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• Proposing a co-pyrolysis model of oil shale with biomass. • Constructing more than 10 pathways and reaction kinetics equations. • The distributions of the products were accurately predicted using this model. In order to fill in the blank of the prediction model about the co-pyrolysis of oil shale with biomass, we proposed a novel co-pyrolysis model based on chemical structure using improved chemical percolation devolatilization ( CPD ) with chain reaction kinetics ( CRK ). Three basic elements of aromatic cluster, aliphatic bridge, and oxygen-containing bridge are chosen as the representative structure units for building the simplified pseudo-grid model. According to the pyrolysis characteristic, we divided the model to five processes: the breakage of bridge bonds, the adsorption of free radicals, the reaction of aliphatic chains, the aromatization reaction and the cross-linking reaction, and described it through 14 reaction pathways and 18 reaction kinetic equations. The predicted results are compared with experimental results of fixed bed and thermogravimetry ( TG ) analysis, while the error is within a reasonable range indicating the accuracy and rationality of our model. We believe that this paper provides a deep understanding of the co-pyrolysis processes and discovery of the distribution characteristics of different kinds of pyrolytic intermediates and free radicals at an atomic level beyond what laboratory experiments could achieve. [ABSTRACT FROM AUTHOR]

High dielectric permittivity (ε) but low loss polymeric composites have presented wide applications. To elevate the overall dielectric performances in raw zinc oxide (ZnO)/polyvinylidene fluoride (PVDF), the prepared aluminum oxide (Al 2 O 3) encapsulated ZnO core-shell particles were incorporated into the polypropylene (PP) modified PVDF blend to generate high ε and breakdown strength (E b) but low loss nanocomposites. The Al 2 O 3 shell' impacts on the dielectric performances of the ZnO/PVDF-PP were investigated. The results indicate that the insulating Al 2 O 3 shell induces concurrent interparticle polarization and intraparticle polarization leading to evidently enhanced ε , and effectively restrains the leakage current resulting in simultaneously suppressed loss and elevated E b in the nanocomposites. Further, the introduced alumina shell can induce traps and capture charge carrier thus resulting in enhanced E b. Through facilitating the intra-particle polarization and repressing the charge migration, the 50 wt% ZnO@Al 2 O 3 /PP-PVDF present a much higher ε (16) and E b (11 kV/mm) but lower dielectric loss (0.08), respectively, far exceeding 9.6, 9 kV/mm and 0.18 at 100 Hz for the unmodified ZnO nanocomposites. Further, the dielectric parameters of the nanocomposites can be effectively tuned via tailoring the Al 2 O 3 shell thickness. The fitting via the Havriliak-Negami equation theoretically interpret the experimental results and uncover the underlying multiple polarization mechanisms. This work provides deep insight into the design and development of flexible polymeric nanodielectrics with eminent integrated dielectric properties for appealing applications in electronic device and power system. [ABSTRACT FROM AUTHOR]

Anomalous dielectric relaxation appears in Nb-doped SrTiO 3 (SNT) single crystal with relaxation rate displaying unusual slowing down with increasing temperature. Dielectric measurements show that the resistivity increases with temperature. Raman spectrum and the spherical aberration-corrected transmission electron microscope (STEM) show the existence of polar nano regions (PNRs) in the crystal. The temperature-dependence of DC conductivity and current-voltage (I–V) curves suggest that this anomalous behavior happens at the interfaces of PNRs. The evolution of the anomalous relaxation peak in the annealed samples indicates that this effect is simultaneously affected by the carrier concentration and the interface structure. The anomalous dielectric relaxation is reminiscent of the positive temperature coefficient of resistance (PTCR) effect in a polycrystalline material. The resistive switching effect makes such materials to have potential application value in switches, sensors, and device miniaturization. [ABSTRACT FROM AUTHOR]

To reveal the co-pyrolysis characteristics of oil shale mixing with wheat straw in different reaction steps, three temperature stages of 348 °C-T 1 , 476 °C-T 2 and 521°C-T 3 , which were obtained through the thermogravimetric analysis results, were chosen as the collection temperature of the liquid products. The volatiles of each temperature stage would be condensed and collected separately and successively for the depiction of the detailed co-pyrolysis characteristics. Through the comprehensive analysis of the product distributions and their GC-MS, NMR experimental results, the main formation temperature stages of the co-pyrolysis products are T 1 and T 2 respectively. The synergistic effects of T 1 stage mainly consist of the catalytic effect of minerals in oil shale and the effect of micro-molecule free radicals on kerogen macromolecular restructuring process, while the synergistic effect of T 2 stage comes from the catalysis of bio-char on the cracking process of the critical bitumen. Moreover, the synergistic effects significantly enhanced the H/C atomic ratio from 1.571 to 1.668 in bio-oil, causing a transfer of oxygen from pyrolytic oil to pyrolysis gas and promoting the generation of long straight carbon chains in shale oil. • A hierarchical collection method for pyrolysis continuity is proposed. • Combination of GC-MS, NMR and TG experiment for constructing the co-pyrolysis process. • The synergistic effects of different temperature stage were obtained. [ABSTRACT FROM AUTHOR]

Polymeric dielectrics with large dielectric constants (ε) and breakdown strength (E b) coupled with low loss are highly pursued in modern electrical power systems. To synergistically bolster the ε and E b and restrain the dielectric loss in the barium strontium titanite (BST)/poly(vinylidene fluoride, PVDF), in this research, a crystalline titanium dioxide (TiO 2) shell was introduced onto the BST to generate PVDF nanocomposites with high ε and E b but low loss. The findings show that, in comparison to pure BST/PVDF, the BST@TiO 2 /PVDF nanocomposites present largely enhanced ε , higher E b and suppressed dielectric loss. The elevated ε results from the synergistic promotion of inter-particle and intra-particle polarizations in the nanocomposites. The TiO 2 shell as a buffer layer availably mitigates the interface mismatch in dielectric parameters between BST and PVDF, thereby heightening the E b. Additionally, by precisely controlling the TiO 2 shell thickness, the best dielectric performances of the nanocomposites can be realized at low filler loadings. The underlying multiple polarization mechanisms are theoretically revealed by analyzing the dielectric data using the Havriliak-Negami equation. The present work provides new insight and paradigm for the design of polymeric dielectrics possessing simultaneously high ε and E b yet low loss for applications in electrical power systems. [Display omitted] • The BST@TiO 2 /PVDF nanocomposites present superior overall dielectric properties than unmodified BST/PVDF. • Fast intra-particle polarization and slow inter-particle polarization are enhanced and can be tuned by the TiO 2 shell thickness. • The simulation reveals the BST@TiO 2 structure's influence on enhanced permittivity and suppressed loss. • The enhanced polarization in BST@TiO 2 /PVDF is contributed by a fast intra-particle polarization and a slow inter-particle polarization. [ABSTRACT FROM AUTHOR]

Polymer dielectrics with a high dielectric constant (high ε), low dielectric loss and high thermal conductivity (k) are constantly pursued for advanced electrical power systems, driven by the continuous demands of device miniaturization and high operating temperature. In this paper, we present an effective approach to concurrently improve the dielectric properties and thermal conductivity of composites by tailoring filler interface. Core@double-shell structured aluminum particles are synthesized, with the metallic aluminum core encapsulated by a double-shell of amorphous and crystalline aluminum oxide. The double-shell filler structure enables a substantial increase in dielectric constant and reduction in dielectric loss for the corresponding composites, surpassing the performance of the unfilled polymer and the polymer composites containing the single-shell fillers. The improved dielectric properties can be attributed to the enhanced interfacial polarization. Furthermore, the thermal conductivity of the composites is also significantly improved when the low- k amorphous aluminum oxide shell is transformed into its crystalline phase with high thermal conductivity. [ABSTRACT FROM AUTHOR]

Different oxygen treatment methods, including O 2 and N 2 annealing, were conducted on Ca 0.6 Sr 0.4 TiO 3 (CST) ceramics with varying Mn content (0 mol%, 0.5 mol% and 2.0 mol%). Structure characterization, including XRD and SEM, indicated the minimal effect of annealing on the microstructure. Grain boundaries were found to be sensitive to oxygen treatments, and annealing in O 2 resulted in increased grain boundary resistance, while in N 2 led to the opposite result. The insulating properties of bulk ceramics were found to be dominated by grain boundaries. Both the concentration and mobility of oxygen vacancies were confirmed to affect the energy storage properties to some extent in this work. [ABSTRACT FROM AUTHOR]

• Achieving a deeper investigation of thermochemical transformation of organic carbon during the oil shale retorting. • The enhancement role of H free radical in the pyrolysis of oil shale was investigated. • The effect of functional groups has been studied using DFT theory . • The schematic energy profiles for each reaction route were obtained. In this paper, the authors conduct an in-depth investigation for the thermochemical reaction of organic carbon and H free radical during oil shale retorting process. A set of carbon chain and reaction models were constructed and calculated through the transition state theory (TST) of quantum chemistry with Gaussian-16 package. The effect of functional groups during the reactions was explored through the density functional theory (DFT) at the B3LYP/6-311G (d) level. To make the calculation results more trustful and reliable, we choose reasonably simplified straight carbon chain models and construct the corresponding multiple reaction paths, which could elucidate the mechanisms of the thermochemical reaction. In the presence of H free radical, the cracking process of carbon chains in kerogen is promoted because of lower energy barriers. The charge re-distribution causing by the functional group also changes the H adsorption capacity of the organic carbons in different positions (α, β, γ, etc.). Moreover, different measuring methods of the rate constants are evaluated in this paper. The results could provide direct insight into the limitation of the conventional transition state theory (TST), which deserves more attention in further theoretical research. [ABSTRACT FROM AUTHOR]