Transition Temperature Region Research Articles

Grafting of maleic anhydride onto waste acrylonitrile butadiene styrene (ABS) and its application for compatibilization of ABS blends

AbstractIncorporating recycled plastics into the manufacturing process is an essential way to establish a sustainable plastics economy. However, current processes are limited by the degradation of mechanical properties, high cost, and inconsistent product quality compared with their virgin counterparts. Here, we present an upcycling strategy for waste plastics where waste acrylonitrile‐butadiene‐styrene (reABS) is first grafted with maleic anhydride (MAH), then utilized to compatibilize nylon 6(PA6)/ABS and PA6/ABS/CaCO3 blends. The reABS‐g‐MAH exhibits improved Young's modulus and tensile strength, but lower strain at break and impact strength compared with reABS. As an additive, reABS‐g‐MAH effectively compatibilizes PA6/ABS and PA6/ABS/CaCO3 blends, indicated by greatly decreased PA6 domain size, homogeneous dispersion of fillers, and narrowed glass transition temperature regions between PA6 and ABS. Adding only 5 wt% reABS‐g‐MAH increases the Young's modulus, strain at break, and impact strength of PA6/ABS blends by 26%, 180%, and 110%, respectively, compared with uncompatibilized samples. Similarly, for PA6/ABS/CaCO3 blends, the strain at break and impact strength increase by 370% and 150%, respectively, while the Young's modulus and tensile strength show increases of 5% and 10%. The results show that this strategy of using polar groups to functionalize waste plastics as compatibilizers may open numerous opportunities for upcycling waste plastics.

Data-driven prediction of fracture toughness size effect in ductile-to-brittle transition using Two-Step-Scaling procedure

The fracture properties of ferritic steels in transition temperature region are usually statistically treated by models that presuppose the existence of various forms of quenched disorder (critical cleavage triggers). In this study, the fracture toughness from the Euro fracture toughness dataset (stress intensity factor used in the master curve KJc) for reactor steel 22NiMoCr37 is used with the aim of outlining a methodology for using the recently proposed two-step scaling (2SS) method. Three widely different temperatures (−154 °C, −91 °C, and 0 °C), which cover the entire range from lower shelf to upper shelf fracture, are selected to demonstrate the accuracy of extrapolation and interpolation of the fracture toughness CDF (cumulative distribution function) and the pertinent issues related to the procedure application. The obtained predictions at the two lower temperatures are in good agreement with the experimental results and well within the inherent experimental data scatter, while 2SS method is shown not to be applicable in upper-shelf transition region. Special attention is devoted to the effect of statistical sample size on prediction accuracy/reliability along with the minimum sample size requirement. Moreover, the reduction in random sample size affects the Weibull parameters, which in turn impacts the accuracy of predictions, introducing a degree of uncertainty and highlighting limitations in the method.

Investigation of Residual Stress Effect on Cleavage Fracture Toughness in the Transition Temperature Region by Considering the Crack-Tip Constraint

Investigation of Residual Stress Effect on Cleavage Fracture Toughness in the Transition Temperature Region by Considering the Crack-Tip Constraint

First-order phase transition in perovskites Pr0.67Sr0.33MnO3 – magneto-caloric properties – effect of multi-spin interaction

We show by extensive Monte Carlo simulations that we need a multi-spin interaction in addition to pairwise interactions in order to reproduce the temperature dependence of the experimental magnetization observed in the perovskite compound Pr0.67Sr0.33MnO3. The multi-spin interaction is introduced in the Hamiltonian as follows: each spin interacts simultaneously with its four nearest-neighbors. It does not have the reversal invariance as in a pairwise interaction where reversing the directions of two spins leaves the interaction energy invariant. As a consequence, it competes with the pairwise interactions between magnetic ions. The multi-spin interaction allows the sample magnetization M to increase, to decrease or to have a plateau with increasing T. In this paper we show that M increases with increasing T before making a vertical fall at the transition temperature TC, in contrast to the usual decrease of M with increasing T in most of magnetic systems. This result is in an excellent agreement with the experimental data observed in Pr0.67Sr0.33MnO3. Furthermore, we show by the energy histogram taken at TC that the transition is clearly of first order. We also calculate the magnetic entropy change |ΔSm| and the Relative Cooling Power (RCP) by using the set of curves of M obtained under an applied magnetic field H varying from 0 to 5 T across the transition temperature region. We obtain a good agreement with experiments on |ΔSm| and the values of RCP. This perovskite compound has a good potential in refrigeration application due to its high RCP.

Geo-temperature response to reinjection in sandstone geothermal reservoirs

To study the evolution rules and behaviors of heat transport in a sandstone geothermal reservoir caused by cooled water reinjection, this research focuses on the quantitative relationship among reinjection parameters and the thermal breakthrough time of production wells. The permeation, tracer, and reinjection tests were conducted in a simulation model using a large sand tank in conjunction with the numerical simulation method based on COMSOL Multiphysics. Subsequently, sensitivity analysis and nonlinear fitting were performed to investigate the effects of fluid viscosity and density on the reinjection process, and to analyze the impact of reinjection parameters on the thermal breakthrough time of production wells, along with their underlying mechanisms and law. The results indicate that the migration velocity of reinjection water is greater in coarse sand layer compared to that in medium sand layer, and the thermal breakthrough time t is linearly correlated with reinjection rate (Q) raised to the power of − 0.85, temperature difference (ΔT) raised to the power of − 0.21, and spacing between the production and reinjection wells (R) raised to the power of 1.4. The correlation equation and analysis show that when the temperature difference between production and reinjection ΔT is more than 30 ℃, the influence of ΔT on the thermal breakthrough time of production well becomes weak, because ΔT exerts an effect on the thermal breakthrough time of production well t by influencing the relative position of the 18.5 ℃ isotherm in the temperature transition region. The error in reinjecting high-temperature fluid into low-temperature fluid may be corrected by introducing a viscosity correction coefficient αμ.

The Activation Energy of Viscous Flow and Liquid–Liquid Structure Transition in Co-B Alloys

The temperature dependences of the kinematic viscosity during heating and cooling have been investigated in Co-B melts with a boron content of up to 30.8 at. A liquid–liquid structural transition was found, which is accompanied by an increase in the activation energy and cluster size, as well as a significant decrease in the density of the melt. The liquid–liquid structural transition was associated with the formation of clusters with a short-range order of Co23B6 in the intermediate temperature region. At low and high temperatures, clusters of the order of an atomic size are active participants in the viscous flow. It was shown that with an increase in the cluster size, the activation energy increases and the viscosity of melts decreases. The formation of large Co23B6 clusters during the cooling of melt with low boron content leads to undercooling and the appearance of the transition temperature region with high activation energy, although this region does not exist during the heating stage.

Correlation between charpy-V notch impact energy and KJIC of ferrite ductile iron in the transition-temperature region

Fracture toughness is an important index for the structural integrity assessment of ductile iron spent fuel transportation casks. Fracture toughness tests require a long test period, high cost, and difficult operation. Therefore, the Charpy V-notch impact energy value (KV) is considered to predict fracture toughness (KJIC).In this study, Charpy V-notch impact tests(−80 °C, −60 °C, −40 °C, −20 °C, 0 °C, 20 °C, 40 °C, 60 °C, 80 °C) and fracture toughness tests(−60 °C, −40 °C, −20 °C, 0 °C, 20 °C) of ferrite ductile iron(FDI) were carried out. A KJIC-KV model for FDI in the transition temperature region was proposed, taking into consideration the influence of test temperature(T) and yield strength(σ YS), then the proposed model was compared to the KIC-KV empirical equations of steel in the transition-temperature region, using the test data of FDI. The results indicate that the KJIC-KV model proposed in this work is more accurate and applicable for predicting fracture toughness values in the transition-temperature region than others, the residual between the estimated value of the KJIC-KV correlation model (KJIC-E) and the experimental value of KJIC(KJIC-T) was less than 4.1 MPa·m0.5, and the error was less than 5%.

Ductile-to-brittle transition of ferritic steels: A historical sketch and some recent trends

The phenomenon of ductile-to-brittle transition in ferritic steels has been a ubiquitous research challenge for the last 50 years. The characterization of this problem using the fracture mechanics concept, from the earliest studies based on the linear-elastic fracture mechanics to the application of the elastic–plastic fracture mechanics, has become inevitable over time. The fracture toughness is not an intrinsic material property but depends on geometrical factors (such as the specimen shape, thickness, and surface roughness), defect type and distribution, loading mode, and environmental conditions. The pronounced scatter of experimental data on fracture toughness, characteristic of all ferritic steels in the ductile-to-brittle transition temperature region, necessitated the use of statistical methods for data processing. That approach, which emerged in the 1970 s, can still be found today as the basis for interpreting fracture toughness data in ductile-to-brittle transition problems. This paper presents a brief historical overview of such studies along with the problems that have arisen as a consequence of using fracture mechanics concepts, such as constraint effects, as an example. In the time-honored research tradition, all the proposed methods and models, as well as their criticisms, provided the basis for the development of new approaches to the ductile-to-brittle characterization of ferritic steels. Specifically, these include size effects and scaling of geometrically similar samples, with the aim of predicting material behavior beyond experimental limits. Brief outlines of two new approaches are provided in this succinct review. The criticisms of all presented methods are oriented mostly on the application domain, as well as their capability to predict fracture toughness, with short overview of their most conspicuous advantages and disadvantages.

Table-like magnetocaloric effect due to field-induced inter-cluster interactions in Eu0.5Sr0.5MnO3–EuMnO3 composites

The table-like behavior of the magnetic entropy change is generally observed in rare-earth-based alloys (e.g. La(Fe,Si)13, Gd50Co45Fe5, Gd56Ni15Al27Zr2, GdCo x Al y etc). Here, we report similar table-like behavior in a bulk perovskite Eu0.5Sr0.5MnO3–EuMnO3 composite system with a working temperature span of ∼80 K for a field change of ∼70 kOe. AC susceptibility and time-dependent DC magnetization relaxation measurements confirm the presence of interacting ferromagnetic clusters with a Vogel–Fulcher freezing temperature of 42.7 K. The Langevin function fittings of the isothermal magnetization curves show a non-monotonous variation of cluster size with temperature. We propose a model for the high-field dependency of the ferromagnetic cluster coupling in the composite system. This widens the transition temperature region of long-range order formation and hence gives rise to the table-like magnetocaloric effect in Eu0.5Sr0.5MnO3–EuMnO3 composite systems.

Surface Glass Transition Temperature Region of Diarylethene Films Determined by Nano-Marangoni Effect.

For the last two decades, research has addressed whether the glass transition temperature and the molecular motions on the surface of organic films are significantly different from those inside the bulk glasses. It is reported that the surface of the photochromic diarylethene film prepared by vacuum deposition has fluidity and the vacuum deposition of small amount of rubrene molecules induces surface tension fluctuations, generating dents due to the Marangoni flow in nanoscale. The depth of the dents increases in proportion to these radii for the colorless diarylethene film with a bulk glass transition temperature (Tg) close to room temperature. On the other hand, in the colored diarylethene obtained by UV irradiation to the colorless film, the depth becomes constant at a certain level. The Tg distribution in the depth direction is clarified based on an analysis of the dent depth. By approximating the obtained Tg depth distribution with an exponential function, the outermost surface Tg is about 100 K lower than the bulk Tg in the case of photoisomerized diarylethene.

4D Printing of Triple-Shape Memory Cyanate Composites Based on Interpenetrating Polymer Network Structures.

The triple-shape memory polymer (TSMP) can be programmed into two temporary shapes (S1 and S2) and shows an ordinal recovery from S2 to S1 and eventually to the permanent shape upon heating, which realizes more complex stimulus-response motions. We introduced a novel strategy for forming triple-shape memory cyanate ester (TSMCE) resins with high strength and fracture toughness via three-step curing, including four-dimensional (4D) printing, UV post-curing, and thermal curing. The obtained TSMCE resins presented two separated glass transition temperature (Tg) regions due to the formation of an interpenetrating polymer network (IPN), which successfully endowed the polymers with the triple-shape memory effect. The two Tg increased with the increasing cyanate ester (CE) prepolymer content; their ranges were 82.7-102.1 °C and 164.4-229.0 °C, respectively. The fracture strain of the IPN CE resin was up to 10.9%. Moreover, the cooperation of short carbon fibers (CFs) and glass fibers (GFs) with the polymer-accelerated phase separation resulted in two well-separated Tg peaks exhibiting better excellent triple-shape memory behaviors and fracture toughness. The strategy for combining the IPN structure and 4D printing provides insight into the preparation of shape memory polymers integrating high strength and toughness, multiple-shape memory effect, and multifunctionality.

КРИСТАЛЛИЗАЦИЯ СТЕКОЛ В РАЗРЕЗЕ Nа2O·2B2O3 — BaO·2B2O3 НАТРИЕВО-БАРИЕВО-БОРАТНОЙ СИСТЕМЫ

The results of crystallization of glass powders of the diborate section of the Na2O BaO B2O3 system are presented. The glass transition temperatures and temperature regions of crystallization at a heating rate of 10 K/min were determined by DTA and XRD methods; the formed crystalline phases were identified, and the nature and temperatures of their melting were established. It is shown that the section under study is not a pseudobinary system, but only a partial section of the sodium-barium borate system. It is shown that the Na2O·2BaO·9B2O3 compound is the phase of primary crystallization in the section; its field covers the majority of the section. The second known ternary compound, Na2O·2BaO·5B2O3, apparently melts peritectically. It has been established that during long-term heat treatment of glasses in a monolithic state, a new phase is formed in them with an approximate composition of Na2O·2BaO·6B2O3.

Enhanced Ferromagnetism Induced by Chemical Doping and Epitaxial Strain in La0.8Sr0.2CoO3 Films

The perovskite LaCoO3 and La0.8Sr0.2CoO3 thin films were synthesized successfully by a polymer-assisted deposition method. The structural characterization and thermal decomposition measurements indicate that appropriately increasing the annealing temperature is helpful in improving the film crystallinity. Compared with LaCoO3 films, the Curie temperature is enhanced to a higher temperature in La0.8Sr0.2CoO3 films, which is attributed to the changes in both the valence state and spin state induced by the chemical doping. In addition, a broad transition temperature region is observed in La0.8Sr0.2CoO3 films, revealing the existence of inhomogeneous ground states in this system.

Study on Diffusion Kinetics and Law of Chromium on the Surface of Low-Carbon Steel

Cr/low-carbon steel surface composites were prepared by aqueous solution co-deposition and high-temperature solid-state diffusion technology, and the macro rule of the solid-state diffusion of chromium on the surface of low-carbon steel was analyzed. The molecular dynamics (MD) method was used to simulate and calculate the diffusion process of the Cr/Fe interface, and the macro and micro diffusion mechanisms were analyzed. The results show that the diffusion of the chromium in iron is the combined action of the temperature, crystal structure and lattice distortion, and the diffusion coefficients of chromium in α-Fe and γ-Fe have little difference. The vacancy diffusion mechanism of the first adjacent transition is the main diffusion mode. In practice, chromium atoms diffuse along the grain boundaries of the low-carbon steel matrix and provide pinning at the grain boundaries to prevent grain growth. The simulation law is in good agreement with the experimental law. The variation law of the average diffusion coefficient of chromium atoms with temperature is obtained. The diffusion rate of chromium in the bcc crystal structure is obviously higher than that in the fcc crystal structure. In the same crystal structure, the diffusion coefficient of chromium increases with the increase in temperature. However, in the lattice transition temperature region, the diffusion coefficient of chromium gradually decreases with the increase in temperature until the end of the transformation.

Effect of reclaimed bio-oil and waste crumb rubber on bitumen viscoelasticity

ABSTRACT The application of reclaimed bio-oil has demonstrated many merits in modifying asphalt rubber (AR). However, the traditional rheological methods tend to be ineffective in scoring asphalt rubber modified by bio-oil (BoAR). This study aimed to assess how asphalt viscoelasticity is affected by the complicated interactions of three components in BoAR. Two different liquid additives were incorporated into AR utilizing three mixing sequences. Then the temperature and time dependence of these BoARs were investigated through the total dissipated energy function and process-accelerated fatigue testing, respectively. Furtherly, the master curves were constructed to detect their overall viscoelastic response. Finally, two evaluating methods, i.e. measured transition temperature and functional analysis region, were proposed by applying the time-temperature superposition principle (TTSP) and statistical methods. As a sequence, adding CRM tends to weaken the bitumen viscoelasticity, whereas the bio-oil presents the opposite result. Also, adjusting manufacturing processes utilizing liquid biological oil was proven a practical approach to optimizing the time-temperature sensibility of BoARs. In addition, the proposed rutting analysis region showed superior representativeness and practicability in evaluating the high-temperature properties of viscoelastic materials.

Improved energy storage density and energy efficiency of Samarium modified PMNT electroceramic

We report the improved energy storage density and efficiency after 2.5% of Samarium substitution in ferroelectric Pb[(Mg1/3Nb2/3)0.80Ti0.20]O3 (PMNT) electroceramic. The microstructure and surface morphology were analyzed and correlated with various functional properties. The energy storage density, leakage current density, ferroelectric and dielectric properties were investigated thoroughly, indicating that Samarium's substitution significantly modified the microstructure, the dielectric strength, breakdown electric field, and turned ferroelectric PMNT to relaxor ferroelectrics. Due to the relaxor nature, the gap between remanent polarization and maximum polarization increases with the substitution of Samarium in PMNT matrix, which further increases the recoverable energy storage density and energy efficiency. A nearly 100% increase in recoverable energy density and efficiency was obtained at an electric field strength of 35 kV/cm at room temperature (∼296 K). The electroceramic shows maximum energy density near the ferroelectric phase transition temperature (325 K–345 K) region and provides a moderate energy storage density for possible applications in power microelectronics.

A study on the conductivity, dielectric, and microwave properties of SrNbxYxFe12-2xO19 (0.00 ≤ x ≤ 0.05) nanohexaferrites

In this paper, conductivity, dielectric, and microwave properties of SrNbxYxFe12-2xO19 (0.00 ≤ x ≤ 0.05) hexaferrites (SrNbY HFs) synthesized by the citrate sol–gel method were investigated. Some key parameters compatible with the electrical and dielectric functions of SrNbY HFs have been extensively evaluated as functions of bias frequency, measurement temperature, and co-substitution ratios in logarithmic 3D graphs by complex impedance spectroscopy. It has been observed that although the co-substitution ratio is highly functional on dielectric parameters such as both the dielectric constant and dielectric loss, as well as the dissipation factor, it has a very low influence on the conductivity mechanism. Depending on the substitution ratios of Nb and Y ions and the transition temperature region, the activation energy was calculated to vary between 58 and 476 meV. Microwave properties were measured as S-parameters using a coaxial line in the range of 2–12 GHz. It was analysed the frequency dependences of the real/imaginary parts of the permittivity and permeability for all samples. Reflection losses vs. frequency were calculated as a function of the substitution level. Coefficients of the RL (−12.5 … −16.8 dB) confirm practical importance for electromagnetic compatibility at high frequencies.

History of ductile-to-brittle transition problem of ferritic steels

This paper presents a review of different approaches through history concerning DTB transition phenomenon of ferritic steels and their characterization using FM concept, from the earliest studies based on LEFM to the application of the EPFM concept. The large scattering of the experimental fracture toughness data, characteristic of all ferritic steels in the transition temperature region, has imposed the need of including statistical methods for data processing. Such approach that began in the 1970s can be encountered even nowadays as the base of fracture toughness data interpretation in DTB problems. An overview of studies with statistical interpretation of experimental data in the transition temperature region is also given. Aforementioned provides a foundation for novel approaches in DTB transition problems, which include size effects and scaling of geometrically similar specimens.

Tuning the magnetocaloric effect by optimizing thickness-induced three-dimensional strain states

The effect of 3-dimensional strain state on the magnetocaloric properties of epitaxial La0.8Ca0.2MnO3 (LCMO) thin films grown on two types of substrates, SrTiO3 (001) (STO) and LaAlO3 (001) (LAO) has been studied as a function of film thickness within the range of 25 to 300 nm. The STO substrate imposes an in-plane tensile biaxial strain while LAO substrate imposes an in-plane compressive biaxial strain. The in-plane biaxial strain on LCMO by STO substrate gets relaxed more rapidly than that by LAO substrate but both LCMO/STO and LCMO/LAO show a maximum entropy change of 12.1 J/Kg-K and 3.2 J/Kg-K, respectively at a critical thickness of 75 nm (at 6 T applied magnetic field). LCMO/LAO is found to exhibit a wider transition temperature region with full width at half maxima (FWHM) 40 K of the dM/dT vs T curve compared to LCMO/STO with FWHM 33 K of that curve. This broadening of the transition region indicates that the Table like magnetocaloric effect (MCE) is attainable by changing the strain type. The maximum Relative Cooling Power, 361 J/Kg of LCMO/STO and 339 J/Kg of LCMO/LAO is also observed at the thickness 75 nm. The Curie temperature varies with the thickness exploring the variation of ferromagnetic interaction strength due to strain relaxation. The film thickness and substrate induced lattice strain are proved to be the significant parameters for controlling MCE. The highest MCE response at a particular thickness shows the possibility of tuning MCE in other devices by optimizing thickness.

Temperature-dependent anomalous energy transport in finite-length quasi-one-dimensional MoS2 : Crossover from phonons to solitons

Anomalous energy transport is a widely investigated character in one-dimensional lattice and both phonons and solitons are candidate energy carriers responsible for the thermal conductivity divergence before their mean-free paths. However, it was long believed the contribution of solitons could be neglected even close to the melting point in a real crystalline solid. In this paper, we show that a crossover of wave-packet dynamics, from a phonon- to a soliton-dominated state, occurs in a quasi-one-dimensional molybdenum disulfide $({\mathrm{MoS}}_{2})$ sheet at high temperatures far below its melting point by nonequilibrium and equilibrium molecular dynamics simulations. Divergent sound speed variation and the corresponding heat capacity peaks are observed in the transition-temperature region that is related to a second-order phase transition. We also find that its anomalous energy transport falls into a universality class with thermal conductivity divergence exponent $\ensuremath{\alpha}=2/5$ at a finite length scale within 2000 nm when solitons are excited above 600 K, and the scaling relations derived from the L\'evy walk of energy carriers is fulfilled as $\ensuremath{\alpha}=2\ensuremath{-}1/\ensuremath{\gamma}=\ensuremath{\beta}\ensuremath{-}1$ in the soliton-dominated state above 1800 K. Our results reveal the peculiar solitonlike contribution to thermal conduction at high temperatures in the low-dimensional crystalline solids.