Strontium aluminates activated by Eu, Dy 3+ ions has recently attracted more attention due to not only their bright luminescence and super long afterglow without radioactivity but also the extensive application. SrAl 2 O 4 :Eu, Dy coatings were prepared by low power plasma thermal spraying (2.5-4W). The optimum spraying conditions have been established with spray parameters. The effects of the plasma conditions on the porosity rate of the coatings were investigated by many techniques, respectively X-ray diffraction (XRD) and scanning electron microscopy (SEM). To better qualify the characteristics of these coatings prepared from spray-dried powders, luminescence characteristics were also studied.

Al-Cu-Cr quasicrystalline (QC) coatings were deposited onto mild steel Q235A substrate by low power plasma spraying. The plasma torch was designed such that the powders can be injected axially (parallel to the axis of the plasma arc) into the region between the anode and cathode, and the carrier gases were transferred to the plasma flame, so the heating efficiency of the powders is greatly increased and the velocity of particles is much higher than an externally-fed powder system. The Al-Cu-Cr QC coatings were sprayed via this new technique at different plasma power (3~7kW) by controlling the secondary plasma gases (H 2 and N 2 ) flow or changing the arc current. The results show that, the original powder was mainly composed of a dominant icosahedral quasicrystalline phase I-Al 65 Cu 24 Cr 11 and a minor monoclinic θ-Al 13 Cr 2 . However, besides these two phases, body-centered cubic α- Al 69 Cu 18 Cr 13 , the approximant to quasicrystal I-Al 65 Cu 24 Cr 11 , has been detected in as-sprayed coatings. On the other hand, peak intensity of QC phase I-Al 65 Cu 24 Cr 11 decreased and that of crystalline phases (θ-Al 13 Cr 2 or α-Al 69 Cu 18 Cr 13 ) increased as the plasma power was increased.