Titanium Metal Substrate Research Articles

Investigation of structure, morphology, and corrosion behavior of carboxylic acids/hydroxyapatite/chitosan coatings on Ti discs for implants

Titanium (Ti) and its alloys are widely used in bone defect repair owing to their advantages, including high strength, corrosion resistance, and biocompatibility. The formation of a stable oxide layer on Ti implants enhances the osseointegration process. Nevertheless, additional progress is required to improve the incorporation of these implants at the microscopic and nanoscopic levels to achieve a biocompatible interface. The main objective of this study was to enhance the morphology of hydroxyapatite and the corrosion resistance of Ti implants by applying hydroxyapatite/chitosan (HA/Cs) nanocomposite coatings embedded with carboxylic acids. The coatings were fabricated by electrodeposition, wherein various acid concentrations (acrylic and acetic acids) were employed as Cs electrolyte solvents to enhance the adhesion and bond strength with the titanium metal substrate. The microstructures of the HA/Cs coatings were analyzed using X-ray diffraction. The results demonstrated that the structure of HA was affected by the type of acid used and its concentration as the crystallinity increased with a high concentration of acrylic acid. Additionally, the morphology of HA/Cs was analyzed using a transmission electron microscope. The results showed that the morphology of HA/Cs changed from a hexagonal rod-like shape with acrylic acid samples into a needle-like shape in acetic acid samples. The corrosion behavior was investigated using electrochemical impedance spectroscopy (EIS) in a simulated body fluid (SBF) at 37±2ºC. The EIS results showed a high corrosion resistance with phase angles close to −80° and high impedance values of 80.5 kΩ cm2 with a high concentration of acrylic acid. These results indicated the formation of a highly adhesive and stable film on the implants in the test solution. In conclusion, based on this study and our previous work, the corrosion resistance, good biocompatibility, and biomineralization properties of the prepared HA/Cs-coated Ti recommend it as an alternative implant for clinical applications.

Construction of Z-scheme MnCo2O4/Sn3O4 heterostructured photoanodes with enhanced photoelectrocatalytic degradation of reactive brilliant blue KN-R

Rapid and efficient handling of the printing and dyeing wastewater benefits environmental conservation. Photoelectrocatalysis (PEC) technology is a novel method used to mineralize large molecules of non-degradable organic dye molecules in water completely into small molecules in recent years. By generating intermediate reactive species (e.g., superoxide radicals and hydroxyl radicals) during the processing, the products of PEC technology are cleaner and pollution-free, making it a desirable environment-friendly approach. In this work, a composite semiconductor material with Z-Scheme heterostructure was constructed as a photoanode to promote the generation of intermediate reactive radicals for the efficient degradation of organic dyestuff wastewater. A series of composite materials with Sn3O4 nanosheets decorated spinel-type MnCo2O4 nanorods were synthesized through a simple two-step hydrothermal process on the titanium metal substrate. The degradation reaction cell was assembled with these Ti/MnCo2O4-Sn3O4 photoanodes, and the PEC approach was used to decolorize the reactive brilliant blue KN-R. The synthesized photoelectrode exhibited a large electroactive region, low charge transfer resistance, high hydroxyl radical generation efficiency, and excellent PEC activity. The optimal composite photoanode presented 86.4 % reactive brilliant blue KN-R removal in 2 h and practical stability in 5 circulation tests. The mechanism during the PEC process was also analyzed and discussed on the basis of radical trapping experiments. In this work, MnCo2O4-Sn3O4 materials possessing Z-scheme heterojunction were constructed, providing insight into the techniques for catalytic purification of organic wastewater.

Active Area of Anodic TiO2 Nanotube Arrays in Photo and Electrochemical Energy Storage Devices

The anodic TiO2 nanotube (TNT) has been promising as both electrocatalysts in electro-energy synthesis and storage devices, and photoelectrocatalysts in solar energy conversion and storage devices. The active area of the (photo)electrocatalyst materials must be clarified because the current density can be normalized to an electrochemically active surface area. Herein, it is discussed whether the active area of anodic TNT electrodes in photo- and electrochemicial energy storage devices reported clearness. In literature, the sizes of the titanium (Ti) metal substrate, the anodic TNT, and the active area of the electrode have been misunderstood in different applications. Clarifying the three sizes, Ti metal substrate, TNT array, and active area, with respect to the Ti substrate shapes in different device applications is important in both academic research and commercialization due to the scale-up size effect.

Effect of annealing temperature and atmosphere on the structural, morphological and luminescent properties of TiO2 nanotubes

Titanium dioxide (TiO2) nanotubes prepared on titanium metal substrate are thermally annealed at various temperatures in nitrogen, air, oxygen and vacuum. In all annealing atmospheres, except in vacuum, the anatase phase becomes less prominent than the rutile phase for annealing temperatures above 600 °C. The anatase phase is stable above 600 °C in vacuum but does not evolve significantly up to 900 °C. The morphologies of the nanotubes tend to deteriorate with increased annealing temperature, particularly in nitrogen, air and oxygen atmospheres. However, the integrity of the nanotubes is maintained up to 900 °C in vacuum. The photoluminescence emissions suggest mainly the presence of oxygen vacancies and self-trapped excitons, with respective emission bands around 2.5 eV and 2.3 eV. The results show that the annealing temperature and atmosphere strongly influence the crystalline and optical properties of the TiO2 nanotubes.

Titanium Surface Modification for Implantable Medical Devices with Anti-Bacterial Adhesion Properties.

Pure titanium and titanium alloys are widely used in dentistry and orthopedics. However, despite their outstanding mechanical and biological properties, implant failure mainly due to post-operative infection still remains a significant concern. The possibility to develop inherent antibacterial medical devices was here investigated by covalently inserting bioactive ammonium salts onto the surface of titanium metal substrates. Titanium discs have been functionalized with quaternary ammonium salts (QASs) and with oleic acid (OA), affording the Ti-AEMAC Ti-GTMAC, Ti-AUTEAB, and Ti-OA samples, which were characterized by ATR-FTIR and SEM-EDX analyses and investigated for the roughness and hydrophilic behavior. The chemical modifications were shown to deeply affect the surface properties of the metal substrates and, as a consequence, their bio-interaction. The bacterial adhesion tests against the Gram-negative Escherichia Coli and Gram-positive Staphylococcus aureus, at 1.5 and 24 h of bacterial contact, showed good anti-adhesion activity for Ti-AUTEAB and Ti-OA samples, containing a long alkyl chain between the silicon atom and the ammonium functionality. In particular, the Ti-AUTEAB sample showed inhibition of bacteria adhesion against Escherichia Coli of about one log with respect to the other samples, after 1.5 h. The results of this study highlight the importance of chemical functionalization in addressing the antimicrobial activity of metal surfaces and could open new perspectives in the development of inherent antibacterial medical devices.

Formation of anodic TiO2 nanotube arrays with ultra-small pore size

TiO2 nanotubes prepared by anodization of titanium metal substrates are widely used as functional materials in various fields. Small pore size TiO2 nanotube arrays are demanded because of their excellent performance in applications. However, the minimum pore size of TiO2 nanotube arrays has been limited to ~15 nm (nm) despite of long time extensive studies. In the present work, we have fabricated TiO2 nanotube arrays with diameter down to an unprecedented low value of ~6 nm in ammonium fluoride-containing ethylene glycol electrolyte by a simple one-step anodic oxidation method under optimized condition. The influences of concentration of ammonium fluoride, viscosity of solution, amount of adding water and applied voltage on the anodic growth of small pore TiO2 nanotubes are studied systematically. Pore initiation and widening determined by the competition between chemical dissolution and field driven growth of anodic oxides under relative low formation field strength are investigated, where local concentration of fluoride anions and acidity near pore bottom are believed to play significant roles in the formation of nanoporous or nanotubular TiO2 with ultra-small pore diameter and cell size. By sealing the reaction cell to prevent the solution from absorbing ambient water, typical TiO2 nanotube arrays with a pore diameter of ~10.8 nm can grow up to ~1.1 μm in length, i.e. an aspect ratio up to 100, which is remarkable for TiO2 nanotubes with such small pore size.

Characteristics of Wollastonite Ceramic Coatings Obtained by Pulsed Laser Deposition

The paper aims at the synthesis and characterization of a wollastonite ceramic layer (belonging to the CaO-SiO2 system) deposited by PLD (pulsed laser deposition) method on a titanium metal substrate, in order to improve titanium biocompatibility and bioactivity. The silicate precursor mixture was synthesized by the sol–gel method. From this precursor was obtained the ceramic target by sintering at 1150 °C for 6 h. The obtained films on the titanium metal substrate were characterized by x-ray diffraction, scanning microscopy and by determination of the contact angle. Also, the materials were tested in vitro to determine the bioactivity and biocompatibility of thin films. The obtained results indicate the presence of wollastonite in films composition and a good bioactivity in the presence of cells, which suggests that this type of thin films is suitable for medical implants.

HA-hybrid matrix composite coating on Ti-Cp for biomedical application.

Calcium phosphate coatings have been applied to titanium metal substrates and their alloys as a synergistic alternative capable of combining the mechanical properties of metals and the excellent bioactive properties provided by ceramic materials. However, the unsatisfactory adhesion of hydroxyapatite coatings on metallic substrates, as well as their limitation when subjected to mechanical stresses have been reported as a limitation. Biofunctional coatings have been proposed as an alternative to single ceramic coatings, aiming at optimizing the long-term clinical success of biomaterials such as Ti. This work aims at evaluating the morphological properties and biological behavior of Ti-cp coated with matrix composite coating hydroxyapatite-containing hybrid. The hybrid matrix was obtained from TEOS and MTES silicon precursors, with dispersed hydroxyapatite suspended by dip coating. For the morphological characterization FTIR, SEM/FEG, AFM and contact angle measurement were used. Biological behavior was evaluated for toxicity, cell viability and the osteogenic differentiation capacity of mesenchymal stem cells. The composite coatings obtained showed regular dispersion of hydroxyapatite particles in the hybrid matrix, with uniform coating adhering to the Ti-Cp substrate. Nevertheless, although they provided similar viability behavior of mesenchymal stem cells to the Ti-Cp substrate, the evaluated coatings did not present osteoinductive properties. This result is probably due to the pronounced hydrophobic behavior caused by the incorporation of HA.

Characterisation of titanium oxide layers using Raman spectroscopy and optical profilometry: Influence of oxide properties

Abstract This study evaluates the use of a combination of Raman spectroscopy and optical profilometry as a surface characterisation technique for the examination of oxide layers grown on titanium metal substrates. The titanium oxide layers with thickness of up to 8 µm, were obtained using a low-pressure oxygen microwave plasma treatment of the titanium metal substrate. The effect of the microwave plasma processing conditions (input power, pressure and treatment time) on the Raman bandwidth, intensity and peak position was evaluated. Also, the effect of these processing conditions on the surface roughness parameters (Sa, Sdq, Ssk and Sku) of the oxide layers was investigated. Analysis of the peak positions of Eg and A1g modes indicated that the effects of input power and chamber pressure was to induce a shift towards the lower frequency with increasing input power and pressure (1–2 kPa). The intensity of the Raman bands was found to be dependent on the morphology and surface chemistry of the oxide layer. The intensity of Raman band (A1g), was found to be particularly influenced by the average surface roughness (Sa) and the crystallite size. Exponential and polynomial relations were found to correlate with these properties. A two-latent variable Partial Least Squares Regression model developed on Raman spectral data could predict surface roughness with a coefficient of determination (R2) of approx. 0.87 when applied to the testing of an independent set of titanium oxide test coatings.

Simple, low-cost, sensitive and label-free aptasensor for the detection of cardiac troponin I based on a gold nanoparticles modified titanium foil

This research demonstrated the electrochemical modification of low-cost titanium (Ti) metal substrate with gold nanoparticles (AuNPs) for the aptamer-based detection of cardiac troponin I (cTnI). AuNPs were deposited onto Ti sheets by the potential-step deposition method with high density and homogeneity as well as good crystallinity. It was then applied as a transducer to immobilize a thiol-functionalized DNA aptamer via the self-assembled monolayer mechanism for the specific binding of cTnI. This was verified through electrochemical and morphological analyses. The aptasensor could detect cTnI in a linear range of 1–1100 pM with a detection limit of ca. 0.18 pM. The aptasensor showed high sensitivity and specificity to cTnI over other interfering compounds with good recoveries in the diluted human serum samples.

Area selective CVD of metallic films from molybdenum, iron, and ruthenium carbonyl precursors: Use of ammonia to inhibit nucleation on oxide surfaces

The authors demonstrate that the addition of an ammonia coflow during the chemical vapor deposition of MoCxNy, Fe, or Ru thin films at ≤200 °C from the metal carbonyl precursors Mo(CO)6, Fe(CO)5, or Ru3(CO)12 affords area-selective growth: film grows readily on titanium metal or vanadium nitride substrate surfaces, but no nucleation occurs on air-exposed SiO2, TiO2, Al2O3, or MgO within the investigated times of 1–2 h. By contrast, in the absence of ammonia, nucleation and deposition on these oxide surfaces can either be slow or rapid, depending strongly on the oxide surface preparation. NH3 is also the source of N in MoCxNy, which has a resistivity of 200 μΩ cm and becomes superconducting at a critical temperature of 4 K. The authors hypothesize that the passivating effect of NH3 on oxide surfaces involves site blocking to prevent precursor adsorption, or an acid–base interaction to stabilize surface-bound metal subcarbonyl intermediates, or a combination of these mechanisms. A key finding is that surface selective growth is often crucially dependent on the sample history of the substrate, which must be specified in detail if reproducible results are to be obtained.

Electro-chemical deposition of nano hydroxyapatite-zinc coating on titanium metal substrate

BackgroundTitanium is an inert metal that does not induce osteogenesis and has no antibacterial properties; it is proposed that hydroxyapatite coating can enhance its bioactivity, while zinc can contribute to antibacterial properties and improve osseointegration.AimsA nano-sized hydroxyapatite-zinc coating was deposited on commercially pure titanium using an electro-chemical process, in order to increase its surface roughness and enhance adhesion properties.MethodsThe hydroxyapatite-zinc coating was attained using an electro-chemical deposition in a solution composed of a naturally derived calcium carbonate, di-ammonium hydrogen phosphate, with a pure zinc metal as the anode and titanium as the cathode. The applied voltage was −2.5 for 2 h at a temperature of 85 °C. The resultant coating was characterized for its surface morphology and chemical composition using a scanning electron microscope (SEM), energy dispersive x-ray spectroscope (EDS), and Fourier transform infrared (FT-IR) spectrometer. The coated specimens were also evaluated for their surface roughness and adhesion quality.ResultsHydroxyapatite-zinc coating had shown rosette-shaped, homogenous structure with nano-size distribution, as confirmed by SEM analysis. FT-IR and EDS proved that coatings are composed of hydroxyapatite (HA) and zinc. The surface roughness assessment revealed that the coating procedure had significantly increased average roughness (Ra) than the control, while the adhesive tape test demonstrated a high-quality adhesive coat with no laceration on tape removal.ConclusionsThe developed in vitro electro-chemical method can be employed for the deposition of an even thickness of nano HA-Zn adhered coatings on titanium substrate and increases its surface roughness significantly.

Influence of a silicon-bearing film on the early stage oxidation of pure titanium

Oxidation of pure titanium with and without silicon-bearing thin films was investigated using transmission electron microscopy, X-ray energy-dispersive spectroscopy, and nanoindentation to understand the initial stages of scale formation mechanisms. For pure titanium, results showed a two-layer oxide scale with dense outer and porous inner layers attributed to the simultaneous outward titanium and inward oxygen diffusion fluxes assessed through the use of a marker layer. Titanium specimens coated with Si before oxidation yielded a thinner oxide with an outer columnar scale and minimal porous inner oxide growth. These findings suggest that Si hinders oxygen transport to the oxide/metal interface, thus reducing overall oxide growth and oxygen ingress into the titanium metal substrate over short-term exposures.

Cold sprayed WO3 and TiO2 electrodes for photoelectrochemical water and methanol oxidation in renewable energy applications.

Films prepared by cold spray have potential applications as photoanodes in electrochemical water splitting and waste water purification. In the present study cold sprayed photoelectrodes produced with WO3 (active under visible light illumination) and TiO2 (active under UV illumination) on titanium metal substrates were investigated as photoanodes for the oxidation of water and methanol, respectively. Methanol was chosen as organic model pollutant in acidic electrolytes. Main advantages of the cold sprayed photoelectrodes are the improved metal-semiconductor junctions and the superior mechanical stability. Additionally, the cold spray method can be utilized as a large-scale electrode fabrication technique for photoelectrochemical applications. Incident photon to current efficiencies reveal that cold sprayed TiO2/WO3 photoanodes exhibit the best photoelectrochemical properties with regard to the water and methanol oxidation reactions in comparison with the benchmark photocatalyst Aeroxide TiO2 P25 due to more efficient harvesting of the total solar light irradiation related to their smaller band gap energies.

First-principles investigation of oxygen diffusion mechanism in -titanium crystals

How impurity atoms move through a crystal is a fundamental and renewed issue in condensed matter physics and materials science. Diffusion of oxygen (O) in titanium (Ti) affects the formation of titanium-oxides and the design of Tibased alloys. Moreover, the kinetics of initial growth of titania-nanotubes via anodization of a titanium metal substrate also involves the diffusion of oxygen. Therefore, the understanding of the migration mechanism of oxygen atoms in -Ti is extremely important for controlling oxygen diffusion in Ti alloys. In this work, we show how the diffusion coefficient can be predicted directly from first-principles studies without any empirical fitting parameters. By performing the first-principles calculations based on the density functional theory (DFT) through using the Vienna ab initio Simulation Package (VASP), we obtain three locally stable interstitial oxygen sites in the hexagonal closed-packed (hcp) lattice of titanium. These sites are octahedral center (OC) site, hexahedral center (HE) site, and TiTi bond center crowdion (CR) site with interstitial energies of -2.83, -1.61, and -1.48 eV, respectively. From the interstitial energies it follows that oxygen atom prefers to occupy the octahedral site. From electronic structure analysis, it is found that the TiO bonds possess some covalent characteristics and are strong and stable. Using the three stable O sites from our calculations, we propose seven migration pathways for oxygen diffusion in hcp Ti and quantitatively determine the transition state and diffusion barrier with the saddle point along the minimum energy diffusion path by the climbing image nudged elastic band (CI-NEB) method. The microscopic diffusion barriers (E) from the first-principles calculations are important for quantitatively describing the temperature dependent diffusion coefficients D from Arrhenius formula D = L2v* exp(-((E)/(kBT)), where v* is the jumping frequency and L is the atomic displacement of each jump. The jumping frequency v* is determined from where vi and vj are the vibration frequency of oxygen atom at the initial state and the transition state respectively. This analysis leads to the formula for calculating the temperature dependent diffusion coefficient by using the microscopic parameters (vi and E) from first-principles calculations without any fitting parameters. Using the above formula and the vibration frequencies and diffusion barriers from first-principles calculations, we calculate the diffusion coefficients among different interstitial sites. It is found that the diffusion coefficient from the octahedral center site to the available site nearby is in good agreement with the experimental result, i.e., the diffusion rate D is 1.046510-6 m2s-1 with E of 0.5310 eV. The jump from the crowdion site to the octahedral interstitial site prevails over all the other jumps, as a result of its low energy barrier and thus leading to markedly higher diffusivity values. The diffusion of oxygen atoms is mainly controlled by the jump occurring between OC and CR sites, resulting in high diffusion anisotropy. This finding of oxygen diffusion behavior in Ti provides a useful insight into the kinetics at initial stage of oxidation in Ti which is very relevant to many technological applications of Ti-based materials.

Reversible phase transition in vanadium oxide films sputtered on metal substrates

Vanadium oxide films, deposited on aluminium (Al), titanium (Ti) and tantalum (Ta) metal substrates by pulsed RF magnetron sputtering at a working pressure of 1.5 x10−2 mbar at room temperature are found to display mixed crystalline vanadium oxide phases viz., VO2, V2O3, V2O5. The films have been characterized by field-emission scanning electron microscopy, X-ray diffraction, differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy, and their thermo-optical and electrical properties have been investigated. Studies of the deposited films by DSC have revealed a reversible-phase transition found in the temperature range of 45–49 °C.

Titania nanotube arrays surface-modified with ZnO for enhanced photocatalytic applications

Well ordered titanium dioxide nanotube arrays (TNA) of average diameter 129nm and wall thickness of 25nm were fabricated through potentiostatic anodisation of titanium (Ti) metal substrates. Such TNA were subsequently surface-modified with various amounts of zinc oxide (ZnO) nanopowders using hydrothermal technique to obtain heterogeneous TNA/ZnO nanostructures. The crystalline phase and surface microstructure of the heterostructures were determined by X-ray diffraction, Raman spectroscopy and scanning electron microscopy respectively. The morphology of the heterostructures strongly depended on the hydrothermal conditions employed. The photocatalytic activity of the heterostructures have also been investigated and correlated with their surface morphology and texture.

Influence of pH Preparation on the Photo-Response of Electrodeposited Titanium Dioxide (TiO<sub>2</sub>) Thin Films

The anodic oxidation method has been used to prepare thin films of titanium dioxide (TiO2) in acid and alkaline electrolytes. The influence of pH on the structure, the morphology and the photo response of the deposited TiO2 has been evaluated by measuring the current density. The experimental results showed that the photo current response was pH dependent. The acid electrolytes being the best medium in producing stable oxide films with good adhesion to titanium metal substrate and good charging rate and current density.

Silver Nanowire Top Electrodes in Flexible Perovskite Solar Cells using Titanium Metal as Substrate.

Flexible perovskite solar cells (FPSCs) have various applications such as wearable electronic textiles and portable devices. In this work, we demonstrate FPSCs on a titanium metal substrate employing solution-processed silver nanowires (Ag NWs) as the top electrode. The Ag NW electrodes were deposited on top of the spiro-MeOTAD hole transport layer by a carefully controlled spray-coating method at moderate temperatures. The power conversion efficiency (PCE) reached 7.45 % under AM 1.5 100 mW cm(-2) illumination. Moreover, the efficiency for titanium-based FPSCs decreased only slightly (by 2.6 % of the initial value) after the devices were bent 100 times. With this and other advances, fully solution-based indium-free flexible photovoltaics, advantageous in terms of price and processing, have the potential to be scaled into commercial production.

Precipitation of bone-like apatite on anodised titanium in simulated body fluid under UV irradiation

Fabricating a photocatalytic oxide layer on biomaterial surfaces has recently attracted a great deal of attention owing to its effect in accelerating the osseointegration process. Anodic oxidation is a widely used electrochemical method to deposit ceramic coatings of photocatalytic titania on titanium metal substrates. The current study aims to investigate the effect of UV irradiation during in vitro testing on the precipitation of bone-like apatite on the anodised surface. High purity titanium foils were anodised with varying voltages (50–350 V) in a mixture of 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP) and 0.4 M calcium acetate monohydrate (CA) for 10 min. Subsequently, the anodised titanium foils were soaked in simulated body fluid (SBF) for 7 days with illumination under ultraviolet light C. The titanium foil produced using high voltage (350 V) appeared to be highly porous and demonstrated high crystallinity as well high hydrophilic properties. After soaking in SBF for 7 days, highly crystallised bone-like apatite was covered on the surface of anodised titanium. Interestingly, the smooth and partially porous surface of the anodised titanium was observed to be fully covered by the bone-like apatite layer, contradicting previous findings that smooth surfaces lack sufficient nucleation sites needed for the growth of bone-like apatite. The suggested mechanism for the formation of bone-like apatite under UV irradiation is illustrated in this article. The findings of this study indicate that UV irradiation is able to accelerate the formation of bone-like apatite on the surface of titanium.