Carbon Atomic Ratio Research Articles

Collectorless flotation of marmatite with pine oil

The interaction between pine oil and marmatite without collectors and activators was investigated by flotation, scanning electron microscope and energy-dispersive spectrometer (SEM–EDS), infrared (IR) spectroscopy, Zeta potential, and first-principle theory calculations. The flotation results show that marmatite exhibits considerable floatability with the addition of pine oil. SEM–EDS results show that carbon atomic ratios on the surface are significantly high, which suggests that the flotation of marmatite is caused by the adsorption of pine oil. Further evidence of the adsorption mechanism was given by IR, and Zeta potential examining pine oil depends on the physical adsorption on the surface independently. The first-principle theory calculations indicate that pine oil molecule adsorbs on Zn and Fe atom surfaces by ionic bond and covalent bond of adsorption energies of −1.23 and −1.51 eV, respectively. P orbital of O atom, s orbital of Zn atom, and d orbital of Fe are the major participants.

Reduced humic acid nanosheets and its uses as nanofiller

Leonardite is highly oxidized form of lignite coal and contains a number of carboxyl groups around the edges of a graphene-like core. A novel approach has been developed to synthesize graphene oxide-like nanosheets in large scale utilizing leonardite as a starting material. Humic acid extracted from leonardite has been reduced by performing a high pressure catalytic hydrogenation. The reaction was carried out inside a high pressure stirred reactor at 150°C and 750psi (~5.2×106Pa). Morphology of the as-synthesized samples showed porous platy particles and EDAX analysis indicates the carbon and oxygen atomic ratios as 96:4–97:3%. The as-synthesized material has been used as nanofiller in polyurethane. The reduced humic acid–polyurethane nanocomposite showed over 250% increase of Young’s modulus. This new approach provides a low cost and scalable source for graphene oxide-like nanosheets in nanocomposite applications.

Relating hygroscopicity and optical properties to chemical composition and structure of secondary organic aerosol particles generated from the ozonolysis of α-pinene

Abstract. Secondary organic aerosol (SOA) were generated from the ozonolysis of α-pinene in the CESAM (French acronym for Experimental Multiphasic Atmospheric Simulation Chamber) simulation chamber. The SOA formation and aging were studied by following their optical, hygroscopic and chemical properties. The optical properties were investigated by determining the particle complex refractive index (CRI). The hygroscopicity was quantified by measuring the effect of relative humidity (RH) on the particle size (size growth factor, GF) and on the scattering coefficient (scattering growth factor, f(RH)). The oxygen to carbon atomic ratios (O : C) of the particle surface and bulk were used as a sensitive parameter to correlate the changes in hygroscopic and optical properties of the SOA composition during their formation and aging in CESAM. The real CRI at 525 nm wavelength decreased from 1.43–1.60 (±0.02) to 1.32–1.38 (±0.02) during the SOA formation. The decrease in the real CRI correlated to the O : C decrease from 0.68 (±0.20) to 0.55 (±0.16). In contrast, the GF remained roughly constant over the reaction time, with values of 1.02–1.07 (±0.02) at 90% (±4.2%) RH. Simultaneous measurements of O : C of the particle surface revealed that the SOA was not composed of a homogeneous mixture, but contained less oxidised species at the surface which may limit water absorption. In addition, an apparent change in both mobility diameter and scattering coefficient with increasing RH from 0 to 30% was observed for SOA after 14 h of reaction. We postulate that this change could be due to a change in the viscosity of the SOA from a predominantly glassy state to a predominantly liquid state.

Sources and fluxes of organic nitrogen in precipitation over the southern East Sea/Sea of Japan

Abstract. We measured total dissolved reactive nitrogen in precipitation samples collected at Uljin, a Korean coastal site upwind of the southern East Sea/Sea of Japan (EJS), selected as a representative study site of atmospheric deposition over the northwestern Pacific margin. NO3- was found to be the most abundant nitrogen species, followed by NH4+ and dissolved organic nitrogen (DON). Air-mass back-trajectory (AMBT) analysis revealed that a significant fraction of the inorganic nitrogen (NO3- and NH4+) originated from mainland Asia, whereas the DON was primarily derived from Korea. Using varimax-rotated factor analysis in combination with major ions as tracers, agricultural activities in Korea were identified as the primary sources of DON in these samples. In addition, a positive correlation was found at Uljin between the size of organic fraction in total reactive nitrogen and nitrogen to carbon atomic ratio in organic matter. This correlation has also been observed at other locations worldwide, implying the utilization potential of atmospheric organic nitrogen might increase with its proportion in total nitrogen. Combining wet deposition measurements in this study with literature values for dry deposition observed at a remote island in the EJS, the total atmospheric depositional flux of reactive nitrogen was estimated to be 115 mmol N m−2 yr−1 over the southern EJS. Our study sheds new light on the potentially significant contribution to primary productivity of the northwestern Pacific Ocean by atmospheric deposition of nitrogen, especially the organic fraction.

The investigation of the C–Si interface structure in diamond/Si nano-composite films with first principle method

In order to improve the quality of nano-diamond films, a new type of diamond/Si nano-composite films was proposed. The monolayer Si interface and monolayer SiC interface were studied in this paper. The system total energies and adsorption energies of monolayer Si and monolayer SiC on diamond (001) surface were calculated with first principle method based on the density functional theory (DFT) to investigate the stability of the two kinds of interface structures in the Diamond/Si nano-composite films. Moreover, the variation of the configuration energy and structures when the hydrogen atom and CH2 radical adsorbed on the two kinds of interfaces were researched to verify whether the diamond phase was able to nucleate and grow or not in the process of diamond/Si nano-composite films deposition. It turned out that (1) the diamond surface structure which is terminated by monolayer silicon atoms is not very stable. It is difficult to form the stable monolayer Si interface in diamond/Si nano-composite films; (2) the monolayer SiC interface with the carbon and silicon atomic ratio of 1:1in which the carbon and silicon atoms are located in the same row respectively is a more stable structure. The interface is conductive to the second nucleation in the process of diamond growth.

Microscopic characteristics of solid particles in opposed multi-burner gasifier

The microscopic characteristics of solid particles have important influence on the formation of fluid slag, coarse slag and fine slag during entrained-flow gasification process. Based on the bench-scale opposed multi-burner (OMB) gasifier, solid particles were sampled at different axial distances along the gasifier chamber under typical operating conditions (oxygen and carbon atomic ratio at 1.0). The microscopic characteristics of solid particles were studied by using N2 adsorption-desorption and scanning electron microscopy (SEM) methods. The results show that the solid particles are comprised mainly of porous irregular particle and spherical particle, and few solid particles generated at burner plane perform as dense irregular and hollow shape. As the gasification reaction proceeds along the axis of gasifier, the surface structure of particles becomes rougher, and the pore structure increases. The isotherms of particle samples are all type II, and the particle samples consist of continuous and complete system of pores. The hysteresis loops are H3-type, and there are a large amount of fractured pores. BET surface area and pore volume increase with increasing distance from the burner plane, and average pore diameter gradually reduces, and larger changes occur in the vicinity of the burner plane. The mesopores less than 10 nm vary apparently and increase with increasing distances from the burner plane, while the pores larger than 10 nm are almost unchanged.

Flash Pyrolysis of Coal with Solid Heat Carrier in a Fluidized Bed

Flash pyrolysis of Shenmu coal with solid heat carrier was carried out in a fluidized bed using semi-coke as the solid heat carrier and nitrogen as the carrier gas. The effects of pyrolysis temperature, reaction time and mass ratio of heat carrier to coal on the yields of products were studied. It is found that the best operating conditions involving pyrolysis temperature 550°C, reaction time 6 min and mass ratio of heat carrier to coal 2. The properties of coal tar from fluidized bed, such as density, viscosity, freezing point, carbon residue and hydrogen carbon atom ratio, are almost higher than that of the above water coal tar and lower than that of the below water coal tar, while the above and below water coal tar obtained from Sanjiang squared retort. The results of simulation distillation show that gasoline and diesel fractions of coal tar from fluidized bed are higher than that of below water coal tar and lower than that of above water coal tar, while the heavy oil fraction is opposed.

Preparation and Mechanical Characterization of Amorphous B-C Films

This study has demonstrated that trimethylboron, B(CH3)3 is a suitable boron source material for the fabrication amorphous boron carbide (a-BC:H) films. a-BC:H films were deposited by pluse plasma chemical vapor deposition on a silicon substrate (100) with different gas pressures and gas flow rates at constant voltage, -5 kV . The grown a-BC:H films were found to be porous surface and their thickness were in the range of 0.95 to 1.56 μm for 3 h of deposition time. Results indicated that the boron contents, morphologies and mechanical properties of the a-BC:H films were dependent on the gas pressures and gas flow rate. The increased of boron content will introduce more porous film surface. The effect of boron content on the mechanical properties such as hardness, Youngs modulus, and wear resistance were discussed. The good quality film is obtained from B(CH3)3 at 5 Pa and gas flow rate of 15 cm3/min which boron to carbon atomic ratio is 0.43. This film has lower friction coefficient (0.3) sliding against stainless steel ball, high hardness (8.1 GPa) and Youngs modulus (62.2 GPa).

Oxygen to carbon atoms ratio effect on the size, morphology and purity of functionalized carbon nanoshells by using alcohol mixtures as carbon source

The effect of the ratio of oxygen to carbon atoms (O/C) on the morphology of carbon nanostructures has been studied by varying the methanol and ethanol ratio in the reaction mixtures. Notable morphological differences in the synthesized carbon nanostructures are observed as a function of the O/C ratio. At a high O/C ratio, i.e., using methanol (O/C=1), the synthesized carbon nanoshells (CNS) are faceted. Moreover, other faceted nanostructures, such as triangular and hexagonal, are observed in this strong oxidative environment. Decreasing the O/C ratio in the mixture by adding ethanol induces changes in the CNSs morphology; they are less faceted and favor only the growth of single-walled carbon nanotubes mixed with the CNSs. The importance of the O/C ratio is corroborated by replacing ethanol (O/C=0.5) with polyethylene glycol (O/C=0.5) in the methanol:ethanol reaction mixture. Finally, at very low O/C ratios, i.e., methanol:octanol mixtures, CNS are obtained and no faceted nanostructures or SWCNT are found. Thus, adjusting the O/C ratio is a method for obtaining high purity samples of CNS. Moreover, the use of the alcohols during the synthetic process is a simple and green method of functionalizing CNS.

Vitamin B1 Derived Blue and Green Fluorescent Carbon Nanoparticles for Cell-Imaging Application

A carbon-based fluorescent nanoparticle is considered to be a new generation nontoxic nanoprobe suitable for various bioimaging and sensing applications. However, the synthesis of such a high-quality nanoparticle is challenging, and its application potential is mostly unexplored. Here we report a vitamin B1 carbonization-based approach for blue and green fluorescent carbon nanoparticles of <10 nm size with a fluorescence quantum of up to 76%. We found that carbonization of vitamin B1 in the presence of phosphate salt at ∼90-130 °C for about 2 h produces highly fluorescent carbon nanoparticles of 1-6 nm size. The particle size and fluorescence property can be controlled by varying the reaction temperature and nature of phosphate salt. Elemental analysis shows the incorporation of a large percentage (up to 48 wt %) of other elements (such as nitrogen, oxygen, phophorus, and sulfur) in the carbon matrix. The chemical structure of vitamin B1 (thiamine) is unique in a sense that it consists of a large number of heteroatoms along with unsaturated bonds and offers low-temperature carbonization with the formation of a nanoparticle having an optimum ratio of sp(2) and sp(3) carbon atoms. These carbon nanoparticles have high colloidal stability and stable fluorescence and have been used as fluorescent imaging probes.

The Influence of Hot Compression on the Surface Characteristics of Poplar Veneer

The surface characteristics of wood veneer are inevitably influenced by hot compression treatment, which is crucial to bonding ability in the production of veneer-based composites such as plywood and laminated veneer lumber (LVL). The objective of this study was to investigate the effect of compression at the temperature of 120 °C on the surface roughness, surface element compositions, and surface free energy (SFE) of poplar veneer. The results showed that the surface roughness of veneer decreased with increasing compression ratio (CR). X-ray photoelectron spectroscopy (XPS) analysis indicated that the oxygen to carbon atoms ratio (O/C ratio) of the veneer surface decreased, while the carbon C1 to C2 atoms ratio (C1/C2 ratio) increased due to hot compression. The SFE of veneer increased by 12% at the CR level of 11%. The improvement in wettability was mainly due to the interfacial contact area increase of the hydrophilic veneer and the decrease in hydrophobic air in the liquid-veneer interface as the CR level increased.

Particulate matter properties in a bench-scale entrained-flow coal water slurry gasifier

Particulate matter (PM) of fly ash and slag is the main solid by-product of the coal gasification process which has significant influence on coal carbon conversion, slag deposition, erosion of the refractory wall and the efficiency of primary syngas cleanup. In this study, experimental work has been carried out to characterize the PM in a bench-scale opposed multi-burner (OMB) coal water slurry (CWS) gasifier. Similar to the industrial gasifier, particles in gasifier were sampled after treatment with high temperature flames. PM samples were taken from multiple ports under different operation conditions, and subsequently SEM, chemical composition and particle size tests were performed. Based on the simplified regional division of this type of gasifier, PMs in the gasifier impinging region perform porous structure and have larger particle size than that in the gasifier plug flow region. Also the unburned carbon content in PM decreases from top to bottom along the gasifier. The average particle size decreases as the oxygen carbon atomic (O/C) ratio increases. Based on the coal used for the experiments, the proposed mineral transformation mechanism also indicates that the calcite first transformed to mullite and then reacted with CaO to generate the anorthite. The investigation on the characteristics of PM will be beneficial to the operation and optimization of the OMB entrained-flow gasifier.

Enhancement of surface photoconductivityin 6H-silicon carbide crystal modified by femtosecond laser pulse irradiation

The photocurrent is very small when the visible light irradiates the semi-insulating silicon carbide. The femtosecond laser pulses are used to modify the silicon carbide surface, and the result shows that the photocurrent is enlarged several times according to the measurement results of photoconductivity. In order to explain the reasons for this change, some characterization means are employed, including the absorption, emission and X-ray photoelectron spectra. There are found some changes in the absorption spectra and emission spectra, and also in the silicon and carbon atom ratio according to the test results of X-ray photoelectron spectrum. We think that the changes of the crystal structure and atom ratio between silicon and carbon lead to the change of electronic energy band structure and the occurrence of many defect states. As a result, the photocurrents are improved in the range of visible light on the surface of 6H-SiC after the femtosecond laser pulses have irradiated the surface.

Chemical Characterization of Gilsonite Bitumen

This research provides new insights into the chemical composition of the Gilsonite in order to ascertain its properties which can assist in the refining and processing paths of the natural resource. Gilsonite, naturally occurring asphaltite bitumen, consists of a complex mixture of organic compounds. It was collected in the Uinta Basin near the town of Bonanza, Utah. The aim of this work is to obtain a more complete picture of molecular structure of Gilsonite, very important in fuel processing industry, matching and interpreting the results from different techniques. The Gilsonite was characterized by elemental analysis (EA) to determine the concentrations of C, H, N, S, and O, by Fourier transform infrared spectroscopy (FTIR) for comparative analysis of the chemical structures, by Nuclear magnetic resonance spectroscopy of hydrogen (1H NMR) to ascertain the aliphatic and aromatic hydrogen fractions, and by Thin layer chromatography-flame ionization detection (Iatroscan TLC-FID) to quantify saturated and aromatic hydrocarbons, and resin/asphaltene fractions. The results were evaluated in combination with the available geological data and with some bitumens to evaluate, chemically, possible mechanisms of Gilsonite formation. Low hydrogen to carbon atomic ratio (1.44), low sulfur (0.27 wt.%) and high nitrogen (3.25 wt.%) contents were the main characteristics of the Gilsonite from Uinta Basin. FTIR revealed the presence of alkane, aromatic rings, phenyl rings, alcohols, carbonyl groups, organic sulfoxides, and sulfate salts, confirming the fact that Gilsonite is composed of high molecular weight polycyclic constituents comprising of nitrogen, sulfur and oxygen heteroatoms. Likewise, FTIR proved that Gilsonite includes fingerprint of clay minerals. Iatroscan data showed interestingly that Gilsonite contains considerable amount of asphaltenes (79.7 wt.%) and nil amount of aromatics (0 wt.%). While, the yields of saturates and resins account only for 1.6 wt.% and 18.7 wt.%, respectively. Furthermore, SARA method estimated that Gilsonite is extremely instable (Colloidal instability index, CII = 4.34). Proton NMR measurements indicated that the aliphatic hydrogen portion is approximately 95.38% and the aromatic hydrogen fraction is about 4.62%.

The neutron scattering length density of kerogen and coal as determined by CH3OH/CD3OH exchange

Small angle neutron scattering (SANS) is an attractive technique for characterizing the structure of shale at length scales less than 100nm that are relevant to the storage and transport of hydrocarbons. The fine structure of hydrocarbon-bearing shale is in large part governed by the mass fraction and thermal maturity of the immobile organic phase known as kerogen. To correctly interpret and normalize SANS data requires knowing the neutron scattering length density (SLD) of the individual phases in the material; for shales this includes mineral, kerogen, and pore phases. While the SLD of many phases can be estimated with reasonable accuracy from compositional data, it is not clear that this is the case for kerogen, as its SLD is expected to vary considerably with type and thermal maturity. To characterize the importance of this variation, we measured the SLD of pure kerogen samples that were separated from the host shale by acid demineralization. By varying the kerogen type (I, II or III) and the associated thermal maturity, samples with a broad range of hydrogen to carbon atomic ratios, 0.5<H/C<1.4 were obtained. The SANS measurements consisted of using deuterated methanol exchange to vary the SLD of the pore space in contact with the kerogen, which allowed the SLD of the solid (kerogen) phase to be directly determined. The SLD of the kerogen was also calculated from the measured elemental composition and mass density. We find that the SLD of kerogen varies over a rather large range, from 1 to 4×1014m−2, increasing significantly with decreasing H/C, and that the measured and calculated values are in fairly good agreement. An implication of our results is that for shales containing immature kerogen with an SLD close to 1, the scattering between the kerogen and mineral phases may be significant, such that the shale cannot be treated as a two-phase material of solid and pore. Moreover, the surface area of extracted kerogen does not increase with thermal maturity. This result is in contrast to the contemporary literature which clearly indicates that catagenesis leaves nanopores in kerogen. Therefore we conclude that the acid demineralization procedure alters the structure of kerogen.

Numerical Simulation of the Multi-Component Slurry Gasification with the Non-Premixed Combustion Model

Considering the volumetric reactions and particle surface reactions in an entrained flow gasifier, the non-premixed combustion model based on the wet particles combustion method is adopted to simulate the multi-component slurry gasification process with FLUENT software. The velocity, temperature and concentration profiles of the gas products in the gasifier are obtained. Simulated results agree well with the commercial data, which verified the validity and applicability of the present model. Simultaneously, the reaction subarea in the gasifier has turned out to be obvious, the water evaporation, volatiles cracking and combustion reactions mainly appear in the jet region of the gasifier, the char gasification mainly appear in the freeboard region, but few reactions appear in the recirculation region. Moreover, with the increase of the mass fraction of the multi-component slurry, the content of the syngas at the gasifier outlet increases, while with the oxygen carbon atom ratio increasing, the syngas yield is rising early but declining later.

Differential surface properties of commercial crystalline telmisartan samples

The aim of the present study was to investigate differences in surface chemistry of commercially available telmisartan (TMS) samples in Indian market and to correlate them to the surface molecular environment. Comprehensive characterization of material properties of four TMS samples from different sources showed that all samples exhibited same polymorphic form, but different particle shape, particle size distribution, surface energetics and surface chemistry. Wettability and surface free energy were determined using sessile drop contact angle technique. TMS samples exhibited significant variations in their wetting behavior. The role of crystal shape, particle size distribution, surface energetics and surface chemistry in controlling TMS powder wettability was collectively explored by contact angle experiments. Evaluation of work of adhesion (Wa), immersion (Wi) and spreading (Ws) indicated that samples had differential wetting behavior. The surface chemistry was elucidated by X-ray photoelectron spectroscopy (XPS). The surface polarity index was determined by XPS and expressed as (oxygen+nitrogen)-to-(carbon) atomic concentration ratio. It was found to be different for all four TMS samples. Crystal morphology of TMS polymorph A was predicted using Bravais–Friedel Donnay–Harker (BFDH) method. Molecular lipophilic surface potential (MLSP) data for TMS showed the varied surface lipophilic environment throughout the molecule. Hence it can be concluded that the differential abundance of surface elements play an important role in controlling the biopharmaceutical performance of TMS powder samples.

Synthesis and characterization of nitrogen-doped carbon nanotubes by pyrolysis of melamine

The typical bamboo-like nitrogen doped carbon nanotubes (N-CNTs) have been successfully synthesized via pyrolysis of melamine (C3N6H6). The morphology of the samples is characterized by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The synthesized nanotubes are structurally uniform. The nitrogen to carbon atomic ratio of N-CNTs determined by chemical element analysis is found to be 0.23. The corresponding binding energy of the samples is obtained through X-ray photoelectron spectroscopy (XPS) and the characteristic infrared peaks are recorded by using Fourier transform infrared spectroscopy (FTIR). The characterization of thermal stability is obtained by thermo-gravimetric analysis (TGA) under flowing argon. The photoluminescence (PL) spectrum of the product shows that all the emission peaks are located in the blue–violet wavelength region, which indicates that N-CNTs may have potential applications in nano-optical device fields. Moreover, the growth mechanism of N-CNTs is carefully discussed.

Iron complexated lignin from electrolysis of wheat straw soda black liquor and its characterization

Electrolysis experiments were carried out with wheat straw soda black liquor with stainless steel (SS) electrodes. Electroactive lignin anions were found to form complex with the iron in the matrix of the SS anode surface to form a solid deposit. The deposits were examined with SEM and found to be in the form of irregular small granular mass. The granular solids so obtained were characterized with Energy Dispersive X-ray (EDX) analysis, TEM, XRD, and Selected Area Electron Diffraction (SAED) techniques. The electrodeposited lignin contained an unusually high iron to carbon atomic ratio. The granules varied in size from 1 to 1.5μm, with each granule itself made up of individual particles of different size and shape. The solids were amorphous in nature as confirmed by their XRD and SAED analyses.

Thermal Durability of Diamond Like Carbon Films Containing Tungsten Fabricated by Focused-Ion-Beam Chemical Vapor Deposition

Diamond like carbon film containing tungsten (W-DLC) was fabricated by focused-ion-beam chemical-vapor deposition (FIB-CVD), and its thermal durability was investigated using near the carbon K-edge X-ray absorption fine structure (C-K NEXAFS) spectroscopy and a combination of Rutherford backscattering and elastic recoil detection analysis, in comparison with those of commercial DLC and W-DLC films. The concentration of W in the films did not decrease when the annealing temperature was increased, while the concentration of H did. The sp2/(sp2+sp3) ratio of carbon atoms in the films increased with annealing temperature. The W-DLC film fabricated by FIB-CVD unchanged after annealing for 32 h at 873 K in vacuum. Its thermal durability was comparable to that of commercially available films.