The effect of shearing conditions in the coating process on the uniformity of the coated layer of dense silica slurry is investigated. The pH 6.8 test slurry mainly used in this study forms a nonuniform coated layer only on the condition of large shear strain and low shear rate. The same shearing dependency was observed using not only a laboratory-scale doctor blade but also a pilot-scale comma coater. The test slurry exhibits two-step yielding, and the internal structure of the slurry is gradually destroyed after the second yielding. When the shear strain applied is within the second yielding, the test slurry is in equilibrium and a uniform coated layer is formed. As strain is increased further, the slurry changes from the viscoelastic fluid to Newtonian. When the shear strain is beyond the second yielding but the structural destruction is not completed, a nonuniform coated layer is formed. A higher coating speed or sufficiently large shear deformation, which effectively destroys the internal structure, is favorable to obtain a uniform coated layer.

研究了涂覆过程中剪切条件对致密二氧化硅浆料涂覆层均匀性的影响。本研究中主要使用的 pH 6.8 测试浆料仅在大剪切应变和低剪切速率的条件下形成不均匀的涂层。不仅使用实验室规模的刮刀而且使用中试规模的逗号涂布机也观察到相同的剪切依赖性。试验浆液呈两步屈服，二次屈服后浆液内部结构逐渐破坏。当施加的剪切应变在第二次屈服范围内时，试验浆料处于平衡状态，形成均匀的涂层。随着应变进一步增加，浆液从粘弹性流体变为牛顿流体。当剪切应变超过二次屈服但结构破坏未完成时，形成不均匀的涂层。较高的涂布速度或足够大的剪切变形，有效破坏内部结构，有利于获得均匀的涂层。