Crystallization Activation Energy Research Articles

Nonisothermal crystallization of poly(L‐lactic acid) promoted by polyols

AbstractThe inherent weak crystallization capacity has an impact on the processability and serviceability of poly(lactic acid) (PLA) and limits its application. D‐mannitol (DM) and xylitol (Xy), acting as a nucleation accelerant, were melt‐blended with poly(L‐lactic acid) (PLLA) and the nonisothermal crystallization behavior was investigated. At 1% dosage, the crystallization temperatures of polyol‐modified PLLAs are 10–15°C higher than those of neat PLLA in the cooling rate range of 5–20°C. The theoretical half‐time of crystallization (t1/2) of the Jeziorny model remains constant over the cooling rate range of 10–20°C min−1, in contrast to the greatly reduced t1/2 reported for heterogeneous nucleating agents. Xy is more effective than DM in promoting crystallization. It increases the crystallinity of PLLA to ~40% within the 1%–5% dosage; and the activation energy of nonisothermal crystallization calculated by the Friendman method follows the order of magnitude: neat PLLA ˃ PLLA/DM ˃ PLLA/Xy. Polyols promote the crystallization of PLLA by a mechanism different from heterogeneous nucleation, providing an efficient and biosafety approach to improve the performance of PLA.

Thermal analysis and non-isothermal crystallization kinetics of Ag–Ga2Te3–SnTe telluride glasses

In this paper, the microstructure evolutions and crystallization kinetics of the newly developed Agx-[(Ga2Te3)34(SnTe)66]100−x (x = 6, 8 and 10%) telluride glasses were comprehensively investigated under non-isothermal conditions. The microscopic structure of the investigated samples were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM) and the selected area electron diffraction (SAED). The crystalline products were identified as the SnTe phase (primary crystalline phase) and Ga6SnTe10 phase. The exothermic crystallization process for any investigated samples was actually on the envelope of two overlapped peaks and could be assigned to the first crystallization event of SnTe precipitation and followed by the second crystallization event of Ga6SnTe10 phase. The crystallization mechanism and activation energies were estimated by Matusita–Sakka model under continuous heating based on the differential scanning calorimeter (DSC). For the first crystallization event, the Avrami exponent n values for each of the three investigated samples was approximately 3, suggesting the crystallization occurred through the two-dimensional growth with increasing number of nucleation. The values of n for the second crystallization event of Ga6SnTe10 phase were close to 4, indicating three-dimensional growth with a increasing number of nuclei. The activation energy Ec for both the first and second crystallization events was gradually decreased as the Ag content increased.

Prominent β-relaxation and stress relaxation decoupling phenomenon in Gd-Ni-Al metallic glasses

GdxNi20Al80−x (x = 50, 60, 65, 70 at%) metallic glasses (MGs) with prominent β-relaxation were developed, which provide a new model system for studying some controversial issues concerning β-relaxation. The relaxation behavior and thermal stability of GdxNi20Al80−x MGs were probed by dynamic mechanical relaxation, static stress relaxation, and differential scanning calorimetry. In view of the temperature and frequency dependence of the dynamic mechanical relaxation spectrum, we investigated the β-relaxation and α-relaxation separation phenomena of Gd50Ni20Al30 and Gd60Ni20Al20 MGs. With increasing Gd/Al ratio, the activation energy of the β-relaxation decreased, which was conducive to the flow units and prominent β-relaxation. The Gd70Ni20Al10 alloy had the most significant β-relaxation phenomenon, although some nanocrystalline Gd3Ni phase was distributed in the amorphous matrix. The Gd50Ni20Al30 glass had a crystallization activation energy of 476 kJ/mol, corresponding to the highest thermal stability. At a constant strain, the static stress relaxation process of the Gd70Ni20Al10 alloy was analyzed over a wide time window and temperature range. A decoupling phenomenon of the relaxation into a two-step process occurred in the Gd70Ni20Al10 alloy, namely, a fast relaxation process and a slow relaxation process, at different time scales. Analysis of the relaxation dynamics and time scales of the relaxation confirmed that the fast relaxation process differed from the β-relaxation process. This study elucidates the β-relaxation behavior and stress relaxation decoupling phenomenon in Gd-Ni-Al MGs and should, therefore, help clarify the mechanical relaxation behavior and intrinsic characteristics of MGs in future work.

Effect of Gold Tailing Addition on the Mechanical Properties and Microstructure of Foam Ceramics

Tailings, with their low utilisation rate and value, pose an urgent problem that needs to be solved. This study focused on foam ceramics and glass granules, which were prepared using gold tailings as the main raw materials, and the prepared microcrystalline foam ceramics were investigated. The optimum sample (S6) of foam ceramics consists of 77 wt% of gold tailings, 6 wt% of talc, 9 wt% of bentonite, 2 wt% of calcite, 0.9 wt% of foaming agent and 0.6% of water reducer. The optimum foaming temperature is 1190 °C, and the holding time is 60 min. The compressive strength and bulk density of the samples are 7.4 MPa and 396.4 kg/m3; nucleation temperature, crystallisation temperature, and crystallisation activation energy of glass particles are 700 °C ± 50 °C, 1100 °C ± 50 °C, and 1572 kJ/mol, respectively. Microanalysis results showed that the crystal phases of foam ceramics were mainly quartz, calcium silicate, and aluminium silicate, and crystallinity increases with increasing gold tailing content. Wollastonite appeared in the crystalline phase of microcrystalline foam ceramics. When the glass granule addition reached 30% (2–3 samples), the compressive strength was increased by 19% (8.81 MPa), and the pore size distribution was more uniform.

Non-isothermal crystallization kinetics of CaO-SiO2-B2O3-TiO2 glass studied by differential thermal analysis in the case of “site saturation”

Crystallization characteristics of the CaO-SiO2-B2O3-TiO2 glass have been studied using scanning electron microscopy, X-ray diffraction and differential thermal analysis techniques. The crystallization kinetic parameters of this glass were estimated under non-isothermal conditions using the Matusuta-Sakka equation. Glass with fine particles (<74 μm), case referred to as ‘‘site saturation’’, was used to obtain the non-isothermal differential thermal analysis curves. Bulk glass-ceramics with dense and nonporous morphology are obtained after the heating treatment indicating the strong heterogeneous nucleation at the junction of gain boundaries in the case of “site saturation”. As the content of TiO2 exceeds 18%, the predominant crystal phase changes from CaSiO3 to CaTiSiO5, until CaTiSiO5 becomes the only crystal phase of the glass at 26% TiO2. The crystallization activation energies, EG, are in the range of 245–514 kJ/mol. As TiO2 increases from 10% to 18%, crystallization ability of the glass decreases gradually and the crystallization corresponds to one-dimensional growth mechanism or surface crystallization, while as TiO2 further increases from 18% to 26%, not only does the glass show an increasing crystallization ability, but also the crystal growth changes to the two-dimensional growth mechanism. Within the range of 22%–26%, TiO2 plays the role of strengthening the crystallization of the glass by acting as a major component in the glass to form Ti-bearing compound. From the standpoint of glass-ceramics preparation, the glass containing more TiO2 (such as 26%) with CaTiSiO5 as the only crystal phase is favorable in the present study.

Shear strain rate sensitivity and crystallisation kinetics investigation in melt spun Cu64Zr36 binary metallic glass

Abstract Shear strain rate effect on crystallisation behaviour and characteristic temperatures of the three well-known glass formers in Cu–Zr binary amorphous system, namely Cu50Zr50, Cu56Zr44 and Cu64Zr36, were investigated. The crystallisation behaviour of Cu64Zr36 was uniquely found to be heavily dependent on shear strain rate. Crystallisation kinetics were studied through Isochronal transformation and isothermal transformation. The activation energy of crystallisation of each case was compared and contrasted. Johnson-Mehl-Avrami (JMA) analyses were also employed to study its kinetics behaviour. Finally, high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) combined with laser-assisted local electrode atom probe (LEAP) investigation revealed no detectable clustering or phase separation.

Effect of Yttrium Doping on Glass-Forming Ability, Thermal Stability, and Corrosion Resistance of Zr50.7Cu28Ni9Al12.3 Bulk Metallic Glass

Metallic glasses (MGs) possess excellent corrosion resistance due to their amorphous nature. Zr-Cu-Ni-Al is one of the most investigated metallic glass (MG) systems due to its excellent corrosion resistance, relatively low cost, and nontoxic qualities. Yet the application of the Zr-Cu-Ni-Al MGs is still limited by its glass forming ability (GFA). It has been found that the doping of yttrium can purify the Zr-Cu-Ni-Al melt and increase GFA. However, research on the yttrium doping’s corrosion resistance is still lacking. In the present work, (Zr50.7Cu28Ni9Al12.3)100−xYx (x = 0 (Y0), 1 (Y1), 2 (Y2), 3 (Y3)) alloys were prepared, and the effects of the yttrium doping on the thermodynamic parameters, crystallization activation energy, and corrosion resistance were studied. It was found that the doping of yttrium can improve the GFA and the crystallization-activation energy of the Zr50.7Cu28Ni9Al12.3 MG. The largest GFA is obtained when the yttrium-doping content reaches 2 at.%. The parameter γ is found to be most suitable for the GFA evaluation of the (Zr50.7Cu28Ni9Al12.3)100−xYx alloy system. Y2 alloy exhibits the best corrosion resistance among the Y0–Y3 alloys according to the potentiodynamic polarization results. The simultaneous increase of the GFA, thermal stability, and corrosion resistance was achieved in the Zr50.7Cu28Ni9Al12.3 MG by proper yttrium doping.

Non-isothermal crystallization behavioral analysis of detonation sprayed Fe-based amorphous coating

The non-isothermal crystallization behaviors of a detonation sprayed Fe-based amorphous coating (AMC) was systematically investigated through differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. The crystallization mechanism of the Fe-based AMC is analyzed and discussed in detail using a combination of the Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall approaches, as well as the local Avrami exponent. The results indicate that the crystallization process of the Fe-based AMC is affected by the non-isothermal heating rate with a significantly higher initial crystallization activation energy (917.7 kJ mol−1) and first peak activation energy (479.6 kJ mol−1), indicating excellent thermal stability. After four stages of amorphous crystallization and phase transformation, the crystallization products of the equilibrium state were primarily composed of 78.5%, 11.3%, and 5.8% (Cr, Fe)23(C, B)6, α-Fe phases, and FeMo2B2 phases, respectively.

Kinetic Behavior of the Nonisothermal Crystallization of Highly Refracted Glass Microspheres

The SiO2–TiO2–BaO (STB) system glasses were prepared by the melt-quenching technique. The crystallization kinetics of the STB glasses were studied by the kinetic modeling of Kissinger and Augis–Bennett equations in combination with complementary characterization methods such as X-ray powder diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), IR, and Raman. The crystallization of Ba2TiSi2O8 was observed during the heat treatment process. The crystallization activation energy of Ba2TiSi2O8 is Ep = 207.64 kJ/mol. The average crystallization index is n = 1.14, suggesting a mechanism of surface nucleation in one-dimensional space. Glass microspheres (GMSs) made from the given STB glasses are prone to crystallization during the spheroidization process, and the consequent surface nucleation reduced the brightness of GMSs. By adjusting the spheroidization from 2 to 0.8 s, the brightness increased from 52 to 63 cd*1 x–1 m–2. In addition, it was found that the higher BaO content of the STB glasses facilitated the observed surface nucleation.

Crystallization of Slag Films of CaO-Al2O3-BaO-CaF2-Li2O-Based Mold Fluxes for High-Aluminum Steels' Continuous Casting.

In this study, solidified films of CaO-Al2O3-BaO-CaF2-Li2O-based mold fluxes with different contents of Al2O3 addition were acquired by immersing an improved water-cooled copper probe in bulk molten slags. This probe can obtain films with representative structures. Different slag temperatures and probe immersion times were employed to investigate the crystallization process. The crystals in the solidified films were identified using X-ray diffraction, the morphologies of the crystals were observed using optical microscopy and scanning electron microscopy, and the kinetic conditions, especially the activation energy of devitrified crystallization in glassy slags, were calculated and discussed based on the differential scanning calorimetry. The results indicated that after adding extra Al2O3, the growing speed and thickness of the solidified films increased, and more time was required for the film thickness to reach a steady state. In addition, fine spinel (MgAl2O4) precipitated in the films at the early stage of solidification after adding 10 wt% of extra Al2O3. Together with LiAlO2, spinel (MgAl2O4) acted as nuclei for the precipitation of BaAl2O4. The apparent activation energy of initial devitrified crystallization decreased from 314.16 KJ/mol (original slag) to 297.32 KJ/mol (5 wt% Al2O3 added) and 269.46 KJ/mol (10 wt% Al2O3 added). The crystallization ratio of the films also increased after adding extra Al2O3.

Nb5+-doped SrTiO3-based glass-ceramics: Insight into crystallisation kinetics, microstructure, and dielectric properties

Nb5+-doped SrTiO3-based glass-ceramics composed of SrO–B2O3–SiO2–TiO2 were modified by Nb2O5 doping and prepared via a melt-quenching process accompanied by controlled crystallisation. The effect of the Nb2O5 concentration on the crystallisation, microstructure, and dielectric properties of the glass-ceramics was investigated. Surface analysis conducted by XPS revealed that with the addition of Nb2O5, the number of non-bridging oxygens (NBO) decreased while the number of bridging oxygens (BO) increased, increasing the interconnection of the structural units. The crystallisation activation energies of the samples tended to decrease from 376.06 kJ/mol to 271.50 kJ/mol (Kissinger model), and the crystal growth modes changed from two-dimensional to three-dimensional (Avrami indexes n: 2.38–4.23) with increasing Nb2O5 concentration. The XRD, SEM, and EDS analyses showed that the addition of Nb5+ promoted the growth of crystals (0.44–1.35 μm). The dielectric properties show that an appropriate amount of Nb2O5 greatly improves the dielectric constant of the glass-ceramics. The dielectric constant of the glass-ceramic doped with 1.5 mol% Nb2O5 is 178.1 (300 K, 1 MHz), which is approximately 6.7 times higher than that of the undoped Nb2O5-doped glass-ceramics (26.5). The introduction of Nb2O5 reduced the activation energy of glass devitrification, promoted crystal development, and improved the dielectric properties of the glass-ceramics.

Non-isothermal crystallization kinetics study of sodium niobium phosphate glasses

Sodium niobium phosphate (SNP) glasses of composition xNb2O5–(50-x/2)Na2O–(50-x/2) P2O5 (x = 20, 30, 40 mol. %) are prepared by the conventional melt–quench technique. The non-isothermal kinetics of glass transition & crystallization of SNP glasses are studied by a differential scanning calorimeter (DSC). The dependence of glass transition temperature on the heating rate is used to deduce the activation energy of glass transition. The average activation energies of crystallization are calculated by model-free peak kinetic methods (Kissinger, Boswell, Augis-Bennet, and Ozawa). The local activation energies for crystallization with the volume fraction crystallized is estimated by linear iso-conversional methods (Kissinger-Akahira-Sunose, Starink, Tang, Flynn-Wall-Ozawa, and Various heating rates (VHR)) and by Friedman differential method. Avrami exponents are deduced to understand the nucleation and growth of various crystalline phases formed on heat treatment of SNP glasses. The change in the local Avrami exponent with the crystallized volume fraction confirms that the crystallization process occurs through volume nucleation, mainly with 3D growth. SEM analysis explored the crystalline morphologies and revealed the evolution of sheaf-like crystals.

Alkali-Niobate aluminosilicate glasses: Structure and properties

K0.5Na0.5NbO3 (KNN) based ceramics are considered optimal candidates to replace the toxic Pb-based piezoelectric materials; nonetheless, they are quite difficult to process. Therefore, obtaining an efficient glass-ceramic (GC) will have several advantages in lead-free piezoelectric production. The first step to developing advantageous functional GCs is to determine an adequate glass matrix and the network connectivity of the different structural entities depending on the bulk chemistry. Here, we investigated the structural variations occurring in aluminosilicate systems having Na2O/Al2O3 molar ratios from 1 to 5.7 upon the addition of KNN (0.4 up to 30 mol%) to understand how the bulk composition influences KNN incorporation and the properties of the glasses.Our study shows that more depolymerized aluminosilicate systems incorporate a larger amount of KNN because the Nb structural environment's evolution strongly depends on glass polymerization and the availability of charge compensator ions. No strong crosslinking between [SiO4], [AlO4], and [NbO6] structural entities was found, and there is an evolution from a heterogeneous environment with isolated [NbO6] units having different degrees of distortion to Nb–O–Nb linkages, up to the formation of clusters composed of corner-shared slightly distorted [NbO6]. All glass series tend to move toward these 3D clusters whenever the starting structure includes different entities or a more homogeneous environment. The evolution of the different niobate entities marks the changes in the properties that show non-linear variations with KNN content. Furthermore, the glass chemistry influences the crystallization kinetics, with activation energies for crystallization that vary from ∼300 ± 10 kJ/mol to ∼220 ± 10 kJ/mol depending on the alkali/Al2O3 molar ratios.The developed niobo-aluminosilicate glasses show high refractive indices, high transparency in the visible– NIR region and intense UV absorption. Therefore, these glasses are excellent candidates for photonic applications and optoelectronic devices. The stabilization of a perovskite-like phase upon crystallization confirms the potentiality for use as electro-optical glass-ceramics.

Dual roles of Cr2O3 in preparation of glass-ceramics from ferronickel slag

The dual effects of Cr2O3 in the fabrication of glass-ceramics from ferronickel slag (FNS) with the addition of coal fly ash (CFA) were investigated by varying the content of Cr2O3 from 0 wt % to 2.0 wt %. The crystallization kinetics results showed that as the Cr2O3 content increased from 0 wt % to 1.6 wt %, the crystallization activation energy of the parent glass decreased from 448.23 kJ/mol to 232.65 kJ/mol with the change of crystallization mode from surface crystallization to bulk crystallization. When the content of Cr2O3 reached 1.6 wt %, there existed the highest degree of depolymerization of the glass network and the strongest crystallization tendency. The prepared glass-ceramic was composed of enstatite as the main crystalline phase and spinel as the secondary crystalline phase. The microstructure changed from a loose tabular structure to a dense spherical structure. As the Cr2O3 content further increased to 2.0 wt %, the crystallization activation energy increased to 304.21 kJ/mol and the spherical structure became inhomogeneous due to the coexistence of enstatite particles with different sizes. By controlling the Cr2O3 content of 1.6 wt %, an optimal glass-ceramic with density of 3.17 g/cm3, bending strength of 175 MPa, Vickers microhardness of 9.51 GPa, acid resistance of 99.99% and alkali resistance of 99.97% was obtained. This study provided a novel method for promoting conversion of FNS to glass-ceramics.

Utilization of gasification slag and petrochemical incineration fly ash for glass ceramic production.

This study investigated glass ceramics produced using coal gasification slag (CGS) and petrochemical incineration fly ash (PIFA) to immobilize hazardous heavy metals such as Cr and As. However, the crystallization kinetics and stabilization behavior mechanism of different heavy metals in the petrochemical incineration fly ash-derived glass-ceramics remains unclear. And X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and inductively coupled plasma mass spectrometry were used to characterize glass and crystalline products. In this paper, we reported the crystallization kinetics and chemical leaching characteristics of the glass ceramic. A low crystallization activation energy of 121.49kJ/mol was achieved from crystallization peak of several different heating rates around 850°C, implying that it is easier to produce the glass ceramics at that temperature. The Avrami parameter of the former crystallization was determined to be 1.23 ± .12, which indicated two-dimensional crystal growth with heterogeneous nucleation. The toxicity characteristic leaching procedure results indicated that the heavy metals were well solidified, and that the leaching concentration was significantly lower than the limit specified by governmental agencies. The potentially toxic element index of the parent glass and the two glass ceramics were 11.7, 5.8, and 3.6, respectively. Therefore, the conversion of hazardous petrochemical incineration fly ash and other solid waste into environmentally friendly glass ceramics shows considerable potential and reliability.

Degradation mechanism of near stoichiometric SiC fibers after air and Ar–H2O–O2corrosion at 1000–1500°C

AbstractThe near stoichiometric SiC fiber has been reported to play significant roles in the application of aeroengine field. An in‐depth understanding on the degradation mechanism of the fiber during its corrosion in air and under a simulated aeroengine environment (PH2O:PO2:PAr = 14:8:78 kPa) will shine a light on the performance evaluations of the near stoichiometric SiC fiber‐based materials as well as the development of their potential applications. In this study, X‐ray diffraction, scanning electron microscope, and FIB‐TEM were utilized to analyze the mechanical properties and microstructure of the fiber. After oxidation in dry air and Ar–H2O–O2for 1 h, respectively, the fiber strength retention rate has been found to decrease with the increased oxidation temperature. The raise in oxidation temperature also led to the increase of the thickness and the crystallization rate of the oxide scale. The most different oxidation behaviors of SiC being treated under the simulated environment than in air are the lower oxidation activation energy and the higher crystallization activation energy for cristobalite. Water vapor can promote the oxidation reaction and inhibit the crystallization of cristobalite in the oxide scale. Few significant differences have been observed otherwise in the oxidation process and oxidation chromatography crystallization mechanism of fibers being treated under different conditions. The increase of oxide layer thickness and the formation of cristobalite impair the structural integrity and compactness of the oxide scale and thus lead to the deterioration of the mechanical properties of SiC fibers. Therefore, it is proposed that oxidation resistance of SiC fiber can be improved by insulating the reaction between the oxidizing agents and the SiC fiber or by increasing the crystallization temperature of cristobalite in the oxidation process and reducing the crystallization rate.

Microstructure and Crystallization Kinetics of Silica-Based Ceramic Cores with Enhanced High-Temperature Property.

Silica-based ceramic cores play key roles in the casting of aeroengine blades, but they are highly limited by the poor high-temperature mechanical property. Here, fused mullite (FM) and sintered mullite (SM) powders were modified in silica-based ceramic cores, and the microstructure evolution and crystallization kinetics of ceramic cores depending on mullite types were studied. The ceramic cores with FM showed a dense microstructure and superior mechanical properties compared to those with SM. The ceramic cores with 10 wt.% of FM showed a crystallization activation energy of 1119.5 kJ/mol and a crystallization exponent of 1.74, and the values of 938.4 kJ/mol and 1.86 as SM were employed; the decreased crystallization activation energy and the elevated crystallization exponent by SM suggested that the excess impurities of alkali oxides and alkaline-earth oxides significantly promoted the crystallization of cristobalite. Even though the ceramic cores with mullite powders decreased slightly in the room-temperature mechanical property, their high-temperature flexure strength and creep deformation resistance were enhanced. The ceramic cores with 10 wt.% of FM showed excellent comprehensive performance, with linear shrinkage of 0.69%, room-temperature strength of 18.9 MPa, and high-temperature strength of 15.5 MPa, which satisfied the demands for hollow-blade casting.

Synthesis, characterization and crystallization kinetics of a bio-based, heat-resistance nylon 5T/10T.

The rapid consumption of fossil resources and its adverse impact on the environment require the use of bio-based materials to replace petrochemical products. In this study, we present a bio-based, heat-resistant engineering plastic, poly(pentamethylene terephthalamide) (nylon 5T). To address the issues of the narrow processing window and difficulty in melting processing of nylon 5T, we introduced more flexible decamethylene terephthalamide (10T) units to create a copolymer, nylon 5T/10T. The chemical structure was confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (13C-NMR). We investigated the influence of 10T units on the thermal performance, crystallization kinetics, crystallization activation energy, and crystal structures of the copolymers. Our results demonstrate that the crystal growth mode of nylon 5T is a two-dimensional discoid growth pattern, while nylon 5T/10T exhibits a two-dimensional discoid or three-dimensional spherical growth pattern. The melting temperature, crystallization temperature, and crystallization rate first decrease and then increase, and crystal activation energy first increases and then decreases as a function of 10T units. These effects are attributed to the combined impact of molecular chain structure and polymer crystalline region. Bio-based nylon 5T/10T shows excellent heat resistance (melting temperature > 280 °C) and a wider processing window than nylon 5T and 10T, which is a promising heat-resistant engineering plastic.

Terpyridine-zinc(ii) coordination nanosheets as modulators of perovskite crystallization to enhance solar cell efficiency

ZnTPY-chelated PbI2 nuclei effectively reduce the activation energy of perovskite crystallization resulting in higher conversion of PbI2 into uniform perovskite crystalline films, which ultimately improves the performance of perovskite solar cells.

Molecular dynamics simulation and non-isothermal crystallization kinetics of polyamide 4 and different bio-based polyamide blends.

The effects of the structural units and blending ratio on the crystallization behavior of blends of polyamide 4 (PA4) with polyamide 56 (PA56) and polyamide 11 (PA11) were studied using molecular dynamics simulations and non-isothermal crystallization kinetics. The simulation results show that the crystallinity of PA4/PA56 blends (B4/56) with a PA56 content of 30-50% was 3.5-10.8% lower than that of B4/56 with a PA56 content of 20%, and the crystallinity of PA4/PA11 blends (B4/11) decreased by 9.5% as PA11 content increased from 20% to 50%. The experimental results show that both B4/56 and B4/11 form PA4- and PA56-rich (PA11-rich) phases through crystallization-induced phase separation. The interplanar spacing of the PA4-rich phase of B4/56 changed relative to that of PA4, indicating that some PA56 entered the PA4-rich phase unit cell. As the PA56 content increased from 20% to 50%, the crystallinity of B4/56 decreased by 11.2%, and the crystallization-induced phase separation grew distinct. The B4/56 with a higher PA4 content crystallized more easily. As the PA11 content increased from 20% to 50%, the crystallinity of B4/11 decreased by 12.5%, and PA11 barely participated in the crystallization of the PA4-rich phase. The blending ratio had no significant effect on the crystallization rate and crystal-growth degree of B4/11, and the non-isothermal crystallization activation energy of B4/11 was significantly higher than that of B4/56, indicating that the crystallization ability of the B4/11 blend system is worse. This study provides a theoretical basis for the design and performance regulation of PA4-based polyamide blends.