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Post by DCish on May 19, 2014 18:44:38 GMT -8
Just stumbled on what appears to be a good deal -- $50 (shipped) for a 50lb bucket of refractory mortar (http://www.ebay.com/itm/like/321355894111?lpid=82). If I got some ceramic paper, saturated it with refractory cement and wrapped it around a form for 1.5cm, then followed it with a refractory mortar / perlite blend (a la Matthew Walker) for another 2cm as insulation, would that give me a sturdy, insulative single-piece core? Would it be likely to crack?
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Post by Deleted on May 20, 2014 4:40:58 GMT -8
Mortar is not cement, but cement mixed with bigger particles.
Refractory mortar usually contains lots of grog.
The particle size is likely much to big to saturate ceramic paper with it.
You could use clay and waterglass for this.
There are two basic solutions against cracks:
1). fiber-reinforcement
2). lots of small cracks
Paper serves the first and grog the second.
However perlite makes the structure weak.
You could add some loose fiber as compensation.
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Post by Robert on May 20, 2014 12:33:43 GMT -8
i ave just used a ceramic blanket soaked in with ridgidizer for a riser... after few burns i can see that the ridgidizer while burning hot (yes i have a window to look inside the riser) creates some sort of a foam, and looks like it is melting... at the beggining the riser was hard and now it is soften... i am not sure wheter it will survive for long... Karl do you have any idea about the ridgidizer and ceramic blanket used as a riser? and if the ridgidizer same as water glass?
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Post by DCish on May 20, 2014 13:02:44 GMT -8
Whew, think I'm getting close to grasping this finally.
When you suggest clay, is it raw clay or fireclay (assuming fireclay)?
You say "add loose fiber as compensation"... you mean to the clay / waterglass/ perlite part, yes?
Also, do the thicknesses (1.5 cm paper based core, 2cm insulative layer) seem reasonable for a batch box core?
Many thanks, there's no way I could pull this off without everyone's valuable input - this forum is fantastic!
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Post by smarty on May 20, 2014 15:14:32 GMT -8
Robert. I think that rigidiser is usually colloidal silica of some kind. colloidal silica needs baking to a cherry red at least and for about a half hour in order to fuse into amorphous silica. At least that is my understanding. when it is used in kilns, etc. this occurs naturally the first time the kiln is fired. I think also you need quite a lot to turn ceramic blanket rigid, about 30 litres per square metre of blanket I seem to remember as a figure. usually it is more of a surface treatment that just stabilises the ceramic blanket and stops fibres floating about in the working environment too much, through gas flow etc.
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Post by Deleted on May 21, 2014 3:56:18 GMT -8
creates some sort of a foam, and looks like it is melting... at the beggining the riser was hard and now it is soften... Gels are substantially dilute three dimensional cross-linked networks. The networks are formed by physical or chemical bonds. In this way gels are a dispersion of molecules of a liquid within a solid. The strength of gels comes to a significant part from surface tension effects between liquid and solid. Once the liquid has vanished there will not longer be any surface tension effects. Colloidal silica forms and maintains the network by electric charge. Electric bonds are weakened by heat. The purpose of rigidisers is to make blankets moldable, not to give substantial strength. Quite a lot colloidal silica is needed to get a substantial strength. To form stronger bonds aluminosilicates like fire clay are needed to form chemical bonds with the colloidal silica. en.wikipedia.org/wiki/GelFor stronger risers I would recommend multible layers. A a tough inner layer then blanket and maybe even a third outer layer. |
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Post by Deleted on May 21, 2014 4:26:43 GMT -8
When you suggest clay, is it raw clay or fireclay (assuming fireclay)? Fireclay Yes. Yes. |
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Post by DCish on May 21, 2014 6:19:15 GMT -8
Karl, this information is pure gold -- concise, clear, relevant, factual, deeply insightful... Thank You!!! Time to sketch up a mold for my core.
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Post by Robert on May 23, 2014 12:42:59 GMT -8
i am glad you understood it DCish. my english is to poor for all of that technological language. please keep us updated on your experiment and if you can please make photos:)
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Post by DCish on May 23, 2014 17:18:04 GMT -8
Hah! Trust me, Robert, I'm a native English speaker, but I'm no chemist! I only understand about a quarter of what Karl writes on some of his posts, but thankfully he was patient enough to entertain the follow-up questions on this thread and it finally all clicked. I have more brainstorming time available than I do building time, but I will most certainly post pics... and more questions as I go along. I'm very excited about this core build method, though, it seems much more flexible for a novice like me than trying to get a casting done up right without botching it.
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Post by DCish on May 31, 2014 5:14:18 GMT -8
OK, so I'm thinking about buying materials to experiment with before finalizing mold design, and realize I don't know what proportions to use. Suggestions for clay to water glass proportions? Would it be the same proportions for impregnating the ceramic paper as well as making the insulative perlite mix? I'm thinking to use cement floor sealer as source of water glass (https://www.google.com/search?q=sodium+silicate+cement+hardener&client=ms-android-sprint-mvno-us&espvd=1&source=lnms&tbm=shop&sboxchip=Shopping&sa=X&ei=INSJU_b0OoWGqgarq4GoBA&ved=0CAcQ_AUoAQ&biw=360&bih=519#spd=12964581696941642455). From a link ( chiefio.wordpress.com/2014/02/12/some-notes-on-geopolymer-cement-clay-bricks-unfired-and-diy/) on geopolymers on another thread they say, "The physical properties of the hardened geopolymer are influenced by the Si/Al ratio of the geopolymer network. Below a Si/Al ratio of 3:1, the resultant 3D nets are rigid, suitable as a concrete, cement or waste encapsulating medium. As the Si/Al ratio increases above 3, the resultant geopolymer becomes less rigid and more flexible or “polymer-like”. With higher Si/Al ratios, up to 35:1, the resultant crosslinked 2D chains are more suited as an adhesive or sealant, or as an impregnating resin for forming fibre mat composites." Not sure if that applies to the water glass/fireclay mix I am planning or not... |
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Post by Deleted on May 31, 2014 6:39:42 GMT -8
Molar Mass and Mass Percent Composition Calculator www.caymanchem.com/app/template/chemAssistant,Tool.vm/itemid/4002 Kaolinite Al2O3 · 2SiO2 · 2H2O Molar mass (g/mol): 258.16080 Molecular Formula in Hill Notation: H4 Al2 O9 Si2 Symbol Element Name Number of Atoms Atomic Mass Mass Percent Category H Hydrogen 4 1.007947 1.561735 Nonmetal Al Aluminum 2 26.98153868 20.90289 Other metal O Oxygen 9 15.99943 55.7772 Nonmetal Si Silicon 2 28.08553 21.75817 Metalloid Metakaolin Al2O3 · 2SiO2 Molar mass (g/mol): 222.13014 Molecular Formula in Hill Notation: Al2 O7 Si2 Symbol Element Name Number of Atoms Atomic Mass Mass Percent Category Al Aluminum 2 26.98153868 24.29345 Other metal O Oxygen 7 15.99943 50.4191 Nonmetal Si Silicon 2 28.08553 25.28746 Metalloid Natriummetasilicat Pentahydrate Na2O3Si · 5 H2O Molar mass (g/mol): 212.13998 Molecular Formula in Hill Notation: H10 Na2 O8 Si Symbol Element Name Number of Atoms Atomic Mass Mass Percent Category H Hydrogen 10 1.007947 4.75133 Nonmetal Na Sodium 2 22.989769282 21.67415 Alkali metal O Oxygen 8 15.99943 60.33537 Nonmetal Si Silicon 1 28.08553 13.23915 Metalloid caustic soda NaOH Molar mass (g/mol): 39.99715 Molecular Formula in Hill Notation: H Na O Symbol Element Name Number of Atoms Atomic Mass Mass Percent Category H Hydrogen 1 1.007947 2.520047 Nonmetal Na Sodium 1 22.989769282 57.47852 Alkali metal O Oxygen 1 15.99943 40.00143 Nonmetal |
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Post by DCish on Jun 1, 2014 18:34:20 GMT -8
I'm sorry for my ignorance, but I have no idea how to interpret what you've give me in order to get a practical fireclay to water glass ratio for layering ceramic paper onto a mold.
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Post by Deleted on Jun 2, 2014 1:58:01 GMT -8
I'm sorry for my ignorance, but I have no idea how to interpret what you've give me in order to get a practical fireclay to water glass ratio for layering ceramic paper onto a mold. The ratio of Si/Al in Kaolin is 1 and should be similar for other fire clays with high alumina content. To increase the ratio you need some more silica. For geopolymers The ratio of sodium metasilicate(Na2O3Si) to lye(NaOH) should be about 2.5. Waterglass is sodium metasilicate pentahydrate (Na2O3Si · 5 H2O) Na2O3Si Molar mass (g/mol): 122.06336 Na2O3Si · 5 H2O Molar mass (g/mol): 212.13998 The ratio of Na2O3Si · 5 H2O to Na2O3Si is 1.7379. 1.7379 * 2.5 = 4.34 Waterglass solution has about 40% 4.34 * 2.5 = 10.85 So you have to add about 92g lye per 1Kg of waterglass solution. Thats then enough for about 2.7 kg of metakolin. If you want to use waterglas only to get more and earlier green strengs of the clay you need to add just enough lye to reduce the needed mount of water. BTW Having an extremely rare disease I am forced to DIY my medicine. I bet by life evere day on my knowledge and skills since a long time. Today I am at the second stage (drying) of my pharmaceutical production by removing alcohol and acid with a vacuum pump. Quite boring task as I have to densify the material regularly, so that the pump will not draw air. The first stage is the production ot the required substances by chemical modifiction. |
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Post by DCish on Jun 2, 2014 4:43:05 GMT -8
If you want to use waterglas only to get more and earlier green strengs of the clay you need to add just enough lye to reduce the needed mount of water. Hmmmm. "Waterglass only" sounds positive in that it is simpler. If it is stronger, too, then that is also a plus. If I use no lye at all, what happens then? And making your own medication!? Jeepers, no wonder you're so comfortable with all the chemistry! |
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