Carbon In Nitrogen Atmosphere Research Articles

Preparation and electrochemical application of porous carbon materials derived from extraction residue of Ganoderma lucidum

As a valuable biomass resource, a large number of Chinese medicine residue have not been effectively utilized and are often treated as garbage, which not only causes environmental pollution, but also leads to the waste of resources. Ganoderma lucidum is a common raw material of Chinese herbal medicine, its natural mycelium and tube structure is conducive to the formation the porous structure of carbon materials. In this paper, porous carbon materials with high specific surface area and high pore volume were prepared by high temperature carbonization in nitrogen atmosphere using Ganoderma lucidum residue as a raw material and KOH as an alkali activator. The morphology and pore structure of the prepared carbon materials were analyzed and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction, Raman spectroscopy and nitrogen adsorption method. When the mass ratio of carbon to alkali was 1:4 and the temperature was 800 °C, ultra-high specific surface area microporous carbon materials were obtained with specific surface area of 3425 m3 g−1 and total pore volume of 1.74 cm3 g−1. The prepared porous carbon material was assembled into hydrogen peroxide electrode and cholesteric oxide modified electrode, which showed good catalytic performance.

Synthesis of unused-wood-derived C-Fe-N catalysts for oxygen reduction reaction by heteroatom doping during hydrothermal carbonization and subsequent carbonization in nitrogen atmosphere.

There is an urgent need to develop renewable sources of energy and use existing resources in an efficient manner. In this study, in order to improve the utilization of unused biomass and develop green processes and sustainable technologies for energy production and storage, unused Douglas fir sawdust (SD) was transformed into catalysts for the oxygen reduction reaction. Fe and N were doped into SD during hydrothermal carbonization, and the N- and Fe-doped wood-derived carbon (Fe/N/SD) was carbonized in a nitrogen atmosphere. After the catalyst had been calcined at 800°C, its showed the highest current density (-5.86 mAcm-2 at 0.5 V versus reversible hydrogen electrode or RHE) and Eonset value (0.913 V versus RHE). Furthermore, its current density was higher than that of Pt/C (20 wt% Pt) (-5.66 mA cm-2 @0.5 V versus RHE). Finally, after 50 000 s, the current density of sample Fe/N/SD (2 : 10 : 10) remained at 79.3% of the initial value. Thus, the synthesized catalysts, which can be produced readily at a low cost, are suitable for use in various types of energy generation and storage devices, such as fuel cells and air batteries. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'.

Derivation of carbonaceous nanoparticles from glucose-modified nickel-titanium oxide nanoparticles grown on Nitinol fiber for solid phase microextraction of several polycyclic aromatic hydrocarbons in water samples

A facile strategy was developed for the fabrication of new nanoparticles-templated carbonaceous coating on a Nitinol (NiTi) fiber substrate. The NiTi fiber was first electrochemically anodized for the growth of nickel-titanium oxide nanoparticles (NiTiONPs). Thereafter, NiTiONPs were used as supporting templates for the derivation of carbonaceous nanoparticles (CNPs) via the hydrothermal reaction of glucose followed by carbonization in nitrogen atmosphere. The adsorption performance of the NiTi@NiTiONPs and the NiTi@NiTiO@CNPs fibers was evaluated using typical aromatic compounds as model analytes coupled to high-performance liquid chromatography with UV detection. The results clearly indicated that the NiTiO@CNPs coating exhibited higher extraction capability for polycyclic aromatic hydrocarbons (PAHs) than UV filters. For this purpose, several parameters of SPME with the NiTi@NiTiO@CNPs fiber were examined for the enrichment of PAHs in water. Under the obtained conditions, the calibration curves were linear over the concentration ranges of 0.05–200 μg·L–1 with correlation coefficients above 0.999. Limits of detection were between 0.012 μg·L–1 and 0.15 μg·L–1. Relative standard deviations (RSDs) of the intra-day and the inter-day analyses with the single fiber varied from 3.03% to 5.34% and from 3.31% to 5.82%, respectively. Moreover, RSDs for the fiber-to-fiber reproducibility with five fibers fabricated in different batches were between 4.89% and 7.10%. Finally, the applicability of the proposed method was validated via determination of target PAHs in real water samples with the relative recoveries of 82.6%–114%. Notably, the superior extraction performance of the fabricated fiber was still maintained even after more than 250 extraction/desorption cycles due to strong adhesion of the CNPs coating to NiTiONPs.

Preparation and characterization of coal-based carbon foams by microwave heating process under ambient pressure

Abstracts To reduce significantly the preparation time and cost in energy of coal-based carbon foams and to develop facile synthesis condition, a microwave heading process (MHP) for fabricating coal-based carbon foams was suggested. The preparation time, the structure and the compressive strength of carbon foams fabricated respectively by MHP and carbonization in nitrogen atmosphere at high pressure (CNHP) were contrastively studied. The results show that MHP exhibited three distinct characteristics in contrast to CNHP. First, the preparation time of green foam is shortened by 55.2% based on the microwave heating principle. Secondly, the preparation conditions are more moderate, only under ordinary pressure instead of high pressure. Thirdly, the resultant carbon foams display small pore diameter with narrow pore size distribution and high compressive strength. More importantly, the strategy of coal-based carbon foam by microwave heating process can be applied to other thermoplastic precursor foaming to obtain macro-porous materials.

Synthesis of C–N dual-doped Cr2O3 visible light-driven photocatalysts derived from metalorganic framework (MOF) for cyclohexane oxidation

A series of novel C–N dual-doped Cr2O3 photocatalysts were synthesized from MIL-101(Cr), using a two-step method, including initial carbonization in nitrogen atmosphere without adding any carbon source and subsequent calcination in air.

Graphene‐containing ordered mesoporous carbons synthesized by one‐pot aqueous route and its electrochemical performance

Graphene‐containing ordered mesoporous carbons (GOMCs) with low inner resistance, well‐defined mesoporous, and high specific surface area was prepared via a one‐pot aqueous route, followed by carbonization in nitrogen atmosphere. A sandwich‐like microstructure was built by a cooperative self‐assembly reaction among graphene oxide (GO) sheets, resorcinol–hexamethylenetetramine (HMTA) aqueous solution and amphiphilic triblock copolymer. By adjusting the ratio of GO and the soft template F127 in the precursor mixture, carbons with a controllable pore structure and a maximum surface area of 1,195 m2/g has been prepared. The supercapacitor based on GOMC‐2.0‐F1.5 shows a high electric conductivity (no obvious IR drop was found during charge/discharge process), high specific capacitance (209 F/g), and excellent cycling stability (no capacitance loss was found after 5,000 cycles). POLYM. COMPOS., 38:1438–1446, 2017. © 2015 Society of Plastics Engineers

Catalytic degradation of Acid Orange 7 with hydrogen peroxide using CoxOy-N/GAC catalysts in a bicarbonate aqueous solution

The cobalt-based catalysts CoxOy-N/GAC were prepared by pyrolysis of a cobalt–phenanthroline complex on granular active carbon in nitrogen atmosphere, and tested for the degradation of Acid Orange 7 with H2O2 in a bicarbonate aqueous solution.

High Temperature Behavior of Si3N4 and Yb2SiO5 Coated Carbon Fibers for Silicon‐Nitride CMC

For oxide‐free ceramic matrix composites (CMC), with Si3N4 matrix and carbon fiber reinforcement, for extreme high temperature applications, protective coatings of the C‐fibers are investigated. Two different coatings are compared: reactive CVD‐derived pure Si3N4 coatings to investigate C‐fiber‐matrix reactions and powder based Yb‐silicate coatings to reveal potential reactions with the Yb‐silicate additive serving as sintering aid for Si3N4. The reactivity toward carbon in nitrogen atmosphere is studied in the temperature interval from 20 °C up to 1700 °C. A new ceramic phase – an Yb‐carbido‐nitiridosilicate, Yb2Si4CN6–is found as product of carbothermal reduction of the Yb‐silicate. The carbothermal reduction occurs also with other RE‐silicates, RE = Yb, Er, Y, Gd, and Sm while SiC is found as reaction product on carbon fibers coated with pure Si3N4. The oxidation resistance of the coated fibers in air was investigated in the temperature interval up to 1000 °C, and the apparent activation energy of oxidation was analyzed based on DTA‐EGA results. The oxidation kinetic reveals a significant increase of onset point of oxidation temperature by up to 150 K for Si3N4 coated short carbon fibers obtained from the reactive CVD coating process. Such fibers have a high application potential for carbon‐fiber reinforced Si3N4‐CMC. The role of Yb2Si4CN6 as reinforcement for Si3N4‐CMC is discussed based on bond strength comparison of carbides (SiC), nitride silicates (SiAlON), and nitrides (Si3N4).

Synthesis of resorcinol–formaldehyde/silica composite aerogels and their low-temperature conversion to mesoporous silicon carbide

Resorcinol–formaldehyde/silica composite (RF/SiO 2) gels were acid-catalyzed formed in one pot at 27 °C within 60 min, and then dried to aerogels with supercritical fluid CO 2. After carbonization in nitrogen atmosphere and a magnesiothermic reaction at 700 °C, RF/SiO 2 aerogels were successfully converted to monolithic mesoporous silicon carbide (SiC aerogels). The starting RF/SiO 2 aerogels had an interpenetrating organic/inorganic network and the resulting SiC products preserved monolithic mesoporous morphology similar to the original templates. The as-synthesized SiC aerogels consisted of nanocrystalline β-SiC, possessed a BET surface area of 232 m 2/g and showed sufficient mesoporosity. They had a direct band gap of about 3.2 eV (less than that of bulk β-SiC) and showed photoluminescence at room temperature. The mechanisms about the formation of RF/SiO 2 gels and the conversion to SiC aerogels were discussed. Potentially, the reported method can be used to convert many metal or semimetal oxide/carbon composite aerogels to carbide aerogels at relatively low temperature for many catalytic, electronic, photonic and thermal applications.

Methylene blue adsorption on activated carbon prepared from Posidonia oceanica (L.) dead leaves: Kinetics and equilibrium studies

Posidonia oceanica (L.) is an endemic species in the Mediterranean Sea, which, like terrestrial plants, loses it leaves seasonally. The dead leaves are accumulated on the beaches in huge quantities as waste material, causing great environmental and economical problems. The dead biomass offers an abundant, renewable and low cost precursor for the production of activated carbon (AC). In that respect ACs were prepared by chemical activation of P. oceanica (L.) dead leaves. The preparation process consisted of zinc chloride impregnation at ratios up to 45%, followed by carbonization in nitrogen atmosphere at temperatures up to 873 K. The prepared P. oceanica (L.) activated carbons (POAC) were studied by SEM and Nitrogen porosimetry and the pore structural characteristics were determined. Concerning the POAC45 sample, a specific surface area of 1483 m 2/g and a total pore volume of about 1 cm 3/g were achieved, while both microporosity and mesoporosity were obtained. The adsorption potential of POAC for the removal of methylene blue (MB) from aqueous solutions was also investigated under varying conditions of initial concentration, carbon dosage, pH, temperature and the optimum experimental conditions were determined. The samples revealed relatively fast kinetics reaching equilibrium in around 60 min, which follow the second order rate equation, while adsorption was unaffected by the pH of the solution. The Langmuir model provided the best fit to the experimental data and sorption capacity increased with increasing temperature. The results showed that proposed precursor lead to AC with increased sorption capacity for MB reaching a value of 285.7 mg/g at 318 K. In conclusion, P. oceanica (L.) dead leaves can be used as a raw material for preparation of high quality activated carbon.

Synthesis of nanocrystalline titanium carbonitride during milling of titanium and carbon in nitrogen atmosphere

Mixtures of elemental titanium and carbon with Ti/C atomic ratio of 1:0, 1:0.125, 1:0.25, 1:0.5 and 1:0.75 were milled in nitrogen atmosphere using a high-energy ball mill, Spex8000. Nanocrystalline titanium carbonitride powders have been synthesized when milling the mixtures with Ti/C atomic ratio not less than 0.25. The formation of the titanium carbonitride phase has been found to undergo an abrupt reaction. It is suggested that this reaction appears to be a self-propagating high-temperature synthesis (SHS) process. During the incubation duration of the SHS reaction, small amount of titanium carbonitride phase has been detected by X-ray diffraction (XRD). The composition and lattice parameter of the synthesized titanium carbonitride phase can be adjusted by changing the composition of the starting mixture of elemental titanium and carbon.

Preparation and characterization of morph-genetic C/TiN composites from filter paper

Morph-genetic C/TiN composites with cablelike structure was prepared from filter paper template through the surface sol–gel process and carbothermal nitridation reaction. The resulting materials have a hierarchical structure originating from the morphology of cellulose paper. The C/TiN composites formed the core-shell microstructure, the core is graphitic carbon, and the shell is TiN nanocoating formed by carbothermal nitridation reduction of titania with the interfacial carbon in nitrogen atmosphere. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscope were employed to characterize the structural morphology and phase compositions of the final products.

Preparation and characterization of morph-genetic aluminum nitride/carbon composites from filter paper

Morph-genetic aluminum nitride/carbon composites with cablelike structure were prepared from filter paper template through the surface sol–gel process and carbothermal nitridation reaction. The resulting materials have a hierarchical structure originating from the morphology of cellulose paper. The aluminum nitride/carbon composites have the core–shell microstructure, the core is graphitic carbon, and the shell is aluminum nitride nanocoating formed by carbothermal nitridation reduction of alumina with the interfacial carbon in nitrogen atmosphere. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscope were employed to characterize the structural morphology and phase compositions of the final products.

Preparation of activated carbons from bituminous coal pitches

High-porosity carbons were prepared from bituminous coal pitches by combining chemical and physical activation. The chemical activation process consisted of potassium hydroxide impregnation followed by carbonization in nitrogen atmosphere. The effect of the KOH impregnation ratio on the surface area and pore volumes evolution of the carbons derived from mesophase pitch was studied. The optimum KOH:pitch ratio was fixed to realize a physical activation process in order to increase the textural parameters of the KOH-activated carbons. Physical activation was performed by carbonizing the KOH-activated carbons followed by gasifying with air. The influence of the carbonization temperature and the residence time of the gasification with air were explored to optimize those preparation parameters.

The Reaction of Magnesia and Carbon in Nitrogen Atmosphere (1 atm) at 1400°-1800°C

The Reaction of Magnesia and Carbon in Nitrogen Atmosphere (1 atm) at 1400°-1800°C