What is the thermal conductivity of alumina ceramics?
2021 09/08
Alumina has high chemical activity, and it produces a strong chemical reaction with O2, N2, H2, CO, CO2, water vapor, ammonia, etc. in the atmosphere. When the carbon content is greater than 0.2%, it will form hard TiC in the titanium alloy; when the temperature is higher, it will also form a hard surface layer of TiN when it interacts with N; when the temperature is above 600℃, titanium absorbs oxygen to form a hardened layer with high hardness ; When the hydrogen content increases, an embrittlement layer will also be formed. The depth of the hard and brittle surface layer produced by absorbing gas can reach 0.1~0.15 mm, and the degree of hardening is 20%~30%. Alumina also has a high chemical affinity and is easy to Alumina Ceramic Polishing Ring adhere to the friction surface. The thermal conductivity of alumina λ=15.24W/(m·K) is about 1/4 of nickel, 1/5 of iron, and 1/14 of aluminum. The thermal conductivity of Alumina Ceramic Polishing Ring various titanium alloys is about lower than that of titanium. 50%. The elastic modulus of titanium alloy is about 1/2 of that of steel, so it has poor rigidity and is easy to deform. It is not suitable to make slender rods and thin-walled parts. The springback of the machined surface during cutting is very large, about 2~3 of stainless steel. Times, causing severe friction, adhesion, and adhesive wear on the flank of the tool. Alumina is an allotrope, with a melting point of 1668°C, and a close-packed hexagonal lattice structure below 882°C, called α titanium; above 882°C, a body-centered cubic lattice structure called β titanium. Using the different characteristics of the above two structures of titanium, adding appropriate alloying elements to gradually change the phase transformation temperature Alumina Ceramic Polishing Ring and phase content to obtain titanium alloys with different structures. At room temperature, titanium alloys have three matrix structures, and titanium alloys are divided into the following three categories: α alloys, (α+β) alloys and β alloys. China is represented by TA, TC, and TB respectively. It is a single-phase alloy composed of α-phase solid solution. It is α-phase regardless of normal temperature or higher practical application temperature, with stable structure, higher wear resistance than pure titanium, and strong oxidation resistance. At a temperature of 500°C to 600°C, it still maintains its strength and creep resistance, but cannot be strengthened by heat treatment, and its room temperature strength is not high. It is a single-phase alloy composed of β-phase solid solution. It has high strength without heat treatment. After quenching and aging, the alloy is further strengthened. The room temperature strength can reach 1372 to 1666 MPa; but the thermal stability is poor and it is not suitable for use at high temperatures. .