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Refractory metals - titanium and zirconium

1 Properties of titanium and zirconium

Both titanium and zirconium have high melting points and are refractory metals. In addition, their common characteristics are: low density, coefficient of expansion, work function and evaporation rate in vacuum.

The thermal conductivity of titanium and zirconium is very low, but their resistivity is higher than other metals. The most important property of titanium and zirconium is that they can absorb gas and not release it within a large temperature range. After titanium and zirconium absorb gas, their brittleness increases and their elongation decreases.

After degassing, zirconium can reliably absorb 02, 00, 00, N2, and form solid solutions or compounds; it can already absorb gases significantly at 400°C, and as the temperature increases, the activity of zirconium in absorbing the above gases also increases.

Zirconium can dissolve a large amount of hydrogen. At atmospheric pressure, the volume of dissolved hydrogen can exceed 1000 times its own volume. Zirconium begins to absorb hydrogen at 300°C, and the solubility increases with increasing temperature; but after 800°C, zirconium begins to release hydrogen again. Since Zr can change its properties drastically when heated in a hydrogen furnace, it cannot be pre-degassed in a hydrogen furnace.

Be careful! Dry zirconium powder is prone to spontaneous combustion and explosion, so it must be kept moist during storage or transportation.

Titanium, like zirconium, has the ability to absorb various gases, but it does not explode like zirconium.

At 700°C, titanium can absorb O2, N2, and 0O₂ very well. At room temperature, 1g of titanium can absorb 407mL of hydrogen, and at 1000°C, it can absorb 66mL of hydrogen to form a solid solution. Titanium can also absorb water vapor very well. After absorbing a large amount of gas, titanium becomes very brittle.

Titanium (at 500~600°C) and zirconium (at 600~800°C) can both absorb a large amount of nitrogen.

Both titanium and zirconium can be corroded by a mixture of hydrofluoric acid and nitric acid.

2 Application of titanium and zirconium

Titanium and zirconium materials are widely used in vacuum technology as an important means to obtain and maintain vacuum; titanium sublimation pumps with a pumping speed of 2100L/s are often used to maintain ultra-high vacuum; titanium powder and zirconium powder can not only be used as getters after sintering, but also have a higher thermal radiation coefficient, which allows heat to be dissipated more quickly. Zirconium oxide ZrO: and zirconium silicate (ZrSiOs) are the cold end insulation coating materials of metal halide lamps. Ductile titanium and zirconium can be used to make high-temperature resistant structural parts and also play a role in getting air.

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