The report will present the results of work carried out jointly with the Scientific-Practical Materials Research Centre of the National Academy of Sciences of Belarus (SSPA “Scientific-Practical Materials Research Centre”), Minsk, Belarus. Currently, the fields of application of composite materials (composites) are very wide, ranging from mechanical engineering to electronics. Composites based on copper disulfide, which serves as the basis for solar energy converters; composites based on cubic boron nitride, Ti, and Al, which can be used in high-energy and high-temperature electronics, solid-state dosimetry, have been investigated. The obtained composites were analyzed by X-ray diffraction and scanning electron microscopy. Neutron activation analysis was used to determine impurities in composite materials synthesized at the Scientific-Practical Materials Research Centre, to determine the optimal conditions for synthesis, and to identify sources of impurities, for that purpose the elemental composition of the synthesis equipment and burden materials was studied.