Single-Cycle Atomic Layer Deposition on Bulk Wood Lumber for Managing Moisture Content, Mold Growth, and Thermal Conductivity

Abstract

Wood is a universal building material. While highly versatile, many of its critical properties vary with water content (e.g., dimensionality, mechanical strength, and thermal insulation). Treatments to control the water content in wood have many technological applications. This study investigates the use of single-cycle atomic layer deposition (1cy-ALD) to apply <1 nm Al2O3, ZnO, or TiO2 coatings to various bulk lumber species (pine, cedar, and poplar) to alter their wettability, fungicidal, and thermal transport properties. Because the 1cy-ALD process only requires a single exposure to the precursors, it is potentially scalable for commodity product manufacturing. While all ALD chemistries are found to make the wood’s surface hydrophobic, wood treated with TiO2 (TiCl4 + H2O) shows the greatest bulk water repellency upon full immersion in water. In situ monitoring of the chamber reaction pressure suggests that the TiCl4 + H2O chemistry follows reaction-rate-limited processing kinetics that enables deeper diffusion of the precursors into the wood’s fibrous structure. Consequently, in humid or moist environments, 1cy-ALD (TiCl4 + H2O) treated lumber shows a 4 times smaller increase in thermal conductivity and improved resistance to mold growth compared to untreated lumber.

Interpreting inorganic compositional depth profiles to understand the rate-limiting step in vapor phase infiltration processes

“…From the atomic layer deposition (ALD) literature, TiCl 4 is known to be less reactive towards oxidants than TMA, often resulting in reaction-limited processes. 31,32 Fig. 6 presents XPS depth profiles for Ti 2p at TiCl 4 infiltration temperatures of 90 °C (Fig.…”

“…From the atomic layer deposition (ALD) literature, TiCl 4 is known to be less reactive towards oxidants than TMA, often resulting in reaction-limited processes. 31,32 At 90 1C, minimal titanium (o2%) is infiltrated into the films at all exposure times up to 2880 min (2 days). Note that these timescales are significantly longer than those explored in Fig.…”

Vapor Phase Infiltration Doping of the Semiconducting Polymer Poly(aniline) with TiCl4 + H2O: Mechanisms, Reaction Kinetics, and Electrical and Optical Properties

“…All selected peaks increase and then plateau with VPI exposure time except the quinoid absorption peak at 644 nm, which decreases with exposure time. We attribute this plateauing to a diffusion-limited process that subsequently reaches saturation. , To quantify the rates and times required for these doping saturations to occur, we employ an effective diffusion model used by Vijayakumar and co-workers . They quantified F4TCNQ solution doping in kinetics PBTTT using the F4TCNQ anion absorbance peak at 875 nm and provided the following function to relate optical changes over time to the effective diffusion coefficient (eq ).…”

Atomic layer deposited TiO2 on a foam-formed cellulose fibre network – Effect on hydrophobicity and physical properties

“…In its native form, cellulose has a hydrophilic nature due to the hydroxyl functionalities on the surface. Many research groups have been studying the effect of ALD modification on the hydrophilicity/hydrophobicity of the various kind of cellulose substrates (Kemell et al 2005;Lee et al 2012b;Gregorczyk et al 2015;Mirvakili et al 2016;Short et al 2019;Gregory et al 2020;Li et al 2020;Wooding et al 2020). Gregory et al (2020) tested the effect of single cycle ALD on bulk wood lumber.…”

“…Many research groups have been studying the effect of ALD modification on the hydrophilicity/hydrophobicity of the various kind of cellulose substrates (Kemell et al 2005;Lee et al 2012b;Gregorczyk et al 2015;Mirvakili et al 2016;Short et al 2019;Gregory et al 2020;Li et al 2020;Wooding et al 2020). Gregory et al (2020) tested the effect of single cycle ALD on bulk wood lumber. They tested aluminum oxide (Al2O3), zinc oxide (ZnO), and titanium oxide (TiO2) depositions against mold growth, moisture content, and thermal conductivity.…”