采用大气等离子喷涂系统,制备了常规和超细Al2O3-3wt％TiO2涂层.利用 X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)对涂层相组成和显微结构进行了表征.测量了涂层直流电阻,介电常数和介电损耗.在等离子喷涂过程中,α-Al2O3氧化铝大部分转变为γ-Al2O3.氧化钛在常规涂层中主要以非计量的Ti2O3形式存在;对于超细涂层,氧化钛与氧化铝反应形成固溶体.常规Al2O3-3wt％TiO2涂层呈现典型的板条层结构,而超细Al2O3-3wt％TiO2涂层除了具有板条层外,还含有大量的等轴α-Al2O3晶粒,其尺寸在150～800nm之间,在常规涂层中,组成板条层的柱状γ-Al2O3晶粒直径约为700nm;而对于超细涂层,其绝大部分<200nm.与常规Al2O3-3wt％TiO2涂层相比,超细Al2O3-3wt％TiO2涂层具有较高的直流电阻;但在相同频率下,超细涂层介电常数和介电损耗都较常规涂层小.
Conventional and nanostructured Al2O3-3wt%TiO2 coatings were deposited by plasma spraying with conventional and nanostructured powders, respectively. The phase compositions and microstructure of the as-spraying coatings were characterized by XRD,
SEM and TEM. The electrical resistivity, dielectric constant and dielectric loss of coatings were measured. In both conventional and nanostructured
Al2O3-3wt%TiO2 coatings, alumina mainly existed in the form of γ-Al2O3 with some α-Al2O3. Non-stoichiometric Ti2O3 was found in the conventional coating; while in the
nanostructured coating, titania reacted with alumina to form solid solution. The conventional Al2O3-3wt%TiO2 coating exhibited a typical splat
microstructure. For the nanostructured Al2O3-3wt%TiO2 coating, many equiaxed α-Al2O3 grains besides splat lamellae were also observed.
The size of equiaxed α-Al2O3 grains was about 150～800nm. Compared to the conventional Al2O3-3wt%TiO2 coating, electrical
resistivity of the nanostructured Al2O3-3wt%TiO2 coating increased. But the nanostructured coating exhibited lower dielectric constant and
dielectric loss.
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