Processing and characterization of porous titanium for implants by using NaCl as space holder

Porous samples of commercially pure titanium (CP Ti) were fabricated by using sodium chloride (NaCl) as space-holder with percentages between 40 and 70 vol%. The dissolution of NaCl in distilled water, the structural integrity of samples and the reproducibility of the procedure were studied as a step prior to sintering. All these parameters were evaluated in terms of the compaction pressure, temperature and agitation of water, and dissolution time. The characterization of samples included density, porosity and dynamic Young's modulus. The results indicate that the most efficient lixiviation, according to the desired balance of properties, was by immersion in hot water, without agitation and for prolonged cycles of immersion time.     

Fabrication and evaluation of oxidation resistance performance of open-celled Fe(Al) foam by space-holder technique

First, fabrication of Fe(Al) open-cell foams by using space-holder technique, in which NaCl powder and polyester resin were utilized as space holder and binder, was investigated. Fe(Al) powder were prepared via mechanical alloying method after 5 h milling process. Then, the influences of fabrication parameters, alloying element Al content, time of milling process, sintering temperature and soaked time on the oxidation resistance performance of foam specimens at 800 °C were mainly studied. The experimental results exhibit that alloying with 2 wt.% Al resulted in acceleration of the oxidation rate of foam samples, additionally, alloying with 4 wt.% Al had a little positive effect on oxidation rate at 800 °C. However, the oxidation resistance of the 10 wt.% Al-containing sample greatly improves compared to pure Fe. In addition, the oxidation resistance performance of prepared foam was improved by increasing the milling time up to 15 h, and followed by a decrease gradually. The increase of sintering temperature and the prolongation of soaked time to 1100 °C and 90 min, respectively had significant positive effect on the oxidation resistance.     

A New Approach for Manufacturing a High Porosity Ti-6Al-4V Scaffolds for Biomedical Applications

Titanium and its alloys are currently considered as one of the most important metallic materials used in the biomedical applications, due to their excellent mechanical properties and superior biocompatibility. In the present study, a new effective method for fabricating high porosity titanium alloy scaffolds was developed. Porous Ti-6Al-4V scaffolds are successfully fabricated with porosities ranging from 30% to 70% using spaceholder and powder sintering technique. Based on its acceptable properties, spherical carbamide particles with different diameters （0.56, 0.8, and 1mm） were used as the space-holder material in the present investigation. The Ti-6Al-4V scaffolds porosity is characterized by using scanning electron microscopy. The results show that the scaffolds spherical-shaped pores are depending on the shape, size and distribution of the space-holder particles. This investigation shows that the present new manufacturing technique is promising to fabricate a controlled high porosity and high purity Ti-6Al-4V scaffolds for hard tissue replacement.     

Effects of SiC,SiO2 and CNTs nanoadditives on the properties of porous alumina-zirconia ceramics produced by a hybrid freeze casting-space holder method

Highly porous alumina-zirconia ceramics were produced by adding space-holder materials during freeze casting. To increase the strength of porous ceramics, different amounts of nanoadditives (silicon carbide-SiC, silica-SiO₂, and multi-wall carbon nanotubes-CNTs) were added. Space-holder materials were removed by preheating, and solid samples were produced by sintering. Up to 68% porosity was achieved when 40% space-holder was added to the solid load of slurry. Wall thicknesses between pores were more uniform and thinner when nanoadditives were added. Compressive tests revealed that SiC nanoparticles increased the strength more than other nanoadditives, and this was attributed to formation of an alumina-SiC phase and a uniform distribution of SiC nanoparticles. Results indicated that by including 20% space-holder materials and 15% SiC nanoparticles, the density decreases by 33.8% while maintaining a compressive strength of 132.5 MPa and porosity of 43.4%. Relatively low thermal conductivities, less than 3.5 W/K-m, were measured for samples with SiC nanoparticles.