High Degree Of Graphitization Research Articles

Catalytic combustion synthesis of CNTs/MgO composite powders and the influences on the thermal shock resistance of low-carbon Al2O3–C refractories

Using MgC2O4, Mg powders as raw materials and Ni(NO3)2∙6H2O as a catalyst, CNTs/MgO composite powders were prepared by a catalytic combustion synthesis method. The CNTs/MgO composite powders were characterized by XRD, Raman spectroscopy, FESEM/EDS and HRTEM. The effects of catalyst content on the degree of graphitization and aspect ratio of the CNTs in composite powders were investigated. Moreover, the thermal shock resistance of low-carbon Al2O3–C refractories after adding the composite powder was investigated. The results indicated that the CNTs prepared with 1 wt% Ni(NO3)2∙6H2O addition had a higher degree of graphitization and aspect ratio. In particular, the aspect ratio could reach approximately 200. The growth mechanism of hollow bamboo-like CNTs in the composite powders was proven to be a V-L-S mechanism. The thermal shock resistance of Al2O3–C samples could be improved significantly after adding CNTs/MgO composite powders. In particular, compared with CM0, the residual strength ratio of Al2O3–C samples with added 2.5 wt% composite powders could be increased 63.9%.

A green and efficient method for preparing graphene using CO2@Mg in-situ reaction and its application in high-performance lithium-ion batteries

It has been a long-standing challenge to prepare graphene with green and efficient synthesis technique. In this work, we report a simple and cost-effective approach to fabricate few-layer graphene through the reaction between Mg melt and CO2 gas at conventional melting conditions. The results indicated that the as-fabricated graphene has high graphitization degree and small thickness. In addition, the reaction temperature has great impact on the quality of the as-fabricated graphene, and they possess relatively the best quality when prepared at 750 ℃. When serving as lithium storage materials, the as-fabricated graphene exhibits excellent rate capability and cycling performance with a reversible capacity of 130 m Ah g−1 after 1000 cycles at a current density of 1.0 A g−1. The porous graphene produced by removing nano-sized MgO particles contains numerous defects and CO groups, which could provide more adsorption sites for lithium storage. This study opens up an avenue to synthesize graphene from greenhouse gases. The as-fabricated graphene possesses great potential employed as lithium storage materials. Data availabilityThe raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

On the Tribological Properties of RGO–MoS2 Composites Surface Modified by Oleic Acid

To study the effect of oleic acid surface modified RGO/MoS2 composite lubricating additives on the friction and wear properties of 10# White Oil (10# WO). The influences of different concentrations of reduction graphene oxide/molybdenum disulfide (RGO–MoS2) and oleic acid surface modified reduction graphene oxide/molybdenum disulfide (OA-RGO–MoS2) on the lubricating properties in 10# WO was investigated using a four-ball long-term friction and wear tester. The microscopic morphology, lattice structure, composition and element valence of the prepared material were characterized by scanning electron microscope, Raman spectroscopy, Infrared Spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, element analyzer and other instruments. The diameter, structure, morphology, composition and element valence state of the wear scar were obtained by multifunctional universal tool microscope, scanning electron microscope and X-ray photoelectron spectroscopy. In the RGO–MoS2 white oil system, when 0.4 wt% RGO–MoS2 is added, the anti-friction effect is the best, and the average friction coefficient (AFC) reduced by 21.8%. When 0.2 wt% RGO–MoS2 is added, the anti-wear effect is the optimal, and the average wear scar diameter (AWSD) decreased by 12.4%. In the OA-RGO–MoS2 white oil system, when 0.2 wt% OA-RGO–MoS2 is added, the anti-friction and anti-wear effects are the best, and the AFC reduced by 33.3%, and AWSD reduced by 14.1%. Compared with RGO–MoS2, OA-RGO–MoS2 has a higher degree of graphitization, larger interlayer spacing, lower degree of layered accumulation, higher MoS2 load, and weaker thermal stability. Both lubricating additives have good anti-friction and anti-wear effects at low concentrations, and the anti-friction and anti-wear effects are more prominent after being modified by oleic acid. Analysis of friction mechanism shows that a lubricating protective film containing iron, oxygen, molybdenum, carbon, and sulfur is formed through adsorption or tribochemical reaction during the friction process, which improves the lubrication state and plays a role in reducing friction and anti-wear.

Bio-Based Trivalent Phytate: A Novel Strategy for Enhancing Fire Performance of Rigid Polyurethane Foam Composites

Biomass phytic acid has potential flame retardant value as the main form of phosphorus in plant seeds. In this study, phytate-based flame retardants aluminum phytate (PA-Al) and iron phytate (PA-Fe) were synthesized and characterized. Subsequently, they were introduced into rigid polyurethane foam (RPUF) as flame retardants by one-step water-blown method. The results indicated that RPUF/PA-Fe30 exhibited the highest char residue of 22.1 wt%, significantly higher than 12.4 wt% of RPUF. Cone calorimetry analysis showed that the total heat release (THR) of RPUF/PA-Al30 decreased by 17.0% and total smoke release (TSR) decreased by 22.0% compared with pure RPUF, which were the lowest, demonstrating a low fire risk and good smoke suppression. Thermogravimetric analysis-Fourier transform infrared spectrometer (TG-FTIR) implied the release intensity of flammable gases (hydrocarbons, esters) and toxic gases (isocyanate, CO, aromatic compounds, HCN) of composites was significantly reduced after the addition of PA-Fe. The analysis of char residue indicated that the RPUF composites formed a dense char layer with a high degree of graphitization after the addition of PA-Al/PA-Fe, endowing RPUF composites with excellent mass & heat transmission inhibition effect and fire resistance in the combustion process.

One Step Fabrication of Aligned Carbon Nanotube Sheet via FC‐CVD Technique

The rising need for lightweight and strong mechanical structures has contributed significantly towards the development of CNT macrostructures; however, the interplay of parameters and their discontinuous synthesis have obstructed their delivery to commercial level. Herein, floating catalyst chemical vapor deposition technique (FC‐CVD) has been employed for the fabrication of 90 cm long CNT sheet via continuous production of CNT aerogel. High degree of graphitization, thermal stability and purity have been indicated by Raman spectroscopy (IG/ID = 10.03), thermogravimetric analysis, and SEM studies. Continuous winding of CNT aerogel has increased the alignment into the sample which resulted into high electrical conductivity value of 21400 S/m. Furthermore, the alignment has been quantified by calculating optical anisotropic ratio via polarized Raman technique and conductivity anisotropic ratio κ‖ /κ⊥ which were calculated to be 4.63 and 3.4, respectively, and show reasonable agreement. These findings indicate that a well correlation of synthesis parameters results in highly aligned CNT sheet structure in a single step.

Constructing two-dimensional lamellar monometallic carbon nanocomposites by sodium chloride hard template for lightweight microwave scattering and absorption

Low-dimensional carbon matrix nanocomposites are promising for lightweight and efficient electromagnetic wave absorption considering their large specific surface area and the multi-interface interaction. However, it remains a challenge to maintain the uniform dispersion of magnetic nanoparticles, which plays a vital role in regulating both dielectric and magnetic loss abilities. In this paper, by sodium chloride (NaCl) hard template, two-dimensional (2D) lamellar Co/C (NCC) and Fe/C (NFC) nanocomposites with well dispersed magnetic nanocomposites are prepared consecutively. An in-depth study of the construction of 2D lamellar structure on the electromagnetic dissipation and impedance matching has been carried out. The result shows that the 2D lamellar NCC and NFC prepared by NaCl hard template own the higher degree of graphitization and dielectric loss than those three-dimensional (3D) bulk composites without the addition of NaCl. Furthermore, the series of 2D lamellar nanocomposites exhibit excellent microwave absorption properties. The minimum reflection loss (RL) value of NCC and NFC can reach −52.2 and −46.7 dB, respectively. Particularly, accompanied by the thin thickness of only 2.0 mm, the effective absorption bandwidth (EAB, RL ≤ −10 dB) of NFC can reach 5.4 GHz (11.5–16.9 GHz). Furthermore, the smallest RCS value of only −8.098 dBm2 for NFC under vertical incidence can be obtained for excellent electromagnetic wave scattering and absorption.

A green flexible and wearable biosensor based on carbon nanofibers for sensitive detection of uric acid in artificial urine.

Wearable biosensors have great advantages and application potential in the field of real-time detection. However, it is still a challenge to construct an electrically conductive and mechanically flexible sensing interface as the working electrode in an electrochemical sensor. In this work, a green and efficient strategy is proposed to optimize the chemical structure of precursor materials for the preparation of a flexible biosensor. The introduction of phosphated lignin effectively increases the molecular interaction in the electrospinning system, improving the micro-morphology, flexibility, and thermal stability of biomass-based carbon nanofibers (CNFs). The rich active sites and high graphitization degree provide abundant access to uric acid molecules and accelerate electron transmission. Benefiting from these compelling features, the fabricated wearable biosensor can accurately and selectively detect uric acid in artificial urine. This work offers a promising approach for the fabrication of wearable biosensors and has a broad application prospect in personalized diagnostic and miniaturized power device fields.

Carbon foams derived from emulsion-templated porous polymeric composites for electromagnetic interference shielding

A series of carbon foams (CFs) were fabricated from the emulsion-templated porous polymeric composites, following with hypercrosslinking and carbonization. The polymeric composites were constituted by syndiotactic polystyrene (sPS), carbon nanotubes (CNTs) and magnetic Ni@CNTs. The addition of nanofillers was beneficial to the carbonization, resulting in less shrinkage, higher graphitization degree, lager emulsion-templated voids and nanofibrous pore walls. The composite CFs showed higher robustness (up to 19.7 MPa cm3 g−1), more hydrophobic surface (water contact angle up to 148°) and larger specific surface area (up to 144 m2 g−1). In particular, the electrical conductivity (up to 97 S m−1) and electromagnetic interference (EMI) shielding effectiveness (EI) (up to 78.0 dB) were greatly enhanced when the CNTs and Ni@CNTs were simultaneously employed. The conduction losses caused by conductive network of residual carbon network of carbonized sPS and the nanofillers, polarization losses from interfacial polarization between carbonized sPS and nanofillers, dielectric loss within mesopores and magnetic loss from Ni@CNTs contributed to the enhanced shielding effectiveness. The carbon foams can be prefect succedanea of the commercial EMI shielding materials in the aerospace and wireless telecommunication fields.

Preparation of Mn2+ Doped Piperazine Phosphate as a Char-Forming Agent for Improving the Fire Safety of Polypropylene/Ammonium Polyphosphate Composites.

A piperazine phosphate doped with Mn2+ (HP-Mn), as a new char-forming agent for intumescent flame retardant systems (IFR), was designed and synthesized using 1-hydroxy ethylidene-1,1-diphosphonic acid, piperazine, and manganese acetate tetrahydrate as raw materials. The effect of HP-Mn and ammonium polyphosphate (APP) on the fire safety and thermal stability of polypropylene (PP) was investigated. The results showed that the combined incorporation of 25 wt.% APP/HP-Mn at a ratio of 1:1 endowed the flame retardant PP (PP6) composite with the limiting oxygen index (LOI) of 30.7% and UL-94 V-0 rating. In comparison with the pure PP, the peak heat release rate (PHRR), the total heat release (THR), and the smoke production rate (PSPR) of the PP6 were reduced by 74%, 30%, and 70%, respectively. SEM and Raman analysis of the char residues demonstrated that the Mn2+ displayed a catalytic cross-linking charring ability to form a continuous and compact carbon layer with a high degree of graphitization, which can effectively improve the flame retardancy of PP/APP composites. A possible flame-retardant mechanism was proposed to reveal the synergistic effect between APP and HP-Mn.

Formation of coal-based carbon nanotubes by Fe-K catalyst

Carbon nanotubes were successfully synthesized by Fe-K catalytic pyrolysis of coal. The co-pyrolysis of coal and ferrocene can only form fewer carbon nanotubes due to the few available carbon sources. Potassium carbonate can significantly eliminate the defects in the plane between the basic structural units of coal and promote the formation of carbon nanotubes, but its catalytic graphitization effect was limited when potassium carbonate was dry mixed with coal. In addition, the results show that Fe and K had a synergistic effect. Fe atoms and C atoms formed Fe-C solid solution during pyrolysis, K-based catalyst etched amorphous carbon atoms of coal, and finally Fe-K co-catalyzed the growth of a large number of carbon nanotubes with a higher degree of graphitization. The catalytic pyrolysis process had great impact on the aromatic structure and oxygen-containing functional group structure, but slight impact on the aliphatic structure of coal. The molten state of the catalyst during pyrolysis and its affinity for amorphous carbon was higher than that of graphitic carbon, leading to the migration of the catalyst and the change of crystal plane, which may be the reason for the formation of "carbon nanofiber-tube".

Pyrolysis of coal pitch-infused melamine foam to construct N-doped carbon anodes for high-performance sodium-ion battery

• Carbonization of pitch-infused melamine foam would reduce graphitization degree. • Fe(NO 3 ) 3 was used to adjust carbon porosity for high performance Na-ion battery. • The carbon anode can gain a capacity of 111 mA h g −1 after 1000cycles at 8.0 C. Coal pitch is a promising precursor to construct carbonaceous anode for lithium-ion battery and sodium-ion battery because of its rich natural resource and low development cost. Nonetheless, quite unsatisfactory Na-storage performance had been gained using the pitch-based carbon anodes obtained by direct pyrolysis of pitch where the high graphitization degree nature of the carbon would result in a small interlayer distance. In this study, low-graphitized pitch-based carbon with N-containing functional groups for sodium ion batteries was successfully constructed by ferric nitrate-assist carbonization of coal pitch-infused melamine foam. Melamine foam skeleton can effectively reduce the graphitization of the final carbon material while the ferric nitrate can adjust the pore structure of the carbon framework, so that the obtained N-doped carbon has a larger layer spacing distance which makes it easier to insert and extract the sodium ions into and out the carbon structure during the discharge–charge process. When evaluated as sodium ion batteries anodes, the obtained carbon material presents a high reversible storage capacity (111 mA h g −1 ) and stable cyclability (1000 cycles at 8.0C rate, nearly 3.0 A g −1 ).

Activation of peroxydisulfate by ball-milled α-FeOOH/biochar composite for phenol removal: Component contribution and internal mechanisms

Persulfate-based advanced oxidation process is considered as a promising technology for the degradation of phenol, where efficient, cost effective, and green methods with high peroxydisulfate (PS) activation capacity is of increasing demand. In this work, an in-situ liquid phase precipitation combined with ball milling method was applied for the synthesized of α-FeOOH/biochar, as be the PS activator for phenol degradation. Results showed that the ball-milled α-FeOOH and red pine wood biochar prepared at 700 °C (BM-α-FeOOH/PBC700) exhibited the highest catalytic property with PS for phenol oxidation (a phenol removal rate of 100%), compared with the BM-α-FeOOH (16.0%) and BMPBC700 (66.3%). The presence of intermediate products such as hydroquinone and catechol, and total organic carbon (TOC) removal rate (88.9%) proved the oxidation of phenol in the BM-α-FeOOH/PBC700+PS system. The characterization results showed that the functional groups (e.g., CO, C–O, Fe–O, and Si–O), the dissolved organic matter (DOM) in biochar, the loading of Fe element, and higher degree of graphitization and defect structures, contributed to the activation of PS to form free radicals (i.e., SO4·−, ·OH, ·O2−, and hVB+) for phenol oxidation, of which, SO4·− and ·OH account for 72.1% of the phenol removal rate. The specific contribution to the PS activation for phenol oxidation by each part of the materials was calculated based on the “whole to part” experiment. The contribution of DOM, acid-soluble substance, and carbon matrix and basal part in BM-α-FeOOH/PBC700 were 6.0%, 40.9%, and 53.1%, respectively. The reusability experiments of BM-α-FeOOH/PBC700 demonstrated that the composite was relatively stable after four cycles of reuse. Among three co-existing anions (NO3−, Cl−, and HCO3−), HCO3− played the most significant inhibition effects on phenol removal through reducing the phenol removal rate from 89.6% to 77.9%. This work provides guidance for the design of high active and stable carbon materials that activate PS to remove phenol.

Impact of multi-injection strategies on morphology, nanostructure and oxidation reactivity of diesel soot particles

The objective of the present study was to investigate and optimize the multi-injection parameters that were able to match the diesel particulate filter (DPF) after-treatment system for reduction of particulate matter (PM) generated from diesel engines. Three representative multi-injection strategies, including main plus post-injection (designated as M+Po), one pilot injection plus M+Po (Pi1+M+Po) and two pilot injections plus M+Po (Pi2+Pi1+M+Po), were selected to generate soot particles in a diesel engine. The morphology and nanostructure of soot particles, including primary particle size, fringe length, thermal stability of organic carbon (OC) and graphitization degree, were analyzed by transmission electron microscopy (TEM) and Raman spectroscopy. The OC content and oxidation reactivity were quantified by thermalgravimetric analyzer (TGA). Results revealed that pilot injection led to the formation of soot particle with smaller primary particle size, more ordered nanostructure, and higher graphitization degree, ascribing to the better air-fuel mixing, higher cylinder temperature, as well as longer residence time. On the contrary, post injection (e.g., M+Po) resulted in soot particles with more OC exhibiting larger size and more ambiguous boundary. Overall, the soot particles with more disordered nanostructure and more OC content showed better oxidation reactivity. Interestingly, the soot particle morphology and nanostructure were observed to be varying under TEM electron irradiation, which might be due to the OC heating dissolution.

Molecular Engineering toward High-Crystallinity Yet High-Surface-Area Porous Carbon Nanosheets for Enhanced Electrocatalytic Oxygen Reduction.

Carbon‐based nanomaterials have been regarded as promising non‐noble metal catalysts for renewable energy conversion system (e.g., fuel cells and metal–air batteries). In general, graphitic skeleton and porous structure are both critical for the performances of carbon‐based catalysts. However, the pursuit of high surface area while maintaining high graphitization degree remains an arduous challenge because of the trade‐off relationship between these two key characteristics. Herein, a simple yet efficient approach is demonstrated to fabricate a class of 2D N‐doped graphitized porous carbon nanosheets (GPCNSs) featuring both high crystallinity and high specific surface area by utilizing amine aromatic organoalkoxysilane as an all‐in‐one precursor and FeCl3·6H2O as an active salt template. The highly porous structure of the as‐obtained GPCNSs is mainly attributed to the alkoxysilane‐derived SiO x nanodomains that function as micro/mesopore templates; meanwhile, the highly crystalline graphitic skeleton is synergistically contributed by the aromatic nucleus of the precursor and FeCl3·6H2O. The unusual integration of graphitic skeleton with porous structure endows GPCNSs with superior catalytic activity and long‐term stability when used as electrocatalysts for oxygen reduction reaction and Zn–air batteries. These findings will shed new light on the facile fabrication of highly porous carbon materials with desired graphitic structure for numerous applications.

Co-Existence of Iron Oxide Nanoparticles and Manganese Oxide Nanorods as Decoration of Hollow Carbon Spheres for Boosting Electrochemical Performance of Li-Ion Battery.

Here, we report that mesoporous hollow carbon spheres (HCS) can be simultaneously functionalized: (i) endohedrally by iron oxide nanoparticle and (ii) egzohedrally by manganese oxide nanorods (FexOy/MnO2/HCS). Detailed analysis reveals a high degree of graphitization of HCS structures. The mesoporous nature of carbon is further confirmed by N2 sorption/desorption and transmission electron microscopy (TEM) studies. The fabricated molecular heterostructure was tested as the anode material of a lithium-ion battery (LIB). For both metal oxides under study, their mixture stored in HCS yielded a significant increase in electrochemical performance. Its electrochemical response was compared to the HCS decorated with a single component of the respective metal oxide applied as a LIB electrode. The discharge capacity of FexOy/MnO2/HCS is 1091 mAhg−1 at 5 Ag–1, and the corresponding coulombic efficiency (CE) is as high as 98%. Therefore, the addition of MnO2 in the form of nanorods allows for boosting the nanocomposite electrochemical performance with respect to the spherical nanoparticles due to better reversible capacity and cycling performance. Thus, the structure has great potential application in the LIB field.

High potential of microalgal sludge biochar for a flexible all-solid-state microsupercapacitor

Biorefinery is drawing attention as an environmentally friendly technology due to increasing interest in sustainable development. Microalgal biomass is a promising feedstock for biorefinery because of its fast growth rate and low requirement for land. It is essential to treat the remained microalgal sludge (90 wt% of total microalgal biomass) after biorefinery to construct a true zero-waste microalgal biorefinery. However, few studies have reported methods of utilizing microalgal sludge, a by-product of biorefinery. In this study, the microalgal sludge was converted to biochar through pyrolysis. Physicochemical and electrochemical properties of microalgal sludge biochar (MASB) were then analyzed. A flexible all-solid-state microsupercapacitor was fabricated by manufacturing a composite with a conductive polymer. Element components of MASB presented the inherent presence of doping nitrogen compared to those of lignocellulosic biochar such as Miscanthus biochar (MB) and rice straw biochar (RB). The pyrolysis temperature of MASB was optimized to obtain a high degree of graphitization and 900 °C (range, 600 °C–1000 °C) was found to be an appropriate pyrolysis temperature. Nitrogen doping and graphitic structure of MASB-900 (MASB produced at 900 °C) affected the capacitive performance of the fabricated microsupercapacitor. The capacitance was 262.8 F g−1 at a current density of 0.1 A g−1 and the energy density was 36.5 Wh kg−1 at a power density of 224.4 W kg−1. These results were superior to those of other previously studied biochar-based supercapacitors. The proposed microsupercapacitor demonstrates the possibility of zero-waste biorefinery and a high value-added application of microalgal sludge.

Self-assembled supramolecule for synthesizing highly thermally conductive Cellulose/Carbon nitride nanocomposites with improved flame retardancy

The fabrication of polymer composites with excellent thermal conductivity typically involves complex matrix or fillers modifications. This study proposed a simple technique based on precursor selection for obtaining highly thermally conductive cellulose nanofiber (CNF)/supramolecule-synthesized carbon nitride (SCN) composites. Fourier-transform infrared tests demonstrated the construction of hydrogen bonds between CNF and SCN; a highly ordered structure and relatively compact in-plane stacking were confirmed via scanning electron microscopy and X-ray diffraction characterizations. Consequently, the resultant CNF/SCN composites exhibited remarkable in-plane thermal conductivity of 11.83 ± 0.41 W m−1 K−1 at 30 wt% SCN content, which was attributed to the significantly reduced interfacial phonon scattering. It also showed evident improvements in electrical insulation and flame retardancy compared with the pure CNF film, where the volume resistivity, peak heat release rate, and total heat release were remarkably enhanced by 1242% and reduced by 59.9% and 15.8%, respectively. Further analysis of char residuals revealed a relatively dense surface, high concentration of carbon materials, and a high degree of graphitization, indicating that the char residual functioned as a robust physical barrier to effectively inhibit combustion. This study provides a facile approach to achieving high-efficiency improvements in thermal conductivity and flame retardancy, and simultaneously facilitating broader applications of carbon nitride in thermal management.

Microwave-Assisted Coal-Derived Few-Layer Graphene as an Anode Material for Lithium-Ion Batteries.

A few-layer graphene (FLG) composite material was synthesized using a rich reservoir and low-cost coal under the microwave-assisted catalytic graphitization process. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to evaluate the properties of the FLG sample. A well-developed microstructure and higher graphitization degree were achieved under microwave heating at 1300 °C using the S5% dual (Fe-Ni) catalyst for 20 min. In addition, the synthesized FLG sample encompassed the Raman spectrum 2D band at 2700 cm−1, which showed the existence of a few-layer graphene structure. The high-resolution TEM (transmission electron microscopy) image investigation of the S5% Fe-Ni sample confirmed that the fabricated FLG material consisted of two to seven graphitic layers, promoting the fast lithium-ion diffusion into the inner surface. The S5% Fe-Ni composite material delivered a high reversible capacity of 287.91 mAhg−1 at 0.1 C with a higher Coulombic efficiency of 99.9%. In contrast, the single catalyst of S10% Fe contained a reversible capacity of 260.13 mAhg−1 at 0.1 C with 97.96% Coulombic efficiency. Furthermore, the dual catalyst-loaded FLG sample demonstrated a high capacity—up to 95% of the initial reversible capacity retention—after 100 cycles. This study revealed the potential feasibility of producing FLG materials from bituminous coal used in a broad range as anode materials for lithium-ion batteries (LIBs).

Turning waste into treasure: Carbonized walnut shell for solar-driven water evaporation

Waste walnut shell was selected and carbonized in different atmospheres to prepare excellent light-to-heat conversion materials for efficient solar-driven water evaporation. Carbonized walnut shell has a unique concave structure and rough surface, and its light absorption rate is higher than 88% in the full-spectrum range of 200–2500 nm. Moreover, under one-sun irradiation, carbonized walnut shell in a hydrogen/argon atmosphere mixture has better water evaporation performance (1.22 kg m-1h−1) and a higher η value (81.4%) than the carbonized walnut shell in an argon atmosphere. The main reason was due to its higher degree of graphitization and smaller surface pores, which are beneficial to light-to-heat conversion. Our work highlights the great potential of the waste biomass material (walnut shell) for realizing a highly effective solar energy-driven water evaporation.

Impact of dimethoxymethane-diesel fuel blends on the exhaust soot’s evolutionary behavior

Physicochemical properties of soot, such as graphitization degree and surface functional groups of dimethoxymethane (DMM)–diesel blends, have been conducted with Raman spectrum, FT-IR (Fourier transform infrared spectroscopy), and XPS (X-ray photoelectron spectroscopy), respectively. The experimental samples are collected in a four-cylinder, turbocharged engine at two different speeds (2200 and 1400 rpm), different loads (1.2 and 0.6 MPa), and different fuels (D100, DMM6.4, and DMM13). The results show that with the increase in loads, the difference of graphitization degree is gradually disappeared with different fuels, and a higher graphitization degree can be obtained. Moreover, the use of DMM reduces the proportion of unsaturated fuels, thereby leading to lower amounts of CH groups. In terms of oxygenated surface functional groups’ content of particulate matter (PM), the CO functional group accounts for 4%-12%, the COO functional group accounts for 1%-4%, and the CO functional group accounts for 3%-8%. Sensitivity analysis of the microscopic properties of soot found that the O/C ratio and sp3/sp2 ratio have the lowest effect on the apparent activation energy (Ea) of soot. And AD1/AG, AD2/AG, and AD4/AG significantly affect Ea.