Papers by Keyword: Ti

Abstract: In this research, smooth commercial Ti grade 2 corroded by ErCl₃.6H₂O under an electrochemical process with difference electrochemical current ranging from 0.5 – 4A, providing a rougher surface conducive to the adsorption on the Ti surface. A thin layer of TiO₂ nanotubes synthesized via the anodization method on microporous Ti surfaces for application in the biomedical field. The results reveal that the smooth titanium surface was completely corroded, resulting in the formation of a microporous structure, with a thin layer of TiO₂ successfully formed on the microporous titanium surfaces. The digital optical images obtained using digital microscope (VHX) showed that the micropore depth is around 41.94 - 55.83 µm. On the other hand, the SEM results revealed that the diameter of TiO₂ nanotubes ranged from 50 – 80 nm. The EDS and XRD techniques indicated that no impurities were present, and the TiO₂ phase was successfully formed. SEM images show positive results regarding the formation of a bone-like CaP mineral layer after 14 days of immersion in simulated body fluid (SBF), indicating suitability for biomedical applications.

Abstract: Porous Titanium (Ti) is one of the leading biomedical materials with high biocompatibility, durability, high stability, and non-toxic to the human body. In this study, highly porous Ti have been fabricated by spark plasma sintering process using NaCl as a pore former (70% wt.), and then, NaCl was dissolved in water. All the samples were sintered at 625 °C and held there for 10 min under applied pressure ranging from 20 to 50 MPa with heating rate of 100 °C/min in vacuum. The results suggested that NaCl is a proficient porogen, the porosity of all samples was in the range of 66.95 - 68.8%. When the pressing pressure increased from 20 - 50 MPa, the porosity of the samples decreased but the size of the pores increased. The pore size concentrated in the range of 300 - 350 µm. This implies that the compression pressure plays a crucial role in influencing both the porosity and pore size of the titanium material produced using the SPS technique. The compressive strength is 18.42 - 25.23 MPa, and the elastic modulus is 0.35 - 1.05 GPa, which matches the strength and the modulus of elasticity of biological implants.

Abstract: The main aim of the present paper is evaluated the mechanical properties, microstructures and porosity of Ti6Al4V and CoCrW alloys produced by Laser Powder Bed Fusion (L-PBF) as an additive manufacturing (AM) technology. The mechanical properties were follows: For Ti6Al4V alloy the UTS was 1180 MPa; the YS was in the range <600; 745 MPa>. For CoCrW alloys, the UTS were in range <750; 950 MPa> and YS was in range <400; 500>. Evaluation of porosity was realized on non-etched samples using by quantitative image analysis in order to describe the dimensional and morphological porosity characteristics. The pores in the Ti6Al4V alloy showed homogeneous distribution without significant large pores.

Abstract: Al 7xxx alloy is a heat treatable Al alloy with superior strength. Solution treatment in precipitation hardening sequence of the alloy has an important role to dissolve second phases and bring vacancies out to form precipitates in the ageing process. Another strengthening can be done by Ti addition as grain refiner. As cast alloy by squeeze casting was homogenized at 400 °C for 4 h. Solution treatment was conducted at 220, 420, and 490 °C, followed by rapid quenching. Subsequent ageing was conducted at 130 °C for 48 h. Characterization was performed by optical microscope, SEM-EDS (Scanning Electron Microscopy – Energy Dispersive Spectroscopy), Rockwell hardness testing, XRD (X-Ray Diffraction), and STA (Simultaneous Thermal Analysis). Ti added alloy showed rounder grains, lower hardness, and more reduction in second phase volume fraction along with increasing solution treatment temperature than those in alloys without Ti addition. Otherwise, the alloy final hardness was increasing and higher after the ageing process due to higher second phase dissolution which leads to more precipitates formed.

Abstract: TiO₂ coating was prepared by a novel approach on pure titanium substrates. In this study, we presented a new method to induce the crystal growth of rutile on pure Ti which covered with uniform Na₂O·2B₂O₃ glass powders, and through heating to control the grow process of TiO₂ crystal. The results showed that during the heating process, the crystal of rutile grew on the interface between the glass coating and the Ti substrates. To keep the growth of TiO₂ crystal controllably, the presence of Na₂O·2B₂O₃ glass powder was essential. Meanwhile, TiO₂ crystal grew fast with a higher heating temperature. The mechanism about the growth of TiO₂ coating was also investigated in this work.

Abstract: In this paper, the microstructural evolution of the composite formed by fibre laser deposition of Ti-6Al-4V wire and WC-W₂C powder was investigated and reported. Nine single tracks were deposited using combinations of four laser processing parameters (laser power, traverse speed, wire feed rate and powder feed rate) with each having three levels based on Taguchi design of experiments. The samples of the deposited composites were subjected to microstructural examinations using scanning electron microscopy with energy dispersive spectroscopy and X-ray Diffractometry, and microhardness tests. The resultant microstructure is characterised by uniform distribution of the reinforcement particles (WC-W₂C) and dispersion of in-situ synthesised TiC and W solid solution precipitates in a β-stabilised Ti matrix. The TiC precipitates have blocky and fine eutectic morphologies, while the W solid solution precipitates have blocky and leaf-like equiaxed morphologies. The retained W composition in the β-Ti was found to range from 7.5-9 at%, and it helped to β-stabilise the matrix which was considered beneficial for the composite matrix to retain its ductility. Increasing laser power was found to decrease the amount of W retained in the Ti matrix which resulted in a lower cooling rate, favourable for the nucleation of W solid solution. The uniform dispersion of the TiC and W solid solutions in the β-Ti matrix phase has significantly enhanced its hardness which ranged from 455-543 HV_0.3. It is anticipated that the composite formed will possess excellent wear resistance and contact deformation characteristics.

Abstract: This paper presents the novel microstructure design, called Harmonic Structure, which gives structural metallic materials outstanding mechanical properties through an innovative powder metallurgy process. Homogeneous and ultra-fine grain (UFG) structure enables the materials high strength. However, such a “Homo-“ and “UFG” microstructure does not, usually, satisfy the need to be both strong and ductile, due to the plastic instability in the early stage of the deformation. As opposed to such a “Homo-and UFG“ microstructure, “Harmonic Structure” has a heterogeneous microstructure consisting of bimodal grain size together with a controlled and specific topological distribution of fine and coarse grains. In other words, the harmonic structure is heterogeneous on micro-but homogeneous on macro-scales. In the present work, the harmonic structure design has been applied to pure metals and alloys via a powder metallurgy route consisting of controlled severe plastic deformation of the corresponding powders by mechanical milling or high pressure gas milling, and subsequent consolidation by SPS. At a macro-scale, the harmonic structure materials exhibited superior combination of strength and ductility as compared to their homogeneous microstructure counterparts. This behavior was essentially related to the ability of the harmonic structure to promote the uniform distribution of strain during plastic deformation, leading to improved mechanical properties by avoiding or delaying localized plastic instability.

Abstract: Electroless Ni deposition is often used in presence of Cu, Ti and Au. Recently TiW has also started to be employed, but with this alloy the Ni deposition is not always neat. In our work we investigate the effect of different wet treatments on the Ni growth by means of XPS analyses and SEM inspections. It is found that an oxidized surface inhibits the activator deposition. The de-oxidized Ti atoms in TiW on the other hand are believed to act as the principal sites for Pd seed deposition and subsequent Ni growth.

Abstract: MgO and silver-containing MgO (AgMgO, 3.3, 9.1 at% Ag) films were sol-gel coated on titanium to improve its antibacterial property. Thermal analyses of MgAc₂·4H₂O powder revealed that MgO was crystallized at 400 °C. X-ray diffraction analysis showed that MgO was converted to Mg(OH)₂ or Mg₅(CO₃)₄(OH)₂·4H₂O during the ageing in air. Silver nanoparticles at the surface of AgMgO films were identified by scanning electron microscopy and x-ray photoelectron spectroscopy. The MgO film was about 1.5 um thick. The potentiodynamic polarization test in the Ca-free Hank’s balanced salt solution showed that the coated titanium samples had better corrosion resistance than the polished one. The dissolution of silver nanoparticles resulted in a current peak in the polarization plots. In the antibacterial test against E. Coli, the inhibition zone width was 0.3, 1.6, 2.0 mm for the films with 0, 3.3, 9.1 at% Ag, respectively. The bactericidal mechanisms of the MgO and AgMgO films were discussed. The present work would provide a facile method for antibacterial surface modification of titanium based osteo-implants.

Abstract: The AlCl₃/Ti co-doped 4MgH₂-Li₃AlH₆ has been successfully synthesized using solid ball-milled method. The effect of AlCl₃/Ti and different preparation conditions on reversible hydrogen storage of 4MgH₂-Li₃AlH₆ were investigated. It was found that the formed Al₃Ti and Al can improve the de/rehydriding performance. The onset temperature of the system dehydrogenation decreased to 58 °C, and it can release hydrogen of 7.2 wt.% at 400 °C. The hydriding of the system was found that the adsorption rate greatly increased from 0.02 to 0.35 wt.% min^-1. The activation energy (E_a) of MgH₂ dehydrogenation decreased from 147 to 113.7 kJ mol^-1 by adding additive AlCl₃ and Ti. The AlCl₃/Ti improved the thermodynamic and kinetic performance of the 4MgH₂-Li₃AlH₆ composite, which was attributed to the high catalytic activity of Al₃Ti and Al.