GB2164581A

GB2164581A - Chemical method

Info

Publication number: GB2164581A
Application number: GB08524913A
Authority: GB
Inventors: Michael Paul Neary; Thomas Andrew Wilson
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-04-13
Filing date: 1985-10-09
Publication date: 1986-03-26
Also published as: GB8524913D0

Abstract

A chemical method comprises creating a reagent gas in a metastable state, the reagent gas being mixed with a sample gas, with the result that at least part of the sample gas is energised by the reagent gas to give neutral atoms or molecules in an excited state, the sample gas comprising at least one hydrocarbon.

Description

SPECIFICATION Improvements in or Relating to a Chemical Method This invention relates to a chemical method.

According to this invention, there is provided a chemical method comprising creating a reagent gas in a metastable state, the reagent gas being mixed with a sample gas, with the result that at least part of the sample gas is energised by the reagent gas to give neutral atoms or molecules in an excited state.

The metastable state may be created before or after the said mixing of gases.

Preferably, the method comprises the additional step of providing the thus energised sample gas with additional energy in an amount corresponding to the difference between the respective energies of the excited and ionized states of the sample gas or of a selected component of the said sample gas, thus causing selective ionization of the said gas or component.

Suitably, the method comprises the additional step of imposing an electrical or magnetic force on the ions resulting from the said ionisation step to cause them to deposit on a substrate as stable atoms or molecules.

Thus, this specification describes a new manner of carrying out chemical reactions by the inception of selected forms of energy into the reaction zone by a novel means. By applying this principle, many new processes have resulted with, it is thought, application in a large number of different industries. Methods in accordance with the invention have been found to be generally capable of operation at room temperatures, which has advantages in the creation of certain sensitive products including uniformly doped semiconductors, new catalysts, pure gases, high purity materials of any kind, controlled coatings and new polymers, and also leads to advantages in connection with combustion enhancement, difficult separations, petroleum refinery operations, and carrying out any reaction in which the injection of specific energy types is helpful.

A particular example of the invention is a method for producing coatings of selected metals, non-metals and other molecules. Multiple layer coatings have been formed in accordance with the invention with many combinations of materials. The purity of the material of each layer has been as high as 100% and the thickness of each layer has been controlled to a single atomic or molecular layer.

Heretofore, it has been impossible to produce bodies or deposits of metals, non-metals, crystals and substances generally, and to achieve a purity of approximately 100%, when the processes involved are carried out at room temperatures. Similarly, it has been found to be impossible to dope such bodies at room temperature since doping has required diffusion, and high temperatures have been needed to permit diffusion of the dopant into the body. For instance, ultra-pure silicon must be heated to dope it by diffusion methods. The heating, however, for this purpose, causes imperfections in the crystalline silicon causing large numbers of rejects.

So that the invention may be more readily understood and so that further features may be appreciated, various methods in accordance with the invention will now be described by way of example.

The following features have been observed: 1. It has been found possible to generate large flows (ca 1 081 014/Sec) of so-called metastable atoms and/or molecules by passing neutral or ionized ground state atoms or molecules in the gas phase through a 200 to 300 volt potential. Optimum metastable atom or molecule production has usually occurred when the reagent gas (i.e. the atoms or molecules from which the metastable atoms or molecules are formed) is at a low pressure such as 1 to 5 torr (133 to 667 Pa). An atom, molecule or ion is said to be metastable when it possesses excess energy over its ground energy state and when it tends to be slow to dissipate its excess energy by radiative processes. The excess energy possessed by such a metastable entity is usually transferred in part or completely during inelastic collisions.

2. Due to the relatively long life-time of such metastable entities, it has been found that they can be easily brought into contact with metal or non-metal atoms or molecules in the gas phase so that, through inelastic collisions, the excess energy of the metastable reagent gas is transferred to them. The metal or non-metal atoms and/or molecules thus energized may become neutral atoms or molecules in the excited state or ionized species.

3. Neutral atoms or molecules in excited states (i.e. with excess energy) may be further excited to the point where an electron is ejected (thus forming the atomic or molecular ion) by supplying more energy in an amount corresponding to the energy difference between the ionized and excited states of the species of interest. It is often the case that the energy difference is small and can be supplied by a light source (such as a dye laser etc.) that emits in the ultra-violet and visible portion of the electromagnetic spectrum.Thus, by irradiating a collection of differing neutral atoms or molecules in the same excited state (i.e. each atom or molecule having the same amount of excess energy above the ground state) with monochromatic radiation whose energy corresponds exactly to the energy difference between the excited and ionized states of the atoms or molecules of the species of interest, only these atoms or molecules have been ionized.

Because of the uniqueness of the energy difference between an excited state of a particular atom or molecule and its ionized state, nearly absolute selectivity has been achieved. It is often the case that the energy difference referred to above can be altered by using a different reagent gas, because the energy difference of the metastable atoms or molecules of a given reagent gas is different from that of those of another reagent gas. For example, the characteristic metastable energy for some selected reagent gases is as follows: helium (23S) 19.7 eV, argon (33pro,2) 11.7 eV and nitrogen (32ù) 6.1 eV.An added degree of selectivity has been attained by using a reagent gas whose metastable energy differs from the ionization energy of the metal, non-metal or molecule of interest by such an amount that ionization of any other material but that of interest is not possible at all.

4. Ions thus produced are charged particles (by definition) and therefore can be caused to move in a particular desired direction and then accumulate, as a thin, uniform film, at a particular desired location by the imposition of an electric or magnetic field. Furthermore, by proper selection of the shape of the imposed field, mass discrimination can be achieved, although it has been rarely necessary with this technique.

In summary, a preferred method in accordance with the invention is described as follows. A flow of argon (2000 p moles/min) is established in a soft vacuum (1--5 torr, 133 to 667 Pa). The argon (3to,2) metastable states 11.7 eV is generated in large quantities (108--10'3 atoms/sec) as the argon is passed through two spaced apart annular electrodes across which 200--300 Vdc is applied. These argon metastable atoms, referred to as the reagent gas, are brought into contact with a molecule of interest referred to as the sample gas (e.g. W(CO)6, Ni(CO)6 silanes, perfluorobutane, etc.) where the argon metastable reagent gas transfers its excess energy to the sample gas.

Many complex reactions have been found to proceed in such an energy-rich environment. However, a dominant one is the formation of metal, or non-metal, molecules of the sample gas in a neutral, high-energy state and still in the gas phase.

The output from a nitrogen-laser-pumped pulsed tunable dye laser is set to the wavelength corresponding to the exact energy necessary to cause ionization of the sample gas, given the energy of its neutral high-energy state. The configuration of the cavity or container in which the above occurs is such that an electric or magnetic field can be applied to couple the site of formation of the ions of interest to the site of their deposition without entraining other non-ionic products present in the reaction zone, The layers thus deposited on a suitable target have been controlled in thickness to a monoatomic or monomolecular layer by controlling the rate at which sample ions are formed. Using such a process, layers of preselected uniform thickness of metals, non-metals and molecules can be deposited in virtually any order, thus giving "sandwich"-type layers.

Alternatively, two or more metals have been deposited simultaneously, thus forming an "alloy"-like layer and other molecules, such as monomers, have been deposited as ions on a surface so that polymerization occurs. Furthermore, certain chemical reactions, known to proceed as ion reactions, have been caused to occur at a specific location and at a specific controlled rate.

The invention may be more readily understood by referring to the following detailed Examples: Six Examples of the processes broadly described above will be presented. The first will deal with the non-metal silicon and the second with the metal tungsten.

EXAMPLE 1 By passing a 2000 micromole/minute flowing stream of helium gas through a conduit such as glass tubing which has two annular electrodes around the outer surface of the conduit separated by 3--5 cm and across which 200 Vdc are imposed, from 108 to 1014 metastable helium atoms (in the 23S state) were formed. Avolatile silicon compound, silane in this Example, was mixed into the stream of helium metastable atoms and, by a collisional process, the metastable energy was transferred to the silane, forming neutral silicon atoms in the excited state. The difference in energy between the excited neutral atom and the ionic form of the atom is 3.18rev which is equivalent to the energy of light having a wavelength of 390.53 nanometers (nm).Thus, light with a wavelength of 390.53 nm was directed onto the neutral excited silicon atoms, which absorbed the incident light and, in doing so, become ionized. By imposing either an electric or magnetic field gradient between the ions and a suitable target, the ions, and only the ions, migrated to the target where they took on an electron and were deposited uniformly as ground state neutral atoms.

EXAMPLE 2 The same procedure as is described above in the case of silicon was used for the metal tungsten. The volatile tungsten compound used was tungsten hexacarbonyl W(CO)6. Neutral excited tungsten atoms were formed in a manner similar to that described in Example 1 by mixing the tungsten hexacarbonyl with metastable helium gas. The difference in energy between the neutral tungsten atom and its ionic form is 2.54 eV which is equivalent to the energy of light having a wavelength of 489.73 nm. Thus, light with wavelength 489.73 nm was directed onto the neutral excited tungsten atoms, which absorbed the incident light and, in doing so, became ionized. As before, an electric or magnetic field gradient caused the migration of the ions to a target where they picked up an electron and were deposited uniformly on the target surface as neutral tungsten atoms in the ground state.

Table 1 summarizes the energy relationship described or referred to above in Examples 1 and 2.

TABLE 1 A nm Kcal eV Kcal eV Non-metal Si" 2506.9 250.69 114.1 4.95 - Si+ 1526.8 152.68 187.3 8.12 - - Energy difference 3905.3 390.53 - - 73.2 3.18 between excited neutral atom and its ionized form Metal W" 4008.8 400.9 71.3 3.09 - We 2204.5 220.5 129.7 5.63 - - Energy difference 4897.3 389.7 - - 58.4 2.54 between excited neutral atom and its ionized form Many target materials were found to be suitable for use in Examples 1 and 2, including metal, non-metal, inorganic and organic substances. The target actually used in Examples 1 and 2 was a quartz plate.

EXAMPLE 3 P-N Junction-Photovoltaic Cell The following Example represents a principle application of the invention.

Photovoltaic cells used as a means of generating electrical power have come under intense investigation in recent years due to the necessity of generating electrical power in remote places such as space. In the past, the use of photovoltaic cells for power production has been very expensive (e.g. up to U.S. $175,000/kilowatt). The high cost cited was the result of the necessity of employing very complicated and costly fabrication procedures so that the device could be made at all. Even so, the rejection rate was as great as 90%. With interest in photovoltaic cells expanding to include commercial use to provide an alternative power source to fossil fuels, any reduction in the cost of producing photovoltaic cell would further current goals.

In this Example, we will consider a photovoltaic cell based on a silicon matrix where the P layer is silicon doped with antimony and arsenic or phosphorus. The P and N layers are so formed that a sandwich configuration results.

Methods in accordance with the invention to produce P-N junction devices (photovoltaic cells, etc.): 1. have been carried out at ambient (room) temperatures, thus eliminating the use of the high-temperature induction furnaces previously required by current processes; 2. have been such that the doping process is carried out continuously and in a precisely controlled manner at room temperatures, resulting in concentrations of dopant at the bottom of the silicon layer that are equal to that found at any other depth in the layer, thus eliminating the normal non-linear diffusion of the dopant as a function of depth that has always resulted from the high-temperature diffusion process previously used;; 3) have permitted the formation of a P-N junction device with layer thickness, dopant type and dopant concentration controlled remotely so that the substrate (the surface to which the photovoltaic cell is connected), once mounted, is not handled or otherwise physically removed from the apparatus employed for the deposition of the P-N junction material.

In this Example the N dopant was boron and the P dopants were antimony and phosphorus. Because these dopants were selected for this Example it is not implied that other dopants could not be employed in exactly the same manner, that is to say, by the application of a method in accordance with the invention.

This Example differs from the previous one as follows in the previous Example the manner in which a metal or non-metal had been deposited with very high levels of purity was presented; however in this present Example the means by which a controlled amount of a specific impurity and no other has been incorporated into a high purity matrix where the amount of specific impurity may be very small (down to parts per 100 trillion), is discussed.

The source of silicon was picked from the wide variety and large number of volatile silicon compounds, and tetramethyl silicon was selected. The choice was made from the volatile compounds of silicon which have high vapour pressures, or readily form gases at room temperature.

An amount of the silicon compound equivalent to one or two grams of silicon was placed in a closed vessel that could: 1) have its temperature controlled to within +0.01"C from 1 00 C to -200C, 2) be connected to a manifold through a metering valve.

The valve was initially closed so that the gas-solid in the vessel could be brought into thermal equilibrium with the vessel. The temperature controller was adjusted to the temperature that would result in the desired pressure for the gaseous silicon compound. In the case oftetramethyl silicon (TMS), for example, 27"C resulted in a gaseous TMS pressure of approximately 150 mm of Hg (20 kPa).

The source of boron was picked from a large number of boron-containing compounds, such as the hydrides and diborane, that are volatile. The selection was made from volatile compounds because they have high vapour pressures, or readily form gases at room temperature. Diborane was selected and an amount of diborane equivalent to one or two milligrams of boron was placed in a closed vessel with characteristics similar to the vessel containing the silicon compound described above and the boroncontaining vessel was connected to the same manifold so that the two gases from the two vessels could be mixed as required. Because the amount of dopant is usualiy very small relative to the silicon (parts per billion or less) in a semiconductor device, the low temperature capabilities of the boron-containing vessel must be employed.That is to say, by maintaining the temperature at approximately 165"C, a vapour pressure of approximately 1 to 2 mm of Hg results (133 to 267 Pa). Therefore, when the two gases (TMS and diborane) were allowed to mix freely in the manifold at their respective vapour pressures, the diborane was approximately 1 part per trillion with respect to the TMS. In order to reduce the concentration of diborane further, it was useful to use the metering valves that separate each vessel from the manifold and apply a soft vacuum to the manifold. In this way, chosen low concentrations of borane could be achieved in the flowing mixture of the two gases. The soft vacuum applied to the manifold provided the driving force or means to transfer the gas mixture to other locations within the apparatus.

As above (i.e. in the previous Exampie) a gas such as helium was selected for the purpose of forming a reactant gas. It will be recalled that, by passing approximately 2 mols/minute of helium through a conduit such as glass tubing which at some convenient point has two annular electrodes around the outer surface of the conduit separated by 3 to 5 cm with 200 Vdc imposed across them, energetic or excited neutral atoms of helium were be formed. These neutral excited atoms are referred to as the metastable gas or reactant gas.

The manifold into which the TMS and borane gases were allowed to flow was connected to the glass tubing or conduit in which the metastable gas was formed in such a way that the TMS and borane gas mixture flowed into the metastable gas where energy was transferred from the metastable atoms (neutral excited atoms) to TMS and diborane. This configuration was selected (instead of one in which both the TMS and diborane gas mixture and the helium mix prior to the formation of the reactant or metastable gas) so that silicon and boron ions were not formed prior to irradiation with light of wavelength(s) corresponding to energy(ies) equal to that (those) required to ionize silicon and boron from their neutral excited states. The reason for this was that, by avoiding indiscriminate ionization, very high purity levels could be achieved as well as high coating rates.

It is to be noted, however, that under some circumstances it might be useful to form ions of either the dopant or silicon by mixing with the helium prior to the formation of the metastable gas, namely when the need or desire to eliminate the use of one light source such as a laser exists, and/or lower standards of purity can be tolerated but higher coating rates are necessary. However, in this Example that case will not be considered in detail. In either case, though, when energy is transferred from the metastable gas to the TMS and diborane, the excited neutral silicon and boron atoms are formed. Table 2 summarizes the energy content of the most prominent excited neutral states and ionized states of silicon, boron, phosphorus, antimony and arsenic. Included in the Table are the various energy differences between the excited neutral and ionized states of the elements mentioned.

TABLE 2 Energy Difference Between State Energy Neutral & lonized States Element & State eV eV Matrix Silicon: neutral 2881.578 4.303 ionized 1533.550 8.121 3.818 3247.774 P Layer Dopant Boron: neutral 2497.733 4.965 ionized 1362.460 8.296 3.331 3722.606 N.Layer Dopants Antimony: neutral 2060.380 5.995 ionized 1435.351 8.639 3.644 3402.854 Phosphorus: neutral 2534.010 4.893 ionized 1182.755 10.484 5.591 2218.021 Arsenic: neutral 1890.500 6.559 ionized 1264.010 9.810 3.251 3814.211 At this point, the gas containing the neutral excited silicon and boron was passed through an electric and/or magnetic field in order to remove any unwanted ions that were formed during energy transfer from the metastable gas, such as impurities whose ionization energy is less than that of silicon and boron. This procedure resulted in very high purity of the gas stream.In fact, in order to achieve the highest purity, a gas such as helium was selected because its large energy content in the metastable state (approximately 21 eV) caused efficient ionization of impurities (with low ionization energy and inefficient ionization of atoms or molecules with high ionization energies).

The gas containing the silicon and boron atoms in their excited neutral states was then irradiated by intense light from a source such as a hollow cathode lamp or a laser of, for example, the tunable dye type.

The light was monochromatic (or nearly so) with a wavelength of 3247.774 Angstroms ( ) or 3.818 electron volts (eV). Either a single pass or multiple pass configuration of the light path through the gas was employed, depending on the intrinsic intensity of the light source and the concentration of neutral excited silicon and boron atoms. A multiple pass optical configuration was preferred.

When the neutral excited silicon and boron absorbed light of this wavelength, the respective ions were formed because light of wavelength 3247.774 A meets the ionization energy requirements of silicon in its most long-lived neutral state and exceeds that required by boron in its most long-lived neutral state.

The ions thus formed, while still in the moving gas stream, were passed through an electric and/or magnetic field and the ions were diverted from the stream by their interaction with the field and were directed thereby to a suitable surface for coating.

If further purification of the gas stream was required prior to the point at which silicon and boron ions were formed (namely when irradiated with monochromatic light of wavelength 3247.774 A), then the gas stream was first irradiated with monochromatic light of wavelength slightly less than 3722.61 A. By doing so, any undesirable atomic or molecular species that can be ionized by 3722.61 A light was removed from the gas stream by passing it through an electric and/or magnetic field located between the 3722.61 A light sources.

The ions, silicon and boron, were deposited on a negatively-charged target where they formed a crystal or crystals while picking up an electron, and thus became neutral in a crystal lattice. The deposition process proceeded for as long as was necessary to achieve the desired thickness.

Once the desired thickness of P layer had been deposited, the N layer was deposited on top of the P layer without the necessity of removing the substrate-P layer for inspection or polishing. Any one or combination of the N layer dopants could be used in forming the N layer with silicon as the matrix. The method and apparatus employed were exactly the same as that described for forming the P layer using boron, exceptthat the wavelength of light used to form the ions was selected to correspond to the energy difference between the neutral excited and ionized states of the particular atoms being used.

One further refinement that was found useful in producing the maximum purity of a particular atomic species is worth mentioning. Though a particular atom, silicon, has been used for illustrative purposes, it will be appreciated that the refinement could be applied to any atom, for example germanium, etc.

Once the silicon atom was formed in its excited neutral state, other neutral excited atoms, of an unwanted sort, could also be formed. If these contaminant atoms can be ionized by 32477.774 A light then they can be ionized along with the silicon. Therefore, by irradiating all of the neutral excited atoms with another monochromatic light source having a wavelength corresponding to an energy slightly less than that required for the neutral excited atoms to be ionized (for example 3250 A), neutral excited silicon atoms would proceed with the gas stream unchanged but the other neutral excited atoms that could be ionized would be diverted out of the gas stream by application of an electric and/or magnetic field.It is also clear that any other neutral excited atoms, not ionized by the 3250 A wavelength light, as well as silicon will continue with the gas stream so that when the monochromatic light of 3247.774 irradiates the stream, in practical terms, only the neutral excited silicon atoms will be ionized and all other atoms will pass on with the gas stream. Thus the refinement under discussion provides an energy filter of approximately 3 Aso that those neutral excited atoms that can be ionized at energies lower than neutral excited silicon are ionized and those neutral excited atoms that require more energy to become ionized than neutral excited silicon never become ionized and pass on with the gas stream to waste or collection.

Four additional Examples of the application of methods in accordance with the invention to useful processes are presented below, namely: 1) a two-laser metal purification application, 2) a combustion application, 3) catalyst formation, and 4) hydrocarbon cracking.

EXAMPLE 3 Metal Purification with Two Lasers A summary of this use can be briefly stated as follows. A gas such as helium was passed through an electric field in such a way that a large concentration of the excited neutral form of helium was created, referred to as metastable helium atoms; a volatile form of a selected metal, non-metal or other molecule referred to as the reactant gas was introduced into the stream of helium metastable atoms whereby energy transfer from the metastable atoms to the reactant gas atoms/molecules occurred, thus increasing the energy ofthe reactant molecules/atoms to an energy state referred to as a neutral excited state (the energy of which is less than that required to cause ionization of the reactant gas atoms/molecules); and, by irradiation of the neutral excited reactant gas atoms/molecules with light of a wavelength corresponding exactly to the energy difference between the excited neutral reactant species and the ionized reactant species, ionization occurred for those species in the reactant gas for which the sum of the metastable energy and the energy of the irradiation light equalled or exceeded the ionization energy.

Thus any impurity species in the reactant gas having an ionization energy requirement exceeding this value were not ionized and were therefore eliminated as a candidate for deposition in a thin film, since deposition in this method depends on ions. It is also clearthat impurity species in the reactant gas whose ionization energy is less than this value would be ionized along with the reactant and subsequently deposited in the thin film, and thus be regarded as an impurity. However, by organizing the method appropriately, it was possible to avoid the inclusion in the thin film of impurity species whose ionization energy requirement is less than or equal to the reactant species. The discussion below illustrates such a method for a mixture of nickel, iron and tungsten where the object is to make a thin film of nickel but one with no inclusions of iron or tungsten. Referring to Table 3 below and bearing in mind-the principles of a method in accordance with the invention, it is clear that once the metastable reactant gas of nickel has been formed along with those of the impurities (iron and tungsten), irradiation with 6316.9 A light will cause ionization of the nickel and iron neutral excited species but will not cause ionization of the tungsten neutral excited species.

TABLE 3 Difference Neutral Excited lonized State in Energy W 4008.8 2204.5 A 4897.3 A (Tungsten) 30.93 eV 5.625 eV 2.532 eV Fe 3581.2 A 2382.0 A 7114.2 A (Iron) 3.463 eV 5.206 eV 1.743 eV Ni 3414.8 2216.5 A 6316.9 A (Nickel) 3.631 eV 5.594 eV 1:963 eV.

Thus, after deposition, the nickel thin film was found to include only one of the two impurity species, that is to say iron but not tungsten. If, however, the neutral excited reactant species and impurity species were first irradiated with light of wavelength greater than 6316.9 , the iron was ionized but none of the rest.

The iron ions could then be diverted, electrically or magnetically, from the reactant gas species (the nickel) and the only remaining impurity species (the tungsten). The remaining mixture was then irradiated with light of wavelength less than or equal to 6316.9 A but greater than 4897.3 A, thus forming nickel ions but not tungsten ions. In this way, a reactant species whose ionization energy requirement is between those of two impurity species was separated and deposited as a thin film free from impurities.

In actual form, the process was run as follows: bypassing a 2 millimole/minute stream of helium, enclosed in a glass conduit, through two annular electrodes across which 300 Vdc was applied, approximately 10t4 metastable helium atoms per second were formed. The reactant gas, composed of gaseous reactant Ni(CO)6 (nickel carbonyl) and two impurities, Fe(CO)6 iron carbonyl and W(CO)6 (tungsten carbonyl), was introduced into the helium metastable stream and mixed by turbulence and diffusion. The neutral excited states of each metal were formed by collisional energy transfer and/or Foster processes and helium was left in its neutral ground state.The reactant gas stream, then containing the neutral excited species iron, nickel and tungsten, was conducted by pressure difference along the glass conduit to a point at which it was irradiated by light of wavelength greater than 6316.9 A (say 6500 ) whereupon the iron neutral excited species was ionized but not the nickel and tungsten neutral excited species. The ionized iron was attracted to a negatively-charged target within the glass conduit and thereby eliminated from the reactant gas.The reactant gas stream, then containing the neutral excited species nickel and tungsten only, was conducted by pressure difference further along the glass conduit to a point at which it was irradiated by light of wavelength less than or equal to 6316.9 but not less than or equal to 4897.3 A whereupon the nickel neutral excited species was ionized but not the tungsten neutral excited species. The ionized nickel was attracted to another negatively-charged target within the glass conduit where it was deposited and formed a layer of nickel free from iron and tungsten, because the iron was previously eliminated as described above and the tungsten was never ionized and as such was not deposited with the nickel.

EXAMPLE 4 Enhanced Combustion of Hydrocarbon Fuels With this discussion we shall present an Example of a new means by which the metastable gases nitrogen and oxygen have been employed to improve the efficiency with which hydrocarbon fuels can be burned.

The efficiency of combustion is related to the amount of useful work that can be extracted from the combustion products. A typical prior internal combustion engine uses 15 parts of air for every part of fuel; however, when the means to be described was employed with the internal combustion engine, 33 parts of air for every part of fuel were consumed. Thus the efficiency of combustion was increased by a factor of 2.2.

The means of combusting hydrocarbon fuels in accordance with the invention provided for: 1) the production of more useful work per unit mass of fuel than previous combustion methods, 2) more complete combustion of fuel and therefore lower levels of polluting or harmful gases (e.g. NO, NO2, CO, etc.) in the exhaust, 3) the elinvination of the need for costly pollution abatement equipment in automobiles, and 4) more cost-effective use of fuel.

The method of combustion in accordance with the invention comprises the fuel-oxidant mixture (i.e. O2 in air) being passed through an electrostatic or magnetic field created by applying a DC voltage across two axially aligned annular electrodes that surrounded the channel through which the gas mixture passed on its way to the combustion chamber. The resulting gas mixture had a high concentration of "metastable" oxygen and nitrogen molecules. Because the physical nature of metastable atoms and/or molecules has been explained above, no further discussion of their physical nature will be presented; however, it is worth noting that the metastable atoms and/or molecules were not ions, hence the process does not depend on ionization or a plasma.

When metastable energy was collisionally transferred from either oxygen or nitrogen, or both, to gas phase fuel and/or fuel aerosol (as droplets) the increase in energy resulted in a reduction in the "activation energy" for combustion in the case of the vapour phase fuel molecules and an increase in vapour pressure of the fuel in the fuel aerosol particles. The last observation flowed from the fact that liquid phase fuel does not burn but vapour phase fuel does burn.Thus, in the case where thefuel is not well vaporised (i.e. in an aerosol), a substantial amount of heat derived from the combustion of gas phase fuel is required to supply the heat of vaporization for the fuel droplets in the aerosol. The heat used to vaporise fuel droplets cannot be converted into work.

When a fuel droplet in the aerosol received additional energy such as collisionally-transferred metastable energy, an increase in the vapour pressure of the fuel aerosol droplet occurred due to the well-accepted and widely used principle of thermodynamic equilibrium. Any open chemical system is constantly seeking a state of thermodynamic equilibrium because it is by definition the most stable state.

Thermodynamic equilibrium is achieved by the re-distribution of excess energy into the electronic, translational, vibrational and rotational energy modes of the open chemical system. Thus if metastable energy was added to an aerosol fuel droplet it entered into the electronic mode of the system but, as the system tended to thermodynamic equilibrium, the excess electronic energy was quickly (ca. 1 of6 sec) redistributed into the translational, vibrational and rotational modes. These are the energy modes that most influence the vapour pressure of the fuel droplet, in descending order of importance.

It is thought that it was by both the reduction of the activation energy of combustion for gas phase fuel molecules and the increase in vapour pressure of the aerosol fueldroplets that the 2.2 factor increase in combustion efficiency was achieved.

The practical application of this method will now be described in terms of an internal combustion 4-cycle engine, as in an automobile.

The fuel/air mixture used therein was conducted to each cylinder by the intake manifold. Opposite each intake port, to which the intake manifold was connected mechanically, a conventional airtight electrical feed-through was located on the said manifold and was insulated therefrom. A one millimetre diameter metal rod was welded to the electrical connector on the inside of the manifold. The length of the rod was so adjusted that it did not interfere with the operation of the valve and the metal of the rod was selected to have a high electronic work function and to be inert. Tantalum was used in this example. To the exterior portion of the electrical connector, a positive connection to a 300 volt D.C. power supply was attached. The negative connector of the power supply was attached to the metal of the manifold.This completed the electrical circuit which included the air gap between the tantalum metal rod and the interior metal surface of the manifold through which the hydrocarbon fuel-air mixture flowed during operation. The power supply was selected to operate on a 12 volt D.C. input and to deliver a 300 volts D.C. output at 10 watts of power.

As a result of this operation, increased power and decreased deleterious exhaust causes resulted, the exhaust gas being largely carbon dioxide and water vapour.

EXAMPLE 5 Catalyst Fabrication Many industrial processes rely on catalysts such as the metals platinum, rhodium, silver, nickel, gold, iron, copper and zinc. Even alloys of some of these metals are used as catalysts. Even though any or all of the above catalysts could be formed by the method to be described, only the platinum catalyst will be considered, in connection with the ammonia oxidation process for the formation of nitric acid.

A platinum gauze is used as the catalyst in the usual ammonia oxidation industrial process. The majority of the mass of the platinum gauze is provided to assure a mechanically stable physical structure and a large surface area. Due to the expense of the metal it would be desirable to produce a platinum coating on a much less expensive mechanical support.

Ordinarily, a catalyst is not consumed during the course of the reaction it initiates. However, in the case of the platinum gauze used in the ammonia oxidation process, the platinum appears to be consumed because impurities in the platinum gauze react with ammonia or nitrous oxide or nitric acid, although the platinum does not. The result is physical erosion of the platinum gauze which leads to its disintegration and the need to replace it with fresh gauze. Thus, if ultrapure platinum could be coated on to a mechanically stable high surface area substrate such as aluminium oxide (Al203), the catalyst might last virtually indefinitely and be much less expensive. The process described below achieves that end.

The method employed was similar to that described in Example 3 above. The volatile form of platinum was platinum hexafluoride (PtF6) or Pt(PF3)4. The first light irradiation source had a wavelength greater than 2858.8 A to eliminate all impurities whose ionization energy requirement was less than that of platinum.

The second light irradiation source had a wavelength less than or equal to 2858.8 A, although no more than 100 A less, which caused the ionization of the platinum neutral excited species and no others. The second target was Awl203 (although quartz wool could have been used) to which a negative static charge was applied. The platinum ions were neutralized and simultaneously deposited onto the substrate, building up a surface of desired thickness and of virtually 100% purity. The amount of platinum required was 0.001% the mass of that required for the conventional platinum gauze catalyst and was found to last 10 to 100 times longer.

EXAMPLE 6 This Example describes a method in accordance with the invention relating to the production of petroleum products such as gasoline, jet fuel, fuel oil and the like from crude oil by a means not requiring a catalyst. Previously, substantial amounts of costly cracking catalyst were required to produce petroleum products from crude oil in the majority of oil refining processes. The useful life-time of cracking catalysts ranges from a few hours to weeks, depending on the quality and chemical characteristics of the crude oil being refined. Further, the cost of a fresh catalyst charge for a medium size oil refinery can be as high as U.S. $400,000. Thus it is clear that a new means of carrying out crude oil cracking that does not require an expensive catalyst could reduce production costs and therefore the consumer costs.

A brief description of the process is as follows: So-called "cracking" of hydrocarbons is a non-technical way of referring to or designating the rupture of a carbon-carbon bond in the hydrocarbon. The tendency of any chemical bond, such as a carbon-carbon bond, to resist rupture can be expressed in terms of bond energy. Thus, the rupture of such a bond requires at least the application of an acceptable form of energy to the bond to be ruptured and in an amount adequate to cause the desired rupture. Catalysts have been successfully applied to this process because they can reduce the energy required to rupture the carbon-carbon bond.Hence, catalyst "cracking" of crude oil to yield petroleum products can be thought of as a process whereby long chain hydrocarbons (crude oil) are broken up into short chain hydrocarbons (petroleum products) by means of a catalyst that facilitates the rupture of carbon-carbon bonds in long chain hydrocarbons. The resulting mixture is then distilled in the normal or conventional way.

The new method to be described does not require catalyst use because a new means of providing the required energy for carbon-carbon bond rupture is used. The energy source used was a metastable form of one or more of the fixed gases or inert gases such as nitrogen, argon, helium, neon and krypton. Because of the abundance of nitrogen, it is considered to be the preferred choice although the other gases work as well.

A metastable gas molecule or atom is one that has excess energy in an amount sufficient to produce an excited state that is "metastable", i.e., relatively long-lived (10 milliseconds). Metastable gases are generated by passing a stream of ground state gas molecules/atoms through a DC potential gradient or by exposing the gas stream to a microwave field. When a large collection of metastable gas molecules exists it is referred to as a metastable gas. When such a gas has been brought into contact, that is to say mixed, with hydrocarbons, to cause collision between the hydrocarbon molecules and metastable molecules/atoms, the metastable gas species mentioned above all have been found to have sufficient energy to rupture the carbon-carbon bond in the host hydrocarbon molecule.The metastable gas molecule, after energy transfer, returns to the ground state (i.e., the state of minimum electronic, vibrational and rotational energy).

More specifically, in order to break a carbon-carbon chemical or covalent bond homolytically, 84.4 Kcal per mol (353.4 kJ/mol) must be applied to the hydrocarbon. This amount of energy corresponds to 3.66 eV.

The metastable energy of certain fixed and inert gases is shown in Table 4 below.

TABLE 4 Atom/ Spectroscopy Metastable Molecule Notation Energy in eV He 21S 20.6 23S 19.82 Ne 3PO 16.7 3P2 16.6 Ar 3P0 11.7 3P2 11.5 Kr 3PO 10.5 3P2 9.9 Xe 3PO 9.44 3P1 8.43 3P2 8.31 N2(g) 32+ 6.03 Thus, by passing gas through an annular pair of spaced electrodes across which 200 volts DC was applied or through a microwave generator or magnetic field, substantial amounts of the metastable species of nitrogen were produced. The amount per unit time of metastable gas produced depended on the power applied to the electrical, magnetic or microwave field and on the flow rate of the ground state gas through the electromagnetic force (EMF) field. For example, a 200 VDC 5 watt EMF field was adequate to produce 6x1023 metastableatoms/molecules per 10 min. Because the production of metastable atoms/molecules is physically similar to an optical absorption process which depends on instantaneous concentration of ground state gas in the field, scale-up was readily feasible. Thus, petroleum products were formed at a rate equal to that of the production of metastable gas molecules diminished by losses to the walls and recombination processes. The loss has been found to be less than about 10%.

With crude oil in the vapour phase, such as in a fluidized bed cracker combination with a metastable gas of the type described above, it has been straightforward to maintain a 50-50 ratio of metastable gas to crude oil vapour by means of concentric annularjets.

Experimental evidence of the principle was obtained using a long chain hydrocarbon, n-decane. When n-decane vapour was mixed with nitrogen gas metastable molecules by means of a concentric annular jet, the following products were obtained: TABLE 5 Carbon iZa Relative % 1-6 41.0 7 4.3 8 13.4 9 10.7 10 6.7 11 13.0 12 a includes isomers.

Thus it is clear that hydrocarbon cracking can be promoted as described.

Other preferred applications envisaged for methods in accordance with the this invention are: 1) catalyst metal deposition on inexpensive substrates; 2) the formation of microelectric units or components (diodes, transistors and the like); 3) metal our polymer coating to retard or prohibit corrosion and/or wear; 4) the formation of special optical surfaces and crystals; 5) low cost conductor formation; 6) the manufacture of high purity materials of many kinds; 7) the replacing of many high temperature epitaxial processes; 8) the separation in relatively pure form of many difficultly separable elements, including (but not limited to) the rare earth elements, metals of the platinum group, rare gases such as argon, neon, etc., hydrogen, helium or other gases, atmospheric gases generally, and the halogens; and 9) the carrying out of many chemical reactions in which the injection of specific energy types is helpful.

Claims

1.A A chemical method comprising creating a reagent gas in a metastable state, the reagent gas being mixed with a sample gas, with the result that at least part of the sample gas is energised by the reagent gas to give neutral atoms or molecules in an excited state, wherein the sample gas comprises at least one hydrocarbon.

2. A method according to claim 1, wherein the said metastable state is created before the reagent gas is mixed with the sample gas.

3. A method according to claim 1, wherein the said metastable state is created after the reagent gas is mixed with the sample gas.

4. A method according to any one ofthe preceding claims, wherein the said metastable state is created by passing the reagent gas between two spaced-apart substantially coaxial annular across which a D.C.

voltage is applied.

5. A method according to claim 4, wherein the D.C. voltage is between 200 and 300 volts.

6. A method according to any one of the preceding claims, wherein the reagent gas comprises air.

7. A method according to any one of the preceding claims, wherein the hydrocarbon is combusted in an internal combustion engine.

8. A method according to any one of the preceding claims comprising the additional step of providing the thus energised sample gas with additional energy in an amount corresponding to the difference between the respective energies of the excited and ionised states of the sample gas or of a selected component of the sample gas, thus causing selective ionisation of the said gas or component.

9. A method according to claim 8, wherein the additional energy supplied is sufficient to crack the hydrocarbon.

10. A method according to claim 9, wherein the sample gas comprises a mixture of heavy hydrocarbons which are cracked as said to form gasoline and other lesser hydrocarbons.

11. A method according to claim 1, and substantially described herein with reference to Example 6.

12. A hydrocarbon whenever obtained by a method according to any one of the preceding claims.

13. Any novel feature or combination of features disclosed herein.