Temperature Dependent Phase Transformation Research Articles

Equivalent plate model of shape memory polymer composite based variable height corrugated structure

In this work, an equivalent plate model for a shape memory polymer composite based corrugation structure with varying height, for morphing application, is developed. A thermodynamically consistent constitutive relation based on temperature dependent phase transformation concept for shape memory polymer matrix is used in the composite model. The homogenization model is based on the equivalence of strain energy of a representative unit volume. Following validation, as an application, commonly used airfoil profile NACA 63210 was considered to demonstrate the model utility. Parametric studies have been undertaken to investigate the influence of corrugation parameters like thickness and number of corrugations.

Effect of sintering temperatures on the physical, structural properties and microstructure of mullite-based ceramics

<abstract> <p>This study explored the impact of sintering temperature variations on the synthesis and characteristics of mullite ceramics derived from a composite blend of kaolinite clay, silica (silicon dioxide), and feldspar. Sintering temperatures ranging from 1100 to 1200 ℃ were systematically examined to analyze alterations in shrinkage, density, microstructure, elemental composition, and phase formation. The study revealed that an increase in sintering temperature led to decreased shrinkage due to improved particle packing and reduced porosity. Ceramic density showed a direct relation with sintering temperature, reaching the optimal density at 1175 ℃ and indicating efficient particle packing and compaction. Analysis through field emission scanning electron microscopy (FESEM) provided insights into microstructural changes, including alterations in grain morphology, porosity, and connectivity. Energy dispersive X-ray spectroscopy (EDS) clarified element distribution within the microstructure, offering valuable information on compositional variations. X-ray diffraction (XRD) examinations unveiled temperature-dependent phase transformations, which confirmed the successful formation of mullite during the sintering process. A sintering temperature of 1175 ℃ yielded the optimal ceramic quality and cost-effectiveness for high-temperature heating processes.</p> </abstract>

Phase transformation and mechanical properties of heat-treated nickel-titanium rotary endodontic instruments at room and body temperatures

BackgroundThe aim of this study was to evaluate the phase composition, phase transformation temperatures, bending property, and cyclic fatigue resistance of different heat-treated nickel-titanium (NiTi) rotary instruments with the same tip diameter and taper at room (RT; 25 ± 1 °C) and body (BT; 37 ± 1 °C) temperatures.MethodsFive heat-treated NiTi rotary instruments, HyFlex EDM (EDM), HyFlex CM (CM), Vortex Blue (VB), RE file CT (RE) and JIZAI, and a non-heat-treated NiTi rotary instrument (Mtwo) with a size 40, 0.04 taper were investigated. Temperature-dependent phase transformation was examined with differential scanning calorimetry (DSC). The bending loads of the instruments at RT and BT were evaluated using a cantilever-bending test. Cyclic fatigue resistance at RT and BT was measured using a dynamic test, during which the instruments were rotated in combination with a 2-mm back-and-forth motion in an artificial curved canal, and the number of cycles to failure (NCF) was determined. The results were analyzed using two-way repeated measures analysis of variance, a simple main effect test, and the Bonferroni test (α = 0.05).ResultsDSC results indicated that EDM and Mtwo were primarily composed of martensite/R-phase and austenite, respectively, while the other heat-treated instruments were composed of a mix of martensite/R-phase and austenite at the tested temperatures. Regardless of the temperature setting, the bending loads of heat-treated instruments were significantly lower than those of Mtwo (p < 0.05). EDM showed the lowest bending loads and highest NCF at both temperatures (p < 0.05). CM, VB, and JIZAI showed significantly higher bending loads at BT than at RT (p < 0.05). The NCF of all the heat-treated instruments, except VB, was lower at BT than at RT (p < 0.05). At BT, the NCF of CM, VB, RE, and JIZAI were not significantly higher than that of Mtwo (p > 0.05).ConclusionsHeat-treated NiTi instruments exhibited lower bending loads and higher NCF values than Mtwo. However, this tendency was less pronounced at BT than at RT, especially in the NCF values of instruments with a mixture of martensite/R-phase and austenite phases at the tested temperatures.

The Temperature-Dependent Phase Transformation and Microstructural Characterisation in In-Sn Solder Alloys

Indium-based solder alloys are considered candidates for the next generation of low-temperature solder materials, especially for superconducting joints because of the properties of the β-In3Sn phase. The temperature-dependent phase transformation and thermal expansion behaviour of two different solder compositions including In-35Sn (in wt.%) and In-25.6Sn have been characterised using an in situ synchrotron powder X-ray diffraction method. The c-axis of the β-In3Sn unit cell in the In-35Sn alloy exhibited a complex relationship with increasing temperature compared to the positive increasing trend in In-25.6Sn due to the temperature-dependent solubility of Sn in β-In3Sn and change in the volume fraction of phases commencing at 80°C. In situ heating scanning electron microscopy recorded a real-time melting-solidification microstructure variation and phase transition during annealing at 90°C that was further analysed using energy dispersive X-ray spectroscopy. The observations are discussed with respect to the lattice parameters of the γ-InSn4 and β-In3Sn phases and the proportions and composition of both phases present within the alloys.

Synthesis of V2AlC thin films by thermal annealing of nanoscale elemental multilayered precursors: Incorporation of layered Ar bubbles and impact on microstructure formation

Periodically stacked nanoscale V/C/Al multilayered thin film precursors were deposited by magnetron sputtering using elemental targets. Their temperature-dependent phase transformation during subsequent thermal annealing in argon towards V2AlC MAX phase formation was investigated. Compositional and microstructural analyses at the nanoscale revealed undulation growth of the nanolayers and preferential incorporation of Ar atoms into amorphous carbon nanolayers within the as-deposited multilayered precursors. Single-phase and basal-plane-oriented V2AlC films were formed at annealing temperatures above 560 °C. The incorporated Ar atoms migrated and aggregated into high-density nanoscale Ar clusters/bubbles located essentially at grain boundaries after annealing, displaying pronounced layered distribution characteristics especially adjacent to the substrate/film interface. The heterogeneous incorporation of argon atoms or clusters in heterostructured films composed of multicomponent sublayers likely represents a common phenomenon during thin film nucleation and growth, while its impact on the macroscopic properties of films remains to be explored.

Phase conversion during MnC2O4 pyrolysis and the application on high photothermal catalytic degradation of toluene

Monoclinic Mn5O8, spinel Mn3O4, and perovskite Mn 2O3were prepared by thermal decomposition of MnC2O4. The formation of different MnOx species observed by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) measurements showed temperature-dependent phase transformation following the path of MnC2O 4[Formula: see text]Mn5O8[Formula: see text]Mn3O4[Formula: see text]Mn2O 3occurring during the heat treatment process. Among these manganese oxides, the MO-1 (Mn5O8 ) showed the best light-driven photothermal catalytic performance reaching up to 99% of toluene degradation and 75% of mineralization efficiencies reached within 30 min. Besides, it is found that structural defects decrease with the increase of the calcinated temperature, and the Mn[Formula: see text]/Mn[Formula: see text]active sites and oxygen vacancies play an important role in improving the light-driven photothermal catalytic performance.

Temperature induced phase transformation in Co

Temperature dependent phase transformation behavior in cobalt from hexagonal close-packed (hcp) to face centered cubic (fcc) has been found to be contradictory to that reported earlier. It is found that hcp phase stabilizes at both low and high temperature (sim 873 K) while fcc phase is stabilized at sim 500 K. At 298 K, hcp Co has been found to be predominant (sim 70%) where hcp magnetic phase is sim 60%. At 973 K, hcp phase is again predominant (sim 73%), but it is mainly the non-magnetic phase (sim 67%). Contrary to present results, it was found earlier that fcc phase was stabilized at high temperature and hcp to fcc transformation occured at sim 700 K. Present results from perturbed angular correlation measurements, therefore, requires a new theoretical interpretation for Co phase transformation. From present measurements, hyperfine magnetic fields in Co at room temperature for the hcp and fcc phases have been found to be 18.7(6) and 12.8(3) T, much lower than earlier reported results. The hyperfine magnetic fields at ^{181}Ta impurity atom have been calculated by density functional theory (DFT) employing the full potential (linearized) augmented plane wave method (FP-LAPW). Present calculated results for both hcp and fcc phases corroborate our experimental results.

Temperature-Stimulated Morphological Features of Advanced High-Strength Medium-Mn TRIP Steel.

Advanced High-Strength Steels (AHSSs) are one of the most rapidly developing group of Fe-based metallic materials. Their excellent combination of high strength, ductility and formability is due to their complex microstructure and strain-induced martensitic transformation of metastable retained austenite (RA), which favors extra ductility of the sheet steels. A deformation temperature is one of the most important factors affecting the phase transformation behavior in these Fe–C–Mn–Al–Si systems. Therefore, the present study aimed at understanding the temperature-dependent phase transformations and structural phenomena in an advanced medium-Mn–Al-alloyed steel. The 3Mn steel was thermomechanically processed and subjected to tensile testing in a temperature range from 20°C to 200°C. The different extent of the strain-induced martensitic transformation and some softening phenomena of bainitic ferrite matrix were revealed using transmission electron microscopy and electron backscatter diffraction techniques. It was found that the thermal stability of RA is strongly dependent on the deformation temperature. Moreover, the dynamic recovery and carbide precipitation play a key role when the deformation temperature is increased to 140°C and higher temperatures.

Pyroelectric power generation in PLZST material by temperature dependent phase transformation

Efforts are being made to increase the efficiency of energy consumption by effectively using the dissipated heat as a source of renewable energy. Herein, we focused on a heat source wherein the temperature varies with time and recovers electrical energy from thermal energy by the pyroelectric effect. Further, we evaluated the net power density of the (Pb, La) (Zr, Sn, Ti)O3 material that is produced by its phase transformation as a result of increase in temperature. It was measured by the Sawyer-Tower circuit that was installed a diode and switch. The results showed that when the low or high temperature side of the measurement environment is in the antiferroelectric phase, the net power density decreased or became negative. Additionally, we estimated the range of temperature wherein a high-power density could be attained by examining the changes in it due to phase transformation.

A review on the preparation, microstructure, and photocatalytic performance of Bi2O3 in polymorphs.

In recent years, the semiconductor bismuth oxide (Bi2O3) has attracted increasing attention as a potential visible-light-driven photocatalyst due to its simple composition, relatively narrow bandgap (2.2-2.8 eV), and high oxidation ability with deep valence band levels. Owing to the symmetry of its unit cell, Bi2O3 exists in more than one crystal form and exhibits phase-dependent photocatalytic properties. However, the phase-selective synthesis of Bi2O3 is a complex process, and its phase transformation usually occurs in a wide temperature range. Therefore, the development of Bi2O3 phases with a controllable microstructure and good photocatalytic properties is a great challenge. Hundreds of articles have been reported on the phase-selective synthesis and photocatalytic performance of Bi2O3. However, an interacting and critical review has rarely been reported, and thus it is essential to fill the gap in the literature. In this review, the phase-dependent photocatalytic performance of Bi2O3 is presented in detail. The phase-selective synthesis and temperature-dependent phase stability of highly active Bi2O3 are explored. The phase junction in Bi2O3 is reviewed, and the future perspective with an outlook on contemporary challenges is provided finally.

In Situ Analysis of the Thermal Evolution of Electrodeposited Fe-C Coatings

Fe-C coatings with a high amount of carbon were electrodeposited from an iron-sulfate electrolyte. Citric acid as an additive in the electrolyte not only served as a carbon source during electrodeposition but also caused the reproducible codeposition of oxygen and hydrogen. The various codeposited elements (C, O, H) result in the complex nature of the as-deposited coatings and allow for deliberate alterations of the coating properties by postdeposition annealing. The thermal evolution of electrodeposited Fe-C coatings was investigated in situ during isochronal annealing. In situ synchrotron diffraction analysis revealed temperature-dependent phase transformations, which were supplemented with in situ thermal analysis for investigating the evolution of codeposited elements and associated mass changes during annealing. Based on the determined activation energies of identified thermal events, the underlying mechanisms are discussed. The results clearly indicate the role of codeposited elements in the coatings and suggest that they partly exist in the form of organic compounds, which decompose during annealing. In addition to revealing the thermal stability of the coatings and quantifying the coatings’ thermal evolution, the complementary methods of in situ analysis considerably improved the understanding of the as-deposited Fe-C coatings—both are essential prerequisites for the successful application of the Fe-C coatings.

Temperature Dependent Phase Transformation Kinetics of Reverted Austenite during Tempering in 13Cr Supermartensitic Stainless Steel

The formation and growth kinetics of the reverted austenite during tempering in 13Cr supermartensitic stainless steel were investigated by a combination X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). The reverted austenite precipitated at the martensite blocks, sub-blocks, laths and grain boundaries. The growth kinetics was established by Johnson-Mehl-Avrami (JAM) kinetics equation according to the volume fraction of the equilibrium reverted austenite at room temperature. The Avrami exponent value is 0.5, and the activation energy was estimated to be 369 kJ/mol, the kinetic model indicates that the mechanism of reverted austenite is diffusion-controlled and the growth of reverted austenite closely relies on the diffusion of the nickel (Ni) element. The experimental measured orientations of the reverted austenite are in good agreement with the theoretical ones, implying that the reverted austenite has the same orientation with the surrounding martensite, which meets the Kurdjumov–Sachs (K-S) orientation relationship. The orientation relationships minimize the strain energy of the phase transformation by reducing the crystallographic mismatch between phases.

Mechanism of high temperature induced phase transformation and magnetic properties of Mn3O4 crystallites

Abstract This paper is an experimental study of the different phases of oxides of manganese, prepared by solution combustion method using mixture of urea and glucose as fuels. To validate the thermal stability of Mn2O3, the as-synthesized sample was subjected to heat treatment from 350 °C to 1000 °C with 100 °C interval. The change in Mn2O3 to Mn3O4 was identified by powder X-ray diffraction (PXRD) to show the temperature dependent phase transformation that occur during the heat treatment process. The PXRD patterns show that Mn2O3 is stable between temperatures of 350 °C to 850 °C, and a new phase i.e Mn3O4 appears at 1000 °C. The Mn2O3 and Mn3O4 have their distinct surface morphologies viz., spherical and rod shapes. The detailed morphology, elemental compositions and structure investigation were carried out by using Scanning Electron Microscopy (SEM-EDAX) and Raman spectroscopy. Sintered sample of Mn3O4 were subjected to magnetic measurements. The Mn3O4 crystallite with diameters of 50 nm shows ferromagnetic behavior with a phase transition from ferromagnetic to paramagnetic phase at 48 K. A large coercivity up to 3000 Oe and a small remanence of 0.1092 emu/g at 10 K, was observed. The temperature dependent magnetization measured in a magnetic field of 100 Oe, increases significantly with decreasing temperature around 45 K, both for the FC and ZFC measurements. The susceptibility measurement of the Mn3O4 crystallites were investigated between 0 and 300 K by applied magnetic fields up to 5 T. A magnetic transition is observed near 48 K which is attributed to the formation of the ferrimagnetic Mn3O4.

Influences of W Content on the Phase Transformation Properties and the Associated Stress Change in Thin Film Substrate Combinations Studied by Fabrication and Characterization of Thin Film V1- xW xO2 Materials Libraries.

The mechanical stress change of VO2 film substrate combinations during their reversible phase transformation makes them promising for applications in micro/nanoactuators. V1- xW xO2 thin film libraries were fabricated by reactive combinatorial cosputtering to investigate the effects of the addition of W on mechanical and other transformation properties. High-throughput characterization methods were used to systematically determine the composition spread, crystalline structure, surface topography, as well as the temperature-dependent phase transformation properties, that is, the hysteresis curves of the resistance and stress change. The study indicates that as x in V1- xW xO2 increases from 0.007 to 0.044 the crystalline structure gradually shifts from the VO2 (M) phase to the VO2 (R) phase. The transformation temperature decreases by 15 K/at. % and the resistance change is reduced to 1 order of magnitude, accompanied by a wider transition range and a narrower hysteresis with a minimal value of 1.8 K. A V1- xW xO2 library deposited on a Si3N4/SiO2-coated Si cantilever array wafer was used to study simultaneously the temperature-dependent stress change σ( T) of films with different W content through the phase transformation. Compared with σ( T) of ∼700 MPa of a VO2 film, σ( T) in V1- xW xO2 films decreases to ∼250 MPa. Meanwhile, σ( T) becomes less abrupt and occurs over a wider temperature range with decreased transformation temperatures.

Mn5O8 nanoflowers prepared via a solvothermal route as efficient denitration catalysts

Well-crystalline monoclinic Mn5O8, tetragonal Mn3O4 and cubic Mn2O3 were synthesized via a solvothermal route followed by distinct heat treatment. The formation of different MnOx species observed by X-ray diffraction (XRD) measurements showed temperature dependent phase transformation occurring during the heat treatment process. XRD patterns showed that Mn3O4 and Mn5O8 were formed at calcination temperature range of 573–673 K and a new phase Mn2O3 appeared at 773 K, respectively. And a tendency to the formation of Mn5O8 was found as the solvothermal temperature turns higher. The catalytic activities of various MnOx for selective catalytic reduction (SCR) of nitrogen oxides were evaluated between 353 and 573 K using ammonia as reducer. Mn5O8 appeared to exhibit the highest activity, followed by Mn3O4, Mn2O3.

Temperature-dependent phase transformation of TiO2 nanoparticles synthesized by sol-gel method

Nanocrystalline TiO2 particles were prepared to study the calcination temperature dependent phase transformation. X-ray diffraction (XRD) patterns showed the strong Bragg peaks correspond to anatase (101) and rutile (110) phases with their crystallite size 12 and 49 nm for the samples T1 and T2 calcined at 450 and 700 °C respectively. Raman spectroscopy investigation showed the phase transformation with the dominating rutile peaks from the pure-anatase phase. By UV–vis absorption spectroscopy, the strong ultraviolet-light absorption below 400 nm was observed. Using Kubelka-Munk function, the estimated band gap values were found to be 3.38 and 3.03 eV. The transmission scanning microscopy (TEM) images exhibited the slightly agglomerated nanoparticles while the selected area diffraction (SAED) patterns endorsed the polycrystalline nature.

Modelling and simulation of hydrogen redistribution in a heterogeneous alloy during the cooling down to 200 °C

Hydrogen embrittlement induced by internal hydrogen has been identified as a critical issue for heavy components manufactured from either plain or hollow ingots made of 16MnNIMo5 through 20MnNiMo5 alloys that have the particularity to be heterogeneous at various scales. Based on available data of solubilities, diffusivities and temperature dependent phase transformations for the matrix and segregated bands, a model of hydrogen distribution in such a heterogeneous microstructure has been developed. Additionally, penny-shaped thin cavities have been introduced to account for the presence of incoherent MnS inclusions leading to a potential decohesion at MnS/matrix interface. Pressure increase in such cavities has been evaluated using ideal gas behavior for hydrogen. A unidimensional Finite Difference numerical approach has been implemented in order to simulate hydrogen redistribution among matrix, segregation_band and cavity. This model has allowed to quantitatively evaluate the redistribution of hydrogen at the scale of the microstructural heterogeneities during the cooling down to 200 °C: first, close to the component surface where important kinetic effects have been demonstrated due to high cooling rate and second, in the bulk, where hydrogen redistribution was close to the thermodynamic equilibrium during the whole cooling period. It has been shown that the final equilibrium pressure of hydrogen in the cavity at 200 °C is negligible even for a high initial hydrogen content.

Synthesis of Mn3O4 nanoparticles via a facile gel formation route and study of their phase and structural transformation with distinct surface morphology upon heat treatment

Mn3O4 nanoparticles (NPs) were synthesized from the reduction of KMnO4 with glycerol at 80°C in aqueous media via a gel formation route. In order to investigate the thermal stability and phase transformation, Mn3O4 NPs were subjected to heat treatment from 200°C to 700°C. The formation of different MnOx species observed by X-ray diffraction (XRD) measurements showed temperature dependent phase transformation occurring during the heat treatment process. XRD patterns showed that Mn3O4 NPs were formed at a temperature of 80°C and two new phases Mn5O8 and Mn2O3 were appeared at 350°C and 700°C respectively. The three different oxides having their distinct surface morphologies viz., spherical, rod and cube shape respectively, were observed. Detailed morphological and structural investigations using Field Emission Scanning Electron Microscopy (FESEM), XRD, Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) revealed the temperature dependent phases, crystal structures, lattice constants, particle sizes and surface morphologies of the MnOx species.

Heat treatment of 34CrNiMo6 steel used for mooring shackles

This study presents an experimental investigation of the heat treatment of 34CrNiMo6 steel used for shackles. Indeed, industrial requirements impose specific mechanical properties to the materials which constitute shackles. The aim of this work is to propose a method to relate heat treatment parameters and the resulting mechanical properties. Instrumented cylindrical specimen are submitted to successive heat treatments under conditions representative of the industrial process. Core and surface temperatures are recorded during cooling. Metallographic observations and hardness measurements are performed after each heat treatment, in order to characterise the final phase distribution and mechanical properties. A model based on the one-dimensional heat conduction equation in cylindrical coordinates is developed within an implicit scheme, taking into account the temperature-dependent phase transformations. The results firstly provide a validation of the input data using specific dilatometric experiments, which then leads to a comparison between the experimental and numerical evolution of the core temperature under each cooling condition, as well as the prediction of the phase volume fractions and the resulting hardness. It is shown that the proposed approach yields a very good representation of the material properties.

Adaptive Fuzzy Sliding-Mode Position Control of a Shape Memory Alloy Actuated System

Shape memory alloy (SMA) actuators are promising for miniature applications. They accomplish the shape memorization via a temperature dependent phase transformation process. Control of SMA actuators is challenging because the actuators exhibit highly hysteresis behavior. This paper presents a fuzzy-based position control scheme for a SMA actuated mass system. The control system consists of an outer-and an inner-control loop. The inner loop controls the temperature of the SMA actuators using a PI controller, whereas the outer loop, which is affected by the hysteresis of the SMA actuators, controls the position. To deal with the hysteresis in the position control loop, an adaptive fuzzy sliding-mode control method is adopted. Experimental results illustrate the success of the proposed control scheme.