Brush plating of bearing alloys on aluminium alloy shells

The turbocharging of diesel engines has led to increase in temperature, load and corrosive attack of plain bearings. To meet these requirements, overlay plated aluminium alloys are now preferred. Currently, lead-tin alloys are deposited using a zincate layer and nickel strike, as intermediate stages in the process. The nickel has undesirable seizure characteristics and the zincate can given rise to corrosion problems. Consequently, brush plating allows the possible elimination of these stages and a decrease in process together with greater automation. The effect of mode application, on the formation of zincate films, using film growth weight measurements, potential-time studies, peel adhesion testing and Scanning Electron Microscopy was studied, for both SIC and AS15 aluminium alloys. The direct plating of aluminium was also successfully achieved. The results obtained indicate that generally, although lower adhesion resulted when a brush technique was used, satisfactory adhesion for fatigue testing was achieved. Both lead-tin and tin-cobalt overlays were examined and a study of the parameters governing brush plating were carried out using various electrolytes. An experimentally developed small scale rig, was used to produce overlay plated bearings that were fatigue tested until failure. The bearings were then examined and an analysis of the failure mechanisms undertaken. The results indicated that both alloy systems are of the regular codeposition type. Tin-cobalt overlays were superior to conventional lead-tin overlays and remained in good condition, although the lining (substrate) failed. Brush plated lead-tin was unsatisfactory. Sufficient understanding has now been gained, to enable a larger scale automated plant to be produced. This will allow a further study of the technique to be carried out, on equipment that more closely resembles that of a full scale production process.

Application of wear resistant coatings by the brush plating technique

The development of cobalt molybdenum and cobalt tungsten brush plating electrolytes is described. Their optimum compositions and operating conditions for commercial applications have been determined. The effects of composition, pH, applied voltage, stylus speed and pressure upon deposit composition and efficiency have been investigated. Transmission and Scanning Electron Microscopy have been employed to study the cobalt alloy deposits produced. Evaluation of the wear resistant properties of the cobalt alloys developed in this work was carried out in the laboratory using a pin and disc technique and a simulated hot forging test, and by industrial trials involving the "on site" plating of hot forging dies and cold pressing tools. It was concluded that the electrolytes developed in tl1is work enabled cobalt alloys containing 6% Mo or 8% W to be deposited at 17-20V. Brush plated cobalt deposits possessed a mixed CPU and FCC crystallographic structure at room temperature. The application of 13µm of either of the cobalt alloys resulted in improved wear performance in both pin and disc and simulated hot forging tests. The results of the industrial trials indicated that by the use of these alloys, the life of hot forging dies may be increased by 20-100%. A commercial forging organisation is using electrolytes developed in this work to coat dies prior to forging nimonic alloys. Reductions in forging temperature and improved forging qualities have been reported. Cold pressing tools coated with the alloys showed a reduced tendency to "pick-up" and scoring of the pressed panels. Reports of a reduced need for lubrication of panels before pressing have also been received.

The formation and impact of hazard control policy:a study of the regulation of white lead paint in Britain

Government regulation of industrial hazards is examined in the context of the economic and technical processes of industrial development. Technical problems and costs of control are considered as factors in both the formation and impact of regulation. This thesis focuses on an historical case-study of the regulation of the hazard to painting workers from the use of lead pigments in paint. A regulatory strategy based on the prohibition of lead paints gained initial acceptance within the British state in 1911, but was subsequently rejected in favour of a strategy that allowed continued use of lead paint subject to hygiene precautions. The development of paint technology and its determinants, including concern about health hazards, are analysed, focusing on the innovation and diffusion into the paint industry of the major white pigments: white lead (PbC03 .PB(OH)2)and its substitutes. The process of regulatory development is examined, and the protracted and polarised regulatory d~bate contrasted to the prevailing 'consensual' methods of workplace regulation. The rejection of prohibition is analysed in terms of the different political and technical resources of those groups in conflict over this policy. This highlights the problems of consensus formation around such a strategy, and demonstrates certain constraints on state regulatory activity, particularly regarding industrial development. Member-states of the International Labour Organisation agreed to introduce partial prohibition of lead paint in 1921. Whether this was implemented is related to the economic importance of lead and non-lead metal and pigment industries to a nation. An analysis is made of the control of lead poisoning. The rate of control is related to the economic and technological trajectory of the regulated industry. Technical and organisational characteristics are considered as well as regulatory factors which range from voluntary compliance and informal pressures to direct legal requirements. The implications of this case-study for the analysis of the development and impacts of regulation are assessed.

The pH-induced swelling and collapse of a polybase brush synthesized by atom transfer radical polymerization

We have used neutron reflectometry to characterize the swelling behaviour of brushes of poly[2-(diethyl amino)ethyl methacrylate], a polybase, as a function of pH. The brushes, synthesized by the "grafting from" method of atom transfer radical polymerization, were observed to approximately double their thickness in low pH solutions, although the pK is shifted to a lower pH than in dilute solution. The composition-depth profile obtained from the reflectometry experiments for the swollen brushes reveals a region depleted in polymer between the substrate and the extended part of the brush.

The relationship between charge density and polyelectrolyte brush profile using simultaneous neutron reflectivity and in situ attenuated total internal reflection FTIR

We report on a novel experimental study of a pH-responsive polyelectrolyte brush at the silicon/D2O interface. A poly[2-(diethylamino)ethyl methacrylate] brush was grown on a large silicon crystal which acted as both a substrate for a neutron reflectivity solid/liquid experiment but also as an FTIR-ATR spectroscopy crystal. This arrangement has allowed for both neutron reflectivities and FTIR spectroscopic information to be measured in parallel. The chosen polybase brush shows strong IR bands which can be assigned to the N-D+ stretch, D2O, and a carbonyl group. From such FTIR data, we are able to closely monitor the degree of protonation along the polymer chain as well as revealing information concerning the D2O concentration at the interface. The neutron reflectivity data allows us to determine the physical brush profile normal to the solid/liquid interface along with the corresponding degree of hydration. This combined approach makes it possible to quantify the charge on a polymer brush alongside the morphology adopted by the polymer chains. © 2013 American Chemical Society.

Experimental studies of lobe growth in the lichen Parmelia conspersa (Ehrh. Ex Ach.) Ach.

The radial growth of individual lobes of the foliose lichen, Parmelia conspersa (Ehrh. Ex Ach.) Ach. was studied to determine whether (1) adjacent lobes exchange carbohydrate and (2) marginal competition between lobes influences radial growth. In a survey of thalli of different size, the number of marginal lobes was linearly related to thallus circumference. However, the relationship between mean lobe width and thallus circumference was fitted by a second order polynomial. Hence, mean lobe width may reach a maximum in thalli approx. 3 cm in diameter. The interactions between marginal lobes were studied by either painting single lobes with acrylic paint or by removing lobes from the thallus. Painting the whole lobe virtually stopped its radial growth while partially painted lobes grew less than control lobes. The radial growth of a lobe was unaffected by either completely painting or removing its neighbour. Removal of both neighbouring lobes did not influence the radial growth of a lobe but severing the lobe from the thallus reduced its radial growth. In addition, lobe width increased significantly when both neighbouring lobes were removed. These results suggest that adjacent lobes have a considerable degree of independence and that there is little exchange of carbohydrate between them. In addition, marginal competition between adjacent lobes may restrict the lateral extension of the lobe and this may maintain a more constant mean lobe width in larger thalli. It is possible that the intensity of marginal competition between adjacent lobes may vary with thallus size and this could be a factor determining the growth curve of a foliose lichen throughout its life.

Does radial growth of the lichen Parmelia conspersa depend exclusively on growth processes at the lobe tip?

The objective of this study was to test the hypothesis that the radial growth of lobes of the lichen Parmelia conspersa depends largely on growth processes which occur at the lobe tip. First, individual lobes were removed from thalli and portions of the lobe removed to within various distances from the tip. Radial growth of the lobe was unaffected until less than 2 mm of the lobe tip remained. Second, the surfaces of individual lobes were painted with acrylic paint leaving different portions of the lobe exposed. Painting lobes to within 0.5 mm and 1 mm of the tip substantially reduced radial growth. Third, the levels of ribitol, arabitol and mannitol were measured in different regions behind the lobe tip on four occasions during 1994. The concentration of the three carbohydrates was greatest at the lobe tip and the levels declined linearly with distance from the tip. Fourth, painting one vertical half of the lobe tip did not affect radial growth but artificially bisecting the lobe tip with a scalpel reduced radial growth. Although transport of carbohydrate from other regions of the lobe cannot be ruled out, the results support the hypothesis that radial growth in P. conspersa depends largely on processes within a region approximately 2 mm behind the lobe tip.

Studies in organobismuth chemistry

Perturbations in the bismuth market resulted in Mining and Chemical Products Ltd., seeking further outlets in the market. Together with Manchem Ltd. they were anxious to evaluate the possibility of using bismuth compounds as a replacement for lead/calcium soaps in paint driers. A range of new organobismuth compounds were synthesised of the type RBiX2 and R3BiX2 (X= halogen, OOCR, dithiocarbamate). A variety of synthetic techniques were explored, including the use of mathematical reactions, phase-transfer catalysis and microwave energy. The preparation of a range of trivalent and pentavalent organobismuth carboxylates is reported and their infra-red , 13C, lH nmr spectra. The compounds were evaluated as paint driers and in cases found to enhance paint drying to a greater degree than the standard driers, to which they were being compared. The drying times of paint films containing the organobismuth compounds are reported, together with a comparison of the drying times with the addition of bismuth tris-diethyldithiocarbamate, which may promote the cross-linking reaction that occur in paint films during the drying process. Examples are reported to illustrate the great reductions in reaction times possible when using microwave energy. Reactions such as metallation of aromatic rings, ligand redistribution and synthesis were carried out in PTFE containers in a conventional domestic microwave oven. An X-ray diffraction study of (phenylazophenyl-C,N')mercury(II) chloride has shown it to be dimeric via long Hg-Cl bridging interactions of 3.367A. Its crystal structure is reported, together with its 13C nmr spectra and mass spectrum. The Lewis acidity of compounds of the type RBiX2 was investigated. The donor group being anchored to the organo group (R). The dithiocarbamates bis- (diethyldithiobarbamato)phenylbismuth(Ill) and [2-2-pyridyl)phenylbismuth(III) were synthesised, and their crystal structures, 14N, 13C nmr ar1d infra-red spectra are reported. Both compounds are pseudo-pentagonal bipyramidal in geometry, with two long Bi-S bonds and two short Bi-S bonds. The reaction of RBiBr2 (R= 2-(pyridyl) with various ligands is reported. The infra-red evidence suggesting that the coordination of extra ligands is accompanied by a reduction of the strength of the Bi-interaction.

An investigation into the use of knowledge representation in computer-integrated manufacturing

In a certain automobile factory, batch-painting of the body types in colours is controlled by an allocation system. This tries to balance production with orders, whilst making optimally-sized batches of colours. Sequences of cars entering painting cannot be optimised for easy selection of colour and batch size. `Over-production' is not allowed, in order to reduce buffer stocks of unsold vehicles. Paint quality is degraded by random effects. This thesis describes a toolkit which supports IKBS in an object-centred formalism. The intended domain of use for the toolkit is flexible manufacturing. A sizeable application program was developed, using the toolkit, to test the validity of the IKBS approach in solving the real manufacturing problem above, for which an existing conventional program was already being used. A detailed statistical analysis of the operating circumstances of the program was made to evaluate the likely need for the more flexible type of program for which the toolkit was intended. The IKBS program captures the many disparate and conflicting constraints in the scheduling knowledge and emulates the behaviour of the program installed in the factory. In the factory system, many possible, newly-discovered, heuristics would be awkward to represent and it would be impossible to make many new extensions. The representation scheme is capable of admitting changes to the knowledge, relying on the inherent encapsulating properties of object-centres programming to protect and isolate data. The object-centred scheme is supported by an enhancement of the `C' programming language and runs under BSD 4.2 UNIX. The structuring technique, using objects, provides a mechanism for separating control of expression of rule-based knowledge from the knowledge itself and allowing explicit `contexts', within which appropriate expression of knowledge can be done. Facilities are provided for acquisition of knowledge in a consistent manner.

Nitrogen implantation of tool steels and engineering coatings

Ion implantation modifies the surface composition and properties of materials by bombardment with high energy ions. The low temperature of the process ensures the avoidance of distortion and degradation of the surface or bulk mechanical properties of components. In the present work nitrogen ion implantation at 90 keV and doses above 1017 ions/cm2 has been carried out on AISI M2, D2 and 420 steels and engineering coatings such as hard chromium, electroless Ni-P and a brush plated Co-W alloy. Evaluation of wear and frictional properties of these materials was performed with a lubricated Falex wear test at high loads up to 900 N and a dry pin-on-disc apparatus at loads up to 40 N. It was found that nitrogen implantation reduced the wear of AISI 420 stainless steel by a factor of 2.5 under high load lubricated conditions and by a factor of 5.5 in low load dry testing. Lower but significant reductions in wear were achieved for AISI M2 and D2 steels. Wear resistance of coating materials was improved by up to 4 times in lubricated wear of hard Cr coatings implanted at the optimum dose but lower improvements were obtained for the Co-W alloy coating. However, hardened electroless Ni-P coatings showed no enhancement in wear properties. The benefits obtained in wear behaviour for the above materials were generally accompanied by a significant decrease in the running-in friction. Nitrogen implantation hardened the surface of steels and Cr and Co-W coatings. An ultra-microhardness technique showed that the true hardness of implanted layers was greater than the values obtained by conventional micro-hardness methods, which often result in penetration below the implanted depth. Scanning electron microscopy revealed that implantation reduced the ploughing effect during wear and a change in wear mechanism from an abrasive-adhesive type to a mild oxidative mode was evident. Retention of nitrogen after implantation was studied by Nuclear Reaction Analysis and Auger Electron Spectroscopy. It was shown that maximum nitrogen retention occurs in hard Cr coatings and AISI 420 stainless steel, which explains the improvements obtained in wear resistance and hardness. X-ray photoelectron spectroscopy on these materials revealed that nitrogen is almost entirely bound to Cr, forming chromium nitrides. It was concluded that nitrogen implantation at 90 keV and doses above 3x1017 ions/cm2 produced the most significant improvements in mechanical properties in materials containing nitride formers by precipitation strengthening, improving the load bearing capacity of the surface and changing the wear mechanism from adhesive-abrasive to oxidative.

A study of the growth and differentiation of the human adenocarcinoma of the colon cell line HT-29

The HT-29 human colon adenocarcinoma cell line, like many epithelial cells, displays an undifferentiated phenotype when cultured on plastic substrata. Biochemical markers of differentiation, such as brush border associated enzymes and carcinoembryonic antigen were expressed at very low levels. The differentiation-inducing effects of the culture of HT-29 cells on collagen type I gels were evaluated, and were assessed by morphological appearance, brush border associated enzyme activities and the secretion of CEA. The effect that this more physiological environment had on their chemosensitivity to a panel of chemotherapeutic agents was determined, so as to indicate whether this system could be used to improve the selectivity of screening for novel anticancer agents. Initial studies were performed on HT-29 cells derived from cells seeded directly from plastic substrata onto the collagen gels (designated Non-PPC gels). Their time of exposure to the collagen was limited to the time course of a single experiment and the results suggested that a longer, more permanent exposure might produce a more pronounced differentiation. HT-29 cells were then passaged continuously on collagen gels for a minimum of 10 passages prior to experimentation (designated PPC gels). The same parameters were measured, and compared to those for the cells grown on plastic and on the non-passaged collagen gels (Non-PPC) from the original studies. Permanently passaged cells displayed a similar degree of morphological differentiation as the non-passaged cells, with both culture conditions resulting in a more pronounced differentiation than that achieved by culture on plastic. It was noted that the morphological differentiation observed was very heterogeneous, a situation also seen in xenografted tumours in vivo. The activity of alkaline phosphatase and the production of CEA was higher in the cells passaged on collagen (PPC) than the cells cultured on non-passaged collagen gel (Non-PPC) and plastic. The biochemical determination of aminopeptidase activity showed that collagen gel culture enhanced the activity in both non-passaged and passaged HT-29 cells above that of the cells cultured on plastic. However, immunocytochemical localization of aminopeptidase and sucrase-isomaltase of samples of cells grown on the various substrata for 7, 14, 21 and 28 days showed a reduction in both enzymes in the cells grown on collagen gels when compared to cells grown on plastic. The reason for the discrepancy between the two assays for aminopeptidase is at this stage unexplained. Although, there was evidence to suggest that the culture of HT-29 cells on collagen gels was capable of inducing morphological and biochemical markers of enterocytic differentiation, there were no differences in the chemosensitivity of the different cell groups to a panel of anticancer agents. Preliminary studies suggested that the ability of the cells to polarize by their culture on porous filter chambers without any exogenous ECM was sufficient to enhance HT-29 differentiation and the onset of differentiation was probably correlated with the production of ECM by the cells themselves.

Isotropic compression of mixtures of hard and soft spheres

The compaction behaviour of powders with soft and hard components is of particular interest to the paint processing industry. Unfortunately, at the present time, very little is known about the internal mechanisms within such systems and therefore suitable tests are required to help in the interpretative process. The TRUBAL, Distinct Element Method (D.E.M.) program was the method of investigation used in this study. Steel (hard) and rubber (soft) particles were used in the randomly-generated, binary assemblies because they provided a sharp contrast in physical properties. For reasons of simplicity, isotropic compression of two-dimensional assemblies was also initially considered. The assemblies were first subject to quasi-static compaction, in order to define their behaviour under equilibrium conditions. The stress-strain behaviour of the assemblies under such conditions was found to be adequately described by a second-order polynomial expansion. The structural evolution of the simulation assemblies was also similar to that observed for real powder systems. Further simulation tests were carried out to investigate the effects of particle size on the compaction behaviour of the two-dimensional, binary assemblies. Later work focused on the quasi-static compaction behaviour of three-dimensional assemblies, because they represented more realistic particle systems. The compaction behaviour of the assemblies during the simulation experiments was considered in terms of percolation theory concepts, as well as more familiar macroscopic and microstructural parameters. Percolation theory, which is based on ideas from statistical physics, has been found to be useful in the interpretation of the mechanical behaviour of simple, elastic lattices. However, from the evidence of this study, percolation theory is also able to offer a useful insight into the compaction behaviour of more realistic particle assemblies.

Cathodic protection of reinforced concrete:anodic processes in cements and related electrolytes

The nature and kinetics of electrode reactions and processes occurring for four lightweight anode systems which have been utilised in reinforced concrete cathodic protection systems have been studied. The anodes investigated were flame sprayed zinc, conductive paint and two activated titanium meshes. The electrochemical properties of each material were investigated in rapidly stirred de-oxygenated electrolytes using anodic potentiodynamic polarisation. Conductive coating electrodes were formed on glass microscope slides, whilst mesh strands were immersed directly. Oxygen evolution occurred preferentially for both mesh anodes in saturated Ca (OH)2/CaC12 solutions but was severely inhibited in less alkaline solutions and significant current only passed in chloride solutions. The main reactions for conductive paint was based on oxygen evolution in all electrolytes, although chlorides increased the electrical activity. Self-corrosion of zinc was controlled by electrolyte composition and the experimental set-up, chlorides increasing the electrical activity. Impressed current cathodic protection was applied to 25 externally exposed concrete slabs over a period of 18 months to investigate anode degradation mechanisms at normal and high current densities. Specimen chloride content, curing and reinforcement depth were also variables. Several destructive and non-destructive methods for assessing the performance of anodes were evaluated including a site instrument for quantitative "instant-off- potential measurements. The impact of cathodic protection on the concrete substrate was determined for a number of specimens using appropriate methods. Anodic degradation rates were primarily influenced by current density, followed by cemendtious alkalinity, chloride levels and by current distribution. Degradation of cementitious overlays and conductive paint substrates proceeded by sequential neutralisation of cement phases, with some evidence of paint binder oxidation. Sprayed zinc progressively formed an insulating layer of hydroxide complexes, which underwent pitting_ attack in the presence of sufficient chlorides, whilst substrate degradation was minimal. Adhesion of all anode systems decreased with increasing current density. The influence of anode material on the ionic gradients which can develop during cathodic protection was investigated. A constant current was passed through saturated cement paste prisms containing calcium chloride to central cathodes via anodes applied or embedded at each end. Pore solution was obtained from successive cut paste slices for anion and cation analyses. Various experimental errors reduced the value of the results. Characteristic S-shaped profiles were not observed and chloride ion profiles were ambiguous. Mesh anode specimens were significantly more durable than the conductive coatings in the high humidity environment. Limited results suggested zinc ion migration to the cathode region. Electrical data from each investigation clearly indicated a decreasing order of anode efficiency by specific anode material.

Formability of high strength aluminium sheet

An initial review of the subject emphasises the need for improved fuel efficiency in vehicles and the possible role of aluminium in reducing weight. The problems of formability generally in manufacture and of aluminium in particular are discussed in the light of published data. A range of thirteen commercially available sheet aluminium alloys have been compared with respect to mechanical properties as these affect forming processes and behaviour in service. Four alloys were selected for detailed comparison. The formability and strength of these were investigated in terms of underlying mechanisms of deformation as well as the microstructural characteristics of the alloys including texture, particle dispersion, grain size and composition. In overall terms, good combinations of strength and ductility are achievable with alloys of the 2xxx and 6xxx series. Some specific alloys are notably better than others. The strength of formed components is affected by paint baking in the final stages of manufacture. Generally, alloys of the 6xxx family are strengthened while 2xxx and 5xxx become weaker. Some anomalous behaviour exists, however. Work hardening of these alloys appears to show rather abrupt decreases over certain strain ranges which is probably responsible for the relatively low strains at which both diffuse and local necking occur. Using data obtained from extended range tensile tests, the strain distribution in more complex shapes can be successfully modelled using finite element methods.Sheet failure during forming occurs by abrupt shear fracture in many instances. This condition is favoured by states of biaxial tension, surface defects in the form of fine scratches and certain types of crystallographic texture. The measured limit strains of the materials can be understood on the basis of attainment of a critical shear stress for fracture.