- Ultra High Vacuum Systems, Hydrogen Storage Materials, Tribology, corrosion and surface engineering, Triboelectricity and tribology, Tribochemistry, Characterization of Gas Content in Materials, and 11 moreTribology, Triboluminescence, Triboelectrification, Vacuum Tribology, Tribocorrosion, Materials Science, Hydrogen Storage, Physics, Chemistry, Nanotechnology, and Nanoscienceedit
Force measuring is used in various surface characterization techniques such as indentation, scratch tests, tribological analysis, determination of gas content, etc. The main problems related with force measurement under extreme conditions... more
Force measuring is used in various surface characterization techniques such as indentation,
scratch tests, tribological analysis, determination of gas content, etc. The main
problems related with force measurement under extreme conditions have been analysed.
A strategy that should be followed to solve these problems has been discussed and several
examples of successive solutions that recently were developed by the authors are
presented. The need to carry out the characterization under extreme conditions poses
serious problems for the designers of the measuring systems that may include the
incompatibility of the sensors with the test conditions, undesirable interactions with other
components, stability, precision and uncertainty issues, the measurement range, etc.
Resolving these problems must be based on a global approach in which the characterization
system is considered as a whole, while the designer must analyse and solve the
possible conflicts between the subsystems. The way how an appropriate force measuring
system can be selected is described. The proposed method is illustrated by an example
in which an indirect force measurement using optical fibre displacement sensor was used.
Another example describes measuring system developed for vacuum high-temperature
nanoindentation. At high temperature, proper heat management based on noncontact
heating and laminar flow cooling system is mandatory to avoid experimental data
being affected by external noise and thermal drift.
scratch tests, tribological analysis, determination of gas content, etc. The main
problems related with force measurement under extreme conditions have been analysed.
A strategy that should be followed to solve these problems has been discussed and several
examples of successive solutions that recently were developed by the authors are
presented. The need to carry out the characterization under extreme conditions poses
serious problems for the designers of the measuring systems that may include the
incompatibility of the sensors with the test conditions, undesirable interactions with other
components, stability, precision and uncertainty issues, the measurement range, etc.
Resolving these problems must be based on a global approach in which the characterization
system is considered as a whole, while the designer must analyse and solve the
possible conflicts between the subsystems. The way how an appropriate force measuring
system can be selected is described. The proposed method is illustrated by an example
in which an indirect force measurement using optical fibre displacement sensor was used.
Another example describes measuring system developed for vacuum high-temperature
nanoindentation. At high temperature, proper heat management based on noncontact
heating and laminar flow cooling system is mandatory to avoid experimental data
being affected by external noise and thermal drift.
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The theoretical foundation of the formation and distribution of the flow of small dispersible particles in vacuum [1] creates some insight in different sorts of behaviour of powder-like micro particles at normal atmospheric pressure and... more
The theoretical foundation of the formation and distribution of the flow of small dispersible particles in vacuum [1] creates some insight in different sorts of behaviour of powder-like micro particles at normal atmospheric pressure and at different pressure ranges: from normal atmospheric pressure to high vacuum. The behaviour of powder-like micro particles as a result of the action of residual
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As was previously shown, modern vacuum technology uses a large number of different vacuum mechanisms, and most of them are vacuum feedthroughs and drives. The research of feedthroughs for the purpose of enhancing their precision, for the... more
As was previously shown, modern vacuum technology uses a large number of different vacuum mechanisms, and most of them are vacuum feedthroughs and drives. The research of feedthroughs for the purpose of enhancing their precision, for the improvement of power parameters, longevity and reliability, as well as for the reduction of the outgassing rate is performed by designers simultaneously with
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The required precision of vacuum installations in most technologies (thin film coating, electron beam welding, diffusionwelding) is the same as in traditional engineering industry, but operating conditions of the mechanisms work are much... more
The required precision of vacuum installations in most technologies (thin film coating, electron beam welding, diffusionwelding) is the same as in traditional engineering industry, but operating conditions of the mechanisms work are much worse, because of vacuum and periodical outgassing baking (see Tables 1.1, 1.2, 1.4). At the same time, the equipment of surface research, electron beam-, ion beam lithography, Table 1.3, atomic force scanning microscopy, Table 1.6, requires much higher precision of the mechanisms, which should work in ultrahigh vacuum (up to 10-9 Pa). The first peculiarity of vacuum mechanisms is the existence of additional elements in their kinematic chains including: motion feedthroughs, sealing elements, devices for baking, heating elements, holes and grooves on the coupling surfaces for the evacuation of residual gases. All these elements reduce the rigidity of the drives and generate additional disturbing forces that result in the appearance of additional components in the total error. In some cases these new error components can be 10–100 times higher (!) than the errors of basic elements of transmission. The second peculiarity of vacuum mechanisms is, from one side, the absence of a work load as that is contrast to atmospheric machines and, from another side, the existence of large and non-constant friction forces, additional forces generated by atmospheric pressure, forces generated by deformed sealing elements. It is necessary to emphasize the accidental character of friction forces and their non-linear character as well as anisotropy of elastic sealing elements and intensive wear of friction surfaces.
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The vacuum mechanisms are used in vacuum technological equipment described in Chapter 1 for transportation of components (samples, wafers, cathodes, etc.) from one working position to another, for their orientation and positioning against... more
The vacuum mechanisms are used in vacuum technological equipment described in Chapter 1 for transportation of components (samples, wafers, cathodes, etc.) from one working position to another, for their orientation and positioning against the instruments (electron-, ion-, molecular, X-ray beam), or for their positioning against other components (for example, cathode against anode of the gauge). In scanning microscopy they are used for the instrument (probe or cantilever) positioning and scanning of the analyzed surface. In most cases it is enough to have one or two degrees of freedom (linear motion and rotation). However, some technological processes (surface analysis, scanning nanomicroscopy, X-ray lithography) require 3–6 degrees of freedom. The main element in any vacuum mechanism is the motion feedthrough which plays a role of the mechanical element of transmission as well as a sealing element. It is the most critical mechanical element of the kinematic chain of the drive because it controls the required precision of the mechanism and at the same time it should protect vacuum elements against the atmospheric air. In many cases the motion feedthrough plays a role of the final vacuum mechanism on a technological position. In some cases for small micro- or nanotravels independent piezo drive situated in the vacuum chamber can be used. In these cases vacuum feedthroughs are not used.
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Analysis of linear-motion feedthrough schemes (see Figure 4.2, Chapter 4) shows that sliding speed (V parameter) in kinematic pairs of feedthrough can vary from the maximum value corresponding to the traditional nut-screw couple to zero.... more
Analysis of linear-motion feedthrough schemes (see Figure 4.2, Chapter 4) shows that sliding speed (V parameter) in kinematic pairs of feedthrough can vary from the maximum value corresponding to the traditional nut-screw couple to zero. The sliding speed variation from maximum value to minimum value leads to a great variation in the design schemes of the feedthroughs. In general, it
The angular precision of the most widespread bellows-sealed rotary-motion feedthroughs is about 10 and in many cases that is not enough for the user. That is why many designers create more precise feedthroughs. An example of more precise... more
The angular precision of the most widespread bellows-sealed rotary-motion feedthroughs is about 10 and in many cases that is not enough for the user. That is why many designers create more precise feedthroughs. An example of more precise gear is the airtight harmonic drive rotary-motion feedthrough. This type of drive does not have a wide application, because the manufacturing process
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There are several groups of vacuum technological equipment equippedwith vacuum transporting systems. These groups include: thin films coating equipment [1–4], electron and ion lithography [5], molecular epitaxy [6], surface research [7,... more
There are several groups of vacuum technological equipment equippedwith vacuum transporting systems. These groups include: thin films coating equipment [1–4], electron and ion lithography [5], molecular epitaxy [6], surface research [7, 8], electron beam equipment for welding, melting, crystal growing; equipment for outgassing, tubeless pumping, assembling vacuum devices (in ultrahigh vacuum up to 10−8 Pa) [9]. It is necessary to
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The principles of design of vacuum mechanims of nanoscale precision are presented. Physical basics of the mechanisms nanoscale precision are discussed. Vacuum multicoordinate drives and manipulators are also shown. The analysis of vacuum... more
The principles of design of vacuum mechanims of nanoscale precision are presented. Physical basics of the mechanisms nanoscale precision are discussed. Vacuum multicoordinate drives and manipulators are also shown. The analysis of vacuum technological equipment and vacuum research equipment shows that the most strict requirements for the object transference are in electron beam micro lithography equipment. For example, electron beam
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The idea of these mechanisms was born between 1970–1980 in the former USSR and it was realized by Professor A.T. Alexandrova. The group of Professor Alexandrova designed and manufactured different vacuum manipulators, vacuum drives,... more
The idea of these mechanisms was born between 1970–1980 in the former USSR and it was realized by Professor A.T. Alexandrova. The group of Professor Alexandrova designed and manufactured different vacuum manipulators, vacuum drives, vacuum rotary-motion and linear-motion feedthroughs, gates and valves based on the principle of controlled elastic deformation. This work was pioneer in the field of vacuum technique
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Research Interests: Elastomers and XPS
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The purpose of this work is to study the dynamics between the matrix of a contaminated marine sediment, its contaminants and various desorbing solutions by means of equilibrium tests, sedimentation trials and zeta potential, with the... more
The purpose of this work is to study the dynamics between the matrix of a contaminated marine sediment, its contaminants and various desorbing solutions by means of equilibrium tests, sedimentation trials and zeta potential, with the focus on assessing optimum enhancing solutions for decontamination purposes. The sediment samples were analysed to determine their physico-chemical characteristics: particle size distribution, solids concentration, total organic carbon (TOC), content of heavy metals, organic contaminants, mineralogical phases, zeta potential and buffer capacity. Twelve extracting solutions of different nature were used for equilibrium tests, in which the dynamic behaviour of the sediment was evaluated. Elemental analysis was carried out for the sediment samples and the solutions before and after the tests. The sediment was mainly composed of clay and lime, with a high content of iron, which has a strong influence on sorption-desorption processes. The sediment had a considerable buffer capacity at low and high pH values. The desorption of the metals was not proportional to pH. The highest decrease in the concentration of metals from the sediment was obtained with 0.2 M ethylenediaminetetra-acetic acid (EDTA) and 1 M nitric acid, while the lowest degree of metal extraction occurred in pure water and potassium iodide (KI). The most important parameters for contaminant release were complexation ability of the solution for the sediment components and pH of the solution. A promising design for the remediation treatment for the investigated sediment includes complexation and strong acid agents.
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Abstract Wear assessment of critical components subjected to relative sliding is a key factor for the development of advanced materials and surface treatments in automotive industry. Simulation of wear process of the engine components is... more
Abstract Wear assessment of critical components subjected to relative sliding is a key factor for the development of advanced materials and surface treatments in automotive industry. Simulation of wear process of the engine components is considered as a good alternative for experimental testing which is costly and time-consuming, but it requires a reliable experimental data for model fine-tuning. Therefore, friction and wear of cylinder liner against a piston ring were experimentally studied in simulated laboratory tests. The parameters which were controlled in these tests included oil type, lubrication starvation, surface finishing and surface coatings. The obtained experimental data were fed into a specific simulation model (AVL Excite-Power Unit). Comparison of experimental and simulated results yielded the error below 5%.
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BACKGROUND Photocatalytic degradation of pollen components on titanium dioxide nanofunctionalized materials was studied for gymnosperm (Cupressus Arizonica) and angiosperm (Platanus Hybrida acerifolia). RESULTS Scanning electron... more
BACKGROUND Photocatalytic degradation of pollen components on titanium dioxide nanofunctionalized materials was studied for gymnosperm (Cupressus Arizonica) and angiosperm (Platanus Hybrida acerifolia). RESULTS Scanning electron microscopy revealed structural degradation of both exine and intine strata. Fourier-Transformed Infrared Spectroscopy was applied to characterize chemical modification of the pollen grains subjected to photocatalysis. Study of physical properties modification for the pollen extracts was carried out through spectrophotometry and wettability tests. It was found that photocatalysis resulted in significant decrease of C–H and C–O groups and a moderate decrease in C = O. Also, chromaticity values of the pollen extract after photocatalysis tended to approach those of the substrate. Contact angle of water dispersion of the pollen extract was not altered by photocatalysis, but adherence of the components of the pollen extract to Si substrate considerably decreased. CONCLUSIONS Taken together these results provided solid evidence for the degradation of all pollen components including exine and intine enzymes on nanofunctionalized photocatalytic materials. © 2016 Society of Chemical Industry
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According to the most famous publications [1–7] in the field of vacuum mechanics, the vacuum is considered as an aggressive medium, which increases friction forces and accelerates the wear of friction couples of vacuum mechanisms. For the... more
According to the most famous publications [1–7] in the field of vacuum mechanics, the vacuum is considered as an aggressive medium, which increases friction forces and accelerates the wear of friction couples of vacuum mechanisms. For the illustration of this position the known [3, 5, 6, 8] data about friction coefficients in atmosphere and in vacuum for traditional materials are
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In previous studies, it was demonstrated that photocatalysis by TiO2 nanoparticles can be effective for decomposition of pollen grains and pollen allergen extracts (PAEs) for Cupressus arizonica and Platanus hybrida species. In this work,... more
In previous studies, it was demonstrated that photocatalysis by TiO2 nanoparticles can be effective for decomposition of pollen grains and pollen allergen extracts (PAEs) for Cupressus arizonica and Platanus hybrida species. In this work, the chemical and photochemical processes of five types of PAEs belonging to family Asteraceae, tribe Astereae, and family Poaceae, tribes Poeae and Triticea, were studied. It was confirmed that the PAEs suffered almost complete decomposition, which likely led to gaseous final products. For the species of Poeae tribe, i.e., Poa pratensis, Festuca pratensis, and Avena sativa, an unusual surface chemical modification of the photocatalyst consisting in the appearance of new bands on fine core level spectra of Ti 2p, C 1s, and O 1s was observed. These changes were associated with possible doping of TiO2 with C and N by pollen extracts. This was accompanied by a red shift of absorption spectra. The results suggest that some components of Poeae pollen can be grafted on TiO2 surface and they can activate the photocatalyst in the visible range. These findings can open a new pathway to eco-friendly chemical engineering of photocatalysts using organic biological compounds.
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Adsorbent materials for the control of dye pollutants in water were synthetized from stainless steel slag (SSS) using different acid-base treatments. Using HCl (SS-Cl) and HNO3 (SS-NO3) produced high-capacity adsorbents, with BET areas of... more
Adsorbent materials for the control of dye pollutants in water were synthetized from stainless steel slag (SSS) using different acid-base treatments. Using HCl (SS-Cl) and HNO3 (SS-NO3) produced high-capacity adsorbents, with BET areas of 232 m2/g and 110 m2/g respectively. Specifically, the SS-Cl had a structure of amorphous silica sponge. Treatment with H2SO4 (SS-SO4) did not enhance the adsorption capabilities with respect to the raw sample (SSS). Activated carbon (AC) was also tested as reference. The materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 adsorption-desorption isotherms, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) zeta potential, and infrared spectroscopy (FTIR). Batch adsorption experiments with methylene blue (MB) showed that the maximum sorption capacities were 9.35 mg/g and 8.97 mg/g for SS-Cl and SS-NO3 at 240 h, respectively. These values, even at slower rate, were close to the adsorption capaci...
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Wear of wheels and rails is a major problem in railway transportation industry. Solid lubricants constitute a cost-efficient alternative to control wear and friction at the wheel–rail interface, especially when a fine-tuned balance... more
Wear of wheels and rails is a major problem in railway transportation industry. Solid lubricants constitute a cost-efficient alternative to control wear and friction at the wheel–rail interface, especially when a fine-tuned balance between traction force and energy consumption is sought. In this work, composite friction modifiers (CFMs) composed of a vinyl ester matrix reinforced with molybdenum disulfide and carbon nanotubes were developed. The total solid additive content was less than a half in comparison with a commercial product available on the market, which was used as a reference. A benchmarking study of the CFM was carried out by means of tribological tests in a twin-disc machine at a contact pressure of 1.1 GPa and different slip values. The results indicated that the developed CFM reduce coefficient of traction by 10% compared to unlubricated conditions that is similar to the reference. However, the total mass loss of steel components due to wear under CFM lubrication was...
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A dynamic model based on mass balance of fine aerosol particles was developed in order to tackle the problem of accurate quantification of mechanically stimulated particle emission (MSPE) from nanofunctionalized and solid lubricating... more
A dynamic model based on mass balance of fine aerosol particles was developed in order to tackle the problem of accurate quantification of mechanically stimulated particle emission (MSPE) from nanofunctionalized and solid lubricating materials. In contrast to the conventional approach, the model accounts for the effect of air turbulization caused by moving parts of the experimental tribological setup on the enhancement of particle deposition velocity. The increase of the velocity of the moving parts results in an increase of the deposition velocity that leads to a significant underestimation of experimentally measured particle emission rates. The developed model was experimentally verified using natural and artificial nanoparticle aerosols. Finally, the new methodology of particle emission rate quantification was employed for the analysis of fine particle emission produced when the solid lubricating materials were tested against a sliding steel surface. The developed method paves th...
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A study of outgassing by impacting surfaces in ultra high vacuum using mass spectrometry is presented. The substrate, which receives the impact, is a stainless steel AISI 304 sheet. The impacting surface is a carbon chromium ball. Impacts... more
A study of outgassing by impacting surfaces in ultra high vacuum using mass spectrometry is presented. The substrate, which receives the impact, is a stainless steel AISI 304 sheet. The impacting surface is a carbon chromium ball. Impacts were performed at energies of 3.36 and 9.8mJ. The average pressure increases over 20 impacts for the first desorption peak in the
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ABSTRACT A study of the tribodesorption of hydrogen stimulated by the friction of an alumina pin on stainless steel in ultrahigh vacuum at room temperature is presented. A special two-chamber ultrahigh-vacuum system separated by a... more
ABSTRACT A study of the tribodesorption of hydrogen stimulated by the friction of an alumina pin on stainless steel in ultrahigh vacuum at room temperature is presented. A special two-chamber ultrahigh-vacuum system separated by a well-defined orifice of low conductance is used to determine minute amounts of desorbed gases. The friction cell allows the control of the normal force of the alumina pin on the stainless-steel surface, the frequency of sweeping, as well as the dwell, i.e., the time between consecutive strokes. The profile of the p(H2)-t desorption curve shows a near-exponential increase in pressure to a stable value; then, after the friction cessation, the pressure decreases back to the initial value. The desorption curve presents an oscillating signal over the continuous one that corresponds with the sweeping frequency. An important aspect of the present research has been to elucidate the origin of the desorbed hydrogen: bulk or surface of materials. In this respect, the amount of tribodesorbed hydrogen is compared with the amount of adsorbed hydrogen at dwell times from 0.5 to 4 s. This adsorption is 50 and 5 times lower than the desorbed hydrogen at normal forces of 0.072 and 0.218 N, respectively, and a dwell time of 4 s. An important finding is that the amount of desorbed hydrogen is irrespective of the dwell time, and the desorption rate increases linearly with sweeping frequency. The authors conclude that the origin of the desorbed hydrogen is in the bulk.
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Tribochemical decomposition of magnesium hydride (MgH2) induced by deformation at room temperature was studied on a micrometric scale, in situ and in real time. During deformation, a near-full depletion of hydrogen in the micrometric... more
Tribochemical decomposition of magnesium hydride (MgH2) induced by deformation at room temperature was studied on a micrometric scale, in situ and in real time. During deformation, a near-full depletion of hydrogen in the micrometric affected zone is observed through an instantaneous (t < 1 s) and huge release of hydrogen (3-50 nmol/s). H release is related to a nonthermal decomposition process. After deformation, the remaining hydride is thermally decomposed at room temperature, exhibiting a much slower rate than during deformation. Confocal-microRaman spectroscopy of the mechanically affected zone was used to characterize the decomposition products. Decomposition was enhanced through the formation of the distorted structure of MgH2 with reduced crystal size by mechanical deformation.
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ABSTRACT Mechanically Stimulated Gas Emission (MSGE) spectroscopy was used for investigation into tribochemical reactions and gas emission for four types of amorphous hydrogenated carbon (a-C:H) coatings, which were obtained by either ion... more
ABSTRACT Mechanically Stimulated Gas Emission (MSGE) spectroscopy was used for investigation into tribochemical reactions and gas emission for four types of amorphous hydrogenated carbon (a-C:H) coatings, which were obtained by either ion beam deposition (IBD) or plasma enhanced chemical vapour deposition (PECVD). The results of statistical analysis, which was employed to identify the components of the emitted gases from the mass-spectrometry data, argue against the hypothesis that considerable amount of CH3 could be present in the emitted gases. For the IBD coatings the main components of the emitted gases were methane and/or argon, whereas for the PECVD coatings they were mainly methane and hydrogen. Noticeable emission of ethane, propane, carbon mono- and dioxides was also detected under sliding of PECVD coatings deposited with the lowest ion energy. While frictional heating has been definitely ruled out as the driving mechanism for MSGE, there are experimental evidences that MSGE has to be associated with structural degradation of the coating.
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This study investigates the outgassing of bare stainless steel and MoS2 coated ball bearings, both of which are widely used in modern high vacuum technological equipment. Three well-distinguished stages of outgassing are observed as a... more
This study investigates the outgassing of bare stainless steel and MoS2 coated ball bearings, both of which are widely used in modern high vacuum technological equipment. Three well-distinguished stages of outgassing are observed as a function of time, which correspond to different phases of a ball bearing&amp;amp;#39;s lifetime. For both type of bearings, hydrogen, carbon oxide and methane were the
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An UHV dynamic expansion system to study gassing and outgassing of metals under friction in vacuum has been developed. The vacuum chamber of the system has two main parts separated by a wall with a central orifice of nominal conductance... more
An UHV dynamic expansion system to study gassing and outgassing of metals under friction in vacuum has been developed. The vacuum chamber of the system has two main parts separated by a wall with a central orifice of nominal conductance of 5.27l s−1 for N2 at 300K. The main part of the system is equipped with a quadrupole mass-spectrometer, ion
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Tribological properties and surface characteristics of ethylene–propylene-diene elastomers were studied as a function of carbon black (CB) content. The surface analysis was performed inside and outside the wear track by X-ray... more
Tribological properties and surface characteristics of ethylene–propylene-diene elastomers were studied as a function of carbon black (CB) content. The surface analysis was performed inside and outside the wear track by X-ray photoelectron spectroscopy (XPS) in order to evaluate possible compositional changes produced by rubbing. Carbon black content had only a small influence on the surface chemistry of the unworn surfaces. However, on the surfaces subjected to friction, the oxygen concentration decreased with increasing CB content. Neither the surface analysis by XPS nor the wettability tests revealed important thermal degradation of the polymer in these friction tests.
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The dynamic characteristics of an ideal (without intrinsic gas desorption and adsorption on the walls) vacuum system have been studied during controlled gas injection—gas impulses supplied in the form of a series of rectangular peaks. It... more
The dynamic characteristics of an ideal (without intrinsic gas desorption and adsorption on the walls) vacuum system have been studied during controlled gas injection—gas impulses supplied in the form of a series of rectangular peaks. It is shown that the behavior of the vacuum system can be described by the function of an aperiodic link.
Dynamic tribochemical processes for dicationic ionic liquid containing a geminal imidazolium cation head group bridged by a poly(ethylene glycol) and a bis(trifluoromethylsulfonyl)imide anion were studied using time-resolved mechanically... more
Dynamic tribochemical processes for dicationic ionic liquid containing a geminal imidazolium cation head group bridged by a poly(ethylene glycol) and a bis(trifluoromethylsulfonyl)imide anion were studied using time-resolved mechanically stimulated gas emission mass-spectrometry (MSGE-MS). In comparison with similar monocationic imidazolium ionic liquids with short alkyl or long polyether side chains, the dicationic ionic liquid had a lower coefficient of friction on Ti6Al4V alloy and smoother behavior. The analysis of volatile decomposition products suggested multiple tribochemical reactions in which both anionic and cationic moieties are involved. The tribochemical degradation of cations was mainly through the detachment of the side and bridging chains from the imidazolium head groups. The absence of volatile products containing nitrogen implies that the imidazole group remained unchanged. Hydrogen and water desorption were attributed to the reactions of hydrogen fluoride being a product of anion degradation with titanium and titanium oxide, respectively.
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A B S T R A C T The tribological performance of three types of amorphous carbon coatings was screened in search of potential candidates for solid lubricants suitable for working under both atmospheric and vacuum conditions. A coating... more
A B S T R A C T The tribological performance of three types of amorphous carbon coatings was screened in search of potential candidates for solid lubricants suitable for working under both atmospheric and vacuum conditions. A coating obtained through ion assisted condensation of silicon oil vapours behaved well under atmosphere but failed in vacuum. Two types of hydrogenated amorphous carbon coatings, with and without Si doping, obtained by physical vapour deposition showed good performance in vacuum reaching superlow friction. The Si-doped amorphous carbon coatings were likewise good under atmospheric conditions with the coefficient of friction ranged between 0.1 and 0.15. The degradation of the coatings under vacuum was further studied using Mechanically Stimulated Gas Emission Mass-Spectrometry and Fourier-Transformed Infra-Red Spectrometry.
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The effect of TiO2 photocatalytic treatment on allergen proteins of pollen was evaluated. The allergenic activity and chemical composition of pollen allergenic extracts (PAE) of two species: Cupressus Arizonica and Platanus Hybrida... more
The effect of TiO2 photocatalytic treatment on allergen proteins of pollen was evaluated. The allergenic activity and chemical composition of pollen allergenic extracts (PAE) of two species: Cupressus Arizonica and Platanus Hybrida acerifolia were characterized using three experimental techniques: scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fluorescence spectrophotometry with the fluorescein diacetate probe (FDA). SEM and XPS experiments have shown that the total amount of organic matter of PAE decreased during the photocatalytic treatment. Furthermore, FDA fluorescence probe provided an indication that the enzymatic activity was completely inhibited after photocatalytic treatment. This result demonstrated evidences of the efficiency of the photocatalysis process in deactivation of pollen allergens.
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Analysis of Mechanically Stimulated Gas Emission Spectrometry data combined with characterization of chemical composition, structure and mechanical properties of various hydrogenated amorphous carbon coatings has allowed shedding light on... more
Analysis of Mechanically Stimulated Gas Emission Spectrometry data combined with characterization of chemical composition, structure and mechanical properties of various hydrogenated amorphous carbon coatings has allowed shedding light on the possible reactions of tribochemical degradation. These reactions are conceivably driven by the mechanical deformation and stress rather than by frictional heating. A close correlation between the increase in proportion of sp3 CHx groups in the coating and the rate of CH4 emission was observed. Emission of methane is suggested to involve abstraction of methyl radical followed by recombination with hydrogen atom. Generation of ethane has to be due to recombination of two abstracted methyl radicals rather than an ethyl radical with hydrogen atom. The rate of H2 emission steeply and non-linearly increased with the hydrogen content in the coating. Hydrogen generation can involve both liberation of occluded H2 and re-combinative reaction.
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Tribochemical decomposition of magnesium hydride (MgH2) induced by deformation at room temperature was studied on micrometric scale, in situ and in real time. During deformation, a near-full depletion of hydrogen in the micrometric... more
Tribochemical decomposition of magnesium hydride (MgH2) induced by deformation at room temperature was studied on micrometric scale, in situ and in real time. During deformation, a near-full depletion of hydrogen in the micrometric affected zone is observed through an instantaneous (t < 1 s) and huge release of hydrogen (3-50 nmol/s). H-release is related to a non-thermal decomposition process. After deformation, the remained hydride is thermally decomposed at room temperature exhibiting a much slower rate than during deformation. Confocal-microRaman spectroscopy of the mechanically affected zone was used to characterize the decomposition products. Decomposition was enhanced through formation of the distorted structure of MgH2 with reduce crystal size by mechanical deformation.
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The main difficulty in designing of an ultrahigh vacuum (UHV) tribometer combined with tribophysical and tribochemical characterization techniques is to find the critical compromise between the scientific requirements and technical or... more
The main difficulty in designing of an ultrahigh vacuum (UHV) tribometer combined with
tribophysical and tribochemical characterization techniques is to find the critical compromise between
the scientific requirements and technical or technological limitations from different subsystems and
components. The principal conflicts, their possible solutions and the recommended tribometer
configurations are analysed. The developed methodological principles were applied for designing and
construction of two UHV experimental tribological systems: TriDes-2 and Ca3UHV. The advances in the
design and development of the vacuum system as well as the UHV force sensor and sample holder are
presented and discussed.
tribophysical and tribochemical characterization techniques is to find the critical compromise between
the scientific requirements and technical or technological limitations from different subsystems and
components. The principal conflicts, their possible solutions and the recommended tribometer
configurations are analysed. The developed methodological principles were applied for designing and
construction of two UHV experimental tribological systems: TriDes-2 and Ca3UHV. The advances in the
design and development of the vacuum system as well as the UHV force sensor and sample holder are
presented and discussed.
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Mechanically Stimulated Gas Emission (MSGE) spectroscopy was used for investigation into tribochemical reactions and gas emission for four types of amorphous hydrogenated carbon (a-C:H) coatings, which were obtained by either ion beam... more
Mechanically Stimulated Gas Emission (MSGE) spectroscopy was used for investigation into tribochemical reactions and gas emission for four types of amorphous hydrogenated carbon (a-C:H) coatings, which were obtained by either ion beam deposition (IBD) or plasma enhanced chemical vapour deposition (PECVD). The results of statistical analysis, which was employed to identify the components of the emitted gases from the mass-spectrometry data, argue against the hypothesis that considerable amount of CH3 could be present in the emitted gases. For the IBD coatings the main components of the emitted gases were methane and/or argon, whereas for the PECVD coatings they were mainly methane and hydrogen. Noticeable emission of ethane, propane, carbon mono- and dioxides was also detected under sliding of PECVD coatings deposited with the lowest ion energy. While frictional heating has been definitely ruled out as the driving mechanism for MSGE, there are experimental evidences that MSGE has to be associated with structural degradation of the coating.