DSC Peak Research Articles

Development of an applied variant of the kolmogorov–johnson–mehl theory of crystallization for processing thermal analysis data. Temperatures and enthalpies of melting germanium isotopes

An applied kinetic model has been developed for processing DSC peaks of transitions between states, determining the temperature–time dependence of the degree of transition and combining the fundamental theory of Kolmogorov–Johnson–Mehl crystallization, simplified for practice, with the semi-empirical Erofeev model. In the development of this applied model, the concept of a “thermodynamic factor” is introduced, which allows a transition in the kinetics of phase transformations of condensed matter. The application of the new approach is demonstrated by the example of studying the dependences of temperature and enthalpy of fusion on the average atomic mass of stable germanium isotopes, data on which, as new chemical individuals, are of a fundamental nature and can serve as reference information.

Preparation, Characterization and Evaluation of Antioxidant Flavonosomes

The objective of the present study was to prepare flavonosomes loaded with kaempferol and curcumin in order to improve the bioavailability of the flavonoids. The flavonosomes loaded with kaempferol and curcumin were prepared using bulk co-loading method using lecithin as the lipid molecule. The particle size of the flavonosomes was determined using zeta sizer and ranged from 497.3 nm to 167.1 nm. The results indicated that increase the ratio of lipid to extract was able to reduce the particle size of the flavonosomes. The flavonosomes prepared using 4:1 ratio of lipid to flavonoids were found to be rigid, spherical as seen in SEM with smooth regular surface. Sharp and distinct endothermic peaks in DSC revealed the formulation of stable flavonosomes due to molecular interactions between the extract and lecithin. The entrapment efficiency of flavonosome preparation F4 was determined by measurement of the non-entrapped flavonoids and subtracting from the total flavonoids used to obtain the flavonoids entrapped in the formulation. The entrapment efficiency of F4 has been calculated to be 94.12%. The flavonosome F4 was studied for release of the entrapped flavonoids by dialysis method. The amount of flavonoids released at 1, 2, 3, 4, 6, 8, 10 and 12 hours was determined using UV spectrophotometry. After the first hour, the entrapped flavonoids released in a steady manner from the flavonosome depicting and almost complete release (90.52% for kaempferol and 94.67% for curcumin) from the formulation. The flavonosomes were found to be stable under the storage conditions. The best formulation with respect to particle size and anti-inflammatory action was F4 that contained 4:1 ratio of lecithin: flavonoids. DPPH radical scavenging assay was used to determine the antioxidant action of the individual flavonoids and the flavonosome formulation. It was found that the formulation F4 was having higher antioxidant activity in comparison to kaempferol and curcumin. The IC50 of kaempferol, curcumin and flavonosome were found to be 228.20 µg/mL, 175.51 µg/mL and 158.19 µg/mL respectively. Keywords: Flavonosome, Kaempferol, Curcumin, Bulk co-loading, antioxidant

Effect of amine-based burning rate suppressants on the HTPB propellants: Thermal decomposition and combustion characteristics

Slow-burn propellants are crucial for aerospace advancement. This study focuses on the development of slow-burn propellants by replacing a small amount of AP (3–9 %) with various amine-based burning rate suppressants (BRSs). The consistency between thermal analysis and combustion test results indicates a direct link between the main exothermic decomposition process and combustion performance, with changes in onset temperature positively correlated with decreases in combustion parameters. Upon adding 3 % oxamide, the onset temperature of the main decomposition peak in DSC shifted backward by 16.2 °C, significantly higher than the formulations containing ammonium sulfate at 2.6 °C and ammonium oxalate at −0.8 °C. As the content of oxamide further increased from 3 to 9 %, the ignition delay time increased simultaneously by 0.300–1.638 s, atmospheric burning rate decreased by 14.01–45.45 %. These values represent the maximum among formulations with the same content of the BRSs, mainly attributed to its higher heat absorption capacity.

In vitro and in vivo assessment of gallic acid-chitosan/polycaprolactone conjugate electrospun nanofibers for wound healing

The development of innovative multifunctional wound healing materials based on natural bioactives has attracted a great deal of attention in recent years due to their ability to potentiate the healing process and minimize the challenges linked with conventional wound dressings. The current study demonstrates the development and evaluation of a novel nanofibrous wound healing mat made of Gallic acid-chitosan conjugate (GAC) incorporated within a polycaprolactone (PCL) matrix using an electrospinning technique. The GAC conjugate was synthesized by green synthesis using a free radical polymerization reaction to improve the chitosan's free radical scavenging properties. FTIR, DSC, XRD, and UV spectral analysis characterized the formation of GAC conjugate. The red shift observed in the UV spectrum suggested alterations in electronic transitions resulting from the creation of covalent bonds between Chitosan (CA) and Gallic acid (GA). The appearance of broader and weaker peaks in DSC and the reduced crystallinity in XRD spectrum, signify structural modifications, thereby providing valuable insights into the interaction and structural changes occurring in the GAC conjugates.The SEM image revealed a porous flake-like structural network of GAC conjugate due to the reduced intermolecular hydrogen bonding between them. The functional layer of the nanofibrous mat was produced by electrospinning GAC conjugate with polycaprolactone (PCL) to provide mechanical integrity to the nanofibrous mat. The electrospun nanofibers were characterized using FTIR, DSC, and SEM and evaluated for cell cytotoxicity, angiogenesis, and in vivo wound healing potential in female Wistar rats. The FTIR spectra confirmed the presence of GAC conjugate in the nanofibers, validating the conjugation process. The results demonstrated the successful incorporation of GAC conjugate within the PCL nanofibrous mat, thereby confirming the improvement in the biological properties of the mats. The nanofibrous mat showed angiogenesis activity in the yolk sac membrane assay confirming the property of nanofibers to facilitate cellular adhesion, migration and promotion of angiogenesis with no cytotoxic effect on the viability of mouse stromal cells. On the sixteenth day of therapy, wounds dressed with GAC/PCL nanofibrous mat exhibited a significant improvement in the percent wound closure (94.43%) as compared to the control group (p < 0.05). These results supported the application of GAC/PCL as a novel biomaterial for wound dressing to accelerate the process of wound healing.

Comparison of water and benzene as probe liquids in thermoporometry of mesoporous carbons

Water and benzene were compared as probe liquids for thermoporometric characterization of mesoporous carbons. For testing, four different carbonaceous materials were prepared by soft- or hard-templating procedures with mesopore diameters in the range 3–12 nm. In addition, all materials were tested in hydrophobic (pristine, carbonized at 900 °C) and hydrophilic (moderate oxidation by persulphate) form. The results show that both tested liquids express a good linear correlation between heat of melting in pores (measured as DSC peak area) and volume of mesopores. Melting point depression of probe liquid confined in pores related to mesopore size was found out to be steeper for benzene confirming a higher value of Gibbs-Thomson constant of benzene compared to water. Neither heat of melting in pores nor melting point depression were affected by carbon surface oxidation. Contrary, the non-freezing layer (δ layer) of a liquid in pores was considerably wider for most of hydrophilic samples than hydrophobic ones when water was employed, while it stayed nearly constant when benzene was applied. Nevertheless, both tested probe liquids generally enable to obtain similar pore size distributions if appropriate values of δ layers are used. Benzene as a probe liquid in thermoporometry of carbons have some advantages compared to water but only in limited cases. Benzene can be recommended for characterisation of large mesopores and its usage can be beneficial for comparison of analogous samples with different surface chemistry.

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.

Anti-aging performance improvement and enhanced combustion efficiency of boron via the coating of PDA

Boron is an ambitious fuel in energetic materials since its high heat release values, but its application is prohibited by low combustion efficiency and oxidization during storage. The polydopamine (PDA) was introduced into boron particles, investigating the impact of PDA content on the energetic behavior of boron. The results indicated that the PDA coating formed a fishing net structure on the surface of boron particles. The heat release results showed that the combustion calorific value of B@PDA was higher than that of the raw boron. Specifically, the actual combustion heat of boron powder in B@10%PDA increased by 38.08%. Meanwhile, the DSC peak temperature decreased by 100.65 °C under similar oxidation rate compared to raw boron. Simultaneously, the B@PDA@AP and B@AP composites were prepared, and their combustion properties were evaluated. It was demonstrated that B@10%PDA@AP exhibited superior performance in terms of peak pressure and burning time, respectively. The peak pressure is 12.43 kPa more than B@AP and burning time is 2.22 times higher than B@AP. Therefore, the coating of PDA effectively inhibits the oxidization of boron during storage and enhances the energetic behavior of boron and corresponding composites.

FORMULATION AND EVALUATION OF PHYTOSOMES LOADED WITH PITHECELLOBIUM BIJENINUM LEAF EXTRACT

The objective of the present study was to prepare phytosomal formulation loaded with aqueous extract of Pithecellobium bijeninum leaves. The extraction of leaf powder was done by maceration technique using 90:10 ethanol-water mixture with an extraction yield of 6.12%. The extract was found to contain alkaloids, and flavonoids and the total phenolic content was found to be 23.2 ± 0.827 %w/w. Phytosomes of the extract were prepared by solvent evaporation method using lecithin as the lipid molecule. The particle size of the phytosomes was from 468 nm to 1827 nm in size with a polydispersity index varying between 0.178 - 0.464. The phytosomes were visible as rigid, almost spherical vesicles in SEM image. The surface of the phytosome vesicles was found to be regular and smooth. The point prediction suggested level 3 (0.3 g) of lipid concentration and level 2 (0.2 g) of extract concentration to present the lowest particle size. Sharp and distinct endothermic peaks in DSC revealed the formulation of stable phytosomes due to molecular interactions between the extract and lecithin. The phytosomes were found to possess good antioxidant action against DPPH radical in the in vitro scavenging assay. The IC50 value of the extract against DPPH was found to be 48.24 µg and that of the phytosomal formulation loaded with the extract (F4) was obtained to be 48.90 µg. KEYWORDS: Phytosome, extraction, lecithin, Pithecellobium, antioxidant

Thermal Investigations of Annelated Triazinones-Potential Analgesic and Anticancer Agents.

In this article, for the first time, TG-DSC and TG-FTIR investigations of potential pharmaceutics, i.e., analgesic and anticancer active annelated triazinones (1-9) have been presented. The thermal behaviour of these molecules was established in oxidative and inert conditions. The solid-liquid phase transition for each compound (1-9) was documented by one sharp DSC peak confirming the high purity of each sample studied. All the molecules were characterised in terms of calorimetric changes and mass changes during their heating. They revealed high thermal stability in oxidative and inert conditions. The observed tendency in thermal stability changes in relation to a substituent present at the phenyl moiety was found to be similar in air and nitrogen. It was confirmed that annelated triazinones 1-9 were stable up to a temperature range of 241-296 °C in air, and their decomposition process proceeded in two stages under oxidative conditions. In addition, it was established that their thermal stability in air decreased in the following order of R at the phenyl moiety: 4-Cl > 3,4-Cl2 > H > 3-Cl > 4-CH3 > 2-CH3 > 3-CH3 > 2-Cl > 2-OCH3. The volatile decomposition products of the investigated molecules were proposed by comparing the FTIR spectra collected during their thermogravimetric analysis in nitrogen with the spectra from the database of reference compounds. None of annelated triazinones 1-9 underwent any polymorphic transformation during thermal studies. All the compounds proved to be safe for erythrocytes. In turn, molecules 3, 6, and 9 protected red blood cells from oxidative damage, and therefore may be helpful in the prevention of free radical-mediated diseases.

Polyhydroxy butyrate biosynthesis by Azotobacter chroococcum MTCC 3858 through groundnut shell as lignocellulosic feedstock using resource surface methodology

This work appraises the prospect of utilising groundnut shell hydrolysate as a feedstock used for PHB biosynthesis by Azotobacter chroococcum MTCC 3853 under SMF conditions. Sugar reduction: untreated and pretreated 20% H2SO4 (39.46 g/l and 62.96 g/l, respectively), untreated and enzymatic hydrolysis (142.35 mg/g and 568.94 mg/g). The RSM-CCD optimization method was used to generate augment PHB biosynthesis from groundnut shell hydrolysate (30 g/l), ammonium sulphate (1.5 g/l), ammonium chloride (1.5 g/l), peptone (1.5 g/l), pH 7, 30 °C, and a 48 h incubation time. The most convincing factors (p < 0.0001), coefficient R2 values of biomass 0.9110 and PHB yield 0.9261, PHB production, highest biomass (17.23 g/l), PHB Yield(11.46 g/l), and 66.51 (wt% DCW) values were recorded. The control (untreated GN) PHB yield value of 2.86 g/l increased up to fourfold in pretreated GN. TGA results in a melting range in the peak perceived at 270.55 °C and a DSC peak range of 172.17 °C, correspondingly. According to the results, it furnishes an efficient agricultural waste executive approach by diminishing the production expenditure. It reinforces the production of PHB, thereby shrinking our reliance on fossil fuel-based plastics.

A Relatively Simple Look at the Rather Complex Crystallization Kinetics of PLLA.

This work demonstrates that, despite the existence of a significant number of works on PLA crystallization, there is still a relatively simple way, different from those already described, in which its complex kinetics can be observed. The X-ray diffraction (XRD) results presented here confirm that the PLLA under study crystallizes mostly in the α and α' forms. An interesting observation is that at any temperature in the studied range of the patterns, the X-ray reflections stabilize with a given shape and at a given angle, different for each temperature. That means that both α and α' forms coexist and are stable at the same temperatures so that the shape of each pattern results from both structures. However, the patterns obtained at each temperature are different because the predominance of one crystal form over the other depends on temperature. Thus, a two-component kinetic model is proposed to account for both crystal forms. The method involves the deconvolution of the exothermic DSC peaks using two logistic derivative functions. The existence of the rigid amorphous fraction (RAF) in addition to the two crystal forms increases the complexity of the whole crystallization process. However, the results presented here show that a two-component kinetic model can reproduce the overall crystallization process fairly well over a broad range of temperatures. The method used here for PLLA may be useful for describing the isothermal crystallization processes of other polymers.

Influence of the milling conditions on the compressive strength of Ti/TiC composite materials sintered at atmospheric pressure

High compressive strength composite materials based on commercially pure titanium were synthesized from Ti Cp grade 2 powders processed by high-energy ball milling using n-hexane as PCA and subsequent sintering in a tubular furnace under argon atmosphere at 1100 °C for 2 h, at atmospheric pressure. The study focused on two main aspects: (i) The effect of speed and milling time on the microstructure and (ii) the relationship between the microstructure and the mechanical resistance of the obtained material. It was found that the presence of TiC was related to the mechanochemical process during milling that occurs under specific conditions of speed and time when enough energy was transferred to the powder coupled with the thermal process at elevated temperature. According to the DSC peaks, the activation energy for the transformations is close to 171 kJ/mol. The microstructure of the sintered samples was characterized by SEM EDS, XRD, and TEM, and the mechanical properties by compression and hardness tests. The high compressive strength of the specimens was attributed to three aspects: (i) the distribution of particles in the sintered samples, (ii) the fine grain size derived from the milling process and (iii) the formation of titanium carbide. A maximum compressive strength of 2.8 GPa makes this material sintered by a simple and low-cost route, very competitive with other advanced Ti composites.

MgCl2-MXene based nanohybrid composite for efficient thermochemical heat storage application

Thermochemical heat storage is a practical approach for overcoming the challenge in solar energy applications. Herein, we synthesize a novel MgCl2/MXene (Ti3C2Tx) composite sorbent by impregnation method for low-temperature thermochemical heat storage application. Various techniques, including Thermogravimetric coupled with Differential Scanning Calorimetric (TG-DSC), X-Ray, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were applied to characterize the mechanical and thermal properties of MgCl2/MXene composites. The result showed that Ti3C2Tx possess a larger specific surface area and the hydrophilic groups allow maximum MgCl2 adsorption without structural distortion. The TG-DSC studies showed that the fourth DSC peak of MgCl2 (181.33 °C) is shifted in composites MX/Mg 15 % (159.63 °C) and MX/Mg 10 %, (141.67 °C) toward lower dehydration temperature. The cyclicability study demonstrated that in the 10 consecutive rehydration cycles, MgCl2 shows 45 % decrease in the enthalpy, while Mg/MX 10 % and Mg/MX 15 % composites record 4 % and 10 % decrease, respectively. Water uptake kinetics highlighted that at 85 % RH, the highest water sorption was recorded for Mg/MX 15 % where it absorbs 2.21 g/g mass. The energy storage density result reveals that the maximum loading rate of MgCl2·6H2O reaches 97.6 wt% for Mg/MX 15 % showed the highest enthalpy 2227 J/g at 85 % RH. Therefore, all the results indicate that MXene-based salt composites play an important role in thermochemical heat storage application, leading to a potential candidate for long-term heat storage.

Nanoencapsulation of R-phycoerytrin extracted from Solieria filiformis improves protein stability and enables its biological application as a fluorescent dye

We aimed to encapsulate R-PE to improve its stability for use as a fluorescent probe for cancer cells. Purified R-PE from the algae Solieria filiformis was encapsulated in polymeric nanoparticles using PCL. Nanoparticles were characterised and R-PE release was evaluated. Also, cellular uptake using breast and prostate cancer cells were performed. Nanoparticles presented nanometric particle size (198.8 ± 0.06 nm) with low polydispersity (0.13 ± 0.022), negative zeta potential (−18.7 ± 1.10 mV), and 50.0 ± 7.3% encapsulation. FTIR revealed that R-PE is molecularly dispersed in PCL. DSC peak at 307 °C indicates the presence of R-PE in the nanoparticle. Also, in vitro, it was demonstrated low release for nanoparticles and degradation for the free R-PE. Finally, cellular uptake demonstrated the potential of R-PE/PCL nanoparticles for cancer cell detection. Nanoparticles loaded with R-PE can overcome instability and allow application as a fluorescent probe for cancer cells.

Unusual crystallization pathways revealed in six barium disilicate (BaSi2O5) glasses

Due to the unusual crystallization of (nominally) stoichiometric BaSi2O5 (BS2) glass, which shows unexpected and diverse crystal phases, a series of six glasses with different chemicals and melting procedures were prepared in three laboratories and characterized before and after crystallization by differential scanning calorimetry, density measurements, X-ray diffraction, FTIR, and Raman spectroscopy. The aim of this study was to assess whether there is systematic behavior in the crystallization pathways in relation to precursor chemicals, impurities, and hydroxyl content of this glass. Small glass monoliths were treated at the first DSC crystallization peak and quenched to determine which phases formed in the early-stages of crystallization. The glass transition temperatures (Tg) divide these six glasses between those with a Tg near 690 °C versus those near 700 °C. The DSC peak crystallization temperatures varied even more; from 855 to 917 °C. In these six glasses, our results are best explained by a combination of metastable high-BaSi2O5 and Ba6Si10O26. Monotonic trends in crystallization show that the DSC signal from the Ba-rich phases increases as the Tg and the crystallization temperatures increase. The BS2 glasses with both the lowest Tg and lowest DSC crystallization temperatures show the most barium disilicate crystal. This leads to the conclusion that the metastable monoclinic high-BaSi2O5 is favored in these conditions. The small differences in glass synthesis conditions and chemicals used strongly influence the relative proportions of phases which crystallize and their kinetics. In-situ and ex-situ diffraction measurements confirm the conclusions above. The structural distinctions between the barium silicate crystals and the BS2 supercooled liquid, and the implications for the role of structural polymerization are discussed. We conclude that high-BaSi2O5 or Ba6Si10O26 are the predominant phases in the earliest stages of crystallization. This study highlights the extreme sensitivity of BS2 glass crystallization kinetics and pathways to minor differences in composition and synthesis conditions and explains the different conclusions reached by distinct authors that worked on the crystallization of BS2 glasses.

Zaltoprofen-layered double hydroxide hybrids to enhance zaltoprofen solubility and dissolution rate

The zaltoprofen-LDH hybrid was successfully synthesized by coprecipitation method, and its dissolution profile and solubility in different fluids, that simulate the gastro-intestinal environment, were investigated. The zaltoprofen-LDH hybrid stoichiometry was determined by EDS and TGA, and the Zn0.70Al0.30(OH)2Z0.30·0.76H2O chemical formula was obtained, which well compares to the Zn/Al molar ratio of the pristine LDH (nitrate-LDH hybrid: Zn0.73Al0.27(OH)2(NO3)0.27·0.44H2O), synthesized to prepare the zaltoprofen-LDH physical mixture for the dissolution tests. The XRPD results confirmed the successful insertion of the zaltoprofen in the interlayer space of the LDH structure: the 003 reflection, detected at d-value of 8.7 Å in the pristine LDH, was observed at d-value of 21.8 Å, and the drug occupied a gallery of about 17 Å. Based on the zaltoprofen size (9.9 × 4.9 Å), a drug arrangement in which the molecules form a monolayer of partially superimposed drug anions into the brucite-like layer is suggested. The DSC peak due to the melting process of the pure zaltoprofen was not observed in the zaltoprofen-LDH hybrid, thus indicating the loss of the long-range structural order in the active principle. FT-IR spectroscopy confirmed that the zaltoprofen entered the host structure in the anionic form (COO−). Deep insights in the drug-LDH interaction were obtained by 13C and 27Al solid state NMR: the zaltoprofen molecules strongly interacted with the LDH layers involving the COO- and the OH moieties respectively, while the packing of the drug molecules in the layers was comparable to the conformation of the pure zaltoprofen crystals. The zaltoprofen anion insertion caused local structural changes within the host crystal structure. The solubility and dissolution tests, performed on the synthesized hybrid and compared to the pure zaltoprofen and zaltoprofen-LDH physical mixture, demonstrated enhanced solubility and dissolution rate of the drug in the hybrid system.

Formulating Ternary Inclusion Complex of Sorafenib Tosylate Using β-Cyclodextrin and Hydrophilic Polymers: Physicochemical Characterization and In Vitro Assessment.

Sorafenib tosylate (SFNT) is the first-line drug for hepatocellular carcinoma. It exhibits poor solubility leading to low oral bioavailability subsequently requiring intake of large quantities of drug to exhibit desired efficacy. The present investigation was aimed at enhancing the solubility and dissolution rate of SFNT using complexation method. The binary inclusion complex was prepared with β-cyclodextrin (β-CD). The molecular docking studies confirmed the hosting of SFNT into hydrophobic cavity of β-CD, while the phase solubility studies revealed the stoichiometry of complexation with a stability constant of 735.8M-1. Theternary complex was prepared by combining the SFNT-β-CD complex with PEG-6000 and HPMC polymers.The results from ATR-IR studies revealed no interaction between drug and excipients. The decreased intensities in ATR-IR peaks and changes in chemical shifts from NMR of SFNT in complexes indicate the possibility of SFNT hosting into the hydrophobic cavity of β-CD.The disappearance of SFNT peak in DSC and XRD studies revealed the amorphization upon complexation.The ternary complexes exhibited improved in vitro solubility (17.54µg/mL) compared to pure SFNT (0.19µg/mL) and binary inclusion complex (1.52µg/mL). The dissolution profile of ternary inclusion complex in 0.1 N HCl was significantly higher compared to binary inclusion complex and pure drug. In cytotoxicity studies, the ternary inclusion complex has shown remarkable effect than the binary inclusion complex and pure drug on HepG2 cell lines.

Kinetics of the thermolysis of 3‐nitro‐2,4‐dihydro‐3H‐1,2,4‐triazol‐5‐one (NTO) and nanosize NTO the presence of nickel‐zinc‐cobalt ferrite

This study deals with the evaluation of the catalytic activity of quaternary nickel-zinc-cobalt ferrite (NiZnCoF) nanoparticles on the thermal decomposition of 3-nitro-2,4-dihydro-3H-1,2,4-triazol-5-one (NTO). Nanosize NiZnCoF has been successfully synthesized using the co-precipitation method. The effect of 5% by mass NiZnCoF on the thermolysis of NTO and NTO with nanosize (nNTO) has been studied using simultaneous thermal analysis. In the presence of NiZnCoF additive, the decomposition of NTO and nNTO was increased by 8.55 and 7.68°C, indicating that the additive stabilizes NTO and nNTO. The DSC peak temperature also suggests the presence of NiZnCoF decreases the nNTO's exothermic curve by 5.62°C. The DSC peak curve of NTO in the presence of NiZnCoF was shifted from 276.35 to 272°C. The activation energy calculations suggested that the high activation energy of NTO can be reduced ∼82–87 kJ mol−1 by nanosizing NTO followed by the incorporation of NiZnCoF.

Rheological, Thermal, Structural, and Chemical Changes during Oxidation of Gum Arabic by Ozone

ABSTRACT Gum Arabic (GA) samples with 6% (w/v) concentration in water were ozonated for 5, 30, and 60 min, corresponding to 0.0030, 0.0125, and 0.0140 g consumed ozone/L, respectively. Ozonation steadily reduced the viscosity, flow, and consistency index of GA suspensions significantly (P < 0.05). Although no apparent changes were observed in the general chemical structure of GA samples, an increase in the absorbance of -OH bends was detected by FTIR analysis. DSC peak temperatures (292.0 ± 0.1 to 281.0 ± 0.9 °C) and pH values of samples (4.84 ± 0.13 to 2.90 ± 0.09) were decreased upon ozonation. Small but statistically significant differences (P < 0.05) were obtained for water solubility and water absorption index of samples after ozonation. Phenolic compounds and radical scavenging activities in GA were increased significantly (P < 0.05) by ozonation. Ozonation, which is an environmental-friendly unit operation, would offer valuable contributions to relevant industries with improved properties of GA.

Atomic-scale study on the precipitation behavior of an Al–Zn–Mg–Cu alloy during isochronal aging

• The phase evolution of an Al−Zn−Mg−Cu alloy during isochronal aging at three different heating rates—3, 10 and 30 K/min is revealed. • The characteristic DSC peaks related to the formation of GPI and GPII zones have been identified. • A novel type of metastable phase η 1 ’ as the precursor of η 1 is identified. A pathway for the formation of η 1 via η 1 ’ is demonstrated. It is found that the precipitation kinetics of η’ cannot be evaluated solely by one characteristic DSC peak, because η’, η 1 and η 1 ’ contribute to the same DSC peak. • The role of quenched-in dislocation in promoting the precipitation of η phase is revealed. • Based on quantitative analysis, the influence of heating rate and ending temperature on the cross section and number density of phases is further discussed. The precipitation behavior of a 7075 Al alloy during isochronal heat treatments at three different heating rates has been studied using differential scanning calorimetry, high-angle-annular-dark-field scanning-transmission-electron microscope and density functional theory calculation. In the early stage of aging, GPI and GPII zones form sequentially and cause two characteristic DSC peaks. Subsequently, the formation of η 1 precipitates takes place concurrently with η’. A novel type of metastable phase η 1 ’ is identified as the precursor of η 1 , which can lower the lattice misfit between η 1 and Al matrix along the direction of [10 1 ¯ 0] η1 // [001] Al . Accordingly, a pathway for the formation of η 1 via η 1 ’ is demonstrated. Precipitates η’ together with η 1 and η 1 ’ contribute to the third DSC peak. With the further increase of temperature, η precipitates become prevailing. Based on the quantitative analyses, the influence of the heating rate and ending temperature on the cross section and number density of phases formed is discussed.