300°Csourceproducer's maximum application temperature (optical components)
Values for
Cleveland-Cliffs / AK Steel ARMCO Pure Iron Product Data Bulletin (07/2022): Table 1 typical physical properties, Table 2 typical mechanical properties after SRA/recrystallization anneal.
Synthetic single-crystal silicon (cubic, diamond structure), Korth Kristalle (crystal grower) material data; Korth usually supplies Floating Zone (FZ) material, Czochralski (Cz) also offered. Silicon is elastically anisotropic; the producer quotes one modulus and the solver is isotropic.
Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Is Iron stronger than Silicon?
Iron is stronger: its yield strength is 186 MPa against tensile strength 130 MPa for Silicon (43%).
Which is lighter, Iron or Silicon?
Silicon is lighter: 2,329 kg/m³ against 7,860 kg/m³ for Iron.
Which is stiffer, Iron or Silicon?
Iron is stiffer: Young's modulus 207 GPa against 131 GPa for Silicon, so the same part in Iron deflects less under the same load.
Which is lighter for the same job, Iron or Silicon?
For the same stiffness or strength: Silicon is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
Part that must be
Iron
Silicon
Stiff rod or tie (tension)
2.14x heavier
lighter
Stiff beam (bending)
2.68x heavier
lighter
Stiff panel or plate
2.9x heavier
lighter
Strong rod or tie
2.36x heavier
lighter
Strong beam
2.66x heavier
lighter
Strong panel or plate
2.82x heavier
lighter
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).
Which conducts heat better, Iron or Silicon?
Silicon conducts heat better: 163 W/m·K against 73.2 W/m·K for Iron.
Which expands less with temperature?
Silicon expands less: 2.62 µm/m·K against 13.7 µm/m·K for Iron.