Titanium density of 4.506 4.516 g/cm3 (20 ℃), higher than aluminum and lower than that of iron, copper, nickel. But the specific strength is higher than that of metals. Melting point 1668 + 4 ℃, the latent heat of fusion 3.7 5.0 kcal/gram atom, the boiling point of 3260-20 ℃, latent heat of vaporization 102.5 112.5 kcal/gram atom, critical temperature 4350 ℃, the critical pressure of 1130 atmospheres. Titanium has poor thermal conductivity and conductivity, similar to or slightly lower than stainless steel, titanium has superconductivity, pure titanium superconductivity critical temperature is 0.38-0.4k. At 25 ℃, titanium heat capacity of 0.126 CARDS/gram atom, enthalpy 1149 CARDS/gram atom, entropy card/gram atom 7.33 degrees, titanium is paramagnetic substance, permeability is 1.00004.
Titanium has plasticity, the elongation of high purity titanium can reach 50-60%, the reduction rate of section can reach 70-80%, but the strength is low, not suitable for structural materials. The presence of impurities in titanium has a great impact on its mechanical properties, especially the interstitial impurities (oxygen, nitrogen, carbon) can greatly improve the strength of titanium and significantly reduce its plasticity. Titanium as a structural material has good mechanical properties, is through strict control of the appropriate content of impurities and alloy elements to achieve.
Titanium reacts with many elements and compounds at higher temperatures. Various elements can be divided into four categories according to their different reactions with titanium:
The first group: halogen and oxygen elements form covalent and ionic bond compounds with titanium;
The second kind: transition elements, hydrogen, beryllium, boron group, carbon group and nitrogen group elements form intermetallic compounds and finite solid solution with titanium;
The third kind: zirconium, hafnium, vanadium group, chromium group, scandium and titanium forming infinite solid solution;
The fourth category: inert gases, alkali metals, alkaline earth metals, rare earth elements (except scandium), actinium, thorium and other elements do not react with titanium or almost do not react. (1) react with compound HF and fluoride hydrogen fluoride gas to form TiF4 when heated with titanium. Non-aqueous hydrogen fluoride liquid can generate a dense titanium tetrafluoride film on the surface of titanium to prevent HF from immersing into the titanium. Hydrofluoric acid is the strongest solvent for titanium. Even the concentration of 1% hydrofluoric acid, also can have a strong reaction with titanium, see the equation; The anhydrous fluoride and its aqueous solution did not react with titanium at low temperature, but only the fluorides melted at high temperature reacted significantly with titanium. Ti + 4 hf = TiF4 + 2 h2 + 135.0 kilocalorie (2 Ti tif3 hf + 6 = 2 + 3 h2 diction HCl and chloride hydrogen chloride gas corrosion of titanium, dry hydrogen chloride in > 300 ℃ with titanium reaction TiCl4, see type (3); Concentration <5% of hydrochloric acid at room temperature does not react with titanium, 20% of hydrochloric acid at room temperature with titanium melon in the formation of purple TiCl3, see the equation in recent years; Even dilute hydrochloric acid can corrode titanium at higher temperatures. Various anhydrous chlorides, such as magnesium, manganese, iron, nickel, copper, zinc, mercury, tin, calcium, sodium, barium and NH4 ions and their aqueous solutions, do not react with titanium, which has good stability in these chlorides. Ti+4HCl=TiCl4+2H2+94.75 kka 3 Ti+6HCl=TiCl3+3H2 (4) of sulfuric acid and titanium sulfide and 5% of sulfuric acid has obvious reaction, at room temperature, about 40% of sulfuric acid on titanium the fastest, when the concentration of more than 40%, 60% of the corrosion speed is slow, 80% and the fastest. The heated dilute acid or 50% concentrated sulfuric acid can react with titanium to generate titanium sulfate, which is set as 5, •, and the heated concentrated sulfuric acid can be reduced by titanium to generate SO2, as shown in the lilitide equation. When titanium reacts with hydrogen sulfide at room temperature, a protective film is formed on the surface to prevent further reaction between hydrogen sulfide and titanium. But under high temperature, hydrogen sulfide precipitation reaction with titanium hydrogen, see being, titanium powder at 600 ℃ began to react with hydrogen sulfide to produce titanium sulphide, reaction products mainly for TiS in 900 ℃, 1200 ℃ for Ti2S3. Ti+H2SO4=TiSO4+H2 2Ti+3H2SO4=Ti2(SO4)3+3H2 • 2Ti+6H2SO4=Ti2(SO4)3+ 3H2SO4 +202 3+3SO2+6H2O+202 3+ 3H2SO4=Ti2(SO4)3+ 3H2SO4 +202 3+3H2 +6H2O+202 3+ 3H2SO4=Ti2(SO4)3+ 3H2SO4 +202 3+ 3H2SO4=Ti2(SO4)3+ 3H2SO4 +202 2 Higher than 70 ℃ concentrated nitric acid can react with titanium, see type ⑾; Titanium does not react with aqua regia at room temperature. At high temperature, titanium can react with aqua regia to form TiCl2. 3Ti+4HNO3+4H2O=3H4TiO4+4NO 3Ti+4HNO3+H2O=3H2TiO3+4NO Ti+8HNO3=Ti(NO3)4+4NO2+4H2O 2 above, the properties of titanium and temperature and the existence of morphology, purity has a very close relationship. Compact titanium is fairly stable in nature, but powder titanium can cause spontaneous combustion in air. Impurities in titanium significantly affect the physical, chemical, mechanical and corrosion resistance of titanium. In particular, some interstitial impurities can distort the crystal lattice of titanium and affect various properties of titanium. At room temperature, the chemical activity of titanium is very small, can react with a few substances such as hydrofluoric acid, but the activity of titanium increases rapidly when the temperature increases, especially at high temperature, titanium can react with many substances violently. Titanium smelting process is generally under the high temperature of 800 ℃ above, must therefore be in a vacuum or under inert atmosphere protection operation. Physical properties of metallic titanium metallic titanium (Ti), gray metal. Atomic number 22, atomic mass 47.87. The electron distribution in the subshell is 1S2, 2S2, 2P6, 3S2, 3P6, 3d2, 4S2. The activity of metals is between magnesium and aluminum, and it is not stable at room temperature, so it only exists in combination state in nature. The common titanium compounds include ilmenite (FeTiO3), rutile (TiO2), etc. Titanium is the ninth most abundant mineral in the earth's crust, at 5,600 parts per million, or 0.56 percent. Pure titanium has a density of 4.54 103kg/m3 and a molar volume of 10.54cm3/mol, with poor hardness and only about 4 Mohr hardness, so its ductility is good. Titanium has a good thermal stability, melting point is 1660 plus or minus 10 ℃, boiling point is 3287 ℃. The chemical properties of titanium the metal titanium is highly reactive at high temperatures, combining with oxygen, carbon, nitrogen, and many other elements. At room temperature, titanium and oxygen combine to form an extremely thin and dense oxide film. This oxide film does not react with most strong acids and bases at room temperature, including the king of acids -- aqua aqua. It only reacts with hydrofluoric acid, hot concentrated hydrochloric acid, and concentrated sulfuric acid, so titanium exhibits corrosion resistance.