Heating device, use thereof, ohmic resistance coating, method for depositing the coating using cold spraying, and particle mixture for use therein

Abstract

A heating device (60) and its use. The heating device (60) comprises an ohmic resistance coating (30) and is made from a mixture of particles (18; 20) using a "cold spray" method. The ohmic resistance coating has a layer (32) with a thickness between 2 and 300 microns and comprises one or more ductile or malleable metals (18); and particles (20) comprising one or more of the following: resistive metal oxides, carbides, silicides, disilicides, nitrides, borides or sulfides. The one or more ductile or malleable metals (18) bond the particles (20) to the surface (42) of a substrate (40).

Description

Technical Field

[0001] The present invention relates to a heating device and its use. It also relates to an ohmic resistance coating, a method of depositing the coating on a substrate using "cold spraying" and a particle mixture for use therein.

[0002] The heating device includes a heating element that includes an ohmic resistive coating. The heating device and coating are produced using a low-cost manufacturing method known in the art as "cold spray" or "solid-state" deposition. The method deposits a particle mixture that includes: (i) a ductile or malleable metal that deforms upon impact with a substrate, thereby adhering to the surface, and (ii) particles comprising one or more resistive metal oxides, carbides, silicides, disilicides, nitrides, borides, or sulfides that combine to produce an ohmic resistive coating on the substrate. A typical ratio of ductile or malleable metal to resistive particles is 2:1 to 1:2.

[0003] Technicians will be able to distinguish coatings produced by cold spray from those produced by "melting" particles. Figures 4A to 4C and Figure 5 The comparison was made because, under a microscope, the “cold spray” coatings are less heterogeneous than coatings produced by a process that melts the particles.

[0004] The heating element can then be powered with an AC or DC power source to ohmically heat the coating. Background Art

[0005] Various techniques are known for producing surface coated heating elements using deposition techniques that heat one or more metals and / or oxides, carbides, silicides, disilicides, nitrides, borides and sulfides to sufficiently high temperatures, typically above 3000° C., to enable the deposition process to proceed via a semi-molten phase. Due to the high operating temperatures, such processes impose restrictions on the substrate and have cost issues, making the production of articles for many applications extremely expensive.

[0006] These semi-molten phase applications use powder or wire feedstocks and include, in particular, flame spraying, high velocity oxygen-fuel technology (HVOF), and plasma spraying devices using a range of oxygen-fuel combustion gases, each operating at progressively higher operating temperatures and / or kinetic energy inputs. These technologies are commercially mature, but there are limitations in their application, particularly because, as high temperature applications, the uncontrolled release of inherent stresses in the substrate from the manufacturing process can be problematic. This can lead to instabilities and distortions, particularly when larger surface lengths and / or areas (i.e., on the order of one square meter or more) are of concern, particularly in the case of thin substrates. Established custom and practice is to cool such sensitive substrates during high temperature spraying using water-cooled platens, dry ice baths, and the like in order to cool the article being sprayed. These measures are not always feasible or increase the complexity of the deposition process. As a result, productivity and production costs are adversely affected, while the risk of producing inferior articles increases.

[0007] In PCT / GB2005 / 003949, PCT / GB2007 / 004999 and PCT / GB2009 / 050643 the applicant described the production of electrical heating elements using flame spraying techniques. Although intended for the manufacture of a variety of items such as domestic white goods, commercial cookers and large scientific applications using ultra-high vacuum facilities, the applicant identified a huge new market opportunity, for example, based on the application of ultra-thin surface coating heating elements to particularly high grade building panels, comprising a mild steel core having a thin ceramic coating on one or both surfaces, this coating having a high dielectric resistance strength even when heated to high temperatures (e.g. 400°C) under moderate electrical loads.

[0008] It is currently understood that brittle or hard metal compounds or salts (e.g., one or more metal oxides and / or carbides, silicides, disilicides, nitrides, borides and sulfides) cannot be deposited on a substrate by any means other than semi-molten phase application because the compounds or salts (being abrasive) would otherwise damage the surface on which they are deposited. In fact, it is accepted industry practice when applying using cold spray to include a low percentage of brittle metal oxides to prepare and clean the surface being treated so as to better "lock in" the subsequently applied ductile metal particles. Applicants have overcome this problem by co-depositing them with a ductile or ductile metal at a temperature below the melting point of the ductile or ductile metal, and using sufficient ductile or ductile metal (typically at least 30% by weight, more specifically at least 40% by weight) to bond the one or more metal oxides and / or carbides, silicides, disilicides, nitrides, borides and sulfides to the surface of the substrate.

[0009] The general prior art falls into one of two groups:

[0010] High temperature, thermal spray technology (not cold spray) and products, including:

[0011] WO2016 / 084019, which discloses a resistive heater comprising at least one thermally sprayed resistive heating layer, the resistive heating layer comprising an electrically conductive first metal component, an electrically insulating derivative of the first metal component and a third component, the third component stabilizing the resistivity of the heating layer;

[0012] US3922386, which discloses a heating element produced by thermal spraying of molten aluminum globules in an oxidizing atmosphere;

[0013] GB2344042, which discloses a method of making a resistive heating element by heating previously oxidized particles to render them semi-molten and depositing them on a substrate; and

[0014] US2008 / 0075876 discloses a method of forming an electric heating element using flame spraying.

[0015] In contrast to the above, the following references deal with "cold spray" technology and products:

[0016] WO2014 / 184146 teaches cold spraying of metals, either alone or in alloys. The teaching is specific to producing a ferromagnetic heating effect to "nudge" the temperature above the solidification point, which is then switched off due to the inherent Curie point temperature provided by the design of the metal alloy combination. They cite a series of ferromagnetic metal alloys, particularly Cu-Ni and Fe-Ni, with or without Cr, Al, Mn.

[0017] WO 2005 / 079209 discloses the production of nanocrystalline layers. It teaches the use of metals and alloys and their reinforcement with ceramics to produce sintered compacts.

[0018] US2018 / 0138494 relates to depositing cathode or anode materials using a cold spray process.

[0019] CN107841744 discloses a method for producing nanoparticle ceramic-doped metal matrix composites using cold spraying, the composites being fully pre-ground and vacuum dried. After the cold spray application, the surface is subjected to high-speed friction treatment. It does not teach the production of ohmic resistance coatings or heating devices.

[0020] None of the cold spray-related disclosures teach forming a heating element by co-depositing particles of a resistive metal compound or salt (eg, a metal oxide) with a ductile or malleable metal.

[0021] Applicants have unexpectedly determined that brittle or hard metal compounds or salts, including those typical commercial powder particles used in current thermal spray applications, can be deposited at temperatures considered low in the context of spray deposition (i.e., temperatures below their melting points) by depositing the brittle or hard metal compounds or salts together with one or more ductile or malleable metals, at a temperature at which they remain solid, with controlled momentum, such that the ductile or malleable metals deform upon contact with a surface and the brittle or hard metal compounds or salts become embedded in the ductile or malleable metal without causing the co-deposited ductile metal or the surface on which application is made to be removed by blasting. The resulting coating adheres to the substrate.

[0022] In this regard, it is particularly advantageous to use zinc, which has a melting point of approximately 419.5° C., as the ductile or malleable metal, although higher melting point ductile or malleable metals such as copper, aluminum and manganese may also be used.

[0023] The appearance of cold spray deposited coatings is different from coatings deposited in a semi-molten state. A person skilled in the art will be able to distinguish cold spray deposited coatings from coatings produced in a semi-molten state because of their less heterogeneous appearance under a microscope and less porosity.

[0024] By applying these metal compounds or salts together with ductile or malleable metals to a substrate surface, Applicants are able to produce heating devices that can be used in a variety of applications, including for space heating purposes in, for example, domestic, commercial and industrial settings.

[0025] An ideal substrate for such applications is a building panel comprising a steel core and a thin ceramic coating, such as those available from Polyvision BV. Preferred panels include those coatings sold as Polyvision Flex 1 or Flex 2 panels.

[0026] Preferred coatings include those resulting from a mixture of nickel oxide and zinc, however many other combinations have been successfully demonstrated.

[0027] Other heating applications include automotive applications, particularly in the field of electric and hybrid powertrains for low power cabin heating appliances, aerospace applications for anti-icing and / or de-icing purposes, and construction industry applications where the coating is applied to cementitious and other building materials. SUMMARY OF THE INVENTION

[0029] According to a first aspect of the invention, there is provided a heating device comprising a substrate, the surface of the substrate having a heating element, the heating element comprising an ohmic resistance coating deposited on the substrate surface by cold spraying, the ohmic resistance coating having a layer thickness between 2 and 300 micrometers and comprising:

[0030] i) one or more ductile or malleable metals selected from the group consisting of copper, gold, lead, aluminum, platinum, nickel, zinc, magnesium, iron, manganese, chromium, titanium, vanadium, niobium, indium, terbium, strontium, cerium, and lutetium; and

[0031] ii) particles comprising one or more resistive metal oxides, carbides, silicides, disilicides, nitrides, borides or sulfides,

[0032] wherein the one or more ductile or malleable metals bind the particles to the surface of the substrate,

[0033] and at least one pair of electrical contacts disposed thereon,

[0034] In operation, the heating element is connected to an AC or DC power source.

[0035] Preferably, the heating device comprises a plurality of heating elements, each heating element sharing a common feed terminal and having an independent return terminal.

[0036] The heating elements can be connected to an AC or DC power source by mechanical means, welding, laser brazing and laser welding, additive manufacturing solid state deposition of ductile metals, or by using conductive adhesives or inks. Connections can be made at their respective ends or at midpoints along their length.

[0037] In one mode of operation, the power supply is mains operated.

[0038] In a preferred mode of operation, the power supply is a low voltage power supply operating in the range of 1 to 110 volts, more preferably still below 30 volts.

[0039] Preferably, the substrate surface comprises a dielectric barrier material.

[0040] In a particularly advantageous embodiment, the dielectric barrier material comprises a ceramic.

[0041] Preferably, the substrate comprises a sheet, most preferably a building panel.

[0042] The sheets may comprise a steel core and a ceramic surface.

[0043] Alternatively, the sheet material may comprise ceramic, glass or mirrored glass.

[0044] The size of the sheet can vary and includes 150cm 2 Up to 20000cm 2 The heating surface area between.

[0045] Preferably, the heating element is a self-regulating resistive heating element.

[0046] The coating may also be "protected" by covering it with a protective layer. The protective layer may be in the form of, for example, a film, sheet, coating or applied screed which may prevent wear or penetration of, for example, water or substances that corrode the heating element and provide a degree of protection from accidental contact with such hot surfaces or from accidental contact with live components that could cause electric shock.

[0047] Furthermore, the protective / additional layer may be used to make cleaning easier, as it is a low-effort wipeable surface and / or a thermal management coating.

[0048] In a particularly advantageous embodiment, there is provided a vehicle comprising a heating element according to the first aspect of the invention.

[0049] In another particularly advantageous embodiment, there is provided a building comprising a heating element according to the first aspect of the invention.

[0050] The heating device can be used to generate localized heat or provide protection from the cold.

[0051] By way of illustration only, examples include:

[0052] Horizontal and vertical building structures, including all forms of housing, including social housing, commercial buildings (including offices, shops and retail centres), sports complexes and industrial sites (including logistics centres, workshops, etc.);

[0053] Bridges, tunnels, covered walkways, bus and train stations, shelters, and designated outside smoking areas;

[0054] Aircraft exterior panels or interior panels that are easily exposed to low temperatures;

[0055] Railway tracks, more specifically points;

[0056] Stadium terraces and steps, running tracks, forecourts, roads and sidewalks;

[0057] Signs and billboards;

[0058] Industrial cold rooms and freezers; and

[0059] Car washes, factories, airports, stables, farm and livestock buildings, sports stadiums, distribution, exhibition and entertainment centers / complexes, warehouses and other large area / volume buildings.

[0060] By way of illustration only, examples of building structures include:

[0061] ·wall;

[0062] ·ceiling;

[0063] Support columns;

[0064] ·floor;

[0065] Roof (underside and exposed surfaces to prevent snow accumulation / weight), and

[0066] Functional heat generating units within the structure including sauna, hot room, pizza oven and tandoori oven.

[0067] The structure can be made from many different materials. Preferred materials that can be processed include building materials such as:

[0068] Cement, ceramics and similar materials, including concrete;

[0069] Asphalt, bitumen and similar oil-based materials;

[0070] Plastics and polymers;

[0071] Composite materials; and

[0072] Metal, insulated metal surfaces and enamel.

[0073] The invention also provides a method of heating a space, comprising supplying power to a heating device according to the first aspect of the invention.

[0074] Preferably, the method of heating the space heats the coating to >90°C within 5 minutes.

[0075] Preferably, the heat generated is primarily in the form of infrared radiant heat energy.

[0076] The heat output can be controlled to some extent by the configuration of the tracks. The tracks can be deposited in series, parallel, or series-parallel to produce the required resistance per unit area for the desired heating output. Examples include:

[0077] For infrared radiation room heaters, for example, 400-800 W / m 2 ,

[0078] For walkways, signs, terraces, for example, 200-300 W / m is typical 2 ,

[0079] For building structures, for example, 40-100 W / m is typical 2 ,

[0080] For an aircraft wing, for example, 100-200 W / m is typical 2 ,as well as

[0081] For electric vehicle cabin heaters, for example, 400-800 W / m 2 .

[0082] According to a second aspect of the present invention, there is provided an ohmic resistance coating comprising a layer deposited on a surface of a substrate, the layer having a thickness between 2 and 300 microns and comprising:

[0083] i) one or more ductile or malleable metals selected from the group consisting of copper, gold, lead, aluminum, platinum, nickel, zinc, magnesium, iron, manganese, chromium, titanium, vanadium, niobium, indium, terbium, strontium, cerium and lutetium; and

[0084] ii) particles comprising one or more resistive metal oxides, carbides, silicides, disilicides, nitrides, borides or sulfides,

[0085] And wherein the one or more ductile or malleable metals bind the particles to the surface of the substrate.

[0086] Most preferably, the layer has a thickness between 20-70 microns.

[0087] Preferably, the layer covers at least 10% (by area) of the substrate surface.

[0088] Most preferably, the layer covers at least 50% (by area) of the substrate surface.

[0089] The layer may be deposited as single or multiple tracks, separate or overlapping.

[0090] The coating may be deposited in such a way that it has a constant dimension (uniform width and thickness), or may be deposited in a variable manner so that the resistance (and the resulting heating effect) at a given point or area can be controlled, so that a non-uniform effect can be achieved when required. This can be done by varying the shape or configuration of the tracks, for example by varying the width or thickness of the deposit, and / or by varying the formulation and / or level of the resistive metal compound (particularly the metal oxide present), or by varying the spacing between adjacent tracks. In this way, it may be possible, for example, to achieve a greater heating effect at the periphery of the structure than at its centre, or to provide independently controllable heating zones within a larger heater surface, so that when connected via an intelligent central control unit, an adjustable heating output can be obtained. An adjustable system can accommodate seasonal heating variations or provide improved energy efficiency during regular use.

[0091] According to a third aspect of the present invention, there is provided a mixture for cold spraying or solid state deposition, comprising:

[0092] i) at least one ductile or malleable metal, and

[0093] ii) particles comprising any of the following:

[0094] a) one or more metals and / or one or more metalloids and their compounds or salts; or

[0095] b) compounds or salts of one or more metals or metalloids;

[0096] The at least one ductile or malleable metal is present in an amount (by weight) sufficient to allow the mixture to form a coating on a substrate surface when deposited at a temperature below 1000°C.

[0097] Preferably, the one or more metal or metalloid compounds or salts include one or more of oxides, carbides, silicides, disilicides, nitrides, borides or sulfides.

[0098] Most preferably, the one or more metal or metalloid compounds or salts are oxides.

[0099] Preferably, the one or more metal compounds comprise copper, gold, lead, aluminum, platinum, nickel, zinc, chromium, magnesium, iron, manganese, titanium, vanadium, niobium, indium, terbium, strontium, cerium and lutetium.

[0100] Most preferably, the one or more metal compounds comprise nickel.

[0101] Preferably, the one or more metalloids are selected from the group consisting of: boron, silicon, germanium, arsenic, antimony, tellurium and astatine.

[0102] Preferably, the one or more ductile or malleable metals are selected from the group consisting of: gold, silver, aluminum, copper, tin, lead, zinc, iron, manganese, platinum, nickel, tungsten and magnesium.

[0103] Most preferably, the one or more ductile or malleable metals is zinc or a mixture of zinc and nickel.

[0104] The mixture may contain from 10 to 90 weight percent of one or more ductile or malleable metals.

[0105] Most preferably, the mixture comprises from 40 to 60% of one or more ductile or malleable metals.

[0106] Typically, particles comprising any of the following have an average particle size of 0.1-150 μm:

[0107] a) one or more metals and / or one or more metalloids and their compounds or salts; or

[0108] b) Compounds or salts of one or more metals or metalloids.

[0109] Most preferably, the particles have an average particle size of 5-35 μm.

[0110] In particularly advantageous embodiments, the particles comprise oxides of nickel, iron and / or chromium.

[0111] The one or more metals and / or one or more metalloids and compounds or salts may be obtained, for example, as pre-oxidized (or other) powders by passing the metal powders through a heating zone of a thermal deposition apparatus under an air atmosphere (or other suitable gas) so that the metal powders are melted and oxidized (or other) to a controllable degree, followed by quenching, separation and drying.

[0112] Preferably, the resistive metal oxides (carbides, silicides, disilicides, nitrides, borides, sulfides and other non-metals and / or metalloids or any combination thereof) and mixtures thereof are selected from those oxides that exhibit an increase in electrical resistance with increasing temperature.

[0113] According to a fourth aspect of the present invention, there is provided a method of depositing a mixture comprising the following components to form a coating on a substrate surface:

[0114] i) at least one ductile or malleable metal and

[0115] ii) particles comprising any of the following:

[0116] a) one or more metals and / or one or more metalloids and their compounds or salts, including salts thereof; or

[0117] b) compounds or salts of one or more metals or metalloids;

[0118] The method comprises the steps of causing the mixture to adhere to the surface by:

[0119] i) supplying the mixture components to a cold spray device; and

[0120] ii) Depositing the mixture particles by a heated, compressed, supersonic gas jet, which accelerates the mixture particles at a certain temperature and pressure, passes through a nozzle to a substrate surface at a certain distance from the nozzle, causing the mixture particles to adhere to the surface, thereby forming a coating thereon.

[0121] The temperature may be between 100°C and 1200°C.

[0122] Most preferably, the temperature is below 600°C.

[0123] More preferably, the temperature is still below that which would cause the ductile or malleable metal particle or particles to melt or partially soften, so when zinc is used the temperature should be below 400°C.

[0124] Preferably, the pressure is between 1 and 10 Atm.

[0125] Preferably, the method is performed in the absence of a vacuum.

[0126] Preferably, the distance is less than 1 m, more preferably between 1 and 30 cm.

[0127] Preferably, the particles have an average particle size of 0.1 to 150 μm, more preferably 15 to 35 μm.

[0128] Preferably, the gas is air, oxygen, nitrogen, carbon dioxide, argon or neon, but other gases can also be used, for example during welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0130] Embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0131] Figure 1 is a schematic representation of a mixture formed of at least one ductile or malleable metal and particles comprising any of:

[0132] a) one or more metals and / or one or more metalloids and their compounds or salts; or

[0133] b) compounds or salts of one or more metals or metalloids;

[0134] Figure 2 An apparatus suitable for the method of the third aspect of the present invention is shown;

[0135] Figure 3 is a schematic diagram of a coating of the present invention deposited on a substrate;

[0136] Figures 4A to 4C are progressively magnified microscopic images of a coating formed on a substrate by thermal spraying in accordance with the prior art, wherein the particles are deposited in a semi-molten state;

[0137] Figure 5 is a microscope image of a coating formed on a substrate by cold spraying in accordance with the present invention, wherein the particles are deposited in a solid state; and

[0138] Figure 6 A heating device according to a fourth aspect of the invention is shown. DETAILED DESCRIPTION OF THE INVENTION

[0140] refer to Figure 1 , shows a mixture 10 for cold spraying or solid state deposition, which is prepared by mixing i) at least one ductile or malleable metal 18 (typically in particulate form) with ii) particles 20, wherein the particles 20 include a) one or more metals 12 and / or metalloids 14 and compounds or salts 16 thereof or b) one or more compounds or salts 16 of metals or metalloids.

[0141] The mixture 10 may be premixed and introduced into a cold spray apparatus or other solid state deposition apparatus for use in the method of the present invention, or may be introduced separately and mixed in situ.

[0142] refer to Figure 2 The mixture 10 can be supplied to a cold spray device 50 so that the mixture particles 22 enter a heated 52, compressed 54, supersonic gas jet 56, where they are accelerated at temperature (T) and pressure (P), pass through a nozzle 58 to a surface 42 of a substrate 40 at a certain distance (D) from the nozzle, so that the mixture particles 22 adhere to the surface 42, thereby forming a coating 30.

[0143] The result is a coating of 30, see Figure 3 , wherein i) at least one ductile or malleable metal 18 is used to "bond" ii) particles 20 to the surface 42 of the substrate 40, wherein the particles 20 include a) one or more metals 12 and / or metalloids 14 and their compounds or salts 16 or b) one or more metal or metalloid compounds or salts 16.

[0144] A person skilled in the art can distinguish the cold sprayed coatings of the present invention from those produced by thermal spraying techniques which melt the deposited particles. Cold sprayed coatings exhibit less heterogeneity and porosity than thermally sprayed coatings.

[0145] HVOF thermal spraying using highly ductile materials enables high density deposition with low porosity when operating at particularly high temperatures and speeds with very ductile components alone. However, most thermal deposition techniques (e.g. flame spraying) or sprayed compositions result in density levels that vary widely (in the range between 50%-85%) (i.e. porosity levels of 15%-50%). Typically, denser levels are achieved in areas where the level of ductile material is particularly high (or in the entire coating), while lower density (higher porosity) levels are achieved in areas where the (brittle) ceramic component is more prominent.

[0146] In contrast, density levels achieved by cold spraying current ductile metals with brittle ceramic-type components result in overall levels of >90% density (<10% porosity).

[0147] In fact, the porosity of the coating of the present invention can be less than 10%, up to 8%, 6%, 4%, as low as 3%, 2% or 1%.

[0148] This is through Figures 4A to 4C (Thermal spray coatings) and Figure 5 (cold spray coating of the present invention) is shown in comparison.

[0149] Figure 4AThe complex microstructure of the flame sprayed mixed metal / metal oxide deposits is shown. There is a random distribution and segregation of the different phases after thermal spraying. The metal particles 18 appear white due to their high backscattered light reflectivity. The mixed metal oxide 20 appears gray, while the darker areas are voids or "voids," which result in high overall porosity in these coatings.

[0150] At higher magnifications, the high (but variable) degree of deformation experienced by the metal particles during the application of the melt phase becomes more apparent. The particles go through varying degrees of deformation from being completely "splattered" (due to exposure to higher temperature regions within the flame and / or a shorter flight path, with less opportunity for cooling prior to impact), to some particles remaining nearly spherical. The most severely deformed species will also undergo varying degrees of oxidation, reacting with the available ambient oxygen present in the flame, resulting in very complex microstructures in and around the "splat".

[0151] Figure 4B shows a 2.5-fold increase in magnification Figure 4A Surface. The highly complex microstructure is more evident in the metal (lighter) areas 18 and metal oxide (greier) areas 20. Voids still appear as darker areas.

[0152] Figure 4C The coating is shown at 5X magnification. The metal region 18 shows porosity and is surrounded by a metal oxide shell region 20. The elemental distribution of region 18 shows high levels of nickel metal with the presence of embedded oxide particles, but contains higher concentrations of iron and chromium oxides, both of which are expected to react preferentially with the available oxygen present in the flame during the molten phase flight. Similarly, it should be noted that small metal particles are present in large numbers within the broken shell of the metal oxide phase. This clearly illustrates the complexity of thermal spray deposits and the resulting heterogeneity.

[0153] These can be contrasted with structures with significantly less heterogeneity resulting from cold spray application processes, which occur in the form of solid-state deposition processes, such as Figure 5 As shown, metal oxide 20 particles are embedded in ductile metal 18.

[0154] Although the distribution is still non-uniform, the component regions (i.e., the conductive ductile metal regions and the non-conductive brittle metal oxide or metal salt regions) have not undergone any melt phase transformation, and accordingly their respective compositions have not been chemically modified. The challenge in making such coatings is to carefully control the physical application conditions of the cold spray unit used so as not to simply "sandblast" away the coated substrate and / or any material that has been deposited. This is due to the brittle nature of the metal oxides / metal salts, which are typically used as blasting powders to clean the substrate surface when depositing 100% ductile metals.

[0155] By carefully controlling the powder mixing and feeding in defined ratios through a cold spray gun, Applicants are able to achieve reproducible compositions with uniform heating properties.

[0156] In an exemplary method, the mixture 10 may be as shown in any one of Examples 1-7.

[0157] Particles with an average diameter of 5 to 35 microns are heated to a temperature below 600° C. in an air stream and leave the device at a pressure of about 5 Atm and travel a distance of 8 mm to 300 mm, where they are deposited on a ceramic surface 42, and they form a coating 30 on the ceramic surface in a layer 32 with a thickness of about 45 microns.

[0158] The coating 30 may be deposited in a controlled manner to form one or more tracks 44 that may form, for example, a functional component. Figure 6 As shown, the heating device 60 comprises a steel substrate 40 having a ceramic surface 42, on which a heating element 62 has been deposited in a track manner, the heating element comprising a coating 30 comprising, for example, nickel oxide and zinc. A pair of electrical contacts 64; 66 are provided which are connectable to a power supply 68 to enable heating of the heating device.

[0159] Alternatively, the arrangement may comprise a plurality of heating elements sharing a common feed terminal 64 and having separate return terminals 66 .

[0160] Preferably, the power supply is a low voltage power supply of less than 30V.

[0161] The heating device can be used in many different applications, but two particularly advantageous applications are in vehicles, such as but not limited to cars, trucks, trains, ships and airplanes, and in buildings, such as but not limited to: houses, offices, hospitals and warehouses.

[0162] To further illustrate the present invention, the following are some exemplary mixtures and details of their deposition onto a substrate to form a heating element.

[0163] Example 1

[0164] Using cold spray or solid state equipment, a mixture 10 of mixed zinc metal powder 18, nickel metal powder 12 and aluminum oxide powder 16 (with a weight ratio of 75:23:2 and a particle size range of 15 to 30 μm) was deposited onto an enameled 42 steel substrate 40 at 10 mm intervals, using 5.6 bar compressed air as a carrier gas, heated at ~600°C, and the as-deposited parallel component tracks were about 0.45 cm wide, with a spray speed of 4 cm / sec. When a 20V AC power supply was connected across the length of the deposited component tracks, the component tracks were heated to 120°C, generating a current of 4 amps.

[0165] Example 2

[0166] The same mixture of zinc powder, nickel powder and alumina used in Example 1 was mixed 1:1 with thermally pre-oxidized Inconel 600 alloy (total oxidation level of about 10% and 45 μm dust) at a pressure of 5.6 bar and deposited onto a plasma sprayed alumina steel substrate using a 12 mm spacing and a 4 cps spray rate, using compressed air as a carrier gas, heated at about 600° C., and the total width of adjacent tracks as deposited was 0.45 cm. When a 10 V AC power supply was connected across the length of the deposited component track, the component track was heated to 60° C., generating a current of 3 amps.

[0167] Example 3

[0168] The mixture according to Example 2 was spray coated onto a tempered glass substrate at 400°C using a 10 cm standoff and a traverse speed of 8 cps and deposited into parallel elements approximately 0.45 cm wide.

[0169] Example 4

[0170] The mixture of Example 2 was sprayed onto a SiN ceramic block at 600°C and 5.6 bar pressure using a spacing of 8 cm and a traverse speed of 4 cps, producing adjacent tracks to a total width of -4.5 cm.

[0171] Example 5

[0172] A 4:1 mixture of nickel oxide powder 16 (15 μm) and zinc metal powder 18 was sprayed onto ceramic coated steel building panels at 600°C and 4.4 bar pressure using an 8 cm spacing and a traverse speed of 8 cps, depositing parallel element tracks approximately 0.45 cm wide.

[0173] Example 6

[0174] The mixture of zinc metal powder 18, nickel metal powder 12 and thermally preoxidized Inconel 600 alloy 16 used in Example 2 was sprayed onto a ceramic coated steel building panel at 400°C and 5.6 bar pressure using an 8 cm spacing and a 12 cps travel speed to deposit parallel component tracks approximately 0.45 cm wide. When a 40 V DC power supply was connected across the length of the deposited component tracks, the component tracks were heated to 110°C, producing a current of 2 amps.

[0175] Example 7

[0176] The 6:1 mixture of the heat pre-oxidized Inconel 600 alloy 16 and zinc metal powder 18 used in Example 2 was sprayed onto the ceramic coated steel building panel at 570°C and 5.6 bar pressure using a spacing of 8 cm and a travel speed of 4 cps to deposit parallel component tracks of about 0.45 cm width. When 240V AC mains power was connected across the length of the deposited component tracks, the component tracks were heated to 250°C, producing a current of 0.9 amps.

Claims

1. A heating device (60) comprising a substrate (40) whose surface (42) has a heating element (62), the heating element comprising an ohmic resistance coating (30) deposited on the surface (42) of the substrate (40) by cold spraying, the ohmic resistance coating having a layer thickness of between 2 and 300 micrometers and comprising: i) at least 30% by weight of one or more ductile metals (18) selected from the group consisting of copper, aluminum, zinc and manganese; and ii) resistor particles (20), the resistor particles comprising a compound or salt (16) of a metal (12) and / or a metalloid (14), the compound being selected from oxides, carbides, nitrides or borides, and the salt being selected from silicides; wherein the one or more ductile metals (18) bond the resistive particles (20) to a surface (42) of a substrate (40) to form an ohmic resistive coating (30) as a result of the cold spraying, the cold spraying being performed at a temperature (T) below the temperature at which the one or more ductile metals (18) melt or partially soften, and wherein the ohmic resistive coating (30) has a density greater than 90% and a porosity less than 10%, and exhibits less heterogeneity and porosity than a thermally sprayed coating, and is characterized by The resistor particles (20) are located in the ductile metal (18); and at least one pair of electrical contacts disposed on the ohmic resistance coating (30) for connection to an AC or DC power source (68).

2. The heating device according to claim 1, wherein in ii) the metal (12) is nickel, iron and / or chromium, the metalloid (14) is boron, silicon, germanium, arsenic, antimony, tellurium or astatine, and in i) the ductile metal (18) is zinc.

3. A heating device according to claim 1 or 2, wherein the device comprises a plurality of heating elements (62), each heating element sharing a common feed terminal (64) and having an independent return terminal (66).

4. The heating device according to claim 1, wherein the salt is selected from disilicides.

5. The heating device according to claim 1 or 2, wherein the surface (42) comprises a dielectric barrier material. The heating device according to claim 5 , wherein the dielectric barrier material is ceramic.

7. The heating device according to claim 1, wherein the substrate (40) comprises a sheet material.

8. A heating device according to claim 7, wherein the sheet material is a building panel.

9. A heating device according to claim 7 or 8, wherein the sheet material comprises a steel core and a ceramic surface, or the sheet material is glass.

10. The heating device according to claim 9, wherein the sheet material is a mirror glass sheet.

11. The heating device according to claim 1 or 2, wherein the surface has a diameter of 150 cm 2 Up to 20000 cm 2 The heating surface area between.

12. The heating device of claim 1 or 2, wherein the heating element is a self-regulating resistive heating element.

13. A vehicle comprising the heating device according to any one of claims 1 to 7.

14. A building comprising a heating device according to any one of claims 1 to 12.

15. An ohmic resistance coating (30) comprising a layer (32) deposited on a surface (42) of a substrate (40) by cold spraying, the layer having a thickness between 2 and 300 micrometers and comprising: i) at least 30 wt. % of one or more ductile metals (18) selected from the group consisting of copper, aluminum, zinc and manganese; and ii) resistor particles (20), the resistor particles comprising a compound or salt (16) of a metal (12) and / or a metalloid (14), the compound being selected from oxides, carbides, nitrides or borides, and the salt being selected from silicides; wherein the one or more ductile metals (18) bond the resistive particles (20) to a surface (42) of a substrate (40) to form an ohmic resistive coating (30) as a result of the cold spraying, the cold spraying being performed at a temperature (T) below the temperature at which the one or more ductile metals (18) melt or partially soften, and wherein the ohmic resistive coating (30) has a density greater than 90% and a porosity less than 10%, and exhibits less heterogeneity and porosity than a thermally sprayed coating, and is characterized by The resistor particles (20) are embedded in the ductile metal (18).

16. The ohmic resistance coating (30) according to claim 15, wherein the salt is selected from disilicides.

17. The ohmic resistance coating (30) according to claim 15, wherein the layer (32) has a thickness between 20-70 microns.

18. The ohmic resistance coating according to any one of claims 15 to 17, wherein the layer covers at least 10% by area of ​​the surface (42) of the substrate (40).

19. An ohmic resistance coating according to any one of claims 15 to 17, wherein the layer is deposited as single or multiple separate or overlapping tracks (44).

20. A method of forming an ohmic resistance coating (30) as claimed in any one of claims 15 to 19 on a surface (42) of a substrate (40), the method comprising the step of attaching the mixture (10) to the surface (42) by: a) supplying a mixture (10) into a cold spraying device (50); the mixture (10) comprising the following components: i) at least 30 wt. % of one or more ductile metals (18) selected from copper, aluminum, zinc and manganese, and ii) resistive particles (20) comprising a compound or salt (16) of a metal (12) and / or metalloid (14), the compound selected from oxides, carbides, nitrides or borides, and the salt selected from silicides; and b) depositing the mixture particles (22) by a heated (52), compressed (54), supersonic gas jet (56), the gas jet accelerating the mixture particles (22) at a temperature (T) and pressure (P), through a nozzle (58) to a surface (42) of a substrate (40), the temperature being below the temperature at which the one or more ductile metals (18) melt or partially soften, the surface (42) being a distance (D) from the nozzle, so that the mixture particles (22) adhere to the surface (42), thereby forming an ohmic resistive coating (30) on the surface (42), wherein the ohmic resistive coating (30) has a density greater than 90% and a porosity less than 10%, and exhibits less heterogeneity and porosity than a thermally sprayed coating, and is characterized in that The resistor particles (20) are embedded in the ductile metal (18).

21. The method of claim 20, wherein the salt is selected from disilicides.

22. The method of claim 20, wherein the temperature is between 100°C and 1200°C, depending on the ductile metal (18); the pressure is between 1 and 10 Atm; the distance (D) is between 1 and 30 cm; the resistive particles (20) have an average particle size of 15 to 35 microns; and the gas is air, oxygen, nitrogen, carbon dioxide, argon or neon.

23. A method of heating a space (70), comprising supplying power to a heating device (60) according to any one of claims 1 to 12, wherein the heating device is heated to >90°C in less than 5 minutes and the heat generated is in the form of infrared radiant heat energy.

24. A method of heating a space (70) according to claim 23, wherein the heating means is a mains powered power source, or a low voltage power source operating in the range of 1 to 110 volts or less than 30 volts.

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