Browsing by Author "Szenti, Imre"
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Item Fast and accurate lacunarity calculation for large 3D micro-CT datasets(Elsevier, 2021) Sebők, Dániel; Vásárhelyi, Lívia; Szenti, Imre; Vajtai, Róbert; Kónya, Zoltán; Kukovecz, ÁkosMicrocomputed-tomography (micro-CT) is a 3D imaging method capable of revealing the complete inner structure of materials. Besides imaging, micro-CT also provides quantitative information about numerous structural features including lacunarity, which describes the heterogeneity of samples quantitatively. Theoretically, lacunarity is easily calculated using the gliding box method. However, when implemented in 3D, the computational costs of this method increase enormously, thus preventing its widespread use for large micro-CT datasets. Here we suggest a faster alternative method, based on the fixed-grid algorithm, which offers a viable alternative and renders 3D lacunarity calculations on micro-CT data feasible. Since a possible shortcoming of this alternative is that its reduced data could result in an inferior description of the real spatial heterogeneity of the structures, the two methods are compared concerning the accuracy, computational time, and applicability in materials science. The calculations are carried out on real 3D micro-CT datasets. Our implementation of the fixed-grid method can approximate gliding box lacunarity values rapidly and accurately, especially for large datasets of homogeneous structures. Therefore, we propose adding the fixed-grid method lacunarity calculation to the routine micro-CT analysis toolbox. Our image acquisition platform-independent software (Lac3D) to carry out this calculation is made freely accessible here.Item Flexible planar supercapacitors by straightforward filtration and laser processing steps(IOP, 2020) Pitkänen, Olli; Eraslan, Toprak; Sebők, Dániel; Szenti, Imre; Kukovecz, Ákos; Vajtai, Robert; Kordas, KrisztianThere is ever increasing demand for flexible energy storage devices due to the development of wearable electronics and other small electronic devices. The electrode flexibility is best provided by a special set of nanomaterials, but the required methodology typically consists of multiple steps and are designed just for the specific materials. Here, a facile and scalable method of making flexible and mechanically robust planar supercapacitors with interdigital electrode structure made of commercial carbon nanomaterials and silver nanowires is presented. The capacitor structure is achieved with vacuum filtration through a micropatterned contact mask and finished with simple laser processing steps. A maximum specific capacitance of 4 F cm−3 was measured with cyclic voltammetry at scan rate of 5 mV s−1. The reliability and charge transfer properties of devices were further investigated with galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy, respectively. Furthermore, mechanical bending tests confirmed the devices have excellent mechanical integrity, and the deformations have no adverse effects on the electrochemical charge-discharge behavior and stability.Item Lacunarity as a quantitative measure of mixing—a micro-CT analysis-based case study on granular materials(Oxford University Press, 2023) Vásárhelyi, Lívia; Sebők, Dániel; Szenti, Imre; Tóth, Ádám; Lévay, Sára; Vajtai, Róbert; Kónya, Zoltán; Kukovecz, ÁkosIn practically every industry, mixing is a fundamental process, yet its 3D analysis is scarce in the literature. High-resolution computed tomography (micro-CT) is the perfect X-ray imaging tool to investigate the mixing of granular materials. Other than qualitative analysis, 3D micro-CT images provide an opportunity for quantitative analysis, which is of utmost importance, in terms of efficiency (time and budget) and environmental impact of the mixing process. In this work, lacunarity is proposed as a measure of mixing. By the lacunarity calculation on the repeated micro-CT measurements, a temporal description of the mixing can be given in three dimensions. As opposed to traditional mixing indices, the lacunarity curve provides additional information regarding the spatial distribution of the grains. Discrete element method simulations were also performed and showed similar results to the experiments.