[en] There has been considerable interest in the impact of mechanical stresses on the thermodynamic state of glassy materials over the past quarter century - beginning with Struik's hypothesized erasure of ageing by large stresses. In particular, there has been a recent application of the ideas of erasure or rejuvenation in the general literature on glasses and glass-like substances. For this reason we here examine the evidence for and against rejuvenation and show several sets of data that argue strongly against rejuvenation or erasure of ageing as viable explanations for the interactions between large mechanical stimuli and the structure of the glass. Two particular experimental conditions are of significance here. First, measurements that are made in the sub-yield region and close to the glass transition allow the direct measurement of the evolution of the glassy response both with and without applying any stress. For example, in torsional dilatometry experiments where the volume recovery is measured simultaneously and in the same apparatus as the mechanical response, it is found that the baseline volume recovery is unaffected by the applied stress. The second class of experiments has been post-yield experiments, where the rejuvenation hypothesis is more difficult to reject. However, observations that post-yield ageing leads to evolution into a different 'equilibrium' state as measured by the recovered yield stress suggest that yielding does not rejuvenate the glass, but it may lead to a sort of polyamorphism or new deformation induced phase. We also present results of mechanically induced 'implosion' in polymers far below the glass temperature that suggest that mechanical stimuli may actually accelerate ageing rather than rejuvenating the glass. Finally, the origins of the power-law dependence on ageing time (also termed elapsed or waiting time) of the mechanical relaxation time are discussed, and the use of the elapsed time as a natural variable to describe ageing is shown not to be appropriate for structural glasses

No abstract available

[en] Previously known exactly solvable models of 2D semiclassical dilaton gravity admit, in the general case, only non-extreme black holes. It is shown that there exist exceptional degenerate cases that can be obtained by some limiting transitions from the general exact solution, which include, in particular, extremal and ultraextremal black holes. We also analyse properties of extreme black holes without demanding exact solvability, and show that for such solutions quantum backreaction forbids the existence of ultraextreme black holes. The conditions under which divergencies of quantum stresses in a free-falling frame can disappear are found. We derive the closed equation with respect to the metric as a function of the dilaton field that enables one, choosing the form of the metric, to restore corresponding Lagrangian. It is demonstrated that exactly solvable models, found earlier, can be extended to include an electric charge only in two cases: either the dilaton-gravitation coupling is proportional to the potential term, or the latter vanishes. The second case leads to the effective potential with a negative amplitude and we analyse how this fact affects the structure of spacetime. We also discuss the role of quantum backreaction in the relationship between extremal horizons and the branch of solutions with a constant dilaton

[en] Thermal analysis is a branch of material science where the properties of materials are studied with respect to the change in temperature, in a predetermined manner, under specific environment. The versatility of thermoanalytical techniques remain unmatched among the techniques invented over last hundred years. Thermoanalytical techniques provide a large amount of information over a wide range of temperature in a single measurement extending from few minutes to few hours, depending on the temperature region of interest. The main purpose of making thermal analysis measurement is seldom merely the evaluation of the property itself as a function of temperature but majorly it is to use the thermal analysis curve for studying the physical and chemical changes occurring in the sample with respect to the temperature. These techniques have been categorized on the basis of property to be measured like the volume of the material can be monitored using Dilatometry (DLA) or heat effects of a reaction process through differential thermal analysis (DTA) or differential scanning calorimetry (DSC) measurements

[en] In this paper glass forming capabilities of chalcogenide glasses based on As²Se³ with T1²Se concentrations are discussed. The studies were made using the differential thermal analysis (DTA) technique. These studies show that the glass forming tendency of As²Se³ decreases as the concentrations of T1²Se molecules are increased. Also these studies show that with addition of T1²Se, the glass transition temperature Tsub(g) of As²Se³ decreases, suggesting a tendency for weaker bonding and hence less stability of T1-rich compositions. (author)

No abstract available

[en] The heat exchange between the horizontal furnace of a differential thermal analyzer (DTA) and the sample is analyzed with the aim of understanding the parameters governing the thermal signal. The resistance due to radiation and conduction through the gas has been calculated and compared to the experimental values of the thermal-lag between the sample and furnace and apparatus sensitivity. The overall evolution of these parameters with the temperature and their relative values are well understood by considering the temperature differences that arise between the sample and holder. Two RC thermal models are used for describing the apparatus performance at different temperature ranges. Finally, the possibility of improving the signal quality through the control of the leak resistances is stressed

[en] An extended analytical model is derived for non-isothermal solid-state phase transformation assuming interface-controlled growth mode, e.g. polymorphic or allotropic transformation. In the modeling, incorporation of thermodynamic factor into kinetics of nucleation and growth is performed, so that the model can be used to describe the transformation occurring either near or far from the equilibrium state. Furthermore, the effect of the initial transformation temperature is included through a special treatment for the “temperature integral”, so that the model can be used to depict the transformation during either continuous heating or continuous cooling. Numerical calculations demonstrate that the extended analytical model is accurate enough for practical use. On this basis, a general rate equation for non-isothermal (isochronal heating and cooling) transformation is derived. Applying the present model, the overall kinetic behavior of γ/α transformation in binary substitutional Fe-based alloys (e.g. Fe–Mn and Fe–Cu) upon cooling, measured by dilatometry, is described successfully. Compared with previous work, where a site saturation assumption is generally made, the prevalence of continuous nucleation deduced using the present model prediction seems more reasonable.

[en] By combining the best practices in optical dilatometry with numerical methods, a high-speed and high-precision technique has been developed to measure the volume of levitated, containerlessly processed samples with subpixel resolution. Containerless processing provides the ability to study highly reactive materials without the possibility of contamination affecting thermophysical properties. Levitation is a common technique used to isolate a sample as it is being processed. Noncontact optical measurement of thermophysical properties is very important as traditional measuring methods cannot be used. Modern, digitally recorded images require advanced numerical routines to recover the subpixel locations of sample edges and, in turn, produce high-precision measurements

[en] Purpose of the work is choice of optimal conditions of object's registration by noncontact method on photo-dilatometer, assembled on the base of high-temperature furnace with heating elements of lanthanium chromites. Furnace construction allows to conduct heat treatment at temperature up 1700 deg C in oxidation medium. In the capacity of measuring device the camera have been used. Focus distant of tele-objective make up 80-200 mm. Accuracy of dilatometric measurements is defining by error of measuring device which depends from error of linear size measurements and value of object shrinkage after thermal treatment