COMPARISON OF THE EFFICIENCY OF DIFFERENT DETECTORS OF THE SCANNING ELECTRONIC MICROSCOPE «MIRA-LMH» FOR STUDYING MICROSTRUCTURE OF NANOMATERIALS

На первом этапе были синтезированы объекты исследования - диоксид кремния методом Штобера, где в качестве прекурсора использовали тетраэтоксисилан, и нанокомпозит ZnO - Au золь-гель методом с использованием в качестве прекурсора 2 - водного ацетата цинка. На втором этапе, микроструктуру и морфологию полученных образцов исследовали методом растровой электронной микроскопии на сканирующем электронном микроскопе «MIRA-LMH» фирмы «Tescan» с применением как классического детектора вторичных электронов, так и дополнительных детекторов - внутрилинзового детектора вторичных электронов и детектора отраженных электронов. В результате исследований установлено, что при использовании детектора вторичных электронов получаются изображения с топографическим контрастом и практически без шумов. При использовании внутрилинзового детектора вторичных электронов создаются изображения только материального контраста, без влияния рельефа поверхности. Также использование данного детектора позволило получить высококачественные изображения с большим разрешением на расстоянии от образца 5 мм. При использовании детектора отраженных электронов с рабочим расстоянием до образца 8 мм и увеличении разрешающей способности микроскопа, полученные изображения имеют низкий контраст границ, но представляют композиционную информацию с высокой чувствительностью. Таким образом, установлено, что внутрилинзовый детектор вторичных электронов, с рабочим расстоянием до образца 5 мм, является оптимальным для получения четких изображений микроструктры поверхности наноматериалов при многократном увеличении. At the first stage, the objects of study were synthesized - silicon dioxide by the Stober method, where tetraethoxysilane was used as a precursor, and a nanocomposite ZnO - Au by the sol-gel method using the aqueous zinc acetate dihydrate as a precursor. At the second stage, the microstructure and morphology of the obtained samples were investigated by scanning electron microscopy on a «MIRA-LMH» scanning electron microscope (Tescan company) using both a classical secondary electron detector and additional detectors - intralens secondary electron detector and back-scattered electrons detector. As a result of the research, it was found that when using the secondary electron detector, practically no noise images with topographic contrast are obtained. When using the intralens secondary electron detector, images of only material contrast are created, without the influence of the surface relief. Also, the use of this detector made it possible to obtain high-quality images with a high resolution at a distance of 5 mm from the sample. When using a back-scattered electrons detector with a working distance to the sample of 8 mm and increasing the resolution of the microscope, the resulting images have low border contrast, but represent compositional information with high sensitivity. Thus, it was found that the intralens secondary electron detector with a working distance of 5 mm to the sample is optimal for obtaining clear images of the microstructure of the surface of nanomaterials at multiple magnifications.

Metal-wire-embedded alumina insulating material using micro and nanoscale 3D printing for surface flashover mitigation in vacuum

Micro and nanoscale 3D printing technic is applied to fabricate functional insulating material which mitigates surface discharge in vacuum based on the microscopic electron multipactor suppression. The proposed alumina ceramic insulator design consists surface-embedded thin metal wires which introduce a local gradient of secondary electron emission yield, such that the trajectories of multipactor electrons are distorted by accumulated negative surface charges and the secondary electron emission avalanche across the insulator surface is intermitted. Considerable increases of surface flashover threshold and surface charging reduction are verified by experiment. Also, additional efforts are made to determine the optimal size and spatial distribution of the metal wire. A convex-shape flashover voltage trace is observed when increasing the wire width, suggesting a trade-off between the multipactor mitigation and the insulator strength. Wire position between the adjacency of cathode triple junction and middle of the insulator is proved to be favorable for flashover mitigation. The physical details of surface flashover mitigation by the proposed insulator design are revealed by an ab initio particle-in-cell (PIC) simulation code, corroborating the experiment from microscopic aspect.

The Applications of Ultra-Thin Nanofilm for Aerospace Advanced Manufacturing Technology

With the development of industrial civilization, advanced manufacturing technology has attracted widespread concern, including in the aerospace industry. In this paper, we report the applications of ultra-thin atomic layer deposition nanofilm in the advanced aerospace manufacturing industry, including aluminum anti-oxidation and secondary electron suppression, which are critical in high-power and miniaturization development. The compact and uniform aluminum oxide film, which is formed by thermal atomic layer deposition (ALD), can prevent the deep surface oxidation of aluminum during storage, avoiding the waste of material and energy in repetitive production. The total secondary electron yield of the C/TiN component nanofilm, deposited through plasma-enhanced atomic layer deposition, decreases 25% compared with an uncoated surface. The suppression of secondary electron emission is of great importance in solving the multipactor for high-power microwave components in space. Moreover, the controllable, ultra-thin uniform composite nanofilm can be deposited directly on the complex surface of devices without any transfer process, which is critical for many different applications. The ALD nanofilm shows potential for promoting system performance and resource consumption in the advanced aerospace manufacturing industry.

SECONDARY ELECTRON EMISSION FROM THIN ALUMINIUM FOILS PRODUCED BY HIGH ENERGY ELECTRON BEAMS

The description of the experimental equipment and technique for measuring the secondary emission of elec-trons (SEE) with application of accelerated electrons at the linear accelerator of the IHEPNP NSC KIPT with ener-gies up to 30 MeV and a standard secondary emission monitor [1] are presented. Experimental data of secondary electron emission yields from thin aluminum targets (8 and 50 μm) for primary electron beam energies of 16 and 25 MeV have been experimentally measured. The analysis of the experimental data and their comparison with the theory are carried out. It is shown that the proposed technique for measuring the yields of secondary electron emis-sion is useful and applied for study of low-energy and δ-electrons yields from thin foils, as well as to research the effect of the density effect depending on the energy of the primary electron beam.