A. Craft

PLASTIC WASTE MANAGEMENT IN CONSTRUCTION: TECHNOLOGICAL AND INSTITUTIONAL ISSUES

Abstract The main objective of a solid waste management system is to effectively safeguard the public health, safety, and welfare. The various options involved in a waste management process are landfilling, incineration, and recycling wastes into useful products. Plastics recycling, in particular, would not be successful unless the proper infrastructure to collect the waste is being set, the technology to economically reprocess the waste into new products is available, and the establishment of markets for the cost-effective use of recycled products are developed. The development of new construction materials using recycled plastics is important to both the construction and the plastics recycling industries. Extensive research investigated the use of resins based on recycled poly (ethylene terephthalate) (PET) plastic waste for the production of a high performance composite material, namely polyester concrete (PC). Resins using recycled PET offer the possibility of a lower source cost of materials for forming good quality PC. PC products also allow the long-term disposal of PET waste, an important advantage in recycling applications.

Hydrogen-induced phase separation in PdRh alloys

The principal result of this research is the demonstration that phase separation takes place in RdRh alloys at moderate to elevated temperatures in the presence of H2: it occurs to a much lesser extent under similar conditions but in the absence of hydrogen. The main technique employed for determining whether or not lattice changes have occurred are ‘diagnostic’ isotherms measured before and after exposure to hydrogen. These isotherms are measured at a much lower temperature than those employed for the hydrogen heat treatment (HHT). This diagnostic technique has the advantage that it is more sensitive than other methods to lattice changes in alloys: however, it has the disadvantage that the nature of the changes must be inferred. Direct evidence for segregation following HHT in these alloys has been obtained from electron microprobe analysis via a wavelength-dispersive spectrometer. X-ray diffraction revealed that the original f.c.c. reflections of the XRh = 0.20 alloy were broadened after HHT so as to suggest the presence of two sets of f.c.c. reflections. It is suggested that the segregation corresponds to phase separation according to the PdRh binary phase diagram, at least in the elevated temperature range employed for HHT. 673 to 873 K, where the hydrogen solubility is small and where consequently the binary phase equilibrium should not be perturbed by the small amounts of dissolved hydrogen. The lattice changes were more marked in the presence of hydrogen than in its absence in all of the experiments which were carried out. This research demonstrates the potential utility of employing H-induced changes for phase diagram determination of Pd alloys and possibly for other alloy systems, e.g. Ni-based alloys.

Electrical resistance anomalies and hydrogen solubilities in the disorder-order system Pd3Mn

The maximum in electrical resistance is caused by a combination of two factors which affect the resistance oppositely, i.e., the scattering of electrons from the boundaries between the partially ordered domains and the disordered matrix increases resistance, and the growth and ordering of the domains decreases the resistance. Electron diffraction and TEM studies of samples quenched from temperatures corresponding to the maximum in resistance confirm that ordering occurs and that domains grow as resistance decreases.

Hydrogen-induced metal atom rearrangements in pd3+χmn1−χ alloys with χ⩾0 using transmission electron microscopy, electrical resistivities and H2 solubilities

Abstract In this research we have characterized the products of the hydrogen-induced ordering of disordered and of L12−χ ordered Pd3+χMn1−χ alloys with χ⩾0. The long-period superstructure (L12−s) form is produced by a heat treatment at a temperature of about 700 K in vacuo. An L12 ordered form can be prepared by exposing Pd-Mn alloys to hydrogen (1 MPa or above) at temperatures of 500 K or above; this ordering is induced by hydrogen under conditions where ordering does not occur in its absence. After the alloys have transformed to their L12 form, they remain in this form if the hydrogen is removed at moderate temperatures. Large dislocation densities appear from the hydrogen-induced ordering of the disordered alloys; the density of these dislocations appears to decrease with increase in χ. Dislocations are also introduced by the disorder → L12−s transformation which occurs in vacuo. The mechanism of the hydrogen-induced ordering is unknown but it must be related to the lattice expansion caused by the hydrogen. It should be noted that not very much dissolved hydrogen is needed to cause these transitions, i.e. a hydride phase does not form.

The transition of the hydrogen-induced LI2 ordered structure of Pd3 Mn to the Ag3Mg structure

Etude experimentale par mesures de conductivite electrique, microscopie electronique en transmission et diffraction electronique

Tensile Properties of a Series of Palladium-Silver Alloys Exposed to Hydrogen

AbstractThe effects on the strength, hardness, and ductility of a series of well-annealed palladium-silver alloys due to hydrogen exposure were investigated at various temperatures. The results indicate that the temperature at which hydrogen exposure occurs can have a significant effect on the degree to which these mechanical properties are altered. At relatively low temperatures, it was found that the strength and hardness of the alloy are increased, while ductility is decreased upon hydrogen exposure. In alloys where such changes are observed, the magnitude of these changes was found to diminish as the silver content increases. Above a certain hydrogen exposure temperature—the value of which decreases with increasing silver content—the strength, hardness, and ductility of the alloy show no significant changes as a result of hydrogen exposure.

Influence of hydrogen-induced ordering on the tensile and fatigue characteristics of the alloy system Pd1 − xMnx (x = 0.1–0.25)

Abstract Tensile, microhardness and fatigue tests were carried out on palladium-manganese alloys with manganese contents in the range 10–25 at.%. Each alloy was examined in three structural forms: a disordered form, an Al 3 Zr-ordered form and a hydrogen-induced L1 2 -ordered form. While the disordered and Al 3 Zr-ordered forms of a particular alloy have quite similar mechanical properties, the L1 2 -ordered form of the alloy differs markedly from the others. It has been found that the L1 2 -ordered form of an alloy has enhanced strength and hardness, together with reduced ductility and fatigue life, compared with either the disordered or Al 3 Zr-ordered forms. These differences are attributed to the formation of a hydride phase in each alloy during the preparation of the L1 2 -ordered structure.

Blocking of hydrogen-dislocation interactions in palladium by interstitial carbon (boron) solutes

Abstract It has been shown that the segregation of hydrogen to dislocations at 323 K decreases markedly in palladium doped with interstitital carbon or boron after a relatively low temperature annealing, 423 K. By contrast, after a similar treatment, pure palladium continues to show a large segregation of hydrogen to dislocations. TEM studies have shown, however, that the dislocation densities are large in both the pure palladium and the carbon doped samples after annealing at 423 K. These results are consistent with the explanation that the heavy interstitial atoms, carbon or boron, migrate to dislocations at 423 K and block these dislocations for occupation by hydrogen.

Mechanical properties of the order-disorder alloy system Pd1−xMnx (x = 0.1–0.2)

Abstract Tensile and hardness tests were carried out on palladium-manganese alloys with manganese contents in the range 10–20 atomic percent. Each alloy studied can exist in one of three forms: a disordered form: an Al 3 Zr-ordered form; or a hydrogen-induced L1 2 -ordered form. While the disordered and Al 3 Zr-ordered forms have quite similar mechanical properties, the L1 2 -ordered form of each alloy differs markedly from the other forms. These differences have been attributed to the formation of a hydride phase in each alloy during preparation of the L1 2 -ordered structure.