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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a boundary layer (BL) semiconducting SrTiO3-based ceramic condenser, the BL structure has been investigated using high-resolution field-emission scanning electron microscopy (FE-SEM) and field-emission (scanning) transmission electron microscopy (FE-(S)TEM). In an initial TEM observation, a double layered structure was observed at the grain boundary region. It consisted of a grain boundary (second phase) and a pair of the metal diffusion layers of up to several nanometres in width across the grain boundary where the change of the crystal lattice distance was undetected by the high-resolution TEM image. A facet structure was often observed on the grain boundaries. It was particularly formed on (020) plane of the grain crystal. High resolution SEM showed a jagged striped structure on the surface of the bulk material and on the inside grain as revealed by fracture. Using the similarity in shape and size, it can be identified to correspond to the facet boundary structure. Its formation mechanism can be explained as that during the reoxidization process when the oxide flux of the mixture of Bi2O3, PbO and CuO, painted on the bulk material, surfaces migrates into the ceramic along the grain boundary. The oxide corrodes the grain surfaces including the bulk surfaces. This corrosion particularly occurs on (020) plane of the grain so that the facet structure is produced. In this paper, by using the atomic scale high angle annular dark field STEM, it has been determined that Bi atoms preferentially replace Sr atoms on (020) in the diffusion layers. The atom position displacement was also detected at the grain surfaces and this altered atomic assignment can be determined as an origin of production of Sr2Bi4Ti5O18 at the grain boundary. Also, it was observed that the layer width of the metal diffusion layers was often different between the both grains and changed locally so that the ribbon of the diffusion layers meandered around the straight grain boundary. Its possible mechanism is also proposed.
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PMID:Electron microscopy analysis of the boundary layer structure of SrTiO3 semiconducting ceramic 1079 23

Copper corrosion in the presence of orthophosphate and chlorine has indicated the formation of a protective scale containing either CuO or Cu2O depending on the pH. Furthermore, the scale forms relatively quickly, after 15 days of immersion EIS showed very little change. The scale is initially porous, but after prolonged immersion, the porous structure disappears, as evidenced by SEM. The equivalent circuit that is used to model the EIS spectra fits the data well and yields useful information on values, such as Rct, which varies from 2 to 10 kohms and Rfilm, which varies from 15 to 80 kohms when the immersion time is extended from 2 to 30 days.
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PMID:Copper corrosion kinetics and mechanisms in the presence of chlorine and orthophosphate. 1498 66

Two experiments were conducted to study effects of high-level Cu supplementation on measures of Cu status and forage utilization in beef cattle. In Exp. 1, eight steers randomly received an intraruminal bolus containing 12.5 g of CuO needles (n = 4) or no bolus (n = 4). Steers were individually offered free-choice ground limpograss (Hemarthria altissima) hay. On d 12 (Period 1) and d 33 (Period 2) steers were placed in metabolism crates, and total forage refused and feces produced were collected for 7 d. Daily samples of forage offered and refused and of feces excreted for each steer within period were analyzed for DM, ash, NDF, ADF, and CP. Liver biopsies were collected on d 0, 12, and 33. Copper oxide bolus administration resulted in greater (P < 0.03) liver Cu (DM basis) accumulation in Period 1 (556 vs. 296 mg/kg) and Period 2 (640 vs. 327 ppm). Apparent digestibilities of NDF and CP were greater (P < 0.04) for steers receiving no bolus in Period 2 (62.2 vs. 57.1% and 50.2 vs. 43.4% for NDF and CP digestibility, respectively). In Exp. 2, 24 crossbred heifers were assigned to individual pens and received a molasses-cottonseed meal supplement fortified with 0, 15, 60, or 120 ppm of supplemental Cu (Cu sulfate; six pens per treatment). All heifers were offered free-choice access to ground stargrass (Cynodon spp.) hay. Heifer BW and liver biopsies were collected on d 0, 42, and 84. Forage refusal was determined daily, and diet DM digestibility was estimated over a 21-d period beginning on d 42. Heifers consuming 120 ppm of supplemental Cu gained less (P < 0.05; 0.04 kg/d) than heifers consuming 15 (0.19 kg/d) and 60 ppm of Cu (0.22 kg/d), but their ADG did not differ from that by heifers consuming no supplemental Cu (0.14 kg/d; pooled SEM = 0.07). Heifers supplemented with 15 ppm of Cu had greater (P < 0.05) liver Cu concentrations on d 84 than those on the 0-ppm treatment and the high-Cu treatments (60 and 120 ppm). Forage intake was less (P = 0.07) by heifers receiving no supplemental Cu than by heifers on all other treatments (6.6 vs. 5.8 +/- 0.37 kg/d). Apparent forage digestibility was not affected by Cu treatment. These data suggest that high rates of Cu supplementation (Cu sulfate; > 60 ppm of total Cu) resulted in less liver Cu accumulation by beef heifers compared with heifers consuming diets supplemented with moderate dietary Cu concentrations (i.e., 15 ppm). As well, the administration of CuO boluses might depress the digestibility of forage nutrient fractions in steers.
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PMID:Effects of copper oxide bolus administration or high-level copper supplementation on forage utilization and copper status in beef cattle. 1628 29

Nanowires (NWs) of metal oxides (Fe(2)O(3), CuO, V(2)O(5) and ZnO) were grown by an efficient non-catalytic economically favorable method based on resistive heating of pure metal wires or foils at ambient conditions. The growth rate of iron oxide NWs exceeds 100 nm s(-1). Produced NWs were typically 1-5 microm long with diameters from 10 to 50 nm. The produced metal oxide NWs were characterized by means of SEM, TEM, EDX, XPS and Raman techniques. The field emission measurements from the as-produced CuO NWs were found to have a threshold field as low as 4 V microm(-1) at 0.01 mA cm(-2). The formation mechanism of the NWs is discussed.
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PMID:A novel method for metal oxide nanowire synthesis. 1942 May 73

Cu2(OH)2CO3 and CuO hierarchical nanostructures with variable morphologies were synthesized by controlled heating hydrated nanoparticles. The growth of nanostructures started with nanoparticles which formed loose aggregates. The nanoparticles within aggregates reorganized to form urchin-like structures which consisted of dense nanorods. With the growth of nanorods, regular microspheres were formed. At the same time, the nanorods coalesced to form wedge-like structures. The various surface subunits were just the outer display of wedge-like structures under different conditions. CuO nanostructures were gained by pyrolysis of malachite precursors. The attractive electrostatic force was responsible for aggregation of nanoparticles. During growth of aggregates, nanorods acted as growing tips which adsorbed adjacent nanoparticles. The Brownian motion was responsible for reorientation of nanoparticles to achieve low-energy configuration. Adsorbed water played an important role during formation of malachite nanostructures. The effect of growing environments on nanostructures was investigated. XRD, SEM, TEM and BET and so on were used to characterize the products.
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PMID:Formation process of Cu2(OH)2CO3 and CuO hierarchical nanostructures by assembly of hydrated nanoparticles. 1990 73

The porous Cu film was deposited on a Pt/Ti/Si substrate by electrochemical deposition accompanied by hydrogen evolution at very high current densities. CuO films with similar morphologies were obtained by subsequent annealing of the porous copper films. The morphology, composition and structure of the porous Cu and porous CuO were investigated by FE-SEM, EDS and XRD methods. The complete transformation of Cu to CuO after annealing was indicated. The sensing performances of the porous CuO film were evaluated in alkaline solution with the porous CuO film showing a wide linearity range from 1microM to 2.5mM with sensitivity of 2.9mAcm(-2)mM(-1), and detection limit of 0.14microM. The sensor showed good selectivity to conventional intermediates such as AA and UA and long term stability.
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PMID:The porous CuO electrode fabricated by hydrogen bubble evolution and its application to highly sensitive non-enzymatic glucose detection. 2000 1

We demonstrate a simple method to synthesize silver wires by thermal reduction of aqueous AgNO(3) droplet with catalytic anatase TiO(2) nanoparticles which were spin-coated on Si wafer. Structural characterization of the silver wires shows that the nanowires grow primarily along the [011] direction. SEM image of the silver wires clearly shows the catalytic TiO(2) nano-cluster attached to the end of the each silver wire. Since the process was surfactant-free, the silver nanowires prepared by our method retain the excellent electrical conductivity. The intrinsic resistivity calculated from the current-voltage curve for a wire with 12880.41 nm(2) cross-section area was 18.72 microohm cm, which is about 11.6 times higher than that of bulk silver (1.61 microohm cm). Our simple method can be also applied to generate CuO with ring-shaped microstructure by using ITO conducting glass as matrix. We have found that the size and reproducibility are well-controllable. A single phase of CuO ring-shaped microstructure with outer diameters ranging from approximately 13 to 17 microm and inner diameters ranging from approximately 1.4 to 3.3 microm was obtained. The composition of CuO microring was confirmed by thin-film XRD and XPS analyses.
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PMID:Constructions of silver nanowires and copper oxide microrings by a surface-formation technique. 2002 20

The processing conditions to prepare nano-sized Cu and Mo dispersed Al2O3 (Al2O3/Cu and Al2O3/Mo) composites by pressureless sintering were explored. The composite powders of Al2O3/Cu and Al2O3/Mo were obtained by the hydrogen reduction of Al2O3/CuO and Al2O3/MoO3 powder mixtures and consolidated by pressureless sintering using infrared heating furnace with a heating rate of 200 degrees C/min. SEM and TEM analyses for the composite showed that the nano-sized metal particles were well distributed and situated on the grain boundaries of the Al2O3 matrix. The nanocomposites, sintered at 1300 to 1500 degrees C for 4 min, showed the relative density of above 90%. Maximum hardness of 16.1 GPa was obtained in Al2O3/Cu nanocomposites with sintering additive of 1 wt% MgO. The sintered nanocomposites exhibited the enhanced fracture toughness of above 4.5 MPa x m(1/2), compared with monolithic Al2O3. The mechanical properties were discussed in terms of observed microstructural characteristics.
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PMID:Fabrication of alumina-based metal nanocomposites by pressureless sintering and their mechanical properties. 2035 63

In order to reduce the negative impact of coal utilization for energy generation, the pollutants present in the flue gas of coal combustion such as sulfur dioxide (SO(2)) and nitrogen oxide (NO) must be effectively removed before releasing to the atmosphere. Thus in this study, sorbent prepared from rice husk ash that is impregnated with copper is tested for simultaneous removal of SO(2) and NO from simulated flue gas. The effect of various sorbent preparation parameters; copper loading, RHA/CaO ratio, hydration period and NaOH concentration on the sorbent desulfurization/denitrification capacity was studied using Design-Expert Version 6.0.6 software. Specifically, Central Composite Design (CCD) coupled with Response Surface Method (RSM) was used. Significant individual parameters that affect the sorbent capacity are copper loading and NaOH concentration. Apart from that, interaction between the following parameters was also found to have significant effect; copper loading, RHA/CaO ratio and NaOH concentration. The optimum sorbent preparation condition for this study was found to be 3.06% CuO loading, RHA/CaO ratio of 1.41, 8.05 h of hydration period and NaOH concentration of 0.80 M. Sorbent characterization using SEM, XRD and surface area analysis were used to describe the effect of sorbent preparation parameters on the desulfurization/denitrification activity.
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PMID:Rice husk ash sorbent doped with copper for simultaneous removal of SO2 and NO: optimization study. 2072 75

CuO nano/microspheres with a wide diametric distribution were prepared by thermal decomposition of Cu(2)(OH)(3)NO(3) nano/microspheres formed in a simple asymmetric-electrode based cathodic-plasma electrolysis. The morphological, componential, and structural information about the two kinds of spheres were characterized in detail by SEM, TEM, EDX, XPS and XRD, and the results revealed that the morphology of the spheres were well kept after the componential and structural transformation from Cu(2)(OH)(3)NO(3) into CuO. The TGA/DSC study showed that the CuO nano/microspheres could be explored to be a promising additive for accelerating the thermal decomposition of ammonium perchlorate (AP). Combining with the current curve and emission spectrum measured in the plasma electrolysis, formation mechanism of the Cu(2)(OH)(3)NO(3) spheres was also discussed.
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PMID:Preparation, characterization and catalytic property of CuO nano/microspheres via thermal decomposition of cathode-plasma generating Cu2(OH)3NO3 nano/microspheres. 2134 43


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