(Table I, page 1348) Composition of ferromanganese oxide concretions from lake Ontario (Extract)

A large deposit of ferromanganese oxide concretions has been found in the northern portion of Lake Ontario. The concretions occur mainly in the form of coatings on sand grains but manganese nodules are present at several localities. Mineralogically, the ferromanganese oxide phases are amorphous, and their Fe and Mn contents are similar to those in concretions from other environments. However, their Ni, Co, and Cu contents are significantly higher than those reported in previously described North American lacustrine ferromanganese concretions, and this may, in part, be a reflection of their probable low rates of accumulation.

Influence of pretreatment on corrosion behaviour of duplex zinc/polymer coatings on steel substrates

An investigation has been undertaken to determine the major factors influencing the corrosion resistance of duplex-zinc coatings on steel substrates.Premature failure of these systems has been attributed to the presence of defects such as craters and pinholes in the polymer film and debonding of the polymer film from the zinc substrate.Defects found on commercially produced samples have been carefully characterised using metallographic and scanning electron microscopy techniques. The influence of zinc substrate surface roughness, polymer film thickness and degassing of conversion coatings films on the incidence of defects has been determined.Pretreatments of the chromate, chromate-phosphate, non chromate, and alkali-oxide types were applied and the conversion coatings produced characterised with respect to their nature and composition. The effect of degassing on the properties of the films was also investigated. Electrochemical investigations were carried out to determine the effect of the presence of the eta or zeta phase as the outermost layer of the galvanized coating.Flow characteristics of polyester on zinc electroplated hot-dip continuous and batch galvanized and zinc sprayed samples were investigated using hot-stage microscopy. The effects of different pretreatments and degassing after conversion coating formation on flow characteristics were determined.Duplex coatings were subjected to the acetic acid salt spray test. The effect on adhesion was determined using an indentation debonding test and the results compared with those obtained using cross-cut/peel and pull-off tests. The locus of failure was determined using scanning electron microscopy and X-ray photoelectron spectroscopy techniques.

Rearrangement of α-pinene oxide using a surface catalysed spinning disc reactor (SDR)

Isomerisation of α-pinene oxide to campholenic aldehyde was performed by immobilising zinc triflate based catalysts on the surface of a spinning disc reactor (SDR). Two types of catalyst have been studied and the influence of operating parameters such as rotational speed, feed flow rate and reaction temperature on conversion and selectivity towards campholenic aldehyde has been investigated in considerable detail. The findings of the study suggest that immobilising the catalyst on the reactor surface and performing the reaction in continuous mode has potential for achieving benefits of Green Chemical Technology (GCT).

Element abundances, loss on ignition, total analyzed abundances, CIA values, and Al-oxide/Ti-oxide ratios of sediment core CRP-2A (Table1)

The CRP-2/2A core, drilled in western McMurdo Sound in October and November 1998, penetrated 624 m of Quaternary. Pliocene, lower Miocene, and Oligocene glacigenic sediments. The palaeoclimatic record of CRP-2/2A is examined using major element analyses of bulk core samples of fine grained sediments (mudstones and siltstones) and the Chemical Index of Alteration (CIA) of Nesbitt & Young (1982). The CIA is calculated from the relative abundances of AI, K, Ca, and Na oxides, and its magnitude increases as the effects of chemical weathering increase. However, changes in sediment provenance can also affect the CIA, and provenance changes are recorded by shifts in the Al2O3/TiO2 ratios and the Nb contents of these CRP-2/2A mudstones. Relatively low CIA values (40-50) occur throughout the CRP-2/2A sequence, whereas the Al2O3/TiO2 ratio decreases upsection. The major provenance change is an abrupt onset of McMurdo Volcanic Group detritus at ~300 mbsf and is best characterized by a rapid increase in Nb content in the sediments. This provenance shift is not evident in the CIA record, suggesting that a contribution from the Ferrar Dolerite to the older sediments was replaced by an input of McMurdo Volcanic Group material in the younger sediments. If this is true, then the relatively uniform CIA values indicate relatively consistent palaeoweathering intensities throughout the Oligocene and early Miocene in the areas that supplied sediment to CRP-2/2A.

Synthesis and characterization of Tellurium oxide glasses for photonic applications

Tellurite glasses are photonic materials of special interest to the branch of optoelectronic and communication, due to its important optical properties such as high refractive index, broad IR transmittance, low phonon energy etc. Tellurite glasses are solutions to the search of potential candidates for nonlinear optical devices. Low phonon energy makes it an efficient host for dopant ions like rare earths, allowing a better environment for radiative transitions. The dopant ions maintain majority of their individual properties in the glass matrix. Tellurites are less toxic than chalcogenides, more chemically and thermally stable which makes them a highly suitable fiber material for nonlinear applications in the midinfrared and they are of increased research interest in applications like laser, amplifier, sensor etc. Low melting point and glass transition temperature helps tellurite glass preparation easier than other glass families.In order to probe into the versatility of tellurite glasses in optoelectronic industry; we have synthesized and undertaken various optical studies on tellurite glasses. We have proved that the highly nonlinear tellurite glasses are suitable candidates in optical limiting, with comparatively lower optical limiting threshold. Tuning the optical properties of glasses is an important factor in the optoelectronic research. We have found that thermal poling is an efficient mechanism in tuning the optical properties of these materials. Another important nonlinear phenomenon found in zinc tellurite glasses is their ability to switch from reverse saturable absorption to saturable absorption in the presence of lanthanide ions. The proposed thesis to be submitted will have seven chapters.

Electrolytes for ceramic oxide fuel cells

The main objective of this dissertation is the development and processing of novel ionic conducting ceramic materials for use as electrolytes in proton or oxide-ion conducting solid oxide fuel cells. The research aims to develop new processing routes and/or materials offering superior electrochemical behavior, based on nanometric ceramic oxide powders prepared by mechanochemical processes. Protonic ceramic fuel cells (PCFCs) require electrolyte materials with high proton conductivity at intermediate temperatures, 500-700ºC, such as reported for perovskite zirconate oxides containing alkaline earth metal cations. In the current work, BaZrO3 containing 15 mol% of Y (BZY) was chosen as the base material for further study. Despite offering high bulk proton conductivity the widespread application of this material is limited by its poor sinterability and grain growth. Thus, minor additions of oxides of zinc, phosphorous and boron were studied as possible sintering additives. The introduction of ZnO can produce substantially enhanced densification, compared to the un-doped material, lowering the sintering temperature from 1600ºC to 1300ºC. Thus, the current work discusses the best solid solution mechanism to accommodate this sintering additive. Maximum proton conductivity was shown to be obtained in materials where the Zn additive is intentionally adopted into the base perovskite composition. P2O5 additions were shown to be less effective as a sintering additive. The presence of P2O5 was shown to impair grain growth, despite improving densification of BZY for intermediate concentrations in the range 4 – 8 mol%. Interreaction of BZY with P was also shown to have a highly detrimental effect on its electrical transport properties, decreasing both bulk and grain boundary conductivities. The densification behavior of H3BO3 added BaZrO3 (BZO) shows boron to be a very effective sintering aid. Nonetheless, in the yttrium containing analogue, BaZr0.85Y0.15O3- (BZY) the densification behavior with boron additives was shown to be less successful, yielding impaired levels of densification compared to the plain BZY. This phenomenon was shown to be related to the undesirable formation of barium borate compositions of high melting temperatures. In the last section of the work, the emerging oxide-ion conducting materials, (Ba,Sr)GeO3 doped with K, were studied. Work assessed if these materials could be formed by mechanochemical process and the role of the ionic radius of the alkaline earth metal cation on the crystallographic structure, compositional homogeneity and ionic transport. An abrupt jump in oxide-ion conductivity was shown on increasing operation temperature in both the Sr and Ba analogues.