Carbonization of Graphene-Doped Isocyanate-Based Polyimide Foams to Achieve Carbon Foams with Excellent Electromagnetic Interference Shielding Performance

Lightweight carbon foams with excellent electromagnetic interference (EMI) shielding performance were prepared by carbonization process, using isocyanate-based polyimide foams as carbon precursors. The influence of carbonization temperature and graphene-doping on the morphological, electrical and EMI shielding effectiveness (SE) of corresponding carbon foams was studied in detail. Results showed that the addition of graphene was beneficial to the improvement of electrical conductivity and EMI shielding performance of carbon foams. The electrical conductivity of carbon foams increased with the carbonization temperature which was related to the increase of graphitization degree. Collapse of foam cells was observed at higher carbonization temperatures, which was detrimental to the overall EMI SE. The optimal carbonization temperature was found at 1100 °C and the carbon foams obtained from 0.5 wt% graphene-doped foams exhibited a specific EMI SE of 2886 dB/(g/cm3), which shows potential applications in fields such as aerospace, aeronautics and electronics.

Prospects for obtaining phenol-formaldehyde oligomers

The article provides an overview of recent studies in the development of new methods for the synthesis and use of phenolformaldehyde oligomers. Prospects for carrying out scientific work in this direction, associated with the availability of raw materials, technological and applied aspects, have been substantiated. The main areas of application of phenolic resins have been identified. Special attention is paid to coatings, adhesives, binders, as well as carbon foams based on them. New methods for the modification of phenol-formaldehyde oligomers are described, as well as new compositions of modifying agents for the purposeful change in the complex of their properties.

Immobilization of mercury in contaminated soils through the use of new carbon foam amendments

Background Mercury (Hg) is recognized as one of the 10 most toxic elements in nature and is much more persistent in soils than in other environmental compartments. However, an effective, environmentally friendly, economical, and large-scale applicable technology for the remediation of soils contaminated by Hg has not yet been established. This study evaluates the feasibility of a new carbon foam-based product for the remediation of three soils contaminated with Hg, and infers the mobilization or immobilization mechanism through a detailed study of Hg speciation. Results Soil treatment with carbon foams, one of them impregnated with goethite, reduced Hg availability by 75–100%. The proportion of mercury associated to humic acids (Hg–HA) determined the mobility and the availability of Hg when soils were treated with carbon foams. The drop of pH promotes changes in the structure of HA, a consequence of which is that Hg–HA becomes part of the unavailable fraction of the soil along with HgS. The carbon foam impregnated with goethite did not mobilize Fe as occurred with zero valence iron nanoparticles. The presence of acidic groups on the surface of the foam (carboxyl, quinone and phenolic groups) can strongly improve the binding of metal cations, enhancing Fe immobilization. Conclusions A novel carbon foam-based amendment was efficient in immobilizing Hg in all the soils studied. The carbon foam impregnated with goethite, in addition to not mobilizing Fe, had the additional advantage of its low effect on the electrical conductivity of the soil. This novel approach could be considered as a potential amendment for other industrial and/or abandoned mining areas contaminated with Hg and/or other metal(loid)s.

Immobilization of mercury in contaminated soils through the use of new carbon foam amendments

Background: Mercury (Hg) is recognized as one of the 10 most toxic elements and is much more persistent in soils than in other environmental compartments. However, an effective, environmentally friendly, economical, and applicable at large-scale technology for the remediation of soils contaminated by Hg has not yet been established. This study evaluates the feasibility of a new carbon foam-based product for the remediation of three soils contaminated with Hg, and infers the mobilization or immobilization mechanism through a detailed study of Hg speciation. Results: Soil treatment with the carbon foams, one of them impregnated with goethite, reduced Hg availability by between 75 and 100%. Mercury associated to humic acid (Hg-HA) determined the proportion of mobility and availability of Hg when soils were treated with carbon foams. When the pH dropped, the structure of HA changed causing the Hg-HA to become part of the unavailable fraction of the soil along with HgS. The carbon foam impregnated with goethite did not mobilize Fe as occurred with ZVI nanoparticles. The presence of acid groups on the surface of the foam (carboxyl, quinone and phenolic groups) can bind metal cations strongly improving Fe immobilization. Conclusions: A novel carbon foam-based amendment was efficient in immobilizing Hg in all the soils studied. The carbon foam impregnated with goethite, in addition to not mobilizing Fe, had the additional advantage of its lesser effect on the electrical conductivity of the soil. This novel approach could be considered as a potential amendment for other sites contaminated with Hg and/or other metal(loid)s.