ISO 21822:2019 pdf download – Fine ceramics (advanced ceramics, advanced technical ceramics) — Measurement of iso-electric point of ceramic powder.
Materials that do not elute in the range of pH 2 to pH 10 should be used. Special care is needed for soda lime glass, which may elute in a strong base condition. 5.4 Sonicator The sample should be dispersed by a tip sonicator, preferably, or a bath-type sonicator. A homogenizer, mortar, or vacuum degassing machine can be applied when needed. 5.5 Balance A balance with a measuring capacity of 200 g or above with 10-mg precision. 5.6 Temperature-control device A thermometer with a measuring range of 0 °C to 50 °C with a precision of 0,5 °C. A built-in temperature sensor is also applicable. 5.7 Magnetic stirrer A stirrer or magnetic stirrer coated with polytetrafluoroethylene resin. 6 Operational procedures 6.1 Dispersion solution This shall be ion-exchanged distilled water with a conductivity of less than 1 × 10 −4 S/m (25 °C) in an electrolyte solution. 6.2 pH-adjusting acid or base and electrolyte solution The pH-adjusting acids or bases and the type of electrolyte solution shall be selected as follows. a) The pH-adjusting acid and base shall be hydrochloric acid (HCl) or nitric acid (HNO 3 ) and sodium hydroxide (NaOH) or ammonium hydroxide (NH 4 OH), respectively. The electrolyte solution shall be a salt, sodium chloride (NaCl) or ammonium nitrate (NH 4 NO 3 ) solution with a concentration of 0,1 mol/l for acid and base and 1 mmol/l to 10 mmol/l for the electrolyte solution. b) Any combination of inorganic acid and base with an oxidation number 1, except those in a), may be selected, and their electrolyte (1 mmol/l to 10 mmol/l) may be selected. 6.3 Sample preparation and dispersion 6.3.1 Preparation The dispersion solution of ion-exchanged distilled water shall be selected as in 6.1 and an electrolyte solution of 10 −3 –10 −2 mol/l prepared. The powder sample shall be dispersed in the electrolyte solution to produce a ceramic slurry of suspension. 6.3.2 Dispersion The ceramic slurry shall be well dispersed by using a tip sonicator or ultrasonic bath. The ultrasonic irradiation shall be carried out as follows. If the ultrasonic bath is applied, place the sample above the spot of oscillation for no less than 3 min below 300 W power. If using an ultrasonic tip sonicator, place the sonicator tip in the middle of the beaker bottom and top liquid interface of the ceramic slurry, sonicate for 1 min to 5 min and stabilize for 5 min to prevent any temperature increase.
The recommended concentration of the ceramic slurry is a mass fraction of 1 % to 10 % (depending on particle size). If the suspension (or colloid) is well dispersed, it may be measured without the assistance of sonication. 6.3.3 Stabilization The suspension shall be stabilized after sonication, for a recommended time of 30 min, and the supernatant taken for sampling.
ISO 21822:2019 pdf download – Fine ceramics (advanced ceramics, advanced technical ceramics) — Measurement of iso-electric point of ceramic powder
