Low temperature thermal radiative properties of gold coated metals

• Published in: International journal of refrigeration 2017-10, Vol.82, p.51-55
• Main Authors: Frolec, Jiří, Králík, Tomáš, Srnka, Aleš
• Format: Article
• Language: English
• Subjects: Absorptivity; Coating effects; Copper; Cryogenics; Cryogénie; Deposition; Emissions; Emissivity; Films d’or; Gold; Gold films; Heat transfer; Low temperature; Low temperature physics; Metals; Radiation; Rayonnement thermique; Substrates; Temperature dependence; Thermal radiation; Titanium base alloys; Transfert de chaleur
• ISSN: 0140-7007; 1879-2081
• DOI: 10.1016/j.ijrefrig.2017.06.034

•Emissivity and absorptivity of Ti–6Al–4V, Cu and various Au layers are investigated.•Au layer reduces large emissivity/absorptivity difference between Ti alloy and Cu.•Sputtered Au layer has the lowest emissivity/absorptivity among deposited samples.•Thermal radiative properties of gold layers strongly depend on purity of the gold. In order to assess the effect of gold deposition on thermal radiative properties of metallic materials, we measured total hemispherical emissivity and absorptivity of Au layers with a minimal thickness of 1 µm in dependence on the temperature TR of thermal radiation (from 20 K up to 320 K). Technically pure copper or titanium alloy (Ti–6Al–4V) was used as substrate while three types of Au layers were deposited by a sputtering process or a galvanic method. Emissivities among samples with Au layers ranged from 1.8% to 3.9% at room temperature. Galvanic deposition of pure Au lowered the original emissivity of Ti–6Al–4V alloy at 300 K from 15.8% to 3.4%, whereas the same deposition on mechanically polished Cu resulted in increase of emissivity by a factor of three, up to 3.2%. Absorptivity of each sample with Cu or Au surface was lower than its emissivity and showed a weaker dependence on TR.