Abstract
In humid air, the substantial charge-dipole attraction and electrostatic acceleration of surrounding water vapour molecules towards charged combustible nanoparticles cause intense electrostatic hydration and preferential oxidation of these nanoparticles by electrostatically accelerated polar water vapour molecules rather than nonaccelerated nonpolar oxygen gas molecules. Intense electrostatic hydration of charged combustible nanoparticles converts the nanoparticle's oxide-based shells into the hydroxide-based electrolyte shells, transforming these nanoparticles into reductant/air core-shell nanobatteries, periodically short-circuited by intraparticle field and thermionic emission. Partially synchronized electron emission breakdowns within trillions of nanoparticles-nanobatteries turn a cloud of charged nanoparticles-nanobatteries into a powerful radiofrequency aerosol generator. Electrostatic oxidative hydration and charge-catalyzed oxidation of charged combustible nanoparticles also contribute to a self-oscillating thermocycling process of evolution and periodic autoignition of inflammable gases near to the nanoparticle's surface. The described effects might be of interest for the improvement of certain nanotechnological heterophase processes and to better understand ball lightning phenomenon.
1. About the Possible Magnitude and Polarity of a Net Electrostatic Charge of Ball Lightning
Despite numerous attempts, including the most recent ones [1–7], an adequate theoretical and experimental simulation of ball lightning still remains incomplete. At the same time, a simple analysis of the numerous witness descriptions of this phenomenon [8, 9] can provide us with useful information, in particular, concerning the possible magnitude and polarity of a net electrostatic charge of lightning balls. Some witnesses described a strong attraction of their hair towards lightning balls flying in immediate proximity to them (at distances of about two-three feet). It is interesting that such a strictly directed attraction of human hair to lightning balls with diameters of ~10–20 centimetres was repeatedly observed by different witnesses indoors [9]. Our own experience of experimental work, both with highly charged water-based artificial clouds and with megavoltage equipment, shows that an attraction of human hair towards such highly charged objects becomes apparent when an average electrostatic intensity reaches ~1-2 kV/cm. Therefore, in the above cases, one can assume that a potential difference between the visible surfaces of lightning balls and the witnesses’ hair could be at least ~60–120 kV, and so, a net electrostatic charge of such lightning balls could be at least ~1 microcoulomb. The most probable polarity of these lightning balls was negative with respect to the grounded witnesses. Several descriptions from other witnesses of ball lightning [9] show that lightning balls can sometimes relatively uniformly and slowly fall from thunderclouds, only appreciably accelerating downwards when approaching the earth's surface. This sudden acceleration, which takes place not far from the earth's surface, and the lightning balls’ final elongation to the form of an ellipse before they touch the earth's surface, can indirectly indicate that these balls were charged negatively rather than positively—the earth's surface is almost always positively charged with respect to the base of thunderclouds during a thunderstorm.
There are also several detailed descriptions of direct observations of a relatively low-temperature process of ball lightning formation, that is, ball lightning formation without a previous visible stroke of normal lightning [8, 9]. In particular, such ball lightning formation was repeatedly observed on grounded metal objects, for example, on cast-iron and steel pins of previously destroyed pin-type insulators that were found on pylons of old inoperative electric lines [8, 9]. During a thunderstorm, these grounded rusty pins could probably generate invisible positive streamers, simultaneously electrostatically spraying the positively charged iron/carbon-based aerosol particles. Such an intense selective corrosion process accompanied by electrospraying of combustible particles from relatively cold corona-forming metal emitters along with a synchronous local generation of a water gas-based reducing atmosphere could be named “field-assisted metal dusting corrosion” because of its high physical similarity to ordinary metal dusting corrosion processes [10–16]. At this point, however, it is only important to note that a cloud of the unipolar charged combustible nano-or microparticles, which are possibly produced in this high-voltage corrosion-electrospraying process, could be a material basis of lightning balls, generated from the grounded conductors during thunderstorms, and probably such lightning balls could be charged positively rather than negatively.
The positive polarity of the charged lightning balls generated from grounded conductors can also explain their typical horizontal flying trajectories at relatively low heights of about 0.5–2 metres above the ground.
In these cases, the identical polarity of the charged lightning balls and the ground might be responsible for a Coulomb repulsion of these balls from grounded objects. Having analyzed various witness observations, we can assume the following. (a)The net electrostatic charge of lightning balls can be both positive and negative.(b)Sometimes lightning balls can be exposed to a partial discharging due to corona or spark discharges from their surface; the discharging processes can perhaps reduce the magnitude of an initial electrostatic charge of lightning balls. (c)Sometimes a corona discharge from the surface of lightning balls can cause a corona charging of neighbouring low conducting objects with a polarity similar to the polarity of these balls; such a process can cause a subsequent immediate electrostatic repulsion these balls from neighbouring low conducting objects.(d)A net electrostatic charge of the lightning balls, which attract human hair at distances of about two-three feet, can perhaps reach at least ~1 microcoulomb.(e)The lightning balls that are frequently described as avoiding contact with grounded conductors and maintaining their approximately constant low flying heights above the ground can be charged with the same polarity as the ground (i.e., positively rather than negatively during thunderstorms), consequently the force of electrostatic repulsion of these balls from the ground and grounded objects at short distances can partially compensate for their weight, contributing to a buoyancy of these balls; a net electrostatic charge of such relatively long-living lightning balls with typical diameters of ~10–20 centimetres can be much higher than it was supposed in [17]; thus, the magnitude of the net electrostatic charge of lightning balls avoiding contact with grounded conductors can probably also reach at least ~1 microcoulomb, being in fact limited by a voltage of corona ignition from their surface.
It was repeatedly assumed, for example in [18, 19], that the high electrostatic charge of lightning balls could play a major role in the existence of ball lightning. Equally we share this opinion, and in the present paper, we will examine the possible role electrostatic charge plays in the life of ball lightning, still assuming that ball lightning is a cloud of combustible aerosol particles that are exposed to a slow, predominantly electrochemical oxidation [20]. Such a process of the electrochemical oxidation of nano or submicron aerosol particles converts these combustible particles into aerosol batteries—further, for short “nanobatteries”—that are periodically (and perhaps with very high frequencies) short-circuited by intra-particle breakdowns.
According to [20], we can assume the following. (a)The aerosol particles-batteries can exist either in the form of nano or submicron aggregates, or in the form of nano or submicron core-shell capsules, or in a more realistic combination of these two simplest types, that is, in the form of aerosol aggregates consisting of mixed nano or submicron core-shell particles. (b)The aerosol particles-batteries can contain at least one reductant component, for example, a metal or carbon-based component, and at least one electrolyte component.(c)These aerosol particles can use either an internal compact oxidant or external oxidant from ambient air, that is, oxygen gas and/or water vapour.(d)During the electrochemical oxidation the aerosol particles automatically turn into aggregated or core-shell structured aerosol nanobatteries periodically short-circuited by the intra-particle breakdowns due to both field and thermoionic electron emission taking place within and on the surface of particles-batteries.(e)The short-circuited aerosol nanobatteries are free magnetic dipoles, and so they can be exposed to an intense mutual magnetic dipole-dipole attraction, forming ball-shaped clouds with high magnetic polarizability.(f)The non-short-circuited aerosol nanobatteries are free electric dipoles with substantial electric dipole moments, and so they can be exposed to an intense mutual electric dipole-dipole attraction, forming ball-shaped self-assembling clouds with high electric polarizability (Figure 1).(g)The repeating processes of the short circuits within the separate aerosol nanobatteries can be partially or totally synchronized within a ball lightning cloud; such repeating synchronized collective short circuits of trillions of nanobatteries can generate powerful electromagnetic radiation, which could explain the repeatedly observed cases of red heat of incandescent bulbs’ filaments switched off from power sources; such a temporary red heat of the filaments repeatedly was distantly induced during the slow flying of ball lightning at distances of about one-two feet from the switched off bulbs [9].
When discussing the simplest possible processes of spontaneous formation of the short-circuited aerosol nanobatteries from combustible aerosol nanoparticles in a storm atmosphere, it was assumed in [20] that a high concentration of water vapour in the air can significantly modify the mechanism of oxidation of many metal aerosol nanoparticles, converting a normal process of direct oxidation of these nanoparticles by neutral oxidizing species into the predominantly electrochemical, that is, ion-mediated oxidation process in this highly humid atmosphere. During such an electrochemical oxidation, water vapour from humid air contributes to the formation of the hydrated, hydroxide or oxyhydroxide-based, thermolabile porous layers on the surface of metal nanoparticles rather than contributing to the formation of more thermostable layers of mixed anhydrous metal oxides [19], normally growing on the surface of nanoparticles either at very high, dehydrating temperatures or only in dry oxygen [21–26].
In humid air, a quick diffusion transfer of ions can take place through the hydroxide-based electrolyte layers growing on the surface of the nanoparticles due to their oxidation by water vapour. The quick processes of the diffusion of ionized oxidizing species, such as ions OH−, , , that easily migrate through the dynamic surface electrolyte layers of the mixed hydroxides towards the metal core of the nanoparticle, can considerably prevail above the much slower alternative processes of the inward diffusion of neutral oxidizing species, such as molecular O2, H2O, CO2, or neutral radicals like OH.
Similarly, the quick processes of the diffusion of ions of metal core, such as Fe2+, Fe3+, Fe(OH)+, or Fe(OH)2+, to the nanoparticle surface also can significantly prevail above much slower alternative processes of diffusion of neutral atoms from the metal core to the surface of the nanoparticle.
Thus, at relatively low temperatures, while electrolyte layers growing on the surface of metal nanoparticles remain thermostable, a process of the water vapour -induced electrochemical oxidation of combustible nanoparticles can become a most preferable process of their oxidation in humid air because of the possibility of the quick intra-particle transport of ions, and particularly because of the possibility of the quick transport of ionized oxidizing species through the hydrated surface electrolyte layers towards oxidable cores of the combustible nanoparticles.
It seems that in addition to high air humidity another extremely important complementary condition is necessary in order that the process of electrochemical oxidation of combustible aerosol nanoparticles can substantially prevail over the alternative process of their normal oxidation by neutral oxidizing species from ambient air. We suppose that such a complementary condition, radically changing the process of oxidation of combustible nanoparticles in humid air, can be a high electrostatic charge of these nanoparticles. Further it will be shown how and why a presence of electrostatic charges on combustible aerosol nanoparticles can make an important contribution to their preferential oxidation by water vapour molecules but not by much more numerous oxygen gas molecules in humid air that is, how and why electrostatic charges distributed on the surface of combustible aerosol nanoparticles can become powerful selective catalysts of water vapour-induced oxidation of these nanoparticles.
2. Electrostatic Hydration of Atmospheric Ions and Charged Aerosol Nanoparticles
As is well known, in normal, humid air, intense charge-dipole interaction between atmospheric ions and highly polar molecules of water vapour causes immediate hydration of the ions. A hydrated ion includes a central ion and a water shell normally consisting of several H2O molecules. The hydrated ions are extremely stable because of the huge electrostatic energy which keeps polar water molecules in immediate proximity to the central ion (the typical energies of complete dehydration of atmospheric ions can be ~several electron-volts). Therefore the hydrated ions are a standard form of gaseous ions in the lower troposphere [8, 18, 27]. The charge-dipole interaction between gaseous ions and surrounding polar gas molecules is a powerful and long-range attraction, and intense hydration of gas ions caused by the ion-dipole attraction finds useful applications, for example for an effective operation of the Wilson chamber where gaseous ions generated by ionizing radiation act as condensation nuclei in order to visualize tracks of ionizing particles. In this well known case, hydrated or alcohol-solvated gaseous ions quickly turn into water or alcohol based charged nanoparticles. These charged nanoparticles quickly grow into micrometre-sized droplets due to their further intense electrostatic hydration/solvation under supersaturation conditions.
Electrostatically charged aerosol nanoparticles, especially “small” nanoparticles with characteristic sizes of about several nanometres, almost do not differ from gaseous ions in their ability to attract surrounding polar gas molecules, including water vapour molecules, from ambient atmosphere due to the powerful long-range charge-dipole interaction. In humid air, a surplus electrostatic charge of such nanoparticles is almost always localized to trapping sites on the nanoparticles surface (in the form of either one or several adsorbed hydrated ions), that is, very close to surrounding polar gas molecules.
If the charged nanoparticles are conducting, surplus electrostatic charges can migrate around their surface in a random manner. In addition, both the conducting and nonconducting charged aerosol nanoparticles can freely and irregularly revolve on their axes due to continuous stochastic Brownian collisions with surrounding gas molecules. In this case, a time-average density of surplus electrostatic charge on the nanoparticle surface can be practically equivalent to the time-average charge density on the surface of the same charged nanoparticle whose surplus electrostatic charge is localized in its centre that is, the surplus electrostatic charge is quasidistributed on the surface of the nanoparticle.
One way or another, it is very likely that the surplus charges distributed on the surface of the hydrophobic or hydrophilic nanoparticles will make a major contribution to their local or total surface hydration in humid air due to the powerful charge-dipole attraction of surrounding polar molecules of water vapour, which is very similar to the hydration of atmospheric ions mentioned above.
In fact, in this case the charge-dipole attraction of water vapour molecules towards the charged surface of the nanoparticle plays the role of a powerful electrostatic water pump.
If the charged nanoparticle is cold enough, the electroadsorbed water molecules can strongly hold on to the cold charged surface of the nanoparticle.
If the charged nanoparticle is heated to a high enough temperature, the water vapour molecules previously electroadsorbed on the charged surface of this nanoparticle can be thermally desorbed when heating.
If the electroadsorbed water molecules are not consumed on the surface of the cold charged nanoparticle, for example due to some possible surface reactions, the surface of the charged nanoparticle will remain highly hydrated till the nanoparticle is cold enough.
If the charged nanoparticle consists of a substance that can be oxidized by water vapour at a given temperature, the water vapour-induced oxidative reactions will inevitably take place on the surface of such a charged nanoparticle.
In many cases, during water vapour-induced oxidation of combustible nanoparticles, for example metal nanoparticles, a complete cascade of the primary and secondary oxidative reactions accompanying the water vapour-induced nanoparticle oxidation can be highly exothermal, and so, because of the series of such highly exothermal oxidative reactions, a temperature of the charged “electrohydrated” nanoparticle will grow to some limiting value, while the electroadsorbed water vapour molecules will be subject to thermal desorption from the heated nanoparticle surface, despite the continuous functioning of the “electrostatic water pump”. The thermal desorption of the water molecules will reduce the rate of the water vapour-induced oxidative surface reactions, consequently the charged nanoparticle will quickly cool, and so the process of the electrostatic, charge-dipole adsorption of the water vapour molecules will recommence. Again, the rate of the exothermal oxidative reactions will grow, and it will again cause the growth of temperature of the charged nanoparticle and so on. This cyclical oxidative process will repeat until the combustible charged nanoparticle is completely oxidized. Probably a frequency of such a self-oscillating oxidative process might be very high, as possible rates of heating/cooling of the nanoparticles are extremely high.
Clearly, a balance between the competing processes of the electrostatic oxidative adsorption of water vapour molecules on the surface of the charged nanoparticle and thermal desorption of water molecules from this surface can be achieved either in a mode of a synchronous running of both these processes, or in the self-oscillating mode of a successive alternation of these processes, or in a combination of these two modes. It seems, however, that the self-oscillating mode of the successive alternation of the processes of the electrostatic oxidative adsorption of the water vapour molecules on the surface of the charged nanoparticle and their thermal desorption from this surface would be one of the most probable modes. The additional reasons for the high probability of such a self-oscillating mode of water vapour induced oxidation of combustible charged nanoparticles will be discussed in the next section.
3. The Mechanisms and Products of Water Vapour-Induced Oxidation of Combustible Nanoparticles Radically Differ from the Mechanisms and Products of Their Oxidation by Oxygen Gas
At least two main gas oxidants with substantial partial pressures are available in the air to oxidize combustible aerosol nanoparticles, irrespective of whether these nanoparticles are electrostatically charged, and consequently, they can actively electroadsorb polar molecules of water vapour from ambient air, or these nanoparticles are electrostatically neutral, and consequently, they will be much more indifferent to surrounding water vapour.
These two main atmospheric oxidants are the following: (a)oxygen gas, O2, with a mole fraction of oxygen molecules in the air at Sea level, , ~0.21 (i.e., ~0.21 mol of oxygen gas per one mol of air), (b)water vapour, H2O, with a mole fraction of water molecules, , ranging in the air at sea level between ~0.002 (at very low air temperatures, in particular, in Antarctica) to ~0.01-0.02 (at normal summer temperatures in temperate latitudes), to ~0.03 air humidity maximum (in the tropics or during summer thunderstorms in temperate latitudes).
In this paper, we will use the term “humid air” for normal air atmosphere, where a mole fraction of molecules of water vapour, , ranges from 0.01 to 0.03 mol of water vapour per one mol of air.
Thus, the term “humid air” will be in fact equivalent to the term “normal air”, as the humidity of such “humid air” is typical not only for most thunderstorms, but also practically for any summer weather.
In this paper, we also conditionally use the term “combustible nanoparticles”, which requires a more precise definition. This term is used by us to denote aerosol nanoparticles or substrate-integrated/substrate-precipitated nanostructures consisting of condensed materials, which are able to be oxidized by surrounding molecules of both oxygen gas, and water vapour, irrespective of the specific mechanism, rate and optimal temperature of such oxygen-gas or water vapour-induced oxidation.
And so the term “combustible nanoparticles” can be, in particular, applied to aerosol nanoparticles or substrate-integrated/substrate-precipitated nanostructures consisting of the overwhelming majority of metals, metalloids, sulfides, hydrides, carbides, phosphides, nitrides, silicides, borides, lower oxides, many organic compounds, particularly unsaturated organic compounds, many polymer and biopolymer structures. A lot of carbon-based nanoparticles, for example soot nanoparticles, fullerenes, or carbon nanotubes can also be considered as “combustible nanoparticles”, because they can be theoretically oxidized by both surrounding oxygen gas molecules and/or water vapour molecules. Thus, in this paper, a wide range of nanoparticles will be conditionally considered as “combustible nanoparticles” in the above aspect.
The mechanisms of oxidation of combustible aerosol nanoparticles by each of the two competing atmospheric oxidants are radically differing. As mentioned above, reactions of the dry oxygen oxidation of many combustible (e.g., metal or metalloid) aerosol nanoparticles can give reaction products in the form of solid or molten layers of mixed oxides, growing on the surface of the nanoparticles during the process of their oxidation. Alternatively, reactions of oxidation of the combustible aerosol nanoparticles by molecules of pure water vapour usually give simultaneously two types of different reaction products:(a)solid reaction products in the form of the more or less hydrated, more or less thermostable, more or less porous metal hydroxide shells on the surface of the nanoparticles, and in addition,(b)combustible gases, in particular, hydrogen gas, when oxidizing the nanoparticles of the great number of reactive metals or metalloids, for example, when oxidizing the nanoparticles of such different substances such as aluminium, iron, tungsten, molybdenum, zirconium, calcium, cadmium, and silicon
As an example, let us compare the reaction products synthesized when oxidizing the silicon based aerosol nanoparticles either in dry oxygen, or in pure water vapour, or in humid air.
Aerosol nanoparticles that consist of pure silicon can be oxidized in dry oxygen to generate nanolayers of the mixed silicon oxides growing on their surface where —the Avogadro constant (mol−1).
Consequently, in the case of this relatively high temperature humid air oxidation of the charged iron metal aerosol nanoparticle Let us again recall that (J) is the additional average kinetic energy acquired by the polar molecule of water vapour in the electrostatic field of minimally charged nanoparticle at a distance of the mean free path from the nanoparticle.
Thus, the fraction of the reactive oxygen gas molecules, that is, oxygen gas molecules possessing enough kinetic energy to climb the activation energy barrier of the oxygen gas-induced oxidative reactions on the surface of the discussed iron nanoparticle at a temperature of about 573 K, is Consequently, the competing fraction of the reactive water vapour molecules possessing enough kinetic energy to climb the activation energy barrier of the water vapour-induced oxidative reactions on the surface of the discussed minimally charged iron nanoparticle at a temperature of about 573 K is Thus, in this relatively high temperature case of oxidation of the charged iron metal particle:(a)the absolute quantity of the reactive non-polar molecules of oxygen gas, which is able to climb the activation energy barrier of the oxidative reactions on the surface of the discussed minimally charged nanoparticle at a temperature of about 573 K, and which are contained in one mole of humid air(b)the absolute quantity of the reactive polar molecules of water vapour, which is able to climb the activation energy barrier of the oxidative reactions on the surface of the discussed minimally charged nanoparticle at a temperature of about 573 K, and which are contained in one mole of humid air As one can see, the number of reactive water vapour molecules, which are able to oxidize the discussed minimally charged iron nanoparticle suspended in humid air at a temperature of ~573 K is times larger than the number of reactive oxygen gas molecules, which are able to oxidize the charged surface of this nanoparticle under such relatively high-temperature conditions of humid air oxidation when the mole fraction of water vapour molecules, , in humid air is ~0.02.
Indeed, an unexpectedly large (approximately one million times!) difference is found between the number of reactive water vapour molecules, which are able to oxidize the minimally charged iron nanoparticle in humid air and the number of alternative reactive molecules of oxygen gas, competitively participating in this humid air oxidation. This means that relatively few polar molecules of water vapour in humid air, being additionally electrostatically accelerated by their charge-dipole attraction towards the minimally charged iron nanoparticle, become practically the only air oxidant of the discussed minimally charged iron nanoparticle, and non-polar molecules of oxygen gas actually do not take part in humid air oxidation of this charged nanoparticle both at an oxidation temperature of ~300 K and especially at an oxidation temperature of ~573 K. Thus, probably, that one of the main oxidative reactions on the surface of the minimally charged iron nanoparticle will be a water vapour-induced exothermal reaction of oxidation of iron metal with formation of the hydrated, iron hydroxide Fe(OH)2 and/or iron oxy-hydroxide FeOOH-based porous electrolyte surface layers with synchronous evolution of hydrogen gas The solid reaction products, growing on the surface of the charged iron nanoparticle in the form of the hydrated electrolyte layers, will limit diffusion and direct oxidation of the nanoparticle by external neutral oxidizing species, but at the same time, these electrolyte layers will effectively transport:(a)ionized oxidizing species, such as OH− ions and ions into the iron core, (b)iron metal ions, such as Fe2+, or Fe3+, or Fe(OH)+, Fe(OH)2+, in the opposite direction, to the outer surface of the iron metal nanoparticle.
The solid reaction products in the form of the hydrated hydroxide or oxy-hydroxide surface electrolyte layers are quite thermostable, and reactions of their thermal decomposition proceed only at relatively high temperatures Therefore, electrochemical oxidation of the discussed minimally charged iron metal nanoparticle is the process that can effectively compete with the process of oxidation of this nanoparticle by neutral oxidizing species even at quite high temperatures.
At such temperatures, hydrogen gas evolved in exothermal reaction (44), can be auto-ignited directly on the surface of the discussed aerosol nanoparticle in humid air, because an autoignition temperature of the air-hydrogen gas mixtures is about 858 K (i.e., 585°C). Preferential electrochemical oxidation of the continuously electroydrated charged iron nanoparticles in humid air will convert these nanoparticles into the short—circuited iron/air core-shell nanobatteries, or more precisely into the short-circuited iron metal/iron oxy-hydroxide/water vapour nanobatteries, that is, into the short-circuited core-shell nanobatteries with the iron metal-based core reductant, with the iron hydroxide/iron oxy-hydroxide-based porous electrolyte shell, and with the external gas oxidant—that is, predominantly with water vapour (Figure 10).
Thus, the charged iron metal nanoparticle can be spontaneously transformed into the nanoscale battery with an internal reductant—iron metal core—an anode of the battery. During the process of humid air oxidation, the internal iron metal anode is periodically emitting electrons outwards, through the porous surface electrolyte layers, to the outer surface of the nanoparticle, that is, to a virtual cathode of this core-shell nano capsule-nanobattery.
The diffusion flux of the oxidizable iron-containing ions, that is, Fe2+, Fe3+, Fe(OH)+, or Fe(OH)2+, also moves from the iron metal core through the FeOOH/Fe(OH)2 containing surface electrolyte layers to the outer surface of the charged iron metal nanoparticle. These positively charged iron-containing ions are exposed to oxidation on and within the hydroxide-based nanoparticle shell where these ions meet and recombine with electrons that are periodically emitted from iron metal core (i.e., only when the electrochemically generated intra-particle electrostatic intensity reaches limiting values permitting field and/or thermionic electron emission from the iron metal core.
One of numerous possible oxidative reactions, which can take place directly on the hydrated iron hydroxide based surface of the charged iron metal nanoparticle-nanobattery, with the participation of the surrounding electrostatically accelerated water vapour molecules and the oxidizable iron-containing ions The counter diffusion flux of negative hydroxyl ions through the containing surface electrolyte layers transports new electrons to the nanoparticle iron metal core also contributing to an additional negative charging of the iron metal core.
The hydroxyl ions that combine with the iron metal core will oxidize the iron and leave additional electrons on this metal core of the nanoparticle. These diffusion processes, involving hydroxyl ions, will also provoke the subsequent field and/or thermionic electron emission intra-particle breakdowns.
In humid air, an iron metal nanoparticle, being even uncharged with a surplus charge, can still be electrostatically hydrated by surrounding water vapour molecules because of its initial oxygen-induced oxidative charging due to electron diffusion from the iron metal core to the growing semi-conductor FeO/Fe3O4 based-shell (Figure 11).
During electrochemical oxidation of the charged iron metal nanoparticle, quick-alternating electric dipole moments and huge potential differences can arise within the nanoparticle between the randomly arising local oxidative spots of positive charges on the outer surface of the nanoparticle and the corresponding uncompensated residual negative charges of the iron metal core.
Successive random “Brownian” collisions of the nanoparticle with surrounding gas molecules will not only continuously and irregularly change the coordinates of the aerosol nanoparticle but also, in a random manner, they will change the instantaneous values of the electric dipole moment of the nanoparticle because of the stochastic, “spotty”, nature of the nanoparticle oxidation.
The electrochemically generated fluctuating electric dipole moments, continuously arising within the nanoparticles-nanobatteries during oxidation, will cause a powerful electric dipole-dipole attraction between the separate aerosol nanoparticles-nanobatteries within a cloud of such nanobatteries. At the same time, the huge intra-particle core-shell voltage, electrochemically generated, will also cause repeating processes of the field and/or thermoionic electron emission breakdowns from the iron metal core to the outer surface of the nanoparticle during oxidation.
As these core-shell nanobatteries, spontaneously generated from the combustible iron metal aerosol nanoparticles during their oxidation, can be exposed to such continuously repeating relaxation processes (i.e., the intra-particle electron emission breakdowns), these periodically short-circuited aerosol nanoparticles-nanobatteries can be also described as pulsating aerosol current loops [20].
The strong alternating currents and corresponding magnetic moments generated within the periodically short-circuited aerosol nanobatteries can cause an additional powerful magnetic dipole-dipole attraction within a cloud of such nanobatteries.
Within a ball lightning cloud, despite the presence of unipolar charges on the surface of many aerosol nanoparticles-nanobatteries, both the electric and magnetic dipole-dipole attractions take place between the unipolar charged nanoparticles-nanobatteries. Both these alternating types of electromagnetic dipole-dipole attraction between charged aerosol nanobatteries contribute to significant dipole-dipole electromagnetic cohesion of the aerosol substance of such a cloud. (Certainly, the greater part of surplus electrostatic charges of the nanoparticles-nanobatteries within ball lightning will be probably localized on the peripheral aerosol nanoparticles due to mutual Coulomb repulsion between these unipolar charged nanoparticles and also due to a minimal air electroconductivity.)
Reaction (43) is only slightly exothermal, with a moderate heat-evolution ~150 kJ per one mol of the produced Fe(OH)2. However, a concomitant auto-ignition and combustion of the evolved hydrogen gas in ambient air could give considerable additional heat and water vapour The repetitive processes of heating the nanoparticles-nanobatteries, caused by the repetitive processes of heat-evolution from reactions (36) and (39), can periodically and probably with a high frequency dehydrate the FeOOH/Fe(OH)2-based surface electrolyte layers, which grow on these iron metal nanoparticles, and so this thermal nanoparticle dehydration will periodically inhibit the process of electrochemical oxidation of the charged iron metal nanoparticles with a temporary conversion of the iron hydroxide based surface electrolyte layers into the dehydrated, -based, semi-conducting surface layers of mixed iron oxides (Figure 12).
However, a fast electrostatic rehydration of the charged iron metal aerosol nanoparticle by surrounding polar molecules of water vapour in humid air will contribute to immediately cooling this combustible nanoparticle, and so the process of predominantly electrochemical, ion-mediated oxidation of the iron nanoparticle through its rehydrated FeOOH/Fe(OH)2 based electrolyte shell will be reactivated again. Probably, such self-oscillating processes of electrochemical oxidation of the charged combustible nanoparticles, continuously electrostatically re-hydrated by surrounding molecules of water vapour, could be quite high-frequency due to the extremely low heat capacity and the extremely high specific surface area of the aerosol nanoparticles.
These oxidative self-oscillating thermocycling processes can be partially (or totally) synchronized between all the charged aerosol nanoparticles-nanobatteries within ball lightning. Probably, such synchronization of the self-oscillating oxidative processes within ball lightning could also contribute to similar synchronization of the thermoionic electron emission processes of nanobatteries’ short circuits with corresponding generation of powerful coherent radio frequency radiation by such a ball lightning cloud.
Within a ball lightning cloud, possibly, there is another mechanism in order that to synchronize an alternation of the stages of electrostatic oxidative hydration of nanoparticles-nanobatteries with the stages of electron emission breakdowns within these nanobatteries. The collective electron emission breakdowns of the aerosol nanobatteries within ball lightning are probably able to generate a wideband radio frequency radiation. At the same time, radio frequency radiation with resonant wavelengths, which are correlated with the specific diameter of the specific lightning ball, could become most strong. If a ball lightning nanobattery cloud is predominantly resonant self-oscillating radio frequency generator with the inner oxidative energy source, such model of the self-sustaining nanoparticle-based resonant radio frequency aerosol generator can be considered as a similar and, at the same time, inverse model in relation to the theoretical and experimental mechanisms described in [5, 6, 34–38]. Within ball lightning, the collective short circuits of trillions of the charged nanobatteries could generate the self-coordinated resonant oscillations (namely, the very high frequency or ultra-high frequency or super-high frequency oscillations according to the typical ball lightning diameters). Such resonant electromagnetic oscillations probably could in turn synchronize the successive intra-cloud processes of the periodic total dehydration, total heating, and total thermoionic electron emission breakdowns within all or almost all the aerosol nanobatteries. A presence of such electromagnetic negative feedback within the cloud of the electrostatically charged and periodically short-circuited nanobatteries could help to understand a normal constancy of the ball lightning diameter during its life time if certainly indeed ball lightning is a self-oscillating resonant radio frequency generator.
So, oxidation of the charged iron nanoparticles in humid air is a predominantly water vapour induced process. Correspondingly, this oxidative process can proceed predominantly through electrochemical, that is, ion-mediated mechanism with formation of hydroxide or oxy-hydroxide or hydroxo-carbonate-based nanoporous electrolyte layers on the charged nanoparticle’s surface and evolving potentially inflammable hydrogen gas. Correspondingly, this humid air oxidative process can be accompanied by periodic auto-ignition of the evolved hydrogen gas and so this process can have a self-oscillating thermocycling character with significant temperature pulsations.
With reference to the problem of ball lightning, it would also be interesting to find out whether minimally charged aluminium aerosol nanoparticles can be exposed to a similar strong electrostatic attack by accelerated high-reactive surrounding polar molecules of water vapour in humid air.
10. Humid Air Oxidation of a Spherical (~2 nm in Diameter) Aluminium Metal Aerosol Nanoparticle Charged with the Minimum Positive Charge (C) at the Aluminium Melting-Point of about 933 K
Let us again suppose that in humid air the mole fraction of molecules of water vapour, , is ~0.02. Let us also suppose that at aluminium’s melting-point of ~933 K (i.e., ~660°C), an average value of both activation energies, (J/mol), for the competing processes of water vapour and oxygen gas induced oxidation of aluminium metal (i.e., an average value of the activation energy for the process of water vapour induced oxidation of an aluminium nanoparticle, (J/mol), and the activation energy for the process of oxygen gas induced oxidation of this nanoparticle (J/mol) can be of ~200,000 (J/mol) [39] Thus, at K: where —the Avogadro constant (mol−1).
Consequently, in the case of humid air oxidation of the minimally charged aluminium aerosol nanoparticle at aluminium’s melting point Let us again recall that (J) is the additional average kinetic energy acquired by the polar molecule of water vapour in the electrostatic field of a minimally charged nanoparticle at a distance of the mean free path from the nanoparticle.
Thus, the fraction of the reactive oxygen gas molecules, that is oxygen gas molecules possessing enough kinetic energy to climb the activation energy barrier of the oxygen gas induced oxidative reactions on the surface of the discussed aluminium nanoparticle at a temperature of about 933 K, is Consequently, the competing fraction of the reactive water vapour molecules possessing enough kinetic energy to climb the activation energy barrier of the water vapour induced oxidative reactions on the surface of the discussed minimally charged aluminium nanoparticle at a temperature of about 933 K is Thus, in this relatively high temperature case of oxidation of the minimally charged aluminium nanoparticle: (a)the absolute quantity of the reactive non-polar molecules of oxygen gas, which is able to climb the activation energy barrier of the oxidative reactions on the surface of the discussed minimally charged nanoparticle at a temperature of about 933 K, and which are contained in one mole of humid air(b)the absolute quantity of the reactive polar molecules of water vapour, which is able to climb the activation energy barrier of the oxidative reactions on the surface of the discussed minimally charged nanoparticle at a temperature of about 933 K, and which are contained in one mole of humid air As one can see, the number of reactive water vapour molecules, which are able to oxidize the discussed minimally charged molten aluminium nanoparticle suspended in humid air at a temperature of ~933 K is times larger than the number of reactive oxygen gas molecules, which are able to oxidize the charged surface of this nanoparticle under such relatively high-temperature conditions when the mole fraction of competing water vapour molecules, , in humid air is ~0.02.
In this case, also an unexpectedly large (approximately two thousand times) difference is found between the number of reactive water vapour molecules, which are able to oxidize the minimally charged aluminium nanoparticle in humid air and the number of reactive molecules of oxygen gas, competitively participating in this humid air oxidation. This means that relatively few polar molecules of water vapour in humid air, being additionally electrostatically accelerated by their charge-dipole attraction towards the minimally charged aluminium nanoparticle, become practically the only essential air oxidant for the discussed minimally charged aluminium nanoparticle, and non-polar molecules of oxygen gas actually do not take part in humid air oxidation of this charged nanoparticle even at a temperature of aluminium melting of ~933 K.
Thus, probably, that one of the main oxidative reactions on the surface of the minimally charged aluminium nanoparticle will be a water vapour-induced exothermal reaction of oxidation of aluminium metal with formation of the hydrated, aluminium hydroxide Al(OH)3 and/or aluminium oxy-hydroxide AlOOH based porous electrolyte surface layers with synchronous evolution of hydrogen gas In the case of such predominantly water vapour induced oxidation of the charged aluminium aerosol nanoparticles, the solid reaction products, growing on the surface of these nanoparticles mainly in the form of the thermolabile hydrated aluminium oxy-hydroxide-based electrolyte layers saturated with hydrogen, will limit diffusion and direct oxidation of these aluminium nanoparticles by external neutral oxidizing species, for example such as oxygen gas, but at the same time, these electrolyte shells will effectively transport ionized species, such as Al3+ or Al(OH)2+ or hydroxyl ions, contributing to the preferential electrochemical mechanism of oxidation of the charged aluminium nanoparticles.
One of numerous possible oxidative reactions, which could take place directly on the hydrated aluminium hydroxide based surface of the charged aluminium metal nanoparticle-nanobattery, with the participation of the surrounding electrostatically accelerated water vapour molecules and the oxidizable aluminium-containing ions: Thus, in humid air, minimally electrostatically charged aluminium metal-based aerosol nanoparticles might be oxidized by surrounding water vapour molecules rather than by non-polar oxygen gas molecules even at the aluminium melting point ~933 K. Such processes of intense electrostatic hydration and corresponding predominantly water vapour induced oxidation of the charged aerosol molten aluminium nanodroplets can automatically convert these nanoparticles into aluminium/air core-shell nanobatteries with the aluminium core anodes and the aluminium oxy-hydroxide based porous electrolyte shells, which play the role of air-depolarized cathodes of such aluminium/air nanobatteries.
As mentioned above, numerous electron emission breakdowns could probably occur within a cloud consisting of the electrostatically charged metal, metalloid, or carbon based nanobatteries, for example within aluminium metal based ball lightning, during preferential electrochemical oxidation/burning of such charged nanoparticles in humid air. Even only partially synchronized intra-particle electron breakdowns within ball lightning consisting of trillions of aerosol nanobatteries could generate a powerful radiofrequency radiation, including microwave radiation.
It seems that a possible generation of radio frequency radiation over the range of ~0.1 gigahertz up to ~20 gigahertz from burning aerosol clouds consisting of charged combustible particles could be found in corresponding aerosol combustion experiments. Probably, a condensed disperse phase of such radio frequency emitting slowly burning aerosol clouds could consist of bipolar or unipolar charged nano or submicron combustible particles, e.g., such as aluminium-, or iron-, or magnesium-, or zirconium-based nanoparticles, or also carbon- or silicon-based combustible nanoparticles co-aggregated with additional electrolyte nanoparticles. In standard humid air, predominantly electrochemical burning of such electrostatically charged nanoparticles could be accompanied with intense thermoemission and ultra-violet induced photoemission charging processes, sustaining spontaneous electrostatic charging of these burning nanoparticles.
In particular, the formation of electrochemically burning aerosol clouds, capable of generating powerful radio frequency radiation, could be spontaneously realized in various hypervelocity flight processes, for example in a troposphere movement of iron-nickel-based meteors or in a flight of hypervelocity rockets. During the troposphere movement of hypervelocity objects, aerosol clouds consisting of the short-circuited nanobatteries can be produced either by high-temperature ablation of heat-insulating materials or by incomplete combustion of carbon based fuels. The presence of combustion-generated water vapour, highly charged soot nanoparticles and additional electrolyte impurities in plasma-condensation trails of hypervelocity rockets can probably contribute to activation of a charge-catalyzed water vapour induced electrochemical oxidation of these soot nanoparticles-nanobatteries with a resultant generation of powerful radiointerference.
11. Some Final Remarks
Clearly, the discussed effect of the charge-catalyzed water vapour-induced oxidation of unipolar and/or bipolar, electrostatically or electrodynamically charged aerosol nanoparticles/substrate-integrated nanostructures can take place in the processes of humid air oxidation of various combustible nanoobjects, not only metal or metalloid ones, as the large additional kinetic energy, acquired by surrounding polar molecules of water vapour in the electrostatic field of the charged nanoparticles at a distance of their mean free path from the nanoparticles, is independent of the materials constituting these nanoobjects. A change in polarity of the surplus charge of the combustible nanoparticles is also not able to change the value of the additional kinetic energy acquired by surrounding polar gas molecules in the electrostatic field in immediate proximity to the charged nanoparticles.
Correspondingly, combustible particles charged with equal, either negative or positive, electrostatic charges can be equally intensively attacked by surrounding water vapour molecules accelerated in the electrostatic field of these nanoparticles, absolutely irrespective of the polarity of the nanoparticle’s surplus charges.
In many cases, in humid air, such an intense charge-catalyzed water vapour induced oxidation of the charged metal or metalloid nanoparticles can mainly proceed through the electrochemical mechanism just due to the preferential growth of the hydrated hydroxide based dynamic electrolyte surface layers, resaturated with hydrogen gas. These thermally unstable, continuously renewed and again decomposed, passivating surface electrolyte layers can significantly inhibit further oxidation of combustible nanoparticles by gas phase neutral oxidizing species. At the same time, these surface electrolyte layers will stimulate the relatively low-temperature process of the intra-particle ion diffusion and ion-mediated oxidation of the combustible nanoparticles. A time-average temperature of such electrochemical oxidation of the combustible nanoparticles can be relatively low, probably ranging from ~300 to 900°C, particularly taking into account the above-described scenario of the self-oscillating electrochemical oxidation with the alternating thermocycling processes of oxidative electrostatic hydration and thermal flame dehydration of the combustible particles.
According to [20], when an average diameter of the soot-based aerosol nanoparticles-nanobatteries constituting a soot-based ball lightning cloud is ~100 nm and when a total mass of this condensed phase of the ball lightning cloud is ~4 grammes, then the average number of such carbon/air nanoparticles-nanobatteries can be of ~1015 in this ~20 cm diameter ball lightning cloud. If a net electrostatic charge of such “average” ball lightning ranges at least from ~0.1 to 1 microcoulomb, that is, from to elementary charges, then large aerosol nanoaggregates consisting of ~200–2.000 such nanoparticles can be charged only with a single surplus mobile ion per one large nanoaggregate (or also with a single surplus mobile ion per one submicron- or micrometre-sized large compact combustible aerosol particle).
In any case, it is evident that combustible aerosol particles constituting ball lightning can only have ~one surplus ion per one aerosol particle on average. Correspondingly, within ball lightning, the charge-catalyzed water vapour induced oxidation of combustible particles will practically always proceed through the step-by-step successive mechanisms, which are illustrated in the Figures (2–5). Equally, it is clear that a high hydrophility of the oxidized surface of these combustible nanoparticles (the high hydrophility is a typical property of the overwhelming majority of metal oxides, metal oxy-hydroxides, and metal hydroxides) could enable a fast redistribution of locally electroadsorbed water vapour molecules over all the reacting surface of such large, submicron- or micrometre-sized, either aggregated or compact, combustible aerosol particles.
Probably, a lot of the combustible aerosol particles constituting the ball lightning cloud are in fact uncharged. At the same time, within ball lightning these particles are strongly polarized, so these oxidizable particles can still be exposed to an intense local charge-catalyzed water vapour induced oxidation.
For the sake of brevity, a lot of important additional aspects cannot be considered in this paper. Although discussion of certain additional aspects, such as a temperature-dependent core-shell jumping of mobile surplus charges inside the nanoparticles, the effect of the polarity, mobility and intra-particle location of the surplus ions on the rate of electrochemical oxidation of the combustible nanoparticles, the charge-dependent activated “anodic” oxidation of negatively multiply charged combustible nanoparticles or, on the contrary, the charge-dependent inhibited oxidation of positively multiply charged combustible nanoparticles (“cathodic protection”)—the effects, which are somewhat similar to those described in [40, 41], could be also useful, all these important aspects fall outside the limits of this paper. At the same time, various possible versions of electrochemical redistribution of charges inside some metal aerosol nanoparticles, that could spontaneously form the short-circuited metal/air aerosol nanobatteries, minimally charged and hence actively electrostatically hydrated in humid air, are shown in the Figures 13, 14, 15, 16, 17 and 18.
The additional kinetic energy of the electrostatic acceleration acquired by polar gas molecules near to a charged nanoparticle is independent not only of the specific material components of the charged nanoparticle and the polarity of the nanoparticle’s surplus charge, but also of the presence and type of chemical reactions on the surface of the nanoparticle.
This means that the substantial additional kinetic energy of (J), which can be acquired by various electrostatically accelerated polar gas molecules in immediate proximity to charged aerosol nanoparticles (or charged surface-integrated nanostructures), could contribute to powerful catalysis of various heterophase reactions, not only oxidative ones, on the charged surface of such particles or surface-integrated structures which are in contact with any potential polar gas phase reactants.
In such cases, electrostatic charges (solvated ions or electrons), either adsorbed by these nanoparticles/nanostructures or induced on their surface by external fields, could probably act as local catalysts of various heterophase reactions.
Of course, the successive process of the charge-catalyzed predominantly water vapour induced electrochemical oxidation can take place in a humid atmosphere not only in relation to highly charged nano- or micrometer-sized combustible aerosol particles or substrate-integrated structures, but also in relation to certain highly charged macroscopic objects, for example, such as the corona-forming highly porous rusty iron/carbon-based electrodes, where a secondary electrospraying effect, which we earlier named “field-assisted metal dusting corrosion”, could be caused by a local charge-catalyzed water vapour-induced oxidation of both carbon and iron metal components of corona-forming corrodible electrodes, with an additional local generation of water gas. In this case, the charge-dipole attraction between the charged porous surface of the steel or cast iron based high-voltage electrodes and the surrounding molecules of water vapour could play the role of an electrostatic water pump to transport and accelerate the water vapour polar molecules, but not the oxygen gas molecules, towards the charged oxidizable surface of the high-voltage electrodes.
Normally, uncharged pure carbon based nanomaterials, for example soot nanoparticles are quite inert in humid air. However, in view of the aforesaid it seems that highly charged carbon based nanoparticles can be much more reactive. One of the possible direct reactions of the surrounding electrostatically accelerated molecules of water vapour with the charged carbon based aerosol nanoparticle can be the so-called water gas endothermic reaction Though this reaction is able to generate a combination of the two high-calorific fuel gases, this first stage of process of the water vapour induced oxidation of the carbon-based nanoparticle absorbs a lot of heat.
Alternative reactions of the charged carbon nanoparticle with the non-polar and, accordingly, electrostatically non-accelerated molecules of ambient oxygen gas are exothermal reactions: with carbon monoxide as the predominant product at a temperature above 800°C, and with carbon dioxide as the predominant product at a temperature ~600–700°C.
Intense electrostatic hydration of the oxygen gas preoxidized carbon based nanoparticles by the surrounding polar molecules of water vapour will contribute both to a temporary cooling of these red hot nanoparticles and to a pulse evolution of the secondary inflammable gases, that is, hydrogen gas and carbon monoxide gas. In ambient humid air, the heat released from subsequent auto-ignition of these high-calorific fuel gases is again able to dehydrate and make the charged carbon based nanoparticles red-hot. This flame dehydration is able to restart the relatively high-temperature process of oxygen gas-induced oxidation of these electrostatically charged carbon-based nanoparticles. The high heat emission of these nanoparticles and their relatively low reactivity in normal humid air will again contribute to the fast cooling of these nanoparticles with restarting of their electrostatic hydration and their relatively low-temperature water vapour-induced oxidation. Thus, such a prolonged self-oscillating thermocycling process of the fast alternation of oxygen gas and water vapour-induced oxidation of the charged soot nanoparticles can probably take place in humid air.
Probably, pure water-based dynamic shells, consisting only of the water vapour molecules, electrostatically attacking the surface of the charged soot nanoparticles, are not able to directly convert these charged carbon nanoparticles into short-circuited carbon/air nanobatteries. The electroadsorbed dynamic layers of the pure superheated water are still a weak surface electrolyte to efficiently transport the ionized oxidizing species into the oxidizable surface of the carbon core.
It is possible that additional strong electrolyte surface impurities, such as sodium hydroxide/sodium carbonate or potassium hydroxide/potassium carbonate or calcium hydroxide/calcium carbonate or barium hydroxide/barium carbonate aerosol impurities, cocondensed and/or co-aggregated along with soot nanoparticles, could contribute to a conversion of such molten salt electrolyte aggregated charged soot nanoparticles into the short-circuited carbon/air aerosol nanobatteries in humid air.
The intense electrostatic acceleration and corresponding substantial activation of polar gas molecules, for example, such as molecules of hydrogen peroxide, nitric acid, nitrogen monoxide, carbon monoxide, ozone, sulphuric acid, ammonia, hydrogen sulphide, hydrochloric acid, as well as many organic polar molecules, which take place in immediate proximity to naturally or artificially electrostatically charged oxidizable nanoobjects, can perhaps be successfully used in many nanotechnological applications, for example in those such as heterophase catalysis, heterophase copolymerization with the participation of polar monomers (e.g., methyl methacrylate, styrene, etc.) on the surface of highly charged nanoscale catalysts of polymerization, in exhaust systems with the purpose of a secondary combustion of soot nanoparticles artificially highly precharged, either with the help of a high-frequency corona discharge, or by bipolar direct current corona discharge, either by contact, or microwave or plasma charging. Such electrostatic or electrodynamic catalysis of the oxidation/combustion processes with an intense high-frequency bipolar charging of solid or liquid fuel particles in engines or power generating plants could also be of practical interest.
Generally speaking, similar intense charge-dipole attacks of electrostatically extra accelerated polar gas molecules, directed against adjacent highly charged nanoobjects, can probably be a widespread phenomenon in nature. In particular, such electrostatic oxidative attacks of the polar gas molecules (e.g., blood nano-bubble contained polar gas molecules of hydrogen peroxide vapour, water vapour, hydrogen sulphide, hydrochloric acid, nitrogen monoxide, carbon monoxide etc.), directed against naturally or artificially, electrostatically or electrodynamically charged nano-bio-objects, for example, such as lipoproteins open to injury by oxidation or DNA’s open to injury by mutations (that can be generated due to possible high-energy collisions DNA’s based biopolymers with the surrounding charge-dipole extra accelerated epithermal polar gas molecules), can probably play the important role in both natural biological processes and potential biomedical uses.
So, we assume that a ball lightning substance consists of short-circuited aerosol nanobatteries. Also, we assume that electrostatic oxidative hydration of highly charged combustible aerosol nanoparticles can substantially change the rate and mechanism their atmospheric oxidation in humid air, converting such nanoparticles into reductant/air aerosol nanobatteries, periodically short-circuited by internal electron emission breakdowns. At the same time, we would like to emphasize that such reductant/air nanobatteries, that can be spontaneously generated from highly charged combustible nanoparticles in humid air, could be an electrogenerating solid fuel aerosol component for only one type of ball lightning, that is, for the electrochemical nanobatteries based ball lightning that use mainly external gas oxidants, water wapour and oxygen.
To avoid misunderstanding and/or excessive generalizations concerning a possible key role of atmospheric water vapour in a life of any types of the nanobattery based lightning balls, we would also like to emphasize that certain hypothetic sorts of the short-circuited aerosol nanobatteries can contain their own, solid or liquid phase, compact oxidant nanocomponents. Such completely self-contained electrochemical aerosol nanobatteries can exceptionally use the internal condensed fuel and oxidant nanocomponents, either aggregated or core/shell structured [20]. Thus, an influence of external atmospheric gas oxidants on the internal redox and discharge processes in such completely self-contained aerosol nanobatteries could be negligible.
Moreover, it is clear that not only electrochemical processes inside composite nanoparticles can contribute to their spontaneous transformation into short-circuited nanobatteries, constituting an electrogenerating aerosol substance of ball lightning. For example, it would be reasonable to assume that highly exothermic self-propagating processes of flameless combustion, that is, self-propagating high-temperature synthesis or SHS, could frequently arise inside either composite aerosol micro- or nanoaggregates or inside composite aerosol micro- or nanodroplets, containing at least two adjacent condensed heterogeneous reactants. Probably, such highly exothermic SHS processes could proceed in a self-oscillating mode inside composite aerosol particles, contributing to a partial or total melting of constituting them micro- or nanoreactants, also contributing to intra-particle formation of new phases in the form of intermetallic/ceramic reaction products, and also contributing to an intense interphase charge separation. Such interphase charge separation inside the composite aerosol particles—microscopic aerosol SHS reactors—could be caused by several reasons, for example, both thermoelectric and thermionic interphase processes due to extremely high temperature gradients and extremely high rates of heating (~103 to 106 K/sec), that generally take place in a SHS combustion wave. The intra-particle processes of the self-propagating high-temperature synthesis can probably generate a very intense, thermoelectrically and thermionically caused, interphase charge separation inside the composite aerosol/aerogel nanoaggregates or nanodroplets, which will automatically convert such composite nanoparticles into thermoelectric nanobatteries or thermionic nanoconverters. Such thermoelectric nanobatteries and thermionic nanoconverters, being formed from the intra-particle SHS-reacting condensed aerosol nanoreactants, and being periodically short-circuited by intra-particle/surface electron emission breakdowns, could, in principle, be another type of an electrogenerating solid fuel aerosol substance for a nanobattery based ball lightning. In this case, inside such “thermoelectric” or “thermionic” nanobattery based ball lightning, an influence of external gas oxidants on the intra-particle SHS and electric processes could also be substantially minimized due to passivating oxide shells growing on outer surface of such high-temperature thermoelectric or thermionic nanobatteries.
It is clear, when highly exothermic SHS processes take place inside the heterogeneous composite aggregated aerosol particles/droplets, a formation of the passivating dense oxidelayers on the outer surface of these aerosol composite particles can contribute to a vital protection of such internally burning hot particles from their external oxidation by atmospheric gas oxidants.
Probably, a lot of different pyrotechnic aerosol nanocomposites, spontaneously formed from combustible aerosol nanoparticles in a local reducing or inert atmosphere, could be transformed into the short-circuited high-temperature thermoelectric/thermionic aerosol nanobatteries through the intra-particle highly exothermic SHS processes. In particular, bimetallic composite particles consisting, for example, of aluminium metal and nickel metal could form self-contained micro- or nanoaggregates/nanodroplets, externally covered with a dense alumina shell. In such Ni/Al nanocomposites, highly exothermic intra-particle SHS reactions between metallic aluminium and nickel will synthesize new numerous intermetallic phases of nickel aluminides. The intra-particle high-temperature processes of flameless synthesis of nickel aluminides can be correspondingly accompanied with synchronous formation of numerous interphase nanothermocouples, such as the nickel/aluminium, or nickel/nickel aluminide, or aluminium/nickel aluminide nanothermocouples and so forth.
Similarly, composite aerosol particles, consisting, for example, of titanium metal and soot carbon nanoparticles-nanoreactants, or titanium metal and silicon nanoparticles-nanoreactants, could form micro- or nanoaggregates/droplets, externally covered with either a porous soot carbon shell or with a dense silica shell, inside which highly exothermic intra-particle liquid/solid SHS reactions between titanium and carbon, or between titanium and silicon, will synthesize titanium carbides reaction products, such as TiC (with enthalpy of formation ~186 kJ/mol), or titanium silicides, such as TiSi (with enthalpy of formation ~73 kJ/mol).
Similarly, numerous nanothermocouples, such as titanium/silicon or titanium/titanium carbide, or titanium/ titanium silicide nanothermocouples and so forth, could be formed, and then be periodically short-circuited by the electron emission breakdowns, inside the intra particle combustion waves.
A lot of aerosol nanoreactants, such as nanoparticles of aluminium, titanium, silicon, tantalum, zirconium, calcium, boron, carbon, platinum, palladium, molybdenum, tungsten, zinc, sulfur, selenium and so forth, are able to mutual highly exothermic SHS reactions, accompanied with formation of intermetallic and/or ceramic nanocompositions. Being formed from the arc-, or microwave-, or laser-produced high-temperature condensation aerosol nanoreagents in a local reducing or inert atmosphere, carbides of tantalum, or zirconium, or vanadium, or titanium, or niobium; silicides of platinum, or palladium, or molybdenum, or tungsten, or zirconium; aluminides of nickel, or cobalt, or calcium, or platinum, or palladium, or iron; borides of tantalum, or zirconium, or vanadium, or titanium, or niobium, or molybdenum; sulphides of magnesium, or zinc, or molybdenum, or tungsten; all these flameless combustion products could be primary products of the particularly highly exothermic intra particle SHS reactions.
Consequently, a lot of the bi-component or multi-component composite aerosol particles, consisting of widespread mutually reacting condensed substances, could be excellent candidates to spontaneously form the short-circuited thermoelectric/thermionic aerosol nanobatteries in the highly exothermic intra-particle SHS processes. In nature, a lightning induced, total or subtotal high-temperature gas phase reduction of ordinary aluminosilicate/clay minerals by carbon or hydrogen, that can be generated by a synchronous pyrolysis of adjacent organic substances, could form unipolar charged, bi- or polymetal composite aerosol nanoparticles, that is, burning hot nanoaggregates or nanodroplets that contain the reacting condensed SHS nanocomponets. Such aluminosilicate-derived, hot aerosol composite nanoparticles can consist, for example, of the mutually highly reactive Al-Ca-Si-Fe-Ti metals, partially mixed with metal oxide nanocomponents and partially protected from atmospheric gas phase oxidation by outer mixed metal oxide shells. Inside such clay-derived polymetal nanocomposites, numerous thermoelectric and thermionic nanobatteries can probably be formed from the high-temperature interphase contacts, due to huge local temperature gradients, that continuously arise in intra-particle self-propagating combustion waves.
Probably, even in many other aspects relatively well studied thermite based nanocomposites, particularly, so-called aerosol nanothermites, consisting, for example, of the Al/Fe3O4 or Al/CuO nanomixtures with some over-stoichiometric excess of aluminium metal, also could spontaneously form burning ball lightning like clouds, containing the short-circuited thermoelectric and/or thermionic aerosol nanobatteries, that can be based on the spontaneously formed Al/Fe-, or Al/FeO-, Al/Fe3O4-, or Al/Cu-, or Al/Cu2O-nanocontacts/nanothermocouples, and that can be periodically shortcircuited by internal electron emission breakdowns. During the highly exothermic SHS reactions, self-propagating intra-particle waves of thermionic electron emission short-circuits, arising on the developed surface of the thermoelectric/thermionic aerosol nanobatteries, can probably be closely coupled with the intra-particle self-propagating combustion waves.
Inside a cloud that consist of trillions of such flameless burning composite nanoparticles-SHS nanoreactors-periodic intra-particle electron emission breakdowns could generate powerful total microwave radiation, contributing to interparticle electromagnetic dipole-dipole attraction that will compress this luminous ball lightning cloud.
Thus, as one can see, the preliminary described effect of the preferential water vapour induced oxidation of the highly charged combustible aerosol nanoparticles in humid air can be only one of many important, interesting, and mutually complementary phenomena, which careful study could help us to understand the mysterious nature of ball lightning.