Quantitative analysis of grain subdivision in cold rolled aluminium

A procedure is proposed for a statistical characterisation of deformed microstructures from the data collected using Orientation Imaging Microscopy (OIM). This procedure has been applied for a characterisation of 352 grains in commercial purity aluminium cold-rolled to a reduction of 40%. The results demonstrate the different behaviour of grains with different orientations: (i) grains having orientations near the {001}<100> and {025}<100> components develop orientation gradients over distances of 10–20 μm; (ii) grains with orientations close to the {205}<502> component form fragments with relatively large misorientations, and (iii) grains within the β-fibre form fragments with relatively small misorientations. The experimental results are compared to previous observations by transmission electron microscopy (TEM) and good agreement is found. Finally, possible applications of the present observations for advanced texture modelling are discussed.     

Indentation modulus and hardness of polyaniline thin films by atomic force microscopy

Polyaniline (PANI) thin films with different thicknesses have been deposited on indium tin oxide (ITO) coated glass substrates by electrochemical polymerization of the aniline monomer in H₂SO₄ aqueous solution. By using the tip of an atomic force microscopy (AFM) apparatus as an indenter, cantilever deflection versus sample vertical displacement curves have been acquired and analyzed for evaluating the contact stiffness, by using an approach analogous to that developed for standard depth sensing indentation (DSI) tests. After the calibration performed using a set of polymeric reference materials, indentation modulus and hardness of PANI films have been deduced as a function of the reached maximum penetration depth. By using a model originally proposed for the analysis of standard DSI measurements, indentation modulus and hardness values of only PANI are finally deduced from the corresponding apparent values measured for the film-substrate systems, although they have to be considered as semi-quantitative estimations, since the roughness of the films does not allow a certain determination of the local thickness in correspondence of the probed points.     

Nano-tribological characteristics of PZT thin film investigated by atomic force microscopy

In this work, the nano-scale tribological characteristics of PZT thin films (Pb(Zr_xTi_1 − x)O₃: PZT) with various Zr/Ti ratios were investigated using an Atomic Force Microscope (AFM). The PZT thin films deposited by the sol-gel method were characterized by using an AFM, X-Ray Diffraction (XRD), and a nano-indentation technique. From the experimental results, the friction coefficient of the PZT thin film was found to be about 0.1-0.2 under a 0.1-10 μN normal force. It was determined that the wear rate of the PZT thin film was in the order of 10^− 8 mm³/N·cycle. Also, it was observed that the crystalline structure of the PZT was amorphized due to mechanical stress.     

Analysis of intergranular corrosion attack of stainless steels by means of atomic force microscopy and optical microscopy. Part 2: Influence of impurity content

The aim of this study is to compare different methods to quantify intergranular corrosion attack caused by impurity segregation in different austenitic stainless steels with varying impurity contents escpecially of sulfur. Therefore, the boiling nitric acid chromate test was used to produce the intergranular corrosion attack. The methods for quantification of these attacks were weight loss measurements and grooves depth measurements either by optical microscopy at cross sections or by AFM at topography images. Comparison of the results from the different methods show that with any method used the corrosion attack increases with increasing sulfur content. Grooves depth measurements by AFM is therefore an advantageous method to quantify changes to susceptibility to intergranular corrosion because of its high selectivity to grain boundary attack compared to the other methods.     

Analysis of intergranular corrosion attack on stainless steels by means of atomic force microscopy and optical microscopy. Part 1: Influence of heat treatment

The aim of this study is to quantify intergranular corrosion attack of heat treated low carbon austenitic stainless steel caused by segregation processes of P (0.2 at% P) by different methods. After nitric acid chromate test the intensity of intergranular corrosion attack was investigated by weight loss measurements as well as determination of depths of grooves by both the optical microscopy and AFM measurements. Generally, the largest attack of corrosion is noticed on samples heat treated at 550 °C. Results of weight loss include the corrosion of matrix, inhomogenities and grain boundaries. The depths of corrosion attack were determined by optical microscope on cross sections. This method can not distinguish between attacks at grain boundaries and attack of inhomogenities. Whereas, measurements of depths by line profiling of AFM‐surface images is related to grain boundary attack directly. The weight loss measurements as well as the optical microscopy and AFM‐measurements were compared for tested heat treatment conditions. It is concluded that the use of the AFM offers an advantageous method for quantifying intergranular attack.     

Friction and wear characteristics of multi-layer graphene films investigated by atomic force microscopy

Friction and wear characteristics of multi-layer graphene films deposited on a Si substrate by mechanical exfoliation were investigated by atomic force microscopy (AFM). The graphene films consisted of a few layers of carbon basal plane. The number of graphene layers was determined by AFM and Raman spectroscopy. For the AFM friction measurement, loads in the range of − 5 to 30 nN were applied on the Si tip that slid against the graphene specimen. It was found that graphene films exhibited much lower friction (from 0.36 to 0.62 nN) than bare Si surface (from 1.1 to 4.3 nN) when the applied loads ranged from 3 to 30 nN. The wear characteristics were also assessed using the AFM. Detectable wear of graphene was generated when sliding was performed for 100 cycles under 5 μN applied load. The wear mechanism of graphene was proposed to be due to breakage of in-plane bonds between carbon atoms and shearing at the interface of graphene layers.     

Studies of adsorption of palladium nanoparticles on silicon oxide using methods of spectrophotometry and atomic force microscopy

In this work, the method of UV-VIS spectrophotometry was used to study the adsorption of palladium nanoparticles Pd NPs on silicon dioxide (silochrome S-120). Pd NPs were synthesized using a radiation-chemical method in micelle 0.15 M solutions of the AOT surfactant at different degrees of hydration ω₀ = [H₂O]/[AOT]. It is shown that adsorption depends on the structure of nanoparticles, conditions of synthesis in reverse micelles, including the ω₀ value, which determines the NP size, as well as the chemical and physicochemical properties of the silochrome surface.     

Surface topography of La-Ti composite oxide nanocrystallines examined with atomic force microscope

1　INTRODUCTIONAtomicforcemicroscope (AFM )isakindofscanningprobemicroscope(SPM )derivedfromscan ningtunnelmicroscope(STM ) [1,2 ] .Basedontheprinciplethatoscillationfrequency (ω)ofatomsap proximatestoorismorethan 10 13Hz ,theatomicmass (m )isamountto 10 2 5kg ,theatomicforcee lasticconstantk =ω2 m ,whosescaleis 10N/m ,thereforewithanelasticconstantlessthanatomice lasticconstant,theprobecantilevertipperformsfric tionactionwiththesamplesurface ,thecantileverfluctuatesaccordingtotheap…     

Comparison of anodised aluminium surfaces from four fabrication methods

This study presents a comparative analysis of surface characteristics and properties of anodised aluminium cylinders produced by sand casting, permanent mould casting, extrusion, and high pressure die casting. Differences in micro structure and distribution of silicon particles in the aluminium, due to the fabrication method and the silicon content in the alloy, resulted in varying thickness of the oxide layers (mean thicknesses between 7 and 19 μm) and surface topography. The oxide layer was unevenly thick for the permanent mould cast and the sand cast cylinders, resulting in a surface with higher plateaus and lower areas. This was more prominent for the sand cast surface. The oxide of the extruded cylinder was thick and even and its surface was smooth. The high pressure die cast surface had an oxide that was very thin and uneven. The surfaces displayed different results in the scratch test due to the variations in the surface structure. For the permanent mould cast and the sand cast surfaces the silicon particles present in the oxide deflected the cracks that were formed during the scratching. This resulted in smaller wear debris. The nanohardness values of the oxides had a large scattering due to the inhomogeneous nature of the oxide layers, with pores and particles. However, the highest nanohardness values were between 5000 and 6000 MPa for the four surfaces, which is significantly lower than that of sintered alumina. In the micro abrasion test the wear mechanism for all four surfaces was microcutting resulting in chippings.     

Mapping nanoscale wear field by combined atomic force microscopy and digital image correlation techniques

Surface wear of coatings occurring at extremely low loads and in nanocontacts is of great importance for the development and the reliability of structural/functional nanocomponents in micro/nanoelectromechanical systems. To date, appropriate tools for mapping the nanoscale wear of thin coatings are still lacking. In this study, a new method combining atomic force microscopy (AFM) and digital image correlation (DIC) techniques has been developed and applied for the determination and visualization of the nanoscale wear of a gold coating. It has been shown that the initiation and development of nanowear, which is usually difficult to detect directly from AFM topographical images, can be efficiently revealed by monitoring the correlation coefficient change in DIC analysis. A linear relation between the correlation coefficient and the wear depth is found and may be used to quantify the nanowear. The nanowear of gold coating is dominated by material removal without any plastic deformation.     

Observation of local internal friction and plasticity onset in nanocrystalline nickel by atomic force acoustic microscopy

Atomic force acoustic microscopy (AFAM) is a near-field microscopy technique exploiting the vibrational behavior of the atomic force microscope cantilever. With its tip in contact with a surface, it is sensitive to its elastic and anelastic properties. We show how AFAM can be used to investigate the onset of plasticity in nanocrystalline nickel. To this end cantilever resonance curves are recorded with varying tip-loading force P. From the resonance frequencies and the width of the resonance curves, one obtains the contact stiffness k¹ and the contact damping Q^?1. Plotting these quantities vs. P, one observes damping peaks, as well as a reduction of the contact stiffness at specific P (≈1 μN) due to the nucleation of partial dislocation loops at grain boundaries. The local Q^?1 value is most likely caused both by the nucleation and by the interaction of the loop with the phonon and the electron baths. There is a background damping which is related to the global ultrasonic absorption.     

Study of silver electrodeposition in deep eutectic solvents using atomic force microscopy

The electrodeposition of metals in ionic liquids and deep eutectic solvents leads to deposits with significantly different morphologies to those seen with aqueous solutions. The classical methods of fitting amperometric data to nucleation and growth mechanisms do not fit the data well in ionic systems and tend to focus on the short time-scale aspects of nucleation. In the current study, ex-situ AFM was used to model crystallite sizes and distributions by digitising and modelling the images. The deposition of silver from a deep eutectic solvent was chosen as it has been studied by several groups with a variety of techniques. The crystallite size data obtained from AFM and chronoamperometry for long time-scale deposition studies are compared and it is shown that the trends are similar, but there is a discrepancy in the nuclear number density of approximately an order of magnitude. The nuclear number density was found to be consistent with aqueous nucleation studies once differences in concentration and mass transport were accounted for.     

The nanostructure and microstructure of steels: Electrochemical Tafel behaviour and atomic force microscopy

The influence of chemical composition and heat treatment on a low-carbon steel, chromium steel and high speed steel has been examined by polarisation curves and electrochemical parameters deduced from the Tafel plots. The electrochemical corrosion resistance, which is small between the as-received steels become greater after heat treatment, following the order: carbon steel < chromium steel high speed steel. To explain these differences, the nano- and microstructure of the steels has been characterized by the ex situ techniques of atomic force microscopy and optical microscopy, before and after surface etching with Nital (a solution of 5% HNO₃ in ethanol). This causes preferential attack of the ferrite phases showing the carbide phases more clearly. From these nanostructural studies it was possible to better understand why the passive films formed on chromium steel and high speed steel have superior protective properties to those formed on carbon steel.     

Fractal growth of the dense-packing phase in annealed metallic glass imaged by high-resolution atomic force microscopy

Unlike crystalline metals, which have a well-understood periodical structure, the amorphous structure of metallic glasses (MGs) is still poorly understood, particularly when such a structure rearranges itself at the nanoscale under external agitations. In this article, we provide compelling evidence obtained from a recently developed high-resolution atomic force microscopy (HRAFM) technique that reveals the nanoscale structural heterogeneity after thermal annealing in a Zr–Ni metallic glass. Through the HRAFM technique, we are able to uncover the annealing-induced fractal growth of the dense-packing phases in the binary MG thin film, which exhibits a fractal dimension of ～1.7, in line with a two-dimensional diffusion limited aggregation process. The current findings not only reveal the evolution process of atomic packing in the annealed MG thin film, but also shed light on the possible cooling rate effect on the atomic structure of MGs.     

Observations on the growth of Al–Ni–Co decagonal thin films by atomic force microscopy and transmission electron microscopy

Thin films of Al–Ni–Co alloy were produced by vacuum deposition technique using a substrate material of amorphous carbon thin-foil. Attempts were made to obtain a homogeneous decagonal quasicrystalline film, where the preparation technique was based on the direct evaporation of pre-alloyed ingot of Al₇₂Ni₁₅Co₁₃ onto the heated substrates. In order to explore early stages of the decagonal film growth, the Al–Ni–Co films with different thicknesses ranging from 2 nm to 30 nm were deposited on either substrates heated at 500 °C or non-heated substrates. The film samples so obtained were examined mainly by atomic force microscopy in combination with transmission electron diffraction and imaging techniques. On the basis of these observations, deposition conditions necessary for the growth of decagonal phase in the resulting films as well as the growth mechanism of the decagonal film will be discussed.     

Analytical solution of flexural vibration responses on nanoscale processing using atomic force microscopy

An analytical solution is developed to deal with the flexural vibration problem during a nanomachining process which involves an atomic force microscope (AFM) cantilever. The modal superposition method is employed to analyze the response of an AFM subjected to a cutting force with an excitation force of an arbitrarily chosen frequency. The cutting forces were transformed into distributed transversal and bending loading, and were applied to the end region of the AFM by means of the tip holder. The effects of transverse stress and bending stress were adopted to solve the dynamic model. Based on the result, applying a cutting force with an excitation force near the high-order modal frequencies and using a wide tip holder are recommended when nanoscale processing using AFM is performed.     

Producing micro-droplet of dilute sulphuric acid on pure iron surface and observing its corrosion behaviour by atomic force microscopy

A simple method was presented to produce a micro-droplet of sulphuric acid on a pre-selected micro-zone on a pure iron surface with the tip of an AFM cantilever. The three-dimensional shape of the droplet was imaged with the AC non-contact mode of the AFM, and the liquid/solid interface was observed in situ during corrosion using the contact mode. The substrate surface beneath the droplet was lowered by approximately 19 nm after 3.6 ks of adhesion. This method has important implications for experimental studies of micro-zone corrosion or lubrication.