ASTM F2024-10(R2021) pdf free download
ASTM F2024-10(R2021) pdf free download.Standard Practice for X-ray Diffraction Determination of Phase Content of Plasma- Sprayed Hydroxyapatite Coatings
1. Scope
1.1 This practice is for the determination, by the Reference Intensity Ratio External Standard Method, of the percent by weight of the crystalline phases, hydroxyapatite (HA), beta- (whitlockite) tricalcium phosphate (β-TCP), and calcium oxide (CaO) in coatings deposited upon metallic substrates by plasma spraying hydroxyapatite. 1.2 A major component in plasma-sprayed HA coatings other than HA is expected to be amorphous calcium phosphate (ACP). Crystalline components other than HA that may be present include alpha- and beta- (whitlockite) tricalcium phosphates, tetracalcium phosphate (TTCP), calcium oxide, and calcium pyrophosphates. Quantification of the minor crystalline components has proven to be very unreliable due to extreme overlap and confounding of X-ray diffraction peaks. Therefore, this practice addresses the quantification of only HA, β-TCP, and CaO. 1.3 This practice was developed for plasma-sprayed HA coatings with HA contents of at least 50 % of the total coating. It is recognized that the analysis of the crystalline components uses diffraction from regions of the pattern that also include a small contribution from the amorphous component. However, within the limits of applicability of this practice, the effect of such interference is believed to be negligible. 1.4 The coating analyzed shall be produced and processed under manufacturing conditions equivalent to those used on the device of interest. 1.5 This practice requires the use ofmonochromated copper Kα radiation and flat samples. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use.
3. Significance and Use
3.1 Calcium phosphate coatings have been shown in animal and clinical studies to be biocompatible and to enhance the early attachment of bone to implant surfaces (see Refs. (1-5)). 3 3.2 It is believed that the form of calcium phosphate ceramic and its purity with respect to secondary crystalline phases and amorphous material have an effect on its physical, mechanical, and biological properties. However, no definitive studies ofeffects on biological properties have been completed. To achieve reproducible clinical results and to permit the determination of the effects of properties of the coating on biological performance, it is essential that the properties of both clinical and experimental materials be well-characterized and consistent. 3.3 This practice provides procedures for determination of the percentage by weight of the crystalline phases identified as hydroxyapatite, β-TCP, and CaO in plasma-sprayed hydroxy- apatite coatings.
5. Procedure
5.1 Sample Preparation: 5.1.1 Plasma-sprayed coating samples in the form of flat coupons of nominal dimensions 2.5 by 2.5 by 0.6 cm may be analyzed directly on the coated surface. The coating must be at least 44 µm thick to provide a sample opaque to the X-ray beam. Thinner samples must be removed from the substrate and either deposited in a layer of at least 44-µm thickness and area sufficient to exceed the dimensions of the irradiated area. 5.1.2 Reliable quantitative analysis cannot be performed by X-ray diffraction on curved surfaces because of errors caused by absorption and defocusing. 5.1.3 Microabsorption caused by variations in either particle size or surface roughness will produce errors in the measured diffracted intensity. The effective particle size and variation in surface roughness of the alpha-corundum external standard must be less than 5 µm. 5.2 X-ray Equipment: 5.2.1 A standard Bragg-Brentano focusing diffractometer equipped with a pyrolytic graphite monochromator is recom- mended. Because of the need to resolve closely spaced and overlapping peaks, a diffracted beam monochromator is re- quired unless a solid-state detector is used. Linearity of the instrument and associated electronics must be verified daily prior to utilizing this method. Use of NIST silicon powder standard, SRM 640, is suggested. 4 5.2.2 An X-ray source with a copper target is required. Characteristic copper radiation provides the needed X-ray diffraction peak resolution and allows for separation of peaks from contaminant phases at a suitable range of diffraction angles from nominally 20 to 60° 2θ. A 1.0° incident beam divergence, a 0.2° receiving slit, and soller slits in either the incident or diffracted beam, or both, are suitable.
