ASTM F2024-10(2021)

Standard Practice for X-ray Diffraction Determination of Phase Content of Plasma-Sprayed Hydroxyapatite Coatings

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 of effects 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 hydroxyapatite coatings.
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 of monochromated 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 appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2021
• ICS: 25.220.99 - Other treatments and coatings
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.13 - Ceramic Materials

Overview

ASTM F2024-10(2021): Standard Practice for X-ray Diffraction Determination of Phase Content of Plasma-Sprayed Hydroxyapatite Coatings provides a standardized methodology for determining the quantitative phase composition of plasma-sprayed hydroxyapatite (HA) coatings commonly used on metallic substrates in biomedical applications. This ASTM International standard ensures the consistency and reliability of the analysis of HA, beta-tricalcium phosphate (β-TCP), and calcium oxide (CaO) in these coatings via X-ray diffraction (XRD) using the Reference Intensity Ratio (RIR) External Standard Method.

This standard is significant in medical device manufacturing, particularly for orthopedic and dental implants, where the biocompatibility and early bone attachment of plasma-sprayed hydroxyapatite coatings are crucial. Ensuring precise phase quantification assists in maintaining the required physical, mechanical, and biological properties of the coatings for optimal clinical and experimental outcomes.

Key Topics

• Purpose: Specifies the procedure to determine the percent by weight of key crystalline phases-hydroxyapatite (HA), β-TCP, and CaO-in plasma-sprayed coatings using X-ray diffraction.
• Methodology: Utilizes the Reference Intensity Ratio (RIR) External Standard Method, applying monochromated copper Kα radiation and requiring flat sample geometry for accurate results.
• Scope:
  • Targets coatings containing at least 50% hydroxyapatite by weight.
  • Addresses analysis of crystalline phases in the presence of amorphous calcium phosphate (ACP), recognizing that minor crystalline phase quantification may be unreliable due to peak overlap.
  • Applicable to coatings produced under equivalent manufacturing conditions as the device of interest.
• Reporting: Requires comprehensive documentation, including sample identification, sample condition, analytical results (percentages of HA, β-TCP, CaO), and residual amorphous or unquantified phases.
• Quality Assurance: Stresses the importance of periodic validation of analytical procedures using known standards, with emphasis on reproducibility and instrument calibration.

Applications

• Medical Devices: The primary application is in the assessment of plasma-sprayed hydroxyapatite coatings for medical implants such as orthopedic and dental devices. Biocompatibility and optimization of bone-implant integration are directly influenced by the phase content, purity, and consistency determined by this method.
• Manufacturing Quality Control: Enables manufacturers to verify the phase composition and homogeneity of HA coatings, supporting consistent product quality and performance.
• Research and Development: Supports materials research by facilitating the controlled study of relationships between phase composition and coating properties, contributing to the development of advanced biomaterials.
• Regulatory Compliance: Assists in meeting international standards and regulatory requirements for implantable medical devices, aligning with globally recognized practices in the assessment of surface coatings.

Related Standards

• ASTM F1185 – Standard for hydroxyapatite coatings on metallic substrates.
• ASTM F1609 – Standard Specification for Calcium Phosphate Coatings.
• ISO 13779-2 – International standard related to hydroxyapatite ceramic coatings on surgical implants.
• ASTM F1147 – Test Method for Tension Testing of Calcium Phosphate and Metal Coatings.
• ISO/IEC 17025 – General requirements for the competence of testing and calibration laboratories, relevant to X-ray diffraction analysis.

Keywords: plasma-sprayed hydroxyapatite coatings, X-ray diffraction, phase analysis, ASTM F2024, tricalcium phosphate, calcium oxide, hydroxyapatite, medical implants, crystalline phase composition, Reference Intensity Ratio, RIR method, quality control, orthopedic implants, dental implants, biomaterials testing.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2024 − 10 (Reapproved 2021)
Standard Practice for
X-ray Diffraction Determination of Phase Content of Plasma-
Sprayed Hydroxyapatite Coatings
This standard is issued under the fixed designation F2024; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This practice is for the determination, by the Reference
mine the applicability of regulatory limitations prior to use.
Intensity Ratio External Standard Method, of the percent by
1.8 This international standard was developed in accor-
weight of the crystalline phases, hydroxyapatite (HA), beta-
dance with internationally recognized principles on standard-
(whitlockite) tricalcium phosphate (β-TCP), and calcium oxide
ization established in the Decision on Principles for the
(CaO)incoatingsdepositeduponmetallicsubstratesbyplasma
Development of International Standards, Guides and Recom-
spraying hydroxyapatite.
mendations issued by the World Trade Organization Technical
1.2 A major component in plasma-sprayed HA coatings
Barriers to Trade (TBT) Committee.
other than HAis expected to be amorphous calcium phosphate
(ACP). Crystalline components other than HA that may be
2. Terminology
present include alpha- and beta- (whitlockite) tricalcium
2.1 Definitions:
phosphates, tetracalcium phosphate (TTCP), calcium oxide,
2.1.1 crystalline phases:
and calcium pyrophosphates. Quantification of the minor
Chemical and Mineral Formula PDF Card No.
crystalline components has proven to be very unreliable due to
Names
extreme overlap and confounding of X-ray diffraction peaks.
whitlockite β-Ca (PO ) 9-169
Therefore, this practice addresses the quantification of only 3 4 2
beta-tricalcium phosphate
HA, β-TCP, and CaO.
calcium phosphate α-Ca (PO ) 9-348
3 4 2
1.3 This practice was developed for plasma-sprayed HA
alpha-tricalcium phosphate
coatings with HAcontents of at least 50 % of the total coating.
It is recognized that the analysis of the crystalline components lime CaO 37-1497
calcium oxide
uses diffraction from regions of the pattern that also include a
small contribution from the amorphous component. However,
hydroxyapatite Ca (PO ) OH 9-432
5 4 3
within the limits of applicability of this practice, the effect of (hydroxylapatite)
such interference is believed to be negligible.
2.2 plasma-sprayed hydroxyapatite coating—a coating,
consisting of at least 50 % hydroxyapatite by weight, prepared
1.4 The coating analyzed shall be produced and processed
by plasma spraying hydroxyapatite on a substrate.
undermanufacturingconditionsequivalenttothoseusedonthe
device of interest.
3. Significance and Use
1.5 This practice requires the use of monochromated copper
3.1 Calcium phosphate coatings have been shown in animal
Kα radiation and flat samples.
and clinical studies to be biocompatible and to enhance the
1.6 The values stated in SI units are to be regarded as
early attachment of bone to implant surfaces (see Refs. (1-5)).
standard. No other units of measurement are included in this
3.2 It is believed that the form of calcium phosphate
standard.
ceramic and its purity with respect to secondary crystalline
1.7 This standard does not purport to address all of the
phases and amorphous material have an effect on its physical,
safety concerns, if any, associated with its use. It is the
mechanical, and biological properties. However, no definitive
studiesofeffectsonbiologicalpropertieshavebeencompleted.
To achieve reproducible clinical results and to permit the
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.13 on Ceramic Materials.
Current edition approved Feb. 1, 2021. Published February 2021. Originally Joint Committee on Powder Diffraction Standards, Swarthmore, PA.
approved in 2000. Last previous edition approved in 2016 as F2024 – 10 (2016). The boldface numbers in parentheses refer to the list of references at the end of
DOI: 10.1520/F2024-10R21. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2024 − 10 (2021)
determination of the effects of properties of the coating on surface roughness of the alpha-corundum external standard
biological performance, it is essential that the properties of must be less than 5 µm.
both clinical and experimental materials be well-characterized
5.2 X-ray Equipment:
and consistent.
5.2.1 A standard Bragg-Brentano focusing diffractometer
equipped with a pyrolytic graphite monochromator is recom-
3.3 This practice provides procedures for determination of
the percentage by weight of the crystalline phases identified as mended. Because of the need to resolve closely spaced and
overlapping peaks, a diffracted beam monochromator is re-
hydroxyapatite, β-TCP, and CaO in plasma-sprayed hydroxy-
apatite coatings. 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
4. Quantitative Phase Analysis by the External Standard
standard, SRM 640, is suggested.
Technique
5.2.2 An X-ray source with a copper target is required.
4.1 The external standard technique allows the determina-
Characteristic copper radiation provides the needed X-ray
tion of weight fractions of individual phases in a mixture
diffraction peak resolution and allows for separation of peaks
containing an amorphous fraction by comparison of the inte-
from contaminant phases at a suitable range of diffraction
grated intensity of one or more peaks from the phase(s) of
angles from nominally 20 to 60° 2θ. A 1.0° incident beam
interest to the external standard under identical instrumental
divergence, a 0.2° receiving slit, and soller slits in either the
conditions (6). The sample analyzed may be a solid such as a
incident or diffracted beam, or both, are suitable.
plasma-sprayed coating or may be a powder. The mass
5.3 X-ray Method and Data Reduction Strategy:
absorption coefficients of the sample and standard must be
5.3.1 Collect a diffraction pattern from 20 to 60° 2θ at 0.02°
known.
increments for a minimum of 1s/point.
4.2 The weight fraction of the analyte phase in the mixture
5.3.2 X-ray diffraction peaks (or peak groups) from the
is given by Equation 11 of Ref (6), as follows:
crystalline phases must be separated in order to quantify the
hkl
I χ 1
HA content. The following outline provides a data reduction
i m
W 5 · · (1)
S D S D S D
i REL Pure
I χ I ·RIR
strategy in order to provide the integrated intensities necessary
i s s i
to determine the HA, β-TCP, and CaO content of mixtures of
where:
amorphous calcium phosphate, α-TCP, β-TCP, CaO,
W = weight fraction,
i
β-Ca P O , tetracalcium phosphate, and hydroxyapatite. Ac-
hkl 2 2 7
I = integratedintensityoftheanalytephase(hkl)peakor
i
complish the determination of integrated intensities using
sum of peaks,
computer techniques, with least-squares fitting of the selected
REL
I = relative intensity of the analyte phase (hkl) peak or
i
peakshapetotheexperimentaldata.Manualfittingofpeakand
sum of peaks,
background is not permitted under this standard practice.
χ = mass absorption coefficient of the mixture,
m
5.3.2.1 Obtain the β-TCP content by integration from 30.5
χ = mass absorption coefficient of the standard,
s
Pure
to 31.5° 2θ. The β-TCP peak being used for quantification is
I = integrated intensity of the mo
...