Contents lists available at ScienceDirect Vacuum journal homepage: www.elsevier.com/locate/vacuum Getters for vacuum insulated glazing K. Chuntonov a,* , A.O. Ivanov b , B. Verbitsky a , J. Setina c a Mechemlab Ltd., Bar Yehuda Road 52, 3688102 Nesher, Israel b Ural Federal University, Lenin Avenue, 51, 620000 Yekaterinburg, Russia c Institute of Metals and Technology, Lepi pot 11, SI-1000, Ljubljana, Slovenia ARTICLE INFO Keywords: Vacuum insulated glasses VIGs life time Getter reactants Parabolic sorption law Ca-Li-Mg alloys ABSTRACT The vacuum problem in sealed off chambers of VIGs type has been solved. The solution is based on two in- novations. The first one is the usage of activationless getters in a form powders or granules of the composition Ca 0.35 Li 0.45 Mg 0.20 instead of barium. The second one – the changed sequence of assembling the vacuum window at which the getter is introduced into the window under vacuum but after the thermal outgassing and edge sealing of the VIG. A mathematical model of the sorption process for getter powders or granules, which follow the parabolic sorption law, has been built. The model analysis leads to an easy method of calculating the lifetime of the vacuum window, when the thermal-insulating properties are maintained by the getters of the class of reactants. Also a criterion of usefulness of technical solutions as applied to VIGs is provided. 1. Introduction Among vacuum applications of getter materials, the technical so- lutions, where the role of vacuum is to minimize the heat flows through the wall separating a certain object from the environment, form a se- parate group. This is the case of a double wall with an inner evacuating gap the gas pressure in which is maintained by the getter at the level, which practically excludes such mechanisms of heat transfer as con- vection and thermal conductivity. Let us refer here to thermoses, Dewar vessels, vacuum insulation panels, vacuum insulated glasses, etc. [1–4]. The mass production of the last product, vacuum insulated glasses (VIG), has been limited due to the number of problems, one of which is the problem of vacuum. The assembly of vacuum windows is a rather complex process, which can pay off only under the condition that the window would keep its ability to thermal isolation during tens of years. However, there is no confidence in that: none of the currently used ways of gettering the residual gases has been proved with any theore- tical or experimental data, which would speak about the feasibility of the window lifetime of ∼40 years. The doubts concerning the durability of VIGs become clear as soon as we address the analysis of the technology of their assembly. The assembly has been based on the concept of simultaneous thermal treatment of the glass plates and the getter, which is introduced into the glass construction before the edge sealing of the window [5–9]. After the hermetization of the window along the edges, it is subjected to degassing by heating under pumping down at 200 °C and higher, up to 600 °C, which quite naturally leads to the deterioration of the getter material. The intensive volume degassing of the glass increases the gas pressure in the gap between the glass sheets by orders of magnitude so that the getter, being activated at heating, rapidly saturates with the released from the glass gases spending its sorption potential in vain. Poor design solutions [7–9], according to which the getter recess is located in the aperture of the evacuation channel, also adds to this. As a result all the gases, emitted by the heated surface of the sheets, flow in the process of pumping down to the place where the getter is located, and saturate it. This procedure has nothing to do with the standard thermal acti- vation of the getter, when before heating the getter, and only the getter, high vacuum is created in the chamber. If the getter is heated in the atmosphere of active gases it just fails. In the case of the traditional NEGs the forming them transition metals at heating turn from ad- sorbents into absorbents [10] and, dissolving in themselves the max- imum possible amount of gas, lose the ability to sorb them in the future. If Ba EGs (barium evaporable getters [11]) are used then their powder mixture Al 4 Ba + Ni at the above mentioned temperatures reacts with active gases even more vigorously than the transition metals of NEGs. All these issues were discussed earlier although in connection with other systems with sealed off vacuum chambers [12]. The drawbacks of the current VIGs technologies are not limited to the above. Thus, getters based on transition metals at normal tem- perature are characterized by negligibly small sorption capacity com- pared with barium films or granules of its alloys [12–14]. At the same https://doi.org/10.1016/j.vacuum.2018.06.012 Received 16 April 2018; Received in revised form 3 June 2018; Accepted 4 June 2018 * Corresponding author. E-mail address: konstantin@mechemlab.com (K. Chuntonov). Vacuum 155 (2018) 300–306 Available online 06 June 2018 0042-207X/ © 2018 Elsevier Ltd. All rights reserved. T