High-solids content slurries, with their advantages of high solids content per unit volume, high subsequent processing efficiency, and low energy consumption, are widely used in ceramics, lithium batteries, coatings, fine chemicals, and other fields. Uniform dispersion, as the core step in the preparation of high-solids content slurries, directly determines their rheological properties, storage stability, and final product quality. Uneven dispersion leading to particle agglomeration can cause abnormal slurry viscosity, uneven coating, and even affect the mechanical properties and functional stability of the finished product. Therefore, overcoming the challenge of uniform dispersion of high-solids content slurries has significant industrial value.
The uniform dispersion of high-solids content slurries faces two major challenges: First, the strong van der Waals forces and hydrogen bonds between solid particles easily form dense agglomerates, and the higher the solids content, the smaller the interparticle spacing, and the more pronounced the agglomeration tendency. Second, high solids content easily leads to a sharp increase in slurry viscosity and a decrease in fluidity. Traditional dispersion methods are insufficient to completely break up agglomerates and easily cause uneven dispersion and excessively high local concentrations. Balancing "high solids content" and "uniform dispersion" is the key technology.
Achieving uniform dispersion of high-solids-content slurries requires a systematic approach: pretreatment, precise agent selection, and scientific processes, progressively overcoming technical bottlenecks. First, pretreatment of the solid powder is fundamental. Strict control of particle size distribution is crucial, prioritizing powders with a D50 of 1-3 μm and a D90 ≤ 5 μm to reduce the proportion of fine powder and lower the probability of agglomeration. Simultaneously, high-temperature calcination removes organic matter from the powder surface, followed by surface modification to reduce interparticle forces, laying the foundation for subsequent dispersion.
The appropriate selection of dispersants is the core support for uniform dispersion. Based on the characteristics of the slurry system, dispersants capable of forming a stable adsorption layer on the particle surface should be selected. Electrostatic repulsion and steric hindrance prevent particle agglomeration. For example, polycarboxylic acid ammonium and polyacrylic acid dispersants are suitable for most inorganic slurry systems. The amount of dispersant used needs precise control, typically 0.5-2 wt% of the powder mass. The dosage can be optimized through zeta potential testing; optimal dispersion stability is achieved when the absolute value of the zeta potential is >30 mV.
A scientific mixing and dispersion process is the key to achieving uniform dispersion. Equipment with strong shearing force and uniform mixing capabilities is required. Double planetary ball mills and three-roll mills are both effectively suited for high-solids-content slurries. Double planetary ball mills, through a combination of revolution and rotation, can improve the dispersion consistency of batch slurries, while three-roll mills, with their purely mechanical shearing advantages, are suitable for scenarios requiring extremely high fineness. Simultaneously, process parameters need to be optimized, controlling the ball-to-powder ratio, rotation speed, and dispersion time to avoid over-dispersion leading to uneven particle size or abnormal viscosity.
Furthermore, temperature and pH control during dispersion and subsequent stability maintenance are indispensable. The slurry temperature must be controlled within a reasonable range, and the pH value adjusted to be far from the powder's isoelectric point to reduce the risk of agglomeration. During subsequent storage, low-speed stirring or circulation can maintain dispersion uniformity.
In summary, the uniform dispersion of high-solids-content slurries is a systematic project that requires a combination of pretreatment, dispersant selection, process optimization, and other measures to overcome the challenges of agglomeration and viscosity. With the continuous upgrading of dispersion technology, the stability and efficiency of uniform dispersion are constantly improving, which will further promote the efficient application of high solids content slurries in various fields and help industrial production reduce costs, increase efficiency, and achieve green upgrading.
