Room-temperature synthesis of χ-Al2O3 and ruby (α-Cr:Al2O3)

Cortes-Vega, Fernando D.; Yang, Weidong; Zárate‐Medina, J.; Brankovic, Stanko R.; Ramirez, José Martin Herrera; Hernandez, Francisco C. Robles

doi:10.1039/c8ce00360b

Cited by 12 publications

(16 citation statements)

References 35 publications

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“…The XPS and XDR techniques show no traces of Fe. Fe contamination during mechanical milling is normally found in other reports including our previous work . Nevertheless now it has been clearly reduced due to the soft nature of the precursors in use.…”

Section: Resultssupporting

confidence: 67%

“…Other reports have also demonstrated the successful synthesis of χ‐Al 2 O 3 and α‐Al 2 O 3 by milling . However, to the best of our knowledge there are no reports of room‐temperature synthesis of ruby, except for our previous work where we use two precursors (pseudoboehmite and Cr 2 O 3 ), instead of pure Cr‐doped pseudoboehmite. The formation of χ‐Al 2 O 3 is evident from XRD, however, to identify α‐Al 2 O 3 we resorted to use Raman.…”

Section: Resultsmentioning

confidence: 88%

“…The formation of χ‐Al 2 O 3 is evident from XRD, however, to identify α‐Al 2 O 3 we resorted to use Raman. In a parallel research we have demonstrated that ruby can be produced by milling pure pseudoboehmite and pure chromium oxide (Cr 2 O 3 ) . In the current work we start with Cr‐doped pseudoboehmite.…”

Section: Resultsmentioning

confidence: 99%

“…For those characteristics, ruby has emerged as desirable pressure and temperature sensor . Conventionally, ruby is synthesized at temperatures as high as 1200°C, and recently we demonstrated its potential synthesis at lower temperatures (<1000°C) …”

Section: Introductionmentioning

confidence: 99%

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Mechanochemical synthesis of α‐Al₂O₃‐Cr³⁺ (Ruby) and χ‐Al₂O₃

et al. 2018

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In this work we present a unique method to synthesize χ‐Al2O3 and α‐Al2O3 doped with Cr3+ (ruby). The ruby is synthesized by mechanical milling of pseudoboehmite that is doped in‐situ with chromium. The doping is carried by adding chromium sulfate hydrate to an aqueous solution rich in aluminum sulfate hydrate. The pH in the solution is controlled to be between 9 and 10 by using ammonia, which induces the pseudoboehmite precipitation. The Cr3+ is added for its remarkable effects on the detectability of ruby emitting luminescent R1 and R2 bands that are traceable in Raman spectroscopy. The formation of ruby is detected at milling times as short as 5 hours and increased with the milling time. Ruby phase is further confirmed by means of true atomic resolution Transmission Electron Microscopy (TEM).

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Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanochemical synthesis of α‐Al₂O₃‐Cr³⁺ (Ruby) and χ‐Al₂O₃

et al. 2018

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“…Al 2 O 3 is, after diamond, the second hardest material, susceptible to high temperatures, resistant to high mechanical stress, and chemically stable. [ 11–13 ] Among the many stable and metastable phases (α, β, γ, η, θ, κ, δ, χ), [ 14 ] γ‐Al 2 O 3 is particularly important in modern industries and has no shortage of applications. As a multifunctional metal coating, it is used for the prevention of abrasive and thermal wear; it is also used as a catalyst in spacecraft, power supplies, electronics, optics, and other applications.…”

Section: Introductionmentioning

confidence: 99%

Supersensitive Sm²⁺‐Activated Al₂O₃ Thermometric Coatings for High‐Resolution Multiple Temperature Read‐Outs from Luminescence

Ćirić

Stojadinović

Ristić

et al. 2021

Adv Materials Technologies

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The introduction of additional functionalities to materials is exceptionally important as it opens new applications for them. Aluminum, one of the most abundant and important materials, is coated with luminescent Sm2+‐doped γ‐aluminium oxide to impart thermometric functionality. Considering the potential industrial applications, two of the most widely used aluminum alloys, 6061 and 7075, are also coated. For this purpose, plasma electrolytic oxidation (PEO), an effective technique for producing hard ceramic coatings on various metal surfaces, is used. It is shown that thermometric coatings can be produced on aluminum in one‐step process by adding the raw precursor to the electrolyte. The valence reduction of Ln3+ to Ln2+ is achieved during the PEO process. The intense and broad (orange to deep red) emission from the coating shows supersensitivity to temperature changes over the 100–648 K range. The temperature is obtained from the coating emission using i) the emission intensity ratio method, ii) emission lifetime, and iii) emission band position with sensitivities of 4.8% K−1, 1.2% K−1, and 8 cm−1 K−1, respectively. Several applications would benefit from the thermometric coating's excellent temperature resolution of 0.04 K and the choice of three temperature read‐outs that facilitate the coating's use in different luminescence thermometry setups.

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