Introduction
Dispersants play a key role in the production of high-quality advanced ceramics. They ensure uniform particle distribution, improve process efficiency, and enhance the performance of the final product. As the industry develops, selecting the appropriate dispersant has become increasingly complex.
Common ceramic dispersants include: inorganic dispersants (such as sodium silicate, sodium hexametaphosphate), organic dispersants (such as sodium stearate, fatty alcohol polyethylene ether), and polymer dispersants (such as cellulose polymer, polyvinyl alcohol, polyvinyl alcohol, polyvinylpyrrolidone).
Comparison of Common Dispersants:
inorganic dispersant | Organic small molecule dispersant | Polymer dispersant (synthetic polymer) | ||
Characteristics: It primarily functions through electrostatic repulsion. In water, it ionizes to release multivalent anions (such as SiO₃²⁻, PO₃⁻), which adsorb onto the surfaces of ceramic particles with slight positive charges (such as clay, oxides), thereby increasing their surface negative charge density. According to DLVO theory, particles repel each other due to the same surface charge, thus overcoming van der Waals attractions to achieve dispersion. | Characteristics: • Anionic type: Functions through electrostatic repulsion; its hydrophilic anionic groups adsorb on the particle surface, while the hydrophobic tail chain extends into the solution. • Non-ionic type: Primarily functions through steric hindrance. Its hydrophilic polyethylene oxide chains extend in water to form a polymer coating, and when particles approach, inter-chain repulsion can prevent agglomeration. It is less affected by pH value and electrolytes. | Characteristics: Mainly rely on a strong spatial steric hindrance stabilization mechanism. The molecular structure consists of two parts: 'anchoring groups' and 'solventization chains'. | ||
| Application Areas: Mainly used for traditional ceramic body slurries with low performance requirements (such as building ceramics, daily-use ceramics), often used in combination with other types of dispersants as auxiliary dispersants to reduce costs. Its application in modern high-performance ceramics is gradually decreasing. | Application areas: Often used in the dispersion of glazes and pigments, and also as a grinding aid in ball milling processes. Non-ionic surfactants are suitable for specific systems due to their pH-insensitive characteristics and are commonly used in combination with polymer dispersants to enhance synergistic effects. | Application areas: The preferred choice for the preparation of advanced ceramic (structural ceramics, functional ceramics, electronic ceramics, etc.) and modern sanitary ware ceramic slurries. Particularly suitable for slurry systems in advanced forming processes such as gel casting, strip casting, and spray drying. |
Application of dispersants in ceramic processing:
• Slurry casting: Dispersants are crucial for preparing stable low-viscosity slurry, enabling high-density complex shape casting.
• Surface modification: Certain dispersants (such as stearic acid) can act as surface modifiers to enhance the dispersibility of powders like zirconia.
• Performance optimization: The selection of dispersants significantly affects the final performance of sintered ceramics, including density, thermal conductivity, and dielectric properties.
The interaction mechanism between dispersants and ceramic powders is complex, resulting from the synergistic effect of multiple factors. Highly efficient powder dispersion can be achieved through the rational selection of dispersants and the control of the media environment.
The selection of dispersants is a crucial step in optimizing ceramic processes. From traditional inorganic dispersants to high-performance polymer dispersants, their mechanism of action has evolved from simple electrostatic repulsion to electrostatic-steric synergistic stabilization. In practical applications, precise selection is required based on the characteristics of the ceramic system (such as particle surface charge and pH environment) and molding process requirements (such as casting stability and slurry rheology). Only through scientific formulation and compounding techniques, fully leveraging the synergistic effects of various dispersants, can high slurry stability, low viscosity, and high-performance products be ultimately achieved, providing a solid foundation for advanced ceramic manufacturing.