Papers by Keyword: Transmission Electron Microscope

Abstract: This research uses a transmission electron microscopy (TEM) approach to analyze the deterioration of the crystallinity of poly-Si placed on the textured substrate. On the textured substrate, we created a poly-Si photovoltaic film with a RMS roughness, σ of 64 nm. Based on TEM findings, we discovered that growth collisions are present in the poly-Si photovoltaic layer that was deposited on the textured substrate with an RMS roughness, σ of 64 nm. The growth direction of the columnar-like grains tends to be perpendicular to the slant slope of the textured substrate. The diagonally oriented columnar growth collisions may be seen clearly at V-shaped formations in the textured substrate. There are also cavities and fissures that were created by the collisions. There are also cavities and fissures that were created by the collisions. The crystallinity of poly-Si grown above the V-shape structure has worsened, as compared to poly-Si grown above the Λ-shape structure, according to the TEM and SAED pictures.

Abstract: Recently, the researchers gave a great interest in the superconducting topic, as the preparation method is importance to reach a high critical temperature. In this study, the Bi₂Sr₂Ca₂Cu₃O₁₀ (Bi-2223) compound prepared by thermal treatment method at different sintering temperatures such as (600, 700, 850) °C at (7) PH for (20 hrs). The phase formation was observed by X-ray diffraction, as well as information about the crystal structure, as the peaks were almost identical to the international standard document. the peaks are well indexed by tetragonal phase of Bi-2223. The results of the electrical resistance test showed that there is a difference in the critical temperature depending on the difference of the sintering temperatures The best result was at a temperature of 850 ° C. The sizes of the nanoparticles ranged from (22 - 123) nm, this is what the TEM measurements showed. It has been shown to be a successful method for preparing superconducting nanoparticles as (Bi-2223) compound

Abstract: The integration of germanium (Ge) into silicon-based microelectronics technologies is currently attracting increasing interest and research effort. One way to realize this without threading and misfit dislocations is the so-called nanoheteroepitaxy approach. We demonstrate that a modified Si nanostructure approach with nanopillars or bars separated by TEOS SiO₂ can be used successfully to deposit SiGe dots and lines free of misfit dislocations. It was found that strain relaxation in the pseudomorphically grown SiGe happens fully elastically. These studies are important for the understanding of the behavior of nanostructured Si for the final goal of Ge integration via SiGe buffer.

Abstract: The nanosized silica (SiO₂) with the size less than 100 nm have successfully been prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) via a modified Stöber method at room temperature. The experiment was conducted by controlling the amount of the catalyst used, i.e., ammonium hydroxide (NH₄OH). The morphology observation of the synthesized silica nanoparticles was conducted by using a transmission electron microscope (TEM). It was found that the size of the silica depending on the amount of the catalyst used, with homogenous size ranging from 10 to 360 nm. The doping of silver nanoparticles was done by mixing the synthesized silica with the silver ions (Ag⁺) solutions. Then the sample was annealed for 75 min which results in the nucleation of the silver nanoparticles less than 20 nm onto the silica surfaces, depending on the temperature used.

Abstract: The nanostructural characteristics of direct-current magnetron sputter-deposited Ni₄Al alloy films were studied during in situ isothermal annealing in a transmission electron microscope (TEM). An expansion of the lattice by nearly 5% was observed for the synthesized films in their low-thickness and as-deposited state. The lattice size approaches the bulk value when the film thickness increases or after vacuum annealing heat-treatment. The Ni₄Al films have a nanocrystalline structure in which the ordered L1₂ phase appears upon annealing at above 500°C. A grain coalescence trend was found for the Ni₄Al films during the in situ annealing above 500°C. This can be the main reason for the abnormal grain growth of these films at these high temperatures.

Abstract: In this paper, high resolution transmission electron microscopy (HRTEM) has been used to observe a Zr_41.25Ti_13.75Ni₁₀Cu_12.5Be_22.5 (at. %) bulk metallic glass (BMG) prepared from different methods, i.e. ion milling and electropolishing. The ion thinning brings out the white bulb pattern on the specimen surface and induces localized temperature increasing. The electropolishing does not influence microstructure of the amorphous phase. A new preparation technique of grinding method is introduced. For BMG, the electropolishing and grinding are the better method for TEM specimen preparation as compared with the ion thinning.

Abstract: MFe₂O₄ (Where M = Cu²⁺, Co²⁺ and Ni²⁺) has been synthesized using a citrate sol-gel self-ignition process in order to investigate their catalytic performance for reduction of p-nitrophenol. The ignited precursors were annealed at 400, 600, 800 and 1000 ^°C for 2 hrs. to obtain nanoferrite particles. The prepared samples were characterized using various instrumental techniques like FT-IR, XRD, and UV-VIS. X-ray analysis confirms the formation of single phase. Powder X-Ray diffraction patterns showed the formation of body centered tetragonal structure for CuFe₂O₄ and cubic structure for CoFe₂O₄ and NiFe₂O₄. It was observed that as the annealing temperature increases from 400 to 1000 ^°C, the XRD peaks grow sharper attributing to an increase in particle size with increasing temperature; which is consistent with TEM. Transmission Electron micrographs analysis revealed an enhancement in grain size with the annealing temperature. The disappearance of yellow colour indicated the conversion of p-nitrophenol to p-aminophenol and the occurrence of colour disappearance has been observed in one minute using CuFe₂O₄ (8mol %). This suggested the efficiency of CuFe₂O₄ in catalyzing p-nitrophenol reduction. FT-IR and UV-Visible spectroscopy has been used to confirm this reduction process. FT-IR spectra showed N-H stretching vibrations at ~3365 cm^-1 and 3350 cm^-1 attributing to the formation of primary amine using CuFe₂O₄ for catalyzing reduction of p-nitrophenol. The disappearance of the absorption band at 400 nm in the UV-Visible spectrum also confirms the conversion of p-nitrophenol to p-aminophenol.

Abstract: Multiwalled Carbon Nanotubes (MWCNTs) have been synthesized using a low cost arc discharge method without using metal catalyst and vacuum devices. Effect of magnetic field on the synthesis of MWCNTs and their purity has been scrutinized. A magnetic field of 310 gauss has been found to give better purity of carbon nanotubes as confirmed by Raman spectroscopy. However, the removal of amorphous carbon from the surface of so prepared multiwalled carbon nanotubes has been achieved by different oxidizing conditions. It has been observed that the maximum removal of amorphous carbon found by using the strong oxidizing agent HNO₃/H₂O₂. This strong oxidizing agent HNO₃/H₂O₂ removes most of the carbonaceous impurities leading to thermal stability of carbon nanotubes suggested by thermo gravimetric analysis. X-ray diffraction show the formation of carbon nanotubes having a peak indexed at (002) as the fingerprint for multiwalled carbon nanotubes. Fourier Transform Infrared (FTIR) spectra confirmed the formation of the multiwalled carbon nanotubes showing a characteristic stretching band at 1615 cm^-1 corresponding to the C=C bonds of tubular carbon. Raman spectroscopy revealed invaluable insights into the purification of nanotubes. G-band (1577 cm^-1) corresponds to the confirmation of MWCNTs. Defect induced D-band (1355 cm^-1) has been minimized after purifying CNTs with HNO₃/H₂O₂ for 24 hrs. Transmission Electron microscopic (TEM) studies indicate the formation of CNTs with controlled alignment having diameter in the range 2-8 nm.

Abstract: Microstructures of the Fe-29.6at%Pd alloy ribbons were observed with an X-ray diffractometer and a transmission electron microscope. The X-ray diffraction profiles at room temperature showed that the ribbon consists of FCT martensitic phase and FCC parent phase. Moreover, the ribbon exhibits a strongly 200-oriented texture analyzing with pole figure measurements. TEM bright field images for the cross section of the ribbon showed high-density striation in the FCT martensite variants. Twin-related two sets of reflections were observed in the SAED patterns taken of the FCT martensite variants. _FCT was nearly parallel to the thickness direction according to the analysis of the SAED patterns. This result corresponds to the pole figure measurements.

Abstract: By the use of YH₂ and NiO, oxide particles were introduced in Ni-base ODS alloys through reactive ball milling, which shows the advantages of energy-saving and uniform distribution of the oxide dispersion. The mophological and size evolution of ball milled powder were investigated, and the synthesized oxides were characterized. The results shows that the ball milled powder exhibits the feather of severe deformation. The disintegration of particles occurs after 10 h, and the balance of powder welding and fracturing is achieved around 25 h. the formation of Y₂O₃ with the size of 20~50 nm was confirmed by XRD and TEM results.