Thermal Properties Of Materials Research Articles

Investigation on the mechanical and thermal properties of metal-PLA composites fabricated by FDM

Purpose The aim of this study is to investigate the printing parameters of fused deposition modeling (FDM), a material extrusion-based method, and to examine the mechanical and thermal properties of their polylactic acid (PLA) components reinforced with copper, bronze, and carbon fiber micro particles. Design/methodology/approach Tensile test samples were created by extruding composite filament materials using FDM-based 3D printer. Taguchi method was used to design experiments where layer thickness, infill density, and nozzle temperature were the printing variables. Analysis of variance (ANOVA) was applied to determine the effect of these variables on tensile strength. Findings The results of this study showed that the reinforcement of metal particles in PLA material reduces strength and increases elongation. The highest tensile strength was obtained when the layer thickness, infill density, and nozzle temperature were set to 100 µm, 60%, and 230 °C, respectively. As a result of thermal analysis, cooper-PLA showed the highest thermal resistance among metal-based PLA samples. Originality/value It is very important to examine the mechanical and thermal quality of parts fabricated in FDM with metal-PLA composites. In the literature, the mechanical properties of metal-reinforced composite PLA parts have been examined using different factors and levels. However, the fabrication of parts using the FDM method with four different metal-added PLA materials has not been examined before. Another unique aspect of the study is that both mechanical and thermal properties of composite materials will be examined.

Combining linear and cyclic sulfones as a strategy for elaborating more efficient high-dielectric polymer materials: A second case of dipolar glass copolymers

Motivated by the excellent features exhibited by sulfone functional groups in the development of high-dielectric polymer materials, this work assesses the combination of linear and cyclic sulfone structures through copolymerization to prepare novel polymer materials exhibiting high dielectric constants (ԑr'), low dissipative behavior, and improved thermal properties. Five new polymethacrylate-based copolymers with varying compositions were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization. The correct structure and macromolecular nature of the devised materials were confirmed by infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H/13C NMR), and gel permeation chromatography (GPC), while their thermal properties were evaluated using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). All specimens exhibited adequate thermal properties for most capacitor applications in terms of onset degradation (Ti) and glass transition (Tg) temperatures. All materials degraded well above 250 °C, with increased Ti and Tg values depending on the final composition of the cyclic sulfone monomer in the material. The incorporation of cyclic sulfones not only increased the thermal robustness of the specimens but also raised their Tg values to as high as 189 °C, notably expanding the range of temperatures where these systems can operate without dissipative phenomena. More importantly, broadband dielectric spectroscopy (BDS) revealed that all samples exhibited dielectric properties notably superior to those of conventional polymer materials, with high ԑr' values between 6.0 and 8.9 (at 25 °C and 1 Hz) and low loss factors (Tan(δ) < 0.018). Overall, the present work successfully demonstrates the advantages of including cyclic structures with high dipole moments in polymeric backbones, offering a new strategy to enhance the thermal and dielectric properties of high-dielectric polymer materials.

Thermophysical properties and energy efficiency of a sustainable construction materials produced from local natural waste

Improving the energy efficiency of buildings is crucial for reducing energy demand and moderating the environmental impact due to its large energy consumption and greenhouse gas emissions. Integrating waste into construction materials can offer sustainable and cost-effective solutions for energy-efficient buildings. This study aims to develop new construction materials (plasterboards) formed by gypsum and natural wastes (5% in mass) including Posidonia-Oceanica, sawdust, sheep's wool, and cork granules to substitute filasse in conventional plasterboards. The main objective of this work is to evaluate and compare the thermal properties of the composite materials manufactured and to determine energy saving, optimal insulation thickness and environmental impact when adding the developed plasterboards in the envelope of an office building in a Mediterranean climate. An experimental study is performed to evaluate the thermo-physical properties and a numerical simulation is conducted using design builder software to discuss the energy efficiency of these materials. Results shows that the incorporation of natural waste reduces the thermal conductivity and can reduce heating and cooling needs compared to conventional plasterboard. Specially, plasterboard made with Posidonia-Oceanica fibers which exhibits a reduction of 32 % in thermal conductivity. It achieves an improvement in energy efficiency of 8 % when it is used in roof ceiling. When used as coating-panels in building walls with a thickness of 24 cm, it achieves about 17 % of energy saving. In addition, this study determines the optimum insulation thickness leading to minimize the sum of the insulation investment and the energy costs over the building's lifetime. Four values of building’s lifespan were chosen (10, 20, 30 and 50 years). Results show that for a 10-year building life, the optimum insulation thickness is 9cm, whereas for a longer building life (50 years), the optimum insulation thickness is 19cm. It saves 15.64kWh/m2 of energy required for heating and 2.09kWh/m2 needed for cooling and reduces of about 8.8tons ofCO2 emitted. The use of natural waste as fillers to prepare plasterboards showed a good effectiveness. It provides important energy saving and reduces CO2 emissions. Creating effective insulating materials using local natural waste, could be a valuable step towards establishing a sustainable development approach.

Estimation of heat source, specific heat, and thermal conductivity of insulation materials using modified conjugate gradient method

The use of insulation materials is crucial for minimizing thermal losses in various industries like automotive, building, solar, and aerospace. Plexiglass and Expanded Polystyrene (EPS) foam are popular choices due to their effective temperature regulation, lightweight nature, and cost-effectiveness. Accurate measurement of their thermal properties is vital for achieving conservation goals. While the parallel hot wire technique provides valuable insights, accurately determining heat source strength (HW) poses a challenge, impacting measurement accuracy. To address this, the modified Conjugate Gradient Method (CGM) is employed for simultaneous estimation of thermal conductivity (λ), specific heat (c) and HW of Plexiglass and EPS foam. The direct problem result has been validated with published experimental work that shows deviations less than 2 %. The study investigates the impact of sensor positioning relative to the hot-wire (rm) and introduces artificial Gaussian error with standard deviations (θ) of 0.01 °C, 0.02 °C and 0.1 °C. At θ = 0.1 °C the percentage relative errors in the estimation of λ, c and HW with rm = 5 mm for Plexiglass are 5 %, 1.442 %, and 4.651 % respectively. For EPS foam the corresponding errors are 2.44 %, 1.26 %, and 1.74 %. The modified CGM emerges as a reliable algorithm for the measurement of thermal properties of insulation materials.

Measurement of thermal contact resistance and the design of thermal contacts at cryogenic temperatures

The prevalence of technologies that operate at cryogenic temperatures requires that the cooling systems used to maintain these systems be carefully designed. This research focuses on understanding the thermal performance of the heat path between the heat source (the technology being cooled) and the cooling source (the cryocooler). Specifically, this work characterizes through measurement the thermal properties of common heat path materials, with a focus on bulk thermal conductivity and thermal contact resistance of pressed contacts. A framework for using these measurements to optimize a bolted contact is proposed and demonstrated.

Thermal performance of shaded roofs: investigating the impact of material properties and efficacy of building performance simulation

This research investigates the thermal performance of shaded roofs in the composite climate of Roorkee, India, by examining four shading materials (three opaque, one translucent) over an unobstructed roof for eight consecutive days. Using ‘Designbuilder’ software simulations and a mathematical model, the study meticulously triangulates experimental, simulated, and modelled data. The hourly temperature profile of the roof under different shades is analysed and the results showed negligible differences among opaque shading materials, while the translucent material significantly altered the roof’s thermal performance due to solar transmittance. Opaque shades reduced peak heat gain through the roof by up to 77% and 71.5% on cloudy and sunny days, respectively, and reduced nighttime heat loss by 40% and 33%, respectively. This research underscores the importance of considering shading material properties in sustainable building design and confirms the reliability of simulation tools. Highlights The study finds that in parasol roofs, the shading material's thermal properties do not impact the roof's thermal performance, but the solar transmittance does. The study also found that opaque shading could reduce the hourly peak heat gain through the roof by up to 77% and 71.5% on a cloudy day and sunny day, respectively, and reduced the nighttime hourly peak heat loss from the roof by up to 40% and 33%, respectively. Despite considering shading elements in BPS tools to be thermally inactive, the tools perform valid energy simulations.

Navigating the frontier: Additive Manufacturing’s role in synthesizing piezoelectric materials for flexible electronics

Additive manufacturing (AM) has significantly transformed the fabrication of functional materials, particularly in electronics and biomedical engineering. This study reviews stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), direct ink writing (DIW), and inkjet printing for flexible electronic applications. The review highlights SLA-based 3D printing’s better ability to optimize material compositions, printing procedures, and post-processing methods to improve material characteristics. Photosensitive materials and shrinkage-induced internal tensions seems to be its major constraint. Additionally, SLS 3D printing has improved composite materials' electrical, mechanical, and thermal properties. It has drawbacks including permeable structures and internal tensions. In FDM 3D printing, mechanical and electrical qualities are improved for piezoelectric sensor manufacture. Warping and nozzle blockage require additional study. DIW’s versatility in constructing complicated structures with increased features for energy harvesting and sensor development is also mentioned. We identify ink development and printer nozzle clogging issues. The review concludes that inkjet printing can provide a variety of materials for flexible electronics. Since it integrates the latest discoveries with technological developments, this study may help guide future research and promote innovation in the sector. Overall, additive manufacturing methods provide a new era of sensor technology by offering unrivalled flexibility and versatility.

Thermal Material Property Evaluation Using through Transmission Thermography: A Systematic Review of the Current State-of-the-Art

Determining thermal material properties such as thermal diffusivity can provide valuable insights into a material’s thermal characteristics. A well-established method for this purpose is flash thermography using Parker’s half-rise equation. It assumes one-dimensional heat transfer for thermal diffusivity estimation through the thickness of the material. However, research evidence suggests that the technique has not developed as much as the reflection mode over the last decade. This systematic review explores the current state-of-the-art in through-transmission thermography. The methodology adopted for this review is the SALSA framework that seeks to Search, Appraise, Synthesise, and Analyse a selected list of papers. It covers the fundamental physics behind the technique, the advantages/limitations it has, and the current state-of-the-art. Additionally, based on the Population, Intervention, Comparison, Outcome, and Context (PICOC) framework, a specific set of inclusion and exclusion criteria was determined. This resulted in a final list of 81 journal/conference papers selected for this study. These papers were analysed both quantitatively and quantitatively to identify and address the current knowledge gap hindering the further development of through-transmission thermography. The findings from the review outline the current knowledge gap in through-transmission thermography and the challenges hindering the development of the technique, such as depth quantification in pulsed thermography and the lack of a standardised procedure for conducting measurements in the transmission mode. Overcoming some of these obstacles can pave the way for further development of this method to aid in material characterisation.

A new type of high thermal shock resistance tool for inhibiting thermal crack

Due to the periodic alternation of hot and cold in the cutting process, cutting tools often fail owing to thermal cracks, making it difficult to intermittently cutting materials. Therefore, in order to suppress the initiation of thermal cracks in cutting tools, a new type of high thermal shock resistance oblique gradient cutting tool (marked as TDZ-X) has been fabricated. The material system of the cutting tool is designed by the temperature field model of the cutting tool. The direction angle of TDZ-X is accurately designed based on the thermal crack initiation area of the tool. A new method for studying the thermal fatigue properties of tool materials is proposed, the tool is heated by ultra-fast picosecond laser to simulate the thermal shock in the milling process. The thermal fatigue resistance and the thermal shock resistance of TDZ-X, the gradient tool and the homogeneous tool are compared and studied, the results show those of TDZ-X are best than those of the other two tool materials. Through the design of TDZ-X, the thermal shock resistance of the tool material has been significantly improved, and the effectiveness of inhibiting thermal crack initiation has been verified by cutting experiments, which provides a new method for design and fabrication of discontinuous cutting tools with long tool life and high reliability.

Assessment of the thermal and mechanical properties of bio-based materials for thermal insulation: A review

Assessment of the thermal and mechanical properties of bio-based materials for thermal insulation: A review

Micro-encapsulated phase change material suspensions for heat and mass transfer: A thermo-physical characterization

Despite the growing popularity of phase change materials (PCM) and suspensions of micro-encapsulated phase change materials (mPCM) in both industrial and scientific applications, their properties characterization remains partial and mainly limited to thermal properties. The characterization of such suspension is a crucial aspect for comprehending their behavior and optimizing their performance. This paper is dedicated to a wide characterization of two suspensions containing micro-encapsulated phase change material. In pursuit of a thorough understanding, we also extend our characterization efforts to the bulk PCM encapsulated within the particles.Our primary focus is on determining the materials thermal properties such as latent heat and specific heat capacity using differential scanning calorimetry. Different cooling and heating rates have been employed in our measurements. Regarding our experiments, the bulk phase change material is predominantly identified as octadecane. Results obtained from calorimetry are then compared between the bulk PCM and the mPCM suspensions. By comparing the magnitudes of latent heat obtained for suspensions with the bulk material, we can accurately determine the mass fraction of PCM within each suspension. Noteworthy, during the solidification process an additional latent heat peak is observed only for the encapsulated PCM.The density of the materials is also measured. The phase change of PCM included in the capsules can be observed in densimetry: within the studied temperature range (283.15–306.15 K), the most significant density variations occur during intervals associated with phase change transitions. In ranges where the PCM, included in the capsules, is in a single-phase state (solid/liquid), we provide linear laws that account for density variations with temperature.Finally, our characterization work focuses on the rheological properties of the materials. While the bulk PCM in liquid phase exhibits a Newtonian viscosity, mPCM suspensions present a non-Newtonian viscosity. Both shear-thinning and shear-thickening behaviors are observed depending on the suspension particle volume fraction ϕ of mPCM. This paper concludes with a full comparison of our characterization results with models and correlations proposed in the literature.

Size-dependent vibration analysis of porous 3D-FG microshells in complex thermal environments using a neural network enhanced finite element model

This work aims to investigate the vibration behavior of porous three-directional functionally graded (3D-FG) microshells in thermal environments, where both mechanical and thermal material properties vary along three spatial directions following a power-law distribution, based on the modified couple stress theory (MCST). An isoparametric thermal element is employed for uncoupled heat conduction analysis, followed by dynamic analysis using a penalty solid element with three translation degrees of freedom (DOFs) and three rotation DOFs per node. However, due to the strong nonlinearity of the temperature field in 3D-FG microshells, obtaining exact temperature values at integration points in dynamic analysis requires a pretty dense mesh of the solid element. To overcome this issue, a back propagation (BP) neural network is utilized to predict the temperature field for various gradient indexes, enhancing the efficiency and precision of temperature distribution calculation. Numerical results demonstrate the effectiveness of the neural network enhanced finite element model. Furthermore, the effects of the material length scale parameter (MLSP), temperature difference, and gradient indexes on the natural frequencies are investigated. It is shown that higher structural stiffness weakens the impact of temperature difference on the frequency.

BIM/BES INTEROPERABILITY: A CASE STUDY BETWEEN REVIT®, DESIGNBUILDER®, IES-VE®, AND E-QUEST®

Objective: This study proposes a BIM/BES interoperability test through a case study involving Revit® and three BES software programs: DesignBuilder®, IES-VE®, and e-Quest®. Theoretical Framework: For thermo-energy analyses, a recognized combination is the BIM (Building Information Modeling) / BES (Building Energy Simulation) pair. This requires data transfer from one software to another. To export the virtual model, it is necessary to generate the energy analytical model in BIM and use transfer protocols for BES software. Various studies have indicated failures in this process. Method: A case study was used to analyze the interoperability between the software programs, through a 58m² single-family residence. The geometric model was created with its dimensions and layers, input data such as location, thermal properties of materials, and usage data, generating the energy analytical model and exporting it to each BES software. Interoperability was tested based on data transfer analysis, establishing seven criteria. Results and Discussion: The results indicated failures in interoperability, as none of the software programs exported all the criteria correctly. The BES software with the best results was IES-VE®, with 70.90% of the criteria exported, followed by e-Quest® (65.45%) and DesignBuilder® (45.45%). Research Implications: The results of this study demonstrate that interoperability challenges limit the potential of the BIM/BES pair. Originality/Value: Despite studies on this topic, interoperability challenges remain, representing a gap to be filled.

Divertor heat load estimates on NSTX and DIII-D using new and open-source 2D inversion analysis code

A thermography inversion algorithm has been developed in the open-source Python-based computer code, HYPERION, to calculate the heat flux incident on plasma-facing components (PFCs) in axisymmetric tokamaks. The chosen mesh size at the surface significantly affects the calculated transient heat flux results. The calculated transient heat flux will exceed the real value when the mesh size tends to zero but will underestimate the real value when the mesh size is large. A criterion for determining the appropriate mesh size for the transient heat flux calculation will be discussed. The numerical scheme for HYPERION uses a 2D fully implicit finite-difference approach, allowing temperature-dependent thermal properties of PFC materials. The inversion algorithm is benchmarked against established heat flux calculation codes, TACO and THEODOR, based on thermography data from NSTX and DIII-D respectively. The primary benefits of HYPERION compared to TACO and THEODOR are that it is open-source and it allows for the optimization of mesh thickness along the substrate. The algorithm also accounts for the thermal properties of thin surface layers that characteristically form on PFCs due to plasma-material interactions. The agreement between HYPERION and THEODOR is excellent, as the percent difference between the codes is ∼5% on average in the case of the DIII-D data for moderate to high heat flux. Verification tests with TACO show slightly higher average percent differences of 8% and 12%. In using HYPERION to study filaments in heat flux, the initial results indicate that small ELMs filaments significantly broaden the divertor heat flux, and decrease divertor peak flux. Compared to the inter-ELM, the small ELM filaments decrease the divertor peak surface temperature. With intermittent divertor filaments, the divertor heat flux width is comparable with that found in L-mode.

Effect of functionalization on adsorption and thermal property of graphene nanosheet/paraffin composite

Functionalization of graphene nanosheet (GNS) is found to be useful for improving the thermal property of materials. However, the mechanism responsible for the enhancement is still open. In this article, molecular dynamic simulation is adopted to investigate the effects of four functionalized groups, including -COOH, -NH2, -OH, and -CH3, on the adsorption and thermal properties of GNS/paraffin (PA) composites. The results show that it forms a spherical structure after GNS absorbs in PA. The loading rate of the systems follows the order: GNS-COOH/PA > GNS-NH2/PA > GNS-OH/PA > GNS-CH3/PA > GNS/PA, which is determined by the adsorption free energy. Due to the functionalization, the latent heats of the composites undergo a significant change and the thermal conductivities are significantly enhanced. GNS-OH/PA exhibits the most substantial improvement with the latent heat increasing by 11.2% and the thermal conductivity increasing by 107.4% compared to GNS/PA. The study demonstrates the potential of these composites for energy storage applications, highlighting the improved performance through functionalization.

3D Printing Elastocaloric TiNiCu Thermoelectric Shape Memory Alloys.

The development of new thermoelectric conversion and cooling materials is an important means of addressing global climate and heat emissions in the future. While heavy and toxic elements like tellurium and lead are traditionally used to make thermoelectric materials with poor mechanical properties, recent decades have seen a gradual push towards greener and more sustainable alternatives. One such potential alternative material for thermoelectric and thermal management applications would be the Nitinol (TiNi) shape memory alloy, due to their superior mechanical properties. In this study, we have investigated the use of 3D melt printing techniques that can be used to achieve thermoelectric performance and efficiency of elastic memory alloys below 500 °C. The electrical and thermal properties of TiNiCu materials and their relation to morphology were investigated. All the alloys show similar effect sizes, their fatigue behavior is however different. By adjusting the composition of Ti and Ni elements and we have obtained memory alloys with high thermoelectric properties, with a 50% increase in power factor and a 100% increase in ZT values.

Thermal Spreading Resistance of Near Surface Localized Heating-Induced Size Effects in Semiconductors

Abstract Localized heating is encountered in various scenarios, including the operation of transistors, light-emitting diodes, and some thermal spectroscopy techniques. When localized heating occurs on a scale comparable to the mean free path of the dominant energy carriers, additional thermal resistance is observed due to ballistic effects. The main objective of this study is to find a relation between this resistance, problem geometry, and material thermal properties in situations involving localized heating. Models based on the solution of the Fourier heat diffusion equation and the gray phonon Boltzmann Transport Equation are solved simultaneously to calculate the additional thermal resistances that arise from localized heating. Subsequently, the results are analyzed to derive the desired relationship. It is noted that in the context of localized heating resistance, the effects of geometrical variables are non-linear and substantial, particularly when the Knudsen numbers for the boundary and heat source exceed certain thresholds. Specifically, when the Knudsen number for the heat source becomes comparable to 1 localized heating resistance is observed. However, when the Knudsen number based on heat source height and width surpasses 8 and 20, respectively the heat source behaves akin to a point source, no longer significantly affecting the localized heating resistance. At this juncture, the maximum resistance limit is reached.

Investigating thermal properties of 2D non-layered material using a NEMS-based 2-DOF approach towards ultrahigh-performance bolometer

Abstract Two-dimensional (2D) non-layered materials in many aspects differ from their layered counterparts, and the exploration of their physical properties has produced many intriguing findings. However, due to challenges in applying existing experimental techniques to such nanoscale samples, their thermal properties have remained largely uncharacterized, hindering further exploration and device applications using this promising material system. Here, we demonstrate an experimental study of thermal conduction in β-In2S3, a typical non-layered 2D material, using a resonant nanoelectromechanical systems (NEMS) platform. We devise a new two-degrees-of-freedom technique, more responsive and sensitive than Raman spectroscopy, to simultaneously determine both the thermal conductivity to be 3.7 Wm−1K−1 and its interfacial thermal conductance with SiO2 as 6.4 MWm−2K−1. Leveraging such unique thermal properties, we further demonstrate a record-high power-to-frequency responsivity of −447 ppm/μW in β-In2S3 NEMS sensors, the best among drumhead NEMS-based bolometers. Our findings offer an effective approach for studying thermal properties and exploring potential thermal applications of 2D non-layered materials.

Preparation, electronic structure and thermal properties of Zn-doped LaMgAl11O19 materials

LaMgAl11O19 (LMA) with magnetoplumbite structure is a promising thermal barrier material due to its excellent thermal properties. In this work, Zn-doped LMA materials were studied in order to improve the thermal performance, and LaZnxMg1-xAl11O19 (x = 0, 0.1, 0.3, 0.5, 0.7, 1.0) were prepared by sol-gel method. The as-synthesized powder materials possess pure LMA phase and show the morphology of hexagonal plates. X-ray photoelectron spectroscopy result shows that there are AlO4 tetrahedra and AlO6 octahedra units in the target materials, and Zn2+ ions replace Mg2+ ions to occupy the tetrahedral position of magnetoplumbite structure. The composition LaZn0.3Mg0.7Al11O19 material exhibits the lowest thermal conductivity of 0.38 W/(m·K) at 1000oC while maintaining a high coefficient of thermal expansion (10.86 × 10−6 K−1). Therefore, the thermal properties of LMA materials can be improved by adding an appropriate amount of Zn ions.

Graphene nanoribbon hydrogel scaffold for highly conductive and robust polyimide nanocomposite

Although highly loaded graphitic nanocarbon materials effectively enhance the electrical, mechanical, and thermal properties of polymeric materials, their practical implementation has been hindered by severe aggregation issues. Here, we propose a method to achieve homogeneous nanocarbon-polyimide (PI) composites by integrating graphene oxide nanoribbons (GONRs) with polyamic acid ammonium (PAA) salt, a precursor of PI. Self-assembled scaffold structure of GONRs hydrogel enables the uniform integration and immobilization of PAA within the GONR scaffold, mitigating aggregation concerns. The resulting GONR/PAA hydrogel, formed through physical interactions, can be coated onto substrates via a shear stress-induced bar coating method due to its viscoelastic rheological properties. Subsequent heat treatment at 400 °C triggers the imidization reaction of PAA and the reduction of GONR, facilitating the formation of uniformly integrated GNR/PI nanocomposite coatings. Under optimized conditions, incorporating a high-loading GONR content in PAA (95 wt% of GONR and 5 wt% of PAA) yielded GNR/PI composites with excellent mechanical properties, exhibiting a hardness of 0.75 GPa and an elastic modulus of 8.3 GPa. Additionally, this GNR/PI composite displayed a good electrical conductivity of 3890 S/m, attributed to the electrical pathways formed by GNRs within the PI matrix.