NiO-CaO materials as promising catalysts for hydrogen production through carbon dioxide capture and subsequent dry methane reforming

In this work, CaO-NiO mixed oxide powders were evaluated as consecutive CO;chemisorbents and catalytic materials for hydrogen production thought the CH;reforming process. Between the NiO impregnated CaO and CaO-NiO mechanical composite, the first one presented better chemical behaviors during the CO;capture and CH;reforming processes, obtaining syngas（H;+ CO） as final product. Results showed that syngas was produced at two different temperature ranges, between 400 and 600 °C and at T > 800 °C, where the first temperature range corresponds to the CH;reforming process but the second temperature range was attributed to a different catalytic reaction process: CH;partial oxidation. These results were confirmed through different isothermal and cyclic experiments as well as by XRD analysis of the final catalytic products, where the nickel reduction was evidenced. Moreover, when a CO-O;flow was used during the carbonation process a triple process was achieved:（i） CO oxidation,（ii） CO;chemisorption and（iii） CH;reforming. Using this gas flow the hydrogen production was always higher than that obtained with CO;.

Generalized BCS Equations and the Iron-Pnictide Superconductors

A detailed quantitative study of the pnictide composite superconductor (CS) Ba0.6K0.4Fe2As2 is presented in the frame-work of the recently derived set of generalized BCS equations. Invoking multiple Debye temperatures to take into account anisotropy of the CS, we address the current experimental data on its Tc and the (not so clear-cut) gap-values via different theoretical scenarios that attempt to identify the ion species responsible for pairing in it. This is done with the aid of the Bogoliubov’s restriction on the BCS dimensionless electron-phonon coupling constant. Significantly, our study sheds light on the gaps which have recently been observed in different iron-pnictide CSs as nodes or line-nodes on the Fermi surface and have evinced considerable interest.

Experimental model standardizing polyvinyl alcohol hydrogel to simulate endoscopic ultrasound and endoscopic ultrasoundelastography

BACKGROUND Endoscopic ultrasound(EUS)and endoscopic ultrasound elastography(EUS-E)simulation lessens the learning curve;however,models lack realism,diminishing competitiveness.AIM To standardize the mechanical properties of polyvinyl alcohol(PVA)hydrogel for simulating organs and digestive lesions.METHODS PVA hydrogel(Sigma Aldrich,degree of hydrolysis 99%)for simulating EUS/EUS-E lesions was investigated in Unidad de Investigación y Desarrollo Tecnológico at Hospital General de México“Dr.Eduardo Liceaga”,Mexico City.We evaluated physical,contrast,elasticity and deformation coefficient characteristics in lesions,applying Kappa’s concordance and satisfaction questionnaire(Likert 4-points).RESULTS PVA hydrogel showed stable mechanical properties.Density depended on molecular weight(MW)and concentration(C).PVA bblocks with the greatest density showed lowest tensile strength(r=-0.8,P=0.01).Lesions were EUSgraphically visible.Homogeneous and heterogeneous examples were created from PVA blocks or PVA phantoms,exceeding(MW2=146000-186000,C9=15%and C10=20%)with a density under(MW1=85000-124000,C1=7%and C2=9%).We calculated elasticity and deformation parameters of solid(blue)areas,contrasting with the norm(Kappa=0.8;high degree of satisfaction).CONCLUSION PVA hydrogels were appropriate for simulating organs and digestive lesions using EUS/EUS-E,facilitating practice and reducing risk.Repetition amplified skills,while reducing the learning curve.

Citrus oils as chain transfer agents in the cross-metathesis degradation of polybutadiene in block copolymers using Ru-alkylidene catalysts

The cross-metathesis degradation of poly(styrene-co-butadiene) (styrene, 30 wt%) (SB-1) and poly(styrene-co-butadiene) (styrene, 21 wt%) (SB- 2) in the presence of essential oils and d-limo-nene as chain transfer agents (CTAs) using Rualkylidene catalysts (PCy3)2(Cl)2Ru = CHPh (I) and (1,3-diphenyl-4,5-dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (II) was studied. Terpene-terminated butadiene oligomers and polystyrene blocks were obtained as products of the degradation of SB-1 and SB-2. Catalysts I and II showed high activity in the degradation of SB copolymers to produce the low molecular weight products (Mn = 276 - 335 g·mol-1) and yields ranging from 91% - 95%. The cross-metathesis degradation of copolymers in organic solvents and in citrus oils (mandarin, orange and lemon oils) proceeded with similar efficiency and resulted in the same molecular weight butadiene oligomers. According to GS/MS (EI) analysis, the main products of the degradation of SB-1 copolymer with d-limonene were limonene-terminated oligomers of series Am (m = 1 - 4).

Bright Green Luminescence from Zirconium Oxide Stabilized with Tb³⁺Ions Synthesized by Solution Combustion Technique

In this research, the structural phase composition and room temperature luminescence properties of terbium doped zirconium oxide powders obtained by solution combustion synthesis method are presented as a function of the terbium content. The doping with terbium ions was performed during the redox combustion process and after annealing at 900°C during 20 hours. With the incorporation of the terbium ions into the zirconium oxide host, the stabilization of the high temperature tetragonal crystalline phase, as determined by x-ray diffraction technique, was obtained. Under ultraviolet radiation a bright green luminescence was observed at room temperature corresponding to the (4f) electron configuration of the Tb3+ ion, namely the electronic transitions 5D4 → 7Fn with n = 3 - 6. In addition, the undoped ZrO2 material showed green photoluminescence with high intensity.

Quenching Photoluminescence of Eu(III) by Cu(II) in ZnO:Eu3++Cu2+ Compounds by Solution Combustion Method

In this study Cu2++Eu3+ co-doped ZnO(ZnO/Cu2++Eu3+) solid solution powders were synthesized by solution combustion method using as oxidant agent zinc nitrate hexahydrate and as fuel urea;the Cu2+ concentrations were 0, 1, 2, 3, 10, and 20 %Wt;the Eu3+ ion concentration was fixed in 3%Wt. The samples after were annealed at 900°C by 20 h in air. The structural results showed the largely presence of a wurtzite solid solution of Cu2++Eu3+doped ZnO, at high Cu2+ doping CuO and Eu2CuO4 phases are also present. Morphological properties were analyzed using scanning electron microscopy (SEM) technique. However it is important to remark that the Cu2+ ions suppress the Eu3+ ion photoluminescence (PL) by means of an overlap mechanism between Cu2+ absorption band and Eu3+emission band (e.g. 5D0→7F2) of the Eu3+ emission spectra.

Bright Red Luminescence and Structural Properties of Eu³⁺Ion Doped ZnO by Solution Combustion Technique

Pure, and Europium ion doped Zinc oxide nanocrystals (ZnO:Eu3+) were synthesized by a solution combustion technique. The X-ray diffraction patterns (XRD) reveals the existence of the Eu2O3 phase. From the results of both, X-ray diffraction and photoluminescence spectra (PL) reveal that Eu3+ ions successfully substitute for Zn2+ ions in the ZnO lattice, moreover, when the amount of doped Europium was varied, this changes are showed in changes in the luminescence intensity. The PL is broad and a set of colors was emitted which originates from ZnO and the intra 4f transitions of Eu3+ ions. The existence of the Zn-O, Eu3+-O and O1s bonding energies were confirmed by X-ray photoelectron spectroscopy (XPS) technique. The samples morphology was registered by a scanning electron microscopy (SEM) technique, and reveals that Europium ions are present on the surface of the ZnO nanocrystals.

Correlation between Hardness, Structure and Electrochemical Performance of an AlZnMnMg Alloy

In this work the structural changes induced by aged treatment have shown a connection with differences of hardness and electrochemical performance. Al-base alloys have been investigated by means of Vickers hardness, X-ray diffraction, scanning electron and short-term electrochemical test. X-ray diffraction result reveals the formation of (MgZn)49Al32 phase for two conditions, the first one is when the magnesium content is upper to 5.49% in as-cast condition and the second one after the thermal treatment carried out at 450?C for 5 h. In addition, the hardness and electrochemical performance has been influenced by the presence and quantity of the (MgZn)49Al32 phase. The addition of magnesium alloying modifies the microstructure, increases the content of (MgZn)49Al32 phase and provides a localized corrosion which conduced to the breakdown of the oxide film (?-Al2O3) formed on the Al alloy surface.

Photoluminescence and Structural Properties of ZnO Nanorods Growth by Assisted-Hydrothermal Method

Semiconducting zinc oxide (ZnO) nanorods were obtained in bulk quantity by an hexamethylenetetramine (HMTA)-assisted hydrothermal method at low temperature (90°C) with methenamine ((CH3)6N4 as surfactant and catalyst and zinc nitrate Zn(NO3)2·6H2O as Zn source. The structure and phase of ZnO nanorods were studied using x-ray diffraction (XRD) and high resolution transmission electron microscopy techniques (HRTEM). The morphology of the nanostructures was studied by scanning electron microscope (SEM) method. The photoluminescence (PL) properties were investigated founding two emission bands under UV excitation.

Thermokinetic and conductivity analyzes of the high CO2 chemisorption on Li5AlO4 and alkaline carbonate impregnated Li5AlO4 samples:Effects produced by the use of CO2 partial pressures and oxygen addition

The effect of COpartial pressure was evaluated during the COchemisorption in penta lithium aluminate（LiAlO）, using different COand Opartial pressures in the presence or absence of alkaline carbonates. Results showed that using low PO（0.1） did not affect the kinetic and final COchemisorption process. Moreover, small additions of oxygen（PO= 0.05） into the mixture flue gas, seemed to increase the COchemisorption. Additionally, the presence of alkaline carbonates modified the COcapture temperature range. COchemisorption kinetic parameters were determined assuming a double exponential model where direct COchemisorption and COchemisorption controlled by diffusion processes are considered.Finally, ionic diffusion was analyzed by ionic conduction analysis, where all the gravimetric and ionic measurements were in good agreement showing different diffusion processes depending on temperature.Finally, the oxygen and alkaline carbonate additions have positive effects during the COchemisorption process in LiAlO, and a possible reaction mechanism is presented.

Synthesis and evaluation as CO2 chemisorbent of the Li5(Al1-xFex)O4 solid solution materials:Effect of oxygen addition

Pentalithium aluminate（β-LiAlO） and the corresponding iron-containing solid solution(Li(AlFe)O)were synthetized by solid-state reaction. All the samples were characterized structural and microstructurally by X-ray diffraction, solid-state nuclear magnetic resonance, scanning electron microscopy, Nadsorption-desorption and temperature-programmed desorption of CO. Results showed that 30 mol% of iron can be incorporated into the β-LiAlOcrystalline structure at aluminum positions. Moreover, iron addition induced morphological and superficial reactivity variations. Li(AlFe)Osamples chemisorbed CObetween 200 and 700 °C, where the superficial chemisorption presented the highest enhancement,in comparison to β-LiAlO. Additionally, Li(AlFe)Osamples sintered at higher temperatures thanβ-LiAlO. Isothermal COchemisorption experiments of β-LiAlOand Li(AlFe)Owere fitted to a first order reaction model, corroborating that iron enhances the COchemisorption, kinetically. When oxygen was added to the gas flow, COchemisorption process was mainly enhanced between 400 and 600 °C for the Li(AlFe)Osample in comparison to β-LiAlO. Hence, Li(AlFe)Osolid solution presented an enhanced COchemisorption process, in the presence and absence of oxygen, in comparison to β-LiAlO.

Porous Carbon Grown by Chemical Vapor Deposition on Copper Substrates

Amorphous porous carbon was synthesized by chemical vapor deposition on copper substrates. The average size of the pores is around 1.2 microns with some small pores decorating the big ones. Lamellar samples of this carbonaceous material can be separated from the copper support and may be useful as electrode due to its low electrical resistivity of the order of 0.4 Ωcm.

Parametric Dirac Delta to Simplify the Solution of Linear and Nonlinear Problems with an Impulsive Forcing Function

The Laplace transform is a very useful tool for the solution of problems involving an impulsive excitation, usually represented by the Dirac delta, but it does not work in nonlinear problems. In contrast with this, the parametric representation of the Dirac delta presented here works both in linear and nonlinear problems. Furthermore, the parametric representation converts the differential equation of a problem with an impulsive excitation into two equations: the first equation referring to the impulse instant (absent in the conventional solution) and the second equation referring to post-impulse time. The impulse instant equation contains fewer terms than the original equation and the impulse is represented by a constant, just as in the Laplace transform, the post-impulse equation is homogeneous. Thus, the solution of the parametric equations is considerably simpler than the solution of the original equation. The parametric solution, involving the equations of both the dependent and independent variables in terms of the parameter, is readily reconverted into the usual equation in terms of the dependent and independent variables only. This parametric representation may be taught at an earlier stage because the principle on which it is based is easily visualized geometrically and because it is only necessary to have a knowledge of elementary calculus to understand it and use it.

Doping Graphene by Chemical Treatments Using Acid and Basic Substances

We prepared single-layer graphene films through mechanical exfoliation of Kish graphite and chemical vapor deposition techniques. These samples were treated in nitric acid, sulfuric acid, sodium hydroxide and ammonium hydroxide solutions to induce doping. We used Micro Raman Spectroscopy before and after the chemical functionalization to monitor differences in the Raman spectrum. We found shifting for both G and 2D peaks of graphene and a significant upshifting in samples treated with sulfuric acid, similar to those reported for nitric acid.

Influenza of the Cu Ion on the Structural and Optical Properties in Cu + Ce Co-Doped ZnO Compounds

This article showed and explained the effects of the Cu2+ ions on the structural and photoluminescent properties of Ce3+ doped ZnO compounds (ZnO: Ce3+) in Cu2+ + Ce3+ co-doped ZnO (ZnO: Cu2+ + Ce3+) solid solutions powders. The samples were synthesized by a solution combustion method maintaining the Ce3+ ion concentration constant in 3%wt and varying the Cu2+ ion concentration in 0%wt, 1%wt, 2%wt, 3%wt, 10%wt and 20%wt. However, pristine ZnO and Ce3+ doped ZnO were synthesized by the same method for comparison. After the synthesis process all the samples were annealed at 900°C by 24 h. The pure ZnO, ZnO: Ce3+ and ZnO/Cu2+ + Ce3 powders were structurally characterized using X-ray diffraction (XRD) technique, the XRD patterns showed that for either undoped and doped with the Cu2+ ion both exhibited the hexagonal wurtzite ZnO crystalline structure, also the diffraction peaks of both samples types showed a little change toward lesser angles. The morphology and particle size of the samples were observed by means of a scanner electron microscopy (SEM);from SEM imagen is observed that the crystallites of the samples are agglomerated forming cage-like hollow structures caused by the combustion process. The cage-like structures have approximate size of 800 nm. In addition, the photoluminescence of pure ZnO, ZnO: Ce3+and ZnO: Cu2+ + Ce3+ compounds was measurement as a function of Cu2+ ion concentration under a excitation wavelength of 378 nm in the UV region. As an important result, it is observed that by Auger phenomena of non-radiative recombination, the UV emission of the ZnO is quenching.

Biocompatibility and electrochemical evaluation of ZrO_(2) thin films deposited by reactive magnetron sputtering on MgZnCa alloy

Biodegradable magnesium alloys are promising candidates for temporary fracture fixation devices in orthopedics;nevertheless,its fast degradation rate at the initial stage after implantation remains as one of the main challenges to be resolved.ZrO_(2)-based coatings to reduce the degradation rate of the Mg-implants are an attractive solution since they show high biocompatibility and stability.In this work,the degradation,cytotoxicity,and antibacterial performance of ZrO_(2)thin films deposited by magnetron sputtering on a Mg-Zn-Ca alloy was evaluated.Short-term degradation of ZrO_(2)-coated and uncoated samples was assessed considering electrochemical techniques and H_(2)evolution(gas chromatography).Additionally,long term degradation was assessed by mass-loss measurements.The results showed that a 380 nm ZrO_(2)coating reduces the degradation rate and H_(2)evolution of the alloy during the initial 3 days after immersion but allows the degradation of the bare alloy for the long-term.The ZrO_(2)coating does not compromise the biocompatibility of the alloy and permits better cell adhesion and proliferation of mesenchymal stem cells directly on its surface,in comparison to the bare alloy.Finally,the ZrO_(2)coating prevents the adhesion and biofilm formation of S.aureus.

Some Implications of an Alternate Equation for the BCS Energy Gap

A set of generalized-BCS equations (GBCSEs) was recently derived from a temperature-dependent Bethe-Salpeter equation and shown to deal satisfactorily with the experimental data comprising the Tcs and the multiple gaps of a variety of high-temperature superconductors (SCs). These equations are formulated in terms of the binding energies W1(T),W2(T),… of Cooper pairs (CPs) bound via one- and more than one-phonon exchange mechanisms;they contain no direct reference to the gap/s of an SC. Applications of these equations so far were based on the observation that for elemental SCs |W01|=△0 at T = 0 inthe limit of the dimensionless BCS interaction parameter λ→0. Here △0 is the zero-temperature gap whence it follows that the binding energy of a CP bound via one-phonon exchanges at T = 0 is 2|W01|. In this note we carry out a detailed comparison between the GBCSE-based W1(T) and the BCS-based energy gap △(T) for all 0≤T≤Tc and realistic, non-vanishingly-small values of λ. Our study is based on the experimental values of Tc Debye temperature , and ?0 of several selected elements including the “bad actors” such as Pb and Hg. It is thus established that the equation for W1(T) provides a viable alternative to the BCS equation for △(T). This suggests the use of, when required, the equation for W2(T) which refers to CPs bound via two-phonon exchanges, for the larger of the two T-dependent gaps of a non-elemental SC. These considerations naturally lead one to the concept of T-dependent interaction parameters in the theory of superconductivity. It is pointed out that such a concept is needed both in the well-known approach of Suhl et al. to multi-gap superconductivity and the approach provided by the GBCSEs. Attention is drawn to diverse fields where T-dependent Hamiltonians have been fruitfully employed in the past.

Electrical Conductivity of Collapsed Multilayer Graphene Tubes

Synthesis of multilayer graphene on copper wires by a chemical vapor deposition method is reported. After copper etching, the multilayer tube collapses forming stripes of graphitic films, their electrical conductance as a function of temperature indicate a semiconductor-like behavior. Using the multilayer graphene stripes, a cross junction is built and owing to its electrical behavior we propose that a tunneling process exists in the device.

Monodisperse ZnO Solid Spheres by an Assisted Structure Directing Agent-Hydrothermal Method

Monodisperse ZnO solid spheres nanostructures were synthesized and deposited on Si (100) silicon substrates by the hexamethylenetetramine (HMTA)-assisted hydrothermal method at high temperature (200°C). In this case the HMTA is used as structure directing agent (SDA) to growth of the ZnO solid spheres. The source material used was zinc nitrate hexahydrate under a chemical reaction of hydrolysis-condensation of the Zn2+ salt aqueous solution. The structure and morphology of the ZnO solid spheres were studied by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Furthermore, the photoluminescence (PL) of the ZnO solid spheres was measured to optical characterization of the product. The remarkable influence of the HMTA as structure directing agent and the reaction temperature to the formation of the solid spheres nanostructures is demonstrated.