Surface Quality and Free Energy Evaluation of s275 Steel by Shot Blasting, Abrasive Water Jet Texturing and Laser Surface Texturing

Surface modification by different technologies prior to joining operations or improving tribological properties is a point of great interest. Improving surface activation by increasing the roughness of the metal is a relationship that is becoming more defined. In turn, an increase in surface wettability by evaluating contact angles indicates surface activation by obtaining a high surface free energy. Technologies such as shot blasting and laser surface texturing (LST) have generated several scientific studies where they have identified the influence of parameters on the formation of rough surfaces with defined patterns. However, the application of abrasive water jet texturing (AWJT) has been little studied as an alternative. This article compares these technologies in the texturing of a carbon steel s275 in order to identify the relationship between surface quality and surface activation. It has been determined that AWJT produces the highest Rt values close to 64 mu m with a cross feed of 0.45 mm and a traverse speed of 5000 mm/min. Furthermore, LST obtains the best values of free surface energy by combining a power of 20 W with a frequency of 20 kHz and a sweeping speed of 10 mm/s. Finally, contour diagrams have been obtained which relate these variables to the texturing parameter

On the Machinability of an Al-63%SiC Metal Matrix Composite

This paper presents a preliminary study of aluminium matrix composite materials during machining, with a special focus on their behavior under conventional processes. This work will expand the knowledge of these materials, which is considered to be strategic for some industrial sectors, such as the aeronautics, electronics, and automotive sectors. Finding a machining model will allow us to define the necessary parameters when applying the materials to industry. As a previous step of the material and its machining, an experimental state-of-the-art review has been carried out, revealing a lack of studies about the composition and material properties, processes, tools, and recommended parameters. The results obtained and reflected in this paper are as follows; SiC is present in metallic matrix composite (MMC) materials in a very wide variety of sizes. A metallographic study of the material confirms the high percentage of reinforcement and very high microhardness values registered. During the machining process, tools present a very high level of wear in a very short amount of time, where chips are generated and arcs are segmented, revealing the high microhardness of the material, which is given by its high concentration of SiC. The chip shape is the same among other materials with a similar microhardness, such as Ti or its alloys. The forces registered in the machining process are quite di erent from conventional alloys and are more similar to the values of harder alloys, which is also the case for chip generation. The results coincide, in part, with previous studies and also give new insight into the behavior of this material, which does not conform to the assumptions for standard metallic materials, where the hypothesis of Sha er is not directly applicable. On the other hand, here, cutting forces do not behave in accordance with the traditional model. This paper will contribute to improve the knowledge of the Al-63%SiC MMC itself and the machining behavior

Evaluation of the creation of a web page with six open educational resources as a tool to enhance the learning of the English Language on Higher Education

Los Recursos Educativos abiertos, actualmente, ocupan un papel muy importante en el proceso de la Enseñanza del idioma inglés. Son herramientas gratuitas que se le ofrecen a los docentes para una mejor calidad en sus clases y para que los estudiantes tengan un mayor aprovechamiento y aprendan de una manera más sencilla y mediática. Este mundo digital en el que se vive actualmente, con estudiantes conocidos como nativos digitales, exige a los docentes (inmigrantes digitales) un esfuerzo cada vez mayor e implica una capacitación constante para los requerimientos actuales. El presente artículo tiene como objetivo presentar un proyecto de investigación acerca de la creación y evaluación de una página Web que cuenta con seis recursos educativos abiertos, todos ellos enfocados en ser una herramienta importante para la enseñanza del idioma inglés. En dicho proyecto de investigación, para realizar la evaluación del proyecto fue utilizado el método cualitativo y el método de casos, y se realizó mediante el uso de distintos instrumentos, principalmente encuestas, aplicadas a docentes del idioma inglés de 4 universidades de los países de México y Colombia y expertos relacionados al campo de la educación a nivel superior y de la informática que laboran en dichas universidades. Como conclusión del proyecto, de acuerdo a los instrumentos utilizados, estos arrojaron resultados positivos en la evaluación de la página web, en la mayoría de las ocasiones los recursos con los que contaba la página favorecieron en la enseñanza del idioma en los docentes, y como consecuencia, en el aprendizaje de los estudiantesOpen Educational Resources nowadays have an important role in the process of Teaching as a second language. They are free tools offered for teachers to increase the classes´ quality and for students to have academic progress in order they learn in an easy and fun way. The digital world in which we live now, with students known as digital natives, demands to the teachers (digital immigrants) an important effort and involves a constant training for the current requirements. The objective of this article is to present a research project about the creation and evaluation of a Web Page that has six open educational resources; all of them focused on being an important instrument for the English language teaching. To evaluate the research project it was used the qualitative method and the case study method, through the use of different instruments, mainly surveys, for teachers of the English language from four different universities of Mexico and Colombia and experts related to the field of higher education and in computer science that work in those universities. As a conclusion, through the instruments used to evaluate the web page, there were found positive results and in most of the cases the resources that the web page had contributed in the English language teaching process, and consequently, in the learning of the students

Er-W codoping of TiO2-anatase: structural and electronic characterization and disinfection capability upon UV, visible, and near-IR excitation

The codoping of the anatase structure with tungsten and erbium was carried out using a microemulsion preparation procedure. Tungsten and erbium single doped and pure anatase nanomaterials were also prepared. The corresponding solids were characterized using X-ray diffraction, surface area, transmission electron microscopy, X-ray photoelectron and absorption (X-ray near-edge and extended X-ray absorption) spectroscopies as well as UV–vis and photoluminescence spectroscopies. Results provided a complete structural and electronic characterization of the solids, showing the unique features generated by the copresence of tungsten and erbium at substitutional positions of the anatase structure. The disinfection capability of these single and codoped TiO2-based materials was tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and under ultraviolet, visible and near infrared light excitations. The ErW-anatase solid presents significant photoactivity in the elimination of both microorganisms in the whole UV–vis-nearIR range of excitation wavelengths. The biocidal results were interpreted with the help of a kinetic modelling of the experiments and correlated with results from the physico-chemical characterization of the samples and from an electron paramagnetic resonance and optical study of the radicals species produced under illumination. This procedure indicates a different physical origin of the photoactivity for light excitation above and below ca. 500 nm

Highly active catalytic Ru/TiO2 nanomaterials for continuous production of γ-valerolactone

Green energy production from renewable sources is an attractive but challenging topic to face the likely energy crisis scenario in the future. In the current work, a series of versatile Ru/TiO2 catalysts were simply synthesized and employed in continuous flow catalytic transfer hydrogenation of industrially derived methyl levulinate biowaste (from Avantium Chemicals B.V.) to γ-valerolactone. Different analytical techniques were applied in the characterization of the as-synthesized catalysts, including XRD, SEM, EDX, TEM and XPS etc. The effects of various reaction conditions (e.g. temperature, concentration and flow rate) were investigated. Results suggested that optimum dispersion and distribution of Ru on the TiO2 surface could efficiently promote production of γ-valerolactone, with 5% Ru/TiO2 catalyst providing excelling catalytic performance and stability as compared to commercial Ru catalysts