WO2015061159A1

WO2015061159A1 - Composite silica-metal oxide particles for magnesiothermic reduction

Info

Publication number: WO2015061159A1
Application number: PCT/US2014/061067
Authority: WO
Inventors: Vasgen A. Shamamian; Robert Larsen; Dimitris Elias Katsoulis; JR. Michael WEBERSKI; Mercouri Kanatzidis; Kyriaki POLYCHRONOPOULOU
Original assignee: Dow Corning Corporation; Northwestern University
Priority date: 2013-10-21
Filing date: 2014-10-17
Publication date: 2015-04-30

Abstract

New end products having silicon, metal silicide(s), and/or metal phase(s), and methods of making the same are disclosed. The methods may include ball milling silica particles with metal oxide particles to produce composite silica-metal-oxide particles, where the composite silica-metal-oxide particles comprise at least some silicon-oxygen bonds. The composite silica-metal-oxide particles may be contacted by a magnesium-containing material, thereby reducing at least some of the silicon-oxygen bonds of the composite silica- metal-oxide particles to silicon. At least some metal of the composite silica-metal-oxide particles may react with at least a portion of at least one of (I) the material having silicon- oxygen bonds and (II) the silicon, thereby producing at least one metal silicide. In turn, end products having silicon, metal silicide(s), and/or metal phase(s) may be recovered.

Description

COMPOSITE SILICA-METAL OXIDE PARTICLES FOR MAGNESIOTHERMIC

REDUCTION

BACKGROUND

[001] Silica (Si0₂) is a chemical compound that is most commonly found in nature as sand or quartz. Manufactured forms of silica include fused quartz, colloidal silica, silica gel, and aerogel, among others. Silica is used in glass for windows, drinking glasses, optical fibers for telecommunications and in ceramics, among others.

SUMMARY OF THE DISCLOSURE

[002] Broadly, the present patent application relates to methods of producing composite silica-metal oxide particles for use in magnesiothemiic reduction. After magnesiothermic reduction, an end product having at least one of silicon, metal silicide(s), metal phase(s), and/or metal oxide(s), may be recovered.

[003] Referring now to FIG. 1, composite silica-metal oxide particles may be produced (10) by mixing (15) metal oxide particles with silica particles. For instance, ball milling may be used to mix (15) the metal oxide particles and the silica particles. The ball mil ling may comprise, for example, rotating a container having the metal oxide particles and the silica particles. The rotating may occur for from several minutes to several hours, in one embodiment, the rotating occurs for at least 10 minutes. In another embodiment, the rotating occurs for at least 30 minutes. In yet another embodiment, the rotating occurs for at least 60 minutes ( I hour). In another embodiment, the rotating occurs for at least 3 hours. In yet another embodiment, the rotating occurs for at least 6 hours. In another embodiment, the rotating occurs for at least 9 hours. In one embodiment, the container is rotated at a speed of at least 50 RPM. In another embodiment, the container is rotated at a speed of at least 100 RPM, In yet another embodiment, the container is rotated at a speed of at least 150 RPM. In another embodiment, the container is rotated at a speed of at least 200 RPM. In yet another embodiment, the container is rotated at a speed of at least 250 RPM. In another embodiment, the container is rotated at a speed of at least 300 RPM.

[004] The ball milling may include using one or more mixing ball(s) ("mixing ball(s)"). The mixing ball(s) may add energy to the ball milling, which may facilitate at least one of (i) physical degradation of the metal oxide particles and/or the silica particles, and/or (ii) mixing of the metal oxide particles and/or the silica particles, and/or (iii) causing of a mechano-chemical reaction between of the metal oxide particles and/or the silica particles. The mixing bali(s) may be made of metal (s), plastic(s), and/or ceramic(s) (e.g., alumina, tungsten carbide), and multiple different mixing ball(s) of multiple different materials may be used during the bail milling. When used, the mass ratio of mixing ball(s) to total particles (sum of the metal oxide particles and the silica particles) may be tailored. In one embodiment, the mass ratio of mixing balls-to-total particles is in the range of from 1.8:1 to 3.8:1.

[005] The metal oxide particles may be any particles having one or more metal oxide(s) ("metal oxide(s)"), and which particles are suitable for producing composite silica- metal-oxide particles. In one embodiment, the metal oxide particles include metal oxide(s) selected from the group consisting of molybdenum (Mo) oxides, iron (Fe) oxides, nickel (Ni) oxides, cobalt (Co) oxides, chromium (Cr) oxides, titanium (Ti) oxides, copper (Cu) oxides, vanadium (V) oxides, lanthanum (La) oxides, and mixtures thereof. In one embodiment, the metal oxide particles are copper oxide particles. In another embodiment, the metal oxide particles are chromium oxide particles. In yet another embodiment, the metal oxide particles are molybdenum oxide particles. In another embodiment, the metal oxide particles are manganese oxide particles.

[006] The silica particles used to produce the composite silica-metal oxide particles may be any particles containing at least some silica (Si0₂), and which particles are suited for producing composite silica-metal oxide particles. The silica particles have silicon- oxygen bonds (Si-O bonds) due to, for example, the silica of those silica particles. In one embodiment, the silica particles comprise at least 25 wt. % silica (Si0₂). In another embodiment, the silica particles comprise at least 50 wt. % silica. In yet another embodiment, the silica particles comprise at least 75 wt. % silica. In another embodiment, the silica particles comprise at least 90 wt. % silica. In yet another embodiment, the silica particles comprise at least 95 wt. % silica. In another embodiment, the silica particles comprise at least 99 wt. % silica. In yet another embodiment, the silica particles consist essentially of silica.

[007] In one embodiment, the silica of the silica particles is a naturally occurring silica, such as diatomaceous earth silica, mined quartz, and silica-containing plant matter (e.g., rice hull ash, wheat husks), to name a few. The silica of the silica particles may be crystalline or amorphous. The silica particles may be porous, e.g., may have a specific surface area of at least 1 m /gram. [008] Due to the mixing (15), composite silica-nietal-oxide particles may he produced. The composite silica-metal oxide particles have at least some Si-0 bonds, which Si~0 bonds may be due to the silica. The Si-0 bonds may also be due to, or alternatively due to, the mixing step that produces the composite silica-metal oxide particles, whereby Si-0 bonds may be formed during the mixing (15), The composite silica-metal-oxide particles may be contacted (100) with a magnesium-containing material (e.g., Mg gas), thereby reducing at least some of the Si-0 bonds of the composite silica-metal oxide particles, as described below. Accordingly, an end product may be recovered (200), as described below. The end product may include one or more metal silicides ("metal silicide(s)"), one or more metal phases ("metal phase(s)"), and/or silicon, among other things, as described below. Thus, end products having distinct metal silicide(s) and/or metal phase(s), optionally with one or more distinct silicon phase(s), may be prepared. In some embodiments, the end product may be substantially free of silicon (e.g., when a product consists essentially of metal silicide(s) and/or metal phase(s)), i.e., a trace amount or less of elemental silicon is measured.

[009] To prepare the end product, the contacting step (100) may include reducing at least some of the silicon-oxygen bonds of the composite silica-metal-oxide particles to silicon via the magnesium-containing material. Concomitantly, at least some metal (M) of the composite silica-metal-oxide particles may react with at least a portion of at least one of (I) a material having silicon-oxygen bonds (e.g., silica) and (II) the silicon, thereby producing the metal silicide(s). Thus, the metal(s) of the composite silica-metal-oxide particles may correspond to the metal(s) of the metal silicide(s). For instance, when an iron oxide is used in the metal oxide particles, an iron silicide material may be produced due to the contacting step (100), which iron silicide material may be included in the end product. In one embodiment, metal silicide(s) include at least one monosilicide. In one embodiment, the metal silicide(s) include at least one disilicide. In one embodiment, the metal silicide(s) include at least one monosilicide and at least one disilicide. In one embodiment, the metal silicide(s) include a multiple metal silicide, wherein the multiple metal silicide is a metal silicide having at least two different metals. The end product may comprise other types of metal silicide(s), as shown below.

[0010] The end product may comprise metal phase(s) (e.g., a "metal only" crystalline phase), which metal phase(s) may be present in combination with the metal silicide(s), such as any of the metals mentioned below. The metal(s) of the metal oxide particles may correspond to the metal(s) of the metal phase(s). Such metal phase(s) are distinct from the metal silicide(s) of the end product (if any metal silicides are present). For instance, when iron oxide particles are used to produce the composite silica-metal-oxide particles and then contacted with a magnesium-containing material, a crystalline iron phase may be produced, which crystalline iron phase may be included in the end product. In one embodiment, a copper metal phase is present in the end product in combination with a copper silicide phase. In one embodiment, a titanium metal phase is present in the end product in combination with a titanium silicide phase. In one embodiment, a nickel metal phase is present in the end product in combination with a nickel silicide phase. In one embodiment, a NiTi phase is present in the end product in combination with one of a nickel silicide phase and/or a titanium silicide phase. In one embodiment, a molybdenum metal phase is present in the end product in combination with a molybdenum silicide phase.

[0011] Two or more different metal oxide particles (or metal oxide particles containing at least two different metals) may be used during the producing step (10), and, thus, the end product may comprise two or more metal silicide(s) and/or two or more metal phase(s), among other things. Similar principles apply when three or more metal oxide particles (or metal oxide particles containing at least three different metals) are used during the producing step (10). Thus, end products having a plurality of metal silicide(s) and/or a plurality of metal phase(s) may be recovered (200).

[0012] In one approach, the metal silicide(s) include a metal silicide of the formula M_xSi_y, where M is a metal. In one embodiment, M is Ti, and x is 1 and y is 2, or x is 5 and y is 3. In one embodiment, M is V, and x is 3 and y is 1, or x is 5 and y is 3. In one embodiment, M is Cu, and x is 3 and y is 1 , or x is 0.875 and y is 0.125. In one embodiment, M is Ni, and x is 1 and y is 2, or x is 3 and y is 1 , In one embodiment, M is Mo, and x is 3 and y is 1. In one embodiment, M is Fe, and x is 1 and y is 1, or x is 1 and y is 2. In one embodiment, M is Co, and x is 1 and y is 1, or x is 1 and y is 2. In one embodiment, M is Cr, and x is 1 and y is 1 , or x is 3 and y is 1. In one embodiment, M is Zr, and x is 1 and y is 1. In one embodiment, M is Mg, and x is 2 and y is 1. In one embodiment, M is La, and x is 1 and y is 2.

[0013] In one approach, the metal silicide(s) include a metal silicide of the formula Ml_xiM2_X2Siy, where Ml is a first metal, and M2 is a second metal, different than the first metal. In one embodiment, Ml is Ti, M2 is Ni, and xl is 6, x2 is 16 and y is 7. In one embodiment, Ml is V, M2 is Ni, and xl is 3, x2 is 2 and y is 1. or l is 6, x2 is 16 and y is 7.

[0014] The mixing (16) may be controlled to control the amount of metal silicide(s) and/or metal phase(s) in the end product. For instance, the ratio of silica particles to metal oxide particles may be controlled. When a relatively large amount of metal silicide(s) are needed, excess silica particles may be used. When a relatively small amount of metal silicide(s) and/or a large amount of metal phase(s) is needed, excess metal oxide particles may be used.

[0015] The composite silica-metal oxide particles may be contacted (100) with a magnesium-containing material, The "magnesium-containing material" may be a solid, liquid and/or gas that contains magnesium. As used herein, "magnesium-containing fluid" and the like means a fluid (liquid and/or gas) containing magnesium, in one embodiment, the magnesium-containing material contains a predominate amount of magnesium. In one embodiment, the magnesium-containing material contains more than 50% magnesium. In another embodiment, the magnesium-containing material contains at least 75% magnesium. In yet another embodiment, the magnesium-containing material contains at least 90% magnesium. In another embodiment, the magnesium-containing material contains at least 95% magnesium. In yet another embodiment, the magnesium-containing material contains at least 99% magnesium. In one embodiment, the magnesium-containing material is a fluid and consists essentially of magnesium optionally with one or more other inert fluids. In one embodiment, the magnesium-containing material is a gas.

[0016] The contacting step (100) may include reducing at least some of silicon-oxygen bonds of the composite silica-metal-oxide paiticies to silicon via the magnesium-containing material. Concomitantly, at least some metal (M) of the composite silica-metal-oxide particles may react with at least a portion of at least one of (1) a material having silicon- oxygen bonds (e.g., silica) and (II) the silicon, thereby producing metal silicide(s). The magnesium contacting step may not materially degrade the initial form of the composite silica-metal oxide particles, and, thus, the form of the end product may correspond to the initial form of the composite silica-metal oxide particles. Likewise, the average pore size, average pore volumes and/or specific surface area of the end product may also correspond to the composite silica-metal oxide particles. In one embodiment, the end product is a porous end product (e.g., porous particle(s)). In one embodiment, the end product has a specific surface area of at least 1 m /gram. In another embodiment, the end product has a specific surface area of at least 5 m²/gram. In another embodiment, the end product has a specific surface area of at least 25 m'/gram. In yet another embodiment, the end product has a specific surface area of at least 100 m /gram. The end product may have an average pore size of from 2 nanometers (nm) to 1 micron (μτη). The end product may have a pore volume of at least 0,01 mL/gram. Specific surface area, average pore size, and/or pore volume may be measured by BET analysis.

[0017] The contact step (100) may occur for a time and at a temperature suitable to reduce at least some of (e.g., a majority of) the silicon-oxygen bonds of the composite silica-metal oxide particles. The contacting step (100) may occur in any environment that facilitates reduction of such silicon-oxygen bonds via the magnesium-containing material. The contacting step may occur in a batch or a continuous process. The contacting step may be repeated, as necessary.

[0018] In one embodiment, the contacting step (100) occurs in an inert environment, such as a sealed vessel having an input and optionally an output. The input may be used to deliver the magnesium-containing material (e.g., a magnesium-containing fluid) into the vessel, the vessel holding composite silica-metal oxide particles. In one embodiment, the magnesium-containing material is magnesium-containing gas, which may be used with or without a carrier gas (e.g., argon as the carrier gas). The output may be used to remove effluent, such as a earner gas, so as to maintain the pressure within the sealed vessel. Thus, the contacting step (100) may comprise flowing a magnesium-containing gas into a vessel, wherein the vessel includes composite silica-metal oxide particles. In turn, the contacting step (100) may also comprise purging gas from the vessel Other configurations may be used to facilitate contacting the composite silica-metal oxide particles with the magnesium- containing material. Similar arrangements may be used when the magnesium-containing material is magnesium-containing liquid. As an example of a solid-to-solid reduction, solid magnesium and composite silica-metal oxide particles may be mixed (e.g., at elevated temperature).

[0019] The contacting step (100) may occur at any temperature that facilitates reduction of silicon-oxygen bonds by the magnesium-containing material. As may be appreciated, the thermodynamics and/or kinetics surrounding reduction of the silicon-oxygen bonds and production of metal silicide(s) may be more favorable at higher temperatures. In dne embodiment, the temperature of at least one of the composite silica-metal oxide particles and the magnesium-containing material is at least 200°C during at least a portion of the contacting step, In another embodiment, the temperature is at least 400°C, In yet another embodiment, the temperature is at least 600°C. In another embodiment, the temperature is at least 800°C. In yet another embodiment, the temperature is at least 900°C. Higher temperatures may be more useful when the magnesium-containing material is a magnesium- containing gas.

[0020] In one embodiment, the contacting step (100) comprises agitating (not illustrated) the product. Agitating may facilitate mass transfer so that the magnesium- containing material may more readily reach the silicon-oxygen bonds and/or a more- homogeneous end product is realized. The agitating may occur via any suitable agitation method and/or apparatus, such as via stirring, a rotary furnace, fluidized bed, vibratory apparatus, and the like.

[0021] As mentioned, concomitant to the contacting step (100) metal silicide(s) may be produced from the metal of the composite silica-metal oxide particles. In this regard, and as described above, the contacting step (100) may include reducing at least some of the silicon-oxygen bonds of the composite silica-metal oxide particles to silicon (Si) via the magnesium-containing material. For instance, the silica may be reduced to silicon, as shown in reaction (1):

(1) 2Mg + Si0₂→ 2MgO + Si

Concomitantly, some of the metal is in the form of a metal oxide (MO), and at least some of the metal oxide (MO) may be reduced to metal (M) via at least one of the silicon and the magnesium-containing material, as shown in equations (2) and (3), below.

(2) 2MO + Si→ 2M + Si0₂

(3) MO + Mg→ M: + MgO

Concomitantly, the metal (M) may react with the silica and/or the silicon to produce metal silicidefs), as shown in equations (4) and (5), below.

(4) M + Si→ M_xSiy

(5) M + Si0₂ + 2Mg -→ M_xSiy + 2MgO

Similar reactions may occur when the metal is not in oxide form.

[0022] After the contacting step (100), the end product may include at least some magnesium. In one approach, an end product includes at least some MgO, such as at least 0.1 wt. % MgO. In another embodiment, an end product includes at least 1.0 wt. % MgO. In one embodiment, an end product includes not greater than 75 wt. % MgO, In another embodiment, an end product includes not greater than 60 wt, % MgO,

[0023] In another embodiment, an end product comprises at least some magnesium silicates (e.g., Mg₂Si0₄). In one approach, an end product comprises at least some magnesium silicates, such as at least 0.1 wt. % of magnesium silicates. In another embodiment, an end product comprises at least some magnesium silicates, such as at least 1,0 wt. % magnesium silicates. In one embodiment, an end product comprises less than 50 wt. % magnesium silicates (e.g., not greater than 49.5 wt, % magnesium silicates).

[0024] In embodiments where MgO is produced and is contained in an end product, the MgO may be removed. T hus, a method may comprise removing at least some MgO from an end product. In one embodiment, the method comprises removing at least some MgO from an end product via an acid (e.g., via HC!), In one embodiment, substantially all of the MgO is removed from an end product. In other embodiments, tailored or preselected amounts of MgO may be removed via the removing step. Thus, an end product may comprise substantially no MgO (e.g. trace amounts or less), or may comprise tailored or preselected amounts of MgO. Similarly, Mg₂Si and/or magnesium silicates may be removed via the acid etch. The acid HC1 also appears to non-selectively etch (remove) LaSi₂, so end products solely containing the silicide of LaSi₂ may be used "as is" without etching the MgO (if present) and/or the magnesium silicates (if present) and/or Mg₂Si (if present).

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a flow chart illustrating one embodiment of a new method for producing end products having metal silicide(s), silicon, metal phase(s), and/or metal oxide(s), among others.

[0026] Production of Particulates Via Ball Milling and Magnesiothermic Reduction

[0027] Materials and Methods, Silica, metal oxides, and Mg were purchased commercially and were used as received. Magnesiothermic reduction experiments were carried out in stainless steel boats that were sealed in a stainless steel autoclave. The autoclave was then placed into a quartz tube under continuous nitrogen flow. Typically, the reductions were performed at 950 °C for 12 h. Intimate mixing of silica and metal oxides were conducted in a Retsch Planetary Bali Mill, Model PM 100 with alumina grinding jars and balls.

[0028] Physical and Analytical Measurements, The powder X-ray diffraction patterns were collected on an Inel CPS 120 (40kV, 20 mA) diffractometer equipped with graphite nionochromatized CuKa (1.5418A) radiation used in asymmetric reflection mode to obtain diffraction intensity data from 10 to 100° in 2 theta. Scanning electron microscopy (SEM) was performed using a Hitachi S3400 system. Powered samples were gently deposited on carbon tape and placed in the SEM chamber for image capture.

[0029] Representative Example 1-A - Molybdenum oxide

[0030] Under nitrogen, an alumina canister was charged with alumina spheres, 1.76 g (29.3 mmole) SiG₂, and 2.05 g (14.2 mmole) MoG₃. The alumina canister was sealed and brought out of the glovebox and placed into the ball mill. The powders were milled for 6 h at 300 rpm. The resulting powder was subsequently used in a magnesiothermic reduction reaction. Specifically, under nitrogen, 0.5 g of the resulting powder and 2,0 g Mg powder were placed in a stainless steel boat, which was sealed in a stainless steel autoclave. The autoclave was placed into a quartz tube under continuous nitrogen flow. The quartz tube containing the autoclave reactor was then placed in a tube furnace and heated to 950°C for 12 hours. After cooling to room temperature, the steel reactor was opened in air and the contents were washed with 6M HQ for 2 hours with stirring. After etching, the solid was washed with water, isolated via centrifuge, and dried at 70°C overnight. XRD showed that the recovered solid contained crystalline phases of Mo₃Si and Si.

[0031] Similar experiments were conducted with oxides of iron, nickel, lanthanum, cobalt, titanium, chromium and zirconium. Details are provided in Table 1, below (including the representative example 1-A.

- Details of Example 1 Experiments (part 1}

12.4 mmoles Ti0₂)

[0032] As shown above, particles with silicon, metal silicide(s) and/or metal phase(s) were produced in multiple instances. As shown, multiple metal oxides may be used, which can result in a recovered product having a plurality of metal silicides (e.g., 1-P with CrSi and ZrSi), which metal silicides may be mono-, di-, and/or tri- silicides, among others. Distinct metal phase(s) can also be present in addition to the metal silicide phase(s) (e.g., 1-1 with all of Mo₃Si, Fe, and Mo), It is expected that varying operating conditions would result in others of the above particle mixtures achieving similar results (e.g., two or more metal silicide phases being present; two or more distinct metal phases being present; multiple-metal silicides (e.g., Ml_xM2_ySi_z) being present). Thus, mixing metal oxide(s) with silica particles may be used to produce composite silica-metal oxide particles, which composite silica-metal oxide particles may be converted to particles having distinct metal silicide(s) and/or metal phase(s).

Example 2

[0033] Production of Particulates Via Ball Milling and Magnesiothermic Reduction

[0034] General Procedure for the Preparation of Composite Oxides and their Magnesiothermic Redaction, Under Argon, a tungsten carbide (WC) canister (38 mm tall x 41 nam diameter) was charged with two WC spheres (11 mm diameter), Si0₂ powder, and metal oxide powders. The WC canister was sealed and brought out of the glovebox and placed into a ball mill, The powders were milled for 1 , 6, or 9 hours. After milling, the resulting powder was subsequently used in a magnesiothermic reduction reaction. Under Argon, a steel reactor was charged with an amount of the milled composite oxide and Mg powder (Mg:0 total ^::: 1.0), The steel reactor was then sealed and placed inside an alumina tube inserted into a rotary furnace. The rotation was then engaged (8 rpm) and the furnace was heated at 20 °Cmin-l to 950 °C and held for 6.5 h. After cooling to room temperature, the steel reactor was opened in air and the contents were washed with 6M HCl for 2 h with stirring under Ar. After etching the dark brown/black solid was isolated via centrifuge (washed 3x 15mL ¾0; lx acetone).

[0035] Materials and Methods. The silica gel (Davisil 636), V205 (99.6%), NiO (99.99%), ΊΊ02 (99.8%), and Cu20 (97%) were purchased from Sigma Aldrich. Mg powder (99%) was purchased from Strem Chemicals. The silica was heated to 400 °C (1 °Cmin-l) overnight in air to remove the physisorbed water prior to use. The metal oxides and Mg powder were used as received. The ball mill used was a SPEX 8000D that completes 1060 cycles/minute.

Table 2 - Details of Example 2 Experiments (part 1)

7 able 3 - Bet ails oj ^"Example 2 E xperiments (part 2 )

"Crystalline phases detected by powder XRD after 6M HC1 etching.

^Diffraction peaks from Cu, NiOo.97, Mg₂Si0₄, and Cuo.s75Sio.125 were observed in the raw product prior to HCl-etch.

[0036] Like Example 1, particles with silicon, metal silicide(s) and/or metal phase(s) were produced in multiple instances. As shown, multiple metal oxides can be used, which can result in an end product having a plurality of metal siiicides, which metal silicides may be mono-, di~, and/or tri- silicides, among others. Distinct metal phase(s) can also be present in addition to the metal silicide phase(s). It is expected that varying operating conditions would result in others of the above particle mixtures achieving similar results (e.g., two or more metal silicide phases being present; two or more distinct metal phases being present; multiple-metal silicides (e.g., Ml_xM2_ySi_z) being present). Thus, mixing metal oxide(s) with silica particles may be used to produce composite silica-metal oxide particles, which composite silica-metal oxide particles may be converted to particles having metal silicide(s) and/or metal phase(s).

Claims

What is claimed is:

1 , A method comprising:

(a) mixing silica particles with metal oxide particles, thereby producing composite silica-metal-oxide particles, wherein the composite silica-metal-oxide particles comprise at least some silicon-oxygen bonds, and wherein the mixing comprises ball milling;

(b) contacting the composite silica-metal-oxide particles with a magnesium- containing material;

wherein the contacting step (b) comprises:

(i) reducing at least some of the sil icon-oxygen bonds of the composite silica-metal-oxide particles to silicon via the magnesium-containing material;

(c) concomitant to the contacting step (b), reacting at least some metal of the composite silica-metal-oxide particles with at least a portion of at least one of (I) a material having silicon-oxygen bonds and (II) the silicon, thereby producing at least one metal silicide;

(d) after the reacting step, recovering an end product having at least one of (i) silicon and (ii) the at least one metal silicide.

2, The method of claim 1 , wherein the ball milling comprises:

rotating a container comprising the silica particles and the metal oxide particles for at least 10 minutes and at a speed of at least 50 RPM.

3, The method of claim 1, wherein the at least one metal silicide comprises a monosilicide,

4, The method of claim 1, wherein the at least one metal silicide comprises a disilicide.

5, The method of claim 1 , wherein the at least one metal silicide comprises both monosilicides and disilicides,

6, The method of claim 1, wherein the end product comprises a crystalline metal phase distinct from the at least one metal silicide,

7. The method of claim 1, wherein the end product comprises at least two different crystalline metal phases, wherein each of the at least two different crystalline metal phases is distinct from the at least one metal silicide.

8. The method of claim 1. wherein the at least one metal silicide is at least two different metal silicides, and wherein the end product comprises a crystalline metal phase distinct from the at least two different metal silicides,

9. The method of claim I, wherein the at least one metal silicide comprises a multiple metal silicide, wherein the multiple metal siiicide is a metal silicide having at least two different metals.

10. The method of claim 1 , wherein the at least one metal silicide comprises a metal silicide of the formula M_xSi_y.

11. The method of claim 10, wherein M is Ti, and wherein x is 1 and y is 2, or x is 5 and y is 3.

12. The method of claim 10, wherein M is V, and wherein x is 3 and y is 1, or x is 5 and y *^s 3.

13. The method of claim 10, wherein M is Cu, and wherein x is 3 and y is 1, or x is 0.875 and y is 0.125.

14. The method of claim 10. wherein M is Ni, and wherein x is 1 and y is 2, or x is 3 and y is 1.

15. The method of claim 10, wherein M is Mo, and wherein x is 3 and is 1.

16. The method of claim 10, wherein M is Fe, and wherein x is 1 and y is 1, or x is 1 and y is 2.

17. The method of claim 10, wherein M is Co, and wherein x is 1 and y is 1, or x is 1 and y is 2.

18. The method of claim 10, wherein M is Cr, and wherein x is 1 and y is 1, or x is 3 and y is 1.

19. The method of claim 10. wherein M is Zr, and wherein x is 1 and y is 1.

20. The method of claim 10, wherein M is Mg, and wherein x is 2 and y is 1.

21. The method of claim 10, wherein M is La, and wherein x is 1 and y is 2.

22. The method of claim 1, wherein the at least one metal silicide comprises a metal silicide of the formula Ml_xsM2_X2Si_y.

23. The method of claim 22, wherein Ml is Ti and M2 is Ni, and wherein xl is 6, x2 is 16 and y is 7.

24. The method of claim 22, wherein Ml is V and M2 is Ni, and wherein xl is 3, x2 is 2 and y is 1 , or xl is 6. x2 is 16 and y is 7.

25. The method of any of claims 1-24. comprising etching the end product with an acid, wherein, due to the etching, at least some of at least one of MgO, g₂Si, and magnesium silicates are removed from the end product.

26. The method of claim 25, wherein the end product is in the form of porous particles.

27. The method of claim 26, wherein the porous particles comprise a specific surface area of at least 1 m /gram.

28. The method of claim 27, wherein the porous particle have an average pore size of from 2 nanometers (nm) to 1 micron (μηι), and a pore volume of at least 0.01 mL/gram.

29. The method of any of claims 1-24, wherein the end product is in the fonn of porous particles, wherein the porous particles comprise a specific surface area of at least 1 rn²/gram_s an average pore size of from 2 nanometers (nm) to 1 micron (μιη), and a pore volume of at least 0.01 niL/gram.