The string model for the glass transition can quantitatively describe the universal a-relaxation in glassformers. The string relaxation equation （SRE） of the model simplifies the well-known Debye and Rouse-Zimm rela...The string model for the glass transition can quantitatively describe the universal a-relaxation in glassformers. The string relaxation equation （SRE） of the model simplifies the well-known Debye and Rouse-Zimm relaxation equations at high and low enough temperatures, respectively. However, its initial condition, necessary to the further model predictions of glassy dynamics, has not been solved. In this paper, the general initial condition of the SRE for stochastically spatially configurative strings is solved exactly based on the obtained special initial condition of the SRE for straight strings in a previous paper （J. L. Zhang et al. 2010 Chin. Phys. B 19, 056403）.展开更多
The string model for the glass transition can quantitatively describe the universal a-relaxation in glassformers, including the average relaxation time, the distribution function of the relaxation time, and the relaxa...The string model for the glass transition can quantitatively describe the universal a-relaxation in glassformers, including the average relaxation time, the distribution function of the relaxation time, and the relaxation strength as functions of temperature. The string relaxation equation （SRE） of the model, at high enough temperatures, simplifies to the well-known single particle mean-field Debye relaxation equation, and at low enough temperatures to the well-known Rouse-Zimm relaxation equation that describes the relaxation dynamics of linear macromolecules. However, its initial condition, necessary to the further model predictions of glassy dynamics, has not been solved. In this paper, the special initial condition （SIC） of the SRE, i.e. for straight strings and the dielectric spectrum technique that is one of the most common methods to measure the glassy dynamics, was solved exactly. It should be expected that the obtained SIC would benefit the solution of the general initial condition of the SRE of the string model, i.e. for stochastically spatially eonfigurating strings, as will be described in separate publications.展开更多
We present findings on the effect of nanometer-sized silica-based pores on the glass transition of aqueous solutions of lithium bis(trifluoromethane)sulfonimide(LiTFSI)and lithium difluorosulfimide(LiFSI),respectively...We present findings on the effect of nanometer-sized silica-based pores on the glass transition of aqueous solutions of lithium bis(trifluoromethane)sulfonimide(LiTFSI)and lithium difluorosulfimide(LiFSI),respectively.Our experimental results demonstrate a clear dependence of the confinement effect on the anion type,particularly for water-rich solutions,in which the precipitation of crystalized ice under cooling process induces the formation of freeze-concentrated phase confined between pore wall and core ice.As this liquid layer becomes thinner,the freeze-concentrated phase experiences glass transition at increasingly higher temperatures in solutions of LiTFSI.However,differently,for solutions of LiFSI and LiCl,this secondary confinement has a negligible effect on the glass transition of solutions confined wherein.These different behaviors emphasize the obvious difference in the dynamic properties’response of LiTFSI and LiFSI solutions to spatial confinement and particularly to the presence of the hydrophilic pore wall.展开更多
Both tetrahydrofuran （THF） and 2-methyltetrahydrofuran （MTHF） are studied systematically at desired temperatures using molecular dynamics simulations. The results show that the calculated densities are well consis...Both tetrahydrofuran （THF） and 2-methyltetrahydrofuran （MTHF） are studied systematically at desired temperatures using molecular dynamics simulations. The results show that the calculated densities are well consistent with experiment. Their glass transition temperatures are obtained： 115 K - 130 K for THF and 131 K - 142 K for MTHF. The calculated results from the dipolar orientational time correlation functions indicate that the ＂long time＂ behavior is often associated with a glass transition. From the radial and spatial distributions, we also find that the methyl has a direct impact on the structural symmetry of molecules, which leads to the differences of physical properties between THF and MTHF.展开更多
Strain glass is a frozen short-range strain ordered state found in shape memory alloys recently, which exhibits novel properties around the ideal glass transition temperature T_(0). However, the T_(0) of current strai...Strain glass is a frozen short-range strain ordered state found in shape memory alloys recently, which exhibits novel properties around the ideal glass transition temperature T_(0). However, the T_(0) of current strain glass systems is still very low, limiting their potential applications and experimental studies. In this paper, we reported two new strain glass systems with relatively high T_(0). In Ti_(50)Au_(50-x)Cr_(x) alloys, the strain glass appears at x = 25, and exhibits a T_(0) of 251 K, while in Ti_(50)Pt_(50-y)Fey alloys, the strain glass takes place at y = 30, and shows a T_(0) of 272 K. Both of them are comparable with the highest T_(0) value reported so far. Moreover, the phase diagrams of main strain glass systems in Ti-based alloys were summarized. It is found that the influence of the martensitic transformation temperature of the host alloy on the T_(0) of the strain glass is limited. This work may help to design new strain glass systems with higher T_(0) above ambient temperature.展开更多
The relaxation dynamics of liquids is one of the fundamental problems in liquid physics, and it is also one of the key issues to understand the glass transition mechanism. It will undoubtedly provide enlightenment on ...The relaxation dynamics of liquids is one of the fundamental problems in liquid physics, and it is also one of the key issues to understand the glass transition mechanism. It will undoubtedly provide enlightenment on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied. In this paper, we first give five microparameters to describe the individual molecular string （MS） relaxation based on the dynamical Hamiltonian of the MS model, and then simulate the images of individual MS ensemble, and at the same time calculate the parameters of the equilibrium state. The results show that the main molecular orientation flipping image in liquids （including supercooled liquid） is similar to the random walk. In addition, two pairs of the parameters are equal, and one can be ignored compared with the other. This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of the general Glauber type, and the computer simulation time of interaction MS relaxation. Moreover, the conclusion is of reference significance for solving and simulating the multi-state MS model.展开更多
Zein,a class of alcohol-soluble prolamines in maize endosperm,is mainly composed of α-zein,β-zein,andγ-zein.It has been recognized as a structural protein for various gluten-free systems since it can form glutenlik...Zein,a class of alcohol-soluble prolamines in maize endosperm,is mainly composed of α-zein,β-zein,andγ-zein.It has been recognized as a structural protein for various gluten-free systems since it can form glutenlike viscoelastic network.The formation of viscoelastic zein network can make up for the structural defect of gluten-free doughs caused by the lack of gluten.To make the most of structural functionality of zein in glutenfree foods,it is important to clearly elucidate the fundamental properties of zein network.In this article,these properties have been discussed,analyzed and summarized from the relationship between protein network and structural functionality of zein,the feature and formation mechanism of zein network,factors affecting zein network and the applications of zein network in improving the quality of gluten-free food.In addition,this article also looks forward to potential research areas on zein network.展开更多
Five types of polyurea elastomers were synthesized by changing the isocyanate component and the mechanical properties of polyurea materials were measured. Fiber-reinforced cement boards(FRCB)strengthened by polyurea w...Five types of polyurea elastomers were synthesized by changing the isocyanate component and the mechanical properties of polyurea materials were measured. Fiber-reinforced cement boards(FRCB)strengthened by polyurea with different formulations were processed, and a series of experiments were carried out on the specimens with gas explosion devices. The results showed that the conventional mechanical properties of different types of polyureas had their own advantages. Based on the gas explosion overpressure criterion, the blast resistances of reinforced plates were quantitatively evaluated,and the best polyurea was selected to guide the formulation design. The three typical failure modes of polyurea-reinforced FRCBs were flexural, shear, and flexural-shear failure. Dynamic thermodynamics and shock wave spectral analysis revealed that the polyurea did not undergo a glass transition in the gas explosion tests but retained its elastic properties, allowing it to effectively wrap the fragments formed by the brittle substrates.展开更多
Dynamic mechanical properties of nanocomposite films with different ratios of single walled carbon nanotubes/polymethyl methacrylate（SWCNTs/PMMA） are studied. Nanocomposite films of different ratios（0, 0.5, 1.0, an...Dynamic mechanical properties of nanocomposite films with different ratios of single walled carbon nanotubes/polymethyl methacrylate（SWCNTs/PMMA） are studied. Nanocomposite films of different ratios（0, 0.5, 1.0, and2.0 weight percent（wt%）） of SWCNTs/PMMA are fabricated by using a casting technique. The morphological and structural properties of both SWCNT powder and SWCNTs/PMMA nanocomposite films are investigated by using a high resolution transmission electron microscope and x-ray diffractometer respectively. The mechanical properties including the storage modulus, loss modulus, loss factor（tan δ） and stiffness of the nanocomposite film as a function of temperature are recorded by using a dynamic mechanical analyzer at a frequency of 1 Hz. Compared with pure PMMA film, the nanocomposite films with different ratios of SWCNTs/PMMA are observed to have enhanced storage moduli, loss moduli and high stiffness, each of which is a function of temperature. The intensity of the tan δ peak for pure PMMA film is larger than those of the nanocomposite films. The glass transition temperature（T g） of SWCNTs/PMMA nanocomposite film shifts towards the higher temperature side with respect to pure PMMA film from 91.2？C to 99.5？C as the ratio of SWCNTs/PMMA increases from 0 to 2.0 wt%.展开更多
Thermally driven diffusive motion of a particle underlies many physical and biological processes. In the presence of traps and obstacles, the spread of the particle is substantially impeded, leading to subdiffusive sc...Thermally driven diffusive motion of a particle underlies many physical and biological processes. In the presence of traps and obstacles, the spread of the particle is substantially impeded, leading to subdiffusive scaling at long times. The statistical mechanical treatment of diffusion in a disordered environment is often quite involved. In this short review, we present a simple and unified view of the many quantitative results on anomalous diffusion in the literature, including the scaling of the diffusion front and the mean first-passage time. Varioust analytic calculations and physical arguments are examined to highlight the role of dimensionality, energy landscape, and rare events in affecting the particle trajectory statistics. The general understanding that emerges will aid the interpretation of relevant experimental and simulation results.展开更多
For aqueous solutions with freezable bound water, vitrification and recrystallization are mingled, which brings difficulty to application and misleads the interpretation of relevant experiments. Here, we report a quan...For aqueous solutions with freezable bound water, vitrification and recrystallization are mingled, which brings difficulty to application and misleads the interpretation of relevant experiments. Here, we report a quantification scheme for the freezable bound water based on the water-content dependence of glass transition temperature, by which also the concentration range for the solutions that may undergo recrystallization finds a clear definition. Furthermore, we find that depending on the amount of the freezable bound water, different temperature protocols should be devised to achieve a complete recrystallization. Our results may be helpful for understanding the dynamics of supercooled aqueous solutions and for improving their manipulation in various industries.展开更多
基金supported by the National Natural Science Foundations of China (Grant Nos. 10774064 and 30860076)the Key Foundation of Xinjiang Education Department (Grant No. XJEDU2007137)the Natural Science Foundations of Xinjiang Science and Technology Department (Grant Nos. 200821104 and 200821184)
文摘The string model for the glass transition can quantitatively describe the universal a-relaxation in glassformers. The string relaxation equation （SRE） of the model simplifies the well-known Debye and Rouse-Zimm relaxation equations at high and low enough temperatures, respectively. However, its initial condition, necessary to the further model predictions of glassy dynamics, has not been solved. In this paper, the general initial condition of the SRE for stochastically spatially configurative strings is solved exactly based on the obtained special initial condition of the SRE for straight strings in a previous paper （J. L. Zhang et al. 2010 Chin. Phys. B 19, 056403）.
基金Project supported by the National Natural Science Foundations of China (Grant Nos. 10774064 and 30860076)the Key Foundation of Xinjiang Education Department (Grant No. XJEDU2007137)the Natural Science Foundations of Xinjiang Science and Technology Department of China (Grant Nos. 2008211042 and 200821184)
文摘The string model for the glass transition can quantitatively describe the universal a-relaxation in glassformers, including the average relaxation time, the distribution function of the relaxation time, and the relaxation strength as functions of temperature. The string relaxation equation （SRE） of the model, at high enough temperatures, simplifies to the well-known single particle mean-field Debye relaxation equation, and at low enough temperatures to the well-known Rouse-Zimm relaxation equation that describes the relaxation dynamics of linear macromolecules. However, its initial condition, necessary to the further model predictions of glassy dynamics, has not been solved. In this paper, the special initial condition （SIC） of the SRE, i.e. for straight strings and the dielectric spectrum technique that is one of the most common methods to measure the glassy dynamics, was solved exactly. It should be expected that the obtained SIC would benefit the solution of the general initial condition of the SRE of the string model, i.e. for stochastically spatially eonfigurating strings, as will be described in separate publications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974385 and 91956101).
文摘We present findings on the effect of nanometer-sized silica-based pores on the glass transition of aqueous solutions of lithium bis(trifluoromethane)sulfonimide(LiTFSI)and lithium difluorosulfimide(LiFSI),respectively.Our experimental results demonstrate a clear dependence of the confinement effect on the anion type,particularly for water-rich solutions,in which the precipitation of crystalized ice under cooling process induces the formation of freeze-concentrated phase confined between pore wall and core ice.As this liquid layer becomes thinner,the freeze-concentrated phase experiences glass transition at increasingly higher temperatures in solutions of LiTFSI.However,differently,for solutions of LiFSI and LiCl,this secondary confinement has a negligible effect on the glass transition of solutions confined wherein.These different behaviors emphasize the obvious difference in the dynamic properties’response of LiTFSI and LiFSI solutions to spatial confinement and particularly to the presence of the hydrophilic pore wall.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11025524 and 11161130520)the National Basic Research Program of China (Grant No. 2010CB832903)
文摘Both tetrahydrofuran （THF） and 2-methyltetrahydrofuran （MTHF） are studied systematically at desired temperatures using molecular dynamics simulations. The results show that the calculated densities are well consistent with experiment. Their glass transition temperatures are obtained： 115 K - 130 K for THF and 131 K - 142 K for MTHF. The calculated results from the dipolar orientational time correlation functions indicate that the ＂long time＂ behavior is often associated with a glass transition. From the radial and spatial distributions, we also find that the methyl has a direct impact on the structural symmetry of molecules, which leads to the differences of physical properties between THF and MTHF.
基金Project supported by China Postdoctoral Science Foundation(Grant No.2019M650880)the National Natural Science Foundation of China(Grant Nos.51901243,61888102,and 11790291)+1 种基金the Natural Science Foundation of Guangdong Province,China(Grant No.2019B030302010)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)。
文摘Strain glass is a frozen short-range strain ordered state found in shape memory alloys recently, which exhibits novel properties around the ideal glass transition temperature T_(0). However, the T_(0) of current strain glass systems is still very low, limiting their potential applications and experimental studies. In this paper, we reported two new strain glass systems with relatively high T_(0). In Ti_(50)Au_(50-x)Cr_(x) alloys, the strain glass appears at x = 25, and exhibits a T_(0) of 251 K, while in Ti_(50)Pt_(50-y)Fey alloys, the strain glass takes place at y = 30, and shows a T_(0) of 272 K. Both of them are comparable with the highest T_(0) value reported so far. Moreover, the phase diagrams of main strain glass systems in Ti-based alloys were summarized. It is found that the influence of the martensitic transformation temperature of the host alloy on the T_(0) of the strain glass is limited. This work may help to design new strain glass systems with higher T_(0) above ambient temperature.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10774064 and 30860076)the National Basic Research Program of China (Grant No. 2012CB821503)the Natural Science Foundations of Xinjiang Uygur Autonomous Region,China (Grant Nos. 200821104 and 200821184)
文摘The relaxation dynamics of liquids is one of the fundamental problems in liquid physics, and it is also one of the key issues to understand the glass transition mechanism. It will undoubtedly provide enlightenment on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied. In this paper, we first give five microparameters to describe the individual molecular string （MS） relaxation based on the dynamical Hamiltonian of the MS model, and then simulate the images of individual MS ensemble, and at the same time calculate the parameters of the equilibrium state. The results show that the main molecular orientation flipping image in liquids （including supercooled liquid） is similar to the random walk. In addition, two pairs of the parameters are equal, and one can be ignored compared with the other. This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of the general Glauber type, and the computer simulation time of interaction MS relaxation. Moreover, the conclusion is of reference significance for solving and simulating the multi-state MS model.
文摘Zein,a class of alcohol-soluble prolamines in maize endosperm,is mainly composed of α-zein,β-zein,andγ-zein.It has been recognized as a structural protein for various gluten-free systems since it can form glutenlike viscoelastic network.The formation of viscoelastic zein network can make up for the structural defect of gluten-free doughs caused by the lack of gluten.To make the most of structural functionality of zein in glutenfree foods,it is important to clearly elucidate the fundamental properties of zein network.In this article,these properties have been discussed,analyzed and summarized from the relationship between protein network and structural functionality of zein,the feature and formation mechanism of zein network,factors affecting zein network and the applications of zein network in improving the quality of gluten-free food.In addition,this article also looks forward to potential research areas on zein network.
基金funded by National Natural Science Foundation of China(No.12002392).
文摘Five types of polyurea elastomers were synthesized by changing the isocyanate component and the mechanical properties of polyurea materials were measured. Fiber-reinforced cement boards(FRCB)strengthened by polyurea with different formulations were processed, and a series of experiments were carried out on the specimens with gas explosion devices. The results showed that the conventional mechanical properties of different types of polyureas had their own advantages. Based on the gas explosion overpressure criterion, the blast resistances of reinforced plates were quantitatively evaluated,and the best polyurea was selected to guide the formulation design. The three typical failure modes of polyurea-reinforced FRCBs were flexural, shear, and flexural-shear failure. Dynamic thermodynamics and shock wave spectral analysis revealed that the polyurea did not undergo a glass transition in the gas explosion tests but retained its elastic properties, allowing it to effectively wrap the fragments formed by the brittle substrates.
基金Project supported by Taif University(Grant No.1/435/3524)
文摘Dynamic mechanical properties of nanocomposite films with different ratios of single walled carbon nanotubes/polymethyl methacrylate（SWCNTs/PMMA） are studied. Nanocomposite films of different ratios（0, 0.5, 1.0, and2.0 weight percent（wt%）） of SWCNTs/PMMA are fabricated by using a casting technique. The morphological and structural properties of both SWCNT powder and SWCNTs/PMMA nanocomposite films are investigated by using a high resolution transmission electron microscope and x-ray diffractometer respectively. The mechanical properties including the storage modulus, loss modulus, loss factor（tan δ） and stiffness of the nanocomposite film as a function of temperature are recorded by using a dynamic mechanical analyzer at a frequency of 1 Hz. Compared with pure PMMA film, the nanocomposite films with different ratios of SWCNTs/PMMA are observed to have enhanced storage moduli, loss moduli and high stiffness, each of which is a function of temperature. The intensity of the tan δ peak for pure PMMA film is larger than those of the nanocomposite films. The glass transition temperature（T g） of SWCNTs/PMMA nanocomposite film shifts towards the higher temperature side with respect to pure PMMA film from 91.2？C to 99.5？C as the ratio of SWCNTs/PMMA increases from 0 to 2.0 wt%.
基金supported by the National Natural Science Foundation of China (Grant No. 11175013)the Research Grants Council of the Hong Kong Special Administrative Region,China (Grant No. N HKBU 213/10)
文摘Thermally driven diffusive motion of a particle underlies many physical and biological processes. In the presence of traps and obstacles, the spread of the particle is substantially impeded, leading to subdiffusive scaling at long times. The statistical mechanical treatment of diffusion in a disordered environment is often quite involved. In this short review, we present a simple and unified view of the many quantitative results on anomalous diffusion in the literature, including the scaling of the diffusion front and the mean first-passage time. Varioust analytic calculations and physical arguments are examined to highlight the role of dimensionality, energy landscape, and rare events in affecting the particle trajectory statistics. The general understanding that emerges will aid the interpretation of relevant experimental and simulation results.
基金Project supported by the Knowledge Innovation Project of Chinese Academy of Sciences on Water Science Research(Grant No.KJZD-EW-M03)the National Natural Science Foundation of China(Grant Nos.11474325 and 11290161)
文摘For aqueous solutions with freezable bound water, vitrification and recrystallization are mingled, which brings difficulty to application and misleads the interpretation of relevant experiments. Here, we report a quantification scheme for the freezable bound water based on the water-content dependence of glass transition temperature, by which also the concentration range for the solutions that may undergo recrystallization finds a clear definition. Furthermore, we find that depending on the amount of the freezable bound water, different temperature protocols should be devised to achieve a complete recrystallization. Our results may be helpful for understanding the dynamics of supercooled aqueous solutions and for improving their manipulation in various industries.
