The nanomaterials have been widely used in various fields, such as photonics, catalysis, and adsorption, because of their unique physical and chemical properties. Therefore, their production methods ...are of utmost importance. Compared with traditional synthetic methods, the template method can effectively control the morphology, particle size, and structure during the preparation of nanomaterials, which is an effective method for their synthesis. The key for the template method is to choose different templates, which are divided into hard template and soft template according to their different structures. In this paper, the effects of different types of templates on the morphology of nanomaterials during their preparation are investigated from two aspects: hard template and soft template, combined with the mechanism of action.
Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech ...and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation.
The high temperature treatment of wood is one of the alternatives to chemical treatment. During this process, the wood is heated to higher temperatures than those of conventional drying. The wood ...structure changes due to decomposition of hemicelluloses, ramification of lignin, and crystallization of cellulose. The wood becomes less hygroscopic. These changes improve the dimensional stability of wood, increase its resistance to micro-organisms, darken its color, and modify its hardness. However, wood also might loose some of its elasticity. Consequently, the heat treatment conditions have to be optimized. Therefore, it is important to understand the transformation of the chemical structure of wood caused by the treatment. In this study, the modification of the surface composition of the wood was followed with Fourier transform infrared spectroscopy (FTIR) and inverse gas chromatography (IGC) under different experimental conditions. The effect of maximum treatment temperatures on the chemical composition of Canadian birch and aspen as well as the correlations between their chemical transformation and different mechanical properties are presented. FTIR analysis results showed that the heat treatment affected the chemical composition of birch more compared to that of aspen. The results of IGC tests illustrated that the surfaces of the aspen and birch became more basic with heat treatment. The mechanical properties were affected by degradation of hemicellulose, ramification of lignin and cellulose crystallization.
In order to reduce greenhouse gas (GHG) emissions, biocoke modified with different additives was used to replace part of the petroleum coke. Previously, a number of researchers attempted to ...manufacture anodes using biocoke. However, the majority of these efforts were unsuccessful because the quality of the anodes deteriorated with this replacement. The deterioration was due to the weak interactions between the pitch and biocoke compared to those between the pitch and petroleum coke. In this study, a chemical modification of biocoke was carried out using three additives (i.e., A(1), A(2), and A(3)) with the aim of improving biocoke–pitch interactions to prevent the deterioration of anode quality. The results of this study showed that biocoke–pitch interactions improved when the biocoke was modified with A(1) and A(3). The anodes containing biocoke modified with these two additives had properties similar to those of the standard anode (i.e., without biocoke). The utilization of additive A(2) did not show the same trend.
Calcined biocokes were successfully produced from wood precursors through pyrolysis at high temperature (1200 °C). The resultant material mimics the microstructure of calcined petroleum coke and ...presents high carbon content, making them a potential raw material for carbon anodes used for the production of aluminum. The properties of these biocokes that are important for anode production, such as real density, crystalline length, carbon content, particle surface area, and chemical surface characteristics, were determined using gas pycnometer, energy dispersive X-ray spectroscopy, BET, and FTIR. The microstructure and the morphology of biocokes were characterized using SEM. The degree of structural disorder in the biocokes was evaluated by Raman spectroscopy. The objective of this work is to study how the partial replacement of calcined petroleum coke by a biocoke affects the properties of corresponding laboratory anodes. Also, an anode without any biocoke was fabricated as a standard for comparison with those made with the addition of biocoke. Tests were carried out on green anodes, and the core samples taken from them were characterized in green state and after baking according to the appropriate standards. Experimental results show that the replacement of 3% of petroleum coke by biocoke in the fine fraction results in anodes with properties similar to those of the standard anodes.
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•Modification of coal tar pitch improves the wettability of petroleum coke by pitch.•Modification of pitch enriches the surface functional groups of pitch.•Modified pitch interacts ...better with the petroleum coke.•The percentages of additive and modified pitch used affect the anode properties.•In general, pitch modification improved the anode properties.
Prebaked carbon anodes are manufactured from a dry aggregate (calcined petroleum coke, recycled butts, and rejected green and baked anodes) and a pitch as the binder. The process involves the mixing of the dry aggregate and the pitch according to an appropriate recipe followed by the compaction of the resulting paste and its baking to produce baked anodes for use in electrolysis cells for aluminum production. A good bonding between pitch and dry aggregate particles improves the anode quality which leads to reduction in process cost, energy and carbon consumptions, and emission of greenhouse gases (GHG). One of the potential avenues to improve such bonding is the modification of pitch by an additive. It enriches the surface functional groups of pitch and makes it more compatible with coke. The objective of the current study is to investigate the effect of the modification of a pitch containing a high amount of primary quinoline insolubles (HQI pitch) on the anode quality.
The wettability of coke by modified and non-modified pitches was measured using the sessile drop method. Fourier Transform Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses of these pitches were carried out to determine the change in their surface chemistry upon modification. Laboratory anodes were produced using the non-modified and modified HQI pitches at different pitch levels and additive percentages. The anodes were characterized by measuring their density, electrical resistivity, air and CO2 reactivities, and permeability. Then, these properties were compared for anodes containing non-modified (standard) and modified pitches. In general, the results showed that the modification improved the anode properties compared to those of the standard anodes. The most suitable additive percentage was 2 % and the best pitch percentage was 16 % to obtain good quality anodes. The wettability tests showed that the HQI pitch modified with 2 % additive wetted the coke best. XPS and FTIR tests showed the chemical changes occurring on the pitch surface after the modification with the additive. The results show the potential for the improvement of anode quality based on the pitch modification which renders pitch more compatible with coke.
► Surface degradation of coated heat-treated wood species during aging was studied. ► A coating was developed to delay the discoloration and degradation of wood. ► The discoloration of coated jack ...pine was much less compared to birch and aspen. ► The discoloration was due to the surface degradation of wood beneath the coating. ► Chain scission of urethane main linkage of the coating was noticed by XPS analysis.
High temperature heat-treatment of wood is a very valuable technique which improves many properties (biological durability, dimensional stability, thermal insulating characteristics) of natural wood. Also, it changes the natural color of wood to a very attractive dark brown color. Unfortunately, this color is not stable if left unprotected in external environment and turns to gray or white depending on the wood species. To overcome this problem, acrylic polyurethane coatings are applied on heat-treated wood to delay surface degradations (color change, loss of gloss, and chemical modifications) during aging. The acrylic polyurethane coatings which have high resistance against aging are further modified by adding bark extracts and/or lignin stabilizer to enhance their effectiveness in preventing the wood aging behavior. The aging characteristic of this coating is compared with acrylic polyurethane combined with commercially available organic UV stabilizers. In this study, their performance on three heat-treated North American wood species (jack pine, quaking aspen and white birch) are compared under accelerated aging conditions. Both the color change data and visual assessment indicate improvement in protective characteristic of acrylic polyurethane when bark extracts and lignin stabilizer are used in place of commercially available UV stabilizer. The results showed that although acrylic polyurethane with bark extracts and lignin stabilizer was more efficient compared to acrylic polyurethane with organic UV stabilizers in protecting heat-treated jack pine, it failed to protect heat-treated aspen and birch effectively after 672h of accelerated aging. This degradation was not due to the coating adhesion loss or coating degradation during accelerated aging; rather, it was due to the significant degradation of heat-treated aspen and birch surface beneath this coating. The XPS results revealed formation of carbonyl photoproducts after aging on the coated surfaces and chain scission of CN of urethane linkages.
Semi-dry desulfurization is an efficient means of SO2 removal from the effluent gases from electrolysis cells in aluminum smelters. These gases are at low temperature and contain low concentrations ...of SO2, as opposed to thermal power plants. The removal is carried out by injecting powdered alkaline sorbent, hydrated lime (solid particles), into the SO2-containing gas (gas phase) in the presence of humidity. The reaction is controlled by the adsorption of SO2 onto the surface of lime. This study involves the mathematical modelling of a lab-scale scrubber using a Lagrangian-Eulerian approach in order to analyze the desulfurization efficiency. The model was validated based on experimental data. A parametric study was carried out to investigate the effects of particle size, sorbent amount, and relative humidity (RH) on the desulfurization efficiency. The results show that the particle size is the most important parameter; as the particle size decreases, the desulfurization efficiency increases. However, using finer particles may increase the process cost. The loss in SO2 capture efficiency due to the use of coarser particle size could be compensated by increasing the relative humidity (RH) of the gas, another key parameter of the process.
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•A new unit is needed after the GTC to separate SO2 from the electrolysis gas.•The humidity enhances the desulfurization efficiency.•The sorbent size is slightly more effective than relative humidity in SO2 removal.•The particle phase effect on continuous phase is determined by two-way coupling with DPM.•Increasing humidity can compensate the negative effects of increasing particle size.
The interactions of pyrolyzed and calcined bio-cokes with three coal tar pitches of different properties were studied using a sessile drop test at 170°C. A model was employed to characterize and ...quantify the spreading and penetration of pitch into bio-coke bed. The pyrolyzed bio-cokes were produced from softwood materials by heat treatment at 426°C. The calcined bio-cokes were produced by calcining the pyrolyzed bio-coke at 1200°C. Optical microscope, SEM/EDS, XRD, and FTIR techniques were used to analyze the coke–pitch interface and study their interaction mechanisms. The results show that the wettability of bio-coke is related to both pitch and coke properties. It is found that the presence of small amount of uniformly distributed small size quinoline insolubles (QI) in pitch seems to help pitch spread and penetrate into the bio-coke bed. Besides, calcination changes the chemical structure of bio-coke, enriches its carbon (C%) content, increases its crystalline length (Lc), and lowers its wettability by pitch.
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