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Carbondale, United States

Peikertova P.,VSB - Technical University of Ostrava | Vaculik M.,VSB - Technical University of Ostrava | Filip P.,VSB - Technical University of Ostrava | Filip P.,Center for Advanced Friction Studies | Kukutschova J.,VSB - Technical University of Ostrava
NANOCON 2012 - Conference Proceedings, 4th International Conference

The study deals with characterization of wear debris generated from commercial brake pad. Brake pads are multicomponent composites which contain more than 10 constituents and polymer matrix. Braking process produces wear particles in form of elements, organic and inorganic compounds. Wear debris may contain several hazardous materials, which may potentially interact with DNA, or cause carcinomas. Wear debris was collected after standard brake dynamometer test and microscopic techniques were used for their characterization. Transmission electron spectroscopy was used to determine size of the emitted nonairborne wear particles. Elemental analysis was performed by scanning electron microscopy with energy dispersive spectroscopy as well as size of the wear particles. Detailed chemical and phase composition of the commercial brake pad is not provided by manufacturers. Furthermore the braking process is accompanied with significant stress and heat generation leading to release wear debris which may significantly differ from initial brake pad. Therefore, Raman microspectroscopy was chosen as additional technique for the characterization of wear particles. In general, Raman spectroscopy provides information about molecular vibrations, which are specific to the chemical bonds and symmetry of molecules, thus these information can be powerful tool for the identification of composition of wear debris emitted by braking. Using the methods described the presence of nano-sized particles and various components based on metal compounds and elemental carbon revealed. Source

Kukutschova J.,VSB - Technical University of Ostrava | Roubicek V.,VSB - Technical University of Ostrava | Maslan M.,Palacky University | Jancik D.,Palacky University | And 4 more authors.

Wear performance of automotive brake material is addressed and debris collected after brake dynamometer test and after ball-milling of identical semimetallic friction lining is characterized using a combination of analytical techniques. The differences between dynamometer wear debris and ball-milled samples are demonstrated. Wear debris is typified by the presence of numerous nanoparticles formed during wear process. Their chemistry resembles the chemistry of friction layer described previously. Contradicting findings by different research groups addressing automotive wear particulates are discussed and further refinement of analytical and testing techniques as well as their combination is suggested. Source

Kukutschova J.,VSB - Technical University of Ostrava | Moravec P.,Czech Institute of Chemical Process Fundamentals | Tomasek V.,VSB - Technical University of Ostrava | Matejka V.,VSB - Technical University of Ostrava | And 5 more authors.
Environmental Pollution

The paper addresses the wear particles released from commercially available "low-metallic" automotive brake pads subjected to brake dynamometer tests. Particle size distribution was measured in situ and the generated particles were collected. The collected fractions and the original bulk material were analyzed using several chemical and microscopic techniques. The experiments demonstrated that airborne wear particles with sizes between 10 nm and 20 μm were released into the air. The numbers of nanoparticles (<100 nm) were by three orders of magnitude larger when compared to the microparticles. A significant release of nanoparticles was measured when the average temperature of the rotor reached 300 °C, the combustion initiation temperature of organics present in brakes. In contrast to particle size distribution data, the microscopic analysis revealed the presence of nanoparticles, mostly in the form of agglomerates, in all captured fractions. The majority of elements present in the bulk material were also detected in the ultra-fine fraction of the wear particles. © 2010 Elsevier Ltd. All rights reserved. Source

Peikertova P.,VSB - Technical University of Ostrava | Kukutschova J.,VSB - Technical University of Ostrava | Vavra I.,VSB - Technical University of Ostrava | Vavra I.,Slovak Academy of Sciences | And 6 more authors.

The paper addresses characterization of nanosized particles which may be potentially mobilized from nonairborne brake wear debris when being suspended in the water environment. Wear particles were generated in a fullscale automotive brake dynamometer simulation using a model low metallic friction composite and a gray cast iron disc. The three types of samples were analyzed: (a) nontreated wear debris, (b) wear debris particles dissolved in water and (c) filtered suspension of dissolved wear debris particles. Samples were subjected to a combination of analyses (XRD, TEM, SEM with EDS, Raman microspectroscopy and vibration magnetometry). Raman microspectroscopy revealed the presence of Fe2O3, Fe3O4, BaSO4, CaCO3, MoS2, graphite and amorphous carbon in the wear debris samples. The TEM analysis of particles in water suspension proved that the nanosized particles are released into water. Barite particles were detected in the water suspension by Raman microanalysis most often. The prepared filtered suspension exhibited magnetic character which is probably related to the presence of magnetic forms of iron and iron oxides. © 2013 Elsevier B.V. Source

Lee P.W.,Center for Advanced Friction Studies | Filip P.,Center for Advanced Friction Studies

The purpose of this research was to study the friction and wear performance of Cu-free and Sb-free environmentally friendly automotive brake friction materials. Model brake material samples were manufactured and put to the test in the full scale automotive brake dynamometer (Dyno) using a SAE J2430 test procedure. The SAE recommended a J2430 test procedure provided the necessary data for the Brake Effectiveness Evaluation Procedure (BEEP) by the Brake Manufacturers' Council. The modified Cu-free and Sb-free brake materials were formulated using the Akebono brake formula. The modified formula contains environmentally friendly geopolymer and natural hemp fibers as a fraction replacement of phenolic resin and synthetic kevlar fibers, respectively. The Dyno results indicate that the friction level of the Cu-free samples was higher than when compared to the baseline material (T-baseline). The samples T-baseline and modified Cu-free and Sb-free materials (T303 and T403) exhibit average effectiveness of 0.32, 0.41 and 0.33, respectively. All tested brakes have passed the Brake Effectiveness Evaluation Procedure (BEEP). The Dyno results show that the modified samples had better performance when compared to the T-baseline as the temperature of the brake increased in the fade section of the SAE J2430 test. The average effectiveness in the fade section of T-baseline, T303 and T403 are 0.33, 0.41 and 0.37, respectively. However, the modified samples exhibit higher wear rate than the T-baseline. The T-baseline has a thickness loss of 0.37. mm, but the T303 and T403 samples lost 1.43. mm and 2.36. mm in thickness, respectively. Analyses using scanning electron microscopy and energy dispersive x-ray microanalysis on the tested samples show that the friction surface of sample T-baseline is covered with a fully developed and stable friction layer (third body) consisting mostly of Fe oxides, different formats of carbon and compounds of materials originally present in the bulk brake material. The T303 and T403 samples, formulated without Cu and Sb did not develop the sufficient friction layer. The friction layer seems to be responsible for the detected lower wear rate in T-baseline compared to T303 and T403 samples, and it acts as a solid lubricant on the interface between the rubbing pad and the cast iron disc lowering the adhesive forces. The friction and wear of the T-baseline sample is controlled by adhesive mechanisms. The T403 material, formulated without Cu and Sb and with the highest content of geopolymer replacing phenolic resin matrix, exhibited extensive abrasive wear in addition to adhesive mechanisms. Higher adhesion forces in T403 as well as in T303 samples, when compared to the T-baseline sample, are responsible for higher detected friction values and for the efficient removal of the dominant part of the friction layer. The capacity to form a friction layer on the surface plays a considerable role when lowering the wear of brake materials. The friction layer is formed by the compaction and interaction of friction wear debris particles and its stability and character depend on the chemistry of the bulk materials in contact as well as the temperature, pressure and sliding speed during a friction process. © 2013 Elsevier B.V. Source

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