Differential Scanning Calorimetric Measurements Research Articles

Experimental study on suppression of thermal runaway propagation of lithium-ion battery by salt hydrate based dry powder extinguishants

To develop the high cooling effect, high fire extinguishing performance, non-conductive and low cost extinguishant for fighting lithium-ion battery (LIB) fire, seven salt hydrates with different amounts of crystal water were systematically studied as the dry powder extinguishants in this work. The results of the differential scanning calorimeter (DSC) measurement demonstrate that the highest endothermic enthalpies of the salt hydrates below 150 °C is larger than 800 kJ kg−1, which can effectively suppress the thermal runaway (TR) propagation between LIBs. Moreover, the heat absorption capacity of the salt hydrate can be enhanced by increasing the reaction entropy, which can be achieved by increasing the crystal water content. The electric breakdown voltages of the salt hydrates were ranged from 4 kV to 60 kV, which are mainly determined by the crystal water content and the melting point. Furthermore, the fire extinguishing performances of the salt hydrates have no obvious relationship with their heat absorption capacities, but are related to their chemical component. This work systematically studied the factors that affect the cooling effect, the fire extinguishing performance and the conductivity of the salt hydrates, which provides an essential basis for developing high performance salt hydrate based dry powder extinguishants in fighting LIB fire.

Hydrogen bond‐reinforced double‐network hydrogels with enhanced mechanical strength: Preparation, characterization and swelling behavior

AbstractRecently, double network (DN) gels with dynamic non‐covalent interaction such as hydrogen bonds has drawn much attention as an innovative material having both high water content and high mechanical strength. Research efforts have identified DN gels as a promising class of materials due to their unique network architecture. These gels comprise two interpenetrating networks formed by different types of polymer. Herein, we report a tough DN hydrogel with high mechanical strength and high swelling ability. The DN gel is synthesized via a two‐step network formation. The first network gel was synthesized via frontal polymerization. Then, the first gel is immersed in an aqueous solution of a second monomer and carrying out a second polymerization in the presence of first network. The spectroscopic analysis and thermal behavior with differential scanning calorimeter measurements corroborated the existence of hydrogen bonds. The mechanical test and microscopic morphology were further explored to explain the strength and high imbibing characteristics. We expect that this facile strategy may explore a dynamic and tunable hydrogel to expand its potential applications in biomedical field.

Stabilizing high-Ni cathodes with gradient surface Ti-enrichment

High-Ni cathodes are being intensely pursued worldwide for electric vehicles and other energy-dense applications due to their high capacity and low cost. However, structural instabilities during electrochemical cycling and when subjected to thermal treatment have been the major issues hindering their practical deployment. We here report a rational design of coating-integrated-into-synthesis protocol for fabricating surface Ti-enriched LiNi0.8Mn0.1Co0.1O2 (NMC811#Ti) material. The coating to intermediates is crucial to obtain high structural ordering, both in the bulk and surface of high-Ni cathodes, and the Ti substitute has a unique tri-valence (Ti3+) in a gradient surface distribution. The simulations of projected density of states in the atomistic understanding further certify significantly enhanced stability of lattice oxygen for the NMC811 through such a Ti3+-based structure reinforcement. Consequently, the NMC811#Ti cathode delivers a high capacity up to 200 mAh g−1 at 0.1 C, along with superior stabilities during air-storage and thermal treatment (up to 297 °C at the fully charged state under differential scanning calorimetric measurements). The corresponding NMC811#Ti||graphite full cell exhibits a desired 83.6 % capacity retention after 1000 cycles at 0.5 C in a voltage range of 2.8–4.3 V. This work demonstrates a delicate surface reinforcement to stabilize high-Ni cathodes for long-life and safe lithium-ion batteries.

Post-annealing in ultra-high vacuum or nitrogen plasma for MoS2 thin films deposited by magnetron sputtering

The thin films of amorphous molybdenum disulfide were deposited at room temperature by magnetron sputtering technique. Post-annealing process in ultra-high vacuum (∼10−8 Pa) or nitrogen plasma environments at the temperatures of 300, 400, 500, and 700 °C have been first proposed to enhance the microstructure and optical properties of MoS2 thin films. The phase transformation of MoS2 thin films from amorphous to polycrystalline was characterized by in situ reflection high-energy electron diffraction during the post-annealing process. The microstructure of MoS2 thin films was also analyzed by Raman spectrum and X-ray diffractometer after the post-annealing process. In addition, the thermal analysis of the differential scanning calorimeter and optical measurement of photoreflectance confirmed the phase transformation of MoS2 thin films. The analysis of photoreflectance also estimated the exciton transition at the bandgap energy of 2.038 eV at 0 K, attributed by the crystalline MoS2 film annealed at 700 °C in ultra-high vacuum. The surface chemical composition of MoS2 thin films has been identified by X-ray photoelectron spectroscopy, but the desulfurization of MoS2 was observed after post-annealing in ultra-high vacuum. Moreover, the preferred orientation of (004) plane in the MoS2 films was performed as the increase in post-annealing temperature.

Mechanical, Rheological, and Heat Seal Properties of 1‐Octene Grafted Low Density Polyethylene Films

AbstractHeat seal and mechanical properties of 1‐octene grafted low density polyethylene films containing various concentrations of Dicumyl peroxide as the initiator and 1‐octene grafting agent is investigated through using experimental measurements. The results of differential scanning calorimeter (DSC) measurements revealed that the melting temperature shifts to higher values and the peak of the DSC curve becomes wider with the increase of 1‐octene concentrations. Thermogravimetric analysis (TGA) revealed a higher thermal stability up to 20 °C for 1‐octene grafted PE compared with neat LDPE alloy. The results of stress–strain measurements revealed that the 1‐octene grafted PE alloys has higher tensile strength in comparison with neat PE alloy and samples containing only DCP initiator. The results of heat seal analysis indicated that both DCP initiator and 1‐octene tended to offer a moderate increase peel strength of PE alloy. DMTA measurements for various grafted PE alloys show a higher damping factor in comparison with neat LDPE alloy. Rheological measurements indicated a higher storage modulus up to 25% and higher complex viscosity for grafted PE samples containing 1‐octene comonomer.

Microstructure and hydrogen storage properties of the Mg2−xYxNi0.9Co0.1 (x = 0, 0.2, 0.3, and 0.4) alloys

Rare earth elements have excellent catalytic effects on improving hydrogen storage properties of the Mg2Ni-based alloys. This study used a small amount of Y to substitute Mg partially in Mg2Ni0.9Co0.1 and characterized and discussed the effects of Y on the solidification and de-/hydrogenation behaviors. The Mg2−xYxNi0.9Co0.1 (x = 0, 0.2, 0.3, and 0.4) hydrogen storage alloys were prepared using a metallurgy method. The phase composition of the alloys was studied using X-ray diffraction (XRD). Additionally, their microstructure and chemical composition were studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The hydrogen absorption and desorption properties of the alloys were studied using pressure-composition isotherms and differential scanning calorimetric (DSC) measurements. The structure of the as-cast Mg2Ni0.9Co0.1 alloy was composed of the peritectic Mg2Ni, eutectic Mg–Mg2Ni, and a small amount of pre-precipitated Mg–Ni–Co ternary phases, and was converted into the Mg2NiH4, Mg2Ni0.9Co0.1H4, and MgH2 phases after hydrogen absorption. Furthermore, the XRD patterns of the alloys showed the MgYNi4 phase and a trace amount of the Y2O3 phase along with the Mg and Mg2Ni phases after the addition of Y. After hydrogen absorption, the phase of the alloys was composed of the Mg2NiH4, MgH2, MgYNi4, YH3, Y2O3, and Mg2NiH0.3 phases. With the increase of Y addition, the area ratios of the peritectic Mg2Ni matrix phase in the Mg2−xYxNi0.9Co0.1 (x = 0, 0.2, 0.3, and 0.4) alloys gradually decreased until they disappeared. However, the eutectic structure gradually increased, and the microstructures of the alloys were obviously refined. The addition of Y improves the activation performance of the alloys. The alloy only needed one cycle of de-/hydrogenation to complete the activation for x = 0.4. The DSC curves showed that the initial dehydrogenation temperatures of Mg2Ni0.9Co0.1 and Mg1.8Y0.2Ni0.9Co0.1 were 200 and 156 °C, respectively. The desorption activation energies of the hydrides of the Mg2Ni0.9Co0.1 and Mg1.8Y0.2Ni0.9Co0.1 alloys calculated using the Kissinger method were 94.7 and 56.5 kJ/mol, respectively. Moreover, the addition of Y reduced the initial desorption temperature of the alloys and improved their kinetic properties.

A comprehensive overview of the performance of polyamide 6 in the consolidation of vegetable-tanned leathers

Sometimes, vegetable-tanned leathers in museums, excavations, libraries, and storehouses deteriorate due to unsuitable environmental conditions that affect their properties. Accordingly, leather becomes weak. This study evaluates some mechanical, chemical, and physical characteristics of vegetable-tanned leather treated with polyamide 6 (PA6). The authors prepared new vegetable-tanned leather samples. PA6 at different concentrations was applied to the aged leather samples. The accelerated heat aging was applied on the new sample (reference before aging) and treated samples (aged untreated sample after treatment with PA6). Analytical techniques used were: test of the mechanical properties (tensile strength and elongation), attenuated total reflectance/Fourier Transform Infrared (ATR/FTIR), differential scanning calorimeter (DSC) measurement, contact angle, and pH measurement. The results proved that the accelerated heat aging affected the properties studied, as it reduced in the mechanical properties, pH value, and contact angle. Treating aged leather samples with PA6 improved all the properties studied. The mechanical properties, pH value, and contact angle of the treated and aged treated samples increased compared to the aged- untreated- sample. FTIR and DSC analysis proved the stability of the treated and aged treated samples compared to the aged untreated sample. The concentration of 2 % of PA6 gave the best concentrations used, and it is recommended to treat fragile vegetable-tanned leather.

Studies on pre-irradiation thermal annealing induced new phase formation in a PADC polymer: The influence of phase transition on heavy ion detection

Stimulation with thermal pulses can realize and manipulate states of matter with emergent structural and electronic phenomena. The transition phases are often non-transient, and the challenge is to understand them as persistent states. Isochronal annealing experiment at annealing temperatures of 130, 140, 150 and 160 °C for 8 h, was conducted on PADC (so-called CR-39) detectors prior to their irradiation to 252Cf source. Reversing the sequence, other detector films were first subjected to 252Cf irradiation and then thermally treated only at 130 °C for 8 h as above. for example, as a standard comparison between both processes: irradiation post-annealing and irradiation pre-annealing. The bulk etch rates were measured by using the weight loss method (WLM) and the fission track diameter method (FTDM). The qualitative impacts of these treatments have been characterized by means of X-ray diffraction, differential scanning calorimetric (DSC) and spectroscopic measurements of FT-IR. Specifically, the dependences of structural, thermal and chemical parameters on the thermal pulses passed through PADC polymer films treated at different annealing temperatures for annealing time 8 h have been measured. The phase transition of the PADC films was found to be dependent on the annealing temperature, in addition, phase transition proved to be clearly formed by increasing the annealing temperature at 130 °C. This paper shows how the well-controlled thermal treatment of the PADC detector can alter its radiation detection thresholds and its detection sensitivity in the near-surface layer of thickness beyond a couple of hundreds of nanometers. This finding is more pronounced for cases of higher annealing temperatures and larger annealing time intervals. The obtained results demonstrate that the heavy ions (with higher ionization rates e.g., fission fragments), are clearly detected in the near-surface layer of the thermally treated PADC.

Microencapsulation of eutectic phase change materials for temperature management of the satellite electronic board

In the present study, microencapsulation of phase change materials (PCMs) has been carried out for effectively managing the temperature of satellite electronic boards. Eutectic fatty acids are chosen as the core material, and melamine–formaldehyde is utilized as the shell material to synthesize microcapsules tailored to meet the specific operating conditions of the electronic board. The synthesized microcapsules are characterized by different analyses. The Fourier transform infrared spectrometer (FTIR) indicates no chemical interactions between the core and shell materials, ensuring the stability of the encapsulation process. Differential scanning calorimeter (DSC) measurements show the highest encapsulation ratio of 73.26% for the core–shell ratio of 2:1. The MPCMs exhibit a well-defined core–shell structure, with a spherical shape and an average diameter of 4.5 µm, as observed through scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses. Furthermore, the practical application of these microencapsulated PCMs (MPCMs) in managing the temperature of the satellite electronic board is explored. At constant electric powers of 4, 6, 8, and 10 W, the microcapsules introduce significant delays in reaching the critical temperature of 55 °C, with delays of 17, 12, 11, and 4.5 min, respectively. Additionally, under pulsed electric power conditions (8 W, 10 min on/80 min off), the maximum temperature with microcapsules reaches 50 °C, while without MPCMs, it reaches a much higher 73 °C. The results of this study demonstrate that the synthesized MPCMs are an effective and promising approach for temperature management of satellite electronic boards.

Guest molecule optimum aggregation hypothesis and optimal concentrations for energy storage from the perspective of hydrate phase change-induced liquid layer

Tetrabutylammonium bromide (TBAB) semi-clathrate hydrate possesses a unique clathrate structure for capturing and sequestering small-molecule gases, such as CH4, H2 and, CO2 and the advantage of phase change energy storage. Elucidating the diversified reactions and determining the optimal phase change characteristics of TBAB hydrate is crucial to discovering and overcoming specific limitations hindering the large-scale applications. In this study, in situ macroscopic visualization, three-dimensional reconstruction via X-ray Computed Tomography, and differential scanning calorimeter measurements were performed to discover, verify, and analyze the distinct characteristics of TBAB hydrate phase change, including phase separation, three-dimensional structure, and thermal effects. The optimal concentration of TBAB hydrate energy storage was found and verified experimentally for the first time. A peculiar liquid layer (liquid-liquid phase separation) caused by hydrate-solution phase separation was observed after multiple formation-dissociation cycles. The liquid layer separated a region that optimized the hydrate phase change. The solutions with different initial concentrations could evolve an optimized phase-change region of the same concentration (37 wt%) via multiple cycles. The region of the same concentration was shown to be the result of optimal aggregation of molecules. In proving the particularity of the concentration in the optimized region, TBAB hydrate dissociation exhibit thermal effects that can be easily ignored (TBAB molecules ionization and ionic bond synthesis), which affected the TBAB hydrate latent heat measurement. Finally, the optimal concentration of TBAB hydrate phase change was determined as 37 ± 1 wt%, and the characteristics of the concentration, including the volume fraction, complete conversion of water molecules and TBAB molecules, and latent heat, were confirmed by the liquid layer. The experimental results obtained for the first time in this study are important guidance for TBAB hydrate in the field of gas capture and energy storage.

In-situ synthesis of AP@Co/BIM composites with improved thermal performance and anti-hygroscopicity

Reducing the hygroscopicity and thermal decomposition temperature of ammonium perchlorate (AP) is of great significance for its application in solid rocket propellants. The AP@Co/BIM composites was prepared in this work by the coordination reaction of benzimidazole (BIM) and Co2+ on the surface of small-size AP (s-AP) particles, which can significantly reduce the hygroscopicity and improve the thermal performance of s-AP. The prepared AP@Co/BIM composites were characterized by scanning electron microscopy, infrared spectroscopy, x-ray diffraction, differential scanning calorimeter, thermogravimetric analysis and contact angle measurement. The results show that a dense and uniform Co/BIM complex is successfully coated on the surface of s-AP particles. Compared with the s-AP, the decomposition peak temperature of AP@Co/BIM decreases by 75.3 °C when the coating content is 25 wt% and its contact angle with water increases by 69.25°. At the same time, the hygroscopicity test shows that the moisture content of s-AP is only 3.2% of the s-AP after being placed at a relative humidity of 88% for 72 h. In addition, the burning rate of AP@Co/BIM based propellant increases by 5.28 mm s−1 compared with that of the s-AP. This study provides a reference for improving the thermal property and reducing the hygroscopicity of s-AP. It also has a certain application prospect in improving the combustion performance of propellants.

Structure of absorbed water in cis-1,4-polyisoprene rubber and its effect on properties of polymers

To investigate the structures of absorbed water in cis-1,4-polyisoprene rubber (IPR) and their effects on the properties of IPR, differential scanning calorimetric (DSC) measurements were performed with heating from 200 K to 298 K. The result shows that the melting point of water and glass transition point of IPR depend on water content. The shift of the melting point indicates that the water exists as nanometer-sized droplets in IPR. The glass transition point of IPR changes with the specific surface area of the water droplets. It is concluded that absorbed water in hydrophobic rubbers affects thermal properties of the rubbers.

Stereoselective Ring-Opening Deacetonation Polymerization of Racemic 2,2,5-Trimethyl-1,3-dioxolan-4-one by Using Homosalen–Aluminum Complexes: A Novel Approach to Isotactic ­Poly(rac-lactic acid)

AbstractA novel approach is reported for the synthesis of the highly isotactic poly(racemic lactic acid) [P(rac-LAA)] from racemic 2,2,5-trimethyl-1,3-dioxolan-4-one by using achiral homosalen–Al catalysts. The polymerization proceeded through two steps: stereoselective ring-opening and deacetonation. The effects of substituents on the homosalen–Al catalyst were clarified regarding the polymerization rates and polydispersity of the obtained P(rac-LAA), but were still unclear regarding the iso-stereoselectivity. The P(rac-LAA) obtained by using an isopropyl-substituted homosalen–Al catalyst showed the highest isotacticity (P m = 0.96), a moderate number-average molecular weight (M n = 6,200), and broad polydispersity (PDI = 2.20). Differential scanning calorimetric measurements indicated that the polymer was semicrystalline with a melting temperature of 156 °C.

In situ emulsion polymerization of poly (vinyl acetate) and asparagus racemosus biopolymer composites for flexible energy storage applications

AbstractPolymer composites reinforced with synthetic materials are losing acceptability due to significant environmental concerns and high costs. Natural fillers are becoming increasingly popular due to their non‐toxicity, lightweight, low energy consumption, and environmental friendliness. In the present work, poly (vinyl acetate) (PVAc) and asparagus racemosus (AR) bio‐composites have been prepared by an in‐situ emulsion polymerization method. The composite films were subsequently examined by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction, atomic force microscopy (AFM), field emission scanning electron microscopy (FE‐SEM), optical microscope, differential scanning calorimeter (DSC), and thermogravimetric analysis. The formation of AR in PVAc composite was confirmed by the characteristic AR band at 3300 cm−1 in FT‐IR spectra. X‐ray diffraction studies showed a shift in the amorphous peak of PVAc/AR composites compared to pure PVAc. The AFM, FE‐SEM, and optical microscopic results revealed the uniform distribution of AR in the polymer matrix. DSC and TGA measurements showed that the glass transition temperature and thermal stability of PVAc increased with the inclusion of bio‐filler. The tensile strength, hardness, dielectric constant and AC conductivity of PVAc were observed to increases with boehmite inclusion, whereas elongation at break is reduced. As a result, environmentally friendly PVAc/AR composites with good mechanical, thermal and electrical properties could be a viable green substitute for energy storage, flexible electronic, and other electrochemical devices.

Preparation and Spectroscopic Characterization of Ternary Inclusion Complexes of Ascorbyl Palmitate and Urea with γ-Cyclodextrin

A three-component inclusion complex of ascorbyl palmitate (ASCP), urea (UR), and γ-cyclodextrin (γCD) with a molar ratio of 1/12 has been prepared for the first time using the evaporation method (EVP method) and the grinding and mixing method (GM method). Also, we investigated changes in the physicochemical properties of the three-component complexes. The powder X-ray diffraction (PXRD) measurements showed ASCP, UR, and γCD characteristic peaks in the physical mixture (PM) (AU (ASCP/UR = 1/12)/γCD = 1/2). In GM (AU (ASCP/UR = 1/12)/γCD = 1/1), new diffraction peaks were observed around 2θ = 7.5° and 16.6°, while characteristic peaks derived from EVP (ASCP/UR = 1/12) were observed at 2θ = 23.4° and 24.9°. On the other hand, new diffraction peaks at 2θ = 7.4° and 16.6° were observed in GM (1/2). In the differential scanning calorimeter (DSC) measurement, an endothermic peak at around 83 °C was observed in the GM (1/1) sample, which is thought to originate from the phase transition of urea from the hexagonal to the tetragonal form. An endothermic peak around 113.9 °C was also observed for EVP (ASCP/UR = 1/12). However, no characteristic phase transition-derived peak or EVP (ASCP/UR = 1/12)-derived endothermic peak was observed in GM (1/2). Near infrared (NIR) spectroscopy of GM (1/2) showed no shift in the peak derived from the CH group of ASCP. The peaks derived from the NH group of UR shifted to the high and low wavenumber sides at 5032 cm−1 and 5108 cm−1 in EVP (ASCP/UR = 1/12). The peak derived from the OH group of γCD shifted, and the peak derived from the OH group of ASCP broadened at GM (1/2). These results suggest that AU (ASCP/UR = 1/12)/γCD prepared by the mixed grinding method formed inclusion complexes at the molar ratio (1/2).

Evaluation of the state of practice asphalt binder and mixture tests for assessing the compatibility of complex asphalt materials

The present study aims to evaluate binder and mixture testing methods for capturing the compatibility of complex asphalt materials consisting of different virgin binder sources, reclaimed asphalt pavement (RAP) materials and recycling agents (RA). Binder evaluation methods include the saturate, aromatic, resin and asphaltene (SARA) fractionation, advanced polymer chromatography (APC) analysis, differential scanning calorimeter (DSC) and rheological measurements. Mixture performance tests include the complex modulus (E*), direct tension cyclic fatigue (DTCF), disk-shaped compact tension (DCT) and semi-circular bending (SCB) fracture tests. The results from the testing and analysis indicate that the rheological characterisation of asphalt binder or mixture may not capture the incompatibility between virgin binder, RAP and RA. Binder DSC analysis as well as mixture fracture tests have shown promise to evaluate the compatibility of complex asphalt materials with different virgin binders, RAP and RA, as well as the effect of incompatibility on mixture performance.

In-Situ Formed Phosphorus Modified Gel Polymer Electrolyte with Good Flame Retardancy and Cycling Stability for Rechargeable Lithium Batteries

The gel polymer electrolyte (GPE) is a promising substitution for traditional liquid electrolytes. However, GPE is still troubled mainly by its sluggish ionic conductivity and inferior interfacial compatibility with electrodes. Herein, a phosphorus-modified GPE was fabricated by in situ incorporation of black phosphorus (BP) nanosheets into a poly(methyl methacrylate) (PMMA) matrix during the self-polymerization of monomers. The developed GPE exhibited high ionic conductivity (1.083 mS·cm–1 at 30 °C), an enhanced Li+ transference number (0.43), and a wide electrochemical stability window (5.2 V vs Li+/Li), while good thermal stability and improved flame retardancy can also be achieved. Differential scanning calorimeter measurements confirmed that the crystallinity of the PMMA matrix was not changed as BP nanosheets were incorporated. Further investigation proved that BP nanosheets contained in PMMA segments effectively immobilized the anions to decrease the coordination number around Li+. As a result, Li+ ion transport through the GPE was facilitated, which promoted the uniform stripping/plating of lithium while cycling the lithium symmetry cell. Based on the phosphorus-modified GPE, the Li|LiFePO4 and Li|LiNi0.5Co0.2Mn0.3O2 batteries and graphite|LiFePO4 soft-package battery exhibited encouraging electrochemical performances and safety properties.

Impact and structure of water in aqueous octanol mixtures: Hz-GHz dielectric relaxation measurements and computer simulations

Temperature (283 ≤ T/K ≤ 323) dependent dielectric relaxation (DR) measurements of aqueous binary mixtures of octanol at three different water mole fractions (XH2O = 0.05, 0.10, 0.20) were performed employing two different frequency windows: 0.00002 ≤ν/MHz≤ 10 and 0.2 ≤ν/GHz≤ 50. In addition, DR measurements were carried out for pure octanol and water saturated octanol at 298 K. All these measurements showed, irrespective of solution temperature, a small decrease of the static dielectric constant (εs) upon addition of water in octanol. Two-step relaxation process with time constants ∼ 3–0.3 ns and ∼ 120–40 ps characterized the measured DR spectra with no signature of bulk water-like DR time constant (∼10 ps). Differential scanning calorimetric (DSC) measurements of octanol + water mixtures reflect only water concentration dependent depression of octanol freezing temperature. Our computer simulations of aqueous octanol mixtures with SPC/E water suggests a dramatic decrease of the average number of water-water H-bonds 〈NHBw-w〉 per water molecule and a spectacular increase of water populations possessing OOO angles distributed over 0°≤θ≤ 60°. Consequently, a negative value for the average tetrahedral order parameter (〈Q〉) and an εs as low as ∼ 2 for water have been predicted. A severe damage to the global tetrahedrality of water in these mixtures has been predicted and the angle distributions corresponding to negative and positive Q values explicitly shown. These simulation results therefore explain the microscopic origin for small effects of water at low mole fractions on εs of octanol + water binary mixtures.

Influence of the particle size on a MnFe(P,Si,B) compound with giant magnetocaloric effect

How the microstructure affects first-order magnetic transitions (FOMT) in materials with giant magnetocaloric effect remains poorly understood. Here, we study the FOMT and giant magnetocaloric effect occurring near room temperature in MnFe0.95P0.575Si0.36B0.065 particles with sizes ranging from 300 μm down to less than 15 μm. While this materials system shows a volume preserving FOMT, large anisotropic lattice discontinuities make it particularly sensitive to particle size. Grinding and sieving may lead up to 80% difference on the isothermal entropy change (ΔS). Differential scanning calorimetric measurements reveal that the decrease in ΔS does not only originate from the broadening of the transition but also involves a sudden drop in latent heat when particles are reduced from 54 μm to 31 μm, a range corresponding to about the average grain size of the bulk (26 μm). Thermal hysteresis is the largest in large particles and decreases when reducing the particle size.

Cassava starch-derived aerogels as biodegradable packaging materials

Biodegradable and natural materials can provide transformational solutions to environmental issues, particularly those associated with ubiquitous fossil-resources-derived conventional polymers like polyolefin thermoplastics and polystyrene foam as packaging materials. Herein, a facile approach is presented for preparing biodegradable and biocompatible lightweight structural scaffolds as an alternative to conventional plastic-based packaging materials. A variable dosage of polyvinyl alcohol (PVA) is used along with cassava starch to govern the structural integrity, mechanical properties, and porosity of resultant aerogels. The incorporation of PVA as a strengthening precursor improved the compressive modulus of starch aerogel from 2.0 to 18.2 MPa. Hydrogen-based interactions between the starch and PVA components, as revealed by infrared spectroscopic and differential scanning calorimetric measurements, extended the structural integrity. The high and regulated porosity of these aerogels furnished significantly low density (0.13–0.21 mg mm−3). A 98.5% of the starch-PVA aerogel is converted to CO2 by the microbial consortia within 23 days, signifying excellent biodegradability of these aerogels. Moreover, cassava starch-PVA aerogel is demonstrated as alternative packing material to conventional non-biodegradable black plastic bags for growing, transporting, and transplanting young plants. The improved thermal stability (<270 °C), low density, good compressive modulus (2.0–18.2 MPa), and excellent biodegradability reveal the potential of starch-based aerogels as excellent alternatives to conventional polyolefin thermoplastics and polymer-foam-based packaging materials.