Changes in the microstructure of birch wood after hydrothermal treatment

Birch wood (Betula pendula) samples were treated in a thermal regime (140, 160, 180 °C) for 1 h and investigated by means of scanning electron microscopy (SEM). SEM microimages of the wood cross-section were taken from one and the same place before and after the thermal treatment (magnification 100–2,000×). The results of measurements of areas and linear sizes of the birch wood cells show significant changes, which depend on the thermal treatment conditions and the type of the cell: libriform, tracheid, vessel and ray. After the treatment at 180 °C, the integrity of wood morphological structure begins to break up. Voids and cracks are formed between fibres, thus leading to a decline in the mechanical properties of the wood.     

Changes in wettability of wood surface using electron beam irradiation

ABSTRACT

This study deals with the influence of electron beam irradiation (EBI) on the wettability of Norway spruce surface samples. To evaluate this possible effect in detail, the changes in chemistry and wood structure were analysed using the methods of IR spectroscopy and Scanning Electron Microscopy (SEM). The surface wettability was determined by the contact angle measurement method. The results of infrared spectra show decreased relative numbers of available hydrophilic groups (e.g. hydroxyl and carbonyl groups) in the wood surfaces due to the electron beam irradiation. This behaviour is consistent with the values from the surface wettability measurements. Structural differences of the wood surfaces after electron beam irradiation were not detectable. Based on these findings pre-treatment of wood surfaces for industrial usages can be a potential field of application of this technology.     

木质材料激光表面处理研究进展

激光以其能量密度高、运行轨迹自如、方向性好等优点,被广泛用于木质材料切削加工以及表面处理等领域.其中,木质材料激光表面处理,即利用激光热/光电子效应促进材料发生物理、化学变化,以实现改性的目的.笔者对木质材料激光表面处理原理、激光类型与用途以及激光表面处理技术特点与应用领域等内容的研究现状进行了综述与分析.现有研究表明...     

关于人造板高耐磨固化液体表层的探讨

人造板表现高耐磨处理工艺,是当今人造板精细加工工业发展的首要方向。本文所探讨的高耐磨固化液体表层的 是将表层的所有组份按比例制成液体形态,使每个耐磨颗粒被胶液包裹着,均匀地分布于胶层的各个层面中,级固化后,从而生产更高的耐磨强度,它改变了传统工艺中耐磨颗粒只能不均匀地置于表层纸最外层的弊端,大幅度地提高了耐磨表层的质量,降低了生产成本。     

Chemical composition of wood and its connection with wood anatomy in Betula pubescens

ABSTRACT

The connection between chemical composition and anatomy of wood is poorly studied. Abiotic and biotic growth conditions affect the synthesis of structural compounds and the anatomy of wood at the same time as they affect growth. In this study, the wood chemical composition, and connections between wood chemistry and anatomy were studied in downy birch (Betula pubescens Ehrh.) grown on four growth sites possessing mineral and peat soils. Lignin, holocellulose, extractive and ash contents, and effective heating value were analysed and compared with libriform fibre double wall thickness and lumen diameter, vessel size and number, and ray and axial parenchyma numbers. Measured lignin and extractive contents were exceptionally high and holocellulose content low. Correlations between wood anatomy and effective heating value were partly different on different soils. Correlations between holocellulose and anatomy were the opposite of the correlations between other chemical compounds and anatomy. The significant correlations between chemical composition and anatomy were commonly opposite in trees grown on peat than in trees grown on mineral soil. Particularly, vessel characteristics and fibre wall thickness correlated significantly with wood chemistry in trees grown on mineral soil. The connections between wood anatomy and chemistry proved to be soil-dependent.     

Evaluation of surface smoothness by laser displacement sensor 1: effect of wood species

The best methods for determining surface roughness in an industrial environment are of the noncontact variety, with reproduction of the profile. The objective of this work was to compare the roughness profile obtained by a contact stylus with a commercial laser displacement sensor (LDS). Measurements were done using 15 wood species with different densities and colors, based on which special triangle profiles were prepared. The accuracy of the laser sensor was examined by statistical analysis of roughness parameters measured from the profiles. Experimental results show that LDS profiles were imitated correctly. However, LDS accuracy depends on the scanned wood properties (density and color), installation position of the sensor, and profile shape. It was found that evaluation of dark and high-density wooden surfaces was imperfect.Part of this work was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000; and at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001     

Changes in surface properties of tropical wood species exposed to the Indonesian climate in relation to mold colonies

Changes in mold populations and genera on the exposed surfaces of tropical hardwoods — albizia (Paraserianthes falcata), kapur (Dryobalanop lanceolata), mahoni (Switenia macrophylla), nangka (Artocarpus heterophyllus), puspa (Schima wallchii) — were investigated. The wood specimens were exposed to the Indonesian climate for 32 weeks. Properties including mass loss, wettability, mold growth (colony-forming units), and mold genera were evaluated. The change in properties after exposure was significantly affected by the wood species, but there was no clear relation between mass loss and the initial chemical components or between wettability and wood density. The number of mold populations was different by exposure period and wood species, but there was no significant effect of climate conditions, such as rainfall and ultraviolet radiation. Of the genera identified,Aureobasidium, Cladosporium, andPenicillium were dominant molds on the exposed wood surfaces.     

Connection of growth and wood density with wood anatomy in downy birch grown in two different soil types

Soil affects the anatomy of downy birch wood (Betula pubescens), which raises the question whether the growth of this species differs between mineral and peat soils. The aim of this study was to compare growth, density and structure of xylem of B. pubescens between trees grown in different soils. Both growth and density differed between trees grown in different soils. All measured anatomical characteristics, except double thickness of fibre walls, percentage vessel area and ray number, showed differences between the soil types: the cell dimensions were larger and numbers smaller in trees grown in mineral soil. In peat, high growth rates decreased the wall:lumen ratio of fibres in maturing wood, while no such correlation was observed in trees grown in mineral soil at any studied cambial age. In addition, axial parenchyma may have a different role in trees grown in different soils, as the rapid growth decreased and increased axial parenchyma in mineral and peat soil, respectively. The characteristics affecting wood strength were more similar between trees grown in different soils than those affecting water conductance. The observed differences between trees grown in different soils emphasise rapid growth particularly at young ages and shorter reasonable rotation period in mineral soil.     

Impregnation of Scots pine and beech with tannin solutions: effect of viscosity and wood anatomy in wood infiltration

The impregnation process of Scots pine and beech samples with tannin solutions was investigated. The two materials involved in the process (impregnation solution and wood samples) are studied in depth. Viscosity of mimosa tannin solutions and the anatomical aspect of beech and Scots pine were analysed and correlated. The viscosity of tannin solutions presents a non-newtonian behaviour when its pH level increases, and in the case of addition of hexamine as a hardener, the crosslinking of the flavonoids turns out to be of great importance. During the impregnation of Scots pine (Pinus sylvestris L.) and beech (Fagus sylvatica L.), the liquid and solid uptakes were monitored while taking into consideration the different conditions of the impregnation process. This method allowed to identify the best conditions needed in order to get a successful preservative uptake for each wooden substrate. The penetration mechanism within the wood of both species was revealed with the aid of a microscopic analysis. Scots pine is impregnated through the tracheids in the longitudinal direction and through parenchyma rays in the radial direction, whereas in beech, the penetration occurs almost completely through longitudinal vessels.     

Temperature effects on wood anatomy, wood density, photosynthesis and biomass partitioning of Eucalyptus grandis seedlings

Wood density, a gross measure of wood mass relative to wood volume, is important in our understanding of stem volume growth, carbon sequestration and leaf water supply. Disproportionate changes in the ratio of wood mass to volume may occur at the level of the whole stem or the individual cell. In general, there is a positive relationship between temperature and wood density of eucalypts, although this relationship has broken down in recent years with wood density decreasing as global temperatures have risen. To determine the anatomical causes of the effects of temperature on wood density, Eucalyptus grandis W. Hill ex Maiden seedlings were grown in controlled-environment cabinets at constant temperatures from 10 to 35 degrees C. The 20% increase in wood density of E. grandis seedlings grown at the higher temperatures was variously related to a 40% reduction in lumen area of xylem vessels, a 10% reduction in the lumen area of fiber cells and a 10% increase in fiber cell wall thickness. The changes in cell wall characteristics could be considered analogous to changes in carbon supply. Lumen area of fiber cells declined because of reduced fiber cell expansion and increased fiber cell wall thickening. Fiber cell wall thickness was positively related to canopy CO2 assimilation rate (Ac), which increased 26-fold because of a 24-fold increase in leaf area and a doubling in leaf CO2 assimilation rate from minima at 10 and 35 degrees C to maxima at 25 and 30 degrees C. Increased Ac increased seedling volume, biomass and wood density; but increased wood density was also related to a shift in partitioning of seedling biomass from roots to stems as temperature increased.     

Douglas-fir wood quality studies part I: Effects of age and stimulated growth on wood density and anatomy

Douglas-fir trees about 21 years old and growing on a poor site were thinned and fertilized causing accelerated growth. The characteristics of the wood across the 30-year age span were studied for 7 trees from the treated plot. Four trees of nearly uniform ring growth were also studied for some characteristics. Radial and tangential tracheid diameters, tracheid length and percent latewood were correlated quite well with log of age, coefficients ranged from 0.76 to 0.88 on pooled data. All tracheid dimensions when correlated with log of age gave high coefficients on a within-tree basis. The strongest relationship in all age-related factors was between 0 and 12 to 14 years. Specific gravity increased with age in all trees to about 16 to 18 years, then leveled off.Fertilization and thinning caused immediate production of lower density wood with somewhat lower percent latewood, a slight decrease in tracheid diameter tangentially but slightly greater radially, and a small decrease in tracheid length. The effects were mainly in the first 3 to 4 years after treatment, then there was recovery to normal wood density and cell dimensions. Wood from the trees of uniform growth showed no significant change over the same time period in percent latewood, specific gravity, and tracheid length.The research was financed by funds from State of Washington Initiative 171, Institute of Forest Products and the College of Forest Resources, University of Washington, Seattle.     

Changes in soil chemistry and element uptake by Oak seedlings after application of soil amendment

ABSTRACT

The purpose of this study is to investigate the effect of cellulosic wastes and nanoscale zero-valent iron (nZVI) on the soil properties and the nutrient uptake by Quercus castaneifolia C.A.Mey seedlings. The seedlings were planted in pots (unpolluted soil) and cadmium (Cd) was added to the pots in three concentrations (10, 20, 30?mg.kg^?1). Cellulosic wastes were mixed with the soil (at the same time as the planting) in four levels (W: 0, 10, 20, 30?g.100g^?1 soil). The reduction method was used to prepare nZVI, then the nanoparticles were injected into the polluted pots in four levels (N: 0, 1, 2, and 3?mg.kg^?1). The lowest concentration of Cd in leaves, stems and roots and for all the contamination levels was observed in N3. All the cellulosic wastes and N3 significantly increased the soil pH at all the levels of contamination. An increasing trend of the soil carbon (C) content was observed by adding the cellulosic wastes. The highest pH and C content were observed in W3. The lowest bioavailable Cd contents for all the contamination levels was observed in N3. According to the results, nZVI and cellulosic wastes could help the plants establishing in heavy metal-polluted lands.     

Changes in wood temperature under high-speed friction

Thermal effects at the surface of a sample wood specimen while it is rubbed by reduction with a metal disk rotating at high speed are investigated. The results provide fundamental data for the development of new surface processing methods. The results of high-speed friction tests showed that the wood surface developed high-temperature regions due to the effect of friction heat, and deformed tissue was observed at the wood surface in the region that experienced the rubbing action. The thermal effects extended to a deep range in the deformed region by reduction due to different fiber inclination angles, both parallel and normal to the friction surface. The thermal effects from the rubbed conditions of the reduction and feed speed also extended deeply into the region deformed by reduction, although the thermal effect was decreased at higher feed speed. From the results of these friction tests, the change in wood temperature is described unambiguously by factors related to pressure on the friction surface.     

Browsing affects intra-ring carbon allocation in species with contrasting wood anatomy

Current knowledge on tree carbon (C) allocation to wood is particularly scarce in plants subjected to disturbance factors, such as browsing, which affects forest regeneration worldwide and has an impact on the C balance of trees. Furthermore, quantifying the degree to which tree rings are formed from freshly assimilated vs. stored carbohydrates is highly relevant for our understanding of tree C allocation. We used (13)C labelling to quantify seasonal allocation of stored C to wood formation in two species with contrasting wood anatomy: Betula pubescens Ehrh. (diffuse-porous) and Quercus petraea [Matt.] Liebl. (ring-porous). Clipping treatments (66% shoot removal, and unclipped) were applied to analyse the effect of browsing on C allocation into tree rings, plus the effects on tree growth, architecture, ring width and non-structural carbohydrates (NSCs). The relative contribution of stored C to wood formation was greater in the ring-porous (55-70%) than in the diffuse-porous species (35-60%), although each species followed different seasonal trends. Clipping did not cause a significant depletion of C stores in either species. Nonetheless, a significant increase in the proportion of stored C allocated to earlywood growth was observed in clipped birches, and this could be explained through changes in tree architecture after clipping. The size of C pools across tree species seems to be important in determining the variability of seasonal C allocation patterns to wood and their sensibility to disturbances such as browsing. Our results indicate that the observed changes in C allocation to earlywood in birch were not related to variations in the amount or concentration of NSC stores, but to changes in the seasonal availability of recently assimilated C caused by modifications in tree architecture after browsing.     

Comparative study of anatomy and lignin distribution in normal and tension wood of Salix gordejecii

Fibre morphology, anatomy and ultrastructure in cell wall of Salix gordejecii normal wood were examined by transmission electron microscopy (TEM). S. gordejecii tension wood can be recognized anatomically by the presence of gelatinous (G) fibres, which contain a conspicuously thickened inner cell wall layer. TEM images showed that cell wall of S. gordejecii normal wood was typically divided into three layers including the primary wall (P), the middle lamellar (ML) and the secondary wall (S₁, S₂ and S₃). Lignin distribution was determined by using confocal laser scanning microscopy (CLSM) and transmission electron microscopy with energy dispersive X-ray analysis (TEM-EDXA). Confocal images (530 nm) of S. gordejecii normal wood showed strongly lignified CCML, and weakly lignified ML and S2 layer. Weakly lignified fibres (F) and strongly lignified vessels (V) were also detected by using CLSM. Results obtained from confocal microscopy were further confirmed by using TEM-EDXA, indicating that the ratio of lignin concentration in CCML, ML and S2 is 1.72 (1321):1.31 (1006):1 (768). Lignin distribution in tension wood is similar to that in normal wood, except for the non-lignified G layer.     

Prediction of the surface roughness of wood for machining

The surface quality of solid wood is very important for its effective response in manufacturing processes. The effects of feed rate, cutting depth and rake angle on surface roughness and power consumption were investigated and modeled. Neuro-fuzzy methodology was applied and shown that it could be useful, reliable and an effective tool for modeling the surface roughness of wood. Thus, the results of the present research can be successfully applied in the wood industry to reduce time, energy and high experimental costs.     

Changes in the acid structure of wood due to ageing and fossilisation processes

Summary Some fossil woods, differing in botanical species, age, degree of degradation and chemical composition, were analysed with respect to their acid structure. A comparison was carried out with corresponding modern species which, in the case of softwoods, contain carboxylic groups as well as ester groups in almost equal amounts. Moreover the former are subdivided into protonated (20%) and salified forms (80%). The determination of the acid structures in woods was made by means of cation exchange measurements.In all examined fossils the initially protonated form is changed into the salified one because of the leaching carried out by water containing soluble salts. Despite the loss of polyoses, an increase in the content of carboxylic groups was achieved due to hydrolysis of the ester groups. In more degraded samples the amount of carboxylic groups was larger than in the other fossils even if the former possessed only traces of polyoses due to an attack on lignin assessed by acidity of the trifluoroacetic (TFA) derivatives. Proof of these changes and further information on fossils were obtained by I.R. spectroscopy.The authors wish to thank Prof. D. Fengel for the fossils coming from Wackersdorf (Germany)     

Analysis of Wood Anatomy Characteristics by Fast Fourier Transfer Image Analysis

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