Study on the surface changes of heat-treated aspen wood due to aging by different techniques

Heat-treated wood undergoes degradation induced by weathering factors such as solar radiation, temperature variations, rain, and snow. The aging of heat-treated wood affects significantly its surface properties. In this study, the artificial aging test of heat-treated wood using a UV chamber was carried to see the effect of aging on the wood surface. The net radiative heat transfer to the wood sample surfaces in this chamber was estimated in order to determine the corresponding natural weathering times. A complete understanding of the surface changes during the weathering process would allow the development of new treatments and finishes that would greatly enhance the durability of heat-treated wood against degradation due to weathering. Study of the heat-treated wood surface before and after weathering by different techniques helps provide an insight into the degradation process. The techniques and tools for studying heat-treated wood surfaces include color measurement, contact angle test for wettability analysis, light microscopy, FTIR, XPS, and SEM. Each technique gives information on different aspects such as chemistry, structure, and appearance. In this article, the utilization of these techniques is discussed. A number of results for different cases are presented. The aging affects the color of the tangential and radial surfaces differently. During aging, lignin decreases and OH increases; and this increases the wettability of wood.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

A novel high temperature heat treatment process for wood

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.Wood is heated to temperatures in the range of 180–240°C in heat-treatment furnaces. At these temperatures, the wood structure undergoes changes leading to better dimensional stability, better resistance to biological attacks, and a darker attractive color. The high-temperature heat treatment of wood is an alternate and ecologically-sound wood preservation process to chemically treated wood. During heat treatment, wood goes through simultaneous heat and mass transfer. The heat is transferred from the hot gases to the wood boards in the furnace. As the temperature of wood increases, water content of wood vaporizes and diffuses out of the boards. At higher temperatures, a number of irreversible structural changes take place in wood cells. The furnace design is important to carry out the heat treatment process uniformly and effectively. A new heat treatment furnace design has been proposed at UQAC and a prototype furnace has been built and tested. Also, a 3D model of the furnace was developed to complement the experimental work and to gain insight into the heat treatment process taking place in the furnace. In this article, the new furnace design and its advantages are discussed. Results of the measurements and predictions of the mathematical model are presented to show the effectiveness of the new furnace design for heat treating standard wood boards as well as pieces of wood with different geometries.The authors would like to thank the administration of the University of Quebec at Chicoutimi (UQAC), the Foundation of the University (FUQAC), The Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Economic Development for Quebec Regions (CED), Ministère de l’Économie, de l’Innovation et des Exportations (MEIE, previously MDEIE) and SOVAR.am201

Effect of heating rate during baking on the properties of carbon anodes used in aluminum industry

Carbon anodes are called the heart of aluminum electrolysis cells and contribute to about 15% of total production cost of aluminum. In case of poor quality, this contribution can reach 25%. The final quality of the carbon anodes and their behavior in the electrolysis cells depend on the conditions during the baking process. In any case, a low-quality green anode cannot be improved during baking. However, the quality of green anodes can deteriorate if the parameters of the baking process are not properly adjusted. The objective of this work is to study the effect of introducing a plateau during baking on the properties of carbon anodes. The samples were characterized before and after baking by measuring their density and electrical resistivity which are important in defining the final quality of the anode samples. The experimental data were also analysed using the artificial neural network model (ANN). The article will present the results of this study

Traceability of raw materials in silos in an anode plant

Carbon anodes, regularly consumed in primary aluminum production, are made of calcined petroleum coke, coal tar pitch, and recycled materials. The properties of calcined coke depend on the source of crude oil and the calcination conditions. Similarly, pitch properties depend on the coal tar source and the manufacturing process. Different calcined coke and pitch mixtures are commonly used in anode manufacturing to meet various regulations and/or due to economics and availability. This makes it hard to maintain the anode quality. Calcined coke and pitch are placed in silos and used when required for production. It is hard for the industries to track the source of raw materials used in their daily recipes. This article presents an approach to trace back the details of the use of particulate raw materials with a custom-made software, which takes into account the type (mass flow or funnel flow) of silos. Such tracking can help identify the causes of problems and maintain/improve anode quality

Description and applications of a 3D mathematical model for horizontal anode baking furnaces

In aluminum industry, carbon anodes are consumed continuously during alumina reduction in the electrolysis cells. Anodes are made of calcined coke, butt, and recycled anode particles and pitch as the binder. Green anodes are baked in large furnaces where they attain specific properties in terms of density, mechanical strength, and electrical conductivity. Baking is an important and costly step in carbon anode production. The proper operation of the furnace provides the required anode quality. Mathematical modeling allows the prediction of the heating profile of anodes during baking. Taking into account all the relevant phenomena, a 3D transient mathematical model was developed to simulate the different stages of the baking process in the furnace. The predictions give a detailed view of the furnace operation and performance. In this article, the 3D model is described, and the results on the impact of various parameters on furnace behavior are presented

Kefiran biopolymer: Evaluation of its physicochemical and biological properties

Kefiran, an exopolysaccharide produced by lactic acid bacteria, has received a great interest due to a variety of health claims. In this study, we aim to investigate the physicochemical and biological properties of Kefiran polysaccharide extracted from Portuguese kefir grains. The kefir growth rate was about 56% (w/w) at room temperature and the kefir pH after 24 h was about 4.6. The obtained yield of Kefiran polysaccharide extracted from the kefir grains was about 4.26% (w/w). The Kefiran structural features were showed in the 1H nuclear magnetic resonance spectrum. The bands observed in the infrared spectrum confirmed that the Kefiran had a β-configuration; and the X-ray photoelectron spectroscopy analysis confirmed the structure and composition of Kefiran and revealed a C/O atomic ratio of 1.46. Moreover, Kefiran showed an average molecular weight (Mw) of 534 kDa and a number-average molecular weight (Mn) of 357 kDa. Regarding the rheological data obtained, Kefiran showed an interesting adhesive performance accompanied by a pseudoplastic behavior, and the extrusion force of Kefiran was 1 N. Furthermore, Kefiran exhibited a higher resistance to hyaluronidase degradation than hyaluronic acid. Finally, Kefiran showed a lack of cytotoxic response through its ability to support metabolic activity and proliferation of L929 cells, and had no effect on these cells’ morphology. Our research suggested that Kefiran polymer has attractive and interesting properties for a wide range of biomedical applications, such as tissue engineering and regenerative medicine.H.R., C.G., and F.R.M. were supported by grants with reference SFRH/BPD/100957/2014, SFRH/ BPD/94277/2013, and SFRH/BPD/117492/2016, respectively, of Fundação para a Ciência e a Tecnologia (FCT) from Portugal. J.M.O. thanks the FCT for the funds provided under the program Investigador 2015 (IF/01285/2015).info:eu-repo/semantics/publishedVersio

Surface engineering of wood substrates to impart barrier properties: a photochemical approach

In this study, sugar maple and white pine, two species of wood commonly used in indoor and outdoor applications, were treated by photo-initiated chemical vapor deposition to impart barrier properties. After treatment, wood wettability decreased significantly, as evidenced by water contact angle measurements (from 50° to 113° for sugar maple and 87° to 172° for white pine). Further, beyond being able to repel water, the coating shows the ability to breathe, evidenced by standardized vapor sorption tests. However, accelerated weathering via ASTM G155 testing determined that the treatment could not protect the wood from photo-degradation, or retain its properties post-weathering. This treatment could therefore be best suited for wood pre-treatment in combination with other coatings

Análisis de niveles de resiliencia en escolares antioqueños expuestos a problemáticas de violencias: propuesta pedagógica para la implementación de la cátedra de la paz

Este trabajo tiene como investigar, evaluar los niveles de resiliencia en los escolares de una de las instituciones públicas del municipio, una institución de inclusión donde se recibe a los estudiantes expulsados de las demás instituciones municipales, realidades atravesadas por el dolor, la guerra, la pobreza y la esperanza agónica. Analizar los niveles de resiliencia de los estudiantes grado de décimo y once y su relación con el contexto de violencia al que están expuestos los adolescentes, permitir a través de este análisis, presentar a la comunidad académica y social una estrategia pedagógica para ser desarrollada a través de la cátedra de la paz, que favorezca la convivencia y la construcción de paz desde el colegio.Magister en EducaciónMaestrí