The present work is devoted to the search for new electrode materials for lowtemperature thermionic energy converters (TECs). As shown, the carbon nanostructures (СNS) adding to pure powdered titanium in an amount of 3-9% wt. and their subsequent mechanical mixing leads to the formation of composites that acquire new qualities that were not present in any of their original pure constituents. Thus, the significant changes in the mechanical and electrical characteristics of composites are observed. For example, the electrical conductivity is changed up to 2 orders in initial state of composites as well as its maximum values after samples' compaction are increased (1.6-5 times) in comparison with both the pure Ti powder and the pure thermally extended graphite (TEG) in corresponding compression states. Such changes are caused by the presence of contacts between the metal particles and the CNS in the metal-nanocarbon composites and, accordingly, the possibility of the transition of free charges, including hot charges, from the metal to the CNS.

The advantages and restrictions of different positron spectroscopy methods in the study of electronic properties of multilayer carbon nanotubes (MWCNTs) with metallic and semiconductor types of conductivity are considered. The defects' influence on the parameters of the MWCNTs' electronic structure is established via method of the angular correlation of annihilation radiation (ACAR). Analysis of the results shows that annihilation occurs with both σ-electrons (within the interlayer intervals), quasi-free electrons, and electrons of unsaturated covalent bonds. As determined, the increase in the defects' concentration results to an increase in the radius of localization of the electron wave function (r m1) within the interlayer intervals and to an increase in the quasi-free electron concentration. Due to the formation of edge dislocations in the MWCNTs, the doubling of r m1 (up to 0.25 nm), the hybridization of unsaturated and stretched σ-bonds, and, as a consequence, the increase of the concentration of conduction electrons occurs. The high sensitivity of the positrons to defects can be used to develop methods of MWCNTs' attestation and defect identification; the 2r mb , 2r mi , and R values obtained from the ACAR spectra are the thickness of the layer, the interlayer distance, and the effective radius of free volume of the MWCNTs, respectively.

No abstract

В роботі узагальнено на випадок динамічно «товстого» кристалу модель для опису деформаційних залежностей повної інтеґральної інтенсивності динамічної дифракції в монокристалах з мікродефектами декількох типів. Запропонована модель в явному вигляді враховує явище аномального проходження дифузної складової повної інтеґральної інтенсивності динамічної дифракції. Виконані розрахунки демонструють можливість проведення кількісної оцінки характеристик хаотично розподілених дефектів даним методом. Ключові слова: динамічна дифракція, монокристали, мікродефекти, повна інтеґральна інтенсивність, деформація, фазоваріаційна діагностика. The model of the deformation dependences (DD) of total integrated intensity

No abstract