Development and implementation of a sequential compaction device to obtain radial graded porosity cylinders

A new processing route is proposed to produce graded porous materials by placing particles of Ti6Al4V with different sizes in different configurations to obtain bilayer samples that can be used as bone implants. The sintering behavior is studied by dilatometry and the effect of the layers’ configuration is established. To determine pore features, SEM and computed microtomography were used. Permeability is evaluated by numerical simulations in the 3D real microstructures and the mechanical properties are evaluated by compression tests. The results show that a graded porosity is obtained as a function of the size of the particle used. The mechanical anisotropy due to the pore size distribution and the sintering kinetics, can be changed by the particle layer arrangements. The Young modulus and yield stress depend on the relative density of the samples and can be roughly predicted by a power law, considering the layers’ configuration on the compression behavior. Permeability is intimately related to the median pore size that leads to anisotropy due to the layers’ configuration with smaller and coarser particles. It is concluded that the proposed processing route can produce materials with specific and graded characteristics, with the radial configuration being the most promising for biomedical applications.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Processing and Characterization of Bilayer Materials by Solid State Sintering for Orthopedic Applications

Téllez-Martínez

Olmos

Solorio-García

et al. 2021

“…These alloys are based on refractory alloy elements of low toxicity for cells (such as Nb, Mo, Zr, and Ta) and, therefore, they present excellent biocompability [8,9]. In recent decades, several studies have addressed the problem of stress shielding by designing and manufacturing porous materials with lower Young modulus [10][11][12]. The morphologies and size of the pores, the percentage of porosity, and the degree of interconnectivity of the porous structure play an important role in bone tissue formation throughout the implant [13,14].…”

Section: Introductionmentioning

confidence: 99%

Surface Modification of Porous Titanium Discs Using Femtosecond Laser Structuring

Rodríguez

Trueba²,

Amado

et al. 2020

The failure of titanium implants is associated with two main problems that include the bone resorption and fracture of the surrounding bone tissue (stiffness incompatibility) and implant loosening (poor osseointegration). The development of porous titanium implants with low Young modulus solve the stress shielding phenomenon, while the modification of the implant surface must be implemented to promote a fast bond between the implant and bone. In this work, femtosecond laser micromachining was applied to modify the topography of the surface of Ti porous samples obtained by a space-holder technique to obtain hierarchical structures (micro and nano roughness patterns) to enhance osseointegration. Scanning electron microscopy, confocal laser microscopy, and image analysis were used for characterization of the surface morphology, roughness, and porosity before and after performing the laser treatment. Based on these results, the effect of the treatment on the mechanical behavior of the samples was estimated. In addition, a preliminary in-vitro test was performed to verify the adhesion of osteoblasts (filopodia presence) on modified titanium surface. Results revealed that laser texturing generated clusters of micro-holes and micro-columns both on the flat surface of the samples and inside the macro-pores, and periodic nanometric structures across the entire surface. The porous substrate offers suitable biomechanics (stiffness and yield strength) and bio-functional behavior (bone ingrowth and osseointegration), which improves the clinic success of titanium implants.

“…A potential solution to mitigate the stress-shielding effect phenomenon is the manufacture of functional materials with a controlled porosity designed to reduce Young's modulus of the materials, such as metal foams, addressed by the scientific community [20,21]. From the implant point of view, the metallic foams have high-energy absorption capacity because they can allow higher deformation before reaching their yield strength, increasing the area under the stress-strain curve [22], in the same way that a structure with open pores provides channels for bone ingrowth and neovascularization, which promotes the osseointegration process [23,24].…”

Section: Introductionmentioning

confidence: 99%

“…There are different ways to obtain Ti foams [21], such as grow of pressurized gas bubbles [25], additive manufacturing [26], and replication [27], among the alternatives [28]. However, the space-holder technique is one of the powder metallurgy (PM) methods, which is extensively used for their simplicity generate porous structures needed for metallic foams [29], permitting to control the size and distribution of the pores [30].…”

Section: Introductionmentioning

confidence: 99%

Study of the Effect of the Floating Die Compaction on Mechanical Properties of Titanium Foams

Sauceda

Lascano

Béjar

et al. 2020

Titanium (Ti) and its alloys are used for biomedical applications because of their high resistance to corrosion, good strength-to-weight ratio, and high fatigue resistance. However, a problem that compromises the performance of the material is the mismatch between Young’s modulus of Ti and the bone, which brings about stress shielding. One strategy that has been investigated to reduce this difference is the manufacture of Ti-based foams, using powder metallurgy (PM) methods, such as the space-holder technique. However, in the uniaxial compaction, both non-uniform density distribution and mechanical properties remain because of the compaction method. This work studies the influence of compaction by adopting a floating-action die related to a single-action die (SAD), on the density of green and sintered Ti foams with porosities around 50 vol.% characterized by optical microscopy, ultrasound analysis, compression tests, and microhardness. The compaction process employing a floating-action die generates Ti foams with a higher density up to 10% with more control of the spacer particle added compared to the single-action die. Furthermore, compaction method has no relevant effect on microhardness and Young’s modulus, which allows getting better consolidated samples with elastic modules similar to those of human bone.