Re: My new 'Thorium' "Avitar/Icon" !!? - Page 1
Forum section: electronics / general

author: GlennSprigg
author_rank: Super Contributor
timestamp: December 01, 2020, 12:08:59 pm
content: Being a lover & enthusiast of oldValve/Tuberadios and equipment, this is an element (No. 90) that was discovered to be VERYuseful, in adding to theTungstenfilaments/heated-cathodes to GREATLY increase the Electron emissions of these tube plates/coils!And would do so, at a much reduced/necessary temperature. Such filaments etc, became what was called 'Thoriated-Tungsten'.The Thorium covering was only1 Atom thick!! but that's all it took for 300-400% improvement in Electron emissions!Thorium is a malleable silver colored metal, but slowly blackens under oxidization to Thorium-Dioxide (Th-O2) on the outside.It isRadioActive, and interestingly... the most stable Isotope (232) has aHalf-Lifeof over14 Billion years!! which is slightlyolder than the current calculated life of the Universe. It has/had many other uses in the past, and to-date.

author: bsfeechannel
author_rank: Super Contributor
timestamp: December 01, 2020, 03:50:44 pm
content: Nice choice of avatar. But let's take this opportunity to remember the humble barium, used on flashed getters. It easily oxidizes, capturing any air molecules left in the tube and turning white when the vacuum system seal totally fails.

author: helius
author_rank: Super Contributor
timestamp: December 01, 2020, 05:11:04 pm
content: The low work-function of thorium was also used to make brighter gas mantles for portable lamps. Once installed, the paper backing was charred away by the flame so only a microscopically-thin layer of thoriated graphite remained. After burning, they couldn't be removed without being destroyed.

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 01, 2020, 05:21:05 pm
content: The old (WW2 era ) amateur operators in the club used to say about the thoriated tungsten transmitting tubes:Do not apply plate voltage until the cathode filament is fully warmed up.Do not allow long periods with heaters on and plate voltage off.Both of these were related to the life of thoriated tungsten cathodes.I was just of an age to have worked briefly on the 40 to 200 kW triodes before they went mostly obsolete.Tubes were like the YD 1202 with a filament rating of 12.2 Volt 250 amp.My notebook from 1984:Storage : 2 years max without filament voltageTransport and keep verticalConditioning: Apply Fil voltage for 15 minutes before HT on plate to reduce risk of flashover.Thoriated Tungsten needs exactly T_cathode @ 2000 KelvinIf V_filament 3% too high:Filament power up by 5%T_cathode up by 1 %Emission up by 20%Life down by 50%The filament transformers had many taps to get the voltage in spec.I recall there was a timer for delaying HT On, and a few other interlocks.I don't think tha above applies to small consumer grade tubes.The 6.3 V could have swings following the residential supply,and the later ones had solid state rectifiers with plate voltageinstantly applied before the filamants warmed.

author: duckduck
author_rank: Frequent Contributor
timestamp: December 01, 2020, 05:40:25 pm
content: Quote from: GlennSprigg on December 01, 2020, 12:08:59 pmIt was added (1%-2%) to electrodes for TIG welding. This was a thing in the 1990's, and I don't know if anyone still makes these. Having a little ionizing radiation sure helps start that arc easier. The big risk is from inhalation of the dust from grinding the electrode wire, which you have to do every now and then to keep a sharp tip on them.http://files.aws.org/technical/facts/FACT-27.pdf

author: Syntax Error
author_rank: Frequent Contributor
timestamp: December 01, 2020, 10:02:16 pm
content: @GlennSpriggThis makes perfect sense... nowMy father was always telling us not to shoot up redundant radio valves with airguns because it released Thallium and Caesium into the air. My friend's dad worked for a TV repair business and there were hundreds of old valves in his garden shed, which we eagerly blasted in our backyard firing range. Well back then, the only hazardous materials we had were asbestos, and those artifical coffee granules that stained your teeth yellow. No doubt there's an atom or two of Thorium-232 somewhere in my bone structure.

author: Gregg
author_rank: Super Contributor
timestamp: December 02, 2020, 03:10:39 am
content: An early use of thorium was for gas lantern mantles. These mantles are pretty hard to find these days because of the radioactivity scare mongers. I believe the early mantles were made of silk and dipped in a thorium salt solution. I remember the thoriated Coleman lantern mantles were quite sturdy and lasted a lot longer than the new ones. Now days with LED lanterns and rechargeable lithium batteries have largely replaced the old mantle lanterns; but those old fuel powered lanterns sure made some nice heat in the winter time.

author: helius
author_rank: Super Contributor
timestamp: December 02, 2020, 03:32:18 am
content: Thorium was also used in optical glass, notably by Nippon Kogetsu (Nikon) and Asahi Pentax in the 1950s. Not much danger of release, but it does have the funny effect that it turns brown over time. The cure is exposure to bright UV light.

author: GlennSprigg
author_rank: Super Contributor
timestamp: December 04, 2020, 10:24:22 am
content: Re: TIG welding tips... I noticed that too, somewhere recently.I 'thought' within my mental capacity that this would/may have been for the same reason as in valves/tubes ?Increasing the electron flow from the heated tip, but the result this time being more direct & efficient welding.