Chemical and Mechanical Characterization of Thermally Modified Gmelina arborea Wood

Gmelina arborea (Roxb. ex. Sm.) wood samples were thermally modified at 180 °C, 200 °C and 220 °C for 3 h, by employing a process similar to ThermoWood®. The resulting effects on the basic chemical composition and mechanical properties were determined. The results were analyzed statistically with ANOVA, and Least Square Deviation was used to compare means. Generally, after the thermal modification (TM) process, the cellulose, hemicelluloses and extractives content decreased significantly. By contrast, lignin proportions increased significantly. Untreated wood and samples modified at 180 °C indicated comparable modulus of elasticity (MOE), modulus of rupture (MOR), degree of integrity (I), fine fraction (F) and resistance to impact milling (RIM). Noteworthy reductions however occurred at 200 °C and 220 °C. Significant increases in Brinell hardness (BH) took place at 180 °C, recording a high decrease at 220 °C. Gmelina arborea could be modified suitably at 180 °C for structural and other purposes. To take advantage of other improved properties, modification at 200 °C could be employed for non-structural uses.

Recycling of Niobium Slag by Disintegrator Milling

The main aim of the study is recycling of niobium slag, separating valuable metallic Nb and mineral ballast – calcium aluminate. Niobium slag is a waste product from Nb production at NPM Silmet OÜ. For the retreatment of slag, an efficient disintegrator milling technology was used. Laboratory grindability tests of slags were carried out. We propose a potential principal scheme of slag treatment, consisting of preliminary size reduction by impact milling at direct mode and final at separative mode using a disintegrator milling system DSL-115. As a result of slag pretreatment, pure Nb from a coarse fraction was separated. To elaborate an industrial technology, semi-industrial tests for specifying recycling modes and finding optimal milling parameters were performed. Granulometry studies of milled products and chemical composition as of Nb as well as that of remained products were conducted. Yield of Nb with purity 90–95% was in the range of 0.4–1.0%. Preliminary cement tests for using the main product as a binder or a substitute of cement confirmed its potential for use in building materials production.

The Impact of Anatomical Characteristics on the Structural Integrity of Wood

The structural integrity of wood is closely related to its brittleness and thus to its suitability for numerous applications where dynamic loads, wear and abrasion occur. The structural integrity of wood is only vaguely correlated with its density, but affected by different chemical, physico-structural and anatomical characteristics, which are difficult to encompass as a whole. This study aimed to analyze the results from High-Energy Multiple Impact (HEMI) tests of a wide range of softwood and hardwood species with an average oven-dry wood density in a range between 0.25 and 0.99 g/cm³ and multifaceted anatomical features. Therefore, small clear specimens from a total of 40 different soft- and hardwood species were crushed in a heavy vibratory ball mill. The obtained particles were fractionated and used to calculate the ‘Resistance to Impact Milling (RIM)’ as a measure of the wood structural integrity. The differences in structural integrity and thus in brittleness were predominantly affected by anatomical characteristics. The size, density and distribution of vessels as well as the ray density of wood were found to have a significant impact on the structural integrity of hardwoods. The structural integrity of softwood was rather affected by the number of growth ring borders and the occurrence of resin canals. The density affected the Resistance to Impact Milling (RIM) of neither the softwoods nor the hardwoods.