Mass Loss Rate Research Articles

Corrosion effects of Na2CO3/NaCl molten salt eutectic on 316L stainless steel under isothermal and cycling conditions

Using phase-change materials in thermal energy storage systems for concentrating solar thermal plants can significantly reduce the volume of storage media and, therefore, the cost of the system. However, this approach introduces new material compatibility issues between the thermal energy storage material and the containment vessel in the form of corrosion and thermal transients, which are inherent in these systems. Rods and sheet coupons of stainless steel 316L were corroded for up to 768 h in 59.4/40.6 wt% Na2CO3/NaCl eutectic salt under isothermal (650 °C) and cycled conditions (between 600 and 650 °C). The testing methodologies correspond to actual service conditions, as isothermal degradation may not represent material loss under typical solar thermal cycling conditions. Mass losses were calculated via the Dynamic Gravimetric Analysis technique while Scanning Electron Microscopy utilizing Energy Dispersive Spectroscopy was used to analyze the corrosion layers. Isothermal mass loss plateaued at 75 mg/cm2 at 96 h with no further measurable loss after this time, while cycled samples had a fast initial mass loss rate of 60 mg/cm2 in the first 96 h and lost 0.0331 mg/cm2 every hour thereafter. The results indicate that isothermal samples corrode more slowly than the predominant industry cases of thermal cycling. Spalling is responsible for the degradation in both sets; the continual temperature changes in the cycled samples lead to additional stresses, exacerbating the effect.

Research on the Resistance Performance and Damage Deterioration Model of Fiber-Reinforced Gobi Aggregate Concrete

Concrete prepared using Gobi sand and gravel instead of ordinary sand and gravel is referred to as Gobi concrete. In order to explore the effect of fibers on the frost resistance of Gobi concrete, as well as to enhance the service life of Gobi aggregate concrete in Northwest China, experiments were conducted with fiber types (polypropylene fibers, basalt fibers, polypropylene–basalt fibers) and fiber volume fractions (0%, 0.1%, 0.2%, 0.3%) as variable parameters. This study investigated the surface morphology, mass loss rate, and relative dynamic elastic modulus of fiber-reinforced Gobi concrete after different freeze–thaw cycles (0, 25, 50, 75, 100). Corresponding frost damage deterioration models were proposed. The results indicate that fibers have a favorable effect on the anti-peeling performance, mass loss rate, and dynamic elastic modulus of Gobi aggregate concrete. The improvement levels of different fiber types are in the following order: 0.1% basalt-polypropylene fibers, 0.2% polypropylene fibers, and 0.3% basalt fibers. Compared to Gobi concrete exposed to natural environmental conditions, the freeze–thaw cycle numbers increased by 343, 79, and 69 times, respectively. A quadratic polynomial damage model for fiber-reinforced Gobi concrete, using relative dynamic elastic modulus as the damage variable, was established and demonstrated good predictive performance.

Study on the influence of fractal dimension and size effect of coarse aggregate on the frost resistance of hydraulic concrete

In cold regions, hydraulic concrete structures are exposed to harsh environmental conditions that greatly impact their durability and safety. The role of aggregates in influencing concrete performance is paramount. This study aims to investigate how the fractal distribution and size of aggregates affect the frost resistance of hydraulic concrete, with air void characteristics, mass loss rate, Elastic Modulus of dynamic, and strength serving as primary references. Two experiment series, fractal distribution influence and aggregate size influence of concrete frost resistance, were conducted to analyze the frost resistance of hydraulic concrete with different aggregates. Based on the fractal theory, four grading fractal distributions were utilized to fractalize aggregate gradation, aiming to investigate the influence of aggregate fractal dimension on the frost resistance of hydraulic concrete. Simultaneously, concrete specimens of fully graded aggregate and wet-screened aggregate were also constructed to simultaneous freeze-thaw cycle tests, the impact of aggregate size on concrete's frost resistance performance was also studied by analyzing the air void structure in the frost-resistant concrete specimens. Results indicate that the specimens exhibit varying frost resistance performance under different aggregate gradation fractals, ranking from strongest to weakest as follows: D=2.5, D=2.3, D=2.1, D=2.7, which is attributed to the differences of air void spacing factors. Increasing aggregate size leads to greater internal structural heterogeneity in concrete, resulting in an increase in defects and weak points. This causes microcracks to develop more rapidly in the transition zone of fully graded concrete during freeze-thaw cycles, leading to more severe damage. The findings of this study can serve as a fundamental scientific basis for the designing and constructing of hydraulic concrete structures in cold areas.

Study on the Performance Evolution of Hydraulic Concrete under the Alternating Action of Freeze–Thaw and Abrasion

The hydraulic concrete in the alpine region is subjected to alternating actions of freeze–thaw (F) and abrasion (W) during operation, resulting in significant deterioration of concrete durability. In this paper, the water/binder ratio (W/B) was employed as the test variable, the working condition F group and W group were set as the control group, and the working condition F-W group was used as the test group. Fast-freezing and underwater methods are used for the alternating test. By measuring the mass loss, relative dynamic elastic modulus (RDEM), surface morphological characteristics, fractal dimension of concrete in each alternating cycle, and the evolution law of concrete performance under the alternating action of F and W was explored. The results show that compared with the control group, the alternating action will accelerate the mass loss of concrete, reduce the RDEM, and cause the deterioration of surface wear. The maximum increase in mass loss and RDEM of concrete is 1.92% and 20.11%, respectively. During this process, the fractal dimension of the concrete increases as the number of alternating cycles increases, but it still does not exceed the limit of 2.4. In addition, a relationship function between the fractal dimension and the mass loss rate, volume loss, was established. It was found that the experimental group had a good linear correlation, and the correlation was close to 95%, which was about 20% higher than that of the control group.

Physical and mechanical characteristics deterioration and crack evolution of sandy mudstone in an open-pit mine under multiple freeze–thaw cycles

In open-pit mines located in cold regions north of the 38°N latitude, there are significant freeze–thaw phenomena in slope rocks. This study conducted freeze–thaw cycle tests, considering the number of freeze–thaw cycles and the freezing temperature, on sandy mudstone commonly found in the slopes of open-pit mines. The investigation focused on the effects of freeze–thaw cycles on the physical and mechanical properties and acoustic emission (AE) characteristics of sandy mudstone. The results show that, with an increase in the number of freeze–thaw cycles and a decrease in freezing temperature, the sandy mudstone specimens exhibit nonlinear exponential changes in mass loss rate, P-wave velocity loss rate, peak strain, uniaxial compressive strength (UCS) and elastic modulus, and the amplitude of these changes gradually decreases. The stress–strain curves of specimens shift gradually from apparently brittle to plastic. Simultaneously, the microstructure changes from dense to loose, the micro surface transitions from flat to rough, and cracks and pore defects gradually develop. The peak AE ringing counts, cumulative AE ringing counts, crack initiation stress, and crack damage stress of the specimens all decrease with an increase in the number of freeze–thaw cycles and a decrease in freezing temperature. This suggests a shift from brittle failure to ductile failure. However, the ratio of crack initiation stress and crack damage stress to peak stress does not vary significantly with the number of freeze–thaw cycles and freezing temperature.

Physics of nova outbursts: Theoretical models of classical nova outbursts with optically thick winds on 1.2 M⊙ and 1.3 M⊙ white dwarfs

Abstract We present time-dependent nova outburst models with optically thick winds for 1.2 and 1.35$\, M_{\odot }$ white dwarfs (WDs) with a mass-accretion rate of $5 \times 10^{-9}\, M_{\odot }$ yr−1 and for a 1.3$\, M_{\odot }$ WD with $2 \times 10^{-9}\, M_{\odot }$ yr−1. The X-ray flash occurs 11 d before the optical peak of the 1.2$\, M_{\odot }$ WD and 2.5 d before the peak of the 1.3$\, M_{\odot }$ WD. The wind mass-loss rate of the 1.2$\, M_{\odot }$ WD (1.3$\, M_{\odot }$ WD) reaches a peak of $6.4 \times 10^{-5}\, M_{\odot }$ yr−1 ($7.4 \times 10^{-5}\, M_{\odot }$ yr−1) at the epoch of the maximum photospheric expansion with the lowest photospheric temperature of log Tph (K) = 4.33 (4.35). The nuclear energy generated during the outburst is lost in the form of radiation (61% for the 1.2$\, M_{\odot }$ WD; 47% for the 1.3$\, M_{\odot }$ WD), gravitational energy of ejecta (39%; 52%), and kinetic energy of the wind (0.28%; 0.29%). We found an empirical relation for fast novae between the time to optical maximum from the outburst tpeak and the expansion timescale τexp. With this relation, we are able to predict the time to optical maximum tpeak from the ignition model (at t = 0) without following a time-consuming nova wind evolution.

Transformation of polyester fibre microplastics by sulfate based advanced oxidation processes

Advanced oxidation processes (AOPs) are a potential solution to microplastics (MPs) polluted wastewater but incomplete degradation can result in the formation of smaller fragments with altered surface chemistry. In this work, the impact of sulfate based oxidation on polyester MPs was investigated. Light, heat and ultrasound activation of persulfate resulted in varied degrees of mass loss and surface degradation, as probed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). Ultrasonic activation of persulfate resulted in significantly increased fragmentation and formation of smaller microplastic fibrils. Optimised UVC/peroxydisulfate (UVC/PDS) treatment (31.8 mW cm−2, 500 mg L−1) resulted in an 18.5% mass loss over 9 h with clear surface pitting and cracking. Extended treatment under these conditions for 24 h did not result in significantly increased mass loss but did cause an increased degree of surface degradation and increased roughness, indicating that incomplete mineralisation is likely in wastewater systems accompanied by MP transformation. The influence of a real laundry wastewater matrix was also studied and a decreased rate of mass loss was observed due to competing radical reactions with the organic content of the wastewater. Results advance understanding and therefore contribute to mitigating water pollution by MPs, since their physical and chemical transformation in real water treatment systems substantially affects the interaction with organic contaminants and changes the potential environmental risk of MPs.

Impact of main sequence mass loss on the appearance, structure, and evolution of Wolf-Rayet stars

Stellar winds are one of the most important drivers of massive star evolution and are a vital source of chemical, mechanical, and radiative feedback on the galactic scale. Despite its significance, mass loss remains a major uncertainty in stellar evolution models. In particular, the interdependencies between the different approaches and the subsequent evolutionary stages and predicted observable phenomena are far from being systematically understood. In this study, we examine the impact of main sequence mass loss on the structure of massive stars throughout their entire evolution. Particular focus is placed on the consequences in terms of entrance into the Wolf-Rayet regime and the subsequent evolution. Using the Geneva stellar evolution code (GENEC), we computed grids of single, nonrotating stellar models at solar and Large Magellanic Cloud (LMC) metallicities of initial masses between 20 and 120 solar masses, with two representative prescriptions for high and low main sequence mass loss. We obtain detailed numerical predictions regarding the structure and evolution of massive stars, and infer the role of main sequence mass loss by comparison of the mass-loss rate prescriptions. We present implications for the overall evolutionary trajectory, including the evolution of WR stars, as well as the effect on stellar yields and stellar populations. Mass loss during the main sequence plays an important role because of its ability to affect the sequence and duration of all subsequent phases. We identify several distinct evolutionary paths for massive stars, which are significantly influenced by the chosen main sequence mass-loss description. We also discuss the impact of uncertainties ---other than that regarding mass loss--- on the evolution, in particular those relating to convection. We further demonstrate that not only the total mass loss but also the specific mass-loss history throughout a star's life is a crucial determinant of many aspects, such as the resulting stellar yields.

Magic speed under radiation drag for the optically thick outflows and SS 433 jets

Abstract One of the promising mechanisms to explain the stable jet speed of SS 433 is the magic speed, which is established by the balance between radiation pressure and radiation drag (and gravity). We examine the magic speed in the optically thick sub-relativistic flows for several typical situations, such as plane-parallel and spherical cases, and show that it is difficult to establish the magic speed in the simple optically thick flows in contrast to the optically thin ones. Instead, we propose the funnel jets as an improved model. That is, we consider the optically thick flows in the funnel, which is formed by the supercritical accretion disk, and mass and radiation energy are injected from the funnel wall. In this model the mass-accretion rate determines the configuration of the funnel, the increasing mass-loss rate of jets, the radiative environments, and then the sub-relativistic magic speed is naturally established.

Reading tea leaves worldwide: Decoupled drivers of initial litter decomposition mass-loss rate and stabilization.

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models.

Effect of equal channel angular pressing on magnesium alloys − A review

Magnesium (Mg) alloys own excellent properties that includes better castability, low density and great specific strength. Mg and its alloys are easily available and economical. Necessity of Mg and its alloys for manufacturing and engineering purposes has increased, predominantly in the area of aircraft and automobile applications. The known limitation of magnesium is its poor formability at room temperature, with inadequate slip systems due to hexagonal closed packed construction of magnesium. Formability of magnesium alloys will be enhanced at room temperature by grain structure refinement which improves ductility with grain refined structure. Severe plastic deformation (SPD) procedure induces extreme strain within the sample to produce ultrafine grained structure. Additionally, few shortcomings of magnesium is increased wear mass loss and corrosion rate obstructing the use of Mg and its alloys in several industrial appliances. Wear resistance and corrosion behaviour can be enhanced by SPD thereby increasing the requirement of magnesium alloys for engineering applications. Among SPD, equal channel angular pressing (ECAP) is an efficient approach to develop and vary the mechanical and microstructural properties as per the need. In ECAP approach, the workpiece undergoes shear deformation and large strains are induced in the workpiece with no variation in cross sectional aspect of the workpiece. Microstructure plays a very important role in achieving the required mechanical properties. ECAP process creates ultrafine-grained microstructure with different number of ECAP passes with varying temperatures inducing high strain rate.

Pyrolysis-based modelling of 18650-type lithium-ion battery fires in thermal runaway with LCO, LFP and NMC cathodes

This study presents a modelling approach for simulating fires in thermal runaway and here, it is applied to 18650-type batteries with LCO, NMC, and LFP cathodes at 100% SOC. The model assumes a single-step pyrolysis, where a solid lumped substance, representing the battery components, degrades into volatiles which are vent gases here. Coupling an in-house MATLAB code and FDS solver, a parameter estimation using Bayesian optimization was performed to fit the simulated mass loss and heat release rate to the experimental measurements. One-step kinetics are used for vent gas combustion, with CO yield obtained from literature and soot yield determined via 1-D diffusion flame simulations with CRECK kinetic mechanism in Cantera solver. 3-D simulations using the obtained models yielded maximum values of flame temperature, CO2 and H2O mole fractions, velocity, radiative heat flux, and flame height as 2520 K, 0.47, 0.15, 10.08 m/s, 13.29 kW/m2, and 0.62 m, respectively. The novelties associated with this approach are that, unlike the past studies, there is no need to model the thermal runaway process prior to flaming and, the resulting heat release rate is experimentally verified which makes further analyses, such as flame temperature, height and heat emissions possible.

The improvement on calcium leaching resistance of high SCMs content cement in ammonium chloride solution using particle gradation technique

Particle gradations of Portland cement (PC), fly ash (FA), and blast furnace slag (BFS) were optimized to improve the calcium leaching resistance of blended cement with high contents (up to 70%)of supplementary cementitious materials (SCMs). The results showed that optimized blended cement showed refined initial pore volume distribution, reduced portlandite (CH) content, finer CH macrocrystals and enhanced stability of C-(A)-S-H gel. Consequently, it displayed exceptional calcium leaching resistance with reduced losses in mechanical performance, mass and pore degradation after calcium leaching. Blended cement with 30% PC (D50 = 14.46 μm), 30% FA (D50 = 10.94 μm), 20% BFS (D50 = 10.52 μm), 13% BFS (D50 = 5.31 μm) and 7% BFS (D50 = 4.71 μm), showing compressive strength retention rate of 79.05% and mass loss rate of 1.64%, was suggested as viable choice for calcium leaching resistant concrete.

Gasification study of Meulaboh coal under limited synthetic air and carbon dioxide environments

Gasification characteristics of Meulaboh coal have been investigated using chemical, petrographical, and thermogravimetry–mass spectrometry (TG-MS) approaches. The coal is classified as sub-bituminous C and dominated by huminite maceral (77% vol.). Based on proximate analysis, the coal comprises 12.56% moisture, 17.36% ash, 38.92% volatile matter, and 31.16% fixed carbon (adb). The coal is low in rank and dominated by reactive maceral. Thus, it is suitable for gasification study. TG-MS measurement revealed that the main pyrolysis product consists of H2O, CO2, and CH4, which generated significantly in slow and fast pyrolysis stages (180-294°C and 194-529°C, respectively). Gasification was performed using limited synthetic air and CO2 environments. TG and DTG thermograms show that gasification using CO2 resulted a higher mass loss rate than that using limited synthetic air. Moreover, gasification in a limited air atmosphere produced higher contents of H2O and CO2, while gasification in a CO2 atmosphere produced primarily CO.

Comparative study on the thermal runaway characteristics of Li(NixCoyMnz)O2 batteries

Lithium-ion batteries (LIBs) generate substantial gas during the thermal runaway (TR) process, presenting serious risks to electrochemical energy storage systems in case of ignition or explosions. Previous studies were mainly focused on investigating the TR characteristics of Li(NixCoyMnz)O2 batteries with different cathode materials, but they were conducted in isolation. In this study, the thermal runaway characteristics of prismatic cells that use Li(NixCoyMnz)O2 (with x ranging from 0.33 to 0.9) cathode materials in an inert environment, which are commonly used or proposed for energy storage applications, are examined. The findings of this research show that the normalized gas generation rate remains consistent, regardless of the battery capacity or experimental chamber volume, with a value of 0.1 ± 0.03 mol∙Ah⁻1. High-capacity cells have short jetting durations, and a high nickel content leads to increased mass loss rates. The flammability limits of the gases expelled during thermal runaway, represented by the lower flammability limit (LFL), remain stable at 8 ± 1.8% with minimal variations. However, the upper flammability limit (UFL) varies significantly, ranging from 30% to 60%. Increasing the battery capacity or reducing the experimental chamber volume increases the explosion index. The explosive, combustibility, and jetting duration characteristics of the emitted gases from five different battery chemical compositions provide valuable insights for risk assessment in future electrochemical energy storage systems.

Hall-magnetohydrodynamic simulations of X-ray photoevaporative protoplanetary disc winds

Abstract Understanding the evolution and dispersal via energetic stellar radiation of protoplanetary disks (PPDs) is a prominent challenge in astrophysics. It has been established that X-ray luminosity from the central protostar can significantly heat the surface of the disk, causing powerful photoevaporative winds that eject a considerable fraction of the disc’s mass. Recent work in the field has moreover shown the importance of global PPD simulations that simultaneously take into account non-ideal magnetohydrodynamic (MHD) effects and detailed thermochemistry. In this paper we combine these two aspects and figure out how they interact. Focus is put on the Hall Effect (HE) and the impact it has on the overall field topology and mass loss/accretion rates. Utilizing a novel X-ray temperature parametrisation, we perform 2D-axisymmetric MHD simulations with the nirvana-iii fluid code, covering all non-ideal effects. We find that, in the aligned orientation, the HE causes prominent inward displacement of the poloidal field lines that increase the accretion rate through a laminar Maxwell stress. We find that outflows are mainly driven by photoevaporation – unless the magnetic field strength is considerable (i.e., βp ≤ 103) or the X-ray luminosity low enough (i.e., log LX ≤ 29.3). Inferred mass loss rate are in the range of the expected values 10−8 to 10−7 M⊙ yr−1. Moreover, we performed pure hydrodynamic (HD) runs and compared them with the equivalent MHD runs. We concluded that the magnetic field does indeed contribute to the mass loss rate, albeit only discernibly so for low enough LX (i.e., log LX ≤ 30.8).

An empirical view of the extended atmosphere and inner envelope of the asymptotic giant branch star R Doradus

Context. The mass loss experienced on the asymptotic giant branch (AGB) at the end of the lives of low- and intermediate-mass stars is widely accepted to rely on radiation pressure acting on newly formed dust grains. Dust formation happens in the extended atmospheres of these stars, where the density, velocity, and temperature distributions are strongly affected by convection, stellar pulsation, and heating and cooling processes. The interaction between these processes and how that affects dust formation and growth is complex. Hence, characterising the extended atmospheres empirically is paramount to advance our understanding of the dust formation and wind-driving processes. Aims. We aim to determine the density, temperature, and velocity distributions of the gas in the extended atmosphere of the AGB star R Dor. Methods. We acquired observations using ALMA towards R Dor to study the gas through molecular line absorption and emission. We modelled the observed 12CO v = 0,  J = 2 − 1, v = 1,  J = 2 − 1, and 3 − 2 and 13CO v = 0,  J = 3 − 2 lines using the 3D radiative transfer code LIME to determine the density, temperature, and velocity distributions up to a distance of four times the radius of the star at sub-millimetre wavelengths. Results. The high angular resolution of the sub-millimetre maps allows for even the stellar photosphere to be spatially resolved. By analysing the absorption against the star, we infer that the innermost layer in the near-side hemisphere is mostly falling towards the star, while gas in the layer above that seems to be mostly outflowing. Interestingly, the high angular resolution of the ALMA Band 7 observations reveal that the velocity field of the gas seen against the star is not homogenous across the stellar disc. The gas temperature and density distributions have to be very steep close to the star to fit the observed emission and absorption, but they become shallower for radii larger than ∼1.6 times the stellar sub-millimetre radius. While the gas mass in the innermost region is hundreds of times larger than the mass lost on average by R Dor per pulsation cycle, the gas densities just above this region are consistent with those expected based on the mass-loss rate and expansion velocity of the large-scale outflow. Our fits to the line profiles require the velocity distribution on the far side of the envelope to be mirrored, on average, with respect to that on the near side. Using a sharp absorption feature seen in the CO v = 0,  J = 2 − 1 line, we constrained the standard deviation of the stochastic velocity distribution in the large-scale outflow to be ≲0.4 km s−1. We characterised two blobs detected in the CO v = 0,  J = 2 − 1 line and found densities substantially larger than those of the surrounding gas. The two blobs also display expansion velocities that are high relative to that of the large-scale outflow. Monitoring the evolution of these blobs will lead to a better understanding of the role of these structures in the mass-loss process of R Dor.

Failure Mechanism and Thermal Runaway in Batteries during Micro-Overcharge Aging at Different Temperatures.

This paper provides insights into the four key behaviors and mechanisms of the aging to failure of batteries in micro-overcharge cycles at different temperatures, as well as the changes in thermal stability. The test results from a scanning electron microscope (SEM) and an energy-dispersive spectrometer (EDS) indicate that battery failure is primarily associated with the rupture of cathode materials, the fracturing and pulverization of electrode materials on the anode current collector, and the formation of lithium dendrites. Additionally, battery safety is influenced by environmental temperatures and the battery's state of health (SOH), with failed batteries exhibiting the poorest stability and the highest mass loss rates. Under isothermal conditions, micro-overcharge leads to battery failure without thermal runaway. Thus, temperature stands out as the most influential factor in battery safety. These insights hold significant theoretical and practical value for the development of more precise and secure battery management systems.

Sublimation and oxidation measurements of graphite and carbon black at high temperatures in a shock tube using absorption imaging and thermal emission

Surface mass loss rates due to sublimation and oxidation at temperatures of 3000–7000 K have been measured in a shock tube for graphite and carbon black (CB) particles. Diagnostics are presented for measuring surface mass loss rates by diffuse backlit illumination extinction imaging and thermal emission. The surface mass loss rate is found by regression fitting extinction and emission signals with an independent spherical primary particle assumption. Measured graphite sublimation and oxidation rates are reported to be an order of magnitude greater than CB sublimation and oxidation rates. It is speculated that the difference between CB and graphite surface mass loss rates is largely due to the primary particle assumption of the presented technique which misrepresents the effective surface area of an aggregate particle where primary particles overlap and shield inner particles. Measured sublimation rates are compared to sublimation models in the literature, and it is seen graphite shows fair agreement with the models while CB underestimates, likely a result of the particle shielding affect not being considered in the sublimation model.

Study on the encapsulation effect and mechanism of hollow ceramsite to phase change materials (PCMs)

In order to promote the development of phase change materials (PCMs) and make them better applied, more in-depth research on the PCMs encapsulation is needed. The hollow ceramsite prepared in this study is a new type of PCMs carrier. Due to its unique structure, the encapsulation of PCMs by hollow ceramsite differs from that of ordinary porous ceramsite. In this paper, the adsorption and sealing effect of hollow ceramsite on PCMs was studied, the key factors affecting the adsorption and sealing effect were determined, and the encapsulation mechanism was revealed. The results show that the driving force of PCMs into the cavity of hollow ceramsite is mainly from the external pressure; the pore size and PCMs properties are the key factors determining the adsorption effect of hollow ceramsite. The pressure on the pore is proportional to the square of the pore diameter; increasing pore size enhances the possibility of the PCMs entering the cavity of ceramsite. The contact angle between PCMs and pores is smaller, and the surface tension of the PCMs in the pores is greater, making it difficult for PCMs to enter the cavity of ceramsite. The sealing mechanism of the coating on infiltrating PCMs is achieved by reducing the pore diameter of the sealing coating and increasing the resistance of PCMs to break through the pore. The sealing mechanism of the coating on non-infiltrating PCMs is achieved by changing the contact property between the PCMs and pore, increasing the energy barrier. After coating, the mass loss rate of infiltrating paraffin was controlled within 5 %, and the leakage rate of non-infiltrating hydrated salt was controlled within 1 %.