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

High silicon content SAPO(4)-5 (up to 0.511 atoms per unit cell) has been synthesised, using sodium 3-bromopropanesulfonate, sodium 1-butanesulfonate, sodium naphthalene-1-sulfonate or sodium n-decyl sulfate as surfactants; the SiO2 in the reaction gels ranged up to 3.0 (molar ratio), silicon incorporation was confirmed by XRD, XRF, TG-DTA, FT-IR and SEM techniques.
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PMID:Synthesis of high silicon content SAPO(4)-5 using anionic surfactants in a hexanol/aqueous two phase media. 1212 Mar 53

Regard to the poor adsorbability of the fixing film photocatalyst, a new TiO2 thin film by doping the nanosized SiO2 power with large specific surface area into sol for coating film was prepared. According to the results of characterization by XRD, SEM, FTIR techniques, it was found that the films were mainly anatase structure, containing a little rutile and its mean crystallite size was about 27 nm. And doped SiO2 was dispersed into films forming the amorphous cluster with the size form more than ten nanometers to scores of nanometers. The doping of SiO2 had no effect on the crystal structure and the surficial group of TiO2, except for increasing specific surface area. The result of photocatalytic degradation showed that activity of the film doped by SiO2 largely increased and was greatly influenced by the size and amount of doped SiO2. Besides, this photocatalyst also had very good stability. During the course of continuous experiment for more than 30 days, removal efficiency of reactive brilliant red X-3B was kept at about 80% all the time.
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PMID:[Influence of doping the nanosized SiO2 powder on structure and activity of photocatalytic films]. 1261 76

The morphology and composition of the composite coating of the Ni-P-SiO2 were analyzed by using the methods of SEM, AES and XPS. The results show the composite deposit is very smooth, uniform and good appearance. The coating is approximately 6.40 microns thick and has stronger corrosion resistance. The relative atomic percent contents of the coating is Ni 74.56%, P 12.38%, Si 2.77%, O 6.65% and Fe 2.32%.
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PMID:[XPS and AES studies of the Ni-P-SiO2 composite coating]. 1294 75

The siliceous skeletons of six hexactinellids and demosponges were compared using a series of physical and chemical tests. The sponges were two hermit-crab sponges (Class Demospongiae, family Suberitidae), one from Scotland, Suberites domuncula, and the other, Pseudospongosorites suberitoides, from the Gulf of Mexico, and four hexactinellids, Hyalonema sp., Euplectella aspergillum, Rhabdocalyptus dawsoni, and Aphrocallistes vastus. The operating hypothesis was that differences in the amorphous hydrated silica skeletons in Demosponges and Hexactinellids might prove taxonomically useful. Physical properties studied included SEM, glass density, glass transition temperature (Tg), TG/DTA to determine water content, and FTIR spectra. Chemical determinations were made using energy dispersive X-ray fluorescence (EDXRF). Spicular skeletal material is deposited in concentric layers around the axial canal. With the exception of differences at several bands in the IR spectra, the siliceous skeletons in demosponges and hexactinellids are largely indistinguishable. Density was similar in all sponges (range 2.03-2.13 g/cc) and similar to the density of opal (SiO2 x 1.5H2O) (mean = 2.09 g/cc). IR spectra were similar, with prominent absorption bands at 460-470, 800, and 1,090-1,100 cm(-1) (due to different vibrational modes of Si-O-Si linkages) and at 1,650 and 3,450-3,560 cm(-1) (due to water). The skeletons of all six showed similar spectra to that of silica gel both before and after heating to 1,200 degrees C. Water comprised 10-14% of the skeleton by weight, slightly higher in the demosponges. Average spicule chemical composition was 85.2% SiO2, 12.3% water, and 2.5% other elements (mainly S, Al, K, Ca, and Na). The percent amounts of Si did not differ significantly between the demosponges and the hexactinellids.
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PMID:Physical and chemical analysis of the siliceous skeletons in six sponges of two groups (demospongiae and hexactinellida). 1453 7

This study applies sintering technology to convert water sludge to a useful and stable adsorption material. The properties of the sintered materials were characterized using SEM and BET. Additionally, adsorption experiments were conducted to elucidate interactions of Cr(III) and Hg(II) at the interface between water and sintered material. Elemental analysis of original water sludge indicates its main constituents to be SiO2 (54%), Al2O3 (21%), and Fe2O3 (6.6%). The BET measurement indicated that the specific surface area of the sintered material is 4.6 m2/g. Since the SiO, content exceeds 50%, the surface of the sintered material becomes negatively charged. Adsorption of Cr(III) and Hg(II) on sintered material shows that sorption depends on the systems' pH. The sorption densities are 1.40 mg Cr/g at equilibrium pH 4.6 and 0.43 mg Hg/g at equilibrium pH 6.0. Background electrolyte does not affect the sorption of Cr(III) but markedly affects the sorption of Hg(II). The affinity of Cr(III) for surface reacting sites seem to exceed that of Hg(II). Competitive adsorption experiments were performed to determine the magnitude of the variations in adsorption due to competitive interactions among Cr(III) and Hg(II). The experimental results indicate that a higher competitive solute concentration results in a more significant competitive effect on Hg(II).
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PMID:Regeneration and reuse of water treatment plant sludge: adsorbent for cations. 1505 37

The photocatalytic removal rates r of dichloroacetic acid (DCAA), 4-chlorobenzoic acid (4-CBA) and 4-chlorophenol (4-CP) in water were compared for TiO2 samples used either as a powder or as a coating on a fiber glass tissue, SiO2 being the binder. From SEM-EDX measurements it was deduced that SiO2 prevails over TiO2 in the coating top layers and 18O2-Ti16O2 isotopic exchange showed that the accessibility of O2 to TiO2 was markedly reduced when TiO2 was thus coated. The unfavorable effect of the restricted TiO2 accessibility on r was drastic for DCAA, much less pronounced for 4-CBA, and still smaller for 4-CP. It is inferred that DCAA can be attacked only when it directly interacts with TiO2, whereas 4-CP can also react within the near-TiO2 surface water layers. The 4-CBA intermediate behavior is in line with the structural similarities of 4-CBA with DCAA and 4-CP.
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PMID:Mechanistic implications of the effect of TiO2 accessibility in TiO2-SiO2 coatings upon chlorinated organics photocatalytic removal in water. 1507 63

Preparation and characterization of porous hollow silica nanoparticles (PHSN) for controlled release applications were investigated. Through orthogonally designed experiments, the optimal synthesis conditions for the preparation of PHSN were obtained and the produced PHSN were characterized by BET, SEM, TEM and IR. Scanning and transmission electron microscopy images revealed their hollow shell-core structure and also demonstrated that the size and shape of PHSN are determined by the templating CaCO3 nanoparticles. The produced PHSN were applied as a carrier to study the controlled release behaviors of Brilliant Blue F (BB), which was used as a model drug. Being loaded into the inner core and on the surfaces of the nanoparticles, BB was released slowly into a bulk solution for about 1140 min as compared to only 10 min for the normal SiO2 nanoparticles, thus exhibited a typical sustained release pattern without any burst effect. In addition, higher BET of the carriers, lower pH value and lower temperature prolonged BB release from PHSN, while stirring speed showed little influence on the release behavior. It showed that PHSN have a promising future in controlled drug delivery applications.
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PMID:Fabrication of porous hollow silica nanoparticles and their applications in drug release control. 1526 16

The aim of this work was to study the influence of the phosphorus on the crystallization and bioactivity of glass-ceramics obtained from sol-gel glasses. For this purpose two sol-gel glasses with a similar composition but one of them containing P2O5 (70% SiO2; 30% CaO and 70% SiO2; 26% CaO; 4% P2O5, mol%) were prepared. Pieces of these glasses were treated at temperatures ranging between 700 degrees C and 1400 degrees C for 3 h. The obtained materials were characterized by XRD, FTIR, SEM-EDS and the biaxial flexural strength was determined in samples heated at 1100 degrees C. In addition, an in vitro bioactivity study in simulated body fluid (SBF) was carried out. The results showed that phosphorus plays an important role in the crystallization of the glasses: it induced the crystallization of calcium phosphate phases, the stabilization of the wollastonite phase at high temperature as well as the crystallization of SiO2 phases at low temperatures. Moreover, the presence of phosphorus produced a heterogeneous distribution of defects in the pieces and, therefore, the flexural strength of samples containing this element decreased. Finally, glass-ceramics obtained from glasses containing phosphorus showed the fastest formation rate of the apatite layer when soaked in SBF.
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PMID:The influence of the phosphorus content on the bioactivity of sol-gel glass ceramics. 1527 55

Europium-doped Gd2O3 with an average size of approximately 15 nm was coated on the surface of preformed silica nanospheres by the wet chemical method. SEM and TEM photographs showed that SiO2/Gd2O3:Eu core-shell submicrospheres are obtained. XRD patterns indicated that the Gd2O3:Eu shell is crystalline after heat treatment. FTIR and XPS spectra showed that the Gd2O3:Eu shell is linked to the silica surface by forming a Si-O-Gd bond. Photoluminescence studies showed that the luminescent properties are still retained after coating on an inert silica core; additionally, we noted that the emitting peaks are broadened, which results from size effects and interface effects of nanocrystal.
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PMID:Synthesis and characterization of SiO2/Gd2O3:Eu core-shell luminescent materials. 1531 46

Metallurgical slags from primary lead smelting were submitted to a 30-day batch leaching procedure in 20 and 8 mM citric solutions in order to determine the kinetics of release of Pb, Cu, Zn and As. The experiment was coupled with the PHREEQC-2 speciation-solubility modelling and mineralogical study of newly formed products (SEM/EDS, XRD, TEM/EDS and Raman spectrometry). A strong scavenging of metals and metalloids from the 8 mM citric leachate was observed due to the formation of newly formed products. The secondary precipitate consisted of well-developed calcite (CaCO3) crystals and amorphous organo-mineral matrix composed of hydrous ferric oxides and amorphous SiO2. Metals (Pb, Zn, Cu) and arsenic released into the solution were subsequently bound onto the newly formed product (adsorption on oxides) or trapped within the calcite structure (Zn, Mn). Similar scavenging mechanism can be taken into account in real soil systems with lower concentration of citric acid. Then, the covering of slag dumps with a thick soil layer and subsequent re-vegetation might be a possible scenario for slag management on some metallurgical sites.
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PMID:Leaching of lead metallurgical slag in citric solutions--implications for disposal and weathering in soil environments. 1548 18


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