Search results for "MATERIA"

Simplified feedback control system for scanning tunneling microscopy

2021

A Scanning Tunneling Microscope (STM) is one of the most important scanning probe tools available to study and manipulate matter at the nanoscale. In a STM, a tip is scanned on top of a surface with a separation of a few \AA. Often, the tunneling current between tip and sample is maintained constant by modifying the distance between the tip apex and the surface through a feedback mechanism acting on a piezoelectric transducer. This produces very detailed images of the electronic properties of the surface. The feedback mechanism is nearly always made using a digital processing circuit separate from the user computer. Here we discuss another approach, using a computer and data acquisition thr…

Improving the high temperature oxidation resistance of Ti-β21S by mechanical surface treatment

2020

The improvement of the high temperature oxidation resistance of titanium alloys is currently a technological challenge. Mechanical surface treatments as shot-peening (SP) have shown their ability to improve the behaviour of pure zirconium and titanium. However, shot-peening treatments can induce a significant surface contamination. Laser shock peening (LSP) appears as a good alternative. Here, we have investigated the effect of SP and LSP treatments on the HT oxidation behavior of Ti-β21S. Samples treated by these methods have been compared to untreated ones for long exposures (3000 h) at 700 °C in dry air. The samples placed in a furnace at 700 °C were periodically extracted to be weighed.…

Effect of surface disorder on the domain structure of PLZT ceramics

2017

ABSTRACTPb1-xLax(Zr0.65Ti0.35)1-x/4O3 (PLZT x/65/35) ceramics were studied by Piezoresponse Force Microscopy in order to understand the origin of domain structure as a function of La content. We show that the domain topology is mainly determined by the composition and grain size. The characteristic correlation length decreases with increasing La content, being sensitive also to the synthesis method. The behavior of the correlation length is linked to the macroscopic properties, showing a strong increase of disorder with La doping. The roughness exponent for the domain wall in PLZT 9/65/35 is close to 2/3 indicating 1D character of domain walls in relaxors.

Optical studies of MBE-grown InN nanocolumns: Evidence of surface electron accumulation

2009

Finite element analysis of stress concentration between surface coated implants and non surface coated implants - An in vitro study.

2019

Background To determine qualitative comparison in stress distribution between surface coated implants and non surface coated implants using 2 different lengths and vertical, oblique, and lateral forces. Material and Methods 3 dimensional finite element study was carried out at first molar site with 4 surface coated and 4 non surface coated implants using mimic 8.11, solid edge 2004, hypermesh 9.0, and ansys12.1 software. Results The pattern of stress distribution was almost similar between vertical and oblique loading but varied with lateral loads between surface coated and non surface coated implants. As the length of the implants increased stress concentration had no significant variation…

ZnMgO-based UV photodiodes: a comparison of films grown by spray pyrolysis and MBE

2016

Detecting the UV part of the spectrum is fundamental for a wide range of applications where ZnMgO has the potential to play a central role. The shortest achievable wavelength is a function of the Mg content in the films, which in turn is dependent on the growth technique. Moreover, increasing Mg contents lead to an electrical compensation of the films, which directly affects the responsivity of the photodetectors. In addition, the metal-semiconductor interface and the presence of grain boundaries have a direct impact on the responsivity through different gain mechanisms. In this work, we review the development of ZnMgO UV Schottky photodiodes using molecular beam epitaxy and spray pyrolysis…

Optical properties and microstructure of 2.02-3.30 eV ZnCdO nanowires: effect of thermal annealing

2013

International audience; ZnCdO nanowires with up to 45% Cd are demonstrated showing room temperature photoluminescence (PL) down to 2.02 eV and a radiative efficiency similar to that of ZnO nanowires. Analysis of the microstructure in individual nanowires confirms the presence of a single wurtzite phase even at the highest Cd contents, with a homogeneous distribution of Cd both in the longitudinal and transverse directions. Thermal annealing at 550 C yields an overall improvement of the PL, which is blue-shifted as a result of the homogeneous decrease of Cd throughout the nanowire, but the single wurtzite structure is fully maintained.

Thermal oxidation of the intermetallic phases Al 8 Mo 3 and AlMo 3

2017

Abstract The thermal oxidation reactions of the intermetallic phases Al8Mo3 and AlMo3 were investigated and analyzed by ex-situ powder-x-ray diffraction (XRD), difference thermal analysis (DTA), thermogravimetry (TGA), and infrared spectroscopy (IR). The initial oxidation reactions in air were found to yield Al2O3 and AlMo3 in the case of Al8Mo3 (Tonset =725 °C), and MoO3 as well as Al8−xMo3 (Tonset =435 °C) for the pure intermetallic phase AlMo3, respectively. Thus, both intermetallic phases are coexisting in an equilibrium within a temperature range of 300 °C under oxidizing conditions. The formation of β-Al2(MoO4)3 followed the second oxidizing process of the respective minority componen…

Controlled thermal oxidation of nanostructured vanadium thin films

2016

Abstract Pure V thin films were dc sputtered with different pressures (0.4 and 0.6 Pa) and particle incident angles α of 0°, 20° and 85°, by using the GLancing Angle Deposition (GLAD) technique. The sputtered films were characterized regarding their electrical resistivity behaviour in atmospheric pressure and in-vacuum conditions as a function of temperature (40–550 °C), in order to control the oxidation process. Aiming at comprehending the oxidation behaviour of the samples, extensive morphological and structural studies were performed on the as-deposited and annealed samples. Main results show that, in opposition to annealing in air, the columnar nanostructures are preserved in vacuum con…

Gasdynamic ECR ion source for negative ion production

2018

H− ion sources are needed in various areas of accelerator technology, such as beam injection into cyclotrons and storage rings and as a part of neutral beam injectors for plasma heating in experimental facilities studying thermonuclear fusion. It was recently demonstrated that gasdynamic ion source based on ECR discharge in a simple mirror trap is very efficient for proton beam production [1]. Here we use the gasdynamic plasma source as the first stage driver of volumetric negative ion production through dissociative electron attachment (DEA) [2]. Experiments were performed with a pulsed 37 GHz / up to 100 kW gyrotron radiation in a dual-trap magnetic system, which consists of two identical…