The crystallization behavior of two commercial polyolefin elastomer(POE)samples was investigated using the fast scanning chip calorimetry(FSC)technique.Non-isothermal crystallization of the POE samples during cooling ...The crystallization behavior of two commercial polyolefin elastomer(POE)samples was investigated using the fast scanning chip calorimetry(FSC)technique.Non-isothermal crystallization of the POE samples during cooling to low temperatures cannot be inhibited under the largest efficient cooling rate employed in the current work.Thus,the isothermal crystallization of POE samples was limited to a narrow temperature range.When the POE samples were cooled to a certain temperature below the non-isothermal crystallization temperature for crystallization,a crystallization time dependent melting peak appeared in the low temperature region besides the high temperature melting peak originated from the non-isothermal crystallization.This low temperature melting peak was arisen from the melting of crystals isothermally crystallized at the selected crystallization temperature.At each crystallization temperature,the lengths of crystallizable segments were different,thus,the low melting peak increased with increasing the crystallization temperature.In terms of the high melting peak attributed to the non-isothermally crystallized crystals,it somehow decreased with increasing crystallization time and then became constant with further increasing crystallization time at the selected crystallization temperature.This could be explained by the fact that the crystallizable sequences with longer length would nucleate and crystallize first to form thicker crystals during cooling.The subsequent crystallization contributed by the shorter crystallizable sequences will result in the formation of thinner crystals,causing the melting peak to shift to the lower temperature.展开更多
A leukocyte image fast scanning method based on max min distance clustering is proposed.Because of the lower proportion and uneven distribution of leukocytes in human peripheral blood,there will not be any leukocyte i...A leukocyte image fast scanning method based on max min distance clustering is proposed.Because of the lower proportion and uneven distribution of leukocytes in human peripheral blood,there will not be any leukocyte in lager quantity of the captured images if we directly scan the blood smear along an ordinary zigzag scanning routine with high power(100^(x))objective.Due to the larger field of view of low power(10^(x))objective,the captured low power blood smear images can be used to locate leukocytes.All of the located positions make up a specific routine,if we scan the blood smear along this routine with high power objective,there will be definitely leukocytes in almost all of the captured images.Considering the number of captured images is still large and some leukocytes may be redundantly captured twice or more,a leukocyte clustering method based on max-min distance clustering is developed to reduce the total number of captured images as well as the number of redundantly captured leukocytes.This method can improve the scanning eficiency obviously.The experimental results show that the proposed method can shorten scanning time from 8.0-14.0min to 2.54.0 min while extracting 110 nonredundant individual high power leukocyte images.展开更多
CONSPECTUS:The global production of polymer products currently exceeds 400 megatons annually.To ensure effective and environmentally responsible use of this vast resource,optimizing the properties of the products is e...CONSPECTUS:The global production of polymer products currently exceeds 400 megatons annually.To ensure effective and environmentally responsible use of this vast resource,optimizing the properties of the products is essential.Achieving this requires precise control over the internal structure of the polymers.Depending on the materials used,polymers can exist in either amorphous or semicrystalline states.Processing is often performed from the melt state,and the cooling rate plays a critical role in determining whether amorphous or semicrystalline products are formed alongside other process parameters such as the pressure and shear rates.To understand the structure formation during processing,knowledge of the cooling rate dependence is therefore essential.As all of these processes are associated with thermal effects,calorimetry is universally applicable here.Achieving cooling rates that are comparable to those during processing has therefore long been a challenge for calorimetric measurement methods.With the introduction of MEMS-based chip sensors for calorimetry,significant progress has been made in reproducing conditions,such as those that occur during injection molding.These special calorimetric techniques are often summarized under the terms Fast Scanning Calorimetry(FSC)or Nanocalorimetry,alluding to nanogram samples.Investigations with controlled cooling rates of up to 1×10^(6)K/s are now possible with special chip sensors and allow the study of material properties under extreme conditions.Technological issues such as crystallization and nucleation processes under processrelevant conditions can be investigated in most cases with commercial devices that achieve cooling rates of 10^(4)K/s.The cooling rates to be considered in relation to various manufacturing processes are discussed here,and the functionality of corresponding chip calorimeters is briefly presented.Since calorimetry only provides general information on the processes taking place in the material,but not directly on the resulting structures,combinations of FSC and methods for structure elucidation,e.g.,microscopy,are also presented.The main part of this Account deals with contributions of FSC to the understanding of crystallization processes under conditions as they occur in different manufacturing processes.Not only the influence of the cooling rate during injection molding but also the multistage cooling by chill rolls during film production is considered.Thanks to the high scanning rate of FSC,needed to bypass crystallization in the low-supercooling temperature range where heterogeneous nucleation dominates,an important aspect of polymer structure formation-homogeneous crystal nucleation-has become accessible for direct observation.Homogeneous nucleation can occur not only during cooling but also during storage at temperatures close to or even below the glass transition temperature in the amorphous state.The possibilities of FSC for the generation and investigation of amorphous states are illustrated by an example.Finally,possible further developments of FSC and expected further applications of this fascinating technology are considered.展开更多
Viscosity is a crucial dynamic property for alloy liquids.For alloy liquids with glass-forming ability,their viscosity undergoes a change of more than ten orders of magnitude upon cooling,and eventually,a transition f...Viscosity is a crucial dynamic property for alloy liquids.For alloy liquids with glass-forming ability,their viscosity undergoes a change of more than ten orders of magnitude upon cooling,and eventually,a transition from liquid to glassy state occurs when viscosity reaches 1012 Pa s.Nevertheless,the viscosity measurement in the supercooled liquid region(SLR)has been an experimental challenge.Here,in this work,by combining conventional and fast scanning calorimeters,the accurate viscosity of supercooled liquids for Au_(49)Ag_(5.5)Pd_(2.3)Cu_(26.9)Si_(16.3) and Zr_(44)Ti_(11)Cu_(10)Ni_(10)Be_(25) metallic glasses(MGs)was measured over a wide viscosity range of 10^(6)-10^(12) Pa s.Moreover,the viscosity range of 10^(6)-10^(8) Pa s is generally selected for thermoplastic forming(TPF),which takes advantage of the dramatic softening that MGs exhibit after being heated into the SLR.We further gave the TPF process window covering the range of processing temperature and time by utilizing the obtained viscosity data and timetemperature-transformation curves.The optimal time window avoiding property degradation was also determined,based on that there was no marked effect on the mechanical properties of MGs when crystallinity was below~5%.Our findings not only provide the accurate viscosity data in the SLR,but also determine the optimal process parameters for the TPF process.展开更多
The phenomenon of vitrification,or glass transition,remains one of the most intriguing unsolved issues in condensed matter physics[1].Differential scanning calorimetry(DSC)has long been considered a valuable technique...The phenomenon of vitrification,or glass transition,remains one of the most intriguing unsolved issues in condensed matter physics[1].Differential scanning calorimetry(DSC)has long been considered a valuable technique for addressing this question[2].Since its commercialization in the 1960s,DSC has become a widely used tool in materials science for characterizing thermodynamic and kinetics properties[3],phase transitions[4],and enthalpy changes[5]in glasses.Traditional DSC features a time constant of approximately 1 s and scanning rate ranging from 0.1 to 300 K min^(-1).With the emergence of fast scanning calorimetry(FSC),this tool has evolved from a basic characterization method to an advanced and versatile technique for various aspects of glassy materials.The first generation of commercial FSC,utilizing a twin-chip sensor designed for the Mettler Toledo Flash 1 DSC[6,7],achieved a signal time constant below 1 ms,enabling high heating rate(qh)up to 40000 K s^(-1) and cooling rate(qc)of 10000 K s^(-1) within a temperature range of 173 to 793 K.The second generation,FDSC 2+,further increased these rates to 60000 K s^(-1) for heating and 40000 K s^(-1) for cooling,expanding the maximum temperature to 1273 K and facilitating the in-situ melting of various alloys[8].展开更多
To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specif...To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specifically,in the proposed scanning method,the piezoelectric actuator tracks a well-designed smooth periodic signal in x-direction,and simultaneously tracks a step signal in y-direction.The advantage of the proposed method is that it does not require additional data reprocessing to construct the morphology of the sample surface,while significantly increasing the scanning bandwidth restricted by the raster scanning method.Particularly,to directly utilize the height data collected by scanning to produce the sample morphology,the forward process in the common raster scanning mode is retained in the proposed method,the tracking signal in the forward process is thus set to a ramp function in x-direction.In addition,to ensure the continuity and smoothness of the entire tracking signal in x-direction,a segment of a sine curve is uniquely determined as the backward tracking signal by position and acceleration constraints,so as to ensure that the forward and backward curves are continuous and acceleration-continuous at the intersection point.Moreover,the frequency spectrum analysis of the designed smooth signal is carried out to exhibit the depressed amplitudes of high-frequency components,which demonstrates that the proposed method is able to reduce the resonance in AFM high-speed scanning,so as to improve the capacity of rapidly generating high-quality images.Finally,convincing comparison experiments are implemented to verify the imaging performance of the designed scanning algorithm.展开更多
Fast differential scanning calorimetry is an advanced thermal-analysis instrument.It can perform fast heating and fast cooling on matters with the maximum temperature of 1273 K,with scanning rates spanning five orders...Fast differential scanning calorimetry is an advanced thermal-analysis instrument.It can perform fast heating and fast cooling on matters with the maximum temperature of 1273 K,with scanning rates spanning five orders of magnitude and a maximum of many tens of thousands Kelvin per second.Thus,it is possible to vitrify a wide range of polymers,molecular liquids and alloys in-situ,enabling isothermal and non-isothermal testing for thermodynamic or kinetic investigations.In this work,the most recent results obtained with fast differential scanning calorimetry for non-metallic glasses are reviewed.The physics underlying the functions of the instrument is explained,along with the specializations of sample preparation,data correction,and result interpretation.The paper covers key findings in the field of non-metallic glass research,such as crystallization dynamics,liquidliquid transition and glass stability.The purpose of this work is to provide beginners with high-quality data by preparing samples on chips and adjusting for thermal lags,and to help experienced scientists to investigate novel perspectives on metallic glasses using the same methodology as non-metallic glasses.展开更多
Liquid-liquid transition in metallic melts is an intriguing phenomenon often confused with liquid-liquid separation,oxidation or precipitation.Here,we employ a state-of-the-art ultrafast chip-based differential scanni...Liquid-liquid transition in metallic melts is an intriguing phenomenon often confused with liquid-liquid separation,oxidation or precipitation.Here,we employ a state-of-the-art ultrafast chip-based differential scanning calorimeter to investigate the thermal behavior of six metallic melts,ranging from unary to quinary systems,at temperatures above their liquidus.Calorimetric signals of liquid-liquid transition vary across systems:Sn melts showed no direct endothermic or exothermic events,though liquid-liquid transition influenced solidification and melting temperatures,while Yb-Zn melts exhibited an exothermic peak during cooling,indicating liquid-liquid transition.Thermal signals in other systems including Li,Pd-Ni-P,Yb-Mg-Zn-Cu and Au-Ag-Pd-Cu-Si,are primarily driven by compositional changes.Our in-situ analysis provides new insights into the structural and compositional evolution of metallic melts,offering significant implications for the design and processing of novel materials.展开更多
The precipitation behaviour during cooling from solution annealing of high alloyed 7049A aluminium alloy was investigated, covering the complete cooling-rate-range of technical interest. This ranges from slow cooling ...The precipitation behaviour during cooling from solution annealing of high alloyed 7049A aluminium alloy was investigated, covering the complete cooling-rate-range of technical interest. This ranges from slow cooling rates close to equilibrium up to rates above complete supersaturation and is covering seven orders of magnitude in cooling rate （0.0005 to 5000 K/s）. The continuous cooling precipitation behaviour of 7049A alloy was recorded by combining different differential scanning calorimetry （DSC） techniques and microstructure analysis by SEM and Vickers hardness testing. The high alloyed, high strength and quench sensitive wrought aluminium alloy 7049A was investigated during quenching from solution annealing by conventional DSC in the cooling rate range of 0.0005 to 4 K/s. In this range at least two exothermal precipitation reactions were observed： a high temperature reaction in a narrow temperature interval of 450-430℃, and a low temperature reaction in a broad temperature interval down to about 200 ℃. Intensities of both reactions decreased with increasing cooling rate. Quenching from solution annealing with rates up to 1000 K/s was investigated by differential fast scanning calorimetry （DFSC） and the differential reheating method （DRM）. A critical quenching rate to suppress all precipitation reactions of 100-300 K/s was been determined.展开更多
The preparation and solidification of metallic droplets attract more and more attention for their signiifcance in both engineering and scientiifc ifelds. In this paper, the preparation and characterization of Sn-based...The preparation and solidification of metallic droplets attract more and more attention for their signiifcance in both engineering and scientiifc ifelds. In this paper, the preparation and characterization of Sn-based al oy droplets using different methods such as atomization and consumable electrode direct current arc （CDCA） technique are reviewed. The morphology and structure of these droplets were determined by optical microscopy, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The solidiifcation behavior of single droplet was systematical y studied by means of scanning calorimetry （DSC）, and the nucleation kinetics was also calculated. In particular, the development of fast scanning calorimetry （FSC） made it possible to investigate the evolution of undercooling under ultrafast but control able heating and cooling conditions. The combination of CDCA technique and FSC measurements opens up a new door for quantitative studies on droplet solidiifcation, which is accessible to demonstrate some theories by experiments.展开更多
Using micromachined sensors,fast scanning calorimetry(FSC)is a revolutionary calorimetric technique that offers ultrahigh scanning rate of up to 10^(6) K s^(-1) and ultrahigh sensitivity with a heat capacity resolutio...Using micromachined sensors,fast scanning calorimetry(FSC)is a revolutionary calorimetric technique that offers ultrahigh scanning rate of up to 10^(6) K s^(-1) and ultrahigh sensitivity with a heat capacity resolution better than 1 nJ K^(-1).With a focus on the thermophysical properties of various glasses,it has garnered a lot of interest in the field of glasses science.It is used to conduct quantitative analyses of glass transition,crystallization,and fusion,creating a window for studying fast dynamics that were previously largely unexplored.In light of this,we are pleased to present a state-of-the-art analysis of advances in calorimetric investigations of glasses science,via organizing a special topic that includes three Research Articles,one Invited Review and one News&Views.These articles provide an overview of FSC investigations of hybrid,metallic,polymeric and molecular glasses.展开更多
Hybrid glasses are a novel class of glass formers that possess unique coordination bonds.Size effects on vitrification have been observed in other glassy materials such as metallic glasses and polymers,but their impac...Hybrid glasses are a novel class of glass formers that possess unique coordination bonds.Size effects on vitrification have been observed in other glassy materials such as metallic glasses and polymers,but their impact on hybrid glasses has yet to be explored.In this study,we examine the size-dependent vitrification behavior of hybrid glasses using fast scanning calorimetry across a broad range of heating and cooling rates.Our results are similar to that observed in polymer and metallic glasses,the glass transition temperature(T_(g))is not significantly influenced by sample size at the micro-meter scale at cooling rates larger than or equal to 30 K/s.Furthermore,the vitrification enthalpy displays a clear dependence on sample size,with smaller samples exhibiting a larger overshoot enthalpy,which is attributed to a reduction of fictive temperature values(T_(f))with size.These features originate from the network structure and flexibility of coordination bonding.Our findings suggest that the vitrification enthalpy is more fundamental than the temperature in size effects and that the low enthalpy state of smaller hybrid glass samples has implications for their functional properties.展开更多
Fragility is one of the central concepts in glass and liquid sciences,as it characterizes the extent of deviation of viscosity from Arrhenius behavior and is linked to a range of glass properties.However,the intervent...Fragility is one of the central concepts in glass and liquid sciences,as it characterizes the extent of deviation of viscosity from Arrhenius behavior and is linked to a range of glass properties.However,the intervention of crystallization often prevents the assessment of fragility in poor glass-formers,such as supercooled metallic liquids.Hence experimental data on their compositional dependence are scarce,let alone fundamentally understood.In this work,we use fast scanning calorimetry to overcome this obstacle and systematically study the fragility in a ternary La–Ni–Al system,over previously inaccessible composition space.We observe fragility dropped in a small range with the Al alloying,indicating an alloying-induced fragility crossover.We use x-ray photoelectron spectroscopy,resistance measurements,electronic structure calculations,and DFT-based deep-learning atomic simulations to investigate the cause of this fragility drop.These results show that the fragility crossover can be fundamentally ascribed to the electronic covalency associated with the unique Al–Al interactions.Our findings provide insight into the origin of fragility in metallic liquids from an electronic structure perspective and pave a new way for the design of metallic glasses.展开更多
The stability of glass against crystallization is of importance in practical applications and theoretical understanding of the nature of glass materials.Annealing has complicated influences on glass stability.It induc...The stability of glass against crystallization is of importance in practical applications and theoretical understanding of the nature of glass materials.Annealing has complicated influences on glass stability.It induces either delayed or early crystallization,depending on detailed protocols and specific materials.By interrogating the thermal behaviors of twelve metallic glasses(MGs),we find that enhanced stability is correlated to another process:the so-called shadow glass transition and its evolution.Delayed crystallization can be observed when the shadow glass transition is shifted to cross the temperature of crystallization.Concurrently,the shadow glass transition evolves to an enthalpy overshoot.Molecular dynamics simulations support these findings and suggest that the suppressed string-like motion,relating to the shadow glass transition and the enthalpy overshoot,is likely the origin of the postponed nucleation ordering and enhanced glass stability.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52422301)Natural Science Foundation of Jilin Province(No.SKL202302033)。
文摘The crystallization behavior of two commercial polyolefin elastomer(POE)samples was investigated using the fast scanning chip calorimetry(FSC)technique.Non-isothermal crystallization of the POE samples during cooling to low temperatures cannot be inhibited under the largest efficient cooling rate employed in the current work.Thus,the isothermal crystallization of POE samples was limited to a narrow temperature range.When the POE samples were cooled to a certain temperature below the non-isothermal crystallization temperature for crystallization,a crystallization time dependent melting peak appeared in the low temperature region besides the high temperature melting peak originated from the non-isothermal crystallization.This low temperature melting peak was arisen from the melting of crystals isothermally crystallized at the selected crystallization temperature.At each crystallization temperature,the lengths of crystallizable segments were different,thus,the low melting peak increased with increasing the crystallization temperature.In terms of the high melting peak attributed to the non-isothermally crystallized crystals,it somehow decreased with increasing crystallization time and then became constant with further increasing crystallization time at the selected crystallization temperature.This could be explained by the fact that the crystallizable sequences with longer length would nucleate and crystallize first to form thicker crystals during cooling.The subsequent crystallization contributed by the shorter crystallizable sequences will result in the formation of thinner crystals,causing the melting peak to shift to the lower temperature.
基金supported by the 863 National Plan Foundation of China under Grant No.2007AA01Z333 and Special Grand National Project of China under Grant No.2009ZX02204-008.
文摘A leukocyte image fast scanning method based on max min distance clustering is proposed.Because of the lower proportion and uneven distribution of leukocytes in human peripheral blood,there will not be any leukocyte in lager quantity of the captured images if we directly scan the blood smear along an ordinary zigzag scanning routine with high power(100^(x))objective.Due to the larger field of view of low power(10^(x))objective,the captured low power blood smear images can be used to locate leukocytes.All of the located positions make up a specific routine,if we scan the blood smear along this routine with high power objective,there will be definitely leukocytes in almost all of the captured images.Considering the number of captured images is still large and some leukocytes may be redundantly captured twice or more,a leukocyte clustering method based on max-min distance clustering is developed to reduce the total number of captured images as well as the number of redundantly captured leukocytes.This method can improve the scanning eficiency obviously.The experimental results show that the proposed method can shorten scanning time from 8.0-14.0min to 2.54.0 min while extracting 110 nonredundant individual high power leukocyte images.
基金support by Wenzhou City’s key R&D project,“Unveiling the List and Assigning the Leader”(ZG2023044)Anhui Provence key R&D project(202304a05020081)the DFG SPP2122 project ZH 662/3−2 and Open Research Fund of the State Key Laboratory of Polymer Physics and Chemistry,Changchun Institute of Applied Chemistry,Chinese Academy of Sciences.
文摘CONSPECTUS:The global production of polymer products currently exceeds 400 megatons annually.To ensure effective and environmentally responsible use of this vast resource,optimizing the properties of the products is essential.Achieving this requires precise control over the internal structure of the polymers.Depending on the materials used,polymers can exist in either amorphous or semicrystalline states.Processing is often performed from the melt state,and the cooling rate plays a critical role in determining whether amorphous or semicrystalline products are formed alongside other process parameters such as the pressure and shear rates.To understand the structure formation during processing,knowledge of the cooling rate dependence is therefore essential.As all of these processes are associated with thermal effects,calorimetry is universally applicable here.Achieving cooling rates that are comparable to those during processing has therefore long been a challenge for calorimetric measurement methods.With the introduction of MEMS-based chip sensors for calorimetry,significant progress has been made in reproducing conditions,such as those that occur during injection molding.These special calorimetric techniques are often summarized under the terms Fast Scanning Calorimetry(FSC)or Nanocalorimetry,alluding to nanogram samples.Investigations with controlled cooling rates of up to 1×10^(6)K/s are now possible with special chip sensors and allow the study of material properties under extreme conditions.Technological issues such as crystallization and nucleation processes under processrelevant conditions can be investigated in most cases with commercial devices that achieve cooling rates of 10^(4)K/s.The cooling rates to be considered in relation to various manufacturing processes are discussed here,and the functionality of corresponding chip calorimeters is briefly presented.Since calorimetry only provides general information on the processes taking place in the material,but not directly on the resulting structures,combinations of FSC and methods for structure elucidation,e.g.,microscopy,are also presented.The main part of this Account deals with contributions of FSC to the understanding of crystallization processes under conditions as they occur in different manufacturing processes.Not only the influence of the cooling rate during injection molding but also the multistage cooling by chill rolls during film production is considered.Thanks to the high scanning rate of FSC,needed to bypass crystallization in the low-supercooling temperature range where heterogeneous nucleation dominates,an important aspect of polymer structure formation-homogeneous crystal nucleation-has become accessible for direct observation.Homogeneous nucleation can occur not only during cooling but also during storage at temperatures close to or even below the glass transition temperature in the amorphous state.The possibilities of FSC for the generation and investigation of amorphous states are illustrated by an example.Finally,possible further developments of FSC and expected further applications of this fascinating technology are considered.
基金supported by the Taishan Scholars Program of Shandong Province(Grant No.tsqn201909010)the Key Basic and Applied Research Program of Guangdong Province(Grant No.2019B030302010)+1 种基金the National Natural Science Foundation of China(Grant Nos.51901139,51971120,and U1902221)the Key R&D Program of Shandong Province(Grant No.2022CXGC020308)。
文摘Viscosity is a crucial dynamic property for alloy liquids.For alloy liquids with glass-forming ability,their viscosity undergoes a change of more than ten orders of magnitude upon cooling,and eventually,a transition from liquid to glassy state occurs when viscosity reaches 1012 Pa s.Nevertheless,the viscosity measurement in the supercooled liquid region(SLR)has been an experimental challenge.Here,in this work,by combining conventional and fast scanning calorimeters,the accurate viscosity of supercooled liquids for Au_(49)Ag_(5.5)Pd_(2.3)Cu_(26.9)Si_(16.3) and Zr_(44)Ti_(11)Cu_(10)Ni_(10)Be_(25) metallic glasses(MGs)was measured over a wide viscosity range of 10^(6)-10^(12) Pa s.Moreover,the viscosity range of 10^(6)-10^(8) Pa s is generally selected for thermoplastic forming(TPF),which takes advantage of the dramatic softening that MGs exhibit after being heated into the SLR.We further gave the TPF process window covering the range of processing temperature and time by utilizing the obtained viscosity data and timetemperature-transformation curves.The optimal time window avoiding property degradation was also determined,based on that there was no marked effect on the mechanical properties of MGs when crystallinity was below~5%.Our findings not only provide the accurate viscosity data in the SLR,but also determine the optimal process parameters for the TPF process.
文摘The phenomenon of vitrification,or glass transition,remains one of the most intriguing unsolved issues in condensed matter physics[1].Differential scanning calorimetry(DSC)has long been considered a valuable technique for addressing this question[2].Since its commercialization in the 1960s,DSC has become a widely used tool in materials science for characterizing thermodynamic and kinetics properties[3],phase transitions[4],and enthalpy changes[5]in glasses.Traditional DSC features a time constant of approximately 1 s and scanning rate ranging from 0.1 to 300 K min^(-1).With the emergence of fast scanning calorimetry(FSC),this tool has evolved from a basic characterization method to an advanced and versatile technique for various aspects of glassy materials.The first generation of commercial FSC,utilizing a twin-chip sensor designed for the Mettler Toledo Flash 1 DSC[6,7],achieved a signal time constant below 1 ms,enabling high heating rate(qh)up to 40000 K s^(-1) and cooling rate(qc)of 10000 K s^(-1) within a temperature range of 173 to 793 K.The second generation,FDSC 2+,further increased these rates to 60000 K s^(-1) for heating and 40000 K s^(-1) for cooling,expanding the maximum temperature to 1273 K and facilitating the in-situ melting of various alloys[8].
基金supported by the National Natural Science Foundation of China(Nos.62003172,61633012,and 21933006).
文摘To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specifically,in the proposed scanning method,the piezoelectric actuator tracks a well-designed smooth periodic signal in x-direction,and simultaneously tracks a step signal in y-direction.The advantage of the proposed method is that it does not require additional data reprocessing to construct the morphology of the sample surface,while significantly increasing the scanning bandwidth restricted by the raster scanning method.Particularly,to directly utilize the height data collected by scanning to produce the sample morphology,the forward process in the common raster scanning mode is retained in the proposed method,the tracking signal in the forward process is thus set to a ramp function in x-direction.In addition,to ensure the continuity and smoothness of the entire tracking signal in x-direction,a segment of a sine curve is uniquely determined as the backward tracking signal by position and acceleration constraints,so as to ensure that the forward and backward curves are continuous and acceleration-continuous at the intersection point.Moreover,the frequency spectrum analysis of the designed smooth signal is carried out to exhibit the depressed amplitudes of high-frequency components,which demonstrates that the proposed method is able to reduce the resonance in AFM high-speed scanning,so as to improve the capacity of rapidly generating high-quality images.Finally,convincing comparison experiments are implemented to verify the imaging performance of the designed scanning algorithm.
基金supported by the National Natural Science Foundation of China(Grant Nos.52471188,and 92263103)。
文摘Fast differential scanning calorimetry is an advanced thermal-analysis instrument.It can perform fast heating and fast cooling on matters with the maximum temperature of 1273 K,with scanning rates spanning five orders of magnitude and a maximum of many tens of thousands Kelvin per second.Thus,it is possible to vitrify a wide range of polymers,molecular liquids and alloys in-situ,enabling isothermal and non-isothermal testing for thermodynamic or kinetic investigations.In this work,the most recent results obtained with fast differential scanning calorimetry for non-metallic glasses are reviewed.The physics underlying the functions of the instrument is explained,along with the specializations of sample preparation,data correction,and result interpretation.The paper covers key findings in the field of non-metallic glass research,such as crystallization dynamics,liquidliquid transition and glass stability.The purpose of this work is to provide beginners with high-quality data by preparing samples on chips and adjusting for thermal lags,and to help experienced scientists to investigate novel perspectives on metallic glasses using the same methodology as non-metallic glasses.
基金supported by the National Natural Science Foundation of China(Grant Nos.92263103,and 52471188).
文摘Liquid-liquid transition in metallic melts is an intriguing phenomenon often confused with liquid-liquid separation,oxidation or precipitation.Here,we employ a state-of-the-art ultrafast chip-based differential scanning calorimeter to investigate the thermal behavior of six metallic melts,ranging from unary to quinary systems,at temperatures above their liquidus.Calorimetric signals of liquid-liquid transition vary across systems:Sn melts showed no direct endothermic or exothermic events,though liquid-liquid transition influenced solidification and melting temperatures,while Yb-Zn melts exhibited an exothermic peak during cooling,indicating liquid-liquid transition.Thermal signals in other systems including Li,Pd-Ni-P,Yb-Mg-Zn-Cu and Au-Ag-Pd-Cu-Si,are primarily driven by compositional changes.Our in-situ analysis provides new insights into the structural and compositional evolution of metallic melts,offering significant implications for the design and processing of novel materials.
基金funding of this work by a scholarship of the German State of Mecklenburg-Vorpommern via University of Rostock,Interdisciplinary Faculty
文摘The precipitation behaviour during cooling from solution annealing of high alloyed 7049A aluminium alloy was investigated, covering the complete cooling-rate-range of technical interest. This ranges from slow cooling rates close to equilibrium up to rates above complete supersaturation and is covering seven orders of magnitude in cooling rate （0.0005 to 5000 K/s）. The continuous cooling precipitation behaviour of 7049A alloy was recorded by combining different differential scanning calorimetry （DSC） techniques and microstructure analysis by SEM and Vickers hardness testing. The high alloyed, high strength and quench sensitive wrought aluminium alloy 7049A was investigated during quenching from solution annealing by conventional DSC in the cooling rate range of 0.0005 to 4 K/s. In this range at least two exothermal precipitation reactions were observed： a high temperature reaction in a narrow temperature interval of 450-430℃, and a low temperature reaction in a broad temperature interval down to about 200 ℃. Intensities of both reactions decreased with increasing cooling rate. Quenching from solution annealing with rates up to 1000 K/s was investigated by differential fast scanning calorimetry （DFSC） and the differential reheating method （DRM）. A critical quenching rate to suppress all precipitation reactions of 100-300 K/s was been determined.
基金supported by the National Natural Science Foundation of China(Grant Nos.51171105 and 50971086)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningthe 085 project in Shanghai University
文摘The preparation and solidification of metallic droplets attract more and more attention for their signiifcance in both engineering and scientiifc ifelds. In this paper, the preparation and characterization of Sn-based al oy droplets using different methods such as atomization and consumable electrode direct current arc （CDCA） technique are reviewed. The morphology and structure of these droplets were determined by optical microscopy, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The solidiifcation behavior of single droplet was systematical y studied by means of scanning calorimetry （DSC）, and the nucleation kinetics was also calculated. In particular, the development of fast scanning calorimetry （FSC） made it possible to investigate the evolution of undercooling under ultrafast but control able heating and cooling conditions. The combination of CDCA technique and FSC measurements opens up a new door for quantitative studies on droplet solidiifcation, which is accessible to demonstrate some theories by experiments.
文摘Using micromachined sensors,fast scanning calorimetry(FSC)is a revolutionary calorimetric technique that offers ultrahigh scanning rate of up to 10^(6) K s^(-1) and ultrahigh sensitivity with a heat capacity resolution better than 1 nJ K^(-1).With a focus on the thermophysical properties of various glasses,it has garnered a lot of interest in the field of glasses science.It is used to conduct quantitative analyses of glass transition,crystallization,and fusion,creating a window for studying fast dynamics that were previously largely unexplored.In light of this,we are pleased to present a state-of-the-art analysis of advances in calorimetric investigations of glasses science,via organizing a special topic that includes three Research Articles,one Invited Review and one News&Views.These articles provide an overview of FSC investigations of hybrid,metallic,polymeric and molecular glasses.
基金supported by the National Thousand Young Talents Program of China,the National Natural Science Foundation of China(Grant Nos.52201180 and 22071273)the Foundation of Chongqing Normal University(Grant No.24XLB019)the China Postdoctoral Science Foundation(Grant Nos.2023T160241 and 2023M731176).
文摘Hybrid glasses are a novel class of glass formers that possess unique coordination bonds.Size effects on vitrification have been observed in other glassy materials such as metallic glasses and polymers,but their impact on hybrid glasses has yet to be explored.In this study,we examine the size-dependent vitrification behavior of hybrid glasses using fast scanning calorimetry across a broad range of heating and cooling rates.Our results are similar to that observed in polymer and metallic glasses,the glass transition temperature(T_(g))is not significantly influenced by sample size at the micro-meter scale at cooling rates larger than or equal to 30 K/s.Furthermore,the vitrification enthalpy displays a clear dependence on sample size,with smaller samples exhibiting a larger overshoot enthalpy,which is attributed to a reduction of fictive temperature values(T_(f))with size.These features originate from the network structure and flexibility of coordination bonding.Our findings suggest that the vitrification enthalpy is more fundamental than the temperature in size effects and that the low enthalpy state of smaller hybrid glass samples has implications for their functional properties.
基金National Thousand Young Talents Program of China,and the National Natural Science Foundation of China(NSFC 52201180).
文摘Fragility is one of the central concepts in glass and liquid sciences,as it characterizes the extent of deviation of viscosity from Arrhenius behavior and is linked to a range of glass properties.However,the intervention of crystallization often prevents the assessment of fragility in poor glass-formers,such as supercooled metallic liquids.Hence experimental data on their compositional dependence are scarce,let alone fundamentally understood.In this work,we use fast scanning calorimetry to overcome this obstacle and systematically study the fragility in a ternary La–Ni–Al system,over previously inaccessible composition space.We observe fragility dropped in a small range with the Al alloying,indicating an alloying-induced fragility crossover.We use x-ray photoelectron spectroscopy,resistance measurements,electronic structure calculations,and DFT-based deep-learning atomic simulations to investigate the cause of this fragility drop.These results show that the fragility crossover can be fundamentally ascribed to the electronic covalency associated with the unique Al–Al interactions.Our findings provide insight into the origin of fragility in metallic liquids from an electronic structure perspective and pave a new way for the design of metallic glasses.
基金supported by the National Thousand Young Talents Program of China,the National Natural Science Foundation of China(52071147 and 52201180)the China Postdoctoral Science Foundation(2023T160241 and2023M731176)S.W.thanks the support of Novo Nordisk Foundation(NNF21OC0071257)
文摘The stability of glass against crystallization is of importance in practical applications and theoretical understanding of the nature of glass materials.Annealing has complicated influences on glass stability.It induces either delayed or early crystallization,depending on detailed protocols and specific materials.By interrogating the thermal behaviors of twelve metallic glasses(MGs),we find that enhanced stability is correlated to another process:the so-called shadow glass transition and its evolution.Delayed crystallization can be observed when the shadow glass transition is shifted to cross the temperature of crystallization.Concurrently,the shadow glass transition evolves to an enthalpy overshoot.Molecular dynamics simulations support these findings and suggest that the suppressed string-like motion,relating to the shadow glass transition and the enthalpy overshoot,is likely the origin of the postponed nucleation ordering and enhanced glass stability.
