Difference between revisions of "Refractory material"

Revision as of 17:17, 26 February 2015

Diamond is not suitable for applications that involve very high temperatures. It is metastable and thus starts to turn into graphite.

Other diamondoid materials like the carbides of the titanium vanadium and chromium group (interstitial carbides) can be used for high temperature applications. Materials that retain their structural strength at high temperatures are called refractory (wikipedia).

About consistent design

Obviously a systems should be designed such that there are no single parts that limit the temperature resilience way below the potential. This is a special case of "consistent design for external limiting factors". Complete sets of high temperature DMEs are needed) - single ones have no use.

Nanscale limitations

That a material does not melt does not mean that it shows no surface diffusion.

Stability of free or mutual contacting or environmentally contacting passivated surfaces (that are possibly strained) will reduce the allowed temperatures well below the bulk material melting points. Interstitial diffusion may too be a limiting factor.

For really high temperature applications minimal sized DMEs will thus likely not work. Bigger scale (interlocking) refractory tiles will still be usable though. But they'll need regular replacement before they fuse together. Disposal of them might proove diffecult.

List of some refractory materials

4th period:

• TiC (3,160 °C; 5,720 °F; 3,430 K; abundant elements, simple cubic)
• VC (2810 °C; 9-9.5 Mohs, cubic)
• Cr₃C₂; Cr₇C₃; Cr₂₃C₆ (1,895 °C; 3,443 °F; 2,168 K; extremely hard; very corrosion resistant)

5th period:

• ZrC (3532 °C; extremely hard; highly corrosion resistant; very metallic, cubic)
• Nb₂C (3490 °C; extremely hard; highly corrosion resistant)
• Mo₂C (2692 °C) [1]; MoC; Mo₃C₂ [2]

6th period:

• HfC (3900 °C; very refractory; low oxidation resistance, cubic)
• TaC_X (3880 °C (TaC) 3327 °C (TaC_0.5); extremely hard; metallic conductivity, cubic)
• WC (2,870 °C; 5,200 °F; 3,140 K; ~9 on Mohs scale, hexagonal)

mixed:

• Ta₄HfC₅ (record holder: 4,215 °C; 7,619 °F; 4,488 K)

Note: Many elements here are neither abundant nor prime targets for mechanosynthesis.

[Todo:]

• add notes on SiC
• add notes on recycling and disassembly
• add notes on self repair