Thermal Diffusion Behavior Research Articles

Spectroscopic Study of [Mg, H, N, C, O] Species: Implications for the Astrochemical Magnesium Chemistry.

Magnesium is an abundant metal element in space, and magnesium chemistry has vital importance in the evolution of interstellar medium (ISM) and circumstellar regions, such as the asymptotic giant branch star IRC+10216 where a variety of Mg compounds bearing H, C, N, and O have been detected and proposed as the important components in the gas-phase molecular clouds and solid-state dust grains. Herein, we report the formation and infrared spectroscopic characterization of the Mg-bearing molecules HMg, [Mg, N, C], [Mg, H, N, C], [Mg, N, C, O], and [Mg, H, N, C, O] from the reactions of Mg/Mg+ and the prebiotic isocyanic acid (HNCO) in the solid neon matrix. Based on their thermal diffusion and photochemical behavior, a complex reactivity landscape involving association, decomposition, and isomerization reactions of these Mg-bearing molecules is developed, which can not only help understand the chemical processes of the magnesium (iso)cyanides in astrochemistry but also provide implications on the presence of magnesium (iso)cyanates in the ISM and the chemical model for the dust grain surface reactions. It also provides a new paradigm of the key intermediate nature of the cationic complexes in the formation of neutral interstellar species.

Evaluation of the dispersion properties of graphene oxide/cetyltrimethylammonium bromide for application in nanocomposite materials.

The properties of thermal diffusivity and Z potential of the GONPs/CTAB nanofluid were studied as a function of GO concentration (in the range between 4 and 12% w/v), temperature (35 and 50 °C) and time (30 and 60 min) under ultrasound. In turn, the structural properties of GONPs/CTAB were measured by XRD, Raman, SEM and TEM. The GO previously modified with CTAB was used to obtain a PLA/GO nanocomposite. It was found that the behavior of thermal diffusivity provides information in situ on the dispersion properties of the nanofluid, finding values from 0.0013 to 0.0024 cm2 s-1. The hydrodynamic diameter of the GONP dispersions was also determined to range from 75.83 to 360.3 nm with an increase in Z potential from 17 to 30 mV. The most stable GONPs/CTAB dispersion conditions were 6% w/v GO, 50 °C and 30 min. Under these conditions, the GONPs/CTAB materials present an increase in the spacing between GO layers, associated with a greater multilayer stacking of the GO and CTAB layers. The Raman spectrum allowed us to demonstrate that the modification with CTAB did not affect the crystallinity of GO, which was verified by the intensity ratio of the D band and the G band (ID/IG) for the GO/CTAB samples, with the exception of the GO 6% sample, where an increase in the ID/IG ratio (0.9) was observed compared to GO (0.82), associated with greater intercalation of CTAB between the GO sheets. Finally, an SEM analysis of the PLA/GO nanocomposite was carried out and the homogeneous distribution of GO in PLA was demonstrated when it is used as a filler in proportions of 0.1%. This treatment, in turn, contributed to improving the mechanical flexural properties of the nanocomposite materials.

Structural and Thermal Diffusivity Analysis of an Organoferroelastic Crystal Showing Scissor-Like Two-Directional Deformation Induced by Uniaxial Compression.

A two-directional ferroelastic deformation in organic crystals is unprecedented owing to its anisotropic crystal packing, in contrast to isotropic symmetrical packing in inorganic compounds and polymers. Thereby, finding and constructing multidirectional ferroelastic deformations in organic compounds is undoubtedly complex and at once calls for deep comprehension. Herein, we demonstrate the first example of a two-directional ferroelastic deformation with a unique scissor-like movement in single crystals of trans-3-hexenedioic acid by the application of uniaxial compression stress. A detailed structural investigation of the mechanical deformation at the macroscopic and microscopic levels by three distinct force measurement techniques (including shear and three-point bending test), single crystal X-ray diffraction techniques, and polarized synchrotron-FTIR microspectroscopy highlighted that mechanical twinning promoted the deformation. The presence of two crystallographically equivalent faces and the herringbone arrangement promoted the two-directional ferroelastic deformation. In addition, anisotropic heat transfer properties in the parent and the deformed domains were investigated by thermal diffusivity measurement on all three axes using microscale temperature-wave analysis (μ-TWA). A correlation between the anisotropic structural arrangement and the difference in thermal diffusivity and mechanical behavior in the two-directional organoferroelastic deformation could be established. The structural and molecular level information from this two-directional ferroelastic deformation would lead to a more profound understanding of the structure-property relationship in multidirectional deformation in organic crystals.

Simulation of the temperature distribution of lithium-ion battery module considering the time-delay effect of the porous electrodes

The porous electrodes have the fractal characteristics of self-similarity and discontinuity at the microscopic scale, which is an important physical condition in the fractional-order system. During the charging and discharging, the multiple heat transfer modes occur simultaneously on the porous electrodes. Due to the different heat transfer rates of various modes, the thermodynamics of batteries is essentially a discontinuous time-delay system, which cannot be ignored. A fractional-order heat transfer model (FOHTM) is proposed to analyze the time-delay effect of the lithium-ion battery module. The fractional derivative order (FDO) of the proposed model is identified. The temperature distribution of the tested battery module is simulated and the cooling system is optimized. The results indicate that the simulation accuracy of FOHTM is higher than that of the classical integer-order heat transfer model (IOHTM). The maximum error of transient temperature of FOHTM under various operating conditions is less than 1.1%. The FOHTM can approach the true temperature faster through updating the historical weighted terms. The FOHTM is a statistical analysis of non-standard thermal diffusion behavior under the action of multiple heat transfer modes, as a result of which, it is more suitable for the modeling of battery thermodynamics.

Experimental investigation on fabrication, characterization and properties of spark plasma sintered alumina-based tungsten carbide composites reinforced by carbon nanotubes

In this study, the alumina-based tungsten carbide (WC-Al2O3) composites reinforced by different weight percentages of carbon nanotubes were successfully prepared by the advanced spark plasma sintering technique. This study has the novelty that such composites with the given compositions were never sintered before using spark plasma sintering. The WC-Al2O3-CNTs composites were fabricated to design advanced tool materials with an optimum set of mechanical and thermal properties for high-temperature cutting applications. The experimental results revealed considerable growth in micro-hardness and fracture toughness in WC-Al2O3-CNTs composites as compared to WC-Al2O3 composites. The ideal set of mechanical properties was acquired by WC-Al2O3-CNTs-0.5 composite which also exhibited a minimum value of grain size. At higher concentrations of carbon nanotubes, the mechanical properties of composites tend to degrade due to the agglomeration of carbon nanotubes. The study presented better results in sintered composites than the composites fabricated through other sintering techniques. The improved strengthening and toughening results of WC-Al2O3-CNTs composites along with the fine microstructures were mainly acquired by inhibiting grain growth during sintering, improved dispersion of the constituents in the composites (electron probe microscopy analysis/wavelength dispersive spectroscopy mapping) and consolidation at shorter sintering periods in spark plasma sintering. A thermal study was also conducted to discuss the thermal stability of sintered composites at ambient as well as at higher temperatures to estimate the behavior of thermal conductivity and thermal diffusivity of composites at different temperatures.

Morphology and concentration-dependent thermal diffusivity of biofunctionalized zinc oxide nanostructures using dual-beam thermal lens technique

• Preparation of Casein based zinc oxide nanocolloids using the two-step approach. • Thermal diffusivity studies of prepared samples using dual-beam thermal lens techniques. • Tunable behavior of thermal diffusivity depending on volume fraction and morphology. Nanofluids with suitable heat transfer properties were found to be applied in thermal insulators, transport, nanodevices, medicine, etc. Their heat transfer properties are influenced by the particle size, morphology, and concentration of the nanoparticles present in the nanofluids. Nanofluids of different morphologies of zinc oxide such as nanospheres, nanoflowers, and nanorods were synthesized and their thermal properties were evaluated using a dual-beam thermal lens technique. All these nanofluids were found to exhibit tunable thermal diffusivity depending on concentration. The nanofluids with flower-like morphology show maximum deviation in diffusivity due to the layered structure and the increased surface area. As compared to pristine zinc oxide nanofluids, casein-capped zinc oxide nanofluids show excellent thermal insulation properties at 60 μg/ml. The findings suggest that biofunctionalized zinc oxide nanofluid is a promising candidate for a variety of thermal applications.

Development of Reversible Ni-Fe Metal Supported Solid Oxide Cells

Reversible Solid Oxide Cells (RSOCs) are bi-functional energy conversion devices for generating electricity and producing fuels (H2 and CO) with high efficiency and fuel flexibility. Conventional ceramic supported RSOCs have limitations in commercialization due to mechanical issue, so a metal support with thermomechanical stability has been proposed. Thermal expansion coefficient (TEC), conductivity and diffusion behavior of metal support can be simply adjusted by composition control. Herein, we maximized the electrical, chemical and contact properties of the Ni-Fe metal support by controlling the Fe2O3 contents to 10-90 wt% (10 NiFe, 50 NiFe, and 90 NiFe). 50NiFe showed high electrical conductivity and low Fe diffusion into the functional layer based on high alloy content. In addition, good contact was obtained without structural defects due to the appropriate TEC difference with the other components. 50 NiFe | Ni-YSZ | ScSZ | LSM-ScSZ single cell showed excellent performance with maximum power density of 2.4 W cm-2 in 3%H2O/H2 in fuel cell mode and a current density of 2 A cm-2 at 1.4 V in 50%H2O/H2 in electrolysis cell mode at 800oC. The electrochemical performance of the cell shows stable operation during 30 cycles electrolysis cell/fuel cell for 5 hours. The results demonstrate the potential for commercialization of long-lasting high performance and cost-efficient RSOCs in a broad range of fields.

Thermal diffusion behavior of Fe/Cu/Ni multilayer coatings: a molecular dynamics study

In this paper, the thermal diffusion behavior of Fe/Cu/Ni multilayer coatings was investigated by molecular dynamics. The results show that the Fe, Cu, and Ni elements can diffuse each other at 1250 K. Meanwhile, the intrinsic diffusion coefficients and interdiffusion coefficients of the Fe, Cu, and Ni were calculated. Besides, the diffusion mechanism for high melting-point elements of Fe and Ni at 1250 K was analyzed in the paper. According to the simulation result, the Fe and Ni lattices were disturbed by the active Cu particles. Fe and Ni particles at higher energies may move out of their original positions and migrate into the Cu lattice randomly. Thus, the Fe and Ni elements were involved in the thermal diffusion. This can be confirmed by the decrease of the peak and the disappearance of the secondary peak in the radial distribution function curves. However, the position of the curve peaks did not change. Thus, the lattice structure was still maintained during the whole diffusion process. The thermal diffusion of the three elements was carried out by particle substitution at the lattice positions. It was a solid phase diffusion process. Furthermore, there was a clear particle diffusion asymmetry at the original interface of the element. It was consistent with the diffusion asymmetry of diffusion-couple experiments. The primary reason for this diffusion asymmetry was the difference in the interaction potential of the three elements. This asymmetry was ultimately reflected in the intrinsic diffusion coefficient and the interdiffusion coefficient of each element. For the Fe–Cu–Ni ternary system, the largest diffusion coefficient was copper and the smallest was iron at 1250 K.

High Performance of Patterned Solution-Processed WZnSnO Thin Film Transistor Using Fiber-Coupler Semiconductor Laser Annealing

In this work, the fiber-coupler semiconductor laser annealing (FCSLA) is tried to process the patterned solution-processed tungsten&#x2013;zinc&#x2013;tin oxide (WZTO) as an active layer of thin-film transistor (TFT). Thermal diffusion behavior for the laser-annealed solution-processed WZTO TFT has been simulated by the COMSOL Multiphysics model, and combined with the morphologies of the films under different laser power densities, the preferred 70-W/cm² laser-annealed WZTO thin films exhibit smooth surface with a root mean square roughness of 0.307 nm and a high transmittance of 88&#x0025;. When the laser power density increases to 100 W/cm², the thermal damage of WZTO thin films occurs, and then, the preferred 70-W/cm² laser-annealed WZTO TFT exhibits the highest mobility of 7.01 cm<inline-formula> <tex-math notation="LaTeX">$^{{2}}\text{V}^{-{1}}\text{s}^{-{1}}$ </tex-math></inline-formula> and the best stability in terms of storage time for one month. In addition, the comprehensive performance of device is comparable to those of thermal annealing WZTO TFTs. The demonstration of simple and efficient FCSLA functionalization of solution-processed WZTO TFTs is developed and can be applied to high-throughput display manufacturing.

Повышение эффективности поверхностно-термического упрочнения деталей машин в условиях совмещения обрабатывающих технологий, интегрируемых на единой станочной базе

Introduction. In the manufacturing industry, there is a particular interest in the development of a new type of technological equipment, which makes it possible to implement methods for modifying the parts surface layers by processing it with concentrated energy sources. The combination of two processing technologies (mechanical and surface-thermal operations) in the conditions of integrated equipment makes it possible to neutralize the disadvantages of monotechnologies and obtain new effects that are unattainable when using technologies separately. The use of hybrid machine tools in conjunction with the developed technological recommendations will allow achieving a multiple increase in the technical and economic efficiency of production, resource and energy saving, which in turn will contribute to an increase in the competitiveness of products and the renewal of the technological paradigm. Purpose of work: increasing productivity and reducing energy consumption during surface-thermal hardening of machine parts by exposure to concentrated energy sources under conditions of integrated processing. Theory and methods: studies of the possible structural composition and layout of hybrid equipment during the integration of mechanical and surface-thermal processes are carried out taking into account the main provisions of structural synthesis and the components of metalworking systems. Theoretical studies are carried out using the basic provisions of system analysis, geometric theory of surface formation, design of metalworking machines, finite-element method, mathematical and computer simulation. Mathematical simulation of thermal fields and structural-phase transformations in the case of HEH HFC is carried out in the ANSYS and SYSWELD software packages, using numerical methods for solving the differential equations of unsteady thermal conductivity (Fourier's equation), carbon diffusion (Fick's second law), and elastoplastic behavior of the material. The verification of the simulation results is carried out by conducting field experiments using: optical and scanning microscopy; mechanical and X-ray methods for determining residual stresses. In the study, Uone JD520 and Form Talysurf Series 2 profilograph-profilometers are used to simultaneously measure shape deviations, waviness and surface roughness. Surface topography is assessed using a Zygo New View 7300 laser profilograph-profilometer. The microhardness of the hardened surface layer of parts is evaluated on a Wolpert Group 402MVD device. Results and discussion. An original method of structural-kinematic analysis for pre-design research of hybrid metalworking equipment is presented. Methodological recommendations are developed for the modernization of metal-cutting machine tools, the implementation of which will allow the implementation of high-energy heating by high-frequency currents (HEH HFC) on a standard machine-tool system and ensure the formation of high-tech technological equipment with expanded functionality. A unified integral parameter of the temperature-time effect on a structural material is proposed when the modes of hardening by concentrated heating sources are assigned, which guarantee the required set of quality indicators of the surface layer of machine parts, while ensuring energy efficiency and processing productivity in general. It is experimentally confirmed that the introduction into production of the proposed hybrid machine tool in conjunction with the developed recommendations for the purpose of the HEH HFC modes in the conditions of integral processing of a “Plunger bushing” type part in relation to the factory technology allows increasing the productivity of surface hardening by 3.5 ... 4.1 times, and reduce energy consumption by 9.5 ... 11.3 times.

Three-dimensional heat transfer analysis of flat-plate oscillating heat pipes

• Three-dimensional heat transfer model for flat-plate OHP is proposed. • Model includes both thermal hydrodynamic phenomena and thermal diffusion in casing. • The model is validated with experimental results of Aluminum flat-plate OHP. • Relation of temperature distribution in casing to liquid-vapor behavior is studied. • Novel outcome is that moving hot spots on flat-plate OHP surface are evaluated. This paper presents a three-dimensional heat transfer analysis of a flat-plate oscillating heat pipe (OHP). To enhance implementation of OHPs in various applications, it is important to understand the comprehensive phenomena that include thermal diffusion in the whole structure and thermal hydraulics in the channel. We developed an OHP model that includes the effect of thermal diffusion and thermo-fluid behavior. The model was validated with experimental results of a flat-plate aluminum OHP which has a size of 200 mm × 90 mm × 3.8 mm, a channel diameter of 1.0 mm, and a turn number of 42. The effect of surface roughness in the channel and liquid film thickness on operating temperature is investigated. The relation between thermo-fluid behavior in the channel and temperature distribution of the OHP is analyzed. For aluminum OHP, the temperature difference across the thickness direction is 0.1 °C which is relatively small, whereas, the moving hot spot: local high-temperature region, is found in the planer surface. The maximum hot spot superheat temperature reached 5.4 °C for 200 W. The novelties of this paper are to develop the three-dimensional comprehensive OHP model and to reveal the combined effect of thermo-hydraulic phenomena and thermal diffusion in OHP structure.

An Enhanced Non-Equilibrium Molecular Dynamics Algorithm to Simulate the Soret Coefficient in Heptane/Benzene Mixtures

In this work, the accuracy of the Soret effect was investigated at the situation of T = 303.15 K and P = 1.0 atm. The eHEX (enhanced heat exchange) algorithm and the TraPPE-UA force field were applied to simulate this thermal diffusion behavior. The equimolar mixtures of heptane isomers (n-heptane, 2-methylhexane, 3-methylhexane and 2, 3-dimethylpentane) and benzene were chosen to be the research fluids. The Soret coefficients were calculated to compare with the experimental data and other NEMD simulated results. The results showed great agreement with experimental data and a better accuracy compared to other NEMD simulated results. Moreover, the results shows that more branches may decrease the heat affinity of the component and increase the relaxation time of the thermal diffusion behavior.

Non-Equilibrium Molecular Dynamics Study of the Influence of Branching on the Soret Coefficient of Binary Mixtures of Heptane Isomers

Abstract Equimolar mixtures composed of isomers were firstly used to investigate the molecular branching effect on thermal diffusion behavior, which was not disturbed by factors of molecular mass and composition in this work. Eight heptane isomers, including n-heptane, 2-methylhexane, 3-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane and 3-ethylpentane, were chosen as the researched mixtures. A non-equilibrium molecular dynamics (NEMD) simulation with enhanced heat exchange (eHEX) algorithm was applied to calculate the Soret coefficient at T = 303.15 T=303.15 K and P = 1.0 atm P=1.0\hspace{0.1667em}\text{atm} . An empirical correlation based on an acentric factor was proposed and its calculation coincides with the simulated results, which showed the validity of the NEMD simulation. It is demonstrated that the isomer with higher acentric factor has a stronger thermophilic property and tends to migrate to the hot region in the heptane isomer mixture, and the extent of thermal diffusion is proportional to the difference between the acentric factors of the isomers.

Hexagonal boron nitride and alumina dual-layer coating for space solar thermal shielding

Reducing the temperature of a solar probe or an orbital spacecraft has been successful in the spectral selectivity regime by maximizing the sunlight reflection and irradiating heat to the cold universe. Despite the extensive work on the adjustment of the absorbance/emissivity ratio, few efforts have been devoted to the modulation of heat conduction. In fact, the backlit-side of the spacecraft facing the cold universe is ideal for radiative cooling, as long as the sunlight generated heat is transferred effectively to the backlit surface with minimum heating of the interior structures. Here, by using a hexagonal‑boron nitride (h-BN) and Al 2 O 3 dual-layer coating, we demonstrate a strategy for space solar thermal shielding that combines radiative cooling and anisotropic thermal conduction. The in-plane alignment of the top-layer h-BN flakes to the coating surface leads to a highly anisotropic thermal diffusion behavior, enabling rapid in-plane heat transfer and effective out-of-plane thermal insulation. The spectral selectivity optimization allows the dual-layer coating to reflect nearly 89% of solar irradiation while having an emissivity >0.86 across the thermal infrared wavelength. Moreover, the coating exhibits remarkable spectral stability under proton irradiation, showing its great potential in aerospace applications. • An h-BN/Al 2 O 3 dual-layer coating with radiative cooling and anisotropic thermal conduction functions was designed. • The coating was fabricated by a facile one-step LPES method. • The coating cools a spacecraft by conducting heat to the backlit-side and radiates it to the cold universe.

Dependence of thermal diffusivity on nanoparticle shape deduced through thermal lens technique taking ZnO nanoparticles and nanorods as inclusions in homogeneous dye solution

We are presenting our results of comparison of thermal diffusion behavior of composite media of nanoparticles and nanorods of ZnO in a homogeneous solution of fluorescein dye, done using the dual beam, pump-probe thermal lens technique. It was observed that both nanorods and nanoparticles can be used to control the thermal diffusivity of the composite fluid by changing the relative volume fractions. It was also observed that there is an optimum value for this volume fraction in the two cases considered. We have also explained this behavior using theoretical approach taking into account the Unit cell model, Brownian motion and the near field effects. We expect that this work will enhance the understanding of the influence of particle size, shape and the thermal properties of this novel composite which can widely find application in thermoelectric coolers, high performance thermal transfer liquids and in random lasing.

Thermal, Magnetic, and Magnetotransport Properties of a Rapidly Quenched Ni50Mn35Al2Sn13 Tape Sample

The heat capacity, thermal diffusivity, thermal conductivity, magnetization, and electrical resistance of the rapidly quenched Ni50Mn35Al2Sn13 alloy have been studied. Pronounced anomalies in the form of minima associated with magnetic and magnetostructural transformations have been observed on the temperature dependence of the thermal diffusivity. The behavior of thermal conductivity and thermal diffusivity indicates that the free path of heat carriers is limited by structural imperfections of the tape. The transition of the sample to the martensitic phase is accompanied by a sharp increase in electrical resistance, suggesting increasing the electron relaxation rate on structural distortions inherent in martensite. The magnitude of the magnetoresistive effect Δρ/ρ0 in a field of 1.8 T near the martensitic transition reaches 40%. A temperature hysteresis, indicating the structural heterogeneity of the austenitic phase, was detected on the dependence of ρ(T) near TC.

A Preliminary Study on Leakage Detection of Deteriorated Underground Sewer Pipes Using Aerial Thermal Imaging

Due to less visibility, underground facilities such as sewer pipelines are subjected to degradation until a major failure occurs. So, leakage detection of deteriorated underground sewer pipes is necessary to prevent expensive rehabilitation costs. The major causes of the frequent occurrence of ground subsidence and sewer leakage are excessive use of groundwater, reckless exploitation of natural resources, etc. In this study, the aerial thermal imaging (ATI) technique has been used to identify the leakage points in sewer pipelines by analyzing surface thermal diffusion behavior of the ground surface. Leakage is suspected at points of anomalous temperature variation. Then, ground-penetrating radar and closed-circuit television surveys have been carried out to strengthen the suspicion of sewer leakage. Irregular, erratic parabolic-shaped lines are observed at the points where the leakage is suspected through ATI. Finally, the test-pit excavation and simple cone penetration tests have been carried out which confirms the sewer leakage points. The leakage points are confirmed by a greater depth of penetration. The results of the cone penetration test carried out in E-21 and 23-24 sewer pipelines show that the depth of penetration at the leakage points is about 35 cm, which is greater than the depth of penetration at other points. So, it can be concluded that the aerial thermal imaging technique is an effective method to predict leakage in deteriorated underground sewer pipelines.

Effect of metallic-waste aggregates on microwave self-healing performances of asphalt mixtures

Some metallic waste, such as steel slag, has great potential for microwave heating to heal asphalt mixtures as an excellent microwave absorbing material. Prior to this study, hot braised steel slag (HBSS) was firstly selected from three kinds of metallic wastes according to the microwave heat releasing test results. Afterwards, the self-healing performance of the purpose-designed asphalt mixtures was evaluated by cyclic crack-healing tests with the semi-circular bending method. During microwave heating, the temperature distribution and thermal diffusion of asphalt mixtures were observed using an infrared camera. The spatial distribution of the HBSS inside the asphalt mixtures was analyzed using X-ray computed tomography (CT). Results indicated that the asphalt mixtures with a 60% replacement in volume by HBSS of coarse aggregate (4.75–9.5 mm) produced better healing performance after 30 s heating. The infrared images indicated thermal diffusion behavior and confirmed the temperature of mixtures can be increased by microwave. The three-dimensional reconstruction data based on X-ray CT scan demonstrated the HBSS was uniformly distributed inside the asphalt mixtures, and as such it converted the energy of microwave irradiation effectively into thermal energy.

Thermal Diffusivity Measurement of Laser-Deposited AISI H13 Tool Steel and Impact on Cooling Performance of Hot Stamping Tools

Additive manufacturing is a technology that enables the repair and coating of high-added-value parts. In applications such as hot stamping, the thermal behavior of the material is essential to ensure the proper operation of the manufactured part. Therefore, the effective thermal diffusivity of the material needs to be evaluated. In the present work, the thermal diffusivity of laser-deposited AISI H13 is measured experimentally using flash and lock-in thermography. Because of the fast cooling rate that characterizes the additive process and the associated grain refinement, the effective thermal diffusivity of the laser-deposited AISI H13 is approximately 15% lower than the reference value of the cast AISI H13. Despite the directional nature of the process, the laser-deposited material’s thermal diffusivity behavior is found to be isotropic. The paper also presents a case study that illustrates the impact of considering the effective thermal conductivity of the deposited material on the hot stamping process.

Investigation of thermal property of spark plasma sintered Ti-Zr-Ta shape memory alloys

There is increasing demand for the performance improvement of novel shape memory alloys (SMAs), such as the Ti-Zr-based systems. The effects of fabrication parameters and material compositions are critical to the thermal properties of the alloys. This study is designed to investigate the effects of ternary Ta additions on the thermal properties of spark plasma sintered (SPSed) novel Ti-Zr based SMAs for high temperature applications. The SPSed Ti-Zr/Ta specimens were characterized for their microstructural and crystallographic features using scanning electron microscopy (SEM) incorporated with Energy Dispersive X-ray Spectroscopy (EDS), and X-ray powder diffractometry (XRD). Thermal property measurements were conducted using the Laser Flash technique to obtain the thermal diffusivity behaviour, while the phase transformation properties were determined by the differential scanning calorimetry (DSC). The presence of both alpha martensite, and beta structures were revealed by the SEM/EDX and XRD respectively. High thermal diffusivity values were obtained, and they show an increasing trend with temperature. The DSC measurement revealed high reversible martensitic transformation (above 200 deg Celcius) for all the alloys, a two-stage phase transformation in the binary alloy, and a single-phase transformation event in the ternary alloys. A downward parabolic gradient of the specific heat and thermal conductivity with respect to temperature was recorded in the alloys, thus revealing an interaction between phonon-mediated and electron-mediated thermal transport processes. Two-stage phase transformations, noticed in the binary alloy indicate the reversible transformation events of alpha-Ti and alpha-Zr phases at different temperatures to-and-fro the austenite phase, whereas, in the ternary phase the single transformation event indicates the presence of only alpha-Ti phase. These results further strengthen the understanding of material atomic compositions effect on the thermal behaviour of the as-sintered alloys. The high thermal diffusivity and high martensitic transformation behaviour of the Ti-Zr/Ta alloys suggest they can be suitable candidates for high temperature applications in the aerospace technologies.