Ratio Of Carbon Content Research Articles

Low-energy Ar+ ion beam induced chemical vapor deposition of silicon carbide films using dimethylsilane

In this paper, a methodology for silicon carbide (SiC) film formation by ion beam induced chemical vapor deposition (IBICVD) using dimethylsilane (DMS) is presented. Both pure DMS gas and Ar+ ion beam were simultaneously injected to a Si substrate. The Ar+ ion energy was 100 eV. The Si substrate temperature was 400, 600, or 800 °C. The duration of each ion beam injection experiment was 10 h. When the substrate temperature was 400 °C, no film formation occurred by the IBICVD experiment. In the case of 600 °C, a film was found to be formed on the substrate by the injection of both DMS gas and Ar+ ion beam. Although Fourier transform infrared (FTIR) spectroscopy measurement of the film showed that the film consisted of SiC, the film thickness was not enough to analyze the film characteristics further. When the Si substrate was set at 800 °C, a film was formed on the substrate by IBICVD. FTIR, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) measurements of the film showed the occurrence of SiC deposition. The XPS measurement also showed that the atomic concentration ratio of carbon to silicon (C/Si ratio) of the film was 1.36. Therefore, excessive C atoms were incorporated to the deposited films. On the contrary, the C/Si ratio of a SiC film prepared by the thermal CVD method using DMS was 1.88. These results suggest that the Ar+ ion beam induced chemical vapor deposition using DMS is useful for reducing of the amount of C atoms to be excessively included in the film.

Contributions of Fe(III) to UV–Vis absorbance in river water: a case study on the Connecticut River and argument for the systematic tandem measurement of Fe(III) and CDOM

Dissolved organic matter (DOM) impacts the structure and function of aquatic ecosystems. DOM absorbs light in the UV and visible (UV–Vis) wavelengths, thus impacting light attenuation. Because absorption by DOM depends on its composition, UV–Vis absorbance is used to constrain DOM composition, source, and amount. Ferric iron, Fe(III), also absorbs in the UV–Vis; when Fe(III) is present, DOM-attributed absorbance is overestimated. Here, we explore how differing behavior of DOM and Fe(III) at the catchment scale impacts UV–Vis absorbance and evaluate how system-specific variability impacts the effectiveness of existing Fe(III) correction factors in a temperate watershed. We sampled five sites in the Connecticut River mainstem bi-weekly for ~ 1.5 years, and seven sites in the Connecticut River watershed once during the summer 2019. We utilized size fractionation to isolate the impact of DOM and Fe(III) on absorbance and show that variable contributions of Fe(III) to absorbance at 254 nm (a254) and 412 nm (a412) by size fraction complicates correction for Fe(III). We demonstrate that the overestimation of DOM-attributed absorbance by Fe(III) is correlated to the Fe(III):dissolved organic carbon concentration ratio; thus, overestimation can be high even when Fe(III) is low. a254 overestimation is highly variable even within a single system, but can be as high as 53%. Finally, we illustrate that UV-Vis overestimation might impart bias to seasonal, discharge, and land-use trends in DOM quality. Together, these findings argue that Fe(III) should be measured in tandem with UV–Vis absorbance for estimates of CDOM composition or amount.

Hydrogenation and hybridization in hard W-C:H coatings prepared by hybrid PVD-PECVD method with methane and acetylene

The investigations the influence of methane and acetylene additions in the hybrid PVD-PECVD W-C:H coatings driven by DCMS and HiPIMS on plasma polymerization processes, carbon matrix content, its hybridization, hydrogenation and hardness revealed numerous differences related to hydrocarbon gas type and sputtering method. Close correlations between the hydrogen to carbon concentration ratio in the hydrocarbon precursor and contents of carbon phase, its hydrogenation and hybridization were established. The increase of each of these parameters had detrimental effects on hardness due to the consumption of σ bonds for CH at the expense of cross-linking among CC chains. HiPIMS and acetylene were found to provide the highest hardness (~20 GPa) in W-C:H coatings within the hybrid PVD-PECVD regime, most probably due to the best combination of hybridization, hydrogenation and cross-linking of the carbon phase. A qualitative model of growth mechanism of W-C:H coatings during hybrid PVD-PECVD with different hydrocarbon precursors and sputtering methods was proposed.

Microstructural Factors That Decrease the Local Strength of Grain Boundaries in Martensitic Steels

As a result of the phase transformation of austenite to martensite during steel quenching, weakened structural regions, specifically the boundaries of the original austenite grains, have been formed. They are weakened because of microstructural factors, such as the residual internal microstrains and segregation of embrittling impurities. The joint effect of microstructural factors, namely, residual microstrains and segregation of phosphorus and carbon at grain boundaries, on reducing the local strength of the boundaries of the initial austenite grains in martensitic steels is quantitatively evaluated, and the impacts of these microstructural factors have been separated. The dependences of the local grain-boundary strength on the ratio of various levels of residual microstrains and on the atomic concentration of phosphorus impurities at the grain boundary in segregation spots have been determined. It has been shown quantitatively that the adsorption enrichment of the austenite grain boundaries with phosphorus leads to a decrease in the intergrain adhesion and facilitates the emergence and development of cracks along the boundaries of the initial austenite grains. The quantitative dependence of the local strength of grain boundaries on the concentration ratio of carbon and phosphorus in them has been shown. Carbon in concentrations of up to 0.04% reduces the embrittlement of the boundaries due to the segregation of phosphorus and loses its neutralizing effect on the phosphorus segregation at concentrations of more than 0.04%, so the phosphorus concentration at the grain boundaries increases and the embrittlement resistance of the latter decreases. The applicability of the developed technique for the quantitative evaluation of the local strength of hardened steel grain boundaries by using tests on delayed fracture and applying the method of finite elements to determine the local strains has been shown.

Exploring the Feasibility of Adsorptive Removal of ZnO Nanoparticles from Wastewater.

This study tested the feasibility of adsorptive removal of ZnO nanoparticles using activated carbon from wastewater. The effects of pH (5, 6, 7, 8, and 9) and nanoparticle/activated carbon concentration ratios (10, 1, 0.1, 0.01, and 0.001) on the removal were studied in batch kinetic studies in both deionized water and wastewater. The adsorption capacity of activated carbon for ZnO nanoparticles were found to be 9.3 ± 0.8 mg/g (93% removal) and 8.2 ± 3.7 mg/g (85% removal) at 640 and 780 min in deionized and wastewater respectively at optimum conditions (pH 8; 10g/L activated carbon concentration, 100mg/L ZnO nanoparticle concentration). The rate constant was lowest at ratio 0.01 and pH 8, and highest at ratio 10 and 1 and pH 5 and 6. Pseudo-second-order and the Weber-Morris model best described the adsorption process. Characterization analysis also confirmed the deposition of ZnO nanoparticles onto activated carbon. Overall activated carbon successfully removed ZnO nanoparticles using the adsorptive process.

Correlations between aromaticity of dissolved organic matter and trace metal concentrations in natural and effluent waters: A case study in the Sagami River Basin, Japan

Chemical speciation, reactivity, and bioavailability of trace metals in aqueous systems arestrongly influenced by dissolved organic matter (DOM). DOM is a mixture of diverse components, so a range of organic molecules potentially participates in the occurrence of dissolved trace metals. In this study, we investigated water quality variables that influence dissolved trace metal concentrations in natural and effluent water systems with a particular attention given to the relationship between DOM optical properties and dissolved copper and iron concentrations. We found that specific UV absorbance (SUVA254: an indicator of DOM aromaticity) has a significant correlation with dissolved trace metal to dissolved organic carbon concentration ratios ([Me]T/[DOC]) for copper and iron in natural freshwaters and treated municipal wastewater in the Sagami River basin, Japan. This trend was also prevalent for other freshwaters in temperate climates except for Fe-rich waters. Our findings indicate that the concentrations of dissolved copper and iron in natural and effluent waters are significantly influenced not only by DOM concentration, but also by aromaticity of DOM, and that this DOM property can be inferred from spectrophotometric measurements.

Xanthan exopolysaccharide: Acid–base reactivity related to structure and conformation. A model for understanding the reactivity of degraded and colloidal soil organic matter

Bacterial cells and bacterial exopolysaccharides differ strongly in their respective colloidal and polymeric habits. This suggests different reactivities toward metals and protons, although recent studies point to the similarity of such substrates in terms of site density and metal complexation strength. The aim of this paper is to investigate the causes of this surprising uniqueness by studying the reactivity of a model exopolysaccharide, xanthan. NMR and molecular analysis were used to unambiguously determine the total density of reactive carboxylic sites of the xanthan molecule (1.65mmol/g xanthan dry weight dw). This allowed the independent determination of the average protonation constant of xanthan (Xan), which is more acidic than its constitutive reactive ligands, glucuronic and pyruvic acids (Glc+Pyr) at high (0.5) and medium (0.1), but not at low (0.01) ionic strength. This shows that xanthan is intrinsically more acidic than its constitutive reactive ligands, and that electrostatic effects developed at low ionic strength can limit the relative lability of xanthan's protons. A cylindrical electrostatic model based on the molecular structure of xanthan identified a single intrinsic constant (pKI=0=1.95±0.1) as the only adjustable parameter needed to fit our experimental data.The density of xanthan reactive sites (1.65mmol/g dw) is comparable to that of whole bacterial cells and with known highly reactive biopolymers such as humic substances, nucleic acids, proteins, and polysaccharides (~1 to 5mmol/g dw). The surprising similarity in site densities of these substrates is explained by the constitutive reactive site versus carbon concentration ratio, which is 1/23 in xanthan (one out of 23 carbons bears an acid–base reactive functional group), which is about the same in bacteria, and which increases to 1/6 in fulvic acids. These high ratios suggest the physical limits of stability for these polymers, and thus their high and similar site densities.

Carbonaceous Particulate Matter Air Pollution and Human Exposure from Indoor Biomass Burning Practices

Using both stationary air samplers and personal air samplers, concentrations of total suspended particulates, particulate matter with a diameter less than 2.5 μm, elemental carbon, and organic carbon were measured in the kitchen, bedroom, and outdoors of a rural, nonsmoking household in northern China. The household used a traditional biomass cookstove in winter and summer and a more modern liquified petroleum gas cookstove on the first day in the summer. Most of the particulate matter concentrations both indoors and outdoors exceeded the national air quality standards of China (0.15 mg/m3 for indoor particulate matter with a diameter of 10 μm or less; 0.30 mg/m3 for ambient air total suspended particulate). In the kitchen in the winter, the daily mean concentration of particulate matter with a diameter less than 2.5 μm was 16 times larger than the national indoor air quality standard for particulate matter with a diameter of 10 μm or less. On average, 53% of the total suspended particulate concentration was due to particulate matter with a diameter less than 2.5 μm. While all of the residents of the household were exposed to high concentrations of particulate matter with a diameter less than 2.5 μm, the housewife had the highest exposure. High daily variation in concentrations was due primarily to differences in fuel burning rates. Significant differences between kitchen/outdoor and bedroom/outdoor concentration ratios and between winter and summer indoor/outdoor concentration ratios suggested that bedroom particulate matter concentrations were due to emissions from the kitchen in winter and the outdoors in the summer. The average winter and summer elemental carbon/organic carbon concentration ratios were 0.20±0.14 (n=24) and 0.32±0.16 (n=18), respectively. In the bedroom and outdoors, the elemental carbon and organic carbon concentrations were correlated linearly with each other and with the concentration of particulate matter with a diameter less than 2.5 μm. When only liquefied petroleum gas was used in the summer, the kitchen concentrations of particulate matter with a diameter less than 2.5 μm and organic carbon were similar to or higher than the concentrations measured when the biomass burning stove was used.

Effects of carbon substrates on biodegradable polymer composition and stability produced by Delftia tsuruhatensis Bet002 isolated from palm oil mill effluent

The effects of carbon substrate (C8:0–C18:1) on the biosynthesis and the properties poly-3-hydroxybutyrate and its copolymer (PHA) produced by Delftia tsuruhatensis Bet002 were investigated. Growth-associated accumulation yielded PHA at 76.7% cell dried weight with molecular weight ranging from 131 to 199 kDa. Carbon source type also influences the thermal stability of the PHA. The molar concentration ratio of carbon to nitrogen source has little effect on the PHA composition, but affected the biomass, PHA yield and polymer degradation stability. In general, polymer composition of even and odd carbon atom chain length (C4–C10) was obtained. The PHA produced is semi-crystalline polymer with good thermal stability with thermal degradation temperature (Td) 269.8 to 391.8 (±0.2) °C, melting temperature (Tm) 163.6 to 177.4 (±0.2) °C, glass transition temperature (Tg) −1.0 to 4.4 (±0.2) °C and apparent melting enthalpy of fusion (ΔHf) of 53.2 to 210.9 (±0.1) J g−1.

Effects of carbon concentration on properties of nano-diamond films

Nano-diamond films synthesized by chemical vapor deposition (CVD) have attracted a great deal of interest for their smooth surface. The work focuses on the carbon concentration of nano-diamond films deposition and its effects on the microstructure of films. Nano-diamond films were deposited by hot filament chemical vapor deposition (HFCVD) method and effects of carbon concentration on the microstructure of nano-diamond films were characterized using scanning electron microscope, atomic force microscope, Raman spectroscopy and X-ray diffraction (XRD). The results indicate that the grain size decreases from 90nm to 30nm, the roughness decreases from 52.3nm to 30.6nm, the line width of peaks of Raman and XRD becomes broader and the intensity ratio of diamond decreases with the increase of carbon concentration from 2% to 3%. The sp3 carbon phase decreases while the sp2 carbon phase increases in nano-diamond films with the decrease of grain size, when the carbon concentration ratio increases.

Seasonal variation in molecular mass and optical properties of chromophoric dissolved organic material in coastal waters of southwest Florida

One of the most important natural sunlight absorbing substances in water is the chromophoric dissolved organic material (CDOM). Its influence on optical properties has been studied for many years, but questions of how its structural and optical characteristics change in the environment still remain. CDOM water samples were collected from coastal waters of southwest Florida during three cruises in the year 2001: one in the dry season (June) and two in the rainy season (September and November). Analyses of molecular mass (MM) distribution and optical characteristics were done using the flow field-flow fractionation (FlFFF) separation technique with absorbance and fluorescence detectors. On the basis of the results, mixing, source variability, degradation, and excited state quenching processes are important determinants of CDOM composition and optical properties in this region. During the dry season, the MM distribution did not change significantly spatially. In September and November, higher MM compounds and an increase of CDOM fluorescence were observed, found inside the rivers and in near-coastal samples, consistent with the rivers being a significant CDOM source. Results suggest that chromophores were broken down to smaller MM compounds faster than fluorophores, indicating that the fluorescent moieties are more resistant to degrading/removal processes than the non-fluorescing compounds, even though the fluorophores were always centered at lower MM. On the other hand, the fluorescence quantum yield decreased faster than absorbance coefficients, suggesting that fluorophores were quenched by complexing with some metals. For all months, the chromophores' MM for offshore samples remained the same. The carbon concentration ratio between chromophores and fluorophores changed from lower to higher salinities, suggesting that the composition of the waters changed toward offshore. The differences in the optical characteristics, MM distributions, and carbon concentration observed suggest that the CDOM sources, physical, and photochemical degradation processes change seasonally.

Optical and strucutral properties of hydrogen implanted silicon carbon alloys

The hydrogen effects on the optical and structural properties of amorphous silicon carbon alloys are investigated for different hydrogen concentration (0–20 at.%) and a fixed silicon to carbon concentration ratio ( χ Si χ c = 1 ). Hydrogen was introduced into a preamorphized SiC sample by ion implantation of H ions with energies in the range 5–20 keV and fluences in the range 10 17−5 × 10 17 ions/cm 2 obtaining an uniform concentration in the amorphous layer (130 nm thick). Raman spectra evidences the presence of both a-Si and a-C structures even in the unhydrogenated samples and the optical energy gap increases with hydrogen concentration. Thermal annealing at 350°C induces a further increase of the optical energy gap, in particular from 1.45 to 1.65 eV in the 20 at.% hydrogen containing a-SiC:H. These and other results, compared to those obtained in pure amorphous silicon and carbon layers, suggest a similarity between the optical and structural behaviour of silicon carbon alloys and that of amorphous carbon.

Beam induced compositional changes in rbs analysis of polymers

In this paper we address the question of whether Rutherford backscattering (RBS) can be applied to the study of polymers in such a way that experimental results will provide accurate information on the depth composition of the polymer. Our scanned-beam RBS results suggest that, for room temperature analysis of polyethylene terephthalate (PET), there is a fluence limit below which beam induced compositional changes can be neglected. Cooling to the sample of LN 2 temperature during RBS analysis causes the oxygen to carbon concentration ratio to remain unchanged, apparently because no significant outdiffusion of beam generated gas molecules can occur at LN 2 temperature.

Particulate carbon in Los Angeles air

A selective combustion method has been applied to the determination of total, organic and elemental particulate carbon in Los Angeles air. Carbon concentrations (10–56 μ m −3) and their temporal variations are presented for multiday smog episodes. Organic carbon/elemental carbon concentration ratios ranged from ∼ 3 during the winter months to ∼ 10 during the smog season. Photochemical production of particulate organic carbon is estimated to be ∼ 76–118 × 10 3 kg/day, as compared to ∼ 31 × 10 3 kg/day from direct emissions. This estimate is also consistent with gas-to-particle conversion considerations for precursor hydrocarbons.

上昇気泡による脱ガスプロセスの理論解析

A mathematical model for degassing process by rising bubbles is developed on the basis of material and heat balances in gas phase and material balance in liquid phase. From this model, the volume of inert gas which is necessary to degass hydrogen, oxygen and carbon in molten steel down to the required concentrations can be estimated.The effects of the initial diameter of inert gas bubble, the depth of blowing point of inert gas, the pressure of gas at the surface of molten steel, the residence time of rising bubble and the concentration ratio of carbon to oxygen on the degassing rate and on the concentrations of CO and H2 in rising bubble were determined by numerical calculations of the model with the aid of digital computer.