Properties of Al2O3-based ceramics with the addition of ultrafine Al2O3 powder synthesized by electrochemical method

The results of studies of the regularity of sintering and properties of corundum-based ceramics with the addition of ultrafine powder (UFP) Al2O3 synthesized by electrochemical method are presented. It is shown that with an increase in the calcination temperature and the concentration of UFP Al2O3, a regular increase in linear shrinkage, microhardness and strength of ceramics is observed (the maximum values at 1550 °С are 27,8 %, 17 GPa and 340 MPa, respectively). The introduction of UFP Al2O3 allows even at a calcining temperature of 1550 °C to achieve an apparent ceramic density of 3,87 g/cm3. Ref. 12. Tab. 3.

Оптически индуцированные эффекты в облученных ультрадисперсных керамиках Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=--BeO

Optically induced effects in ultrafine Al2O3-BeO ceramics irradiated with high doses of a pulsed electron beam (130 keV) were investigated. It is found that optical (470 nm) excitation of ceramics results in optically stimulated luminescence due to the emptying of traps associated with thermoluminescence peaks at 380 and 530 K. It is found that these traps are characterized by a complex energy spectrum with a non-uniformly distributed photoionization cross section. The prospect of using optically stimulated luminescence of Al2O3-BeO ceramics in high-dose dosimetry (3-30 kGy) is proved.

The Mechanical Milling Behavior of Ductile Cu Flakes when Using Ultrafine Al2O3 Reinforcements

In this study the effects of harder ultrafine Al2O3 particles on the mechanical milling of ductile Cu flakes (200mesh, 70μm) have been investigated. The small hard Al2O3 particle in the mixture acted as an effective milling agent not only by inducing a drastic change of the Cu morphology from flattened flakes to equiaxed crystals but also by reducing the milling time required for a uniform dispersion of Al2O3 in the Cu matrix. This was more pronounced as the Al2O3 concentration increased. A critical concentration of the reinforcing Al2O3 required for a shape change was observed at the range of 8 to 9wt. %. All the hard Al2O3 particles were uniformly embedded in the ductile Cu matrix regardless of the concentration of Al2O3. By increasing the milling time, the weldment and fragmentation of the Cu flakes became significant and a uniformly distributed equiaxed composite structure (13wt.% Al2O3) was obtained at above 70 min..