China
Africa
Explore chapters and articles related to this topic
Thermally-based Modification Processes
Published in Dick Sandberg, Andreja Kutnar, Olov Karlsson, Dennis Jones, Wood Modification Technologies, 2021
Dick Sandberg, Andreja Kutnar, Olov Karlsson, Dennis Jones
The property improvements gained are highly dependent on the process conditions, the treatment intensity (temperature, duration), the wood species and the dimensions of the sawn timber. Thermally-modified wood has a lower density than untreated wood, due to the thermal degradation of cell-wall components and the loss of mass during treatment. The durability generally increases with the applied temperature and the exposure period. At the same time, mechanical properties of the wood are reduced. Thus, thermal treatment always constitutes a compromise between increased resistance against fungi and decreased strength properties.
Effect of wood drying and heat modification on some physical and mechanical properties of radiata pine
Published in Drying Technology, 2018
René Herrera-Díaz, Víctor Sepúlveda-Villarroel, Natalia Pérez-Peña, Linette Salvo-Sepúlveda, Carlos Salinas-Lira, Rodrigo Llano-Ponte, Rubén A. Ananías
The wood quality for fast-growing conifers initially depends on the rotation time, in which plantations with short rotations usually present higher amount of juvenile wood in contrast to mature wood.[8,9] This particularity alters the properties after drying, and therefore, wood from short rotations usually present low stiffness (modulus of elasticity, MOE), greater longitudinal shrinkage and low hardness.[10,11] Therefore, it is fundamental to follow changes that occur in the physical–mechanical properties from green sawn timber to the thermally modified wood, to know the factors those are significantly influenced by the drying process and which alter the wood dimensions or its strength values, in this particular case with radiata pine, due to its low-dimensional stability compared to other commercial species.
Effect Of vacuum plasma on structure and function of fibers of Ichnocarpus frutescens
Published in Radiation Effects and Defects in Solids, 2021
Subrajeet Rout, Biswajit Mallick, Debabrata Dash, Nihar Ranjan Nayak, Chhatrapati Parida
Several works have been cited in the literature regarding exposure of cold plasma on natural fiber and their composites have been reported by many researchers. Liu et al (2) in 2017 investigated the influence of low temperature plasma treatment on properties of ramie fibers with output power, viz. 100 W(1 min), 150 W(1.5 min), 200 W(2 min), 250 W(2.5 min) and 300 W(3 min) and compared with untreated fibers. The surface energy of ramie fibers increased from 117.0% in untreated ramie fiber to 122.9% in treated fiber. The coefficient of friction in ramie fiber is enhanced from 10.7% at 300 W(3 min) exposure to 13.4% at 100 W(1 min exposure). Altgen et al. (3) studied that the effect of air plasma treatment at atmospheric pressure on thermally modified wood surfaces and reported enhancement in surface energy, wettability and thermal stability of plasma-exposed wood fiber. Barra et al (4) in 2012 studied the effects of methane cold plasma exposed on sisal fiber with an exposure time 10, 20 and 30 min. Major changes in structural and mechanical property of sisal fiber were reported when treated with 10 min of exposure. However, there is complete lack of scientific data about the cold plasma irradiated IF fiber. The main objective of this study is therefore to modify the surface of IF fiber by plasma treatment with an exposure time for 3 min at 2 kV and evaluate its spectroscopic behavior. Also complete lack of information about compositional analysis of IF fiber in the literature motivated us to calculate the percentage of cellulose, hemicelluloses and lignin in the IF fiber.
Using acoustic emission technique for detecting checks on industrial-size beech wood disks during drying
Published in Drying Technology, 2022
Hasan Hüseyin Ciritcioglu, Asghar Tarmian, Hızır Volkan Görgün, Öner Ünsal
Acoustic emission (AE) is a transient elastic wave generated by the rapid release of energy due to a local change in a material. It is generally used as a “passive” nondestructive testing technique to detect checking at a very early signs of the failure development before it intensifies. This technique not only detects new checks but also is able to detect the propagation of existing checks.[1] Mechanical properties, wood machining, classification of thermally modified wood, biodegradation, moisture and drying effects are some examples of AE applications to wood as an extremely dynamic material.[2–6] The potential use of this technique has been investigated for optimizing lumber drying processes, especially in drying of check-prone woods like oak since the 1980s.[7–14] Generally, AE sources during wood drying are the cell collapse, surface or internal check (honeycomb) initiation and propagation. However, it should be kept in mind that there could be low energy AE events resulted from other effects like moisture movement, while drying check generates high-energy AE signals.[11] Generally, low-frequency and high-amplitude AE events denote the drying check.[13] Various AE parameters including ring down count,[8,9] peak amplitude,[13] energy[11] and event rate[9,11,15] can be used for this purpose. One of the limitations of using acoustic emission in the kiln drying of lumber is noises with different frequencies generated in the kiln due to factors other than cracking. Therefore, a threshold should be set at an optimal level during kiln drying of lumber to eliminate noises caused by fan movement, ventilation and humidification systems.[14] The question usually accompanies in this technique that where transducers should be placed and how many of them are required for a good monitoring of the lumber drying checks because a transducer can only monitor a limited area of lumber near the AE source.[13]