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1.6 Million metric tons of spent carbon electrodes modify carbon-rich solid wastes from aluminum electrolysis are produced annually, threatening ecosystems by cyanide and fluoride pollution. Here, we review carbon-rich solid wastes with focus on sources and hazards, detoxification, separation, recovery, recycling and disposal. Treatment techniques include roasting, calcination, vacuum distillation, flotation, water leaching, acid leaching, alkali leaching, complexation leaching, and alkali fusion. Waste can be disposed of alone or in combination with other waste such as cooper slag, sludge, red mud, and coal gangue. Recovery of fluorides and applications of recycled carbon are presented. Fluoride and carbon materials are separated based on differences in hydrophobicity, volatility, flammability, acidity, and alkalinity. The fluorides prepared from the solution are mainly aluminum hydroxyfluoride hydrate and cryolite. [ABSTRACT FROM AUTHOR]

The development of highly thermally conductive composites that combine visible light/infrared camouflage and information encryption has been endowed with great significance in facilitating the application of 5G communication technology in military fields. This work uses aramid nanofibers (ANF) as the matrix, hetero‐structured silver nanowires@boron nitride nanosheets (AgNWs@BNNS) prepared by in situ growth as fillers, which are combined to fabricate sandwich structured thermally conductive and electrically insulating (BNNS/ANF)‐(AgNWs@BNNS)‐(BNNS/ANF) (denoted as BAB) composite films by "filtration self‐assembly, air spraying, and hot‐pressing" method. When the mass ratio of AgNWs@BNNS to BNNS is 1 : 1 and the total mass fraction is 50 wt %, BAB composite film has the maximum in‐plane thermal conductivity coefficient (λ∥ of 10.36 W/(m ⋅ K)), excellent electrical insulation (breakdown strength and volume resistivity of 41.5 kV/mm and 1.21×1015 Ω ⋅ cm, respectively) and mechanical properties (tensile strength of 170.9 MPa). 50 wt % BAB composite film could efficiently reduce the equilibrium temperature of the central processing unit (CPU) working at full power, resulting in 7.0 °C lower than that of the CPU solely integrated with ANF directly. In addition, BAB composite film boasts adaptive visible light/infrared dual camouflage properties on cement roads and jungle environments, as well as the function of fast encryption of QR code information within 24 seconds. [ABSTRACT FROM AUTHOR]

Overhaul slag, aluminum ash, and carbon slag produced by the electrolytic aluminum process are typical hazardous wastes, which contain a large amount of valuable elements such as A1 and F, and have the dual attributes of environmental pollution and resource recovery. The classification and characteristics of typical hazardous wastes generated from aluminum electrolysis are summarized. Furthermore, the research progress of green and clean recycling methods for typical hazardous wastes in aluminum electrolysis is described. The advantages and disadvantages of flotation and chemical leaching methods are emphatically introduced. Finally, the development trend and direction of recycling technologies for typical hazardous waste in aluminum electrolysis are proposed. [ABSTRACT FROM AUTHOR]

Highlights: m-BN/PNF nanocomposite paper with nacre-mimetic layered structures prepared via sol–gel film transformation approach presents excellent thermal conductivity, incredible electrical insulation, outstanding mechanical property and thermal stability. When the mass fraction of m-BN is 50 wt%, m-BN/PNF nanocomposite paper exhibits excellent thermal conductivity and electrical insulation. The λ∥ and λ⊥ are 9.68 and 0.84 W m−1 K−1, and the volume resistivity and breakdown strength are as high as 2.3 × 1015 Ω cm and 324.2 kV mm−1, respectively. The m-BN/PNF nanocomposite paper with 50 wt% m-BN also presents outstanding mechanical properties (tensile strength of 193.6 MPa) and thermal stability (thermal decomposition temperature of 640 °C). With the rapid development of 5G information technology, thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent. In this work, "high-temperature solid-phase & diazonium salt decomposition" method is carried out to prepare benzidine-functionalized boron nitride (m-BN). Subsequently, m-BN/poly(p-phenylene benzobisoxazole) nanofiber (PNF) nanocomposite paper with nacre-mimetic layered structures is prepared via sol–gel film transformation approach. The obtained m-BN/PNF nanocomposite paper with 50 wt% m-BN presents excellent thermal conductivity, incredible electrical insulation, outstanding mechanical properties and thermal stability, due to the construction of extensive hydrogen bonds and π–π interactions between m-BN and PNF, and stable nacre-mimetic layered structures. Its λ∥ and λ⊥ are 9.68 and 0.84 W m−1 K−1, and the volume resistivity and breakdown strength are as high as 2.3 × 1015 Ω cm and 324.2 kV mm−1, respectively. Besides, it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640 °C, showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment. [ABSTRACT FROM AUTHOR]

A sol–gel film transformation and spraying approach has been developed to fabricate double-layered PBO nanofiber (PNF) nanocomposite paper nanocomposite paper. The construction of stable double-layered structures and nanofiber networks with extensive hydrogen bonds and coordination bonds led to ultraflexibility and excellent folding endurance of the nanocomposite paper. In addition, the nanocomposite paper possessed high wave-transparent coefficient, super-hydrophobicity, and self-cleaning performances. [Display omitted] Poly(p -phenylene-2,6-benzobisoxazole) nanofiber (PNF) paper is facing unprecedented challenges in enhancing the interaction between the PNFs and improving its hydrophobicity. In this work, a sol–gel film transformation approach was developed to fabricate high-strength PNF paper. Iron ions formed coordination bonds between PNFs to obtain a preforming three-dimensional, interconnective nanofiber network. Subsequently, polytetrafluoroethylene (PTFE) particles were sprayed onto the surface of the paper, followed by thermal treatment to obtain double-layered PTFE-P/PNF nanocomposite paper. The nanocomposite paper presents incredible tensile strength (271.6 MPa, increased by 52.9%), folding endurance, super-hydrophobicity, and self-cleaning performances. Moreover, it exhibits low dielectric constant (2.06) and dielectric loss tangent (0.0133) values. According to the wave-transparent model for a double-layered dielectric established by Maxwell's equations, the wave-transparent coefficients of electromagnetic waves incident from both sides of the paper are 97.6% (PNF side) and 96.0% (PTFE/P(S- co -BCB- co -MMA) side), respectively. The PTFE-P/PNF nanocomposite paper possesses great potential in the fields of wave-transparent applications. [ABSTRACT FROM AUTHOR]

NiFe layer double metal hydroxide nanosheets (NiFe LDHs) have been extensively investigated as one of the best promising candidates to construct efficient bifunctional catalysts. In this research, element (vanadium) doping into NiFe LDHs grown in nickel foam were synthesized by the one-step method and applied in overall water splitting. The content and structure of the composites were adjusted to regulate the catalyst's electronic structure and reduce the onset potential and achieved unprecedented electrocatalysis for OER and HER. The V-NiFe-LDH/NF showed perfect OER and HER activities with low Tafel slopes of 31.3 and 89.8 mV dec−1, and small overpotentials of 195 and 120 mV at 10 mA cm−2 in 1.0 m KOH solution, respectively. Electrochemical analysis indicated that the efficient catalytic activity of V-NiFe-LDHs/NF mainly benefited from V doping, which optimized the electronic structure and produce defects, thereby resulting in an enhanced conductivity, facile electron transfer, and adequate active sites. [ABSTRACT FROM AUTHOR]

Modified bisphenol A dicyanate ester (m-BADCy) wave-transparent laminated composites reinforced with functionalized poly(p-phenylene-2,6-benzobisoxazole) (f-PBO) fibers were fabricated using an optimized method of impregnation-winding followed by lamination-molding. m-BADCy was synthesized from copolymerization between (2-((3-trifluoromethyl)phenoxy)methyl)oxirane and the BADCy matrix. f-PBO fibers were obtained by modifying with lysozyme followed by polyhedral oligomericsilsesquioxane (POSS). Lysozyme was coated on the surface of PBO fibers (PBO@lysozyme) and polyhedral oligomericsilsesquioxane (POSS) was grafted onto the PBO@lysozyme fibers (POSS-g-PBO@lysozyme, f-PBO fibers). The dielectric constant (ε), 2.81, and dielectric loss (tan δ), 0.0028, for f-PBO fiber/m-BADCy wave-transparent laminated composites were lower than those of PBO fiber/m-BADCy wave-transparent laminated composites (ε = 2.91 and tan δ = 0.0043). The interlaminar shear strength (ILSS) and the flexural strength of the f-PBO fiber/m-BADCy wave-transparent laminated composites were significantly increased to 47.6 and 805.8 MPa, increased by 23.0% and 33.5% in comparison to those of PBO fiber/m-BADCy wave-transparent laminated composites (ILSS = 38.7 MPa and flexural strength = 603.5 MPa), respectively. In addition, the corresponding heat resistance index (THRI, representing thermal stability) and glass transition temperature (Tg) of the f-PBO fiber/m-BADCy wave-transparent laminated composites were 228.3 and 252.1 °C, respectively. [ABSTRACT FROM AUTHOR]

The enhancement of electromagnetic wave absorption at high‐temperature as well as oxidation is cutting‐edge issue in current electromagnetic functional materials due to the strong demand of stealth aircrafts or aero‐engines working in harsh environments. In this contribution, the excellent electromagnetic wave absorption at 1158 K (885 °C) with a minimum reflection coefficient (RCmin) of −12.62 dB and a wide effective absorption bandwidth (RCmin < –10 dB) of 3.2 GHz was achieved on iron‐containing siliconboron carbonitride (SiBCN) monolithic ceramics by using polymer‐derived ceramics (PDC) route, setting a new record for EM wave absorption materials at high‐temperature. In addition, these materials exhibited desirable mechanical properties and excellent high‐temperature resistance until 1400 °C in argon atmosphere and 885 °C in air atmosphere, respectively. This ingenious strategy is generally benefiting the promotion of EM wave absorption materials with great potential in antenna housings, radomes, areo‐engines, and stealth aircrafts in harsh environments. [ABSTRACT FROM AUTHOR]

In this contribution, we present a new strategy for the fabrication of modified cyanate ester resins combined with ultralow dielectric properties, improved mechanical properties and high thermal and dimensional stabilities. The fluoride-containing compound 2-((3-(trifluoromethyl)phenoxy)methyl)oxirane (TFMPMO), synthesized from m-(trifluoromethyl)phenol (TFMP) and epichlorohydrin (ECH), was used to modify bisphenol A dicyanate ester (BADCy) resins via copolymerization reaction. The BADCy resin modified with 15 wt% TFMPMO presented ultralow dielectric constant (ε, 2.75) and dielectric loss tangent values (tan δ, 6.7 × 10−3), high mechanical properties (impact strength of 15.4 kJ m−2 and flexural strength of 141.0 MPa), and superior thermal and dimensional stability (THeat-resistance index of 206 °C and coefficient of thermal expansion of 6.4 × 10−5), and it possesses great potential application in radomes and antenna systems of aircraft. [ABSTRACT FROM AUTHOR]

In this paper, we presented a new strategy for fabrication of polymeric composites combined with low dielectric loss and desirable thermal conductivity. With the incorporation of hyperbranched polyborosilazane (hb-PBSZ) into bisphenol A cyanate ester (BADCy) matrix, the modified hb-PBSZ/BADCy resin with 4 wt% hb-PBSZ possessed a low dielectric constant (?) value of 2.37 and relatively low dielectric loss tangent value of 0.008 at 1MHz. Furthermore, by integrating micrometer boron nitride particles (mBN) into hb-PBSZ/BADCy matrix, the mBN/hb-PBSZ/BADCy composites presented relatively low ? of 3.09, desirable thermally conductive coefficient (? of 0.63 W/(m?K)) and thermal diffusivity (? of 0.42 mm2/s) values. It provides an important perspective for designing dielectric and thermally conductive polymeric composites for electrical packaging and energy storage fields. [ABSTRACT FROM PUBLISHER]

Epoxy-capped polyhedral oligomeric silsesquioxane (EP-POSS) is performed to modify bisphenol A cyanate ester (BADCy) to regulate its dielectric constant and thermal resistance. EP-POSS can be incorporated in the cross-linked network of BADCy via covalent bonds, which catalyzes BADCy self-polymerization to decease the initial temperature of forming triazine rings. EP-POSS is distributed in the BADCy matrix uniformly and there is no aggregation and phase separation between EP-POSS and BADCy matrix at a micrometer scale. The dielectric constant values of EP-POSS/BADCy are decreased with the addition of EP-POSS, but increased slightly when the mass fraction of the EP-POSS is more than 2 wt%. The thermal resistance of EP-POSS/BADCy is increased slightly with the addition of EP-POSS. [ABSTRACT FROM AUTHOR]

Quartz fibers (QFs) and two polyhedral oligomeric silsesquioxane (POSS) (epoxy-POSS and hydroxy-POSS) are performed to regulate the dielectric properties, heat resistance, and mechanical properties of cyanate ester (CE) resins. With the introduction of POSS, the dielectric constant and dielectric loss tangent values of the POSS/QFs/CE laminated composites are decreased obviously. The heat resistance properties and flexural strength values of the laminated composites are increased, but the interlaminar shear strength values of the laminated composites are decreased slightly. The EP-POSS/QFs/CE laminated composites have relatively better dielectric, heat resistance, and mechanical properties than those of HO-POSS/QFs/CE laminated composites. POLYM. COMPOS., 36:2017-2021, 2015. © 2014 Society of Plastics Engineer [ABSTRACT FROM AUTHOR]

A new series of liquid crystal (LC) monomers – not only contain a double bond but also contain an azo group – were designed and synthesised. The length of side groups in the LC monomers containing azobenzene ester varied from 1 to 2 methylene units, and the length of the substituted groups in the main chain varied from 1 to 3 methylene units. The molecular structures of the intermediates and target compounds were confirmed by Fourier transform infrared, ultraviolet and visible spectrum and nuclear magnetic resonance (NMR) spectroscopy. The thermal phase behaviour of the LC monomers was investigated by polar optical microscopy coupled with hot stage and differential scanning calorimetry (DSC). In this paper, the effect on the LC zone with the substituents were investigated, and with the increased methylene of main chain, the melting point and the phase transition temperature of the substance will be lowered and LC regions will be narrower. [ABSTRACT FROM AUTHOR]

The surface of high modulus poly( p-phenylene-2,6-benzobisoxazole) (HMPBO) fibers were treated by the combination method of oxygen plasma/polyhedral oligomeric silsesquioxane (POSS). The chemical compositions and surface morphologies of HMPBO fibers were characterized by Fourier transform infrared, X-ray photoelectron spectroscopy, thermogravimetric analyzer, and scanning electron microscopy. The interfacial shearing strength (IFSS) of the HMPBO/cyanate ester (HMPBO/CE) micro-composites was measured by single fiber pull out test. Results showed that the POSS was grafted on the surface of HMPBO fibers, and the grafting amount was about 0.82 wt%. After the treatment, the HMPBO fibers became coarser and the diameter was also increased. Compared with that of pure HMPBO/CE micro-composites, the IFSS of treated HMPBO/CE micro-composites was increased by 20.7%. POLYM. COMPOS., 34:2026-2030, 2013. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A new series of nematic liquid crystal (LC) monomers containing double bonds in the side chain were designed and synthesized via the Steglich esterification reaction. Length of the side groups varied from 1 to 2 methylene units. The molecular structures of the intermediates and the LC monomers were confirmed by Fourier transform infrared spectrum, elemental analysis, and nuclear magnetic resonance spectroscopy. The thermal phase behavior of the LC monomers was investigated by differential scanning calorimetry and polar optical microscopy coupled with hot stage. All of these LC monomers showed only one nematic mesophase at room temperature during the cooling process. [ABSTRACT FROM PUBLISHER]

Two nematic liquid crystal (LC) monomers containing double bonds in the side chain were designed and synthesised. Length of the side groups varied from 1 to 2 methylene units. The side-chain polymers were synthesised by hydrosilylation reaction. The molecular structures of the intermediates and the LC monomers were characterised by Fourier transform infrared, elemental analysis and nuclear magnetic resonance spectroscopy. The thermal phase behaviour of the monomers and polymers were investigated by differential scanning calorimetry and polar optical microscopy coupled with hot stage. The LC monomers showed only one nematic mesophase in the cooling process. And, the two polymers exhibit an enantiotroppic nematic mesophase either in the heating or in the cooling process. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the performance of aluminum borate whisker reinforced cyanate ester resin. Gel time and differential scanning calorimeter (DSC) were considered in investigating the effect of coupling agent and content of whisker on reaction activity. The authors also studied the thermal stability, mechanical properties, and hot-wet resistance of a resin system.