Electrochemical and Mechanical Properties of Hexagonal Titanium Dioxide Nanotubes Formed by Sonoelectrochemical Anodization.

This study aimed to investigate the fabrication and characterization of hexagonal titanium dioxide nanotubes (hTNTs) compared to compact TiO2 layers, focusing on their structural, electrochemical, corrosion, and mechanical properties. The fabrication process involved the sonoelectrochemical anodization of titanium foil in various electrolytes to obtain titanium oxide layers with different morphologies. Scanning electron microscopy revealed the formation of well-ordered hexagonal TNTs with diagonals in the range of 30-95 nm and heights in the range of 3500-4000 nm (35,000-40,000 Å). The electrochemical measurements performed in 3.5% NaCl and Ringer's solution confirmed a more positive open-circuit potential, a lower impedance, a higher electrical conductivity, and a higher corrosion rate of hTNTs compared to the compact TiO2. The data revealed a major drop in the impedance modulus of hTNTs, with a diagonal of 46 ± 8 nm by 97% in 3.5% NaCl and 96% in Ringer's solution compared to the compact TiO2. Nanoindentation tests revealed that the mechanical properties of the hTNTs were influenced by their diagonal size, with decreasing hardness and Young's modulus observed with an increasing diagonal size of the hTNTs, accompanied by increased plastic deformation. Overall, these findings suggest that hTNTs exhibit promising structural and electrochemical properties, making them potential candidates for various applications, including biosensor platforms.

Structural, Electrical and Corrosion Properties of Bulk Ti-Cu Alloys Produced by Mechanical Alloying and Powder Metallurgy.

Binary Ti100-x-Cux (x = 1.6 and 3.0 wt.%) alloys were produced by the application of mechanical alloying and powder metallurgy processes. The influence of the copper concentration in titanium on the microstructure and properties of bulk alloys was investigated. The synthesized materials were characterized by an X-ray diffraction technique, scanning electron microscopy, and chemical composition determination. The electrochemical and corrosion properties were also investigated. Cold compaction and sintering reduced the content of α-Ti content in Ti98.4-Cu1.6 and Ti97-Cu3 alloys to 92.4% and 83.7%, respectively. Open Circuit Potential measurements showed a positive shift after the addition of copper, suggesting a potential deterioration in the corrosion resistance of the Ti-Cu alloys compared to pure Ti. Electrochemical Impedance Spectroscopy analysis revealed significant improvement in electrical conductivity after the addition of copper. Corrosion testing results demonstrated compromised corrosion resistance of Ti-Cu alloys compared to pure Ti. In summary, the comprehensive investigation of Ti100-x-Cux alloys provides valuable insights for potential applications in biosensing.

Ultrafine-Grained Ti-31Mo-Type Composites with HA and Ag, Ta2O5 or CeO2 Addition for Implant Applications.

Ultrafine-grained Ti31Mo alloy and Ti31Mo5HA, Ti31Mo5HA-Ag (or Ta2O5, CeO2) composites with a grain size of approximately 2 µm were produced by the application of mechanical alloying and powder metallurgy. Additionally, the surface of the Ti31Mo alloy was modified. In the first stage, the specimens were immersed in 5M NaOH for 24 h at 60 °C. In the second stage, hydroxyapatite (HA) was deposited on the sample surface. The cathodic deposition at -5 V vs. open circuit potential (OCP) in the electrolyte containing 0.25M CaNa2-EDTA (di-calcium ethylenediaminetetraacetic acid), 0.25M K2HPO4 in 1M NaOH at 120 °C for 2 h was applied. The bulk Ti31Mo alloy is a single ß-type phase. In the alkali-modified surface titanium oxide, Ti3O is formed. After hydrothermal treatment, the surface layer mostly consists of the Ca10(PO4)6(OH)2 (81.23%) with about 19% content of CaHPO4·2H2O. Using optical profiler, roughness 2D surface topography parameters were estimated. The in vitro cytocompatibility of synthesized materials was studied. The cell lines of normal human osteoblasts (NHost) and human periodontal ligament fibroblasts (HPdLF) was conducted in the presence of tested biomaterials. Ultrafine-grained Ti-based composites altered with HA and Ag, Ta2O5 or CeO2 have superior biocompatibility than the microcrystalline Ti metal. NHost and HPdLF cells in the contact with the synthesized biomaterial showed stable proliferation activity. Biocompatibility tests carried out indicate that the ultrafine-grained Ti31Mo5HA composites with Ag, Ta2O5, or CeO2 could be a good candidate for implant applications.

Low-Temperature Hydrothermal Treatment Surface Functionalization of the Ultrafine-Grained TiMo Alloys for Medical Applications.

Hydroxyapatite (HAp) is the most widely used material for bio coating. The functional layer can be produced by many methods, however, the most perspective by its utility, easy to scale up, and simplicity aspects remains a hydrothermal treatment approach. In this work, an HAp coating was produced by low-temperature hydrothermal treatment on the ultrafine-grain beta Ti-xMo (x = 23, 27, 35 wt.%) alloys. The proposed surface treatment procedure combines acid etching, alkaline treatment (AT), and finally hydrothermal treatment (HT). The uniqueness of the approach relies on the recognition of the influence of the molar concentration of NaOH (5 M, 7 M, 10 M, 12 M) during the alkaline treatment on the growth of hydroxyapatite crystals. Obtained and modified specimens were examined structurally and microstructurally at every stage of the process. The results show that the layer after AT consist of titanium oxide and phases based on sodium with various phase relations dependent on NaOH concentration and base composition. The AT in 7 M and 10 M enables to obtain the HAp layer, which can be characterized as the most developed in terms of thickness and porosity. Finally, selected coated samples were investigated in terms of surface wettability test managed in time relation, which for the results confirm high hydrophilicity of the surfaces. Conducted research shows that the low-temperature hydrothermal processing could be considered for a possible adaptation in the drug encapsulation and delivery systems.

Composite and Surface Functionalization of Ultrafine-Grained Ti23Zr25Nb Alloy for Medical Applications.

In this study, the ultrafine-grained Ti23Zr25Nb-based composites with 45S5 Bioglass and Ag, Cu, or Zn additions were produced by application of the mechanical alloying technique. Additionally, the base Ti23Zr25Nb alloy was electrochemically modified in the two stages of processing: electrochemical etching in the solution of H3PO4 and HF followed by electrochemical deposition in Ca(NO3)2, (NH4)2HPO4, and HCl. The in vitro cytocompatibility studies were also done with comparison to the commercially pure titanium. The established cell lines of Normal Human Osteoblasts (NHost, CC-2538) and Human Periodontal Ligament Fibroblasts (HPdLF, CC-7049) were used. The culture was conducted among the tested materials. Ultrafine-grained titanium-based composites modified with 45S5 Bioglass and Ag, Cu, or Zn metals have higher biocompatibility than the reference material in the form of a microcrystalline Ti. Proliferation activity was at a stable level with contact with studied materials. In vitro evaluation research showed that the ultrafine-grained Ti23Zr25Nb-based composites with 45S5 Bioglass and Ag, Cu, or Zn additions, with a Young modulus below 50 GPa, can be further used in the biomedical field.

Crystal Structure Evolution, Microstructure Formation, and Properties of Mechanically Alloyed Ultrafine-Grained Ti-Zr-Nb Alloys at 36≤Ti≤70 (at. %).

Titanium ß-type alloys are preferred biomaterials for hard tissue replacements due to the low Young modulus and limitation of harmful aluminum and vanadium present in the commercially available Ti6Al4V alloy. The aim of this study was to develop a new ternary Ti-Zr-Nb system at 36≤Ti≤70 (at. %). The technical viability of preparing Ti-Zr-Nb alloys by high-energy ball-milling in a SPEX 8000 mill has been studied. These materials were prepared by the combination of mechanical alloying and powder metallurgy approach with cold powder compaction and sintering. Changes in the crystal structure as a function of the milling time were investigated using X-ray diffraction. Our study has shown that mechanical alloying supported by cold pressing and sintering at the temperature below αâ†’ß transus (600°C) can be applied to synthesize single-phase, ultrafine-grained, bulk Ti(ß)-type Ti30Zr17Nb, Ti23Zr25Nb, Ti30Zr26Nb, Ti22Zr34Nb, and Ti30Zr34Nb alloys. Alloys with lower content of Zr and Nb need higher sintering temperatures to have them fully recrystallized. The properties of developed materials are also engrossing in terms of their biomedical use with Young modulus significantly lower than that of pure titanium.

Response of inflammatory cells to biodegradable ultra-fine grained Mg-based composites.

Ultra-fine grained biodegradable Mg-based Mg1Zn1Mn0.3 Zr - HA and Mg4Y5.5Dy0.5 Zr - 45S5 Bioglass composites have shown great medical potential. Two types of these Mg-based biomaterials subjected to different treatments were tested and as shown earlier they are biocompatible. The aim of the study is to determine how much culture media incubated with these ultra-fine trained Mg-based composites can cause inflammatory reactions and /or periodontal cell death. The incubation of composites in the medium releases metal ions into the solution. It can be assumed that this process is permanent and also occurs in the human body. The results have shown that the effect of proinflammatory IL-6 and TNF- cytokines results in the strongest production of the acute phase proteins in the first day on the Mg1Zn1Mn0.3 Zr-5 wt.% HA-1 wt. % Ag HF-treated biocomposite after immersion for 2 h in 40 % HF and then the fastest decrease in these processes on the third day. In turn, the inflammatory process induced on the Mg1Zn1Mn0.3 Zr-5 wt.% HA-1 wt. % Ag biomaterial, in BAX / BCL ratio assessment, is the strongest on the third day and maintains a significantly high level on the following day, which, at the same time, confirms its persistence and development. In addition, these results confirm the successively generated necrotic processes. Ions can induce inflammatory reactions, which in the case of the implant may take a long time, which results in the loss of the implant. Even if the material is biocompatible in rapid in-vitro tests, it can induce inflammation in the body after some time due to the release of ions. Not every treatment improves the material's properties in terms of subsequent safety.

Mechanical Alloying and Electrical Current-Assisted Sintering Adopted for In Situ Ti-TiB Metal Matrix Composite Processing.

In this work, mechanical alloying and electrical current-assisted sintering was adopted for in situ metal matrix composite material processing. Applied at the initial powder stage, mechanical alloying enables a homogeneous distribution of the starting elements in the proposed precursor powder blends. The accompanying precursor preparation and the structurally confirmed size reduction allow obtainment of a nanoscale range for the objects to be sintered. The nano precursors aggregated in the micro-sized particle objects, subjected to electrical current-assisted sintering, characterize the metal matrix composite sinters with high uniformity, proper densification, and compaction response, as well as maintaining a nanoscale whose occurrence was confirmed by the appearance of the highly dispersed reinforcement phase in the examined Ti-TiB material example. The structural analysis of the sinters confirms the metal matrix composite arrangement and provides an additional quantitive data overview for the comparison of the processing conditions. The mechanical alloying examined in this work and the electrical current-assisted sintering approach allow in situ metal matrix composite structures to create their properties by careful control of the processing steps.

Nanoscale size effect in in situ titanium based composites with cell viability and cytocompatibility studies.

Novel in situ Metal Matrix Nanocomposite (MMNC) materials based on titanium and boron, revealed their new properties in the nanoscale range. In situ nanocomposites, obtained through mechanical alloying and traditional powder metallurgy compaction and sintering, show obvious differences to their microstructural analogue. A unique microstructure connected with good mechanical properties reliant on the processing conditions favour the nanoscale range of results of the Ti-TiB in situ MMNC example. The data summarised in this work, support and extend the knowledge boundaries of the nanoscale size effect that influence not only the mechanical properties but also the studies on the cell viability and cytocompatibility. Prepared in the same bulk, in situ MMNC, based on titanium and boron, could be considered as a possible candidate for dental implants and other medical applications. The observed relations and research conclusions are transferable to the in situ MMNC material group. Aside from all the discussed relations, the increasing share of these composites in the ever-growing material markets, heavily depends on the attractiveness and a possible wider application of these composites as well as their operational simplicity presented in this work.

Nanostructured Titanium-10 wt% 45S5 Bioglass-Ag Composite Foams for Medical Applications.

The article presents an investigation on the effectiveness of nanostructured titanium-10 wt% 45S5 Bioglass-1 wt% Ag composite foams as a novel class of antibacterial materials for medical applications. The Ti-based composite foams were prepared by the combination of mechanical alloying and a "space-holder" sintering process. In the first step, the Ti-10 wt% 45S5 Bioglass-1 wt% Ag powder synthesized by mechanical alloying and annealing mixed with 1.0 mm diameter of saccharose crystals was finally compacted in the form of pellets. In the next step, the saccharose crystals were dissolved in water, leaving open spaces surrounded by metallic-bioceramic scaffold. The sintering of the scaffold leads to foam formation. It was found that 1:1 Ti-10 wt% 45S5 Bioglass-1 wt% Ag/sugar ratio leads to porosities of about 70% with pore diameter of about 0.3-1.1 mm. The microstructure, corrosion resistance in Ringer's solution of the produced foams were investigated. The value of the compression strength for the Ti-10 wt% 45S5 Bioglass-1 wt% Ag foam with 70% porosity was 1.5 MPa and the Young's modulus was 34 MPa. Silver modified Ti-10 wt% 45S5 Bioglass composites possess excellent antibacterial activities against Staphylococcus aureus. Porous Ti-10 wt% 45S5 Bioglass-1 wt% foam could be a possible candidate for medical implants applications.

Development of ß Type Ti23Mo-45S5 Bioglass Nanocomposites for Dental Applications.

Titanium ß-type alloys attract attention as biomaterials for dental applications. The aim of this work was the synthesis of nanostructured ß type Ti23Mo-x wt % 45S5 Bioglass (x = 0, 3 and 10) composites by mechanical alloying and powder metallurgy methods and their characterization. The crystallization of the amorphous material upon annealing led to the formation of a nanostructured ß type Ti23Mo alloy with a grain size of approximately 40 nm. With the increase of the 45S5 Bioglass contents in Ti23Mo, nanocomposite increase of the α-phase is noticeable. The electrochemical treatment in phosphoric acid electrolyte resulted in a porous surface, followed by bioactive ceramic Ca-P deposition. Corrosion resistance potentiodynamic testing in Ringer solution at 37 °C showed a positive effect of porosity and Ca-P deposition on nanostructured Ti23Mo 3 wt % 45S5 Bioglass nanocomposite. The contact angles of glycerol on the nanostructured Ti23Mo alloy were determined and show visible decrease for bulk Ti23Mo 3 wt % 45S5 Bioglass and etched Ti23Mo 3 wt % 45S5 Bioglass nanocomposites. In vitro tests culture of normal human osteoblast cells showed very good cell proliferation, colonization, and multilayering. The present study demonstrated that porous Ti23Mo 3 wt % 45S5 Bioglass nanocomposite is a promising biomaterial for bone tissue engineering.

Nanostructured nickel-free austenitic stainless steel/hydroxyapatite composites.

In this work Ni-free austenitic stainless steels with nanostructure and their nanocomposites with hydroxyapatite are presented and characterized by means of X-ray diffraction and optical profiling. The samples were synthesized by mechanical alloying, heat treatment and nitriding of elemental microcrystalline powders with addition of hydroxyapatite (HA). In our work we wanted to introduce into stainless steel hydroxyapatite ceramics that have been intensively studied for bone repair and replacement applications. Such applications were chosen because of their high biocompatibility and ability to bond to bone. Since nickel-free austenitic stainless steels seem to have better mechanical properties, corrosion resistance and biocompatibility compared to 316L stainless steels, it is possible that composite made of this steel and HA could improve properties, as well. Mechanical alloying and nitriding are very effective technologies to improve the corrosion resistance of stainless steel. Similar process in case of nanocomposites of stainless steel with hydroxyapatite helps achieve even better mechanical properties and corrosion resistance. Hence nanocrystalline nickel-free stainless steels and nickel-free stainless steel/hydroxyapatite nanocomposites could be promising bionanomaterials for use as a hard tissue replacement implants, e.g., orthopedic implants. In such application, the surface roughness and more specifically the surface topography influences the proliferation of cells (e.g., osteoblasts).