Equipment

Besides its expertise in wood science, UGent-Woodlab is well-equipped with infrastructure allowing to carry out its activities. The combination of know-how and this equipment drives the laboratory to address research topics dealing with variations in wood structure and properties as well as technological testing at various scale-levels and multiple stages along the forestry-wood chain, i.e. ranging from wood cell walls to finished wood products. The equipment is categorized according to the research activities: A. Structure, B. Service Life, C. Forest Products -  Materials, D. Forest Products -  Bioenergy.

For more information contact Prof. dr. ir. Joris Van Acker.

A. Structure

1. X-ray tomography

Nanowood is the latest multi-resolution X-ray tomography setup developed at UGCT. It consists of a stage combined with two X-ray tubes and two X-ray detectors, specifically designed to permit very high resolution scans as well as scans of larger objects. Reconstructed voxel size can be chosen arbitrarily ranging from 200μm to 400nm with maximal scan-efficiency. The combination of both tubes and two detectors covers all resolutions in an optimal way. The system offers a large range of operation freedom with an 8-axis motorized stage for sample rotation/magnification/positioning, tube and detector selection and tiling; all combined in versatile acquisition routines (standard or fast scanning, tilling, helix,...). This scanner can be used in any field of wood biology and technology. In the publication list of the lab, several papers refer to X-ray tomography. More information can also be found on the website of UGCT, the consortium of X-ray tomography UGent-Woodlab belongs to.

2. Cryo-SEM and SEM

The goal of cryo-SEM (Scanning Electron Microscope) is to vitrify the liquid phase with all the constituents thus preserving them in their natural and original state. Liquid N₂ (-210°C) is used for the fast freezing to minimize any damage ice crystals may cause. The sample can be fractured, etched and coated to expose internal microstructure. Cryo-SEM imaging with high resolutions (<100 nm) at UGent-Woodlab includes the study of ultrastructural wood cell features, which is highly relevant in tree biological (growth analysis), wood technological (material research) and biological degradation (both bacterial as well as fungal) contexts. The cryo-SEM also allows elemental imaging using a state-of the-art EDX detector. As such it is very complementary tool to our other set of imaging instruments, such as light microscopy, fluorescence microscopy and X-ray tomography. The cryo-SEM is available at the Department of Food Technology, Safety and Health within the Bio-imaging consortium, of which UGent-Woodlab is a partner.

An older JEOL JSM-T330A SEM Scanning Electron Microscope is available as well at UGent-Woodlab, for fast screening of samples.

3. Wood anatomical research

Wood is composed of different cell types and tissues. Wood anatomy is the discipline where different shapes, dimensions and functions of wood cells and tissues are examined. Particularly, wood anatomy is applied to identify woody species. To do so, small wood samples are pre-treated (cooked, impregnated...) and mounted on a sled microtome with a stainless steel knife. Next, thin sections are trimmed, dehydrated (alcohol) and fixated in synthetic or natural resin between two glass slides. Sometimes, thin sections are stained with colour agents before fixation in order to accentuate specific cell types. Finally, these thin sections are studied using transmitted light microscopy and fluorescence microscopy. UGent-Woodlab is equipped with a mechanic sled microtome, an electric sled microtome, reusable and non-reusable microtome knifes, a knife sharpener, more than a dozen transmitted light microscopes (Leitz, Zeiss, Nikon), a fluorescence light microscope (Olympus Vanox), a reflected light microscope (Leitz Laborlux) and a large range of pre-treatment agents, colour agents and resins. UGent-Woodlab also has a modest xylarium, with a range of species from all around the world. The samples are conveniently stored in Milletia laurentii cabinets.

4. Dendrochronology

Dendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree-rings. It is an important discipline delivering information on tree growth and development, ecophysiology of trees, etc. The relation with climate is studied in what is called the research field of dendroclimatology, contributing to ourknowledge of how trees and tree communities react to a changing environment as trees can be considered as long-term archives of environmental changes. UGent-Woodlab disposes of a Lintab measuring system for cores or discs, with the accompanying TSAP software for recording, synchronisation and interpretation of results. The X-ray tomography scanner, discussed on this page, is also used for dendrochronological purposes to quantify density at the microscale (microdensitometry), as such delivering valuable data. This last technique is especially useful when dealing with tropical trees with growth rings which are very difficult to discern. We also have an in-house imaging system for large surfaces (~60cm x 60cm) at high resolution (~5µm).

B. Service Life

1. Fungal testing

The resistance of solid wood or wood based materials against white rot and brown rot is tested according to European standards (CEN/TS15083-1/EN113, ENV12038). Preconditioning such as leaching (EN84) or evaporation (EN73) can be performed. UGent-Woodlab is equipped with two CTS and two petersime incubation rooms. In this way it holds a total capacity of ca. 1800 Kolle flasks (equals ca. 3600 specimens under test). Test Basidiomycetes fungi as Coniophora puteana, Trametes versicolor, Poria placenta, Pleurotus ostreatus, Lentinus cyathiformis and Gloeophyllum trabeum are available.
Soft rot testing is also performed on a laboratory scale according to CEN/TS15083-2/ENV807. Therefore an incubation room of ca. 8m² with controllable relative humidity and temperature gives room to several test boxes.
Field testing is performed with focus on EN 252 in ground and EN330 related accelerated above ground testing.
EN152 and an adapted version of BSI3900-G6 are applied to evaluate the susceptibility of wood coating systems, treated and untreated solid wood and wood based materials to blue stain (Aureobasidium pullulans) and moulds respectively. All fungi are maintained as required to retain their virulence.

2. Accelerated ageing

To assess aesthetical changes and/or resistance against weathering of wood coating systems (EN927-6), solid wood or wood based materials artificial weathering is performed by means of an UV2000. Condensation cycles and specimen spray induces water initiated erosion or thermal shock. Different cycles can be programmed to mimic outdoor conditions in an accelerated way. Several research projects in the past have searched for the optimal settings in order to approach outdoor conditions as close as possible, avoiding to induce different damage patterns.

3. Coating testing

Coatings are preferably applied on wooden window frames to evaluate the overall performance of the ‘wood-coating system’. Resistance against weathering is tested outdoors by natural weathering (EN927-3). The set-up is in analogy with EN927-3: the frames are exposed facing southwest at an angle of 90° to mimic a realistic situation. Aesthetical changes of coatings such as gloss can be monitored using a triple-angle (20°, 60° and 85°) Zehntner ZGM 1120 Glossmeter. Its small orifice allows measurements on very small surfaces and in more-difficult-to-access spots. The ZGM 1120 is run by Zehnter GlossTools software and displays the gloss measurements directly on the computer. Colour measurements are performed using a Konica Minolta CM 2600d. A value for adhesion strength of a coating on wood is measured by means of a mechanical torque device. Therefore metal studs are glued on the sample surface. After curing a groove is drilled in the coating film around the studs. The maximum moment to disconnect the stud and the damage that occurs are both converted into a measure of adhesion strength. The test can be performed when the substrate-coating interphase is dry or wetted. Water uptake and water vapour evaporation of a wood coating system is studied by means of a laboratory floating test as described in the section moisture dynamics.

4. Moisture dynamics

A continuous moisture measurement set up (CMM) aims at monitoring water absorption and desorption behaviour of (un)treated solid wood or wood based materials during natural weathering. In this way the impact of individual rain events and the drying out afterwards of the wooden material can be recorded. Consequently, the test method allows differentiating between the moisture related properties of several wooden materials in a fast and accurate way. Data on moisture dynamics can be linked to weather data. Therefore a weather station consisting of a pyranometer, a pluviometer, a relative humidity probe, a thermometer, an anemometer and a windvane is installed adjacent the test set up. All data is collected by a logging unit. The test set up consists of a wooden table upon which two parallel series of single load cells are fixed. All specimens are inclined 45° facing south west direction. On a related laboratory scale test specimens of 50 x 50 mm² are left to float freely on the surface of water in plastic containers in a conditioned chamber (20 °C, 65 % RH). At regular intervals the water uptake of the specimens is determined by recording the mass increase. Afterwards the specimens are reconditioned to constant mass. During the reconditioning or desorption phase the mass decrease is registered as well on a regular base. From the mass increase and decrease, respectively, the absorption and desorption rate can be calculated.

5. General outdoor testing

The proof of the pudding is in the eating, which is the same for wooden materials. If wood is intended for outdoor use, there is need for outdoor testing and assessment. This is an example of an outdoor test-house consisting of a series of different wood species as well as different treatments (see a.o. the EU Life+ Silex project) that shows the potential of outdoor testing. The house is located in an urban area and is exposed to sun, rain and wind.

C. Forest Products - Materials

1. Mechanical testing

Standard test methods of static tests of timber (clear specimens and smaller structural sizes) are possible using a mechanical testing machine (Zwick 1465) with 50 kN maximum load capacity.

2. Dimensional stability (currently not active)

A range of climatic test cabinets  (Heraeus Vötsch, CTS) are used to condition wood (solid, lignocellulosic fibres) under steady state relative humidity conditions enabling to follow hysteresis and define sorption isotherms. 
Dimensional changes are measured using several tools from Mitutoyo (digital callipers, indicators, gauges, gage blocks,…).
This equipment is used to study moisture dynamics of wood species in relation to application and to qualify modified wood.

3. Treating plant (not active - future upgrade commissioned)

The laboratory treating plant of UGent-Woodlab consists of a standard vacuum pressure unit (30 cm diameter, 1.5 m long) complemented by smaller units for treatment with gas or developed to treat fibres. This equipment can be used for modification of wood or other lignocellulosic materials and for assessing treatability of timber and wood based panels.

4. Drying

Different drying cabinets are available both for drying small specimens and larger timber. One is specifically equipped with programmable temperature and horizontal air flow control.

5. Machining

UGent-Woodlab has a fully equipped work shop covering a panel saw, a planer-thicknesser and a combined machine including a spindle. This equipment is used for sample preparation but also to assess processing of wood species.

6. Wood based panels laboratory press

For the production of (wood) composites a 60 by 60 cm programmable laboratory press is available at UGent-Woodlab (De Mets – Valmet).

D. Forest Products - Bioenergy

1. Bioenergy

The DSC-TGA at UGent-Woodlab is a top-notch system with dedicated software for simultaneous and ultraprecise monitoring of both calorimetric and gravimetric changes occurring in small samples upon heating (room temperature up to 830°C). Scanning experiments can be set up in DSC, TGA or coupled mode, with different carrier or reactive gases, and with heating rates variably programmable from 0.01 up to 30°C/min. The 3D DSC sensor technology inside is unique, as it captures up to 94% of all heat exchanges throughout the entire temperature range (compared to ca. only 25% in temperature-dependent plate-type sensors) and detects changes as small as 0.4 μW. The high precision TGA balance has a resolution of 0.03 μg. A separate module allows controlling relative humidity up to 75%. DSC-TGA scans are used to simulate and measure physical or chemical transition phenomena (e.g. glass transitions, lignification, cell wall chemistry), thermochemical decomposition processes (combustion, pyrolysis, gasification), energy contents (cf. wood formation, carbon storage, wood degradation by fungi, bioenergy research), adsorption processes (cell wall-moisture interactions) and reaction kinetics (wood modification).

The Parr bomb calorimeter with 1108 style oxygen bomb is a microprocessor controlled, isoperibol oxygen bomb calorimeter used for determination of the higher heating value (HHV) on samples weighing maximum 1,5g. The sample is put in a capsule and touched by a 10 cm long fuse wire. This is installed in the bomb, which is filled with oxygen, hung in a jacket with cooling water and connected with the ignition wires. The temperature change caused by ignition and sample burning is detected and used to calculate the HHV using the energy equivalent of the bomb and the sample mass. The HHV is corrected for nitric and sulphuric acid formation and the heat produced by the heating wire. The robust set-up of this equipment allows a straightforward analysis of the energetic content of a material and is therefore vital in research regarding bioenergy from lignocellulosic biomass.