Thermal properties of pressure sintered alumina–graphene composites

Abstract

The work concerns the alumina-graphene materials sintered by two different pressure methods. The different particle sizes of graphene were used. The preparation route of the matrix-graphene mixture was discussed in the paper. The so-prepared compositions with different amount of graphene were hot-pressed and spark plasma sintered. The influence on uniaxial pressure during the sintering process on the microstructure was presented by the SEM microstructural observations and ultrasonic measurements. The material with unidirectional oriented graphene particles was prepared, and the anisotropy was even higher than 30 % for 10 mass% of graphene additive. The influence of graphene orientation as an effect of pressing process on the thermal properties was analysed. The anisotropy of thermal conductivity was 90 % for 10 mass% of graphene. The thermal diffusivity and thermal conductivity of composites manufactured by hotpressing and spark plasma sintering method were compared. The experiment-based calculation of the specific heat versus temperature was presented in the paper. The thermal expansion coefficient was determined by dilatometric method. The thermal stability was analysed by thermogravimetric method, and it showed that composites with up to 2 mass% of graphene can work at temperatures higher than 700°C.

Temperature-dependent thermal properties of spark plasma sintered alumina

“…The increase in thermal conductivity, thermal diffusivity, and heat capacity with the increase in sintering temperature and sintering time is due to the increase in relative density and the decrease in porosity as explained above. This trend is in agreement with what published in literature [34]. In addition, the increase in crystallite size and the decrease in sub-grain boundaries contribute to the increase in these thermal properties.…”

Thermal diffusivity characterization of bond-coat materials used for thermal barrier coatings

“…Cowan's model was used for thermal diffusivity calculation in the case of single-layer analysis. This method gives the possibility to measure thermal diffusivity and heat capacity with high precision and is relatively simple in sample preparation and interpretation of results [11][12][13][14]. The analysed samples were placed in the sample carrier in such a way that their original surface (for example, rough top surface of NiCrAlY coating) was faced down.…”

Synergistic effects between iron-graphene and ammonium polyphosphate in flame-retardant thermoplastic polyurethane

“…As is known that graphene is a single carbon atom thick two-dimensional material that can be effectively utilized as a nanofiller for improving the mechanical, thermal, optical, and electrical properties of composites even at a low content, as many reports at home or abroad indicated [16][17][18]. Bao et al [19] found that with the masterbatch-melt-blending technique, graphene can be well dispersed and exfoliated in polystyrene as thin layers and the fire safety properties of PS were obviously improved, getting an increased thermal degradation temperature (18°C, PS/Ni-Gr-2), decreased peak heat release rate (40 %, PS/Zr0-Gr-2), and reduced CO concentration (54 %, PS/Ni-Gr-2).…”