We have proposed and developed a method for measuring the thermal conductivity of highly efficient thermal conductors. The measurement method was tested on pure metals with high thermal conductivity coefficients: aluminum (99.999 wt.% Al) and copper (99.990 wt.% Cu). It was demonstrated that their thermal conductivities at a temperature of T = 22 ± 1 °C were <λ_Al> = 243 ± 3 W/m·K and <λ_Cu> = 405 ± 4 W/m·K, which was in good agreement with values reported in the literature. Artificial graphite (${\rho }_{\mathrm{G}1}$ = 1.8 g/cm³) and natural graphite (${\rho }_{\mathrm{G}2}$ = 1.7 g/cm³) were used as reference carbon materials; the measured thermal conductivities were <λ_G1> = 87 ± 1 W/m·K and <λ_G2> = 145 ± 3 W/m·K, respectively. It is well established that measuring the thermal conductivity coefficient of thin flexible graphite foils is a complex metrological task. We have proposed to manufacture a solid rectangular sample formed by alternating layers of thin graphite foils connected by layers of ultra-thin polyethylene films. Computer modelling showed that, for equal thermal conductivities of solid products made of compacted thermally exfoliated graphite and products made of a composite material consisting of 100 layers of thin graphite foil and 99 layers of polyethylene, the differences in temperature fields did not exceed 1%. The obtained result substantiates our proposed approach to measuring thermal conductivity of flexible graphite foil by creating a multi-layer composite material. The thermal conductivity coefficient of such a composite at room temperature was <λ_GF> = 184 ± 6 W/m·K, which aligns well with measurements by the laser flash method.

An automated system for measuring the thermal conductivity of functional and structural materials was developed. The main building blocks of the setup are the following: heating unit and cooling unit creating a heat flux gradient in the test sample; thermal resistances for temperature registration and control; and thermal pads for better contact between parts of the setup and the sample. The effect of the thermal conductivity of thermal pads and thermal resistances on the distribution of thermal fields in the developed setup was studied by computer modelling. A control software for the measuring setup was developed based on the hardware implementation of the steady-state Fourier’s law-based method for the determination of thermal conductivity. The stopping criterion for the setup control software is the equality of heat fluxes in the heating and cooling units, as well as the stability of the thermal conductivity coefficient readings. The testing and calibration of the device were carried out using a sample of pure aluminum (99.999 wt.% Al). It was found that the experimental value of the thermal conductivity coefficient of the aluminum sample at room temperature (T = 22 °C) is <λ> = 243 ± 3 W/m·K. This value of the thermal conductivity coefficient is consistent with the literature data and experimental values obtained by the laser flash method, which ranges within λ = 210–260 W/m·K.

This study investigates the influence of the thermal expansion parameters during the production of a multigraphene-based composite gasket on its performance properties. Under laboratory conditions (near-laminar flow), compared with 700 °C, expansion at 1000 °C increased recovery from 7.5 to 9.2% and tensile strength from 3.8 to 5.6 MPa. For continuous industrial-scale production, MGS was pneumatically transported to increase process productivity. At the expansion temperature of 1000 °C, the material obtained under these conditions exhibited lower mechanical performance than that produced in the laboratory-scale process. The transport parameters themselves also had a measurable effect on the resulting properties. At pressures of 0.2 and 0.6 MPa, recovery increased from 8.6 to 9.1%, while tensile strength increased from 3.4 to 3.7 MPa. The highest recovery (10.0%) was obtained at a feed pipe insertion depth of 100 mm within the investigated range of 50–200 mm. Increasing the feed pipe diameter from 8 to 16 mm also improved the mechanical performance, with recovery increasing from 9.0 to 10.4% and tensile strength from 3.7 to 5.4 MPa. The experimental results, supported by thermal and gas-dynamic simulations, show that processing conditions alter the length, tortuosity, and fragmentation of multigraphene structures before compaction, which in turn affects the mechanical performance of the final material. These results establish a link between thermal and gas-dynamic processing conditions and the mechanical properties of CMGMs, providing a basis for optimizing their continuous production for sealing applications.

A measurement setup was developed for leakage determination in flanged joints with diameters up to 654 mm at temperatures ranging from −196 °C to +500 °C and pressures up to 200 bar. The operating principle is based on the differential pressure method, enabling the utilization of both helium and gaseous hydrocarbons as working media. The setup was validated through specific leak rate measurements on standard DN40/PN40 multigraphene gaskets in accordance with EN 13555, showing close agreement with data obtained from the reference Amtec TEMES fl.ai1 test rig. An intrinsically safe architecture combined with strain-gauge monitoring of tightening loads enabled the transition from bench-scale characterization to in situ testing of large-scale gaskets.