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Influence of Chemical Additions on the Reduction of Tungsten Oxides

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Influence of Chemical Additions on the Reduction of Tungsten Oxides Influence of chemical additions on the reduction of tungsten oxides Citation for published version (APA): Spier, H. L. (1961). Influence of chemical additions on the reduction of tungsten oxides. Technische Hogeschool Eindhoven. https://doi.org/10.6100/IR73050 DOI: 10.6100/IR73050 Document status and date: Published: 01/01/1961 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Download date: 30. Sep. 2021 INFLUENCE OF CHEMICAL ADDITIONS ON THE REDUCTION OF TUNGSTEN OXIDES PROEFSCHRIFT TEl{ vEltKRIJGING VAN DE GRAAD VAN DOCTOR IN DE TECHNISCHE. WETEN­ SCHAP AAN DE TECHNISCHE HOGE· SCHOOL TE EINDHOVEN or GEZAG VAN DE RECTOR MAGNIFICUS PROF. DR. K. rOS..... H Lj MUS, HOOGLERAAR IN DE AFOE­ )...)NO DER SCHEIKUNDIGE TECH NOLO­ GlE, VOOR EEN COMMISSrE VIT DE SENAAT TE VERDEDlGEN OP DINSDAG .';28 NOVEMBER 1961 DES NAMIDDAGS TE 16 UUR. DOOR HENRl LOUIS SPIER SCHEIKUND"tG lNOENIEUR OP.BOREN TE ZUTPHEN D1T PROEFSCHRIFT WERD GOEDOEKEURD DOOR DE PROMOTOR PROF. DR. C. ZWIKKER Aan. de Heer en Mevrouw Reesink-Bonebakker 1Ioor hun daadwerkelijke mensenliefde in de periode 1940-1945 VOORWOORD nit proefschrift beoogt een bijdrage te leveren tot het begrip van het fabricage­ proces van wolfraampoeder, een der grondstoffen voor de vervaardiging van gloeilampen. Ben belangrijk gedeelte van het experimente]e werk is dOor mij ven-icht op het Natuurkundig Laboratorium van deN.V. Philips'Gloeilampen­ fabrieken te Eindhoven. De Rontgenogrammen en de metingen aan 66nkristallen kwamen tot stand op het Wolfraam- en Molybdetnlaboratorlum van de Hoofdindustriegroep Licht van dit concern. De suggestic om het verrichte onderzoek in de vorm van ecn dissertatie te gieten dank ik aan dr. E. W. Verwey en Prof. J. D" Fast. Op deze plaats wil ik voorts gaarne mijn dank uitspreken VOOr de vruchtbarC discussies over het onderhavige onderwerp met dr. J. de Jonge, drs B. G. $uurmond en dr. W. L Wanmaker, en voor de experimentele medewerking van de Heren A" W. Verheyen en W. E. P. Parchen. Ik ben de Directie van de Hoofdindustriegroep Licht bijzonder erkentelijk VOOr hun toestemming tot publicatie Van het onderzock. Mr. R. H.Bathgate dank ik voor zijn kvendige belangstelling en zijn uit­ nemende engelse vertaling. Bij het persklaar maken van het proefschrift heb ik grote medewerking ontvangen van de Redactie van Philips Rcsearch Re­ ports, van Mej. dr. ie C. H. de Minjer en Mej" Heesakkers en van de Heren A. de Jong en E, J. Verspaget, resp. Uitgevers Mij Centrex en Lichtadvies. bureau. Ten slotte wi! ik de morcle steun gedenken die ik van mijn vrouw op critkke momenten tijdens de vrij lange tijdsduur -van de totstandkoming van dit proef­ schrift steeds heb mogen ondervinden. CONTENTS Pllg. Sllmmary Resume, Zusammellfassung I,ntroduction Ch"pt~r l. Di~cuS&ion of the tungsten coml;lounds involved in this investigation 7 1.1. Structure~ in which the octahedra ~harc cornen only. 7 U. Stfllctul'es in which the octahedra share cornets and edges 10 '-.', Stm,tures contai ning tungst~n'Oxygen tetr",hedr~: al k",li tU\lgSt!ltcs and polyWngstlll,cs 16 IA. M~tallic tung,ten . 22 Chapte\, Z. The reduction of alkalipolyt"ngstates and silicotl,ngstates 26 2.1. H'IDeri mental rnctho(l 2() 2.2. Experimentlli results 28 Chapter ]. ',[,he r"dlletion mechanism 46 Chapter 4. The jr\f\uence of the dope during the redlletion of tllngsten oxides 52 4,1. The growth of primary tllngsten crystals 52 4,2. The final state of the dope in the lUngstcn powder. 55 -1- Slimmary The investigations of the re<;i\lction of alkali pol)ltun~tatc5 and silico­ t\lngstates by hydrogen wbich are described here throw some light on the mechanism of reduction of "doped." t\lngsten oxidcs- The fact that the primary oA\lngsten crystals formed by the reduction arc much larger when potas~i\lm is used as the alkali component of the dope can also be explaiDe<;l Qn the basis of these experiments. Resume Ocs recherches. ptincipalement par diffractions radiograpbiq\le$, ef­ fect\lees sur Ie comportement dcs polytW1gstatcs et des silicot\lngstates akalins, au cours de rMuctioos pat hydrogeoe, ont permis d'6lucider entr'"utres Ie m6canisme de la rMuction des anhydrides tungstiques "dop68". Principalement 5i Ie potassium "'51 choisi conuno cOnstituant alcalin du "dopage", la croi~sance des Cri5tal,lX primaires dl,l tungstllne" pourrait 5e j\lstifier en raison des donnees en presencc_ ZusammemaSSling Durcb RQntgendiffraktionsuntersuekungen fiber das Verhalten von AlkaJipolywolframat", \lnd Silikowolframate bei der Reduktioll mit Wasscrstoffwurde <;Iio Kenntnis Uber den Reaktionsmechanismus von "doped" Wolframoxyden erweitcrl_ Das bei der Redl,lktion von "doped" WOlfram-Oxyden auftretende Wachstum oer primllren ,,-Wolfram­ Kristalle. besonders wenn Kalium als Alkalibestandteil im "Dope" angewendet wk<;l, kann auf Grund der erhaltcncn Untersuchungsergeb­ nisse erkl~rt werden. INTRODUCTION The gas-filled lamp with a coiled-coil tungsten filament is $0 far man's best solution of the problem of how to make an efficient electric incandescent light with a long life. The filament must obviously be able to conduct electricity. Since the emission of light from an incandescent body is proportional to about the tenth power of the absolute temperature while the emission of heat is only proportional to about the 4'7th power, it must be possible to heat the filament to a high tem­ perature; in other words, the filament material must have a high melting point and relatively low evaporation losses at temperatures ncar its melting point if the proportion of the energy used in the production of light and the hfe of the filament are both to be high. The coiled-coil form of the filament increases the efficiency by reducing the heat losses, and the gas filling increases the life by reducing the evaporation of the metal. Tungsten is used as the filament material because it is a metal, i.e. conductive, with the highest melting point of all metals (3410 ± 25°C) and low evaporation losses (about 10-6 g/cm2 sec at 3000 0c) 1). The conventional metallurgical methods of melting and casting could not until recently be used to prepare this metal, since there were no refractories which could stand the very high temperatures involved. It was not until after -2- the second wodd war that it became possible to produce tungsten in rod form by <irc casting. Wcl~bach 2) showed in 1898 that osmium powder mixed with a binder could be extruded into wire form, removal of the binder giving ductile osmium wire. Werner VOn Rolton S) used this technique to make tantalum wires from the pure tantalum powder he had prepared. The German firm or Siemens and Halske brought out a tantalum lamp based on this process in the years 1905 to 19IO. It proved impossible to make ductile tungsten win~ by the extrusion method. It goes without saying that the very bdttle wire which could be produced by this method was exceptionally difficult to work with; even so, it was used for some years in the manufacture or electric lamps. In 1910 Coolidge 4) of General Electric succccdd in making ductih: tungsten wire from tungsten powder by a completely new method. The Coolidge method. which Was protected by several U.S. patents, consists in pressing tungsten powder into bars of square cross-section (about 60 cm long and 1-2 em thick) in high-pressure steel prcsses. These bars are very bdttle, and must be ~ubjected to a preliminary sintering before they can be handled. This is done by heating them at 1000" 1200 "C in a hydrogen atmosphere. The bars are then sintcred by the direct passage of current until the density reaches about 90 X) of the thcoro:tical value. This procc~~ is also carried out in a hydro­ gen atmosphere, in order to prevent reoxidation of the metal. The bars arc then swaged in a rl)tating hammering machine, which increases the density even further and makes them longer and of approximatdy circular cross-section. Thc tungsten crystals are deformed to fibres by the swaging, and the length of these fi bres is enormously increased during the subsequent drawing process which produces wire to a diameter of 20 f1 and less.
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