We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Mic...We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Microwave irradiation induced periodic patterns of precipitation because polar molecules vibrate and rotate in an electromagnetic field. For example, the number of patterns increased with the irradiation power. Accordingly, microwave irradiation nonlinearly accelerated the diffusion of ionic molecules.展开更多
We studied precipitation patterns in a Liesegang system under MW （microwave） irradiation in order to investigate metal salt diffusion in an electrolyte gel. The gel and salt concentrations were varied. MW irradiatio...We studied precipitation patterns in a Liesegang system under MW （microwave） irradiation in order to investigate metal salt diffusion in an electrolyte gel. The gel and salt concentrations were varied. MW irradiation induced periodic patterns of precipitation because polar molecules vibrate and rotate in an electromagnetic field. For example, the number of patterns increased by the irradiation. Accordingly, microwave irradiation nonlinearly accelerated the diffusion of ionic molecules.展开更多
We show that an enslaved phase-separation front moving with diffusive speeds U=C/√T can leave alternating domains of increasing size in their wake.We find the size and spacing of these domains is identical to Liesega...We show that an enslaved phase-separation front moving with diffusive speeds U=C/√T can leave alternating domains of increasing size in their wake.We find the size and spacing of these domains is identical to Liesegang patterns.For equal composition of the components we are able to predict the exact form of the pattern analytically.To our knowledge this is the first fully analytical derivation of the Liesegang laws.We also show that there is a critical value for C below which only two domains are formed.Our analytical predictions are verified by numerical simulations using a lattice Boltzmann method.展开更多
The dynamics of the Liesegang type pattern formation is investigated in a centrally symmetric two-dimensional setup.According to the observations in real experiments,the qualitative change of the dynamics is exhibited...The dynamics of the Liesegang type pattern formation is investigated in a centrally symmetric two-dimensional setup.According to the observations in real experiments,the qualitative change of the dynamics is exhibited for slightly different initial conditions.Two kinds of chemical mechanisms are studied;in both cases the pattern formation is described using a phase separation model including the CahnHilliard equations.For the numerical simulations we make use of an adaptive grid PDE method,which successfully deals with the computationally critical cases such as steep gradients in the concentration distribution and investigation of long time behavior.The numerical simulations show a good agreement with the real experiments.展开更多
We carry out a chemical treatment(acidization or basification)of typical rock specimens in-situ,and characterize the emerging pattern resulting from the infil-tration-precipitation scenario.Galena and limestone sam-pl...We carry out a chemical treatment(acidization or basification)of typical rock specimens in-situ,and characterize the emerging pattern resulting from the infil-tration-precipitation scenario.Galena and limestone sam-ples were treated with sulfuric acid,while pyrite was reacted with sodium hydroxide.Various infiltration tech-niques were employed,after selection of the most feasible method for each rock separately.The patterns of anglesite(PbSO_(4)),anhydrite(CaSO_(4))and goethite(FeOOH)depo-sition presented different alteration modes of the bare rock textures.Among the three deposited minerals,only the anhydrite(CaSO_(4))displayed a band stratification.The formation of a Liesegang pattern in the rock of highest porosity indicates a plausible correlation between the band formation and a minimum porosity requirement.A banded rock of compact texture could then be formed by a cementation mechanism,governing the long time evolution of the rock.展开更多
文摘We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Microwave irradiation induced periodic patterns of precipitation because polar molecules vibrate and rotate in an electromagnetic field. For example, the number of patterns increased with the irradiation power. Accordingly, microwave irradiation nonlinearly accelerated the diffusion of ionic molecules.
文摘We studied precipitation patterns in a Liesegang system under MW （microwave） irradiation in order to investigate metal salt diffusion in an electrolyte gel. The gel and salt concentrations were varied. MW irradiation induced periodic patterns of precipitation because polar molecules vibrate and rotate in an electromagnetic field. For example, the number of patterns increased by the irradiation. Accordingly, microwave irradiation nonlinearly accelerated the diffusion of ionic molecules.
基金E.F.acknowledges support by the National Science Foundation under grant DMR-0513393.
文摘We show that an enslaved phase-separation front moving with diffusive speeds U=C/√T can leave alternating domains of increasing size in their wake.We find the size and spacing of these domains is identical to Liesegang patterns.For equal composition of the components we are able to predict the exact form of the pattern analytically.To our knowledge this is the first fully analytical derivation of the Liesegang laws.We also show that there is a critical value for C below which only two domains are formed.Our analytical predictions are verified by numerical simulations using a lattice Boltzmann method.
基金support from the Dutch BSIK-project BRICKSthe financial support of the Bolyai Research Fellow-ship,the Hungarian Scientific Research Fund(OTKA K68253 and K81933)the European Union and the European Social Fund(TAMOP 4.2.1./B-09/KMR-2010-0003).
文摘The dynamics of the Liesegang type pattern formation is investigated in a centrally symmetric two-dimensional setup.According to the observations in real experiments,the qualitative change of the dynamics is exhibited for slightly different initial conditions.Two kinds of chemical mechanisms are studied;in both cases the pattern formation is described using a phase separation model including the CahnHilliard equations.For the numerical simulations we make use of an adaptive grid PDE method,which successfully deals with the computationally critical cases such as steep gradients in the concentration distribution and investigation of long time behavior.The numerical simulations show a good agreement with the real experiments.
基金supported by a grant from the University Research Board(URB)of the American University of Beirut(AUB).
文摘We carry out a chemical treatment(acidization or basification)of typical rock specimens in-situ,and characterize the emerging pattern resulting from the infil-tration-precipitation scenario.Galena and limestone sam-ples were treated with sulfuric acid,while pyrite was reacted with sodium hydroxide.Various infiltration tech-niques were employed,after selection of the most feasible method for each rock separately.The patterns of anglesite(PbSO_(4)),anhydrite(CaSO_(4))and goethite(FeOOH)depo-sition presented different alteration modes of the bare rock textures.Among the three deposited minerals,only the anhydrite(CaSO_(4))displayed a band stratification.The formation of a Liesegang pattern in the rock of highest porosity indicates a plausible correlation between the band formation and a minimum porosity requirement.A banded rock of compact texture could then be formed by a cementation mechanism,governing the long time evolution of the rock.
