What specific factors should be considered when selecting binders for alumina ceramics?
At present, binders in the market can be divided into lubricants, plasticizers, dispersants, surfactants, etc. To meet the forming needs, a combination of multiple organic materials is usually used. When choosing an alumina ceramic binder, it is first required that it can be wetted by the powder, and only when the critical surface tension or surface free energy of the powder is greater than the surface tension of the binder can it be well wetted.
Secondly, good binders are easy to be fully wetted by the powder and have high cohesion. When the binder is wetted by the powder, a gravitational interaction occurs between the molecules, and a binding occurs between the binder and the powder. At the same time, cohesion is generated within the binder molecules due to orientation, induction, and dispersion effects. Although water can fully wet the powder, it is volatile, has a small molecular weight, and low cohesion, making it not a good binder for alumina ceramics.
In addition, the molecular weight of the binder used in alumina ceramics should be moderate. As the molecular weight increases, the binding ability of Su Ri'an increases. But when the molecular weight is too large, the cohesive force is too high to be easily wetted, and it is easy to cause deformation of the billet. In order to assist in the movement of chain segments within the molecule, it is necessary to add plasticizers appropriately at this time. While it is easy to wet, it makes the binder softer and easier to form.
In addition, to ensure the quality of alumina ceramics, it is also necessary to prevent impurities from being mixed from the binder, raw materials, and preparation process, which can cause harmful defects in the product. Therefore, it is necessary to choose organic materials that are easy to remove and do not contain harmful inorganic salts and metal ions in order to ensure product quality.
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