An in-depth understanding of the competition mechanism between olefins and different types of sulfides in gasoline is essential to improve the desulfurization selectivity of the adsorption desulfurization process(ADS)...An in-depth understanding of the competition mechanism between olefins and different types of sulfides in gasoline is essential to improve the desulfurization selectivity of the adsorption desulfurization process(ADS).In this study,the competitive adsorption and diffusion mechanism of two systems,diethyl sulfide/cyclohexene and n-butyl mercaptan/cyclohexene,with different adsorption amounts in siliceous faujasite zeolite(FAU) were investigated by Monte Carlo(MC) and molecular dynamics(MD).The systems exhibited a two-stage loading-dependent competitive adsorption and diffusion mechanism,with an inflection point of 32 molecule/UC(moleculers per microcoulomb).Before the inflection point(4-32molecule/UC),the competition mechanism of the two systems was the "optimal-displacement" mechanism.After the inflection point,the mechanism of the diethyl sulfide/cyclohexene changed to "relocation-displacement",while that of the n-butyl mercaptan/cyclohexene system changed to "dominantdisplacement".Compared to ether functional groups,the alcohol functional group has higher polarity and stronger adsorption stability,thus occupying more favorable adsorption sites within the supercages(SCs),while ethyl sulfide shifts outward to other sites within other SCs.In addition,the diffusion performance of adsorbent is related to the adsorption energy.The lower the adsorption energy,the weaker the diffusion ability.Meanwhile,the diffusion performance of adsorbates is better at high temperatures and low adsorption capacity.The effect of temperatu re on the desulfu rization selectivity was determined.A lower temperature is favorable for the adsorption capacity of the two systems and the removal selectivity of sulfides.This study provides fundamental insights into the competitive adsorption and diffusion mechanisms among sulfides,mercaptans and olefins,offering theoretical guidance for adsorbent design and reaction temperature optimization.展开更多
Adsorption rates of n-hexane on the 5A zeolite at 100 to 300 ℃ and 0.01 to 10 kPa are determined by an intelligent gravimetric analyzer （IGA-100）, and the adsorption diffusion performance of n-hexane on 5A zeolite ...Adsorption rates of n-hexane on the 5A zeolite at 100 to 300 ℃ and 0.01 to 10 kPa are determined by an intelligent gravimetric analyzer （IGA-100）, and the adsorption diffusion performance of n-hexane on 5A zeolite pellets with different secondary pore distributions is analyzed. The results indicate that 5A-1 and 5A-6 zeolites have similar micropore and mesopore size distribution, while the 5A-6 zeolite has a larger secondary pore volume when the pore diameter is between 0.1 and 1 μm and more secondary pores when the pore diameter is less than 0.01 μm. The effective diffusion coefficient of nhexane on the 5A-6 zeolite pellet is 10 ^-6 to 10 4 cm^2/s, about 2 to 5 times higher than that on the 5A-1 zeolite. The effective diffusion coefficient of n-hexane on the 5A-1 zeolite pellet improves from 5 × 10^-7 to 2 × 10 6cm^2/s when the temperature increases from 100 to 300 ~C. However, the effective diffusion coefficient of n-hexane on the 5A-6 zeolite remains almost unchanged at different temperatures. The molecular average free path of n-hexane decreases from 627.15-963.28 to 0.63-0, 96 Ixm with the adsorption pressure increasing from 0.01 to 10 kPa. Such a flee path is close to the secondary pore diameter, resulting in significant Knudsen diffusion in the secondary pores. Thus, the effective diffusion coefficient of n-hexane on the 5A zeolite pellets increases before 1 kPa and decreases after 1 kPa.展开更多
In this study,chitosan(CS)was combined with microcrystalline cellulose(MCC)to fabricate composite hydrogel beads.These beads were further modified through blending and grafting with polyethyleneimine(PEI)to develop ch...In this study,chitosan(CS)was combined with microcrystalline cellulose(MCC)to fabricate composite hydrogel beads.These beads were further modified through blending and grafting with polyethyleneimine(PEI)to develop chitosan/microcrystalline cellulose@polyethyleneimine(CS/MCC@PEI)composite gel spheres for the efficient adsorption of diclofenac sodium(DS)from aqueous solutions.The adsorbent was characterized using scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),X-ray pho-toelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).The CS/MCC@PEI composite exhibited a spherical morphology with a porous structure,abundant surface functional groups,and a high adsorption capac-ity of 274.84 mg/g for DS.Kinetic studies revealed that the adsorption process followed the pseudo-second-order model,dominated by physical adsorption,with both surface and internal diffusion influencing the adsorption rate.The Freundlich isotherm model best described the adsorption behavior,indicating multilayer adsorption on heterogeneous surfaces.Environmental adaptability tests demonstrated minimal interference from co-existing anions and humic acid,while regeneration experiments confirmed excellent reusability(>77%removal after five cycles).The adsorption mechanism involved electrostatic interactions and hydrogen bonding between the hydroxyl/amino groups of the composite and DS.These findings highlight the potential of CS/MCC@PEI as a cost-effective and sustainable adsorbent for DS removal from water.展开更多
The flotation separation of argentite from sphalerite using ammonium dibutyl dithiophosphate(ADD)was studied.Molecular simulation(MS)calculation shows that ADD is chemisorbed on argentite and sphalerite surface in the...The flotation separation of argentite from sphalerite using ammonium dibutyl dithiophosphate(ADD)was studied.Molecular simulation(MS)calculation shows that ADD is chemisorbed on argentite and sphalerite surface in the form of S—P bond.The ADD adsorption on argentite and sphalerite surface in Ag^(+)system was revealed by ICP,Zeta potential and XPS analyses.It is shown that the dissolved Ag^(+)from argentite surface can be absorbed on sphalerite surface in the form of silver hydroxide,and AgOH hydrophilic colloid prevents the adsorption of ADD on sphalerite surface.The ADD adsorption on argentite and sphalerite surface in the pulp containing silver and zinc ions was revealed by adsorption capacity and surface wettability analyses.It is shown that the combined Zn(OH)_(2) and AgOH hydrophilic colloid leads to greater ADD adsorption capacity on argentite surface and stronger surface hydrophobicity than sphalerite.Flotation tests demonstrate that ADD enables efficient separation of argentite from sphalerite in the pulp containing silver and zinc ions.展开更多
This study presents a thorough investigation into the use of single and twin-tailed cationic and anionic surfactant-modified chitosan(SMCS)hydrogel beads as effective adsorbents for the elimination of hazardous polycy...This study presents a thorough investigation into the use of single and twin-tailed cationic and anionic surfactant-modified chitosan(SMCS)hydrogel beads as effective adsorbents for the elimination of hazardous polycyclic aromatic hydrocarbons(PAHs)from aqueous solutions.The Chitosan(CS)hydrogel beads were modified with single/twin-tailed anionic surfactants,sodium dodecyl sulfate(SDS)and sodium bis(2-ethylhexyl)sulfosuccinate(AOT),and cationic surfactants,dodecyltrimethylammonium bromide(DTAB)and didodecyldimethylammonium bromide(DDAB),to enhance their adsorption capacity of PAHs.The CS and SMCS beads were evaluated for their structural,mechanical,and adsorption properties using a range of techniques,including infrared spectroscopy(IR),energy-dispersive X-ray spectroscopy(EDX),rheometry,and field emission scanning electron microscopy(FESEM).Adsorption experiments of naphthalene(Nap),acenaphthene(Ace),and phenanthrene(Phe)on SMCS beads demonstrate that they have significantly higher adsorption capacities than CS beads,due to increase in hydrophobic interactions.Adsorption capacity followed the trend,Phen>Ace>Nap for all the beads revealing that twin-tailed SMCS bead possess much higher adsorption capacities(Qmax)compared to single-tailed SMCS beads.For twin tailed surfactants,the maximum adsorption capacities for Nap,Ace and Phe varied as CS-AOT(CS-DDAB):430.0(323.8)611.60(538.18)633.39(536.99)mg/g respectively,outperforming other reported hydrogel beads.The study highlights the simplicity,eco-friendliness,and enhanced performance of surfactant modification for developing high-efficiency adsorbents,paving the way for cost-effective solutions in water re-mediation.展开更多
In order to address the evolving emission characteristics of oxygenated volatile organic compounds(OVOCs),it is essential to develop adsorbent materials specifically designed for the efficient adsorption of OVOCs with...In order to address the evolving emission characteristics of oxygenated volatile organic compounds(OVOCs),it is essential to develop adsorbent materials specifically designed for the efficient adsorption of OVOCs with large kinetic diameters.In this study,we used co-pyrolysis to prepare a series of graded porous carbon materials with well-developed micropores by adjusting the doping ratios of root nodules and pretreated cellulose.The material with root nodule to cellulose mass ratio of 1:1(TCC-RN-1)exhibited the highest saturated adsorption capacity for butyl acetate(834 mg/g).This can be attributed to enhanced pore size distribution from nodule doping,which facilitates the development of a micropore-graded structure.Additionally,the nodules acted as auxiliary activating agents that enhanced the KOH micropore regulation effect during the activation stage,resulting in the highest micropore volume(0.863 cm^(3)/g).The doping of root nodules facilitated the formation of additional defects on the surface of the porous carbon material,leading to a more disordered arrangement that improved pollutant adsorption.Furthermore,TCC-RN-1 demonstrated good thermal stability in an air atmosphere,main-taining a butyl acetate adsorption capacity exceeding 95%after five adsorption-desorption cycles.This indicates its favorable potential for industrial applications.展开更多
Porous carbon microspheres are widely regarded as a superior CO_(2) adsorbent due to their exceptional efficiency and affordability.However,better adsorption performance is very attractive for porous carbon microspher...Porous carbon microspheres are widely regarded as a superior CO_(2) adsorbent due to their exceptional efficiency and affordability.However,better adsorption performance is very attractive for porous carbon microspheres.And modification of the pore structure is one of the effective strategies.In this study,multi-cavity mesoporous carbon microspheres were successfully synthesized by the synergistic method of soft and hard templates,during which a phenolic resin with superior thermal stability was employed as the carbon precursor and a mixture of silica sol and F108 as the mesoporous template.Carbon microspheres with multi-cavity mesoporous structures were prepared,and all the samples showed highly even mesopores,with diameters around 12 nm.The diameter of these microspheres decreased from 396.8 nm to about 182.5 nm with the increase of silica sol.After CO_(2) activation,these novel carbon microspheres(APCF0.5-S1.75)demonstrated high specific surface area(983.3 m^(2)/g)and remarkable CO_(2) uptake of 4.93 mmol/g at 0℃ and1 bar.This could be attributed to the unique multi-cavity structure,which offers uniform mesoporous pore channels,minimal CO_(2) transport of and a greater number of active sites for CO_(2) adsorption.展开更多
Human motion modeling is a core technology in computer animation,game development,and humancomputer interaction.In particular,generating natural and coherent in-between motion using only the initial and terminal frame...Human motion modeling is a core technology in computer animation,game development,and humancomputer interaction.In particular,generating natural and coherent in-between motion using only the initial and terminal frames remains a fundamental yet unresolved challenge.Existing methods typically rely on dense keyframe inputs or complex prior structures,making it difficult to balance motion quality and plausibility under conditions such as sparse constraints,long-term dependencies,and diverse motion styles.To address this,we propose a motion generation framework based on a frequency-domain diffusion model,which aims to better model complex motion distributions and enhance generation stability under sparse conditions.Our method maps motion sequences to the frequency domain via the Discrete Cosine Transform(DCT),enabling more effective modeling of low-frequency motion structures while suppressing high-frequency noise.A denoising network based on self-attention is introduced to capture long-range temporal dependencies and improve global structural awareness.Additionally,a multi-objective loss function is employed to jointly optimize motion smoothness,pose diversity,and anatomical consistency,enhancing the realism and physical plausibility of the generated sequences.Comparative experiments on the Human3.6M and LaFAN1 datasets demonstrate that our method outperforms state-of-the-art approaches across multiple performance metrics,showing stronger capabilities in generating intermediate motion frames.This research offers a new perspective and methodology for human motion generation and holds promise for applications in character animation,game development,and virtual interaction.展开更多
The equivalence between multilayered barriers regarding diffusion and adsorption was studied. The bottom boundary of the liner system is defined by assuming concentration continuous and flux continuous conditions of t...The equivalence between multilayered barriers regarding diffusion and adsorption was studied. The bottom boundary of the liner system is defined by assuming concentration continuous and flux continuous conditions of the contaminant between the bottom liner layer and the underlying soil. Five different liner systems were compared in terms of solute breakthrough time. The results of the analysis showed that breakthrough time of the hydrophobic organic compounds for a 2-meter-thick compacted clay liner （CCL） could be 3-4 orders of magnitude is greater than the breakthrough time for a geosynthetic clay liner （GCL） composite liner. The GM/GCL and GM/CCL composite liner systems provide a better diffusion barrier for the hydrophilic organic compounds than that for the hydrophobic compounds due to their different Henry＇s coefficient. The calculated breakthrough times of the organic contaminants for the Chinese standard liner systems were found to be generally greater than those for the GCL alternatives, for the specific conditions examined. If the distribution coefficient increases to 2.8 for the hydrophobic compounds or 1.0 for the hydrophilic compounds, the thickness of the attenuation layer needed to achieve the same breakthrough time as the standard liner systems can be reduced by a factor of about 1.9-2.4. As far as diffusive and adsorption contaminant transport are concerned, GM or GCL is less effective than CCL.展开更多
Metal hydrides with high hydrogen density provide promising hydrogen storage paths for hydrogen transportation.However,the requirement of highly pure H_(2)for re-hydrogenation limits its wide application.Here,amorphou...Metal hydrides with high hydrogen density provide promising hydrogen storage paths for hydrogen transportation.However,the requirement of highly pure H_(2)for re-hydrogenation limits its wide application.Here,amorphous Al_(2)O_(3)shells(10 nm)were deposited on the surface of highly active hydrogen storage material particles(MgH_(2)-ZrTi)by atomic layer deposition to obtain MgH_(2)-ZrTi@Al_(2)O_(3),which have been demonstrated to be air stable with selective adsorption of H_(2)under a hydrogen atmosphere with different impurities(CH_(4),O_(2),N_(2),and CO_(2)).About 4.79 wt%H_(2)was adsorbed by MgH_(2)-ZrTi@10nmAl_(2)O_(3)at 75℃under 10%CH_(4)+90%H_(2)atmosphere within 3 h with no kinetic or density decay after 5 cycles(~100%capacity retention).Furthermore,about 4 wt%of H_(2)was absorbed by MgH_(2)-ZrTi@10nmAl_(2)O_(3)under 0.1%O_(2)+0.4%N_(2)+99.5%H_(2)and 0.1%CO_(2)+0.4%N_(2)+99.5%H_(2)atmospheres at 100℃within 0.5 h,respectively,demonstrating the selective hydrogen absorption of MgH_(2)-ZrTi@10nmAl_(2)O_(3)in both oxygen-containing and carbon dioxide-containing atmospheres hydrogen atmosphere.The absorption and desorption curves of MgH_(2)-ZrTi@10nmAl_(2)O_(3)with and without absorption in pure hydrogen and then in 21%O_(2)+79%N_(2)for 1 h were found to overlap,further confirming the successful shielding effect of Al_(2)O_(3)shells against O_(2)and N_(2).The MgH_(2)-ZrTi@10nmAl_(2)O_(3)has been demonstrated to be air stable and have excellent selective hydrogen absorption performance under the atmosphere with CH_(4),O_(2),N_(2),and CO_(2).展开更多
As a potential adsorption material,it is still a challenge for activated carbon fiber(ACF)in efficient adsorption of ethanol due to its nonpolar surface,which is mainly emitted from the grain drying industry.This stud...As a potential adsorption material,it is still a challenge for activated carbon fiber(ACF)in efficient adsorption of ethanol due to its nonpolar surface,which is mainly emitted from the grain drying industry.This study prepared surface polarity-modified ACF using the heteroatom doping method.The modified ACF possessed a richer array of strongly polar oxygen/nitrogen-containing functional groups(primarily phenolic hydroxyl and lactone groups),a larger specific surface are1,and a more developed micropore structure.The adsorption capacities of ethanol for O-ACF and N-ACF were 4.110 mmol/g and 1.698 mmol/g,respectively,which were 11.3 times and 4.7 times those of unmodified ACF.This was a significant improvement over our previous work(0.363 mmol/g).The improvement of adsorption capacity for the N-ACF was mainly due to the higher specific surface are1,greater number of micropores(more adsorption sites)and abundant existence of defects,whereas,for O-ACF,the improvement mainly relied on the abundant presence of oxygen-containing functional groups on the surface.However,water had a negative effect on the adsorption of ethanol for the modified ACF due to competitive adsorption and the disappearance of capillary condensation.It was further revealed that the adsorption process of ethanol and water was quite different.It obeyed the linear driving force(LDF)model for ethanol adsorption,however,the intraparticle diffusion(IPD)model for water adsorption.展开更多
In this work, the adsorption and diffusion behavior of nitrate ions into polycationic P（DMAEMA/HEMA） hydrogels is analyzed. Experimental results indicated that nitrate ions can be removed efficiently from aqueous so...In this work, the adsorption and diffusion behavior of nitrate ions into polycationic P（DMAEMA/HEMA） hydrogels is analyzed. Experimental results indicated that nitrate ions can be removed efficiently from aqueous solutions. Adsorption isotherm of gels was well according to the Langmuir and Langmuir-Freundlich models. At the same time, the diffusion behavior of nitrate ions from P（DMAEMA/HEMA） hydrogels was investigated. The diffusion coefficients are strongly influenced by the changes of temperature and pH value of solutions. At the same time, D does not depend on the gels cross-linking ratio and initial solute concentration.展开更多
Para-xylene was chosen as the probe molecule to study adsorption thermodynamics and diffusion kinetics on NaY zeolite and composite structured NaY zeolite synthesized by in-situ crystallization from kaolin microsphere...Para-xylene was chosen as the probe molecule to study adsorption thermodynamics and diffusion kinetics on NaY zeolite and composite structured NaY zeolite synthesized by in-situ crystallization from kaolin microsphere(designated as Na Y/kaolin composites) separately, using a high precision intelligent gravimetric analyzer(IGA). The adsorption isotherms showed normal Langmuir type-Ⅰ behaviors. The increased adsorption heat with an increasing p-xylene coverage supported a mechanism of phase transition, diffusion and re-arrangement of p-xylene molecules during the adsorption process. The rearrangement seemed to be most pronounced at an adsorption loading of 2.13 and 2.29 mmol/g for Na Y zeolite and Na Y/kaolin composites respectively. Compared with Na Y zeolite, a 2—3 times higher in the diffusion coefficient of p-xylene was observed on Na Y/kaolin composites when the pressure was more than 50 Pa. Temperature-programmed desorption(TPD) of p-xylene on two samples from room temperature to 450 ℃ at a special loading has also been investigated by IGA. Results showed only single desorption peak appeared for Na Y zeolite, indicating that adsorption can only occur in the super-cage structure. Comparably, there were two different peaks for in-situ synthesized Na Y zeolite, corresponding to the two thermo desorption processes in both super-cage structure and the channels provided by kaolin, respectively.Key words:展开更多
The diffusion and adsorption behaviors of benzene and propylene in zeolites MFI, MWW and BEA have been studied by molecular dynamics（MD） and grand canonical Monte Carlo（GCMC） simulations. The diffusion coefficient...The diffusion and adsorption behaviors of benzene and propylene in zeolites MFI, MWW and BEA have been studied by molecular dynamics（MD） and grand canonical Monte Carlo（GCMC） simulations. The diffusion coefficients of benzene and propylene in MFI, MWW and BEA zeolites were calculated by simulating the mean-square displacements（MSD） at 298 and 600 K. Benzene and propylene showed the different adsorption rules in the channels of the three zeolites. For propylene, the molecular loadings decreased in the order： BEA（linear channel）〉BEA （tortuous channel）〉MFI（linear channel）〉MWW（12-membered rings, 12MR channel）〉MFI（tortuous channel）〉MWW （10-membered rings, 10MR channel）; for benzene, the molecular loadings decreased in the order： BEA（linear chan-nel）〉BEA（tortuous channel）〉MWW（12MR channel）〉MFI（linear channel）〉MFI（tortuous channel）〉MWW（10MR channel）. Besides, the adsorption isotherms of benzene and propylene in the three zeolites at 298 and 443 K were simulated. The results show that the different factors influenced the molecular adsorption at various temperatures and pressures, leading to the different rules for the adsorption of benzene and propylene molecules in the zeolites. At a low pressure, the unfavorable energy would make the loadings of propylene lower than those of benzene. When pressure was higher than 0.25 kPa, the adsorption of benzene in MFI would nearly reach saturation.展开更多
To improve the understanding of the transport mechanism in shale gas reservoirs and build a theoretical basic for further researches on productivity evaluation and efficient exploitation, various gas transport mechani...To improve the understanding of the transport mechanism in shale gas reservoirs and build a theoretical basic for further researches on productivity evaluation and efficient exploitation, various gas transport mechanisms within a shale gas reservoir exploited by a horizontal well were thoroughly investigated, which took diffusion, adsorption/desorption and Darcy flow into account. The characteristics of diffusion in nano-scale pores in matrix and desorption on the matrix surface were both considered in the improved differential equations for seepage flow. By integrating the Langmuir isotherm desorption items into the new total dimensionless compression coefficient in matrix, the transport function and seepage flow could be formalized, simplified and consistent with the conventional form of diffusion equation. Furthermore, by utilizing the Laplace change and Sethfest inversion changes, the calculated results were obtained and further discussions indicated that transfer mechanisms were influenced by diffusion, adsorption/desorption. The research shows that when the matrix permeability is closed to magnitude of 10^-9D, the matrix flow only occurs near the surfacial matrix; as to the actual production, the central matrix blocks are barely involved in the production; the closer to the surface of matrix, the lower the pressure is and the more obvious the diffusion effect is; the behavior of adsorption/desorption can increase the matrix flow rate significantly and slow down the pressure of horizontal well obviously.展开更多
First-principle calculations,especially by the density functio nal theory(DFT),is used to study the structure and properties of oxygen/metal interfaces.Adsorption of oxygen molecules or atoms on metal surfaces plays a...First-principle calculations,especially by the density functio nal theory(DFT),is used to study the structure and properties of oxygen/metal interfaces.Adsorption of oxygen molecules or atoms on metal surfaces plays a key role in surface science and technology.This review is dedicated to the adsorption of oxygen molecules or atoms on metal surfaces and diffusion behavior from first-principle investigation.We hope that this review can provide some useful contributions to understa nd the study of adsorption properties and diffusion behavior on a metal surface at an atomic-scale,especially for those interested in catalytic oxidation and application of corrosion.展开更多
In the article the Grand Canonical Monte Carlo （GCMC）, molecular dynamics（MD）, and kinetic Monte Carlo （KMC） simulations with particular focus on ascertaining the loading dependence of benzene diffusion in the z...In the article the Grand Canonical Monte Carlo （GCMC）, molecular dynamics（MD）, and kinetic Monte Carlo （KMC） simulations with particular focus on ascertaining the loading dependence of benzene diffusion in the zeolite were performed. First, a realistic representation of the structure of the sorbate-sorbent system was obtained based on GCMC simulation. The simulation clearly shows the characteristics of the adsorption sites of the benzene-NaY system, from which two kinds of preferably adsorbing sites for benzene molecules, called SⅡ and W sites, are identified. The structure thus obtained was then used as a basis for KMC and MD simulations. A compara-tive study by introducing and comparing two different mechanisms underlying jump diffusion in the zeolite of in-terest shows that the.MS diffusivity values predicted by the KMC and MD methods are fairly close to each other,leading to the conclusion that for benzene diffusion in NaY, the SⅡ→W→SⅡ jumps of benzene molecules are dominated,while the W→Wjumps do not exist in the process. These findings provide further support to our previous conclusion about the absence of the W→W jumps in the process of benzene diffusion in NaY. Finally, to relations, for predicting the self-and MS difthsivities were derived and found to be in fair agreement with the KMC and MD simulations.展开更多
First-principles calculations based on density functional theory are used to investigate the adsorptions and diffusions of carbon atoms on the surface and in the subsurface of Co （200）. The preferred site for the ca...First-principles calculations based on density functional theory are used to investigate the adsorptions and diffusions of carbon atoms on the surface and in the subsurface of Co （200）. The preferred site for the carbon atom on the surface is the hollow site, and the preferred site in the subsurface is the octahedral site. There is charge transfer from the surface to the adsorbed carbon atom, and for the most favorable adsorbed structure the charge transfer is largest. Moreover, the energy barriers for the diffusions of carbon atoms on the surface and from the surface into the subsurface and then back to the surface are calculated in detail. The results indicate that the energy barrier for the diffusion of carbon atoms on the surface is comparable to that from the subsurface to the surface. The results imply that both the direct surface nucleation and the surface segregation from Co bulk can be observed in the chemical vapor deposition growth of graphene on Co （200） substrate, which can gain a new insight into the growth mechanism of graphene.展开更多
The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree ...The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree of damage is different, were selected from Tongchun, Qilin, and Pingdingshan mines. Using a series of experiments in an electrostatic field, we analyzed the characteristics of gas adsorption and diffusion in tectonic coal. We found that gas adsorption in coal conforms to the Langmuir equation in an electrostatic field. Both the depth of the adsorption potential well and the coal molecular electroneg- ativity increases under the action of an electrostatic field. A Joule heating effect was caused by changing the coal-gas system conductivity in an electrostatic field. The quantity of gas adsorbed and AP result from competition between the depth of the adsorption potential well, the coal molecular electronegativ- ity, and the Joule heating effect. △P peaks when the three factors control behavior equally. Compared with anthracite, the impact of the electrostatic field on the gas diffusion capacity of middle and high rank coals is greater. Compared with the original coal, the gas adsorption quantity,△P, and the gas diffusion capacity of tectonic coal are greater in an electrostatic field. In addition, the smaller the particle size of tectonic coal, the larger the△P.展开更多
基金support from the National Natural Science Foundation of China (22325808,U22B20140,22021004)。
文摘An in-depth understanding of the competition mechanism between olefins and different types of sulfides in gasoline is essential to improve the desulfurization selectivity of the adsorption desulfurization process(ADS).In this study,the competitive adsorption and diffusion mechanism of two systems,diethyl sulfide/cyclohexene and n-butyl mercaptan/cyclohexene,with different adsorption amounts in siliceous faujasite zeolite(FAU) were investigated by Monte Carlo(MC) and molecular dynamics(MD).The systems exhibited a two-stage loading-dependent competitive adsorption and diffusion mechanism,with an inflection point of 32 molecule/UC(moleculers per microcoulomb).Before the inflection point(4-32molecule/UC),the competition mechanism of the two systems was the "optimal-displacement" mechanism.After the inflection point,the mechanism of the diethyl sulfide/cyclohexene changed to "relocation-displacement",while that of the n-butyl mercaptan/cyclohexene system changed to "dominantdisplacement".Compared to ether functional groups,the alcohol functional group has higher polarity and stronger adsorption stability,thus occupying more favorable adsorption sites within the supercages(SCs),while ethyl sulfide shifts outward to other sites within other SCs.In addition,the diffusion performance of adsorbent is related to the adsorption energy.The lower the adsorption energy,the weaker the diffusion ability.Meanwhile,the diffusion performance of adsorbates is better at high temperatures and low adsorption capacity.The effect of temperatu re on the desulfu rization selectivity was determined.A lower temperature is favorable for the adsorption capacity of the two systems and the removal selectivity of sulfides.This study provides fundamental insights into the competitive adsorption and diffusion mechanisms among sulfides,mercaptans and olefins,offering theoretical guidance for adsorbent design and reaction temperature optimization.
基金the Yunnan Engineering Research Center Innovation Ability Construction and Enhancement Projects[2023-XMDJ-00617107]Natural Science Foundation of Yunnan Province[202401AS070646]Natural Science Foundation of Jiangxi Provincial[20232BAB214038].
文摘Despite progress in suppressing polysulfide shuttling,this challenge persists in lithium-sulfur battery commercialization.While existing strategies emphasize polysulfide adsorption and catalytic conversion,the critical role of diffusion kinetics in conversion–deposition processes remains underexplored.We design an MXene-based array architecture integrating 2D structural advantages and strong polysulfide affinity to regulate diffusion pathways.Combined experimental and multiscale computational studies reveal diffusion-mediated conversion-deposition dynamics.The sodium alginate-constructed MXene array enables three synergistic mechanisms:(1)Enhanced ion/electron delocalization reduces diffusion barriers,(2)Continuous ion transport channels facilitate charge transfer,and(3)Exposed polar surfaces promote polysulfide aggregation/conversion.Synchrotron X-ray tomography coupled with comprehensive electrochemical analyses reveals distinct mechanistic differences between conversion and deposition processes arising from diffusion heterogeneity.In situ characterization techniques combined with DFT simulation calculations demonstrate that diffusion kinetics exerts differential regulatory effects on these coupled electrochemical processes,exhibiting particular sensitivity toward the deposition mechanism.This work provides fundamental insights that reshape our understanding of diffusion-mediated phase transformation in complex multi-step electrochemical systems,offering new perspectives for advanced electrode architecture design in next-generation energy storage technologies.
基金The National Natural Science Foundation of China ( No.20876074)
文摘Adsorption rates of n-hexane on the 5A zeolite at 100 to 300 ℃ and 0.01 to 10 kPa are determined by an intelligent gravimetric analyzer （IGA-100）, and the adsorption diffusion performance of n-hexane on 5A zeolite pellets with different secondary pore distributions is analyzed. The results indicate that 5A-1 and 5A-6 zeolites have similar micropore and mesopore size distribution, while the 5A-6 zeolite has a larger secondary pore volume when the pore diameter is between 0.1 and 1 μm and more secondary pores when the pore diameter is less than 0.01 μm. The effective diffusion coefficient of nhexane on the 5A-6 zeolite pellet is 10 ^-6 to 10 4 cm^2/s, about 2 to 5 times higher than that on the 5A-1 zeolite. The effective diffusion coefficient of n-hexane on the 5A-1 zeolite pellet improves from 5 × 10^-7 to 2 × 10 6cm^2/s when the temperature increases from 100 to 300 ~C. However, the effective diffusion coefficient of n-hexane on the 5A-6 zeolite remains almost unchanged at different temperatures. The molecular average free path of n-hexane decreases from 627.15-963.28 to 0.63-0, 96 Ixm with the adsorption pressure increasing from 0.01 to 10 kPa. Such a flee path is close to the secondary pore diameter, resulting in significant Knudsen diffusion in the secondary pores. Thus, the effective diffusion coefficient of n-hexane on the 5A zeolite pellets increases before 1 kPa and decreases after 1 kPa.
基金supported by the Open Project Funding of Key Laboratory of Intelligent Health Perception and Ecological Restoration of Rivers and Lakes,Ministry of Education,Hubei University of Technology(No.HGKFZ03).
文摘In this study,chitosan(CS)was combined with microcrystalline cellulose(MCC)to fabricate composite hydrogel beads.These beads were further modified through blending and grafting with polyethyleneimine(PEI)to develop chitosan/microcrystalline cellulose@polyethyleneimine(CS/MCC@PEI)composite gel spheres for the efficient adsorption of diclofenac sodium(DS)from aqueous solutions.The adsorbent was characterized using scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),X-ray pho-toelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).The CS/MCC@PEI composite exhibited a spherical morphology with a porous structure,abundant surface functional groups,and a high adsorption capac-ity of 274.84 mg/g for DS.Kinetic studies revealed that the adsorption process followed the pseudo-second-order model,dominated by physical adsorption,with both surface and internal diffusion influencing the adsorption rate.The Freundlich isotherm model best described the adsorption behavior,indicating multilayer adsorption on heterogeneous surfaces.Environmental adaptability tests demonstrated minimal interference from co-existing anions and humic acid,while regeneration experiments confirmed excellent reusability(>77%removal after five cycles).The adsorption mechanism involved electrostatic interactions and hydrogen bonding between the hydroxyl/amino groups of the composite and DS.These findings highlight the potential of CS/MCC@PEI as a cost-effective and sustainable adsorbent for DS removal from water.
基金the support from the National Key Research and Development Program of China (No. 2022YFC2904504)the Science and Technology Research Project of Jiangxi Provincial Department of Education, China (No. GJJ2200864)the Gansu Provincial Key Research and Development Project, China (No. 22YF7GA073)。
文摘The flotation separation of argentite from sphalerite using ammonium dibutyl dithiophosphate(ADD)was studied.Molecular simulation(MS)calculation shows that ADD is chemisorbed on argentite and sphalerite surface in the form of S—P bond.The ADD adsorption on argentite and sphalerite surface in Ag^(+)system was revealed by ICP,Zeta potential and XPS analyses.It is shown that the dissolved Ag^(+)from argentite surface can be absorbed on sphalerite surface in the form of silver hydroxide,and AgOH hydrophilic colloid prevents the adsorption of ADD on sphalerite surface.The ADD adsorption on argentite and sphalerite surface in the pulp containing silver and zinc ions was revealed by adsorption capacity and surface wettability analyses.It is shown that the combined Zn(OH)_(2) and AgOH hydrophilic colloid leads to greater ADD adsorption capacity on argentite surface and stronger surface hydrophobicity than sphalerite.Flotation tests demonstrate that ADD enables efficient separation of argentite from sphalerite in the pulp containing silver and zinc ions.
基金the Department of Science and Technology(DST),Govt.of India for providing funds under the FIST program and PURSE grant vide No.SR/PURSE/2020/31 to the department of Chemistry,University of Kashmir.
文摘This study presents a thorough investigation into the use of single and twin-tailed cationic and anionic surfactant-modified chitosan(SMCS)hydrogel beads as effective adsorbents for the elimination of hazardous polycyclic aromatic hydrocarbons(PAHs)from aqueous solutions.The Chitosan(CS)hydrogel beads were modified with single/twin-tailed anionic surfactants,sodium dodecyl sulfate(SDS)and sodium bis(2-ethylhexyl)sulfosuccinate(AOT),and cationic surfactants,dodecyltrimethylammonium bromide(DTAB)and didodecyldimethylammonium bromide(DDAB),to enhance their adsorption capacity of PAHs.The CS and SMCS beads were evaluated for their structural,mechanical,and adsorption properties using a range of techniques,including infrared spectroscopy(IR),energy-dispersive X-ray spectroscopy(EDX),rheometry,and field emission scanning electron microscopy(FESEM).Adsorption experiments of naphthalene(Nap),acenaphthene(Ace),and phenanthrene(Phe)on SMCS beads demonstrate that they have significantly higher adsorption capacities than CS beads,due to increase in hydrophobic interactions.Adsorption capacity followed the trend,Phen>Ace>Nap for all the beads revealing that twin-tailed SMCS bead possess much higher adsorption capacities(Qmax)compared to single-tailed SMCS beads.For twin tailed surfactants,the maximum adsorption capacities for Nap,Ace and Phe varied as CS-AOT(CS-DDAB):430.0(323.8)611.60(538.18)633.39(536.99)mg/g respectively,outperforming other reported hydrogel beads.The study highlights the simplicity,eco-friendliness,and enhanced performance of surfactant modification for developing high-efficiency adsorbents,paving the way for cost-effective solutions in water re-mediation.
基金supported by the National Natural Science Foundation of China(No.52370112).
文摘In order to address the evolving emission characteristics of oxygenated volatile organic compounds(OVOCs),it is essential to develop adsorbent materials specifically designed for the efficient adsorption of OVOCs with large kinetic diameters.In this study,we used co-pyrolysis to prepare a series of graded porous carbon materials with well-developed micropores by adjusting the doping ratios of root nodules and pretreated cellulose.The material with root nodule to cellulose mass ratio of 1:1(TCC-RN-1)exhibited the highest saturated adsorption capacity for butyl acetate(834 mg/g).This can be attributed to enhanced pore size distribution from nodule doping,which facilitates the development of a micropore-graded structure.Additionally,the nodules acted as auxiliary activating agents that enhanced the KOH micropore regulation effect during the activation stage,resulting in the highest micropore volume(0.863 cm^(3)/g).The doping of root nodules facilitated the formation of additional defects on the surface of the porous carbon material,leading to a more disordered arrangement that improved pollutant adsorption.Furthermore,TCC-RN-1 demonstrated good thermal stability in an air atmosphere,main-taining a butyl acetate adsorption capacity exceeding 95%after five adsorption-desorption cycles.This indicates its favorable potential for industrial applications.
基金supported by the National Key R&D Program of China(No.2021YFB3501102).
文摘Porous carbon microspheres are widely regarded as a superior CO_(2) adsorbent due to their exceptional efficiency and affordability.However,better adsorption performance is very attractive for porous carbon microspheres.And modification of the pore structure is one of the effective strategies.In this study,multi-cavity mesoporous carbon microspheres were successfully synthesized by the synergistic method of soft and hard templates,during which a phenolic resin with superior thermal stability was employed as the carbon precursor and a mixture of silica sol and F108 as the mesoporous template.Carbon microspheres with multi-cavity mesoporous structures were prepared,and all the samples showed highly even mesopores,with diameters around 12 nm.The diameter of these microspheres decreased from 396.8 nm to about 182.5 nm with the increase of silica sol.After CO_(2) activation,these novel carbon microspheres(APCF0.5-S1.75)demonstrated high specific surface area(983.3 m^(2)/g)and remarkable CO_(2) uptake of 4.93 mmol/g at 0℃ and1 bar.This could be attributed to the unique multi-cavity structure,which offers uniform mesoporous pore channels,minimal CO_(2) transport of and a greater number of active sites for CO_(2) adsorption.
基金supported by the National Natural Science Foundation of China(Grant No.72161034).
文摘Human motion modeling is a core technology in computer animation,game development,and humancomputer interaction.In particular,generating natural and coherent in-between motion using only the initial and terminal frames remains a fundamental yet unresolved challenge.Existing methods typically rely on dense keyframe inputs or complex prior structures,making it difficult to balance motion quality and plausibility under conditions such as sparse constraints,long-term dependencies,and diverse motion styles.To address this,we propose a motion generation framework based on a frequency-domain diffusion model,which aims to better model complex motion distributions and enhance generation stability under sparse conditions.Our method maps motion sequences to the frequency domain via the Discrete Cosine Transform(DCT),enabling more effective modeling of low-frequency motion structures while suppressing high-frequency noise.A denoising network based on self-attention is introduced to capture long-range temporal dependencies and improve global structural awareness.Additionally,a multi-objective loss function is employed to jointly optimize motion smoothness,pose diversity,and anatomical consistency,enhancing the realism and physical plausibility of the generated sequences.Comparative experiments on the Human3.6M and LaFAN1 datasets demonstrate that our method outperforms state-of-the-art approaches across multiple performance metrics,showing stronger capabilities in generating intermediate motion frames.This research offers a new perspective and methodology for human motion generation and holds promise for applications in character animation,game development,and virtual interaction.
基金supported by the National Science Fundfor Distinguished Young Scholars (No. 50425825)the National Natural Science Foundation of China (No.50538080)
文摘The equivalence between multilayered barriers regarding diffusion and adsorption was studied. The bottom boundary of the liner system is defined by assuming concentration continuous and flux continuous conditions of the contaminant between the bottom liner layer and the underlying soil. Five different liner systems were compared in terms of solute breakthrough time. The results of the analysis showed that breakthrough time of the hydrophobic organic compounds for a 2-meter-thick compacted clay liner （CCL） could be 3-4 orders of magnitude is greater than the breakthrough time for a geosynthetic clay liner （GCL） composite liner. The GM/GCL and GM/CCL composite liner systems provide a better diffusion barrier for the hydrophilic organic compounds than that for the hydrophobic compounds due to their different Henry＇s coefficient. The calculated breakthrough times of the organic contaminants for the Chinese standard liner systems were found to be generally greater than those for the GCL alternatives, for the specific conditions examined. If the distribution coefficient increases to 2.8 for the hydrophobic compounds or 1.0 for the hydrophilic compounds, the thickness of the attenuation layer needed to achieve the same breakthrough time as the standard liner systems can be reduced by a factor of about 1.9-2.4. As far as diffusive and adsorption contaminant transport are concerned, GM or GCL is less effective than CCL.
基金supported by the National Natural Science Foundation of China(22175136)the State Key Laboratory of Electrical Insulation and Power Equipment(EIPE23127)the Fundamental Research Funds for the Central Universities(xtr052024009).
文摘Metal hydrides with high hydrogen density provide promising hydrogen storage paths for hydrogen transportation.However,the requirement of highly pure H_(2)for re-hydrogenation limits its wide application.Here,amorphous Al_(2)O_(3)shells(10 nm)were deposited on the surface of highly active hydrogen storage material particles(MgH_(2)-ZrTi)by atomic layer deposition to obtain MgH_(2)-ZrTi@Al_(2)O_(3),which have been demonstrated to be air stable with selective adsorption of H_(2)under a hydrogen atmosphere with different impurities(CH_(4),O_(2),N_(2),and CO_(2)).About 4.79 wt%H_(2)was adsorbed by MgH_(2)-ZrTi@10nmAl_(2)O_(3)at 75℃under 10%CH_(4)+90%H_(2)atmosphere within 3 h with no kinetic or density decay after 5 cycles(~100%capacity retention).Furthermore,about 4 wt%of H_(2)was absorbed by MgH_(2)-ZrTi@10nmAl_(2)O_(3)under 0.1%O_(2)+0.4%N_(2)+99.5%H_(2)and 0.1%CO_(2)+0.4%N_(2)+99.5%H_(2)atmospheres at 100℃within 0.5 h,respectively,demonstrating the selective hydrogen absorption of MgH_(2)-ZrTi@10nmAl_(2)O_(3)in both oxygen-containing and carbon dioxide-containing atmospheres hydrogen atmosphere.The absorption and desorption curves of MgH_(2)-ZrTi@10nmAl_(2)O_(3)with and without absorption in pure hydrogen and then in 21%O_(2)+79%N_(2)for 1 h were found to overlap,further confirming the successful shielding effect of Al_(2)O_(3)shells against O_(2)and N_(2).The MgH_(2)-ZrTi@10nmAl_(2)O_(3)has been demonstrated to be air stable and have excellent selective hydrogen absorption performance under the atmosphere with CH_(4),O_(2),N_(2),and CO_(2).
基金supported by the National Key R&D Program of China(Nos.2022YFB4101500 and 2022YFE0209500)the National Natural Science Foundation of China(Nos.22276191 and 21976177)the Qinghai Province Air Pollution Assessment and Fine Management Support Project,and the University of Chinese Academy of Science.
文摘As a potential adsorption material,it is still a challenge for activated carbon fiber(ACF)in efficient adsorption of ethanol due to its nonpolar surface,which is mainly emitted from the grain drying industry.This study prepared surface polarity-modified ACF using the heteroatom doping method.The modified ACF possessed a richer array of strongly polar oxygen/nitrogen-containing functional groups(primarily phenolic hydroxyl and lactone groups),a larger specific surface are1,and a more developed micropore structure.The adsorption capacities of ethanol for O-ACF and N-ACF were 4.110 mmol/g and 1.698 mmol/g,respectively,which were 11.3 times and 4.7 times those of unmodified ACF.This was a significant improvement over our previous work(0.363 mmol/g).The improvement of adsorption capacity for the N-ACF was mainly due to the higher specific surface are1,greater number of micropores(more adsorption sites)and abundant existence of defects,whereas,for O-ACF,the improvement mainly relied on the abundant presence of oxygen-containing functional groups on the surface.However,water had a negative effect on the adsorption of ethanol for the modified ACF due to competitive adsorption and the disappearance of capillary condensation.It was further revealed that the adsorption process of ethanol and water was quite different.It obeyed the linear driving force(LDF)model for ethanol adsorption,however,the intraparticle diffusion(IPD)model for water adsorption.
文摘In this work, the adsorption and diffusion behavior of nitrate ions into polycationic P（DMAEMA/HEMA） hydrogels is analyzed. Experimental results indicated that nitrate ions can be removed efficiently from aqueous solutions. Adsorption isotherm of gels was well according to the Langmuir and Langmuir-Freundlich models. At the same time, the diffusion behavior of nitrate ions from P（DMAEMA/HEMA） hydrogels was investigated. The diffusion coefficients are strongly influenced by the changes of temperature and pH value of solutions. At the same time, D does not depend on the gels cross-linking ratio and initial solute concentration.
基金financial support from the National Natural Science Foundation of China(20976077,21076100)the National 973 Foundation of China(2007CB216403)
文摘Para-xylene was chosen as the probe molecule to study adsorption thermodynamics and diffusion kinetics on NaY zeolite and composite structured NaY zeolite synthesized by in-situ crystallization from kaolin microsphere(designated as Na Y/kaolin composites) separately, using a high precision intelligent gravimetric analyzer(IGA). The adsorption isotherms showed normal Langmuir type-Ⅰ behaviors. The increased adsorption heat with an increasing p-xylene coverage supported a mechanism of phase transition, diffusion and re-arrangement of p-xylene molecules during the adsorption process. The rearrangement seemed to be most pronounced at an adsorption loading of 2.13 and 2.29 mmol/g for Na Y zeolite and Na Y/kaolin composites respectively. Compared with Na Y zeolite, a 2—3 times higher in the diffusion coefficient of p-xylene was observed on Na Y/kaolin composites when the pressure was more than 50 Pa. Temperature-programmed desorption(TPD) of p-xylene on two samples from room temperature to 450 ℃ at a special loading has also been investigated by IGA. Results showed only single desorption peak appeared for Na Y zeolite, indicating that adsorption can only occur in the super-cage structure. Comparably, there were two different peaks for in-situ synthesized Na Y zeolite, corresponding to the two thermo desorption processes in both super-cage structure and the channels provided by kaolin, respectively.Key words:
基金Supported by the National Natural Science Foundation of China(No.20576012)the Doctoral Fund of Qingdao University of Science and Technology China(No. 0022430)
文摘The diffusion and adsorption behaviors of benzene and propylene in zeolites MFI, MWW and BEA have been studied by molecular dynamics（MD） and grand canonical Monte Carlo（GCMC） simulations. The diffusion coefficients of benzene and propylene in MFI, MWW and BEA zeolites were calculated by simulating the mean-square displacements（MSD） at 298 and 600 K. Benzene and propylene showed the different adsorption rules in the channels of the three zeolites. For propylene, the molecular loadings decreased in the order： BEA（linear channel）〉BEA （tortuous channel）〉MFI（linear channel）〉MWW（12-membered rings, 12MR channel）〉MFI（tortuous channel）〉MWW （10-membered rings, 10MR channel）; for benzene, the molecular loadings decreased in the order： BEA（linear chan-nel）〉BEA（tortuous channel）〉MWW（12MR channel）〉MFI（linear channel）〉MFI（tortuous channel）〉MWW（10MR channel）. Besides, the adsorption isotherms of benzene and propylene in the three zeolites at 298 and 443 K were simulated. The results show that the different factors influenced the molecular adsorption at various temperatures and pressures, leading to the different rules for the adsorption of benzene and propylene molecules in the zeolites. At a low pressure, the unfavorable energy would make the loadings of propylene lower than those of benzene. When pressure was higher than 0.25 kPa, the adsorption of benzene in MFI would nearly reach saturation.
基金Foundation item： Project（PLN1129）supported by Opening Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation （Southwest Petroleum University）, China
文摘To improve the understanding of the transport mechanism in shale gas reservoirs and build a theoretical basic for further researches on productivity evaluation and efficient exploitation, various gas transport mechanisms within a shale gas reservoir exploited by a horizontal well were thoroughly investigated, which took diffusion, adsorption/desorption and Darcy flow into account. The characteristics of diffusion in nano-scale pores in matrix and desorption on the matrix surface were both considered in the improved differential equations for seepage flow. By integrating the Langmuir isotherm desorption items into the new total dimensionless compression coefficient in matrix, the transport function and seepage flow could be formalized, simplified and consistent with the conventional form of diffusion equation. Furthermore, by utilizing the Laplace change and Sethfest inversion changes, the calculated results were obtained and further discussions indicated that transfer mechanisms were influenced by diffusion, adsorption/desorption. The research shows that when the matrix permeability is closed to magnitude of 10^-9D, the matrix flow only occurs near the surfacial matrix; as to the actual production, the central matrix blocks are barely involved in the production; the closer to the surface of matrix, the lower the pressure is and the more obvious the diffusion effect is; the behavior of adsorption/desorption can increase the matrix flow rate significantly and slow down the pressure of horizontal well obviously.
基金supported by the National Key R&D Program of China(Nos.2017YFB0305600 and 2017YFB0306000)the Fok Ying Tung Education Foundation(No.171101)the Youth Innovation Team of Shaanxi Universities(No.2019-2022)。
文摘First-principle calculations,especially by the density functio nal theory(DFT),is used to study the structure and properties of oxygen/metal interfaces.Adsorption of oxygen molecules or atoms on metal surfaces plays a key role in surface science and technology.This review is dedicated to the adsorption of oxygen molecules or atoms on metal surfaces and diffusion behavior from first-principle investigation.We hope that this review can provide some useful contributions to understa nd the study of adsorption properties and diffusion behavior on a metal surface at an atomic-scale,especially for those interested in catalytic oxidation and application of corrosion.
基金Supported by the StaLe Key Development Program for Basic Research of China （2004CB719505）, and the National Natural Science Foundation of China （20625621）.
文摘In the article the Grand Canonical Monte Carlo （GCMC）, molecular dynamics（MD）, and kinetic Monte Carlo （KMC） simulations with particular focus on ascertaining the loading dependence of benzene diffusion in the zeolite were performed. First, a realistic representation of the structure of the sorbate-sorbent system was obtained based on GCMC simulation. The simulation clearly shows the characteristics of the adsorption sites of the benzene-NaY system, from which two kinds of preferably adsorbing sites for benzene molecules, called SⅡ and W sites, are identified. The structure thus obtained was then used as a basis for KMC and MD simulations. A compara-tive study by introducing and comparing two different mechanisms underlying jump diffusion in the zeolite of in-terest shows that the.MS diffusivity values predicted by the KMC and MD methods are fairly close to each other,leading to the conclusion that for benzene diffusion in NaY, the SⅡ→W→SⅡ jumps of benzene molecules are dominated,while the W→Wjumps do not exist in the process. These findings provide further support to our previous conclusion about the absence of the W→W jumps in the process of benzene diffusion in NaY. Finally, to relations, for predicting the self-and MS difthsivities were derived and found to be in fair agreement with the KMC and MD simulations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51002014,51202017,and 51372095)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120061120039)+2 种基金the Funds from the Science and Technology Department of Jilin Province,China(Grant Nos.20120745 and 20130101029JC)the Funds from the Department of Education of Jilin Province,China(Grant No.2013279)the Youth Science Research Foundation of Liaoning University,China(Grant No.2013LDQN20)
文摘First-principles calculations based on density functional theory are used to investigate the adsorptions and diffusions of carbon atoms on the surface and in the subsurface of Co （200）. The preferred site for the carbon atom on the surface is the hollow site, and the preferred site in the subsurface is the octahedral site. There is charge transfer from the surface to the adsorbed carbon atom, and for the most favorable adsorbed structure the charge transfer is largest. Moreover, the energy barriers for the diffusions of carbon atoms on the surface and from the surface into the subsurface and then back to the surface are calculated in detail. The results indicate that the energy barrier for the diffusion of carbon atoms on the surface is comparable to that from the subsurface to the surface. The results imply that both the direct surface nucleation and the surface segregation from Co bulk can be observed in the chemical vapor deposition growth of graphene on Co （200） substrate, which can gain a new insight into the growth mechanism of graphene.
基金the National Natural Science Foundation of China(No.41272177)the Henan Polytechnic University Doctor Foundation(No.WS2013A11)
文摘The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree of damage is different, were selected from Tongchun, Qilin, and Pingdingshan mines. Using a series of experiments in an electrostatic field, we analyzed the characteristics of gas adsorption and diffusion in tectonic coal. We found that gas adsorption in coal conforms to the Langmuir equation in an electrostatic field. Both the depth of the adsorption potential well and the coal molecular electroneg- ativity increases under the action of an electrostatic field. A Joule heating effect was caused by changing the coal-gas system conductivity in an electrostatic field. The quantity of gas adsorbed and AP result from competition between the depth of the adsorption potential well, the coal molecular electronegativ- ity, and the Joule heating effect. △P peaks when the three factors control behavior equally. Compared with anthracite, the impact of the electrostatic field on the gas diffusion capacity of middle and high rank coals is greater. Compared with the original coal, the gas adsorption quantity,△P, and the gas diffusion capacity of tectonic coal are greater in an electrostatic field. In addition, the smaller the particle size of tectonic coal, the larger the△P.
