The melting of crystals is one of the most common and general phase transition phenomena.However, the mechanism of crystal melting is not well understood, and more experimental measurements and explorations are still ...The melting of crystals is one of the most common and general phase transition phenomena.However, the mechanism of crystal melting is not well understood, and more experimental measurements and explorations are still needed.The mechanical spectra of propylene carbonate and 1,3-propanediol during the crystal melting processes are measured by the reed vibration mechanical spectroscopy for liquids(RMS-L) for the first time.The experimental results show that as the temperature increases, the real part of the complex Young modulus first decreases slowly, and then quickly drops to zero;meanwhile, its imaginary part increases slowly at first, then goes up and drops quickly to zero, showing a peak of internal friction.Preliminary analyses indicate that both the real and imaginary parts can present some characteristics of the melting process, such as the transition from the disconnected liquid regions to the connected liquid regions, that from the connected crystal regions to the disconnected crystal regions, and so on.In addition, the results show that the melting rate per unit volume of crystalline phase versus temperature satisfies the Arrhenius relation at the initial stage of melting, and deviates from this relation as the temperature increases to a certain value.Therefore, the RMS-L will provide an effective supplement for the further study of melting.展开更多
A measurement scheme for detecting theαrelaxation time(τ)of glass-forming liquid is proposed,which is based on the measured ionic conductivity of the liquid doped with probing ions by low-and middle-frequency dielec...A measurement scheme for detecting theαrelaxation time(τ)of glass-forming liquid is proposed,which is based on the measured ionic conductivity of the liquid doped with probing ions by low-and middle-frequency dielectric spectroscopy and according to the Nernst-Einstein,Stokes-Einstein,and Maxwell equations.The obtainedτvalues of glycerol and propylene carbonate by the scheme are consistent with those obtained by traditional dielectric spectroscopy,which confirms its reliability and accuracy.Moreover,theτof 1,2-propanediol in a larger temperature range is compared with existing data.展开更多
Due to the obvious deviations of the existing theoretical models from the experimental results of ferroelectric phase transition, a new model is proposed on the basis of the coupling between spontaneous polarization a...Due to the obvious deviations of the existing theoretical models from the experimental results of ferroelectric phase transition, a new model is proposed on the basis of the coupling between spontaneous polarization and spontaneous strain in ferroelectrics. The spontaneous polarization and specific heat of ferroelectric phase transition predicted by the model are in better agreement with the corresponding data of triglyceride sulfate, a typical ferroelectric.In addition, the model predicts a new type of ferroelectric in which a phase transition and a phase-like transition coexist.展开更多
Combining Brownian dynamics simulations and self-consistent field theory,we demonstrate that the architectural parameters of coreshell comb-like chains have a decisive influence on their final self-assembled conformat...Combining Brownian dynamics simulations and self-consistent field theory,we demonstrate that the architectural parameters of coreshell comb-like chains have a decisive influence on their final self-assembled conformations.When the ratio of hydrophilic and hydrophobic segments is N_(g,g)∶N_(g,r)=3∶1,no core-shell structure is observed,and unsegregated chains or clusters are substituted.When N_(g,g)∶N_(g,r)=3∶2or 3∶3,the core-shell comb-like chains can be assembled into single micelles or structures where several small micelles are strung together by the backbone,which is similar to the pearl-necklace structure formed by the polyelectrolytes in poor solvent.With the increase of backbone length or grafting density,the probability of forming single micelles becomes lower,but the structures of two,three or more small micelles strung together are more observed.Our results indicate how to obtain the desired self-assembled structures of core-shell comb-like chains by regulating the architectural parameters,which could provide insights for the optimization of molecular design in various applications.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11664042)
文摘The melting of crystals is one of the most common and general phase transition phenomena.However, the mechanism of crystal melting is not well understood, and more experimental measurements and explorations are still needed.The mechanical spectra of propylene carbonate and 1,3-propanediol during the crystal melting processes are measured by the reed vibration mechanical spectroscopy for liquids(RMS-L) for the first time.The experimental results show that as the temperature increases, the real part of the complex Young modulus first decreases slowly, and then quickly drops to zero;meanwhile, its imaginary part increases slowly at first, then goes up and drops quickly to zero, showing a peak of internal friction.Preliminary analyses indicate that both the real and imaginary parts can present some characteristics of the melting process, such as the transition from the disconnected liquid regions to the connected liquid regions, that from the connected crystal regions to the disconnected crystal regions, and so on.In addition, the results show that the melting rate per unit volume of crystalline phase versus temperature satisfies the Arrhenius relation at the initial stage of melting, and deviates from this relation as the temperature increases to a certain value.Therefore, the RMS-L will provide an effective supplement for the further study of melting.
基金Project supported by the National Natural Science Foundation of China(Grant No.11664042)
文摘A measurement scheme for detecting theαrelaxation time(τ)of glass-forming liquid is proposed,which is based on the measured ionic conductivity of the liquid doped with probing ions by low-and middle-frequency dielectric spectroscopy and according to the Nernst-Einstein,Stokes-Einstein,and Maxwell equations.The obtainedτvalues of glycerol and propylene carbonate by the scheme are consistent with those obtained by traditional dielectric spectroscopy,which confirms its reliability and accuracy.Moreover,theτof 1,2-propanediol in a larger temperature range is compared with existing data.
基金Supported by the National Natural Science Foundation of China under Grant No 11664042
文摘Due to the obvious deviations of the existing theoretical models from the experimental results of ferroelectric phase transition, a new model is proposed on the basis of the coupling between spontaneous polarization and spontaneous strain in ferroelectrics. The spontaneous polarization and specific heat of ferroelectric phase transition predicted by the model are in better agreement with the corresponding data of triglyceride sulfate, a typical ferroelectric.In addition, the model predicts a new type of ferroelectric in which a phase transition and a phase-like transition coexist.
基金financially supported by the Scientific Research Project of Yili Normal University(No.2022YSYB009)the National Natural Science Foundation of China(No.2019M651340)。
文摘Combining Brownian dynamics simulations and self-consistent field theory,we demonstrate that the architectural parameters of coreshell comb-like chains have a decisive influence on their final self-assembled conformations.When the ratio of hydrophilic and hydrophobic segments is N_(g,g)∶N_(g,r)=3∶1,no core-shell structure is observed,and unsegregated chains or clusters are substituted.When N_(g,g)∶N_(g,r)=3∶2or 3∶3,the core-shell comb-like chains can be assembled into single micelles or structures where several small micelles are strung together by the backbone,which is similar to the pearl-necklace structure formed by the polyelectrolytes in poor solvent.With the increase of backbone length or grafting density,the probability of forming single micelles becomes lower,but the structures of two,three or more small micelles strung together are more observed.Our results indicate how to obtain the desired self-assembled structures of core-shell comb-like chains by regulating the architectural parameters,which could provide insights for the optimization of molecular design in various applications.
