Mohammad Mahdi Taheri

Thick hydroxyapatite coating on Ti-6Al-4V through sol-gel method

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) powder along with other additives such as P2O5, Na2Co3 and KH2PO4are used for biocompatible coating of Ti-6Al-4V through sol-gel method. An in-house dip coating machine was developed to control dipping and withdrawal rates of the substrate. After passivating of the samples in nitric acid, coating of HA gel was performed followed by sintering in a vacuum furnace. Characterization of the coating layer was evaluated by the XRD and SEM. Imagej software was used for analysis of the data. It was found that increasing the sintering temperature decreases the pore size, resulting in a denser structure of hydroxyapatite and decrease in surface roughness of the coating. High sintering temperatures produced cracked surface of HA due to the α to β transition temperature of Ti and its alloys. HA with coating thickness of about 100 µm free cracks was obtained for sintering temperatures lower than 800 °C.

Bioactive Coating on Stainless Steel 316 L through Sol-Gel Method

In this work hydroxyapatite coating through Sol-Gel method on stainless steel 316 L was investigated. Biocompatible additives such as P2O5, Na2CO3, KH2PO4 and HA commercial powder were used for preparation of hydroxyapatite Sol-Gel. Corrosion behavior of the ground and passivated stainless steel was evaluated. Characterization of the coated samples was performed by using SEM and XRD. The results showed that by increasing the sintering temperature, a denser structure of hydroxyapatite was obtained, and volume fraction and size of porosities decreased. Thick hydroxyapatite coatings with a thickness range of 50-70 µm free from cracks were obtained.

Green synthesis of silver nanoneedles using shallot and apricot tree gum

Abstract A green synthesis method to produce silver nanoneedles was described using shallot and apricot tree gum (ATG). A fast, simple, and low cost method was used to synthesize silver with nanoparticle and nanoneedle shape from the silver nitrate solution. Shallot as a reducing agent and apricot tree gum (ATG) as a stabilizer and a capping agent were utilized to reduce and form silver ions into silver atoms with needle and particle shape. Moreover, high crystalline structures of silver nanoparticles (AgNPs) with diameters of 8–20 nm and silver nanoneedles with average diameters of 50–60 nm and lengths of 5–10 μm were consequently synthesized by shallot and the mixture of shallot and ATG. A self-assembly mechanism was proposed to indicate the formation of needle-like structures of spherical AgNPs via carbon chains of ATG. The results indicate that the presence of ATG with shallot can transfer the reduced AgNPs into the silver nanoneedle. The findings were characterized using X-ray diffraction (XRD), ultra violet visible (UV-Vis) spectrometry, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques.

Evaluating hydrothermal synthesis of fluorapatite nanorods: pH and temperature

ABSTRACT In this study, the fluorapatite was synthesised by a hydrothermal technique in different pH and temperature using apricot tree gum surfactant. The fluorapatite was synthesised in different shapes such as spherical, Chrysanthemum flower and rod. The effect of two factors (pH and temperature) on the shape and dimension of synthesised fluorapatite was investigated through the full factorial design. An experimental strategy was developed based on the analysis of variance to create mathematical models for the shape and dimension of synthesised fluorapatite. Findings revealed that the pH of hydrothermal solution is more significant factor than temperature in terms of shape and dimension of the synthesised fluorapatite. It was illustrated that similar nanorods structure to the human tooth enamel can be achieved in pH of 10 and temperature of 70 °C The transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) spectroscopy were carried out for characterisation of synthesised fluorapatite.

In situ synthesis of hydroxyapatite-grafted titanium nanotube composite

ABSTRACT The present study is an investigation to demonstrate the effectiveness of in situ approach in the synthesis of hydroxyapatite-grafted titanium nanotube composite (HA-TNT). This method involves combining the process of HA sol–gel and rapid breakdown anodisation of titanium in a novel solution consisting of NaCl and N3PO4. This new synthesis approach produced a uniform dispersion of Anatase and Rutile phases of TiO2 nanotubes with minimal agglomeration in the matrix of crystalline HA. The characterisation of homogenised HA-TNT composite was investigated via field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD). FESEM and TEM images indicated the nanostructure of composite with TiO2 nanotube diameter of approximately 10 nm. XRD and EDS analyses confirmed the formation of HA crystalline with the Ca/P ratio of 1.58 and formation of Anatase and Rutile phase of TiO2 nanotubes.

Fabrication and Mechanical Testing of the Aluminum Foam Produced by Sintering and Dissolution Process

In the present study, fabrication of the aluminum (Al) foam through sintering and dissolution process and effect of space holder (NaCl) mean size on compressive behavior of metallic foam has been investigated. Due to improper cold bonding between Al particles in low compaction pressure spalling of the foam was observed. Appropriate compacting pressure and sintering temperature of the compacts resulted in production of high quality Al foams. SEM was used to characterize the morphology of produced Al foam and mechanical behavior of produced foams was evaluated using compression test machine. The results show that open-cell Al foam free from cracks was obtained and an increase in NaCl mean size resulted in increases of the compressive strength, Young modulus and plateau stress of the stress-strain curves.