Hydroxyapatite (HA, Ca10PO4(OH)2) is a widely explored material in the experimental domain of biomaterials science, because of its resemblance with natural bone minerals. Specifically, in the bioceramic community, HA doped with multivalent cations (e.g., Mg2+, Fe2+, Sr2+, etc.) has been extensively investigated in the last few decades. Experimental research largely established the critical role of dopant content on mechanical and biocompatibility properties. The plethora of experimental measurements of mechanical response on doped HA is based on compression or indentation testing of polycrystalline materials. Such measurements, and more importantly the computational predictions of mechanical properties of single crystalline (doped) HA are scarce. On that premise, the present study aims to build atomistic models of Fe2+-doped HA with varying Fe content (10, 20, 30, and 40 mol%) and to explore their uniaxial tensile response, by means of molecular dynamics (MD) simulation. In the equilibrated unit cell structures, Ca(1) sites were found to be energetically favourable for Fe2+ substitution. The local distribution of Fe2+ ions significantly affects the atomic partial charge distribution and chemical symmetry surrounding the functional groups, and such signatures are found in the MD analyzed IR spectra. The significant decrease in the intensity of the IR bands found in the Fe-doped HA together with band splitting, because of the symmetry changes in the crystal structure. Another important objective of this work is to computationally predict the mechanical response of doped HA in their single crystal format. An interesting observation is that the elastic anisotropy of undoped HA was not compromised with Fe-doping. Tensile strength (TS) is systematically reduced in doped HA with Fe2+ dopant content and a decrease in TS with temperature can be attributed to the increased thermal agitation of atoms at elevated temperatures. The physics of the tensile response was rationalized in terms of the strain dependent changes in covalent/ionic bond framework (Ca–P distance, P–O bond strain, O–P–O angular strain, O–H bond distance). Further, the dynamic changes in covalent bond network were energetically analyzed by calculating the changes in O–H and P–O bond vibrational energy. Summarizing, the current work establishes our foundational understanding of the atomistic phenomena involved in the structural stability and tensile response of Fe-doped HA single crystals.

Vanadium oxide: Phase-1 and Phase-2 nano powers were synthesized from vanadium pentoxide in the presence of glucose using hydrothermal technique. The polypyrrole/vanadium oxide (PV P-1 and PV P-2) nano composites were synthesized with 15, 30, 45 and 60 weight percents of vanadium oxide: Phase-1 and Phase-2 in pyrrole, by the chemical polymerization (oxidation) method. The SEM micrographs of vanadium oxide: Phase-1 and Phase-2 nano powders have shown  mixture of nano belts & rods and PV P-1 & PV P-2 nano composites indicate that the composites have cluster formation with almost spherical nature particles and form elongated chains at some places. Conductivity versus frequency  plots shown that exponential increase for conductivity. The value of s increases to 1.13x10-3 S/cm for 15 wt. % of VO2 P-1 in polypyrrole & to 2.43x10-3 S/cm for 30 wt. % of VO2 P-2 in polypyrrole at 1 MHz.

The wear of acetabular liner is one of the key factors determining the longevity and osseointegration of Total Hip Replacement (THR) implants. The long-term experimental measurements of wear in THR components are time and cost-intensive. A finite element (FE) model of a 32 mm Ceramic on Polymer system consisting of ZTA (Zirconia-toughened Alumina) femoral head and UHMWPE (Ultrahigh molecular weight polyethylene) liner was developed to predict the dynamic wear response of the liner. Archard-Lancaster equation, consisting of surface contact pressure, wear rate, and sliding distance, was employed to predict the wear in the liner. The contact pressure and wear at the articulating surface were found to decrease over time. A new computational method involving 3D point clouds from the FE analyzed results were used to construct wear maps. The model was able to predict the linear wear with relative errors ranging from 9% to 36% over 2 million cycles when compared to the published results. The increasing error percentage occurring primarily from the use of a constant wear rate was reduced to a maximum of 17% by introducing a correction factor. Volumetric wear rate was predicted with a maximum relative error of 7% with the implementation of the correction factor. When the model was implemented to study liners of diameters ranging from 28 mm to 36 mm, the linear wear was seen to decrease with an increase in femoral head diameter, which is in agreement with the clinical data.

Hydroxyapatite (HA, Ca10PO4(OH)2) is a widely explored material in the experimental domain of biomaterials science, because of its resemblance with natural bone minerals. Specifically, in the bioceramic community, HA doped with multivalent cations (e.g., Mg2+, Fe2+, Sr2+, etc.) has been extensively investigated in the last few decades. Experimental research largely established the critical role of dopant content on the changes in mechanical and biocompatibility properties. The plethora of experimental measurements of mechanical response on doped HA is based on compression or indentation testing of polycrystalline materials. Such measurements, as well as computational predictions of mechanical properties on single crystalline (doped) HA are scarce. On that premise, the present study aims to build atomistic models of Fe2+-doped HA, a model system, with varying Fe content (10, 20, 30, and 40 mol%) and to explore their uniaxial tensile response by means of molecular dynamics (MD) simulation, together with the calculation of IR spectrum. In the equilibrated unit cell structures, Ca(1) sites were found to be energetically favourable for Fe2+ substitution. The local distribution of Fe2+ ions significantly affects the atomic partial charge distribution and chemical symmetry surrounding the functional groups. These signatures are reflected in the significant decrease in the intensity of IR peaks found in the Fe-doped HA, together with peak splitting because of the symmetry change in the crystal structure. Another important objective of this work is to computationally predict the mechanical response of doped HA in their single crystal format. An interesting observation is that the elastic anisotropy of undoped HA was not compromised with Fe-doping. Tensile strength (TS) is systematically reduced in doped HA with Fe2+ dopant content and a decrease in TS with temperature can be attributed to the increased thermal agitation of atoms at elevated temperatures. The physics of the tensile response was rationalized in terms of the strain dependent changes in covalent/ionic framework (Ca-P distance, P-O bond strain, O-P-O angular strain, O-H bond distance). Further, the dynamic changes in covalent bond network were energetically analyzed by calculating the changes in O-H and P-O bond vibrational energy. Summarizing, the current work develops our foundational understanding of the atomistic phenomena involved in the phase stability and tensile response of Fe-doped HA single crystals.