Ag and Cu powders were mechanically alloyed using high-energy planetary milling to evaluate the sinter-bonding characteristics of a die-attach paste containing particles of these two representative conductive metals mixed at atomic scale. This resulted in the formation of completely alloyed Ag-40Cu particles of 9.5 µm average size after 3 h. The alloyed particles exhibited antioxidation properties during heating to 225°C in air; the combination of high pressure and long bonding time at 225°C enhanced the shear strength of the chip bonded using the particles. Consequently, the chips sinter-bonded at 225°C and 10 MPa for 10 min exhibited a sufficient strength of 15.3 MPa. However, an increase in bonding temperature to 250°C was detrimental to the strength, due to excessive oxidation of the alloyed particles. The mechanically alloyed phase in the particle began to decompose into nanoscale Ag and Cu phases above a bonding temperature of 225°C during heating.
This paper presents the results of an extensive investigation of asphalt concrete beams with geosynthetics interlayer. The subject of the research is an evaluation of infl uence of geosynthetics interlayer applied to bituminous samples on their fatigue life. The results of the tests evidences that when geosynthetics are used, the fatigue life depends mainly on the type of bituminous mixture, the type of geosynthetics, and the type and the amount of bitumen used for saturation and sticking. The amount of bitumen used to saturate and fix the geosynthetic signifi cantly changes the samples fatigue properties. Essential positive correlation between fatigue and parameters of interlayer bonding (shear strength, shear stiffness) occurs in both testing temperatures.
The paper presents the results of an extensive investigation of asphalt concrete specimens with geosynthetic interlayer. The subject of this research is evaluation of influence of geosynthetics interlayer applied to bituminous pavements on interlayer bonding of specimens. The results of the tests proves that when geosynthetic is used, the bonding of interlayer depends mainly on the type of bituminous mixture, the type of geosynthetic, and the type and amount of bitumen used for saturation and sticking of geosynthetic. The amount of bitumen used in order to saturate and fix the geosynthetic significantly changes the interlayer bonding of specimens.
There are 40 coal mines in Poland now. One of them (coal mine “Bogdanka”) is situated in Lublin Coal Basin, other are localised in Silesia and Małopolska regions. Coal mining is a source of large amounts of wastes. Mean annual production of wastes in only Lublin Coal Basin exceeds 2 million Mg, 65% of which is disposed on a heap. The rest is used to restore opencast excavations, to construct and repair local roads and to produce building materials. It seems that large amount of these wastes could be used to construct or modernize flood embankments and dykes. Using mine wastes as building materials requires the knowledge of their geotechnical parameters. A characteristic feature of mine wastes is their gradual weathering which affects geotechnical parameters largely determined by their mineral and petrographic composition.
This paper describes analyses of geotechnical parameters of mine wastes from Lublin Coal Basin (heap near coal mine “Bogdanka”) of various storage times and of samples collected after 10 years of exploitation of a dyke between ponds made of these wastes at the break of 1993 and 1994. Detailed analyses involved: grain size distribution, natural and optimum moisture content, maximum dry den-sity, shear strength and coefficient of permeability. Obtained results were compared with literature data pertaining to mine wastes from Upper Silesian Coal Basin and from other European coal basins.
Performed studies showed that coal mining wastes produced in Lublin Coal Basin significantly differed in the grain size distribution from wastes originating from Upper Silesian Coal Basin and that weathering proceeded in a different way in wastes produced in both sites.
A paste containing Cu(II) formate rods was prepared, and characteristics of sinter bonding at 250°C under a pressure of 10 MPa were investigated to accomplish a high-speed die attachment for wide-bandgap power chips on Cu finish in air. Synthesis of the plate-type Cu formate particles from CuO was accomplished through a wet reaction for 180 min. Cu, formed in situ in the bondline by pyrolysis of the formate during heating for the attachment, was sufficiently active to lead high-speed sintering within a carbon dioxide-hydrogen atmosphere derived from the pyrolysis, and the oxide layer on the Cu finish was reduced by the hydrogen. As a result, sinter bonding for 10 min formed a robust bonding with a shear strength approaching 27 MPa.
The article presents a new approach to testing the strength of asphalt interlayer bonding. Two loading methods were used: static load and cyclic load. Before carrying out static shear strength tests, the interlayer bonding was subjected to cyclic loads with a constant number of cycles but with different frequencies. A number of layered samples with and without geosynthetic interlayers were tested at the set temperature. The comparative analyses allowed to determine the functions approximating the impact of the cyclic load frequency on the static strength of bonding at selected interlayer contact conditions. It was also possible to indicate the frequency of cyclic load at which this parameter has the largest and smallest impact on the static strength of the asphalt interlayer bonding.