Advanced titanium scaffolds obtained by directional freeze-drying: on the influence of processing conditions

Ministry of Science and Innovation of Spain under Grant No. MAT2010-20855Junta de Andalucía (Spain) / FEDER (EU), through the project Ref. P12-TEP-140

Porous Titanium Cylinders Obtained by the Freeze-Casting Technique: Influence of Process Parameters on Porosity and Mechanical Behavior

 The discrepancy between the stiffness of commercially pure titanium and cortical bone  tissue compromises its success as a biomaterial. The use of porous titanium has been widely studied,  however, it is still challenging to obtain materials able to replicate the porous structure of the bones  (content, size, morphology and distribution). In this work, the freeze‐casting technique is used to  manufacture cylinders with elongated porosity, using a home‐made and economical device. The  relationship between the processing parameters (diameter and material of the mold, temperature  gradient), microstructural features and mechanical properties is established and discussed, in terms  of ensuring biomechanical and biofunctional balance. The cylinders have a gradient porosity  suitable for use in dentistry, presenting higher Young’s modulus at the bottom, near the cold spot  and, therefore better mechanical resistance (it would be in contact with a prosthetic crown), while  the opposite side, the hot spot, has bigger, elongated pores and walls.  Ministry of Economy and Competitiveness of Spain  grant  MAT2015‐71284‐P  FEDER‐Junta de Andalucía Research  Project (Modeling and implementation of the freeze casting technique: gradients of porosity with a tribomechanical equilibrium and electro‐stimulated cellular behavior).

A simple and economical device to process Ti cylinders with elongated porosity by freeze-casting techniques: design and manufacturing [Póster]

Design, manufacture and validation of a simple and economic device that allows producing Ti cylinders with directed porosity applying the freeze-casting technique, and the study of the influence on the internal structure of the Ti porous samples when different materials are used for the vessel (alumina or Teflon).Junta de Andalucía (Spain) Grant No. P12-TEP-1401Ministry of Economy and Innovation of Spain project MAT2015-71284-

Titanium with elongated porosity: design, manufacture and optimization of frezze-casting device [Póster]

Junta de Andalucía (Spain) Grant No. P12TEP-1401Ministry of Economy and Innovation (Spain) project MAT2015-71284-

Internal stress plasticity due to chemical stresses

Abstract—Internal stress plasticity occurs when a small external stress biases internal mismatch strains pro-duced by, e.g., phase transformation or thermal expansion mismatch. At small applied stresses, this defor-mation mechanism is characterized by a deformation rate which is proportional to the applied stress and is higher than for conventional creep mechanisms. In this work, we demonstrate the operation of internal stress plasticity due to internal chemical stresses produced by chemical composition gradients. We subject speci-mens of β-phase Ti-6Al-4V to cyclic charging/discharging with hydrogen (by cyclic exposure of specimens to gaseous H2), under a small external tensile stress. As expected for internal stress plasticity, the average strain rate during chemical cycles at 1030°C is larger than for creep at constant composition (hydrogen-free or-saturated), and a linear stress dependence is observed at small applied stresses. Additionally, we present an analytical model which couples elastic and creep deformation with a transient diffusion problem, wherein the diffusant species induces swelling of the host lattice. Without the use of any adjustable parameters, the model accurately predicts both the observed strain evolution during hydrogen cycling of Ti-6Al-4V and th