Publications de Hossein Najafi

Fabrication and Characteristics of Yb-Doped Silica Fibers Produced by the Sol-Gel Based Granulated Silica Method

Valerio Romano, Duncan Thomas Lindsay Alexander, Hossein Najafi, Ali El Sayed

Combining the sol-gel method for fiber material production with the granulated silica method for preform assembly results in a robust method that offers a high degree of freedom regarding both the composition and the geometry of the produced fiber. Using t ...

2018

Structure and electronic properties of AlCrOxN1-x thin films deposited by reactive magnetron sputtering

Alireza Karimi, Hossein Najafi, Emad Oveisi

In this study, the main attempt is devoted to investigating the microstructure and electronic properties of AlCrOxN1 - x films in a wide range of oxygen concentrations from 0 to 1. These oxynitride films were deposited by pulsed DC magnetron sputtering fro ...

Elsevier Science Sa2014

Development of sol-gel-derived multi-wall carbon nanotube/hydroxyapatite nanocomposite powders for bone substitution

Hossein Najafi

Carbon nanotubes with unique physical and mechanical properties have shown great potential for biological applications, including tissue engineering and mimicking the structure and properties of human bones. In the present work, sol-gel synthesized nanocom ...

Sage Publications Ltd2014

Growth kinetics of Al-Fe intermetallic compounds during annealing treatment of friction stir lap welds

Hossein Najafi

In this study, we explored the growth kinetics of the Al-Fe intermetallic (IM) layer at the joint interface of the St-12/Al-5083 friction stir lap welds during post-weld annealing treatment at 350, 400 and 450 degrees C for 30 to 180 mm. Optical microscope ...

Elsevier Science Inc2014

Effects of Si and Y in structural development of (Al,Cr,Si/Y)OxN1 (-) (x) thin films deposited by magnetron sputtering

Alireza Karimi, Duncan Thomas Lindsay Alexander, Hossein Najafi

Silicon (Si) and yttrium (Y) are believed to have a strong influence on functional properties of oxynitrides due to their effects in the growth process and incorporation in solid solution phases. It is worthwhile noting that the presence of these elements ...

Elsevier Science Sa2013

Formation of cubic structured (Al1-xCrx)(2+delta)O-3 and its dynamic transition to corundum phase during cathodic arc evaporation

Alireza Karimi, Hossein Najafi

Mixed aluminum-chromium oxide coatings in the form of (Al,Cr)(2)O-3 solid solutions have attracted extensive research interest during the past years due to their successful use for challenging wear applications and the comparative ease of their moderate-te ...

Elsevier Science Sa2013

Formation Mechanisms and Structural Properties of Aluminium-Chromium Based Oxynitride Thin Films Synthesized by Physical Vapor Deposition

Hossein Najafi

Oxynitride thin films, a novel class of mixed anionic solid structures, have gained an intense interest during recent years related to the unique interplay of oxygen (O) and nitrogen (N) with metals in the material structure. This matter can result in spec ...

EPFL2012

Effect of tool travel and rotation speeds on weld zone defects and joint strength of aluminium steel lap joints made by friction stir welding

Hossein Najafi

In this study, Al-5083 and St-12 alloy sheets were friction stir lap welded at different travel (7-23 cm min(-1)) and rotation (750-1125 rev min(-1)) speeds of the welding tool. The welded joints were characterised by various methods including shear tensil ...

2012

Microstructure of Al95.5Cr2.5Si2(N1-xOx) thin films covering from nitrides to oxides

Alireza Karimi, Hossein Najafi

Al95.5Cr2.5Si2(N1-xOx) thin films were prepared using pulsed DC-magnetron sputtering at 650 degrees C by changing the oxygen to nitrogen ratio (O-2/(O-2 + N-2)) in the reactive gas. The obtained films were characterized by various techniques including XRD, ...

2011

Correlation between anionic substitution and structural properties in AlCr(OxN1-x) coatings deposited by lateral rotating cathode arc PVD

Alireza Karimi, Hossein Najafi

The influence of oxygen content on the properties of cathodic arc-deposited AlCr(OxN1-x) coatings has been studied. All samples were prepared in a nitrogen-rich mixture of N-2 and O-2 at 550 degrees C using lateral rotating arc cathodes (LARC) technology t ...

2011

Deposition and characterization of pulsed direct current magnetron sputtered Al95.5Cr2.5Si2 (N1-xOx) thin films

Alireza Karimi, Hossein Najafi

Aluminum rich oxynitride thin films were prepared using pulsed direct current (DC) magnetron sputtering from an Al95.5Cr2.5Si2 (at.%) target. Two series of films were deposited at 400 degrees C and 650 degrees C by changing the O-2/(O-2 + N-2) ratio in the ...

2010

Inclusion of carbon nanotubes in a hydroxyapatite sol-gel matrix

Hossein Najafi

In this study, the inclusion of multi-walled carbon nanotubes as the second phase in the hydroxyapatite matrix, in order to improve the mechanical strength, has been performed via the sol-gel process. The stability of carbon nanotube sol with the changes o ...

2009