CP Ti Research Articles

Enhancing Antibacterial Performance and Biocompatibility of Pure Titanium by a Two-Step Electrochemical Surface Coating.

A two-step electrochemical surface treatment has been developed to modify the CP Ti surface on commercially pure titanium grade 2 (CP Ti): (1) anodic oxidation to form TiO2 nanotube precoatings loaded with silver (Ag) and (2) microarc oxidation (MAO) to produce a porous Ca-P-Ag coating in an electrolyte containing Ag, Ca, and P. One-step MAO in the same electrolyte has also been used to produce porous Ca-P-Ag coatings without anodic oxidation and preloaded Ag as a control. Surface morphologies and alloying chemistry of the two coatings were characterized by SEM, EDS, and XPS. Biocompatibility and antimicrobial properties have been evaluated by the MTT method and co-culture of Staphylococcus aureus, respectively. It is demonstrated that porous coatings with high Ag content can be achieved on the CP Ti by the two-step treatment. The optimized MAO voltage for excellent comprehensive properties of the coating is 350 V, in which a suitable chemical equilibrium between Ag, Ca, and P contents and a Ca/P ratio of 1.67 similar to HA can be obtained, and the Ag particles are in the size of less than 100 nm and embedded into the underneath of the coating surface. After being contacted with S. aureus for 1 and 7 days, the average bactericidal rates were 99.53 and 89.27% and no cytotoxicity was detected. In comparison, the one-step MAO coatings contained less Ag, had a lower Ca/P ratio, and showed lower antimicrobial ability than the two-step treated samples.

Characterization of titanium powders processed in n-hexane by high-energy ball milling

The effect of speed and milling time on the morphology, crystallite size, and phase composition of Ti Cp powders processed in n-hexane by high-energy ball milling (HEBM) using a E-max Retsch equipment was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Lattice parameters, mean crystallite size, lattice strain, and dislocation density were obtained from Rietveld analysis. The XRD and TEM results show that the HEBM process of the Ti Cp promotes the transition from HCP to FCC after 6 h of milling at 1400 rpm. The transformation process could be attributed to the energy generated in the milling process which induces high deformation and presence of high-density dislocations in the powder. Graphical Abstract

Sintering behavior and alloying elements effects on the properties of CP-Titanium sintered using pulsed electric current

Mechanical properties of grade 1 commercially pure titanium (CP–Ti) are characterized by a good combination of strength and ductility at elevated temperatures. CP-Ti mechanical properties at room and elevated temperature can be enhanced by alloying with other elements to meet up with its demand for industrial applications. In this study, the effect of Al–Mo addition and sintering temperature on the densification, microstructure, and mechanical properties of spark plasma sintered CP-Ti compacts were investigated. CP-Ti and Ti–7Al–1Mo (wt.%) compacts sintering were carried out at a constant holding time of 10 min, pressure of 50 MPa and sintering temperature of 800 °C, 1000 °C, and 1100 °C under vacuum. Full densification with Vickers hardness values of 352 ± 17 H V was obtained for the developed Ti–7Al–1Mo alloy at 1000 °C. Different microstructural transformations and phase evolution were observed in the as-sintered compact with respect to sintering temperature. The role of the alloying element and sintering temperature on the relative density, microstructure, hardness, and wear of the as-sintered samples were discussed. This paper shows that alloying of CP-Ti with Al and Mo enhances its microstructure and mechanical properties.

Influence of Annealing Temperature on Corrosion Resistance of TiO2 Nanotubes Grown on Ti–30Ta Alloy

With little success, researchers has been searching for alloys with elements such as tantalum to improve the long-term life of implants. The Ti–30Ta alloy presents an elastic modulus E = 69 GPa that is close to that of bone (E = 17–25 GPa) than Ti cp (E = 105 GPa). In addition, nanostructure surface modification influences cell behavior and antimicrobial activity. So, this study investigates the corrosion behavior of surface modification by TiO2 nanotube grown on Ti–30Ta alloy after anodization process in the electrolyte glycerol + NH4F 0.25% at 30 V, for nine hours without annealing and annealed in 450 °C, 530 °C and 600 °C (5 °C/min). The electrochemical behavior was evaluated by three electrodes cell. The counter-electrode of graphite, reference-electrode of saturated calomel electrode and working-electrode at electrolyte of 0.15 M NaCl + 0.03 M NaF, with pH = 6 for 8000 s. The scanned region ranged from −0.8 V to values up to 3.5 V with a sweep rate 0.166 mV/s. Potentiodynamic polarization curves were obtained with a potentiostat. The sample was characterized by scanning electron microscopy (SEM) imaging, X-ray diffraction analysis (XRD) and wettability with a contact angle goniometer. We concludes from the obtained results that all treatment surfaces are hydrophilic (<90°). The surface covered with TiO2 nanotube crystallinity showed anatase phase after annealing at 450 °C, 530 °C and 600 °C; the exceptions were the anodized-without-annealing treatment and without-surface-modification alloys. The electrochemical behavior of the five groups investigated showed similar high resistance to corrosion solution under all conditions.

Production of Ultrafine-Grained Titanium with Suitable Properties for Dental Implant Applications by RS-ECAP Process

The only problem of pure titanium for dental implant applications is its low strength and failure under different loadings. Various studies have shown that the utilization of severe plastic deformation processes such as Equal Channel Angular Pressing (ECAP), through reducing the grain size of titanium, can improve not only its mechanical properties but also its corrosion resistance and biocompatibility. In this study, a reduced-scale ECAP process on pure titanium was performed to investigate the effects of scale reduction. An ECAP die was made with an internal diameter of d = 3 mm, and the tests were performed at 250 °C for several number of passes. It was found out that after 10 passes of reduced-scale ECAP, the grain size of CP Ti had strongly been reduced from 25 to 122 nm. This sharp reduction in grain size resulted in an increase in micro-hardness from 205.5 to 321.3 Hv. Moreover, Nano-hardness test results showed that after 10 passes, the hardness of titanium increased from 2461 to 3812 MPa, and simultaneously elastic modulus decreased from 108.1 to 94.8 GPa. Such reduction of elastic modulus of titanium for dental implant applications decreased stress-shielding and jaw bone damages. According to the results of this research, after RS-ECAP process the strength of titanium is greatly increased and its elastic modulus is reduced, which are desirable features for dental implant applications. Since dental implants are small in size, the reduced ECAP process (d = 3–5 mm) can produce titanium implants with improved properties.

Comparative analysis of a human tooth using different materials based on the finite element method

This study deals with the biomechanical analysis of a human tooth using Finite Element Method (FEM). For the analysis, a three-dimensional (3D) CAD model of the human tooth is modelled from the online available tooth scanning data in dicom format, which is processed using ITK-Snap and Meshlab software to generate a file in iges format. The tooth’s CAD model in iges format is imported in a FEM based software called Ansys. The analysis is performed using five materials namely, natural tooth material, Gold, Zirconia, Commercially Pure Titanium (CP Ti) alloy, and Ceramics. All the five considered materials are analysed for the same boundary and compressive loading conditions. The resulting stresses and deformations are compared for the different considered materials.

Microstructural Evolution and Mechanical Properties of Ultrafine‐Grained Ti Fabricated by Cryorolling and Subsequent Annealing

Ultrafine‐grained (UFG) commercial purity titanium (CP Ti) has a significant potential for use in medical implants and aerospace structural parts. Herein, UFG CP Ti sheets are processed by cryorolling and room‐temperature rolling (RTR), respectively, followed by annealing for 1 h at temperatures from 250 to 350 °C. The grain size is reduced from ≈75 μm to ≈85 and ≈220 nm after cryorolling and RTR, respectively. The results show that the curves of tensile stress versus engineering failure strain for samples subjected to cryorolling and subsequent annealing are above those for samples subjected to RTR and subsequent annealing. In addition, the curves of ultimate tensile stress × fracture elongation versus grain size after cryorolling and annealing are above those for RTR and annealing. It is demonstrated that a combination of cryorolling and annealing leads to improved toughness compared with the processing by RTR and annealing.

In situ micro gas tungsten constricted arc welding of ultra-thin walled 2.275 mm outer diameter grade 2 commercially pure titanium tubing

Ultra-thin walled cooling tubes for heat exchangers and condenser units have applications in multiple high-value manufacturing industries. Grade 2 commercially pure titanium (CP-2 Ti) requires far less mass to achieve the same mass flow handling abilities as stainless steel tubing yet it is more challenging to join, particularly at wall thicknesses less than 500 μm (termed ultra-thin walled tube). This paper presents a single-pass joinery method that produces reliable welds on 2.275 mm outer diameter (OD), 160 ± 10 μm wall thickness tubing with a service life of 20 of more years. This is achieved through an automated orbital gas tungsten constricted arc welding (GTCAW) process incorporating enveloping low-mass sleeves used in tandem with a buttressing internal gas pressure to support the molten metal and maintain consistent internal diameter inside the tube. The industrial applicability is demonstrated through the production of a 1:1 scale mock-up of a fixed geometry CO2 cooling circuit for a next-generation particle detector. The tensile strengths of the joints, 403.8 ± 4.2 MPa, exceed the tensile strength of the parent CP-2 Ti.

RETRACTED: Hybridisation of microstructures from three classes of titanium alloys

A ternary hybrid Ti alloy (HYTA) was produced by selective laser melting (SLM), combining all three classes of the titanium system. The hybridisation of the α CP Ti, α-β Ti-64 and β Ti-5553 gave rise to a highly heterogeneous microstructure encompassing all the possible phases and structures which do not co-exist in conventional monolithic Ti alloys. The details of the complex microstructure were comprehensively characterised, revealing the roles played by such important factors as the distribution of the ingredient alloy particles, the Marangoni convection and diffusion of solute during melting, and microsegregation of solute during solidification. The ternary HYTA exhibited an excellent combination of high tensile yield strength of 1000 MPa and enhanced ductility with uniform elongation of ∼15% and total elongation of ∼20%, superior to conventional Ti alloys of various types. Such exceptional performance is attributed to the high-degree heterogeneity and the operation of most major deformation mechanisms which coordinate effectively and transfer smoothly between various parts with a wide range of hardness (4–6 GPa). The outcome has further demonstrated the potential of hybridisation of microstructures as a new strategy for future alloy development.

Influence of milling parameters on the structural and phase formation in Ti-20%Al alloy through mechanical milling

Titanium aluminides are considered the choice material for next generation propulsion systems due to their high specific strength and high temperature performance coupled with good oxidation resistance. They are considered best materials for specific applications in the aerospace and automobile industry. Their production process, however, determines the final phase in the alloy, which greatly affects their mechanical properties. The effect of the milling parameters on the particle size and the formation of phases were studied on mechanically alloyed Ti-Al powder. A high-energy ball mill (HEBM) was used to mill a mixture of CP Ti and Al to produce titanium aluminide. The alloy was produced at a fixed ball-to-powder weight ratio of 10:1 whilst varying the milling speed and milling time. The mechanically produced powders were analysed using SEM with EDX and XRD to investigate the chemical homogeneity and the formation of phases after the mechanical alloying technique. The analysis of the mechanically alloyed powders from the mill are reported in terms of the morphology evolution during different milling speed, milling time, elemental composition and the phases formed. Alloys milled at a speed of 500 rpm for a milling time range of 5–20 h revealed the formation of Ti alpha (α-Ti) and gamma phase (γ-TiAl).

Stress-strain state and structure of pure copper and Grade 4 titanium after free bending

This paper investigates the stress-strain state and the features of structural transformation in materials with different types of crystalline lattices in the process of deformation by free bending of axis-symmetrical billets. As the materials for the study, we selected oxygen-free M00B Cu and Grade 4 CP Ti. Using mathematical modeling, we study the stress-strain state of the samples from the selected materials in the process of bending via different routes. We study the structure in the mesoscale and determine the features of structural transformation. It is found that in the process of bending of Cu, a refined surface layer with a thickness of 20-30 μm and a cell size of ≈1 μm forms already after 1 processing cycle. In the process of bending of Ti, twinning occurs in peripheral regions, and the efficiency of twinning via route C is higher than that via route A. The most efficient, in terms of strengthening, processing routes of bending are determined.

Texture Evolution Behavior and Its Triggered Mechanical Anisotropy of CP Ti During Severe Cold Rolling and Subsequent Annealing

The texture evolution behavior and its triggered mechanical anisotropy of commercially pure titanium (CP Ti) during severe cold rolling and subsequent annealing are discussed based on the optical microscopy and the electron backscattered diffraction analyses. Some enlightening results are found. It is shown that planar textures exist under all treatments, namely the {11–29}<10–10> under rolling state, the {11–27}<10–10> under 300 °C annealing state and the {11–24}<10–10> under 500 °C annealing state. This indicates that the crystal plane indices of planar texture change toward {− 12–10} with increasing annealing temperature, which is a result of crystal lattice rotation. Planar texture triggers anisotropy of the mechanical properties for CP Ti sheets under all treatments. In particular, CP Ti sheets exhibit severe and similar anisotropy behavior under rolling and 300 °C annealing states. Generally speaking, the rolling direction (RD) specimens get relatively low yield strength, high ultimate tensile strength and good plasticity, and RD + 45° specimens show relatively high yield strength, low ultimate tensile strength and good plasticity. The transverse direction specimens, however, usually exhibit high yield strength and low plasticity. It is proved that the above anisotropy behavior is mainly determined by the Schmid factor distribution of the (10–10)[11–20] prismatic slip system in different directions. Due to the non-negligible influence exerted by the (0001)[11–20] basal slip system after 500 °C annealing, the anisotropy behavior under this state is obviously different.

Effect of Electrolyte Temperature and Anodization Time on Formation of TiO2 Nanotubes for Biomedical Applications

We have investigated the formation of self-organized titanium oxide nanotube layers by anodic oxidation on titanium alloys in electrolyte solutions with different temperatures (5, 10, 25, 30, 50 and 70 °C). Pore diameter and the wall thickness of nanotube arrays were controlled by varying anodization time and temperature. We have observed significant outcomes in the formation of TiO2 nanotube arrays at 25 °C with an average inner pore diameter of 125 nm, length of ∼250 nm, the wall thickness of 30 nm and an inter-tube space 35 nm. Nanotube arrays were smooth and circular without any defect in morphology. In addition, anodization of Commercially Pure Titanium (CP Ti) and titanium alloys (Ti-6Al-4 V, Ti-6Al-7Nb, Ti-13Nb-13Zr, and β-21 s) was carried out at optimized parameter to understand their significance on TiO2 nanotube arrays formation.

Mechanism of TiC formation in laser surface treatment of the commercial pure titanium pre-coated by carbon using PVD process

The physical evaporation deposition (PVD) and titanium (CP–Ti) plate. The influence of area scanning speed on the structure of coating were studied by changing the laser working distances and Nd:YAG laser traveling speeds. Scanning electron microscopy (SEM) and also field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive spectroscopy (EDS) were utilized to investigate the samples. The structure of produced coating mainly was affected by area scanning speed. At area scanning speeds lower than 7.5 mm2/s, one layer low TiC composite was produced due to the formation of deep melt pool with long melting time. One layer high TiC composite formed at area scanning speeds higher than 20 mm2/s as a result of shallow melt pool. Between theses values, two layers coating consisting of high and low TiC composite was obtained because the melt pool was relatively large and the required melting time for homogenization was not provided. The micro-hardness measurements showed that, the highest hardness (up to 6 times higher than the substrate) was obtained when two layers coating were synthesized. The dry sliding wear test demonstrated 62–93% reduction in the mass losses and wear rates in the two layers coatings. The average friction coefficient of the two layers coating reduced about 77%.

Thermal analysis and morphology of the ball-milled Ti-Ni powder

The initially spherical titanium (Ti) powder particles were flattened to ‘pan-cake” shape during Ball milling (BM) of the Ti-Ni powder mixture. Ultrafine Ni particles coated the pancakes of Ti particles after the final milling process of 8 h (h). The XRD patterns of the milled TiNi powders did not show obvious alloying. However, analysis of the (1 1 1) planes revealed a slight shifting on peak positioning which is attributable to powder deformation. Thermal analysis of unmilled Ti50Ni powder exposed the Ni Curie point at ∼353 °C. The normal α → β phase transformation in CP Ti was suppressed due to the presence of Ni powder. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the milled and annealed powders.

Sintering of titanium in argon and vacuum: Pore evolution and mechanical properties

Reducing porosity can help to improve the mechanical properties of an as-sintered material. An alternative is, however, to tailor the size, distribution and morphology of the residual pores without having to further reduce porosity. This study investigates the sintering of commercially pure titanium (CP Ti) in a flowing argon (Ar) atmosphere and compares the results with sintering in a vacuum of 10−2 Pa. The CP Ti sintered in Ar at 1300 °C for 2–3 h exhibited a marginally lower density but clearly better tensile ductility than Ti sintered in vacuum. The sensitivity of tensile ductility to residual pores was analyzed. Samples sintered in Ar exhibited much lower sensitivity than those sintered in vacuum. The superior ductility arises from the beneficial effect of sintering in Ar, which resulted in a greater number of but smaller residual pores with lower pore aspect ratios and finer matrix grains due to the grain-growth inhibiting role of the residual pores. The reason is attributed to the entrapped Ar in the closed pores during sintering, which is insoluble in Ti at the sintering temperature. The ever-increasing internal pore pressure prevents further pore shrinkage after reaching a critical size. The final pore size range is predicted and compared with experimental observations. Sintering of titanium in Ar is advantageous over sintering in vacuum in terms of both pore size distribution and pore morphology within a reasonable isothermal sintering period (e.g., 3 h at 1300 °C). Therefore, it can be more attractive for non-fatigue critical applications than sintering in vacuum.

Investigation of formability of metallic bipolar plates via stamping for light-weight PEM fuel cells

Bipolar plates (BPs) are one of the main members which constitute a significant percentage of a fuel cell system in terms of cost, weight and structural strength. Although frequently used graphite BPs have low density, high conductivity and corrosion resistance, machining the desired flow channels on the graphite plates is an important issue. On the other hand, metallic BPs can be considered a reasonable alternative material to graphite in the view of the material cost, fabrication of flow channels and some post-processes in which the large-scale manufacturing of graphite BPs is more complex compared to cutting and stamping processes for metal ones. This study offers a comparison of the formability of four different metals with four flow channel depths as bipolar plates formed by stamping. 304 Stainless Steel (SS 304), pure Titanium - Grade2 (CP–Ti) and Aliminium (Al 6016 and Al 3104) are chosen as the BP materials. A serpentine type flow channel with two different channel widths are formed on to 0.1 mm thick sheets. The channel width is chosen as 1.2 mm and 1.8 mm for the channel depths of 0.36 mm–0.55 mm, and 0.54 mm–0.82 mm, respectively. The stamping processes of the BPs materials are simulated via commercially available eta/Dynaform v5.9.4. software and formability characteristics are obtained for sixteen various cases. As a result, it is determined that SS 304 is the more appropriate material in the view of the formability for such a complex form.

A comparative study of cell growth on a cold sprayed Ti–Ta composite

This study aims to explore the biocompatibility and cell growth of a Ti–Ta composite coating made from solid state cold spraying deposition. Unlike the traditional Ti–Ta alloy structures, cold spray additive manufacturing provides an opportunity to create intimate contact between Ti and Ta free of phase transformation. Experimental results of a comparative study to determine successful cell growth on as sprayed and polished Ti–Ta composite were presented. In particular, improved cell propagation on composite Ti–Ta was observed compared to the wrought CP Ti (reference material) which perhaps related to the surface potential variation resulting from the intimate contact between Ti and Ta through cold spraying. Outcomes of this study, for example, could potentially benefit osseointegrity by understanding the relationship between coupling of biocompatible materials and the mechanism that encourages cell growth.

Material optimization for femur bone implants based on vibration analysis

The aim of this study is to carry out vibration analysis based on finite element technique. Both end fix and both end free conditions are taken as boundary conditions. Three-dimensional CAD model of femur bone is created using MRI and CT-Scan data by utilizing ITK-Snap freeware. Vibration pattern for first six modes were studied on ANSYS 19. Two materials, magnesium alloy (AZ31) and Commercially Pure Titanium alloy (CP Ti) along with natural bone are considered for analysis. The mode shapes show that the natural frequency of AZ31 is closer to the natural frequency of natural bone than that of CP Ti. Moreover, weight of natural bone is 1.28 Kgs, that of AZ31 is 1.14 and of CP Ti is 2.89 Kgs. AZ31 is lighter than natural bone and can be concluded as best suited material for artificial bone implants rather than CP Ti. Biomechanical analysis of AZ31 femur implant is carried out for daily life activities such as standing, walking and jumping. Femur head is kept fixed whereas loading is done at knee joint. The maximum stress and maximum deformation generated for standing, walking and jumping condition are 36.4 MPa, 38.7 MPa and 43.9 MPa and 0.296 mm, 0.316 mm and 0.357 mm respectively.

Corrosion behavior of implant coated with different biocompatible material

Aim: implant ology in oral cavity provide a reliable and rather safer solution to replacing missing teeth The aim was to evaluate the corrosion behavior of commercially pure titanium implant samples without coating and with hydroxyapatite, mixture of strontium and hydroxyapatite and titanium oxide and comparison between them through electrochemical polarization tests in 37 0 C Hank's solution. Materials and methods: coating commercially pure titanium implant by Electrophoretic deposition technique (EPD) with three types of the coating materials (HA, Tio2 and mixture of 50% HA and 50% Sr) and fourth group without coating. The sample exposed to Hank's solution prepared in the laboratory electrochemical corrosion test was done when polarization potential, corrosion rate and the open circuit potential of the samples were measured. Results: The corrosion rate indicated that is significantly higher for uncoated Cp Ti. The three types of coating significantly reduced the corrosion rate in compared Cp Ti while the sample coated with TiO2 has the minimum corrosion (1.709 × 10-3 mm/y) rate. Conclusions: the corrosion rate of Cp Ti coating significantly decreased, the best coating to reduce corrosion of implant is titanium oxide coating. Clinical significance: Resistance to corrosion is critically important for dental materials because corrosion can lead to roughening of the surface, weakening of the restoration, liberation of elements from the metal or alloy, and toxic reactions. Coating might have potential in reduction corrosion dental implant. Further studies to improve surface characteristics of implant are recommended.