Patent Application
20050097991
The present invention relates to methods and apparatuses for producing a solid metallic composition by reacting a gaseous metal halide with a reducing agent. More particularly, the invention relates to the use of such methods and apparatuses to produce high-purity metallic compositions. The invention is well suited for producing titanium particles and alloys thereof for use in powder metallurgy applications.
Transition metals such as titanium are plentiful in earth's crust, occur in abundance in the form of oxides (e.g., as rutile-TiO2 and ilmenite-FeTiO3), and have highly useful properties. Titanium, in particular, is a metal suitable for applications that require a material having a low specific gravity, high relative strength and strength-to-weight ratio, even at high temperatures. For example, titanium metal has been used since the 1950s as a structural material, first in aerospace and defense applications. Subsequently, titanium has been used in chemical applications, to form biomedical prosthesis, and in leisure and sport equipment. In addition, titanium is generally highly resistant to corrosion, and often forms surface layers that are stable to chlorides and acids.
Like many other transition metals, however, titanium is generally considered difficult to process. It is expensive to extract and reduce from its ores, and relatively difficult to fabricate into useful products in view of its high melting point, and oxidation properties. In addition, metal powders having a precisely controlled composition and/or microstructure are typically required in powder metallurgy techniques such as hot isostatic processing. For transition metals such as titanium, known techniques for purification and powder preparation are relatively expensive, particularly if the metal is to be rendered suitable for advanced powder metallurgical manufacturing processes.
Two commercial multi-step titanium extraction processes coexisted until the early 1990s: the Kroll and the Hunter processes. Currently, titanium metal is typically produced by reducing titanium tetrachloride with molten magnesium or sodium metal in a steel batch retort. When TiCl4 (“tickel”) is mixed with the magnesium or sodium metal reducing agent, highly exothermic reactions occur, thereby producing a crude intermediate titanium “sponge.” The sponge typically contains titanium metal as well as intimately mixed contaminants and by-products such as magnesium or sodium chloride, titanium subchlorides, and impurities originally present in the reducing agent. The titanium sponge is then refined to produce titanium ingots for manufacturing use. Sponge refining typically also involves costly processes such as the use of vacuum arc technologies.
Numerous titanium production paths have been proposed, and exemplary paths are listed in Table 1. They generally suffer from different drawbacks. For example, production paths that require chemical reduction of titanium compounds typically involve the formation of intermediate compounds that contain high levels of impurities. Purity, separation, oxidation and other issues associated with intermediate compounds may present technical and economic challenges. In particular, intermediate products formed by chemically reducing titanium halides tend to be highly contaminated with halides. Impurities such as oxides, carbon, and in some instances, nitrides may be formed as well. In addition, plasma thermal reduction of titanium chlorides utilizes heating to extremely high temperatures, and is accordingly very energy intensive. All of these processes are also disadvantageous since they are expensive.
Electrochemical processes also suffer from technical and economic disadvantages. While it is possible to deposit metallic Ti onto an electrode, such deposition typically must be carried out using a molten salt system. These electrochemical processes are typically associated with high energy cost as well as labor costs of removing and stripping the electrode onto which metallic Ti is deposited. Such costs represent substantial economic obstacles in commercializing electrolytic Ti processing techniques. Furthermore, molten salt processes typically require high current densities for high industrial throughputs. However, high current densities tend to favor dendrite growth. As a result, technical issues such as electrical shorts, separation from the melt, and product densification must be addressed in such molten salt processes.
In processes under development based on electrochemical deoxidation of TiO2, for example, the use of molten chloride electrolytes typically containing CaCl2 results in the production of fine Ti powder that is intermixed with the remaining calcium species. If this powder is then washed, a significant amount of surface titanium oxide is formed that must later be removed. Since it is difficult and expensive to remove oxygen below the about 300 ppm level required for most modern uses, the need for further cleaning and purification steps results in significantly increased costs.
*Where X is a halogen such as F, Cl, Br, or I; e− indicates an electrochemical reduction; and i, j represent subscripts with different values.
Similarly, processes based on the reduction of titanium tetrachloride with an alkali or alkaline earth metal such as liquid sodium, e.g., according to the Armstrong et al. process of U.S. Pat. No. 6,409,797 also result in the production of fine titanium powders mixed with byproducts such as NaCl and excess reactants. Typically, such processes require additional means and process steps, e.g., elaborate systems of vacuum distillation and leaching, to provide clean titanium.
Processes utilizing fluidized bed reactors in which TiCl4 is reduced by a gaseous metal such as Mg have also been disclosed. In U.S. Pat. No. 4,877,445 to Okudaira et al., for example, titanium pellets are produced by reducing titanium tetrachloride in vapor form using magnesium or sodium vapor as the reducing agent. However, the Okudaira et al. process requires the injection of reducing agent vapors and continuous operation at high temperature to recover, e.g., MgCl2 as a condensable vapor. Impurities in the vapor reducing agent such as Mg will also appear at least to some degree in the titanium product. In addition, the use of magnesium results in titanium production costs similar to those of the Kroll process.
Once ingots are formed, a number of techniques may be used to produce parts having a complex geometry. For example, ingots may be melted, poured into a mold, cooled, and removed from the mold. Such casting processes are generally unsuited for low volume production runs due the cost of the molds. In addition, it is sometimes difficult to control the microstructure of parts made via casting processes. Alternatively, machining techniques may be used to selectively remove portions of ingots to produce parts of a desired shape. The removed portions of the ingot, of course, represent a source of waste. While powder metallurgy techniques have been developed that allow complex shapes to be formed quickly, titanium metal powders are currently quite expensive. Beside the costs associated with ingot production, powders incur the added costs associated with subsequent alloying and atomizing steps for producing uniform powders from the refined ingot.
Thus, there is a need in the art for technologies useful in lowering the cost associated with the production of high-purity metallic compositions, particularly for transition metals such as titanium and alloys thereof. In addition, there is a need to overcome the problems associated with known processes for producing metallic compositions that involve the production of halide-contaminated intermediate products by providing alternative, economically attractive methods for directly forming high-purity, dry and clean metallic granules, including the direct production of metal alloys, from metal halides. More particularly, it would be very desirable to provide a process for the direct production of titanium and titanium alloys in which there is no need to further clean and purify such metals using subsequent processing steps and wherein the cost is substantially reduced through the use of a cheap, abundant and clean reducing agent.
It is a general object of the present invention to overcome the afore-mentioned disadvantages of the prior art by providing improved methods and apparatuses for producing a solid metallic composition that is substantially free from halides, by reducing one or more metal halides.
Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by through routine experimentation during the practice of the invention.
In one embodiment, a method for producing a solid metallic composition is provided that involves reacting a gaseous metal halide with a reducing agent. The metal halide has the formula MXi, M is a metal that includes transition metals of the periodic table, aluminum or boron, X is a halogen, and i is greater than 0. The reducing agent is typically, but not necessarily, gaseous, and may include, for example, hydrogen, a compound that releases hydrogen, and combinations thereof. A combination of reducing agents, or of metals M, may also be used. As a result, a nonsolid reaction product is formed, which is then solidified to form a metallic composition comprising M. The reaction product is preferably substantially free from halides. In another embodiment, the metallic composition formed by the method is substantially free from halides, oxygen, nitrogen, and carbon comprising M, the reducing element, and substantially no halides, oxygen, nitrogen, and carbon.
In an additional embodiment, a method for producing a solid metallic composition is provided, comprising reducing a metal subhalide by reaction with a gaseous reducing agent to form a nonsolid reaction product; and solidifying the reaction product, thereby forming a metallic composition comprising the metal that is substantially free from halides, oxygen, nitrogen, and carbon.
In another embodiment, titanium subhalide such as TiCl3 is reduced to form a nonsolid reaction product, which is then solidified to form a metallic composition comprising Ti that is substantially free from halides, oxygen, and carbon. The metallic composition formed may be a Ti alloy or may consist essentially of pure Ti, depending on the reducing agents used and the reaction conditions. Suitable reducing agents include, for example, H2, a compound that releases hydrogen, and combinations thereof.
In a further embodiment, a titanium halide is reacted with H2 in a manner effective to form a nonsolid reaction product. Solidification of the reaction product results in the formation of metallic composition comprising Ti that is substantially free from halides, oxygen, nitrogen, and carbon. Again, the metallic composition may consist essentially of titanium or be a titanium alloy.
An apparatus for producing a metallic solid composition is also provided. The apparatus includes a source of a metal halide and a source of a reducing agent, as described above. A reactor in communication with the metal halide and the reducing agent sources is used to provide conditions effective to carry out a gas phase reaction between the metal halide and the reducing agent to form a nonsolid reaction product. Also included is a means for solidifying the reaction product to form a metallic composition. For example, the reactor may be comprised of a first reaction zone in fluid communication with the source of metal halide, and a second reaction zone downstream from the first reaction zone. In such a case, the first and second reaction zones may be maintained at different reaction temperatures.
Before describing the invention in detail, it must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a reaction product” includes a single reaction product as well as combinations of reaction products, reference to “reducing agent” includes a single reducing agent as well as mixtures of reducing agents, and the like.
In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below.
The term “group” as in “groups 4 to 7 of the period table” is used herein to refer to an assemblage of elements forming one of the vertical columns of the periodic table according to the International Union of Pure and Applied Chemistry (IUPAC). For example, titanium, zirconium and hafnium are members of group 4, and chromium, molybdenum and tungsten are members of group 7. In general, the term “transition metal” refers to an element selected from groups 3 to 12 of the periodic table.
“Optional” or “optionally” means that the subsequently described circumstance may or may not occur, so that the description includes instances where the circumstance occurs and instances where it does not
The term “microstructure” is used herein to refer to a microscopic structure of a material and encompasses concepts such as lattice structure, degrees of crystallinity, dislocations, grain boundaries and the like.
The term “substantially free” as in the phrase “substantially free from halides,” for example, refers to compositions that contain a low concentration of halides, e.g., less than about 5 atomic percent halides, preferably less than about 1 atomic percent halides. Still further, it is preferred that metallic compositions according to the invention are “substantially free” from halides in that they contain less than about 0.1 atomic percent of halides, more preferably less than about 0.01 atomic percent of halides, and most preferably less than about 0.001 atomic percent of halides. The same compositional limits also apply for other elements that may be present in small amounts such that the metallic composition is “substantially free” from these elements including, but not limited to, oxygen, nitrogen, and carbon.
The terms “consisting essentially” and “consists essentially,” as in the phrase “consists essentially of pure Ti or a Ti alloy,” are generally used in the context of their ordinary meanings. That is, by these terms it is meant that additional components materially affecting the basic and novel characteristics of the metallic compositions are to be excluded. For example, as concerns the presence of certain elements such as halides, oxygen, nitrogen, and carbon, these terms refer to metallic compositions that contain less than about 0.1 atomic percent of one or more of such halides, oxygen, nitrogen, and/or carbon.
In general, the invention provides an improved method for producing a solid metallic composition having a high purity or controlled alloying that involves reacting a gaseous metal halide with a reducing agent. As a result, a nonsolid reaction product is formed. After solidification, the reaction product forms the metallic composition. Unlike prior commercial processes such as the Kroll process, the inventive process does not require the formation of intermediate compounds containing high levels of halides. As a result, the metallic compositions produced by the inventive process typically do not need further purification and/or processing for use. In general, the invention may be practiced in conjunction with any halide of a transition metal. Of particular commercial and technical significance is the practice of the invention with metals selected from groups 4 to 7 of the periodic table. For example, the invention is particularly suited to form metallic compositions containing one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Re. In addition, metal halides particularly suited for the practice of the invention include fluorides, chlorides, bromides, and iodides. Thus, for example, the inventive method may be used to produce metallic Ti and Ti alloys by reducing TiCl4, TiCl3, or TiCl2, to produce metallic Zr and Zr alloys from Zr by reducing ZrI2, to produce Hf and Hf alloys from HfI2, and to produce V and V alloys from VCl4.
Typically, the metal M is an element selected from groups 4 to 7 of the periodic table, although, in general, M is a transition metal, aluminum, silicon, boron, or a combination of metals. Exemplary elements include Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Re, with Ti preferred. In addition, X may be selected from F, Cl, Br, I and combinations thereof. Exemplary reducing agents include hydrogen, either by itself or hydrogen produced from a compound that releases hydrogen. Suitable compounds that release hydrogen include without limitation NaH, MgH2, AlH3 and combinations thereof. To avoid the formation of nitrides, the reducing agent may not contain nitrogen. In addition, the reaction may be carried out in the presence of an alloying agent. For example, Ti alloys containing transition metals, V, Zr, Nb, or other elements such as Al, B, Sn, Fe, Si, or combinations thereof may be formed using a vaporizable metal halide that differs from MXi. The metal halides used in the inventive method may share the same halide, or contain combinations of halides or different halides.
A number of different reaction schemes may be utilized to form metal or, more specifically, titanium-based compositions. For example, TiX4 may be reacted with the reducing agent to form a subhalide, TiX3. In turn, TiX3 may be further reduced to form the reaction product. In some instances, TiX2 may be used as a starting or intermediate material for reduction to form the reaction product.
Unlike processes that require plasma processing, the inventive reaction is typically carried out at a temperature less than about 1500° C. In some instances, the reaction temperature may be less than about 1300° C. or less than about 1300° C., or in the range of about 1100° C. to 1300° C. While the reduction of the metal halide is usually carried out as a gas-phase reaction, the metal halide may be initially provided in a nongaseous form, e.g., as liquid droplets and/or solid particles, and vaporized to effect the reaction. Similarly, the reducing agent may be provided in a nongaseous form, e.g., as liquid droplets, before the agent is vaporized.
The reaction product may be deposited (e.g. solidified) on any of a number of substrate surfaces. For example, the substrate may be comprised of a plurality of individual or agglomerated particles. In addition, substrate may be comprised of a material that is compositionally the same or different from the reaction product. When different in composition from the reaction product, the substrate material may have a higher melting point than the reaction product. The substrate may also be comprised of the reaction product. The solid metallic composition formed is typically, but not necessarily, produced in the form of a plurality of particles.
As noted, the metallic compositions of the invention are substantially free from halides. Typically, the metallic compositions contain no more than about 1 atomic percent of halides. In some instances, halides represent no more than about 0.1 atomic percent of the compositions. Under certain conditions, the halide content in the metallic compositions does not exceed about 0.01 atomic percent. In addition, the compositions are typically substantially free from the reducing agent and any element therefrom. Optimal reaction conditions will yield a metallic composition comprised of a plurality of particles that is substantially free from oxygen, nitrogen, and carbon as well as halides.
The method of the invention is not particularly limited to a specific reactor design or configuration and, in fact, a number of different reactor designs may be employed. For example, moving bed reactors, rotary kiln reactors, entrained reactors,. falling wall reactors, and fluidized bed reactors may be used singly or in combination to carry out the inventive method. Typically, the reactor includes first and second reaction zones, wherein the first reaction zone is in fluid communication with the source of metal halide, and the second reaction zone is downstream from the first reaction zone. The first reaction zone may be located below or alongside the second reaction zone. In addition, the reaction zones may be located in a single chamber or in different chambers. In any case, the first and second reaction zones are typically maintained at different reaction temperatures.
The metal halide may be provided in gaseous form or in a nongaseous form wherein the metal halide is vaporized (prior to the reaction between the gaseous metal halide with the reducing agent) to effect the reaction between the gaseous metal halide and the reducing agent. For example, the metal halide may be provided as solid particles or as a liquid, such as in droplet form, before vaporization.
The reactor may be designed to collect and reuse any byproduct formed as a result of the inventive reaction. For example, when a halide byproduct is produced, a means may be provided to process the byproduct to recover a halogen gas. Similarly, when an element from the reducing agent is produced as a byproduct, the byproduct may be processed to recover the reducing agent. Preferably, the recovered reducing agent is reused to carry out the method in a continuous manner.
The invention is particularly well adapted to the production of spherical powders or granules of high-purity titanium alloys allowing for the use of standard powder processing techniques to form titanium alloy ingots. In this case, the overall method includes the purification of Ti by chemical vapor transport followed by redeposition of Ti and simultaneous reaction to form alloys with Al, V, or the other transition metals and elements noted above and as follows. One important aspect of the process is that it uses only low cost starting materials, minimum energy and a proven process technology to produce titanium alloy powders directly. In one embodiment, the method makes use of readily available and low cost starting material, TiCl4, and reacts it at elevated temperatures with a low cost titanium sponge, titanium scrap or recently deposited Ti on the bed pellets to generate titanium subhalides (TiCl2 and TiCl3) in situ. These subhalides are then disproportionated and reduced in a manner effective to form the reaction product such as by reaction with hydrogen to produce titanium metal. Schematically, the chemical reactions involved include:
Generation of Subhalides:
3TiCl4(g)+Ti→4TiCl3(g)
TiCl4(g)+Ti→2TiCl2(g)
Reduction or Disproportionation of Subhalides to Titanium:
4TiCl3(g)+6H2(g)→4Ti+12HCl(g)
2TiCl2(g)+2H2(g)→2Ti+4HCl(g)
2TiCl2(g)→TiCl4(g)+Ti
Based on experimentally determined values of thermochemical parameters for the titanium vapor species, the generation of titanium subhalides from the reaction of TiCl4 with Ti as a function of temperature has been calculated and is shown in
Similarly, the temperature necessary for the reduction of TiCl3 with H2 has been calculated as shown in
In practice, and in accordance with one embodiment of the invention for producing titanium and titanium alloys, the generation of titanium subhalides may be performed by passing TiCl4 over a hot fixed bed of titanium sponge and/or titanium scrap at a temperature in the range of about 900° to 1200° C. The vapors generated are mostly TiCl2, TiCl3, and unreacted TiCl4. These vapors will be mixed with hydrogen (and Al, V, or other precursor vapors, if required for alloying purposes) and fed directly to an upper fluidized bed containing small (˜100 μm diameter) seed particles of Ti as shown in
In a second embodiment, the TiCl4 is reduced directly by H2 in the bed to form TiCl3, which in turn, almost instantaneously is converted to Ti. While not intending to be limited thereto, all these reactions are thought to occur simultaneously in the reactor.
The formation of alloys is straightforward and one of the great advantages of the invention. Adding vapors of AlCl3 or VCl4 (also low-cost starting materials) to the H2 stream results in the reduction of these halides on the surface of the titanium granules in the bed to form TiAl or TiAlV alloys (or many other desirable alloy compositions) according to
In some cases, the addition of a second reactant halide may act as an accelerator for the overall reaction. Such is the case when VCl4 is added.
By controlling the partial pressure of the added vapors, powders of different compositions can be produced. Such powders may be produced in spherical form and ready for further processing by powder metallurgy. Although not limited thereto, the deposition of a wide variety of materials including titanium, chromium, silicon, aluminum, tungsten, niobium, zirconium, vanadium and other metal alloys such as titanium alloys having the general formula Ti-Mi Mii, where Mi and Mii are metals including any transition metal, may also be carried out. Other particularly beneficial alloys that may be prepared according to the invention include, in the case of titanium, for example, Ti—V, Ti—Al, and Ti—Al—V alloys. More specifically, such titanium alloys include without limitation alpha or near alpha alloys such as Ti—Ni—Mo, Ti—Al—Sn, Ti—Al—Mo—V, Ti—Al—Sn—Zr—Mo—Si, Ti—Al—Nb—Ta—Mo, Ti—Al—Sn—Zr—Mo, Ti—Al—Sn—Zr—Mo, and the like; alpha beta alloys such as Ti—Al, Ti—Al—V—Sn, Ti—Al—Mo, Ti—Al—Mo—Cr, Ti—Al—Sn—Zr—Mo, Ti—Al—Sn—Zr—Mo—Cr, Ti—V—Fe—Al, and the like; and beta alloys such as Ti—Mn, Ti—Mo—Zr—Sn, Ti—V—Fe—Al, Ti—V—Cr—Al—Sn, Ti—V—Cr—Al, Ti—Mo—V—Fe—Al, Ti—Al—V—Cr—Mo—Zr, and the like. Similarly, alloys of V, Nb, W, as well as the other metals noted above, may be prepared according to the inventive process.
The use of an atmospheric pressure fluidized bed chemical vapor deposition (FB-CVD) reactor leads to very high efficiency metal deposition due to the proven high heat and mass transfer available in the fluidized bed. Operation at atmospheric pressure both speeds the deposition process and minimizes costs associated with both low and high-pressure processes.
Impurities such as carbon and nitrogen in the titanium sponge (and scrap) should be relatively stable as carbide or nitride, and should not be transported in the gas-phase. While the fate of oxygen is less clear since, e.g., the formation of TiOCl2 is possible, according to thermochemical calculations, the formation of such oxygen-containing compounds is not favored.
The following examples are included to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the compositions and methods of the invention. Efforts have been made to ensure accuracy with respect to numbers but some experimental error and deviations should, of course, be allowed for. Unless indicated otherwise, proportions are percent by weight, temperature is measured in degrees centigrade and pressure is at or near atmospheric. All components were obtained from commercially-available sources unless otherwise indicated.
For the purposes of demonstrating the direct production of metallic and metal alloy compositions, a fluidized bed reactor (FBR) was used. As generally depicted in
In general, the operating parameters of the FBR were selected as described in the following examples. As the skilled artisan will appreciate, these parameters are dependent on a variety of factors including the reaction and the type of reactor and may be necessarily varied according to the reaction kinetics as well as differences in reactor design. It is within the level of skill in the art to vary such parameters as needed without resorting to undue experimentation.
As described above, the FBR was operated by introducing H2 (500 cc/min) and Ar (1200 cc/min) gas into the bottom of the FBR, providing a linear velocity in the bed of about 7 cm/sec. An alumina powder bed having a particle diameter of approx. 165 μm was used. The FBR was operated in the range of 1230-1250° C. Resublimed TiCl3 and Ar (150 cc/min) were introduced into the bottom of the FBR. Results for run nos. 1 and 2 are shown below in Table 1.
As described in Example 1 above, the FBR was operated by introducing H2 (500 cc/min) and Ar (1200 cc/min) gas into the bottom of the FBR, providing a linear velocity of about 7 cm/sec. An alumina powder bed having a particle diameter of approx. 165 μm was used. Resublimed TiCl3 and Ar (150 cc/min) were introduced into the bottom of the FBR. Results for run no. 3 in which TiCl3 and VCl3 were sequentially introduced into the FBR are shown below in Table 2. The total weight gain was 0.6 g, corresponding to an efficiency (i.e., the total weight gain divided by the sum of the Ti and V feed amounts) of about 90%.
The FBR was operated by introducing H2 (400 cc/min) and Ar (1200 cc/min) gas into the bottom of the FBR, providing a linear velocity of about 7 cm/sec. An alumina powder bed having a particle diameter of approx. 165 μm was used. The FBR was operated at 1250° C. Results for run no. 4 in which VCl4 was introduced into the FBR are shown below in Table 3.
As described above, a study was undertaken to determine the feasibility of producing Ti—Al—V alloys. The FBR was operated according to the above examples in which TiCl3, VCl3, and AlCl3 were introduced into the bottom of the FBR along with argon carrier gas. An alumina powder bed having a particle diameter of approx. 165 μm was used. The FBR was operated at 1250° C. Results for run nos. 5 and 6 are shown below in Table 4.
The FBR was operated according to the above examples in which TiCl4 and VCl4, were introduced into the bottom of the FBR along with argon carrier gas (in separate inlets of 250 cc/min that were mixed and supplied to the bottom of the FBR). Argon gas (250 cc/min) and H2 (100 cc/min) were separately introduced into the bottom of the reactor. An alumina powder bed having a particle diameter of approx. 175-250 μm was used. The FBR was operated at 1350° C. Results for run nos. 7-10 are shown below in Table 5.
The FBR was operated according to Example 5 above in which TiCl4 and VCl4, were introducted into the bottom of the FBR along with argon carrier gas (in separate inlets of 300 and 200 cc/min, respectively, that were mixed and supplied to the bottom of the FBR). Argon gas (250 cc/min) and H2 (1500 cc/min) were separately introduced into the bottom of the reactor. A separate H2 stream (250 cc/min) was introduced into the center of the FBR. An alumina powder bed having a particle diameter of approx. 175-250 μm was used. The FBR was operated at 1350° C. Results for run nos. 11 and 12 are shown below in Table 6.
*H2 introduced into the FBR via the central tube inlet
The FBR was operated according to Example 6 above in which TiCl4 and VCl4, were introduced into the bottom of the FBR along with argon carrier gas (in separate inlets of 300 and 200 cc/min, respectively, that were mixed and supplied to the bottom of the FBR). Argon gas (250 cc/min) and H2 (1500 cc/min) were separately introduced into the bottom of the reactor. A separate H2 stream (250 cc/min) was introduced into the center of the FBR. The bed contained Si sphere particles having a particle diameter of approx. 650 μm. The FBR was operated at 1260° C. Results for run no. 13 are shown below in Table 7.
*H2 introduced into the FBR via the central tube inlet
All patents, publications, and other published documents mentioned or referred to herein are incorporated by reference in their entireties.
It is to be understood that while the invention has been described in conjunction with the certain specific embodiments thereof, that the foregoing description as well as the examples, are intended to illustrate and not limit the scope of the invention. It should be further understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention, and further that other aspects, advantages and modifications will be apparent to those skilled in the art to which the invention pertains.
This application claims priority under 35 U.S.C. §119(e)(1) to Provisional U.S. Patent Application Ser. Nos. 60/504,369 and 60/504,652, both filed Sep. 19, 2003. The disclosures of the aforementioned applications are incorporated by reference in their entireties.
This invention was made with Government support under Contract No. MDA972-03-C-0032 awarded by the Defense Advanced Research Projects Agency. The Government has certain rights in this invention.
| Number | Date | Country | |
|---|---|---|---|
| 60504369 | Sep 2003 | US | |
| 60504652 | Sep 2003 | US |
