Thermal Features Research Articles

Online monitoring of direct laser metal deposition process by means of infrared thermography

Direct laser metal deposition (LMD–DED) is an additive manufacturing (AM) process that is used to build up and repair high-quality metal components. It works by overlapping layers of powder material and melting them with a laser. To get a stable process without defects and to reach, at the same time, high mechanical properties, a robust assessment and control of the process parameters, and above all of their combination, is required. The ideal goal is to assure the online control, to stop or correct the process in case of unexpected anomalies. In this work, a robust online monitoring of the laser metal deposition (LMD–DED) process based on the use of infrared thermography was developed and proposed. After choosing the suitable process parameters, a customized design of experiments (DOE) was set, and the statistical analysis of different thermal features was carried out to develop the most robust models that correlate them with the input process parameters (laser power, scanning speed, and powder flow rate). The proposed procedure was based on the extraction of different thermal features from suited regions of interest (ROI), performing statistical analyses by means of analysis of variance (ANOVA) and building regression models to correlate the process parameters with the thermal behavior. The obtained results demonstrated the possibility to control the process by means of the chosen thermal features, independent of the position of the ROI. Moreover, the possibility to use the models to detect typical AM defects, and anomalies, online directly during the process, has been proved and verified by destructive macrographs carried out on the manufactured coupons.

Mathematical modelling for peristaltic flow of fourth‐grade nanoliquid with entropy generation

AbstractNanomaterials having excellent thermal properties are employed in producing energy, extrusion processes, engineering processes, nuclear interactions, industrial domains and aero‐spaces, etc. Therefore, current study scrutinizes the aspects of entropy optimization and Ohmic heating on MHD peristalsis of fourth‐grade nanoliquid in a channel. Flexible channel walls retain concentration, thermal slip and velocity conditions. The consequences of viscous dissipation and Arrhenius activation have been accounted. The lubrication approximation is used in mathematical modelling. Nanofluid model is used by considering thermophoresis and Brownian motion. Furthermore, thermal radiation features are included in the energy equation. By using an appropriate similarity transformation, a system of PDEs is simplified to a solvable system of ODEs. Numerical techniques are used to solve the problem of governance. Detailed exploration of the sundry variables of concern on the flow quantities like velocity profile, nanoparticle concentration, temperature and entropy of the system is graphically examined. Heat transfer is examined in tabular form. Based on the derived outcomes, the velocity rises via thermal Grashof and slip variables. Further, an increment in Brownian motion and radiation parameters shows opposite behaviour on temperature.

Thermal features of Darcy-Forchheimer on a micropolar fluid flow over a curved stretching surface with homogenous-heterogeneous reactions

The main focus of contemporary study is to explore the Darcy magnetized flow of a micropolar second-grade fluid by consideration of homogeneous-heterogeneous reactions over a curved stretching surface. The thermal aspects of the fluid flow are analyzed with the inclusion of joule heating and thermal radiation effects. Moreover, magnetic field is imposed normal to the surface and thermal stratification condition is considered on the boundary of surface. An appropriate transformation is used to convert the flow model into a set of ordinary differential equations, which are nonlinear in the nature. The numerical solutions of this nonlinear system of equations are obtained using the bvp4c technique on MATLAB. The velocity, temperature, concentration, and micro-rotation distribution variation for various parameter is shown graphically and with numerical data. The main finding in the current problem to see that that greater estimation of micropolar parameter improves the angular velocity of the fluid, whereas linear velocity of fluid declines for larger values of magnetic parameter because of the resistance effect take place due to magnetized flow. Furthermore, it seems that curvature parameter produces the improvement in the linear and angular velocity of the fluid.

First-principles calculations to investigate structural, elastic, electronic, optical and thermal properties of La-based ternary intermetallic superconductors LaM2Si2 (M=Co, Cu, Rh, Pd, Ag, Ir, Pt, Au)

Different physical properties of ternary intermetallic La-based superconducting materials LaM2Si2 (M = Co, Cu, Rh, Pd, Ag, Ir, Pt, Au) are examined through the self consistent ab-initio scheme depending on the DFT replication. The main purpose of this study is to comprehend several different crucial characteristics of these compounds, including their crystal phase, stability manner, bulk features, band configuration, dielectric, conductivity as well as thermal features. Good accordance in the structural analysis of superconducting materials LaM2Si2 (M = Co, Cu, Rh, Pd, Ag, Ir, Pt, Au) has been observed between the optimized and synthesized lattice parameters. The phonon dispersion curve indicates that the compounds LaCo2Si2, LaCu2Si2, LaRh2Si2, LaPd2Si2, and LaIr2Si2 are dynamically stable, but LaAg2Si2, LaPt2Si2, and LaAu2Si2 are dynamically unstable in nature. Mechanical crystal constancy of the selected materials is verified from the investigated elastic constants. Ductility behaviors of these compounds are ensured by the values of Pugh's and Poisson's ratios. High Young's modulus of LaIr2Si2 ensured its elevated hardness along with huge melting temperature compared than other phases. Anisotropic character of these materials can be ensured through the calculations of elastic anisotropy. The electrical properties of the superconducting LaM2Si2 (M = Co, Cu, Rh, Pd, Ag, Ir, Pt, Au) compounds were also studied in details. Metallic character of the selected solids is observed through the investigation of DOS and band structure calculations. The investigated dielectric function, conductivity, and absorption also reflect the conductive behavior of superconducting LaM2Si2 (M = Co, Cu, Rh, Pd, Ag, Ir, Pt, Au) materials. The optical phenomena ensured their huge absorption as well as optical conductive nature at the site of ultraviolet energy region. Moreover, high reflectivity in the UV region makes these superconductors good solar reflectors for this energy site. Very low minimum thermal conductivity of these compounds especially of LaPt2Si2 and LaAu2Si2 makes them useful and fascinating for thermal barrier coating (TBC) materials.

Structural, mechanical, electronic, optical and thermodynamic features of lead free oxide perovskites AMnO3 (A=Ca, Sr, Ba): DFT simulation based comparative study

Perovskite oxides with transition metals have been subjected to a lot of concern in the recent time having their exclusive physical and chemical property. Due to ferroelectric character these types of materials have huge technological applications in worldwide. In the existing project, the crystal structure stability, single and polycrystalline bulk properties, electron-charge density, photon and temperature related optical as well as thermal features of perovskite oxides AMnO3 (A = Ca, Sr, Ba) have been investigated through DFT simulation with CASTEP code. Very good accordance in the investigated and synthesized lattice parameters is found. Mechanical stabilities of phases AMnO3 (A = Ca, Sr, Ba) are ensured from the investigated elastic stiffness constants. Ductile nature of compounds AMnO3 (A = Ca, Sr, Ba) are ensured from the study of Pugh's and Poisson's ratios. Hardness calculations ensured that all the studied materials are hard in nature where SrMnO3 has little bit higher hardness nature compared to others. Very high machinability index of CaMnO3 confirmed its suitable industrial application compared to the rest two compounds. Anisotropic character of AMnO3 (A = Ca, Sr, Ba) is observed from the analysis of elastic anisotropy factor. Band structure calculations with up-spin and down-spin reveal the metallic and semi-metallic nature of AMnO3 (A = Ca, Sr, Ba) respectively. Ionic and covalent bonded nature of AMnO3 (A = Ca, Sr, Ba) are confirmed from the Mulliken atomic population and charge density calculations. Very high absorption and conductivity of AMnO3 (A = Ca, Sr, Ba) have been observed in the ultraviolet energy site which ensure their possible applications in optical devices operates at UV energy regions. The dielectric function make sure the metallic nature of AMnO3 (A = Ca, Sr, Ba) as the actual value approaches to zero from negative energy region. Comparatively high Debye temperature of AMnO3 (A = Ca, Sr, Ba) revealed that these compounds are thermally more conductive where CaMnO3 is more conductive than the rest two materials. Very low value of Kmin of material BaMnO3 ensured that this phase has more possibility to use in thermal barrier coating materials (TBC) than CaMnO3 and SrMnO3 materials.

Effect of different sweeteners on the thermal, rheological, and water mobility properties of soft wheat flour and their application to cookies as an alternative to sugar

The effects of different sweeteners on the physicochemical properties of soft wheat flour were investigated mainly in terms of thermal, rheological, and water mobility features, and their feasibilities as an alternative to sugar were evaluated in the cookie system. Kestose significantly reduced the solvent retention capacity of wheat flour, followed by sucrose, fructose, and allulose. Thermal analysis showed that the sucrose and kestose distinctly led to an increase in the gelatinization temperature of wheat flour, which was explained by lower T2 relaxation times. In addition, the pasting viscosities and thermo-mechanical properties of wheat flour containing kestose became lower compared to allulose, and these differences were morphologically confirmed by the real-time microscopic measurements during heating. Furthermore, when the sweeteners were incorporated into the cookie formulations, kestose played a positive role as a sugar replacer in the cookie system by presenting a comparable spread factor, texture, and color to cookies with sucrose.

Electrochemical and thermal features of aging lithium-ion batteries cycled at various current rates

In the present work, three types of battery samples with 90% state of health (SOH) are prepared, to demonstrate the electrochemical and thermal features of aging lithium-ion batteries after the long-term cycling at various rates (1C, 2C and 4C), by reference to the fresh battery. With the aging of batteries, battery capacity declines stably; meanwhile, the phenomena of electrolyte decomposition and lithium depositing on the electrode materials' surface gradually prominent. As a result, the thermal stability of both electrode materials scraped from aged batteries decreases compared with the fresh battery, which further worsens the thermal runaway behavior of full batteries when over-heated. Moreover, the severity aggravates as the current rate increases. In addition, a more severe thermal runaway phenomenon is also demonstrated by the aged batteries. A parameter (α) is defined here to determine the advancement ratio of the ignition time and thermal runaway time during thermal runaway testing for the aged batteries, referred by the fresh battery. In virtue of the rapid evolution of thermal runaway, the aged batteries experience a gentler mass loss during this process, especially for the 4C cycled one.

Green synthesis of a mesoporous hyper-cross-linked polyamide/polyamine 3D network through Michael addition for the treatment of heavy metals and organic dyes contaminated wastewater

Environmental pollution is the greatest challenge of the modern age due to unprecedented industrialization and urbanization that has led to the contamination of water resources with a wide range of pollutants. The release of untreated industrial and municipal wastewater to water bodies further intensifies the problem. The presence of heavy metals and organic contaminants in water poses significant threats to humans, aquatic life, and the environment. Adsorption is one of the famous water treatment technologies due to its simplicity, low cost, efficiency, and minimal secondary pollution. The selection or synthesis of an effective adsorbent is key to the success of the adsorptive removal of pollutants. In this work, we synthesized an adsorbent consisting of a mesoporous hyper-cross-linked polyamide/polyamine 3D network through a single-step Michael addition reaction. The adsorbent was characterized by FTIR, PXRD, TGA, SEM, and TEM to investigate its functional moieties, material nature, thermal, morphological, and internal structural features, respectively. Due to its mesoporous structure, presence of functional groups, and 3D hyper-cross-linked network, it efficiently removed heavy metals (Cd, Cr, and Pb) from aqueous media. The effect of various parameters such as sample pH, adsorbent dosage, contact time, and adsorbate concentrations was thoroughly investigated. The experimental data were analyzed by a variety of isotherm models wherein Langmuir was found to be the best fit for explaining the adsorption of all the metals. The adsorption kinetics was best explained by the pseudo-second-order model. The maximum adsorption capacities for Cd, Cr, and Pb were 60.98 mg g−1, 119 mg g−1, and 9.302 mg g−1, respectively. The synthesized adsorbent was also tested for removal of organic dyes, and it showed selective and fast removal of Eriochrome Black T. Polymeric resins can be promising materials for adsorptive remediation of pollutants in aqueous media.

A numerical approach to investigate the effect of various fluids on the performance of a heat pipe

The present study is carried out using CFX, a commercial computational fluid dynamics (CFD) software, to estimate the thermal characteristics of a heat pipe. A heat pipe consists of three concentric circular tubes with three different split sections: Evaporator, adiabatic, and condenser sections. A detailed parametric study takes water and methanol as working fluids – Additionally, a study investigates the heat pipe with condenser section subjected to ambient air. The complete analysis is performed for an existing heat pipe with given design characteristics such as orientation, diameter and length, wick structure, and the stated circumstances and intake flow to the evaporator. The results are reported and compared in graphical form. It is observed that the water improves the heat pipe thermal features in terms of temperature than that of methanol. The maximum surface temperature is recorded in the evaporator zone at 132 oC, while the lowest temperature was measured at the conclusion of the condenser portion at 87.6 oC. The condenser portion's extreme surface temperature is 79.93 oC, whereas the evaporator portion's extreme surface temperature is 127 oC. When attributes are compared at atmospheric pressure, water outperforms methanol in terms of merit. This shows that compared to methanol, water has greater heat transfer properties.

Soret and Dufour effects on dissipative Jeffrey nanofluid flow over a curved surface with nonlinear slip, activation energy and entropy generation

Nanofluids have potential abilities and thermal features and provide more efficient results of heat transfer when compared with common liquid. Therefore, the major novel aspect of the current analysis is to analyze the entropy production and thermal feature of the system in the presence of cross-diffusion, nonlinear radiation, endothermic/exothermic reaction, activation energy and dissipation effects. Slip factor is additionally considered to slowing down the nanomaterial velocity. Furthermore, the effects of Lorentz force and nonlinear mixed convection are accounted. The governing differential equations for considered nanofluids are first converted into dimensionless ODEs utilizing proper variables. The obtained system is then computed using NDsolve technique. The approximated results for different distributions are shown through curves and tables. The impact of dimensionless parameters is visualized on fluid velocity, temperature, concentration, Nusselt number, skin friction and entropy generation. It has been observed that velocity steps up with curvature, ratio of buoyancy, solutal mixed convection and thermal convection parameters but declines for upgrading slip parameter. The temperature step down by upgrading exothermic/endothermic parameter, Dufour number and Brownian diffusion parameter, thermophoretic parameter and radiation parameter. It is also noticed that the concentration of the nanofluid upsurges for increasing activation energy and soret number, but concentration minimizes for growing the temperature difference parameter. Numerical results show that the Nusselt number decays for rising Soret number, Dufour number, thermophoretic parameter and Brownian diffusion parameter but a reverse trend is seen for radiation parameter and activation energy. Also, skin friction coefficient declines by enhancing thermal convection parameter, solutal mixed convection parameter and slip parameter but upgrades for boosting buoyancy parameter.

Bioconvective flow of bi-viscous Bingham nanofluid subjected to Thompson and Troian slip conditions

This paper describes the bioconvection phenomenon and its significant influence on the thermal features of the flow of bi-viscous Bingham (BVB) nanofluid past a vertically stretching flat surface. The analysis of the impact of convection parameters is considered along with various other forces. Meanwhile, the flow of BVB nanofluid is put through the slip conditions defined by Thompson and Troian for the velocity at the boundary. The flow of BVB nanofluid is modeled using the partial differential equations (PDEs) under the assumptions of thermophoresis and Brownian motion which occur due to the movement of nanoparticles. Along with these forces, the radiation is also considered so that the obtained results are close to the practical scenarios. Thus, using the proper Lie group similarity transformations, the intended mathematical model is converted into ordinary differential equations (ODEs). The resulting equation system is encoded using the RKF-45 technique, and the outcomes are explained using graphs and tables. The solutions found for the model showed that, for higher ranges of the non-Newtonian fluid parameter, the velocity decreases while the heat transferred by the nanofluid increases. The availability of motile density at the surface grows as the Péclet number rises, whereas the Schmidt numbers decline in their respective profiles.

Potassium and Cesium Fluorinated β-Diketonates: Effect of a Cation and Terminal Substituent on Structural and Thermal Properties.

As potential precursors for the synthesis of fluoroperovskites, a family of heavy alkali metal (MI = K, Cs) fluorinated β-diketonates were prepared and characterized by elemental analysis, IR, and powder-XRD. The crystal structures of the new six complexes, MI(β-dikF)(H2O)X, X = 0 or 1, were also determined. The structural diversity of this poorly explored class of complexes was discussed, including the preferred types of cation polyhedra and the ligand coordination modes, and the thermal properties of the metal β-diketonates were studied by TG-DTA in an inert (He) atmosphere. The data obtained allowed us to reveal the effect of the metal cation and the terminal substituent on the structural and thermal features of this family of complexes.

Upcycling waste phosphogypsum as an alternative filler for asphalt pavement

Mineral fillers are an essential component of asphalt concrete. Significant amounts of mineral fillers are used in constructing asphalt pavement. However, mineral fillers are an important non-renewable natural resource which needs to be preserved. In addition, the production of mineral fillers also consumes much energy and affects environment negatively. This study set out to explore the feasibility of upcycling waste phosphogypsum as an alternative filler for asphalt concrete. The phosphogypsum was first pretreated at 60, 160, and 800 °C, and the crystalline phase of phosphogypsum was evaluated by X-ray diffraction (XRD). Phosphogypsum with three crystalline phases and limestone powder were then mixed with base asphalt binders to prepare asphalt mastic at the filler-asphalt ratio of 1:1 at 150 °C. The chemical structural changes and thermal stability features of phosphogypsum asphalt mastic were analyzed using Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). The viscoelasticity, high-temperature performance, and fatigue characteristics of different asphalt mastics were measured by frequency sweep, multiple stress creep and recovery (MSCR), and linear amplitude sweep (LAS), respectively. The results indicate that phosphogypsum had different crystalline phases after pretreatment at different temperatures. The addition of phosphogypsum as fillers in asphalt is mainly a physical hardening effect. The 600 °C residual mass ratio of asphalt mastic prepared from phosphogypsum pretreated at 60, 160, and 800 °C was 53.9%, 56.2%, and 58.6%. As the temperature increased, the different crystallized water states in phosphogypsum were decomposed. The replacement of mineral powder with phosphogypsum can improve the high-temperature properties of asphalt mastic and the percent recovery (R), while the nonrecoverable creep compliance (Jnr) was reduced. At the extremely high-temperature of 70 °C, the improvement of the high-temperature performance of phosphogypsum asphalt mastic is more evident than that of 46 °C. Furthermore, the addition of phosphogypsum also reduced the fatigue life of asphalt mastic. This study is expected to paving the road for the upcycling of waste phosphogypsum as an alternative filler in asphalt pavement.

A Promising Radiation Thermal Protection Coating Based on Lamellar Porous Ca‐Cr co‐Doped Y3NbO7 Ceramic

AbstractDissipation of heat efficiently from a hot object via radiation while minimizing the inward heat conduction is the key requirement of radiation thermal protection. In this study, a Ca‐Cr co‐doped Y3NbO7 coating with lamellar porous structure is fabricated, which shows an ultra‐low thermal conductivity (<0.7 W m−1 K−1) and near‐unity emissivity (>0.9) across a broad wavelength range of ≈1–24 µm. This record high emissivity to thermal conductivity ratio (≈1.3) is experimentally and theoretically revealed from a multi‐scale perspective. The diffusoin‐mediated thermal conduction feature of niobates combined with lamellar porous structure of the coating reduces its thermal conductivity to an impressive 0.5 W m−1 K−1 at 25 °C, surpassing the theoretical amorphous limitation of 0.72 W m−1 K−1. Experiments and FDTD calculation results demonstrate that the intrinsic emissivity dips at shallow extinction wavelengths (1 and 8 µm) and strong phonon‐polariton resonances wavelengths (>13 µm) can be effectively compensated by the multiple scattering/absorption and gradual modulation of conical shape/effective refractive index induced by surface micro‐protrusion structures, respectively. Furthermore, the coating exhibits robust mechanical and thermal stability with a high bonding strength (18.3 MPa) and thermal expansion coefficient (≈11 × 10−6 K−1 at 1200 °C) comparable to YSZ, showing great potential in the radiation thermal protection field.

Hexagonal boron-carbon fullerene heterostructures; Stable two-dimensional semiconductors with remarkable stiffness, low thermal conductivity and flat bands

Among exciting recent advances in the field of two-dimensional (2D) materials, the successful fabrications of the C60 fullerene networks has been a particularly inspiring accomplishment. Motivated by the recent achievements, herein we explore the stability and physical properties of novel hexagonal boron-carbon fullerene 2D heterostructures, on the basis of already synthesized B40 and C36 fullerenes. By performing extensive structural minimizations of diverse atomic configurations using the density functional theory method, for the first time, we could successfully detect thermally and dynamically stable boron-carbon fullerene 2D heterostructures. Density functional theory results confirm that the herein predicted 2D networks exhibit very identical semiconducting electronic natures with topological flat bands. Using the machine learning interatomic potentials, we also investigated the mechanical and thermal transport properties. Despite of different bonding architectures, the room temperature lattice thermal conductivity of the predicted nanoporous fullerene heterostructures was found to range between 4 and 10 W/mK. Boron-carbon fullerene heterostructures are predicted to show anisotropic but also remarkable mechanical properties, with tensile strengths and elastic modulus over 8 and 70 GPa, respectively. This study introduces the possibility of developing a novel class of 2D heterostructures based on the fullerene cages, with attractive electronic, thermal and mechanical features.

Thermal Runaway Behaviors and Kinetics of NCM Lithium-Ion Batteries at Different Heat Dissipation Conditions

The lithium-ion battery (LIB) thermal runaway is triggered by the exothermic reactions between electrode materials and other active substances such as electrolytes. In this study, the effects of ambient temperature and heat transfer coefficient on the thermal responses and chemical kinetic features of LiNi1/3Co1/3/Mn1/3O2/graphite battery thermal runaway at high-temperature abuse conditions are investigated using a validated 2D axisymmetric model. With varied heat transfer coefficients of the LIB, the corresponding runaway, critical, and safety operation zones at different ambient temperatures are quantitatively distinguished. The results reveal that, with increased heat transfer coefficient, the critical ambient temperature, T c, triggering thermal runaway increases. However, T c almost remains 430 K when the heat transfer coefficient is higher than 25 W/(m2K). Additionally, based on the thermal response of LIB, the ambient heat absorption stage, ambient heat dissipation stage, and dramatic heat release stage in thermal runaway are defined. It is found that a higher heat transfer coefficient efficiently causes a shorter ambient heat absorption stage, which is the primary reason for the reduced delay time for the thermal runaway. Further, kinetic analysis is conducted at different heat exchange conditions, and the correlation between LIB thermal responses and the heat release of side reactions in different operation zones is clarified. Specifically, the reactions between the electrolyte and negative/positive electrodes are the most exothermic and most influential of all side reactions, and their influence on the maximum temperatures and runaway delay times is promoted with an elevated heat transfer coefficient.

Traditional vs. Energetic and Perchlorate vs. "Green": A Comparative Study of the Choice of Binders and Oxidising Agents.

The aim of this article is to compare rocket propellants containing a traditional binder (hydroxyl-terminated polybutadiene) and an energetic binder (glycidyl azide polymer), as well as a perchlorate oxidising agent and a "green" one, i.e., ammonium perchlorate and phase-stabilised ammonium nitrate. We have outlined the effects of individual substances on the sensitivity parameters and decomposition temperature of the produced solid propellants. The linear combustion velocity was determined using electrical methods. Heats of combustion for the propellant samples and the thermal decomposition features of the utilised binders were investigated via differential scanning calorimetry (DSC). Activation energy values for the energetic decomposition of the propellants were determined via the Kissinger method, based on DSC measurements at varied heating rates.

Molybdenum disulfide polymeric nanoarchitectures and applications: A review

AbstractThe advent of nanotechnology has escalated the quest for novel 2‐D nanomaterials (NMs) with the capability of surpassing all known advantages of graphene (GN), and more, resulting in the recent discovery of molybdenum disulfide (MoS2). MoS2 is a 2‐D sheet‐like NM, possessing unique layered “sandwich” architecture, in addition to chemical, electronic, and optical features similar to those of GN, thereby expanding their scope of applications for transistors, solar cells, catalysts, sensors, and so on. The embedment of MoS2 inside polymeric substrates (PP, PEG, epoxy, and so on), have resulted in the construction of MoS2 polymer nanoarchitectures exhibiting superior mechanical, thermal, and flame retardant features with multifunctional and versatile applications. Hence, this elucidation discusses recently emerging research activities in MoS2 polymeric nanoarchitectures and multifaceted applications.

Eminence of ferrite particle shapes in stratified nanofluids concerning the melting phenomenon: Lie group and spectral analysis

The current study is being done to determine how the shape factors of NiZnFe2O4 (nickel zinc ferrite) nanosolid particles affect the free convective flow of engine oil (C8H18) based stratified nanofluid over a melting stretchable surface, which play a part in establishing flow patterns and thermal features. NiZn ferrite nanoparticles of needle, platelet, and brick shapes are used to assess the impact of shape factors in the presence of melting phenomena, heat generation/absorption, and viscous dissipation. Optimal solutions are obtained by the spectral local linearization method via Lie group analysis, with an emphasis on residual errors. According to the evaluation, this type of nanofluid is found to have a lower friction factor, entropy, and Bejan number when compared to conventional fluids. In the presence of viscous dissipation, brick-shaped particles are found to have a higher heat transport rate, whereas needle-shaped particles minimize entropy by 58.66%. Suspended ferrite nanoparticles with a melting effect reduce the entropy up to 62.4% and stratified nanofluid with a brick shape has a higher heat transfer rate as compared to ordinary nanofluid. It is also observed that heat absorption produces less heat transport compared to heat generation. This research is found to be useful in many sectors, such as tumor treatments, electromagnetic interfaces (EMI), microwave applications, bone plate surgeries, and aerodynamic extrusion processes.

Engineering novel phenolic foams with lignin extracted from pine wood residues via a new levulinic-acid assisted process

Phenolic foams are typically produced from phenolic resins, using phenol and formaldehyde precursors. Therefore, common phenolic foams are non-sustainable, comprising growing environmental, health, and economic concerns. In this work, lignin extracted from pine wood residues using a “green” levulinic acid-based solvent, was used to partially substitute non-sustainable phenol. The novel engineered foams were systematically compared to foams composed of different types of commercially available technical lignins. Different features were analyzed, such as foam density, microstructure (electron microscopy), surface hydrophilicity (contact angle), chemical grafting (infrared spectroscopy) and mechanical and thermal features. Overall, it was observed that up to 30 wt% of phenol can be substituted by the new type of lignin, without compromising the foam properties. This work provides a new insights on the development of novel lignin-based foams as a very promising sustainable and renewable alternative to petrol-based counterparts.