Effects of Different Energy Intensities of Microwave Treatment on Heartwood and Sapwood Microstructures in Norway Spruce

Sauradipta Ganguly,Angela Balzano,Jure Žigon,Marko Petrič,Sadhna Tripathi,Davor Kržišnik,Maks Merela

doi:10.3390/f12050598

Sauradipta Ganguly, Angela Balzano + Show 5 more

Open Access

https://doi.org/10.3390/f12050598

Copy DOI

Journal: Forests	Publication Date: May 10, 2021
Citations: 14	License type: CC BY 4.0

Affiliation: Forest Research Institute, University of Ljubljana

Abstract

Microwave modification can increase the permeability of wood by delaminating and rupturing its anatomical microstructures at their weak points. A high degree of intensity of microwave modification can cause significant structural damage to the microstructures of wood, resulting in poorer strength properties. The objective of this study was to evaluate the changes in the anatomical structure of Norway spruce (Picea abies (L.) Karst.) heartwood and sapwood after microwave modification in order to develop the most effective treatment in terms of applied energy without causing significant structural damage. Analysis with light and scanning electron microscopy were performed to evaluate the effect of microwave treatment for two different energy intensities, moderate and high intensity. The results indicated structural changes in the tracheid cells. Microscopy showed varying degrees of modification within the wood microstructure, with the heartwood samples showing a greater anatomical distortion compared to their sapwood counterparts. Furthermore, the samples were subjected to pycnometric density measurements, which indicated a reduction in skeletal and absolute density after microwave modification, for both high and moderate intensity treatment on sapwood and heartwood samples. With increasing microwave energy, a gradual increase in specific pore volume and porosity percentage of the samples were also detected.

Highlights

Wood is used in various sectors due to its environmentally friendly nature, standard mechanical properties, machinability, natural origin, ability to sequester carbon in service and aesthetic appearance, and these properties make it an excellent natural building material
Scanning electron microscopy analysis of microstructural changes in Norway spruce heartwood and sapwood after MW treatments of different energy intensities provided new insights that are important in the selection of parameters for optimizing the microwave process
The MW treatment resulted in evident changes in wood microstructure in both cross- and radial sections

Summary

Introduction

Wood is used in various sectors due to its environmentally friendly nature, standard mechanical properties, machinability, natural origin, ability to sequester carbon in service and aesthetic appearance, and these properties make it an excellent natural building material. The diversity of woody biomass available worldwide almost guarantees the use of different types of wood species with the required properties for specific end-uses [1]. Despite its undeniable superiority over other building materials, the use of wood is often limited due to its inherent properties such as biological decay, poor dimensional stability, poor treatability, and high fire susceptibility, which are highly undesirable in service [2,3]. Wood species with low permeability are associated with many difficulties in impregnation with preservatives and resins. Low permeability causes problems associated with wood-drying processes, which can be time consuming, expensive, and even ineffective

Objectives

Methods

Results

Conclusion