Rejuvenation of a Metallic and Oxide Glass by Cooling from the Supercooled Liquid State at Laboratory Rates

Abstract

Calorimetric study of relaxation and rejuvenation of PdNiP and SiO 2 -based glasses by cooling from the supercooled liquid state at laboratory rates is performed. For the former glass, cooling at the highest rate of 54 K min À1 recovers 34-36% of the enthalpy released upon relaxation. The interplay between relaxation and rejuvenation leads to a dependence of the heat absorption peak above the glass transition temperature T g on the cooling rate. The oxide glass displays a similar effect with analogous dependence on the cooling rate. Qualitative explanations for the observed phenomena are presented.Glasses are labile systems undergoing continuous relaxation toward metastable equilibrium. [1] The latter, however, in most cases is kinetically unachievable on the experimental time scale. Any annealing at temperatures below the glass transition temperature T g is accompanied by structural relaxation, which leads to the changes of practically all physical properties. However, independent of glass nature, it is generally possible to reverse structural relaxation making the structure to evolve toward higher energy states with concurrent change of the properties. This phenomenon is termed the recovery or rejuvenation. For polymer glasses, it was documented long ago. [2,3] From both scientific and application viewpoints, it is very important and challenging.In the case of metallic glasses (MGs), structural relaxation leads as a rule to undesirable structural changes, which result in the deterioration of practically important properties, e.g., causing the loss of plasticity, embrittlement, etc. However, rejuvenation provides partial or even full restoration of these properties. There are quite a few reports on the rejuvenation of MGs in the literature. The first reports on partial or even full disembrittlement produced by annealing below T g were published in the 1980s and beginning of 1990s of the past century. [4][5][6] There are several later papers dealing with the recovery of mechanical properties deteriorated by the preceding structural relaxation below T g . [7][8][9][10][11][12][13][14][15] The rejuvenation procedure in the majority of instances included heating of aged samples into the supercooled liquid region (i.e., above T g ) and subsequent fast cooling at the rates comparable with the production quenching rate (%10 2 K s À1 ) or even bigger. [7][8][9][10][11][12][13][14] In the latter case, the rejuvenation can lead to opposite property changes exceeding by the absolute value those occurring upon preceding structural relaxation below T g . [9,10] Besides thermal processing, rejuvenation of MGs can be achieved by plastic deformation, [7,16] loading within the elastic limit, [17] cryogenic thermocycling, [18] applying hydrostatic stress, [19] ultrasound, [20] or irradiation. [16] Detailed reviews on MGs' thermo-mechanical rejuvenation were published recently. [16,17] On the other hand, any rejuvenation experiments on oxide glasses are unknown to us. In part, this is due to the complexity of fast cooling of sampl...

Geological timescales’ aging effects of lunar glasses

“…The rejuvenated samples for these glassy particles were obtained by heating them up to the supercooled liquid region of 973 K, holding for 60 s, and then cooling down to RT at controlled cooling rates. Such rejuvenation treatment has been frequently applied in many glasses ( 88 , 89 ). A slower cooling rate of ~40 K/min was applied for all the glassy particle, by which the sample is termed as the L-R one.…”