Papers by Keyword: Electron Microscopy

Abstract: Object of researches is continuous laser radiation sources on the mineral samples, the objects of alluvial layers, which contain gold, not extracted by gravitational methods. The formation of different structural surfaces of gold is established, general laws governing agglomeration and concentration of sub-micron gold are revealed.

Abstract: Nanocrystalline hydroxyapatite (HAp) powders were successfully synthesized by natural biopolymers based sol-gel technique. The biopolymers were extracted from the leaves of Yanang (Tiliacora triandra), Krueo Ma Noy (Cissampelos pareira) and Konjac (Amorphophallus konjac). To obtain HAp powders, the prepared precursors were calcined in air at 600, 700, and 800 °C for 2 h. The phase composition of the calcined samples was studied by X-ray diffraction (XRD) technique. The XRD results confirmed the formation of HAp phase with a small trace of β-tricalcium phosphate (β-TCP). The crystalline sizes of the samples were found to be 20-50 nm as evaluated by the XRD line broadening method. TEM investigation revealed that the synthesized HAp samples consisted of nanoparticles with a particle size in the range of 50-100 nm in diameter. The corresponding selected area electron diffraction (SAED) analysis further confirmed the formation of hexagonal structure of HAp.

Abstract: A simple hydrothermal method was developed to prepare shaped-controlled CeO₂ nanomaterials, in which, Ce (NO₃)₃· 6H₂O was used as Ce source and H₂O₂ was used as oxidant and morphologies controlling agent. Different morphologies of CeO₂ including nanoparticles, nanooctahedrons, nanorods and nanocubes could be obtained by simply adjusting the concentration of H₂O₂ in reaction system. These nanoCeO₂ could be dispersed in water and ethanol very well after reaction without using any surfactant. A possible growth mechanism was put forward to explain the morphologies evolution process based on TEM, SEM observations. There are not any other impurities were introduced into reaction, and the production ration is high enough, which supply a potential large-scale preparation method for CeO₂ nanomaterials.

Abstract: This study presents the use of physical and laboratory rolling simulations for the development of a novel direct quenching and partitioning (DQ&P) process for the development of tough ductile ultra-high strength structural steels with yield strengths ~1100 MPa and reasonable ductility and toughness. Suitable compositions were designed based on high silicon and/or aluminium content. The DQ&P parameters were established with the aid of physical simulation on a Gleeble simulator. Two types of dilatation tests were carried out: with or without prior straining in the no-recrystallization regime to establish the influence of controlled deformation on subsequent transformation structures and properties. Based on dilatation results, simulated rolling trials were conducted on a laboratory rolling mill and the rolled samples were direct quenched in water to the desired quench stop temperatures followed by partitioning in a furnace held at this temperature. Detailed microstructural examination confirmed that the desired martensite-austenite microstructures were achieved. Besides high strengths, the ductility (including uniform elongation) and impact toughness were quite improved in comparison to that of a direct quenched carbon steel in the same strength class.

Abstract: 0.7BaO·0.3SrO·0.3Nb₂O₅·0.7TiO₂ (SBN/BST) composite ceramics werefabricated using a Powder-Sol (P-S) method with Nb₂O₅fine powder suspended in the barium strontium titanate (abbreviated as BST) solsolution. By X-ray diffraction (XRD) investigations, it is found that thetetragonal tungsten bronze (TTB) phase and perovskite phase were co-present incompositions. The average grain size of BST and SBN phase is 140 nm and 2.2 μm,respectively. The room temperature relative dielectric constant is 1445 forthis sample measured at 1 kHz and zero bias. In the room temperature, thepyroelectric coefficient of the 0.7BaO·0.3SrO·0.3Nb₂O₅·0.7TiO₂is 39 nc/cm²·°C. The maximum value of F_D is about 2.4×10^-5 Pa^-1/2at 45°C.

Abstract: Pure and Ni-doped ZnFe2O4 nanoparticles, Zn1-xNixFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by microwave combustion method (MCM). The structural, morphological and magnetic properties of the products were determined by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM) and vibrating sample magnetometer (VSM). X-ray analysis showed that all the compositions crystallize with cubic spinel structure. The broadband visible emission is observed in the entire photoluminescence (PL) spectrum and the estimated energy band gap is about 2.1 eV. VSM measurements shows superparamagnetic behavior for lower concentration of Ni (x ≤ 0.2), whereas for higher concentration (x ≥ 0.2), it becomes ferromagnetic. The saturation magnetization (Ms) varies considerably with Ni content to reach a maximum value for Ni0.5Zn0.5Fe2O4 composition, i.e. 57.89 emu/g.

Abstract: Organofunctionalized phyllosilicates containing both amino and mercapto groups were synthesized and used as support for silver nanoparticles in situ deposition. Depending on silver concentration in relation to phyllosilicate different amount of nanoparticles size and distributions were obtained, even with smallest silver used causes strong exfoliation of the phylosilicate lamella. Also such condition favors nanoparticles formation with homogeneous distribution with smaller diameters and narrower particle particles size distributions. With highest silver amounts preferential external phyllosilicate surface crystallization is obtained, as given by particle diameters up to 30 nm. Scanning and transmission electron microscopies were successfully employed to characterize morphological and structural features for these synthesized materials, enabling atomic visualization for the silver nanoparticles. These new phyllosilicates containing silver nanoparticles are extensively employed to design inorganic light emission diodes and also in applying in biological fields.

Abstract: Objective observation of Tibetan medicine rhodiola on high altitude Pulmonary edema in rats and HIF-1a expression changes. Method Will 50 only male SD rats randomly divided into 5 group , are often oxygen control group (Xi'an , altitude 5m ), acute hypoxia control group (Xi'an , altitude 5m ), acute hypoxia Group (naqu , elevation 4500m ), rhodiola acclimatization control group ( Xi'an , altitude 5m ), rhodiola altitude acclimatization group (naqu, elevation 4500m ) , light and electron microscopic observation of lung tissue samples , immunohistochemical detection of various groups of lung tissue HIF-la expression, RT-PCR method detection altitude hypoxia group animal lungs HIF-la mRNA expression changes. Results Acute hypoxia group lung tissue microstructure and Ultrastructure of a discernible high altitude pulmonary edema, and after the Tibetan medicine rhodiola after high altitude pulmonary edema is significantly reduced, ( as in Figure 123456). Lung tissue within the immunohistochemical detection not see HIF-la protein expression, RT-PCR detection SD big rat intraperitoneal injection of rhodiola extract 40g BGE/kg, 2h open back began to rise 4h, peak, after declining 24h, basically back to their normal control group , level rhodiola medicine acclimatization group HIF a 1 am RNA expression are clearly higher than the atmospheric oxygen control group and acute hypoxia group (p < 0.01). Conclusions Tibetan medicine rhodiola on lung tissue HIF-lamRNA expression of conducive to reduce hypoxic rats high altitude pulmonary edema.

Abstract: Pt-Pd bimetallic nanoparticles were characterized using aberration (Cs) corrected scanning transmission electron microscopy (STEM) along with molecular dynamics simulations. The nanoparticles were synthesized through a microwave-assisted process. This technique has been applied to synthesize metallic nanoparticles at relatively short times, allowing a good control of size distribution. The structure of the bimetallic nanoparticles is fcc-like with an average size of 5 nm. To understand the properties of the bimetallic nanoparticles, it is necessary to know the positions of all the atoms in the nanostructure. We have used a recent quantitative method to analyze HAADF STEM images which allowed us to measure the total intensity of the scattered electrons for each atomic column. Beside with the characterization of the nanoparticles, we have performed classical molecular dynamics simulation for the structural and dynamical analysis of the cuboctahedral Pt-Pd bimetallic nanoparticles.

Abstract: Carbon nanotubes The discovery of ‘fullerenes’ added a new dimension to the knowledge of carbon science1; and the discovery of ‘carbon nanotubes’ (CNTs, elongated fullerene) added a new dimension to knowledge of technology2. Today, ‘nanotechnology’ is a hot topic attracting scientist, industrialists, journalist, governments, and even the general public. Nanotechnology is the creation of functional materials, devices and systems through control of matter on the nanometer scale and the exploitation of novel phenomena and properties of matter (physical, chemical, biological, electrical, etc.) at that length scale. CNTs are supposed to be the key component of nanotechnology. Almost every week a new potential application of CNTs is identified, stimulating scientists to peep into this tiny tube with ever increasing curiosity.