BS ISO 21821:2019 pdf free.Fine ceramics [advanced ceramics, advanced technical ceramics) – – Determination of densification properties of ceramic powders on natural sintering.
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. 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. U pper 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]. Press, capable of applying sufficient force with a precision of +2 %.， Balance, capable of weighing at least 10 g with a resolution of +0,001 g.BS ISO 21821 pdf download.