Large Mass Loss Research Articles

SN 2016coi (ASASSN-16fp): An Energetic H-stripped Core-collapse Supernova from a Massive Stellar Progenitor with Large Mass Loss

Abstract We present comprehensive observations and analysis of the energetic H-stripped SN 2016coi (a.k.a. ASASSN-16fp), spanning the γ-ray through optical and radio wavelengths, acquired within the first hours to ∼420 days post explosion. Our observational campaign confirms the identification of He in the supernova (SN) ejecta, which we interpret to be caused by a larger mixing of Ni into the outer ejecta layers. By modeling the broad bolometric light curve, we derive a large ejecta-mass-to-kinetic-energy ratio (M ej ∼ 4–7 M ⊙, E k ∼ (7–8) × 1051 erg). The small [Ca ii] λλ7291,7324 to [O i] λλ6300,6364 ratio (∼0.2) observed in our late-time optical spectra is suggestive of a large progenitor core mass at the time of collapse. We find that SN 2016coi is a luminous source of X-rays (L X > 1039 erg s−1 in the first ∼100 days post explosion) and radio emission (L 8.5 GHz ∼ 7 × 1027 erg s−1 Hz−1 at peak). These values are in line with those of relativistic SNe (2009bb, 2012ap). However, for SN 2016coi, we infer substantial pre-explosion progenitor mass loss with a rate ∼ (1–2) × and a sub-relativistic shock velocity v sh ∼ 0.15c, which is in stark contrast with relativistic SNe and similar to normal SNe. Finally, we find no evidence for a SN-associated shock breakout γ-ray pulse with energy E γ > 2 × 1046 erg. While we cannot exclude the presence of a companion in a binary system, taken together, our findings are consistent with a massive single-star progenitor that experienced large mass loss in the years leading up to core collapse, but was unable to achieve complete stripping of its outer layers before explosion.

Microstructure and oxidation behavior of MoSi2-based coating on carbon/carbon composites

MoSi2-based oxidation protective coating was fabricated on carbon/carbon (C/C) composites by combining pack cementation and supersonic atmospheric plasma spraying techniques. This work firstly studied the effect of spraying power on the phase composition of MoSi2 coating. Proper power at 50–55 kW could suppress the phase transition and powder oxidation of MoSi2 during spraying, which facilitated the coating densification. In addition, the static oxidation behavior of MoSi2-based coating at 900 °C, 1200 °C and 1500 °C was systematically investigated, and its oxidation resistance at 1500 °C was better than 900 °C and 1200 °C. More specifically, the MoSi2-based coating continued to reduce mass during the oxidation at 900 °C without significant mass addition, and the mass loss rate rapidly increased with the promotion of oxidation process, eventually showing a large mass loss percentage. However, it exhibited varying degrees of mass gain during oxidation at 1200 °C and 1500 °C, and the ultima mass loss percentage was relatively low. The mass gain phenomenon is correlated with the produced SiO2 glass scale covering on the coating surface, while the mass loss behavior may be attributed to the immoderate depletion of MoSi2-based coating and the considerable evaporation of gaseous products accompanied by the oxidation reaction ongoing.

High-temperature oxidation behavior and oxidation mechanism of C/SiBCN composites in static air

Abstract On account of the excellent oxidation resistance of precursor-derived SiBCN ceramics, carbon-fiber-reinforced SiBCN (C/SiBCN) composites are increasingly being used in high-temperature aerospace applications. However, very few studies have investigated the high-temperature oxidation behavior of C/SiBCN composites for their application to high-heat engines. Herein, C/SiBCN composites prepared by precursor infiltration and pyrolysis were tested in static air up to an oxidation temperature of 1700 °C. The composites’ structural evolution after oxidation and their potential oxidation mechanisms were investigated in detail. The carbon fibers were preferentially oxidized at temperatures in the range of 1200–1500 °C and completely oxidized at 1500 °C. The oxidation of the fibers at 1500 °C resulted in the formation of abundant oxygen channels and consequently a high oxide scale growth rate of 5–7 μm2 h−1 and a large mass loss of 54.6 wt%. At elevated temperatures in the range of 1600–1700 °C, a dense SiO2 oxide layer was formed by the sacrificial oxidation of the SiBCN matrix. The oxidation rate of the composites was therefore controlled by the diffusion rate of oxygen through the protective SiO2 oxide layer and the weight loss of the composites decreased to 28.6% after oxidation at 1600 °C for 60 min. The structural integrity of the composites was maintained after long-term oxidation at 1600 °C.

PeV neutrinos from wind breakouts of type II supernovae

Recently, rapid multiwavelength photometry and flash spectra of supernova (SN) 2013fs imply that the progenitor stars of regular type II supernovae (SNe II) may be commonly surrounded by a confined, dense stellar wind ejected from the progenitor star at a large mass loss rate over few years before the SNe. Based on the assumption that the pre-SN progenitor stars of SNe II emit wind similar to SN 2013fs, with a mass loss rate $$\dot{M}\;\sim\;3\times10^{-3}(v_w/100\;{\rm{km}\;s^{-1})}M_\odot\;\rm{yr}^{-1}$$ , we investigated neutrino emissions during the wind breakouts of SN shocks. We find that a typical SNe II can convert ~ 10.3 of their bulk kinetic energy into neutrino emissions, contributing a significant fraction of the IceCube-detected neutrino flux at ≳ 300 TeV. Moreover, ≲ 200 TeV IceCube neutrinos can be accounted for by the cosmic rays produced by shocks of all SN remnants, losing energy in their host galaxies, i.e., the starburst galaxies. The future follow-up observations of high energy neutrinos and gamma-rays from nearby individual SNe II, days to weeks after the explosions, will test this model.

A Long-duration Luminous Type IIn Supernova KISS15s: Strong Recombination Lines from the Inhomogeneous Ejecta–CSM Interaction Region and Hot Dust Emission from Newly Formed Dust*

Abstract We report the discovery of an SN 1988Z–like type IIn supernova KISS15s found in a low-mass star-forming galaxy at redshift z = 0.038 during the course of the Kiso Supernova Survey (KISS). KISS15s shows long-duration optical continuum and emission line light curves, indicating that KISS15s is powered by a continuous interaction between the expanding ejecta and dense circumstellar medium (CSM). The Hα emission line profile can be decomposed into four Gaussians of narrow, intermediate, blueshifted intermediate, and broad velocity width components, with a full width at half maximum of ≲100, ∼2000, and ∼14,000 km s−1 for the narrow, intermediate, and broad components, respectively. The presence of the blueshifted intermediate component, of which the line-of-sight velocity relative to the systemic velocity is about −5000 km s−1, suggests that the ejecta-CSM interaction region has an inhomogeneous morphology and anisotropic expansion velocity. We found that KISS15s shows increasing infrared continuum emission, which can be interpreted as hot dust thermal emission of T ∼ 1200 K from newly formed dust in a cool, dense shell in the ejecta-CSM interaction region. The progenitor mass-loss rate, inferred from bolometric luminosity, is , where v w is the progenitor’s stellar wind velocity. This implies that the progenitor of KISS15s was a red supergiant star or a luminous blue variable that had experienced a large mass loss in the centuries before the explosion.

The effect of polybenzimidazole coating on the morphology and abrasion of silk screen stencil film

It is of practical significance to prolong the service life of the silk screen plate used for screen printing by a simple method. To our knowledge, no attempt has been made to coat silk screen stencil film with polybenzimidazole (PBI) to improve its abrasion resistance against squeegee in order to prolong the service life of the silk screen plate. In this study, the synthesized PBI with 2,6-disubstituted benzimidazole structure was coated on the silk screen stencil film by solution casting, and its effect on the morphology, roughness and abrasion resistance of stencil film was investigated by scanning electron microscope, atomic force microscope and Taber abrasion tester. The abrasion resistance of the silk screen stencil films with 1 and 19 μm thick PBI coating is improved by 18.6% and 87.6% compared with that of pure stencil film, respectively. The stencil film undergoes two wear stages: the first stage with a larger mass loss is characterized by the wear of photosensitive film; and the second one with a relatively smaller mass loss is characterized by the wear of both photosensitive film and silk screen. The thickness of PBI coating has an important effect on the substrate strength and surface properties of films during the wear, thus resulting in changes in the abrasion resistance of stencil films. It shows that 8 μm thick PBI coating is enough to protect the stencil film from wear.

Interannual variability in glacier contribution to runoff from a high‐elevation Andean catchment: understanding the role of debris cover in glacier hydrology

AbstractWe present a field‐data rich modelling analysis to reconstruct the climatic forcing, glacier response, and runoff generation from a high‐elevation catchment in central Chile over the period 2000–2015 to provide insights into the differing contributions of debris‐covered and debris‐free glaciers under current and future changing climatic conditions. Model simulations with the physically based glacio‐hydrological model TOPKAPI‐ETH reveal a period of neutral or slightly positive mass balance between 2000 and 2010, followed by a transition to increasingly large annual mass losses, associated with a recent mega drought. Mass losses commence earlier, and are more severe, for a heavily debris‐covered glacier, most likely due to its strong dependence on snow avalanche accumulation, which has declined in recent years. Catchment runoff shows a marked decreasing trend over the study period, but with high interannual variability directly linked to winter snow accumulation, and high contribution from ice melt in dry periods and drought conditions. The study demonstrates the importance of incorporating local‐scale processes such as snow avalanche accumulation and spatially variable debris thickness, in understanding the responses of different glacier types to climate change. We highlight the increased dependency of runoff from high Andean catchments on the diminishing resource of glacier ice during dry years.

Oxidation resistance of a Mo-W-Si-B alloy at 1000–1300 °C: The effect of a multicomponent Mo-Si-B coating

The oxidation behavior and microstructures of a three phase Mo50W20Si15B15 alloy containing (Mo, W) solid solution, (Mo, W)5Si3 and (Mo, W)5SiB2 were investigated over the 1000–1300 °C temperature range. At 1300 °C, the alloy exhibited a large initial mass loss and eventually transitioned to a steady state behavior associated with the development of an amorphous borosilica scale. The oxidation resistance at lower temperature was unsatisfactory due to the pesting of Mo and W. Grazing Incident Angle X-ray Diffraction (GIXRD) measurements during the initial transient stage of oxidation identified the evolution of surface oxide products that were responsible for the large weight loss and pesting behavior. In order to address the large initial weight loss and the low temperature pesting behavior, the alloy was coated with a Mo-Si-B based coating by employing the pack cementation process followed by a conditioning treatment at 1450 °C. The microstructures of the coatings and the interlayer between the base alloy and the coating were studied, and the oxidation resistance of the coated alloys was evaluated over the 800–1300 °C temperature range. The coated alloy showed improved oxidation resistance with nearly zero mass change for extended period of time over the entire range of temperatures studied.

Massive destabilization of an Arctic ice cap

Ice caps that are mostly frozen at the bedrock-ice interface are thought to be stable and respond slowly to changes in climate. We use remote sensing to measure velocity and thickness changes that occur when the margin of the largely cold-based Vavilov Ice Cap in the Russian High Arctic advances over weak marine sediments. We show that cold-based to polythermal glacier systems with no previous history of surging may evolve with unexpected and unprecedented speed when their basal boundary conditions change, resulting in very large dynamic ice mass losses (an increase in annual mass loss by a factor of ∼100) over a few years. We question the future long-term stability of cold and polythermal polar ice caps, many of which terminate in marine waters as the climate becomes warmer and wetter in the polar regions.

Outbursts of luminous blue variable stars from variations in the helium opacity

Luminous blue variables are massive, evolved stars that exhibit large variations in luminosity and size on timescales from months to years, with high associated rates of mass loss1-5. In addition to this on-going variability, these stars exhibit outburst phases, during which their size increases and as a result their effective temperature decreases, typically to about 9,000 kelvin3,6. Outbursts are believed to be caused by the radiation force on the cooler, more opaque, outer layers of the star balancing or even exceeding the force of gravity, although the exact mechanisms are unknown and cannot be determined using one-dimensional, spherically symmetric models of stars because such models cannot determine the physical processes that occur in this regime7. Here we report three-dimensional simulations of massive, radiation-dominated stars, which show that helium opacity has an important role in triggering outbursts and setting the observed effective temperature during outbursts of about 9,000 kelvin. It probably also triggers the episodic mass loss at rates of 10-7 to 10-5 solar masses per year. The peak in helium opacity is evident in our three-dimensional simulations only because the density and temperature of the stellar envelope (the outer part of the star near the photosphere) need to be determined self-consistently with convection, which cannot be done in one-dimensional models that assume spherical symmetry. The simulations reproduce observations of long-timescale variability, and predict that convection causes irregular oscillations in the radii of the stars and variations in brightness of 10-30 per cent on a typical timescale of a few days. The amplitudes of these short-timescale variations are predicted to be even larger for cooler stars (in the outburst phase). This short-timescale variability should be observable with high-cadence observations.

Thermal Failure Propagation in Lithium-Ion Battery Modules with Various Shapes

Thermal failure propagation is one of the most severe challenges for battery modules and it usually aggravates the thermal hazards, further resulting in serious accidents. This work conducted two groups of experiments to investigate the influence of discharging treatment and module shape on the thermal failure propagation of battery modules, where the triangle module, rectangle module, parallelogram module, line module, hexagon module, and square module were researched. Based on the results, it can be found that an evident domino effect existed on the thermal failure propagation of battery modules. Namely, the failure propagation process consisted of several phases and the number of phases depended on the shape of the module. Besides, it is indicated that discharging treatment on a battery module when it was in a high-temperature environment would aggravate its thermal failure propagation by bringing an earlier thermal failure, a quicker failure propagation, and a larger mass loss. Combining the results of safety and space utilization, it is revealed that the triangular module may be the best choice of battery module due to its smaller failure propagation speed and higher space utilization.

Wood properties of Larix sibirica naturally grown in Tosontsengel, Mongolia

ABSTRACTThe wood properties were examined for Larix sibirica naturally grown in Tosontsengel, Mongolia. The dynamic Young's modulus of the logs ranged from 6.31 to 9.65 GPa. The mean values of wood properties were as follows: water-extracted basic density = 0.44 g cm−3, air-dry density = 0.59 g cm−3, shrinkage at 1% moisture content change in the radial and tangential directions = 0.18% and 0.32%, modulus of elasticity = 11.24 GPa, modulus of rupture = 102.4 MPa, compressive strength parallel to the grain = 53.1 MPa, and mass loss by Fomitopsis palustris and Trametes versicolor = 10.4% and 18.6%. Mass loss in the heartwood was higher than that in the sapwood, indicating that the larger mass loss values in the heartwood of L. sibirica might be related to the larger amount of arabinogalactan.

Ionized Gas Motions and the Structure of Feedback near a Forming Globular Cluster in NGC 5253

We observed Brackett $\alpha$ 4.05$\mu$m emission towards the supernebula in NGC 5253 with NIRSPEC on Keck II in adaptive optics mode, NIRSPAO, to probe feedback from its exciting embedded super star cluster (SSC). NIRSPEC's Slit-Viewing Camera was simultaneously used to image the K-band continuum at $\sim$$0.1''$ resolution. We register the IR continuum with HST imaging, and find that the visible clusters are offset from the K-band peak, which coincides with the Br $\alpha$ peak of the supernebula and its associated molecular cloud. The spectra of the supernebula exhibit Br $\alpha$ emission with a strong, narrow core. The linewidths are 65-76 km s$^{-1}$, FWHM, comparable to those around individual ultra-compact HII regions within our Galaxy. A weak, broad (FWHM$\simeq$150-175 km s$^{-1}$) component is detected on the base of the line, which could trace a population of sources with high-velocity winds. The core velocity of Br $\alpha$ emission shifts by +13 km s$^{-1}$ from NE to SW across the supernebula, possibly indicating a bipolar outflow from an embedded object, or linked to a foreground redshifted gas filament. The results can be explained if the supernebula comprises thousands of ionized wind regions around individual massive stars, stalled in their expansion due to critical radiative cooling and unable to merge to drive a coherent cluster wind. Based on the absence of an outflow with large mass loss, we conclude that feedback is currently ineffective at dispersing gas, and the SSC retains enriched material out of which it may continue to form stars.

Experimental investigation on the rock erosion characteristics of a self-excited oscillation pulsed supercritical CO2 jet

Supercritical CO2 (SC-CO2) jet is now widely considered to have great potential for application in oil-gas exploration and development. In order to further improve the performance of SC-CO2 jet, the rock erosion characteristics of a self-excited oscillation pulsed SC-CO2 jet (SOPSJ) were preliminarily analyzed and then experimentally studied as a pioneering effort. A Helmholtz oscillation nozzle was employed to generate a SOPSJ. Numerous rock erosion tests were conducted. Rock erosion area and depth, erosion intensity evaluated by mass loss, and erosion rate were applied to characterize the erosion performance of a SOPSJ. Results show that unlike the continuous SC-CO2 jets, the erosion areas caused by the SOPSJs are almost unchanged at first and then decrease slowly with the growing standoff distance, while the erosion depths increase first and then decrease. The erosion pits caused by the SOPSJs are relatively large, shallow, and irregular, especially at the initial several standoff distances. Moreover, the SOPSJs can cause larger mass losses than the continuous jets, but this only happens at the initial several standoff distances. The SOPSJs generated with the use of the optimum chamber lengths can maximally enhance the mass loss by about 32.3%, 27.7%, 21.5%, and 17.3% at inlet pressures of 25, 30, 35, and 40 MPa, respectively. In addition, for all the jets, the erosion rates always remain the tendency to decrease with the increase of erosion time. Whereas, the specimens can be eroded by the SOPSJs at a higher rate than the continuous jets, which is independent of the inlet pressure.

Comparison of precipitation collectors used in isotope hydrology

Many hydrologic studies require data on the oxygen and hydrogen stable isotope composition (δ18O, δ2H) of precipitation and various collector designs have been suggested for gathering corresponding samples. Yet, it is crucial that these collectors, also known as totalizers, prevent evaporation and associated isotope fractionation. Surprisingly, we were unable to find a comprehensive collector intercomparison in the literature, and much less one that addressed hot and arid conditions.In this study, we tested six different collector designs over a period of 32 days. They were filled to 20% of their total volume with water of known isotope composition and placed in a modified laboratory drying oven with a low relative humidity (5%) and a diurnal temperature change of 26 to 45 °C. Evaporative mass losses were determined gravimetrically daily while samples for isotope analyses were collected every four days.The classic Oil collector, featuring a layer of paraffin oil to prevent evaporation, showed the smallest mass losses and no detectable isotope shift. The Tube-dip-in-water collector with pressure equilibration tube also performed well, although we noted somewhat larger mass losses and isotope shifts. The latter accounted for 0.28‰ (Δδ18O) and 0.9‰ (Δδ2H) after 32 days, which is significant, but in view of the extreme conditions, these changes should be still acceptable for most studies. The remaining collectors (Ball-in-funnel, Floating balls, and Float based) all failed.Under the prevailing conditions, the Tube-dip-in-water collector with pressure equilibration tube seems to represent a good, oil- and thus contamination-free compromise. Nonetheless, also in this system small precipitation amounts are problematic. This may necessitate modifications of the standard design in terms of funnel diameter and bottle geometry. We strongly advise researchers to conduct own tests with their intended collector before field deployment.

The world\u2019s largest High Arctic lake responds rapidly to climate warming

Using a whole-watershed approach and a combination of historical, contemporary, modeled and paleolimnological datasets, we show that the High Arctic’s largest lake by volume (Lake Hazen) has succumbed to climate warming with only a ~1 °C relative increase in summer air temperatures. This warming deepened the soil active layer and triggered large mass losses from the watershed’s glaciers, resulting in a ~10 times increase in delivery of glacial meltwaters, sediment, organic carbon and legacy contaminants to Lake Hazen, a >70% decrease in lake water residence time, and near certainty of summer ice-free conditions. Concomitantly, the community assemblage of diatom primary producers in the lake shifted dramatically with declining ice cover, from shoreline benthic to open-water planktonic species, and the physiological condition of the only fish species in the lake, Arctic Char, declined significantly. Collectively, these changes place Lake Hazen in a biogeochemical, limnological and ecological regime unprecedented within the past ~300 years.

Impact of small-scale saline tracer heterogeneity on electrical resistivity monitoring in fully and partially saturated porous media: Insights from geoelectrical milli-fluidic experiments

Abstract Time-lapse electrical resistivity tomography (ERT) is a geophysical method widely used to remotely monitor the migration of electrically-conductive tracers and contaminant plumes in the subsurface. Interpretations of time-lapse ERT inversion results are generally based on the assumption of a homogeneous solute concentration below the resolution limits of the tomogram depicting inferred electrical conductivity variations. We suggest that ignoring small-scale solute concentration variability (i.e., at the sub-resolution scale) is a major reason for the often-observed apparent loss of solute mass in ERT tracer studies. To demonstrate this, we developed a geoelectrical milli-fluidic setup where the bulk electric conductivity of a 2D analogous porous medium, consisting of cylindrical grains positioned randomly inside a Hele–Shaw cell, is monitored continuously in time while saline tracer tests are performed through the medium under fully and partially saturated conditions. High resolution images of the porous medium are recorded with a camera at regular time intervals, and provide both the spatial distribution of the fluid phases (aqueous solution and air), and the saline solute concentration field (where the solute consists of a mixture of salt and fluorescein, the latter being used as a proxy for the salt concentration). Effective bulk electrical conductivities computed numerically from the measured solute concentration field and the spatial distributions of fluid phases agree well with the measured bulk conductivities. We find that the effective bulk electrical conductivity is highly influenced by the connectivity of high electrical conductivity regions. The spatial distribution of air, saline tracer fingering, and mixing phenomena drive temporal changes in the effective bulk electrical conductivity by creating preferential paths or barriers for electrical current at the pore-scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy of the effective bulk electrical conductivity, especially for partially saturated conditions. We highlight how these phenomena contribute to the typically large apparent mass loss observed when conducting field-scale time-lapse ERT.

Assessing water resources under climate change in high-altitude catchments: a methodology and an application in the Italian Alps

Assessment of the future water resources in the Italian Alps under climate change is required, but the hydrological cycle of the high-altitude catchments therein is poorly studied and little understood. Hydrological monitoring and modeling in the Alps is difficult, given the lack of first hand, site specific data. Here, we present a method to model the hydrological cycle of poorly monitored high-altitude catchments in the Alps, and to project forward water resources availability under climate change. Our method builds on extensive experience recently and includes (i) gathering data of climate, of cryospheric variables, and of hydrological fluxes sparsely available; (ii) robust physically based glacio-hydrological modeling; and (iii) using glacio-hydrological projections from GCM models. We apply the method in the Mallero River, in the central (Retiche) Alps of Italy. The Mallero river covers 321 km2, with altitude between 310 and 4015 m a.s.l., and it has 27 km2 of ice cover. The glaciers included in the catchment underwent large mass loss recently, thus Mallero is largely paradigmatic of the present situation of Alpine rivers. We set up a spatially explicit glacio-hydrological model, describing the cryospheric evolution and the hydrology of the area during a control run CR, from 1981 to 2007. We then gather climate projections until 2100 from three Global Climate Models of the IPCC AR5 under RCP2.6, RCP4.5, and RCP8.5. We project forward flow statistics, flow components (rainfall, snow melt, ice melt), ice cover, and volume for two reference decades, namely 2045–2054 and 2090–2099. We foresee reduction of the ice bodies from − 62 to − 98% in volume (year 2100 vs year 1981), and subsequent large reduction of ice melt contribution to stream flows (from − 61 to − 88%, 2100 vs CR). Snow melt, now covering 47% of the stream flows yearly, would also be largely reduced (from − 19 to − 56%, 2100 vs CR). The stream flows will decrease on average at 2100 (from + 1 to − 25%, with − 7%), with potential for increased flows during fall, and winter, and large decrease in summer. Our results provide a tool for consistent modeling of the cryospheric, and hydrologic behavior, and can be used for further investigation of the high-altitude catchments in the Alps.

Morphology and Thermal Characteristics of Polysaccharide Extracted by Ultrasound from <i>Ophiopogon japonicas</i>

The crude polysaccharide UPOJ was extracted by ultrasound from Ophiopogon japonicas and purified by DEAE-cellulose52 column and Sephadex G-150 gel column. Purified polysaccharide UPOJ-DS was obtained. The thermal characteristics of UPOJ-DS were studied by using the thermal analysis system Q1000DSC LNCS FACS Q600SDT. The heating rate was 10°C/min and the test temperature was 20°C ~ 800°C. The results showed that there were three large mass losses in the process of heating, in which the maximum weight loss rate was 66.68% at 220°C ~ 330°C and the decomposition reaction took place in the polysaccharide itself, which indicated that the composition, water content, intermolecular interaction and aggregation behavior of UPOJ-DS were affected by temperature. The surface morphology of UPOJ-DS was observed by environmental scanning electron microscope (ESEM). The results indicated that the polysaccharide molecules were lamellar or clastic, with smooth surface, strong intermolecular interaction and close binding.

Kinetic simulation and prediction of pyrolysis process for non-metallic fraction of waste printed circuit boards by discrete distributed activation energy model compared with isoconversional method.

Kinetic studies on the pyrolysis process for non-metallic fraction (NMF) of waste printed circuit boards (WPCBs) were conducted using both the isoconversional SKAS method and the discrete distributed activation energy model (discrete DAEM). The pyrolysis process of the NMF sample could be classified into three stages, and a large mass loss was observed from 98 to 570°C, attributed to thermal degradation of epoxy resins in the NMF sample. The kinetic parameters, including activation energies (E i), pre-exponential factors (A i), and contributed fractions (f i,0), were determined. It indicated that the discrete DAEM could predict the pyrolysis process of the NMF more accurately and completely when compared with the isoconversional SKAS method. In the discrete DAEM, E i and A i values were evaluated at 99 equally spaced intervals of conversion. The E i and A i (in the form of lnA i) transformed with reaction progress, ranging from 80.9 to 240.5kJ/mol and 19.07 to 39.55s-1, respectively, with the conversion increased from 0.01 to 0.99. The pyrolysis of the NMF of WPCBs could be accurately characterized as 17 dominating reactions from f i,0 results. Graphical abstract ᅟ.