Tribología de nuevas capas autolubricantes producidas mediante PVD

Las 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.MoS2 coatings, deposited by PVD show a low friction under vacuum conditions, but degrade easily under atmospheric conditions. This work describes the development of a new type of MoSx, coating, modified with WC. These coatings presented a very low and stable friction coefficient lower than 0.04 when tested under vacuum at 0.75 GPa in a ball on disc tribometer. Durability was higher than 1 million wear cycles, showing a wear rate of 1.3 10e-16 m3 /Nm. When tested under atmospheric conditions and up to 70 % RH, friction increased to 0.15 and durability reached a lower value of up to 3 x 10e5 cycles. Surface analyses in these coatings showed S/Mo ratios higher than 1.2 and with oxygen levels lower than 2 %, demonstrating the lubricant character of the coating.Ministerio de Ciencia y Tecnología (proyecto MAT2001-1399-C02-02) Departamento de Educación, Universidades e Investigación del Gobierno Vasco (proyecto PI-2001-12)

Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.This study was carried out under a MNT ERA-Net Project named NANOMED. The authors gratefully thank the Midi-Pyrénées region (MNT ERA Net Midi-Pyrénées Région, NANOMED2 project) and the Institute National Polytechnique de Toulouse (BQR INPT 2011, BIOREVE project) for supporting this research work, especially the financial support for research carried out in the CIRIMAT and the LGP laboratories (France), and the Basque government and Tratamientos Superficiales Iontech, S.A. for their financial and technical support under the IG-2007/0000381 grant for the development of the LEPS device and deposition of the coatings carried out in Inasmet-Tecnalia. The French industrial collaborators (TEKNIMED SA and 2PS SA) were financed by the OSEO programs

Método automático de clasificación de color en dientes humanos usando aprendizaje de máquina

Trabajo de InvestigaciónActualmente el proceso de identificación del color de los dientes para la fabricación de prótesis dentales es realizado manualmente por un experto que, utilizando un método de identificación visual, determina el color de las piezas dentales en la boca del paciente, usando guías de color como la VITA®. A pesar de que el método visual es el más utilizado para la identificación del color de dientes, este se ve afectado por distintas variables tales como: el cansancio del experto, la luminosidad en el ambiente, salud visual del especialista, entre otras que influyen en la identificación del color en los dientes. Los errores en la clasificación del color de los dientes pueden generar pérdidas de tiempo lo que implicaría en consecuencia sobrecostos que afectarían directamente al fabricante y la satisfacción final del cliente.1. Planteamiento del problema 2. Pregunta de investigación 3. Objetivos 4. Estado del arte 5. Marco de referencia 6. Alcances y limitaciones 7. Metodología 8. Diseño metodológico 9. Discusión y resultados 10. Conclusiones 11. Trabajos futuros 12. Bibliografía 13. ANEXOSPregradoIngeniero de Sistema

Risk analysis and implants

According to the Medical Devices Directive, both the preparation for clinical trials and marketing of implants require that a risk analysis is performed. This paper presents a risk analysis for a dental implant in the framework of the risk management process carried out for the preparation of a multi-centre clinical trial, where likely hazards, failure modes and their severities, probabilities and detectabilities are assessed, together with a review of the related scientific literature. The clinical study aimed to evaluate a new ion implantation-based implant surface designed for the promotion of more extensive and faster osseointegration.Peer reviewe

X-ray photoelectron spectroscopy characterization of high dose carbon-implanted steel and titanium alloys

A study has been made of the depth dependence of the atomic fraction and chemical bonding states of AISI 440C martensitic stainless steel and Ti-6Al-4V alloy implanted with 75 keV C + at very high doses (above 10 18 ions cm -2 ), by means of X-ray photoelectron spectroscopy combined with an Ar + sputtering. A Gaussian-like carbon distribution was observed on both materials at the lowest implanted dose. More trapezoidal carbon depth-profiles were found with increasing implanted doses, and a pure carbon layer was observed only on the titanium alloy implanted at the highest dose. The implanted carbon was combined with both base metal and carbon itself to form metallic carbides and graphitic carbon. Furthermore, carbon-enriched carbides were also found by curve fitting the C 1s spectra. The titanium alloy showed a higher carbidic contribution than the steel implanted at the same C + doses. A critical carbon concentrations of about 33 at.% and 23 at.% were measured for the formation of C-C bonds in Ti-6Al-4V and steel samples, respectively. The carbon atoms were bound with metal to form carbidic compounds until these critical concentrations were reached; when this C concentration was exceeded the proportion of C-C bonds increased and resulted in the growth of carbonaceous layers.This work has been carried out under the project MAT 95-0980-C02-02 financed by the Spanish `Comision Interministerial de Ciencia y Tecnologı́a' (CICYT).Peer reviewe

In vivo low-density bone apposition on different implant surface materials

During osseointegration, new bone may be laid down on the implant surface and/or on the old bone surface; the former is known as contact osteogenesis and the latter as distance osteogenesis. Implant surface topography and material composition affect this process. The present study evaluates Ca and P apposition onto three different dental implant material surfaces (carbon monoxide (CO) ion implantation on Ti6Al4V, sand blasting and acid etching on commercially pure titanium and untreated Ti6Al4V) on the mandibles of beagles after healing periods of 3 and 6 months. Energy dispersive spectroscopy is useful for identifying low-density bone relative to surrounding mature bone, allowing for discrimination of the osteogenesis source. Low-density bone was only found at the apical end; there was none on the surface of untreated implants. Low-density bone arising from mature bone towards the implant at month 3 (i.e. distance osteogenesis) was only present on the CO ion implanted samples, due to the modification of the surface nano-topography and the chemistry and structure of the material.The authors would like to express their gratitude for the financial assistance provided by the Spanish Ministry of Science and Technology –CDTI- under Project n.20020327.Peer reviewe

Vacuum tribology testing of alloyed MoS2 films at VTM model of TriboLAB

TriboLAB is an experiment on space tribology that will be carried out at the EuTEF module of ESA Columbus Laboratory at the ISS. A Vacuum TriboLAB Model (VTM) has been designed and developed prior to the Flight Model (FM) to serve as a testing equipment and evaluate "on ground" tribological data of selected lubricants, comparing the results with those to be obtained at the environment of the ISS. The VTM of TriboLAB can perform ball bearing and pin-on-disc tests of lubricants. The characteristics and performance of this experimental equipment will be presented in this conference. This work reports on the performance of these solid lubricant films in the pin-on-disc section of VTM model. Tribological tests have been carried out under vacuum with the VTM using previously developed and tested solid lubricants. Thin films of MoS 2 alloyed with WC and produced by magnetron sputtering PVD have been used for these tests. The wear conditions at the VTM, due to the variation of normal load (5 N +/- 1 N) produced as a consequence of the load application by a pivot flexure, are more severe than conditions previously applied on commercial tribo-testers and as a consequence the durability of these films has been lower. The friction force measuring system at the VTM is highly sensitive and friction traces have reproduced this situation, however, the results still demonstrate the lubricating performance of the thin film with mean values of about 0.02.Peer reviewe