Papers by Keyword: Nanocrystallite

Abstract: Gas atomized Al88Ce8Fe4 alloy powders were ball-milled and investigated at charge ratiosof 5:1, 15:1 and 30:1 and milling speeds of 150 and 200 [RPM], respectively. The morphology,microstructure and composition of the powders were examined by laser diffraction technique, SEM,EDS and XRD. The result indicates the evolution of the powders under milling experiences initiallycold welding, aggregating the powders into larger-sized disk-shaped particles; followed byfragmentation, forming smaller-sized equiaxed particles; and finally leading to a steady state, whereparticles morphology, composition and phases keep constantly unchanged. This procedure has beentestified as a general rule for milling at each of the charge ratios of 5:1, 15:1 and 30:1 and at millingspeeds of 150 and 200 [RPM] while milling at larger charge ratios or higher speeds drives faster toreach the steady state at which homogeneous, fine-sized glassy powders can be obtained.

Abstract: An array of GaSb nanocrystallites (NCs) was formed on Si(001) substrate by solid-phase epitaxy at 500 °C. Owing to the embedded GaSb NCs, p⁺‑Si/NC‑GaSb/n‑Si mesa diode spectral sensitivity has extended up to 1.6 µm at room temperature, and its integral sensitivity has increased by 4–5% in the wavelength range of 1200–1600 nm, as compared to a conventional Si diode. This result was achieved by embedding only 10 nm of GaSb in the form of NCs inside a silicon matrix. In addition, we could obtain a significant electroluminescence (EL) signal at 120 K in a very wide wavelength range from 1.3 to 2.1 µm (0.95–0.59 eV). The EL spectrum has a broad maximum at 1700 nm (0.73 eV). The threshold pumping current density was as low as 0.75 A/cm².

Abstract: We present a direct soft templating method to synthesise mesoporous tin dioxide network that maintains a porous structure after calcination at 400 °C and 500 °C and has a relatively high BET surface area of 220 and 100 m² g^-1, respectively. TEM, BET and XRD results confirm that both crystal and pore sizes increase as a result of increasing the temperatures during the calcination step. This method is highly reproducible.

Abstract: Formation of GaSb by means of solid phase epitaxy of amorphous Ga:Sb (1:1) layer on Si (001) substrate at 500 °C has been studied. At amorphous layer thickness of 16 nm, a continuous nanocrystalline layer of GaSb was formed. Decreasing of amorphous layer thickness up to 0.8 nm resulted in formation of separated GaSb nanocrystallites (NCs), which had a mean lateral size of 30–80 nm and mean height of 2–3 nm, while their concentration reached 3×10⁹ cm^-2. Atomic force microscopy and low energy electron diffraction data showed that GaSb NCs could be fully embedded into silicon lattice by deposition of 25-nm-thick silicon layer at 650 °C. Nevertheless, on a surface of the silicon layer, some holes have been formed because of NCs moving toward to the surface. The holes formation can be almost completely suppressed by deposition of additional 25-nm-thick silicon layer at 500 °C – so-called “stop-layer”.

Abstract: Under the conditions of the presence of surfactants and ultrasonication, the use of different cerium salt, respectively, with carbonate under solid state chemistry reactions, the synthesis of nanorare earth metal complexes of cerium carbonate crystals was formed. The solid phase was characterized by powder X-ray diffraction (XRD) and electron diffraction (ED). The particle size, its distribution, and morphology of the prepared nanocrystallite were observed by transmission electron microscopy (TEM). The results show that particle sizes are relatively uniform, the morphology of the crystal is spherical, the average particle diameter is about 60 nm, and the yield rate is approximately 93.2%. Furthermore, during the synthesis, the solid-state reaction conditions including raw materials, matching proportion of reactants, additions of inert substance, addition of trace solvents, surfactants and porphyrization time, etc, all have some influence on the morphology, particle size and size distribution of the final products. During the synthesis of the cerium carbonate nanocrystallites, the solid state reaction conditions such as changing reactant, matching proportion of reactant, adding inert substance, joining a little solvent or surface active solvent and grinding at different times may influence morphology, particle size and the size distribution of final products.

Abstract: Cobalt ferrite nanocrystalline powder was synthesized from the powder mixture of cobalt carbonate and iron oxide by mixed oxide ceramic method. The effects of temperature of calcination as well as molar ratio of CoCO₃/Fe₂O₃ on the phase structure, morphology and magnetic properties of the products were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM) techniques, respectively. The samples calcined at 800 and 900 C consisted of cobalt ferrite, iron oxide and cobalt oxide. In the sample calcined at 1000 C, the reaction was completed and single phase CoFe₂O₄ with a mean crystallite and particle sizes of 49 and 300 nm, respectively was obtained. The above sample showed hard magnetic behavior with a coercivity of 337 Oe, saturation magnetization of 76 emu/g and remanence of 19 emu/g.

Abstract: Under the conditions of the presence of surfactants and ultrasonication, the use of different cerium salt, respectively, with 8-quinolinolate under solid state chemical reactions, the synthesis of nanorare earth metal complexes of cerium 8-quinolinolate crystals was formed. The solid phase was characterized by powder X-ray diffraction (XRD) and electron diffraction (ED). The particle size, its distribution, and morphology of the prepared nanocrystallite were observed by transmission electron microscopy (TEM). The results show that particle sizes are relatively uniform, the morphology of the crystal is spherical, the average particle diameter is about 30 nm, and the yield rate is approximately 89.9%. Furthermore, during the synthesis, the solid-state reaction conditions including raw materials, matching proportion of reactants, additions of inert substance, addition of trace solvents, surfactants and porphyrization time, etc, all have some influence on the morphology, particle size and size distribution of the final products. During the synthesis of the cerium 8-quinolinolate nanocrystallites, the solid state reaction conditions such as changing reactant, matching proportion of reactant, adding inert substance, joining a little solvent or surface active solvent and grinding at different times may influence morphology, particle size and the size distribution of final products.

Abstract: By adding CuO into heated Fe (NO₃)₃ aqueous solution, a precipitation reaction takes place to form nanosized iron oxide. The product obtained were characterized by transmission electron microscopy (TEM), vibrating sample magnetized (VSM), X-ray diffraction (XRD), energy disperse X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The experimental results showed that the product is weakly magnetic nanoclusters based on smaller ferrihydrite Fe₅O₇(OH)·4H₂O nanocrystallites. The nanoclusters are of about 40 nm size and absorbed by Fe (NO₃)₃. The experimental results are attributed to the Fe (NO₃)₃ hydrolysis reaction being enhanced by CuO as hydrolyte. A new route is proposed for the preparation of nanosized oxide using hydrolysis enhanced.

Abstract: The presence of crystallites in urine is closely related to stones formation. In this article, the components, morphology of nano- and micro-crystallites in urines of 20 uric acid (UA) stone formers as well as their relationship with the formation of UAstones were comparatively studied using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The main constituent of urinary crystallites was uric acid. Their particle size distribution was highly uneven, ranging from several nanometers to several tens of micrometers, and obvious aggregation was observed. These results showed that there was close relationship among stone components, urinary crystallites composition and urine pH.

Abstract: Under the conditions of the presence of surfactants and ultrasonication, the use of different cerium salt, respectively, with oxalic acid under solid state chemistry reactions, the synthesis of nano-rare earth metal complexes of cerium oxalate crystals was formed. The solid phase was characterized by powder X-ray diffraction (XRD) and electron diffraction (ED). The particle size, its distribution, and morphology of the prepared nanocrystallite were observed by transmission electron microscopy (TEM). The results show that particle sizes are relatively uniform, the morphology of the crystal is spherical, the average particle diameter is about 40 nm, and the yield rate is approximately 91.6%. Furthermore, during the synthesis, the solid-state reaction conditions including raw materials, matching proportion of reactants, additions of inert substance, addition of trace solvents, surfactants and porphyrization time, etc, all have some influence on the morphology, particle size and size distribution of the final products. During the synthesis of the cerium oxalate nanocrystallines, the solid state reaction conditions such as changing reactant, matching proportion of reactant, adding inert substance, joining a little solvent or surface active solvent and grinding at different times may influence morphology, particle size and the size distribution of final products.