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This study presents innovative Ti1–xNbxN–Ag films obtained by a suitable combination of low-energy and high-energy sputtering leading to bacterial inactivation. The bacterial inactivation kinetics by the TiNbN layers was drastically enhanced by the addition of 6–7% Ag and proceeded to completion within 3 h after the film autoclaving. By X-ray photoelectron spectroscopy (XPS), the samples after autoclaving presented in their upper layers TiO2, Nb2O5 and Ag2O with a surface composition of Ti0.81Nb0.19N0.99Ag0.068. Surface potential/pH changes in the Ti1–xNbxN–Ag films were monitored during bacterial inactivation. Surface redox processes during the bacterial inactivation were detected by XPS. The diffusion of Ag in the Ti1–xNbxN–Ag films was followed at 50 and 70 °C pointing. The beneficial thermal treatment points out to the bifunctional bacterial inactivation properties of these films and their potential application in healthcare facilities. Interfacial charge transfer (IFCT) under light irradiation betwee...

This study presents innovative Ti

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 ± 1.5 GPa, while the hardness (H) is 1.0 ± 0.1 GPa. Upon extended exposure to water vapor, both quantities decrease dramatically and the sample changes color from silver-black to yellow. Calculations based on density functional theory support this trend in the mechanical response. Chemical treatment of the degraded crystal in methylammonium iodide solution recovers the color of the pristine sample and the values of E and H within 50%.

International audience; 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 geometrical features. To achieve this goal, experimental pitting and nanoindentation measurement techniques were used together with a model of pit formation based on a Gaussian distribution of the hydrodynamic impact pressure pulse. The pitting tests were performed at four different operating pressures on aluminum alloy samples and the geometrical characteristics of the pits were measured. Then the strain, stress, and load in a cavitation pit were quantified by coupling the pitting test analysis with the material information obtained via the indentation tests. Finally, a Gaussian distribution of the hydrodynamic impact pressure on the material surface has been hypothesized and the peak of this distribution as well as its width have been inferred. This procedure, allowing the evaluation of the hydrodynamic impact pressure and load responsible for the material erosion and the deduction of insightful information on the flow aggressiveness at different operating conditions, could certainly represent a significant step in developing a technique able to evaluate the cavitation intensity from pitting tests.

International audience; 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 the similarities between substrate deformation under liquid impact and indentation testing. First, nanoindentation experiments were used to extract the mechanical parameters of a Nickel-Aluminum-Bronze alloy; second, pitting tests were performed at different operating pressures, and the geometrical characteristics of the pits were measured; and finally, the spectra of impact pressure and loads responsible for material erosion were obtained by coupling the findings of indentation tests with the analysis of pitting tests. Results assessed the capability of the proposed methodology to quantify the hydrodynamic aggressiveness of the cavitating flow. This procedure, which assumes the material itself as a sensor that is able to detect the impact loads, could represent an alternative solution to pressure transducers in estimating the cavitation intensity.

Depth sensing nanoindentation and nanoscratch testing were combined with atomic force microscopy and electron microscopy observations to study mechanical properties and fracture behavior of a number of TiAlN(Si, C,…) hard thin films. Various nanoscale multilayer thin films were deposited onto the cemented carbide substrates using cathodic arc PVD. Failure modes were activated either by a cycle of indentation or by microscratching of the samples to provide an estimation of the fracture toughness and interfacial fracture energies. Load–displacement curves were characterized by small discontinuities due to the formation of nano and microscale cracks through the film thickness. Under sufficiently high load the occurrence of large-scale cracks consists of the successive lateral cracks at the contact site, or corner Palmqvist type radial cracks around the contact area depending on the film structures. Such indentation behaviors can be attributed to small modulus mismatch between the film and the substrate, good adhesion of the film, and in particular high toughness of both substrate and films in spite of great differences in their respective hardness. Various modes of failure and the sequences of fracture events were determined using stepwise or continuously increasing load scratch tests. Some films were found to be more sensitive to tensile stress behind the indenter which generates through thickness vertical microcracks on the scratch track. Other films appeared to be more susceptible to compressive stress ahead of the indenter leading to local delamination at the interface between the layers and irregular microcracks under the contact area.

Reduction of macroparticles embedded within the cathodic arc deposited coatings is important for achieving high quality coatings with superior tribological properties, and it remains a major challenge in cathodic arc depositions. In the present study, the authors aim to understand the nature of macroparticles formed from TiNb alloy cathodes and the role of TiNb cathode nitridation in reducing the amount of generated macroparticles. The microstructure of the macroparticles was investigated using scanning transmission electron microscopy-energy dispersive spectroscopy, scanning electron microscopy, and x-ray diffraction techniques and revealed compositionally different macroparticles, such as macroparticles with a Nb-rich core, Ti-rich macroparticles, and macroparticles with a composition similar to that of the coatings. The examination of the macroparticles indicated the compositional segregation of niobium and titanium. With increasing N2 gas pressure during deposition, the macroparticles showed increased...

International audience; This book provides a comprehensive treatment of the cavitation erosion phenomenon and state-of-the-art research in the field. It is divided into two parts. Part 1 consists of seven chapters, offering a wide range of computational and experimental approaches to cavitation erosion. It includes a general introduction to cavitation and cavitation erosion, a detailed description of facilities and measurement techniques commonly used in cavitation erosion studies, an extensive presentation of various stages of cavitation damage (including incubation and mass loss), and insights into the contribution of computational methods to the analysis of both fluid and material behavior. The proposed approach is based on a detailed description of impact loads generated by collapsing cavitation bubbles and a physical analysis of the material response to these loads. Part 2 is devoted to a selection of nine papers presented at the International Workshop on Advanced Experimental and Numerical Techniques for Cavitation Erosion (Grenoble, France, 1-2 March 2011), representing the forefront of research on cavitation erosion. Innovative numerical and experimental investigations illustrate the most advanced breakthroughs in cavitation erosion research.

This chapter is devoted to the initial stage of cavitation erosion known as the incubation period. During this period, failure and material removal are negligible and the damage consists in isolated pits that result from plastic deformation for metallic samples. Typical distributions of pits with respect to their diameter are presented and the effects of various parameters such as flow velocity and material properties are discussed. The characteristic time of the erosion process is defined as the time needed for the pits to fully cover the eroded area without any overlap, and the characteristic pit size is defined as the size of those pits whose contribution to the covered surface is the largest. A new technique for estimating impulsive pressures from pitting tests is suggested. It is based on the similarity between a cavitation erosion pit and a conventional spherical nanoindentation imprint. This technique allows for the determination of the load spectrum in a wide range of pressure amplitudes by combining pitting tests on different materials of various cavitation resistances. The impulsive load associated with a pit can be deduced and correlated with pit volume.

This chapter is devoted to the advanced stages of erosion characterized by a mass loss curve of a sample exposed to cavitation as a function of exposure time. Depending upon materials, erosion devices, and operating conditions, different regimes of erosion may be identified on the mass loss curve including incubation, acceleration, deceleration, and steady-state periods. Typical mass (or volume) loss curves obtained for different materials using ultrasonic cavitation, cavitating jets, and a high-speed cavitation tunnel are discussed. They can be normalized by introducing a characteristic volume loss and a characteristic time, which are unique functions of the material and the cavitating field condition. By computing the ratio of characteristic volume loss and characteristic time, the characteristic erosion rate can be deduced for allowing material ranking. The ranking deduced from vibratory cavitation tests and from cavitating jet tests is generally in agreement. Some materials, however, do not rank the same way in a cavitating flow of relatively low aggressiveness (such as vibratory cavitation) as compared to the cavitating flow of higher aggressiveness (high speed cavitating jets).

In this chapter, an introduction to cavitation and cavitation erosion is presented. Cavitation involves the development of various types of vapor structures (such as attached cavities, travelling bubbles, vortical cavities, bubble clouds) in liquid flow due to a drop in the local pressure below a critical value usually close to the vapor pressure. These structures generally originate from cavitation nuclei, typically gaseous microbubbles contained in the liquid. The critical pressure of a nucleus is defined as the particular value of the pressure below which no equilibrium is possible. If a nucleus is subject to pressure lower than its critical pressure, it will explosively grow into a macroscopic cavitation bubble. The bubble will collapse when transported by the liquid flow into regions of pressure recovery. If the collapse occurs near a wall, the resulting high amplitude and small duration impulsive loads may cause local damage. Repeated impulsive loads may cause increasing cavitation erosion damage. The response of the material to cavitation impulsive loads is discussed and material properties most relevant to cavitation erosion, such as sensitivity to strain rate, are presented.

In this chapter, a model is proposed for analyzing the response of ductile materials to repetitive cavitation impacts. This model emphasizes those impacts whose amplitudes exceed the material rupture strength and cause material fracture and mass loss. Impacts whose amplitudes are between the material yield stress and rupture strength are assumed to progressively harden the superficial layers of the material and contribute to the erosion acceleration period. The hardening mechanism is described on the basis of hardness profiles measured on cross sections of eroded samples. In particular, a characteristic thickness of the hardened layers is introduced. The model leads to a simple equation for the prediction of the erosion rate during the steady-state period. The equation shows that it is proportional to the characteristic erosion rate defined as the ratio of the hardened layer thickness to the impact coverage time. This approach tends to prove that the length scale and time scale relevant to the erosion process are respectively the hardened layer thickness (mostly a material property) and the impact coverage time (mostly a flow property).

This chapter presents in detail several cavitation erosion testing methods commonly used in the laboratory. The vibratory cavitation apparatus (G32) is described with its two variants, the direct method using a specimen attached to the vibrating tip of the ultrasonic horn and the alternative method using a fixed specimen facing the horn tip. In the cavitating jet apparatus (G134 and its variants), a jet is discharged at high pressure and velocity in a cell whose pressure may be controlled to adjust the cavitation number. This results in a shear type cavitation whose aggressiveness may be enhanced by a proper design of the nozzle shape and piping assembly. A high-speed cavitation tunnel equipped with a radial divergent test section is also presented. This particular test section generates an unsteady cavity attached to the nozzle exit with cavitation erosion damage concentrated in the cavity closure region. Usual testing procedures together with typical erosion patterns and mass loss results obtained in such facilities are also presented.

This chapter is devoted to the measurement and analysis of impulsive pressures generated by cavitation bubble collapse. The measurement technique makes use of pressure sensors which may be directly exposed to the cavitating flow or protected from it to limit the risk of damage. The unsteady pressure signals detected by the sensors are made of a succession of pulses of various amplitudes and durations. The analysis consists of determining their distribution as a function of amplitude and duration. Typical pressure pulse measurements are presented in the cases of a cavitating jet, an ultrasonic horn and an attached cavity generated in a high-speed cavitation tunnel. Pressure pulse height or duration spectra follow a Weibull (or a simple exponential) distribution that involves a limited number of parameters such as a reference rate and a reference amplitude or duration. The influence of flow velocity on the reference rate and amplitude is investigated and normalized spectra independent of flow velocity are presented. The correlation between peak pressure rate and pitting rate on various materials is analyzed assuming that a pressure pulse generates a pit if its amplitude exceeds a critical value connected to the material yield stress.

In-plane mechanical properties of titanium nitride (TiN x ) thin films have been investigated by performing bulge test experiments on square membranes of side of approximately 2 a =4 mm. A layer of about 1 μ m thickness of TiN x ( x =0.84–1.3) was deposited onto an n-type Si(100) wafer using radio frequency magnetron sputtering. Prior to TiN x deposition, free-standing low-stress LPCVD silicon nitride (SiN y ) thin films were fabricated by means of standard micromachining techniques. The edges of windows were aligned with the [110] directions of underlying silicon wafer in order to make perfect squares bounded by (111) planes. The bulge test was first conducted on the silicon nitride films to determine its proper residual stress and Young's modulus, being σ i =227±15 MPa and E =225±10 GPa, respectively. Then, the composite membrane made of TiN x together with underlying SiN y was bulged and the related load-displacement variation was measured. Finally, using a simple rule of mixtures formula, the elastic mechanical properties of TiN x coatings were determined and compared to those obtained during nanoindentation measurements. Both the Young's modulus and residual stress showed increasing values with increasing bias voltage, nitrogen-to-titanium ratio and coating density. The effect of substrate temperature below 600°C was found to be less significant compared to other parameters. These results are presented and discussed in terms of coating porosity, microstructure and chemical composition determined by means of electron probe microscopy.

The ability of laser nitriding to improve water droplet erosion resistance of Ti6Al4V alloy was studied. Using a CO 2 continuous laser, a layer of about 400 μm thickness was nitrided and another layer of 400–500 μm was only heat affected. Electron microscopy observations showed that the microstructure of nitrided layers consists essentially of TiN compounds which are embedded in Ti(α) matrix. Depending on the nitrogen concentrations within the feeding gas, the titanium nitrides exhibited plate-like shape or dendritic morphologies. Below the nitrided layer a thickness of 50–100 μm of samples underwent martensitic structure which in its turn gives rise progressively to bimodal (α + β) base material. Laser nitriding increased microhardness from 370–400 to 650–800kgf mm −2 , and enhanced erosion resistance significantly compared with untreated Ti6A14V and hardened 12% Cr stainless steel. The mechanism of material removal by erosion was changed from work hardening and platelets detachment in untreated samples to brittle fracture by formation of large flakes and spalling in nitrided layers. Advanced stages of erosion are accompanied by the appearance of macrocracks of ten in the nitrided zone, but some of them propagate even into heat-affected area. The annealing at 650 and 700°C of the laser-nitrided samples results in precipitation of β phase rich in vanadium.

The objective of the study is to determine the effect of parent’s socio economic background on Mathematics anxiety and academic achievement in high school students. The sample comprised 540 (268 boys and 272 girls) 8th, 9th and 10th grade high school students from Karnataka, Kerala and Tamil Nadu states. The answers of students were evaluated using a Mathematics anxiety scale (MAS) and parent’s socio economic background estimated by a socio economic background questionnaire. The results have revealed that among the parent’s socio economic background variables, only parent’s education has a negative correlation with Mathematics anxiety and multivariate regression for this model revealed that combination of age, income and education can be a good predictor for Mathematics anxiety. The second part of results also exposed that parent’s income and parent’s education has a significant positive correlation with mathematics anxiety and multivariate regression for this model also revealed that combination of parent’s socio economic background can be a good predictor for Mathematics anxiety. On the basis of these findings, it was recommended that special classes should be provided for training of parents and they should be prepared in counseling and pedagogical classes. Key words: Academic achievement, parent’s socio economic background, mathematics anxiety.

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 in the velocity range 45-90 m/s at a constant cavitation number. The test section was made of a straight nozzle 16 mm in diameter discharged into the radial 2.5 mm space between two flat walls. Cavitation appears in the form of a toroidal cavity attached to the nozzle exit and damage on the samples facing the nozzle is concentrated in a circular ring centered in the cavity closure region. The exposure time was adjusted to avoid pit overlapping. The material surface was examined using a conventional contact profilometer which allowed us to identify the pits, count them, and measure their main characteristics such as depth, surface area, and volume. From these the pitting rate, the coverage rate, and the depth of deformation rate were defined. Pits were classified according to their diameter. For all materials and operating conditions, pitting rate appears to follow an exponential law in relation to the pit diameter. This law depends upon two parameters only, which were identified as the coverage time tau (i.e. the time required for the surface to be covered by erosion pits) and a characteristic pit diameter delta, which corresponds to the pits whose contribution to the coverage process is the highest. Scaling laws for pitting were derived accounting for both material properties and flow velocity, and a procedure to make pitting test results non-dimensional is proposed. The influence of the material on pitting test results was analyzed. It is shown that the damage is not correlated in simple terms with the elastic limit determined from conventional tensile tests and it is conjectured that other parameters such as the strain rate might play a significant role and should be included in the analysis. The effect of flow velocity on both parameters tau and delta was analyzed and a classical power law was found for the influence of the flow velocity on pitting rate for all three materials. Finally, some analysis and discussion is given concerning distributions of pit volume and pit depth. (C) 2011 Elsevier B.V. All rights reserved.

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 drop test technique. Pressure pulse amplitudes were measured at different velocities and constant cavitation number and cavity length. It was found that pressure pulse height spectra follow a simple exponential law, which depends upon two parameters interpreted as a reference peak rate and a reference load. By exploring the dependence of both parameters on flow velocity, it was possible to show that the various histograms measured at different velocities can be reduced to a unique non-dimensional one and derive scaling laws, which enable to transpose results from one velocity to another. The measured values of impact loads are compared to similar data in the literature, and the impact load spectra are discussed with respect to pitting test results available from a previous investigation. It is concluded that an uncertainty remains on the measured values of impact loads and that a special effort should be made to compare quantitatively pitting test results and impact load measurements. To evaluate the coherence of both sets of data with each other, it is suggested to introduce two-dimensional histograms of impact loads by considering the size of the impacted area in addition to the measured impact load amplitude. It is conjectured that the combination of impact load measurements and pitting test measurements should allow the determination of such two-dimensional histograms, which are an essential input for analyzing the material response and computing the progression of erosion with exposure time. [DOI: 10.1115/1.4005342]

The ability of high damping capacity iron-chromium based coatings to absorb mechanical vibrations has been investigated over a wide range of frequencies varying between f= 10 Hz to 10 kHz, and deformation amplitude between ∈ = 10 - 6 to 10 - 3 . The magnetomechanical hysteresis loss (Q - 1 ) was determined based on the modal analysis technique of a flat beam and was found to be very sensitive to internal stress in the samples. Heat treatments usually enhanced the loss capability, but only high-temperature annealing of coatings restored the whole damping capacity to be comparable to that of cast alloys of same chemical composition. The variation of Q - 1 versus vibration amplitude first increased rapidly, passed through a maximum, and then declined relatively slowly to its initial values. The position of the maximum damping was shifted towards lower strains with annealing time and temperature, In contrast to the strain amplitude, the vibration frequency did not influence damping behavior significantly, as expected in ferromagnetic materials. The structure of magnetic domains was observed using the magnetooptical Kerr effect. Modification of structure following heat treatments was associated with different values of the damping capacity. Accordingly, the beneficial effect of annealing on damping capacity arises on the one hand from improved mobility of unpinned domain walls and on the other hand from growth of 90 deg domains, leading rather to equiaxed domain configurations. The irreversible movement of domain walls upon application of an external stress in general occurred suddenly and abruptly between two pinned positions.

Several crystallographic orientations of pure copper and Cu-7.9wt.%Al single crystals have been subjected to vortex cavitation collapse. Specimens damaged by single impacts, multiple impacts and severe erosion have been studied using scanning, transmission and high resolution electron microscopy as well as microhardness measurements. The substructural features at various distances from the eroded surface along a normal cross-sectional plane have been observed. For single impacts, dislocations occur in tangles and microtwins contribute to deformation only under strong impacts causing a rupture in the surface. In eroded copper specimens deformation extends to a depth of about 1.2 mm whereas several mechanisms contribute to hardening. At a depth of 20 μm, twinning is the dominant mechanism which gives rise to cell structures beyond 30 μm. The intersection of these induced twins is accommodated by the formation of secondary microtwins in the crossing area. The cell size of 0.3–0.4 μm near the surface increases to 10–12 μm at a depth of 700 μm and to 40 μm near the end of the hardened layers. The misorientation between cells varies randomly and reaches a maximum of 15°. At intermediate strain regions, corresponding to depths of 100–300 μm, well-defined parallel wall dislocation microbands 0.5 μm wide were superimposed on the cell structures. Transition between twinned regions into cell structures occurs at depths of 20–30 μm by dislocation tangles and incipient cells. Dynamic recrystallization occurs within a depth of 0–120 μm, as shown by the appearance of twin orientation grains. The erosion rate was not significantly affected by crystallographic orientation.

AlN/TiN multilayered thin films with layer thickness ranging from 1 nm to 50 nm were synthesized using rf magnetron sputtering at 400°C. Two series of samples were prepared at the substrate bias of Vb = −25 V and −100 V to modify growth texture of individual layers and verify its influence on the formation of coherent structures. XRD and TEM observations showed that in large period films (tc ≥ 30 nm) each constituent grows under its own kinetic, leading to the formation of nano-crysatlline film randomly oriented with no pronounced texture. Decreasing progressively the layer thickness favours the alignment of (0002) basal plane of w-AlN on (111) plane of TiN, and results in development of strong (111) texture, prerequisite for stabilisation of c-AlN and the formation of epitaxial coherent structures. The degree of crystallographic coherence was found to be higher in TiN(111) oriented films than for TiN(002) textured films. The increase of hardness coincides with the structure transition from a randomly oriented nanocrystalline films to a highly (111) textured multilayers, and the maximum hardness was obtained for epitaxially coherent nanolayers.

The thermal stability of Cr1−xAlxN and Cr1−xAlxSiyN nanocomposite coatings with different composition x, Si content, and phase structure has been investigated. The coatings were deposited in an industrial unit by the cathodic arc evaporation method, using rotating cylindrical cathodes. Further sets of coated WC/Co plates were subjected to an annealing step in a forming gas (92% N2 / 8% H2) atmosphere for several hours at a constant temperature (maximum 1000°C). Chemical composition, microstructure and mechanical properties of the coatings were investigated by the RBS, XRD, TEM, SEM, XPS and nanoindentation techniques.As-deposited Cr1−xAlxSiyN coatings with Al contents x in the range of 0.4 ≤ x ≤ 0.6 showed a single-phase cubic CrAlN structure and a maximum hardness of 38 GPa. With increasing the Al content to x = 0.95 – 0.96, two-phase films consisting of hexagonal AlN and cubic CrAlN structure with hardness of about 31 GPa were obtained. The hardness of Cr1−xAlxSiyN coatings increases during annealing at temperatures in the range of 800 – 1000°C by about 1 – 4 GPa, even though the residual compressive stress in the coatings was found to relax considerably during this procedure. The addition of Si into Cr1−xAlxN delays the appearance of hcp-AlN and thereby improves the thermal stability of the coatings.

Nanoindentation tests were carried out on the surface of polymer nanocomposites exhibiting either graded or homogeneous distributions of Fe3O4@silica core-shell nanoparticles in a photocurable polymeric matrix. The results reveal a complex interplay between graded morphology, indentation depth, and calculated modulus and hardness values, which was elucidated through numerical simulations. First, it was experimentally shown how for small (1 μm) indentations, large increases in modulus (up to +40%) and hardness (up to +93%) were obtained for graded composites with respect to their homogeneous counterparts, whereas at a larger indentation depth (20 μm), the modulus and hardness of the graded and homogeneous composites did not substantially differ from each other and from those of the pure polymer. Then, through a material point method approach, experimental nanoindentation tests were successfully simulated, confirming the importance of the indentation depth and of the associated plastic zone as key factors for a more accurate design of graded polymer nanocomposites whose mechanical properties are able to fulfill the requirements encountered during operational life.

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 motion of superparamagnetic Fe 3O4SiO2 core shell nanoparticles is adopted. It is demonstrated that by lowering the viscosity of the system through particle functionalization and increasing the magnetic force acting on the nanoparticles upon optimization of a simple set up composed of two permanent magnets in repulsion configuration the magnephoretic process can be considerably accelerated. Thus owing to the magnetic responsiveness of the Fe3O4 core and the remarkable mechanical properties of the SiO2 shell approximately 150 µm thick polymeric films with continuous gradients in composition and characterized by considerable increments in elastic modulus (up to ˜70) and hardness (up to ˜150) when going from particle depleted to particle enriched regions can be synthesized even in times as short as 1 hour. The present methods are highly promising for a more efficient magnetic force based synthesis of inhomogeneous soft materials whose composition is required to be locally tuned to meet the specific mechanical demands arising from non uniform external loads. This journal is © The Royal Society of Chemistry 2014.

Multiwalled carbon nanotubes (MWCNTs)/SU8 composites have been produced to enhance the mechanical properties of SU8 photoresist. We have studied the influence of SU8 solvent on the structural homogeneity of composites through nano-indentation testing. It is found that acetone and propylene glycol methyl ether acetate (PGMEA) are very suitable solvents to prepare MWCNTs/SU8 composites with significant increase of the Young's modulus (E-Y). The highest increase of E-Y in respect to the parent material of 104% was obtained with acetone as solvent. It was noticed that the remaining solvent in the composite influences strongly E-Y, as well. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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 the incubation period, where the test sample undergoes localized permanent deformations shaped as individual pits. In this study, samples from three metallic materials, an Aluminum alloy (Al 7075), a Nickel Aluminum Bronze (NAB) and a Duplex Stainless Steel (SS A2205) were subjected to a vast range of cavitation intensities generated by cavitating jets at different driving pressures and by an ultrasonic horn. The resulting pitted sample surfaces were examined and characterized with a non-contact 3D optical scanner and the resulting damage computer-analyzed. A statistical analysis of the pit population and its characteristics was then carried out. It was found that the various cavitation field strengths can be correlated to the measured pit distributions and that two characteristic quantities: a characteristic number of pits per unit surface area and unit time, and a characteristic pit diameter or a characteristic pit depth can be attributed to a given "cavitation intensity level". This characterization concept can be used in the future to study the cavitation intensity of the full scale and to develop methods of full scale predictions based on model scale erosion data. (C) 2012 Elsevier B.V. All rights reserved.