Asymmetry Thermal Analyses of Self-Supporting Friction Stir Welding

Due to the inherent issue of requiring rigid back support, friction stir welding (FSW) has serious limitations for the welding of hollow structures. Self-supporting friction stir welding was proposed to join hollow aluminum extrusions, which could reduce the hindrance of the welding tool and the requirement of rigid back support. In this paper, finite element modeling analyses were carried out for the asymmetric temperature field in the process of self-supporting FSW. The peak temperature of the stir zone appeared in the upper shoulder affected zone, followed by the lower shoulder affected zone. In the upper shoulder affected zone, a peak temperature was not shown at the center of the curve due to the positive correlation between heat generation and radius and different heat dissipation rates. Considering the influence of thermal input and rotation speed on joint formation, 200 mm/min travel speed and 800 rpm rotation speed are the most proper parameters for 5-mm-thick 6082-T6 aluminum alloy self-supporting FSW butt welds.

Nickel(II)-Complex of Ceftibuten Dihydrate: Synthesis, Characterization and Thermal Study

Ceftibuten dihydrate is a semisynthetic, orally administered, third generation cephalosporin antibiotic which is effective against most of the pathogens causing infections in the respiratory tract. Complexation of ceftibuten dehydrate (Ligand, L) was performed with hydrated Ni(II) salt (Metal, M) in the ratio of 2:1 (L:M) in aqueous medium at 90 oC. The metal complex was then characterized by spectral techniques and thermal analyses. The FT-IR spectral data of metal complex suggested the monodentate bonding of metal ion to carboxylate group. Spectral evidence also supported the formation of five-membered ring via coordination of metal ion to β-lactam nitrogen and carboxylate group of parent drug. Thermal behavior of ligand and complex were studied. Thus, thermoanalytical (DSC and TGA) results also supported the formation of new metal complex, indicating the successful interaction of metal ion to ligand. Dhaka Univ. J. Pharm. Sci. 20(2): 219-225, 2021 (December)

Physicochemical Characterization of Cardoon “Cynara cardunculus” Wastes (Leaves and Stems): A Comparative Study

The disposal of vegetable wastes in nature is harmful for marine habitats and biota. These types of waste are frequently used as fuel, generating polluting products, with undesired side effects on the environment. Therefore, it is essential to find better alternatives for the capitalisation of these waste products. Their diversified chemical composition can become a potential resource of high added value raw materials. The knowledge of the physicochemical properties of these wastes is therefore essential. The present work aimed for characterising the physicochemical properties of a plant residue belonging to the Asteraceae Family, collected from a vegetable market in Fez city, Morocco. The vegetal tissues were analysed by Scanning Electron Microscopy coupled with EDX, X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Inductively Coupled Plasma Atomic Emission Spectroscopy, and by Thermogravimetric/Differential thermal analyses. Other additional parameters were also measured, such as moisture, volatile matter, ash, and fixed carbon contents. Acidic and basic surface functions were evaluated by Boehm’s method, and pH points at zero charge were equally calculated. The results revealed a strong congruence between the morphological and structural properties of this plant. These vegetal wastes comprise a homogeneous fibrous and porous aspect both in surface and in profile, with a crystalline structure characteristic of cellulose I. A mass loss of 86.49% for leaves and 87.91% for stems in the temperature range of 100 °C to 700 °C, and pHpzc of 8.39 for leaves and 7.35 for stems were found. This study clarifies the similarities and differences between the chemical composition and morphological structure of these vegetal wastes, paving the way for future value-added applications in appropriate fields.

Novel Polymorphic Cocrystals of the Non-Steroidal Anti-Inflammatory Drug Niflumic Acid: Expanding the Pharmaceutical Landscape

Any time the pharmaceutical industry develops a new drug, potential polymorphic events must be thoroughly described, because in a crystalline pharmaceutical solid, different arrangements of the same active pharmaceutical ingredient can yield to very different physicochemical properties that might be crucial for its efficacy, such as dissolution, solubility, or stability. Polymorphism in cocrystal formulation cannot be neglected, either. In this work, two different cocrystal polymorphs of the non-steroidal anti-inflammatory drug niflumic acid and caffeine are reported. They have been synthesized by mechanochemical methods and thoroughly characterized in solid-state by powder and single crystal X-ray diffraction respectively, as well as other techniques such as thermal analyses, infrared spectroscopy and computational methods. Both theoretical and experimental results are in agreement, confirming a conformational polymorphism. The polymorph NIF–CAF Form I exhibits improved solubility and dissolution rate compared to NIF–CAF Form II, although Form II is significantly more stable than Form I. The conditions needed to obtain these polymorphs and their transition have been carefully characterized, revealing an intricate system.

Solid-Solid Phase Transformations and Their Kinetics in Ti-Al-Nb Alloys

The application of light-weight intermetallic materials to address the growing interest and necessity for reduction of CO2 emissions and environmental concerns has led to intensive research into TiAl-based alloy systems. However, the knowledge about phase relations and transformations is still very incomplete. Therefore, the results presented here from systematic thermal analyses of phase transformations in 12 ternary Ti-Al-Nb alloys and one binary Ti-Al measured with 4–5 different heating rates (0.8 to 10 °C/min) give insights in the kinetics of the second-order type reaction of ordered (βTi)o to disordered (βTi) as well as the three first-order type transformations from Ti3Al to (αTi), ωo (Ti4NbAl3) to (βTi)o, and O (Ti2NbAl) to (βTi)o. The sometimes-strong heating rate dependence of the transformation temperatures is found to vary systematically in dependence on the complexity of the transformations. The dependence on heating rate is nonlinear in all cases and can be well described by a model for solid-solid phase transformations reported in the literature, which allows the determination of the equilibrium transformation temperatures.

The Development of a New Phosphogypsum-Based Construction Material: A Study of the Physicochemical, Mechanical and Thermal Characteristics

Phosphogypsum (PG) is a waste (or by-product) of the production of phosphoric acid, a basic constituent in the manufacturing of modern fertilizers. The annual production of phosphogypsum in Tunisia is currently estimated to be 10 million tons. Its storage in slag in close proximity to production plants generates pollution problems; however, valorization may be a solution. The present paper proposes a simple process for the valorization of this by-product into a construction material. Several physicochemical characterizations are used to prove the characteristics of samples. The chemical composition shows that PG is a gypsum compound with several impurities. The morphological analyses show that the powder materials are mesoporous with a lower specific area. The structural characterizations show that these solids play the role of a water pump as the degree of hydration changes from 2 to 0 and vice versa, depending on the temperature. Mechanical and thermal analyses show that the prepared formulation is brittle and insulating, which presents opportunities for it to be used as a decoration material.

Photocatalytic Activity of Nanocoatings Based on Mixed Oxide V-TiO2 Nanoparticles with Controlled Composition and Size

V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium.

Microencapsulation of Citral and its Antifungal Activity into Pectin Films

Citral is an essential oil with great antimicrobial activity, but its use in the food industry is limited due to its easy decomposition in room conditions. Therefore, this study aimed to microencapsulate citral by the spray drying process and incorporate the powder into pectin films to assess their antifungal activity. For this, solutions of maltodextrin (MD), Arabic gum (AG) sodium alginate (SA) at different concentrations were used to emulsify citral. The emulsion with 10:10:0.1 MD:AG:SA was selected to spray the drying process due to its small droplet size, monomodal size distribution, and low D[3,2], D[4,3], and span index. The dried powder had high solubility (83.4%), and low wettability time (27 s), moisture content (4.05%), and bulk density (0.72 g/cm3), allowing to infer powder stability and showing appropriate handling qualities on a large scale. Thermal analyses reveal that microparticles and pectin films provide thermal protection to citral from 37 to 175 °C. Concerning the antagonistic activity, pectin films added with citral microencapsulated had antifungal activity ranging from 42-68% against Penicillium italicum, Colletotrichum gloeosporioides, and Aspergillus niger under in vitro conditions. Therefore, these films serve as a basis for developing new edible coatings with practical applications in the postharvest management of phytopathogenic fungi.