Dispersants are commonly used in electronic ceramics

01

Dispersants for water-based systems

(1) polyammonium acrylate anionic dispersant

In the water-based system, ammonium polyacrylate dispersant is widely used for wetting and dispersing electronic ceramic slurry,

 such as alumina ceramic granulation powder for dry press forming, alumina ceramic substrate for water-based gel forming, 

zinc oxide varistor for dry press forming, and piezoelectric ceramic dry press forming granulation powder. It has the characteristics of small dosage and good dispersion effect, 

and the mechanism of action is electrostatic steric effect. This series of dispersants includes polyacrylic acid, sodium polyacrylate and ammonium polyacrylate dispersants, 

which respectively contain carboxylic acid group, sodium ion and ammonium group with good wettability, which can very well wet ceramic powder particles, 

and maintain the dispersion stability of powder particles through electrostatic repulsion and steric hindrance effects. Because ammonium polyacrylate is weakly alkaline, 

it has no effect on the insulating properties of the material, so it is widely used in water-based electronic ceramic slurry wetting dispersion.

(2) polyacrylamide dispersant

The molecular chain of polyacrylamide (PAM) contains carboxyl group, which has the effect of reducing surface tension, 

and is conducive to the dispersion of fibers and fillers in water. After PAM is added to the slurry, 

the fiber and haniwa surface can form a bimolecular structure, because PAM has a strong affinity with water, 

it can increase the degree of solid particles being wet by water, and then away from it due to electrostatic repulsion, achieving a good dispersion effect. 

For example, for LiFePO4, a lithium ion battery cathode material using water-based binder, PAM as a dispersant can improve the uniformity of the electrode surface, 

prevent the agglomeration of particles, and the dispersion effect of the slurry is better, and basically no agglomeration occurs after standing.

02

Dispersants for organic systems

In organic system ceramic slurry, non-ionic surfactants are often used to achieve stable dispersion by adsorption of unsaturated polymer organic matter. 

The dispersion mechanism is steric hindrance effect. Oily substances are the most commonly used dispersants for traditional electronic printing pastes, 

which contain unsaturated fatty acids and are easily adsorbed on the surface of the particles to achieve stable dispersion. Commonly used dispersants are as follows:

(1) Lecithin

Can be divided into soy lecithin and egg yolk lecithin. Because phosphatidylcholine PC (lecithin) is an effective component of the dispersant, 

and the lecithin content of egg yolk lecithin is higher after several purification, up to 95%, so egg yolk lecithin is often used as a dispersant. 

Some researchers in the preparation of inorganic ceramic porous film, the addition of lecithin dispersant, with a very small amount of alumina powder in the slurry can be well dispersed, 

greatly reduce the accumulation of particles, can avoid the agglomeration of alumina particles in the slurry, the obtained membrane tube aperture distribution is uneven and other problems.

(2) Span-85 (SPAN-85)

Span-85 is a non-ionic surfactant that can be dispersed in hot water, soluble in hot oil and common organic solvents.

 The unsaturated hydroxyl group contained in the molecule can be adsorbed on the surface of the particle,

 making it an excellent dispersant and can be used for separation and analysis of oxygen-containing compounds.

(3) NP-10 (nonylphenol polyoxyethylene ether)

The hydroxyl and amine groups contained in the NP-10 molecule make NP-10 and the particle surface have good wettability, 

and the unsaturated double bond group makes NP-10 and the particle surface firmly adsorbed together, making it a widely used dispersant, 

which can improve the hydrophilicity of the slurry, and its molecules can form a thick adsorption film when adsorbed on the surface of the slurry. 

It can produce a large steric hindrance effect, which makes the slurry stable.

In SUMMARY:

From the above commonly used dispersants for electronic ceramics, the following characteristics can be summarized: In order to achieve the purpose of stable dispersion, 

the molecular weight of the dispersant is required to be appropriate; Because the traditional oil dispersants have high ineffective dispersion components and large dosage, 

they can be developed into high-efficiency special dispersants with small dosage and high dispersion efficiency.

At present, there are many kinds of dispersants available in electronic ceramics, but the dispersants that are more widely used are dispersants for water-based systems, 

especially in the preparation of positive and negative electrode materials for lithium-ion batteries, which can improve the uniformity of the electrode surface, prevent particles from agglutinating, etc., 

so that the prepared products have better performance. For example, adding a certain amount of dispersant DCS308 in the preparation process of positive slurry can improve the distribution of conductive particles in the electrode plate, 

so that conductive particles dispersed more evenly. Therefore, we can choose the appropriate dispersant according to the characteristics of various electronic ceramics, 

and at the same time, according to the performance and structure characteristics of existing dispersants, new dispersants can be selected to use.