Distinct Endothermic Peaks Research Articles

Chalcopyrite CuFeS2: Solid-State Synthesis and Thermoelectric Properties

The optimal conditions for synthesizing a pure chalcopyrite CuFeS2 phase were thoroughly investigated through the combination of mechanical alloying (MA) and hot pressing (HP) processes. The MA process was performed at a rotational speed of 350 rpm for durations ranging from 6 to 24 h under an Ar atmosphere, ensuring proper mixing and alloying of the starting materials. Afterward, MA-synthesized chalcopyrite powder was subjected to HP at temperatures between 723 K and 823 K under a pressure of 70 MPa for 2 h in a vacuum. This approach aimed to achieve phase consolidation and densification. A thermal analysis via differential scanning calorimetry (DSC) revealed distinct endothermic peaks at the range of 740–749 K and 1169–1170 K, corresponding to the synthesis of the chalcopyrite phase and its melting point, respectively. An X-ray diffraction (XRD) analysis confirmed the successful synthesis of the tetragonal chalcopyrite phase across all samples. However, a minor secondary phase, identified as Cu1.1Fe1.1S2 (talnakhite), was observed in the sample hot-pressed at the highest temperature of 823 K. This secondary phase could result from slight compositional deviations or local phase transformations at elevated temperatures. The thermoelectric properties of the CuFeS2 samples were evaluated as a function of the HP temperatures. As the HP temperature increased, the electrical conductivity exhibited a corresponding rise, likely due to enhanced densification and reduced grain boundary resistance. However, this increase in electrical conductivity was accompanied by a decrease in both the Seebeck coefficient and thermal conductivity. The reduction in the Seebeck coefficient could be attributed to the higher carrier concentration resulting from improved electrical conductivity, while the decrease in thermal conductivity was likely due to reduced phonon scattering facilitated by the grain boundaries. Among the samples, the one that was hot-pressed at 773 K displayed the most favorable thermoelectric performance. It achieved the highest power factor of 0.81 mWm−1K−1 at 523 K, indicating a good balance between the Seebeck coefficient and electrical conductivity. Additionally, this sample achieved a maximum figure-of-merit (ZT) of 0.32 at 723 K, a notable value for chalcopyrite-based thermoelectric materials, indicating its potential for mid-range temperature applications.

Enhancing photovoltaic applications through precipitating agents in ITO/CIS/CeO2/Al heterojunction solar cell

In this groundbreaking study, we successfully synthesized both cerium oxide and copper indium sulphate nanoparticles via co-precipitation method and the same is spray coated on ITO substrate by Jet Nebulizer Spray Pyrolysis (JNSP) technique. A comprehensive characterization of the structural, morphological and Photo-diode properties was conducted using a range of advanced techniques. X-ray diffraction revealed a superior mono-crystalline cubic fluorite structure with a preferred orientation along the (111) plane, indicating exceptional crystal quality. Scanning electron microscopy and transmission electron microscopy images showed the formation of disk-shaped particles with sharp rounded edges, averaging ∼ 5 nm in size. Fourier transform infrared spectroscopy identified the phonon band envelope of the metal oxide (CeO2) network at 848 cm−1 while photoluminescence spectroscopy revealed blue and blue-green emission in the visible spectrum. Thermogravimetric-differential thermal analysis exhibited a total weight loss of 19.52 % with four distinct exothermic and endothermic peaks. X-ray photoelectron spectroscopy confirmed the presence of Ce and O elements, with a minor amount of carbon absorbed from the atmosphere and revealed the dominant occurrence of Ce4+ and minority occurrence of Ce3+. The maximum power conversion efficiency of 0.23 % was achieved for samples prepared using NH3 precipitant making them highly suitable for photovoltaic applications. This work paves the way for future research in optimizing cerium oxide nanoparticles for high-performance photovoltaic devices potentially leading to breakthroughs in renewable energy harvesting.

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

Allylthiourea‐mediated self‐healing hydrogels based on poly(vinyl alcohol): Enhanced cell viability/biocompatibility and sustained drug release

AbstractHydrogel‐based materials represent promising candidates for drug delivery. In our research, we synthesized a series of hydrogels—PVATU‐1 (2:1), PVATU‐2 (1:1), and PVATU‐3 (0.5:1)—by adjusting the poly(vinyl alcohol) (PVA) ratio while maintaining a constant ratio of allylthiourea (ATU) monomer and glutaraldehyde cross‐linker, aiming to understand their impacts on gelation. These PVATU hydrogels displayed impressive swelling in neutral conditions and exhibited visible self‐healing capabilities. Notably, PVATU‐1 shows superior mechanical strength among the variants. Surface analysis using AFM and SEM unveiled porous structures within the hydrogels, while thermal stability tests indicated their resilience up to 200°C. DSC analysis revealed minimal variation in glass transition temperatures (Tg), affirming stability. A distinct endothermic peak around 250–350°C across all hydrogels confirmed their semi‐crystalline nature, corroborated by powder XRD. Noteworthy, PVATU‐1 demonstrated optimal loading and releasing efficiency for levofloxacin, with 74.5% loading and 82.8% releasing efficiency within 18 h. Biocompatibility assessments on HeLa cells affirmed the nontoxicity of PVATU hydrogel treatments.

Influence of vanadium and dysprosium co-doping on phase stability, microstructure, and electrical properties of Bi2O3

Herein, we report the synthesis of Dy–V co-doped Bi2O3 ceramics using the solid–state processing technique under atmospheric conditions. The X-ray diffraction (XRD) patterns demonstrate the stability of the cubic fluorite δ-Bi2O3 in the V-rich ceramics. However, in Dy-rich ceramics, a mixture of phases, including α and δ, gradually diminishes with increased mutual dopant concentrations, suggesting a transition to the single fcc δ-phase with Fm-3 m space group. According to the Rietveld analysis and electron density representation, it is evident that there are no impure peaks present in α-Bi2O3, which highlights the clear transition to the δ-phase polymorphs. The DTA curves for samples M4 and M7 display a distinct endothermic peak at temperatures around 724.5 and 744.5 °C, indicating a phase transition from the monoclinic α-phase to the cubic δ-phase. These peaks are also attributed to an order-disorder transition (ODT). The FESEM micrographs consistently revealed the existence of irregular and aggregated grains, with an average grain size ranging from 0.80 to 5.57 μm. The level of aggregation became more apparent with the escalation of Dy3+ doping, as opposed to the 5–20 wt% V loading. Moreover, the as-sintered pellets M2 demonstrated the absence of any pore formation compared to other samples, confirming a remarkably high degree of densification. As a result, the as-sintered pellets have a low level of void space, with an apparent porosity of no more than 2.5%. Based on the conductivity measurements and electrochemical impedance spectroscopy (EIS), Bi0.85V0.10Dy0.05O1.5 exhibits the highest electrical conductivity of 0.965 (Ω cm)−1 and an optimal activation energy of 0.537 eV at 627 °C compared to other prepared compositions. This remarkable performance is attributed to the high polarizability and mixed valence cations, especially in V5+-rich ceramics, compared to the Dy3+-rich compositions with a reduced conductivity of 0.010 to 0.097 (Ω cm)−1. The Nyquist plots indicate that impedance decreases with vanadium doping increases until it reaches Bi0.85V0.10Dy0.05O1.5. Higher Dy3+ content increases impedance, leading to lower cell performance. The typical composition can be a solid electrolyte in SOFCs operating at moderate temperatures.

Observation of a temperature dependent anomaly in the UV translucency of milk useful for UV-C preservation techniques

Milk fat globules and casein micelles are the dispersed particles of milk that are responsible for its typical white turbid appearance and usually make it difficult to treat with modern ultraviolet light (UV) preservation techniques. The translucency of milk depends largely on the refractive indices of the dispersed particles, which are directly affected by temperature changes, as incorporated triglycerides can crystallize, melt or transition into other polymorphs. These structural changes have a significant effect on the scattering properties and thus on the UV light propagation in milk, especially by milk fat globules. In this study, a temporary minimum in the optical density of milk was observed within UV wavelength at 14 °C when heating the milk from 6 to 40 °C. This anomaly is consistent with structural changes detected by a distinct endothermic peak at 14 °C using differential scanning calorimetry. Apparently, the optical density anomaly between 10 and 20 °C disappears when the polymorphic transition already has proceeded through previous isothermal equilibration. Thus, melting of equilibrated triglycerides may not affect the RI of milk fat globules at ca. 14 °C as much as melt-mediated polymorphic transitioning. An increased efficiency of UV-C preservation (254 nm) at the translucency optimum was demonstrated by temperature-dependent microbial inactivation experiments.

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

Formulation and Evaluation of Amikacin Sulfate Loaded Dextran Nanoparticles against Human Pathogenic Bacteria.

Amikacin sulfate-loaded dextran sulfate sodium nanoparticles were formulated, lyophilized (LADNP), and then analyzed. The LADNP had a -20.9 ± 8.35 mV zeta potential, PDI of 0.256, and % PDI of 67.7. The zeta average nano size of LADNP was 317.9 z. d.nm, while the dimension of an individual particle was 259.3 ± 73.52 nm, and nanoparticle conductivity in colloidal solution was 2.36 mS/cm. LADNP has distinct endothermic peaks at temperatures at 165.77 °C, according to differential scanning calorimetry (DSC). The thermogravimetric analysis (TGA) showed the weight loss of LADNP, which was observed as 95% at 210.78 °C. XRD investigation on LADNP exhibited distinct peaks at 2θ as 9.6°, 10.4°, 11.4°, 18.9°, 20.3°, 24.4°, 28.2°, 33.2°, 38.9°, and 40.4° confirming crystalline structure. The amikacin release kinetics from LADNP revealed zero order kinetics with a linear release showed zero order kinetics with 37% of drug release in 7 h and had an R2 value of 0.99. The antibacterial effect of LADNP showed broad-spectrum activity against tested human pathogenic bacteria. The preset study demonstrated that LADNP is a promising antibacterial agent.

Effect of Sn nanoparticle additions on thermal properties of Sn-Ag-Cu lead-free solder paste

Lead-free nanocomposite solder pastes were prepared with Sn-3Ag-0.5Cu (SAC 305) microsolders, 1–5 wt% Sn nanoparticles, and a flux. The nanocomposite pastes were studied using differential scanning calorimetry (DSC) to understand their thermal properties and the interactions between the different sized powders. DSC measurements showed two distinct endothermic peaks in all nanocomposite pastes with Sn nanoparticle additions, with one peak attributing to the melting of SAC micropowders and another peak to the melting of Sn nanoparticles. With the increased amount of Sn nanoparticle additions, the SAC material showed little change in its melting temperatures due to its large mass fraction. Multi-cycle DSC measurements of the nanocomposite solder pastes showed additional endothermic peaks, suggesting that the SAC 305 microsolder powders and pure Sn nanoparticles may have interacted with each other to form additional alloys. Changes in enthalpy of melting from DSC measurements were also used to analyze the melting characteristics of the nanocomposite pastes. Additionally, thermogravimetric analysis (TGA) showed that more weight was retained for the nanocomposite solder pastes with increasing Sn nanoparticle additions, compared to the baseline SAC solder paste.

Enhancement of Out‐of‐Plane Hole Mobility in Poly(3‐Hexylthiophene)‐b‐Poly(styrene) Film

AbstractTwo or three orders of higher magnitude out‐of‐plane hole mobilities are observed in the films of poly(3‐hexylthiophene)‐b‐poly(styrene) (P3HT‐b‐PSt) compared with those of P3HT fabricated with the same conditions in a diode geometry. From grazing incidence wide angle X‐ray diffraction analysis, it is found that there is a trend that PSt domains hinder the growth of alkyl stacking, and promote that of the π–π stacking. Differential scanning calorimetry thermogram of P3HT‐b‐PSt exhibits distinct double endothermic peaks, and double glass transitions. The larger change of heat capacity in glass transition at higher temperature indicates that the larger content of rigid amorphous region exists compared with P3HT. It is considered that the higher content of rigid amorphous domain (short‐range ordered packing) interconnects the crystallites (long‐range ordered packing) leading to the extraordinary higher mobility in P3HT‐b‐PSt film.

Physical/thermal properties and heat seal ability of bilayer films based on fish gelatin and poly(lactic acid)

Bilayer films of fish gelatin (FG) and poly(lactic acid) (PLA) with different FG/PLA layer thickness ratios (9:1, 8:2, 7:3, 6:4 and 5:5) were prepared by casting and characterized. Bilayer films exhibited lower tensile strength (TS) but higher elongation at break (EAB) than PLA film (p < 0.05). All bilayer films showed lower water vapor permeability (WVP) and transparency, compared to FG film. Bilayer films had the less barrier property toward UV light transmission, especially with increasing PLA layer thickness ratio. All bilayer films exhibited better oxygen barrier property (oxygen permeability of 5.07–5.88 × 10−18 mol m−1 s−1 Pa−1) than PLA film and FG layer thickness had no impact on oxygen permeability of resulting bilayer films. Based on scanning electron microscopic (SEM) study, all films showed smooth surface and two layers of cross-section were observed for all bilayer films. Bilayer films were heat sealable. The lowest seal strength and seal efficiency were attained for film with FG/PLA layer thickness ratio of 5:5 (p < 0.05). DSC analysis revealed that the FG/PLA (6:4) bilayer film exhibited two distinct endothermic peaks, corresponding to the melting transition of gelatin and PLA. Thus, the mechanical and barrier properties as well as heat seal ability of bilayer films were determined by the thickness ratios of FG and PLA layers.

Elemental, Thermal, and Structural Characterization of ZnO Doped 8 mol% Yttria-Stabilized Zirconia (8YSZ) Ceramics

8 mol% of Yttrium oxide doped Zirconia (8YSZ) is one of the most explored compositions which give high ionic conductivities and good power output at 1000 °C. Generally, dopant was added to improve the sinterability of 8YSZ ceramics. In this present study, granulated 8YSZ powders with multimodal size was mixed with ZnO (0,1,2,3 wt%) using mortar and pestle. The mixed powder was compacted and sintered at 1550°C for 2 hours. 2 distinct endothermic peaks were observed in DTA plot of all samples. However, samples contain high amount of ZnO had a broader endothermic peak which resulted from the melting of ZnO. Rietveld refinement results indicate that the tetragonal phase appeared as the dominant phase for all doped and undoped samples, while cubic and monoclinic phase as the secondary phase. The monoclinic phase decreased as the amount of ZnO increased.

Structural, thermal and vibrational study of superprotonic behavior in a cesium-potassium dihydrogen arsenate: Cs0.5K0.5H2AsO4

An investigation of solid solutions of KH2AsO4–CsH2AsO4 has led to the discovery of a new compound Cs0.5K0.5H2AsO4 (denoted CKDA). The compound was characterized by X-ray single crystal analysis performed at room temperature and reveal that it crystallizes in the space group I−42d with the following crystal data: a=7.6288(6) Å, c=7.1808 (7) Å, V=417.91(6) Å3 and Z=4. The arsenic atom as well as the potassium and cesium ions lie on points with site symmetry S4, the oxygen atoms lie in general positions about the arsenic atoms, in a tetrahedral arrangement. The AsO4 tetrahedra are connected by OH…O hydrogen bonds laying essentially in the a,b plane. The infrared spectrum at room temperature confirms a structural disorders and the coexistence of the anions H2AsO43− in the crystal structure. A calorimetric study of the title compound shows two distinct endothermal peaks which are detected at 215 and 465K. Moreover, protonic conduction of the mixed compound determined by impedance and modulus spectroscopy has been studied in the temperature range 180–473K.

Microstructural, thermal and IR spectroscopy characterisation of wheat gluten and its sub fractions.

The gluten and its sub-fractions of good and poor bread quality wheat varieties were studied using scanning electron microscopy, differential scanning calorimetry (DSC) and IR spectroscopy techniques. The gluten of good bread quality wheat variety showed organized foam like matrix, whereas that of poor demonstrated an open gluten matrix. The glutenin of good bread quality wheat (HI 977) exhibited a more striated, organised texture in contrast to a dense, unorganised structure visible in C306. Gliadins of poor bread quality wheat were self-assembled to form a sheet like structure, whereas the gliadin proteins of good bread quality wheat variety showed more open microstructure. DSC thermal profiles of gluten and glutenin proteins of poor bread quality wheat showed exothermic peaks at around 200°C. A distinct endothermic peak was detected in the glutenin fraction of good bread quality wheat, suggesting greater thermostability. Amide I peak at ~1668cm-1 for gluten of good bread quality wheat variety showed higher relative intensities of β-turn as compared to observed for gluten of poor bread quality.

Structural and vibrational study and superprotonic behavior of the new solid acid: K0.47(NH4)0.53H2(PO4)0.52(AsO4)0.48

The new compound K0.47(NH4)0.53H2(PO4)0.52(AsO4)0.48 crystallizes in the tetragonal system I4¯2d with lattice parameters a = 7.606(5) Å and c = 7.401(5) Å. This material has a unit cell volume of 428.16 Å3 and four formula units per cell. The main feature of the structure is the coexistence of two groups with a motive (NH4/K)+-H2(P/As)O4−. In this structure, there are two types of hydrogen bonding (OH⋯O and NH⋯O) which contributes to their stability.The infrared spectra of K0.47(NH4)0.53H2(PO4)0.52(AsO4)0.48 recorded at room temperature in the frequency range 4000–400 cm−1 confirm the presence of two different anions (AsO43− and PO43−) in the same crystal. A calorimetric study of the title compound shows two distinct endothermal peaks which are detected at 248 and 490 K. Samples were examined by impedance and modulus spectroscopy techniques. The first transition (248 K) is attributed to a antiferroelectric–paraelectric type. A high temperature phase transition (490 K) leading to a superionic–protonic phase was found, characterized by an unusual high conductivity. The conductivity relaxation parameters associated with the high-disorder protonic conduction have been determined from analysis of the M″/M″max spectrum measured in a wide temperature range. Transport properties of this material appear to be due to the proton hopping mechanism.

Synthesis, characterization, and crystal structure of modified benzophenone UV-absorber containing reactive group

A modified benzophenone UV-absorber containing reactive group (4-(4,6-dichloro-1,3,5-triazin-2-yloxy)-2-hydroxyphenyl)phenyl)methanone (UV-DTHM) has been prepared in good yield from the nucleophilic substitution reaction of 2,4-dihydroxy benzophenone with 2,4,6-trichlorotriazine, catalyzed by 1.3 equiv. NaOH. The most favorable reaction conditions (the catalyst dosage, the mole ratio of the reactants, and reactive time) were selected. The compound was characterized by IR spectroscopy, 1H NMR, 13C NMR, mass spectrometry, elemental analysis, and single crystal X-ray diffraction. The crystal monoclinic, space group C c with the unit cell parameters a = 3.987(2), b = 30.688(16), c = 12.423(6) A and α = 90.00, β = 92.117(15), γ = 90.00o, Z = 4, R = 0.0620. wR(F 2) = 0.1589. The crystal structure reveals that 2,4,6-trichlorotriazine is boned to 4-seat hydroxyl of 2,4-dihydroxy benzophenone and a intramolecular hydrogen bond is formed with hydrogen of 2-hydroxyl and oxygen of carbonyl group. Moreover, thermogravimetric analysis (TGA) of UV-DTHM was studied, showing two distinct endothermic peaks at temperatures of 281.5 and 358.5 °C. The molar absorption coefficient of UV-DTHM is 1.6 × 104 and 6.3 × 103 at 268 and 330 nm, respectively, and shows excellent ultraviolet absorption property.

Preparation and characterization of β-sitosterol/β-cyclodextrin crystalline inclusion complexes

Inclusion complexes of β-sitosterol and β-cyclodextrin were prepared by mixing an equimolar ratio of the components in distilled water followed by freeze-drying. The solid state complexes were characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Physical mixtures of the two components showed two distinct melting endothermic peaks at 139 and 169 °C. The two melting peaks were attributable to the individual component (i.e., β-sitosterol and β-cyclodextrin). The inclusion complex, however, shows a single sharp melting endothermic peak at 186 °C indicating the formation of a crystalline complex. Scanning electron micrographs show the formation of well-defined needle-like crystals for the inclusion complexes. The crystalline inclusion complexes were readily soluble in water. The inclusion complexes were characterized in the solution state by nuclear magnetic resonance (NMR) spectroscopy. The continuous variation method, using NMR data, suggests the formation of a 1:1 β-sitosterol to β-cyclodextrin inclusion complex. Cross peaks observed in the rotating-frame overhauser effect spectroscopy NMR spectra suggests that both ends of the β-sitosterol i.e., the aliphatic tail and the cyclic head were encapsulated within the β-cyclodextrin cavity. Computational modeling on the inclusion complexes carried out using density functional theory support the conclusions obtained from NMR spectroscopy. The results of the study show that the β-sitosterol and β-cyclodextrin form water soluble inclusion complex.

Mineralogical and thermal characteristics of low-grade Jinlong bauxite sourced from Guangxi Province, China

Characteristic samples from the No. 1 ore body of the Jinlong bauxite deposit in Guangxi Province, China, were assessed to determine their chemical composition using whole-rock geochemical analysis, their mineral components using X-ray diffraction, their thermal characteristics via differential thermal analysis, thermogravimetry and differential thermogravimetry, and their dissemination characteristics by scanning electron microscopy/energy-dispersive spectrometry. The results show that the average Al2O3 content in the Jinlong bauxite deposit is 41 % and that the Al2O3/SiO2 ratio is approximately 2.17, and thus, the ore may be defined as low-grade bauxite. The main minerals found in the ore were diaspore (20.3–43 %), gibbsite, clays and hematite. In differential thermal analysis results, the bauxite samples exhibit two distinct endothermic peaks, with the dehydration of gibbsite occurring in the 200–260 °C range and the dehydration of diaspore occurring in the 524–550 °C range. Thermogravimetry and differential thermogravimetry indicate four decomposition stages: evaporation of adsorbed water (50–160 °C), gibbsite decomposition (190–280 °C), goethite decomposition (190–280 °C) and diaspore dehydroxylation (460–580 °C). The diaspore belongs to the orthorhombic dipyramidal class and exists primarily in three dissemination forms—euhedral and subhedral grain, bean and oolitic shaped, and aphanitic and microcrystalline aggregates, and is always accompanied by kaolinite and pyrophyllite.

Thermal properties of flax fiber scoured by different methods

Thermal properties of flax roves untreated and treated were characterized by differential scanning calorimetry (DSC) and thermal gravity analyzer (TGA) in order to understand their thermal behavior in more detail and to evaluate the effect of scouring processing on the thermal behavior. Flax roves were treated with six kinds of methods including biological scouring, one bath, two bath, bleaching, alkali scouring and industry chemical scouring as standards. Results showed that all treatments improved thermal stability of flax roves. The results indicated that glass transition temperature (Tg) decreased after scouring besides the sample by directly bleaching. It is more difficult to determine the endothermic peak of flax treated by chemical scouring in industry because it takes a very flat course. A distinct endothermic peak was observed for the untreated flax rove, while a distinct exothermic peak in different temperature interval was revealed for other four treated flax rove samples. For TGA analysis, thermal degradation of flax roves studied consists of three regions of the initial, main, and char decomposition, and the third stage consists of secondary weight loss and carbonization for flax roves with biological scouring, one-bath and two-bath. Besides, different residue left indicates that the bio-scoured flax roves are lost with volatile products and does not contribute to char formation. These results provide valuable preferences for mechanism and top value added application of bio-scouring in flax roves.

Formation of a Rigid Amorphous Fraction in Poly(3-(2'-ethyl)hexylthiophene).

Herein, we detail the formation of a rigid amorphous fraction in poly(3-(2'-ethyl)hexylthiophene) (P3EHT) at high relative crystallinity, yielding a more complete picture of the solid-state structure. In the differential scanning calorimetry (DSC) heating scans of isothermally crystallized P3EHT a distinct endothermic peak appears slightly above the crystallization temperature. This previously undescribed endothermic feature of P3EHT's thermal behavior is observed consistently ∼20 °C above the crystallization temperature-shifting to higher temperatures with increasing crystallization temperature-and increases in magnitude with both time and crystallization temperature. Here, we determine the origins of this endothermic peak with DSC and temperature-modulated DSC (TMDSC). TMDSC reveals that the annealing peak observed in the total heat flow (THF)-heat flow equivalent to that of conventional DSC-is a consequence of an enthalpic relaxation observable as an endothermic peak in the nonreversible heat flow (NHF) and a glass transition evident as a step increase in the reversible heat flow (RHF). In conjunction with conventional DSC observations, these results indicate that the observed annealing peak is a consequence of the formation of distinct amorphous regions-a mobile amorphous fraction (MAF) and a rigid amorphous fraction (RAF)-during the isothermal crystallization process and not the melting of a distinct crystallite population or melt recrystallization.