In this work was studied the influence of surface preparation on tribological properties of CrxOy coatings, deposited via flame thermal spray on brass substrates. The substrate surfaces were prepared by sand blasting, shot blasting with alumina particles of metal and abrasive disc. The chemical composition analysis was performed using X-ray fluorescence (XRF) and structural analysis was performed by X-ray diffraction (XRD). The abrasive wear resistance was evaluated by a three-body system on the ASTM standard G65 and the friction coefficient was determined by the ball-on- disk test. The morphology of the wear track was characterized by scanning electron microscopy (SEM) and confocal laser microscopy. Overall, the results show that the coatings deposited on the sandblasted surface improved the abrasion resistance of the substrate and that the wear mechanisms are produced by plastic deformation and grinding.

En este trabajo se estudió la influencia del método de preparación superficial sobre propiedades tribológicas de recubrimientos de Cr xOy fabricados con el sistema de proyección térmica con llama sobre sustratos de latón. Las superficies de los sustratos fueron preparadas por granallado con arena, granallado metálico con partículas de alúmina y por disco abrasivo. Los análisis de composición química se realizaron mediante fluorescencia de rayos X (FRX) y el análisis estructural se realizó mediante difracción de rayos X (DRX). La resistencia al desgaste abrasivo se evaluó con un sistema de tres cuerpos bajo la norma ASTM G65 y el coeficiente de fricción se determinó por medio de la prueba de bola sobre disco. La morfología de las huellas de desgaste fue caracterizada mediante microscopía electrónica de barrido (MEB) y microscopía laser confocal. En general, los resultados muestran que los recubrimientos depositados sobre la superficie granallada mejoraron la resistencia a la abrasión del sustrato y que los mecanismos de desgaste se producen por deformaciones plástica y abrasiva.

We studied the crystallinity, morphology, and surface composition of Nd-doped molybdenum oxide films grown on glass slides through spray pyrolysis. After fabrication, the films were subjected to thermal treatment in oxygen for periods ranging from 2 to 20 hours. The films were structurally characterized through X-ray diffraction (XRD), their bulk chemical composition was determined using Energy-Dispersive X-ray analysis (EDX), and their surface composition was determined using X-ray Photoelectron Spectroscopy (XPS). The XRD results show that the films obtained from different dissolution volumes and at substrate temperature of 300° C exhibit the characteristics of the oxygen-deficient molybdenum trioxide Mo9 O26 phase. The films subjected to different thermal treatments exhibit a mixture of Mo9O26 and Mo17O47 phases. EDX study shows the energy belonging to the L line of Nd. Finally, films doped with Nd and subjected to a thermal treatment of 20h were analyzed through XPS, showing the binding energies at the crystalline lattice correspond to Nd2 (MoO4)3 and Nd2Mo2O7.

En este trabajo se presentan los resultados obtenidos en el crecimiento de recubrimientos de bismuto sobre sustratos de vidrio común, silicio y acero inoxidable 316L, usando un sistema de pulverización catódica dc pulsado con magnetrón desbalanceado y la evaluación de la microestructura, la morfología, la composición química superficial y algunas propiedades electroquímicas se hicieron en función de la frecuencia de los pulsos que genera la fuente de descarga. La microestructura de los recubrimientos fue evaluada por difracción de rayos X (XRD); la morfología se evaluó mediante microscopía de fuerza atómica (AFM); la composición química se determinó mediante espectroscopia de fotoelectrones emitidos por rayos X (XPS), las pruebas electroquímicas mediante ensayos de ventanas de corrosión y la adherencia entre el sustrato y el recubrimiento se evaluó mediante pruebas de rayado. El análisis DRX indica que los recubrimientos son policristalinos, los análisis de AFM determinaron que los valores de rugosidad son del orden de 25 nm. El análisis de XPS mostró que hay energías de ligadura asociadas a Bi metálico y oxido de Bi, las pruebas electroquímicas establecieron que los recubrimientos de Bi presentan un rango de potencial entre -0,315 y 1,49 mV. Finalmente, el estudio de adherencia mostró que el recubrimiento se desprende del sustrato cuando es sometido a una carga de 4.5 N.

In this work present the results obtained in the growth of Bi coatings onto common glass, silicon and stainless steel 316 L substrates through dc unbalanced magnetron sputtering and evaluation of the microstructure, morphology, chemical superficial composition and electrochemical properties was made as a function of the frequency pulse of the power supply are presented. The microstructure of the coatings was evaluated through x-ray diffraction (XRD); the morphology was evaluated through atomic force microscopy (AFM); the superficial chemical composition was analyzed by x-ray photoelectrons spectroscopy (XPS), electrochemical test was evaluated by means of corrosion windows and the adherence between coating and substrate was evaluated by streaked test. The XRD analysis shows that the coatings are polycrystalline, the AFM analysis determined that the mean rugosity of Bi coatings was of the 25 nm. The XPS analysis shows that there are binding energies associated to metallic bismuth and oxide bismuth. The electrochemical test established that the Bi coatings show a range of potential between -0,315 y 1,49 mV. Finally, the adherence test show that the coatings failure occurs when is subjected to a load of 4.5 N.

Porous Silicon thin films were produced in this work by the electrochemical anodizing method. The samples were fabricated anodizing p type Si substrates with different resistivities in hydrofluoric acid. Samples were prepared at different current densities. The films were characterized through reflectance and room photoluminescence (PL) measurements in the visible region. A simple theoretical model is proposed to calculate the Optical constants of the material using a theoretical simulation of the reflectance spectra. The maximum positions of PL signals are shifted to long wavelengths as the porosity increase in samples prepared with substrates of resistivities of 0.1 and 1 omega-cm, while an opposite behaviour is observed in samples prepared on more doped substrates. The optical constants obtained through the calculation are the spectral variation of the refractive index and extinction coefficient, also are obtained the sample thickness and surface roughness.

In this work, the influence of the substrate bias on the crystalline structure and surface composition of Ti6Al4V thin films prepared by rf magnetron sputtering were studied. Samples were grown onto two different types of substrates: AISI 420 steel and common glass using a Ti6Al4V (99.9 %) target. Substrate bias was varied from -100V to -200 V. Samples were characterized by X-ray diffraction (XRD), Energy Dispersive X-ray Analysis (EDX), Scanning Electron Microscopy (SEM), and X-Ray Photoelectron Spectroscopy (XPS). It was observed that the increase of the substrate voltage improved the crystallinity of the deposited films. The stoichiometry of the deposited thin films was studied by EDX and found to be slightly different from that of the target material. Finally, the passive film spontaneously formed on the deposited films upon exposure to the laboratory atmosphere was studied by XPS. The composition of the passive film is rather complex since it contains several forms of oxidized titanium and vanadium as well as Al2O3.