Nanostructured Materials and Nanotechnology VII, Volume 34, Issue 7 E-Book

Sanjay Mathur

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: Ceramic Engineering and Science Proceedings
• Sprache: Englisch

Seitenzahl: 298

Veröffentlichungsjahr: 2013

Beschreibung

Ceramic Engineering and Science Proceedings Volume 34, Issue 7 - Nanostructured Materials and Nanotechnology VII A collection of 15 papers from The American Ceramic Society's 37th International Conference on Advanced Ceramics and Composites, held in Daytona Beach, Florida, January 27-February 1, 2013. This issue includes papers presented in the 7th International Symposium on Nanostructured Materials and Nanotechnology (Symposium 7) and Nanomaterials for Sensing Applications symposia (Focused Session 3).

Leseprobe

Contents

Cover

Half Title page

Title page

Preface

Introduction

Nanostructured Materials and Nanotechnology

Sol-Gel Approach to the Calcium Phosphate Nanocomposites

Abstract

Introduction

Experimental

Results and Discussion

Conclusions

Acknowledgement

References

Reinforcement Mechanisms in Alumina Toughened Zirconia Nanocomposites with Different Stabilizing Agents

Abstract

Introduction

Experimental Procedure

Results and Discussion

Conclusions

Acknowledgement

References

Synthesis and Characterisation of Nanostructured Copper Oxide.

Abstract

Introduction

Experimental

Results and Discussion

Conclusions

Acknowledgement

References

X-Ray Diffraction Study on the In-Situ Crystallisation Kinetics in Electrospun PVP/TiO2 Nanofibers

Abstract

Introduction

Experimental Procedure

Results and Discussion

Conclusions

Acknowledgments

References

Metal-Catalyzed Growth of ZnO Nanowires

Abstract

Introduction

Experimental

Results and Discussion

Conclusion

References

Graphene-SnO2 Nanocomposites for Lithium-Ion Battery Anodes

Abstract

Introduction

Experimental

Results and Discussion

Conclusion

AcknowledgementS

References

Cobalt-Manganese Spinel Oxides as Visible-Light-Driven Water Oxidation Catalysts

Abstract

Introduction

Experimental

Results and Discussion

Conclusions

Acknowlegedments

References

Eclipse Transparent Electrode and Applications

Abstract

Introduction

THEORY

Experiments

Eclipse TEC Performances, Properties and Applications

Conclusions

References

Plasma Enhanced CVD of Transparent and Conductive Tin Oxide Thin Films

Abstract

Introduction

Experimental Details

Results and Discussion

Conclusion

Acknowledgments

References

Chemically Bonded Phosphate Ceramics Reinforced with Carbon Nanotubes

Abstract

Introduction

Experimental Methodology

Results and Discussion

Conclusion

References

Hardness of Alumina/Silicon Carbide Nanocomposites at Various Silicon Carbide Volume Percentages

Abstract

Introduction

Experimental Procedure

Experimental Results and Discussion

Conclusion

References

Nanomaterials for Sensing Applications

Self-Sustained NO2 Gas Sensor Operating at Room Temperatures Based on Solar Light Activated p-NiO/n-Si Diode

Abstract:

Introduction:

Experimental:

Results and Discussion:

Conclusion:

AcknowledgementS:

References:

Synthesis, Structural Studies of Some Lanthanide Complexes of the Mesogenic Schiff-Base, N,N’-di-(4’-Octadecyloxybenzoate)Salicylidene-1”, 3”-Diamino-2”-Propanol

Abstract:

1. Introduction

2. Experimental Section

3. Results and Discussion

4. Conclusions

AcknowledgementS

References

Development of Single-, Few- and Multiple-Nanowire Gas-Sensor Two-Terminal Devices on Ceramic Substrates and Characterization by Impedance Spectroscopy

Abstract:

Introduction

Results

Conclusion

References

Synthesis and Dispersion of Silica Nanowires for Biosensing Applications

Abstract

Introduction

Experimental

Results and Discussion

Conclusion

Acknowledgement

References

Author Index

Nanostructured Materials and Nanotechnology VII

Copyright © 2014 by The American Ceramic Society. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.Published simultaneously in Canada.

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ISBN: 978-1-118-80762-0ISSN: 0196-6219

Preface

This CESP issue contains papers that were presented during two symposia held during the 37th International Conference and Exposition on Advanced Ceramics and Composites, Daytona Beach, Florida, January 27–February 1, 2013:

Symposium 7: 7th International Symposium on Nanostructured Materials and Nanocomposites

Focused Session 3: Nanomaterials for Sensing Applications: Fundamental Material Designs to Device Integration

Over 90 contributions (invited talks, oral presentations, and posters) were presented by participants from universities, research institutions, and industry, which offered interdisciplinary discussions indicating strong scientific and technological interest in the field of nanostructured systems. This issue contains 15 peer-reviewed papers cover various aspects and the latest developments related to nanoscaled materials.

The editors wish to extend their gratitude and appreciation to all the authors for their cooperation and contributions, to all the participants and session chairs for their time and efforts, and to all the reviewers for their valuable comments and suggestions. Financial support from the Engineering Ceramic Division of The American Ceramic Society (ACerS) is gratefully acknowledged. The invaluable assistance of the ACerS staff of the meetings and publication departments, instrumental in the success of the symposium, is gratefully acknowledged.

We believe that this issue will serve as a useful reference for the researchers and technologists interested in science and technology of nanostructured materials and devices.

SANJAY MATHURUniversity of Cologne, Germany

FRANCISCO HERNANDEZ-RAMIREZCatalonia Institute for Energy Research and University of Barcelona, Spain

Introduction

This issue of the Ceramic Engineering and Science Proceedings (CESP) is one of nine issues that has been published based on manuscripts submitted and approved for the proceedings of the 37th International Conference on Advanced Ceramics and Composites (ICACC), held January 27–February 1, 2013 in Daytona Beach, Florida. ICACC is the most prominent international meeting in the area of advanced structural, functional, and nanoscopic ceramics, composites, and other emerging ceramic materials and technologies. This prestigious conference has been organized by The American Ceramic Society’s (ACerS) Engineering Ceramics Division (ECD) since 1977.

The 37th ICACC hosted more than 1,000 attendees from 40 countries and approximately 800 presentations. The topics ranged from ceramic nanomaterials to structural reliability of ceramic components which demonstrated the linkage between materials science developments at the atomic level and macro level structural applications. Papers addressed material, model, and component development and investigated the interrelations between the processing, properties, and microstructure of ceramic materials.

The conference was organized into the following 19 symposia and sessions:

Symposium 1

Mechanical Behavior and Performance of Ceramics and Composites

Symposium 2

Advanced Ceramic Coatings for Structural, Environmental, and Functional Applications

Symposium 3

10th International Symposium on Solid Oxide Fuel Cells (SOFC): Materials, Science, and Technology

Symposium 4

Armor Ceramics

Symposium 5

Next Generation Bioceramics

Symposium 6

International Symposium on Ceramics for Electric Energy Generation, Storage, and Distribution

Symposium 7

7th International Symposium on Nanostructured Materials and Nanocomposites: Development and Applications

Symposium 8

7th International Symposium on Advanced Processing & Manufacturing Technologies for Structural & Multifunctional Materials and Systems (APMT)

Symposium 9

Porous Ceramics: Novel Developments and Applications

Symposium 10

Virtual Materials (Computational) Design and Ceramic Genome

Symposium 11

Next Generation Technologies for Innovative Surface Coatings

Symposium 12

Materials for Extreme Environments: Ultrahigh Temperature Ceramics (UHTCs) and Nanolaminated Ternary Carbides and Nitrides (MAX Phases)

Symposium 13

Advanced Ceramics and Composites for Sustainable Nuclear Energy and Fusion Energy

Focused Session 1

Geopolymers and Chemically Bonded Ceramics

Focused Session 2

Thermal Management Materials and Technologies

Focused Session 3

Nanomaterials for Sensing Applications

Focused Session 4

Advanced Ceramic Materials and Processing for Photonics and Energy

Special Session

Engineering Ceramics Summit of the Americas

Special Session

2nd Global Young Investigators Forum

The proceedings papers from this conference are published in the below nine issues of the 2013 CESP; Volume 34, Issues 2–10:

Mechanical Properties and Performance of Engineering Ceramics and Composites VIII, CESP Volume 34, Issue 2 (includes papers from Symposium 1)

Advanced Ceramic Coatings and Materials for Extreme Environments III, Volume 34, Issue 3 (includes papers from Symposia 2 and 11)

Advances in Solid Oxide Fuel Cells IX, CESP Volume 34, Issue 4 (includes papers from Symposium 3)

Advances in Ceramic Armor IX, CESP Volume 34, Issue 5 (includes papers from Symposium 4)

Advances in Bioceramics and Porous Ceramics VI, CESP Volume 34, Issue 6 (includes papers from Symposia 5 and 9)

Nanostructured Materials and Nanotechnology VII, CESP Volume 34, Issue 7 (includes papers from Symposium 7 and FS3)

Advanced Processing and Manufacturing Technologies for Structural and Multi functional Materials VII, CESP Volume 34, Issue 8 (includes papers from Symposium 8)

Ceramic Materials for Energy Applications III, CESP Volume 34, Issue 9 (includes papers from Symposia 6, 13, and FS4)

Developments in Strategic Materials and Computational Design IV, CESP Volume 34, Issue 10 (includes papers from Symposium 10 and 12 and from Focused Sessions 1 and 2)

The organization of the Daytona Beach meeting and the publication of these proceedings were possible thanks to the professional staff of ACerS and the tireless dedication of many ECD members. We would especially like to express our sincere thanks to the symposia organizers, session chairs, presenters and conference attendees, for their efforts and enthusiastic participation in the vibrant and cutting-edge conference.

ACerS and the ECD invite you to attend the 38th International Conference on Advanced Ceramics and Composites (http://www.ceramics.org/daytona2014) January 26–31, 2014 in Daytona Beach, Florida.

To purchase additional CESP issues as well as other ceramic publications, visit the ACerS-Wiley Publications home page at www.wiley.com/go/ceramics.

SOSHU KIRIHARA, Osaka University, Japan

SUJANTO WIDJAJA, Corning Incorporated, USA

Volume EditorsAugust 2013

Nanostructured Materials and Nanotechnology

SOL-GEL APPROACH TO THE CALCIUM PHOSPHATE NANOCOMPOSITES

Aldona Beganskiene1, Zivile Stankeviciute1, Milda Malakauskaite1, Irma Bogdanoviciene1,2, Valdek Mikli2, Kaia Tõnsuaadu2, and Aivaras Kareiva1

1Department of Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania

2Laboratory of Inorganic Materials, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia

ABSTRACT

The sol-gel chemistry route has been developed to prepare Ca-O-P gels samples. In the sol-gel process 1,2-ethanediol and EDTA were used as complexing agents. Additionally, triethanolamine and polyvinyl alcohol were used as gel network forming materials. Calcium phosphate/hydroxyapatite thin films were obtained on silicon substrate by dip-coating technique. The final nanocomposites were obtained by calcination of coatings for different time at 1000°C. It was shown that adjustment of heating time and dip-coating conditions can be used to control the synthesis processing, phase purity and morphology of thin films. It was concluded, that the formation of calcium phosphate/hydroxyapatite composites in some cases is promoted by dipping time.

INTRODUCTION

Calcium hydroxyapatite (CHA) coatings have received considerable attention because they exhibit bone bonding capabilities, i.e. excellent biocompatibility, bioactivity and osteoconductivity).1,2,3 CHA coatings on different substrates (Ti-6A1-4V alloy, NiTi alloy, Mg, Ti, Si, steel) are being widely used in orthopedics and dentistry.4,5,6,7,8,9 Many preparation techniques are used currently in coating CHA onto different substrates. However, some metastable and amorphous phases appear in the CHA coating during the plasma spraying process10,11 or pulsed laser deposition12 which result in the low crystallinity of CHA coating. The biomimetic CHA coatings have the limitation of poor adhesion and lower growth rates.13,14 The sol-gel and hydrothermal methods are cost effective, low temperature routes for coating hydroxyapatite on various substrates.3,15

Sol-gel processing also provides a convenient method for applying tricalcium phosphate (TCP) films.16,17 Calcium phosphate ceramic is well known for its osteoinductive properties, good degradability, high hydrophilicity.18,19,20 Calcium phosphate cements have been used in medical and dental applications for many years.18 For example, tetracalcium phosphate is one of the major powder components of self-setting orthopedic and dental cements.21,22 However, the low strength and high brittleness of calcium phosphate cements prohibit their use in many stress-bearing locations, which would require an improvement in mechanical properties.23 It was shown that gelatine addition to calcium phosphate bone cement improves its mechanical properties.24

Calcium phosphate ceramics, which are commonly used as implants for bone reconstruction, appear to be good candidates for biocompatible drug carriers, since they can be resorbed by cells and they promote new bone formation by releasing calcium and phosphate ions.25 Drug-loaded polymers and calcium phosphate composites were also tested as cell and drug carrier materials.26,27 Recently calcium phosphate systems, including both hydroxyapatite and tricalcium phosphates (CHA-TCP), have attracted significant interest as drug delivery vehicles. It was demonstrated that protein loading and release behaviour of CHA-TCP can be controlled by tailoring particle size and surface area.28 The CHA-TCP cement was suggested as carrier for different drugs, proteins and chemotherapeutic agents.29,30 Many preparation techniques were suggested for the preparation of CHA-TCP films coating, such as microplasma spray31, high-power ion beam ablation plasma32, rf-magnetron sputtering33,34 or electrochemical/hydrothermal method.35 The sol-gel approach was used only for the preparation of biphasic CHA-TCP powders.36,37 In this paper we report on the synthesis and characterization of CHA-TCP thin films on the silicon33 substrate using dip-coating technique. For the preparation of stable sols a novel sol-gel synthesis approach was suggested.

EXPERIMENTAL

Aqueous sol-gel chemistry route based on phosphoric acid as the phosphorus precursor and calcium acetate monohydrate as source of calcium ions have been developed to prepare Ca-O-P gel samples. These gels were used as precursors for the deposition of Ca10(PO4)6(OH)2-Ca3(PO4)2 (CHA-TCP) composites onto commercial silicon (Si, 1.5×1.5) substrates by dip-coating technique from the Ca-O-P gels stabilized with complexing reagents. In the sol-gel process, 2.6425 g of calcium acetate monohydrate, Ca(CH3COO)2 · H2O (99.9%; Fluka) was dissolved in 50 ml of distilled water under continuous stirring at 65°C. To this solution 4.82185 g of ethylenediaminetetraacetic acid (EDTA; 99.0%; Alfa Aesar) was added. After stirring at 60–65°C for 1 h, 2 ml of 1,2-ethanediol (99.0%; Alfa Aesar) and 9 ml of triethanolamine (99.0%; Merck) were slowly poured to the solution. After stirring at 60–65°C for 10 h, appropriate amount of phosphoric acid, H3PO4 (85.0%; Reachem) was added to the above solution. Finally, 10 ml of 3% polyvinyl alcohol (PVA7200, 99.5%; Aldrich) solution was added. The obtained solution was stirred in a beaker covered with watch glass for 2 h at the same temperature and was used for coating of silicon substrates. Dip-coating method was employed to produce sol-gel coatings.38,39 The standard immersing (85 mm/min) and withdrawal rates (40 mm/min) for dip-coating process were applied for all the samples. The dipping procedure was repeatedly performed 5, 15 and 30 times. After evaporation of solvent the substrates were dried in an oven for 10 min at 110°C and heated at 1000°C for 5 h with heating rate of 1°C/min.

For the characterization of surface properties, the X-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM) and the contact angle measurements were recorded. XRD analysis was performed on a Bruker AXE D8 Focus diffractometer with a LynxEye detector using Cu Kα radiation. The measurements were recorded at the standard rate of 1.5–2θ/min. The scanning electron microscope JEOL JSM 8404 and atomic force microscope Veeco Bioscope 2 were used to study the surface morphology and microstructure of the obtained thin films. For the characterization of surface hydrophobicity of coatings, the measurements of a contact angle on dip-coating apparatus KVS Instrument CAM 100 were performed. A micro-droplet of water (volume 6 μl) was allowed to fall onto the sample from a syringe tip to produce a sessile drop. The Raman spectra were registered with confocal Raman spectrometer/microscope LabRam HR 800 using 632.8 nm laser for excitation.

RESULTS AND DISCUSSION

Fig. 1 represents the XRD patterns of films obtained from Ca-O-P gel using dip-coating technique. These results present the influence of the number of coating procedures on the crystallization of calcium phosphate coatings. As seen from Fig. 1, after first immersing, withdrawal and annealing procedure no peaks attributable to the Ca10(PO4)6(OH)2 or Ca3(PO4)2 crystal phases are observed. The layer formed contains only amorphous materials. However, already after five dipping and annealing times the main characteristic peaks attributable to tricalcium phosphate Ca3(PO4)2 and dicalcium diphosphate Ca2P2O7 (DCDP) crystal phases appear in the XRD pattern. The repetition of immersing, withdrawal and annealing procedures for 15 times did not change phase composition of coating. However, such repeating increased the crystallinity of phosphates significantly since the diffraction lines became more sharp and intense. Finally, with further increasing of calcium phosphate layers up to 30, the formation of calcium hydroxyapatite is evident (diffraction lines of CHA are marked as solid rhombus).11 The Ca3(PO4)2 and Ca2P2O7 phases also remain in the sample obtained after 30 immersing and annealing procedures. Thus, suggested sol-gel chemistry route could be successfully used for the preparation of CHA-TCP coatings containing dicalcium diphosphate onto silicon substrate.

Figure 1. XRD patterns of the Ca-O-P gel samples annealed at 1000°C after each dipping procedure for 5 h in air. Diffraction lines are marked: ♦ - Ca10(PO4)6(OH)2, - Ca3(PO4)2 and - Ca2P2O7.

The textural properties of the synthesized samples were investigated by scanning electron microscopy (SEM). Fig. 2 shows SEM micrographs (secondary electron (SE) and back scattered electron (BSE) images) of pure silicon substrate and sample obtained after first immersing, withdrawal and annealing procedure calcined at 1000°C.

Figure 2. SEM micrographs of silicon substrate (at left) and sample containing 1 layer of Ca-O-P gel calcined at 1000°C (at right) in SE (at top) and BSE (at bottom) modes.

The brightness of the silicon substrate on BSE image is highly homogeneous over the entire measuring area. Moreover, the SEM micrographs clearly show that already first layer contains Ca-O-P intermediate amorphous products which consist of differently shaped particles. The additional homogenization of the intermediates and further sol-gel processing are necessary to get CHA-TCP. The SEM micrographs of other three samples are presented in Fig. 3.

Figure 3. SEM micrographs of sample containing 5 layers (at left), 15 layers (at middle) and 30 layers (at right) of Ca-O-P gel calcined at 1000°C in SE (at top) and BSE (at bottom) modes.

A progressive change in morphology of specimens is evident with increased immersing time. The formation of differently shaped crystallites (spherical particles and plate-like grains) with an average grain size ranging between 1 and 2 μm is evident from these investigations. According to the SEM micrographs presented in Fig. 3 the coatings of 15 and 30 layers have similar structural characteristics. There are no macro cracks or pores. However, the amount of spherical particles slightly decreases with increasing amount of the layers on the substrate. Finally, the micrographs of Ca-O-P gel calcined at 1000°C show highly uniform and crystalline particles with smooth surfaces. Therefore, the proposed sol-gel technique appears to be very attractive way to make a high density, homogeneous CHA-TCP ceramic composites. The BSE images clearly demonstrate that most of the material is finely divided, however, the distribution of its chemical elements is not uniform. The formation of multiphasic system composed of 3 different phases is evident. Such observations partially support previous results obtained by XRD analysis. Fig. 1 clearly shows the formation of Ca10(PO4)6(OH)2, Ca3(PO4)2 and Ca2P2O7 crystalline phases only in the sample obtained after 30 immersing and annealing procedures.

On the other hand, the negligible v1(PO4) band attributable to CHA40 could be determined in the Raman spectra of the samples prepared using 5, 15 and 30 immersing and annealing procedures. The Raman spectra of the CHA-TCP specimens are shown in Fig. 4. So, the formation of amorphous Ca10(PO4)6(OH)2 phase along with crystalline calcium phosphates is also possible.41

Figure 4. Raman spectra of the Ca-O-P gel samples annealed at 1000°C after each dipping procedure for 5 h in air.

Typical AFM 3D images of the calcium phosphate/hydroxyapatite thin films prepared with different number of coating procedures are presented in Figs. 5–8. AFM images reveal a substantial difference of their surface morphology.

Figure 5. Surface morphology of film (1 layer) obtained by calcination Ca-O-P gel.

Figure 6. Surface morphology of film (5 layers) obtained by calcination Ca-O-P gel.

Figure 7. Surface morphology of film (15 layers) obtained by calcination Ca-O-P gel.

Figure 8. Surface morphology of film (30 layers) obtained by calcination Ca-O-P gel.

The surface of 1 layer film (see Fig. 5) exhibits smooth and homogeneous surface morphology with no special surface features. Only few submicroscopic bumps of about 250 nm diameter are visible. The intensity and size of bumps on the surface increases monotonically with increasing amount of layers up to 15. The bumps on the surface of calcium phosphate films originate from the explosive elimination of the residual solvent and complexing reagents.39 Interestingly, with further sol-gel processing (30 layers) the surface of film appeared more smooth and less defected (see Fig. 8). This may be associated with changes in phase composition of CHA-TCP coatings. The roughnesses measured by AFM are shown in Table 1.

Table 1. Surface roughness measured by AFM on phosphate/hydroxyapatite samples deposited using different dipping times.

Number of layers

RMS (Rq, nm)

Surface area 2/2 μm

Surface area 10/10 μm

0

0.2

0.2

1

17.1

20.0

5

22.2

90.7

15

45.3

174.8

30

19.1

166.1

The RMS roughness values measured by AFM were compared for different surface areas. As seen, the tendency of variation of surface roughness remains the same. Moreover, the RMS roughness results show very good correlation with SEM results.

In order to estimate hydrophobic properties of the produced thin films the contact angle measurements (CAM) were performed. Surprisingly, me hydrophobicity of CHA-TCP films was found to be slightly dependent on the number of coating procedures. The representative results are presented in Fig. 9 and Table 2.

Figure 9. Images of water droplets on the surfaces of substrate (at left, top) and CHA-TCP coatings obtained by forming 1 layer (at right, top), 15 layers (at left, bottom) and 30 layers (at right, bottom).

Table 2. Surface properties measured by CAM on phosphate/hydroxyapatite samples deposited using different dipping times.

Number of layers

Mean contact angle (degrees)

0

67.2

1

79.0

5

77.3

15

86.7

30

75.0

As seen from Fig. 9 and Table 2, the contact angle of the silicon substrate is about 67°. The substrate coated with 1 and 5 layers from Ca-O-P gel showed a higher contact angle (~77–79°). The contact angle of specimen produced with 15 dipping times has the highest value (~87°). Finally, the contact angle of the surface coated with 30 dipping times decreased till 75°. Thus, hydrophobicity of obtained thin films clearly depends on the chemical composition of the coating. The last composite material contains the highest amount of crystalline Ca10(PO4)6(OH)2 phase. Since only calcium hydroxyapatite contains hydroxy groupings, it is not surprising that the samples with higher concentration of Ca3(PO4)2 and Ca2P2O7 crystalline phases possess relatively higher hydrophobic properties. Moreover, the results of contact angle measurements are in a good agreement with the results of surface roughness measured by AFM.

The optical properties of CHA-TCP thin films synthesized using sol-gel process were also investigated. It is interesting to note, that UV-vis reflectance spectra of all samples are very similar. In Fig. 10 the UV-vis reflectance spectra of substrate and thin films obtained using different number of coating procedures are compared.

Figure 10. The reflectance spectra of substrate and of CHA-TCP coatings obtained using different number of coating procedures.

Evidently, the reflectance spectra of substrate and thin films obtained by the sol-gel processing are very similar independent on dipping time. This observation let us to conclude that sol-gel derived CHA-TCP films are very thin. As seen, several periodically repeating absorptions could be observed in the wavelength region of 200–450 nm. However in the higher wavelength region (≥ 450 nm), in whole wavelength region the reflectance is almost constant, i.e. not wavelength dependent. Such composites additionally doped by rare-earth elements would have an excellent optical quality.42,43

CONCLUSIONS

New sol-gel method for the preparation of calcium phosphate/hydroxyapatite thin films on silicon substrate using dip-coating technique has been developed. For the first time to the best our knowledge, it was demonstrated that an aqueous sol-gel technique is suitable for the formation of calcium phosphate/hydroxyapatite composite coatings containing dicalcium diphosphate. It was shown that adjustment of dip-coating conditions can be used to control the process of synthesis, phase purity and morphology of the bioceramic thin films. It was concluded, that the formation of calcium phosphate/hydroxyapatite mixture is promoted by dipping time. According to XRD analysis data, the concentration of hydroxyapatite in the mixture increases with increasing the repetition of dip-coating. The formation of differently shaped crystallites (spherical particles and plate-like grains) with an average grain size ranging between 1 and 2 μm was determined from SEM measurements. The roughness of thin films measured by AFM and hydrophobic properties measured by CAM are associated with changes in phase composition of CHA-TCP coatings. The optical behaviour of obtained coatings was investigated by UV-vis reflectance spectroscopy. The recorded optical reflectance spectra of calcium phosphate/hydroxyapatite samples showed that these compounds are excellent candidates as host material for advanced optical applications.

ACKNOWLEDGEMENT

Postdoctoral fellowship of Z. S. is being funded by European Union Structural Funds project “Postdoctoral Fellowship Implementation in Lithuania”.

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REINFORCEMENT MECHANISMS IN ALUMINA TOUGHENED ZIRCONIA NANOCOMPOSITES WITH DIFFERENT STABILIZING AGENTS

Sergio Rivera1, Luis A. Díaz2, Adolfo Fernández2, Ramón Torrecillas2, José S. Moya3

1Nanoker Research, S.L., Edificio CEEI, Parque Tecnológico de Asturias, 33428 - Llanera, Asturias, Spain.

2Centro de Investigación en Nanomateriales y Nanotecnología (CINN) Consejo Superior de Investigaciones Científicas (CSIC) - Universidad de Oviedo (UO) - Principado de Asturias (PA), Parque Tecnológico de Asturias, 33428 - Llanera, Asturias, Spain.

3Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), C/ Sor Juana Inés de la Cruz 3, 28049 - Cantoblanco, Madrid, Spain.

ABSTRACT

A colloidal processing route has been applied to obtain ATZ nanocomposites in order to develop strong and tough materials for structural applications. An initial composition of 35 vol% of Al2O3 as the disperse phase and two different stabilizing agents for ZrO2 as the matrix, Y2O3 (3 mol %) and CeO2 (10 and 12 mol %), is proposed. The Y2O3-stabilized nanocomposite has obtained a fracture toughness of 4.5 MPa√m and a strength of 685 MPa, clearly insufficient for high-demanding structural applications. The CeO2-stabilized nanocomposite, specifically the 10% mol Ce-TZP/Al2O3, has reported a fracture toughness that exceeds all the values obtained up to date in monolithic ceramics and in ATZ composites. The critical fracture toughness (KIC), measured under the presence of a long natural crack (13 MPa·√m), and the stress intensity threshold factor (KIO