Structure, elemental composition, and mechanical properties of films prepared by radio-frequency magnetron sputtering of hydroxyapatite

Abstract

The phase composition, substructure, and surface morphology of 0.1-to 5.0-µ m-thick films grown on different substrates by radio-frequency magnetron sputtering of a hydroxyapatite ceramic target are investigated using transmission electron microscopy (TEM), high-energy electron diffraction, X-ray diffraction, IR spectroscopy, Auger electron spectroscopy, ultrasoft X-ray emission spectroscopy, Rutherford backscattering spectroscopy, scanning electron microscopy (SEM), and atomic-force microscopy (AFM). The hardness and adhesion strength of these films are studied using the nanoindentation and scratching methods. It is revealed that the structure of the films depends on the spatial inhomogeneity of the plasma discharge. Single-phase dense nanocrystalline hydroxyapatite films are formed when the substrate is located above the erosion zone. According to the X-ray diffraction, high-energy electron diffraction, and IR spectroscopic data, the structure of the films corresponds to the hydroxyapatite structure. As follows from the Auger electron, ultrasoft X-ray emission, and Rutherford backscattering spectroscopic data, the elemental composition of the films is similar to the stoichiometric composition of hydroxyapatite. The analysis of the X-ray diffraction and AFM data demonstrates that the films have a dense structure. The results of the mechanical tests show that the hardness of the coatings is higher than 10 GPa and that the maximum adhesion strength ( L C = 12.8 N) is observed for the hydroxyapatite coatings on the titanium substrate modified by the TiC-TaC-Ca 3 (PO 4 ) 2 composite layer.

Calcium orthophosphate coatings, films and layers

“…To sputter calcium orthophosphates, several types of the physical vapor deposition techniques are used, such as ion beam (Stevenson et al 1989; Barthell et al 1989; Ong et al 1991, 1992, 1994; Yoshinari et al 1994; Cui et al 1997; Kim et al 1998; Luo et al 1999; Choi et al 2000; Wang et al 2001; Hamdi and Ide-Ektessabi 2003; Lee et al 2003; Fujihara et al 2004; Lee et al 2005b; Rabiei et al 2006; Lee et al 2007a; Blalock et al 2007), radio-frequency (RF) magnetron (Cooley et al 1992; Yamashita et al 1994; Jansen et al 1993; Wolke et al 1994; van Dijk et al 1995, 1996; Wolke et al 1998, 2003; Nelea et al 2003, 2004; Feddes et al 2003a, 2003b; Ding 2003; Yamaguchi et al 2006; Wan et al 2007; Ozeki et al 2007; Ueda et al 2007; Snyders et al 2008; Ievlev et al 2008; Toque et al 2009), pulsed laser (Nelea et al 2000, 2002, 2004; Cotell et al 1992, Cotell 1993; Torrisi and Setola 1993; Cotell 1993; Singh et al 1994; Wang et al 1997; Hontsu et al 1997; Fernández-Pradas et al 1998, 1999, 2001; Mayor et al 1998; Arias et al 1998; Craciun et al 1999; Fernandez-Pradas et al 1999; Zeng et al 2000; Cleries et al 2000a; Nelea et al 2000; Zeng and Lacefield 2000; Fernandez-Pradas et al 2001; Nelea et al 2002; Socol et al 2004; Kim et al 2005a; Bigi et al 2005b; Koch et al 2007; Kim et al 2007a; Paital and Dahotre 2008; Paital et al 2009; Dinda et al 2009; Tri and Chua 2009; Sygnatowicz and Tiwari …”

“…Since then, it has become a convenient method for deposition of biocompatible ceramic coatings, layers and films on various substrates (Yamashita et al 1994; Jansen et al 1993; Wolke et al 1994, 1998, 2003; van Dijk et al 1995, 1996; Nelea et al 2003, 2004; Feddes et al 2003a, 2003b; Ding 2003; Yamaguchi et al 2006; Wan et al 2007; Ozeki et al 2007; Ueda et al 2007; Snyders et al 2008; Ievlev et al 2008; Toque et al 2009). The advantages of magnetron sputtering over other sputtering processes include a high deposition rate, an excellent adhesiveness and an ability to coat implants with difficult surface geometries (Table 3).…”

Density Functional Theory studies on interactions of phosphoryl ligands with the Ca2+ cation: Affinity and associated parameters

“…Calcium, with an ionic radio of 0.99 Å A 0 , is the fifth most abundant element on earth [11]. This ion is essential in the formation of the bone structure of mammals by virtue of the insolubility and mechanical strength of hydroxyapatite, Ca 5 (PO 4 ) 3 OH [12]. It also acts as a second messenger in signal transduction, in the triggering of muscle contractions, and in the transmission of nerve impulses [13][14][15].…”

Evaluation of the Role of Hydroxyapatite in TiO2/ Hydroxyapatite Photocatalytic Materials

“…To achieve biocompatibility, osteoconduction, and osseointegration, the surface of titanium or its alloy, which is used as a permanent implant material, must be modified by developing hydroxyapatite (HAp, Ca 10 (PO 4 ) 6 (OH) 2 ) coating on the surface [3][4][5][6][7][8][9]. By inserting TiO 2 inner layer between HAp coating and Ti substrate, the adhesion strength of the coating and the substrate increases [10]. The addition of TiO 2 inner layer is expected to reduce a thermal expansion mismatch of the layers, to improve the bonding strength between the HAp layer and Ti substrate, to prevent the corrosion of the Ti substrate, as well as to obtain an abundance of surface hydroxyl and superoxide radical groups, sequentially, to achieve a surface free of cracks and a high adhesion of the modified surface to the substrate [7,[11][12][13].…”