Table of Contents - Volume 16 Number 2

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Polyindole (PIn) is hetroatomic organic molecule which belongs to the fused-ring family have emerged in the past several decades as promising materials due to their unique physical and electrochemical properties. PIn was successfully synthesized by chemical polymerization of indole. Properties of PIn can be improved by mixing polymer with conducting metals, metal oxide, carbon nanocomposites and other materials. Polyindole nanocomposites (PNCs) were characterized through various spectral, thermal and electrical methods. FT-IR (Fourier transform infrared spectroscopy) spectra confirmed the formation of PNCs and SEM (Scanning electron microscopy) reveal the microstructure of surface of PNCs. Thermal characterization revealed that thermal stability of PNCs increases with addition of metal, metal oxide, carbon nanocomposites and other materials. These studies revealed that PNCs of PIn with other metals have an important influence on supercapacitors electrochemical devices, catalysis, anticorrosion, diodes, sensor and biology related applications. This review provide an overview of the preparation of PIn and their composites, followed by their application in various fields with future perspectives.

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This paper reports a short summary of some procedures that allow to evaluate crack growth propagation rate. Numerical models developed using the equations of linear elastic fracture mechanics are described. Confirmation of the numerical results needs comparison with experimental results. The crack replica method and crack growth gages application are reported and prove to be powerful tools for crack propagation rate evaluation.

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The Portland cement clinker consists of 95% calcium oxide, silicon, aluminium and iron and 5% impurities of magnesium, sodium, potassium, titanium, sulfur, phosphorus and manganese. From the combination of two or more of the main oxides, the constituents of the white clinker are formed, corresponding to alite(3CaO.SiO₂ or C₃S), belite (2CaO.SiO₂ or C₂S) and celite (Ca₃Al₂O₆ or C₃A), which give cement its characteristic properties. The fundamental properties of cement are its mechanical resistance, chemical resistance, the speed of reaction with water and the heat given off in hydration. In this work, the reactivity of an artificial mixture of white clinker, formed from alite, belite and celite prepared by flame spray pyrolysis was evaluated. The phases were characterized by X-ray diffraction, scanning electron microscopy and microcalorimetry, to evaluate their formation and reactivity. The characterization showed that during the synthesis of belite, a greater amount of the polymorph alpha was produced, with some impurities. On the other hand, the synthesis of celite allowed the production of the polymorph CII. The reactivity was evaluated by microcalorimetry.

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Nanocomposites (NCs) of silver nanoparticles (Ag NPs) and carbon quantum dots (CQDs) have been received increasing attention for diverse applications including sensing, photocatalyst, surface enhanced Raman scattering detection and antibacterial. Herein, we report a unique photosynthesis of Ag NPs-CQD using CQDs as photo-reducing agent. Highly luminescent CQDs were prepared by a hydrothermal method using a mixture of citric acid (CA) and ethylenediamine (EDA) as starting precursors. X-ray diffraction pattern (XRD), transmission electron microscope (TEM), infrared (IR) and Raman spectroscopies confirmed the formation of NCs. We have demonstrated that the formation of Ag NPs accompanied with the degradation of surface fluorophores, which responded for the resolved absorption peak at ca. 346 nm and high luminescence of pristine CQDs. The NCs showed excellent antibacterial affinity to Escherichia coli. The results provide new understandings on the interactions between CQDs and silver ions as well as potential applications of Ag NP – CQD nanocomposites.

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In this study, kaolin bonded alumina-alginate composite beads were fabricated via a facile one-step sol-gel process by using sodium alginate. In order to achieve sintering of the beads at lower sintering temperatures a limited amount of  CC31 commercial-grade kaolin was used as a sintering additive (Al₂O₃:CC31 commercial-grade kaolin=14:1).  Produced composite beads were heat treated at 1300°, 1400° and 1500°C for 1 hour to achieve partial densification of the beads. TG-DTA analysis of the CC31 commercial-grade kaolin showed that mullite phase formation took place approximately at 1000°C. However, XRD measurements revealed that there is only alumina phase in the sintered ceramic beads. Due to the low amount of CC31 commercial-grade kaolin, mullite formation was not detectable via XRD analysis. No significant grain growth was observed at the sintered samples depending on the increasing sintering temperature. However, when the sintering temperature was increased, densification ratio and mechanical properties of the produced beads were enhanced significantly. Microstructural investigations of the sintered beads shown that with the help of the liquid phase sintering process, a good chemical bonding was achieved between the alumina particles.

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Poly (vinyl alcohol) (PVA) – based solid electrolyte films with potassium thiocyanate (KSCN) were prepared by solution-cast technique. The pure and KSCN- doped PVA films have been investigated for the charge transport mechanism in the polymer electrolyte system by using the DC conductivity (The composition dependence and temperature dependence in 300-385K range) and transference number measurements. The graphs related to conductivity – temperature shows that an increase in conductivity with respect to rise in the temperature. At room temperature, the conductivity of the (PVA+KSCN) electrolyte is 10² times greater than that of pure PVA. The transference number data exhibit that the charge transport in this polymer electrolyte system is predominantly due to ions. The ionic transference numbers (t_ion)  lies in the range of 0.92 to 0.99 for the films of PVA with KSCN in the wt% ratios (90:10), (80:20) and (70:30).

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Graphene is a material that has superior mechanical, electrical, and thermal properties. It has drawn the attention of many scientific researchers for this purpose. In this paper, three different types of fillers, GNPs, MWCNTs and EG reinforced epoxy nanocomposites were mainly studied. Different shear mixing speeds and shear mixing times were considered during the study of the nanocomposites with 0.1 wt% loading of the fillers. The effects of various types of fillers and different shear mixing speeds and durations on mechanical and electrical properties of the final composites were examined. The GNPs-reinforced epoxy nanocomposite was the only one that showed a 13% improvement in elastic modulus as compared to pure epoxy when the shear mixing conditions were 3000 rpm for 2 hours. The research also studied the effects of different loadings of GNPs and the addition of acetone as a solvent on the final mechanical, electrical and thermal properties of the composites (with the fixed shear mixing speed and time). The tensile strength of the composites reduced drastically when the loading of GNPs increased while the elastic modulus shows some increase with the growth in GNP loading. The study found that GNPs reinforced composites did not show the percolation threshold even with 5 wt% (with the ratio to the weight of epoxy) loading of the GNPs. The GNPs-reinforced epoxy composites showed an 116% improvement in the thermal conductivity as compared to the pure epoxy samples when the GNPs loading was 5 wt%. The results from the studied literatures also showed that the samples prepared with the addition of acetone had higher thermal diffusivity than the samples prepared without acetone.

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A novel cost-effective, eco-friendly clay composite adsorbent was developed towards fluoride remediation. Clay, Grog, Bone char, and Sawdust were dry mixed within volume ratios of (5:1:1:1), (4:2:2:1), and (3:3:3:1), respectively. The powders were mixed again with distilled water, pressed with disc shape; sun dried for three days and fired for one hour in the muffle furnace at 400^oC, 500^oC, and 600^oC. The cooled discs were ground and sieved to obtain nine different composite powdered with particle size less than 1.18 mm.  The developed composite adsorbent was characterized using advanced techniques: XRD, SEM, and FT-IR. The adsorption studies showed that among the developed adsorbents, composite with the volume ratio of (3:3:3:1) and optimized at firing temperature of 400°C exhibited maximum adsorption capacities of 91.6% fluoride removal efficiency. The XRD analysis revealed mixed phases in the composite, and the presence of OH^¯ functional groups was indicated by FT-IR analysis. The experimental results indicated that the Langmuir model was found to fit better for the removal of fluoride ion and followed the pseudo-second-order rate equation. The composite clay material exhibited excellent removal efficiency for the real water samples analyzed.

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The development of biomedical electronics, biosynthesis of ZnS nanoparticles(NPs) much attracted researchers, due to an eco-friendly and cost-effective routes forsynthesisZnSnanoparticles. In this present work, ZnS NPswas synthesized by using acalypha indica and curcuma longa plant extract using chemical co-precipitation method. The structural, morphological, element composition of biosynthesisZnS NPs was characterized by XRD, SEM and EDAX respectively. Optical and photoluminescence (PL) properties were evaluated by UV Visible spectroscopy. The formation of inhibition zone diameter against human pathogenic microorganisms was screened by in vitro disc diffusion method. From this investigation formation of inhibition zones clearly shows biosynthesizedZnS NPs have high antimicrobial activity against tested organisms, especially curcuma longa plant extract mediated ZnS NPs was formed maximum inhibition against all the tested microorganism.

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Stainless steel has an excellent mechanical property as well as high corrosion resistance. Stainless steel foams, therefore, seemed like an attractive material for impact energy absorption applications where damping capability is required such as in vehicles and buildings. Also when stainless steel foam is produced as stainless steel foam, the material density will be reduced thus the resulting foam will be a combination of light weight and high strength that can also be used in high strength applications. In our analysis, we tried to produce stainless steel foam through powder metallurgy in order to control mechanical properties in a better manner compared to the casting method. Also, we try to compare the pore morphology in foams on changing the space holder from accicular urea to crushed urea using FE-SEM. The properties of stainless steel foam, to a large extent, are found to depend on the arrangement of the pores which is decided by the space holder utilized during its synthesis using powder metallurgy route. The stainless steel obtained using acicular carbamide as space holder is found to possess acicular or irregular pores whereas those produced with crushed urea as space holder possesses nearly circular holes. Also, the previous foams are found to have better mechanical properties contributing towards more useful metallic foam.

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