Papers by Keyword: Porous Structure

Abstract: This study presents the synthesis of carbon composites based on iron powder and hydrolysis lignin, both with and without the addition of oleic acid. The synthesized composites were characterized using X-ray diffraction, gas adsorption-desorption porosimetry, and magnetometry. In addition, the adsorption performance of the composites toward methylene blue and congo red dyes from aqueous solutions was investigated. It was found that the addition of oleic acid does not significantly alter the structural or magnetic properties of the synthesized composite. However, it does affect the composition of oxygen-containing surface groups on the carbon. Analysis of the adsorption isotherms revealed that the carbon composite synthesized with oleic acid is nearly equally effective in adsorbing both methylene blue and congo red dyes. Isotherm modeling demonstrated that the synthesized composites adsorb both dyes via a physisorption mechanism.

Abstract: A method for the synthesizing of carbon composites based on hydrolysis lignin powders and iron oxides (FeO and Fe₂O₃) was proposed in this work. The obtained composites were studied by X-ray diffractometry, adsorption/desorption gas porometry and magnetometry. X-ray phase analysis has revealed the presence of an amorphous carbon phase and crystalline phases of FeO, Fe₃O₄, Fe₂O₃, and Fe in both types of synthesised composites. The synthesized composites demonstrated significantly higher specific magnetisation values compared to the initial iron oxide powders. For Fe₂O₃ powder, the specific magnetisation was σ_s = 6 A·m²/kg, while the saturation specific magnetisation of the composite based on this oxide was σ_s = 34 A·m²/kg. For FeO powder, the specific magnetisation was σ_s = 28 A·m²/kg, with the composite based on it exhibiting a specific saturation magnetisation of σ_s = 40 A·m²/kg. The observed results were explained by the formation of particles with sufficiently high values of specific magnetisation due to thermal reduction of iron oxides in the presence of carbon monoxide, obtained from the pyrolysis of hydrolysed lignin.

Abstract: Triply periodic minimal surface (TPMS) represents a class of porous architectures characterized with continuous curved surface and periodic repetition, demonstrating significant potential for industrial applications requiring high specific surface area. In this work, a Gyroid-type TPMS sheet has been designed and manufactured with acrylonitrile butadiene styrene (ABS) resin via stereolithography 3D printing. The printed surface microstructure was characterized by scanning electron microscopy to evaluate the printing accuracy. Both the quasi-static compression test as well as the numeric finite element analysis were performed to study the mechanical response. Compared with the strut-based Re-entrant lattice, the Gyroid TPMS demonstrated a superior combination of high load-bearing and energy-absorption properties. Comparative analysis of compressive load-displacement curves and cracking behaviors elucidated the distinct deformation mechanisms between TPMS and Re-entrant structures. To validate the practical applicability, a prototype helmet liner with Gyroid TPMS structure was successfully manufactured with ABS resin using the studied printing procedures. These findings substantiate the promising implementation potential of TPMS structures in lightweight engineering and impact protection systems requiring synergistic mechanical performance.

Abstract: The porous structure and magnetic properties of nanostructured Fe₃O₄/C composites based on wheat straw were investigated in this work. The synthesis was carried out by a one- and two-step method using FeCl₃ and ZnCl₂ as activating agents. X-ray diffraction methods have shown the presence of an additional phase of magnetite Fe₃O₄ in both synthesized composites, along with the amorphous carbon phase. Magnetic measurements have shown that the composite synthesized in one step has better magnetic properties, in particular, a higher specific saturation magnetisation. However, the samples of the composite synthesized in two steps are characterised by a higher content of micropores and mesopores, which causes an increase in the specific surface area to 884 m²/g compared to 405 m²/g for the samples synthesized in one step. Based on the dependence of the coercive force on the particle diameter in Fe₃O₄ dispersions, it was found that the average size of the magnetite particles is ~25 nm for both synthesized magnetoresponsive composites.

Abstract: Biorecycling of wood includes many different processes aimed at the complete utilization of the main and by-products. The complete isolation of C5 and C6 sugars from wood and their further use is currently attracting attention worldwide. The C5 sugars can be catalytically converted directly into furfural or into monosaccharides’ aqueous solution for further hydrolytic treatment. The resulting lignocellulose can be used in thermochemical pyrolysis (350-400°C) for the synthesis of levoglucosan. The biochar formed during pyrolysis and the liquid residue after the isolation of levoglucosan are by-products and can be used as precursors to obtain valuable products – activated carbon composites for supercapacitor electrodes and catalysts in fuel cells.

Abstract: The development trend in smart materials has become miniaturization and portability for the last few decades. Therefore, the study on the fabrication and modification of one-dimensional functional fibers has become a popular research field. In this study, we introduce a novel in-situ breath figure (iBF) technique for the preparation of PMMA@HPMs with controllable honeycomb porous microstructures (HPMs) on its surface. Different from the traditional BF method where an outer layer of HPMs will form with the introduced polymer solution, the HPMs formed by the pure solvent-based iBF method is integrated with the material itself, so no mechanical mismatch or interfacial incompatibility will occur. The main influential factors (e.g., immersion time, RH, and temperature) of the iBF are also systematically investigated. Besides, various functional nanomaterials can be directly anchored on the fiber surface during the iBF process, indicating that a kind of advanced fiber with customized functions could be easily achieved by this one-step strategy. Through investigating the formation of iBF-induced HPMs followed by manufacturing of functional fiber that integrated with nanomaterials, this study provides guidance and a new route for the preparation of multifunctional fiber-based materials to meet wider practical requirements.

Abstract: An important practical and fundamental problem in the production of porous polymer membranes is the study of the porous structure and the detection of "defects" or large pores in the area of ​​the membrane. Known porosimetry methods cannot solve this problem. This work proposes a new non-destructive express method for studying the porous structure of asymmetric polymer membranes in high-intensity electric fields. This method can be successfully implemented on both flat sheet and hollow fiber membranes with a known porous structure. On the example of hollow fiber membranes made of polyacrylonitrile and polysulfone an assessment of the chemical structure effect of the membrane material on the high-voltage discharge currents in a highly inhomogeneous electric field through hollow fiber membranes with a given pore size was made. Under normal conditions and an average intensity of an inhomogeneous electric field E = 5 kV/cm, the results obtained allow us to conclude about a certain practical potential of the developed express method.

Abstract: Titanium (Ti) has been used in metallic implants since the 1950s due to various biocompatible and mechanical properties. However, due to its high Young’s modulus, it has been modified over the years in order to produce a better biomaterial. Tantalum (Ta) has recently emerged as a new potential biomaterial for bone and dental implants. It has been reported to have better corrosion resistance and osteo-regenerative properties as compared to Ti alloys which are most widely used in the bone-implant industry. Currently, Tantalum cannot be widely used yet due to its limited availability, high melting point, and high-cost production. This review paper discusses various manufacturing methods of Tantalum alloys, including conventional and additive manufacturing and also discusses their drawbacks and shortcomings. Recent research includes surface modification of various metals using Tantalum coatings in order to combine bulk material properties of different materials and the porous surface properties of Tantalum. Design modification also plays a crucial role in controlling bulk properties. The porous design does provide a lower density, wider surface area, and more immense specific strength. In addition to improved mechanical properties, a porous design could also escalate the material's biological and permeability properties. With current advancement in additive manufacturing technology, difficulties in processing Tantalum could be resolved. Therefore, Tantalum should be considered as a serious candidate material for future bone and dental implants.

Abstract: The paper deals with problematics of the influence of size and shape of test specimens prepared according to the valid standard procedures in comparison to specimens prepared according to the standards used for different types of materials (grouts, coatings). The aim of this paper is to verify the possibility of using non-standard specimen sizes to reduce the economic demands of the development of building materials. The issue is tested on the polymer composites prepared in three different amounts of the filler. The polymer composite based on epoxy resin serves as a representative and homogenous material which achieves the same results under various curing temperatures and humidity. The porous structure of prepared samples was also studied and its effect on the selected mechanical properties was observed. It was shown that the specimen shape and size had impact on the mechanical properties of epoxy-based composites.

Abstract: The efficiency of porous structure formation in aerated concrete can be improved by including the methods of thermal vacuum compaction or thermal vacuum compaction with vibration into the process as a means of creating high-quality composite cellular concrete. A graphic model of a phase composition change in the aerated concrete mix was developed allowing for an evaluation of the recipe and the mode of bubble porosity generation during hardening. This provides a control over the manufacturing processes and helps to produce aerated concrete with the specified porosity balance, which defines product properties.The effect of temperature and vacuum on molding sand during the initial stage of manufacture is proportional to the bubble porosity volume, which is important for a high-quality porous structure formation. In addition to the above, account must be taken of the combined effect of temperature, vacuum and volume ratio of phases in the base mix when using the proposed methods.Introduction of the developed processing methods into the manufacturing process improves the technology of aerated concrete production and allows for a fabrication of the finest advanced heat insulating and structural and heat insulating products.