Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures

Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures

The recently synthesized honeycomb carbon allotrope has numerous potential applications, in particular for storage of gases inside carbon matrices. In this work this carbon form was experimentally studied in its denser form in order to estimate the upper temperature limit for keeping a gas inside...

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Дата:2019
Автори: Krainyukova, N.V., Bogdanov, Y., Kuchta, B.
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Мова:English
Опубліковано: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2019
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Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018)
Онлайн доступ:http://dspace.nbuv.gov.ua/handle/123456789/175961
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Цитувати:Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures / N.V. Krainyukova, Y. Bogdanov, B. Kuchta // Физика низких температур. — 2019. — Т. 45, № 3. — С. 371-376. — Бібліогр.: 30 назв. — англ.

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spelling irk-123456789-1759612021-02-04T01:25:54Z Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures Krainyukova, N.V. Bogdanov, Y. Kuchta, B. Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018) The recently synthesized honeycomb carbon allotrope has numerous potential applications, in particular for storage of gases inside carbon matrices. In this work this carbon form was experimentally studied in its denser form in order to estimate the upper temperature limit for keeping a gas inside the cellular structure. Along with the previously reported random honeycombs of a zigzag type we have also revealed the densest armchair structure. The mechanism of absorption–desorption of carbon dioxide studied by means of high energy electron diffraction at low temperatures showed the two — stage character of the observed desorption at elevated temperatures. This effect is associated to the weaker or stronger bonding of molecules with pore walls depending on the specific configuration of channels with different sizes. We have found that complete desorption of CO₂ does not occur even at the temperatures about three times higher as compared with the sublimation point of carbon dioxide in our vacuum conditions. Нещодавно синтезований вуглецевий стільниковий алотроп має численні потенційні застосування, зокрема для зберігання газів всередині вуглецевих матриць. Таку вуглецеву форму було експериментально досліджено в її більш щільній формі, щоб оцінити верхню границю температури, при якій газ зберігається всередині пористої структури. Поряд з раніше запропонованими випадковими стільниками зиґзаґоподібного типу виявлено найбільш щільну структуру типу armchair. Механізм поглинання–десорбція діоксиду вуглецю, що досліджено за допомогою дифракції електронів високої енергії при низьких температурах, показав двохстадійний характер десорбції, який спостерігається при підвищенні температури. Цей ефект пов’язаний з більш слабким або більш сильним зв’язуванням молекул зі стінками пор в залежності від конкретної конфігурації каналів різного розміру. Виявлено, що повна десорбція СО₂ не відбувається навіть при температурах приблизно в три рази вищих у порівнянні з точкою сублімації вуглекислого газу в наших вакуумних умовах. Недавно синтезированный углеродный сотовый аллотроп имеет множество потенциальных применений, в частности для хранения газов внутри углеродных матриц. Такая углеродная форма была экспериментально исследована в ее более плотной форме, чтобы оценить верхний предел температуры, при которой газ сохраняется внутри ячеистой структуры. Наряду с ранее предложенными случайными сотами зигзагообразного типа обнаружена самая плотная структура типа armchair. Механизм поглощение–десорбция диоксида углерода, изучаемый с помощью дифракции электронов высокой энергии при низких температурах, показал двухстадийный характер наблюдаемой десорбции при повышении температуры. Этот эффект связан с более слабым или более сильным связыванием молекул со стенками пор в зависимости от конкретной конфигурации каналов разного размера. Обнаружено, что полная десорбция СО₂ не происходит даже при температурах примерно в три раза более высоких по сравнению с точкой сублимации углекислого газа в наших вакуумных условиях. 2019 Article Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures / N.V. Krainyukova, Y. Bogdanov, B. Kuchta // Физика низких температур. — 2019. — Т. 45, № 3. — С. 371-376. — Бібліогр.: 30 назв. — англ. 0132-6414 http://dspace.nbuv.gov.ua/handle/123456789/175961 en Физика низких температур Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018)
Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018)
spellingShingle Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018)
Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018)
Krainyukova, N.V.
Bogdanov, Y.
Kuchta, B.
Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures
Физика низких температур
description The recently synthesized honeycomb carbon allotrope has numerous potential applications, in particular for storage of gases inside carbon matrices. In this work this carbon form was experimentally studied in its denser form in order to estimate the upper temperature limit for keeping a gas inside the cellular structure. Along with the previously reported random honeycombs of a zigzag type we have also revealed the densest armchair structure. The mechanism of absorption–desorption of carbon dioxide studied by means of high energy electron diffraction at low temperatures showed the two — stage character of the observed desorption at elevated temperatures. This effect is associated to the weaker or stronger bonding of molecules with pore walls depending on the specific configuration of channels with different sizes. We have found that complete desorption of CO₂ does not occur even at the temperatures about three times higher as compared with the sublimation point of carbon dioxide in our vacuum conditions.
format Article
author Krainyukova, N.V.
Bogdanov, Y.
Kuchta, B.
author_facet Krainyukova, N.V.
Bogdanov, Y.
Kuchta, B.
author_sort Krainyukova, N.V.
title Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures
title_short Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures
title_full Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures
title_fullStr Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures
title_full_unstemmed Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures
title_sort absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures
publisher Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
publishDate 2019
topic_facet Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018)
url http://dspace.nbuv.gov.ua/handle/123456789/175961
citation_txt Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures / N.V. Krainyukova, Y. Bogdanov, B. Kuchta // Физика низких температур. — 2019. — Т. 45, № 3. — С. 371-376. — Бібліогр.: 30 назв. — англ.
series Физика низких температур
work_keys_str_mv AT krainyukovanv absorptiondesorptionofcarbondioxideincarbonhoneycombsatelevatedtemperatures
AT bogdanovy absorptiondesorptionofcarbondioxideincarbonhoneycombsatelevatedtemperatures
AT kuchtab absorptiondesorptionofcarbondioxideincarbonhoneycombsatelevatedtemperatures
first_indexed 2025-07-15T13:34:24Z
last_indexed 2025-07-15T13:34:24Z
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fulltext Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3, pp. 371–376 Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures Nina V. Krainyukova1, Yuri Bogdanov1,2, and Bogdan Kuchta3,4 1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine E-mail: krainyukova@ilt.kharkov.ua 2National Technical University “Kharkiv Polytechnical Institute”, 2 Kyrpychova Str., Kharkiv 61002, Ukraine 3Université Aix-Marseille, CNRS, MADIREL, Marseille 13396, France 4Department of Physics and Astronomy, University of Missouri, Columbia MO, USA Received October 24, 2018 The recently synthesized honeycomb carbon allotrope has numerous potential applications, in particular for storage of gases inside carbon matrices. In this work this carbon form was experimentally studied in its denser form in order to estimate the upper temperature limit for keeping a gas inside the cellular structure. Along with the previously reported random honeycombs of a zigzag type we have also revealed the densest armchair struc- ture. The mechanism of absorption–desorption of carbon dioxide studied by means of high energy electron dif- fraction at low temperatures showed the two — stage character of the observed desorption at elevated tempera- tures. This effect is associated to the weaker or stronger bonding of molecules with pore walls depending on the specific configuration of channels with different sizes. We have found that complete desorption of CO2 does not occur even at the temperatures about three times higher as compared with the sublimation point of carbon diox- ide in our vacuum conditions. Keywords: high-energy electron diffraction, gas absorption, carbon honeycombs. 1. Introduction Many carbon allotropes such as fullerenes [1], nano- tubes [2,3], peapods [4], “schwarzite” forms [5–7], carbon nanowires [8], graphene [9] were discovered and intensive- ly studied during the last few decades. The carbon-based materials possess many potential applications in modern and future technologies. Special attention was focused on investigations [10–13] of light molecules absorption in nanoporous materials. This process is used in technological applications such as reduction of carbon dioxide emissions by vehicles, molecular sieving or fuel cells. In spite of high potential of hydrogen as a fuel, i.e., as a renewable and environmentally friendly energy source, its application is limited by the lack of simultaneously lightweight and effi- cient storage volumes with the high gravimetric ratio be- tween the weight of absorbed hydrogen and the total weight of the system. The recently synthesized carbon honeycomb structure [14] is an exceptionally stable carbon allotrope. Absorption of the heavier rare gases such as krypton and xenon in carbon films obtained by deposition of vacuum sublimated graph- ite was studied a few years earlier [15]. It was found in particular that the levels of gas absorption attain 4–6% in atomic count with respect to the number of carbon atoms in such substrates. This is about twice higher as compared with even theoretical values attainable in carbon nanotubes [16,17]. However, the carbon honeycomb structure was identified only when transmission electron microscopy and the exhaustive structural analysis were applied [14]. Many interesting details of these structures still require much higher resolution technique. In this work we study absorption with consequent de- sorption of carbon dioxide in the denser carbon honey- comb aiming to find the upper temperature limit for gas desorption from this structure. 2. Carbon film preparation As it was reported previously [14,18], in quest of low- density carbon structures with numerous channels accessi- © Nina V. Krainyukova, Yuri Bogdanov, and Bogdan Kuchta, 2019 Nina V. Krainyukova, Yuri Bogdanov, and Bogdan Kuchta ble for gas absorption, we switched from the arc discharge to pure sublimation of graphite rods thinned in their central parts and heated by the electric current (Fig. 1). In this method we allow only sublimation when the weaker bonds between graphitic layers are destroyed while sp2 links inside graphene-like planes are still preserved. In this way we obtain graphene patches with tightly bonded sp2 network. They can easily fly in vacuum and, according to the theoretical prediction [19], may collide with previ- ously deposited flat fragments in a way that they form right or big enough angles with other patches which result in formation of junction structures. Besides the small patches tend to close dangling bonds at their edges that make the “big angle” deposition with collision energetically more favorable. For these reasons the parallel deposition proba- bility is negligible in the total angle distribution. These junction structures called in [14] “carbon honeycomb” (hc) are different from those of common graphitic materials. In carbon honeycombs two “wall-chiralities” (armchair — hcA and zigzag — hcZ) may be formed, and the structures with various widths of walls and therefore different densities of such carbon materials can be synthesized [14,18–24]. In our preparation we varied the electric current be- tween 65 and 85 A to choose the regime when denser films form. In this way we expected to obtain the stronger bond- ing of the absorbed gas with cell walls and to estimate the upper temperature limit for keeping the gas inside the car- bon honeycomb matrices. Carbon films were deposited on cleaved single crystal surface of NaCl and further were separated from salt by means of floating in distilled water. Such films then were put onto the copper grids with a cell size about 0.1 mm transparent for electrons and were placed on the holder inside the column of the diffraction setup. 3. Experimental According to our previous findings the high absorption ability of carbon films prepared by the method described above and in more detail in [18] can be attained if a gas (e.g., gaseous carbon dioxide) is first deposited on carbon substrates inside the low-temperature cryostat well below the sublimation points of polycrystalline films (Tsubl ~ 86 K for considered CO2). The studies are performed with the help of the high energy electron diffraction setup EMR- 100 supplied with the low-temperature cryostat. After dep- osition good quality thin solid polycrystalline films with distinct diffraction peaks formed. But when they are grad- ually heated and kept slightly below the characteristic sub- limation points, the strong diffraction peaks corresponding to a polycrystalline state disappear, but distinct residual sig- nals remain. These residual signals are still observed at tem- peratures far above the sublimation points owing to physi- cal absorption of gases with strong bonding in a carbon matrix. We ascribe these features to specificity of compo- sites formed from the gaseous phase when gas atoms are strongly bonded inside carbon matrices after capillary fill- ing at temperatures slightly below the sublimation points. In our current experiment with CO2 the deposition tempera- ture ~ 80 K was closer to the sublimation point and we ob- served the absorption effect already during deposition. 4. The analysis method The carbon films produced by the method described above as well as composites based on carbon structures filled with absorbed gases were studied by means of Trans- mission High-Energy Electron Diffraction (THEED) in an EMR-100 electron diffraction setup. These studies were sup- ported by the advanced analysis of the obtained data [25]. In the precise analysis of diffraction patterns from car- bon films (see the next section) the experimental intensities Iexp(S) are compared with calculated values 2 2 2 calc calc, 1( ) exp ( ) ( ) (1 ) k k k I S u S f w I S t   = −〈 〉 +  −   ∑ , (1) here 2u〈 〉 are the mean-square atomic displacements, f is the atomic scattering factor for electrons, wk are the varied probabilities of the presence of a structural fragment k comprised of Nk atoms and calc, sin ( )2( ) mn k k mnm n k Sr I S N Sr>   =      ∑ (2) is the Debye formula [26]. Here rmn is a distance between a pair of atoms in a structural fragment k and 1k kw∑ = . The value t (in contrast with isolated clusters [27]) charac- terizes a fraction of atoms belonging to different fragments whose oscillating terms with calc, ( )kI S (Eq. (2)) mutually cancel each other in calc ( )I S (Eq. (1)) giving a contribu- tion only in the monotonic term ~ f 2. The electron diffrac- tion intensities Iexp are the functions of the scattering wave vector 4 sin /S = π θ λ . Here, 2θ is the scattering angle, and λ is the de Broglie wavelength of the electrons. The calculated diffraction intensities are compared with experiment by means of minimization of the reliability factor Fig. 1. The scheme of carbon sublimation from the graphitic rods used for the carbon film preparation. 372 Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3 Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures ( ) exp calc exp calc S S I I R I I − = + ∑ ∑ , (3) with respect to wk, here the summation over S is performed with the step 0.02 Å–1. 5. The structure of carbon films We tested previously [14,18] numerous structural com- ponents including graphite, fullerenes, schwarzites, nano- tubes in order to describe the S dependences of the diffrac- tion intensities Iexp(S) from carbon films. We have found in particular very limited contribution of differently sized graphite fragments with their total amount not exceeding ~ 10% that is also confirmed in the presented study. Car- bon nanotubes, whose probable appearance in our samples could owe to the symbiosis with the carbon honeycomb structures [14] have overall contribution wk as a rule not exceeding 3–4%. The carbon honeycomb structures in ma- jority prevailed under the proposed preparation conditions. For this reason in the study described here we used only honeycomb structures with addition of small pieces of gra- phitic carbon for evaluation of its probable contribution. The carbon honeycomb is not a single structure but is a family of structures. The honeycomb hexagon side sizes are 0 (2.5 1.5 ) NNa n r= + for a zigzag type structure; here 1.44 ÅNNr = is the nearest neighbor distance in a graphitic layer and n is an integer. The total classification of the arm- chair honeycombs is presented in [20]. In Fig. 2 we show the structures, which were found to be the best candidates for the analysis of the experimental diffractogram presented in Fig. 3(a) by means of the fitting procedure described in the previous section. Usually three broadened peaks can be identified in such diffractograms. If we worked with glassy graphite their positions would coincide with vertical lines in Fig. 3(a). The graphitic peaks (100) and (110) correspond to relevant hexagonal spacing inside the graphene plane while the peak (002) — to the distance between graphitic layers. Therefore two peak po- sitions (100) and (110) may also be expected in the honey- combs as well since walls of these structures are essentially graphene ribbons. But no distinct peak in the graphitic po- sition (002) is visible. Instead at the noticeably smaller angle we can see the well identified peak, which is close to the (100) position of the hexagonal honeycomb lattice of an arm- chair type (hcA1) although not exactly. The other honey- combs presented in Fig. 2 also contribute to this peak at a little smaller angles (or S). The total distribution of all contributing structures over cell sizes (a) is shown in Fig. 3(b). For graphite whose Fig. 2. (Color online) The carbon structures corresponding to the best-fit analysis of experimental diffraction intensities: the random honeycomb of a zigzag type (hcZ) found previously in [14], a fragment of a regular densest honeycomb structure also of a zig- zag type (hcZn0) for n = 0 in a0 (see the text), the densest honey- comb structure of an armchair type [20] first identified in our experiment (hcA1, a is a parameter of the hexagonal honeycomb lattice) and a small graphitic fragment (Gr), whose contribution to the total diffraction intensity is ~ 5% (see Fig. 3). Fig. 3. (Color online) The experimental and best-fit calculated diffraction intensities for the carbon films specifically prepared as described in the text to form the cellular structures of a honey- comb type (a). Relative contributions of different structures found from best-fit analysis and presented in Fig. 2(b). Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3 373 Nina V. Krainyukova, Yuri Bogdanov, and Bogdan Kuchta contribution was found ~ 5% we used here the interplanar distance of 3.43 Å. It is obvious that the honeycomb struc- tures are absolutely dominant in our study. In this work we first identified the densest honeycomb structure of an arm- chair type (hcA1) shown in Fig. 2. 6. The absorption–desorption effect As it was described above intensive absorption of carbon dioxide occurs when molecules are deposited on carbon films prepared from vacuum sublimated graphite below the sublimation temperature Tsubl. There were analyzed two options. When we deposited gases well below Tsubl first a good quality polycrystalline films with the intrinsic molec- ular dynamics formed [14,18,28]. After gradual heating and further keeping condensates a few degrees lower Tsubl CO2 molecules were absorbed by the carbon supporting films owing to fast diffusion and stronger interaction with pore walls as compared with interaction between molecules themselves. In this work we condense carbon dioxide at ~ 80 K, i.e., only a few degrees lower Tsubl, and intensive absorption occurs already during deposition. Polycrystalline peaks, which are initially well visible, fast disappear (Fig. 4). We analyze further evolution of formed composites, i.e., CO2 molecules absorbed in carbon honeycomb matri- ces, under heating up to ~ 230 K considering a difference between experimental intensities I from composites and Isubs from a carbon substrate (Fig. 5). The absorbed gases can be identified owing to the wide but well defined peak attributed to molecules captured in the carbon honeycomb matrices. This means that molecules are not randomly dis- tributed in carbon matrix channels but form some kind of short range order. The important question is how atoms Fig. 4. (Color online) The diffraction intensities recorded during deposition of carbon dioxide at ~ 80 K, which indicate fast ab- sorption of the gas during condensation, and angle intensity de- pendences (or on S) for formed composites as compared with a carbon substrate at further heating. Fig. 5. (Color online) An access of experimental diffraction intensities from composites formed by carbon dioxide absorbed in carbon honeycomb matrices during deposition closely to Tsubl of CO2 in vacuum as compared with intensities from a carbon substrate. On the right diffractograms are shifted along vertical to make details visible. A wide but well defined peak is attributed to molecules with short range order captured in the carbon honeycomb matrices and is kept up to ~ 230 K that is about three times higher as compared with Tsubl ~ 86 K. 374 Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3 Absorption–desorption of carbon dioxide in carbon honeycombs at elevated temperatures and molecules can be distributed inside porous carbon ma- trices. The exact answers can be obtained by direct model- ing such composites applying, e.g., the Monte Carlo me- thod [29,30]. During deposition along with the absorbate broad peak we can see also distinct peaks from polycrystalline CO2 films. But these polycrystalline peaks fast disappear al- ready at 82 K. The broad absorbate peak evolves with tem- perature changing its form and height. It is most plausible that this peak is a superposition of two or more contribu- tors. Most diffractograms exhibit this peak splitting into at least two positions. One is close to the (111) diffraction peak of polycrystalline CO2 at S ~ 1.95 Å–1 that imply local molecule arrangements similar to those in crystalline carbon dioxide. The other peak is located at smaller S and mutual molecule positions and orientations corresponding to this peak require more detailed modeling. To analyze the temperature behavior of composites we average intensities shown in Fig. 5 over the main broad peak in the S interval 1–2 Å–1 (marked by “ave”) and con- sider such a signal as a function of temperature (Fig. 6). We see a distinct decay of this signal at elevated tempera- tures from its highest value at the deposition temperature to about three times weaker intensity at T ~ 230 K. We can distinguish at least two stages in the tempera- ture dependence shown in Fig. 6. One stretches from the deposition temperature up to ~ 140 K while the other one exhibits another decay between 140 and ~ 230 K. It is na- tural to suppose that inside cells in carbon honeycombs CO2 molecules can interact with pore walls stronger or weaker depending on channel configurations and sizes. In the less dense random honeycomb structure the CO2 absor- bate cannot be kept at sufficiently high temperatures while in the denser structures hcA1 and hcZn0 bonds with pore walls apparently are much stronger. For fitting the experimental data we use the exponential decay function 1 0 2( ) exp ( ( ) / )f T a b T T c b T= + − − + for re- duction of diffracted intensities (I – Isubs in Fig. 6) with tem- perature T associated with the molecule release from larger or thinner channels in the first and second stages respec- tively (a, b1, b2, c and T0 are fitting parameters). In both stages we observe a slight “linear” growth of intensities that can be ascribed to relaxation of structures formed in carbon nanochannels towards to their better arrangements. Conclusions Varying the preparation conditions under sublimation of carbon patches from the thinned graphitic rods heated by the electric current we have found that at the parameters corresponding to the faster deposition and therefore to the denser structure formations honeycomb structures are still absolutely dominant. In these regimes we could also obtain the armchair type honeycomb structure (hcA1) with thin- nest possible for honeycomb channels, which was earlier not identified. In this work we analyze the behavior of composites formed from the carbon honeycomb structure filled with carbon dioxide at elevated temperatures and have found that complete desorption of carbon dioxide captured in the carbon honeycomb matrix does not occur even at the tem- peratures about three times higher as compared with the sublimation point of CO2 in a polycrystalline state in our vacuum conditions. 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Поряд з рані- ше запропонованими випадковими стільниками зиґзаґоподіб- ного типу виявлено найбільш щільну структуру типу arm- chair. Механізм поглинання–десорбція діоксиду вуглецю, що досліджено за допомогою дифракції електронів високої енергії при низьких температурах, показав двохстадійний характер десорбції, який спостерігається при підвищенні температури. Цей ефект пов’язаний з більш слабким або більш сильним зв’язуванням молекул зі стінками пор в залежності від кон- кретної конфігурації каналів різного розміру. Виявлено, що повна десорбція СО2 не відбувається навіть при темпера- турах приблизно в три рази вищих у порівнянні з точкою сублімації вуглекислого газу в наших вакуумних умовах. Ключові слова: дифракція високоенергетичних електронів, газова абсорбція, вуглецеві стільники. Абсорбция–десорбция углекислого газа в углеродных сотах при повышенных температурах Н.В. Крайнюкова, Ю.С. Богданов, Б. Кухта Недавно синтезированный углеродный сотовый аллотроп имеет множество потенциальных применений, в частности для хранения газов внутри углеродных матриц. Такая угле- родная форма была экспериментально исследована в ее более плотной форме, чтобы оценить верхний предел температуры, при которой газ сохраняется внутри ячеистой структуры. Наряду с ранее предложенными случайными сотами зигзаго- образного типа обнаружена самая плотная структура типа armchair. Механизм поглощение–десорбция диоксида угле- рода, изучаемый с помощью дифракции электронов высокой энергии при низких температурах, показал двухстадийный характер наблюдаемой десорбции при повышении темпера- туры. Этот эффект связан с более слабым или более сильным связыванием молекул со стенками пор в зависимости от кон- кретной конфигурации каналов разного размера. Обнаруже- но, что полная десорбция СО2 не происходит даже при тем- пературах примерно в три раза более высоких по сравнению с точкой сублимации углекислого газа в наших вакуумных условиях. Ключевые слова: дифракция высокоэнергетичных электро- нов, газовая абсорбция, углеродные соты. 376 Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3 https://doi.org/10.1103/PhysRevLett.69.921 https://doi.org/10.1063/1.1516635 https://doi.org/10.3762/bjnano.6.49 https://doi.org/10.1126/science.1102896 https://doi.org/10.1063/1.2790434 https://doi.org/10.1063/1.2790434 https://doi.org/10.1021/jp104889a https://doi.org/10.1021/jp104889a https://doi.org/10.1016/j.carbon.2012.10.049 https://doi.org/10.1021/ja306726u https://doi.org/10.1103/PhysRevLett.116.055501 https://doi.org/10.1063/1.3115812 https://doi.org/10.1063/1.3115812 https://doi.org/10.1063/1.4816119 https://doi.org/10.1063/1.4816119 https://doi.org/10.1063/1.4868528 https://doi.org/10.1063/1.4868528 https://doi.org/10.1007/s10909-016-1727-1 https://doi.org/10.1103/PhysRevB.72.035428 https://doi.org/10.1103/PhysRevB.72.035428 https://doi.org/10.1016/j.carbon.2016.11.020 https://doi.org/10.1103/PhysRevB.74.214104 https://doi.org/10.1021/jp305462w https://doi.org/10.1103/PhysRevLett.109.135501 https://doi.org/10.1103/PhysRevLett.112.026803 https://doi.org/10.1103/PhysRevLett.112.026803 https://doi.org/10.1016/j.tsf.2003.12.126 https://doi.org/10.1103/PhysRevLett.98.195506 https://doi.org/10.1007/s10909-016-1717-3 https://doi.org/10.1023/A:1004870207840 https://doi.org/10.1023/A:1004867910566 1. Introduction 2. Carbon film preparation 3. Experimental 4. The analysis method 5. The structure of carbon films 6. The absorption–desorption effect Conclusions Acknowledgements

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