Ex situ methods (TEM, XRD, and Raman spectroscopy) have been used to study the processes occurring at the multi-walled carbon nanotube/silicon interfaces (MWCNT/Si) during heat treatment of MWCNT-Si composites containing highly dispersed Si particles deposited on the surface of MWCNTs by CVD method. It has been established that during heat treatment, starting from 900 degrees C, the formation of SiC particles occurs. A further increase in temperature leads to the formation of polycrystalline SiC particles and a significant shortening of MWCNTs due to the reaction between Si particles and the surface of MWCNTs. It is shown that one can control the size of the formed SiC crystallites by varying the time and temperature of heat treatment. The kinetic dependences of the SiC formation process were studied within the Avrami-Erofeev model. The activation energy for the formation of SiC is estimated at 470 kJ/mol. The influence of heat treatment on the electrical conductivity and porosity of MWCNT-Si composites in the pressure range of 25-175 MPa has been studied.

Энэхүү судалгааны ажлаар CVD аргаар Fe-Co/Al2O3 биметалл катализаторыг ашиглан аргон хийн орчинд бутан хийн урвалын хугацаа тогтмол 3 мин хугацаанд 590˚С, 640˚С, 690˚С, 740˚С, 790˚С температурын утгуудад НТНХ -г гарган авч, гарцын хэмжээ температураас хамаарч хэрхэн өөрчлөгдөж байгааг туршилтаар олж тогтоов. Катализаторын бүтэц найрлагын шинж чанарыг EDX анализын үр дүнгээр, морфологи гадаргуун шинж чанарыг SEM, TEM зургаас ажиглаж, дундаж диаметрийг тодорхойлоход 7 нм орчим байв. НТНХ –н морфологи, бүтэц гадаргуун шинж чанарыг SEM, TEM зургаас ажиглаж, дундаж диаметрийг тодорхойлоход 14 нм орчим байв.

Chemical vapor deposition (CVD) along with thermal decomposition of monosilane (SiH4) in a fluidized bed of multiwalled carbon nanotubes (MWCNTs) is used to prepare MWCNT-Si composites containing silicon nanoparticles deposited on the nanotube surfaces. The structure of obtained Si nanoparticles in composites based on MWCNTs with different average diameters is studied by TEM, SEM, XRD, Raman spectroscopy, and FTIR spectroscopy of diffuse reflection. The size of Si particles varies from 3 nm to 45 nm and increases together with the MWCNT diameter. The major part of precipitated silica in the nanoparticles occurs in the amorphous state with small (below 3 nm in size) inclusions of nanocrystalline silicon. Specific discharge capacity of prepared composites used as the anode material for lithium-ion batteries is estimated.

Методом газофазного химического осаждения (CVD), с использованием термического разложения моносилана (SiH4) в псевдоожиженном слое многослойных углеродных нанотрубок (МУНТ) получены композиты МУНТ—Si, содержащие наноразмерные частицы кремния, нанесенные на поверхность нанотрубок. С использованием ПЭМ, РЭМ, РФА, КР- и ИК-Фурье спектроскопии диффузного отражения исследована структура получаемых наночастиц Si в композитах на основе МУНТ с различными средними диаметрами. Размер получаемых частиц Si варьируется от 3 нм до 45 нм и возрастает с увеличением диаметра МУНТ. Основное количество осажденного кремния в наночастицах находится в аморфном состоянии с небольшими включениями нанокристаллического кремния (менее 3 нм). Проведена оценка удельной разрядной емкости полученных композитов в качестве анодного материала литий-ионных аккумуляторов.

The present paper is devoted to the influence of the growth temperature of multi‐walled carbon nanotubes (MWCNTs) on their defective structure. The MWCNTs obtained within the range of 610–750 °C have been studied using two methods: Raman spectroscopy and the analysis of the temperature dependence of conductivity. This approach allows us to obtain independent data on the concentration of the defects within the MWCNTs via the intensity ratio of 2D and D bands, on one hand, and charge carrier concentration, on the other hand. The results obtained using Raman spectroscopy and the analysis of the conductivity have provided asymptotic and volcano‐like curves, respectively, of defect concentration within the temperature range studied. This can be attributed to the difference in the probing depth of each method (∼50 nm for Raman spectroscopy, and ∼2–3 nm for conductivity measurements) providing different sensitivity to surface impurities or defects. The secondary factors (the size of the active component, the amount of the lateral carbon deposits) have been shown to mask the influence of the growth temperature. Nevertheless, as these secondary factors and the synthesis temperature independently affect the effective nanotube defectiveness, we have shown the defect concentration to fall with increasing MWCNT growth temperature.