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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ceramic hollow spheres of MoS2 and MoO3 were obtained by sonochemical synthesis of MoS2 and MoO3 templated on silica nanoparticles (diameters 50-500 nm) followed by acid etching to remove the silica core. The resulting hollow materials have been characterized by elemental analysis, XPS, SEM, TEM, optical absorption, and hydrodesulfurization (HDS) studies. The TEM studies on the hollow ceramic materials indicate the formation of dispersed free spheres with a hollow core. The hollow materials obtained from thermally treated MoS2/SiO2 (450-700 degrees C) show the formation of layered MoS2 (lattice fringes approximately 6.2 A) with a wall thickness of 6-8 layers. The MoS2 hollow spheres are extremely active catalysts for the HDS of thiophene. Hollow spheres of MoO3 are prepared in a similar fashion. Surprisingly, upon heating, hollow crystals of MoO3 with sharp-edged truncated cubes containing inner voids are formed from the initial spheres.
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PMID:Sonochemical preparation of hollow nanospheres and hollow nanocrystals. 1572 72

This paper describes organic protective coatings on space material for anti-AO effects and the experiments to assess properties of the coatings. Organic protection was analyzed after exposures to ground state fast atomic (AO) radiation in the atomic oxygen beam facility for ground simulation experiments. The tests results have been analyzed with advanced FTIR, XPS and SEM. The test indicated that epoxy, alkyd and urethane organic coatings were highly reactive to AO with a strong degradation and changed in morphology of the surface layer. It is evident that siloxane coatings have excellent properties for anti-AO effects. The erosion product has SiO2 left on the surface, thus providing protection from further attack by the energetic oxygen atoms.
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PMID:[Studies on organic protective coatings for anti-atomic oxygen effects by spectrum analysis]. 1576 97

A new technology for solidification of digested sewage sludge referred to as converter slag solidification (CSS) has been developed using converter slag as the solidifying agent and quick lime as the solidifying aid. The CSS technology was investigated by analyzing the physicochemical properties of solidified sludge and determining its microstructural characteristics. The feasibility of using solidified sludge as a landfill cover material was considered in the context of the economical recycling of waste. Sludge solidified using the CSS technology exhibited geotechnical properties that are appropriate for replacing currently used cover soil. Microscopic analyses using XRD, SEM and EDS revealed that the main hydrated product of solidification was CSH (CaO . SiO2 . nH2O), which may play an important role in the effective setting process. Negligible leaching of heavy metals from the solidified sludge was observed. The solidification process of the hydrated sludge, slag and quicklime eliminated the coliform bacteria. Recycled sewage sludge solidified using CCS technology could be used as an effective landfill cover.
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PMID:Digested sewage sludge solidification by converter slag for landfill cover. 1576 91

Water molecules adsorbed on SiO2/Si(100) at 140 K to form amorphous solid water (ASW) layers were utilized as a buffer for assisting the growth of gold nanoclusters. It was shown that the average height and diameter of the clusters deposited on the silicon oxide substrate following the buffer annealing/desorption increase as the buffer layer becomes thicker and as more gold is deposited. The clusters' height and diameter were determined by tapping mode AFM and high-resolution SEM imaging, respectively. Typical heights were between 0.5 and 4.5 nm, and the diameters were in the range of 3-9 nm for ASW layer thickness of 7-100 ML and gold deposition in the range of 0.2-1.2 A. The density of the clusters decreased from 65 x 10(10) to 8 x 10(10) cm (-2) in the same buffer layer thickness range. Significantly different morphology of the clusters is obtained when compared to those formed by direct deposition of gold on the silicon oxide surface and to those grown on top of Xe as buffer material.
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PMID:Water as buffer material for gold nanocluster growth. 1614 75

In the present research work, the preparation and characterization of bioactive glass-ceramic scaffolds for bone substitutes are described. The scaffolds were prepared by starch consolidation of bioactive glass powders belonging to the SiO2-Na2O-CaO-MgO system using three different organic starches (corn, potatoes and rice) as reported in a previous screening process. The scaffolds, characterized by scanning electron microscopy, showed a porous structure with highly interconnected pores. The pores sizes assessed by mercury intrusion porosimetry put in evidence the presence of pores of 50-100 microm. The structure of the scaffolds was investigated by X-ray diffraction and revealed the glass-ceramic nature of the obtained material. The mechanical properties of the scaffolds were evaluated by means of compressive tests on cubic samples and the obtained results demonstrated their good mechanical strength. The in vitro bioactivity of the scaffolds was tested by soaking them in a simulated body fluid (SBF) and by subsequently characterizing the soaked surfaces by SEM, EDS and X-ray diffraction. Good in vitro bioactivity was found for the starting glass and for the obtained scaffolds. Moreover, the scaffold bioresorption, tested by measuring the samples weight loss in SBF at different periods of time, showed a partial resorption of the scaffolds. Cell culture testing of the three different scaffolds indicated no differences in cell number and in alkaline phosphatase activity; the morphology of the osteoblasts showed good spreading, comparable to bulk material which was used as the control.
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PMID:Microstructural and in vitro characterization of SiO2-Na2O-CaO-MgO glass-ceramic bioactive scaffolds for bone substitutes. 1616 99

Crack-free homogeneous nanoporous silica films on silicon wafer have been synthesized via supercritical drying of wet gel films obtained by spin-coating the polymeric silica sol, which was prepared using sol-gel method with tetraethoxysilane (TEOS) as precursor. The film is amorphous and nanoporous, and three-dimensional network, cross-linked by the primary particles whose sizes distribute between 10-20 nm showed respectively by XRD and SEM micrograph. The structure of the nanoporous SiO2 thin film was studied by FTIR spectra. The SiO2 thin film was composed of Si-O-Si and Si-OR, and was hydrophobic. The film contained Si-OH and became hydrophilic after being heat-treated at 250 degrees C or above in air. The heat-treated SiO2 thin film becomes hydrophobic by reacting with trimethylchlorosilane(TMCS). The TMCS-modified SiO2 thin film remains hydrophobic and can keep its nanoporous structure at a temperature lower than 450 degrees C in nitrogen.
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PMID:[Preparation and infrared spectral analysis of nanoporous silica thin film]. 1624 Oct 51

Particulate matter with aerodynamic diameters of < 1, 1-2.5, and 2.5-10 microm were collected during two seasons in two urban zones situated northeast and southwest, respectively, of a lead/zinc smelter located in a former mining region of northern France. We demonstrate the effectiveness of the combined use of computer-controlled Raman mapping and multivariate curve resolution (MCR) of the Raman images to determine heterogeneous chemistry at the level of aerosol particle. The resulting molecular images of major species were found to be in accurate agreement with elemental images obtained by WDS X-ray-mapping. Environmental SEM was very useful to localize spare metal-rich particles before Raman mapping. Some spare particles containing pyromorphite (Pb5(PO4)3OH) and franklinite (ZnxFe3-xO4) mixed with mineral dust were detected at the northeast (NE) sampling site, when the wind was blowing from the west (W) sector. These particles were probably suspended in the troposphere by the action of wind or by mechanical disturbance of polluted top soils. The most abundantly encountered particles in the 10-2.5 and 2.5-1 microm fractions were found to be aggregates of NaCl, CaCO3, CaSO4 x 2H2O, CaMg(CO3)2, SiO2, feldspar, clay minerals, alpha-Fe2O3, NaNO3, and Ca(NO3)2 x 4H20. Black carbon and (NH4)2SO4 particles were observed predominantly in the finest fraction. It was not rare to detect Pb and Zn-rich particles in the 10-2.5 and 2.5-1 microm fractions collected at the southwest (SW) sampling site, when the wind was blowing from the NE sector. Most of these mixed particles probably result from the aggregation between PbSO4, PbO x PbSO4, and ZnS particles emitted by the smelters and hydroscopic mineral dust during transport in the troposphere.
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PMID:Confocal microprobe Raman imaging of urban tropospheric aerosol particles. 1657 89

In the present study, we report the chemical vapor deposition (CVD) of nitrogen-doped (N-doped) aligned carbon nanotubes on a silicon (Si) substrate using ferrocene (Fe(C5H5)2) as catalyst and acetonitrile (CH3CN) as the carbon source. The effect of experimental conditions such as temperature, gaseous environment, and substrates on the structure and morphology of N-doped carbon nanotubes arrays is reported. From XPS and EELS data, it was found that the nitrogen content of the nanotubes could be determined over a wide range, from 1.9% to 12%, by adding the addition of hydrogen (H2) to the reaction system. It was also shown by SEM that N-doped carbon nanotube arrays could be produced on Si and SiO2 substrates at suitable temperatures, although at different growth rates. Using these concentrations, it was possible to produce three-dimensional (3D) carbon nanotubes architectures on predetermined Si/SiO2 patterns. The mechanism underlying the effect of nitrogen containing carbon sources on nanotube formation was explored using X-ray photoelectron spectroscopy (XPS).
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PMID:CVD growth of N-doped carbon nanotubes on silicon substrates and its mechanism. 1685 8

The temporal changes to supported Ni sites during the growth of graphitic carbon nanofibers (GCNs) via the decomposition of chlorobenzene over Ni/SiO2 at 873 K have been investigated. The reaction of chlorobenzene with hydrogen also generated benzene, via catalytic hydrodechlorination, as the principal competing reaction. Reaction selectivity was found to be time dependent with a switch from a preferential hydrodechlorination to a predominant decomposition that generated an increasingly more structured carbon product over prolonged time-on-stream. These findings are discussed in terms of Cl/catalyst interaction(s) leading to metal site restructuring, the latter manifest in a sintering and faceting of the Ni metal particles. The pressure exerted on the metal/support interface due to fiber formation was of sufficient magnitude to extract the Ni particle from the support; the occurrence of an entrapped Ni particle at the fiber tip is a feature common to the majority of GCNs with the incorporation of Ni fragments along the length of the GCN. Metal site restructuring has been probed by temperature-programmed reduction of the passivated samples, H2 chemisorption/temperature-programmed desorption (TPD) and XANES/EXAFS analyses. This restructuring serves to enhance destructive chemisorption and/or facilitate carbon diffusion to generate the resultant GCN. The nature of the carbonaceous product has been characterized by a combination of TEM-EDX, SEM, XRD and temperature-programmed oxidation (TPO).
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PMID:Ni/SiO2 promoted growth of carbon nanofibers from chlorobenzene: characterization of the active metal sites. 1686 Aug 17

Chemical composition and toxicity leaching characteristics of fly ash was analyzed. The experiment results show that many heavy metals were contained; leaching concentration of Pb is 67.03 mg/L, which exceeds the limit of identification standard for hazardous wastes. Effect of input mass of H3PO4 on immobilization of heavy metals and its long-term environmental stability was studied. The results show that when input 8% - 14% (H3PO4 mass/ fly ash mass) of H3PO4 sound immobilization effect can be achieved; 8% and 12% of H3PO4 will bring a satisfactory environmental stability of heavy metals, while more H3PO4 led to less buffer capacity to acid conditions. In fly ash treated by 12% H3PO4, a small quantity of crystal Cr2P2O7, ZnP2, Pb3P4O13, Pb3P2O7, NaZnPO4, NaPbP3O9, Ca2ZnSi2O7 can be detected by XRD; many independent fly ash particles and bar-shaped Pb5 (PO4)3Cl with a diameter of 0.3 - 0.5 microm were observed by SEM; concentrated heavy metal materials were not obtained by CHBr3 floatation. Conclusions can be drawn that, through neutralization reaction of H3PO4 with strongly alkaline fly ash, stabilization reaction conditions were improved, entrapped heavy metals were chemically activated and PO4(3-) needed in stabilization was produced. Activated heavy metals combined with PO4(3-) on surface of fly ash,generated phosphates existing as forms of solid solution in SiO2, CaCO3, CaSO4, KCl, NaCl.
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PMID:[Immobilization technology and mechanism of fly ash using H3PO4]. 1711 36


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