Scanning electron microscopy (SEM) of the nanoscale silica is shown in Figure 1. Transmission electron microscopy (TEM) of the dispersibility of the nanoscale silica in the solution is shown in Figure 2. The average particle size of the nanoscale silica is 12 nm in the experiment, the particle size of the nanoscale silica after disjection did not obviously change. The dispersibility of the nanoscale silica in the solution is uniform as shown in Figure 2.

SEM of RC-IJP is shown in Figure 3(a), the surface RC-IJP is smooth and the dispersibility of the nanoscale silica in RC-IJP is uniform. This result is advantageous for ink infiltration. The distribution of the main element composition (C, O and Si) on recording coating surface is shown in Figure 3(b) by energy dispersive spectrum (EDS). The analytical result implies that dispersibility of each composition is uniform in the recording coating.

Microcosmic features of the RC-IJP surface was analyzed by atomic force microscope and is shown in Figure 4. The surface of RC-IJP has a number of heaves, which benefit ink adsorption. On the other side, the dispersibility of the roughness is uniform as seen from Figure 4, preventing the ink from diffusing.

In order to evaluate RC-IJP, the surface infiltration time and the color of the printing image are the most important indexes. If the weight of per unit area recording material is invariant, the dispersibility of the recording coating is more uniform in terms of the short surface infiltration time. The color of the printing image is clearer by preparative RC-IJP.

Figure 5 shows the infiltration time of recording coating surface. In this Figure 5(a), x and y axes show the infiltration time of the sample and the energy of ultrasound, respectively. Figure 5(a) shows the rate at which water infiltrates on recording coating surface, being 0.20 s, while simultaneously RC-IJP receives full energy (100%) under ultrasound. In Figure 5(b), the color of the printing image is clear.

The inorganic pigments-nanoscale silica (the average particle size is 12 nm, specific surface area is 170–230 m²/g) obtained from Degussa A200, Germany. The binder-polyvinyl alcohol (PVA-1788), the substrate-polyethylene terephthalate (PET) and accessory ingredient were provided by Shanghai Chemical Co., Ltd, China. The recording coating prepared is shown in Figure 6.

Silicane dispersing agent (γ-aminopropyltriethoxysilane) is added into distilled water under magnetic stirring for 10 min, nitric acid is subsequently added until solution pH = 4 by ultrasound 10 min. The nanoscale silica is added in the above solution under homogenizer (Fluko Equipment Shanghai Co., Ltd.) for 30 min. The weight scale of the silicane dispersing agent, nanoscale silica and distilled water is 0.02:1:5, respectively. The dispersive nanoscale silica solution is added in 8% PVA solution (distilled water as solvent) by homogenizer for 10 min, a little ethanol (as control assistant of solution viscosity) is added in mixed solution. Finally, the mixed homogeneous solution is added and placed in 40 °C oven for 120 min.

The dispersibility of the nanoscale silica in the solution is analyzed by transmission electron microscopy (TEM, FEI, Quanta 200F, made in the USA). The surface morphologies of RC-IJP are observed using a high-resolution scanning electron microscopy (SEM, Quanta 200 F, made in the USA). The surface roughness of RC-IJP is examined by atomic force microscope (AFM, Solver-P47H, NT-MDT, Russia). The surface infiltration time which is analyzed by liquid infiltration instrument (Emtec EST12 Co., Ltd., Germany) is the time that water infiltrates on the recording coating surface under ultrasound.