Carbonaceous Precursor Research Articles

A comprehensive review on carbon nano-tube synthesis using chemical vapor deposition

The current article reviews on Chemical Vapor Deposition (CVD) methodology to synthesize Carbon Nanotubes (CNTs). CVD is considered the most popular CNT synthesis methodology, which facilitates the utilization of carbonaceous precursor sources, catalysts supplemented with optimized processing conditions. It is considered as comparatively simpler and much more economical synthesis methodology with higher control, purity, and reproducibility of CNT dimensions. The growth mechanisms and process flow are discussed. By adding green nanomaterials, we can make this process more efficient and environment friendly which can be used as a sustainable solution.

Hierarchically carbonized silk/ceramic composites for electro-thermal conversion

Two independent heating steps are currently involved for fabricating carbon fiber/ceramic composites, which include carbonization of fibers and ceramization of ceramic precursors with carbonized fibers together. In this work, silk fabric and silkworm cocoon were used as carbonaceous precursors for fabricating carbonized fiber/ceramic composites through one-step heating processing. This one-step manufacturing method achieved both the carbonization of silk fabric/silkworm cocoon and the formation of mullite simultaneously under nitrogen environment. The as-prepared composite based on three-layer silk fabric reached over 100 °C after 30 s when a voltage of 10 V was applied, and achieved a stabilized temperature of 239 °C after 540 s. The obtained composites also showed stable cyclic heating property, homogeneousheat distribution and electromagnetic shielding properties. These results implicate the great potential for the developed silk-ceramic composites and inspire the further design of silk-based materials for electro-thermal conversion.

Evidence for the presence of chondrule‐ and CAI‐derived material in an isotopically anomalous Antarctic micrometeorite

AbstractWe report the discovery of a unique, refractory phase‐bearing micrometeorite (WF1202A‐001) from the Sør Rondane Mountains, East Antarctica. A silicate‐rich cosmic spherule (~400 µm) displays a microporphyritic texture containing Ca‐Al‐rich inclusion (CAI)‐derived material (~5–10 area%), including high‐Mg forsterite (Fo98‐99) and enstatite (En98‐99, Wo0‐1). The micrometeorite also hosts a spherical inclusion (~209 µm), reminiscent of chondrules, displaying a barred olivine texture. Oxygen isotopic compositions of the micrometeorite groundmass (δ17O = –3.46‰, δ18O = 10.43‰, ∆17O = –1.96‰) are consistent with a carbonaceous chondrite precursor body. Yet, a relict forsterite grain is characterized by δ17O = –45.8‰, δ18O = –43.7‰, ∆17O = –23.1‰, compatible with CAIs. In contrast, a relict low‐Ca pyroxene grain (δ17O = –4.96‰, δ18O = –4.32‰, ∆17O = –2.71‰) presumably represents a first‐generation silicate grain that accreted 18O‐rich gas or dust in a transient melting scenario. The spherical inclusion displays anomalous oxygen isotope ratios (δ17O = –0.98‰, δ18O = –2.16‰, ∆17O = 0.15‰), comparable to anhydrous interplanetary dust particles (IDPs) and fragments from Comet 81P/Wild2. Based on its major element geochemistry, the chondrule size, and oxygen isotope systematics, micrometeorite WF1202A‐001 likely sampled a carbonaceous chondrite parent body similar to, but distinct from CM, CO, or CV chondrites. This observation may suggest that some carbonaceous chondrite bodies can be linked to comets. The reconstructed atmospheric entry parameters of micrometeorite WF1202A‐001 suggest that the precursor particle originated from a low‐inclination, low‐eccentricity source region, most likely either the main belt asteroids or Jupiter family comets (JFCs).

Recycled Energy Storage Materials for the Supercapacitors from Waste Coffee Sludge

Coffee is one of the largest agricultural products generally used in beverages. The international production of coffee is approximately 120 billion bags per year (60 kg per bag) from the International Coffee Organization. It corresponds to an annual production of approximately 8 million metric tons of coffee; therefore, coffee can be considered as a significant agricultural commodity. However, the majority of the produced coffee is disposed of waste sludge by beverage manufacturers. Herein, we report the use of graphitic porous carbon materials that have been derived from waste coffee sludge for developing an energy storage electrode based on a hydrothermal recycling procedure. Waste coffee sludge is used as a carbonaceous precursor for energy storage due to its lower cost, greater abundance, and easier availability as compared to other carbon resources. In addition, excluding the oil components, coffee sludge is mainly composed of cellulose-based materials with many heteroatoms (e.g., nitrogen, oxygen, and sulfur). It is considered good precursors for the fabrication of functionalized carbon materials. The unique graphite porous carbon production by hydrothermal carbonization of coffee sludge is particularly attractive as it addresses waste handling issues, offers a cheaper recycling method, and reduces the requirement for landfills. Therefore, we recycled the coffee slurry into hydrated carbon via sequential hydrothermal carbonization (HTC) as an activation process. The HTC reaction converts the cellulose-based biomass into hydrochar, bio-liquid, and gas at a relatively low temperature range (180°C~230°C). Hydrochar has various surface functional groups; so, it has been investigated for alternative fuels, carbon dioxide sequestration, and heavy metal immobilization for environmental remediation. During sequential hydrothermal activation, a porous and graphitic structure of the hydrochar can be developed, where these features are the most important characteristics of materials for electron accumulation. The porous and graphitic property of carbonaceous materials promotes electron accumulation for capacitive reactions. The electrical double-layer capacitive (EDLC) reaction has attracted considerable interest for next-generation energy storage systems such as supercapacitors. Our investigations revealed that the graphitic porous carbon, which is derived from spent coffee sludge, was employed in EDLCs by manipulating its unique microstructure which has a high hierarchical porous nature and graphitic edges. To activate the synthesized material, the dried hydrochar was mixed with 1 M KOH at a mass ratio of 1:3.5. The mixed sample was also heated at 700°C for 2 h in the hydrothermal reactor. After that, the activated hydrochar (AHC) was washed with pure water until a pH value of 7 was reached; subsequently, it was dried in an oven at 105°C for 24 h. After activation process, to gain deeper insights into the microstructure of HC and AHC regarding the specific surface area and pore size distribution, N2 adsorption/desorption isotherms were conducted. In Figure c, the TEM image of AHC has graphitized structure, which indicates easy pathways for ion and electron transport. AHC provides a higher electrochemical performance as an EDLC electrode than that demonstrated by the HC because of the high surface area (~1067 m2 g−1) and a hierarchical multi-porous structure of AHC as shown in Figure d. In addition, the conductivity of AHC is superior to that of HC; that is expected because AHC has a connected graphitized structure, which is not observed for HC, as confirmed by the TEM data (Figure a-c). The tangent to the curve in the low frequency region for AHC is higher than that for HC in Figure f. This indicates AHC has a better ion propagation and more ideal supercapacitive performance than HC. Figure a-c show the morphological differences due to the activation reaction, suggesting the existence of a well-developed hierarchical porous structure in AHC as compared to that the structure of HC. When the porous electrode is dipped into the electrolyte, the interconnections between the macropores not only provide sites for localization of the electrolyte, but also form pathways. The specific capacitance of the AHC based supercapacitors was 140 F g-1 in Figure e. Also, it demonstrated a good cyclic performance with 3% reduction over 1500 cycles at current density of 0.3 A g-1. Thus, AHC from waste coffee sludge could be an environmentally friendly technique associated with energy storage systems.This research was funded and conducted under the Competency Development Program for Industry Specialists of the Korean MOTIE, operated by KIAT (No. P0012453, Next-generation Display Expert Training Project for Innovation Process and Equipment, Materials Engineers). Figure 1

Concurrent Ce doping and in-situ carbon coating of Li2MnSiO4 nanoparticles with enhanced capacity via a rapid microwave-assisted sol-gel proces

We demonstrate a straightforward microwave-assisted sol-gel (MSG) process to facilely control the crystallization, ion doping and surface carbon coating synchronously for Li2Mn1−xCexSiO4@C (0 ≤ x ≤ 0.05) nanoparticles (NPs) through tuning the velocity of inner gas and the microwave power. In our procedure, Ce3+ ions are used as dopants and play a significant role in the microwave absorbent enhancement, and L-Ascorbic acid is used as the carbon source and the effective reductant to prevent the oxidization of Mn2+. Upon the MSG process, concurrent incorporation of Ce3+ ions into the lattice sites of Li2MnSiO4 and the in-situ carbonization of carbonaceous precursors can readily proceed. The optimal Li2Mn0.97Ce0.03SiO4@C NPs with a narrow particle size distribution in the range of 15–30 nm are demonstrated to show a high initial discharge capacity ~210.5 mAh⋅g−1 at 0.1C with a coulomb efficiency ~90%, and excellent rate performances at various current densities in the voltage range of 1.5-4.5 V.

Potassium-assisted carbonization of chlorobenzene in Ar/H2 to prepare porous carbon with low oxygen content for high withstanding voltage EDLCs

Low energy density is a fatal disadvantage of electric double-layer capacitor (EDLC). The improvement of the operation voltage of EDLCs is a more effective method to increase the energy density of EDLCs. When the operation voltage of EDLCs is higher than 2.7 V, the oxygen-containing functional groups on the surface of electrode materials (porous carbon) will decompose or chemically react with the electrolyte, causing significant deterioration of EDLC performance. In this paper, porous carbon with low oxygen content is prepared by using the potassium-assisted carbonization of chlorobenzene in Ar/H2 mixed gas to improve withstanding voltage characteristic of porous carbon. By constructing a relatively closed and stable pyrolysis environment (employing the nickel crucible with a lid), using the carbonaceous precursor without oxygen atoms (chlorobenzene) and selecting reasonable carbonization operation atmosphere (Ar/H2), the oxygen content of the as-prepared porous carbon (PC-KC-1000) is only 4.02 wt%. When the PC-KC-1000 sample is used as the electrode material of EDLCs, the operation voltage of EDLCs in the TEABF4/PC and EMIMBF4 electrolytes is respectively 3.3 and 3.5 V, and the maximum energy density is respectively 53.5 and 64.4 Wh kg−1. This strategy provides a new idea for the preparation of porous carbon with low oxygen content.

Graphitic Porous Carbon Derived from Waste Coffee Sludge for Energy Storage.

Coffee is one of the largest agricultural products; however, the majority of the produced coffee is discarded as waste sludge by beverage manufacturers. Herein, we report the use of graphitic porous carbon materials that have been derived from waste coffee sludge for developing an energy storage electrode based on a hydrothermal recycling procedure. Waste coffee sludge is used as a carbonaceous precursor for energy storage due to its greater abundance, lower cost, and easier availability as compared to other carbon resources. The intrinsic fibrous structure of coffee sludge is based on cellulose and demonstrates enhanced ionic and electronic conductivities. The material is primarily composed of cellulose-based materials along with several heteroatoms; therefore, the waste sludge can be easily converted to functionalized carbon. The production of unique graphitic porous carbon by hydrothermal carbonization of coffee sludge is particularly attractive since it addresses waste handling issues, offers a cheaper recycling method, and reduces the requirement for landfills. Our investigations revealed that the graphitic porous carbon electrodes derived from coffee sludge provide a specific capacitance of 140 F g−1, with 97% retention of the charge storage capacity after 1500 cycles at current density of 0.3 A g−1.

Synthesis and Characterization of LSX Zeolite/AC Composite from Elutrilithe.

The porous carbonaceous precursor obtained from elutrilithe by adding pitch powder and solid SiO2 was employed for the first time in an in situ hydrothermal synthesis of LSX zeolite/AC composite. The synthesized samples were characterized by XRD, SEM, and N2 adsorption–desorption. The optimum conditions for the hydrothermal synthesis process were set as follows: gelling, aging, and crystallization. The time and temperature required for these steps were 24 h and 65 °C, 12 h and 20 °C, and 48 h and 65 °C, respectively. The molar ratios were (Na2O + K2O)/Al3O2 = 7.7, K2O/(K2O + Na2O) = 3. The potential applicability test of the product showed high CO2 working capacity, excellent CO2/CH4 and CO2/N2 selectivity, and high phenol adsorption capacity. These results suggest that the resultant product has excellent potential value in industrial application.

Noble-metal-free Ni3C as co-catalyst on LaNiO3 with enhanced photocatalytic activity

In this study, Ni3C nanoparticles (NPs) were loaded on LaNiO3 NPs as a co-catalyst during the photocatalytic H2 evolution. The evolution rate of the LaNiO3-3 wt%Ni3C composite (4093.9 μmol g−1 h−1) is about 5 times and 2 times as that of pristine LaNiO3 NPs (819.2 μmol g−1 h−1), and 1 wt% Pt loaded LaNiO3 NPs (1927 μmol g−1 h−1). The effects of co-catalyze with Ni3C on light absorption, electron-hole spatial separation, and surface H2-evolution kinetics are investigated. Loading with Ni3C can enhance the spatial separation of electron-hole pairs, and improve the H2-evolution kinetics. Further investigation shows that surface decomposition of LaNiO3 NPs can only be observed when the Ni3C content is over 3 wt%, caused by the reductive carbon source needed in the loading process. This work indicates that transition metal carbide can be a promising co-catalyst candidate for oxides in photocatalytic applications without concerning corrosion from the reductive carbonaceous precursors in the loading process.

Adsorption isotherms and kinetic modeling of methylene blue dye onto a carbonaceous hydrochar adsorbent derived from coffee husk waste

In this study, activated carbon in the form of carbonaceous hydrochar adsorbents with highly functionalized surface-active sites were produced from coffee husk waste via hydrothermal carbonization under low-temperature conditions (180 °C) and subsequent chemical activation. Thereafter, the hydrochars were characterized using diverse analytical techniques, and batch experiments of methylene blue (MB) adsorption were performed under various operating conditions. The results indicated that the activated hydrochar (AH) had a larger specific surface area (862.2 m2 g−1) compared to that of its carbonaceous precursor (33.7 m2 g−1). The maximum MB sorption capacity of the hydrochar activated with potassium hydroxide was extremely high (415.8 mg g−1 at 30 °C). In addition, adsorption isotherms and kinetics were studied using experimental data fitting to further understand and describe the dynamic equilibrium, dynamic kinetics, and mechanism of MB adsorption onto the prepared hydrochars. As compared to the Freundlich isotherm model, the Langmuir isotherm model provided a better fit with the experimental data exhibiting a maximum monolayer adsorption capacity of 418.78 mg g−1. The linear pseudo-second-order kinetic model was found to be suitable for describing the adsorptive kinetics of the hydrochar. The results demonstrated the immense potential of coffee husk waste to produce activated carbon as an alternative green hydrochar that can be applied to dye removal from wastewater as well as improvement of waste management.

The carbon content of Earth and its core

Earth's core is likely the largest reservoir of carbon (C) in the planet, but its C abundance has been poorly constrained because measurements of carbon's preference for core versus mantle materials at the pressures and temperatures of core formation are lacking. Using metal-silicate partitioning experiments in a laser-heated diamond anvil cell, we show that carbon becomes significantly less siderophile as pressures and temperatures increase to those expected in a deep magma ocean during formation of Earth's core. Based on a multistage model of core formation, the core likely contains a maximum of 0.09(4) to 0.20(10) wt% C, making carbon a negligible contributor to the core's composition and density. However, this accounts for ∼80 to 90% of Earth's overall carbon inventory, which totals 370(150) to 740(370) ppm. The bulk Earth's carbon/sulfur ratio is best explained by the delivery of most of Earth's volatiles from carbonaceous chondrite-like precursors.

Molybdenum carbide clusters for thermal conversion of CO2 to CO via reverse water-gas shift reaction

Abstract Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift (RWGS) reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization efficiency while generating CH4 as a by-product. In this work, a homogeneously dispersed molybdenum carbide hybrid catalyst with sub-nanosized cluster (the average size as small as 0.5 nm) is prepared via a facile carbothermal treatment for highly selective CO2–CO reduction. The partially disordered Mo2C clusters are characterized by synchrotron high-resolution XRD and atomic resolution HAADF-STEM analysis, for which the source cause of the disorder is pinpointed by XAFS analysis to be the nitrogen intercalants from the carbonaceous precursor. The partially disordered Mo2C clusters show a RWGS rate as high as 184.4 μ mol g M o 2 C − 1 s − 1 at 400 °C with a superior selectivity toward CO (> 99.5%). This work highlights a facile strategy for fabricating highly dispersed and partially disordered Mo2C clusters at a sub-nano size with beneficial N-doping for delivering high catalytic activity and operational stability.

Microstructure and properties of in-situ Ti5Si3-TiC composite coatings by reactive plasma spraying

Ti powders, Si powders, and sucrose as a carbonaceous precursor were used to prepare Ti-Si-C composite powders by a spray-drying/precursor-pyrolysis technology. Ti-Si-C composite coatings were in-situ synthesized by reactive plasma spraying of Ti-Si-C composite powders. The microstructure and properties of the composite coatings were investigated. The results showed that the composite coatings consisted of in-situ formed Ti5Si3, TiC and Ti3O. The TiC particles with a diameter of hundreds of microns formed into clusters. The Ti5Si3 and Ti3O with sizes of about 20–40 nm coexisted in the lamellae. The microhardness of Ti5Si3-TiC composite coatings is up to 1906 HV0.1, about 4 times higher than that of TC4 alloys because of the nano Ti5Si3 and the submicron TiC grains. The composite coatings showed excellent wear resistance at room temperature and high temperature (600 °C), about 170 times and 40 times that of TC4 alloys, respectively. The oxidation tests suggested that the Ti5Si3-TiC composite coatings improved the oxidation onset temperature and have an oxidation weight change half of that of the TC4 alloys.

One-Step Site-Specific Activation Approach for Preparation of Hierarchical Porous Carbon Materials with High Electrochemical Performance

Precise control of carbonization and activation for fabricating novel carbon materials and improving practical performance have continued to be a big challenge. Inspired by the aggregation of abundant inorganic elements on a special part in biomass for self-activation, we developed a novel site-specific activation strategy to prepare porous carbon materials with controllable morphology and microstructure based upon regulating the activator molecule distribution for aggregation of activators on specific sites in a carbonaceous precursor. The fabrication of porous carbons was carried out not only in one step of direct calcination but with much reduced use of activators, demonstrating comparative or even preferable structure and performance characteristics of porous carbon compared with that of the conventional activated method. Porous carbons featured with a 3D flake interconnection network were obtained by site-specific activation with hierarchical porosity and unique micropore size distribution. The obtained porous carbon materials displayed excellent electrochemical performance with high specific capacitance (375 F g–1 at 0.1 A g–1) and excellent capacitance retention (276 F g–1 at 20 A g–1) used as electrode materials. Meanwhile, the symmetric supercapacitors assembled by the porous carbon could yield specific energy density up to 7.81 Wh kg–1 with excellent power density (9600 W kg–1) and outstanding cycling stability (99.8% capacitance retention after 10 000 charge/discharge cycles at 2 A g–1) in 1 M H2SO4 electrolytes.

Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds

A valorization process of spent coffee grounds (SCG) was studied. Thus, a two-stage process, the first stage of polyphenols extraction and synthesis of a carbonaceous precursor and a subsequent stage of obtaining activated carbon (AC) by means of a carbonization process from the precursor of the previous stage, was performed. The extraction was carried out with a hydro-alcoholic solution in a pressure reactor, modifying time, temperature and different mixtures EtOH:H2O. To optimize the polyphenols extraction, a two-level factorial experimental design with three replicates at the central point was used. The best results were obtained by using a temperature of 80 °C during 30 min with a mixture of EtOH:H2O 50:50 (v/v). Caffeine and chlorogenic acid were the most abundant compounds in the analysed extracts, ranging from 0.09 to 4.8 mg∙g−1 and 0.06 to 9.7 mg∙g−1, respectively. Similarly, an experimental design was realized in order to analyze the influence of different variables in the AC obtained process (reaction time, temperature and KOH:precursor ratio). The best results were 1 h, 850 °C, and a mixture of 2.5:1. The obtained activated carbons exhibit a great specific surface (between 1600 m2∙g−1 and 2330 m2∙g−1) with a microporous surface. Finally, the adsorption capacity of the activated carbons was evaluated by methylene blue adsorption.

Hurricane resulted in releasing more nitrogenous than carbonaceous disinfection byproduct precursors in coastal watersheds

The frequency of Atlantic hurricanes has been predicted to increase significantly by the end of this century. Watershed disturbance initiated by hurricanes can alter dissolved organic matter (DOM) quantity and quality in source water dramatically. DOM is an important disinfection by-product (DBP) precursor, and thus hurricanes can have a significant impact on water treatability and drinking water safety. The interactions between land use and land cover (LULC) of a watershed and DBP formation potential (FP) in source water under hurricane events have rarely been evaluated. Here, we quantified the FPs of two carbonaceous (trihalomethanes [THMs] and haloacetic acids [HAA]) and two nitrogenous (haloacetonitrile [HAN] and N-nitrosodimethylamine [NDMA]) DBPs at eighteen sub-watersheds with varying LULC along the Yadkin-Pee Dee River basin across North and South Carolina during and after the flooding condition caused by the 2016 Hurricane Matthew. Using chlorine as a disinfectant, THM FP was 238% (±117%) higher (p < .001) under the flooding condition than baseflow condition, while HAA FP did not change significantly as a result of the flooding. DOM composition under the flooding condition changed in favor of the formation of THMs rather than HAAs by a decrease of fulvic acid-like compounds and an increase in DOM aromaticity (SUVA). The FPs of studied DBPs under the flooding condition compared with the baseflow, followed the order of HAN (356.5%) > NDMA (246.4%) > THM (115.2%) using chloramine as a disinfectant. Higher HAN FP and NDMA FP compared to THM FP suggested that more nitrogenous than carbonaceous DBPs precursors were released during this hurricane event. LULC analysis revealed that forested wetlands were the major contributor of THM, HAA, and HAN precursors, whereas NDMA precursor was derived from developed areas. This unique study highlights the dynamic interplay between LULC and exports of carbonaceous and nitrogenous DBPs precursors during and after hurricanes.

Cosmic spherules from Widerøefjellet, Sør Rondane Mountains (East Antarctica)

A newly discovered sedimentary accumulation of micrometeorites in the Sør Rondane Mountains of East Antarctica, close to the Widerøefjellet summit at ∼2750 m above sea level, is characterized in this work. The focus here lies on 2099 melted cosmic spherules larger than 200 μm, extracted from 3.2 kg of sampled sediment. Although the Widerøefjellet deposit shares similarities to the micrometeorite traps encountered in the Transantarctic Mountains, both subtle and more distinct differences in the physicochemical properties of the retrieved extraterrestrial particles and sedimentary host deposits are discernable (e.g., types of bedrock, degree of wind exposure, abundance of metal-rich particles). Unlike the Frontier Mountain and Miller Butte sedimentary traps, the size fraction below 240 μm indicates some degree of sorting at Widerøefjellet, potentially through the redistribution by wind, preferential alteration of smaller particles, or processing biases. However, the cosmic spherules larger than 300 μm appear largely unbiased following their size distribution, frequency by textural type, and bulk chemical compositions. Based on the available bedrock exposure ages for the Sør Rondane Mountains, extraterrestrial dust is estimated to have accumulated over a time span of ∼1–3 Ma at Widerøefjellet. Consequently, the Widerøefjellet collection reflects a substantial reservoir to sample the micrometeorite influx over this time interval. Petrographic observations and 3D microscopic CT imaging are combined with chemical and triple-oxygen isotopic analyses of silicate-rich cosmic spherules larger than 325 μm. The major element composition of 49 cosmic spherules confirms their principally chondritic parentage. For 18 glassy, 15 barred olivine, and 11 cryptocrystalline cosmic spherules, trace element concentrations are also reported on. Based on comparison with evaporation experiments reported in literature and accounting for siderophile and chalcophile element losses during high-density phase segregation and ejection, the observed compositional sequence largely reflects progressive heating and evaporation during atmospheric passage accompanied by significant redox shifts, although the influence of (refractory) chondrite mineral constituents and terrestrial alteration cannot be excluded in all cases. Twenty-eight cosmic spherules larger than 325 μm analyzed for triple-oxygen isotope ratios confirm inheritance from mostly carbonaceous chondritic precursor materials (∼55% of the particles). Yet, ∼30% of the measured cosmic spherules and ∼50% of all glassy cosmic spherules are characterized by oxygen isotope ratios above the terrestrial fractionation line, implying genetic links to ordinary chondrites and parent bodies currently unsampled by meteorites. The structural, textural, chemical, and isotopic characteristics of the cosmic spherules from the Sør Rondane Mountains, and particularly the high proportion of Mg-rich glass particles contained therein, imply a well-preserved and representative new sedimentary micrometeorite collection from a previously unstudied region in East Antarctica characterized by distinct geological and exposure histories.

A carbonaceous chondrite and cometary origin for icy moons of Jupiter and Saturn

The inner structure of icy moons comprises ices, liquid water, a silicate rocky core and sometimes an inner metallic core depending on thermal evolution and differentiation. Mineralogy and density models for the silicate part of the icy satellites cores were assessed assuming a carbonaceous chondritic (CI) bulk composition and using a free-energy minimization code and experiments. Densities of other components, solid and liquid sulfides, carbonaceous matter, were evaluated from available equations of state. Model densities for silicates are larger than assessed from magnesian terrestrial minerals, by 200 to 600 kg.m−3 for the hydrated silicates, and 300 to 500 kg.m−3 for the dry silicates, due to the high iron bulk concentration in CI. The stability of Na-phlogopite in the silicate fraction up to 1300 K favors the trapping of most 40K in the rocky/carbonaceous cores with important consequences for modeling of the thermal evolution of icy satellites. We find that CI density models of icy satellite cores taking into account only the silicate and metal/sulfide fraction cannot account for the observed densities and reduced moment of inertia of Titan and Ganymede without adding a lower density component. We propose that this low-density component is carbonaceous matter derived from insoluble organic matter, in proportion of ∼30-40% in volume and 15-20% in mass. This proportion is compatible with contributions from CI and comets, making these primitive bodies including their carbonaceous matter component likely precursors of icy moons, and potentially of most of the objects formed behind the snow line of the solar system.

Thermodynamic study of phase transition behavior between the isotropic phase and mesophase using benzene-soluble and benzene-insoluble as phase indicators

Preparing carbonaceous mesophase pitch precursor by thermal treatment of isotropic pitch is a feasible and effective method for fabricating various high-performance carbon materials including high-modulus carbon fiber, needle coke, graphite, etc. However, the industrial production of qualified mesophase with desirable properties needs to be further improved in many regions. Especially, during pitch preparation, the transformation from isotropic phase to mesophase is difficult to be controlled since it significantly depends on reaction conditions, raw material and preparation parameters. While the optimization of the production conditions of mesophase with special properties requires time-consuming and costly exploratory experiments due to the lack of the fundamental understanding in the transformation behavior from isotropic phase to mesophase. This paper elaborates a fundamental work seeking a more suitable and accurate thermodynamic model and a parameter estimation method to describe phase transition behavior using benzene-soluble (BS) and benzene-insoluble (BI) fractions of coal tar-based pitch as indicators of isotropic phase and mesophase, respectively. The combined equation of simplified statistical associating fluid theory with anisotropic pseudopotential (SSAFT-APP) is used to describe phase transition, and the related parameters of each equation are estimated based on average molecular weight and carbon aromaticity of BS and BI fractions, respectively. The mesophase content of various samples prepared by annealing the mixtures of BS and BI fractions under different mixing ratios are used to calibrate the computed data. The results show that BS fraction has a restraining effect on the formation of mesophase when BI fraction is lower than 60 wt%, while this effect becomes weak with a higher content of BI fraction. A phase diagram is proposed by substituting the estimated parameters in SSAFT-APP equation with experimental data. Mesophase is able to be generated when the adding amount of BI fraction is increased to 12 wt%, and 100% mesophase could be obtained when the ratio of BI fraction is higher than 94 wt%. This work is expected to shed light on the phase transition behavior between isotropic phase and mesophase during pitch preparation from coal tar. In addition, based on the thermodynamic study optimizing preparation conditions and a novel method for obtaining the products with an optimal proportion between isotropic phase and mesophase is proposed.

Excellent performance of porous carbon from urea-assisted hydrochar of orange peel for toluene and iodine adsorption

In order to promote the physicochemical properties and the pollutants adsorption capacities of porous carbon, a novel urea-assisted hydrothermal method was developed to produce N-doped hydrochar as an ideal precursor from orange peel waste. Different from the modification technologies for nitrogen doping, the highly porous carbon prepared by KOH activation of the urea-assisted hydrochar contained extremely low N content. But such sample showed ultra-high specific surface area up to 3053 m2/g, with 63% and 39% higher than the porous carbons through conventional N-free method and hydrochar-urea mixing activation method respectively. In-depth study revealed that during 600–800 °C activation procedure, the N-containing groups including pyridinic-N, pyridonic-N and graphitic-N in the urea-assisted hydrochar reacted sufficiently with K2CO3, an intermediate of KOH activation, and generated NH3, creating richer porous structures in carbon. Particularly, there was a good linear relationship between the relative increment of specific surface area and the relative reduction of N content in porous carbon when the activation temperature increasing. This connection can be served as a reference to increase the porosity of porous carbon through the activation of N-doped carbonaceous precursor. As for pollutants adsorption, the highly porous carbon from urea-assisted hydrochar possessed excellent toluene adsorption capacity up to 724 mg/g and iodine adsorption capacity up to 2252 mg/g.