화재 시 불을 끄기 위해 (Section 5. 폭발, 화재시 대처방법의 적절한 소화제)을(를) 사용하시오.
NFPA 704
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하프늄 탄화물 C화학적 특성, 용도, 생산
화학적 성질
dark, gray, brittle solid; fcc, a=0.4640 nm; high cross section for absorption of thermal neutrons; resistivity 8.8μohm· cm; most refractory binary material known; hardness 2300kgf/mm2; used in control rods of nuclear reactors; can be prepared by heating HfO2 with lampblack under H2 at 1900°C–2300°C; used in crucible form for melting hafnium oxide, other oxides [KIR80] [HAW93] [CER91]
물리적 성질
Dark gray brittle solid, most
refractory binary material
known. Controls rods in nuclear
reactors, crucible container for
melting HfO and other oxides. 2
Corrosion resistant to liquid
metals such as Nb, Ta, Mo, and
W. Severe oxidation in air above
1100–1400°C and stable up to
2000°C in helium.
용도
Hafnium carbide (HfC) with a melting point over 3890°C is a refractory binary compound. HfC and NbC can also be used as refractory coatings in nuclear reactors. The mixed carbide Ta4HfC5 possesses the highest melting point of any currently known compound at 4215°C.
생산 방법
Hafnium carbide is a dark gray, brittle solid. It can be
prepared by heating a mixture of the elements or by reacting
hafnium tetrachloride with methane at 2100 C. Sufficient
quantities of hafnium oxide or hafnium metal sponge are
obtained during the large-scale production of pure zirconium
for nuclear reactors. On an industrial scale, hafnium carbide
can be produced from the hydrided hafnium sponge at
1500–1700 ℃ or from hafnium oxide at 2000–2200 ℃ by
carburization in vacuo in the presence of hydrogen.
The resulting carbide contains almost the theoretical quantity
of carbon (6.30% °C) and a maximum of 0.1% free carbon
(219). The hafnium carbide obtained is not a true
stoichiometric compound as much as a solution of carbon
at specific interstitial sites of a face-centered cubic hafnium
lattice. Hafnium carbide is inert to most reagents at room temperature
but is dissolved by hydrofluoric acid solutions.
Hafnium carbide reacts exothermally with halogens at
250–500 ℃to form hafnium tetrahalide, and to form hafnium
oxide with oxygen above 500℃. In the presence of hydrogen,
hafnium carbide slowly loses some of its carbon at higher
temperatures.
