Papers by Keyword: TEM

Abstract: The defect structure of Mg implanted GaN substrate was evaluated by TEM observations, AFM surface observations and Raman scattering spectroscopic analysis. Mg ions were implanted at room temperature (RT) and 500 °C. TEM results showed that the defect distribution along depth scale is different between RT and 500 °C condition. The several peaks originated from ion implantation were found from Raman scattering spectra and the characteristics of the defects by implantation were discussed. The crystal quality of the sample implanted at 500 °C was found to be better than that of RT by comparing the FWHM of the E₂ peak.

Abstract: By mechanical blending method or melt extrusion method, several kinds of poymers and OMMT were selected with different mixing progress and conditions, and several polymer/OMMT nanocomposites with different substructure morphology were prepared. The properties of polymer/OMMT nanocomposites were investigated. Firstly, several types of OMMT were prepared with different layer spacing, the results of XRD and TEM showed that the OMMT with larger layer spacing would form exfoliation nanocomposites, and then the schemes explained the mechanism. The polyethylene (such as LDPE, HDPE, LLDPE) composited with the same OMMT indicated the influence of different molecular chain structure. Different morphology of PP/OMMT and EPDM/OMMT nano-composites were discussed to find the relationship of shear force effecting structure.

Abstract: The effects of rolling deformation on the interface bonding strength and microstructure of bimetallic clad plates were simulated. The composition and sub-structure of the interface were analyzed by electron probe micro-analyzer (EPMA) and transmission electron microscope (TEM). The results showed that the interfacial bonding strength of clad plates was significantly depend on the deformation process, and the bonding time was also a significant factor on bonding effect apart from total strain in the two-stage rolling. Chromium, nickel and other alloying elements have a significant diffusion zone at the bonding interface with a diffusion width of about 10µm. High resolution TEM analysis confirmed that there was an sound metallurgical bonding at the interface, and the structure of martensite in transition zone and matrix approximately meet the coherent relationship of(200) Ferrite // (111) Martensite and [020] Ferrite // [211]Martensite.

Abstract: This work aims at optimizing the H₂ reduction time of Fe/rGO as a preparatory step for the use of the reduced catalyst in Fisher-Tropsch synthesis (FTS). The catalytic system used was Iron Nanoparticles (NPs) loaded on reduced graphene oxide (rGO) support. The as prepared sample was analyzed by TEM, FTIR and XRD spectroscopy. Samples of the produced Fe/rGO catalyst were used to optimize the reduction conditions in the FBR reactor. The three samples were reduced under 1atm H₂ gas flow of 50 sccm at 500°C for 8, 12 and 24 hrs. The samples were collected after reduction and analyzed by XRD, FTIR and TEM imaging. The best condition showing full reduction with minimal sintering was at 12hr.

Abstract: Graphene, the most unique member of carbon family has fuelled a huge interest across the globe with its superior mechanical, chemical, optical and electronic properties. It has opened enormous avenues for humankind in terms of different applications. Since its discovery in 2004, people have tried various techniques to extract graphene, such as mechanical exfoliation, chemical exfoliation, epitaxial growth, CVD (chemical vapour deposition) etc. However, the above methods are not optimal for mass production, neither are they simple and cost effective. The present work highlights synthesis of graphene through electrochemical approach and its subsequent characterization. Pyrolytic graphite is subjected to intercalation of two different concentrations of HNO₃ electrolyte. XRD, FESEM and TEM were utilised to understand the structure and morphology of the obtained few-layer graphene nanosheets (FLGNs). Scanning probe spectroscopy is a useful technique for understanding the morphological structure of a sample at atomic level. Authors have utilised AFM which shows the thickness of the FLGNs to be in the range of 5-6 nm. STM studies of graphene nanosheets revealed atomic scaled periodicity and atomic flatness.

Abstract: The joining points between martensite packets (laths) and their microstructure in low-carbon martensitic steel were TEM studied. In order to determine the real microstructure of the packet, martensite examinations were conducted before low-cycle fatigue (LCF) tests, considering the structure of the packets and types of their joining. The changes in microstructure occurred in the above places after austenite-martensite transformation were also analyzed. It was shown that after jointing some packets initiate arch-like contours in the laths, exhibiting a presence of local stresses. Several types of joints are considered, including the penetration of laths of one packet into that of neighboring one. It was revealed that the microstructure changes are exhibited in joining points without any external deformation, and result in the localized plastic deformation at LCF. It is assumed that microcrack initiation and commencement of fatigue failure of the material should be expected to happen just in these areas. All the above is explained from point of view of the peculiarities of martensitic transformation.

Abstract: For a number of years, nanomaterials have been considered as a perfect solution to maintain the stability of different cultural heritage materials. In the present trial, hydroxyapatite nanoparticles (HAp-NPs) have been synthesized via the wet chemical reaction of calcium nitrate and ammonium hydroxide. Then, the possible efficiency of HAp-nanoparticles was evaluated to improve restoration formulas for some archaeological lime-based plasters. A broad series of analytical methods, namely OM, FE-SEM, TEM, AFM, XRD and BET surface area-pore size analysis, was selected for characterizing the archaeological samples and to rate the experimental tests. Further, the physical-mechanical behavior of samples was measured. The emulated modifications induced by the HAp-NPs treatment have been evaluated and discussed.

Abstract: The precipitation of two 6xxx (Al-Mg-Si) alloys with and without copper (Cu) and excess silicon (Si) has been investigated by using the differential scanning calorimetry (DSC), transmission electron microscopic (TEM) and X ray diffraction (XRD) analysis. The analysis of the DSC curves found that the excess Si accelerate the precipitation. The values of activation energies for each peak of DSC curves were determined by using Kissinger–Akahira–Sunose (KAS) and Boswell isoconversional methods. The alloy which has an excess Si and copper require larger activation energy for precipitation despite the acceleration of the precipitation by the excess Si. TEM observation result shows there is smaller size and higher density of precipitate in excess Si alloy than those of excess-free.

Abstract: Carbon Nanosphere (CNs) has been successfully synthesized from bamboo fibers at low temperatures by carbonization and activation. For activation used Potassium Hydroxide (KOH) at temperature 105°C, 155°C, 205°C, 255°C and 305°C. X-Ray Diffraction (XRD) spectra shows hexagonal and amorphous phase and Fourier Transform Infrared (FTIR) spectra shows decrease C-O bond with increasing activation temperature. Transmission Electron Microscopy (TEM) image for activation temperature of 105°C confirmed that sources the formation of Carbon Nanosphere. In this study shows bamboo fiber has a high potential as a carbon nanosphere material.

Abstract: The article presents the results of research on tribological properties and corrosion resistance of hybrid and individual coatings embedded with the ALD (Atomic Layer Deposition) and PVD (Physical Vapour Deposition) technique on aluminum alloy substrates. Al-Si-Cu alloys coated with hybrid ALD+PVD coatings show significantly higher abrasion resistance compared to uncoated samples. In particular, the TiO₂+WC hybrid coating has the highest abrasion resistance. The highest resistance to corrosion is demonstrated by the sample with the TiO₂ type ALD coating. As a result of coating, the surface roughness of the tested samples increases, which is related to the occurrence of morphological heterogeneity in the form of solidified drops.The innovative approach of combining several technologies, while simultaneously selecting proper materials and parameters can significantly affect the future and functionality of products obtained. The technique of combining the hybrid coating technology still requires a lot of researches, the results of which can change the meaning and use of new innovative products. Keyword: PVD, ALD, hybrid coatings, TEM, corrosion resistance,