Search Results

1 - 8 of 8 items :

  • "TEM micrographs" x
Clear All
Preparation and characterization of cobalt and copper oxide nanocrystals

Abstract

Copper oxide and cobalt oxide (Co3O4, CuO) nanocrystals (NCs) have been successfully prepared using microwave irradiation. The obtained powders of the nanocrystals (NCs) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric (TGA) analysis and Fourier-transform infrared spectroscopy. The obtained results confirm the presence of both nanooxides which have been produced during chemical precipitation using microwave irradiation. TEM micrographs have shown that the obtained nanocrystals are characterized by high dispersion and narrow size distribution. The results of X-ray diffraction confirmed those obtained from the transmission electron microscope. Optical absorption analysis indicated the direct band gap for both kinds of the nanocrystals.

Open access
Effect of heat-treatment on grain growth of nanocrystalline tricalcium phosphate powder synthesized via the precipitation method

Abstract

Nanocrystalline tricalcium phosphate powder was synthesized via the solution-precipitation method followed by heat treatment in order to achieve phase evolution, which was then studied by XRD and TEM techniques. The crystallites sizes were estimated by the Scherrer method and results were confirmed by TEM micrographs. The experimental observations showed that nanocrystalline tricalcium phosphate can be successfully prepared from raw materials by the precipitation technique. This technique is a competitive method for nanocrystalline tricalcium phosphate synthesis compared to other techniques. Moreover, a simple kinetic growth investigation was performed on the nanocrystalline growth process during heat treatment. Results have shown growth rate to increase exponentially with temperature and the growth rate constants to increase with time. The average activation energies of tricalcium phosphate grain growth obtained by this method were 84.78 and 134.38 KJ/mol.

Open access
Synthesis and characterization of Co2FeAl Heusler alloy nanoparticles

Abstract

Heusler alloy Co2FeAl (CFA) nanoparticles have been synthesized by reducing a mixture of the precursors: CoCl2·6H2O, Fe(NO3)3·9H2O and AlCl3·6H2O under H2 atmosphere. XRD, SEM and TEM techniques have been used for the characterization of the prepared material. XRD and SAED data from TEM show the formation of mixed phases of L21, B2 and A2 type crystal structure of the alloy. The estimated particle size from XRD data and TEM micrograph has been found in the range of 10 nm to 50 nm. The saturation magnetization has been found of 115 emu/g from M-H characteristics which is close to its bulk value of saturation magnetization. Chemical composition of the elements has also been estimated from EDAX, which shows a ratio of Co:Fe:Al as 2.12:1.06:0.81.

Open access
The Effect of a Complex Stress State on Fatigue Crack Propagation and the Orientation of the Cracking Plane in VT3-1 Aeronautical Titanium Alloy

The Effect of a Complex Stress State on Fatigue Crack Propagation and the Orientation of the Cracking Plane in VT3-1 Aeronautical Titanium Alloy

The subject of the paper is the investigations of fatigue crack imitation and propagation in notched specimens made of the VT3-1 aeronautical russian titanium alloy under combined bending - torsion loading. The presence of short cracks was revealed at various ratios of bending to torsion. Experimental courses of short and long crack growth rates have been proved by the SEM and TEM micrographs which illustrated the changes in the mechanism of cracking in the examined specimens. The attempt was undertaken in order to explain partly brittle fracture that was observed in the range of fatigue short crack growth in the VT3-1 titanium alloy specimens. The results of the study of atmospheric hydrogen absorption capability and its ability for penetration inside the faces of nucleated and propagated microcracks in the surface layer allowed for suggestion that the cleavage mechanism of fracture found in the regime of short crack growth in the VT3-1 titanium alloy specimens was induced by hydrogen.

Open access
Influence of aluminium concentration in Zn0:9V0:1O nanoparticles on structural and optical properties

Abstract

The (V,Al) co-doped ZnO nano-structured powders (Zn0.9-xV0.1AlxO, where x = 0.02, 0.03 and 0.04) were synthesized via the sol-gel technique and their structural and optical properties were investigated. The effect of Al concentration on the structural and optical properties of the Zn0.9-xV0.1AlxO nanopowders was studied using various techniques. The XRD patterns indicate that the samples have a polycrystalline wurtzite structure. The crystallite size increases with increasing the Al content and lies in the range of 23 to 30 nm. The lattice strain, estimated by the Stokes-Wilson equation, decreases when Al content increases. SEM and TEM micrographs show that Zn0.9-xV0.1AlxO powders are the agglomeration of nanoparticles having spherical and hexagonal shapes with dimensions ranging from 20 to 30 nm. FT-IR spectra show a distinct absorption peak at about 500 cm-1 for ZnO stretching modes and other peaks related to OH and H2O bands. Raman spectra confirm the wurtzite structure of the Zn0.9-xV0.1AlxO nanoparticles. The direct band gaps of the synthesized Zn0.9-xV0.1AlxO nanopowders, estimated from the Brus equation and the crystallite sizes deduced from XRD, are around 3.308 eV. The decomposition process of the dried gel system was investigated by thermal gravimetric analysis (TGA).

Open access
Nanoparticle shapes: Quantification by elongation, convexity and circularity measures

using modified circularity and ellipticity measures”, Measurement , vol. 92, pp. 252–263, 2016. [9] M. Mohammadikish, “Hydrothermal synthesis, characterization and optical properties of ellipsoid shape α -Fe 2 O 3 nanocrystals”, Ceramics International , vol. 40, pp. 1351–1358, 2014. [10] L. Kopanja, M. Tadić, S. Kralj and J. Žunić, “Shape and aspect ratio analysis of anisotropic magnetic nanochains based on TEM micrographs”, Ceramics International , vol. 44, pp. 12340–12351, 2018. [11] T. O. Paine, L. I. Mendelsohn and F. E. Luborsky, “Effect of

Open access
Wrinkled graphene: synthesis and characterization of few layer graphene-like nanocarbons from kerosene

-EDS and TEM micrographs of the samples were recorded by means of JSM-6360 A (JEOL) and JEM-2100 (JOEL) systems, respectively. 3 Results and discussion 3.1 XRD analysis The X-ray diffractogram of KS1 ( Fig. 1 ) shows a characteristic peak of heterogeneous structure, indicating a mixture of graphite oxide and amorphous carbon at 25.09° as a result of oxidation of KS. Broadening of this peak is due to the relatively smaller size of the graphene layers or the short range ordering. The peak at 43.02° indicates the hexagonal lattice structure of the carbon

Open access
Synthesis and characterization of small size fluorescent LEEH caped blue emission ZnTe quantum dots

{C}},2{\rm{ h, LEEH}}} \over \longrightarrow {\rm{ZnTe}} + {\rm{NaCl}} + {\rm{HCl}}$$ ZnTe QDs sample was studied using UV-Vis absorption spectrophotometer (UV-1800, Shimadzu). PL measurements were carried out at room temperature using Oriel PL setup (with λ = 355 nm as incident excitation available from NdYAG laser) to calculate the band gap value. TEM micrographs of a nanoparticle sample prepared on carbon coated grid were taken using JEOL JEM-2010 Transmission Electron Microscope at 200 kV beam energy. Higher resolution TEM and SAED patterns of the sample

Open access