Apatite synthetic

Hydroxyapatite, Ca2Q(PO (OH)2, may be regarded as the parent member of a whole series of stmcturaHy related calcium phosphates that can be represented by the formula M2q(ZO X2, where M is a metal or H O" Z is P, As, Si, Ga, S, or Cr and X is OH, F, Cl, Br, 1/2 CO, etc. The apatite compounds all exhibit the same type of hexagonal crystal stmcture. Included are a series of naturally occurring minerals, synthetic salts, and precipitated hydroxyapatites. Highly substituted apatites such as FrancoHte, Ca2Q(PO (C02) (F,0H)2, are the principal component of phosphate rock used for the production of both wet-process and furnace-process phosphoric acid. 

Nelson, D.G.A., Featherstone, J.D.B., Duncan, J.E and Cuttress, T.W. 1982 Paracrystalline disorder of biologieal and synthetic carbonate-substituted apatites. Journal of Denial Research 61 1274-1281. 

Sillen, A. and LeGeros, R 1991 Solubility profiles of synthetic apatites and of modem and fossil bones. Journal of Archaeological Science 18 385-397. 

Takadama, H., Hashimoto, M., Mizuno, M. and Kokubo, T. (2004) Round-robin test of SBF for in vitro measurement of apatite-forming ability of synthetic materials. Phosphorus Research Bulletin, 17, 119-25. 

Fig. 8. Evolution of synthetic and biological apatites in the presence of fluoride ions. The increase of pH and/or phosphate concentration in solution favours the formation of fluoridated apatite, whereas the increase of fluoride and/or calcium concentration favours CaF2 formation. At physiologic pH and mineral ions concentrations (in all body fluids), the formation of fluoridated apatite is favoured.

Synthetic fluor-containing apatites are prepared and investigated for biomedical applications and serve also as models to understand the formation of biological fluorapatites and some of their properties. The synthesis of fluoridated apatites has been accomplished in various ways from simple ion exchange in solution to more elaborate techniques involving sol-gel routes or thermal processes. Two main classes of synthesis routes are presented in this chapter high-temperature routes and low-temperature solution routes. 

Osteoclast cells generally require an apatitic substrate (dentine, enamel, bone slices or synthetic apatite coatings) to attach to and act on and the effect of fluoride ions in solution cannot be readily distinguished from the effect of fluoride on... 

R.Z. Legeros, Biological and synthetic apatites, in P.W. Brown, B. Constantz (Eds.), Hydroxyapatite and Related Materials, CRC Press, Boca Raton, 1994, pp. 3-28. 

A. Barry, H. Zhuang, A.A. Baig, W.l. Higuchi, Effect of fluoride pretreatment on the solibility of synthetic carbonated apatite, Calcif. Tissue Int. 72 (2003) 236-242. 

G. Penel, G. Leroy, C. Rey, E. Bres, Micro-Raman spectral study of the PO4 and CO3 vibrational modes in synthetic and biological apatites, Calcif. Tissue Int. 63 (1998) 475-481. 

The presence of Pr in apatite samples, up to 424.4 ppm in the blue apatite sample, was confirmed by induced-coupled plasma analysis (Table 1.3). The luminescence spectrum of apatite with a broad gate width of 9 ms is shown in Fig. 4.2a where the delay time of500 ns is used in order to quench the short-lived luminescence of Ce + and Eu +. The broad yellow band is connected with Mn " " luminescence, while the narrow lines at 485 and 579 nm are usually ascribed to Dy and the fines at 604 and 652 nm, to Sm +. Only those luminescence centers are detected by steady-state spectroscopy. Nevertheless, with a shorter gate width of 100 ps, when the relative contribution of the short lived centers is larger, the characteristic fines of Sm " at 652 nm and Dy + at 579 nm disappear while the fines at 485 and 607 nm remain (Fig. 4.2b). It is known that such luminescence is characteristic of Pr in apatite, which was proved by the study of synthetic apatite artificially activated by Pr (Gaft et al. 1997a Gaft... 

After a delay of several ps, the luminescence of Eu " is already very weak, and narrow long-lived lines of trivalent RE dominate in the spectrum. The lines at 589, 617, 651, and 695 nm (Fig. 4.1c) have never been detected in natural apatite by steady-state spectroscopy. According to their spectral position they may be ascribed to Eu ", but they are different from known lines in synthetic apatites activated by Eu (Jagannathan and Kottaosamy 1995 Morozov et al. 1970 Piriou et al. 1987 Piriou et al. 2001 Voronko et al. 1991). In order to clarify this problem we studied artificially activated samples by laser-induced time-resolved luminescence spectroscopy. 

Fig. 5.10. a-d Laser-induced luminescence and excitation spectra of synthetic apatite artificially activated by Eu in vacuum (a) and in air (b)... 

Fig.5.18. a-f Laser-induced time-resolved luminescence spectra of synthetic zircon, apatite and scheelite artificially activated by Tb... 

Besides confidently identified centers, the possible participation of Mn and is proposed. The centers, such as Mn ", Cr, Cr +, and V are described, which are not found in minerals yet, but are known in synthetic analogs of minerals, such as apatite, barite, zircon and corundum. Besides that, the centers Ni " and Ti " are discussed as possible participants in mineral luminescence. The last part of this chapter is devoted to unidentified emission lines and bands in apatite, barite, calcite and zircon. 

Glass-ceramics based on natural or synthetic basalts, various zeolites, and apatite/britholite were also developed (Saidl Ralkova 1966 Hayward 1988 Wronkiewicz et al. 1996 Sinkler... 

Laperche, V., Traina, S. J., Gaddam, P. Logan, T. J. 1996. Chemical and mineralogical characterizations of Pb in a contaminated soil reactions with synthetic apatite. Environmental Science Technology, 30, 3321-3326. 

Geoffroy, M. and Tochon-Danguy, H.J. (1982). ESR identification of radiation damage in synthetic apatites a study of the C-Hyperfine synthetic coupling. Calc. Uss. Int. 46. 99. 

Ideally, hydroxyapatite has the formula mentioned above. The synthetic material usually contains fewer than 10 Ca-ions and more than 2 OH-ions per crystal unit. Important differences in crystal structure, composition and specific surface exist between synthetic and biologic apatite. These differences result from the processing method of the raw materials and the synthetic method used. 

LEHR and Me CLELLAN (3) demonstrated numerous natural apatites and a correlation between the amount of fluoride ions and that of the carbonate ions. This led them to propose that PO -ions can be replaced by COg - ions associated with F ions. Such a hypothesis could explain the abnormally high amount of fluoride in some FRANC0LITES. However this type of substitution was not proved by the authors. We studied some synthetic apatites where fluoride and carbonate ions were simultaneously introduced. Samples of B-type carbonated fluorapatite (COj - substituting PO -) were obtained as a powder from an aqueous medium rich in fluoride ions and also an aqueous medium poor in fluoride ions. 

A more recent trend in polymer materials research is the hybridization of cellulosic polysaccharides with inorganic compounds natural and synthetic layered clays, silica, zeolites, metal oxides, and apatites are employable as nanoscale components. In addition, if mesoscopic assemblies such as liquid-crystalline ordering are used in the construction of new compositional systems, the variety of functionalized cellulosic materials will be further expanded. 

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