A Primary Study on Mechanical Properties of Heat-Treated Wood via in-situ Synthesis of Calcium Carbonate

This study aims to improve the value of fast-growing wood and extend the heat-treated wood utilization using inorganic calcium carbonate(CaCO_(3))crystals via an in-situ synthesis method.CaCl_(2)and Na 2CO_(3)solutions with a concentration ratio of 1:1 were successively introduced into the thermally modified poplar wood obtained by steam heat treatment(HT)at 200℃for 1.5 and 3 h,resulting in the in-situ synthesis of CaCO_(3)crystals inside the heat-treated wood.The filling effect was best at the concentration of 1.2 mol/L.CaCO_(3)was uniformly distributed in the cell cavities of the heat-treated wood,and some of the crystals were embedded in the fissures of the wood cell walls.The morphology of CaCO_(3)crystals was mainly spherical and rhombic polyhedral.Three main types of CaCO_(3)crystals were calcite,vaterite,and aragonite.The HT of poplar wood at 200℃resulted in degrading the chemical components of the wood cell wall.This degradation led to reduced wood mechanical properties,including the surface hardness(HD),modulus of rupture(MOR),and modulus of elasticity(MOE).After CaCO_(3)was in-situ synthesized in the heat-treated wood,the HD increased by 18.36%and 16.35%,and MOR increased by 14.64%and 8.89%,respectively.Because of the CaCO_(3)synthesization,the char residue of the 200℃heat-treated wood samples increased by 9.31%and the maximum weight loss rate decreased by 19.80%,indicating that the filling with CaCO_(3)cannot only improve the mechanical properties of the heat-treated wood but also effectively enhance its thermal stability.

Water Absorption Capacity and Coating Adhesion on Thermally Modified and Not-Modified Spruce Wood(Blue Stained or Free of Blue Stained)

This study aimed to investigate the water absorption capacity of thermally modified and non-modified spruce and blue-stained spruce wood.The wettability of wood depends on various factors,including its type,density,porosity,and surface treatment.Wood can swell and become distorted when exposed to water or humidity,impacting its structural integrity.Hence,it is crucial to consider the water and water vapour uptake in the wood when choosing materials for applications that are likely to be exposed to moisture.Various moisture absorption tests were conducted to assess water absorption capacity,including short-term and long-term water absorption and water vapour absorption.The results showed a significant difference in the long-term exposure to water,which was related to the density of the wood.The study examined the influence of thermal treatment on the physical properties of wood and observed significant variations in mass change due to coating,indicating differences in adhesion among different wood types.Vacuum-treated blue-stained Norway spruce demonstrated higher adhesion(5%–15%)compared to air-treated samples.Furthermore,cohesion tests revealed lower cohesion force in blue-stained Norway spruce(approximately 20%–30%)compared to Norway spruce.The study also used industry-standard tests to investigate the adhesion and cohesion of nano-coatings on wood surfaces.The results provided valuable information on the properties of coatings applied to wood,which is vital in protecting and decorating wood while also providing preventive protection against wood pests,weathering,and mechanical influences.Wood modification in vacuum involves subjecting the wood to a low-pressure environment to remove air and moisture,allowing for deeper and more uniform penetration of treatment chemicals.In contrast,wood modification in air relies on the natural circulation of air to facilitate the absorption of chemical treatments,without the need for a vacuum chamber.