Browsing by Keyword "Friction"
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Item Morphological and Tribological Properties of PMMA/Halloysite Nanocomposites(2018-07-25) Vuluga, Zina; Corobea, Mihai; Elizetxea, Cristina; Ordonez, Mario; Ghiurea, Marius; Raditoiu, Valentin; Nicolae, Cristian; Florea, Dorel; Iorga, Michaela; Somoghi, Raluca; Trica, Bogdan; POLIMEROSFrom an environmental and cost-effective perspective, a number of research challenges can be found for electronics, household, but especially in the automotive polymer parts industry. Reducing synthesis steps, parts coating and painting, or other solvent-assisted processes, have been identified as major constrains for the existing technologies. Therefore, simple polymer processing routes (mixing, extrusion, injection moulding) were used for obtaining PMMA/HNT nanocomposites. By these techniques, an automotive-grade polymethylmethacrylate (PMMA) was modified with halloysite nanotubes (HNT) and an eco-friendly additive N,N′-ethylenebis(stearamide) (EBS) to improve nanomechanical properties involved in scratch resistance, mechanical properties (balance between tensile strength and impact resistance) without diminishing other properties. The relationship between morphological/structural (XRD, TEM, FTIR) and tribological (friction) properties of PMMA nanocomposites were investigated. A synergistic effect was found between HNT and EBS in the PMMA matrix. The synergy was attained by the phase distribution resulted from the selective interaction between partners and favourable processing conditions. Modification of HNT with EBS improved the dispersion of nanoparticles in the polymer matrix by increasing their interfacial compatibility through hydrogen bonding established by amide groups with aluminol groups. The increased interfacial adhesion further improved the nanocomposite scratch resistance. The PMMA/HNT-EBS nanocomposite had a lower coefficient of friction and lower scratch penetration depth than PMMA/HNT nanocomposite.Item Solid lubricant behavior of MoS2 and WSe2-based nanocomposite coatings(2017-01-01) Domínguez-Meister, Santiago; Rojas, Teresa Cristina; Brizuela, Marta; Sánchez-López, Juan Carlos; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIESTribological coatings made of MoS2 and WSe2 phases and their corresponding combinations with tungsten carbide (WC) were prepared by non-reactive magnetron sputtering of individual targets of similar composition. A comparative tribological analysis of these multiphase coatings was done in both ambient air (30–40% relative humidity, RH) and dry nitrogen (RH<7%) environments using the same tribometer and testing conditions. A nanostructural study using advanced transmission electron microscopy of the initial coatings and examination of the counterfaces after the friction test using different analytical tools helped to elucidate what governs the tribological behavior for each type of environment. This allowed conclusions to be made about the influence of the coating microstructure and composition on the tribological response. The best performance obtained with a WSex film (specific wear rate of 2 × 10−8 mm3 N–1m–1 and a friction coefficient of 0.03–0.05) was compared with that of the well-established MoS2 lubricant material.Item TiN-Ag as an antimicrobial and wear resistant coating(2021-12) Braceras, Iñigo; Brizuela, Marta; Álvarez, Noelia; Martínez Van Geeteruyen, Miguel; Azkona, Ibon; INGENIERÍA DE SUPERFICIES; BiomaterialesNosocomial infections are a major clinical concern, posing great risks for patients and rising costs for health services providers. This work aims at developing a hard, wear resistant coating, whose antimicrobial properties shall prevent the transmission of infections. TiN coatings deposited by Physical Vapour Deposition, PVD, with different Ag contents have been studied, especially in relation to the hardness and adhesion, their microstructure and morphology. The antimicrobial activity of the surfaces has been assessed against Staphylococcus epidermidis at different time frames, one of the most troublesome source of infections in trauma and orthopaedic surgeries. The electro-tribology properties of different silver contest have been studied. Finally, the coatings have been deposited on surgical acetabular reamers and wear resistance tests have been carried out against synthetic composite bone (simulating cortical and cancellous bone). Results have shown a good coating adhesion on stainless steel (both quantitatively in the scratch tests and qualitatively in the tests against synthetic composite bone), while the hardness decreased with higher Ag percentages. Furthermore, coatings exhibited antimicrobial activity against S.epidermidis, limited silver release, a remarkable wear resistance (vs. uncoated surgical acetabular reamers), while the electrical contact resistance provided valuable information about the evolution of friction and the status of the coating. Therefore TiN-Ag coatings present promising features for reducing the risk of infections, monitoring and extending cutting edge life and quality, and thus limiting damage to living tissues, e.g. necrosis.Item Tribología de nuevas capas autolubricantes producidas mediante PVD(2005) Oñate, J. I.; Brizuela, M.; Garcĩa-Luis, A.; Braceras, I.; Pacheco, S.; Viviente, J. L.; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIES; TECNOLOGÍAS DE HIDRÓGENO; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSLas capas de MoS2 depositadas mediante PVD tienen baja fricción en vacío pero se degradan con facilidad al aire, especialmente en presencia de humedad. Este trabajo describe el desarrollo de nuevas capas de MoS^ modificadas con WC. En ensayos de "bola sobre disco" a 0,75 GPa, las capas presentaron una fricción muy baja y estable (< 0,04) en vacío. Se obtuvo una durabilidad superior a 1 millón de ciclos, mostrando un desgaste de 1,3 X 10e-16 me3 /Nm, mejorado respecto a otras capas de MoS2. El coeficiente de fricción aumentó a 0,15 y la durabilidad disminuyó hasta 1 a 3 x 10e5 ciclos en aire hasta 70 % HR.El análisis superficial mostró ratios de S/Mo superiores a 1,2, con menos del 2 % de oxígeno, demostrando carácter lubricante.