Paper presents the results of evaluation of heat resistance and specific heat capacity of MAR-M-200, MAR-M-247 and Rene 80 nickel

superalloys. Heat resistance was evaluated using cyclic method. Every cycle included heating in 1100°C for 23 hours and cooling for 1

hour in air. Microstructure of the scale was observed using electron microscope. Specific heat capacity was measured using DSC

calorimeter. It was found that under conditions of cyclically changing temperature alloy MAR-M-247 exhibits highest heat resistance.

Formed oxide scale is heterophasic mixture of alloying elements, under which an internal oxidation zone was present. MAR-M-200 alloy

has higher specific heat capacity compared to MAR-M-247. For tested alloys in the temperature range from 550°C to 800°C precipitation

processes (γ′, γ′′) are probably occurring, resulting in a sudden increase in the observed heat capacity.

In the paper, a method for determination of the near-critical region boundary is proposed. The boundary is evaluated with respect to variations of specific heat capacity along isobars. It is assumed that the value of specific heat capacity inside the near-critical region exceeds by more than 50% the practically constant value typical for fluids under normal conditions. It appears that large variations of heat capacity are also present for high-pressure subcritical states sufficiently close to the critical point. Therefore, such defined near-critical region is located not only in supercritical fluid domain but also extends into subcritical fluid. As an example, the boundaries of the near-critical region were evaluated for water, carbon dioxide and R143a.

This paper presents the results of experimental investigations of the basic thermal property – the specific heat capacity of selected heterogeneous materials – graphene oxide rubber composites. The value of specific heat capacity was measured with a PerkinElmer DSC 8000 differential scanning calorimeter using modulated temperature mode of operation. The heterogeneous material under investigation was the graphene oxide/rubber composite, which is used in the production of roller bearing seals. Two types of rubber have been used as the basic matrix of composites: the hydrogenated acrylonitrile butadiene rubber and the fluoroelastomer. Graphene oxide reduced with sodium hypophosphite was applied as a compo-site filler. The main goals of the work was to expand the database of thermophysical properties of materials and to inves-tigate the influence of material heterogeneity on the results of specific heat capacity measurements obtained with small-sized test samples.

Measurements of thermal diffusivity, heat capacity and thermal expansion of hot work tool steel 32CrMoV12-28 have been carried out in the temperature range from room temperature (RT) to 1000℃. 32CrMoV12-28 steel has been tested for military applications as steel for gun barrels. The thermophysical properties of this steel can be used as input data for numerical simulations of heat transfer in gun barrels. Both the LFA 427 laser flash apparatus in the RT1000℃ temperature range and the LFA 467 light flash apparatus in the RT500℃ temperature range were used for thermal diffusivity tests. Specific heat capacity was investigated in the range RT1000℃. The specific heat was determined by two methods, i.e. the classical method, the so-called continuous-scanning method and the stepwise-scanning method according to EN ISO 11357-4. The paper compares both methods and assesses their suitability for testing the specific heat capacity of barrel steels. Thermal expansion was investigated in the range RT1000℃. Inconel 600 was selected as the reference material during the thermal diffusivity test using LFA 467. Light microscopy (LM), scanning electron microscopy (SEM), and Vickers microhardness measurements were performed to detect changes in the microstructure before and after thermo-physical measurements. We compared the results of measurements of the thermophysical properties of 32CrMoV12-28 steel with the results of our tests for other barrel steels with medium carbon content, i.e. X37CrMoV5-1 (1.2343), 38HMJ (1.8509) and 30HN2MFA. The comparison was made in terms of shifting the effect of material shrinkage towards higher temperatures.

Organic phase change materials (PCMs), which are typically used as the accumulating material in latent heat thermal energy storage, provide chemical and thermal stability, but have low thermal conductivity. This limits heat transfer rates and prolongs storage charging/discharging time. A method to improve the thermal conductivity of organic PCMs is to add nanomaterials with high thermal conductivity. The paper presents the research on the effect of the addition of graphene nanoparticles (GNPs) on the thermal conductivity of organic PCM (RT28 HC), and its energy storage properties. The transient hot wire and the pipe Poensgen apparatus methods were used to measure thermal conductivity, and the differential scanning calorimetry method was used to determine the heat capacity and phase change temperature. The achieved characteristics of thermal conductivity depending on the amount of added graphene nanoparticles (and stabilizer) indicate that GNPs allow to increase the thermal conductivity on average by 26–87% in the solid state and by 7–28% in the liquid, but this reduces the PCM heat capacity. Therefore, the paper indicates what mass fraction of dopants is optimal to achieve the greatest improvement in thermal conductivity of RT28 HC and its smallest reduction in heat capacity, to use this nano-enhanced PCM in practice.