Carbon-containing Precursor Research Articles

Thermal Atomic Layer Deposition of Silicon Carbonitride: A Density Functional Theory Study

Silicon carbonitride (SiCN) films have received considerable attention due to their lower dielectric constant and better etch selectivity than silicon nitride (SiN) films [1]. Therefore, SiCN is replacing SiN in a variety of applications, such as dielectric barriers for copper interconnects or sidewall spacers for self-aligned contacts. SiCN films have been mainly prepared by plasma-enhanced chemical vapor deposition (PECVD) or plasma-enhanced atomic layer deposition (PEALD). However, plasma-based deposition techniques suffer from poor film quality and lack of conformability on high-aspect-ratio patterns. Thermal atomic layer deposition at high process temperatures can deposit high-quality thin films with excellent conformality. However, no studies have been published on thermal ALD in SiCN, while there are a few reports on PEALD in SiCN. In this work, we studied the thermal ALD process of SiCN by alternating exposures to a carbon-containing silicon precursor and NH3 and compared it with the thermal ALD of SiN processes using carbon-free precursors. Density functional theory (DFT) calculations were used to model and simulate the continuous ligand exchange reactions between the silicon precursor and the substrate surface. The carbon incorporation in the growing film when using carbon-containing precursors was predicted by DFT, which is in good agreement with the experimental observations. Acknowledgments This work was supported by Hansol Chemical Co., Ltd.

Results on Testing New Process to Make Nitrogen- and Carbon-Containing Precursor Based on Vanadium and Aluminum to Smelt V–Al–N–C Master Alloy

Results on Testing New Process to Make Nitrogen- and Carbon-Containing Precursor Based on Vanadium and Aluminum to Smelt V–Al–N–C Master Alloy

Emission characteristics of benzene series in FCC flue gas

Benzene series are considered as air pollutants in refineries. However, the emissions of benzene series in fluid catalytic cracking (FCC) flue gas are poorly understand. In this work, we conduct stack tests on three typical FCC units. Benzene series, including benzene, toluene, xylene and ethyl benzene, are monitored in the flue gas. It shows that the coking degree of the spent catalysts affect the emissions of benzene series significantly, and there are four kinds of carbon-containing precursors in the spent catalyst. A fixed-bed reactor is used to conduct the regeneration simulation experiments, and the flue gas is monitored by TG-MS and FTIR. The emissions of toluene and ethyl benzene are mainly emitted in the early and middle stage of the reaction (250–650 °C), while the emission of benzene is mainly detected in the middle and late stage of the reaction (450–750 °C). Xylene group is not detected in the stack tests and regeneration experiments. Higher emissions of benzene series are released from the spent catalyst with lower C/H ratio during regeneration process. With the increase of oxygen content, the emissions of benzene series decrease, and the initial emission temperature is advanced. These insights can improve the refinery's awareness and control of benzene series in the future.

Conversion of polyethylene terephthalate waste into high-yield porous carbon adsorbent via pyrolysis of dipotassium terephthalate

A method for conversion of polyethylene terephthalate (PET) waste into porous carbon material is proposed. The recycling of PET bottle waste includes the stages of low-temperature hydrolysis of the polymer and subsequent pyrolysis at 800 °C. To provide PET hydrolysis at ∼150 °C and atmospheric pressure, the polymer was pre-dissolved in dimethyl sulfoxide and then an aqueous solution of potassium hydroxide was added. The potassium terephthalate formed as a result of the alkaline hydrolysis of PET allows the carbon-containing precursor to be preserved for further activation to temperatures beyond 600 °C. The proposed method leads to the formation of a porous carbon material, increasing the yield of carbon residue to 25 wt%, which is higher compared to the yield of carbon residue in the direct pyrolysis of PET. The obtained porous carbon is characterized by graphite-like structure and specific surface area of ∼1100 m2 g−1. It has been shown that PET-derived carbon material can be used to remove pollutants from aqueous media. The adsorption properties of the carbon material were demonstrated by adsorption of methylene blue from an aqueous solution. The capacity of the carbon material was found to be 443 mg g−1.

Разработка технологии получения и апробация нового азот- и углеродсодержащего прекурсора на основе ванадия и алюминия для выплавки лигатуры V – Al – N – C

A technology for obtaining complex nitrogen- and carbon-containing precursor materials V(51 – 43) – Al(30 – 36) – N(13,4 – 16,4) – C(2,7 – 6,0) was developed and tested on an experimental scale by nitriding by the method of self-propagating high-temperature synthesis of mixtures of V(65 – 50) – Al master alloys powders with graphite. The ratio of nitrogen to carbon in precursors can be varied over a wide range — N/C = 5.5 – 2.2. Using X-ray phase analysis, it was found that nitrogen in these materials is in the form of AlN and VN nitrides, and carbon is in the form of V2C, VC and V2Al0.96C1.1 carbides. The possibility of replacing graphite in the charge of out-of-furnace aluminothermal smelting of the V – Al – N – C master alloy with an alternative precursor V(51) – Al(30) – N(15) – C(2.7) has been experimentally confirmed. Using the methods of X-ray phase analysis, electron microscopy, and X-ray spectral microanalysis, it was found that the smelted using this precursor V – Al – N – C master alloy ingot is identical in phase composition and in distribution uniformity of nitride and carbide inclusions to alloy ingots that were smelted using other carbon-containing materials. The content of nitrogen, carbon and oxygen in the ingot meet the requirements of the technical specifications for V – Al – N – C master alloy.

Nitric Oxide Probe Molecule Studies of Iron-Nitrogen-Carbon PEMFC Oxygen Reduction Reaction Electrocatalysts

The highest oxygen reduction reaction (ORR) activities in acidic environments for platinum group metal-free electrocatalysts have been achieved for materials derived from iron, nitrogen, and carbon-containing precursors such as iron-substituted zinc-based zeolitic imidazolate frameworks (ZIF).[1-3] These precursors are typically heat treated in an inert atmosphere at temperatures ranging from 900 to 1100°C to form the ORR-active material. In addition to their high intrinsic activity, under certain preparation conditions these catalysts are free of crystalline iron species, with iron atomically dispersed in a nitrogen-doped carbon matrix, as determined through characterization by high-resolution electron microscopy and X-ray absorption spectroscopy. While the exact nature of the active site in these materials is still a matter of debate, the probe molecule, nitric oxide, has been shown to bind to Fe, using nuclear resonance vibrational spectroscopy, and also to poison the ORR.[4-6] An in-depth study of the interaction of nitric oxide with a variety of Fe-N-C catalysts can thus provide insight into the nature of the ORR active site in this class of catalysts. This presentation will discuss the application of multiple characterization techniques to understand the interaction of nitric oxide with Fe-N-C catalysts, including nuclear resonance vibrational spectroscopy, temperature-programmed desorption, and in situ X-ray absorption spectroscopy as a function of potential in aqueous acidic electrolyte. The implications of the results of these studies on the nature of the ORR active site will be discussed.

Impact of Nickel Content on the Structure and Electrochemical CO2 Reduction Performance of Nickel–Nitrogen–Carbon Catalysts Derived from Zeolitic Imidazolate Frameworks

The electrochemical conversion of CO2 affords a sustainable route to produce chemicals and fuels from renewable sources of electricity. Nickel–nitrogen–carbon (Ni–N–C) materials have shown promise in terms of activity and selectivity toward the electro-conversion of CO2 into CO, a feedstock widely used in the chemical sector. Ni–N–C catalysts, postulated to comprise catalytically active atomically dispersed Ni–Nx/C sites, are commonly prepared by pyrolyzing a mixture of transition metal-, nitrogen-, and carbon-containing precursors. Herein, we use a zeolitic imidazolate framework (ZIF-8)─a subclass of metal organic frameworks─as a platform for synthesizing Ni–N–C electrocatalysts. We systematically investigate the role of the Ni concentration impregnated into the ZIF-8 precursor structure during synthesis in the overall structure and performance of the resulting Ni–N–C catalysts for electrochemical CO2 reduction. Our findings show that increased Ni contents in the catalyst precursor results in the formation of Ni-containing particles that increase the catalytic selectivity toward the competing hydrogen evolution reaction, whereas reduced Ni contents preferentially form atomically dispersed Ni–Nx/C active sites dispersed in heterogeneous carbon structures consisting of carbon nanotubes and carbonaceous particles. As an optimized concentration of Ni in the precursor mixture, we demonstrate a CO2 reduction selectivity toward CO of ca. 99% Faradaic efficiency at an applied potential of −0.68 V versus the reversible hydrogen electrode.

Preparation of porous carbon materials from biomass pyrolysis vapors for hydrogen storage

A novel method for preparing porous carbon materials from biomass pyrolysis vapors with calcium citrate template has been proposed. The effects of pyrolysis temperature, pyrolysis heating rate and carbon-containing precursor preparation temperature on the yield of biomass pyrolysis products, composition of light bio-oil and structure of porous carbons were investigated. The physicochemical characterization and hydrogen adsorption experiments were carried out for the prepared porous carbons. The carbonization mechanism of the carbon-containing precursor was studied and a five-stage reaction kinetic model was established by Gaussian peak separation method according to the DTG curves. Under the optimal conditions of pyrolysis temperature (823 K), heating rate (10 K/min) and carbon-containing precursor preparation temperature (473 K), the prepared porous carbon material has the largest specific surface area of 1703 m2/g, relatively high micropore volume of 0.51 cm3/g and microporosity of 24.17%. The hydrogen adsorption capacity of the carbon material can reach 170.12 cm3/g (1.53 wt%) at 77 K at atmospheric pressure. This paper provides a novel and environmental-friendly method for the preparation of porous carbon materials, and also presents a new way for the utilization of biomass pyrolysis vapors before condensation.

Effects of Plasma-Chemical Composition on AISI 316L Surface Modification by Active Screen Nitrocarburizing Using Gaseous and Solid Carbon Precursors

Low-temperature plasma nitrocarburizing treatments are applied to improve the surface properties of austenitic stainless steels by forming an expanded austenite layer without impairing the excellent corrosion resistance of the steel. Here, low-temperature active screen plasma nitrocarburizing (ASPNC) was investigated in an industrial-scale cold-wall reactor to compare the effects of two active screen materials: (i) a steel active screen with the addition of methane as a gaseous carbon-containing precursor and (ii) an active screen made of carbon-fibre-reinforced carbon (CFC) as a solid carbon precursor. By using both active screen materials, ASPNC treatments at variable plasma conditions were conducted using AISI 316L. Moreover, insight into the plasma-chemical composition of the H2-N2 plasma for both active screen materials was gained by laser absorption spectroscopy (LAS) combined with optical emission spectroscopy (OES). It was found that, in the case of a CFC active screen in a biased condition, the thickness of the nitrogen-expanded austenite layer increased, while the thickness of the carbon-expanded austenite layer decreased compared to the non-biased condition, in which the nitrogen- and carbon-expanded austenite layers had comparable thicknesses. Furthermore, the crucial role of biasing the workload to produce a thick and homogeneous expanded austenite layer by using a steel active screen was validated.

Single-crystal, large-area, fold-free monolayer graphene.

Chemical vapour deposition of carbon-containing precursors on metal substrates is currently the most promising route for the scalable synthesis of large-area, high-quality graphene films1. However, there are usually some imperfections present in the resulting films: grain boundaries, regions with additional layers (adlayers), and wrinkles or folds, all of which can degrade the performance of graphene in various applications2-7. There have been numerous studies on ways to eliminate grain boundaries8,9 and adlayers10-12, but graphene folds have been less investigated. Here we explore the wrinkling/folding process for graphene films grown from an ethylene precursor on single-crystal Cu-Ni(111) foils. We identify a critical growth temperature (1,030kelvin) above which folds will naturally form during the subsequent cooling process. Specifically, the compressive stress that builds up owing to thermal contraction during cooling is released by the abrupt onset of step bunching in the foil at about 1,030kelvin, triggering the formation of graphene folds perpendicular to the step edge direction. By restricting the initial growth temperature to between 1,000kelvin and 1,030kelvin, we can produce large areas of single-crystal monolayer graphene films that are high-quality and fold-free. The resulting films show highly uniform transport properties: field-effect transistors prepared from these films exhibit average room-temperature carrier mobilities of around (7.0±1.0)×103 centimetres squared per volt per second for both holes and electrons. The process is also scalable, permitting simultaneous growth of graphene of the same quality on multiple foils stacked in parallel. After electrochemical transfer of the graphene films from the foils, the foils themselves can be reused essentially indefinitely for further graphene growth.

Synthesis and characterization of Mn-doped C@ZrSiO4 black pigment via non-hydrolytic sol-gel method

With the increasing popularity of the black decorative ceramics, the development of black pigment with good properties has become significant for the ceramic industry. A Mn-doped zirconium silicate encapsulated carbon (C@ZrSiO4) black pigment was successfully prepared via non-hydrolytic sol-gel (NHSG) method at 800 °C, while MnCl2 and carbon-containing precursors (tetraethoxysilane, TEOS) were used as Mn and in-situ carbon sources, respectively. The results demonstrated that the L* value of black pigment first decreased and increased with the increase of MnCl2 content. The as-prepared pigment with the MnCl2 content of 10 mol% showed a deep dark hue (L* = 27.64, a* = 0.67, b* = 0.68), while the pigment without Mn doping exhibited poor chromatic properties (L* = 51.18). Moreover, XPS and EPR results indicated that the Mn(II) and Mn(IV) replaced the Zr(IV) in ZrSiO4, resulting in the formation of oxygen vacancies. In-situ carbon provided by TEOS incorporated into these oxygen vacancies, which can protect carbon from being oxidized. In addition, the prepared pigment exhibited higher chemical stability in acid/alkali solutions, favorable tinting strength and thermal stability in base transparent glaze, which displayed wide application prospect in the field of ceramic decoration.

“Inside out” growth method for high-quality nitrogen-doped graphene

High-quality nitrogen-doped graphene on nickel is prepared by exploiting both the catalytic properties of nickel and the solubility of nitrogen atoms into its bulk. Following the standard chemical vapor deposition procedure, a previously nitrogen-doped nickel substrate is exposed to carbon-containing precursors so that nitrogen atoms, segregating to the surface, remain trapped in the growing graphene network. Morphological and chemical characterization by scanning tunneling microscopy and X-ray photoelectron spectroscopy demonstrates that the process yields a flat, wide, continuous nitrogen-doped graphene layer. Experimental results are combined with a thorough density functional theory investigation of possible structural models, to obtain a clear description at the atomic scale of the various configurations of the nitrogen atoms observed in the graphene mesh. This growth method is potentially scalable and suitable for the production of high-performance nano-devices with well-defined nitrogen centers, to be exploited as metal-free carbon-based catalysts in several applicative fields such as electrochemistry, energy storage, gas storage/sensing or wastewater treatment.

Unsupported CoNixMo sulfide hydrodesulfurization catalysts prepared by the thermal decomposition of trimetallic tetrabutylammonium thiomolybdate: effect of nickel on sulfur removal

Herein we report the synthesis of unsupported bimetallic CoMo and trimetallic CoNiMo sulfide catalysts prepared by thermal decomposition (ex situ activation) of carbon-containing precursors and varying the nickel concentration for the hydrodesulfurization (HDS) of dibenzothiophene. The catalysts prepared were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma mass spectrometry and BET surface area measurements. The results from the characterization showed that the addition of an alkyl chained precursor results in non-porous catalysts with low surface area and high carbon content, which negatively affects the formation of crystalline phases such as molybdenum sulfide and their performance in the HDS reaction. Furthermore, the addition of nickel has a negative effect on the catalysts since it was observed that when it was added, the reaction rate values decreased and the catalyst with the highest catalytic activity turned out to be the CoMo catalyst. Although nickel catalysts generally have more affinity for hydrogenation reactions, unsupported trimetallic catalysts showed a preference for the direct desulfurization pathway.

Strategies for Scalable Gas-Phase Preparation of Free-Standing Graphene

The preparation of graphene with high quality serves as a prerequisite for its usage. Traditional methods of graphene production, represented by liquid-phase exfoliation and chemical vapor depositi...

Nonhydrolytic sol-gel in-situ synthesis of novel recoverable amorphous Fe2TiO5/C hollow spheres as visible-light driven photocatalysts

A novel recoverable visible-light photocatalyst, amorphous Fe2TiO5/C composite, was prepared via nonhydrolytic sol-gel method with carbon-containing precursors as in-situ carbon sources. It is demonstrated that the precursors, iron ethoxide and butyl titanate, react to form Fe-O-Ti bonds in gel through a ether elimination reaction and amorphous Fe2TiO5 at 300 °C, which finally crystallizes at 600 °C. The residual organic groups form uniform-doped C. Interestingly, the photocatalytic activity of amorphous Fe2TiO5/C is distinctly superior to those of its crystalline counterparts without C and P25 (43-fold increase and 12-fold increase, respectively), which is mainly attributed to the incorporation of C (8.17 wt%) and amorphous Fe2TiO5 with a hollow spherical structure and a high BET surface area of 195.5 m2/g. Importantly, the photocatalyst can be recovered with a recovery rate of 100% simply by an external magnetic field, making it have promising applications in the wastewater treatment field.

Synthesis of graphene flakes using a non-thermal plasma based on magnetically stabilized gliding arc discharge

The use of non-thermal plasma at atmospheric pressure has emerged as a technique for the substrate-free, gas-phase synthesis of graphene nanoflakes (GNFs). In this paper, a non-thermal plasma based on magnetically stabilized gliding arc discharge (MSGAD) was employed to prepare GNFs. The effects of the carbon-containing precursor, plasma gas, and arc current on the GNFs synthesis were investigated. The technique produced GNFs with sizes of 50–200 nm and 1–20 layers, spherical carbon nanoparticles with 10–40 nm diameters, and graphitic particles. The results showed that the formation of GNFs depended on the selection of proper process parameters, such as precursors with a high H/C ratio, an Ar-N2 plasma gas, a low arc current, a low precursor flow rate, and a suitable plasma gas flow rate. Correlations between the process parameters and the product morphology indicated that abundant H atoms and fewer polycyclic aromatic hydrocarbons were favorable for the formation of GNFs.

Preparation of hydrogen storage carbon materials using bio-oil heavy components as carbon-containing precursor

A new method for preparing carbon materials using bio-oil heavy components has been proposed and their hydrogen capacity at low temperature was explored. The effects of different templates and mass ratio of template to bio-oil on specific surface area, pore size distribution and yield of carbon materials were studied. The thermal decomposition pathway of calcium citrate was proposed. Carbon materials prepared by calcium citrate have larger specific surface area (1688 m2 g−1), more uniform pore size distribution and higher yield (17.76%). The specific surface area and the microporosity first increased and then decreased with increasing mass ratio of template to bio-oil, and reached the maximum value when the mass ratio was 1:1. The yield of carbon materials increased with increasing mass ratio. Hydrogen adsorption capacity (0.73–1.80 wt%) of carbon materials increased along with the increase of specific surface area and microporosity. Furthermore, the interaction between carbon and hydrogen molecules is strong, as shown by the isosteric heat of adsorption of between 6.13 and 10.56 kJ/mol. This paper provides an economical and environmental-friendly method for the preparation of hydrocarbon storage materials, and also a new idea for the utilization of bio-oil heavy components.

Synthesis of Monodisperse Carbon Nanodots with Variable Photoluminescence Spectrum Using Polyaromatic Precursors

Monodisperse carbon nanodots (CNDs) possessing photoluminescence in the visible spectral range have been obtained by means of template synthesis. An approach to the synthesis of CNDs with controlled position of the emission line is demonstrated by using of polyaromatic carbon-containing precursors with different conjugated systems of multiple bonds.

Получение монодисперсных углеродных наноточек с перестраиваемым спектром фотолюминесценции из полиароматических прекурсоров

The monodisperse carbon nanodots possessing photoluminescence in the visible spectral range were synthesized by the template method. An approach has been proposed that allows to control the spectral position of the emission band of the synthesized carbon nanodots using polyaromatic carbon-containing precursors with various multiple bonds conjugated systems

Generating carbon schwarzites via zeolite-templating

Zeolite-templated carbons (ZTCs) comprise a relatively recent material class synthesized via the chemical vapor deposition of a carbon-containing precursor on a zeolite template, followed by the removal of the template. We have developed a theoretical framework to generate a ZTC model from any given zeolite structure, which we show can successfully predict the structure of known ZTCs. We use our method to generate a library of ZTCs from all known zeolites, to establish criteria for which zeolites can produce experimentally accessible ZTCs, and to identify over 10 ZTCs that have never before been synthesized. We show that ZTCs partition space into two disjoint labyrinths that can be described by a pair of interpenetrating nets. Since such a pair of nets also describes a triply periodic minimal surface (TPMS), our results establish the relationship between ZTCs and schwarzites-carbon materials with negative Gaussian curvature that resemble TPMSs-linking the research topics and demonstrating that schwarzites should no longer be thought of as purely hypothetical materials.