Magnetite nanoparticle mediated catalytic aquathermolysis of Omani heavy crude oil

The worldwide demand for energy continues to grow and the production of heavy crude is escalating due to shortage of conventional light crude. The transportation of heavy crude oil from the head-well to the refinery is a challenging task due to its high viscosity and low API gravity. Catalytic aquathermolysis is one of the most significant and cost-effective viscosity reduction techniques employed in the up gradation of the crude oil at elevated temperatures and hence to enhance oil extraction process. In this study, catalytic aquathermolysis of Omani heavy crude oil was performed using magnetite nanoparticles (NPs). The NPs were synthesised by reverse co-precipitation method using iron salts in alkaline medium. The synthesised NPs were characterized using Scanning Electron Microscopy (SEM), X-Ray Powder Diffraction (XRD), Energy Dispersive X- Ray analysis (EDX) and Fourier Transform Infrared Spectroscopy (FTIR). The XRD results exhibited a characteristic peak confirming the high purity of iron oxide nanoparticles. The FTIR spectral analysis designated two well-defined peaks corresponding to wave numbers of 500 ?cm^?1 and 630 ?cm^?1, endorses the presence of Fe–O. The catalytic aquathermolysis experiments were carried out in a Parr high temperature-high pressure batch reactor at different experimental conditions. The processing parameters in temperature range of 250 ?°C - 300 ?°C, 0.1% to 0.3% catalyst loading, water to oil ratio of 1:7 to 3:7 with 24–72 ?h of reaction time. The initial pressure in the reactor was maintained at 32 ?bars and the optimization was performed using the Taguchi method to maximize the level of heavy oil. An orthogonal array was employed to analyse the effects of mean response and mean signal-to-noise ratio (S/N) to upgrade the heavy oil. The regression analysis was used to establish a relationship between the viscosity and experimental parameters. The experimental outcomes indicates that the maximum reduction in viscosity occurred at a processing temperature of 300 ?°C, 1:7 ?W/O ratio, 0.1 ?wt% of catalyst concentration and 48 ?h of reaction time. Similarly, the optimum conditions for the reduction in API gravity were obtained at 280 ?°C temperature, 3:7 ?W/O ratio, 0.2 ?wt% of catalyst concentration and a reaction time of 24 ?h.     

Investigation of roman age pigments found on pottery fragments

This work deals with the study of the physico-chemical characteristics of pigments found on pottery fragments from an excavation in Vicenza (Contrà Pedemuro S. Biagio). The examined pigments were: a blue colour on a terracotta fragment; an olive green on a black pot bottom; yellow traces on a red depurated terracotta; an olive green plate bottom with an amaranth “a fresco” test; a deep red on a depurated terracotta; a white trace, again on a depurated terracotta. The techniques used were optical microscopy, scanning electron microscopy (SEM), equipped with an energy dispresive (EDS) microanalysis detector, X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Most of those techniques were non-destructive and able to provide the required results. All the pigments belonged to the group of basic colours, we did not find “precious” pigments. They have many similarities to those discovered in other European sites in France and Switzerland, witnessing the active trading exchange in which X^a Regio, Venetia et Histria played an important role.     

Characterization of new natural cellulosic fiber from the Ipomoea staphylina plant

Natural fibers extracted from plants play a major role as reinforcement in polymer composite materials due to their superior properties. This work aims to comprehensively characterize the physical and chemical properties of Ipomoea staphylina fibers (ISFs), which are extracted from the stem of the Ipomoea staphylina plant. The ISFs show cellulose content (72.76 wt%), hemicelluloses content (13.6 wt%), density (1401 kg cm^?3), and tensile strength of 173–658 MPa with a strain rate of 2.03–6.63%. The thermal stability of ISFs illustrate that the fibers are stable up to a temperature of 311°C with kinetic activation energy of 99.82 kJ mol^?1.     

Ionic conductivity, structural and thermal properties of pure and Sr doped Y2Ti2O7 pyrochlores for SOFC

In the present study, SrO doped Yttrium titanate pyrochlore was synthesized using solid state reaction technique. The sintering characteristics, crystal structure, thermal and conductivity behavior of doped and undoped pyrochlores have been studied to find their suitability in solid oxide fuel cells (SOFC). The as-prepared samples were characterized using X-ray diffraction (XRD), Fourier-Transform-Infrared spectroscopy (FT-IR), thermal-gravimetric analysis (TGA) and ac conductivity up to 900 °C. The results are discussed in light of oxygen vacancy formation and structural disordering. Undoped and doped yttrium titanate with SrO (x = 0.1) exhibits single Y₂Ti₂O₇ phase with relative density of 94%. It was observed that further doping of SrO (x = 0.2–0.4) leads to formation of Y₂Ti₂O₇ phase along with SrTiO₃ phase. Excessive SrO (x = 0.4) results in increase in ionic conductivity to 1.50 × 10⁻¹ S cm⁻¹ whereas it impedes the densification process with relative density of 85%.     

Raman spectroscopy and structural properties of InxBi40−xSe60 system

In_xBi_40−xSe₆₀ (x = 1.6, 4.4, 7, 10 and 13.2) alloys were synthesized by melt-quenching technique. The X-ray diffraction and Raman spectroscopy investigations confirm that the materials are in single phase. Archimedes method and Energy Dispersive Spectroscopy (EDS) have been used for density and chemical characterization of the obtained materials. Indium content dependences of different parameters such as the density (D), the compactness (δ), and the average coordination number (Z) have been investigated and discussed in light of chemical order network and topological models.     

Preparation of stable dispersion of graphene using copolymers: dispersity and aromaticity analysis

In this study, effectiveness of non-ionic block copolymers such as Lugalvan BNO12 and Triton X series (Triton X100 & Triton X405) has been reported for graphene dispersion in aqueous solutions. Stability of the aqueous graphene dispersions is investigated using UV–visible spectroscopy, Rheological, and Conductivity studies. Adsorption isotherms are constructed to determine the amount of polymers adsorbed on the surface of graphene by the spectroscopic analysis. Lugalvan BNO12 has been found to be adsorbed in higher amounts on the graphene surface compared to the Triton X series polymers. Thermogravimetric analysis (TGA) and Fourier Transform Infrared (FTIR) Spectroscopy investigations indicated grafting of polymers chains to the graphene surfaces. The dispersions prepared with optimum concentrations (as determined from adsorption isotherms) of polymers have shown lower viscosity and conductivity values. Lugalvan BNO12 has been found to be a better stabilizer for graphene than the Triton X series dispersants because the former contains two aromatic rings in its structure that acts as an anchoring group and helps in the stabilization of graphene dispersion in comparison to the single aromatic group in the Triton X series. The experimental results reported have shown that the aromaticity of polymeric dispersants plays significant role in the aqueous graphene dispersions. The non-ionic block copolymers that assisted dispersed graphene are potential candidates for the fabrication of various devices such as sensors, batteries, and supercapacitors applications.     

Investigation of Commercial Graphenes

For graphene to achieve its full scientific and commercial potential, reliable mass production of the material on the multi-tonne scale is essential. We have investigated five samples of graphene obtained from commercial sources that state they can supply the product on the tonne scale per annum. From electron microscopy at the micrometre to the nanometre scale, and neutron vibrational spectroscopy, we find that none of the materials examined were 100 % isolated graphene sheets. In all cases, there was a substantial content of graphite-like material. The samples exhibited varying oxygen contents, this could be present as carboxylic acid (although other oxygenates, quinones, phenols may also be present) or water. We emphasise that INS spectroscopy is particularly useful for the investigation of inorganic materials that will be used commercially: it provides atomic scale information from macroscopic (10’s of g) amounts of sample, thus ensuring that the results are truly representative.     

Spectroscopic investigation of a ‘Virgin of Sorrows’ canvas painting: A multi-method approach

The investigation of unmatched ancient objects is an attentive and arduous activity to conservation scientists. An important aspect of art analysis is the question on sampling and avoiding damage on the artefact during the study. A possible way to maximize the information that is extracted from the historical object is using several sensitive micro-analytical techniques on the same micro samples. As an illustration of this multi-method approach, in this work, a canvas painting ‘Virgin of Sorrows’ was studied and its materials were analysed in order to roughly date and to authenticate this object of art. Proton induced X-ray emission (PIXE), neutron activation analysis (NAA), optical microscopy, scanning electron microscopy (SEM), micro-Raman spectroscopy (MRS) and Fourier transform infrared spectroscopy (FT-IR) were used, obtaining successful results. These methods allowed identifying the different inorganic pigments (iron oxide, carbon black, white lead, Prussian blue) as well as indigo. Optical microscopy and SEM revealed the layered structure of the samples, while FT-IR enabled to determine the nature of the varnish used (shellac). By using these complementary techniques, it was possible to identify the materials in the painting, which are indicative for the period of manufacturing the artwork.     

Physicochemical properties of new cellulosic fibers from the bark of Acacia arabica

With the growing environmental consciousness toward carbon emissions, natural fibers are the best alternative and act as a substitute for synthetic fibers due to their potential properties. New cellulosic fibers were identified from Acacia arabica bark. This study aimed at understanding the characteristics of Acacia arabica fibers (AAFs) extracted from the bark of the A. arabica, and its physicochemical properties were examined by thermal stability analyses, X-ray diffraction, chemical constitutions, and Fourier transform infrared spectroscopy analysis. Cellulose content (68.1 wt%), density (1028 kg m^?3), and crystallinity index (51.72%) properties were identified.     

Chemical Liquid Phase Deposition of Thin Aluminum Oxide Films

Introduction Inorganic oxide films have attracted a lot of interest in the last several decades. Among them, silicon dioxide films are widely used in modern microelectronics, optics and mechanics. This material has been grown by various methods including thermal oxidation, chemical vapor phase deposition, plasma-enhanced chemical vapor phase deposition, and so on.1,2 Recently, Nagayama et al.3 have reported that SiO2 thin films could be produced by a new chemical method of liquid phase depos…     

Sequestration of Aqueous Lead(II) Using Modified and Unmodified Red Onion Skin

The efficacy of onion skins, both unmodified and chemically modified with thioglycolic acid, was investigated as alternative low-cost adsorbents for the sequestration of aqueous lead(II) ions from aqueous solution. The adsorbents were characterised using Fourier transform infrared spectroscopy and scanning electron microscopy – energy dispersive X-ray spectroscopy. Adsorption experiments were performed using batch sorption processes. The effects of contact time, pH, initial Pb(II) concentration, adsorbent dose, and temperature were investigated. Optimum sorption conditions were found at pH 4 and a 150?min equilibrium time for the modified onion skin and unmodified onion skin. The Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models were used to characterize the equilibrium experimental results. The equilibrium process was best described by the Freundlich isotherm. The maximum adsorption capacities of 4.878 and 6.173?mg/g were obtained for modified and unmodified adsorbents, respectively, using the Langmuir model. Kinetic studies indicated that the sorption of Pb(II) ions followed a pseudo-second-order model. Thermodynamic parameters such as standard enthalpy change (ΔH°), entropy change (ΔS°), and free energy change (ΔG°) were evaluated from the sorption experimental measurements. The results showed that the sorption process of Pb(II) ions on unmodified and modified onion skins was feasible and exothermic under the conditions used in this study. The sorption process followed the mechanism of physisorption.     

Investigations on poly(methyl methacrylate)-poly(ethylene oxide) hybrid polymer electrolytes with dioctyl phthalate, dimethyl phthalate and diethyl phthalate as plasticizers

Plasticizers can be used to change the mechanical and electrical properties of polymer electrolytes by reducing the degree of crystallinity and lowering the glass transition temperature. The transport properties of gel-type ionic conducting membranes consisting of poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), LiClO₄ and dioctyl phthalate, diethyl phthalate or dimethyl phthalate (DMP) are studied. The polymer films are characterized by X-ray diffraction, Fourier transform infrared and impedance spectroscopic studies. It is found that the addition of DMP as the plasticizer in the PEO-PMMA-LiClO₄ polymer complex favours an enhancement in ionic conductivity. The maximum conductivity value obtained for the solid polymer electrolyte film at 305 K is 3.529×10^{– 4} S cm^–1. Electronic Publication     

Lead determination in glasses by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been used to determine the lead content of different types of lead silicate glasses commercially designed as sonorous glass (which contain ∼ 10 wt.% PbO); crystal glass (with at least 24 wt.% PbO) and superior crystal glass (with at least 30 wt.% PbO). Seven different types of glass samples were selected, including historic-original, model and commercially available. The selected samples were artificially weathered under neutral, acid and alkaline attack. Analysis by LIBS was carried out in vacuum under excitation at 266 nm and results were compared with those obtained by conventional techniques used for glass characterization. Composition of the bulk glasses was analyzed by XRF (X-ray fluorescence) and the corroded surfaces were characterized by SEM/EDX (scanning electron microscopy/energy dispersive X-ray microanalysis). A linear correlation was obtained between the intensity of selected Pb lines in the LIB spectra and the PbO content. The effect of corrosion could be characterized by comparing successive LIB spectra recorded on the same area; acid attack resulted in a decrease of PbO, CaO and Na₂O content in the surface with respect to the bulk of the sample, while minor changes in the composition were noticed under alkaline attack. These results show LIBS as a useful technique to classify the different types of lead glasses by their lead content and to determine and asses the degree and type of corrosion.     

Optical properties of single crystals of heavy lanthanide chlorides

Studies of heavy lanthanide chlorides may provide important information on the degree of Ln³⁺–ligand bond covalency. Monocrystals of LnCl₃·6H₂O, where Ln = Dy, Ho and Er, were grown and spectroscopic investigations were performed at room temperature and at low temperatures down to 4.2 K in order to understand the nature of the Ln³⁺–L bonds. The intensities of the electronic lines and the Judd–Ofelt parameters were calculated and compared with those obtained for chlorides of light lanthanides (i.e. Ce(III), Pr(III) and Nd(III)). Room temperature Raman and IR studies of the compounds under investigation were also performed. The relationship between hypersensitivity and covalency is discussed. The change of vibronic coupling strength along the lanthanide ion series does not modify monotonically. The ion-pair interactions are especially visible for the ⁵I₈ → ⁵F₂ and ⁵I₈ → ⁵F₃ transitions in the HoCl₃·6H₂O low temperature spectra.     

Optical characteristics of europium and terbium doped strontium orthogermanate phosphors

In this work, europium and terbium activated Sr₂GeO₄ phosphors were successfully developed by traditional solid state method. Powders XRD, FESEM, EDS, FTIR, DRS and PL techniques have been used to probe the as prepared phosphors. Powder XRD patterns of the phosphors are indexed. The elemental composition of phosphors was obtained from their EDS. FTIR spectra are employed to detect different vibrational groups in phosphor compositions. The DRS profiles of both pristine and Eu³⁺ (Tb³⁺) substituted samples exhibit broad and strong band in the 230–370 ​nm region. The photoluminescence studies of europium and terbium doped phosphors exhibited optimistic red emission at 617 ​nm (⁵D₀ → ⁷F₂ of Eu³⁺ ions) and intense green emission at 543 ​nm (⁵D₄ → ⁷F₅ of Tb³⁺ ions) upon ultraviolet (UV) excitations respectively. The CIE chromaticity co-ordinates are produced in deep red and green regions. Therefore, these materials may become potential alternatives for red and green phosphors in the display devices and in lamp industry.     

Novel route to synthesize CuO nanoplatelets

A new synthesis route to obtain high-purity cupric oxide, CuO, using the hydrothermal reaction of copper sulfide and a NaOH solution in an oxygen atmosphere has been developed. The synthesized products showed nanoplatelet-like morphologies with rectangular cross-sections and dimensions at the nanometric scale. Variations in the oxygen partial pressure and synthesis temperature produced changes in size and shape, being found that the proliferation of nanoplatelet structures occurred at 200 °C and 30 bar.     

Characterization of Two Bulgarian Herbs for Use as Biosorbents for Copper(II)

Abstract

Two biomaterials based on the abundant Bulgarian medicinal plants Mentha spicata L. (denoted as MS) and Ruta graveolens L. (denoted as RG) were investigated as environmentally friendly biosorbents for Cu(II) removal from aqueous solutions. Grain size distribution, slurry pH, texture parameters, thermal behavior and mineralogical composition of MS and RG were determined. Instrumental methods such as scanning electron microscopy (SEM), X-ray-diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, differential thermal analysis (DTA), and thermogravimetric analysis (TGA) were used for their characterization. It was demonstrated that the surface morphology of both materials is rough and contains pores that could entrap different pollutants, as well as functional groups that can attach metal ions. In order to examine the feasibility of these materials for use as biosorbents for heavy metals, adsorption experiments were performed. The results for the removal of Cu(II) ions from aqueous solution reveal capabilities suggesting that both materials have potential to be used as promising, efficient and low-cost biosorbents.     

Characterization of New Natural Cellulosic Fiber from Acacia leucophloea Bark

There is a need to explore the possibility of natural fibers as a novel reinforcement to fabricate lightweight composite structures. This investigation was aimed at understanding the characteristics of fiber extracted from the bark of the Acacia leucophloea (AL) plant and its physico-chemical properties. Cellulose content (68.09 wt.%), density (1385 kg/m³), crystallinity index (51%), tensile strength (317–1608 MPa), and Young’s modulus (8.41 ? 69.61 GPa) properties were identified in the AL fibers, and thermal studies using TG and DTG analysis revealed that they degraded at a temperature of 220°C with kinetic activation energy of 73.1 kJ/mol.     

Nanosized LiMn2O4 from mechanically activated solid-state synthesis

The synthesis of pure and Cr-doped nanosized LiMn₂O₄ particles has been carried out by solid-state process on high-energy ground mixtures. In situ X-ray analysis demonstrates the spinel forms as single phase at 623 K passing through the Mn₃O₄ precursor at temperatures as low as 573 K. In the doped high-energy ground mixture Li-rich spinel phase forms at 623 K and Cr ions insert in the spinel octahedral site only at 723 K.A mean particle size value of 60 Å, quite independent of the reaction time, is obtained for T<673 K. For higher temperature the growing of the particles as a function of time is observed, independent of doping. The mechanical grinding seems to be the most suitable way to obtain impurity-free spinel phases at lower temperature and with smaller particle size with respect to manually ground mixtures by solid-state reaction and via sol-gel synthesis.     

Advanced TEM Characterization for Single-atom Catalysts: from Ex-situ Towards In-situ

Clean energy innovation has triggered the development of single-atom catalysts(SACs) due to their excellent catalytic activity, high tunability and low cost. The success of SACs for many catalytic reactions has opened a new field, where the fundamentals of catalytic property-structure relationship at atomic level await exploration, and thus raises challenges for structural characterization. Among the characterization techniques for SACs, aberration-corrected transmission electron microscopy(TEM) has become an essential tool for direct visualization of single atoms. In this review, we briefly summarize recent studies on SACs using advanced TEM. We first introduce TEM methods, which are particularly important for SACs characterization, and then discuss the applications of advanced TEM for SAC characterization, where not only atomic dispersion of single atoms can be studied, but also the distribution of elements and the valence state with local coordination can be resolved. We further extend our review towards in-situ TEM, which has increasing importance for the fundamental understanding of catalytic mechanism. Perspectives of TEM for SACs are finally discussed.