The diversity of the processing conditions is a significant factor in the often widely varying property values reported in the literature for polycrystalline TiB2. In this section, the available mechanical and thermal properties are examined to provide a better understanding of how the properties depend on the composition, grain size, and density of the material. For isotropic polycrystalline materials, the elastic properties may be expressed in terms of two independent moduli, the elastic modulus E and the shear modulus G. Values of E determined at room temperature by ultrasonic velocity and resonance methods for various grain sizes and densities fall roughly into two groups that are distinguished by density, but which have little perceptible dependence on grain size. This observation is consistent with numerous models that consider elastic properties to vary principally as a function of porosity. Over a large range of porosity (as much as 50 %), the dependence is well described by an exponential model, E = Es e−bϕ. However, the modulus decreases more rapidly for lower degrees of densification. In this expression, Es and b are parameters, and ϕ is the volume fraction of porosity for a wide variety of ceramics, b ≈ 4.1±1.8. Hence, for porosity that is less than about 10 %, expanding the exponential to first order in ϕ yields E ≈ Es′ + b′ ρ using ϕ = 1−ρ/ρtheo for total porosity and setting Es′ = Es (1−b) and b′ = Esb/ρtheo. Consequently, it can be expected that the elastic modulus will be linear in the measured density. If you are looking for high quality, high purity, and cost-effective Titanium diboride, or if you require the latest price of Titanium diboride, please feel free to email contact mis-asia.