Structure and properties of biomorphic carbon scaffolds based on pressed birch and alder wood
Data for the article "Structure and properties of biomorphic carbon scaffolds based on pressed birch and alder wood". File contains data on sample sizes, density, pyrolysis shrinkage, strength, resistivity.
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Birch wood (Betula pendula) and alder (Alnus incana) were used as starting materials. The wood was dried at 140 °C for at least 6 hours until the mass remained constant, after which samples of the required size were made. The mass and dimensions of the samples at all stages of the study were measured with a digital scale (accuracy 0.005 g) and a caliper (accuracy 0.01 mm). The alder and birch densities were 0.52 and 0.65 g/cm3, respectively. The dimensions of the initial samples in the axial and tangential directions for alder and birch were 59.5×19.8 and 59.6×19.5 mm, respectively. The size in the radial direction (loading direction) was varied so that, after pressing, samples of the same species, differing in density, had the same shape and size. Before pressing, the samples were heated to a temperature of 140 °C and kept for 1 hour, after which they were placed in a heated press mold with a cross section of 20.2×60.1 mm and deformed until the desired thickness was reached. The final dimensions of the samples after pressing in the radial, tangential and axial directions were ~ 20×20×60 and ~ 13×20×60 mm, for alder and birch, respectively. The samples were pyrolized in at 120 °C/hour to the temperature of 140 °C, at 10 °C/hour from 140 to 600 °C, at 100 °C/hour up to 900 °C, followed by holding at this temperature for 1 hour. The pyrolysis was carried out in the self-generated atmosphere of the wood decomposition products in a closed reactor, separated from exterior atmosphere by a water seal. Inside the reactor, the samples were placed in two different ways. Part of the samples was in the "free" mode, while the second group of samples was located between two steel plates that were tightened with screws, preventing their expansion in the radial direction ("fixed" samples).The obtained samples were additionally annealed in a vacuum furnace with a graphite heater at 1500 °C for 30 minutes for complete decomposition of organic components. The electrical resistance at room temperature was measured by a voltmeter-ammeter, with potential contacts attached directly to the sample. The resistivity of biocarbon (r) was calculated by the formula. r=R∙(1-p)=R∙ρ1/ρ2 Where R is the measured electrical resistance; p is the porosity of the material; ρ1 is the geometric density of the sample; and ρ2 is the specific density of biocarbon (was assumed to be 1.5 g/cm3). Bending strength was measured by three-point bending method with a 25 mm span in an Instron 1195 mechanical testing machine. For each density 5 samples with a cross section of 2.5×5 mm were tested.