Key words: nanocomposite, single-walled carbon nanotubes, suspensions, supercritical impregnation, polymethylmethacrylate, supercritical carbon dioxide, Raman spectroscopy, thermogravimetry, differential scanning calorimetry
A technique is described for dispersing single-walled carbon nanotubes to obtain stable suspensions with a high concentration of individual nanotubes in 2-pyrrolidone. The resulting suspensions were investigated using Raman spectroscopy and were used to modify poly(methylmethacrylate) samples with average molecular weights 15000 and 996000 g/mol by impregnation in supercritical carbon dioxide. The thermal properties of the obtained composite materials are studied. It is shown that the glass transition temperatures of the samples are increased with comparison with the initial polymers. Glass transition temperatures of composites increased by 26°С and 32°С for PMMA with an average molecular weight of 15000 and 996000 g/mol accordingly.
doi:10.34984/SCFTP.2021.16.1.001
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ГОСТ
7.0.100-2018
Thermal Properties of Poly(Methyl Methacrylate) Samples with Different Molecular Weights Impregnated with Single-Walled Carbon Nanotubes in a Supercritical Carbon Dioxide Medium / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2021. – Т. 16. – № 1. – С. 3-16. - DOI: 10.34984/SCFTP.2021.16.1.001
TRANSLIT
Termicheskie svojstva obrazcov polimetilmetakrilata s razlichnymi molekulyarnymi massami, impregnirovannyh odnoslojnymi uglerodnymi nanotrubkami v srede sverhkriticheskogo dioksida ugleroda / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2021. – Т. 16. – № 1. – S. 3-16. - DOI: 10.34984/SCFTP.2021.16.1.001
En
Thermal Properties of Poly(Methyl Methacrylate) Samples with Different Molecular Weights Impregnated with Single-Walled Carbon Nanotubes in a Supercritical Carbon Dioxide Medium. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 1, 3-16 (2021). https://doi.org/10.34984/SCFTP.2021.16.1.001
Key words: zinc oxide, cold sintering, recrystallization, solid-phase mobility in an aqueous medium, crystal size distribution, coalescence, surface spreading
An effect of mechanical pressure on the crystal size distribution during the treatment of zinc oxide in an aqueous medium in the presence of zinc acetate or ammonium chloride as activating additives was studied by analyzing scanning electron microscopy images. The results of ZnO cold sintering at 220—296 °C and its thermovaporous treatment (TVT) without applying mechanical pressure in an autoclave under similar conditions were compared. It was concluded that due to the presence of the additives in an aqueous medium, the hydration of the structure increased and the solid-phase mobility was activated, leading to the redistribution of the mass of crystals. Mechanical pressure during the cold sintering enhanced the effect of solid-phase mobility activation and led to the predominance of crystal coalescence in mass transfer. During the TVT with no mechanical pressure applied, surface spreading as the mass transfer mechanism prevailed. A scheme illustrating the effect of the aqueous medium on the mass transfer during the recrystallization of ZnO was proposed.
doi:10.34984/SCFTP.2021.16.1.002
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ГОСТ
7.0.100-2018
Effect of Mechanical Pressure on Zinc Oxide Recrystallization in Aqueous Medium during Cold Sintering / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2021. – Т. 16. – № 1. – С. 17-51. - DOI: 10.34984/SCFTP.2021.16.1.002
TRANSLIT
Vliyanie mekhanicheskogo davleniya na rekristallizaciyu oksida cinka v vodnoj srede pri holodnom spekanii / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2021. – Т. 16. – № 1. – S. 17-51. - DOI: 10.34984/SCFTP.2021.16.1.002
En
Effect of Mechanical Pressure on Zinc Oxide Recrystallization in Aqueous Medium during Cold Sintering. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 1, 17-51 (2021). https://doi.org/10.34984/SCFTP.2021.16.1.002
Key words: supercritical carbon dioxide, electron paramagnetic resonance spectroscopy, optical spectroscopy, PDLLA, spin probe 2,2,5,5-tetramethyl-4-phenyl-3-imidazoline-1-oxyl-3-oxide
The optical spectroscopy and EPR spectroscopy methods were used together for the first time to quantitatively describe the release of a nitroxyl probe from poly-D,L-lactide (PDLLA) films into a phosphate buffer solution. The bifunctional probe 2,2,5,5-tetramethyl-4-phenyl- 3-imidazoline-1-oxyl-3-oxide (IMNO) contains a paramagnetic nitroxyl fragment and has a high extinction coefficient in the UV spectrum. Polymer films were obtained from porous matrices based on PDLLA, formed and doped with IMNO in a supercritical CO2 environment. It has been established that the combined use of spectrophotometry and EPR spectroscopy is promising for obtaining more detailed information on the processes of the release of probes from PDLLA films, the duration of which does not exceed three weeks.
doi:10.34984/SCFTP.2021.16.1.003
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ГОСТ
7.0.100-2018
Kinetics Of Release of the Bifunctional Probe 2,2,5,5-Tetramethyl-4-Phenyl-3-Imidazoline-1-Oxyl-3-Oxide from Poly-D, L-Lactide Films Formed with the Use of Supercritical Carbon Dioxide / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2021. – Т. 16. – № 1. – С. 52-59. - DOI: 10.34984/SCFTP.2021.16.1.003
TRANSLIT
Kinetika vysvobozhdeniya bifunkcional'nogo zonda 2,2,5,5-tetrametil-4-fenil-3-imidazolin-1-oksil-3-oksida iz plenok poli-D,L-laktida, sformirovannyh s ispol'zovaniem sverhkriticheskogo dioksida ugleroda / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2021. – Т. 16. – № 1. – S. 52-59. - DOI: 10.34984/SCFTP.2021.16.1.003
En
Kinetics Of Release of the Bifunctional Probe 2,2,5,5-Tetramethyl-4-Phenyl-3-Imidazoline-1-Oxyl-3-Oxide from Poly-D, L-Lactide Films Formed with the Use of Supercritical Carbon Dioxide. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 1, 52-59 (2021). https://doi.org/10.34984/SCFTP.2021.16.1.003
Key words: water-soluble polymers, supercritical carbon dioxide, extraction, recovery, benzoic acid, caffeine, thiophene
This work presents the experimental study results of the benzoic acid, caffeine, and thiophene recovery from polymer phases by supercritical fluid extraction. The extraction efficiency dependences of the studied compounds on the conditions of fluid existence — temperature, and pressure were obtained. It has been shown that benzoic acid, caffeine, and thiophene are extracted in one step into supercritical CO2 with the extraction degree of 43, 48.5, and 84 % respectively.
doi:10.34984/SCFTP.2021.16.1.004
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ГОСТ
7.0.100-2018
Extraction of Organic Substances with Supercritical CO<sub>2</sub> from Liquid Phases Based on Water-Soluble Polymers / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2021. – Т. 16. – № 1. – С. 60-66. - DOI: 10.34984/SCFTP.2021.16.1.004
TRANSLIT
Ekstrakciya benzojnoj kisloty, kofeina i tiofena sverhkriticheskim CO2 iz zhidkih faz na osnove PEG-400 i PEG-1500 / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2021. – Т. 16. – № 1. – S. 60-66. - DOI: 10.34984/SCFTP.2021.16.1.004
En
Extraction of Organic Substances with Supercritical CO<sub>2</sub> from Liquid Phases Based on Water-Soluble Polymers. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 1, 60-66 (2021). https://doi.org/10.34984/SCFTP.2021.16.1.004
Key words: biomass, agricultural waste, supercritical conditions, ideal mixing reactor, ecology, energy
The efficiency of processing organic liquid and solid wastes of the agro-industrial complex in supercritical conditions is shown. The conversion is at least 99,7 %. The dependence of the volume of a continuous reactor on the content of organic substances has been established. High rates of oxidation of waste in supercritical conditions make it possible to reduce the volume of the reactor (up to 100—140 l) with a capacity of up to 100 kg of waste per hour. The heat density of the reactor can reach 730 kW/m3.
doi:10.34984/SCFTP.2021.16.1.005
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ГОСТ
7.0.100-2018
Efficiency of Hydrothermal Processing of Organic Waste in a Full Mixed Flow Type Reactor / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2021. – Т. 16. – № 1. – С. 67-76. - DOI: 10.34984/SCFTP.2021.16.1.005
TRANSLIT
Effektivnost' gidrotermal'noj pererabotki organicheskih othodov v reaktore polnogo smesheniya protochnogo tipa / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2021. – Т. 16. – № 1. – S. 67-76. - DOI: 10.34984/SCFTP.2021.16.1.005
En
Efficiency of Hydrothermal Processing of Organic Waste in a Full Mixed Flow Type Reactor. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 1, 67-76 (2021). https://doi.org/10.34984/SCFTP.2021.16.1.005
Key words: statistical physics, critical phenomena, Rayleigh light scattering
For the first time, the temperature dependence of the density variance and the correlation length of critical density fluctuations is determined from the experimental data on small-angle light scattering by critical CO2. It is found that at critical density of CO2 in the temperature range 10-8 Tc < |T - Tc| < 10-4 Tc (where Tc is the critical temperature) the correlation length of density fluctuations decreases by 20 % as the critical point is approached. The value of density variance shows no power-law-type divergence: it remains practically constant in the temperature ranges T > Tc and T < Tc, but undergoes a 25 % stepwise change when passing through the critical point, likely due to the peculiarities of the experiment setting up.
doi:10.34984/SCFTP.2021.16.1.006
Cite
ГОСТ
7.0.100-2018
Diagnostics of the Critical State of Carbon Dioxide / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2021. – Т. 16. – № 1. – С. 77-89. - DOI: 10.34984/SCFTP.2021.16.1.006
TRANSLIT
Diagnostika kriticheskogo sostoyaniya dioksida ugleroda / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2021. – Т. 16. – № 1. – S. 77-89. - DOI: 10.34984/SCFTP.2021.16.1.006
En
Diagnostics of the Critical State of Carbon Dioxide. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 1, 77-89 (2021). https://doi.org/10.34984/SCFTP.2021.16.1.006