Publications by Ayat Karimi | EPFL Graph Search

Mechanical signatures of degradation of the photovoltaic perovskite CH3NH3PbI3 upon water vapor exposure

László Forró, Ayat Karimi, Wanda Andreoni, Bálint Náfrádi, Massimo Spina, Endre Horvath

We report on the mechanical properties of CH3NH3PbI3 photovoltaic perovskite measured by nanoindentation. The Young's modulus (E) of the pristine sample is 20.0 +/- 1.5GPa, while the hardness (H) is 1.0 +/- 0.1GPa. Upon extended exposure to water vapor, bo ...

2017

Structural and mechanical properties of Nb-1 (-) xTixN thin films deposited by rf magnetron sputtering

Ayat Karimi, Daniela Dumitriu La Grange, Alireza Karimi

Nb1-xTixNy thin films with different nitrogen contents (0.5 < y < 1.2) and Nb/Ti ratios (0

Elsevier2016

NbTiN thin films deposited by hybrid HiPIMS/DC magnetron co-sputtering

Ayat Karimi, Rosendo Sanjines, Daniela Dumitriu La Grange, Alireza Karimi, Samy Adjam

Nb1 - xTixNy thin films (with 0

Elsevier Science Sa2016

A novel synthetic strategy for bioinspired functionally graded nanocomposites employing magnetic field gradients

Ayat Karimi, Yves Leterrier, Tommaso Nardi

In order to mimic the complex architecture of many bio-materials and synthesize composites characterized by continuously graded composition and mechanical properties, an innovative synthetic strategy making use of magnetic field gradients and based on the ...

2014

Formation of (113) texture in fcc nitride thin films and its influence on the film properties

Ayat Karimi, Alireza Karimi, Akshath Raghu Shetty

This work presents a study of XRD measurements on the development of the (113) preferential orientation with film thickness for Ti0.67Al0.33N films grown on Si(100) substrates by pulsed DC magnetron sputtering. The buildup of (113) texture was observed usi ...

Elsevier Science Sa2013

Texture mechanisms and microstructure of biaxial thin films grown by oblique angle deposition

Ayat Karimi, Alireza Karimi, Akshath Raghu Shetty

In order to understand the texture formation mechanism in thin films grown under oblique angle deposition (OAD), TiAlN films were deposited at room temperature (RT) under various incident angles. We show that both in-plane and out-of-plane crystallographic ...

Wiley-V C H Verlag Gmbh2012

Evaluation of the hydrodynamic pressure of cavitation impacts from stress-strain analysis and geometry of individual pits

Ayat Karimi, Jean-Pierre Franc, Davide Carnelli

The present paper focuses on the development of an inverse procedure able to infer the hydrodynamic pressure distribution acting on the material surface and responsible for the creation of the cavitation pit based on the stress in a cavitation pit and its ...

2012

Application of spherical nanoindentation to determine the pressure of cavitation impacts from pitting tests

Ayat Karimi, Jean-Pierre Franc, Davide Carnelli

This article focuses on the use of spherical nanoindentation measurements to estimate the pressure of cavitation impacts and its statistical distribution. Indeed, nanoindentation techniques are supposed to represent an effective tool in this field due to t ...

Cambridge University Press2012

Material and velocity effects on cavitation erosion pitting

Ayat Karimi, Jean-Pierre Franc

Cavitation erosion during the incubation period was investigated via pitting tests conducted on three different materials: an Aluminum alloy, a Nickel Aluminum Bronze alloy and a Duplex Stainless Steel. Pitting tests were conducted in a cavitation tunnel i ...

2012

Scaling study of cavitation pitting from cavitating jets and ultrasonic horns

Ayat Karimi, Jean-Pierre Franc

Cavitation erosion prediction and characterization of cavitation field strength are of interest to industries suffering from cavitation erosion detrimental effects. One means to evaluate cavitation fields and materials is to examine pitting rates during th ...

Elsevier Science Sa2012

Texture change through film thickness and off-axis accommodation of (002) planes

Ayat Karimi, Alireza Karimi, Akshath Raghu Shetty

We present our recent experimental results on the formation of off-axis texture and crystallographic tilting of crystallites that take place in thin film of transition metal nitrides. For this purpose, the microstructural development of TiAlN film was stud ...

2011

Impact Load Measurements in an Erosive Cavitating Flow

Ayat Karimi, Jean-Pierre Franc

Impact load measurements were carried out in a high-speed cavitation loop by means of a conventional pressure sensor flush-mounted in the region of closure of the cavity where maximum damage was observed. The sensor was dynamically calibrated by the ball d ...

2011