Sharif Digital Repository

Atomic force microscopes (AFM) are widely used for feature detection and scanning surface topography of different materials. Contrast of topography images is significantly influenced by the sensitivity of AFM micro cantilever which means enhancement of sensitivity leads to increase of topography images resolution So, in the last years numerous scientists interested in studying the effects of different parameters such as geometric one on the sensitivity of AFM micro cantilevers. V-shape micro cantilever types of AFMs probe are widely used to scan various types of surfaces. In V-shape micro cantilevers, there are many geometric and design parameters which influence the flexural sensitivity of... 

In this work, formation of gold nanoparticles in radio frequency (RF) reactive magnetron co-sputtered Au-SiO 2 thin films post annealed at different temperatures in Ar + H 2 atmosphere has been investigated. Optical, surface topography, chemical state and crystalline properties of the prepared films were analyzed by using UV-visible spectrophotometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD) techniques, respectively. Optical absorption spectrum of the Au-SiO 2 thin films annealed at 800 °C showed one surface plasmon resonance (SPR) absorption peak located at 520 nm relating to gold nanoparticles. According to XPS analysis, it was... 

We have investigated the effect of bias voltage on sheet resistance, surface roughness and surface coverage of Co/NiO x magnetic bilayer. In addition, interface topography and corrosion resistance of the Ta/Co/Cu/Co/NiO x /Si(1 0 0) system have been studied for Co layers deposited at an optimum bias voltage. Atomic force microscopy (AFM) and four point probe sheet resistance (Rs) measurement have been used to determine surface and electrical properties of the sputtered Co layer at different bias voltages ranging from 0 to -80 V. The Co/NiO x bilayer exhibits a minimum surface roughness and low sheet resistance value with a maximum surface coverage at Vb=-60 V resulted in a slight increase of... 

Anatase nanostructured coating has been prepared on 316 L stainless steel by sol-gel dip coating. The topography of the coatings surface has been analyzed using atomic force microscopy. The anticorrosion performance of the coatings has been evaluated using polarization curves. Effects of calcination temperature, withdrawal speed and times of coating on corrosion protection have been studied. The results showed calcination temperature of 400°C and withdrawal speed of 10 cm/min are desirable conditions to achieve high corrosion protection of 316 L stainless steel in chloride containing environments. Coatings with 3 times exhibit better resistance against corrosion in 0.5 molar NaCl solutions.... 

Asphaltene deposition during oil production and transportation causes extensive damage to reservoirs and wellhead equipment. In this study, the effects of native and non-native resins as well as those of their mixtures on the asphaltene deposition process are investigated. A novel pressure, volume, and temperature (PVT) visual cell is used to check the effect of resin on asphaltene deposition at different pressures and reservoir temperatures. Two Iranian crude oil samples with different potentials of asphaltene deposition (low and high) were used in these tests. During depressurizing in the presence of native and non-native resins, the amount of asphaltene deposited was measured. To monitor... 

Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel setup has been designed and manufactured for utilizing ultrasonic vibrations in external cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina-zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the... 

Low temperature plasma (LTP) is nowadays an intensively investigated superficial treatment of wool. In this work we have investigated the effect of LTP on wool fabric under different conditions. The effect of the position of samples inside the reactor and the kind of gases used as discharge medium has been also investigated. The results show that not only the topography of the surface is modified but also the chemical composition of the surface. It is shown that the hydrophilicity of the samples and also their shrink resistance and anti-felting behavior have improved significantly under LTP treatment. The results show that the shrinkage of 30.1% for untreated samples has reduced to about... 

The resonant frequencies and torsional sensitivities of an atomic force microscope (AFM) with assembled cantilever probe (ACP) are studied. This ACP comprises a horizontal cantilever, a vertical extension and two tips located at the free ends of the cantilever and the extension which makes the AFM capable of simultaneous topography at top-surface and sidewalls of microstructures especially microgears which consequently leads to a time-saving swift scanning process. In this work, the effects of the sample surface contact stiffness and the geometrical parameters such as the ratio of the vertical extension length to the horizontal cantilever length and the distance of the vertical extension... 

The resonant frequencies and flexural sensitivities of an atomic force microscope (AFM) assembled cantilever probe which comprises a horizontal cantilever, a vertical extension and two tips located at the free ends of the cantilever and the extension are studied. This probe makes the AFM capable of simultaneous topography at top-surface and sidewalls of microstructures especially microgears which leads to a time-saving swift scanning process. In this work, the effects of the sample surface contact stiffness and the geometrical parameters such as the ratio of the vertical extension length to the horizontal cantilever length and the distance of the vertical extension from clamped end of the... 

This paper analyses the three-dimensional (3-D) surface texture of Co/CP/X (X = Cu, Ti, SM and Ni, CP: carbonaceous paste) nanoflakes prepared electrochemically using a conventional three electrode system. The surface chemical composition of the samples was investigated by X-ray photoelectron spectroscopy (XPS). Surface images were recorded using scanning electron microscopy (SEM) and analyzed by means of the fractal geometry. Statistical, fractal and functional surface properties of the prepared samples were computed. The statistical functions applied to the SEM data were employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of... 

Atomic force microscope (AFM) is one of the most versatile and powerful devices capable of producing high-resolution images of nanomaterial. Many researchers are widely investigating to improve the scanning speed and image quality of AFM by proposing different techniques. Here, we aim to present a novel approach based on the smooth orthogonal decomposition for the estimation of the surface topography in AFM. The technique proposed in this research not only eliminates the need for a closed-loop controller but also acquires the surface three-dimensional shape (topography) very quickly and accurately. The proposed technique relies on the fact that in the tapping mode of atomic force microscopy,... 

In this study, a nonlinear observer for high-speed estimation of the sample surface topography in a small duration of the probe transient motion utilizing a 2DOF model of TR-AFM is proposed. Since the time duration to reach the steady-state periodic motion of the oscillating probe in conventional imaging methods is relatively high, the proposed nonlinear observer in this research is able to address this limitation and estimate the surface topography throughout transient oscillation of the microcantilever. With this aim, topography estimation process utilizing a Thau observer without any linearization of the system dynamics is designed and coupled with the system dynamics to achieve sample... 

Commercially pure titanium samples were exposed to grit blasting and acid-alkali treatments to obtain a variety of surface compositions and morphologies. Contact roughness test and microstructural studies were employed to study the surface topography of the samples. The nature and chemical composition of surface phases were evaluated using X-ray diffraction and microanalysis techniques. Selected samples first exposed to in vitro environment were then tested to determine the surface morphology and surface microstructure. Based on the data presented in this work, it is suggested that grit blasting process utilized prior to chemical treatment stage, yields a high quality surface morphology.... 

Models capable of accurate simulation of the microcantilever dynamics coupled with complex tip-sample interactions are essential for interpretation of the imaging results in non-contact atomic force microscopy (AFM). In the present research, a combination of finite element and molecular dynamics methods are used for modelling the AFM system to overcome the drawbacks of conventional approaches that use a lumped system with van der Waals interaction. To illustrate the ability of the proposed scheme in providing images with atomic resolution, some simulations have been performed. In the conducted simulations, a diamond tip is interacting with nickel samples having different surface plane... 

The resonant frequencies and flexural sensitivities of an atomic force microscope (AFM) with assembled cantilever probe (ACP) are studied. This ACP comprises a horizontal cantilever, a vertical extension and two tips located at the free ends of the cantilever and the extension, which makes the AFM capable of simultaneous topography at top surface and sidewalls of microstructures especially microgears, which consequently leads to a time-saving swift scanning process. In this work, the effects of the sample surface contact stiffness and the geometrical parameters such as the ratio of the vertical extension length to the horizontal cantilever length and the distance of the vertical extension... 

In this work, the effect of strain rate on the ductility, intermediate temperature brittleness and fracture surface of Zr-based BMG over a wide range of temperatures from 0.1 Tg to near Tg, has been systematically investigated. The results showed two remarkable ductile to brittle transition at low cryogenic and intermediate temperatures. At low temperatures, below 0.4 Tg, the activation of diffusion mediated phenomena is negligible and the combined effects of strain rate and temperature contribute to the plasticity of material by changing the STZ volume, hence the possibility of forming multiple shear bands. At the temperature range from 0.4 Tg to the temperature at which the intermediate...