BS ISO 21821 pdf free download
BS ISO 21821-2019 pdf free download.Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of densification properties of ceramic powders on natural sintering.
This document specifies the test method to determine the extent to which ceramic powder compacts made of granulated or ungranulated ceramic powders are densified, when they are sintered at a high temperature without the application of any external pressure or external densification force. The test method is applicable to pure oxides, mixtures of oxides and solid solutions, and is also applicable to non-oxides (e.g. carbides, nitrides) that can be sintered under vacuum or constant gas pressure (1 bar or less) to prevent oxidation or decomposition. The test method is not applicable to ceramics that can only be sintered using pressure-assisted sintering techniques such as hot pressing (HP), hot isostaticpressing (HIP), gas pressure sintering (GPS) or spark plasma sintering (SPS). Inorganic sinteringadditives can be used where their presence is reported.
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 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers for external measurements — Design and metrological characteristics
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO 17172, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of compaction properties of ceramic powders
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle When ceramic powder compacts are heat-treated at high temperatures, they shrink and are densified due to sintering. The mass, dimensions (diameter and height), volume and apparent density of a ceramic powder compact are measured before and after sintering through thermal treatment. The variations in mass, dimensions, volume and apparent density depend on maximum temperature, dwell time, heating rate and apparent density after compaction, and can be expressed as a function of these parameters. For example, the variation in relative density can be plotted as a function of sintering temperature for each compacting pressure.
5 Symbols and designation
Symbols used throughout this document and their designations are given in Table 1.
6 Apparatus
6.1 Cylindrical die, either double acting (floating type – see Figure 1) or single acting (see Figure 2), shall be made from hard material, preferably hardened steel or tungsten carbide. Upper and lower punches of adequate dimensions as indicated in Figure 1 and Figure 2 shall be used for producing cylindrical powder compacts. The upper part of the die shall be preferably designed to avoid damage to the powder compact during ejection due to spring-back. An ejection cone of height 5 mm, allowing an increase of the diameter at the top and the bottom of the die of approximately 1 %, as shown in Figure 1 and Figure 2, should be used. The die shall be of the floating type or of the type suspended from a spring (mode 1, see Figure 1), or of stationary type with only one moveable upper punch (mode 2, see Figure 2). The die shall be capable of making cylindrical powder compacts with a diameter of 10 mm to 26 mm and a height-to-diameter ratio of between 0,3 and 0,5 (mode 1), or with a diameter of 10 mm to 32 mm and a height-to-diameter ratio of between 0,15 and 0,25 (mode 2).
6.2 Furnace, should have a hot zone large enough to accommodate the required size and number of test pieces, and be capable of maintaining the test temperature (T) so that the maximum temperature variation in the hot zone is 10 °C. The furnace shall allow a constant heating rate, which can be controlled to within 2 °C/h. The furnace heating elements, thermal insulation and kiln furniture shall be selected to be chemically compatible with the test pieces, avoiding both surface reaction and generation of vapour pressure. The kiln furniture used to support the test pieces shall be a sintered piece of the test material with at least 80 % of theoretical density. If required, as is for non-oxides, the furnace shall be additionally capable of supplying constant vacuum or constant gas pressure (1 bar or less) of, for example, argon or nitrogen.BS ISO 21821 pdf download.
