Preparation and modulation of a novel thin-walled carbon foam

By foaming and carbonization processes under atmospheric pressure, a novel thin-walled carbon foam with developed foam structure was successfully prepared from loose medium component(LMC) separated from raw coal by extraction and back-extraction method. The influences of foaming time, carbonization time, and micromolecule content on foam structure were investigated by scanning electron microscope and mercury injection data. Moreover, foaming mechanism of LMC was analyzed and expounded. The results showed that spherical pores and uniform ultrathin pore walls constitute threedimensional foam structure of carbon foam and foam structure is developed with well connectivity.The effects of foaming time, carbonization time, and micromolecule content on foam structure are significant. Especially, average pore diameters of carbon foams prepared from the extracts of LMC are much smaller. With the rise of extraction rate, average pore diameter decreases and pore size distribution is more concentrated on the aperture section of 0–10 μm.

Semi-quantitative analysis of the structural evolution of mesophase pitch-based carbon foams by Raman and FTIR spectroscopy

Graphitized carbon foams(GFms)were prepared using mesophase pitch(MP)as a raw material by foaming(450℃),pre-oxidation(320℃),carbonization(1000℃)and graphitization(2800℃).The differences in structure and properties of GFms prepared from different MP precursors pretreated by ball milling or liquid phase extraction were investigated and compared,and semi-quantitative calculations were conducted on the Raman and FTIR spectra of samples at each preparation stage.Semi-quantitat-ive spectroscopic analysis provided detailed information on the structure and chemical composition changes of the MP and GFm de-rived from it.Combined with microscopic observations,the change from precursor to GFm was analyzed.The results showed that ball milling concentrated the distribution of aromatic molecules in the pitch,which contributed to uniform foaming to give a GFm with a uniform pore distribution and good properties.Liquid phase extraction helped remove light components while retaining large aromatics to form graphitic planes with the largest average size during post-treatment to produce a GFm with the highest degree of graphitization and the fewest open pores,giving the best compression resistance(2.47 MPa),the highest thermal conductivity(64.47 W/(m·K))and the lowest electrical resistance(13.02μΩ·m).Characterization combining semi-quantitative spectroscopic ana-lysis with microscopic observations allowed us to control the preparation of the MP-derived GFms.

Mixed‑Dimensional Assembly Strategy to Construct Reduced Graphene Oxide/Carbon Foams Heterostructures for Microwave Absorption,Anti‑Corrosion and Thermal Insulation

Considering the serious electromagnetic wave(EMW)pollution problems and complex application condition,there is a pressing need to amalgamate multiple functionalities within a single substance.However,the effective integration of diverse functions into designed EMW absorption materials still faces the huge challenges.Herein,reduced graphene oxide/carbon foams(RGO/CFs)with two-dimensional/three-dimensional(2D/3D)van der Waals(vdWs)heterostructures were meticulously engineered and synthesized utilizing an efficient methodology involving freeze-drying,immersing absorption,secondary freeze-drying,followed by carbonization treatment.Thanks to their excellent linkage effect of amplified dielectric loss and optimized impedance matching,the designed 2D/3D RGO/CFs vdWs heterostructures demonstrated commendable EMW absorption performances,achieving a broad absorption bandwidth of 6.2 GHz and a reflection loss of-50.58 dB with the low matching thicknesses.Furthermore,the obtained 2D/3D RGO/CFs vdWs heterostructures also displayed the significant radar stealth properties,good corrosion resistance performances as well as outstanding thermal insulation capabilities,displaying the great potential in complex and variable environments.Accordingly,this work not only demonstrated a straightforward method for fabricating 2D/3D vdWs heterostructures,but also outlined a powerful mixeddimensional assembly strategy for engineering multifunctional foams for electromagnetic protection,aerospace and other complex conditions.

Ultralight pyrolytic carbon foam reinforced with amorphous carbon nanotubes for broadband electromagnetic absorption

For electromagnetic wave-absorbing materials,maximizing absorption at a specific frequency has been constantly achieved,but enhancing the absorption properties in the entire band remains a challenge.In this work,a 3D porous pyrolytic carbon(PyC)foam matrix was synthesized by a template method.Amorphous carbon nanotubes(CNTs)were then in-situ grown on the matrix surface to obtain ultralight CNTs/Py C foam.These in-situ grown amorphous CNTs were distributed uniformly and controlled by the catalytic growth time and can enhance the interface polarization and conduction loss of composites.When the electromagnetic wave enters the internal holes,the electromagnetic energy can be completely attenuated under the combined action of polarization,conductivity loss,and multiple reflections.The ultralight CNTs/Py C foam had a density of 22.0 mg·cm^(-3)and a reflection coefficient lower than-13.3 d B in the whole X-band(8.2-12.4 GHz),which is better than the conventional standard of effective absorption bandwidth(≤-10 dB).The results provide ideas for researching ultralight and strong electromagnetic wave absorbing materials in the X-band.

Layered Structural PBAT Composite Foams for Efficient Electromagnetic Interference Shielding

The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.

Preparation and oxidation resistance of B_2O_3-coated boron-modified carbon foams

To improve the oxidation resistance of boron-modified carbon foams, the B2O3 coating was prepared on boron-modified carbon foams by low-cost slurry method. The microstructures and phase compositions of the coated carbon foams were characterized by scanning electron microscopy and X-ray diffraction, respectively. Oxidation resistances of uncoated and coated boron-modified carbon foams were investigated at 873 K in air. The results showed that as-received B2O3 coating could protect boron-modified carbon foams from oxidation at 873 K. B2O3-coated carbon foam doped with 7% B2O3 （mass fraction） （BO-7） had better oxidation resistance, exhibiting mass loss of 17.40% after oxidation at 873 K for 120 min. The melting glass layer formed on the surface of BO-7 could prevent oxygen from diffusing into boron-modified carbon foams substrate during oxidation to some extent.

Carbon foam with microporous structure for high performance symmetric potassium dual-ion capacitor

A novel carbon foam with microporous structure(CFMS),with the advantages of a simple fabrication process,low energy consumption,large specific surface area and high conductivity,has been prepared by a facile one-step carbonization.In addition,the carbon foam possesses suitable interlayer spacing in short range which is flexible to accommodate the deformation of carbon layer caused by the ion insertion and deinsertion at the charge and discharge state.Furthermore,a low cost carbon-based symmetric potassium dual-ion capacitor(PDIC),which integrates the virtues of potassium ion capacitors and dual-ion batteries,is successfully established with CFMS as both the battery-type cathode and the capacitor-type anode.PDIC displays a superior rate performance,an ultra-long cycle life(90%retention after 10000 cycles),and a high power density of 7800 W kg^-1 at an energy density of 39Whkg^-1.The PDIC also exhibits excellent ultrafast charge and slow discharge properties,with a full charge in just 60 s and a discharge time of more than 3000 s.

Dual template approach for the synthesis of hierarchically mesocellular carbon foams

We demonstrated a simple and effective dual-templating approach for the synthesis of hierarchically mesocellular carbon foams by using nonionic surfactant of sorbitan monooleate and silica colloid particles as sacrificial templates, and resorcinol/ formaldehyde as carbon source. The representative carbon foam has dual mesopore sizes of 4 and 10 nm, and possesses the specific surface area of 580 m^2/g and the total pore volume of 0.80 cm^3/g.

Investigation of carbon contamination in lost foam castings of low carbon steel

Lost foam casting(LFC) process is a special casting method in which polymeric foam patterns with refractory coatings are utilized as a mould component. In this work, four types of foam: expandable polyethylene(EPE), expandable polypropylene(EPP) and expandable polystyrene(EPS) foams with two different densities were employed as pattern materials. LFC and conventional green sand mould casting methods were used to cast a low carbon steel, A216 Grade WCB. Both casting processes were carried out at 1,580 °C. Chemical analysis results showed that the carbon contamination level was high and was influenced by pattern type. Metallographic investigations revealed a significant increase in the percentage of pearlite phase in all LFC samples. Densities of manufactured samples were calculated in order to evaluate porosity of the products. It was determined that the densities of the LFC samples were lower than the green sand mould cast reference sample(RS). Vickers hardness tests were also carried out and increments in hardness values with increased carbon content was observed.

An Equivalent Substitute Strategy for Constructing 3D Ordered Porous Carbon Foams and Their Electromagnetic Attenuation Mechanism

Three-dimensional(3D)ordered porous carbon is generally believed to be a promising electromagnetic wave(EMW)absorbing material.However,most research works targeted performance improvement of 3D ordered porous carbon,and the specific attenuation mechanism is still ambiguous.Therefore,in this work,a novel ultra-light egg-derived porous carbon foam(EDCF)structure has been successfully constructed by a simple carbonization combined with the silica microsphere template-etching process.Based on an equivalent substitute strategy,the influence of pore volume and specific surface area on the electromagnetic parameters and EMW absorption properties of the EDCF products was confirmed respectively by adjusting the addition content and diameter of silica microspheres.As a primary attenuation mode,the dielectric loss originates from the comprehensive effect of conduction loss and polarization loss in S-band and C band,and the value is dominated by polarization loss in X band and Ku band,which is obviously greater than that of conduction loss.Furthermore,in all samples,the largest effective absorption bandwidth of EDCF-3 is 7.12 GHz under the thickness of 2.13 mm with the filling content of approximately 5 wt%,covering the whole Ku band.Meanwhile,the EDCF-7 sample with optimized pore volume and specific surface area achieves minimum reflection loss(RL_(min))of−58.08 dB at 16.86 GHz while the thickness is 1.27 mm.The outstanding research results not only provide a novel insight into enhancement of EMW absorption properties but also clarify the dominant dissipation mechanism for the porous carbon-based absorber from the perspective of objective experiments.

Nitrogen-rich hierarchically porous carbon foams as high-performance electrodes for lithium-based dual-ion capacitor

Nitrogen-rich porous carbonaceous materials have shown great potential in energy storage and conversion applications due to their facile fabrication,high electronic conductivity,and improved hydrophilic property.Herein,three-dimensional porous N-rich carbon foams are fabricated through a one-step carbonization-activation method of the commercial melamine foam,and displaying hierarchically porous structure(macro-,meso-,and micro-pores),large surface area(1686.5 m2 g^-1),high N-containing level(3.3 at%),and excellent compressibility.The as-prepared carbon foams as electrodes for quasi-solid-state supercapacitors exhibit enhanced energy storage ability with 210 F g^-1 and 2.48c at 0.1 A g^-1,and150 F g^-1 and 1.77 F cm^-2 at 1 A g^-1,respectively.Moreover,as an electrode for lithium-based dual-ion capacitor,this distinctive porous carbon also delivers remarkable specific capacitance with 143.6 F g^-1 at0.1 A g^-1 and 116.2 F g^-1 at 1 A g^-1.The simple preparation method and the fascinating electrochemical performance endow the N-rich porous carbon foams great prospects as high-performance electrodes for electrochemical energy storage.

Self-Floating Efficient Solar Steam Generators Constructed Using Super-Hydrophilic N,O Dual-Doped Carbon Foams from Waste Polyester

Solar evaporation is recognized as a prospective technique to produce freshwater from non-drinkable water using inexhaustible solar energy.However,it remains a challenge to fabricate low-cost solar evaporators with obviously reduced water evaporation enthalpy to achieve high evaporation rates.Herein,N,O dual-doped carbon foam(NCF)is fabricated from the lowtemperature carbonization of poly(ethylene terephthalate)(PET)waste by melamine/molten salts at 340℃.During carbonization,melamine reacts with carboxylic acids of PET degradation products to yield a crosslinking network,and then molten salts catalyze the decarboxylation and dehydration to construct a stable framework.Owing to rich N,O-containing groups,3D interconnected pores,super-hydrophilicity,and ultra-low thermal conductivity(0.0599 W m^(−1) K^(−1)),NCF not only achieves high light absorbance(ca.99%)and solar-to-thermal conversion,but also promotes the formation of water cluster to reduce water evaporation enthalpy by ca.37%.Consequently,NCF exhibits a high evaporation rate(2.4 kg m^(−2) h^(−1)),surpassing the-state-of-the-art solar evaporators,and presents good antiacid/basic abilities,long-term salt-resistance,and self-cleaning ability.Importantly,a large-scale NCF-based outdoor solar desalination device is developed to produce freshwater.The daily freshwater production amount per unit area(6.3 kg)meets the two adults’daily water consumption.The trash-to-treasure strategy will give impetus to the development of low-cost,advanced solar evaporators from waste plastics for addressing the global freshwater shortage.

Physical and electromagnetic shielding properties of green carbon foam prepared from biomaterials

100%green carbon foam from the fibrous fruits of Platanus Orientalis-L(Plane)along with the tar oil as binder has been prepared using a powder molding technique.The objective was to develop a porous monolithic carbon from biomaterials with a considerable strength necessary for various physical,thermal and electromagnetic shielding applications.Fast carbonization was carried out at1000°C under the cover of Plane tree pyrolyzed seeds without using any external protective gas.For comparative analysis,some samples were mixed with5%(mass fraction)iron chloride during the molding process.Iron chloride being a graphitization catalyst and activating agent helped in increasing the specific surface area from88to294m2/g with a25%decrease in flexural strength.Thermal stability was improved due to the incorporation of more graphitic phases in the sample resulting in a little higher thermal conductivity from0.22to0.67W/(m·K).The catalytic carbon foam exhibited shielding effectiveness of more than20dB over the X-band frequency.Absorption was dominant with only8.26%?10.33%reflectance,indicating an absorption dominant shielding mechanism.The new material is quite suitable for high temperature thermal insulation being lightweight,highly porous with interconnected porous morphology most of which is preserved from the original biomaterial.

Three-dimensional graphitic carbon sphere foams as sorbents for cleaning oil spills

Frequent offshore oil spill accidents, industrial oily sewage, and the indiscriminate disposal of urban oily sewage have caused seri- ous impacts on the human living environment and health. The traditional oil-water separation methods not only cause easily environmental secondary pollution but also a waste of limited resources. Therefore, in this work, three-dimensional (3D) graphitic carbon sphere (GCS) foams (collectively referred hereafter as 3D foams) with a 3D porous structure, pore size distribution of 25-200 μm, and high porosity of 62vol% were prepared for oil adsorption via gel casting using GCS as the starting materials. The results indicate that the water contact angle (WCA) of the as-prepared 3D foams is 130°. The contents of GCS greatly influenced the hydrophobicity, WCA, and microstructure of the as-prepared samples. The adsorption capacities of the as-prepared 3D foams for paraffin oil, vegetable oil, and vacuum pump oil were approximately 12-15 g/g, which were 10 times that of GCS powder. The as-prepared foams are desirable characteristics of a good sorbent and could be widely used in oil spill accidents.

Carbon foams prepared from coal tar pitch for building thermal insulation material with low cost

A new approach is provided to resolve the large-scale applications of coal tar pitch. Carbon foams with uniform pore size are prepared at the foaming pressure of normal pressure using coal tar pitch as raw materials. The physical and chemical performance of high softening point pitch(HSPP) can be regulated by vacuumizing owing to the cooperation of vacuumizing and polycondensation. Results indicate that the optimum softening point and weight ratio of quinoline insoluble are about 292℃ and 65.7%, respectively. And the optimum viscosity of HSPP during the foaming process is distributed in the range of 1000-10000 Pa·s. The resultant carbon foam exhibits excellent performance, such as uniform pore structure, high compressive strength(4.7 MPa), low thermal conductivity(0.07 W·m^(-1) ·K^(-1)), specially, it cannot be fired under the high temperature of 1200 ℃.Thus, this kind of carbon foam is a potential candidate for thermal insulation material applied in energy saving building.

Preparation of Carbon Nano-fiber Washcoat on Porous Silica Foam as Structured Catalyst Support

This paper reports how a hairy layer of carbon nano-fibers can be prepared on the macro-porous silica foam produced by the sphere templating method. Firstly, three-dimensional close-packed crystals of polystyrene spheres are assembled on porous disk substrate by vacuum filtration or evaporation. The polystyrene template is annealed slightly above the glass transition temperature in order to strengthen the colloidal crystal and ensure interconnection of the spheres so as to obtain porous materials with open structure. Following the treatment of hexdecyltrimethylammonium bromide, the polystyrene template is filled with silica colloidal solution, which solidifies in the cavities. Then the polystyrene particles are removed by calcination at 843K, leaving behind porous silica foam. Scanning electron microscopy images demonstrate that silica foam has uniform and open structured pores. Nickel particles were deposited on porous silica foam layer by the dipping method and porous carbon nano-fiber washcoat was prepared by catalytic decomposition of ethene over small nickel particles.

A Molecular Foaming and Activation Strategy to Porous N-Doped Carbon Foams for Supercapacitors and CO2 Capture

Hierarchically porous carbon materials are promising for energy storage,separation and catalysis.It is desirable but fairly challenging to simultaneously create ultrahigh surface areas,large pore volumes and high N contents in these materials.Herein,we demonstrate a facile acid-base enabled in situ molecular foaming and activation strategy for the synthesis of hierarchically macro-/meso-/microporous N-doped carbon foams(HPNCFs).The key design for the synthesis is the selection of histidine(His)and potassium bicarbonate(PBC)to allow the formation of 3D foam structures by in situ foaming,the PBC/His acid-base reaction to enable a molecular mixing and subsequent a uniform chemical activation,and the stable imidazole moiety in His to sustain high N contents after carbonization.The formation mechanism of the HPNCFs is studied in detail.The prepared HPNCFs possess 3D macroporous frameworks with thin well-graphitized carbon walls,ultrahigh surface areas(up to 3200 m^2 g^-1),large pore volumes(up to 2.0 cm^3 g^-1),high micropore volumes(up to 0.67 cm^3 g^-1),narrowly distributed micropores and mesopores and high N contents(up to 14.6 wt%)with pyrrolic N as the predominant N site.The HPNCFs are promising for supercapacitors with high specific capacitances(185-240 F g^-1),good rate capability and excellent stability.They are also excellent for CO2 capture with a high adsorption capacity(~4.13 mmol g^-1),a large isosteric heat of adsorption(26.5 kJ mol^-1)and an excellent CO2/N2 selectivity(~24).

Preparation and Morphological Study of Coal-tar-based Carbon Foam

A novel process for fabricating coal-tar pitch derived carbon foam was introduced. The coal-tar based mesophase pitch was characterized by Infrared Spectrum and Wide Angle X-ray Diffraction. Scanning Electron Microscope was used for the morphological study of carbon foam. The results showed that the pitch foam with pores of 300 -500 μm and low density of 0.2-0.5 g/cm^-3 could be successfully fabricated and further carbonized and graphtized to obtain a novel carbon foam

Carbon Foam Anode Modified by Urea and Its Higher Electrochemical Performance in Marine Benthic Microbial Fuel Cell

Electrode materials have an important effect on the property of microbial fuel cell(MFC). Carbon foam is utilized as an anode and further modified by urea to improve its performance in marine benthic microbial fuel cell(BMFC) with higher voltage and output power. The electrochemical properties of plain carbon foam(PC) and urea-modified carbon foam(UC) are measured respectively. Results show that the UC obtains better wettability after its modification and higher anti-polarization ability than the PC. A novel phenomenon has been found that the electrical potential of the modified UC anode is nearly 100 m V lower than that of the PC, reaching-570 ±10 m V(vs. SCE), and that it also has a much higher electron transfer kinetic activity, reaching 9399.4 m W m-2, which is 566.2-fold higher than that from plain graphite anode(PG). The fuel cell containing the UC anode has the maximum power density(256.0 m W m-2) among the three different BMFCs. Urea would enhance the bacteria biofilm formation with a more diverse microbial community and maintain more electrons, leading to a lower anodic redox potential and higher power output. The paper primarily analyzes why the electrical potential of the modified anode becomes much lower than that of others after urea modification. These results can be utilized to construct a novel BMFC with higher output power and to design the conditioner of voltage booster with a higher conversion ratio. Finally, the carbon foam with a bigger pore size would be a potential anodic material in conventional MFC.

Effect of Ultrasonication on the Properties of Multi-walled Carbon Nanotubes/Hollow Glass Microspheres/Epoxy Syntactic Foam

Multi-walled carbon nanotubes（MWCNTs） reinforced hollow glass microspheres（HGMs）/epoxy syntactic foam was fabricated. The effects of ultrasonication on the density, compression strength, and water absorption properties were studied. Better dispersed MWCNTs can be obtained after ultrasonication treatment, but an increasing viscosity will lead to a larger amount of voids during syntactic foam preparation especially when the content of HGMs is more than 70 vol%. The existing voids will decrease the density of epoxy syntactic foam. However, the ultrasonication does not change the compression strength much. Ultrasonication treatment will decrease the water absorption content due to the better dispersion and hydrophobic properties of MWCNTs. But a significant increase of water absorption content occurs when HGMs is more than 70 vol%, which is attributed to the higher viscosity and larger amount of voids.