Liquid Flame Spray Deposition on Temperature Sensitive Substrates Antti Toropainen

What is liquid flame spray deposition? Materials: metals & metal oxides Particle size: < 100 nm Some applications: Surface hydrophobicity control, Adhesion control Evaporation Nucleation Nano particles Figure 1. Stepien et al. 2011, Applied Surface Science, 6, 1911 Teisala et al. 2010, Surface and Coatings Technology, 2, 438

Process Parameters Precursor concentration Precursor feed rate Combustion gas feed rates (O 2 and H 2 ) Distance Line speed Substrate Teisala et al. 2010, Surface and Coatings Technology, 2, 438 Mäkelä et al. 2011, Aerosol Science and Technology, 45, 831

Problem Flame temperature can range from 450 C to over 2000 C Paper, plastic and electronics can’t handle that high temperatures Solution: Adjust the process parameters so that the temperature won’t be too high on the substrate surface. Teisala et al. 2010, Surface and Coatings Technology, 2, 438

Solution – LFS on Paperboard T at the surface varies between C [1] Adjust: Distance (temperature) Precursor concentration and feed rate (flame) Line speed Figure 2. Teisala et al. 2010, Surface and Coatings Technology, 2, 438

Conclusions LFS is a method to produce and deposit nano particles on substrates LFS produces a hot flame which could destroy the temperature sensitive substrate Temperature on the substrate can be controlled by adjusting the process parameters of LFS: Substrate distance from the flame Precursor and combustion gas feeds Line speed

Questions?

Liquid Flame Spray Deposition Liquid flame spray deposition (LFS) is a method to produce and deposit nano-sized particles. It is used to coat different kinds of substrates such as metals and ceramics. Various surface properties such as hydrophobicity, wear, adhesion, electrical properties and bacteria growth can be engineered through LFS. [1] The process works as follows: metal or metal oxide precursors that are diluted in alcohol are led to a spray gun together with oxygen and hydrogen. Hydrogen and oxygen react in the chamber together and produce the flame that exits the spray gun through a nozzle. As the liquid precursors exit the nozzle they are atomized to micron-sized droplets instantly. These droplets are vaporized in the flame. As these vapors move with the gas stream further from the nozzle, the temperature decreases and the precursors in the vapor react and form nanoparticles. These nanoparticles grow bigger in the flame before hitting the substrate. [1] The particle size can be controlled by precursor concentration and flow rate and by adjusting the distance between the nozzle and the substrate. The particle concentration on the substrate can be controlled by line speed of the substrate (figure 1, two slides forward). [1] The flame temperature and size can be controlled by precursor and combustion gas feed rates [3].

LFS on Paperboard Since the flame temperature can vary from 400 to over 2000 C, the paperboard needs to be far enough from the flame so that it won’t burn. According to Seitala et al. the temperature can vary from 72 to 115 C on the paperboard substrate. [1] This is still a safe temperature for a paperboard. Distance from the flame can be controlled either by adjusting the flame size or by moving the substrate closer to or further from the flame. Flame size can be controlled by feed rate of the precursors and combustion gases. [3] One way to use LFS on paper is by way of roll-to-roll process as described in figure 1. In this process the substrate is rolled from one roll to another. While the substrate is rolled, it is hit by nano particles generated by LFS. The LFS process parameters that lead to a good quality coating and keep the temperature sufficiently low are also displayed in figure 1.

Figure 1 Figure 1. Teisala et al. 2010, Surface and Coatings Technology, 2, 438

References 1. Teisala et al. 2010, Surface and Coatings Technology, 2, Stepien et al. 2011, Applied Surface Science, 6, Mäkelä et al. 2011, Aerosol Science and Technology, 45, 831