PROCESS FOR PREPARING METAL POWDERS AND METAL HYDRIDE POWDERS OF THE ELEMENTS TI, ZR, HF, V, NB, TA AND CR

Abstract

A method for the production of metal powders or metal hydride powders of the elements Ti, Zr, Hf, V, Nb, Ta, and Cr is disclosed, whereby an oxide of the said elements is mixed with a reducing agent and said mixture, optionally with a hydrogen atmosphere (for the production fo metal hydrides), is heated until the reduction reaction commences, the reaction product is quenched, then washed and dried. The oxide used has an average particle size of 0.5 to 20 m, a BET specific surface of 0.5 to 20 m.sup.2/g and a minimum content of 94 wt %.

Claims

1. A process for preparing a zirconium metal powder or a zirconium hydride powder comprising the steps of: a) mixing zirconium oxide with solid calcium metal, solid magnesium metal, and/or solid barium metal, and mixtures of any two or more of the foregoing, to form a mixture, wherein the zirconium oxide has a mean particle size of 0.5 to 20 m, a BET specific surface area of 0.5 to 20 m.sup.2/g and a minimum content of 94 wt %; b) heating the mixture at 800 to 1400 C. in an oven, until a reduction reaction starts, to obtain a reaction product, wherein when forming a zirconium hydride, the reduction reaction occurs in a hydrogen atmosphere; c) leaching the reaction product to obtain a leached product; and d) washing and drying the leached product to yield the zirconium metal powder or zirconium hydride powder; wherein the zirconium metal powder or the zirconium hydride powder has an oxygen content of 1.6% or less, an ignition energy of 1J to 1 mJ, a burning time of 4 s per 50 cm to 3000 s per 50 cm and an ignition point of from 160 C. to 400 C.

2. The process of claim 1, wherein the reducing agent is magnesium metal.

3. The process of claim 1, wherein the reducing agent is calcium metal.

4. The process of claim 1, wherein the reducing agent is barium metal.

5. A process according to claim 1, wherein the reducing agent has a minimum content of 99 wt %, and/or wherein the leaching is with hydrochloric acid.

6. A process as in claim 1 wherein the zirconium oxide has one or more of the following properties: a BET specific surface area of 1 to 12 m.sup.2/g; a mean particle size of 1 to 6 m; and/or a minimum content of 96 wt %.

7. A process according to claim 1, wherein the zirconium oxide has a BET specific surface area of 1 to 8 m.sup.2/g and/or a minimum content of 99 wt %.

8. The process of claim 1, wherein the zirconium oxide has a BET specific surface area of 0.5 to 1.5 m.sup.2/g.

9. The process of claim 1, wherein the zirconium oxide has a BET specific surface area of 0.5 to 1.5 m.sup.2/g, a mean particle size of 4 to 6 m, and a minimum content of 99 wt %, and optionally wherein the reducing agent is calcium.

10. The process of claim 1, wherein the zirconium oxide has a BET specific surface area of 3 to 4 m.sup.2/g, a mean particle size of 3 to 5 m, and a minimum content of 99 wt %, and optionally wherein the reducing agent is magnesium.

11. A process according to claim 1, wherein the zirconium oxide has one or more of the following properties: the proportion of Fe and Al impurities in the oxide are each <0.2 wt %, calculated as the oxides; the proportion of Si impurities in the oxide is <1.5 wt %, calculated as SiO.sub.2; the proportion of Na impurities in the oxide is<0.05 wt %, calculated as Na.sub.2O; and/or the proportion of P impurities in the oxide is<0.2 wt %, calculated as P.sub.2O.sub.5.

12. A process according to claim 11, wherein the content of Fe and Al impurities in the zirconium oxide are each <0.1 wt %; calculated as the oxide of said Fe and Al impurities, and/or wherein the content of Si impurities in the zirconium oxide is <0.3 wt %, calculated as SiO.sub.2.

13. A process according to claim 1, wherein up to 15 wt % of the zirconium oxide is replaced by one or more additives selected from the group consisting of MgO, CaO, Y.sub.2O.sub.3 and CeO.sub.2, and/or wherein the zirconium oxide has a loss on ignition of at 1000 C. at constant weight of<1 wt %, and/or wherein the zirconium oxide has a tamped down bulk density according to EN ISO 787-11 of 800 to 1600 kg/m.sup.3.

14. The process of claim 1, wherein the process consists of said mixing, heating, leaching, washing and drying steps.

15. A process as in claim 1, wherein said zirconium metal powder has a mean particle size of 1 m to 8 m.

16. A process as in claim 1 wherein the zirconium metal powder or zirconium hydride powder has a BET specific surface area of 0.2 to 5 m.sup.2/g and/or a mean particle size of 1 to 15 m.

17. A process as in claim 1 wherein the zirconium metal powder or the zirconium hydride powder has a BET specific surface area of 0.2 to 5 m.sup.2/g and/or a mean particle size of 1 to 8 m.

18. A zirconium metal powder or a zirconium hydride powder having an oxygen content of 1.6% or less, an ignition energy of 1 J to 1 mJ, a burning time of 4 s per 50 cm to 3000 s per 50 cm and an ignition point of from 160 C. to 400 C.

19. A zirconium metal powder or a zirconium hydride powder as in claim 18 which has a BET specific surface area of 0.2 to 5 m.sup.2/g and/or a mean particle size of 1 to 15 m.

20. A zirconium metal powder or a zirconium hydride powder as in claim 18 which has a BET specific surface area of 0.2 to 5 m.sup.2/g and/or a mean particle size of 1 to 8 m.

21. A zirconium metal powder or a zirconium hydride powder as in claim 18 which is a zirconium metal powder.

22. A zirconium metal powder or a zirconium hydride powder as in claim 18 which is prepared by a process comprising the steps of: a) mixing zirconium oxide with solid calcium metal, solid magnesium metal, and/or solid barium metal, and mixtures of any two or more of the foregoing, to form a mixture, wherein the zirconium oxide has a mean particle size of 0.5 to 20 m, a BET specific surface area of 0.5 to 20 m.sup.2/g and a minimum content of 94 wt %; b) heating the mixture at 800 to 1400 C. in an oven, until a reduction reaction starts, to obtain a reaction product, wherein when forming a zirconium hydride, the reduction reaction occurs in a hydrogen atmosphere; c) leaching the reaction product to obtain a leached product; and d) washing and drying the leached product to yield the zirconium metal powder or zirconium hydride powder.

Description

EXAMPLE 1

Preparation of Zirconium Powder

[0020] 43 kg of ZrO.sub.2 (powdered zirconium oxide (natural baddeleyite)) with the following properties: ZrO.sub.2+HfO.sub.2 min. 99.0%; HfO.sub.2 1.0-2.0%; SiO.sub.2 max. 0.5%; TiO.sub.2 max. 0.3%; Fe.sub.2O.sub.3 max. 0.1%; loss on ignition max. 0.5%; mean particle size (using FSSS) 4-6 m; proportion of monoclinic crystal structure min. 95%; specific surface area (BET) 0.5-1.5 m.sup.2/g) and 31.5 kg of Ca (calcium in the form of granules with the following properties: Ca min. 99.3%; Mg max. 0.7%) were mixed for 20 minutes under an atmosphere of argon. Then the mixture was introduced into a container. The container was placed in an oven that was subsequently closed and filled with argon up to a pressure of 100 hPa above atmospheric pressure. The reaction oven was heated to a temperature of about 1250 C. over the course of one hour. As soon as the reaction material had reached the temperature of the oven, the reduction reaction started:

ZrO.sub.2+2 Ca.fwdarw.Zr+2 CaO

[0021] 60 minutes after switching on the oven heating system, it was then switched off. When the temperature had dropped to <50 C., the reaction material was removed from the crucible and leached with concentrated hydrochloric acid. A zirconium powder with the following analytical characteristics was obtained: Zr+Hf 96.1%; Hf 2.2%; O 0.7%; Si 0.21%; H 0.16%; Mg 0.11%; Ca 0.13%; Fe 0.07%; Al 0.1%; Cl 0.002%; mean particle size 4.9 m; particle size distribution d.sub.50 9.9 m; specific surface area 0.5 m.sup.2/g; ignition point 220 C.; burning time 80 sec/50 cm.

EXAMPLE 2

Preparation of Zirconium Powder

[0022] 36 kg of ZrO.sub.2 (powdered zirconium oxide with the following properties: ZrO.sub.2+HfO.sub.2 min. 99.0%; HfO.sub.2 1.0-2.0%; SiO.sub.2 max. 0.2%; TiO.sub.2 max. 0.25%; Fe.sub.2O.sub.3 max. 0.02%; loss on ignition max. 0.4%; mean particle size (using FSSS) 3-5 pm; proportion of monoclinic crystal structure min. 96%; specific surface area (BET) 3.0-4.0 m.sup.2/g) and 17 kg of Mg (magnesium in the form of granules with the following properties: Mg min. 99.8%; bulk density max. 0.4-0.5 g/cm.sup.3) were placed in a container in the oven, in the same way as described in example 1. The oven was heated to 1050 C. As soon as the reaction material reached the temperature of the oven, the reduction reaction started:

ZrO.sub.2+2 Mg.fwdarw.Zr+2 MgO

[0023] The oven heating system was switched off 20 minutes after the start of the reduction reaction. When the temperature had dropped to <50 C., the reaction material was removed from the crucible and leached with concentrated hydrochloric acid. A zirconium powder with the following analytical characteristics was obtained: Zr+Hf 91.7%; O 1.6%; Si 0.14%; H 0.13%; Mg 0.59%; Ca<0.001%; Fe 0.045%; mean particle size 2.5 m; particle size distribution d.sub.50 4.3 m; ignition point 175 C.; burning time 24 sec/50 cm.