Exploration into the microstructural, mechanical, and biological characteristics of the functionally graded 3Y-TZP/Ti6Al4V system as a potential material for dental implants.

This study investigated the mechanical, microstructural, and biological properties of 3Y-TZP/Ti6Al4V functionally graded material (FGM) fabricated by the spark plasma sintering (SPS) method. For this purpose, 11 layers of 100-x vol% Ti6Al4V/x vol% Yttria stabilized zirconia (YSZ) (x = 0 to 100) were sintered at 1450 °C and a pressure of 30 MPa for 8 min. To investigate the properties of each layer in more detail, 11 batches of 100-x vol% (Ti6Al4V)/x vol% YSZ (x = 0 to 100) composites were sintered separately with the same sintering conditions mentioned for the FGM sample. Phase identification of the FGM sample showed the formation of Ti3O, c-ZrO2, and Zr3O phases as by-products. A schematic model was proposed for the formation of the mentioned phases with the aid of thermodynamic calculations. The formation of these phases was confirmed by microstructural and elemental tests. The results of the relative density of the samples showed that these values were obtained for each layer above 99%. The microhardness of 590 ± 18 Vickers was obtained for Ti6Al4V; by increasing the amount of 3Y-TZP, this value reached 1510 ± 24 Vickers for the YSZ sample. The fracture toughness value for Ti6Al4V was 39.2 ± 2 MPa m0.5, which was significantly reduced to 4.84 ± 1 MPa m0.5 by adding 10 vol% YSZ. After that, with the further increase of YSZ, this value increased slowly. A similar trend was observed for the bending strength of the samples. By increasing 3Y-TZP from 0 to 30 vol%, the bending strength was decreased from 1556 ± 32 to 272 ± 62 MPa. By further increasing the amount of 3Y-TZP from 30 to 100 vol%, an increase in the bending strength was observed in the samples, which reached 1180 ± 71 MPa for the YSZ sample. The FGM sample showed a brittle fracture despite a metal layer, but a higher bending strength (982 ± 44 MPa) was obtained for this structure than the composite samples. The biological results show that increasing YSZ content leads to a decrease in antimicrobial activity. Additionally, all samples demonstrated high biocompatibility based on MTT cytotoxicity tests after 1 and 7 days of culture.

Adsorption system for Mg2+ removal from aqueous solutions using bentonite/γ-alumina nanocomposite.

Calcium and magnesium are the most common sources of water hardness. These divalent ions can react with soap anions decreasing the cleaning efficiency and hence, high consumption of detergents occurred as a result. Development of novel low-cost adsorbents for metals removal has attracted a great attention. In this study, bentonite/γ-alumina nanocomposites were used to remove Mg2+ from water. Effects of process parameters including γ-alumina content, initial ion concentration, adsorbent dosage, contact time and pH on adsorption process were investigated. Increasing the amount of alumina in composite from 1 to 3 and 5 wt%, caused a negative effect on the amount of adsorbed magnesium ions per gram of adsorbent; while increasing the initial ion concentration from 60 ppm to 100 ppm resulted in higher uptake per unit mass of the adsorbent from 2.15 mg/g to 2.80 mg/g, respectively. Langmuir, Freundlich and D-K-R isotherm models were used for data analysis, among which the Langmuir model was found to be more successful (R2 = 0.9955), obtaining the maximum adsorption capacity (Qm) of 3.478 mg/g. Moreover, calculation of the adsorption energy (E) from DKR isotherm model depicted the physical nature of the adsorption of Mg2+ onto bentonite/γ-alumina nanocomposite powder.