The objective of this work is the mechanical characterization of disks made from Cuban synthetic hydroxyapatite (HA) and Strem Chemicals - USA powders. With different particle sizes and semi-spherical shape with porous surfaces. Without pore-forming additives, by uniaxial compaction and sintering in electric furnace at different sintering regimes. Obtaining ranges of apparent porosities between 3 and 40%, with pore sizes between 18 and 100 nm and their dimensions smaller than 20 mm in diameter and 2 mm thick. The hardness, fracture toughness and diametrical compression of the discs were evaluated. To determine the hardness, the Vickers microhardness test and fracture toughness were used for the radial cracking and palmqvist analysis method produced by Vickers prints. Samples with larger particle size powders presented behavior in the values of hardness and toughness to nonlinear fracture with porosity. In general, the samples with lower mean powder size presented higher results.

El objetivo de este trabajo es la caracterización mecánica de discos fabricados a partir de polvos de hidroxiapatita (HA) sintética cubana y de la StremChemicals - USA, con tamaños de partículas diferentes y de forma semiesféricas con superficies porosas, sin aditivos formadores de poros, por compactación uniaxial y sinterización en horno eléctrico a diferentes regímenes de sinterización, Se obtuvieron porosidades aparente entre 3 y 40 % con tamaños de poros entre 18 y 100nm, dimensiones menores a 20 mm de diámetro y 2 mm de espesor. Se evaluó la dureza mediante el ensayo de microdureza Vickers y la tenacidad a la fractura a travésdel ensayo de compresión diametral. Muestras con polvos de mayor tamaño de partículas presentaron comportamiento no lineal con la porosidad en los valores de dureza y de tenacidad a la fractura. Las muestras con menor tamaño medio de polvos presentaron resultados superiores.

The chromium carbide coatings are widely used in the mechanical industry due to its corrosion resistance and mechanical properties. In this work, we evaluated a new source of chromium and silicon with micro-additions of boron on the deposition of multi-component coatings of chromium carbides in W108 steel. The coatings were obtained by the pack cementation method, using a simultaneous deposition at 1000 oC for 4h. The coatings were analyzed by X-ray diffraction, X-ray energy dispersive spectroscopy, optical microscopy, microhardness test method and pin-on-disc wear test. It was found that the coatings formed on W108 steel were mainly constituted by (Cr,Fe)23C6, (Cr,Fe)7C3, Cr5-xSi3-xCx+z, Cr3B0,44C1,4 and (or) Cr7BC4. The carbide layers showed thicknesses between 14 and 15 µm and maximum values of microhardness between 15.8 and 18.8 GPa. Also, the micro-additions of boron to the mixtures showed statistically significant influence on the thickness, microhardness and abrasive wear resistance of the carbide coatings.

Objective: the main purpose of the study is to evaluate in vitro bioactivity in sodium alginate layers of hydroxyapatite disks. Methods: the hydroxyapatite disks were manufactured by successive pressing and sintering in an electric furnace. The sodium alginate layers were obtained by overpressure and a 5% sodium alginate aqueous solution. For the bioactivity assay, the study samples were soaked in simulated biological fluid. Characterization of the samples was conducted by scanning electron microscopy and energy dispersive X rays. Results: the bioactivity assay of hydroxyapatite samples with and without sodium alginate layers revealed the formation of precipitates rich in calcium and phosphorus. It was also found that an increase in the time of immersion in the simulated biological fluid brought about an increase in the size of agglomerates of apatite particles. Conclusions: experimental results show that hydroxyapatite is indeed bioactive, and that the sodium alginate layers of hydroxyapatite disks which were studied behave bioactively.

Objetivo: el propósito central de este trabajo es evaluar la bioactividad in vitro de capas de alginato de sodio en discos de hidroxiapatita. Métodos: los discos de hidroxiapatita fueron elaborados mediante procesos sucesivos de prensado y de sinterizado en un horno eléctrico. Las capas de alginato de sodio se obtuvieron empleando el método de sobrepresión y una disolución acuosa de alginato de sodio al 5 %. En el ensayo de bioactividad las muestras a estudiar fueron sumergidas en fluido biológico simulado. La caracterización de las muestras se realizó empleando microscopia electrónica de barrido y energía dispersiva de rayos X. Resultados: en las muestras de hidroxiapatita sometidas al ensayo de bioactividad, con y sin capas de alginato de sodio, se observó la formación de precipitados ricos en calcio y fósforo. Además, se determinó que con el aumento del tiempo de inmersión en el fluido biológico simulado se incrementan las dimensiones de los aglomerados formados por partículas apatíticas. Conclusiones: los resultados experimentales corroboran que la hidroxiapatita es bioactiva y demuestran que las capas estudiadas de alginato de sodio en discos de hidroxiapatita poseen un comportamiento bioactivo.