Reza Mahmoodian

Surface characterization and corrosion behavior of calcium phosphate-base composite layer on titanium and its alloys via plasma electrolytic oxidation: A review paper.

In recent years, calcium phosphate-base composites, such as hydroxyapatite (HA) and carbonate apatite (CA) have been considered desirable and biocompatible coating layers in clinical and biomedical applications such as implants because of the high resistance of the composites. This review focuses on the effects of voltage, time and electrolytes on a calcium phosphate-base composite layer in case of pure titanium and other biomedical grade titanium alloys via the plasma electrolytic oxidation (PEO) method. Remarkably, these parameters changed the structure, morphology, pH, thickness and crystallinity of the obtained coating for various engineering and biomedical applications. Hence, the structured layer caused improvement of the biocompatibility, corrosion resistance and assignment of extra benefits for Osseo integration. The fabricated layer with a thickness range of 10 to 20 μm was evaluated for physical, chemical, mechanical and tribological characteristics via XRD, FESEM, EDS, EIS and corrosion analysis respectively, to determine the effects of the applied parameters and various electrolytes on morphology and phase transition. Moreover, it was observed that during PEO, the concentration of calcium, phosphor and titanium shifts upward, which leads to an enhanced bioactivity by altering the thickness. The results confirm that the crystallinity, thickness and contents of composite layer can be changed by applying thermal treatments. The corrosion behavior was investigated via the potentiodynamic polarization test in a body-simulated environment. Here, the optimum corrosion resistance was obtained for the coating process condition at 500 V for 15 min in Ringer solution. This review has been summarized, aiming at the further development of PEO by producing more adequate titanium-base implants along with desired mechanical and biomedical features.

Modified smoothed particle hydrodynamics (MSPH) for the analysis of centrifugally assisted TiC-Fe-Al2O3 combustion synthesis

A modified smoothed particle hydrodynamic (MSPH) computational technique was utilized to simulate molten particle motion and infiltration speed on multi-scale analysis levels. The radial velocity and velocity gradient of molten alumina, iron infiltration in the TiC product and solidification rate, were predicted during centrifugal self-propagating high-temperature synthesis (SHS) simulation, which assisted the coating process by MSPH. The effects of particle size and temperature on infiltration and solidification of iron and alumina were mainly investigated. The obtained results were validated with experimental microstructure evidence. The simulation model successfully describes the magnitude of iron and alumina diffusion in a centrifugal thermite SHS and Ti + C hybrid reaction under centrifugal acceleration.

Study of Ti+C Combustion Synthesis Reaction in a Controlled Declining Temperature State

The purpose of this article is to synthesize a Ti-C system under a known cooling rate by applying a secondary hybrid system in the form of semi-reacted titanium carbide. The synthesis reaction is performed in a hot, inert, shielded crucible. The portions of reacting and interacting materials are determined using the Rietveld phase quantification method. The product microstructure is studied, and the nanomechanical properties are measured via a nanoindentation technique. The experimental results revealed that the reaction behavior and mechanical properties of Ti+C elemental powder were initiated at a particular temperature level. At 2610°C, the titanium carbide phase formed 14% of the compound composition, with 65 GPa Young’s modulus and 563 MPa hardness.

Surface Modification of valve metals using Plasma Electrolytic Oxidation (PEO) for antibacterial applications: A Review

Plasma electrolytic oxidation (PEO) is an advance technique to develop porous oxidation layer on light metals, primarily to enhance corrosion and wear resistance. The oxidation layer can also offer a wide variety of mechanical, biomedical, tribological, and antibacterial properties through the incorporation of several ions and particles. Due to the increasing need of antimicrobial surfaces for biomedical implants, antibacterial PEO coatings have been developed through the incorporation of antibacterial agents. Metallic nanoparticles that have been employed most widely as antibacterial agents are reported to demonstrate serious health and environmental threats. To overcome the current limitations of these coatings, there is a significant need to develop antibacterial surfaces that are not harmful for patients health and environment. Attention of the readers has been directed to utilize bioactive glasses as antibacterial agents for PEO coatings. Bioactive glasses are well known for their excellent bioactivity, biocompatibility, and antibacterial character. PEO coatings incorporated with bioactive glasses can provide environment-friendly antimicrobial surfaces with exceptional bioactivity, biocompatibility, and osseointegration.

Mechanical and Chemical Characterization of a TiC/C System Synthesized Using a Focus Plasma Arc.

Titanium carbide-graphite (TiC/C) composite was successfully synthesized from Ti and C starting elemental powders using self-propagating high-temperature synthesis technique in an ultra-high plasma inert medium in a single stage. The TiC was exposed to a high-temperature inert medium to allow recrystallization. The product was then characterized using field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Rietveld refinement, nanoindentation, and micro-hardness to determine the product’s properties. The recorded micro-hardness of the product was 3660 HV, which is a 14% enhancement and makes is comparable to TiC materials.

Low-melting-point polymeric nanoshells for thermal-triggered drug release under hyperthermia condition

Abstract Purpose: The aim of this paper was to synthesise core-shell nanostructures comprised of mesoporous silica core and a low melting-point polyethylene glycol (PEG) nanoshell with a sharp gel–liquid phase transition for rapid drug release at hyperthermia temperature range. Materials and methods: The phase transition behaviours of PEGs with molecular weights of 1000, 1500, and 2000 Da were analysed using differential scanning calorimetry (DSC) to determine the optimal formulation with phase transition in the hyperthermia range. The ‘graft-to’ method was employed to synthesise core–shell nanostructures using the selected PEG formulation. The drug loading and release behaviours of these nanocarriers were examined by ultra-violet visible spectroscopy (UV-Vis) using doxorubicin as a model drug. Magnetic resonance-guided focused ultrasound (MRgFUS) was also applied as a typical thermal modality to evaluate the rate of drug release from the core-shell nanostructures. Results: The PEG molecular weight of 1500 Da presented the optimal phase transition temperature for thermal-triggered release under hyperthermia conditions. Drug release measurements at different temperatures using UV-Vis methods showed a 20.2 ± 4.3% leakage in aqueous solution at 37 °C after 30 min, while this value was significantly increased to 68.2 ± 3.7% at 50 °C. A 45.5 ± 3.1% drug release was also obtained after sonication of the drug-loaded nanoparticles for 5 × 20 s using MRgFUS. Conclusion: Although the ratio of drug leakage at physiological temperatures was relatively high, the sharp transition temperature, high loading efficiency, and fast drug release at hyperthermia temperature range could make these core-shell nanoparticles prominent for enhancing the efficacy of various hyperthermia modalities in the treatment of cancer tumours.

Intermetallic compounds in 3D integrated circuits technology: a brief review

Abstract The high performance and downsizing technology of three-dimensional integrated circuits (3D-ICs) for mobile consumer electronic products have gained much attention in the microelectronics industry. This has been driven by the utilization of chip stacking by through-Si-via and solder microbumps. Pb-free solder microbumps are intended to replace conventional Pb-containing solder joints due to the rising awareness of environmental preservation. The use of low-volume solder microbumps has led to crucial constraints that cause several reliability issues, including excessive intermetallic compounds (IMCs) formation and solder microbump embrittlement due to IMCs growth. This article reviews technologies related to 3D-ICs, IMCs formation mechanisms and reliability issues concerning IMCs with Pb-free solder microbumps. Finally, future outlook on the potential growth of research in this area is discussed.

Comparative study on microstructure, crystallite size and lattice strain of as-deposited and thermal treatment silver silicon nitride coating on Ti6Al4V alloy

Silver silicon nitride coating were deposited on Ti6Al4V alloy using physical vapor deposition magnetron sputtering technique. Field Emission Spectroscopy (FESEM), Electron Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) were used to characterize as-deposited and after heat treatment of AgSiN coatings in order to understand the morphology, compositions and structure. Meanwhile, in determining the crystallite size and lattice strain, the simplified Williamson-Hall plot method was utilized. The heat treated coated sample shown to reveal granular surface structure, bigger crystallite size and lattice strain as compared to the as-deposited coated sample.

Enhancement of as-sputtered silver-tantalum oxide thin film coating on biomaterial stainless steel by surface thermal treatment

Stainless steel 316L (SS316L) is extensively used as surgical/clinical tools due to its low carbon content and excellent mechanical characteristic. The fabrication of metal ceramic based on this metallic biomaterial favor its biofunctionality properties. However, instability phase of amorphous thin film lead to degradation, corrosion and oxidation. Thus, thin film coating requires elevated adhesion strength and higher surface hardness to meet clinical tools criteria. In this study, the SS316L was deposited with micron thickness of Ag-TaO thin film by using magnetron sputtering. The microstructure, elemental analysis and phase identification of Ag-TaO thin film were characterized by using FESEM, EDX and XRD, respectively; whereas the micro scratch test and micro hardness test were performed by using Micro Scratch Testing System and Vickers Micro Hardness Tester, respectively. It was found that the coating thin film’s adhesion and hardness strength were improved from 672 to 2749 mN and 142 to 158 Hv respectively. It was found that the as-deposited surface were treated at 500 °C of temperatures with 2 °C/min ramping rate enhance 4.1 times of the adhesion strength value. Furthermore, FESEM characterization revealed coarsening structure of the thin film coating which can provide high durability service.Stainless steel 316L (SS316L) is extensively used as surgical/clinical tools due to its low carbon content and excellent mechanical characteristic. The fabrication of metal ceramic based on this metallic biomaterial favor its biofunctionality properties. However, instability phase of amorphous thin film lead to degradation, corrosion and oxidation. Thus, thin film coating requires elevated adhesion strength and higher surface hardness to meet clinical tools criteria. In this study, the SS316L was deposited with micron thickness of Ag-TaO thin film by using magnetron sputtering. The microstructure, elemental analysis and phase identification of Ag-TaO thin film were characterized by using FESEM, EDX and XRD, respectively; whereas the micro scratch test and micro hardness test were performed by using Micro Scratch Testing System and Vickers Micro Hardness Tester, respectively. It was found that the coating thin film’s adhesion and hardness strength were improved from 672 to 2749 mN and 142 to 158 Hv respect...

Investigation of Embedded Si/C System Exposed to a Hybrid Reaction of Centrifugal-Assisted Thermite Method.

A novel method is proposed to study the behavior and phase formation of a Si+C compacted pellet under centrifugal acceleration in a hybrid reaction. Si+C as elemental mixture in the form of a pellet is embedded in a centrifugal tube. The pellet assembly and tube are exposed to the sudden thermal energy of a thermite reaction resulted in a hybrid reaction. The hybrid reaction of thermite and Si+C produced unique phases. X-ray diffraction pattern (XRD) as well as microstructural and elemental analyses are then investigated. XRD pattern showed formation of materials with possible electronic and magnetic properties. The cooling rate and the molten particle viscosity mathematical model of the process are meant to assist in understanding the physical and chemical phenomena took place during and after reaction. The results analysis revealed that up to 85% of materials converted into secondary products as ceramics-matrix composite.