Pub Date : 2024-11-18DOI: 10.1134/S0036024424702029
Majid Monajjemi, Fatemeh Mollaamin
Protonated methane, ({text{CH}}_{5}^{ + }), has unusual vibrational and rotational behavior because its three nonequivalent equilibrium structures have nearly identical energies and its five protons scramble freely. The highly flexible ({text{CH}}_{5}^{ + }), molecular ion has been shown by ab initio calculations to have 120 symmetrically equivalent minima of Cs symmetry in its ground electronic state. Complete proton rearrangement, making all minima accessible to each other, is possible as a result of two large-amplitude internal motions: an internal rotation about the C3 axis with an ab initio barrier of 30 cm–1 and an internal flip motion with an ab initio barrier of 300 cm–1 that exchanges protons between the H2 and ({text{CH}}_{3}^{ + }) groups. We calculate the structure of the J = 2 ( leftarrow )1 and 1 ( leftarrow ) 0 rotational transitions of ({text{CH}}_{5}^{ + }), ({text{CD}}_{5}^{ + }) and also other variants containing ({text{C}}{{{text{H}}}_{x}}{text{D}}_{{(5 - x)}}^{ + }). Although many theoretical papers have been published on the quantum mechanics of these systems, a better understanding requires spectral and conformational analysis. Post Hartree-Fock, Møller-Plesset and DFT calculation with the correlation consistent polarized valence double and triple zeta basis sets have done for the zero-point energies of ({text{C}}{{{text{H}}}_{x}}{text{D}}_{{(5 - x)}}^{ + }). The present results indicates the mode 8, 12, and 10 agree with qualitative of ({text{CH}}_{5}^{ + }), which is highly fluxional and has a complex spectrum while the C–X bonds which are broken and reformed all the time. The spectrum of mode 12 is highly complex with huge red-and some blue shifts. In particular, they can be attributed to the rapid coupling of the original CH-stretching normal mode to motions more closely related to isomerization, i.e., bending or rocking. There has thus been a long debate whether ({text{CH}}_{5}^{ + }) has a structure at all or not and is it real rotational motions or artificial. In addition, we include the contribution to the torsional barrier from the zero point energies of the other (high-frequency) vibrations, the effect of centrifugal distortion, and the effect of second-order rotation-vibration interactions.
{"title":"Real or Artificial Stability of ({text{CH}}_{5}^{ + }) Ions and Deuterated Variants ({mathbf{C}}{{{mathbf{H}}}_{x}}{mathbf{D}}_{{left( {5 - x} right)}}^{ + }) Based on Ab Initio Calculation and Rotational Spectrum","authors":"Majid Monajjemi, Fatemeh Mollaamin","doi":"10.1134/S0036024424702029","DOIUrl":"10.1134/S0036024424702029","url":null,"abstract":"<p>Protonated methane, <span>({text{CH}}_{5}^{ + })</span>, has unusual vibrational and rotational behavior because its three nonequivalent equilibrium structures have nearly identical energies and its five protons scramble freely. The highly flexible <span>({text{CH}}_{5}^{ + })</span>, molecular ion has been shown by ab initio calculations to have 120 symmetrically equivalent minima of <i>Cs</i> symmetry in its ground electronic state. Complete proton rearrangement, making all minima accessible to each other, is possible as a result of two large-amplitude internal motions: an internal rotation about the <i>C</i><sub>3</sub> axis with an ab initio barrier of 30 cm<sup>–1</sup> and an internal flip motion with an ab initio barrier of 300 cm<sup>–1</sup> that exchanges protons between the H<sub>2</sub> and <span>({text{CH}}_{3}^{ + })</span> groups. We calculate the structure of the <i>J =</i> 2 <span>( leftarrow )</span>1 and 1 <span>( leftarrow )</span> 0 rotational transitions of <span>({text{CH}}_{5}^{ + })</span>, <span>({text{CD}}_{5}^{ + })</span> and also other variants containing <span>({text{C}}{{{text{H}}}_{x}}{text{D}}_{{(5 - x)}}^{ + })</span>. Although many theoretical papers have been published on the quantum mechanics of these systems, a better understanding requires spectral and conformational analysis. Post Hartree-Fock, Møller-Plesset and DFT calculation with the correlation consistent polarized valence double and triple zeta basis sets have done for the zero-point energies of <span>({text{C}}{{{text{H}}}_{x}}{text{D}}_{{(5 - x)}}^{ + })</span>. The present results indicates the mode 8, 12, and 10 agree with qualitative of <span>({text{CH}}_{5}^{ + })</span>, which is highly fluxional and has a complex spectrum while the C–X bonds which are broken and reformed all the time. The spectrum of mode 12 is highly complex with huge red-and some blue shifts. In particular, they can be attributed to the rapid coupling of the original CH-stretching normal mode to motions more closely related to isomerization, i.e., bending or rocking. There has thus been a long debate whether <span>({text{CH}}_{5}^{ + })</span> has a structure at all or not and is it real rotational motions or artificial<b>.</b> In addition, we include the contribution to the torsional barrier from the zero point energies of the other (high-frequency) vibrations, the effect of centrifugal distortion, and the effect of second-order rotation-vibration interactions.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2778 - 2791"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S0036024424702066
D. Yu. Lenev, S. A. Zakharov, V. V. Pisarev
Molecular dynamics is used to calculate the vapor–liquid equilibrium and liquid–vapor surface tension for a methane–ethane system. Good agreement of the parachor value for ethane between the molecular model and experimental data is shown for the 203–253 K range of temperatures and pressures up to 60 atm. The dependence of the surface tension of the mixture on pressure in the range of 4–40 atm at a temperature of 213 K shows a drop in both the surface tension and the difference in densities between the liquid and vapor as the pressure rises and approaches the critical locus. Approximating the density profiles obtained for the same conditions, it is concluded that the width of the interphase boundary also grows. The amount of methane adsorbed on the surface of the liquid film is calculated. The dependence of the molar adsorption of methane on the difference between the densities of the components in the liquid and gas phases is obtained, along with its analytical expression in the context of the Gibbs theory. Features of the approach that is used include no need for approximations of the ideal gas or the ideal solution, and the use of only experimentally obtained data as input. The resulting values of methane adsorption are in good agreement with the derived analytical dependence.
{"title":"Surface Tension and Adsorption at the Vapor–Liquid Interface in a Methane–Ethane System","authors":"D. Yu. Lenev, S. A. Zakharov, V. V. Pisarev","doi":"10.1134/S0036024424702066","DOIUrl":"10.1134/S0036024424702066","url":null,"abstract":"<p>Molecular dynamics is used to calculate the vapor–liquid equilibrium and liquid–vapor surface tension for a methane–ethane system. Good agreement of the parachor value for ethane between the molecular model and experimental data is shown for the 203–253 K range of temperatures and pressures up to 60 atm. The dependence of the surface tension of the mixture on pressure in the range of 4–40 atm at a temperature of 213 K shows a drop in both the surface tension and the difference in densities between the liquid and vapor as the pressure rises and approaches the critical locus. Approximating the density profiles obtained for the same conditions, it is concluded that the width of the interphase boundary also grows. The amount of methane adsorbed on the surface of the liquid film is calculated. The dependence of the molar adsorption of methane on the difference between the densities of the components in the liquid and gas phases is obtained, along with its analytical expression in the context of the Gibbs theory. Features of the approach that is used include no need for approximations of the ideal gas or the ideal solution, and the use of only experimentally obtained data as input. The resulting values of methane adsorption are in good agreement with the derived analytical dependence.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2816 - 2822"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S0036024424702236
A. S. Gizzatov, M. A. Petrov, Yu. S. Eremin, A. M. Grekhov
Membranes have been prepared from polysulfone and graphene oxide with mass concentrations from 0 to 0.4%. A series of experiments were conducted to study the permeability of the obtained samples at pressures of 10, 15, and 20 atm. The experimental time dependences of the permeated water volume at a constant pressure were obtained. The dependence of the membrane permeability on the graphene oxide concentration and pressure was calculated. Conclusions were drawn about the influence of graphene oxide concentration and pressure on the permeability of the samples.
{"title":"Effect of Graphene Oxide on the Permeability of Asymmetric Polysulfone Membranes","authors":"A. S. Gizzatov, M. A. Petrov, Yu. S. Eremin, A. M. Grekhov","doi":"10.1134/S0036024424702236","DOIUrl":"10.1134/S0036024424702236","url":null,"abstract":"<p>Membranes have been prepared from polysulfone and graphene oxide with mass concentrations from 0 to 0.4%. A series of experiments were conducted to study the permeability of the obtained samples at pressures of 10, 15, and 20 atm. The experimental time dependences of the permeated water volume at a constant pressure were obtained. The dependence of the membrane permeability on the graphene oxide concentration and pressure was calculated. Conclusions were drawn about the influence of graphene oxide concentration and pressure on the permeability of the samples.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2921 - 2925"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S0036024424701929
J. V. Mattos, M. J. Molina, S. B. Rodriguez-Reartes, L. Ferreira-Pinto, M. S. Zabaloy, P. F. Arce, L. Cardozo-Filho
In this study, experimental carry out of liquid–vapor and solid–liquid phase transitions were conducted for the ternary system {CO2 (1) + ethanol (2) + acetaminophen (3)} at different concentrations of paracetamol in ethanol for temperatures from 313 to 333 K and pressures up to 12 MPa. Experimental high pressure phase transition data were obtained using the static method in a variable volume view cell. Experimental data were compared with the literature for systems containing acetaminophen in a saturated solution. The presence of paracetamol in the binary system {CO2 (1) + ethanol (2)} significantly alters the behavior of the phase under the conditions of temperature and concentration studied. It was observed that in the ternary system {CO2 (1) + ethanol (2) + acetaminophen (3)} with a saturated solution at the lowest temperature, 313 K, CO2 acts as a cosolvent for mole fractions lower than 0.6. Thermodynamic simulations employing the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) Equations of State (EoS) aligned the experimental results adequately. The observed minimal deviations in pressure and temperature validate the efficacy of the thermodynamic models applied in this study.
{"title":"Experimental Data and Thermodynamic Modeling of Solid–Liquid and Liquid–Vapor Equilibria in the CO2 + Ethanol + Acetaminophen System","authors":"J. V. Mattos, M. J. Molina, S. B. Rodriguez-Reartes, L. Ferreira-Pinto, M. S. Zabaloy, P. F. Arce, L. Cardozo-Filho","doi":"10.1134/S0036024424701929","DOIUrl":"10.1134/S0036024424701929","url":null,"abstract":"<p>In this study, experimental carry out of liquid–vapor and solid–liquid phase transitions were conducted for the ternary system {CO<sub>2</sub> (1) + ethanol (2) + acetaminophen (3)} at different concentrations of paracetamol in ethanol for temperatures from 313 to 333 K and pressures up to 12 MPa. Experimental high pressure phase transition data were obtained using the static method in a variable volume view cell. Experimental data were compared with the literature for systems containing acetaminophen in a saturated solution. The presence of paracetamol in the binary system {CO<sub>2</sub> (1) + ethanol (2)} significantly alters the behavior of the phase under the conditions of temperature and concentration studied. It was observed that in the ternary system {CO<sub>2</sub> (1) + ethanol (2) + acetaminophen (3)} with a saturated solution at the lowest temperature, 313 K, CO<sub>2</sub> acts as a cosolvent for mole fractions lower than 0.6. Thermodynamic simulations employing the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) Equations of State (EoS) aligned the experimental results adequately. The observed minimal deviations in pressure and temperature validate the efficacy of the thermodynamic models applied in this study.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2706 - 2716"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S0036024424702170
M. B. Pshenitsyn, O. A. Boeva
The catalytic and adsorption properties of supported mono- and bimetallic nanoparticles of the copper–silver and copper–gold systems were studied. The particle sizes were 5–9 nm. The catalytic properties of the samples were studied at 77 K in deuterium–hydrogen exchange reactions and ortho-to-para conversion of protium. A comparison of the obtained data on the catalytic properties of the samples in isotope exchange reactions in molecular hydrogen and ortho-to-para conversion of protium showed that the mono- and bimetallic nanoparticles of the systems have magnetic properties. A comparison of the activities of the mono- and bimetallic systems in the deuterium–hydrogen exchange reaction revealed a more significant synergistic effect for the copper–gold system relative to the copper–silver system, which is explained by the greater difference between the electronegativities of atoms in the systems.
研究了铜-银和铜-金体系的单金属和双金属纳米颗粒的催化和吸附特性。颗粒大小为 5-9 纳米。研究了这些样品在 77 K 下进行氘氢交换反应和氕氘正向转化时的催化特性。对样品在分子氢同位素交换反应和氕氕钡正钡转换反应中的催化特性数据进行比较后发现,系统中的单金属和双金属纳米粒子都具有磁性。通过比较单金属和双金属体系在氘氢交换反应中的活性,发现铜-金体系比铜-银体系具有更显著的协同效应,这是因为体系中原子的电负性差异更大。
{"title":"The Use of Isotopic Exchange in Molecular Hydrogen to Study the Physicochemical Properties of Bimetallic Nanoparticles","authors":"M. B. Pshenitsyn, O. A. Boeva","doi":"10.1134/S0036024424702170","DOIUrl":"10.1134/S0036024424702170","url":null,"abstract":"<p>The catalytic and adsorption properties of supported mono- and bimetallic nanoparticles of the copper–silver and copper–gold systems were studied. The particle sizes were 5–9 nm. The catalytic properties of the samples were studied at 77 K in deuterium–hydrogen exchange reactions and <i>ortho-</i>to-<i>para</i> conversion of protium. A comparison of the obtained data on the catalytic properties of the samples in isotope exchange reactions in molecular hydrogen and <i>ortho-</i>to<i>-para</i> conversion of protium showed that the mono- and bimetallic nanoparticles of the systems have magnetic properties. A comparison of the activities of the mono- and bimetallic systems in the deuterium–hydrogen exchange reaction revealed a more significant synergistic effect for the copper–gold system relative to the copper–silver system, which is explained by the greater difference between the electronegativities of atoms in the systems.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2888 - 2890"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S0036024424702078
Yu. K. Tovbin
An analysis of the literature shows that all surface characteristics of dispersed systems (surface tensions, contact angles, disjoining pressure, and the properties of small systems) have ambiguous thermodynamic definitions. The second law of Clausius thermodynamics, which requires additional experimental data on the periods of relaxation of momentum, energy, and mass transfer processes, is used to eliminate this ambiguity.
{"title":"The Second Law of Thermodynamics and the Surface Characteristics of Dispersed Systems","authors":"Yu. K. Tovbin","doi":"10.1134/S0036024424702078","DOIUrl":"10.1134/S0036024424702078","url":null,"abstract":"<p>An analysis of the literature shows that all surface characteristics of dispersed systems (surface tensions, contact angles, disjoining pressure, and the properties of small systems) have ambiguous thermodynamic definitions. The second law of Clausius thermodynamics, which requires additional experimental data on the periods of relaxation of momentum, energy, and mass transfer processes, is used to eliminate this ambiguity.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2823 - 2827"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S0036024424701917
V. A. Lysenko
Thermodynamic models of liquid and ternary solid solutions in the Ag–Al–In system are constructed on the basis of available experimental information. These models and ones of other phases of this system known in the literature are used to determine the coordinates of invariant points of the Ag–Al–In system and a projection of its liquidus surface. Polythermal cross sections of the phase diagram of this system are calculated for compositions xAl/xIn = 4.255, xIn/xAl = 2.096, and xAg/xIn = 1.064, along with isothermal cross sections at 973 and 573 K.
{"title":"Thermodynamic Modeling of the Ag–Al–In System","authors":"V. A. Lysenko","doi":"10.1134/S0036024424701917","DOIUrl":"10.1134/S0036024424701917","url":null,"abstract":"<p>Thermodynamic models of liquid and ternary solid solutions in the Ag–Al–In system are constructed on the basis of available experimental information. These models and ones of other phases of this system known in the literature are used to determine the coordinates of invariant points of the Ag–Al–In system and a projection of its liquidus surface. Polythermal cross sections of the phase diagram of this system are calculated for compositions <i>x</i><sub>Al</sub>/<i>x</i><sub>In</sub> = 4.255, <i>x</i><sub>In</sub>/<i>x</i><sub>Al</sub> = 2.096, and <i>x</i><sub>Ag</sub>/<i>x</i><sub>In</sub> = 1.064, along with isothermal cross sections at 973 and 573 K.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2697 - 2705"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S003602442470211X
I. M. Rumyantsev, V. A. Kashcheev, V. I. Petrov, A. N. Shabalin
The authors study the experimental conditions for determining the diffusion mobility of impurities in solid bodies. Considering these conditions shows the need to continue developing the familiar Gruzin technique. In studying a large group of elements in metallic beryllium, Gladkov’s research group analyzed the effects of refining, which includes the absorption of radiation of an isotope by a sample and the dynamics of changes in the source in the process of diffusion annealing. Mathematical tools for considering these effects are developed. It is concluded that the new ways of processing the experimental results can be used in studying the diffusion characteristics of a wide range of contaminants in solid matrices.
{"title":"Developing the Isotopic Technique of Studying Diffusion in Metals","authors":"I. M. Rumyantsev, V. A. Kashcheev, V. I. Petrov, A. N. Shabalin","doi":"10.1134/S003602442470211X","DOIUrl":"10.1134/S003602442470211X","url":null,"abstract":"<p>The authors study the experimental conditions for determining the diffusion mobility of impurities in solid bodies. Considering these conditions shows the need to continue developing the familiar Gruzin technique. In studying a large group of elements in metallic beryllium, Gladkov’s research group analyzed the effects of refining, which includes the absorption of radiation of an isotope by a sample and the dynamics of changes in the source in the process of diffusion annealing. Mathematical tools for considering these effects are developed. It is concluded that the new ways of processing the experimental results can be used in studying the diffusion characteristics of a wide range of contaminants in solid matrices.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2849 - 2854"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S0036024424702030
P. A. Chernavskii, S. V. Maksimov, G. V. Pankina, R. Yu. Novotortsev, A. V. Shumiytsev, S. I. Panfilov, A. A. Novakova, O. L. Eliseev
Cobalt nanoparticles embedded in a carbon matrix were obtained by thermolysis of glucose deposited on Co3O4/SiO2. The magnetic characteristics of the obtained nanoparticles were measured. This process formed single-domain (d < 20 nm) carbon-coated Co nanoparticles. The average size and the size distribution of Co nanoparticles depend on the amount of glucose used for the preparation. The use of a relatively small amount of glucose (glucose/cobalt < 1 mol/mol) leads to the formation of carbon shells enveloping Co nanoparticles, which are resistant to oxidation in air up to 200°C. In contrast, the use of a larger amount of glucose leads to the formation of an amorphous carbon layer with metal particles enclosed in it. Thus, the resulting nanoparticles are more susceptible to oxidation, and approximately half of the deposited cobalt is oxidized to CoO within a few days of exposure to air.
通过热解沉积在 Co3O4/SiO2 上的葡萄糖,获得了嵌入碳基质中的钴纳米粒子。测量了所获纳米粒子的磁特性。这一过程形成了单域(d < 20 nm)碳包覆 Co 纳米粒子。Co 纳米粒子的平均尺寸和尺寸分布取决于制备过程中使用的葡萄糖量。使用相对较少的葡萄糖(葡萄糖/钴 < 1 mol/mol)会形成包覆 Co 纳米粒子的碳壳,这种碳壳在高达 200°C 的空气中具有抗氧化性。相反,使用较多的葡萄糖则会形成无定形碳层,其中包裹着金属颗粒。因此,生成的纳米粒子更容易被氧化,大约一半的沉积钴在暴露于空气中几天后就会被氧化成 CoO。
{"title":"Characteristics and Magnetic Properties of Carbon-Coated Cobalt Nanoparticles Deposited on Silica","authors":"P. A. Chernavskii, S. V. Maksimov, G. V. Pankina, R. Yu. Novotortsev, A. V. Shumiytsev, S. I. Panfilov, A. A. Novakova, O. L. Eliseev","doi":"10.1134/S0036024424702030","DOIUrl":"10.1134/S0036024424702030","url":null,"abstract":"<p>Cobalt nanoparticles embedded in a carbon matrix were obtained by thermolysis of glucose deposited on Co<sub>3</sub>O<sub>4</sub>/SiO<sub>2</sub>. The magnetic characteristics of the obtained nanoparticles were measured. This process formed single-domain (<i>d</i> < 20 nm) carbon-coated Co nanoparticles. The average size and the size distribution of Co nanoparticles depend on the amount of glucose used for the preparation. The use of a relatively small amount of glucose (glucose/cobalt < 1 mol/mol) leads to the formation of carbon shells enveloping Co nanoparticles, which are resistant to oxidation in air up to 200°C. In contrast, the use of a larger amount of glucose leads to the formation of an amorphous carbon layer with metal particles enclosed in it. Thus, the resulting nanoparticles are more susceptible to oxidation, and approximately half of the deposited cobalt is oxidized to CoO within a few days of exposure to air.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2792 - 2797"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1134/S0036024424702017
E. V. Votyakov, Yu. K. Tovbin
The authors calculate the concentration dependence of the coefficient of mass transfer and mean-root-square fluctuations of attracting molecules under sub- and supercritical conditions for different approximations of cluster variation (CV) that allow for indirect correlations. The simplest lattice structure is considered: a uniform flat face (100) that provides an exact solution to the problem of multiple bodies. A comparison is given of characteristics calculated for a series of simplest CVM basis clusters (2 × n, n = 2–5, 3 × 3, 3 × 4) and a quasi-chemical approximation (cluster 2 × 1) that reflects only the effects of direct correlations. The coefficient of mass transfer is calculated within the theory of the absolute reactions rates of nonideal reaction systems. The effects the dependence of the motion of molecules has upon attraction from the side of neighboring molecules that block an available volume for movements on root-mean-square fluctuations are discussed. It is shown that a region near (above and below) the critical point can be selected in which there is an abrupt drop in the coefficient of diffusion because of large fluctuations of the material’s density. The increased accuracy of indirect correlations expands the area of thermodynamic parameters responsible for hindering mass transfer. The concept of transcritical first-order phase transitions and its relationship to the effects of kinetic resistivity to mass transfer are discussed.
{"title":"Mass Transfer and Fluctuations in the Root-Mean-Square Density of Molecules around the Critical Point","authors":"E. V. Votyakov, Yu. K. Tovbin","doi":"10.1134/S0036024424702017","DOIUrl":"10.1134/S0036024424702017","url":null,"abstract":"<p>The authors calculate the concentration dependence of the coefficient of mass transfer and mean-root-square fluctuations of attracting molecules under sub- and supercritical conditions for different approximations of cluster variation (CV) that allow for indirect correlations. The simplest lattice structure is considered: a uniform flat face (100) that provides an exact solution to the problem of multiple bodies. A comparison is given of characteristics calculated for a series of simplest CVM basis clusters (2 × <i>n</i>, <i>n</i> = 2–5<i>,</i> 3 × 3, 3 × 4) and a quasi-chemical approximation (cluster 2 × 1) that reflects only the effects of direct correlations. The coefficient of mass transfer is calculated within the theory of the absolute reactions rates of nonideal reaction systems. The effects the dependence of the motion of molecules has upon attraction from the side of neighboring molecules that block an available volume for movements on root-mean-square fluctuations are discussed. It is shown that a region near (above and below) the critical point can be selected in which there is an abrupt drop in the coefficient of diffusion because of large fluctuations of the material’s density. The increased accuracy of indirect correlations expands the area of thermodynamic parameters responsible for hindering mass transfer. The concept of transcritical first-order phase transitions and its relationship to the effects of kinetic resistivity to mass transfer are discussed.</p>","PeriodicalId":767,"journal":{"name":"Russian Journal of Physical Chemistry A","volume":"98 12","pages":"2767 - 2777"},"PeriodicalIF":0.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}