Search

Low power density and low heating rate are the key constraints for the development of conductive polymer materials in the field of electric heating. The carbon nanotubes (CNTs)–graphene (GR)–polydimethylsiloxane (PDMS) composite film was prepared by vacuum filtration and spin coating to solve the problem in this study. Moreover, an AC electric field was used to orient the CNTs to enhance the electrothermal performance. The structure and properties of composite films were analyzed. The results show that the composite film with CNT:GR = 2:1 has the lowest permeation threshold, and can heat up within 30 s and stabilize at 260 °C at 10 V. The electric field-oriented CNTs reduced the insulating polymer layer, increasing the heating rate of the composite film by 1.2 times, and increasing the theoretical thermal conductivity. The flexible electrothermal composite film prepared in this study can be used in thermal insulation, deicing, and wearable electronic devices. [ABSTRACT FROM AUTHOR]

In order to study the role of metal sodium in the spray pyrolysis of biomass tar, this paper designs a sodium-containing naphthalene pyrolysis system (NSS) and a pure naphthalene pyrolysis system (PNS) using naphthalene as the carbon source and sodium chloride as the sodium metal donor for comparison. This enables an exploration of the effect of sodium on the initial nucleation of carbon fumes formed by naphthalene pyrolysis using reaction molecular dynamics (ReaxFF MD). The simulation results show that NSS undergoes pyrolysis reactions earlier and faster than PNS at the same temperature. Simulated at 3250 K temperature for 2 ns, the naphthalene pyrolysis consumption rate of the NSS was faster than that of the PNS, and the addition of sodium atoms during the condensation process provided more active sites and accelerated the condensation of macromolecular products. Moreover, Na+ and carbon rings form a Na+-π structure to promote the bending of graphite lamellae to facilitate the formation of carbon nuclei. Molecular dynamics simulations were used to simulate the formation of carbon nuclei during the initial stage of naphthalene pyrolysis, revealing that the mechanism of sodium salt catalyzed the acceleration of organic matter pyrolysis from a microscopic visualization perspective. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) pollution from coal combustion is a leading contributor to the influence of atmospheric visibility, photochemical smog, and even global climate. A drop tube furnace was employed to explore the effects of temperature and chemical speciation of mineral elements on PM formation during the combustion of Zhundong coal. Chemical fractionation analysis (CFA), X-ray fluorescence (XRF), and inductively coupled plasma-atomic emission spectrometry (ICP-AES) were used to investigate the chemical and physical characteristics of the solid samples. It can be indicated that the combustion of similarly sized coal particles yielded more PM10 when the combustion temperature was increased from 1000 to 1400 °C. Zhundong coal is fractionated with deionized water, ammonium acetate, and hydrochloric acid, and pulverized coal, after fractionation, is burned to study the influence of mineral elements with different occurrence forms, such as water-soluble mineral elements, exchangeable ion elements, hydrochloric acid soluble elements and acid-insoluble elements, on the formation of particles. The results show that water-soluble salts play an important role in forming ultrafine particles (PM0.2); Fe, Ca, and other elements in organic form are distributed in flue gas through evaporation during pulverized coal combustion. When the flue gas temperature decreases, PM1 is formed through homogeneous nucleation and heterogeneous condensation, resulting in the distribution of these two elements on PM1. Different fractionation methods do not significantly affect the distribution of Si and Al in the PM1–10 combustion process. [ABSTRACT FROM AUTHOR]

This study presented new field measurement data on the particle size distributions, morphological characteristics, and elemental composition of particulate matter (PM)2.5 (particle diameter less than 2.5 mm) from 12 industrial boilers, including eight circulating fluidized bed boilers (CFB) and four bubbling fluidized bed boilers (BFB). Measurement in situ was taken with an electrical low-pressure impactor equipped with a two-stage dilution sampling system. Morphological characteristics were determinded by electron microscope (SEM), and elemental compositions of the samples were determinded by X-ray fluorescence (XRF) and inductively coupled plasma (ICP). The results show that before and after the dust removal, the number concentration distributions of PM2.5 display bimodal distributions, one peak is between 0.07 and 0.12 μm, and the other peak is between 0.32 and 0.48 μm. And the particle concentrations of PM2.5 depended mainly on submicron particles (less than 1 µm in diameter), formed by gasification-condensation mechanisms. The mass concentration distributions of PM2.5 showing no peak distribution and increase with the particle size. Compared to electrostatic precipitators (ESPs) and fabric filters (FFs) , the ESPs has a lower removal efficiency of PM2.5. The morphological characteristics of PM2.5 before and after dust removal contain irregular particles and spherical particles. The mass percentages of Na, K, and Fe in PM2.5 after the dust removal are nearly the same as those before the dust removal, but Si, Ca, and Al in PM2.5 decreased after dust removal and S in PM2.5 increased after dust removal. Although the hazardous elements Cr, V, Mn, and Ni in PM2.5 after dust removal did not change significantly, the Pb, Cd, As, Se, and Hg increased after dust removal. These data clearly show that the composition of PM2.5 changes as dust are removed by air pollution control devices. [ABSTRACT FROM AUTHOR]

The monosized spherical model was established originally to study the process of char combustion and residual ash formation. On this basis, a modified spherical model was obtained by introducing the multi-size mineral inclusions and pores to the spherical char. The results show that the surface ash mean size is proportional to the mineral volume fraction in monosized model. In addition, a significant bimodal characteristic occurs on the distribution curve of isolated ash mean size in cases of large porosity and pore size, which is in good agreement with experiment results. As a contrast, the planar model is more beneficial to form a large number of small isolated ash particles, whereas the mineral inclusions in monosized spherical model are inclined to coalesce into a large surface ash particle eventually. As regards the modified spherical model, the separation effects of both small and large surface ash particles can be strengthened with respect to number density. It can be expected that the modified model is more aligned with the actual conditions. [ABSTRACT FROM AUTHOR]