An experimental investigation of ultrathin metallic films on face centred cubic(111) surfaces using medium energy ion scattering as a primary experimental technique is reported. A suite of custom software written for data-processing, calibration and analysis has also been described. The specific experimental systems investigated are 0.25 ML to 3.89 ML of palladium on copper(111) and 0.23 ML to 3.74 ML of silver on aluminium(111). The Pd CU(111) system was shown to exhibit 42% twinning at 0.25 ML through 4.74 ML. At 0.25 ML coverage it has been shown that the Pd migrates into the top three layers of the substrate. The Pd was shown to be distributed 27% ± 3%, 67% ± 3% and 6% ± 3% in the 1st, 2nd and 3rd layers. The first and second interlayer spacings we also found to contract by 4% and expand by 4% respectively for the 0.25 ML coverage.

It is known that good adhesion of melt-coated polyethylene to metals occurs when the polyethylene can oxidise. The present work confirms that adhesion to copper with a copper (I) oxide film is poor because the copper inhibits polyethylene oxidation. The adhesion may be improved if the copper is chemically oxidised to produce a copper (II) oxide and previous work claims that this oxide is able to oxidise the polyethylene and become reduced to copper (I) oxide. Using a coulometric reduction technique of oxide assay it is shown that the copper (II) oxide does not behave in this way. However during heating in the presence or absence of polyethylene some of the copper (II) oxide is converted to copper (I) oxide. Infra-red spectroscopy shows that very little polyethylene oxidation occurs for coating tines at 200°C which are needed to provide good adhesion measured by a 180° peel test. Further, it is shown that good adhesion is still obtained when polyethylene oxidation is inhibited. No serious conflict with previous observations for this adhesd.ve system are encountered, but the previous observations are re-interpreted by showing that it is the ability of copper (II) oxide to adopt a whisker growth mode which accounts for the good adhesion. Pretreatments are devised for steel and for zinc which produce a fibrous surface comparable to the oxidised copper, and it is found that these afford good adhesion of polyethylene even when polymer oxidation is inhibited. For the oxidised copper it was found that failure was always cohesive in the polyethylene and that the measured peel strength was associated with the amount of polyethylene which underwent deformation. If the mechanical properties of the interfacial polymer were altered by quenching or by introducing voids the peel strength was increased. Purifying the polyethylene or contaminating it with low molecular weight material has only a small effect on adhesion. This importance of fibrous or porous surfaces in polymer-metal adhesion may encourage the development of pretreatments for other metals. They have the advantage that not only is adhesion improved but heavily stabilised polymers may be successfully melt coated directly to the substrates.

An ultrasonic study of the elastic behaviour and phase stabilities of single crystals of In alloys - many grown and characterised for the first time - with Cd, T1 and Pb is presented. In both the fct and fee In-Cd alloys, the shear modulus ½ (C11 - C12) is much smaller than in In and tends to even smaller values as the fct-fcc structural transformation is approached from either the tetragonal or the cubic phase: the onset of instability is manifested as softening of the [110], q // [110] acoustic phonon mode near the Brillouin zone centre. However, in contrast to its behaviour in the In-rich, In-Tl alloys, ½(C11-C12) does not go to zero in the In-Cd alloys. This finding corresponds to the more recognisable first-order character of the transformation in the In-Cd compared to that in In-Tl alloys. Calorimetric measurements indicate enhancement of the fusion entropies due to the acoustic phonon mode softening. In the primary solid solution range (fct, c/a > 1), addition of tetravalent Pb to In (valency 3) also reduces the shear modulus ½ (C11 -C12) contrast to that of the divalent Cd and trivalent T1 alloys, this modulus is much larger than that of In in the other fct (c/a < 1) phase; neither is mode softening evident in the Pb-rich fee phase - the anisotropy ratio A (= 2C44/(C11-C12)) close to unity and the elastic behaviour is isotropic. The shear constants of bee Tl-rich, In-Tl alloys are in agreement with Zener's prediction namely that ½(C11-C12) should be small compared with C44 for a closed ion shell bcc material. The alloy data has been used to obtain the first estimate of the elastic constants of the high temperature bcc polymorph of Tl. The. stability of this polymorph has been found to be - in accordance with Zener's arguments - due to its lower Debye temperature and consequently greater entropy than that of the normally occurring hcp form.

A sensitive method of measuring hydrogen permeation is presented, whereby hydrogen is introduced to the entry side of a thin metallic membrane by applying a sinusoidal oscillation about an appropriate value of electrical potential to a cell containing 0.1N NaOH. The corresponding current is taken as the hydrogen incident flux to the surface. The exit side of the membrane is in contact with an ultra-high vacuum chamber where hydrogen partial pressure is measured using a mass spectrometer against a known pump rate in order to obtain a measure of the exit flux. Measurements have been made on a thin nickel membrane as a material with well known and stable hydrogen permeation parameters, and these have been used to assess the sensibility of the technique. A newly developed mathematical model is presented that uses Fourier analysis to determine the phase lag (φ) and amplitude ratio (Λ) between the current or potential and hydrogen partial pressure. Analytical relationships between (φ), (Λ) and the applied frequency (the newly introduced parameter) have been used to determine the relevant thermodynamic and kinetic parameters (such as hydrogen diffusion coefficient and solubility) which enable the effects of both surface and bulk kinetics to be distinguished. Results from the experiments on nickel showed a very good consistency with the literature [diffusion coefficient, D = (3.6±0.5)×10-14 and (1.8±0.29)×10-13 m2/s at 22°C and 60°C, respectively, and solubility of (2.11±0.09)×10-2 and (3.2±0.18)×10-2 mol H2/m3mbar0.5 at 22°C and 60°C, respectively]; this formed a well established calibration for undertaking and interpreting experiments on heat-treatable En24 low alloy steel. Permeation experiments were done for three heat treatment conditions and the results for diffusion coefficient were (6±1)×10-10 m2/s for the annealed, (7.89±1.2)×10-12 m2/s for the quenched and (3.25±0.8)×10-11 m2/s for the quenched and tempered condition. Solubilities were (5.3±1.5)×10-9 for the annealed, (3.28±0.94)×10-5 for the quenched and (1.22±0.6)×10-7 mol H2/m3mbar0.5 for the quenched and tempered condition and trapping parameters measured here were = 7 p kN , = 834 p kN and = 2055 p kN , respectively. Results from these experiments helped to explain the variability reported in the literature for the values of the diffusion coefficient and solubility. The differences in behaviour from classical permeation are more easily attributed to trapping than to surface kinetic effects.

No description available.

No description available.

Sticker wrench marks are a surface defect which affects steel strip produced by the batch annealing route. The defect has a three stage formation mechanism; interlap diffusion bonding (sticking) which alters the pay-off geometry during uncoiling (wrenching), leading the Luders band formation (marking). It is estimated that sticker wrench marks cost British Steel Strip Products £1.73 million per annum in rejections for surface quality. The objectives of the project were to improve the understanding of the formation mechanism, seeking to identify procedures to detect and prevent the formation of wrench marks. Three main areas of work undertaken were interlap pressure prediction, wrench detection and wrench prevention. The calculation of the interlap pressure formed during coiling and in the cooling cycle of annealing was carried out using published algorithms. The results were used to justify modifications to the coiling tension pattern on the five stand mill and to introduce a retarded cool to the annealing cycle. Wrench detection involved the detection and analysis of noise emitted during uncoiling at the temper mill. The noise was found to contain characteristic frequency peaks, which were related to the breaking of the interlap bonds. The frequency of the spectral signatures is related to the dimensions of the defect and to strip gauge, uncoiling speed and, to a lesser extent, uncoiling tension. The intensity of the signatures was found to be related to the strength of the interlap bonds. Using these conclusions, an integrated signal processing and archiving system was designed which could determine the likelihood of a coil to form wrench marks. A method to control the pay-off geometry of the strip using electro-magnets was developed. The device, consisting of a magnet, stablising arm and positioning system, is placed over the pay-off point of the coil. Trials carried out on a narrow strip mill showed an alteration of the pay-off geometry to the desired tangential case, which should eliminate stick wrench marking.

Efficient basic oxygen steelmaking (BOS) depends on the rapid formation of a highly basic slag and, hence, on the properties of the lime (CaO) added as a flux during BOS converter operation. To evaluate the factors influencing the quality of lime supplied to the steelplants at Port Talbot and Llanwern, laboratory studies and plant trials were undertaken on limestone samples from two different quarries at Shapfell and Batts Combe. Despite significant differences in the microstructures of the two limestones, the rates of weight loss with time were similar at the same calcination temperatures, as was the average crystal size for the lime-crystal aggregates produced under the identical calcination conditions. Moreover, the predicted rates of slag formation appeared comparable, as judged by the results derived from water reactivity tests completed for lime obtained under a wide range of calcination conditions for both limestone samples. In contrast, for equivalent calcination treatments, the porosity values and the amounts of fines generated during abraidability tests were lower for lime samples derived from Shapfell than from Batts Combe limestone. Although the commercial limes supplied from both sources meet the composition specifications set by British Steel, it is proposed that the higher impurity levels in the Shapfell limestone create larger quantities of intergranular viscous silicates during calcination, improving the sintering characteristics of the calcined lime. This view is supported by the observation that, during calcination of Batts Combe limestone, surface 'doping' of the lime with sodium carbonate resulted in a discernible reduction in the percentage of fines generated during subsequent abraidability experiments. In line with the laboratory-based results, plant trials indicated that the slag/metal distributions of sulphur and phosphorous, as well as slag basicities were comparable for commercial lime from the two suppliers. However, in agreement with the abraidability data, dust losses from the converters were substantially greater using the Batts Combe lime.

No description available.

No description available.