Surface Carbon Content Research Articles

Effects of Starch on Latex Migration and on Paper Coating Properties

With increasing awareness of environmental protection and the surging cost of petroleum chemicals, eco-friendly polymer starches are being increasingly used as cobinders to partly replace synthetic polymer latex in the production of high quality coated papers. In this work, the influences of starch on latex migration and on properties of model clay coatings were investigated, in order to better understand interactions between starch and latex and their effects on coating structure development. The results showed that surface carbon content determined from XPS measurements decreased significantly with increasing starch content. This unexpected finding of lower surface carbon content for coatings of higher binder content was explained by assuming that water-soluble starch migrated to the surface would move back into the coating pores as an integral part of the aqueous phase, as the air–water interfaces recede from the coating surface into the capillaries during drying. It has also been found that gloss and ...

Surface reconstruction of W2C(0001)

A single crystal surface of ditungsten carbide,W2C(0001) was investigated using low-energy (LEED) and high-energy electron diffraction, Augerelectron spectroscopy, x-ray photoelectron spectroscopy (XPS), and high-resolution electronenergy loss spectroscopy (HREELS). A new reconstruction, , was found as a clean surface structure after annealing theW2C at > 1900 K.The surface carbon content is shown as larger than that in the bulk. Our preliminary results showedthat the same structure is realized also on WC(0001). The same surface periodicity is described foran Mo2C(0001) LEED pattern in the literature. This reconstruction phase is presumablycommon on the (0001) surface of hexagonal group-6 transition-metalcarbides. In the off-specular HREELS, an atomic vibration of 44.8 meV (361 cm − 1) appeared within the gap energy region of the bulk phonon bands, which was assigned to asurface carbon vibration perpendicular to the surface. One possible explanation of the lowvibrational frequency is very low adsorption height of the surface carbon atoms.

Lead patination in the atmosphere of Athens, Greece

Pure metallic Pb foils were exposed to the atmosphere of Athens for different periods of time (up to 150 non-rainy days) in the summer of 2005. The interacted Pb surfaces were probed using the 12C(d,p) 13C reaction ( E d: 1100 keV) at the Tandem accelerator of the NCSR “DEMOKRITOS”. Laser-μRaman and SEM–EDS were also complementary applied. Using the above methodology we recorded surface carbon profiles and concentrations as a function of the exposure time, corresponding to the evolution of the carbonate layer formed onto Pb foils due to the interaction with atmospheric H 2O and CO 2. The C-containing surface layer was found to be stabilized after ∼120 days. Further investigation by means of laser-μRaman and SEM–EDS indicated that the patina initially consists of Pb-hydroxycarbonates (hydrocerussite) overgrowing Pb-oxides, whereas Pb-sulfates (anglesite) and possibly basic Pb-sulfates are formed at the end of the patination process. The crystal growth of Pb-sulfates, or most likely the transformation of hydroxycarbonates to sulfates, is attributed to the pollution of Athens atmosphere by SO 2.

The production of a carbon-coated alumina foam

A method for producing ultra light carbon-coated alumina foam with a density of 0.04 g cm −3 and 99% porosity has been developed. It was synthesised from an aqueous aluminum nitrate–sucrose solution. The resin formed by heating this solution underwent foaming and set into solid green foam, which was sintered in the temperature range 1073–1873 K. The thermogram obtained by heating the green foam in argon showed 62 wt% mass loss occurring in three stages. The sintered foam constituted 81 wt% of γ-alumina in three-dimensional network and 19 wt% of carbon present as coating over the alumina framework. Phase analysis by X-ray diffraction revealed that carbon is in outer phase and γ-alumina is in the inner phase. Surface morphology of this foam, examined by scanning electron microscope showed open, fully interconnected and near spherical pores held together by hexagonal edges with a 300 μm average pore size. Energy dispersive X-ray spectroscopy revealed peaks corresponding to carbon, oxygen and aluminum indicating that the foam is free from nitrogen impurity. The surface concentration of carbon is nearly 85 wt% while it coating thickness is about 10 μm.

Phase evolution of tantalum nitride and tantalum carbide films with PBII parameters

Tantalum nitride and tantalum carbide films were fabricated using magnetron sputtering of tantalum followed by nitrogen and carbon plasma-based ion implantation (N-PBII and C-PBII). The phase evolution and morphology of the films were studied using glancing angle X-ray diffraction (GXRD) and transmission electron microscopy (TEM). It was found that the main phase in the tantalum nitride films was crystalline TaN0.1 whose grain size increases with increasing implantation voltage and phase content increases with increasing implantation dose. In the tantalum carbide film, the main phase was Ta2C. TaC phase also appeared as the implantation dose increased. XRD results from various glancing angles show that the phases with high nitrogen or carbon content, Ta4N5 and TaC, are present in the surface of the films. X-ray photoelectron spectra (XPS) from the tantalum carbide film reveal that the surface carbon content is higher than that of the inner film.

Sorption Mechanisms of Phenanthrene, Lindane, and Atrazine with Various Humic Acid Fractions from a Single Soil Sample

The sorption behavior of organic compounds (phenanthrene, lindane, and atrazine) to sequentially extracted humic acids and humin from a peat soil was examined. The elemental composition, XPS and (13)C NMR data of sorbents combined with sorption isotherm data of the tested compounds show that nonspecific interactions govern sorption of phenanthrene and lindane by humic substances. Their sorption is dependent on surface and bulk alkyl carbon contents of the sorbents, rather than aromatic carbon. Sorption of atrazine by these sorbents, however, is regulated by polar interactions (e.g., hydrogen bonding). Carboxylic and phenolic moieties are key components for H-bonding formation. Thermal analysis reveals that sorption of apolar (i.e., phenanthrene and lindane) and polar (i.e., atrazine) compounds by humic substances exhibit dissimilar relationships with condensation and thermal stability of sorption domains, emphasizing the major influence of domain spatial arrangement on sorption of organic compounds with distinct polarity. Results of pH-dependent sorption indicate that reduction in sorption of atrazine by the tested sorbents is more evident than phenanthrene with increasing pH, supporting the dependence of organic compound sorption on its polarity and structure. This study highlights the different interaction mechanisms of apolar and polar organic compounds with humic substances.

Sputtered neutral Si nC m clusters as a monitor for carbon implantation during C 60 bombardment of silicon

The incorporation of carbon atoms into a silicon surface under bombardment with 40-keV C 60 + ions is investigated using time-of-flight mass spectrometry of sputtered neutral and ionized Si n C m clusters. The neutral particles emitted from the surface are post-ionized by strong field infrared photoionization using a femtosecond laser system operated at a wavelength of 1400/1700 nm. From the comparison of secondary ion and neutral spectra, it is found that the secondary ion signals do not reflect the true partial sputter yields of the emitted clusters. The measured yield distribution is interpreted in terms of the accumulating carbon surface concentration with increasing C 60 fluence. The experimental results are compared with those from recent molecular dynamics simulations of C 60 bombardment of silicon.

Thermal destruction of rice hull in air and nitrogen

In this study, we ashed rice hull in air and nitrogen, respectively, and systematically investigated the effects of ashing temperature and atmosphere on the structures, morphologies, and pore characteristics of rice hull ash (RHA). All RHA samples are amorphous materials with porous structures. IR spectra revealed that RHA that ashed in air (WRHA) exhibit more polar groups on the surface than that of ashed in nitrogen (BRHA). The silica and carbon contents, BET surface area, and pore volume of BRHA increase with ashing temperature. When ashed in air, however, the silica content of WRHA increases and carbon content decreases with temperature. The BET surface area and pore volume of WRHA increase with temperature firstly and decline subsequently due to the closure of pores. Compared with WRHA, BRHA shows higher surface areas, micropore volumes, carbon contents, and lower mesopore fractions and silica contents. This study provides essential information for choosing a suitable thermal treatment of rice hull for a given adsorbate.

Effect of interconnected porosity on carbon diffusion depth in vacuum carburising process of iron compacts

The research work was aimed at determining the influence of macro- and micropores on carbon diffusion depth in the process of vacuum carburising of iron compacts with density within 5·6 to 6·4 g cm–3. Vacuum carburising of the compacts made of iron powder ASC100·29 was performed at 1050°C in a laboratory vacuum furnace. The carburising effects were compared and evaluated in terms of thickness, structure and surface carbon content of the case. Simplified carbon concentration gradients in the carburised layers were determined for the examined densities. Empirical relationships were formulated for carbon content in the case at a fixed distance from the surface as a function of the compact density for the accepted process parameters. It was found that interconnected macropores are decisive for the carburising depth.

Effect of water on the oxidation of dichlorobenzene over V2O5/TiO2 catalysts

The addition of water during the oxidation of m-dichlorobenzene over a 3.6wt.% V2O5/TiO2 catalyst resulted in an unusual bimodal activation/deactivation behavior at different temperatures. Catalyst activity increased at temperatures up to 300°C, with a maximum observed at 270°C, while it decreased at temperatures above 300°C with a minimum observed at 350°C. This effect was proportional to the concentration of water in the feed stream. At lower reaction temperatures (i.e., <270°C), the addition of water resulted in a lower concentration of surface chloride and carbonaceous deposits. In contrast, at higher reaction temperatures (i.e., >350°C), the presence of water did not affect the surface carbon and chlorine contents, but resulted in the deactivation of the catalyst due to the competitive adsorption on the active sites. Characterization of used catalyst samples indicated no changes in bulk characteristics, suggesting that the effect of water was limited to only reversible changes taking place on the catalyst surface. Finally, the presence of water also favored the formation of partial oxidation products, although the overall selectivity towards such products still remained low (i.e., yields below 3%).

The Migration of Styrene Butadiene Latex during the Drying of Coating Suspensions: When and How Does Migration of Colloidal Particles Occur?

Surface elemental compositions of model latex clay coatings on an impervious substrate consolidated under various conditions were measured using the XPS technique, in order to clarify when and how colloidal latex particles migrate to the surface during drying. Under similar drying conditions, surface carbon content decreased with the addition of a water-soluble polymer to the coating colors, while remaining virtually unchanged for coatings of different coat weights made with a given color, indicating that surface carbon content variation is mainly caused by migration of latex rather than of water-soluble polymer. The results also showed that for coatings made with a given suspension, surface carbon content decreased with increasing delay time between coating and heating. For coatings frozen during consolidation and dried by sublimation, surface carbon content increased with increasing drying time before freezing. These results suggest that for the model coatings studied, latex migration mainly occurs after coating application before capillary formation during the initial drying stage when coatings are in the liquid phase, contradicting both the conventional capillary transport and boundary wall migration mechanisms. An alternative mechanism which attributes latex migration to surface trapping effect and to higher Brownian mobility of the smaller latex particles compared with pigment appears to provide a systematically consistent explanation to those phenomena. The new particle migration mechanism implies that segregation of colloidal particles is a ubiquitous phenomenon that would occur not only during the drying of paper coatings but also during consolidation of colloidal films containing particles of different sizes. This is of great importance in the control of surface compositions of nanocomposite coatings.

A modeling study of the climate effects of sulfate and carbonaceous aerosols over China

In this paper, the RIEMS 2.0 model is used to simulate the distribution of sulfate, black carbon, and organic carbon aerosols over China (16.2°–44.1°N, 93.4°–132.4°E) in 1998. The climate effects of these three anthropogenic aerosols are also simulated. The results are summarized as follows: (1) The regional average column burdens of sulfate, BC, OC, and SOC were 5.9, 0.24, 2.4, and 0.49 mg m−2, with maxima of 33.9, 1.48, 7.3, and 1.1 mg m−2, respectively. The column burden and surface concentration of secondary organic carbon accounted for about 20% and 7%, respectively, of the total organic carbon in eastern China. (2) The radiative forcings of sulfate, organic carbon, and black carbon at the top of the atmosphere were −1.24, −0.6, and 0.16 W m−2, respectively, with extremes of −5.25, −2.6, and 0.91 W m−2. (3) The surface air temperature changes caused by sulfate, organic carbon, and black carbon were −0.07, −0.04, and 0.01 K, respectively. The air temperature increase caused by black carbon at 850 hPa was higher than that at the surface. The net effect of the three kinds of anthropogenic aerosols together decreased the annual average temperature by −0.075 K; the maximum value was −0.3 K. (4) Black carbon can reduce the precipitation in arid and semi-arid areas of northern China and increase the precipitation in wet and semi-wet areas of southern China. The average precipitation increase caused by black carbon in China was 0.003 mm d−1. The net effect of the three kinds of anthropogenic aerosols was to decrease the precipitation over China by 0.008 mm d−1.

Empirical ocean color algorithms for estimating particulate organic carbon in the Southern Ocean

We have examined empirical algorithms for estimating surface concentration of particulate organic carbon (POC) from remotely sensed ocean color in the Southern Ocean using field data of POC, spectral remote‐sensing reflectance, Rrs(λ), and the inherent optical properties (IOPs) of seawater collected during a number of cruises. Several algorithm formulations have been considered, including direct relationships between POC and the blue‐to‐green band ratios of reflectance and a single‐wavelength two‐step algorithm that consists of relationships linking reflectance to the backscattering coefficient and POC to the particulate backscattering coefficient at 555 nm. The best error statistics among the algorithms tested were obtained for the power function fit POC (in mg m−3) = 189.29 [Rrs(443)/Rrs(555)]−0.87. This band ratio algorithm is based on 85 pairs of field data and shows a small mean bias of about 3%, the normalized root mean square error of 27%, and the determination coefficient of 0.93. These error statistics as well as the analysis of matchup comparisons of satellite‐derived POC and in situ POC determinations support the prospect for reasonably good performance of this algorithm in the Southern Ocean. The two‐step empirical algorithm operating at 555 nm shows inferior error statistics of the regression fits and matchup comparisons compared with the band ratio algorithm. The analysis of our data set also indicates that a general trend of variation in the blue‐to‐green reflectance band ratio over the examined range of POC values is driven primarily by the green‐to‐blue ratio of particulate absorption coefficient.

Aerosol Regional Background in Developing Countries

To determine the aerosol regional background in three experimental sites in Brazil, South Africa and India modelled and measured surface concentrations of black carbon, organic carbon, sulphate, nitrate and ammonium were analysed. The South American site is characterised by a seasonal variation of the observed aerosol components. Measured ammonium and sulphate compare well with the model results. The model overestimates the elemental and organic carbon concentrations in the dry season, probably due to overestimation of the biomass burning emission inventories. In India modelled and measured concentrations in the wet season are very similar in level. In the dry season the observed concentrations are much higher than modelled due to air masses passing over New Delhi before arriving at the site. The South African site is influenced mainly by the local anthropogenic sources, thus the model estimates are substantially lower than the measured levels. A strong underestimation of modelled NO3 concentration is evident in all sites: in warm environment nitrogen shifts from the aerosol to the gas phase, and condenses on larger particles and the model does not take this into account.

Prediction of carbon segregation on the surface of continuously annealed hot-rolled LCAK steel

An attempt has been made to predict the segregation of carbon in continuously annealed hot-rolled low-carbon aluminum-killed steel (LCAK) through thermodynamic calculations. It is found that the surface carbon content calculated by the Guttmann model is comparable with the experimental results for inert atmosphere condition, whereas a large discrepancy is observed for the conventional continuous annealing furnace atmosphere. The main reason for this difference is the water–gas reaction that takes place on the surface of the steel sheet. It is proposed that this reaction, along with furnace atmosphere, determines the extent of carbon content on the sheet's surface. Based on this, the surface carbon content for various furnace conditions could be predicted.

Investigation of Variables Affecting Impedance Plane in Eddy Current Testing of Carburized Steels

Impedance plane is one of the most important ways for presenting results in Eddy current testing, which includes major data for evaluation of results. In this study, the impedance plane was drawn for carburized steel with different surface carbon content. The influences of temperature, fill factor, and edge effect on impedance plane were investigated. The ability of Eddy current testing for determination of surface carbon content using normalized impedance was also shown. Results demonstrate a strong relationship between normalized impedance and surface carbon content (R 2 = 0.82). Besides the effects of temperature, fill factor, and edge effect on determination of surface carbon content were investigated. The fill factor and temperature have the largest and the least effect on correlation coefficient between surface carbon content and impedance plane, respectively.

High Rate Capability of a Dual-Porosity LiFePO4/C Composite

Mesoporous intercalation compounds consisting of two different distributions of pores represent a potentially attractive material for high-rate cathodes. A mesoporous LiFePO4/C composite with two sizes of pores is prepared for the first time via a solution-based polymer templating technique. The precursor of the LiFePO4/C composite is heated at different temperatures in the range from 600 to 800 °C to study the effect of crystallinity, porosity, and morphology on the electrochemical performance. The composite is found to attain reduction in the surface area, carbon content, and porosity upon increasing temperature. Nonetheless, the composite prepared at 700 °C with pore-size distributions of around 4 and 50 nm exhibits a high rate capability and stable capacity retention upon cycling.

Functionalization of Polyester Fabric by Ar/N2 Plasma and Silver

The objective of this research was to use Ar/N2 (50%:50%) plasma to increase the adhesion of nano silver particles to raw polyester fabric. RUCO-BAC AGP was applied using the exhaust method. X-ray photoelectron spectroscopy revealed differences in surface composition between the Ar/N2 plasma-treated and untreated raw fabrics. The Ar/N2 plasma treatment was found to increase the surface carbon concentration and decrease the concentration of C-O and O-C=O groups on the surface. After plasma etching, the specific surface of the polyester fabric and properties related to it were found to change significantly. This change was confirmed by a decrease in the whiteness index and an increase in the dyeability of the polyester fabric with disperse dye. Morphological changes in the surface of plasma-treated polyester fabric enabled greater adhesion of nano silver particles and increased the antimicrobial effect with respect to Pseudomonas aeruginosa, Escherichia coli and Streptococcus faecalis.

Low‐temperature sintered conductive silver patterns obtained by inkjet printing for plastic electronics

AbstractSilver metal patterns onto plastic substrates have been obtained by inkjet printing with commercial ink based on silver nanoscale particles. Morphological characterization by scanning electron microscopy of spin‐coating processed films indicates that a sintering treatment at 250 °C for 30 min is enough to sinterize the silver metal nanoparticles. X‐ray photoelectron spectroscopy characterization of sintered metal films shows that the sinterization is accompanied by a reduction of carbon surface concentration coming from carbon‐containing chemical compounds present in the ink formulation. After sintering at 250 °C for 30 min, the material shows typical electrical resistivity of 4.6 × 10−6 Ωcm (i.e. about three times the value of bulk silver).Printed test structures show typical resistivity after sintering at 250 °C for 30 min in the range of 5–7 × 10−6 Ωcm. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Synthesis, Characterization, and Electrocatalytic Properties of Ultra Highly Densely Packed Carbon Sub-Micrometer Sphere Chains and Sheathed Carbon Microfiber Composites

In this work, we introduce the on-substrate preparation and characterization of ultra highly densely packed sub-micrometer carbon of perfect sphericity and well-connecting to each other forming chainlike compounds. These carbon sub-microsphere (CSMS) chains are highly pure with no catalyst remaining encapsulated within their core as revealed by transmission electron microscopy. X-ray photoelectron spectroscopy survey revealed a surface concentration of carbon being of 97.68 at %, whereas micro-Raman assessment of their quality showed that they are of high graphitic structure. In addition, the static contact angle between a water droplet and the CSMS chains surface is about 151° indicating superhydrophobicity feature. Thermogravimetric analysis showed that CSMS chains are very resistant to oxidation up to 637 °C. Furthermore, the CSMS chains possess enhanced electronic transfer properties. Given these interesting physicochemical properties, the CSMS chains developed here present a distinctive opportunity f...