Synthesis and Thermal Characterization of Solar Salt-Based Phase Change Composites with Graphene Nanoplatelets

Thermal energy storage(TES) systems use solar energy despite its irregular availability and day-night temperature difference.Current work reports the thermal characterizations of solar salt-based phase change composites in the presence of graphene nanoplatelets(GNP).Solar salt(60:40 of NaNO_(3):KNO_(3)) possessing phase transition temperature and melting enthalpy of 221.01℃ and 134.58 kJ/kg is proposed as a phase change material(PCM) for high-temperature solar-based energy storage applications.Thermal conductivity must be improved to make them suitable for widespread applications and to close the gap between the system needs where they are employed.GNP is added at weight concentrations of 0.1%,0.3%,and 0.5% with solar salt using the ball milling method to boost its thermal conductivity.Morphological studies indicated the formation of a uniform surface of GNP on solar salt.FTIR spectrum peaks identified the physical interaction between salt and GNP.Thermal characterization of the composites,such as thermal conductivity,DSC and TGA was carried out for the samples earlier and later 300 thermal cycles.0.5% of GNP has improved the thermal conductivity of salt by 129.67% and after thermal cycling,the enhancement reduced to 125.21% indicating that thermal cycling has a minor impact on thermal conductivity.Phase change temperature decreased by around 2.32% in the presence of0.5% GNP and the latent heat reduced by 4.34% after thermal cycling.TGA thermograms depicted the composites initiated the weight loss at around 550℃ after which it was rapid.After thermal cycling,the weight loss initiated at ~40℃ lower compared to pure salt,which was found to be a minor change.Thermal characterization of solar salt and GNP-based solar salt composites revealed that the composites can be used for enhanced heat transfer in high-temperature solar-based heat transfer and energy storage applications.

Characterization of Failure Mechanisms of Duplex and Graded Thermal Barrier Coatings Exposed to Thermal Shock Test

The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.

Synthesis Characterization Non-isothermal Kinetics of the Thermal Decomposition and Redox Properties Derived from Copper(Ⅱ) Binuclear Coordination Compound of 1,4-Bis-(1'-Phenyl-3'-Methyl-5'-Pyrazolone-4')-1,4-Butanedione

The paper reports the synthetic procedure and character of Copper(II) binuclearcoordination compound of 1,4-bis-(1'-phenyl-3'-methyl-5'-pyrazolone Thenon-isothermal kinetics of thermal decomposition of the complex has been stUdied from the TG-DTGcurves by means of the Achar et al. and Coats-Redfern methods,the most probab1e kinetic equation canbe expressed as dofdtrAe -E / RT * l /(2Q).The corresponding kinetic compensation effect expressions arefound to be lnuA=0. 1794E+0. 1689.The non-isothermal thermal decomposition process of the complex isone-dimensional diffusion.But electrochemical studies of the complex(Cu2L'2)from cyclic voltamrnetriccurves by means of powder microelectrodes technique'',shows one two-electron irreversible process.

Effect of Phenolation, Lignin-Type and Degree of Substitution on the Properties of Lignin-Modified Phenol-Formaldehyde Impregnation Resins: Molecular Weight Distribution, Wetting Behavior, Rheological Properties and Thermal Curing Profiles

Here,the effects of substituting portions of fossil-based phenol in phenol formaldehyde resin by renewable lignin from two different sources are investigated using a factorial screening experimental design.Among the resins consumed by the wood-based industry,phenolics are one of the most important types used for impregnation,coating or gluing purposes.They are prepared by condensing phenol with formaldehyde(PF).One major use of PF is as matrix polymer for decorative laminates in exterior cladding and wet-room applications.Important requirements for such PFs are favorable flow properties(low viscosity),rapid curing behavior(high reactivity)and sufficient self-adhesion capacity(high residual curing potential).Partially substituting phenol in PF with bio-based phenolic co-reagents like lignin modifies the physicochemical properties of the resulting resin.In this study,phenol-formaldehyde formulations were synthesized where either 30%or 50%(in weight)of the phenol monomer were substituted by either sodium lignosulfonate or Kraft lignin.The effect of modifying the lignin material by phenolation before incorporation into the resin synthesis was also investigated.The resins so obtained were characterized by Fourier Transform Infra-Red(FTIR)spectroscopy,Size Exclusion Chromatography(SEC),Differential Scanning Calorimetry(DSC),rheology,and measurements of contact angle and surface tension using the Wilhelmy plate method and drop shape analysis.

Synthesis and Characterization of Hydrogels Based on Potato Starch/Poly(vinyl Alcohol)/N,N′-Methylenebisacrylamide

Several hydrogels were synthesized by free-radical polymerization in an aqueous medium based on potato starch(PS),poly(vinyl alcohol)(PVA),and N,N′-Methylenebisacrylamide(MBAm),being possible to study these hydrogels as a function of the proportion of components incorporated.In this way,the products generated from the synthesis were characterized by swelling and deswelling kinetics,the first swelling being verified with Schott and statistical models,allowing to contrast the proximity between the experimental and theoretical behavior.Additionally,water retention in soil(R%),spectroscopy(FTIR),morphological(SEM),and thermal(TGA and DSC)analysis allowing to know the intrinsic characteristics of the material,increasing in general terms the knowledge of this type of material.In this context,it was possible to verify the characteristics and effectiveness of the synthesis and crosslinking of the main components.The experimental results obtained show that the synthesized hydrogels present representative swellings consistent with kinetic and statistical models,optimal thermal stability depending on the amount of crosslinker,and excellent water retention in environments such as soil,presenting it as an excellent alternative to be used in agro-industrial applications in an eco-friendly way.

Thermomechanical Characterization of Three Soils of Abeche in Chad

The study carried out concerns the valorization of agricultural waste for the development of biosourced materials that can be used as insulation in homes. This article is devoted to the influence of gum arabic on the mechanical and thermal properties of clay soils in the town of Abéché. The mechanical tests were carried out using the CBR press equipped with two devices (bending device and compression device). Thermal property such as thermal conductivity was determined by the hot wire method and thermal resistance was derived by calculation. Thus, the tests were carried out on test pieces made from a mixture of clay and gum arabic in solution. The experimental program includes seven formulations (0%, 2%, 4%, 6%, 8%, 10% and 12%). The results obtained showed that the best flexural and compressive strengths are obtained by using gum arabic with a rate of 8% and a maximum stress of 4.3 MPa. In addition, the thermal results also showed that the thermal conductivity decreases when the percentage of gum arabic increases, which makes it possible to increase the thermal resistance, thus confirming the capacity of gum arabic to provide thermal insulation.

Glycated Hemoglobin HbA1c:Permittivity Experimental Applications with Some Mathematical Concepts,Temperature and Frequency Variations

Diabetes disorder turns smoothly to be a global epidemic disorder and the glycated hemoglobin(HbA1c)starts to be an efficient marker of it.The dielectric spectroscopy on different human normal-and diabetic-blood samples is used to characterize and to estimate the HbA1c concentration.“dc-”and ac-measurement of the complex conductivity in the temperature range from 280 K up to 320 K,and in the frequency range from one Hz up to 32 MHz have been performed.The thermal activation energy,ΔEσ,of dc-electric conductivity lies in the range 95 meV<ΔEσ<115 meV;while the thermal activation energy,ΔEτ,of RBCs relaxation time is aboutΔEτ=140 meV.The experimental data have been modeled by a physical-model and good fittings have been found between calculated and experimental values.The effective number of charges,nG,T,is estimated after Cole and Cole curves.One has found that nG,T increases with both temperature,T,and with the glycation rate GG.This increase may shed some light on an effective and possible way to treat(and to detect)diabetes disorders via eliminating the excess electric charges produced by glycation processes.The present work sheds the light on the possible combination of focused ultrasound with magnetic resonance imaging to study the dielectric-thermal variations of glycated-RBCs,which can lead to very precise and non-invasive monitoring of glycation concentration in vivo and in vitro via magnetic resonance-thermometry.

Preparation and characterization of conducting polymer-coated thermally expandable microspheres

The thermally expandable microspheres（TEMs） were prepared via suspension polymerization with acrylonitrile（AN）, methyl methacrylate（MMA） and methyl acrylate（MA） as monomers and n-hexane as the blowing agent. Meanwhile, a novel type of functional and conductive thermal expandable microsphere was obtained through strongly covering the surface of microsphere by conductive polymers with the mass loading of 1.5%. The optimal conditions to prepare high foaming ratio and equally distributed microcapsules were investigated with AN-MMA-MA in the proportion of 70%/20%/10%（m/m/m）, and 25 wt% of n-hexane in oil phase. The further investigation results showed that the unexpanded TEMs were about 30 μm in diameter and the maximum expansion ratio was nearly 125 times of original volume. The polypyrrole（PPy） was smoothly coated on the surface of the TEMs and the expansion property of PPy-coated TEMs was almost the same as the uncoated TEMs. Moreover, the structure and expanding performance of TEMs and PPy-coated TEMs were characterized by scanning electron microscopy（SEM）, laser particle size analyzer and dilatometer（DIL）.

Multimodal epidermal devices for hydration monitoring

Precise,quantitative in vivo monitoring of hydration levels in the near surface regions of the skin can be useful in preventing skinbased pathologies,and regulating external appearance.Here we introduce multimodal sensors with important capabilities in this context,rendered in soft,ultrathin,‘skin-like’formats with numerous advantages over alternative technologies,including the ability to establish intimate,conformal contact without applied pressure,and to provide spatiotemporally resolved data on both electrical and thermal transport properties from sensitive regions of the skin.Systematic in vitro studies and computational models establish the underlying measurement principles and associated approaches for determination of temperature,thermal conductivity,thermal diffusivity,volumetric heat capacity,and electrical impedance using simple analysis algorithms.Clinical studies on 20 patients subjected to a variety of external stimuli validate the device operation and allow quantitative comparisons of measurement capabilities to those of existing state-of-the-art tools.