THE INVESTIGATION OF THE ELECTROLYTIC BEHAVIOR OF TUNGSTEN DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By KURT THEURER, B.A., M.S. The Ohio State University 1955 Approved by: ^ A J L V A t (.A C Jo -Xdvi sera' Department of Chemistry ACKNOWLEDGEMENT The author* wishes to express his sincere appreciation t o his advisors Dr. Thomas R. Sweet, and Dr. W i l l i a m M. MacNevin, for their generous assistance an d guidance in this investigation. ii TABLE OF CONTENTS Page INTRODUCTION........................................ 1 HISTORICAL REVIEW................................... 2 THE UTILIZATION OF RADIOACTIVE TUNGSTEN AS A TRACER 10 Experimental Procedure........................11 Experimental Results and Discussion........ 14 Conclusi ons............. .................... 21 THE ELECTROLYTIC BEHAVIOR OF TUNGSTEN WITH VARIOUS METALLIC IONS AND ELECTRODES....... 25 Part I Metallic Ions....................... 25 Cobalt ................................ 26 Zinc...................................... 30 Palladium................................. 34 Rhenium................................... 3$ Part II Metallic Cathodes................. 40 Platinum........................ 40 Copper.................................... 41 Palladium................................. 46 Zinc...................................... 46 Cobalt................................... 49 Results and Conclusions..................... 55 THE ELECTROLYTIC BEHAVIOR OF TUNGSTEN ON OXIDE AND OXIDE FREE TUNGSTEN ELECTRODES.............. 5S The Effect of Cathode Oxides on the Rate of Deposition of Tungsten-Cobalt Deposits.. 59 1. Constant Current Density................ 59 Apparatus and Materials............. 59 Procedure............................. 6l Results and Conclusions............... 62 iii Page 2. Constant Cathode Potential.............. 62 Results and Conclusions............... 62 The Electrodeposition of Tungsten on an Oxide Free Tungsten Electrode............. 64 Apparatus and Materials................... 64- Pro cedure.................................. 69 Results and Conclusions................... 71 The Study of the Electrolytic Behavior of Tungsten from Current-Time Measurements... 71 1. Untreated Tungsten Surface............ 72 2. Flashed Tungsten Surface.............. 72 3. Untreated Tungsten Surface at Atmospheric Pressure................ 73 4. Untreated Tungsten Surface.. 73 5. Flashed Tungsten Surface.............. 34 6. Flame Oxidized Tungsten Surface....... 34 7. Electrolytically Oxidized Tungsten Surface............................. 34 9. Deposition of Copper on a Flame Oxidized Tungsten Surface.......... 35 10. Deposition of Copper on an Untreated Copper Surface...................... 35 Results and Conclusions..................... 35 SUMMARY............................................. 94 BIBLIOGRAPHY........................................ 95 AUTOBIOGRAPHY.............................. 93 iv LIST OF TABLES Table Page I Absorption Data for Cobalt-Tungsten Sample... 15 II Absorption Data for Tungstate Solution.. 16 III Absorption Data for Zinc-Tungsten Sample 19 TV Separation of Tungsten from Rhenium. ...... 22 V Cobalt Standardization............ 29 VI Electrolytic Data for Cobalt-Tungsten Deposits..................................... 31 VII Zinc Standardization.......................... 33 VIII Electrolytic Data for Zinc-Tungsten Deposits. 35 IX Absorption Data for Palladium-Tungsten Sample......... 36 X Activity Data for Rhenium-Tungsten Deposit... 39 XI Plating Conditions with Platinum Cathodes.... 41 XII Absorption Data for Platinum Cathode Deposits 42 XIII Plating Conditions with Copper Cathodes..... 42 XIV Aosorption Data for Copper Cathode Deposits.. 44 XV Plating Conditions with Palladium Cathodes... 46 XVI Absorption Data for Palladium Cathode Deposits..................... 47 XVII Plating Conditions with Cobalt Cathodes..... 49 XvTIII Absorption Data for Cobalt Cathode Deposits.. 50 XIX Cathode Gain at a Constant Current Density... 63 XX Cathode Gain at a Constant Cathode Potential. 63 v Table Page XXI Current-Time Data for the Deposition of Tungsten on an Untreated Tungsten Surface.................................... 73 XXII Current-Time Data for the Deposition of Tungsten on a Flashed Tungsten Surface.. 74 XXIII Current-Time Data for the Deposition of Tungsten on an Untreated Tungsten Surface at Atmospheric Pressure........... 76 XXIV Current-Time Data for the Deposition of Tungsten on an Untreated Tungsten Surface................................. 79 XXV Current-Time Data for the Deposition of Tungsten on a Flashed Tungsten Surface.. SO XXVI Current-Time Data for the Deposition of Tungsten on a Flame Oxidized Tungsten Surface.................................. Si XXVII Current-Time Data for the Deposition of Tungsten on an Electrolytically Oxidized Tungsten Surface.................. 82 XXVIII Current-Time Data for the Deposition of Tungsten on an Untreated Copper Surface. 86 XXIX Current-Time Data for the Deposition of Copper on a Flame Oxidized Tungsten Surface.................................. 88 XXX Current-Time Data for the Deposition of Copper on an Untreated Copper Surface... 89 vi LIST OF FIGURES Figure Page 1 Absorption Curves of an Electrolytic Cobalt-Tungsten Deposit.................. 17 2 Absorption Curve of a Standard Tungstate Soluti on.................................. 1^ 3 Absorption Curves of an Electrolytic Zinc-Tungsten Deposit.................... 20 4 Growth Curve for Tungstate Fraction and Decay Curve for Rhenium Fraction........ 23 5 Absorption Curve of an Electrolytic Palladium-Tungsten Deposit........ 37 6 Absorption Curves of Electrolytic Tungsten Deposits on Platinum Cathodes............ 43 7 Absorption Curves of Electrolytic Tungsten Deposits on Copper Cathodes.............. 45 & Absorption Curves of Electrolytic Tungsten Deposits on Palladium Cathodes........... 4d 9 Absorption Curves of Electrolytic Thungsten Deposits on Cobalt Cathodes....... *..... 51 10 Electrolytic Cell............................ 60 11 Electrolytic Vacuum Cell.................... 66 12 Vacuum System................................ 6d 13 Current-Time Curves for „he Deposition of Tungsten on an Untreated Tungsten Surface and on a Flashed Tungsten Surface....... 75 14 Current-Time Curve for the Deposition of Tungsten on an Untreated Tungsten Surface at Atmospheric Pressure. 77 15 Current-Time Curves for the Deposition of Tungsten on Various Tungsten Surfaces.... S3 vii Figure Page 16 Current-Time Curve for the Deposition of Tungsten on a Copper Surface....,......... 67 17 Current-Time Curve for the Deposition of Copper on an Untreated Copper Surface and on a Flame Oxidized Tungsten Surface 90 viii THE INVESTIGATION OF THE ELECTROLYTIC BEHAVIOR OF TUNGSTEN INTRODUCTION The purpose of this investigation was to study the conditions that inhibit the continued deposition of tungsten from an aqueous tungstate solution. The electrodeposition of tungsten, like that of molybdenum, tends to diminish rapidly or stop altogether as soon as a thin layer is deposited. No satisfactory explanation has been published. Foremost among the questions to be settled is whether the formation and presence of oxide is responsible for cessation of the deposition. Deposition of metals capable of inducing codeposition of tungsten and simultan­ eous oxide formation were studied. The influence of cathode material on the deposition has also been determined. 1 HISTORICAL REVIEW Electrolytic Deposition of Tungsten and Tungsten Alloys The problem of obtaining metallic tungsten by electrolytic reduction has been studied for almost a century. During this period many investigators have claimed success­ ful deposition of metallic tungsten. However the electro­ deposits were always so very thin that their chemical purity is questionable. The literature of tungsten plating goes back to 1367 when Zettnow (1) electrolysed a sodium tungstate solution and obtained a thin deposit of tungsten on an iron cathode. The electrolytic deposition of tungsten powder on a mercury cathode was successfully accomplished by Feree (2) In 1393, and by Jackson, Russell, and Merrill (3) in 1929. The electrolyte consisted of tungsten trioxide dissolved in hydrofluoric acid. A few milligrams of tungsten were deposited after eight hours. Fink and Jones (4) claimed successful deposition of tungsten from an alkaline carbonate bath. Holt (5) was able to show that a trace of "depolar­ ising metal" was necessary and that this metal was present as an impurity in the reagents used. Successful deposition of tungsten has been claimed from sodium hydroxide (6), citrate (7), and phosphate (3) solutions, but only very thin layers of metal were deposited. These layers were too thin to determine accurately the purity of the metal. A series of patents were issued to Armstrong and Menefee (9) which dealt with the deposition of tungsten from fluoride baths. A reaction product of tungsten trioxide or a derivative in an alkaline bifluoride bath constituted the electrolyte. Harford (10) deposited tungsten from an aqueous solution of an alkyl hydrocarbon polyamine (diethylene triamine), but attempts to repeat this work have been unsuccessful (11). Broughall (12) plated tungsten from liquid ammonia solutions, but Merlub-Sobel (13) was unable to repeat this work. Two patents were issued to Wolfram-Lampen AG, one for plating tungsten from pertungstic acid (WO^HgOg-HgO) dissolved in water, alcohol, or ether (14)> and the other