Solid Carbon Source Research Articles

Direct Growth of Highly Stable Patterned Graphene on Dielectric Insulators using a Surface-Adhered Solid Carbon Source.

A novel method is described for the direct growth of patterned graphene on dielectric substrates by chemical vapor deposition (CVD) in the presence of Cu vapor and using a solid aromatic carbon source, 1,2,3,4-tetraphenylnapthalene (TPN), as the precursor. The UV/O3 treatment of the TPN film both crosslinks TPN and results in a strong interaction between the substrate and the TPN that prevents complete sublimation of the carbon source from the substrate during CVD. Substrate-adhered crosslinked TPN is successfully converted to graphene on the substrate without any organic contamination. The graphene synthesized by this method shows excellent mechanical and chemical stability. This process also enables the simultaneous patterning of graphene materials, which can thus be used as transparent electrodes for electronic devices. The proposed method for the synthesis directly on substrates of patterned graphene is expected to have wide applications in organic and soft hybrid electronics.

Plastic carrier polishing chamber reduces pollution swapping from denitrifying woodchip bioreactors

Denitrifying bioreactors with solid organic carbon sources (i.e., “woodchip bioreactors”) have proven to be relatively simple and cost effective treatment systems for nitrate-laden agricultural and aquacultural waters and wastewaters. However, because this technology is still relatively new, design modifications, such as the addition of a post-bioreactor polishing chamber filled with inert media, may offer potential to increase nitrate removal and mitigate unintended bioreactor by-products. Paired-column configurations filled with woodchips followed by plastic biofilm carrier media showed significant nitrate removal within the woodchip bioreactor columns (37, 26, and 88% nitrate removal efficiencies at woodchip column retention times of 7.1, 18, and 52 h), but no significant additional nitrate removal benefit of the post-processing plastic media chamber (41, 22, and 89% nitrate removal efficiencies, respectively). Releases of chemical oxygen demand from the woodchips were likely not sufficient to fuel significant nitrate removal in the polishing chamber. However, the polishing chamber significantly reduced nitrite releases from the bioreactor columns, and provided some mitigation of reduced sulfate during the 52-h retention time testing period (influent, woodchip effluent, and plastic chamber effluent sulfate concentrations of 23.6, 18.8, and 20.7 mg SO42− L−1, respectively). A full-scale post-woodchip polishing chamber filled with inert plastic media generally may not be worth the added cost unless the receiving waters are particularly sensitive to nitrite or hydrogen sulfide.

Partial denitrification coupled with immobilization of anammox in a continuous upflow reactor.

Based on the stable operation of a continuous upflow reactor, immobilized anammox coupling with partial denitrification (DEAMOX), was successfully achieved after 94 days operation with a 63.5% accumulation rate of NO2−–N and a 98.4% removal rate of NO3−–N. Moreover, the findings show that the optimum range of COD/NO3−–N ratio for the coupling reaction was 2.3–2.7. The nitrogen removal performance of the coupling reactor decreased in response to the increase of pH value to 8.0 or 8.5, which was inconsistent with previously published results. Complete denitrification was successfully coupled with DEAMOX by adding polycaprolactone (PCL) as solid carbon source. As a result, the NO3−–N produced via anaerobic ammonium oxidation could be completely removed; the removal rate of total nitrogen increased from 80.3% to 88.5%. In addition, a large number of denitrifying biofilms were attached to the surface of PCL particles.

Research on denitrification efficiency of three types of solid carbon source

C/N rates can greatly influence efficiency of denitrification. It is difficult for current treated effluent to reach GB18918-2002 primary effluent standard because of its low C/N rate. To improve the efficiency of denitrification, the quality of effluent, and realize the waste recycling, this article selected magnolia leaves, loofah and degradable meal box as the solid carbon source and set different solid-liquid ratio of magnolia leaves for periodic denitrification stage to study the change of NO3--N, TN, COD, NO2--N, NH4+, PO43- and color. The results showed that in the condition of influent nitrate concentration of 40 mg/L, carbon dosage of 10 g, the reaction temperature of 25°C, the nitrate removal rates of magnolia leaves and loofah reached 89.0% and 96.8% respectively, rather higher than degradable meal box (56.3%). The TN removal rates of magnolia leaves (91.7%) and loofah (77.7%) were both higher than degradable meal box (53.9%), and the effluent TN concentration of loofah and degradable meal box reached 25.4 mg/L and 21.1 mg/L respectively, which couldn’t be discharged according to the primary effluent concentration standard of GB18918-2002. The released concentration of ammonia nitrogen and phosphate: loofah> magnolia> degradable meal box. The high solid-liquid ratio of magnolia leaves helped to improve the TN removal rate, which reached 75.0% (1:200) and 91.7% (1:100), but it caused higher released concentration of carbon, ammonia nitrogen and phosphate to effect system heavily. Under the integrated analysis, the low solid-liquid ratio (1:200) of magnolia leaves was more suitable to be the denitrification external carbon source.

Use of a solid carbon precursor for DC plasma nitrocarburizing of AISI 4140 steel

A new surface treatment concept of solid carbon source plasma nitrocarburizing (SCS-PNC) was proposed. Carbon fiber carbon composite (CFC) was used as a solid carbon precursor for conventional DC plasma nitriding process in a nitrogen-hydrogen plasma. The effect of plasma power on the phase composition of the compound layer on AISI 4140 steel was investigated. The results of the SCS-PNC process were compared to conventional DC plasma nitriding (PN) and plasma nitrocarburizing (PNC) using methane as carbon-bearing gas. The SCS-PNC process provides increasing carbon concentration within the compound layer with increasing plasma power density. In the compound layer a constant carbon content of 1.5 wt.-% C was obtained for high plasma power densities and the ε-carbonitride Fe2-3(C,N)x formation was significantly promoted reducing the porous seam zone. Moreover, precipitation of unwanted cementite Fe3C in the compound layer was effectively suppressed for SCS-PNC compared to treatment by PNC with methane addition.

Effects of Growth Temperature on Electrocatalytic Properties of Three-dimensional Sulfur-doped Graphene Foam

Three-dimensional sulfur-doped graphene (3DSG) has been grown by chemical vapor deposition (CVD) using nickel foam as substrate and thianthrene as the solid carbon and sulfur source. The results show that the growth temperature of 3DSG has significant influence on the electrocatalytic activity for hydrogen evolution reaction (HER). The 3DSG sample under optimal growth temperature of 800 °C has the best electrocatalytic activity. The excellent electrocatalytic activity can be attributed to its well-designed porous, conductive and 3D sulfur-doped graphene structure.

Engineering a PVD-Based Graphene Synthesis Method

Graphene is an important nanomaterial with extraordinary properties. An established physical vapor deposition (PVD) based Graphene synthesis method is engineered in order to demonstrate the versatility of the growth method with respect to the quality and number of layers of synthesized Graphene. A statistical method known as factorial Design-of-Experiments (DoE) is demonstrated in this paper to determine key factors for synthesis of Graphene on Copper (Cu) using amorphous carbon (a-C) as the solid carbon source. Both qualitative and quantitative analysis are performed to determine a suitable recipe. Carbon source thickness (which is a-C) annealing temperature and annealing duration are varied to study their effect on the growth. Annealing temperature and a-C thickness are found to be significant factors for growth feasibility in a PVD-based growth, whereas annealing time is found to play a crucial role in growing different number of layers of Graphene with different quality. The quality and number of layers of Graphene are verified by Raman characterization.

Selective Fabrication of SiC/Si Heterojunction Diodes by Local Laser Annealing Process for Microwave Circuit Applications

This paper presents the RF characterization of SiC/Si heterojunction diodes fabricated using a novel localized laser process. Selective growth of SiC on Si is carried out by utilizing excimer laser-based annealing in the presence of carbon source. Use of ambient conditions (atmospheric pressure and room temperature) during growth makes this process simple and low cost. The Si wafer is first coated with carbon rich film and then locally annealed using high power laser which causes dissociation of solid carbon sources and a simultaneous melting of the silicon leading to the growth of SiC. The Raman spectrum shows peaks for acoustical and optical phonon modes for ${\beta }$ -SiC between 940 and 980 cm $^{-1}$ . The fabricated diodes show high breakdown voltage (>200 V) and low leakage current density of 3- $5~\mu \text{A}$ /cm2 (−5 V). Experimental results for the dc characteristics, microwave rectification and frequency multiplication are presented. The measured results show good RF rectification (e.g., 21 V/W at 3 GHz) up to 6 GHz using a large diode ( $70\times 70\mu \text{m}^{2}$ ). The diodes also work well as frequency doublers over a wide frequency range of 2–6 GHz. The diode area can be scaled down to design circuits operating at higher frequencies.

Scalable Dry Production Process of a Superior 3D Net‐Like Carbon‐Based Iron Oxide Anode Material for Lithium‐Ion Batteries

AbstractCarbon‐based transition‐metal oxides are considered as an appropriate anode material candidate for lithium‐ion batteries. Herein, a simple and scalable dry production process is developed to produce carbon‐encapsulated 3D net‐like FeOx/C materials. The process is simply associated with the pyrolysis of a solid carbon source, such as filter paper, adsorbed with ferrite nitrate. The carbon derived from filter paper induces a carbothermal reduction to form metallic Fe, the addition of carbon and iron increase the conductivity of this material. As expected, this 3D net‐like FeOx/C composite delivers an excellent charge capacity of 851.3 mAh g−1 after 50 cycles at 0.2 A g−1 as well as high stability and rate performance of 714.7 mAh g−1 after 300 cycles at 1 A g−1. Superior performance, harmlessness, low costs, and high yield may greatly stimulate the practical application of the products as anode materials in lithium‐ion batteries.

Scalable Dry Production Process of a Superior 3D Net-Like Carbon-Based Iron Oxide Anode Material for Lithium-Ion Batteries.

Carbon-based transition-metal oxides are considered as an appropriate anode material candidate for lithium-ion batteries. Herein, a simple and scalable dry production process is developed to produce carbon-encapsulated 3D net-like FeOx /C materials. The process is simply associated with the pyrolysis of a solid carbon source, such as filter paper, adsorbed with ferrite nitrate. The carbon derived from filter paper induces a carbothermal reduction to form metallic Fe, the addition of carbon and iron increase the conductivity of this material. As expected, this 3D net-like FeOx /C composite delivers an excellent charge capacity of 851.3 mAh g-1 after 50 cycles at 0.2 A g-1 as well as high stability and rate performance of 714.7 mAh g-1 after 300 cycles at 1 A g-1 . Superior performance, harmlessness, low costs, and high yield may greatly stimulate the practical application of the products as anode materials in lithium-ion batteries.

Enhanced nitrogen removal using solid carbon source in constructed wetland with limited aeration

In this study, the performances of nitrogen removal in constructed wetlands using solid carbon source with limited aeration were investigated. The blends of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and polyacetic acid (PLA) were used as the carbon source and biofilm support. The performances of nitrogen removal, microbial abundance and microbial community structure in the biofilm attached on PHBV/PLA were investigated. Higher ammonia removal efficiency (91.00%) and total nitrogen removal efficiency (97.03%) than non-aerated constructed wetland (System NA) were achieved in constructed wetland with limited aeration (System A). The limited aeration decreased the average concentrations of COD in effluent. And, System A had higher microbial abundance than System NA. Pyrosequencing analysis showed that denitrifying bacteria Brevinema (41.85%) and Thiothrix (12.33%) were the predominant genus in the biofilm attached on the carbon source in System NA and System A, respectively.

Three-Dimensional Printed Graphene Foams.

An automated metal powder three-dimensional (3D) printing method for in situ synthesis of free-standing 3D graphene foams (GFs) was successfully modeled by manually placing a mixture of Ni and sucrose onto a platform and then using a commercial CO2 laser to convert the Ni/sucrose mixture into 3D GFs. The sucrose acted as the solid carbon source for graphene, and the sintered Ni metal acted as the catalyst and template for graphene growth. This simple and efficient method combines powder metallurgy templating with 3D printing techniques and enables direct in situ 3D printing of GFs with no high-temperature furnace or lengthy growth process required. The 3D printed GFs show high-porosity (∼99.3%), low-density (∼0.015g cm-3), high-quality, and multilayered graphene features. The GFs have an electrical conductivity of ∼8.7 S cm-1, a remarkable storage modulus of ∼11 kPa, and a high damping capacity of ∼0.06. These excellent physical properties of 3D printed GFs indicate potential applications in fields requiring rapid design and manufacturing of 3D carbon materials, for example, energy storage devices, damping materials, and sound absorption.

Quasi-free-standing graphene nano-islands on Ag(110), grown from solid carbon source

Structural, electronic, and mechanical properties of graphene islands grown by depositing carbon atoms directly onto a hot single crystal Ag(110) surface are experimentally investigated. First, graphene nano-islands with morphologies tuned by carbon flux and substrate temperatures are fabricated. Moiré superstructures are found to be superposed on the graphene islands, corresponding to the islands' varied orientations and periodicities with respect to the underlying Ag(110) substrate. Both Scanning tunnelling spectroscopy and Raman spectroscopy indicate a weak interaction between graphene and the substrate, which is further confirmed by scanning tunnelling microscopy tip induced graphene flake movement.

Spectroscopic Fingerprints of Carbon Monomers and Dimers on Ir(111): Experiment and Theory

By combining high-resolution photoelectron spectroscopy and ab initio calculations, we show that different carbon clusters can be formed on Ir(111) upon low temperature molecular beam epitaxy using a solid state carbon source. Besides carbon monomers, also dimers, trimers, and larger clusters are detected through C 1s core level measurements. The spectroscopic signal of carbon monomers is then used as a fingerprint to detect their presence during the early stages of graphene growth by ethylene chemical vapor deposition at high temperature. We demonstrate that our spectroscopic approach can be employed to investigate the role of carbon monomers and dimers in the nucleation and growth of graphene on different metal surfaces.

Effects of Temperature on the Characteristics of Nitrogen and Phosphorus Removal and Microbial Community in SCSC-S/Fe

In order to investigate the effect of temperature on the cellulose-degrading bacteria and denitrifying bacteria, the denitrification and phosphorus removal of solid carbon source of cellulose corncob+sulfur/sponge iron nitrogen and phosphorus removal composite system, abbreviated as SCSC-S/Fe, was analyzed under different temperature conditions, and the surface structure and microbial properties of corncob before and after reaction were analyzed by scanning electron microscope (SEM) and MiSeq high-throughput sequencing technologies. The results indicated that when temperature increased from 15, 20, 25 to 30℃, the average TN removal rate of the system increased from 78.88% to 92.70%, the average removal rate of TP increased from 82.58% to 89.15%;microbial properties showed that the surface reaction after corncob was dominated by spherical and rod-shaped microorganisms; the proportion of cellulose-degrading bacteria was 11.01% higher at 30℃ than 20℃, and the proportion of denitrifying bacteria decreased by 21.26%. It can be seen that the cellulose -degrading bacteria were more sensitive to the temperature than the denitrification bacteria, and more obviously affected by the temperature.

Comparison research on denitrification efficiency of two types of solid carbon source

C/N rates can greatly influence efficiency of denitrification. It is difficult for current treated effluent to reach GB18918-2002 primary effluent standard because of its low C/N rate. To improve the efficiency of denitrification, the quality of effluent, and realize the waste recycling, this article selected magnolia leaves and degradable meal box as the solid carbon source for periodic denitrification stage to study the change of NO3--N, TN, COD, NO2--N, NH4+, PO43- and color. The results showed that in the condition of influent nitrate concentration of 40 mg/L, carbon dosage of 10 g, the reaction temperature of 25°C the nitrate removal rates of magnolia leaves and degradable meal box reached 89.0% and 56.3% respectively, and the TN removal rates reached 91.7% and 53.9% respectively. But in the aspect of final treated effluent COD concentration level, magnolia leaves experiment (608 mg/L) was much higher than the degradable meal box (78 mg/L). Besides, the accumulation of nitrite, the released concentration of ammonia nitrogen and phosphate of magnolia leaves experiment were also higher than the degradable meal box. Under the integrated analysis, the magnolia leaves are more suitable than the degradable meal box as the denitrification external carbon source.

Synthesis of a Graphene-Like Nanofilm from Polyacrylonitrile

There are various different approaches in synthesizing graphene including chemical vapor deposition (CVD) and solid-phase method, where gas or solid type carbon source, to be converted into graphene, interacts with transition metals such as nickel and copper. When any thin nickel layer coated atop the polyacrylonitrile (PAN) film is pyrolyzed at a sufficiently high temperature, it is impossible to grow a continuous graphene film with a large area owing to dewetting, which has restricted the subsequent utilization in practical applications. Herein, we suggest a method to synthesize a continuous graphene-like nanofilm with a nickel coated thin PAN film through pyrolysis at 750 to 800 °C in a high-vacuum furnace without a reductive gas flow. The graphene-like nanofilm obtained was characterized using Raman spectroscopy, Raman mapping, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, and field-emission transmission electron microscopy.

Three-Dimensional Rebar Graphene.

Free-standing robust three-dimensional (3D) rebar graphene foams (GFs) were developed by a powder metallurgy template method with multiwalled carbon nanotubes (MWCNTs) as a reinforcing bar, sintered Ni skeletons as a template and catalyst, and sucrose as a solid carbon source. As a reinforcement and bridge between different graphene sheets and carbon shells, MWCNTs improved the thermostability, storage modulus (290.1 kPa) and conductivity (21.82 S cm-1) of 3D GF resulting in a high porosity and structurally stable 3D rebar GF. The 3D rebar GF can support >3150× the foam's weight with no irreversible height change, and shows only a ∼25% irreversible height change after loading >8500× the foam's weight. The 3D rebar GF also shows stable performance as a highly porous electrode in lithium ion capacitors (LICs) with an energy density of 32 Wh kg-1. After 500 cycles of testing at a high current density of 6.50 mA cm-2, the LIC shows 78% energy density retention. These properties indicate promising applications with 3D rebar GFs in devices requiring stable mechanical and electrochemical properties.

Direct graphene growth on transitional metal with solid carbon source and its converting into graphene/transitional metal oxide heterostructure

The oxide/semiconductor structure is key to controlling current in electronic devices and HfO2 is a common gate material in conventional electronic devices due to its favorable dielectric properties. Graphene devices also require insulating gates. We demonstrate a unique direct growth approach to obtain the bottom gate structure (graphene/HfO2/n-SiC). The present approach involves transfer of graphene grown by chemical vapor deposition (CVD) on Cu to oxidized Si wafers, a complex process prone to low yield and reduced performance. Furthermore, HfO2 is preferred to SiO2 because of its superior properties. The proposed concept consists of the direct deposition of graphene by solid carbon molecular beam epitaxy on Hf metal coated n-type SiC, followed by oxygen intercalation to form HfO2. The oxygen intercalation will then convert the underlying Hf into HfO2 due to the strong affinity of Hf with oxygen. We identify the graphene/HfO2 formation by Raman, X-ray photoelectron spectroscopy (XPS), Low energy electron diffraction (LEED), Low energy electron microscopy (LEEM) and electrical properties including Hall mobility and leakage current measurement.

Three-dimensional nitrogen-doped graphene derived from poly-o-phenylenediamine for high-performance supercapacitors

We report here that poly-o-phenylenediamine as a solid carbon source can be facilely carbonized to produce three-dimensional nitrogen-doped graphene (3DNGN) with the aid of Ni(NO3)2 powder. In situ formed Ni nanoparticles by decomposition of Ni(NO3)2 serve as both template and catalyst for the formation of 3DNGN. The 3DNGN with interconnected porous structure and high content of nitrogen doping can ensure large electrolyte-accessible surface area, rapid ion transportation, and fast electron transport, resulting in high electrochemical performance. The 3DNGN shows a high specific capacitance of 312Fg−1 at 1Ag−1 with good capacitance retention capability and good cycling stability, and outputs a high average energy power density of 10.8Whkg−1 and a high maximum power density of 595kWkg−1 in aqueous KOH electrolyte. Due to the great pseudocapacitance in aqueous H2SO4 electrolyte, the specific capacitance of the 3DNGN can reach a high value of 345Fg−1 at 1Ag−1.