion. [doi:10.2320/matertrans.M2009160](Received May 7, 2009; Accepted July 7, 2009; Published August 19, 2009)Keywords: laser chemical vapor deposition (CVD), -tricalcium phosphate, hydroxyapatite, Hanks’ solution1. IntroductionTi and its alloys have been widely used in artificialimplants such as artificial hip joints and teeth implantsbecause of their good mechanical properties, corrosionresistance and biocompatibility.1,2) However, it takes morethan 3 months for Ti alloys to adhere to bones.3,4) In orderto shorten the adherence time, bio-ceramic films on implantshave been widely investigated by using sol-gel,5,6) plasmaspray,7,8) sputtering9,10) and an alkali heating process.11,12)Chemical vapor deposition (CVD) is advantageous toobtain a wide range of films at a relatively high depositionrate with good morphology controllability and good adher-ence to substrates, as commonly demonstrated in thepreparation of TiO213) and ZrO214) films. In our previouswork, we prepared calcium titanate (CaTiO3),15) -tricalciumphosphate (-Ca3(PO4)2, -TCP) and hydroxyapatite(Ca10(PO4)6(OH)2, HAp)16) films by MOCVD and immersedthem in a pseudo body fluid to investigate apatite regener-ation behavior.17,18) In the case of CaTiO3 films, the apatiteregeneration rate significantly depended on the surfacemorphology of films, and the nucleation of apatite occurredat hollow places on the film surface. However, in the caseof -TCP and HAp films prepared by MOCVD, a smoothand dense microstructure was obtained. If Ca-P-O films hada more complicated surface morphology, the precipitationwould be more promoted.We have previously reported the use of the laser chemicalvapor deposition (LCVD) process to prepare Ca-P-O films onalumina substrates.19) -TCP and HAp films in a single phasewere obtained and their surface morphology had a morecomplicated texture compared with those prepared byMOCVD, where -TCP film had orientations of (290) and(400), while HAp film showed orientations of (002) and (300)when the deposition conditions were changed.In the present study, Ca-P-O films were prepared on CP-Tisubstrates by LCVD, and the precipitate regeneration behav-ior on the Ca-P-O films prepared on CP-Ti substrates byLCVD was studied in a Hanks’ solution.2. Experimental ProceduresCa-P-O films were prepared by a vertical cold-wall typeLCVD apparatus. Figure 1 is a schematic of the LCVDapparatus. Ca(dpm)2 (bis-dipivaloylmethanato-calcium) and(C6H5O)3PO (triphenylphosphate) precursor powders wereevaporated at 523 to 573 and 493 to 533K, respectively. Themolar ratio of Ca to P (RCa/P) was controlled by changing theevaporation temperature (Teva). The precursor vapors werecarried into the reactor by Ar gas. O2 gas was separatelyintroduced by a double-tube nozzle. The total gas flow rate(FRtot ¼ FRAr þ FRO2 ) was fixed at 3:33 106 m3 s1.The substrate was pre-heated (Tpre) at 673 to 873K. Thetotal pressure (Ptot) in the CVD reactor was kept at 0.6 kPa.A Nd:YAG laser (wavelength,  ¼ 1064 nm) was irradiatedto a substrate through a quartz window. The size of thelaser beam was expanded by an optic lens to about 15mmin diameter. The laser power (PL) was changed from 0Fig. 1 Schematic of laser CVD apparatus.Materials Transactions, Vol. 50, No. 10 (2009) pp. 2455 to 2459#2009 The Japan Institute of Metalsto 200W. A commercially pure titanium (CP-Ti) plate(10 10 1:0mm) was used as a substrate. A thermocouplewas inserted into a pre-cut slot at the backside to measuredeposition temperature (Tdep). The distance between thenozzle and the substrate was fixed at 20mm. The depositionconditions are summarized in detail in Table 1. The crystalstructure of the films was analyzed by X-ray diffraction(XRD). The microstructure and thickness were examined byscanning electron microscopy (SEM). Precipitation behavioron Ca-P-O film was investigated by an immersion test ina Hanks’ solution for 6 h to 7 d. The composition of theHanks’ solution is listed in Table 2.3. Results and DiscussionFigure 2 shows the relationship between PL and Tdepfor Al2O3 and CP-Ti substrates. The Tdep increased withincreasing PL and the Tdep of CP-Ti substrate was slightlyhigher than that of the Al2O3 substrate. This may have beencaused by the laser absorbance of CP-Ti being higher thanthat of Al2O3.20,21) Since the surface of the CP-Ti substratewas partially melted at PL > 50W, the deposition of Ca-P-Ofilms on the CP-Ti substrates was conducted at PL  50W.Figure 3 shows the relationship between the evaporationrate of precursors (Reva) and the Tdep of CP-Ti substrate. TheTdep increased with increasing PL under the same Tpre.However, the Tdep was almost independent of Reva. We havepreviously reported that plasma appeared around the sub-strate due to the interaction between laser emission andexothermic chemical reactions between precursor vapors andO2 gas. The plasma combined with the laser emission to thesubstrate caused the temperature increase from Tpre to Tdep.Since the PL was small at less than 50W, the temperatureincrease (T ¼ Tdep  Tpre) was 100 to 200K, almostindependent of Reva.Figure 4 shows a CVD phase diagram of Ca-P-O filmsprepared on CP-Ti substrate at PL ¼ 30W and Ptot ¼0:6 kPa. At Tdep > 850K and RCa/P < 0:45, mixed phasesof HAp and -TCP were obtained. At Tdep ¼ 750 to 850K,RCa/P < 0:45 and at Tdep > 850K, RCa/P ¼ 0:45 to 0.6, HApfilms in a single phase were obtained, whereas at RCa/P > 0:6,mixed phases of HAp and tetracalcium phosphate (TTCP,Ca4(PO4)2O) or those of HAp and CaO were obtained. ACaO phase tended to be co-deposited in a low Tdep region.Figure 5 shows a CVD phase diagram of Ca-P-O filmsprepared on a CP-Ti substrate at PL ¼ 50W and Ptot ¼0:6 kPa. At Tdep > 900K and RCa/P < 0:4, -TCP in a singlephase was obtained. At Tdep > 900K, RCa/P ¼ 0:4 to 1.0 andat Tdep < 900K, RCa/P < 0:45, a mixed phase of -TCP andHAp was obtained. At Tdep > 900K, RCa/P > 1:0 and Tdep <900K, RCa/P > 0:45, HAp in a single phase was obtained.Comparing with Fig. 4, CaO and TTCP were not identified atPL ¼ 50W. In general, CaO cannot react with P-compoundsat a low temperature probably less than Tdep ¼ 800K as canbe seen from Fig. 4. At PL ¼ 50W, due to the high PL, theTdep was always more than 800K and then no CaO wasidentified. The reactivity of P-compounds with CaO is ratherlow. Due to higher excitation in higher PL, the P richercompounds could be likely to form at higher PL. This may beTable 1 Deposition conditions of Ca-P-O films.Precursor Ca(dpm)2(C6H5O)3POVaporization temperature (Tprec) 553–593K (Ca(dpm)2)473–513K ((C6H5O)3PO)Substrate CP-TiLaser power (PL) 30–50WPreheating temperature (Tpre) 673–873KTotal pressure (Ptot) 0.6 kPaAr gas flow rate (FAr) 8:3 107 m3s1 (50 sccm)O2 gas flow rate (FO2 ) 1:6 106 m3s1 (100 sccm)Distance between nozzle and substrate (d) 20mmDeposition time 10minTable 2 Chemical composition of Hanks’ solution.Concentration (g/m3)NaCl KCl Na2HPO4 KH2PO4 MgSO4 MgCl2 CaCl2 Glucose8000 400 47.9 60 48.8 46.8 140 1000Fig. 2 Relationship between Tdep and PL for alumina and CP-Ti substrate.Fig. 3 Relationship between Tdep and Reva at Ptot ¼ 0:6 kPa.2456 M. Sato, R. Tu, T. Goto, K. Ueda and T. Narushimathe reason of the formation of TTCP at PL ¼ 50W, but not ateven the same Tdep as shown in Figs. 4 and 5. Generally, incommon thermal CVD, the kind of deposited phases areprimarily determined thermodynamically by temperature(Tdep) and chemical potentials of source gases. On the otherhand, the deposited phases in the present LCVD weresignificantly affected by PL, suggesting that the laser itselfaffected the deposited phase due to photochemical effects.Figure 6 shows XRD patterns of -TCP and HAp filmsprepared on CP-Ti substrate at PL ¼ 50W and Ptot ¼0:6 kPa. The lattice parameters of -TCP film were a ¼1:042 and c ¼ 3:731 nm, almost in agreement with theliterature data of -TCP (hexagonal, a ¼ 1:0429 and c ¼3:738 nm).22) The lattice parameters of HAp (a ¼ 0:946 andc ¼ 0:687 nm) were also close to the values of HAp filmsprepared by MOCVD.19) -TCP and HAp films had signifi-cant orientations of (220) and (300), respectively.Figure 7 shows the surface morphology of -TCP andHAp films prepared on CP-Ti substrate at PL ¼ 50W andPtot ¼ 0:6 kPa. The surface morphology of -TCP filmshowed an elongated and angular roof-shaped texture thatis often observed in (110)-oriented films (Fig. 7(a)). Thecross-sectional morphology of -TCP had a dense texture10 mm in thickness. The surface morphology of HAp filmhad a granular texture 3 mm in diameter (Fig. 7(b)), similar tothat of HAp film prepared on Al2O3 substrate by laser CVD,as previously reported.19) The cross-sectional morphology ofHAp film also had a dense texture.Figure 8 shows the surface morphology of -TCP filmprepared on CP-Ti substrate at PL ¼ 50W and Ptot ¼ 0:6 kPabefore and after immersion in a Hanks’ solution. Almost nochanges were observed until 24 h of immersion (Fig. 8(b),(c)). The edges of the roof-shaped crystals in the -TCP filmbecame round after 3 d (Fig. 8(d)). It is known that -TCPmay dissolute in a simulated body fluid more than HAp.23)The microstructure change may be related to the dissolutionof -TCP film. Spherical particles were preferentiallyprecipitated at hollow places on the -TCP film after 3 d(Fig. 8(d)). In our previous study, similar precipitates wereobserved on -TCP films prepared by MOCVD afterFig. 4 CVD phase diagram of Ca-P-O films prepared at PL ¼ 30W andPtot ¼ 0:6 kPa.Fig. 5 CVD phase diagram of Ca-P-O films prepared at PL ¼ 50W andPtot ¼ 0:6 kPa.Fig. 6 XRD patterns of -TCP and HAP films prepared at RCa/P ¼ 0:22and Tdep ¼ 938K (a) and RCa/P ¼ 0:72 and Tdep ¼ 848K (b), respectively.(PL ¼ 50W, Ptot ¼ 0:6 kPa)Fig. 7 Surface morphology of -TCP and HAp films prepared atRCa/P ¼ 0:19 and Tdep ¼ 933K (a) and RCa/P ¼ 1:16 and Tdep ¼ 936K(b), respectively. (PL ¼ 50W, Ptot ¼ 0:6 kPa)Precipitation Behavior in a Hanks’ Solution on Ca-P-O Films Prepared by Laser CVD 2457immersion in the Hanks’ solution for 3 d.18) The precipitatesgrew with time, and finally identified as hydroxyapatite byXRD after immersion for 14 d. In the present study, theprecipitates were too small to be determined by XRD, butanalyzed as a Ca-P-O compound by energy-dispersive X-rayspectroscopy (EDS). The Ca/P molar ratio were ratherscattered in the range between 1.1 and 1.4 due to too smallsizes. These precipitates may be a kind of embryo or performof apatite.Figure 9 shows the surface morphology of HAp filmprepared on CP-Ti substrate at PL ¼ 50W and Ptot ¼ 0:6 kPabefore and after immersion in a Hanks’ solution. No changeswere observed until 24 h of immersion (Fig. 9(b), (c)).Spherical particles were preferentially precipitated along thegrain boundaries of cone texture in the HAp film after 3 d(Fig. 9(d)). Sugino et al. studied the hydroxyapatite regen-eration on two pieces of pre-oxidized V-shaped Ti plateschanging the distance between the Ti plates.24–26) Theydemonstrated the regeneration of hydroxyapatite on bothfacing Ti surfaces after immersing in a simulated body fluid.The regeneration of hydroxyapatite strongly depended on thedistance, and was significant at a narrow spacing less than0.6mm. In the present study, the regeneration at a narrowspace such as the boundaries of cone texture was evident asshown in Fig. 9(d). After 7 d, needle-like precipitates whollycovered the surface of HAp films (Fig. 9(e)). For both of theMOCVD and LCVDHAp films, the precipitates were formedpreferentially at the grain boundaries. However, the regen-erated precipitates wholly covered the MOCVD HAp filmswithin 6 h, which was much faster than that of LCVD HApfilms. MOCVD HAp films consisted of granular grains insub-micron size whereas LCVD HAp films composed oflarge grains 1 to 3 mm in size. The LCVD HAp grains had aflat surface probably due to high crystallinity. In our previousstudies on the MOCVD CaTiO3 films, the regeneration rateof hydroxyapatite on a complicated surface was much fasterthan that on a flat surface. The flat surface of large grainswith high crystallinity of LCVD HAp films might haveresulted in a slow regeneration rate.4. ConclusionCa-P-O films were prepared on a CP-Ti substrate byLCVD. -TCP films in a single phase were obtained atTdep > 900K, RCa/P < 0:4 and PL ¼ 50W, while HAp filmsin a single phase were obtained at PL ¼ 50W, Tdep > 900K,RCa/P > 1:0 and Tdep < 900K, RCa/P > 0:45. The surfacemorphology of -TCP films showed an elongated and angularroof-shaped texture with a (220) orientation. The surfacemorphology of HAp films had a granular texture with a(300) orientation. Spherical apatite crystals were regeneratedat hollow places on -TCP and HAp films after 3 d. Needle-like apatite crystals covered the whole surface of HAp filmsafter 7 d.Fig. 8 Surface morphology of -TCP film (a) before immersion and afterimmersion in a Hanks’ solution for (b) 6 h, (c) 24 h, (d) 3 d and (e) 7 d.Fig. 9 Surface morphology of HAp film (a) before immersion and afterimmersion in a Hanks’ solution for (b) 6 h, (c) 24 h, (d) 3 d and (e) 7 d.2458 M. Sato, R. Tu, T. Goto, K. Ueda and T. NarushimaAcknowledgementsThis study was partially supported by the Japan Society forthe Promotion of Science (JSPS), Grant-in-Aids for ScientificResearch (B), 18360310, Grant-in-Aids for JSPS fellow,global COE ‘‘Materials Integration’’, Tohoku University,Asian CORE program and Research and Education Fundingfor Inter-University Research Project, MEXT, JAPAN.REFERENCES1) M. Papakyriacou, H. Mayer, C. Pypen, H. Plenk Jr. and S. Stanz-Tschegg: Int. J. Fatigue 22 (2000) 873–886.2) A. Yamamoto, R. Honma and M. Sumita: J. Biomed. Mater. Res. 39(1998) 331–340.3) P. I. Branemark, U. Breine, R. Adell, B. O. Hansson, J. Lindstrom andA. Ohlsson: Scand. J. Plast. Reconstr. Surg. 3 (1969) 81–100.4) P. I. Branemark: J. Prosthet. Dent. 50 (1983) 399–410.5) D.-M. Liu, T. Troczynski and W. J. Tseng: Biomaterials 22 (2001)1721.6) W. Wheng: J. Am. Ceram. Soc. 82 (1999) 27.7) H. Ji, C. B. Ponton and P. M. Marquis: J. Mater. Sci.: Mater. Med. 3(1992) 283.8) I. Baltag, K. Watanabe, H. Kusakari, N. Taguchi, O. Miyakawa, M.Kobayashi and N. Ito: J. Biomed. Mater. Res. 53 (2000) 76.9) T. Narushima, K. Ueda, T. Goto, H. Masumoto, T. Katsube, H.Kawamura, C. Ouchi and Y. Iguchi: Mater. Trans. 46 (2005) 2246–2252.10) K. Yamashita, T. Arashi, K. Kitagaki, S. Yamada and T. Umegaki:J. Am. Ceram. Soc. 77 (1994) 2401.11) H. M. Kim, F. Miyaji, T. Kokubo and T. Nakamura: J. Biomed. Mater.Res. A 32 (1996) 409–417.12) M. Uchida, H. M. Kim, T. Kokubo, S. Fujibayashi and T. Nakamura:J. Biomed. Mater. Res. B 63 (1996) 522–530.13) R. Tu and T. Goto: Mater. Sci. Forum 475–479 (2005) 1219–1222.14) T. Kimura and T. Goto: Mater. Trans. 44 (2003) 421–424.15) M. Sato, R. Tu and T. Goto: Mater. Trans. 47 (2006) 1386–1390.16) M. Sato, R. Tu and T. Goto: Mater. Trans. 48 (2007) 3149–3153.17) M. Sato, R. Tu, T. Goto, K. Ueda and T. Narushima: Mater. Trans. 48(2007) 1505–1510.18) M. Sato, R. Tu, T. Goto, K. Ueda and T. Narushima: Mater. Trans. 49(2008) 1848–1852.19) M. Sato, R. Tu, T. Goto, K. Ueda and T. Narushima: J. Ceram. Soc. Jpn.117 (2009) 461–465.20) D. W. Lynch and W. R. Hunter: Handbook of optical constants ofsolids, (1985) 240–249.21) F. Gervais: Handbook of optical constants of solids, (1985) 761–775.22) P. M. deWolff: Technisch Physische Dienst, Delft, The Netherlands,ICDD Grant-in-Aid, PDF #09-0169.23) J. Dong, T. Uemura, Y. Shirasaki and T. Tateishi: Biomaterials 23(2002) 4493–4502.24) A. Sugino, K. Uetsuki, K. Tsuru, S. Hayakawa, A. Osaka and C.Ohtsuki: Mater. Trans. 49 (2008) 428–434.25) X. X. Wang, S. Hayakawa, K. Tsuru and A. Osaka: J. Biomed. Mater.Res. 54 (2001) 172–178.26) X. X. Wang, W. Yan, S. Hayakawa, K. Tsuru and A. Osaka:Biomaterials 24 (2003) 4631–4637.Precipitation Behavior in a Hanks’ Solution on Ca-P-O Films Prepared by Laser CVD 2459

Preparation behavior in a Hanks' solution on Ca-P-O films prepared by laser CVD

https://tohoku.repo.nii.ac.jp/?action=repository_action_common_download&item_id=44067&item_no=1&attribute_id=18&file_no=1

Preparation behavior in a Hanks\u27 solution on Ca-P-O films prepared by laser CVD

Preparation behavior in a Hanks\u27 solution on Ca-P-O films prepared by laser CVD

Abstract

Similar works

Full text

Available Versions

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ