Nanoparticle Deposition from Liquid Flame Spray onto Moving Roll-to-Roll Paperboard Material

Figures & data

FIG. 1 Photograph of the practical situation for LFS nanocoating the roll-to-roll paperboard. The distance from burner face to paperboard is 15 cm.

FIG. 2 Schematic of the LFS-coating process. The precursor liquid is fed by a syringe pump. The hydrogen (atomizing gas) and oxygen flows are controlled by mass flow controllers. Also the two heights used in the calculation, boundary layer height δ above the paperboard surface and the turbulent transport layer height h, are shown.

FIG. 3 Schematic of using only one coaxial burner for coating the moving paperboard, i.e., creating a narrow stripe for testing the method principles. The dashed rectangular area denotes the 1 cm × 15 cm sized area from where the chemical analysis was performed.

FIG. 4 Schematic of the main particle transport mechanisms in the liquid-flame-spray-driven nanoparticle coating of moving flexible roll-to-roll material. Only one half of the flame (shooting downward) is illustrated. Convective transport of particles occurs in the actual flame impinging toward the paperboard, turbulent transport moves the particles to the boundary layer, and finally, thermophoresis transports the particles through the boundary layer onto the paperboard. The particle losses are assumed to occur both by diffusion perpendicular to the downward flow (LOSS 1) and by horizontal convection above the paperboard (LOSS 2).

FIG. 5 Flame (gas) temperatures at various distances from the burner face. Measurements in this study using gas flows of H₂ = 50 l/min and O₂ = 15 l/min, and varying the IPA feed rate: (a) no IPA feeding, (b) feed rate of IPA = 8 ml/min, (c) feed rate of IPA = 15 ml/min, (d) feed rate of IPA = 30 ml/min.

TABLE 1 Temperatures (°C) of the paperboard surface directly after the flame, measured from a spot 50 cm downstream of the flame using a pyrometer. The IPA feed rate of 23 ml/min corresponds to the “base case” used in this article

IPA feed rate (ml/min)	30 m/min	50 m/min	70 m/min	100 m/min	150 m/min
12	105	110	90	90	72
23	110	112	102	95	77
32	115	112	105	97	75

FIG. 6 A set of FEG-SEM graphs for four different line speeds: (a) 30 m/min, (b) 70 m/min, (c) 100 m/min, and (d) 150 m/min. Liquid feed rate, 23 ml/min; (atomic) Ti concentration in precursor, 50 mg/ml; distance from burner face to paperboard, 15 cm (base case).

FIG. 7 (a) Particle size on the paperboard (bullets), estimated from FEG-SEM graphs, such as shown in Figure 8, given here as a function of the estimated residence time of substrate within the flame. The shortest residence time refers to a line speed of 150 m/min, and the highest time refers to a line speed of 30 m/min. (b) A TEM image of the particles collected from the flame with a TEM sampler. One fast sweep of collection through the flame was taken.

FIG. 8 A FEG-SEM graph of the paperboard coated with parameters: line speed, 150 m/min; liquid feed rate, 32 ml/min; Ti concentration, 50 mg/ml; distance from burner face to paperboard, 15 cm.

FIG. 9 Three 3D-AFM images of (a) the uncoated reference paperboard, (b) coated paperboard, and (c) the coated aluminum foil using identical parameters: line speed, 30 m/min; liquid feed rate, 32 ml/min; Ti concentration, 11.9 mg/ml. Comparison of (a) and (b) indicates the clear sintering of the titania nanoparticles on the paperboard. The aluminum foil is assumed to conduct some of the excess heat away from the surface to eventually weaken the particle sintering. Furthermore, coverage of around 100% is also suggested in this case.

TABLE 2 Data set for the amount of deposited material. In the determination of the “yield,” the precursor mass feed rate is converted into TiO₂ and calculated to be deposited onto a 15-cm wide stripe, to obtain an upper limit for the deposited amount. Parameters used in calculation (columns 3, 4, and 5) according to the base case: liquid (TTIP in IPA) feed rate 23 ml/min, (atomic), Ti concentration in precursor 50 mg/ml, distance from burner face to paperboard 15 cm, gas flows of H₂ 50 l/min and O₂ 15 l/min. Columns 6, 7, and 8 correspond to same parameters, but liquid feed rate was 32 ml/min. Reference water CA for uncoated Natura paperboard is 54°

		Ti feed rate of 1150 mg/min			Ti feed rate of 1600 mg/min
Line speed (m/min)	Water CA with IPA only	Water CA	Deposited mass (ICP-MS; mg/m^2)	Yield (%)	Water CA	Deposited mass (ICP-MS; mg/m^2)	Yield (%)
30	74°	139°	–	–	140°	47	5
50	49°	135°	18	5	141°	47	9
70	39°	105°	–	–	–	–	–
100	–	90°	11	6	110°	43	16
150	–	65°	–	–	104°	38	20