Nanoporous active carbons at ambient conditions: a comparative study using X-ray scattering and diffraction, Raman spectroscopy and N2 adsorption

Shiryaev, А. A.; Волощук, А. М.; Volkov, V. V.; Аверин, А. А.; Artamonova, S. D.

doi:10.1088/1742-6596/848/1/012009

Cited by 18 publications

(17 citation statements)

References 35 publications

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“…As shown in [ 53 , 54 ], SAXS is able to provide topological information from the molecular to mesopore scale, regardless of the sample crystallinity. Characterization of the carbons by SAXS is shown in Figure 3 .…”

Section: Resultsmentioning

confidence: 99%

Thermodynamics of Adsorbed Methane Storage Systems Based on Peat-Derived Activated Carbons

et al. 2020

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Two activated carbons (ACs) were prepared from peat using thermochemical K2SO4 activation at 1053–1133 K for 1h, and steam activation at 1173K for 30 (AC-4) and 45 (AC-6) min. The steam activation duration affected the microporous structure and chemical composition of ACs, which are crucial for their adsorption performance in the methane storage technique. AC-6 displays a higher micropore volume (0.60 cm3/g), specific BET surface (1334 m2/g), and a lower fraction of mesopores calculated from the benzene vapor adsorption/desorption isotherms at 293K. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and small-angle X-ray scattering (SAXS) investigations of ACs revealed their heterogeneous morphology and chemical composition determined by the precursor and activation conditions. A thermodynamic analysis of methane adsorption at pressures up to 25 MPa and temperatures from 178 to 360K extended to impacts of the nonideality of a gaseous phase and non-inertness of an adsorbent made it possible to evaluate the heat effects and thermodynamic state functions in the methane-AC adsorption systems. At 270 K and methane adsorption value of ~8 mmol/g, the isosteric heat capacity of the methane-AC-4 system exceeded by ~45% that evaluated for the methane-AC-6 system. The higher micropore volume and structural heterogeneity of the more activated AC-6 compared to AC-4 determine its superior methane adsorption performance.

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Section: Resultsmentioning

confidence: 99%

Thermodynamics of Adsorbed Methane Storage Systems Based on Peat-Derived Activated Carbons

et al. 2020

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“…Porod curves and double-log SAXS patterns of the original, programmed, and recovered SiO 2 /SMPU samples are shown in Figure 9, and their fractal dimensions corresponding to double-log curves of SiO 2 /SMPU are all summarized in Table 4. [36]. It can be seen that the Porod curves presented some obvious positive deviations at the larger angle range, and maintained a similar change rate.…”

Section: Interphase Structure Changesmentioning

confidence: 70%

“…Figure 9 a displays the typical Porod curves of ln[ q 3 I ( q )] − q 2 based on the SAXS test results of the original, programmed, and recovered SiO 2 /SMPU samples [ 36 ]. It can be seen that the Porod curves presented some obvious positive deviations at the larger angle range, and maintained a similar change rate.…”

Section: Resultsmentioning

confidence: 99%

The Difference in Molecular Orientation and Interphase Structure of SiO2/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process

Shi

Wang

et al. 2020

Polymers

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In order to further understand the shape memory mechanism of a silicon dioxide/shape memory polyurethane (SiO2/SMPU) composite, the thermodynamic properties and shape memory behaviors of prepared SiO2/SMPU were characterized. Dynamic changes in the molecular orientation and interphase structures of SiO2/SMPU during a shape memory cycle were then discussed according to the small angle X-ray scattering theory, Guinier’s law, Porod approximation, and fractal dimension theorem. In this paper, a dynamic mechanical analyzer (DMA) helped to determine the glass transition start temperature (Tg) by taking the onset point of the sigmoidal change in the storage modulus, while transition temperature (Ttrans) was defined by the peak of tan δ, then the test and the calculated results indicated that the Tg of SiO2/SMPU was 50.4 °C, and the Ttrans of SiO2/SMPU was 72.18 °C. SiO2/SMPU showed good shape memory performance. The programmed SiO2/SMPU showed quite obvious microphase separation and molecular orientation. Large-size sheets and long-period structures were formed in the programmed SiO2/SMPU, which increases the electron density difference. Furthermore, some hard segments had been rearranged, and their gyration radii decreased. In addition, several defects formed at the interfaces of SiO2/SMPU, which caused the generation of space charges, thus leading to local electron density fluctuations. The blurred interphase structure and the intermediate layer formed in the programmed SiO2/SMPU and there was evident crystal damage and chemical bond breakage in the recovered SiO2/SMPU. Finally, the original and recovered SiO2/SMPU samples belong to the surface fractal system, but the programmed sample belongs to the mass fractal and reforms two-phase structures. This study provides an insight into the shape memory mechanism of the SiO2/SMPU composite.

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“…Thus, for this sample, a set of variations of XRD patterns as a function of the burn-off reflects the loss of volatile amorphous matter and ordering of the crystalline phase during the activation process. Figure 6 b shows the SAXS intensity curves of all the samples, which are typical for activated carbons exhibiting a hierarchical system with micro, meso, and macropores e.g., [ 60 ]. The low-q region of the SAXS curve corresponds to scattering from relatively large crystallites, whereas a signal in the high-q range is caused by scattering from pores.…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic Behaviors of Adsorbed Methane Storage Systems Based on Nanoporous Carbon Adsorbents Prepared from Coconut Shells

et al. 2020

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The present work focused on the experimental study of the performance of a scaled system of adsorbed natural gas (ANG) storage and transportation based on carbon adsorbents. For this purpose, three different samples of activated carbons (AC) were prepared by varying the size of coconut shell char granules and steam activation conditions. The parameters of their porous structure, morphology, and chemical composition were determined from the nitrogen adsorption at 77 K, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and scanning electron microscopy (SEM) measurements. The methane adsorption data measured within the temperature range from 178 to 360 K and at pressures up to 25 MPa enabled us to identify the most efficient adsorbent among the studied materials: AC-90S. The differential heats of methane adsorption on AC-90S were determined in order to simulate the gas charge/discharge processes in the ANG system using a mathematical model with consideration for thermal effects. The results of simulating the charge/discharge processes under two different conditions of heat exchange are consistent with the experimentally determined temperature distribution over a scaled ANG storage tank filled with the compacted AC-90S adsorbent and equipped with temperature sensors and heat-exchanger devices. The amounts of methane delivered from the ANG storage system employing AC-90S as an adsorbent differ from the model predictions by 4–6%. Both the experiments and mathematical modeling showed that the thermal regulation of the ANG storage tank ensured the higher rates of charge/discharge processes compared to the thermal insulation.

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Nanoporous active carbons at ambient conditions: a comparative study using X-ray scattering and diffraction, Raman spectroscopy and N2 adsorption

Cited by 18 publications

References 35 publications

Thermodynamics of Adsorbed Methane Storage Systems Based on Peat-Derived Activated Carbons

Thermodynamics of Adsorbed Methane Storage Systems Based on Peat-Derived Activated Carbons

The Difference in Molecular Orientation and Interphase Structure of SiO2/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process

Thermodynamic Behaviors of Adsorbed Methane Storage Systems Based on Nanoporous Carbon Adsorbents Prepared from Coconut Shells

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