ISO 21822:2019 pdf – Fine ceramics (advanced ceramics, advanced technical ceramics) — Measurement of iso-electric point of ceramic powder.
1 Scope This document specifies the test method to determine the iso-electric point of fine ceramic powders, which is measured in the state of suspension. 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 4316, Surface active agents — Determination of pH of aqueous solutions — Potentiometric method ISO 13099-1, Colloidal systems — Methods for zeta-potential determination — Part 1: Electroacoustic and electrokinetic phenomena ISO 13099-2, Colloidal systems — Methods for zeta-potential determination — Part 2: Optical methods ISO 13099-3, Colloidal systems — Methods for zeta potential determination — Part 3: Acoustic methods 3? Terms? and? definitions For the purposes of this document, the terms and definitions given in ISO 13099-1, ISO 13099-2 and ISO 13099-3 and the following apply. 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/ 3.1 zeta potential ζ-potential difference between the electric potential at the slipping plane and that of the bulk liquid, where the electric potential difference is proportional to the electrophoretic mobility of the charged particle to the electrode when the electric field is applied to the dispersed particles in the solution
4 Principle Zeta potential is the potential in the interfacial double layer at the location of the slipping plane versus a point in the bulk fluid away from the interface. According to general colloid chemistry principles, an electrostatically stabilized dispersion system typically loses stability when the magnitude of the zeta potential decreases. As a result, there will be some region surrounding the condition of zero potential (i.e. the iso-electric point) for which the system is not particularly stable. Within this unstable region, the particles may agglomerate, thereby increasing the particle size. Determining the pH conditions where the zeta potential becomes zero (the iso-electric point) is, therefore, important for zeta potential analysers. Zeta potential may be determined by the electrophoretic light-scattering (ELS) method, the streaming potential method and the electroacoustic method, according to ISO 13099-1, ISO 13099-2 and ISO 13099-3, respectively. 5 Apparatus and calibration The usual laboratory apparatus and, in particular, the following. 5.1 Zeta potential analyser and calibration The zeta potential analyser may vary according to the measurement principle, such as electroacoustic and electrokinetic phenomena, the optical method or the acoustic method, and shall conform to ISO 13099-1, ISO 13099-2 and ISO 13099-3, respectively. The calibration of the analyser shall be performed using the standard sample with a predefined zeta potential. NOTE The standard sample provided by the zeta potential analyser supplier could be applied. 5.2 pH meter The pH meter should be within the measuring range of pH 2 to pH 10. The calibration of the pH meter shall conform to the standard procedure detailed in ISO 4316. 5.3 Sample dispersion vessel A vessel of polypropylene or glass in the dimension range of 100 cm 3 to 1 000 cm 3 . It is used for dispersing the powder sample in the electrolyte solution.
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.