AU2005281918A1 - Deoxidisation of valve metal powders - Google Patents
Deoxidisation of valve metal powders Download PDFInfo
- Publication number
- AU2005281918A1 AU2005281918A1 AU2005281918A AU2005281918A AU2005281918A1 AU 2005281918 A1 AU2005281918 A1 AU 2005281918A1 AU 2005281918 A AU2005281918 A AU 2005281918A AU 2005281918 A AU2005281918 A AU 2005281918A AU 2005281918 A1 AU2005281918 A1 AU 2005281918A1
- Authority
- AU
- Australia
- Prior art keywords
- powder
- valve metal
- tantalum
- ppm
- deoxidation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000000843 powder Substances 0.000 title claims description 112
- 229910052751 metal Inorganic materials 0.000 title claims description 63
- 239000002184 metal Substances 0.000 title claims description 63
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 47
- 239000011734 sodium Substances 0.000 claims description 38
- 238000000034 method Methods 0.000 claims description 29
- 229910052708 sodium Inorganic materials 0.000 claims description 29
- 239000011575 calcium Substances 0.000 claims description 27
- 239000011777 magnesium Substances 0.000 claims description 27
- 239000003795 chemical substances by application Substances 0.000 claims description 26
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 24
- 229910052791 calcium Inorganic materials 0.000 claims description 24
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 22
- 229910052749 magnesium Inorganic materials 0.000 claims description 20
- 229910052700 potassium Inorganic materials 0.000 claims description 20
- 239000012535 impurity Substances 0.000 claims description 19
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 18
- 229910052746 lanthanum Inorganic materials 0.000 claims description 18
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 15
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 15
- 239000011591 potassium Substances 0.000 claims description 15
- 229910052684 Cerium Inorganic materials 0.000 claims description 9
- 229910052788 barium Inorganic materials 0.000 claims description 9
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 claims description 9
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 9
- 229910052727 yttrium Inorganic materials 0.000 claims description 9
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 9
- 229910052758 niobium Inorganic materials 0.000 claims description 8
- 239000010955 niobium Substances 0.000 claims description 8
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical group [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 8
- 229910044991 metal oxide Inorganic materials 0.000 claims description 6
- 150000004706 metal oxides Chemical class 0.000 claims description 6
- 229910001362 Ta alloys Inorganic materials 0.000 claims description 2
- RHDUVDHGVHBHCL-UHFFFAOYSA-N niobium tantalum Chemical compound [Nb].[Ta] RHDUVDHGVHBHCL-UHFFFAOYSA-N 0.000 claims description 2
- ZYTNDGXGVOZJBT-UHFFFAOYSA-N niobium Chemical group [Nb].[Nb].[Nb] ZYTNDGXGVOZJBT-UHFFFAOYSA-N 0.000 claims 1
- 229910052715 tantalum Inorganic materials 0.000 description 24
- 239000002253 acid Substances 0.000 description 21
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 21
- 229910052760 oxygen Inorganic materials 0.000 description 21
- 239000001301 oxygen Substances 0.000 description 21
- 238000005406 washing Methods 0.000 description 20
- 239000003990 capacitor Substances 0.000 description 15
- 238000006243 chemical reaction Methods 0.000 description 12
- 238000001816 cooling Methods 0.000 description 12
- 239000000463 material Substances 0.000 description 11
- 239000000203 mixture Substances 0.000 description 11
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 10
- 238000002161 passivation Methods 0.000 description 10
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 7
- 239000012300 argon atmosphere Substances 0.000 description 7
- 239000000292 calcium oxide Substances 0.000 description 7
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 7
- 229910017604 nitric acid Inorganic materials 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 6
- 150000002739 metals Chemical class 0.000 description 6
- 238000005245 sintering Methods 0.000 description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 5
- 239000003638 chemical reducing agent Substances 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 description 5
- 239000011574 phosphorus Substances 0.000 description 5
- 229910052698 phosphorus Inorganic materials 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 description 4
- 239000011698 potassium fluoride Substances 0.000 description 4
- 239000007858 starting material Substances 0.000 description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 3
- 229910000403 monosodium phosphate Inorganic materials 0.000 description 3
- 235000019799 monosodium phosphate Nutrition 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 239000001103 potassium chloride Substances 0.000 description 3
- 235000011164 potassium chloride Nutrition 0.000 description 3
- 239000011541 reaction mixture Substances 0.000 description 3
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 description 3
- 239000007784 solid electrolyte Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 229910001936 tantalum oxide Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 150000004673 fluoride salts Chemical class 0.000 description 2
- 229910052735 hafnium Inorganic materials 0.000 description 2
- 229910001026 inconel Inorganic materials 0.000 description 2
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 2
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 235000003270 potassium fluoride Nutrition 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000011833 salt mixture Substances 0.000 description 2
- PBCFLUZVCVVTBY-UHFFFAOYSA-N tantalum pentoxide Inorganic materials O=[Ta](=O)O[Ta](=O)=O PBCFLUZVCVVTBY-UHFFFAOYSA-N 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 101100235010 Arabidopsis thaliana LCV1 gene Proteins 0.000 description 1
- 101100352919 Caenorhabditis elegans ppm-2 gene Proteins 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000001636 atomic emission spectroscopy Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 230000003292 diminished effect Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- XONPDZSGENTBNJ-UHFFFAOYSA-N molecular hydrogen;sodium Chemical compound [Na].[H][H] XONPDZSGENTBNJ-UHFFFAOYSA-N 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/12—Dry methods smelting of sulfides or formation of mattes by gases
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
- B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/20—Obtaining niobium, tantalum or vanadium
- C22B34/24—Obtaining niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/04—Dry methods smelting of sulfides or formation of mattes by aluminium, other metals or silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/04—Electrodes or formation of dielectric layers thereon
- H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
- H01G9/052—Sintered electrodes
- H01G9/0525—Powder therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/15—Solid electrolytic capacitors
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Manufacturing & Machinery (AREA)
- Power Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Powder Metallurgy (AREA)
Description
CERTIFICATE OF VERIFICATION of 2.o 4r~qsno4d P.*D-S%, LCV1.t)(1 &JL S2TD, Ei4. state tjut to the best of my knowledge the attached document is a truead complete transation of Internationl PCT Applicaionl No. PCTEPZO0 92 O Date Signarure of traw~latc'r TOTAiL P.03 Deoxidation of valve metal powders The invention relates to a process for the deoxidation of valve metal powders, in particular of niobium powders, tantalum powders or their alloys, by treating the 5 valve metal powder with a deoxidising agent from the group calcium, barium, lanthanum, yttrium and cerium, and to valve metal powders distinguished by a low content of sodium, potassium and magnesium. Valve metals, which are to be understood as being especially niobium and its alloys, 10 tantalum and its alloys, as well as the further metals of groups IVb (Ti, Zr, Hf), Vb (V, Nb, Ta) and VIb (Cr, Mo, W) of the periodic system of the elements, and their alloys, are widely used in the manufacture of components. Particular mention is to be made of the use of niobium or tantalum in the 15 manufacture of capacitors, especially of solid electrolyte capacitors. In the manufacture of niobium or tantalum capacitors there are conventionally used as starting material corresponding metal powders, which are first compressed and then sintered in order to obtain a porous body. This body is anodised in a suitable electrolyte, whereby a dielectric oxide film forms on the sintered body. The physical 20 and chemical properties of the metal powders used have a critical influence on the properties of the capacitor. Critical characteristics are, for example, the specific surface, the content of impurities and, as the most important electrical parameter, the specific capacitance at a given forming voltage Uf. The specific capacitance is generally given in the unit microfarad * volt per gram (pFV/g). 25 General trends in circuit design in the electronics industry are towards ever higher clock frequencies at ever lower operating voltages with minimal electric losses. For the solid electrolyte capacitors used in such applications this means that ever lower forming voltages are used and at the same time ever lower leakage currents are 30 required.
-2 Valve metal powders which are to be used in the manufacture of capacitors must therefore meet ever higher demands, with the content of impurities being of great importance. This applies, for example, to the content of oxygen in the valve metal powder, which must not be too high, but also to metallic impurities, which have a 5 decisive influence on the leakage current properties of the capacitor. Such impurities are especially Na, K, Mg, but also C, Fe, Cr, Ni. However, the impurities Na, K and Mg in particular are introduced during preparation of the valve metal powders owing to the process that is used. Thus, for 10 example, the preparation of tantalum powder is generally still carried out today according to the reduction, known from US-A 2,950,185, of K 2 TaF 7 with sodium or potassium, which results in high contents of sodium and potassium in the product. According to US-A 4,141,720, tantalum powders having a high oxygen and sodium 15 content can be worked up by adding K 2 TaF 7 and alkali halides and heating the reaction mixture. The contents of oxygen, sodium and potassium can be reduced in that manner. However, even the powders so treated have a sodium content of from 10 to 87 ppm and a potassium content of from 112 to 289 ppm. 20 For the preparation of tantalum powder having a high specific surface and a minimal content of sodium and potassium, US-A 5 442 978 proposes reducing highly diluted
K
2 TaF 7 by the stepwise addition of sodium, the addition being carried out at a high rate. According to Example 1 it is possible in this manner to obtain a tantalum powder having a sodium content 3 ppm and a potassium content < 10 ppm. 25 However, a deoxidation step is necessary to adjust the oxygen content. To that end, the tantalum powder is mixed with magnesium and then heated, as a result of which magnesium is introduced into the tantalum powder. In addition to the reduction of fluoride salts of the valve metals with alkali metals, 30 oxides of the valve metals are increasingly being used as starting material recently, which oxides, as described in US 6,558,447 B1, are reduced with gaseous -3 magnesium to form the corresponding valve metal. The content of alkali metal can be kept low in this manner. However, there is an increased introduction of magnesium. In addition, this procedure generally requires a deoxidation step to reduce the oxygen content after the reduction, whereby the magnesium content in the 5 valve metal powder increases further. Owing to their high ionic conductivity and the formation of crystalline phases with the dielectric layer of amorphous valve metal oxide produced during capacitor manufacture, the impurities sodium, potassium and magnesium cause an increased 10 leakage current in the electric field or on thermal loading during the processing process of the capacitor manufacturer. This is particularly pronounced in the case of the ever thinner valve metal oxide layers of < 100 nm which capacitors have today. (1 V forming voltage corresponds, for example, to about 2 nm tantalum oxide film thickness). 15 The object of the present invention is accordingly to provide an economical process for the preparation of valve metal powders which makes available valve metal powders that are distinguished by a low content of the elements sodium, potassium and magnesium, which are critical for the residual current of a capacitor. During 20 capacitor manufacture, such valve metal powders form very uniform amorphous oxide layers at a high specific charge (> 35,000 CV/g). The object is achieved by subjecting the valve metal powder to a deoxidation step in which a deoxidising agent having low ionic mobility is used. 25 The invention accordingly provides a process for the deoxidation of valve metal powders, wherein calcium, barium, lanthanum, yttrium or cerium is used as the deoxidising agent. 30 The process according to the invention permits the preparation of valve metal powders that have a very low content of impurities having high ionic conductivity.
-4 As a result, no crystalline phases form with the resulting valve metal oxide during further processing of such valve metal powders to capacitors, so that defects in the oxide lattice and high residual currents are avoided. 5 The process according to the invention is suitable for the deoxidation of a wide variety of valve metal powders. Preference is given, however, to the deoxidation of niobium powder, tantalum powder or niobium-tantalum alloy powder, particularly preferably tantalum powder. 10 Accordingly, the valve metal is preferably tantalum. According to the invention, calcium, barium, lanthanum, yttrium or cerium is used as the deoxidising agent. Calcium or lanthanum is preferably employed, particularly preferably calcium. The valve metal powder to be deoxidised is mixed with the 15 deoxidising agent. This mixture of the valve metal powder with the deoxidising agent is heated to a temperature above the melting point of the deoxidising agent. It is preferably heated to a temperature that is at least 20*C above the melting point of the deoxidising 20 agent used. If calcium is used as the deoxidising agent, the deoxidation is preferably carried out at a temperature of from 880 to 1050*C, particularly preferably at a temperature of from 920 to 1000*C. When lanthanum is used, the preferred deoxidation temperature 25 is from 940 to I 150*C, particularly preferably from 980 to I 100*C. The deoxidation is preferably carried out at normal pressure. However, it is also possible to work at a lower pressure. The presence of hydrogen is not necessary in the process according to the invention. The process can be carried out, for example, 30 in vacuo or under inert gas, such as neon, argon or xenon. Nor does the process require a solvent or agent for suspending the solids in a liquid phase, such as, for -5 example, a salt melt, as is conventionally used in the reduction of valve metal compounds to valve metals. The amount of deoxidising agent added and the treatment time may vary within wide 5 limits and depend especially on the oxygen content of the valve metal powder to be deoxidised and on the deoxidation temperature. A deoxidation time of from 2 to 6 hours is generally sufficient. Preferably, deoxidation is carried out for from 2 to 4 hours. 10 There is preferably used a 1.1- to 3-fold stoichiometric excess of deoxidising agent, based on the amount that is theoretically required to reduce the oxygen content to 0. It has been shown that it is generally sufficient to use the deoxidising agent Ca in an amount of from 3 to 6 wt.% and the deoxidising agent La in an amount of from 6 to 15 14 wt.%, based on the amount of valve metal powder to be deoxidised, in order to achieve the desired lowering of the oxygen content and of the elements sodium, potassium and magnesium. There are preferably used from 3.5 to 5.9 wt.% of deoxidising agent Ca or from 9 to 11.5 wt.% La, based on the amount of valve metal powder to be deoxidised, particularly preferably from 4 to 4.7 wt.% Ca or from 10 to 20 11.5 wt.% La. After the deoxidation, the oxides of the deoxidising agent used that form during the deoxidation are preferably extracted with an acid. The acid used is preferably nitric acid or hydrochloric acid. It is to be noted that the use of sulfuric acid is to be 25 avoided when calcium is used as the deoxidising agent. The deoxidation according to the invention is preferably carried out in two steps. In this case, further deoxidising agent is added to the valve metal powder after the above-described deoxidation and acid extraction, and the mixture is subjected to the 30 described heat treatment again. The amount of deoxidising agent is chosen to be lower in the second deoxidation step than in the first deoxidation step and preferably -6 corresponds to a stoichiometric excess of from 1.3 to 2.0, based on the amount of oxygen in the valve metal powder. The deoxidising agent is used in the second deoxidation step preferably in an amount of from I to 3 wt.% when Ca is used as the deoxidising agent and in an amount of from 1.5 to 7 wt.% when La is used, based on 5 the amount of valve metal powder to be deoxidised. Preferably, from 1 to 1.3 wt.% Ca or from 3 to 6.1 wt.% La are used as the deoxidising agent, based on the amount of valve metal powder to be deoxidised. The process according to the invention is suitable for the deoxidation of valve metal 10 powders prepared by any method. For example, it is possible to deoxidise niobium and tantalum powders that are prepared by reduction of a fluoride salt of the valve metal by means of sodium in the presence of a diluting salt. Such a procedure is known from US-A 5,442,978, for example. 15 In the deoxidation of tantalum powders, particularly advantageous results are achieved when the tantalum powder used as starting material is obtained by reaction of K 2 TaF 7 with sodium in the presence of potassium chloride and potassium fluoride under the following reaction conditions: The salt mixture of K 2 TaF 7 , potassium chloride and potassium fluoride is placed in a test retort and heated preferably for 20 6 hours at 400*C in order to remove residual moisture from the salts. The test retort is then heated to a temperature of from 850*C to 950*C, preferably from 850*C to 920'C, particularly preferably to a temperature of 900*C, whereby the salt mixture liquefies. The liquid melt is stirred under an argon atmosphere (1050 hPa) for the purpose of homogenisation. When the reduction temperature is reached, liquid 25 sodium is added in portions. The total amount of sodium corresponds to a 3 to 6 wt.% excess, based on the amount of potassium heptafluorotantalate used. During the addition it must be ensured that the temperature in the test retort always remains in the range of the reduction temperature (T +/- 20*C). In order to adjust the surface of the precipitated tantalum powder, an additive that influences the surface tension 30 of the salt melt, for example anhydrous sodium sulfate, is added to the mixture before the first addition of sodium. When the reduction is complete, stirring is -7 continued for a further 0.5 to 3 hours in the range from 800*C to the reduction temperature. Preferably, stirring is continued for about 3 hours while simultaneously cooling from the reduction temperature to 800*C. The reaction material is cooled to room temperature and steam is passed through the test retort in order to passivate 5 excess sodium. The retort is then opened and the reaction material is removed and pre-comminuted by means of jaw breakers (< 5 cm, preferably < 2 cm). The inert salts are then removed by washing, and the resulting tantalum powder is dried. A step of doping with phosphorus can optionally be inserted here, in which the tantalum metal powder is treated with a (NH 4
)H
2
PO
4 solution in order to adjust the P 10 content of the finished tantalum metal powder. The powder is then exposed to a high temperature in vacuo. For example, heating is carried out for 30 minutes at from 1250*C to 1500*C, preferably from 1280*C to 1450*C, particularly preferably from 1280*C to 1360*C. The tantalum powder so prepared is then subjected to the deoxidation according to the invention. 15 If is, of course, also possible to use as starting materials valve metal powders which are obtained by reduction of the valve metal oxides using gaseous magnesium, as described in US 6,558,447 BI. 20 It has been shown that it is particularly advantageous to use calcium, barium, lanthanum, yttrium or cerium as the reducing agent in this case instead of magnesium. In a particularly preferred embodiment of the process according to the invention, 25 therefore, there is used as the valve metal powder to be deoxidised a valve metal powder that is obtained by reduction of a valve metal oxide using gaseous calcium, barium, lanthanum, yttrium or cerium. The procedure for the preparation of the corresponding valve metal powder is 30 according to US 6,558,447 BI, but calcium, barium, lanthanum, yttrium or cerium is used as the reducing agent.
- 8 For the preparation of a tantalum powder, which is preferably used, tantalum oxide (Ta 2 0 5 ) is, for example, placed on a tantalum gauze in a tantalum dish. A 1.1-fold stoichiometric amount, based on the oxygen content in the tantalum oxide, of 5 calcium, barium, lanthanum, yttrium or cerium is placed beneath the tantalum gauze. The reduction is carried out at a temperature that is sufficiently high to convert the reducing agent to the gaseous state. In order to increase the vapour pressure of the reducing agent at a given reduction temperature, it is possible to work at a reduced overall pressure in the reactor. Accordingly, the process is generally carried out at an 10 overall pressure in the reactor of less than or equal to 1000 mbar, preferably at an overall pressure in the reactor of less than or equal to 500 mbar. The reduction temperature is then preferably from 950 to I 100*C, particularly preferably from 980 to 1050*C. In general, reducing times of up to 8 hours are sufficient. When the reduction is complete, the reaction material is removed and the resulting oxide of the 15 reducing agent is extracted with nitric acid or hydrochloric acid. Analogously to the above-described procedure, a P-doping step may also optionally be inserted here. Finally, the valve metal powder so obtained is subjected to a deoxidation according to the invention. 20 Valve metal powders that are distinguished by a content of Na, K and Mg of less than 3 ppm, based on a capacitance of 10,000 pFV/g, are accessible for the first time by means of the deoxidation process according to the invention. The invention accordingly further provides valve metal powders that have a ratio of 25 the sum of the impurities sodium, potassium and magnesium to the capacitance of the valve metal powder of less than 3 ppm/10,000 pFV/g. The ratio of the sum of the impurities sodium, potassium and magnesium to the capacitance of the valve metal powder is preferably less than 2 ppm/10,000 pFV/g, 30 particularly preferably less than 1 ppm/10,000 tFV/g.
-9 The content of the impurities K, Na, Mg is determined after acid decomposition of the valve metal sample by means of HN0 3 /HF. K and Na are determined by the method of flame atom adsorption spectroscopy (FAAS) in an acetylene/air mixture, 5 and magnesium is determined by the ICP-OES method (inductive coupled plasma optical emission spectroscopy). For the acid decomposition, 2 ml of 65 wt.% HN0 3 and 10 ml of 40 wt.% HF are added to 1.0 g of the valve metal sample to be tested, and stirring is carried out for 10 hours at a temperature of 105*C under normal pressure. After cooling, 5 ml of 30 wt.% HCI are added, and the volume of the 10 sample is made up to 100 ml with H 2 0. The solution so obtained is then tested by means of FAAS or ICP-OES. The contents that are determined are indicated in ppm (parts per million). The capacitance of the valve metal powder is determined by the following 15 procedure: Cylindrical compressed bodies having a diameter of 4.1 mm and a length of 4.26 mm and having a compressed density of 4.8 g/cm 3 are each prepared from 0.296 g of a deoxidised valve metal powder, a tantalum wire of 0.2 mm diameter being inserted axially into the compression mould as contact wire before the valve metal powders are introduced. The compressed bodies are sintered at a sintering 20 temperature of from 1330'C to 1430*C for 10 minutes under a high vacuum (< 10- mbar) to form anodes. The anode bodies are immersed in 0.1 wt.% phosphoric acid and formed at a current intensity limited to 150 mA to a forming voltage of 30 V. After the current intensity has diminished, the voltage is maintained for a further 100 minutes. In order to measure the capacitor properties, a cathode of 25 18 wt.% sulfuric acid is used. Measurement is carried out at a frequency of 120 Hz. The residual current is then measured in phosphoric acid of conductivity 4300 pLS. The resulting values of the capacitance of the individual anode and the residual current of the individual anode are standardised to pFV/g, where pF = capacitance, V = forming voltage, g = anode mass, or pA/g, where ptA = measured residual 30 current and g = anode mass used, or A/pFV.
- 10 The valve metal powders according to the invention preferably have a capacitance of at least 35,000 pFV/g, particularly preferably of at least 40,000 pFV/g. 5 The valve metal powders according to the invention are preferably niobium or tantalum powders, which are optionally doped with one another and/or with one or more of the metals Ti, Mo, V, W, Hf and Zr. Further doping elements, such as, for example, phosphorus, are possible. 10 The valve metal powders according to the invention can be used for a wide variety of applications and are suitable in particular for the manufacture of solid electrolyte capacitors. The examples which follow serve to illustrate the invention in greater detail, the 15 examples being intended to facilitate comprehension of the principle according to the invention and not to limit it.
- 11 Examples Unless indicated otherwise, percentages are by weight (wt.%). 5 Example 1 A tantalum primary powder was prepared at a reduction temperature of 900*C starting from a mixture of 150 kg of K 2 TaF 7 , 136 kg of KCl, 150 kg of KF, 4 kg of a superfine tantalum powder and 300 g of Na 2
SO
4 in a nickel-coated INCONEL retort 10 by the increment-wise addition of sodium, analogously to US-A 5 442 978. The tantalum powder was isolated from the cooled and comminuted reaction mixture by washing with weakly acidified water, a cleaning treatment with a washing solution comprising sulfuric acid and hydrogen peroxide subsequently also being carried out. The material was doped with 20 ppm of phosphorus using a sodium dihydrogen 15 phosphate solution containing 1 mg of P per ml of solution. After drying, heat treatment was carried out under a high vacuum at 1430*C. Following this, the phosphorus content of the tantalum powder was adjusted to 60 ppm by means of the sodium dihydrogen phosphate solution (1 mg of P per ml). The powder exhibited the following impurities (in ppm): 20 Mg: < I ppm Na: 0.7 ppm K: 7 ppm 2 kg of this powder (starting powder) were mixed with 90 g (4.5 wt.%) of calcium 25 powder and heated at 980*C for 3 hours in a covered tantalum crucible in a retort under an argon atmosphere. After cooling and the controlled introduction of air for passivation, the reaction material was removed and calcium oxide that had formed was removed with a washing solution of dilute nitric acid and hydrogen peroxide solution. The washing solution was decanted off, and the powder on the suction 30 filter was washed with demineralised water until free of acid. The dried powder had an oxygen content of 2831 ppm.
- 12 1.8 kg of this powder were then subjected to a second deoxidation step. To that end, 19.2 g of calcium powder (based on the oxygen content, the 1.5-fold stoichiometric amount) were mixed into the powder and the mixture was likewise heated at 980*C 5 for 3 hours. After cooling and passivation, the CaO that had formed was again removed by acid washing, and the powder was washed until free of acid. The powder so prepared exhibited the following impurities: Mg: < I ppm 10 Na: I ppm K: 8 ppm The electric test gave a capacitance of 37,419 jFV/g at a sintering temperature of 1400 0 C. 15 Example 2 (comparison example) 2 kg of the starting powder from Example I were mixed with 50 g of magnesium turnings (2.5 wt.%) and heated at 980 0 C for 3 hours in a covered tantalum crucible 20 in a retort under an argon atmosphere. After cooling and the controlled introduction of air for passivation, the reaction material was removed and magnesium oxide that had formed was removed with a washing solution of dilute sulfuric acid and hydrogen peroxide solution. The washing solution was decanted off, and the powder on the suction filter was washed with demineralised water until free of acid. The 25 dried powder had an oxygen content of 2781 ppm. 1.8 kg of this powder were then subjected to a second deoxidation step. To that end, 11.4 g of magnesium turnings (based on the oxygen content, the 1.5-fold stoichiometric amount) were mixed into the powder and the mixture was likewise 30 heated at 980*C for 3 hours. After cooling and passivation, the MgO that had formed was again removed by acid washing, and the powder was washed until free of acid.
-13 The powder so prepared exhibited the following impurities: Mg: 8 ppm Na: 1 ppm 5 K: 6 ppm The electric test gave a capacitance of 38,261 piFV/g at a sintering temperature of 1400 0 C. 10 Example 3 200 g of the starting powder from Example I were mixed with 22 g of lanthanum powder (11 wt.%) and heated at 980*C for 3 hours in a covered tantalum crucible in a retort under an argon atmosphere. After cooling and the controlled introduction of 15 air for passivation, the reaction material was removed and lanthanum oxide that had formed was removed with a washing solution of dilute nitric acid and hydrogen peroxide solution. The washing solution was decanted off, and the powder on the suction filter was washed with demineralised water until free of acid. The dried powder had an oxygen content of 3045 ppm. 20 180 g of this powder were then subjected to a second deoxidation step. To that end, 6.5 g of lanthanum powder (based on the oxygen content, the 1.5-fold stoichiometric amount) were mixed into the powder and the mixture was likewise heated at 980*C for 3 hours. After cooling and passivation, the La 2 0 3 that had formed was again 25 removed by acid washing, and the powder was washed until free of acid. The powder so prepared exhibited the following impurities: Mg: < 1 ppm Na: 0.7 ppm 30 K: 8 ppm -14 The electric test gave a capacitance of 38,093 pFV/g at a sintering temperature of 1400 0 C. Example 4 5 A tantalum primary powder was prepared at a reduction temperature of 920 0 C starting from a mixture of 75 kg of K 2 TaF 7 , 125 kg of KCI, 225 kg of KF, 5 kg of a superfine tantalum powder and 500 g of Na 2
SO
4 in a nickel-coated INCONEL retort by the increment-wise addition of sodium, analogously to US-A 5 442 978. The 10 tantalum powder was isolated from the cooled and comminuted reaction mixture by washing with weakly acidified water, a cleaning treatment with a washing solution comprising sulfuric acid and hydrogen peroxide subsequently also being carried out. The material was doped with 100 ppm of phosphorus using a sodium dihydrogen phosphate solution containing 1 mg of P per ml of solution. After drying, heat 15 treatment was carried out under a high vacuum at 1280*C. The powder exhibited the following impurities (in ppm): Mg: < 1 ppm Na: I ppm K: 49 ppm 20 2 kg of this powder were mixed with 90 g (4.5 wt.%) of calcium powder and heated at 960*C for 3 hours in a covered tantalum crucible in a retort under an argon atmosphere. After cooling and the controlled introduction of air for passivation, the reaction material was removed and calcium oxide that had formed was removed with 25 a washing solution of dilute nitric acid and hydrogen peroxide solution. The washing solution was decanted off, and the powder on the suction filter was washed with demineralised water until free of acid. The dried powder had an oxygen content of 3700 ppm. 30 1.8 kg of this powder were then subjected to a second deoxidation step. To that end, 25 g of calcium powder (based on the oxygen content, the 1.5-fold stoichiometric - 15 amount) were mixed into the powder and the mixture was likewise heated at 960*C for 3 hours. After cooling and passivation, the CaO that had formed was again removed by acid washing, and the powder was washed until free of acid. 5 The powder so prepared exhibited the following impurities: Mg: < I ppm Na: 1 ppm K: 12 ppm 10 The electric test gave a capacitance of 59,764 pFV/g at a sintering temperature of 1400 0 C. Example 5 15 500 g of tantalum pentoxide (Ta 2
O
5 ) having a particle size < 400 ptm are placed on a tantalum gauze in a tantalum crucible. The 1.1-fold stoichiometric amount, based on the oxide content in the tantalum pentoxide, of calcium (249.4 g) is placed beneath the tantalum gauze. The tantalum dish is introduced into a sealable retort. 20 The reduction is carried out for 8 hours under an argon atmosphere at 980 0 C and at a reaction pressure of 600 mbar. The reaction material is removed, and the resulting calcium oxide is extracted with nitric acid. The tantalum powder, which has been washed until free of acid, is doped with 100 ppm of P on the suction filter using a sodium dihydrogen phosphate solution containing 1 mg of P per ml of solution, and 25 then dried. The tantalum powder so prepared has an oxygen content of 7143 ppm. 400 g of this powder are mixed with 18 g (4.5 wt.%) of calcium powder and heated at 960'C for 3 hours in a covered tantalum crucible in a retort under an argon atmosphere. After cooling and the controlled introduction of air for passivation, the 30 reaction material is removed and calcium oxide that has formed is removed with a -16 washing solution of dilute nitric acid and hydrogen peroxide solution. The washing solution is decanted off, and the powder on the suction filter is washed with demineralised water until free of acid. The dried powder has an oxygen content of 4953 ppm. 5 300 g of this powder are then subjected to a second deoxidation step. To that end, 5.6 g of calcium powder (based on the oxygen content, the 1.5-fold stoichiometric amount) are mixed into the powder and the mixture is likewise heated at 960*C for 3 hours. After cooling and passivation, the CaO that has formed is again removed by 10 acid washing, and the powder is washed until free of acid. The powder so prepared exhibits the following impurities: Mg: < I ppm Na: < 1 ppm 15 K: 2 ppm The electric test gave a capacitance of 70,391 CV/g at a sintering temperature of 1400 0
C.
Claims (10)
1. Process for the deoxidation of valve metal powders, characterised in that calcium, barium, lanthanum, yttrium or cerium is used as deoxidising agent. 5
2. Process according to claim 1, characterised in that the valve metal powder is a niobium powder, a tantalum powder or a niobium-tantalum alloy powder.
3. Process according to either claim 1 or 2, characterised in that calcium or 10 lanthanum is used as deoxidising agent.
4. Process according to any one of claims 1 to 3, characterised in that the deoxidising agent is calcium and the deoxidation is carried out at a temperature of from 880 to 1050*C. 15
5. Process according to any one of claims I to 3, characterised in that the deoxidising agent is lanthanum and the deoxidation is carried out at a temperature of from 940 to 11 50*C. 20
6. Process according to any one of claims I to 5, characterised in that the deoxidation is carried out in two steps.
7. Process according to any one of claims 1 to 6, characterised in that valve metal powder obtained by reduction of a valve metal oxide with gaseous 25 calcium, barium, lanthanum, yttrium or cerium is deoxidised.
8. Valve metal powder, characterised in that the ratio of the sum of the impurities sodium, potassium and magnesium to the capacitance of the valve metal powder is less than 3 ppm/10,000 pFV/g. 30 -18
9. Valve metal powder according to claim 8, characterised in that the ratio of the sum of the impurities sodium, potassium and magnesium to the capacitance of the valve metal powder is less than 1 ppm/10,000 pFV/g. 5
10. Valve metal powder according to claim 8 or 9, characterised in that it is a niobium or tantalum powder.
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DE102004043343.7 | 2004-09-08 | ||
DE102004043343A DE102004043343A1 (en) | 2004-09-08 | 2004-09-08 | Deoxidation of valve metal powders |
PCT/EP2005/009230 WO2006027119A2 (en) | 2004-09-08 | 2005-08-26 | Deoxidisation of valve metal powders |
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AU2005281918A1 true AU2005281918A1 (en) | 2006-03-16 |
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AU2005281918A Abandoned AU2005281918A1 (en) | 2004-09-08 | 2005-08-26 | Deoxidisation of valve metal powders |
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US (1) | US20080011124A1 (en) |
EP (1) | EP1793950A2 (en) |
JP (1) | JP2008512568A (en) |
KR (1) | KR20070098988A (en) |
CN (1) | CN101052488A (en) |
AU (1) | AU2005281918A1 (en) |
BR (1) | BRPI0515172A (en) |
DE (1) | DE102004043343A1 (en) |
IL (1) | IL181782A0 (en) |
MX (1) | MX2007002717A (en) |
RU (2) | RU2404881C2 (en) |
SV (1) | SV2006002222A (en) |
TW (1) | TW200624200A (en) |
WO (1) | WO2006027119A2 (en) |
ZA (1) | ZA200701902B (en) |
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CN101574741B (en) * | 2009-06-25 | 2011-05-18 | 宁夏东方钽业股份有限公司 | Preparation method of tantalum powder for capacitor |
US10737320B2 (en) | 2014-02-27 | 2020-08-11 | Ningxia Orient Tantalum Industry Co., Ltd. | High-purity tantalum powder and preparation method thereof |
FR3038623B1 (en) * | 2015-07-10 | 2017-06-30 | Fives | PROCESS FOR REMOVING OXIDES PRESENT AT THE SURFACE OF NODULES OF A METAL POWDER BEFORE USING THE SAME IN AN INDUSTRIAL PROCESS |
CN107236868B (en) | 2017-05-23 | 2019-02-26 | 东北大学 | A kind of method of multistage drastic reduction preparation high-melting metal powder |
CN112828279B (en) * | 2020-12-31 | 2022-08-12 | 昆明理工大学 | Metal powder gas phase deoxidation method |
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NL252366A (en) * | 1958-06-13 | |||
US4141720A (en) * | 1978-05-16 | 1979-02-27 | Nrc, Inc. | Tantalum powder reclaiming |
DE3590793T1 (en) * | 1985-05-27 | 1987-09-17 | ||
US4722756A (en) * | 1987-02-27 | 1988-02-02 | Cabot Corp | Method for deoxidizing tantalum material |
US5022935A (en) * | 1988-09-23 | 1991-06-11 | Rmi Titanium Company | Deoxidation of a refractory metal |
US4923531A (en) * | 1988-09-23 | 1990-05-08 | Rmi Company | Deoxidation of titanium and similar metals using a deoxidant in a molten metal carrier |
EP0528974B1 (en) * | 1990-05-17 | 1997-07-23 | Cabot Corporation | Method of producing high surface area low metal impurity tantalum powder |
US5448447A (en) * | 1993-04-26 | 1995-09-05 | Cabot Corporation | Process for making an improved tantalum powder and high capacitance low leakage electrode made therefrom |
US5442978A (en) * | 1994-05-19 | 1995-08-22 | H. C. Starck, Inc. | Tantalum production via a reduction of K2TAF7, with diluent salt, with reducing agent provided in a fast series of slug additions |
US5993513A (en) * | 1996-04-05 | 1999-11-30 | Cabot Corporation | Method for controlling the oxygen content in valve metal materials |
US6051326A (en) * | 1997-04-26 | 2000-04-18 | Cabot Corporation | Valve metal compositions and method |
DE19847012A1 (en) * | 1998-10-13 | 2000-04-20 | Starck H C Gmbh Co Kg | Niobium powder and process for its manufacture |
US6558447B1 (en) * | 1999-05-05 | 2003-05-06 | H.C. Starck, Inc. | Metal powders produced by the reduction of the oxides with gaseous magnesium |
DE19953946A1 (en) * | 1999-11-09 | 2001-05-10 | Starck H C Gmbh Co Kg | Capacitor powder |
DE10030387A1 (en) * | 2000-06-21 | 2002-01-03 | Starck H C Gmbh Co Kg | capacitor powder |
US20030104923A1 (en) * | 2001-05-15 | 2003-06-05 | Showa Denko K.K. | Niobium oxide powder, niobium oxide sintered body and capacitor using the sintered body |
CN1169643C (en) * | 2001-09-29 | 2004-10-06 | 宁夏东方钽业股份有限公司 | Preparation method of high specific surface area tantalum powder and/or niobium powder |
JP3610942B2 (en) * | 2001-10-12 | 2005-01-19 | 住友金属鉱山株式会社 | Method for producing niobium and / or tantalum powder |
DE10307716B4 (en) * | 2002-03-12 | 2021-11-18 | Taniobis Gmbh | Valve metal powders and processes for their manufacture |
US6802884B2 (en) * | 2002-05-21 | 2004-10-12 | H.C. Starck, Inc. | Tantalum-silicon and niobium-silicon substrates for capacitor anodes |
BR0204587A (en) * | 2002-11-04 | 2004-06-29 | Cbmm Sa | High Surface Area Niobium and / or Tantalum Powder Production Process |
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- 2002-08-26 US US11/574,675 patent/US20080011124A1/en not_active Abandoned
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- 2004-09-08 DE DE102004043343A patent/DE102004043343A1/en not_active Withdrawn
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- 2005-08-26 CN CNA200580037624XA patent/CN101052488A/en active Pending
- 2005-08-26 MX MX2007002717A patent/MX2007002717A/en unknown
- 2005-08-26 AU AU2005281918A patent/AU2005281918A1/en not_active Abandoned
- 2005-08-26 WO PCT/EP2005/009230 patent/WO2006027119A2/en active Application Filing
- 2005-08-26 JP JP2007530614A patent/JP2008512568A/en not_active Withdrawn
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ZA200701902B (en) | 2008-08-27 |
CN101052488A (en) | 2007-10-10 |
MX2007002717A (en) | 2008-03-11 |
BRPI0515172A (en) | 2008-07-08 |
IL181782A0 (en) | 2007-07-04 |
DE102004043343A1 (en) | 2006-03-23 |
JP2008512568A (en) | 2008-04-24 |
RU2007112796A (en) | 2008-10-20 |
TW200624200A (en) | 2006-07-16 |
RU2010116085A (en) | 2011-10-27 |
WO2006027119A3 (en) | 2006-06-15 |
EP1793950A2 (en) | 2007-06-13 |
SV2006002222A (en) | 2006-05-25 |
WO2006027119A2 (en) | 2006-03-16 |
KR20070098988A (en) | 2007-10-08 |
US20080011124A1 (en) | 2008-01-17 |
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