ISO 23071:2021

Refractory products - Determination of reduced species in carbon containing refractories by XRD

This document describes methods for the determination of mineralogical phases often present as additives or reaction products in carbon containing or graphitic refractory products by X-ray Diffraction (XRD) using a Bragg-Brentano diffractometer. It includes details of sample preparation and general principles for qualitative and quantitative analysis of mineralogical phase composition. Quantitative determination of α-Si3N4, β-Si3N4, AlN, aluminium metal, Al4C3, silicon metal, boron carbide and BN are described. The problems encountered with some determinations are highlighted. Additional reduced species present in some refractories could include Al2O3⋅AlN solid solutions (so called Alons), Si3N4⋅SiO2 solid solutions and Si3N4⋅Al2O3 solid solutions (Sialons). The presence of some of these solid solution components will cause problems with both identification and quantification as they are not well-defined structures. NOTE For rationalisation of nitrogen containing phases, the total nitrogen content, analysed in accordance with EN 12698-1 is used.

Produits réfractaires - Détermination par DRX des espèces réduites dans les réfractaires contenant du carbone

General Information

• Status: Published
• Publication Date: 07-Apr-2021
• ICS: 81.080 - Refractories
• Technical Committee: ISO/TC 33 - Refractories
• Drafting Committee: ISO/TC 33/WG 17 - Chemical analysis
• Current Stage: 6060 - International Standard published
• Start Date: 08-Apr-2021
• Due Date: 19-Jan-2021
• Completion Date: 08-Apr-2021

Relations

• Consolidated By: ISO 19160-4:2023 - Addressing - Part 4: International postal address components and template language
• Effective Date: 06-Jun-2022

Overview

ISO 23071:2021 - Refractory products: Determination of reduced species in carbon containing refractories by XRD - specifies X‑ray diffraction (XRD) methods using a Bragg‑Brentano diffractometer to identify and quantify mineralogical reduced species and reaction products in carbon‑containing or graphitic refractory products. The standard covers sample preparation, instrument performance, qualitative phase ID and quantitative phase analysis (notably using Rietveld refinement), plus limitations when solid solutions or peak overlap interfere with results.

Key topics and technical requirements

• Scope: Applies to refractories with >20% carbon (graphite, pitch, resin); excludes SiC‑dominated carbon (see EN 12698‑2).
• Apparatus & calibration:
  • Bragg‑Brentano XRD (typically Cu tube; use Co tube when iron causes Cu fluorescence).
  • Instrument performance checks (e.g., peak position within 0.05° 2θ; NIST SRM 640f cited).
• Sample preparation:
  • Grind to <45 µm (95% <45 µm); note ideal ~10 µm for Rietveld but risk of amorphisation if over‑ground.
  • Keep samples dry (Al4C3 hydrolyses rapidly); backfill cavity holders to reduce preferred orientation.
• Measuring parameters:
  • Typical scan: 2θ from 10° to 70° (Co tube equivalents noted).
  • Aim for 5 000–10 000 counts on largest peaks; step size ~0.02° 2θ (or 1/5–1/3 of peak FWHM).
• Qualitative and quantitative analysis:
  • Use databases (ICDD/JCPDS) for phase ID.
  • Quantification via Rietveld refinement - uses crystal structure models, refines scale factors, unit‑cell params, peak shapes, preferred orientation and applies micro‑absorption corrections.
• Target phases quantified: α‑/β‑Si3N4, AlN, aluminium metal, Al4C3, silicon metal, boron carbide, BN. Notes on problematic species: Alons, Sialons and Si–O/N solid solutions are poorly defined and can impede ID/quantification.
• Limitations: Peak overlap (e.g., Si vs monoclinic ZrO2, BN vs graphite), non‑crystalline content increases with over‑grinding, and complex solid solutions reduce certainty.

Applications and users

• Quality control and acceptance testing of carbon‑containing refractories in steel, foundry and high‑temperature industries.
• Materials analysis labs performing XRD phase quantification and troubleshooting reaction products.
• R&D groups developing refractory formulations or assessing corrosion/oxidation behavior.
• Regulatory/compliance testing where mineralogical composition and reduced species content are critical.

Related standards

• ISO 5022, ISO 8656‑1 (sampling)
• EN 13925‑1 / EN 13925‑3 (XRD principles and instrument performance)
• EN 12698‑1 (total nitrogen analysis)
• ISO 836, ISO 10081 series (terminology & classification)

Keywords: ISO 23071:2021, refractory products, XRD, Bragg‑Brentano, Rietveld refinement, silicon nitride, aluminium nitride, Al4C3, boron carbide, BN, carbon containing refractories.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23071
First edition
2021-04
Refractory products — Determination
of reduced species in carbon
containing refractories by XRD
Produits réfractaires - Détermination par DRX des espèces réduites
dans les réfractaires contenant du carbone
Reference number
©
ISO 2021
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Apparatus . 2
5 Instrument performance . 2
6 Sampling . 2
7 Procedure. 3
7.1 Sample preparation . 3
7.2 Measuring parameters . 3
7.3 Qualitative analysis . 3
7.4 Quantitative analysis . 4
7.4.1 General. 4
7.4.2 Quantitative phase determination using Rietveld Refinement. 4
7.5 Rationalisation of results . 5
7.5.1 Calculation refinement for α-Si N , β-Si N , Si ON , BN and AlN . 5
3 4 3 4 2 2
8 Limitations of method. 6
9 Test report . 6
Bibliography . 7
Foreword
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iv © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 23071:2021(E)
Refractory products — Determination of reduced species
in carbon containing refractories by XRD
1 Scope
This document describes methods for the determination of mineralogical phases often present as
additives or reaction products in carbon containing or graphitic refractory products by X-ray Diffraction
(XRD) using a Bragg-Brentano diffractometer. It includes details of sample preparation and general
principles for qualitative and quantitative analysis of mineralogical phase composition. Quantitative
determination of α-Si N , β-Si N , AlN, aluminium metal, Al C , silicon metal, boron carbide and BN are
3 4 3 4 4 3
described. The problems encountered with some determinations are highlighted.
Additional reduced species present in some refractories could include Al O ⋅AlN solid solutions (so
2 3
called Alons), Si N ⋅SiO solid solutions and Si N ⋅Al O solid solutions (Sialons). The presence of some
3 4 2 3 4 2 3
of these solid solution components will cause problems with both identification and quantification as
they are not well-defined structures.
NOTE For rationalisation of nitrogen containing phases, the total nitrogen content, analysed in accordance
with EN 12698-1 is used.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 836, Terminology for refractories
ISO 5022, Shaped refractory products — Sampling and acceptance testing
ISO 8656-1, Refractory products — Sampling of raw materials and unshaped products — Part 1:
Sampling scheme
ISO 10081-1, Classification of dense shaped refractory products — Part 1: Alumina-silica
ISO 10081-2, Classification of dense shaped refractory products — Part 2: Basic products containing less
than 7 % residual carbon
ISO 10081-3, Classification of dense shaped refractory products — Part 3: Basic products containing from
7 % to 50 % residual carbon
ISO 10081-4, Classification of dense shaped refractory products — Part 4: Special products
EN 13925-1, Non-destructive testing. X-ray diffraction from polycrystalline and amorphous materials.
General principles
3 Terms and definitions
For the purposes of this document the terms and definitions given in ISO 836, ISO 10081-1, ISO 10081-2,
ISO 10081-3, ISO 10081-4, EN 13925-1 and the following apply.
3.1
carbon containing refractories
refractory products containing greater than 20% carbon where carbon is dominantly added in the
manufacturing process in the form of graphite, pitch, tar, resin or similar
Note 1 to entry: For refractories in which silicon carbide is the dominant form of carbon isare beyond the scope of
this document, refer to EN 12698-2.
4 Apparatus
4.1 X-ray diffractometer
Generally comprising of but not limited to:
Bragg-Brentano X-ray diffractometer. The diffractometer will comprise of goniometer, X-ray source
(normally copper X-ray tube), incidence beam optics, diffracted beam optics, specimen stage, detector
and data collection system. More detail on suitable systems can be found in EN 13925-3.
The equipment should be aligned and calibrated as detailed in EN 13925-3.
The equipment should be capable of attaining the performance criteria given in Clause 5.
[1]
For samples containing a considerable amount of an iron (as Fe), a Cobalt X-ray tube shall be used
[1]
instead of a Copper X-ray tube due to fluorescence of the iron by the copper X-rays . In the case of
Cobalt X-ray tube, the diffractometer angles stated in this standard will need to be re calculated.
4.2 Software
Capable of peak matching, whole pattern fitting and Rietveld refinement for phase quantification.
5 Instrument performance
The instrument should be capable of the following performance parameters as defined in Annex C of
EN 13925-3):
The peak position of major peaks for a certified reference material shall not deviate by more than
0.05° 2θ.
NOTE A suitable certified reference material to check instrument performance is NIST SRM 640f-
alumina powder.
6 Sampling
Sample shaped and unshaped products using the procedures given in ISO 5022 and ISO 8656-1. When
sampling large fr
...