Differential Scanning Calorimetry Techniques Research Articles

Novel Starch-Modified NiCrMn-LDH-Based Composite for Photocatalytic Degradation of Reactive Orange 13

Water pollution has become a great challenge today. To address this problem regarding wastewater treatment by removing toxic synthetic dyes from wastewater, this research focused on the synthesis of a novel starch-modified NiCrMn-layered double hydroxide composite through the coprecipitation method and applied it as a photocatalyst for the degradation of reactive orange 13 dye. The synthesized photocatalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), point of zero charges (PZC), dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Zeta potential techniques. These techniques revealed different characteristics of photocatalysts, like surface and structural properties. According to BET analysis, the final composite had 2.5 × 102 m2/g BET-specific surface area with a 45.56 nm pore radius value, and the overall composite found as mesoporous. Similarly, in DLS analysis, bare NiCrMn-LDH had 404 nm hydrodynamic size, which increased for the final starch composite up to 667 nm. Zeta potential value changed from −14.56 mV to 0.95 mV after the incorporation of starch with NiCrMn-LDH. They confirmed the incorporation of starch with trimetallic NiCrMn-layered double hydroxide (2:1:2). Starch association improved the properties of the photocatalyst like surface area. Different parameters like pH value, initial dye concentration, photocatalyst dose, hydrogen peroxide concentration, effect of sacrificial reagent, and effect of inorganic anions were studied for degradation of RO13. Overall, the photocatalysis process for RO13 followed pseudo-first-order kinetics. Photocatalytic degradation reactions for reactive orange 13 were conducted with an initial dye concentration of 10 mg/L, photocatalyst dosage of 20 mg/50 mL, and pH value at 3 in the presence of sunlight, resulting in an impressive degradation removal rate of 86.68%. This remarkable degradation ability of the photocatalyst for reactive orange 13 proves this composite was highly efficient.

Effect of the accelerated aging process on the thermal decomposition of LiAlH4-based composite solid propellants

In the present work, a study was carried out on the effect of the accelerated aging process on the thermal decomposition of two composite solid propellants based on ammonium perchlorate (AP) and hydroxy-terminated polybutadiene (HTPB). The first one (CP1) was enriched with aluminum (Al) powders, while the second (CP2) contained a mixture of aluminum and lithium alanate (LiAlH4) as a high-energy fuel additive. The thermal properties of the investigated propellant samples were determined using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The obtained results clearly demonstrated the effect of the aging process on the thermal degradation of the aged samples compared to the unaged ones, by shifting the temperature peaks of their main decomposition step to lower temperatures with a decrease in their DSC heat release. In addition, the residual unburnt propellant was increased, particularly for the complex metal hydride-based propellant. Kinetic modeling of the main thermal degradation phase, applying two advanced isoconversional methods, revealed a significant decrease in activation energy for the aged samples. Furthermore, the three-dimensional diffusion model involved during the investigated decomposition phase of the unaged samples was changed to a random nucleation model after 60 days of aging time.

Protic ionic Liquids-Water Interactions: A study on 2-Hydroxypropylammonium formate through experimental analysis and computer simulations

In this study, interactions within a mixture of the protic ionic liquid 2-hydroxypropylammonium formate and water were investigated across the entire range of ionic liquid compositions and a wide temperature range from 283.15 K to 333.15 K. This investigation was based on the measurement results of density, viscosity, and electrical conductivity, and was supported by computational simulations. The synthesized ionic liquid was further characterized thermally using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) techniques. The study focuses on the analysis of excess molar quantities of volume, thermal expansion coefficients, viscosity, and Gibbs energy of viscous flow, aiming to examine the influence of temperature and mixture composition on thermophysical properties. The impact of temperature on the system’s viscosity and Angell’s strength parameter was investigated to assess the influence of the ionic liquid’s content on the system’s structural organization. The dependency of molar conductivity on viscosity was analyzed through the Walden rule. Based on this analysis, the effect of temperature and mixture composition on deviations from the ideal behavior in diluted solutions of strong electrolytes was estimated. Computational molecular dynamics simulations were employed for a more detailed study of the structural organization of the system’s components.

Characterization of surface and bulk properties of α-Tocopherol blended and γ irradiated UHMWPE sandwich nanocomposites

In the present study, an unconventional approach in compression molding is chosen to fabricate Ultra High Molecular Weight Polyethylene (UHMWPE) sandwich composites with Graphene (Gr) and Nano-diamond (ND) as fillers. A unique comparison is done between the surface and bulk properties of UHMWPE nano-composites and UHMWPE sandwich composites. Influence of gamma irradiation at doses of 50, 100 kGy doses and vitamin E (vit-E) on crystal structure, mechanical, thermal and tribological characteristics of UHMWPE composites were studied through x-ray diffraction (XRD), raman spectroscopy, dynamic mechanical analysis (DMA), rheology, differential scanning calorimetry (DSC), tensile, nano-indentation and wear characterization techniques. Fracture regions and surface wear of the samples were analysed through scanning electron microscopy (SEM) to understand the dispersion behavior of fillers in matrix. The concentration of vit-E content in UHMWPE greatly influenced the crosslinks and surface properties in gamma irradiated composites. Gamma irradiation have shown significant improvement in crystallinity, viscous behavior and bulk properties of UHMWPE composites. Irradiated UHMWPE nano-composites have shown better tensile results when compared with sandwich composites, with 22 % increase in young's modulus and 16 % increase in yield stress. Wear rate has been reduced by 25 % for irradiated sandwich UHMWPE composites when compared with UHMWPE nano-composites.

Rheological insights into the degradation behavior of PP/HDPE blends

The (re-)processing and degradation behavior of polypropylene (PP) blends with high-density polyethylene (HDPE) is a crucial topic in mechanical recycling due to the prevalence of PP/HDPE mixtures. In particular, small amounts of cross-contamination (below 10.0 wt.%) between these polyolefins are quite common. While much empirical data is available, systematic studies on such blends are scarce and rarely account for the polymers’ chain structure. This study employs time-resolved rheology, atomic force microscopy (AFM), differential scanning calorimetry (DSC) and chemiluminescence techniques to study the degradation of different PP types containing 0.5 to 10.0 wt.% of HDPE. It is observed that the addition of small amounts of HDPE can result in a prominent change in the viscoelastic properties of PP during the thermo-oxidative degradation. The substantial evolution of elasticity in the blends is mainly related to the gelation of fine PE particles dispersed within the PP matrix. It is also shown that a smaller viscosity ratio between the blend components can lead to a more significant degradation through morphology alterations. Remarkably, time-resolved rheology studies revealed that even a small amount of HDPE (2.5 wt.%) can lead to a reduction in the thermo-oxidative stability of the PP/HDPE blend through excessive branching/crosslinking of the HDPE phase. This effect was particularly more pronounced when the PP contained an ethylene comonomer in its backbone. The finer morphology of PE particles in PP copolymer can exacerbate the thermo-oxidative stability of the blend. These insights are essential in designing new life cycles for recycled PP cross-contaminated with HDPE, typically found in the light fraction of municipal solid plastic waste.

Thermal annealing gradient tailoring on ammonium nitrate-capped CdS nanospheres synthesized via green precipitation

This study explores the impact of thermal annealing gradients on the physical properties and structural evolution of cadmium sulphide (CdS) nanospheres capped with ammonium nitrate as a modifier, which were fabricated through precipitation and subsequent annealing within 160–480 °C temperature range. The properties were characterized using X-ray diffraction (XRD), ultraviolet–visible (UV–Vis), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques The XRD results show that the present CdS exhibits superior crystallinity compared to pure CdS without capping, transitions from a cubic to a hexagonal phase structure, and increases in crystallite size and crystallinity with increasing temperature. The FTIR spectra postulate that a vibrational band presence evidences ammonium nitrate capping on CdS, with another distinct band that represents CdS in the lower wavenumber region, both intensifying at elevated temperatures. The UV–Vis analysis reveals that CdS exhibits strong ultraviolet (UV) absorption suitable for effective photoreaction under UV light and has a broader band gap compared to bulk CdS. SEM images show an extensive distribution of homogeneous nanospheres over the surface, with increased growth in size when capped with ammonium nitrate and at higher temperatures. As validated by TGA and DSC results, CdS with a smaller crystallite size improves thermal stability and energy transfer, as evidenced by reduced weight loss and a lower endothermic temperature, respectively. Varying the annealing temperature with ammonium nitrate capping can improve the structural and physical properties of CdS, which are beneficial for varied applications such as optoelectronics, energy storage, and photocatalysts.

Sulfonated poly(ether ether ketone)-Protic ionic Liquid-Based anhydrous Proton-Conducting composite polymer electrolyte membranes for High-Temperature fuel cell applications

A high-temperature polymer electrolyte membrane fuel cell (PEMFC) has enormous potential to produce clean energy with minimal environmental pollution along with high energy density and conversion efficiency. In the present work, anhydrous proton-conducting polymer electrolyte membranes for prospective high-temperature fuel cell application were successfully prepared using different protic ionic liquids (PILs) and sulfonated poly(ether ether ketone) (SPEEK). The protic ionic liquids (PILs), 2-hydroxyethylammonium formate, diethylmethyl ammonium triflate, 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide, 1,2-dimethyl imidazolium bis(trifluoro methylsulfonyl)imide, and diethylmethylammonium methanesulfonate were selected based on their favorable physicochemical properties. The effect of the incorporation of the PIL on the structural, thermal, and electrical transport properties of the composite SPEEK polymer electrolyte membranes was studied. The prepared polymer electrolyte membranes (PEMs) were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and electrochemical impedance spectroscopy (EIS) techniques. FTIR results indicated an interaction between the PIL and the SPEEK, which resulted in homogeneous and flexible membranes. The DSC results confirmed good miscibility and elucidated plasticizing effect of the incorporated PIL on the SPEEK polymer matrix. All the PEMs showed good thermal stability and high-temperature anhydrous proton conductivity, achieving best proton conductivity, ≈8 × 10–3 S cm−1 at 120 °C and low activation energy ≈0.26 eV, making it suitable for prospective high-temperature PEMFC applications.

Morphological, Thermal, Physicomechanical and Optical Properties of Crosslinked Poly (Ester-Urethane-Acrylate): Effect of Added Methyl Methacrylate

Poly (ester-urethane-acrylate) (PEUA) macromonomer was prepared by reacting two moles of isophorone diisocyanate (IPDI) with one mole of bis (1,4-butanediol ortho-phthalate) (BPE), followed by end-capping with two moles of 2-hydroxyethyl methacrylate (HEMA) in the presence of dibutyltin dilaurate (DBTDL) catalyst. Thereafter, different ratios of methyl-methacrylate (MMA) were added to the PEUA macromonomer to prepare crosslinked PEUA/MMA sheets. Fourier transform infrared spectrometry (FTIR), ultraviolet-visible spectrophotometry (UV-vis) and differential scanning calorimetry (DSC) techniques were employed to investigate the structure, optical transparency and thermal properties of the crosslinked sheets. The effect of MMA on the polymerization shrinkage and abrasive wear properties of PEUA and their copolymers were also studied. The polymerization shrinkage study showed that PEUA copolymer containing 40 wt% MMA had a more rigid microstructure with improved volume shrinkage and abrasive wear properties as compared with the other compositions of PEUA copolymers with MMA loadings of 80, 60 and 20%. The improvement was attributed to the better miscibility and compatibility of 40 wt% MMA with the PEUA as revealed by DSC, heat deflection temperature (HDT) and scanning electron microscope (SEM) studies.

Quantitative observation of water phase transition in gas diffusion layers utilizing advanced in situ differential scanning calorimetry

The study investigates the freezing behavior of supercooled water in gas diffusion layers (GDLs) of polymer electrolyte fuel cells (PEFCs). Using an innovative advanced in situ differential scanning calorimetry (advanced DSC) technique, we analyze phase transitions within GDLs at a single-cell scale, excluding impacts of catalyst layers and membranes. This method overcomes the limitations of traditional DSC, allowing variable water saturation and distribution. We find that freezing-thawing and drying-saturating cycles contribute to noticeable variations in the freezing temperature (Tonset) of supercooled water, ranging from −6 °C to −15 °C, attributed to the heterogeneous surface of GDL and water redistribution. Repeated drying-saturating cycles remove nucleation seeds, lowering the freezing point of water − a "cleaning effect." The freezing probability reduces at lower saturation levels, influenced by waterproof treatment uniformity on GDLs. Residual ice can be detrimental to the cold-start capability of PEFCs, as it promotes freezing of supercooled water around −1 °C. Our findings enhance understanding of water behavior in GDLs and its impact on PEFC cold-start performance. Applying this technique to other cell components, such as the catalyst layer, could further elucidate water freezing dynamics in PEFCs and guide the innovation of more reliable cell components for PEFC applications in broader climates.

Investigations on magnesium ion conducting gellan gum-based biopolymer blend electrolytes for energy storage applications

The economical and ecological polymer electrolytes are essential for energy storage devices. The key problem we are trying to resolve is how to improve ionic conductivity and safety in polymer electrolytes, which are essential for energy storage devices to operate effectively. We have prepared biopolymer blend electrolytes with different concentrations of magnesium chloride (MgCl2) by solution casting technique and the prepared electrolytes are investigated. Increase of amorphous nature of the polymer membranes is confirmed by X-ray diffraction analysis. Fourier transform infrared (FTIR) spectroscopy used to define complex formation between salt and polymers. Thermal properties of the electrolytes are confirmed by differential scanning calorimetry technique. The higher ionic conductivity of 1.04 × 10−5 S/cm has been achieved for 8 wt.% MgCl2 mixed gellan gum: polyvinyl alcohol (PVA) polymer blend at the room temperature. The present work highlights the preparation and characterization of gellan gum: PVA: MgCl2 polymer blend electrolytes with enhanced ionic conductivity and safety. The optimized polymer electrolyte is applied for energy storage devices.

Hygrothermal ageing of dry gelatine adhesive films: Microstructure-property relationships

Gelatine adhesives, also known as animal glues, are collagen-based water-soluble biopolymers derived from vertebrate connective tissues. One of the various fields in which gelatine adhesives are widely used is the conservation of cultural heritage such as decorated furniture and panel paintings. It is observed that, with time, the failure in these objects often occurs along the adhesive bondlines. Given the moisture and temperature sensitivity of these adhesives, obtaining knowledge of their long-term behaviour, when exposed to climate variations, is pivotal. Here, the influence of hygrothermal ageing (exposure to a combination of elevated temperature and relative humidity (RH) cycling) on the microstructure and macroscopic properties of four different types of gelatine adhesives is investigated. These adhesives were selected from different animal origins namely bovine, rabbit, and fish with different Bloom strengths. It was observed that ageing cycles interfere with the most critical structural feature of protein chains namely triple helices. A clear decay in triple helix content at the micro-scale, determined by Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) techniques, was observed which had implications on the macroscopic properties of these adhesives such as reduction of strain to failure and toughness (strain energy density to failure). The rate of decay in properties was revealed to be the highest in the adhesives with the lowest triple helix content. This study provides a scientific view of microstructure-property relationships in gelatinous adhesives as a function of environmental ageing, and stipulates the underlying mechanism of the degradation of mechanical properties as the loss of structural triple helices, regardless of the animal origin.

To Study the Effect of Nanoparticle TiO2 on Sodium (Na+) – Ion Conducting Solid Polymer Electrolyte System: [80PEO:20NaPF6

AbstractTo study the effect of nanofiller particle TiO2 on sodium (Na+) – ion conducting solid polymer electrolyte (SPE) film: [80PEO:20NaPF6] and nanocomposite polymer electrolyte (NCPE): [80PEO:20NaPF6] + xTiO2, where x = 1–9 wt. (%) have been prepared. SPE film composition: [80PEO:20NaPF6] selects as Ist‐phase host and nano‐sized (<100 nm) filler materials TiO2 as IInd‐phase dispersoid. Both SPE and NCPE films have been prepared by the hot‐press technique. Filler particle‐dependent conductivity study reveals the NCPE system: [80PEO:20NaPF6] + 8TiO2 as the highest conducting composition with σrt − 3.53 × 10−6 S cm−1, which is approximately one order of magnitude higher than the SPE optimum conducting composition (OCC) (σrt) ≈ 7.78 × 10−7 S cm−1. Ion transport properties for both SPE and NCPE system have been evaluated in terms of ionic conductivity (σ) and total ionic (tion)/cationic (t+) transference numbers using combined AC/DC techniques in order to evaluate its usefulness in all‐solid‐state battery applications. Structural/thermal properties have been characterized using X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. A cyclic voltammetry (CV) study has been performed in SPE and NCPE OCC film to evaluate the electrochemical performance for battery application.

Specific role of Al in the synthesis of electrospun Al:ZnO nanofibers: Thermal and elemental analysis

In this contribution, the thermal behavior and elemental analysis of a series of transparent conductive layer based on pure and Al doped ZnO nanofiber samples produced by the electrospinning method was studied. The nanofibers are spun from a PVA based solution where we added zinc acetate and doped by 1, 2, 3, and 4 wt% aluminum acetate. First, we carried out a qualitative study of nanofibers electro-spun on a glass substrate before and after annealing by scanning electronic microscopy (SEM). For all samples, these images show the quality of the deposited nanofibers and the good crystallization for the ZnO one after annealing. The decomposition of ZnO-Al (AZO) fibers after annealing is noticed and discussed justifying the quantitative analysis made in the rest of this work using the coupled techniques of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) performed under air atmosphere. We observe changes in the mass loss process with temperature between the various samples, explained by the role of each compound, i.e. PVA, Zn and Al. This study particularly shows the influence of zinc and aluminum doping in the production of nanofibers by electrospinning for high-performance transparent conductive layers. To validate the results obtained by thermal analysis, complementary study of elemental composition by fluorescent X-ray (XRF) was performed to check the initial composition of the fibers before any heat treatment. Finally, results obtained by inductively coupled plasma spectroscopy show that as soon as Al is added to the initial solution, the elements precipitate out due to the neutral pH of this solution. Consequently, new prospects for the deposition of Al-doped ZnO nanofibers by electrospinning can be envisaged by modifying the acidity of the initial solutions.

Thermotropic Structure Phase Transitions and Two Types of Thermochromic Behaviors in a Bromoargentate Cluster [Pr-dabco]2Ag4Br6.

Organic-inorganic silver halide hybrids show abundant phase transitions and thermochromism. However, it is very rare that silver halides exhibit thermochromism related to thermotropic structure phase transition. Herein, a bromoargentate hybrid, [Pr-dabco]2Ag4Br6 (1) (Pr-dabco+ = 1-propyl-1,4-diazabicyclo-[2.2.2]octan-1-ium), with tetranuclear [Ag4Br6]2- clusters was prepared and characterized by microanalysis, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, and thermogravimetric (TG) and differential scanning calorimetry (DSC) techniques. Interestingly, 1 undergoes an irreversible structure phase transition at ∼436 K in the first heating process, which is accompanied by an abrupt color change from colorless to yellow; however, a reversible color change between pale yellow and yellow is observed in the next heating-cooling cycles. Notably, DSC measurement revealed that a reversible phase transition is associated with the change in color between pale yellow and yellow, while the powder X-ray diffraction (PXRD) patterns corresponding to pale yellow and yellow phases are quite similar to each other. These observations demonstrate that thermochromism in the next heating-cooling runs is associated with a reversible structure phase transition, which perhaps concerns the disorder-order transformation of alkyl chains in the cationic ligand [Pr-dabco]+, and relevant to the anharmonic fluctuations of the Ag-Br and Ag-N bonds, a strong electron-phonon coupling effect is seen within the bromoargentate cluster.

Facile Grinding Method for Preparing Nano-Cu-Cr-Fe Composite Metal Oxides with Enhanced Catalytic Activity for Thermal Decomposition of Ammonium Perchlorate

ABSTRACT Ammonium perchlorate (AP) is a commonly used oxidant for solid propellants, and improving the thermal decomposition performance of AP has been the focus of research, as its thermal decomposition performance directly affects the performance of the propellant. Among a variety of catalysts, nanocomposite metal oxides have demonstrated a significant role in facilitating the thermal decomposition of AP. In this study, Cu-Cr-Fe ternary metal oxides with different molar ratios (5:2:8, 5:4:6, 5:6:4, 5:8:2) were prepared by a facile mechanical grinding method to investigate their catalytic effect on the thermal decomposition properties of AP. The structure and morphology of Cu-Cr-Fe ternary metal oxides were investigated using X-ray diffractometer (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the catalytic effect of different ternary catalysts on the thermal decomposition performance of AP was also investigated using thermal weight (TG) and differential scanning calorimetry (DSC) techniques. The results show that Cu-Cr-Fe ternary nanocomposite metal oxides with a molar ratio of 5:2:8 prepared by mechanical grinding exhibit excellent catalytic effect on the thermal decomposition of AP, as well as nanometallic oxides (Cu-Cr-Fe = 5:2:8) prepared using the co-precipitation and physical mixing methods. Furthermore, the ternary Cu-Cr-Fe (molar ratio of 5:2:8) composite metal oxide prepared by mechanical grinding resulted in a significant decrease in the thermal decomposition temperature of AP, which decreased from 441.3°C to 352.5°C, the heat of decomposition increased from 941 J/g to 1680 J/g, and the Gibbs free energy of AP decreased from 199.8 kJ/mol to 173.2 kJ/mol. This demonstrates the good synergistic catalytic effect between CuO, Cr2O3 and Fe2O3 nanoparticles, which is expected to facilitate the application of ternary nanocomposite metal oxides in the field of solid propellants.

Structural insights into novel therapeutic deep eutectic systems with capric acid using 1D, 2D NMR and DSC techniques with superior gut permeability.

Therapeutic deep eutectic solvents (THEDSs) are the best exemplification of green alternative formulations of active pharmaceutical ingredients (APIs) that offer superlative properties of APIs. Previously, THEDESs of risperidone, fentanyl and levofloxacin with capric acid (CA) were developed by our group. These APIs share cyclic tertiary amine nuclei. Herein, DESs of two drugs bearing cyclic tertiary amine nucleus, namely, droperidol and aripiprazole, in the presence of CA, were investigated as model drugs. Comprehensive analyses were conducted using liquid-state 1D and 2D NMR and differential scanning calorimetry (DSC) to elucidate the regiochemistry and thermodynamic mechanisms bringing about those THEDESs. Everted gut sac technique was used to study the flux of the developed THEDESs. 1D and 2D NMR techniques analyses revealed the importance of cyclic tertiary amine nuclei in forming interactions with CA. This was confirmed by the downfield shift of the protons proximal to the tertiary amine groups compared to the individual drugs. Diffusion NMR analysis (DOSY) showed a significant reduction in the diffusion coefficient of CA in the mixed system compared with CA in isolation. Thermal analysis of the two drugs revealed that the drugs have a low tendency to recrystallise upon melting but rather vitrify from a melt to form an amorphous solid. Interestingly, the superior absorption and flux of the THEDES formulation of droperidol was demonstrated using the ERIS. Collectively, this work provides a green method to attain liquid formulations of APIs with enhanced pharmacokinetic features.

Hydration effects on thermal transitions and molecular mobility in Xanthan gum polysaccharides.

In this work, the xanthan gum (XG) polysaccharide is studied over a wide range of temperatures and water fractions 0 ≤ hw ≤ 0.70 (on a wet basis) by employing differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). The investigation reveals that the critical water fraction for ice formation is about 0.35. Glass transition temperature (Tg) was determined through calorimetry experiments for all the samples studied. Water acts as a strong plasticizer, i.e., decreasing Tg, for water fractions up to about 0.35. A secondary (local) relaxation process is recorded in both dry and hydrated samples, which is sensitive to the presence of water molecules. This fact indicates that this process originates due to the orientation of small polar groups of the side chain, or/and due to the local main chain dynamics. Two types of long-range charge transport processes were resolved. The first is related to the conductive paths being formed via bulk-like ice structures (at high hydration levels), whereas the second can be attributed to proton mobility via the hydrogen bond (HB) network of non-freezing water existing in XG. Interestingly, this process is exactly the same in all the hydrated samples with hw > 0.25. With respect to the sample with hw = 0.27, a Vogel-Tammann-Fulcher (VTF)-like polarization process has also been recorded which seems to be related to long-range charge mobility via interconnected water clusters. As far as we are aware, this is the first time that XG is studied in terms of glass transition and molecular mobility over a wide range of hydration levels combining DSC and BDS techniques.

Green Synthesis, Characterization and Thermal Investigation of Ni(II) and Cu(II) Complexes Constructed by Pyridine-2,6-Dicarboxylic Acid

Two complexes [Ni(pda)(H2pda)]·3H2O (1) and [Cu(pda)(H2pda)] (2) containing pyridine-2,6-dicarboxylic acid (H2pda) were synthesized by room-temperature solid state reaction and characterized by elemental analyses, powder X-ray diffraction (PXRD), single crystal X-ray diffraction and infrared spectroscopy. The powder complexes were confirmed as single phase with their PXRD. The thermal property was studied using simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC) techniques. The complexes were decomposed in several stages and the final products of their thermal decomposition were NiO and CuO, respectively. In order to explore application of the complexes, the nano-NiO and nano-CuO particles were produced by using the powder complexes as precursors at different temperatures. The particles were characterized and observed by PXRD and scanning electron microscope (SEM), and their average diameters of the pyrolysis products at 500 and#176;C were about 12 and 30 nm, respectively.

Supramolecular crystals of Mn(15-crown-5)(MnCl4)(DMF) with dielectric phase transition, high quantum yield and phase transition-induced luminescence enhancement behavior.

The supramolecular crystals, Mn(15-crown-5)(MnCl4)(DMF), (1; 15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane), were synthesized via a self-assembly strategy under ambient conditions. Comprehensive characterization of the crystals involved microanalysis for C, H, and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC) and single-crystal X-ray diffraction techniques. The results reveal that 1 undergoes a two-step thermotropic and isostructural phase transition at around 217 K and 351 K upon heating. All three phases belong to the same space group (P212121) with analogous cell parameters. These two phase transitions primarily involve the thermally activated ring rotational dynamics of the 15-crown-5 molecule, with only the transition at ca. 351 K being associated with a dielectric anomaly. 1 exhibits intense luminescence with a peak at ∼600 nm and a high quantum yield of 68%. The mechanisms underlying this intense luminescence are likely linked to low-symmetry ligand fields. Additionally, 1 displays phase transition-induced luminescence enhancement behavior, and the possible mechanism is further discussed.

THERMAL ANALYSIS OF SELECTED PRIMARY EXPLOSIVES

The article presents basic information about selected primary explosives commonly used in warfare agents. Special attention was focused on the thermal properties of such compounds as mercury fulminate, tetrazene, lead azide, lead trinitroresorcinate. Knowledge of the thermal properties of the above-mentioned primary explosives, allows their safe use. Thermal properties have been studied by using DSC (differential scanning calorimetry) and TGA (thermo-gravimetric analysis) techniques. The results obtained confirm that thermal analysis (DSC and TGA) is a fast and safe method to study the thermal properties of primary explosives as well as other high-energy materials.