Degree Of Graphitization Research Articles

In Situ Chemical Modulation of Graphitization Degree of Carbon Fibers and Its Potassium Storage Mechanism.

Graphite is considered to be the most auspicious anode candidate for potassium ion batteries. However, the inferior rate performances and cycling stability restrict its practical applications. Few studies have investigated the modulating the graphitization degree of graphitic materials. Herein, a nitrogen-doped carbon-coated carbon fiber composite with tunable graphitization (CNF@NC) through etching growth, in-situ oxidative polymerization, and subsequent carbonization process is reported. The prepared CNF@NC with abundant electrochemical active sites and a rapid K+/electron transfer pathway, can effectively shorten the K+ transfer distance and promote the rapid insertion/removal of K+. Amorphous domains and short-range curved graphite layers can provide ample mitigation spaces for K+ storage, alleviating the volume expansion of the highly graphitized CNF during repeated K+ insertion/de-intercalation. As expected, the CNF@NC-5 electrode presents a high initial coulombic efficiency (ICE) of 69.3%, an unprecedented reversible volumetric capacity of 510.2 mA h cm-3 at 0.1 A g-1 after 100 cycles with the mass-capacity of 294.9 mA h g-1. The K+ storage mechanism and reaction kinetic analysis are studied by combining in-situ analysis and first-principles calculation. It manifests that the K+ storage mechanism in CNF@NC-5 is an adsorption-insertion-insertion mechanism (i.e., the "1+2" model). The solid electrolyte interphase (SEI) film forming is also detected.

Low residual stress SiC coatings on C/CA composites by a strategy of matching their expansion behaviors to improve thermal shock resistance

The poor thermal shock resistance of coated C/CA composites limits the applications with rapid temperature fluctuations due to the huge thermal mismatch between the coating and the substrate. A facile strategy of tailoring coefficient of thermal expansion (CTE) of C/CA is proposed to match their thermal deformation behaviors. The optimized C/CA by heat treatment has a positive correlation between CTE and temperature, and thus the as-prepared SiC coating has a decreased macroscopic residual strain of 80.7% due to their coordinated thermal response compared to the original C/CA. Meanwhile, benefited from the structural improvement of larger pore size and higher degree of graphitization of C/CA, a significantly decreased tensile stress of 60.3% in the coating is achieved due to the formation of small SiC spheres in the carbon network. Resultantly, the coated C/CA shows remarkably improved thermal shock resistance with narrower and fewer microcracks, and lower mass and linear cyclic ablation rates of 0.252 mg/s and 0.607 μm/s, respectively.

Wood-Derived Graphite: A Sustainable and Cost-Effective Material for the Wide Range of Industrial Applications

The study explored the graphitization of wood through two distinct methods: a high-temperature approach at 2400 °C and a low-temperature technique at 1400 °C using a catalyst. The graphitization properties were assessed by conducting thermal experiments at various temperatures (1100 °C, 1400 °C, 1800 °C, 2000 °C, and 2400 °C), both with and without a catalyst. The development of graphite lattices was quantitatively analyzed using an array of techniques: X-ray diffractometer (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared spectroscopy (FTIR). The XRD analysis highlighted temperature-dependent changes in lattice parameters (d002, La, and Lc), while Raman spectroscopy tracked alterations in the D to G peak ratio (D/G) with temperature. An increase in temperature is correlated with a rise in the number of graphene layers and the degree of graphitization. Notably, the process of graphite lattice formation varied across the experimental temperature spectrum. The use of a catalyst resulted in a reduced d002 spacing, signifying an enhanced degree of graphitization. Moreover, the catalyst promoted a consistent and smooth graphitization process throughout the heating stages. In contrast, graphitization without a catalyst occurred at higher temperatures, specifically between 1800 °C and 2000 °C, with the d002 value stabilizing around 0.338 nm. The catalyst proved instrumental in transforming the initial structure into well-ordered graphite at lower temperatures. This investigation underscores the potential and benefits of employing a catalyst to generate high-quality graphite from wood at reduced temperatures, paving the way for sustainable and economically viable applications of this material.

The total use of rice husk to create highly porous silicon and sulfur-doped activated carbon for the fabrication of high-performance silicon-anode lithium-ion capacitors

The promising advantages between the high energy density of lithium-ion batteries and the high power density of supercapacitors are hybridized to construct lithium-ion capacitors (LICs). The high capacity of anode materials is challenging for high-performance LICs. Simultaneously, the quest for sustainable and environmentally friendly energy storage materials has attracted attention. In this work, rice husk was treated with alkaline to separate silica and biochar, followed by magnesiothermic reduction and thermal activation to produce porous silicon (PSi) and sulfur-doped activated carbon (SAC), respectively. The PSi had high porosity for accommodating volumetric expansion during cycling, resulting in outstanding rate capability and cycling stability, whereas the SAC had a high surface area with micro- and mesopores (2511 m2 g−1), a high degree of graphitization, and excellent electrochemical performance. For the fabrication of half-cell lithium-ion batteries, PSi gave a specific capacity of 1005.3 mAh g−1 between 0.01 and 2 V, while SAC provided a specific capacity of 108 mAh g−1 (2.0–4.5 V), and showed a better electrochemical stability than the both commercial silicon and activated carbon. When a full-cell LIC was fabricated, the optimized P-Si//SAC LIC had a high energy density of 107 Wh kg−1 at a power density of 163 W kg−1 and a capacitance retention of 81.3 and 61.8% between a potential range of 2.0–4.5 V after 1000 and 3000 charge-discharge cycles, respectively. This study not only turned agricultural waste into valuable, high-performance LICs but also made significant progress toward the creation of environmentally responsible, long-lasting, and sustainable energy storage systems.

Novel cow dung-doped sludge biochar as an efficient ozone catalyst: Synergy between graphitic structure and defects induces free radical pathways

A composite material, cow dung-doped sludge biochar (Zn@SBC-CD), was synthesized by one-step pyrolysis using ZnCl2 as an activating agent and applied to a catalytic ozonation process (COP) for methylene blue (MB) removal. SEM, XRD, FTIR, XPS and BET analyses were performed to characterize the biochar (BC) catalysts. Zn@SBC-CD had high graphitization degree, abundant active sites and uniform distribution of Zn on its surface. Complete removal of MB was achieved within 10 min, with a removal rate much higher than that of ozone alone (32.4%), implying the excellent ozone activation performance of Zn@SBC-CD. The influence of experimental parameters on MB removal efficiency was examined. Under the optimum conditions in terms of ozone dose 0.04 mg/mL, catalyst dose 400 mg/L and pH 6.0, COD was completely removed after 20 min. Electron paramagnetic resonance (EPR) analysis revealed radical and non-radical pathways were involved in MB degradation. The Zn@SBC-CD/O3 system generated superoxide anion radicals (•O2−), which were the main active species for MB removal, through adsorption, transformation, and transfer, Furthermore, Zn@SBC-CD exhibited good reusability and stability in cycling experiments. This study provides a novel approach for the utilization of cow dung and sludge in synthesis of functional biocatalysts and application in organic wastewater treatment.

Insight into the role of lanthanide metal oxides on the carbon deposition resistance of Ni/MSS catalysts for dry reforming of methane

Dry reforming of methane (DRM) can well convert CO2 and CH4 into syngas to further synthesize valuable chemicals, thereby realizing the resource utilization of greenhouse gases. However, the sintering and carbon deposition vulnerabilities of Ni-based dry reforming catalysts prevent them from being commercialized. The ethylene glycol impregnation method was used in this study to create a group of Ni/MSS catalysts added with lanthanide metal oxides (CeO2、La2O3、Sm2O3、Nd2O3). A range of characterization techniques were employed to examine the impact on the resistance to carbon deposition and sintering. Studies have shown that lanthanide metal oxides enhance the metal support interaction, promote active metal Ni dispersion and reduce Ni particle size. Meanwhile, the catalyst's alkali strength and basic site count both rise, and a large number of surface oxygen vacancies are produced, among which CeO2 has the most obvious effect. As a result, the catalyst's activity and resistance to carbon deposition and sintering are greatly increased, while also inhibiting the degree of graphitization of carbon deposition. According to the kinetic studies, the catalyst containing lanthanide metal oxides had an apparent activation energy for CH4 and CO2 that was lower than the Ni/MSS catalyst.

Exploring a novel approach for the synthesis of MIL-53(Fe)/reduced graphene oxide composites with preserved structural integrity for high performance for electromagnetic wave shielding

Efficient electromagnetic waves absorbing materials while preserving structural integrity based on MIL-53(Fe)/reduced graphene oxide composites remains a challenging task. Most reported preparation techniques compromise structural integrity which limits its practical applications. This study reports innovative method by carefully controlling pyrolysis in a tubular furnace to produce Pyrolyzed MIL-53(Fe)/reduced graphene oxide (P-MIL-53(Fe)/RGO) composites to safeguard structural integrity while preserving RGO’s structure and achieving high EMI shielding efficiency. Various mass ratios of reduced graphene oxide were investigated (15%, 20%, and 30%) to indicate the impact of calcination in changing the degree of graphitization and its effect on the shielding performance. P-MIL-53(Fe)/RGO30 stands out, achieving notable total shielding effectiveness (SET) of 46.5 dB and absorption shielding efficiency (SEA) of 40.3 dB with 2 g of reduced graphene oxide (5 mm thick). The study offers a simple strategy to produce the desired composite with preserved reduced graphene oxide’s structural integrity which has a potential EMI shielding performance. These insights hold promise for diverse applications demanding robust, high-performance electromagnetic wave shielding materials.

Analysis of the correlation between mechanical and physicochemical properties of particles based on a diesel oxidation catalytic system

The mechanical and physicochemical properties of diesel engine exhaust particles before and after diesel oxidation catalyst (DOC) treatment are analyzed. It is considered important to explore the interrelationships between these attributes in order to understand their relevance. Understanding of these properties provides insights into the deposition characteristics of particles within the system and the evolution of the particles after the DOC treatment, which may help the selection of appropriate aftertreatment strategies. In this paper, particle samples were collected before and after the DOC to explore the variations in the mechanical and physicochemical properties of the particles under different operating conditions. Atomic force microscopy, thermogravimetric analysis, transmission electron microscopy, and Raman spectroscopy were employed to investigate the attraction force, adhesion force, adhesion energy, oxidative reactivity, primary particle size, nanostructure, and graphitization degree of the particles. The results indicated that under post-injection conditions, the attraction force, adhesion force, and adhesion energy of the particles increased significantly. However, when the particles passed through the DOC, these properties decreased to varying degrees. By analyzing the combination of physicochemical properties, it was determined that the attraction force of the particles was primarily influenced by the primary particle size and the particle's graphite structure. The adhesion force was found to be closely related to the content of soluble organic matter. Additionally, the soluble organic matter affected the degree of particle agglomeration by altering the adhesion energy of the particles.

Co-pyrolysis and activation of microalgae and waste polypropylene in the synthesis of nitrogen doped and porous carbon for pollutant adsorption

Algae and waste plastics are two promising raw materials for the preparation of carbon-based adsorbents, which are regarded as the promising adsorbent to remove pollutants in wastewater. To obtain an activated carbon with well-developed porous structure and abundant functional groups, the mixture of H-rich disposable waste polypropylene (WP) and N-rich Chlorella vulgaris (CV) were selected as precursors through co-pyrolysis and KOH activation. The optimum mass ratio of WP and CV for preparing co-pyrolysis carbon (CPC) was 1:3, while the optimum mass ratio of CPC and KOH for preparing co-pyrolysis activated carbon (CAC) was 1:5 at the activation temperature of 800 °C. The morphologies, mean pore diameter, material surface element and degree of graphitization of CAC were analyzed by SEM, BET, XRD, XPS and Raman spectroscopy, respectively. The adsorption kinetics and thermodynamics of tetracycline (TC) onto CPC were investigated. And the sustainability of algal-based activated carbon in adsorption of pollutants has been tested. This study provides a synthesis method of CAC by using algal-based biomass and waste plastics for the absorption of organic pollutants in wastewaters.

Preparation of nitrogen-doped carbon pyrolyzed from ZIF-8 and its performance in electrocatalytic oxygen reduction to hydrogen peroxide

As an environment-friendly strategy, electrocatalytic hydrogen peroxide (H2O2) generation via two-electron oxygen reduction reaction (2e– ORR) has attracted significant scientific and technological attention. Nevertheless, limited to the low catalytic activity and high cost of noble metal-containing catalysts, forging desired electrocatalysts with high catalytic activity, low cost, and sustainability is still challenging. In this work, nitrogen doped porous carbon materials named p-ZIF-800 and p-ZIF-950 were obtained by pyrolysis of zeolitic imidazolate framework-8 (ZIF-8) nanocrystals at 800 °C and 950 °C, respectively. Then, they were employed as a catalytic layer in the gas diffusion electrodes p-ZIF-n/Ni/CB (n = 800 °C or 950 °C, CB = acetylene black). The production rates of H2O2 are up to 1.18 mg h−1 cm−2 and 1.25 mg h−1 cm−2 for p-ZIF-800/Ni/CB and p-ZIF-950/Ni/CB, respectively. Noticeably, although p-ZIF-800 had a lower degree of graphitization the difference in catalytic activity between p-ZIF-800 and p-ZIF-950 is negligible. This can be construed as a higher total nitrogen and richer mesoporous structure in p-ZIF-800 than in p-ZIF-950. Under optimized conditions of an electrode spacing of 3 cm, a pH value of 6.5, and a current density of 7.5 mA cm−2, the H2O2 production rate of p-ZIF-800/Ni/CB in the “floating-cathode” cell is up to as high as 2.09 mg h−1 cm−2, which is about 3.3 times higher than that of the cell with the “submerged-cathode” under aeration and stirring. Also, the p-ZIF-800/Ni/CB cathode demonstrates remarkable stability, it maintains its structure without losing catalytic activity after 5 catalytic cycle experiments. These results indicate that the state-of-the-art pyrolysis-based nitrogen-doped porous carbon materials exhibit a high potential for the advanced electrocatalyst of H2O2 electrogeneration.

Effects of polyoxymethylene dimethyl ethers (PODEn) on soot characteristics in isooctane inverse diffusion flames

Polyoxymethylene dimethyl ethers (PODEn, n = 1–3) such as dimethoxymethane (DMM) and PODE3 are considered highly promising alternative fuels due to their lack of C–C bonds and significant oxygen contents. Particularly, PODE3-blends with diesel have been proven to substantially reduce soot emissions and fuel consumption rates under optimized engine conditions, although the impact on soot nanostructure properties remains unclear. This study explored the effects of DMM and PODE3 on soot characteristics in isooctane (i-octane) inverse diffusion flames, focusing on soot morphology, soot nanostructure, soot nanocrystallite, and soot spectral features. To compare soot particles behavior, DMM and PODE3 blended as the isooctane substitute (by 20% and 40% volumetric fractions) were examined with various diagnostic techniques, including high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).The results showed that DMM and PODE3 contributed to a reduction in sooting tendency from i-octane flames, whereas the average soot mass decreased significantly as the PODE3 ratio increased, consistent with a higher oxygen concentration. Therefore, 20% PODE3/i-octane exhibited growing disorganized arrangements of soot particles with shorter fringes, smaller crystallite sizes, and a relatively lower degree of graphitization than 20% and 40% DMM additions. However, XPS analysis indicated that soot produced from PODE3/i-octane mixtures had less oxygen atoms because PODE3 has multiple –CH2O- chain groups that can convert oxygen into carbon monoxide with little soot production. Moreover, HRTEM, XRD, and Raman spectra analyses of 40% PODE3-doped flames confirmed an exceptional correlation with turbostratic soot structure, as manifested by the shortest fringe length, longest fringe tortuosity, more amorphous soot with the smallest crystallite dimensions, and least degree of graphitization.

Graphitizable Pitch from Microwave Plasma Pyrolysis of Natural Gas.

An innovative approach of microwave plasma was utilized to convert natural gas into tar, from which a highly graphitizable pitch was derived using fractional distillation. The natural gas-derived pitch (NGDP) was thoroughly characterized, and the graphitizability of the carbonized NGDP was assessed using polarized light microscopy. The NGDP and, for comparison, needle coke, petroleum coke, and shot coke were subjected to graphitization heat treatment (GR) at 2500 °C. Results indicate that the graphitizability of the NGDP exceeds those of all industrial standard cokes. The GR-NGDP showed the highest degree of graphitization and crystallite size among all samples.

Fluorescent Carbonized Polymer Dots Derived from o-phenylenediamine and its Photonic Application.

Optimizing the optoelectronic characteristics of low-dimensional carbon dots (CDs) through surface modifications and doping has proven instrumental in tailoring them for diverse applications. This study explores a facile and economical hydrothermal synthesis method for generating Carbonized Polymer Dots using o-phenylenediamine at different temperatures. The resulting materials exhibit structural and morphological variations linked to the synthesis temperature. A transition from carbon dots (CDs) embedded in reduced graphene oxide (rGO)-like sheet structures at low temperatures to the core-shell structure at the highest temperature is observed in HR-TEM, implying the formation of CPDs. X-ray photoelectron spectroscopy (XPS) corroborates these findings, showing an augmented degree of graphitization in alignment with HR-TEM results. The photoluminescence spectra of CPDs synthesized at the lowest temperature exhibit multiple emission peaks, resulting in a yellowish-orange color. Utilizing these CPDs to fabricate light-emitting diodes (LEDs) produces a vivid bright-green emission with CIE coordinates (0.378, 0.522). Moreover, the CPDs demonstrate solvatochromism across diverse solvents of varying polarity, covering the entire visible spectrum. This intriguing solvatochromic effect positions the CPDs as promising materials for polarity probing applications.

Valorising lignocellulosic biomass to high-performance electrocatalysts via anaerobic digestion pretreatment

AbstractAnaerobic digestion (AD) was initially evaluated as a potential preprocessing method for preparing biomass-based carbon electrocatalysts in this study. The AD pretreatment succeeded in the structural depolymerization and nitrogen enrichment of Hybrid Pennisetum, which provided favorable conditions to achieve efficient and homogeneous nitrogen introduction due to microorganism community enrichment and provided a porous structure by degradation of the biodegradable components. The resulted biochar exhibited improved physiochemical properties including higher specific surface areas, nitrogen content and graphitization degree than that obtained from pyrolyzing raw biomass. These improvements were positively correlated with the AD time and showed to have enhanced the performance in oxygen reduction reaction and practical microbial fuel cell applications. Amongst the investigated samples, the obtained biochar pretreated by AD for 15 days exhibited the most excellent performance with an onset potential of 0.17 V (VS. saturated calomel electrode) and the maximal power density of 543.2 mW cm−2 assembled in microbial fuel cells. This study suggested applying AD as a new biological pretreatment in the preparation of biomass-based electrocatalysts, and provided a unique pathway for fabricating high-performance biochar-based catalysts by structure optimization and N-containing active sites construction via gentle biological method, thereby providing a cost-effective method to fabricate metal-free catalysts for oxygen reduction reaction. Graphical Abstract

Pushing the Efficiency of the Selective and Base‐Free Air‐Oxidation of HMF by Varying the Properties of Carbon‐Based Supports

AbstractThe selective oxidation of 5‐(Hydroxymethyl)furfural (HMF) to 2,5‐Furandicarboxylic acid (FDCA) is highly attractive for the production of renewable monomers as substitute for fossil‐based monomers. To achieve a sustainable synthesis, we report on advances for a base‐free approach, reducing waste from the process, using air as oxidant and heterogeneous catalysts. Various Carbon‐based supports, which can be bio‐sourced and cost‐efficient, for Pt particles were investigated as they allow for an easy reuse and at the end‐of‐life Pt can be recycled to enable a closed cycle. Commercially available supports with varying properties, which might replace the base, were studied with Pt particles of similar size and loading. Significant differences in the catalytic activity were observed, which were correlated with the O‐functionalities and graphitization degree of the supports derived from Raman spectroscopy, temperature‐programmed desorption, and X‐ray photoelectron spectroscopy. An activated carbon (Norit ROX) rich in quinone/pyrone‐type groups and a carbon black‐based catalyst with graphene‐layers pushed the efficiency with enhanced FDCA‐yields enabling the complete substitution of the homogeneous base. This allows to circumvent the base in this process which together with high selectivity, air as oxidant, a reusable catalyst, and the use of bio‐based feedstock contributes to the sustainability of the production of renewable monomers.

Comparison of torrefaction and hydrothermal carbonization of high-moisture microalgal feedstock

A comprehensive comparison is conducted to explore the conversion performance of torrefaction and hydrothermal carbonization of high-moisture microalga for producing solid biofuel with low expense and environmental impact. The results suggest that when their solid yields are close, the hydrochar has higher HHV (higher heating value) (21.10–25.39 MJ kg−1) and energy yield (72.48–92.29%) than the biochar. The graphitization degrees of the biochar and hydrochar are 1.298–3.107 and 2.193–3.049, respectively. Considering fuel grade, the biochar is in biomass and peat zones, but the hydrochar is only in the biomass zone. The biochar's elemental valence transformation and graphitization degree are better than hydrochar's. The pyrolysis and combustion characteristics of the hydrochar are better than those of the biochar when considering the thermodegradation data, leading to a lower expense and environmental impact. The results are conducive to efficiently figuring out a solution with a comparative advantage for microalgal thermochemical conversion. The hydrothermal carbonization conditions at 160 °C for 2 h are the best operation for microalgal solid biofuel production.

Direct carbonization of cellulose toward hydroxyl-rich porous carbons for pseudocapacitive energy storage

Designing carbon materials with specific oxygen-containing functional groups is very attractive for the precise decoration of carbon electrode materials and the basic understanding of specific charge storage mechanisms, which contributes to the further development of high-performance carbon materials for energy storage and conversion applications. In this contribution, a hydroxyl-rich micropore-dominated porous carbon material was obtained by direct carbonization of cellulose. The content of oxygen atoms in hydroxyl form in the obtained carbon is nearly 6 at.%. With the pyrolysis temperature changed, the macroscopic morphology, the specific surface area, surface functional groups, and graphitization degree of the carbon materials were changed strongly. Besides, the carbon material obtained with a carbonization temperature of 900 °C (C9) showed enhanced specific capacitance in sulfuric acid, sodium hydroxide, and sodium sulfate aqueous electrolytes, which mainly originates from the contribution of pseudocapacitance. The pseudocapacitance mainly depends on the presence of surface hydroxyl functional groups. Besides, the pseudocapacitance value of C9 material in neutral electrolytes (151.34 F g−1) is about twice that in acidic (75.9 F g−1) and alkaline (75.78 F g−1) electrolytes.

A honeycomb-inspired carboxymethyl chitosan-covalently link NH2-black phosphorene biobased cellulose green nanocomposites with tremendously enhancement fire safety and thermal conductivity

Biobased carboxymethyl chitosan-modified black phosphorene (BP-CMC) was prepared through an amidation reaction between amino group functionalized black phosphorene (NH2-BP) and CMC. Density functional theory (DTF) express that the adsorption energy between urea and phosphene is −6.28 eV, indicating a strong interaction. The resulting BP-CMC was further applied to reinforce the mechanical, flame-retardant and thermal conductivity performance of honeycomb cellulose nanofiber (CNF) film via vacuum filtration. Cone calorimetry test (CCT) result exhibits that the introduction of 30 wt% BP-CMC significantly promoted the fire safety of CNF. For instance, a 98.41% reduction in smoke production rate (SPR), 92.00 % decline in CO release and a 61.31% decrease in heat release rate (HRR) were observed compared to neat CNF. Furthermore, Thermogravimetric infrared (TG-IR) indicates a significant decrease in the release of flammable gases. Raman spectra verify that the incorporation of 30 wt% BP-CMC improves the graphitization degree of residual chars, thus limiting the transfer of heat and oxygen. The improvement in fire safety is attributed to the formation of an intumescent flame-retardant system, which is rich in carbon source (CMC), acid source (BP) and gas source (amino). Simultaneously, the introduction of 30 wt% BP-CMC into CNF leads to considerable enhancement in thermal conductivity (up to 17.49 %), thermal diffusion (utmost to 43.45 %) and heat capacity (increased by 19.23 %). Moreover, the 30 wt % addition of BP-CMC into CNF possesses excellent mechanical properties with the improvement of toughness (increased by 143.50 %) and tensile strength (increased by 140.90 %). This strategy not only provides a new strategy for functionalizing BP but also upgrades the application potential of BP nanosheets in the fire safety of polymer composite films.

Effects on of Blended Biodiesel and Heavy Oil on Engine Combustion and Black Carbon Emissions of a Low-Speed Two-Stroke Engine

Abstract The effects of heavy fuel oil and biodiesel blends on engine combustion and emissions were studied in a marine two-stroke diesel engine. The engine was operated under propeller conditions using five different fuels with biodiesel blends of 10% (B10), 30% (B30), 50% (B50), and sulphur contents of 0.467% low sulphur fuel oil (LSFO) and 2.9% high sulphur fuel oil (HSFO). Tests have shown that using a biodiesel blend increases the engine fuel consumption due to its lower calorific value. Heavy fuel oil has a high Polycyclic aromatic hydrocarbons (PAH) content, which leads to higher exhaust temperatures due to severe afterburning in the engine. A comparison of engine soot emissions under different fuel conditions was carried out, and it was found that the oxygen content in biodiesel promoted the oxidation of soot particles during the combustion process, which reduced the soot emissions of biodiesel. Compared to HSFO, B10, B30, B50 and LSFO, the soot emission concentrations were reduced by 50.2%, 56.4%, 61% and 37.4%, respectively. In our experiments, the soot particles in the engine exhaust were sampled with a thermal float probe. Using Raman spectroscopy analysis, it was found that as the biodiesel ratio increased, the degree of carbonisation of the soot particles in the exhaust became less than that in the oxygenation process, resulting in a decrease in the degree of graphitisation.

Microstructure and nanomechanical characterization of tectonic coal based on SEM, AFM, XRD and DSI

The microstructure and mechanical properties of tectonic coal are the key to the efficient development of tectonic coal reservoir coalbed methane. The microstructure and mechanical properties of coal samples were studied and analyzed by SEM-EDS-PCAS, AFM, XRD and DSI experiments. The results show that the fractal dimension (D) of WJB, QL, and FR coal samples of pores is 2.356, 1.946, and 1.721 respectively. The fractal dimension (Ds) of PSD is 2.26, 2.25, and 2.23 respectively. The porosity (φ) values are 2.64 %, 2.76 %, and 3.98 % respectively. and porosity (Ф) values are 2.55 %, 2.67 %, and 3.16 % respectively. With the enhancement of tectonic action, the number of pores in coal increases, the fractal dimension of pores increases, and the surface morphology and pore structure become more complex. The depth and residual depth of nanoindentation increase with the increase of load. The hardness (Hx), fracture toughness (Kc) and creep stress exponent (n) of coal are negatively correlated with the aromatic interlayer spacing d002, and positively correlated with the degree of graphitization (Gd), while the elastic modulus (Ex) has no obvious relationship with it. The linear correlation between Hx and Ex is less than that between Kc and Ex. The relationship between Ex and Hx of coal samples and different peak loads is not obvious, but the Kc and n of coal samples increase with the increase of peak load. Under a certain load, the plastic energy, fracture energy and elastic energy increase with the increase of load. The tectonic coal with high metamorphic degree is prone to elastic deformation, while the coal with low coal quality is prone to plastic deformation. The research results can provide theoretical guidance for coalbed methane mining in tectonic coal reservoirs.