Generation of urban road dust from anti-skid and asphalt concrete aggregates

Road dust forms an important component of airborne particulate matter in urban areas. In many winter cities the use of anti-skid aggregates and studded tires enhance the generation of mineral particles. The abrasion particles dominate the PM10 during springtime when the material deposited in snow is resuspended. This paper summarizes the results from three test series performed in a test facility to assess the factors that affect the generation of abrasion components of road dust. Concentrations, mass size distribution and composition of the particles were studied. Over 90% of the particles were aluminosilicates from either anti-skid or asphalt concrete aggregates. Mineral particles were observed mainly in the PM10 fraction, the fine fraction being 12% and submicron size being 6% of PM10 mass. The PM10 concentrations increased as a function of the amount of anti-skid aggregate dispersed. The use of anti-skid aggregate increased substantially the amount of PM10 originated from the asphalt concrete. It was concluded that anti-skid aggregate grains contribute to pavement wear. The particle size distribution of the anti-skid aggregates had great impact on PM10 emissions which were additionally enhanced by studded tires, modal composition, and texture of anti-skid aggregates. The results emphasize the interaction of tires, anti-skid aggregate, and asphalt concrete pavement in the production of dust emissions. They all must be taken into account when measures to reduce road dust are considered. The winter maintenance and springtime cleaning must be performed properly with methods which are efficient in reducing PM10 dust.     

Characterization of PM10 fraction of road dust for polycyclic aromatic hydrocarbons (PAHs) from Anshan, China

Nineteen road dust samples were collected during 2005 in different parts of the urban area of Anshan, Liaoning Province, China, and 11 polycyclic aromatic hydrocarbons (PAHs) species were quantitatively analyzed using GC–MS. The results indicated that the total average concentration of PAHs over the investigated sites ranged from 48.73 to 638.26 μg/g, with a mean value of 144.25 μg/g, higher than the concentrations measured in previous studies. PAHs concentrations were higher with high molecular weight homologues (4–6 rings PAHs), accounting for 83.24–96.98%, showing combustion of petroleum fuels was a potential source. Organic carbon in road dust was considered one of the important factors that influenced the concentrations of PAHs in this study, and it was found that concentrations of total PAHs were correlated with those of organic carbon in road dust. The results of diagnostic ratios analysis showed traffic emission (gasoline or diesel) was one of the most important sources of road dust PAHs. Principal component analysis (PCA) indicated that the major sources of road dust PAHs might be emission from traffic, steel industry, cooking and coal combustion.     

Chemical mass balance source apportionment of PM10 and TSP in residential and industrial sites of an urban region of Kolkata, India

Daily average PM(10) (particulate matter which passes through a size selective impactor inlet with a 50% efficiency cut-off at 10 microm aerodynamic diameter), TSP (total suspended particulate matter) and their chemical species mass concentrations were measured at residential and industrial sites of an urban region of Kolkata during November 2003-November 2004. Source apportionment using chemical mass balance model revealed that the most dominant source throughout the study period at residential site was coal combustion (42%), while vehicular emission (47%) dominates at industrial site to PM(10). Paved road, field burning and wood combustion contributed 21%, 7% and 1% at residential site, while coal combustion, metal industry and soil dust contributed 34%, 1% and 1% at industrial site, respectively, to PM(10) during the study period. The contributors to TSP included coal combustion (37%), soil dust (19%), road dust (17%) and diesel combustion (15%) at residential site, while soil dust (36%), coal combustion (17%), solid waste (17%), road dust (16%) and tyre wear (7%) at industrial site. Significant seasonal variations of the particulate matters have been observed during the study period. In the monitoring sites total carbon, organic carbon and iron were found to be the marker species of road dust, while organic carbon, total carbon, chloride and sulfate have been observed as the marker species of soil dust in TSP.     

Effect of air plasma treatment on mechanical and tribological properties of PBO fabric composites

Friction and wear behavior of one-step or two-step air plasma treated and untreated PBO fabric composites has been evaluated in a pin-on-disc friction and wear tester. Tensile property of impregnated fabric and bond property between fabric and metallic substrate have also been studied. A comparison has been made between untreated and plasma treated fibers by using XPS, FTIR, FESEM and SEM. The results indicated that, air plasma treatment could increase the friction coefficient but decrease the wear rate of the PBO fabric composites. The most suitable condition of plasma treatment was 50 W and 15 min. After two-step plasma treatment, the tensile strength of the PBO fabric was decreased by 40%. While the antiwear property and bonding strength of the PBO fabric composites could be improved by 40–67% and 64%, respectively, which was due to the improvement of the bond property among the fiber, the adhesive and substrate.     

Influence of Surface Modification on Tribo-Performance of Hybrid Glass/PTFE Fabric Composite with Phenolic Resin Binder

The fabric/phenolic composites with the pure and silanized hybrid glass/PTFE fabric were prepared by dip-coating of the hybrid glass/PTFE fabrics in a phenolic resin. The friction and wear performances of the resulting fabric composites were evaluated using pin-on-disc wear tester. The composition change of the glass fabric in hybrid glass/PTFE fabric after silanization was analyzed by FTIR spectroscopy. The morphologies of the composite structures and the worn surfaces of the composites were analyzed by means of scanning electron microscopy (SEM). The results show that the fabric/phenolic composite with the β-aminoethyltrimethoxylsilane silanized hybrid glass/PTFE fabric can obtain the highest load-carrying capacity and the best wear-resistance, followed by the composite with γ-glycidoxypropyltrimethoxysilane silanized hybrid glass/PTFE fabric. Chemical reactions have achieved as the hybrid glass/PTFE fabric was silanized with β-aminoethyltrimethoxyl silane or γ-glycidoxypropyltrimethoxy silane, which contribute to strengthen the bonding strength between the fabric and the adhesive and hence to improve the tribological properties of the hybrid glass/PTFE fabric composites.     

A black tournai “marble” tombslab from Belgium imported to Trondheim (Norway) in the 12th century: Provenance determination based on geological, stylistic and historical evidence

Black Tournai “marble”, a fine-grained Lower Carboniferous (Tournaisian) limestone able to take a good polish has been widely used in the Flanders region (Belgium). Highly crafted baptismal fonts and tombslabs were also exported to England, France and elsewhere during the Middle Ages. Such objects are particularly valuable since their distribution aids the dating of historical events and the reconstruction of medieval trade. Similar black “marble” was extracted in the Meuse valley (Belgium) in the Middle Ages, and there are exploited sources in the UK, Ireland and elsewhere. Thus, it is not straightforward to determine the provenance of black “marble”. Based on geological, stylistic and historical evidence, this paper shows the likelihood that a black “marble” tombslab found in Nidaros Cathedral in Trondheim (Central Norway) was extracted and crafted in Tournai and shipped northwards around 1160, possibly for the grave of the first Norwegian archbishop, Jon Birgerson. The tombslab represents the first known crafted stone imported to Norway from the European continent/British Isles and is thus unique in a historical context. The properties of the Trondheim tombslab match those of black Tournai “marble”: It is a silicified, bioclastic packstone loaded with crinoids, featuring bryozoa and fragments of brachiopods and ostracods. The high silica content and absence of foraminifers distinguish the stone from the Viséan black “marble” quarried in the Meuse valley.     

Drop tower experiments on sticking, restructuring, and fragmentation of preplanetary dust aggregates

For the determination of the aggregation efficiency of preplanetary dust, we performed impact experiments with fractal dust aggregates in the drop tower Bremen. We found that for the lowest impact velocities, the dust aggregates, which consisted of micron-sized, monodisperse SiO₂ spheres, hit and stuck with no measurable impact restructuring. For intermediate collision velocities, compact aggregate structures formed, and at the highest impact velocities, aggregates were fragmented. Our experimental results are in quantitative agreement with a numerical dust aggregate collision model (Dominik, C., Tielens, A. G. G. M. 1997, Astrophysical Journal vol. 480, p. 647), when the latest experimental values for the rolling-friction and break-up energies are used. However, the presence of a rarefied gas flow, in which the incoming aggregates were embedded, increased the threshold velocity for sticking. Although the impinging aggregates were disintegrated at high impact velocities, the resulting fragments were dragged back to the target on which they could stick due to a then considerably lower collision velocity. This aerodynamically-supported aggregation process might be responsible for the rapid growth of preplanetary bodies in the size range from ∼0.1 m to ∼10 m. Such a rapid growth is necessary to prevent a loss of most of the solid bodies of these sizes due to gas-drag-induced fast orbital decay.     

Cavitation resistance of VT5 alloy after surface mechanical pulsed treatment

The mechanical pulsed hardening of VT5 -titanium alloy in the course of the friction contact of the working surface with a special tool in various technological media significantly increases its resistance to cavitation-erosion wear. Moreover, the corrosion-electrochemical characteristics remain high and the microhardness of the surface becomes 2–2.5 times higher. This leads to the increase in the cavitation-erosion resistance of the material. The obtained effect depends on the composition of the applied technological medium. The liquid intended for carbonization proves to be more efficient for increasing the wear resistance of the alloy than the PMS-100 liquid.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 4, pp. 95–97, July–August, 2004.     

Influence of functional graphene as filler on the tribological behaviors of Nomex fabric/phenolic composite

Graphene and polystyrene functionalized graphene (PS-graphene) had been synthesized, and were employed as fillers to improve the anti-wear property and load-carrying capacity of Nomex fabric/phenolic composites. Pin-on-disk type wear tests show that the friction coefficients and wear rates for both graphene and PS-graphene filled fabric/phenolic composites were reduced, when compared with unfilled fabric composite. Moreover, it was found that the 2 wt% PS-graphene filled Nomex fabric/phenolic composites exhibited the optimal tribological properties. The enhancement on the wear property of graphene and PS-graphene filled Nomex fabric composite was mainly due to the self-lubrication of graphene and the easy-formed transfer film on the counterpart pin. We also investigated the effect of filler content, applied load, and sliding speed on the tribological properties of the Nomex fabric/phenolic composites.     

Abrasive wear of thick silica films prepared by vacuum evaporation

We investigate the wear behaviour of thick silica films 2–3m thick evaporated on a polymethylmethacrylate substrate in vacuum. The wear test is performed with kaolin mineral powder suspended in water. Abrasive wear is not affected by silica film hardness varying from 100 to 550 kg mm^–2, which corresponds to film preparation pressures ranging from 5×10^–3 to 5×10^–5 torr. The wear characteristics and the appearance of the wear tracks are strong evidence that abrasive wear of the deposited silica films consists of the mechanical and molecular removal of a hydrolysed silica film surface by abrasive kaolin grains. This is very similar to the case of glass polishing.     

Investigation of the properties of a magnetofluidized bed and development of a new gas purification technology based on them for simultaneous removal of solid and gaseous substances from hot waste gases

The results of investigation of the influence of the mechanical, thermal, structural, catalytic, and regenerative characteristics of granular oxide catalysts on the efficiency of decontamination of volatile organic substances in the catalyst unit and of the filtration rate, amount, and concentration of dust, the size of filter particles, the direction and intensity of a magnetic field, and other parameters on the behavior of the particles, the structure, the porosity, the resistance, the optimum fluidization rates, and the efficiency of collection of dust in magnetofluidization of magnetic particles have been given. The diagram and operating principles of a new technology for simultaneous decontamination of volatile organic matter and collection of dust have been presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 77, No. 6, pp. 59–73, November–December, 2004.     

Identifying airborne objects with two-coordinate meters

A system is considered for identifying airborne objects, which is based on two-coordinate circular-survey radars. Simulation shows that the proposed approach is constructed for typical situations.Translated from Izmeritelnaya Tekhnika, No. 11, pp. 19–21, November, 2004. Original article submitted June 3, 2004.     

Tribological properties of gray cast irons alloyed with phosphorus

We study the influence of phosphorus on the wear resistance of gray cast irons. We have established that, in the course of friction engagement, the inclusions of the phosphide phase elongate and are accumulated near the surface, which favors a decrease in the temperature in the friction zone, friction coefficient, and mass losses as well as an increase in the wear resistance of materials.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 4, pp. 70–74, July–August, 2004.     

Tribological and mechanical properties of the composites made of carbon fabrics modified with various methods

Carbon fabric (CF) was modified with strong HNO₃ etching, plasma bombardment, and anodic oxidation, respectively. The modified carbon fabric was then used to prepare carbon fabric composites (CFC) by dip-coating in a phenolic resin and the relative mass content of carbon fabric in the carbon fabric composites is 65%. The friction and wear behaviors of the carbon fabric composites were evaluated with a Xuanwu-III high temperature friction and wear tester, and their mechanical properties were evaluated on a Shimadzu™ universal materials testing machine, respectively. The changes in the chemical compositions of the unmodified and modified carbon fabrics were analyzed by means of X-ray photoelectron spectroscopy. The morphologies of the worn surfaces of the unmodified and modified carbon fabric composites were analyzed by means of scanning electron microscopy. It was found that the friction-reduction and anti-wear properties of the carbon fabric composites were improved by anodic oxidation, plasma bombardment, and strong HNO₃ etching, so were the mechanical properties and load-carrying capacity. The composite made of the carbon fabric modified with anodic oxidation showed the best tribological and mechanical properties, and the one made of the carbon fabric etched with HNO₃ had the poorest tribological and mechanical properties among the three kinds of the tested composites. The active groups were produced during the oxidation process, which contributed to strengthen the bonding strength between the carbon fabric and the adhesive and hence to improve the tribological and mechanical properties of the composites made of the modified carbon fabric. The friction and wear properties of the carbon fabric composites were closely dependent on the environmental temperature. Namely, the wear rates of the composites at elevated temperature above 180 °C were much larger than that below 180 °C, which was attributed to the degradation and decomposition of the adhesive resin at excessively elevated temperature. Moreover, the composite made of the carbon fabric modified with anodic oxidation had better thermal stability than the one made of the unmodified carbon fabrics.     

Dusty plasma of a dc glow discharge: methods of investigation and characteristic features of behavior

Results are given of experimental investigations of a dusty plasma in the strata of a dc glow discharge. Characteristic forms of plasma-dust structures formed by dust particles of spherical and highly asymmetric shapes are described. Results are given of observation of self-excited dust-acoustic waves, as well as of high-amplitude waves generated under pulsed gasdynamic stimulation. A method of measuring charges of dust particles levitating in strata is described, as well as a method of measuring the radial field of forces acting on dust particles in a plasma trap. Mention is made of methods for the investigation of plasma-dust structures under conditions of microgravity.Translated from Teplofizika Vysokikh Temperatur, Vol. 42, No. 6, 2004, pp. 821–834.Original Russian Text Copyright © 2004 by V. I. Molotkov, O. F. Petrov, M. Yu. Pustylnik, V. M. Torchinskii, V. E. Fortov, and A. G. Khrapak.     

Studies on mechanical and wear properties of alloyed hypereutectic gray cast irons in the as-cast pearlitic and austempered conditions

The mechanical and wear behavior of a series of as-cast gray iron alloys were compared with properties obtained after austempering at 360 °C. The austempered alloys showed equivalent or moderately enhanced mechanical strength than the as-cast pearlitic gray irons. The specific wear rates of all the austempered alloys decreased significantly by 7–15 times and friction coefficient reduced by 30–50% compared to pearlitic alloyed gray irons. The dry sliding wear studies of as-cast alloys against high carbon 1%Cr through-thickness hardened steel shows that the specific wear rate ranged from 5.6 to 19.1 (×10⁻⁷) g/Nm with friction coefficient from 0.55 to 0.7. While, the austempered alloys showed wear rates from 0.5 to 2.6 (×10⁻⁷) g/Nm with friction coefficient ranging from 0.23 to 0.4. The improved wear resistance was attributed to the layer wise surface phase transformation associated with strain induced martensite formation of the stabilized austenite in the austempered matrix, lubrication of the interface by the flake graphite and better heat conduction from the rubbing interface by higher volume fraction of the graphite. Cast iron alloyed with Ni shows enhanced mechanical properties and wear resistance. The tensile strength shows decreasing trend with increase in carbon equivalent and graphite volume. The specific wear rate and friction coefficient shows decreasing trend with increase in hardness and graphite flake volume.     

Friction and wear of a glass woven roving/modified phenolic composite

The friction and wear behaviour of a glass woven roving/poly(vinyl) butyral modified phenolic composite, sliding under dry conditions against a cast iron counterface, has been investigated. Friction and wear of the composite show a marked dependence both on sliding velocity and normal pressure. Microscopic observations of the worn surface indicate that the higher wear loss and low friction coefficient for the composites at higher sliding velocities as well as at higher normal loads is probably due to fracture of weft fibres of the glass woven roving fabric reinforcement. The results are discussed on the basis of existing wear models of composite materials.     

Experimental Observation of 2 – Anion and its para → ortho Conversion in Solid para hydrogen Using High–Resolution ESR Spectroscopy

We present experimental observations and study of in solid parahydrogen. Since the parahydrogen molecule does not produce local magnetic fields, high–resolution ESR spectra of trapped radicals can be observed in the solid parahydrogen matrices. Using this high–resolution ESR spectroscopy, new quartet ESR signals were observed in –rays irradiated solid parahydrogen and assigned as In addition, para– was observed to convert into ortho– on the storage at 4.2 K. On the other hand, ortho–H ₂ molecule converts into para– at cryogenic temperatures. The difference in the conversion between the H ₂ molecule and the anion is explained by the parity conservation law of wavefunctions on exchanging the protons in homonuclear diatomic molecules such as the anion and H ₂ molecule.     

Carbon fabric reinforced polyetherimide composites: Influence of weave of fabric and processing parameters on performance properties and erosive wear

Woven carbon fabric reinforced (55 vol.%) polyetherimide (PEI) composites were fabricated using three types of weaves viz. plain (P), twill (T), and satin-4 H (S) by impregnation technique. Three more similar composites were fabricated with film technique to study the influence of both, weave of fabric and processing technique on the performance properties of the total seven composites including neat PEI. The composites were evaluated for physical and mechanical properties along with erosion wear behavior studied in identical conditions. In almost all properties viz. tensile strength (TS), modulus (TM), elongation to break (e), flexural strength and modulus, interlaminar shear strength (ILSS), etc., film technique proved far inferior to impregnation technique because of improper wetting of fiber strands, as evidenced by SEM studies. CF reinforcement enhanced all the properties of PEI manifold except elongation to break. None of the weaves proved best performer in all the mechanical properties. In case of erosive wear studies, plain weave composite proved slightly better than satin weave composite. Composite with twill weave proved poorest performer. In case of film technique, however, trends were different where plain weave composite proved poorest and satin proved best. Efforts were made to correlate various strength properties with wear resistance W_R. The factor (elongation × toughness) showed fairly good correlation with W_R. SEM studies were conducted to understand wear mechanisms.     

Abrasive wear of plasma coatings with different structures on titanium alloys

We study the influence of plasma coatings having different structural and phase compositions on the serviceability of TS-5 titanium alloy under different kinds of abrasive wear. By means of X-ray phase analysis, we have detected significant changes in the composition of plasma coatings in comparison with the initial composition of the powders, interphase interaction between the components of these coatings, and the formation of complex coatings with nonidentified phases. We have corroborated that the intensity of abrasive wear under conditions of nonrigidly fastened abrasive particles is lower. The greatest changes in the test chart take place in the case of abrasive wear of the plasma coating POAN-30. The highest abrasive resistance is characteristic of a plasma coating with complex titanium and chromium carbide.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 4, pp. 63–69, July–August, 2004.