Thermal Behavior Research Articles

Unveiling the untapped potential of Hibiscus Rosa-sinensis lignocellulosic fiber: A multifaceted characterization for advancing sustainable biocomposite applications

In the pursuit of sustainable advancements in bio-inspired fiber reinforced polymer composite materials, the exploration of novel natural fibers has become a focal point of research. This experimental study aims to elucidate the unexplored potential of Hibiscus Rosa-sinensis fiber (HRF) as a versatile reinforcement material for high-performance composites. Through an integrated approach, this research offers a meticulous analysis of the HRF's physico-chemical properties, and single fiber tensile strength. The crystalline structure are revealed by X-ray diffraction (XRD), thermal behavior are characterized through thermo-gravimetric analysis (TGA), and surface morphology has been visualized using field emission scanning electron microscopy (FESEM) studies. From the results, it is found that the HRF contains a cellulose content of 79.50 %, positioning it as a prime bast fiber among its counterparts. This composition is complemented by hemicellulose (10.36 %), lignin (4.62 %), wax (0.84 %), and ash (2.96 %). The Fourier-transform infrared spectroscopy (FTIR) spectra unveils the intricate functional groups present in the fibers. XRD analysis highlights a crystallinity index (CI) of 66.93 %, confirming a well-organized and structured crystalline arrangement. The thermal stability established through TGA underscores HRF's resilience up to 284 °C, presenting it is an optimal reinforcement material for bio-inspired green composites operating within 280 °C. The surface morphology of HRF is examined through FESEM and three-dimensional profiling, showcasing its inherent morphological intricacies. The multidimensional characterization provided herein contributes significantly to the evolving landscape of biocomposite research, fostering a platform for future advancements and innovations in HRF-based composite materials.

Thermal Stability and Thermal Fatigue Resistance Improvement of New High Toughness 5% Cr Hot Working Die Steel

This work developed a new high toughness 5% Cr martensitic hot working die steel (GYDCK-20), which exhibits better thermal stability and thermal fatigue resistance than AISI H13 steel. The concrete study involves: conducting on the evolution of microstructures and mechanical properties of two steels during the 60-hour holding process at 600°C, as well as the thermal fatigue behavior under the cyclic heating-water quenching conditions. The experimental results showed that in the case of ensuring the same initial hardness of two steels (43-43.5 HRC), GYDCK-20 emerged better thermal stability and superior toughness after 60-hour holding process at 600°C. After thermal cycling was increased from 1000 to 2000 times, the average crack length growth rate of GYDCK-20 was 31.8% lower than that of H13 and the maximum crack width growth rate was 35.1% lower than that of H13. It was found that thermal fatigue cracking was dominated by transgranular propagation at lower cycle numbers, while more inclined to propagate along the grain boundaries at higher cycle numbers. The higher toughness of GYDCK-20 steel promotes the dispersion of thermal stress, thereby enhancing the thermal fatigue resistance. It is mainly attributed to the lower V content of GYDCK-20 steel, which reduces the density of large-sized MC primary carbides. On the other hand, the lower Si content promotes the dissolution of cementite particles, and the secondary carbides precipitate in a smaller and uniformly distributed form, which hinders the propagation of thermal fatigue cracks, while also delays the coarsening of the fatigue-adverse phase M23C6 carbides.

Drying temperature effect on the characteristics of cationically polymerized kraft lignin

In this work, the effect of drying temperature (55–130 °C) on the properties of kraft lignin (KL) polymerized with [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride, as a sustainable polymer (KLM) was investigated. KLM exhibited a 3-fold drop in charge density and a 10 % reduction in water solubility. These alterations were found to be associated with both chemical and physical changes determined by NMR and XPS analyses. At 55 °C, chain interactions were predominant due to electrostatic interactions amongst the pMETAC chains with the electronegative atoms present in KL. At 80, 105, and 130 °C drying temperatures, hydrolysis reactions predominated. The KLM polymer possessed, comparatively, a lesser resistance to thermal degradation than KL, and the KLM polymer had a more uniform thermal degradation behavior across the drying temperatures. Glass transition temperature, Tg, was shown to be comparable for KL across the various drying temperatures. KLM, however, showed an increasing trend as drying temperature increased, up to 130 °C, at which point Tg dropped due to KL degradation. Therefore, the drying temperature has a significant impact on the properties of kraft lignin and its cationic polymerized derivative, and it should be carefully selected to minimize the undesired changes in lignin properties.

Enhancement of luminescence and thermal stability in Eu3+-doped K3Y(BO2)6 with Li+ and Na+ co-doping

Eu3+-doped and Li+/Na+ co-doped K3Y(BO2)6 (KYBO) phosphors were synthesized through a microwave-assisted sol–gel method, and their structural and photoluminescent (PL) characteristics were examined. X-ray diffraction (XRD) and Rietveld refinement confirm effective dopant incorporation and preservation of the crystalline structure. Fourier Transform Infrared (FTIR) spectroscopy indicates the maintenance of the borate structure, confirming the structural integrity of the phosphors upon doping. The addition of Li+ and Na+ co-dopants notably enhances luminescent efficiency and thermal stability, making these phosphors promising candidates for solid-state lighting (SSL) applications. PL analysis reveals strong red emission peaks at 612 nm, attributed to the 5Do → 7F2 transition of Eu3+ ions. The study indicates that electric dipole-quadrupole interactions are the primary mechanism for energy migration, with a critical distance of approximately 22.68 Å. This mechanism contributes to concentration quenching at higher doping levels. High temperature PL measurements indicated an activation energy of 0.1389 eV for thermal quenching in the Li+ co-doped sample. Additionally, the Na+ co-doped sample exhibited an abnormal thermal stability behavior, with an even higher activation energy of 0.2536 eV. This suggests that Na+ co-doping significantly enhances the thermal resilience of the phosphor, making it more suitable for high-power light-emitting applications that operate under extreme conditions. CIE chromaticity diagrams highlight the potential for optimizing Eu3+ doping levels, combined with Li+ and Na+ co-doping, to improve luminescent performance and thermal stability for advanced SSL applications.

Exploring the Thermal Behavior of Cu-water and CuO-water Power-law Nanofluids on a Rotating Circular Disc: A Computational Analysis

The current theoretical investigation focuses on the thermal behavior of a power-law nanofluid flow on a rotating circular disc. In which nanofluid is made by taking colloidal suspension of copper (Cu) and copper oxide (CuO) nanoparticles in a base fluid like water. A theoretical investigation is conducted by formulating a mathematical model of a power-law fluid (which exhibits shear thickening and thinning effects) along with the Tiwari and Das model. A similarity transformation is employed to transform the nonlinear partial differential equations (PDEs) into ordinary differential equations (ODEs) and these ODEs are then numerically solved using the shooting technique. The study's findings are analyzed graphically by plotting radial, tangential, and axial velocity profiles, temperature profiles, Nusselt number, and skin friction coefficients to show how various factors affect the fluid's flow and heat transfer. It is revealed that drag force reduces in Cu-water nanofluid as compared to CuO-water nanofluid for all types of fluids (Newtonian, pseudoplastic, and dilatant fluids) and Nusselt number becomes high in Cu-water nanofluid for both Newtonian and dilatant fluids as compared to CuO-water nanofluid but in case of pseudoplastic reverse behavior is observed. Heat transfer rate in Cu-water dilatant and pseudoplastic nanofluids increases up to 20.4% and 12.5% with respect to base fluid and in CuO-water dilatant and pseudoplastic water nanofluids, it increases up to 18.6% and 15.2%.

Studies of Kinetics and Non-Isothermal Decomposition of Synthesized Novel Organic Terpolymer Resin

Abstract: The terpolymer resin 2,4-DHP-4-PAF-III was prepared by condensation of 2,4-dihydroxypropiophenone, 4- pyridylamine and formaldehyde in the presence of 2M hydrochloric acid as a catalyst in the temperature range 125 ± 2 0C for 5 hrs in 3:1:5 molar ratios of reactants. Elemental analysis, FT-IR, and 1H-NMR spectral studies have been carried out to confirm the structure of the resin. The thermal degradation behavior of terpolymer was studied using thermogravimetric analysis (TGA) in air atmosphere at a heating rate of 10 0C/min. Sharp-Wentworth and Freeman-Carroll methods were used to calculate thermal activation energy (Ea), entropy change (∆S), free energy change (∆F), apparent entropy change (S*), frequency factor (Z) and order of reaction (n). Thermal activation energy (Ea) calculated by Sharp-Wentworth (28.81 KJ/mole) method and Freeman-Carroll (29.47 KJ/mole) method are in good agreement.

Abnormal Temperature Dependence of Huang-Rhys Factor and Exciton Recombination Kinetics in CsPbBr3 Perovskite Quantum Dots.

Anomalous thermal behaviors of excitonic luminescence in CsPbBr3 perovskite quantum dots (PQDs) were observed. It is found that the main luminescence peak originated from the excitonic radiative recombination assisted by the longitudinal-optical (LO) phonon, and its integrated intensity first declines as the temperature varies from 10 to 150 K and then turns to increase at ∼160 K, reaching a maximum value at 300 K. A model considering the thermal detrapping and transfer of electrons from a trap level is developed to interpret these abnormal thermal behaviors of the luminescence from the PQDs. On the other hand, the quantum-mechanical multimode Brownian oscillator model was employed to unravel that the Huang-Rhys factor exclusively characterizing the exciton-phonon coupling in the studied CsPbBr3 PQDs decreases from 1.65 at 10 K to 1.31 at 200 K.

Tailoring thermal behavior and luminous performance in LuAG:Ce films via thickness control for high-power laser lighting applications

Tailoring thermal behavior and luminous performance in LuAG:Ce films via thickness control for high-power laser lighting applications

Investigating the Role of TiC Precipitation in Dynamic Recrystallization Behavior of a Novel Ship Steel

This study examines the single‐pass thermal compression behavior of Ti‐bearing ship plate steel across a temperature range of 850–1150 °C and strain rates from 0.01 to 7 s−1, employing the Gleeble‐2000D thermomechanical simulator. It delves into the evolution of TiC precipitation and dynamic recrystallization (DRX), along with the austenite decomposition transformation during hot compression and subsequent cooling. Active dynamic recrystallization commences at deformation temperatures above 1050 °C, facilitated by the diminished pinning pressure of TiC carbides. This leads to the development of fine DRX austenite grains, influenced by an increase in strain rates and a decrease in temperature. Simultaneously, the fraction of TiC dispersions decreases as the deformation temperature increases, yet they maintain a consistent size of 5–10 nm. The refined particle size is attributed to their low interfacial energy with the austenite matrix, determined by the first principle to be 0.21 J m−2. Due to the severe deformation and numerous dispersions, specimens subjected to a thermal deformation regime at 850 °C and a strain rate of 7 s−1 present a peak in hardness, reaching a maximum of 324 HV. The Ti microalloying approach offers pivotal insights into improving the rollability and mechanical characteristics of ship plate steel.

Thermal transport in metal halide perovskites and other third-generation photovoltaic materials

Third-generation photovoltaic materials, including metal halide perovskites (MHPs), colloidal quantum dots (QDs), copper zinc tin sulfide (CZTS), and organic semiconductors, among others, have become attractive in the past two decades. Unlike their first- and second-generation counterparts, these advanced materials boast properties beyond mere photovoltaic performance, such as mechanical flexibility, light weight, and cost-effectiveness. Meanwhile, these materials possess more intricate crystalline structures that aid in understanding and predicting their transport properties. In particular, the distinctive phonon dispersions in MHPs, the layered architecture in quasi-two-dimensional (2D) perovskites, the strong quantum confinement in QDs, and the complex crystal structures interspersed with abundant disorders in quaternary CZTS result in unique and sometimes anomalous thermal transport behaviors. Concurrently, the criticality of thermal management in applications such as photovoltaics, thermoelectrics, light emitting diodes, and photodetection devices has received increased recognition, considering that many of these third-generation photovoltaic materials are not good thermal conductors. Effective thermal management necessitates precise measurement, advanced modeling, and a profound understanding and interpretation of thermal transport properties in these novel materials. In this review, we provide a comprehensive summary of various techniques for measuring thermal transport properties of these materials and discuss the ultralow thermal conductivities of three-dimensional (3D) MHPs, superlattice-like thermal transport in 2D perovskites, and novel thermal transport characteristics inherent in QDs and CZTS. By collecting and comparing the literature-reported results, we offer a thorough discussion on the thermal transport phenomenon in these materials. The collective understanding from the literature in this area, as reviewed in this article, can provide guidance for improving thermal management across a wide spectrum of applications extending beyond photovoltaics.

Degradation of Decabromodiphenyl Ether Dispersed in Poly (Acrylo-Butadiene-Styrene) Using a Rotatory Laboratory Pilot Under UV-Visible Irradiation

The growing volume of plastics derived from electronic waste (e-waste) underscores the imperative for environmentally sustainable strategies for the management of this waste. In light of the paramount importance of this issue, a pilot demonstrator for the decontamination of polymers containing Brominated Flame Retardants (BFRs) has been developed. The objective is to investigate the potential for decontaminating BFR-containing polymers from e-waste via UV-visible irradiation using a rotatory laboratory pilot operating under primary vacuum conditions. This report focuses on binary model blends composed of 90 weight% (wt%) poly(Acrylo-Butadiene-Styrene) (ABS) pellets and 10 wt% Deca-Bromo-Diphenyl Ether (DBDE), which is one of the most toxic BFRs. The efficiency of the irradiation process was evaluated as a function of pellet diameter and irradiation time using Fourier Transform InfraRed spectroscopy (FTIR) and High-Resolution Laser Desorption/Ionization Mass Spectroscopy (HR-LDI-MS). As a consequence, ABS + DBDE achieved a decontamination efficiency of 97% when irradiated with pellets of less than 1 mm in diameter for a period of 4 h. Additionally, the thermal behavior of the irradiated samples was investigated through thermogravimetric analysis and differential scanning calorimetry. It was thus established that the application of UV-visible irradiation had no significant impact on the overall thermal properties of ABS.

Upcycling waste polypropylene with basalt fibre reinforcement enhancing additive manufacturing feedstock for advanced mechanical performance

This research seeks to overcome the printing and processing challenges of using waste polypropylene (PP) reinforced with short basalt fibres, transforming them into upcycled feedstock for additive manufacturing. It introduces an optimised method for producing filaments and 3D printing with these materials, addressing common issues such as adhesion and warpage through innovative techniques while achieving maximum mechanical performance in the resulting composites. Basalt fibre weight fractions of 0 %, 2 %, 5 %, 8 %, 15 %, 30 %, and 50 % were used to reinforce the recycled polypropylene, improving both printability and mechanical properties. The tensile strength reached 53.58 MPa at 15 % fibre content, while the flexural strength peaked at 34.06 MPa with 30 % fibre content, revealing distinct interactions between the fibres and polymer under tensile and flexural loading that were not previously observed. Microstructure, voids, debonding, and dispersion were examined using optical and scanning electron microscopy. Differential Scanning Calorimetry (DSC) was performed to assess the thermal behaviour and crystallinity of the recycled polymer during filament production and printing, revealing slight matrix degradation during these processes. The findings highlight the potential of waste basalt fibre-reinforced PP as a valuable filament feedstock for 3D printing, supporting a circular economy approach to composite manufacturing.

Synthesis and characterization of two asymmetrical 2-cyclohexylsulfenyl-5-alkylsulfenyl[1,3,4]thiadiazoles and study the impact of substituents on the structural features, thermal behavior, and anti-bacterial activity

Regarding the importance of 1,3,4-thiadiazoles due to versatile biological activity and for investigation of the symmetry impact on thermal behavior and antibacterial activity of 2,5-bisalkylsulfenyl[1,3,4]thiadiazole, two new derivatives viz. 2-cyclohexylsulfenyl-5-cyclopentylsulfenyl[1,3,4]thiadiazole and 2-cyclohexylsulfenyl-5-dodecylsulfenyl[1,3,4]thiadiazole, were synthesized through the nucleophilic substitution reaction appropriate alkyl halide with 5-cyclohexyl-3H-[1,3,4]thiadiazole-2-thione in ethanol under reflux conditions. The chemical structure of the products was elucidated by the physical and spectroscopic techniques. After tedious work, the suitable snow-like crystals of 2-cyclohexylsulfenyl-5-dodecylsulfenyl[1,3,4]thiadiazole for single-crystal X-ray diffraction analysis could be isolated from a mixed solvent, namely ethanol and water in volume ratio of 9:1. Then, the influence of symmetry and cyclic or non-cyclic aliphatic substituents on the important structure parameters of the 2,5-bisalkylsulfenyl[1,3,4]thiadiazole derivatives were negligible, however, those structure characteristics were different for 5–cyclohexylsulfenyl–3H–[1,3,4]thiadiazole–2–thione, due to its thione structure. TGA/DTA study demonstrated the effect of the symmetry and van der Waals interaction on thermal stability, and the robust influence of the pseudo hydrogen bonding NH with C = S on the melting and crystallization phase transitions was revealed by DSC analysis. The pharmacokinetics, drug-likeness, medicinal chemistry friendliness, and toxicology of three derivatives of bis-alkylsulfenyl[1,3,4]thiadiazole were evaluated by two prediction tools of SwissADME and T.E.S.T tools predicted good pharmacokinetics, drug-likeness, and anti-toxicant properties in developmental toxicity for the bis-alkylsulfenyl[1,3,4]thiadiazoles and 5–cyclohexylsulfenyl–3H–[1,3,4]thiadiazole–2–thione. Finally, the in vitro antibacterial activity of two new 2-cyclohexylsulfenyl-5-cyclopentylsulfenyl[1,3,4]thiadiazole and 2-cyclohexylsulfenyl-5-dodecylsulfenyl[1,3,4]thiadiazole against S. aureus and E. coli, confirmed them as promising anti-bacterial agent. All obtained results proved that the physicochemical, thermal, pharmacokinetic, and biological properties of 2,5-bisalkylsulfenyl[1,3,4]thiadiazoles can be tuned by selecting appropriate substituents.

A Numerical Study of the Effect of Graphene Nanoparticle Size on Brownian Displacement, Thermophoresis, and Thermal Performance of Graphene/Water Nanofluid by Molecular Dynamics Simulation

Brownian motion, often known as BM, is an inherent characteristic of minute particles suspended in a fluid. It plays an important role in several physical and chemical processes. Thermophoresis refers to the process where particles in a fluid are carried along with a gradient in temperature (Temp). This feature has significant importance in several applications, including microfluidics, thermal control, and energy conversion. Through the examination of the thermophoresis phenomenon in water/graphene nanofluid (NF), researchers might get valuable knowledge on the potential uses of these materials. The current study examined the effect of various sizes of graphene nanoparticles (NPs) (5, 6, 9, and 10 Å) on the thermal behavior (TB), BM, and thermophoresis of water/graphene NF using molecular dynamics (MD) simulation. This study reported the changes in heat flux (HF), thermal conductivity (TC), average Brownian displacement (BD), and thermophoresis. It is concluded that by increasing the size of graphene NPs from 5 to 10 Å, the average BD and thermophoresis increased from 3.06 Å and 23.88 Å to 4.16 Å and 31.46 Å, respectively. Due to their higher kinetic energy (KE) and momentum, larger graphene NPs experienced more BM, enabling them to withstand random thermal fluctuations more effectively than smaller particles. In addition, as the size of graphene NPs increased, the HF and TC values ​​increased from 39.54 W/m2 and 0.36 W/(m.K) to 47.19 W/m2 and 0.51 W/(m.K) after 10 ns. Therefore, the size-dependent changes in BD and thermophoretic effects led to a simultaneous increase in HF and TC of the NF, which was attributed to the larger heat transfer (HT) surface area, improved HT properties, and synergistic effects of larger graphene NPs. The maximum (Max) Temp increased from 1415 K to 1504 K. These findings were useful in a variety of industries, particularly for improving TB in different NFs.

Additive manufacturing of polyamide 12 bulk structures using directed energy deposition with a thulium laser: Effect of process conditions on morphology and mechanical performance

Laser-based directed energy deposition of polymers (DED-LB/P) is a highly flexible additive manufacturing process capable of fabricating three-dimensional structures with a high degree of customization on free-form surfaces. In this article, the manufacturability of polyamide 12 bulk structures using DED-LB/P in combination with a thulium laser operating at a wavelength of 1.94 μm is investigated for the first time. The typical absorption bands at this wavelength eliminate the need for additives such as carbon-based nanoparticles, which would limit the range of applications. The generated structures were analyzed regarding porosity, thermal behavior, and mechanical properties to evaluate the potential of DED-LB/P with a thulium laser. As a consequence of the evaporation of absorbed moisture or ethanol residues resulting from powder preparation, a thermal pretreatment of the polymer powder reduced the porosity of the DED-LB/P structures to 0.9%. Depending on the processing parameters, the crystallinity of the produced structures ranged from 25.6% to 29.9%. For the tensile tests, the required geometries were milled from the DED-LB/P bulk structures. The results show that an ultimate tensile strength of up to 52 MPa, an elongation at break of up to 58%, and Young's modulus of up to 1590 MPa can be achieved. These remarkable mechanical properties are primarily attributed to the complete melting of the powder particles in DED-LB/P and the improved surface quality resulting from the milling process.

Mechanical, thermal, and water absorption properties of HDPE/barley straw composites incorporating waste rubber

This study investigates the mechanical, thermal, and water absorption properties of high-density polyethylene (HDPE) composites filled with barley straw and varying amounts of waste rubber. The research aims to develop sustainable materials that repurpose agricultural and industrial waste while addressing resource scarcity and waste management challenges. Composites were prepared using a twin-rotor mixer and hydraulic press, with waste rubber content varying from 0 to 20 wt%. Mechanical properties were evaluated through tensile testing, thermal behavior was analyzed using TGA, DTG, and DSC, and long-term water absorption was measured. Results show that increasing waste rubber content from 0 to 20% led to a decrease in tensile strength (11.3 to 8.9 MPa) and tensile modulus (1760 to 790 MPa), while relative extension increased (2.4–5.9%). Thermal analysis revealed a slight reduction in onset degradation temperature (270 °C to 240 °C) and increased char residue (8–18%) with higher rubber content. Water absorption decreased significantly, from 12 to 13% to 6–7% after 600 h of immersion, as waste rubber content increased. These findings demonstrate that incorporating waste rubber into HDPE/barley straw composites results in materials with enhanced flexibility and water resistance at the cost of some strength and stiffness. In conclusion, the results of this study offer a clear pathway for the development of sustainable polymer composites that have broad potential applications across industries like construction, marine infrastructure, automotive, and packaging. By replacing traditional, resource-intensive materials with eco-friendly alternatives, these composites not only provide functional benefits but also support global efforts toward sustainable development and environmental conservation.

O-carboxymethylchitosan hydrogel loaded with dexamethasone for intraocular use

This study aimed to develop hydrogels from carboxymethyl chitosan (CMC), and carboxymethyl chitosan (CMC) with dexamethasone (DEX) for intraocular application, aiming to provide structural stability to the eye and attenuation of inflammatory processes. CMC hydrogels were prepared at concentrations of 0.5%, 1% and 2% (w/v) and incorporated with 10% (v/v) DEX. The samples were characterized by FT-IR spectroscopic, thermogravimetric analysis, injectability, rheology, and cytotoxicity. The results showed that the incorporation of DEX did not significantly alter the absorption bands and thermal behavior of the CMQ hydrogels. Injectability tests revealed that hydrogels with DEX require injection force similar to the commercial material. In rheological tests, pseudoplastic and linear viscoelastic behavior was identified. Cytotoxicity tests confirmed the biocompatibility of the hydrogels. These results demonstrate that the developed hydrogels have properties suitable for biomedical applications, especially aimed at the ophthalmological context.

Design and Modulation of Negative Thermal Expansion for Epoxy Polymers.

Modulating the coefficient of thermal expansion (CTE) and realizing low or negative thermal expansion (NTE) for epoxy polymers are challenging issues. In this study, we developed an effective strategy to prepare epoxy polymers with an NTE performance. A novel motif DBCOD-NH2 based on the dibenzocyclooctadiene (DBCOD) was designed, synthesized, and utilized as a curing agent for several commercial epoxy resins. DBCOD-NH2 suppressed the thermal expansion of the epoxy polymer due to the conformational transition of DBCOD from boat to chair, resulting in low or negative CTE. The AFG90-based polymer showed the most significant thermal contraction behavior (-43.6 ppm/K, 40-80 °C) in the glassy state due to the high DBCOD content, chain rigidity, and cross-link density, which resulted from the high epoxy values, rigidity, and functionality of AFG90 resins. The structure-property interactions were examined and applied to modulate the NTE of epoxy polymers. Our findings are useful for the regulation of thermal expansion and the preparation of materials with desired CTE values.

Temporal and spatial use of a freshwater lake by upstream and downstream migrating adult Atlantic salmon Salmo salar.

Atlantic salmon Salmo salar typically enter fresh water several months prior to spawning and just as pools can provide areas of refuge in river systems, lakes may also provide important refuge habitat during the spawning migration. Using acoustic telemetry we examined the spatial and temporal movements of wild and a ranched strain of Atlantic salmon in a freshwater lake where the main spawning areas were located upstream of the lake. Over the study period (2011-2014), returning adult wild salmon spent an average of 228 days in fresh water and 90% of that time in the lake. On entering the lake, most wild salmon moved quickly to the northern part of the lake, close to the main inflow, spending an average 76% of the time in this location. The average number of days wild fish were absent from the lake during the main spawning period varied between years, ranging from 10 to 26 days for females and 32 to 35 days for males. Seventy four per cent (17/23) of salmon spawners returned to the lake and two salmon subsequently died in the lake post-spawning. Atypically, two salmon were resident in the lake for the whole period in 2013/14. During the study, wild salmon were detected at depths within the top 5 m for 73% of the time. Median depths post-spawning were greater than in the pre-spawning period, when salmon were found to spend extensive periods at depths in excess of 10 m. In July 2013, when the lake was stratified, thermal regulation behaviour was observed in wild salmon, whereby salmon moved to cooler deeper water when water temperatures at 1 m exceeded 20°C. In contrast to wild salmon, the majority of ranch salmon returned to the traps downstream of the lake prior to the spawning period, which would be expected as they were released as smolts below the freshwater lake. Ranch fish spent an average 80% of the time in the vicinity of receivers in the south of the lake and an average 98% of the time within the top 5 m. However, two ranch females were resident in the lake until the following spring and one ranch female moved upstream into the river during the spawning period. Clearly, in this catchment the lake provides an important habitat for migrating adult salmon. In the context of climate change, where thermal and hydrological regimes in rivers are expected to change in response to changes in air temperature and precipitation patterns, the availability of deep lakes that stratify in the summer and cool water refuges in river systems is likely to play a key role in the sustenance and conservation of salmonid species. Information about the migration patterns of Atlantic salmon in undisturbed freshwater systems may also assist in resolving issues associated with fish passage in impacted rivers and inform management decisions.

The effect of NaY‐zeolite on mechanical, thermal, and spectroscopic behavior of crosslinked polyvinyl alcohol films

AbstractThe effects of sodium y zeolite (NaY‐zeolite) on crosslinked Polyvinyl alcohol (CrPVA) composite films were investigated. The spectroscopic analysis showed that crosslinks were formed between PVA, Tartaric acid (TA), and NaY‐zeolite particles. The thermal stability of the CrPVA film was improved with the addition of zeolite. Optimum thermal stability was observed for 5 wt % zeolite content. It can be seen that the mechanical properties also improved for 5 wt % zeolite‐doped CrPVA composite films when compared with CrPVA. It was observed that Young's modulus increased 54.14 to 74.49 MPa. While the degree of crystallinity of the composite film decreased from 20.42 to 14.77% due to zeolite content. This is thought to be due to the increase in the structure's crosslinking rate. The utilization of TA and NaY zeolite in membrane applications may be considered an advantage for improving the mechanical characteristics and the recyclability of membrane technology.