EP0454522A1 - Process for preparing by milling a composite material comprising an oxide phase and a metallic phase - Google Patents

Abstract

Preparation of oxide-metal composite materials comprising an oxide phase and a metal phase. <??>The process for the preparation of composite materials consisting essentially of an oxide phase and of a metal phase is characterised in that at least one oxide precursor of the metal phase and at least one reducing agent precursor of the oxide phase are mixed and in that the mixture is subjected to high-energy mechanical milling without any external heat input,   - the quantity of reducing agent representing from 90 to 110 % of the stoichiometric quantity corresponding to the reaction of reduction of the oxide precursor by the reducing agent,   - the duration of milling being chosen so as to reduce at least 80 % of the metal atoms of the oxide precursor to the metallic state, pure or in alloy form. <??>The process of the invention is particularly advantageous for the preparation of oxide-metal composite materials whose mechanical or electrical properties or radiation-absorption properties are improved.

Description

The present invention relates to the preparation of oxide - metal composite materials comprising an oxide phase and a metal phase.

The oxide-metal composite materials, which comprise from 10 to 80% of metallic phase and from 90 to 20% of ceramic phase consisting essentially of oxides, simultaneously exhibit the properties of each of the constituent phases, that is to say a good chemical stability, high hardness, high melting point, good ductility, good breaking strength.

The development of these materials however presents difficulties linked to the problem of wetting between the metallic phase and the ceramic phase. This problem arises during the hot sintering operation which follows the step of grinding and mixing the initial ceramic and metal powders.

Attempts have been made to remedy these difficulties by using surface-active metals, preferably in the form of a pulverulent compound which can be decomposed under the action of heat (European patent 0 277 450).

The present inventors have now developed a process for the preparation of oxide-metal composite materials by in situ formation of the oxide.

This process leads to a better bond between the oxide phase and the metallic phase, which results in certain cases in a reciprocal solubility of the constituent elements of the metal and the oxide, while ensuring a homogeneous distribution of the different phases in the powders obtained. .

The subject of the present invention is a process for the preparation of oxide-metal composite materials and the materials obtained.

• la quantité d'agent réducteur représentant de 90 à 110 % de la quantité stoechiométrique correspondant à la réaction de réduction de l'oxyde précurseur par l'agent réducteur.
• la durée du broyage étant choisie de manière à réduire à l'état de métal, pur ou sous forme d'alliage, au moins 80 % des atomes de métal de l'oxyde précurseur.

According to the invention, the process for the preparation of composite materials essentially consisting of an oxide phase and a metallic phase, is characterized in that at least one oxide which is a precursor of the metallic phase is mixed and at least one reducing agent, precursor of the oxide phase, and in that the mixture is subjected to high-energy mechanical grinding, without external heat input,

• the quantity of reducing agent representing from 90 to 110% of the stoichiometric quantity corresponding to the reaction for reduction of the precursor oxide by the reducing agent.
• the duration of the grinding being chosen so as to reduce to the state of metal, pure or in the form of an alloy, at least 80% of the metal atoms of the precursor oxide.

Analysis of the X-ray diffraction patterns carried out on samples taken at different times during grinding makes it possible to determine the end of the reaction.

The reduction of the precursor oxide is obtained by grinding, without the need for an external supply of heat. It is however possible to heat the mixture introduced into the mill without harming the result, provided that the temperature remains below about 200 ° C. In some cases, it is advantageous to cool the reactor, the grinding causing a rise in temperature. The cooling then makes it possible to carry out the continuous grinding and, consequently, to obtain the desired degree of reduction more quickly.

Although a total reduction can be obtained by the process of the invention, it may be desirable to limit itself to a partial reduction, in certain cases, in order to make a subsequent sintering more efficient.

The process of the invention is particularly advantageous for the preparation of oxide-metal composite materials whose mechanical or electrical properties, or the radiation absorption properties are improved.

To this end, a metal element capable of forming an oxide advantageous for its hardness and its chemical and thermal stability will advantageously be used as reducing agent.
As reducing metal element, there may be mentioned aluminum, titanium, yttrium, zirconium, magnesium or thorium, taken alone or in the form of an alloy or mixture of powders containing at least 90% by weight of reducing element. Aluminum is a particularly preferred reducing agent. It can advantageously be used in the form of recycled aluminum or in the form of an alloy containing at least 90% by weight of aluminum.

The metal phase precursor oxides which can be used in the process of the present invention are oxides whose thermodynamic stability at room temperature is less than or equal to that of the oxide derived from the reducing agent. Among these oxides, there may be mentioned the oxides of the following elements: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ag and W.
These oxides can be used pure or in the form of an ore containing them.

High energy mechanical grinding can be carried out using different high energy grinders. Among these, there may be mentioned, by way of example, impact mills such as ball mills, annular ball mills, vibratory ball mills, planetary mills, roller mills, autogenous mills, attrition mills and gas or liquid jet disintegrators. For a more complete description of these crushers, reference may be made to "Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ad. Vol. 21, p 132 to 161".
As an example of such a grinder, mention may be made of the vibratory ball mill SPEX 8000® marketed by SPEX Industries Inc., USA, or the planetary ball mill Pulverisette 7® marketed by FRITSCH.

The present invention is described in more detail by the following examples, given by way of illustration, without limitation.

For examples 1 to 9, a planetary ball mill "Pulverisette 7" sold by Fritsch was used to carry out the high-energy mechanical grinding.

This crusher is equipped with two cylindrical jars with a capacity of 45 ml each, corresponding to a useful volume of 20 ml, and 15 mm diameter balls which are either stainless steel (18% Cr, 8% Ni), or tungsten carbide (93% WC + 6% Co). Each cylindrical jar contains 7 balls. The powder mixture is introduced into a glove box under an argon atmosphere, a teflon seal ensuring the seal. The effective centrifugal force resulting from the planetary movement corresponds to an acceleration of the order of 15 to 20 g. The grinder is at room temperature.

• la masse totale de poudre utilisée était de 3 g lorsque les jarres du broyeur étaient en acier, de 4 g lorsque les jarres étaient en carbure de tungstène ;
• le broyage a été effectué sous atmosphère d'argon.

In these examples 1 to 9,

• the total mass of powder used was 3 g when the jars of the mill were made of steel, 4 g when the jars were made of tungsten carbide;
• the grinding was carried out under an argon atmosphere.

EXAMPLE 1

Preparation of an Mn / Al₂O₃ material

La durée totale du broyage était de 3 heures.
Le rapport en masse de la poudre aux billes était de 1/31.
La perte en masse des billes au cours du broyage était de 0,16%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du manganèse α cubique : raie (330) d = 0,210 nm, raie (332) d = 0,1908 nm, raie (510) d = 0,1749 nm.
• les raies caractéristiques de l'alumine α rhomboédrique : raie (012) d = 0,3484 nm, raie (104) d = 0,2549 nm, raie (113) d = 0,210 nm (superposée à une raie de Mn α), raie (024) d = 0,1749 nm (superposée à une raie de Mn α), raie (116) d = 0,1602 nm, raie (214) d = 0,1406 nm, raie (300) d = 0,1377 nm.
  Les raies de MnO₂ et de Al ont disparu.

The jars and balls of the grinder were made of stainless steel.
2.121 g of MnO₂ and 0.879 g of Al were used, the amount of Al being calculated so as to reduce all of the MnO₂ oxide, according to the reaction scheme: $$\text{3MnO₂ + 4Al → 3Mn + 2Al₂O₃}$$

The total grinding time was 3 hours.
The mass ratio of the powder to the beads was 1/31.
The mass loss of the beads during grinding was 0.16%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the lines characteristic of cubic α manganese: line (330) d = 0.210 nm, line (332) d = 0.1908 nm, line (510) d = 0.1749 nm.
• the lines characteristic of rhombohedral alumina: line (012) d = 0.3484 nm, line (104) d = 0.2549 nm, line (113) d = 0.210 nm (superimposed on a line of Mn α), line (024) d = 0.1749 nm (superimposed on a line of Mn α), line (116) d = 0.1602 nm, line (214) d = 0.1406 nm, line (300) d = 0, 1377 nm.
  The lines of MnO₂ and Al have disappeared.

Traces of steel pollution from the jars and balls are visible.

EXAMPLE 2

Preparation of a V / Al₂O₃ material

La durée totale du broyage était de 3 heures.
Le rapport en masse de la poudre aux billes était de 1/31.
La perte en masse des billes au cours du broyage était de 0,26%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte les raies caractéristiques de l'alumine α rhomboédrique citées dans l'exemple 1 et les raies caractéristiques du vanadium cubique parmi lesquelles les plus intenses sont : raie (110) d = 0,2158 nm, raie (200) d = 0,1514 nm, raie (211) d = 0,1239 nm. Des traces de pollution par l'acier des jarres et des billes sont visibles. Les raies de V₂O₅ et d'Al ont disparu.The jars and balls of the grinder were made of stainless steel.
2.007 g of V₂O₅ and 0.993 g of Al were used, the amount of Al being calculated so as to reduce all of the oxide V₂O₅, according to the reaction scheme $$\text{3V₂O₅ + 10Al → 6V + 5Al₂O₃}$$

The total grinding time was 3 hours.
The mass ratio of the powder to the beads was 1/31.
The mass loss of the beads during grinding was 0.26%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises the lines characteristic of rhombohedral alumina α cited in Example 1 and the lines characteristic of cubic vanadium among which the most intense are: line (110) d = 0 , 2158 nm, line (200) d = 0.1514 nm, line (211) d = 0.1239 nm. Traces of steel pollution from the jars and balls are visible. The lines of V₂O₅ and Al have disappeared.

EXAMPLE 3

Preparation of a Cu / Al₂O₃ material

La durée totale du broyage était de 90 mn.
Le rapport en masse de la poudre aux billes était de 1/40.
La perte en masse des billes au cours du broyage était de 0,20%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du cuivre métal cubique : raie (111) d = 0,2086 nm, raie (200) d = 0,1807 nm, raie (220) d = 0,1278 nm, raie (311) d = 0,1090 nm, raie (222) d = 0,1043 nm.
• les raies caractéristiques de l'alumine α.

On note aussi la présence de carbure de tungstène.
Les raies de CuO et de Al ont disparu.The jars and balls of the grinder were made of tungsten carbide.
3.262 g of CuO and 0.738 g of Al were used, the amount of Al being calculated so as to reduce all of the CuO oxide, according to the reaction scheme $$\text{3CuO + 2Al → 3 Cu + Al₂O₃}$$

The total grinding time was 90 min.
The mass ratio of the powder to the beads was 1/40.
The mass loss of the beads during grinding was 0.20%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the characteristic lines of cubic metal copper: line (111) d = 0.2086 nm, line (200) d = 0.1807 nm, line (220) d = 0.1278 nm, line (311) d = 0.1090 nm, line (222) d = 0.1043 nm.
• the characteristic lines of α alumina.

We also note the presence of tungsten carbide.
The CuO and Al lines have disappeared.

EXAMPLE 4

Preparation of a Ni / Al₂O₃ material

La durée totale du broyage était de 90 mn.
Le rapport en masse de la poudre aux billes était de 1/42.
La perte en masse des billes au cours du broyage était de 0,03%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du Ni métallique : raie (111) d = 0,2037 nm, raie (200) d = 0,1765 nm, raie (220) d = 0,1248 nm, raie (311) d = 0,1064 nm, raie (222) d = 0,1019 nm.
• les raies caractéristiques de l'alumine α rhomboédrique

On note aussi la présence de carbure de tungstène.
Les raies de NiO et de Al ont disparu.The jars and balls of the grinder were made of tungsten carbide.
3.224 g of NiO and 0.776 g of Al were used, the amount of Al being calculated so as to reduce all of the NiO oxide, according to the reaction scheme $$\text{3NiO + 2Al → 3Ni + Al₂O₃}$$

The total grinding time was 90 min.
The mass ratio of the powder to the beads was 1/42.
The mass loss of the beads during grinding was 0.03%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the characteristic lines of metallic Ni: line (111) d = 0.2037 nm, line (200) d = 0.1765 nm, line (220) d = 0.1248 nm, line (311) d = 0.1064 nm , line (222) d = 0.1019 nm.
• the characteristic lines of rhombohedral alumina

We also note the presence of tungsten carbide.
The NiO and Al lines have disappeared.

EXAMPLE 5

Preparation of a Cr / Al₂O₃ material

La durée totale du broyage était de 90 mn.
Le rapport en masse de la poudre aux billes était de 1/42.
La perte en masse des billes au cours du broyage était de 0,02%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du chrome métallique α cubique : raie (110) d = 0,2046 nm, raie (200) d = 0,1445 nm, raie (211) d = 0,1181 nm, raie 220 d = 0,1021 nm.
• les raies caractéristiques de l'alumine α rhomboédrique.
  Les raies de Cr₂O₃ et de Al ont disparu. On note la présence de traces de carbure de tungstène.

The jars and balls of the grinder were made of tungsten carbide.
2.952 g of Cr₂O₃ and 1.048 g of Al were used, the amount of Al being calculated so as to reduce all of the oxide Cr₂O₃, according to the reaction scheme $$\text{Cr₂O₃ + 2Al → 2Cr + Al₂O₃}$$

The total grinding time was 90 min.
The mass ratio of the powder to the beads was 1/42.
The mass loss of the beads during grinding was 0.02%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the lines characteristic of cubic metallic chromium α: line (110) d = 0.2046 nm, line (200) d = 0.1445 nm, line (211) d = 0.1181 nm, line 220 d = 0.1021 nm .
• the characteristic lines of rhombohedral alumina.
  The lines of Cr₂O₃ and Al have disappeared. Note the presence of traces of tungsten carbide.

EXAMPLE 6

Preparation of a Zn / Al₂O₃ material

La durée totale du broyage était de 90 minutes.
Le rapport en masse de la poudre aux billes était de 1/42.
La perte en masse des billes au cours du broyage était de 0,02%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du zinc métallique hexagonal : raie (002) d = 0,2457 nm, raie (100) d = 0,2308 nm, raie (101) d = 0,2089 nm, raie (102) d = 0,1684 nm, raie (103) + raie (110) d = 0,1336 nm, raie (004) d = 0,1232 nm, raie (112) d = 0,1173 nm, raie (200) d = 0,1156 nm, raie (201) d = 0,1125 nm, raie (104) d = 0,1087 nm, raie (202) d = 0,1046 nm, raie (203) d = 0,0945 nm.
• les raies caractéristiques de l'alumine α rhomboédrique. Les raies de ZnO et de Al ont disparu. On note la présence de traces de carbure de tungstène.

The jars and balls of the grinder were made of tungsten carbide.
3.276 g of ZnO + 0.724 g of Al was used, the amount of Al being calculated so as to reduce all of the ZnO oxide, according to the reaction scheme $$\text{3ZnO + 2Al → 3Zn + Al₂O₃}$$

The total grinding time was 90 minutes.
The mass ratio of the powder to the beads was 1/42.
The mass loss of the beads during grinding was 0.02%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the lines characteristic of hexagonal metallic zinc: line (002) d = 0.2457 nm, line (100) d = 0.2308 nm, line (101) d = 0.2089 nm, line (102) d = 0.1684 nm, line (103) + line (110) d = 0.1336 nm, line (004) d = 0.1232 nm, line (112) d = 0.1173 nm, line (200) d = 0.1156 nm , line (201) d = 0.1125 nm, line (104) d = 0.1087 nm, line (202) d = 0.1046 nm, line (203) d = 0.0945 nm.
• the characteristic lines of rhombohedral alumina. The ZnO and Al lines have disappeared. Note the presence of traces of tungsten carbide.

EXAMPLE 7

Preparation of an Nb / Al₂O₃ material

La durée totale du broyage était de 90 minutes.
Le rapport en masse de la poudre aux billes était de 1/42.
La perte en masse des billes au cours du broyage était de 0,02%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du niobium cubique : raie (110) d = 0,2335 nm, raie (200) d = 0,1648 nm, raie (211) d = 0,1347 nm, raie (220) d = 0,1163 nm, raie (310) d = 0,1043 nm.
• les raies caractéristiques de l'alumine α rhomboédrique
  Les raies de Nb₂O₅ et de Al ont disparu. On note la présence de traces de carbure de tungstène.

The jars and balls of the grinder were made of tungsten carbide.
2.899 g of Nb₂O₂ and 1.011 g of Al were used, the amount of Al being calculated so as to reduce all of the oxide Nb₂O₂, according to the reaction scheme: $$\text{3Nb₂O₅ + 10Al → 6Nb + 5Al₂O₃}$$

The total grinding time was 90 minutes.
The mass ratio of the powder to the beads was 1/42.
The mass loss of the beads during grinding was 0.02%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the characteristic lines of cubic niobium: line (110) d = 0.2335 nm, line (200) d = 0.1648 nm, line (211) d = 0.1347 nm, line (220) d = 0.1163 nm , line (310) d = 0.1043 nm.
• the characteristic lines of rhombohedral alumina
  The lines of Nb₂O₅ and Al have disappeared. Note the presence of traces of tungsten carbide.

EXAMPLE 8

Preparation of a Fe + Cr / Al₂O₃ material

Fe et Cr formant un alliage.
La durée totale du broyage était de 3 heures.
Le rapport en masse de la poudre aux billes était de 1/31. La perte en masse des billes au cours du broyage était de 0,38%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu montre la présence d'alumine et d'une solution solide Fe-Cr dont les raies caractéristiques sont : raie (110) d = 0,2029 nm, raie (200) d = 0,1431 nm, raie (211) d = 0,1172 nm, raie (220) d = 0,1018 nm. La solution solide Fe-Cr est aussi bien visible par spectrométrie Mössbauer ⁵⁷Fe.The jars and balls of the grinder were made of stainless steel.
1.141 g of Fe₂O₃, 1.087 g of Cr₂O₃ and 0.772 g of Al were used, the amount of Al being calculated so as to reduce the entire mixture 50% of Fe₂O₃ + 50% of Cr₂O₃ (atomic), according to the scheme reactive $$\text{Fe₂O₃ + Cr₂O₃ + 4Al → 2Fe + 2Cr + 2Al₂O₃,}$$

Fe and Cr forming an alloy.
The total grinding time was 3 hours.
The mass ratio of the powder to the beads was 1/31. The mass loss of the beads during grinding was 0.38%.
The X-ray diffraction diagram (CoKα) of the product obtained shows the presence of alumina and a solid solution Fe-Cr whose characteristic lines are: line (110) d = 0.2029 nm, line (200) d = 0.1431 nm, line (211) d = 0.1172 nm, line (220) d = 0, 1018 nm. The solid Fe-Cr solution is also clearly visible by Mössbauer ⁵⁷Fe spectrometry.

EXAMPLE 9

Preparation of a Fe + Cr + Ni / Al₂O₃ material

La durée totale du broyage était de 3 heures.
Le rapport en masse de la poudre aux billes était de 1/32.
La perte en masse des billes au cours du broyage était de 0,37%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu montre la présence d'alumine et d'un alliage Fe-Ni-Cr dont les raies caractéristiques sont : raie (110) d = 0,2030 nm, raie (200) d = 0,1429 nm, raie (211) d = 0,1170 nm, raie (220) d = 0,1015 nm. L'alliage Fe-Ni-Cr (cubique centré) est aussi bien visible par spectrométrie Mössbauer ⁵⁷Fe.The jars and balls of the grinder were made of stainless steel.
1.688 g of Fe₂O₃ + 0.391 g of Cr₂O₃ + 0.171 of NiO + 0.750 g of Al were used, the amount of Al being calculated so as to completely reduce a mixture according to the reaction scheme $$\text{0.37Fe₂O₃ + 0.09Cr₂O₃ + 0.08NiO + 0.9733Al → 0.4866₅Al₂O₃ + 0.74Fe + 0.18Cr + 0.08Ni}$$

The total grinding time was 3 hours.
The mass ratio of the powder to the beads was 1/32.
The mass loss of the beads during grinding was 0.37%.
The X-ray diffraction diagram (CoKα) of the product obtained shows the presence of alumina and an Fe-Ni-Cr alloy whose characteristic lines are: line (110) d = 0.2030 nm, line (200) d = 0.1429 nm, line (211) d = 0.1170 nm, line (220) d = 0.1015 nm. The Fe-Ni-Cr alloy (centered cubic) is also well visible by Mössbauer ⁵⁷Fe spectrometry.

Examples 10 to 13 were carried out using a Spex 8000 ball mill, from Spex Industries Inc, USA.

This mill has a cylindrical container and hexagonal tungsten carbide balls. The material "tungsten carbide" contains the usual elements present in sintered materials in tungtene carbide, that is to say W, C, and as minor elements, Ta, Ti, Nb, Co. The cylinder has a diameter 2 1 / 4˝ (≅5.7 x 10⁻²m) and a height of 2 1 / 2˝ (≅ 6.3 x 10⁻²m). Mixtures of reducing agent and oxide powders are placed there, as well as two tungsten carbide balls (with a diameter of 7 / 16˝, ie ≅ 1.1 x 10⁻²m, total mass 19 x 10⁻³kg). The charge is prepared in a glove box under an argon or nitrogen atmosphere. The mass ratio of powder to the mass of the beads is of the order of 1/10. The powders are commercial powders with grain sizes of a few µm to a few tens of µm. The cylinder is closed in a glove box (a Teflon seal ensures sealing) and then placed in the grinder. The grinding is obtained by vigorous stirring of the container in three directions perpendicular to a frequency of about 20 Hz. The grinder is at room temperature.

EXAMPLE 10

Preparation of a W / TiO₂ material

• les raies caractéristiques du tungstène métallique cubique : raie (110) d = 0,2236 nm, raie (200) d = 0,1581 nm, raie (211) d = 0,1292 nm, raie (220) d = 0,1118 nm, raie (310) d = 0,1000 nm.
• les raies caractéristiques du rutile TiO₂ parmi lesquelles celles qui ne sont pas masquées par les raies du tungstène sont les suivantes : raie (110) d = 0,3304 nm, raie (101) d = 0,2487 nm, raie (210) d = 0,2078 nm, raie (211) d = 0,1701 nm, raie (220) d = 0,1654 nm, raie (002) d = 0,1476 nm, raie (301) d = 0,1376 nm, raie (112) d = 0,1341 nm.

The tungsten oxide and titanium powders were mixed in the proportions defined by the reaction scheme 2WO₃ + 3Ti → 2W + 3TiO₂.
The initial mass of powder was 2.79 g. The mass ratio of the powder to the beads was 1/9.
The grinding was carried out for 24 hours under a nitrogen atmosphere. The consumption of the beads was 0.3%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the characteristic lines of cubic metallic tungsten: line (110) d = 0.2236 nm, line (200) d = 0.1581 nm, line (211) d = 0.1292 nm, line (220) d = 0.1118 nm, line (310) d = 0.1000 nm.
• the characteristic lines of the TiO₂ rutile among which those which are not masked by the tungsten lines are the following: line (110) d = 0.3304 nm, line (101) d = 0.2487 nm, line (210) d = 0.2078 nm, line (211) d = 0.1701 nm, line (220) d = 0.1654 nm, line (002) d = 0.1476 nm, line (301) d = 0.1376 nm, line (112) d = 0.1341 nm.

The characteristic lines of WO₃ have disappeared. Note the presence of traces of tungsten carbide.

EXAMPLE 11

Preparation of a W / Al₂O₃ material

La masse initiale de poudre était de 2,43 g. Le rapport en masse de la poudre aux billes était de 1/7. Le broyage a été effectué pendant 24 heures sous atmosphère d'azote. La consommation de billes était de 2,6%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du tungstène métallique cubique: raie (110) d = 0,2234 nm, raie (200) d = 0,1578 nm, raie (211) d = 0,1290 nm, raie (220) d = 0,1116 nm, raie (310) d = 0,0999 nm.
• les raies caractéristiques de l'alumine α. On note aussi la présence de carbure de tungstène. Les raies caractéristiques de WO₃ et de l'aluminium ont disparu.

The jar and the balls of the mill were made of tungsten carbide.
The tungsten oxide and aluminum powders were mixed in the proportions defined by the reaction scheme: $$\text{WO₃ + 2Al → W + Al₂O₃}$$

The initial mass of powder was 2.43 g. The mass ratio of the powder to the beads was 1/7. The grinding was carried out for 24 hours under a nitrogen atmosphere. The consumption of beads was 2.6%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the characteristic lines of cubic metallic tungsten: line (110) d = 0.2234 nm, line (200) d = 0.1578 nm, line (211) d = 0.1290 nm, line (220) d = 0.11116 nm, line (310) d = 0.0999 nm.
• the characteristic lines of α alumina. We also note the presence of tungsten carbide. The characteristic lines of WO₃ and aluminum have disappeared.

EXAMPLE 12

Preparation of a Mo / Al₂O₃ material

This example was carried out using a SPEX 8000 ball mill.

La masse initiale de poudre était de 1,74 g. Le rapport en masse de la poudre aux billes était de 2/20. Le broyage a été effectué pendant 24 h sous atmosphère d'azote. La consommation des billes était de 2,3%.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du molybdène métallique cubique : raie (110) d = 0,2226 nm, raie (200) d = 0,1573 nm, raie (211) d = 0,1292 nm, raie (220) d = 0,1113 nm, raie (310) d = 0,0996 nm.
• les raies caractéristiques de l'alumine α. On note aussi la présence de carbure de tungstène. Les raies caractéristiques de MoO₃ et de l'aluminium ont disparu.

The jar and the balls of the mill were made of tungsten carbide.
The molybdenum oxide and aluminum powders were mixed in the proportions defined by the reaction scheme: $$\text{MoO₃ + 2Al → Mo + Al₂O₃}$$

The initial mass of powder was 1.74 g. The mass ratio of the powder to the beads was 2/20. The grinding was carried out for 24 h under a nitrogen atmosphere. The consumption of the beads was 2.3%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the characteristic lines of cubic metallic molybdenum: line (110) d = 0.2226 nm, line (200) d = 0.1573 nm, line (211) d = 0.1292 nm, line (220) d = 0.1113 nm, line (310) d = 0.0996 nm.
• the characteristic lines of α alumina. We also note the presence of tungsten carbide. The characteristic lines of MoO₃ and aluminum have disappeared.

EXAMPLE 13

La masse initiale de poudre était de 1,88 g. Le rapport en masse de la poudre aux billes était de 1/11. Le broyage a été effectué pendant 20 h sous atmosphère d'azote. La consommation de billes était de 0,8 %.
Le diagramme de diffraction des rayons X (CoKα) du produit obtenu comporte :

• les raies caractéristiques du fer métallique cubique : raie (110) d = 0,2030 nm, raie (200) d = 0,1433 nm, raie (211) d = 0,1172 nm, raie (220) d = 0,1015 nm,
• les raies caractéristiques de l'alumine α.

On note aussi la présence de carbure de tungstène.
Les raies caractéristiques de l'hématite α-Fe₂O₃ et de l'aluminium ont disparu. La spectrométrie Mössbauer (⁵⁷Fe) montre bien qu'il n'y a plus d'hématite. Elle met en évidence la présence d'un peu d'aluminium dans le fer cubique centré et d'un peu de fer dans l'alumine α.Preparation of a Fe / Al₂O₃ material
The jar and the balls of the mill were made of tungsten carbide.
The iron oxide and aluminum powders were mixed in the proportions defined by the reaction scheme: $$\text{Fe₂O₃ + 2Al → 2Fe + Al₂O₃}$$

The initial mass of powder was 1.88 g. The mass ratio of the powder to the beads was 1/11. The grinding was carried out for 20 h under nitrogen atmosphere. The consumption of beads was 0.8%.
The X-ray diffraction diagram (CoKα) of the product obtained comprises:

• the characteristic lines of cubic metallic iron: line (110) d = 0.2030 nm, line (200) d = 0.1433 nm, line (211) d = 0.1172 nm, line (220) d = 0.1015 nm,
• the characteristic lines of α alumina.

We also note the presence of tungsten carbide.
The characteristic lines of α-Fe₂O₃ hematite and aluminum have disappeared. Mössbauer spectrometry (⁵⁷Fe) clearly shows that there is no longer any hematite. It highlights the presence of a little aluminum in the centered cubic iron and a little iron in the α alumina.

Claims (4)

Process for the preparation of composite materials essentially consisting of an oxide phase and a metallic phase, characterized in that at least one oxide precursor of the metallic phase and at least one reducing agent, precursor of the oxide phase are mixed, and what the mixture is subjected to a high energy mechanical grinding, without external heat input - The quantity of reducing agent representing from 90 to 110% of the stoichiometric quantity corresponding to the reaction for reduction of the precursor oxide by the reducing agent. the duration of the grinding being chosen so as to reduce in the state of metal, pure or in the form of an alloy, at least 80% of the metal atoms of the precursor oxide. Process according to Claim 1, characterized in that the precursor oxide is chosen from the oxides of the following elements: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ag, W. Process according to either of Claims 1 and 2, characterized in that the reducing agent is chosen from aluminum, titanium, yttrium, zirconium, magnesium or thorium, taken alone or in the form of an alloy or a mixture of powders containing at least 90% by weight of reducing element. Composite materials obtained by a process according to any one of Claims 1 to 4.