DSC Curves Research Articles

Study on combustion characteristics and pyrotechnic cutting effects of bimetal thermite Ni/Al/Fe2O3 system

AbstractNano‐thermite has become a subject of significant interest in the composite energetic materials field due to its high energy release rate. To cater to diverse engineering needs, thermite formulations are often customized to fulfill specific criteria. This study investigates the potential of metal nickel (Ni) as an additive to modify nano‐thermite formulations, selected for its optimal calorific values and chemical reactivity. The base materials, nano‐aluminum (Al) and iron oxide (Fe2O3), are blended with varying mass ratios of Ni (1 %, 3 %, 5 %, 7 %, 9 %) using the wet ball milling method. Pre‐reaction and post‐reaction morphological and compositional alterations in the resultant thermite samples are scrutinized through SEM and XRD characterization tests. Moreover, DSC analysis and combustion experiments were conducted to examine the pyrolysis and combustion behaviors of the evaluated samples. The results reveal a reduced exothermic peak on the DSC curves with the introduction of Ni, making the liquid‐solid (L‐S) phase reaction more challenging compared to the Al/Fe2O3 thermite. Intriguingly, Ni addition progressively decreases the combustion temperature of thermites as the Ni's mass ratio increases, with a peak efficiency at 7 % in the perforation tests on stainless‐steel plates. This research further reveals that the thermite reaction mechanism is a combined consequence of the “pre‐ignition‐fusion” and “fusion‐diffusion” mechanisms. These insights can provide valuable guidance for designing thermite formulations for potential applications in storage, management, and pyrotechnic cutting areas.

Determination of Wax Deposition Rate Model of Blended Oils with Different Blending Ratios

Blending with light oil is a commonly used and reliable method of crude oil transportation, and the blending ratio is a crucial operating parameter in determining the safe and efficient operation of the pipeline. In this paper, in-house flow and deposition experiments are used to evaluate the flow and deposition characteristics of crude oils with varying blending ratios. The results show that (1) blending with light oil basically does not affect the shape of the DSC curve of crude oil; (2) blending with light oil will not eliminate the thermal treatment effect, and the mixed oil flowability still remains highly dependent on the thermal treatment temperature; (3) blending with light oil can greatly decrease the abnormal point and oil viscosity, in which the low-temperature viscosity decreases more significantly; and (4) a wax deposition model of mixed oil is obtained through the fitting of Huang’s model, where the blending ratio is a crucial factor in the determination of the model parameters k, m, and n.

A thermochromic salicylaldehyde Schiff bases derivative with AIE properties due to twisted structure

Great attention has been attracted to the salicylaldehyde Schiff base due to its thermochromic and photochromic characteristics in the solid state. However, the boundary between photochromic and thermochromic salicylaldehyde Schiff base structures is still unclear, and few studies have been conducted to investigate their thermochromic behavior and structures in depth and systematically. In the present work, we have synthesized a novel salicylaldehyde Schiff base derivative (2,2′-((1E,1′E)-((2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)-bis(azaneylylidene))bis(methaneylylidene))diphenol, BTB) with twisted structure, which possesses both thermochromic and aggregation-induced emission (AIE) characteristics, and systematically investigated its thermochromic properties, enol-keto isomerization, AIE properties, aggregated state, and excited state intramolecular proton transfer (ESIPT) process. Interestingly, in our study, we found that the color of the BTB molecule changed gradually during the heating process, and it can be found that the thermochromism of BTB is produced by the reversible equilibrium shift of the enol form and the keto forms due to the temperature change by the color difference test, the in-situ IR spectra and the DSC curves. Finally, the pathway of BTB proton transfer was analyzed through quantum chemical calculations, and it was found that enol ketone isomerization is achieved through single excited state intramolecular proton transfer, rather than the expected double excited state intramolecular proton transfer.

Syntheses of high molecular mass polyglycolides via ring‐opening polymerization with simultaneous polycondensation (ROPPOC) by means of tin and zinc catalysts

AbstractGlycolide was polymerized in bulk by means of four different ROPPOC catalysts: tin(II) 2‐ethylhexanoate (SnOct2), dibutyltin bis(pentafluoro‐phenoxide) (BuSnOPF), zinc biscaproate (ZnCap), and zinc bis(pentafluoro‐phenyl sulfide) (ZnSPF). The temperature was varied between 110 and 180°C and the time between 3 h and 7 days. For the few polyglycolides (PGAs) that were soluble extremely high molecular masses were obtained. The MALDI TOF mass spectra had all a low signal‐to‐noise ration and displayed the peaks of cyclic PGAs with a “saw‐tooth pattern” indicating formation of extended‐ring crystallites in the mass range below m/z 2500. The shape of DSC curves varied considerably with catalyst and reaction conditions, whereas the long‐distance values measured by SAXS were small and varied little with the polymerization conditions.

Influence of foaming-induced crystallization behavior on the structure of poly(butylene adipate-co-terephthalate) supercritical foamed beads

The crystallization behavior during foaming directly affects the foaming properties. For crystalline polymers, there is no consensus on the influence of the crystallization behavior during foaming process on the stabilization of the cell structure. In this work, PBAT foamed bead and unfoamed pellets were prepared by controlling the saturated temperatures in supercritical CO2, soaking step (one or two) and the depressurization rate, respectively. Double melting peaks were observed in the DSC curve of supercritical CO2 foamed PBAT beads. By comparing the outgassing rates we find that the stretching-induced crystallization caused by the rapid expansion of the gas during foaming plays an important role in the stabilization of the cells. Although the crystalline perfection or crystal size at this time is much smaller than that of the crystalline grains formed during static cooling, the rapid crystallization is effective in stabilizing the cell structure of the foamed pores. Compared to normal supercritical foaming processes, the two-step foaming process of soaking CO2 at high temperatures followed by foaming at low temperatures results in an increase in cell size and expansion ratio. At high temperatures, more CO2 diffuses into the PBAT pellets, increasing the instantaneous gas concentration in the pellets for foaming, and the rapid stretching produces stretching-induced crystallization that raises the average size of the cells, further increasing the expansion multiplicity of individual cells. The average cell size of foam beads rises from 37.8 to 48.8 µm and the expansion ratio also increases to 8.6 with saturated temperature increasing form 95 to 105°C. The two-step soaking foaming method is a more efficient way of manufacturing industrial foamed beads, allowing for the preparation of better foam beads at low temperatures.

Estimation of the repeatability and reproducibility of test results in determining the degree of cure of protective paint coatings using differential scanning calorimetry

The degree of curing of protective paint-and-varnish coatings for oil country tubular goods is a parameter characterizing the completeness of their polymerization, and allows drawing a conclusion about the final physicomechanical properties and the possibility of using the material under specific conditions. This parameter is considered decisive in conducting acceptance tests and incoming quality control of pipe products with plated protective epoxy coatings despite a low accuracy of the obtained results and the impact of various instrumental factors and methodological approaches. The authors have developed a methodology for determining the curing degree of coatings based on the procedures given in regulatory documents (CSA Z245.20 Series-18, GOST R ISO 21809-2), taking into account the analysis of factors affecting the results of determining the curing degree carried out in the previous work. According to the conducted studies, the rates of heating and cooling during the measurement process, the temperature test program (in particular, the presence and duration of isothermal exposures before heating cycles), and curve processing methods were corrected and selected in the proposed methodology. The aim of this work is the analysis of the precision of the developed method for determining the curing degree of protective coatings to confirm the high accuracy of the obtained values under observing the prescribed procedure. The analysis was carried out by statistical processing of the results obtained in comparative tests performed in four testing laboratories, and included calculation of the repeatability of the results by their standard deviation, reproducibility and assessment of the acceptability of these parameters. The developed procedure for determining the curing degree of protective coatings, from sampling to processing of DSC curves, showed good precision, which indicates the reproducibility and repeatability of the proposed method. The developed method can be used as a unified sequence for determining the curing degree of paints and varnishes used as protective coatings in different laboratories.

Structure, Antioxidant Activity and Antimicrobial Study of Light Lanthanide Complexes with p-Coumaric Acid.

This paper presents the results of a study of the effects of the lanthanide ions Ce3+, Pr3+, Nd3+ and Sm3+ on the electronic structure and antioxidant and biological (antimicrobial and cytotoxic) properties of p-coumaric acid (p-CAH2). Structural studies were conducted via spectroscopic methods (FTIR, ATR, UV). Thermal degradation studies of the complexes were performed. The results are presented in the form of TG, DTG and DSC curves. Antioxidant properties were determined via activity tests against DPPH, ABTS and OH radicals. The reducing ability was tested via CUPRAC assays. Minimum inhibitory concentrations (MICs) of the ligand and lanthanide complexes were determined on E. coli, B. subtilis and C. albicans microorganisms. The antimicrobial activity was also determined using the MTT assay. The results were presented as the relative cell viability of C. albicans, P. aeruginosa, E. coli and S. aureus compared to controls and expressed as percentages. In the obtained complexes in the solid phase, lanthanide ions coordinate three ligands in a bidentate chelating coordination mode through the carboxyl group of the acid. Spectroscopic analysis showed that lanthanide ions increase the aromaticity of the pi electron system of the ligand. Thermal analysis showed that the complexes are hydrated and have a higher thermal stability than the ligand. The products of thermal decomposition of the complexes are lanthanide oxides. In the aqueous phase, the metal combines with the ligand in a 1:1 molar ratio. Antioxidant activity tests showed that the complexes have a similar ability to remove free radicals. ABTS and DPPH tests showed that the complexes have twice the ability to neutralise radicals than the ligand, and a much higher ability to remove the hydroxyl radical. The abilities of the complexes and the free ligand to reduce Cu2+ ions in the CUPRAC test are at a similar level. Lanthanide complexes of p-coumaric acid are characterised by a higher antimicrobial capacity than the free ligand against Escherichia coli bacteria, Bacillus subtilis and Candida albicans fungi.

Preparation, luminescence and thermal stability of Tb3+/Eu3+ doped glass ceramics containing KAlSiO4 crystalline phase

The melt-crystallisation process was used to successfully synthesised Tb3+/Eu3+ doped glass ceramics with KAlSiO4 crystalline phase. The optimum heat treatment condition was determined to be 560 °C/90 min by DSC, XRD, SEM and optical transmittance curves, under which the optical transmittance of the glass ceramic in the visible region can reach 80%. Fluorescence spectroscopy was used to determine the energy transfer between Tb3+ and Eu3+, and it was discovered that the energy transfer mechanism was brought on by dipole-dipole interactions. The chromaticity coordinates of the 0.9%Eu3+-0.9%Tb3+ doped sample are (0.3627, 0.3389), it is close to the color of white light. According to variable temperature spectroscopy analysis, emission intensity of Eu3+/Tb3+ co-doped glass ceramics at 458 K can be maintained at 97% and 70% of room temperature at 543 and 614 nm, respectively, demonstrating that the sample has good thermal stability. The results of this study demonstrate the potential of Eu3+/Tb3+ co-doped glass ceramics with KAlSiO4 crystalline phase for use in white light emitting diodes, solid state colour development and other fields.

Modification of bacterial cellulose using silk fibroin β-sheet crystals induced by ultrasonication

Silk fibroin (SF) has been continuously explored as a biomaterial due to its biocompatibility, tunability, and self-healing properties. In this work, we present a novel approach to the modification of bacterial cellulose (BC) with SF β-sheet dominant structures induced via ultrasonication. Secondary structure analysis through infrared spectroscopy, thioflavin T assay, and circular dichroism spectropolarimetry revealed a conversion of silk I to silk II structures within the protein mixture. Cold field emission scanning electron microscope images revealed the tightly packed fibers coated with the protein. Thermogravimetric curves demonstrated higher resistance to temperature degradation supplemented by broader and flatter DSC curves attributed to the highly bonded and dense composite. Successful conversion of amide I to amide II and amide III allowed for the more stable β-crystals to contribute to a more thermodynamically stable double-network hydrogel. The conversion of silk I to silk II structures offers a viable and highly biocompatible material that is both thermodynamically and biochemically stable for various potential biomedical applications.

Structural and thermoanalytical characterization of self-healing polymer: the effect of cross-linking density

The effect of the gradually formed cross-linked structure on the thermal properties and swelling behaviour of modified poly(vinyl alcohol) was investigated. To this aim, the semi-crystalline polymer was functionalized with aldehyde and amino moieties to produce polymers with dynamic imine cross-links, and, thus, with self-healing or curing ability. With increasing degree of functionalization (0.89–7.12%), denser polymer networks cross-linked by dynamic imine bonds were formed, the samples systematically developed thermoset-like properties compared to the pristine, initially thermoplastic PVA. As a result, the introduction of new moieties into the initial PVA lowered the glass transition (from 65.3 to 35.0 °C) and melting temperatures (from 194 to 161 °C), however, a new peak (Tcrd) with growing enthalpy values appeared on the DSC curves, which indicates that more and more energy must be supplied in order to break the imine cross-links formed between the introduced aldehyde and amino groups. The significant impact of the degree of functionalization and cross-linking density on the polymer structure was also clearly demonstrated: the crystallinity decreased as the abundance of the introduced moieties increased and the formation of cross-links proceeded. At the same time, the water desorption enthalpies of the samples increased, suggesting a stronger, chemically cross-linked thermoset-like polymer network compared to the thermoplastic poly(vinyl alcohol).Graphical abstract

Enhancing RDX Thermal Decomposition in Al@RDX Composites with Co Transition Metal Interfacial Layer

In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition temperature of RDX in the DSC curve was decreased by 26.3 °C in the presence of Al/Co, which could be attributed to the nano-sized Co transition metal catalyzing the decomposition reaction of nitrogen oxides in RDX decomposition products. The decomposition peak temperature of RDX and the heat released by the thermal decomposition of RDX in the Al/Co@RDX composite were decreased by 26.3 °C and increased by 74.5 J·g−1, respectively, in comparison with those of pure RDX. The types of major gaseous products released from Al/Co@RDX were found to be identical to those of pure RDX, encompassing N2O, CH2O, CO2 and HCN. However, the concentrations of those gaseous products for Al/Co@RDX were higher than those observed for pure RDX, which may owe to the fact that the Al/Co composite can interact with the –CH2 and –NO2 within RDX molecules, which leads to the weakening of the C-N and N-N bonds. In addition, the decomposition of RDX in the Al/Co@RDX composite was observed as a one-step process with an apparent activation energy (Ea) of 115.6 kJ·cm−3. The decomposition mechanism of the RDX in the Al/Co@RDX composite was identified to follow the chain scission model (L2), whereas the two-step decomposition physical models observed for pure RDX were found to closely resemble the L2 and autocatalytic models.

Development of Magnesium Aluminate (MgAl2O4) Nanoparticles for refractory crucible application.

Ceramics are the oxides of metals and nonmetals with excellent compressive strength. Ceramics usually exhibit inert behavior at high temperatures. Magnesium aluminate (MgAl2O4), a member of the ceramic family, possesses a high working temperature up to 2000°C, low thermal conductivity, high strength even at elevated temperatures, and good corrosion resistance. Moreover, Magnesium Aluminate Nanoparticles (MANPs) can be used in the making of refractory crucible applications. This study focuses on the thermal behavior of Magnesium Aluminate Nanoparticles (MANPs) and their application in the making of refractory crucibles. The molten salt method is used to obtain MANPs. The presence of MANPs is seen by XRD peaks ranging from 66° to 67°. The determination of the smallest crystallite size of the sample is achieved by utilizing the Scherrer formula and is found to be 15.3 nm. The SEM micrographs provided further information, indicating an average particle size of 91.2 nm. At 600°C, DSC curves show that only 0.05 W/g heat flows into the material, and the TGA curve shows only 3% weight loss, which is prominent for thermal insulation applications. To investigate the thermal properties, crucibles of pure MANPs and the different compositions of MANPs and pure alumina are prepared. During the sintering, cracks appear on the crucible of pure magnesium aluminate. To explore the reason for crack development, tablets of MgAl2O4 are made and sintered at 1150°C. Ceramography shows the crack-free surfaces of all the tablets. Results confirm the thermal stability of MANPs at high temperatures and their suitability for melting crucible applications.

Transient liquid phase bonding of Sn-Pb solder with added Cu particles

In this paper, the 1%-20% Cu particles were uniformly distributed in SnPb solder by mechanical mixing method to prepare composite solder. The solder was welded by eutectic welding and the high temperature failure test was carried out. The melting point and internal structure of solder were observed before reflow, after welding and after aging, and the existence of high-temperature resistant skeleton was found. It could be seen from the DSC curve that the solder absorption peak changes in a step-like manner, and the proportion of the high melting point absorption peak gradually increases with the aging process. The micro-structure of solder joints showed that a thin layer of IMC was formed around the Cu particles in the solder joints after welding, and the IMC in the solder joints had grown continuously until they contacted each other and formed a skeleton structure with aging. The skeleton structure improved the high temperature resistance of the solder joint. EDS analysis showed that the distribution of Cu element in the solder was similar to that of Sn, and the Pb element was enriched. The distribution of metal elements indicates that the solder joint was mainly composed of Cu6Sn5 IMC skeleton and Pb rich phase, and the solder component phase was high melting point component transformation.

Синтез и строение сольвата бис[3,5-динитробензоата] трис(2-метокси)(5-бром)фенилсурьмы [C6H3(2-OMe)(5-Br)]3Sb[OC(O)C6H3(NO2)2-3,5]2 ∙ PhH ∙ ½ C8H18

Tris(2-methoxy)(5-bromo)phenylantimony bis[3,5-dinitrobenzoate] (1) was obtained from 3,5-dinitrobenzoic acid by oxidative addition to triarylantimony in the presence of tertiary butyl hy-droperoxide in ether, and was isolated by recrystallization from a benzene-octane mixture in the form of a crystal solvate with benzene and octane molecules in its crystal lattice. The structure of solvate 1 was established by the IR spectroscopy and X-ray diffraction analysis (XRD). In the IR spectrum of complex 1, in addition to the absorption bands related to the stretching vibrations of the Sb–C, СAr–О–Ме, and carbonyl groups, there are bands corresponding to the stretching vibra-tions of the C–Br bonds (524 and 555 cm–1). The X-ray diffraction data show that the antimony at-oms in complex 1 have a distorted trigonal bipyramid coordination with carboxylate ligands in the axial position. The antimony atom and two oxygen atoms do not lie on the same straight line and are located in such a way that the OSbO angle is 170.79°. The O…Sb distances (2.134(4) and 2.110(5) Å) are close to the sum of the covalent radii of antimony and oxygen. In addition, accord-ing to the X-ray diffraction data, compound 1 crystallizes in the monoclinic crystal system, space group P21/n. The structural organization in the crystal is formed due to short contacts of oxygen atoms in the nitro groups of the carboxylate ligands with carbon and bromine atoms of the aryl lig-ands of neighboring molecules, as well as hydrogen O...H (2.524–2.715 Å) bonds. In addition, a certain contribution to the formation of the crystal structure is made by the p-p stacking between the aromatic rings of crystallization benzene and the methoxy-bromo-phenyl ligands. The aro-matic rings are displaced in relation to each other and the distance between them is 3.367 Å. Melt-ing point of solvate 1 is 172.6 °C, according to the thermal analysis data. However, further in-crease in temperature is accompanied by decomposition of compound 1, and therefore an exo-thermic peak is observed on the DSC curve at 255.7 °C, corresponding to a mass loss of 31 % ac-cording to the TGA data. Complete tables of atom coordinates, bond lengths, and valence angles are deposited at the Cambridge Crystallographic Data Center (No. 2060562, depos-it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/cif)

Investigation of Raman spectra and ionic conductivity of composites based on NaClO4 and KClO4 salts obtained by mechanoactivation

The work is aimed at studying the effect of mechanical activation on the structure and electrical conductivity of the NaClO4 – and KClO4 – basedcomposites. Based on the result of the analysis of the DSC curves of the (1–x) NaClO4 – x Al2O3 and (1–x) KClO4 – x Al2O3 composites measured while heating and cooling the samples, it was established that the enthalpy of phase transitions in them decreased with an increase in the concentration of the nanosized dopant. A complication of all active vibrational contours corresponding to internal vibrations of the molecular anion in the composites with increasing Al2O3 concentration and a shift of the band of the fully symmetric stretching vibration v1 (A) to a low-frequency region was revealed by Raman spectroscopy. Based on electrochemical impedance spectroscopy data, it was determined that for the 0.4NaClO4 – 0.6Al2O3 system subjected to mechanoactivation, the values of specific ionic conductivity increased by two orders of magnitude as compared to that of pure NaClO4, while for the 0.4KClO4 – 0.6Al2O3 system, the values of specific ionic conductivity increased by three orders of magnitude as compared to the initial salt at T = 320 °C.

Thermal Analysis in the Evaluation of Solid Lipid Microparticles in the Form of Aqueous Dispersion and Fine Powder

In the presented study, an attempt was made to investigate the most important attributes of solid lipid microparticles (SLM) using thermal analysis (DSC/TG) in order to determine the importance of this technique in the research and development of lipid microparticles. Particularly interesting in our studies were drug–lipid interactions and modifications of the SLM matrix structure induced by the production method (the hot emulsification method) and further processing (e.g., spray drying), as well as changes occurring during the stability studies. Cyclosporine A, indomethacin and spironolactone were used as model active substances incorporated into SLM. The conducted research demonstrated the significant potential of DSC/TG, especially for the analysis of SLM in the form of fine powder. The method of sample preparation, consisting of evaporation of water at room temperature, turned out to be crucial for the DSC/TG analysis of SLM dispersion. In the case of the tested SLM, the basic and usually the only observed thermal transformation in the DSC spectrum was the endothermic peak associated with the lipid forming a microsphere matrix. This peak is the main source of information about the properties and stability of the tested SLM. The obtained results show that glyceryl behenate (Compritol) is a significantly better lipid for forming lipid microparticles than stearic acid. Although thermal transformations of the incorporated drug substances are not directly visible in the DSC spectra, their impact on the SLM properties can be assessed indirectly, based on changes in the lipid melting point and the shape of the DSC and TG peaks and curves. DSC/TG studies confirmed the lack of an effect of the spray drying process on the properties of drug-loaded SLM with Compritol. Studies have also shown up to a 2-year stability of SLM with CsA.

Li4Mo5O17 crystal as possible scintillating material: Growth and luminescence properties

Transparent Li4Mo5O17 crystals with dimensions 60 × 30 × 20 mm were grown by low-thermal-gradient Czochralski technique. Optimal growth parameters were determined. According to SCXRD, Li4Mo5O17 compound crystallizes in the triclinic space group of P1¯ and the unit cell parameters at 150 K are a = 6.7596(2) Å, b = 9.4546(3) Å, c = 10.7909(3) Å, α = 73.1610(10)°, β = 88.8810(10)°, γ = 69.7460(10)°, V = 616.75(3) Å3. Uniformity of obtained crystals was confirmed by XRD analysis. Li4Mo5O17 crystal structure and cell parameters were studied by SCXRD. Li4Mo5O17 melting point at 546 °C was determined by DSC curve in 300–1000 K range. Luminescence was registered with peak maximum 670 nm at 370 nm excitation and 645 nm at 300 nm excitation.

Effect of Zn/B molar ratio on the structure, crystallization mechanism and properties of ZnO-B2O3-SiO2 glasses for LTCC applications

ZnO-B2O3-SiO2 glass-ceramics, with the same Si/B molar ratio (0.7) and different Zn/B molar ratios (1.6–2.1) have been prepared by quenching glass melt and heat treatment between 680 °C and 720 °C. DSC analysis has demonstrated that the crystallization activation energy (Ea) of the Zn2SiO4 phase increased with increasing Zn/B ratio, and the glass crystallization process was transformed from a two-dimensional to a one-dimensional growth. DSC curves are consistent with the deformation and viscosity curves and can be attributed to the crystallization behavior of glass. The glass-ceramic with Zn/B = 1.7 sintered at 700 °C for 30 min exhibited the best properties: εr = 6.35; tanδ = 4.3 × 10−3 (11.39 GHz); CTE = 3.8 × 10−6 /K.

Chloroaluminate ionic liquids for low-temperature aluminum-ion batteries

The paper discusses the feasibility of 1-ethyl-3-methylimidazolium ([EMIm]Cl) and 1-butyl-3-methylimidazolium ([BMIm]Cl) chloroaluminate ionic liquids (ILs) as electrolytes for aluminum-ion batteries capable of delivering high performance at subzero temperatures. The melting temperatures of AlCl3–[EMIm]Cl and AlCl3–[BMIm]Cl ILs with the molar ratio of aluminum chloride to the chloride of imidazolium salt (N) equal to 1.3 and 1.5 were determined using DSC. The melting temperature of AlCl3–[EMIm]Cl is –21 and –32 °C at N = 1.3 and N = 1.5, respectively. The conductivity of AlCl3–[EMIm]Cl IL increases sharply at heating and decreases sharply near its melting temperature at cooling. The DSC curves for [BMIm]Cl-based ILs do not contain any peaks related to the melting or crystallization of the IL, and temperature dependences of conductivity contain no inflection points. Galvanostatic cycling and cyclic voltammetry demonstrated efficient performance of the aluminum-ion battery with an aluminum anode, graphene cathode and AlCl3–[BMIm]Cl IL, which delivered coulombic efficiency approaching 100 % at temperatures as low as –30 °C. The capacity of the graphene cathode was found to be 82.4, 63.0 and 48.5 mA∙h∙g−1 at 0, –20 and –30 °C, respectively.

Curing treatments of silica gel for fire-retardant glass by intumescence

Silica hydrogels are used as fire-retardant materials due to the occurrence of intumescence that limits heat and mass transfer. They act as heat-sink, through continuous endothermic condensation reactions, meantime shrinking to a more connected network, towards the correspondent crystalline compound. Which compositions and treatments amplify this phenomenon is still of interest. To this aim, two silica sols containing two different complexing agents: ethylene glycol and glycerol has been prepared and analyzed. The samples were subjected to different treatments to induce gelation and densification: exposure to ultraviolet or microwave or infrared irradiation. Thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC) and scanning electron microscopy analyses has been also carried out. Moreover, dynamic mechanical spectroscopy (DMS) let to evaluate simultaneously the mechanical and intumescence behavior of the gels at increasing curing times for each type of irradiation. Intumescence of gels occurs up to 200 °C and appears as an endothermal group of peaks visible on the heat-flux DSC curves. DMS analyses let to assess that a MW cured glycerol-containing gel (GL-0-MW 6d) shows a glass transition above 150 °C, measured as the maximum of damping peak. Accordingly, this sample is a good option for the application: a few bubbles nucleate and grow fast at high temperature.Article HighlightsTransparent fire doors contain silica gel, which absorbs heat and releases water by foaming. Two different silica gels were synthetized using different chelating agents.The foaming depends on the reagents used to produce the gel, on the treatments for stabilizing it and also on ageing.Both foaming and consolidation of the gel were studied with thermogravimetric and dynamic-mechanical analysis.