Piotr Kowalczyk

Positron annihilation lifetime spectroscopy (PALS) has been used to analyse ultramicropore structures in silica-based porous materials. Energy-related applications increasingly demand improved characterisation of ultramicropore structures in carbon materials. However, PALS porosimetry has not been well established for porous carbons. Therefore, this study aimed to apply the PALS-aided ultramicroporosimetry to carbon materials. We employed single-walled carbon nanotube (SWCNT) bundles with tube diameters of 1.5 and 2.0 nm to determine the key parameter δ which reflects the collision between positronium and the carbon electron clouds and is an essential factor for analysing PALS data related to carbon materials. The SWCNT bundles featured two types of pores—internal tube spaces and interstitial subnanoscale spaces—which were characterised using X-ray diffraction. PALS measurements of these SWCNT samples yielded the parameter δ for carbon materials. The obtained δ was 0.23 nm. Using this value, we performed PALS analysis of reduced graphene oxide, which revealed the presence of pores approximately 0.13 nm wide. These pores are attributed to the staggered structure of GO prior to thermal reduction.
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New superhydrophobic, anti-icing tetrafluorethylene-hexafluorpropylene-vinylidenfluoride terpolymer (THV)-based materials: nonporous solids as well as porous sponges were created and deeply characterized using thermal analysis, spectroscopy, resistivity measurements, cyclic compression tests, and confocal microscopy. Single walled carbon nanohorns (SWCNHs), biosilica (BS) as well as carbonized biosilica (CB) were applied as fillers. The “combined” origin of superhydrophobicity is explained based on experimental water contact angles (WCA) and molecular dynamics (MD) as well as Hansen Solubility Parameters (HSP) analysis. For all materials thermal resistance is improved after the addition of fillers, but among the studied samples only for the sample containing SWCNHs the application of electrothermal/Joule heating to reinforce anti-icing properties is possible. We propose a new forcefield for MD simulation of THV wetting. Moreover, MD results revealed that water freezing at the “flat” THV surface was moderately inhibited with respect to the bulk freezing and considerably inhibited with respect to the graphene surface. Introduction of SWCNHs to THV causes not only remarkable improvement of mechanical properties but also the improvement of anti-icing properties, especially to the stage of recalescence. The comparison of results for porous and nonporous materials led to new correlations describing freezing on the cold plate process, being a starting point for future studies on a new model describing the freezing mechanism. The most important conclusion of the complex study (around 100 samples altogether) is that the creation of mechanically resistant THV-SWCNHs-containing sponges is the most promising strategy in modern anti-icing science leading not only to enhancement of the compression Young's modulus and the time to recalescence, but also to the drop of freezing temperature.
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Accurate determination of the surface area of nanoporous carbons and carbon-containing polymer composites is essential for designing advanced energy storage devices, including electrodes, supercapacitors, and batteries. Current methods, such as the Brunauer-Emmett-Teller (BET) approach, have limitations when applied to complex pore structures. This study evaluates the accuracy of these methods using molecular simulations and experimental data. Surface area estimates for 20 model nanocarbons and 59 experimental samples show that the proposed graphene-domain theory (GDT) provides more reliable results, particularly for carbonaceous nanomaterials with high surface areas. GDT reproduces geometric surface areas up to 2600 m2/g with an average error of 6 %, whereas the BET method with the Rouquerol criterion shows an average error of 12 % and overestimates surface areas by up to 30 % for nanocarbons exceeding 2000 m2/g. These results establish GDT as a promising approach for characterizing advanced carbonaceous materials and as a theoretical framework for porosity analysis across a wide range of nanostructured porous frameworks.

We present a new atomistic model for evaluating the surface area and porosity of micro-mesoporous carbons. This method, referred to as the atomistic pore domain model (APDM), advances the adsorption porosity methodology by calculating textural properties of micro-mesoporous carbons without relying on assumptions about pore geometry. A thorough analysis of porosity across eleven porous carbons demonstrates a robust correlation between the surface area accessible to N2 molecules, as computed using APDM and the Brunauer-Emmett-Teller method with Rouquerol criterium. This correlation is observed across a spectrum of nanoporous carbons, ranging from ultramicroporous activated carbon fibers and nanoporous carbon beads to supermicro-mesoporous activated carbons and activated carbon fibers. APDM facilitates the extraction of the information regarding the N2 surface area accessibility and the intrinsic geometric surface area of micro-mesoporous carbons. The N2-to-He surface area accessibility ratio of the investigated porous carbons varies from approximately 57 %–94 %, indicating varying degrees of pore sieving among studied carbon samples. Except for ACF-25 micro-mesoporous activated carbon fiber, the intrinsic geometric surface areas of the studied micro-mesoporous carbons are smaller than the geometrical surface area of a single graphene sheet (2640 m2/g).
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Triply periodic minimal surfaces (TPMS) inspired by nature serve as a foundation for developing novel nanomaterials, such as templated silicas, graphene sponges, and schwarzites, with customizable optical, poroelastic, adsorptive, catalytic, and other properties. Computer simulations of reactions on TPMS using reactive intermolecular potentials hold great promise for constructing and screening potential TPMS with the desired properties. Here, we developed an off-lattice, surface-constrained Metropolis Monte Carlo (SC-MMC) algorithm that utilized a temperature quench process. The presented SC-MMC algorithm was used to investigate the process of graphitization reactions on the Schwarz primitive, Schwarz diamond, and Schoen gyroid TPMS, all with a cubic lattice parameter of 8 nm. We show that the optimized carbon TPMS exhibits a low energy, approximately −7.1 eV/atom, comparable to that of graphite and diamond crystals, along with a variety of topological defects. Furthermore, these structures showcase extensive and smooth surfaces characterized by a negative discrete Gaussian curvature, a distinctive feature indicative of an interconnected morphology. They possess specific surface areas of ∼2700 m2/g, comparable to graphene, and exhibit a significant porosity of around 90%. The theoretical X-ray correlation functions and nitrogen adsorption isotherms confirm that the constructed TPMS exhibit remarkably similar surface properties, although the pore space topology varies significantly.

THV, a relatively new hydrophobic polymer, has found wide application from explosives to sensors. Therefore, we decided to determine its Hansen Solubility Parameters (HSP) – one of the most important parameters in polymers processing. Studied 41 liquids can be divided into four groups: very good solvents (1), causing gelation (2) causing soaking or color change (3), and inert (4) and HSP values were calculated. We also proposed green chemistry solvents for THV. At the next stage, two solvents from group 1, and two from group 2, and their mixtures, were selected to determine the effect of a solvent on the THV sponge properties. The sponges were characterized by total pore volumes, porosity, mechanical properties, and surface morphology. Moreover, thermal, and anti-icing properties were studied for different film thicknesses. This holistic approach, together with a theoretical description of the icing process via a dynamic growth angle model, makes it possible to relate the sponge morphology to thermal, mechanical, hydrophobic, and anti-icing properties, showing that the studied sponges are strongly hydrophobic or superhydrophobic with a water contact angle (WCA) as large as 160° for THVAC. Considering anti-icing properties, total freezing time, delaying of recalescence, and possible ice removal by wind or vibration, the sponge obtained from the mixture of DMF and acetone (THVDMFAC) seems to be optimal. This sponge has the highest Young’s modulus, high thermal stability, and anti-freezing properties thus, it can be successfully applied in anti-icing covers in, for example, wind turbine blades.

This study focuses on enhancing sustainability through energy-efficient methods in producing hierarchically structured porous carbons. A novel approach, utilizing an ultrasonic spray nozzle-quartz tube reactor (USN-QTR), is introduced for fabricating carbon beads with customizable ultra-, super-, and mesopores. This study showcases noteworthy results from subjecting spherical char particles to activation processes involving carbon dioxide, a mixture of carbon dioxide and micron-sized water droplets, and highly concentrated supercritical steam at a temperature of 1173 K for durations of 3 and 5 h. Through pulse-field gradient nuclear magnetic resonance measurements, it was noted that carbon beads produced using USN-generated highly concentrated supercritical steam displayed remarkably elevated intrabead self-diffusivity of n-hexane. Inductively coupled plasma-optical emission spectroscopy demonstrates superior gold recovery kinetics from cyanide solutions compared to that from an industrial benchmark. The energy expenditure for USN-generated steam, producing carbon beads with an apparent surface area of 2691 m2/g, is estimated at 97 J per 1 m2 of carbon. This contrasts with the traditional steam generation method requiring approximately the energy of 190 J/m2 for activated carbon with an SBET of 2130 m2/g, making the USN-assisted activation method a more environmentally friendly and sustainable option with nearly half the energy consumption.

Thermal feathering of modern carbon nanomaterials (CNM), among them single walled carbon nanohorns (SWCNH) and carbon nanoonions (CNO), in polyethylene (PE) is applied to produce new durable, transparent hydrophobic, superhydrophobic and omniphobic surfaces. To increase SWCNH reactivity, they were converted into open sensu shaped graphene oxide (OSSGO). Next omniphobicity was introduced by fluorination. New superhydrophobic and hydrophobic translucent surfaces were deeply characterized by using spectroscopic methods, tribological analysis and contact angle (CA) measurements. Thermal feathering and fluorination by perfluorooctyl trichlorosilane (PFOTS) led to creation of grafted polysiloxanes and the attachment of fluorine-containing chains. The analysis of the Zisman plots, the adhesion tension vs. surface tension plots, CA and roll-off and hysteresis measurements results, together with Molecular Dynamics simulations, allowed to explain wetting mechanisms and the derivation on the adhesion tension vs. surface tension of liquids plots, suggesting surface freezing under the droplet as a new potential cause. Some new correlations describing the process of wetting are also discussed and explained. Fluorination creates translucent surfaces, and thus obtained materials can be used for red color filtering in self-cleaning coatings invisible for flying insects, which are a source of biological pollution of electronics that emit light in the open air at night.

To accelerate the design and production of porous carbons targeting desired performance characteristics, we propose to incorporate machine learning (ML) regression into pore size distribution (PSD) analysis. Here, we implemented a ML algorithm for predicting paracetamol adsorption capacity of porous carbons from two pore structure parameters: total surface area and surface area of supermicropores-mesopores. These structural parameters of porous carbons are accessible from the software provided with automatic volumetric gas adsorption analyzers. It was shown that theoretical paracetamol capacities of porous carbons predicted using the ML algorithm lies within the range of experimental uncertainty. Nanoporous carbon beads with a high surface area of supermicropores (997 m2/g) and mesopores (628 m2/g) had the highest adsorption capacity of paracetamol (experiment: 480 ± 24 mg/g, ML predicted: 498 mg/g). The novel strategy for designing of porous carbon adsorbents using ML-PSD approach has a great potential to facilitate production of novel carbon adsorbents optimized for purification of aqueous solutions from non-electrolyte contaminates.