Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products ...Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products in comparison with low-density polyethylene(LDPE).This work aimed to accelerate the crystallization of PBAT by adding a self-assembly nucleating agent octamethylenedicarboxylic dibenzoylhydrazide(OMBH).PBAT/OMBH composites with various OMBH contents(0 wt%,0.5 wt%,0.7 wt%,1 wt%,2 wt%,3 wt%and 5 wt%)were prepared through melt-mixing.The effect of OMBH on the crystallization behavior,morphologies and mechanical properties of PBAT was investigated.The highest nucleation efficiency value of 59.6%was achieved for PBAT with 0.7 wt%OMBH,much higher than that of 22.7%for PBAT with 0.7 wt%talc.Atomic force microscopy results showed that OMBH formed fine fibers and induced the formation of transcrystalline layers of PBAT.Fourier transform infrared spectroscopy(FTIR)combined with two-dimensional correlation spectra suggested that the intermolecular dipole-dipole N—H…O=C interactions but not hydrogen bond between OMBH and PBAT promoted the crystallization of PBAT in the initial period of crystallization.The presence of OMBH did not change the crystal form of PBAT but had positive contribution in enhancing its crystallinity and mechanical properties.This work is essential for preparing PBAT with high crystallization rate,enhancing its potential applications in injection-molded products.展开更多
Poly(lactide acid)(PLA)foams have shown considerable promise as eco-friendly alternatives to nondegradable plastic foams,such as polystyrene(PS)foams.Nevertheless,PLA foam typically suffers from low heat-resistance an...Poly(lactide acid)(PLA)foams have shown considerable promise as eco-friendly alternatives to nondegradable plastic foams,such as polystyrene(PS)foams.Nevertheless,PLA foam typically suffers from low heat-resistance and poor cellular structure stemming from its inherent slow crystallization rate and low melt strength.In this study,a high-performance PLA foam with well-defined cell morphology,exceptional strength and enhanced heat-resistance was successfully fabricated via a core-back microcellular injection molding(MIM)process.Differential scanning calorimetry(DSC)results revealed that the added hydrazine-based nucleating agent(HNA)significantly increased the crystallization temperature and accelerated the crystallization process of PLA.Remarkably,the addition of a 1.5 wt%of HNA led to a significant reduction in PLA’s cell size,from 43.5µm to 2.87µm,and a remarkable increase in cell density,from 1.08×10^(7)cells/cm^(3)to 2.15×10^(10)cells/cm^(3).This enhancement resulted in a final crystallinity of approximately 55.7%for the PLA blend foam,a marked improvement compared to the pure PLA foam.Furthermore,at 1.5 wt%HNA concentration,the tensile strength and tensile toughness of PLA blend foams demonstrated remarkable improvements of 136%and 463%,respectively.Additionally,the Vicat softening temperature of PLA blend foam increased significantly to 134.8°C,whereas the pure PLA foam exhibited only about 59.7℃.These findings underscore the potential for the preparation of lightweight injection-molded PLA foam with enhanced toughness and heat-resistance,which offers a viable approach for the production of high-performance PLA foams suitable for large-scale applications.展开更多
The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(...The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR) . The analysis on kinetics demonstrates that TBC8-eb can not only accelerate the crystallization rate but also transform most of the original spherulite crystals of PLLA into sheaf-like crystals. Furthermore,the free energy of folding(σe) of PLLA and PLLA with TBC8-eb is 0.15 and 0.06 J·m-2,respectively,which suggests that the addition of TBC8-eb favors the regular folding of molecule chains in the crystallization of PLLA,improv-ing its crystallization rate. The FTIR results show that TBC8-eb can accelerate the conformational ordering of PLLA in the isothermal crystallization. The conformational ordering of PLLA nucleated with TBC8-eb begins with the interchain interaction of CH3,and then a short helix emerges where a couple of CH3 groups interact.展开更多
The crystallization behavior and transparent property of MgO-A1203-SiO2 （MAS） glasses with TiO2 and TiO2＋ZrO2 as nucleating agents were discussed by differential thermal analysis, X-ray diffraction, field emission-...The crystallization behavior and transparent property of MgO-A1203-SiO2 （MAS） glasses with TiO2 and TiO2＋ZrO2 as nucleating agents were discussed by differential thermal analysis, X-ray diffraction, field emission-environment scanning electron microscope, energy dispersive spectrum and UV-VIS-NIR scanning spectrophotometer. It was found that the glass crystallized at 950 ℃ with ZrO2 less than 3% could obtain transparent glass ceramic, which presented purple to colorless. With the nucleating agent additives （5% TIO2＋3% ZrO2）, the colorless transparent glass-ceramics with spinel as the main crystal phase could be prepared, and the transmittance reached about 80%. As the crystallized temperature increase to 1 000 ℃, besides spinel（MgA1204）, sapphirine （Mg3.5A19Si1.5O20） and ZrTiO4 precipitated from matrix glass, and the transmitance of glass-ceramic decreased.展开更多
Zinc phenylphosphonate （PPZn）, a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly（ethylene adipate） （PEA） to investigate its effect on the crystallization beha...Zinc phenylphosphonate （PPZn）, a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly（ethylene adipate） （PEA） to investigate its effect on the crystallization behavior, crystallization kinetics and spherulite morphology of PEA. Upon addition of PPZn, the crystallization temperature and crystallinity of PEA in the non-isothermal crystallization process increased significantly. Analysis of crystallization kinetics by Avrami equation suggests that the crystallization time shortened greatly and crystallization rate increased markedly after addition of PPZn. In the presence of PPZn, the spherulite size decreased and spherulite density increased significantly. It suggests that PPZn is an efficient nucleating agent for the crystallization of PEA. The accelerated crystallization in the presence of PPZn is mainly attributed to the epitaxial nucleation of PEA crystals on the surface of PPZn crystals, that is, a perfect lattice matching between PEA crystal and PPZn crystal occurs.展开更多
It is deduced from thermodynamic relations and confirmed by experiment results that the nucleation rate and nucleation temperature of nucleating agents in the glass are dependent upon their melting entropy Delta S//m ...It is deduced from thermodynamic relations and confirmed by experiment results that the nucleation rate and nucleation temperature of nucleating agents in the glass are dependent upon their melting entropy Delta S//m melting temperature T//m and crystal - type transition in terms of some mathematical expressions. (Author abstract) 10 Refs.展开更多
The melting behavior of polypropylene (PP) and low ethylene content polypropylenecopolymer with and without nucleating agent samples crystallized under both isothermal and non-isothermal conditions were studied by Dif...The melting behavior of polypropylene (PP) and low ethylene content polypropylenecopolymer with and without nucleating agent samples crystallized under both isothermal and non-isothermal conditions were studied by Differential Scanning Calorimeter (DSC) and X-raydiffraction. Multiple melting behavior were observed depending on the existence of nucleatingagent and crystallization conditions. The observed phenomena have been discussed by the effect ofnucleating agent on perfection of crystal and the melting and recrystallization of imperfect crystalto a more perfect crystal during the heating process of samples.展开更多
Impregnation of isotactic polypropylene (iPP) with nucleating agent (NA21) using supercritical carbon dioxide as the swelling agent at different temperature and pressure and its non-isothermal crystallization kinetics...Impregnation of isotactic polypropylene (iPP) with nucleating agent (NA21) using supercritical carbon dioxide as the swelling agent at different temperature and pressure and its non-isothermal crystallization kinetics were investigated. The results showed that NA21 was dispersed at a nanometer-scale in the PP matrix, resulting in the formation of different typesof crystal phases of iPP and the enhancement of its mechanical properties.展开更多
ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient t...ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient temperature furnace, DTA and XRD. Then, sintering process of the glass-ceramics was investigated by testing sintering shrinkage, dielectric constant and loss. The experimental results shows that the glass-ceramics doped with nucleating additives represents higher crystallization, with ZrO2 as an exceptional effective dopant to promote the precipitation of wollastonite crystal. Finally, ZrO2 containing glass-ceramics was chosen to study the influence of sintering temperature and soaking time with the help of X-ray diffraction analysis and density measurement. The glass-ceramics can be well consolidated at 850 ℃ for 10 min, with low dielectric constant （5.87） and loss （3.21×10^-4）, which is desirable for LTCC application.展开更多
Glass ceramics was made by the one-time sintering method using the main raw material of iron tailings. On the basis of quaternary system of CaO-MgO-Al2O3-SiO2, using DTA, XRD and SEM, the effects of different nucleati...Glass ceramics was made by the one-time sintering method using the main raw material of iron tailings. On the basis of quaternary system of CaO-MgO-Al2O3-SiO2, using DTA, XRD and SEM, the effects of different nucleating agents and mixing amounts as well as heat treatment on the crystallization of railings glass ceramics were studied. The experimental results show that, nucleating agent and heat treatment are two necessary conditions for one-time sintering preparation of tailings glass ceramics namely, only adding nucleating agent or experiencing heat treatment, the quaternary system can not crystallize. The composite nucleating agent consisting of Cr2O3 and TiO2 can further lead to the crystallization of the CaO-MgO-A1203-SiO2 quaternary system at the lower temperature, with the major phase of diopside. In the range of mass content, 0%-4%, crystal intensity and crystal content grow. But when mass content is more than 4%, the crystal size will become coarser and the crystal distribution will be less regular. Different heat treatment regimes do not change the composition of the crystalline major phase in the glass ceramics crystallization of CaO-MgO-Al2O3-SiO2 system. In the range of 30-60 minutes, with the extension of nucleation and crystallization, crystallization degree enhanced, but if the holding time surpasses 60 minutes, the crystallization is worse.展开更多
The influence of cyanuric acid（CA） as an efficient nucleating agent on the crystallization behavior and morphology of biodegradable poly（ε-caprolactone）（PCL） was extensively studied in this work with several te...The influence of cyanuric acid（CA） as an efficient nucleating agent on the crystallization behavior and morphology of biodegradable poly（ε-caprolactone）（PCL） was extensively studied in this work with several techniques for the first time. The nonisothermal melt crystallization behavior and overall isothermal melt crystallization rate of PCL were significantly enhanced by only a small amount of CA. The addition of CA apparently improved the nonisothermal melt crystallization peak temperature, overall isothermal melt crystallization rate, and nucleation density of PCL spherulites, but did not modify the crystallization mechanism and crystal structure of PCL, indicating that CA was an efficient nucleating agent for the crystallization of PCL. The possible nucleation mechanism of CA on the crystallization of PCL was also discussed on the basis of their crystal structures.展开更多
Glass-ceramics obtained from the electric arc furnace molten slag of incinerator fly ash was produced by applying nucleation and crystallization through heat treatment process. The effects of nucleating agent （TiO2 a...Glass-ceramics obtained from the electric arc furnace molten slag of incinerator fly ash was produced by applying nucleation and crystallization through heat treatment process. The effects of nucleating agent （TiO2 and Cr2O3） on the crystallization kinetics and heat treatment schedule of the slag were investigated. The results show that the nucleating agents changed the crystallization phase and morphology of the obtained glass-ceramics. The optimum heat treatment schedule of the glass with TiO2 was determined as nucleation at 952 K for 1.5 h and crystal growth at 1 258 K for 1.5 h, while those values with Cr203 were estimated at 971 K for 2 h and at 1 238 K for 2 h. TiO2 acting as nucleating agent could decrease the activation energy of the slag and shorten the total thermal treatment time in comparison with Cr2O3. The glass-ceramics obtained under the optimum heat treatment condition was environmentfriendly and had remarkable physical/mechanical properties and chemical durability.展开更多
The reference test methods are carried out parallelly, by means of chemical analysis, X-ray diffraction, differential scanning calorimetry-thermogravimetry, scanning electron microscopy and polarized optical microscop...The reference test methods are carried out parallelly, by means of chemical analysis, X-ray diffraction, differential scanning calorimetry-thermogravimetry, scanning electron microscopy and polarized optical microscope to study the formation of C4A3S in the presence and absence of nucleating agent. The results show that nucleating agent with high calcium and low heat consumption as tricalcium silicate （C3S） promotes the formation of C4A3S and increases desulfurization degree obviously. During calcining raw meals doped with C3S, the grain sizes of C4A3S are larger compared with that without C3S. And at the same calcining level, the mass loss and the heat consumption belonged to CaCO3 decomposition is reduced.展开更多
An aryl dicarboxylic acid amide compound TMB-5 is an efficient β-form nucleating agent for isotactic polypropylene （iPP）. Because of the solubility of TMB-5, superstructure and morphology of iPP crystals changed wi...An aryl dicarboxylic acid amide compound TMB-5 is an efficient β-form nucleating agent for isotactic polypropylene （iPP）. Because of the solubility of TMB-5, superstructure and morphology of iPP crystals changed with melting conditions. Effects of final heating temperature （Tf） on heterogeneous nucleation of iPP/TMB-5 were investigated. It was discovered that the crystallization temperature increased with decreasing Tf value. The optical microscopic images indicated that when TMB-5 partially dissolved in iPP melt, the remaining （non-dissolved） TMB-5 facilitated the recrystallization of dissolved nucleating agent from the melt, which promoted crystallization. Complete solubility of nucleating agent caused the decreasing efficiency. TMB-5 recrystallized in the form of tiny needles, whose aggregates induced dendritic iPP crystals.展开更多
The influence of aryl amide compounds（TMB）as b-nucleating agents, on the non-isothermal crystallization of a wood-flour/polypropylene composite（WF/PP）prepared by compression molding was investigated by wide-angle ...The influence of aryl amide compounds（TMB）as b-nucleating agents, on the non-isothermal crystallization of a wood-flour/polypropylene composite（WF/PP）prepared by compression molding was investigated by wide-angle X-ray diffraction and differential scanning calorimetry. TMB was proved to be an effective b-crystalline nucleating agent for WF/PP. The DSC data showed that the crystallization peak temperature（Tp） increased and the half-time（t1/2） decreased with the addition of TMB.Three theoretical models were used to analyze the nonisothermal crystallization process. The modified Avrami method and Mo method successfully explained the nonisothermal crystallization behavior of PP and its composites. Their activation energies for non-isothermal crystallization were determined basing on the Kissinger method.展开更多
The crystallization behavior of polyethylene (PE) and polypropylene (PP), including the neat ones and the ones nucleated with the same nucleating agent (NA), was studied by DSC. It was found that the nucleating agent ...The crystallization behavior of polyethylene (PE) and polypropylene (PP), including the neat ones and the ones nucleated with the same nucleating agent (NA), was studied by DSC. It was found that the nucleating agent decelerated the PE nonisothermal crystallization process. NA did enhance the nucleating rates for both PE and PP, but the linear growth rate dominated the volumetric growth rate for PE, and the volumetric growth rate dominated the overall crystallization rate. That is why PE nucleated with NA had a slower overall crystallization rate than the neat one.展开更多
For glass-ceramics, how to realize the collaborative optimization of BDS and permittivity is the key toimprove the energy storage density. In this work, ZrO2 is introduced into BPKNAS glass-ceramics asnucleating agent...For glass-ceramics, how to realize the collaborative optimization of BDS and permittivity is the key toimprove the energy storage density. In this work, ZrO2 is introduced into BPKNAS glass-ceramics asnucleating agent to promote crystal development of glass-ceramics and then achieve high permittivity.When 1.5 mol% ZrO2 is added, the glass-ceramics have the highest permittivity (~128.59) and meanwhilepossess high BDS (1948.90 kV/cm) due to the dense microstructure. Therefore, BPKNAS-1.5ZrO2 glass-ceramics has the highest theoretical energy storage density (21.62 J/cm3). Moreover, the permittivityvariation of BPKNAS-1.5ZrO2 glass-ceramics is less than 6 % in the wide temperature range from 80 to300 C, showing excellent temperature stability. In addition, BPKNAS-1.5ZrO2 glass-ceramics possessesultrahigh power density, which reaches up to 382.40 MW/cm3 in overdamped circuit. The above evi-dence shows that BPKNAS-1.5ZrO2 glass-ceramics with ultrahigh energy storage density and powerdensity is very competitive in the field of energy storage applications.展开更多
Two kinds of high efficient Agl pyrotechnics BR-88-5 and BR-91-Y have been developed.The tests in the cloud chamber show that the AgI ice nucleating effectiveness can reach up to 10^(15)/g,and the BR-91-Y has even hig...Two kinds of high efficient Agl pyrotechnics BR-88-5 and BR-91-Y have been developed.The tests in the cloud chamber show that the AgI ice nucleating effectiveness can reach up to 10^(15)/g,and the BR-91-Y has even higher ice nucleating rate.Two kinds of foreign AgI pyrotechnics have been made according to the given formulations and also tested in the cloud chamber for comparison.X-ray diffraction analysis for the aerosols produced by burning BR-91-Y shows that AgI in acrosols still retains the hexagonal crystal form and the lattice parameters are smaller than those of pure AgI and other AgI composite nuclei,and closer to ice.Combining with the other tests,the reasons for the high effi- ciency of BR-91-Y have been discussed.展开更多
It is difficult to generate coherent twin boundaries in bulk Al alloys due to their high intrinsic stacking fault energy. Here, we report a strategy to induce high-density growth twins in aluminum alloys through the h...It is difficult to generate coherent twin boundaries in bulk Al alloys due to their high intrinsic stacking fault energy. Here, we report a strategy to induce high-density growth twins in aluminum alloys through the heterogeneous nucleation of twinned Al grains on twin-structured TiC nucleants and the preferred growth of twinned dendrites by laser surface remelting of bulk metals. The solidification structure at the surface shows a mixture of lamellar twinned dendrites with ultra-fine twin boundary spacing (∼2 µm), isolated twinned dendrites, and regular dendrites. EBSD analysis and finite element method (FEM) simulations have been used to understand the competitive growth between twinned and regular dendrites, and the solidification conditions for the preferred growth of twinned dendrites during laser remelting and subsequent rapid solidification are established. It is shown that the reduction in the ratio of temperature gradient G to solidification rate V promotes the formation of lamellar twinned dendrites. The primary trunk spacing of lamellar twinned dendrites is refined by the high thermal gradient and solidification rate. The present work paves a new way to generate high-density growth twins in additive-manufactured Al alloys.展开更多
Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can res...Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can result in solidification defects and reduced mechanical properties.In this work,a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition(CET)in the FZ of TIG-welded AZ31 alloy.The results show the achievement of a fully equiaxed grain structure in the FZ,with a significant 71.9%reduction in grain size to 41 μm from the original coarse columnar dendrites.Furthermore,the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm.Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ.The application of pulse current results in an increase in the number density of MgO(1-2 μm)from 5.16 × 10^(4) m^(-3) to 6.18 × 10^(4) m^(-3).The good crystallographic matching relationship between MgO and α-Mg matrix,characterized by the orientation relationship of[11(2)0]α-Mg//[0(1)1]MgO and(0002)_(α-Mg)//(111)_(MgO),indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling.According to the Hunt criteria,the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites.In addition,the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map,leading to the realization of CET.The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints.This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52073261 and U1704162).
文摘Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products in comparison with low-density polyethylene(LDPE).This work aimed to accelerate the crystallization of PBAT by adding a self-assembly nucleating agent octamethylenedicarboxylic dibenzoylhydrazide(OMBH).PBAT/OMBH composites with various OMBH contents(0 wt%,0.5 wt%,0.7 wt%,1 wt%,2 wt%,3 wt%and 5 wt%)were prepared through melt-mixing.The effect of OMBH on the crystallization behavior,morphologies and mechanical properties of PBAT was investigated.The highest nucleation efficiency value of 59.6%was achieved for PBAT with 0.7 wt%OMBH,much higher than that of 22.7%for PBAT with 0.7 wt%talc.Atomic force microscopy results showed that OMBH formed fine fibers and induced the formation of transcrystalline layers of PBAT.Fourier transform infrared spectroscopy(FTIR)combined with two-dimensional correlation spectra suggested that the intermolecular dipole-dipole N—H…O=C interactions but not hydrogen bond between OMBH and PBAT promoted the crystallization of PBAT in the initial period of crystallization.The presence of OMBH did not change the crystal form of PBAT but had positive contribution in enhancing its crystallinity and mechanical properties.This work is essential for preparing PBAT with high crystallization rate,enhancing its potential applications in injection-molded products.
基金supported by the National Natural Science Foundation of China(No.52003280)the Zhejiang Provincial Natural Science Foundation of China(No.LQ21B040003)+1 种基金the S&T Innovation 2025 Major Special Programme of Ningbo(No.2021Z052)the Chinese Academy of Sciences Pioneer Hundred Talents Program.
文摘Poly(lactide acid)(PLA)foams have shown considerable promise as eco-friendly alternatives to nondegradable plastic foams,such as polystyrene(PS)foams.Nevertheless,PLA foam typically suffers from low heat-resistance and poor cellular structure stemming from its inherent slow crystallization rate and low melt strength.In this study,a high-performance PLA foam with well-defined cell morphology,exceptional strength and enhanced heat-resistance was successfully fabricated via a core-back microcellular injection molding(MIM)process.Differential scanning calorimetry(DSC)results revealed that the added hydrazine-based nucleating agent(HNA)significantly increased the crystallization temperature and accelerated the crystallization process of PLA.Remarkably,the addition of a 1.5 wt%of HNA led to a significant reduction in PLA’s cell size,from 43.5µm to 2.87µm,and a remarkable increase in cell density,from 1.08×10^(7)cells/cm^(3)to 2.15×10^(10)cells/cm^(3).This enhancement resulted in a final crystallinity of approximately 55.7%for the PLA blend foam,a marked improvement compared to the pure PLA foam.Furthermore,at 1.5 wt%HNA concentration,the tensile strength and tensile toughness of PLA blend foams demonstrated remarkable improvements of 136%and 463%,respectively.Additionally,the Vicat softening temperature of PLA blend foam increased significantly to 134.8°C,whereas the pure PLA foam exhibited only about 59.7℃.These findings underscore the potential for the preparation of lightweight injection-molded PLA foam with enhanced toughness and heat-resistance,which offers a viable approach for the production of high-performance PLA foams suitable for large-scale applications.
基金Supported by the National Natural Science Foundation of China （20876042） Program of Shanghai Subject Chief Scientist （10XD1401500） Research Fund for the Doctoral Program of Higher Education of China
文摘The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR) . The analysis on kinetics demonstrates that TBC8-eb can not only accelerate the crystallization rate but also transform most of the original spherulite crystals of PLLA into sheaf-like crystals. Furthermore,the free energy of folding(σe) of PLLA and PLLA with TBC8-eb is 0.15 and 0.06 J·m-2,respectively,which suggests that the addition of TBC8-eb favors the regular folding of molecule chains in the crystallization of PLLA,improv-ing its crystallization rate. The FTIR results show that TBC8-eb can accelerate the conformational ordering of PLLA in the isothermal crystallization. The conformational ordering of PLLA nucleated with TBC8-eb begins with the interchain interaction of CH3,and then a short helix emerges where a couple of CH3 groups interact.
基金Funded by the National Natural Science Foundation of China(No.50472309)
文摘The crystallization behavior and transparent property of MgO-A1203-SiO2 （MAS） glasses with TiO2 and TiO2＋ZrO2 as nucleating agents were discussed by differential thermal analysis, X-ray diffraction, field emission-environment scanning electron microscope, energy dispersive spectrum and UV-VIS-NIR scanning spectrophotometer. It was found that the glass crystallized at 950 ℃ with ZrO2 less than 3% could obtain transparent glass ceramic, which presented purple to colorless. With the nucleating agent additives （5% TIO2＋3% ZrO2）, the colorless transparent glass-ceramics with spinel as the main crystal phase could be prepared, and the transmittance reached about 80%. As the crystallized temperature increase to 1 000 ℃, besides spinel（MgA1204）, sapphirine （Mg3.5A19Si1.5O20） and ZrTiO4 precipitated from matrix glass, and the transmitance of glass-ceramic decreased.
基金financially supported by the National Natural Science Foundation of China(No.21304070)Natural Science Foundation of Tianjin City(No.15JCYBJC47300)+1 种基金Major Program of National Natural Science Foundation of China(No.11432016)the Municipal Key Program of Natural Science Foundation of Tianjin(No.14JCZDJC40700)
文摘Zinc phenylphosphonate （PPZn）, a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly（ethylene adipate） （PEA） to investigate its effect on the crystallization behavior, crystallization kinetics and spherulite morphology of PEA. Upon addition of PPZn, the crystallization temperature and crystallinity of PEA in the non-isothermal crystallization process increased significantly. Analysis of crystallization kinetics by Avrami equation suggests that the crystallization time shortened greatly and crystallization rate increased markedly after addition of PPZn. In the presence of PPZn, the spherulite size decreased and spherulite density increased significantly. It suggests that PPZn is an efficient nucleating agent for the crystallization of PEA. The accelerated crystallization in the presence of PPZn is mainly attributed to the epitaxial nucleation of PEA crystals on the surface of PPZn crystals, that is, a perfect lattice matching between PEA crystal and PPZn crystal occurs.
文摘It is deduced from thermodynamic relations and confirmed by experiment results that the nucleation rate and nucleation temperature of nucleating agents in the glass are dependent upon their melting entropy Delta S//m melting temperature T//m and crystal - type transition in terms of some mathematical expressions. (Author abstract) 10 Refs.
文摘The melting behavior of polypropylene (PP) and low ethylene content polypropylenecopolymer with and without nucleating agent samples crystallized under both isothermal and non-isothermal conditions were studied by Differential Scanning Calorimeter (DSC) and X-raydiffraction. Multiple melting behavior were observed depending on the existence of nucleatingagent and crystallization conditions. The observed phenomena have been discussed by the effect ofnucleating agent on perfection of crystal and the melting and recrystallization of imperfect crystalto a more perfect crystal during the heating process of samples.
基金an International Cooperation Research Program，key project from National Science Foundation of China for multiscale methodology，SINOPEC supported fundamental research project，an Association Franco-Chinoise pour la Recherche Scientifique et Technique(AFCRST) supported project
文摘Impregnation of isotactic polypropylene (iPP) with nucleating agent (NA21) using supercritical carbon dioxide as the swelling agent at different temperature and pressure and its non-isothermal crystallization kinetics were investigated. The results showed that NA21 was dispersed at a nanometer-scale in the PP matrix, resulting in the formation of different typesof crystal phases of iPP and the enhancement of its mechanical properties.
基金Funded by the Shanghai Leading Academic Discipline Project (B502)Shanghai Key Laboratory Project (08DZ2230500)
文摘ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient temperature furnace, DTA and XRD. Then, sintering process of the glass-ceramics was investigated by testing sintering shrinkage, dielectric constant and loss. The experimental results shows that the glass-ceramics doped with nucleating additives represents higher crystallization, with ZrO2 as an exceptional effective dopant to promote the precipitation of wollastonite crystal. Finally, ZrO2 containing glass-ceramics was chosen to study the influence of sintering temperature and soaking time with the help of X-ray diffraction analysis and density measurement. The glass-ceramics can be well consolidated at 850 ℃ for 10 min, with low dielectric constant （5.87） and loss （3.21×10^-4）, which is desirable for LTCC application.
基金Funded by The National Key Technology R & D Program of China for the 11th Five-Year Plan(2006BAJ04A04)
文摘Glass ceramics was made by the one-time sintering method using the main raw material of iron tailings. On the basis of quaternary system of CaO-MgO-Al2O3-SiO2, using DTA, XRD and SEM, the effects of different nucleating agents and mixing amounts as well as heat treatment on the crystallization of railings glass ceramics were studied. The experimental results show that, nucleating agent and heat treatment are two necessary conditions for one-time sintering preparation of tailings glass ceramics namely, only adding nucleating agent or experiencing heat treatment, the quaternary system can not crystallize. The composite nucleating agent consisting of Cr2O3 and TiO2 can further lead to the crystallization of the CaO-MgO-A1203-SiO2 quaternary system at the lower temperature, with the major phase of diopside. In the range of mass content, 0%-4%, crystal intensity and crystal content grow. But when mass content is more than 4%, the crystal size will become coarser and the crystal distribution will be less regular. Different heat treatment regimes do not change the composition of the crystalline major phase in the glass ceramics crystallization of CaO-MgO-Al2O3-SiO2 system. In the range of 30-60 minutes, with the extension of nucleation and crystallization, crystallization degree enhanced, but if the holding time surpasses 60 minutes, the crystallization is worse.
基金financially supported by the National Natural Science Foundation of China(Nos.51373020,51573016 and 51521062)
文摘The influence of cyanuric acid（CA） as an efficient nucleating agent on the crystallization behavior and morphology of biodegradable poly（ε-caprolactone）（PCL） was extensively studied in this work with several techniques for the first time. The nonisothermal melt crystallization behavior and overall isothermal melt crystallization rate of PCL were significantly enhanced by only a small amount of CA. The addition of CA apparently improved the nonisothermal melt crystallization peak temperature, overall isothermal melt crystallization rate, and nucleation density of PCL spherulites, but did not modify the crystallization mechanism and crystal structure of PCL, indicating that CA was an efficient nucleating agent for the crystallization of PCL. The possible nucleation mechanism of CA on the crystallization of PCL was also discussed on the basis of their crystal structures.
基金Supported by the National Natural Science Foundation of China(No.51378332 and No.20806051)Science and Technology Project of Housing and Urban-Rural Ministry(No.2014-K4-014)Chinese Postdoctoral Science Foundation(No.2013M530872)
文摘Glass-ceramics obtained from the electric arc furnace molten slag of incinerator fly ash was produced by applying nucleation and crystallization through heat treatment process. The effects of nucleating agent （TiO2 and Cr2O3） on the crystallization kinetics and heat treatment schedule of the slag were investigated. The results show that the nucleating agents changed the crystallization phase and morphology of the obtained glass-ceramics. The optimum heat treatment schedule of the glass with TiO2 was determined as nucleation at 952 K for 1.5 h and crystal growth at 1 258 K for 1.5 h, while those values with Cr203 were estimated at 971 K for 2 h and at 1 238 K for 2 h. TiO2 acting as nucleating agent could decrease the activation energy of the slag and shorten the total thermal treatment time in comparison with Cr2O3. The glass-ceramics obtained under the optimum heat treatment condition was environmentfriendly and had remarkable physical/mechanical properties and chemical durability.
基金the National Natural Science Foundation of China (No. 50972116)
文摘The reference test methods are carried out parallelly, by means of chemical analysis, X-ray diffraction, differential scanning calorimetry-thermogravimetry, scanning electron microscopy and polarized optical microscope to study the formation of C4A3S in the presence and absence of nucleating agent. The results show that nucleating agent with high calcium and low heat consumption as tricalcium silicate （C3S） promotes the formation of C4A3S and increases desulfurization degree obviously. During calcining raw meals doped with C3S, the grain sizes of C4A3S are larger compared with that without C3S. And at the same calcining level, the mass loss and the heat consumption belonged to CaCO3 decomposition is reduced.
文摘An aryl dicarboxylic acid amide compound TMB-5 is an efficient β-form nucleating agent for isotactic polypropylene （iPP）. Because of the solubility of TMB-5, superstructure and morphology of iPP crystals changed with melting conditions. Effects of final heating temperature （Tf） on heterogeneous nucleation of iPP/TMB-5 were investigated. It was discovered that the crystallization temperature increased with decreasing Tf value. The optical microscopic images indicated that when TMB-5 partially dissolved in iPP melt, the remaining （non-dissolved） TMB-5 facilitated the recrystallization of dissolved nucleating agent from the melt, which promoted crystallization. Complete solubility of nucleating agent caused the decreasing efficiency. TMB-5 recrystallized in the form of tiny needles, whose aggregates induced dendritic iPP crystals.
基金financially supported by‘‘the Fundamental Research Funds for the Central Universities’’(2572015AB07)the Forestry Industry Research of China(No.201204802)the National Natural Science Foundation of China(No.31100425)
文摘The influence of aryl amide compounds（TMB）as b-nucleating agents, on the non-isothermal crystallization of a wood-flour/polypropylene composite（WF/PP）prepared by compression molding was investigated by wide-angle X-ray diffraction and differential scanning calorimetry. TMB was proved to be an effective b-crystalline nucleating agent for WF/PP. The DSC data showed that the crystallization peak temperature（Tp） increased and the half-time（t1/2） decreased with the addition of TMB.Three theoretical models were used to analyze the nonisothermal crystallization process. The modified Avrami method and Mo method successfully explained the nonisothermal crystallization behavior of PP and its composites. Their activation energies for non-isothermal crystallization were determined basing on the Kissinger method.
基金finically supported by the National Basic Research Program of China (973 Project, 2005CB623800)
文摘The crystallization behavior of polyethylene (PE) and polypropylene (PP), including the neat ones and the ones nucleated with the same nucleating agent (NA), was studied by DSC. It was found that the nucleating agent decelerated the PE nonisothermal crystallization process. NA did enhance the nucleating rates for both PE and PP, but the linear growth rate dominated the volumetric growth rate for PE, and the volumetric growth rate dominated the overall crystallization rate. That is why PE nucleated with NA had a slower overall crystallization rate than the neat one.
基金The authors acknowledge the Ministry of Science and Technol-ogy of China for its support through Project 973(Grant No.2015CB654601).
文摘For glass-ceramics, how to realize the collaborative optimization of BDS and permittivity is the key toimprove the energy storage density. In this work, ZrO2 is introduced into BPKNAS glass-ceramics asnucleating agent to promote crystal development of glass-ceramics and then achieve high permittivity.When 1.5 mol% ZrO2 is added, the glass-ceramics have the highest permittivity (~128.59) and meanwhilepossess high BDS (1948.90 kV/cm) due to the dense microstructure. Therefore, BPKNAS-1.5ZrO2 glass-ceramics has the highest theoretical energy storage density (21.62 J/cm3). Moreover, the permittivityvariation of BPKNAS-1.5ZrO2 glass-ceramics is less than 6 % in the wide temperature range from 80 to300 C, showing excellent temperature stability. In addition, BPKNAS-1.5ZrO2 glass-ceramics possessesultrahigh power density, which reaches up to 382.40 MW/cm3 in overdamped circuit. The above evi-dence shows that BPKNAS-1.5ZrO2 glass-ceramics with ultrahigh energy storage density and powerdensity is very competitive in the field of energy storage applications.
基金This study is supported by the fund for scientists return from foreign countriesthe fund of cloud physics of SMA.
文摘Two kinds of high efficient Agl pyrotechnics BR-88-5 and BR-91-Y have been developed.The tests in the cloud chamber show that the AgI ice nucleating effectiveness can reach up to 10^(15)/g,and the BR-91-Y has even higher ice nucleating rate.Two kinds of foreign AgI pyrotechnics have been made according to the given formulations and also tested in the cloud chamber for comparison.X-ray diffraction analysis for the aerosols produced by burning BR-91-Y shows that AgI in acrosols still retains the hexagonal crystal form and the lattice parameters are smaller than those of pure AgI and other AgI composite nuclei,and closer to ice.Combining with the other tests,the reasons for the high effi- ciency of BR-91-Y have been discussed.
基金supported by the National Natural Science Foundation of China(grant no.52371029)the Science and Technology Development Program of Jilin Province,China(grant no.20210402083GH).
文摘It is difficult to generate coherent twin boundaries in bulk Al alloys due to their high intrinsic stacking fault energy. Here, we report a strategy to induce high-density growth twins in aluminum alloys through the heterogeneous nucleation of twinned Al grains on twin-structured TiC nucleants and the preferred growth of twinned dendrites by laser surface remelting of bulk metals. The solidification structure at the surface shows a mixture of lamellar twinned dendrites with ultra-fine twin boundary spacing (∼2 µm), isolated twinned dendrites, and regular dendrites. EBSD analysis and finite element method (FEM) simulations have been used to understand the competitive growth between twinned and regular dendrites, and the solidification conditions for the preferred growth of twinned dendrites during laser remelting and subsequent rapid solidification are established. It is shown that the reduction in the ratio of temperature gradient G to solidification rate V promotes the formation of lamellar twinned dendrites. The primary trunk spacing of lamellar twinned dendrites is refined by the high thermal gradient and solidification rate. The present work paves a new way to generate high-density growth twins in additive-manufactured Al alloys.
基金supported by the National Natural Science Foundation of China(No.51871155).
文摘Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can result in solidification defects and reduced mechanical properties.In this work,a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition(CET)in the FZ of TIG-welded AZ31 alloy.The results show the achievement of a fully equiaxed grain structure in the FZ,with a significant 71.9%reduction in grain size to 41 μm from the original coarse columnar dendrites.Furthermore,the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm.Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ.The application of pulse current results in an increase in the number density of MgO(1-2 μm)from 5.16 × 10^(4) m^(-3) to 6.18 × 10^(4) m^(-3).The good crystallographic matching relationship between MgO and α-Mg matrix,characterized by the orientation relationship of[11(2)0]α-Mg//[0(1)1]MgO and(0002)_(α-Mg)//(111)_(MgO),indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling.According to the Hunt criteria,the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites.In addition,the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map,leading to the realization of CET.The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints.This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.
