1,721,122 research outputs found
Measurement of the friction of thin films by means of a quartz microbalance in the presence of a finite vapor pressure
No full textIn recent years, the quartz-crystal microbalance technique (QCM) has been succesfully applied to the field of nanotribology. In this paper we examine the effect of a finite vapor pressure on the accuracy of thin-film friction measurements taken with a QCM by solving the Navier-Stokes equation of the combined system quartz-crystal-adsorbed film-bulk vapor. We also discuss the details of the calibration procedure of the QCM carried out at both room temperature and low temperature, and describe the data acquisition and analysis specific to tribological applications. Finally, we present some preliminary data of the friction of a Kr monolayer adsorbed on gold at low temperatures that show the sliding of the film
Adsorption Within and On Regularly Patterned Substrates
No full textAdvances in nanofabrication techniques have made possible the realization of highly-regular patterned surfaces. In this paper, we review recent experiments involving the adsorption of simple classical fluids in regular arrays of microscopic channels with different cross-section profiles and of straight, not interconnected mesopores, which show a rich interplay between geometry and physics. The attention will be devoted to the features of wetting transitions in microchannels and of capillary filling in cylindrical mesopores
Triple-point wetting of Xe on NaF
No full textWe have measured high-precision adsorption isotherms of Xe on NaF by using a torsional oscillator microbalance. In contrast to theoretical predictions, we find that this system undergoes triple-point wetting. [S0163-1829(98)06624-7]
Triple-point wetting of Argon and Methane on gold
No full textWe have performed high sensitivity quartz microbalance measurements of argon and methane adsorbed on gold. On smooth and flat gold electrodes we have found that both of these systems undergo the common triple-point wetting. Vice versa, on some heterogeneous gold electrodes the temperature scans of argon along the solid-vapor coexistence line show pronounced hysteresis loops between cooling and heating, while those of methane were, within the experimental resolution, reproducible
Adsorption isotherms of Helium on Na and on Rb
No full textAdsorption isotherms of He-4 on Na and on Rb measured with a quartz crystal microbalance are presented. The isotherms on Na indicate complete wetting at coexistence and the growth of a thin film at low relative pressures, which may become superfluid at lower temperatures. The results on Rb indicate clear prewetting jumps near coexistence from a thin film (less than 0.1 monolayers) to a thick superfluid film. Our results are in good agreement with the phase diagram found by Phillips et al. (Phys. Rev. B 58 (1998) 3361)
Triple-point wetting of Ne on solid CO2
No full textWe have studied the wetting behavior of Ne adsorbed on solid CO2 by means of a quartz crystal microbalance technique. In contrast to recent density functional calculations that predict a prewetting transition near the bulk critical point of Ne, we have observed the more common triple-point wetting behavior
Influence of graphene coating on the adsorption and tribology of Xe on Au(111) substrate
No full textThe adsorption and tribological properties of graphene have received increasing attention for the further development of graphene-based coatings in applications. In this work, we performed first principles calculations with the inclusion of the nonlocal van der Waals correction to study the effect of graphene coating on the adsorption geometries, sliding frictions and electronic properties of Xe monolayer on the Au(1 1 1) substrate. The calculated activation energies indicate that Xe becomes movable on pure Au(1 1 1) surface at a temperature of around 30 K, whereas its motion can be activated only at a high temperature of similar to 50 K on graphene and on graphene-coated Au(1 1 1) substrates, in good agreement with recent experimental measurements by quartz crystal microbalance technique
Level meter for dielectric liquids
No full textWe describe a novel device which can measure, with low dissipation and high resolution, the level of a dielectric liquid. This device can also be used with cryogenic liquids, in particular with liquid helium. The high degrees of stability and of reproducibility make this apparatus an instrument of performances largely competitive with respect to others commonly used
Inexpensive but accurate driving circuits for the quartz microbalance
No full textThe quartz crystal microbalance (QCM) is a common technique which finds a wide variety of applications in many different areas like adsorption, catalysis, analytical chemistry, biochemistry, etc., and more generally as a sensor in the investigation of viscoelastic films. In this article we describe some driving circuits of the quartz which we have realized and tested in our laboratory. These can be assembled with standard components which can be easily found. Their performance, in some cases, is as good as that of the much more expensive frequency modulation technique employed in very precise QCM measurements and which requires high-quality commercial radiofrequency generators and amplifiers. (C) 1999 American Institute of Physics
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