Rheological and volumetric properties of TiO2-ethylene glycol nanofluids

Homogeneous stable suspensions obtained by dispersing dry TiO₂ nanoparticles in pure ethylene glycol were prepared and studied. Two types of nanocrystalline structure were analyzed, namely anatase and rutile phases, which have been characterized by scanning electron microscopy. The rheological behavior was determined for both nanofluids at nanoparticle mass concentrations up to 25%, including flow curves and frequency-dependent storage and loss moduli, using a cone-plate rotational rheometer. The effect of temperature over these flow curve tests at the highest concentration was also analyzed from 283.15 to 323.15 K. Furthermore, the influence of temperature, pressure, nanocrystalline structure, and concentration on the volumetric properties, including densities and isobaric thermal expansivities, were also analyzed.     

Comparative study of the consumption of virgin olive oil or seje on lipid profile and oxidation resistance of high density lipoprotein (HDL) of rat plasma

We compared the effect of the consumption of seje oil (Oenocarpus bataua), with that of olive oil, on plasma lipids and susceptibility in vitro to oxidation of high density lipoprotein (HDL) in the rat. Two groups often male Sprague Dawley rats were fed ad libitum, for a lapse of eight week, with a purified diets with 10g de seje oil or olive oil/100 g of diet (GS y GO respectively). The animals were exsanguinated at the end of the experimental after a 14 hour fast. Plasma was isolated by centrifugation, and the fractions of lipoproteins were separated from the plasma by sequential ultracentrifugation. Rats of GO had a statistically significant lower in concentration of TG (p < 0.05) compared with GS group. HDL fractions in both groups were oxidatively modified by incubation with copper ions. Differences in the fractions susceptibilities to peroxidation were studied by measuring the formation of thiobarbituric acid reactive substance (TBARS) for 3 hours. HDL in GS had a statistically significant decrease in TBARS formation (p < 0.05) relative to HDL of GO. This may be explained by the lower concentration of polyunsaturated fatty acids of HDL in GS compared with HDL in GO.     

The effect of ion and particle losses in a diffusion charger on reaching a stationary charge distribution

Bipolar charging of nanometer-sized aerosol particles in a tube containing a radioactive source has been investigated theoretically. A model has been developed which accounts for diffusion losses of particles and ions to the tube wall, as well as for the spatial dependency of the ion-pair generation rate. The ion generation rate profile along the tube axial direction as a function of the source size and of the tube length and radius has been evaluated and, subsequently, used to examine the aerosol charging process. Comparative calculations were also performed for uniform ion generation and negligible diffusion losses. In a real charger, where diffusion losses are unavoidable, particles cannot attain a steady charge distribution. On the contrary, provided the nt product (ion mean concentration × mean aerosol residence time) is large enough, the number concentration of charged particles of a given size reaches a maximum at a certain axial location and thereafter decreases. The extrinsic charging efficiency (fraction of originally neutral particles which carry a net charge at the ionizer outlet) depends in a complex manner on a number of parameters: particle size and polarity, tube length and radius, nt product, and relative aerosol-to-ion concentration.     

Interpretation of Colloidal Dyeing of Polyester Fabrics Treated with N‐Cetylpyridinium Chloride in Terms of Zeta Potential and Surface Free Energy Balance

In this work are presented results about the effect on the surface free energy and zeta potential for the adsorption process of the colloidal dye Disperse Blue 3 (DBlue3) onto polyester fabric (dacron 54, stile 777), when the fabric is pretreated with N‐cetylpyridinium chloride (NCPCl). The zeta potential of the fabric as a function of the pH of the liquid phase shows that both H⁺ and OH^? ions are involved in determining the potential. The negative charge of the fiber is caused by the presence of the carboxyl end‐groups of the polyester, which are generated by the acidic and basic hydrolysis of the fabric in these media. The zeta potential of the DBlue3 as a function of the pH of the liquid phase shows that the negative charge of the dye particles are because of the presence of an OH^? group, ionized in aqueous media, in the molecular structure of the dye. The zeta potential of the fabric treated with a 10^?3 M solution of NCPCl as a function of the pH of the liquid phase is positive over the whole pH range. This behavior can be attributed to the presence of the pyridinium group in the molecular structure of the surfactant, which is positively charged. The adsorption isotherms of the dye DBlue3 onto a polyester pretreated with NCPCl at 293 K, shows that the presence of the surfactant on the surface of the fabric favors the adsorption of the dye onto the fabric. This fact shows that the pretreatment with NCPCl is a very interesting aspect in the textile industry. On the other hand, the isotherms of the adsorption of the above dye onto the polyester pretreated with a 10^?4 M solution of NCPCl, at different temperatures, shows that the amount of the dye absorbed onto the pretreated fabric increases with the increase in temperature. These behaviors can be justified by the analysis of the components of the surface free energy and zeta potential.

Electron microscopy photographs of the fabric pretreated with NCPCl before (top) and after (bottom) dyeing with DBlue3.     

Elimination of polycyclic aromatic hydrocarbons by bleaching of olive pomace oil

A detailed study of the efficacy of the bleaching process for elimination of polycyclic aromatic hydrocarbons in Spanish olive pomace oils has been carried out. For this purpose active carbon with bleaching earth was used as absorbent. The amount of benzo‐(α)‐pyrene was determined by reversed‐phase high‐performance liquid chromatography with a Fluorimetric detector. The use of exhausted filter‐cakes in countercurrent processes with a cake formed of active carbon and bleaching earth is very efficient for reducing the initial content of benzo‐(α)‐pyrene before the addition of fresh adsorbent, thus reducing the amounts of carbon and earth required.     

Reduction of CuO in H2: In Situ Time-Resolved XRD Studies

CuO is used as a catalyst or catalyst precursor in many chemical reactions that involve hydrogen as a reactant or product. A systematic study of the reaction of H₂ with pure powders and films of CuO was carried out using in situ time-resolved X-ray diffraction (XRD) and surface science techniques. Oxide reduction was observed at atmospheric H₂ pressures and elevated temperatures (150-300 °C), but only after an induction period. High temperature or H₂ pressure and a large concentration of defects in the oxide substrate lead to a decrease in the magnitude of the induction time. Under normal process conditions, in situ time-resolved XRD shows that Cu¹⁺ is not a stable intermediate in the reduction of CuO. Instead of a sequential reduction (CuO Cu₄O₃ Cu₂O Cu), a direct CuO Cu transformation occurs. To facilitate the generation of Cu¹⁺ in a catalytic process one can limit the supply of H₂ or mix this molecule with molecules that can act as oxidant agents (O₂, H₂O). The behavior of CuO-based catalysts in the synthesis of methanol and methanol steam reforming is discussed in the light of these results.     

{alpha}-Amylase from Bacillus licheniformis mutants near to the catalytic site: effects on hydrolytic and transglycosylation activity

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Synthesis of Cu–Pd alloy thin films by co-electrodeposition

This paper presents results on the synthesis of Cu–Pd alloy thin films on Ti substrates by co-electrodeposition of Pd and Cu from nitrate-base electrolytic baths. The deposition rates of Cu and Pd were determined by Electrochemical Quartz Crystal Microbalance as a function of the electrode potential and Cu⁺² and Pd⁺² concentrations. It is shown that electrodeposition of copper and palladium occurs simultaneously at −0.50 V vs. SCE and that Cu–Pd thin films over the entire composition range were obtained by changing the composition of the solution. X-ray diffraction analyses indicated that these films have a nanocrystalline single-phase face-centered cubic structure and scanning electron microscopy analyses showed that potentiostatically deposited films are rough and porous, which is appropriate for electrocatalysis applications. In an attempt to get denser deposits as required for H₂ purification applications, pulsed potential co-electrodeposition was performed and the effect of the deposition conditions on the roughness of the films was assessed by double layer capacitance measurements. It was shown that smooth Cu–Pd films (with R_f value as low as 8, as opposed to more than 120 for films prepared in the potentiostatic mode) could be obtained with a proper choice on the deposition conditions.     

Low-temperature growth of well-crystalline Co3O4 hexagonal nanodisks as anode material for lithium-ion batteries

Uniform hexagonal-shaped cobalt oxide (Co₃O₄) nanodisks were prepared in large scale via facile aqueous solution based hydrothermal process at 110 °C. The detailed structural characterizations confirmed that the synthesized products are hexagonal cobalt oxide nanodisks, possessing very well-crystalline cubic spinel structure. A coin cell of type −2032 was assembled using the synthesized Co₃O₄ nanodisks and its charge–discharge profile was analyzed between the voltages 0.01 and to 2.5 V vs. Li/Li⁺ reference electrode. The electrochemical cell composed of Li/Co₃O₄ delivered an initial lithium insertion capacity of 2039 mAh/g. Although the cell exhibited high irreversible capacity during the first four cycles, the columbic efficiency has been improved upon cycling.