Effect Of Thermal History Research Articles

Effects of superheating magnitude on olivine growth

Magmatic superheating is a condition with relevance to natural systems as well as experimental studies of crystallization kinetics. Magmas on Earth and other planetary bodies may become superheated during adiabatic ascent from the mantle or as a consequence of meteorite impact-generated crustal melting. Experimental studies of igneous processes commonly employ superheating in the homogenization of synthetic starting materials. We performed 1-atmosphere dynamic crystallization experiments to study the effects of superliquidus thermal history on the morphologies and compositions of subsequently grown olivine crystals. An ultramafic volcanic rock with abundant olivine was fused above the experimentally determined liquidus temperature (1395 °C), held for 0, 3, or 12 h, cooled at 25 °C h−1, and quenched from 200 °C below the liquidus, all at constant fO2, corresponding to FMQ-2 ± 0.2 log units. An increase in olivine morphologic instability is correlated with superheating magnitude, parameterized as the integrated time the sample is held above the liquidus (“TtL”; °C h). We infer that a delay in nucleation, which intensifies monotonically with increasing TtL, causes crystal growth to be increasingly rapid. This result indicates that the structural relaxation time scale controlling the formation of crystal nuclei is (a) far longer than the time scale associated with viscous flow and (b) exceeds the liquidus dwell times typically imposed in crystallization experiments. The influence of magmatic superheating on crystal morphology is similar in sense and magnitude to that of subliquidus cooling rate and thus, both factors should be considered when interpreting the thermal history of a volcanic rock containing anhedral olivine.

Thermo-viscoelastic Modeling of Nonequilibrium Material Behavior of Glass in Nonisothermal Glass Molding

Nonisothermal Glass Molding (NGM) has become a viable replicative manufacturing technology for the cost-efficient production of complex precision optical components made of glass. During the pressing stage in NGM, glass materials undergo a huge temperature change in the glass transition range. In this range, glass exhibits thermo-viscoelastic responses, and the temperature drop through the glass transition leads glass structure to depart from an equilibrium to a nonequilibrium state. Thermo-viscoelastic properties of the nonequilibrium glass material greatly depend on temperature and thermal history. This paper presents a phenomenological constitutive model developed for modeling the thermo-viscoelastic responses of nonequilibrium glass. We propose a direct incorporation of the temperature -and thermal history effects into each parameter of the phenomenological model. This novelty allows the model to describe the nonequilibrium phenomena and to study temperature-dependent viscoelasticity of glass without assuming thermo-rheologically simple characteristics. Furthermore, the phenomenological model enables the coupling of structural -and stress relaxation phenomena. The model validation conducted for creep experiments demonstrates an enhancement in numerical predictions of the nonequilibrium material behaviors of glass over wide ranges of temperature and thermal history.

The effect of thermal history on the atomic structure and mechanical properties of amorphous alloys

The influence of thermal processing on the potential energy, atomic structure, and mechanical properties of metallic glasses is examined using molecular dynamics simulations. We study the three-dimensional binary mixture, which was first relaxed near the glass transition temperature and zero pressure, and then rapidly cooled deep into the glass phase. It was found that glasses annealed at higher temperatures are relocated to higher energy states and their average glass structure remains more disordered, as reflected in the height of the first two peaks in the pair distribution function. The results of mechanical testing demonstrate that both the shear modulus and yielding peak increase significantly when the annealing temperature approaches Tg from above. Moreover, the shear modulus becomes a strong function of strain rate only for glasses relaxed at temperatures sufficiently higher than the glass transition temperature. Based on the spatial distribution of nonaffine displacements, we show that the deformation mode changes from brittle to ductile upon increasing annealing temperature. These results can be useful for the design and optimization of the fabrication processes of bulk glassy alloys with improved plasticity.

Thermal Emission Spectroscopy of Single, Isolated Carbon Nanoparticles: Effects of Particle Size, Material, Charge, Excitation Wavelength, and Thermal History

Results are presented for thermal emission from individually trapped carbon nanoparticles (NPs) in the temperature range from ∼1000 to ∼2100 K. We explore the effects on the magnitude and wavelength dependency of the emissivity, ε(λ), of the NP size and charge and of the type of carbon material, including graphite, graphene, diamond, carbon black, and carbon dots. In addition, it is found that heating the NPs, particularly to temperatures above ∼1900 K, results in significant changes in the emission properties, which is attributed to changes in the distribution of surface and defect sites caused by annealing and sublimation.

Investigation of the reduction roasting of saprolite ores in the Caron process: reaction mechanisms and reduction kinetics

ABSTRACT Laboratory studies have been undertaken to investigate the mechanisms and kinetics of reactions occurring during the reduction roasting of saprolite ores. Reduction was undertaken using a H2/N2 gas mixture at temperatures between 400 and 800°C. The focus of the study was to determine the effect of dehydration, reduction, sintering and olivine recrystallisation reactions on nickel recovery. The effects of thermal history, temperature and time on the rates and extents of these processes have been investigated. The results provide valuable insights into the relative contributions of the elementary processes taking place during the reduction roast process, and help to explain some of the behaviour observed in industrial practice.

Anomalous self-diffusion, structural and energy relaxations and temporal scaling laws in pure tantalum and pure vanadium metallic glasses

While most studies have considered diffusion in metallic glasses (MGs) to be normal, with a temporally asymptotic diffusivity at a given temperature (T), we report that the diffusion is anomalous and should be described as subdiffusion in pure Ta and pure V MGs—two examples chosen here because of chemical simplicity, fast relaxation, and minimal ambiguity. The diffusivity at a constant T (below the glass transition temperature) drops continuously with time t according to a negative power law instead of the commonly assumed exponential decay. To understand this, we trace the dynamic evolution of potential energy (Ep) and icosahedral short-range ordering (fico) of the system. We find that at large t, fico increases linearly with ln(t), causing Ep to decrease linearly with ln(t), with a remarkably simple linear correlation between fico and Ep. Based on Ep, we infer a continuously increasing effective migration energy barrier, also scaling linearly with ln(t), which perfectly recovers the negative power law time-dependence of diffusivity. The finding of anomalous diffusion and its origin in the fast-relaxing MGs calls out the need to distinguish potentially anomalous diffusion from normal diffusion in MGs, which is critical in disentangling time and temperature in experimental data and developing a robust theory for diffusion in MGs. The temporal scaling laws for diffusivity and structural and energy relaxations reported here may find their validity in other MGs and aid future theory development. In addition, we also discuss the effect of sample thermal history on the time-dependent diffusivity and how to prevent confusion caused by such effect.

The effect of thermal history on structure and mechanical properties of Cu64Zr36 metallic glass

It is well known that the thermal history can affect the local atomic structure and thus may possibly affect the mechanical properties of metallic glasses (MGs). In spite of considerable efforts on the thermal history, its effect on the microstructure remains controversial at the present time. In this work, the combined effect of cooling rate and liquid temperature on the microstructure and mechanical properties are systematically investigated by molecular dynamics simulations. With the decrease of cooling rate, the polyhedrons with higher local five-fold symmetry is greatly enhanced, and thereby the ultimate compressive strength is increased. However, the effect of liquid temperature on the formation of MGs is negligible, mainly due to the relatively high cooling rates adopted. This work may increase our understanding in the effect of thermal formation history on the formation of MGs and provide a promising avenue for improving the mechanical properties.

The effect of indoor thermal history on human thermal responses in cold environments of early winter.

Human thermal adaptation is an important factor of indoor thermal comfort and energy conservation. To study the effect of indoor thermal history on cold adaptation in the early winter, climate chamber tests were conducted in cold environments at 16 °C with two different thermal experience groups. The groups are divided as follows: the natural ventilation (NV) group consisted of subjects living in naturally ventilated buildings (approximately 11.8 ± 3.4 °C in winter (Liu, H., Wu, Y., Li, B., Cheng, Y., Yao, R., 2017. Seasonal variation of thermal sensations in residential buildings in the Hot Summer and Cold Winter zone of China. Energy and Buildings 140, 9-18)) and the air conditioning (AC) group consisted of subjects living in air-conditioned buildings for at least one year before the climate chamber experiments. The experiments on the NV and AC groups were conducted between December 1-13 and December 15-25, respectively. Each group consisted of 20 subjects wearing winter clothes (1.15 ± 0.05 clo). The thermal sensation votes (TSVs) and thermal comfort votes (TCVs) in both groups were investigated and the subjects' skin temperatures were monitored during the experiments. The results showed that the mean TCV and TSV of both groups were not significantly different in the early winter. However, differences were observed in the subjects' localized body parts. The skin temperatures of the chest and arms of subjects in the NV group were higher than those in the AC group after exposure for 60 min at 16 °C, while calves skin temperatures of subjects in the NV group were lower. In addition, subjects in the AC group were found to feel colder compared to those in the NV group in cold environments at the same skin temperature. Thus, this study provides information about thermal comfort based on thermal experience in early winter.

Rheological characterization of BCC and FCC structures in aqueous diblock copolymer liquid crystals

Low molecular weight, amphiphilic diblock copolymers in selective solvent exhibit complex phase behavior and macroscopic properties that affect the processing and application of these materials. The mechanical properties of the crystalline phases seen in concentrated solutions are dependent on nanoscale structure and sample history. The goal of this study is to characterize macroscopic properties and thermal history effects of lyotropic liquid crystals in aqueous diblock copolymer solutions. Rheological temperature ramps are used to characterize three aqueous concentrations of diblock copolymer [Brij-58®, C16H33(CH2CH2O)20OH]. Between these three samples the order-disorder transitions (ODTs) for BCC and FCC are accessible in addition to the order-order transition (OOT) between BCC and FCC. These transitions are distinguished using rheology. Frequency sweeps are performed across a range of temperatures and parameterized with a loglinear fit to the phase angle data to extract the crossover frequency. We find that a single frequency sweep does not distinguish BCC and FCC structures. By normalizing the temperature with respect to the ODT, we are able to use a series of frequency sweeps to distinguish characteristic trends in the response of BCC and FCC structures to thermal history.

Effect of long-term indoor thermal history on human physiological and psychological responses: A pilot study in university dormitory buildings

The present study aimed to explore the effect of long-term indoor thermal history on the psychological and physiological responses of occupants. Based on a field study, 465 and 345 data sets were obtained from healthy students in naturally ventilated (NV) and split air-conditioned (SAC) dormitory buildings, respectively. The physiological and psychological responses were explored. Physical variables were measured by calibrated instruments; the psychological response was rated by occupants through questionnaires; physiological measurement included four upper extremity skin temperatures (i.e., finger, wrist, hand and forearm), heart rate, systolic blood pressure, and diastolic blood pressure. The results indicated that indoor thermal history had no significant effect on physiological response (i.e., upper extremity skin temperatures, blood pressure, and heart rate), and induced psychological adaptation. The neutral temperature of the NV group was 26.2 °C, 0.7 °C higher than that of the SAC group (25.7 °C). The upper limit of 90% acceptable temperature range was 28 °C for the NV group, 0.7 °C higher than that of the SAC group (27.3 °C). Compared to the SAC group, a warm long-term indoor thermal history of the NV group produced a shift to higher neutral temperature and higher acceptable temperature. The clothing adjustment of NV group was more sensitive to indoor temperature than the SAC group.

Prediction of the zirconium hydride precipitation barrier with an anisotropic 3D phase-field model incorporating bulk thermodynamics and elasticity

A phase-field model is developed to elucidate a long-standing question about zirconium hydride nucleation by extending the applicability of bulk equilibrium thermodynamics to the nanoscale. A significant hysteresis is observed between the conditions of hydride dissolution and precipitation during power cycling which can degrade the mechanical stability of nuclear fuel cladding but depends on availability of heterogeneous nucleation sites. The modelling approach combines anisotropic interfacial energy, a comprehensive 3D anisotropic elastic treatment, and stress driven diffusion with quadratic approximations of thermodynamic potentials. New experimental evidence of the effect of thermal history on hydride precipitation is presented which provides support and enhanced interpretation of the model predictions. Simulation results indicate that the interfacial energy of an embryotic hydride is augmented by the elastic contribution from the coherent interface, resulting in effective interfacial energies in the basal and prismatic planes in excess of 0.80 and 1.44 J m−2 respectively, more than a factor of 20 larger than typically considered. Along with the strain energy of accommodation, a significant homogenous nucleation barrier is formed which is overcome by a sufficient thermodynamic driving force for the growth of the embryo, determined by the H supersaturation in the surrounding matrix and the bulk equilibrium thermodynamics, which changes dramatically with temperature.

Effect of hot-press thermal history on joint strength of A5052/Polyamide-6 hybrid structure via a porous layer

Abstract The influence of the joining temperature history on the mechanical behavior of an Al alloy (A5052)/Polyamide-6 (PA6) lap joint was investigated. PA6 is a semi-crystalline thermoplastic and its mechanical behavior depends on its crystalline properties, which are affected by thermal processing. The A5052/PA6 joining process was carried out at 215 °C using a hydraulic hot-press. The temperature was decreased from 215 °C to various pre-set temperatures at a cooling rate of about 2 °C/s followed by air cooling under the application of pressure. The crystallinity of PA6 and strength of the lap joint increased with a decrease in the joining temperature from 215 to 190 °C and remained constant at temperatures below 190 °C. The thermoanalytical examination revealed that the crystallinity increase was caused by slow cooling. The results demonstrated that slow cooling is an effectual approach to improve the bonding strength. The fractography analysis results showed that the fracture mode of PA6 changed from ductile to brittle with an increase in its crystallinity.

Aromatic Embrace Motifs for Bulk Supramolecular Polymers.

Frequently encountered in crystalline materials, aromatic embraces (AEs) are formed when arylated molecules interact through multiple concerted aromatic interactions. AEs are a robust motif that is suitable for the preparation of amorphous bulk supramolecular polymers (BSPs). Crystal engineering revealed that the polymorphic compound (PPh3 )(Cp)Fe(CO){CO(CH2 )5 CH3 } (Cp=cyclopentadienyl), known as FpC6 , assembled into various chain structures through several AE motifs. Upon melting, FpC6 always adopted the same AE motif, which extended into the corresponding embracing "ladder" chains. The resultant BSP displayed typical polymer behaviour, including the presence of a glass transition and viscoelasticity, which allowed the effect of thermal history on the polymerisation behaviour to be explored. The ladder chains formed by the AE remain assembled at temperatures of up to 130 °C and were able to effectively suppress crystallisation during cooling. The ability of the AE to form chains at high temperatures and suppress crystallisation is a new opportunity to advance the field of BSPs and supramolecular chemistry.

Quantification of location-dependence in a large-scale additively manufactured build through experiments and micromechanical modeling

Wire-based directed energy deposition additive manufacturing techniques (AM) permit the rapid production of large-scale structural components which are not currently possible using the more common powder bed fusion (PBF) AM methods. However, due to larger melt pool widths and higher energy inputs than PBF methods, local thermal history effects produce significant location-dependent microstructure, porosity, and mechanical behavior that necessitates thorough quantification of this emergent technology. Wire + Arc Additive Manufacturing (WAAM) was used to produce austenitic stainless-steel single bead walls in order to statistically quantify the variation of critical material properties within the build. Individual grain geometric properties evaluated using electron back scatter diffraction at different points in the build were well fit by a three-parameter Weibull cumulative distribution function, yet sufficiently different from averaged values. X-ray diffraction for each location disclosed a strong wire texture in the build direction, leading to anisotropic elastic moduli values that were well described by directionally-dependent modulus predictions obtained from diffraction peak analysis. Location-dependent mechanical behavior was examined and accurately captured by an elasto-viscoplastic model based on the Fast-Fourier Transforms (EvpFFT) using the local microstructure orientation data as input. Overall, a high-quality build was realized, with minimal porosity of less than 0.32%, and median yield and tensile strength values of approximately 320.4 ± 8.0 MPa and 531.6 ± 8.2 MPa, respectively. In conclusion, mean values for mechanical behavior within the wall build were found to closely resemble single pass weldments, with statistical variation between individual locations mainly occurring in the weld direction due to local thermal history effects.

Effect of Thermal History and Shear on the Viscoelastic Response of iPP Containing an Oxalamide-Based Organic Compound.

We report on the role of temperature and shear on the melt behavior of iPP in the presence of the organic compound N1,N1′-(propane-1,3-diyl)bis(N2-hexyloxalamide) (OXA3,6). It is demonstrated that OXA3,6 facilitates a viscosity suppression when it resides in the molten state. The viscosity suppression is attributed to the interaction of iPP chains/subchains with molten OXA3,6 nanoclusters. The exact molecular mechanism has not been identified; nevertheless, a tentative explanation is proposed. The observed viscosity suppression appears similar to that encountered in polymer melts filled with solid nanoparticles, with the difference that the OXA3,6 compound reported in this study facilitates the viscosity suppression in the molten state. Upon cooling, as crystal growth of OXA3,6 progresses, the decrease in viscosity is suppressed. Retrospectively, segmental absorption of iPP chains on the surface of micrometer-sized OXA3,6 crystallites favors the formation of dangling arms, yielding OXA3,6 crystallites decorated with partially absorbed iPP chains. In other words, the resulting OXA3,6 particle morphology resembles that of a hairy particle or a starlike polymer chain. Such hairy particles effectively facilitate a viscosity enhancement, similar to branched polymer chains. This hypothesis and its implications for the shear behavior of iPP are discussed and supported using plate–plate rheometry and slit-flow experiments combined with small-angle X-ray scattering analysis.

Effect of Thermal History on Hot Workability of Fe-Cr Multiphase Steel during Hot Working

Effect of Thermal History on Hot Workability of Fe-Cr Multiphase Steel during Hot Working

Effects of Thermal History and Monoglyceride on the Distribution of Ceramide Molecules Dispersed into Adhesive Rubber Sheet

Effects of Thermal History and Monoglyceride on the Distribution of Ceramide Molecules Dispersed into Adhesive Rubber Sheet

Reconstructing the basin thermal history with clumped isotope

<p indent=0mm>Due to the lack of effective paleo-geothermometers, it has often been difficult to reconstruct the thermal history of marine carbonate strata, resulting in unreliable conclusions. As emerging paleo-geothermometers, the clumped isotope of carbonate rocks could directly provide the temperature information without relying on the assumed isotopes of paleo-fluids, which has shown excellent potential in the study of the thermal history of carbonate reservoirs. To exclude the interference from late diagenesis, this study examined multiple carbonate samples under minor diagenetic alteration, which were selected from several wells in the Tarim Basin and Sichuan Basin to examine the clumped isotope (measured as Δ₄₇ values). Considering the temperature range and acid fractionation factors of various clumped isotope formulae, the Deflieses formula was selected to calculate the temperature of clumped isotope. By analyzing the experimental results, the meaning of Δ₄₇ temperature in the naturally evolved limestones and dolomites, the reordering rules of ¹³C–¹⁸O solid-state bond in calcite clumped isotope, and the effects of thermal history on clumped isotope in different lithologies have been comprehensively discussed herein. The Shun-Ka area located in the center of the Tarim Basin has been subjected to simple tectonic movements and continuous subsidence, because of which the strata of this area are currently experiencing the highest burial depth and temperature, which provide ideal conditions for studying the influence of temperature on Δ₄₇ values. The measured Δ₄₇ values of 17 samples from the Shun-Ka area were in the range 0.443‰–0.634‰, and the calculated temperatures of the clumped isotope were in the range 49.9–201.7°C. The Δ₄₇ temperatures of these samples were higher than their diagenetic temperatures, indicating that Δ₄₇ was affected by the burial process with the reordering of solid-state ¹³C–¹⁸O bonds. Based on the relationship between the Δ₄₇ temperature and borehole temperature in the Shun-Ka uplift of the Tarim Basin, it was suggested that the blocking temperature of ¹³C–¹⁸O solid-state bond reordering in the naturally evolved calcites would not be higher than 120°C and the equilibrium temperature would not be lower than 160°C, which was consistent with the foreign laboratory results. Furthermore, to compare the effect of clumped isotope in different lithologies, another 11 dolomite samples were selected from the central uplift of the Sichuan Basin for analyzing the clumped isotope. The measured Δ₄₇ values of dolomites from the Sichuan Basin were in the range 0.423‰–0.537‰, and the calculated temperatures of the clumped isotope were in the range 105.7–233.5°C. Similarly, it is possible that the warming effect associated with increased burial depth resulted in ¹³C–¹⁸O solid-state bond reordering and a higher temperature, which was the result of both diagenesis and burial heating. To investigate the effects of thermal history on clumped isotope, the first-order approximation model was used to simulate the clumped isotope values based on the thermal history reported in previous research. The initial diagenesis temperature was set to 20°C, and it was assumed that the Δ₄₇ temperatures of samples were only affected by diagenesis temperature and thermal history. Results revealed that the Δ₄₇ temperature calculated using the first-order approximation model of limestone samples from the Yingshan Formation of the Tarim Basin exhibited good agreement with the measured temperature, but the calculated Δ₄₇ temperature in the dolomites considerably differed from the actual measured temperature. This conflict could have occurred due to various thermodynamic properties (such as frequency factors and activation energy) and the complex diagenesis process between limestones and dolomites. Therefore, the first-order approximation model could be used more accurately to describe the effect of the basins thermal history on ¹³C–¹⁸O solid-state reordering in calcites. However, further research should be conducted on dolomites to build an inversion model focusing on the thermal history of the basin and clumped isotope.

Damage mechanisms in a toughened acrylic resin: Effect of temperature and thermal history

The effect of temperature on the damage mechanisms occurring in a toughened acrylic resin was investigated by studying volume changes during tensile tests, analyzing the reversibility of the damage after applying proper thermal histories and by direct transmission electron microscope observations. It was found that an increase of temperature, from 0°C to 60°C, shifts the predominant mechanism from crazing to cavitation and shear yielding. When the latter occur, the material response is very susceptible to previous thermal treatments; and in particular to the cooling rate from above glass transition temperature. Crazing on the other hand is not influenced by the thermal history of the material. POLYM. ENG. SCI., 59:566–572, 2019. © 2018 Society of Plastics Engineers

Investigation into the morphology, crystallization and melting behaviour of nylon 6,6/LCP blends

The morphology, isothermal crystallization and melting behaviour of melt-mixed nylon 6,6/Vectra A950 liquid crystalline polymer (LCP) blends were investigated. The blends formed an immiscible system for all compositions, and the inclusion of LCP, especially at low content, accelerated the bulk crystallization rate of the matrix. The addition of LCP was also found to decrease the crystallite size in the growth direction. The effect of thermal history on the triple melting behaviour and the equilibrium melting temperature was discussed. The equilibrium meting temperature was determined to be lower in the blends. Lauritzen-Hoffman analysis on the crystallization data revealed an apparent regime I to II transition in all the samples. The blends showed lower fold surface energy and work of chain folding as compared to nylon 6,6.