Keeping sustainability and the circular economy in mind, numerous studies have been conducted on the feasibility of the utilization of industrial wastes in friction material formulations for braking ...applications. One such highly produced waste is slags from blast furnaces. The present work focuses on the friction, wear, and emissions behavior of a commercially employed friction material formulation observing the inclusion of three kinds of slags. Two types of slags were obtained from a blast furnace; the difference was the cooling method. The third type of slag was collected from a basic oxygen steel furnace. The prepared samples were tested in the form of pins on a pin on disc equipment at 1.51 m/s, 1 MPa, and ambient conditions to replicate a mild braking scenario. Irrespective of the type of slag, the addition of the wastes observed either a decrease or similar emissions when compared to the virgin formulation. The friction and wear were in the range comparable to that of the reference composition; the CoF for slag specimens ranged between 0.49 and 0.51 compared to 0.45 for the reference composition. On the other hand, by inspection of the worn surfaces of the pins, it was seen that the slag-containing specimens had compact and expansive secondary contact plateaus with the inclusion of slag particles in their composition. Through this preliminary analysis, the possibility of the utilization of different slags is highlighted, especially in an already implemented commercial formulation, paving the path for further testing and validation.
•Three types of slags were added to a commercial friction material to evaluate their friction and emission properties.•The CoF and wear were similar and the emissions in a few cases were lower than the virgin specimens.•The slags contributed to the formation of smooth, compact, and extended secondary contact plateaus.•The analysis sheds light on the positive attributes of slag addition in commercial formulations.
The tribological behavior of materials used for vehicular car brakes is investigated using pin-on-disc tests. In particular, the disc was made of a commercial gray cast iron, used for real brake ...discs. The pins were made of newly developed formulations of friction materials, whose thread-line is the elimination of copper. This element was present in the selected bench-mark friction material, which is a low-metallic material, in which copper is replaced by re-arranging the overall composition and by adding increasing amounts of barite, up to a total maximum concentration of 33.5wt%. Wear products, namely the friction layers that formed on the mating surfaces of the pin materials, have been characterized to identify the main phenomena involved and influencing wear rate and friction coefficient. The main outcome of the research is the beneficial influence of barite, the compositional range that is important to target, the possible routes to be pursued, to improve the results achieved so far.
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•A set of new friction materials were specifically designed adding different amounts of barite on a copper-free NAO base friction material.•The role of barite in determine the features of the friction layer and the consequent wear behavior has been investigated.•A mechanism of formation of a peculiar friction layer, observed in the highest barite containing material, has been proposed.
The role of metallic fibers, present in brake pad materials, have been investigated with particular attention to the formation of the friction layer. The aim of the research was to establish an ...effective approach for the development of less polluting copper-free friction materials. Starting from a reference material, two more compositions were prepared: one obtained just by removing copper; in another, the quota of the removed copper fibers was replaced by steel fibers. The samples were wear tested and the results compared with those obtained with the reference material.
The worn surfaces exhibit specific features, like cracks and compacted wear debris, that provide useful indications for interpreting the main wear phenomena and for a further development of novel friction materials.
•Steel fibers have been studied with the aim of develop copper-free friction materials.•Pin-on-disc tests were carried out comparing three innovative friction materials.•Balanced primary and secondary plateaus are the key for a stable friction layer.
Machine learning is increasingly integrated into chemistry research by guiding experimental procedures, correlating structure and function, interpreting large experimental datasets, to distill ...scientific insights that might be challenging with traditional methods. Such applications, however, largely focus on gaining insights via big data and/or big computation, while neglecting the valuable chemical prior knowledge dwelling in chemists’ minds. In this paper, we introduce an Electrochemistry‐Informed Neural Network (ECINN) by explicitly embedding electrochemistry priors including the Butler–Volmer (BV), Nernst and diffusion equations on the backbone of neural networks for multi‐task discovery of electrochemistry parameters. We applied the ECINN to voltammetry experiments of
Fe2+/Fe3+
${{\rm F}{{\rm e}}^{2+}/{\rm F}{{\rm e}}^{3+}}$
and
RuNH362+/RuNH363+
${{\rm R}{\rm u}{\left({\rm N}{{\rm H}}_{3}\right)}_{6}^{2+{\rm \ }}/{\rm R}{\rm u}{\left({\rm N}{{\rm H}}_{3}\right)}_{6}^{3+{\rm \ }}}$
redox couples to discover electrode kinetics and mass transport parameters. Notably, ECINN seamlessly integrated mass transport with BV to analyze the entire voltammogram to infer transfer coefficients directly, so offering a new approach to Tafel analysis by outdating various mass transport correction methods. In addition, ECINN can help discover the nature of electron transfer and is shown to refute incorrect physics if imposed. This work encourages chemists to embed their domain knowledge into machine learning models to start a new paradigm of chemistry‐informed machine learning for better accountability, interpretability, and generalization.
Electrochemistry‐Informed Neural Network (ECINN) embeds chemistry prior knowledge including the Butler‐Volmer, Nernst and Diffusion equations to discover electrode kinetics and mass transport parameter simultaneously from sparse experiments. ECINN seamlessly integrates mass transport and BV equation and provides arguably the best Tafel analysis method. This work encourages embedding domain knowledge to realize strong intelligence with sparse data.
A novel analysis was conducted on the friction and wear properties of a commercial friction material formulation with the addition of bulk (named: gCN) and exfoliated (named: TEX6) graphitic carbon ...nitride in varying quantities: 4.5, 9, 13.5, and 18 wt%. The analysis was two-fold. In the first part, the samples were tested in the form of pins on a pin on disc testing equipment. The typical trend was that the friction coefficient magnitude increased with the addition of gCN. On the other hand, the friction coefficient decreased with the TEX6 addition. The pin wear reduced with the addition of gCN until 9 wt%. Beyond this amount, an increase in pin wear was observed. The TEX6 samples generally noted a decrease in pin wear with the increase in its content. An improvement in the characteristics of the secondary plateaus was seen with the increase in both gCN and TEX6 content. Through this study, the 13.5 wt% addition of both gCN and TEX6 was considered to display permissible friction and wear magnitude, and desirable extension and compaction of secondary contact plateaus. In the second part of the study, the formulation with 13.5 wt% of gCN and TEX6 was tested on a subscale dynamometer to replicate a real-life braking scenario. The friction and wear magnitudes were similar to the pin on disc study and the extension of the secondary contact plateaus was better than the virgin formulation. This study provides a complete analysis of the feasibility of the inclusion of g-C3N4 variations in automotive braking applications.
•Wear analysis on two kinds of gCN in a friction material formulation was conducted.•Bulk gCN behaved as an abrasive and exfoliated gCN behaved as a lubricant.•The most feasible gCN and TEX6 addition was 13.5 wt% in the CFM formulation.•The pin on disc and subscale dynamometer tests fetched similar, desirable results.
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•g-C3N4 (CN) was synthetized from melamine in air and nitrogen.•CN prepared in air contained the lower content of oxygen due to decarboxylation.•Oxygen was present mainly in the form ...of hydroxyl groups.•Influence of oxygen on the CN properties was investigated.
Two types of bulk graphitic carbon nitrides (CN) were synthetized by heating melamine at 550 °C for 4 h in the air (CN/air) and nitrogen (CN/N2) atmosphere for us to find the effect of present oxygen on their properties. Bulk CN was exfoliated by further heating at 500 °C for 1–3 h in air and nitrogen as well. The obtained materials were studied in terms of structural, textural and physico-chemical properties including photocatalytic activity.
The CN/air materials contained less oxygen (2.3–5.0 wt%) than the CN/N2 ones (about 7 wt%) due to decarboxylation during their synthesis and exfoliation in air. The CN/N2 materials had more structural defects, which were attacked by oxygen from the moment the materials came into contact with air. In both types of materials oxygen was supposed to be present mostly in the form of hydroxyl groups. As a result, the CN/N2 materials were slightly exfoliated and their surfaces were more hydrophilic than the CN/air ones. The photocatalytic activity of CN materials was dependent on their specific surface area (SSA). It was found that native oxygen existed in the CN materials and was important for their properties.
The electrochemical properties of metal oxides are very attractive and fascinating in general, making them a potential candidate for supercapacitor application. Vanadium oxide is of particular ...interest because it possesses a variety of valence states and is also cost effective with low toxicity and a wide voltage window. In the present study, vanadium oxide nanorods were synthesized using a modified sol-gel technique at low temperature. Surface morphology and crystallinity studies were carried out by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy analysis. To the best of our knowledge, the as-prepared nanorods were tested with magnesium ion based polymer gel electrolyte for the first time. The prepared supercapacitor cell exhibits high capacitance values of the order of ~ 141.8 F g
with power density of ~ 2.3 kW kg
and energy density of ~ 19.1 Wh kg
. The cells show excellent rate capability and good cycling stability.
Running-in process of low metallic brake pads and cast iron discs are investigated using full scale inertia brake dynamometer designed for particle emission studies. The airborne particles are ...measured using ELPI+ and collected on filters. The pads and disc contact surfaces are studied using microscopy techniques. It is observed that the particle emissions from the new pads and discs are significantly higher compared with the used ones and indicates importance of proper running-in of the pads and disc for wear particle emission tests. The results also indicate that pads and disc pairs which are able to stabilize friction behavior faster will produce less particle emissions which could influence the strategies of brake material formulations or steps during their production.
•Difference in particle emissions for new and used pads.•Running in of pads and discs is necessary to reach stable wear particle emissions.•Running-in of brake discs takes longer than running-in of pads.•Proper running-in has to be taken in consideration for tests focused on wear particle emissions.•Brake pads which develop stabile friction layer faster produce less wear particles.
The composites of graphitic carbon nitride (g-C3N4) and BiOIO3 with different weight ratios of both components (1:1, 2:1, 4:1 and 6:1) were prepared by heating of their mechanical mixtures. Bismuth ...iodate was prepared by hydrothermal treatment of aqueous solutions of Bi(NO3)3·5H2O and I2O5. Pure g-C3N4 was prepared by thermal polycondenzation of melamine at 620 °C. All of the samples were characterized using X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), UV-VIS diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, X-ray photoelectron (XPS) and Fourier transformed infrared (FTIR) spectroscopy. The measurement of photocurrents was used for the study of photogenerated charge carriers and nitrogen physisorption for the evaluation of specific surface area (SSA) and pore size distribution of the samples. The photodegradation activity of the samples was tested by the UVA light photocatalytic decomposition of N2O. The highest photodegradation activity was observed for the 1:1 composite, which was 2 and 2.5 times higher in comparison to pure BiOIO3 and g-C3N4, respectively. The enhanced photocatalytic activity was explained by a significant reduction of charge carriers’ recombination due to the formation of a heterojunction between g-C3N4 and BiOIO3.
Photocatalytical nanocomposites: a review Matejka, Vlastimil; Tokarský, Jonás
Journal of nanoscience and nanotechnology,
02/2014, Volume:
14, Issue:
2
Journal Article
This review focuses on photocatalytically active nanocomposites that are based on the photoactive nanoparticles, or nanostructured particles captured on the surface of the different powderized ...carriers. Nanosized and nanostructured oxides and sulfides with selected metal cations (Ti, Zn, Cd, Fe, etc.) are intensively studied as the photocatalysts for different purposes. The nanodimension of these particles brings several disadvantages, among them being the negative impact on human health, which is a widely discussed topic nowadays. The nanoparticles can permeate through living tissue and enter living cells and thus a strong effort focused on diminishing this problem is the subject of research activities by many groups. One possible way to achieve control of the nanoparticles' mobility is capturing them on the surface of suitable particulate carriers with dimensions on the order of tenths and hundredths of microns whereas this approach leads to formation of new composite material. Clay minerals, silicates, carbonaceous materials, and other particulate matter are intensively studied for these purposes and proper selection of the substrate can bring additional functionality to the final composite. Very often the photoactivity, antibacterial properties, electrical conductivity, and other properties are significantly enhanced in the case of this kind of composite materials. Strong adhesion between the nanoparticles and the surface of the selected substrate is essential for the stability of the final composites. Characterization of the adhesion energies using laboratory experiments is quite difficult and molecular modeling can bring valuable information about the character of interactions at the interface of nanoparticles and substrate.
