Talk:Ceramic

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From the article: "A couple of decades ago, Toyota researched on producing a ceramic engine which can run at a temperature of over 6000°."

How many decades ago, and is that 6000°C or 6000°F? Kind of important. Bryan Derksen

Has to be 6000°F. 6000°C is up to solar temperatures. Edited to include the F. Don't know any more about it, although 6000F is still incredably high. I can only find a couple of materials with a melting point in that range or higher (tungsten (6010F), Diamond (6240F) and Hafnium carbide (6940F)). Even with HfC (which, might I add, I've never actaully heard of being used anywhere), that's stil close to the melting point, it would have to have pretty serious mechanical properties at that temp to be usable (not unknown, nickel superalloys can be used up to about 30°C from it's melting point, but damn rare), particularly considering that it's got to contain the explosions. Plus, to run an engine at over 6000°F your talking about buringing something exotic like oxy-acetalyne, or possible hydrolox. My suspicion is that the engine is a petrol engine made of ceramics that have a melting point over 6000°F, and not that it can run over 6000°F. Granted, my experience is in the electrical ceramics, and not the structural, so I'm going to leave it in, pending research. Syntax 05:13, 23 Jan 2004 (UTC)

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Right, bit of a major update there. Notable points:

1) My spelling sucks. Plus, I tend to the British spellings. 2) Traditional cermaic crafts are over at pottery. MatSci ceramics are here. Anyone forsee any problems with that? 3) I've tried to pitch the entry at the right level. Please holler if something is unclear - I'm too used to writing technical stuff on this. 4) Did I mention my spelling sucks?

Syntax 23:11, 29 Jan 2004 (UTC)

Contents 1 handicrafts: ceramics 2 negative resistance 3 Why have the refractory and elec properties been removed? 4 Sintering 5 Move Ceramics to Ceramic? 6 Building construction vs. Pottery... 7 Requested move 7.1 Voting 7.2 Discussion 8 ceramic 9 Brittle 10 Ceramin? 11 Stoke on Trent Museum

[edit] handicrafts: ceramics

An interesting article but I cannot understand why it has been included under handicrafts. More appropriately it should be under science of materials. I think the author is also puzzled by this classification. Pottery is also known as ceramics. It is simply that one word has an Old English origin and the other a Latinate origin. They both used to refer to the same craft/product and have done so for many centuries. See the OED. People working as artists with clay may choose to be known as potters, ceramists, ceramic artists, ceramicists or clay workers. Those who choose to identify as potters usually produce work that can be used in some way as well as appreciated for its intrinsic beauty. Potters also make one-off pieces. Nonetheless they may still choose to identify as potters. I suggest you refer to William Morris, Bernard Leach, Soetsu Yanagi and the Mingei movement in Japan which will give a philosophical background to this choice. Ceramic artists may either be people who have trained in ceramics, acquiring skills in both the making and designing of art works in clay (which may well be referential to the long and rich history of ceramics) or they can be artists like Grayson Perry who simply choose clay as one of several media in which they work. There is also a growing tendency to place ceramists under visual arts and design rather than art or pottery. I would suggest to the editors that there be entries under both categories (pottery and visual arts and design). Maybe artists/potters and their work could be listed under visual arts and design and practical/technical information under pottery with cross-referencing to each. Karen Weiss

[edit] negative resistance

These are devices that exhibit the unusual property of negative resistance. Once the voltage across the device reaches a certain threshold, there is a breakdown of the electrical structure in the vicinity of the grain boundaries, which results in its electrical resistance dropping from several mega-ohms down to a few hundred.

This confuses me. I understand that, as explained at negative resistance, negative resistance can be taken to mean merely that current is a decreasing function of voltage in a particular region of the current-voltage curve. But the above doesn't describe that. In fact it describes a situation where current in increasing greater than linearly with voltage. So if these materials really have negative resistance, the above does not describe their behavior. Josh Cherry 01:52, 25 Jun 2004 (UTC)

• Or maybe I'm just confused. Does a given voltage actually have two possible values of voltage in some regions for these devices, with slopes of opposite signs? Josh Cherry 02:14, 25 Jun 2004 (UTC)

• You're quite right, the resistance drops sharply at high voltage, but the resistance (both V/I and dV/dI) remains positive.

• That is confusing. The device you refer to is called a varistor, for variable resistor. A varistor has a change in resistance when it is subject to relative high voltage to its device rating. The term variable is misleading. Once the arrester is hit with high voltages its performance continue to degreed and it is irreversible.

The basis of an arrester, and this would make a good article is to fail like a fuse, but not on the same principle of a fuse, and protect its more expensive part. These arresters are also termed lightning arresters fail when there is lightning nearby. They normally fail as 99% or more when there is a lightning direct hit. The part it is protecting is also often destroyed.

Anyway, a ceramic component called an MOV Block, also called Metal Oxide Varistor (Variable Resistor). Ceramics such Zinc Oxide, Cobalt Oxide, and other oxide ceramics are manufactured though a ceramic process (see Ceramic Engineering).

After the blocks are manufactured and put into a surge arrester the arrester has as a kV value that is directly related to the number of blocks with its own kV value put in a stack. Put simply a 10 kV arrester has three, 3.3 kV blocks.

A 36 kV arrester has 12, 3 kV blocks.

Now going through all that, this industrial part example may explain the confusion.

- A surge in terms of a voltage strike crosses a line. If the voltage is <3000 V and the arrester is a 3 kV arrester. The arrester absorbs the spike, but it "weakens" so the initial resistance has degraded to a new lower resistance, due to the internal rearrangement of the grains. The arrester can withstand spikes over 3000 V, which is over voltage. Again, the durability of the part is unique to each part due to many factors. The over voltage will weaken the part, but may not cause it to fail.

-Not only do spikes cause degradation on an arrester, but also that the arresters are powered up as part of the circuit they are in.

-When the arrester has been hit repeatedly with surges and is in operation over a "long time" as in many years, it degrades to where it no longer arrests spikes, and the equipment it protecting is now subject to degradation. However, their can be a second layer, such as surge redirection to ground. or third layer of protection like a circuit breaker. The arrester is cheap, cost effective, efficient device and effective in protective sensitive parts..

-Note, your surge protecting multi-plug test strip warn that after the a warning signal shows as in it has been hit with a surge, they recommend you repair or replace the unit. There is a good reason for that. The company I worked for made arresters for those very same protection strips.

-As for the phrase of "these devices" I believe what I explained is one example of what the phrase alluded to.

Deekayfry (talk) 06:37, 21 May 2008 (UTC)

[edit] Why have the refractory and elec properties been removed?

I thought the content before 9 March 2005 was quite relevant

[edit] Sintering

There's a decent, but incomplete article on sintering that I tried to improve until I saw the excellent section of this article. Perhaps there should be a link and some moving of content?--Joel 22:56, 26 May 2005 (UTC)

[edit] Move Ceramics to Ceramic?

Should this article not be entitled Ceramic instead of Ceramics. Right now Ceramic redirects to Ceramics, but I think it should be the other way around --b4hand 20:34, 4 October 2005 (UTC)

Agree. Ceramics seems to violate WP policy on plural article titles. And since I don't see any other discussion or reason for it, I'm being bold. -dmmaus 06:27, 14 January 2006 (UTC)

Oh, darn, it's not that easy. The existing redirect blocks the renaming. I'm listing on WP:RM. -dmmaus 06:32, 14 January 2006 (UTC)

[edit] Building construction vs. Pottery...

Can reach a better separation between the "Fine arts" subject of "Ceramics" and the building material? I have created a new but short page: "Ceramic material" for building stuff. Sorry about the I18N chars corrupt. I am fixing it now. -- Fplay 23:20, 20 December 2005 (UTC)

It's more than just "building material". Ceramic materials are used for a lot of different things in engineering. At a glance, this article seems to be entirely about the engineering usage of the term, and not at all about the art form. In your new category scheme, this article, as-is, should be the "main article" for Category:Ceramic materials. Category:Ceramics does not currently have a main article as far as I know.--Srleffler 00:38, 21 December 2005 (UTC)

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Change and reasons From “Earthenware, which is made from potash, sand, feldspar and clay.” Why? Because it’s not To “Earthenware, which is often made from clay, quartz and feldspar.” Why? Because it is! Regards, Andy

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Hello all, I've added an the ASTM definition of ceramics ... or at least ceramc article Regards, Andy

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Hello 70.52.112.133 Thank you for your comments but cement is produced by the action of heat on raw materials, and therefore would comply with the listed definition. To quote from the wikipedia entry on Portland cement “ ...and similar materials are made by heating limestone (as source of calcium) with clay or sand (as source of silicon) and grinding the product (clinker), with a source of sulfate (most commonly gypsum). “

As an aside whilst the catergorisation of cement as a ceramic material is agreed by some it is not universal

Regards,

Andy

Hello again 70.52.112.133,

Whilst the final articles, such as concrete blocks, do not require the action of heat the manufacture of cement does, and therefore complies with the listed definition. Please see the wikipedia entry on Portland cement. Should you still not be happy with this please use the talk pages rather than changing the entry

Please have a look at http://www.cement.org.au/technical/cement_production.htm hwere you will see it noted that temperatures of up to 1450˚C are found in the kiln to produce cement Regards, Andy

[edit] ceramic

what is ceramic? i want to know...my teacher ask me and friends to do a research on ceramic

Hello 60.52.20.66,

Have you read the article to which these talk pages are attached? It contains a useful definition: “The American Society for Testing and Materials (ASTM) defines a ceramic article as “an article having a glazed or unglazed body of crystalline or partly crystalline structure, or of glass, which body is produced from essentially inorganic, non-metallic substances and either is formed from a molten mass which solidifies on cooling, or is formed and simultaneously or subsequently matured by the action of the heat.” Rememebr if you do use this you need to give a proper citation

Regards, Andy

[edit] Brittle

Hi all, I've just re-read the article, and thought about "Historically, ceramic products have been hard, porous and brittle." Call me stupid but what ceramics are not hard & brittle? Regards, Andy

At room temperature most ceramics are hard and brittle. At elevated temperatures that's not necessarily true--glass for example. 134.84.54.209 18:28, 4 January 2007 (UTC)Julia

But the description does not mention temperature Theriac 16:36, 5 January 2007 (UTC)

[edit] Ceramin?

Any chance some mention of what ceramin is can be added to the article? I don't know personally, but I have seen it mentioned in various places. Aristoi 19:43, 6 December 2006 (UTC)

[edit] Stoke on Trent Museum

Hi Cbdorsett. I don't think it POV to have use the phrase "The finest collection of Staffordshire ceramics in the world" as

• It is.
• These are the words used by the museum itself, and which is a non-profit, non-commercial organisation that is a globally respected authority. (and one I have no association with!)

ThanxTheriac 16:56, 20 February 2007 (UTC)

Calling something the "finest" is necessarily putting a value judgment on something, and I think it's out of place here, especially since there is a perfectly fine, neutral way to describe the collection. Cbdorsett 17:01, 20 February 2007 (UTC)

Hi Cbdorsett. But by not using the full description readers will not be aware of significance of the collection (and this is surely undisputed) and so may not realise why it is worth listing ThanxTheriac

Good point. Let me suggest that you read Wikipedia's POV policy Wikipedia:Neutral point of view. Then figure out a way to word the description so that it attracts people, without starting off a competition about who's the "finest", "greatest," "most ..." etc. Cbdorsett 19:34, 20 February 2007 (UTC)

Thanks, Theriac. It's much better now. :) Cbdorsett 17:16, 22 February 2007 (UTC)

ThanksTheriac 17:26, 22 February 2007 (UTC)