Thermal Properties Of Materials Research Articles

Utilizing bio-based and industrial waste aggregates to improve mechanical properties and thermal insulation in lightweight foamed macro polypropylene fibre-reinforced concrete

This research intends to examine the potential of incorporating waste materials in place of coarse aggregates to augment the mechanical characteristics and thermal insulation of lightweight foamed concrete (LWFC), along with the inclusion of polypropylene (PP) fibres. The PP fibre exhibits excellent tensile strength and enhancement on thermal insulation properties of cementitious materials. In this study, eco-friendly bio-based oil palm shell (OPS) and robust solid polyurethane (SPU) aggregates derived from industrial waste were utilized as substitutes for conventional aggregates. Additionally, silica fume was partially incorporated as supplementary cementitious materials. The addition of PP fibre impacted the workability of the LWFC with the inverted slump value decreased by 1.7 %–17.5 %. The inclusion of PP fibre proportion increased from 0 % to 0.5 % revealed a positive result in mechanical properties and thermal insulation performance. The OPSSPU/0.5 showed the significantly increment of 40.4 % compressive strength, 102.9 % of splitting tensile strength, and 70.8 % flexural strength, respectively. The optimum result was obtained in the OPSSPU/0.5 mixture, which exhibited 3.74 MPa residual compressive strength. Furthermore, utilizing PP fibres brought about a significant reduction in thermal conductivity in the environmentally sustainable LWFC, leading to improvements ranging from 0.2 % to 16.3 % when compared to the control composition. Thus, these findings are essential for encouraging the adoption of such practices in the construction industry and contributing to the reduction of environmental impacts associated with sustainable concrete production.

Exploiting Waste towards More Sustainable Flame-Retardant Solutions for Polymers: A Review.

The development of sustainable flame retardants is gaining momentum due to their enhanced safety attributes and environmental compatibility. One effective strategy is to use waste materials as a primary source of chemical components, which can help mitigate environmental issues associated with traditional flame retardants. This paper reviews recent research in flame retardancy for waste flame retardants, categorizing them based on waste types like industrial, food, and plant waste. The paper focuses on recent advancements in this area, focusing on their impact on the thermal stability, flame retardancy, smoke suppression, and mechanical properties of polymeric materials. The study also provides a summary of functionalization methodologies used and key factors involved in modifying polymer systems. Finally, their major challenges and prospects for the future are identified.

Temperature-dependent thermal buckling and free vibration behavior of smart sandwich nanoplates with auxetic core and magneto-electro-elastic face layers

This article addresses the thermomechanical thermal buckling and free vibration response of a novel smart sandwich nanoplate based on a sinusoidal higher-order shear deformation theory (SHSDT) with a stretching effect. In the proposed sandwich nanoplate, an auxetic core layer with a negative Poisson’s ratio made of Ti-6Al-4V is sandwiched between Ti-6Al-4V rim layers and magneto-electro-elastic (MEE) face layers. The MEE face layers are homogenous volumetric mixtures of cobalt ferrite (CoFe2O4) and barium titanate (BaTiO3). The mechanical and thermal material properties of the auxetic core and MEE face layers are temperature-dependent. Using Hamilton’s principle, governing equations are constructed. To characterize the size-dependent behavior of the nanoplate, governing equations are adapted with the nonlocal strain gradient theory (NSGT). By applying the principles of Navier’s technique, closed-form solutions are obtained. Parametric simulations are carried out to examine the effects of auxetic core parameters, temperature-dependent material properties, nonlocal parameters, electric, magnetic, and thermal loads on the free vibration and thermal buckling behavior of the nanoplate. According to the simulation results, it is determined that the auxetic core parameters, temperature-dependent material properties, and nonlocal factors significantly affect the thermomechanical behavior of the nanoplate. The outcomes of this investigation are expected to contribute to the advancement of smart nano-electromechanical systems, transducers, and nanosensors characterized by lightweight, exceptional structural integrity and temperature sensitivity. Also, the auxetic core with a negative Poisson’s ratio provides a metamaterial feature, and thanks to this feature, the proposed model has the potential to be used as an invisibility technology in sonar and radar-hiding applications.

High throughput screening of thermal interface materials by machine learning

Till now, it remains a challenge for effective prediction and screening of novel materials with high thermal conductivity, as well as further optimization of the interface thermal resistance. Normally, people have to spend long time on tedious calculations when predicting and screening these materials. In this paper, I combined machine learning with molecular dynamics simulations to investigate the thermal conductive properties of materials with the aim of significantly reducing computational consumption. I first applied molecular dynamics simulations to obtain the relevant properties of materials, then generated models for predicting physical properties by machine learning, and finally made predictions of thermophysical properties of materials. The use of machine learning significantly reduces the prediction time compared to direct molecular dynamics simulations. Especially when the XGBoost and the neural network models are employed, the prediction efficiency is significantly improved. This work guides a new way for the future screening of high-performance thermal interface materials.

Micro-CT image-based computation of effective thermal and mechanical properties of fibrous porous materials

Fibrous porous materials are extensively employed as heat shielding material for space vehicles and capsules. To predict the performance of these materials using computational modeling at the vehicle/capsule scale, the effective material properties are needed. In this work, the effective thermal conductivity and elastic constants of a carbon fibrous porous material called FiberForm (precursor of PICA) were calculated using a direct image-based approach. In this image-based approach, the microstructures obtained using X-ray computed tomography technique are represented as binary voxel data. Nonlocal interactions are introduced between neighboring voxels. Integro-differential equations, with respect to spatial and temporal dimensions respectively, are developed to govern material thermal and mechanical behaviors. Using this approach, energy-based computational procedures were developed to calculate the effective material properties of fibrous and porous materials irrespective of the periodicity of underlying microstructures. The size of representative volume element was determined by convergence of effective properties with respect to microstructure size.

Thermal insulation performance of non-load-bearing light gauge slotted steel stud walls

Light gauge steel stud walls have been widely used in buildings as load-bearing members. But if used as non-load-bearing walls, more rows of perforations can be placed on stud webs and then the thermal bridge effect can be reduced. Experiments on six non-load-bearing light gauge slotted steel stud walls were conducted using a calibrated hot box. The temperatures of the steel studs and gypsum plasterboard were monitored for subsequent analysis of thermal bridging. The effects of parameters (number of rows of perforations, stud web height, and the ratio of window area to wall area) on the insulating capacity of the wall were identified and analyzed. Thermal transmittance decreases by 18.5% and 29.6% for specimens with 3 and 7 rows of perforations in comparison with the specimen without perforations, while it decreases by 29.8% and 42.7% respectively for 150 mm and 200 mm thick walls compared with that of the 100 mm thick wall. However, thermal transmittance increases obviously for the wall with a window opening relative to the wall without a window opening, reaching 14.7% in this test since more studs are placed around the window opening. A three-dimensional finite element (FE) model of the wall was developed and validated against experimental results, and then was used for parametric studies. A general method of calculating the thermal transmittance of the light gauge slotted steel stud wall was suggested based on the experiment and the FE model results, which can consider influences of wall thickness, web perforations, window openings, and thermal properties of materials.

Experimental setup for thermal measurements at the nanoscale using a SThM probe with niobium nitride thermometer.

Scanning Thermal Microscopy (SThM) has become an important measurement technique for characterizing the thermal properties of materials at the nanometer scale. This technique requires a SThM probe that combines an Atomic Force Microscopy (AFM) probe and a very sensitive resistive thermometer; the thermometer being located at the apex of the probe tip allows for the mapping of temperature or thermal properties of nanostructured materials with very high spatial resolution. The high interest of the SThM technique in the field of thermal nanoscience currently suffers from a low temperature sensitivity despite its high spatial resolution. To address this challenge, we developed a high vacuum-based AFM system hosting a highly sensitive niobium nitride (NbN) SThM probe to demonstrate its unique performance. As a proof of concept, we utilized this custom-built system to carry out thermal measurements using the 3ω method. By measuring the V3ω voltage on the NbN resistive thermometer under vacuum conditions, we were able to determine the SThM probe's thermal conductance and thermal time constant. The performance of the probe is demonstrated by performing thermal measurements in-contact with a sapphire sample.

1D modelling of a latent heat thermal energy storage prototype using boiling water as heat transfer fluid

This paper presents a numerical model to simulate the thermohydraulic behaviour of a shell-and-tubes Latent Heat Thermal Energy Storage (LHTES) during discharging period, involving a boiling heat transfer fluid (HTF). It is based on a 1D homogeneous approach for the HTF (water) and a 1.5D approach for the phase-change material (sodium nitrate) allowing calculation times significantly shorter than those of CFD. This approach has been validated with experimental data in a previous study for a LHTES with a monophasic HTF. The two highlights of this paper are as follows: On the one hand, computational fluid dynamics has been used to develop equivalent homogeneous materials for PCM side, integrating the thermal properties of the phase-change material and the helical and longitudinal fins present in the LHTES. On the other hand, the model uses the asymptotic correlation of Steiner and Taborek to describe boiling heat transfers and usual correlations for single phase heat transfers. The paper focuses on the validation of the model against experimental data from the InPower project. The prototype is a 340 kWh storage that has been tested under different conditions. The model reproduces the total energy retrieved during a system discharge with relative error of 8.5% and an absolute mean error of 8.23 kW on outlet power. The main weakness of the model is the homogeneous model for the HTF that generates error in water level and local temperatures.

Cryogenic Deep Drawing Tool Design for Reduced Heat Transfer

Subject of this study is the usage of macro-structured tools for deep drawing of aluminum alloys at cryogenic temperatures in order to increase the drawing depth. The advantage of the macro-structure is the reduced contact area, which primarily leads to a reduction in frictional forces in the flange area and also minimizes the heat transfer from the tool to the cooled sheet metal. In addition to the geometry of the tools, the heat transfer is also influenced by the thermal properties of the tool materials. Therefore, the tool must be designed to reduce heat flux and thermal diffusivity. In this regard, substitute materials for the tools, specifically polymer, and steel-shielded polymer, were investigated. In this context, the heat transfer coefficients between the tool material and the aluminum blank are determined experimentally. The influence of thermal conditions on the cryogenic deep drawing process are investigated numerically and experimentally. The result of the study is an improved process understanding to ensure the blank temperature in a cryogenic range and increase the resistance against bottom cracks.

In situ synthesis of tin oxide nanoparticles on cotton fabrics-physicochemical and photocatalytic properties

Different concentrations of Tin Oxide nanoparticles have been successfully synthesized by the sol-gel method using Tin Chloride and Sodium Hydroxide precursors. Cotton fabrics were impregnated by the synthesized tin oxide (SnO2) nanoparticles and the physicochemical properties of the treated fabrics were investigated. The crystalline structure and their size were studied by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), and field emission scanning electron microscopy (FESEM). Elemental analysis, photocatalytic properties, and thermal properties of fabrics were investigated by energy dispersion X-ray spectroscopy (EDX), absorption spectrophotometry, and determination of residual ash content, respectively. Fabric hydrophilic properties have also been studied. The thermal properties of the impregnated fabrics have been improved compared to the raw material. The results show that, the pH of the medium play very important role in synthesizing Tin Oxide nanoparticles.

The influence of natural wind patterns on the thermal and humidity comfort of the “one seal” building in Yunnan, China

ABSTRACT The thermal and humidity environments of buildings under the influence of the Heating, Ventilation and Air Conditioning (HVAC) systems constitute a mature topic in the field of architecture, but there are few studies on the thermal and humidity environments of traditional rural buildings under natural wind conditions. In this paper, a traditional one-seal residential building in Kunming, Yunnan Province, was adopted as the research object. By arranging monitoring instruments, we collected thermal and humidity environment and natural wind data of the building under three weather conditions: cloudy, sunny and rainy days. The results showed that climate change can alter the thermal and humidity stability levels of the building, and there are differences in thermal and humidity stability among the different spatial structures inside the building. Natural wind plays a significant role in reducing the humidity of the environment and building surfaces, and the thermal and humidity properties of the building materials play an important role in maintaining the thermal and humidity stability levels of the building. The results of this study provide a basis for obtaining a greater understanding of heat and humidity comfort levels in naturally ventilated areas and thermal and humidity environments of traditional buildings at the later stage.

Nonlinearity effects on thermal transport properties of a mass-spring chain

Using Green’s function technique, we present a self-consistent formalism to study the phonon transport properties of an extended nonlinear mass-spring chain. We calculate the phonon transmission coefficient, thermal conductivity, and specific heat for some chains with different configurations of masses feeling the nonlinearity potential. The numerical results show that in a critical value of the nonlinearity coefficient, a sharp decrease in thermal conductivity will be observed. The same scenario happens in a critical temperature proportional to the inverse of the nonlinearity coefficient for the specific heat. Indeed, thermal conductor-insulator transition can occur in the system depending on the strength and distribution of nonlinearity. The model can aid our understanding of the effect of lattice nonlinearity on the thermal properties of one-dimensional materials to design the thermal switches.

Multimodal learning of heat capacity based on transformers and crystallography pretraining

Thermal properties of materials are essential to many applications of thermal electronic devices. Density functional theory (DFT) has shown capability in obtaining an accurate calculation. However, the expensive computational cost limits the application of the DFT method for high-throughput screening of materials. Recently, machine learning models, especially graph neural networks (GNNs), have demonstrated high accuracy in many material properties’ prediction, such as bandgap and formation energy, but fail to accurately predict heat capacity(CV) due to the limitation in capturing crystallographic features. In our study, we have implemented the material informatics transformer (MatInFormer) framework, which has been pretrained on lattice reconstruction tasks. This approach has shown proficiency in capturing essential crystallographic features. By concatenating these features with human-designed descriptors, we achieved a mean absolute error of 4.893 and 4.505 J/(mol K) in our predictions. Our findings underscore the efficacy of the MatInFormer framework in leveraging crystallography, augmented with additional information processing capabilities.

Suppressed Lone Pair Electrons Explain Unconventional Rise of Lattice Thermal Conductivity in Defective Crystalline Solids.

Manipulating thermal properties of materials can be interpreted as the control of how vibrations of atoms (known as phonons) scatter in a crystal lattice. Compared to a perfect crystal, crystalline solids with defects are expected to have shorter phonon mean free paths caused by point defect scattering, leading to lower lattice thermal conductivities than those without defects. While this is true in many cases, alloying can increase the phonon mean free path in the Cd-doped AgSnSbSe3 system to increase the lattice thermal conductivity from 0.65 to 1.05Wm-1K-1 by replacing 18% of the Sb sites with Cd. It is found that the presence of lone pair electrons leads to the off-centering of cations from the centrosymmetric position of a cubic lattice. X-ray pair distribution function analysis reveals that this structural distortion is relieved when the electronic configuration of the dopant element cannot produce lone pair electrons. Furthermore, a decrease in the Grüneisen parameter with doping is experimentally confirmed, establishing a relationship between the stereochemical activity of lone pair electrons and the lattice anharmonicity. The observed "harmonic" behavior with doping suggests that lone pair electrons must be preserved to effectively suppress phonon transport in these systems.

On optimizing the experimental setup for estimation of the thermal conductivity of thin films

The aim of this study is to show the optimal arrangement of a measurement system for estimating the thermal conductivity of thin films from temperature profiles. For this purpose, two different experimental setup systems, with square and circular cross sections, were designed to estimate the thermal conductivity of thin films and, in particular, of two ion exchange membranes. Both systems were placed horizontally and vertically in order to evaluate the best orientation to more accurately determine thermal conductivity. A three-dimensional numerical simulation was performed using Comsol Multiphysics to predict the heat flow and temperature gradient and to evaluate the effect of the geometry and the orientation on the contact resistances. Each system was first calibrated without the membrane inside in order to estimate all the necessary thermal properties of the different materials of the model. Next, the membrane was placed inside the model, so that the model now includes the thermal conductivity of the membrane as the only unknown parameter. The numerical results were compared with the various measured temperature profiles to estimate the thermal conductivity. The thermal conductivity values of the well-known Nafion 117 membrane and other thicker membrane were determined. A very good agreement with reliable literature values was obtained. The approach presented here, combining experimental and simulated temperature profiles, may provide the basis for a practical alternative to better estimate the thermal conductivity of thin films.

Nanomaterials for advanced energy applications: Recent advancements and future trends

Nowadays, one of the most promising and significant challenges for our society is achieving highly efficient energy utilization. To address the upcoming demands in energy applications, which demonstrate considerable potential for future trends, continuous efforts are necessary to develop improved and higher-performing inorganic multifunctional nanomaterials. Multifunctional inorganic nanomaterials have been extensively researched to meet the requirements of various energy applications or to enhance them further. Specific attention is given to inorganic nanomaterials for advanced energy storage, conservation, transmission, and conversion applications, which strongly rely on the optical, mechanical, thermal, catalytic, and electrical properties of energy materials. At the nanometer-scale range, triboelectric, piezoelectric, thermoelectric, electrochromic, and photovoltaic materials have made significant contributions to numerous energy sector applications. Functional inorganic materials possess unique properties, including excellent thermal and electrical conductivity, chemical stability, and a large surface area, which enhance their competitiveness in energy-related applications. Herein, recent research, development, and advances in inorganic multifunctional nanomaterials to enhance their performance are discussed, highlighting how devices combine the functionalities of nanomaterials. In this manner, we aim to provide insights into future applications and elucidate the ongoing research challenges currently facing this field.

Mechanical properties of lightweight 3D-printed structures made with carbon-filled nylon

Material extrusion additive manufacturing is a widely used 3D-printing process involving depositing molten thermoplastic materials layer by layer to create a 3D object. Combining material extrusion with composites creates strong, lightweight, and functional parts with unique properties. This study uses chopped carbon fiber reinforcement to investigate polyamide's thermal, rheological, and mechanical properties. The study includes an analysis of the material's thermal properties via differential scanning calorimetry and its flow behavior via rotational rheometry. This study provides a comprehensive understanding of carbon-filled nylon PA material's economic and mechanical properties, which will help optimize its performance for various applications. Tensile and flexural tests were used to appraise the material's strength and stiffness under different loading conditions. A cost analysis was performed to compute the specimen cost as a function of orientation and infill density. The aim was to understand how the type and strategy of infill design impact the material's mechanical properties, helping optimize the performance of components and evaluating its cost.

Volumetric Modification of Transparent Materials with Two-Color Laser Irradiation: Insight from Numerical Modeling.

Traditionally, single-color laser beams are used for material processing and modifications of optical, mechanical, conductive, and thermal properties of different materials. So far, there are a limited number of studies about the dual-wavelength laser irradiation of materials, which, however, indicate a strong enhancement in laser energy coupling to solid targets. Here, a theoretical study is reported that aimed at exploring the volumetric excitation of fused silica with dual-wavelength (800 nm and 400 nm) ultrashort laser pulses focused on the material's bulk. Numerical simulations are based on Maxwell's equations, accounting for the generation of conduction electrons, their hydrodynamic motion in the laser field, and trapping into an excitonic state. It is shown that, by properly choosing the energies of the two laser harmonics successively coupling with the material, it is possible to strongly enhance the laser energy absorption as compared to the pulses of a single wavelength with the same total energy. Laser energy absorption strongly depends on the sequence of applied wavelengths, so that the shorter wavelength pre-irradiation can yield a dramatic effect on laser excitation by the following longer-wavelength pulse. The predictions of this study can open a new route for enhancing and controlling the highly localized absorption of laser energy inside transparent materials for optoelectronic and photonic applications.

Analysis of Mechanical and Thermal Properties of Polymer Materials Derived from Recycled Overprinted Metallized PP Films.

Polymer materials and their composites are one of the most frequently used materials in the packaging and food industries. This applies to both disposable and reusable packaging, layered films with barrier properties, as well as densely overprinted polymer films and metallized food wrap films. According to statistical data from Plastics Europe, approximately 40% of processed thermoplastics are used to produce packaging, including single- and multi-layer film packaging. Growing requirements and new EU directives require the use of recycled materials in new products, which is not easy because the properties of recyclates may differ significantly from those of the primary materials with which the former are mixed. This work attempts to analyze the properties of the primary material used to produce a film using the casting method in comparison with the industrial recyclate obtained by the processing of film made of the primary material and then overprinted and metallized. The process of obtaining re-granulates and preparing test samples was presented, and the mechanical, structural, and thermal properties of the tested materials were compared. The conducted research and the obtained results demonstrated the advisability of conducting advanced mechanical recycling, which leads to obtaining re-granulates with repeatable processing properties and thermal and mechanical properties comparable to the original material despite the impurities they contain.

Robust, thermally insulating, and high-temperature resistant phosphate-enhanced mullite fiber porous ceramic composites

Porous mullite ceramics with high porosity and low thermal conductivity are urgently required as high-temperature thermal insulators in harsh environments. How to improve the strength of Porous mullite ceramics dramatically under the premise of no sacrificing its thermal insulating properties has remained an extremely challenging. Inspired by the freezing rain phenomenon in nature, high-strength and high-temperature resistant phosphate coatings were applied to the surface of mullite fibers, which significantly improved the mechanical properties of porous mullite ceramics without significantly increasing their thermal conductivity. The Al(H2PO4)3 solution concentration significantly affected the mechanical and thermal properties of the composite material, where the mechanical performance improved with an increasing Al(H2PO4)3 solution concentration. The phosphate coating phase stabilized with an increasing calcination temperature. The mechanical properties of the ceramics were improved by the excellent interfacial bonding strength between the coating and mullite fiber, and the forms of phosphate in the porous ceramics. The optimum composite preparation process increased its compressive strength by approximately nine-fold to 4.1 MPa and resulted in a thermal conductivity of only approximately 0.09 W/(m·K), demonstrating that the composite exhibited a significantly higher comprehensive performance than other previously reported porous ceramics and aerogels. Such new composites with excellent mechanical and thermal insulation properties exhibit excellent potential for high-strength thermal insulation in the chemical, metallurgical, pharmaceutical, aerospace, and other fields.