Reactive deposition for electrochemical cell production Number:7,521,097 from the United States Patent and Trademark Office (PTO) owispatent Light reactive deposition can be adapted effectively for the deposition of one or more electrochemical cell components. In particular, electrodes, electrolytes, electrical interconnects can be deposited form a reactive flow. In some embodiments, the reactive flow comprises a reactant stream that intersects a light beam to drive a reaction within a light reactive zone to produce product that is deposited on a substrate. The approach is extremely versatile for the production of a range of compositions that are useful in electrochemical cells and fuel cell, in particular. The properties of the materials, including the density and porosity can be adjusted based on the deposition properties and any subsequent processing including, for example, heat treatments.<H electrochemical, production, Reactive, deposi, 7521097.html, Patent, pto, 7521097

Title: Reactive deposition for electrochemical cell production

Abstract: Light reactive deposition can be adapted effectively for the deposition of one or more electrochemical cell components. In particular, electrodes, electrolytes, electrical interconnects can be deposited form a reactive flow. In some embodiments, the reactive flow comprises a reactant stream that intersects a light beam to drive a reaction within a light reactive zone to produce product that is deposited on a substrate. The approach is extremely versatile for the production of a range of compositions that are useful in electrochemical cells and fuel cell, in particular. The properties of the materials, including the density and porosity can be adjusted based on the deposition properties and any subsequent processing including, for example, heat treatments.

Patent Number: 7,521,097 Issued on 04/21/2009 to Horne, et al.

Inventors: Horne; Craig R. (Sunnyvale, CA), McGovern; William E. (LaFayette, CA), Lynch; Robert B. (Livermore, CA), Mosso; Ronald J. (Fremont, CA)
Assignee: NanoGram Corporation (Milpitas, CA)

Appl. No.: 10/854,931

Filed: May 27, 2004

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
60476451	Jun., 2003
60479698	Jun., 2003

Current U.S. Class: 427/585 ; 427/115; 427/248.1; 427/596; 429/12; 429/122

Current International Class: C23C 8/00 (20060101); B05D 5/12 (20060101); C23C 14/30 (20060101); H01M 8/00 (20060101)

Field of Search: 427/585,596,115,248.1 429/12,34,40,122,209

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Primary Examiner: Meeks; Timothy H
Assistant Examiner: Turocy; David
Attorney, Agent or Firm: Dardi & Associates, PLLC Dardi; Peter S.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to copending U.S. Provisional Patent Application Ser. No. 60/476,451 to Horne, filed on Jun. 6, 2003,entitled "Improved Material Preparation Approaches For Fuel Cells," incorporated herein by reference, and copending U.S. Provisional Patent Application Ser. No. 60/479,698 to Horne filed on Jun. 19, 2003,entitled "Material Processing For Tubular Ceramic Fuel Cells And Metallic Interconnects," incorporated herein by reference.

Claims

What we claim is:

1. A method for forming an electrochemical cell, the method comprising performing the sequential reactive deposition of an elemental metal or metal alloy, and a metalloid oxide, wherein the reactive deposition comprises moving a substrate or platen relative to a product flow for at least a portion of the time period when deposition is being performed and wherein the sequential reactive depositions are performed with respect to a single reaction zone, wherein a reactant flow intersects with a light beam to drive a reaction that forms the product flow and wherein the reactant flow is generated from an inlet nozzle.

2. The method of claim 1 wherein the metalloid oxide comprises silicon oxide.

3. The method of claim 1 wherein the sequential deposition is performed on a metal support layer.

4. The method of claim 1 wherein the elemental metal or alloy comprises copper.

5. The method of claim 1 wherein the reactant flow comprises an aerosol.

6. A method for forming a fuel cell component, the method comprising contacting a cell assembly with a solvent to dissolve a soluble material and to form reactant flow channels to an electrode wherein the soluble material is deposited from a reactive flow involving a reactant stream that intersects a light beam to form a product flow that intersects with the substrate to deposit a reaction product onto the substrate.

7. The method of claim 6 wherein the soluble material comprises a soluble metal/metalloid composition.

8. A method of sealing fuel cells comprising heating a stack of cells wherein each cell has a rim that contacts the rim of an adjacent cell and wherein a sealing material is deposited along the rim, the sealing material having been deposited from a reactive flow wherein the reactive flow involves a reactant flow that intersects a light beam that drives a reaction to form a product flow that intersects a substrate to deposit the product material.

9. The method of claim 8 wherein the sealing material is a glass.

10. The method of claim 8 wherein the sealing material comprises a metal ceramic.

Description

FIELD OF THE INVENTION

This invention relates to approaches for the formation of electrochemical cells, in particular fuel cells. In particular, the invention relates to reactive deposition approaches for the formation of electrochemical cell structures. The invention further relates to improved structures for electrochemical cells.

BACKGROUND OF THE INVENTION

Electrochemical cells in general involve reduction-oxidation reactions in separated half-cells that are appropriately connected for ionic flow as well as electrical flow across an external circuit. Batteries and fuel cell produce useful work in the form of the electrical flow across a load generated from the reduction-oxidation reactions. In other electrochemical cells, a load is applied to the cell to induce desired chemical reactions at the electrodes to form desired chemical products. Fuel cells differ from batteries in that both the reducing agent and the oxidizing agent can be replenished without dismantling the cell. Fuel cells and in some cases batteries can comprise individual cells stacked in series to increase the resulting voltage. Adjacent cells connected in series can have an electrically conductive plate, e.g., a bipolar plate or electrical interconnect, linking adjacent cells. Since the reactants of a fuel cell can be replenished, appropriate flow paths can be integrated into the cell.

Several types of fuel cells have gained recognition as distinct classes of fuel cells that are distinguishable from each other due to the nature of their construction and the materials used in their construction. Particular fuel cell designs introduce specific challenges in material performances. Common features generally found in different fuel cell designs involve the flow of fuel and oxidizing agent for long-term performance with appropriate design consideration for heat management, electrical connection and ionic flow. Different fuel cell designs differ from each other in the construction of the electrodes and/or electrolyte, which separates the electrodes, and in some cases the particular fuel. Many fuel cell designs operate with hydrogen gas, H.sub.2, although some fuel cells can operate with other fuels, such as methanol or methane.

Several types of hydrogen fuel-based fuel cell differ in the electrolyte within the fuel cell. For example, proton exchange membrane fuel cells have a separator that conducts effectively only protons, i.e., hydrogen cations, to maintain electrical neutrality. Phosphoric acid fuel cells use phosphoric acid as the electrolyte, which also conducts protons. Molten carbonate fuel cells use molten mixed carbonate salts as the electrolyte in which the carbonate ions are transported through the electrolyte to maintain electrical neutrality. Solid oxide fuel cells use a ceramic separator, such as yttrium-stabilized zirconia, which transport oxygen ions. The conventional operating temperatures generally are dependent on the electrolyte material, with proton exchange membrane fuel cells operating at temperatures on the order of 80.degree. C., phosphoric acid fuel cells operating at temperatures on the order of 190.degree. C., molten carbonate fuel cells operating at temperatures on the order of 650.degree. C. and solid oxide fuel cells operating at temperatures on the order of 650.degree. C. to 1000.degree. C. The fuel suitable for a fuel cell generally depends on the catalyst material, electrolyte composition, operating temperature and other performance properties.

In addition to hydrogen based fuel cells, direct methanol fuel cells operate with methanol directly used as the fuel. These cells can operate alternatively with either liquid methanol or vapor methanol. These cells generally are formed with polymer separators and liquid ionic electrolytes. Catalyst particles are generally included in the anodes and cathodes, respectively.

SUMMARY OF THE INVENTION

In a first aspect, the invention pertains to a method for the production of an electrolytic cell component, the method comprising performing sequential reactive deposition for the formation of a plurality of layers wherein at least one layer comprises an electrically conductive material.

In another aspect, the invention pertains to a method for forming an electrolytic cell component, the method comprising impregnating a powder coating with a polymer to form a polymer membrane wherein the polymer is ion conducting.

In a further aspect, the invention pertains to a method for coating a rod shaped substrate, the method comprising rotating the rod within a product flow from a reactive flow.

In addition, the invention pertains to a polymer electrode membrane comprising a powder coating and an ion conducting polymer.

In other aspects, the invention pertains to a power cell comprising a powder coating with primary particle size that varies along the thickness of the coating wherein the powder coating comprises an electrically conductive material.

Moreover, the invention pertains to a fuel cell comprising an electrode with a powder coating comprising a catalyst material wherein the powder coating has a higher concentration of catalyst downstream in the reactant flow.

Furthermore, the invention pertains to a method for forming an electrical interconnect, the method comprising depositing an electrically conductive coating onto a metallic structure with flow channel wherein the deposition is performed from a reactive flow.

In additional aspects, the invention pertains to a method for forming an electrochemical cell, the method comprising performing the sequential reactive deposition of an electrode and a separator.

Additionally, the invention pertains to a method for forming a fuel cell component, the method comprising contacting a cell assembly with a solvent to dissolve a soluble material and to form reactant flow channels to an electrode.

Also, the invention pertain to a method for forming a component for an electrochemical cell, the method comprising depositing an electrically conductive material on a curved surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of a reaction chamber for performing laser pyrolysis synthesis of powders at high production rates.

FIG. 2 is a schematic representation of a reactant delivery system for the delivery of vapor/gas reactants to a flowing reaction system, such as the laser pyrolysis reactor of FIG. 1.

FIG. 3 is a sectional side view of a reactant inlet nozzle with an aerosol generator for the delivery of aerosol and gas/vapor compositions into a reaction chamber, wherein the cross section is taken along line 3-3 of the insert. The insert shows a top view of an elongated reactant inlet.

FIG. 4 is a sectional side view of the reactant inlet nozzle of FIG. 3 taken along the line 4-4 of the insert in FIG. 3.

FIG. 5 is a schematic diagram of a light reactive deposition apparatus formed with a particle production apparatus connected to a separate coating chamber through a conduit.

FIG. 6 is a perspective view of a coating chamber where the walls of the chamber are transparent to permit viewing of the internal components.

FIG. 7 is perspective view of a particle nozzle directed at a substrate mounted on a rotating stage.

FIG. 8 is a schematic diagram of a light reactive deposition apparatus in which a particle coating is applied to a substrate within the particle production chamber.

FIG. 9 is a perspective view of a reactant nozzle delivering reactants to a reaction zone positioned near a substrate.

FIG. 10 is a sectional view of the apparatus of FIG. 9 taken along line 10-10.

FIG. 11 is a perspective view of an embodiment of a light reactive deposition apparatus.

FIG. 12 is schematic diagram of the reactant delivery system of the apparatus in FIG. 11.

FIG. 13 is an expanded view of the reaction chamber of the apparatus of FIG. 11.

FIG. 14 is sectional view of the reaction chamber of FIG. 13 taken along line 14-14 of FIG. 13.

FIG. 15 is an alternative sectional view of the reaction chamber of FIG. 13 with the substrate holder portions removed and the baffle system visible.

FIG. 16 is a top view of a substrate holder.

FIG. 17 is a sectional view of the substrate holder of FIG. 16 with a substrate with the section taken along line 17-17 of FIG. 16.

FIG. 18 is a top view of the reactant inlet nozzle for the reaction chamber of FIG. 13.

FIG. 19 is a perspective view of a dual linear manipulator, which is part of the drive system for the nozzle of the reaction chamber of FIG. 13, where the dual linear manipulator is separated from the reaction chamber for separate viewing.

FIG. 20 is a schematic diagram of a light reactive deposition apparatus in which a particle coating is applied to a rod shaped substrate within the particle production chamber.

FIG. 21 is a top view of a substrate with a powder coating covered in part with a mask.

FIG. 22 is a schematic, perspective view of a fuel cell stack.

FIG. 23 is a top view of a corrugated platen.

FIG. 24 is a sectional view of a cell with electrodes have layers with different particle sizes.

FIG. 25 is a sectional view of a fuel cell electrode and electrolyte layer with the electrode having increasing catalyst concentrations downstream from the reactant flow.

FIG. 26 is an x-ray diffractogram for a sample produced under the conditions specified in column 1 of Table 1.

FIG. 27 is an x-ray diffractogram for a sample produced under the conditions specified in column 1 of Table 2.

FIG. 28 is an x-ray diffractogram for a sample produced under the conditins specified in column 2 of Table 2.

DETAILED DESCRIPTION OF THE INVENTION

Improved processing approaches for performing reactive deposition of materials can be adapted advantageously for the formation of electrochemical cells, especially fuel cells, or components thereof with improved material properties. In particular, techniques can be adapted for fuel cell application for the high rate deposition of layered materials or corresponding patterned layered materials. Individual layers or patterned layers of materials can be deposited to form individual fuel cell components, such as coatings, electrical interconnects or seals, and/or multiple layers can be deposited to form one or more components or portions thereof. The deposition approaches generally are based on light reactive deposition, which involves depositing materials from a reactive flow. These improved approaches have considerable versatility in tuning the composition and can reproducibly produce high quality layers/structures with selected characteristics. The efficient production of highly reproducible structures allows for the construction of long lasting electrochemical cells with consistent and reproducible performance.

Electrochemical cells have an anode and a cathode for performing oxidation and reduction half reactions, respectively. A separator/electrolyte is placed between the cathode and anode to provide ionic conductivity but electrical insulation. Electrons flow from the anode toward the cathode as a result of an electromotive force. An external load can be applied to drive a particular reaction within the cell. In contrast, in a battery or fuel cell, the reactions within the cell generate an external load that can be used to perform work. If cells are stacked in series, an electrical conductor is placed between adjacent cells to prevent flow of reactants or electrolyte between adjacent cells, but allow for electrical flow such that the voltage of the adjacent cells is additive. Generally, the approaches described herein can be used to deposit a component of the cell or portion thereof, the entire cell or a series of cells. To simplify the discussion herein, the description below focuses on fuel cells, although a person of ordinary skill in the art can similarly apply the described approaches for batteries, other electrochemical cells and components thereof.

A process has been developed involving reactive deposition driven by a light beam (e.g., a laser beam), to form coatings with material characteristics that are tightly controlled. The coating can be used to form particular structures with either a simple or complex configuration. In one embodiment, reactive deposition driven by a light beam (e.g., a laser beam) involves a reactor with a flowing reactant stream that intersects an electromagnetic radiation beam proximate a reaction zone to form a product stream configured for the deposition of product particles onto a surface following formation of the particles in the flow. The particles are deposited in the form of a powder coating, i.e. a collection of unfused particles or a network of fused or partly fused particles in which at least some characteristics of the initial primary particles are reflected within the coating. Light reactive deposition incorporates features of laser pyrolysis, a light reactive process for driving the reaction of a flowing reactant stream to form submicron powders, into a direct coating process. In laser pyrolysis, particle formation incorporates an intense electromagnetic radiation, e.g., light, beam to drive a reaction in a flow for the production of submicron particles in a monodispersed powder form.

In laser pyrolysis, the reactant stream is reacted by an intense light beam, such as a laser beam, which heats the reactants at a very rapid rate. While a laser beam is a convenient energy source, other intense radiation (e.g., light) sources can be used in laser pyrolysis. Laser pyrolysis can provide for formation of phases of materials that are difficult to form under thermodynamic equilibrium conditions. As the reactant stream leaves the light beam, the product particles are rapidly quenched. The reaction takes place in a confined reaction zone at the intersection of the light beam and the reactant stream. For the production of complex materials, such as materials with three or more elements and/or doped materials, the present approaches have the advantage that the composition of the materials can be adjusted over desirable ranges.

Submicron inorganic particles with various stoichiometries, non-stoichiometric compositions and crystal structures, comprising amorphous structures, have been produced by laser pyrolysis, alone or with additional processing. Specifically, amorphous and crystalline submicron and nanoscale particles can be produced with complex compositions using laser pyrolysis. Similarly, using light driven reaction approaches a variety of new materials can be produced.

Reactant delivery approaches developed for laser pyrolysis can be adapted for light reactive deposition. In particular, a wide range of reaction precursors can be used in gaseous/vapor and/or aerosol form, and a wide range of highly uniform product particles can be efficiently produced for the deposition in the form of a coating, such as a powder coating. Specifically, light reactive deposition can be used to form highly uniform coatings of materials, optionally comprising dopant(s)/additive(s) and/or complex composition(s). The coating formed by light reactive deposition can be a collection of particles on a surface or a powder coating, depending on the deposition conditions. For convenience, this application refers interchangeably to light-driven pyrolysis and laser pyrolysis. For convenience, this application also refers interchangeably to light reactive deposition and laser reactive deposition. In other words, as used herein, laser pyrolysis and light reactive deposition refer generally to all electromagnetic radiation based particle synthesis and electomagnetic radiation based coating approaches, respectively, unless explicitly indicated otherwise.

In some embodiments, the reactor apparatus, e.g., a light reactive deposition apparatus, includes an extended reactant inlet such that a stream of particles is generated within a flowing sheet forming a reactant/product stream. Generally, the reactant flow is oriented to intersect the radiation such that most or all of the reactant flow intersects with the radiation such that high yields are obtained. Using an extended reactant inlet, a line or stripe of particles at a high throughput can be, at least in part, simultaneously deposited onto a substrate. It has been discovered how to obtain high reactant throughput such that a high particle production rate can be maintained without sacrificing control of the product particle properties and/or corresponding uniformity of the deposited powder coating. For coating deposition, by depositing a line or stripe of particles, the coating process can be performed more rapidly.

More specifically, in a reactor with an elongated reactant inlet, particle production rates are readily achievable in the range(s) of at least about 1 gram per hour (g/h) and in other embodiments in the range(s) of at least about 100 g/h. These rates can be used to achieve particles with a wide range of compositions and with high particle uniformity. Specifically, particles within the flow can be formed with a distribution of particle diameters that is highly peaked at or near the average such that the distribution of a majority of the particles is narrow and that has a cut off in the tail of the distribution such that effectively no particles have a diameter larger than a cut off value of a low multiple of the average diameter. Corresponding high coating rates also can be achieved. The uniformity of the particles in the flow can result in desirable properties for the corresponding coating formed from the particles.

Light reactive deposition has considerable advantages for the production of particles for coating substrate surfaces. First, light reactive deposition can be used in the production of a large range of product particles. Thus, the composition of the corresponding coating can be adjusted based on the features of the light reactive deposition approach. Furthermore, light reactive deposition can produce very small particles with a high production rate and high uniformity.

Submicron inorganic particle coatings with various stoichiometries and/or non-stoichiometric compositions can be produced by light reactive deposition. Similarly, deposited materials can be formed with various crystal structure(s), including, for example, amorphous structures. Specifically, light reactive deposition can be used to form highly uniform coatings of glasses, i.e., amorphous materials, and crystalline materials (either single crystalline or polycrystalline), optionally with additive/dopants comprising, for example, complex blends of stoichiometric and/or additive/dopant components.

Depending on the particular component to be formed, suitable materials for incorporation into a fuel cell can be, for example, catalytic/electrocatalytic, inert, electrically conductive, ion conductive, electrically insulating, or suitable combinations thereof. Suitable inert materials and electrically insulating materials include, for example, metal oxides or other suitable metal compositions or combinations thereof. Suitable catalysts can be, for example, metals, metal alloys, metal oxides, metal nitrides, metal carbides, oxynitrides, oxycarbides and combinations thereof. Suitable electrically conductive materials include, for example, metals, metal alloys, carbon materials and combinations thereof. Suitable ionically conductive materials include, for example, doped BaCeO.sub.3, doped SrCeO.sub.3, yttria stabilized zirconia, scandia stabilized zirconia, La.sub.1-xSr.sub.xGa.sub.1-yMg.sub.y, with x and y between about 0.1 and about 0.3,glasses, such as P.sub.2O.sub.5--TiO.sub.2--SiO.sub.2 glasses, and carbonates.

A basic feature of successful application of laser pyrolysis/light reactive deposition for the production of particles and corresponding coatings with desired compositions is generation of a reactant stream containing an appropriate precursor composition. In particular, for the formation of doped materials by light reactive deposition, the reactant stream can comprise host glass precursors or crystal precursors and dopant precursors. The reactant stream includes appropriate relative amounts of precursor compositions to produce the materials with the desired compositions and/or dopant concentrations. Also, unless the precursors are an appropriate radiation absorber, an additional radiation absorber can be added to the reactant stream to absorb radiation/light energy for transfer to other compounds in the reactant stream. Other additional reactants can be used to adjust the oxidizing/reducing environment in the reactant stream.

By adapting the properties of laser pyrolysis, light reactive deposition is able to deposit highly uniform, very small particles in a coating. Due to the uniformity and small size of the powders, light reactive deposition can be used to form uniform and smooth coating surfaces. The desirable qualities of the particles are a result of driving the reaction with an intense light beam, which results in the extremely rapid heating and cooling. Appropriate controls of the deposition process can result in high uniformity of coating thickness, whether or not densified, across the surface of a substrate and with respect to average coating thickness between substrates coated under the equivalent conditions.

Multiple layers can be formed by additional sweeps of the substrate through the product particle stream. Since each coating layer can have high uniformity and smoothness, a large number of layers can be stacked while maintaining appropriate control on the layered structure such that structural features can be formed throughout the layered structure without structural variation adversely affecting performance of the resulting structures. Composition can be varied between layers, i.e., perpendicular to the plane of the structure, and/or portions of layers, within the plane of the structure, to form desired structures. Thus, using light reactive deposition possibly with other patterning approaches, it is possible to form complex structures with intricate variation of materials with selectively varying compositions.

To form a densified layer, a powder coating layer deposited by light reactive deposition can be consolidated or sintered. For convenience, the term consolidated is used herein to described densification of an amorphous or crystalline material. To consolidate the materials, the powders are heated to a temperature above their flow temperature. At these temperatures, the powders densify and upon cooling form a layer of densified material. Suitable densities for some fuel cell embodiments are described below. In general, a desired density may depend on the suitable gas porosity. By controlling the composition and/or dopants of the deposited particles, the composition of a subsequently densified material can be controlled to be a desired composition. Generally, amorphous particles can be consolidated to form a glass material, and crystalline particles can be consolidated to form a crystalline material. However, in some embodiments, appropriate heating and quenching rates can be used to consolidate an amorphous material into a crystalline layer, either single crystalline or polycrystalline, (generally slow quenching rates) and a crystalline powder into a glass layer (generally a rapid quench).

Efficient approaches have been developed for the patterning of compositions for the formation of desired structures, as described in detail below. Patterning of materials with respect to composition or other property can be performed during deposition and/or following deposition, for example, by etching the coated substrate using photolitography and/or other etching approaches.

Central to the formation of more complex structural components for an electrochemical cell is the variation of the material properties at different physical locations. For example, variation in electrical conductivity, porosity, ionic conductivity and/or catalytic ability generally is used to distinguish functional components. Material properties can be varied by changes in chemical composition and/or by changes in physical properties, such as density or particle size. As described herein, complex structures are described that involve composition variations in three dimensions organized within a plurality of layers. By stacking many layers with a plurality of layers having composition variation within appropriate plane(s), structures can be formed with a plurality of planes comprising integrated components of an electrochemical structure.

In general, the use of the processing approaches described herein can be effectively used to form individual structures of a fuel cell or fuel cell stack, an entire fuel cell stack or various portions of a fuel cell stack. For example, the approaches described herein can be used to form a coating on component that is then assembled into a fuel cell. In other embodiments, the approaches can be used to form a plurality of layers, such as electrodes, separators/electrolytes, electrical connections/bipolar plates/interconnects, etc. The patterning of layers can be used to form flow channels, electrical connection, seals and other desired structures.

In some embodiments, the formation of the three dimensional structures described herein generally is based on the deposition of a plurality of layers, each of which may or may not be contoured or patterned to form a particular structure within a specific layer. For example, different functional structures, such as electrodes, electrolytes/separators or electrical connections, by varying deposited material in the z-plane, i.e., the plane perpendicular to the coated substrate plane. Alternatively or in addition, a plurality of structures can be formed within a single layer by selectively depositing desired materials over only a portion of a layer or by appropriately etching or otherwise contouring the materials to form isolated domains within the layer, i.e., within the x-y plane of the substrate.

Layers generally can be applied sequentially, although near-simultaneous or even simultaneous application at displaced locations can also occur. With embodiments based on particle deposition, one or several passes of the product particle stream over the substrate surface can be used to form a single layer. The composition of the product particles may or may not be varied within a single pass or between passes. In other words, several passes can be used to form a single layer with a particular composition to obtain a layer with a desired thickness. Generally, particle compositions vary at least between portions of adjacent layers, although significant sections of adjacent layers can have identical compositions. By depositing layers with uniform structures and desired composition variation, complex structures spanning many layers can be formed. Similarly, particle sizes can be varied or density can be varied to impose different porosities or other properties to the material. Some specific desirable structures are described below.

In general, the composition along the x-y plane at a particular level or layer within the three dimensional structure can be varied during the deposition process or following deposition by patterning the materials, either before, during or after consolidation. To form patterned structures following deposition, patterning approaches, such as lithography and photolithography, along with etching, such as chemical etching or radiation-based etching, can be used to form desired patterns in one or more layers. This patterning generally is performed on a structure prior to deposition of additional material.

Using the deposition approaches described herein, the composition of product particles deposited on the substrate can be changed during the deposition process to deposit particles with a particular composition at selected locations on the substrate to vary the resulting composition of the material along the x-y plane. Using light reactive deposition, the product composition can be varied by adjusting the reactants that react to form the product particle or by varying the reaction conditions. The reactant flow can comprise vapor and/or aerosol reactants, which can be varied to alter the composition of the products. The reaction conditions can also affect the resulting product particles. For example, the reaction chamber pressure, flow rates, radiation intensity, radiation energy/wavelength, concentration of inert diluent gas in the reaction stream, temperature of the reactant flow can affect the composition, particle size and other properties of the product particles.

While product particle composition changes can be introduced by changing the reactant flow composition or the reaction conditions while sweeping a substrate through the product stream, it may be desirable, especially when more significant compositional changes are imposed to stop the deposition between the different deposition steps involving the different compositions. For example, to coat one portion of a substrate with a first composition and the remaining portions with another composition, the substrate can be swept through the product stream to deposit the first composition to a specified point at which the deposition is terminated. The substrate is then translated the remaining distance without any coating being performed. The composition of the product is then changed, by changing the reactant flow or reaction conditions, and the substrate is swept, after a short period of time for the product flow to stabilize, in the opposite direction to coat the second composition in a complementary pattern to the first composition. A small gap can be left between the coatings of the first composition and the second com