Calorimetric Analysis Research Articles

Preparation and Performance of ATH-OPC-PEG Bilayer Microcapsules Based on Targeted Flame Retardation Against Spontaneous Coal Combustion

ABSTRACT In order to solve the problem of spontaneous combustion of coal in the air-mining area, ATH-OPC-PEG double-layer flame retardant microcapsules were prepared. The environmentally friendly flame retardant aluminum hydroxide (ATH) was selected as the core material of the microcapsules. Due to the high action temperature and late action time of ATH, sodium alginate-modified melamine-melamine resin was used as the first layer of shell material of microcapsules to coat ATH. Then molten polyethylene glycol (PEG) mixed with the environmentally friendly strong antioxidant proanthocyanidin (OPC) was used as the second layer of shell material for the secondary coating of microcapsules. Providing antioxidant properties to microcapsules. The surface morphology, dispersion, encapsulation, pyrolysis, and flame retardant properties of the microcapsules were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TG), and cone calorimeter. On this basis, the microcapsules were mechanically mixed with coal samples, and four coal samples were prepared for combustion tests. The results showed that ATH-OPC-PEG microcapsules prolonged the water locking time and increased the TGA by 1.162%. According to the cone calorimeter analysis, the CO and CO2 release rates of microcapsule-treated coal were reduced by 27.90% and 13.98% compared with that of pure coal. This study provides directional solution ideas for solving different stages of spontaneous combustion of coal in the mining area, and enriches the technical means of fire prevention and extinguishing.

Titanate nanorod/reduced graphene oxide-filled poly (vinylidene fluoride) fibers as piezoelectric nanogenerators

To investigate the influence of nanorod ceramic powders MTiO3 (M: Mg, Co, Ni) as fillers on the electrical performance, piezoelectric nanogenerators (PENG) device, were constructed using the electrospinning method with polyvinylidene fluoride (PVDF), reduced graphene oxide (RGO), and ceramic powders. The composite nanofibers were characterized using SEM, EDX, ATR-FTIR, EDS-mapping analysis, and XRD. Sensing capacity of the PVDF-RGO-MTiO3 nanofiber-based PENG were compared. Utilizing CoTiO3 (CT) in the PENG resulted in a voltage output of 17.03, which exhibited the best piezoelectric response. Observations revealed that mechanical stimulation could charge different capacitors, suggesting a viable platform for removing the requirement of an external power source for operating portable devices. With varying resistances in the circuit, the resistance of 104 Ω produced the maximum power density of 1.40 mW/cm2. When comparing the P-RGO-CT composite to pure PVDF, the differential scanning calorimetric analysis revealed that the thermal stability and crystallinity percentage increased. Tensile testing was used to evaluate the mechanical characteristics of P-RGO-CT PENG. The maximum stress and breaking strain that the nanofiber film can tolerate are 50 kPa and 33.9%, respectively. EIS investigations obtained that the real intrinsic internal resistance of the P-RGO-CT PENG electrode is lower than PVDF, demonstrating the good conductivity of the synthesized PENG electrode. The impedance spectrum of the PENG electrode is almost parallel to the Zim axis, demonstrating good capacitance performance.

Study on the Mechanical and Thermal Properties and Shape Memory Behaviors of Blends of Bio-Based Polybenzoxazine and Polycaprolactone with Different Molecular Weights

In this research, blends of bio-based polybenzoxazine (V-fa) and polycaprolactone (PCL) with different molecular weights (Mn) (14,000, 45,000, and 80,000 Da) were prepared with varying PCL content from 10 to 95 wt%. The spectra measured using Fourier Transform Infrared Spectroscopy (FTIR) may indicate the presence of hydrogen bonding between two polymeric components. The thermograms obtained using a Differential Scanning Calorimeter (DSC) and dynamic mechanical analyzer (DMA) exhibited a shift in glass transition temperature (Tg), which indicated partial miscibility between V-fa and PCL. The thermograms obtained using a thermogravimetric analyzer (TGA) revealed that the addition of PCL led to an increase in the maximum decomposition temperature (Tdmax). The tensile strength and modulus decreased with an increase in PCL, thus indicating a decrease in brittleness. Interestingly, only the samples with an Mn of 80,000 Da were bendable. The blends with 80 wt% PCL were revealed to have shape memory behaviors with a shape fixity of approximately 81%. The shape recovery ratio of the blends with 95 wt% PCL was approximately 78%.

Spectroscopic, calorimetric, and radiation shielding analysis of lead-free transparent dysprosium-doped phosphate glasses

Eco-friendly phosphate glasses with 50P2O5-(50 – x)BaO-xDy2O3 (x = 0, 0.5, 1.0, 2.0, 3.0, 4.0 mol %) compositions were prepared and studied focusing on their potential for radiation attenuation and shielding applications. The glasses were synthesized by melting and subsequently characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, densitometry, refractive index, optical absorption, and differential scanning calorimetry (DSC). XRD confirmed the amorphous nature of the glasses, while FT-IR spectra indicated that the glass structure was preserved upon Dy2O3 inclusion. It was observed that both the density and refractive index generally increased with higher Dy2O3 content. Optical absorption data showed a linear increase in Dy3+ ion absorption with Dy2O3 concentration, confirming the effective incorporation of Dy3+ ions. Tauc and Urbach plots were also employed to analyze the absorption edges of the glasses. DSC thermograms revealed that the glass transition temperatures increased while glass stability improved with higher Dy2O3 content. The radiation shielding properties were assessed by evaluating parameters such as mass attenuation coefficients, linear attenuation coefficients, tenth value layer, mean free path, effective conductivity, and effective electron density against gamma-ray photons. Dysprosium doping was found to enhance gamma-ray shielding (from 1 keV to 100 GeV) based on theoretical methods. Additionally, the 3 mol % Dy2O3 doped sample exhibited greater fast neutron removal cross-sections. However, the undoped barium phosphate host demonstrated better stopping potential and lower projected ranges against ions (protons and carbon). Photon trajectories and dose attenuation properties were also investigated using the Particle and Heavy Ions Transport System (PHITS) Monte Carlo code, indicating that the Dy3+ doped lead-free transparent glass protects against ionizing radiation. Hence, the barium phosphate host and Dy3+-doped counterparts are attractive for use in ionizing radiation and nuclear facilities, such as hospitals, research centers, and industries.

Effect of tea polyphenols on the quality of frozen cooked noodles

AbstractBackground and ObjectivesThe growing consumer demand for natural, healthy, and convenient food options has led to the rising popularity of frozen cooked noodles (FCN). Tea polyphenols (TPs), known for their diverse biological activities, are increasingly being utilized as a natural food additive in research and development. Therefore, this study aims to investigate the effects of TPs on the thermal and pasting properties of wheat flour as well as their influence on the quality of FCN.FindingsThe results from differential scanning calorimeter and RVA analyses showed that TPs did not significantly affect the thermal and pasting properties of wheat flour. However, the addition of low‐dose TPs (<1.5%) improved the quality of FCN during storage. Texture and tensile analyses demonstrated an enhancement in hardness, chewiness, resistance, and an increase in resistant starch content in the noodles. Low‐field nuclear magnetic resonance findings revealed an increase in the proportion of strongly bound water, accompanied by a decrease in free water content. Scanning electron microscopy observations illustrated a well‐developed gluten network structure. In contrast, the incorporation of 1.5% TPs adversely affected the quality of FCN.ConclusionsThe appropriate integration of TPs plays a significant role in alleviating the quality degradation of FCN during storage.Significance and NoveltyThis study provides a theoretical basis for the development of polyphenol‐enriched flour products and functional foods.

Direct and indirect assessment of the elastocaloric properties of cast NiMnTi alloys

The study of the elastocaloric effect of NiMnTi alloys is a key topic for developing materials for sustainable and efficient solid-state cooling and heating applications. In the current work, the mechanical behavior of two arc melted and heat treated NiMnTi alloys with 15 and 18 at% of Ti has been investigated. The effects of heat treatments and operating conditions on the mechanical and caloric properties of the alloys have been assessed through calorimetric analysis, isothermal stress-strain compressive measurements, and adiabatic tests. To evaluate the caloric performance of the NiMnTi alloys, both experimental and theoretical adiabatic temperature changes have been identified, and the isothermal entropy change involved in the stress-induced martensitic transformation has been computed from the discrete integration of the stress-strain curves. The NiMnTi alloys treated at 900 °C exhibited better caloric performance than those treated at 1000°C. Specifically, the sample that achieved the highest experimental positive and negative ΔT values (10.2 °C and −12.6 °C, respectively) was the NiMnTi alloy with 15 at% of Ti and heat treated at 900 °C. This study provides a detailed analysis of the physical properties, functionality, and caloric properties of polycrystalline NiMnTi fabricated through a melting process, considering its potential use in solid-state cooling and heat pumping technologies.

Locally Acting Budesonide-Loaded Solid Self-Microemulsifying Drug Delivery Systems (SMEDDS) for Distal Ulcerative Colitis.

Budesonide (BUD) is a BCS class II medication with poor water solubility and limited oral bioavailability. In this study, innovative solid self-microemulsifying drug delivery systems (BUD-SMEDDS) were developed for effective local management of distal ulcerative colitis (UC). Based on solubility and emulsification tests, the components of the self-microemulsifying drug delivery system (SMEDDS) were Capryol™ 90, Tween 80, and Transcutol HP. The impacts of BUD-SMEDDS ingredients (as inputs) on the average globule size (AGS), polydispersity index (PDI), and self-emulsification time (SET) as responses were investigated using the Box-Behnken design methodology. Solid rectal systems were then fabricated using the optimized values of SMEDDS components in Lutrol® bases. The developed systems were evaluated for in vitro characteristics and in vivo efficacy using a rat colitis model. For all responses, the greatest impact was attributed to the oil content of SMEDDS. An optimized BUD-SMEDDS with AGS of 33 ± 2.9 nm, PDI of 0.29 ± 0.03 and SET of 25 ± 2.5 s) was selected for rectal formulations. The developed formulations demonstrated acceptable physical characteristics and mucoadhesive abilities. Differential scanning calorimetric (DSC) analysis revealed the absence of BUD crystallinity in the SMEDDS formulations. The drug release patterns could be regulated by selecting the grade and composition of the incorporated Lutrols. Clinical and histopathological assessments revealed considerable improvements in animals treated with BUD-SMEDDS formulations. Overall findings confirmed the superior capability of solid SMEDDS as BUD carriers to manage distal colitis in tested animals.

Rheological, Thermal and Physicochemical Properties of Bioprocessed Flour From Cowpea, Sorghum and Orange Fleshed Sweet Potato

ABSTRACTThis study investigated the rheological, physicochemical, and thermal properties of fermented and germinated whole reddish‐brown cowpea, white sorghum and orange‐fleshed sweet potato. Germination substantially reduced the pasting and rheological attributes of flour suspensions compared to the fermentation process. This study observed notable increases in the hot paste, setback, and final viscosities after the fermentation of cowpea and sorghum, indicating an improvement in the ease of cooking and greater retrogradation tendency of starch molecules. Among the fermented flours, sorghum had the highest hot paste viscosity (848 mPa s) and final viscosity (1451 mPa s). The mechanical fingerprint revealed a viscoelastic solid character, with G′ > G″ over the frequency range of 0–10 rad/s for all samples. Temperature sweep data showed a sharp increase in G′ at about 80°C, corresponding to the onset of starch gelatinization. Shear‐thinning behavior was observed, except in germinated and raw sorghum flours, where molecular rearrangement resulted in an initial viscosity rise at a low share rate (< 20 s−1). Differential scanning calorimetric analysis revealed a marginal variation in the peak transition temperature of gelatinization (98°C–104°C for all flours except raw sorghum flour, 83.87°C). The fermented sweet potato flour indicated good flour particle flowability expressed as Carr's compressibility index (30.99) and the Hausner ratio (1.45); however, the available reducing sugars could have influenced its high percentage solubility (49.83%), thus impacting low pasting viscosities. The contrasting technological features suggest an avenue to intensify efforts in exploring composite bioprocessed flours for applications in novel foods.

Phase equilibria and guest gas occupancy characteristics of H2-DIOX sII hydrates based on calorimetric and Raman analysis

Hydrogen (H2) as the most abundant element offers a clean energy solution for a sustainable future. Thermodynamic hydrate promoters can enhance hydrate-based H2 storage under mild pressure conditions. 1,3-dioxolane (DIOX) as a low-toxicity promoter has attracted attention for its potential to improve H2 hydrate kinetics. However, the phase equilibria of H2-DIOX in the presence of DIOX and its thermodynamic promotion mechanism are not fully elaborated and warrant thorough investigation. In this study, the phase equilibria of H2-DIOX hydrates were measured for DIOX concentrations (CDIOX) ranging from 2.0 mol% to 5.56 mol%. The equilibrium temperature of H2-DIOX hydrates shifted rightward by 2.3 K at 15.0 MPa for 5.56 mol% DIOX compared to 2.0 mol% DIOX. The measured thermodynamic data were validated by fitting the H2-DIOX hydrate phase equilibira using the Clausius–Clapeyron equation. The cage occupancy of H2 and DIOX in H2-DIOX sII hydrates was revealed through Raman spectroscopy and DSC thermal analysis. Two types of hydrates (DIOX and H2-DIOX) were observed for all CDIOX. Single H2 molecules were enclathrated in the 512 cages of H2-DIOX hydrates and increasing CDIOX effectively enhanced DIOX molecules enclathration in the 51264 cages but had limited effect on the H2 molecules in the 512 cages. The findings of this study provide fundametnal thermodynamic data and cage occupancy charateristics for H2-DIOX sII hydrates below 15.0 MPa. The results provide guidance on the optimal thermodynamic promoter concentrations for future large-scale hydrate-based H2 storage application.

Environmental Degradation Study of Polypropylene Films Incorporating Pro-Oxidants: Comprehensive Analysis and Ecotoxicological Assessment

Our research described in this paper investigated the environmental degradation of polypropylene (PP) films incorporating pro-oxidants and assessed their impact on the ecosystem. Weathering aging effects were monitored through Fourier-Transform Infrared (FTIR) analysis, revealing significant changes in carbonyl, hydroxyl and amorphous regions post-aging. The presence of pro-oxidants intensified these changes, indicating higher oxidation levels. Contact angle measurements demonstrated decreased hydrophobicity upon aging, particularly pronounced in pro-oxidant-containing films (initial contact angle: 87.79° for PP/1% Co/1% Fe, sample (F6) decreased to 79.24° after aging). Differential Scanning Calorimetric (DSC) analysis revealed decreased melting temperatures (initial Tm: 159.5 °C for F6 decreased to 148 °C after aging) and the crystallinity post-aging (initial χ: 73.25% for F6 decreased to 60.17% after aging), suggesting increased susceptibility to degradation. Thermogravimetric Analysis (TGA) showed decreased thermal stability after aging, especially in PP/pro-oxidant films; the Tonset (T5); 432.00 °C for F6, decreased to 268.00 °C after aging; where Tonset is the temperature corresponding to 5% weight loss. Biodegradation tests indicated enhanced biodegradability in the pro-oxidant-containing films, with cobalt and ferrous stearate mixtures showing the highest degradation degrees (e.g., PP/1% Co/1% Fe: ≈ 77% biodegradation after 140 days). Ecotoxicological evaluations, including microbial toxicity and plant germination and growth tests, revealed no inhibitory effects of the degradation products on soil flora or plant growth, confirming their nontoxic nature. Overall, we believe this comprehensive study provides insights into the environmental fate of PP films with pro-oxidants, highlighting their potential for accelerated degradation without adverse ecological impacts.

Manufacture of Solid Propellants Based on Renewable Succinic Acid Polyols

AbstractModern energy policies encourage the replacement of fossil fuels with a more sustainable type. Succinic acid is a promising renewable material that can react with ethylene glycol and 1,4‐butanediol in a two‐step polycondensation reaction to form hydroxylated polyesters. Copolymerization reactions were investigated to produce novel green binders for manufacture of solid propellants. The ester of the first step of polycondensation was used as a plasticizer in the propellant formulation. These products can be an alternative to binders of fossil sources, such as hydroxyl‐terminated polybutadiene (HTPB), frequently used as fuel of commercial propellants. Initially, analyses of Fourier transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography indicated the formation of polymeric products and adequate chain growth at reaction conditions. Then, the obtained copolymers were characterized by rheological analyses, which revealed that the processability of the copolymer materials was similar to that of the HTPB samples. Additionally, thermogravimetric analyses indicated that the copolymers presented good thermal stability below 200°C. Furthermore, differential scanning calorimetric (DSC) analyses indicated that the glass transition temperatures of the obtained copolymer samples ranged from −20 to −60°C, a suitable range for the intended use. Solid propellants were then prepared with solid loadings above 70 wt %, heat of combustion above 11,300 J g−1 and heat of explosion above 4,980 J g−1, which are compatible with values expected for solid propellants. Finally, oxygen balance calculations showed that the intrinsic oxygen content of the polyesters can allow the reduction of amounts of oxidizers in the final propellants.

Effect of functionalized halloysite nanotubes on fire resistance and water tolerance of intumescent fire-retardant coatings for steel structures

To improve the comprehensive performance of intumescent fire-retardant coatings, the functionalized halloysite nanotubes (HNTs-D, HNTs@Fe3O4, and HNTs-D@Fe3O4) were synthesized as synergistic flame retardants and incorporated into intumescent fire-retardant coatings (IFRC) for steel structures, demonstrating significant flame retardant properties. Among these modified halloysite nanosheets, HNTs-D@Fe3O4 showed the best flame retardancy and water resistance. Adding the optimal addition amount (3 wt%) of HNTs-D@Fe3O4 can increase the residual weight of coating from 28.10 % to 38.40 % and reduce the backside temperature of the coated steel plate from 288 °C to 177 °C, indicating that HNTs-D@Fe3O4 can effectively improve the thermal stability and insulation performances of intumescent fire-retardant coatings. Cone calorimetric analysis showed HNTs-D@Fe3O4 can effectively suppress the heat and smoke release of the intumescent fire-retardant coatings. Compared with the unmodified coating sample, the total heat release (THR) and total smoke release (TSR) of the HNTs-D@Fe3O4-containing coating sample were reduced by 66.04 % and 11.36 %. HNTs-D@Fe3O4 facilitates the formation of dense char layers confirmed by the micro morphology characterization. Further mechanism analysis shows that HNTs-D@Fe3O4 has obvious catalytic carbonization effect and is helpful to construct the dense expanded char layer with higher graphitization degree. The uniformly dispersed HNTs-D@Fe3O4 improved the water resistance of intumescent fire-retardant coatings, which is mainly due to the hydrophobicity and barrier effect, thus effectively preventing the loss of water-soluble components.

Thermal Degradation Behavior of Thermally‐Oxidized Hydroxyl‐Terminated Polybutadiene (HTPB): An Assessment of Thermal Stability

AbstractThermal analysis was performed on different thermally oxidized hydroxyl‐terminated polybutadiene (HTPB) samples, varying in molecular weights, polydispersities, and viscosities. The HTPB sample was subjected to thermal ageing at 65 °C for 10 weeks and periodically withdrawn for thermal analysis. During thermal ageing, HTPB undergoes chain rearrangements that may include scission and subsequent crosslinking, leading to a higher average molecular weight and viscosity. Differential scanning calorimeter (DSC) and thermogravimetric analyses were performed on thermally oxidized HTPB samples under inert heating conditions to investigate their degradation behavior. The DSC results revealed no significant correlations between the glass transition (Tg) and the samples' molecular weight, viscosity, and polydispersity. In TGA, all HTPB samples showed a two‐step thermal decomposition process characterized by two distinct mass loss stages. Notably, the first stage exhibited a lower total mass loss and a considerably lower peak rate of mass loss than the second stage. The thermal stability of HTPB is significantly compromised by thermal‐oxidative degradation, leading to a pronounced decrease in the initial degradation temperature (TIDT) values, from 372 °C (pristine or 0 week) to 228 °C (10 weeks). Furthermore, we measured the energy of activation (Ea) and the pre‐exponential factor (A) from TGA data using the Coats–Redfern integral equation. Notably, we observed a slight but systematic increase in both Ea and A as the molecular weight of the aged samples increased.

Development, characterization and themo-physical analysis of energy storage material doped with TiO2 and CuO nano-additives

The paper presents the results of an experimental investigation on chemical stability, surface morphology, and thermo-physical properties of phase change material integrated with nano additives. The research aims to evaluate impact of varying nano-particle concentration on thermal performance of phase change material. The phase change material magnesium dichloride hexahydrate and potassium chloride mixed in different mass ratio along with different wt% concentration of nano-additives titanium dioxide and copper oxide to prepare novel phase change material. Characterization methods such as Fourier Transform Infrared Spectroscopy, Scanning electron microscope, Energy-dispersive X-ray analysis, and Differential scanning calorimeter analysis were employed. The Fourier transform infrared spectra indicated physical interactions between phase change material and nano-additives, while Energy-dispersive X-ray analysis confirmed elemental composition, and Scanning electron microscope demonstrated uniform distribution. The improved thermal properties of samples were reflected in their phase change enthalpy (284.57 J/g to 324.63 J/g), minimal energy loss (0.91 %–2.96 %), and low supercooling (0.3 %–5.26 %). Notably, doping with 1.5 wt% of titanium dioxide and copper oxide enhanced thermal conductivity by up to 117.07 % and specific heat capacity by up to 48.09 %. The introduction of nanoparticles significantly improves heat transfer characteristics, resulting in enhanced energy retention, reduced energy loss during phase transitions, decreased supercooling, and increased physical stability. These results suggest that optimized phase change material with nano-additives is highly effective for applications requiring stable and efficient thermal management.

Regulating the interaction between protein and starch in noodles through heat loss: Used to improve the edible quality of noodles

The impact of heat loss during water-cooling process on the edible quality of cooked noodles currently remains unclear. This study aimed to explore the effects of different water-cooling times (0, 20, 40, 60, 80, 100, and 120 s) on changes in gluten and starch structures and their impact on the sensory evaluation and texture of noodles. Results showed that the control group had a higher core temperature, while the core temperature of the noodles equilibrated with the water temperature after water-cooling for 100 s. Within the range of 20–100 s of water-cooling time, a sudden drop in the core temperature of the cooked noodles caused the gluten conformation to transition toward more compact β-sheets. Surface hydrophobicity decreased, while S-S and hydrogen bonds increased. The microstructure of the noodles became more compact, reducing gaps between protein and starch molecules. Small-angle X-ray scattering and atomic force microscopy analyses demonstrated that gluten chains aggregated after water-cooling, resulting in increased chain width and height. The wheat gluten protein structure transitioned from a disordered state to a random coil. Ultimately, the hardness, springiness, and chewiness of the noodles gradually increased. Water distribution results revealed that the free water content of the noodles increased after 120 s of water-cooling, enhancing the hydration between protein and water molecules but decreasing the noodle texture. According to X-ray diffraction and differential scanning calorimeter analyses, heat loss did not alter the gelatinized starch crystal structure of noodles. Therefore, changes in core temperature were the primary cause of gluten structural changes prior to 100 s of water-cooling. After 120 s of water-cooling, increased hydration between noodle surface gluten and water negatively affected the edible quality of noodles. This study provides theoretical data on noodle edible quality and is of significant practical importance.

A novel temperature-controlled media milling device to produce drug nanocrystals at the laboratory scale

Poor aqueous solubility of preexisting and emerging drug molecules is a common issue faced in the field of pharmaceutics. To address this, particle size reduction techniques, including drug micro- and nanonisation have been widely employed. Nanocrystals (NCs), drug particles with particle sizes below 1 µm, offer high drug content, improved dissolution, and long-acting capabilities. Media milling is the most used method to prepare NCs using of-the-shelf machinery, both at the laboratory and industrial scales. However, early NCs development, especially when limited amounts of the active are available, require the use of milligram-scale media milling. This study introduces a novel mini-scale milling device (Mini-mill) that incorporates temperature control through a water-cooled jacket. The device was used to produce NCs of three model hydrophobic drugs, itraconazole, ivermectin and curcumin, with lowest particle sizes of 162.5 ± 0.4 nm, 178 ± 2 nm, and 116.7 ± 0.7 nm, respectively. Precise control of milling temperature was achieved at 15, 45, and 75°C, with drug dependent particle size reduction trends, with no adverse effects on the milling materials or polymorphic changes in the NCs, as confirmed by calorimetric analysis. Finally, a scale-up feasibility study was carried out in a lab-scale NanoDisp®, confirming that the novel Mini-mills are a material-efficient tool for early formulation development, with potential for scale-up to commercial mills.

Hexa-(2-ethylhexyl)-hexa-peri-hexabenzocoronene as archetypal model compound of asphaltenes and MAONs

Hexa(ethylhexyl)-hexa-(peri)-hexabenzocoronene (HEH-HBC) was selected as model compound of asphaltenes. In fact, in the “island” model the asphaltenes are described with a relatively large aromatic core surrounded by aliphatic chains attached to the edges of the core. In their turn the asphaltenes are considered model compounds of MAONs (Mixed Aromatic-aliphatic Organic Nanoparticles), the possible carriers of the Unidentified Infrared Bands (UIBs), i.e. a set of certain infrared features found in very different astrophysical objects. The differential scanning calorimetric analysis (DSC) shows that HEH-HBC displays a discotic liquid crystal behavior, similar to that observed also in a selected authentic petroleum asphaltene sample. The electronic absorption spectrum of HEH-HBC was recorded for the first time in hydrocarbon solvents fully transparent in the UV, permitting to observe the UV part of HEH-HBC and to compare it with that of unsubstituted HBC. The FT-IR spectrum of HEH-HBC was recorded not only at room temperature but also at higher resolution at the liquid nitrogen temperature. The molar extinction coefficients and integrated molar absorptivity of the main bands were also estimated. The results are briefly discussed from an astrochemical perspective.

Modification of Sulfur Cake—Waste from Sulfuric Acid Production

In the production of sulfuric acid, sulfur cake—a waste product of the sulfur purification process—is formed in large quantities, which requires its disposal and use. For its use in composite materials, modification is necessary to convert sulfur into a polymer form. The aim of the study was to develop a method for modifying sulfur cake—a waste product of sulfuric acid production—for its disposal. Available reagents—styrene, glycerol, and oleic acid—were tested as modifiers in the work. The sample compositions consisted of 100% sulfur cake (no. 1) and its mixtures: 97% sulfur cake + 3% styrene (no. 2), 97% sulfur cake + 3% glycerol (no. 3), 97% sulfur cake + 3% oleic acid (no. 4), 95% sulfur cake + 3% styrene, 1% glycerol, and 1% oleic acid (no. 5). Modification of sulfur cake was carried out at a temperature of 140 °C for 30 min. The composition, crystal structure, and thermal properties of the samples of the original and modified sulfur cake were studied using X-ray phase and X-ray structural analyses, IR spectroscopy, differential scanning calorimetry, differential thermal and thermogravimetric analysis. The optimal modifier for sulfur cake was a mixture of styrene, glycerol, and oleic acid, which led to the formation of acetal (polyoxymethylene) and an improvement in the structure due to a decrease in the content of impurities. Modification of sulfur cake with styrene resulted in the appearance of a CAr–S bond band at 571 cm−1, and modification with oleic acid a C–S band in the region of 694 cm−1 in the IR spectra. The results of differential scanning calorimetric analysis showed an increase in the heat of fusion of sulfur by 12.45 J/g in the samples of sulfur cake modified with glycerol and styrene. Modification of sulfur cake with oleic acid and a mixture of reagents resulted in the appearance of a third peak with maxima at 244.2 and 264.0 °C, which demonstrated a significant effect of the indicated additives on the thermal behavior of the sulfur cake. Proposed schemes for modifying sulfur cake with styrene and oleic acid are presented.

Quinolone Derivative Physicochemical Studies: Phase Equilibria in Water and Alcoholic Solutions, Ionization Constants, and Calorimetric Analyses

Quinolone Derivative Physicochemical Studies: Phase Equilibria in Water and Alcoholic Solutions, Ionization Constants, and Calorimetric Analyses

Determination of surface acidity of mixed oxide of silicon and titanium by calorimetric titration

Silica-titania mixed oxide with catalytic and adsorption properties has been of great academic and industrial interest. Metal oxides supported on silica have been used as a matrix for immobilizing electron transfer mediators, generating materials with diverse properties. The characterization of the surface acidity of these materials is essential and has been carried out using various techniques, including IR spectroscopy and calorimetry. However, no single technique completely analyses the present acidic sites. This study used calorimetric titration to investigate a mixed oxide containing titanium and silica, prepared by the sol-gel method, and its interaction with pyridine. The results showed that thermal treatment increased the enthalpy values (ΔH), indicating water removal from the matrix surface. The presence of pyridine resulted in a decrease in ΔH values, suggesting a preferential occupation of the stronger acidic sites. After thermal treatments between 473 and 573 K, the solids exhibited similar ΔH values, indicating a homogenization of the surface acidic sites. Calorimetric analysis revealed that the acidic sites were occupied in descending order of strength, with the strongest sites being filled initially. The increase in temperature did not result in new acidic sites but rather in greater occupation of the existing ones. Correlation between calorimetric and infrared data is suggested as the next investigation step. Thus, the results of this study contribute to a deeper understanding of the physicochemical properties, especially regarding their surface acidity, with the potential for more effective and controlled practical applications of this silica-titania mixed oxide in catalysis and adsorption.