Nitrogen Adsorption Analysis Research Articles

Petrophysical characteristics of shales with different lithofacies in Jiaoshiba area, Sichuan Basin, China: Implications for shale gas accumulation mechanism

Abstract The petrophysical characteristics of unconventional reservoirs have significant impacts on hydrocarbon storage and transport. In this study, 26 shale samples with various lithofacies from Lower Silurian Longmaxi shales in the Jiaoshiba area of Sichuan Basin are investigated. The pore network (morphology, porosity, and pore structure parameters) is comprehensively characterized using scanning electron microscopy, helium pycnometry, and low-pressure gas adsorption techniques. Permeability coefficients are derived from pulse-decay measurements on parallel to bedding samples. Geological controls on the pore shape, porosity, pore size, pore size distribution, and permeability of the shales are analyzed, and quantitative relationships with which to estimate the permeabilities and pore-throat apertures controlling gas flow are developed. Three general lithofacies are summarized in view of their mineralogy: siliceous, argillaceous/siliceous mixed, and argillaceous shales. Pore structure parameters (porosity, specific surface area, and pore volume) show positive correlations with total organic carbon (TOC) content. Organic matter-hosted pores contribute to approximate 67% of the porosity of siliceous shales, while inorganic matter contributes to 55% of the porosity of argillaceous shales. Klinkenberg-corrected permeabilities range between 0.01 and 46.4 μD, and are controlled by the alignment of clay flakes. Negative relationships exist between TOC content, porosity, and permeability values. Siliceous shales generally have the lowest permeabilities, whereas the argillaceous shales with developed oriented clay flakes have relatively high permeabilities. The seepage-pore apertures, estimated using the Winland correlation, range from 9 to 476 nm. These values are much higher than those obtained from nitrogen adsorption analysis (adsorption-pore apertures). A power correlation exists between seepage-pore apertures and total clay minerals content of shales studied. A fracture model (sheet) is used to predict absolute permeability based on seepage-pore apertures. The predictions are reasonable, and justify the application of the sheet model and seepage-pore apertures. The siliceous shales are featured by a high TOC content, large porosity and specific surface area, and low permeability, which are favorable to gas preservation.

Facile synthesis to tune size, textural properties and fiber density of dendritic fibrous nanosilica for applications in catalysis and CO2 capture

Morphology-controlled nanomaterials such as silica play a critical role in the development of technologies for use in the fields of energy, environment (water and air pollution) and health. Since the discovery of Stöber's silica, followed by the discovery of mesoporous silica materials (MSNs) such as MCM-41 and SBA-15, a surge in the design and synthesis of nanosilica with various sizes, shapes, morphologies and textural properties (surface area, pore size and pore volume) has occurred. Dendritic fibrous nanosilica (DFNS; also known as KCC-1) is one of the recent discoveries in morphology-controlled nanomaterials. DFNS shows exceptional performance in large numbers of fields, including catalysis, gas capture, solar energy harvest, energy storage, sensors and biomedical applications. This material possesses a unique fibrous morphology, unlike the tubular porous structure of various conventional silica materials. It has a high surface area to volume ratio, with improved accessibility to the internal surface, tunable pore size and pore volume, controllable particle size and, importantly, improved stability. However, synthesis of DFNS with controllable size, textural properties and fiber density is still tricky because of several of the steps involved. This protocol provides a comprehensive step-wise description of DFNS synthesis and advice regarding how to control size, surface area, pore size, pore volume and fiber density. We also provide details of how to apply DFNS in catalysis and CO2 capture. Detailed characterization protocols for these materials using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and thermal gravimetric analysis (TGA) studies are also provided.

Silica aerogel/polyester blankets for efficient sound absorption in buildings

In this paper sound absorption characteristics of silica aerogel/polyester (PET) blankets are investigated. PET fibers were made on an industrial scale compact melt spinning line and then processed on a laboratory scale needling line to produce nonwoven fabrics. The silica aerogel blankets were prepared by in situ synthesis of silica aerogel on the nonwoven fabrics via a two-step sol-gel process of tetraethoxysilane which was followed by drying at ambient pressure. In order to achieve aerogel particles with different pore structure and properties, various synthesis conditions were used. The nonwoven samples were characterized in terms of thickness, fiber diameter, porosity and pore size by X-ray micro-computed tomography and scanning electron microscopy. Moreover, nitrogen adsorption analysis was carried out to determine the specific surface area and pore structure of aerogel particles.The effect of pore structure, physical properties and hydrophobicity of aerogel particles on sound absorption coefficient (SAC) of blankets was investigated using two-microphone transfer function method. Also, the effect of sol volume and nonwoven thickness was investigated. The results indicated that at all frequency levels, silica aerogel/PET blankets enjoy higher SAC than their untreated counterparts. It was found that, SAC is strongly affected by the pore structure of aerogel particles. Silica aerogels with lower bulk densities, larger pore size and higher porosities exhibited better sound absorption performance. The results also indicated that hydrophobic aerogel blankets exhibit higher SAC as compared with hydrophilic blankets. The results also showed that the thickness of nonwoven fabric strongly affects the SAC of aerogel blankets.

Development of MWCNT/α-MnO2/MoS2 Ternary Composite for High-Performance Supercapacitor Application

Development of MWCNT/α-MnO2/MoS2 ternary composite is presented in this work as an electrode material for supercapacitor application. MWCNT/α-MnO2/MoS2 ternary composite was synthesized by facile hydrothermal method. The structural details of MoS2, α-MnO2/MoS2 and MWCNT/α-MnO2/MoS2 ternary composite were studied by powder X-ray diffraction technique and nitrogen adsorption analysis. The surface morphology of the synthesized materials was analyzed by field emission electron microscope technique and the elemental analysis was carried out using EDS analysis. High-resolution transmission electron microscope analysis revealed the detailed surface analysis of MWCNT/α-MnO2/MoS2 ternary composite. The active material was mixed with a polymeric binder and drop coasted on the nickel surface and the electrochemical performances of the active material were elucidated from cyclic voltammetry, charge-discharge, and electrochemical impedance spectroscopy techniques. We observed a linear relation between the square root of the scan rate and peak current, which were confirmed the diffusion controlled ion transportation. The specific capacitance values of prepared MoS2, α-MnO2/MoS2, and MWCNT/α-MnO2/MoS2 ternary composite were calculated from charge-discharge technique at a various applied current density (1 to 5 A g-1) in 1 M Na2SO4 aqueous electrolyte. We found that the synthesized MWCNT/α-MnO2/MoS2 ternary composite electrode exhibits higher specific capacitance value than MoS2, and α-MnO2/MoS2 electrodes. Further, the resistive and capacitive behavior of the electrodes was studied from Nyquist and bode diagrams within the frequency range of 10 mHz to 100 kHz.

A model for porosity evolution in shale reservoirs: An example from the Upper Devonian Duvernay Formation, Western Canada Sedimentary Basin

The influence of thermal maturity on porosity in shale samples from the Upper Devonian Duvernay Formation is examined. The samples span a maturity range from immature to the wet gas window. Porosity decreases from immature to the oil window, primarily because of compaction. Relatively high porosity of wet gas window samples is ascribed to formation of secondary organic pores, feldspar dissolution pores, and primary pore preservation by the quartz framework. The final decline in the porosity of the dry gas window samples is explained by greater compaction, the disappearance of secondary organic pores, and feldspar dissolution pores. Porosity correlates positively to quartz content and negatively to carbonate content; no relationship was evident between porosity and clay or total organic carbon content. No obvious correlations exist between rock composition and permeability except that SiO2 content shows a weakly positive correlation to permeability. Permeability is highest in immature samples, which have the greatest pore and pore-throat sizes. Nitrogen adsorption and mercury injection analysis show that pore and pore-throat sizes decrease with increasing maturity. Visible pores, imaged by scanning electron microscopy and helium ion microscopy, exist as organic pores, including bubblelike pores developed within organic matter (OM) and fissure-type pores, intraparticle pores mainly developed within carbonate grains, and interparticle pores either within a clay-rich matrix or between rigid mineral grains. In immature samples, the primary pores are interparticle pores between clay minerals and other mineral grains. The OM fissures are ubiquitous in oil window samples, and secondary bubblelike OM–hosted pores are well developed within gas window samples.

Interactions between mesocellular foam silica carriers and model drugs constructed by central composite design

In this work, the influences of the four factors including hydrogen bond acceptor (HBA) count (X1), MCF pore size (X2), drug loading degree (X3) and dissolution stirring rate (X4) as well as their cross-interactions for drug release behaviors were investigated. The factors were chosen from all drug release aspects consisting of drug, carrier, formulation and dissolution, respectively. A five-level four-factorial composite central design (CCD) was performed for the investigation with cumulative release over 1 h (Y1), cumulative release over 24 h (Y2) and rate constant k (Y3) as three dependent response variables. A series of MCFs (4MCF, 7MCF, 12MCF, 17MCF and 22MCF) with various pore diameters were synthesized to be applied as drug carriers, and five BCS II drugs including disulfiram (DIS), loratadine (LOR), celecoxib (CEL), metronidazole (MET) and nimodipine (NIM) were selected as model drugs possessing different numbers of HBAs. The morphologies, structures and pore size distributions of the MCFs were systematically studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption analysis (BET), and the drug loading samples were analyzed using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The release behavior was examined by in vitro dissolution. The interactions between the model drugs and the MCFs were analyzed in detail using response surface plots. The present work may provide some scientific references for selecting the appropriate mesoporous silica carrier for a specific drug.

How does delignification influence the furfurylation of wood?

To investigate the influence of delignification on wood furfurylation, poplar wood (Populus euramericana Cv.) was partly delignified prior to the impregnation of furfuryl alcohol (FA) at concentration of 25%. The observation by using scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM) showed that many intercellular spaces appeared in middle lamella and cell corners in the wood with 8.86% lignin loss (LL), after further furfurylation, these spaces were filled with polymerized furfural resin, which contributed to the more uniform distribution of modifier and larger bulking of cell wall in furfurylated wood with low lignin (LF) than furfurylated control (CF). The size distribution of mesopores increased after delignification but decreased after furfurylation, and the specific surface area was reduced over 20% for LF with about 50% total pore volume decrease compared with the control from the analysis of nitrogen adsorption. Lignin loss and chemical polymerization of furfural resin were confirmed but without chemical reaction between FA and cell wall components by both results of Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Delignification resulted in increased equilibrium moisture content (EMC) and dimensional instability, after further furfurylation, the EMC and dimensional changes of LF decreased and were lower than those of control by 16.3% on average, suggesting the availability of furfurylation in reducing moisture sorption and improving dimensional stability of low lignin content wood. The number of accessible hydroxyl groups in wood calculated by using Hailwood-Horrobin theory exhibited in the following order: LL > control > LF > CF. The results can potentially help with understanding the action of delignification in wood furfurylation, as well as providing information on the possibility of make sustainable use of wood products with degraded lignin by furfurylation.

Multi-walled carbon nanotube-based systems for improving the controlled release of insoluble drug dipyridamole.

Applicability of multi-walled carbon nanotubes (MWCNTs) in loading dipyridamole (DDM), a poorly soluble drug, was evaluated. Additionally, the effect of drug-loading efficiency on the release behavior of the MWCNT-DDM system was also investigated. DDM as a model drug was incorporated into MWCNTs with different drug-loading rates (10, 25 and 50%) using the solvent deposition method. The MWCNT-DDM system was successfully established and characterized using common solid-state characterization methods. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption analysis and Fourier transform-infrared (FT-IR) spectroscopy were carried out to observe the progress of drug loading. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to systematically assess the crystalline state of the DDM after being loaded into the MWCNTs. Improvements in dissolution rate were evaluated by the dissolution test. The results revealed that with the increase of drug loading, the form of DDM in the MWCNTs changed from amorphous to crystalline state. Also, the release rate of DDM decreased upon increasing the drug-loading rate of carriers. In conclusion, MWCNTs are proven to be promising carriers for loading DDM.

Nanostructured ZnO as Multifunctional Carrier for a Green Antibacterial Drug Delivery System-A Feasibility Study.

The physico–chemical and biological properties of nanostructured ZnO are combined with the non-toxic and eco-friendly features of the scCO2-mediated drug loading technique to develop a multifunctional antimicrobial drug delivery system for potential applications in wound healing. Two nanostructured ZnO (NsZnO) with different morphologies were prepared through wet organic-solvent-free processes and characterized by means of powder X-ray diffraction, field emission scanning electron microscopy (FESEM), and nitrogen adsorption analysis. The antimicrobial activity of the two samples against different microbial strains was investigated together with the in vitro Zn2+ release. The results indicated that the two ZnO nanostructures exhibited the following activity: S. aureus > C. albicans > K. pneumoniae. A correlation between the antimicrobial activity, the physico–chemical properties (specific surface area and crystal size) and the Zn2+ ion release was found. Ibuprofen was, for the first time, loaded on the NsZnO carriers with a supercritical CO2-mediated drug impregnation process and in vitro dissolution studies of the loaded drug were performed. A successful loading up to 14% w/w of ibuprofen in its amorphous form was obtained. A preliminary drug release test showed that up to 68% of the loaded ibuprofen could be delivered to a biological medium, confirming the feasibility of using NsZnO as a multifunctional antimicrobial drug carrier.

Preparation and photocatalytic performance of graphene Oxide/WO3 quantum Dots/TiO2@SiO2 microspheres

In order to enhance the interaction between GO/TiO2 nanostructure and SiO2 microsphere, graphene oxide/WO3 quantum dots/TiO2@SiO2 (GOWTS) microspheres were prepared by using urchin-like SiO2 microsphere as template, and were characterized with X-ray diffractometer (XRD), nitrogen adsorption analyzer, scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscope (XPS), respectively. Furthermore, the photocatalytic activity was tested by degrading Rhodamine b (RhB) solution. The resultant GOWTS microsphere possesses very good photocatalytic performance under UV light or nature solar light, in which the decomposition rate of Rhodamine B (RhB) reached 100% within 60 min under nature solar light without stirring. The degradation rate constant of GOWTS is about 3 times of GOTS. Moreover, the GOWTS microspheres display very good photocatalytic stability, indicating a potential industrial application in sewage treatment.

Effect of different initiators on temperature‐sensitive monolithic columns and application in online enrichment of β‐sitosterol

ABSTRACTThree temperature‐sensitive monolithic columns were prepared by atom transfer radical polymerization and oxidation–reduction method using the initiator systems of CCl4/FeCl2, BPO/DMA, and APS/TEMED, respectively. The three monoliths were characterized by scanning electron microscopy, nitrogen adsorption, and thermogravimetric analysis. The obtained monolithic columns were used as on‐line solid phase extraction sorbent coupled with high‐performance liquid chromatography for the enrichment of β‐sitosterol. By comparing some influencing factors on the adsorption, the optimum temperature‐sensitive monolithic column which was initiated by CCl4/FeCl2 was selected for enrichment of β‐sitosterol from plant oil. The maximum adsorption capacity of the monolith for β‐sitosterol was 10.0031 mg/g. The limit of detection and limit of quantitation were 0.039 and 0.13 mg/mL, respectively. The recovery was in the range of 90.21–98.26%. The results showed that the monolith had better selectivity for β‐sitosterol and could be used for enrichment of β‐sitosterol in food samples. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47683.

A Drug Release Model Constructed by Factorial Design to Investigate the Interaction Between Host Mesoporous Silica Carriers and Drug Molecules.

A drug release model based on mesocellular foam silica (MCF) for Biopharmaceutics Classification System (BCS) II drugs was conducted. A three-level two-factorial factorial design was carried out for the exploration of the influence of the pore size of MCF (X1) and drug-loading degree (X2) for drug release behaviors. Cumulative release in 1h (Y1), cumulative release in 24h (Y2), and rate constant k (Y3) were selected as dependent response variables. A series of MCFs (7MCF, 12MCF, and 17MCF) with arithmetic increased pore diameters was synthesized as drug carriers. The morphologies and structures of MCFs and pore size distributions were detected by scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption analysis. With celecoxib as a model drug, nine drug-loaded samples were prepared and further characterized by differential scanning calorimetry and X-ray diffraction analyses. The release behavior was examined by in vitro dissolution. Factorial design results demonstrated that cumulative release in 1h and the rate constant k were mainly affected by X2, while cumulative release in 24h was influenced by both X1 and X2. Furthermore, quadratic equations of Y1, Y2, and Y3 were conducted, respectively. This work was expected to provide some scientific references for designing specific drug delivery models with mesoporous silica carrier.

The Function of Surface Hydroxyl Groups of Incorporated Alumina on Catalytic Ozonation of Heavy Oil Produced Water

ABSTRACTγ-Al2O3 was incorporated with SiO2 and used as carrier to support Ni and Cu oxides for catalytic ozonation of heavy oil produced water. The change of catalytic activity was in accordance with that of surface hydroxyl density after incorporation or reuse of catalysts. Nitrogen adsorption and X-ray power diffraction analysis indicated that the specific surface area decreased and the mineral phase and crystal structure of metal oxides unchanged after incorporation. The results confirmed that the neutral surface hydroxyl groups of the carrier were the active sites during catalytic ozonation. Increasing of surface hydroxyl could be another way of improving the catalytic efficiency of catalytic ozonation.

Solvent effect on adsorption and fluorescence properties of perylene and pyrene dyes bonded to SBA-15 network

Abstract Synthesis and adsorption studies of the SBA-15 immobilizing perylene and pyrene dyes are described in this work. The functionalization is carried out with amine groups through post-synthesis using amino-propyl triethoxysilane (APTES) and ethanol or toluene as solvent. The resulting functionalized material is investigated as a matrix for the immobilization of perylene-3,4,9,10-tetracarboxylic dianhydride (PDA). Further exploration of the immobilization of 1-Pyrenecarboxaldehyde (PCA) is detailed. The obtained materials were characterized by FTIR and fluorescence spectroscopy, nitrogen adsorption analysis and X-ray diffraction (XRD). The textural characterization of the functionalized samples shows the decrement of the average pore sizes and the surface area as consequence of the APTES and fluorescent dyes immobilization. Compared with the pristine SBA-15, the solids obtained by functionalization with PDA yielded red-coloured samples, which show absorption bands at λ = 670 nm in solid state and λ = 570 nm in solution. The PDA dye is bonded to the SBA-15 network and it shows absorption or emissions properties for the new hybrid solids. The fluorescence of these species are preserved if the PDA molecules remains with a more flexible structure.

Shape-controlled synthesis of bare ZnO nanomaterials with improved photoactivity and photostability

ABSTRACTUnderstanding the growth mechanisms of nanomaterials usually leads to the successful preparation of targeted micro-structures with excellent properties. In this paper, flower-like and roughly spherical ZnO nanocrystals have been successfully synthesised through facile wet chemical methods, i.e. hydrothermal pathways and homogeneous precipitation method. The photocatalytic activities of the prepared photocatalysts were evaluated by degradation of rhodamine B (RhB) and phenol under ultraviolet (UV) irradiation. Remarkably, the ZnO powder via homogeneous precipitation (urea/Zn2+ = 2.0) exhibited better photocatalytic performance and photostability than those of flower-like ZnO substrate. The enhanced photocatalytic properties could be attributed to more active catalytic sites and effective separation of carriers, which were confirmed by low-temperature nitrogen adsorption, photocurrent responses, and photoluminescence spectral analysis. A possible mechanism for the excellent photocatalytic activity of ZnO substrates was proposed.

A Polymer-Oriented Self-Assembly Strategy toward Mesoporous Metal Oxides with Ultrahigh Surface Areas.

Mesoporous metal oxides (MMOs) have attracted comprehensive attention in many fields, including energy storage, catalysis, and separation. Current synthesis of MMOs mainly involve use of surfactants as templates to generate mesopores and organic reagents as solvents to hinder hydrolysis and condensation of inorganic precursors, which is adverse to adjusting the interactions between surfactants and inorganic precursors. The resulting products have uncontrollable pore structure, crystallinity, and relatively lower surface areas. Here, a facile and general polymer‐oriented self‐assembly strategy to synthesize a series of MMOs (e.g., TiO2, ZrO2, NbO5, Al2O3, Ta2O5, HfO2, and SnO2) by using cationic polymers as porogens and metal alkoxides as metal oxide precursors in a robust aqueous synthesis system are reported. Nitrogen adsorption analysis and transmission electron microscopy confirm that the obtained MMOs have ultrahigh specific surface areas and large pore volumes (i.e., 733 m2 g−1 and 0.485 cm3 g−1 for mesoporous TiO2). Moreover, the structural parameters (surface area, pore size, and pore volume) and crystallinity can be readily controlled by tuning the interactions between cationic polymers and precursors. The as‐synthesized crystalline mesoporous TiO2 exhibits promising performance in photocatalytic water splitting of hydrogen production and a high hydrogen production rate of 3.68 mol h−1 g−1.

Fresh and hardened properties of self-compacting concrete using silicon carbide waste as a viscosity-modifying agent

The aim of this paper was to evaluate the preparation of self-compacting concrete (SCC) with silicon carbide waste (SCW) as an alternative of the viscosity-modifying agent. Fresh properties like flowability, viscosity, filling and passing abilities as well as segregation resistance were measured while hardened properties such as strength, drying shrinkage, water absorption and chloride permeability were determined. The mechanisms responsible for the performance variations were explored by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and nitrogen adsorption analyses. Results show that SCW improves the viscosity, filling and passing abilities, segregation resistance and flowability retention of SCC at proper replacement ratios although superplasticizer demand is increased. Besides, strength, drying shrinkage, water absorption and chloride permeability are closely related to SCW amount. Specifically, drying shrinkage, initial absorption and chloride permeability decreases as SCW increases and SCW improves strengths and final absorption at ratio no less than 15%. It is proved that SCW has porous structure with high water absorption, mainly accounting for its viscosity regulating performance. Water absorption and chloride impermeability improvement of SCC can be explained by the microstructure densification. Drying shrinkage is reduced due to the high water absorption and timely releasing ability of SCW. And the combined effects of internal curing, reinforcing filling and further hydration promotion of SCW boost the strength development of SCC. These results favor the reutilization of SCW and the sustainable development of cement and concrete industries.

Highly selective hydrogenation of levulinic acid catalyzed by Ru on TiO2-SiO2 hybrid support

Abstract Levulinic acid is an important molecule of biomass and the gamma-valerolactone (GVL) is one of the most promising compound from levulinic acid. We have developed an efficient catalyst for the catalytic conversion of LA into GVL, ruthenium based catalyst in silica, titania and a silica-titania hybrid support The prepared catalysts were characterized by TEM, XRD, TPR and nitrogen adsorption analysis. The results have shown higher catalytic activity of Ru/TiO2-SiO2 than Ru/TiO2 either Ru/SiO2. Herein, we report that yields higher than 90% were obtained for gamma-valerolactone from levulinic acid hydrogenation catalyzed by Ru/TiO2-SiO2 at 100 °C and 20 atm of hydrogen without additives.

Three-dimensional carbon foam nanocomposites for thermal energy storage

Nanocomposites consisting of paraffin/graphene nanoplatelets mix embedded in carbon foams via vacuum infiltration were fabricated with the aim of developing new phase change material (PCM) formulation with excellent shape stabilization, improved thermal conductivity and outstanding thermal reliability and structural stability. Physicochemical and thermal properties of the nanocomposites were evaluated using a suite of techniques such as scanning and transmission electron microscopy, X-ray diffraction, attenuated total reflection - Fourier transform infrared spectroscopy, nitrogen adsorption analyzer, differential scanning calorimetry, mechanical tester, Raman spectroscopy, thermal conductivity analyzer and thermogravimetric analyzer. The carbon foams exhibited good cyclic compressive behavior at a strain of up to 95% and kept part of their elastic properties after cyclic testing. Due to the robust mechanical integrity and layered meso-/macroporous morphology of these carbon foams, the nanocomposites are well equipped to cope with volume changes without leaking during thermal cycling. A 141% thermal conductivity enhancement observed for the carbon foam nanocomposite demonstrates the contributing role of the carbon foam in creating effective heat transfer through its conductive 3D network. The results have shown that proper chemical modification and subsequent carbonization of the low cost porous foams can lead to ultralight multifunctional materials with high mechanical and physical properties suitable for thermal energy storage applications.

Preparation of Large Carbon Nanofibers on a Stainless Steel Surface and Elucidation of their Growth Mechanisms

Abstract In this work different shapes of carbon nanofibers (CNFs) were successfully synthesised on a treated commercial steel substrate by catalytic chemical vapour deposition (CCVD) utilising ethanol at 700 °C. The formation of the nanofibers with average diameter of 200–400 nm was confirmed via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The BET surface area, pore volume and pore size of the obtained CNFs were sequentially: 182 m2/g, 10.5 cm3/g and 103.3 Å as determined by nitrogen adsorption analysis. The influence of the surface treatment on the size and shape of CNFs was investigated and the results indicated a positive correlation that can be employed to tailor CNFs of desired morphology. Accordingly, a growth mechanism due to the deposition of carbonaceous materials on large size nanoparticles was proposed. As the CCVD is a facile and economical route for CNFs synthesis, thus, it can be efficiently adopted for the growth of CNFs on pretreated steel substrates as proved by this study.