Germanium-tin films with rather high Sn content(28.04% and 29.61%) are deposited directly on Si(100) and Si(111)substrates by magnetron sputtering. The mechanism of the effect of rapid thermal annealing on the Sn surf...Germanium-tin films with rather high Sn content(28.04% and 29.61%) are deposited directly on Si(100) and Si(111)substrates by magnetron sputtering. The mechanism of the effect of rapid thermal annealing on the Sn surface segregation of Ge_(1-x)Sn_x films is investigated by x-ray photoelectron spectroscopy(XPS) and atomic force microscopy(AFM). The x-ray diffraction(XRD) is also performed to determine the crystallinities of the Ge_(1-x)Sn_x films. The experimental results indicate that root mean square(RMS) values of the annealed samples are comparatively small and have no noticeable changes for the as-grown sample when annealing temperature is below 400℃. The diameter of the Sn three-dimensional(3 D) island becomes larger than that of an as-grown sample when the annealing temperature is 700℃. In addition, the Sn surface composition decreases when annealing temperature ranges from 400℃ to 700℃. However, Sn bulk compositions in samples A and B are kept almost unchanged when the annealing temperature is below 600℃. The present investigation demonstrates that the crystallinity of Ge_(1-x)Sn_x/Si(111) has no obvious advantage over that of Ge_(1-x)Sn_x/Si(100) and the selection of Si(111) substrate is an effective method to improve the surface morphologies of Ge_(1-x)Sn_x films. We also find that more severe Sn surface segregation occurs in the Ge_(1-x)Sn_x/Si(111) sample during annealing than in the Ge_(1-x)Sn_x/Si(100) sample.展开更多
Electrochemical insertion/extraction of Li on cathode materials of spinel type LiMn2O4 and ordered rock-salt type LiCo0.5 Ni0.5O2 was measured on samples of which structures were well characterized. On the basis of ex...Electrochemical insertion/extraction of Li on cathode materials of spinel type LiMn2O4 and ordered rock-salt type LiCo0.5 Ni0.5O2 was measured on samples of which structures were well characterized. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materiaIs on electrochemical Li insertion/extraction performance was discussed. These two transition metal oxides belong to onegroup that the crystallinity of these oxides affects to the performance.展开更多
WS2 exhibits tremendous potentials for Na-ions storage owing to high capacity(433 mAh g^(-1)). Nevertheless, WS2 layered structure is often exfoliated with rapid capacity decay and sluggish reaction kinetics.In this w...WS2 exhibits tremendous potentials for Na-ions storage owing to high capacity(433 mAh g^(-1)). Nevertheless, WS2 layered structure is often exfoliated with rapid capacity decay and sluggish reaction kinetics.In this work, WS2 nanosheets with different crystallinities are controlled by different synthesis methods.The high crystallinity WS2 exhibits high degree of interlayer order and strong interlayer force. It exhibits superior electrochemical properties, at the current density of 200 mA g^(-1) after 300 cycles with reversible capacity of 471 mAh g^(-1). Even at 5.0 A g^(-1), the capacities can still arrive at 240 mAh g^(-1) after 250 cycles, exhibiting stable cycling performance. Further electrochemical research finds that the high degree of interlayer order of layered WS2 structure can perform highly conducive Na+insertion/extraction with greatly improved contribution of intercalation capacity. Moreover, the strong interlayer force can effectively restrain the exfoliating of the WS2 nanosheets, guaranteeing the stability of the structure. Combining the above result reveals that controlling the order and force of the interlayer is an effective way to enhance the electrochemical properties of WS2 as SIBs anode materials. This work can provide new insight for inhibiting the exfoliation of layered compounds to pursue excellent electrochemical performance in Na-ion storage systems.展开更多
The dependence of polarization fatigue on crystallinity of vinylidene fluoride and trifluoroethylene copolymer films was studied.Experimental data indicated that the higher the crystallinity of the film was,the slower...The dependence of polarization fatigue on crystallinity of vinylidene fluoride and trifluoroethylene copolymer films was studied.Experimental data indicated that the higher the crystallinity of the film was,the slower the fatigue rate of the film became.A possible explanation was put forward,and it was regarded that the space charges,trapped at the boundaries of crystallites and/or captured by the defects lying both in amorphous and crystalline phases,should make the major contribution to polarization fa...展开更多
Electrochemical insertion/extraction of Li on cathode materials of anatase type TiO2, quasilayered structure V2O5 and layered structure MoO3 was measured on samples of which structures were well characterized and show...Electrochemical insertion/extraction of Li on cathode materials of anatase type TiO2, quasilayered structure V2O5 and layered structure MoO3 was measured on samples of which structures were well characterized and showed a wide range of crystallinity. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materials on electrochemical Li insertion/extraction pedermance was discussed. These three transition metal oxides were classified as one group on the basis of whether the crystallinity of these oxides affects to the performance or not; LiMn2O4 and LiCo0.5O2 belongs to the former group and TiO2, V2O5 and MoO3 to the latter.展开更多
The objective of this paper is to investigate the relative variations of the constants of the thermal properties and the degree of crystallinity of the mixtures (PP/EPR)/Calcium carbonates elaborated with the Micro Bi...The objective of this paper is to investigate the relative variations of the constants of the thermal properties and the degree of crystallinity of the mixtures (PP/EPR)/Calcium carbonates elaborated with the Micro Bivis. We have strengthened the basic copolymer PP/EPR of a low level (5%) by three calcium carbonates models socal312, socal322v, Winnofil spm. We then subjected the different mixtures obtained, two cycles of a thermal loading under differential scanning calorimetry DSC. We finally focused on the thermal properties of isotactic polypropylene (TfP, TcP, ΔHfP, ΔHcP) and we calculated the degree of crystallinity of the mixtures. Reducing the energy cost of implementing mixtures is one of the objectives of this work. We quantified the relative variations of the above properties with those of the base copolymer. It shows that at a low loading rate of calcium carbonate, there is a decrease in the enthalpies of crystallization during the second exothermic cycle, with values that can reach 5.53 J/gPP for the basic copolymer PP/EPR. During the second endothermic cycle, there is an overall increase in isotactic polypropylene melting temperature values for all the blends as well as for the basic copolymer PP/EPR. There is evidence that calcium carbonates are useful for lowering the melting energy of isotactic polypropylene, even at a low loading rate for the majority. The number of endothermic cycles accentuates this phenomenon which is linked to the presence in our composites, of a so-called confined amorphous phase.展开更多
Based on the X- ray scattering intensity theory, the correction factors of the degree ofcrystallinity formulae of the multicomponent polymers have been clearly defined. The formulae ofthe degree of crystallinity of th...Based on the X- ray scattering intensity theory, the correction factors of the degree ofcrystallinity formulae of the multicomponent polymers have been clearly defined. The formulae ofthe degree of crystallinity of the multicomponent polymers were derived in terms of WAXDtheory and improved graphic multipeak resolution methods. The results calculated aresatisfactory in comparison with the density measurement.展开更多
By means of the intensity theory of X-ray scattering and the two-phase concept of high polymer, the basic formula of the crystaUinity in block copolymers has been proposed after the corrections of atomic, temperature,...By means of the intensity theory of X-ray scattering and the two-phase concept of high polymer, the basic formula of the crystaUinity in block copolymers has been proposed after the corrections of atomic, temperature, absorption, Lorentz and polarization factor. Application of this method to different type poly (oxyethylene-styrene)block copolymers and the same type block copolymers with different EO contents indicates that the crystallinity in poly (oxyethylene-styrene ) block copolymers increases with the increase of the EO content and decreases in the order: PEO-PS-PEO】PEO-PS】PS-PEO-PS.展开更多
Based on the X-ray scattering intensity theory,the correction factors of thedegree of crystallinity formulae of the multicomponent polymers have been clearly defined.Theformula of degree of erystallinity of the multic...Based on the X-ray scattering intensity theory,the correction factors of thedegree of crystallinity formulae of the multicomponent polymers have been clearly defined.Theformula of degree of erystallinity of the multicomponent polymers was derived in terms of theWAXD theory ahd improved graphic multipeak resolution methods.The results calculated arecompatible with the density measurement.展开更多
Based on the X-ray scattering intensity theory and using the atomic scattering factorapproximate expression,the correction factors for three main crystalline peaks and an amorphouspeak of Nylon-1010 were calculated an...Based on the X-ray scattering intensity theory and using the atomic scattering factorapproximate expression,the correction factors for three main crystalline peaks and an amorphouspeak of Nylon-1010 were calculated and the formula of degree of crystallinity of Nylon-1010 wasderived by graphic multipeak resolution method. The results calculated are compatible with the density measurement and calorimetry.展开更多
As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potentia...As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potential of halide PVK solar cells as a highly competitive substitute to replace silicon-based solar cells in the photovoltaic market [2–6].展开更多
We investigated the impure phase problem and summarized its two formation mechanisms of YAG powders synthesized via the co-precipitation method.The ions loss problem caused by high concentration reaction solution in t...We investigated the impure phase problem and summarized its two formation mechanisms of YAG powders synthesized via the co-precipitation method.The ions loss problem caused by high concentration reaction solution in the titration process was emphatically studied,and the corresponding thermodynamic explanation was carried out.In addition,influence of powder crystallinity and its new qualitative and quantitative standards were studied.One reason of impure phase is the local nonuniform mixture of Y and Al elements in precursor,which easily causes intermediate phases during calcination and difficulty of high pure powders at low temperatures.The other reason is the precipitation dissolution during titration and then the Y^(3+)/Al^(3+) loss,caused by high concentration of reaction solution.The powder crystallinity can be promoted by increasing calcination temperature or holding time of precursor.Besides the routine XRD method,the TEM-EDX method should be also introduced to directly determine the quality of crystallinity.展开更多
In this paper the measurement of crystallinity(C)ofacrylic copolymer(PAC),by Swelling Differential Scan-ning Calorimetry(SDSC)is discussed.Common DSC isonly used for measuring the crystallinity of polymers withmelting...In this paper the measurement of crystallinity(C)ofacrylic copolymer(PAC),by Swelling Differential Scan-ning Calorimetry(SDSC)is discussed.Common DSC isonly used for measuring the crystallinity of polymers withmelting point,(T_m),below their decomposition temper-ature,(T_d).As temperature rises,polymers with swell-ing agent added become swollen and dissolved,goingthrough whole process of breaking solid structures.Thus,SDSC makes it possible to measure the crystallini-ty of polymers even with T_d below T_m.But the C mea-sured by WAXD and the total endothermal melting(swelling)heat in SDSC thermograms,(△H_l),are notlinearly correlated.It has been found that,instead of the△H_l,△H_l’obtained from the △H_l by subtracting the en-dothermal heat,△H_l,and the C measured by WAXDare linearly correlated.On the basis of this linear rela-tion,the unknown C of another PAC sample is measuredby SDSC.The result is in good accordance with thatmeasured by WAXD.展开更多
A modified mathematical model based on the melting and recrystallization of an initial distribution of melting temperatures predicts the melting behavior of polymer in differential scanning calorimetry ( DSC ), taking...A modified mathematical model based on the melting and recrystallization of an initial distribution of melting temperatures predicts the melting behavior of polymer in differential scanning calorimetry ( DSC ), taking into account of changes in heat of fusion with melting temperature of crystal and average heat capacity of sample. It has been used to analytically prove that the crystallinity measured on a DSC diagram could not be equal to the weight percentage of crystalline state in the initial specimen. The deviation of the measured crystallinity, as observed relevant to the melting and recrystallization processes, is caused by the changes of the heat of fusion with the melting temperature of crystals, as well as the difference of heat capacities of liquld and solid state polymer. Furthermore, upper and lower limits of the deviation have been discussed.展开更多
Covalent organic frameworks(COFs)are emerging as powerful electrochemical energy storage/conversion materials benefiting from the controlled pore and chemical structures,which are usually determined by the regulation ...Covalent organic frameworks(COFs)are emerging as powerful electrochemical energy storage/conversion materials benefiting from the controlled pore and chemical structures,which are usually determined by the regulation of the molecular building blocks.In contrast,the substituents are not considered significant for the electrochemical reactivity as they are usually removed during carbonization,which is necessary for improving the electrical conductivity of an electrode material.Here we show that the substituents play key roles not only in synthesizing COFs but also in controlling the COF structures during carbonization and thus the related electrochemical reactivity.Five characteristic substituents were used when synthesizing a new COF structure and it was found that electron-withdrawing strength of the substituents significantly influences the crystallinity of the COFs by tuning the reactivity of building blocks,or even determines whether the crystalline COF can be constructed.Moreover,the differences in chemical groups,sizes,and thermal stabilities of the substituents result in varied pore-collapse behaviors and the structures of the carbonized COFs,which show diverse effects on the electrochemical performances.An optimal material shows the highest surface area of 2131 m^(2)/g,rich pores around 1 nm,and the highest ratio of sp^(2) carbon among the samples,corresponding to the largest double-layer specific capacity over 125 F/g in an ionic liquid electrolyte,while another material with the lowest surface area and N-doping level exhibits a high H_(2)O_(2) production selectivity over 80%through selective oxygen reduction.This study shows guiding significance for the design of building blocks and substituents for COFs and further the carbonized carbons,and also exhibits the great potential of substituent engineering in modulating the electrochemical reactivity.展开更多
Free radical polymerized palladium polyacrylate was characterized by X-ray diffraction. Various parameters including mean crystallite size, interchain separation and radius of gyration have been calculated and discuss...Free radical polymerized palladium polyacrylate was characterized by X-ray diffraction. Various parameters including mean crystallite size, interchain separation and radius of gyration have been calculated and discussed with respect to the concentration of Pd in the polymeric salt. The results show that polymer is predominantly amorphous in nature.展开更多
Phase change material microcapsules (MicroPCMs) with nano composite structures (NC-MicroPCMs) were fabricated to meet higher demand of thermal stability and hold core better. Degree of crystallinity (DOC) of the NC-Mi...Phase change material microcapsules (MicroPCMs) with nano composite structures (NC-MicroPCMs) were fabricated to meet higher demand of thermal stability and hold core better. Degree of crystallinity (DOC) of the NC-MicroPCMs was evaluated by the differential scanning calorimeter (DSC). The effectiveness of some processing variables, in terms of formaldehyde and melamine molar ratio F/M, weight ratio of core and shell material C/S, and the dosage of silver nano particles D(%), were analyzed statistically. It was found that: (1) DOC was dependent on these processing variables; (2) doping silver nano particles was beneficial to the formation of shell crystallite structure; and (3) higher F/M was helpful in getting a higher DOC for both NC-MicroPCMs and MicroPCMs. Also, DOC was found to be associated with thermal stability and the two features were confirmed, which showed a closely positive correlation.展开更多
Cenospheres are produced in very large amount in thermal power plants. They are always looked upon as fillers used to reduce the density and cost of the polymer. If cenosphere particles are allowed to remain properly ...Cenospheres are produced in very large amount in thermal power plants. They are always looked upon as fillers used to reduce the density and cost of the polymer. If cenosphere particles are allowed to remain properly dispersed by taking it in lower concentration, significant improvement in its mechanical, thermal, electrical, crystallinity, colorimetric and morphological properties are expected. To make it happen, epoxy/cenosphere composites were prepared, having lower concentration of cenosphere. Concentration of cenosphere in epoxy, cured with triethylenetetramine, was changed as 0, 3, 5, 7 and 10. Tensile Strength, Tensile Modulus, Percentage Elongation at Break and Crystallinity decreased, whereas, Flexural Strength and Flexural Modulus were found to have increased by 50% and above 100% respectively at 7 phr loading of cenosphere in epoxy. Thermal and electrical stability also increased with increase in concentration of cenosphere in the epoxy, however, the samples became blackish with increased addition of cenosphere. Using SEM analysis it was found that, cenospheres were properly and uniformly dispersed at 7 phr concentration and formed aggregates at 10 phr concentration.展开更多
In this paper,the relation between the tensile strength,breaking elongationand the Crystallinity,Orientation of silk was studied,which obtalned from thecocoons with different silk worm races,sexes,cocooning conditions...In this paper,the relation between the tensile strength,breaking elongationand the Crystallinity,Orientation of silk was studied,which obtalned from thecocoons with different silk worm races,sexes,cocooning conditions.The Crystallinity and degree of Crystal Orientation of fibroin were determinedby the X-ray diffraction.and the birefringence of fibroin was measured withInterference microscope.The research showed that the dependence of strength and elongation of rawsilk on Its crystailinity was not so closed.Although there was linear correlation ofstrength with the birefringence and the degree of crystal orientation of fibroin.But the correlation coefficient of the former was larger than the latter.Therefore,adopting birefringence method which would reflected the degree of orlentation ofboth the amorphous and crystalline region of fibroln was suitable for consideringthe strength.The correlation coefficients of strength and elongation withbirefringence were 0.96 and 0.77 respectively.The latter one was展开更多
A range of blends of polypropylene-polyethylene are investigated for their mechanical performances. These speciality polymer blends are chemically designed to suit high modulus/high load bearing mining wire rope appli...A range of blends of polypropylene-polyethylene are investigated for their mechanical performances. These speciality polymer blends are chemically designed to suit high modulus/high load bearing mining wire rope applications subjected to continued bending and tensile stresses and fluctuating loads and are exposed to extreme weather conditions. In this paper we study the influence of different parameters on the performance of the wire ropes: chemistry of polymer, crystallinity of the polymer matrix, and the morphology. The FTIR and SEM studies revealed that the high fraction of polypropylene in polypropylene-polyethylene matrix lead to early failure as a result of incompatibility and phase segregation and high spherulite sizes of the polymer matrix.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61474085 and 61704130)the Science Research Plan in Shaanxi Province,China(Grant No.2016GY-085)+1 种基金the Opening Project of Key Laboratory of Microelectronic Devices&Integrated Technology,Institute of Microelectronics,Chinese Academy of Sciences(Grant No.90109162905)the Fundamental Research Funds for the Central Universities,China(Grant No.61704130)
文摘Germanium-tin films with rather high Sn content(28.04% and 29.61%) are deposited directly on Si(100) and Si(111)substrates by magnetron sputtering. The mechanism of the effect of rapid thermal annealing on the Sn surface segregation of Ge_(1-x)Sn_x films is investigated by x-ray photoelectron spectroscopy(XPS) and atomic force microscopy(AFM). The x-ray diffraction(XRD) is also performed to determine the crystallinities of the Ge_(1-x)Sn_x films. The experimental results indicate that root mean square(RMS) values of the annealed samples are comparatively small and have no noticeable changes for the as-grown sample when annealing temperature is below 400℃. The diameter of the Sn three-dimensional(3 D) island becomes larger than that of an as-grown sample when the annealing temperature is 700℃. In addition, the Sn surface composition decreases when annealing temperature ranges from 400℃ to 700℃. However, Sn bulk compositions in samples A and B are kept almost unchanged when the annealing temperature is below 600℃. The present investigation demonstrates that the crystallinity of Ge_(1-x)Sn_x/Si(111) has no obvious advantage over that of Ge_(1-x)Sn_x/Si(100) and the selection of Si(111) substrate is an effective method to improve the surface morphologies of Ge_(1-x)Sn_x films. We also find that more severe Sn surface segregation occurs in the Ge_(1-x)Sn_x/Si(111) sample during annealing than in the Ge_(1-x)Sn_x/Si(100) sample.
文摘Electrochemical insertion/extraction of Li on cathode materials of spinel type LiMn2O4 and ordered rock-salt type LiCo0.5 Ni0.5O2 was measured on samples of which structures were well characterized. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materiaIs on electrochemical Li insertion/extraction performance was discussed. These two transition metal oxides belong to onegroup that the crystallinity of these oxides affects to the performance.
基金supported by the National Natural Science Foundation of China (Nos. 21701107, 51672165, and 51472152)the China Postdoctoral Science Foundation (No. 2016M592897XB)+3 种基金Technology and Natural Science Foundation of Shaanxi (No. 2018JQ5107)Key Program for International S&T Cooperation Projects of Shaanxi ProvinceXi’an Key Laboratory of green manufacture of ceramic materials Foundation No. 2019220214SYS017CG039China Graduate Innovation Fund of Shaanxi University of Science and Technology。
文摘WS2 exhibits tremendous potentials for Na-ions storage owing to high capacity(433 mAh g^(-1)). Nevertheless, WS2 layered structure is often exfoliated with rapid capacity decay and sluggish reaction kinetics.In this work, WS2 nanosheets with different crystallinities are controlled by different synthesis methods.The high crystallinity WS2 exhibits high degree of interlayer order and strong interlayer force. It exhibits superior electrochemical properties, at the current density of 200 mA g^(-1) after 300 cycles with reversible capacity of 471 mAh g^(-1). Even at 5.0 A g^(-1), the capacities can still arrive at 240 mAh g^(-1) after 250 cycles, exhibiting stable cycling performance. Further electrochemical research finds that the high degree of interlayer order of layered WS2 structure can perform highly conducive Na+insertion/extraction with greatly improved contribution of intercalation capacity. Moreover, the strong interlayer force can effectively restrain the exfoliating of the WS2 nanosheets, guaranteeing the stability of the structure. Combining the above result reveals that controlling the order and force of the interlayer is an effective way to enhance the electrochemical properties of WS2 as SIBs anode materials. This work can provide new insight for inhibiting the exfoliation of layered compounds to pursue excellent electrochemical performance in Na-ion storage systems.
基金supported by Science and Technology Commission of Shanghai Municipality(No.0652NM028)ShanghaiLeading Academic Discipline Project(No.B113)+1 种基金National Natural Science Foundation of China(No.10804020)Specialized Research Fund for the Doctoral Program of Higher Education of China(No.200802461088).
文摘The dependence of polarization fatigue on crystallinity of vinylidene fluoride and trifluoroethylene copolymer films was studied.Experimental data indicated that the higher the crystallinity of the film was,the slower the fatigue rate of the film became.A possible explanation was put forward,and it was regarded that the space charges,trapped at the boundaries of crystallites and/or captured by the defects lying both in amorphous and crystalline phases,should make the major contribution to polarization fa...
文摘Electrochemical insertion/extraction of Li on cathode materials of anatase type TiO2, quasilayered structure V2O5 and layered structure MoO3 was measured on samples of which structures were well characterized and showed a wide range of crystallinity. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materials on electrochemical Li insertion/extraction pedermance was discussed. These three transition metal oxides were classified as one group on the basis of whether the crystallinity of these oxides affects to the performance or not; LiMn2O4 and LiCo0.5O2 belongs to the former group and TiO2, V2O5 and MoO3 to the latter.
文摘The objective of this paper is to investigate the relative variations of the constants of the thermal properties and the degree of crystallinity of the mixtures (PP/EPR)/Calcium carbonates elaborated with the Micro Bivis. We have strengthened the basic copolymer PP/EPR of a low level (5%) by three calcium carbonates models socal312, socal322v, Winnofil spm. We then subjected the different mixtures obtained, two cycles of a thermal loading under differential scanning calorimetry DSC. We finally focused on the thermal properties of isotactic polypropylene (TfP, TcP, ΔHfP, ΔHcP) and we calculated the degree of crystallinity of the mixtures. Reducing the energy cost of implementing mixtures is one of the objectives of this work. We quantified the relative variations of the above properties with those of the base copolymer. It shows that at a low loading rate of calcium carbonate, there is a decrease in the enthalpies of crystallization during the second exothermic cycle, with values that can reach 5.53 J/gPP for the basic copolymer PP/EPR. During the second endothermic cycle, there is an overall increase in isotactic polypropylene melting temperature values for all the blends as well as for the basic copolymer PP/EPR. There is evidence that calcium carbonates are useful for lowering the melting energy of isotactic polypropylene, even at a low loading rate for the majority. The number of endothermic cycles accentuates this phenomenon which is linked to the presence in our composites, of a so-called confined amorphous phase.
基金This work is supported by the National Natural Science Foundation of China and the National Basic Research Project- Macromolecular Condensed State
文摘Based on the X- ray scattering intensity theory, the correction factors of the degree ofcrystallinity formulae of the multicomponent polymers have been clearly defined. The formulae ofthe degree of crystallinity of the multicomponent polymers were derived in terms of WAXDtheory and improved graphic multipeak resolution methods. The results calculated aresatisfactory in comparison with the density measurement.
文摘By means of the intensity theory of X-ray scattering and the two-phase concept of high polymer, the basic formula of the crystaUinity in block copolymers has been proposed after the corrections of atomic, temperature, absorption, Lorentz and polarization factor. Application of this method to different type poly (oxyethylene-styrene)block copolymers and the same type block copolymers with different EO contents indicates that the crystallinity in poly (oxyethylene-styrene ) block copolymers increases with the increase of the EO content and decreases in the order: PEO-PS-PEO】PEO-PS】PS-PEO-PS.
文摘Based on the X-ray scattering intensity theory,the correction factors of thedegree of crystallinity formulae of the multicomponent polymers have been clearly defined.Theformula of degree of erystallinity of the multicomponent polymers was derived in terms of theWAXD theory ahd improved graphic multipeak resolution methods.The results calculated arecompatible with the density measurement.
基金This project was supported by the National Natural Science Foundation of China and the National Basic Research Project Macromolecular Condensed State.
文摘Based on the X-ray scattering intensity theory and using the atomic scattering factorapproximate expression,the correction factors for three main crystalline peaks and an amorphouspeak of Nylon-1010 were calculated and the formula of degree of crystallinity of Nylon-1010 wasderived by graphic multipeak resolution method. The results calculated are compatible with the density measurement and calorimetry.
基金supported by the National Key R&D Program of China (2018YFE0208500)the Japan Science and Technology Agency (JST) Mirai program (JPMJMI17EA)。
文摘As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potential of halide PVK solar cells as a highly competitive substitute to replace silicon-based solar cells in the photovoltaic market [2–6].
基金Funded by the Science Fund of Educational Department of Henan Province of China (No. 19A430002)。
文摘We investigated the impure phase problem and summarized its two formation mechanisms of YAG powders synthesized via the co-precipitation method.The ions loss problem caused by high concentration reaction solution in the titration process was emphatically studied,and the corresponding thermodynamic explanation was carried out.In addition,influence of powder crystallinity and its new qualitative and quantitative standards were studied.One reason of impure phase is the local nonuniform mixture of Y and Al elements in precursor,which easily causes intermediate phases during calcination and difficulty of high pure powders at low temperatures.The other reason is the precipitation dissolution during titration and then the Y^(3+)/Al^(3+) loss,caused by high concentration of reaction solution.The powder crystallinity can be promoted by increasing calcination temperature or holding time of precursor.Besides the routine XRD method,the TEM-EDX method should be also introduced to directly determine the quality of crystallinity.
文摘In this paper the measurement of crystallinity(C)ofacrylic copolymer(PAC),by Swelling Differential Scan-ning Calorimetry(SDSC)is discussed.Common DSC isonly used for measuring the crystallinity of polymers withmelting point,(T_m),below their decomposition temper-ature,(T_d).As temperature rises,polymers with swell-ing agent added become swollen and dissolved,goingthrough whole process of breaking solid structures.Thus,SDSC makes it possible to measure the crystallini-ty of polymers even with T_d below T_m.But the C mea-sured by WAXD and the total endothermal melting(swelling)heat in SDSC thermograms,(△H_l),are notlinearly correlated.It has been found that,instead of the△H_l,△H_l’obtained from the △H_l by subtracting the en-dothermal heat,△H_l,and the C measured by WAXDare linearly correlated.On the basis of this linear rela-tion,the unknown C of another PAC sample is measuredby SDSC.The result is in good accordance with thatmeasured by WAXD.
文摘A modified mathematical model based on the melting and recrystallization of an initial distribution of melting temperatures predicts the melting behavior of polymer in differential scanning calorimetry ( DSC ), taking into account of changes in heat of fusion with melting temperature of crystal and average heat capacity of sample. It has been used to analytically prove that the crystallinity measured on a DSC diagram could not be equal to the weight percentage of crystalline state in the initial specimen. The deviation of the measured crystallinity, as observed relevant to the melting and recrystallization processes, is caused by the changes of the heat of fusion with the melting temperature of crystals, as well as the difference of heat capacities of liquld and solid state polymer. Furthermore, upper and lower limits of the deviation have been discussed.
基金supported by the National Natural Science Foundation of China (51603114)the Natural Science Foundation of Shandong Province (ZR2016EMQ03 and ZR2019PB002)the Doctoral Fund of Qingdao Agriculture University (663-1115046 and 663-1117016)。
文摘Covalent organic frameworks(COFs)are emerging as powerful electrochemical energy storage/conversion materials benefiting from the controlled pore and chemical structures,which are usually determined by the regulation of the molecular building blocks.In contrast,the substituents are not considered significant for the electrochemical reactivity as they are usually removed during carbonization,which is necessary for improving the electrical conductivity of an electrode material.Here we show that the substituents play key roles not only in synthesizing COFs but also in controlling the COF structures during carbonization and thus the related electrochemical reactivity.Five characteristic substituents were used when synthesizing a new COF structure and it was found that electron-withdrawing strength of the substituents significantly influences the crystallinity of the COFs by tuning the reactivity of building blocks,or even determines whether the crystalline COF can be constructed.Moreover,the differences in chemical groups,sizes,and thermal stabilities of the substituents result in varied pore-collapse behaviors and the structures of the carbonized COFs,which show diverse effects on the electrochemical performances.An optimal material shows the highest surface area of 2131 m^(2)/g,rich pores around 1 nm,and the highest ratio of sp^(2) carbon among the samples,corresponding to the largest double-layer specific capacity over 125 F/g in an ionic liquid electrolyte,while another material with the lowest surface area and N-doping level exhibits a high H_(2)O_(2) production selectivity over 80%through selective oxygen reduction.This study shows guiding significance for the design of building blocks and substituents for COFs and further the carbonized carbons,and also exhibits the great potential of substituent engineering in modulating the electrochemical reactivity.
文摘Free radical polymerized palladium polyacrylate was characterized by X-ray diffraction. Various parameters including mean crystallite size, interchain separation and radius of gyration have been calculated and discussed with respect to the concentration of Pd in the polymeric salt. The results show that polymer is predominantly amorphous in nature.
基金Education Commission of Shaanxi Province for Providing Funding Support,China ( No. 2010JS006)
文摘Phase change material microcapsules (MicroPCMs) with nano composite structures (NC-MicroPCMs) were fabricated to meet higher demand of thermal stability and hold core better. Degree of crystallinity (DOC) of the NC-MicroPCMs was evaluated by the differential scanning calorimeter (DSC). The effectiveness of some processing variables, in terms of formaldehyde and melamine molar ratio F/M, weight ratio of core and shell material C/S, and the dosage of silver nano particles D(%), were analyzed statistically. It was found that: (1) DOC was dependent on these processing variables; (2) doping silver nano particles was beneficial to the formation of shell crystallite structure; and (3) higher F/M was helpful in getting a higher DOC for both NC-MicroPCMs and MicroPCMs. Also, DOC was found to be associated with thermal stability and the two features were confirmed, which showed a closely positive correlation.
文摘Cenospheres are produced in very large amount in thermal power plants. They are always looked upon as fillers used to reduce the density and cost of the polymer. If cenosphere particles are allowed to remain properly dispersed by taking it in lower concentration, significant improvement in its mechanical, thermal, electrical, crystallinity, colorimetric and morphological properties are expected. To make it happen, epoxy/cenosphere composites were prepared, having lower concentration of cenosphere. Concentration of cenosphere in epoxy, cured with triethylenetetramine, was changed as 0, 3, 5, 7 and 10. Tensile Strength, Tensile Modulus, Percentage Elongation at Break and Crystallinity decreased, whereas, Flexural Strength and Flexural Modulus were found to have increased by 50% and above 100% respectively at 7 phr loading of cenosphere in epoxy. Thermal and electrical stability also increased with increase in concentration of cenosphere in the epoxy, however, the samples became blackish with increased addition of cenosphere. Using SEM analysis it was found that, cenospheres were properly and uniformly dispersed at 7 phr concentration and formed aggregates at 10 phr concentration.
文摘In this paper,the relation between the tensile strength,breaking elongationand the Crystallinity,Orientation of silk was studied,which obtalned from thecocoons with different silk worm races,sexes,cocooning conditions.The Crystallinity and degree of Crystal Orientation of fibroin were determinedby the X-ray diffraction.and the birefringence of fibroin was measured withInterference microscope.The research showed that the dependence of strength and elongation of rawsilk on Its crystailinity was not so closed.Although there was linear correlation ofstrength with the birefringence and the degree of crystal orientation of fibroin.But the correlation coefficient of the former was larger than the latter.Therefore,adopting birefringence method which would reflected the degree of orlentation ofboth the amorphous and crystalline region of fibroln was suitable for consideringthe strength.The correlation coefficients of strength and elongation withbirefringence were 0.96 and 0.77 respectively.The latter one was
文摘A range of blends of polypropylene-polyethylene are investigated for their mechanical performances. These speciality polymer blends are chemically designed to suit high modulus/high load bearing mining wire rope applications subjected to continued bending and tensile stresses and fluctuating loads and are exposed to extreme weather conditions. In this paper we study the influence of different parameters on the performance of the wire ropes: chemistry of polymer, crystallinity of the polymer matrix, and the morphology. The FTIR and SEM studies revealed that the high fraction of polypropylene in polypropylene-polyethylene matrix lead to early failure as a result of incompatibility and phase segregation and high spherulite sizes of the polymer matrix.
