Shell Wall Research Articles

Mechanical properties and durability of lightweight cenosphere cementitious composites under coupling effect of dry-wet cycles and salt erosion

Cenospheres are suitable as supplementary cementitious materials to partially replace cement in the production of environmentally friendly lightweight cenosphere cementitious composites (LCCC). In this study, the correlation between the content and particle size of the cenosphere, the early curing system and the performance of LCCC was analyzed. The macroscopic properties and microstructural changes of LCCC under the conditions of dry-wet cycles and salt erosion were studied with different early curing conditions. The durability changes of LCCC mortar under the coupling effect of salt erosion and dry-wet cycles were studied by examining the mass loss rate, relative dynamic modulus of elasticity and salt corrosion resistance coefficient of LCCC mortar. Finally, a comparative analysis of the impact of existing cracks on the performance of LCCC under the coupling effect of dry-wet and salt erosion was conducted. The main innovation of the study includes the mechanical properties and durability of LCCC under dry-wet-salt erosion conditions, as well as the clarification of the impact of prefabricated cracks on the mechanical properties and durability of LCCC. It is found that the flexural strength and the compressive strength of specimens cured at high temperature is generally lower than that of the specimens cured under normal temperature conditions. The wet-dry salt corrosion can exacerbate the erosion the outer shell and inner wall of cenospheres and disrupt the stability of the internal interface transition zone (ITZ) in LCCC. LCCC with CsS exhibits better macroscopic performance and microstructural properties. Pre-existing cracks accelerates the erosion in the cenosphere shell and inner wall under salt solution.

Experimental and numerical study on the flow and heat transfer of ring-ribbed tank in deep-sea manned submersible

The ring-ribbed tank is the key equipment of cooling system of deep-sea manned submersible. The heat transfer characteristics of the outer wall and the heat transfer and flow characteristics of the inner flow channel of the ring-ribbed tank for different inlet and outlet temperatures and flow rates were studied through a water tank test. The results indicate that Nusselt number for the inner flow channel correlates with Reynolds and Prandtl numbers, while for the outer wall, it correlates with Grashof and Prandtl numbers with an overall error within 5%. A numerical study using the Realizable k-ε turbulence model and Boussinesq approximation of the flow-solid conjugate heat transfer is conducted, which can accurately determine the heat exchange capacity and the import and export differential pressure with an average relative error of 1.98% for hot water temperature and 7.73% for shell wall temperature. Additional simulations for determining the heat transfer capacity and flow resistance characteristics of the ring-ribbed tank in open water results demonstrate that the differential pressure and its coefficient are basically consistent with model test results. The cooling system can achieve a heat transfer rate of up to 17 kW with an external seawater flow velocity of approximately 2 knots.

Protection of α-Tocopherol from UV-Induced Degradation by Encapsulation into Zein Nanoparticles.

Vitamin E is a fat-soluble vitamin with several forms. Among these, α-tocopherol (TOC) is preferentially absorbed and accumulated in humans. In the body, it acts as an antioxidant, helping to protect cells from the damage caused by free radicals. It is an organic chemical compound that undergoes degradation upon irradiation with UV light. To protect this bioactive chemical compound from UV light degradation, encapsulation was carried out using zein as a shell material. Due to the unique phase diagram of TOC in aqueous ethanol, the encapsulation efficiency was >99%. The size of encapsulated particles was ~300 nm or smaller, and the thickness of the shell wall was ~30 nm. The presented procedure offers the most simple and efficient encapsulation process that yields edible products. The investigation of the irradiation effect of UV on TOC revealed that the encapsulation effectively blocks UV light and prevents TOC from being degraded. The presented procedure offers an instantaneous and highly efficient encapsulation process, which yields edible products.

Snail shell shape, force of attachment, and metabolic rate together cope with the intertidal challenge

Inhabitants of rocky intertidal shores, including gastropods, require specific adaptations to cope with numerous challenges that vary across the intertidal levels. We collected Stramonita biserialis snails from upper (wave-protected and intense predation) and lower (wave-exposed and low predation) intertidal sites to compare the following traits: shell skeleton (ventral and abaxial lateral views of shell shape, thickness, and mass), foot size, energy metabolism, and attachment strength to determine whether the trait values of snails from each zone fit the environmental challenges they face. We used a Principal Component Analysis to reduce the dimensionality of the data. Multivariate Analysis of Covariance (MANCOVA) for comparing characteristics between the two intertidal zones, and Partial Least Squares (PLS) analyses for testing the integration of overall snail characteristics. The traits of the snails of the two intertidal sites matched with the adaptations expected to allow them to cope with their contrasting challenges. The snails from the lower intertidal had more streamlined shells (which reduces drag forces) and a larger aperture and foot extension (which increase the strength of their attachment to the substrate) compared to snails from the upper sites. Snails from the lower intertidal also had a high mass-specific metabolism and soft body proportion, indicating that these snails from the wave-exposed sites have an energetically active musculature that matches their strong substrate attachment. The thin shell walls of the snails of the lower intertidal match the relatively low predatory pressure there.

Bellerophontid molluscs in the Grimsby Formation (Llandovery, lower Silurian), Hamilton, Ontario, Canada and their paleoecological and taphonomic implications

Specimens of a small bellerophontid mollusc, considered conspecific with Planorbis bilobatus Conrad 1839 from coeval strata in New York State, were recovered from the Grimsby Formation (lower Llandovery, lower Silurian), exposed in the Niagara Escarpment of western Hamilton, Ontario. Because Conrad’s species name is pre-occupied and is a secondary homonym, the new material is assigned to Tritonophon grimsbyensis n. sp. As Conrad’s original specimens are lost and where he collected them is unknown, a neotype from the Grimsby Formation is designated. These bellerophonts are preserved as casts on the soles of thin, fine-grained, sandstone beds interbedded with shale. These beds are probably tempestites Most are juvenile forms oriented on their sides, but in some beds adults with a widely expanded aperture are oriented aperture-down. Some specimens exhibit a V-shaped sinus on the median lobe, which is rarely preserved in Silurian examples. The aperture-down orientation suggests that this was the stable position during gentle wave action as well as probably their life position. Beds containing only juveniles may be evidence that the bellerophonts occasionally experienced a population boom but then were killed off during the storm event. Fine-grained sandstone fills the shell interiors, likely emplaced during wave-induced agitation. However, the shell walls are cast in mudstone, indicating that they dissolved during shallow burial and mud was pumped into the moulds. This may have been aided by episodic ground motion due to earthquakes that mobilized the adjacent sediment.

Test design and theoretical calculation of cook-off characteristics and thermal safety venting area of RBOE charge

RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive, whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead. Based on the thermal decomposition reaction characteristics and combustion characteristics of each component of RBOE explosive, the cook-off calculation models of RBOE warhead before and after ignition were established. In addition, closed and vented warheads were designed, as well as fast and slow cook-off test devices. The cook-off characteristics and thermal safety venting area of RBOE warhead were extensively studied. The results showed that the closed RBOE warhead underwent deflagration reaction under both slow and fast cook-off conditions. The calculation result of the shell wall temperature before slow cook-off ignition response of the warhead was 454.06K, with an error of +1.75% compared to the test result of 462.15K, and the temperature rise rate calculated was in good agreement with the test. The calculated ignition time of RBOE warhead under fast cook-off was 161s, with an error of + 8.8% compared to the test result of 148 s, which verified the accuracy of cook-off model of RBOE warhead before ignition. According to the cook-off calculation model of the warhead after ignition and cook-off test of the vented warhead, it was determined that the thermal safety venting area was 1124.61 mm2 for fast cook-off and 530.66 mm2 for slow cook-off, effectively preventing the reaction of warhead above combustion. Therefore, this study provides a scientific basis for the thermal safety design and evaluation of insensitive warheads.

Weld-joint design to optimize groove weld depth and mechanical properties for welding of nozzle onto pressure vessel

Full and partial set-in weld-joints connect the nozzle to pressure vessels to prevent lamellar tearing. This investigation aims to compare full and partial set-in weld-joints through computer simulations, numerical modelling, welding experiments, nondestructive examination and destructive testing. The nozzle-to-shell opening connection’s weld-joint design model is DN20, with a 50 mm shell wall thickness. The optimal groove weld depth, at a safety factor of 3.5, ranges from 20 to 50 mm. We investigated weld-joint design variations using design-of-experiment, which included actual welding and mechanical testing. The inter-run temperature and its interaction with the heat input were found to be statistically significant. The mechanical properties of welded joint are better than those of the specified material, A516 Grade 70, which include an average impact toughness of 89.5 J at -50 °C, a microhardness of 195 Hv10, an ultimate tensile strength of 533 MPa, a yield strength of 391.5 MPa and an elongation of 56.5%. The coefficients of determination of impact toughness and microhardness, which have R2 values of 88.73% and 76.65%, respectively, conclude a successful welding experiment. The design and mechanical testing results conclude the reliability of the weld-joints.

Tailoring microstructure and conductivity of porous hollow carbon spheres to enhance their performance as electrode materials for supercapacitors

Porous carbon materials are widely used in electrical double-layered capacitors for energy storage applications due to their abundant pores, high specific surface area and excellent electrochemical stability although their intrinsic electrical conductivity is generally low. Traditional high-temperature treatment was always adopted to boost the electrical conductivity of porous carbon materials by enhancing their graphitization degree, while this would always be accompanied by severe damage to pore structure and corresponding electrochemical performance. To solve the dilemma between boosting electrical conductivity and retaining pore structure, in this research, we proposed a low-temperature catalytic graphitization for hollow carbon spheres (HCSs) prepared by modified Stöber method accompanied with a special pore structure tailoring strategy. By altering the timing of adding carbon source, followed by secondary pore-forming and catalytic graphitization, HCSs with thin and porous shell walls along with enhanced conductivity were synthesized. Compared with the untreated HCSs or high-temperature graphitized HCSs, HCSs fabricated by the aforementioned combined strategies exhibited enhanced pore volume, specific surface area (2160.1 m2·g−1, 165.3 % of the untreated group) and conductivity (16.44±0.05 S·cm−2, 221.5 % of the untreated group), demonstrating much better electrochemical performance as the mass specific capacitance reached 256.7 F·g−1 and a volume specific capacitance reached 102.7 F·cm−3 at a current density of 1 A·g−1. Moreover, due to the largely promoted conductivity, the capacitance with the catalytic graphitized HCSs as the electrode material could be further boosted up to 273.4 F·g−1 at 1 A·g−1 by exempting the generally indispensable conductive agents and a high capacitance retention of 100.7 % was achieved after 5000 cycles at a relatively high current density of 10 A·g−1. This could be attributed to local graphitization brought by dispersed catalyst particles instead of entire atom rearrangement during high-temperature graphitization which would result in severe pore vanishing. The synergy of low-temperature catalytic graphitization and secondary pore-forming might be a novel strategy in electrode material fabrication for advanced supercapacitors or other energy storage devices.

Benzoyl peroxide encapsulation in poly(urea‐formaldehyde) microcapsules for use in dental materials

AbstractNew self‐healing resin composites with tertiary amine microcapsules enhance the mechanical performance of dental restorations. However, a higher concentration of dibenzoyl peroxide (BPO) must be added to the composite to react with the core material when the microcapsules rupture, reducing the shelf life of dental materials due to their reactivity. As a result, one approach to reducing the amount of BPO dissolved in dental resin is to microencapsulate it. Thus, this manuscript described the encapsulation of BPO in poly(urea‐formaldehyde) (PUF) microcapsules (MC) and investigated its effect on the flexural strength of BisGMA/TEGDMA composites. To synthesize hollow MC, poly(acrylic acid) (PAA) was tested as a continuous phase viscosity modifier. The MC were then infiltrated with BPO dissolved in linseed oil as core materials. PAA in continuous phase increased MC diameter due to improved air bubble stability. BPO dissolved in linseed oil was successfully infiltrated into empty PUF MC, causing the MC shell wall to expand. The dental resin had adequate adhesion to the PUF shell, which ruptured under induced stress. Thus, the MC filled with BPO as a healing agent has the potential to reduce the amount of BPO that is typically dissolved in the monomeric phase of dental materials, which can increase the shelf life of self‐healing dental materials.Highlights The reactivity of dibenzoyl peroxide (BPO) affects resin stability in dental materials. When combined with tertiary amines, BPO acts as a healing agent in self‐healing composite materials. BPO dissolved in linseed oil can be infiltrated in PUF microcapsules and increase its size. Hollow microcapsules synthesized in a more viscous continuous phase have a larger diameter. Microencapsulated BPO is released during stress stimuli in dental resin.

Simulation of ultrasonic shear effect on the viscoelastic soft scale of heat exchangers

The shear effect on the viscoelastic soft scale of heat exchangers is simulated in this study, focusing on a chemical company’s heat exchanger and the associated fouling on its inner tube shell wall. The finite element software ABAQUS simulates the ultrasonic descaling process, incorporating viscoelastic soft scale materials into the calculations through software fitting functions. Based on ABAQUS data transfer technology, the model was first subjected to implicit static analysis, followed by explicit kinetic analysis containing pre-stress. The vibration propagation of ultrasonic waves on the heat exchanger model was simulated under different working conditions. Distribution of shear stresses of the fouling on different paths of the pipeline wall was obtained, and the results revealed the influence of different parameters of the ultrasonic waves on the shear descaling effect, which provides a reference for selecting appropriate parameters to improve the efficiency of ultrasonic descaling.

Single-nucleus RNA and ATAC sequencing analyses provide molecular insights into early pod development of peanut fruit

Peanut (Arachis hypogaea L.) is an important leguminous oil and economic crop that produces flowers aboveground and fruits belowground. Subterranean fruit-pod development, which significantly affects peanut production, involves complex molecular mechanisms that likely require the coordinated regulation of multiple genes in different tissues. To investigate the molecular mechanisms that underlie peanut fruit-pod development, we characterized the anatomical features of early fruit-pod development and integrated single-nucleus RNA-sequencing (snRNA-seq) and single-nucleus assay for transposase-accessible chromatin with sequencing (snATAC-seq) data at the single-cell level. We identified distinct cell types, such as meristem, embryo, vascular tissue, cuticular layer, and stele cells within the shell wall. These specific cell types were used to examine potential molecular changes unique to each cell type during pivotal stages of fruit-pod development. snRNA-seq analyses of differentially expressed genes revealed cell-type-specific insights that were not previously obtainable from transcriptome analyses of bulk RNA. For instance, we identified MADS-box genes that contributes to the formation of parenchyma cells and gravity-related genes that are present in the vascular cells, indicating an essential role for the vascular cells in peg gravitropism. Overall, our single-nucleus analysis provides comprehensive and novel information on specific cell types, gene expression, and chromatin accessibility during the early stages of fruit-pod development. This information will enhance our understanding of the mechanisms that underlie fruit-pod development in peanut and contribute to efforts aimed at improving peanut production.

Shell microstructure of Styliolina clavulus (Tentaculita) from the Middle Devonian of Czech Republic: implications for phylogenetic affinities and biomineralization of thin-walled tentaculitids

Based on shell microstructure, pelagic tentaculitids have been affiliated with molluscs in the past. Species of the genus Styliolina were among the most important pelagic tentaculitids in the Devonian. The shell wall of Styliolina clavulus is single-layered and composed of thin calcareous lamellae that are parallel to the wall of the shell. The thickness of individual lamellae varies about two times but the thickness of each lamella in the shell wall is constant. The structure is clearly laminar and is similar to bryozoan, brachiopod and molluscan calcitic regularly foliated structures. Based on the structure of S. clavulus alone and the reinterpretation of published SEM images, it is impossible to rule out molluscan affinities for styliolinids, as both regularly foliated and semi-nacreous structures are known in molluscs. However, considering the whole shell structure spectrum of tentaculitoids, one should conclude that the structure of S. clavulus fits well within the group of tentaculitoids and lophophorates in general. The biomineralization of styliolinids was likely advanced and organic matrix controlled; the secreting epithelium was located within the shell and secretion likely took place lamella by lamella. Olev Vinn [olev.vinn@ut.ee], Institute of Ecology and Earth Sciences, University of Tartu, Ravila 14A, 50411 Tartu, Estonia Abdullah A. Alkahtane [aalkahtane@ksu.edu.sa], College of Science, King Saud University, Kingdom of Saudi Arabia Magdy El Hedeny [magdy.elhedeny@alexu.edu.eg], Geology Department, Faculty of Science, Alexandria University, Egypt; Saleh Al Farraj [alfarraj@ksu.edu.sa], College of Science, King Saud University, Kingdom of Saudi Arabia.

New taxa of the superorder Spirillinoida (Foraminifera)

New taxa of the superorder Spirillinoida (Foraminifera)

Hefting Heavy Shells: Sustenance Demands Caused by Various Abodes of the Hermit Crab Pagurus granosimanus

Marine hermit crabs inhabiting different species of shells in the rocky intertidal may receive varied benefits and costs. Thick shell walls, sculpture, and certain silhouettes may increase protection against crushing predators and waves, but also the energy cost for bearing such a shell. To determine the relative energy demands on Pagurus granosimanus supporting one of three different species of shells commonly inhabited in nature, we measured the consumption of food by free-roaming, size-matched individuals after four days of food deprivation in the laboratory. Surprisingly, while all hermit crabs consumed a significant amount of food, that amount did not differ significantly across the types of shells inhabited, despite the significantly heavier weight of one type of shell (>150% of each of the other two species), and markedly different shell silhouettes. Whether our results were due to the inherent abilities of arthropods to support proportionally immense weights (physiology), reduced movements by animals in heavier shells (plastic behavior), or the way the hermit crabs bear the burden of the shell requires further investigation. Regardless, our results suggest that individuals of P. granosimanus that inhabit heavier shells that likely provide increased protection do not experience corresponding elevated food consumption requirements over the short term, even if those shells are not centered over the body mass of the hermit crab. Pagurus granosimanus crabs can bear the burden.

Natural frequencies and modes of parametric vibrations of reservoir shell with shape imperfections

Development of software on the basis of the finite element method led to intensive creation of the numeral methods for the decision of static and dynamic problems of the thin shells. The finite element model of the thin shell has an infinite number of freedom degrees and natural frequencies, so solving the dynamics problem of the shell is difficult. If behavior of natural vibrations of the shell was researched, it is possible to talk about shell internal properties which take a great place at the forced vibrations including parametric one. It is important to take into account influence of the constant component of parametric load on natural frequencies and modes of the shell. Nowadays forming of an effective model of parametric vibrations of the shell with shape imperfections and choice of the most dangerous imperfections model remain relevant. Influence of real and modelled imperfections on natural frequencies and modes of reservoir shell parametric vibrations excited by axial load and on shell stability loss was investigated in this article. The finite element models of the shell was formed by software NASTRAN. The modelled shape imperfections as a lower buckling form of perfect shell under static pressure were presented. The real imperfections as the deviations of the shell wall from the vertical were obtained by theodolite surveying. The natural frequencies and modes of the imperfect shell taking into account the its previous stress state from action of the constant component of the parametric load were received by the Lanczos method. Investigations showed that the real imperfections of shell a little influenced on natural frequencies and modes of parametric vibrations. These decreased the critical loads on the first natural frequency on 0,58 % and increased on the second natural frequency shells on 0,79 %, but qualitatively changed the form of stability loss on these frequencies. Modelled imperfections had a greater but not considerable influence on natural frequencies and modes of the shell. But the modelled imperfections of the shell under constant component of parametric load considerably increased the critical load on the first and second natural frequency accordingly on 12,3 % and 5,26 % and changed the shell forms of stability loss. So the modelled imperfections of the shell in the form of the regular circular half-waves increased shell carrying capacity, but not decreased. This positive effect takes place at constructing of cylinder shells from the corrugated rolled sheets.

Tailored engineering of rod-shaped core@shell ZnO@CeO2 nanostructures as an optical stimuli-responsive in sunscreen cream

The catalytic efficiency of the materials can be boosted with the selective designing (nanostructures) including the core@shell which aids in attaining the separation of photoinduced charge carriers. However, to effectively separate the carriers and reduce the rate of recombination, tuning the thickness of the shell wall is a vital one. The one-dimensional (1D) rod-like shell wall-controlled ZnO@CeO2 core@shell structures were successfully prepared via co-precipitation and hydrothermal methods using the hexamethylenetetramine (HMTA) as a reagent. The CeO2 shell wall thickness was fine-tuned between 15 and 70 nm with a variation in the concentration of HMTA reagent. The results revealed that the concentration of HMTA played a significant role in the formation of ZnO@CeO2 core@shell structures and in tuning their thickness. The FE-SEM images evidenced the core-shell structures formation with the specific thickness and uniformity. The HR-TEM images confirmed the homogeneity and regular form of the shell thickness. The unit cell and crystallite size were identified from the XRD analysis. The constructed core-shell structures were further employed in the formula of the prototypes of sunscreen and their photoprotective performance was analyzed in the view to cut the solar light irradiation in a new sunscreen formulation. The developed core-shell ZnO@CeO2 structures showed the excellent optical absorption in both the UV as well as visible regions.

Late Ordovician and early Silurian virgianid and stricklandioid brachiopods from North Greenland: implications for a warm‐water faunal province

AbstractAn unusually rich and diverse suite of virgianid brachiopods, hitherto poorly known, is systematically described here for the first time from the Ordovician–Silurian boundary interval (late Katian – Aeronian) of North Greenland. The Late Ordovician virgianids comprise typical taxa of the warm‐water Tcherskidium fauna (e.g. Tcherskidium tenuicostatum, Proconchidium schleyi, Holorhynchus giganteus and Deloprosopus dawesi sp. nov.). Among the early Silurian taxa, Virgiana hursti sp. nov. occurs as abundant shell beds, similar to other congeneric species in Laurentia, but has somewhat larger internal skeletal structures, albeit not as extravagantly developed as in the late Katian virgianids; Borealoides balderi gen. et sp. nov. shows extreme thickening of the shell wall and internal structures, approaching the extravagant calcification of Katian virgianids. The highly distinctive mid‐Aeronian stricklandioid brachiopod genus, Kulumbella, characterized by a shell with criss‐cross (divaricate) ribbing, also occurs in North Greenland, represented by K. heimdali sp. nov., which has the largest and most strongly biconvex shells for the genus. Palaeogeographically, the Late Ordovician virgianid fauna of Laurentia was highly distinct, confined to the low–mid tropical latitudes north of the palaeoequator. In comparison, the early Silurian (Rhuddanian) Virgiana and some related taxa in Laurentia spanned the tropics of both hemispheres, forming extensive shell beds in carbonate basins, although Borealis and Borealoides gen. nov. remained confined largely to the northern hemisphere, suggesting a certain level of provincialism extending into the earliest Silurian. A palaeoecological preference for warm‐water carbonate settings would explain the unusual abundance and richness of the virgianid faunas in North Greenland.

Defective phase engineering of S-Scheme TiO2-SnS/SnS2 core-shell Photocatalytic nanofibers for elevated Visible light responsive H2 generation and Nitrogen fixation

To promote the fast separation of photogenerated charge carriers and promote stability, we designed the core-shell TiO2-SnS/SnS2 heterostructures with a mixed-phase shell wall of the SnS/SnS2 composition with enriched oxygen-related...

Taphonomic significance of Aristotle's 'Wheel Paradox': an example with the cerithid gastropod Cerithium atratum (Born, 1778) from Conceição Lagoon, Santa Catarina State, Southern Brazil

In the book Mechanical Problems, attributed to Aristotle, the author relates the differential degrees of wearing and rounding of pebbles and shells moved by waves on the seashore to the variable radii and diameters of these particles. This phenomenon, which became known as Aristotle’s ‘Wheel Paradox,’ seems to explain the pattern of abrasion observed in shells of gastropods Cerithium atratum (Born) found in Conceição Lagoon, on the Island of Santa Catarina, Brazil. In situ observations show that the elongated turriform shells of C. atratum deposited at shallow (< 30 cm) depths on a sandy bottom with pavements of disarticulated valves of Anomalocardia flexuosa Gmelin are subject to bidirectional wave-generated currents under fairweather conditions. The 47 specimens analyzed exhibit a pattern of abrasion characterized by the loss of the shell wall, apparently proceeding from the wider last whorl toward the narrow apex, culminating in the exposure of the columella. Experiments designed to test whether this pattern could be related to the ‘Wheel Paradox’ principle show that under bidirectional flow, the shells describe circles on the vertical plane around the longitudinal axis (rolling) and a pendulum movement (revolution) on the horizontal plane centered on the apex. The whorls located farther from the apex have larger diameters and describe broader arc segments. Thus, they have higher tangential velocities and travel longer paths, which could explain why they are abraded earlier than the narrower whorls. Recognizing similar abrasion features in fossil shells can provide information on the local paleo-currents, hydrodynamics, and relative time-averaging of death assemblages and allow distinguishing between natural or anthropogenic modification in archaeological specimens. Although the effects vary between shells with different shapes, Aristotle’s ‘Wheel Paradox’ principle explains the general abrasion pattern among gastropods under certain hydrodynamic conditions. Keywords: Actualistic Taphonomy, Aktuopaläontologie, shell abrasion, shell orientation, biostratinomy, hydrodynamics

Polydopamine based silver coated cenosphere microcapsule for thermal energy storage

In the present work, low-cost and eco-friendly metallic multi-shell wall microcapsules having paraffin wax were synthesized by encapsulating them with industrial waste cenosphere. Acid etching of the cenosphere shell wall was carried out to create multiple pores through which liquefied paraffin was vacuum infiltrated. Later, metallic coating of Ag was done through surface functionalizing the microcapsule with bio-polymer polydopamine (PD). The metallic coating is adapted to provide a dual function in terms of sealing the pores as well as increasing the thermal conductivity of the microcapsules. Further, the coating also provides additional mechanical strength of the microcapsule. Scanning electron microscopy (SEM) images showed that the mean diameter of the cenospheres was ∼67 µm and the pore diameter was ∼2 µm. The thickness of the Ag coating was ∼773 nm. The Fourier transform infrared (FTIR) Spectroscopy and X-ray photoelectron spectroscopy (XPS) results of the functionalized microcapsules showed additional peaks attributing to functional groups introduced after PD polymerization. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) results inferred that the thermal storage capacity of the microcapsule was 99.92% with high thermal reliability. Furthermore, silver coated microcapsules showed ∼33% enhanced heat transfer performance than uncoated microcapsules as evidenced by TT-curve. The metallic coating at the outer shell and PCM at the inner core of the cenosphere enable it to be a potential thermal energy storage (TES) material for versatile engineering applications.