Antioxidant capacities of phenolic compounds and tocopherols from Tunisian pomegranate (Punica granatum) fruits

This article aims to determine the phenolic, tocopherol contents, and antioxidant capacities from fruits (juices, peels, and seed oils) of 6 Tunisian pomegranate ecotypes. Total anthocyanins were determined by a differential pH method. Hydrolyzable tannins were determined with potassium iodate. The tocopherol (α-tocopherol, γ-tocopherol, and δ-tocopherol) contents were, respectively, 165.77, 107.38, and 27.29 mg/100 g from dry seed. Four phenolic compounds were identified and quantified in pomegranate peel and pulp using the high-performance liquid chromatography/ultraviolet method: 2 hydroxybenzoic acids (gallic and ellagic acids) and 2 hydroxycinnamic acids (caffeic and p-coumaric acids). Juice, peel, and seed oil antioxidants were confirmed by ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) methods. The highest values were recorded in peels with 25.63 mmol trolox equivalent/100 g and 22.08 mmol TE/100 g for FRAP and ORAC assay, respectively. Results showed that the antioxidant potency of pomegranate extracts was correlated with their phenolic compound content. In particular, the highest correlation was reported in peels. High correlations were also found between peel hydroxybenzoic acids and FRAP ORAC antioxidant capacities. Identified tocopherols seem to contribute in major part to the antioxidant activity of seed oil. The results implied that bioactive compounds from the peel might be potential resources for the development of antioxidant function dietary food.     

Synthesis of Aluminium-Cementite Metal Matrix Composite by Mechanical Alloying

Cementite powder was prepared from elemental iron and graphite powder by mechanical alloying (MA) in a specially built dual-drive planetary mill. The phase evolution, particle-size distribution, and morphology of particles were studied during 40 hours grinding period. X-ray diffraction (XRD) shows formation of cementite and other iron carbides along with elemental iron after milling, whereas after annealing only cementite is present. Initially particle size increases with milling due to ductility of iron powder and then reduces with further milling.

Al-cementite composite was synthesized by mixing cementite with Al powders, and then by hot pressing or cold compaction and sintering. XRD analysis of Al-Fe₃C composite shows Fe₃C, FeAl, Al, and other iron carbides along with Al₄C₃ after sintering. Scanning electron microscope (SEM) micrograph of hot-pressed samples shows excellent compatibilility between Al matrix and cementite particles.     

Efficient Synthesis and Characterization of Nanostructured TiC Powder by Reaction Milling

Nanocrystalline TiC powder is synthesized from corresponding elemental constituents by reaction milling in a dual drive planetary mill. The study shows nanocrystalline TiC powder could be produced from Ti + graphite and Ti + activated carbon powder after 10 h of milling. Raman spectroscopy provides evidence in support of formation of TiC after 10 h of milling. Scanning electron microscopy reveals the size reduction and morphology of particles at different stages of milling. Transmission electron microscopy shows the formation of nanocrystalline TiC powder with particle size in the range of 50–200 nm. The lattice parameter of TiC (fcc) has been precisely calculated from first two strong peaks as 0.42 nm.     

Copolymers from methyl methacrylate and butyl acrylate with hyperbranched architecture

This is a first report of the synthesis and characterization of acrylic copolymers from methyl methacrylate (MMA) and butyl acrylate (BA) with hyperbranched architecture. The copolymers were synthesized using a free radical polymerization (Strathclyde method) in emulsion technique. Divinyl benzene was used as the brancher which acted as a comonomer and 1‐dodecanethiol was used as a chain terminating agent. A linear copolymer from MMA and BA was also synthesized for comparison. The hyperbranched architecture was established from spectroscopic and rheological measurements. The gel permeation chromatography showed all hyperbranched copolymers were low molecular weight with lower polydispersity index (PDI) ( 23,000, PDI ～ 2.00) compared to the linear grade ( 93,000, PDI ～ 2.20). They were more spherical and achieved lower viscosity (yet higher solubility, >90%) than the linear grade (<50%) which was mostly open ended. Lower viscosity at equivalent solid content made the hyperbranched polymers a potential binder for adhesive and coating application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45356.     

Ni–ZrO2 Composite Coating by Electro-Co-Deposition

In the present investigation Ni–ZrO₂ metal matrix composite coatings were prepared on steel substrate using watt’s type solution through electro-co-deposition process with different weight percentages of zirconia powder dispersed in the bath. In the coating, nickel is present with faceted appearance along with ZrO₂. The microhardness and wear resistance of the coatings increase with increasing weight percentage of particles content in the coating. The hardness of the resultant coatings was found to be 325 VHN for pure Ni coating whereas 401VHN for Ni–ZrO₂ (15 g/l ZrO₂) coating depending on the particle volume in the Ni matrix. The results also showed that the wear resistance of the composite coatings was improved as compared to unreinforced Ni deposited material. Strengthening of the coating was attributed to the ZrO₂ dispersion and partially favorable texture.     

Be2+ and Mg2+-decorated sulflower: Potential systems for molecular hydrogen storage

The hydrogen binding efficiency of multiple metal-ion (Be²⁺, Mg²⁺)-decorated “First Generation” Sulflower (C₁₆S₈) systems has been investigated for the first time using density functional ω-B97XD method and 6311++G(d,p) basis set. Our calculations show that the central ring of the aforesaid system can be decorated by a single di-positive metal ion, followed by favorable decoration of at most one pair of metal ions (di-positive each) on the peripheral five-membered rings, both on same and opposite faces with certain preferences. All of the metal ion-decorated complexes are capable of efficient hydrogen binding. Be²⁺ and Mg²⁺-decked single ion complexes effectively bind six and four H₂ molecules respectively. Moreover, each of the double ion-decorated systems can adsorb ten H₂ molecules irrespective of the facial orientation of the metal ions. The average interaction energy (ΔE) between sulflower and metal ions (single and double ions) as well as the average binding energy (ΔBE) per molecular hydrogen of the concerned metal-ion-decorated complexes is found to be much higher for Be²⁺-decked systems. The nature of interaction between hydrogen molecules and metal ions is explicated by the topological analysis (AIM Analysis) and NBO formalisms. In case of Be²⁺-decked systems, the amount of charge transfer from H₂ bonding orbital to metal anti-bonding orbital is much higher than analogous Mg²⁺-decorated systems. The Natural Population Analysis (NPA) evaluates the charge variation on the acceptor metal ions due to hydrogen adsorption. In short, our theoretical study gives a comprehensive account of the relationship between the metal ion-decorated sulflower systems and hydrogen molecules, which will further motivate researchers in the field of efficient hydrogen storage materials.     

Effects of Nano-Y_2O_3 and Sintering Parameters on the Fabrication of PM Duplex and Ferritic Stainless Steels

Here we report the effects of nano-Y_2O_3 addition,sintering atmosphere and time during on the fabrication of PM duplex and ferritic stainless steels composites by dual-drive planetary milling of elemental Fe,Cr and Ni powders followed by conventional pressureless sintering.Yttria-free and yttria-dispersed duplex and ferritic stainless steels are fabricated by conventional sintering at 1000,1200 and 1400 ℃ temperatures under argon atmosphere.In another set of experiment,yttria-free and yttria-dispersed duplex and ferritic stainless steels are consolidated at 1000 ℃ for 1 h under nitrogen atmosphere to study the effect of sintering atmosphere.It has been found that densities of duplex and yttriadispersed duplex stainless steel increase from 71%to 91%and 78%to 94%,respectively,with the increase in sintering temperature.Similarly,hardness value increases from 257 to 567 HV_(25) in case of duplex,and from 332 to 576 HV_(25) in yttria-dispersed duplex stainless steel.X-ray diffraction analysis shows the domination of more intense austenite phase than ferrite at higher sintering temperature and also in nitrogen atmosphere.It is also evident that addition of yttria enhances phase transformation from α-Fe to γ-Fe.Duplex and yttria-dispersed duplex stainless steels exhibit the maximum compressive yield strength of 360 and 312 MPa,respectively.