Differential Scanning Calorimetry Thermograms Research Articles

Vesicle‐to‐micelle transition in aqueous mixtures of cationic lipids with Pluronic F127

AbstractAqueous solutions of vesicle‐forming lipids mixed with micelle‐forming copolymers may result in stabilized and biocompatible aggregates. Differential scanning calorimetry (DSC) and dynamic light scattering (DLS) techniques were used here to investigate the effects of the nonionic triblock copolymer Pluronic F127 (F127) on the thermal behavior, structural changes, and hydrodynamic size of cationic vesicles from dioctadecyldimethylammonium chloride (DODAC), dioctadecyldimethylammonium bromide (DODAB), and didodecyldimethylammonium bromide (DDAB) in aqueous dispersion. The DSC thermograms indicate that upon the addition of up to 5.0 mM F127, a vesicle‐to‐micelle transition occurs in three stages. First, there is a predominance of lipid‐F127 mixed vesicles, followed by the co‐existence of mixed vesicles and micelles, and finally, the system is dominated by mixed micelles. DLS results reveal that with the addition of F127 to the lipid dispersions, the size of the assembled structures tends to decrease, also indicating structural changes of vesicles to micelles. These results indicate that the borders between these stages depend on the lipid chain length and counterion type.

Structural, Crystallization Kinetics and Physical Properties of Se85Te15−xAgx Chalcogenide Glasses

In this study, Se85Te15−xAgx (x = 3, 6, 9 and 12) chalcogenide glasses were examined for their structure, crystallization kinetics, and physical characteristics. The kinetics of crystallization in these glasses were studied using various methods. By using the melt quenching process, Se85Te15−xAgx bulk alloys were created. The amorphous nature of the alloys was confirmed using High Resolution X-Ray Diffraction (HRXRD). The crystallization kinetics of the Se85Te15−xAgx glasses were studied using non-isothermal differential scanning calorimetry (DSC) measurements at heating speeds of 5, 10, 15, 20 and 25 K/min. The different characteristic temperatures, including the glass transition (Tg) and on-set crystallization (Tc) temperatures, have been determined from a variety of DSC thermograms. Using the Kissinger and Moynihan techniques, the activation energies of the glass transition (ΔEt) were computed.

CHEMO-MECHANICAL EXTRACTION AND CHARACTERIZATION OF SAYOTE (SECHIUM EDULE) FIBERS AT VARYING FIBER MATURITY

"Cellulosic plant fibers are good reinforcing materials for composites because they are cheap, light weight, and exhibit good mechanical properties. The isolation of the crystalline portion exposes the stable hydrogen bond network that can form intermolecular bonding with other matrices, such as starch, polyvinyl alcohol and chitosan, among others. Sundried and undried sayote (Sechium edule) vines, of varying degrees of maturity, were subjected to uniform chemomechanical extraction procedures to obtain crystalline fibers. The chemo-mechanically extracted fibers were characterized using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). DSC thermograms revealed that the sun-dried and mature sample exhibited the narrowest endotherm, indicating the presence of fewer amorphous structures. FTIR spectra showed that the numbers of functional groups present in the fiber samples decreased with increasing degree of maturity. SEM micrographs reveal that the mature portion of the sayote vine had more fibrous and orderly features, compared to the samples extracted from the younger and intermediate portions. Further, chemo-mechanical extraction and X-ray diffraction (XRD) analysis of fibers from mature, sun-dried sayote vines also revealed a relative crystallinity index of the extracted fiber of 65%. The fiber yield from the mature portion of the vine was 9%. Sayote (Sechium edule) vine can be a promising source of crystalline fibers for composite fabrication."

Physical characterization of chocolates prepared with various soybean and milk powders.

The physical characterization of chocolate products is vital in manufacturing, and the chocolate's processing time and composition directly influence physical properties, such as rheology and melting. The objective of this study was to investigate the effects of processing time and the ingredient types on the physical properties of milk chocolates containing soy milk powder and soy protein isolate. Characteristics of skimmed milk chocolate (SMC) and whole milk chocolate (WMC) were compared to soy milk chocolate and soy protein chocolate (SPC). Rheological data of chocolate products were fitted to Casson, Herschel-Bulkley, and Bingham models. The highest viscosity was observed for SPC samples, whereas yield stress was the highest for SMC samples after 2hr of processing. The increase in milk and soy fats in the formulation softened the texture and decreased the whiteness index significantly (p < .05). PSD results show that SPC had the highest D90 (40.1μm) and the lowest specific surface area (893 m2 /kg) after 6hr of processing. SPC samples had the narrowest particle size distribution observed by the span values. X-ray diffraction analysis showed that all the samples had the desired Form V, crystal form. The differential scanning calorimetry thermogram was used to determine phase transitions and melting behaviors. At the end of processing, melting enthalpies (ΔHmelt ) were significantly lower (p < .05) in milk chocolates.

Investigations of axioms of twist grain boundary phases (TGBPs) in binary mixture of liquid crystals

In this paper, the investigated mixture of liquid crystals shows a spacious range of twist grain boundary phases (TGBPs). Thermo dynamical, optical and dielectric measurements confirmed the presence of TGBPs in the mixtures of nematic and cholesteric liquid crystals. In the heating cycle, differential scanning calorimetry (DSC) thermogram shows the mixed different TGBPs at the high scanning rate. Cylindrical and cone-like textures with brushes of TGBA* is observed under the optical investigation. The grain boundaries and blocks of smectic phases are twisting two times around an axis. Wide-ranging dielectric investigation of nematic and cholesteric liquid crystal mixture have been performed in the 50 Hz–10 MHz range of frequency for the homogeneous conditions. In the absence of direct bias, TGBA* phase exhibits two dielectric relaxation processes, soft mode (SM) and process in the grain boundaries (PGBs). In the presence of electric field, grain boundaries steadily demolished the phases. Whereas the weak dielectric relaxation processes have been distinguished in the presence of the electric field in the TGBPs.

Synthesis and properties of biophenol‐furfural based bioresin for curing of styrene butadiene rubber

AbstractIn the present work, biophenol and furfural‐based resol resin was synthesized and utilized for the very first time to cure styrene butadiene rubber (SBR). The reaction was studied over a range of times, temperatures, pH, and furfural to biophenol ratios to fix the optimum conditions. Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy revealed the functional groups and chemical structure of the synthesized resin, respectively. An exothermic peak for the resin curing appeared at 143°C in the differential scanning calorimetry thermogram of the resin. Then, the biophenol‐furfural resin was utilized for the curing of SBR. The synthesized resin increased the tensile strength of the raw rubber from 0.20 ± 0.01 MPa to 1.22 ± 0.10 MPa at 10 phr loading, and the crosslink density was 2.56 × 10−5 mol/mL. The activation energy for curing SBR containing 10 phr resin was 97 kJ/mol. The storage modulus of the resin‐cured compound was improved. The glass transition temperature of the raw SBR was also shifted from −43.8 to −42.3°C when 10 phr resin was used for the curing. Hence, for the first time, this work reported the utilization of biophenol‐biosourced furfural resin to cure rubbers.

FORMATION AND CHARACTERIZATION OF MULTICOMPONENT CRYSTAL OF TRIMETHOPRIM AND MANDELIC ACID BY SOLVENT DROP GRINDING METHOD

Objective: To increase the solubility of trimethoprim by forming multicomponent crystals using mandelic acid as a coformer.&#x0D; Methods: Multicomponent crystals of trimethoprim and mandelic acid were prepared at a ratio of 1:1 mol by the Solvent Drop Grinding (SDG) method. Solid state characterization was carried out using Differential Scanning Calorimetry (DSC), Powder X-ray Diffraction (PXRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), and polarized microscope. The solubility test of trimethoprim was carried out in CO2-free distilled water using a sonicator for 5 min and then determined by High-Performance Liquid Chromatography (HPLC) using acetonitrile and phosphoric acid in a 10:90 ratio as the mobile phase and octadecylsilane (C18) as the stationary phase.&#x0D; Results: The results showed a decrease in the melting point and enthalpy of fusion on the DSC thermogram, a new peak in the X-ray diffraction pattern, and a slight shift of wave number in the FTIR spectroscopy. Those characterizations indicated that the multicomponent crystal formed a salt type. SEM analysis showed morphological changes and formation of new crystal habits. The polarization microscopy analysis showed birefringent with various colors in all samples. The solubility of multicomponent crystal is 2.73-times higher compared to intact trimethoprim.&#x0D; Conclusion: The formation of cocrystals of trimethoprim and mandelic acid by SDG method increased the solubility of trimethoprim.

Polymorphs, Solvatomorphs, Hydrate, and Perhydrate of Dabrafenib

Crystal form screening of the anticancer drug dabrafenib (DBF) was performed using a wide range of nonpolar aprotic, polar aprotic, and polar protic solvents. Extensive crystallization in these solvent systems produced three crystal forms (I, II, and III) of the drug, a monohydrate, an isomorphous peroxo solvate, and eight different solvates with ethyl acetate, dichloromethane, chloroform, carbon tetrachloride, 1,1,2,2-tetrachloroethane, tetrachloroethylene, benzene, and anisole of DBF. Surprisingly no solvates were crystallized with the alcohol solvents attempted. The novel crystalline forms were characterized by single-crystal X-ray diffraction (SC-XRD) or structure determination from powder data (SDPD). The neutral drug derived from the mesylate salt of DBF by neutralization (form Ia) and the crystallized form I exhibited almost a similar powder XRD line pattern but their differential scanning calorimetry (DSC) thermograms comparison showed significant differences. Thus, the structure of microcrystalline powder form Ia was solved from SDPD reflections and showed the same molecular packing but different conformational strain compared to form I (structure by SC-XRD). The relative stability of the drug polymorphs was calculated using dispersion-corrected density functional theory with an intramolecular conformational energy correction. The calculations suggest that form II is the most stable polymorph and form III, form I, and form Ia are progressively less stable. Residual water content analysis of the isomorphous peroxosolvate showed that it is a mixed hydrate/peroxosolvate with ∼9.5% water occupancy quantified by 31P nuclear magnetic resonance analysis of the peroxosolvate content using triphenylphosphine oxide. The supramolecular analysis and molecular packing of DBF crystal forms suggest that the molecule has a propensity to form solvates with aprotic solvents and more specifically with chlorohydrocarbons. With its high molecular flexibility, prolific solvate potential, and drug polymorphism, the present work opens the opportunity for further solid-form landscape study of the popular anticancer drug DBF.

Thermal, dielectric and optical studies on cellulose acetate butyrate-gold nanocomposite films prepared by laser ablation

This work employed pulsed laser ablation to produce cellulose acetate butyrate-gold (CAB-Au) nanocomposite films and the evaluation of their structural and thermal characteristics using Raman, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Differential Scanning Calorimetry (DSC). In the frequency range 0.1–10 MHz, nanocomposite films' dielectric constant, loss, and electric modulus behavior were investigated as a function of temperature. The refractive index, finesse coefficient, Brewster coefficient, critical angles, dielectric function, and color properties of nanocomposite films were examined in the wavelength range 190–800 nm. X-ray diffraction shows a strong Au diffraction signal in all samples, confirming Au NPs. The SEM micrograph shows Au embedded in CAB. The CAB-Au nanocomposites had higher thermal stabilities (Tm) than pure CAB, and the DSC thermograms showed a fluctuating glass transition temperature due to the dynamics of organic-inorganic interactions in the nanocomposite films. Dielectric dispersion is caused by hidden dipolar polarization. The CAB (5 min) sample had the highest ac conductivity as a function of frequency at various temperatures as the Au content in the Au/CAB composite rose. The simplest quantum mechanical tunneling (QMT) model also best explains the ac conduction property. We found a relationship between the nanocomposites' refractive index and the amount (extent of incorporation) of Au in the materials, with laser irradiation time determining the various color constants. Tauc plots reveal a permitted transition with an optical energy gap of 5.1eV for the polymer film and 4.75eV after 10 and 20 min of laser irradiation.

Evaluation of Lapatinib-Loaded Microfibers Prepared by Centrifugal Spinning.

Lapatinib (Lap) is a lypophilic drug frequently used in cancer treatment; however, due to its limited solubility and permeability, achieving therapeutic dose through oral administration proves to be a challenge. There are various methods for enhancing the solubility of Lap and other similar drugs, one being the preparation of amorphous solid dispersions (ASD). In this study, a Lap-loaded polyvinylpyrrolidone (PVP) fiber mat was created with centrifugal spinning from a PVP/Lap solution in dimethyl formamide and ethanol. The production rate was 12.2 g/h dry fibers, and the fibers had an average thickness of 2.55 ± 0.92 μm. In the differential scanning calorimetry (DSC) thermogram of the fiber mat, the melting peak of the crystalline Lap was not visible, suggesting that Lap was in an amorphous state. A dissolution study was carried out in 0.2 M phosphate buffer saline solution at 37 °C. UV spectrophotometry data indicated that in the sample containing the fiber mat, the Lap concentration was 332 μg/mL (66%) in 10 min, decreasing to 227 μg/mL by 45 min. Meanwhile the crystalline Lap formed a 30-40 μg/mL (6-8%) solution in 5 min, maintaining that concentration. We conclude that centrifugal spinning can be an effective and easy method to produce ASDs.

Effect of quaternary ammonium surfactant on&lt;em&gt; &lt;/em&gt;buccal permeation of budesonide film formulation: &lt;em&gt;in silico&lt;/em&gt; docking studies

Budesonide, an immunosuppressant glucocorticosteroid generally used to ameliorate chronic inflammation. Low bioavailability due to first pass metabolism decreases its therapeutic activity. The present study focuses on the formulation of a biodegradable buccoadhesive film for improvement of buccalpermeation. Transparent buccoadhesive films were prepared by incorporating budesonide in HPMC matrix with triethalonamine as a plasticizer and a number of surfactants. Absence of the characteristic drug melting peak at 252°C in Differential Scanning Calorimetry (DSC) thermogram study confirmed almost complete amorphization of the drug to a homogenous solid-solid mixture in the film. The characteristic Fourier-Transform Infrared Spectroscopy (FTIR) peak of pure drug showed the carbonyl stretching in between 1600–1900 cm −1 and C–O stretching at 1095 cm −1 . Broadening of C–O stretching and masking of carbonyl stretching confirmed the drug polymer interaction. In vitro dissolution and ex-vivo buccal tissue permeation revealed upto 72% and more than 58% respectively using surfactants upto 6 hour of study. Enhanced buccal permeability and flux were found in presence of surfactant compared to its absence. New film formulation could be developed including surfactant for improved buccal permeation with expected increased bioavailability. The in silico study confirmed about a stable interaction between drug and polymer (−3.1 kcal/mol).

Preparation of Atorvastatin Calcium-Dipicolinic Acid Multicomponent Solids by Liquid-Assisted Grinding Method to Increase Solubility

Atorvastatin calcium is a cholesterol-lowering drug that is very potent but difficult to dissolve in water, so its bioavailability is low. In this study, atorvastatin calcium-dipicolinic acid multicomponent solids were prepared using the liquid-assisted grinding method to improve atorvastatin calcium's solubility. Characterization of multicomponent solids was carried out using powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Solubility test was carried out by shaking method using distilled water media. The results showed that the particles of atorvastatin calcium - dipicolinic acid multicomponent solids had an irregular shape with rough and porous surface topography. The multicomponent solids have a diffractogram with specific peaks of 2θ at 8.8, 9.9, 11.5, 16.7, 19.1, 21.2, 22.4, 23.4, and 27.7°. The DSC thermogram of multicomponent solids showed a sharp endothermic peak at 181.9 °C (∆H=17.69 J/g), indicating its melting point. The FTIR spectra of atorvastatin calcium-dipicolinic acid multicomponent solids indicated an intermolecular interaction that was thought to be a hydrogen bond between the molecules of atorvastatin calcium and dipicolinic acid. The results of the solubility test showed that the atorvastatin calcium-dipicolinic acid multicomponent solids had a significantly increased solubility (p&lt;0.05) compared to the solubility of pure atorvastatin calcium.

Production and statistical optimization of cholesterol-oxidase generated by Streptomyces sp. AN strain

BackgroundCholesterol oxidases (CHOs) have attracted enormous attention because of their wide biotechnological potential. The present study explores the production of CHOs by Streptomyces sp. AN. Evaluation of culture conditions affecting enzyme production, medium optimization and released metabolite characteristics were also investigated. ResultsThe current work reports the isolation of 37 colonies (bacteria/actinobacteria) with different morphotypes from different soil/water samples. The isolate-coded AN was selected for its high potency for CHO production. Morphological characteristics and the obtained partial sequence of 16srRNA of AN showed 99.38% identity to Streptomyces sp. strain P12–37. Factors affecting CHO production were evaluated using Plackett-Burman (PB) and Box-Behnken (BB) statistical designs to find out the optimum level of the most effective variables, namely, pH, starch, NH4NO3 and FeSO4.7H2O with a predicted activity of 6.56 U/mL. According to this optimization, the following medium composition was considered to be optimum (g/L): cholesterol 1, starch 6, MgSO4.7H2O 0.1, CaCl2 0.01, FeSO4.7H2O 0.1, NH4NO3 23.97, yeast extract (YE) 0.2, K2HPO4 0.01, KH2PO4 0.1, NaCl 0.01, Tween 20 0.01, pH 6.36 and incubation temperature (30 °C) for 9 days. Spectophotometric analysis for released metabolites against cholesterol (standard) via Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) was carried out. FTIR spectrum showed the appearance of new absorption peaks at 1644 and 1725cm−1; this confirmed the presence of the Keto group (C=O) stretch bond. Besides, fermentation caused changes in thermal properties such as melting temperature peak (99.26; 148.77 °C), heat flow (− 8; − 3.6 Mw/mg), capacity (− 924.69; − 209.77 mJ) and heat enthalpy (− 385.29; 69.83 J/g) by comparison to the standard cholesterol as recognized through DSC thermogram. These changes are attributed to the action of the CHO enzyme and the release of keto derivatives of cholesterol with different properties. ConclusionStreptomyces sp. AN was endowed with the capability to produce CHO. Enzyme maximization was followed using a statistical experimental approach, leading to a 2.6-fold increase in the overall activity compared to the basal condition. CHO catalyzed the oxidation of cholesterol; this was verified by the appearance of a new keto group (C=O) peak at 1644 and 1725 cm−1 observed by FTIR spectroscopic analysis. Also, DSC thermogram demonstrates the alteration of cholesterol triggered by CHO.

One pot synthesis of bio-based porous isocyanate-free polyurethane materials

In the current study, synthesis of porous isocyanate-free polyurethane materials derived from xylose is reported through a one-pot process, and the impact of varying amounts of crosslinker is studied. The synthesized materials were characterized using various techniques. The formation of the urethane bridge was confirmed using Fourier Transform Infra-Red (FTIR) spectra that exhibited characteristic bands around 1700 cm−1, 1600 cm−1, and 3400 cm−1. The characteristic peak observed at 21◦ (2θvalue) in Powder X-ray (PXRD) diffractogram further confirms the synthesis of segmented polyurethane porous materials. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) thermograms indicate that thermal stability and glass transition temperature (Tg) of synthesized non-isocyanate polyurethane (NIPU) materials increase with increase in the amount of crosslinker. The increase in Limiting Oxygen Index (LOI) values with an increment in the amount of crosslinker suggests improvement in flame retardant behavior of NIPU material due to formation of highly crosslinked network in the polyurethane matrix. These porous NIPU materials align well with the principles of sustainable development.

Characterization of compatibility of Polypropylene/Poly(butylene succinate) blends: Impact of weight ratios on interfacial polarization

The main focus of the present work is the investigation of the aliphatic polyesters blend’s compatibility from the viewpoint of dielectric and structural properties. Polypropylene/poly(butylene succinate) (PP/PBS) polymer blends with different weight ratios were prepared using a twin-screw extruder and then a molded injection. The impact of blending PP and PBS on the molecular relaxation process and interfacial polarization of PBS was studied via broadband dielectric spectroscopy (BDS) over a large temperature domain varying between 20 °C and 100 °C and a frequency range from 0.1 Hz to 1 MHz. Three significant dielectric processes α-primary relaxation attributed to glass transition, and two interfacial polarizations due to the semi-crystalline character of PBS and the blended PP polymer are revealed and examined using the Havriliak-Negami (HN) fit. The most important point of the HN fit analysis is the study of the interaction of the dipoles trapped at the interfaces PP/PBS that allowed us to understand the state of the PP and PBS blend in terms of adhesion and compatibility. Atomic force microscope (AFM) and its electric mode electrostatic force microscopy (EFM) and differential scanning calorimetry (DSC) were performed as complementary techniques. AFM/EFM analysis and DSC thermograms confirm the poor compatibility and immiscibility between the two phases of the polymer blends (PP/ PBS).

Biobased Polyamide Blends (PA610/PA1010)—A Miscibility Analysis

In the present work, blends of biobased polymers were formulated using two polyamides made from biorenewable resources. Polyamide 610 (PA610) and polyamide 1010 (PA1010) were meltmixed in different compositions, producing polymer blends with renewable carbon content from 74 to 89%. Physical properties of the PA610/PA1010 blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and impact strength testing. From the DMTA results, it was possible to identify a single glass transition temperature (Tg) for each PA610/PA1010 blend. The measurements of the impact testing show intermediate values compared to the pure polymers. The DSC thermograms show melting point depression for the PA610 crystals with increasing PA1010 content. All those results indicate the two polyamides are fully miscible in the melt in the composition range investigated.

Development and characterization a novel leakage-proof form stable composite of graphitic carbon nitride and fatty alcohol for thermal energy storage

The form-stabilization ability of the produced graphitic carbon nitride (g-C3N4) for preventing the leakage of stearyl alcohol (SAOH) as promising organic phase change material (O-PCM) was investigated comprehensively. The SEM analysis showed that the g-C3N4 had well defined pores which is capable to confine the molten SAOH in them. The FTIR and XRD confirm the chemical compatibility of g-C3N4 and SAOH. The differential scanning calorimetry thermogram showed that the melting and freezing temperature of the FS-OPCMs including 70 wt% SAOH were 54.57 °C and 55.25 °C with respective high latent heats as 191 kJ/kg and 187 kJ/kg respectively. The thermal aging test for 1000 melt/freeze cycles confirmed that structure and thermal degradation durability are excellent. The thermal conductivity of developed FS-OPCM is enhanced by 122 %, which were resulted in about 50–54 % reduction in the charging/discharging time of FS-OPCM relative to the SAOH. The results exposed that the developed g-C3N4/SAOH (70 wt%) composite can be considered as potential solar energy storage material in different implementations such thermal cooling of photovoltaic panels, automotive and electronic units as well as solar residential water heating and passive solar space heating.

THERMAL STABILITY AND THERMAL EXPANSION BEHAVIOR OF AlFeCoNiCu AS-CAST HIGH-ENTROPY DUAL-PHASE ALLOY

This work is devoted to the thermal stability and thermal expansion of dual-phase AlFeCoNiCu as-cast high-entropy alloy of equiatomic composition. The mix FCC + BCC phases is in AlFeCoNiCu high entropy alloy. According to characterized by EDS-analysis, Fe and Co are almost uniformly distributed in both phases in comparison with other elements. The BCC phase is rich in Ni and Al, and the FCC phase is Cu. Our measurement results of hardness and elastic modulus values for inter dendrites (FCC phase) and dendrites (BCC phase) of as-cast AlFeCoNiCu alloy showed the difference between there. Hardness values for inter dendrites and dendrites: 3.4±0.4GPa and 4.1±0.6GPa. Elastic modulus values for inter dendrites and dendrites: 130.5±2.0GPa and 166.5±5.6GPa. The thermal stability of the phases presented in AlFeCoNiCu as-cast high-entropy alloy has been studied with dilatometry and differential scanning calorimetry (DSC). The DSC thermogram shows an endothermic peak at 1000K. The coefficient of thermal expansion (CTE) curve shows linear increment from room temperature up to 1370K from (10.6 ± 0.3)×10-6K−1 to (27.7 ± 0.3) ×10-6K−1. The CTE temperature curve also shows the peak at 1000K. The peaks in the CTE temperature and the DSC curve suggest a phase transformation with increasing temperature up to~1000K.

High entropy steel processed through mechanical alloying and spark plasma sintering: Alloying behaviour, thermal stability and mechanical properties

In present investigation, a non-equiatomic high entropy steel (HES) was synthesized by mechanical alloying (MA) followed by spark plasma sintering (SPS). The Fe40Mn14Ni10Ti10Al15Si10–C1 HES milled up to 30 h was found to have a metastable dual-phase containing a major BCC (a = 2.872 Å; cI2) and a γ-brass type (a = 8.890 Å; cI52) phase having nanostructured grains of ∼10 ± 2 nm. The differential scanning calorimetry (DSC) thermogram exhibited the four exothermic heating events at 530 °C, 690 °C, 860 °C and 1000 °C. The phase transformation corresponding to the heating events was correlated with the ex-situ XRD of the as-milled powder. The phases evolved were Fe–Si solid solution, FCC, Fe5Si3 type and TiC phases. Fe40Mn14Ni10Ti10Al15Si10–C1 milled HES powder was consolidated through SPS at 900 °C and at 50 MPa. The SPSed HES were found to have a dual-phase structure containing a major FCC phase (a = 3.602 Å; cF4) and a minor BCC phase (a = 2.876 Å; cI2) along with the intermetallic phases like Fe5Si3 type (a = b = 6.808 Å, c = 4.745 Å; hP16) and TiC (a = 4.301 Å; cF8). The mechanical properties of these SPSed samples were discerned through instrumented microhardness and compression tests. The microhardness, elastic modulus, ultimate compressive strength and strain were found to be ∼10.4 GPa, ∼209 GPa, ∼2305 MPa and ∼15% respectively. This SPSed HES showed an excellent room temperature microhardness and strength which can be attributed to the co-existence of FCC phase along with the minor phases and hard intermetallics. The strengthening mechanism suggested that the grain boundary, dislocation, and precipitates strengthening were dominant. Attempts have been made to understand the phase evolution and the consequent mechanical properties in these HES.

Formulation of Topical Flurbiprofen Solid Lipid Nanoparticle Gel Formulation Using Hot Melt Extrusion Technique.

Hot melt extrusion (HME) has been used for the formulation of topical solid lipid nanoparticle (SLN) gel without using any other size reduction technique including high pressure homogenization or sonication. SLN formulation solely using HME has not been applied to other drugs except IBU. Therefore, the purpose of the present study was to formulate FLB SLN solely using HME technique and evaluate the SLN formulation in inflammation animal model. Stable 0.5%w/v FLB SLN gel with particle size < 250nm, PI < 0.3 and EE of > 98% was prepared. Differential scanning calorimetry (DSC) thermogram showed that the drug was converted to amorphous form in the HME process. Additionally, rheological studies demonstrated that FLB SLN gel and marketed FLB gel showed shear thinning property. FLB SLN formulation showed significantly (p < 0.05) higher peak force required to spread the formulation as compared to marketed FLB formulation. Stability studies showed that FLB SLN gel was stable for a month at room temperature and 2-4°C. Moreover, in vitro permeation test (IVPT) and ex vivo skin deposition study results revealed that FLB SLN gel showed significant (p < 0.05) increase in drug deposition in dermal layer and drug permeation as compared to control marketed formulation. Further, in vivo anti-inflammatory study showed equivalent inhibition of rat paw edema using 0.5% w/v FLB SLN gel which has 10 times less strength compared to control formulation. Overall, FLB SLN formulation was successfully manufactured solely using HME technique which resulted in enhanced the skin permeation of FLB and superior anti-inflammatory activity.