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Devices of solar water desalination confront many problems including the low thermal properties of phase change materials (PCMs) such as heat transfer, storage of heat capacity, charging and discharging capability. Thus, these properties need to be improved by using a simple and novel procedure. So, incorporation and dispersion of hybrid nano-powders inside PCMs is considered a simple and novel procedure to improve the thermal properties of solar water desalination devices. The present article is focused on incorporating different nano-powders of MWCNTs and Al2O3 inside PCMs to improve the thermal characteristics of solar water desalination applications. Different nano-powders of MWCNTs and Al2O3 have been incorporated as: (i) 1.0 mass% Al2O3, (ii) 1.0 mass% MWCNTs, and (iii) hybrid 1.0 mass% of Al2O3 + 1.0 mass% MWCNTs, inside a constant amount of 250 gm RT-65HC paraffin wax. An innovative prototype was designed and produced to measure the thermal characteristics of solar water desalination devices. Various analyses have been carried out to study the influence of nano-powders scattering on the morphological, microstructural observations, chemical and thermal characteristics, including SEM, XRD, FT-IR, TGA, DSC, thermal conductivity, and infrared thermography. Microstructural observations showed that the excellent dispersion of nano-powders was at hybrid nano-additives of 1.0 mass% MWCNTs + 1.0 mass% Al2O3 inside PCMs. The uniform scattering of hybrid 1.0 mass% MWCNTs + 1.0 mass% Al2O3 inside PCMs assists to eliminate any defects. Finally, thermal characteristics of hybrid nano-additives phase change materials (NAPCMs) were improved specially in thermal stability, latent heat temperature, and thermal conductivity at 89%, 80%, and 32.8%, respectively. [ABSTRACT FROM AUTHOR]

The aim of this study is to design viable eco-friendly adsorbents that may be further employed for detoxifying living organisms or decontaminating polluted waters of heavy metal ions. Here are highlighted some results concerning the surface chemistry modification of pectins via oxidation of apple-fruits with ozone in water, concentrated hydrogen peroxide or ozone in hydrogen peroxide. The quality and quantity of carboxylic and phenolic functional groups on intact and chemically-modified pectins were established by using the Boehm titration method, which has shown that these have increased in all cases—especially for three times when using ozone in hydrogen peroxide. Textural changes in the surface of were determined by scanning electron microscopy (SEM) and adsorption–desorption of nitrogen; by oxidation, both the specific surface area and total volume of pores increase, the most significant one being encountered in the case of the sample oxidized with ozone in hydrogen peroxide (three times and, respectively, four times higher). The thermal behaviour and stability of the oxidized pectins versus intact pectins from apple-fruits was studied by thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA) in both inert (nitrogen) and oxidative (air) atmospheres; the thermal behaviour indicates just slight modifications due to the appearance of carboxylic and phenolic functional groups, while the overall stability was basically not affected. The sorption properties of these materials were investigated for the immobilization of Pb2+ and Hg2+ from aqueous solutions, by measuring the adsorption isotherms; the chemical modification of pectins by oxidation has significantly improved the adsorption capacity. [ABSTRACT FROM AUTHOR]

The research article addresses the effect of multi-wall carbon nanotube (MWCNT) and nano-boron nitride (NBN) hybrid composite powders on thermal properties of the paraffin wax for thermal storage applications. Five different phase change material (PCM) samples were prepared with 100 paraffin wax, 99.5 paraffin wax + 0.5 MWCNT, 99.5 paraffin wax + 0.5 BN, 99 paraffin wax + 0.5 MWCT + 0.5 BN and 98 paraffin wax + 1 MWCNT + 1 BN mass percentage compositions. The size of the secondary particles MWCNT and NBN was assessed using transmission electron microscope (TEM). After PCM preparation, the morphology and distribution of the secondary particles were evaluated using field emission scanning electron microscope (FE-SEM). The phase change of MWCNT and NBN was evaluated using X-ray diffraction (XRD) technique. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and thermal conductivity tests were carried out on the PCMs to assess physical and thermal properties. The results revealed that hybrid nano-composite powders with paraffin wax provide better thermal conductivity of paraffin wax which increased from 0.18 to 0.31 W m−1 K−1. However, the distribution of MWCNT and NBN extended the thermal degradation of paraffin wax and solidification temperature. Increasing the mass % of MWCNT and NBN reduced the melting point of paraffin wax from 64.70 to 62.52 °C. Further, the solidification temperature of paraffin wax increased while increasing the mass % of MWCNT and NBN from 56.01 to 60.13 °C. This research revealed that thermal properties of paraffin wax were significantly increased with the increment of mass % of composite powders (MWCNT and NBN) addition. [ABSTRACT FROM AUTHOR]

In the present study, various properties, viz. physiochemical, rheological, tribological and thermal properties of polyolester (POE) lubricant, a widely used lubricant in household refrigerator compressor, is evaluated by loading it with alumina nanoparticles and also blending it with sesame oil (SESO)—an environment-friendly lubricant and the results are compared in order to visualize the effects. The mass fraction of alumina nanoparticles used is from 0.05 to 0.15% and the blend ratio of sesame oil is from 12.5 to 87.5%. The rheological properties were evaluated for the temperature ranges from 25 to 100 °C. High-frequency reciprocating rig is used to perform tribological studies. The results show that the values of viscosity, viscosity index, flash and fire point enhanced for all the synthesized lubricants with an increase in alumina nanoparticles proportion and the sesame oil ratio in the base POE oil and all of the synthesized lubricants showed Newtonian behaviour as well. The thermal stability (TGA results) of the POE + SESO blend and POE + Al2O3 nanolubricant was found increasing with the increase in the proportion of sesame oil and the alumina nanoparticles in the base POE oil. The contact angle and surface tension of the synthesized lubricants were initially found decreasing with the addition of sesame oil and alumina nanoparticles to the base POE oil and then increased, as the sesame oil and alumina nanoparticles proportion in the base oil approached the maximum limit. Among the POE + Al2O3 nanolubricants, the POE + 0.125%Al2O3 and among the POE + SESO blend 15POE + 25SESO exhibited much better results in tribological studies. The sesame oil-blended POE oil was found less toxic and more biodegradable when compared to the POE + Al2O3 nanolubricant. [ABSTRACT FROM AUTHOR]

Uses of aluminium (Al)-based metal matrix composites (MMCs) have been emerging in variety of applications since several decades. Hence, in the present study, hybrid Al-MMCs were developed using rice husk-extracted highly pure silica (SiO2) and commercial graphite (Grt) as reinforcing materials by powder metallurgical route followed by unique re-sintering. Effect of reinforcements on mechanical as well as thermal properties of Al-MMCs has been determined in this study by various tests. The microscopy, spectroscopy, and X-ray diffraction studies were conducted to characterize the purity and homogeneity of the composites. The hybrid MMCs had shown excellent physical and mechanical properties in terms of surface strength along with being light mass. The Vickers hardness (up to 250 MPa) and compressive strength (up to 341 MPa) of the hybrid nanocomposites has increased significantly on the addition of reinforcements. Thermal properties, including conductivity and linear expansion, were found to be lower for the composites compared to pure Al. Hence, the newly developed rice husk-extracted pure silica and graphite-reinforced hybrid Al-MMCs, particularly the samples of 5SiO2/5Grt/90Al (mass%), can be used as reliable potential materials for several advanced applications including, engine piston, automobile, aviation, and spacecraft components where both mechanical and thermal properties play vital role. [ABSTRACT FROM AUTHOR]

The aim of this work was to improve mechanical properties of a biocomposite of polylactic acid (PLA) reinforcing with fibrillated methacrylate-silanized hemp fibre. The effect of hemp fibre on photo-oxidation and hydrolytic degradation of PLA was evaluated through a QUV accelerated weathering test. Incorporation of 20 mass% fibre filler into neat PLA matrix resulted in increased tensile and flexural modulus for 150% and 200%, respectively. The outdoor degradation of neat PLA and PLA biocomposites was simulated in a 30 days of QUV accelerated weathering test in accordance with ISO 11507 method B. Glass transition temperature (Tg) was periodically recorded to measure the rate of degradation. Differential scanning calorimetry (DSC) analysis indicated that the degradation rate of the PLA matrix of the biocomposites tended to decrease proportionally to exposure time. The statistical regression method revealed a linear relationship between ln(Mn) and lnTg (R2 = 0.96). The 20 mass% hemp/PLA biocomposite was mostly destroyed over neat PLA after 30 days. The rate of degradation tended to have a linear proportion with hemp content. The results of FTIR 13C-NMR analysis confirmed that the substantial degradation of hemp/PLA biocomposites was due to the lignin content of the hemp fibre. The sensitivity of the PLA biocomposite to UVB light and moisture absorption accelerated photo-oxidation and hydrolytic degradation to the lowest molecular weight of PLA. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyse the thermal properties of glazes from the SiO2-Al2O3-CaO-MgO-Na2O system during the addition of zirconium oxide. The paper describes the effect of the addition of zirconium oxide on characteristic temperatures obtained with a high-temperature microscope and a mechanical dilatometer. Based on these data, the course of the logarithm curves of the viscosity of the glazes was determined on the basis of the Vogel–Tamman–Fulcher model. The analysis of thermal effects during the heating and cooling of glazes was also carried out on the basis of measurements made by means of differential scanning calorimetry and analysis of the phase composition at selected temperatures. The obtained results constitute a comprehensive characteristic of the thermal properties of glazes, in which the amount of zirconium oxide increases—from 0 to 24 mass%. [ABSTRACT FROM AUTHOR]

Natural brightness of epoxy adhesives can be reduced by adding cork. Besides, when cork was magnetized, it was possible to move them depending on the properties required in each section of the adhesive bond (PAT354/2019). The main objective of this work was to study possible changes in the thermal properties of the adhesive due to the addition of magnetic cork particles. If changes were significant, the use of magnetic cork particles would be compromised. To this end, natural cork particles and magnetic cork particles, with two different particle size (53–38 and 250–125 μm) and percentage (1 and 5 v/v%), were compared as reinforcement material. Magnetic cork was obtained by co-precipitated coating, according to patent number WO2019025651. The thermal properties studied by Differential Scanning Calorimetry were activation energy of curing reaction, glass transition temperature (Tg) and thermal conductivity. Two different hardeners were studied and a factorial design (2k with k = 4) was carried out. It allowed to determine which variable or combination of variables had most impact on thermal properties. Results showed that the main parameter affecting thermal properties was the hardener, regardless of the kind of particle used. However, the presence of magnetic cork highlights further the differences found between hardeners. The conclusion of this study was that magnetic cork particles can be used as fillers in epoxy resin to make graded joints, since they do not affect the thermal properties of the resin. [ABSTRACT FROM AUTHOR]

Silica nanoparticles were reported that can improve the fire safety and mechanical properties of polymers simultaneously due to excellent rigidity and physical barrier effect. However, its efficiency was limited by the agglomeration in polymers due to their high specific surface energy. Silica@ polydopamine (SiO2@PDA) was prepared by a facile self-polymerization method to comprehensively improve fire safety, thermal stability, and mechanical properties of plant fiber-reinforced polymer (PFRP) composites. The results of micro-morphology confirmed that the SiO2@PDA nanoparticles exhibit better dispersion state in epoxy matrix. The introduction of SiO2@PDA further increased the thermal decomposition temperature and the yield of graphitized char residue of PFRP composites compared to pure silica nanoparticles. And the fire safety of composites including limiting oxygen index, heat parameters, smoke parameters and mass loss rate was improved effectively. Particularly, the time to ignition of composites was delayed by 30 s, which was beneficial for individuality escape and rescue. Meanwhile, the improvement of storage modulus suggested the SiO2@PDA enhanced the mechanical properties of the PFRP composites. And it was proved that PDA can improve the graphitization degree of char layer and release inert gas including NH3 and CO2 during combustion. The effectiveness of non-toxic PDA in enhancing the quality of char layer and optimizing the interface to improve the dispersion state of nanoparticles appeared promising potential in the field of manufacturing fire-safe polymer-matrix composites. [ABSTRACT FROM AUTHOR]

The main objective of this work is to investigate how the addition of the magnesium hydroxide particles affects thermal properties and consequently the mechanism of thermal degradation of polyethylene oxide. With this aim, polyethylene oxide composites, with different composition of magnesium hydroxide particles derived from the sea bittern residual, were prepared via hot melt extrusion. Non-isothermal thermogravimetry in nitrogen atmosphere was utilized, and on gained data, the kinetic analysis was performed. Activation energy, pre-exponential factor and kinetic model were calculated and compared. TG analysis revealed that thermal degradation of composites starts at lower temperatures, which could be an indication of magnesium hydroxide destabilizing effect on polyethylene oxide. Kinetic analysis showed that all composites degrade through three degradation stages. In the first stage, the sample with max load of inorganic particles resulted in the diffusion as the rate-controlling process, while in the second, denoted as the main stage, thermal degradation of all samples proceeded via the same accelerating reaction type. However, at higher mass fraction of inorganic particles, the addition of the magnesium hydroxide particles altered the mechanism of thermal degradation of polyethylene oxide. [ABSTRACT FROM AUTHOR]

Sunset Yellow (E110) is an azoic dye synthetized from aromatic hydrocarbons, which is used to improve the physical–chemical properties of food products and their conservation; its chemical formula is C16H10N2Na2O7S2. Here, in order to characterize this azoic dye in powder and solution form, five spectral techniques were employed: Fourier Transform Infrared (FTIR), UV–Vis, Raman, Laser fluorescence and Terahertz (THz) spectroscopy. The Sunset Yellow's morphology, structure and its chemical composition were studied by scanning electron microscopy (SEM), X-ray diffraction and energy-dispersive X-ray spectroscopy (EDXS). The thermal behaviour of Sunset Yellow was studied in correlation with its physical (refractive index, electric susceptivity, optical anisotropy) and chemical (acidity) properties. Thermal analysis effectuated in air indicates the evaporation of absorbed and physically bonded water up to 188 °C, after which the material possesses thermal stability up to 330 °C. The oxidative decomposition takes place in four exothermic steps of which the strongest between 510 and 643 °C develops a heat of 4519.6 J g−1; at 913 °C, a residue of 31.77% is obtained. The study of optical properties of Sunset Yellow shows that the refractive indexes are decreasing when the temperature of the solution increases. The optical anisotropy of Sunset Yellow was studied under polarized light at room temperature. Sunset Yellow exhibits the phenomenon of birefringence on resulted crystallites by drying and crystallization at RT from aqueous solutions with concentrations of 1% and 5%. THz spectroscopy identified the THz spectral "signature" of Sunset Yellow at a few wavelengths. Sunset Yellow has biophysical properties when interacting with proteins (bovine serum albumin (BSA) and collagen). The biological properties of Sunset Yellow were observed through its antioxidant activity and phytotoxicity; while the antioxidant activity is proportional with increasing its concentration, the phytotoxicity study indicates that the Sunset Yellow does not present wheat (Triticum aestivum) growth phytotoxicity at low concentrations (when treating with aqueous solutions of 0.01–0.05%, it could increase its resistance to drought conditions), but at concentrations of 0.25% or higher, there are negative changes in wheat growth. [ABSTRACT FROM AUTHOR]

The focus of this research was on the thermal conductivity and rheological properties of poly(ethylene glycol) with a molecular mass of 200 g mol−1 (i.e., PEG200) loaded with four different types of multi-walled carbon nanotubes (MWCNTs) in a wide concentration range up to 10 mass%. MWCNTs used differ in size (both diameter and length) and the content of COOH (oxidized) functional groups on their surface. It was found that the use of oxidized, shorter and wider MWCNTs in PEG200 results in highest enhancement in thermal conductivity by 133% for 10 mass% MWCNTs-PEG200 nanofluids. Investigation of the shear rate dependence of dynamic viscosity (η) showed that the use of MWCNTs in concentrations greater than 0.1 mass% changes the Newtonian behavior of PEG200 and results in the shear-thinning behavior. This behavior is strongly influenced by the MWCNT concentration in the nanofluid. When comparing the same nanofluid concentration, the highest degree of MWCNT agglomeration in PEG200 nanofluids was observed when long, thin and pristine MWCNTs were used. The thermal conductivity results were correlated with the most commonly used theoretical models: Maxwell, Hamilton-Crosser, Xue, and Murshed. Dynamic viscosity results were correlated with Einstein, Brinkman, and Brenner-Condiff theoretical models. The best agreement with the experimental results was obtained by the Maxwell and Einstein models, indicating the formation of sphere-like MWCNT agglomerates in each PEG200 nanofluid studied. [ABSTRACT FROM AUTHOR]

Bi doped 2CaO-Al2O3-SiO2 (gehlenite) glasses were prepared by conventional melting. The concentration of Bi3+ was 0, 0.25, 0.50 and 1.50 mol. %. The prepared samples were X-ray amorphous except of the undoped sample and the sample with the highest content of Bi3+, for which XRD records revealed traces of crystalline gehlenite. Differential thermal analysis (DTA) was used to study the thermal properties of prepared glasses, performed in the atmosphere of nitrogen at 5 different heating rates. The DTA records of all studied samples contained only one exothermic effect. Based on the results of XRD analysis, the exothermic effect was attributed to the crystallization of gehlenite. The XRD patterns of all samples measured after DTA analysis contained gehlenite as the main crystalline phase (01–074-164 COD). The DTA records measured at a heating rate of 10 °C.min−1 revealed a significant decrease in the temperatures of maxima of the exothermic peaks (from 982 °C to 943 °C) with the increasing Bi doping. The model approach using the Johnson–Mehl–Avrami-Kolgomorov (JMAK) equations with six different values (1.5, 2, 2.5, 3, 3.5 and 4) of Avrami parameters (m) was used to study crystallization kinetics of gehlenite glasses. The model that best describes the experimental data was found, using the AIC (Akaike criterium) and wAIC (Akaike weight) criteria: A (frequency factor) and Eapp (apparent activation energy) were determined. Based on kinetic parameters values, it is concluded that the nucleation rate is constant. Irrespective of the Bi content, the movement of the growth zone is controlled by diffusion and 3D growth is characteristic for the gehlenite crystals growth. [ABSTRACT FROM AUTHOR]

MXene, a recently created nanomaterial, offers significant potential for thermal, electrical, and a variety of other uses. MXene was utilized to generate heat transfer nanofluids with improved thermophysical properties for thermal applications and to establish the optimal parameters for achieving the best thermal performance. In this study, a palm oil/MXene nanofluid was used as the heat transfer fluid in a circular pipe to evaluate its thermal impact at different Reynolds numbers and applied heat fluxes at a range of introduced MXene nanoparticles' concentrations. Thermal conductivity and viscosity were shown to be linked to temperature and nanoparticle concentrations ranging from 0.01 to 0.1 mass%. The influence of concerted MXene nanoparticles (0.01 to 0.1 mass%) on the behavior of the PO/MXene nanofluid was studied using CFD simulations at various flow Reynolds numbers (2,500–5,000) and wall heat fluxes (40,000–90,000 W.m−2). The results indicate that increasing the nanoparticle concentration resulted in higher heat transfer coefficients and lower Nusselt numbers. MXene nanoparticles were more efficient at lowering the wall temperature and increasing the pace of cooling when applied at larger heat fluxes and lower Re numbers. The results reported in this article indicate that MXene nanomaterials have a strong potential for overcoming the low heat transfer difficulties encountered in heat exchange systems. [ABSTRACT FROM AUTHOR]

In the present study, effect of europium on the structural and thermal properties of iron phosphate glass was studied and compared with that of pristine iron phosphate glass. Europium-loaded iron phosphate glass [composition-3 mass% Eu2O3-97 mass% (40 mol% Fe2O3-60 mol% P2O5)] was synthesized by conventional melt quench technique, and its amorphous nature was ascertained by X-ray diffraction method. The presence of europium in iron phosphate glass lowered the glass stability and glass forming ability of pristine iron phosphate glass. The presence of europium also resulted in lower specific heat capacity and higher thermal expansion. This is due to the depolymerization of glass network connectivity in the presence of europium, which was further confirmed from the Raman spectra. However, the major network linkage is pyrophosphate as that of pure iron phosphate glass. [ABSTRACT FROM AUTHOR]

The structural and thermal properties of sodium niobium phosphate glass are studied to analyse its suitability for immobilizing long-lived radioactive waste from nuclear reprocessing plants. Two series of sodium niobium phosphate glasses such as (A) xNb2O5–(50−x)Na2O–50P2O5 and (B) xNb2O5–(50−x/2)Na2O–(50−x/2) P2O5 (x = 0, 10, 20, 30, 40 mol.%) are prepared by the conventional melt–quenching technique. The influence of the incremental addition of Nb2O5 on the structural and thermal properties of the above two series is investigated. The FTIR and Raman spectra of these glasses revealed that the number of [NbO6] octahedral chain increases with Nb content and dominates as the major structural unit over the number of PO4 tetrahedra unit. The glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) are measured by using a differential scanning calorimeter (DSC). Other thermal stability parameters such as Hruby (KH), Angell (KA), Saad–Poulain (KSP) and Weinberg (KW), the total relaxation time of transformation and fragility are evaluated and compared between different composition of glasses. For both series A and B, the glass transition temperature increases with Nb content, suggesting the formation of a larger number of P–O–Nb or Nb–O–Nb linkages compared to the PO4 tetrahedra, resulting in a more rigid network. This is confirmed by Raman spectra which show an increase in the number of Nb–O–Nb bonds with Nb content. The major crystalline phases formed by devitrifying these glasses are identified by XRD and are found to be mainly NaPO3, NbOPO4, Na2Nb6P4O26 and Na4Nb8P4O32. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the aging of poly(ether-ether-ketone) (PEEK) submitted to different media: in air, in water bubbled with nitrogen, in water bubbled with air, and in water at pH 4, for 90 days at temperatures of 120, 140 and 160 °C. The physical, thermal and mechanical properties of PEEK specimens were evaluated before and after aging. The density measurements showed that the aging conditions employed did not promote water absorption or mass loss; thermogravimetric analyses (TGA) showed that all aging media exerted the same effects on the material's thermal stability, with variation in the initial thermal degradation (Tonset) below 5 °C concerning the unaged polymer. The thermal history obtained by differential scanning calorimetry (DSC) did not show significant variations in thermal transition temperatures in the first heating cycle, indicating that the aging conditions did not cause internal degradation in PEEK samples within the studied period. The degree of crystallinity calculated by X-ray diffractometry (XRD) and DSC demonstrated a slight increase over time due to thermal annealing at temperatures above the Tg of the unaged PEEK. The mechanical properties of the aged PEEK showed low variations in Young's modulus and greater variations in the tension at rupture and elongation at rupture, being more drastic in the aqueous media saturated in air and acid solution. [ABSTRACT FROM AUTHOR]

The crystal structure, magnetic and thermal properties of M-type BaFe11.9In0.1O19-doped hexaferrite were investigated. It was found that the crystal structure of this solid solution has hexagonal symmetry with P63/mmc space group (No 194) and a = 5.8992(1) Å, c = 23.2275(7) Å unit cell parameters. It was determined that the average grain size is d ¯ = 6 μm. The ferromagnetic-paramagnetic phase transition occurs near TC = 420 °C. It was also established that the water steams that react in active centers are shattered on the surface as a result of the solvothermic reaction being in a weak mutual influence on the temperature interval 30 ≤ T ≤ 317 °C. Thermal transitions repeated as the temperature rises to the highest available values have been established. The oxidation behavior was determined using thermogravimetric spectra in a wide temperature range. [ABSTRACT FROM AUTHOR]

Thermal resistance is a very important parameter when assessing the therapeutic usefulness of potential pharmaceutics. Therefore, the thermal behaviour and the decomposition mechanism in the atmosphere of helium and synthetic air of disubstituted fused 1,2,4-triazoles—which may be potential anticancer and antibacterial agents—were studied with a use of simultaneous thermal analysis: thermogravimetry/differential scanning calorimetry (TG/DTG/DSC) coupled online with Fourier transform infrared spectroscopy. It was confirmed that the thermal stability of the tested compounds is directly depended on their structure and thus on the number of chlorine atoms as substituents. The pyrolysis process of disubstituted fused 1,2,4-triazoles in inert conditions runs in two main, non-well-separated stages connected with the emission of NH3, HCN, acetonitrile, aromatics with an OH group, aromatics with a NH2 groups, H2O, CO2 and alkene fragments. However, the thermal stability of those compounds in synthetic air atmosphere is comparable or lower than their thermal stability in helium atmosphere. The decomposition of the tested compounds runs through at least three main stages, resulting in the emission of the same type of volatiles as in inert conditions plus the additional emission of CO and some carbonyl fragments for compounds with no or one chlorine atom as a substituent. The results indicate a simultaneous cleavage of C–N, N–N and C–O bonds during heating of the tested disubstituted fused 1,2,4-triazoles in inert conditions and additional combustion process of pre-formed residues in oxidative conditions. [ABSTRACT FROM AUTHOR]

Natural fibers have emerged as a potential alternate to synthetic fibers, because of their excellent performance, biodegradability, renewability and sustainability. This research has focused on investigating the thermal, visco-elastic and fire-retardant properties of different hybrid Cytostachys Renda (CR)/kenaf fiber (K) (50/0; 35/ 15, 25/25, 15/ 35, 0/50)-reinforced MWCNT (multi-walled carbon nanotubes)-modified phenolic composites. The mass% of MWCNT-modified phenolic resin was maintained 50 mass% including 0.5 mass% of MWCNT. In order to achieve homogeneous dispersion ball milling process was employed to incorporate the MWCNT into phenolic resin (powder). Thermal results from thermogravimetric analysis and differential scanning calorimetric analysis revealed that the hybrid composites (35/15; 35 mass% CR and 15 mass% K) showed higher thermal stability among the composite samples. Visco-elastic results revealed that kenaf fiber-based MWCNT-modified composites (0/50; 0 mass% CR and 50 mass% K) exhibited higher storage and loss modulus due to high modulus kenaf fiber. Fire-retardant analysis (UL-94) showed that all the composite samples met H-B self-extinguishing rating and exhibited slow burning rate according to limiting oxygen index (LOI) test. However, (15/35; 15 mass% CR and 35 mass% K) hybrid composites showed the highest time to ignition, highest fire performance index, lowest total heat release rate, average mass loss rate, average fire growth rate index and maximum average rate of heat emission. Moreover, the smoke density of all hybrid composites was found to be less than 200 which meets the federal aviation regulations (FAR) 25.853d standard. Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was carried out to select an optimal composite sample considering the thermal, visco-elastic and fire-retardant behaviors. Through TOPSIS analysis, the hybrid (15/35; 15 mass% CR and 35 mass% K) composite sample has been selected as an optimal composite which can be used for high-temperature aircraft and automotive applications. [ABSTRACT FROM AUTHOR]

In this study, a series of hydroxyl functionalized styrene acrylate latex particles were prepared using the 2-hydroxyethyl methacrylate (HEMA) monomer as a hydroxyl source via the seeded emulsion polymerization method. The effect of anionic/nonionic surfactant on the morphology and thermal behaviors of the prepared polymer latex particle was studied. The structure and morphology of polymer latex particles were characterized using FT-IR, 1H-NMR, DSC, TGA, DLS, and SEM techniques. The water-soluble HEMA monomer led to homogeneous nucleation, in addition to micellar nucleation observed due to the water-insoluble styrene and butyl acrylate monomers. The unmodified polymer latex particle had a glass transition temperature (Tg) of 7.5 °C. The Tg of hydroxyl functionalized polymer latex particle had 13.9, 14.8, 19.0, and 18.8 °C in the presence of 2.5, 4.0, 6.0, and 10.0 mass % HEMA, respectively. The average particle size was 95.30, 98.30, 115.90, 167.00, and 153.50 nm at the polymer latex content of 0, 2.5, 4.0, 6.0, and 10.0 mass % HEMA, respectively. With the addition of 1.35 mass % NP-40, the particle size of polymer latex increased from 167.00 to 218.50 nm in the presence of 0.9 mass % SLS. The addition of nonionic surfactant NP-40 affected the microstructure of polymer latex film and, consequently, its thermal characteristics. [ABSTRACT FROM AUTHOR]

Ethylene–norbornene copolymers were synthesized in a low-content norbornene window with rac-ethylene-bis(indenyl)zirconiumdichloride (EBI) catalyst to deeply investigate the microstructure of ethylene norbornene and thermal properties of copolymers with the addition of chain shuttling agent (CSA). Copolymers with norbornene content from 3 to 16% were obtained by changing the feed ratio in copolymerization. The melting temperatures (Tm) of the obtained copolymers were between 126.5 and 131 °C depending copolymer content. However, the copolymer with the highest norbornene in feed did not show any melting point and it was shown the glass-transition temperature (Tg) at 63.2 °C. The viscosity average molecular mass (Mv) of the produced copolymers without CSA was between 25,500 and 55,000 g mol−1; however, in the presence of CSA the Mv contents decreased between 6600 and 20,000 g mol−1 depending on CSA contents. The addition of CSA increased the catalyst activity in copolymerization, especially diethylzinc (DEZ) compared to tri isobutyl aluminum (TIBA). 13CNMR exhibited the presence of triads with a norbornene unit isolated between ethylene units or alternated meso-sequences of comonomer s. There were not detected any significant amount of two norbornene (NN) sequences. It was observed that with increasing chain shuttling agent in spite of decreasing norbornene content the heterogeneity of microstructure was increased. The results of thermal separation indicate more dispersion and heterogeneity in the presence of chain transfer agents (CTA). Dynamic mechanical thermal analysis (DMTA) results also indicate that the copolymerization with diethyl zinc, despite reducing the amount of norbornene, has led to the production of heterogeneous blocks in the polyethylene microstructure. [ABSTRACT FROM AUTHOR]

Ionanofluids (INF) are combinations of ionic liquid (IL) and nanoparticles (NP) with superior thermophysical properties. In the present study, measurement of thermophysical profile of IL, 1-ethyl-3-methylimidazolium chloride ([EMiM]Cl) in which Al2O3 NPs are dispersed were undertaken in the temperature range of 303.15–333.15 K. INFs were prepared by dispersing Al2O3 NPs in different mass concentrations of 0.5, 1.0, 2.5, 5.0, and 10%. The results showed that specific heat and thermal conductivity increase with both concentration and temperature. In contrast, the viscosity and density increase with concentration and decrease with temperature rise. The maximum INF thermal conductivity and viscosity enhancements were 21.9% and 77.6% for a mass concentration of 10% compared to IL at 333.15 K and 303.15 K. Electrical conductivity decreases with NP addition and increases linearly with an increment in temperature. Based on the measured results, a correlation for the specific heat, thermal conductivity, and viscosity of INF was proposed. Further, the heat transfer performance of studied INF is theoretically estimated based on the experimental thermophysical properties. Finally, for high-temperature applications methylimidazolium chloride-based INFs can be used as an efficient candidate as primary heat transfer fluid. [ABSTRACT FROM AUTHOR]

Melamine–formaldehyde resin-coated bamboo fiber (MFBF) and ammonium polyphosphate (MFAPP) were prepared, and then flame-retardant polypropylene (PP)/bamboo fiber composites based on MFBF/MFAPP were obtained by melt blending. The water resistance, flame retardant, and thermal properties of the composites were studied. The results show that MFBF and MFAPP have excellent water resistance with the water contact angles 130.85° and 119.78°, respectively. Compared with pure PP, the limit oxygen index (LOI) of the prepared composite increased from 18.5 to 25.5% with the UL-94V-0 rating. The peak heat release rate of the composite decreased from 1011.8 to 344.3 kW·m−2 and the total heat release decreased from 100.6 to 58.8 MJ·m−2. Meanwhile, the total smoke release decreased from 1453.3 to 922.0 m2·m−2. After soaking in 70 °C water for 36 h, the composite still reached the V-0 rating in UL-94 test, demonstrating a good water resistance. This work provides an effective method to improve the water resistance and flame retardancy of PP/bamboo fiber composites. Melamine–formaldehyde resin-coated bamboo fibers (MFBF) and ammonium polyphosphate (MFAPP) were prepared, then flame-retardant PP/BF composites were obtained based on MFBF/MFAPP. The results show that prepared composite exhibited excellent water resistance and flame-retardant properties. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries should continuously be operated at the optimum temperature range 15 ∼ 40 ∘ C for the best performance. Surface temperature monitoring is critical for the safe and efficient operation of the battery. In this study, initially, the electrical parameters of the battery are determined by applying a second-order equivalent circuit model. This model then is integrated with a thermal model based on the temperature dependent behavior of the electrical parameters and the heat generated. The input parameters to the electro-thermal model include the current, the ambient fluid temperature and the output parameters include the terminal voltage, state of charge, cell core temperature and cell surface temperature. In this research, the entropic coefficient and battery thermal parameters have been taken into consideration concurrently, which will lead to both saving plenty of time and cost compared to other methods. The accuracy of the suggested analytical approach for estimating the surface temperature and the amount of heat generation is validated with the pulse-rest tests of an 18,650 cylindrical lithium-ion battery with a nominal capacity of 2600 mAh at three different ambient temperatures and three charge/discharge current rates. The comparison of results indicate that the maximum error of the proposed algorithm is about 0.6 K under a wide range of test conditions. [ABSTRACT FROM AUTHOR]

The influence of four different quantities of niobium (Nb) on some physical and chemical properties of Ni-Ti alloy was examined in this study. Furthermore, the effect of thermal cycling at different temperatures on some thermodynamic parameters was examined. The arc melting technique was conducted for the sample fabrication procedure. Differential scanning calorimetry (DSC) with different heating rates was utilized to investigate the impact of Nb additive on transformation temperatures and some thermal properties of the Ni-Ti-Nb SMAs. Also scanning electron microscopy (SEM) was used to investigate the microstructural properties of samples, and the microhardness of all samples was determined by the Vickers microhardness technique. The transformation temperatures and other thermodynamic parameters, such as; enthalpy change, entropy change, elastic energy, and Gibbs free energy, were decreased by both Nb additive and thermal cycling, however, it increased the temperature hysteresis of the martensitic phase transformation. Nb additive diminished the activation energy, while had an opposite effect on the microhardness of the Ni-Ti-Nb alloy. The corrosion resistance test results also demonstrated that Nb has a positive effect on the biocompatibility improvement in Ni-Ti alloy because it increased the corrosion resistance of the SMAs. [ABSTRACT FROM AUTHOR]

In the present research work, we investigated the effect of loading mass concentrations (0.05%, 0.15%, and 0.25 mass %) and temperature (10–50 °C) on the thermal properties of graphene oxide-ethylene glycol (GO-EG) nanofluids. A two-step approach was adopted to prepare the GO-EG nanofluids with different mass proportions without any surfactant. The thermal kinetic analysis was performed by modulated DSC and TGA. Thermal stability and particle size distribution of the nanofluids were monitored by using UV–visible spectroscopy and dynamic light scattering. The experimental findings on the thermal transport characteristics of the as-prepared nanofluid samples are influenced by loading mass concentration, increasing temperature because of the high relative area of dispersed nanoparticles at higher particle concentration, dispersion quality of nanofluids. The thermal conductivity (TC) of GO-EG nanofluid shows an enhancement of 36.72% for (sample no. 3, i.e., GO 3) and shows a semi-linear dependence profile between temperature and TC, with increasing mass concentration due to the decrease in interfacial thermal resistance between GO and EG. The observed results are in good agreement with previously reported literature and reveal the promising prospect for usage as a state-of-the-art heat transport fluid in the coolant industry. [ABSTRACT FROM AUTHOR]

In this study, Ti-27Ni-19Nb-4Ta and Ti-27Ni-19Nb-4 V (at./%) alloys were produced by arc-melting alloyed. The thermal properties of alloys were investigated by differential scanning calorimeter (DSC). The DSC results showed that the phase transformation temperatures of the Ta-added alloy were significantly higher than the V-added sample. Also, the Ta-added sample showed B19/ → R → B2 phase transformation, while the V-added sample exhibited B19/ → B2 phase transformation in two steps. When TiNiNbTa and TiNiNbV SMAs are compared, it is seen that the Ta-added sample exhibits a better corrosion resistance. In addition, β-Nb phase was found in the dendritic structures of the alloys in scanning electron microscopy-energy-dispersive X-ray spectroscopy(SEM–EDX) analysis. Using the X-ray diffraction(XRD) results, the crystallite size for TiNiNbTa and TiNiNbV samples was found as 33.76 and 46.86 nm, respectively. It was determined that the microhardness of the V-added alloy was much higher than the Ta-added alloy. [ABSTRACT FROM AUTHOR]

In this work, poly(ethylene glycol) (PEG)/boron nitride nanosheets (BNNS) masterbatch was prepared by freeze-drying their ultrasonically homogenized aqueous suspension, followed by melt-mixing with poly(lactic acid) (PLA) to fabricate the nanocomposites. The effect of PEG and BNNS on the crystallization behavior of PLA was investigated. The dynamic mechanical properties, thermal conductivity and thermal stability of the nanocomposites were also evaluated. It was found that, under quiescent conditions, PEG and BNNS had a synergistic effect on accelerating the nonisothermal crystallization of PLA. Unexpectedly, under injection molding conditions, the combination of PEG and BNNS had a negative effect on PLA crystallization. This can be ascribed to the plasticizing effect of PEG, which relaxes the orientation of PLA chains and retards flow-induced crystallization. Dynamic mechanical analysis (DMA) showed that the presence of BNNS enhanced the heat resistance of PLA only when PLA was crystallized, while further incorporation of PEG had a negative effect. Nevertheless, simultaneous use of PEG and BNNS had a synergistic effect on enhancing the thermal conductivity of PLA. [ABSTRACT FROM AUTHOR]

The thin film of nanocomposites was prepared by solution casting methods and characterized by UV–Vis spectra, Raman spectra and scanning electron microscopy (SEM). The optical band gap was determined by Tau plots. The band gap of PVDF was determined with and without BaZrO3 nanoparticles. It could be seen that the band gap decreases from 4.98 to 3.32 eV in the presence of BaZrO3 nanoparticles in PVDF matrix. The Raman study identifies the interacting species with PVDF due to structural change by the addition of BaZrO3 nanoparticles. This helps to understand the potential of new nanocomposites. The structural changes were analyzed by crystallinity, nature of bonds, phase transition from G to B-phase, etc. SEM images represent the change in spherulitic morphology of PVDF by incorporation of BaZrO3 nanoparticles. SEM images are presented the aggregation of BaZrO3 nanoparticles in PVDF matrix causes the generation of larger particles in PVDF chain. DSC supports the crystallization of PVDF nanocomposites upon heating due to the rearrangement of PVDF structure in the presence of BaZrO3 nanoparticles. It is observed that BaZrO3 nanoparticles enrich the structural, thermal and piezoelectric properties due to the change in spherulitic morphology, which creates a large number of micro- to nano-sized pores, increases the β-phase content of the PVDF. [ABSTRACT FROM AUTHOR]

Wood impregnated with a multicomponent mixture of fatty acids as a bio-based phase change material (BPCM) to improve its thermal characteristics was studied. The studied wood/BPCM composites can be used as internal elements in buildings for energy storage. Scots pine and beech sapwood were impregnated with a multicomponent mixture of linoleic acid and coconut oil fatty acids at a ratio of 20:80. Leakage test was conducted and revealed that the maximum leakage for pine and beech were 9 and 8%, respectively. Light microscopy was employed to demonstrate the distribution of the BPCM in the wood structure. Rays in both pine and beech wood served as pathways for impregnation of the BPCM to partly fill the tracheid lumens (pine) and vessels (beech). Thermal characterization of the studied samples employed T-history and DSC methods, concluding that the impregnated wood had significant thermal mass, ability to store excessive energy in terms of latent heat and keep the temperature constant for long time. The specific heat capacity of the impregnated samples was 4–5 J g−1 K−1 i.e., higher than that of the untreated control samples of ca. 2 J g−1 K−1. The thermal conductivity of the samples before and after the impregnation was measured using heat flow meter method and the results showed that the untreated beech wood had higher thermal conductivity compared to pine and the parameter improved when the cell lumens were filled with the BPCM. Scots pine wood with to 80% mass percentage gain (MPG) after impregnation demonstrated an increment in thermal conductivity of 33% while Scots pine and beech with 43 and 38% MPG demonstrated an increase of the conductivity with 8 and 11%, respectively. [ABSTRACT FROM AUTHOR]

This research explores the enhancement of single-slope solar still performance using phase change material (PCM), specifically paraffin, incorporating Al2O3 nanoparticles. The application of paraffin, a PCM, improves energy storage density and maintains a consistent temperature during the phase transition. Adding Al2O3 nanoparticles to the PCM improves its thermal properties, increasing production rates. Three scenarios were tested for comparison: (1) a standalone solar still, (2) a solar still with PCM, and (3) a solar still with PCM containing Al2O3 nanoparticles. The productivity yields for these systems were 0.837 kg, 0.924 kg, and 1.145 kg, respectively. The results indicate a significant improvement in the solar still’s performance upon adding PCM and Al2O3 nanoparticles, yielding a 10.38% increase in daily output and a 36.77% increase in daily distillate compared to the standalone solar still. Optimizing the temperature difference between the water and the glass surface through ideal water spraying conditions also bolstered the distillate production rate. The outcomes from this research suggest that solar distillation plants, which provide an efficient source of clean drinking water, can significantly improve performance and productivity by leveraging the benefits of innovative materials such as nanoparticles. [ABSTRACT FROM AUTHOR]

This study deals with the modification of a predominantly amorphous poly(lactic acid) (PLA) by blending it with a semi-crystalline biopolymer, polyhydroxybutyrate-co-valerate (PHBV), which has a high crystallinity. The blends with different concentrations of PLA and PHBV were compounded with spent coffee grounds (SCGs) and processed by injection moulding. The structural, thermal and mechanical properties of the produced samples were investigated. Particular attention was paid to the effect of the presence of SCG and the concentration of PHBV in the blend on the crystallization kinetics and the heat deflection temperature (HDT). For equimolar blends, only a slight increase in HDT (about 5 °C) was observed, but the addition of PHBV suppressed the cold crystallization of PLA, which otherwise negatively affects the dimensional stability of injection moulded parts. A similar effect, but to a lesser extent, was achieved by adding SCG to the PLA matrix. Thus, it is clear that the material structures of PLA/PHBV blends and composites help to minimize additional shrinkage of the parts and increase their dimensional stability. Due to the co-continuous structure of the symmetric PLA/PHBV blends and the increase in the degree of crystallinity from 36 to 47% by annealing the produced samples, the heat deflection temperature increased from 65 up to 90 °C. [ABSTRACT FROM AUTHOR]

Thermoregulating composites were produced by using a thermoregulating slurry (NPCS) containing nanoencapsulated phase change material (NPCM) from poly(styrene-co-divinylbenzene) as shell and the commercial paraffin Rubitherm®RT27 as core material. These composites were synthesized by using the constitutive water of the slurry as setting water and changing the NPCM/Hemihydrate (NPCM/Hem) mass ratio within 0.0–0.41. It was found that nanoparticles were uniformly dispersed into the gypsum, and the gypsum crystal morphology was tuned by the addition of the slurry. Attending to the thermal properties, these materials can work either as insulating or thermal energy storage materials, decreasing the thermal conductivity up to ~ 50%, whereas the thermal energy storage (TES) capacity is enlarged in a ~ 140%, respect to the pure gypsum, when the maximum NPCM/Hem mass ratio was used. This composite had a latent heat of 30.2 J g−1 and a heat capacity of equivalent 3.5 J g−1 K−1. Composites from a NPCM/Hem mass ratio up to 0.15 satisfied European mechanical standard EN 13,279–1 for gypsum binders and gypsum plasters and all of them, presented a bulk density higher than 0.60 g cm−3. The addition of a 41% in mass of nanocapsules allowed to save 13.5 kWh m−3 and, reducing the CO2 emissions up to 3.4 kg of CO2 per operating cycle. The use of this new material would lead to significant energy and economic savings, as well as a considerable reduction in the emission of polluting gases into the atmosphere. [ABSTRACT FROM AUTHOR]

Reinvestigation of the V2O5–SrO system allowed final confirmation of formation of four compounds of the following stoichiometric formulas: Sr(VO3)2, Sr2V2O7, Sr3(VO4)2 and Sr4V2O9. The results presented permitted solving literature controversies regarding low- and high-temperature polymorphs of strontium metavanadate(V), i.e. Sr(VO3)2-I and Sr(VO3)2-II. The polymorphic transformation of both varieties that crystallize in the orthorhombic system was proved to be reversible and take place at 530 °C. Strontium metavanadate(V) was found to melt incongruently at 670 °C with deposition of solid Sr2V2O7. Both polymorphic forms of Sr(VO3)2 were studied by IR and SEM methods. According to the results of tests using the UV-Vis-DRS method, both polymorphs Sr(VO3)2 belong to the semiconductor class. Thermal stabilities of Sr2V2O7, Sr3(VO4)2 and Sr4V2O9 were verified. The powder diffractogram of Sr4V2O9 was indexed. [ABSTRACT FROM AUTHOR]

The synergistic effect and mechanism of the spherical CoSn(OH)6 (T-CHS) and ammonium polyphosphate (APP) on epoxy resin (EP) were investigated by limiting oxygen index (LOI), vertical combustion test (UL-94), cone calorimeter, tensile machine, thermogravimetric analysis-coupled with a Fourier transform infrared spectrometer (TGA/FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, and Raman spectrometer. The results indicate that when the mass ratio of APP and T-CHS is 5.9:0.1 and 5.5:0.5, respectively, there is a synergistic effect between APP and T-CHS, and the flame retardant EP samples could pass the V-0 level of UL-94 test and their tensile properties have little difference to that of the blank EP. Compared with the blank EP, the total heat release and total smoke production of EP/5.9APP/0.1 T-CHS are decreased by 25% and 26%, respectively. TGA/FTIR results of the EP samples under N2 atmosphere indicate the NH3 production of EP/5.9APP/0.1 T-CHS is decreased by 47% and the CO2 and H2O production is increased by 991% and 210%, respectively, when compared with that of the blank EP. APP and T-CHS show a good synergistic effect on promoting the retention of C, Co, Sn, and N elements in the char residues. The char residues of EP/5.9APP/0.1 T-CHS and EP/5.5APP/0.5 T-CHS samples contain Co3O4, CoO, SnO, SnO2, oxides of phosphorus, and Sn element, which form a more compact physical barrier. [ABSTRACT FROM AUTHOR]

The hydrogels are three-dimensional networks, and commonly, they exhibit a water-swollen structure, utilized as a part of biomedical medicine, where the thermal conduction of hydrogels required to be better understood. In the present article, different models of cellulose-based hydrogels were presented. The thermal aspect shown by the conductivity of the prepared hydrogel systems was measured at the nanoscale by the Fourier method based on the heat flow. On the other hand, different reports of (cellulose fibers/hydrogel) were produced in order to study their effects on the thermal conductivity of hydrogel. The structure, gel fraction, thermal, optical and rheological behaviors were investigated to achieve a better characterization of biohydrogels. This work reveals that the thermal properties of biohydrogels were related to the amount of polymer cellulose and its density; more crosslinking bonds mean a reduction in the average diffusion paths for phonons. The close interface that binds between the cellulosic polymer and the water solvent (H2O) will produce a great impact on the properties of hydrogels, in particular thermal conductivity. The incorporation of more cellulosic fibers will cause angular confinement and fixation of air in the nanoporosities, leading to a decrease in the thermal conductivity (below 0.60 W m−1 K−1). [ABSTRACT FROM AUTHOR]

We dried the orange slices massed 100 ± 0.10 g from the initial moisture content of 6.97 ± 0.02 kg water kgDM−1 to the final moisture ones of 0.12 ± 0.01 kg water kgDM−1 using two different drying methods defined as convective drying at 50, 75, 100, and 125 °C along with microwave drying at eight output power between 90 and 1000 W. In the study, we measured the drying methods' energy consumption and observed that the microwave drying method's energy consumption was very low at high and low powers. Also, we modeled the results using twenty-one different thin-layer drying equations and obtained results closest to experimental data with the modified Henderson and Pabis equation for all powers in microwave drying and all temperatures in convective drying. We calculated both effective moisture diffusivities and activation energy using the drying data. Some thermal properties such as specific heat, thermal conductivity, thermal diffusivity, and thermal effusivity were calculated and recorded to be decreasing in all thermal properties with drying. Also, we measured the color parameters known as L, a, b, C, α°, and ΔE, browning index (BI), whitening index (WI), and vitamin C (ascorbic acid) in the study. We concluded that the most suitable drying method is microwave drying at medium powers of 350 and 500 W by considering both drying and quality parameters. [ABSTRACT FROM AUTHOR]

In recent years, with the adaptation of nanotechnological engineering applications to complex systems, the use of nanofluids with better thermo-physical properties compared to conventional fluids has become widespread. In addition, studies on the preparation techniques of nanofluids, improving their thermal properties and evaluating their thermal performance are increasing. This study presents a review about preparation, evaluating and enhancement of the stability and thermal properties of nanofluids. Furthermore, the recent advances about the thermo-hydraulic, thermodynamic and thermo-economic performances of nanofluids in different types of thermal systems are summarized as well. The stability of nanofluid is a significant factor affecting its applicability. Various techniques have been used in the literature to enhance the stability of nanofluids such as surfactant addition, ultrasonic mixing and pH control. By using nanofluids, the desired thermo-physical properties can be obtained in order to improve the heat transfer property in the system. Some researchers recommend to hybrid nanofluids because of the hybrid effect of two or more particle types they contain. The reviewed literature also indicates that the use of nanofluids instead of conventional working fluids is an effective way to increase the thermo-hydraulic performance of thermal systems. In addition, according to the literature review, minimum entropy generation is an effective way to increase the energy efficiency and improve thermodynamic performance of the thermal system and the use of nanofluids provide a significant reduction in entropy production. [ABSTRACT FROM AUTHOR]

This study proposes to characterize the effect of long-term thermal cycling on transformation temperatures and thermodynamic parameters of polycrystalline CuAlBeCr shape memory alloy. Structural, morphological and thermal characterizations were performed. The samples were submitted up to 1000 cycles using a dual-bath thermal cycler apparatus. The results show that the thermal cycling has a considerable impact on the transformation behavior of the alloy. Up to 500 cycles, the alloy experienced a one-stage reverse martensitic transformation; after this, it was split into two reactions. From 100 cycles, an increase in temperature ranges ( A f - A s ) values of the reverse martensitic transformation was observed, associated with the increase in elastic energy. Our study expands the spectrum of knowledge regarding thermal and structural properties, for CuAlBe system alloys, indicating the thermal cycling conditions to which the alloy must be subjected in order to preserve the characteristics required in a given practical application. [ABSTRACT FROM AUTHOR]

In this study, a series of phase change nanocomposites using microencapsulated phase change material and graphene nanoplatelet (as an additive material) is synthesized to enhance PCM thermal properties. Paraffin as a PCM is encapsulated by melamine–formaldehyde as a shell material via in situ polymerization method. Graphene nanoplatelet as a heat transfer promoter is added among the microencapsulated phase change materials (MPCMs) in different mass fractions to form phase change nanocomposites. By the applied technique, the defect of leakage and the low thermal conductivity of the phase change material can be overcome simultaneously. The experimental measurements show that the thermal conductivity of the PCNs effectively enhances without a significant influence on their phase change enthalpy. The results indicate that when the amount of the graphene nanoplatelets increases, the thermal diffusivity and thermal conductivity enhance. By using 10 mass % graphene nanoplatelets in the PCN, the PCN's thermal diffusivity and thermal conductivity are raised by 93% and 48%, respectively. The DSC results show that the maximum latent heat of the PCNs is 95.97 J g−1 (PCN with 1 mass % of graphene). However, the maximum difference in the latent heat of PCNs with different graphene percentages is less than 4%. Thermal stability experiments show that the PCNs have a stable structure up to 165 °C without damaging the microcapsule shell. The fabricated PCNs, compared to many previous works, have good thermal properties and low cost which can properly be considered in thermal energy storage and thermal management applications. [ABSTRACT FROM AUTHOR]

In the present study, un-densified silica fume was reacted with a 10 M sodium hydroxide solution to produce the sodium silicate gel having a pH of 14. The calorimetry of the reaction was evaluated. The gel was dried to increase its density by almost 35%. Thereafter, the thermogravimetry of the gel was performed at temperatures up to 1000 °C. Except the loss in mass caused by the departure of physical and chemical water at temperatures below 200 °C, no other mass loss process was identified in the gel. The potential applications of the gel as high-temperature lubricants for automotive and metallurgical engineering and as alkaline activator in geopolymer binder were discussed. Since silica fume is a by-product material that do not require heating or grinding and can react with sodium hydroxide solution at ambient temperature, the results suggested potential for enhanced sustainability in the reduction of embodied energy for the production of the materials like high-temperature inorganic lubricant and alkaline activator for geopolymer binder. [ABSTRACT FROM AUTHOR]

A non-invasive sensor equipped with a programmable thermostat has been developed to assess in vivo the heat flow transmitted by conduction from human skin to the sensor thermostat. This device enables the assessment of the thermal properties of a 2 × 2 cm2 skin surface with a thermal penetration depth of 3–4 mm. In this work, we report the thermal magnitudes recorded with this sensor in 6 different areas (temple, hand, abdomen, thigh, wrist and heel) of 6 healthy subjects of different genders and ages, which were measured under resting conditions. Heat flow and equivalent thermal resistance are proportionally related to each other and are highly variable in magnitude and different for each zone. The heat capacity is also different for each zone. The heat flow values varied from 362 ± 17 mW at the temple to 36 ± 12 mW at the heel for the same subject, when the sensor thermostat was set at 26 °C. The equivalent thermal resistance ranged from 23 ± 2 K W−1 in the volar area of the wrist to 52 ± 4 KW−1 in the inner thigh area. The heat capacity varies from 4.8 ± 0.4 J K−1 in the heel to 6.4 ± 0.2 J K−1 in the abdomen. These magnitudes were also assessed over a 2 × 1 cm2 second-degree burn scar in the volar area of the wrist. The scar area had 27.6 and 11.6% lower heat capacity and equivalent thermal resistance, respectively, allowing an increased heat flow in the injured area. This work is a preliminary study of the measurement capacity of this new instrument. [ABSTRACT FROM AUTHOR]

The more efficient and hydrophobic modificated ammonium polyphosphate (M-APP) and charring agent (M-CA) were prepared based on sol–gel method, and they were used in the preparation of water-resistant and flame-retardant polypropylene (PP) composites. The results showed that the contact angles of M-APP and M-CA were 135.11° and 137.89°, respectively. The flame-retardant and thermal properties of the PP composites were also studied. The results showed that the flame retardancy of PP loaded with 30 mass% intumescent flame retardant (M-APP/M-CA = 3:1) was significantly increased. The limiting oxygen index (LOI) reached 36.8% and passed UL-94 V-0. The peak heat release rate and total heat release of the PP composite decreased from 1011.77 to 134.43 kW·m−2 and 100.58 to 6.86 MJ·m−2, respectively. The peak smoke production rate and total smoke release decreased from 0.13 to 0.0056 m2·s−1 and 1453.09 to 74.82 m2·m−2. The PP composite with M-APP/M-CA = 3:1 also exhibited excellent water resistance, and it could still reach UL-94 V-0 after soaking in 70 ℃ water for 168 h. [ABSTRACT FROM AUTHOR]

Examinations of two-component mixtures, namely: triphenylamine + centralite I (TPA + CI) and triphenylamine + akardite II (TPA + AkaII) were carried out using differential scanning calorimetry (DSC), which served to determine phase diagrams. Experimental data were described with NRTL model and eutectic points for both systems were determined. For TPA + CI system, they were equal to xEu,TPA = 0.2899, TEu = 62.9 °C, whereas for TPA + AkaII system they amounted to xEu,TPA = 0.7868, TEu = 117.5 °C. Granules contain mixtures of eutectic composition were obtained. The physicochemical and thermal properties of resultant single base granules were studied. The helium density of both granules was approx. 1.47 g cm−3, the average dynamic force amounted to 0.55–0.60 bar−1 s−1, and the calorific value ranged from 3060 to 3095 J g−1. Both granules should be chemically stable for 10 years of storage at 25 °C; they meet the requirements of STANAG 4582 standard. DSC analysis of decomposition processes was used to determine kinetic parameters and to adjust the chemical reaction model of nth order with autocatalysis (CnB). Reaction order ranged from 2.6 to 3.0, while the activation energy was similar (197–198 kJ mol−1). Based on examination of thermal properties, it was observed that both eutectic mixtures of stabilizers prevent the decomposition reaction more efficiently than the use of individual compounds as stabilizers. [ABSTRACT FROM AUTHOR]

Polymer/clay-based composites were prepared via solution intercalation method using natural clay and poly (ethylene) glycol (PEG4000) as organic dispersed phase. The present work consists of studying the effect of PEG content on the hybrids surface morphology, thermal stability and thermophysical properties. On the other hand, the TGA data and the measured thermophysical properties are, respectively, fitted with a logistic-like laws and virial expansions for different polymer contents. The results showed that the experimental data agree with the proposed theoretical models. Furthermore, the incorporation of the PEG chains into the clay matrix improves both the thermal stability and thermal characteristics of the raw clay. The thermophysical properties data showed that the elaborated hybrid acts as good thermal insulator for polymer contents higher than 2.5 % . Finally, the resulting clay-based composite showed not only interesting characteristics in terms of insulation, but also satisfies both economic and environmental requirements. [ABSTRACT FROM AUTHOR]

A novel smart solid-gel phase change materials (PCMs) with the photoluminescence and thermochromic properties were designed and fabricated in a simple way. In this work, luminescent mesoporous alumina (LMAa) was firstly prepared through pomelo peel bio-template method, which showed a better photoluminescence performance under the condition of 254 nm light. Next, LMAa and thermochromic pigment (TP) were evenly dispersed in the gelled capric–myristic–stearic fatty eutectic (CA-MA-SA) using magnetic stirring method, in which hydroxypropyl cellulose served as gelling agent, CA-MA-SA as good thermal storage PCM, LMAa as excellent fluorescent material, and TP as visible temperature change indicator. Some advanced techniques were introduced to characterize physical, chemical, and thermal properties of composite PCMs. Results showed that the CA-MA-SA/LMAa1.0 displays obvious luminescence under 254 nm UV light, excellent thermochromic ability from off-white to red as rising the ambient temperature from 35 to 45 °C, limited fluidity at 60 °C, suitable phase change temperature around 19.11 °C, high latent heat about 114.3 J g−1, and so on. The ideal shape stability, thermal, photoluminescent, and reversible thermochromic properties of composite PCMs had not only great application prospect in the field of thermal energy storage, but also brought convenience in practical application. [ABSTRACT FROM AUTHOR]

Polyethylene glycol (PEG) is widely used as phase change materials (PCMs). However, the leakage and low thermal conductivity issues restrict its practical application. Herein, a series of novel MWCNTs/HPC/PEG PCMs (named as PCMMHP) have been synthesized by hydroxypropyl cellulose grafting onto PEG for the first time and doping multi-walled carbon nanotubes (MWCNTs). The results indicate that the PCMMHP exhibit excellent shape stability and without leakage keeping warm for an hour at 353.2 K. The melting and freezing enthalpy of the PCMM1HP7 is 134.7 J g−1 and 131.2 J g−1, respectively; and corresponding melting point and crystallization temperature are about 324.9 K and 308.8 K, respectively. The PCMMHP show a good reversible thermal stability after 100 heating/cooling cycles. In addition, adding 4 mass% MWCNTs, the PCMM4HP7 possess a higher thermal conductivity of 0.6019 W m−1 K−1, which is 2.1 times that of the PCMHP without MWCNTs (0.2895 W m−1 K−1) and 1.9 times that of pure PEG (0.3228 W m−1 K−1). In a word, the fabricated PCMMHP is a kind of shape-stabilized PCM and has good latent ability. It will have a broad potential application in thermal energy storage applications. [ABSTRACT FROM AUTHOR]

The knowledge of the thermal properties of textiles is important with regard to their vast applications in most industries. Thermal properties, as one of the physical features of a textile, are influenced by its structural parameters such as thickness, density, and so on. In this study, a new structural model is developed to predict the effective thermal conductivity in knitted spacer fabrics. In the first step, a spacer fabric was considered as a three-layer set. The thermal conductivity of each layer was calculated separately, and then the effective thermal conductivity of fabric was determined based on its structural parameters. The performance of the proposed model was evaluated using spacer fabrics, and the results were compared with those of other models. The results of the new model and the experimental method showed that the most effective parameters involved in thermal conductivity are thickness, porosity and density. A good agreement (with R2 = 0.91) was found between the results of the proposed model and the experimental values. [ABSTRACT FROM AUTHOR]

Metal ions, as common impurities in the crystallization process of explosives, have a significant influence on the crystal quality and performance. The effects of Fe3+, Zn2+, Ca2+ and Na+ ions on the crystallization and thermal properties of octogen (HMX) were studied. And the defect distribution as well as formation process of the explosive crystals doped with the metal ions were analysed. ICP, XPS and an etching method were utilized to characterize the contents and distributions of residual metal ions in the HMX crystals. The effects of the metal ions on the thermal decomposition and phase transition of HMX were obtained based on DSC-TG and in situ XRD. The mechanism of the influence of the metal ions on the crystallization of HMX was also explored. The results showed that the metal ions would change the nucleation growth mode of HMX to form dispersed crystalline HMX. The residual metal ions were mainly adsorbed on the crystal surface and included in the crystal. The metal ions had a significant influence on the thermal properties of HMX, with Ca2+ and Fe3+ inhibiting the thermally induced phase transition of HMX, Na+ promoting the phase transition of HMX, and the effect of Zn2+ on the phase transition of HMX depending on its concentration. The growth mechanism of doped HMX was lamellar stacking, and the metal ions changed the quality of the crystal by hindering the growth step of the HMX crystal. Since the crystal quality is highly related to the thermal performance, the safety of the explosive is affected. [ABSTRACT FROM AUTHOR]