Increased Mass Loss Research Articles

A comprehensive study on the impact of heating position on thermal runaway of prismatic lithium-ion batteries

Thermal runaway (TR) is a primary safety problem on the application of lithium-ion batteries (LIBs), while TR characteristics and mechanism of LIBs under varied heating positions are still unclear. In this study, the impact of heating position on TR is investigated employing an experimental approach. Due to the prismatic battery shape, the heated positions of LIBs are selected as the front, bottom and side surfaces. The results indicate the maximum temperature, peak temperature increase rate and mass loss rate of LIBs are significantly affected by heating position. The onset times of safety valve opening, internal short circuit and TR are almost consistent when the battery bottom and side surfaces are heated. The maximum jet flow velocity occurs at the instant of the safety valve opening, and the values are 74.79 m/s and 77.26 m/s for bottom and side surface heating, which are about three times that of front surface heating. Compared with front surface heating, bottom and side surface heating modes cause more significant damage on LIBs owing to higher mean thermal conductivities and more intense exothermic reactions. This study can provide guidance for the safe design of LIBs and the prevention of TR propagation between LIB modules. • The influence of heating position on thermal runaway behavior is investigated. • The jet flow velocity of lithium-ion battery is estimated based on mass loss rate. • Bottom and side surface heating lead to severer thermal runaway and jet phenomena. • Thermal runaway mechanism of the battery under varied heating positions is reveal.

Warming and grazing enhance litter decomposition and nutrient release independent of litter quality in an alpine meadow

Abstract Warming and grazing, and litter quality jointly determine litter decomposition and nutrient releases in grazing ecosystems. However, their effects have previously been studied in isolation. We conducted a two factorial experiment with asymmetric warming using infrared heaters and moderate grazing in an alpine meadow. Litter samples were collected from all plots in each treatment, among which some subsamples were placed in their original plots and other samples were translocated to other treatment plots to test the relative effects of each treatment on litter decomposition and nutrient releases. We found that warming rather than grazing alone significantly increased total losses of litter mass, total organic carbon, total nitrogen (TN) and total phosphorus (TP) per unit area due to increases in both mass loss rates and litter biomass. However, grazing with warming did not affect their total mass losses because increased mass loss was offset by decreased litter biomass compared with the control. Seasonal mean soil temperature better predicted litter decomposition than litter lignin content or carbon to nitrogen ratio. There were interactions between warming and grazing, but there were no interactions between them and litter quality on litter decomposition. The temperature sensitivity of TN loss was higher than that of TP loss per unit area. Our results suggest that increased temperature has a greater effect on litter decomposition and nutrient release than change in litter quality, and that more N release from litter could result in greater P deficiency in the alpine meadow.

Sea-Level Rise: From Global Perspectives to Local Services

Coastal areas are highly diverse, ecologically rich, regions of key socio-economic activity, and are particularly sensitive to sea-level change. Over most of the 20th century, global mean sea level has risen mainly due to warming and subsequent expansion of the upper ocean layers as well as the melting of glaciers and ice caps. Over the last three decades, increased mass loss of the Greenland and Antarctic ice sheets has also started to contribute significantly to contemporary sea-level rise. The future mass loss of the two ice sheets, which combined represent a sea-level rise potential of ∼65 m, constitutes the main source of uncertainty in long-term (centennial to millennial) sea-level rise projections. Improved knowledge of the magnitude and rate of future sea-level change is therefore of utmost importance. Moreover, sea level does not change uniformly across the globe and can differ greatly at both regional and local scales. The most appropriate and feasible sea level mitigation and adaptation measures in coastal regions strongly depend on local land use and associated risk aversion. Here, we advocate that addressing the problem of future sea-level rise and its impacts requires (i) bringing together a transdisciplinary scientific community, from climate and cryospheric scientists to coastal impact specialists, and (ii) interacting closely and iteratively with users and local stakeholders to co-design and co-build coastal climate services, including addressing the high-end risks.

Electromechanical modeling for triboelectric nanogenerators considering the distribution of polymer transfer film

When there exits continuous dry friction between the metal electrode and the polymer in the working process of triboelectric nanogenerators (TENGs), the polymer will suffer serious wear, and the wear debris adsorbed to the surface of metal electrode will form the transfer film, resulting in the decrease in electrical output. However, the quantitative relationship between wear characteristics and electrical output still remains unclear. In this paper, a charge density-dependent wear model for rotary freestanding TENG (RF-TENG) is established first, and then the numerical algorithms such as augmented Lagrange algorithm and Newton Rapson iterative method are employed to investigate the mapping relationship between the mass loss and the transfer film area fraction. Next, an electrostatic induction model considering the distribution of transfer film for RF-TENG is presented in combination with Monte Carlo random sampling, and the quantitative relationship between the transfer film area fraction and the electrical output is explored. The results show that, the transfer film area fraction increases first and then remains almost unchanged with the increasing mass loss of polymer; the increase in the transfer film area fraction causes the triboelectric charge density to decay, and the decay rate decreases gradually because the growth rate of transfer film area fraction decreases. The larger electrostatic force resulting from larger charge density will aggravate the polymer wear and intensify the attenuation amplitude of electrical output. This study can reveal the mapping relationship between polymer wear and electrification performance of TENGs, thus providing a theoretical basis for the design of TENGs with high durability and stability.

Effect of pH on the Properties of Hydrogels Cross-Linked via Dynamic Thia-Michael Addition Bonds.

Hydrogels cross-linked with dynamic covalent bonds exhibit time-dependent properties, making them an advantageous platform for applications ranging from biomaterials to self-healing networks. However, the relationship between the cross-link exchange kinetics, material properties, and stability of these platforms is not fully understood, especially upon addition of external stimuli. In this work, pH was used as a handle to manipulate cross-link exchange kinetics and control the resulting hydrogel mechanics and stability in a physiologically relevant window. Poly(ethylene glycol)-based hydrogels were cross-linked with a reversible thia-Michael addition reaction in aqueous buffer between pH 3 and pH 7. The rate constants of bond exchange and equilibrium constants were determined for each pH value, and these data were correlated with the resulting mechanical profiles of the bulk hydrogels. With increasing pH, both the forward and the reverse rate constants increased, while the equilibrium constant decreased. These changes led to faster stress relaxation and less stiff hydrogels at more basic pH values. The elevated pH values also led to an increased mass loss and a faster rate of release of an encapsulated model bovine serum albumin fluorescent protein. The connection between the kinetics, mechanics, and molecular release profiles provides important insight into the structure–property relationships of dynamic covalent hydrogels, and this system offers a promising platform for controlled release between physiologically relevant pH values.

Automated detection and analysis of surface calving waves with a terrestrial radar interferometer at the front of Eqip Sermia, Greenland

Abstract. Glacier calving is a key dynamical process of the Greenland Ice Sheet and a major driver of its increasing mass loss. Calving waves, generated by the sudden detachment of ice from the glacier terminus, can reach tens of meters in height and provide very valuable insights into quantifying calving activity. In this study, we present a new method for the detection of source location, timing, and magnitude of calving waves using a terrestrial radar interferometer. This method was applied to 11 500 1 min interval acquisitions from Eqip Sermia, West Greenland, in July 2018. Over 7 d, more than 2000 calving waves were detected, including waves generated by submarine calving, which are difficult to observe with other methods. Quantitative assessment with a wave power index (WPI) yields a higher wave activity (+49 %) and higher temporally cumulated WPI (+34 %) in deep water than under shallow conditions. Subglacial meltwater plumes, occurring 2.3 times more often in the deep sector, increase WPI and the number of waves by a factor of 1.8 and 1.3, respectively, in the deep and shallow sector. We therefore explain the higher calving activity in the deep sector by a combination of more frequent meltwater plumes and more efficient calving enhancement linked with better connections to warm deep ocean water.

Glacier Velocity Changes in the Himalayas in Relation to Ice Mass Balance

Glacier evolution with time provides important information about climate variability. Here, we investigated glacier velocity changes in the Himalayas and analysed the patterns of glacier flow. We collected 220 scenes of Landsat-7 panchromatic images between 1999 and 2000, and Sentinel-2 panchromatic images between 2017 and 2018, to calculate surface velocities of 36,722 glaciers during these two periods. We then derived velocity changes between 1999 and 2018 for the early winter period, based on which we performed a detailed analysis of motion of each individual glacier, and noted that the changes are spatially heterogeneous. Of all the glaciers, 32% have sped up, 24.5% have slowed down, and the rest 43.5% have remained stable. The amplitude of glacier slowdown, as a result of glacier mass loss, is significantly larger than that of speedup. At regional scales, we found that glacier surface velocity in winter has uniformly decreased in the western part of the Himalayas between 1999 and 2018, while increased in the eastern part; this contrasting difference may be associated with decadal changes in accumulation and/or melting under different climatic regimes. We also found that the overall trend of surface velocity exhibits seasonal variability: summer velocity changes are positively correlated with mass loss, i.e., velocity increases with increasing mass loss, whereas winter velocity changes show a negative correlation. Our study suggests that glacier velocity changes in the Himalayas are spatially and temporally heterogeneous, in agreement with studies that previously highlighted this trend, emphasising complex interactions between glacier dynamics and environmental forcing.

The Role of Differential Ablation and Dynamic Detachment in Driving Accelerating Mass Loss From a Debris‐Covered Himalayan Glacier

AbstractSustained mass loss from Himalayan glaciers is causing supraglacial debris to expand and thicken, with the expectation that thicker debris will suppress ablation and extend glacier longevity. However, debris‐covered glaciers are losing mass at similar rates to clean‐ice glaciers in High Mountain Asia. This rapid mass loss is attributed to the combined effects of; (a) low or reversed mass balance gradients across debris‐covered glacier tongues, (b) differential ablation processes that locally enhance ablation within the debris‐covered section of the glacier, for example, at ice cliffs and supraglacial ponds, and (c) a decrease in ice flux from the accumulation area in response to climatic warming. Adding meter‐scale spatial variations in supraglacial debris thickness to an ice‐flow model of Khumbu Glacier, Nepal, increased mass loss by 47% relative to simulations assuming a continuous debris layer over a 31‐year period (1984–2015 CE) but overestimated the reduction in ice flux. Therefore, we investigated if simulating the effects of dynamic detachment of the upper active glacier from the debris‐covered tongue would give a better representation of glacier behavior, as suggested by observations of change in glacier dynamics and structure indicating that this process occurred during the last 100 years. Observed glacier change was reproduced more reliably in simulations of the active, rather than entire, glacier extent, indicating that Khumbu Glacier has passed a dynamic tipping point by dynamically detaching from the heavily debris‐covered tongue that contains 20% of the former ice volume.

A multi-dimensional non-uniform corrosion model for bioabsorbable metallic vascular stents

Bioabsorbable metallic vascular stents (BMVSs) are an innovative technological advancement in the medical engineering field of vascular implants. BMVSs have great potential to revolutionize vascular intervention, but the lack of understanding of the construction material's natural corrosion within the body inhibits the use in clinical medicine. In this study, a corrosion function concept for in vivo implants was created to develop a multi-dimensional, non-uniform corrosion model with a larger goal of simulating the mechanical integrity of BMVSs. This proposed corrosion model simulates the corrosion rate and its effects on magnesium (Mg) alloy AZ31 based on continuum damage mechanics. The model was calibrated using three degradation experiments on Mg alloy specimens. These experiments focused on multi-dimensional corrosion, mass loss rate, and mechanical integrity during the corrosion process. Lastly, to verify the applicability of the proposed model, the resulting corrosion behaviors and mechanical characteristics of the BMVSs were implemented into a finite element framework to produce an overarching simulation of the BMVS's degradation in vivo. The results of the experiments and simulations revealed a proportional link between the corrosion of BMVSs and the number of exposed surfaces. A non-linear decline in mechanical integrity with increasing mass loss was also discovered through experimentation and modeling. Furthermore, the model and simulation can provide some details about changes in morphology and mechanics during BMVS corrosion. This work gives new insights into accurately modeling for BMVS degradation and can be used to optimize product development of BMVSs. Statement of significanceBioabsorbable metallic vascular stents (BMVSs) are an innovative technological advancement in the medical engineering field of vascular implants. Despite BMVSs have great potential to revolutionize vascular intervention, the lack of understanding of the construction material’s natural corrosion within the body inhibits their use in clinical medicine. In this study, a novel multi-dimensional non-uniform corrosion model was proposed to unveil the mechanisms during the in vivo degradation of bioabsorbable metallic implants, which can accurately capture the overlooked changes in morphology and mechanics during BMVS corrosion. This work provides a technical solution to enhance the modeling accuracy in BMVS degradation and can be further used to optimize the design of BMVSs in the future.

Tribological investigation of abrasion resistant steels with martensitic and retained austenitic microstructure in single- and multi–asperity contact

Steel making companies are developing new steels with complex microstructure to satisfy abrasion resistance issues. Three newly developed steels (fresh martensitic, tempered martensitic and a TRIP steel) were investigated under single and multi-asperity abrasion test conditions. Abrasive performance was linked to material properties. In the multi-asperity test, increasing the normal load and abrasive particle size resulted in increasing mass loss and in transition in micro-mechanisms from ploughing to micro-cutting. Martensitic materials showed better wear performance due to their higher hardness. As a result of the abrasive action a newly formed tribo-layer was observed in the contact zone of all steel specimen. In the single asperity testing a diamond spherical indenter was used with different normal loads. Wear micro-mechanisms were analysed during the scratching using optical microscopy and 3D-profilometry. The fresh and tempered martensitic steels showed a transition in micro-mechanism from micro-ploughing to micro-cutting at higher loads and smaller tip radius. For the multiphase steel with retained austenite, despite its TRansformation Induced Plasticity effect, micro-cutting was reached already at lower loads. The tempered martensitic material outperformed the fresh martensitic material despite the similar hardness and microstructure. For all materials single-asperity test data showed similar ranking in abrasion wear resistance as in the multi-asperity test.

Influences of reprocessing separation efficiency on the fuel cycle performances for a Heavy Water moderated Molten Salt Reactor

Reprocessing separation efficiency (RSE) is one important fuel cycle indicator which determines the loss of actinides left in the nuclear waste and the recovered actinides for reuse in the core, affecting the nuclear waste management, fuel utilization and other fuel cycle characteristics. By changing the reprocessing cycle time (RCT) from 10 days to 360 days, the impacts of RSE varying from 99.9% to 99.999% on the core actinides inventory evolution, breeding ratio (BR) and nuclear waste radiotoxicity were investigated for a Heavy Water moderated Molten Salt Reactor (HWMSR), which is a newly proposed molten salt reactor (MSR) that adopts heavy water rather than graphite as the moderator while employs the usual liquid fuel as in a traditional MSR. The obtained results demonstrate that the inventories of transuranic (TRU) and uranium except U-233 at equilibrium and their transition time to equilibrium both decreases as RSE declines due to their increased mass loss in reprocessing, which in turn brings down the parasitic neutron absorption in the core. Consequently, the U-233 inventory required for maintaining critical operation for a lower RSE drops. While the Th-232 inventory rises, since it is online refueled to maintain the total heavy metal (HM) content in the core constant to ensure the electrochemical stability of the fuel salt. As a result, BR is relatively improved as RSE decreases. But the increased U-233 production resulting from the improved BR could not compensate for the U-233 loss during reprocessing and leads to a longer doubling time for a lower RSE. The radiotoxicity of nuclear waste increases as RSE decreases since more actinides are lost to the nuclear waste. The above effects caused by RSE are mitigated as the RCT prolongs since the frequency for reprocessing the fuel salt of primary loop over a given period decreases, leading to a decrease of HM loss. For an RSE level of 99.9%, the shortest doubling time appears at the RCT of 30 days rather than 10 days because the mitigation of U-233 loss overwhelms the efficiency decrease of FPs removal and Pa-233 extraction. By balancing the Th-U breeding and radiotoxicity, an RCT of 60 days is recommended for HWMSR for the RSE of 99.9%.

A Large Fraction of Hydrogen-rich Supernova Progenitors Experience Elevated Mass Loss Shortly Prior to Explosion

Abstract Spectroscopic detection of narrow emission lines traces the presence of circumstellar mass distributions around massive stars exploding as core-collapse supernovae. Transient emission lines disappearing shortly after the supernova explosion suggest that the material spatial extent is compact and implies an increased mass loss shortly prior to explosion. Here, we present a systematic survey for such transient emission lines (Flash Spectroscopy) among Type II supernovae detected in the first year of the Zwicky Transient Facility survey. We find that at least six out of ten events for which a spectrum was obtained within two days of the estimated explosion time show evidence for such transient flash lines. Our measured flash event fraction (>30% at 95% confidence level) indicates that elevated mass loss is a common process occurring in massive stars that are about to explode as supernovae.

Binary pathways to SLSNe-I: SN 2017gci

ABSTRACT Some hydrogen-poor superluminous supernovae (SLSNe) exhibit bumps in the tails of their light curves associated with hydrogen features in their late time spectra. Here we use the explosion parameters of one such SLSN – SN 2017gci – to search the stellar models of the Binary Population And Spectral Synthesis (BPASS) code for potential progenitors. We find good matches for a 30 M⊙ progenitor star in a binary system and no matches from single-star models. Common envelope and mass transfer after the giant branch, combined with increased mass loss from strong stellar winds immediately before death, allow the progenitor to lose its hydrogen envelope decades before the explosion. This results in a hydrogen poor SLSN and allows for delayed interaction of the ejecta with the lost stellar material.

Calving at Ryder Glacier, Northern Greenland

AbstractRecent evidence has shown increasing mass loss from the Greenland ice sheet, with a general trend of accelerated mass losses extending northwards. However, different glaciers have been shown to respond differently to similar external forcings, constituting a problem for extrapolating and upscaling data. Specifically, whilst some outlet glaciers have accelerated, thinned, and retreated in response to atmospheric and oceanic warming, the behavior of other marine terminating glaciers appears to be less sensitive to climate forcing. Ryder glacier, for which only a few studies have been conducted, is located in North Greenland and terminates with a floating ice tongue in Sherard Osborn Fjord. The persistence or disintegration of floating ice tongues has impacts on glacier dynamics and stability, with ramifications beyond, including sea level rise. This study focuses on understanding the controls on calving and frontal ablation of the Ryder glacier through the use of time‐lapse imagery and satellite data. The results suggest that Ryder glacier has behaved independently of climate forcing during recent decades, with fjord geometry exerting a first order control on its calving.

The Impacts of a Subglacial Discharge Plume on Calving, Submarine Melting, and Mélange Mass Loss at Helheim Glacier, South East Greenland

AbstractAlmost half of the Greenland ice sheet's mass loss occurs through iceberg calving at marine terminating glaciers. The presence of buoyant subglacial discharge plumes at these marine termini are thought to increase mass loss both through submarine melting and by undercutting that consequently increases calving rates. Plume models are used to predict submarine melting and undercutting. However, there are few observations that allow these relationships to be tested. Here, we use airborne lidar from the terminus of Helheim Glacier, SE Greenland to measure the bulge induced at the surface by the upwelling plume. We use these measurements to estimate plume discharge rates using a high‐resolution, three‐dimensional plume model. Multiyear observations of the plume are compared to a record of calving from camera and icequake data. We find no evidence to suggest that the presence of a plume, determined by its visibility at the surface, increases the frequency of major calving events and also show that mass loss at the terminus driven directly by plume discharge is significantly less than mass loss from major calving events. The results suggest that the contribution of direct plume‐driven mass loss at deep marine‐terminating glaciers may be less than at shallower termini.

The GRISLI-LSCE contribution to the Ice Sheet Model Intercomparison Project for phase 6 of the Coupled Model Intercomparison Project (ISMIP6) – Part 1: Projections of the Greenland ice sheet evolution by the end of the 21st century

Abstract. Polar amplification will result in amplified temperature changes in the Arctic with respect to the rest of the globe, making the Greenland ice sheet particularly vulnerable to global warming. While the ice sheet has been showing an increased mass loss in the past decades, its contribution to global sea level rise in the future is of primary importance since it is at present the largest single-source contribution after the thermosteric contribution. The question of the fate of the Greenland and Antarctic ice sheets for the next century has recently gathered various ice sheet models in a common framework within the Ice Sheet Model Intercomparison Project for the Coupled Model Intercomparison Project – phase 6 (ISMIP6). While in a companion paper we present the GRISLI-LSCE (Grenoble Ice Sheet and Land Ice model of the Laboratoire des Sciences du Climat et de l'Environnement) contribution to ISMIP6-Antarctica, we present here the GRISLI-LSCE contribution to ISMIP6-Greenland. We show an important spread in the simulated Greenland ice loss in the future depending on the climate forcing used. The contribution of the ice sheet to global sea level rise in 2100 can thus be from as low as 20 mm sea level equivalent (SLE) to as high as 160 mm SLE. Amongst the models tested in ISMIP6, the Coupled Model Intercomparison Project – phase 6 (CMIP6) models produce larger ice sheet retreat than their CMIP5 counterparts. Low-emission scenarios in the future drastically reduce the ice mass loss. The oceanic forcing contributes to about 10 mm SLE in 2100 in our simulations. In addition, the dynamical contribution to ice thickness change is small compared to the impact of surface mass balance. This suggests that mass loss is mostly driven by atmospheric warming and associated ablation at the ice sheet margin. With additional sensitivity experiments we also show that the spread in mass loss is only weakly affected by the choice of the ice sheet model mechanical parameters.

Assessment of the chemical degradation of PFPE lubricants and greases for space applications: implications for long-term on-ground storage

Liquid lubricants and greases used in space applications are generally susceptible to degradation or aging. Depending on the specific material combination and storage conditions, aging effects are also relevant for long-term storage (LTS). An overview on both physical and chemical aging processes for liquid lubricants and greases is given and processes which are seen as relevant for LTS and may impact the long-term performance of these materials are identified. Individual degradation processes as well as causes and potential risks are discussed, providing complementary data for two liquid perfluoropolyether (PFPE) lubricants (Fomblin Z25 and Brayco 815Z) and a PFPE grease (MAPLUB PF 100-b), focussing on thermo-oxidative and catalytic degradation. For these lubricants, monitoring of degradation effects is done indirectly by their mass loss at different temperatures and in the presence of a catalyst over a total duration of 1000 h. An increased mass loss during accelerated thermo-oxidative aging at temperatures above 200 °C is observed, with overlapping effects of thickener degradation for the investigated grease. Noticeable catalytic degradation effects are further seen for accelerated thermo-oxidative aging in the presence of Al2O3 above 200 °C.

Leaf litter identity rather than diversity shapes microbial functions and microarthropod abundance in tropical montane rainforests.

In tropical forest ecosystems leaf litter from a large variety of species enters the decomposer system, however, the impact of leaf litter diversity on the abundance and activity of soil organisms during decomposition is little known. We investigated the effect of leaf litter diversity and identity on microbial functions and the abundance of microarthropods in Ecuadorian tropical montane rainforests. We used litterbags filled with leaves of six native tree species (Cecropia andina, Dictyocaryum lamarckianum, Myrcia pubescens, Cavendishia zamorensis, Graffenrieda emarginata, and Clusia spp.) and incubated monocultures and all possible two‐ and four‐species combinations in the field for 6 and 12 months. Mass loss, microbial biomass, basal respiration, metabolic quotient, and the slope of microbial growth after glucose addition, as well as the abundance of microarthropods (Acari and Collembola), were measured at both sampling dates. Leaf litter diversity significantly increased mass loss after 6 months of exposure, but reduced microbial biomass after 12 months of exposure. Leaf litter species identity significantly changed both microbial activity and microarthropod abundance with species of high quality (low C‐to‐N ratio), such as C. andina, improving resource quality as indicated by lower metabolic quotient and higher abundance of microarthropods. Nonetheless, species of low quality, such as Clusia spp., also increased the abundance of Oribatida suggesting that leaf litter chemical composition alone is insufficient to explain variation in the abundances of soil microarthropods. Overall, the results provide evidence that decomposition and microbial biomass in litter respond to leaf litter diversity as well as litter identity (chemical and physical characteristics), while microarthropods respond only to litter identity but not litter diversity.

Erosion Mechanism of a Cavitating Jet on Groove Roughness

The erosion behavior of a cavitating jet on groove roughness was investigated experimentally using mass-loss characteristics, scanning electron microscopy (SEM) observation, time-resolved shadowgraph, and schlieren flow visualizations. The wall morphology of the cavitating-jet erosion on the groove roughness indicated an increased mass loss, which was highly increased along the groove rather than across the groove. Furthermore, increased erosion pits were observed on the groove bottom along the grooves. The shadowgraph imaging of the cavitating jet on the rough wall showed noncircular cavitation bubble distributions along and across the grooves, which corresponds to the increased number of cavitation bubbles along the grooves and the decreased number of bubbles across the grooves. This result is consistent with the erosion morphology of the groove roughness. Schlieren imaging indicated that the frequency and intensity fluctuation of the shockwave formation did not change significantly on the groove roughness along and across the grooves. The findings in the study show that the increased erosion mechanism on groove roughness is caused by the increased number of impulsive forces and the shockwave focusing effect on the groove bottom.

Synergistic Effects of Catalyst Mixtures on Biomass Catalytic Pyrolysis.

This paper studied the synergistic effects of catalyst mixtures on biomass catalytic pyrolysis in comparison with the single catalyst in a microwave reactor and a TGA. In general, positive synergistic effects were identified based on increased mass loss rate, reduced activation energy, and improved bio-oil quality compared to the case with a single catalyst at higher catalyst loads. 10KP/10Bento (a mixture of 10% K3PO4 and 10% bentonite) increased the mass loss rate by 85 and 45% at heating rates of 100 and 25°C/min, respectively, compared to switchgrass without catalyst. The activation energy for 10KP/10Bento and 10KP/10Clino (a mixture of 10% K3PO4 and 10% clinoptilolite) was slightly lower or similar to other catalysts at 30 wt.% load. The reduction in the activation energy by the catalyst mixture was higher at 100°C/min than 25°C/min due to the improved catalytic activity at higher heating rates. Synergistic effects are also reflected in the improved properties of bio-oil, as acids, aldehydes, and anhydrosugars were significantly decreased, whereas phenol and aromatic compounds were substantially increased. 30KP (30% K3PO4) and 10KP/10Bento increased the content of alkylated phenols by 341 and 207%, respectively, in comparison with switchgrass without catalyst. Finally, the use of catalyst mixtures improved the catalytic performance markedly, which shows the potential to reduce the production cost of bio-oil and biochar from microwave catalytic pyrolysis.