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•Ti(IV) similarity to Fe(III) hints towards its function and storage in humans.•Ti(IV) can inhibit intracellular Fe bioavailability and function.•Properties of in vitro ligands of Ti ...important in identifying in vivo ligands.•Redox, structural, growth, and antibacterial functions proposed for Ti.•Better tools are needed to decipher the in vivo fate of Ti(IV)
Despite its natural abundance and widespread use as food, paint additive, and in bone implants, no specific biological function of titanium is known in the human body. High concentrations of Ti(IV) could result in cellular toxicity, however, the absence of Ti toxicity in the blood of patients with titanium bone implants indicates the presence of one or more biological mechanisms to mitigate toxicity. Similar to Fe(III), Ti(IV) in blood binds to the iron transport protein serum transferrin (sTf), which gives credence to the possibility of its cellular uptake mechanism by transferrin-directed endocytosis. However, once inside the cell, how sTf bound Ti(IV) is released into the cytoplasm, utilized, or stored remain largely unknown. To explain the molecular mechanisms involved in Ti use in cells we have drawn parallels with those for Fe(III). Based on its chemical similarities with Fe(III), we compare the biological coordination chemistry of Fe(III) and Ti(IV) and hypothesize that Ti(IV) can bind to similar intracellular biomolecules. The comparable ligand affinity profiles suggest that at high Ti(IV) concentrations, Ti(IV) could compete with Fe(III) to bind to biomolecules and would inhibit Fe bioavailability. At the typical Ti concentrations in the body, Ti might exist as a labile pool of Ti(IV) in cells, similar to Fe. Ti could exhibit different types of properties that would determine its cellular functions. We predict some of these functions to mimic those of Fe in the cell and others to be specific to Ti. Bone and cellular speciation and localization studies hint toward various intracellular targets of Ti like phosphoproteins, DNA, ribonucleotide reductase, and ferritin. However, to decipher the exact mechanisms of how Ti might mediate these roles, development of innovative and more sensitive methods are required to track this difficult to trace metal in vivo.
Reducible supports can affect the performance of metal catalysts by the formation of suboxide overlayers upon reduction, a process referred to as the strong metal-support interaction (SMSI). A ...combination of operando electron microscopy and vibrational spectroscopy revealed that thin TiO
overlayers formed on nickel/titanium dioxide catalysts during 400°C reduction were completely removed under carbon dioxide hydrogenation conditions. Conversely, after 600°C reduction, exposure to carbon dioxide hydrogenation reaction conditions led to only partial reexposure of nickel, forming interfacial sites in contact with TiO
and favoring carbon-carbon coupling by providing a carbon species reservoir. Our findings challenge the conventional understanding of SMSIs and call for more-detailed operando investigations of nanocatalysts at the single-particle level to revisit static models of structure-activity relationships.
Sodium-ion storage technologies are promising candidates for large-scale grid systems due to the abundance and low cost of sodium. However, compared to well-understood lithium-ion storage mechanisms, ...sodium-ion storage remains relatively unexplored. Herein, we systematically determine the sodium-ion storage properties of anatase titanium dioxide (TiO
(A)). During the initial sodiation process, a thin surface layer (~3 to 5 nm) of crystalline TiO
(A) becomes amorphous but still undergoes Ti
/Ti
redox reactions. A model explaining the role of the amorphous layer and the dependence of the specific capacity on the size of TiO
(A) nanoparticles is proposed. Amorphous nanoparticles of ~10 nm seem to be optimum in terms of achieving high specific capacity, on the order of 200 mAh g
, at high charge/discharge rates. Kinetic studies of TiO
(A) nanoparticles indicate that sodium-ion storage is due to a surface-redox mechanism that is not dependent on nanoparticle size in contrast to the lithiation of TiO
(A) which is a diffusion-limited intercalation process. The surface-redox properties of TiO
(A) result in excellent rate capability, cycling stability and low overpotentials. Moreover, tailoring the surface-redox mechanism enables thick electrodes of TiO
(A) to retain high rate properties, and represents a promising direction for high-power sodium-ion storage.
TiAl alloys are lightweight, show decent corrosion resistance and have good mechanical properties at elevated temperatures, making them appealing for high-temperature applications. However, ...polysynthetic twinned TiAl single crystals fabricated by crystal-seeding methods face substantial challenges, and their service temperatures cannot be raised further. Here we report that Ti-45Al-8Nb single crystals with controlled lamellar orientations can be fabricated by directional solidification without the use of complex seeding methods. Samples with 0° lamellar orientation exhibit an average room temperature tensile ductility of 6.9% and a yield strength of 708 MPa, with a failure strength of 978 MPa due to the formation of extensive nanotwins during plastic deformation. At 900 °C yield strength remains high at 637 MPa, with 8.1% ductility and superior creep resistance. Thus, this TiAl single-crystal alloy could provide expanded opportunities for higher-temperature applications, such as in aeronautics and aerospace.
Titanium oxide nanoparticles were doped with copper and characterized by XRD, FT‐IR, TEM, and SEM. The surface morphology was spherical with 15–26 nm as particle size. The doped titanium oxide ...(Co/TiO2) nanomaterial was used for photodegradation of amido black dye in water. The maximum photodegradation of amido black obtained was 90%. The values of free energy and enthalpy were negative, indicating spontaneous photodegradation of amido black dye. The photodegradation of amido black dye obeyed first‐order kinetic model. The photodegradation mechanism of amido black involved adsorption of the dye on the surface of cobalt doped titanium oxide and its degradation under UV radiation. The electron (e−) and hole (h+) pairs were generated by Co/TiO2, which consequently generated superoxide oxygen anion and hydroxyl free radical. These species degraded amido black dye. The reported method was fast, effective, and economic, which may be utilized to remove amido black in water. The doped TiO2 catalyst was quite stable and can be used up to 5 cycles.
The cobalt doped TiO2 (Co/TiO2) nanoparticles were prepared and characterized for photodegradation of amido black dye in water. The thermodynamics and kinetics studies of photodegradation were carried out. The intelligent artificial neural network modeling of amido black photodegradation was carried out. The photo‐degradation of amido black dye in water is fast, economic, and ecofriendly.
Abstract Heterogeneous catalysts play a pivotal role in the chemical industry. The strong metal-support interaction (SMSI), which affects the catalytic activity, is a phenomenon researched for ...decades. However, detailed mechanistic understanding on real catalytic systems is lacking. Here, this surface phenomenon was studied on an actual platinum-titania catalyst by state-of-the-art in situ electron microscopy, in situ X-ray photoemission spectroscopy and in situ X-ray diffraction, aided by density functional theory calculations, providing a novel real time view on how the phenomenon occurs. The migration of reduced titanium oxide, limited in thickness, and the formation of an alloy are competing mechanisms during high temperature reduction. Subsequent exposure to oxygen segregates the titanium from the alloy, and a thicker titania overlayer forms. This role of oxygen in the formation process and stabilization of the overlayer was not recognized before. It provides new application potential in catalysis and materials science.
Category:
Hindfoot
Introduction/Purpose:
Lateral column lengthening (LCL) is a common procedure for reconstruction of stage II flexible adult acquired flatfoot deformity (AAFD). The recent ...development of porous titanium wedges for this procedure provides an alternative to allograft and autograft. The purpose of this study was to report radiographic and clinical outcomes achieved with porous titanium wedges in LCL.
Methods:
A retrospective analysis of 34 feet in 30 patients with AAFD that received porous titanium wedges for LCL from January 2011 – October 2014. Deformity correction was assessed using both radiographic and clinical parameters. Radiographic correction was assessed using the lateral talo-first metatarsal angle, the talonavicular uncoverage percentage, and the first metatarsocuneiform height. The hindfoot valgus angle was also obtained.
Results:
Patients were followed from a minimum of six months up to 48 months (mean 16.1 months). Patients underwent concomitant procedures including medial displacement calcaneal osteotomy (94.1%), flexor digitorum longus transfer (70.6%), posterior tibial tendon tenolysis (64.7%), gastrocnemius recession (20.6%), and cotton osteotomy (4.9%). Postoperative radiographs demonstrated significant correction in all three radiographic criteria as well as the hindfoot valgus angle compared to their preoperative measurements. There were no cases of nonunion, no wedge migration, no infections, and no patients required removal of hardware. The most common complication was calcaneocuboid joint pain (14.7%).
Conclusion:
AAFD is a problem with various treatment modalities. Porous titanium wedges in LCL can achieve good radiographic and clinical correction of AAFD with a low rate of nonunion and other complications.
Category:
Bunion
Introduction/Purpose:
Proximal first metatarsal crescentic osteotomies are an effective means for correction of moderate to severe hallux valgus deformities. The originally described ...fixation construct included an intramedullary screw and a Kirschner wire which crossed the joint and required removal at 6 weeks. Elevation malunion of the first ray was also frequently noted postoperatively. The purpose of this study was to evaluate the outcomes of utilizing a low-profile titanium plate and screw construct for rigid fixation of proximal crescentic osteotomies.
Methods:
There were 53 patients (60 feet, 7 bilateral) with hallux valgus deformities enrolled in the study. They were all treated operatively with a proximal crescentic osteotomy and distal soft tissue correction with or without an Akin osteotomy. The crescentic osteotomy was fixed with a low-profile titanium plate and screws. Postoperatively patients were assessed at 3 months, 6 months and 1 year. Outcomes assessed included the need for hardware removal, change in elevatus of the first ray, as well as pre- and post-op VAS pain scores, radiographic evaluation, AOFAS score, MTP joint range of motion, and complications.
Results:
Of the 60 hallux valgus cases enrolled, 56 have completed their final follow-up (93%). At 1 year 55/56 patients had achieved radiographic union of their osteotomy. Nine patients had their hardware removed (16%). Range of motion at the 1st MTP joint decreased from 76.5 to 59.6 degrees. Hallux valgus angle improved from a mean of 28.8 to 9.6 degrees. The mean 1-2 intermetatarsal angle decreased from 14.1 to 6.4 degrees. Elevatus of the first ray increased from a mean of 2.5 mm pre-op to 3.2 mm (<1 mm) post-op. Mean VAS score improved from 4.43 to 0.68 (3.75 points). AOFAS score improved from 54.7 to 88.5 points. Complications included 4 superficial infections, 2 delayed wound healing cases and one DVT.
Conclusion:
Proximal crescentic metatarsal osteotomy with distal soft tissue repair is a safe and reliable method for operative treatment of hallux valgus. Utilization of a low-profile titanium plate and screw construct to rigidly fix the osteotomy yields a high rate of union and deformity correction with a low incidence of hardware removal and minimal increase in elevation of the first ray at final follow up.
•Oxidation of Ti6242S alloy at 560 °C in air follows a parabolic kinetics law.•Oxide growth and oxygen dissolution kinetics obey to parabolic laws.•Oxide scales are thin and mainly composed of rutile ...and anatase.•Nitrogen enrichment of a thin layer in the metal.•Oxygen dissolution in the metal results in lattice dilatation.
High temperature oxidation of titanium alloy Ti6242S was studied in air at 560 °C up to 10000 h. Oxidation kinetics obeys a parabolic law (kp = 8.7 × 10−15 g². cm−4.s-1). Oxygen dissolution in the metal was found to represent between 80 and 90% of the total mass gain. Thin oxide scales are mainly composed of TiO2, in top of which some alumina is present. Titanium nitride was detected as a very thin layer at the outer part of the metallic substrate. Underneath, the oxygen dissolution area was found to reach the maximum brittleness after 1000 h of oxidation.
Titanium and nickel alloys are used in the creation of components exposed to harsh and variable operating conditions. Such components include thin-walled structures with a variety of shapes created ...using milling. The driving factors behind the use of thin-walled components include the desire to reduce the weight of the structures and reduce the costs, which can sometimes be achieved by reducing the machining time. This situation necessitates, among other things, the use of new machining methods and/or better machining parameters. The available tools, geometrically designed for different strategies, allow working with similar and improved cutting parameters (increased cutting speeds or higher feed rates) without jeopardizing the necessary quality of finished products. This approach causes undesirable phenomena, such as the appearance of vibrations during machining, which adversely affect the surface quality including the surface roughness. A search is underway for cutting parameters that will minimize the vibration while meeting the quality requirements. Therefore, researching and evaluating the impact of cutting conditions are justified and common in scientific studies. In our work, we have focused on the quality characteristics of horizontal thin-walled structures from Tisub.6Alsub.4V titanium alloys obtained in the milling process. Our experiments were conducted under controlled cutting conditions at a constant value of the material removal rate (2.03 cmsup.3⁄min), while an increased value of the cut layer was used and tested for use in finishing machining. We used three different cutting tools, namely, one for general purpose machining, one for high-performance machining, and one for high-speed machining. Two strategies were adopted: adaptive face milling and adaptive cylindrical milling. The output quantities included the results of acceleration vibration amplitudes, and selected surface topography parameters of waviness (Wsub.a and Wsub.z) and roughness (Rsub.a and Rsub.z). The lowest values of the pertinent quantities were found for a sample machined with a high-performance tool using adaptive face milling. Surfaces typical of chatter vibrations were seen for all samples.
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