A simplified hydrokinetic model for a steady‐state microwave discharge sustained by traveling waves at atmospheric pressure conditions

The properties of a microwave‐induced argon plasma produced by traveling surface wave at atmospheric pressure are investigated theoretically. A hydrokinetic model is elaborated to obtain the nonequilibrium one‐dimensional profiles of electron temperature Te (average electron energy), electron density ne, and the first excited state population density n4s, along the axis of a steady‐state discharge. A three‐level atomic structure is assumed for the argon atom. A particle balance is included through the continuity equations for ne and n4s. These equations are coupled with an energy balance equation for the electrons. The effects of different parameters on the properties of the argon discharge are investigated: discharge tube radius, gas flow rate, resonant radiation‐escape factor, and neutral gas temperature.Ministerio de Educación y Ciencia. Gobierno de España-PB91- 0847 y PB94-145

Mastitis bovina de orígen micótico: descripción de un caso.

El estudio se realizó en una hacienda ubicada en un municipio de Cundinamarca a una altitud de 340 metros y una temperatura promedio de 26 grados centígrados, con 185 animales de la raza Pardo Suizo y mestizo (Pardo Suizo x Cebú) de los cuales 105 estaban en producción de leche y los demás estaban en el horro o en proceso de cría y levante. Se practicó una visita a la finca para evaluar y diagnosticar un brote de mastitis que afectaba a 63 animales del hato en forma clínica aguda. Se realizó un chequeo general con la prueba de mastitis california (MC) en todos los animales del hato dando un resultado positivo en 148 cuartos de 68 vacas. Se procedió a tratar a los animales afectados con productos antibacterianos pero con resultados negativos. Posteriormente se tomaron muestras de secreciones de los cuartos afectados que se cultivaron en agar sangre al 5 por ciento con incubación a 37 grados centígrados por 72 horas, agar sabouraud incubado a 28 grados centígrados por 4 días y agar MacConkey a 37 grados centígrados por 72 horas. Los resultados microbiológicos e histopatológicos definen el diagnóstico de mastitis micótica. Establecido el carácter micótico de la enfermedad, se suspendió todo producto antibacteriano y se inició una terapia para atacar al hongo. Una vez terminado el tratamiento se hizo notoria la recuperación clínica y productiva en 50 animales. Los 13 restantes desarrollaron un estado de fibrosis de la glándula mamaria que obligó a su eliminación Para buscar el origen de la infección se examinó el antibiótico y las sondas plásticas empleadas en el tratamiento. Descartada la fuente de contaminación en el antibiótico y en las sondas la misma se puede atribuír al agua utilizada durante los tratamientos como diluyenteGanado de leche-Ganadería lech

Isotope Labelling for Reaction Mechanism Analysis in DBD Plasma Processes

Dielectric barrier discharge (DBD) plasmas and plasma catalysis are becoming an alternative procedure to activate various gas phase reactions. A low-temperature and normal operating pressure are the main advantages of these processes, but a limited energy efficiency and little selectivity control hinder their practical implementation. In this work, we propose the use of isotope labelling to retrieve information about the intermediate reactions that may intervene during the DBD processes contributing to a decrease in their energy efficiency. The results are shown for the wet reforming reaction of methane, using D2O instead of H2O as reactant, and for the ammonia synthesis, using NH3/D2/N2 mixtures. In the two cases, it was found that a significant amount of outlet gas molecules, either reactants or products, have deuterium in their structure (e.g., HD for hydrogen, CDxHy for methane, or NDxHy for ammonia). From the analysis of the evolution of the labelled molecules as a function of power, useful information has been obtained about the exchange events of H by D atoms (or vice versa) between the plasma intermediate species. An evaluation of the number of these events revealed a significant progression with the plasma power, a tendency that is recognized to be detrimental for the energy efficiency of reactant to product transformation. The labelling technique is proposed as a useful approach for the analysis of plasma reaction mechanisms

Colored semi-transparent Cu-Si oxide thin films prepared by magnetron sputtering

Colored semi-transparent Cu-Si oxide thin films have been prepared by reactive magnetron sputtering from a single cathode of copper-silicon composition. Thin films of different composition and optical response were obtained by changing process parameters like the relative amount of copper in the target and the O2/Ar mixture of the reactive plasma gas. The film characteristics were analyzed by several techniques. Their optical properties (refractive index, absorption coefficient, color) have been correlated with the process parameters used in the film preparation as well as with the film stoichiometry and chemistry.Ministerio de Ciencia e Innovación CEN-20072014, MAT2010-18447, MAT2010-21228, CSD2008–00023Junta de Andalucía P09-TEP5283, CTS-518

Influence of the angular distribution function of incident particles on the microstructure and anomalous scaling behavior of thin films

The microstructure and the scaling properties of films grown by plasma enhanced chemical vapor deposition are reproduced with a discrete model that takes into account the angular distribution function of the particles and the lateral growth of the films. Both the experimental and simulated surfaces exhibit a granular microstructure and an anomalous scaling behavior characterized by values of the growth exponent β that vary with the scale of measurement. Depending on the angular distribution function used in the model, values of β ranging from 0.86 to 0.2 are obtained

Nanostructured Ti thin films by magnetron sputtering at oblique angles

The growth of Ti thin films by the magnetron sputtering technique at oblique angles and at room temperature is analysed from both experimental and theoretical points of view. Unlike other materials deposited in similar conditions, the nanostructure development of the Ti layers exhibits an anomalous behaviour when varying both the angle of incidence of the deposition flux and the deposition pressure. At low pressures, a sharp transition from compact to isolated, vertically aligned, nanocolumns is obtained when the angle of incidence surpasses a critical threshold. Remarkably, this transition also occurs when solely increasing the deposition pressure under certain conditions. By the characterization of the Ti layers, the realization of fundamental experiments and the use of a simple growth model, we demonstrate that surface mobilization processes associated to a highly directed momentum distribution and the relatively high kinetic energy of sputtered atoms are responsible for this behaviourJunta de Andalucía P12-FQM- 2265Ministerio de Ciencia e Innovación CSD2008- 00023, MAT2013-42900-P, MAT2013-40852-R, MAT2014-59772-C2-1, MAT2011- 2908

Scaling behavior and mechanism of formation of Si O2 thin films grown by plasma-enhanced chemical vapor deposition

This paper reports a study of the kinetic roughening of Si O2 thin films prepared by plasma-enhanced chemical vapor deposition (PECVD). Tetramethylsilane has been used as a precursor, and the synthesis has been carried out under remote and in-plasma configurations. The analysis of surface topography of the films by atomic force microscopy shows an anomalous scaling behavior that cannot be represented by the Family-Vicsec scaling relation of dynamic scaling theory. The application of different methods for obtaining the roughness exponent α yields different values of this exponent (α=0.7 for the height-height correlation function and α=1.3 for the power spectral density function for long deposition times) in all experimental conditions. Moreover, a strong variation of the α exponent with deposition time has been determined for the samples grown in remote mode. This correlates with the presence of a crossover region of the growth exponent β, which varies from a first value of 1.3 for low deposition times to another of 0.3 for longer deposition times. Such a variation is not found for the samples grown in the plasma, characterized by a β value of 0.28. The results obtained can be explained by the combined effect in the growth process of a low diffusivity of the physisorbed species along with the existence of nonlocal interactions due to shadowing effects. These two assumptions are in agreement with the empirical knowledge existing about the kinetics of the growth of Si O2 thin films by PECVD and establish a link between the scaling properties of the films with the surface chemistry during the film growth.Ministerio de Educación y Ciencia MAT2004-01558 y MAT2007-6576

Relationship between scaling behavior and porosity of plasma-deposited TiO2 thin films

The growth of TiO2 thin films prepared by plasma enhanced chemical vapor deposition has been studied by analyzing their roughness with the concepts of the dynamic scaling theory. Differences in the growth and roughness exponents have been found depending on the composition of the plasma by using either O2 or mixtures Ar+ O2 as plasma gas and titanium isopropoxide as the precursor. The slope of the representations of the film roughness against the deposition time yielded values of the exponent β of 0.45 and 0.32 for, respectively, thin films prepared with plasmas of O2 or mixtures Ar+ O2. Meanwhile, values of the exponent α of 1.15 and 1.89/0.35 were deduced from the power spectral density representations for the films prepared under these two experimental conditions. These values are congruent with growth processes dominated, respectively, by shadowing or diffusion processes. A columnar microstructure was observed by scanning electron microscopy for the thin films prepared with pure oxygen. Meanwhile, homogeneous films were obtained with mixtures of Ar+ O2. The open porosity of the films was determined by measuring water adsorption-desorption isotherms with a quartz crystal monitor. This analysis showed that in the samples prepared with mixtures of Ar+ O2 the porosity consisted exclusively of micropores (d2 nm). It is concluded that the different growth mechanisms found by just changing the chemistry of the plasma are responsible for the quite distinct microstructures, porosities, and optical properties obtained for the films.Ministerio de Educación y Ciencia NAN2004-09317-C04-01 y MAT2007-6576

Superhydrophobic supported Ag-NPs@ZnO-nanorods with photoactivity in the visible range

In this article we present a new type of 1D nanostructures consisting of supported hollow ZnO nanorods (NRs) decorated with Ag nanoparticles (NPs). The 3D reconstruction by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) electron tomography reveals that the Ag NPs are distributed along the hollow interior of the ZnO NRs. Supported and vertically aligned Ag-NPs@ZnO-NRs grow at low temperature (135 °C) by plasma enhanced chemical vapour deposition on heterostructured substrates fabricated by sputtered deposition of silver on flat surfaces of Si wafers, quartz slides or ITO. The growth mechanisms of these structures and their wetting behavior before and after visible light irradiation are critically discussed. The as prepared surfaces are superhydrophobic with water contact angles higher than 150°. These surfaces turn into superhydrophilic with water contact angles lower than 10° after prolonged irradiation under both visible and UV light. The evolution rate of the wetting angle and its dependence on the light characteristics are related to the nanostructure and the presence of silver embedded within the ZnO NRs. ÂEuropean Union NMP3-CT-2006- 032583Ministerio de Ciencia e Innovación MAT2010-21228, MAT2010-18447, CSD2008-00023Junta de Andalucía P09-TEP-5283, CTS-518

Kinetic Energy-induced Growth Regimes of Nanocolumnar Ti Thin Films Deposited by Evaporation and Magnetron Sputtering

We experimentally analyze different growth regimes of Ti thin films associated to the existence of kinetic energy-induced relaxation mechanisms in the material's network when operating at oblique geometries. For this purpose, we have deposited different films by evaporation and magnetron sputtering under similar geometrical arrangements and at low temperatures. With the help of a well-established growth model we have found three different growth regimes: (i) low energy deposition, exemplified by the evaporation technique, carried out by species with typical energies in the thermal range, where the morphology and density of the film can be explained by solely considering surface shadowing processes, (ii) magnetron sputtering under weak plasma conditions, where the film growth is mediated by surface shadowing mechanisms and kinetic-energy-induced relaxation processes, and (iii) magnetron sputtering under intense plasma conditions, where the film growth is highly influenced by the plasma, and whose morphology is defined by nanocolumns with similar tilt than evaporated films, but with much higher density. The existence of these three regimes explains the variety of morphologies of nanocolumnar Ti thin films grown at oblique angles under similar conditions in the literature.EU-FEDER and MINECO-AEI 201560E055EU-FEDER and MINECO-AEI MAT2014-59772-C2-1-PEU-FEDER and MINECO-AEI MAT2016-79866-REU-FEDER and MINECO-AEI MAT2015-69035-REDCUniversity of Seville V and VI PPIT-U