Sharif Digital Repository

Mechanical alloying and sintering were used to fabricate nanostructured Ti6Al4V scaffolds of highly controllable pore geometry and fully interconnected porous network. Elemental powders were milled for different periods of time (10, 20, 30, 40 and 60 h), mixed with 40-60 vol.-% of 200-400 μm cuboidal NaCl, compacted at 500-600 MPa and sintered according to single or double stage heat treatment regimes at 790 and 950°C under vacuum. After sintering, the samples were soaked in distilled water to washout the NaCl. Foamy microstructures were obtained showing well shaped biopores and fragmentary embedded micropores. The shape of initial NaCl was copied into the biopores which had highly... 

As one of the most important additive manufacturing (AM) techniques, laser metal deposition (LMD) has been extensively studied specially during the last few years. Similar to other AM techniques, the quality of LMD parts is highly dependent on the processing parameters that need to be optimized so as to obtain geometrically accurate parts as well as favorable microstructures and, thus, mechanical properties. The present review paper therefore aims to present a critical analysis and overview of the relationship between processing parameters, microstructure, and mechanical properties of LMD components made from the Ti–6Al–4V alloy. Moreover, we discuss the applications of LMD parts in the... 

Scoliosis, kyphosis, and bone fracture are health problems, especially of the elderly throughout the world. The vertebra protects the spinal cord. Any impairment to the vertebra can lead to pain and nervousness. NiTi alloy (Nitinol) helps to resolve the problem by fulfilling such requirements as for strength, durability, resistance to wear, and shockwave damping which is due to the shape memory effect. Nitinol medical applications have so far been restricted to surgical devices and orthopaedics. Little has been said about Nitinol use for medication of the spinal vertebra disorder. This article appraises the potential features of Nitinol for vertebral implantation and therapeutic prescription... 

Hydrogen evolution and electrosorption on/in TiHg alloy have been investigated in acidic solution using cyclic voltammetry, open circuit potential transient, steady-state polarization, chronopotentiometry and electrochemical impedance measurements. Comparison has been made with pure Ti. Cyclic voltammetry and open circuit potential measurements show that hydrogen absorption into the electrode material occurs during proton discharge. The steady-state polarization curves in the course of positive and negative potential scans illustrate that the formation of absorbed hydrogen slightly improves the electrocatalytic properties of the electrode. The hydrogen diffusion coefficient into the bulk of... 

Fixtured sintering of up to 5 hours at 1223 to 1323 K is successfully used to diminish the dimensional change of NiTi memory alloys produced from mixtures of elemental Ni and Ti powders packed and pressed at room temperature under 400, 500, and 600 MPa pressure. The improvements obtained can help near-net-shape technology via powder metallurgy that overcomes the traditional casting problems such as oxygen, nitrogen, hydrogen, and carbon absorption and intermetallic compound precipitation, which lower the workability and the homogeneity of the final alloy. The effects of compaction pressure, sintering time, and sintering temperature on dimensional change, porosity, hardness, and morphology of... 

Nanostructured and mesoporous TiO2-Ga2O3 thin films with various Ti:Ga atomic ratios were prepared by a new straightforward particulate sol-gel route. Titanium isopropoxide and gallium (III) nitrate hydrate were used as precursors, and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the specific surface area (SSA). XRD and TEM analysis of the powders revealed that the Ga2O3 formed from the nitrate precursor retarded anatase-to-rutile transformation, crystallization and crystal growth. The average crystallite size of pure TiO2 powder annealed at 600-1000 °C were in the range 4-10 nm; the values that could be decreased to 2-6 nm for TiO2-Ga2O3... 

The main challenges of biological implants are suitable strength, adhesion, biocompatibility and corrosion resistance. This paper discusses fabrication, characterization and electrochemical investigation of anodized Ti6Al4V without and with a hydroxyapatite (HA) layer, HA/TiO2 nanoparticles (NPs) and HA/TiO2 nanotubes (HA/anodized). X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS) were used to characterize and compare properties of different samples. Dense HA with uniform distribution and 12.8 ± 2 MPa adhesive strength enhanced to 19.2 ± 4 MPa by the addition of TiO2 nanoparticles and enhanced to 23.1 ± 4 MPa by the... 

In this study, titanium alloy (Ti-6Al-4V) and austenitic stainless steel (AISI 304) biomedical alloys were subjected to surface severe plastic deformation (SSPD) via severe shot peening (SSP) with the conditions of A28-30 Almen intensity. SSP is widely accepted as much more effective than the conventional surface modification techniques since it forms a nano-grain layer with large number of dislocations and grain boundaries. The SSP treatment in this study was led to a very thin rough layer in Ti-6Al-4V titanium alloy compared to that of AISI 304. The thicker layer of AISI 304 was created by twin-twin intersections and a martensite structure transformations. SSP treatment was resulted in a... 

This study aims to 3D print titanium alloy constructs incorporating gradient of porosities, from the fully dense core to the porous outer surface. Gradient porous specimens were prepared using selective laser melting (SLM). Fully dense specimens fabricated by SLM were used as the control group. Characterization of samples was done using X-ray tomography, uniaxial compression testing, and optical and scanning electron microscopes. The biocompatibility of fabricated samples was investigated using human periodontal ligament stem cells via assessment of cell attachment, viability, and proliferation by direct and indirect assays. The data were analyzed using ANOVA and Tukey’s post hoc test.... 

Abstract: Commercially pure titanium and titanium alloys have been among the most commonly used materials for biomedical applications since the 1950s. Due to the excellent mechanical tribological properties, corrosion resistance, biocompatibility, and antibacterial properties of titanium, it is getting much attention as a biomaterial for implants. Furthermore, titanium promotes osseointegration without any additional adhesives by physically bonding with the living bone at the implant site. These properties are crucial for producing high-strength metallic alloys for biomedical applications. Titanium alloys are manufactured into the three types of α, β, and α + β. The scientific and clinical... 

Titanium alloys are widely used in various areas, particularly in medical and dental industries, due to their remarkable properties. Still, the optimum cutting conditions for titanium alloys are under consideration. Ti alloyed with Cu has been reported to provide unique properties such as good mechanical performance, good biocompatibility, acceptable corrosion resistance, and relatively lower melting point. The properties of Ti-Cu alloys mentioned above are sensitive to microstructure. They are highly dependent on microstructural characteristics such as the formation, growth, and morphological features of intermetallics and precipitates, dependent on the amount of Cu and the manufacturing... 

In this research, the effect of various surface treatments including laser processing, grit blasting and anodizing on chemical structure, surface topography, and bioactivity of Ti-6Al-4V was investigated. Six groups of samples were prepared by a combination of two alternative laser processes, grit blasting and anodizing. Selected samples were first evaluated using microanalysis techniques and contact roughness testing and were then exposed to in vitro environment. Scanning electron microscopy was used to characterize the corresponding final surface morphologies. Weight measurement and atomic absorption tests were employed for determination of bioactivity limits of different surface... 

Titanium alloys, in particular Ti6Al4V, are increasingly used recently due to high strength-to-weight ratio, biocompatibility and robust mechanical-properties at high temperatures. However, Ti6Al4V have poor machinability because of their poor thermal conductivity and high reactivity. Usually in conventional grinding (CG) of these alloys, surface burning is unavoidable. Ultrasonic assisted grinding (UAG) is an efficient method for overcoming the poor machinability of such materials. In this research, effect of imposed vibration on grinding of Ti6Al4V is studied. Obtained results show forces and surface roughness are reduced 18% and 12% by UAG comparing to CG respectively. It also results in...