Pure Columbium

Section: Effect Of Surface Preparation On Corrosionmentioning

confidence: 99%

A Review of The Electrochemistry of Stressed Metals

Simnad

1950

“…Von Bolton (18) suggested that the oxide contained in tantalum could be removed by adding a little carbon to the metal and eliminating both the carbon and oxygen as CO in a vacuum at an elevated temperature. Recently Balke (2) stated that pure columbium could be made by heating columbium oxide with carbon in a carbon resistor furnace. The possibility of such a method had been mentioned by Rohn (14) who allowed carbides dissolved in a metal bath to react with an oxide at a high temperature in a vacuum.…”

Section: Review Of Previous Workmentioning

confidence: 99%

“…The results obtained with zirconium oxide and graphite, and with zirconium oxide plus zirconium carbide, indicate that this oxide is not reduced to a metal even at extremely high temperatures, a question which was recently brought up for discussion (2). The carbide-oxide mixture was heated to 1960~ which is well above the melting point of zirconium, and yet the briquettes contained 6.2 per cent carbon and 63.7 per cent zirconium which would indicate the presence of about 7.5 per cent oxygen.…”

Section: Reduction Of Other Metalsmentioning

confidence: 99%

Reactions of Carbon and Metal Oxides in a Vacuum

Kroll¹,

Schlechton²

1948

Vol. 93,No. 6 CARBON AND METAL OXIDES IN A VACUUM 247 conium containing 0.2 per-cent dissolved oxygen or more would be cold workable only with difficulty. It is known that nitrogen too increases the hardness of zirconium although to what extent has not yet been determined. ABSTRACT The literature on the reactions of carbon and metal oxides in a vacuum is reviewed and the results of an experimental study of the reduction of several metal oxides by carbon in a vacuum are reported. None of the refractory oxides studied were stable in contact with carbon in a vacuum at temperatures above 1380~Oxides of multivalent metals reacted at temperatures of 700~ or less. As a method for producing pure metals, best results were obtained with chromium, vanadium, columbium, and tantalum. A chromium metal analyzing 97 per cent Cr and a vanadium metal analyzing 93 per cent V were obtained. It is concluded that the vacuum reduction method would be practical only for the production of the more expensive and rare metals.

“…Niobium as powders or dendrites can be electrodeposited from oxide-fluoride melts (7,8) but only as a brittle rather impure material (9). Only NbP can be obtained from oxide-phosphate melts (10).…”

mentioning

confidence: 99%

“…Despite the considerable body of literature on the electrodeposition of niobium, this metal has not been electrodeposited previously in coherent sheets and its electrodeposition even as powder has been unsuccessful commercially. Niobium as powders or dendrites can be electrodeposited from oxide-fluoride melts (7,8) but only as a brittle rather impure material (9). Only NbP can be obtained from oxide-phosphate melts (10).…”

mentioning

confidence: 99%

Electrodeposition of Coherent Deposits of Refractory Metals

Mellors¹,

Senderoff²

1965

111

A general method has been found for the electrodeposition of coherent, dense deposits of refractory metals by electrolysis of molten salts. By dissolving the refractory metal fluoride in mixtures of alkali metal fluorides, one may deposit coherent thick coatings of chromium, hafnium, molybdenum, niobium, tantalum, tungsten, vanadium, and zirconium. Not only do the deposits in all cases have the theoretical density, but in most cases are extremely pure and equal to or better in mechanical properties than electron beam melted material available commercially. While differences exist from metal to metal in the details of the compositions of the electrolyte and the valence state of the refractory metal, the general process can be described in terms of one of the first metals studied, niobium. Niobium metal is eleetrodeposited from a solution about I0 w/o NbFs in a mixture of alkali fluorides at a temperature of about 775~ and a current density of about 50 ma/cm 2 with commercially pure niobium as anode material. Anode and cathode efHciencies are close to 100% and deposits with hardness of 85-100 DPH are obtained regularly. Deposits with densities of 99.8% of theoretical and higher are obtained and the throwing power of the bath is better than that usually associated with commercial nickel plating. There is no major restriction on substrates, since steel, stainless steel, graphite, copper, Hastelloy alloys, and others have been used. Thicknesses up to I/4 in. have been electrodeposited with a surprisingly smooth surface. The microstructures of the deposits are the typical columnar grain structure usually observed in electrodeposits without addition agents and their soundness has been confirmed by mechanical testing. Also, successful electrorefining has been accomplished.