This study paves way to examine the influence of different annealing conditions (temperature range of 830-850°C and duration intervals 24-48 h) on the fundamental mechanical performance and characteristic quantities of polycrystalline Bi_2.1Sr_2.0Ca_1.1Cu_2.0O_y (Bi-2212) superconducting ceramics by means of Vickers microindentation hardness tests at the various indentation test loads (0.245 N≤F≤2.940 N) and some available theoretical approaches. The annealing ambient plays an important role on the operable slip systems and crystal quality. The bulk Bi-2212 superconducting compound prepared at 840 °C and 24 h is found to be the least sensitive to the applied test load due to less structural problems, voids, cracks and stress raisers in the crystal system. Conversely, the excess annealing ambient complicates remarkably the control of crack growth size and velocity. Thus, relatively lower load can lead to the formation of crack and acceleration of crack rate up to the critical size and terminal velocity. The samples exhibit the typical indentation size effect (ISE) behavior as a result of predominant character of elastic recovery mechanism. As for the theoretical examination in the saturation limit regions, the indentation-induced cracking (IIC) model wins the comparison as it provides the most accurate results to the experimental findings.

In this study, the hydroxyapatite biomaterials are produced by the precipitation method and the role of silver doping within the different molar ratios of 2.0, 5.0, and 10.0% are investigated with some fundamental analysis, including powder XRD, SEM, EDS, FTIR, Raman, and material densities. In vitro biocompatibility assessment is conducted with cytotoxicity and agar diffusion tests. Moreover, genotoxicity tests determine whether the biomaterials produced cause the mutations or not. In addition, a hemolytic effect test examines the variation of hemolytic behavior of compounds. Also, the cell migration experiments inspect the influence of silver ion levels in biomaterials on many biological processes. The experimental results reveal that the honeycomb-patterned morphological structures are obtained for all the products. FTIR and Raman analyses reveal that the dramatic changes in the characteristic functional group peaks are obtained with the increment in the amount of silver ions. The experimental parts related to the biocompatibility assessment of the study show that there seems to be deterioration in biocompatibility as the silver ion-doping level increases in the system. To sum up, the ideal doping value for bone tissue engineering applications is found to be 2%.

This study achieves a strong link between microscopy architecture and fundamental characteristics including electrical conductivity, superconducting, and key mechanical design properties of Bi_2.1-xDy_xSr_2.0Ca_1.1Cu_2.0O_y (Bi-2212) ceramic structures with different dysprosium molar ratio ranges of 0.00 ≤ x ≤ 0.10. The Dy/Bi substituted Bi-2212 ceramics are characterized by scanning electron microscopy (SEM), electrical resistivity (ρ-T), Electron Dispersive x-ray (EDX) investigations, and microindentation Vickers hardness (H_v) tests. Powder x-ray diffraction (XRD) experimental inspection is also studied to support SEM and H_v results. All experimental findings show significant improvement with an increase in the Dy impurity molar ratio to x = 0.01. On this basis, the Bi_2.09Dy_0.01Sr_2.0Ca_1.1Cu_2.0O_y ceramic structure exhibits the lowest resistivity of 8.95 mΩ.cm at 300 K and transition width of 4.75 K, and the highest T c o n s e t of 85.00 K and T c o f f s e t of 80.25 K. Additionally, XRD examinations show that optimum Dy ion substitution in the Bi-2212 system stabilizes the high superconducting phase by improving crystallinity, crystallite size, grain orientation distributions, texturing, and interlayer interactions. In contrast, excessive substitution severely deteriorates crystallographic properties. Further, SEM images reveal that the presence of optimum Dy impurity enhances the crystallinity, couplings between the adjacent layers, homogeneous surface appearance, and microstructure. Moreover, the key mechanical design features and stability of the durable tetragonal phase improve significantly for x = 0.01. As a result, the material exhibits superior mechanical properties, including a microhardness of 0.5556 GPa, fracture toughness of 0.5390 MPa.m^1/2, elastic modulus of 45.5389 GPa, shear modulus of 18.2156 GPa, yield strength of 0.1852 GPa, and resilience of 0.3766 MPa under a 0.295 N load.