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3D Thin-Walled Ceramic and Ceramic-Metal Components using Electrolytic Plasma Processing

Periodic Reporting for period 1 - 3D Cer-Met (3D Thin-Walled Ceramic and Ceramic-Metal Components using Electrolytic Plasma Processing)

Reporting period: 2019-01-01 to 2020-03-31

The work on transformation of shaped aluminium foil into ceramic article has been carried out on corrugated samples by plasma electrolytic oxidation. Corrugated foil samples were prepared with bespoke table top forming machine, which allows operation in real-to-real regime. Analysis of electrical regimes revealed that under certain polarisation conditions a special dynamic instability named as “scanning waves of current density” can be observed. Such scanning waves migrating along the sample surface provide uniform conversion of aluminium into oxide on the samples with complex shapes. The composition of the generated ceramic structures is mainly determined by electrolyte solution composition and includes crystalline and amorphous alumina as well as silicate phases. The wall thickness of the final ceramic articles reaches 100 microns, when 50 micron foil was employed as a precursor. Experimental results demonstrated that both ceramics obtained from either silicate and phosphate based electrolytes are stable for 10 days in 5% sulphuric acid, however, in alkaline solutions (10% NaOH) undergo relatively fast disintegration. This can be associated with dissolution of linking amorphous alumina in alkali giving sodium aluminate. It was found that because of high fragility of the final ceramic articles an evaluation of their mechanical properties requires development of special delicate techniques, whereas standard equipment is hardly applicable in this case. However, point estimates of hardness have shown typical values for PEO coatings between 800-1700HV. The process has great potential for use in healthcare devices and in more efficient transportation innovations.