Customizing the Pore Structure and Properties of Freeze‐Cast Porous Titanium by Zirconium Acetate Additive

Abstract

Porous titanium scaffolds with high porosity and connected macropores are fabricated by adding zirconium acetate to control the ice crystal growth during freeze casting. The influences of zirconium acetate additives on the phase composition, pore structure, and mechanical properties of porous titanium are studied. As modified by zirconium acetate, the X‐ray diffraction peaks of titanium moves to a smaller angle, and the zirconium is evenly distributed on the titanium matrix. With the increase in the concentration of zirconium from 0 to 60 g L−1, the pore morphology of porous titanium changes from typical lamellar to the honeycomb, the pore size distribution becomes wider. The average pore size and porosity increases from 44 ± 11 to 126 ± 35 μm and from 46.4 ± 1.3 to 59.1 ± 1.3%, respectively. As the concentration of zirconium acetate is 40 g L−1, the porosity and the pore size of the porous titanium scaffolds are comparable with those modified by 10 g L−1 zirconium acetate, but the compressive strength is 2.3 times higher. Zirconium acetate as an additive has an excellent performance in optimizing the pore structure and mechanical properties of water‐based freeze‐cast porous titanium.

Fabricating Honeycomb Titanium by Freeze Casting and Anodizing for Biomedical Applications

“…Our previous studies have shown that during the preparation of the titanium scaffold by the freeze casting, as the zirconium concentration increases, the pore structure changes from lamellar to honeycomb. [ 25 ] This article first discussed the effect of freezing temperature on the honeycomb structure with the same addition of zirconium acetate. The morphology of titanium scaffolds prepared at different freezing temperatures was characterized by scanning electron microscope (SEM).…”

“…Due to the presence of zirconium acetate in the slurry, the polyhedral structure of ice crystals was changed during the freezing, and the honeycomb pores were obtained after sublimation to remove the ice crystals. [ 25 ] In addition, significant differences in the pore size and wall thickness of the honeycomb pores were observed. Figure shows the average pore size and wall thickness variation of porous titanium with freezing temperature.…”

“…Slurry Preparation: The honeycomb porous titanium scaffolds were prepared by freeze casting with a zirconium acetate additive, reported in detail in our previous study. [25] The operational procedure was to mix 2 wt% polyvinyl alcohol (PVA,17-99, Guizhou Crystal Chemical Co., Ltd., China) solution (with 0.5 wt% xanthan gum dispersant) with zirconium acetate solution (Zr, 16.0%, ρ ¼ 1.279 g mL À1 , Aladdin), controlling the zirconium concentration in the slurry to 40 g L À1 , followed by the addition of titanium powder (D 50 ¼ 10.2 μm, Chengdu Guoheng Technology Co., Ltd., China) ensuring a solid phase fraction of 20 vol%. Afterward, the slurry was milled with a ball mill at a speed of 200 rpm for 24 h to uniform thoroughly.…”

“…In our previous study, we showed that multichannel porous honeycomb titanium prepared by the freeze casting method had a porosity of 60% and an average pore size greater than 100 μm and that the mechanical properties of honeycomb titanium were superior to those of conventional lamellar porous titanium when the porosity and average pore size were close. [25] In addition, titanium metal is a biologically inert material that can lead to low levels of cellular interaction at the biological interface, which is detrimental to the interfacial bonding of the implant to the bone tissue. [26] However, surface modification of titanium can be an effective solution to this problem.…”

“…In our previous study, we showed that multichannel porous honeycomb titanium prepared by the freeze casting method had a porosity of 60% and an average pore size greater than 100 μm and that the mechanical properties of honeycomb titanium were superior to those of conventional lamellar porous titanium when the porosity and average pore size were close. [ 25 ]…”