Enhanced Hardness of Transparent HAp Ceramic by Microstructure Refinement

Abstract

Transparent hydroxyapatite (HAp) ceramics with the grain size ranging 86–1 300 nm were successfully synthesized by spark plasma sintering (SPS) at 925–1 200°C. All the sample achieved final density higher than 99.7%. The phase stability was identified by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The experimental results indicate that there is no decomposition or dehydroxylation during the SPS processes. The influences of microstructure refinement on the hardness were investigated using Hall- Petch (H-P) relationship, and the hardness of transparent HAp ceramic increases with the decrease of grain size. It is demonstrated that the grain boundaries and defects play important roles on the hardness.

Keywords

hydroxyapatite / transparent / hardness / grain size / microstructure refinement

References

[1] Krell A, Blank P. Grain Size Dependence of Hardness in Dense Submicrometer Alumina[J]. J. Am Ceram. Soc., 1995, 78: 1 118-1 120.

[2] Quinn JB, Quinn GD. Indentation Brittleness of Ceramics: a Fresh Approach[ J]. J. Mater. Sci., 1997, 32: 4 331-4 346.

[3] Štubňa I, Šín P, Viljus M, Trník A. The Effect of the Firing Temperature on the Hardness of Alumina Porcelain[J]. Mater. Tehnol., 2014, 48: 331-336.

[4] Rice RW, Wu CC, Borchelt F. Hardness–grain–size Relations in Ceramics[ J]. J. Am Ceram. Soc., 1994, 77: 2 539-2 553.

[5] Gong JH, Miao HZ, Peng ZJ, Qi LH. Effect of Peak Load on the Determination of Hardness and Young’s Modulus of Hot–pressed Si3N4 by Nanoindentation[J]. Mat. Sci. Eng. A–Struct., 2003, 354: 140-145.

[6] Cheng YT, Cheng CM. Scaling, Dimensional Analysis, and Indentation Measurements[J]. Mat. Sci. Eng. R., 2004, 44: 91-149.

[7] Muralithran G, Ramesh S. The Effects of Sintering Temperature on the Properties of Hydroxyapatite[J]. Ceram. Int., 2000, 26: 221-230.

[8] Messing GL, Stevenson AJ. Toward Pore–Free Ceramics[J]. Science, 2008, 322: 383-384.

[9] Guo XK, Yu L, Chen LH, et al. Organoamine–assisted Biomimetic Synthesis of Faceted Hexagonal Hydroxyapatite Nanotubes with Prominent Stimulation Activity for Osteoblast Proliferation[J]. J. Mater. Chem. B, 2014, 2: 1 760-1 763.

[10] Tang CY, Uskokovic PS, Tsui CP, et al. Influence of Microstructure and Phase Composition on the Nanoindentation Characterization of Bioceramic Materials Based on Hydroxyapatite[J]. Ceram. Int., 2009, 35: 2 171-2 178.

[11] Gu YW, Loh NH, Khor KA, et al. Spark Plasma Sintering of Hydroxyapatite Powders[J]. Biomaterials, 2002, 23: 37-43.

[12] Vijayan S, Varma H. Microwave Sintering of Nanosized Hydroxyapatite Powder Compacts[J]. Mater. Lett., 2002, 56: 827-831.

[13] Ramesh S, Tan CY, Bhaduri SB, et al. Rapid Densification of Nanocrystalline Hydroxyapatite for Biomedical Applications[J]. Ceram. Int., 2007, 33: 1 363-1 367.

[14] Mazaheri M, Haghighatzadeh M, Zahedi A M, et al. Effect of a Novel Sintering Process on Mechanical Properties of Hydroxyapatite Ceramics[ J]. J. Alloy. Compd., 2009 180-184.

[15] Wang J W, Shaw L L. Grain–size Dependence of the Hardness of Submicrometer and Nanometer Hydroxyapatite[J]. J. Am Ceram. Soc., 2010, 93: 601-604.

[16] Eriksson M, Liu Y, Hu JF, et al. Transparent Hydroxyapatite Ceramics with Nanograin Structure Prepared by High Pressure Spark Plasma Sintering at the Minimized Sintering Temperature[J]. J. Eur. Ceram. Soc., 2011, 31: 1 533-1 540.

[17] Ramesh S, Tan CY, Sopyan I, et al. Consolidation of Nanocrystalline Hydroxyapatite Powder[J]. Sci. Technol. Adv. Mat., 2007, 8: 124-130.

[18] Thangamani N, Chinnakali K, Gnanam F D. The Effect of Powder Processing on Densification, Microstructure and Mechanical Properties of Hydroxyapatite[J]. Ceram. Int., 2002, 28: 355-362.

[19] Dasgupta S, Tarafder S, Bandyopadhyay A, Bose S. Effect of Grain Size on Mechanical, Surface and Biological Properties of Microwave Sintered Hydroxyapatite[J]. Mat. Sci. Eng. C–Mater., 2013, 33: 2 846-2 854.

[20] Krell A. A New Look at Grain Size and Load Effects in the Hardness of Ceramics[J]. Mat. Sci. Eng. A–Struct., 1998, 245: 277-284.

[21] Sangwal K. Review: Indentation Size Effect, Indentation Cracks and Microhardness Measurement of Brittle Crystalline Solids–some Basic Concepts and Trends[J]. Cryst. Res. Technol., 2009, 44: 1 019-1 037.

[22] Viswanath B, Raghavan R, Ramamurty U, et al. Mechanical Properties and Anisotropy in Hydroxyapatite Single Crystals[J]. Scripta. Mater., 2007, 57: 361-364.

[23] Chiang SS, Marshall DB, Evans AG. The Response of Solids to Elastic/Plastic Indentation. I. Stresses and Residual Stresses[J]. J. Appl. Phys., 1982, 53: 298-311.

[24] Krell A. A New Look at the Influences of Load, Grain Size and Grain Boundaries on the Room Temperature Hardness of Ceramics[J]. Int. J. Refract. Met. H., 1998, 16: 331-335.

[25] Gong JH, Wu JJ, Guan Z Z. Analysis of the Indentation Size Effect on the Apparent Hardness for Ceramics[J]. Mater. Lett., 1999, 38: 197-201.