《复合材料 Composites》课程教学资源（学习资料）第五章 陶瓷基复合材料_The yttria-stabilized zirconia and interfacial coating on NicalonTM fiber

CIENCEODIRECT. E≈RS ELSEVIER Journal of the European Ceramic Society 26(2006)1725-1736 www.elsevier.com/locate/jeurcera The yttria-stabilized zirconia and interfacial coating on Nicalon fiber N I Baklanova a, * A.T. Titoy b.A. l Boronin.s v. Kosheey c a Institute of Solid State Chemistry and Mechanochemistry, SB RAS, Kutateladze St. 18, Novosibirsk 630128, Russian Federation b General Institute of Geology, Geophysics and Mineralogy, SB RAS, Nou 630090. Russian Federation Received 15 November 2004: received in revised form 24 February 2005: accepted 5 March 2005 Available online 3 May 2005 Abstract Sols of yttria-stabilized zirconia may be used as simple, readily processable and accurate controllable precursors for the ZrO2 interfacial oatings on SiC-based Nicalon fibers. The ZrO2 interfacial coatings of predictable crystal phase compositions were obtained in dependend of yttria dopant level. The morphology, composition and oxidation resistance of coated fibers were evaluated by SEM, EDs, XPS, XRD and Raman analysis. All coatings obtained are uniform, continuous and adherent to substrates. The delamination within the ZrO2 interfacial coating was found. Possible reasons of this phenomenon are discussed. The peculiarities of the behavior of Y-stabilized ZrO2-coated fibers in air at elevated temperature are considered. o 2005 Elsevier Ltd. All rights reserved Keyword: Y ttria-stabilized zirconia: Fibres; Interfaces; SiC; ZrO2; Coatings 1. Introduction within ZrO2 layer occurred as result of the martensitic trans- formation of t-ZrO nuclei to m-ZrO, on reaching a critical Ceramic matrix composites(CMCs) reinforced by Sic grain size and the development of significant compressive based fibers such as Nicalon, Hi-Nicalon, Sylramic@ oop stresses due to volume dilation and shear associated iC/SiC) achieve high toughness and damage tolerance with the martensitic transformation. The delamination to be through the disposal of weak fiber coating which can deflect bserved for the ZrO2 coating provides the retention of fiber cracks and promote debonding at the fiber/matrix region. It strength. It should be noted that the delamination process can is stated that conventional interphase materials, such as car- lead to breaking of the integrity of the fiber coating. It is un bon and bn exhibit the environmental instability at operating desirable feature considering the necessity of protection the temperatures. Therefore, there is a strong interest to study fiber surface from matrix infiltration on following stages of alternative interfaces that would be more oxidation-resistant the fabrication CMCs. Therefore. a dense undelaminated but than carbon and Bn coatings. Among alternative interphases compressively stressed coating might be preferred before in- the refractory oxide-based systems are considered as the most filtration. Thus, in order to optimize the interfacial properties of ZrO2 as the fiber coating for SiC/SiC composites it is nec- The feasibility of using a CVD ZrO2 fiber coating as an essary accurately to control phase composition, morphology oxidation-resistant and weak interphase for SiC/SiC com- and an extent of phase transformation in the ZrO2 coating posites was thoroughly examined by Lee and coworkers7-9 layer They found that the CVd ZrO2 coating exhibited desired Numerous studies demonstrated(see, e.g. review ) that tensile failure behavior and extensive crack deflection within an addition of Y203 or other oxides, such as CaO, Mg the interface region. They concluded that the delamination CeO results in an appearance of oxygen vacancies and the formation of the stabilized tetragonal phase of ZrO. The Corresponding author. Tel. +7 3832 363839: fax: +7 3832 32284 toughness of Ysz ceramics is strongly dependent on the E-mail address: baklanova@ solid nsc. ru(NI. Baklanova volume fraction of tetragonal phase with toughness de 0955-2219/S-see front matter 2005 Elsevier Ltd. All rights reserved. doi: 10. 1016/j-jeurceramsoc. 2005.03.241

Journal of the European Ceramic Society 26 (2006) 1725–1736 The yttria-stabilized zirconia and interfacial coating on NicalonTM fiber N.I. Baklanova a,∗, A.T. Titov b, A.I. Boronin c, S.V. Kosheev c a Institute of Solid State Chemistry and Mechanochemistry, SB RAS, Kutateladze St. 18, Novosibirsk 630128, Russian Federation b General Institute of Geology, Geophysics and Mineralogy, SB RAS, Novosibirsk 630090, Russian Federation c Boreskov Institute of Catalysis, SB RAS, Novosibirsk 630090, Russian Federation Received 15 November 2004; received in revised form 24 February 2005; accepted 5 March 2005 Available online 3 May 2005 Abstract Sols of yttria-stabilized zirconia may be used as simple, readily processable and accurate controllable precursors for the ZrO2 interfacial coatings on SiC-based NicalonTM fibers. The ZrO2 interfacial coatings of predictable crystal phase compositions were obtained in dependence of yttria dopant level. The morphology, composition and oxidation resistance of coated fibers were evaluated by SEM, EDS, XPS, XRD, and Raman analysis. All coatings obtained are uniform, continuous and adherent to substrates. The delamination within the ZrO2 interfacial coating was found. Possible reasons of this phenomenon are discussed. The peculiarities of the behavior of Y-stabilized ZrO2-coated fibers in air at elevated temperature are considered. © 2005 Elsevier Ltd. All rights reserved. Keyword: Yttria-stabilized zirconia; Fibres; Interfaces; SiC; ZrO2; Coatings 1. Introduction Ceramic matrix composites (CMCs) reinforced by SiC￾based fibers such as NicalonTM, Hi-NicalonTM, Sylramic® (SiC/SiC) achieve high toughness and damage tolerance through the disposal of weak fiber coating which can deflect cracks and promote debonding at the fiber/matrix region.1 It is stated that conventional interphase materials, such as car￾bon and BN exhibit the environmental instability at operating temperatures.2,3 Therefore, there is a strong interest to study alternative interfaces that would be more oxidation-resistant than carbon and BN coatings. Among alternative interphases the refractory oxide-based systems are considered as the most promising ones. 4–6 The feasibility of using a CVD ZrO2 fiber coating as an oxidation-resistant and weak interphase for SiC/SiC com￾posites was thoroughly examined by Lee and coworkers7–9 They found that the CVD ZrO2 coating exhibited desired tensile failure behavior and extensive crack deflection within the interface region. They concluded that the delamination ∗ Corresponding author. Tel.: +7 3832 363839; fax: +7 3832 322847. E-mail address: baklanova@solid.nsc.ru (N.I. Baklanova). within ZrO2 layer occurred as result of the martensitic trans￾formation of t-ZrO2 nuclei to m-ZrO2 on reaching a critical grain size and the development of significant compressive hoop stresses due to volume dilation and shear associated with the martensitic transformation. The delamination to be observed for the ZrO2 coating provides the retention of fiber strength. It should be noted that the delamination process can lead to breaking of the integrity of the fiber coating. It is un￾desirable feature considering the necessity of protection the fiber surface from matrix infiltration on following stages of the fabrication CMCs. Therefore, a dense undelaminated but compressively stressed coating might be preferred before in- filtration. Thus, in order to optimize the interfacial properties of ZrO2 as the fiber coating for SiC/SiC composites it is nec￾essary accurately to control phase composition, morphology and an extent of phase transformation in the ZrO2 coating layer. Numerous studies demonstrated (see, e.g. review10), that an addition of Y2O3 or other oxides, such as CaO, MgO, CeO2 results in an appearance of oxygen vacancies and the formation of the stabilized tetragonal phase of ZrO2. The toughness of YSZ ceramics is strongly dependent on the volume fraction of tetragonal phase, with toughness de- 0955-2219/$ – see front matter © 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2005.03.241

1726 N.I. Baklanova et al /Journal of the European Ceramic Sociery 26(2006)1725-1736 creasing as a fraction of either the monoclinic or cubic phase 97 mol% ZrO2. The coating stage involved firstly the immer increases. Besides, it was detected the relationships between sion of the Nicalon fabrics into sols with different content the oxygen partial pressure and the nucleation and morpho- of yttria. Then the specimens were dried on air at ambient by CVD or magnetron sputtering methods. -9, These at atmospheric pressure. To increase of thickness of interfa- relationships were attributed to the grain size and oxygen cial coating the dipping-annealing procedure was repeated deficiency effects, which appear to cause the stabilization of several times t-ZrO2. Thus, one can see that the Zro2 coating composed Also the air-dried powders with different Y2O3 content of predominantly tetragonal or cubic transformable phases were prepared using sol-gel approach to compare the prop- can be fabricated with different experimental approaches erties of coatings and powders of the same composition. Early we reported about the particularities of the formation of refractory oxide interfacial coatings including ZrOz coat- 2.2. Specimen characterization ing on Nicalon fibers by sol-gel technique. A mixture of the monoclinic and tetragonal modifications was detected in The phases in sol-gel derived ZrO2 and Y-PSZ powders the ZrO2 coating derived from sol-gel precursors, with the and coatings were characterized by x-ray diffraction analysis monoclinic being predominant. The columnar morphology (XRD)using monochromatic Cu Ko radiation with DRON-3 was observed that could provide an easy, low-energy path for diffractometer(Russia). Scanning electron microscope SEM crack propagation. In order to either tough transformation or LEO 1430VP, supplied by EDX(Oxford)spectrometer was crack deflection mechanism to operate within interface zone used for studying of morphology and composition of coated the columnar morphology of ZrO2 coating must be modified fibers The aim of this work is to develop an approach to the The FT-Raman spectra of sol-gel derived ZrO2 and Y-pSZ formation of yttria-stablilized Zro, interfacial coatings on powders were recorded using a Bruker RFS 100/S spectrom- Nicalon TM fiber and to study the peculiarities of their compo- eter equipped with Nd- YAG laser operating at the 1064 nm sition, morphology and oxidation resistance. For this purpose excitation wavelength. The laser output was 100 m V. For each a sol-gel approach was chosen as main. The sol-gel pre spectrum 100 scans were accumulated. Micro Raman spectra could be considered as one of the most convenient technique of the Y-PSZ-coated Nicalon fibers were recorded using allowing us to produce the oxide interfacial coatings includ- a Triplemate SPEX spectrometer equipped with CCD spec ing zirconia coatings with controlled content of yttria and as ometric detector and microscope attachment for back scat- a consequence with predictable phase composition and mor tering geometry. The 488 nm radiation from an argon laser phology. was used for spectral excitation. XPS spectra were measured using VG ESCALAB spec trometer using al Ko irradiation and calibrated against au 2. Experimental 4f7/2(Eb=840eV) and Cu 2p3/2(Eb=932.7eV) lines Be- fore measurements specimens were heated for 30 min at 2.1. Substrate and coating preparation 600C in vacuum. All of spectra are represented in bind- ing energy scale that was obtained with respect to C ls peak Woven Nicalon TM NLM202(Nippon Carbon Co Japan) of carbon at 284.8eV For spectroscopic analysis of electron fiber cloths were used as substrate materials. Prior to coat- spectra the original software CALC was applied to extract the ing, Nicalon TM fiber cloths were immersed for 24 h in 50: 50 detailed information about electron structure of coated fiber acetone-ethanol mixture for removing a sizing agent, after that they were dried at ambient temperature. Then they were 23. Oxidation tests thermally treated in air at 450C. The coating process was based on the dipping of Thermal oxidation resistance of coated NicalonTM fab- NicalonM fabrics into sols of hydrated oxide metals.Pre- rics was examined in air under static conditions at 1000C cursors for the Y203-partially-stabilized zirconia (Y-Psz The samples of Nicalon fabrics(100-200 mg)were placed in the preliminary heated furnace(Ko-14, German)and oatings were the sols of hydrated yttrium-zirconium oxides kept during definite time intervals. Then the samples were with different Zro2: Y2O3 ratio. The preparation of initial sols taken out, cooled in dessicator and weighted with accu- was similar to that described by Yan and coworkers. 4The coating solution was prepared by dissolving yttrium nitrate racy +O 1 mg. A total time of testing was 26h hexahydrate Y(NO3)3-6H2O and zirconyl chloride octahy drate ZroCl2-8H20(CG, the Hf content not more than 1% 3. Results at given molar ratio in appropriate amount of ethanol-water solution. The coating solution contained metal ion concen- 3.1. SEM/EDS analvsis trations of 0. 1 M. Sols with the 3 and 9 mol% Y203 content were prepared Samples derived from these sols were named SEM images of the undoped and Y-doped ZrO2 coatin after the yttria content, i.e. 3Y-Zr02 means 3 mol%Y2O3 and Nicalon M fiber are represented in Fig. 1a-d.One can see

1726 N.I. Baklanova et al. / Journal of the European Ceramic Society 26 (2006) 1725–1736 creasing as a fraction of either the monoclinic or cubic phase increases. Besides, it was detected the relationships between the oxygen partial pressure and the nucleation and morpho￾logic characteristics of the ZrO2 coating that was formed by CVD or magnetron sputtering methods.7–9,11 These relationships were attributed to the grain size and oxygen deficiency effects, which appear to cause the stabilization of t-ZrO2. Thus, one can see that the ZrO2 coating composed of predominantly tetragonal or cubic transformable phases can be fabricated with different experimental approaches. Early we reported about the particularities of the formation of refractory oxide interfacial coatings including ZrO2 coat￾ing on NicalonTM fibers by sol–gel technique.12 A mixture of the monoclinic and tetragonal modifications was detected in the ZrO2 coating derived from sol–gel precursors, with the monoclinic being predominant. The columnar morphology was observed that could provide an easy, low-energy path for crack propagation. In order to either tough transformation or crack deflection mechanism to operate within interface zone the columnar morphology of ZrO2 coating must be modified. The aim of this work is to develop an approach to the formation of yttria-stablilized ZrO2 interfacial coatings on NicalonTM fiber and to study the peculiarities of their compo￾sition, morphology and oxidation resistance. For this purpose a sol–gel approach was chosen as main. The sol–gel process could be considered as one of the most convenient technique allowing us to produce the oxide interfacial coatings includ￾ing zirconia coatings with controlled content of yttria and as a consequence with predictable phase composition and mor￾phology. 2. Experimental 2.1. Substrate and coating preparation Woven NicalonTM NLM202 (Nippon Carbon Co. Japan) fiber cloths were used as substrate materials. Prior to coat￾ing, NicalonTM fiber cloths were immersed for 24 h in 50:50 acetone–ethanol mixture for removing a sizing agent, after that they were dried at ambient temperature. Then they were thermally treated in air at 450 ◦C. The coating process was based on the dipping of NicalonTM fabrics into sols of hydrated oxide metals. Pre￾cursors for the Y2O3-partially-stabilized zirconia (Y-PSZ) coatings were the sols of hydrated yttrium–zirconium oxides with different ZrO2:Y2O3 ratio. The preparation of initial sols was similar to that described by Yan and coworkers13,14 The coating solution was prepared by dissolving yttrium nitrate hexahydrate Y(NO3)3·6H2O and zirconyl chloride octahy￾drate ZrOCl2·8H2O (CG, the Hf content not more than 1%) at given molar ratio in appropriate amount of ethanol–water solution. The coating solution contained metal ion concen￾trations of 0.1 M. Sols with the 3 and 9 mol% Y2O3 content were prepared. Samples derived from these sols were named after the yttria content, i.e. 3Y-ZrO2 means 3 mol% Y2O3 and 97 mol% ZrO2. The coating stage involved firstly the immer￾sion of the NicalonTM fabrics into sols with different content of yttria. Then the specimens were dried on air at ambient temperature and then slowly heated till 960 ◦C in argon flow at atmospheric pressure. To increase of thickness of interfa￾cial coating the dipping–annealing procedure was repeated several times. Also the air-dried powders with different Y2O3 content were prepared using sol–gel approach to compare the prop￾erties of coatings and powders of the same composition. 2.2. Specimen characterization The phases in sol–gel derived ZrO2 and Y-PSZ powders and coatings were characterized by X-ray diffraction analysis (XRD) using monochromatic Cu K
radiation with DRON-3 diffractometer (Russia). Scanning electron microscope SEM LEO 1430VP, supplied by EDX (Oxford) spectrometer was used for studying of morphology and composition of coated fibers. The FT-Raman spectra of sol–gel derived ZrO2 and Y-PSZ powders were recorded using a Bruker RFS 100/S spectrom￾eter equipped with Nd-YAG laser operating at the 1064 nm excitation wavelength. The laser output was 100 mV. For each spectrum 100 scans were accumulated. Micro Raman spectra of the Y-PSZ-coated NicalonTM fibers were recorded using a Triplemate, SPEX spectrometer equipped with CCD spec￾trometric detector and microscope attachment for back scat￾tering geometry. The 488 nm radiation from an argon laser was used for spectral excitation. XPS spectra were measured using VG ESCALAB spec￾trometer using Al K
irradiation and calibrated against Au 4f7/2 (Eb = 84.0 eV) and Cu 2p3/2 (Eb = 932.7 eV) lines. Be￾fore measurements specimens were heated for 30 min at 600 ◦C in vacuum. All of spectra are represented in bind￾ing energy scale that was obtained with respect to C 1s peak of carbon at 284.8 eV. For spectroscopic analysis of electron spectra the original software CALC was applied to extract the detailed information about electron structure of coated fibers. 2.3. Oxidation tests Thermal oxidation resistance of coated NicalonTM fab￾rics was examined in air under static conditions at 1000 ◦C. The samples of NicalonTM fabrics (100–200 mg) were placed in the preliminary heated furnace (KO-14, German) and kept during definite time intervals. Then the samples were taken out, cooled in dessicator and weighted with accu￾racy ± 0.1 mg. A total time of testing was 26 h. 3. Results 3.1. SEM/EDS analysis SEM images of the undoped and Y-doped ZrO2 coating on NicalonTM fiber are represented in Fig. 1a–d. One can see

N.I. Baklanova et al / Journal of the European Ceramic Society 26 (2006)1725-1736 1727 Fig 1(a-d) SEM of the undoped (one cycle)and 9Y-ZrO2 coating on Nicalon M fiber(two cycles). (Fig. la), that the surface of undoped ZrO2 coating is rather other elements were detected in EDS spectra. They appear to smooth and adherent to fiber. No fiber bridging, no spalling of originate from a contamination by glue and sample holder. coating was observed. The non-uniformities shaped as crys- An increase of number of dipping-annealing till to tallized traces of coating sol that was retained between fila- 5 leads to strong nonuniformity of coating not only on ments within a tow bundle are seen on the surface of separate length but cross-section of a filament too(Fig. 3a-d), filaments. It should be noted that this is a rare occurrence. the thickness being about 1 um or more and variable at The thickness of coating after the first cycle, determined by different filaments. a great number of large well-developed SEM. is less than 80 nm crystals and aggregates are observed on the surface of A doping by yttrium(9Y-PSZ, two cycles) leads to sig filaments. One could be proposed that nonuniformaties nificant change in the surface morphology(Fig. Ib). Sepa- arising from the first cycles(see, e.g. Fig. 1b-d) could rate well-developed crystals and aggregates of crystals can serve as centers of crystallization on the following steps of be observed at the edge of cross-section and the surface of processing. Upon a closer view one can see that aggregates each filament, especially on contacts of filaments in a bundle are consisted from nanosized (less than 100 nm) crystals (Fig. Ic). Nevertheless, no bridging was observed(Fig. 1d).(Fig. 3b). They have isometric round-shaped form. One can The thickness of coating evaluated from SEM image is about observe places where a delamination within coating occurs 300-400 nm. Upon a closer view one can see that the mor(Fig. 3c). A crack deflection phenomenon is distinctly phology of crystals is isometric unlike of columnar one that detected at interfacial zone(ig. 3d). Crack direction is was observed for undoped ZrO2 coating. The presence of Si, changed from perpendicular to parallel to a fiber surface Zr, Y,O at areas which are marked in Fig. Id is detected by This is accompanied by debonding at the coating/fiber inter EDS analysis(Fig. 2). In addition, the peaks belonging to face

N.I. Baklanova et al. / Journal of the European Ceramic Society 26 (2006) 1725–1736 1727 Fig. 1. (a–d) SEM images of the undoped (one cycle) and 9Y-ZrO2 coating on NicalonTM fiber (two cycles). (Fig. 1a), that the surface of undoped ZrO2 coating is rather smooth and adherent to fiber. No fiber bridging, no spalling of coating was observed. The non-uniformities shaped as crys￾tallized traces of coating sol that was retained between fila￾ments within a tow bundle are seen on the surface of separate filaments. It should be noted that this is a rare occurrence. The thickness of coating after the first cycle, determined by SEM, is less than 80 nm. A doping by yttrium (9Y-PSZ, two cycles) leads to sig￾nificant change in the surface morphology (Fig. 1b). Sepa￾rate well-developed crystals and aggregates of crystals can be observed at the edge of cross-section and the surface of each filament, especially on contacts of filaments in a bundle (Fig. 1c). Nevertheless, no bridging was observed (Fig. 1d). The thickness of coating evaluated from SEM image is about 300–400 nm. Upon a closer view one can see that the mor￾phology of crystals is isometric unlike of columnar one that was observed for undoped ZrO2 coating. The presence of Si, Zr, Y, O at areas which are marked in Fig. 1d is detected by EDS analysis (Fig. 2). In addition, the peaks belonging to other elements were detected in EDS spectra. They appear to originate from a contamination by glue and sample holder. An increase of number of dipping–annealing till to 5 leads to strong nonuniformity of coating not only on length but cross-section of a filament too (Fig. 3a–d), the thickness being about 1m or more and variable at different filaments. A great number of large well-developed crystals and aggregates are observed on the surface of filaments. One could be proposed that nonuniformaties arising from the first cycles (see, e.g. Fig. 1b–d) could serve as centers of crystallization on the following steps of processing. Upon a closer view one can see that aggregates are consisted from nanosized (less than 100 nm) crystals (Fig. 3b). They have isometric round-shaped form. One can observe places where a delamination within coating occurs (Fig. 3c). A crack deflection phenomenon is distinctly detected at interfacial zone (Fig. 3d). Crack direction is changed from perpendicular to parallel to a fiber surface. This is accompanied by debonding at the coating/fiber inter￾face.

1728 N.I. Baklanova et al /Journal of the European Ceramic Sociery 26(2006)1725-1736 Zr zr key Full Scale 1139 cts kev Full Scale 581 cts Fig. 2. EDS spectrum of the 9Y-zrO2( two cycles)coating on NicalonM fiber 3. 2. XPS analysis elemental composition of surface layer can be evaluated. 5 The results are represented in Table 1. One can see from Fig 4 Survey XPS spectrum recorded from the 9Y-PSZ (five cy- that traces of sodium and nitrogen are present in coating. Ni- cles)coated Nicalon fabrics revealed a presence of oxy- trogen can be originated from the initial yttrium nitrate. Ear- gen, silicon, carbon, zirconium, yttrium as main components lier, the traces of sodium were revealed by XPS analysis in (Fig 4). After correction of intensities of C ls, O 1s, Si 2p, Zr initial Nicalon M fiber. 2 They could be introduced during 3d and Y 3d lines for their atomic sensitivity factors(ASF)the processing of fiber or handling Fig3(a-d)SEM images of the 9Y-zrO2 coating on Nicalon M fiber(five cycles)

1728 N.I. Baklanova et al. / Journal of the European Ceramic Society 26 (2006) 1725–1736 Fig. 2. EDS spectrum of the 9Y-ZrO2 (two cycles) coating on NicalonTM fiber. 3.2. XPS analysis Survey XPS spectrum recorded from the 9Y-PSZ (five cy￾cles) coated NicalonTM fabrics revealed a presence of oxy￾gen, silicon, carbon, zirconium, yttrium as main components (Fig. 4). After correction of intensities of C 1s, O 1s, Si 2p, Zr 3d and Y 3d lines for their atomic sensitivity factors (ASF) the elemental composition of surface layer can be evaluated.15 The results are represented in Table 1. One can see from Fig. 4 that traces of sodium and nitrogen are present in coating. Ni￾trogen can be originated from the initial yttrium nitrate. Ear￾lier, the traces of sodium were revealed by XPS analysis in initial NicalonTM fiber.12 They could be introduced during processing of fiber or handling. Fig. 3. (a–d) SEM images of the 9Y-ZrO2 coating on NicalonTM fiber (five cycles)

N.I. Baklanova et al / Journal of the European Ceramic Society 26 (2006)1725-1736 1729 O1s coated Nicalon M fiber is only slightly shifted to lower bind ing energy in comparison with peak for uncoated Nicalon M fiber. A slight shift to lower binding energy is observed also for Si 2p peak (Table 1). Analogous shifts O ls and si C1s 2p lines in XPS spectrum of Y203 film on silicon was found 11s by Chambers et al. 7 They detected also a shift of the Y 3ds/ Z3z30 peak to higher binding energy (158.3 eV). On this basis they concluded that the formation of interfacial structure with the Y3d Y-O-Si bonds possible to occur. According to data listed in Table I and in Fig 5b, the Y 3dsn peak for Y-PSZ-coated Nicalon is in a good accordance with data by Moulder et al.for pure Y203 and data reported by Zou et al.8There fore, one could be reliably proposed that the formation of the Binding energy, ev Zr-0-Si, but not the Y-o-Si bonds is more expectab\e TM The XPS Zr 3dsn spectrum of Y-PSZ-coated Nicalon fiber is shown in Fig. 5c. Deconvolution of this spectrum re- 4. Survey XPS spectrum of the 9Y-PSZ (five cycles) coated Nical sults in detection of two spin-orbital doublets. The position of one of them is in a good accordance with that reported for t YSZsingle crystal 6 Moreover, a strong broadening of peaks Fig 5 shows theO 1s, Y 3d and Zr 3d photopeaks Decon- is observed. It can be connected with disordering of the oxide volution of theo Is spectrum gives two components at 530.6 structure due to yttrium doping. 9, 20 Actually, from the SEM and 532.8eV. Earlier Boronin et al. 6 studied a XPS spe analysis results it follows that the oxide coating is strongly trum of the Y-stabilized ZrO2 single crystal in details. They nonuniform one and its integrity is disturbed(Fig. 3).An detected a single 1s peak at 5306e V which was assigned to additional doublet appears to be an evidence of presence of oxygen in the metal-oxygen-metal bond, namely Y-o-Zr. zirconium bonded with Sio2 surface layer of Nicalon fiber. One can propose that the low binding energy component that was observed in spectrum of Y-PSZ-coated Nicalon M fiber 3.3. Xrd and raman studies in this study also belongs to oxygen in the Y-o-zr bond Broadening of this peak (2.7e V) can be as evidence in The XRD patterns of the 3Y-( three cycles) and 9Y-PSZ favor of strong disordering of Y-doped zirconia phase. The ( five cycles)coated Nicalon fiber are represented in Fig. 6 second component at 532. 8eV inO ls spectrum of Y-PSz Very small intensity peaks are present in XRD pattern of sam- O1s Zr 3d 5328 535 150155160165178 181 184 187 Fig. 5. XPS spectra of the 9Y-ZrO2(four cycles) coating on Nicalon fiber: O Is, Y 3d(c)and Z 3d photopeaks Table 1 Elemental composition and binding energies for the 9Y-ZrO2- coated Nicalon fibers Elemental composition(at %o) 63 124 Binding energies(ev 5306,5328(0ls)102.5(Si2p)281.0,2848,289.6(ls)182.3(r3d5/2)182.3(Y3d5/2)10727(Nals) 1537(Si2s)

N.I. Baklanova et al. / Journal of the European Ceramic Society 26 (2006) 1725–1736 1729 Fig. 4. Survey XPS spectrum of the 9Y-PSZ (five cycles) coated NicalonTM fiber. Fig. 5 shows the O 1s, Y 3d and Zr 3d photopeaks. Decon￾volution of the O 1s spectrum gives two components at 530.6 and 532.8 eV. Earlier Boronin et al.16 studied a XPS spec￾trum of the Y-stabilized ZrO2 single crystal in details. They detected a single O 1s peak at 530.6 eV which was assigned to oxygen in the metal–oxygen–metal bond, namely Y–O–Zr. One can propose that the low binding energy component that was observed in spectrum of Y-PSZ-coated NicalonTM fiber in this study also belongs to oxygen in the Y–O–Zr bond. Broadening of this peak (∼2.7 eV) can be as evidence in favor of strong disordering of Y-doped zirconia phase. The second component at 532.8 eV in O 1s spectrum of Y-PSZ￾coated NicalonTM fiber is only slightly shifted to lower bind￾ing energy in comparison with peak for uncoated NicalonTM fiber.12 A slight shift to lower binding energy is observed also for Si 2p peak (Table 1). Analogous shifts O 1s and Si 2p lines in XPS spectrum of Y2O3 film on silicon was found by Chambers et al.17 They detected also a shift of the Y 3d5/2 peak to higher binding energy (158.3 eV). On this basis they concluded that the formation of interfacial structure with the Y–O–Si bonds possible to occur. According to data listed in Table 1 and in Fig. 5b, the Y 3d5/2 peak for Y-PSZ-coated NicalonTM is in a good accordance with data by Moulder et al.15 for pure Y2O3 and data reported by Zou et al.18 There￾fore, one could be reliably proposed that the formation of the Zr–O–Si, but not the Y–O–Si bonds is more expectable. The XPS Zr 3d5/2 spectrum of Y-PSZ-coated NicalonTM fiber is shown in Fig. 5c. Deconvolution of this spectrum re￾sults in detection of two spin-orbital doublets. The position of one of them is in a good accordance with that reported for the YSZ single crystal.16 Moreover, a strong broadening of peaks is observed. It can be connected with disordering of the oxide structure due to yttrium doping.19,20 Actually, from the SEM analysis results it follows that the oxide coating is strongly nonuniform one and its integrity is disturbed (Fig. 3). An additional doublet appears to be an evidence of presence of zirconium bonded with SiO2 surface layer of NicalonTM fiber. 3.3. XRD and Raman studies The XRD patterns of the 3Y- (three cycles) and 9Y-PSZ (five cycles) coated NicalonTM fiber are represented in Fig. 6. Very small intensity peaks are present in XRD pattern of sam￾Fig. 5. XPS spectra of the 9Y-ZrO2 (four cycles) coating on NicalonTM fiber: O 1s, Y 3d (c) and Z 3d photopeaks. Table 1 Elemental composition and binding energies for the 9Y-ZrO2-coated NicalonTM fibers O Si C Zr Y Na Elemental composition (at.%) 63 12.4 10 10 3.6 1 Binding energies (eV) 530.6, 532.8 (O 1s) 102.5 (Si 2p) 281.0, 284.8, 289.6 (C 1s) 182.3 (Zr 3 d5/2) 182.3 (Y 3d5/2) 1072.7 (Na 1s) 153.7 (Si 2s)