NANOSIZED CERAMIC PLASMA CATALYST FOR STABILIZING AND ASSISTING PLASMA COMBUSTION

Abstract

A new plasma catalyst in the form of a ceramic-matrix nanocomposite is disclosed for application to the plasma-assisted combustion. The new functionality of the nanoceramic plasma catalyst is driven by the synergistic effect of plasma and solids. The plasma catalyst is based on combinations of valve metal oxides, polar transition-metal oxides, rare-earth oxides and phosphides, alkali metal oxides, silicon oxides and nitrides, etc. are disclosed. The advantage of combining a heterogeneous catalytic and plasma catalytic effect allows utility for large area applications and is scalable for large-scale industries.

Claims

1. A plasma catalyst in the form of ceramic-matrix nanocomposite, said nanocomposite comprising at least first part and second part, wherein said: first part comprises a nanoporous wafer; and second part comprises a crystalline nanowhiskers.

2. The plasma catalyst according to claim 1, wherein: said nanoporous wafer comprising at least one of the IUPAC Group 4, Group 5, Group 6 and Group 13 valve metal oxides of the Periodic Table, silicon/silicon dioxide and silicon carbide, and said nanowhiskers comprise at least one of perovskite-like poly- and/or single-crystal ferroelectric with pyroelectric properties, transition metals, conductive metal-oxide-metal ceramic or complexes of ones.

3. The plasma catalyst according to claim 1 or 2, where said first and second part are covered by a top cover in the form a multilayer thin film or wafer.

4. The plasma catalyst according to claim 3, where said the top cover comprises at least three layers: a catalyst grid; an oxidation and alkaline preventing layer; and a transparent conductive oxide ceramic layer.

5. The plasma catalyst according to any previous claim, where said nanocomposite is in the form of a sintered solid thin ceramic tile.

6. The plasma catalyst according to any previous claims, where said nanoporous wafer of the first part is in the form plane-parallel wafer comprising an array of self-organized, honeycomb-like and nearly monodisperse pores either cylindrical or V-type population, which are either open on both sides or only one-side and directed perpendicular to the upper/bottom surface of the wafer.

7. The plasma catalyst according to any previous claim, where said nanoporous wafer is a ceramic, synthesized according to the formula:
(Me.sup.4).sub.I(Me.sup.4).sub.J(Me.sup.6).sub.K(Me.sup.13).sub.L(Si).sub.M(SiC).sub.N(O).sub.Z, where Me.sup.4 is a valve metal of IUPAC Group 4 transition metals of the Periodic Table, where Me.sup.5 is a valve metal of IUPAC Group 5 transition metals of the Periodic Table, where Me.sup.6 is a valve metal of IUPAC Group 6 transition metals of the Periodic Table, where Me.sup.13 is a valve metal of IUPAC Group 13 transition metals of the Periodic Table, and where indexes I, J, K, L, M and Z are numerical proportions of atoms of each type; and one of I, J, K, L, M and Z are greater than 0 elsewise N=1.

8. A plasma catalyst according to claim 2, where said ferroelectric with pyroelectric properties is a perovskite-like crystalline nanowhisker in the form either poly- or single-crystal, synthesized according to the formula:
Σ[(Me.sup.1-2).sub.I(Me.sup.1-2).sub.J](Me.sup.3).sub.KΣ[(Me.sup.4-6).sub.L(Me.sup.4-6,8).sub.M]Σ[(Me.sup.4-6).sub.N(Me.sup.12-15).sub.R](sMe.sup.13-16).sub.X(nMe.sup.14-16).sub.Y(O).sub.Z, where a superscript index denotes IUPAC Group of the Periodic Table, where a subscript indexes I, J, K, L, M, N, R, X, Y, Z denote numerical proportions of atoms of each type, where Σ[ . . . ] denotes formation of a complex comprising several elements of the Group(s) of superscript indices, where Me, sMe, nMe denote metal, metalloid and nonmetal respectively, and where at least one of I, J, L, Z is greater than 0, in general 0≤I, J, K, L, M, N, R, X, Y, Z≤30.

9. Use of plasma catalyst according to any previous claim as component of lining of combustion chamber, said lining serving as an additional thermal, oxidation and alkaline preventing shield of combustion chamber walls.

10. Combustion chamber lining comprising plasma catalyst according to any previous claim 1-8, wherein said lining serves an additional thermal, oxidation and alkaline preventing shield of combustion chamber walls.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0057] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure and in which:

[0058] FIG. 1 depicts a summary of disclosed embodiments;

[0059] FIG. 2 illustrates size-driven effects in nanoscale ferroelectric perovskites;

[0060] FIG. 3 illustrates an electrophysical phenomena;

[0061] FIG. 4 illustrates the synergistic effect in plasma catalysis;

[0062] FIG. 5 illustrates Plasma Catalyst-LTPs-Solid Catalyst Interaction;

[0063] FIG. 6 illustrates plasma catalyst, overall architectural concept of ceramic-matrix nanocomposite;

[0064] FIG. 7 illustrates nanoporous wafer, its structure and materials;

[0065] FIG. 8 illustrates nanowhiskers, their structure and materials;

[0066] FIG. 9 illustrates top cover, its structure and materials:

[0067] FIG. 10 illustrates wafer bonding technique of the plasma catalyst.

MODE(S) FOR CARRYING OUT THE INVENTION

[0068] The present invention has been described and illustrated in detail with references to the accompanying drawings. However, the present invention is not limited to the embodiments described above nor illustrated in the accompanying drawings. There are other possible embodiments and combination of characteristic features which can be derived and implemented according to the present description and accompanying claims.

[0069] At least one exemplary embodiment of the present invention is disclosed herein. It is understood that modifications, substitutions and alternatives are apparent to those skilled in the art and may be made without departing from the spirit and scope of this disclosure. This description is intended to cover any device or variants of an exemplary embodiment(s). Furthermore, in this specification, the terms “comprise” or “comprising” or “include” or “including” does not exclude other elements or steps, the terms “one” or “single” does not exclude a plurality, and the term “and/or” means that either or both. Furthermore, features or steps which have been described can also be used in combination with other features or steps and in any order, unless the description or context suggests otherwise.

[0070] For the purpose of better understanding of the invention and its embodiments, first are given explanations of the physical effects and phenomena upon which the present invention is based on.

[0071] Pyroelectricity of Nanoscale Ferroelectrics

[0072] When the dimensions of ferroelectric perovskites are actually limited to 0-2D nanoscale, the laws that govern the properties of bulk ferroelectrics are no longer implemented. In accordance with the phenomenological theory of Landau-Ginzburg-Devonshire and the computational model, the dimensional effect could be used to fine-tune the polarization value (pyroelectric coefficient) and the temperatures of phase transitions in ferroelectric nanostructures, thus providing systems with a tunable giant pyroelectric response.

[0073] Variations in the electrophysical, optical, and mechanical properties of 0-2D ferroelectrics are associated with a change in surface tension, which induces internal pressure in the radial direction. The internal pressure in 0-2D nanostructures increases with decreasing size, for instance, in 1D cylindrical crystal in the form of a nanowhisker with a radius, and not the aspect ratio. The effect of pressure depends on the direction of polarization relative to the axis of the crystal.

[0074] FIG. 2 depicts the family of curves for size-driven effects of nanowhiskers. In FIG. 2, a) and b) indicate the typical dependences of the Curie temperature T.sub.C and the pyroelectric coefficient P (polarization) of various ferroelectrics on the radius R of a cylindrical nanocrystal, where T.sub.C is the temperature of the second-order phase transition from the ferroelectric phase to the paraelectric. When the polarization vector is directed along the axis, T.sub.C and pyroelectric coefficient P (polarization) are increased with decreasing radius (up to the critical radius R.sub.CR, at which long-range interactions favoring ferroelectricity become weakened), while for polarization perpendicular to the axis, T.sub.C and P fall with decreasing radius.

[0075] Field-Enhanced Emission

[0076] FIG. 3, part a) reveals the conditions for the field emission and field-enhanced emission of electrons, Typically for field emission, an electric field with a strength E˜10.sup.7 V/cm (1 V/nm) on the emitting surface is a necessary condition for electron tunneling through the surface barrier.

[0077] In fact, it is impossible to obtain a uniform electric field with strength of 10.sup.7 V/cm in a plane-parallel electrode system. An exception is the case when an inhomogeneous field is created due to a change in the shape of the emitting surface, for instance, using nanoscale cylinders, cones, etc. Thus, the field strength of emitter-anode system can be increased E=γ.Math.U, where U is voltage applied to the emitting surface and γ (1/cm) is the field enhancement factor.

[0078] FIG. 3, plot b) shows the dependence of the field enhancement factor γ(d,D) of the coaxial cylindrical system on the diameter d and the distance D between the emitting surface and the anode. As can be seen in the plot, if the field enhancement factor is in the range 2.3×10.sup.4 cm.sup.−1≤γ≤2.6×10.sup.6 cm.sup.−1 and the voltage applied to the emitting surface is 4V≤U≤450V, then the field strength becomes E≥10.sup.7 V/cm, which is a which necessary condition for field-enhanced emission of electrons.

[0079] Electron Scattering into Films

[0080] FIG. 3, sketches c) and d) illustrate difference between electron scattering in solids and multilayer films. Electron scattering into multilayer films has a more complicated looking, not only due to the different matters of the layers, but also scattering at the inner interlayer boundaries (Braggs' effect) and interlayer exchange interaction.

[0081] In case of solids, the depth of electron penetration (electron track length) R.sub.KO into matter can be estimated by the Kanaya-Okayama expression as:

R.sub.KO=(0.0276•A•E.sub.0.sup.1.67)/ρ•Z.sup.0.89,

where A is the atomic mass; E.sub.0 is initial electron energy; ρ is matter density; and Z is atomic number. In the case of compounds (with simplifying assumption, multilayer films could be taken as compounds), the average values are taken into calculations.

[0082] The depth of X-ray production can be estimated by Anderson-Hasler expression as:

R.sub.AH=0.064(E.sub.0.sup.1.68−E.sub.C.sup.1.68)/ρ,

where E.sub.C is the absorption edge (critical excitation) energy,

[0083] In general, electronic paths are calculated using mathematical modelling techniques based on Monte Carlo simulations.

[0084] Synergistic Effect of Plasma and Heterogeneous Catalyst

[0085] FIG. 4 depicts the diagram with experimental data related to evaluation the effectiveness of various catalytic techniques in the destruction of toluene. The relative efficiency (product yield) during the destruction of toluene reaches a maximum of 65% when combining the catalytic properties of the discharge plasma with a solid-state catalyst, additionally placed in a chemical reactor.

[0086] FIG. 5 shows the interaction mechanism in the system of plasma catalyst-LTPs-solid catalyst. There are the following types of interaction: ionizing radiation—substance; plasma—surface; recombination plasma radiation—environment; and substance—heterogeneous catalyst.

[0087] VUV-soft X-ray ionizing radiation efficiently creates reactive radical fragments and vibrationally and electronically excited species. These chemically active species drive reaction kinetics and path, produce unique structures in the gas phase, which cannot be obtained in other ways, at least not in an economically significant way.

[0088] The presence of boundaries around the plasma creates strong gradients in which the properties of the plasma change dramatically. It is in these boundary regions that the incident VUV-soft X-ray radiation interacts most strongly with the plasma, often causing unique reactions. And it is precisely on the bounding surfaces that complex interactions of the plasma with the surface occur.

[0089] Photons generated by the recombination of excited species in the plasma interact with other species in the plasma or with the boundaries of the plasma, and they can exit the plasma in the form of UV-VIS-IR irradiance.

[0090] Basically, three reaction mechanisms have been proposed for redox reactions on the solid catalysts surface: [0091] Langmuir-Hinshelwood mechanism (LH) is that two molecules are adsorbed on neighboring sites, and the adsorbed molecules undergo a bimolecular reaction; [0092] Eley-Rideal mechanism (ER) considers that only one of the molecules adsorbs on the surface of the catalyst and the other one reacts with it directly from the gas phase, without adsorbing; and [0093] Mars and Van Krevelen (MvK) mechanism assumes that some products of the reaction leave the solid catalysts surface with one or more constituents of the catalysts lattice.

[0094] The plasma catalyst according to invention performs thermal energy harvesting of the combustion in the form UV-VIS-IR irradiation band, generating electricity pyroelectrically, converting electricity through internal field-enhanced emission and electron scattering into VUV-soft X-ray ionizing radiation band as plasma forming medium.

[0095] The plasma catalyst in accordance with the present invention is embodied as a ceramic-matrix nanocomposite based on a combination of valve metal oxides, polar transition-metal oxides, rare-earth oxides and/or phosphides, alkali metal oxides, silicon and/or silicon oxides, silicon carbides and/or nitrides, including ternary and higher complexes in the form of at least one wafer with/without additional coating.

[0096] FIG. 6 depicts the design of one of the possible freely scalable architectural embodiments of the plasma catalyst. The plasma catalyst is a composite comprising at least one wafer (602) with the array of self-organized, honeycomb-like and nearly monodisperse pores (603), where each pore contains at least one of the three nanowhisker (604) either (605) or (606). It is possible that the plasma catalyst may have an additional top cover (601) and a coating (607) of the wafer (602).

[0097] FIG. 7 presents the form and materials of nanoporous wafer (602) and coating (607). The wafer contains either one-side or double-side opened pores, in the first case, the wafer has a so-called residual bed, which remains after electrochemical processing of an original wafer material.

[0098] Also, the wafer may have pores either cylindrical or V-type population and additional one-side coating. The wafer is a ceramic of valve metal oxides, either silicon/silicon dioxide or silicon carbide synthesized by the formula:

(Me.sup.4).sub.I(Me.sup.5).sub.J(Me.sup.6).sub.K(Me.sup.13).sub.L(Si).sub.M(SiC).sub.N(O).sub.Z,

where Me.sup.XX is a valve metal of IUPAC Group XX transition metals; a subscript index is numerical proportions of atoms of each type; and one of I, J, K, L, M and Z are greater than 0 elsewise N=1.

[0099] The wafer (602) without the top cover (601), synthesized according to the formula:

(Me.sup.4).sub.I(Me.sup.5).sub.J(Me.sup.6).sub.K(Me.sup.13).sub.L(Si).sub.M(O).sub.Z,

where one of I, J, K, L, M and Z are greater than 0,
and is heterogeneous redox catalyst, for instance γ-Al.sub.2O.sub.3. The wafer could be synthesized by customized formula as required.

[0100] The wafer coating (607) is a multilayer coating comprising either nothing or the residual bed, and/or several layers of thin films of compounds according to the formula:

(Me.sup.3).sub.I(Me.sup.4).sub.J(Me.sup.5).sub.K(Me.sup.6).sub.L(Me.sup.10).sub.M(Me.sup.11).sub.N(O).sub.Z,

where at least one of I, J, K, L, M, N and Z are greater than 0.

[0101] The family of nanowhiskers (604), (605) and (606) plays a major role in the absorption of UV-VIS-IR irradiation, generating electricity pyroelectrically, converting electricity through internal field-enhanced emission and electron scattering into VUV-soft X-ray ionizing radiation.

[0102] FIG. 8 depicts the family of nanowhiskers deposited into pores of the wafer (702), and includes at least one of the nanowhiskers of a cylindrical or V-type: [0103] The nanowhisker (604) is at least one of perovskite-like whisker or conductive whisker; [0104] The nanowhisker (605) is a composite comprising a perovskite-like whisker and conductive whisker; [0105] The nanowhisker (606) is a composite comprising a perovskite-like whisker and conductive whisker on both sides.

[0106] The perovskite-like nanowhiskers have homogeneous or inhomogeneous crystalline structure, and there are in the form either poly- or monocrystals, synthesized according to the general formula:

Σ[(Me.sup.1-2).sub.I(Me.sup.1-2).sub.J](Me.sup.3).sub.KΣ[(Me.sup.4-6).sub.L(Me.sup.4-6,8).sub.M]Σ[(Me.sup.4-6).sub.N(Me.sup.12-15).sub.R](sMe.sup.13-16).sub.X(nMe.sup.14-16).sub.Y(O).sub.Z,

where a superscript index denotes IUPAC Group; a subscript index denotes numerical proportions of atoms of each type;
Σ[ . . . ] denotes (possible) formation of a complex comprising several elements of the Group(s) of superscript indices;
Me, sMe, nMe are metal, metalloid and nonmetal respectively; and at least one of I, J, L, Z are greater than 0 (e.g. LiNbO.sub.3-perovskite-like lattice, homogeneous, monocrystal), in general 0≤I, J, K, L, M, N, R, X, Y, Z≤30, for instance, Barium sodium niobate Ba.sub.2NaNb.sub.5O.sub.15 perovskite-like crystal.

[0107] Conductive nanowhisker materials are at least one of transition metals, metal-oxide-metal (MOM) or so-called transparent conductive oxide (TCO) ceramics with low resistance at a temperature of several hundred degrees Celsius.

[0108] FIG. 9 depicts the top cover (601), structure and materials. In the case of using the top cover, it should be transparent in the wavelength range in accordance with FIG. 9a and may be in the form of a thin film coating or wafer.

[0109] The top cover (601) as a thin film coating is comprising at least a catalyst grid layer (901), oxidation and alkaline preventing layer (902) and TCO ceramic layer (903).

[0110] The catalyst grid layer (901) is at least one of a transition-metal thin film or MOM thin film according to the general formula:

(Me.sup.3).sub.I(Me.sup.4).sub.J(Me.sup.5).sub.K(Me.sup.6).sub.L(Me.sup.10).sub.M(Me.sup.11).sub.N(O).sub.Z,

where at least one of I, J, K, L, M, N and Z are greater than 0.

[0111] When the top cover (601) is a Si wafer (904), it comprises at least the following layers: the catalyst grid layer (901); oxidation and alkaline preventing layer (902) and TCO ceramic layer (903).

[0112] FIG. 10 depicts the wafer bonding techniques for packaging the plasma catalyst and materials used to. In the case where the plasma catalyst contains several wafers, the packaging can be performed in one of the following ways: [0113] Adhesive bonding, FIG. 10a; [0114] Glass frit bonding, FIG. 10b.

[0115] Adhesive bonding technique is based on applying a specific mixture (1001) of an inorganic binder and fillers, which are selected taking into account the following parameters of wafers (601, 602) and calcined adhesive (1002): [0116] The spread of the coefficient of thermal expansion (CTE) for all materials used is not more than ±5%; [0117] The service temperature and bonding pressure should not lead to damage to any plasma catalyst components; and [0118] Electroconductivity.

[0119] Glass frit bonding technique is based on using a specific mixture (1003) of an organic binder, glass powder and, if necessary, conductive fillers, which are selected taking into account the following parameters of wafers (601, 602) and glass (1004): [0120] The spread of the coefficient of thermal expansion (CTE) for all materials used is not more than ±5%; [0121] The service temperature and bonding pressure should not lead to damage to any plasma catalyst components; and [0122] Electroconductivity.

[0123] The plasma catalyst in the form of ceramic-matrix nanocomposite is the sintered solid thin ceramic tile in which there are no moving parts, self-powered and inherently reliable.

[0124] The plasma catalyst is placed inside the combustion chamber in the form of a lining and, in parallel, can serve as a thermal shield of the chamber walls.

[0125] For person skilled in the art it is obvious that the present invention is not limited to the embodiments depicted in the attached drawings and described above, but within the scope of attached claims many other embodiments are possible.