Microstructure evolution, mechanical properties, and enhanced bioactivity of Ti-13Nb-13Zr based calcium pyrophosphate composites for biomedical applications

Tribological behavior and in vitro biocompatibility of powder metallurgical Ti-15Mo/HA composite for bone repair

Ti-15Mo/HA composite was prepared by powder metallurgy, and the influence of Hydroxyapatite (HA) on the microstructure, tribological behavior and in vitro biocompatibility was studied by comparison with TC4. The results show that the Ti-15Mo/HA composite consists of increased α-Ti, decreased β-Ti and a variety of ceramic phases (CaTiO3, Ca3(PO4)2, CaO, etc.) with the increase of HA content. The friction coefficient and wear rate of Ti-15Mo/HA composite is apparently lower than those of TC4 due to solid solution strengthening of Mo in Ti and dispersion strengthening of ceramic phases. Ti-15Mo/5HA displays more excellent wear resistance than the other composite. TC4 alloy is dominated by adhesive wear, however, Ti-15Mo alloy is a combination of adhesive wear and abrasive wear. Ti-15Mo/HA composite is mainly subjected to abrasive wear, together with adhesive wear. The viability and the number of mouse osteoblasts in Ti-15Mo/5HA extract are higher than that of Ti-15Mo. The morphology of the osteoblasts is clear and full, and the growth and proliferation are satisfactory with the increased cell pseudopodia with the culture time. The Ti-15Mo/HA composite displays good wear resistance and biocompatibility, and accordingly has a potential application in bone repair materials.

Influence of Low Temperature Plasma Oxidizing on the Bioactivity of NiTi Shape Memory Alloy for Medical Applications

The present study elucidates the impact of glow discharge oxidation within a low-temperature plasma environment on the bioactivity characteristics of an NiTi shape memory alloy. The properties of the produced surface layers, such as structure (TEM observations), surface morphology (SEM observations), chemical and phase composition (EDS and XRD measurements), wettability (optical gonimeter), and the biological response of osteoblasts and platelets to the oxidized surface compared with the NiTi alloy without a surface layer are presented. The presented surface modification of the NiTi shape memory alloy, achieved through oxidizing in a low-temperature plasma environment, led to the creation of a continuous surface layer composed of nanocrystalline titanium oxide TiO2 (rutile). The findings obtained from this study provide evidence that the oxidized layer augments the bioactivity of the shape memory alloy. This augmentation was substantiated through the spontaneous biomimetic deposition of apatite from a simulated body fluid (SBF) solution. Furthermore, the modified surface exhibited improved osteoblast proliferation, and enhanced platelet adhesion and activation. This proposed surface modification strategy holds promise as a prospective solution to enhance the biocompatibility and bioactivity of NiTi shape memory alloy intended for prolonged use in bone implant applications.

Synthesis, structural and luminescent properties of Mn-doped calcium pyrophosphate (Ca2P2O7) polymorphs

In the present work, three different Mn²⁺-doped calcium pyrophosphate (CPP, Ca₂P₂O₇) polymorphs were synthesized by wet co-precipitation method followed by annealing at different temperatures. The crystal structure and purity were studied by powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR), solid-state nuclear magnetic resonance (SS-NMR), and electron paramagnetic resonance (EPR) spectroscopies. Scanning electron microscopy (SEM) was used to investigate the morphological features of the synthesized products. Optical properties were investigated using photoluminescence measurements. Excitation spectra, emission spectra, and photoluminescence decay curves of the samples were studied. All Mn-doped polymorphs exhibited a broadband emission ranging from approximately 500 to 730 nm. The emission maximum was host-dependent and centered at around 580, 570, and 595 nm for γ-, β-, and α-CPP, respectively.

Cyclic Oxidation of Titanium Grade 2

This paper presents the results of research into the cyclic oxidation of titanium Grade 2. The value of titanium Grade 2 oxidation activation energy was determined based on an analysis of the Arrhenius diagram. The result was 205.3 kJ/mol. After cyclic oxidation at a temperature of 600 °C, the presence of oxides in an acicular system was observed on the surface. The specimen surface after oxidation at 650 °C was characterised by the presence of fine oxide particles, while after oxidation at 700 °C, the obtained oxide layer was composed of large oxide particles. The layers obtained after oxidation at 600 °C had the lowest thickness (1.26 and 2.12 µm), while those obtained at 700 °C had the highest thickness (5.17 and 9.45 µm). Examination of the phase composition after cyclic oxidation showed that the oxide layers obtained at temperatures of 600, 650 and 700 °C were composed of TiO₂ (rutile) only. No presence of other phases was found. The oxide layers formed in the cyclic oxidation process were characterised by different thicknesses, depending on the oxidation parameters. It was found that cyclic oxidation contributed to a considerable increase in the surface hardness of titanium Grade 2.

The Tensile Properties, Scratch Behaviors and Sliding Wear of Oxide Scale Formed on Titanium Grade 2

The tensile properties, scratch behaviors and sliding wear of an oxide scale obtained on the surface of titanium Grade 2 in the process of isothermal oxidation at 600, 700 and 800 °C were determined in the study. It was shown that the intensity of the oxidation process increased along with an increase in temperature and extension of the oxidation time, which translated directly into the thickness of the deposited oxide layers. The tests showed that isothermal oxidation had an adverse effect on the tensile properties of titanium. After oxidation, it was found that the maximum reduction in tensile strength, R_m, was approximately 17.5%, and of the yield point, R_p0.2, approximately 13.9%. Examination of scratch behaviors of the oxide scale showed that the layers obtained at temperatures of 700 (72 h) and 800 °C (2 and 6 h) had the best adhesion properties. The best resistance to scratching was exhibited by the layer obtained after 6 h oxidation at 800 °C (critical load: L_c1 = 63 N, L_c2 = 85 N). The study showed that after oxidation, a considerable reduction in wear factor of a disc made of titanium Grade 2 was observed for both the friction couples used (Al₂O₃, steel 100Cr6). The maximum reduction in wear factor of the oxidized titanium disc during interaction with Al₂O₃ balls was ca. 79%, and with 100Cr6 balls, ca. 96%.

Strengthening mechanism and corrosion resistance of beta-type Ti-Nb-Zr-Mn alloys

In order to achieve an effective balance between plasticity and strength, a group of Ti-26Nb-xZr-yMn (x = 4, 7, 10 wt% and y = 3, 5 wt%) alloys were designed to evaluate the effects of Mn and Zr on the microstructures, mechanical properties and strengthening effects of the TiNb system. All the investigated alloys illustrate a monolithic β phase in their microstructure and they all possess substantial true plasticity (~160%) and true maximum strength (~ 950 MPa) without fracture during the compression tests within the load capacity of 100 kN. The contribution of solid-solution, grain-boundary and dislocation strengthening mechanisms have been evaluated using the strengthening model for β Ti alloys for all the investigated alloys. Among the investigated alloys, Ti-26Nb-4Zr-5Mn demonstrates the highest true yield strength (654 MPa), dislocation density (2.45 × 10¹⁵ m^-2) and hardness (242 HV) along with improved strain hardening ability in terms of strain hardening indices (0.42 and 0.09). Furthermore, based on the superior mechanical properties among the investigated alloys, the electrochemical performance of Ti-26Nb-4Zr-3Mn and Ti-26Nb-4Zr-5Mn have also been analyzed in this work. The electrochemical measurements show that both alloys have almost similar corrosion potential and corrosion current density in simulated body fluid, i.e., -0.45 V and 0.838 nA/cm² for Ti-26Nb-4Zr-3Mn, -0.48 V and 0.839 nA/cm² for Ti-26Nb-4Zr-5Mn, respectively.