The effect of CuFe2O4 ferrite phase evolution on 3–5 μm waveband emissivity

Entropy-Assisted High-Entropy Oxide with a Spinel Structure toward High-Temperature Infrared Radiation Materials

“…Based on the ratio of the peak areas of Fe 2+ and Fe 3+ , the contents of Fe 2+ and Fe 3+ are 65.5 and 34.5%, respectively. As shown in Figure f, the O 1s spectrum consists of three peaks located at 529.9 eV (noted as O L ), 531.7 eV (noted as O V ), and 533.4 eV (noted as O H ), which can be attributed to lattice oxygen in the HEO, oxygen vacancy with low coordination, and surface-adsorbed water, respectively. ,,− The difference in bond energy and bond length between the disorderly distributed metal cations and the O L leads to a rebalancing of the density around the O L , causing the cations to deviate from their original positions and producing a severe lattice distortion. The lattice distortion increases the O L in an unbalanced bonding state, resulting in the separation of oxygen atoms from the lattice and the formation of O V .…”

Band gap and oxygen vacancy engineering of honeycomb‐like CuFe2O4 spinels toward enhanced high infrared emissivity

“…However, these OVs may polish the energy levels of the original sample and induce the narrowing of the band gap, thus improving its infrared radiation performance in the 3-5 µm band. 28 Raman scattering is considered a technique to present the vibrational modes in both crystalline and amorphous materials; thus, it was applied to obtain further insight into the structure and OVs of the as-prepared CNFO-X samples with various chemical compositions. Figure 3A which separately correspond to the T 2g (1), E g , T 2g (2), F 2g , and A 1g (1) modes of spinel CFO structure.…”

“…Figure 3A which separately correspond to the T 2g (1), E g , T 2g (2), F 2g , and A 1g (1) modes of spinel CFO structure. 28,29 In specific, the peak located above 670 cm −1 , that is, A 1g (1) is associated with the stretching vibration of metal-oxygen at the tetrahedral site, whereas the low-frequency characteristic peaks, including T 2g (1), E g , and T 2g (2), commonly represent the symmetric and asymmetric stretching vibrations of the cation at the octahedral site. Compared to the original CNFO-0 sample, the other four samples show no obvious shift in the peak at 670 cm −1 , whereas they demonstrate a slight blueshift in the characteristic peaks at 470 cm −1 , thus further verifying the successful incorporation of Ni 2+ in the CFO spinel octahedral coordination and the increase of OVs.…”

A Novel Optimization Model and Application of Optimal Formula Design for CuxCo1−xFe2O4 Spinel-Based Coating Slurry in Relation to Near and Middle Infrared Radiation Strengthening

“…This indicates that the spinel structure was prepared. However, there existed other compositions like Fe 2 O 3 and delafossite (CuFeO 2 ), which are not conducive to the increase of emissivity because they are transparent to infrared radiation [16]. The reason for the presence of Fe 2 O 3 in sample S1 is that improper stoichiometric ratio in the raw materials led to excessive Fe 2 O 3 existed as remnant.…”

“…The energy-saving mechanism of this coating has been the subject of considerable research, and a number of conclusions have been obtained: (a) the coating can improve the emissivity of the wall surface and thus strengthen the radiation heat transfer by absorbing more heat from the incident radiation and by reflecting less [9][10][11]; (b) the coating absorbs the incoming radiation from combustion gases, which have an intermittent spectral distribution, and it then radiates out continuous spectral radiation. It thus enables the heated material to absorb more heat by radiation [12][13][14][15]; (c) the wavelength of the high-temperature radiation within the furnaces is of 1-5 µm, and the coating can improve emissivity in this waveband [16][17][18].…”