Thermophysical Behavior Research Articles

Exploring Co2TiRE (RE = Nd and Tb) as a promising shape memory alloy using DFT methods

Our study employs self-consistent ab-initio calculations using highly precise spin-polarized density functional theory with both GGA and GGA+U approaches, coupled with the Boltzmann transport scheme. This comprehensive approach investigated the structural stability, magneto-electronic behavior, thermophysical characteristics, and thermoelectric transport properties of Co2TiRE (RE = Nd, Tb) Heusler alloys. Through structural optimizations, we confirm that these materials exhibit ferromagnetic behavior. Analysis of band occupation and density of states using GGA and GGA+U methods reveals that both compounds are metallic in both spin configurations. We evaluated key transport properties such as the Seebeck coefficient, electrical and thermal conductivity and the figure of merit to understand their potential in thermoelectric applications. Conservative estimates of the Seebeck coefficient and the figure of merit suggest promising applications in thermoelectric energy harvesting technologies. Additionally, we provide a comprehensive analysis of the thermophysical behavior, including the Debye temperature, thermal expansion, and specific heat, to assess the alloys thermodynamic stability across varying temperature and pressure conditions.

Geopolymer-based insulated wall incorporating construction and demolition waste: Experimental assessment of thermo-physical behavior

The benefit of the application of geopolymers in the building sector is nowadays undisputed. In addition to good structural characteristics, these are characterized by interesting thermophysical properties, obtained through a production process, that reduces CO2 emissions and could incorporate recycled material, thus responding to environmental sustainability. However, it is noted the lack of studies regarding the in-field thermal performance. Thus, the aim of the present study is to investigate the thermal performance, under real conditions, of an innovative geopolymer-based insulated wall. It incorporates over 70% of net weight of Construction and Demolition Waste materials. The wall is conceived within the European project called “Green INSTRUCT” aimed to realize modular prefabricated building elements, for retrofitting and new construction of buildings. Two wall prototypes are analysed, which differ for the type of lightweight aggregate of geopolymer matrix, 3% by weight: expanded polystyrene or extruded polystyrene. The study refers to almost one year of continuous monitoring within a full-scale test room located in southern Italy. The method developed consists of 5 different phases and it involves also a normative-insulated reference wall. The results show higher insulation level of the proposed wall package, with a reduction of the heat flux of about 66% and more stable indoor thermal conditions, compared to the reference wall. Also the inertial properties are satisfactory, showing an experimental decrement factor equal to 0.05 and a time-shift of decrement factor higher than 6 h. All told, the experimental results can provide valuable insights into the real impact of innovative technology on energy efficiency and indoor thermal comfort.

Exploring the potential of ethylenediamine based protic ionic liquids for carbon capture: A study on thermophysical properties and CO2 absorption behavior

The objective of the study is to synthesize economical and facile ethylenediamine (ED) based protic ionic liquids (PILs) containing various carboxylate anions for CO2 capture for post-combustion method. The PILs were synthesized using a straightforward process, and the behavior of their CO2 absorption was investigated in relation to the alkyl chain of odd and even chain anions. The PILs were characterized using 1H NMR, 13C NMR, and HRMS techniques. The study results indicate that ED-ILs with longer alkyl chains are better at absorbing CO2. Among all the PILs, [ED][Hep] exhibited the highest absorption capacity except [ED][But], absorbing 0.26 CO2/mol of IL at 298K and 0.1 MPa. The thermophysical properties, including density, sound speed, viscosity, and refractive index of neat ED-based PILs, were tested at different temperatures and 0.1 MPa. Furthermore, the derived parameters such as expansion coefficient (α), molecular volume (V), isentropic compressibility (βs), lattice potential energy (UPOT), standard entropy (S0), Intermolecular free length (Lf) and free volume (Vm) were determined using experimental parameters. It was shown that these characteristics were directly related to the PILs ability to absorb CO2. Overall, the investigation demonstrated that [ED][But] offers a great potential for utilization as a CO2 absorption solvent because of its high absorption capacity and special qualities as a PIL.

Influence of monomer structure and catalyst concentration on topological transition and dynamic properties of dicarboxylic acid‐epoxy vitrimers

AbstractThis study delineates the dependence of thermophysical behavior of acid‐epoxy vitrimers on their formulation. The stress relaxation due to the bond exchange reaction and the glass transition temperature of acid epoxy vitrimers are investigated, with respect to the influence of catalyst content and acid chain length. This is carried out for a range of dicarboxylic acids and catalyst concentrations formulated and characterized using calorimetry and dynamic mechanical analysis. The influence of acid chain length on the bond exchange rate, topological transition, and glass transition temperatures of the vitrimers is found to be significant. The activation energy of the exchange reaction varies over a wide range from 73 to 104 kJ/mol and the topology freezing temperature from 66 to 136°C with the behavior governed by the interplay between crosslinking density, network flexibility and density and distance of functional groups, with an increase of catalyst concentration leading to lower topological transition temperature and the dependence on chain length showing non‐monotonic behavior. The glass transition decreases by about 30°C as the carbon chain length increases from 6 to 14 carbons due to enhanced monomer flexibility and is not affected by the concentration of catalyst.

Advancing reinforcement of sustainable gypsum composites: High-performance design by reusing waste materials

This study tends to optimize and develop an innovative gypsum material by incorporating hybrid waste compounds. Using a Doehlert design, this work explores the effects of introducing paper (X1), polystyrene (X2), and polyester fibers (X3), as well as their interactions, on gypsum's thermophysical and mechanical behavior. Bulk density, thermal conductivity, flexural strength, compressive strength, and the fire resistance test were performed on the developed formulations. Statistical analysis emphasizes the significant influence of all process variables on gypsum properties. Polyester fibers notably enhance flexural strength when combined with the cooperative effect of paper and polystyrene wastes, which strike a balance between physical and mechanical characteristics. The optimum formulation parameters lead to a significant 33% decrease in bulk density, a 43% reduction in thermal conductivity, a notable 42% increase in flexural strength, and a significant reduction in compressive strength of around 50%, but still meet the 2 MPa standard. The new samples show ductile behavior, highlighting gypsum's potential as a load-bearing material with excellent thermal insulation properties and impressive fire resistance. This research significantly improves our understanding of the effectiveness of a gypsum compound incorporating waste in a hybrid manner, bringing this approach into line with sustainable development objectives.

Analysis of cryopreservation media thermophysical characteristics after ultra-rapid cooling through differential scanning calorimetry

Cryoprotective agents play a critical role in minimizing cell damage caused by ice formation during cryopreservation. However, high concentrations of CPAs are toxic to cells and tissues. Required concentrations of CPAs can be reduced by utilizing higher cooling and warming rates, but insight into the thermophysical properties of biological solutions in the vitrification method is necessary for the development of cryopreservation protocols. Most studies on thermophysical properties under ultra-rapid cooling conditions have been qualitatively based on visualization. Differential scanning calorimetry methods are ideal for studying the behavior of biomaterials in various freezing conditions quantitatively and accurately, though previous studies have been predominantly restricted to slower cooling rates. Here, we developed an ultra-rapid cooling method for DSC that can achieve minimal cooling rates exceeding 2000 °C/min. We investigated the thermophysical vitrification behavior of ternary solutions of phosphate buffer saline (1X), dimethyl sulfoxide or glycerol and ice blocking polymers (X-1000 or Z-1000). We quantified the impact of solute concentration on ice crystal formation during rapid cooling. Our findings support the expectation that increasing the solute concentration reduces the amount of ice formation, including devitrification. Devitrification increases from 0 % to 40 % (v/v) Me2SO and then reduces significantly. The relative amounts of devitrification to the total ice formation are 0 %, 60 %, 0 % in 20 %, 40 %, 60 % (v/v) Me2SO, and 2 %, 48 %, 49 % in 20 %, 40 %, 60 % (v/v) glycerol, respectively. The results suggest that at low concentrations, such as below 20 % (v/v) for Me2SO or glycerol, increasing the warming rate after ultra-rapid freezing is not essential to eliminate devitrification. Furthermore, ice blocking polymers do not reduce ice formation substantially and cannot eliminate devitrification under ultra-rapid cooling conditions. In conclusion, our results provide insights into the impact of solute concentration on ice formation and devitrification during rapid cooling, which can be practical for optimizing cryopreservation protocols.

Optimizing the thermophysical behavior of a novel ternary hybrid nanofluid for energy applications through experimental research

The continual use of fossil fuel technologies has negatively impacted on the environment and has caused huge health challenges globally. Despite the growth of renewable energy technologies, their efficiency issues have hindered widespread adoption. The use of nanofluids as heat transfer fluids in renewable energy technologies have further improved their overall efficiency, resulting in a more environmentally friendly performance of these systems. For automotive fuel and coolant systems, hybrid nanofluids are gaining appeal due to their remarkable ability to enhance thermal performance and accelerate heat transfer rates. Ternary-hybrid nanofluids, which combines three different types of nanoparticles in a wide range of mixing ratios, are an intriguing but mostly speculative concept. Optimizing the mixing ratio for effective heat transfer characteristics is important for energy applications. A unique Al2O3/ZnO/Fe3O4 ternary nanofluid is synthesized and its density is measured in this investigation. The nanofluid preparation included three different mixing ratios (1:1:1, 2:1:1, and 1:2:1), with the volume fraction between 0.5 % and 1.25 %. This study also includes a discussion of the density prediction analysis. The result shows that at a temperature of 25 °C and a volume fraction of 1.25 %, the maximum density is determined to be 1165 kg/m3. The Random Forest algorithm gives the best prediction accuracy with an R2 value of 0.928.

Thermophysical properties of equiatomic CrMnFeCoNi, CrFeCoNi, CrCoNi, and CrFeNi high- and medium-entropy alloys

High- and medium-entropy alloys have emerged as promising materials with significant potential for diverse technical applications. Notably, their use in the field of energy technology has attracted particular interest, where thermophysical properties play a pivotal role. In this context, this study aims to investigate the thermophysical properties, namely thermal expansion behavior, thermal diffusivity, specific heat capacity, thermal conductivity, and the electric resistivity of single-phase face-centered cubic alloys between 300 K and 773 K. In addition to thermal conductivity, the electric resistivity was measured. Based on the Wiedemann-Franz law, electronic and phononic contributions to the overall thermal conductivity were evaluated. Complementary insights into the electronic state of the investigated materials were obtained by electron spin resonance measurements, revealing the presence of short-range ordering in all alloys. The specific heat capacity is found to dominate the thermal conductivity. Furthermore, the study shows the decisive influence of chemical complexity on the thermophysical properties. Notably, the observed influences extend to the electronic thermal conductivity, pointing out the correlation between composition and heat transport properties. This comprehensive investigation provides a foundation for understanding and tailoring the thermophysical behavior of the studied alloys, offering valuable insights for their targeted deployment in advanced energy applications.

Unsteady axisymmetric hybrid graphene-copper nanofluid slip flow over a permeable radially shrinking disk with the Soret and Dufour effects

This study investigates the unsteady axisymmetric flow of a hybrid graphene-copper nanofluid over a permeable radially shrinking disk, accounting for velocity slip, Dufour, and Soret effects. Examining such boundary layer flows of hybrid nanofluids is crucial for understanding the underlying fluid mechanics and thermophysical behavior. The fluid flow model is solved using a finite difference scheme in MATLAB to generate the numerical solutions. Since dual solutions are attainable, stability analysis is performed to analyze the nature of the solutions. The existence of dual solutions enables exploring flow separation dynamics through selected control parameters. Results indicate that higher copper volume fraction and velocity slip effectively prevent the boundary layer separation. The 2 % copper volume fraction delays the boundary layer separation approximately 6 % better compared to the usage of 1 % copper volume fraction. The heat transfer is improvable by reducing the shrinking intensity of the disk and maximizing the velocity slip and Soret parameters. The comprehensive mathematical model presented herein lay a solid foundation for future research endeavors, particularly in the field of hybrid nanofluids and their applications in thermal management systems.

Thermophysical Behavior of Carbonated Aqueous Solutions Containing Monoethanolamine and Degradation Products

Thermophysical Behavior of Carbonated Aqueous Solutions Containing Monoethanolamine and Degradation Products

Research on melting behavior of coaxially fed powder in diode laser cladding process

The purpose of this study was to investigate the thermal interaction between coaxially fed powder and diode laser, which is extremely complex and difficult to be detected in thermal real-time monitoring by the infrared camera system. In order to analyze the dynamic melting behavior of the powder, a high-speed camera system was established to capture the melting behavior of a single powder coaxially fed into the laser, which can reflect the entire melting process. There is a transition of “solid → solid-liquid two-phase state → liquid state” after a single powder enters the laser, and the duration and thermophysical behavior in different transition stages are not the same. Different states and duration determine distinct heat absorption effects. Based on high-speed camera detection results, the thermophysical behavior in different characteristic stages of the melting process in single powder was studied to develop a mathematical model, which is able to simulate and predict the temperature and state of the powder about to enter the melting pool. The experimental and simulation results show that (1) for a well-tested powder melting process, where the laser power ranges from 100 to 1500 W, the duration of the powder particle's absorption stage is between 4.41 and 18 ms, the duration of the solid-liquid two-phase state is between 0.52 and 2.63 ms, and the duration of the liquid state is between 4.67 and 13.48 ms. (2) The laser power ranges from 100 to 1500 W, and the temperature of the powder particles as they enter the melt pool ranges from 745 to 3200 °C.

Unsymmetrical and C3-Symmetrical Partially Fluorinated Hexaarylbenzenes: Effect of Terminal Alkoxy Chain Length on Photophysical and Thermophysical Behavior

Solution-state photoluminescence (PL) is affected by the electronic state; however, solid-state PL varies widely depending on the aggregated state. Although the synthesis and photophysical properties of unsymmetrical and C3-symmetrical hexaarylbenzenes (HABs) have been reported, the influence of their terminal alkoxy chains on their physical properties remains unclear. Therefore, we synthesized a series of unsymmetrical and C3-symmetrical partially fluorinated HABs with different alkoxy chains and investigated the effects of alkoxy chain length on the thermophysical and photophysical properties. While investigating phase transition behavior, the ethoxy-substituted unsymmetrical derivative revealed a columnar liquid-crystalline phase, whereas the other derivatives only exhibited a phase transition between crystalline and isotropic phases. While evaluating PL behavior, both the unsymmetrical and C3-symmetrical analogs exhibited relatively strong blue PL, independent of the alkoxy chain length. Through-space π-conjugation caused the PL spectra of C3-symmetrical derivatives to redshift compared to those of unsymmetrical derivatives. Partially fluorinated HABs exhibited relatively strong fluorescence, even in the crystalline state, depending on the alkoxy chain length, owing to the formation of various aggregated structures. Crystalline fluorinated HABs exhibited photochromism, resulting in the appearance of long-wavelength PL bands when exposed to ultraviolet (UV) irradiation, making them promising candidates for PL sensing materials for UV detection.

Deciphering the Liquid Continuum: Thermophysical and Slippage Dynamical Behavior of Water in Graphene Oxide Nanochannels

Deciphering the Liquid Continuum: Thermophysical and Slippage Dynamical Behavior of Water in Graphene Oxide Nanochannels

Artificial compressibility method for high-pressure transcritical fluids at low Mach numbers

Supercritical fluids possess unique properties that makes them relevant in various scientific and engineering applications. However, the experimental investigation of these fluids is challenging due to the high pressures involved and their complex thermophysical behavior. To overcome these limitations, computational researchers employ scale-resolving methods, such as direct numerical simulation and large-eddy simulation to study them. Nonetheless, these methods require substantial computational resources, especially in the case of low-Mach-number regimes due to the disparity between acoustic and hydrodynamic/thermal time scales. This work, therefore, addresses this problem by extending the artificial compressibility method to high-pressure transcritical fluids. This method is based on decoupling the thermodynamic and hydrodynamic parts of the pressure field, such that the acoustic time scales can be externally modified without severely impacting the flow physics of the problem. In addition, the method proposed has two key characteristics: (i) the splitting method presents low computational complexity, and (ii) an automatic strategy for selecting the speedup factor of the approach is introduced. The effectiveness of the resulting methodology is demonstrated through comprehensive numerical tests of increasing complexity, showcasing its ability to accurately simulate a wide range of high-pressure transcritical flows including turbulence. The results obtained indicate that the approach proposed can readily lead to computational speedups larger than 10× without significantly compromising the accuracy of the numerical solutions.

Phase diagram-guided composition design and property investigation of Ni-based filler metals

The fundamental mechanism underlying the formation of brazed joints involves the diffusion of elements between the base metal (BM) and the brazing filler metal (FM). The formation of brittle compounds in FM during the brazing process frequently results in a significant deterioration of the mechanical properties of the brazed joints. Ni and Cu elements exhibit infinite solubility, and the incorporation of Cu element results in a decrease in the liquidus temperature of FM, thereby enhancing its surface wettability on the BM. The present investigation involves the preparation of as-cast and amorphous FMs with varying Cu element concentrations to examine their material properties, such as weldability, wettability, thermophysical behavior, and creep resistance. The thermophysical and mechanical properties of the nickel-based filler metal BNi-2 were evaluated using the JMatPro software for material thermodynamic simulation and compared with data obtained from existing literatures. An analysis is conducted on the creep properties of a novel FM comprising of Ni, Cr, Fe, Si, B, and Cu. The results suggest that the thermophysical properties of BNi-2 filler are minimally impacted by the presence of Cr (6–8 wt%), Fe (2.5–3.5 wt%), Si (4–5 wt%), and B (2.75–3.5 wt%). Furthermore, alterations in the composition of Si and B elements have a significant impact on the distribution of γ and γ′ phases, consequently influencing the creep properties of the material. At 25 °C, the equilibrium phase of BNi-2 with different Cu contents indicates a gradual decrease in the content of γ phase, while the content of γ′ and Cu–Ni phases increases with an increase in Cu content. The BNi-2 filler with 3 % Cu exhibits the most favorable properties in terms of steady creep rate and fracture life compared to other fillers. This is attributed to the competitive equilibrium between the γ phase and Cu–Ni phase. The addition of 6 % Cu element results in the optimal wettability of the filler metal and creep resistance of the brazed joints. It is also observed that as the concentration of Cu reaches 9 %, there is a gradual increase in the FeB phase, a rise in the proportion of brittle compounds, and a decline in the amorphous forming ability.

Effect of microwave radiation temperature and content of different solid waste on the microstructure and physicomechanical properties of lightweight aggregates

Microwave radiation in the production of lightweight aggregates, it has not yet been thoroughly explored. Therefore, the main goal of the research is to analyze the possibility of using various types of waste, such as waste rock (0–30 %) and glass cullet (10 %), fly ash (50–80 %) and waste solution using different microwave temperature (1000, 1050, 1100 °C) in order to obtain lightweight aggregates. Above factors and, chemical and mineral composition of the waste materials, affect the microstructure and physico-mechanical parameters of the aggregates.). The thermophysical behavior (DTG/TG), grain composition, chemical composition (XRF), phase composition (XRD) and microstructure (SEM, μ-CT) were analyzed. The microstructure, as well as the related characteristics of aggregates, i.e. water absorption, density, and compressive strength, depend on the sintering temperature, chemical composition and mineral waste raw material. The best properties were obtained for a raw material mixture containing 80 % coal fly ash, 10 % glass cullet, 10 % clay and 48 g of the waste solution (per 100 g of raw mixture), sintered in the microwave at 1100 °C. The aggregates were characterized by water absorption of 6.96 %, bulk of 1.70 g/cm3, loose bulk density 0.60 g/cm3, and compressive strength 5.95 MPa. Closed porosity determined by micro-CT was 8.41 %, open - 0.24 %, sphericity 0.62. The total porosity depends on the loose bulk density and particle density of lightweight aggregates.Furthermore, washout tests meet environmental requirements. The proposed technology, moreover, enables a short time of thermal processing of raw materials, and thus energy savings and a sustainable approach to the production of green pellets. Thanks to the high strength, the obtained aggregates can replace commercial aggregates.

Improving the thermo-physical behavior of Li2O-Al2O3-P2O5-SiO2 glass–ceramic system by triple-step heat treatment processes

Improving the thermo-physical behavior of Li2O-Al2O3-P2O5-SiO2 glass–ceramic system by triple-step heat treatment processes

Keller box computation for entropy generation analysis in the coating flow of magneto viscoelastic polymer nanofluid over a circular cylinder

PurposeThe need for precise synthesis of customized designs has resulted in the development of advanced coating processes for modern nanomaterials. Achieving accuracy in these processes requires a deep understanding of thermophysical behavior, rheology and complex chemical reactions. The manufacturing flow processes for these coatings are intricate and involve heat and mass transfer phenomena. Magnetic nanoparticles are being used to create intelligent coatings that can be externally manipulated, making them highly desirable. In this study, a Keller box calculation is used to investigate the flow of a coating nanofluid containing a viscoelastic polymer over a circular cylinder.Design/methodology/approachThe rheology of the coating polymer nanofluid is described using the viscoelastic model, while the effects of nanoscale are accounted for by using Buongiorno’s two-component model. The nonlinear PDEs are transformed into dimensionless PDEs via a nonsimilar transformation. The dimensionless PDEs are then solved using the Keller box method.FindingsThe transport phenomena are analyzed through a comprehensive parametric study that investigates the effects of various emerging parameters, including thermal radiation, Biot number, Eckert number, Brownian motion, magnetic field and thermophoresis. The results of the numerical analysis, such as the physical variables and flow field, are presented graphically. The momentum boundary layer thickness of the viscoelastic polymer nanofluid decreases as fluid parameter increases. An increase in mixed convection parameter leads to a rise in the Nusselt number. The enhancement of the Brinkman number and Biot number results in an increase in the total entropy generation of the viscoelastic polymer nanofluid.Practical implicationsIntelligent materials rely heavily on the critical characteristic of viscoelasticity, which displays both viscous and elastic effects. Viscoelastic models provide a comprehensive framework for capturing a range of polymeric characteristics, such as stress relaxation, retardation, stretching and molecular reorientation. Consequently, they are a valuable tool in smart coating technologies, as well as in various applications like supercapacitor electrodes, solar collector receivers and power generation. This study has practical applications in the field of coating engineering components that use smart magnetic nanofluids. The results of this research can be used to analyze the dimensions of velocity profiles, heat and mass transfer, which are important factors in coating engineering. The study is a valuable contribution to the literature because it takes into account Joule heating, nonlinear convection and viscous dissipation effects, which have a significant impact on the thermofluid transport characteristics of the coating.Originality/valueThe momentum boundary layer thickness of the viscoelastic polymer nanofluid decreases as the fluid parameter increases. An increase in the mixed convection parameter leads to a rise in the Nusselt number. The enhancement of the Brinkman number and Biot number results in an increase in the total entropy generation of the viscoelastic polymer nanofluid. Increasing the strength of the magnetic field promotes an increase in the density of the streamlines. An increase in the mixed convection parameter results in a decrease in the isotherms and isoconcentration.

Advances in Ablation or Oxidation Mechanisms and Behaviors of Carbon Fiber-Reinforced Si-Based Composites.

Composites with excellent thermomechanical and thermochemical properties are urgently needed in the aerospace field, especially for structural applications under high-temperature conditions. Carbon fiber-reinforced Si-based composites are considered the most promising potential high-temperature materials due to their excellent oxidation resistance and ablative behaviors, good structural designability, and excellent mechanical properties. The reinforcement of the relevant composites mainly involves carbon fiber, which possesses good mechanical and temperature resistance abilities. In this paper, the ablation behaviors and mechanisms of related composites are reviewed. For carbon fiber-reinforced pure Si-based composites (C/SiM composites), the anti-ablation mechanism is mainly attributed to the continuous glassy SiO2, which inhibits the damage of the substrate. For C/SiM composite doping with refractory metal compounds, the oxides of Si and refractory metal together protect the main substrate from ablation and oxidation. Moreover, in addition to thermochemical damage, thermophysical and thermomechanical behavior severely destroy the surface coating of the substrate.

Prediction of the Thermophysical Behavior of Amorphous Alloys Ni0.333Zr0.667 and La80Al20 Using the Properties of the Metals

Prediction of the Thermophysical Behavior of Amorphous Alloys Ni0.333Zr0.667 and La80Al20 Using the Properties of the Metals