D. Dykes

A new method of analysing electro-osmosis using FET models

Abstract To reduce volumes of liquid or slurry waste, it may be necessary to extract water, and the best way to achieve this in practice is often by flow current adjustments. Current has been observed to reach a maximum at some point after the application of a voltage, and to decrease thereafter. The cause for this seems to lie in the movement of impurity particles, so-called electrophoresis. By controlling this movement, it is possible to increase flow rates. Analyses of the problem in the past have included studies into transfer characteristics, mutual conductance and amplification. In contrast to this earlier work, the authors have experimented with placing a gate electrode between the upper and lower electrodes in order to approach the whole reaction in the manner of a field effect transistor (FET) problem. It is well known that varying the gate voltage in a FET leads to a corresponding change in the drain current. If the displaced particles are regarded in a similar way to electrons, the same method of analysis can be used in the case of electro-osmosis. In the experiment reported, this method was used to investigate associated transfer characteristics. It was found that the insertion of the gate allowed a greater liquid flow rate to be obtained than would be possible with more traditional methods.

Manufacture of insulating agents for electric field relaxation using functionally graded materials, with electric field calculations

The authors of this paper have previously developed a successive layer accretion method based on vacuum filtration, for the manufacture of functionally graded materials (FGMs) by a progressive lamination procedure. For this, they have been granted a U.S. Patent. Using this method, it is possible to manufacture FGMs with thicknesses ranging from several millimetres to several centimetres. The authors have previously manufactured functionally graded materials consisting of iron (III) oxide-kaolin, copper oxide-kaolin and titanium oxide-kaolin, using the said successive layer accretion method. The manufactured FGMs were examined using an SEM to investigate their grading characteristics. Electrical properties such as resistivity, permittivity and permeability were also measured. In the present paper, they report results of permittivity and resistivity measurements conducted on an FGM consisting of titanium oxide and kaolin.

An experiment to purify diesel exhaust gas using an electric trap and three types of catalysers

Abstract Diesel engine exhaust gas is known to be one cause of photochemical smog, which is so damaging to city environments. However, because of its high thermal efficiency and economic advantages, the diesel engine is not easily dispensable. The authors have previously conducted a series of experiments to assess the purifying effects of a diesel gas purification device employing an electric trap. It has been confirmed that an extraction rate of 60 ∼ 75 % for black smoke can be achieved using this apparatus, but the extraction effect for nitrogen oxides (NOx) is insufficient if the electro-trap device is used on its own. To improve its performance, experiments have now been undertaken using the same device in combination with various types of attached catalysers to oxidise and remove the nitrogen in the exhaust gas. Utilising a commercial 3-way catalyser, it proved difficult to maintain the gas at a suitable temperature, so that no outstanding result could be obtained. Nor was any significant result observed from the use of an ozoniser. However, with a zeolyte catalyser, it was possible to achieve a NOx reduction of 20 ∼ 30 %. This latter experiment is reported in the present paper.

Field relaxing materials: production temperature and relaxation effectiveness

To prevent breakdown in the insulation of electric equipment requires the development of new materials and the control of electric fields. The authors have previously been engaged in the manufacture of functionally graded materials (FGMs) based on titanium oxide and barium titanate. These FGMs possess structured properties that cause a graded change in relative permittivity. It has been found that a change in the manufacturing temperature causes the relative permittivity to vary. The present paper describes an attempt to discover optimal conditions for field control by manufacturing FGMs at a range of temperatures from 673 K to 1273 K and investigating the properties of the resulting materials. The FGM studied was composed of barium titanate and kaolin. The highest values for relative permittivity were obtained at 1273 K. Investigations with a scanning electron microscope (SEM) showed that in comparison with the materials produced at lower temperatures, the pores between the grains were smaller. Similarly, the porosity and water absorption properties showed minimal values for material manufactured at 1273 K. It was concluded that this was because this material contained less air. The smaller the porosity, the larger the value for relative permittivity.

Purification of Diesel Exhaust Gas Using Reducing Catalysers

Abstract Diesel engine exhaust gas is known to be one cause of photochemical smog, which is so damaging to city environments. However, because of its high thermal efficiency and economic advantages, the diesel engine is not easily dispensable. The authors have previously conducted a series of experiments to assess the purifying effects of a diesel gas purification device employing an electric trap. It has been confirmed that an extraction rate of 60∼75 % for black smoke can be achieved using this apparatus. But the extraction effect for nitrogen oxides (NOx) is insufficient if the electro-trap device is used on its own. To improve its performance, experiments have now been undertaken using the same device in combination with various types of attached catalysers to oxidise and remove the nitrogen in the exhaust gas. Utilising a commercial 3-way catalyser, it proved difficult to maintain the gas at a suitable temperature, so that no outstanding result could be obtained. Nor was any significant result observed from the use of an ozoniser. However, with a zeolyte catalyser, it was possible to achieve a NOx reduction of 20∼30 %. This latter experiment is reported in the present paper.

Development of stainless steel / PSZ functionally graded materials by means of an expression operation

Recently, with advances in technology, materials for the construction of machinery are now being utilized in various kinds of severe environment. It is in order to cope with difficulties of this kind that recourse to “functionally graded materials” (FGMs) has been proposed in Japan. However, although various techniques are currently available for the manufacture of FGMs, it is very difficult to produce FGMs of the greater thickness widely required in manufacturing industry. This paper attempts to present a method of production for FGMs by means of an expression operation resulting in a mechanical separation of solids and liquids, using the two processes vacuum filtration and expression consolidation. It examines how this expression technology can be used to produce FGMs of greater thickness more simply and cheaply than has hitherto been possible. In this way, compressed FGM cakes materials could be manufactured using ZrO 2 as the ceramic material and stainless steel powder as the metallic material. FGM cakes produced in this way were air dried and then baked in an electrically powered reducing furnace. FGM cakes produced in the above described way observed the case that it use an addition agent and an effect of the graded layer steps and an effect by the thickness of it.

The Use of a Functionally Graded Material in the Manufacture of a Graded Permittivity Element

1. ABSTRACT The authors of this paper have previously developed a vacuum filtration technique for the manufacture of functionally graded materials (FGMs) by a progressive lamination method. For this, they have been granted a U. S. patent. Using this method, it is possible to manufacture FGMs with thicknesses ranging from several millimetres to several centimetres. The authors have already produced an iron (III) oxide-kaolin FGM, the graded condition of which they have verified by means of a scanning electron microscope. In addition, they have performed measurements to determine this material’s electrical properties viz: conductivity, relative permittivity and magnetic permeability. The present paper reports an experiment to create a different type of FGM, characterised by graded permittivity. The constituent materials used are titanium oxide and kaolin. The graded condition of manufactured specimens was investigated by mean of scanning electron microscope photographs and measurements of relative permittivity. Relative permittivity was found to vary between 2 and 5, while the photographs confirmed that the specimens were smoothly graded. On the basis of these results, it seems probable that graded permittivity elements can be manufactured using the authors’ method.

Potential energy in the electrical double layer and slipping plane potential

Previously, the authors have analysed a model of the electrical double layer, demonstrating the positiveness of the /spl zeta/ potential arising when aluminium particles are introduced into distilled water. Further, they demonstrated that an increase in conductivity led to the appearance of a negative /spl zeta/ potential. The same type of phenomenon can be found when electrostatic potential energies are analysed by applying the Poisson-Boltzmann equation. The present paper provides a comparison of these two double layer models obtained from experimental measurements and from calculation respectively. From the comparison, a value of 5.3/spl times/10/sup -11/ m/sup 2//s is deduced for the coefficient of molecular diffusion. This is close to the value of 7.35/spl times/10/sup -11/ m/sup 2//s given by the Chemical Handbook for polyethylene oxide.

A new manufacturing method for functionally gradient materials, and its applications

The concept of functionally gradient materials (FGMs) has emerged recently in Japan. Application fields for such materials are found in mechanical, chemical, biological and electrical engineering. In electrical engineering, they have utilisation potential in feeler sensors, resistors, magnetic shields, lossless optical fibres and superconductors. Hitherto two kinds of techniques have been available for the manufacture of FGMs: chemical and physical vapour deposition methods. Physical vapour deposition methods include sputtering and injection of ions. This paper proposes a new physical manufacturing method developed by the authors: a progressive and gradual introduction of additives. The method itself is explained and the materials produced by it are examined with respect to their resistivity and heat emitting properties.<<ETX>>